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.ED. I
THE
COMPARATIVE ANATOMY
OF THE
DOMESTICATED ANIMALS
THE
COMPARATIVE ANATOMY
OF THE
DOMESTICATED ANIMALS
BY
A. CHAUVEAU, M.D., LL.D.
MEMBER OF THE INSTITUTE (ACADEMY OF SCIENCES); INSPECTOR-GENERAL OF VETERINARY
SCHOOLS IN FRANCE; PROFESSOR AT THE MUSEUM OF NATURAL HISTORY, PARIS
JElctiiseli antJ IBnlargeti, toftl) ti)e ©o^opcratfon ot
S. ARLOING
DIRECTOR OF THE LYONS VETERINARY SCHOOL
PROFESSOR OF EXPERIMENTAL AND COMPARATIVE MEDICINE AT THE LYONS FACULTY OF MEDICINE
SECOND ENGLISH EDITION
TRANSLATED AND EDITED
By GEORGE FLEMING, C.B., LL.D., F.R.C.V.S.
LATE PRINCIPAL VETERINARY SURGEON OF THE BRITISH ARMY ; FOREIGN CORRESPONDING MEMBER
or THE SOClETfe ROYALE DE MfeDKCINE, AND OF THE SOClfiTfi ROYALE DE mSdECINE PUBLIQUE, OF BELGIUM
FOREIGN ASSOCIATE OF THE SOClllTfi CENTRALE DE MfeOECINE VfiT^RINAIRE OP FRANCE
HONORARY LIFE MEMBER OF THE ROYAL AGRICULTURAL SOCIETY OF ENGLAND
FOREIGN MEMBER OF THE SOClfiTfi NATIONALE D'AGRICULTURE OF FRANCE, ETC
EXAMINER IN ANATOMY FOR THE ROYAL COLLEGE OF VETERINARY SURGEONS
WITH 585 ILLUSTRATIONS
NEW YORK
D. APPLETON AND COMPANY
1905
IN COMMEMORATION OF THE CENTENARY
OF THE
ROYAL YETERINAEY COLLEGE, LONDON;
THE PARENT OF VETERINARY SCHOOLS IN ENGLISH-SPEAKING COUNTRIES.
AND IN MEMORY OF
CHARLES VIAL DE SAINT-BEL,
EQUERRY TO LOUIS XVI. OF FRANCE, PRINCIPAIi OF THE LYONS ACADEMY,
PROFESSOR IN THE ROYAL VETERINARY SCHOOL OF THAT CITY,
AND
DEMONSTRATOR OF COMPARATIVE ANATOMY AT MONTPELLIER ;
WHO, WHEN A REFUGEE FROM THE GREAT FRENCH REVOLUTION, WAS
CHIEFLY INSTRUMENTAL IN ESTABLISHING THE FIRST ENGLISH VETERINARY SCHOOL,
IN WHICH HE WAS THE FIRST TEACHER,
1791.
PEEFACE TO THE SECOND ENGLISH EDITION.
Since the translation of this work into English, seventeen years ago, it
has been several times reprinted, the last occasion being in 1889. Cir-
cumstances had, however, for some time indicated that there was need
for a revision of the work in order to bring it up to the requirements
of the present day, and the issue of a fourth French edition last year was
considered a favourable opportunity for undertaking the task.
In preparing this second edition, the necessities of advancing veteri-
nary education in the English-speaking schools was kept in view, and this
entailed considerable amendments, alterations, and additions, in order
to adapt it more perfectly to the conditions it should fulfil as a text-
book and standard work of reference on the subject.
The high esteem in which the first edition has been held for so many
years in this country, in our Colonies, and in the United States of America,
amply testifies to the value of the work ; and in this new edition every-
thing has been done to render it still more comprehensive, complete, and
useful. The anatomy of the Ass, Mule, and Eabbit has been added, as
well as that of the Camel — that animal being utilized not only in our
army in different parts of the world, but also in some of our Colonies.
The number of illustrations has been increased by more than one hundred
and thirty, the pages have been enlarged, and the letterpress so modified
as to make reading and reference much easier.
A copious index — there is none in the French edition — has also been
added, with the view of enhancing the usefulness of the book as a work
of reference for students and practitioners.
With these alterations, additions, and modifications, I trust the work
may continue to be accepted as in every way worthy of the position
accorded to it as the best on the subject.
The editorial remarks — for which, as well as for the translation, I
assume the entire responsibility — are included in brackets, as in the first
edition.
GEORGE FLEMING.
London,
April, 1891.
TABLE OF CONTENTS.
Dedication
Preface to the Second Edition
Table of Contents
Table of Illustrations
Vll
ix
xxvii
GENERAL CONSIDERATIONS.
Definition and Division of Anatomy .......
Enumeration and Classification of the Species of Domesticated Animals
General Ideas of the Organization of Animals, and the order followed in studying the
various apparatuses ........
BOOK I.
IiOCOMOTORY APPARATUS.
[RST SECTION.— THE BONES
7
Chapter I.— The Bones in General ....
7
Article I. — The Skeleton ......
8
Article II.— General Principles applicable to the Study of all
the Bones 11
Name, Situation, Direction, and Configuration of Bones
12
Internal Conformation of Bones. Structure of Bones
15
Development of Bones ......
19
Chapter II.— The Bones of Mammalia in Particular
24
Article I.— Vertebral Column . . . .
24
Characters Common to all the Vertebrae ....
24
Characters Proper to the Vertebrae in each Region .
26
1. Cervical Vertebrae ......
27
Differential Characters ......
30
2. Dorsal Vertebrae ......
32
Differential Ciiaracters ... , .
35
3. Lumbar Vertebrae ......
36
Differential Characters ......
37
4. Sacrum .......
39
Differential Characters ....
40
5. Coccygeal Vertebrae .....
41
Differential Characters .....
41
The Spine in General ......
42
Varieties in the Vertebral Column ....
43
Comparison of the Vertebral Column of Man with that of the 1
Domesticated
Animals ......
45
Article II.— The Head . . . c . .
46
The Bones of the Cranium .....
46
1. Occipital .......
46
Differential Characters .....
48
2. Parietal .......
49
Differential Characters .....
49
3. Frontal
49
Differential Characters .....
52
TABLE OF CONTENTS.
4. Ethmoid .
DiflTerentiiil Characters
5. Sphenoid .
Diflferentiiil Characters
6. Temporal .
DiflFerential Characters
The Bones of the B'ace .
1. Supermaxillii .
Diflferential Characters
2. Premaxilla
DiflFerential Characters
3. Palatine
Differential Characters
4. Pterygoid
Differential Characters
5. Malar .
Differential Characters
6. Lachrymal
Differential Characters
7. Nasal .
Differential Characters
8. Turbinated
Differential Characters
9. Vomer .
Differential Charaeters
10. Inferior Maxilla
Differential Characters
11. Hyoid
Differential Characters
12. Wormian Bunes
Of the Head in General .
1. General Configuration
2. Conformation of the Cranium in Particular
3. Relations between the Cranium and Face .
4. Modifications due to Age .
Comparison of the Head of Man with that of Animals
Article III. — The Tuobax
The Bones of the Thorax in Particular
Differential Characters
Ribs ......
Differential Characters in the Ribs of other Animals
The Thorax in General ....
Comparison of the Thorax of Man with that of other Animals
1. Sternum
2. Ribs
Article IV.— Anterior Limbs
Shoulder
Scapula .
Differential Characters
Arm
Humerus
Differential Ciiaracters
Forearm
1. Radius
2. Ulna
Differential Characters
Anterior (or Fore) Foot, or Hand
1. Carpal Bones .
Differential Characters
2. Metacarpal Bones
Differential Characters
TABLE OF CONTENTS.
that of the Domesticated
AND THEIR PARALLELISM
8. Bones of the Phalanges or Digital Region ....
Differential Characters ......
Comparison of tJje Thoracic Limb of Man with that of the Domesticated Animal
Article V. — The Hand in General .....
Article VI. — Posterior or Pelvic Limb
Pelvis ....
A. Coxa, or Os Innomatura
B. The Pelvis in General
Differential Characters
Thigh ....
Femur ....
Differential Characters
Leg .....
1. Tibia
2 Fibula, or Peroneus . .
3. Patella
Differential Characters
Posterior Foot .
1. Bones of the Tarsus
Differential Characters
2. Bones of the Metatarsus
Differential Characters
3. Bones of the Digital Region
Differential Characters
Comparison of the Abdominal Limb of Man with
Animals.
Article VII. — The Foot in General
Article VIII. — The Limbs in General,
Chapter III.— The Bones in Birds
Chapter IV.— Theory of the Vertebral Constitution of the Skeleton
SECOND SECTION —THE ARTICULATIONS ....
Chapter I.— The Articulations in General ....
General Characters of the Diarthroses .....
General Characters of the Synarthroses .....
General Characters of the Amphiarthroses, or Symphyses .
Chapter II. — The Articulations in Mammalia in Particular .
Article I. — Articulations op the Spine .....
Intervertebral Articulations ......
Differential Characters .......
Article II.— Articulations of the Head
1. Atlo-axoid Articulation . . . . . .
2. Occipito-atloid Articulation .....
3. Articulations between the Bones of tlie Head ....
4. Temporo-maxillary Articulation .....
5. Hyoideal Articulations .......
Article III. — Articulations of the Thorax ....
Extrinsic Articulations .......
Costo-vertebral, or Articulations of the Ribs with the Vertebral Column
Intrinsic Articulations .......
A. Chondro-sternal or Costo-sternal Articulations
B. Chondro-cdsta! Articulations, or Articulations between the Ribs and their
Cartilages ... ....
C. Articulations between the Costal Cartilages
D. Sternal Articulation peculiar to the Ox and Pig
The Articulations of the Thorax considered in a General Manner, with respect to
their Movements ....
A.RTICLE IV. — Articulations of the Anterior Limbs
1. Scapulo-humeral Articulation
2. Humero-radial Articulation
3. Radio- ulnar Articulation
4. Articulations of the Carpus . ,
xii
TABLE OF CONTENTS.
5. Intermetacarpal Articulations ....
6. Metacarpo-plialangeal Articulations
7. Articulation of the First Phalanx with the Second, or First
Articulation ....
8. Articulation of the Second Phalanx with tlie Third, Second Interphalangeal
Articulation, or Articulation of the Foot
, \bticle V. — Articulations of the Posterior Limbs
1. Articulations of tlie Pelvis
2. Coxo- femoral Articulation .
3. Femoro-tibial Articulation
4. Tibio- fibular Articulation .
5. Articulations of the Tarsus, or Hock .
Chapter III.— The Articulations in Birds .
THIRD SECTION. -THE MUSCLES
Chapter I.— General Considerations on the Striped Muscles
The Striped Muscles in General .....
Structure of the Striped Muscles ....
Physico-chemical Properties of Striped Muscles
Physiological Properties of Striped Muscles
Appendages of the Muscles ......
Manner of Studying the Muscles
Chapter II.— The Muscles of Mammalia in Particular
Article I. — The Muscles of the Trunk
Subcutaneous Region ......
Flesliy Pannicuius (Panniculus Carnosus)
Cervical Region .......
A. Superior Cervical or Spinal Region of the Neck
1. Rhomboideus ......
2. Angularis Muscle of the Scapula (Levator Anguli Scapulae)
3. Splenius .......
4. Complexus (Complexus Major) ....
5. Trachelo-mastoideus (Complexus Minor)
6. Spinalis or Semispinalis Colli ....
7. Intertransversales Colli .....
8. Great Oblique Muscle of the Head (Obliquus Capitis Auticus or Inferioris)
9. Small Oblique Muscle of the Head (Obliquus Capitis Posticus or
Superioris)
10. Great Posterior Straight Muscle of the Head (Rectus Capitis Posticus
Major) ........
11. Small Posterior Straight Muscle (Rectus Capitis Posticus Minor)
Differential Ciiaracters .......
B. Inferior Cervical or Trachelian Region
1. Subcutaneous Muscle of the Neck (Cervical Panniculus) .
2. Mastoido-humeralis (Levator Humeri)
3. Sterno-maxillaris ......
4. Sterno-thyro-hyoideus .....
5. Subscapulo-hyoideus ......
6. Great Anterior Straight Muscle of the Head (Rectus Capitis Auticus
Major) ........
7. Small Anterior Straight Muscle of the Head (Rectus Capitis Auticus
Minor) .......
8 Small Lateral Straight Muscle (Rectus Capitis Lateralis)
9. Scalenus .......
10. Long Muscle of the Neck (Longus Colli)
Differential Characters ......
Spinal Region of the Back and Loins
1. Trapezius .......
2. Great Dorsal (Latissimus Dorsi)
3. Small Anterior Serrated Muscle (Seiratus Anticue)
4. Small Posterior Serrated Muscle (Serratus Posticus)
5. Ilio-spiualis Muscle (Longissimus Dorsi)
TABLE OF CONTENTS.
6. Common Intercostal Muscle (Transversalis Costarum) .
7. Transverse Spinous Muscle of the Back and Loins (Semispinalis of the
Back and Loins) ......
Differential Characters .....
Comparison of the Muscles of the Back, Neck, and Cervix in Man with
analogous Muscles in tbe Domesticated Animals
1. Muscles of the Back and Cervix ....
2. Muscles of the Neck .....
Sublumbar or Inferior Lumbar Region ....
1. Iliac Fascia or Lumbo-iliac Aponeurosis
2. Great Psoas Muscle (Psoas Magnus) ....
3 Iliac Psoas Muscle (Iliacns) ....
4. Small Psoas Muscle (Psoas Parvus) ....
5. Square Muscle of the Loins (Quadratus Lumborum)
6. Intertransversales of the Loins (Intertraiisversales Lumborum)
Differential Characters ......
Comparison of the Sublumbar Muscles of Man with those of Animals
Coccygeal Region ......
1. Sacro-coccygeal Muscles ....
2. Ischio-coccygeus (Compressor Coccygeus) .
Region of the Head ......
A. Facial Region ......
1. Labialis or Orbicularis of the Lips (Orbicularis Oris)
2. Zygomatico-labialis (Zygomaticus)
3. Supermaxillo-labialis (Levator Labii Superioris Proprius, or Nasalis
Longus) ......
4. Maxillo-labialis (Depressor Labii Inferioris)
5. Mento-labialis, or Muscle of the Chin (Levator Menti)
6. Intermediate Posterior Muscle ....
7. Alveolo-labialis (Buccinator) ....
8. Supernaso -labialis (Levator Labii Superioris alaequi Nasi)
9. Great Supermaxillo-nasalis (Dilatator Naris Lateralis)
10. Small Supermaxillo-nasalis (Dilatator Naris Superioris) .
11. TransversalLs Nasi (Dilatator Naris Transversalis) .
B. Palpebral Region ......
1. Orbicularis of the Eyelids (Orbicularis Palpebrarum)
2. Frouto-Palpebral, or Corrugator Supercilii
3. Lachrymalis Muscle .....
C. Auricular or Conchal Region ....
1. Zygomaticus-auricularid (AttoUens Anticus) .
2. Temporo-auricularis Externus (Attollens Maximus)
3. Scuto-auricularis Externus ....
4. Cervico-auriculares (Retrahentes Aurem)
5. Parotido-auricularis (Abducens, or Deprimens Aurem)
6. Temporo auricularis Internus (Attollens Posticus)
7. Scuto-auricularis Internus ....
8. Mastoido-auricularis .....
D. Masseteric or Temporo-maxillary Region
1. Masseter. ......
2. Temporalis ......
3. Internal Pterygoid (Pterygoideus Internus)
4. External Pterygoid (Pterygoideus Externus)
5. Digastricus (Stylo-maxillaris) ....
Z. Hyoideal Region .....
1. Mylo-hyoideus . . . ...
2. Genio-hyoideus .....
3. Stylo-hyoideus ......
>. Kerato-hyoideus (Hyoideus Parvus) . , ,
J. Occipito-styloideus .....
6. Hyoideus Transversus ....
Differential Characters ......
PAGE
265
jdT
TABLE OF CONTENTS.
1. Facial Regrion . > . .
2. Palpebral Region . « . . .
3. Masseteric or Temporo-maxillary Region .
4. Hyoideal Region . . . . .
Comparison of the Muscles of the Human Head with those of the Domesticated
Animals . ......
1. Epicranial Muscles .....
2. Muscles of the Face .....
3. Muscles of the Lower Jaw . „ . .
4. Hyoideal Muscles . . , . .
Axillary Region ... , .
1. Superficial Pectoral (Pectoralis Anticus and Transversua) .
2. Deep Pectoral (Pectoralis Magnus and Parvus) ,
Differential Characters ......
Costal Region .... .
1. Serratus Magnus ......
2. External Intercostala . . .
3. Internal Intercostuls o . . . .
4. Leva tores Costarum .....
5. Triangularis Stemi .....
Differential Characters .....
Comparison of the Thoracic Muscles of Man with those of the Domesticated
Animals ......
Inferior Abdominal Region .....
1. Abdominal Tunic (Tunica Abdominalis, Tunica Elastica)
2. White Line (Linea Alba) .....
3. Great or External Oblique of the Abdomen (Obliquus Abdominis
Externus) .... ...
4. Small or Internal Oblique of the Abdomen (Obliquus Abdominis
Internus) .......
5. Great Straight Muscle of the Abdomen (Rectus Abdominis)
6. Transverse Muscle of the Abdomen (Transversalis Abdominis)
Differential Characters ......
Comparison of the Abdominal Muscles of Man with those of Animals
Diaphragmatic Region . . o . .
Diaphragm . . . . . . = . .
Differential Characters .......
Comparison of the Diaphragm of Man witli that of Animals
Article II. — Muscles of the Anterior Limbs . « . o
Muscles of the Shoulder . . ....
A. External Scapular Region .....
1. External Scapular Aponeurosis ......
2. Long Abductor of the Arm, or Scapular Portion of the Deltoid (Teres
Externus) ..... . .
3. Short Abductor of the Arm (Po.itea Spinatus Minor), or Teres Minor
4. Supra-spinatus (Antea Spinatus) . . . .
5. lufra-spinatus (Postea Spinatus) .....
B. Internal Scapular Region .......
1. Subscapuliiris .....
2. Adductor of the Arm (Teres Internus, or Teres Major)
3. Coraco-humeralis, Coraco-brachialis, or Omo-brachialis
4. Small Scapulo-humeralis (Scapulo-Humeralis Gracilis, Scapulo-Hume-
ralis Posticus) .......
Differential Characters ........
Comparison of the Muscles of the Shoulder of Man with those of Animals .
Muscles of the Arm . . , . . .
A. Anterior Brachial Region ... . .
1. Long Flexor of the Forearm (Flexor Braehii), or Brachial Biceps
2. Short Flexor of the Forearm (Humeralis Obliquus, Brachialis Anticus,
or Humeralis Externus) ......
B. Posterior Brachial Region , o ...
PAGE
289
290
290
291
291
291
292
292
292
293
296
296
296
297
297
298
299
299
300
305
305
307
307
308
308
310
310
310
310
310
311
311
312
312
313
314
314
315
315
316
316
316
316
317
317
319
TABLE OF CONTENTS.
1. Large Extensor of the Forearm (Caput Magnum)
2. Short Extensor of the Forearm (Caput Medium)
3. Middle Extensor of the Forearm (Caput Parvum), luternal portion of the
Triceps .......
4. Small Extensor of the Forearm, or Anconeus
Dififerential Characters .......
Comparison of the Muscles of the Arm of Man with those of Animals
Muscles of the Forearm .......
Antibrachial Aponeurosis ......
A. Anterior Antibrachial Region .....
1. Anterior Extensor of the Metacarpus (Extensor Metacarpi Magnus)
2. Oblique Extensor of the Metacarpus (Extensor Metacarpi Obliquus)
3. Anterior Extensor of the Plialanges (Extensor Pedis)
4. Lateral Extensor of the Phalanges (Extensor Suffragiuis)
B. Posterior Antibrachial Region .....
1. External Flexor of the Metacarpus (Flexor Metacarpi Externus, or Pos-
terior Ulnaris) ....
2. Oblique Flexor of the Metacarpus (Flexor Metacarpi Medius, or Anterior
Ulnaris) ........
3. Internal Flexor of the Metacarpus (Flexor Metacarpi laternus, or Pal
maris Magnus) ......
4. Superficial Flexor, Sublimis of the Phalanges (Flexor Pedis Perforatus)
5. Deep Flexor of the Phalanges (Flexor Pedis Perforans) .
Dififerential Characters ....
Muscles proper to the Forearm in Carnivora .
1. Proper Extensor of the Tliumb and Index
2. Long Supinator ....
3. Short Supinator ....
4. Round Pronator ....
5. Square Pronator ......
Comparison of the Muscles of the Forearm of Man with those of Animals
1. Anterior Region ......
2. External Region ....
3. Posterior Region ....
Muscles of the Anterior Foot or Hand .
A. Muscles of the Anterior Foot in Carnivora
1 Short Abductor of tlie Thumb
2. Opponens of the Thumb
3. Short Flexor of the Thumb
4. Adductor of the Index
5. Cutaneous Palmar (Palmaris Brevis)
6. Adductor of the Small Digit
7. Short Flexor of the Small Digit
8. Opponens of the Small Digit
9. Lumbrici .....
10. Metacarpal Interosseous Muscles
B. Muscles of the Anterior Foot in the Pig .
C. Muscles of the Anterior Foot in Solipeds
D. Muscles of the Anterior Foot in Ruminants
Comparison of the Hand of Man with that of Animals
A. Muscles of the Thenar Eminence .
B. Muscles of the Hypothenar Eminence .
C. Interosseous Muscles ....
Article III.— Muscles of the Posterior Limbs
Muscles of the Gluteal Region, or Croup
1. Superficial Gluteus (Gluteus Externus)
2. Middle Gleuteus (Gluteus Medius, Gluteus Maximus)
3. Deep Gluteus (Gluteus Internus)
Dififerential Characters .....
Comparison of the Gluteal Muscles of Man with those of Animals
Muscles of the Thigh ....
PAGE
319
320
rvi TABLE OF CONTENTS.
A. Anterior Crural, or Femoral Region ....
1. Muscle of the Fascia Lata (Tensor Fascia Latae, Tensor Vaginae Femoris)
2. Crural Triceps .......
3. Crureus, Rectus Parvus, Anterior Gracilis
B. Posterior Crural Region ......
1. Biceps Femoris, Triceps Abductor Femoris
2. Semitendinosus Muscle (Biceps Rotator Tibialis) .
3. Semimembranosus (Adductor Magnus) ....
C. Internal Crural Region ......
1. Great Adductor of the Leg (Sartorius) ....
2. Short Adductor of the Leg (Gracilis) ....
3. Pectineus . ...
4. Small Adductor of the Thigh (Adductor Parvus, Adductor Brevis) .
5. Great Adductor of the Thigh (Adductor Maguus, Adductor Longus)
6. Quadrate Crural (Quadratus Femoris, Iscliio-Femoralis)
7. External Obturator (Obturator Externus)
8. Internal Obturator (Obturator Internus) ....
9. Gemelli .......
Differential Characters .......
1. Anterior Crural Region ......
2. Posterior Crural Region ......
3. Internal Crural Region ......
Comparison of the Muscles of Man's Thigh with those of the Thigh of Animals
1. Anterior Muscles .......
2. Muscles of the Posterior Region .....
3. Muscles of the Internal Region .....
Muscles of the Leg .... . .
Tibial Aponeurosis ........
A. Anterior Tibial Region ......
1. Anterior Extensor of the Phalanges (Extensor Pedis)
2. Lateral Extensor of the Phalanges (Peroneus) .
3. Flexor of the Metatarsus (Flexor Metatarsi)
B. Posterior Tibial Region ......
1. Gastrocnemius, or Gemelli of the Tibia (Gastrocnemius Externus) .
2. Soleus (Plitntaris) ......
3. Superficial Flexor of the Phalanges (Flexor Perforatus, Gastrocnemius
Internus) . . .....
4. Popliteus .......
5. Deep Flexor of the Phalanges (Perforans, Flexor Pedis)
6. Oblique Flexor of the Phalanges (Flexor Accessorius) .
Differential Characters ......
1. Anterior Tibial Region ......
2. Posterior Tibial Region ......
Comparison of the Muscles of the Leg of Man with those of Animals .
1. Anterior Region .......
2. External Region .......
3. Posterior Region .......
Muscles of the Posterior Foot
Pedal Muscle (Extensor Pedis Brevis, Extensor Brevis Digitorum) .
Differential Characters .......
Comparison of the Muscles of the Foot of Man with those of Animals
\. Dorsal Region .......
2. Plantar Region .......
3. Interosseous Muscles ....
Chapter IIL— The Muscles in Birds .....
Chapter IV.— General Table of the Attachment of the Muscles in
Solipeds .......
^^
TABLE OF CONTENTS.
XTii
BOOK 11.
THE DIGESTIVE APPARATUS.
Chapter I.— General Considerations on the Digestive Apparatus
Chapter II.— The Digestive Apparatus in Mammalia
Article I.— Preparatory Organs of the Digestive Apparatus .
The Mouth .......
1. Lips ........
2. Cheeks .......
3. Palate .......
4. Tongue .......
5. Soft Palate .......
6. Teeth .......
7. The Mouth in General .....
DifiFerential Characters in the Mouth of the other Animals
Comparison of the Mouth of Man with that of Animals
Table of Dentition ......
The Salivary Glands ......
1. Parotid Gland ......
2. Maxillary or Submaxillary Gland ....
3. Sublingual Gland ......
4. Molar Glands .......
5. Labial, Lingual, and Staphyline Glands
DiflFereutial Characters in the Salivary Glands of the other Animals
Comparison of the Salivary Glands of Man with those of Animals
The Pharynx .......
DiflFereutial Characters in the Pharynx of the other Animals .
Comparison of the Pharynx of Man with that of Animals
The (Esophagus ......
DiflFereutial Characters in the (Esophagus of the other Animals .
Comparison of the (Esophagus of Man with that of Animals
Article II. — The Essential Organs of Digestion
The Abdominal Cavity .....
DiflFereutial Characters in the Abdominal Cavity of the other Animals
Comparison of the Abdominal Cavity of Man with that of Animals
The Stomach .......
1. The Stomach of Solipeds ....
DiflFereutial Characters in the Stomach of the other Animals
1. The Stomach of the Rabbit . . . .
2. The Stomach of the Pig .... .
3. The Stomach of Carnivora .....
4. The Stomach of Ruminants .....
Comparison of the Stomach of Man with that of Animals
The Intestines .......
1. The Small Intestine .....
2. The Large Intestine ......
A. Csecum .......
B. Colon .......
0. Rectum .......
Diflferential Characters in the Intestines of the other Animals
1. The Intestines of the Rabbit ....
2. The Intestines of Ruminants ....
3. The Intestines of the Pig ....
4. The Intestines of Carnivora . ....
Comparison of the Intestines of Man with those of Animals
General and Comparative Survey of the Abdominal or Essential Portion of the
Digestive Canal ......
Organs Annexed to the Abdominal Portion of the Digestive Canal
1. Liver .......
2. Pancreas .......
8. Spleen .....
TABLE OF CONTENTS.
Diflferential Characters in the Organ8 annexed to the Abdonainal Portion of the
Digestive Canal in the other Animals ..... 508
Comparison of the Organs annexed to the Abdominal Portion of the Digestive
Canal of Man with those of Animals ..... 510
Chapterlll.— The Digestive Apparatus of Birds . . . .511
BOOK III.
RESPIRATORY APPARATUS.
Chapter I.— Respiratory Apparatus in Mammalia ... 517
The Nasal Cavities ...... c . 517
1. The Nostrils ....... 518
2. The Nasal Fossae .... . . 519
3. The Sinuses ..... , . 524
DifTerential Characters in the Nasal Cavities of the other Animals . . 526
Comparison of the Nasal Cavities of Man with those of Animals . 527
The Air- tube succeeding the Nasal Cavities ..... 527
1. The Larynx ........ 527
2. The Trachea ....... 536
3. The Bronchi ........ 539
Differential Characters in the Air-tube succeeding the Nasal Cavities in the
other Animals ........ 541
Comparison of the Larynx and Trachea of Man with these Organs in the
Domesticated Animals ....... 542
The Thorax ......... 542
Differential Characters in the Thorax of the other Animals . . 545
The Lungs ......... 546
Differential Characters in the Lungs uf the other Animals . . 552
Comparison of the Larynx, Trachea, and Lungs of Man with those of Animals . 553
The Glandiform Bodies connected with the Respiratory Apparatus . 554
1. The Thyroid Body or Gland . . . . . .554
2. The Thymus Gland ....... 555
Differential Characters in the Glandiform Bodies annexed to the Respiratory
Apparatus in the other Animals ...... 556
Comparison of the Glandiform Bodies annexed to the Respiratory Apparatus
in Man with those of Animals ...... 557
Chapter II.— The Respiratory Apparatus of Birds . . .557
BOOK IV.
URINARY APPARATUS.
1. The Kidneys 568
2. The Ureters ........ 574
3. The Bladder 575
4. The Urethra . . . . . . . . 578
5. The Supra-renal Capsules ...... 578
Differential Characters of the Urinary Apparatus in the other Animals . 579
Comparison of the Urinary Apparatus of Man with that of Animals . 581
BOOK V.
CIRCULATORY APPARATUS.
rlRST SECTION.— THE HEART . .... 583
1. The Heart as a Whole ...... 583
2. External Conformation of the Heart ..... 584
3. Internal Conformation of the Heart ..... 587
TABLE OF CONTENTS.
4. Structure of the Heart ....
5. The Pericardium ..••••
6. The Action of the Heart
Differential Characters in the Heart of the other Animals
Comparison of the Heart of Man with that of Animals .
SECOND SECTION.— THE ARTERIES
Chapter I.— General Considerations .
Chapter II.— Pulmonary Artery .
Chapter III.— Aorta .....
Article I.— Common Aorta, or Aortic Trunk
Cardiac, or Coronary Arteries,
Article II. — Posterior Aorta ....
Parietal Branches of the Posterior Aorta
1. Intercostal Arteries ....
2. Lumbar Arteries ....
3. Diphragmatic Arteries ....
Middle Sacral Artery ....
Visceral Branches of the Posterior Aorta .
1. Broncho-CEsophageal Trunk
2. Cceliac Artery .....
3. Anterior or Great Mesenteric Artery
4. Posterior or Small Mesenteric Artery
5. Renal or Emulgent Arteries
6. Spermatic Arteries . . . ' •
7. Small Testicular Arteries (Male), Uterine Arteries (Female)
Differential CLaracters in the Posterior Aorta and its Collateral Branches in
the other Animals . . . . •
1. Posterior Aorta in Ruminants
2. Pesterior Aorta in the Pig ....
3. Posterior Aorta in Carnivora
Comparison of the Aorta of Man with that of Animals
Article III.— Internal Iliac Arteries, or Pelvic Trunks
1. Umbilical Artery . . • • •
2. Internal Pudic Artery, or Artery of the Bulb
3. Lateral Sacral or Subsacral Artery
4. Ilio-lumbar Artery, or Iliaco-muscular
5. Gluteal Artery . . . • •
6. Obturator Aitery . . • • •
7. Uiaco-femoral Artery . . • • • •.
Differential Characters in the Internal Iliac Arteries of the other Animals
1. Internal Iliac Arteries of Ruminants
2. Internal Iliac Arteries of the Pig
3. Internal Iliac Arteries of Carnivora ....
Comparison of the Internal Iliac Arteries of Man with those of Animals
iiETicLE IV.— External Iliac Arteries, or Crural Trunks
Femoral Artery ...•••
1. Prepubic Artery . • • * . " ^ x,"
2. Profunda Femoris, Great Posterior Muscular Artery of the
Deep Muscular Artery . . • • •
3. Superficialis Femoris, Superficial Muscular, or Great Anterior
Artery ..-••••
4. Innominate or Small Muscular Arteries .
5. Saphena Artery ..••••
Popliteal Artery ..••••
Terminal Branches of the Popliteal Artery
1. Posterior Tibial Artery . . • • •
2. Anterior Tibial Artery . . . • •
3. Pedal Artery . • • • ',/».,
Differential Characters in the External Iliac Arteries of the other Animals
1. External Iliac Arteries of Ruminants
2. External Iliac Arteries of the Pig ....
Thigh
Muscular
TABLE OF CONTENTS.
3. External Iliac Arteries of Carnivora.
Comparison of the External Iliac Arteries of Man with those of Animals
Article V. — Anterior Aorta .....
Article VI.— Brachial Trunks, or Axh.lary Arteries
Collateral Branches of the Axillary Arteries
1. Dorsal, Dorso-muscular. or Transverse Cervical Aiteiy .
2. Superior Cervical, Cervico-muscuiar, or Deep Cervical Artery
3. Vertebral Artery ......
4. Internal Tiioiacic Pectoral, or Internal Mammary Artery
5. External, Infi-rior Thoracic, or External Mammary Artery
6. Inferior Cervical Artery . ^ . . .
7. Supra-scapular Artery ......
8. Infra-scapular or Subscapular Artery
Humeral Artery, or Terminal Artery of the Brachial Trunk .
1. Anterior Radial (or Spiral) Artery ....
2. Posterior Radial Artery ......
(1) First Terminal Branch of the Posterior Radial (Radio-Palmar) Artery,
ur Common Trunk of the Interosseous Metacarpals
(2) Second Terminal Branch of the Posterior Radial Artery, or Collateral
Artery of the Cannon ....
Dififerential Characters in the Axillary Arteries of tht other Animals
1. Axillary Arteries of Ruminants ....
2. Axillary Arteries of the Pi^ ....
3. Axillary Arteries of Carnivora ....
Comparison of the Axillary Arteries of Man with those of Animals
Article VII.— Common Carotid Arteries ....
Occipital Artery ......
Internal Carotid Artery ......
External Carotid Artery ......
Collateral Branches of the External Carotid Artery
1. Submaxillary, Facial, or Glosso-facial Artery
2. Maxillo-muscular Artery .....
3. Posterior Auricular Artery . . . '.
Terminal Branches of the External Carotid Artery
1. Superficial Temporal Artery, or Temporal Trunk
2. Internal Maxillary, or Gutturo-maxillary Artery
Differential Chaiaftt-rs in the Carotid Arteries of the other Animals
1. Carotid Arteries of Carnivora ....
2. Carotid Arteries of the Pig ....
3. Carotid Arteries of Ruminants ....
Comparison of the Carotid Arteries of Man with those of Animals
THIRD SECTION. -THE VKINS .....
Chapter I.— General Considerations .
Chapter II.— Veins of the Lesser Circulation, or Pulmonary Veins
Chapter III.— Veins of the General Circulation
Article I.— Cardiac or Coronary Veins
Abticle II. — Anterior Vena Cava
Jugular Veins .....
Roots of the Jugular ....
1. Superficial Temporal Vein
2. Internal Maxillary Vein .
3. The Sinuses of the Dura Mater
Axillary Veins ....
1. Brachial or Subscapular Vein
2. Humeral Vein ....
3. Subcutaneous Thoracic or Spur Vein
4. Deep Veins of the Forearm
5. Superficial Veins of the Forearm
6. Metacarpal Veins
7. Digital Veins ....
8. Veins of the Ungual Region, or Foot
TABLE OF CONTENTS.
a External Venous Apparatus
b. Internal or lutra-osseous Venous Apparatus
Article III. — Posterior Vena Cava
Plirenic or Diaphragmatic Veins
Vena Portse
1. Roots of the Vena Portse
2. Collateral AflBnents of the Vena Portse
Renal Veins .
Spermatic Veins .
Lumbar Veins
Common Iliac Veins
1. Internal Iliac Vein
2. External Iliac Vein .
3. Femoral Vein
4. Popliteal Vein
5. Deep Veins of the Leg
6. Superficial Veins of the Leg
7. Metatarsal Veins
8. Veins of the Digital Region
Diiferential Characters in the Veius of the other Animals
Comparison of the Veins of Man with those of Animals
FOURTH SECTION.— THE LYMPHATICS
Chapter I. — General Considerations
Lymphatic Vessels .....
Lymphatic Glands, or Ganglia
Chapter II.— The Lymphatics in Particular
Article I. — The Thoracic Duct . • •
Article II.— The Lymphatics which constitute the Affluents of the Thoracic
Duct .
Lymphatics of the Abdominal Limb, Pelvis,
inguinal Organs
Abdominal Parietes, and Pelvi
1. Sublumbar Glands
2. Deep Inguinal Glands
3. Superficial Inguinal Glands
4 Popliteal Glands
5. Iliac Glands
6. Precrural Glands
Lymphatics of the Abdominal Viscera
1. Glands and Lymphatic Vessels of the Rectum and Floating Colon
2. Glands and Lymphatic Vessels of the Double Colon
3. Glands and Lymphatic Vessels of the Csecum
4. Glitnds and Lymphatic Vessels of the Small Intestine
5 Glands and Lymphatic Vessels of the Stomach
6. Glands and Lymphatic Vessels of the Spleen and Liver .
Glands and Lymphatic Vessels of the Organs contained in the Thoracic Cavity
Glands and Lymphatic Vessels of the Thoracic Parietes
Lyijiphatic Vessels of the Head, Neck, and Anterior Limb
1. Prepectoral Glands .....
2. Pharyngeal Glands .....
3. Submaxillary, or Subglossal Glands
4. Prescapular Glands .....
5. Brachial Glands ......
Article III. — Great Lymphatic Vein
Diflerential Characters in the Lymphatics of the other Animals
Chapter III.— The Circulatory Apparatus in Birds .
Article I.— The Heart ......
Article II. — The Arteries .....
Article III.— The Veins • . , , ,
Article IV. — The Lymphatics
xm TABLE OF CONTENTS.
BOOK VI.
APPARATUS OF INNERVATION.
FIRST SECTION.— THE NERVOUS SYSTEM IN GENERAL
General Conformation of the Nervous System
Structure of the Nervous System ....
Properties and Functions of the Nervous Systems ....
SECOND SECTION.— THE CENTRAL AXIS OF THE NERVOUS SYSTEM
Chapter I.— Protective and Enveloping Parts of the Cerebro-spinal Axis
The Bony Case containing the Central Cerebro-spinal Axis
1. The Spinal Canal
2. The Cranial Cavity .
The Envelopes of the Cerebro-spinal Axis
1. The Dura Mater
2. The Arachnoid ....
3. The Pia Mater .......
Differential Characters in the Protecting and Enveloping Parts of the Cerebro-
spinal Axis in the other Animals .
Comparison of the Protective and Enveloping Parts of the Cerebro-spinal Axis
of Man with those of Animals ......
Chapter II.— The Spinal Cord ......
External Conformation of the Spinal Cord
Internal Conformation and Structure of the Spinal Cord
Differential Characters in the Spinal Cord of the other Animals .
Comparison of the Spinal Cord of Man with that of Animals
Chapter III.— The Brain, or Eneephalon ....
Article I.— The Brain as a Whole .....
Article II. — The Isthmus ......
External Conformation of the Isthmus ....
1. The Medulla Oblongata .....
2. The Pons Varolii ......
3. The Crura Cerebri ......
4. The Crura Cerebelli ......
5. The Valve of Vieusseus .....
6. The Corpora Quadrigemina, or Bigemina
7. The Optic Tiialami ......
8. The Pineal Gland ......
9. The Pituitary Gland .....
Internal Conformation of the Isthmus .....
1. The third or Middle Ventricle, or Ventricle of the Thalami Optici
2. The Aqueduct of Sylvius .....
3. The Posterior, or Cerebellar Ventricle
Structure of the Isthmus ......
Differential Characters in the Isthmus of the other Animals
Comparison of the Isthmus of Man with that of Animals
Article III. — The Cerebellum .....
1. External Conformation of the Cerebellum ....
2. Internal Conformation of the Cerebellum
Differential Characters of the Cerebellum in the other Animals
Comparison of the Cerebellum of Man with that of Animals
Article IV. — The Cerebrum ......
External Conformation of the Cerebrum .
1. The Longitudinal Fissure
2. The Cerebral Hemispheres .
Internal Conformation of the Brain
1. The Corpus Callosum
2. The Lateral or Cerebral Ventricles
8. The Septum Lucidum
4. The Trigonum, or Fornix
5. The Hippocampi
TABLE OF CONTENTS.
xxiii
6. The Corpora Striata ....
7. The Choroid Plexus and Velum Interpositum
Structure of the Brain ....
DifFereutial Characters in the Brain of the other Animals
Comparison of the Cerebrum of Man with that of Animals
THIKD SECTION.— THE NERVES* .
Chapter I.— The Cranial or Encephalic Nerves
1. First Pair, or Olfactory Nerves
2. Second Pair, or Optic Nerve*
3. Third Pair, or Common Oculo-:JIotor Nerves
4. Fourth Pair, or Pathetici Nerves .
5. Fifth Pair, or Trigeminal Nerves
6. Sixth Pair, or External Motor Ocular Nerves
7. Seventh Pair, or Facial Nerves
8. Eighth Pair, Auditory, or Acoustic Nerves
9. Ninth Pair, or Glosso-Pharyngeal Nerves
10. Tenth Pair, Vagus, or Pneumogastric Nerves
11. Eleventh Pair, Spinal, or Accessory Nerves of the Pneumogastrics
12. Twelfth Pair, or Great Hypoglossal Nerves
Differential Characters in the Cranial Nerves of the other Animals
Comparison of the Cranial Nerves of Man with those of Animals
Chapter II.— Spinal Nerves ...
Article I.— Cervical Nerves (Eight Pairs)
Article II.— Dorsal Nerves (Seventeen Pairs)
Article III. — Lumbar Nerves (Six Pairs)
Article IV.— Sacral Nerves (Five Pairs) ....
Article V. — Coccygeal Nerves (Six to Seven Pairs)
Article VI. — Composite Nerves formed by the Inferior Branches of
Spinal Branches ......
Diaphragmatic (or Phrenic) Nerve ....
Brachial Plexus .......
1. Diaphragmatie Branches .....
2. Levator Anguli Scapulae and Rhomboideal Branch
3. Serratus Magnus, or Superior Thoracic Branch .
4. Pectoral or Inferior Thoracic Branches
5. Subcutaneous Thoracic Branch ....
6. Latissimus Dorsi Branch ....
7. Axillary or Circumflex Nerve ....
8. Nerve of the Teres Major ....
9. Subscapular Branches ....
10. Supra-scapular Nerve
11. Anterior Brachial or Musculo-Cutaneous Nerve .
12. Radial (or Mu^culo-spiral) Nerve
13. Ulnar or Culdto-cutaneous Nerve
14. Median or Cubito-plantar Nerve
Differential Characters in the Brachial Plexus of the other Animals
Compa4son of the Brachial Plexus of Man with that of Animals
Lumbo-Sacral Plexus ......
A. Anterior Portion .....
1. Iliaco-muscular Nerves ....
2. Crural or Anterior Femoral Nerve
3. Obturator Nerve .....
B. Posterior Portion .....
4. Small Sciatic or Anterior and Posterior Gluteal Nerves
5. Great Sciatic or Great Femoro-popliteal Nerve
Collateral Branches ......
Terminal Branches ......
Differential Characters in the Lumbo-sacral Plexus of the other Animals
Comparison of the Lumbo-sacral Plexus in Man with that of Animals
Chapter III.— The Great Sympathetic ....
1. Cranial Portion of the Sympathetic ....
887
TABLE OF CONTENTS.
2. Cervical Portion of the Sympathetic ....
3. Dorsal Portion of the Sympathetic ....
4. Lumbar Portion of the Sympathetic ....
5. Sacral Portion of the Sympathetic ...
Differential Characters in the Great Sympathetic of the other Animals
Ciimparison of the Great Sympathetic of Man with that of Animals .
Chapter IV.— The Nervous System of Birds ....
PAGE
887
891
892
893
894
894
BOOK VII.
APPARATUSES OF SENSE.
Chapter I.— Apparatus of Touch . . . . -
Article I. — The Skin ......
Article II. — The Appendages of the Skin . . .
Hairs ........
Horny Productions ......
1. The Hoof of Solipeds .....
a. The Parts container! in the Huof ....
b. Description of the Hoof ....
2. The Claws of Kuminants and Pachyderms
3. The Claws of Carnivora .....
4. The Frontal Horns ......
5. The Chestnuts ......
(6. The Ergots). ......
Chapter II.— Apparatus of Taste ....
Differential Characters in the Apparatus of Taste in the other Animals
Comparison of the Apparatus of Taste in Man with that of Animals
Chapter III.— Apparatus of Smell .....
Chapter IV.— Apparatus of Vision ....
Article I.— Essential Organ of Vision, or Ocdlar Globe
Membranes of the Eye .....
A. Fibrous Membranes ......
1 The Sclerotica ......
2. The Cornea ......
B. Musculo-vascular . . c . .
1. The Choroid Membrane . , , . .
2. The Iris ......
C. Nerve Membrane ......
3. The Betina ......
The Media of the Eye ......
1. Crystalline Lens ......
2. Vitreous Humour . . ...
3. Aqueous Humour .....
Article II.— Accessory Organs of the Visual Apparatus
Orbital Cavity ......
Muscles of the Globe of the Eye .....
Protective Organs of the Eye .....
1. Eyelids .......
2. Membrana Nictitans .....
Lachrymal Apparatus ......
Differential Characters in the Visual Apparatus of the other Animals
Comparison of the Visual Apparatus of Man with that of Animals .
Chapter V.— Auditory Apparatus ....
Article I. — Internal Ear, or Labyrinth ....
The Osseous Labyrinth .....
1. The Vestibule ......
2. The Semicircular Canals ....
899
904
904
907
908
908
914
921
921
922
922
922
922
924
924
924
925
926
927
927
927
929
933
936
936
937
938
938
938
939
941
941
943
944
946
947
947
947
947
948
TABLE OF CONTENTS.
3. The Cochlea
The Membranous Labyrinth
1. The Membranous Vestibule
2. The Membranous Semicircular Canals
3. The Membranous Cochlea
Fluids of the Labyrinth . . . . ,
Distribution and Termination of the Auditory Nerve in the Membranous
Labyrinth ••■•..
Article II.— Middle Ear, ob Case of the Tympanum
1. Membrane of the Tympanum ....
2. The Promontory, Fenestra Ovalis, and Fenestra, Rotunda
3. The Mastoid Cells ....
4. The Bones of the Middle Ear
5. The Mucous Membrane of the Tympanum
6. The Eustachian Tube
7. Tlie Guttural Pouches .
Article III.— The External Ear .
The External Auditory Canal.
The Concha, or Pavilion .
1. Cartilages of the Concha.
2. Muscles of the External Ear .
3. Adipose Cushion of the External Ear
4. Integuments of the External Ear
Differential Characters in the Auditory Apparatus of the other Animals
Comparison of the Auditory Apparatus of Man with that of Animals
PAGE
948
949
949
950
950
951
951
951
951
952
953
953
955
955
956
957
957
957
958
958
958
958
958
958
BOOK VIII.
GENERATIVE APPARATUS.
Chapter I.— Genital Organs of the Male
Tiie Testicles, or Secretory Organs of the Semen .
1. The Tunica Vaginalis . .
2. The Testicles . . .'.*.*."
Excretory Apparatus of the Semen .
1. The Epididymis and Deferent Canal. ..'.*.
2. The Vesiculse Seminales and Ejaculatory Ducts
3. The Urethra . . . •.".*."
4. The Glands annexed to the Urethra .'.'.'.*
5. The Corpus Cavernosum . .
6. The Penis
Diiferential Characters in the Male Genital Organs of the otlier Animals .
Comparison of the Genital Organs of Man with those of Animals
Chapter II.— Genital Organs of the Female
1 The Ovaries ....
2. The Fallopian or Uterine Tubes, or Oviducts
3. The Uterus .... ...
4. The Vagina . • . .
5. The Vulva . . .'.'.*.'
6. The Mammae
Differential Characters in tlie Female Genital Organs of the othpr Animals .
Comparison of the Genital Organs of Woman with those of Domesticated Female
Animals
Chapter III.— Generative Apparatus of Birds ... *
1. Male Generative Organs ......
2. Female Generative Organs .....
960
960
963
967
967
968
970
973
973
975
976
984
993
995
997
999
1002
1003
1003
1004
UTi
TABLE OF CONTENTS.
BOOK IX.
EMBRYOLOGY.
Chapter I. -The Ovum and its Sarly Embryonic Developments
Article I.— The Ovum ......
Article II. — First Embryonic Developments ....
Article III. — General Direction of Development.— Vertebral Type
Chapter II.— The Foetal Envelopes of Solipeds
1. The Chorion ......
2. The Amniou .....
3. The Allantois .......
4. The Umbilical Vesicle . . ...
5. The Placenta .......
6. The ITmbilical Cord ... . .
Differential Cliaracters in the Annexes of the Foetus of the other Animals
Comparison of the Annexes of the Human Foetus with those of Animals
Chapter III.— Development of the Foetus
Article I.— Formation of the Embryo .....
Development of the Chorda Dorsalis and Vertebral Laminae
Article II. — Development of the Various Organs in the Animal Economy
Development of the Nervous System.
Development of the Organs of Sense
Development of the Locomotory Apparatus .
Development of the Circulatory Apparatus
Development of the Respiratory Apparatus .
Development of the Digestive Apparatus
Development ot the Genito-urinary Apparatus
PAGR
1005
1005
1005
1011
1016
1018
1019
1019
1023
1023
1025
1027
1032
1032
1033
1033
1035
1038
1040
1045
1046
1049
TABLE OF ILLUSTRATIONS.
FIG.
1.
2.
3.
4.
5.
Skeleton of the Dog .
Skeleton of the Cat . .
Skeleton of the Pig .
Skeleton of the Rabbit .
Skeleton of the Horse
Skeleton of the Cow
Skeleton of the Slieep
Skeleton of the Camel .
Vertical section of bone
Minute structure of bone
Lacunae, or osteoplasts of osseous substance
Cartilage at the seat of ossification
Elements of a vertebra
A cervical vertebra
Atlas (inferior surface)
The axis or dentata (lateral view)
Axis and sixth cervical of the Horse and Ass
Type of a dorsal vertebra (the fourth) .
Middle dorsal vertebra of the Horse, viewed from three typical lines
Dorsal vertebra of the Horse and Ass (the eleventh) .
Lumbar vertebra (front view)
Upper surface of lumbar vertebrae .
Lumbar vertebra of the Horse and Ass . ,
Lumbar vertebrae of the Cat and Rabbit .
Lateral view of sacrum ....
Horse's head (front view) ....
Head of the Cat (posterior aspect)
Head of the Pig (anterior face) . . ,
Head of tiie dog (anterior face) .
Ox's head (anterior face) ....
Head of a hornless Ox . . . ,
Ram's head (anterior face) ....
Anterior bones of the head of a foetus at birth
Posterior bones of the head of a foetus at birth
Head of the Rabbit (posterior face)
Head of the Rabbit (antero-lateral face)
Ox's head (posterior lace) . . , ,
Posterior aspect of Horse's skull
Head of the Pig (posterior face).
Dog's head (posterior view) ....
Longitudinal and transverse section of the Horse's head ,
Antero-posterior and vertical section of the Horse's head
Median and vertical section of the Ox's head
Inferior maxilla . . . , ,
Head of the Camel . , ,
Head of the Cat .
Hyoid bone
Wormian bones of the Ox
Chauveau .
PAGK
8
Chauveau .
8
Chauveau .
9
Chauveau .
9
Original
10
Original
10
Chauveau .
11
Chauveau .
12
Carpenter .
16
Carpenter .
17
Carpenter .
17
Carpenter .
20
After Owen .
25
Original
27
Original
28
(Jriginal
28
Chauveau .
29
Original
32
Chauveau .
33
Chauveau .
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Original
36
Chauveau .
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Chauveau .
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( 'hauveau .
39
Original .
40
Original .
46
Chauveau .
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Chauveau .
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Chauveau .
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Chauveau .
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Chauveau .
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Chauveau .
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Chauveau .
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Chauveau .
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Chauveau .
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Chauveau ■
62
Chauveau .
65
Original
66
Chauveau .
67
Chauveau .
68
Chauveau .
72
Chauveau .
72
Chauveau .
74
Chauveau .
76
Chauveau .
77
Chauveau .
78
Cliauveau .
78
Cornevin .
80
TABLE OF ILLUSTRATIONS.
pro.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
G4.
65.
66
67.
68.
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
81.
82.
83.
84.
85.
86.
87.
100.
101.
102.
103.
104.
105.
106.
107.
108.
109.
mb)
Horse's head (anterior face)
Horse's head (posterior face)
Horse's head (lateral face
Ass's head (lateral face)
Crania of different breeds of Dogs
Front view of the human cranium
External or basilar surface of human skull .
The sternum
Typical ribs of the Horse
Thorax of Man (anterior face)
Scapula of the Horse (external face)
Scapula of the Horse (internal face)
Scapula of the Cat and Rabbit
Antero-external view of right humerus
Posterior view of right humerus . .
Humerus of the Cat and Rabbit
External face of the radius and ulna
Forearm bones of the Ass
Right fore foot of a Horse .
Carpus of the Horse (anterior face)
Carpus of the Horse (posterior face)
Posterior view of right metacarpus
Forearm and foot of the Ox (front view)
Lateral view of the digital region (outside of right li
Posterior view of anterior digital region
Plantar surface of third phalanx
Navicular bone ....
Anterior limb of the Pig
Forearm and foot of the Dog (anterior face)
Human scapula (external aspect)
Right human humerus (anterior surface)
Human arm-bones (front view) .
Palmar surface of left human hand . .
Hand of Man and the domestic Mammalia, normal and
The ossa innominata (seen from helow) .
Pelvis (antero-lateral view) .
Pelvis (lateral view) ....
Pelvis of the Horse ....
Pelvis of the Mare ....
Pelvic bones of the Cat and Rabbit .
Left femur (anterior view)
Left femur (posterior view) .
Section of left femur, showing its structure
Femur of the cat and rabbit
Posterior view of right tibia
Leg-bone of the Mule
Patella of the Horse (superior and posterior face)
Patella of the Horse (anterior face) .
Leg-bones of the Cat and Rabbit
Left hind foot (external aspect)
Tarsus of the Horse ....
Left hock (front view)
Left hock (internul aspect)
Posterior aspect of left metatarsus .
Human pelvis (female) ....
Right human femur (anterior aspect)
Human tibia and fibula of right leg (anterior aspect)
Dorsal surface of left human foot
Anterior limb of the Horse (antero-external view)
Posterior limb of the Horse (antero-external view)
Skeleton of a Fowl ....
Original
PAGE
81
. Original
81
Chauveau .
84
. . Chauveau .
85
. Chauveau .
89
Wilson
90
. Wilson
91
Chauveau .
93
, . Chauveau .
94
Wilmn
97
. Chauveau .
99
Chauveau .
99
. Chauveau .
100
, . Original
101
. . Original
102
Chauveau .
103
. Original
104
, Chauveau
106
. Original
108
Chauveau
109
, . Chauveau .
109
Original
111
e Chauveau
113
) . Original
114
. Original
114
. . Original
116
G . Original
117
Chauveau
118
Chauveau
118
Wilson
119
. Wilson
120
Wilson
120
Wilson
121
teratological Chauveau
122
Chauveau
127
. Original
129
Original
129
. Chauveau
132
. . Chauveau
133
. Chauveau
136
Original
138
Original
138
m . Original
139
Chauveau
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Original
141
. Chauveau
142
Chauveau
143
Chauveau
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Chauveau
144
. Original
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Chauveau
146
. Original
147
Original
147
. . Original
149
Wilson
151
. Wilson
152
Wilson
152
. Wilson
152
Chauveau
155
Chauveau
156
Chauveau
159
TABLE OF ILLUSTRATIONS.
FIG.
110. Head of a Fowl (natural size : posterior view)
111. Sternum and bones of the wing .
112. Thoracic or pectoral vertebra of a Mammal •
113. Caudal vertebra of the Turbot .
114. Cephalic vertebrae of the Dog .....
115. Plans of the different classes of articulations . . Beaunis
116. Section of branchial cartilage of Tadpole ....
117. Fibro-cartilage .....
118. White or non-elastic fibrous tissue .
119. Yellow or elastic fibrous tissue .
120. Cervical ligament and deep muscles of the Horse's neck
121. Intervertebral articulations
122. Cervical ligament of the Ox ...
123. Cervical ligament of the young Camel .
124. Atlo-axoid and occipito-atloid articulations .
125. Temporo-maxillary articulation .
126. Articulations of the ribs with the vertebrae (upper plane)
127. Articulations of the ribs with the vertebrae (inferior plane)
128. Scapulo-liumeral and humeroradial articulations (external face)
129. Carpal articulations (front view) ....
130. Lateral view of the carpal articulations . . . .
131. Details of the metacarpo-phalangeal articulation of the Horse .
132. Carpal, metacarpal, and inter-phalangeal articulations of the Horse .
133. Section of inferior row of carpal bones, and metacarpal and suspensory
ligament ........
134. Posterior view of metacarpo-phalangeal and interphalangeal articu-
lations .......
135. Metatarso-phalangeal and interphalangeal articulations of the Horse
136. Articulation of the foot (inferior face) ....
137. Longitudinal and vertical section of the digital region of the Horse
138. Tendons and ligaments of the posterior face of the digital region of
the Ox
139. Sacro-iliac and coxo-femoral articulations ....
140. Sacroiliac and coxo-femoral articulations
141. Femoro-tibial articulation ......
142. Ligaments attaching the three bones of the leg .
143. Tarsal articulations (front view) .....
144. Articulations of the tarsus (lateral view)
145. Ultimate fibril of muscle ......
146. Striated muscular-tissue fibre .....
147. Primitive fibre of red muscle .....
148. Torn muscular fibre ......
149. Primitive muscular fibre ......
150. Relation of primitive muscular fibres with tendon
151. Transverse section of frozen muscle . . . * .
152. Arrangement of the fibres of a muscle . . . Beaunis
1 53. Distribution of capillaries in muscle .....
154. Portion of elementary muscular fibre ....
155. Striated fibre of muscle during contraction ....
156. Horse fixed in first position .....
157. Horse fixed in second position .....
158. Lateral view of the neck (superficial muscles) .
159. Superficial muscles of the neck and spinal region of the back and loins
160. Lateral view of the neck (middle layer of muscles) .
161. Cervical ligament and deep muscles of the neck .
162. Muscles of the spinal region of the neck, back, and loins
163. Deep ditto .......
164. Muscles of the back and cervix of Man ....
165. Muscles of the sublumbar, patellar, and internal crural regions .
166. Deep muscles of the sublumbar region ....
167. Sacro-iliac and coxo-femoral muscles ....
Chauveau .
PAGh
160
Chauveau .
164
Chauveau .
168
Chauveau .
168
Lavocat
168
and Bouchard
171
Carpenter .
172
Wilson
173
Carpenter .
174
Carpenter .
174
Chauveau .
181
Chauveau .
182
Chauveau .
184
Chauveau .
185
Chauveau .
187
Chauveau .
188
Chauveau .
191
Chauveau .
191
Chauveau .
196
Chauveau .
201
Chauveau .
202
Chauveau .
204
Chauveau .
205
Chauveau .
207
Original .
208
Chauveau .
210
Chauveau .
210
Chauveau .
211
Chauveau .
211
Chauveau .
213
Chauveau .
214
Chauveau .
217
Chauveau .
220
Chauveau .
222
Chauveau .
224
Bowman
232
Bowman
232
Renaut
233
Renaut
233
Renaut
234
Renaut
234
Kiihne
235
and Bouchard
236
Berres
236
Beale
237
Bowman
237
Chaiiveau .
240
Chauveau .
241
Original .
245
Chauveau .
247
Original .
248
Chauveau .
251
Chauveau ,
261
Chauveau .
264
Wilson
267
Chauveau .
270
Chauveau .
271
Chauveau .
273
TABLE OF ILLUSTRATIONS.
168. Superficial muscles of the face and head ....
169. Muscles of external ear of Mule .
170. Muscles of the ear .......
171. Hyoideal and pharyngeal regions ....
172. Superficial muscles of the Ox's head ....
173. Muscles of the human head . . . .
174. Muscles of the axillary and cervical regions ....
175. Axillary und thoracic muscles .....
176. Muscles of the inferior abdominal region (Ass)
177. Muscles of the anterior aspect of the body of Man
178. Diaphragm (posterior face) ......
179. External muscles of the anterior limb ....
180. Muscles of anterior aspect of Man's upper arm
181. Internal aspect of left anterior limb ....
182. Deep muscles on external aspect of right anterior limb ,
183. Tendons and burtse of anterior limb of Horse
184. Flexor tendons of phalanges of Horse ....
185. Muscles of the forearm of the Ox ... .
186. Tendinous and ligamentous apparatus in the digital region of the Ox
187. Anterior antibrachial region of the Pig
188. Muscles of the forearm and paw of the Dog
189. Superficial muscles of human forearm ....
190. Deep layer of superficial muscles of human forearm
191. Muscles of human hand = . . . .
192. Dissecting- table .......
193. Superficial muscles of the croup and thigh . .
194. Superficial muscles of the croup and thigh
195. Muscles of the sublumbar, patellar, and internal crural regions
196. Deep muscles of the coxo-femoral region
197. Coccygeal and deep muscles surrounding the coxo-femoral articu-
lation ......
198. Superficial muscles of the croup and thigh in the Cow
199. Muscles of the anterior femoral region in Man
200. Muscles of the posterior femoral and gluteal region in Man
201. External deep muscles of right posterior limb
202. Flexor muscle of metatarsus
203. Muscles on inner aspect of left posterior limb
204. Articular capsules and bursse in posterior limb .
205. External muscles of the leg of the Ox
206. Muscles of the human leg (anterior tibial region)
207. Superficial posterior muscles of the human leg
208. First layer of plantar muscles of human foot
209. Third and part of second layer of plantar muscles of human foot
210. Squamous epithelium from the mouth ....
211. Columnar epithelium . . ...
2 1 2. Columnar ciliated epithelium ....
213. Conical villi on mucous membrane of small intestine
214. Fusiform cells of smooth muscular fibre . .
215. Hard and soft palate .....
216. Composite papilla from tongue of Dog . . . ,
217. Simple filiform papillae .....
218. Foramen of Morgagni ......
219. Vertical section of a foramen csecum
220. Muscles of the tongue, soft palate, and pharynx .
221. Lobe of racemose gland from the floor of the mouth
222 Follicular gland .......
223. Section of an amysdaloid follicle ....
224. Median longitudinal section of the head and upper part of neck
225. Magnified section of a canine tooth .....
226. Section through the fang of a molar tooth . ,
227. Transverse section of enamel . . . . c
Original
Cliauveau
275
280
Original
Original
Chauveau
282
287
290
Wilson
291
Chauveau
294
Original
Chauveau
295
304
Wilson
306
Chauveau
309
Chauveau
311
Wilson
317
Original
Original
Chauveau
318
321
329
Chauveau
331
Chauveau
333
Chauveau
334
Chauveau .
335
Chauveau
337
Wilson
339
Wilson
339
Wilson
342
Chauveau
344
Chauveau
345
Original
Chauveau
347
354
Chauveau
356
Chauveau
358
Chauveau
359
Wilson
361
Wilson
361
Original
Chauveau
363
365
Original
Chauveau
367
370
Chauveau
372
Wilson
375
Wilson
375
Wilson
377
Wilson
377
Wilson
393
Kolliker
393
Carpenter
Wilson
393
394
Bowman
395
Chauveau
399
Chauveau
402
Chauveau
402
Chauveau
403
Chauveau
403
Chauveau
405
KSlliker
406
KdlUker
406
Chauveau
407
Original
Wilson
4f)9
412
Carpenter
Carpenter
413
414
TABLE OF ILLUSTRATIONS.
zxxi
FIG. ''■*<5E
228. Theoretical section of dental sac of permanent incisor . Chauveau . 415
229. Section of dentine and pulp of an incisor tooth . . . Carpenter , 416
230. Dentition of inferior jaw of Horse ..... Chauveau . 418
231 . Section of incisor tooth of Horse .... Chauveau . 418
232. Incisor teeth of Horse (details of structure) .... Chauveau . 419
233. Profile of upper teeth of the Horse .... Chauveau . 421
234. Transverse section of Horse's upper molar .... Chauveau . 422
235. The teeth of the Ox . . . . . Chauveau . 425
236. Ox's incisor tooth ....... Chauveau . 425
237. Incisor teeth of a Sheep two years old . . . . Chauveau . 427
238. Teeth of the Pig ... ... Chauveau . 428
239. General and lateral view of the Dog's teeth . . . Chauveau . 429
240. Anterior view of the incisors and canine teeth of Dog . . Chauveau . 429
241. Lateral and general view of the Cat's teeth . . . Chauveau . 429
242. Dentition of the Rabbit ..... Chauveau . 430
243. Section of the human face ..... Quain . 432
244. Lobule of parotid gland ... . . Wagner . 434
245. Capillary network of follicles of pirotiil gland . . . Berres . 434
246. Termination of the nerves in the salivary glands . . . Pfliiger . 435
247. Inferior aspect of head and neck .... Origincd . 436
248. Maxillary and sublingual glands ..... Chauveau . 437
249. Pharyngeal and laryngeal region .... Original . 441
250. Median lengitudinal section of head and upper part of neck . Original . 442
251. Pharynx of the Horse (posterior view) .... Chauveau . 443
252. Muscles of the pharyngeal and hyoideal regions . - . Original . 445
253. Human pharynx ...... Wilson . 447
254. Transverse vertical section of head and neck . . Original . 448
255. Pectoral cavity and mediastinum .... Chauveau . 449
256. Theoretical transverse section of abdominal cavity . . . Chauveau . 452
257. Theoretical, longitudinal, and median section of abdominal cavity Chauveau . 453
258. The abdominal cavity, with the stomach and other organs . . Origiiuil . 456
259. Stomach of the Horse ...... Chauveau . 457
260. Interior of the Horse's stomach ..... Chauveau . 458
261. Muscular fibres of stomach (external and middle layers) . Chauveau . 460
262. Deep and middle muscular fibres of stomach . . . Chauveau . 460
263. Peptic gastric gland ...... KoUiker . 461
264 Portion of a peptic caecum ...... Kolliher . 461
265. Mucous gastric gland ... . . KoUiker . 462
266. Capillaries of mucous membrane of stomach . . . Carpenter . 462
267. Stomach of the Dog ... . . Chauveau . 463
268. Stomach of the Ox . . . . . Chauveau . 464
269. Interior of the stomacli of Ruminants . . , Chauveau . 465
270. Section of the wall of the omasum of Sheep o . , , Chauveau . 467
271. Stomach of the Sheep ...... Chauveau . 468
272. Section of the omasum of the Sheep .... Chauveau . 469
273. Section of a leaf of the omasum ..... Chauveau , 470
274. Longitudinal section of a large papilla from the omasum . . Chauveau . 470
275. Villi of human and Sheep's intestine .... Teichmann . 474
276. Portion of Brunner's gland -...,. Thomson . 474
277. Section through Peyer's patch of Sheep . . . Teichmann . 475
278. Section through solitary follicle . . . . . Teichmann . 476
279. Injected villi of intestine ..... KoUiker . 476
280. Blood-vessels in Peyerian glandulse ..... KoUiker . 477
281. Diagram of origin of lacteals in villi .... Funke . 477
282. General view of the intestines of the Horse (right side) . . Chauveau . 479
283. General view of the Horse's intestines (inferior aspect) » . Chauveau . 480
284. The colon of the Horse ...... Original .. 481
285. Plan of the colon ...... Chauveau . 482
286. Intestines of the Rabbit (sreneral view) • c . . Cliauveau . 486
287. Stomach and intestines of the Sheep .... Chauveau . 487
288. General view of the intestines of the Ox . , . Chauveau . 488
TABLE OF ILLUSTRATIONS.
FIG.
289.
290.
291.
292.
293.
294.
295.
296.
297.
298.
299.
300.
3(Jl.
302.
303.
304.
305.
306.
307.
308.
3ii9.
310.
311.
312
313.
314.
315.
316.
317.
318.
319.
320.
321.
322.
323.
324.
325.
326.
327.
331.
332.
334.
335.
339.
340.
341.
342.
343.
344.
345.
346.
347.
348.
349.
General view of the intestines of the Pig . . . Chauveau .
Intestines of the Dog ...... Chauveau .
Digestive apparatus of the Cat ..... Chauveau .
Human intestines ....... Wilson
Abdominal cavity, with the liver and other organs . . Original
Portion of a hepatic column, with secreting cells . . . Leidy
Biliary capillaries and ducts ..... Irminrjer and Frey
Blood-vessels in lobules of liver ..... Kiernan
Section of lobules of liver, witli intra-lobular veins . . Kiernan
Excretory apparatus of the Horse's liver .... Chauveau .
Structure of the spleen (diagrammatic) . . . Beaunis and Bouchard
Malpighian corpuscles attached to splenic artery . . . KSlliker
Splenic corpuscle from the spleen of Ox . . . . Kdlliker
Liver of the Ox ...... . Cliauveau .
Liver of the Dog, with its excretory apparatus . . . Chauveau .
Under surface of the human liver .... Wilson
General view of the digestive apparatus of a Fowl . . Chauveau .
Cartilages of the nostrils ...... Chauveau .
Transverse section of the head of a Horse . . . Chauveau .
Longitudinal section of the head and upper part of neck . . Original
Cells of the olfactory mucous membrane . . Clarke and Schultze
Fibres of olfactory nerve ...... Ecker
Cartilages of the larynx disarticulated .... Chauveau .
Superior face of larynx ...... Chauveau .
Inferior face of larynx ...... Chauveau .
Muscles of tlie Horse's larynx ..... Chauveau .
Postero-lateral view of larynx ..... Original
Entrance to the larynx of the Horse .... Chauveau .
The respiratory organs (inferior aspect) .... Original
Trachea, bronchi, and lungs of the Horse .... Chauveau .
Ciliated epithelium from the trachea .... Kdlliker
Bronchial tube, with its bronchules ..... Heale
Mucous membrane of a broncliial tube .... Heale
Theoretical section of thoracic cavity, behind the heart . . Chauveau .
Theoretical section of thoracic cavity, at root of lungs . . Chauveau .
Theoretical section of thoracic cavity, in front of right ventricle . Chauveau .
Lungs of the Horse ...... Chauveau .
Lungs of the Horse ....... Chauveau .
Cast of bronchiole ...... Chauveau .
Cast of bronchial divisions ...... Chauveau .
Plan of a pulmonary lobule . . , . Waters
Infundibula of lung ....... Kdlliker
Capillaries around the infundibula of lung . . . Carpenter .
Lung of the Sheep (inferior view) ..... Chauveau .
Human lungs and heart ...... Wilson
Gland-vesicles of thyroid ..... Kdlliker
Portion of thymus of Calf ..... Kdlliker
Course and termination of ducts in thymus gland of Calf . . Wilson
General view of the air-sacs in the Duck . . , Chauveau .
General view of the genito-uriuary apparatus in the Horse . . Chauveau .
Horizontal longitudinal section of the Horse's kidney . Chauveau .
Section of the cortical substance of the kidney . . . Ecker
Course of the uriniferous tubuli ..... Hertz
Diagram of the circulation in the kidney
Transverse horizontal section of kidney .
The kidneys and bladder in the foetus of Solipeds
Right kidney of Ox (upper and external face) .
Left kidney of Ox (internal and inferior face)
The calices in left kidney of Ox
Theoretical plan of the circulatory system .
The heart and principal vessels (left face)
Original
Chauveau
Chauveau
Chauveau
Chauveau
Colin
PAGE
489
490
491
492
496
498
498
499
499
500
504
505
505
508
509
510
513
519
520
521
523
524
.'i28
531
531
532
533
535
537
538
539
540
541
545
545
545
546
548
549
550
551
551
551
553
.')53
554
556
556
564
569
371
572
573
573
574
577
580
580
680
582
585
TABLE OF ILLUSTRATIONS.
FIG.
350.
351.
352.
353.
354.
855.
356.
357.
358.
359.
360.
361.
362.
363.
364.
365.
366.
367.
370.
371.
372.
373.
374.
375.
376.
377.
378.
379.
380.
381.
385.
387.
391.
392.
395.
396.
397.
400.
401.
402.
403.
404.
405.
406.
407.
408.
The heart and principal vessels (right face) . . . Chauveau
Right side of the heart laid open ..... Wilson
Section of the heart at the level of the valves . . . Sibson
Left cavities of the heart laid open ..... Wilson
Auriculo-ventricular fibro-cartilaginous rings . . . Parchappe
Anastomosing muscular fibres of heart .... KoUiker
Muscular whorl at point of heart .... Bourgery
Posterior unitive fibres of auricles ..... Bourgery
Epithelium of the endocardium ..... KoUiker
Human lungs and heart (front view) .... WiUon
Web of Frog's foot, showing blood-vessels and their anastomoses Wagner
Epithelial cells of blood-vessels ..... KoUiker
Fenestrated membrane from the carotid artery of the Horse . KoUiker
Coarse elastic tissue from pulmonary artery of the Horse . KoUiker
Transition of a minute artery of the brain into capillary vessels . KoUiker
Abdominal or posterior aorta and cceliac axis in the Horse . Chauveau
Distribution of the small mesenteric artery .... Chauveau
Arteries of the stomach of Ruminants .... Chauveau
Lateral view of ttie genito-urinary organs in the male . . Chauveau
Abdominal aorta, with its branches, in Man . . . Wilson
The external and internal iliac arteries in the Mare . . Chauveau
Principal arteries of posterior foot of Horse . . . Cliauveau
Anterior aspect of human leg and foot .... Wilson
Posterior aspect of human leg . . . . . Wilson
Arteries of sole of human foot ..... WiUmi
Distributiou of the anterior aorta .... Chauveau
Terminations of the axillary artery in the Horse , . . Chauveau
Arteries of the anterior foot (seen from behind) . . Chauveau
Arteries of the anterior foot of the Horse .... Chauveau
Arteries of the human forearm and hand . . . Wilson
Arteries of the brain ...... Chauveau
Arteries of the head ...... Chauveau
Rete mirabile of the Sheep (seen in profile) .... Chauveau
Rete mirabile of the Ox (posterior face) .... Cliauveau
Arteries of the face and head of Man .... Heath
Radicles and collateral branches of the jugular vein in the Horse Chauveau
Sinuses of the dura mater and radicles of the jugular vein of tiie
Horse ........ Chauveau
Subsphenoidal confluents in the Horse .... Cliauveau
Veins of the foot ....... Bouley
General view of the veins in the Horse .... Chauveau
Vena portae and its roots ...... Chauveau
A lymphatic vessel with its valves .... Chauveau
Section of a lymphatic rete mirabile .... Teichmann
Section of lymphatic gland ..... KoUiker
Section of simple lymphatic gland ..... Teichmann
Section of the medullary substance of lymphatic glaud of Ox . KoUiker
Ordinary disposition of the thoracic duct .... Colin
Double variety of the thoracic duct .... Colin
Triple variety of the thoracic duct ..... Colin
Lymphatic system of the Horse ..... Colin
Great lymphatic vein and entrance of the thoracic duct . . Colin
Great lymphatic duct (another variety) .... Colin
Thoracic duct in the Ox . . . . . . Colin
A variety of the thoracic duct in the Ox . . . Colin
Another variety of the thoracic duct . . . . Colin
A fourth variety of the thoracic duct .... Colin
Thoracic duct of small Ruminants ..... Colin
Diagram of structure of nerve-fibre .... Carpenter
Nerve-tube ....... Ranvier
Multipolar or stellate nerve-cell .... Ecker
PAGE
586
587
589
591
592
594
594
595
597
599
603
604
604
604
605
614
619
622
627
628
630
637
642
642
643
647
651
653
655
678
680
681
695
700
704
707
714
717
718
718
719
723
723
723
725
731
731
732
733
733
733
7:-<4
740
740
741
TABLE OF ILLVSTBATIONS.
410. Several multipolar nerve-cells
411. Pyriimidal cell of the grey substance
412. Ganglion from heart of Frog
413. Bipolar ganglionic cells and nerve'
414. Stellate nerve-cell . « . .
415. Structure of ganglionic cells ....
416. General view of tlie spinal cord ...
417. Spinal cord at the cervical bulb or brachial plexus
418. Section of the spinal cord of the Horse at the lumbar region
419. Transverse section of spinal cord in the lumbar region .
420. Transverse section of spinal cord of Man in the middle of the lumbar
region ......
421. Ganglionic cell from the inferior cornu of spinal cord
422. Longitudinal secti>m through cervical bulb of spinal cord of the Cat
423. Brain of tlie Horse (upper surface) .
424. General view of the brain (lower surface)
425. Superior view of the encephalic isthmus
426. Lateral view of the isthmus ....
427. Transverse section of the brain . . •
428. Dissection of the medulla oblongata . .
429. Median and vertical section of the brain
430. Layers and cells of grey matter of cerebellum . .
431. Section of the cortical substance of the cerebellum .
432. Antero-posterior and vertical section of the brain .
433. Brain of the Horse (lateral face)
434. Corpus callosum . . . . ,
435. Anterior portion of the lateral ventricles
436; Transverse section of human brain
437. Course of association nerve-fibres . . .
438. Course of association fibres in corpus callosum . •
439. Course of radiating fibres in the corona radlata
440. Layers and cells of a frontal convolution , .
441. Corticle substance; of the cerebral hemispheres
442. Brain of the Ox .
443. Brain of the Slieep .....
444. Brain of the Pig .....
445. Lateral face of the Dog's brain
446. Brain of the Dog (upper face) ...
447. Brain of the Cat ... .
448. Base of the human brain ....
449. Muscular fibres, with termination of motor nerve .
450. Nerves of the eye .....
451. Section of the pons Varolii ....
452. Lateral view of the medulla oblongata .
453. General view of the superior and inferior maxillary nerves
454. Section of medulla oblongata and pons Varolii .
455. Section of middle portion of medulla oblongata
456. Origin of the nerves arising from the medulla oblongata
457. Origin and distribution of the eighth pair of nerves in Man
458. Distribution of the nerves in the larynx of the Horse
459. Deep nerves of the head ....
460. Nerves of the guttural region in the Ox.
461. Innervation of submaxillary and sublingual glands .
462. Nerves of the face and scalp of Man
463. Distribution of eighth pair of nerves on left side
464. Ganglion of a spinal nerve from the lumbar region
465. Nerves of the brachial plexus
466. External nerves of anterior limb . . .
467. Nerves of the digit of Horse
468. Nerves of tlie digital region of Ruminants
469. Nerves of the palmar face of Dog's foot
PAOB
, . Chauveau .
741
Chauveau .
741
. Ecker
742
Ecker
742
. Beale
742
. Beale and Arnold
742
. Colin
755
Colin
755
. Chauveau .
757
Deiters
758
e lumbar
. I. L. Clarke
759
Kraus^e
760
the Cat I. L. Clarke
761
. CJiauveau .
764
Chauveau .
766
Chauveau .
770
Chauveau .
773
Cliauveau .
775
Solly and Carpenter
776
. Cliauveau .
780
Duval
781
. Kolliher .
782
Chauveau .
783
. Cliauveau .
787
Cliauveau .
789
. Chauveau .
789
Edinger
793
. Edinger
794
. Edinger
795
. Edinger
795
. Cliauveau .
796
. Kolliher .
796
, Chauveau .
797
, . Cliauveau .
798
. Chauveau .
799
Chauveau .
800
Chauveau .
801
. Chauveau .
801
Emchfeld and LeveilU
802
, . Cohnheim .
806
Chauveau .
812
. Duval
814
Erb
815
Chauveau .
818
Duval
825
. Duval
833
Toussaint .
836
. Wihon
837
Toussaint ,
838
Chauveau .
843
Toussaint .
845
Bernard
848
Eirschfeld and LeveilU
850
Hirschfeld and LeveilU
851
KolUker .
854
. Chauveau .
863
Chauveau .
863
. Bouley
866
, Cliauveau .
868
. Chauveau .
870
TABLE OF ILLUSTRATIONS.
FIG.
470. Nerves of the palmar face of Cat's foot . , , . Chauveau .
471. Nerves of the axilla of Man .... Hirschfeld ami LeveilU
472. Nerves of the front of forearm and hand of Man . Hirschfeld and Leveill€
473. Lumbo-sacral plexus and internal nerves of posterior limb . . Cliauveau .
474. Posterior portion of the lumbo-sacral plexus . . . Chauveau .
475. External nerves of posterior limb ..... Chauveau .
476. Lumbar plexus of Man ..... Hirschfeld and Leveill^
'ill. Nerves at the posterior aspect of human leg . . Hirschfeld and Leveill^
478 Nerves at the front aspect of human leg . . Hirschfeld and Leveill€
479. Sympathetic ganglion from a Puppy .... Kolliker
480. Sympathetic system of the Horse .... Cliauveau .
481. Brain of a Bird ....... Chauveau .
482. Section of Horse's skin ...... Chauveau .
483. Capillary loops in cutaneous papillae .... Berres
484. Tactile papillae from the skin ..... Ecker
485. Interungulate sinus of Sheep ..... Owen
486. Branches of cutaneous nerves in skin .... Ecker
487. Sudoriparous gland ....... Wagner
488 Oblique section of epidermis ..... Carpenter .
489. Hair-follicle ...... Morel and Villemin
490 Longitudinal median section of Horse's foot . . « Original
49L Horizontal section of Horse's foot ..... Original
492. Lower surface of the Horse's foot .... Original
493. Lateral view of the Horse's foot ..... Original
494. Horizontal section of hoof ..... Chauveau .
495. Horizontal section of the junction of the wall with the sole of hoof . Leisering .
496. Horizontal section of wall, and horny and vascular lamiuse . Leisering .
497. Hoof removed from the foot ...... Leisering .
498. Hoof with outer portion of wall removed . . . Leisering
499. Plantar surface of hoof ...... Leisering .
600. Horn-cells from the sole of hoof ..... Leisering .
501. Constituent elements of the wall ..... Leisering .
502. Theoretical section of the Horse's eye .... Chauveau .
503. Anterior segment of a transverse section of the globe of the eye
(human) ........ Wilson
504. Cells from pigmentum nigrum ..... Carpenter .
505. The eye (human) with the sclerotic coat removed . . . Holden
506. Muscular structure of the iris ..... Kolliker
507. Vertical section of retina ...... MUller
508. Diagram of the structure of the retina .... Krause
509. Capillaries in the vascular layer of the retina . . . Berres
510. Muscles of the eyeball (viewed from above) , . . Original
511. Labyrinth in Fishes, Birds, and Mammals .... Gegenbaur .
512. Section of lamina spiralis of the cochlea . , , Carpenter
513. Section of the cochlea parallel to its axis .... Breschet
514. Cochlea opened ....... Chauveau .
515. Eight tympanic cavity of Horse's ear .... Chauveau
516. Bones of the middle ear of the Horse .... Lavocat
517. Diagram of the testicle ••.... Holden
518. Human testis, injected with mercury .... Lauth
519. Vertical section of the Horse's testis .... Chauveau
520. Internal genito-urinary organs of the foetus of a Mare , . Chauveau .
521. Spermatozoa of various animals ..... Carpenter
522. Superior view of the genito-uriuary organs . . . Chauveau
523. Transverse section of penis ...... Chauveau
524. Longitudinal section of the free extremity of the Horse's penis . Chauveau
525. Internal genital organs of a young Bull .... Chauveau
526. Sections of the urethra of the Ox at different points . . Chauveau
527. Penis and muscles of the sheath of the Bull .... Chauveau
528. Section of human pelvis ...... Gray
629. Section of the ovary ....... Schroen
PAGE
870
871
872
876
877
879
884
895
900
900
901
901
902
902
903
905
908
909
910
912
912
914
914
915
916
916
919
919
927
931
931
932
933
935
936
936
940
948
949
949
950
953
954
963
963
964
965
967
969
974
976
977
978
979
982
TABLE OF ILLUSTRATIONS.
FIG.
530. Ovaries, oviducts, and uterus of a foetus (equine)
531. Ovarium of the Rabbit ....
532. Constituent parts of Mammalian ovum, entire .
533. Constituent parts of Mammalian ovum, ruptured .
534. Formation of the corpus luteum
535. Generative organs of the Mare, isolated
536. Generative organs of the Mare, in situ .
537. Termination of milk-duct in cluster of follicles
538. Ultimate follicles of mammary gland, with secreting cells
539. Microscopic appearance of milk
540. Human uterus, witii its appendages
541. Ovary of the Bird .....
542. Graafian vesicle .....
543. Optical section of ovum of Eabbit .
544. Ovum of Rabbit .....
545. Blastodermic vesicle of Rabbit
546. Section of a Fowl's unhatched egg
547. Area pellucida in early blastoderm
548. Transverse section of blastoderm
549. Area pellucida of blastoderm
550. Area pellucida in blastoderm ....
551. Transverse section of blastoderm
552. Transverse section of dorsal region
553. Manner in which embryo and envelopes are formed
554. Diagram of foetal membranes ....
555. Exterior of the chorial sac (Mare) .
556. Different parts of foetal Horse ....
557. Foetus of the Mare, with its envelopes
558. Portion of ultimate ramifications of umbilical vessels .
559. Vertical section of injected placenta
560. Portion of one of the foetal villi
561. Equine foetus, opened on left side to show umbilical vessels
562. Blood-vessels in liver of an equine foetus at mid-term .
563. Liver of a Lamb at birth ....
564. Foetus of the Slieep ....
565. Vertical section of a maternal cotyledon
566. Embryo of the Chick ....
567. Section of embryo Duck ....
568. Embryo of the Chick ....
569. Transverse section of embryo of Chick on third day
570. Plan of development of eye ....
571. Origin of encephalic centres in human embryo of fourth week
572. Plan of chorda dorsalis at period of formation of embryo
573. Plan of vertebra at an early period of development
574. Head of a foetal Lamb, showing Meckel's cartilage
575. Plan of first system of vessels (embryo)
576. Embryonic heart at an early period (anterior view)
577. Ditto, seen from behind
578. Heart of an equine foetus
579. Plan of the aorta and its arches at an early period
580. Plan of the circulation in the human embryo (side view)
581. Section of embryo of Rabbit
582. First appearance of the lungs .
583. Embryo of Dog at twenty-five days
584. Origin of liver from intestinal wall of embryo Chick
585. Urinary and genital apparatus in embryo Chick
Chauveau .
PAGE
986
Pouchet
987
Coste
988
Coste
988
Pouchet
989
Chauveau .
991
Chauveau .
994
Sir A. Cooper
998
Lehert
998
Funke
999
Wilson
1002
Chauveau
1004
BalUani
1006
VanBeneden 1006
Van Beneden 1007
Kdlliker
1008
Thomson
1010
Balfour
1010
Balfour
1011
Balfour
1012
Balfour
1012
Balfour
1013
Balfour
1014
Balfour
1015
Turner
1017
Chauveau
1018
Chauveau
1020
Chauveau
1022
Carpenter
1023
Turner
1024
Eclcer
1025
Cliauveau
1026
Colin
1026
Colin
1027
Cliauveau
1028
Turner
1029
Balfour
1032
Balfour
10.33
Balfour
1034
Kolliker
1035
Kdlliker
1035
Wagner
1037
Kdlliker
1039
Kolliker
1039
Huxley
. 1039
Kolliker
1041
Kolliker
. 1042
Kdlliker
1042
Chauveau
. 1043
Kolliker
. 1043
Coste
. 1044
Balfour
. 1045
Wagner
. 1046
Bischoff
. 1046
Muller
. 1049
Muller
. 1050
THE COMPARATIVE ANATOMY
OF THE
DOMESTICATED ANIMALS.
GENERAL CONSIDERATIONS.
DEFINITION AND DIVISIONS OP ANATOMY.
Anatomy is the science of organization ; it studies the structure of animals
when these are dead. It comprises two grand divisions — physiological anatomy ^
which describes healthy organs, and pathological anatomy, the object of which is
the description of diseased organs.
Physiological anatomy, which alone is treated of in this book, in its turn
embraces —
1. General anatomy, which is occupied with similar substances or tissues of
the animal body, with regard to their texture, and their physical, chemical, and
physiological properties, irrespective of the organs in which these tissues are
found. The particular study of the anatomical elements entering into the
composition of the tissues, is named histology. Histology necessarily requires
the aid of the microscope.
2. Descriptive anatomy, which studies the situation, form, and relations of
organs, as well as the relative arrangement of the various tissues composing
them, with the exception of the structure and properties of these tissues.
If this study be devoted to a single species, it is designated special anatomy.
Example : human anatomy, or anthropotomy ; the anatomy of the Horse, or
hippotomy.
"When descriptive anatomy embraces the study of the organization of the
entire animal kingdom, and examines the differences which characterize the same
organ or the same series of organs in each class, family, genus, or species, it is
named comparative anatomy. Restricted to the domesticated animals, this study
constitutes veterinary anatomy.
Philosophical or transcendental anatomy differs from comparative anatomy,
in that it indicates the analogies of organs or apparatus, rather than their
differences, in order to exhibit as clearly as possible the general laws of
organization.
Finally, if descriptive anatomy be limited to denoting the relations existing
between the various organs of a region, particularly with a view to the perform-
ance of operations and the diagnosis of external diseases, it takes the names of
topographical, regional, or surgical anatomy.
GENERAL CONSIDERATIONS.
Enumeration and Classification of the Species of
Domesticated Animals.
The object of this book is the study of veterinary anatomy. The animals of
which it treats belong to the Mammiferous class and to that of Birds.
The domesticated Mammals of om- clunates have their representatives in a
large number of orders. Thus, we find among them —
1. Of the Carnivora, the Dog and Cat;
2. A Rodent, the Rahhit ;
3. A Pachyderm, the Pig ;
4. Of Solipeds, the Horse and Ass ; the produce of the Male Ass with the
mare, i.e. the 3fule, and that of the Horse with the Female Ass, known
by the name of Hinny ;
5. Of Ruminants, the Ox, Sheep, and Goat.
With regard to Poultry, they range themselves —
1. In the Gallinaceous or Columba order, the genera to which the Common
Fowl, Guinea Foivl, Turkey, and Pigeon belong ;
In the order of Palmipeds, the Goose and Duclc.
Girard has proposed a special classification for the domesticated Mammals,
based upon the number of digits terminating each of their limbs, and has defined
four categories : the first comprises the Horse, Ass, Mule, and Hinny, which take
the name of monodactyles, because their digital region is composed of a single
digit ; in the second, under the denomination of didactyles or bisulcate animals,
those with two digits, such as the Ox, Sheep, and Goat ; in the third, or regular
tetradactyles, is found the Pig, each of whose limbs has four digits ; lastly, the
Dog and Cat, which most frequently have four digits on the posterior members
and five on the anterior ones, and form the class of irregular tetradactyles.
This nomenclature will not be followed here, as it is opposed to the general
laws of organization. Philosophical anatomy has, in fact, demonstrated that there
are really no true monodactyles, didactyles, etc. ; all are materially or virtually
pentadactyles. It is therefore considered better to keep to the classification
established by zoologists, because it prevents confusion in scientific language.
The regimen and habits of the domesticated animals bring about diiferences
in their organization ; these appear very great at first sight, though in reality they
are not so marked as they seem.
In order to study the descriptive anatomy of all these annuals, we will not
pass them in review, one after another, giving for each the description of every
organ ; but shall take a type, which will most frequently be the Horse, implicitly
compared with man, and briefly compare all the others with it. In this com-
parison, the animals will be generally classed according to their domestic value ;
though exceptions will be made to the rule which has been instituted by our
predecessors, whenever any advantage m point of concision or perspicuity is likely
to be obtained.
General Ideas of the Organization of Animals.
Order followed in studying the Various Apparatuses.
The bodies of animals contain fluid and solid organic matters, as well as gases
and some mineral substances.
Organic Fluids. — The fluids are very abundant in the animal economy ;
GENERAL CONSIDERATIONS. 3
not only do they fill certain vessels constructed for them, but they also
impregnate all the solid parts of the body. Their importance is very great, for
without them the organic solids would perish ; an element deprived of humidity
is ipso facto deprived of life.
These fluids vary in their nature and composition. Apart from those that
the solids imbibe, there is not one which is completely amorphous. In the
midst of a liquid holding organized matter in solution, there are always formed
elements which will be referred to hereafter. Examples : the blood and lymph.
Organic Solids. — In studying the organic solids, we will proceed from the
simple to the complex.
Solid organized matter is amorphous — as in the hyaline substance of cartilage
and the fundamental substance of bone tissue, or it assumes the form of more
or less voluminous particles in every instance invisible to the naked eye, and to
which the name of anatomical elements has been given. They may be reduced to
three principal : the granule, the cell, and the fibre.
Granules. — These are the smallest known elements. They may be held in
suspension in animal fluids, remain free among the other elements, or be enclosed
in the interior of cells. Their nature is not always the same : they are proteic,
fatty, or pigmentary. The pigmentary granules are of a brown colour.
Cells. — The cell is pre-eminently the anatomical element.
Theoretically, the cell is a microscopic mass of a nitrogenous substance, viscid
{protoplasm or sarcode), uniformly transparent, or slightly granular. Frequently
in the midst of this protoplasm there is perceived a nucleus provided with a
nucleolus, and at its periphery an enveloping membrane.
The cell lives like an entire organism : it feeds, grows, multiplies, absorbs,
secretes, moves, etc. It behaves like a complete animal, though it be a micro-
scopic one.
The form of the cell, as well as its volume and nature, vary. It has therefore
received various names.
There are round, polyhedral, fusiform, conical, stellate, and other shaped
cells. Some have a diameter of 1-1 2000th part of an inch, while others are
l-2000th part. Cells multiply in various ways : 1st, by the division of the
nucleus and segmentation of the protoplasm in the interior of the enveloping
membrane {endogenous multiplication) ; 2nd, by constriction, then division of the
nucleus, protoplasm, and enveloping membrane {flssiparous multiplication) ; 3rd,
by a kind of bulging or swelling of the enveloping membrane, and constriction
and separation of the enlargement thus formed {gemmation).
A large number of cells only temporarily remain in this condition. In con-
sequence of modifications that cannot be referred to here, they are converted
into fibrillse or other elements, in which it is difiicult to recognize the primordial
element.
Others maintain the cellular form : then they develop, live, and die in several
ways. Sometimes they are worn by the contact of foreign bodies, as on the sur-
face of the skin ; sometimes they become liquefied, as in some glands ; and at
other times they undergo fatty degeneration, which gradually brings about their
complete destruction.
The permanent cells are —
1. Hcematies or red corpuscles, which are found in a state of suspension in the
blood ; they are round and discoid in Mammalia, with the exception of the
Camel and Llama, in which they are elliptical, as well as in Birds, Reptiles, and
4 GENERAL CONSIDERATIONS.
the majority of Fishes. These cells have an envelope, but they do not have
a nucleus in JVIammalia ;
2. Leucocytes, white corpuscles, or lymph cells, which float in the blood, lymph,
chyle, and the connective tissue interspaces. These cells are susceptible of amae-
boid movements, and their fundamental form is spherical ; though they are often
Irregular in shape, owing to the contractile prolongations they throw out, called
pseupodes. They may have one or more irregular nuclei ;
3. Connective cells, which are flat, nucleated, and irregular ; they are applied
to the fasciculi of connective fibres ;
4. Adipose cells, lying in the connective tissue and filled with fat, which has
pushed the protoplasm and nucleus towards the envelope ;
5. Medullary cells, with a budding nucleus or multiple nuclei (myeloplaxes
and medullo-cells), forming the principal elements of the marrow of bones ;
6. Cartilage cells, which have no envelope, and which, single or associated
with a variable intermediate substance, form cartilages ;
7. Bone cells, lodged in a space remarkable for its elliptical shape and the
numerous prolongations on its margin. The cells are nucleated, have no envelope,
and secrete the fundamental solid substance of the bony tissue ;
8. Contractile cells, which constitute the basis of muscular tissue. They are
fusiform and nucleated ;
9. Nerve cells, met with in the cerebro-spinal centres and the ganglia of the
cerebro-spinal and sympathetic systems. They are provided with one, two, or
more prolongations called poles ; hence they are uni-, bi-, or multipolar.
10. Epithelial cells, found on the surface of tegumentary membranes, or laid
over the interior of more or less diverticulated cavities (glandular cavities or glands).
The epithelial element is lamellar or polyhedric, cylindrical, calcif orm, vibratile, etc.
11. Endothelial cells, always lamellar, and hning serous cavities and vascular
canals.
Fibres. — A fibre is an elongated element of variable dimensions and com-
position. Thus, it may be very fine {connective fibre), or thick and limited by
two borders more or less apart (muscidar fibre) ; it is homogeneous throughout
{elastic fibre), or has a contents and a distinct envelope {nerve fibre). The vitality
of fibres is not comparable with that of cells. Once formed, they are only
nourished, for it is not yet definitely ascertained whether they can multiply.
In the animal economy there are four kinds of fibres —
1. Connective fibre, an extremely fine element, but in which, nevertheless,
two borders can be distinguished if it be examined by a power of from 800 to
1000 diameters. The fibres form fasciculi in the connective tissue, or are distri-
buted in the midst of a fundamental substance — as in the fibro-cartilages. The
connective fibre constitutes the most solid organs of the animal economy — the
ligaments, tendons, etc.
2. Elastic fibre, found closely packed in certain organs, such as the cervical
ligament and abdominal tunic, or forming a network in the midst of connective
tissue ; it is even found in the framework of bones.
3. Muscular fibre, smooth or striped (striated), which has the property of
contracting under the influence of stimuli. Smooth (or unstriped), is found
in a large number of viscera ; striped is more especially in the domain of the
locomotory apparatus.
4. Nerve fibre, very remarkable for its continuous axis-cylinder. It is found
in the nerve centres, cerebro-spinal nerves, and great sympathetic system.
GENEBAL CONSIDERATIONS. 5
I
Inorganic Substances. — These substances (gases and mineral matters) are
usually found in solution in the animal fluids. Their presence is indispensable
in the constitution of the living body.
Sometimes the mineral matters are solid, amorphous, or crystallized. In this
condition they are rarely met with in healthy organs (iriternal ear) ; but they are
frequently found in diseased ones.
Tissues. — The anatomical elements, by being grouped in different manners,
form tissues. Some tissues are constituted by one kind of element ; these are
simple tissues — for example, epithelial tissue. But the larger number are formed
by a combination of several different elements ; these are composite tissues — for
example, nerve tissue.
The anatomical, physico-chemical, and physiological characters of the tissues,
are repeated, it need scarcely be remarked, in the anatomical, physico-chemical,
and physiological properties of the elements which enter into their composition.
Only four simple types of fundamental tissue are described, and which are
based on the morphological, chemical, and physiological characters of the
constituent elements —
1. In the first place, there are to be noted the tissues of connective substance
or framework, comprising the varieties of connective tissue, fibrous tissue, elastic
tissue, cartilaginous tissue, and bone tissue.
2. Then there are the cellular tissues, formed entirely of persistent cells ;
they are the epithelial tissue proper, and the glandular tissue.
The cells of the epithehal tissue are differently arranged. If they are
disposed in a single layer, they constitute a simple epithelium ; but if superposed
so as to form two or more layers, then it is a stratified epithelium. According to
the form of the superficial layer of cells, the epithelium is polyhedric, pavement.,
cylindrical, spherical, or calciform. In certain parts the superficial cells are
furnished with vibratile cilia, and the epithehum is then called vibratile (or ciliated).
3. The third type is represented by the muscular tissue, the agent of move-
ment, which is divided into striated and non-striated muscle.
4. Lastly, there is the nerve tissue, which is present under two aspects —
white substance and grey substance. The first is formed entirely of nerve fibres
and a supporting tissue or neuroglia ; the second by fibres and nerve cells united
by neurogha. The grey substance belongs to the most important portions of the
nervous system — the brain, spinal cord, and gangha, where it co-exists with the
white substance. The latter entirely constitutes the peripheral ramifications of
the nervous system.
Organs. — The term " organ " is given to any portion of the body having a
determinate form and a function to fulfil. A bone, a muscle, the stomach, the
liver, and the brain, are organs.
General Arrangement of the Organs and Apparatus. — All animal
organs are enclosed between two membranes named limitary or tegumentary
membranes, which are continuous with one another at the margin of the natural
openings. These are the skin and the mucous membranes, in the composition of
which are included a layer of connective tissue and an epithelium
Organs protected by these membranes are solid or hollow.
Among the first, a certain number act as supports : such are the organs formed
by the connective tissue, and particularly the cartilages and bones.
Others are destmed to produce movements : these are the muscles. The
action of the muscles is communicated directly to the organs that are to be
e GENERAL CONSIDERATIONS
moved, or it is transmitted through the medimn of oth%r organs, such as the
tendons and the aponeuroses.
The central nervous organs — the nerves properly so called — belong to this group
of solid organs. The activity of muscles and the sensibility of limitary membranes
are due to them.
With regard to the hollow organs, they are everywhere formed by an envelope
of smooth (or unstriped) muscular tissue, lined by an internal tegumentary or
mucous membrane. Examples : the bladder and stomach. There must also be
included the vessels formed by elastic and contractile membranes arranged as
canals, in which the blood and lymph circulate ; the glands, and, lastly, the serous
membranes which line the interior of the splanchnic cavities, cover the surface of
the organs contained in them, and the inner face of the articulations and synovial
sheaths.
It is remarkable that, in the trunk, the bones form two superposed cylinders,
one of which lodges the organs of circulation, digestion, and respiration, and the
other the central nervous system (neural and luemal ajUnder).
Apparatus. — Organs are very numerous in the animal economy, and in order
to study them profitably it is necessary to classify them in a methodical manner,
according to their physiological affinities. Consequently, there have been col-
lected into a single category all those organs which are destined to achieve the
same physiological finality, and to such a group has been given the name of
apparatus.
Bichat has grouped the apparatuses according to the ultimate object of their
functions, and has thus formed two great categories : one, comprising the
apparatuses which maintain the individual {apparatuses of nutrition and relation) ;
the other, the apparatus destined for the preservation of the species {apparatus of
generation).
We will describe these apparatuses in the following order : —
1. Locomotory Apparatus ;
2. Digestive Apparatus ;
3. Respiratory Apparatus ;
4. Urinary Depurative Apparatus ;
5. Circulatory Apparatus ;
6. Inner vatory Apparatus ;
7. Sensory Apparatus ;
8. Generative Apparatus.
This description will be terminated by a brief notice of the evolution of ths
/(Btus^ and its appendages.
BOOK I.
LocoMOTORY Apparatus.
The locomotory apparatus is composed of all those organs which minister to the
movements an animal may execute. It is certainly one of the most important in
the economy, from the nmnber and size of the pieces which enter into its
formation, and by the necessary co-operation it affords the majority of the other
apparatuses in the performance of the physiological acts allotted to them.
It is constituted of two kinds of organs— the bones and muscles. The hones,
hard and resisting, stony in appearance, are really inert levers, joined by firm
and movable articulatmis, which permit their playing upon each other with the
greatest facility, at the same time maintaining them in their relative positions.
The muscles, grouped around the bones and attached to them, are soft organs
which possess the property of contraction, under certain determinate conditions,
and of involving in that movement the bones to which they are fixed by their
extremities. The bones are altogether passive in their motion, while the muscles
are really the active organs of locomotion — the power intended to move the bony
levers.
We will study, successively —
1. The bones, a particular branch of descriptive anatomy which has received
the name of Osteology ;
2. The articulations, or Arthrology ;
3. The muscles, or Myology.
FIRST SECTION.
The Bones.
CHAPTER I.
THE BONES IN GENERAL.
Bones, properly speaking, are only to be found in vertebrate animals, and
constitute their principal zoological character. In the animal body they form
an internal framework which consolidates the entire edifice, and gives it its
general form and dimensions. It is advantageous, before commencing a particular
description of each bone, to survey them in a general manner. This study
comprises: 1. The description of the skeleton; 2. A summary indication of
8 TEE BONES.
ihQ general principles which should be known, in order to comprehend the details
of the special descriptions.
Aeticle I. — The Skeleton.
The whole of the bones, considered in their natural relations to each other,
constitute the skeleton. In order to prepare the skeleton of any animal, it is
SKELETON OF THE DOG.
sufficient to free it from the soft parts surrounding it. The skeleton should be
designated natural, if in this operation the ligaments that naturally join the
Fig. 2.
SKELETON OF THE CAT.
various pieces together are allowed to remain ; and artificial if, after these liga-
ments have been destroyed, it is necessary to replace them by materials foreign
to the organization, such as iron or brass wire.
THE SKELETON. 9
The skeleton is divided into trunk and limbs.
1. The trunk offers for consideration, in the middle line, the spine or
vertebral column — a flexible stalk measuring the entire length of the animal, and
composed of a series of distinct pieces articulated one behind the other. An-
teriorly, this stalk supports the head — a pyramidal mass which results from the
assemblage of a large number of bones. On each side of the middle portion of
Fig. 3.
SKELETON OF THE PIG.
I
the spine, there are detached bony arches which have received the name of ribs,
and which rest, directly or indirectly, by their inferior extremities, on a single
bone called the sternum. These bony arches in this way circumscribe the thorax —
a spacious cavity destined for the reception of the principal organs of respiration
and circulation.
2. The limbs, four in number — two anterior and two posterior — are the ap-
Fig. 4.
SKELETON OF THE RABBIT.
pendages which support the trunk of the domestic Mammals. They are usually
distinguished as anterior and posterior (or fore and hind), but it will be more
convenient to name them according to their relations, as thoracic (or pectoral) and
abdominal limbs. Each represents a column divided into several rays resting upon
one another, and generally forming more or less open angles. The anterior limbs
10
THE BONES.
are each divisible into four principal regions : the shoulder, applied against the
front part of the thorax ; the arm, which succeeds the shoulder ; and the fore-
SKELETON OP THE HORSE.
arm, and foot. The posterior limbs also comprise four regions : the haunch or
pelvis, which articulates with the posterior part of the spine ; and the thigh, leg^
and posterior foot.
Fig. 6.
SKELETON OF THE COW.
In Birds, the posterior limbs alone assume the function of columns of support.
The thoracic limbs, formed for flight, constitute the wings.
GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 11
The number of bones entering into the composition of the skeleton of the
principal domesticated animals, arrived at the adult period of life, varies accord-
Fig. 7.
SKELETON OF THE SHEEP.
ing to the species. They are apportioned to the regions of the trunk and limbs
just mentioned, in the manner indicated in the following table : —
Designation.
SOLIPEDS.'
Ruminants.
Pig.
Dog.'
Vertebral Column'
Head^
48
28
37
1- 2
1— 2
2— 2
16-32
1— 2
1- 2
3— 6
15-30
45
28
27
1— 2
1- 2
2- 4
20-40
1- 2
1— 2
3- 6
19—38
50
29
29
1— 2
1— 2
2— 4
36—72
1— 2
I— 2
3— 6
36-72
46
28
27
1— 2
1— 2
2— 4
36—72
1- 2
1— 2
3— 6
32—64
Thorax
Shoulder
Arm .
Forearm
Fore foot
Pelvis
Thigh
Leg .
Hind fool
^ Double regions -
Tc
tals
191
196
270
255
AeTICLE II. — GElfEEAL PkINCIPLES APPLICABLE TO THE StUDY OF ALL
THE Bones,
The description of a bone comprises its name, situation, shape, internal cori'
formation, structure, and mode of development.
' One lumbar vertebra less is found in the Ass, and sometimes also in the Mule.
* The 08 penis has not been included.
' The sacrum is reckoned as a single bone, and the number of coccygeal vertebrae at aa
average of 16 for the Horse, 18 for the Ox, 22 for the Pig, and 18 for the Dog.
* The OS hyoides is reckoned as a single bone.
12
THE BONES.
Name.
The nomenclature of osteology does not rest on any basis capable of confer-
ring upon it a methodic form. Consequently, we find bones which derive their
name from their shape (example : the fibula) ; others from their resemblance
to known objects (the tibia and vomer). Some owe it to their position (the
frontal bone), or their uses (the axis and parietal bones). Several attempts
have been made to submit the nomenclature of the bones to more precise
GENERAL PRINCIPLES APPLICABLE TO TEE STUDY OF ALL THE BONES. 13
and uniform rules, but the new designations proposed have not been sanctioned
by custom.
Situation.
The situation of a bone should be viewed in two ways : 1st, Relative to the
median plane of the body ; 2nd, Relative to the other portions of the skeleton.
A. Situation relative to the median plane of the body. — The designation of
median plane, improperly median line, is given to an imaginary vertical plane
passing through the middle of the skeleton, which it divides from before to
behind, into two equal portions. The bones may be situat|^ on the median
plane, in which case there is only one of each kind, and they are called single ;
they are also named symmetrical bones, because the median plane divides them
into equal lateral halves exactly alike.^ The bones disposed in a double and
regular manner on the sides of the median plane bear, for this reason, the name
of pair bones ; they are also called asymmetrical bones, because their form does
not admit of their being divided, in any sense, into two similar portions. On the
contrary, a bone of this kind always offers the most perfect symmetry with its
fellow on the opposite side.^
B. Relative situation to the other parts of the skeleton. — To indicate the
situation of a bone, considered from this point of view, is to make known the
place it occupies in the region to which it belongs, and the connections it may
have with adjoining regions. Thus, the radius is situated in front of the ulna,
between the arm-bone and the carpus.
Direction.
This is absolute or relative.
A. The absolute direction is related to the axes of the bones themselves. Thus
it is that a bone may be rectilinear, curvilinear, or twisted.
B. The relative direction is determined by the relation to the fictitious planes
established around or in the interior of the skeleton, or with regard to the
neighbouring bones. For example, a bone is vertical, horizontal, or oblique. In
the latter case it may be downwards and backwards, or in the reverse direction.
Example : the scapula is placed obliquely downwards and forwards.
Shape of the Bones.
Form. — This is also absolute or relative.
A. Absolute Form. — The absolute form of a bone is that which it owes to
the relations existing between its three dimensions — length, width, and thickness.
a. A bone in which one of its dimensions much exceeds those of the other two is
a long bojie (example : the femur), provided it be hollowed out internally by an
elongated space— the medullary canal. Long bones belong exclusively to the
limbs. In the animal economy there are found bones which resemble them in
their dimensions, but they have no medullary canal (example : the ribs).
These differ essentially from the true long bones, and are also distinguished from
them by the appellation of elongated bones, b. A bone that offers two dimensions
much more developed than the third, is a flat or tvide bone (example : the
parietal bone). The bones of this category, destitute of a medullary cavity, are
• Instances have been recorded of asymmetry in single bones. Lesbre has seen the sixth
cervical vertebra of the Horse tricuspid on one side and bicuspid on the other, and a last dorsal
vertebra with one of its transverse processes having the characters of the lumbar vertebraj.
* But there might be slight differences in weight, torsion, etc. In Man there is nearly
always a difference between the right and the left side.
4
14 TEE BONES.
met with in the head and the upper regions of the Umbs. c. A bone which
offers nearly the same development in all its dimensions, is called a short bone
(example : the astragalus). Destitute, like the preceding, of a medullary canal,
the short bones are found in the spine and some regions of the limbs.
B. Relative Form. — To make known the relative form of a bone, is to indicate
the greater or less exact resemblance it may bear to geometrical figures, or to
familiar objects. Thus, the scapula is a bone of a triangular shape.
Regions of the Bones. — When describing the eminences and external
cavities of bone^ it is essential not to allude to them casually by passing
indifferently from one to another. To avoid the diificulties resulting from the
application of such an irrational system, it is necessary to divide the bone to be
studied into several regions, in which external peculiarities can be examined
successively, as they present themselves. The general course to be followed in
order to learn the regions of a long, a flat, and a short bone, is as follows : —
a. A long bone is always divided into three parts — a body and two extremities.
The bod// or middle portion, or diaphysis, is the narrowest part of the bone. In
shape it is a geometrical solid, inclining somewhat to that of a very long prism.
On the body of a bone, therefore, there are studied as many faces and planes,
angles or borders, as on the prism it represents.
The extremities, or epiphyses, are more or less considerable enlargements,
formed primarily by a special bony nucleus, and offering articular surfaces, as
well as surfaces for muscular or ligamentous insertion.
b. A flat bone must necessarily have two faces, and borders and angles.
c. A short bone has more or less faces, and plane or salient angles which are
often ignored, because of their trifling ijnportance.
External Peculiarities of Bones. — These markedly attract the attention,
because they modify the general shape of bones, and singularly assist in
distinguishing one bone from another. These peculiarities, which are real
distinctive features that permit their description to be precisely established, are
always either eminences or cavities, according to their different uses.
A. Eminences. — The eminences that stand out in relief from the surfaces
of bones, are divided into two different categories. One class concurs in the
formation of the articulations which join the bones to each other ; they are
named articular eminences, in which, again, are distinguished diarthrodial and
synarthrodial eminences, according as they belong to movable or immovable
articulations. The others, usually destined for the insertion of ligaments and
muscles, are called non-art icidar eminences or eminences of insertion.
(The term imp-int is also used in anatomy, and signifies a collection of small
rugged eminences which make the surface of the bone uneven and rough. There
are muscular, tendinous, ligamentous, and aponeurotic imprints, according as
they give attachment to muscles, tendons, ligaments, or aponeuroses.)
a. The synarthrodial eminences are always indentations more or less deep and
finely cut, which stud the border of large bones.
b. The diarthrodial eminences are volimiinous, smooth, and in a fresh state
covered with cartilage. They are named heads and condyles : heads, when they
describe the segment of a sphere (head of the femur, head of the humerus) ;
condyles, when they represent an ovoid segment cut parallel to its larger axis
(condyles of the femur).
c. The non-articular eminences receive various names. If they are volumi-
nous and much detached from the bone, they are called processes or apophyses.
GENERAL PBINOIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 15
Apophyses receive qualificatives derived from the analogies perceived between
them and known objects (examples : the styloid, clinoid, coronoid, and coracoid
processes). The appellations of protuberances and hiherosities are given to non-
articular eminences when they are large and round, and slightly detached.
Lastly, they are named lines, crests, and ridges, when they are narrow and
very long.
The processes are sometimes epiphysary in early life, and formed by a special
nucleus.
B. Cavities. — The cavities of bones have also been divided into articular,
diarthrodial or synarthrodia! , and non-articular cavities.
a. The diarthrodial cavities correspond to the eminences of the same name in
the bony joints. They take the designation of glenoid cavities when they are
oval and shallow, and cotyloid cavities when they are deeply excavated, like a
basin or the cup of an acorn (examples : the glenoid cavity of the scapula, and the
cotyloid cavity of the coxa). The synarthrodial cavities fit into the dentations
opposed to them.
b. The non-articular cavities serve either for hgamentous or muscular
insertion, or for the passage of vessels, nerves, tendons, etc.
They are termed channels or furrows, when they are wide, deep, and smooth ;
grooves, when they are long, narrow, and smooth at the bottom ; and fissures,
when they are narrow and rugged. Digitcd impi'essions is the name given to
those excavations in bones which look as if produced by the pressure of the
finger. The fossce, sinuses, cells, and notches are also non-articular cavities of
bones. The sinuses and cells are formed by open spaces in the interior of
bones ; notches, by cavities excavated on their margins.
When a cavity passes quite through a bone, it is termed a foramen. If this
foramen has a certain length, it is designated a conduit or canal. Fissures are
long, narrow openings ; hiatus is the term applied to a wide opening with an
irregular outline.
In order to aid the memory, the external peculiarities of bones are grouped
in the following synoptical table : —
i Non-Articulars
( Synarthrodials . Dentations.
JDiarthrodials . ( gf^^^^s.
I Styloids.
Coracoids.
Mastoids.
1 1 uoerosiiies.
Lines.
^Crests.
i
Articulars. . ..
aynarmroaiaiB -J Dentation
^Diarthrodials .{^^^^
Channels.
^,
Furrows.
•< '
Grooves.
o
Digital impressions.
pa
Fossae.
Sinuses.
Non-Articulars .<
Cells.
Notches.
Foraminse.
Canals.
Ducts.
Slits.
, Hiatuses.
Internal Conformation of Bones.
Sections made in various directions through the substance of bones, show
that their internal conformation varies, according as they belong to the category
of long, flat, or short bones The diaphysis of long bones is hollowed out into a
large fusiform cavity — the medullary canal. This' canal is absent in the flat and
short bones, and is replaced by irregular cavities which communicate with each
other, called medullary spaces. Its walls are formed by a very dense bony tissue,
16
TEE BONES.
the pores of which are scarcely visible to the naked eye, and which is called the
compact substance. The extremities of long bones are surrounded by a thin
layer of compact substance, while the remainder of their mass is constituted by
the spongy substance — bony tissue channeled into medullary spaces. { Reticulated
bony tissue is but another form of spongy substance, the only difference between
the two consisting in the cells or meshes of the first being formed of intercrossed
osseous fibres, while those of the second are formed of lameUce.) The medullary
canal, and areolae of the spongy tissue, are filled by the marrow (or medulla).
The flat bones are constituted by a layer of spongy tissue placed between two
plates of compact substance. (In the flat bones of the cranium, the two layers
of compact tissue are termed the vitreous tables, while the cells of the spongy
tissue are designated diploe.) In certain points of their extent, the spongy
substance disappears, and then the bone is composed of a single lamina of
compact tissue.
The short bones have a nucleus of spongy substance, enveloped in a layer^
more or less thick, of compact tissue.
The compact substance of the bones, being very resisting, is found in all
those situations which have to sustain violent efforts. The spongy substance is
very hght when compared with its volume, and is met with in the wider portions of
the bones, to which it affords increased size without adding sensibly to their weight.
Structure of Bones.
Bones are formed of a proper tissue, covered externally by a particular
membrane — the periosteum, and occupied internally by the medulla, vessels, and
nerves.
A. Proper tissue. — The elements of the proper tissue of bone are always and
everywhere the same ; the texture alone is modified in
the compact and spongy substance.
Everywhere the bone tissue is composed of a funda-
mental substance, which is amorphous or slightlj
granular, white, and more or less opaque, according to
the thickness it offers. This fundamental substance is
penetrated by an infinite number of vascular canaliculi
[bone cavities), with prolongations {hone canaliculi),
which contain cells {bone cells). The cavities and their
contents are named osseous corpuscles or osteoplasts. In
a dried plate of bone, the corpuscles appear dark when
viewed by reflected light, white and shining by direct
light.
In the spongy tissue, the bone corpuscles, anasto-
mosing by the ends of their canahcuh, are distributed
throughout the lamellte of fundamental substance, which
is intercrossed in such a way as to circumscribe the
numerous medullary spaces.
In the compact tissue, the corpuscles are regularly distributed in the
substance of the bony lamellae, which are arranged in concentric layers.
In a transverse section of the diaphysis of a long bone, it is noticed that the
fundamental substance is excavated by an infinite number of vascular canaliculi,
named Haversian canals (Figs. 9, 10). These canals measure from l-2500th to
l-200th of an inch in diameter, and are parallel to each other and to the larger
Fig. 9.
VERTICAL SECTION OF BONE,
showing the network of
Haversian canals.
GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 17
axis of the bone ; they communicate frequently by transverse branches. "While
the most superficial open on the surface of the bone, beneath the periosteum,
and the deepest into the medullary canal, a certain number terminate in the
areolae of the spongy substance at the
ends of the bones. '^" *
The wails of these canals are con-
stituted by several concentric lamellae
of fundamental substance, in which are
lodged the essential elements of the
bony tissue. Each canal, with its
vessels, its system of concentric lamellae,
its osteoplasts, and its osseous canaliculi,
forms a whole (the Haversian system)
which represents the complete bone in
miniature. All the Haversian systems
preserve a certain independence ; the
canalicuh of each, after reaching the minute structure of bone, as shown iu a thia
. , 1 11 n , 1 , section cut transversely to the direction of the
periphery, are nearly all reflected to- Haversian canals.
wards the centre (the recurrent canaliculi l, A Haversian canal surrounded by its concentric
lamellse ; the lacunae are seen between the
lamella', but the radiating tubuli are omitted;
2, ibid., with its concentric laminae, lacunae, and
radiating tuhuli; 3, the area of one of the
canals ; 4, 4, intervening lamelljE, and between
them, at the upper part, several very long
lacunae with their tubuli.
Fig. 11.
of Ranvier) and rejoin the canaliculi of
the same system, instead of anasto-
mosing with those of the neighbouring
system.
Between the Haversian systems,
there are the intermediate systems of
lamellae which fill the spaces left through
the imperfect contact of the former.
In all the long bones there is a system
of periphercd lamellae, enveloping, ex-
ternally, all the Haversian systems ;
while a system of perimediiUary lamellce,
more or less perfect, also exists at the
inner surface of the medullary canal. ^*«^^^^' ^^ '^'''^*?rf ™ °!- ''''f''' substance,
,,, , ^ , 1-11 magnified 500 diameters.
Sharpey observed that the peripheral ^^ ^^^^,^1 ^^^-^^ . j^ j^s ramifications,
bony lamellte were traversed by fibres
{Sharpey's ov perforating fibres), and J. Renaut has remarked in the same lamellae
the presence of elastic fibres.
The proper tissue of bones is a framework of organic matter which has
gelatine for its base, and in which are deposited the calcareous phosphates
and carbonates which give to this tissue its characteristic hardness. This
is easily rendered evident by immersing any bone in dilute nitric or hydro-
chloric acid ; acid dissolve the calcareous salts, but do not act upon the organic
framework. So it is, that after some days' maceration the bone becomes
flexible, like cartilage, and loses part of its weight, although it preserves its
volume and shape. The counterpart of this experiment may be made by
submitting it to the action of fire. It is then rendered quite friable, because its
organic skeleton has been destroyed, without the earthy salts it contained being
affected.
B. Periosteum. — This is a very vascular and nervous fibrous membrane which
covers the entire bone, with the exception of the articular surfaces and the
18 THE BONES.
insertions of tendons and ligaments. Its thickness and adherence are not the
same everywhere ; it adheres most closely near the ends of bones. By its inner
face it corresponds to the surface of the bone, into which it sends prolongations
{arciform fibres) which ultimately become Sharpey's fibres ; by its external face,
it is continuous with the surrounding connective tissue and that of the muscular
aponeuroses.
The periosteum may be resolved into two layers, though these are not always
very distinct. The superficial layer is essentially fibrous, and is formed by a
network of elastic fibres containing bundles of longitudinal fibres and cells.
The deep layer is a closer elastic network, with finer connective tissue fibres, and
a larger quantity of cells and vessels. This is called the osteogenous layer ,
because of its functions.
C. Medulla. — The medulla, or marrow, is a pulpy, fatty substance, which fills
the medullary canal and the areola of the spongy tissue of the bones, and
partly the Haversian canals. Somewhat consistent, and of a rosy tint in the
bones of young animals, the marrow becomes diffluent and yellow in the bones
of those advanced in age, except in the vertebrae of the Horse, Ox, Dog, etc.,
and in the limbs of the Rabbit. In the first state, it is also mucous or fibrous in
the cranial and facial bones undergoing development, and, rosy in colour, it
only contains traces of fat ; while in the second, it has 96 per cent, of this
substance. The medulla of bones is composed of : 1st, some trabecul^e of
delicate connective tissue and a network of stellate cells, to support the vessels
and nerves ; 2nd, fat cells ; 3rd, particular cells, named by M. Robin medullo-
cells and myeloplaxes.
The medullo-cells, abundant in the red or foetal marrow, are small cells with a
spherical or budding nucleus {Bizzozero's cells), analogous to the lymph cells ;
some are impregnated with hgemoglobine. With regard to the myeloplaxes, these
are enormous flat cells, irregular in outline, and containing a large number of
nuclei. Rare in the yellow marrow, they are more particularly found adhering
to the walls of the medullary canal, or the alveoli of the spongy tissue.
D. Blood-vessels. — The arteries of bones belong to three orders — a distinction
based on their volume and the extent of their distribution.
The arteries of the first order penetrate to the interior of the medullary
canal of long bones, by a particular orifice — the nutrient foramen. They soon
divide into two branches, which break up into a network that lines the walls
of the canal and enters the tissue of the medulla. This network communicates
with the arteries of the second order, which go to the spongy tissue of the
extremities of the long bones, penetrating them by the numerous nutritive
foramina that surround the epiphyses. Lastly, the arteries of the third order
are branches of the periostic network that enters the superficial Haversian
canals. These canals may be considered, strictly speaking, as a third category
of nutrient conduits. In the flat and short bones there are no arteries of the
first order.
Veins accompany the arteries, and are always more voluminous than these ;
they frequently make their exit by special and very large openings at those
points where the spongy tissue is abundant. The veins of bones sometimes
exhibit saccular dilatations on their course. Certain veins in the cranial bones
have their walls partly or entirely channeled in the bony tissue ; they are lined
by a simple endothelium.
E. Lymphatic vessels. — The existence of these cannot be affirmed.
GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 19
Nerves. — These belong to the eerebro-spinal and ganglionic system of nerves ;
the latter are always vaso-motor nerves.
Almost constantly, a somewhat volmninous nerve enters the medullary canal,
by passing through the nutrient foramen, and is distributed to the medulla.
The compact tissue receives few nerve filaments ; while, on the contrary, the
spongy tissue at the extremities of the long bones, as well as the short bones,
contains many. Certain short bones, such as the vertebrse, are
remarkable for the numerous nerves they receive.
DEVELOPMENT OP BONES.
The bones, before arriving at the condition in which we see them in the
adult animal, pass through several successive phases, the study of which consti-
tutes Osteogemj.
Nearly all the bones were originally cartilaginous, those of the roof of the
cranium and the face being only represented by fibrous tissue. We will examine
the development of these cartilaginous and fibrous bones.
A. Development of the Cartilaginous Bones. — In the embryo at an early period,
the bones are composed of a mucous material analogous to that which enters into
the composition of all the other organs ; this matter is constituted by a mass of
embryonic cells. Later, they become harder, white, and elastic — that is, cartila-
ginous. Certain portions of the skeleton persist in this condition during the life
of the animal. These permanent cartilages are found where the bony skeleton
must have a certain amount of flexibility, and on the articular surfaces.
The temporary cartilages, like the permanent, have a fundamental amorphous :
01 hyahne substance, in which are embedded round cells containing one or several
nuclei. But they soon undergo modifications, which result in giving to the
pieces they form the hardness and structure of perfect osseous tissue.
These modifications gradually cause the cartilage to disappear, and to be
replaced by bony tissue, without the skeleton ceasing for an instant to preserve
its form and functions. The process commences by calcification of the peri-
chondrium and of the middle part of the diaphysis, which ensures the stability
of the organ. Then the blood-vessels, which are constantly present in temporary
cartilages, pass through the diaphysary nucleus, ramify, and are directed in a
parallel manner towards the extremities. Simultaneously, the chondroplasts are
arranged in parallel series in front of the vessels (rivulation of the cartilage), and
finish by merging into large, irregular, elongated cavities, incompletely separated
by bands of fundamental substance of the calcified cartilage, designated the
directing lines of ossification.
The blood-vessels enter these cavities, carrying to their surface cells which
proliferate, and are differentiated into osteoblasts or productive cells of bone.
The osteoblasts are deposited, layer upon layer, against the walls of the spaces
limited by the lines of ossification, and form, by a kind of secretion, concentric
strata of the osseous fundamental system which surrounds them ; then the
osteoblasts become osteoplasts. The cavities made in the cartilage finish by
becoming filled up, except at the centre, where a central cylindrical space
remains (Haversian canal), and a blood-vessel.
In the extremities of the bones, where there are no Haversian canals, the
preparatory modifications are the same as in the diaphysis, only the cartilaginous
cells collect in small irregular masses, and not in parallel piles. Each of these
20
THE BONES.
masses forms layers of bone substance, that finish by constituting the lamellaB of
spongy tissue at the periphery and medullary tissue at the centre, to fill the
areola of the latter.
In this way is accomplished the transformation of cartilage into bone. As
will have been observed, it is not a mere calcification of the cartilaginous tissue,
«^A, but a real substitution of bone tissue, presentmg the following phases : 1. Peri-
tijfe*^- , ( chondrial and endochondral calcification in places (nuclei or centres of ossifica-
tion). 2. Invasion of the centres of ossification by vessels, rivulation of the
cartilage. 3. MedulHzation of the cartilage, and
formation of^ osteoblasts. 4. Development of the
'Jt^ <^^ .^^^ ■'• '■ " bone tissue, appearance of the osteoplasts.
J"^ ^§ e^^ /^:r^ B. Development of the Fibrous Bones. — The bones
originally fibrous are not merely charged with lime
salts in order to acquire a bony appearance. They
do not pass through a transitory cartilaginous state,
but the phenomena of ossification take place in the
fibrous tissue in the following manner : —
The fasciculi of connective tissue become calcified,
separate here and there from one another to form
spaces, into which blood-vessels enter or osteoblasts
appear. To this phase of medullization succeeds the
phase of ossification, which is accomplished in the
same manner as in the cartilaginous bones. Only
the directing lines are represented by connective
fasciculi, which later become Sharpey's fibres.
0. Progress of Ossification. — Ossification com-
mences simultaneously in several parts of the skeleton,
and in each of the bones in particular— though not
throughout their entire extent at the same time. On
CARTILAGE AT THE SEAT OF thc coutrary, lu certain determinate points of the carti-
ossiFicATioN, showing at its lagiuous or fibrous mass, osseous tissue is developed
ir^'lsCi:;...'": c:lr™: ^Wch, gradually extendmg, ends by completely in-
each of which is enclosed in a vadiug it. These points are named nuclei (or centres)
sheath of calcified intercellular ^f ossificatiou. The nuclei are primitive or comple-
mentary. The latter, termed epiphyses, are in a
fashion added to the bone, and wholly or partly form certain' apophyses, rtjlj* , '^'
Although these centres of ossification increase from day to day, they never-
theless remain for a long time independent of each other, and are united only by
cartilage. When the skeleton is completely developed, the various centres of
ossification become joined to each other, and the entire bone forms one piece ;
there are no longer any apophyses.
Up to the present time, attempts to discover the laws which govern the
appearance of the centres of ossification have been futile ; the size of the bone
counts for nothing ; and the influence of proximity to the centres of circulation,
which has been sometimes brought forward (for the sternum, for example,
which is never completely ossified), cannot be accepted. The law which
presides over the union of the centres of ossification has also been sought
for. A. Berard imagined he could formulate it in the following proposition .-
Of the two extremities of along bone, it is always that towards ivhich the nutrient
foramen is directed that is first united to the body of the bone. But to Berard's
GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 21
law there are nmnerous exceptions ; and in order to demonstrate that it is not
absolute, it is sufficient to indicate that the direction of the nutrient foramen
varies much, not only in similar bones of different species of animals, but also in
similar bones of the same species^ ; and yet the progress of ossilication is alwajs
the same.
The period when fusion of the epiphyses terminates in the domestic animals
is still little known ; fusion is evidently complete when growth is achieved, but
this period is markedly modified by hygiene and the :'ood animals receive. Renault
and some breeders have observed, that in the proocious breeds of cattle the
evolution of the teeth is more rapid than in the common breeds. More recently,
Sanson has affirmed that precocity, characterized by this prompt dental evolution,
is marked by a more rapid fusion of the epiphyses, and he believes there is a
direct relation between the evolution of the teeth and that of the bones.
According to this principle, in the Horse the fusion of the epiphyses should
commence and terminate between three and five years of age.
Toussaint, however, did not share this opinion. In the Ox, Sheep, and
Horse, he remarked that the first centres of ossification appeared in the body
of the flat and the longbone^and in the centrum and arches of the vertebrae.
When the first half of ^esrajtionnad not been passed, no other points of ossifica-
tion were seen. It is necessary to add, however, those of the second and third
phalanges and the calcis, which comport themselves as long bones.
In the last half of gestation, ossification invades the complementary nuclei, as
well as the short bones ; the exceptions are the pisiform bone and the inner condyle
of the humerus in the Calf and Foal, and the large and small sesamoid bones in
the Calf only. Ossification of these bones of the skeleton is slow. It must also
be mentioned that at birth the complementary nuclei of the coxas^ are not yet
visible, and they are net seen until ten months or a year afterwards. ^^ ^ ""' ^^^J
With regard to fusion of the epiphyses, it occurs at the following periods in
the principal bones of the Horse ; at the twelfth to the fifteenth month in the
second phalanx at first, then in the first phalanx ; at the fifteenth to the
eighteenth month in the middle metacarpal, afterwards in the metatarsal. At
this age fusion also occurs at the upper end of the radius and inferior ex-
tremity of the humerus : from twenty months to two years, at the lower end of
the tibia ; from three to three and a half years, at the upper extremity of the
humerus, at the two ends of the femur, and at the upper end of the tibia ;
lastly, about five years, in the bodies of the vertebrae and in the coxae.
In the Ox, ossification progresses at about the same rate as in the Horse,
except that there is a little greater precocity in the fusion of the epiphyses of the
humerus and radius, which are fused at the same time as those of the phalanges,
and matacarpal and metatarsal bones. In this animal, the two lateral halves of
the latter bones are united before union of the inferior epiphysis to the body of
the bone. The Sheep offers an interesting peculiarity, in that the humero-
radial epiphyses are consolidated before those of the phalanges, and towards the
tenth month.
If the results of these observations, made on our principal domestic animals,
are compared with the evolution of the dental system, we are compelled to con-
clude, with Toussaint, that fusion of the epiphyses does not commence at the
same time as the eruption of the first permanent teeth. If a relationship exists
between the evolution of the teeth and that of the bones, it has yet to be
demonstrated in an exact manner.
22 THE BONES.
Toussaint has also studied the course of ossification in the Bog, Pig, and
Rabbit. In the Dog at birth, none of the complementary nuclei have been
invaded by ossification. Consequently, bone tissue is only found in the dia-
physis of the long and flat bones. In the thrge months after birth, the great
majority of the epiphyses commence to ossify ; and after this period there only
remain the pyramidal bone and the complementary nuclei of the coxffi, in the
cartilaginous condition ; the ossification of these latter commence at from five to
six months.
The skeleton of the Rabbit is, at birth, in a condition almost identical with
that of the Dog ; nearly all the epiphysary nuclei of the humerus and that of
the lower end of the femur, however, show osseous points.
In the Fig, at birth ossification is much more advanced than in the Dog ;
but it is less so than in the larger Herbivora.
The fusion of the epiphyses has been studied in the Dog. It commences at
five months, in the phalanges and metacarpals, and continues in the humerus
and radius, the corresponding epiphyses of which are consolidated at nine
months ; at eighteen months there can be distinguished the nuclei at the upper
border of the scapula, the upper end of the humerus, inferior extremity of the
radius and uhia, the epiphyses of the femur, and the bodies of the vertebrae.
The latter facts support the preceding ones, and likewise demonstrate that the
conclusions of Sanson are probably too absolute.
Growth of the Bones.
Bones increase by the superposition of new elements, while the soft parts of
the organism grow by the interposition of new elements in the mass of pre-
existing elements. The manner in which this apposition of new elements is
accomplished is not the same in the long, the flat, or the short bones.
1. Long Bones. As a general rule, the long bones elongate by the growth
and ossification of the temporary cartilage situated between the diaphysis and
the osseous nuclei at the extremities. Consequently, elongation ceases when the
primitive or complementary nuclei are fused with one another. The increase in
length in the bones of the Ihnbs does not take place everywhere in the same
proportion. Duhamel, Flourens, and particularly Oilier and Humphry, have
remarked that, in the thoracic limb, the extremity furthest removed from the
humero-radial articulation grows fastest ; while in the abdominal limb, the
extremity most distant from the femoro-tibial articulation grows the least.
With regard to the increase in thickness of the bone, this occurs by ossifica-
tion of the deeper layer of the periosteum — the osteogenous lager. The experiments
of the authors just mentioned irrefutably demonstrate this, and those of Oilier
have even proved that the periosteum may produce bone at a point where it has
been transplanted.
The periostic bone is developed according to the process of ossification in the
fibrous tissue. In a transverse section of the diaphysis of a growing long bone,
there is seen, as Laulaine has indicated, concentric circumferences united by
radii of osseous substance. The diaphysary portion of the periostic bone is
fused with the extremities, through the medium of the ossification notch of
Ranvier — a prolongation of the periosteum into the articular enlargement around
the cartilage of conjugation. The formation of bone tissue in the deeper layer
of the periosteum is very active during the youth of animals, but it soon
diminishes, and ceases completely in advanced age.
GENERA L PRINCIPLES A PPLICABLE TO THE STUD Y OF ALL TEE BONES. 23
If the phenomena of growth were not counterbalanced by those of absorption,
long bones would acquire an enormous thickness and weight. But in the first
period of life, in proportion as new layers are applied to the surface of bones, the
deeper parts — those occupying the axis of the diaphysis — disappear by absorption.
In this way the medullary canal is formed, and a just proportion established
between the volume and weight of the skeleton.
When the bones are completely formed, during the entire adult period the
process of destruction is equal to that of growth, so that their weight and com-
position does not vary. At a later period, absorption is greater than the forma-
tive force, which in old age is altogether in abeyance ; so that the organic
matter of the bones is rarefied, and these lose their elasticity and gain in
fragility.
It has been remarked that the development of the bones is subordinate, in
a certain measure, to the activity and resistance of the organs in their vicinity.
Lesshoft and Popoff beheve that the development of a bone is in proportion to
the activity of the neighbouring muscles, that the pressure of external organs-
such as an aponeurosis — may produce torsion in a bone and retard its growth,
so that its greatest thickness will correspond to the point where the surrounding
Ijf^ resistances are at a minimum. Oilier, however, has noted that the long bones
i^*^"^ become more elongated when they do not sustain pressure on their extremities.
2. Flat Bones. — These bones have sometimes only one primary nucleus of
ossification, placed in the centre. They grow by the increase of this nucleus,
which gradually invades the mass of the bone in radiating from the centre towards
the periphery. When they have several nuclei, some of these are at the margin,
and in such a case the bones increase by ossification of the marginal efpiphyses
and growth of the central nucleus.
Flat bones increase in thickness by the formation of sub-periosteal layers,
and by the development of the spongy tissue between the two compact plates.
3. Short Bones. — These grow in thickness by the progressive ossification of
the osteogenic layer of the periosteum ; and in length by ossification of the
• epiphysary cartilages, when they possess complementary nuclei.
Nutrition of Bones.
The experiments which consisted in feeding young animals with madder, and
afterwards examining their osseous system, have for a long period demonstrated
the nutrition of bones. When bones cease to grow, nutrition becomes less active ;
but it is evident that it does go on, in order to maintain the organic matter of
the osseous tissue in a proper condition.
The abundance of vessels carrying blood to all parts of the bone tissue, alone
suffices to prove the existence of a nutritive movement in these apparently stony
organs.
THE BONES.
CHAPTER 11.
THE BONES OF MAMMALIA IN PARTICULAR.
Article I. — Vertebral Column.
The vertebral column, or spine, is a solid and flexible stalk situated in the middle
and upper part of the trunk, of which it forms the essential portion. It protects
the spinal cord and sustains the thorax, as well as the principal or2:ans of circu-
lation, respiration, and digestion. Articulated anteriorly with the head, and
terminating in a point at its posterior extremity, this stalk is formed by a some-
what considerable assemblage of short, single, tuberous bones, to which has been
given the name of vertehne. These bones, though all constructed on a uniform
type, yet do not offer the same configuration throughout the whole spine. The
differences they present in this respect have permitted their being divided into
five principal groups ; whence the division of the vertebral column in five regions,
which are, enumerating them from before to behind : 1. Cervical region. 2,
Dorsal region. 3. Lumbar region. 4. Sacral region. 5. Coccygeal region. The
first comprises seven vertebrse, which serve as a base for the animal's neck ; the
second has eighteen, against which the ribs are placed ; the third has only six,
which correspond to the loins ; in the fourth there are five, constantly fused into
one mass in the adult, to constitute a single bone — the sacrum ; while the fifth
possesses a variable number of small degenerate vertebrte, gradually decreasing
in size to form the tail. The pieces constituting the first three regions are called
true veiieircB ; those of the last two are designated /(v/se vertehrce.
The subjoined table indicates the number of vertebrae in each of the regions
of the spine, in the horse and other domestic Mammalia.
Animals.
Vertebra.
Cervical.
Dorsal.
Lumbar.
Sacral.
COCCTGEAL.
Horse
Ox
Sheep
Goat
Camel
Pig
Dog
Cat
Rabbit
7
7
7
7
7
7
7
7
7
18
13
13
13
12
14
13
13
12
6 or 5
6
6—7
6
7
6—7
7
7
7
5
5
4
4
4
4
3
3
4
15-18
16—20
16—24
11-12
15—18
21-23
16—21
21
16-18
The characters belonging to all these vertebrae will be first studied ; then a
particular description of those of each region will be given ; and, finally, an
examination will be made of the spine as a whole.
Characters common to all the Vertebrae.
Each of these small bones is pierced from before to behind by a wide opening —
the spinal foramen., or vertebral canal ; whence results, for the entire spine, a long
canal traversing its whole length, and which lodges a very important portion of
the nervous centres— the spinal cord. This canal, which traverses the vertebrae
VEBTEBB^. 25
from one end to the other, transforms it into a ring in which we recognize, for
facility of description, two parts — the one inferior, the other superior. The first,
or hotly, is very thick, and forms the base of the vertebras ; the second, which
is thin, has been designated spinous or spinal — from one of the pecuUarities it
presents, or annular — because it circumscribes the major portion of the spinal
foramen. This division is not altogether an arbitrary one, for the body and the
annular portion constitute, in the foetus, two distinct pieces, which do not become
united for a long time after birth.
Body {centrum). — The shape of the body of a vertebra is that of a prism
Fig. 13.
k
B A.
A
i
w.
•{{
ELEMENTS OF A VERTEBRA. (AFTER OWEN.)
A, Ideal typical vertebra ; B, Actual thoracic vertebra of a bird ; c, Centrum (or
body), giving off, d, d, the diapophyses, and p,p, the parapophyses (transverse and
articular processes) ; the neural arch, enclosing the spinal cord, is formed by
n, n, the neurapophyses (lamince), saxd n, s, the neural spine {spinous process);
the hamal arch, enclosing the great centres of the circulation, is formed by h, h,
the haemapophyses (costal cartilages) ; and h, s, the haemal spine (sternum).
From both the neurapophyses and haemapophyses may be given off the zygapo-
physes, z, z. The lateral arches, which may enclose the vei'tebral arteries, o, o,
are completed by the pleurapophyses (ribs), pi. ; these in B are bent downwai-ds,
so as to form part of the hasmal arch, and give off the diverging appendages, a, a.
with four faces, of which two only — the superior and inferior — are free, and can
be studied in the adult ; the two lateral faces are united and confounded with
the annular portion. This prism also presents two extremities — an anterior and
posterior.
Faces. — The superior face, limited in extent, forms part of the spinal foramen,
constituting its floor. It exhibits : 1. On the middle line, two roughened,
prominent surfaces, representing two triangles, whose summits are opposed.
2. On the sides, two depressed smooth surfaces, perforated by one or more
openings that lead to the interior of the bone. The inferior face is divided into
two lateral portions by a median crest (the htemal spine).
Extremities. — The anterior has a prominent convex head, more or less
detached. The posterior offers a cavity for the reception of the head of the
next vertebra. These two planes — the one convex, the other concave — do not
come into immediate contact ; an elastic, flexible fibro-cartila^e, firmly attached
to each, is interposed between them.
26 THE BONES.
Annulae Portion {neurcd arch or neuropophyses). — This is formed by an
osseous plate that curves suddenly downwards, in the shape of an arch, the two
extremities of which approach each other, enclose the body, and become united
to it. It offers for study : 1. An internal and an external surface. 2. An
anterior and &, posterior border.
Surfaces. — The internal surface, concave and smooth, forms, with the superior
face of the body, the spinal foramen. The external, convex and irregular, pre-
sents : 1 . A single prominence, raised in the middle of the superior portion, and
named the spinous process {neural spine). 2. The transverse processes (diapo-
physes) are a double pair of eminences, one on each side, and projected trans-
versely outwards.
Borders. — The anterior border has two articular facets looking upwards :
these are the anterior articular processes {prezygopophyses), right and left. In
each is a notch which, when placed in opposition to a similar excavation in the
preceding vertebra, forms the inter vertehrcd foramen. The posterior border pre-
sents the same pecuUarities, with this difference, that the articular faces of the
posterior articular processes {postzygopophyses) are inclined downwards, to corre-
spond with the anterior facets of the succeeding vertebra.^
Structure of the vertebrce. —The compact substance, which is abundant in the
spinous portion, forms in the body an extremely thin layer, inclosing a volumi-
nous nucleus of spongy tissue. The latter is traversed by numerous venous
canals, which open on the surface of the bone.
Development. — It has been already shown that the body and spinous
portion of a vertebra constitute, in yoimg animals, two distinct pieces. Each
was primarily formed from two lateral centres, which met on the median line.
In the body, the fusion of these centres is so prompt, that it is generally believed,
perhaps justly, that the development of this part of the vertebra proceeds from
a single centre of ossification. The union of the two centres in the annular
portion, usually designated the vertebral lamince {parapophyses), is slower. It
commences in the most anterior vertebrae, and is latest in the sacral and coccy-
geal regions. To the three principal pieces of the vertebra in process of
ossification, are added, at a subsequent period, complementary centres of ossifi-
cation, variable in number according to the regions and species of animal ;
there is always one for each of the anterior and posterior surfaces of the
vertebral bodies ; while others, much less constant, concur to form the spinous
and transverse processes.
Characters proper to the Vertebrae of each Region.
A casual inspection of a vertebra might suffice, strictly speaking, to dis-
tinguish the region of the spine to which it belonged. For instance, a cervical
vertebra is recognized by its volume, the absence of a spinous process, and the
foramen which traverses the base of its transverse processes. The dorsal
vertebra is conspicuous by its tubercular transverse processes, and by being
furnished, outwardly, with an articular surface, as well as by the depressions on
its body destined to receive the heads of the ribs. The lumbar vertebra has its
long flattened transverse processes ; while the coccygeal vertebra offers rudi-
(' Vertebrae which have centra concave at both ends, are designated amphicselous. Those
distinguished by a concavity in front and a convexity behind, are known as procxlous ; but if
the cavity is behind and tlie convexity before, they are then named opisthocxlous. A vertebra
of the above description belongs therefore, to the opisthocaslous class.)
VEBTEBRM 27
mentary laminae and processes. There is no necessity for noticing the sacrum,
the five pieces of which form one bone— a feature that markedly distinguishes
it from the other regions of the vertebral column. But these few distinctive
characteristics do not satisfy the requirements of descriptive anatomy ; so that
it is necessary to undertake a more extensive study of each of these regions.
1. Cekvical Vertebe^.
General Characters. — These vertebrae, the longest and thickest in the
spine, present generally a cubical form. They are usually distinguished from the
vertebrae of the other regions by the following characters : The inferior spine of
the body is strongly marked, especially behind, where it terminates in a small
tubercle. The head is well detached from the remainder of the bone, and
describes a very short curve. The posterior cavity,
wide and deep, represents a veritable cotyloid de-
pression, which is too large to fit the head exactly;
the intermediate fibro-cartilage on these two sur-
faces is also of a great thickness. The spinous
process forms a simple roughened, and but slightly
prominent, ridge. The transverse processes, very
developed, are elongated in an antero-posterior
direction, and inclined downwards. In this region
they are designated the trachelian processes, be- ^ cervical vertebra.
cause of their relations with the trachea ; a j^ Superior spinous process ; 2, an-
f oramen that traverses them from before to terior articuiaj processes ; 3, pos-
behind at their base has been, for the same f^tr ^^n^et fac^'^o^Tod^ f 'e!?;
reason, named the trachelian foramen {^vertebral transverse processes, with their
foramen). The articular processes, large and tubercles or rudimentary ribs ; 8,
' . , -TIT 1 J • J inferior crest, or spine : 9, concave
promment, are mchned downwards and mwards. posterior face.
The notches are wide and deep.
Specific Characters. — The seven cervical vertebrae are reckoned from
before to behind, and receive numerical names indicating their place in the
region.
First. — The first vertebra of the neck, which has been named the atlas,^
deserves a very careful description. At first sight there is recognized the great
development of its transversal diameter, the considerable dimensions of the
spinal foramen, and the thinness of its body. The intra-spinal face of the latter
is divided into two portions by a transverse ridge : one anterior, furnished with
hgamentous imprints, exhibits, laterally, two deep excavations, which lodge the
venous sinuses ; the other, posterior, is smooth and concave from side to side,
and forms an articular surface into which is received the odontoid process of the
axis ; this surface takes the place of the cotyloid cavity. The inferior spine of
the body appears as a large tubercle (Fig, 15, 6), The head is absent, and is
replaced by two concave facets. The anterior articular processes have their
gliding surfaces looking downwards ; they are joined to the two preceding facets
to constitute two large diarthrodial cavities, which articulate with the occipital
condyles (Fig, 15, 1), There is no spinous process, but a roughened surface
instead. The transverse processes are large, flattened above and below, inclining
forwards and downwards, and are provided with a thick rugged lip. Posteriorly,
* Rudimentary ribs are sometimes attached by ligaments to the ends of the transverse
processes (.Leshre).
28
THE BONES.
Fig. 15.
atlas; inferior sitrface.
1, Articular cavities for condyles of
the occipital bone ; 2, articulai facet ;
3, vertebral or antero-internal fora-
men ; 4, posterior, or cervical fora-
men ; 5, transverse process or wing
quite at their base, and on each side of the spinal foramen, they show two large
vertical facets which represent the posterior articular processes ; these facets are
uneven, are confounded with the articular cavity
of the upper face of the body, and correspond to
the two analogous facets of the axis. Each trans-
verse process is pierced at its base by two foramina,
which traverse it from below upwards. The
posterior represents the vertebral foramen of the
other vertebrae ; while the anterior is continued
to the external surface of the process by a wide,
deep, but very short channel, running from with-
out to within, and joins a third foramen, which
enters the spinal canal. These last two openings,
with the demi-canal which unites them, replace
the anterior notch ; the posterior is altogether
absent. Lastly, an inflected venous canal, the
position of which varies, and it is also sometimes
tubercle representing the inferior absent, crosscs the lamiuffi of the atlas, and opens,
spinous process; 7, superior arch, qjj Qjjg ^[^q^ j^to the Spinal caual, and on the
forming the roof of the spinal fora- , , ^t ^^ ^ mi- ^i
^gn ^ other, beneath the transverse process, ihe atlas
contains much compact tissue, and is generally
developed from six centres of ossification : two for the body, which at an early
period becomes a solid piece, and two for the annular part ; the other two are
complementary centres, each of which forms one of the two posterior undulated
facets and lip of the corresponding transverse process.
Second. — This is named the axis, or dentata (Fig. 16). It is the longest of
all the cervical vertebrae ; those which
succeed it gradually diminish in length
and in thickness. The body of the axis
has no increase anteriorly, but a conical
process termed the odontoid, which is
flattened above and below, concave and
rough from one side to the other on its
superior face ; convex in the same direc-
tion and perfectly smooth on its inferior
face. The latter represents an articular
half-hinge, around which glides the con-
cave articular surface on the superior
face of the body of the atlas. The
anterior articular processes are carried
to the base and to each side of the
odontoidian pivot, in the shape of two
undulated facets, which are confounded with the gliding surface of the latter,
the destination of which has been already noted. The spinous process, very
large and elongated antero-posteriorly, is divided behind into two roughened lips.
The transverse processes are slightly developed, and terminate posteriorly in a
single tubercle, directed backwards. The anterior notches are very deep, and
are most frequently converted into foramina. This vertebra, although voluminous,
is light, in consequence of its containing much spongy substance. In the young
animal, the odontoid process and the articular surfaces on each side, constitute
Fig. 16.
THE AXIS, OR dentata; LATERAL VIEW.
1, Superior spinous process ; 2, odontoid pro-
cess; 3, intervertebral foramen, or hole of
conjugation; 4, body; 5, inferior spinous
process ; 6, 7, inferior and superior articu-
lating processes.
VERTEBRM 29
two centres, distinct from each other and from the body of the vertebra. After
the axis, the cervical vertebrae diminish in length and increase in thickness ;
while the obliquity of their articular processes becomes more pronounced the
more distant they are from that vertebra.
Third, fourth, and fifth.— Each, of these has, at its transverse processes, two
prolongations — one anterior, the other posterior. The inferior face of their bodies
AXIS AND SIXTH CKRVICAL OF THE HORSE AND ASS.
A. Axis of the Horse. 1, spinous process ; 2, transverse process ; 3, odontoid process ;
4, lateral articular facet.
B. Axis of the Ass. Same numbers and same signification.
a', Sixth cervical vertebra of the Horse. 1, Articular head ; 2, posterior articular process ;
3. articular cavitv ; 4, posterior prolongation of the transverse process : 5, anterior ditto.
b', Sixth cervical vertebra of the Ass. Same numbers and same signification.
exhibits a median spine terminated posteriorly by a tubercle, which gradually
increases in volimie from the third to the fifth vertebra.
The third presents, between its anterior and posterior articular processes, an
almost complete gap ; if its anterior extremity be placed on a horizontal plane,
it will touch that plane by its articular and transverse processes and its head.
30 TEE BONES.
In the fourth, the articular processes are united by a thin, sharp osseous plate,
notched only in front. Laid on a horizontal plane, the head remains some
distance from that plane. The fifth is recognized by the continuous, thick, and
rugged lamina which unites the articular processes, and by the tubercle of the
inferior spine on the body, which is in shape like the heart on a playing-card.
Sixth.— T\n& is distinguished by the slight prominence of the spinous process,
but particularly by the almost total disappearance of the inferior spine, and the
presence of a third prolongation, very strong and inchning downwards at its
transverse process — a circumstance to which this vertebra owes its designation of
tricuspid.
Seventh. — This has received the name of prominens, because its spinous pro-
cess, terminating in a point, is more distinct than in the preceding vertebrae, the
axis excepted. It exhibits, besides : deep imprints, which replace the inferior
spine ; a concave demi-facet on each side of the posterior cavity of the articulation,
of the head of the first rib ; a particular disposition of its transverse processes,
which are unituberculous ; the complete absence of the vertebral foramen ; and,
lastly, the depth and width of its notches. The spinal foramen, which has
already assumed a somewhat considerable diameter in the sixth cervical vertebra,
is still larger in the seventh.
Ass. — The cervical vertebra3 in this animal much resemble those in the
Horse. Studying them more closely, however, it is possible to discover certain
differences which distinguish them from those of the other Equidfe. Thus, the
rugosities on the arch of the atlas are much less marked than in the Horse, and
form a kind of thick depressed tubercle. The vertebral foramen is very large
in proportion to the size of the vertebra, and the canal uniting the two portions
of the anterior foramen of the transverse process is deep and protected by a
well-defined rim. The axis has a less elevated spinous process than that of the
Horse ; its upper border, nearly parallel with the transverse process, is more
deeply divided into two lips, and the summit of its transverse process extends,
backwards to the articular process, while in the Horse it does not go beyond the
origin of the latter. In the third, the lamina uniting the two prolongations or
points of the transverse processes, is notched behind the anterior prolongation,
instead of being notchless as in the Horse. In the fourth Siud fifth this notch is
still more marke4. In every instance the anterior prolongation of the transverse
process is always more detached and better circumscribed in the Ass than in the
Horse. The same remark applies to the tricuspid ; the posterior prolongation is
also better detached, and the middle prolongation extends nearly to the articular
cavity of the vertebra — a prolongation which, in the Horse, does not exceed one-
half the length of the posterior one. The seventh differs little from that of the
Horse ; nevertheless, the uni-tubercular transverse process has, in front, a small
sharp projection which resembles somewhat the anterior prolongation of the
bicuspid processes.
In the Mule and Hinny, the cervical vertebrae hold the middle place between
those of the Ass and the Horse.
Differential Characters of the Cervical Vertebra in the other Domesticated
Animals.
A. Ox, Sheep, and Goat. — The cervical vertebrae of these animals differ from those of
Solipeds by their shortness, and the greater development of their insertion eminences. In the
Sheep and Goat they are relatively longer than in the Ox. The transverse processes of the
VERTEBRA. 31
atlas are less inclined than in the Horse, and have no vertebral foramina ; the posterior facets
for articulation with the axis, are nearly flat and join each other. The axis has a semi-cylindri-
cal, not a conical, odontoid process, which is so concave on its upper t^urface that it looks like
a groove. Its spinous process is not so thick as in the Horse, and is not bitid posteriorly.
In the Jive succeeding vertebras, a rugged continuous lamina unites the anterior articular
processes to the posterior. The spinous process inclines forward, and is flattened transversely
at its summit, which is sometimes bifid ; it progressively increases in height from the third to
the fifth vertebra.
In the sixth, the transverse processes have only two prolongations — a superior and inferior;
the latter, large and flattened on both sides, is bent abruptly downwards. The spinous process
has already attained the height of 1| to 2 inches in this vertebra, and is flattened laterally.
The seventh well deserves the name of prominens, its spinous process being no less than
from 4 to 4f inches (see Figs. 6 and 7).
B. Camel.— In the Camel, the cervical vertebrae are longer and thinner than in the other
large domestic animals. Altogether, they form oue-third of the total length of the spine.
Their vertebral lamiiise are deeply notched before and behind, which allows them to easily
enter tlie spinal canal. Their articular processes are convex, and from the second to the sixth
inclusively, the vertebral foramen is small and deeply placed in the laminae.
The atlas is distinguished from that of the Horse and Ox by the absence of the tubercle on
the inferior face of the body, and the shortness of the transverse processes, of which the border
is thin and sharp. The vertebral foramen makes a somewhat long course in the transverse
process of this vertebra, and opens at the bottom of the excavation in which the anterior inter-
vertebral foramina meet — the latter being double.
The axis is very long and constricted in its middle ; the inferior crest is only slightly
salient ; there are ilouble invertebral foramina, the largest of which is divided by a bony
septum ; the odontoid process is as in the Ox. The other cervical vertebrae gradually diminish
in size and increase in thickness from before to behind.
In the third, fourth, and fifth, the transverse processes are bi-tuberculated.
In the sixth, the transverse process is a wide and thick plate, inclining downwards.
The seventh is recognized by its long spinous process and the smallness of its transverse
process, which has a larger and more obvious vertebral foramen than the other vertebras
(see Fig. 8).
C. Pig. — Of all the domesticated animals, this has the shortest, the widest, the most
tuberous, and consequently tlie strongett cervical vertebrae. The body of these bones has no
crest on the inferior face ; the head, but little detached, is scarcely round, and looks as if driven
back on itself; consequently, tiie posterior cavity is not deep. The vertebral laminae are very
narrow, and scarcely extend from one part of the vertebra to the other in the superior portion,
so that the spinal canal appears at this point to be incomplete.
In the atlas, the transverse processes are less inclined than in Ruminants ; the vertebral
foramen is not constant, and when it exists, opens on one side, under the transverse process,
and on the other, on its posterior margin, after pursuing a certain tiack in the substance of
the bone.
The odontoid process of the axis is constricted at its base. This verte*bra is distinguished
by its high and thin spinous process inclining slightly back, by its transverse processes being
but slightly prominent, and perforated by an enormous vertebral foramen.
In the four succeeding vertebrae, the spinous process terminates in a blunt point, and inclines
forward ; slightly salient in the first, it gradually rises in the others. The transverse processes
form two prolongations : one, the superior, is tuberous, and is joined to the anterior articular
process by a plate of bone, which is pierced by a foramen ; the other, the inferior, flattened on
both sides, bent downwards, and large, as it belongs to a posterior vertebra, transforms the
inferior face of these vertebral bodies into a large groove. The seventh has a spinous process
as long as those of the dorsal region. A peiforated bony plate, as in the preceding vertebrae,
unites the anterior articular process to the single tubercle composing the transverse process;
the latter is continued back nearly to the posterior notch by a second plate, also perforated
with a foramen (see Fig. 3).
D. Dog and Cat. — In these animals, the cervical vertebrae are long and thick, and much
resemble those of Solipeils. Nevertheless, besides their smaller volume, they are distinguished :
1. By the disposition of their corresponding articular surfaces ; the anteiior, or head, is nearly
flat, and is even slightly excavated in its centre ; the posterior, or cavity, is l.ut little hollowed
to receive the head of the next vertebra; 2. By the width of the vertebral laminae, which
overlap one another; 3. By the height of their spinous processes, which increases as the
vertebrae extend back ; 4. By the great extent of the anterior and posterior articular processes,
32 THE BONES.
which are united by means of a continuous and very salient bony plate, that considerably
augments the transversal diameter of each vertebra.
In the atlas, the articular surface for the odontoid pivot is confounded in front with the
cavities which correspond to the occipital condyles. The two facets which are annexed
posteriorly to this articular surface, instead of being plane or gently undulated, as in the
other domesticated animals, are transformed into real glenoid cavities. The triinsverse pro-
cesses are carried directly outwards and a little backvvanl ; the lip wljicli borders eacli is
slightly raised ; of the two foramina wiiich replace the anterior notch, one only exists, and
this penetrates to the interior of the spinal canal ; the other is merely a simple notch.
In the axis, the odontoid process is cylindrical, narrow at its base, and bent a little upwards ;
the lateral facets of this eminence represents true condyles. The spinous process is very thin
and undivided, and is curved forward above the laminae of the atlas. The anterior notches are
never converted into foramina.
The third cervical vertebra is the largest : and the succeeding ones gradually diminish in
thickness to the last, contrary to what occurs in the other species. The seventh does not show
the spinous process so developed as in Ruminants and Pachyderms (see Figs. 3, 4, 7).
E. Rabbit. — The cervical vertebrae in this animal somewhat resemble those in the Cat,
though they differ in certain general and particular characters. Thus, in the Rabbit they
become larger as they proceed backward ; the atlas has its transverse processes horizontal, and
they are narrow at their oriain ; the axis has a bifid tubercle at the posterior extremity of its
spinous process, and a notch below it ; the succeeding vertebrae are thin ; the fourth, fifth, and
sixth are trifid in their transverse processes ; and the seventh has a short spinous process.
2. DoESAL Vertebe^ (Fig. 18).
Geneeal Chaeacters. — In the dorsal vertebrae the body is very short, and
in front has a large slightly projecting head ; behind, it has a shallow cavity.
Laterally, these vertebrae present, at the base of
the transverse processes, four concave articular
Jacets, the two anterior of which are situated near
the head, while the posterior two are hollowed out
of the border of the articular cavity of the body.
Each of these facets is joined to an analogous
facet on the neighbouring vertebra to form a
small excavation, into which is received the head
(or capitulum) of the corresponding rib. The
spijious process is very high, is compressed on
both sides, inclines backwards, and its summit
is terminated by a tubercle. The transverse
processes are unitubercular, and directed obliquely
outwards and upwards ; on their external aspect
they have a diarthrodial plane facet which corre-
sponds to the tuberosity (or tuberculum) of the
rib (and may therefore be named the tubercular
transverse process). The articular processes are
narrow, and constitute simple unrelieved facets
cut on the base of the spinous process. The
posterior notches are deep, and sometimes con-
verted into foramina.
Specific Charactees. — None of the eigh-
teen dorsal vertebrae differ much from the type
just described ; and it is difficult to establish
special characters for each. It is, nevertheless
possible to assign to a dorsal vertebra, approximately, the rank it should occupy,
in accepting the following facts as a guide : 1. The vertical diameter of the
ttpe op a dorsal vertebra (the
fourth).
1, Body, 2, 2, articular facets for the
head of the rib; 3, articular facet for
tuberosity of the rib; 4, articular
processes ; 5, spinal foramen ; 6,
tuberous base of spinous process;
7, posterior articular face of body ;
8, 8, transverse processes ; 9,
superior spinous process ; 10, an-
terior articulation of body.
TEE VERTEBRA.
vertebral bodies augments progressively from before to behind. Their lateral
diameter, which determines that of the spinal canal, becomes, on the contrary,
less from the first to the tenth vertebra ; after which it assumes increasing
proportions to the last one. The articular surfaces, which serve for the mutual
contact of head and cavity, become
larger and shallower in proportion
as the vertebrae are more posterior.
The inferior spine on the body is
very salient and tuberculated in the
two first vertebrae, very acute in the
third and fourth ; it disappears in
the sixth and ninth, to reappear and
become more marked from the tenth
to the last. 2. The intervertehral
cavities, intended for the reception
"of the heads of the ribs, diminish
in depth and extent from the first to
the last. 3. The longest spi^ious pro-
cess belongs to the third, fourth,
and fifth vertebra ; those which
follow gradually decrease to the
eighteenth. Their width diminishes
from the second to the eighth : it
afterwards increases in a progressive
manner in the succeeding vertebrfe ;
from the second to the tenth vertebra,
the summit of the spinous process is
large and tuberculated ; in the last
seven it is flattened laterally. Their
obliquity is less marked as they pro-
ceed backwards ; in the sixteenth and
seventeenth vertebrae, the spinous
process is nearly vertical ; it inclines
slightly forward in the eighteenth.
Those of the tenth, eleventh, and
twelfth vertebrae are slightly curved
like an S. 4. The articular processes,
from the first to the tenth vertebra,
gradually contract and approach the
median line ; in the succeeding
vertebrae they, on the contrary,
increase, and become concave and
wider apart from those of the oppo-
site side. 5. The volume of the transverse processes and the size of their diarthrodial
facets, diminish from before to behind. In the three first vertebrte this facet is
concave ; in the first nine the articular facet looks outwards and backwards,
while the facet on the body looks forwards ; in the last the two facets are
directed forwards. These two facets are generally confounded in the seventeenth
and eighteenth vertebrae. The first dorsal vertebra much resembles the
prominens ; it is distinguished from it, however, by the presence of four
MIDDLE DORSAL VERTEBRA OF THE HORSE,
VIEWED FROM THREE TYPICAL LINES.
The first line, A B, passes from before to behind by
the most salient point of the transverse process,
intersecting the middle of the lateral facet in-
tended for the tuberosity of the rib, and of the
cavity on the border of the posterior articular
surface of the body. Below is the intervertebral
foramen, the spinous process, and the articular
facets on the base of the latter. The line c D
is tangent to the summit of the transverse pro-
cess and head of the vertebra ; it intersects the
anterior articular processes. The line M N is
horizontal, and tangent to the inferior face of
the body.
9i
TEE BONES.
diarthrodial facets on its extremities. It also differs from the other vertebrae by
the shortness of its spinous process, which terminates in a point ; by the size and
prominence ,of its articular processes ; and by the depth of its notches. The
last vertebra never has facets on the contour of its posterior cavity.
Ass. — Besides the smaller volume of the vertebrse, the following differential
characters will serve to distinguish these bones in this animal : 1. The spinous
processes, as far as the tenth vertebra, are a little more inclined backwards than
Fig. 20.
A DORSAL VERTEBRA OF THE HORSE AND ASS (THE ELEVENTH).
A, Vertebra of the Horse {anterior face). 1, Head ; 2, spinous process ;
3, 3, transverse processes.
B, Vertebra of the Ass (anterior face). Same description as for the horse.
a', Vertebra of the Horse (lateral face). 1, Head ; 2, spinous process ;
3, transverse process.
b', Vertebra of the Ass (lateral face). Same description as for the horse.
in the Horse, while the inclination forward of the latter is equally marked ; the
anterior part of the summit of the spinous process is in contact with a horizontal
plane, when the three last vertebrae of the Ass are laid on their anterior portion.
2. From the first to the tenth, the summit of the transverse processes lies behind
the margin of the anterior articular facets in the Ass, while it is beyond them
from the fourth in the Horse. From the eleventh to the thirteenth, the projection
of the transverse processes is equal to that of the anterior articular facets in the
THE VERTEBRA. 35
two species ; then the processes become predominant in the Ass (Fig. 20,
A', B', 3, 3), and they preserve this character to the eighteenth. 3. All the
transverse processes are" less oblique than those in the Horse ; also the line which
intersects, in the middle, the summit of these processes and their lateral articular
facet, passes always in front of the posterior facet on the body ; in the Horse,
this line traverses the latter facet, except in the first and fifth vertebra (Fig. 20,
A. B). 4. There are not seen on the nine last dorsal vertebrse of the Ass, the
anterior articular facets ascending to the base of the spinous process, as usually
occurs in the Horse. 5. Lastly, the notches of the intervertebral foramina are
nearly always closed by a bony bridge in the Ass, and only rarely so in the Horse.
The dorsal vertebrae in the Mule and Hinny off"er the same mixture of
particular characters which are found in their parents ; though it is not doubtful
that the vertebr^ of the Mule (Hinny) produced by the union of the female Ass
-with the Stallion Horse, more resemble the former than the latter, especially
in the transverse processes.
Differential Characters in the Dorsal Vertebrae of other Animals.
A. Ox.— In the Ox, these thirteen bones are longer and thicker than in the Horse. Their
flpinous processes are larger and incline more backward ; their transverse processes are very-
voluminous, and are provided with a convex facet from above to below ; while their posterior
notclies are nearly always converted into foramina.
Considered individually, they are more slender in the middle than at the extremities. Their
spinous processes diminish in width, especially at their summits, from the first to the eleventh
vertebra, and widen again in the two last ; they progressively increase in slope to the tenth,
after which they become more and more upright; tlie first four are the longest, and are nearly
the same in height ; the others gradually decrease.
In the first four or five vertebrae, the articular facet of the transverse processes, while
retaining its vertical convexity, is concave in an antero-posterior direction. This facet is
always absent in the last vertebra, and sometimes even in the preceding one. The two bones
terminating the dorsal region show, in addition, the articular processes disposed like those of
"the lumbar vertebrae.
B. Sheep and Goat.— The thirteen dorsal vertebrae of the Sheep and Goat are relatively
less strong than those of the Ox; their spinous processes are not so wide, and their posterior
notches are never converted into foramina.
C. Camel.— The dorsal vertebrae of the Camel, twelve in number, are remarkable for the
length of their bodies, and the height and width of their spinous processes. The transverse
processes are a little less detached than in the Ox, but they are very tuberous. The posterior
notclies are narrow, deep, and close to the base of the spinous processes; they do not form
foramina. The convexity or concavity of the articular surfaces of the body diminishes from the
first to the last bone; while the spinous processes increase in length and width from the first
to the sixth, and diminish in the last six. These processes are much inclined from the third
to the ninth ; then they gradually become erect in the last three.
D. Pig.— The Pig has fourteen dorsal vertebrae, which, in their general disposition, are
not unlike those of the Ox. As with that animal, the intervertebral foramina are double, each
-vertebral lamina being perforated laterally by an opening situated in front of the posterior
notch. In addition, the vertebrae of the Pig present this peculiarity, that their transverse
processes are generally traversed at the base by a single or multiple foramen, which communicates
with the preceding.
With regard to the special characters proper to some of the vertebrae, these are, as with the
other animals, very few, and may be described as follows: I. The transverse processes of the
four vertebrae preceding the last project but slightly. 2. In the fourteenth this process
resembles those of the lumbar vertebrae. 3. The articular facet of the transverse process in the
four last vertebrae is confounded with the anterior lateral facet corresponding to the head
of the rib. 4. The articular processes of the last five vertebrae are arranged like those of the
lumbar vertebrae ; and the prominence formed by the tubercle on the outside of the anterior
articular process replaces, to a certain degree, the transverse process of these vertebrae.
E. Dog and Cat.— These animals have thirteen dorsal vertebrae formed on the same model
36 TEE BONES.
as those of the Horse ; but their spinous processes are in general narrower and thicker. The
tenth always has its spiuouss process vertical, triangular, and terminated in a sharp point. The
last three liave no posterior facets tor tJie articulation of tlie heads of the ribs, and exhibit, in
the conformation of their articular processes, the same disposition as the lumbar vertebrae. In
the Cat, the transverse processes of the three last dorsal vertebrae are thin, sharp, and turned
backwards ; they never possess facets for the tuberosity of the ribs.
F. Rabbit. — The twelve dorsal vertebrae of this animal are similar to those of the Cat.
But the spinous process of the first nine is thinner and more oblique, while that of the three
last is higher and thinner than in the Cat. Besides, the transverse process is continued, in
the Rabbit, by a triangular portion which increases the width of the vertebral lamina. The
inferior face of the body is more hollowed in its middle portion, and the inferior crest is more
salient than in the Cat.
3. Lumbar Vertebra (Figs. 21, 22).
General Characters. — A little longer and wider than the dorsal vertebrae,
which they resemble in the arrangement of their bodies, these vertebrae are
characterized : 1. By their short, thin, and wide spinous processes, which are slightly
inclined forwards, and are provided at their summits with a scabrous tubercle.
2. By their largely developed trans-
^'S- 21- verse processes, flattened above and
below, and directed horizontally
outwards.^ 3. By the salient an-
terior articular pit'ocesses, hollowed
out on each side, and provided ex-
ternally with a tubercle for inser-
tion. 4. By their equally prominent
posterior articular processes, rounded
in the form of a half -hinge.
Specific Characters. — The
LUMBAR VERTEBRA (FRONT VIEW). charactcristics which may serve to
1. Body ; 2, its articular face ; 3, superior spinous distinguish these Vertebrae from
process ; 4, spinal foramen ; 5, anterior articular Qjjg another, are derived from the
processes ; 6, 6, tran>verse, or costiform processes ; , t , , . -, ,
7, posterior articular process. oody, and the spmous and trans-
verse processes. 1. From the first
to the last there is a progressive diminution in the vertical diameter of the bodies,
and an increase in their transverse diameter. The inferior spine on the body
becomes shorter and wider from the first to the last vertebra ; in the six vertebrae
it resembles an elongated triangle, the summit of which is directed forwards.
2. The spinous processes decrease in width from before to behind, and their
anterior border becomes more and more concave ; their summits are thickened
and tuberculated in the three first, and thin and sloping forward in the three last.
3. The transverse processes are longer in the middle vertebrae than in those placed
before and behind. The processes in the first and second vertebrae incline slightly
backward ; in the third they are more upright ; and in the succeeding ones they
are directed a little forward. In the last two they are remarkable for their thick-
ness ; in the fifth an oval-shaped articular facet is observed on their posterior
])order ; in the sixth, two are present — one in front, corresponding to the pre-
ceding, and one behind, slightly concave, meeting a similar facet on the sacrmn.
The fourth and fifth vertebrae very often correspond, at their transverse processes,
by means of analogous facets.
' Rudimentary ribs are sometimes found attached by ligaments to the extremities of the
transverse processes (Lesbre).
THE VERTEBR^\
37
Fig. 22.
According to Sanson, five is the natural number of lumbar vertebrae in the
specific type of African Horses (see remarks on the Spine in General). The
transverse processes in these animals also offer some peculiarities. Thus the
increase in their length ceases at the second, and from this an almost insensible
diminution occurs to the fifth. The transverse processes of the first lumbar ver-
tebra are alone less inclined backward ; they are perpendicular to the direction
of the body in the second and third, and inclined forward in the fourth and fifth.
The thoroughbred English Horse has sometimes five, sometimes six lumbar
vertebrae, but in every instance the
lumbar region is comparatively short
(Cornevin).
Ass. — The lumbar vertebrae in the
Ass, five in number, are easily distin-
guished from those of the Horse by the
characters special to their spinous and
transverse processes, and articular
tubercles.
1. The spinous processes are propor-
tionately longer that those of the Horse,
and they are also more inclined forward.
If their bodies rest on a horizontal plane,
and if a line be drawn tangent to the
posterior border of the spinous process,
an acute angle is always obtained at the
point of junction of the line and plane ;
but if this be done with the vertebras of
the Horse, there is at least a right angle.
2. The transverse processes increase
in length from the first to the second ;
they are nearly equal in the second and
third, and decrease suddenly in the ffth.
They are usually inclined downwards ; their posterior border and superior face,
near the body, are marked by a vasculo-nervous furrow, which is scarcely visible
in the Horse. Finally, it is not rare to find no inter-transverse articulation
between the two last.
3. The most important differential character is observed in the articular
tubercules. The diarthrodial facets are surmounted by a flat tongue of bone,
which is projected outwards in the direction of the summit (see Fig. 23, A, B, 4,
4). This piece gradually becomes lower from theirs;* to the fifth vertebra ; in the
first, it projects beyond the articulation by more than one-fourth of an inch, and,
up to a certain point, resembles the condition observed in the Rabbit or Dog.
In the Mule there are sometimes six, sometimes only five, lumbar vertebras.
These have the spinous and transverse processes somewhat as in the Horse ; their
articular tubercles resemble those of the Ass.
In the Hinny, of which opportunity has rarely been had for study, Goubaux
and ourselves have found five lumbar vertebrae, which, in their shape, much
resembled those of the Ass.
UPPER SURFACE OF LUMBAR VERTEBRAE.
, SuQimit of spinous process ; 2, 2, anterior
articular jirocesses ; 3, 3, posterior articu-
lar processes ; 4, 4, transverse processes.
Differential Characters in the Lumbar VERTEBRiE of other Animals.
A. Ox, Sheep, and Goat. — The six lumbar vertebrae of the Ox are longer and thicker
than those of the Horse. The transverse processes are also generally more developed, are
38 THE BONES.
coDcave on the anterior border, convex on the posterior, and incline slightly downward, with
the exception of the two first, which remain nearly horizontal. They increase in length from
the/r«< to the fourth vertebra ; in the latter and the fifth, they are nearly of the same dimensions ;
in the last they suddenly become shorter. Their width gradually decreases from before to beliind.
In the fifth and sixth vertebrae, these processes have no articular facets between them and the
sacrum, these being only met with in Solipedd. The articular processes are prominent, and
further removed from the median line as they belong to posterior vertebrae.
«
Fig. 23.
A LUMBAR VERTEBRA OF THE HORSE AND ASS.
A, Lumbar vertebra of the Horse {anterior face). 1, Head ; 2, 2, transverse processes ;
3. spinous process ; 4, 4, articular tubercles.
B, Lumbar vertebra of the Ass {anterior face). Same description as for the horse.
In the Goat the transverse processes are more inclined downwards.
In the Sheep, on the contrary, the processes of the six or seven vertebrae ascend towards
their extremities.
B. Camel. — Apart from number, which is seven, the lumbar vertebrae of this animal offer
nearly the same features as those of the Ox.
C. Pig.— The lumbar vertebrae of the Pig greatly resemble those of ruminant animals. It
commonly happ( ns that seven are met with ; but in this case the supplementary vertebra is
generally a sacral one. It is not denied, however, that seven lumbar vertebrae may exist in the
Pig, along with the normal number of sacral vertebrae.
D. Dog and Cat.— In the Dog and Cat, the lumbar vertebrae, seven in number, are
remarkable for their strength, due to their length, thickness, and the development of the
eminences for insertion. The spinous process is low, and becomes acute in the last vertebra.
TEE VERTEBRA. 39
The transverse processes incline very much forward and downward ; they become longer from
the first to the second-last bone ; in the latter they become contracted, and in the seventh
vertebra they are still more diminislied, and terminate in au obtuse point. The tubercle of the
anterior articular process is extremely prominent, and the posterior notches are surmounted bv
a small, very acute prolongation, directed backwards, which becomes more developed towards
the anterior vertebrae. This small prolongation exactly represents the transverse process of the
dorsal vertebrae.
E. Rabbit.— They are stronger than those of the Cat, and the first three have on the lower
surface of their bodies a very salient crest, which simulates a real inferior spine ; the others
have a median crest which gradually decreases towards the last bone. The tubercle surmount-
Fig. 24.
LUMBAR VERTEBRA OF THE CAT AND RABBIT.
A, Second, third, and fourth lumbar vertebrcB of the Cat (inferior face}. 1, 1, 1,
TraDsverse processes ; 2, 2, 2, crest on the inferior face of the body; 3, articular
tubercles of the first vertebra.
B, Second, third, and fourth lumbar vertebra of the Babbit (inferior face}. 1, 2,
Same signification as in preceding.
C, Third lumbar vertebra of the Cat (lateral face}.
prolongation; 2, ditto posterior prolongation; 3,
4, 4, posterior ditto; 5, spinous process.
D, Third hcmbar vertebra of the Babbit (lateral face}.
prolongation ; 2, ditto posterior prolongation ;
1, Transverse process, anterior
I, anterior articular tubercles;
1, Transverse process, anterior
, anterior articular tubercle :
4, 4, posterior articular tubercles : 5, spinous process.
ing the posterior notches is more developed than in the Cat. The spinous process is prolonged
backward by a translucent bony plate, wliich disappears in the last two. The anterior articular
tubercles are more developed, more erect, and nearer the median line, than in the Caruivora.
Lastly, the transverse processes are relatively longer, and those of the first are remarkable for
the notched enlargement they offer at their free extremities.
4. Sacrum (Fig. 25).
The sacrum results, as already stated, from the consolidation of five vertebrse.
This single bone articulates, in front, with the last lumbar vertebra ; behind,
with the first coccygeal bone, and on the sides with the ossa innominata. It is
triangular, flattened above and below, and from before to behind describes a
slight curve upwards. It offers for study a superior and an inferior face, two
borders, a base, a summit, and a central canal — the extension of the spinal canal.
Faces. — The superior face presents, on its middle, the spinous processes of the
THE BONES.
sacral vertebrae, which together constitute what is called the sacral or supersacral
spine. These processes are united at their base only, and remain isolated for the
remainder of their extent ; they all incline backwards and terminate, with the
exception of the first, by a tuberous summit, which is often bifid ; their length
diminishes from the second to the fifth bone. On each side of the sacral spine
exists a groove, at the bottom of which are four openings — the super-sacral Jara-
raina. These orifices open into the spinal canal, and communicate with four
analogous, but wider apertures, pierced at the inferior face of the bone, and for
this reason named the sub-sacral
Fig- 25. foramina. The inferior face is
smooth, and shows traces of the
N^L ,m^''''. J^S&^fi^^^^ '''•■' primitive separation of the vertebral
^^■-^'"^^^P^^^^^^^i^mS^ V bodies ; the sub-sacral foramina,
~ ' ' ^ which represent, with the corre-
sponding super-sacral openings, the
intervertebral foramina of the other
regions of the spine, are observed
on this surface.
Borders. — The hvo borders, thick
and concave, form, posteriorly, a
rugged lip ; in front, they present
an irregular surface inclining ob-
liquely from above to below, from
within outwards, and from before
to behind. This surface, which is
intended for the articulation of the
sacrum with the ossa innominata, is divided into two parts : one, the inferior —
named in Man the auricular facet — is slightly undulated and diarthrodial ; the
other, the superior, serves for ligamentous insertions.
Base. — This offers : 1. On the median line, the anterior orifice of the sacral
canal, and the anterior articular surface of the body of the first sacral vertebra,
which is oval and slightly convex. 2. On the borders, the articular processes and
anterior notches of this vertebra, as well as the elliptical and somewhat convex
facets which bring it into contact with the transverse processes of the last lumbar
vertebra.
Siimmit. — The summit, thrown back, presents : 1. The posterior orifice of the
sacral canal. 2. The posterior articular surface of the body of the last sacral
vertebra. 3. The vestiges of the articular processes and posterior notches of that
vertebra.
Sacral canal. — This is the portion of the spinal canal which is channeled out
of the sacrum ; it is triangular, and diminishes in width from before to behind.
The sacrum of the Ass much resembles that of the Horse ; nevertheless, it is
possible to distinguish it by the shape of the articular tubercles of the first sacral
vertebrae, which resemble those of the articular tubercles of the lumbar region,
and the traces those tubercles have left between the sacral vertebra3, especially
between the first.
LATERAL VIEW OF SACRUM.
1, Articular surface of body ; 2, 3, articular surfaces
corresponding to those on the transverse processes
of the last lumbar vertebra; 4, spinal foramen; 5,
auricular facet; 6, anterior articular processes;
7, inferior or sub-sacral foramina ; 8, superior
spinous processes ; 9, summit or coccygeal ex-
tremity.
Differential Characters in the Sacral Vertebra op other Animals.
A. Ox. — The sacrum of the Ox is more voluminous and curved than that of the Horse
The spinous processes are entirely consolidated, and are surmounted by a thick rugged lip ;
THE VERTEBRAE. 41
they are bordered at their base and on each side by a ridge that represents the rudiments of the
articular processes. The lateral borders are sharp and bent downwards. The surfaces that
serve to unite the sacrum to the ossa innominata have a somewhat vertical direction. There
are no lateral facets on the base of the bone, for the union of the sacrum with the transverse
processes of the last lumbar vertebra.
B. Sheep and Goat. — In the Sheep and Goat, the sacrum is shorter ; sometimes the con-
solidation of the spinous processes is late, or never occurs.
C. Camel. — Sacrum short ancl composed of four vertebrae; broad and curved on its inferior
face. The spinous processes, rather low, are strong and free throughout their extent. The
auricular facets are cut very obliquely.
D. Pig. — This is formed by four vertebrae, which are a long time in becoming fused
together ; and it is often difficult to discover where the sacrum ends and the coccyx begins.'
The spinous processes are entirely absent. The vertebral laminae are not consolidated ; so that
the spinal canal is half cut through in its upper portion, as in the cervical region ; this canal is
also much compressed above and below.
E. Dog and Cat. — The three vertebrae which form the sacrum of Carnivora are early con-
solidated. The sacral spine constitutes a thin sharp ridge, while the lateral surfaces for
articulation with the ossa innominata are turned quite outwards, and are nearly vertical.
F. Rabbit. — Relatively longer than tliat of Carnivora, the sacrum of this animal is remark-
able for the presence of four vertebrae, the spinous processes of which are isolated from each
other.
5. Coccygeal Vertebe^.
The coccygeal region, or coccyx, comprises from fifteen to eighteen degenerate
vertebrae, which gradually diminish in thickness from the first to the last. In the
first three or four, nearly all the characteristics of true vertebrae are found ; they
show a vertebral foramen, a body, a spinous process, and transverse processes,
directed backwards ; the articular processes only are altogether absent. In the
succeeding vertebrae, these characters become effaced ; the vertebral laminte do not
join completely, and the vertebral canal is only a simple groove, which, gradually
decreasing in depth, at last entirely disappears. The insertion eminences also
become less salient, and the coccygeal vertebrae are soon reduced to small bony
cylinders, narrow in the middle and wider at both extremities, with a convex
articular surface at each end (except the last, which has only one articular surface).
These small cylinders — the last traces of the vertebral bodies — are each developed
from three centres of ossification ; they are very spongy and light. The first
coccygeal vertebra is frequently consolidated with the sacrum in aged animals.
Differential Characters of the Coccygeal Bones in other Animals.
A. Ox, Sheep, and Goat. — In proportion, the coccygeal vertebrae of ruminants are stronger
and more tuberous than those of the Horse. The anterior articular processes exist in a rudi-
mentary condition.
B. Camel. — Fifteen to eighteen in number, they are not so strong and are less tuberous
than in the Ox. The first six are channeled by a triangular canal.
C. Pig. — These vertebrae in tlie Pig are more particularly distinguished by the presence of
articular processes, by means of which the foremost bones correspond with each other.
D. Dog and Cat. — In these animals, the vertebrae of the coccyx are very strong and
tuberous. The first five or six are as perfect as the true vertebrae, and comport themselves in
every respect like them. The last are small V-shaped bones, which M. Goubaux has described
by the name of hypMoid bones.
E. Rabbit. — The coccyx of the Rabbit is analogous to that of the Cat.
' This can always be made out, however, by consulting the disposition of the articular pro-
cesses. Thus, in the sacral vertebrae these eminences — if we except the anterior ones of the
first and the posterior of the last — never exist except in a rudimentary state ; while in the other
five coccygeal vertebrae they reappear with all their characters.
12 THE BONES.
The Spine in General.
The vertebral column has now to be considered in its entirety, and examined
successively in its superior face, its inferior face, its lateral faces, and its spinal
canal. Afterwards its direction and mobility will be noticed.
Superior surface. — This presents, on its median line, the series of spinous pro-
cesses. But little salient in the cervical region, these eminences are much
developed in the dorsal and lumbar, where they constitute a long crest — the
dorso-Iumbar spine, as well as in the sacrum, where they form the sacral spine.
They soon disappear in the coccygeal vertebrae. Outwards, and on each side of
these processes, is seen a succession of tubercles for insertion, represented iu the
cervical and lumbar vertebrae by articular processes, and in the dorsal vertebrae
by the superior or rugose portion of the transverse processes. These tubercles
are disposed in line, and separated from the spinous processes by a channel
designated the vertebral groove, which is more or less deep and wide. It is on
these, and on the spinous processes, that the extensor muscular fascicuU of the
spine receive the greater portion of their fixed or movable insertions.
Inferior surface. — Wide at the neck, this surface becomes narrow in the dorsal
region, to be again widened at the lumbo-sacral region, and once more contracted
at the coccyx. Crests more or less developed, which divide the vertebral bodies
into two lateral portions, right and left, are remarked.
Lateral surfaces. — These offer for study the thirty-six intervertebral foramina,
through which the spinal nerves pass. They exhibit besides, in the neck, the
transverse processes ; in the back, the external facets of these processes, and the
intervertebral facets, all destined to sustain the heads of the ribs ; on the loins,
the transverse or costiform processes. It may be remarked that the ribs and the
transverse processes of the neck and loins furnish points of insertion to the
powerful muscles which produce the lateral movements of the spine. In the sacrum,
the lateral faces are formed for the articulation of the spine with the ossa
innominata.
Spinal canal. — This canal communicates, in front, with the cranial cavity.
Very wide in the atlas, for the reception of the odontoid process and to permit
the rotatory movements of the head without injury to the spinal cord, this canal
suddenly diminishes in the axis. It again dilates at the termination of the
cervical region and the commencement of the dorsal ; there the spinal cord
presents a greater volume, and the movements of the spine are very extensive.
Towards the middle of the back, the spinal canal offers its smallest diameter ; it
widens from this part to the lumbo-sacral articulation ; after which it contracts
rapidly, and disappears altogether near the fourth or fifth coccygeal vertebra.
The lumbo-sacral dilatation coincides with the enlargement of the cord in this
region, and with the enormous quantity of nerves lying beside it.
Direction of the Spine.— The spine does not extend in a straight line from the
head to the posterior extremity of the body. If it is followed from the caudal
extremity — which is free and looks downwards — to the anterior extremity, it will
be observed that it passes upwards and forwards, forming a convex inflexion
corresponding to the roof of the pelvis. In the lumbar and posterior half of the
dorsal region, it is nearly horizontal and rectilinear ; thence it descends to the
cervical region, where it again rises and forms two curves — one, posterior, bend-
ing upwards, the other anterior, passing downwards. This direction "of the spine
gives it the form of a console.
THE VERTEBRA. 43
MoMity of the Spine. — In the cervical region, the almost total absence of
spinous processes, the great development of the articular processes, and the very
short curve described by the surfaces of contact of the vertebral bodies, allow
the spine very extensive and varied movements. In the dorsal region, however,
these movements are very limited, the spinous processes and the costal arches
preventing the play of the vertebrae on each other. In the lumbar region, the
spine can be flexed and extended more than in the dorsal ; but its lateral move-
ments are quite as restricted, owing to the presence of the transverse processes and
the reciprocal union or dovetailing of the articular processes. Lateral motion is
even rendered impossible in the posterior half of this region, from the manner
in which the transverse processes are adapted to each other. It may be remarked,
however, that this disposition singularly favours the integral transmission of the
propulsive efforts communicated to the trunk by the posterior extremities.
The sacral vertebrae, having to afford the ossa innominata a solid fixed point,
could not preserve their independence and mobility if they were like the other
vertebrae ; they are consequently consolidated into a single piece, which fulfils all
that is required of it in this respect. In the coccyx the spine again recovers its
mobility, and to an extent more marked than elsewhere ; the bones, articulating
with each other by means of convex surfaces, and having no long processes at
their extremities, are placed in the best possible conditions for effecting varied
and extensive movements.
Varieties in the Vertebral Column.
To anatomists, the bones of the spine have frequently offered curious varieties
in their shape and number.
1. Shape. — Goubaux has observed varieties of this kind in the last two cervical
vertebrae of the Horse. In one instance, the sixth had the transverse process
biscuspid on the left and tricuspid on the right. This anatomist has collected
several similar examples. Husson has found the sixth cervical vertebra with a
prolongation deficient in the transverse processes ; and the seventh, on the con-
trary, with an additional prolongation.
The dorsal vertebra have also exhibited varieties in shape. Daubenton has
referred to the skeleton of an Ass, in which the last vertebra had on one side
only a transverse process like that of the lumbar vertebrae. We have seen this
variation in the Horse.
In the lumbar region, Goubaux has noticed — as we have done — the fourth and
fifth vertebrae sometimes articulating by their transverse processes ; the articula-
tions may even be fused. Sometimes the transverse processes of the first lumbar
vertebra articulate at their base with the body of the bone, and become floating
ribs.
Thomas has remarked an interesting variation in the sacrum. He found in
the Sheep a long, costiform, transverse process on one of the sides of the first
sacral vertebra. The last vertebra in this region sometimes shows, in the Dog — •
either to the right or left, or on both sides at the same time— one or more articular
facets on the transverse processes, uniting with similar facets on the first coccygeal
bone (Goubaux).
2. Number. — For a long time, instances have been accumulating of variations
in the number of bones in the spine ; but they do not form a very imposing
array, probably because it is difficult to observe them without making a special
and attentive study of the subject.
41 THE BONES.
These variations have been noted in all the regions of the vertebral column,
though they are rare in the cervical region. Sometimes they consist in a dimi-
nution, sometimes in an increase, in the number of the vertebrse.
a. So far as it is known, a decrease in the nimiber of the cervical vertebrae
in the domestic animals has not been observed. Goubaux has sometimes met
with eight cervical vertebrae, though, as the eighth offered relations with the first
rib, he was disposed to place it in the dorsal region. In this case the anomaly was
in the number of bones in the spine.
b. The dorsal region is more frequently abnormal. Bourgelat and Rigot
have dissected Horses which had only seventeen dorsal vertebra. Groubaux and
ourselves have seen similar instances, though the length of the animals afforded
no suspicion of modification in their spines. It is certainly more common to see
the nimiber of dorsal vertebrae increased to nineteen, as is proved by the observa-
tions of Bourgelat, Higot, Husson, Goubaux, and our own.
This increase is observed also in the asinine species. We have the skeleton
of an Ass in which there are twenty ribs on each side, and therefore twenty
dorsal vertebrae. In the Ox, fourteen dorsal vertebrae have been found.
c. The lumbar region is still more frequently modified. The Horse at
times has only five lumbar vertebrae (Daubenton, Chauveau, Goubaux, Sanson,
and several German anatomists) ; the Ass only four (Goubaux). In the other
animals — the Dog, for example — an increase in nunlber has been remarked ;
Girard has seen eight lumbar vertebrae, instead of seven. Goubaux and ourselves
have on several occasions seen seven lumbar vertebrse in the Sheep.
d. The sacrum has often one or two pieces more in old subjects, due to
the fusion of the first or second of the coccygeal vertebrae with its posterior
extremity. At other times, the supernumerary piece is situated at the base.
Earely is the number of sacral vertebrae diminished ; Goubaux has only met with
one instance in which there were four sacral vertebrae in the Horse.
e. The number of coccygeal bones is extremely variable ; and in order to
be convinced of this, one has only to look at the tables drawn up by anatomists.
Nevertheless, it is certain that the normal number is never less than seven or
eight, as Bourgelat stated in the first edition of his Anatomie.
To resume, it is seen that all the regions of the spine may offer variations in
the number of vertebrte, and that these variations — rare between the neck and
the back — are, on the contrary, frequent at the two extremities of the lumbar
region. When the bones are deficient, the diminution is only apparent — that is,
the vertebra which is absent in one region is carried to the adjoining region. It
frequently happens, for instance, when a lumbar vertebra is missing, that the
sixth is united to the sacrum ; or when there are nineteen dorsal vertebrae, there
is one less in the lumbar region. It is not always sufficient to examine the
regions contiguous to the one which is modified, to gain an exact notion as to the
modification. In fact, a change in the number of vertebrae in a region may be
compensated for by an alteration in a distant region. In the museum of the
Lyons school, there is the skeleton of an Ox in which there are fourteen dorsal
vertebrae, with the normal number of cervical, but only four sacral. We also
possess the skeleton of a Horse which has seven lumbar vertebra, with the normal
number in the other regions, though the seventh bone is certainly the first sacral,
as it has all its characteristics ; and with regard to the fifth sacral bone, this
evidently comes from the coccygeal region. In the first skeleton, the increase
in the dorsal region has therefore been com^imsated for by a decrease in the sacral
THE VERTEBRA. 45
region ; and in the second, the augmentation in the lumbar region has been com-
pensated for by a diminution in the coccygeal region.
These transpositions occur more especially on the confines of the dorso-lumbar
and lumbo-sacral regions.
But the increase or decrease in the normal number of vertebrae is sometimes
absolute. Goubaux and Husson have found, in the Horse, nineteen dorsal
vertebrae with the normal number of the other vertebrae. The Ass with twenty
ribs already mentioned, had the usual number of vertebras in the other regions.
The first-named anatomist has counted, under the same conditions, seven lumbar
vertebrae in the Sheep. Hering, Rueff, Leyh, Sanson, etc., have found five lumbar
vertebrae in the Horse, without any modifications in any other parts of the
vertebral column. Sanson has even remarked, that in several oriental Horses
there are generally only five lumbar vertebrae. The presence of this anomaly is
always allied to a particular shape of the cranium and face. In the estimation
of Sanson, these characters are so important that they serve to distinguish specific
types. The specific type with five lumbar vertebrae is pecuHar to north-east
Africa, probably Nubia,
It is not intended in this place to discuss the opinions of Sanson and the
value of his specific types, but merely to remark that the number of vertebrae is very
liable to variation in each region of the spine, and that these variations are even so
frequent in animals of the same origin, that it would be perhaps premature to
attribute to the number of vertebra in a given region the value of an absolutely
specific character.
It has been attempted to explain these variations by an ancestral influence,
or by the influence of surroundings and exercise. But why might they not be
the consequence of irregularities in the fusion of the nuclei which constitute the
vertebral column of the foetus ? Fol has observed that at the fifth week the
human embryo has thirty such pieces, and that at the sixth week the thirty-
eighth, thirty-seventh, and thirty-sixth vertebrae have become one, while the
thirty-fifth has no longer perfect limits — so that an embryo measuring nineteen
millimetres has only thirty-four vertebrae. The spine of the embryo is com-
posed, therefore, of a larger number of pieces than that of the adult. The
reduction in number is due to fusions ; consequently, it is reasonable to admit
the possibility of variations in the extent of these fusions and the places where
they may occur. (For further details, see the Memoirs of Goubaux and Sanson,
in Robin's Journal de VAnatomie de la Physiologie, 1867 and 1868.)
Comparison of the Vertebral Column of Man with that of the Domesticated
Animals.
The vertebral column of Man is composed of twenty-nine bones : twenty -four vertebrae,
the sacrum, and four pieces constituting the coccyx. The twenty-four vertebrae are thus
distributed :
Cervical vertebrae 7
Dorsal „ 12
Lumbar „ 5
In all these vertebrae, the bodies are slightly excavated at the two extremities, while in the
domesticated animals, the superior or anterior is convex, and the inferior or posterior concave.
1. Cervical vertebrae. — These are wide and short. The spinous processes are moderately
developed and bifid at their summits ; the transverse processes are also divided into two
branches — a posterior and an anterior.
2. Dorsal vertebrx.—ln these vertebrae, the bodies increase in thickness from the first to
the last. In the first as well as in the last dorsal vertebrae, the spinous process is almost
46
THE BONES.
immediately directed backwards ; in the middle portion of this region these processes are very
obliquely directed downwards and backwards.
3. Lumbar vertebras. — The lumbar vertebrae are the strongest bones in the spine, and their
bodies are nearly as thick as those of the larger domesti-
cated animals. This enormous development of the lumbar
vertebrae in Man is related to his position as a biped. In
the fifth, the lower face of the body is cut very obliquely
backwards and upwards, and the transverse processes are
more voluminous than those of the other lumbar vertebrae.
4. Sacrum. — The sacrum is formed by the union oi
five pieces. It is very concave from above to below and
before to behind. In becoming united to the lumbar
region, it forms a salient angle in front, to which has
been given the name of promontory or sacro-vertebral angle.
The sacral spine is continuous or interrupted, according
to the subject ; it is always bifid inferiorly.
5. Coccygeal vertebras. — These are little bones or flat-
tened tubercles, four in number, rarely five, and usually
consolidated. Tbe coccyx is conical in shape. Its base
shows two processes directed upwards, which are called
the cornua of the coccyx. Its summit is often deviated
to the right or left.
Article IL— The Head (Fig. 26).
The head is a large, bony, quadrangular
pyramid, elongated from above to below, sus-
pended by its base to the anterior extremity of
the spine. Its direction varies with the atti-
tudes of the animal, but we will suppose it,
for convenience of description, to be nearly verti-
cal. It is formed of a great number of particular
bones, which are only distinct from one another
in very young animals ; for well before the adult
period is reached, the majority of the bones are
united and cannot be separated.
The head is divided into two parts : the
cranium and the face.
horse's head (front view)
I, Occipital tuberosity; 2, origin
of the mastoid crest ; 3, parietal
bone ; 4, saggital suture ; 5, junc-
tion of the parietal and temporal
bones ; 6, zygomatic arch ; 7,
frontal bone ; 8, frontal suture ;
9, temporal fossa; 10, supra-orbital
foramen ; 11, 12, lachrymal bone ;
13, malar bone ; 14, nasal border of
frontal bone ; 15, nasal bone ; 16,
suture of nasal bones; 17, super-
maxillary bone ; 18, infra-orbital
foramen ; 19, anterior, or pre-
maxillary bone; 20, foramen in-
cisivum ; 21, incisor teeth (young
mouth).
Bones of the Craniam.
The cranium, or upper part of the head, is
composed of seven flat bones, five of which are
single : the occipital, parietal, frontal, sphenoid,
and ethmoid; one only, the temporal, is double.
These bones circumscribe a central cavity, the
cranial, which communicates behind with the
spinal canal, and lodges the principal portion of
the nervous centres — the brain.
1. Occipital Bone (Fig. 26, 1).
The occipital bone occupies the superior extremity of the head, which it
supports from the anterior extremity of the spine. This bone is very irregular
m its form, aud is bent at a right angle in front and behind. It has an external
TEE HEAD. 47
and an internal face, and a circumference which brings it into contact with the
adjoining cranial bones ; the latter is subdivided into two anterior lateral borders,
two posterior lateral borders, an anterior and posterior salient angle, and two
lateral re-entering angles.
Faces. — The external face is divided into three portions by the double flexure
of the bone : one looks forward, another upward, and the third backward. It
exhibits : — 1. On the median line, and from before to behind : a, an antero-
posterior ridge which constitutes the origin of the parietal ridges, to be mentioned
hereafter ; b, a transverse, voluminous, and very prominent eminence, marked
posteriorly by deep imprints, with a medium projection named the cervical
tuberosity ; this is the external occipital tuberosity which, in the Horse, corre-
sponds at the same time to the superior curved lines of the occipital bone of Man.
This protuberance forms the culminating point of the head, and divides the
anterior and superior parts of the external face of the bone ; c, the occipital
foramen {foramen magnum), a large orifice that passes through the bone at the
posterior flexure, and establishes a communication between the cranial cavity and
spinal canal ; d, the external surface of the basilar process — a narrow and thick
prolongation formed by the bone as it passes to meet the sphenoid : this surface
is convex laterally. 2. On the sides : a, A sharp crest which prolongs, laterally,
the superior curved lines, and descends on the middle of the lateral anterior
border, to be continued with the superior root of the zygomatic process and the
mastoid crest of the temporal bone ; b, Linear imprints, parallel to the latter,
and prolonged on the base of the styloid process : they are destined for the
insertion of the small oblique muscle of the head, and represent the inferior
curved lines of the occipital bone of Man ; c, Within these imprints is a slightly
roughened cavity for the insertion of the posterior recti muscles ; d, The two
condyles — articular eminences with a double convexity, one superior, the other
inferior : these eminences are situated on each side of the occipital foramen
{foramen magnum), and correspond to the anterior cavities of the atlas ; e, More
outwards are the two styloid {paroccipital) processes, or jugular eminences — long
projections flattened on each side, terminated in blunt points, directed backwards,
and separated from the condyles by a deep space, the stylo-condyloid notch ; f.
Under the condyles is the condyloid fossa — a smooth depression, pierced at the
bottom by the condyloid foramen, which penetrates the cranium.
The internal face of the occipital bone is concave, and shows : behind, the
foramen magnum ; above, an uneven surface, which forms the roof of the
cerebral cavity ; below, the superior face of the basilar process, slightly hollowed
into a groove ; on the sides, the internal orifice of the condyloid foramen.
Circumference. — The anterior lateral borders are thick, and are united by
suture with the parietal bone, and with the tuberous portion of the temporal
bone by the harmonia suture. The posterior lateral borders are sharp, and
constitute the sides of the basilar process ; each concurs in the formation of the
occipito-spheno-temporal hiatus, also termed the foramen lacerum basis cranii — a vast
irregular opening, extending from above downwards, penetrating the cranium, and
divided by a ligament, in the fresh state, into two portions, one inferior, the
anterior foramen lacerum, the other superior, the posterior foramen lacerum. The
anterior angle, which is dentated, is dovetailed into the parietal bone. Theposterior
angle is very thick, and forms the summit of the basilar process ; it is united by
suture with the body of the sphenoid. The lateral re-entering angles, or jugular
notches, correspond to the point where the bone is bent posteriorly ; they separate
48 THE BONES.
the anterior lateral from the corresponding posterior lateral border, and are occupied
by the petrous portion of the temporal bone.
Structure. — The occipital bone contains much spongy substance.
Development.— li is developed from four centres of ossification ; one, the
anterior, is single, and forms the occipital tuberosity ; another, the posterior,
also single, forms the basilar process ; the other two are pairs, and comprise each
a condyle, with a styloid process and the corresponding condyloid foramen.
The occipital bone in the Ass is distinguished by the prominence of the
external occipital tuberosity (see the Head in General), by the depth of the
groove (mastoid) which com^ses over the outer face of the styloid process, and
by the articular surface prolonged to the origin of the basilar process, which
constricts it in a circular manner.
Differential Characters in the Occipital Bone op other Animals.
A. Ox. — The occipital bone of this animal does not show any anterior elbow, neither does
it form a portion of the iinierior part of the head. The external occipital tuberosity is obtuse,
and givts rise on each side to the superior curved lines.
The styloid processes are short and much bent inwards. Tlie basilar process, wide, short,
and thick, has a groove in the middle of its external face ; this groove is sometimes absent in
the Sheep and Goat.
The condyloid foramina are double, sometimes triple ; the superior foramen does not pass
directly into the cranium, but goes to a vast conduit that opens behind on the lateral margin
of the occipital foramen, and wliich terminates in front by two orifices, one entering the parieto-
temporal canal, the other opening on the external surface of the bone. The foramen lacerum
is divided into an anterior aud posterior foramen, by the mastoid portion of the temporal
bone.
B. Sheep and Goat. — The inner tuberosity is only marked by a slight prominence of the
internal plate of the bone. In the occipital bone of these animals are found the peculiarities
noted in that of the Ox ; the groove on the basilar process is sometimes absent, and in the
Sheep the superior curved lines are very salient and occupy the summit of the head. This
feature is still more marked in the Goat, and also more in the Cervine species, in wliich this
bone somewhat resembles that of the Horse.
C. Camel. — The bone shows a double angle as in Solipeds. In its anterior and superior
portions it resembles that of the Horse, and in its posterior portion that of the Ox. The crest,
which constitutes the origin of the parietal crests, as well as the superior curved lines, are
thin, sharp, and very high. The styloid processes are short, wide, thick, and articulated by
harmonic suture with the tuberosity of the temporal bone. The superior curved lines are
scarcely marked in young animals.
D. Pig. — The occipital bone in this animal is not bent anteriorly; but the transverse
protuberance representing the curved lines forms, nevertheless, as in the Horse, the summit of
the Head. This eminence, which is excavated on both sides on the posterior face, unites in
front with the parietal bone, which abuts on the occipital at an acute angle. There is no
externa] occipital protuberance, properly speaking, and the styloid processes are very long and
directed downwards.
E. Camivora.— The external occipital tuberosity is very strong and high. The external
occipital crest is absent or little marked ; the styloid processes are short. The foramen lacerum
is divided into two portions by the mastoid process, and the basilar process is wide, long, and
thick, and hollowed on the side by a channel that joins a similar one in the temporal bone to
form a large venous canal. Tliis last communicates, behind, with the posterior foramen
lacerum, and opens, in front, in the cranium, where it is continuous with the cavernous groove
of the sphenoid. The anterior angle forms a very marked prominence, which is deeply fixed
into the parietal bone, and partly constitutes the internal occipitnl process of that bone. The
latter does not show the lateral excavations at its base; they are found lower, towards the
summit of the petrous bone, on the sides of the occipital. The parieto-temporal canals are,
nevertheless, continued to the base of the process, which they traverse to open into its interior.
In the most intelligent breeds, the occipital foramen is deeply notched above (Faure).
THE HEAD.
2. The Parietal Bone (Fig. 26).
The parietal is a wide and thin bone, very much arched to form the roof of
the cranial cavity. It is bounded above by the occipital bone, below by the
frontal, and laterally by the two temporal bones. It offers for study an external
and internal face, and a circumference divided into four regions or borders.
Faces. — The external face is convex. It exhibits two curved ridges with
concavity directed outwards ; these two crests, which are termed the parietal
ridges, approach each other and unite superiorly, to be continued with the antero-
posterior ridge of the occipital bone ; below they diverge and proceed, one on
each side, to join ike supra-orbital process. They divide the surface of the bone
into three portions : two lateral, which are rough and traversed by vascular
channels, forming part of the temporal f ossa3 ; the
third, or middle, is plane, smooth, and of a triangu-
lar form, and covered by the skin. The interjial
face is concave, covered by digital impressions,
and grooved by small vascular canals ; it offers,
on the middle line, and altogether above, the
parietcd protuberance. This trifacial and very
salient projection presents at its base, on each side,
an excavation elongated transversely, into which
opens the parieto-temporal canal, and which
lodges a venous sinus. It is continued, in front,
by a median crest, which is often replaced by a
slight groove — ^the saggital furrow, bordered by
linear imprints. Two other ridges, resulting from
the abutment of the lateral border of the bone
against the anterior face of the petrous bone, rise
from the sides of this eminence and descend to
the sphenoid bone ; they separate the cerebral
from the cerebellar cavity.
Borders. — The superior border is notched,
thick, and slightly dentated ; it articulates with
the occipital bone. The inferior border, slightly
concave, and deeply dentated, offers an external
bevel in its middle portion, and an internal bevel
on its sides ; it corresponds with the frontal bone.
The lettered borders are very thin, and are cut, at
the expense of the external plate, into a wide, sloping edge, which shows a groove
destined to form the parieto-temporal canal. A very prominent angle separates
each into two portions — an inferior, that articulates by suture with the squamous
portion of the temporal bone ; and a superior, curved inwards towards the centre
of the cranial cavity. The latter portion of the lateral border is in contact with
the anterior face of the petrous portion of the temporal bone, with which it
concurs to form the lateral crest that descends to the parietal protuberance.
Structure. — This bone contains much compact tissue, the spongy substance
existing only in its middle.
Development. — It is developed from two large lateral centres of ossification, to
which is added a single centre to form the parietal protuberance. In early life
the parietal ridges are absent.
head of the cat (posterior
aspect).
1, Occipital bone; 2, zygomatic
process of the temporal bone;
3, tympanic bulb ; 4, condyle of
the temporal bone ; 5, malar
bone ; 6, orbital process of the
malar ; 7, ditto of frontal bone ;
8, 8, palatine bones ; 9, 9, maxil-
lary bone; 10, premaxillary bone;
11, pterygoid bone; 12, sphenoid
bone ; 13, vomer.
50
THE BONES.
Differential Characters of the Parietal Bone in other Animals.
A. Ox. — The parietal bone in the Ox does not occupy the anterior aspect of the head, but
concurs with the occipital to form the base of the neck. It represents a very narrow osseous
plate, elongated transversely, and curved at its two extremities, which descends into the
temporal fossae to rest upon the sphenoid bone. There are no parietal ridges. The internal
protuberance is only marked by a slight elevation of the internal plate ; for the most part it
belongs to the occipital bone. The parietal bone of the Ox is developed from three centres
of ossification, and the middle nucleus is even primarily divided into lateral halves ; but these
centres «re consolidated with each other at an early period, as well as with the anterior
portion of the occipital. It does not aid in the formation of the
parieto-teniporal canal, and is excavated internally by cavities
which communicate with the frontal sinuses.
B. Sheep, Goat.— The parietal bone of the Sheep and Goat
is relatively much larger than that of the Ox. It participates in
the formation of the parieto-temporal canal, and has no sinuses.
C. Camel.— This bone occupies the anterior face of the
cranium ; but it is long, narrow, and deeply lodged between the
squamous portion of the temporal bone and the frontal bone, to
rest on the sphenoid. The parietal crests, thin and elevated, lie
against each other for nearly their entire lengtli, and are not pro-
longed to the frontal bone (Fig. 45). These crests do not exist at
an early age.
D. Pig. — The parietal bone is very thick ; it has two very
marked crests, which do not meet at their upper part (Fig. 28).
E. Dog, Cat. — In the Dog, the parietal bone is distinguished
by the great development of the temporal crests (Fig. 2li).
In the Cat there are scarcely any parietal crests, and the in-
ternal protuberance is replaced by two great transverse bony plates,
which separate the cavity of the cerebrum from that of the
cerebellum.
F. Rabbit.— Almost quadrilateral, the parietal bone of the
Rabbit has its temporal crests carried to near its lateral borders.
3. Frontal Bone (Fig. 26).
The frontal is a flat quadrilateral bone, the sides of
which are bent in the middle at an acute angle, and are
carried back, and a little inwards, to meet the wings of
the sphenoid bone. It assists in forming the cranial roof
and part of the face. It is bordered : above, by the
parietal bone ; below, by the nasal and lachrymal bones ;
and on each side, by the temporal bones. It offers for
study an external and an internal face, and four borders.
Faces. — The external face is divided, by the double
flexure of the bone, into three regions : a middle and
two lateral. The first, nearly plane, is lozenge-shaped,
is covered by the skin, and constitutes the base of the
forehead. It gives rise on each side, at the point where
it is inflected, to a long process, flattened above and
below, which curves backward, forming the orbital arch.
The superior or external face of this process is convex and slightly roughened ;
the internal face is smooth and concave, and forms part of the orbital fossa. Its
posterior border, thick and concave, is continued, inwardly, with the correspond-
ing parietal ridge, and outwardly with the superior border of the zygomatic
process. It limits, in front, the temporal fossa. The anterior border, also
concave, but thin, concurs in the formation of the orbital margin ; the summit,
head of the pig
(anterior face).
1, Summit of occipital
tuberosity. 2, parietal
bone. 3, frontal bone :
A, Supra-orbital fora-
men ; a', channel de-
scending from it. 4,
zgomatic process. 5,
malar bone. 6, lachry-
mal bone : b, Lachrymal
canals. 7, supermax-
illary bone : C, Inferior
orifice of the super-
maxillo-dental canal.
8, nasal bone. 9, pre-
maxillary bone.
THE HEAD.
thickened and denticulated, rests upon, and is united to, the zygomatic process
of the temporal bone ; the base is wide, and is traversed by an opening termed
the supra-orUtal, or superciUarij foramen. The two lateral regions of the external
face of the frontal bone are slightly excavated, and assist, for the greater portion
of their extent, to form the orbits. They often show, near the base of the
orbital arch, a small depression corresponding to the flexure described by the
great oblique muscle of the eye in passing through its pulley.
The interned face of the frontal bone is concave, and divided into two unequal
parts by a transverse ridge, corresponding to the
anterior border of the cribriform plate of the ethmoid
bone. The superior, the most extensive, is covered
with digital impressions, and belongs to the cranial
cavity. It exhibits : 1. On the median line, a slight
furrow, or a crest which is continuous, above, with the
median ridge of the parietal bone, and below, with
the crista-gaJU process. 2. On the sides, and in the
re-entering angle formed by the flexure of the bone,
there is a narrow slit, or mortise, which receives the
wing of the sphenoid bone. The inferior part is united,
on the median line, to the perpendicular plate of the
ethmoid. It assists in forming the bottom of the
nasal cavities, and presents laterally two large openings
which lead to the frontal sinuses — vast anfractuous
spaces excavated between the two plates of the bone.
Borders. — The superior border is denticulated and
cut obliquely in its middle portion, at the expense of
the internal plate, and on the lateral parts at the
expense of the external table ; it is in contact with
the parietal and squamous portion of the temporal
bone. The inferior, prolonged to a point in the middle,
is in apposition with the nasal bones through the
medium of a wide external bevel ; laterally, it is very
thin, faintly serrated, and articulates with the lachrymal
bone. The lateral borders, thin and irregular, present
two notches : one, the superior {incisura spJmioidaUs),
is wide and deep, and occupied by the wing of the sphe-
noid bone ; the other, inferior, is very narrow, and,
uniting with a similar notch in the sphenoid bone, forms
the orbital foramen, which opens into the cranium,
very near, but external to, the ethmoid fossa. Each of these borders, also, is
adapted, for a limited extent, to the corresponding palatine bone.
Structure. — The two compact plates of the frontal bone are separated by
spongy texture towards the middle and in the upper part ; they separate below
to form the frontal sinuses. Laterally, they are very thin and consolidated with
each other.
Development. — The frontal bone is developed from two lateral centres of
ossification, which only coalesce at a late period. In youth the cranial portion
of the bone forms, in front of the head, a large rounded protuberance standing
beyond the facial portion. This prominence disappears when the frontal sinuses
begin to be developed. These cavities do not exist at an early period of foetal
head of dog (anterior
face).
1, Occipital tuberosity; 2,
median spur of the occi-
pital bone ; 3, parietal
bone ; 4, origin of the pa-
rietal crests; 5, zygomatic
process ot the temporal
bone ; 6, frontal bone ; 6',
orbital process ; 7, malar
bone ; 8, lachrymal bone ;
9, nasal bone ; 10, super-
maxilla ; 11, inferior ori-
fice of the supermaxillo-
dental canal; 12, pre-
maxillary bone.
52 THE BONES.
life ; but commence to form about the fourth month of conception, by a process
of resorption, which removes the spongy substance interposed between the two
compact tables of bone, and may even cause the destruction of the internal table.
The sinuses enlarge with age, and remain during life separated from one another
by a vertical septum.
Differential Characters in the Frontal Bone of other Animals.
A. Ox, Sheep, Goat. — In Eumiaants, the frontal bone does not come in contact with
the temporal or palatine bones (Figs. 30, 31, 32).
In the Ox, this bone is extremely developed, occupying alone nearly one-half of the anterior
surface of the head. It is particularly distinguished by: 1. Its great thickness. 2, The
Fig. 30.
ox's head (anterior face).
1, Mastoid process ; 2, superciliary, or supra-orbital foramen ; 3, malar bone ; 4, lachrymal
bone ; 5, maxillary spine ; 6, inferior orifice of the supermaxillo-dental canal.
osseous conical cores which support the horns. These eminences, more or less long and curved,
very rugged, perforated by foramina, and grooved by small vascular channels, are detached
outwards from each side of the bone, near the summit of the head. The proce.-^ses which form
the orbital arches rest by their summits on the zygomatic bone. The supra-orbital foramen is
transforraeil into a veritable and frequently multiple canal ; its anterior orifice opens into a
vasculo-nervous groove, which ascends towards the base of the horns, and descends to near the
lower border of the bone. Between this groove and the base of the orbital arch is the frontal
boss. Thp orbital foramen entirely belongs to this bone. The inferior border is deeply notched
in its middle to receive the nasal bones; the frontal sinuses are prolonged into the horn-cores,
the parietal bone, and even into the occipital bone. ,
The frontal bones of the Angus breed of cattle (^polled cattle) have no horn-cores. The
ablation in the calf of the periosteum, followed by cauterization, at the point where appear
the osseous prolongations which serve as bases for the horns, prevents the development of
these appendages. Cornevin mentions that a farmer of Haute Marne has in this way muti-
lated the cattle bred on his farm for twenty-three years, and yet the mutilation has not become
hereditary. Fig. 31, representing the head of an Ox so mutilated, shows that the removal of the
THE BEAD.
53
periosteum in such animals has the effect of producing a considerable elongation and narrowing
of the upper part of the frontal bone.
In the Sheep and Goat, tlie frontal bone is relatively less extensive and strong than in the
Ox; it does not ascend to the summit of the head, and the frontal sinuses are not prolonged
beyond its superior border (Fig. 32).
B. Camel. — The frontal bone of this animal much resembles that of Solipeds. The
middle portion of its external face is triangular in shape, the base being wide, and the apex
fixed in the deep notch formed on the inferior border of the parietal bone; it is slightly
hollowed in the middle line, and convex on the lateral parts. The orbital arch rests on the
Fig. 32.
HEAD OF A HORNLESS OX.
ram's head (anterior face).
1, Occipital bone ; 2, parietal bone ; 3, core of right
frontal bone ; 4, the left core covered by its horn ;
5, supra-orbital foramen ; 5', channel descending
from it ; 6, lachrymal bone ; 7, malar bone ; 8, nasal
bone ; 9, supermaxillary bone ; 10, premaxillary
bone; 10', its internal process; 11, incisive open-
ing.
zygomatic bone, as in the Ox (Fig. 37). The supra-orbital foramina are transformed into
inflected canals, which open on the anterior face of the bone, near its middle.
On the circumference of the bone are several notches, some of which concur with the
other bones, to form foramina (orbital, nasal) ; two are seen to the right and left of the line of
union of the bone with the supra-nasal, and two others are in the orbital cavity. These open-
ings are partially closed by the Wormian bones ; they open into the upper compartments of the
turbinated bones.
In the young Camel, the middle portion is deeply excavated ; this excavation diminishes
as the animal advances in age, and as the frontal sinuses enlarge.
C. Pig.— The frontal bone of the Pig is very thick and short, and does not join the
temporal or zygomatic bones ; the orbital arch is completed by a ligament. The supra-orbital
foramen, disposed as in the Ox, abuts in a channel that descends on the nasal bones. The
* In the Museum of the Lyons Veterinary School.
54
THE BONES.
orbital foramen is formed by the frontal bone only. There is no mortise for the union of the
frontal with the sphenoid bone ; and the frontal sinuses are prolonged into the parietal. The
frontal bone articulates with the superior maxillarie.s (Fig. 28).
D. Carnivora. — In the Carnivora, the external face of the frontal bone presents in its
middle a more or less deep depression. The ori)ital arch is incomplete, and there is no supra-
orbital foramen or mortise on the inner face.
superior maxilLiry bones
anterior bones of the head op a fcetus
(horse) at birth, disarticulated, and
viewed from behind.
It unites with tht
(Fi-. 29).
E. Rabbit. — In this animal the frontal
bone is long and narrow, and the orbital
process is thin, elevated, and directed upwards
and backwards, but it does not reach the
zygomatic bone, and is deeply notched at its
4. Ethmoid Bone (Fig. 33).
The ethmoid bone, deeply situated
m the limit between the cranium and
the face, is enclosed between the frontal,
the sphenoid, the vomer, the palatine,
and the supermaxillary bones. It is
composed of three portions — a jjer-
pendicular plate, and two lateral masses.
The Perpendicular Lamina of
THE Ethmoid Bone. — Situated in the
mesian plane, and flattened on both
sides, this bone presents tu'o faces, a
left and right, and four borders.
Faces. — The faces, covered by the
., Occipital bone : 1, condyle ; 2, condyloid
foramen ; 3, styloid process ; 4, summit of
basilar process. B, Parietal bone : 8, j)arie-
tal protuberance; 9, channel which concurs
to form the parieto-temporal canal. C, Fron-
tal bone: 10, transverse crests separating
the cranial from the facial portion of the
bone; 11, frontal sinuses; 12, notch on the
lateral border occupied by the wing of the
sphenoid bone ; 13, notch for the formation
of the orbital foramen ; 14, summit of the
orbital process ; 15, supra-orbital foramen.
D, Perpendicular lamina of the ethmoid bone.
E, E, Lateral masses of the ethmoid bone :
16, the great ethmoid cell. F, Squamous
portion of the temporal bone : 17, Supra-
condyloid process ; 18, channel for the forma-
tion of the parieto-temporal canal. G, Pet-
rous portion of the temporal bone : 5,
mastoid process ; 6, internal auditory hiatus ;
7, opening for the Eustachian tube into the
tympanum, h, Lachrymal bone. I, Nasal
bone. J, Superior turbinated bone.
pituitary membrane, present, posteriorly, small sinuous crests ; elsewhere they are
smooth. A very narrow interval, constituting the bottom of the nasal cavities,
separates them from the lateral masses.
Borders. — The superior border looks towards the centre of the cranial cavity,
and constitutes what is called the ethmoidal ridge, or crista-galli ^wocess. It is
THE HEAD. 55
free, concave, and sharp, prolonged in front and above by the median crest of
the frontal bone, and confounded behind with the middle portion of the inferior
sphenoid. The inferior border is continuous with the cartilaginous plate which
separates the nasal cavities. When this plate becomes ossified, which is not
unfrequent, it is impossible to discover the point where it begins or the ethmoid
bone terminates. The middle Septum of the nose has been considered, and
justly, as a prolongation of the perpendicular plate (or lamina) of this bone.
The anterior border is consolidated with the vertical septum which separates the
frontal sinuses. The posterior border is joined above to the median plate which
divides the sphenoidal sinuses into two compartments. Below, it is fixed in the
groove of the vomer, and soon becomes confounded with that bone, which is
itself consolidated with the inferior sphenoid.
Lateral Masses of the Ethmoid Bone. — These are two large pyriform
tuberosities placed on each side of the perpendicular lamina, and offering for
study a middle portion, a base, and a summit. Each of these is formed by an
assemblage of numerous, extremely thin, osseous plates, curved into small and
very fragile convolutions. These, elongated from above to below, become
longer as they are more anterior ; they are attached by their superior extremities
to the transverse plate which separates the cranium from the nasal cavities, and
by one of their borders to a thin leaf of bone which envelops the lateral masses
outwardly. They have received the name of the ethmoidal volutes (or cells).
Middle portion. — This should be studied externally and internally
The external surface of each ethmoidal mass is divided into two sections :
an internal, making part of the nasal cavities ; the other, external, concurs in
forming the walls of the frontal and maxillary sinuses. The first, the least
extensive, is almost plane ; parallel to the perpendicular lamina, it is isolated
from it by the narrow space which forms the bottom of the nasal cavities ; it
presents several openings which separate the most superficial cells, and join the
internal canals to be hereafter noticed. The second, very extensive and convex,
looks outwards in front and behind, and is covered by an osseous plate traced
with shallow furrows, which correspond internally with the small crests to which
the cells are attached. This lamella is prolonged, inferiorly, a little beneath the
inferior extremity of these latter, and turns outwards to articulate with the
palate and superior maxillary bones ; superiorly, it coalesces with the sphenoid
and the orbital portion of the frontal bone.
Internally, the lateral masses are hollowed from above to below by extremely
diverging canals, which open inferiorly into the nasal cavities, and separate the
cells from one another. The latter are so incurvated that the internal cells
communicate with each other. There are some, however, which are completely
closed ; the anterior, or great cell, is frequently so.^
Base. — The base of each lateral mass looks upwards, and is formed by the
transverse septum between the cranium and the nasal cavities. This septum is
perforated by openings which give passage to the ethmoidal nerves ; it is named
the cribriform plate of the ethmoid bone. It is concave on the superior surface,
which constitutes the ethmoidal fossa, and convex on the opposite face, where
attachment is given to the superior extremities of the cells. It is consolidated
internally with the perpendicular plate ; the other points of its circumference
are attached to the sphenoid bone, and to the transverse ridge on the internal
face of the frontal bone.
' It is not rare to find it opening into the superior maxillary sinus.
96 THE BONES.
Summit. — The summit of each lateral mass is formed by the inferioi
extremity of the ethmoidal cells, which is directed downwards, towards the nasal
cavities. One, more volmninous than the others, is carried much lower, and
terminates by a rounded protuberance. It corresponds to the middle cornu
{concha media) of Man.
Structure of the ethmoid hone. — Very little* spongy tissue enters into the
composition of this bone, and this is only found near the anterior border of
the perpendicular plate.
Development. — The ethmoid bone is late in attaining its development, and
the adjoining bones are nearly completely ossified when it is yet entirely
cartilaginous. The bony transformation commences in it at the inferior ex-
tremity of the cells, and advances progressively from below upwards. The per-
pendicular plate is only ossified in part when the cells have passed through the
first half of the process ; at the same time it coalesces with the inferior
sphenoid. The cribriform plate is the last to become ossified, this transforma-
tion having scarcely been achieved when the animal is six or eight months old.
Differential Characters in the Ethmoid Bone of other Animals.
A. Ox, Sheep, Goat. — In Ruminants, the great ethmoidal cell is enormously developed,
and looks like a third turbinated bone prolonged beyond tlie usual two ; it has been named
the olfactory antrum. The bone is closely imprisoned between the adjacent bones, in con-
sequence of the slight development of the sinuses around it. This character otherwise belongs
to all the domesticated animals, except Solipeds (Fig. 36).
B. Camel.— The crista-galli process is very thick, and the ethmoidal fossae are narrow
and deep.
C. Pig.— The superior turbinated bone is very long, and the papyraceous plate appears in
the orbital cavity.
D. Dog, Cat. — The ethmoidal fossa is very deep, and the cells very developed and
diverticulated. The perpendicular lamina is at a late period consolidated with the sphenoid
bone.
5. Sphenoid Bone (Fig. 34).
The sphenoid bone is situated behind the cranium, between the occipital,
ethmoidal, palatine, vomer, pterygoid, frontal, and temporal bones. It is formed
by the union of two pieces, which have been sometimes described as distinct
bones — the anterior or inferior sphenoid, and the posterior or superior sphenoid.
It is now supposed, in the description, that this union has been completed.
It is a bone flattened before and behind, curved from one side to the
other, thick in its middle part, named the bodi/, and thin on the sides, which, in
their inferior half, are prolonged in the form of aJce, or U'ings. It has two
surfaces a,nd four borders.
Surfaces. — The exfermd surface is convex, and presents : 1. On the median
line, the external surface of the body, rounded from one side to the other, is
continued with that of the basilar process, and has marked muscular imprints
superiorly. 2. On the sides and from within outwards : (a) the Vidian (or
pterygoid) fissure, directed from above downwards, and continued by the Vidian
canal, a very smaU foramen which opens into the orbital hiatus ; (b) the sub-
sphenoidal, or pterygoid process, a long eminence, flattened on both sides, inclining
downwards, articulating with the palatine and pterygoid bones, and traversed at
its base by the Vidian canal ; (f) a little behind and above this eminence, the
superior orifice of the sub-sphenoidal (or pterygoid) foramen — a large canal which
bifurcates inferiorly ; (d) more in front, the orbital hiatus, a kind of vestibule into
THE HEAD.
F
Fig. 34.
which open, in common, the principal branch of the subsphenoidal canal, the three
supra-sphenoidal canals, the Vidian and optic canals, and the orbital opening :
this hiatus is surmounted by a thin and sharp bony plate, above which opens
the smallest branch of the subsphenoidal foramen ; (e) altogether without the
hiatus is remarked a smooth surface belonging to the wing of the sphenoid, and
which concurs to form the orbital cavity.
The internal face is concave from side to side. It shows : 1. On the median
line, and from before to behind, a small
projection united to the crista-galli ; the
optic fossa, elongated transversely in the
form of a shuttle, and presenting at the
bottom, and on each side, the superior
orifice of the optic foramen, a cylindrical
canal directed obliquely downwards, for-
wards, and outwards, to reach the orbital
hiatus ; the supra-sphenoidal or pituitary
fossa, also named the sella Turcica, a slight
depression, limited behind by a scarcely
noticeable transverse projection separating
it from the superior channel of the basilar
process. 2. On the sides, and in front, the
internal surface of the wings, depressed by
very superficial digital impressions ; more
behind and outwards, a fossa, elongated
from before to behind, which lodges the
mastoid lobule of the brain ; between this
fossa and the sella Turcica, two vertical
fissures — an internal, named the cavernous
sinus, and an external, wider and deeper,
for the passage of a large nervous branch.
These two fissures open below, near the
junction of the three supra-sphenoidal canals.
Two of these, which are very wide, are placed
one before the other, and separated only by
a slight partition. The superior of these con-
stitutes the great sphenoidal fissure {foramen
lacerum orhitale) ; the other, the lower, is the
foramen rotundum, and opens into the orbital
hiatus. The third, very small {foramen pathe-
ticiim), is situated outside the great anterior
canal, opens above the optic foramen, within
the bony mass surmounting the hiatus, and
sometimes on the free margin of this lamina.
Borders. — The superior is a little con-
cave, and shows, in its middle, the superior
extremity of the body, mammillated and articulated with the summit of
the basilar process ; on each side, two notches which circumscribe below the
occipito-spheno-temporal hiatus {foramen lacerum basis cranii). The internal
notch is the narrowest, and from its affording a passage for the internal carotid
artery, is called the carotid notch ; it is continued on the external face of the
POSTERIOR BONES OF THE HEAD OF A
FOETUS (horse) AT BIRTH, DISARTICU-
LATED AND viewed in FRONT.
A, Sphenoid bone : 1, ma.xillary notch ; 2,
carotid notch ; 3, groove for the passage
of the maxillary nerve ; 4, cavernous
sinus ; 5, optic fossa ; 6, great wing ;
6', unossified portion of the great wing;
7, notch for the formation of the orbital
foramen. B, Vomer. C, Palatine bone.
D, Malar bone. E, Supermaxilla : 8,
inferior orifice of the raaxillo-dental
canal. F, Premaxillary bone.
5^ THE BONES.
bone by a smooth excavation to which Rigot has given the name of carotid fossa.
The external is also prolonged on the exterior surface of the sphenoid, by a short
and wide fissure ; it lodges the inferior maxillary nerve. Outside this is another
very narrow notch, intended for the passage of the middle meningeal artery.
The fibro-cartilaginous substance that partly fills the occipito-spheno-temporal
hiatus, transforms these notches into foramina, the first of which is named the
carotid canal ; the second, the foramen ovale ; and the third, the foramen spinosum.
The inferior' border, also concave, is likewise divided into three portions, a middle
and two lateral. The first is thick, and formed by the inferior extremity of the
body ; it is excavated by two large cavities belonging to the sphenoidal sinus.
These cavities are separated from one another by a vertical osseous plate, often
perforated, which, at an early period, is fused with the perpendicular lamina of
the ethmoid bone. The very thin lateral portions form part of the circum-
ference of the wings ; they are notched near their union with the middle piece
to assist in the formation of the orbital foramen. The ttvo lateral borders are
thin and convex in their anterior half, as is also the contour of the wings, which
are mortised in the frontal bone. For the remainder of their extent they are
thick, denticulated, and bevelled at the expense of the external plate, to articulate
with the squamous portion of the temporal bone.
Structure. — This bone is compact on its sides, and spongy in its middle part ;
inferiorly, it is excavated by the sphenoidal sinuses.
Development. — It is developed from two principal nuclei of ossification ; a
superior forms the subsphenoidal process and the canal of the same name, the
Vidian fissure, pituitary fossa, fissures of the internal face, and the most posterior
of the great supra-sphenoidal canals ; the other, the inferior, forms that portion
of the body hollowed by the sinuses, the lateral alas,^ and the optic fossa and
canals. In meeting each other, these centres form the Vidian canal and the two
anterior supra-sphenoidal canals. They are not consolidated with each other
until a very late period ; for which reason they are sometimes described as two
distinct bones. M. Tabourin has even proposed to attach the description of the
inferior sphenoid to that of the ethmoid, because it is united with this bone a
long time before it is joined to the superior portion.^
Differential Characters in the Sphenoid Bone op other Animals.
A. Ox. — In the Ox, the subsphenoidal or pterygoid processes are large and thin The
subsphenoidal canal is absent. The sella Turcica is deep, and the bony projection separating
it from the basilar process is very high. The three supra-sphenoidal canals are converted into
a single, but wide one. There are no notches in tlie superior border, for the passage of the
internal carotid and spheno-spinous arteries. The oval foramen is entirely confined to this
bone.
B. Sheep. — In the Sheep, the osseous prominence that limits the pituitary fossa posteriorly
forms a lamina curving forwards, and prolonged at its extremities into two points, which
constitute' the posterior clinoid processes.
C. Camel.— The sphenoid is longer and tliicker than in the Ox. The subsphenoidal
or pterygoid processes are narrow and very thick. The oval foramen is relatively small. The
optic canals are covered at their internal ojiening by a bony plate. The optic fossa is nearly
on a level with the pituitary fossa.
D. Pig. — The sphenoid of the Pig is very short, but the subsphenoidal processes are
extraordinarily developed, and flattened before and behind. There is no subsphenoidal canal,
and the sella Turcica is deep, and limited behind by a very salient crest. A single canal
These wings are not analogous to those portions of the sphenoid bone in Man bearing the
( name. They are the processes of Ingrassias enormously developed.
Tabourin, Journal de Med. Ve'tifrinaire, p. 229. Published at Lyons, 1845.
THE READ.
replaces the tbiameu rotimdum and the great sphenoidul fissure, as in the Ox. The wings,
shghtly salient, are articulated by suture witli the frontal bone.
E. Dog, Cat. — The superior sphenoid of the Dog is very short, and bears, laterally, two
wide wings which ascend to the temporal fossa ; they correspond to those of the sphenoid bone
in Man. The inferior sphenoid is, on the contrary, very narrow, and its lateral prolongations,
or processes of Ingrassias, are reduced to very small proportions. The subsphenoidal or
pterygoid process is very short, and the canal is single, and communicates witli the foramen
rotundum. The pituitary fossa is shallow, limited behind and before by the posterior clinoid
and anterior clinoid processes, so named because of their being
compared to the four posts of an ancient bed. The supra-
sphenoidal canals are only two in number: one represents
the great sphenoidal fissure, the other the round foramen.
The carotid notch, joining a similar one in the temporal
bone, forms an opening which may be designated the carotid
foramen, because it gives passage to an extremely remark-
able loop the internal carotid artery describes after passing
through the carotid canal. The oval foramen is the same as
in the Ox.
In the Cat there is the same disposition, with the excep-
tion of no sphenoidal canal or carotid notch being present.
F. Rabbit.— The body of the sphenoid is short, tri-
angular, thick at its upper border, pierced in the middle by
an orifice which opens into the pituitary fossa. Tlie wings
are very developed ; the subsphenoidal processes, bifid, are
closely embraced by the pterygoids and palatine bones ; and
the optic fossa is replaced by a large foramen, which com-
municates at the same time with the two orbital fossae.
6. Tempokal Bone (Figs. 26, 33).
HEAD OF THE RABBIT (POS-
TERIOR face).
Occipital tuberosity; 2, sty-
loid process of the occipital
bone ; 3, condyle of ditto ; 4,
tympanic bulb ; 5, basilar pro-
cess of the occipital bone ; 6,
body i)f the sphenoid ; 7, ptery-
goid bone; 8, zygomatic bone ;
9, 9, condyles of the temporal
bone; 10, palatine bone; 11, 11,
superior maxillary bone; 12, 12,
premaxilla; 13, orbital pro-
cess of the fi-ontal bone ; 14, 14,
superior double incisors.
The temporal ■ bones enclose the cranial cavity
laterally, and articulate with the occipital, parietal,
frontal, sphenoidal, and malar bones ; also with
the inferior maxilla and the hyoid bone. Each
is divided into two pieces, which are never consoli-
dated in the horse ; one forms the squamous portion
of the temporal bone ; the other, the petrous portion.
They will be described separately.
Squamous -portion. — This is flattened on both
sides, oval, and slightly incurvated like a shell, a
shape to which it owes its name. It offers for
study an external and an internal face., and a circum-
ference.
Faces. — The external face is convex, and marked
by some muscular imprints, vascular fissures, and
openings which penetrate the parieto-temporal canal.
It forms part of the temporal fossa, and gives origin near its middle to the zygomatic
process — a long eminence which at first runs outwards, and soon curves forwards
and downwards to terminate in a thin summit. The base of this eminence forms,
in front, a concave surface belonging to the temporal fossa ; behind, it offers the
articular surface which corresponds with the maxillary bone. The latter is com-
posed of : 1. A condyle transversely elongated, convex above and below, and slightly
concave from side to side. 2. A glenoid cavity, limited below by the condyle, above
by a mammilif orm eminence, the supra-condyloid (or anterior mastoid) process^
' In Man this is represented by the inferior or vertical ramus of the upper root of the
zygomatic process.
60 THE BONES.
against %yhich rests the maxillary condyle when this bone is drawn backwards ; it
is immediately above this eminence that the inferior orifice of the parieto-temporal
canal (mastoid foramen) opens. The external face of the zygomatic process is
smooth and convex ; the internal, concave, is also smooth, and bordered outwards
by the temporal fossa. Its anterior border is sharp and convex ; the posterior, very
short, is thick and roughened. Its summit is ilattened from before to behind, and
marked by notches on its two faces ; it somewhat resembles a wedge, fixed as it is
between the orbital process of the frontal bone and the zygoma ; it comes in contact
with the maxillary bone, and by a small portion of its anterior face, which is
deprived of notches, it concurs in circumscribing the orbital cavity. In the
domesticated animals, as in Man, the zygomatic process appears to arise from the
surface of the bone by two roots — one, the inferior or transverse, is represented by
the condyle ; the other, the siqjerior, forms a sharp crest which is continuous with
the anterior border of the process, and above, joins the lateral crest of the occipital
protuberance.
The internal or cerebral face of the squamous portion is divided into two parts
by an almost vertical channel, which terminates above the supra-condyloid
process, and which, meeting a similar furrow on the parietal bone, forms the
parieto-temporcd canal. The superior portion is of small extent, and of a
triangular form ; it articulates by a simple harmonia suture with the external
face of the petrous portion. The inferior part, the widest, present in its middle
some cerebral impressions. For the remainder of its extent or circumference, it
is cut into a wide, dentated, and lamellar bevel, which brings it in contact with
the surrounding bones.
Circumference. — This may be divided into tivo borders .- one, anterior, is
convex and united with the parietal and frontal bones ; the other, posterior, articu-
lates with the sphenoid in its inferior moiety, and is provided, above the level of
the supra-condyloid process, with a deep notch which receives the external
auditory canal. Superiorly, the two borders unite at the summit in a thin point,
which rests on the occipital bone.
Structure. — The squamous portion of the temporal bone is formed of two
very thin compact plates, which have but little spongy tissue between them ; the
latter, however, is very abundant in the body of the zygomatic process.
Development. — It is developed from a single nucleus of ossification.
Petrous Portion. — This is one of the most interesting parts of the
skeleton for study, in consequence of its containing two systems of cavities which
enclose the essential organs of hearing. One of these systems is named the cavity
of the tympanun or middle ear ; the other forms the interned ear. These cavities
will be studied when we come to speak of the auditory apparatus. In the mean
time, only the external surface, and the structure and development of this portion
of the temporal bone, will be noticed.
It is wedged between the antero-lateral border of the occipital bone, the
lateral border of the parietal, and the superior part of the internal face of the
temporal shell. It represents a quadrangular pyramid, the base of which is turned
downwards and a little backwards. It will be studied successively in four faces,
a summit, and base.
Faces. — The anterior face is united by harmonia suture to the parietal bone.
The posterior face articulates in the same manner with the occipital bone. The
external face lies against the squamous portion of the bone. The internal face,
slightly concave and marked by very superficial digital impressions, forms a part
THE HEAD. 61
of the lateral wall of the cerebellar cavity. It presents the canal or internal audi-
tory hiatus {rneatus auditorius internus), a small fossa, the bottom of which is
pierced by several foramina for the transmission of nerves ; the largest of these
is the internal orifice of the aqimdudus Fallopii — a flexuous canal which passes
through the bone and opens at the external surface of its base ; the other
foramina penetrate the cavities of the internal ear.
These faces are separated from each other by so many borders or plane angles,
two of which more particularly merit attention ; one of these isolates the external
from the posterior face, and the other separates the anterior from the internal
face. The first is thick and rugged, and constitutes the mastoid crest ; it is con-
tinuous above with the lateral ridge of the occipital bone, after being united to
the superior root of the zygomatic process, and terminates, near the base of the
bone, by a tuberosity for muscular insertion, to which has been given the name
of (poster io7-) mastoid process. This border is traversed by a slit, the mastoid fissure^
which passes under the squamous portion and enters the parieto-temporal canal.
The second is thin, and, with the superior part of the lateral border of the parietal
bone, forms the crest which establishes the line of demarcation between the
cerebral and cerebellar cavities of the cranium ; it gives attachment to the
tentorium cerebelli.
Summit. — This is slightly denticulated, and articulates with the occipital bone.
Base. — This is very irregular, and offers : outwardly, the external auditory
canal which penetrates the middle ear, and the external orifice of which has been
named in veterinary anatomy the external auditory hiatus ; inwardly, a sharp
crest which circumscribes the external contour of the foramen lacerum basis cranii ;
above, and under the mastoid process, the stylo-mastoid or pre-mastoid forammi, the
external orifice of the aqueduct of Fallopius ; below, the subuliform (or styloid)
process for the attachment of the tensor palati muscle and the Eustachian tube :
this is a long, thin, and pointed process presenting, at its base and within, a canal
(styloid foramen) which enters the cavity of the tympanum, and which is incom-
pletely partitioned by a small bony plate into two parallel portions ; in the centre,
the hyoid prolongation or vaginal process ^ — a little cylindrical eminence surrounded
by a bony sheath, and the mastoid protuberance or auditory bulla — a slightly sahent,
smooth, and round eminence hollowed internally by numerous cells, which form
part of the middle ear.
The several small and very remarkable canals which pass through the petrous
portion of the temporal bone, will be noticed when the nervous and arterial
branches they lodge are described.
Development. — The petrous portion of the temporal bone is developed from
two principal centres of ossification which are consolidated at birth, and which
are often described as two distinct portions — the one as the petrous or stony
portion, the other as the mastoid portion.
The faces, borders, summit, and inner side of the base of the bone are formed
by the petrous part, which contains the cavities of the internal ear and furnishes
the inner wall of the middle ear.
The mastoid portion constitutes almost entirely the base of the temporal
pyramid ; to it belong the external auditory canal, the mastoid process, the
sheath of the hyoid prolongation, and the styloid process ; it forms the external
wall and circumference of the case of the tympanum.
' This is the analogue of the mastoid canal in Man.
* This process is prolonged by a cartilage that unites it to the styloid hone.
7
62 TEE BONES.
For the petrous portion of the temporal bone there are also two small com-
plementary nuclei : one for the vaginal process — the base of which is united to
the petrous portion, and another forming the ring of the tympanum.
Structure. — The petrous portion is the hardest mass of bone in the skeleton,
and scarcely contains any spongy tissue, except at the centre of the mastoid
process ; in the mastoid portion it may be said not to exist.
Differential Characters in the Temporal Bone of other Animals.
In the other domestic animals, the petrous portion of the temporal bone becomes
consolidated with the squamous portion, and the summit of the zygomatic process only
articulates with the malar bone.
A. Ox, Sheep, Goat.— The condyle of the zygomatic process is very wide and convex in
every sense. The parieto-temporal canal is very large, and entirely excavated in the temporal
bone; its superior or internal extremity opens above the petrous portion in an excavation which
represents the lateral cavity of the parietal protuberance in the Horse ; at its inferior extremity
it always shows several orifices.
Tiie mastoid process is very salient, and belon<^s to the squamous portion. The mastoid
cre.st is confounded with the upper root of the zygomatic process ; iiiferiorly, it surpasses the
mastoid process, and is prolonged to the mastoid protuberance. Tlie latter is very voluminous.
The subuliform process is larger and stronger than
in the Horse ; there is no mastoid fissure.
In the Sheep and Goat, the mastoid process is
scarcely distinct from the crest ; and the mastoid
portion of the bone is only at a late period consoli-
dated with the petrous portion.
B. Camel. — The squamous portion of the
temporal is wider than that of the Horse ; it is
excavated in tlie upper part of its external surface.
The zygomatic process has a large and thin base;
its articular surface is nearly level from before to
behind, and is concave from one side to the other ;
the supra-condyloid process is very developed (Fig.
45). The petrous portion is thin, and closely con-
fined between the occipital and squamous bones.
The mastoid crest and process are not markedly
developed. The hyoid prolongation is placed at the
bottom of a great bony sheath.
C. Pig.— The articular surface of this bone
resembles that of Rodents; it is not limited pos-
teriorly by a subcondyloid eminence, and, in addition,
offers a wider transverse surface. The zygomatic
process articulates with the jugal bone by the wliole
extent of its posterior border. A crest leading from
the external auditory hiatus to the mastoid pro-
The mastoid crest is, as in the Ox, confounded with
head of the rabbit (antero-lateral
face).
1, Occipital bone ; 2, parietal ; 3, tym-
panic bulb ; 4, auditory canal ; 8, 8,
nasal bones; 9, supermaxilla; 10, pre-
maxilla; 11, inferior maxilla.
tuberance replaces the mastoid process,
the superior root of the zygomatic process.
D. Carnivora. — In tlie Carnivora, the articular surface of the zygomatic process merely
forms a glenoid cavity, into which the condyle of the msixillary bone exactly fits. Tlie
temporal bone in these animals is alsodistinguisliedby the width of the externul auditorv canal,
the absence of a liyoid prolongation, the small development of the mastoid and styloid pro-
cesses, the enormous volume of the mastoid protuberance, and the presence of two particnlar
canals which cannot be traced in the other animals. One of them— the carotid mmni-tra verses
the mastoid portion, and joins, superiorly, the venous canal which passes between the basilar
process and the temporal bone ; by its inferior extremity it joins the carotid foramen, which
itself pern tiates the cranium, a little beyond the venous canal just mentioned. The other
conduit is pierced in the petrous portion immediately above the carotid canal ; it affords a
passage to tlie fifth pair of cranial nerves.
E. Rabbit. --Tlie squamous portion is circular, and has a shoit process flattened from
before to behind at its base, and from side to side at its extremity. The articular surface is
TBI, HEAD. 63
concave transversely, and elongated from before tobeliind. The petrous portion has a consider-
able tympanic bulb applied closely to the auditory canal, which is large and obliquo behind.
The mastoid process is a simple crest situated above the auditory canal ; the hyoid prolongation
is absent.
Bones of the Pace.
The face is much more extensive than the cranimn in the majority of the
domesticated animals, and is composed of two jmvs — a bony apparatus that serves
as a support to the passive organs of mastication — the teeth. The superior or
anterior jaiv, traversed in its entire length by the nasal cavities, is formed by
nineteen flat bones, only one of which, the vomer, is a single bone. The pairs
are : the superior and intermaxilJaries (or premaxillaries), the palate, piterijgoid,
malar, lachrymal, nasal, and superior and inferior turbinated hones. Of these
only four — the maxillaries — are intended for the implantation of the teeth ; the
others form the union between the cranium and the superior maxilla, or concur
in the formation of the nasal cavities. The loiver jaw has for its base a single
bone — the inferior maxilla, or maxillary hone. «
1. SuPEEioR Maxillary Bone (Fig. 26).
This bone, also named the supermaxillary hone, the most extensive in the
upper jaw, is situated on the side of the face, and is bordered above by the
frontal, palate, zygomatic, and lachrymal bones ; below, by the premaxillary
bones ; in front, 'by the nasal bone ; behind and within, by that of the opposite
side. It is elongated vertically, is irregularly triangular, and exhibits two faces,
two borders, and two extremities.
Faces. — The external face, which is more convex in the young than the old
animal, presents : 1. On the level of the fourth and fifth molar teeth, a vertically
elongated ridge which is continued above with the inferior border of the
zygomatic bone ; this is the maxillary spine. 2. The inferior orifice of the
maxillo-dental canal, or infra-orbited foramen.
The internal face concurs in forming the external parietes of the nasal cavities.
We observe, above and in front, a deep, wide, and diverticulated excavation,
forming part of the maxillary sinus ; above and behind, a surface roughened by
fine lamellffi and denticulations to correspond with the palate bone, and traversed
from above to below by a fissure which forms, in uniting with a similar fissure in
the latter bone, the pcdatine canal. For the remainder of its extent it is unequally
smooth, covered by the membrane of the nose, and divided into two surfaces by
a slightly vertical and sinuous crest that affords attachment to the maxillary
turbinated bone : the anterior surface, which responds to the middle meatus of
the nasal fossa, shows the lower orifice of the osseous lachrymal canal continued
by a fissure to the lower extremity of the bone ; the posterior surface belongs to
the inferior meatus. From this face is detached, near its inferior border, a wide
and long vertical plate, which forms, in Man and short-faced animals, a simple
process — t\iQ palatine process. This plate, uniting in the middle line with that on
the opposite side, concurs in forming the greater portion of the palatine arch. It
shows : an anterior slightly concave face, forming the floor of the nasal fossae ; a
posterior face, buccal, furrowed by small fissures, perforated by fine openings, and
traversed along its length by a somewhat wide groove — the pcdatine fisstfre, which
commences above at the lower orifice, of the palatine canal ; a denticulated border
61 THE BONES.
which articulates with a similar border on the palatine process of the opposite
side.
Borders. — The anterior, thin and convex, is divided into two parts : an
inferior, which is mortised to receive the external border of the nasal bone and
the external process of the premaxilla ; and a superior, cut in a wide bevel, at
the expense of the external plate, to respond to the lachrymal and zygomatic
bones. The external border is very thick, and hollowed into six large quadrilateral
cavities, named alveoli, in which are implanted the molar teeth. Above the last
alveolus it forms a rugged eminence designated the alveolar tuberosity ; below the
first alveolus it becomes thin and sharp, and constitutes part of the interdental
space {diastema) which separates the molar from the incisor teeth.
Extremities. — The superior is the thickest, and represents a smooth rounded
protuberance, into the interior of which the maxillary sinus is prolonged. Above
and within this eminence is a wide and deep excavation, in the formation of
which the palate bones participate. This is the maxillary hiatus, situated directly
opposite the orbital hiatus. At the bottom of this cavity is seen the nasal
foramen, as well as the upper orifice of the infra-orbital and the palatine
canals. The nasal foramen belongs to the palate bone, and enters the nasal cavity.
The infra-orhital cayial traverses the maxillary sinus in passing above the
roots of the molar teeth, and terminates by two branches — one, short and
wide, which opens on the external surface of the bone, on a level with the
third molar ; the other, very narrow, continues the course of the canal in the
substance of the bone, and is prolonged by several small, very fine branches
into the premaxillary bone. The palatine canal, channeled between the super-
maxillary and the palate bone, extends from the maxillary hiatus to the palatine
fissure.
The inferior extremity presents a cavity which forms the alveolus of the tusk,
by uniting with a similar space in the premaxillary bone.
Structure and develojyment. — This bone is developed from a single nucleus, and
is the more spongy- — particularly towards the alveolar border and the superior
extremity — as the animal is young.
Differential Characters in the Superior Maxillary Bone of the other Animals.
A. Ox, Sheep, Goat. — In the Ox, Sheep, and Goat, the maxillary spine does not directly
join the zygomatic crest ; a curved line, with concavity posterior, effects the union between
these two parts. The inferior oriiice of the infra-orbital foramen is pierced above the first
molar tooth. There is no fissure for the formation of the palatine canal. Tlie cavity of the
sinus is more spacious than in the Horse, and is prolonged (in the Ox only) between the two
laminae of the palatine roof. There is no alveolus for the tusk.
B. Camel. — Not so long or wide as in the Horse and Ox, the supermaxilla of the
Camel is deeply excavated iibove the forehead and the orbit. The maxillary spine is replaced
by a round and i?mooth prominence, which disappears at the inferior opening of the superior
dental canal, pierced above the interval separating the second from the third molar. The
posterior face of the palatine process is narrow, has no palatine fissure, but shows the orifice
of the palatine canal.
C. Pig. — In the Pig, the external surface of this bone is hollowed in its middle, and
presents in front a voluminous relief formed by the alveolus of the canine tooth. The cavity
is entirely formed in the supermaxilla. There is no alveolar tuberosity, and the interdental
spaoe is very short, while the cavity for the sinus is little developed. The lower orifice of the
palatine canal is even pierced in the substance of the supermaxilla.
D. — Dog, Cat. — In Carnivora, this bone is very short; its anterior border offers a long
process analogous to the nasal spiiie of Man. It alone furnishes the alveolus of the tusk.
The palatine canal, pierced entirely in the bone of that name, nevertheless opens, by its
TBE HEAD.
65
inferior extremity, at tlie junction of the supermaxilla with the palatine bone. The maxillary
sinus is not very spacious, and there is no maxillary spine (Fig. 29).
E. Rabbit. — The superior maxilla in this animal is less extensive, proportionately, than
that of the other animals. The external table is thin, and even cribriform. The malar tubercle
is narrow and directed outwards. The palatine process is very narrow, and therefore only
very slightly concurs in the formation of the arch of the palate ; it does not extend to the
summit of the internal process of the incisive bone (Fig. 36).
Fig. 37.
ox's HEAD (POSTERIOR FACE),
A, Parietal bone: 1. occiintal foramen; 2, occipital condyle; 3, styloid process of that bone;
4, condyloid foramina; 5, mastoid process; 6, mastoid protuberance; 7, subuliform (temporal)
process; 8, hyoideal sheath ; 9, stylo-mastoid foramen ; 10, external auditory hiatus ; 11, inferior
orifice of the" parieto-temporal canal; 12, temporal condyle; 13, posterior foramen lacerum ;
14, oval foramen ; 17, subsphenoidal process ; 18, orbital hiatus ; 19, optic foramen. B, Frontal
bone : 20, supra-orbital foramen ; 21, orbital foramen ; 22, lachrymal protuberance. C, Malar bone :
23, pterygoid bone, d. Palatine bone : 24, nasal foramen ; 25, inferior orifice of the palatine
canal. E, Supermaxillary bone : 26, maxillary spine. G, Premaxillary bone : 27, its internal
process ; 28, external process ; 29, incisive openings.
2. Premaxillaey, Inteemaxillary, or Incisive Bone (Figs. 26, 38).
This bone occupies the inferior extremity of the head, and is composed of a
thick prismatic jwrtion, lengthened superiorly by two long processes.
Thick portion or base. — This presents a solid mass with three faces : an
external or labial, smooth and convex : an internal, denticulated for union with the
opposite bone, and traversed from before to behind by an inflexed fissure, which
forms, with an analogous one in the other premaxilla, the incisive canal or fora-
men incisivum ; the third or posterior, also called the buccal, is slightly concave, and
66
THE BONES.
shows the continuation of the
foramen. These three faces
Fig. 38.
POSTERIOR ASPECT OF HORSE'S
SKULL.
, Occipital tuberosity ; 2, fora-
men magnum ; 3, 3, occipital
condyles ; 4, 4, styloid pro-
cesses ; 5, 5, petrous bone ; 6,
basilar process ; 7, pterygoid
fissure of the sphenoid bone ; 8,
foramen lacerum ; 9, 9, supra-
condyloid, or anterior mastoid
process ; 10, 10, articular emi-
nence, or temporal condyle ; 11,
body of sphenoid bone ; 12, ptery-
goid process ; 13, ethmoid bone ;
14, temporal bone and sphenoidal
sutuie; 15, lachrymal bone; 16,
vomer; 17, malar bone; 18,
maxillary tuberosity ; 19, pos-
terior nares, or guttural opening
of the nose ; 20, palatine bone ;
21, palatine styloid process ; 22,
palato-maxillary foramen; 23,
palatine process of superior
maxillary bone, with suture ; 24,
ditto of premaxillary bone; 25,
premaxillary bone ; 26, upper
incisor teeth ; 27, point of junc-
tion of the premaxillary with
the supermaxillary bone ; 28, up-
per molar teeth (young mouth).
palatine groove, which terminates in the incisive
are separated by as many borders : two internah
hmitiug the corresponding face before and be-
hind ; and an external, separating the labial from
the buccal face. The latter only merits notice.
It is very thick, and is divided into two parts :
an inferior, which describes a curved line, con-
cavity upwards, and is excavated by three alveoli
for the reception of the incisor teeth ; another, the
superior, is straight, vertical, and somewhat sharp,
and forms part of the dental interspace. It is
limited above, near the base of the external process,
by a cavity for the formation of the alveolus of
the canine tooth.
Processes. — These are distinguished as external
and intei'iial. The first, the longest and strongest,
is flattened on both sides ; its external face is
smooth, and continued with that of the thick por-
tion of the bone ; its internal face is covered by
the mucous membrane of the nose ; the anterior
border is smooth and rounded ; the posterior,
denticulated to respond to the supermaxillary bone,
is in contact with the external border of the base ;
its summit is thin, and is insinuated between the
latter and the nasal bone. The internal {ox palatine)
process, the smallest, is flattened from before to
behind, and forms a very thin tongue of bone, sepa-
rated from the other portions by a narrow and very
deep notch, named the incisive opening or cleft. Its
inferior face constitutes a small portion of the floor
of the nasal fossae ; the posterior, continuous with
the same face of the principal mass of the bone,
forms part of the palatine roof ; its external border
circumscribes, inwardly, the incisive opening ; the
internal is united by dentated suture with the
opposite bone.
Structure and development. — It is a spongy
bone, developed from a single nucleus.
Differential Characters in the Premaxillary Bone
OF OTHER Animals.
A. Ox, Sheep, Goat (Fig. 37).— Tlie iuferior or prin-
cipal portion of this bone is flattened befure and behind,
and deprived of alveoli in its external border; neither is there
any incdsive foramen. It is rarely consolidated with the
adjacent bones, and is never, in the smaller Ruminants
(Sheep and Goat), articulated with the nasal bone by the
summit of the external process.
B. Camel. — By its form, tlie premaxillary bone much
resembles that of the smaller Ruminants. Its base is
not so wide, but it is thicker than in the Ox. This base is
rugged in its lower surface, and excavated by an alveolar
THE HEAD.
67
cavity. The incisive opening is very small, and the external process does not reacli the
nasal bone.
C. Pig. — In the Pig, the external process of tlie premaxillary bone is very long and wide
at its base, and consolidated with the nasal bone fur about the upper two-thirds of its length.
There is no incisive foramen or cavity for the tusk. The incisive openings are oval.
D. Dog, Cat. — Of small size, the premaxilla of Carnivora has no incisive foramen or
alveolar cavity for the canine tooth. The incisive open-
ings are the same as in the Pig. Fig. 39.
E. Rabbit.— Proportionately voluminous, the pre- r ^
maxilla of the Rabbit is remarkable for the great de- '^ ^
velopnient of its ascending processes, which reach the _ ^ {^mWI^^S^^ f
frontal bone, and the width of the incisive slits, which
are conlounded above the internal processes. It carries
two incisors, placed one before the other.
3. Palatine Bones (Fig. 38).
The folate or palatine hones are situated be-
tween the supermaxillaries, at the margin of the
guttural opening of the nasal cavities, and are
articulated with the sphenoid, ethmoid, vomer,
frontal, and pterygoid bones. Elongated from
above to below, flattened laterally, and curved
towards each other at their inferior extremity,
which is flattened from before to behind, these
bones, though irregular in shape, offer for study
two faces, tivo herders, and two extremities.
Faces. — The external face of the palate bone
is divided into three fractions — a superior, or
orbital, an inferior, or palatine, and a middle, or
articular. The first is smooth and slightly ex-
cavated, and participates in the formation of the
maxillary hiatus ; it shows a small groove, the
staphyloid, which reaches the palatine fraction
in passing between the posterior border of the
bone and the alveolar tuberosity. The second is
not extensive, and looks backwards in conse-
quence of the antero-posterior flattening which
the bone presents at its inferior extremity ; it
forms part of the roof of the palate. The third
presents a lamellar and denticulated surface
which corresponds to a similar face on the
superm axillary bone, and is channeled from
above to below by the internal groove of the
palatine canal.
The interned face, smooth and concave, forms
part of the external wall and the floor of the
nasal fossa.
Borders. — The anterior is indented, near its superior third, by a deep notch,
which is often converted into a foramen, the nasal. Below this notch the bone
is thin and denticulated for union with the supermaxillary bone ; above, its two
plates separate widely from one another, giving rise to a very spacious cavity
HEAD OF THE PIG (POSTERIOR FACE).
1, Occipital tuberosity ; 2, occipi-
tal foramen; 3, occipital con-
dyle; 4, condyloiil foramen; 5,
basilar process ; 6, 6, mastoid crest;
7, styloid process of the occipital
bone ; 8, articular surface of the
temporal bone ; 9, mastoid protu-
berance ; 10. foramen lacerum ; 1 1,
subsphenoidal process — external
wing of pterygoid process ; 12,
palatine crest ; 13, pterygoid bone
(internal wing of the ])terygoid
process) ; 14, inferior orifice of the
palatine canal ; 15, 15, incisive
openings.
TEE BONES.
which forms part of the sphenoid sinus. The posterior border presents, above,
a rugged crest called the palatine, flattened from side to side, bent outwards, and
bordered at its base and inwards by a very narrow synarthrodia! surface, which
responds to the pterygoid bone. It is smooth and concave in its inferior half,
and forms, with that of the opposite side, a parabohc arch (palatine arch) which
circumscribes, below and at the side, the double guttural orifice of the nasal
cavities.
Extremities. — The superior, flattened on both sides, is bevelled on the external
side to articulate with the subsphenoidal process. The
inferior, flattened from before to behind, is curved
inwards and united by simple suture with that of the
opposite bone.
Structure and deveJopment. — This is a very com-
pact bone, developed from a single centre of ossifi-
cation.
Differential Characteks in the Palatine Bone in
OTHER Animals.
The principal distinctive feature of this bone in the different
domestic animals is due to the part it takes in forming the
arch of the palate. In this respect there are very great differ-
ences in various species, but in none of them is tliis part so
reduced as in Solipeds, in which the bone is scarcely equal to
one-fifth of tlie palatine surface.
A. Ox, Sheep, G-oat. — Tlie palatine bone in these animals
is very developed, and noticeable for the considerable extent of
the palatine portion of its external surface. The palatine canal
is entirely channeled out in its substauce. The palatine crest,
very thin and elevated, is formed altogether by the posterior
border of the palate bone, the pterygoid, and the subsphenoidal
process. There is no excavation for the sphenoidal sinuses ;
but, instead, all that part of the bone which enters into the roof
of the palate is hollowed, but in the Ox only, by irregular
cavities which communicate with the maxillary sinus of the
same side. The nasal foramen is very wide.
B. Camel. — The staphyline fissure is wide and deep ; the
palatine crest is very developed, and has two rugged depressions
at its base. The palatine canal is not included in the palate
bone ; it opens at the second molar.
C. Pig. — The palatine portion is leas developed than in
Ruminants, for it forms less tlian one-fourth of the palatine
arch ; on the other hand, the orbital portion is very limited.
The palatine crest is rt-placed by a tuberosity, against which
rests, outwardly, the subsphenoidal process, and inwardly the
pterygoid bone. The union of these three parts constitutes, on
tlie posterior surface of the head, a thick and very remarkable
trifid projection or mamelon.
D. Dog, Cat.— It is in the Carnivora that the palatine bones
are of greatest extent in their proper palatine portion, as they
constitute nearly one-half of the palatine arch. They have no
share in t)ie formation of the sphenoidal sinuses, but furnish a
small excavation to the maxillary sinuses.
E. Rabbit. — The palatine bones resemble those of the Horse,
with regard to the part they play in forming the palatine arch.
The palatine canal opens also between the palatine and superior
maxillary bones, but the palatine crests are proportionately
more developed than in Solipeds (Fig. 35).
dog's head (posterior face).
1, Occipital tuberosity ; 2,
occipital foramen ; 3, occi-
pital condyle ; 4, condyloid
foramen ; 5, styloid process
of the occipital ; 6, mastoid
protuberance ; 7, concave
temporo-maxillary articular
surface ; 8, supra-condy-
loid eminence ; 9, inferior
orifice of the parieto-tem-
poral canal ; 10, posterior
foramen lacerum ; 11,
ditto, anterior. On the op-
posite side at a is shown
the orifice communicating
with the Eustachian tube
and the tympanum ; at h
the passage for the carotid
loop. 12, Body of the
sphenoid ; 13, oval fora-
men ; 14, inferior orifice of
the subsphenoidal canal ;
15, pterygoid bone; 16,
nasal surface of the palate
bone; 17, palatine surface
of the same; 18, vomer;
19, supermaxillary bone ;
20.
incisive opening.
THE HEAD. 69
4. Pteeygoid Bone (Figs. 34, 38).*
A small and very short bone, elongated from above to below, flattened on
both sides, and situated on the inner aspect of the subsphenoidal process, but
external to the vomer.
Its external face is in contact with the palate and sphenoid bones ; the
internal is smooth, and covered by the pharyngeal mucous membrane. Its
superior extremity is tapering, and concurs in forming the Vidian canal ; the
inferior is thickened into a small pointed process (the hamular process), the
apex of which, directed backwards, offers outwardly a groove which serves as a
pulley to the tendon of the tensor palati muscle.
This bone is composed entirely of compact tissue, and is developed from a
single centre of ossification.
Differential Characters in the Pterygoid Bone of other Animals.
A. Ox, Sheep, Goat. — The pterygoid of the Ox, Sheep, and Goat is very wide, and closes
an aperture left between the s|ihenoid and palatine bones.
B. Camel. — In the Camel the pterygoid is short, broad, and applied to the internal face
of the subsphenoidal process and palatine crest. It does not concur in the formation of the
Vidian canal. Its inferior extremity has a narrow and deep fissure.
C. Pig. — (See the description of the palatine bone.)
D. Camivora. — This bone is very strong in Carnivora, and quadrilateral in shape.
5. Malar or Zygomatic Bone (Figs. 26, 34).
This bone, also -designated the juf/al bone, is elongated from above
to below, flattened on both sides, and irregularly triangular in shape ; it is
situated on the side of the face, and articulates with the supermaxillary,
lachrymal, and temporal bones. It is described as having tivo faces, two borders^
a base, and a summit.
Faces. — The external face comprises two portions separated from each other
by a semicircular ridge that extends from the summit to the middle of the
anterior border of the bone, and concurs to form the outer margin of the orbit.
The anterior portion, smooth and concave, belongs to the orbital cavity. The
posterior, more extensive, is also smooth and slightly convex. The internal face
is excavated in its central part, which corresponds to the maxillary sinus. On
its margin it shows denticulations and lamellae for articulation with the super-
maxillary bone.
Borders. — The cmterior, thin and denticulated, is joined to the lachrymal
bone. The posterior, or masseteric border, is thicker, and constitutes a roughened
crest, the zygomatic ridge, which is continued above with the posterior border of
the process of the same name, and below with the maxillary spine.
Base and summit. — The base, very thin, is united to the supermaxillary bone.
The summit, flattened from before to behind and bevelled on its anterior face,
joins the zygomatic process, and forms with it the j'l/gal bridge, or zygomatic arch.
SU-ucture and development. — This bone is rather spongy in its upper part, and
is developed from a single nucleus of ossification.
Differential Characters in the Malar Bone op other Animals.
A. Ox, Sheep, Goat. — The malar bone of Kuminants is very developed. The zygomatic
crest is no longer formed by the posterior border of the bone, but is carried to the posterior
part of the external face, and runs parallel with the eyebrow. The summit is bifurcated, the
' This bone is the representative of the internal wing of the pterygoid process in Man.
70 THE BONES.
anterior branch forming a buttress against tlie summit of tbe orbital process of the frontal
bone, while the posterior articulates with the temporal. In these animals, the bone offers
several centres of ossification.
B. Camel. — This bone is very little developed, aud is compressed from before to behind^
Its anterior face is very concave, and circumscribes the orbit posteriorly. Its posterior face
considerably overhangs the maxillary bone, and forms a very salient zygomatic crest. The
summit is bifurcated, as in the Ox.
C. Pig. — The summit of this bone in the Pig is flattened on each side, and divided inta
two brandies, between which is wedged the summit of the zygomatic process ; the anterior
branch is very sliort, and does not join the frontal bone.
D. Camivora.— The malar of the Dog and Cat only articulates with the supermaxillary
bone, and by its base alone. The crest describes a curve, the concavity backwards, and the
summit comports itself as in the Pig.
F. Rabbit. — The bone is flattened on both sides ; the summit, united with the zygomatic
process of the temporal bune, is single ; while the base is confounded entirely with the malar
tuberosity (Fig. 36).
6. Lachrymal Bone (Figs. 26, 51).
A small, thin, and very light bone, bent on itself at a right angle, it is
situated beneath the orbit, which it aids in forming, and is wedged between the
frontal, nasal, snpermaxillary, and malar bones. It is studied on its external
and internal faces and circumference.
Faces. — The external is divided into two regions, superior and inferior, by
a curved crest which forms part of the orbital margin, and is provided with
notches, which are variable in their form and number. The superior region,
named the orbital, because of its situation in the orbit, is slightly concave and
smooth. It presents, near the orbital margin, the orifice of the laclirynud diict,
which traverses the maxillary sinus and opens on the internal face of the super-
maxillary bone, where it is continued by a fissure ; behind this is the lachrymal
fossa. The inferior ov facial region is slightly bulging, and provided sometimes
with a tubercle for insertion, — the lackrymal tubercle. The internal face is
employed, for the whole of its extent, in the formation of the walls of the
maxillary and frontal sinuses ; it exhibits a cylindrical prominence produced by
the bony tube of the lachrymal duct.
Circumference. — This is very irregular, and denticulated for articulation with
the neighbouring bones.
Structure and development. — This bone is entirely compact, and is developed
from a single nucleus of ossification.
In the Ass, the lachrymal tubercle is placed towards the anterior border of
the bone ; usually, it partly belongs to the nasal bone, and is consequently found
on the suture uniting the lachrymal bone to the proper bones of the nose.
Differential Chakactebs in the Lachrymal Bone of other Animals.
A. Ox, Sheep, Goat.— The lachrymal bone, much more extensive than that of tlie
Horse, forms in tlie bottom of the orbit an enormous protuberance, hollowed internally by the
maxillary sinus, and the walls of whicii are so thin and fragile that the slightest jar is sufficient
to cause their fracture (in the skeleton). It would be convenient to designate it the lachrymal
protuberance.^ In the smaller Kuminants, the inferior region of the internal face shows a
depression — the lachrymal fossa.
B. Camel.— This bone is much smaller than in the Horse ; its facial portion especially Is
almost rndimi ntary. There is no lachrymal protuberance nor tubercle, the latter being carried
to the superior maxilla.
C. Pig.— In the Pig there are observed a lachrymal fossa and two lachrymal canals, which
' Girard, who named this eminence the orbital protuberance, wrongly described it as;
belonging to the supermaxillary bone.
THE HEAD. 71
are pierced outside the orbital cavity, and soon coalesce in the substance of the bone to
constitute a single canal. The fossa is very deep.
D. Camivora. — This bone in Carnivora is extremely small. Its external face entirely
belongs to the orbit, and does not descend beneath the margin of tliat cavity; it has no
lachrymal fossa. The reduced dimensions it presents in these animals well justifies the name,
OS unguis, given to it in anthropotomy.
7. Nasal Bones (Fig. 26).
Situated on the anterior aspect of the head, these bones articulate with each
other in the median hne, and are fixed between the frontal, lachrymal, and super-
maxillary bones ; they are triangular in shape, elongated from above to below,
flattened from before to behind, and offer for study two faces, two borders, a base,
and a summit.
Faces. — The external or anterior face, wider above than below, is convex from
side to side, and almost smooth. The posterior, internal, or nasal face exhibits a
vertical crest passing along the external border of the bone, which gives attach-
ment to the turbinated portion of the ethmoid ; at its superior extremity this
crest bifurcates, and between its two branches shows a concave surface which
forms part of the frontal sinus. For the remainder of its extent the internal
face is smooth, and' covered by the mucous membrane of the nasal fossa ; it
is also excavated into a channel to form the superior meatus of this cavity.
Borders. — The extermd border is very thin in its upper two-thirds, and articu-
lates with the lachrymal bone, the anterior border of the supermaxillary, and the
extremity of the external process of the premaxilla. In its lower third it becomes
isolated from the latter bone, in forming with the anterior border of its large pro-
cess a very acute re-entering angle, the opening of which looks downwards. The
interned border is denticulated for contact with the opposite bone.
Base and Summit. — The base occupies the superior extremity of the bone ;
it describes a curved line with the convexity above, and, in uniting on the median
line with that of the opposite bone, forms a notch similar to that of the heart
figured on playing-cards ; it is bevelled, at the expense of the internal plate, to
articulate with the frontal bone. The summit of the two nasal bones, which is
pointed, constitutes the nasal prolongation — the name given to a single triangular
process which comprises all that portion of the nasal bones separated from the
premaxillaries by the re-entering angle before mentioned.
Structure and development. — Almost entirely compact in structure, it is
developed from a single centre.
Differential Characters in the Nasal Bones of other Animals.
A. Ox, Sheep, Goat. — The nasal bones of the Ox are never consolidated with each other,
nor yet with the neighbouring bones. The external border only comes in contact to a small
extent with the supermaxillary bone ; the superior extremity is fixed in the notch of the inferior
border of the frontal bone. At their inferior extremity, they each present a notch which divides
them into two points.
In the Sheep and Goat the nasal spine is unifid, as in the Horse (see Figs. 30, 32).
B. Camel. — In the Camel, the proper bones of the nose are short and narrow; their
external border is in contact only with the superior maxilla; the upper extremity is rounded.
At the inferior extremity, they show a well-marked notch, which divides them into two points,
but the inner point is very small.
C. Pig. — Tliese bnnes are long and narrow, and traversed on their external face by the
fissure that descends from the supra-orbital foramen. The nasal prolongation is short.
D Carnivora.— The two bones of the nose are little developed, and are wider below than
above ; they have no nasal prolongation, but offer, instead, a semicircular notch.
THE BONES.
E Rabbit.— Proportionately long and wide, the nasal bone of the Rabbit articulates, by
the whole of its external border, with the ascending process of the preuiaxillary bone. The
anterior extremity of the nasal bone is very slightly salient.
Fig. 41.
Fig. 42.
LONGITUDINAL AND TRANSVERSE SECTION OP
THE horse's head, SHOWING THE FLOOR OF
THE CRANIAL AND NASAL CAVITIES, WITH
THE MAXILLARY SINUSES.
1, Condvloid foramen. 2, Section of the parieto
tem[ioval canal. 3, Foramen lacerum basis
cranii. 4, Carotid notch. 4', Maxillary
notch: o,supermaxillary fissure ; 6, cavern-
ous fissure. 5, Origin of the supra-sphe-
noidal canals : c, sella Turcica. 6, Optic
fossa. 7, Portion of the crista-galli process.
8, Cribriform plate of the ethmoid bone.
9, Perpendicular plate of the s^ame bone.
10, 10, Its lateral masses. 11, Interior of
the great ethmoidal cell. 12, 12, Bottom of
the maxillary sinuses communicating with
the sphenoidal sinuses. 13, Superior
maxillary sinus. 14, Inferior maxillary sinus.
14', Superior compartment of the maxillary
turbinated bone, forming part of the latter
sinus. 15, Section of ttie supermaxillo-
dental cannl. 16, Channel of the vomer.
17, Internal proc.'ss, or point of the pre-
maxillary bone.
ANTERO-POSTERIOR AND VERTICAL
SECTION OF THE HORSE'S HEAD.
1, Condyloid foramen ; 2, parietal
protuberance ; 3, internal audi-
tory hiatus ; 4, cerebral cavity ;
5, cerebellar cavity; 6, supe-
rior border of the perpendicular
plate of theethmoidbone(crista-
galli process) ; 7, ethmoidal
volutes — nasal face; 8, vestiges
of the right frontal sinus; 9,
ditto of the sphenoidal sinus ;
10, pterygoid process; 11, eth-
moidal turbinated bone; 12,
maxillary turbinated bone ; 13,
crest of the supermaxillary
bone to which the latter is
fixed ; 14, vomer. A, Orifice of
communication between the
nasal cavity and the sinus.
THE BEAD. 73
TUEBINATED BONES (Fig. 42).
The turlinated (or turUnal) hones, two on each side, represent two irregular
bony columns, wider above than below, compressed laterally, hollowed internally,
and lying vertically side by side on the external wall of the nasal fossa, which
they divide into three meatuses or passages.
They are distinguished into anterior and posterior turbinated hones.
The anterior or superior, also named the ethmoidal, is formed by a very thin
plate of compact tissue— fragile and like papyrus, fixed by its anterior border to
the internal crest of the nasal bone, and rolled on itself, from before to behind,
in the same manner as the cells of the ethmoid bone. Above, it is confounded
with the last-named bone, of which it is only, properly speaking, the most anterior
volute. At its inferior extremity, it is prolonged by a fibro-cartilaginous frame-
work to the external orifice of the nose.
Its internal cavity is partitioned by a transverse plate into two portions : the
superior compartment forms part of the frontal sinus ; the inferior is subdivided
by other small lamellEe into a variable number of cells which communicate with
the nasal cavity. This bone, developed from a single nucleus, is ossified at the
same time, and in the same manner, as the ethmoidal cells. Before birth, it is
already intimately consolidated with the nasal bone.
The posterior, inferior, or maxiUary turbinated hone resembles the first, except
in some particulars. Thus, its bony or proper portion is not so long or volu-
minous, while its cartilaginous part is, on the contrary, more developed. It is
attached, by its posterior border, to the vertical and sinuous crest of the super-
maxillary bone, and is rolled from behind to before, or in an inverse direction to
the other. It has no connection with the ethmoid, and its superior cavity forms
part of the inferior maxillary sinus. It is late in becoming ossified, and is
scarcely united in a definite manner to the maxillary bone until the horse is
about a year old.
The meatuses are distinguished into anterior or superior, middle, and posterior
or inferior. The first passes along the front of the ethmoidal turbinated bone ;
the second separates the two turbinated bones, and presents, near its superior
extremity, the opening communicating between the sinuses and the nasal cavities.^
The third is situated behind the maxillary turbinated bone, and is confounded
with the floor of the nasal fossa.
The turbinated bones are essentially disposed to furnish the membrane of the
nose with a vast surface of development. This membrane, indeed, covers their
entire superficies, and even penetrates the anfractuous cells of their lower
compartment.
Differential Characters in the Turbinated Bones of other Animals.
A. Ox, Sheep, Goat. — In the Ox (Fig. 43), the ethmoitlal turbinated bone is very small,
and is united to the nasal bone bv the two borders of its osseous plate ; its internal cavity entirely
belongs to the frontal sinus. The maxillary turbinated bone is very developed, and is joined
to the bone which sustains it at a later period than in the Horse. The bony lamina of which
it is composed, is curved on itself in two different directions — from before to behind by its
posterior border, and behind to before by its anterior border. It is fixed to the supermaxillary
bone by its middle part, through the medium of a particular bony lamina, and it very incom-
' The two turbinated bones, in being applied against the excavation on the inner face of the
supermaxillary, almost entirely close it, only leaving between them a vertical slit which con-
stitutes the opening mentioned above.
74
THE BONES.
pletely closes the excavatioh which coucurs to form the maxillary sinus. In the skeleton there
is also found behind, and at the base of this turbinated bone, a vast opening which is totally
closed in the fresh condition by the pituitary membrane.
The maxillary sinus is not prolonged in its interior.
In the smaller Euminants, tlie cavity of the sinus is
closed by the maxillary turbinated bone in a more
complete manner than in the Ox.
B. Camel. — The ethmoidal turbinated bone is
very small. Otherwise it is as in the other Ruminants.
C. Pig. — The same arrangement as in tlie Sheep
and Goat, except that the bones are mucli longer and
less fragile.
D. Carnivora.— These bones in tlie Dog and Cat
are particularly distinguished for their numerous cou-
volutions. Neither participate in the formation of
the frontal or maxillary sinuses; the latter is not in
any way closed by the maxillary turbinated bone, but
opens into the nasal cavity by a large gaping aperture.
E. Rabbit. — The bones are arranged as in the
Dog, but the folds are less numerous.
9. VoMEE (Figs. 34, 38).
This, a single bone, elongated from above
to below, flattened on both sides, and extending
on the median line from the body of the
sphenoid to the premaxillary bone, offers for
study two lateral faces, two borders, and two
extremities.
The faces are smooth, plane, and covered
by the nasal membrane. The anterior border
is channeled for the whole of its length by a
deep groove, which receives the posterior border
of the cartilaginous septum of the nose. The
posterior border is sharp and smooth in its
upper half, which separates the two guttural
openings of the nasal cavities : it is thick and
slightly denticulated for the remainder of its
extent, and rests on the median suture resulting
from the union of the two supermaxillary
bones. The superior extremity is provided, in
its middle, with a notch which divides it into
two lateral prolongations shaped like a cat's
ears {wings of the vomer) ; it articulates with
the inferior sphenoid, ethmoid, palatine, and
pterygoid bones. The inferior extremity rests
on the prolongations of the premaxillae.
This bone is entirely compact, and is
developed from one centre of ossification.
MEDIAN AND VERTICAL SECTION OF
THE ox's HEAD.
X, Condyloid foramen; 1', posterior ori-
fice of the occipital lateral canal
joining the parieto-temporal canal
in front ; 2, internal auditory hiatus ;
3, anterior foramen lacerum ; 4, pos-
terior ditto ; 5, iutra-cranial orifice
of the parieto-temporal canal ; 6, 6,
median bony plate separating the
frontal sinuses ; 7, lamina which iso-
lates the sphenoidal sinus; 8, lamina
partitioning the palatine portion of
the maxilliary sinuses ; 9, oval fora-
men; 10, optic fossa; 11, vomer;
12, pterygoid bone ; 1.3, large open-
ing leading into the maxillary sinus,
and which, in the fresh state, is closed
by the pituitary membrane ; 14, max-
illary turbinated bone; 15, ethmoidal
turbinated bone; 16, great ethmoidal
cell.
Differential Characteks in the Vomer of
OTHER Animals.
A. Ox, Sheep, Goat. — This is a very wide and
thin bone, resting only on the lower half of the median
suture of the premaxillaries (Fig. 43).
B. Camel.— Wider in its upper part than in the Ox, the vomer reaches, outwardly, the
THE HEAD. 75
orbital cavity. By its inferior border, it rests on the entire length of the median suture of the
palatine and superraaxillary bones.
C. Pig. — The vomer in this animal adheres to the bones of the palatine arch for a great
extent. The free portion of the inferior border is short and but little prominent.
D. Camivora.— In the Dog and Cat, the vomer is short, but its wings are very large.
10. Inferior Maxillary Bone (Fig. 44).
The inferior maxillary hone is not consolidated with any of the preceding bones,
and is only united to two of them — the temporals — by diarthrodial articulation.
It is a considerable bone, situated behind the upper jaw, and composed of two
symmetrical branches, which are flattened on both sides, wider above than below,
curved forwards in their upper third, joined at their lower extremities, and
separated superiorly so as to leave a wide gap between them, like the letter V in
shape, called the intra-maxillary space. Each offers for study tivo faces, two
borders, and two extremities.
Faces. — The external face of the maxillary branches is smooth and rounded in
its inferior two-thirds, and transformed superiorly into a rugged surface, in which
is implanted the fibres of the masseter muscle. The internal face presents, in the
corresponding point, an excavated surface on which is remarked the superior
orifice of the maxillo-dental caned, a long channel which descends between the
two plates of the branch, passing under the roots of the molar teeth, and insensibly
disappearing in the body of the bone after being widely opened externally by the
mental {ov anterior maxillary) foramen. In its inferior two-thirds, the internal
face is smooth, nearly plane, and shows nothing very remarkable. Near the
alveolar border there is a slightly projecting line — the myloid ridge ; and quite
below, or rather at the very summit of the re-entering angle formed by the
separation of the branches, there is a slight rugged excavation confounded with
that of the opposite branch, and named the ye)iicd surface.
Borders. — The anterior, also named the alveolar border, exhibits for study a
straight or inferior, and a curved or superior portion. The first is hollowed by
six alveoU to receive the inferior molar teeth.
The second, thinner, concave, and rugged, serves for muscular insertion.
The posterior border is also divided into straight and curved portions. The latter
is convex, thick, rugged, and margined on each side by an uneven lip ; the first
is regularly rectilinear, so that all its points rest at the same time on a horizontal
plane ; it is thick and rounded in the young animal, but becomes sharp with
age ; an oblique and transverse fissure — the maxillary — separates it from the
curved part. The union of these two portions forms the angle of the jaw.
Extremities. — The superior e.vtremity has two eminences : a condyle, and a
long non-articular process named the coronoid process. The condyle is elongated
transversely, and convex in its two diameters ; it responds, through the medium
of a fibro-cartilaginous disc, to the articular surface of the zygomatic process.
■ The coronoid process is situated in front of the condyle, from which it is sepa-
rated by a division called the sigmoid or corono-condyloid notch ; it is flattened on
both sides, and curved backwards and slightly inwards.
From the union of the branches of the maxillary bone at their inferior
extremity, results a single piece, flattened before and behind, and widened like a
spatula, which has been designated the body of the bone. This merits a special
description.
Its form allows us to divide it into an anterior or buccal face, a posterior or
76
THE BONES.
labial face, and a circumference. The anterior face is smooth and concave, is lined
by the buccal mucous membrane, and supports the free extremity of the tongue.
The posterior face is convex, more extensive than the preceding, and continuous
with the external face of the branches. It presents : 1. On the median line, a
slight crest or small groove— traces of its being originally separated into two
pieces. 2. On the sides and above, the mental foramen — the inferior orifice of the
maxillo-dental canal. On a level with this foramen, the bone very markedly
contracts to form the neck. The circumference describes a parabolic curve, the
concavity being uppermost, and joins, by its extremities, the anterior border
of each branch. It is excavated in its middle part by the six alveoli for the
lodgment of the inferior incisors, and behind these— in male animals only— there
is an additional alveolus for the tusk. The portion included on each side
Fig. 44.
INFERIOR MAXILLA.
1, Mental foramen; 1', superior orifice of the maxillo-dental canal ; 2, surface of implantation for
the masseter muscle ; 3, myloid ridge ; 4, coronoid process ; 5, condyle.
between the last incisor and first molar, forms a more or less sharp ridge, which
constitutes the inferior interdental space or bar {diastema).
Structure and development. — Formed, like all the flat bones, by two compact
plates separated by spongy tissue, the inferior maxilla is developed from two
centres of ossification, which correspond to each branch, and which coalesce some
time after birth.
But in the human foetus, there can oe seen five pieces developed around the
dental canal — the coronary, articular, angular, opercular, and premaxillary —
which proves that the maxilla of Mammalia is formed on the same type as that
of oviparous Vertebrata (Lavocat).
DiFFEKENTIAL CHARACTERS IN THE INFERIOR MaXILLA OP OTHER ANIMALS.
A. Ox, Sheep, Goat.— In these animals, the part of the posterior border of the inferior
maxilla below the molars is convex, and cannot rest on a horizontal plane by all its points at
the same time. The condyle is convex in its small diameter, and slightly concave laterally The
coronoid process is bent backwards and outwards. The body does not show any alveolus for
the tusk, because this tooth is not present in these animals ; but it is hollowed by eight alveoli
for the incisor teeth. The two branches of the bone are never consolidated, but remain
movable on each other during life.
THE HEAD.
77
B. Camel. — The branches are short and thick, the body very long, and the interdental
space considerable. The straight border of tlie branches has a posterior rectilinear border, aa
in the Horse ; the anterior margin of the curved portion is tliin and sharp. Oa its internal
face is seen a plate in front of the superior opening of the inferior dental foramen, and a mylo-
hyoid fissure.
The condyle is convex in front, flat and oblique behind. The coronoid process is very
strong. Below the condyle is a process separated from the latter by a deep notch.
The circumference of the body is excavated by eight alveoli — six for the incisors, and two
for the canines.
C. Pig. — A straight line leading from the greater axis of the alveoli of the molar would
Fig. 45.
HEAD OF THE CAMEL.
1, Occipital bone ; 2', parietal crest ; 3, .squamous temporal ; 4, frontal bone ; 4', supra-orbital
foramen; 5, malar bone; 6, nasal bones; 7, supermaxillary bone; 7', infra-orbital foramen;
8, premaxillary bone; 9, inferior maxilla; 10, 11, openings of the inferior dental foramen.
not traverse the posterior border of the maxillary branches , the bottom of these alveoli corre-
sponds to the relief on the iimer face. The condyle is compressed on both sides, and elongated
from before to behind; while the coronoid process is short and wide. TIjere is no neck; the
interdental spaces are very short ; and the maxillo-dental canal opens inferiorly by multiple
orifices.
D. Carnivora.— In Carnivore, this is hollowed at the point corresponding to the insertion
of the masseter muscle into a somewhat deep fossa. The posterior border is disposed as in
Ruminants, and below the condyle lias a very marked tuberosity. The condyle represents an
ovoid segment, and fits exactly into the temporal cavity. The coronoid process is very strong,
elevated, and wide. The mental foramina are double or treble. There are no interdental
spaces, nor excavated surface on the inner face of tlie branches ; and the latter are never
consolidated.
E. Rabbit. — In the maxilla of the Rabbit, the coronoid process is very short, and the
condyle narrow and elongated from before to behind. The posterior border is deeply notched
8
78
THE BONES.
HEAD OF THE CAT.
Parieto-occipital suture; 2, parietal bone;
3, frontal bone ; 4, orbital piocess of the
frontal bone; 5, malar bone; 6, supermaxil-
lary bone ; 7, 7, premaxilla ; 8, nasal bone ;
9, tympanic bulb ; 10, inferior maxilla.
in its curved portion ; the interdental space is very long ; and the body has only two alveoli
for the incisors.
11.— The Hyoid Bone (Fig. 47).
The hi/oid bone constitutes a small and special bony apparatus which serves
to support the tongue, as well as the
Fig- -iS. larynx and pharynx ; its description is
placed immediately after that of the
bones of the head because of its con-
nection with that region, it being situ-
ated between the two branches of the
supermaxillarybone, and suspended from
the base of the cranium in an oblique
direction from above to below, and from
before to behind.
This apparatus is composed of seven
distinct pieces, arranged in three series :
a middle, constituted by a single bone,
and named the body ; two lateral, form-
ing two quasi-parallel branches, to the
extremities of which the body is articu-
lated.
Body or basihijal. — The body of the
hyoid resembles a fork with two prongs. It presents : 1. A middle part flattened
above and below, and consequently provided with a superior and an inferior face.
2. A single and long pro-
p's- '*^' longation flattened on
both sides, which is de-
tached from the middle
part, and directed forward
and downward to plunge
into the muscular tissue
of the tongue : this is the
anterior appendix of the
hijoideaJ body, or Ungual
prolongation. 3. Two late-
ral cornua, thyroid cornua,
great cornua, or urohyals,
projecting backwards and
upwards, articulating by
their extremities with the
thyroid cartilage of the
larynx, and offering, at
their point of union with
the middle part, two con-
vex diarthrodial facets
looking upwards, and
corresponding with the styloid cormia. The body of the hyoid bone is developed
by three centres of ossification — a middle, and two lateral for the cornua.
Branches. — The three pieces composing these are articulated end to end, by
HYOID BONE OF THE HORSE.
Body or ba^ihyal ; 2, lingual prolongation ; 3. 3, thyi'oid
cornua, great cornua, or urohyals ; 4, 4, styloid cornua.
small cornua. or apohyals ; 5, 5, styloid nuclei or ceratohyals ;
6, 6, styloids, great hyoideal branches, or stylohyais ; 7, 7,
arthrohyals. or cartilaginous nuclei attaching the hyoid to
the temporal bone.
THE HEAD. 79
means of a cartilaginous substance that joins them together ; they are of very
unequal dimensions. The first, which is in relation with the body, is of medium
size, and is named the styloid cormi, small conm, or small branch. The second,
termed the styloid nucleus, is the smallest. The third, the largest, constitutes
the styloid process or bo7ie, or great branch.
1. The styloid cornua {cfpohyaV) is a small cylindrical piece bearing a concave
diarthrodial surface on its inferior extremity to unite it to the body ; it is very
spongy, and is developed from two ossifying centres, one of which, the epiphysary,
is for the inferior extremity.
2. The styloid nucleus {ceratohyal), which is often absent, is embedded in the
uniting cartilaginous substance.
3. The styloid bone, or great hyoideal branch {stylohyal), is long, thin, flattened
on both sides, and directed obliquely from above to below, and before to behind ;
it presents two faces, two borders, and two extremities. The faces — an external
and internal — are marked by some few imprints. The anterior border is sharp
and slightly concave in its upper third. The posterior border is thicker, and is
divided into two portions — a superior or horizontal, which is very short, and an
inferior or vertical, much more extensive. The angle they form at their point
of junction presents a salient, and more or less roughened, tuberosity. The
superior extremity is united to the hyoideal prolongation of the temporal bone
by means of a cylindrical fibro-cartilage. By its inferior extremity, the styloid
bone is united either to the styloid nucleus or the styloid cornu, forming a sharp
elbow directed forwards. The styloid bone, developed from a single centre of
ossification, is almost entirely formed of compact tissue.
Differential Characters of the Htoid Bone in other Animals.
A. Ox, Sheep, Goat. — The hyoid bone of Ruminants is always composed of seven piecea.
the styloid nucleus, the presence of which is not constant in Solipeds, is never absent in these,'
and has the proportions of the second small branch. The anterior appendix is very short, and
only represents a large mamelon.
B. Camel. — The liyoid is in this animal as in the Ox.
C. Pig.— The body is voluminous and deprived of an appendix; the small branches are
short and consolidated with the body ; while the large branches, curved like an S, are very
thin, and are not united to the small branches and the temporal bone by libro-cartilage, but by
veritable yellow elastic ligaments.
D. Carnivora. — The three pieces composing the body of the hyoid in early life are never
consolidated in the adult animal, but always remain isolated, as in Man. The middle piece
has no anterior appendix; the fibro-cartilages uniting the styloid portions to each other and to
the temporal bone are very long and flexible.
12. WoEMiAN Bones (Fig. 48).
This name has been given to small irregular bones which Worms observed
between some of the sutures of the cranial bones. They are developed after
birth, in the cranial, cranio-facial, and facial sutures. Their number and position
varies with the species of animals, and even the breeds of the same species.
Vaguely described by Rigot, they have been recently studied by Cornevin,
who observes that the cranial Wormian bones are rare. In more than sixty
crania, they were found only once or twice in the Ox and Horse at the junction
of the petrous with the occipital bone. The Wormian bones of the cranio-facial
and the facial suture are more frequent ; nevertheless, they have been met with
almost exclusively in the heads of common-bred animals, particularly in the
bovine species. Cornevin has described a fontanelle lachrymo-nasal bone (Fig.
80 THE BONES.
48, 2), and Wormian fronto-nasal (Fig. 48, 1), as well as an interaasal, orbital,
zygomato-maxillary, maxillo-nasal-incisive bone. (Sometimes two Wormian
bones are found in the same head.)
OP THE HEAD IN GENERAL.
1. Geneeal Configueation.
From the union of all the bones which constitute the cranium and faoe,
there results a quadrangular pyramid, with summit inverted, which it is necessary
to study as a whole. We will pass in
^'S- *^" review, successively, its four faces, its
base, and its summit.
A. Anterior Face.— This is
subdivided into four regions (Fig.
49) :
1. Parietal region. — This has for
base the anterior portion of the
occipital bone and the parietal bones.
Limited, above, by the external occi-
pital tuberosity, it presents on the
middle line a spur which soon bifur-
cates to form the parietal or temporal
crests ; the latter join the posterior
border of the zygomatic process. i
2. Frontal region. — Larger than^
the preceding, it is usually plane and
lozenge-shaped. Boimded iuferiorly
by the fronto-nasal suture, this region
projects, laterally, the orbital pro-
cesses, the base of which is pierced
by the supra-orbital foramen, and the
anterior border — somewhat sharp—
is frequently made irregular by small
notches, one of which is often converted into a foramen.
3. Nasal region. — This region has for its base the proper bones of the nose.
It is narrow, convex on each side, and plane, concave, or convex in its length,
according to the animals. It advances above the entrance to the nasal cavities,
where it forms the nasal prolofigation, the summit of which, in the Horse, ceases
at nearly two fingers' breadth from the intermaxillary symphysis.
4. Incisive region. — Principally formed by the incisive bones, this region
presents : the inferior opening of the nasal cavities, divided in the fresh state by
the median cartilaginous septum of the nose ; the incisive slits on the floor of
the nasal fossfe ; the intermaxillary symphysis, channeled above by a more or
less deep groove in nearly all Horses, but raised, on the contrary, into a conical
tubercle in the Ass and Hinny, and perforated in the middle by the incisive canal.
Right and left of the intermaxillary symphysis this region is convex, and elevated
by the prominence which the roots of the incisor teeth form.
B. Posterior Pace. — In this are recognized four distinct regions (Fig. 50) :
1. Sub-occipital region. — This presents : in the middle, the basilar process^
WORMIAN BONES OF THE OX. (AFTER CORNEVIN.)
1, Fronto-nasal Wormian bones; 2, 2, lachrymo-
nasal fontanellar bones.
THE HEAD.
81
a strong piece more or less deeply channeled, according to the animals, and
provided at its inferior extremity with rugosities for the attachment of the anterior
straight muscles of the head ; on the sides, the lacerated foramina — large irregular
Fig. 49.
horse's head (anterior face).
1, Occipital tuberosity ; 2, origin
of the mastoid crest ; 3, parietal
bone; 4, saggital suture ; 5, junc-
tion of the parietal and temporal
bones ; 6, zygomatic arch ; 7,
frontal bone ; 8, frontal suture ;
9, temporal fossa ; 10, supra-orbital
foramen ; 11, 12, lachrymal bone ;
13, malar bone ; 14, nasal border of
frontal bone ; 15, nasal bone ; 16,
suture of nasal bones; 17, super-
maxillary bone ; 18, infra-orbital
foramen; 19, anterior, or pre-
maxillary bone ; 20, foramen in-
cisivum ; 21, incisor teeth (young
mouth).
horse's head (posterior face).
, Occipital tuberosity ; 2, foramen magnum ; 3,
3, occipital condyles; 4, 4, styloid processes;
5, 5, petrous bone ; 6, basilar process ; 7, ptery-
goid fissure of the sphenoid bone ; 8, foramen
lacerum ; 9, 9, supra-condyloid, or anterior mas-
toid process; 10, lo, articular eminence, or
temporal condyle; 11, body of sphenoid bone;
12, pterygoid process; 13, ethmoid bone; 14,
temporal bone and sphenoidal suture; 15,
lachrymal bone; 16, vomer; 17, malar Ijone ;
18, maxillary tuberosity; 19, posterior, or
guttural opening of the nose ; 20, palate bone ;
21, palatine styloid process; 22, palato-maxil-
lary foramen ; 23, palatine process of superior
maxillary bone, with suture ; 24, ditto of pre-
maxillary bone; 25, premaxillary bone; 26,
upper incisor teeth ; 27, point of junction of
the premaxillary with the superior maxillary
bone ; 28, upper molar teeth (young mouth).
openings divided, in the fresh state, into two portions {anterior and posterior
lacerated foramina). To the outside of these openings is the base of the tuberous
portion of the temporal bones, especially the tympanic bulb ov petrous bone ; above
82 THE BONES.
are the condyloid fossae, with their condyloid foramen., and the styloid processes of
the occipital hone or Jugular eminences.
2. Suhsphenoidal region. — This region is notably constricted in its middle
part, where it has for base the body of the posterior sphenoid bone ; it is enlarged
above by the temporal articular surfaces. It is limited by the inferior border
of the foramen lacerum, on which are three notches transformed into foramina
by the tissue that partitions the foramen lacerum basis cranii in the fresh
state. These openings are, passing from within to without, the carotid or cavernous
foramen, the foramen ovcde or foramen rotundum ; they are all preceded by a
groove on the surface of the bone. On each side of the body of the sphenoid is
the narrow Vidian fissure, prolonged by the Vidian canal, and margined outwardly
by the origin of the suhsphenoidcd process. Laterally, is the suhsphenoidal canal
for the passage of the internal maxillary artery, which is continued forward
by two branches, one of which opens into the orbital hiatus, the other into the
temporal fossa.
3. Spheno-pcdatine region. — This extends from the superior sphenoid to the
palatine arch. In the median plane it shows a vast elliptical opening — the
gutturcd opening of the nascd cavities, divided at the bottom into two portions by
the vomer, and bordered laterally by two elevated crests (pterygo-pcdatines)
resulting from the junction of the pterygoids with the palatine crests ; and
limited in front by the posterior border of the palatine bones, which is raised in
its middle by a blunt point directed backwards — the nasal spine. Beyond the
pterygo-palatine orests is a slightly depressed surface, on which run the branches
of the internal maxillary artery and the superior maxillary nerve. This surface
extends, above, to the orhital or sphenoidctl hiatus, below to the maxillary hiatus.
In the maxillary hiatus are : the upper opening of the superior dental canal, the
palatine caned, and the nasal foramen. In passing from the maxillary hiatus on
the margin of the guttural opening of the nasal cavities, we meet with the
staphyline fissure, which is limited above by the alveolar tuberosity.
4. Pcdatine region. — .This is a wide elongated surface, limited laterally by the
molar teeth and interdental spaces, and in front by the incisors. It shows : in
the middle, the pcdcdine and superior maxillary suture, which terminates at the
incisive canal ; on the sides and above, the inferior opening of the pcdatine grooves^
prolonged by the pcdatine fissures ; in front, the incisive slits.
C. Lateral Face. — This is a pair face, and comprises three regions (Fig. 51) :
1. Maxillary region. — This is very extensive. Its shape is triangular, base
superior — the supermaxilla being joined to the premaxilla. Proceeding backward,
there are observed : a fossa, in which opens the infra^rhital foramen ; the lower
orifice of the superior dental canal, pierced above the third molar tooth ; the
malar or zygomatic spine — a long vertical crest for the insertion of the masseter
muscle, commencing above the fourth molar teeth, and continuing upwards with
the malar bone and zygomatic process. Lastly, the maxillary region is limited,
above, by the orbit and the maxillary tuherosity.
2. Orhital region. — This includes the orbit or orbital cavity, for the reception
of the essential and some of the accessory organs of vision. In Man and the
Quadrumana this cavity has complete bony walls, but in the domestic animals it
always largely communicates with the temporal fossa, and it is not always
even circumscribed at its opening by a soHd ring. A fibrous lining {ocular sheath)
converts it into a distinct cavity.
In the Horse, the outline of the orbit is constituted : below, by the lachrymal
THE HEAD. 83
bone ; above and in front, by the frontal bone and its process ; externally, by
the malar bone. If its two largest diameters are measured, it is remarked that
this opening is scarcely ever regularly circular, its width varying from above to
below or from without to within. With nine Horses' heads of various ages and
breeds, equal diameters were found in only one, the other eight being unequal ;
of these, the vertical diameter of the orbit predominated in five, and was least in
three.
In the Ass, as a general rule the vertical diameter is smallest, the relation
between the two diameters varying from ro9 to 1"15. Otherwise, the entrance
to the orbit is irregularly square, and the orbital process which covers it is much
wider and more salient than in the Horse — as Lecoq asserted, and as the
observations of Goubaux and Sanson have confirmed. We have also noticed
these differences, and they are not the only ones which permit the skeleton of
the Ass to be recognized ; for there have been already cited those of the spine
and bones of the head — such as the articular depression surrounding the basilar
process, the vascular furrow on the styloid process, the position of the lachrymal
tubercle, and the conical eminence surmounting the premaxillary symphysis,
above the incisive foramen ; others will be noted hereafter (Figs. 51, 52).
With regard to the cavity of the orbit, it is separated from the maxillary
hiatus and the temporal fossa by two linear imprints, diverging forwards, to
which the ocular sheath is attached. It presents, on its floor, the upper orifice
of the lachrymal canal, the lachrymal fossa, where the small oblique muscle of the
eye has its fixed insertion ; and within this, but higher, the little depression for
the bend of the great oblique muscle of the eye.
3. Temporal region. — This region is more extensive than the preceding, and
is composed of three principal parts — the temporal fossa, zygomatic arch, and
petrous portion of the temporal bone.
The temporal fossa surmoimts the orbit, from which it is incompletely
separated in Solipeds and Ruminants by the orbital arch ; in the other domestic
animals, this arch is incomplete in such a way, that in the skull the temporal
fossa is confounded for the greater part with the orbit. Situated obliquely down-
wards and outwards on the sides of the cranium, the temporal fossa is oval in
shape, and bounded inwardly by the occipital or temporal crest, outwardly by
the anterior border and longitudinal root of the zygomatic process. It lodges
the temporalis muscle ; consequently, its width in our animals is proportionate to
the power of that muscle. It is studded with muscular imprints, and has several
vascular foramina which enter the parieto-temporal canal.
The zygomcitic arch is formed as if by a loop thrown from the cranium on to
the face, outside the temporal fossa and the orbit. It is constituted by the
zygomatic process of the temporal bone and the malar bone, which latter
prolongs it to the maxillary region.
The tuberosity of the temporal bone shows, outwardly, the external auditory
canal, usually larger in the Ass than the Horse. Between this orifice and the
supra-condyloid eminence is the opening of the parieto-temporal canal ; and
behind the latter are several irregular ridges, one of them being the hyoid
process. The external face of the tympanic case is also studded with some
styloid prolotiyations, one of which, more developed than the others, serves for
the insertion of the peristaphyline muscles. Above the hyoid process is the
mastoid process, and between these two parts is the external orifice of the aqueduct
of Fallopius. From the mastoid process extends the mastoid crest, the summit of
84
THE BONES.
which meets the external occipital protuberance ; it is crossed by the mastoid
groove, which gives the mastoid artery passage to the parieto-temporal canal.
All of the petrous portion is surrounded by deep clefts, resulting from the
simple union of this bone with its neighbouring pieces.
D. Base. — The base or superior extremity of the head, formed by the
occipital bone, represents a trapezoid surface, incurvated from before to behind.
It is separated from the anterior face by the external occipital tiiherosity, the
projection of which is always greater in the Ass and Mule than in the Horse,
with the exception of the English Horse, in which it has been found very
developed (Figs. 51, 52). It is separated from the lateral faces by two crests —
Fig. 51.
_ 19 IS 12 17 22
horse's head (lateral face).
1, Occipital condyle; 2, styloid process of the occipital bone; 3, external occipital tuberosity,
4, parietal crest ; 5, external auditory hiatus ; 6, zygomatic process of the temporal bone ; 7,
frontal bone; 8, orbit; 9, lachrymal bone and its tubercle; 10, zygomatic or malar bone ; 11,
nasal bone; 12, supermaxillary bone; 13, zygomatic spine; 14, infia-orbital foramen; 15, pre-
maxillary or intermaxillary bone; 16, incisor teeth; 17, molar teeth; 18, inferior maxilla; 19,
maxillary fissure; 20, maxillary condyle; 21, coronoid process of the maxilla; 22, mental
foramen; 23, supra-orbital foramen ; 24, basilar process of the occipital bone.
the superior curved lines — which are prolonged backwards on the styloid processes
of the occipital bone.
In the middle plane is the occipital crest, behind the tuberosity ; it terminates,
in becoming gradually effaced, at the orripital foramen, which is bordered
on each side by the condyles of the occiput. The condyles are separated
from the styloid processes by two deep notches — the stylo-condyloid notches.
Between the middle line and the superior curved lines, are muscular imprints
irregularly arranged in a half -circle — these are the inferior curved lines.
The base of the skull joins the anterior and posterior faces in forming angles ;
these possess some interest, as they may afford an important differential
character between the Ass and Horse.
THE HEAD. 85
If one of the branches of a goniometer be placed tangentiallj to the surface
of the basilar process, and the other to the summit of the external occipital
tuberosity, the basilo-occipital angle will be obtained. In the measurements
we have taken of eight heads of Horses of diverse ages and breeds, this angle
has varied from 70° to 91°. We except the head of a young English Stallion,
the basilo-occipital angle of which was from 92° to 100°. Measurement of the
heads of Asses showed the angle to be 103°. The average basilo-occipital angle
was 85*36° for the Horse, and 95° for the Ass.
If, instead of taking the basilo-occipital angle, the goniometer be applied to
the origin of the temporal crests and the superior outline of the occipital
Fig. 52.
ass's head (lateral face).
, Occipital condyle ; 2, styloid process of the occipital bone, with a very marked furrow on its
external face; 3, external occipital tuberosity, more developed than in the horse; 4, parietal
crest ; 5, external auditory hiatus ; 6, zygomatic process of the temporal bone ; 7, frontal bone ;
8, orbit, with its external outline more angular than in the horse; 9, lachrymal bone, with its
tubercle partly implanted on the nasal bone; 10, zygomatic or malar bone; 11, nasal bone;
12, supermaxilla ; 13, zygomatic spine; 14, infra-orbital foramen; 15, premaxillary bone, with
its inner border raised by a salient tubercle above the incisive canal ; 16, incisor teeth ; 17,
molar teeth; 18, inferior maxilla; 19, maxillary fissure; 20, maxillary condyle; 21, coronoid
process ; 22, mental foramen ; 23, supra-orbital foramen, carried more to the middle of the orbital
process than in the horse ; 24, basilar process of the occipital bone.
In the Horse, this angle is
and S7° — the average being
foramen, the parieio-occipifal angle is obtained
between 81° and 104° ; in the Ass between 7'
91-12° for the Horse, and 84° for the Ass.
It was foreseen that the value of these angles would be in inverse relation.
In all cases when, on a head, the basilo-occipital angle was found very open and
the parieto-occipital more closed, combined with a great development of the
external occipital tuberosity and the differential characters already described,
it was certain to be the head of an Ass. In the English Horse, the external
Sa TEE BONES.
occipital tuberosity of which is very developed, the two angles in question are
nearly equal. In the JIule and Hinny, the value of the angles is intermediate
between the Horse and Ass. In the Mule, the mean value has been 86-12° for
the basilo-occipital angle, and 88° for the parieto-occipital angle. In the Hinny,
it was 87° for the first, and 81° for the second.
E. Summit. — This results from the union of the four faces ; but, instead of
being acute, it is flattened from behind to before, curved from side to side, and
furnished with the incisor teeth. ^
2. CONFOEMATION OF THE CrANIUM IN PARTICULAR.
Retzius was the first to start the idea of considering the cranium of Man
independently of the fafce. He distinguished the races of mankind as hrachtj-
cephalic (short-headed), and dolichocephalic (long-headed) — that is, crania long
from before to behind, and crania relatively short. Broca more recently compared
the transverse diameter of the cranium with the antero-posterior diameter taken
as a unit, and has expressed this relation in hundredths by the term cephalic
index. For some years, Sanson has endeavoured to introduce into the classifica-
tion of animals the calculations of Retzius and Broca. Taking the dimensions
of the cranium as a basis, he has divided Horses into two groups — the brachy-
cephalic and the dolichocephalic kinds.
If the cerebral cranial cavity — the only important one for this purpose — be
enclosed in a parallelogram, two sides of which shall be at a tangent to the most
salient points of the parietal bones, and the other two pass in front of the
external auditory canals and across the supra-orbital foramina, the dimensions of
the base and height of this parallelogram, measured in a straight line., will
correspond to the longitudmal and transverse diameters of the cranium. In
proceeding thus, Sanson has found that in certain crania the transverse diameter
is greater than the longitudinal {brachycephalic crania), while in certain others
the transverse is shorter than the longitudinal diameter {dolichocq)halic crcmia).^
Toussaint took direct measurements of the interior of the cranium, and, no
matter what the breeds of horses were which he examined, he always observed
that the longitudinal diameter exceeded the transverse. We have made cranio-
metrical investigations on a number of Horses, and are able to confirm Toussaint's
statements. In eight skulls from different sources, the longitudinal diameter
varied between 118 and 1S6 millimetres, the transverse between 88 and 104
millimetres. Consequently, in none of these animals was the transverse diameter
equal to the longitudinal. In the number examined were the skulls of a Syrian
and an English stallion — types which Sanson would have selected as the most
brachycephalic ; the relations between the length and width were 1'17 for the
first, and VSl for the second. The average for the eight heads was 1*24.
We are of opinion that there are no brachycephalic Horses, in the rigorous
sense of the word, such as Sanson admits ; so that, if it is attempted to establish
brachycephalic and dolichocephalic types, it will be necessary to previously fix
what shall be the limit between these two types, and this has not yet been done.
The crania of Asses from the south of France are longer than that of the
' For the regions of the head, see Lavocat's Nouvelle Osteologie compar€e de la tete des
Animaux Domestiques.
^ Sanson, " Me'moire sur la Nouvelle determination d'un type specific de race Chevaline,"
Journal de VAnatomie et de la Physiologie, de Ch. Robin, 1867; also the later works of M,
Sanson.
THE READ. 87
Horse ; for in eight the average relation between the length and width was 1-25,
instead of 1'24 — a difference not very great, certainly. The difference becomes
more marked, however, between the Ass and Horse, if the length of the cerebral
be compared with that of the cerebellar cavity. This comparison has yielded an
average of 1-962 in the Horse, and 1-927 in the Ass — which proves that the
cerebellar cranium is longer in the Ass than the Horse.
The cranium is, as it were, strangled behind the orbital processes of the
frontal bones. In glancing at the cranium of the Horse and Ass, it would at first
appear that that of the Ass is relatively narrower than the cranium of the Horse.
We have measured six heads of each species for the width of the cranium at its
greatest diameter, behind the orbital processes, and, in comparing these two
diameters, have obtained the following results : in the H^orse, the relation varied
between 1-18 and 1-27 ; in the Ass, between 1-20 and 1-47. The average has
been, for the Horse, 1-226, and 1-335 for the Ass. From these figures, it might
be concluded that the cranium of the Ass is relatively more constricted at its
inferior extremity than that of the Horse. In the hybrids of the Horse and
Ass, the cranial cavity is more elongated, and in this respect the Hinny more
resembles the Ass than the Horse. With regard to narrowness of the crauium
behind the orbital processes, the Mide holds the middle place between its parents,
while the Hinny comes nearest to the Ass — the reverse of what is noticed
in the development of the cerebellar cranium.
In Ruminants, the shape of the cranium is more or less masked by the
frontal or parietal sinuses ; consequently, it is difficult to study satisfactorily this
part of the head, particularly in the bovine species.
The cranium of the domestic Dog offers great varieties ; for the creation of
numerous breeds has brought about important differences in the form and
dimensions of this part, which it is impossible to deal with here.
3. Relations between the Cranium and Face.
Instead of studying the cranium alone, we may compare it with the face in
regard to width, length, and the area that each of these two regions occupies in
a vertical and median section. We may also, in measuring the facial angle, form
an idea of the manner in which these two regions unite to form the head.
1. The forehead, properly speaking, measured from the union of the parietal
crests to the fronto-nasal suture, is always, in the Horse, longer than the cerebral
cranium, the second to the first being as 1 : 1"425. The forehead of the Ass is
proportionately less developed, for we have found that the cranium is to the
forehead as 1 : 1-265.
2. This shortness of the Ass's forehead, which renders the head heavy, is
corrected by its narrowness ; the head enlarges at the orbital processes. In com-
paring the distance between the supra-orbital foramina and the transverse
diameter of the cerebral cavity, it has been noted that the width of the cranium
is to the space between these foramina as 1 : 1-454 in the Horse, and 1 : 1-265 in
the Ass. The forehead of the Ass is, therefore, in proportion to the cranium,
shorter and narrower than in the horse. From this point of view, the heads of
the 3I'uIe and Hinny are intermediate to those of their parents ; but the first of
these hybrids is nearer the Horse, and the second approaches the Ass.
3. Cuvier imagined that one of the means of judging of the intelligence ot
animals, would be to compare the area of the cranium with that of the face,
measured on a median section of the head, deprived of the lower jaw. This
TEE BOXEd.
great naturalist remarked that the area of the cranium diminishes as the animals
are further removed from the hmuau type, while the area of the face increases
in the same sense. Colin has studied the heads of the domesticated animals
from this point of view. Putting to one side the surface occupied by the
sinuses, he found that the area of the cranium to the face was as —
1 : 2-69 in the Horse.
1 : 2 09 in the Ass.
1 : 3-43 in the Ox.
1 : 2-20 in the Ram.
1 : 1-95 in the Goat.
1 : 3 24 in the Pig.
1 : 117 in the Dog.
1 : 0-68 in the Cat.
1 : 1-47 in the Rabbit.
1 : 054 in the Lamb.
From this table it will be seen that, if the domesticated animals are classified
according to the area of the cranium, they will stand in the following order :
Cat, Dog, Rabbit, Goat, Ass, Ram, Horse, Pig, and Ox.
4. Camper measured the facial aiigU by drawing two lines, starting from the
entrance to the nasal cavities, and passing towards the middle of the external
auditory canal and towards the most prominent part of the forehead. The facial
angle gives an idea as to the relative volume of the face and cranium, and the
dimensions of the latter ; but with animals it furnishes very imperfect information,
because of the form of the face and the development of the sinuses around the
cranial cavity.
Colin has measured the facial angle of the domestic animals, by drawing two
lines from the upper incisors towards the external auditory canal and the fore-
head, in the point corresponding to the lower end of the brain ; and he obtained
the following average values : from 12° to 15° for the Horse ; 16° for the Ass ;
20° for the Bull ; from 20° to 25° for the Ram ; from 3-4° to 41° for Dogs ; and
41° for the Cat.
On the other hand, we have measured this angle in Equines, and find that it
varies : in the Horse, between 11° and 13° ; in the Ass, between 12° and 16° ;
and in the Mule, between 13° and 15°. In the Hinny, it measures 14°. It is
somewhat remarkable that, in the Equidae, the Ass should have a greater facial
angle than the Horse.
4. Modifications due to Age.
Age brings modifications bearing upon the form of some regions of the head,
the development of external peculiarities of the bones, the shape of the cranium,
and its relations with the surface.
1. It has been remarked that the development of the occipital tuberosity,
the temporal crests, and the lachrymal tubercle, increases with age in the Equine
species ; the infra-orbital foramen, which is frequently only a notch in youth,
becomes a true foramen when the animal is advanced in age. In the Foal, the
forehead is convex ; that bone and the nasal bones become flat as the creature
grows, and sometimes even the line of the nasal bones is concave in old age. The
maxillary region, which is at first convex, becomes gradually hollow as the molar
teeth are pushed out of the alveoli ; while the straight part of the posterior
border of the inferior maxilla becomes thin and sharp in very old Horses. The
entrance to the orbit is also notably modified, though its shape is not identical
in all the animals. In every instance, it has been remarked that the direction of
the larger axis of the orbital cavity, comprised at first in the plane which passes
by the auditory canal and the implantation of the upper incisors, is depressed in
THE HEAD.
front, and at an advanced age is found in a plane passing by the inferior
extremity of the zygomatic crest and the summit of the external occipital
tuberosity.
2. If the cranium be examined by itself, it will be noted that, in proportion,
it is less narrowed behind the orbital processes in the young animal than in the
adult. With regard to the cerebellar cranium, it is elongated when the animal
is aged — a consequence of the natural development of the external occipital
tuberosity.
3. The relation of the areas of the cranium and face change with age. If
the measurements obtained by Colin on the Lamb and Ram are compared, it
will be perceived that the face grows as the creature ages. This change is very
evident if the development of the young Hare is watched. At birth the face is
very short — like that of a common dog, it is said ; but when development is
completed, we know how much the face has become lengthened.
4. Finally, in consulting the table of angles drawn up by Colin, we might
believe that the facial angle widens as the animal advances in age. Thus, in the
young Hinny, Colin estunated the facial angle at 15° ; this angle was 16° on an
Fig. 53.
A, B, C, D. 1, Fronto-parietal crests; 2, external occipital tuberosity; 3, 3, superior root of
the zygomatic process of the temporal bone.
old Hinny, and 17° on another very old one. In every instance, however, according
to the same table, this angle will be equal in a four-years-old Horse and in an
adult Horse ; and even in the Calf it diminishes one degree when it becomes an
adult animal.
The measurements we have taken in domestic Solipeds, have demonstrated
that the facial angle diminishes in a constant manner as the animal grows old.
Thus, this angle is 16° in an Ass three years old ; it is 15° in the adult, and 12°
in the very old Ass. We have found it 13° in a Foal of two years, and 11° in
an old Horse ; 15° in a Mule of eighteen months, and 12*30° in a very aged
Mule.
This question has, therefore, to be again examined ; and, however it may be
decided, it will be seen, by what has been stated, that age induces very interesting
changes in the form and proportions of various parts of the head.
If the crania of different breeds of Dogs are compared, there will be found
very marked diversities in the prominence of the parietal convexity, and the
development and distance apart of the fronto-parietal crests. A mere glance
at the ligures above (Fig. 53), will afford evidence of this.
90 THE BONES.
On the cranium of the Mastiff (a), the parietal bulgings are httle marked ;
the parietal crests are very elevated, and join each other early, so that the
temporal muscles are in contact throughout the greater part of their inner
margin. In the little Lap-dog (d), the parietal crests are widely separated from
one another, and the cranium is so very convex as to resemble that of a Monkey.
Between these extremes are many intermediates (b, c) ; and it would appear
that the development of inteUigence in the Dog results in rendering the parietal
bones more convex, and the temporal fosssB narrower.
Comparison of the Head of Man with that of the Domesticated Animals.
1. Occipital hone. — The occipital of Man is large, flat, incurvated like a shell, and the ex-
ternal tuberosity is slightly developed, and united by a ridge to the occipital foramen, which
is relatively very wide. Two series of ridges arise from
the external tuberosity and pass towards the circum-
ference of tlie bone ; these are the superior and inferior
curved or semicircular lines. There is an anterior and
a posterior condyloid fossa pierced by a foramen at the
bottom; and the jugular eminences, wide and slightly
prominent, replace the styloid processes of the domesti-
cated animals.
The internal face of the occipital of Man corresponds
with the cer( brum and cerebellum ; and for this purpose
it shows four fossae, distinguished into superior or cerebral,
and inferior or cerebellar. These fossse are separated by
a crucial projection whose most developed portion forms
the internal occipital protuberance.
The union of the occipital with the parietal bones, con-
stitutes the liimlidoidal suture. At the point where this
bone meets the parietal and the squamous portion of the
temporal, is found, in the infant, the lateral posterior
fontanel.
2. Parietal hones. — The parietals are always isolated
in early life, and sometimes consolidated with each other
at the adult age. They are very large, quadrilateral,
and occupy the summit and sides of the cranium.
The parietal crests are absent, but are replaced, in
certain individuals, by two faintly marked curved lines
situated a little above the inferior border of the bone.
The middle portion of the external face is very convex.
On the internal face there is no parietal protuberance,
but in its stead the internal occipital tuberosity. It
also exhibits ramous channels, which in disposition are
analogous to the ribs of a tig-leaf ; as well as the parietal
fossa, which corresponds to the parietal eminence.
3. Frontal hone. — The frontal bone of Man forms the
upper part of the face and the anterior portion of the
cranium. Convex from behind forward, then vertical in
its upper three-fourths, the bone suddenly bends at tlie
orbits, so as to become horizontal in its lower fourth.
The external face offers, above the forehead, two Literal
frontal eminences, and above the nose, a middle frontal
boss. To the right and left of the latter are two salient
arches— the supra-orbital ridges. The internal face entirely belongs to the cranial cavity. It
offers, on the median line, the saggital groove terminated by a frontal crest; and on each
side of this line the frontal fosste, corresponding to the eminences of that name, and orbital
bo.sses to match the orbital roofs. There is no mortise for the articulation of the sphenoid bone.
On the middle poition of the superior frontal border, in young persons, is the anterior
angle of the anterior fontanel. The anterior border exhibits three supra-orbital foramina
and the orbital arches.
front view of the human
cranium.
, Frontal bone ; 2, nasal tuberosity ;
3, supra-orbital ridfijp ; 4. optic
foramen ; 5, sphenoidal fissure ;
6, spheno-maxillary fissure ; 7.
lachrymal fossa ; 8, opening of
the nose divided by the vomer; 9,
infra-orbital foramen; 10, malar
bone ; 11, symphysis of the lower
jaw; 12, mental foramen; 13,
ramus of the lower jaw ; 14, parie-
tal bone ; 15, coronal suture ; 16,
temporal bone ; 17, squamous
suture ; 18, upper part of the great
ala of the sphenoid bone; 19, com-
mencement of the temporal ridge ;
20, zygoma of the temporal bone
concurring to form tlie temporal
arch ; 21, mastoid process.
THE HEAD.
91
Fig. 55.
4. Ethmoid hone.— In Man, the external fa^e of the lateral masses— formed by a very
thin lamina, termed the os planum or lamina pap2/r«e«— belongs to the internal wall of the orbit.
5. Sphenoid bone.— TLiis is distinguished, in Man, into a body and four wings- two large
and twfi small.
Tlie inferior surface of the body oflfers nothing remarkable, except the presence of a conical
prolongation named the beak (rostrum) of the .sphenoid. The external face of the greater
wings forms part of the temporal fowsa, as also the external wall of the orbit. At the union
of the wing.s with the body, are detached two bifid
pterygoid proce.-^ses ; their internal branch represents
the pterygoid bones of animals. There is no sub-
sphenoidal canal.
Tlie two lesser wings are very thin and triangular,
and visible only on the superior surface of the bone ;
they constitute the processes of Ingrassias.
On the internal face of the bone are found : (1)
a deep pituitary fossa, limited by four cUnoid pro-
cesses; (2) an optic fossa, shallow, showing very
short optic canals transformed into foramina ; (3) the
sphenoidal fissure, which replaces the great super-
spheiioidal canal in the Horse; (4) the great foramen
rotundum; (5) the internal face of the wings, much
excavated ; (6) the foramen ovale, which transmits
the inferior maxillary nerve ; (7) the small foramen
rotundum that lodges the spheno-spinous artery.
6. Temporal hone. — In the squamous portion of
the temporal bone of Man, the zygomatic process only
rests on the malar bone, as in Ruminants. The glenoid
cavity is concave in every sense, ami divided into two
parts by an opening named t\\e fi'<sura Glaneri ; the
anterior portion only is articular — the posterior, lying
against the external auditory canal, does not belong
to the articulation ; it corresponds to the supra-con-
dyloid eminence of the Horse. The tuberous portion
is consolidated with the squamous. It is divided into
a mastoid and a pyramidal portion ; the latter com-
prises, in its turn, the petrous an^l tympanic portions.
The mastoid portions correspond to the mastoid pro-
cess, mastoid protuberance, and superior border of the
petrous bone in the Horse. It presents a rugged
mast(;id process. Above this is the mastoid canal ;
and aliove and behind it, tlie digastric groove — tlie
pyramid forming a considerable projection in the
interior of the cranium. The styloid process or bone
is altogether separate from the other pieces of the
hyoid, and in the adult is consolidated with the tem-
poral bone.
7. Supermaxilla. — In Man the premaxilla is no
longer found independent, the centre which forms it
coalescing with the supermaxillary bone.
The supermaxilla of man concurs, for the greater
part of its extent, to form the floor of the orbit ; it
is also divided into three faces : an external or facial, a superior or orbital, and an internal
or naso-palatine. The external face presents, from before to behind: (1) a small fossa, into
which is inserted the niyrtiform muscle; (2) the infra-orbital, or canine fossa, showing the
inferior orifice of the infra-orbital canal; (3) a crest corresponding to the maxillary spine of
Solipeds : (4) the alveolar tuberosity. This face carries, in front, a prolongation that forms the
ascending process, also named, because of its relation, the tronto-nasal process. The superior
or orbital face oflfers a fissure which precedes the infra-orbital canal, and, outwards, the malar
process. The internal face is divided by the palatine process. It shows, in front, the half of
the anterior nasal spine and a groove which participates in the formation of the incisive canal.
8. Palatine fcojie.- The palatine bone of Man isformedof two osseous laminae— one horizontal,
the other vertical— which are joined at a right angle. The first part presents : one-half of the
EXTERNAL OR BASILAR SURFACE OF
THE BASE OF THE HUMAN SKULL.
, ], The bony palate; 2, incisive, or
anterior palatine foi-amea; 3, pala-
tine process of p date bone, with the
posterior palatine foramen ; 4, palate
spine with transverse ridge ; 5, vomer ;
6, internal pterygoid palate ; 7, sca-
phoid fossa; 8, external pterygoid
plate, with fossa ; 9, zygomatic fossa ;
10, basilar process of occipital bone ;
11, foramen magnum; 14, glenoid
fossa; 15, meatus auditorius exter-
nus ; 16, foramen lacerum anterius ;
17, carotid foramen of left siile; 18,
foramen lacerum posterius, or jugular
foramen; 19, styloid process; 20,
stylo-mastoid foramen, with jugular
tubercle and digastric fossa ; 21, mas-
toid process ; 22, occipital bone ; 23,
posterior condyloid fossa.
92 THE BONES.
posterior nasal spine, whicli is altogether rudimentary, or even null in animals ; the orifice of
the posterior palatine canal, which belongs entirely to the palate boue; the pterygo-palatine
foramen ; lastly, the pterygoid process, which represents tiie pterygoid bone of animals. The
vertical portion foims the external wall of the nasal cavities by its internal face, and by its
external face concurs in the formation of the zygomatic or temporal fossa.
9. Malar bone. — This oflfers three faces. The external, or cutaneous, serves as a base for the
most salient part of the cheek. The superior, or orbital, forms part of the external wall and
floor of the orbit ; it belongs to a long apophysis — the orbital process — which rests on the
sphenoid and frontal bones. The posterior face is smooth and concave behind, where it aids to
form the temporal fossa; in front it is uneven, and articulates with the supermaxilla. The
posterior, or masseteric border, unites with the zygomatic process of the temporal bone.
10. Lachrymal bone. — This bone is also called the os unguis in Man, because of its likeness
to the nail in shape and tenuity. It is entirely lodged in the orbit, and its external face is
divided into two portions by a vertical crest ; the portion situated in front of this crest forms
part of the lachrymal groove. By its internal face, the lachrymal bone limits, outwardly,
the bottom of the nasal cavities, and covers the anterior cells of the ethmoid ; by its posterior
border, within the orbit, it articulates with the os planum of the ethmoid.
11. Nasal bone. — The proper bones of the nose of Man exhibit a great analogy to those of
the Dog. Tliey do not possess a nasal prolongation, and they articulate with the lateral
cartilage of the nose.
12. Vomer. — The same general form and relations as in Solipeds.
13. Inferior maxillary bone. — This bone in Man is in shape somewhat like a horse-shoe. It
is nearly of the same witlth throughout its whole extent. The symphysis is vertical — a
character peculiar to Man. Below this symphysis is a triangular projection — the mental
eminence. The genial surface of the Horse is replaced by four little tubercles, termed the
genial processes. The alveoli of the molar teeth form a great projection on the inner face of
the bi)ne. The mylo-hyoid ridge is very developed. The superior orifice of the dental canal
is covered by a little sharp lamina. From this oritice begins the mylo-hyoidean groove. The
coronoid process is short ; the condyle is bent towards the median line, and the sigmoid notch
is wide and shallow. The superior border contains fourteen or sixteen alveoli.
Aeticle III. — The Thorax.
The thorax represents a coinoid cage, elongated from before to behind,
suspended under the vertebrae of the dorsal region, and contains the principal
organs of respiration and circulation. It is composed of bony arches named
ribs, thirty-six in number — eighteen on each side — and a single piece — the
sternum, which serves for the direct or indirect support of the inferior extremi-
ties of the ribs.
The Bones of the Thorax in particular.
1. Sternum of the Horse (H^jial Spine) (Fig. 56).
This is an osteo-cartilaginous body, elongated from before backwards,
flattened on each side in two-thirds of its anterior extent, and above and below
in its posterior third ; it is slightly curved on itself, and situated beneath the
thorax in an oblique direction downwards and backwards. It offers for study, a
superior face, two lateral faces, three borders, and two extremities.
Faces. — The superior face, shghtly concave longitudinally, represents an
isoscelated lengthened triangle, the summit of which is directed forwards ; it
constitutes the floor of the thoracic cavity. The inferior face is shaped like the
keel of a ship, having in its middle a longitudinal ridge, which decreases in
height from before to behind. It has two inclined planes placed towards each
other, each of which has two parts — a superior and an inferior. The first shows
eight diarthrodial cavities, which receive the inferior extremity of the cartilages of
the true ribs. These cavities are elongated vertically, and draw closer to each other
THE THORAX. 93
as they extend backwards. The inferior part, which is more extensive before
than behind, offers to the powerful pectoral muscles a large surface for insertion.^
Borders. — The two inferior borders separate the superior from the inferior
faces ; they are situated above the diai-throdial cavities, are united anteriorly, and
each gives attachment to a fibrous band.
Extremities. — The anterior, flattened on each side and curved upwards, exceeds
to some extent the first articular cavity of the lateral faces, and in this way con-
stitutes the cervical prolongation {prcesternum) of the sternum. The posterior
extremity is flattened superiorly and inferiorly, and forms a large cartilaginous
plate, very thin, concave above, convex below, which has received the name of
the abdominal prolongation (ensiform cartilage), or xiphoid appendage.
Structure and development, — The sternum is one of the parts of the skeleton
Fig. 56.
THE STERNUM.
1, The cervical prolongation (prcesternum, or cariniform cartilage) ; 2, the xiphoid appendage (or
ensiform cartilage); 3, 3, cavities for the articulation of the sternal cartilages ; 4, inferior burder.
which do not undergo complete osseous transformation. It is developed, in
Solipeds, from six single nuclei of spongy substance, ranged one behind the
other, like beads on a string. These nuclei never coalesce to form a solid piece,
but remain separated during the life of the animal, by the primary cartilaginous
mass. The latter constitutes the entire anterior prolongation of the bone and its
carina, as well as the xiphoid appendage. When these parts of the sternum
become ossified — which is rare — they are only partially so.
Differential Characters in the Sternum op other Animals.
In all the domesticated animals except Solipeds, tlie sternum is flattened above and below
instead of ou both sides.
A. Ruminants. — In Ruminants, each piece is developed from two lateral centres of ossifi-
cation. The bones wliich compose it are seven in number; they are much more compact than
those in the sternum of the horse, and at an early period are united to each other, with the
exception of tl:e first, which is joined to the secmid by a diarthrodial articulation tliat permits
it to execute lateral movements. There is no cervical prolongation, and the xiphoid cartilage
is feebly developed and well detached from the bodv of tiie bone. In the sternum of the Goat
and Sheep, the two first pieces have no diarthrodial joint, but are simply united by a layer of
cartilage, which, in old animals, becomes completely ossified. The sternum of the Camel has
a very oblique direction downwards and backwards, and is formed by seven pieces ; the first is
somewhat rudimentary, while the two are very strong, and serve as a base for the sternal
callosity or pad.
B. Pig. — Tlie sternum of this animal presents in its general conformation the essential
features of that of large Ruminants. It is provided with a well-defined cervical prolongation,
and is composed of six pieces, which, at least in the four or five last, are each divided into two
lateral nuclei.
C. Carnivora. — ^The sternum of the Dog and Cat is formed of eight pieces, elongated from
before to beliiud, hollowed in their middle part, and thick at their ends— formed, indeed, like
the last coccygeal vertebrae of the Horse. They are never ossified to each other.
9
94
THE BONES.
2. The Ribs (Pleuropophyses) (Fig. 57).
As has been already remarked, on each side of the thorax there are eighteen
ribs. These are nearly parallel to each other, and separated by the intervals
termed the intercostal spaces. Attached by their superior extremity to the
vertebrse of the dorsal region, these bones terminate at their inferior extremity
by an elastic and flexible prolongation, named the costal cartilage, by means of
which they are brought into direct or indirect relations with the sternum. The
characters common to all the
^'S- ^^- ribs will be first noticed, then
the special features which serve
to distinguish them from each
other, and, lastly, the differences
they exhibit in other than Soh-
ped animals.
A. Characters common to
ALL THE Ribs. — These will be
studied from a typical point of
view, first in the rib itseK, and
then in its cartilage.
1. Description of a typical
rib. — A rib is an elongated
asymmetrical bone, oblique from
above to below, and from before
to behind, flattened on both
sides, curved hke a bow, and
twisted on itself in such a fashion
that its two extremities cannot
rest on the same horizontal
plane. It is divided into a
middle portion or bod//, and tivo
extremities.
3Iiddle portion. — This offers
two faces and two borders. The
external face is convex, and
hollowed by a wide groove in
its anterior half ; it shows
superiorly, towards the point
corresponding to the angle of
the rib in Man, some tubercles
and muscular imprints. The
internal face is concave and
smooth, and covered by the
pleura, which separates it from
the lungs. The anterior border
is concave, thin, and sharp ; the posterior — convex, thick, and covered with rugged
eminences — is channeled iuAvardly by a vasculo-nervous groove, which disappears
near the middle of the rib.
Extremities. — The superior has two eminences— a head {capitidum) and a
tuberosity (tuberculum) — which serve for the support of the rib against the spine.
TYPICAL RIBS OF THE HORSE.
, Inner face of the fifth sternal rib. B, External face
of the first asternal rib. 1, Head of the rib; 2, its
fissure ; 3, neck ; 4, tuberosity ; 5, articular facet ;
6, scabrous fossa for the insertion of the interosseous
costo-transverse ligament ; 7, groove on the external
face ; 8, vasculo-nervous groove on the posterior border ;
9, prolonging cartilage ; 10, A, articular tuberosity
for union with the sternum.
THE THORAX. 9S
The first is formed by two articular demi-facets, placed one before the other, and
separated by a groove for ligamentous insertion ; it is isolated from the tuberosity
by a narrow part, named the neck, which exhibits a rugged fossa for the implantation
of a ligament. The second — situated behind the head, and smaller than it — is
provided with imprints on its margin, and presents an almost flat diarthrodial facet
at the summit. Each rib articulates by its head and tuberosity with two dorsal
vertebrse ; the head is received into the intervertebral articular cavity ; the tube-
rosity corresponds, by its facet, to the transverse process of the posterior vertebra.
The inferior extremity is tuberous and excavated by a shallow cavity,
irregular at the bottom, for the reception of the upper end of the costal cartilage.
Structure and development. — The ribs are very spongy bones, especially in their
inferior moiety, and are developed at a very early period from three centres of
ossification — a principal for the middle portion and inferior extremity, and two
complementary for the head and tuberosity.
2. Description of a typiccd costal cartilage. — The costal cartilage QicBmapopliysis)
very evidently represents the inferior rib in Birds ; it is a cylindrical piece,
slightly compressed at the sides, and round and smooth on its faces and borders.
By its superior extremity, it is united to the rib it serves to lengthen, and forms
with it an angle more or less obtuse, opening in front. At its inferior extremity,
it is terminated by an articular enlargement, or by a blunt point. In youth, the
costal prolongations are entirely composed of cartilaginous matter, but they are
soon invaded by ossification ; so that in the adult animal they are already trans-
formed into a spongy, substance, with large areolae which remain during life
surrounded by a thin layer of cartilage.
B. Specific Characters of the Ribs. — The ribs, hke the vertebra of
each region of the spine, have received numerical designations of first, second,
third, etc., computing them from before to behind (Fig. 5). Owing to the
presence of an altogether essential characteristic, they are naturally divided into
two great categories — the sternal or true ribs, and the asternal or false ribs. The
sternal ribs, numbering eight — the first eight — have their cartilages terminated
inferiorly by an articular enlargement, which corresponds to one of the lateral
cavities of the sternimi, and brings the true ribs into direct contact with this
portion of the skeleton. The asternal ribs, ten in number, rest on each other —
the last on the seventeenth, that on the sixteenth, and so on — by the inferior
extremity of their cartilage, which ends in a blunt point. The cartilage of the
first false rib is united somewhat closely to the last sternal rib, and it is through
the medium of this that all the asternal ribs lie indirectly on the sternum.
If, however, the ribs are considered altogether, with regard to the differential
characters presented by them in their length, width, and degree of incurvation,
it will be noted : 1. That their length increases from the first to the ninth, and
from this diminishes progressively to the last, 2. That the same progressive
increase and decrease exists in the cartilages. .3. That they become gradually
wider from the first to the sixth inclusive, and then contract by degrees until the
eighteenth is reached : 4. That the curve described by each is shorter and more
marked as the rib is situated more behind. It may be added, that the channel
on the external face is less conspicuous in proportion as the rib is narrow.
The first rib, considered individually, is always distinguished by the absence
of the groove on its outer surface, by the vasculo-nervous groove on its posterior
border, and the groove or notch intermediate to the two facets of its articular
head. It is also recognized by the deep muscular imprints on its external face,
96 THE BONES.
the shortness and thickness of its cartilage, and particularly by the articular facet
which this cartilas^e exhibits inwardly, to correspond to that of the opposite rib.
The last rib has no channel on its external surface, and the facet of its tuberosity
is confounded with the posterior facet of the head. This last character is also
nearly always remarked in the seventeenth rib, and sometimes even in the
sixteenth.
In the Ass, the ribs in general, but particularly those most posterior, are less
curved than in the Horse. They differ more particularly in the curve of the neck
being much shorter — a difference which is most obvious when the goniometer is
applied to the angle of the rib, and the most salient part of the head and tube-
rosity. By this means we have obtained an angle the value of which was greater
in the Ass than in the Horse : from 7><° to 130° for the external ribs, and from
100° to 132° for the asternal ribs, of the first ; from 60° to 125° for the sternal,
and from 140° to 150° for the asternals, of the second. The upper extremity of
the sternal ribs in the Ass is less twisted outwards than the same part in the
Horse ; and in the latter, the plane which passes by the head of the rib is more
distant than the plane which, in the Ass, passes across the tubercle.
The ribs of the Mule are intermediate between those of the Ass and Horse,
with regard to the value of the angle just indicated ; they approach those of the
Ass by the twist in their superior extremity.
Differential Characters in the Ribs of other Animals.
The number of rib:^ varies like that of tlie dorsal vertebrae. The following table'* indicate
the number uf these bones in the different domesticated animals : —
Pig 14
Ox l.S
Sheep 13
Goat 13
Dog 13
Camel ... 12
Rabbit 12
A. Ruminants. — These animals, with the exception of the Camel, have eight sternal and
five asternal ribs.
In the Ox, they are longer, wider, and less arched than in Solipeds. The articular
eminences of the superior t-xtremity are voluminous and well <letafhed; the neck especially is
very long. The sternal ribs are joined to their cartilage of prolnngment by a real diarthrodiai
articulation. In the last rib, and sometimes in tlie one before it, the tuberosity is scarcely
perceptible, and has no articuhir facet. In the Sheep and Goat, the sternal ribs are consolidated
with the cartilages (Figs. 6. 7).
The Camel has eight sternal and four asternal ribs. The rib.s increase in length to the
tenth, and in width to the si.xth only. They are less curved and are shorter, proportionately,
tiian those of the Ox, the shortness being very marked in the first three. The tubercle is less
de'achefl than in the Ox, but the neck is longer and stronger (Fig. 8).
B. Pig. — In this animal there are fourteen pairs of ribs, seven of which are sternal and
seven asternal. The first are provided with cartilages of prolongment flattened on both sides,
extremely wide and sharp, and convex on their superior border. In the four last asternal ribs,
the fitcet of their tuberosity is confoundi'd with the posterior facet of the head (Fig. 3).
C. Carnivora. — They possess thirteen ribs on each side — nine sternal an.l four asternal.
These are very much arched, narrow, and thick, and their cartilages rarely ossify. In the Dog,
the articular facet of tiie tuberosity remains isolated from the posterior facet of the head in all
the ribs. It is absent in the three last ribs of the Cat (Fig. 2).
The Thorax in General.
The description of the interior of the thoracic cavity will be referred to when
treating of the respiratory apparatus. It is only necessary here to examine the
THE THORAX.
97
Fig. 58.
external surface of this bony ca^e. For this purpose it is divided into six
regions — a superior plane, an inferior plane, tivo lateral pla7ies, a base, and a
summit.
Planes. — The superior plane is separated into two portions bj the spinous
processes of the dorsal vertebra ; each forms, with these spinous processes, the
costo-vertebral furrow, intended to lodge the majority of the muscles belonging
to the spinal region of the back and loins. The inferior plane, less extensive
than the preceding, offers : 1. On the median line, the cariuiform and xiphoid
cartilages of the sternum ; 2. On the sides, the chondro-sternal articulations,
and the cartilages of prolongment of the true ribs. The lateral planes are con-
vex and wider at their middle part than in front or behind, and exhibit the
intercostal spaces. They serve to give support, anteriorly, to the superior
segments of the two anterior limbs.
Base. — This is circumscribed by the posterior border of the last rib, and by
the cartilages of all the asternal ribs ; it is cut ouliquely downwards and for-
wards, and gives attachment, by its internal
circumference, to the diaphragm — a muscle
which separates the thoracic from the ab-
dominal cavity.
Summit. — It occupies the anterior por-
tion of the thorax, and presents an oval
opening, elongated vertically, situated be-
tween the two first ribs. This opening
constitutes the entrance to the chest, and
gives admission to the trachea, the oeso-
phagus, and important vessels and nerves.
Comparison of the Thorax of Man with
THAT OF THE DOMESTICATKD AnIMALS.
1. Sternum.
The sternum of Man is flattened before and
behind, and diminishes in widtii from above to be-
low. The xiplioid ap[)endage is narrow, and single
or bifid. Besides the articular surfaces for the ribs,
there are found on the upper end two lateral
notches for articulation with the clavicles.
2. Ribs.
Of the twelve ribs in Man, seven are eternals
and five asternals. They are short, narrow, and
much incurvated, especially the first ones. In each
rib the curvature is more marked in the posterior
fourth or fifth, than in the anterior three-fourths
or four-fifths ; this sudden change of curvature is
indicated in the external face by a kind of inflection
and thickening, called tlie angle of the ribs. The
prolonging cartilages of the eleventh and twelfth
ribs are short, and are lost in the substance of the
are termed ihe floating {or false) ribs (Fig. 58>
thorax op man (anterior face).
1, Superior piece of the sternum ; 2,
middle piece, or body ; 3, inferior piece,
or ensiform cartilage; 4, first dorsal
vertebra ; 5, hist dor.^al vertebra ; 6,
first rib ; 7, its head ; 8, its neck, rest-
ing against the transverse process of the
first dorsal vertebra ; 9, its tubercle ;
10, seventh, or last true rib ; 11, costal
cartilages of the true ribs ; 12, the last
two false or floating ribs ; 13, the groove
along the lower border of the rib.
abdominal parietes ; for this reason they
Article IV. — Anterior Limbs.
The anterior ( pectoral or thoracic) limb is divided into four secondary regions —
the shoulder, arm, forearm, and fore foot or hand.
98 THE BONES.
SHOULDER.
In Solipeds, this region has for its base a single bone — the scapula or omoplat.
^^ Scapula (Figs. 59, 60).
This islW»^ triangular, and asymmetrical bone, prolonged at its superior
border by a flexible cartilage, articulated interiorly with the humerus only, and
applied against the lateral plane of the thorax in an oblique direction downwards
and forwards. It has two faces, three borders, and three angles.
Faces. — The external face (or dorsum) is divided by the scapidar or acroynian
spine, into two cavities of unequal width — the supra- and infra-spinous (or antea
and 2)ostea spinatus) fosscB. The spine is a very salient crest which runs the whole
length of the external scapular surface ; very elevated in its middle part, which
shows an irregular enlargement — the tuberosity of the spine — it insensibly decreases
towards its two extremities. The supraspinous fossa — the narrowest — is situated
above, or rather in front of the spine ; it is regularly concave from side to side,
and perfectly smooth. The infra-spinous fossa is twice the width of the preceding,
and occupies all the surface behind the spine. It exhibits : 1. Below, and near
the posterior border, several rows of roughened lines for muscular insertion.
2. Near the neck, the nutritient foramen of the bone, and some vascular grooves.
The interned face is excavated in its centre to form a hollow, called the subsca-
pular fossa, which is prolonged superiorly by three diverging points. The median
point extends to the superior border of the bone, and separates two roughened
triangular surfaces.
Borders. — The superior is indented by an irregular groove, to receive the
inferior margin of the cartilage of prolongation. The latter is convex on its
superior border, extends beyond the posterior angle of the bone, and gradually
diminishes in thickness as it leaves its point of attachment. In old horses it is
nearly always found partially ossified. The anterior border, thin and sharp, is
convex in its superior two-thirds, and slightly concave for the remainder of its
extent. The posterior is thicker and a little concave.
Angles. — The anterior, or cerviccd angle, is the thinnest of the three. The
posterior or dorsal angle is thick and tuberous. The inferior, or humeral angle, is
the most voluminous, and is separated from the remainder of the bone by a
slight constriction, which constitutes the neck of the scapula. It exhibits : 1. The
glenoid cavity — an oval diarthrodial surface, excavated to a slight extent to receive
the head of the humerus, nbtched on the inner side, and bearing on the external
margin of the ridge which surrounds it a small tubercle of insertion. 2. The
coracoid process, situated in front, and at a certain distance from the glenoid
cavity. This is a large eminence in which may be distinguished two parts : the
base, a thick rugged process ; and the summit, a kind of beak curved inwards.
Structure and development. — Like all the flat bones, the scapula is formed of
two compact layers separated by spongy tissue. The latter is very scanty
towards the middle of the supra- and infra-spinous fossfe, where it is often alto-
gether wanting ; it is most abundant in the angles. In Solipeds and Ruminants,
the scapula is developed from two principal centres of ossification, one of which
forms the coracoid process.
In the Carnivora, the cartilage of prolongation is replaced by an epiphysary
lip. It may be added that in Mammaha, Meckel, Cuvier, and Strauss-Durckheim
have noted a supplementary nucleus in the glenoid cavity ; and that Lavocat
and Goubaux have observed it in Horses especially. Lavocat has described it as
THE ANTERIOR LIMBS. 99
a pyramidal nucleus, base inferior, and flattened before and behind. In the
Horse, it appears at the centre of the cavity towards the seventh or eighth month ;
it increases and pushes forward the coracoid process beyond the articular sur-
face. In about nine or ten months it is fused with the principal part of the bone,
and in about a year with the coracoid nucleus. In the Ass and Mule, the glenoid
Fig. 59.
Fig. 60.
SCAPULA OF THE HORSE (EXTERNAL FACE). 1, Subscapular fossa ; 2, anterior triangular
1, Tuberosity of the spine ; 2, supra-spinous f ^face ; 3 posterior triangular surface ;
fossa ; 3, infra-spinous fossa ; 4, nutrient *' *' vascular furrow ; 5, glenoid cavity ;
foramen; 5, 5, 5, linear imprints for the ^ base of the coracoid process (insertion
insertion of the coraco-humeralis ; 6, of the coraco-humeralis).
tubercle for the same ; 7, border of the
glenoid cavity ; 8, coracoid process ; 9,
cervical angle; 10, dorsal angle; 11,
cartilage of prolongation.
nucleus appears about the fourth month, and its evolution is completed at the
seventh or eighth month.
In the Ass, the scapula is usually more curved than in the Horse, while the
greater development of its superior border, and the more considerable constric-
tion of its neck, give it a peculiar appearance. It represents a wider and shorter
]00
TEE BOXES.
triangle than in the Horse, and the spine gradually decreases from the tuberosity
until it is nearly lost on the surface of the bone, towards the nutrient foramen.
In the Horse, this subsidence of the spine occurs at the neck, where it takes,
place quite suddenly ; so that it forms a more or less marked prominence.
The scapula of the Hinny has the general form of that of the Ass ; in the
Mule, on the contrary, it is elongated Kke that of the Horse.
Differential Characters in the Scapula of other Animals.
The shoulder is composed of one or two bones, according as the limb is intended exclu-
sivelj' to support the body, or is required for other purposes.
A. Ox, Sheep, Goat.— In these animals the shoulder comprises only one bone— the
scapula— which is more regularly triangular than in the Horse. The spine does not diminish
in passing to the neck, but, on the contrary, terminates at a certain distance above the glenoid
Fig. 61.
R A
scapula of the cat and rabbit.
A, Scapula of the Cat. B, Scapula of the Rabbit. 1, Inferior extremity of the acromian spine v
2, supra-spinous fossa; 3, infra-spinous process; 4, superior border.
cavity by an abrupt ridge prolonged to a point, which represents a rudimentary acromion pro-
cess. It divides the external surfnce of the bone into two fossse, which in extent are as 1 :3.
The neck is more constricted, and the humeral angle better detached, than in Solipeds.
B. Camel. — The scapula of this animal resembles that of the Ox in its general form, but
the spine divides the face into two equal fossae. The acromion process descends to the glenoid
cavity.
C. Pig. — The .spine, depressed at its two extremities, rises considerably at its middle por-
tion, and bends over towards the infra-spinous process.
D. Camivora.— Their shoulder has two bones — the scapula and clavicle. In the Dog ,
the latter is little more than a shell embedded in the muscles in front of the scapulo-humerul
angle ; in the Cat, it constitutes a small styloid bone which is united to the acromion process
and the sternum through the medium of two ligaments. The scapula has no cartilay;e of pro-
longation ; its anterior border is very convex, as if it had been curved over on itself. The fos.'ife
of the external face are equal, and the spine terminates in an acromion process that reaches the
glenoid cavity.
E Rabbit. — Two bones form the shoulder of this animal. The clavicle, although longer
than that of the Cat. nevertheless does not rest directly on the sternum and scapula. The
latter is in shape regularly triangular; the neck is slender; the fos^sse on the external face
are very unequal ; the spine is prolonged by a thin acromion pedicle to the vicinity of the
glenoid cavity ; and the superior border of the bone is [irovided with a cartilage of prolongation.
TEE ANTERIOR LIMBS.
101
Arm.
Fig. 62.
This region has only one bone, the humerus.
Humerus (Figs. 62, 63).
The humerus is a long single bone, situated between the scapula and the bone
of the forearm, in an oblique direction downwards and backwards. Like all the
long bones, it offers for study a bodt/ and two extremities.
Body. — The body of the humerus looks as if it had been twisted on itself from
within to without in its superior extremity, and from
without to within at the opposite end. It is irregularly
prismatic, and is divided into four faces. The anterior
face (Fig. 62), wider above than below, has in its middle
and inferior portions some muscular imprints. The pos-
terior, smooth and rounded from one side to the other,
"becomes insensibly confounded with the neighbouring
faces. The external is excavated by a wide furrow, which
entirely occupies it, and turns round the bone obliquely
from above to below and behind to before ; it is to the
presence of this channel that the humerus owes its ap-
parent twist, and it is in consequence designated the /?/rrow
of torsion (or inusculo-spiral groove) of the body of the
humerus.
This furrow is separated from the anterior face by
a salient border — the deltoid ridge, which ends inferiorly
above the coronoid fossa, and superiorly, towards the
upper third of the bone, by the imprint, or deltoid (or
external) tuberosity. This is a roughened, very prominent
eminence, flattened before and behind, and inclining to-
wards the furrow of torsion ; by its superior extremity,
it gives origin to a curved line which is carried backwards
to join the base of the articular head. Near the inferior
extremity, backwards and outwards, is seen the posterior
deltoid ridge, which separates the latter from the posterior
face of the bone. The internal face of the body of the
humerus, rounded from side to side, is not separated from
the anterior and posterior faces by any marked line of
demarcation. It offers, near its middle, a depressed
scabrous process (the internal tuberosity) for the insertion of
the teres major and latissimus dorsi muscles. Towards its
inferior third it shows the nutrient foramen of the bone.
Extremities. — These are distinguished into superior and
inferior. Both are slightly curved — the first backwards,
the second forwards— a disposition which tends to give to the humerus the form
of an S.
The superior extremity is the most voluminous, and has three thick eminences —
a posterior, external, and internal. The first constitutes the head of the humerus.
It is a very slightly detached articular eminence, rounded like the segment of a
sphere, and corresponding with the glenoid cavity of the scapula, which is too
«mall to receive it entirely. The external eminence — named the trochiter, large
ANTERO-EXTERNAL VIEW
OF RIGHT HUMERUS.
1, Trochlear or bicipital
ridges ; 2, external or
deltoid tuberosity ; 3,
head or articular sur-
face ; 4, external tuber-
cle ; 5, shaft or body
with its twisted fur-
row; 6, 7, articular or
trochlear condyles; 8,
uluar fossa with a sul-
cus; 9, fossa for the
insertion of the exter-
nal lateral ligament.
102
THE BONES.
Fig. 63.
(or external) trochanter, and great fuberositi/—corm[>Y[ses three portions, named
the summit, convexitij, and crest of the great tuberosity. The internal eminence —
the trochin, little (or interned) trochanter, or small tuherosity — also presents three
distinct portions, which, by their position, correspond exactly with the three regions
of the external trochanter ; these are so many muscular facets.
The external and internal trochanters are separated from each other in front
by a channel called the bicipital groove, because the superior
tendon of the biceps muscle glides over it. It consists of
two vertical grooves, with a median ridge between them.
The inferior extremity of the humerus has an articular
surface corresponding with the radius and ulna. This sur-
face— elongated transversely, convex from before backwards,
and of greater extent within than without — exhibits two-
trochlea separated by an antero-posterior relief.
The median or interned trochlea, the deepest, is limited
internally by a kind of voluminous condyle, which corre-
sponds to the inner lip of the humeral trochlea of Man.
The external trochlea is bordered outwardly by a slightly
salient lip, which corresponds to the condyle of the humerus
of Man. Above and behind this articular surface is a wide
deep fossa — the olecranian (or condyloid), so named because
it lodges the rostrom of the olecranon in the extension move-
ments of the forearm. It is bordered by two eminences,
the external of which is less elevated than the internal. The
first represents the epitrochlea, and the second the epicondyle,
of the humerus of Man. In front, and above the inner
trochlea, there is another, but less spacious fossa, which
receives the coronoid process during extreme flexion of the
forearm, and which, for this reason, it would be convenient
to designate as the coronoid fossa. Always in front, but
above the external trochlea, are imprints for the attach-
ment of the capsular ligament of the elbow- joint and the-
extensor metacarpi magnus. Lastly, at the extremities
of the transverse axis of the inferior articular surface is
remarked, outwardly, an excavation for ligamentous insertion;
inwardly, a small tuberosity for the same purpose.
Structure and development. — The humerus, like all the long bones, is only
spongy at its extremities. It is developed from six points of ossification, one of
which alone forms the body, one the head and the internal trochanter, another the-
external trochanter, a fourth the inferior articular surface, a fifth the epicondyle,
and the last for the epitrochlea. The latter is sometimes absent. In the young
animal the humerus is less twisted, and the eminences for muscular insertion less
developed, than in the adult.
In the Ass, the humerus is more twisted and curved in S form than in that
of the Horse, and these modifications replace the eminences on this bone in the
latter. Consequently, the equilibrium of the humerus is altered when it lies on a
horizontal plane by any one of its faces and its lower extremity. Thus, while the
humerus of the Ass may rest in equilibrium on a plane — its trochlea and two other
points of its anterior face touching it — the Horse's humerus can only do so when
the condyle, trochlea, and one or two points of its superior extremity touch it..
POSTERIOR VIEW OF THE
RIGHT HUMERUS.
2, External trochanter;
3, articular head of
the bone; 4, external
tubercle and ridge ;
5, body or shaft of
the bone ; 10, condy-
loid fossa.
THE ANTERIOR LIMBS.
103
Fig. 64.
Laid on its posterior face, the humerus of the Ass is in unstable equiUbrium, if it
has to touch the plane by the epicondyle and epitrochlea ; this is not so with the
humerus of the Horse. If it is placed on its external side, the deltoid imprint
remains above the horizontal plane with the Ass, and touches it with the Horse.
Lastly, the epitrochlea descends nearly to the articular surface in the Ass, so that
the bone is almost in equilibrium when it is placed on its inferior extremity.
The humerus of the Mule and Hinny resembles that of their parents, but
that of the Hinny is more like the Ass's, and that of the Mule the Horse's.
Differential Characters in the Humerus of other Animals.
Proportiot)ately, the Immeius is longer, ami more inflected like an S, as the number of
apparent digits is increased. Therefore it is that, in the C.irnivora, the characters of length
and inflection are most marked.
A. Ox, Sheep, Goat.— In these animals, the furrow of torsion is less marked, and the
deltoid imprint less salient than in the Horse, while
the extremities are larger and more curved. The
bicipital groove is divided into two depressions by
a median ridge ; the external trochanter is enormous,
and its very elevated summit is bent over the
bicipital groove. Tlie head is better detitched and
the trochlea deeper than in the Horse. The medul-
lary eanal of the humerus of the Ox is sometimes
crossed by an osseous band.
B. Camel. — Humerus cylindrical and nearly
straight. Torsion furrow shallow ; nutrient foramen
on its anterior face. Bicipital groove double, the
inner cavity being larger than the external. The
inferior articular surface is relatively very narrow,
and the external trochlea deep.
C. Pig. — The humerus of this animal is com-
pressed on both sides; the head is much bent back-
wards, which increases its S inflection. A single
bicipital groove placed within the superior extremity ;
the external trochanter voluminous, and the summit
turned over the bicipital groove. Deltoid imprint
and internal tuberosity of the body replaced by
simple muscular imprints.
D. Dog and Cat. — The humerus is very elon-
gated and more S-curved than in all the other
animals, and the internal tuberosity is leplaced by
some imprints ; while the bicipital groove is single,
and the nutrient foramen, on the posterior face, is as
in the Ox, Sheep, and Pig. The coronoid fossa com-
municates with that of the olecranon by a foramen.
E. Rabbit. — The humerus of this animal greatly
resembles that of the Dog, except that it is much
more flattened on each side, and the deltoid imprint
is on the anterior face and nutrient foramen on the
inner lace of the bone.
Forearm.
This region has for its base two bones — ^the radius and mtitus (or vino),
united into a single piece {os aniihrachii) at an early period in most of the
domesticated animals.
HUMERUS OF THE CAT AND RABBIT.
, Humerus of the Rabbit. B, Humerus of
the Cat. 1, Condyle; 2, trochlea; 3,
diaphysis ; 4, external trochanter ; 5,
internal trochanter ; 6, bicipital groove.
1. Radius (Figs. 65, 66).
This is a long bone, placed in a vertical direction between the humerus and
the first row of carpal bones, and divided into a body and two extremities.
104
THE BONES.
Body. — Slightly arched and flattened before and behind, it presents for study
two faces and two borders. The anterior face is convex and perfectly smooth. The
posterior, a little concave from one extremity to the other, offers : 1. Near the
external border, a triangular surface, covered with asperities, elongated vertically,
very narrow, commencing near the upper fourth of the bone, and terminating in
a fine point towards the lower fourth ; this surface is brought into contact with
the anterior face of the ulna by an interosseous liga-
^^S- 65. ment, which is completely ossilied before the animal
-^''' reaches adult age. 2. Above, there is a wide, trans-
verse, but shallow groove, which aids in forming the
radio-ulnar arch, and shows, near the point where it
touches the preceding surface, the nutrient foramen of
the bone. 3. Near the internal border, and towards the
inferior third, there is a vertically elongated and slightly
salient eminence for insertion. The two borders — external
and internal — are thick and rounded ; they establish an
insensible transition between the faces.
Extremities. — The superior is larger than the inferior.
It has : 1. An articular surface elongated from one side
to the other, concave from before to behind, wider
within than without, and moulded to the articular sur-
face of the inferior extremity of the humerus ; there
is also seen, outwardly, a double depression (glenoid
cavities), which receives the two lips of the external
trochlea ; in the middle, an antero-posterior ridge,
which is received into the internal trochlea ; within,
an oval cavity corresponding to the internal border
of the former. 2. The external tuberosity, placed at
the extremity of the great diameter of the articular
surface ; it is prominent and well detached. 3. The
interned or bicipital tuberosity — a large, very rugged, and
depressed process, situated within and in front of the
glenoid cavity. 4. A little lower, and on the same side,
there is a strong muscular and ligamentous imprint,
separated from the preceding tuberosity by a transverse
1, Ulna; 2, point of the groove intended for the passage of a tendon. .5. The
coronoid process,^ a small conical eminence, at the
summit of which terminates, anteriorly, the median
ridge of the articular surface. (3. Two diathrodial
facets elongated transversely, cut on the posterior outline
of the large articular surface, with which they are con-
founded by their superior border ; they correspond with
similar facets on the ulna. 7. Below these, a roughened
surface which extends to the radio-ulnar arch, and is in contact with an analogous
surface of the same bone through the medium of an interosseous ligament. In
the Horse, this hgament rarely becomes ossified.
The inferior extremity, flattened before and behind, presents : 1. Inferiorly, an
articular surface elongated transversely and somewhat irregular, responding to
the four bones in the upper row of the carpus. 2. On the sides, two tuberosities
* In Man this belongs to the ulna.
EXTERNAL FACE OF THE
RADIUS AND ULNA.
Ulna; 2, point of the
ulna; 3, beak of ulna or
olecranon ; 4, radio-ulnar
arch ; 5, supero-external
tuberosity; 6, radio-ulnar
articular surfaces for the
humerus; 7, bicipital tu-
b rosity ; 8, shaft or body
of the radius ; 9, grooves
for tendons.
THE ANTERIOR LIMBS. 105
for ligamentous insertion — the internal salient and well circumscribed, the other
external, and excavated by a vertical fissure — in which passes a tendon. 3. In
front, three grooves for the gliding of tendons ; the external is the largest,
and vertical like the median ; the internal, the narrowest, is oblique downwards
and inwards. 4. Posteriorly, a strong transverse ridge which surmounts the
articular surface, and serves for the insertion of ligaments.
Structure and development.— The radius is a very compact bone, and is
developed from three centres of ossification — one for the body, and two for the
extremities.
2. Ulna (Figs. 65, 66).
This is an elongated, asymmetrical bone, in the form of an inverted triangular
pyramid, applied against the posterior face of the radius, to which it is united
in adult Solipeds. It offers for description a middle portion and two extremities.
Middle portion. — This has three faces wider above than below, and three
borders which become joined at the inferior extremity of the bone. The external
face is smooth and nearly plane. The internal is also smooth and shghtly
hollowed. The anterior is formed to correspond with the radius, and presents
pecuharities analogous to those of the posterior face of that bone. Thus, there
is found, in proceeding from above to below : 1. Two small diarthrodial facets.^
2. A roughened surface. 3. A transverse groove for the formation of the radio-
ulnar arch. 4. A triangular surface, studded with rugosities, which occupie^the
remainder of the bone to its lower extremity. The lateral borders — externatand
internal — are sharp, and, like the anterior face, are in contact with the radius.
The posterior border is concave, rounded, and thicker than the other two.
Extremities. — The superior extremity comprises all that portion which exceeds
the articular surface of the radius. It constitutes an enormous process — the
olecranon — flattened on both sides, and presenting : 1. An external face, slightly
convex. 2. An internal excavated face. 3. An anterior border, thin and sharp
superiorly, notched below to form the sigmoid cavity^ — an articular surface
concave from above downwards, rounded from one side to the other, which
corresponds with the humeral cavity, and is surmounted by a salient prolongation
named the bectk of the olecranon. 4. A concave and smooth posterior border. 5.
The summit — a kind of thick roughened tuberosity which terminates the uhia
above, and into which are inserted the extensor muscles of the forearm.
At its inferior extremity, the ulna ends, towards the lower fourth of the
principal portion of the forearm, in an acute point, and sometimes by a small
knob (capitulum ulnce). It is not rare to see it prolonged, especially in the Ass
and Mule, to the inferior external tuberosity of the radius. This tuberosity then
appears to belong to it, at least in part ; and all that portion which is situated
behind its vertical groove might be justly considered as a dependency of the
uhia.
Structure and development. — The ulna contains much compact tissue, even in
the region of the olecranon ; it is also very solid. It is an imperfect bone,
developed from two centres of ossification only, one of these being for the apex
of the olecranon.
In the Ass (Fig. 66), the radius is more curved than in the Horse, and when
its anterior face is placed on a horizontal plane, the bone only rests on its upper
' Tlv smaller siqmmrl cavity of Man.
* 'The qreater f^iijinoid en vity of Man.
106
THE BONES.
end and the middle of the body. It is also distinguished from that of the Horse
by the depth of a narrow groove, which passes through the rough lip above and
behind the inferior surface, superior to the small fossa
F'g- 66. that receives the third bone of the upper row of the
carpus during flexion and extension movements. The
ulna of this animal is more developed than that of the
Horse, and its olecranon is proportionately shorter,
broader, and more hollowed on its internal face. The
inferior extremity (Fig. 66, 9) is nearly always formed
by a particular nucleus, which is also sometimes the case
in the Horse.
In the Hinny, the bone of the forearm resembles
that of the Ass, with the exception of the smallness of
the lower end of the ulna.
Differential Characters in the Forearm Bones of
OTHER Animals.
The principal ditferential characters that they present are con-
nected with the relative dimensions of the two bones and their mode
of union. Regarding these, and as generally applicable, tlie follow-
ing principles may be laid down : —
1 . The development of the ulna is in direct relation to the division
of the foot. — Mouodactylous animals — such as the Horse, Ass, and
Mule — have, in fact, only a rudimentary ulna. In the pentadacty-
lous animals, on the contrary — as Man, the Cat, Elephant, etc., —
this is a veritable long bone which equals, or even exceeds, the
radius in volume.
2. The closeness of union between the radius and ulna is in
increased proportion as the animal exchmvely employs its inferior
extremity for standing and walking. — Thus, in Solipeds and Rumi-
nants, and Pachyderms in general, the two bones are consolidated,
or at least united by an interosseous ligament, and in so firm a
manner that they can only execute very obscure movements on
each other. The anterior limb of these animals is, indeed, only
used to support the body on the ground. In those, on the contrary,
which may employ it to dig up the soil, climb on trees, etc., or as
an organ of preliension, the radius and ulna are merely joined at
their extremities by an articulation, which permits them to move
upon one another with the greatest facility. Rodents, the
majority of the Caniivora, and the Quadrumana, are so provided ;
but it is in Man that the relative independence of the two bones
is carried to the highest degree. No animal can so easily execute
the movements of pronation and supination of tiie hand, which are
determined by the play of tlie two bones of the forearm on each other.
To the indication of these fundamental characters, may be added
some details on a few particular and important points.
A. Ox, Sheep, Goat. — The forearm of the Ox is short;
that of the Sheep and Goat is longer ; but in the three species, the
ulna— thicker than in the Horse— is a long bone developed from
three primary nuclei. It extends the whole length of tlie radius,
and concurs in forming the articular surface corresponding with
the carpal liones.
The inferior articular surface is cut obliquely downwards and
inwards. There are two radio-ulnar arches — a superior and in-
ferior— united externally by a deep fissure. The union of tlie two
bones is more intimate than in the Horse; for ossification always
ends by invading that portion uf the interosseous ligament placed
above the superior vascular arcli (Fig. 71).
forearm bones OF THE
1, Diaphysis of the radius;
2, bicipital tuberosity ;
3, external and superior
tuberosity of the radius ;
4, groove for the passage
ot the anterior extensor
of the phalanges ; 5,
surface for insertion of
branch of the perforans
tendon ; 6, body of the
ulna interrupted at its
lower third, but more
complete than usual ; 7,
summit of the olecranon ;
8, beak of ditto ; 9, in-
ferior extremity of ditto ;
10, radio-ulnar arch ; 11,
crest above the inferior
articular surface of the
radius, behind.
THE ANTERIOR LIMBS. 107
B. Camel. — The radius of this animal has a narrow, superior, articulating surface of two
glenoid cavities, separated by a median salient crest terminating in front by a very marked
coronoid process ; the bicipital tuberosity is large, and on the anterior face. The ulna is very
-concave in its middle part, and tlie olecranon is broad and low.
C. Pig. — The radius is short, its inferior surface cut rather obliquely as in Ruminants, and
partly formed by the inferior extremity of the ulna, which is a voluminous bone provided with
a medullary canal, and solidly united to the radius by an interosseous ligament, the complete
ossification of wliich is rare. It is flattened before and behind, and is spread over the posterior
face of the radius, so as nearly to completely cover it. The olecranon is very prominent (Fig. 7G).
D. Dog, Cat. — The two bones of the forearm are nearly equal in volume, and are in
contact only by their extremities, where they show for this purpose : 1. Above, on the ulna,
a concave articular surface — the small sigmoid cavity ; and on the radius, a rounded hinge-like
facet. 2. Below, two facets analogous to the preceding, but much smaller; that on the radius
is concave, and that on the ulna convex. Tliese two bones slightly cross each other, so that the
upper end of the ulna touches the radius behind and inwards, wliile the inferior terminates
altogether outwards. In the Pig and Ruminants, the lower end is in contact with the upper
row of carpal bones (Fig. 77).
E. Kabblt. — The ulna is still more developed than in the Cat, and more curved length-
ways.
The posterior border of the olecranon is almost vertical, instead of being oblique from
before to behind, and the sigmoid notch is deeper and shorter curved than in the
Carnivora.
ANTERIOR (OR FORE) FOOT, OR HAND.
The anterior foot, or hand, is the region which presents the greatest 0flfe-
rences when it is examined in the various individuals of the animal series.
Nevertheless, notwithstanding these varieties, its constitution is fundamentally
the same, and may be divided into three sections — ^the carpus, metacarpus, and
phalangeal region.
In vertebrate animals, the hand is composed of a certain number of parallel
or quasi-parallel segments, which constitute the digits. Each complete digit is
subdivided into three sections, placed one above the other ; these are, reckoned
from above to below — carpus, metacarpus, and phalanges.
The number of apparent digits varies from one to five ; and, however it may
otherwise appear, philosophical anatomy has shown that the hand of all the
domesticated animals may be considered as belonging to the pentadactylous
type. When it does not appear to be so, this is due to more or less numerous
or extensive atrophies or abortions always occurring according to fixed laws. (See
remarks hereafter on the Hand in General.)
1. Caepal Bones (Figs. 67, 68, 69).
The carpus (or 'knee') forms the base of the hand. Situated between the
inferior extremity of the radius and the superior extremity of the metacarpal bones,
it is composed of several small bones joined to each other, in the fresh state, by
extremely solid articular bands. Collectively, they form an almost quadrilateral
mass, in which may be distinguished two faces and four borders.
The anterior face is slightly convex from side to side, and irregular ; it is
in contact with the tendons of the extensor muscles of the metacarpus and
phalanges.
1h.Q posterior face is very unequal, and converted — especially outwardly — into
a groove, in which the tendons of the flexor muscles of the phalanges glide.
108
THE BONES.
Fig. 67.
The superior border articulates with the radius ; the inferior border with the
metacarpal bones.
The lateral borders are nearly flat ; above and behind the external border is
remarked a considerable eminence, formed by the
bone which will be hereafter studied as the super-
carpal bene (pisiform or trapezium).
In the carpus of the Horse are seven or eight
bones, which are disposed in two superposed rows.
The superior row comprises four bones placed side
by side, and designated by the numerical names of
Jirst, second, third, and fourth, viewing them from
without to within. The inferior row has only
three, which are named in the same manner.
In applying to them the names proposed by
Liser, we have, in the upper row —
1. The pisiform, or supercarpal bone.
2. The cuneiform bone.
3. The lunar bone.
4. The scaphoid bone.
In the inferior row —
1. The unciform bone.
2. The magnum bone.
3. The trapezoid bone.
4. The trapeziimi (not constant).
The description of these bones is most simple,
and may be made in a general manner for all. Thus,
with the exception of the supercarpal bone, they
are solid, nearly cubical in form, and exhibit on
their periphery : 1. Articular surfaces. 2. /Surfaces
for insertion.
The articular surfaces are small, flat, or slightly
undulating facets, distributed on the superior, in-
ferior, and lateral faces ; none are found in front
or behind. The superior and inferior faces are
entirely occupied by a single facet, which responds
either to the radius, the metacarpals, or to the bones
of the other row. The lateral facets are always
RIGHT ANTERIOR FOOT OR HAND multiplc, aud iu coutact with the bones of the same
OF A
tier ; they do not exist, of course, on the outside
of the bones at the ends of each row.
The surfaces for insertion are absent on the
superior and inferior faces ; they separate, in the
form of roughened depressions, the lateral articular
facets. Before and behind, they are covered by
more or less marked rugosities.
Bones of the Upper or Antibrachial Row
(Figs. 68, 69). — The first, or os pisiforme, is outside
the row ; it is situated above and behind the carpus, whence its name of super-
carpal bone, by which it is usually known in veterinary anatomy. This bone,
which merits a special description, represents a disc flattened on both sides.
HORSE.
1, Radius; 2, grooves for the ex-
tensor of the phalanges; 3,
scaphoid; 4, lunar; 5, cunei-
form ; 6, pisiform ; 7, mag-
num; 8, unciform ; 9, great
metacarpal; 10, small meta-
carpal ; 11, sesamoid bone ; 12,
suffraginis ; 13, coronary; 14,
navicular; 15, pedal ; 16, basi-
lar process.
THE ANTERIOR LIMBS.
109
oflFering for study two faces and a circumference. The external face is convex,
roughened, and channeled anteriorly by a groove that traverses it from above to
below, in which glides the inferior tendon of the external flexor of the
CARPUS OF THE HORSE (ANTERIOR FACE).
1, Pisiform or supercarpal bone (first of the
upper row); 2. cuneiform (second ditto) ;
3, lunar (third ditto); 4, scaphoid (fourth
ditto) ; 5, unciform (first of lower row) ;
6, OS magnum (second ditto) ; 7, trape-
zoid (third ditto) ; 9, inferior articular
face of the radius; 10, groove for the
oblique extensor tendon of the meta-
carpus; 11, groove for the anterior ex-
tensor of the metacarpus; 12, groove for
the anterior extensor of the phalanges ;
13, superior extremity of the large meta-
carpal bone ; 14, tubercle for the inser-
tion of the anterior extensor of the meta-
carpus ; 15, superior extremity of the
external small metacarpal bone.
CARPUS OF THE HORSE (POSTERIOR FACE>
1, 2, 3, 4, 5, 6, 7, Same bones as in preced-
ing figure ; 8, trapezium (fourth bone of
the lower row); 9, 9, inferior articular
surface of the radius ; 10, transverse crest
for insertion of common posterior liga-
ment of the carpus; 11, superior extremity
of large metacarpal bone; 12, rugosities
in which are fixed the deep layer of the
suspense) y ligament of the fetlock or
superior sesamoid ligament; 13, external
small metacarpal ; 14, internal ditto.
metacarpus. Its internal face — smooth and concave — concurs in forming the
external wall of the carpal sheath. The circumference presents, in front, two
10
110 THE BONES.
articular facets : the superior, concave, corresponds to the radius ; the inferior,
convex, is in contact with the second bone of the upper row.
The other three bones of this row increase in volume from without to within.
The second bone, os pyramidalis, or cuneiform, articulates with the radius,
the first bone of the lower row, the third of the upper, and the supercarpal
bone ; it has, in all, five articular facets.
The third, or os lunctre, has six facets, and is united below to the first and
second bones of the second row.
The fourth, or os scajjhoides — the most voluminous of the row— has only four
facets, and articulates by its inferior face with the os magnum and trctpezoides.
Collectively, the second, third, and fourth bones of the upper row form two
articular surfaces.
The superior, or radial articular surface, is very irregular ; but in examining
it from without to within, there may be observed : 1. A glenoid cavity on the
cuneiform bone. 2. In front, a transversely elongated condyle on the lunar and
scaphoid bones. 3. A groove placed behind the preceding condyle.
The inferior articulating surface, which corresponds to the second row, is
constituted by several undulated facets ; it is convex outwardly and in front,
concave posteriorly and inwardly.
Bones of the Infekior or Metacarpal Row (Figs. 68, 69). — The thick-
ness of these bones decreases from without to within.
The first, unciform, or hookbone {os hainatum), has four diarthrodial facets,
and responds, above, to the two first bones of the superior row ; below, to the
first and second metacarpals.
The second, os magnum, or os capitatum — ^the largest — has seven articular
facets, three of which are on the interno-lateral face. It articulates, above, with
the lunar and scaphoides ; below, with the principal metacarpal and the internal
rudimentary metacarpal.
The third, or trapezoides — the smallest — is provided with five facets, and is
in contact with the scaphoides above, and the middle and internal metacarpals
below.
Collectively, these bones of the lower row form two large diarthrodial
surfaces. The upper surface responds to the bones of the upper row, and is
constituted in front, and from without to within, by a small condyle and two
glenoid cavities ; behind, by two isolated condyles, formed by the os magnum
and the trapezoides. The inferior articular surface is only formed by more or
less long and plane facets, which incline towards each other. It articulates with
the three portions of the metacarpus.
Structure and deveJopm£nt. — Each carpal bone is formed by a nucleus of
close spongy substance, enveloped in a very thick layer of compact tissue. Each
is developed from a single centre of ossification.
The carpal bones of the Ass much resemble those of the Horse, but the
upper face of the Junar is more concave ; the facet of the cuneiform, for the
pisiform, is less concave, but larger and triangular, and is always separated from
the superior articular surface by a rough, wide, and deep groove. The pisifot m
is more circular than that of the Horse, and is modified in shape to correspond
with the cuneiform ; while the inferior surface of the os magnum is almost plane
in the Ass, but in the Horse it is cut into a condyle in front and a glenoid cavity
behind. Lesbre states that the trapezium is more frequent in the carpus of the
Ass than the Horse.
THE ANTERIOR LIMBS.
Ill
The carpal bones of the Hinny are hke those of the Ass, but those of the
Mule resemble the Horse.
Fi^. 70.
Differential Characters in the Carpal Bones of other Animals.
A. Ox, Sheep, Goat. — In these animals the carpus is composed of only six bones — four
in the upper and two in the lower row, where the os magnum and trapezoid are fused together.
The pisiform bone is in shape as its name implies, has no groove, and has no relation with the
radius. The cuneiform bone articulates with the radius and ulna. The bones of the lower
row only articulate with the large metacarpal bone (Fig. 71).
B. Camel. — Among tlie seven carpal bones of the Camel are seen :
a pisiform bone, having on its external face a large smooth groove ; a
lunar, flattened on each side, and deeply notched laterally ; an unciform
having a pyramidal prolongation behind ; an os magnum, smaller than
the latter ; and a trapezoid, little developed, and entirely removed to
the posterior part of the carpus.
C. Pig. — The carpus of the Pig, like that of Man, contains eight
bones — four in each of the rows. The second bone of the upper row
articulates with the ulna, and to a very small extent with the radius.
In the bones of the lower row, it is observed that the first articulates
witli the two external metacarpals, the second with the great internal
metacarpal, the third with the preceding and the small internal meta-
carpal. The fourth, or trapezium, terminates inferiorly by a blunt
point, and has no relations with the metacarpal bones, because the thumb
is entirely undeveloped in this animal (Fig. 76).
D. Dog, Cat. — In the Cat and Dog there are also eight bones.
Lesbre says, however, that the scaphoid and lunar are sometimes one
bone, and that often a lenticular bone is found in the upper row. The
cuneiform bone is very developed, and occupies all the external border of
the carpus, articulating with the ulna, first bone of the second row, and
the first metacarpal. 'J'he pisiform bone is elongated, prismatic, thick
at both ends, and has in front two contiguous articular facets— one for
articulation with tlie ulna, the other for union with the cuneiform bone.
The bones of the lower row diminish in size from the first to the fourth,
and articulate — the first, with the first and second metacarpals; the
second, with the metacarpal of the third digit; the third, with the
fourth digit ; and the fourth with the metacarpus of the thumb.
E. Rabbit. — This animal possesses nine carpal bones; for it is
stated that between the two rows there is a piece which Blainville has
named the intermediate bone It really belongs to the upper row, and
represents the scaphoid. There are, therefore, five bones in the first
carpal row of the Rabbit, and in this respect the hand of this species
more nearly approaches the typical hand than that of the other domestic
animals (see the Hand in General).
2. Metacarpal Bones (Figs. 67, 70).
In Solipeds, the metacarpus is composed of three bones,
named the " metacarpals," standing parallel to each other.
These are the principal metacarpal and the two rudimentary
metacarpals — an external and internal.
Principal Metacarpal Bone {psmetacarpi magnum').—
This is a long cylindrical bone, situated vertically between the
carpus and the digital region.
Bodij. — The body is a little depressed before and behind, which permits it to
be described as having two faces and two borders. The anterior face is perfectly
smooth and rounded from side to side. The posterior face is flat, and exhibits :
1. Towards the upper third, the nutrient foramen of the bone. 2. On the sides,
posterior view of
right metacarpus.
1, Head of large meta-
carpal bone for ar-
ticulation with the
trapezoi'i, magnum,
and unciform ; 2,
inner splint, rudi-
mentary, or small
metacarpal bone,for
articulation with
the trapezoid ; 4,
scabrous surface for
the attachment of
the suspensory liga-
ment ; 5, nutrinnt
foramen ; 6, median
ridge separating tne
two inferior con-
dyles.
112 THE BONES.
two narrow, rousrhened surfaces, parallel and elongated vertically, commencing
near the superior extremity, to disappear a little below the middle of the bone ;
these surfaces are held in apposition to the rudimentary metacarpals, by an
interosseous ligament which is often ossified in old Horses. The borders — external
and internal — are very thick, round, and smooth, like the anterior face.
Extremities. — The superior is flattened before and behind, and presents. 1.
Above, an undulating articular surface, formed by the union of several flat facets
more or less inclined towards each other ; they articulate with all the lower row
of carpal bones. 2. Anteriorly and inwardly, a tuberosity for muscular insertion.
3. Posteriorly — and directly above the roughened surfaces of the posterior face —
four small diarthrodial facets in pairs, and running into the larger articular
surface by their superior border ; they are adapted to similar facets on the
rudimentary metacarpals. The inferior extremity, elongated transversely, articulates
with the first phalanx and the sesamoid bones by an articular sm-face — convex
from before to behind — which is composed of tivo lateral condyles separated by a
median spine. The two condyles would be exactly alike, if the antero-posterior
diameter of the external condyle were not less extensive than that of the opposite
condyle. Both are hollowed on the sides by an excavation for the attachment
of ligamentous fasciculi.
Structure and development. — The principal metacarpal is one of the most
compact bones in the body. It is developed from two centres of ossification,
one of which is for the inferior extremity.
RuDiMENTAEY METACARPALS (ossa metacctrpi pavva). — The two rudimentary
(sm.aU) metacarpal (or splint) bones are elongated, and placed against the
posterior face of the principal bone, one without, the other within. Each is in
the form of an inverted pyramid, and exhibits a middle part and two extremities.
Middle portion. — Prismatic and triangular, this ofl^ers : 1. Three faces — an
external, smooth and rounded from one border to the other ; an internal, plane,
and equally smooth ; an anterior, covered with asperities to give attachment to
the interosseous ligament uniting the lateral metacarpal bone to the median.
2. Three salient borders which markedly separate the faces from each other.
Extremities. — The superior, the largest, is named the head, and shows : above,
a diarthrodial facet which articulates with one or two bones of the inferior row
of the carpus ; in front, other two small facets continuous with the preceding,
and in contact with similar facets on the large metacarpal bone ; on the other
points of its periphery are rugosities for the attachment of ligamentous and
tendinous fibres. The inferior extremity only reaches to about the lower fourth
of the large metacarpal bone, and terminates in a small button-shaped enlarge-
ment, which is never fused with the latter.
The two small metacarpals, although very much alike, may yet be easily
distinguished from each other. For instance, the internal bone is always the
thickest, and often the longest ; besides, the superior articular surface of its
head results from the union of the two facets articulating with the two last
carpal bones of the lower tier.
Structure and development. — Of a somewhat compact texture, like all the long
bones, these have no medullary canal, and are developed from only one ossifying
centre. Not unfrequently, however, the tubercle is formed from a special centre.
The metacarpus of the Ass is recognized by : 1. The great inequality of the
small metacarpals. 2. The thickness of the large metacarpal (the width is to the
thickness as 1-35 : 1 in the A&s, and as 1*53 : 1 in the Horse). 3. The depth of
THE ANTERIOR LIMBS.
113
the depressions above the inferior articular surface, poste-
riorly. 4. The level form of the facet articulating with the
OS magnum of the second row. 5. The presence of a small,
flat, vertical facet on the posterior contour of the upper
articular surface of the large metacarpal.
In the Mule and Hinny, the small metacarpals are nearly-
alike, as in the Horse ; the large metacarpal is flattened, as
in that animal, with marked depressions posteriorly.
Differential Characters in the Metacarpus of other Animals.
The number of metacarpal bones naturally varies with tliat of the
digits : —
In the Carnivora there are 5
In the Pig there are 4
In Ruminants there are 2 or 3
With regard to their shape and form, they offer interesting differences,
which will now be studied.
A. Ox, Sheep, Goat. — In these animals the metacarpal bones are
two in number — a principal, which itself results from the consolidation
of the second and third metacarpals ; another, altogether rudimentary,
situated outwardly; and a third— not constant — embedded in a fibrous
cord passing along the inner border of tlie principal metacarpal.
The principal metacarpal is channeled on its anterior face, and for
its whole length, by a deep vascular fissure — a trace of the primitive
separation of the bone into two pieces. Tliis fissure presents, inferiorly,
the anterior orifice of a canal that completely traverses the bone. The
posterior face is nlso marked by a very slight longitudinnl groove. The
superior extremity exhibits, externally and posteriorly, a single diar-
throdial facet for articulation with the rudimentary metacarpal. The
inferior extremity is divided by a deep notch into two articular surfaces,
which together resemble the single surface in the Horse ; each articulates
with one of the digits ; the external is always smaller than the internal.
In the foetus, the two long bones that form the great metacarpal are
simply laid together, and their medullary canals are separated from
each other by the double partition which results from this apposition ;
after their coalescence, however, the partitions are completely destroyed
by absorption, and in a short time there is only a single medullary canal
for the entire bone.
Tiie rudimentary metacarpal is only a small osseous stylet, articu-
lating, by a diarthrodial facet, beiiind and to the outside of the superior
extremity of the principal metacarpal; it is sometimes absent in the
Sheep and Goat.
B. Camel.— The metacarpus of the Camel is very long, quadran-
gular in its upper two-thirds, and flattened behind and before in its
inferior third. Its posterior face is converted into a kind of concave
furrow, by the considerably raised borders of the bone. The superior
articular surface is divided into two parts by a large roughened depres-
sion ; the inner part is on a higher level than the outer. The inferior
extn mity is also divided into two articular surfaces by a very deep
notch ; each surface is condyloid in its anterior moiety, and is like
that of the Horse in its posterior moiety.
C. Dog, Cat, Rabbit.— The five metacarpals of the Dog and Cat
articulate with each other, at their superior extremities, by lateral
facets; they offer, at their inferior extremity, a condyle prolonged back-
wards by an articular surface resembling that of the Horse. The
forearm and foot
OF THE ox (front
view).
1, Olecranon ; 2, body
of the ulna ; 3,
body of the radius;
first and second bones
rudimentary metacarpals; 10, principal inetacarpals ; 11, external digit;
4, 5, 6, first, second, and third bones of the upper row of the carpus; 7,
of the lower row ; " " ' '
12, internal digit.
114
THE BONES.
middle two are always longer than the two lateral. The smallest belongs to the fifth digit, or
thumb, and is terminated inferiorly by a trochlea.
D. Pig. — The four metacarpals of the Pig articulate with each other, as in the Carnivora.
The second and third are larger than the first and fourth. The fifth metacarpal is not
developed (Fig. 76).
3. Bones of the Phalangeal or Digital Region (Figs. 72, 73).
Solipeds have apparently only one digit, supported by the principal metacarpal
bone, and composed of three pieces placed end to end, one upon another. The
first comprises three bones — a principal, the first phalanx — and two complemen-
Fig. 72.
Fig. 73.
LATERAL VIEW OF THE DIGITAL
REGION (OUTSIDE OF RIGHT LIMB).
1, Large metacarpal bone ; 2, 3, outer and
inner sesamoids ; 4, first, jiroximal, os suf-
fraginis, or metacarpal phalanx ; 5, its
posterior surface ; 6, tuberosity for liga-
mentous insertion ; 7, inner condyle of
ditto ; 8, eminences on second phalanx for
attachment of lateral ligament; 9, smooth
surface for passage of deep flexor tendon
on second phalanx ; 10, median or second
phalanx, os coronae, or small pastern bone ;
11, navicular bone; 12, third phalanx,
pedal, or coffin bone ; 13, its basilar process.
POSTERIOR VIEW OF THE DIGITAL REGION.
1, Large metacarpal bone ; 2, 3, outer and
inner splint bones ; 4, 5, sesamoid bones ;
6, suffraginis ; 7, 8, tuberosities for inser-
tion of crucial ligaments ; 9, triangular
space for insertion of short sesamoid liga-
ment ; 10, anterior face of suffraginis ;
11, 12, tuberosities for ligamentous inser-
tion ; 13, articular depression separating
condyles ; 14, 15, second phalanx ; 16,
scabrous surface for ligamentous attach-
ment; 17, smooth surface for gliding of
deep flexor tendon ; 1 8, navicular bone ;
19, pedal bone ; 20, basilar process ; 21,
plantar foramen.
tary ones, the sesamoids. The second is formed by the second phalanx, and the
last, which terminates the limb, is constituted by the third phalanx, and an
accessory bone which has received the name of the small sesamoid {navicular
First (proximal) or Metacarpal Phalanx (Large Pastern Bone, or
Os Suffraginis).— The first phalanx (Figs. 72, 73), the smallest of all the
long bones, is situated in an oblique direction from above downwards, and
behind to before, between the principal metacarpal and the second phalanx.
THE ANTERIOR LIMBS. 115
Body. — Flattened before and behind, this bone exhibits : an anterior face^
round from one side to the other, and slightly roughened above and below ;
a posterior face, flat, covered with ligamentous imprints in the form of a triangle
with the base reversed ; two lateral borders, thick, rounded, and provided with
some imprints.
Extremities. — The superior, the largest, presents : Above, an articular surface
adapted to the inferior metacarpal surface, and consequently composed of two
glenoid cavities separated by a groove running from front to back ; laterally,
and a little posteriorly, a well-defined tubercle of iiisertion. The inferior extremity
has a transversely elongated articular surface, to articulate with the second
phalanx ; this surface is formed by tivo condyles separated by a middle groove,
and surmounted laterally by a small tuberosity for ligamentous insertions. The
external condyle is smaller than the internal, and when the bone is placed upon
a horizontal plane, the anterior face turned upwards, it only touches by three
points— the two tubercles of the upper extremity and the internal condyle ; by
pressing on the external condyle, it is easy to make the bone oscillate.
The first phalanx is a very compact bone, and is developed from two points
of ossification, one of which is for the superior extremity alone. Professors
Yachetta and Fogliata, of Pisa, assert that this bone, as well as the second phalanx,
has three centres of ossification during uterine life.
Sesamoids (Figs. 72, 7^). — These are two small, short bones placed side
by side behind the superior extremity of the first phalanx, the articular sur-
face of which it completes, as it has not extent enough to be exactly adapted to
the metacarpal surface. Each of these bones represents a small, irregularly shaped
polyhedron, or, rather, a short trifacial pyramid. It offers : an anterior face,
which is articular, and corresponding to the inferior extremity of the principal
metacarpal bone, moulded, as it were, on one of the condyles and one of the
sides of the median ridge ; a posterior face, covered with cartilage in the fresh
state, and forming, with that of the opposite bone, a gliding concave surface for
the flexor tendons of the phalanges ; a latercd face, studded with ligamentous
imprints ; a summit, directed upwards ; and a base, turned downwards, and
serving for the attachment of several ligaments.
Second (or Median) Phalanx (Os Coron.^, Small Pastern Bone (Figs.
72, 73). — This is a short bone, situated in the same oblique direction as the
first phalanx, and between it and the third. Its general form is that of a
cube flattened before and behind, and offering the following features : an anterior
face, covered with some slight imprints ; a posterior face, provided, above, with a
transversely elongated gliding surface ; a superior face, channeled by two glenoid
cavities, to match the inferior articulating surface of the first phalanx ; an inferior
face, formed on the same plan as the last — being occupied by two unequal condyles,
which articulate with the third phalanx and the navicular bone ; two lateral faces
exhibiting a very marked imprint. In the interior of this bone is found a nucleus
of very condensed spongy substance, enveloped in a layer of compact tissue.
It is usually developed from a single centre of ossification, though in many
subjects there is a complementary nucleus for the superior articular and the
posterior ghding surface.
Third (Distal or Ungual) Phalanx, Os Pedis (Pedal or Coffin Bone)
(Figs. 72, 73, 74). — This is a short bone which terminates the digit, and sustains
the hoof that incloses it and the navicular bone. When completed by a special
tibro-cartilaginous apparidus, it represents the segment of a very short cone.
116 THE BONES.
obliquely truncated behind, from the summit to the base. It offers for study :
three faces, three borders, and two lateral angles.
Faces. — The anterior, convex from side to side, and cribbled by porosities and
vascular openings, shows on each side: 1. The preplantar fissure — a horizontal
groove more or less ramified, which commences behind, between the retrossal and
basilar processes, terminating in front in one of the foramina that penetrate
the bone. 2. The patilohe eminence — a roughened projecting surface, situated
between the preceding fissure and the inferior border of the bone. The superior
face is occupied by an articular surface formed by two glenoid cavities and a slight
median ridge ; it comes in apposition with the inferior face of the second phalanx.
The inferior (or solar) face, hollowed out like an arch, is divided into two regions
by the semilunar crest, a salient line which describes
^'-- '^^- a curve forwards. The anterior region is perforated
with very fine porosities, and corresponds to that part
of the hoof named the sole. The posterior region
shows, immediately behind the semilunar crest, a
median imprint, and two lateral channels designated
the plantar fissures. These originate at the root of
tlie basilar process, are directed obliquely downwards
and inwards, and open into the plantar foramina,
the external orifices of two large canals which enter
PLANTAR SURFACE OF THIRD ^j^g jjQ^g ^ud uultc lu Its luterlor to form the semilunar
PHALANX.
« o sinus.
1, Lower face, or sole \ 2, i, r, i n^^ • ^ ■^ -ii,
wings, or retrossal pro- Borders.— ThQ Superior describes a curve, with
cesses; 4. internal border; the convexity forward, and presents : 1. In its middle,
5, plantar foramina. ^.j^^ pyramidal eminence of the OS pedis — a single tri-
angular process, flat before and behind, roughened on its anterior aspect, and
concurring, by its posterior surface, to form the articular surface which responds
to that of the second phalanx. 2. Laterally, two facets of insertion which
encroach on the anterior surface, and even advance, posteriorly, nearly to the
preplantar fissure. The inferior border is thin, dentated, convex, and semicir-
cular ; it is perforated by from five to ten large foramina, which pass into the
bone. The posterior border is slightly concave ; on it is observed a very narrow,
transversely elongated, diarthrodial facet, which becomes confounded with the
superior large articular surface, and is adapted to a similar facet on the navicular
bone.
Lateral angles. — These are two projections directed backwards, on the summit
of which the three borders of the bone unite, and which gives attachment to the
lateral fibro-cartilages. A deep notch — the origin of the preplantar fissures —
separates. each into two particular eminences: one, the superior, named by
Bouley the basilar process ; the other, the inferior, prolonged behind, and desig-
nated by Bracy Clark the retrossal process (from retro, behind, and ossa, bone).
Sfructvre. — The os pedis exhibits in its interior the semilunar sinus — a cylin-
drical, transversely elongated, and semicircular cavity resulting from the arching
anastomoses of the two plantar canals. From this cavity pass off numerous
channels, which anastomose frequently with each other, and open externally by
the foramina on the anterior face of the bone, or by those on its inferior border.
The OS pedis has for its base a nucleus of spongy substance, surrounded by a
layer of compact tissue. The latter is thicker towards the pyramidal eminence
than elsewhere, and sends into the interior numerous prolongations which form
THE ANTERIOR LIMBS.
11?
the walls of the semilunar sinus, as well as the bony channels which spring
from it.
Development. — The third phalanx, formed from a single nucleus of ossifica-
tion, undergoes numerous changes in its configuration during life. Thus, in the
young animal the lateral angles are thick, obtuse,^ and but little prolonged
posteriorly ; but as it grows older, they increase in length and become salient.
The development they then assume, is due to the progressive ossification of the
lateral cartilages implanted on their surface. It often happens, in very old horses
that this ossifying process is carried to an extreme degree, and nearly the whole
substance of these complementary organs is invaded. From the commencement,
its inevitable result is to convert the notch which separates the basilar from the
retrossal process into a foramen.
The comple me atari/ Jihro-cartilaiiinous apparatus of the as pedis. — To under-
stand properly the disposition of this portion of the .foot, it is necessary that a
previous knowledge of the ligaments
and tendons attached to the os pedis
should have been acquired ; therefore
a detailed description will be given
when the Horse's foot is studied as a
whole, in the article on the Sense of
Touch. It will be sufficient here to state
that this apparatus consists of two
lateral pieces — the fibro-cartilages of the
OS pedis, united behind and below by
iheplantar cushion — a fibrous and elastic
mass on which rests the navicular bone,
through the medium of the perforans
tendon.
The Small Sesamoid or Navicular
Bone (Figs. 72, 75). — This short bone
is annexed to the third phalanx, behind
which it is situated ; it is elongated
transversely, flattened above and below,
and narrow at its extremities. It offers :
1. A superior face, on which are pro-
longed the glenoid cavities and the
median ridge of the articular surface
of the OS pedis ; it articulates with the
second phalanx. 2. An inferior face, dixided by a slight ridge into two undulated
facets, and covered with cartilage to form a gliding surface. An anterior border,
channeled lengthways by a groove of insertion, above which is remarked a diar-
throdial facet that brings the small sesamoid into contact with the posterior border
of the third phalanx. 4. A posterior border and two extremities, for ligamentous
insertion. This bone, as well as the sesamoids, originates from a single centre of
ossification. It is formed of a layer of compact tissue enveloping a nucleus of
very condensed spongy substance. (For differences in the Ass, see Posterior
Limb.)
NAVICULAR BONE OF THE HORSE.
Anterior Border and Inferior Face. 1, articu-
lar facet for the facet on the po.stenor border
of the OS pedis; 2, roughened groove on the
anterior border ; 3, inferior face, smooth and
undulated. B, Posterior Border and Superior
Face. 1, Articular face for the lower end of
the second phalanx; 2, posterior border, with
many foramina.
118 THE BONES.
•
Differential Characters in the Digital Region of other Animals.
In the other domesticated animals, the number of complete digits is as follows : —
Carnivora 5
Pig 4
Ruminants • .... 2
A. Ox, Sheep, Goat. — These animals certainly possess four digits, but only two are perw
feet— the mMius and annularis — and these articulate with the inferior extremity of the principal
metacarpal (Fig. 71). The two others — the index and auricularis — are in a rudimentary con-
dition, and are represented by two small bones situated above and behind the metacarpo-
phalangeal articulation.
In the Ox, Sheep, and Goat, each of the perfect digits comprises (like the single digit of the
Horse) three phalanges and three sesamoids.
The first phalanx fairly represents the moiety of this phalanx in the Horse. It has no
Fig. 77.
Fig. 76. y^
^-
if' '' *~
ANTERIOR LIMB OF THE PIGi.
FOREARM AND FOOT OF THE DOG (AN-
TERIOR face).
1, First digit ; 2, second digit ; 3, third
digit ; 4, fourth digit ; 5, thumb ; 6,
7, 8, 9, first, second, third, and fourth
bones of the lower row of carpnl bones ;
10, 11, first and second bones of the
upper row; 12, supercarpal bone;
13, body of the ulna ; 14, apex of the
olecranon; 15, beak of the olecranon;
16, body of the radius.
posterior imprints, but shows them on its inner surface for the attachment of several ligaments.
This internal face is plane, and the external convex ; these characters are repeated in the other
two phalanges. It is also remarked in all the phalangeal bones, that the external articular
facet of the extremities is always larger than the iuterual. Of the two sesamoids, the external
THE ANTERIOR LIMBS.
119
Fig. 78.
is wider and less elongated than tlie internal. They articulate with each other and with
the first phalanx, by small diarthrodial facets.
The second phalanx is hollowed internally by a small medullary cavity.
The ungual phalanx, as a whole, resembles one of the lateral moieties of the os pedis of
Solipeds. Tills phalanx has no complementary fibro-cartilage, basilar process, or retrossal
eminence, nor yet a cavity for insertion on the sides of the pyramidal eminence. The semilunar
crest is replaced by an obtuse, thick, and rugged ridge, which occupies quite the posterior limit
of tlie inferior face of the bone. Three large canals penetrate the third phalanx— two to the
base of the [lyramidal eminence, and one towards the origin of the preplantar fissure. They
form, in the interior of the bone, a vast sinus, giving rise to several vascular canals which open
on the surface. There is only one foramen at the base of the pyramidal eminence in the smaller
Ruminants.
B. Camel. — In this animal, there are in each digit only three phalanges and two large
sesamoids. The direction and form of these phalanges
differ notably from what is seen iu Ruminants. The
first phalanx is long, very oblique, constricted in the
middle, and very thick at both ends. On the superior
articulating surface is a single glenoid cavity, dirided
posteriorly by a median groove. The inferior surface is
prolonged on the posterior face of the bone, which is
converted into a kind of pulley. The second phalanx is
nearly horizontal, and much flattened above and below.
The ungual phalanx is somewhat like an irregular
trifacial pyramid with a blunt summit ; near its base,
on its upper face, it has a roughened tubercle.
C. Pig. — The Pig has four complete digits articu-
lating from the metacarpals ; the thumb is absent. The
index and auricularis— or fourth and fifth digits — are
short, and do not usually rest on the ground (Fig.
76).
D. Dog, Cat, Rabbit.— The five digits of the
log and Cat are exactly analogous to those of Man.
Thus, the external corresponds to the auricularis, the
second to the annularis, the third to the medius, the
fourth to the index, and the internal to the thumb.
The latter, very small, has only two phalanges, and does
not come into contact with the ground. Each of the
first four is composed : 1. Of a first phalanx, to which are
annexed two sesamoids. 2. A second phalanx, which
represents a veritable long bone. 3. A conical phalan-
gette, pointed, curved downwards, and hollowed at its
base by a circular groove, in which is lodged the matrix
of the claw. The small sesamoid (or navicular bone)
la absent, but is replaced by a prominence of the ungual
phalanx. The auricularis and index are alike, and not
80 long as the annularis and medius, which are the same
in length.
HUMAN SCAPULA (EXTERNAL ASPECT).
1, Supra-spinous fossa; 2, infra-spinous
fossa ; 3, superior border ; 4, supra-
sca|)ular notch; 5, anterior or axil-
lary boi-der ; 6, head of the scapu-
lar and glenoid cavity ; 7, inferior
angle ; 8, neck of the scapula ; 9,
posterior border; 10, spine; 11,
triangular smooth surface, over
which the tendon of the trapezius
glides, with the tuberculum spinse
scapulae between it and 10 ; 12,
acromion process ; 13, nutrient fora-
men ; 14, coracoid process.
Comparison of the Thoracic Limb of Man with that of the Domesticated Animals.
A. Shoulder. — The shoulder of man has for its base two well-developed bones — the scapula
and clavicle. The scapula (Fig. 78) is more distinctly triangular than that of all the domesti-
cated animals ; its vertebral border is also more extensive. The scapular spine, very elevated
is continued by an acromion whose extremity reaches to above the scai)ulo-humeral articulation.
The latter is separated from the remainder of the spine by a constriction called the pedicle of
the acromion. The coracoid process is voluminous, and resembles a semi-flexed finger. The
clavicle extends from the acromion to the sternum ; it is flattened above and below, and flexed
like an italic S. This inflection of the clavicle is more pronounced in the male than the
female.
B. Arm. — The humerus (Fig. 79) of Man is much longer than that of animals. Its dia-
physis is prismatic, and divisible into three faces ; the deltoid imprint has the form of a V with
its point directed downwards. The voluminous articular head is turned inwards ; the bicipital
120
THE BONES.
groove is single, and looks outwards. The inferior articular surface resembles that of animals,
except that the condyle is more distinct.
C. Forearm (Fig. 80). — The two bones of the forearm, as we have already seen, only articu-
late by their extremities; they are separated from one another in their middle part. The
superior extremity of the radius corresponds with the condyle of the humerus ; that of the ulna
articulates with the humeral trochlea. The coroiioid process belongs to the ulna. At the
lower extremity of the forearm, it is reiniirked : 1. That the radius corresponds with tlie greater
portion of the cnrpus, while the ulna only articulates with the pyramidalis. 2. Tliat the radio-
carpal articulation is protected outwardly and inwanlly by two small osseous prolongations —
the styloid processes of thu ulna and radius.
D. Hand. — 1. Carpus (Fig. 81). — The carpus of Man is composed of eight bones — four in
each row. The three tirst of the upper row articulate with the radius ; the fourth responds to
F.2.
Fig. 8U.
RIGHT HUMAN HUMERUS (ANTERIOR
SURFACE).
1, Shaft ; 2, head ; 3, neck ; 4, greater tu-
berosity ; 5, lesser tuberosity ; 6, bici-
pital groove ; 7, interior bicipital groove ;
8, posterior bicipital ridge ; 9, rough sur-
face for insertion of deltoid; 10, nutrient
foramen; 11, eminentia capitata ; 12,
trochlea; 13, external condyle; 14, in-
ternal condyle ; 15, external condyloid
ridge; 16, internal condyloid ridge; 17,
fossa for the coronoid process of ulna.
HUMAN ARM-BONES (FRONT VIEW).
1, Shaft of ulna ; 2, greater sigmoid notch j
3, lesser sigmoid notch ; 4, olecranon
process ; 5, coronoid process ; 6, nutrient
foramen ; 7, ridges for insertion of in-
terosseous membrane ; 8, capitalum ulnae ;
9, styloid process; 10, shaft of radius;
11, its head ; 12, its neck ; 13, its tube-
rosity ; 14, oblique line ; 15, lower end
of bone ; 16, styloid process.
the ulna. In the bones of the lower row, the trapezium responds to the metacarpal of the thumb
and that of the index; the trapezoides to the latter only, the os magnum am unciform to the
metacarpals of the medius, annularis, and little finger. The pisiform bone and the cuneiform
process of the unciform convert the posterior face of the carpus into a channel.
2. Metacarpus (Fig. 81).— The five metacarpals of Man are parallel to each other; they
articulate by their superior extremities witli the bones of the carpus, and by their inferior ex-
tremities witii the phalange-s. They are all concave in their middle portion, and tiiickened at
their ends. Tlie metacarpal of the thumb is the shortest and strongest. The others diminish
in volume from the fourth to the first.
THE ANTERIOR LIMBS.
121
Fig. 81.
3. Digital Region (Fig. 81). — Here we fiurl five digits, each compcsed of three bony colum-
nettes, with tlie exception of the thumb, in which only the second and third phalanges are
present. They decrease in length from the third to the first, and the third to the fifth. The
first and second phalanges are small semi-cylindrical bones, slightly thickened at their ex-
tremities. The ungual phalanges are constricted in their middle, and widened like a horse-
slioe at their inferior extremity ; the palmar face is roughened, the dorsal face smooth.
Article V. — The Hand in General.
1. The limits of this region, as already mentioned, extend from the lower
end of the forearm to the third phalanx, inclusive. If it is examined super-
ficially, the diiferences it presents in the number and arrangement of the parts
composing it are very striking. The digits that
terminate the hand are pieces which, from the earliest
times, have most occupied the attention of observers.
Thus, when we do not go beyond simple appearances,
it might be believed that, with regard to the number
of digits, there were great diiferences in animals.
From this point of view, the domestic animals form
a nearly decreasing series, commencing with the Gar-
ni vora and terminating with Solipeds. And in relying
upon these appearances, some anatomists have dis-
tinguished these animals as monodacti/les, didad ij.es,
and. regular and irregular tetradadijUs ; but in the
generalizations in this work, we have ignored these
designations, as they are in complete disaccord with the
teachings of philosophical anatomy. In fact, although
the Horse appears to have only one digit, the Ox two,
the Pig four, the Dog and Cat five, yet the hand in all
these creatures may be referred to the pentadactylous
type. To demonstrate this unity in composition, the
laws promulgated by Grethe with regard to the vege-
table kingdom, and developed and applied to animals
by Geoff"roy Saint-Hilaire, are accepted ; and we have
indicated in these few words the laws of analogy and
harmony, the principle of relations, the elective affini-
ties, the organic adjustments.
These laws and these principles have been more
particularly applied to the study of the 'hand of
animals by Joly and Lavocat, Paul Gervais, Richard
Owen, Delplanque, and Arloing. Comparisons, and
the attentive study of normal conditions and anomalies, have served as a basis
for the conclusions arrived at by these authorities. The anomalies that certain
zoologists were tempted to regard as proper facts likely to mislead philosophical
anatomists, have, on the contrary, been of assistance to the latter ; because,
according to the expression of Geoffroy Saint-Hilaire, " an anomaly restores that
which \ye term, in zoology, -normal conditions."
2. The Archetypal Hand. The chief type is composed of five digits,
and a complete digit in three sections — the carpus, -which has two bones ; the
metacarpus, which has only one : and the phalangeal section, which has three.
This constitution of the hand has been conceived by Joly and Lavocat, and
reasoning would sanction its acceptance, if it were not presented in some animals
PALMAR SURFACE OF LEFT
HUMAN HAND.
1, Scaphoid bone; 2, semilu-
nare; 3, cuneiform ; 4, pisi-
form ; 5, trapezium ; 6,
groove in trapezium for ten-
don of flexor car))i radialis;
7, trapezoides ; iS, magnum ;
9, unciform ; 10, 10, the
five metacarpal bones; 11,
11, first row of phalanges;
12, 12, second row; 13, 13,
third row; 14, first phalanx
of the thumb; 15, second
and last phalanx.
122
THE BONES.
DESCRIPTION ON OPPOSITB PAGE.
THE ANTERIOR LIMBS. 123
—such as the 3Ioh, Marmot, and Guinea-pig— each, of which have five digits
arising from the two carpal bones. In order to study the hand, these authorities
place it in its natural position — pronation ; and the different pieces are reckoned
from without to within by the numbers 1, 2, 3, 4, 5.
3. Modifications in the Archetype. But the archetypal hand is not
constantly realized, even when five digits— such as they are usually understood
to be — are present. The hmnan hand, for instance, is formed by five digits and
five metacarpal bones, with only eight bones in the carpus. When we go from
Man, the number of bones in the three sections is more or less diminished ; and
in the carpus of the domestic animals, as in that of Man, if the archetypal
number does not exist in all the sections, it is because certain pieces have been
fused with adjoining ones, or they are not developed. In several instances,
certain bones become so atrophied that at the first glance they are not recog-
nizable. Joly and Lavocat at first imagined that these atrophies took place
according to some fixed law ; they believed that the atrophy operated on the
middle part of the bones, extending downwards, and that the last piece to dis-
appear, in an atrophied digit, was that of the carpus.
But since the publication of their first memoires, Lavocat has had occasion
to state that this law is not absolute. After these preliminary remarks, we
will study the modifications in the archetypal hand in Man and the domestic
animals, and demonstrate that in these it may easily be referred to the pentadacty-
lous type.
1. Man. — The human hand having five digits and five metacarpal bones, it
is rational to admit the virtual existence of five pieces to each of the carpal rows.
Materially, there are only four bones in each of these two rows ; but the com-
parative study of the relations of each of these bones in the human carpus, and
in that of animals which are in possession of the archetypal hand, leads to the
belief that the scaphoid is the result of fusion of the fourth and fifth bones of
the upper row, and the unciform the fusion of the first and second bones of the
HAND OF MAN AND THE DOMESTIC MAMMALIA, NORMAL AND TERATOLOGICAL (Fig. 82).
A, Human hand (dorsal face).
B, Dog's hand (same position).
C, Pig's hand (normal condition). 1, Trapezium.
c', Pig's hand : the thumb (1) is completely developed from the trapezium (2).
D, Sheep's hand (normal condition). 1, Principal metacarpal ; 2, rudimentary metacarpal, external ;
3, ditto, mternal (not constant).
E, Hand of the aquatic Chevrotain. 1, Double principal metacarpal; 2, 3, lateral metacarpals
followed by phalanges.
F, Lamb's hand, a. Carpus and superior extremity of metacarpus (seen in profile), on which the
metacarpus of the thumb (1) was shown. 6, Ditto (face) : 1, internal rudimentary metacarpal
completely developed ; 2, horny plate representing the thumb on the surface of the skin ; 3, horny
plate representing the first digit on the surface of the skin.
G, Lamb's hand on which are four complete digits. 1, Principal metacarpal ; 2, 3, lateral meta-
carpals completely developed.
H, Horse's hand (normal condition). 1, Principal metacarpal ; 2, 3, rudimentary metacarpals.
I, Horse's hand, adult (teratological specimen, showing the division of the phalangeal section,
1, 1, of the single digit of Solipeds).
K, Foal's hand (teratological specimen described by Delplanque). 1, Principal metacarpal bifid in
its lower third ; 2, e.\ternal rudimentary metacarpal ; 3, 4, phalangeal sections resulting from
the division of the great digit.
L, Horse's hand, adult (teratological piece), a. Carpus (inner aspect) : 1, trapezium ; 2, trapezoid ;
3, principal metacarpal ; 4, internal rudimentary metacarpal transformed into a complete meta-
carpal ; 5, styliform piece representing the metacarpal of the thumb. 6, Inferior extremity of
the digital region (inner aspect): 1, principal metacarpal, followed by normal phalanges; 2, in-
ternal rudimentary metacarpal transformed into a complete metacarpal, followed by normal
phalanges.
124 THE BONES.
inferior row (Fio;. 82, a). It is easy, therefore, to refer Man to the most perfect
pentadactylous type.
2. Carnii'ora. — The hand of the Dog and Cat has five distinct digits, the
internal of which — the thumb — smaller than the others, does not reach the
ground (Fig. 82, b). By the metacarpus and the phalangeal section, these
animals belong, then, to the pentadactylous type. They appear to be removed
from it by the constitution of the carpus, for it has only seven (Dog) or eight
bones (Cat) ; there has been fusion of the lunar and scaphoid, but the fifth bone
of the upper row is free. The number of bones being thus raised to eight, we
know how they may be referred to the archetype — by proceeding in the same
manner as for the human carpus.
3. Rodents. — The Rabbit has five digits, like the Cat, and nine carpal bones.
Five of the latter are in the upper row, in consequence of the duplication of the
fourth bone, which comports itself as in Carnivora. The scaphoid is between
the two rows, as in the tarsus.
The Rabbit, therefore, only differs from the archetype by the fusion of the
first to the second inferior carpal bone, which sometimes is incomplete.
We have thus demonstrated the pentadactylous composition of the hand in
the domestic Carnivora and Rodents — an easy task, as these animals have five
apparent digits. We will now pass to the Pig.
4. Pig. — This animal has eight carpal bones and four complete digits, with
metacarpals and phalanges — two large and two small (Fig. 82, c). There is no
difficulty in referring the carpus of the Pig to that of Man or the Carnivora, and
from these to the archetype. It suffices to find in this creature a trace of the fifth
digit, in order to place it in the pentadactylous type. Normally, the fifth bone of
the lower row — the trapezium — has no relation with the bones of the metacarpus ;
which proves that the remainder of the thumb is absent. But this thumb has
been found entirely developed, and having the appearance of the other digits.
In Fig. M (c'), this has been shown in the teratological cases observed by
Joly and Lavocat, and Goubaux and ourselves. Consequently, although the Pig
has been classed among bisculcate animals by certain zoologists, yet it has in the
anterior limb five digits, more or less completely developed.
5. Ruminants. — Intended as an organ of support, the hand of Ruminants
offers several fusions or abortions, which increase its solidity at the expense of
its suppleness and flexibility. Thus, in the first place, it appears more difficult
than in other animals to find, materially or virtually, the elements of the five
digits.
Only six bones are found in the carpus of the 0-r, Sheep, and Goat ; but the
study of relations demonstrates that there are : abortion of the fifth bone of the
upper row ; fusion between . the first and second, and between the third and
fourth, and abortion of the fifth bone, of the lower row. So that, in reality, there
are met with, in the carpus of the domestic Ruminants, the elements of ten
bones, with the exception of two not developed (Fig. 82, d).
The metacarpus comprises a principal metacarpal — the inferior articular face
of which is double — and a stylif orm bone placed alongside its external and internal
borders. For a long time, GeofFroy Saiut-Hilaire had demonstrated that the
principal metacarpal is formed by two metacarpals brought together during foetal
life, and separated by a more or less incomplete medullary septum during extra-
uterine existence. Besides, the isolation of the two metacarpals — temporary in the
Ox — is permanent in some other Ruminants, such as the Chevrotain of Guinea and
THE ANTERIOR LIMBS. 125
the Aquatic Chevrotain (Fig. 82, e). With regard to the external stylet, it is
an atrophied metacarpal ; for in some teratological instances it becomes elongated,
and supports a more or less perfect digit. In addition, in the Chevrotain it is
replaced by the metacarpal and a complete digit (Fig. 82, e). It is the same
with the internal stylet, which is usually smaller, and embedded in a fibrous cord
running along the large metacarpal ; it may, like the external stylet, be converted
into a perfect metacarpal (Fig. 82, P and g).
It remains to demonstrate the virtual existence of a fifth metacarpal. Nor-
mally, no traces of it are found in the domestic Ruminants, but it appears in
some anomalies. The museum of the Toulouse Veterinary School possesses the
hand of a Lamb, in which it can be seen, inside the internal stylet, which has
been transformed into a long metacarpal — a small styliform bone which is
assuredly nothing else than the metacarpus of the thumb (Fig, 82, f, i,). Here
is the metacarpus brought to the pentadactylous type ; now for the phalangeal
region.
The digital region of Ruminants presents two perfect digits (the second and
third. Fig. 82, d), and two rudimentary digits reduced to one or two small
phalanges covered by a horny plate (ergot), situated behind the metacarpo-
phalangeal articulation. The two rudimentary digits may, in certain cases, be
reproduced— to the right and left of the normal ones — complete and suspended from
real metacarpals. This was seen in a specimen from a young sheep (Fig. 82, g) ;
and this condition is normal in the Chevrotain (Fig. 82, e), only the lateral
digits are less voluminous than those appertaining to the principal metacarpal.
The presence of the fifth digit is normally indicated, according to Joly and
Lavocat, by a tuft or spike of hair inside the carpus, rather above than below it.
Sometimes it is better marked ; for in the specimen sho^Ti in Fig. 82, f' a,
where the metacarpal of the thumb had appeared, this digit was represented on
the surface of the skin by a plate of horn in the form of an ergot (f, a and b,
2). Otherwise, in order to dispel all doubts, it may be mentioned that Geoff roy
Saint-Hilaire studied a new-born Lamb which had five digits in the anterior
limb.
6. SoUpeds. — In Solipeds, there is apparently only one digit enclosed in one
hoof. Nevertheless, by the aid of analogous facts to those which have already
assisted us in proving pentadactylism in Ruminants, we shall be able to demon-
strate that the hand of the Horse, Ass, etc., is no exception to the general law.
Many anatomists only describe seven bones in the carpus of the Horse — four in
the upper row, three in the lower. But it is not rare to see a pisiform bone on
the inner side of the trapezoid, which raises the number of carpal bones to eight.
And Bourgelat, Girard, Rigot, and Goubaux have observed in the carpus of the
Horse, in addition to the bones mentioned, a similar piece alongside the external
bone of the second row. Lavocat considered this second piece as the first of the
inferior carpal bones — the base of the external digit, and that the bone found
beside the trapezoid was the trapezium or base of the internal digit or thumb,
the trapezoid being the base of the fourth finger. The trapezium and trapezoid
are shown, with the significance attributed to them by Lavocat, on the carpus
represented in Fig. 82 (l a, 1, 2).
The carpus of Solipeds does not differ, then, from the archetype, except in the
frequent abortion of the fifth superior carpal bone, and the first and fifth of the
lower tier.
The metacarpus of Solipeds comprises a large bone articulating with the
11
126 THE BONES.
digital section, and two rudimentary pieces on each side of it, and which are
really atrophied metacarpals ; for in some teratological specimens they are as long
as the principal bone, and terminate in a diarthrodial surface which articulates
with a perfect digit (Fig. 82, l b). At first sight, there are, then, three meta-
carpals in Solipeds.
With several authorities, and particularly Joly and Lavocat, we have
admitted the duplicity of the large median metacarpal bone, basing our admis-
sion on several considerations with regard to form and relations, and especially
on certain anomalies similar to those represented in Fig. 82, i, in which
is seen the single digit of Solipeds divided like that of the Ox — the division
extending to the lower end of that bone. But an attentive study of the
metacarpal region in the Mammalia, and notably in Pachyderms, and of the
arrangement it offers in the various fossil Equidfe, has caused us to abandon
this opinion. "We consider the principal metacarpal of Sohpeds to be the analogue
of the metacarpus of the medius of pentadactylous Mammals. With regard to
the anomaly shown at i and k. Fig. 82, it should be interpreted as an example
of division of an organ normally single.
The Horse, then, has always three metacarpals — one for the medius, the
index, and the annularis ; and it remains to prove the existence of two other
metacarpals. Usually, the metacarpal of the thumb is completely aborted ; but
yet the existence of these bones is indicated by the frequent presence of the
trapezium at the inner side of the carpus. Lastly, as a continuation from the
trapezium there may be found a conical prolongation (Fig. 82, L a, 5), parallel
with the metacarpal bone of the index — a prolongation which, because of its
connections, should be regarded as the metacarpal of the thumb.
With respect to the metacarpal of the auricularis, or little digit, we do not
know of one teratological example in which it can be distinctly seen. But its
existence is virtually indicated by the presence of the small external carpal bone
we have sometimes observed, and which was noted by Bourgelat, Eigot, and
Goubaux.
The phalangeal section only possesses the elements of a single digit. But
besides the hoof, Soliped animals have a horny plate divided by a slight median
groove, and resting on an elastic cushion behind the metacarpo-phalangeal articula-
tion. This plate occupies the same position as the ergots in the Ox ; it has vessels
and nerves from the same source as those of the principal digit ; it lies upon an
elastic bed similar to that belonging to that organ ; and Joly and Lavocat regard
it as the representative of the phalanges, which should be continued with the
rudimentary metacarpals. Otherwise, when one of these metacarpals is developed
into a perfect digit, the horny plate or ergot diminishes in volume, because
a portion of its substance is carried to the extremity of the supplementary digit.
It -is, therefore, easy to find three digits in these animals, but the thumb is more
difficult to render evident. However, the presence of a trapezius, and, much
more rarely, of an atrophied metacarpal succeeding it, would warrant the admis-
sion that this digit exists, if it were not represented on the surface of the skin by
the chestnut — the horny plate situated on the internal aspect of the forearm.
The position of this small mass of horn above the carpus has been invoked
against this signification ; but it is easy to overcome this objection in showing, by
the ascending vessels and nerves of the chestnut, that this is a displaced organ ;
the vessels and nerves arise from the same trunks that supply the other digits.
The fifth digit is not absolutely represented except by its carpal base, which is
TEE POSTERIOR LIMBS. 127
often absent ; however, its presence in a certain number of instances allows it to
be affirmed that Solipeds materially and virtually belong to the pentadactylous
type. This conclusion applies a fortiori to all the domestic animals.
According to statistics drawn up by Cornevin, the return to the pentadacty-
lous type is much more frequently manifested, in Solipeds, in the anterior than
the posterior limbs.
Article YI. — Posterior or Pelvic Limbs.
Each of these is divided, as already noted, into four secondary regions : the
pelvis, thigh, leg, and foot.
Pelvis (Figs. 83, 84, 85).
The pelvis is a kind of bony cavity formed by the union of the sacrum with
two lateral pieces — the ossa innominata, or coxae — which are consolidated with each
Fig. 83.
THE OSSA INNOMINATA (SEEN FROM BELOW).
1, Iliac surface ; 2, auncular facet ; 3, angle or crest of the ilium ; 4, angle of the haunch ; 5,
?eSs. r;^' V^"'\T '^'^'V*"' '\ °°^ ""^ '^' '"P'-'°'^ f""- tl^e insertion of the rec'tu
rator) foramen ; 11, sciatic spine ; 12, 12, ischiatic arch, r ) , ^,
Other in the inferior median line. The description of the sacrum having been
ah:eady given, it now remains to speak of the os inn^ominatum of each side.
A. Coxa, or Os Innominatum.
The OS innominatum—2X^o designated os coxa, os iliacum, os innominatum-is
a very irregularly shaped flat bone, double (with its fellow on the opposite side),
and directed obhquely downwards and backwards. It is contracted in its middle
part, which presents externally a deep cavity-the cotgloid ; anteriorly, where
128 THE BONES.
it rests on the sacrum, it becomes widened, as it also does in its posterior
portion, which is inflected inwards to be united, on the median Hne, with the
OS innominatum of the opposite side.
It is divided, in the foetus, into three distinct pieces, joined by cartilage in
the centre of the cotyloid cavity, which they concur in forming. Although they
soon become consolidated into a single piece, it is customary to describe them as
so many separate bones by the names of ilium, pubis, and ischium.
Ilium (Figs. 83, 84). — The ilium — a flat and triangular bone, curved on itself,
directed obliquely downwards, backwards, and outwards — forms the anterior
portion of the coxa which corresponds with the sacrum. It is the most consider-
able of the three divisions, and has two faces, three borders, and three angles or
processes.
Faces. — The external or superior face (Fig. 83), studded Avith some muscular
imprints, is excavated on both sides, and is named the external iliac fossa. The
internal or inferior face offers for study : 1. An external portion, smooth, and
crossed by some vascular grooves ; this is the iliac surface, which is replaced in
Man by an excavation called the internal iliac fossa. 2. An internal portion,
roughened and uneven, presents, posteriorly, the auricular facet — an irregular
diarthrodial surface, elongated from side to side, a little oblique in front and
inwards, and responding to an analogous surface on the sacrum.
Borders. — The anterior border, or crest of the ilium, is slightly concave, and
bears a roughened lip for muscular insertion. The external border is thick,
concave, and furrowed by vascular fissures ; it presents, inferiorly, the nutrient
foramen. The internal border is thin and concave, particularly in its posterior
part, which constitutes the great sciatic notch.
Angles. — The externcd angle, or anterior and superior spinous 2)rocess, is thick,
wide, and flat, and bears four tuberosities : two superior and two inferior. The
internal angle, or posterior and siqjerior sp)inous j^rocess, represents a rugged tube-
rosity curved backwards and upwards. The posterior — or cotyloid angle — is pris-
matic and very volimiinous. It exhibits : 1. Behind, a wide concave articular facet,
which forms part of the cotyloid cavity. 2. Above this cavity, the supra-cotyloid
crest, represented in Man by the ischiatic spine. This is an eminence elongated
from before to behind, sharp on its summit, smooth inwardly, roughened out-
wardly, and continuous by its anterior extremity with the internal border of the
bone. 3. Outwardly, two deep imprints for the insertion of the rectus femoris
muscle. 4. In'front and inwards, the ilio-2^ectineal spine, a small elongated pro-
minence forming the most salient point of a kind of ridge {linea ilio-pectinea) that
insensibly subsides above on the inner face of the ilium, and is continued below
by the anterior border of the pubis.
Of the three angles of the ilium, the first is also termed the angle of the
haunch, and the second the angle of the croup.
Pubis (Fig. 83). — Situated between the ilium and ischium, elongated from
side to side, flattened above and below, and irregularly triangular, the pubis — the
smallest of the three divisions — is divided, for convenience of description, into
two faces, three borders, and three angles.
Faces. — The superior, smooth and concave, concurs in forming the floor of
the pelvis. It shows one or two nutrient foramina. The inferior is roughened,
and marked throughout its length by a wide channel which reaches the bottom
of the cotyloid cavity. This fissure lodges the pubio-femoral ligament and
a very large vein.
THE POSTERIOR LIMBS.
129
Borders. — The anterior is constituted by a thin rugged lip, which is curved
upwards. The posterior, thick and concave, circumscribes anteriorly a wide
opening, the oval, suhpiiUc, or obturator foramen ; it is channeled near the coty-
Fig. 84.
PELVIS (ANTERO-LATERAL VIEW).
1, Anterior iliac spine ; 2, posterior iliac spine ; 3, shaft of the ilium, with the ilio-pectineal crest ;
4, cotyloid cavity ; 5, symphysis pubis ; 6, inferior ischiatic spine and tuberosity.
loid angle by a fissure which runs obliquely inwards and downwards. The
internal is united with that of the opposite bone, to form the pubic portion of
the pelvic symphysis.
Ayigles. — The ex- Fig- 85.
ternal, also named the
cotyloid angle, is the
thickest of the three.
To it chiefly belongs
the rugged depressed
surface that constitutes
the bottom of the coty-
loid cavity. The in-
ternal unites with the
analogous angle of the
opposite bone. The
•posterior is consolidated
at an early period with
the antero - internal
angle of the ischium, to
enclose, inwardly, the
oval foramen.
Ischium (Figs. 84,
85). — This is the mean,
in volume, of the three
pieces of the coxa. Situated behind the pubis and ilium, it is flattened above
PELVIS (LATERAL VIEW).
1, External angle of the ilium, or anterior iliac spine ; 2, internal
angle, or posterior iliac spine ; 3, shaft of the ilium and ilio-
pectineal line ; 4, cotyloid cavity, or acetabulum ; 6, inferior
ischiatic spine, with tuberosity behind.
130 THE BONES.
and below, and of a quadrilateral form. It offers for study : two faces, four
borders, and four angles.
Faces. — The superior is smooth and nearly plane, and forms part of the floor
of the pelvic cavity. It has a small nutrient foramen directed outwards. The
inferior presents some rugosities, clustered particularly about the symphysis.
Borders. — The anterior, thick and concave, circumscribes the oval foramen
posteriorly. The posterior, straight and directed obliquely forwards and inwards,
forms, with the analogous border of the opposite bone, a large notch named tjie
ischial arch. It exhibits, throughout its extent, a rugged depressed lip (the
spine), arising from the side of the inferior face. The external, thick and
concave, constitutes the lesser ischiatic notch. The internal is joined to the
ischium of the other side, to constitute a portion of the pelvic symphysis.
Angles. — The antero-externcd, or cotyloidean, is the most voluminous of the
four, and affords for study : 1. An excavated diarthrodial facet, making part of
the cotyloid cavity. 2. The posterior extremity of the supra-cotyloidean crest,
limited by a small transverse fissure which separates from the external border of
the bone. The antero-internal angle is consolidated with the posterior angle of
the pubis. The poster o-external angle forms the ischial tuberosity. This is a
large prismatic process which looks upwards, and is prolonged by a salient
ridge, elongated from before to behind, with its sharp border turned outwards
and downwards. The postero-internal angle forms, with that of the other
ischium, the summit of the triangular space which constitutes the ischial arch,
or pubic arch of some species.
The Coxa in General. — This bone, the three constituent parts of which we
have just been studying, presents for consideration, as a whole, a middle portion
and two extremities. The middle, very much contracted, offers, outwards and
downwards, the cotyloid cavity (or acetabulum), which has not yet been described,
because its study does not properly pertain to either of the three regions of the
coxa. This cavity is intended to receive the articulating head of the femur, and
represents the segment of a hollow sphere ; it is circumscribed by a very salient
rim, which is thin at its free margin, and widely notched on the inner side. The
deeper portion is occupied by the roughened and depressed surface already
designated as the bottom of the cotyloid cavity {fundus acetabuli), which
communicates, by the internal notch of the rim, with the inferior groove of the
pubis. The anterior extremity, flattened on both sides, and formed by the
ilium, rests, as has been shown, on the sacrum. The posterior extremity,
flattened in an inverse sense to the preceding, is constituted by the pubis and
the ischium, and is traversed, from above to below, by the sub-pubic (or obturator)
foramen — the large oval aperture which separates these two bones from one
another, and perforates the floor of the pelvis ; this opening is closed in the
fresh staie by muscles.
The two coxae, by uniting in their posterior part, form the articulation to
which has been given the name of ischio-pubic or pelric symphysis ; thus united,
the two bones represent something like a V with the opening in front — a
circumstance which makes the lateral diameter of the pelvis greater in front
than behind.
Structure and Development of the Coxa. — To the three centres of
ossification which constitute the coxa, are added two complementary centres :
one for the anterior spinous process and spine of the ihum, another for the
ischial tuberosity.
THE POSTEBIOB LIMBS. 131
It must be added that there is, within and in front of the cotyloid cavity, a
cotyloid nucleus analogous to the glenoid nucleus of the scapula. This nucleus,
comprised between the three bones of the coxa, has been named by Serres the
Y-shaped bone.
In youth, the different parts of the coxa are very thick, and the spongy
tissue is abundant, while the compact is rare. The pubis is always convex on
its two faces, and the middle part of the coxa — that adjoining the cotyloid
cavity — is of considerable thickness, a feature which much diminishes the extent
of the pelvic cavity. As the animal advances in age, however, the layers of
compact tissue increase in thickness, approaching each other as the spongy
substance is lessened. The pubis becomes thinnest, and at an advanced period
of life is sometimes even translucid.
The compact tissue is always abundant in the neighbourhood of the cotyloid
cavity, as this is the centre on which converge all the impulsive efforts com-
municated to the trunk by the posterior limbs. It is also in this cavity that
ossification commences.
B. The Pelvis in Genekal.
1. External and Internal Conformation of the Pelvis. — The pelvis
is a kind of rear cavity in the form of a cone, which prolongs the abdominal
cavity between the sacrum and coccygeal vertebrae.
It occupies the posterior part of the trunk, and, with regard to its conforma-
tion, presents for study an external and internal surface.
External surface. — This may be resolved into four planes or faces.
The superior plane is slightly oblique from above to below, and before to
behind ; its degree of obliquity, varies. It is contracted from before to behind,
and shows : 1. On the median line, the spinous processes of the sacral and the
first coccygeal vertebrae. 2. On each side the sacral grooves, at the bottom of
which open the supra-sacral canals.
The inferior pla?ie is nearly horizontal. Formed by the pubes and ischial
I)ones, it presents from before to behind : 1. In the middle, the ischio-pubic
symphysis. 2. On each side the subpubic groove, the oval foramina, and the
inferior face of the ischial bones. 3. Quite externally, the cotyloid cavities, by
which the pelvis rests upon the posterior limbs. ,
The lateral faces are oblique downwards and outwards, and are wider in front
than behind. They exhibit : 1. The spine of the ilium and the two anterior
■spinous processes. 2. The external iliac fossa. 3. The ischial arch. 4. The
supra-cotyloid crest or ischiatic spine, which presents, outwardly, the surface of
insertion for the internal or deep gluteus muscles. 5. The lesser ischiatic notch.
6. The ischial tuberosity.
Internal surface. — The internal surface of the Horse's pelvis cannot be
divided into two portions as in Man, because the inner surface of the iliac bones
is not hollowed out to form an anterior cavity.
The pelvis of Solipeds is, therefore, a simple conoid cavity, in which are
distinguished four planes or faces, and two apertures called the inlet and
outlet.
The anterior openinq, or inlet, is nearly circular, especially in the Mare, and a
little oblique downwards and backwards. It is limited above by the inferior face
^f the first vertebra of the sacrum ; inferiorly, by the anterior border of the
182
TEE BONES.
pubis ; and on the sides by a part of the inner face of the iliac bones, and also
the internal aspect of the pectineal crests.
The inlet presents four diameters, a knowledge of which is important in
obstetrics — a vertical, horizontal, and two oblique. The first, the sacro-pubir,
extends from the inferior face of the sacriun to the anterior border of the pubic
symphysis ; its mean length is 8:^ inches. The second, the bis-iliac, is measured
from one pectineal crest or eminence to another ; the mean of this is H^jj inches.
The two last diameters, the ileo-sacral, are estimated from the inferior face of
the sacro-iliac articulation of one side to the ilio-pectineal eminence of the
other ; this is, on an average, SyV inches. These measurements irrefutably
Fig. 86.
PELVIS OF THE HORSE.
demonstrate that the inlet is not elliptical in the vertical direction ; but it may
happen that the transverse diameter is the greatest.
The posterior aperture or outlet, situated at the posterior end of the pelvic
cavity, gives exit to the rectum and genital organs. It is limited by the inferior
face of the summit of the sacrum, the superior face of the ischial bones, the
supra-cotyloid crest or ischiatic spine, and the internal face of the sacro-sciatic
ligaments. At the outlet only two diameters are recognized — a vertical and a
horizontal. The vertical, extending from the inferior face of the sacrum to the
superior face of the ischial symphysis, measures on an average 6yV inches.
The horizontal diameter, comprised between the two supra-cotyloid crests, is
7-j^ inches.
The superior face of the pelvic cavity is a little concave from before to
THE POSTERIOR LIMBS. 133
behind ; it has for base the sacrum, which presents on each side of the median
line the subsacral foramina. This part is also called the sacral plane, or roof of
the pelvis.
The inferior region, or ischio-pubic plane, is formed by the pubes and the
ischial bones. It is concave from side to side ; its anterior border is nearly
straight, and its posterior border is scooped out by a wide notch to form the arch
of the ischium.
It has been remarked by Goubaux, that the portion of this plane correspond-
ing to the pubis presents numerous varieties. The superior face of the pubis
may be convex in its anterior moiety, and concave in its posterior ; or it may be
Fifr. 87.
PKLVIS OF Tllli MARE.
ooncave before and convex behind, the concavity being separated from the
convexity by a transverse ridge. This ridge is sometimes represented by a series
of small conical eminences ; at other times this upper face is disposed as a
smooth inclined plate, directed backwards and upwards, and a kind of rim
surmounts the anterior contour of the oval foramen.^
With regard to the lateral faces, they are formed by a small portion of the
inner face of the iliac bones, and in great part by the sacro-sciatic ligaments.
The foetus must pass through the pelvic canal during parturition ; it is,
therefore, important to know at any time if the female pelvis is of sufficient
dimensions to allow the foetus to leave it. Pelvimetry is the name given to
' It is necessary to be aware of the frequency of these asperities on the floor of the pelvic
cavity, in order not to arrive at false inductions when exploring the bladder per re,etum.
134 THE BONES.
that section of obstetrics dealing with the diameters of the pelvis. These may
be determined in several ways, which, in veterinary surgery, daily receive the
sanction of experience.
Some years ago we indicated one,^ which consists in measuring the horizontal
distances between the two haimches and the two ischiatic tuberosities, and the
vertical distance extending from the coxo-femoral articulation to the most
salient part of the croup ; then to take a fourth of the total of the two first
measurements, in order to obtain the transverse diameter of the inlet, and
three-fourths of the third, to have the vertical diameter of this opening.
Saint-Cyr and Violet have investigated the relation existing between the
height of the Mare and the vertical diameter of the pelvis, then that of the
width of the croup to the bis-iliac diameter ; and they have found that the first
was equal to 0"1515 centimetres ; the second to 0'4654, in a well-bred Mare, to
0*3945 in common-bred Mares. Consequently, according to the pelvimetric
procedure of these authorities, it is sufficient to multiply the height of the Mare
by 0-1515 to have the vertical diameter of the inlet, and the width of the croup
by 0*4654 or 0"3945, according to circumstances, to find the transverse diameter.
But this question rather appertains to obstetrics.^
2. Differences in the Pelvis of the Sexes. — The pelvis of the Mare
exceeds that of the Horse in all its dimensions, but the difference is most,
marked in the transverse diameters (Figs. 86, 87).
The inlet forms a vast circumference, when compared with that of the male ;
the pectineal crests are wide apart, and the distance separating the anterior
border of the pubis from the lower face of the sacrum is considerable.
If the pelvis be viewed in its superior plane, it is found that in the Mare the
ischiatic notches are very deep ; that the internal border of the ilium forms a
regularly curved and very concave line ; and that the supra-cotyloid crests, or
ischiatic spines, are widely separated from each other. It is also noticed that
the floor of the pelvis is wide, and that the bones composing it tend towards the
same horizontal Hne.
In the male, the ischiatic border is only represented by a very curved line ;
this line is composed of two almost straight portions, which join at an obtuse
angle at the origin of the neck of the ilium ; the supra-cotyloid crests are
relatively near each other, and bent towards the longitudinal axis ; while the
two moieties of the pelvic floor are directed very obliquely downwards and
inwards.
In the Mare, the ischial arch is larger than in the male, and forms a regular
curve uniting the two tuberosities of the same name. In the Horse, the two
ischial tuberosities are but little apart, and the ischial arch forms a somewhat
acute angle, with its borders nearly straight.
Lastly, when the pelvis is examined in its inferior plane, in addition to the
features already indicated in the ischial arch, it is found that in the Mare the
obturator foramina are large and nearly circular, while in the Horse they are
elliptical ; the cotyloid cavities are also further removed from the ischio-pubic
symphysis in the female than in the male.
The sacrum of the Mare has appeared to us, in some individuals to be a little
more arched from before to behind than that of the Horse ; but this character
is not constant.
' Arloing;, Journal Vet^rinaire de Lyon. 1868.
= Saint Cyr and Violet, Trait€ cV Ohstetrique VitMnaire, Paris: 1888.
Tn:E POSTERIOR LIMBS.
135
The following figures, relating to the capacity of the pelvis of the Mare and
Horse, confirm what has just been enunciated : —
Mare.
Horizontal Diameters.
Horse.
Horizontal Diameters.
Between the Pectineal
Crests.
Between the Supra-cotyloid
Crest,.
Between the Pectineal
Cre^t8.
Between the Supra-cotyloid
Crests.
Inches.
9|
Inches.
7^
Inches.
8t',
Inches.
Mare.
Vertical Diameters.
Horse.
Vertical Diameters.
Between the Sacrum and
Pubis.
Between the Sacrum and
Ischium.
Between the Sacrum and
Pubis.
Between the Sacrum and
Ischium.
Inches.
8^
Inches.
Inches.
8
Inches.
6^
To recapitulate, there is observed in the pelvis of the Mare : —
1. A great increase in the transverse diameters.
2. A deep and regularly concave ischiatic notch.
3. A wide and concave ischial arch.
4. Circular obturator foramina.
5. The cotyloid cavities distant from the pubic symphysis.
In the Ass, the inlet of the pelvis is a longer oval than in the Horse. The
coxse are distinguished by : 1. The less curvature of the anterior border of the
ilium. 2. A slightly excavated external iliac fossa. 3. The triangular shape of
the obturator foramina. 4. A short and deep notch separating the external
border of the ilium from the angle of the haunch. 5. The direction of the
tuberosities of this angle ; they approach more nearly the parallelism with the
median plane of the trunk than in the Horse. 6. The disposition of the rugo-
sities in tubercles for the insertion of the suspensory ligaments of the corpus
cavernosum on the inferior face of the ischium. In the Ass, also, a line which
would unite the inferior contour of the auricular facet to the most salient
point of the angle of the haunch, would be parallel to the anterior border of the
ihum, while it would be oblique on this border in the Horse.
The inlet of the pelvis in the Hinny resembles that of the Ass ; in that of
the Mule, it holds a middle place between the Ass and Horse. The pelvis of
the Hinny resembles that of the Ass, also, by the form of the obturator foramina,
the direction of the anterior border of the ilium, and the position of the auricu-
lar facet ; while that of the Mule, on the contrary, resembles the pelvis of the
Horse in these features. The reverse is noted with regard to the disposition of
the angle of the haunch.
Differential Characters in the Pelvis op other Animals.
It is remarked : 1. That in all the domesticated animals, with the exception of Solipeds
and the Camel, the direction of the coxse is nearly horizontal. 2. That in all, the ilium is
more oblique than in Solipeds. 3. That in all, the transverse diameters of the pelvis are
relatively less extensive.
A. Ruminants. — In the Ox, the space between the two coxae is scarcely so great in front
THE BONES.
as behind ; the ilium is not voluminous, and has only three processes on the anterior and
superior iliac spines. There is no furrow on the lower face of the pubes, and its upper face,
like that of the ischium, is very concave. Thrt-e eminences are seen on the posteio-external
angle of the ischium. In early life, the ischio-pubic symphysis shows an epiphysary nucleus
in the middle of its inferior face. (The epiphysis on the inner border of the ischium has been
considered by some anatomists as an independent bone, and described by them as the
inter-ischial bone).
Tiie ischio-pubic symphysis has, in the middle of its inferior face, a thick protuberance,
flattened on each side and very pointed; in early life this is an epiphysis, and the epipliysary
nucleus, bifurcated posteriorly, is continued along the posterior border of tlie ischial bones as
far as the ischial tuberosity, in the form of two marginal bands.
The rim of the cotyloid
cavity has also three notches,
and the supra-coryloid crest,
or ischiatic spine, is very ele-
vated and shiirp, and but little
rou;<hened outwardly.
lu the Sheep and Goat, the
coxae are yet more horizontal
and proportionately longer
than in the Ox, but the upper
face of ttie ischium and pubis
i.s less concave ; the external '
iliac fossa is separated into two
portions by a small longi-
tudinal crest.
The pelvis of the Camel ia
remarkable for its great ob-
liquity, its shortness, and its
narrowness. The anterior
border of the ilium is convex ;
the pubis and ischium are
very thick; the rim of the
cotyhiid cavity is elevated and
regular; the ischio-pubic sym-
physis forms a rugged crest
outside the pelvis; and the
ischial tuberosity is disposed
in the same manner as in the
Horse.
B. Pig.— Tlie pelvis of
the Pig closely resembles that
of the smaller Ruminants ;
though the crest of the ilium
is convex, and there is no pro-
tuberance outside the ischio-
pubic symphysis,
height, and the ischio-pubic
PELVIC BONES OF THE CAT AND RABBIT.
1, Pelvis of the Cat. B, Pelvis of the Rabbit. 1, Sacrum ; 2,
external iliac fossa; 3, great ischiatic notch; 4, external border
of the ilium ; 5, supra-cotyloid crest ; 6, cotyloid cavity ; 7,
crest above the shaft or neck of the ilium ; 8, small sciatic
notch; 9, anterior extremity of the symphysis pubis; 10,
ischium; 11, ischial tuberosity; 12, pubis; 13, obturator
foramen.
The pelvic cavity is vast, in proportion to the animal'
symphysis is late in becoming ossified.
C. Dog. — In the Dog, the transverse diameter of the pelvis is greater behind than in front ;
it is smallest between the cotyloid cavities. The ilium is nearly vertical, and its external
face is much depressed. The notch forming the ischial arch occupies no more than the
internal moiety of the posterior border of the ischium ; between this arch and the ischial
tuberosity, is a rugged lip directed downwards. There is no furrow on the lower face of the
pubis. Ossification of the symphysis is even later than in the Pig.
D. Cat. — In the Cat, tlie ilium is proportionately narrow, and the supra-cotyloid crest
liigher, than in the Dog. The posterior border of the ischium is regularly convex from
without to within, and the pubic symphysis has, inferiorly, a somewhat salient crest (Fig. 88).
E. Rabbit. — Pelvis horizontal ; ischium nearly as long as the ilium ; external iliac fossa
divided by a blunt longitudinal crest ; supra-cotyloid crest little elevated, straight, and ending
abruptly behind by a kind of notch ; rim of the cotyloid cavity complete, or having a slight
posterior notch; ischial tuberosities parallel and not divergent, as in the Dog: and posterior
border of the ischium concave, and very obliquely directed forw-ards and inwards (Fig. 88).
THE POSTERIOR LIMBS. 1S7
Thigh.
This has for its base one bone — the femur.
Femur (Figs. 89, 90).
The femur (os femoris) is a long, pair bone situated in an oblique direction
downwards and forwards, between the coxa and the principal bone of the leg ;
it is divided into a bodt/ (or shaft) and two extremities.
Body. — It is irregularly cylindrical, and presents for study four faces. The
external, internal, and anterior, confounded with one another, are regularly
rounded and almost smooth, showing only some slight imprints and vascular
grooves. The posterior, nearly . plane, and wider above than below, offers : 1.
Outwardly and towards the superior third, an uneven circular surface. 2. On
the same level, and inwardly, a shght crest, oblique downwards and outwards.
3. In the middle, a very extensive roughened surface, having the form of an
obliquely angular parallelogram, for the attachment of the great adductor muscle
of the thigh. 4. Below this surface, a large vascular groove running obliquely
outwards and downwards.
On the limit of the posterior and external faces are found, towards the upper
third, a large rugged, flattened eminence, curved in front, and termed the
subtrochanterian crest (or external smcdl trochanter ^), because of its position under
the trochanter ; below, a deep fossa, named the subcondijloid, garnished at its
bottom with asperities, and bordered in front by an uneven lip. On the limit
of the posterior and internal face, there are observed from above to below :
1. The small trochanter — a large scabrous tuberosity, elongated in conformity
with the bone, and situated near its upper fourth. 2. A marked longitudinal
imprint for the attachment of the pectineus ; behind, it is confounded with the
surface for the insertion of the great adductor muscle of the thigh, and presents,
in front, the nutrient foramen of the bone. 3. The origin of the great posterior
fissure. 4. Quite below, a collection of large tubercles which form the supra-
condyloid crest.
Extremities. — The superior extremit)/ is sensibly flattened before and behind,
and shows : 1. Inwardly, an articular head which is received into the cavity of
the acetabuluna. This head is separated from the other portion of the body by
a neck, which is, however, not well marked in the Horse, and forms two-thirds
of a sphere, excavated in its internal part by a very deep cavity for ligamentous
insertion. 2. Outwardly, a very large eminence — the trochanter major, or great
{external) trochanter, in which is recognized, as in the trochlea of the humerus :
a summit, much more elevated than the articular head, and shghtly bent inwards ;
a convexity, encrusted with cartilage, and anterior to the summit, from which
it is separated by a narrow and deep notch ; a crest situated under the convexity,
and formed by a tuberculated surface, on which one of the tendons of the middle
gluteus muscle becomes inserted, after gliding over the convexity. 3. Posteriorly,
the trochanteric or digitcd fossa — a deep cavity studded with imprints, and circum-
scribed, outwardly, by a salient lip {trochanteric ridge), which descends vertically
' This is tlie third trochanter of Cuvier, and takes the place of the external and superior
branch of the linea axpera of Man. (It is the external small trochanter of Percivall, and the
middle trochanter of Leyh )
138
THE BONES.
from the summit of the trochanter to the posterior face of the bone, where it
gradually subsides.
The [inferior extremity is flattened before and behind ; consequently, its laro-er
axis crosses at a right angle that of the upper extremity. It is distinguished by
the presence of tzvo condyles and a trochlea. The two condyles, placed behind,
one beside the other, articulate with the superior extremity of the tibia. They
are separated by a deep depression designated the intercondyloid fossa, which
lodges the spine of the tibia and the interosseous ligaments of the femoro-tibial
Fig. 89.
Fig. 90.
LEFT FEMUR (ANTERIOR VIEW).
1, Head ; 2, 2, trochanter major, with its
crest ; 3, trochanter minor, subtrochan-
terian crest, or third trochanter; 4, in-
ternal trochanter ; 5, notch for insertion
of ligamentum teres ; 7, 8, tuberosities
for tendinous and ligamentous insertion ;
9, trochlea.
LEFT FEMUR (POST^IOR VIEW).
Head ; 2, trochanter major ; 3, trochanter
minor ; 4, internal trochanter ; 5, fossa
for insertion of ligamentum teres ; 6,
trochanteric fossa; 7, 8, tuberosities; 9,
fossa for the insertion of the external
meniscus; 10, supra-condyloid fossa ; 11,
condyles.
articulation. The external condyle bears, outwardly, two fossag — one superior, for
ligamentous insertion ; the other, inferior, for muscular attachment. The
internal condyle presents, posteriorly and inwardly, near the posterior extremity
of the intercondyloid notch, a roughened depression for the insertion of the
fibro-cartilaginous meniscus interposed between the external condyle and the
corresponding articular plane of the tibia. It is surmounted outwardly — on
the side opposite to the intercondyloid notch — by a large tubercle for insertion.
The trochlea, a wide pulley on which the patella glides, is situated in front of
THE POSTERIOR LIMBS.
139
Fig. 91.
the condyles. It is slightly oblique downwards and inwards, and appears to
continue in front the intercondyloid notch. Of the two lips which border its
cavity laterally, the internal is the thickest and the most prominent. Between
the external and the corresponding condyle, is seen a digital fossa for muscular
insertion.
Structure and development. — The femur, very spongy at its extremities, is
developed from four principal centres of ossification : one for the body, another
for the articular head, the third for the trochanter, and the last for the inferior
extremity alone.
The femur of the Ass offers several differential characters, the principal of
which have reference to the length of the neck, the development of the third
trochanter (trochanter minor), and the curvatures of the
diaphysis. The greater length of the neck causes the
internal trochanter to be some distance from the hori-
zontal plane on which the inner face of the bone lies ;
in the Horse this trochanter is always in contact with
the plane. The small trochanter is less developed than
in the Horse, as may be seen on laying the bone on its
external border ; for the femur of the Ass rests by the
trochanter major and external condyle, while in the Horse,
it lies on the latter and the subtrochanteric crest. With
regard to the curvatures, there is remarked a slight
diminution in that which carries the head of the bone
backwards, and a slight increase in the twist of the
diaphysis around its longitudinal axis, which alters the
equilibrium of the bon* so that it is impossible to have
it in stable equilibrium when it rests on the trochanter
major, head, and inner lip of the trochlea ; this is easily
accomplished with the femur of the Horse.
By the dimensions of the neck and internal trochanter,
the femur of the Hinny and Mule holds a middle place
between their progenitors ; while in the development of
the trochanter major, and the degree of torsion around
its longitudinal axis, the femur of the Hinny much resembles that of the Ass,
and the Mule that of the Horse, though the conditions of equilibrium always
remain the same as in the latter.
SECTION OF LEFT FEMUR,
SHOWING ITS STRUCTURE.
Differential Characters in the Thigh-bone of the other Animals.
In all the domesticated animals except Solipeds, the femur tends to become curved longi-
tudinally, prismatic, and triangular; the posterior face contracts, and the surfaces for insertion
that it presents gradually approach each other, until they become confounded, and form a
linea aspera in certain species. The head is more distinct ; the internal trochanter is a rough
tubercle, and is joined to the large trochanter by an oblique ridge ; the large trochanter sub-
sides, and forms a single mass, the summit and convexity of which are confounded ; the third
trochanter, the fossa, and the supra-condyloid crest are more or less effaced. In addition to
these modifications, there are others special to each species.
A. Rvuninants.— In the Ox, there is no subtrochanteric crest ; the supra-condyloid fossa
is shallow, and the crest little noticeable. The head is well detached, and has its centre
excavated by a shallow fossa of insertion. The trochlea is narrow, and its inner border ascends
much higher on the anterior face of the bone than the external.
In the Sheep and Goat, the general form of the femur resembles that of the Ox. It is
observed, however, that the body is slightly curved backwards ; that the supra-condyloid fossa
140
THE BONES.
is nearly obliterated ; that the trochantir has subsiiled nearly to a level with the articulaJ
head; and that the trochha is circumscribed by two equal-sized lips.
The femur of the Camel more nearly resembles that of Man. It is long, slender, and curved
backwards. The body is prismatic in its middle portion, and the two branches of the linea
aspera meet in the middle and diverge towards the ends. Tlie articular head is very much
separated from the trochanter major, which is below the level of tlie most prominent part of the
head. Tiie internal condyle is smaller than the external, and the trochlea is narrow, while its
lips are equal.
B. Pig. — In the femur of the Pig, there is also noticed a supra-condyloid fossa, but it is
wide and sliallow ; the rugosities of the posterior face are replaced by some salient lines ; the
trochanter major is on a level with the heail; the latter is supported by a somewhat constricted
neck,andissituated within, and in front of, the trochanter major. This hitter disposition changes
the direction of the great axis of the superior extremity,
which fibliquely crosses that of the inferior extremity.
C. Camivora. — In the Dog and Cat, the femur is
long and curved like a bow. Tlie rugged surfaces of the
posterior face are confounded, and form two crests repre-
senting the linea aspera of the human femur. These
crests do not lie against each other in the middle portion
of the bone — they are merely parallel ; tlien they diverge
above and below, to terminate beneath the great and
small trochanters, and above the two condyles. The
trochanter major is not so high as the particular head.
The femur of Carnivora is also distinguished: 1. By
the complete absence of the third trochanter and the
supra-condyloid fossa — this last being replaced by a
small tubercle, which terminates below the external
brinch of the linea aspera. 2. By the marked constriction
and length of the neck supporting the articular head.
3. By the depth of the digital fossa.
In the Cat and Rabbit are found small bony nodules,
embedded like sesamoids m the substance of the lateral
ligaments of the femoro-tibial articulation. After mace-
ration, liiey often adhere to the condyles of the femur.
D. Rodents.— The femur of the Rabbit resembles
that of the Dog. It is flat before and behind, and more
bent inwards at its upper end. The internal trochanter
appears as a crest, and not a tubercle ; and the sub-
trochanteric crest is very developed, and placed im-
mediately below the trochanter major.
Leg.
This has for its base three bones : the tibia,
peroneus {pv fibula), and the rotiila {or patella).
A. - B
rEMtJR OF THE OAT AND RABBIT.
L, Femur of the Rabbit. B, Femur
of the Cat. 1, Diaphysis ; 2, head ;
3, internal trochanter; 4, trochanter
major ; 5, subtrochanteric crest ;
6, trochlea; 7, internal condyle;
8, sesamoid imbedded in the internal
ligament of the femoro-tibial articu-
lation.
1. Tibia (Fig. 93).
The tibia is a long prismatic bone, thicker at the superior than the opposite
extremity, and situated between the femur and the astragalus, in an oblique
direction downwards and backwards, constituting the principal portion of the
leg. It has a body or shaft, and two extremities.
Bod//.— Thk offers for study three faces and three borders. The faces are
wider above than below. The external is almost smooth, and is concave in its
superior part and convex below, where it deviates to become the anterior. The
internal, slightly convex on both sides, presents, superiorly, deep imprmts for the
attachment of the adductor muscles of the thigh and the semitendinosus. The
posterior, nearly plane, is divided into two triangular surfaces : one, superior,
THE POSTERIOR LIMBS.
141
Fig. 93.
slightly roughened, serves for the attachment of the popliteus muscle ; the other
inferior, much more extensive, is furrowed into numerous longitudinal crests,
which give attachment to the perforans muscle. On the Hmit of these two
surfaces is remarked the nutrient foramen of the bone.
The borders are distinguished as anterior, external, and
internal. The first is rounded, and not very sahent in its
inferior two-thirds ; it forms, in its superior third, a
curved crest, with the concavity external, which joins the
anterior and superior tuberosity of the bone ; this has
received the name of the tibial crest. The external border
is very thick and concave above, where it constitutes, in
common with the fibula, the tibial arch. The internal is
also very thick, straight, and provided superiorly with some
salient tubercles to which the popliteus is attached.
Extremities. — The superior extremity, the most volumi-
nous, is formed by three tuberosities — an anterior and two
lateral, which are external and internal. The first, the
smallest, is a rugged process continuous with the tibial
crest, and separated from the external tuberosity by a
wide and deep groove, into which passes a tendinous cord ;
it is excavated, in front, by a vertically elongated fossa,
which lodges the middle ligament of the patella. The
externcd tuberosity, medium in size and the most detached,
has outwardly an articular facet for the head of the fibula.
The internal tuberosity, the largest and least detached,
presents : on the sides, ligamentous imprints ; behind, a
small tubercle which gives attachment to the posterior
crucial ligament of the femoro-tibial articulation. The
superior face of the two lateral tuberosities is occupied by
two large, irregular, and undulated articular surf aces, which
respond to the condyles of the femur, through the medium
of the two meniscus-shaped fibro-cartilages interposed
between the two bones. Of these two surfaces, the ex-
ternal is always the widest, because it serves, by its posterior
part, for the gliding movements of the popliteal tendon.
They are separated from each other by the tibial spine — a
conical articular eminence, divided into two lateral parts
by a groove for insertion excavated at its base ; and in front
by two lateral facets for the insertion, anteriorly, of the
two inter-articular cartilages ; it is bordered behind by
another fossa, which receives the posterior insertion of the
internal meniscus.
The inferior extremity, flattened behind and before, ex-
hibits an articular surface moulded on the pulley of the
astragalus, and two lateral tuberosities. The articular
surface is formed by two deep cavities, oblique forwards and outwards, and
separated by a median tenon which terminates posteriorly by a very prominent
projection, on which the bone rests when it is made to stand vertically on a hori-
zontal plane. The external tuberosity ^ projects but little, and is traversed in ItB
* The external malleolus of Man.
12
POSTERIOR VIEW OP
RIGHT TIBIA.
Tibial spine ; 2, fossa
for the insei'tion of the
internal meniscus ; 3,
external tuberosity
with articulation for
the fibula ; 4, fossa for
the insertion of exter-
nal meniscus ; 5, fibula,
forming with the tibia
the tibial arch; 6, shaft,
or body of the tibia;
7, 8, external and in-
ternal malleoli, inferior
tuberosities, or lateral
processes of the tibia;
9, articular trochleas
with a median ridge,
for articulation with
the astragalus.
142
THE BONES.
LEG-BONES OF THE MULE, WITH THE
FIBULA COMPLETELY DETACHED.
I, Nutrient foramen ; 2, insertion sur-
face for the perforans ; 3, insertion
surface for the popliteus ; 4, tibial
ridge ; 5, fossa for the insertion of
the anterior crucial ligament; 6, in-
ternal articular surface; 7, external
articular surface ; 8, tubercle for the
insertion of the posterior crucial liga-
ment ; 9, fossa for the insertion of
the internal meniscus ; 10, tibial
crest ; 11, internal and inferior tu-
berosity; 12, external and inferior
fissure of the tuberosity; 13, pos-
terior prominence formed behind by
the median spur of the inferior articu-
lar surface ;' 14, superior extremity
of the fibula articulating with the
tibia; 15, the body ofthe fibula — com-
pletely developed in this specimen.
middle by a vertical fissure. The infernal
tubcrosif//,^ better defined, is margined pos-
teriorly by an oblique channel.
Structure and development. — The tibia is
very compact in its inferior portion, and is
developed from five chief centres of ossifica-
tion. The body is formed by one and the
superior extremity by two, the anterior tuber-
osity having one of these ; the last develops
the whole of the inferior extremity of the bone,
except the external tuberosity, which is de-
veloped from a separate nucleus, that at an
early period becomes fused with the principal
one of the epiphysis.
The tibia of the Ass is remarkable for
the more or less perfect equality of the promin-
ences around the inferior articular surface, so
that this bone can sometimes lie in stable
equilibrium on its inferior extremity. It is
also distinguished from that of the Horse by :
1. The more or less marked obliquity of the
grooves which articulate with the astragalus.
2. The disposition of the oblique prominence
coursing the surface, for the insertion of the
popliteus muscle. 3. The great development
of the imprint for the semitendinosus muscle,
and the crest above the groove for the oblique
flexor tendon of the phalanges.
The tibia of the Mule and Hinny more
particularly resembles that of the Horse.
2. Fibula, ok Peroneus (Fig. 94).
A small, undeveloped bone, elongated and
styloid in shape, situated outside the tibia,
and extending from the superior extremity of
that bone to the middle or lower third of its
body.
The middle portion of the fibula is thin
and cylindrical, and forms above, in common
with the external border of the larger bone,
the tibial arch. Its superior extremity, wide
and flattened on both sides, has received the
name of head. It offers, on its internal face,
a diarthrodial facet to articulate with the
external and superior tuberosity of the tibia ;
on its external face it shows ligamentous im-
prints. The infei'ior extremity of the fibula
* The internal malleolus.
THE POSTEBIOB LIMBS.
143
terminates in a blunt point, and gives attachment to the ligamentous fibres that
unite it to the tibia.
The fibula is sometimes continued to the external inferior tuberosity of the
latter bone, with which it is confounded ; and as this tuberosity always forms a
special nucleus, particularly in the young Foal, it seems natural, having regard
to the disposition observed in Pachyderms and the Carnivora, to consider it as the
inferior extremity of the fibula fused to the tibia. In these animals, indeed, the
tuberosity or external maleolus is formed by the inferior extremity of the fibula.
Structure and development. — This bone is very compact, and apparently
developed by a single nucleus of ossification ; though, in reality, there are two,
one of which is for the head of the bone.
3. Patella (Figs. 95, 96).
A small, short, and very compact bone, situated in front of the femoral
trochlea, and annexed to the tibia, to which it is attached by three extremely solid
ligamentous bands.
The small polyhedron which it represents only offers for study three faces :
PATELLA OF THE HORSE (SUPERIOR AND
POSTERIOR FACES).
1, Superior face ; 2, posterior articular face ;
3, external border.
PATELLA OF THE HORSE (ANTERIOR FACE).
1, Anterior face ; 2, external border ; 3,
internal border.
the superior, roughened, and serving for the insertion of the triceps cruralis and
rectus muscles ; the anterior, convex and irregular ; and the third, the posterior,
moulded on the femoral trochlea, to which it is but imperfectly adapted. In the
fresh state, however, the articular surface formed by the latter face is completed
by a fibro-cartilaginous apparatus, which will be noticed when describing the
femoro-tibial articulation. This articular surface is composed : 1. Of a median
ridge, which occupies the bottom of the trochlear cavity. 2. Of two depressed,
gliding, lateral facets on the sides of this cavity ; the internal facet is always
larger than the external — a disposition which permits the patella of one hmb to
be distinguished from that of the other.
The Patella of the Ass is usually narrower than that of the Horse, but this
feature would scarcely permit of its being distinguished from that of the other
domestic Equidae.
144
THE BONES.
Fig. 97.
Differential Characters in the Leg-bones op the other Animals.
In the leg-bones there is observed, in the various domesticated animals, differences analo-
gous to those mentioned as existing in the forearm of the pectoral limb. More particularly
is til is the case with regard to the development of the fibula. The relations existing between
the development of that bone and the number of digits, is less marked than that which exists
between the development of the ulna and the division of the digital region. Thus, in Rumi-
nanta the fibula is only represented by its inferior nucleus of ossification, although there are
two apparent and free digits. In these animals the patella is also very narrow ; and in all the
domesticated species except Solipeds, tlie articular
grooves in the lower end of the tibia are directed im-
mediately from before to behind.
A. Ox, Sheep, Goat.— In the Ox, the tibia is
short ; it is longer in the Goat and the Sheep. The
tibia of these animals is remarkable for : 1. The absence
of the lateral facet on the supero-external tuberosity.
2. The absence of a vertical fossa on the anterior tuber-
osity. 3. The absence of roughened lines on the pos-
terior face. 4. The obliquity downwards and inwards
of the inferior articular surface. The most salient point
of this surface is the anterior extremity of the middle
tenon.
The body of the fibula and its upper extremity
are replaced by a fibrous cord, which is sometimes
ossified wholly or in part, and may then resemble the
fibula of Solipeds. The inferior extremity forms a
small isolated bone (the tamal coronoid bone of some
authorities), articulating in one direction with the tibia,
and in another with the calcis and astragalus.
B. Camel The tibia of the Camd is very long.
slightly bent outwards at its upper end, and inwards
at the lower end. The tibial crest is high and sharp.
The posterior face shows only one roughened line
limiting the popliteal surface.
C. Pig.— In the Pig, the fibula is flattened on both
sides, extends the whole length of the leg, and is united
to the tibia by its two extremities : above, by a diar-
throdial facet ; below, by an interosseous ligament.
It is developed from three ossifying centres; the in-
ferior articulates with the calcis and astragalus.
D. Dog, Cat. — In Carnivora, the tibia is long and
slender, and presents a salient anterior crest. The
fibula is also as long as the tibia, and is united to
that bone at three points : at the two extremities by
articular surfaces, in the inferior third and middle by
an interosseous ligament.
E. Rabbit. The leg-bones of this animal much
resemble those of Carnivora, diflering only in : 1. More
pronounced flattening of the tibia on each side at its
upper end, and before and behind inferioily. 2. The slightly salient malleoli. 3. The fibula,
which is fused with the tibia in its lower third.
LEG-BONES OF THE RABBIT AND CAT.
A, Boues of the Rabbit. B, Bones of
the Cat. 1, Diaphysis of the tibia ;
2, crest of the tibia; 3, internal
malleolus or tuberosity of the in-
ferior extremity of the tibia ; 4,
anteiior extremity of the median
tenon on the inferior articular sur-
face of the tibia ; 5, fibula ; 6, ex-
ternal malleolus or tubei'osity.
Posterior Foot.
This region, which bears the o;reatest resemblance to the same region in the
anterior limb, comprises three subdivisions— the tarsus, the metatarsus, and the
digital region.
1. Bones of the Tarsus (Figs. 98, 99).
These are short, very compact bones, six or seven in number, and situated
THE POSTERIOR LIMBS.
145
between the inferior extremity of the tibia and the superior extremity of the
metatarsal bones ; they are arranged, like the bones of the carpus, in two tiers —
a superior and an inferior.
The superior row only comprises two bones,
the largest ; these are the astragalus and the
calcaneum (or calcis). The inferior row is formed,
outwardly, of the cuboides alone ; inwardly and
anteriorly, it is subdivided into two secondary
rows, the superior of which is constituted by the
scaphoides, and the inferior by the large and small
cuneiform bones. The last is sometimes divided
into two, in which case there are three cunei-
forms ; then the total number of the bones is
Astragalus. — An irregular cubical bone, situ-
ated in front of the calcis, between the tibia
and the scaphoid, and divided into Jive faces :
1. A superior and anterior, formed as an articular
pulley to correspond with the inferior extremity of
the tibia. This pulley — oblique from above down-
wards, forwards, and outwards — may be considered
as the type of the most perfect trochlea in the
body ; it forms with the median plane of the body
an angle of from 12° to 15°. Its borders are
slightly spiral, the inner being more prolonged
backwards than the external ; its groove receives
the median tenon of the tibia, and its two ridges
or lips fit into the lateral furrows of that bone ;
the two lips are deeply implanted in the lateral
grooves, and their two fossae are hollowed out of
their lower extremity, to admit the end of the
principal bone during flexion movements, 2. An
inferior face, occupied by a slightly convex articu-
lar surface articulating with the scaphoid ; this
surface is notched outwardly by an excavation for
ligamentous insertion ; behind the internal ex-
tremity of this furrow, the articular face is cut
in such a manner as to present two facets inclined
towards each other, and separated by a sharp
ridge. 3. A posterior face, irregular, cut into three
or four diarthrodial facets adapted for similar
facets on the calcis, and which are separated by
a wide, rugged excavation ; the middle facet is
elliptical, almost vertical, slightly convex, and is
the largest. 4. An external face, covered with
imprints for the tibo-tarsal ligaments. 5. An
internal face, provided below with a small tubercle
for insertion, and, posteriorly, with a badly defined
sinuous furrow for the tendon of the oblique flexor
muscle of the phalanges (Fig. 99).
left hind foot (external
aspect).
1, Tibia ; 2, summit of calcis or cal-
caneum ; 3, astragalus ; 4, cuboid;
5, scaphoid ; 6, cuneiform mag-
num ; 7, large metatarsal bone ;
8, small metatarsal bone ; 9, suf-
fraginis, proximal, or first pha-
lanx ; 10, sesamoid bones; 11,
coronary, second, or middle pha-
lanx ; 12, pedal bone, or third or
distal phalanx; 14, navicular
bone ; 15, basilar process of pedal
bone.
146
THE BONES.
Calcaneum, or Calcis (Figs. 98, 99, 100, 101).-A bone vertically elongated,
flattened on both sides, and presenting tivo faces, hvo borders, and two extremities.
The external face is smooth and nearly plane. The internal face is excavated
into a ghdmg groove to form the tarsal groove, in which passes the tendon of
the perforans. The anterior border is slightly concave. The posterior border is
Fig. 99.
TARSUS OF THE
INTERNAL ASPECT.
1, Calcis; 2, astragalus (first and second bones of the
upper row); 3, cuboid; 4, scaphoid; 5, cuneiform
magnum; 6, vascular canal between the cuboid,
scaphoid, and cuneiform magnum ; 7, smooth sur-
face for the tendon of the gastrocnemius; 8, surface
for insertion of latter ; 9, smooth surface for the
tendon of the perforans ; 10, anterior extremity of
the tibia; 11, superior extremity of the large meta-
tarsal bone. A, Bones of the upper row. b. Bones
of the lower row. T, Tibia, m, Metatarsus. '
ANTERO-EXTERNAL ASPECT.
1, Calcis; 2, astragalus; 3, cunei-
form magnum ; 4, scaphoid ; 5,
cuboid; 6, cuneiform parvum ; 7,
superior extremity of large meta-
tarsal bone ; 8, superior extremity
of inner small metatarsal bone.
A, Bones of the upper row. b,
Bones of the lower row. t, Tibia.
M, Metatarsus,
thicker, straight, and rugged. The superior extremity, slightly enlarged, con-
Btitutes the summit of the calcaneum, and is divided into three parts : a middle
which gives attachment to the tendon of the gastrocnemius ; the other the
anterior, is a smooth surface on which this tendon rests when the foot is much
flexed ; the third, altogether posterior, also constitutes a gliding surface for the
TEE POSTERIOR LIMBS.
147
tendon of the perforatus. The inferior extremity, wide and voluminous, shows in
front three or four articular facets which articulate with the astragalus, and are
(Separated, like those of the last bone, by an irregular and slightly excavated sur-
face for insertion. Below, it shows for articulation with the cuboid a fifth facet,
continuous with one of the preceding.
Developynent. — The calcaneum is developed from two nuclei of ossification,
one of which is for the summit.
Cuboid hone (Figs. 98, 99). — This little bone, situated at the external side of the
scaphoid and the large cuneiform bone, between the calcis and two of the metatar-
sals, does not resemble a cube, but a parellelopiped elongated from before to behind.
It offers six faces : a superior, an articular face, in contact with the calcaneum ;
an inferior, also articular, articulating with the principal and external rudimen-
tary metatarsal hones ; an internal, furnished with three facets for contact with
the scaphoid and great cuneiform, and crossed from before to behind by a fissure,
Fig. 100.
Fig. 101.
LEFT HOCK (FRONT VIEW).
1, Apex of calcaneum ; 2, astragalus, inner
ridge ; 3, cuneiform magnum ; cunei-
form medium ; 5, cuboid.
LEFT HOCK (INTERNAL ASPECT).
1, Apex of calcaneum ; 2, inner articular
ride of astragalus ; 3, navicular, scaphoid,
or cuneiform medium ; 4, cuneiform mag-
num ; 5, cuboid ; 6, cuneiform parvum.
which forms with these two bones a vascular canal ; an external, an anterior, and
B> posterior, covered with imprints.
Scaphoid hone (the large cuneiform of Percivall) (Figs. 98, 99). — Flattened above
and below, it is described as having two faces and a circumference. The faces, both
articular, are furrowed by a channel of insertion, and are distinguished as superior
and inferior. The first is concave, and articulates with the astragalus ; the second
is convex, and in contact with the two cuneiform bones. The circumference offers,
outwardly, two small facets, which are adapted to similar facets on the cuboid
bone. For the remainder of its extent, it is covered with imprints (Fig. 99).
Oreat Cuneiform hone (the middle cuneiform of Percivall) (Figs. 99, 100, 101). —
Flattened above and below, and triangular in shape, this bone is much smaller than
the scaphoid, though resembling it in a striking manner. Its superior face is in
contact with the latter bone, and its inferior face articulates with the middle and
internal lateral metatarsal bones. Its external harder is provided with one or two
facets to correspond with the cuboid bone ; and its internal herder also shows one.
148 THE BONES.
which is in contact with another on the small cuneiform. Its anterior border is
roughened throughout its extent (Figs. 99, 100).
Small Cuneiform hone (Figs. 99, 101). — Situated at the inner side of the tarsus,
this bone — the smallest of any yet examined — is elongated from before to
behind, flattened on both sides, and wedged in between the os scaphoides, the large
cuneiform bone, and the large and internal small rudimentary metatarsal bones,
with which it corresponds by four articular facets : a superior, two inferior, and
one internal. When this bone is in two portions, there are then three cuneiforms,
which may be distinguished, as in Man, by naming them //•«/, second, and third
(Fig. 99).
It is not very rare to find the scaphoid {cuneiform mafjnum) fused with the
great cuneiform {cuneiform medium), and sometimes even the cuboid is joined to
the cunean bones.
Development. — All the bones of the tarsus, with the exception of the calcis,
are developed from a single nucleus of ossification.
The astragalus in the Ass is distinguished from that of the Horse by the
external Hp of the trochlea, which is abruptly deviated outwards at its inferior
extremity ; and by the disposition of the inferior articular surface, which is
regularly convex from side to side, behind the groove for insertion ; in the
Horse this part of the articular surface is formed by the union of two facets
inclined towards each other. In the same animal, the scaphoid {cuneiform
maffnum) is recognized by the shape of the superior diarthrodial surface, which
is a hollowed reproduction of the inferior face of the astragalus ; and the g7-eat
cuneiform {cuneiform medium) by the larger concavity of its scaphoid face.
Differential Characters in the Tarsal Bones of the other Animals.
In the domestic animals, the tarsus differs in the number and shape of the bones enteriug
into its formation.
A. Ox, Sheep, Goat. — The tarsus of these animals is slender, and has only five bones,
the cuboid and scaphoid being fused into one. The astragalus i.s tlongated from above to
below, and is united to the scaphoid by an antero-posterior groove, and to the calcis by a
vertical groove ; so that it has tiiree trochleas. The principal trochlea has its external border
thicker than the internal, and decreases from below to above. The posterior trochlea is not
80 deep as the others. The calcis is lon^' and thin; the posterior gliding surface on the
summit is excavated into a channel. The small cuneiform is pisiform, and but slightly developed.
B. Camel. — In the Camel, there are six tarsal bones, two of which :ire cuneiform. The
astragalus articulates, by means of a double groove, with the scaphoid and cuboid. The
calcis is relatively short, and about equally excavated on its two faces. The cuboid ia
voluminous.
C. Pig. — The tarsus of this animal much resembles that of Ruminants in its general
disposition, and in the astragalus ami calcis; but it lias seven bones, because the cuboid and
scaphoid are separate, and there are constantly three cunfi/nrm bones.
D. Dog, Cat. — There are seven bones in the tarsus of these animals. The astragalus
articulates witli the scaphoid— almost as in Man— by means of a tiue In ad, separated from the
rest of the bone by a constriction named the neck of the astragalus. The cuboid and the three
cuneiform bones articulate with the five metatarsal bones.
2. Bones of the Metatarsus (Figs. 98, 102).
These bones are three in number — a median and two lateral — and offer the
greatest analogy to the metacarpal bones. This enables us to dispense with a
general description of them, and to confine ourselves only to indicating the
differential characters which distinguish them from the corresponding bones in
the anterior limb.
THE POSTERIOR LIMBS.
149
The principal, large, or median metatarsal bone, is longer than the same
metacarpal, and its body, instead of being slightly compressed before and behind,
is nearly a regular cylinder. It presents, outwardly, a fissure which is directed
at first obliquely backwards and downwards (Fig. 99), and afterwards descends
vertically along the lateral external metatarsal bone. The articular surface of
the superior extremity is excavated in its centre by a large fossa for insertion
(Fig. 99). This surface presents, behind and outwards, a
thick tubercle which appears to spring from the body of the Fig. 102.
bone, and which has a facet against which the external rudi-
mentary metatarsal rests. The inferior extremity is at the
same time wider and thicker than that of the metacarpus.
Above and in front of the articular surface, it is hollowed
by a small transverse fossa, which is deeper than in the corre-
sponding bone in the anterior limb.
Of the tivo rudimentary {digital, splint), or lateral meta-
tarsal bones, the external is always longest, if not thickest.
The internal bears on the superior face of its head three
articular facets, two of which articulate with the small
cuneiform, and the third with the large bone of that name.
The length of these rudimentary metatarsals is nearly
equal to three-fourths that of the principal metatarsal.
The metatarsus of the Ass is remarkable for the length
of its rudimentary metatarsals, which are nearly five-sixths
that of the principal bone. The latter is also notable,
because of its length and fineness ; and if it is compared
with that of the Horse, it is distinguished by : 1. The tri-
angular shape of its upper extremity, due to the great
development of the tubercle on which the external rudi-
mentary metatarsal lies. 2. The flat diarthrodial facet which
articulates with the antero-external part of the large cunei-
form, 3. The marked inequality of its condyles.
Differential Characters in the Metatarsal Bones of the
OTHER Animals.
posterior aspect op
left metatarsus.
1, Head of principal
metatarsal bone ; 2,
3, external and in-
ternal splint bones,
or metatarsals of the
rudimentary digits ;
4, rough surface for
insertion of suspen-
sory ligament ; 5,
nutrient foramen ;
6, middle ridge or
tenon of inferior arti-
cular surface.
The metatarsus is also a region in which the number of bones varies
in the domesticated animals. Tlius, in Ruminants there are two, and
five in the Pig, Camivora, and Rodents.
The metatarsals of the latter are exactly like the same bones in
the anterior limb. Those of Ruminants are slightly different.
A. Ox, Sheep, Goat.— In the Ox, Sheep, and Goat are found a
principal and a rudimentary metatarsal bone. The latter is a small
lenticular bone, articulating, posteriorly, with the head of the large
metatarsal bone. The latter differs from the principal metacarpal
bone, in being longer, quadrilateral in form, and having a vascular
canal traversing the posterior face of its upper extremity.
B. Camel. — The metatarsus differs from the metacarpus by its greater width and less
thickness; the articular surface is divided by a depression into two parts, situated on the same
horizontal plane.
C. Pig.— The Pig has four perfect metatarsals, and an internal rudimentary one. The
latter is a small bone flattened on both sides, articulating by means of a diarthrodial facet, and
sometimes fused posteriorly with the upper end of the fourth metatarsal.
D. Dog, Cat.— Ill the Dog and Cat are one rudimentarv and four perfect metatarsals.
The former is articulated with the internal cuneiform, and represents the vestige of the thumb.
150 THE BONES.
3. Bones of the Digital REOrioN (Fig. 98).
Id Man, the digits of the foot — known as toes — are very different to those of
the hand ; but it is otherwise with the domestic animals. The phalangeal region
of the posterior, closely resembles that of the anterior Hmb. The analogy in the
conformation of these bones is even pushed so far, that it becomes very difficult
to distinguish them from one another.
There are some differential characters, however. For instance, it is remarked :
1. That the first phalanx is not so long as in the anterior limb, and less wide
and thick at its inferior extremity ; but it is, on the contrary, wider and thicker at
its superior extremity. 2. That the lateral diameter of the second phalanx is
shorter. 8. That the third phalanx, less expanded towards its inferior border,
has more the shape of a V, and that its inferior face is more concave. 4. That
the sesamoids are less voluminous. 5. That the navicular bone is shorter and
narrower.
In the Ass, the same differential features are observed between the posterior
and anterior phalanges as in the Horse, and there are no very marked differences
between the former in these two animals. The following may, however, serve to
distinguish them.
The ^rs^ phalanx of the Ass is proportionately longer than that of the Horse,
and the rugosities are larger ; the principal nutrient foramen is usually on the
anterior face, and the external glenoid cavity is much smaller than the internal.
The second phalanx is also proportionately longer than that of the Horse.
Its inferior median furrow is deep, especially behind ; it has generally numerous
nutrient foramina below the posterior gliding surface ; the median tenon of its
upper face terminates before and behind by a salient tubercle, which prevents the
bone from resting in equilibrium when it is placed vertically on that face.
The third phalanx of the Ass is higher than that of the Horse, owing to the
development of the pyramidal process ; it is constricted above the preplantar
fissure ; the surface of the sole is proportionately more extensive, and the
concavity of the semilunar crest is less marked ; the extremities of that crest are
saUent, and the plantar fissures very deep.
The navicular bone shows very marked differences. In the Ass its thickness
is very considerable, due to the median ridges on both faces. Its posterior
border is very oblique downwards and backwards, and it is towards this border
that it inclines when Ave attempt to make it lie horizontally on its upper face ;
while its two extremities are more curved than in the Horse.
In the Mule and Hinny, the two first phalanges much resemble those of
the Ass, while the third shows the characters of that of their progenitors.
Nevertheless, that of the Hinny is rather more like the third phalanx of the
Horse than that of the Ass, while the contrary is observed in that of the Mule.
Differential Characters in the Posterior Phalangeal Region of other Animals.
In all the domesticated animals, the posterior digits comport themselves exactly like the
anterior. The Carnivora alone offer a notable difference ; in them, in reality, the inner toe,
the equivalent of the thumb, does not exist — or rather, it is only represented by tiie rudimentary
metatarsal bone alluded to above. Nevertheless, it frequently occurs that a completely de-
veloped thumb is found in this animal ; and in this case the rudimentary metatarsal is ordinarily
followed by a ligamentous cord, to which is suspended a bony stylet that represents either the
inferior extremity of the metatarsal bone, or the first phalanx ; it is to this stylet that are found
articulated in succession the second and third phalanges.
It is not rare to meet with a sixth floating toe in dogs of very large size.
THE POSTEBIOR LIMBS.
151
Comparison of the Abdominal Limb of Man with that of Animals.
A. Pelvis (Fig. 103). — The longitudinal axis of the pelvis of Man forms, with the horizon,
an angle of about 40°.
The bones which compose it are proportionately larger and stronger than in all the
domesticated animals.
The two faces of the ilium, and especially the inner face, are much hollowed ; the iliac
crest has the form of an italic S.
The pubis alone participates in the formation of the pelvic sympliysis, and the concavity
which, in the domesticated animals,
is called the ischial arch, is desig- Fig. 103.
nated in Man the pubic arch.
In consequence of the excavation
on the inner face of the ilium, the
pelvic cavity may be divided into
the great and lesser pelvis. In the
latter are lodged the genital and
urinary organs, as well as the ex-
tremity of the digestive tube.
B. Thigh (Fig. 104).— The femur
of Man is nearly vertical, and situ-
ated in a direction sligiitly oblique
downwards and inwards ; it presents
a curvature forwards. The body of
the bone is prismatic and triangular
in its middle part; the posterior
border of this prism forms a some-
what salient cresf, which takes the
place of all the insertion eminences
on the posterior aspect of the femur
in animals, and is designated the
linea aspera. This line bifurcates
above and below ; below, the branches
margin a triangular or popliteal space.
The head is supported by a long
neck, inserted obliquely into the
superior extremity. The two con-
dyles are joined together in front by
the trochlea, which is wide and*
shallow.
a Leg (Fig. 105) —Three bones :
human pelvis (female).
1, Last lumbar vertebra ; 2, 2, intervertebral substance ;
3, promontory of the sacrum ; 4, anterior surface of the
sacrum ; 5, coccyx ; 6, iliac fossae ; 7, antero-superior
spinous process ; 8, antero-inferior spinous process ;
9, acetabulum, a. Its notch ; 6, body of ischium; c, its
tuberosity ; d, its spine ; e, pubis ; /, symphysis pubis ;
g, arch of the pubes ; h, angle of os pubis; i, spine of
pubes, with crest between it and h; k, k, pectineal line ;
I, I, ilio-pectineal line, with its prolongation, m, m ;
n, ilio-pectineal eminence ; o, smooth surface for femoral
vessels ; p, p, great sacro-ischiatic notch.
the tibia, fibula, and patella.
The tibia is very long ; its crest (or spinous process) is much more developed than in any
of the domesticated animals, and describes a kind of curve like an italic S. On the inner
aspect of the inferior extremity is seen a voluminous process which occupies, inwardly, a
portion of the tibio-tarsal articulation : this is the internal malleolus. The articular surface ia
not exactly formed to correspond with the whole articular surface of the astragalus.
The fibula is as long as the tibia. It is prismatic, and slightly twisted on itself. It articu-
lates above and below with the tibia. The lower extremity responds to the astragalus, and
forms a prominence named the external malleolus.
There is nothing particular to note in the patella.
D. Foot (Fig. 106). — The foot of Man is pLaced in a horizontal direction. Its upper
aspect is convex; its inferior face is excavated, and it rests on the ground by its two
extremities.
1. Tarsus. — In the tarsus there are seven bones, three of which are cuneiform. The astra-
galus articulates with the tibia and fibula ; it responds to the scaphoid by a well-detached
convex articular surface, named the head.
In the bones of the lower row, it is remarked that the cuboid responds to the fifth and
fourth metatarsals; the first cuneiform to the third; the second cuneiform to the second
metatarsal : and the third to the first.
2. Metatarsus. — The metatarsus is composed of five bony columns, nearly parallel to each
152
TEE BONES.
other. They are enumerated from without to within, and increase in length from the first to
the fourth ; the fifth is the shortest and most voluminous.
3. Digital region-— This comprises five digits or toes. The phalanges of these toes are
analogous to those of the fiiigersi, from which they are distinguished by their small size. They
increase in volume from tlie first to the fifth digit.
Article VIL — The Foot in General.
It would be useless to reproduce here the general considerations discussed
when treating of the hand (p. 121), and it may therefore be sufficient to state
Fig. 104. Fig. 105. Fig. 106.
RIGHT HUMAN FEMUR
(ANTERIOR ASPECT).
1, Shaft ; 2, head ; 3, neck ;
4, great trochanter ; 5,
anterior intertrochanteric
line; 6, lesser trochanter;
7, external condyle ; 8,
internal condyle ; 9, tu-
berosity for attachment
of external lateral liga-
ment; 10, fossa for ten-
don of origin of popliteus
muscle ; 11, tuberosity
for attachment of inter-
nal lateral ligament.
HUMAN TIBIA AND FIBULA
OF RIGHT LEG (ANTERIOR
ASPECT).
1, Shaft of tibia; 2, inner
tuberosity; 3, outer tu-
berosity ; 4, spinous pro-
cess ; 5, tubercle ; 6, in-
ternal surface of shaft ;
7, lower extremity of
tibia; 8, internal malleo-
lus; 9, shaft of fibula;
10, its upper extremity;
11, its lower extremity;
between 1 and 6 is the
sharp crest of the tibia.
DORSAL SURFACE OF LEFT
HUMAN FOOT.
1, Astragalus ; 2, its anterior
extremity articulating
with the cuboid bone, 4
3, 3, calcis ; 4, scaphoid
5, internal cuneiform bone
6, middle cuneiform bone
7, external cuneiform
bone ; 8, cuboid bone ; 9,
metatarsal bones of first
and second toes; 10, first
phalanx of great toe ; 11,
second ditto ; 12, 13, 14,
phalanges of second toe.
that the works of the anatomists already mentioned — and especially those of Joly
and Lavocat — have demonstrated that the foot of animals is constructed on the
same type as the hand. In it, as in the hand, three sections are remarked : the
THE FOOT IN GENERAL. 153
tarsus, metatarsus, and phalanges ,- and, in the archetype, each section comprises
five parallel rows, each of which has two tarsal bones, one metatarsal, and three
phalangeal. In the present fauna there is not, perhaps, a Mammal which has
a perfectly typical pentadactylous abominal limb ; for this ideal disposition is
modified in the sense already indicated for the hand. In the following- brief
paragraphs, an attempt will be made to show the manner in which Man and the
domestic animals may be allotted to the archetype.
1. 31 an. — In Man the archetype is realized in the metatarsal and phalangeal
sections, and it will now suttice to examine the tarsal section. This contains
seven separate bones — three in the upper and four in the lower row. It must
not be forgotten that the scaphoid, although situated between the two rows,
nevertheless belongs to the upper, as happens in the carpus of certain species.
Apparently, it is deficient in two bones in the upper row and one in the inferior.
This deficiency arises from fusion of the apex of the calcaneum {first superior
metatarsal hone) with the remainder of the bone {second hone), of the scaphoid
with the fifth hone in the upper row, and of the first inferior tarsal bone with the
cuboid in the second row.
2. Carnivora. — The foot of Carnivora only differs from that of Man in the
arrangement of the thumb ; as this digit has usually no phalanges, and its meta-
tarsal piece is only a small, very short styliform bone. Notwithstanding this
difference, the pentadactylous archetype is as easily recognized in the foot of
these animals as in that of Man.
3. Rodents. — The foot of the Rahhit and Hare is yet less complete than that
of Carnivora, as the metatarsal of the thumb is absent ; but, by the constitution
of the tarsus, Rodents resemble Carnivora and Man, and consequently they can
be also classed in the pentadactylous type.
4. Pig. — In this animal, the tarsus presents the same number of pieces and
the same fusions, as in Rodents, Carnivora, and Man. The metatarsus and
phalangeal section have four complete toes — first, second, third, and fourth ;
and with regard to the fifth digit, it is represented by a short, flat, and irregu-
larly triangular metatarsal, articulating posteriorly with the third metatarsal, and
attached to the third cuneiform by some ligamentous fibres.
5. Ruminants. — The foot of the Ox, Sheep, and Goat present numerous
fusions, and even some abortions. The tarsus has only five distinct bones ; for,
besides the fusions which exist as in the preceding animals, the scaphoid is united
to the cuboid, and the third cuneiform is completely aborted.
The metatarsus of these animals includes a principal metatarsal, provided,
inferiorly, with a double diarthrodial surface, and an internal rudimentary
metatarsal. Must we consider the principal metatarsal as the result of the fusion
of the third and fourth, and admit, in Ruminants, the abortion of the first two
digits ? Several anatomists have professed this opinion. Lavocat did so at first,
and then abandoned it. He considered the principal metatarsal as due to fusion
of the metatarsals of the first four digits, and he expressed himself on this point
as follows : " The first and the fourth metatarsals are visible, and fused above
and behind the united large metatarsals. Each of them has the shape of a thick
pyramid, with its base uppermost, large, and about five centimetres long in the
Ox. Above, they join to form an arch, which is the contour of a wide and short
vascular canal running between them and the two large metatarsals, and which
does not exist in the Goat and SheejJ. Their widened superior extremity is in
contact with the bones of the tarsus, to wit : the first metatarsal with a facet of
154 TEE BONES.
the p-ototarsiis, or first portion of the cuboid ; the fourth metatarsal with all the
inferior facet of the tetrofarsus, or second cuneiform. And each of them has,
for this eminently normal connection, an articular facet well separated from the
diarthrodial surface of the large metatarsals by a large fossa destitute of cartilage.
In this way the first four metacarpals are gathered into a single bundle. . . .
Lastly, the thumb, or fifth digit, is constantly represented in the foot by a
distinct metatarsal bone — at least in the Ox, Goat, and Sheep.'''
Notwithstanding the reasons on which Lavocat bases his last interpretation
as to the metatarsals of the Ox, we prefer adopting the first. In fact, if some
wild Rimiinants are examined — Deer, for example — there will be found a tarsus
identical with that of the Ox, and a principal metatarsal provided with a vascular
canal, with two inverted pyramidal expansions ; and, in addition, two styliform
bones lying to the outside and the inside of the principal bone of the shank.
These bones evidently represent the metatarsals of the second and fifth digits ;
as they exist at the same time as the lateral ridges on the principal metatarsal
bone, it appears to be impossible to give to the latter the same signification.
The posterior phalangeal region of the Ox is almost identical with the an-
terior ; it is, therefore, needless to again demonstrate its constitution. That of
the Sheep and Goat has no rudimentary phalanges to serve as a base for the
ergot, in the hand ; but the two ergots suffice to represent the first and fourth
digits, and so to include these animals in the pentadactylous type.
6. SoUpeds. — The tarsus of these animals has six or seven bones. In the
second case, it is identical with that of Carnivora and Man ; in the first, the
second and third cuneiforms are fused. The metatarsus and posterior phalangeal
section having the same constitution as those of the anterior, the reader is
referred to the description of the Hand in General.
Article VIII. — The Limbs in General and their Parallelism.
A. The Limbs in General. — The bony sections which compose the limbs,
are destined not only to support the trunk in a stationary attitude, but also to
transport it during progression. This double use gives rise to a difference
between the anterior and the posterior members. The front limbs, being nearer
the centre of gravity than those behind, have to sustain the largest share of the
weight. They ought, consequently, to be specially organized as organs of sup-
port. Therefore it is, that the four principal bones composing each of them —
shoulder, arm, forearm, foot — although flexed, or disposed to be flexed, in an
inverse sense to one another, oppose to the pressure of the weight of the trunk —
which tends incessantly to throw them down — obstacles purely mechanical, and
of such energy that we may still understand how the body can be sustained on
the anterior limbs, if we suppose all the muscular masses surrounding these bony
columns to be removed, except one.
Thus, the weight of the body is transmitted to the scapula through the
muscles that attach that bone to the trunk. It then passes to the humerus, and
thence to the radius, to be thrown, finally, on the diflferent pieces composing
the foot. Now, the humerus forming with the scapula an angle which is open
behind, and with the bones of the forearm another angle open in front, the
weight of the body pressing continually on these angles tends to close them,
and thus cause the flexion of these bones. But this result is prevented by the
combined action of two muscular powers — the biceps and the extensors of the
THE LIMBS IN GENERAL AND THEIR PARALLELISM.
155
forearm. With regard to the radius,
carpus, and metacarpus, owing to their
vertical direction, they themselves sup-
port the pressure of the weight of the
body without requiring any muscular
aid. But the digital region, being di-
rected obliquely forward and downward,
forms, with the principal metacarpal, a
third angle open in front, for the main-
tenance of which nature has given solid,
inert, or contractile mechanical bands.
The anterior limbs are also agents
of transport, for they can elevate the
trunk by the spring of their bony rays,
and fix themselves on the ground by
their free extremities.
The posterior limbs are less favour-
ably disposed than those in front to as-
sume the function of columns of support ;
as their rays are, for the most part, in a
state of permanent flexion, and joined in
an angular manner to one another, as
may be seen by glancing at the skeleton
(Figs. 107, 108, 1, 2, 4, 5, 6). It is,
therefore, necessary that muscular agency
should prevent the breaking-down of
these columns. Though defective as
supports, they are nevertheless admirably
designed to serve as agents of locomotion.
The slightest erection of these inclined
bones propels the mass of the body for-
ward, and this impulsion is almost wholly
transmitted to the trunk, in consequence
of the very intimate union of the pelvis
with the vertebral column.
B. Parallel between the An-
terior AND Posterior Limbs. — After
what has just been said, it will be seen
that the anterior limbs are more par-
ticularly destined for the support of the
body, while the posterior ones more
especially play the part of propelling
agents in the locomotory acts.
Notwithstanding this difference in
the functions assigned them, these two
limits offer in their conformation such
striking resemblances to each other, that
some authors have been inclined to con-
sider the posterior as an exact repetition
of the anterior limb. The followina: is
ANTERIOR LIMB OF THE HORSE (ANTERO-
EXTERNAL VIEW).
0, Scapula ; H, humerus ; a, radius ; C, carpus ;
M, metacarpus ; p, phalanges ; s, sesamoid
bone. 1, Coracoid process; 2, head of the
humerus; 3, external trochanter ; 4, deltoid
ridge; 5, inferior articular surface of the
humerus; 6, olecranon; 7, ulna; 9, pisi-
form (trapezium), or supercarpal bone.
156
THE BONES.
Fig. 108.
POSTERIOR LIMB OF THE HORSE (ANTERO-
EXTERNAL VIEW).
C, Coxa ; F, femur ; J, tibia ; 8, tarsus ; M, meta-
tarsus; p, phalanges; S, sesamoid. 1, Ischium ; 1',
pubis; 2, head of the femur; 3, trochanter major;
4, trochanter minor ; 5, condyle of the femur ;
6, patella ; 7, fibula ; tibial ridge ; 9, calcis.
a brief analysis of the analogies ex-
isting between them.
At the end of the last century,
Winslow and Vicq-d'Azyr, and nearer
our own time, Cuvier, Flourens,
Paul Gervais, Martins, Gegenbauer,
Lavocat, Foltz, and Sabatier, have
occupied themselves with the homo-
logy of the anterior and the posterior
members. All these anatomists did
not absolutely arrive at the same
conclusion ; for several of them, for-
getting that the question should be
examined in the whole animal series,
made Man alone the subject of their
studies.
Vicq-d'Azyr and Cuvier recom-
mended that the anterior and pos-
terior limbs of opposite sides should
be compared. Martins and Gegen-
bauer, allowing a torsion of the
humerus of 180°, advised that the
two members of the same side should
be compared, care being taken to
make allowance for the untwisting
of the 180° contortion at the lower
end of the humerus. Lastly,
Flourens and Lavocat contrasted the
two members of the same pair with
each other, after placing the hand
in a position of natural pronation
by rotation of the radius on the ulna,
and without turning either limb or
bone, or even a portion of a bone,
no matter what kind of animal may
be under examination. We will
adopt the latter proceeding, as it is
the simplest and most natural.
Parallel between the coxa and
scapula. — The analogies existing be-
tween these two bones are but little
striking at first sight ; nevertheless,
with attention there is no ditficulty
in finding in the coxa the three pieces
that enter into the composition of
the shoulder (Figs. 107, 108).
The ilium represents the scapula.
The external iliac fossa reminds one
of the supra- and subspinous fossae.
Occasionally, there is met with in the
THE LIMBS IN GENERAL AND THEIR PARALLELISM. 157
Horse a rudiment of the crest dividing the ihac fossa into two parts, and in
some animals — the Pig, Sheep, and Goat— this crest, which is the trace of the
scapular spine, becomes constant and very evident.
With regard to the cotyloid cavity, it repeats in the posterior limb the glenoid
cavity of the scapula. There remains to determine, in the latter bone, the
portions analogous to the ischium and pubis. If we rely upon the evidence
afforded by the muscular insertions, we come to the conclusion that the ischium
corresponds to the coracoid process, and the pubis to the clavicle of animals
which are provided with one. It will also be remarked that the coxa is directed
backwards, while the scapula inclines obliquely forwards ; this opposition in the
direction of the bones in no way alters their analogies ; the functions of the
members to which they correspond require this inverse position.
Parallel hehveen the femur and hwiwus. — The resemblance between these
two bones is remarkable. Thus there is found in the first. 1. An articular
head, better detached than that of the humerus, but shaped in the same manner.
2. A trochanter analogous to the great tuberosity, and also, like it, decomposable
into three distinct parts — summit, crest, and convexity. 2. A lesser trochanter,
representing the small tuberosity. 4. An eminence for the insertion of the
superficial gluteus muscle, which takes the place of the deltoid imprint. 5. An
inferior articular pulley continued between the two condyles by a non-articular
groove ; this trochlea certainly corresponds to the median groove of the inferior
humeral face.
There are, no doubt, differences in the two bones, but they have no bearing
upon the result just indicated. Thus, the linea aspera of the femur is situated
behind ; that of the humerus in front. In the femui' the two condyles of the
inferior extremity are placed behind the trochlea ; the contrary holds in the
humerus. These modifications are necessary, in order to give the movements of
the limbs a convenient direction. The leg is flexed backward on the thigh, while
the fprear is flexed forward on the humerus.
Parallel hetween the bones of the leg and those of the forearm. — It is more
particularly in these two regions that the question of analogies has been resolved
in a contradictory manner by anatomists. It would have appeared less compli-
cated had it been studied in a large number of species.
If we examine the leg-bones of certain Marsupials^ in which the tibia and
fibula are apart as in the radius and ulna in Man, it will be found that : 1. These
two bones articulate with the condyles of the femur. 2. The anterior face of the
tibia has no ridge. 3. The patella is attached to the upper end of the fibula.
From this it might be concluded that, in Man and the domestic animals, the
tibia, with the exception of its anterior and external tuberosities, is the homologue
of the radius, and the fibula and external and anterior tuberosities of the tibia
are the homologues of the body and inferior extremity of the ulna. The patella
corresponds to the olecranon ; the mobility of the first cannot be offered as an
objection to this assimilation, for in Bactrians the olecranon forms, like the
patella, an independent bony nucleus.
Parallel between the bones of the posterior and those of the anterior foot. — The
analogy becomes so marked when these two regions are compared, that it is
scarcely necessary to allude to them. The tarsal bones are to the posterior limb
what the carpals are to the anterior one ; it is even possible to compare, one by
one, the several pieces in these regions. The metatarsals are but a repetition of
the metacarpals ; while the digital bones are so much alike, that it is difficult to
distinguish the anterior from the posterior phalanges.
158 THE BONES,
CHAPTER III.
THE BONES IN BIRDS.
These animals, destined for the most part to sustain themselves in the air,
should exhibit in the conformation of their skeleton all the conditions which
may favour aerial locomotion ; from this arise the differences which distinguish
their skeleton from that of the Mammalia — differences which will now be rapidly
traced.
Veetebeal Column. Cervical vertebne. — The cervical spine represents in
the Bird, as in the Mammal, a kind of balancing-pole curved like an S, which
supports the head, and by its changes in form and direction varies the centre of
gravity. When a Bird rises in the air and flies rapidly, it lengthens the neck
and stretches out the head, to carry the centre of gravity forwards. But when
it rests on the ground, it makes the balancing-pole assume the natural and more
or less graceful inflection, by throwing the head backwards, and transferring the
greater portion of the weight of its body to the columns of support formed by
the posterior Hmbs. These displacements of the centre of gravity are executed
in Birds on a more extensive scale than in Mammalia ; the vertebral limbs in the
former are also longer, hghter, and enjoy an excessive mobility.
The vertebrae composing it number fourteen in Fotvls, twelve in the Fir/eon,
fifteen in the DmJc, aijd eighteen in the Goose ; in the Swan twenty-three have
been counted ; — a curious variety, which singularly contrasts with the numerical
unity noticed as one of the most remarkable characters in Mammalia ! These
vertebras are generally longer than in the latter animals, and are particularly
distinguished by the configuration of the articular surfaces of the inferior part or
body. These are diarthrodial facets convex in one direction and concave in the
other, articulating the vertebral bodies by a veritable and reciprocal clamping.
In this manner, the anterior head of the body of each vertebra is replaced by a
facet concave on both sides, and convex vertically ; while the posterior extremity
of the bone bears, instead of a concavity, a facet convex in the lateral sense, and
concave from above to below. The inferior crest of the body (Fig. 109, 2, 2')
only exists in the first and last vertebrae ; but it forms a veritable spine,
analogous to that observed in the lumbar vertebrae of the Rabbit. The spinous
process (Fig. 109, 1, 1') only forms a simple crest in the middle part of the neck ;
it becomes more salient in the vertebras which occupy the two extremities of this
region. The transverse process represents on the side of the vertebra a thick,
obtuse, and irregular tubercle, situated under the anterior articular process, and
pierced at its base by a large vertebral foramen (Fig. 109, 4, 4'). It is most
frequently furnished with a small styloid prolongation (Fig. 109, 3, 3') directed
backwards and downwards, forming an epiphysis at an early period, and
representing a real undeveloped rib.
The atlas has no transverse processes. This vertebra is shaped like a thin
ring, and is excavated on its anterior contour by a small cavity, into which is
received the single condyle of the occipital bone.
The axis shows a very marked odontoid process, with a single facet under
that eminence.
Dorsal vertebrce (Fig. 109, b, c). — These are seven in the Fotvl and Figeon,
TEE BONES IN BIRDS.
159
and nine in the Goose and Duck; they are nearly always consolidated into a
single piece to which the trunk is fixed, and which gives the wings a sohd
Fig. 109,
SKELETON OF A FOWL.
From A to B, Cervical VertebrcE . 1, spiDous process of the third vertebra; 2, inferior ridge on body
of the same ; 3, styloid prolongation of the transverse process of the same; 4, vertebral foramen
of the same ; 1', 2', 3', 4', the same parts in the twelfth vertebra. From B to C, Dorsal Vertebrae:
6, spinous process of the first ; 7, crest formed by the union of the other spinous processes. From
D to E, Coccygeal Vertebrce. F, G, Head: 8, interorbital septum; 9, foramen of communication
between the two orbits ; 10, premaxillary bone ; 10', external openings of the nose; 11, maxilla;
160
THE BONES.
Fig. 110.
support in the violent efforts that flight demands. The two or three last are
often even covered by the wing-bones, and joined to them. The inferior crest
of the body forms a very long spine, especially in the first vertebras. The
spinous processes — flat, wide, short, and consolidated with each other by their
opposite borders — constitute a long crest extending from the last cer\ical vertebra
to the bones of the wings (Fig. lOD, 7). The trans-
verse processes widen to their summit ; in the FovjI
they are nearly constantly fused with each other.
Lumbar and sacral vertebne. — All these vertebrae
are formed exactly on the same type ; so that it be-
comes difficult, if not impossible, to fix the point where
the lumbar region ends or the sacral begins. At first
independent of each other, these vertebra?, numbering
fourteen, soon become consolidated with one another
and with the ribs ; but their primitive separation is
always indicated by the lateral septa, which form, on
their inferior face, the vestiges of the transverse pro-
cesses. The former are closely united to the latter in
the dorsal region.
Coccygeal vertebrce. — In the coccygeal region, the
spine recovers its mobility. The tail of the Bird,
indeed, fulfils the office of a rudder in directing it during
flight ; and it is absolutely necessary that the vertebr*
which serve as a base for the steering feathers should
preserve their independence, so as to allow these to be
carried to the right, left, downwards, or upwards.
These vertebrje — seven in number — present spinous
processes which are often bifurcated, transverse pro-
cesses very developed, and sometimes even spines more
or less long on the inferior surface of their bodies. The
last vertebra is always the most voluminous ; it is
flattened on both sides, and terminates in a curved-up
point.
Head (Fig. 110, f, g).— The head of the Bird is
small, and of a conical form. The anterior extremity
is elongated, and terminated by a pointed or flattened
beak, which allows the animal to cut the air with more
facility.
Bones of the cranium. — The bones which compose
the cranium are, as in Mammalia, an occipital, parietal,
frontal, ethmoid, sphenoid, and two temporcds. These bones are not isolated from
each other, excepting during early life in the shell ; and the ossifying process
12. OS quadratum ; 13, malar bone. H, Sternum : 14, brisket or keel ; 15, episternal process ; 16,
internal lateral process; 17, lateral external process; 18, membrnne which closes the internal
notch ; 19, membrane of the exte^-nal notch, i. etc., Superior Ribs : 20, posterior process of the
fifth. J, Inferior ribs. K, Scapula. L, Coracoid hone. M, Furculum : m, m, its two branches.
N, Humerus. 0, Ulna : o. radius, p. p', Bones of carpus. Q, q'. Bones of metacarpus. R. First
phalanx of th° large digit of the loinq : r. second phalanx of the same, r'. Phalanx of thumb.
S, Hium. s'. Ischium, s". Pubis : 21. sciatic foramen : 22, foramen ovale. T, Femur, v. Patella.
V, Tibia. X, Fibula : y, single bone of tarsus, y. Metatarsus : 23, superior process representing
a united metatarsal bone ; 24, process supporting the claw. Z, etc.. Digits.
HEAD OF AN OWL (NATURAL
SIZE ; POSTERIOR VIEW).
1, Occipital foramen ; 2, single
occipital condyle ; 3, ptery-
goid ; 4, inferior articular
surface of the os quadratum ;
5, anterior process of ditto ;
6, 6, anterior face of the
palatine bones, forming: the
guttural orifice of the nasal
cavities; 7, posterior ex-
tremity of ditto; 8, zygo-
matic ; 9. lachrymal ; 10.
premaxilla ; 11, orbital pro-
cess ; 12, right zygomatic
process ; 12', zygomatic pro-
cess on the opposite side,
united to the orbital pro-
cess.
TEE BONES IN BIRDS. 161
which unites them is so rapid, that the cranium, shortly after hatching, is already
a single piece. No detailed description of the separate bones will be given here,
but only a few brief observations which may be of some utility.
Thus, the occipital bone shows for articulation with the spine only a single
condyle, situated under the occipital foramen, and excavated by a slight gi'oove.
In Palmipedes, this bone is pierced, behind the crests which give attachment to
the extensor muscles, by two foramina which penetrate the cranium, and represent
permanent fontanella. The parietal bone is feebly developed, and formed from
only two primary nuclei. The frontal is the largest bone of the cranium ; its
orbital process (Fig. 110, 1), incomplete, is supported by a particular piece
(posterior frontal) fixed between the principal frontal bone, parietal, and posterior
sphenoid, with which it is sometimes confounded. The perpendicular lamina of
the ethmoid is considerable, and forms between the two orbits a thin vertical
septum (Fig. 109, 8). Its posterior border is notched opposite to the optic
foramen, and thus constitutes an opening which communicates between the two
orbital cavities (Fig. 109, 9). It is also channeled, near its upper. border, by
a fissm-e which terminates by two openings at its extremities, one entering the
cranium, the other the nasal cavities. Tliis fissure and these foramina pennit the
passage of the ethmoidal nerve, which in this way traverses the orbit before
arriving at its destination. The ethmoidal cells are more membranous than
bony : their base is attached to a very delicate transverse plate, which is often
membranous and not cribbled, and forms part of the anterior orbital wall. These
cells replace, at the same time, the lateral masses of the ethmoid and turbinated
bones of MammaUa. The sphenoid appeal's to be formed of a single piece, and
shows on its sides two diarthrodial facets corresponding to the pterygoids. It is
pierced by one foramen for the passage of the optic nerves ; but this foramen
opens on the outer and opposite side of the posterior notch of the interoi-bital
septum, and thus allows each of the nerves passing through it to reach the eye
for which it was intended.
It is worthy of remark, that an analogous disposition is also noticed in the
Rabbit.^ The temporal bones present at their base an articular surface correspond-
ing to the square bone (os qimdratum) (Fig. 109, 12, 12'). In the Foivl species,
the zygomatic process forms a small flattened tongue, directed forwards, sometimes
free, and at other times united by its superior border to the summit of the
orbital process. These two eminences are exceedingly short in Pigeons. In
Palmipedes they are consolidated and confounded so intimately, that it becomes
impossible to distinguish them from one another. From this union results a
long and strong process, which inclines forward and meets a particular prolonga-
tion of the OS unguis, forming with it a real bony arch. This arch limits, below
and outwardly, the orbital cavity.
Bones of the face. — The supermaxilla comprises : a premaxilla, two nasal, two
lachrymal, two palatine, two pterygoid, two zygomatic hones, and a vomer. The
inferior jaw has for its base a maxillary hone, which articulates with the cranium
by means of two supplementary pieces named the square hones. The premaxillary
hone (Fig. 110, 10) is formed, before hatching is completed, of two lateral pieces,
' This analogy is really striking, and might, in our opinion, serve as a basis for a new
ietermiuation of the interorbital septum. We are tempted, indeed, to consider this bony
lamina as the inferior sphenoid and the middle portion of the ethmoid in Birds. This manner
of viewing it tends to confirm the ideas of M. Tabourin on the inferior sphenoid and the
ethmoid of Mammals.
162 THE BONES.
which represent the two small premaxillaries of Mammals. This bone is very
considerable, and of itself forms the base of the upper beak, the form of which it
determines ; it is pointed and conical in the GalUnacea, and wide and flattened
above and below in Palmipedes. In front it circumscribes the external openings
of the nose, and is prolonged superiorly into two lengthy processes which dovetail
between the nasal bones. Two inferior processes belonging also to this bone
concur in the formation of the palatine roof. The supennaxillaries, analogues of
the supermaxillaries of Mammals, are two rudimentary bones situated on the sides
and at the base of the beak. They form a part of the palatine roof and the walls
of the nasal cavities. The nasal bones circumscribe above, inwardly, and even
outwardly, the external orifices of these cavities. The palatine hones encircle, as
in Mammals, the guttural openings of the nose, and constitute in great part the
roof of the palate ; their posterior extremity lies against the pterygoids ; the
anterior joins the supermaxillaries and the inferior process of the premaxillary
bone. The pterygoids extend obliquely from the sphenoid to the square bones,
and are united to the sphenoid by diarthrodial articulation. The zygomatic hones
have the form of two very thin stylets, and are united to the square bone by their
posterior, and consolidated with the supermaxillary by their anterior, extremity.
The vomer separates the guttural openings of the nose from one another.
The bones of the upper jaw are not fused to each other so rapidly as the
bones of the cranium. The ascending processes of the premaxillary and nasal
bones even remain for a long time tmited to the frontal bone by a simple
synarthrodial articulation. This arrangement allows the upper beak to execute
a certain elevating movement, of which we will speak when describing the
articulations.
The inferior maxillary hone is originally formed of a great number of distinct
segments, which are soon united into a solid piece. The square, petrous., or hone
of the tympanum ought to be considered as detached from the temporal. It is
prismatic in shape, and provided on its upper surface with a diarthrodial facet
which unites it to the temporal, and on its lower face with another facet articu-
lating with the branch of the maxilla. Outwards it joins the zygomatic bone,
and inwards the pterygoid. Behind, it gives attachment to the membrane of
the tympanmn ; and in front it presents a small eminence of insertion, which
Meckel considered a second zygomatic process.
Thokax. — Sternum (Fig. 109, H 1). — The sternum of Birds, serving as a
basis of support to the muscles moving the wings, should offer, and does in
fact show, a remarkable degree of strength, because of the extraordinary volume
of these muscles. And these being more powerful and energetic as the Bird
exhibits a greater degree of aptitude for flight, it results that the structure of
the sternum is solid in proportion as the creature is strong on the wing. For
this reason, we may infallibly pronounce as to the extent and power of a bird's
flight by an inspection of the sternum of individuals of its species. In this
respect, however, we only announce what is well known to be a particular appli-
cation of the rules established by the great law of concordance between the
anatomical disposition of organs and their physiological finality.
Studied in Palmipedes., which will serve as a type for description, the sternum
presents itself in the form of a large rectangular cuirass, elongated from before
to behind, of itself constituting the inferior wall of the thoracic cavity, and also
largely protecting the abdominal cavity. Its superior face is concave, while the
inferior is convex, and entirely occupied by the insertion of the pectoral muscles.
THE BONES IN BIRDS. 1G3
It presents, on the median line, a thin and very salient ridge, named the brisket
{carina or keel) (Figs. 109, 14 ; 111, B. 2), which in a remarkable manner
multiplies the points of attachment of these muscles. The anterior border
offers in its middle a small eminence of insertion, the episternal (Figs. 109, 15 ;
111, A 2). Laterally, two articular grooves are seen which correspond to the
coracoids. The posterior border is cut by two notches which are often converted
into foramina (Fig. Ill, b 3, 3). On the lateral borders are observed small
double articular facets answering to the inferior ribs. The angles which separate
these two borders from the anterior are both prolonged into a httle eminence,
named by some authors the costal process (Fig. Ill, a 33).
In the Fowl, the sternum is not so strong as in the Goose or Duck. On
each side of the brisket it shows two wide notches, which greatly reduce its
substance. These notches (Figs. 109, 18, 19 ; 111, a 6, 7), closed in the fresh
state by membranes, are distinguished as external and internal. The latter, of
greater size than the former, extends nearly to the extremity of the bone.
From this division of the lateral plates of the sternum, result two long and
slender processes directed backwards (Figs. 109, 16, 17 ; 111, a 4, 5). The
external terminates by becoming widened, and forming a kind of bony plate,
which covers the last inferior ribs.
The sternum of Pigeons is distinguished by the enormous development of
the brisket. The two notches of the Fowl are also met with in these birds, but
the internal is nearly always converted into a narrow foramen.
This comparative study of the sternum in the chief domesticated birds, leads
us to appreciate the correctness of the principles just enunciated, with regard
to the form and extent this bone may exhibit. The Gallmaceous Birds, properly
so called, which fly little and badly, have the sterur.-n singularly weakened by
the deep notches cut in its lateral parts. With Palmipedes, the sternum is wide
and but slightly notched, so that the Goose and Duck, which waddle along so
awkwardly in our poultry yards, are capable of sustaining long and rapid flight,
like that of the wild individuals of the same species. With regard to Pigeons,
which are well known to be swift and powerful flyers, may this advantage not
be due to the extraordinary development of the keel which constitutes the
brisket ?
Ribs (Fig. 109, I, etc.).— In the Fowl and Pigeon there are seven pairs
of ribs ; and in the Duck nine pairs. Articulated superiorly with the dorsal
vertebrte, as in Mammals, these bones are provided, near their middle, with a
flat eminence which commences at the posterior border, and is directed back-
wards and upwards, to rest by its free extremity on the external face of the next
rib. These eminences (Fig. 109, 20) form an epiphysis at an early period, and
are usually absent in the first and last ribs. They concur in an efficacious
manner to increase the solidity of the thorax.
The costal cartilages of the Mammalia, are in Birds often transformed into
veritable inferior ribs, joined to the superior ribs by a diarthrodial articulation
(Fig. 109, J). These pieces are long and strong, and all terminate at their lower
extremity by a double facet which articulates with the lateral border of the
sternum ; they are nearly always absent in the two first ribs. It is not rare to
see the last united to the one before it, instead of passing directly to the sternum ;
in which case it comports itself like the asternal ribs of Mammals.
Anterior Limbs. Shoulder-bone. — The shoulder comprises : a scapula ; a
particular bone named the coracoid by Cuvier : and a clavicle, which forms, in
164
THE BONES.
coalescing with that of the opposite side, a single bone called the /or A' (furcidum)^
or osfuradare. The scapula (Figs. 109, k ; 111, a 8) is narrow, elongated, and
falciform, and shows no trace of a spine. Its anterior extremity only forms a
portion of the glenoid cavity, and is united by means of a fibro-cartilage with
the fork of the coracoid bone. The latter (Figs. 109, L ; 111 a 9) is so named
because it represents the coracoid process of Mammals, and is a long prismatic
bone, directed obliquely from above downwards, and before to behind. Its
superior extremity is often fused with the scapula, and united at an acute angle
with that bone to form a portion of the articular cavity which receives the head
of the humerus. Its inferior extremity is flattened from before to behind, and
responds by a diarthrodial articulation to the anterior border of the sternum.
The coracoid is long in Birds which fly slowly ; it is, on the contrary, short,
thick, and therefore very solid, in quick flyers. Th.^ fork (Figs. 109, M; 111,.
Fig. 111.
STERNUM AND BONES OF THE WING.
A, Sternum and mng-bones of the Fowl {upper face). 1, Body of the sternum; 2, its episternal
process; 3, 3, its costal proces>es ; 4, 4, its lateral external processes; 5, 5, its lateral internal
processes; 6, 6, internal notches; 7. 7, external notches; 8, scapula; 9, coracoid; 10, fork;
11, opening for the passage of the elevator of the wing; 13, humerus; 14, air-opening in that
bone; 15, ulna; 16, radius; 17, ulna-cavpal bone; 18, radio-carpal bone; 19, large metacarpal ;
20, small metacarpal ; 21, first phalnnx of the large digit ; 21', second phalanx of ditto ; 22, small
phalanx lying beside the first bone of the large digit, and representing the remains of a third digit ;
23, thumb.
B, Sternum and shoulder-hone of a young Duck (inferior surface). 1, 1, Sternum ; 2, keel ; 3, 3,
lateral notches ; 4, 4, coracoid •, 5, 5, fork ; 6, opening for the passage of the elevator of the wing.
B 5, 5) is a single bone, shaped like a V or U, situated at the base of the two
wings, in front of the trunk, and in an oblique direction downwards and back-
wards. The two branches which form it represent the clavicles ; they meet and
are united at their inferior extremities, where they describe a curvilinear angle
more or less open, attached to the brisket by means of a membranous ligament.
THE BONES IN BIRDS. 165
Their superior extremity rests within and opposite to the glenoid cavity, against
the scapula and coracoid, forming with these bones a remarkable foramen,
through which passes the tendon of the elevator muscle of the wing (Fig. Ill,
A 4, B 6). The forks play the part of an elastic spring, whose office it is to
prevent the wings coming towards each other during contraction of the depressor
muscles. The conformation of this bone is, therefore, like the sternum, related
to the extent and power of flight ; and for this reason it is that, in swift flyers,
the two branches of the furculum are thick, solid, widely separated, and curved
like a U ; while in those which fly heavily and with difficulty, these branches
are thin and weak, and joined at an acute angle. The latter formation greatly
diminishes its strength, and lessens, in a singular manner, the reactionary power
of the bony arch it represents.
Bone of the arm. — The humerus (Figs. 109, n ; 111, a 13) offers an articular
oval-shaped head, and an air-opening placed beneath this eminence. It is long
in Palmipedes, ordinarily so in the Gallinaca, proper, and very short in Pigeons.
Bones of the forearm (Figs. 109, o, o ; 111, A 15, 16).— The radius is much
less voluminous than the ulna. The latter has an extremely short olecranon ;
and the two bones are separated from one another in their middle part to meet
again at their extremities, where they are united by ligamentous bands in such
a way as to render the movements of pronation and supination impossible. This
mode of union, which nevertheless does not prevent the two bones from gliding
slightly on each other in the direction of their length, has been wisely adopted
by nature in order that the wing might strike the air, like an oar, by its inferior
face ; otherwise, the resistance of the aerial medium would make these two bones
pivot, and cause the wing to present itself to the air in a wrong direction.
Bones of the carpus (Figs. 109, p, p' ; 111, a 17, 17).— These are only two,
and are distinguished by the names of radius and ulna, in consequence of their
corresponding more particularly to these bones in other animals.
Bones of the metacarpus (Figs. 109, q, q' ; 111, a, 19, 20).— These also
number only two, and are separated at their middle portion, to be consolidated
at their extremities.
Bones of the digital region. — The wing of a bird is composed of three digits.
One of them, which resembles the thumb and forms the basis of the false wing
is composed of a single styloid-sliaped phalanx, articulated at the base of a small
particular process belonging to the superior extremity of the largest metacarpal
bone (Figs. 109, r' ; 111, A 23). The largest digit comprises two phalanges,
which succeed the last bone (Figs. 109, R, r ; 111, a 21, 21'), The third digit
is represented by a small rudimentary phalanx (Fig. 109, a 22), which corre-
sponds to the inferior extremity of the small metacarpal bone, and lies beside
the first phalanx of the large digit in the closest manner.
It is well to remark that the hand and forearm are longer in proportion to
the quality of flight ; those two regions of the Aving, for example, are very short
in Gallinaceous Birds.
Posterior Limbs, Coxa, or os iliac. — This is a voluminous and very
solid piece, particularly in walking birds, and composed, as in the Mammalia,
of an ilium, ischium, and pubis. The ilium (Fig. 109, s), very long, is con-
solidated with the last two dorsal, the lumbar, and the sacral vertebrae ; it is
excavated on its internal face. The ischium partly incloses the side of the pelvic
cavity ; between its internal border and the external border of the ilium is an
•orifice which replaces the great ischiatic notch. Its inferior border is united to
166 THE BONES.
the pubis. The latter (Fig. 109, s") is thin and elongated, and follows the
direction of the inferior border of the ischium, with it circumscribing an oval
opening more or less spacious (Fig. 109, 22). Its inferior extremity extends
beyond the ischium, to curve inwards towards that of the opposite side, but
without uniting with it. We do not, therefore, find the pelvic symphysis in
Birds, and the pelvis is slightly open below, a circumstance which favours the
passage of the egg through the cavity and out of the cloaca. The cotyloid cavity
is perforated by an opening at the bottom, which passes through the bone.
Thigh-bone. — The femur (Fig. 109, t) is articulated inferiorly with the
patella, tibia, and fibula. In all walking Birds, Uke the Gallinacge, it is long
and strong, as well as the bones below it.
Leg-bones. — The patella (Fig. 109, u) is wide and thin. The tiUa (Fig.
109, v) terminates, below, by two condyles separated by a groove, which becomes
articular behind. The fibula (Fig. 109, x) articulates by its head with the
external condyle of the femur, and is consolidated with the tibia ; it never
descends to the inferior extremity of that bone.
Tarsal bones. — The tarsus appears to be altogether absent in Birds. Never-
theless, we may venture to consider, as a vestige of the bones of this region, a
small bony nucleus buried in a fibro-cartilaginous mass which ghdes on the-
posterior pulley of the tibia. This nucleus (Fig. 109, y) represents the calcaneum
of Mammals.
Metatarsal bone. — A single metatarsal bone Ls found in Birds, articulating
superiorly with the inferior extremity of the tibia, and terminating inferiorly by
three pulleys which support the three principal digits. This bone (Fig. 109, y)
shows in the Fowl, near its inferior third, a conical process turned backwards,
which serves as a base for the spur. Behind its superior extremity, it exhibits
another which may be considered as a consolidated metatarsal bone (Fig.
109, 23).
Bones of the (ligital region (Fig. 109, z, etc.). — All the domesticated Birds have
four digits on the inferior members : three principal, directed forwards, and one
rudimentary, carried backwards. The first, designated as internal, median, and
external, articulate with the inferior pulleys of the metatarsal bones. The in-
ternal is formed by three phalanges, the second has four, and the third five.
These phalanges are formed something like those of the Carnivora ; the last is
pointed, conical, and enveloped in a horny sheath. The fourth digit, or thumb,
is composed of three pieces ; one of these, the first, is generally considered as a
rudimentary metatarsal bone. It is attached by fibro-cartilaginous tissue to the
inner and posterior aspect of the inferior extremity of the principal metatarsal
bone.
THEORY OF THE VERTEBRAL CONSTITUTION OF THE SKELETON. 167
CHAPTER IV.
THEORY OF THE VERTEBRAL CONSTITUTION OF THE
SKELETON.
In the series of vertebrated animals, the bony pieces of the trunk bearing the
name of vertebrse are those which offer the highest degree of fixity, and to which
the existence or the arrangement of the others appears to be subordinate. This
feature in organization, recognized by E. Geoffroy Saint-Hilaire and Professor
Owen, has caused these authorities to assert that the type of construction of
vertebrated animals is the vertebra.
After E. Geoffroy Saint-Hilaire and Professor Owen, several German, English,
and French anatomists have studied the vertebral composition of the skeleton ;
and among the works published in France on this subject, must be specially
noticed those of Lavocat. In principle, all the writers have arrived at the same
conclusions, and only differ in some few details.
It is certain that the base of the vertebral column is formed by a series of
bony segments. Each of these segments is called an osteodesm, and each osteo-
desm represents the bodi/ or centrum of a vertebra.
In examining the dorsal region, it is evident that to the body or centrum of
a vertebra are added two complete osseous arches — a superior and an inferior.
The superior arch is formed by the vertebral laminae ; the inferior by the ribs, their
cartilages, and a portion of the sternum. The first is designated the neural arch,
as it furnishes a protective case for the nervous centres ; and the second, which
more particularly protects the vascular system, is called the hcemal arch (see
Figs. 112, 113).
The hfemal arch may have prolongations or appendices more or less developed,
and comparable to the apophysary prolongations of the ribs in Birds and some
Fishes.
Such is the general composition of a typical vertebra ; but there are also to
be distinguished in the neural and htemal arches the following parts : —
H^MAL ARCH.
1. Haemal parapophysis = the tuberosity of
the rib.
2. Haemal metapophysis = the head of the
rib.
3. Haemal diapophysis = the rib proper.
4. Hsemapophysis = the costal cartilage.
5. Haemal spine = the corresponding sternal
portion.
NEURAL ARCH.
1. Neural parapophysis = the posterior
costal cupola.
2. Neural metapophysis = the anterior costal
cupola.
3. Neural diapophysis = the summit of the
transverse process.
4. Neurapophysis = the vertebral lamina.
5. Neural spine = the summit of the spinous
process.
The vertebrae sometimes depart more or less from the model just described.
They may vary not only from one species to another, but also in the same
animal, and even in the same region. Thus, the neural arch may be absent, as
has been observed in certain coccygeal vertebrae ; or the hsmal arch is incom-
plete or null, as in the cervical or lumbar vertebrae ; or, lastly, the arches are
often unequal ; though this inequality is of no importance, since their size is in
relation to the volume of the parts they should protect.
Notwithstanding these differences and variations, or the transformations
168
THE BONES.
experienced by certain parts, there is not a bone in the skeleton which cannot be
included in the vertebral type.
Fig. 112.
THORACIC OR PECTORAL VERTEBRA
OF A MAMMAL.
C, Centrum ; n, neural arch ; h, hsemal
arch.
Fig. 113.
CAUDAL VERTEBRA OF THE
TURBOT.
c, Centrum , n, neural arch ;
h, hsemai arch.
The vertebra being admitted as the type of construction of the skeleton, it
is easy to find it in all the regions of the bony framework. In the thoraco-
Fig. 114.
CRANIAL VERTEBRiE OF THE DOG. (AFTER LAVOCAT.)
1, Occipito-hyoideal vertebra; 2, parieto-maxillary vertebra; 3, fronto-mandibular vertebra;
4, naso-turbinal vertebra.
THEORY OF TEE YERTEBRAL CONSTITUTION OF THE SKELETON. 169
abdominal region, the centrum, neural arch, and hsemal arch are readily per-
ceived ; for in the lumbar vertebrae, the enormously developed transverse process
indicates the existence of an intra-vertebral arch.
In the sacral region, the bony girdle of the pelvis represents the hsemal arch.
The posterior limbs, articulating with the bones of the pelvis, also belong to the
hsemal arch, and should be considered as appendices of this arch, analogous to
the costal appendices of birds.
The cervical region may be compared to the sacral region ; as in it the
inferior haemal arch is represented by the osseous ring supporting the anterior
hmbs — the scapulo-clavicular girdle. The limbs themselves are appendices of
the cervical haemal arch.
Difficulties begin to appear when the extremities of the trunk — the head and
coccyx — come to be examined. Nevertheless, the composition of the coccyx is
revealed when the caudal vertebrae of certain Fishes, especially those of the
Pleuronectidae, in which the neural and hsemal arches are complete, are examined
(Fig. 113). But the vertebral constitution of the head remained for a long time
an insoluble question, or it was solved in a contradictory manner by the
naturalists who attempted it. Some admitted a single cranial vertebra ; others
included three or four ; while others, again, found six or seven.
These difficulties and contradictory results may be understood, when it is
borne in mind what profound modifications the vertebra must have undergone
to constitute the bones of the head.
At present the problem appears solved. The head is composed of four
vertebrae, in which are found the various parts enumerated in the description of
the typical vertebra.
In the four classes of vertebrata, the head is constantly formed of four
vertebrse, which are determined as follows, according to Lavocat : —
Vertebra.
Centrum.
Neural arch.
Hjemal arch.
Occipito-hyoideal.
Basilar process
of the occipi-
tal.
Occipital (3 pieces).
Mastoid walls of the
tympanum.
Hvoideal apparatus
('five pieces).
Parieto-maxillary.
Body of the
posterior sphe-
noid.
Wing and pterygoid
process of the pos-
terior sphenoid.
S(iiiamnus portion and
zygomatic process of
the temporal.
Parietal.
Inferior maxilla (five
pieces).
Froiito-manflibular.
Body of the
anterior sphe-
noid.
Wing and pterygoid
pr<'cess of the anterior
splienoid.
Posterior Frontal and
its (irhital process.
Frontal.
Malar.
Laclirvnial.
Palatine.
Supermaxillary.
Preriiaxillary.
Naso ttnbinal.
Vomer.
Ftlimoid.
Nasal.
Turbinated.
Sub-ethmoidal.
170 THE ARTICULATIONS.
The number of cranial vertebrae is invariable, as each is destined to lodge
the organs of one of the four senses. The occipito-hyoideal receives the principal
organs of hearing ; the parieto-maxillary osteodesm protects the sense of taste ;
finally, the organs of vision are sustained by the fronto-mandibular vertebra,
while the naso-turbinal contains the sense of smell.
Several anatomists, at the head of whom are Huxley and Gegenbauer, do not
entirely share these views. They certainly admit the existence of the occipital
vertebra, but it appears to them to be impossible to recognize the others. They
remark that all the bones which constitute the spine are found in the primary
cartilaginous skeleton ; so that, in order to establish the vertebral constitution
of the head, it would be necessary to allot to the same cranial vertebra : 1. The
pieces that are found in the cartilaginous cranium. 2. The other pieces which are
developed in the fibrous tissue — those skeletal tegumentary pieces (temporals,
parietals, etc.). It must also be observed that the division into vertebral bodies
of the parts which form the base of the cranium, far from being easy in the lowest
animals, is, on the contrary, only possible, with some trouble, in the highest classes.
So that if the vertebral constitution of the head were a fact, it must be admitted
that the differentiation of the bones at the base of the cranium is less advanced
in Mammals than in the lower vertebrates.
The vertebral type is not, therefore, universally accepted by all anatomists.
SECOND SECTION.
The Articulations.
THE ARTICULATIONS IN GENERAL.
The different pieces constituting the solid framework of the animal body are, a-s
has been said, united in such a manner that they can move one upon the other.
From this union results the articulations, or articular joints, the construction
of which will now be referred to in a general manner, before commencing a
particular description of each.
Arthrology, or Syndesmology , is the name given to that division of anatomy
which treats of the articulations. To form articulations, the bones correspond
with each other by certain determined points of their periphery, which are named
articular surfaces. Every articulation is, therefore, essentially constituted by two
opposite osseous surfaces, simple or complex, which are moulded to each other.
These are either contiguous, independent, and very movable — continuous with
each other by means of a cartilaginous substance which confines them, if not to
total immobility, at least to very limited movements ; or united by a fibro-
cartilage, the elasticity of which permits a certain degree of displacement between
the bones in contact.
In the first case, the articulations are classed as diarthroses, or movable
articulations.
In the second, they are designated synarthroses, sutures, or immovable
articulations.
THE ARTICULATIONS IN GENERAL.
171
In the third, they are amphiarthroses, or mixed articulations; so termed
because they participate in the movements of the other two classes : synarthroses,
by the continuity established between the articular surfaces ; and diarthroses. by
the extensive motion they permit.
The general characters that distinguish each of these three great classes of
articulations will be successively studied.
Fig. 115.
u
rammiQ
1^
a/
/
e
V
pn
4 —
fefjfjft
PLANS OF THK DIFFERENT CLASSES OP ARTICULATIONS.
A, Suture: 1, periosteum ; 2,sutural ligament. B, Amphiarthrosis : a, first degree— 1, periosteum;
2, articular cartilage ; 3, interarticular ligament : b, second degree — 4, single cavity in the
interarticular ligament : c, third degree — 5, double cavity in the interarticular ligament. C,
Diarthrosis: b, simple diarthrosis — 1, periosteum; 2, articular cartilage; 3, epithelial layer of
the synovial membrane (dotted line) ; 4, fibrous capsule ; 5, cul-de-sac of the synovial membrane ;
6, fibrous layer of the synovial membrane : c, double diarthrosis— 7, interarticular meniscus ; 8,
9, cavities of the two synovial membranes.
General Characters of Diarthroses.
"We ought to consider, in the diarthrodial articulations (Fig. 115, c, 6 and c) :
1. The contiguous boni/ surfaces which form them. 2. The cartilaginous layers
(cartilages of incrustation) which cover these. 3. The fibrous or fibro-cartilagi-
nous tissue {articular fihro-cartilages) which complete them, when they are not
shaped so as to be reciprocally adapted to each other. 4. The ligaments which
172
THE ARTICVLATIONS.
maintain them in contact. 5. The serous membranes {synovial capsules) that
cover the internal face of the latter, and which secrete the synovia, a kind of
animal oil that facilitates the gliding of the articular surfaces. 6. The movements
of which these articulations may be the seat. 7. Their methodical classification.
8, Their nomenclature.
Articular Surfaces. — These surfaces have the common character of being
destitute of asperities, so that they can glide with the greatest facility on each
other. They are designated, according to their form, by the names of facets,
heads, condijles, cotyles, glenes, pulleys, etc. There is no need to revert to their
general description, as they have already been suihciently studied in the osteo-
logy ; so we will confine ourselves to repeating that they are found at the
extremities of long bones, on the faces of short bones, and on the angles of wide
bones. We may mention, also, that they are often excavated by one or several
depressions named synovial fossce, or hollows for the insertion of ligaments. The
first are a sort of natural reservoirs which receive the unctuous fluid secreted by
the interarticular serous membranes ; the second give attachment to interosseous
ligaments.
Cartilages of Incrustation. — This designation is given to the layers of
cartilaginous matter which, as it were, varnish the articular surfaces they adhere
to by their inner face ; their free surface
is distinguished by a remarkable polish
and brilliancy. Thicker towards the
centre than at the circumference when
they cover bony eminences, these carti-
lages show an inverse disposition when
they line cavities. They are elastic, of
a pearly whiteness, and resisting — though
they are soft enough to be cut by a sharp
instrument ; in a word, they possess all
the physical characteristics of the primary
cartilage of bones. They appear to be
formed of parallel fibres placed perpen-
dicular to the bony surfaces, and im-
planted in these by one of their ex-
tremities ; the opposite extremity corre-
sponding to the free surface of the
cartilage. Viewed by the microscope,
they are found to present the characters
of true or hyaline cartilage.
The fundamental matter is amorphous and homogeneous ; but under the
influence of slight dessication, there appears in the hyaline substance a partition-
ing formation, which may be regarded as an agent in the distribution of the
nutritive juices in the substance of the cartilaginous tissue (Renaut).
The cavities (cartilage capsules) are irregular, and more or less wide. They
contain from one to five cells without walls, and their contents — slightly granular
— have in the centre of each cell one or two nuclei with nucleoH (Fig. 1 IG). These
cavities are elongated, and are directed almost perpendicularly towards the osseous
articular surface in the deep layer ; in the middle layer they are round ; and
they are lenticular, and parallel to the surface of friction, in the superficial layer.
(It has been stated that a membrane lines these spaces. In addition to the
SECTION OF BRANCHIAL CARTILAGE OF
TADPOLE.
, Group of four cells separating from each
other ; b. pair of cells in apposition ; c, c,
nuclei of cartilage-cells ; d, cavity contain-
ing tiiree cells. These cells are embedded
in the finely granular matrix, or funda-
mental substance.
THE ARTICULATIONS IN GENERAL.
173
granular matter observed in the cells, it is not rare to find fat globules. The
nuclei of the cells vary from ^^V? *o Wmj o^ 8,n inch in diameter. The cells
multiply eudogenously.)
The cartilage cells are insoluble in boiling water ; consequently, so far as
their chemical composition is concerned, they are distinct from the fundamental
substance.
The diarthrodial cartilages have no vessels or nerves.
The presence of cartilages of incrustation in the articulations is of the greatest
importance. When they are worn, absorbed, or transformed into bone in con-
sequence of certain articular maladies, the movements become painful and very
difficult. With regard to the part they play in the economy, it may be said that :
1. They favour, by their smoothness, the gliding and displacement of the bones.
2. They attenuate, by their suppleness and elasticity, the violent shocks to which
the articulations are exposed. S. They resist the wear and deformation of the
articular surfaces.
Complementary Fibro-caetilages. — There are two kinds of complementary
fibro-cartilages. Some (interosseous) represent circular cushions which pad the
margins of certain cavi-
ties, filling up the notches ^' S- ^ ^ '^•
that might render these
imperfect. They in-
crease the depth of these
cavities, and protect their
borders from in j ury — for
example, the coxo-femo-
ral articulation. Others
(infer-articular) are in-
terposed between arti-
cular surfaces when these
do not exactly fit each
other — as when two opposing extremities are convex. It may be remembered
that the lateral tuberosities of each tibial surface present, for articulation with the
condyles of the femur, two convex diarthrodial faces, the coaptation of which is
rendered perfect by the interposition between each condyle and corresponding
tibial surface, of a crescent-shaped fibro-cartilage, which for this reason has been
named a meniscus. In other joints, these interarticular fibro-cartilages are
shaped like discs or biconcave lenses. There then result double diarthroses (Fig.
115, C, e) : example, the temporo-maxillary articulation. (Fibro-cartilage also
covers bony surfaces over which the tendons play, as on the trochlear surface of
the humerus, postero-inferior face of the navicular bone, and elsewhere. In
these situations it is named stratiform fibro-cartilage.) These organs are formed
sometimes by fibrous, at other times by cartilaginous tissue ; their mode of
association need not be referred to here, though it may be observed that the
cartilage is more particularly found in all those points where there is most
articular friction. They receive very few vessels, and it is questionable if they
have nerves.
Ligaments. — These are bands which unite contiguous diarthrodial surfaces.
They are sometimes formed of white fibrous tissue, and sometimes of yellow ;
hence their division into two great classes of white and yeUoiv ligaments.
a. The white ligaments are distinguished by the pearly whiteness of their
14
FIBRO-CARTILAGE, MAGNIFIED 155 TIMES.
Showing interlacement of fibrous fasciculi, with scattered
groups of cartilage-cells.
174
THE ARTICULATIONS.
tissue and want of elasticity. Those which are found around the margin of
articulations are termed peripheral, and those in their interior are designated
interosseous or interarticular ligaments.
The peripheral ligaments are g^erallj composed of parallel fibres collected in
fasciculi, or spread out as membranes. In the first they are called funicular, or
riMon-shaped ; in the second, they are termed membraniform, or capsidar. The
funicular ligaments are short, round, or flattened bands, attached by their
extremities to the two bones they unite ; they are lined on their inner aspect
by the synovial capsule, and are covered .externally by tendons, aponeuroses,
muscles, vessels, or nerves. The capsular ligaments are often complete — that is
Fig. 118.
Fig. 119.
^^S
Wl^m^^UJSlfmije'^^M^KplMwMl''
WHITE OR NON-ELASTIC FIBBOUS
TISSUE.
YELLOW OR ELASTIC FIBROUS TISSUE,
THE LIGAMENTUM NUCH^E.
to say, they envelop the whole articulation like a sack. At other times they are
incomplete, and then they are simple membranes, binding together the different
funicular ligaments of a joint.
The interosseous ligaments — less numerous than the preceding — are often formed
of interlacing fibres ; they are always funicular, and fixed by their extremities
into excavations in the centre of articular surfaces.
J. Hhe yellow ligaments are 2k[[ perijyheral, funicular, or 7nembranous, and enjoy
a marked degree of elasticity, which permits them mechanically to bring back to
their usual position the bony levers that have been momentarily displaced. These
ligaments, which are powerful auxiliaries to the muscular forces, give permanent
equilibrium to the weight in certain parts of the body, which incessantly tend to
fall to the ground ; for instance, the cervical ligament of Solipeds and large
Ruminants. The ligaments are always assisted in their action by atmospheric
pressure, which is exerted over all the surface of the body ; and also frequently by
the tendons and aponeurosis of muscles, and even by the muscles themselves,
when they pass over an articulation or are inserted in its vicinity. In several
regions the ligaments are more or less confounded w^ith tendons or aponeiu-oses —
as in the anterior extensor tendon of the phalanges and superior sesamoid liga-
ment, the ligaments of the femoro-tibial articulation, and the aponeuroses of the
posterior portion of the superficial gluteal muscle.
Synovial Capsules. — These are very thin membranes of a serous character,
intended to secrete the synovia. They are composed of two layers : a deep,
formed by fasciculi of connective tissue ; the other, superficial, formed by an
THE ABTIGULATIONS IN GENERAL. 175
endothelium. The first sometimes adheres intimately to the inner face of the
funicular or membranous ligaments of the articulation ; at other times it is loosely-
attached to them by an abundance of connective tissue. The second layer is con-
stituted by a single row of flattened polygonal cells, except at the bottom of
certain grooves, where they are more or less crowded. Though belonging to the
serous membranes, the synovial membranes do not form complete sacs, as, after
lining the internal surface of the ligaments, they cease at the articular margins.
Direct observation demonstrates that the cartilages have no covering, and
that there is no synovial membrane on their surface. The anatomists who
imagined that the thin pellicle, which can be rendered evident in cutting the
surface of cartilage obliquely and separating it by teazing, was a membrane, were
deceived, as this pellicle has not the texture of a serous membrane ; and it is not
vascular, for it has never been possible to inject vessels on the surface of such
cartilages, nor yet in their substance. Neither is it covered with epithelium, and,
if submitted to microscopical examination, it has all the characters of cartilage.
Pathological facts prove nothing in favour of the existence of a synovial
membrane on cartilages.
It may be accepted, then, that the synovial membrane never extends to the
surface of articular cartilage ; but, after being fixed around the margin of a
diarthrodial surface, it is reflected in every direction to line the internal surface
of the ligaments, and become attached to the periphery of the diarthrodial surface
in contact with the other, so that it entirely isolates the interior of the joint from
the peri-articular connective tissue.
There are generally found within articulations, little masses of fat which push
the synovial membrane enveloping them inwards. Erroneously considered by
Clopton Havers as glands for the secretion of synovia, these accumulations of fat
have been named synovial fringes,- ot villi. They are more particularly numerous
in the neighbourhood of the articular margins — that is, on the border of diarthro-
dial surfaces. They are formed by a prolongation of the synovial membrane,
which covers some connective tissue fibres associated with adipose cells, or an
amorphous substance provided with nuclei.
The synovial membrane, after lining the inner surface of ligaments, sometimes
escapes between these, forming a hernia. The term synovial culs-de-sac has been
given to these external prolongations of the articular serous membrane. This
membrane often covers the inner surface of a tendon or ligament, in order to
facilitate their gliding over a bony eminence.
The synovia is a viscid, colourless, or slightly yellow fluid, in its physical
characters somewhat resembling oil ; it does not possess them, however, so far as
its composition is concerned, for chemical analysis has not demonstrated the
presence of fatty principles. It is the albumen it contains which gives to it its
viscidity, and which fits it for lubricating the articular surfaces over which it is
spread. Its use in the animal economy is absolutely identical with that of the
greasy substances employed to luliricate the axles of carriages.
To the means of union described under the names of ligaments and synovial
membranes, may be added atmospheric pressure, the influence of which is
relatively considerable, as the experiments of Weber have demonstrated.
Movements. — The movements peculiar to diarthrodial articulations are
divided into seven principal classes :
1. Simple gliding, the only movement possible between two plane or undu-
lating facets.
176 THE ARTICULATIONS.
2. Flexion, which brings two bony pieces nearer each other, by closing more
or less their angle of union.
3. Extension, the inverse movement, during which the bones are straightened
on each other.
4. Adduction, which brings the inferior extremity of the movable bone towards
the median line.
5. Abduction, the contrary movement to the preceding.
6. Circumduction, or the sling movement, during which the bone passes
successively through the last four positions.
7. Rotation, in which one bone pivots on another.
Classification of the Diarthroses. — The basis of this classification is
founded on the configuration of the articular surfaces and the nature of the
movements they permit. This double base serves to establish five kinds of
diathrodial articulation :
1. Enr/rfhrosis, characterized by the reception of an articular head within a
cavity of appropriate form. This articulation, the surfaces of which are derived
from a sphere, may be the seat of the most extensive and varied movements —
flexion, extension, abduction, adduction, circumduction, and rotation. Example :
the coxo-femoral articulation.
2. The trochlea?!, angular ginglymoid, or perfect hinge articulation, when the
articular surfaces are formed into trochlea, reciprocally fitting into each other,
and the movements of which — flexion and extension only — are executed, from
before to behind, with the precision of a hinge. Example : the tibio-tarsal
articulation.
3. The piiwt, trochoid, or lateral ginglymoid articulation, is a diarthrosis formed
by a pivot which turns in a semi-cylindrical cavity. Rotation is the only move-
ment. Example : the atlo-axoid articulation. •
4. The condyloid, or imperfect hinge articulation, which permits, like the
preceding, the two principal movements of extension and flexion, and the acces-
sory movements of rotation or lateral inclination. The articular surfaces, though
very diversely shaped, nevertheless exhibit in all the articulations one or more
condyles opposed to an equal number of oval excavations. Example : the femoro-
tibial articulation.
5. Arthrodia, or 'plamform diarthrosis, is constituted by plane or nearly plane
iacets. Gliding is the only possible movement. Example : the carpo-metacarpal
articulation.
Nomenclature. — The names of the articulations are usually those of the
bones which form them. For instance, the scapulo-humeral articulation is the
joint between the scapula and humerus ; the intervertehrnl articulations join to
each other the various bones constituting the spine. When the qualifying name
of an articulation is composed of two elements, as in the first instance, it is well
to place first the word which indicates the bone usually most fixed.
General Characters of the Synarthroses.
Sutures (Fig. 1 1 5, a) are the temporary articulations which exist only at an early
period of life. They nearly all disappear in the adult animal, in consequence of
the bones forming them becoming consolidated. They belong almost exclusively
to the bones of the head.
Articular Surfaces. — The bones forming these come in contact by their
THE ARTICULATIONS IN GENERAL. 177
borders or angles, which, for this purpose, generally present very uneven
surfaces.
Sometimes they arc cut perpendicularly and simply roughened ; at other times
they are bevelled, and joined by means of fine laminse or trifling inequalities ;
again, they are notched into deep and sinuous dentations ; and lastly, one bone
is fixed into a groove cut in the other. It will be understood that such formations
of the articular surfaces will limit their movements, and assure the solidity of
their union.
Modes of Union, — A fibrous tissue interposed between these synarthrodia!
surfaces, unites them closely to each other. It has absolutely the same texture as
the primary cartilage of the bones, and, like it, possesses the property of becoming
ossified after having been vascularized. This ossification, which causes the
disapppearance of the sutures, occurs earlier inwards than outwards. The
periosteum, in passing from one bone to another, also concurs in bringing about
a more complete synarthrosis. It should, therefore, be included in their means
of union.
Movements. — These are very obscure, and only noticeable in young animals,
by the elasticity they communicate to the bony walls of the cranium or face. In
the adult, they may be said to be null.
Classification. — Tliere are four principal descriptions of sutures .-
1. When two wide bones correspond by means of denticulations fitting into
each other, the suture is named frup, Umhosa, serrated, or dentated. Example :
the articulations unitmg the three portions of the parietal bone. 2. If the opposite
borders of two bones in contact are widely bevelled, one inwards, the other out-
wards, it forms a scaly or squamous suture {squamosa). Example : the parieto-
temporal articulations. 3. When the union of bones takes place by plane or
roughened surfaces, cut perpendicularly on their borders or angles ; this constitutes
the harmoaia suture, or suture hij juxtaposition (or apposition). Example : the
occipito-temporal articulations. 4. The schiruii/Iesis, mortised suture, synchron-
drosis, or gomphosis, results from the reception of a bony plate into a groove more
or less deep in another bone. Examples : the spheno-frontal and supermaxillo-nasal
articulations ; the teeth in the alveolar cavities.
General Characters of the Amphiarthroses or Symphyses.
Articulae Surfaces. — They are frequently smooth, and formed almost on
the same model as the diarthrodial surfaces. They are covered by a thin layer of
cartilage ; but, instead of being smooth and polished, they are more or less rugged,
without, however, presenting the anfractuous disposition of the majority of synar-
throdia! surfaces.
Modes of Union. — The organs which perform this office are : 1. Fibro-
cartilage, which establishes continuity between the articular surfaces. 2. Ribbon-
shaped and peripheral ligaments (Fig. 115, b a). These latter do not differ from
the analogous bands attaching the diarthrodial articulations. With regard to the
fibro-cartilage, it is distinguished from the complementary discs of these same
articulations, by a less intimate mixture of the cartilaginous and fibrous elements
entering into its composition. The last may be sometimes absent, as well as the
peripheral bands ; and then the articulation only differs from the synarthroses by
the extent of motion it permits. Occasionally, the interarticular fibro-cartilages
are excavated by one or two little narrow cavities (Fig. 115, b b, c) ; but these
are never lined by a synovial membrane, like the diarthrodial cavities.
178 THE ARTICULATIONS.
Movements. — The amphiarthroses only permit of a see-saw or swinging
movement, the extent of which depends on the thickness of the intermediate
fibro-cartilage.
Classification. — Only one kind of amphiarthrosis is recognized in the Horse,
the most, remarkable of which is found in the articulations between the bodies of
the vertebrae.
CHAPTER II.
ARTICULATIONS OF MAMMALIA IN PARTICULAR.
In the special study of the articulations, the same order will be followed as for the
bones ; the articulations of the spine will be first noticed, then those of the head,
thorax, and anterior and posterior limbs.
Preparation. — The preparation of the bones which have been described, has not been made
the subject of any particular recommendation, because it suffices, in order to study them, to
remove the soft parts by which they are surrounded, either by boiling, maceration, or scraping.
But when we come to examine the soft textures, in order to do so profitably it is necessary to
learn beforehand the rules whicli should be followed in their preparation. The following
directions are given with regard to the study of the articulations : —
1. To prepare the articulations, young subjects are cliosen in preference to those advanced
in years, because the density of tlie connective tissue in them is not so great, and this tissue is
easily removed from around the ligaments. As tiiese are prepared with difficulty when the
external surface is in a dry state, care should be taken, before dissecting them, to have them
excluded from the air by covering them with damp cloths, or with the skin of the animal.
2. It is convenient to separate the articulation we wish to dissect, by sawing through the
bones at a certain distance from the articular surfaces. The manipulation of the part is then
rendered easier, and its dissection can be made under the most favourable conditions.
3. It is necessary to preserve, as carefully as possible, the muscles surrounding the articula-
tions, in order to be able to study their relations with the ligaments which bind these. If it
be absolutely requisite to remove them, their insertions corresponding to the articulation
should always be retained.
4. The capsular ligaments should be first studied, as they have soon to be removed, the
better to show the funicular ligaments. Tliese, in their turn, must be sacrificed in order to
display, by different sections, the interosseous ligaments, when they are present. Lastly, the
two articular surfaces should be completely separated, so as to examine their conformation.
5. The synovial membranes, with their different cuU-de-sac, being a very important study —
with reference to the diagnosis and treatment of articular tumours — it is convenient to devote a
special piece to the examination of these serous membranes. It is very useful to inject their
interior with plaster or tallow coloured black, in order to distend their cavities, and thus aid
the study of their relations with ligaments, tendons, or muscles.
6. When an articulation is completely dissected, it may be left exposed to the air for some
time. When the ligaments begin to dry, they are more visible and easier studied.
For the preparation of each articulation it is not necessary to give any directions ; a glance
at the figures accompanying the description will suffice to dispel any embarrassment the
student may experience, while he always requires particular indications.
Article I. — Articulations of the Spine.
These articulations comprise all those of the vertebrse with each other.
Preparation. — In order to properly study the vertebral joints, the spine of one subject
should be freed from all tlie muscles surrounding it; this being done, portions consisting of at
least two vertebrse from the cervical, dorsal, and lumbar regions, should be detached trum it.
In the portions from the cervical regions, the interlamellar ligaments and the capsules of the
ARTICULATIONS OF TEE SPINE. 179
articular processes are easily dissected ; and on the dorsal region portions, the interspinous,
Bupra-spinous, interlamellar, and common inferior ligaments, can be examined. On those
portions from the lumbar region, in a horizontal section through the spinal canal, the inferior
face of the interlamellar ligaments and the common superior vertebral ligament will be seen ;
while in those from the dorsal region, a good idea will be derived of the common inferior
vertebral ligament. The intervertebral ligaments can be studied in vertical and horizontal
eections of the bodies of the vertebrae from any region.
A second subject, which should be fixed in the third position (see Preparation of the
Muscles), is necessary for the dissection of the supra-spinous, dorso-lumbar, and cervical
ligament. This may be eflPected by removing the muscles which occupy the vertical channels
above the cervical vertebrse (see Preparation of the Cervical Kegions).
Intervertebral Articulations.
The vertebrae articulate : 1. By their bodies. 2. By their spinal or annular
portion. There results from this union two kinds of articulation, which must be
studied separately, as they do not belong to the same class. It is well to mention,
however, that the general details into which this study leads us, apply only to
the articulations uniting the last six cervical vertebrae, all the dorsal and lumbar
vertebrae, and the first sacral vertebra.
Union op the Vertebra by their Bodies. — The articulations forming
this union are so many amphiarthroses.
Articular surfaces. — The vertebral bodies come into contact by the surfaces
which terminate them before and behind. In the cervical region these surfaces
represent, anteriorly, a real head ; posteriorly, a cotyloid cavity which receives the
head of the next vertebra. Beginning from the first dorsal vertebra and passing
on to the sacrum, these surfaces tend to become effaced and more and more
plane, though they still preserve their convexity and concavity.
Means of union. — 1. By fibro-cartilages interposed between the articular
surfaces. 2. By a common superior vertebral ligament. 3. By a common
inferior vertebral ligament,
a. Intervertebral fihro-cartilages (Fig. 121, 1, 1). — These are circular or
elliptical discs, convex in front, concave behind, and soUdly fixed by their faces
to the articular planes which they separate. The fibro-cartilaginous substance
composing them consists of concentric layers, which become denser and closer to
each other as they near the circumference ; they even disappear towards the
centre of the disc, where this substance becomes pulpy, and assumes the histo-
logical characters of pure cartilage. It may be remarked, that each of these
layers is made up of a collection of thick parallel filaments, which cross with
those of other layers Hke an X, and are attached by their extremities to the
articular surfaces. From this aiTangement results so intimate an adherence
between the vertebral bodies and their intermediate fibro-cartilages, that an
attempt to disunite them is more likely to cause a fracture of the former. The
fibro-cartilages, thicker in the cervical and lumber regions than in the dorsal,
respond by their circumference to the two common ligaments. Those which
separate the vertebrte of the back concur to form the intervertebral cavities,
intended for the reception of the heads of the ribs, and give attachment to the
interosseous costo-vertebral ligaments.
h. Common superior vertebral ligament (Fig. 126, 1). — This ligament extends
from the axis to the sacrum, and is lodged in the spinal canal. It is a long
fibrous band cut on its borders into wide festoons. By its inferior face, it is
attached to the intervertebral discs, and the triangular imprints on the upper
faces of the bodies of the vertebrte. Its superior face is in contact with the dura
180 THE ARTICULATIONS.
mater, tlirough the medium of an abundant cellulo-adipose tissue. Its borders
are margined by the intra-vertebral venous sinuses (venm basium vertehrarium).
c. Common inferior vertebral ligament (Fig. 127, 5). — Situated under the
spine, this ligament is absent in the cervical, and the anterior third of the dorsal
region. It only really begins about the sixth or eighth vertebra of the latter
region, and is prolonged in the form of a cord — at first narrow, then gradually
widening until it reaches the sacrum, on the inferior surface of which it
terminates by a decreasing expansion. From its commencement, it is attached to
the inferior crests of the bodies of the vertebrae and the intervertebral discs. By
its inferior face, it is in contact with the posterior aorta.
(Leyh commences this ligament at the seventh cervical vertebra, and says
that it adheres to the crests on the bodies of the dorsal and lumbar vertebrae, as
well as to the lower face of the sacrum and coccyx. At the fifth dorsal vertebra
it widens and thickens, and in the lumbar region is bound up with the pillars
of the diaphragm, and confounded on each side with the large ligaments of the
pelvis.)
Union of the Vertebra by their Spinal Portions. — Each vertebra, in
uniting by its annular portion with that which follows or precedes it, forms a
double arthrodial joint.
Articular surfaces. — These are the facets cut on the anterior or posterior
articular processes, and which have been described when speaking of the vertebrse
themselves. They are covered by a thin layer of cartilage.
Means of union. — 1. A common supra-spinous ligament. 2. Interspinous
ligaments. 3. Interlamellar ligaments. 4. Ligamentous capsules, proper to the
articular processes.
a. Capsules proper to the articular processes (Fig. 124, 5). — Each anterior
articular process is maintained against the corresponding posterior process, by a
direct band. This is a peripheric capsule attached around the diarthrodial facets,
lined by a synovial membrane which facilitates their gliding, and covered,
outwardly, by the insertions of some spinal muscles. These capsules, yellow and
elastic in the cervical region, are composed of white fibrous tissue in the dorso-
lumbar region. Very developed at the neck, in consequence of the thickness of
the articular tubercles they envelop, they become reduced, near the middle of
the back, to some fibres which cover, outwardly, the diarthrodial facets in
contact.
b. Common supraspinous ligament. — This ligament, the name of which suffi-
ciently indicates its situation, extends from the sacrum to the occipital bone, and is
divided into two portions — one posterior, or supraspinous dor so-lumbar ligament ;
the other anterior, or supraspinous cervical ligament. These two ligaments,
although continuous with one another, yet differ so strikins^ly in form and
structure that they are best described separately.
1. Supra-dorso-lumbar ligament (Fig. 127, 2). — This is a cord of white
fibrous tissue, which commences behind on the sacral spine, and ceases in front,
about the inferior third of the dorsal region, by insensibly assuming the texture
and elasticity of the cervical ligament, with which it is continuous. It is attached
in its course to the summits of all the lumbar spinous processes, and to the ten or
twelve last dorsal. On the sacral spine, it is confounded with the superior
ilio-sacral ligaments. In the lumbar region, it is united on each side to the
aponeuroses of the longissimus dorsi muscles.
2. Supraspinous cervical, or simply cervical ligament {ligamentum nucha, liga-
ARTICULATIONS OF THE SPINE.
181
mmtum colli) (Fig. 120, 1, 2). — This ligament is entirely formed of yellow
fibrous tissue, and constitutes, in the median plane of the body, a very remarkable
elastic apparatus, which separates the superior cervical muscles of the right side
from those of the left, and plays the part not entirely of an articular band, but
rather of a permanent stay, charged to balance the weight of the head.
In the cervical ligament there is distinguished a fumriiJar and a lamellar
portion. The first, usually called the cord {funicular or cordiform portion) of the
ligament, is a wide funiculus which extends directly from the first dorsal spinous
Fig. 120.
CERVICAL LIGAMENT AND DEEP MUSCLES OF THE HORSE S NECK.
1, Lamellar portion of the cervical ligament ; 2, funicular portion of the same.
processes to the summit of the head. Divided into two lateral lips by a median
groove, this cord is continued posteriorly by the dorso-lumbar ligament, and is
inserted, anteriorly, into the tuberosity of the occipital bone. It is covered above
by a mass of fibro-adipose tissue, which, in certain common-bred horses, is very
abundant. Below, it gives rise, in its posterior two-thirds, to the majority of the
fibres belonging to the lamellar portion. On the sides, it receives the insertions
of several cervical muscles. The lamellar portion — comprised between the funicular
portion, the spinous processes of the second dorsal vertebra, and the cervical
182
THE ARTICULATIONS.
vertebrae, constitutes a vast triangular and vertical septum, which itself results from
the apposition of the two laminae that lie back to back, and are united by
connective tissue ; they are bordered above by the two lateral lips of the cord. The
elastic fibres which enter into their composition are given off either from the
latter, or from the spinous processes of the second and third dorsal vertebrae ;
they are directed downwards or forwards, and reach the spinous processes of the
last six cervical vertebrae, into which they are inserted by so many digitations,
becoming confounded with the interspinous ligaments of the neck. The fibres
of the two last digitations are few in number, widely separated from one another,
and united by many anastomosing branches, which make them appear as a kind
of wide network. The lamina of the cervical ligament are in relation, outwardly,
with the superior branch of the ilio-spinal ligament, the intertransversalis colli
muscles, and the complexus muscle.
(This important structure, which is, in reality,
the mechanical stay and support of the heavy head
and neck of quadrupeds, and is usually temied the
ligamentvm nucJm, is all but absent in Man, being
represented in him by a tliin narrow band — or rather
two thin planes of fibres, the ligamenta suhflava. It
is described by Leyh as if there were not two portions,
and that excellent anatomist does not appear to insist
suificiently on the difference between the dorso-nuchal
and the dorso-lumbar divisions. Percivall, who almost
entirely neglects the ligaments, also makes no distinc-
tion. The difference in structure, elasticity, and
situation, wairants the distinction made by Chauveau.
As already indicated, the function of this ligament —
and more particularly of its nuchal division — is to
maintain the head and neck in their natural position
during repose, and to allow the most extensive move-
ments at other times.)
c. Interspinous Ugaments (Fig. 121, 3). — Fibrous
laminae fill the interspinous spaces, and are attached,
before and behind, to the opposite borders of the spinous
processes, which they unite. They are confounded
superiorly with the supra-spinous hgament, and are continued inferiorly by the
interlamellar ligaments — forming two lateral planes which are applied against each
other, hke the laminae of the cervical ligament, and covered outwardly by the inter-
transversalis colli muscles.
In the region of the neck, the interspinous ligaments are yellow and elastic.
In the dorso-lumbar region, they are formed by fasciculi of white fibrous tissue,
loosely united to each other at their extremities, and directed very obliquely
backwards and downwards. In consequence of this disposition, and notwith-
standing their inextensibility, they permit the separation of the spinous processes.
Their lateral surfaces are divided by a layer of grey elastic fibres, which cross hke
an X the direction of the preceding fasciculi. Very abundant in the anterior
moiety of the dorsal region, these fibres operate, by their proper elasticity, in
bringing the spinous processes towards each other.
d. Interlamellar, or interannular ligaments. — Situated, as their name indicates,
between the vertebral laminae, and divided into two lateral moieties, these
INTERVERTEBRAL ARTICULA-
TIONS.
A, B, C, Bodies of three dorsal
■vertebrse divided longitudi-
nally ami vertically to show
(1, i) a section of the inter-
vertebral discs ; 2, supra-
spinous dorso-lumbar liga-
ment ; 3, interspinous liga-
ment ; 4, fibrous fascia, con-
stituting the proper capsule
of the articular processes in
the dorsal region.
ARTICULATIONS OF THE SFINE. 183
ligaments appear to be produced by the two fibrous planes of the preceding
ligaments, which, on arriving at the base of the spinous processes, separate from
one another to be carried outwards. Their anterior border is inserted into the
posterior margin of the vertebral lamina in front. Their posterior border is fixed
to the anterior border and inferior face of the lamina behind. Their superior
face is in relation with some spinal muscles, and their inferior face is in contact
with the dura mater. Outwardly, they are confounded with the capsules proper
to the articular processes. Yellow and elastic in the cervical region, these
ligaments are Avhite and inelastic in the dorso-lumbar region.
Ohaeactees proper to some Intervertebral Articulations. 1. Inter-
coccygeal ana sacro-coccijgeal articulations. — These articulations are adapted to the
rudimentary type of the vertebrae they unite. The coccygeal bones only come in
contact by their bodies — their spinal laminse being reduced to the merest traces,
or are altogether absent. The anterior and posterior articular surfaces of each
vertebra are convex, and the interarticular fibro-cartilages, hollow on both faces,
resemble a biconcave lens. With regard to the peripheral bands, they are repre-
sented by a bundle of longitudinal fibres spread over the surface of the bones,
which they envelop in a common sheath.
2. Intersacral articulations. — The sacral vertebras being fused into one piece
— the OS sacrum — there is no occasion to study the true articulations in this
region. It may be remarked, however, that the supra-spinous dorso-lumbar liga-
ment is continued on the sacral spine, and that there exist between the processes
formed by this spine, true interspinous ligaments.
3. Sacro-lumhar articulation. — In this articulation, the great thickness of the
fibro-cartilage is to be remarked ; and, in addition, that the last lumbar vertebra
corresponds with the sacrum not only by its body and articular processes, but
also by the oval and slightly concave facets shown on the posterior border of its
transverse processes, which are adapted to analogous slightly convex facets on the
sides of the base of the sacrum. The bundles of fibres thrown from one bone to
another from around these sacro-transversals (real planiform diarthroses) maintain
the articular surfaces in contact, and cover, outwardly, the synovial membrane
which facilitates their gUding.
4. Articulation of the tivo last lumbar vertebrce. — This is distinguished by the
presence, between the transverse processes, of a planiform diarthrosis, like that of
the sacro-transversal just noticed. These two articulations are only found in
Solipeds.
5. Atlo-axoid articulation. — This is so far removed by its conformation and
special uses from the other intervertebral articulations, that it will be described
as an extrinsic articulation of the head and spine. (See Articulations of the Head.)
The Movements of the Spine in general. — Each intervertebral articula-
tion is the seat of very obscure movements, the separate study of which offers
little interest. But these movements, when conjoined with those of the other
articulations, result in bending the whole spine in a somewhat marked manner,
and producing either the flexion, extension, or lateral inclination of this flexuous
column.
When flexion takes place, the spine is arched upwards, the common inferior
ligament is relaxed, the spinous processes separate from one another, and the
supra-spinous ligament, becoming very tense, soon imposes limits to this movement.
Extension is effected by an inverse mechanism, and is checked by the tension
of the common inferior ligament and the meeting of the spinous processes.
181
THE ARTICULATIONS.
Lateral inclination takes place when the spine bends to one side. This
movement is very easily executed in the cervical and coccygeal regions, but is
arrested by the ribs and the costiform processes in the dorso-lumbar region.
A circumflex movement is possible at the two extremities of the vertebral
column— neck and tail ; for they pass easily from extension to lateral inclination,
and from tliis to flexion, etc.
Owing to the elasticity of the intervertebral fibro-cartilages, the spine is
endowed with a very limited amount of rotation, or rather of torsion.
For the special study of the movements of each spinal region, reference must
be made to what has been already said (,p. U) regarding tlie mobility of this
part.
Fig. 122.
CERVICAL LIGAMENT OF THE OX.
L, l', The two laminse which form the cord of the cervical ligament : 1, 2, 3, 4, the four anterior
digitations of the cordiform portion. R, Its accessory portion : 5, first dorsal vertebrae ; 6, 6, 6,
interspinous ligament of the dorsal region.
Differential Characters in the Vertebral Articulations and Ligaments in the
OTHER Animals.
A. In the Ox the intervertebral discs are much thicker than in the Horse. The common
inferior vertebral ligament is very strong in the lumbar region. The supraspinous dorso-lumhar
ligamsnt is composed of yellow elastic tissue. The cervical ligament is much more developed
than in Solipeds,in consequence of the greater weight of the head ; and it presents a conforma-
tion altogether special, which M. Lecoq has made known in the following terms : " On lenving
the withers, the stipra- spinous ligament ceases to cover the head of the spinous processes, and
extends from each side in a wide and strong band, taking points of attachment on the sides of
the processes, and becoming separated, on leaving that of the first dorsal vertebra, into two
parts — a superior and inferior. The first reaches the cervical tuberosity in the form of a thick
cord united to the cord of the opposite; the other thins off into a band, which is attached to
the posterior half of the spinous process of the axis, and to that of the third and fourth vertebrae.
A production of the same kind — an auxiliary to the principal portion — leaves the anterior border
of the spinous process of the first dorsal vertebra, and is attached to that of the fourth, fifth,
ARTICULATIONS OF THE SPINE.
185
sixth, and seventh vertebrae. The superior border of this auxiliary ligamentous production, is
concealed between the two lamiua of the principal ligament." '
B. Camel. — In this animal, the common supraspinous ligament is entirely composed of
yellow elastic tissue ; it is therefore impossible to distinguish, physically, a dorso-lumbar and a
cervical portion. It is remarkable for its thickness and width ; and its dimensions increase
from behind to before, especially from the second lumbar vertebra. At the fifth, sixth, seventh,
eighth, ninth, and tenth dorsal vertebrae an elastic band is given off fi om its borders ; as this
descends, it gradually becomes thinner until it reaches the external intercostal muscles.
From the ninth dorsal vertebra, the supraspinous ligament divides into two layers, which
are placed against the lateral faces of the spinous processes. In the cervical region, the layers
Fig. 123,
kt^i^l^^-^
^i
x\\\-^
CERVICAL LIGAMENT OF A YOUNG CAMEL.
become rounded, are joined to each other by means of connective tissue, and describing an S-
shaped curve, become inserted into the occipital bone.
They give oflf, from their inferior border, six digitations, which are attached to the spinous
processes of tlie last six cervical vertebrae. An accessory leaf is situated between the two
portions just described : it is detached from the anterior border of the spinous process of the
first dorsal vertebra, and is fixed anteriorly into the two last cervical vertebrae.
C. Pig. — The Pig, remarkable for the shortness of its neck and the limited movements of
this region, does not show any cervical ligament, properly so called. It is replaced by a super-
ficial fibrous raphe', extending from the occipital bone to tlie spinous process of the first dorsal
vertebra.
^Journal de MMecine VeW-inaire, p. 122. Lyons, 1848.
186 TEE ARTICULATIONS.
D. Camivora. — The Cat has no cervical ligament, and shows, instead, a raphe like the
Pig. In the Dog, the ligament is reduced to a simple cord, continued from the dorso-lumbar
ligament, and goes no further than behind the spinous process of the axis. In the Cat, the
interspinous ligaments are replaced by small muscular fasciculi ; in the Dog, this substitution
only takes place in the xiervical region. The laminae of the first coccygeal vertebrae possess
the principal characters which distinguish perfect vertebrae, and are united by vestiges of the
articular bands which exist in the other regions of the spine.
Aeticle IL — Articulations of the Head.
We will first study the two extrinsic articulations which are the centre of the
movements of the head on the spine — the atlo-axoid and occipito-athid articula-
tions. Afterwards, we will pass to the examination of the joints which unite the
different bones of the head.
1. Atlo-axoid Articulation (Fig. 124).
Preparation. — It suffices to remove the soft parts from around the articulation, to expose
the interannular, the interspinous, and the inferior odontoid ligament. To examine the superior
odontoid ligament and the synovial membrane, one half the atlas and axis must be separated
by sawing longitudinally through them from oue side to the other.
This may be considered as the type of the trochoid articulation.
Articular surfaces. — To form this articulation, the axis offers its odontoid
pivot and the undulated diarthrodial facets at its base. The atlas opposes to the
pivot the concave semi-cylindrical surface hollowed on the superior face of its
body ; and for the lateral undulated facets it has analogous facets cut on the
transverse processes, on each side of the vertebral canal.
Mode of union. — 1. An odontoid, or odonto-atloid ligament. 2. An inferior
atlo-axoid ligament. 3. A superior ditto. 4. A fibrous capsule.
a. Odontoid ligament (Fig. 124, 3). — Continuous with the common superior
vertebral ligament, very short and strong, flattened above and below, and triangu-
lar in shape, the odontoid ligament is composed of glistening white fibres, fixed
behind in the superior channel of the odontoid process, and inserted in front on
the transverse ridge which separates the superior face from the inferior arch of
the atlas, as well as on the imprints situated in front of this ridge. It is covered,
on its lower face, by the synovial membrane of the articulation ; and its upper
surface is in contact with the spinal dura mater. It sends some bands within the
condyles of the occipital bone.
b. Inferior atlo-axoid ligament. — This is a wide, thin, and nacrous-looking
band, extending from the inferior face of the axis to the inferior tubercle of the
atlas, and is covered by the longus colli muscle ; it is united to the synovial mem-
brane by its deep face, and confounded on its bordei-s with the fibrous capsule to
be immediately described. It represents the common inferior vertebral ligament.
c. Superior atlo-axoid ligament. — This exactly represents the interspinous liga-
ments of the other cervical articulations. Yellow, elastic, and formed like the
two lateral bands, it is continuous, laterally, with the capsular Ugament. It
represents the interspinous and interlamellar ligaments.
d. Capsular ligament. — This, it may be said, is only the interlamellar ligament
proper to the atlo-axoid articulation. It commences from the sides of the pre-
ceding ligament, and becomes united to the inferior atlo-axoid, after contracting
adhesions with the borders of the odontoid Ugament. In this way it encloses the
articulation and the spinal canal. Before and beliind, it is attached to the anterior
or posterior margin of the bones it unites. Its external face is in contact wiih
ARTICULATIONS OF THE HEAD.
187
the great oblique muscle of the head ; its internal responds, in its inferior half,
to the articular synovial membrane, and its superior moiety to the spinal dura
mater. It is analogous to the capsules in other regions.
(Leyh describes this Ugament as the interannular). Fig. 124.
Synovial membrane. — This lines the odontoid ligament
and atlo-axoid ligaments, and the articular portion of the
peripheral capsule.
Movements. — Rotation, the only movement possible in
the atlo-axoid articulation, is effected in the following
manner : the axis remains fixed, and the first vertebra,
drawn to one side chiefly by the great oblique muscle,
rotates on the odontoid pivot, carrying the head with it.
The rotation movements of the head have, therefore,
this diarthrosis for a centre, and not the atloido-occipital
articulation.
In the Dog and Cat, the odontoid ligament is replaced by three
particular ligaments : 1. Two lateral cords, rising in common from the
summit of the odontoid process, and inserted, each on its own side,
within the condyles of tlie occipital bone. 2 A transverse ligament,
passing over the odontoid process, which it maintains in its place
against the itiferior arch of the atlas, and is attached by its extremities
to the superior face of the latter. A small synovial capsule facili-
tates the gliding of the odontoid process beneath this ligament. The
articular synovial membrane always communicates with that of the
occipito-atloid articulation.
In the Pig, the disposition is nearly the same as in the Caruivora.
2. Occipito-atloid Articulation (Fig. 124).
(^Preparation. — Dissect away all the soft parts that pass from the
neck to the head and cover the articulation, and more particularly
the flexor, the recti, and the small oblique muscles of the head. To
expose the synovial membranes, open the sides of the capsular
ligament.)
This is a condyloid articulation.
Articular surfaces. — In the atlas, the two cavities which
replace the anterior articular processes and the heads of the
other vertebrfe ; in the occipital bone, the two condyles
flanking the sides of the occipital foramen.
Mode of union. — A single capsular ligament envelops
the entire articulation ; it is attached by its anterior border
to the margin of the occipital condyles, and by its posterior
to the anterior contour of the atlas. Thin and slightly
elastic in its inferior half, this ligament presents, supe-
riorly, four reinforcing fasciculi : two middle, which inter-
cross in X — whence the name "cruciform," sometimes
given to this ligament (Fig. 124, 1, 1) ; and two lateral,
which pass from the sides of the atlas to the base of
the styloid processes (Fig. 124, 2, 2). It is lined by
the synovial membranes, and is enveloped externally by a
large number of muscles, which protect the articulation and greatly strengthen
it everywhere. Among these may be particularly noticed the recti muscles of
ATLO-OXOID AND OCCIPI-
TO-ATLOID ARTICULA-
TIONS (the upper arch
of the atlas has been
removed to show the
odontoid ligament).
1, 1, Middle accessory fas-
ciculi ; 2, 2, lateral
fasciculi of the capsular
ligament of the occipi-
to-atloid articulation ;
3, odontoid ligament ;
4, interspinous liga-
ment uniting the second
and third vertebrae of
the neck ; 5, fibrous
capsule uniting the
articular processes of
these vertebrae. A,
Anterior internal fora-
men of the atlas con-
verted into a groove by
the section of the bone;
B, B, vertebral foramina
of the atlas ; C, C, fora-
mina replacing the an-
terior notches of the
axis.
188
THE ARTICULATIONS.
the head, the small oblique, and the complexus. There is also the cord of the
cervical ligament,
Sijiiovial membranes. — These membranes are two in number — one for each
condyle and coiTesponding atloid cavity. Sustained above, below, and outwardly
by the capsular ligament, they are related inwardly to the dura mater and the
fibrous tractus which, from the odontoid ligament, is carried to the internal face
of the occipital condyles.
Movements. — Extension, flexion, lateral inclination, and circumduction, are the
movements of the occipito-atloid articulation.
In the Pig, Dog, and Cat, this articulation— strengthened, as it is, by the capsular and
odontoido-occipital ligaments already mentioned — has only one synovial capsule.
3. Aeticulation of the Bones of the Head with each other.
If we except the articulation which unites the inferior jaw to the cranium —
the temporo-maxillary — and the hyoideal articulations, it will be found that all
the bones of the cranium and face are united to each other by synarthrosis,
forming the different kinds of sutures already generally described (p. 170).
Nothing is to be gained by entering into more detail with regard to these articu-
lations, as it will be found sufficient to call to mind the topographical description
of each bone entering into their formation.
4. Temporo-maxillary Articulation (Fig. 125).
{Preparation. — Remove the masseter muscle and the parotid gland. Saw through the
head about the middle liue. Open the articulation externally, to exhibit the interarticular
meniscus.)
The lower jaw, in its union with the cranium, constitutes a double condyloid
articulation.
F'g 125. Articular surfaces. — With the temporal bone,
these are the condyle, the glenoid cavity, and the
supra-condyloid process at the base of the zygomatic
process. The glenoid cavity is not lined by cartilage,
and appears to be merely covered by synovial mem-
brane. On the maxillary bone is the oljlong condyle
situated in front of the coronoid process.
Interarticular fihro-cartilage. — The articular sur-
faces just named are far from fitting each other
accurately ; this is only accompUshed by the inter-
position of a fibro-cartilaginous disc between the
temporal and maxillary bones. This disc is a kind
of irregular plate, flattened above and below, thicker
before than behind, and moulded on each of the
diarthrodial surfaces it separates. Its superior face,
therefore, presents : in front, a cavity to receive
the condyle of the temporal bone ; behind, a boss
which is lodged in the glenoid cavity. The inferior
face is hollowed by an oblong fossa, in which the
maxillary condyle is lodged (Fig. 125, 1).
Mode of union. — A fibrous envelope — a true capsular ligament — surrounds the
articulation, aiid is attached by its borders to the margin of the articular surfaces
it unites. Formed, outwardly, by a thick fasciculus of white vertical fibres (Fig,
TEMPORO-MAXILLARY ARTICU-
LATION .
1, Interarticular fibro-cartilag;e ;
2, external fasciculus of the
capsular ligament. A, Base of
the coronoid process ; B, neck
of the maxillary condyle; C,
mastoid process ; D, external
auditory hiatus.
ARTICULATIONS OF THE HEAD. 189
125, 2), this ligament becomes greyish-coloured and elastic for the remainder of
its extent, and greatly diminishes in thickness, especially in front. Its inner
face IS covered by the synovial capsules, and adheres to the circumference of the
interarticular fibro-cartilage. Its external face is related, in front, to the temporal
and masseter muscles ; behind, to the parotid gland ; inwardly, to the external
pterygoid muscle ; and outwardly, to a fibrous expansion which separates it from
the skin. (Leyh mentions a lateral external and a posterior ligament for this
articulation, but Chauveau and Bigot evidently look upon these as portions of
the capsular.)
Synovial membranes. — This articulation has two synovial sacs — one above the
other — which are separated by the fibro-cartiiaginous disc.
Movements. — The temporo-maxillary articulation is the centre of all the
movements performed by the lower jaw. These are : depression, elevation, lateral
motion, and horizontal gliding.
The lower jaw is depressed when it separates from the superior one, and is
elevated when it approaches this. These two opposite movements are executed by
a mechanism of such great simplicity, that it need not be described here. Lateral
movements take place when the inferior extremity of the jaw is carried alternately
to the right and left. It then happens that one of the maxillary condyles, taking
with it the fibro-cartilage, is brought into contact with the temporal condyle,
while the other is embedded in tiie glenoid cavity of the opposite side. The
horizontal gliding is effected from behind to before, or vice veisd. In the first
case, the two maxillary condyles are carried at the same time under the temporal
condyles, bearing with them the fibro-cartilages. In the second case, they are
drawn into the glenoid cavities, and rest against the supra-condyloid eminence,
which prevents their going further. It will be understood, after this brief
description, that the presence of the fibro-cartilages singularly favours the lateral
movements and horizontal gliding of the lower jaw.
In the Pig, the temporo-maxillary articulation is formed after the same type as that of
Rodents, and allows very extensive movements from before to behind — a circumstance due to
the complete absence of the supra-condyloid eminence.
In the Dog and Cat, the maxillary condyle is exactly fitted to the temporal cavity. This
disposition, in giving great precision to the movements of depression and elevation, restrains in
a singular manner the lateral and horizontal gliding motions. The interarticular fibro-cartilage
is extremely thin in these animals.
In the Rabbit, the narrow condyle of the maxilla moves from before to behind and to
each side, on the temporal bone, the articular surface of which is very elongated and destitute
of a subglenoid eminence.
5. Hyoideal Aeticulations.
(Preparation. — Disarticulate the lower jaw, and dissect away from the right of each
articulation the muscles that may conceal the view.)
These are of two kinds — extrinsic and intrinsic. The first comprise the two
tempo ro-hyoideal articulations ; to the second belong the joints which unite the
different pieces of the hyoid bone — the interhyoideal articulations.
Temporo-hyoideal Articulations. — These are two amphiarthrodial joints,
in the formation of which each great cornu of the hyoid bone opposes its upper
extremity to the hyoideal prolongation lodged in the vaginal sheath of the
temporal bone. An elastic cartilage, from -^q to i%- of an inch in length, unites
the two bones in a solid manner ; and it is owing to the flexibility of this
cartilage that the hyoid bone can move entirely on the temporal bones.
15
190 THE ARTICULATIONS.
Inter-hyoideal Articulations. — A. The great cornu articulates with the
small one, by an amphiarthrosis analogous to the preceding. To form this articu-
lation, these two pieces of bone are joined at an acute angle, through the medium
of a more or less thick cartilaginous band, in the centre of which there is often
a little bony nucleus— the styloid nucleus, or kerato-hyal bone. This cartilage is
elastic and flexible, and permits the opening and closing of the articular angle at
the summit of which it is placed.
B. Each styloid cornu is united to the body of the hyoid bone, or basihyal,
by an arthrodial articulation. The articular surfaces are : for the hyoideal
branch, the small cavity terminating its inferior extremity ; for the body, the
convex lateral facet situated at the origin of the thyroid cornua. These surfaces
are covered by cartilage, and enveloped by a small synovial sac and a peripheral
fibrous capsule. They can ghde on each other in nearly every direction. (Median
and superior hyoideal capsular ligaments are described by Leyh as sometimes
present. The latter unites the upper and middle branches, and the former the
middle with the inferior branches. They are absent when these branches are
confounded with the superior ones.)
Article III. —Articulations of the Thorax.
These are also divided into extrinsic and intrinsic. The first — named costo-
vertebral—unite the ribs to the spine. The second join the different bones of the
thorax together ; they comprise : 1. The chondro-sternal articulations, 2.
Chondro-costal articulations. 3. The articulations of the costal cartilages with
each other. 4. The sternal articulation perculiar to the larger Ruminants and
the Pig. All these joints will be first studied in a special manner, then examined
in a general way as to their movements.
Extrinsic Articulations.
Articulations of the Ribs with the Vertebral Column, or Costo-
vertebral Articulations.
(Preparation.— This is simple. No difficulty need be experienced except in exposing the
interartieular ligament, and this is efifected by sawing tlirough one of the dorsal vertebra
transversely, close to the posterior intervertebral joint formed by that bone. A few cuts of the
bone forceps will then show the whole extent of the ligament.)
Each rib articulates with the vertebral column by two points — its head and
its tuberosity. The first is received into one of the intervertebral cavities
hollowed out on the sides of the spine, and is therefore in contact with two doi-sal
vertebrfe ; the second rests against the transverse process of the posterior vertebra.
From this an'angement arises two particular articulations belonging to the
arthrodial class, which are named costo-vertehral and costo-transverse.
Costo-vertebral Articulations. — Articular surfaces. — Pertaining to the
rib, we have the two convex facets of the head, separated from each other by a
groove of insertion, and covered by a thin layer of cartilage. On the vertebras,
the concave facets which, by their union, form the intervertebral cavity ; these
facets are also covered with cartilage, and separated, at the bottom of the cavity,
by the con'esponding intervertebral disc.
Mode of union. — 1. An interartieular ligament (Figs. 126, 2 ; 127, 1), fixed
in the groove in the head of the rib, and attached to the superior border of the
ARTICULATIONS OF THE THORAX.
191
intervertebral disc, Avhich it encii-cles upwards and inwards, to unite on the median
line with the ligament of the opposite side. 2. An inferior peripheral ligament
(Fig. 127, 2, 3, 4), flat above and below, thin and radiating (whence it is often
named the stellate ligament), formed of three fasciculi, wliich are fixed in common
on the inferior face of the head of the rib, and in diverging are carried over the
bodies of the two vertebrte and the intervertebral disc. Lmed above by the
synovial membranes, this ligament is covered below by the pleura. (Leyh includes
a capsular ligament for the head of the rib, and another for the costal tuberosity.
He probably considered the synovial membrane of these articulations as such.)
Synovial membranes. — These are two in number — an anterior and posterior,
lying against each other, and separated in part by the interarticular ligament
they cover. Supported below by the stellate ligament, above they are directly in
contact with the levatores costarum muscles, and with vessels and nerves.
CosTO-TRANSVERSE ARTICULATIONS. Avticular surfttces. — In the rib, the
Fig. 127.
Fig. 126.
articulations of the ribs with the ver-
tebra, and of these with each other
(upper plane).
1, Spinal canal, upper face, showing the common
superior ligament; 2, interarticular costo-
vertebral ligament ; 3, interosseous costo-
transverse ligament ; 4, posterior costo-trans-
verse ligament.
ARTICULATIONS OF THE RIBS WITH THE
VERTEBRA, AND OF THESE WITH EACH
OTHER (INFERIOR PLANE).
1, Interarticular costo-vertebral liga-
ment ; 2, 3, 4, fasciculi of the stellate,
or inferior costo-vertebral ligament; 5,
common inferior vertebral ligament.
diarthrodial facet cut on the tuberosity. In the vertebra, the analogous facet on
the outside of the transveree process.
Mode of union. Two ligaments bind this articulation : 1. The posterior costo-
transverse ligament (Fig. 126, 4), a white fibrous band attached by its extremities
behind the transverse process and the costal tuberosity, lined by synovial mem-
brane, and covered by the transverse insertions of several spinal muscles. 2. The
anterior costo-transverse., or interosseous ligament (Fig. 126, 3), a fasciculus of
short, thick, white fibres, fixed on the anterior surface of the transverse process
near its base, and in the rugged excavation on the neck of the rib. This liga-
ment is invested, posteriorly, by the synovial membrane, and covered in front by
pads of adipose tissue which separate it from the costo-vertebral articulation.
Synovial membrane. — This is a small particular capsule, kept apart from the
posterior synovial membrane of the costo-vertebral articulation by the costo-trans-
verse interosseous ligament.
Characters peculiar to some Costo-vertebral Articulations. — 1.
The first, and sometimes the second, costo-vertebral articulation has no inter-
osseous ligament, and only exhibits one synovial membrane. The intervertebral
192 THE ARTICULATIONS.
cavity which concurs in forming the first is often excavated between the last
cervical and first dorsal vertebras.
2. The two or three last costo-transverse articulations are confounded with
the corresponding costo-vertebral joints. They have no proper serous membrane,
but the posterior synovial membrane of the latter is prolonged around their
articular surfaces.
Intrinsic Articulations.
A. The Chondro-sternal or Costo-sternal Articulations.
{Preparation. — To show the articulation of the ribs with the cartilages, these with the
sternum, and the cartilages with each other, carefully remove the pleura, the triangularis
sterui muscle, the diaphragm, tlie transverse muscle of the abdomen, then the pectorals, the
great oblique, the transversalis of the ribs, and the intercostal muscles.)
The first eight ribs, in resting upon the sternum by the inferior extremity of
their cartilages, form eight similar arthrodial articulations.
Articular surfaces. — Each sternal cartilage opposes to one of the lateral cavities
of the sternum, the convex and oblong facet at its lower extremity.
Mode of union. — The diarthrosis resulting from the union of these two surfaces
is enveloped everywhere by bundles of white, radiating, fibrous tissue, which con-
stitute a veritable ligamentous capsule. The superior part of this capsule — known
as the stellate or superior costo-sternal ligament, is covered by the triangularis
sterui muscle ; it is joined to a fibrous cord lying on the superior face of the
sternum, and which is confounded in front with that of the opposite side. The
inferior portion — the irtferior stellate or costo-sternal ligament — is in relation
with the pectoral muscles.
Synovial ccqysule. — There is one for each articulation.
Characters proper to the first costo-sternal articulation. — The first costo-sternal
articulation is not separated from its fellow of the opposite side ; so that these two
joints are, in reality, only one, and the two cartilages lying close to each other
correspond by a small diarthrodial facet, continuous with that for the sternum.
The two sternal facets are inclined upwards, and confounded with one another.
Only one synovial cavity exists for this complex articulation, which unites the
two first ribs to each other and to the sternum.
B. Chrondo-costal Articulations uniting the Ribs to their
Cartilages.
These are synarthrodial articulations, the movements of which are very
obscure. They are formed by the implantation of the cartilages in the nigged
cavities the ribs present at their inferior extremities. The solidity of these articu-
lations is assured by the adherence of the fibro-cartilages to the proper substance
of the ribs, and by the periosteum which, in passing from the bone to the cartilage,
plays the part of a powerful peripheral band.
In the Ox, the sternal ribs, in uniting with their oartilages, form a true ginglymoid diar-
throsis, the movement of whicli is facilitated by a small synovial capsule.
C. Articulations of the Costal Cartilages with each other.
The ribs, attached to each other by means of the intercostal muscles, are not
united by real articulations ; neither are their cartilages of prolongation. But
ARTICULATIONS OF THE THORAX. ■ 193
the asternal cartilages are bound together by a small yellow elastic ligament, which
is carried from the free extremity of each to the posterior border of the preceding
cartilage ; the anterior border of the first asternal cartilage is directly united to
the posterior border of the last sternal cartilage, through the medium of the
perichondrium and very short Kgamentous bands. This same asternal cartilage
is also bound to the inferior face of the xiphoid appendage by a small white
ligament (the chondro-xiphoicl), under which passes the anterior abdominal
artery.
D. Sternal Articulation peculiar to the Ox and Pig.
It has been already shown that in these animals the anterior piece of the sternum is not
consolidated with the second portion. Tlie two are united by a diurthrodial articulation ; and
for this purpose the anterior presents a concave surface, the posterior a convex one. Bundles
of peripheral fibres firmly bind tliem to each other, and a special small synovial capsule facili-
tates their movements, which are very limited.
The Articulations of the Thorax considered in a General Manner,
with Regard to Movements.
The thorax can increase or diminish in diameter, in an antero-posterior and
a transverse direction ; whence arise the dilatation and contraction of this cavity —
the inspiratory movements accompanying the entrance of the external air into
the lungs, and the expiratory movements expelling the air contained in these
organs.
The variations in the antero-posterior diameter of the chest being due to
changes in the figure of the diaphragm, need not be noticed here. But the
transverse variations being the result of the play of the costal arches on tjie spine
and sternum, it is advantageous to study the mechanism which presides in the
execution of theii' movements.
The costal arches, being inclined backwards on the middle plane, the space
they enclose in their concavity is not nearly so extensive as if they were perpen-
dicular to this plane. Owing to their double arthrodial joints, the ribs are
movable on the spine ; and their inferior extremity, also movable, rests either
directly or indirectly on the sternum. Therefore it is that, when they are drawn
forward by their middle portions, they pivot on theii' extremities, and tend to
assume a perpendicular direction, which is the most favourable for the largest
increase of the space they limit ; then there is enlargement of the lateral diameter
of the thorax, which signifies dilatation of its cavity. The inverse movement, by
an opposite mechanism, causes contraction of the chest.
The ribs are said to be elevated during the forward movement, and depressed
when they fall backwards. These expressions, though perfectly applicable to Man,
who stands in a vertical position, are not correct when employed in veterinary
anatomy.
Besides the enlargement of the thorax in the transverse and the antero-posterior
directions, it is necessary to remark on an increase in a vertical direction, caused
by the displacement of the sternum forward, due to elevation of the ribs. In this
movement, the costal arches are erected not only on the median plane, but also
on the spine. The inferior extremity, carried forward, also takes the sternum
with it ; and this movement cannot take place without that piece being farther
removed from the vertebrae above. In Man, the displacement of the sternum is
very marked.
194 THE ARTICULATIONS.
AeTICLE IV.---AETICULATIONS OF TRE ANTERIOR LiMBS.
1. SCAPULO-HUMERAL ARTICULATION (Fig. 128).
(Preparation. — Detach the limb from the trunk. Remove from the upper extremity those
muscles which are inserted in the vicinity of the glenoid cavity of the scapula ; turn down from
its lower extremity those which are inserted into the superior end of the humerus or a little
below, preserving the attachments of their tendons with the capsular ligament. The seapulo-
humeralis gracilis muscle may be allowed to remain, in order to show its relations.)
To constitute this enarthrodial articulation, the scapula is united to the
humerus, and forms an obtuse angle which is open behind.
Articular surfaces. — In the scapula there is the glenoid cavity — the shallow,
oval fossa, elongated in an antero-posterior direction, notched inwardly, and
excavated at its centre, or near the internal notch, by a small synovial f ossette. A
ligamentous band, attached to the brim of the cavity, fills up this notch, and is
the vestige of the glenoid ligament of Man. In the humerus, the articular head,
fixed between the large and small tuberosities, is often excavated by a shallow
synovial f ossette.
Mode of union. — One capsular ligament (Fig. 128, 1), a kind of sac having two
openings — one inferior, embracing the head of the humerus ; and a superior, inserted
into the margin of the glenoid cavity. This capsule presents, in front, two sup-
porting fasciculi, which diverge as they descend from the coracoid process to the
great and small tuberosities. The aponeurotic expansion thus formed is very
thin and loose, so as to allow the two bones to separate to the extent of from
-f*Q to y^o of an inch ; but it is far from being sufficiently strong to bind them
firmly together. The articulation is, therefore, strengthened by the powerful
muscles which surround it, among which maybe noticed : 1. In front, the coraco-
radialis (flexor brachii), separated from the fibrous capsule by an adipose cushion.
2. Behind, the large extensor of the forearm and scapulo-humeralis gracilis (or
teres minor) muscles, the use of which appears to be to pull up this capsule during
the movements of flexion, so as to prevent its being pinched between the articular
surfaces. 3. Outwards, the short abductor of the arm and the infra-spinatus (postea
spinatus) tendon. 4. Inwards, the wide and strong tendon of the subscapularis
muscle. In addition to this powerful retaining apparatus, there is the atmospheric
pressure, the influence of which is of a certain importance. This may be proved
by removing all the surrounding muscles, when it will be found that the capsule
is not relaxed, nor are the articular surfaces separated ; to effect this, it is neces-
sary to make an opening in the capsule, so as to allow the air to enter its cavity,
when the surfaces immediately fall apart.
Synovial capsule. — This is very loose, and entirely enveloped by the peripheral
capsule, the internal surface of which it lines.
Movements. — Like all the enarthrodial articulations, the scapulo-humeral
permits extension, flexion, abduction, adduction, circumduction, and rotation. These
various movements, however, are far from being so extensive as in Man, the arm
in the domesticated animals not being detached from the trunk, but, on the
contrary, is fixed with the shoulder against the lateral parietes of the thorax.
Flexion and extension are the least limited, and the most frequently repeated
movements ; their execution always demands a displacement of the two bones,
wliich are almost equally movable. In flexion, the scapulo-humeral angle is
closed, not only because the inferior extremity of the humerus is carried back-
wards and upwards, but also because the scapula pivots on its superior attach-
ARTICULATIONS OF TEE ANTERIOR LIMBS. 1S5
merits in such a manner as to throw its glenoid angle forward and upward.
Extension is produced by an inverse mechanism. During the execution of the
other movements, the scapula remains fixed, and the humerus alone is displaced,
bringing with it the inferior bones of the limb. If it is carried outwards, we
have abduction, or inwards, adduction ; if the leg passes successively from flexion
to abduction, and from that to extension, etc., in describing a circle by its lower
extremity, then there is circumduction ; if it pivots from left to right, or right to
left, we have rotation.
In the Pig, Dog, and Cat, the synDvial membrane is not exactly enclosed by the fibrous
capsule, but forms in front a cul-de-sac, which descends in the bicipital groove to favour the
gliding of the coraco-radialis tendon.
In Man, the scapulo-humeral articulation is disposed as in animals, but it is also protected
above by the coraco-acromion arch. For the reasons noted above, this articulation allows of
more extensive motion than in animals. As remarked by Cruveilhier, of all the joints in the
human body, tlie scapulo-humeral is that which has the most extensive motion; in movements
forward and outward, the humerus can become horizontal; in those of circumduction it
describes a complete cone, which is more extensive in front and laterally than behind and
inwardly.
2. HuMERO-RADiAL, OE Elbow Aeticulation (Fig. 128).
(^Preparation. — Turn down the inferior extremity of the flexors of the forearm, remove the
•olecranian, epicondyloid, and epitrochlean muscles, taking care not to damage the ligaments
to which they somewhat closely adhere.)
Three bones concur to form this articulation, which presents a remarkable
•example of an angular ginglymus : the humerus, by its inferior extremity, and
the two bones of the arm by their upper extremities.
Artkidar surfaces. — The humeral surface, already described at page 102, is
transversely elongated, and convex from before to behind. It presents : 1. A
median groove excavated by a synovial fossette. 2. An external groove (humeral
trochlea) not so deep as the preceding. 3. A kind of voluminous condyle wliich
borders, inwardly, the internal pulley, and whose antero-posterior diameter is
much greater than that of the external lip of the trochlea of the opposite side.
The antibrachial surface, divided into two portions, is moulded to the humeral
surface ; it is, therefore, concave before and behind, and is composed : 1. Of a
double external groove. 2. Of an internal glenoid cavity, both excavated, on the
superior extremity of the radius. 3. A middle ridge for the middle groove of
the humerus, separating the two preceding surfaces, and prolonged on the ulnar
beak, where it forms the sigmoid notch. This ridge shows a small synovial
fossette hollowed out on the radius and ulna.
Mode of union. — Three ligaments : two lateral and an anterior.
a. The external lateral ligament (Figs. 128, 8) is a thick, short, and strong
funicle, attached above to the crest limiting outwardly and posteriorly the musculo-
.spiral groove, and in the small cavity placed at the external side of the humeral
articular surface. Below, it is inserted into the supero-external tuberosity of the
radius. Its anterior border is confounded with the capsular ligament, and is
margined by the principal extensor of the phalanges, which derives from it
numerous points of attachment. By its posterior border it is in contact with
the external flexor of the metacarpus. Its internal face is lined by synovial
membrane, and its external face is only separated from the skin by the anti-
brachial aponeurosis, and some of the fasciculi from the origin of the lateral
extensor muscle of the phalanges. Its superficial fibres are vertical, and are
196
THE ARTICULATIONS.
continuous, behind, with the arcif orm ligamentous bands which stretch from the
ubia to the radius. Its deep fibres are shghtly obUque downwards and forwards.
b. The lateral internal ligament — also funicular — is longer, but not so strong
as the preceding. It arises from
Fig. 128. the small tuberosity on the inner
side of the superior articular face
of the humerus, and, widening as
it descends, reaches the radius. Its
median fibres, which are the longest,
are directed vertically downwards
to reach the imprints situated below
the bicipital tuberosity ; its anterior
fibres, curved forwards, are united
to the tendon of the coraco-radialis
muscle, or are confounded ^^■ith the
anterior ligament ; the posterior are
turned backwards, near their in-
ferior extremities, to join the arci-
form fibrous fascicuU, which in-
wardly unite the ulna to the radius.
The middle fibres of this Ugament
cover the inferior insertion of the
short flexor of the forearm, and — in
part only — that of the long flexor.
It is covered by the ulna-plantar
nerve and the posterior radial artery
and vein.
c. The anteiior or capsular liga-
ment (Figs. 128, 9) is a membrani-
form band, attached by its superior
border above the humeral articular
surface, and by its inferior to the
anterior margin of the radial sur-
face. By its lateral borders, it is
confounded with the funicular Uga-
ments. Its internal half is formed
of vertical fibres which descend from
the humerus and expand over the
radius, where they become united
with the inferior tendon of the
coraco-radialis muscle. In its exter-
nal moiety it is extremely thin, and
composed of fibres crossed in various
directions. Lined internally by
synovial membrane, this ligament is
in contact, by its external surface,
with the anterior radial vessels and
nerves, the two flexor muscles of
the forearm, the anterior extensor of
the metacarpus, and the anterior extensor of the phalanges. The two latter muscles
6capul0-humeral and humero-radial articula-
tions, with the muscles surrounding them
(external face).
1, Scapulo-humeral capsular ligament ; 2, short ab-
ductor muscle of the arm ; 3, its insertion in the
humerus; 4, insertion of the infra-spinatus muscle
on the crest of the great tuberosity; 5, coraco-radialis
muscle; tj, its tendon of origin ;ittached to the
coracoid process; 7, its radial insertion confounded
with the anterior ligament of the ulnar articula-
tion ; 8, 8, external lateral ligament of that articu-
lation ; 9, anterior ligament ; 10. aconeus, or small
extensor of the forearm ; 11, origin of the external
flexor muscle of the metacarpus; 12, short flexor
muscle of the forearm. A, Tuberosity of the scapii-
lar spine; B, supra-spinous fossa; C, infra-spinous
fossa : D, convexity of the small trochanter ; E,
summit of the ti-ochanter.
ABTICDLATIONS OF THE ANTERIOR LIMBS. 197
are even attached to it in a very evident manner. The elbow articulation, closed
in front and on the sides by the tliree ligaments just described, has no particular
ligaments posteriorly ; but it is powerfully strengthened there by the olecranian
insertion of the extensor muscles of the forearm, and by the tendons of origin of
the five flexor muscles of the metacarpus or phalanges.
Synovial membrane. — This membrane is very extensive, and, stretched out
on the internal face of the before-mentioned hgaments, forms, behind, three great
culs-de-sac of prolongment : a superior, occupying the olecranian fossa, and
covered by a fatty cushion, as well as by the small extensor muscle of the fore-
arm ; ^ two lateral, which descend from each side of the ulnar beak, and are
■distinguished as internal and external — the first lines the tendon of the external
flexor of the metacarpus, the second facilitates the play on the upper radial
extremity of the four flexor muscles of the foot or digits, and which are attached
in common to the epitrochlea. This synovial sac also furnishes the radio-ulnar
articulation with a diverticulum, which descends between the bones of the fore-
arm to below the adjacent diarthrodial facets.
Movements. — Flexion and extension.
In flexion, the two bones do not approach each other directly, the inferior
extremity of the radius deviating a little outwards. This is due more to the
.sHght obliquity of the articular grooves, than to the difference in thickness
between the external and internal extremities of the humeral surface.
Extension is limited by the reception of the beak of the olecranon in its fossa,
and by the tension of the lateral ligaments ; so that the two bones cannot be
straightened on one another in a complete manner, or placed on the same line.
In the Dog and Cat, tlie external lateral ligament is very thick, and forms in its inferior
moiety a fibro-cartilaginous cap wliich is fixed on the ulna and radius, and united in front to
the annular ligament of the superior radio-ulnar joint. This cap, with the last-named liga-
ment, completes the osteo-fibrous ring in wliich the superior extremity of the radius turns.
The internal lateral ligament is inserted, by two very short fasciculi, into the ulna and inner
side of the head of tlie radius. A third fasciculus, deeper and median, much more developed
than the first, and covered by the inferior insertion of the flexors of tlie forearm, descends
between the radius and ulna to the posterior face of the former, and is there inserted near the
inferior attachment of the external ligament, which it appears as if about to join.
In Man, the elbow articulation is formed nearly on the same plan as that of the Dog and
Cat. The radius and ulna move together when the forearm is flexed and extended on the
humerus.
•
3. Radio-ulnar Articulation.
Jirticular surfaces. — The two bones of the forearm articulate by diarthrodial
'and synarthrodial surfaces.
a. The diarthrodial surfaces consist of four undulated, transversely elongated
facets, two of which are radial and two idnar. The first border, posteriorly, the
great articular surface forming the elbow- joint ; the second are situated beneath
the sigmoid notch.
h. The synarthrodial surfaces are plane and roughened, and are also two on
each bone : one, superior, extends below the diarthrodial facets to the radio-ulnar
arch ; the other, inferior, more extensive, occupies all the anterior face of the
ulna from this arch ; on the radius it forms a very elongated triangular imprint,
which descends to the lower fourth of the bone (see pp. 104, 105).
' Some grey elastic fibres which cover this cul-de-sac externally, have been wrongly
described as a posterior membraniform ligament.
198 THE ABTICV LATIONS.
Mode of union. — Two interosseous and two peripheral ligaments.
a. The interosseous ligaments, interposed between the synarthrodia! surfaces,,
are composed of extremely short white fibres passing from one to the other
surface, and which are endowed with a very remarkable power of resistance. The
inferior always ossifies a long time before the animal is full grown — a circum-
stance which caused the older veterinary anatomists to describe — and with some
show of reason — the radius and ulna as a single bone. Ossification of the superior
ligament is very rare.
b. The peripheral bands are bundles of arciform fibres which, from the beak
of the olecranon to the radio-ulnar arch, leave the lateral faces of the ulna to
pass — some inwards, others outwards — to the posterior face of the radius. The
fibres of the external ligament are confounded with the external humero-radial
ligament. The internal fibres are united to the internal humero-radial ligament,.
and to the small ulnar tendon belonging to the short flexor of the forearm.
Analogous fibres are found beneath the radio-ulnar arch ; but they are much
shorter and less apparent. (This is the external transverse radio-idnar ligament
of Leyh.)
Movements. — Very obscure in youth ; nearly null when the two bones are
fused together.
In the Ox, ossification of the superior interosseous ligament is constant at adult age.
In the Dog anti Cat, we have already seen (p. 107) that the radius and uhia are not fused
to each other, but remain independent during life. They are united in their middle portion
by an interosseous ligament, and join by diarthrosis at their two extremities. These animals
therefore exhibit; 1. An interosseous ligament. 2. A superior radio-ulnar articulation. 3.
An inferior radio-ulnar articulation.
Interosseous ligament. — It is composed of very resisting white fibres, attached by their
extremities to the bodies of the bones. Notwithstanding their sliortneas, they are loose enough
to allow movements taking place between the radio-ulnar articulations.
Superior radio-ulnar articulation. — This is a trochoid articulation, which only allows
movements of rotation or pivoting.
The articular swr/'aees which form this articulation are: in the ulna, the small sigmoid
cavity — a surface excavated in the lateral sense, and semicircular; in the radius, a cylindrical
half-liinge received into the preceding cavity.
To unite these there is an annular ligament — a kind of fibrous web thrown around the
superior extremity of the radius, fixed inwardly on the ulna near the inner extremity of the
small sigmoid cavity, attached outwardly to the external lateral ligament of the elbow^
articulation, and confounded superiorly with the anterior ligament of the same articulation.
This fibrous web, in uniting with the fibro-cartilaginous cap of the external humero-radial
ligament, and joining the small sigmoid cavity by its iiiternal extremity, transforms this last
into a complete ring, covered with cartilage in its bony portion. The head or superior
extremity of the radius is also encrusted, over its entire contour, with a layer of cartilage — a con-
dition which pt-rmits it to glide not only in the concave face of the small sigmoid cavity, but
also on the internal face of the two ligaments which complete this cavity.
Inferior radio-ulnar articulation. — This is also a trochoid articulation analogous to the pre-
ceding, but inversely disposed. Thus, the concave articular surface is hollosved on the radius,
outside tlie inferior extremity; the convex surface lies within the ulna. These two facets are
very small, and are maintained in ctmtact by a diminutive peripheral fibrous capsule. A
strong interosseous ligament, situated beneath the articular facets, also consolidates this
diatlirosis, and concurs by its inferior border to form the antibrachial surface of the radio-carpal
articulation. A small synovial capsule is specially devoted to this articulation.
Mechanism of the radio-ulnar joints. — The play of these two articulations is simultaneous,,
and tends to the same end— that is, to the execution of the double rotatory movement which
constitutes supination and pronation.
Supination is when the ulna remains fixed, and the radius pivots on it in such a manner as
to carry its anterior face outwards. Its superior extremity then turns from within forwards —
and even from before outwartls if the movement is exaggerated, in the articular girdle formed
ARTICULATIONS OF THE ANTERIOR LIMBS. 199
by the small sigmoid cavity of the ulna and the ligaments which complete it. The inferior
extremity also rolls on the ulnar facet in describing a similar movement, and the internal
tuberosity of this extremity is carried forwards.
In the movement of pronation, this tuberosity is brought inwards, and the anterior face of
the radius comes forward by an opposite mechanism.
The inferior bone of the anterior limb being articulated in a hinge-like manner with the
radius, it follows this bone in its rotatory movements, the anterior face of the metacarpus
looking outwards during supination and forwards in pronation.
The radio-ulnar articulation in Man resembles that of the Dog and Cat, the articular
surfaces only being larger and the movements more extensive. In supination, the palmar face
is turned forward, and the radius, situated on the outer side of the ulna, is in the same direction
as the latter. In pronation, on the contrary, the palmar face of the hand looks backwards, and
the radius — remaining outwards in its upper part — crosses the ulna in front in such a manner
that its lower extremity is placed witliiu the ulna.
4. Articulations of the Carpus (Figs. 129, 130)
Preparation. — After removing the tendons surrounding the carpus, the ligaments cbmmon
to all the carpal articulations can be studied. The anterior and posterior membraniform
ligament can tben be removed, and the ligaments proper to each row, as well as those uniting
the two rows, and these to adjoining bones, can be dissected. Some time is required for this
dissection, which is not difficult.
These comprise : 1. The articulations uniting the carpal bones of the first
row to each other. 2. The analogous articulations of the second row. 3. The
radio-carpal articulation. 4. The articulation of the two rows with each other.
5. The carpo-metacarpal articulation.
Articulations which unite the Bones of the First Row to each
other. — These bones, four in number, are joined by the diarthrodial facets on
their lateral faces, and form small arthrodial articulations.^ They are maintained
in contact by six ligaments, three anterior, and three interosseous. The anterior
ligaments are small flattened bauds carried from the fourth bone to the first,
from the first to the second, and from that to the third. The first, placed
outside rather than in front of the carpus, is covered by the external lateral
ligament and the inferior tendon of the external flexor of the metacarpus ; the
others adhere to the capsular ligament. The interosseous ligaments are implanted
in the grooves of insertion which separate the diarthrodial facets. One of them,
derived from the common superior ligament, unites the first to the second bone.
The two others, situated between the three last carpal bones, are confounded
with the corresponding anterior ligaments.
Articulations uniting the Carpal Bones of the Second Row. —
These are arthrodial articulations, like the preceding, but numbering only two.
They are fixed by two anterior and two interosseous ligaments. One of the
anterior ligaments joins the first bone to the second, and strongly adheres to the
capsular ligament ; the other is entirely covered by the lateral internal ligament,
and attaches the two last bones to each other. Of the two interosseous ligaments,
the second alone is confounded with the corresponding anterior ligament. That
which is situated between the two first bones is separated from the anterior
hgament by one of the diarthrodial facets between these bones.
Radio-carpal Articulation. — The inferior extremity of the radius, in
becoming united to the upper row of carpal bones, constitutes a diarthrosis
which, from the nature of the movements it permits, may be considered as
an imperfect hinge- joint.
' The facet uniting the supercarpal to the first bone is not situated on one of its faces, but
rather on the anterior part of its circumference.
200 THE ARTICULATIONS.
Articular surfaces. — The radial surface, elongated transversely and very
irregular, presents : 1, Outwardly, a wide groove, limited in front by a small
glenoid cavity, and bounded, posteriorly, by a non-articular excavation which
receives a prolongation of the second bone in the movement of flexion ;
2, Inwardly, a condyle with a more extensive curvature than that of the pre-
ceding groove, and, like it, completed by a small anterior glenoid cavity. The
carpal surface, moulded exactly on the radial, offers depressions corresponding
to the projections on it, and rice verm.
Mode of union. — The radio-carpal articulation is bound by three ligaments
which entirely belong to it ; and by four stronsf ligaments that are common to
it and articulations which will be studied hereafter.
Of the three ligaments proper belonging to the radio-carpal articulation,
one forms a thick, rounded funicle, extending from the radius to the fourth
bone in an oblique direction downwards and inwards, and concealed by the
common posterior ligament. The second (Fig. 130, 5), much smaller, is carried
from the supercarpal bone to the external side of the inferior extremity of the
radius, and is partly covered by the common external ligament. When the
synovial capsule is distended by dropsy, it may form a hernia at the outer side
of the carpus, by passing between this small ligament and the common posterior
ligament. The third, very delicate, but always present, is deeply situated beneath
the last ; it is inserted, for one part, into the radius near the first proper
ligament, and for the other, into the second bone and the interosseous ligament
which unites the supercarpal to that bone.
tSi/norial membrane. — After lining these three ligaments, and the four great
ligaments yet to be described, this membrane is prolonged between the three
first carpal bones, to cover the superior face of the interosseous ligaments which
unite them. It even more frequently descends into the articulation which joins
the supercarpal to the first bone ; though it also sometimes happens that this
has a particular synovial capsule of its own.
Akticulation of the Two Rows between each other. — Like the pre-
ceding, this is an imperfect hinge articulation.
Articnlar surfaces. — These are two, and are both transversely elongated, very
irregular in their configuration, and divided into three portions. The inferior
shows : behind, three small condyles placed side by side ; in front, two slightly
concave facets. The superior corresponds to the first by three glenoid cavities
and two convex facets.
3Io(le of anion. — For this articulation, besides the common great ligaments,
there are three particular ligaments. Two of these are very short, and are
situated behind the carpus, underneath the great common posterior ligament.
They are readily perceived by removing the capsular ligament, and strongly
flexing the carpus. " The strongest extends vertically from the internal bone of
the superior row to the second and third bones of the metacarpal row ; the other
descends obliquely from the first bone of the antibrachial row to the second
of the inferior row " (Rigot). The third ligament proper, much stronger than
the other two, reaches from the supercarpal to the first bone of the inferior row
and the head of the external metacarpal bone. It is confounded, outwardly,
with the great external lateral ligament ; inwardly, with the common posterior
ligament. Its posterior border gives attachment to the fibrous arch which
completes the carpal sheath. This ligament has also a branch which is fixed on
the second bone of the upper row (Fig. 130, 4).
ARTICULATIONS OF THE ANTERIOR LIMBS.
201
Fig. 129.
Synovial membrane. — This lines all the ligaments, and is prolonged above
and below, between the carpal bones, to facilitate the gliding of their articular
facets. Two upper prolongations ascend between the three first bones of the
antibrachial row, to cover the inferior face of the interosseous ligaments uniting
them. Two other prolongations descend between the carpal bones of the second
row ; the external, after covering the first interosseous ligament, passes between
it and the corresponding anterior ligament, and communicates with the synovial
capsule of the carpo-metacarpal articulation. The internal
forms a cul-de-sac which rests on the interosseous ligament.
Carpo-Metacarpal Articulation. — The carpal bones of
the second row articulate with the superior extremity of the
metacarpal bones, constituting a planiform diarthrosis.
Articular surfaces. — These are, on each side, plane facets
more or less inclined one on the other, and continued between
each other. The largest is in the middle, and is generally
hollowed by a small, shallow, synovial fossette.
Mode of union. — There are the four great common liga-
ments, and also six specicd ligaments .- two anterior, two posterior,
and two interosseous.
Of the two anterior ligaments (Fig. 129, 2, 2), one is divided
into two distinct bands, and unites the second bone to the
principal metacarpal ; the other, concealed by the external
lateral ligament, attaches the first bone to the head of the ex-
ternal metacarpal bone.
The two posterior Hgaments described by Rigot do not
appear to us to be suificiently distinct from the great ligament
to merit a special description.
The two interosseous ligaments, completely overlooked by
that able anatomist, start from the interstices which separate
the median metacarpal bone from the lateral metacarpals, and
join the interosseous ligaments of the second row ; they are
thick and short. We have sometimes noted one or other of
them to be absent.
Synovial membrane. — This communicates, as indicated above, with the
synovial capsule of the preceding articulation. It furnishes a superior cul-de-sac,
which rests on the interosseous ligament interposed between the two last cai-pal
bones of the second row. Two inferior culs-de-sac descend into the inter-
metacarpal arthrodial articulations.
Ligaments common to the three preceding Articulations. — As before
mentioned, these are four in number : two lateral, one anterior, and one
posterior.
a. The externcd lateral ligament (Figs. 129, 3 ; 130, 3) is a thick funicular cord
composed of two orders of fibres — a deep-seated and a superficial order, slightly
crossed. It leaves the external and inferior tuberosity of the radius, descends
vertically to the side of the carpus, transmits a fasciculus to the first bone of the
upper row, gives off another fasciculus which stops at the external bone of the
second row, and terminates on the head of the corresponding metacarpal bone.
Traversed obliquely by the lateral extensor of the phalanges, this ligament covers
the external carpal bones. In front, it is united to the capsular ligament ; near
its inferior extremity, it is confounded with the strong ligament which joins the
carpal articula-
tions (front
view).
1, 1, Anterior liga-
ments uniting the
carpal bones of
each row ; 2, 2, an-
terior ligaments
proper to the
carpo -metacarpal
articulation ; 3.
common external
ligament ; 4, com-
mon internal liga-
ment.
ao2
THE ARTICULATIONS.
Fig. 130.
supercarpal bone to the first bone of the inferior row and to the head of the
external metacarpal bone.
b. The internal lateral ligament (Fig. 129, 4), analogous to the preceding
and situated on the opposite side, is wider and thicker than it. It commences on
the internal tuberosity of the radius, and terminates on the upper extremity of
the middle and internal metacarpal bones, after being attached, by two distinct
fasciculi, to the third carpal bone of the upper row, and
the two last of the metacarpal row. In contact by its
external face with the tendon of the oblique extensor muscle
of the metacarpus, this ligament responds, by its deep face,
to the synovial membranes of the carpus and to the bones
to which it is attached. By its anterior border it is united
to the capsular ligament ; the opposite border is intimately
confounded with the posterior ligament, from wliich it is
impossible to distinguish it.
c. The anterior, or capsular ligament, is a membranous
band covering the anterior face of the carpal articulations.
Its superior border is attached to the radius ; the inferior
is inserted into the superior extremity of the principal
metacarpal bone. The two right and left borders are
united with the lateral ligaments. Its external face is in
contact with the tendons of the anterior extensor muscles
of the metacarpus and phalanges. The internal face is
lined at certain points by synovial membrane, and adheres
in others to the carpal bones and the anterior ligaments
binding these to one another. This ligament is composed
of transverse fibres more or less oblique, and arranged cross-
wise ; by its amplitude it can adapt itself to the movements
of flexion of the knee.
d. The posterior ligament, one of the strongest in the
animal economy, covers the posterior face of the carpus,
filling up the asperities which roughen it. It is inserted :
above, on the transverse crest surmounting the articular
surface of the radius ; by its middle portion into all the
carpal bones ; below, into the head of the principal meta-
carpal bone. Confounded inwardly with the internal
lateral ligament, united outwardly to the band which at-
taches the supercarpal to the external metacarpal and the second carpal bone of
the upper row, this ligament is continued, by its inferior extremity, with the carpal
stay (or check ligament) which sustains the perforans tendon. Its posterior face
is perfectly smooth, and is covered by the synovial membrane of the carpal
sheath.
Movements of thf Carpal Articulations. — The carpus is the seat of
two very extensive and opposite movements— flexion and extension; to wliich
are added three very limited accessory movements — adduction, abduction, and
circumduction.
All the carpal articulations do not take an equal part in the execution of
these movements ; for it is easy to discover that they are chiefly performed in the
radio-carpal diarthrosis, and in the imperfect hinge articulation uniting the two
rows of carpal bones. Each of these articulations participates in the movements
LATERAL VIEW OF THE
CARPAL ARTICOLATIONS.
1, 1, Anterior ligaments
uniting the two rows
of carpal bones; 2, 2,
anterior ligaments pro-
per to the carpo-meta-
carpal articulation ; 3,
common external liga-
ment; 4, one of the
ligaments proper to the
articulation of the two
rows (metacarpo-supra-
carpal) ; 5, one of the
ligaments proper to
the radio-carpal articu-
lation (radio-supercar-
pal). A, Groove on the
external surface of the
supercarpal bone, for
the passage of the ex-
ternal flexor of the
metacarpus.
ARTICULATIONS OF THE ANTERIOR LIMBS. 203
of the carpus in nearly the same proportions, and both act in an identical manner.
Their mechanism is most simple.
In flexmi, the first tier of bones rolls backwards on the radius, the inferior
row moves in the same sense on the upper, the metacarpus is carried backwards
and upwards, the common posterior ligament is relaxed, the capsular ligament
becomes tense, and the articular surfaces, particularly those of the second joint,
separate from each other in front. In extensmi, the metacarpus is carried down-
wards and forwards by an inverse mechanism. This movement stops when the
ray of the forearm and that of the metacarpus are in the same vertical line. In
flexion, these bones never directly approach each other, the inferior extremity of
the metacarpus being always carried outwards. It may also be remarked, that
the slight movements of abduction, adduction, and circumduction of the carpus are
only possible at the moment when the foot is flexed on the forearm.
With regard to the planiform diarthroses articulating the carpal bones of the
same row, they only allow a simple gliding between the surfaces in contact ; and
with the carpo-metacarpal arthrodia it is absolutely the same. The restricted
mobility of these various articulations has but a very secondary influence on the
general movements of the carpus ; but it nevertheless favours them by permitting
the carpal bones to change their reciprocal relations, and adapt themselves, during
the play of the radio-carpal and intercarpal hinges, to a more exact coaptation of
the articular planes which they form.
In the other animals, the carpal articulations have the same essential characteristics we
have noticed in Solipeds. The four principal peripheral bands differ but little in them;
though in the Dog and Cat they are lax enough to allow somewhat extensive lateral
movements.
5. Intermetacarpal Articulations.
Each lateral metacarpal bone articulates with the middle one, by means of
diarthrodial and synarthrodial surfaces, for the description of which refer to page
112. An interosseous ligament, composed of very short and strong fasciculi, is
interposed between the synarthrodial surfaces, and binds them firmly together.
Its ossification is not rare. The diarthrodial facets are maintained in contact by
the preceding ligament, and by the carpal ligaments inserted into the head of the
lateral metacarpal bones. The intermetacarpal articulations only allow a very
obscure, vertical, gliding movement.
In the Ox, there is only one intermetacarpal articulation, which is much simpler than
those in the Horse.
In the Pig, the four metacarpal bones correspond, at tlieir upper extremity, by means of
small diarthrodial facets on their sides. Fibrous fasciculi, derived from the great anterior and
posterior ligaments of the carpus, protect these intermetacarpal articulations before and
behind. Other fibres, situated between the adjacent faces of the metacarpal bones, are real
interosseous ligaments.
In the Dog and Cat, the four great metacarpal bones articulate with each other in
almost the same manner as in the Pig, but their mobility is greater
6. Metacarpo-phalangeal Articulation (Figs. 131, 132).
Preparation.— In order to study the whole of this articulation, it is well to have an anterior
limb from the lower fourth of the forearm. From this the tendons of the flexors and extensors
of the phalanges are to be removed, and then the suspensory ligament of the fetlock, anterior
capsular ligament, lateral ligaments, and the superficial inferior sesamoid ligament, can be
dissected. To study the ligaments which bind the bones forming the inferior articular
surface, the first phalanx and sesamoid bones should be removed, which allows of the dissection
2M
THE ARTICULATIONS.
of the inter-, lateral, and inferior sesamoid middle and deep ligaments. An injection of the
eynovinl capsule brings into relief some features which are interesting, from a surgical point
of view.
This is a perfect hinge-joint, formed by the inferior extremity of the median
metacarpal bone on the one part, and the superior extremity of the upper phalanx
and sesamoids on the other.
Articular surfaces. — For the metacarpal bone, there are two lateral condyles
and a median antero-posterior eminence ; for the first phalanx, two glenoid
cavities and an intermediate groove prolonged posteriorly on the anterior face of
the two sesamoids. Divided in this manner into three portions, the digital
surface is well constituted for solidity, because the pressure transmitted to this
region is diminished and.
Fig. 131. diffused by the natural
-*- ^ elasticity of the bands
which unite these three
pieces to each other.
3Iode of union. — The
means of union may be
divided into two cate-
gories : 1. Those which
join together the several
bones of the inferior sur-
face. 2. Those which
maintain in contact the
two opposed articular
surfaces.
A. The firet have re-
ceived the generic name
of sesamoid ligaments,
and are six in number :
an intersesamoid ligament y
which holds together the
two complementary bones
of the digital surface ;
three inferior and two
lateral sesamoid ligaments,
which unite these bones
to the first phalanx.
a. The intersesamoid ligament is composed of fibro-cartilaginous substance,
that appears to be the matrix in which the two sesamoids were developed ; as it
is spread around these bones, after being solidly fixed on their internal face.
Behind, this ligament, in common with the posterior face of the sesamoids, forms
the channel (Fig. 131, 5) in which the flexor tendons glide. In front, it occupies
the bottom of the intersesamoid articular groove.
h. The inferior sesamoid ligaments, situated at the posterior face of the first
phalanx, are distinguished as superficial, middle, and deep.
The superficial ligament (Figs. 131, 14 ; 134, 8), the longest of the three, is a
narrow band flattened before and behind. It arises from the middle of the
fibro-cartilaginous mass which completes, posteriorly, the superior articular surface
of the second phalanx, and, shghtly widening, ascends to the base of the sesamoids.
DETAILS OF THE METACARPO-PHAI.ANGEAL ARTICULATION OF
THE HORSE.
A. Middle inferior sesamoidean
ligaments. P. First phalanx
(posterior face). 1, Inter
sesamoidean ligament (pos-
terior fnce); 2, 2, lateral
sesamoidean ligaments ; 3,
middle inferior sesamoidean
ligament.
B. Deep inferior sesamoidean
ligaments. P. First phalanx :
1, Inter-sesamoidean liga-
ment ; 2, 2, lateral sesa-
moidean ligaments; 3, in-
ferior deep sesamoidean liga-
ment.
ARTICULATIONS OF THE ANTERIOR LIMBS.
Fie;. 1
into which it is inserted by becoming
confounded with the intersesamoid liga-
ments. Its posterior face, lined by the
synovial membrane of the so-called sesa-
moid sheath, is covered by the flexor
tendons ; it partly covers the middle
ligament.
The middle ligament, triangular and
radiating, is composed of three particular
fasciculi : two lateral (seen on each side
of the superficial ligament in Fig. 131,
A 8), and a median which has been
generally confounded with the superficial
ligament, although it is clearly distin-
guished from it by its inferior insertion.
Fixed in common to the posterior imprints
of the first phalanx, these three fasciculi
diverge in ascending to the base of the
sesamoids, where they have their upper
insertion.
The deep ligament is constituted by
two small bands concealed beneath the
middle ligament. Thin, short, flattened
before and behind, and intercrossed (Fig.
131, B 3), these bands are fixed to the
base of the sesamoids in one direction,
and in the other to the superior extremity
of the first phalanx, near the margin of
its articular surface. This ligament is
covered on its anterior face by the synovial
membrane of the articulation.
CARPAL, METACARPAL, AND INTER-PHALANGEAL
ARTICULATIONS OF THE HORSE (POSTERO-
LATERAL view).
R, Radius ; c, carpus ; M, metacarpus ; s, navicular
bone ; P, third phalanx. 1, Supercarpal bone ;
2, its proper ligament ; 3, external lateral liga-
ment of the carpal articulations (superficial
layei'); 3, ditto (deep layer); 4, groove for the
tendon of the external Hexor of the metacarpus;
5, common posterior ligament of the carpal
articulations; 6, superior sesamoidean, or sus-
pensory ligament of the fetlock ; 7, an originating
branch of ditto ; 8, 8, terminal branches of ditto ;
9, band given off by ditto to the anterior extensor
of the phalanges ; 10, tendon of the anterior
extensor of the phalanges ; 11, groove formed by
the posterior face of the intersesamoidean liga-
ment; 12, lateral metacarpo-phalangeal ligament
(superticial layer); 12', ditto (deep layer) ; 14,
inferior superficial sesamoidean ligament ; 15,
ditto (deep layer); 16. elenoidal fibro-cartilage of
the second phalanx ; 17. 18, 19, superior, middle,
and inferior bands of that fibro-cartilage ; 20,
lateral ligament of the first inter-phalangeal
articulation; 21. lateral posterior ligament of
the second inter-phalanceal ai'ticulation ; 22,
anterior lateral ligament of ditto.
16
20»
206 THE ARTICULATIONS.
e. The lateral sesamoid ligaments are two thin layers, extending from the
external face of each sesamoid to the tubercle of insertion on the side of the
superior extremity of the first phalanx (Fig. 131, a 2). They are covered by the
digital vessels and nerves, by the fibrous stay detached from the suspensory liga-
ment to the anterior extensor tendon of the phalanges, and by the supei-ficial
fasciculus of the lateral metacarpo- phalangeal ligament ; they are covered by
synovial membrane on their internal face.
B. The ligaments destined to unite the two articular surfaces of the meta-
cai-po-phalangeal joint are four : tivo lateral, one anterior, and one posterior .
a. Each lateral ligament comprises two fasciculi — a supei-ficial and a deep —
firmly united by their adjacent faces. The superficial fasciculus (Fig. 132, 12)
commences on the button of the lateral metacarpal bone, attaches itself to the
median metacai-pal, and descends vertically to terminate at the superior extremity
of the first phalanx. It covers the phalangeal insertion of the lateral sesamoid
ligament and the deep fasciculus. The latter, attached superiorly in the lateral
excavation of the inferior extremity of the principal metacarpal, radiates as it
reaches the sesamoid and the superior extremity of the first phalanx, where it is
fixed by mixing its fibres with those of the lateral sesamoid ligament. The inner
face of this fasciculus is lined by the articular synovial membrane (Fig. 132, 12').
I. The anterior ligament (Fig. 132) belongs to the class of capsular ligaments.
It is a veiy resisting membraniform expansion, which envelops the anterior face
of the articulation. Attached by its upper border to the anterior margin of the
metacarpal surface, and by its inferior border to the first phalanx, this expansion
is confounded at its sides with the lateral ligaments. It is covered by the extensor
tendons of the phalanges, which glide on its surface by means of small serous
sacs. Its internal face adheres throughout its whole extent to the synovial
capsule.
c. The posterior ligament,^ very appropriately named the suspensory ligament
of the fetloch (Figs. 132, 6 ; 133, 134, 4), is a long and powerful brace, composed
of white fibrous tissue, and often containing fasciculi of fleshy fibres in its textm-e.
Lodged behind the median metacai-pal, and between the two lateral metacarpal
bones, this brace is quite thin at its origin, but it soon becomes enlarged, and pre-
serves its great thickness to the extent of its upper fourth. Examined in section,
it appears to be formed of two superposed portions which are closely adherent to
each other. The superficial portion, the thinnest, commences by three small
branches, which are fixed to the first and second bones of the lower carpal row
(Figs. 132, 133, 5) ; the deep portion, much thicker, is attached to the posterior
face of the principal metacai"pal for about ^ of an inch. It has been
wrongly asserted that the suspensoiy ligament of the fetlock is continuous with
the common posterior ligament of the cai-pus ; it is, on the contrary, quite distinct
from it. The carpal stay {deep palmar aponeurosis of Man) is alone in direct
continuity mth the common posterior ligament of the cai'pus (133, 3). The
suspensory ligament of the fetlock is bifid at its inferior extremity ; its two
branches, after being fixed into the summits of the sesamoid bones, give origin to
two fibrous bands which pass downwards and forwards to become united on each
side to the anterior extensor tendon of the phalanges (Fig. 132, 9). It is in relation,
by its posterior face, Avith the perforans tendon and its carpal stay ; by its anterior
face, with the median metacarpal bone, and arteries and veins ; by its borders,
' It coiresponds to the two muscles which, in Mun, lie alongside the interosseous meta-
carpal muscles. (See Muscles of the Foot.)
ARTICULATIONS OF THE ANTERIOR LIMBS.
207
with two small interosseous muscles, the lateral metacarpal bones, and the digital
vessels and nerves.
Synovial membrane. — Tliis membrane is prolonged as a cul-de-sac between the
terminal branches of the preceding ligament. It is the distension of this sac
which causes the articular swellings vulgarly designated
" windgalls." Fig. 133.
Movements. — The metacarpo-phalangeal articulation
permits the extension and flexion of the digit, and some
slight lateral motion when the movable osseous segment
is carried to the limits of flexion.
In the Ox, Sheep, and G-oat, this articulation constitutes a
dotible hinge, which resembles the simple ginglymus of Solipeds.
They have three intersesamoid ligaments : two lateral, to unite
the large sesamoids of each digit ; and a median, which unites
the interual sesamoids. The inferior sesamoidean ligamentous
apparatus is far from showing the same degree of development
as in the Horse. It is reduced for each digit to four small bands,
which remind one very much of the deep ligament of the latter
animal, as it has been described by Rigot : two lateral bands pass
directly from the sesamoids to the upper extremity of the first
phalanx ; the other two, situated between the first, intercross
and are confounded with the latter by their extremities. A lateral
tesamoid ligament unites the first phalanx to the exterual sesamoid.
For each digit there are two lateral metacarpo-phalangeal
ligaments— a,n external, analogous to that of the Horse, but less
complicated, is attached by its inferior extremity to the first
phalanx only ; the other, internal, fixed superiorly in the bottom
of the inter-articular notch of the metacarpal bone, is inserted
into the inner face of the first phalanx in mixing its fibres with
those of the superior interdigital ligament. This latter is situated
between the two first phalanges, and is composed of short, inter-
crossed fibres, attached to the imprints which in part cover the
internal face of the two first phalangeal bones. In the Sheep
there are only traces of this interdigital ligament, and each internal
metacarpal-phalangeal gives rise, near its phalangeal insertion, to
a fibrous branch which is directed backwards from the interdigital
Bpace, and is terminated in the bone of the ergot (or posterior
rudimentary digit), which it sustains. The anterior or capsular
ligament, single as in Solipeds, unites the two external lateralliga-
ments. The suspensory ligament, single superiorly, is divided inferiorly into eight branches, two
of which are joined to the periuratus tendon, to form with it the double ring through which the
two branches of the perforans pass. Four other branches, in pairs, extend to the summits of
the sesamoids. That which is sent to each external sesamoid gives off, on the side of the first
phalanx, a reinforcing band to the proper extensor of the digit. The two last, profound and
median, descend into the inter-articular notch of the metacarpal bone, after becoming a single
fasciculus ; afterwards, they pass between two internal metacarpo-phalangt-al ligaments, and
separate from each other in passing downwards and forwards on the inner side of the first
phalanx, to join the proper extensor tendon of each digit.
In the Pig, Dog, and Cat, for each metacarpo-phalangeal there is: a proper synovial
membrane; an intersesamoid ligament; an inferior sesamoid ligament composed of two cross-
bands; two small lateral sesamoid ligaments; two lateral metacarpo-phalangeal ligaments,
attached inferiorly to the first phalanx and the sesamoids ; an anterior capsular ligament, in
the centre of which is found a small bony nucleus — a kind of anterior sesamoid— over which
glides one of the branches of the common extensor of the digits. The suspensory ligament is
replaced by real palmar interosseous muscles (see the Muscles of the Anterior Foot). Some
fibres situated between the first phalanges in the great digits of the Pig, resemble the superior
interdigital ligament of the Ox.
In Man, the cavity in the upper extremity of the first phalanx is completed by a glenoid
SECTION OF THE INFERIOR
ROW OF CARPAL BONES,
THE METACARPAL, AND
THE SUSPENSORY LIGA-
MENT OF THE FETLOCK.
1, Os magnum ; 2, common
posterior ligament of the
carpus ; 3, stay, or band
for tlie perforans tendon ,
4, suspensory ligament of
the fetlock ; 5, its super-
ficial layer ; 6, its deep
fasciculus ; 7, principal
metacarpal bone.
TEE ARTICULATIONS.
ligament. The prenoid ligaments of the four first digits are united to each other by a trans-
verse ligament of the metacarpus. The articulations are cousolidated by two lateral ligaments.
The metaciirpo-plialaiigeal articulations allow flexion and ex-
Fig. 134. tension movements, as well as those of abduction and adduction;
but the latter are limited by the lateral ligaments.
M
rosterior view of the
metacarpo-phalangeal
and inter-phalangeal
articulations (right
limb).
1, 3, Outer and inner
rudimentary metatarsal
bones ; 2, perforans tea-
don and its check liga-
ment ; 4, suspensory liga-
ment ; 5, gliding surface
or sheath for the flexor
tendons, f'rmed by the
posterior face of the sesa-
moid bones, and interse-
samoid. transverse, and
annular ligaments; 6,
section of lateral sesamoid
ligament ; 7, lateral fasci-
culus of the middle infer
lateral ligament of the fir
of the perforatus tendon;
surface of navicular bone;
14, perforatus tendon, 15,
7. Abticulation of the Fibst with the Second
Phalanx, or First Interphalangeal Articulation.
(Preparation. — Kemove the extensor tendon ; throw open the
metaearpo-pnalangeal sheath, and turn down the flexor tendons.)
This is an imperfect hinge-joint.
Articular surfaces. — On the inferior extremity of the
first phalanx are two lateral condyles, separated by a
groove. On the superior surface of the second phalanx
are two glenoid cavities, and an antero-posterior ridge.
The latter surface is completed behind by a glenoidal
fihro-cartilage, very dense and thick (Fig. 132, 16), which
also acts as a ligament. It is attached, in one direction,
to the second phalanx, between the superior articular
surface and the kind of fixed sesamoid which margins it
behind ; in the other, it is inserted into the first phalanx
by means of six fibrous bands (Fig. 135, 4, 5, 6) : two
superior, which embrace the inferior, middle, and super-
ficial sesamoid ligaments ; two middle, and two inferior,
which extend to the sides of the inferior extremity of
the first phalanx. This fibro-cartilage is moulded, in
front, to the articular surface of the latter bone, and
forms, by its posterior face, a gliding surface for the
perforans tendon (Figs. 132, 16 ; 134, 5). It is con-
founded, laterally, with the two branches of the per-
foratus, and receives, in the middle of its superior border,
the insertion of the inferior superficial sesamoid liga-
ment.
Mode of union. — Two lateral ligaments (Fig. 135,
7), to which are added, behind, the fibro-cartilage just
described, and in front the tendon of the anterior extensor
of the phalanges. These ligaments are large and thick,
and, passing obliquely downwards and backwards, are
inserted, superiorly, into the lateral tubercles of the
inferior extremity of the first phalanx. They are at-
tached, beneath, to the sides of the second phalanx.
Their most inferior fibres are even prolonged below that
point to reach the extremities of the navicular bone, and
constitute the posterior lateral ligaments of the pedal
articulation.
Synovicd membrane. — This covers the tendon of the
•ior sesamoid ligament; 8, inferior superficial sesamoid ligament ; 9,
st interphalangeal articulation ; 10, section of the terminal branch
11, section of the lateral cartilage of the foot; 12, postero-inferior
13, section of lateral cartilage, plantar cushion, and wing of pedal bone;
perforans tendon.
ARTICULATIONS OF THE ANTERIOR LIMBS. 209
anterior extensor of the phalanges, the lateral ligaments, and the glenoid fibro-
cartilage. Behind, it forms a cul-de-sac, which extends between the latter and the
posterior face of the first phalanx (Fig. 137).
Movements. — This imperfect hinge is the seat of two principal movements :
extension and flexion. It also allows the second phalanx to pivot on the first, and
permits some lateral movements.
In the Ox, Sheep, and Goat, the glenoid fibro-cartilage is confounded with the perforatus
tendon, and is only attached to the first pliahmx by two lateral bands. The internal lateral
ligament comprises two fasciculi : one, very short, which terminates in the st-coml phalanx ;
and another, very long, descending to the internal face of the third phalanx. The external is
very thin, and is also prolonged to the terminal phalanx ; so that the two last inteiphalangeal
articuhitions of each digit are fixed by two common lateral li'j;aments which correspond exactly,
by their position and inferior attachments, to the anterior lateral ligaments of the pedal joint
of Solipeds.
In the Dog and Cat, the glenoid cartilage, also confounded by its posterior face with the
perforatus tendon, only adheres to the first phalanx by some cellular bands. The two lateral
ligaments pass from the inferior extremity of the first phalanx to the superior extremity of the
second.
In the Pig, there is somewhat the same arrangement as in Carnivora. The external
lateral ligament is, nevertheless, more like that of the Horse, in its most anterior fasciculi being
prolonged lo the external extremity of the navicular bone.
8. Aeticulation of the Second Phalanx with the Third, Second
Interphalangeal Articulation, or Articulation op the Foot.
Preparation. — Eemove the hoof according to the directions given hereafter, when treating of
the muscles of the forearm ; then the plantar cushion, the flexor tendons, and one of the lateral
cartilages. A section like that shown in Fig. 137 is useful to show the relations between the %
synovial capsule of this joint and the bursae, behind the second phalanx.
To form this imperfect hinge-joint, the second phalanx is opposed to the tliird,
and to the navicular bone.
Articular surfaces. — On the inferior face of the second phalanx there are two
lateral condyles and a median groove. On the superior face of the third phalanx
and the navicular bone, are two glenoid cavities separated by an antero-posterior
ridge. The two bones which form tliis last surface, articulate with each other by
arthrodia ; the navicular bone presents for tliis purpose an elongated facet on its
anterior border ; the os pedis also offers an analogous facet on the posterior contour
of the principal articular surface.
Mode of union. — Five ligaments : a single interosseous one, which joins the
navicular to the pedal bone ; and four lateral bones, distinguished as anterior and
posterior.
a. Interosseous ligament (Fig. 136, 2). — This is formed of very short fibres,
which are inserted, behind, into the anterior groove of the navicular bone ; and
in front, into the posterior border and inferior face of the third phalanx. This
ligament is lined, on its superior surface, by the synovial membrane, and on its
inferior face is covered by the navicular sheath.
h. Anterior lateral ligaments (Figs. 132, 22 ; 135, 9).— These are two thick,
short, and wide fasciculi, attached by their superior extremities to the lateral
imprints of the second phalanx, and by their inferior extremities into the two
cavities at the base of the pyramidal eminence of the os pedis. Each ligament is
partly covered by the complementary fibro-cartilage of that bone, and appears to
form a portion of it. Its anterior border is continuous with the common extensor
210
TEE ARTICULATIONS.
tendon of the phalanges ; its internal face is covered by the synovial membrane,
which adheres closely to it.
c. Posterior lateral ligaments (Figs. 132, 21 ; 135, 8). — These have been
already noticed. Each is composed of the lowermost fibres of the lateral ligament
of the first interphalangeal articulation ; these fibres, after being attached to the
?econd phalanx, unite into a sensibly elastic fibrous cord, which is chiefly fixed
Fig. 1^5.
M E r ATARSO - PHALANGEAL
AND INTER-PHALANGEAL
ARTICULATIONS OF THE
HORSE.
These are almost the same
as in the anterior limb.
1, Superficial layer of the
external lateral ligament
of the metatarso-phalan-
geal articulation ; 2, sesa-
moid branch of the deep
layer; 3, phalangeal branch
of the same ; 4, superior
branch of the glenoidal
fibro-cartilage; 5, middle
branch of ditto; 6, inferior
branch of ditto ; 7, lateral
ligament of the first inter-
phalangeal articulation ; 8,
posterior lateral ligament
of the pedal articulation ;
9, anteiior lateral ligament
of ditto.
ARTICULATION OF THE FOOT (INFERIOR FACE).
P, Inferior face of the third phalanx. S, Infe-
rior face of the navicular bone. 1, Semilu-
nar crest ; 2, interosseous ligament.
into the extremity and superior border of the navicular
bone, where the Ugaments join each other, and in this
way form a kind of complementary cushion that in-
creases the navicular articular surface. It also sends
off a short fasciculus to the retrossal process, and a
small band to the internal face of the lateral fibro-
cartilage. Partly concealed by the latter and the plantar
cushion, this ligament is covered inwardly by the articu-
lar synovial membrane.
Synovial memlrane. — This descends below the facets
which unite the navicular to the pedal bone. It offers,
posteriorly, a vast cul-de-sac which reaches the posterior
face of the second phalanx, and hes against the two
sesamoidean bursse (Fig. 137, 13). It also forms another
much smaller, by being prolonged between the two lateral
ligaments of the same side. This is very often distended,
and it is liable to be opened in the operation for diseased lateral cartilages.
Movements. — The same as those of the first interphalangeal articulation.
In the Sheep are found : 1. An interosseous ligament to unite the navicular bone to the
third phalanx. 2. Two anterior lateral ligaments commencing:, as already stated, at the first
phalanx. 3. Two lateral posterior ligaments, passina: to the posterior face of the second phalanx
and the navicular bone (the internal is yellow and elastic). 4. A single, anterior, elastic liga-
ment, attached above to the superior extremity of the second phalanx, and fixed below into the
third, between the insertion of the common extensor of the digits and that of the internal
anterior lateral ligament; an inferior interdigital ligament, situated between the ungueal
phalanges, whose separation from each other it limits This ligament is compose<l of parallel
fibres, whicii extend transversely from the one navicular bone to the other, and is covered on
ARTICULATIONS OF THE ANTERIOR LIMBS.
211
its inferior face by the skin of the interdigital Bpace. Its upper face is in contact with an
adipose cushion.
In the Ox, the external anterior lateral ligament, wide and expanding, is almost entirely
covered by the long branch of the proper extensor of the digit, to which it is intimately
adherent. The interdigital ligament has a much more complicated character than that of the
Sheep. It is formed of fibres intercrossed on the median line, and divided at its extremities
into two fasciculi : a superior passes over the perforans tendon, to which it serves as a restrain-
ing band, and is fixed to the outside of the inferior extremity of the first phalanx, after con-
tracting very close adhesions with a strong fibrous web which descends from the posterior
metacarpal region, and which will be more fully noticed when describing the muscles; an
inferior, shorter than the preceding, attached to the internal extremity of the navicular bone
and the internal face of the third phalanx, becoming confounded with the perforans tendon,
the plantar cushion, and the dermis of the keratogenous membrane.
Fig. 138.
Fig. 137.
JffJO i
LONGITTIDrNAL AND VERTICAL SECTION OF THE
DIGITAL REGION IN THE HORSE, SHOWING THE
ARRANGEMENT OF THE ARTICULAR AND TENDI-
NOUS SYNOVIAL APPARATUS.
1, First phalanx ; 2, second phalanx ; 3, third pha-
lanx ; 4, semilunar sinus of ditto ; 5, navicular
bone ; 6, tendon of the anterior extensor of the
phalanges ; 7, its insertion into third phalanx ; 8,
tendon of the perforatus ; 9, ditto perforans ; 10,
its insertion into the third phalanx; 11, inferior
sesamoid ligaments ; 12, posterior ctd-de-sac of
the first synovial interphalangeal capsule; 13,
ditto of second ; 14, infeiior cul-de-sac of the
sesamoid bursa; 15, superior ditto of navicular
bursa ; 16, inferior ditto of same ; 17, station of
the coronary cushion; 18, ditto of plantar
cushion.
TENDONS AND LIGAMENTS OF
THE POSTERIOR FACE OF
THE DIGITAL REGION OF
THE OX.
1, Perforatus tendon ; 2, 2,
its terminal tendons ; 3,
3, theii- bifurcation ; 4,
4, perforans tendon ; 6, 6,
superior branches of the
inferior interdigital liga-
ment attached to the first
phalanx ; 7, inferior inter-
digital ligament ; 8, 8,
suspensory ligament of
the fetlock.
In the Pig, for the maintenance of the second interphalangeal articulation, there are:
1. Two lateral ligaments, carried from the lateral faces of the second phalanx to the external
and internal faces of the third. 2. A third ligament, exactly resembling one of the posterior
lateral ligaments of the pedal articulation of the Horse; this ligament descends from the
inferior extremity of the first phalanx to the internal extremity of the navicular bone. Its
analogue of the inner side appears to be altogether absent ; but in the large digits there is an
anterior yellow elastic ligament like that of Ruminants.
In the Dog, the two last phalanges are united by two lateral ligaments, very simply
arranged. A third ligament, formed of elastic tissue, divided into two lateral portions, and
situated in front of the articulation, plays the part of a spring, which mechanically produces
the retraction of the claw when the flexor muscles cease to contract. In the Cat, this yellow
ligament is very strong; and this animal also exhibits a very striking obliquity of the articular
212 TEE ARTICULATIONS.
pulleys by which the two phalanges correspond : an arrangement that permits the claw to be
lodo'ed between two digits wlien they are raised, and tlius favour its retraction.
Tlie second iuteiphalangeal articulation of the Dog and Cat is also distinguished by another
essential arrangement. The articular surface of the third phalanx is completed by a glenoid
fibrocartiiage analogous to that of the first articulation, but much thicker. This fibro-cartilage
(see Muscles of the Hand) is fixed into the posterior projection of the third phalanx, and
serves, by its inferior face, as a pulley for the perforaus tendon and, with the projection just
named, plays the part of the navicular bone in other animals.
The interphalangeal articulations of Man are formed on the same plan as the metacarpo-
phalangeal articulations They are consolidated by a glenoid and lateral ligaments, and
possess only the two movements oi flexion and extension.
Article V. — Articulations of the Posterior Limbs.
1. Articulations of the Pelvis.
{Preparation.— These ligaments are all exposed to view by carefully removing the soft parts
connected with the sacrum and coxae.)
A. Sacro-iliac Articulation (Figs. 139, 140).— This is a pair articulation
which establishes the union of the posterior limb with the spine, and is formed
by the sacrum and coxa. It belongs to the arthi'odial class.
Articular surfaces. — On the sacrum, the irregular diarthrodial facet named
the " auricular," cut on the sides and near the base of the bone. For the coxa,
the analogous facet on the internal face of the ilium.
3fode of union. — By four ligaments, which, after the example of Rigot, we
will name sacro-iliac, superior ilio-sacral, inferior ilio-sacral, and the sacro-sciatic.
The first is situated immediately around the articular surfaces, and the others are
only in mediate relations with them.
a. Sacro-iliac ligament (Fig. 140, 1). — This is composed of thick fibrous
fasciculi, which envelop the whole articulation in being firmly attached by their
extremities, to the imprints around the diarthrodial facets. The inferior moiety
of this ligament is covered by the iliacus muscle. Its posterior half ^ is much
stronger, is hidden by the ilium, and gives attachment to the longissimus dorsi
muscle.
h. Superior ilio-sacral ligament (Fig. 139, 13). — A thick and short funicle,
which, rising from the internal angle of the ilium, is carried backwards to be
fixed to the sacral spine, where its fibres are confounded with those of the super-
spinous dorso-lumbar ligament.
c. Inferior ilio-sacral ligament (139, 14).— This is very resisting, triangular,
membranous band, formed of parallel fibres passing obliquely downwards and
backwards. It is attached, by its anterior margin, to the upper half of the
sciatic border and the internal angle of the ilium, in becoming confounded with
the preceding ligament. Its inferior margin is inserted into the rugged lip which
borders the sacrum laterally. Its posterior border is united to the aponeurosis
covering the coccygeal muscles, and its external face is in contact with the
principal gluteal and the long vastus muscles ; while the internal lies against the
lateral sacro-coccygeal muscle.
d. Sacro-sciatic or ischiatic ligament (Fig. 140, 2).— This is a vast membranous
expansion situated on the side of the pelvis, between the sacrum and the coxa.
It serves more as a means for enclosing this portion of the pelvic cavity, than to
assure the solidity of the sacro-iliac articulation. Its form is irregularly quadri-
' It represents the interosseous sacro-iliac ligament of Man. The inferior half corresponds
to the anterior sacro-iliac ligament.
ARTICULATIONS OF TEE POSTERIOR LIMBS.
213
lateral, and permits its circumference to be divided into four borders : a suj^erior,
attached to the rugged lateral ridge of the sacrum ; an inferior, fixed to the supra-
cotyloid ridge, as well as the ischial tuberosity, and forming by the portion
comprised between these two insertions, with the small ischiatic notch, the opening
by which the internal obturator and pyramidalis muscles leave the pelvis ; an
anterior, imperfectly limited, along with the great sciatic notch, circumscribes
the opening through which the ghiteal vessels and nerves, and the sciatic nerves
pass ; a posterior, doubled in the form of two layers which embrace the semi-
membranosus muscle, and is confounded superiorly with the aponeurosis envelop-
ing the coccygeal muscles. The external face of this ligament is traversed by the
sciatic nerves, and is covered by the long vastus and the semitendinosus muscles,
which derive numerous insertions from it. Its internal face is covered, in front,
SACRO-ILIAC AND COXO-FEMORAL ARTICULATIONS, WITH THEIR SURROUNDIHG MUSCLES.
11, Sacro-sciatic ligament; 12, great sciatic notch; 13, superior ilio-sacral ligament; 14, inferior
ilio-sacral ligament.
by the peritoneum, and, posteriorly, is in contact with the ischio-coccygeal and
ischio-anal muscles, to which it gives attachment.
Si/novial memhrane. — This lines the sacro-iliac ligament, but only furnishes a
small quantity of synovia.
MovemenU. — The two sacro-iliac articulations, being the centres towards which
all the propulsive efforts communicated to the trunk by the posterior limbs con-
verge, do not offer much mobility, as that would oppose the integral trans-
mission of the propulsion. So that they permit only a very restricted gliding of
the articular surfaces ; while the union of the sacrum and coxa by diarthrosis,
appears to be exclusively designed to prevent the fractures to which these bones
would be incessantly exposed, if they were fixed together in a more intimate
manner.
B. Articulation of the two Cox^, or Ischio-pubic Symphysis. — The
two coxffi are united to each other throughout the whole extent of the inner border
of the pubis and the ischial bones. In youth, this is a veritable amphiarthrosis,
fixed by an interosseous cartilage and bundles of peripheral fibres.
The cartilage is solidly fixed to the small rugged eminences which cover the
adjacent articular surfaces, and becomes ossified, like the sutural cartilages, as
214
THE ARTICULATIONS.
the animal advances in age. In adult Solipeds the coxae are constantly tused to
each other.
The peripheral fibrous fasciculi extend transversely from one bone to the
other, above and below the symphysis ; those on the inferior face are incom-
parably stronger and more abundant than the others.
The movements of this articulation are most restricted, and depend solely
upon the elasticity of the interosseous cartilage. They cease after its ossification.
The fusion of the two coxsb proceeds very slowly in the female of the Cat, Dog, Pig, Ox,
Sheep, and Goat species.
2. COXO-FEMORAL ARTICULATION (Fig. 140).
(Preparation. — Remove the muscles surrounding the articulation. To view the interior,
divide the capsular ligament by a circular incision.)
This is an enarfchrosis, formed by the reception of the head of the femur into
the cotyloid cavity of the coxa.
Articular surfaces. — As already shown, the cotyloid cavity represents the
segment of a hollow sphere,
deeply notched on the inner
side, and provided at the
bottom with a wide depres-
sion, the internal moiety of
which is destined for the
insertion of one of the inter-
osseous ligaments, wliile the
external half plays the part
of a synovial fossa. This
depression is not covered by
cartilage, and communicates
by the internal notch with
the inferior furrow on the
pubis. The Up of the cotyloid
cavity is covered by a com-
plementary fibro-cartilage —
the cotyloid ligament. This
fibro-cartilage is not inter-
rupted at the notch just
mentioned, but passes over it,
forming a remarkable band
(Fig. 140, 5) that converts
it into a foramen, through
which pass the pubio- or ilio-
femoral ligament and the
vessels of the articulation.
Fixed by its adherent border
to the margin of the cotyloid
cavity, this ligament is lined
It is thickest in front and
sacro-iliac and coxo-femoral articulations, with the
small deep muscles surrounding the latter (inferior
surface).
1, Sacro-iliac ligament; 2, sacro-sciatic ligament; 3, great
sciatic notch ; 4, anterior portion of the capsular ligament
of the coxo-femoral articulation ; 5, internal band of the
cotyloid ligament ; 6, coxo-femoral ligament ; 7, pubio-
femoral ligament ; 8, its insertion into the femui-.
by synovial membrane on its faces and free border,
within.
With regard to the head of the femur, it will be remembered that it is exactly
ARTICULATIONS OF THE POSTERIOR LIMBS. 215
moulded to the cavity, and, like it, is excavated by a nigged fossa which is entirely
occwpied by the insertion of the interarticular Ligaments.
llode of union. — This joint is maintained by a peripheral capsule, and by an
interarticular band constituting the coxo-femoral ligament.
a. Capsular ligament (Fig. 140, 4). — This is a membranous sac, like that of
the scapulo-humeral articulation, embracing the head of the femur by its inferior
opening, and attached by its opposite border to the margin of the cotyloid cavity
and its surrounding fibro-cartilage. This Ugament is composed of intercrossed
fibres, and is strengthened in front by an oblique fasciculus which descends to the
body of the femur, along with the crureus muscle, near which it is fixed. Its
internal face is covered by the articular synovial membrane, and its external face
is in contact, through the medium of adipose cushions, with : in front, the crureus
and the rectus femoris ; behind, the gemini, the internal obturator, and the
pyramidalis muscles ; outwards and upwards, the small gluteal muscle ; within
and below, the external obturator.
h. Coxo-femoral ligament {ligammtum teres. Fig. 140, 6). — A thick and short
funicle of a triangular shape, deeply situated between the two bony surfaces, which
it cannot, notwithstanding its shortness, maintain exactly in contact without the
other muscular or ligamentous stiiictures enveloping the articulation. In Solipeds,
it is divided into two portions — a cotyloid and a puhic. The cotyloid portion is
short and entirely concealed in the interior of the articulation (Fig. 140, 6). Its
upper insertion occupies the internal moiety of the bottom of the cotyloid cavity ;
and its inferior extremity is fixed into the rough fossa in the head of the femur.
It is enveloped by the synovial membrane,
T\iQ puhic portion (Fig. 140, 7, 8) arises, like the preceding, from the fossette
in the head of the femur, and, passing upwards and outwards, enters the internal
notch of the cotyloid cavity, is inflected downwards on the fibrous band Avhich
converts that notch into a foramen, and is at last lodged in the inferior fuiTow on
the pubis, becoming confounded with the prepubic tendon of the abdominal
muscles, at the anterior border of the pubis. Longer and stronger tlian the cotyloid
portion, this fasciculus is included, in its pubic part, between the two branches of
the pectineus ; its interarticular part is covered by synovial membrane.
Synovicd membrane. — This membrane is very extensive ; it lines the intemal
face of the capsular and cotyloid ligaments, and is reflected on the interarticular
ligaments, to form around them a serous vaginal covering. It is even prolonged
into the synovial fossa occupying the centre of the cotyloid cavity.
Movements. — The coxo-femoral articulation is one of the joints which are
endowed with the most varied and extensive movements. It permits the flexion,
extension, ahduction, adduction, circumduction, and rotation of the thigh on the
pelvis. The mechanism of these movements is so simple, that they need no
particular consideration.-
The domesticated animals other than Solipeds, are distinguished by the com-
plete absence of the pubio-femoral Ligament ; so that in them the movements of
abduction, which are limited in Solipeds by the tension of this ligament, are much
more extensive ; and it is the absence of the ligament in question which explains
the facility with which the larger Ruminants are enabled to strike sideways — a
movement known as a " cow's kick."
In Man, the head of the femur is more detached than in the domesticated animals, and
the cotyloid cavity, encircled by the cotyloid ligament, is deeper. The femur is united to the
coxa: 1. By a capsular ligament. 2. By a triangular ligament, fixed above, to the cotyloid
216 THE ABTICVLATIONS.
ligament at the notch, and below, into the depression in the head of tlie femur. Also, as the
brothers Weber have shown, the atmospheric pressure is a powerful adjuuct to tliese means
of union.
The coxo-femoral articulation of Man permits more extensive movements than that of
animals, and especially abduction and adduction, which can be carried to 90 degrees.
3. Femoro-tibial Articulation (Fig. 141). ^
Preparation. — Remove the soft parts surrounding the articulation, taking care not to wound
the synovial membrane. To expose the crucial ligaments, make au antero-posterior vertical
section of the femur in such a way as to separate the condyles.
This is the most comphcated joint in the body, and is formed by the union of
the femur with two of the thigh-bones — the tibia and patella. It represents an
imperfect hinge-joint.
Artuular surfaces. — To form this articulation, the femur opposes its two con-
dyles to the wide, conve.K, and undulated facets on the superior face of the lateral
tuberosities of the tibia, and its articular pulley to the posterior face of the patella.
The femoral faces have already been described in detail (p. 137) ; but it may
be repeated that the two condyles, placed side by side, are elongated in an antero-
posterior direction, and are separated by a non-articular notch called the inter-
condyloid ; also, that the femoral trochlea, situated in front of these two condyles,
appears to continue the preceding notch, and that its internal border is much more
elevated than the external — an arrangement which explains why it is so difficult,
if not impossible, for the patella to be dislocated inwards.
The tihial facets ascend on each side to the lateral faces of the tibial spine.
They are separated from one another by the antero-posterior groove cut on the
summit of that bone, and by the fossae of insertion situated at its base before and
behind. The external facet, wider than the internal, is devoted in part to the
gliding of the originating tendon of the popliteal muscle.
The patellar surface, moulded on the femoral pulley, fits it in an imperfect
manner. It is bordered, outwardly, by a small fibro-cartilaginous ring, which is
united to the fibrous capsule of the femoro-patellar ariiculation (Fig. 141, 1).
Inwardly, it is completed by the insertion of the internal patellar ligament, to be
noticed immediately.
Tnterarticular nieniscii {semilunar fihro-cartUages) (Figs. 141, a 1, 2, 3, 4 ;
and 142, 5, G, 7, 8). — By this designation are known the two fibro-cartilages
interposed between the condyles of the femm- and the tibial facets, to assure their
coaptation. They are crescent-shaped bodies, and present : an internal, concave,
thin, and sharj) border, embracing the tibial spine ; an external, thick, and convex
border ; a superior face, excavated and moulded to one of the condyles ; an inferior
face, nearly plane, gliding on the tibia ; and two extremities terminated by liga-
ments, and fixed to the bones in apposition. The articular surfaces are not entirely
separated throughout their extent by these complementaiy meniscii, for the tibial
spine rubs directly against the inner sides of the femoral condyles. The internal
semilunar fihro-cartilage, the widest and thickest, is inserted by its anterior
extremity into one of the excavations situated in front of the spine ; its posterior
1 By this name is understood the joint uniting the femur to the tibia, and that which
articulates it with the patella. Following the example of anthropotomists, it has not been
deemed necessary to describe a femoro-patellar articulation distinct from the femoro-tibial,
properly so called. This innovation appears to be justified by the community of the principal
articular bands which bind these two joints, and by the reciprocal dependence of their
movements.
ABTICULATIONS OF THE POSTERIOR LIMBS.
217
extremity is attached in the fossa behind that eminence. The external semilunar
fiiro-cartilage is fixed, in front, near the anterior insertion of the opposite fibro-
cartilage ; its posterior extremity gives origin to two slips or cords, one superior,
the other inferior. The first, the strongest and longest, terminates in the fossa
near the posterior extremity of the intercondyloid notch. The second, thin and
■flat, is inserted on the posterior outline of the external tibial facet. The external
border of this meniscus is separated from the external lateral ligament by the
tendon of the popliteus muscle, and acts, with regard to this tendon, as a pulley.
Mode of union. — The bands which bind this complicated articulation are veiy
Fig. 141.
FEMORO-TIBIAL ARTICULATION'.
A. — Posterior face : the posterior lignment has been removed. 1, External meniscus ; 2, fibrous
fasciculi fi.xiug it to the femur ; 3, fibrous fascia which attaches it to the posterior contour of the
tibial surface ; 4, internal meniscus ; 5, tibial insertion of the posterior crucial ligament ; 6,
external lateral ligament ; 7, mternal lateral ligament.
B. — External face : the external condyle of the femur and the meniscus have been removed to
show the crucial ligaments. 1, Anterior crucial ligament; 2, posterior ditto; 3, fibular insertion
of the external lateral ligament ; 4, anterior patellar ligaments. A, Internal meni.^^cus ; B, anterior
insertion of the external meniscus ; C, passage for the tendinous cord common to the flexor of the
metatarsus and the anterior extensor of the phalanges ; D, anterior and superior tuberosity of
the tibia; E, tibial crest.
numerous. They will be successively described as : 1 . Those which attach the
patella to the tibia. 2. Those which unite the femur with the tibia.
A. Ligaments attaching the -patella to the tibia. — The patella is bound to the
tibia by three funicular ligaments, designated by the generic epithet of " patellar."
They are situated in front of the articulation, and transmit to the leg the action
of the muscles which are attached to the patella. They are distinguished accord-
ing to their position, as external, internal, and middle (Fig. 142, 2, 3, 4).
a. The external patellar ligament, the largest and most powerful, is a flattened
band, attached, by its lower extremity, to the culminating point of the anterior
tuberosity of the tibia. Its upper extremity is fixed to the anterior face of the
patella, and is confounded with the patellar insertion of the superficial gluteus.
It is joined to the internal ligament by a veiy resisting aponeurotic extension, a
dependency of the fascia lata.
218 THE ARTICULATIONS.
b. Tlie interna] patellar ligament also forms a flattened band, longer, but not
80 wide or thick as the preceding. Its inferior extremity is attached to the inner
side of the anterior tuberosity of the tibia. Its superior extremity becomes much
thickened and fibro-cartilaginous, and is inserted into a prominence inside the
patella. This fibro-cartilaginous portion (Fig. Ii2, 3) of the ligament ghdes on
the internal border of the femoral trochlea, and may justly be considered as a
complementary apparatus of the patellar surface. The ligament, joined to the
preceding by the hbrous fascia ab-eady mentioned, is confounded, inwardly, with
the aponeurosis of the adductor muscles of the leg.
c. The middle patellar ligament is a round cord, situated, as its name indicates,
between the other two, concealed beneath the aponeurosis which unites these, and
in the middle of the adipose tissue protecting the synovial capsules in front. It
leaves the anterior face of the patella, and descends vertically to the tibia, to be
lodged in the fossa in the middle of the anterior tuberosity, where a small synovial
bursa facilitates its movements. Its inferior extremity is inserted into the most
decUvitous part of this excavation.
B. Ligaments which attach the leg and thigh hones. — These are six in number :
1. A femoro-patellar capsule maintaining the patella against the femoral trochlea.
2. Five femoro-tibial ligaments, as follows : two lateral, two external and
internal ; a posterior ; and two interarticular, distinguished with reference to
their inferior insertion into anterior and posterior.
1. T\\Q femoro-patellar capsule is a membranous expansion which covers, above
and laterally, the superior synovial membrane. This capsule is attached by its
borders around the femoral trochlea and the periphery of the patellar surface.
It is extremely thin in its superior part ; but laterally it is thicker, and consti-
tutes two wide fibrous fasciculi which bind the patella to the eccentric sides of
the two condyles, and is described in several works as two special ligaments. Its
external face is covered by the insertion of the superficial gluteus and the triceps
cruralis.
2. Femoro-tibicd ligaments. — a. The lateral ligammts are two ribbon-shaped
cords situated at the extremities of the transversal axis of the articulation, more
behind than before ; they are relaxed during flexion, and very tense in ex-
tension.
The external, the shortest and strongest, proceeds from one of the hollow
facets on the external condyle of the femur, and is inserted into the head of the
fibula by its inferior extremity, after gliding over the external tuberosity of the
tibia by means of a special synovial bursa. It is covered by the crural or tibial
aponeurosis, and covers the tendon of the popliteus, from which it is sometimes
separated by a vesicular synovial membrane.
The internal is attached, superiorly, to the eminence of insertion that sur-
mounts the eccentric face of the internal condyle, and descends vertically to the
tibia, gliding over the margin of its articular surface by means of a small facet
covered with cartilage, and a nd-de-sac prolongation of the internal synovial
membrane. It is fixed by its inferior extremity to the imprints which cover the
internal tibial tuberosity.
Its fil)res are disposed in two layers, which slightly intercross in X fashion ;
those passing downwards and forwards adhere to the border of the internal
meniscus. Covered by the aponeurosis of the adductor muscles of the leg, this
ligament adheres by its deep face to the internal meniscus.
b. The posterior ligament belongs to the class of membranous or capsular
ARTICULATIONS OF TEE POSTERIOR LIMBS. 219
ligaments. It is formed of two aponeurotic layers separated superiorly, but
confounded inferiorly. The superficial layer is composed of strong, fibrous,
intercrossed fasciculi, perforated with vascular openings. It is fixed, above, to
the posterior face of the femur, below the external gastrocnemius muscle. The
deep lamina envelops, like a cap, the femoral condyles. After becoming united,
these two laminse are attached to the posterior face of the tibia, close to the
superior articular face of that bone. Its external face is in contact with the
popliteal vessels, and the gastrocnemius muscle. Its internal face is covered
throughout nearly the whole of its extent by the lateral synovial membranes,
embraces the condyles of the femur, and adheres to the posterior crucial liga-
ment, as well as to the interarticular meniscii.
c. The interosseous ligaments are two funicular bands lodged in the inter-
condyloid notch. They are more commonly designated crucial ligaments, because
they cross each other at their middle part, like the letter X (Fig. 141).
The anterior, oblique downwards and forwards, is attached by its superior
extremity to the bottom of the intercondyloid notch, and inwardly to the external
condyle. Its inferior extremity is fixed in the groove on the summit of the tibial
spine. The fibres entering into its formation are not parallel, but slightly twisted
in a spiral manner.
The posterior,\ongeY than the preceding, and oblique in the opposite dii-ection,
is inserted, inferiorly, into the little eminence behind the internal tibial facet ;
whence it goes to the bottom of the intercondyloid notch, to be attached by its
superior extremity within the internal condyle.
Sgnovial membranes. — For this articulation there are three synovial mem-
branes : a superior and two lateral. The first, very large and strengthened by
the femoro-patellar capsule, facilitates the gliding of the patella on the femoral
pulley ; it is prolonged in a cul-de-sac below the insertion of the crural triceps.
The other two, which lubricate the articular surfaces of the proper femoro-tibial
joint, include the crucial ligaments between them, and cover the posterior
ligament, the lateral ligaments, and the fibrous fasciculi for the attachment of
the meniscii. The external lines, in addition, the tendon of the popliteus muscle,
and furnishes a vast cul-de-sac which descends in the anterior groove of the tibia,
to envelop the tendon common to the anterior extensor of the phalanges and the
flexor of the metatareus. These two femoro-tibial synovial membranes lie against
that of the femoro-patellar articulation, in front of the condyles and the notch
which separates them, and if not always, at least not unfrequently, they com-
municate with it. The three are separated from the ligaments of the patella by
a considerable mass of adipose tissue, which is prolonged into the inter-condyloid
notch, at the bottom of which it appeal's to be fixed.
The synovial cavities sometimes communicate with each other, but, according
to Lesbre, this is rare.
Movements— 'T\m imperfect hinge-joint can execute the two principal and
opposite movements of flexion and extension, and a somewhat limited accessory
movement of rotation. The mechanism of these movements being simple enough
to be readily understood without any preliminary explanation, they will not be
detailed here ; but some remarks will be made with regard to the displacement
the fibro-cartilages undergo, when the articulation is in motion.
During flexion and extension, these bodies, fixed on the tibial facets, which
they transform into glenoid cavities, move with them on the condyles of the
femur, from before to behind, or behind to before, according to the movement
THE ARTICULATIONS.
No. 1.
No. 2.
executed. But at the same time they also glide in an inverse direction, and
to a very appreciable degree, on the superior extremity of the tibia. Therefore,
during flexion, they pass from behind forward on this extremity, and are drawn
backwards during extension.
In rotation — which may take place from within to without, or from without to
within — the movement is produced not only
Fig. 142. by the pivoting of the condyles in their
glenoid cavities, but also by a fusible dis-
placement of the meniscii on the tibial sur-
faces.
In the Dog and Cat, the meniscii are joined
together, near their anterior insertion, by a trans-
verse fibrous band. There is only one patellar liga-
ment, and the posterior ligament shows in its sub-
stance, two !<mall sesamoid bones against which the
condyles of the femur play inwardly, and which give
attachment, outwardly, to the originating branches
of the gastrocnemius muscle. There is no femoro-
patellar capsule, and only one synovial membrane
for the whole articulation.
In the Pig and Sheep, there is also only one
ligament ;iud one synovial capsule.
4. TiBIO-FIBULAR ARTICULATION.
This articulation represents a small plani-
form diathrosis, the movements of which are
very limited and obscure. It is formed by
the union of the irregular diathrodial facet
which occupies the internal face of the head
of the fibula, with the analogous facet on the
external superior tuberosity of the tibia.
Short and strong interosseous or peripheral
fibres envelop these facets on every side,
and maintain them firmly in contact.
The fibula is also attached to the tibia :
" 1. Above, by two small ligamentous fasci-
culi crossed like the letter X, wdiich form the
superior part of the great arch through w^hich
pass the anterior tibial arteiy and vein (Fig.
142, 12). 2. In the middle, by a kind of
aponeurotic membrane, the wddth of which
diminishes from above to below, like that of
the space it fills (Fig. 142, 13). 3. Below,
by a ligamentous cord (Fig. 142, 14) which
prolongs the fibula to the external tuberosity
of the inferior extremity of the tibia, where
to the two external lateral ligaments of the
LIGAMENTS ATTACHING THE THREE BONES
OF THE LEG.
No. 1. Posterior face. No. 2. Anterior face.
1, Complementary fibro-cartilagiuous
pad of the patellar surface ; 2, e.\ternal
patellar ligament; 2', insertion of the
superficial gluteal into this ligament; 3,
internal patellar ligament ; 3', its upper
insertion transformed into a comple-
mentary apparatus of the patellar sur-
face ; 4, midijle patellar ligament; 5,
external meniscus of the tibia; 6, its
branch of insertion into the femur cut
off at its origin ; 7, its posterior tibial
insertion ; 8, external meniscus ; 9, in-
sertion of the anterior crucial ligament
into the fossa of the tibial spine ; 10,
tibial insertion of the posterior crucial
ligament; 11, inferior insertion of the
external femoro-tibial ligament ; 12, 13,
14, tibio-fibular ligaments. A, Tibial
arch ; B, surface of insertion of the
popliteus muscle ; C, surface of insertion
for the perforans muscle.
this cord bifurcates, and is united
tibio-tarsal articulation " (Rigot).
In the Ox, Sheep, and Goat, the fibula being replaced by a ligament, there
tibio-fibular articulation.
no proper
ARTICULATIONS OF THE POSTERIOR LIMBS. 221
In the Dog and Cat, the two principal bones of the leg are united at their extremities
and middle part : •
1. At their superior extremity, by means of a small arthrodial articulation, analogous to
that of the Horse, and, like it, provided witli a particular synovial bursa;
2. At their inferior extremity, by means of a second artiirodial articulation, whose action is
facilitated by a prolongation of the tibio-tarsal synovial membrane;
3. By their middle part, through the interposition, between the two bones, of an inter-
osseous ligament, which is wide and membranous in its upper two-thirds, and formed of
extremely short and strong fibres at its lower third.
5. Aeticulations of TttE Tarsus or Hock (Figs. 141, 144).
Preparntion. — Commence by cutting off the tendons, and so exposing the lateral ligaments
of the tibio-tarsal diathrosis. Tlien the procedure should be as for the carpus — dissect suc-
cessively the ligaments proper to each row, those uniting the two rows, and those binding the
lower row to the metatarsus.
These comprise : 1. The tibio-tarsal articulation. 2. The articulation of the
first row of bones — the astragalu3 and calcaneum or calcis. 3. Those which unite
the bones of the lower row. 4. The articulation of the two rows with each other.
5. The tarso-metatarsal articulation. The first is a perfect ginglymoid, and the
only joint really movable ; all the others are aythrodial, and their action is so
restricted that they appear to be condemned to almost absolute immobility.
This intimate union of the tarsal and metatarsal bones, is evidently chiefly intended
to guarantee precision in the movements of the tibio-tarsal articulation.
Tibio-tarsal Articulation. — Two bones alone concur in the formation
of this angular ginglymoid joint : these are the tibia and astragalus.
Articular surfaces. — For the tibia : 1. The two deep grooves, oblique forwards
and outwards, channeled in the inferior extremity of the bone. 2. The salient
tenon which separates these grooves, and on which there is often a small synovial
fossette. For the astragalus, the pulley occupying its anterior face (see p. 145).
Mode of union. — Seven ligaments bind these articulations : two external
lateral, three internal lateral, an anterior, and a posterior.
a. External lateral ligaments. — These are distinguished, according to their
relative position, into superficial and deep.
The external superficial ligament (Figs. 143, 2 ; 144, 2) is a thick funicular
cord, flattened in its inferior half. It commences above on the external tube-
rosity of the tibia, behind the groove which divides this tuberosity into two
parts ; from thence it descends almost vertically, fixing itseU" successively to the
astragalus, calcaneum, cuboides, middle metatarsal bone, and the external rudi-
mentary metatarsal bone. Passing in front with, and partly covered by, the
lateral extensor of the phalanges, to which it supplies a retaining band (Fig.
143, 2), this ligament is confounded behind, and near its inferior extremity,
with the calcaneo-metatarsal ligament. It covers the external and deep ligament,
the short band which constitutes the external calcaneo-astragaloid ligament, the
insertion of one of the branches of the flexor of the metatarsus, and the small
cuboido-cunean (cuneiform) ligament.
The external deep ligament (Figs. 143, 1 ; 144, 1), much shorter than the pre-
ceding, is attached, superiorly, to the anterior part of the external tuberosity of
the tibia, and is directed obliquely backwards and downwards, to be fixed by two
fasciculi at the external side of the astragalus and calcis. This ligament, covered
by the preceding, which crosses it like an X, is lined on its inner face by a
synovial membrane of the articulation.
17
222
THE ARTICULATIONS.
b. Internal lateral ligaments. — These are also three funicular bands superposed
on one another, and arb consequently designated as superficial, middle, and deep.
The internal superficial ligament (Fig. 14.3, 6), the strongest and longest of
the three, proceeds from the internal and inferior tuberosity of the tibia,
diminishing as it descends on the inner side of the tarsus. It is fixed, in mixing
with the astragalo-metatarsal ligament and with the posterior tarso-metatareal
ligamentous arrangement, to the tuberosity of the astragalus, the scaphoid, the
two cuneifoi-m, the superior extremity of the principal metatarsal, and that of the
internal rudimentary metatarsal bones.
The internal middle ligament (Fig. 143, 5) is com-
posed of two funicular cords, attached in common beneath
the preceding ligament to the internal tibial tuberosity.
These two fasciculi, exactly resembling those of the ex-
ternal deep ligament, are directed downward and back-
ward, and terminate, one at the astragalus, the other
at the calcis.
The internal deep ligament (Fig. 144, 4) is an extremely
slender fasciculus, enveloped by the synovial membrane ;
it is often reduced to a thin shred, scarcely distinct from
the serous covering surrounding it. It is attached, in one
direction, to the tibia below the middle ligament ; in
the other, to the astragalus, and nearly at the same point
as the superior fasciculus of the middle ligament.
c. Anterior ligament. — This is a membraniform band
formed of intercrossed fibres, stronger outwards than in-
wards, attached by its upper border above and in front
of the tibial surface, fixed by its inferior border to the
astragalus, the scaphoid and great cuneiform bones, and
the astragalo-metatarsal ligament ; it is confounded at its
sides with the two superficial lateral ligaments. Its internal
face is lined by articular synovial membrane, while the ex-
ternal is covered by the flexor of the metatarsus, the anterior
extensor of the phalanges, the anterior tibial arteiy, and
several large anastomosing veins, from the junction of
which arises the anterior tibial vein.
d. Posterior ligament. — This is the second membrani-
form or capsular band, which protects the articulation
posteriorly. It presents, in its centre, a fibro-cartilaginous
thickening, on which gUdes the perforans tendon. It is
attached, above, to the tibia ; below, to the astragalus and
calcis ; at its sides it is mixed with the two superficial
lateral ligaments, and the astragalian fasciculus of the middle internal ligament.
Its internal face is lined by articular synovial membrane ; the external is covered
and lubricated by the vaginal serous membrane, which facilitates the gliding of
the perforans tendon in the tarsal sheath.
Synovial membrane. — This membrane is developed at the internal face of the
two capsular ligaments, lines the greater part of the three internal ligaments,
and also the external deep ligament. It communicates, in front and below, with
the synovial membrane proper to the articulation of the two rows of tarsal bones.
When it becomes the seat of dropsical effusion, it is always distended forwards
parsal articitlations
(front view).
, External deep ligament
of the tibio-taisal ar-
ticulation ; 2, 2, ex-
ternal superficial liga-
ment ; 4, internal deep
ligament ; 5, internal
middle ligament ; 6, In-
ternal superficial liga-
ment ; 7, astragalo-
metatarsal ligament ; 8,
small cuboido-cunean
ligament. A, Pulley of
the astragalus; B, cu-
boidal insertion belong-
ing to tne tendinous
cord of the flexor of the
metatarsus ; C, vascular
canal of the tarsus.
ARTICULATIONS OF THE POSTERIOR LIMBS. 223
and inwards, because it is only sustained at that place by the anterior capsular
ligament. But the effusion may also elevate the posterior- ligament, and produce
hernia in the hollow of the hock, behind the lateral ligaments. It is not, there-
fore, absolutely correct to attribute all the synovial tumours in the hollow of the
hock to dilatation of the tarsal tendinous sheath. (See the figure of the tendons
and synovial capsules of the posterior limb, in the description of the perforans
muscle.)
Movements. — Nothing can be less complicated than the mechanism of the
tibio-tarsal articulation, this joint only permitting two opposite movements —
those oi flexion and extension — which are so simple and precise that we may dispense
with a description of the manner in which they are executed. It may only be
remarked that, in order to prevent contact between the leg and foot during flexion,
the latter fraction of the limb deviates a little outwards, owing to the marked
obliquity of the articular grooves.
Articulation of the Bones of the First Row, or Calcaneo-astraga-
LOiD Articulation. — This is a compound arthrodial joint, resulting from the
coaptation of the three or four articular facets of the posterior face of the astragalus
with the analogous facets of the calcis.
This joint is maintained by the lateral ligaments of the tibio-tarsal articulation,
and by four cakaneo-astragaloid ligaments — a superior, external, internal, and the
last interosseous.
The superior calcaneo-astragaloid ligament is formed of short parallel fibres
thrown across from one bone to the other, and is situated towards the superior
extremity of the pulley of the astragalus ; it is lined superiorly by the synovial
membrane of the tibio-tarsal articulation.
The lateral ligaments are two very thin fasciculi concealed by the ligaments
which bind, laterally, the tibia to the tarsal bone.
The interosseous ligament is very strong, and occupies a great portion of the
rugged excavation which separates the articular facets.
This articulation does not usually possess proper synovial capsules. Two
prolongations of the synovial membrane of the two rows, in ascending between
the calcis and astragalus, facilitate the gliding of the two inferior facets. An
analogous prolongation of. the tibio-tarsal synovial membrane is effected for the
superior facets, and it is not rare to find this prolongation form a distinct
capsule.
Movements nearly null.
Articulation of the Bones of the Second Row with each other. —
These bones, four in number, are brought into contact in the following manner :
The cuboides responds to the scaphoid by two facets — one anterior, the other
posterior ; it articulates with the great cuneiform by two similar facets, the
posterior of which is not always present. The scaphoid is united to the two cunei-
forms by the large convex facet occupying its entire lower face. The two cunei-
forms are joined by means of a small articular surface.
The fibrous fasciculi which maintain the diarthrodial surfaces in contact are
somewhat numerous. They are as follows : —
1. The astragalo-metatarsal ligament and tarso-metatarsal apparatus, which
will be described hereafter ; these two bands do not properly; belong to the articu-
lations of the second row of bones.
2. Two anterior ligaments, named cuhoido-scaphoid and cuboido-cunean (Figs.
143, 8 ; 144, 5), which are carried from the cuboid to the scaphoid and to the
224
THE ARTICULATIONS.
great cuneiform bone, one above, the other below the vascular channel formed
between these three bones.
3. Two interosseous ligaments analogous to the preceding two. forming the
superior and inferior walls of the aforesaid channel.
4. An interosseous scaphoido-cunean ligament, passing from the scaphoid to
the two cuneiform bones.
5. An interosseous ligament, named the intercunean, is directed from one
cuneiform bone to the other, and is confounded with
the preceding ligament.
The disposition of the lubricating membranes
varies with that of the articular facets. The follow-
ing is what is most generally observed : A proper
synovial membrane is specially destined for the facets
by which the scaphoid and gi'eat cuneiform bones
correspond ; this synovial membrane belongs also to
the two cuboido-scaphoid and posterior cuboido-
cunean arthrodiae. The anterior cuboido-scaphoid
diarthrosis receives a prolongation from the synovial
membrane of the two rows. The play of the anterior
cuboido-cunean and intercunean facets is facilitated
by two prolongations of the tarso-metatai'sal synovial
membrane.
Movements almost null.
Articulation of the two Rows with each
OTHER. — This arthrodial joint is formed by the union
of the calcis and the astragalus, on the one side, with
the scaphoid and cuboid bones on the other. Its
solidity is assured by six principal bands :
1. The two lateral superficial ligaments of the
tibio-tarsal articulation.
2. The calcaneo-metatarml ligament (Fig. 144,
3), a strong fibrous brace which unites the posterior
border of the calcis to the.cuboides, and to the head
of the external rudimentaiy metatarsal bone. It is
confounded, outwardly, with the external and super-
ficial tibio-tarsal ligament ; inwardly, with the pos-
terior tarso-metatarsal band.
3. The astragalo-metatarsal ligament (Fig. 143,
7), a radiating fasciculus, the fibres of which leave the
internal tuberosity of the astragalus, become mixed
up with the internal and superficial tibio-tarsal liga-
ments in diverging downwards to the scaphoides, the great cuneiform bone, and
the upper extremity of the principal metatarsal bone.
4. The posterior tarso-metatarsal ligament is a vast, very strong, and very
complicated fibrous arrangement, which binds, posteriorly, all the tarsal bones,
and also fixes them to the three portions of the metatarsus. This band, which is
crossed by several tendons and by the artery and vein lodged in the cuboido-
scaphoido-cunean canal, is continued below by the tarsal stay of the perforans
tendon. It therefore closely resembles the posterior carpal ligament. Its posterior
face is covered by the tendinous synovial membrane lining the tarsal sheath for
ARTICULATIONS OF THE TARSUS
(LATERAL VIEW).
1, External deep ligament; 2,
external superficial ligament ;
2', ring furnished by the latter
ligament for the passage of the
lateral extensor tendon of the
phalanges; 3, calcaneo-meta-
tarsal ligament ; 4, astragalo-
metatarsal ligament ; 5, small
cuboido-cunean ligament. A,
Cuboidal insertion of the flexor
muscle of the metatarsus ; B,
anterior orifice of the vascular
conduit of the tarsus ;C, groove
on the external tuberosity of
the tibia for the gliding of the
lateral extensor of the pha-
langes ; D, insertion of the gas-
trocnemius tendon of the leg
into the os calcis ; E, gliding
surface for that tendon.
THE ARTICULATIONS IN BIRDS. 22S
the passage of the perforaiis tendons. It is confounded, on its sides, with the
calcaneo-metatarsal, and the internal and superficial tibio-tarsal ligaments.
5. An interosseous liyamenf, attached to the four bones composing this
articulation.
It is provided with a particular synovial membrane which always communi-
cates, in front, with the tibio-tarsal capsule. This membrane is prolonged,
superiorly, between the calcis and astragalus, to lubrify two of the facets by
which these bones come into contact ; and, in addition, it descends between the
cuboid and scaphoid bones, to form a third prolongation for the anterior cuboido-
scaphoid arthrodia.
Movements almost null.
Takso-metataesal Aeticulation. — This joint, formed by the meeting of
the three tarsal bones — the cuboid and the two cuneiforms — with the three bones
of the metatarsus, is fixed by the lateral superficial ligaments of the tibio-tarsal
articulation, the calcaneo-metatarsal hgament, those which have been named the
astragalo-metatarsal and tarso-metatarsal, and by a strong interosseous ligament
which naturally forms three fasciculi.
The synovial membrane proper to this joint ascends into the small anterior
cuboido-cunean arthrodia, and into that which unites the two cuneiform bones ; it
descends to the intermetatarsal articulations.
Movements nearly null.
In all the domesticated animals except Solipeds, the tarsal articulations offer some differen-
tial peculiarities, the study of which is without interest, as it is without utility. It is only
necessary to remark that the immobility of the tarsal joints, properly so called, is less absolute
than in Solipeds, owing to the peculiar configuration of the articular surfaces of some of the
bones composing them. Thus, in the Ox, Sheep, Goat, and Pig, the calcis is joined to the
astragalus by a real trochlear articulation, and the latter bone is united to the scaphoid by a
diarthrodial joint of the same kind — a mode of articulation much more favourable to motion
than that of the planiform diarthrodial joint. In the Dog and Cat, the same result is
obtained by the reception of the head of tlie astragalus into the superior cavity of the scaphoid.
In Ruminants and the Pig, it is also observed that the tibio-tarsal articulation is formed
by the tibia and fibula in the one direction, and by the astragalus and os calcis in the other.
Lemoigne, who has been again recently studying the mechanical arrangement of the Ox's
hock, remarks that, if the mobility of all the tarsal articulations deprive the posterior limb of
that animal of the rigidity necessary fur speed, yet the nature of the astragalo-calcanean articu-
lation gives it great power. In fact, the posterior trochlea of the astragalus acts as an eccentric
on the calcis during movement, and gradually separates this bone in such a manner that the
tendon of the gastrocnemius always remains nearly perpendicular on the lever arm — no matter
to what degree the hock may be open or closed. But this mechanism may perhaps be disputed.
CHAPTER III.
THE ARTICULATIONS IN BIRDS.
The study of the articulations in birds will only arrest us for a few moments ; as
it will be confined to some remarks on the intervertebral occipito-atloid and
temporo-maxillary joints, the only ones exhibiting a special conformation worthy
of attention.
Intervertebral articulations. — The great mobility of the neck of Birds is not
only due to the fact of its length, relati^'ely considered, but also to the peculiar
manner in which the vertebrae of this portion of the spine are articulated. It will
226 THE ARTICULATIONS.
be remarked that these do not unite by their bodies in the form of a continuous
series of amphiarthroses, as in the domesticated Mammals ; but that, instead of
these mixed articulations, there are real diarthroses, which may be included in the
class created by Cruveilhier under the title of articulation hij reciprocal ball-and-
socket — each vertebra becoming connected with the adjacent vertebra by means of
facets, convex in one sense and concave in the sense perpendicular to the firat.
These facets are manifestly covered by cartilage of incrustation ; and it appears
that, instead of their being applied dii'ectly against the opposite facets, which
present a precisely inverse conformation, they are separated by an extremely thin
fibro-cartilaginous disc, which resembles the interosseous meniscus of the temporo-
maxillary articulation in the Carnivora of the Cat species. Two loose synovial
capsules, separated by this interarticular lamina, complete the framework of each
articulation, and favour the play of the vertebrae on one another. This arrange-
ment has only, so far as we are aware, been observed in the Swan, and that very
imperfectly ; but it probably belongs to the entire class of Birds, for until now
we have met with it in all the individuals submitted to examination.
In its dorso-lumbar and sacral portion, the spine is a single piece, in con-
sequence of the consolidation of the vertebrae, and does not show any proper
articulations.
In the coccygeal region, the mobility of the spine reappears, but it is far
from being so marked as in the cervical region ; the vertebrae here are united by
amphiarthrosis, and not by reciprocal ball-and-socket.
Occiinto-atloid articulation. — It has been shown that there is only one more or
less spheroidal condyle of the occipital bone, and a single cavity on the anterior
margin of the spinal canal of the atlas. The occipito-atloid articulation is there-
fore a true enarthrosis, with varied and very extensive movements — a disposition
which accounts for the facility with which Birds can pivot their heads on the
superior extremity of the vertelbral stalk.
Temporo-maxillary articulation. — The play of this articulation offers one pecu-
liarity, in that it causes, during the separation of the mandibles, not only the
depression of the inferior, but also the elevation of the superior mandible. The
arrangement which permits this movement has been already alluded to (p. 189) ;
but yet it is difficult to understand, because there is no active agent, no proper
muscle to directly effect it. Nevertheless, the mechanism which executes it is
most simple, and may be given in a few words. Thus, we know that the square
bone, interposed between the temporal and maxillary bones, like the interarticular
meniscus of Mammals, is united outwardly with the malar bone, and inwardly
with the pterygoid. We know also that the latter rests, by means of a diarthrodial
facet, on the body of the sphenoid, and that it abuts against the posterior extremity
of the palatine bones (Fig. 109) ; while the first, the zygomaticus, is joined
directly to the supermaxillary bone. The upper jaw, it is also known, is movable
on the cranium, because of the flexibility of the cartilages or bony plates uniting
these two portions of the head. It may then be added, that the square bone
receives on its anterior process one or two small muscles, which are attached to
the base of the cranium, and that these bones may be pushed, or rather drawn
forward, by the contraction of these muscles. It is this projecting or pushing,
transmitted to the upper mandible through the medium of the malar bone on the
one side, and the pterygoid bone on the other, that produces the elevation of that
mandible. Nothing is easier than to prove it ; it is only necessary to take the
head of a Bird, denude it of all its soft parts, and press with the fingers behind
GENERAL CONSIDERATIONS ON TEE STRIPED MUSCLES. 227
the two square bones, to imitate the action of the elevator muscles ; we then see
the internal extremity of the pterygoid bone glide on the facet of the sphenoid,
and push before it the palatine bone, during which the zygomatic bone acts in the
same manner on the maxillary ; and in this way is produced, through the influence
of this postero-anterior propulsion, the ascending movemeijit we undertook to
explain.
THIED SECTION.
The Muscles.
After the study of the bony levers and their articulations, comes the description
of the agents whose function it is to move them. These are the muscles — fibrous
organs possessing the property of contracting under the influence of a stimulus.
They are distinguished as striped or striated, and smooth or non-striated
muscles, according to the character of the anatomical element composing them.
The striped muscles differ from the smooth, in that, with the exception of
the tissue of the heart, their contractile power is immediately placed under the
influence of the will. They are more particularly concerned in the functions of
relation, which cause them to be also named the external muscles, or muscles
of animal life. These muscles are nearly all attached to the skeleton, and are
the active agents in moving the bony framework ; they will, therefore, be the
only ones referred to in this place, in studying the locomotory apparatus.
The unstriped muscles are removed from the influence of the will, and belong
to the organs of vegetative life. They are also designated internal muscles^
involuntary muscles, or muscles of orgastic life.
But before entering upon the particular description of each muscle, we will
allude to the general considerations relating to their history.
CHAPTER I.
GENERAL CONSIDERATIONS ON THE STRIPED MUSCLES.
THE STRIPED MUSCLES IN GENERAL.
In this first paragraph, we will survey, in a general manner, the volume, situation,
form, direction, attachments, relations, and names of the muscles belonging to
the locomotory apparatus.
A. Volume. — Nothing is more variable than the volume of the external
muscles. What a difference there is, for example, between the small scapulo-
humeralis muscle and the biceps femoris or longissimus dorsi, and what a
number of intermediate sizes between these three points of comparison ! There
are consequently very great, great, medium, small, and very small muscles.
The weight of the total mass of these organs varies according to the species.
228 THE MUSCLES.
age, sex, and state of health ; but on taking a general average, it will be found
that it represents nearly one-half the entire weight of the body.
B. Situation. — There is no need to insist upon the fact, that a knowledge
of the situation of the muscles is one of the firet objects to be acquired with
regard to their arrangement.
They may, like the bones, be described in two ways.
1. In relation to the median plane of the body ; whence their division into
pairs and single muscles. The last, very few in number, are far from exhibiting
the symmetry which exists in the bones of the same order, as may be seen in the
diaphragm.
2. In relation to the other organs ; such as the bones and surrounding
muscles.
C. FoEM. — With regard to their absolute form, the muscles, again, like the
bones, are classed as long, wide, and short.
Long muscles. — These muscles are more particularly met with in the limbs.
Provided with a principal axis, to which we may ascribe the effect of their
contraction, they present a middle portion — usually thick, and tivo extremities of
unequal thickness ; the most voluminous, always turned upwards, is metaphori-
cally designated the head, the other the tail. They are most frequently /i<s?/o/7«,
sometimes conical, but rarely cijlindrical, prismatic, ov flattened into thin bands.
Thus, as Bichat remarked a long time ago, there are muscles which have no
other analogy with the long muscles of the limbs than in their external appear-
ance. These are the long muscles lying above or below the spine, and which are
composed of a series of fasciculi indistinguishable at their origin and distinct at
their termination ; or fasciculi, each of which has a distinct origin or termination
on the vertebrfe.
Wide muscles. — Wide muscles are those which have two principal axes, and
are stretched beneath the skin, or around the great cavities of the trunk, which
they concur in enclosing and separating from one another. They are ellipticaly
quadrilateral, triangidar, trapezoid, etc.
Short muscles. — These are found chiefly around the short bones, or at the
periphery of the articulations which are deeply buried under enormous muscular
masses. Although their name indicates that their three axes offer nearly the
same dimensions, yet there is most frequently one, and even two, which pre-
dominate. They may therefore be assimilated, in this respect, to the long or
wide muscles.
D. Direction. — Cruveilhier has justly remarked, that the direction of a
muscle is one of the most important features in its history ; for it allows the
determination of the angle of incidence of the muscle on its arm of the lever, its
power, and its uses.
With regard to the direction of muscles, we may observe : 1. The form of
their principal axis. 2. The relation of this axis to the vertical line. 3. Its
comparison with the axis of the bony levers which the muscles surround or moves.
a. A muscle is termed rectilinear when its principal axis is straight ; it is
curvilinear, or circular, if this axis describes a curve more or less marked ; it
becomes inflected when it proceeds in a certain direction, and afterwards turns
on a bony or cartilaginous pulley in another direction — that is to say, when its
principal axis is broken into several lines. If the muscle offers two axes, it will
\)Qflat or concave, these being one or the other, or straight or curvilinear.
J. With regard to the direction of the muscles to that of the plumb-line, it
GENERAL CONSIDERATIONS ON THE STRIPED MUSCLES. 229
is either vertical, horizontal, or oblique — expressions which carry their own definition
and require no explanation.
c. If the direction of the muscles be compared with that of the bones they
surround and move, it will be found that they are either parallel to these levers,
or form with them angles more or less acute. The proper direction of the bones
being known, it is sufficient to indicate that of the muscles to clearly establish
this comparison. For instance, in saying that the majority of the muscles of
the shoulder are oblique from above to below, and from before to behind, it is
understood that these muscles are parallel to the scapula, and that their incidence
•on the humerus takes place at a right angle.
E. Attachments or Insertions. — This is undoubtedly the most essential
part of the study of the muscles ; for with a knowledge of their insertions, we
may determine then- extent and direction, and even their relations and uses.
By the term attachment, fixed insertion, or „ origin, is meant the point of the
muscle which usually remains fixed while the muscle itself contracts ; the attach-
ment, movable insertion, or terminatio?i is the name given to that portion which
is fixed to the lever displaced by the muscular contraction. Muscles are fre-
quently met with the two insertions of which are alternately fixed or movable ;
and in such cases care is taken not to give these insertions one or other of the
•designations.
The fixed insertion is often confounded with that of other muscles ; the
movable insertion is generally free and independent.
The muscles are sometimes directly attached to the bones by the ends of their
fleshy fibres ; but most frequently they are fixed to these inert levers through the
medium of a tendon or an aponeurosis, the volume of which is less considerable
than that of the fibres. But for this arrangement, the surface of the skeleton
would not be sufficiently extensive to give insertion to all the external muscles.
F. Relations. — The indication of the relations of the muscles completes the
idea of their situation, and is of great importance from a surgical point of view.
They should, therefore, be studied with all the precision possible.
The muscles entertain relations either with the skin, the bones, other muscles,
■or with vessels and nerves.
a. It is only, properly speaking, the subcutaneous muscles — such as the
panniculus carnosus and the muscles of the face — which are really in inmiediate
contact Avith the skin. The others are separated from it by the aponeurotic -^^^-^*'
fas(^a^ which will be described as the appendage of the muscular system. '''^^
The superficial muscles are only related to the bones by their extremities.
Those which are deeply situated are immediately applied by their bodies against
the bones of the skeleton.
c. The muscles are related to each other in a more or less intimate manner.
Sometimes they adhere closely to one another ; and at other times they are
separated by interstices filled with fat or connective tissue, and which are generally
traversed by vessels and nerves.
d. The connections of the muscles with the latter organs sometimes assume
a remarkable character ; this is when one of them accompanies, like a satellite,
the vascular and nervous trunks concealed beneath its deep face. There is in this
circumstance an important fact with regard to surgical anatomy. The borders of
these muscles are usually visible on the surface of the region, and for this reason
may become valuable guides in seeking for important organs in their vicinity.
G. Nomenclature. — a. Before the time of Sylvius, the muscles had not
280 THE MUSCLES.
received particular names. Since the days of Galen they had been distinguished
by the numerical epithets of first, second, third, etc., to indicate their place and
their order of superposition in the regions to which they belonged. It is in this
fashion that they are designated in the Italian work on the Anatomy of the
Horse by Ruini.
b. Sylvius was the fii*st to give the muscles real names ; and, his example
being followed by succeeding anthropotomists, the nomenclature ot these organs
was soon completed. But no general view, no methodic spirit, guided Sylvius
and his successoi-s ; it was sometimes their form, and sometimes their direction
(oblique, straight, transverse muscles), position {intercostal muscles), uses (adductory
abductor tnusctes), etc., to which the muscles owed their names. Bourgelat
applied this nomenclature to the Horse, but modified it in many points.
c. Chaussier, stnick by the imperfections of the nomenclature introduced into
science by Sylvius, sought to substitute for it another, much more methodical.
This anatomist gave to each muscle a name formed by two words, indicating the
insertions of the organ. Girard imported this ingenious idea into veterinary
anatomy. It was in applying this nomenclatm'e to the muscles of the Horse
that he gave the name of supra-acromio-trochanteriiis to the supra-spinatns of
Sylvius and Bourgelat, and subscapulo-trochanterius to the subscapular of these
authorities. When two muscles have the same attachments, they are distin-
guished by adding to the names which indicate their insertions, another which
signifies the relative position or size of these organs. Thus, we distinguish the
long abductor of Bourgelat from the short abdudor, both of which would merit
the name of scapulo-humeral, according to the nomenclature of Chaussier, by
the epithets of great scapulo-humeral and small scapido-humeral. The binary
nomenclature of Chaussier is a useful aid to the memory of students, for a
knowledge of the name of a muscle implies that of its attachments and uses ;
but, nevertheless, notwithstanding its advantages, this new nomenclature did not
supersede the old one ; because it ceased to be correct when applied to com-
parative anatomy, the same muscles not having the same insertions in all the species.^
* It is not, however, that the ancient nomenclature has more advantages in this respect
than the new. What can be more improper, for example, than the names of deltoid, spleuius,
soleus, digastrieus, etc.? Do the muscles which receive these designations, considered in
Mammals only, offer in all species the form or the structure which justifies the employment
of these names in tlie human species? Are the distiuctive epithets of great, medium, little,,
etc., given to many of them, reasonably applicable in every case? May not the same objectiou
be urged against tiie majority of the names derived from their uses, complications, etc. ?
No system of myological nomenclature is really philosophical, and we are of those who
believe it to be indispensably necessary to create one; indeed, we are inclined to think tliat it
would be simple and easy to attain this result in starting from a basis the fixity and invari-
ability of which should be well defined. And this basis is, in our opinion, already discovered ;
it is the principle of connections founded by E. Geoffroy Saint- Hilaire in his immortal Phihsophie
Anatomique — a principle to which modern science certainly owes its finest conquests.
We are desirous that the myolngical nomenclature should rest entirely, in the first place, on
the relations of the muscles with the bones of the skeleton, or with other organs equally fixed and
very important ; in the second place, on the reciprocal connections of the muscles.
Such is our rule ; and it is not precisely new, fur the older anatomists were often inspired
by it, though unwittingly, as the principle on which it is founded was to them entirely
unknown; this circumstance, however, immediately leads us to an appreciation of its value.
For instance, what could be happier than the name of intorcostals given to the inuscleB'
situated between the ribs, and their distinction into external and internal ? Here we have
names which indicate the relations of the muscles tliey designate, with the portions of the skeleton
and the reciprocal connections of these muscles. It can also be applied in an equally rigorous
manner to every species. We may also cite the supra-costals, the intertransverse, the trans-
GENERAL CONSIDEEATIONS ON THE STRIPED MUSCLES. 231
In this work we will follow the nomenclature of Bourgelat, which will, how-
ever, be submitted to some change. But as the names given by Girard are, in
our opinion, of some assistance to students, care will be taken to include them in
the synonymy.
(It only remains for me to add that Chauveau's nomenclature will be followed
as closely as possible. It possesses advantages which are greatly superior to that
adopted by Percivall ; and as, in my opinion, the names and terms imported into
science should be as nearly alike in all languages as may be compatible with cir-
cumstances, in order to facilitate study, comparison, and reference, I the more
readily venture to take this course. Percivall's nomenclature will, however, be
added in brackets to the synonyms, as well as that of Leyh and Gurlt, when
occasion appears to demand it.
Structure of the Striped Muscles.
There enter into the structure of muscles : 1. Muscular tissue, properly
so called. 2. Connective tissue in the form of deUcate lamellse, aponeuroses, or
tendons. 3. Vessels and nerves.
A. Muscular Tissue. — This tissue is composed of prismatic fasciculi, which
it is possible to divide and subdivide into several smaller and smaller fasciculi,
until the muscular fibre or primitive fasciculus is reached.
The muscular fibre is a kind of irregular cylinder, from O'OIO to 0-008 milli-
metres in length. It is sometimes straight, sometimes slightly \\Tinkled, but
always striped either in a longitudinal or transverse direction, or both at once ;
the transverse striae, being usually more marked, gives the fibril a very elegant
scalariform aspect.
This fibre is formed by an envelope and contents.
The envelope is a very delicate, structureless membrane of an elastic nature,
named the sarcolemma or myolemma (Fig. 146). Flat or oval nuclei in greater
or less number can be seen on its inner face.
The contents, or muscular substance, can easily be resolved into parallel fibrillce,
verse spinous, the subscapularis, the eupra-spinatus, the infra-spinatus, etc., as they are found in
a greater or less marked degree in identical conditions.
Other muscles have received names derived in part from their situation, and in part from
their volume. These names are far from being as convenient as the first ; as may be judged
from the following examples : —
In the majority of vertebrate animals, there are three important muscles situated above
and behind the pelvis, and forming the base of the croup ; they have been designated gluteals,
and this name is convenient, because it designates their situation. But to distinguish them
from each other, regard has been had to their volume ; so that there is a great, a medium, and
a small gluteus. This is an error, however, for the volume of the muscles is subject to the
greatest variations, and a voluminous muscle in one species may be a very small one in
anotlier, and vice versa. The muscle analogous to the gluteus maximus in Man has been
described by Bourgelat as the minimus, and by Lafosse and Rigot as the medius. With regard
to the gluteus medius of Man, its representative in the lower animals has been designated as
the maximus by the majority of veterinary anatomists. What confusion ! And how easy it
was to evade it by distinguishing these muscles, not by their volume, but by their reciprocal
connections, which are the same in every species ! Is it not, indeed, more natural to substitute
the names of superficial, middle, and deep gluteals, for those of great, etc. ?
The same remark is applicable to the muscles which, in Man, cover the anterior aspect of
the chest. Designated in common, and justly so, as pectorals, tliese muscles are wrongly
distinguished into great and little ; for the last, which is already an enormous muscle in the
smaller Ruminants, is represented in Solipeds by two considerable muscles, much more
voluminous than the muscle analogous to the great pectoral. It is only necessary, in this
case, to change their names into superficial and deep pectorals.
232
THE MUSCLES.
B, ULTIMATE FIBRIL OF
MUSCLE (according
TO BOWMAN).
C, Muscular fibre more
highly magnified, its
myolemma being so
thin and transparent
as to allow the ulti-
mate fibrillae to be
in the fresh muscles of insects ; in the higher animals, this disassociation into
parallel fibrillae is generally only possible in muscles subjected to the action of
certain reagents. Other reagents favour the breaking up of the fibre into super-
posed discs ; hence it has been concluded that the fundamental element of the
primitive muscular fibre was not a fibril, but a discoid segment of fibrillae, to which
Bowman gave the name of sarcous elements (Fig. 143).
Bowman considered that the transverse striae represent the lines of union of
the sarcous elements. But nowadays the striation of the fibre is explained by
the striation of the primitive contractile cylinder ; in
fact, each of these is divisible into a series of thick, dark-
coloured, contractile discs, joined by bright bands which
play the part of a tissue framework in the cylinder. In
the majority of Mammals, the thick discs are traversed in
their middle by a pale streak named the intermediate band
or streak of Hensen ; in the middle of each bright band is
a thin disc dividing it into two parts. In the Invertebrata
the situation is more complicated, as is seen in Fig. 147.
Kanvier has remarked that there is, in the Skate and
Rabbit, pale and dark striped muscles. The pale muscles
are recognized by the predominance of the transverse
striation and the rarity of nuclei ; wliile the fibres of the
dark muscles present, on the contrary, a great number of
nuclei and prevailing longitudinal striation. Lavocat and
Arloing have examined these difl'erences in the muscular
apparatus of some Fishes, Birds (Fowls, Guinea-fowls),
and domestic Mammals (Dog, Ox, Horse), and their
observations confirm those of Ranvier, apart from some secondary differences
special to the varied species on which they made their investigations.
The muscular fibres are united parallel to each other to form secondary
fasciculi, which are surrounded by a connective sheath — the internal pei'imysium.
The secondary fasciculi are laid together to constitute more voluminous fasciculi,
which, in their turn, form the entire
muscle. The connective sheath enveloping
the muscle is named the external perimy-
sium.
B. Tendons and Aponeuroses. —
The tendons are white, nacreous, round,
or flattened cords fixed to the extremities
of the long muscles. They are composed
of fasciculi of connective-tissue fibres,
covered by a layer of flat cells ; they have a parallel direction, and are united to
one another by loose connective-tissue sheaths.
The elementary fibres succeed the primitive striped fibres ; the latter terminate
in rounded extremities, and are fused to the fibrous fasciculi— hollowed into a kind
of cup — by an intermediate and very solid amorphous substance.
The aponeuroses belong almost exclusively to the wide muscles; they are
foi-med of several planes of parallel fibres which are not intercrossed in their
middle part ; at their superficies, however, the fibrous fasciculi are matted together
in a more or less inextricable manner.
It is very interesting to study the mode of union of the muscular fibres with
Fis;. 146.
MUSCULAR FIBRE BROKEN ACROSS, SHOWING
THE UNTORN SARCOLEMMA CONNECTING
THE FRAGMENTS.
GENERAL CONSIDERATIONS ON THE STRIPED MUSCLES.
233
the tissue of the aponeuroses and tendons, as well as the reciprocal relations of
these two parts.
The muscular fibre may be found passing in the same direction as the tendon,
or it may fall upoji the latter obliquely. In both cases there is no insensible
Fig. 147.
Fig. 148.'
TORN MUSCULAR FI-
BRE : THE TWO
FRAGMENTS ARE
HELD TOGETHER
BY THE SARCO-
LEMMA.
transition between the muscular fibre and the fasci-
culus of the fibrous tissue ; on the contrary, the con-
tractile fibre terminates by a rounded extremity,
which is buried in a corresponding depression in the
tendon or aponeurosis. The union of the muscular
with the fibrous tissue appears to be effected by means
of a kind of amorphous cement, which is very solid ;
so much so, that when the muscles are submitted to a
degree of traction sufficient to cause a rupture, this
never happens at the point of union.
The tendons commence sometimes by a hollow
cone, which receives on its internal face the insertions
of its muscular fibres ; and sometimes by a thin point,
often divided, which is plunged into the substance of
the muscle. It is worthy of remark, that a muscle
provided with two tendons shows the first-named
arrangement at one of its extremities, and the other
at its opposite extremity ; so that all the fibres which
compose the muscle offer nearly the same length, those
which leave the summit of the internal tendon being
fixed to the bottom of the hollow cone formed by the
second tendon, and so on reciprocally.
Tendons are not necessarily placed at the ex-
tremities of muscles. Sometimes the muscle is divided into two bodies or bellies
by a middle tendon ; it is then named a digastric muscle,
', * These figures are from Renaut's work, Trailed' Histologie. Just publisiiedby Lecrosnier,
Paris.
PRIMITIVE FIBRE OF THE RED
MUSCLE OF A RABBIT, MADE
TENSE BY THROBBING.
NS, Superficial nuclei ; np,
deep nuclei ; n, nuclei in
profile beneath the sarco-
lemma; GS, sarcodic drop
resulting from the expression
of the muscular plasma, due
to the contraction of the
muscle under the influence
of alcohol ; G, G, G, proteic
granules from the muscular
plasma, pressed out and united
beneath the sarcolemma, or
squeezed outside of it.
THE MUSCLES.
The muscular fibres which are continued by the fibrous fascicuK may be
divergent or parallel. In the first case — the diaphragm, for example — the con-
nective fibres run in the same direction as the muscular fibres. In the second
case several arrangements may be observed :
1. Tendons may pass in the same direction as the muscular fibres. This is the
most simple manner (Fig. 152, A).
Fig. 150.'
Fig. 149.
PRIMITIVK MUSCCTLAR FIBRE FROM
THE FOOT OF THE LUCAN03
STAG-BEETLE —A COMPLICATED
CONTRACTILE SEGMENT, MADE
TENSE BY THE INTERSTITIAL
INJECTION OF STRONG ALCOHOL.
K, Muscular nucleus ; 8, sarcolem-
ma; SM, limits of a contractile
segment of muscular substance ;
DE, limits of a thick disc system
enclosing discs ; Ep, principal
thick disc ; Ea, Ea, thick acces-
sory discs ; Bi, intervening
bright bands of the thick discs ;
BC, limits of the system of the
bright band containing — Mp,
the thin principal disc, and Ma,
Ma, the two thin accessory discs ;
/, /, /, lines of longitudinal
striation indicating the limits
of the fibrillar fasciculi.
RELATION OF THE PRIMI-
TIVE MUSCULAR FIBRE3
WITH THE TENDON OF
THE STERNO - HYOID
MUSCLE OF THE FROG.
F, Ordinary primitive
fibres ; f', muscular
prolongation ; T, ten-
don of insertion.
2. Muscular fasciculi, passing altogether from the same side to become united
into a tendinous cord (Fig. 152, B and C), constitute a semi^enmfonn muscle.
3. Muscular fasiculi maybe implanted to right and left of the tendon, and
form ^pennated ov penniform muscle (Fig. 152, D).
These various aiTangements of the muscular fibres with their tendons demon-
strate the necessity of not confounding the length of the fleshy body of a muscle
' From Eenaut's work already mentioned.
OENEEAL CONSIDERATIONS ON TEE STRIPED MUSCLES.
235
Fig. 151.
with the length of its fibres ; for the latter alone give an indication of the possible
degree of shortening it is capable of — this shortening being estimated at one-
fourth the length of its contractile fibres. In glancing at the different an'ange-
ments shown in Fig. 152, it will be seen that, with muscles which have the same
total length, that of the contractile elements varies within extensive limits.
C. Vessels and Nerves. — The muscular
tissue receives much blood ; the fibrous tissue
very little. The arteries are large and numerous,
and each is accompanied by two veins. The
capillary vessels anastomose in such a manner
as to form rectangular meshes, the greatest
diameter of which is directed towards the length
of the muscle.
Ranvier has remarked that, in the dark
muscles of the Rabbit, the vascular network has
varicose formations which retain a considerable
mass of blood in the interior of the muscles.
The lymphatic vessels of the muscles are
few ; they sometimes penetrate their interior in
following the capillaries ; at other times they
remain on the sm-face, in the external perimy-
sium. The existence of lymphatics has not yet
been demonstrated in tendons, aponeuroses, or
synovial membranes.
The nerves emanate from the cerebro-spinal
centre. At their tenninal extremity they offer
a small enlargement, called by Rouget the motor
end plate, and by Doyere and Kiihne the nervous
colline (hillock). It is admitted that the motor
tube traverses the sarcolemma, there losing its
envelope ; and that the substance of the axis-
cylinder is spread over the surface of the muscular fibrillae to form the motor
plate.
Physico-chemical Properties of Striped Muscles.
Muscles are soft organs, remarkable for their more or less deep-red colour,
which varies with the species, and even with the age and health of animals of the
same species.
By desiccation, muscles become hard and brown ; by repeated washing they
assume a straw-yellow tint.
Muscles are extensible, elastic, and tenacious ; and their tenacity is more
marked during life than after death.
It has been remarked that the juice impregnating the muscular tissue has a
marked acid reaction when extracted from a muscle which has been actively con-
tracting. (The fluid or " muscle plasma " obtained by pressing flesh, is either
neutral or slightly alkaline. It soon coagulates and separates into two portions —
a semi-solid portion, " myosin," and the fluid serum that at ordinary temperatures
quickly acquires an acid reaction.) It holds in solution a variable quantity of
albumen, casein, fat, a little creatine, creatinine, and a somewhat large proportion
of sarco-lactic acid. The solid substance of the muscle may be partly transformed
TRANSVERSE SECTION OF FROZEN MUS-
CLE, MAGNIFIED 400 DIAMETERS.
N, Nerve. M, Muscular fibre, sur-
rounded by portions of six others :
a, nucleus of the nerve-sheath ;
6, nucleus of the sarcolemma ; c,
section of nucleus of terminal plate
of nerve ; cf, transverse section of
terminal plate, surrounded by gran-
ular material; e, transverse section
of muscle nuclei ; /, fine fat-drops.
The angular dark particles are sec-
tions of sarcous elements ; the clear
intervening spaces represent the
fluid isotropal part of the muscle
substance.
236 THE MUSCLES.
into gelatine by boiling in water ; but its largest portion is a nitrogenous sub-
stance, soluble in dilute hydrochloric acid, called myosine, or muscular fibrine ; it
differs but little from the fibrine of the blood.
Physiological Properties of the Striped Muscles.
In this paragraph will be discussed the development of the muscles, muscular
contractility, and the part the muscles play in locomotion,
A. Development of the Muscles. — A muscle is derived from a mass of
Fig. 152.
T'
ARRANGEMENT OF THE FIBRES OF A MUSCLE.
153-
M, Body of a muscle. T, t', Tendon, a, b, Length of the body of the muscle. A, B, C, D, Various
modes of arrangement of the muscular fibres. (From Beaunis and Bouchard's Anatomiff
descriptive.)
embryonic cells. Each cell becomes considerably elongated, and its nucleus
multiplies, the nuclei extending along the course of the fibre. The cellular mem-
brane, enormously developed, forms the sarcolemma ; while the contents of the cell,
becoming more dense, divide longitudinally, and give
rise to the sarcous elements. When the muscles are
formed, they grow by the augmentation in length
and thickness of their primitive fibres.
B. Muscular Contractility. — Muscles pos-
sess the property of contracting under the influence
of a natural or artificial stimulus. Muscular con-
traction is the phenomenon resulting from the opera-
tion of this property. Muscles in a state of contrac-
tion are the seat of physical and chemical phenomena ;
they change their form and consistence, and produce
a relatively abundant quantity of carbonic acid,
creatinine, and inosinic acid. During contraction, it has been remarked that the
muscular fibres contract by increasing in volume, like an india-rubber tube left to
distribution of CAPILLARIES
IN MUSCLE.
GENERAL CONSIDERATIONS ON THE STRIPED MUSCLES.
237
itself after being inflated, and that the transverse striation becomes much closer ;
though the zigzag doubling mentioned by Prevost and Dumas has not been
observed.
But these physical and chemical modifications, important as they are from a
physiological point of view, cannot longer be dwelt upon here. It is particularly
important to speak of muscular contraction.
A muscle that contracts becomes shortened ; its two extremities approach each
other if they are free ; or one draws near
Fig. 154.
rT%^^--<i-^
m^^'^mx
i
the other if the latter is fixed to an im-
movable point. If the extremities of a
muscle are attached to two movable
levers, its contraction will bring about the
displacement of one or other of these ;
from this a movement is produced.
The degree of shortening of a muscle
varies, according to its being entirely
free, or having a resistance to overcome.
The mean limit of this shortening is
about one-fourth the length of the
muscular fibres. From this it will be
understood, that the movement produced
by the contraction will be in proportion
to the length of the fibres ; though in
this appreciation it will be necessary to
keep in mind the density and energy of
the fibre, as well as the intensity of the
stimulation which induces the con-
traction.
As each fibre represents a force
independent in its action, it results that the power of a muscle may be inferred by
the number of its fibres, or its volume.
Muscles are often aided in their action by mechanical conditions : such as the
disposition of the levers on which they act, the direction of the muscular fibres
in connection with these levers, and, lastly, by the presence of bands or elastic
cords.
C. Uses of Muscles. — There are flexor, extensor, abductor, adductor, rotatory
PORTION OF AN ELEMENTARY MUSCULAR FIBRE,
WITH FOUR DARK-BORDERED FIBRES (a)
CROSSING ITS SURFACE.
b, Capillary blood-vessel, with fine nerve-fibres
(a few only of the transverse markings of the
muscle are represented); c, two of the dark-
bordered nerve-fibres passing over the ele-
mentary fibre to be distributed to adjacent
fibres. This arrangement, in which a dark-
bordered nerve-fibre, distributed to muscle,
divides into branches, one of which passes to
a vessel, while the other ramifies upon a
muscle, is frequent. Magnified 700 diameters.
MUSCULAR FIBRE IN A STATE OF CONTRACTION IN THE CENTRE ; THE STRI^ APPROXIMATED,
THE BREADTH OF THE FIBRE INCREASED, AND THE MYOLEMMA RAISED IN VESICLES ON ITS
and other muscles, for all the movements of which the articulations are the
centre.
To determine the uses of the muscles, it is sufficient to know their insertions
and the mode in which the bones furnishing these insertions articulate with each
other. •
18
238 TEE MUSCLES.
For example, if a muscle is situated in an angle formed by two bones which
have a trochlean articulation, it will be a Jlexar ,- but if it is placed behind the
(Summit of the angle, it becomes an extensor ; if it be located on the external side
of an enarthrosis, it is an abductor ; and when on the inner side of the joint, or
between it and the middle plane of the body, it is then an adductor. A muscle
may be rolled obliquely round the joint it controls — in passing, for instance, from
the inner face of one bone to the outer face of another forming an articulation — and
in such a case the/ea;ors and extensors become also rotators if the diarthroses they
move permit rotation.
Lastly, muscles applied more or less obliquely on bones united by a trochoid,
will pivot one of the bones on the other — for instance, the great oblique muscle
of the head.
It is useless to multiply examples, for, the principle being once understood, it
is easy in nearly every case to determine the uses of a muscle when its situation,
and the number and kinds of articulations included between its insertions, are
known.
The result of the contraction of muscles being influenced by the form of their
principal axis, and the length and direction of their levers, it is necessary to
briefly examine these two points :
1. The immediate effect of the contraction of rectilinear muscles is the approxi-
mation of the bones to which they are attached. This approximation is usually
brought about by the displacement of a single bone — that which receives the
movable insertion of the muscle. Sometimes, however, the two bones move simul-
taneously, or they are alternately fixed and movable.
The first result produced by a curvilinear muscle, is the straightening of its
component fibres ; after which it may act on the bony levers as do the rectilinear
muscles, if its contractile power be not entirely expended. When a muscle is quite
circular, its only action is to contract the opening it circumscribes.
With regard to the inflected muscles, their action can only be estimated from
their point of inflection ; they operate as if this point represented their origin or
fixed insertion,
2. The muscular powers are submitted to the statical and dynamical laws
which govern the theory of levers ; for the bones are only levers moved by the
muscles.
In the locomotory apparatus we find the three kinds of lever recognized by
physicists. Thus the head, extended by the great complexus muscle, represents
an interfixed, or lever of the first class ; the foot, extended by the gastrocnemius
muscle, offers an example of the inter-resisting, or second kind, when the limb
remains fixed on the ground ; lastly, the lower jaw, raised towards the upper by
the masseter muscle, forms an interpuissant, or third kind.
It is worthy of remark that the arm of resistance in the bony levers is always
extremely long ; a circumstance which favours speed and the extent of movement,
but at the expense of power.
On the other hand, muscles are rarely perpendicular to the arm of their levers —
at least at the commencement of their action ; a second circumstance which
diminishes their energy.
Appendages of the Muscles.
These are : 1. The enveloping or containing aponeuroses. 2. The serous or
mucous hursse. 3. The tendinous and synovial sheaths.
GENEBAL CONSIDERATIONS ON TEE STRIPED MUSCLES. 239
A. Containing Aponeukoses. — These are layers or fascia of white fibrous
tissue, which envelop, in common, all the muscles of one or several adjoining
regions — principally those of the inferior bones of the limbs, where they constitute
a kind of hollow cylinder.
The aponeuroses are formed of very resisting interwoven fibres, which are
attached to the bones at numerous points. At their periphery they receive the
insertion of one or several muscles, which keep them more or less tense. Their
external face is in contact with a thin connective-tissue layer that separates them
from the skin. The internal face sends lamellar prolongations between the
muscles, which enclose these in special sheaths.
The aponeuroses maintain the muscles in their position, and sustain them
during their contraction.
B. Sekous Burs^. — The serous or mucous bursae are small cavities, filled
with a serous fluid, which are met with at those points where the muscles glide
over resisting surfaces. They are generally orbicular or circular, and their interior
is often divided by fibrous bands.
Their walls are formed by slightly condensed connective tissue, and may be
lined by a pavement epithelium ; in which case it is believed that the serous
bursa is produced by the simple dilatation of one of the connective-tissue meshes.
They become much enlarged when pressure or friction is great at the points
where they are situated. They may appear in any region, when the conditions
which preside at their physiological development are accidentally produced.
C. Tendinous Sheaths and Synovial Membranes. — Tendinous sheaths is
the name given to the half-bony, half-fibrous, sometimes exclusively fibrous,
gliding grooves in which tendons play when they are inflected to change their
direction, or when they glide over movable articulations.
The tendinous synovial sheaths are serous membranes lining the tendinous
sheaths, and covering the tendons at the points where these two parts are in con-
tact. They secrete a synovial fluid quite like that of the articulations.
When they almost completely envelop the tendon, and are afterwards carried
to the walls of the sheath, they are termed vaginal.
Their walls are composed of : 1. A very fine connective-tissue membrane,
confounded on its external face with the tendinous sheath, by the other face with
the tendon. 2. A simple layer composed of pavement epithelium, extended over
the whole or a part of the internal face of the membrane.
Manner of Studying the Muscles.
A. Classification. — To facilitate the study of the muscles, two methods may be employed
in grouping them. The first consists in classifying them according to their uses ; describing,
for example, all the flexors, extensors, etc., of the same region. In the second method, the uses
of the muscles are not taken into account, their relations only being considered ; and they are
divided into groups or regions, which include all the muscles situated around a bone. The
latter is the method now adopted, because it is the most convenient, useful, and rational.
B. Preparation. — We will limit ourselves to some general remarks on the following
points : —
Choice of a mibject. — If there is for disposal a certain number of subjects from among which
it is possible to make a selection, the preference should be given to those which have the mus-
cular system best developed; not that large, soft, lymphatic Horses with enormous masses of
muscle should be chosen, for these animals are always less convenient than small or middle-
sized, well-bred Horses. Asses and Mules, when very emaciated, answer well for the prepara-
tion of the muscles.
Position of the subject. — It is necessary to place the subject, immediately after death, in a
convenient position, in order that the cadaveric rigidity may set in while it is in that attituda
240
THE MUSCLES.
Without this precaution, the various parts of the body may assume an inconvenient shape oi
direction, and all attempts to amend them will prove almost unavailing, particularly in the
larger animals.
Three principal positions may be given to subjects:
1. The animal is in the first position when it is placed on its back, the four extremities in
the air, and maintained in that posture by means of long cords passed round the pasterns, and
fixed to the movable rings which terminate the extremity of the four bars of the wheeled table
on which the subject is laid. The head should be beyond the end of the table and rest upon a
stool. The animal should always be placed in such a manner that the head be opposite the
fore-part of the table, so that the movements of the pole or shaft be not impeded during the
displacement of the apparatus. In order that the neck be not twisted to the right or left, in
attaching the fore limbs tiie subject i-hould be raised so that the withers rest lightly on the
table. According to the bulk of the animal and the length of the bars, the ropes should be
passed around either the pasterns, above the fetlocks, or even above the knees (Fig. 156).
2. To place the animal in the second position, it is turned on the belly, the two thighs
flexed, the extremities carried beyond the table, and the head fixed between two bars by meana
Fig. 156.
HORSE FIXED IN THE FIRST POSITION ON ONE OF THE WHEELED TABLES IN USE AT THE
LYONS VETERINARY SCHOOL.
of a rope passed under the zygomatic arches; or better, two cords with metal hooks may be
employeil, a hook being fixed into each orbital arch, or through the skin and masseter muscle
to beneatii the zygomatic arch, the cords being tied short to the uprights of the table (Fig.
157). A block of wood or small stool may be employed to prop the trunk by placing it in the
Bublumbar region (Fig. 157).
3. The hubject is in the third position when it rests on its side.
Rules to he observed during the preparation. — 1. By no means, if possible, remove the skin
from the regions to be dissected until quite ready to begin the dissection. If this is impossible,
then take the precaution of enveloping these regions in damp cloths, or in the animal's skin,
to prevent desiccation of the aponeuroses and tiie superficial muscles.
2. To rlissect a muscle, it is necessary to remove the aponeuroses or the other muscles which
cover it, the eonnective tissue enveloping it, and the fat, glands, vessels, and nerves lodged m the
neigiibouring interstices. The aponeuroses should be removed in shreds by making them very
tense with the forceps, but without raising them, and causing the blade of tlie scalpel to glide
between the fibrous and muscular surfaces, keeping it always parallel to these two planes. The
GENERAL CONSIDERATIONS ON THE STRIPED MUSCLES. 241
coverin- muscles sliould not be entirely excised, but ought to be cut through tlie middle, across
tbeir fibres and the euds thrown back ; in this way it is always pc^sible to replace a muscle
bv brlDcring the two portions together ; the study of its relations is then much more easy. The
cellular^issue is got rid of by removing it with the forceps, and carrying the edge of the
scalpel in the re-entering angle formed by the cellular layer and the surface of the muscle.
This method also suffices for removing aponeuroses when they are slightly adherent to the
muscular fibres. But when they give attachment to these by their under face, as may be
noticed in the external scapular aponeurosis, it is necessary to have recourse to the method
indicated above. To remove fat, glands, etc., scissors will be found very advantageous.
Order tofolloio in preparing all the muscles of the same subject, so as to derive most advantage
therefrom 1. Place the subject in the first position, and commence by studying the muscles of
the inferior abdominal region. Then excise them, leaving the posterior extremity of the
deep pectoral muscle, the prepubic tendon, and the crural arch intact. The abdommal cavity
having been emptied of the viscera it contains, dissect and study successively the diaphragm.
Fig. 157.
HORSE FIXED IN THE SECOND POSITION ON A WHEELED TABLE.
the internal crural region-^xcept the deep muscles-the sublumbar region, the femoral and
posterior crural regions, the superficial muscles of the inferior cervical region, and the pectoral
'^^^ 2'°After detaching for future use one of the anterior limbs, the animal is placed in the second
position, and one after another may be dissected the muscles of the ear, those of the superior
cervical region, the croup and costal regions-except the triangularis sterni-and the spinal
region of the back and loins. . ,. . ,
3. The regions of the anterior limb may be prepared at the same time, or immediately
* ^I'^Separate the two posterior limbs by sawing the femurs through their middle, and proceed
to the dissection of the muscles of the posterior leg and foot.
5. By means of another application of the saw across the middle of the loms, the pelvis is
completely isolated for the preparation of the coccygeal muscles, and the deep muscles of the
internal crural region, nearly as they are represented in figures 39 and 40.
6. The animal being placed on its side, the pectoral cavity is opened by sawing through
the ribs near their extremities ; on the two particular portions thus obtained may be
studied, in one part, the triangularis sterai, and in the other the deep muscles of the inferior
242 TEE MUSCLES.
cervical region, including the longus colli and the anterior and lateral straight muscles of the
head.
7. Lastly, tlie head is disarticulated and the muscles of this region are prepared.
The subject may afterwards serve for the study of nearly all the articulations.
Preservation of the muscles.— The muscles may be preserved by immersing them in appro-
priate fluids, and the muscular preparations by drying them.
A large number of liquids preserve muscles from putrefaction. We may mention alcohol ;
a mixture of alcohol and oil of turpentine; alcohol, water, and chloroform; a solution of
sulphate of iron, bichloride of mercury, or arsenious acid. The best preservative fluid, how-
ever, is nitric acid diluted with water, in the proportion of one of the former to three of the
latter. The acid hardens the muscles and softens the connective tissue ; this allows all the
interstices to be completely cleared out, and even permits the primitive muscular fasciculi
which have been concealed by the white tissues, to be exposed.
Desiccation, after immersion in a bath of arsenious acid or sulphate of iron, causes the
muscles to become hardened and distorted. It is therefore a bad procedure, though it preserves
the muscles. Steeping in carbolized glycerine is sometimes resorted to.
(A careful dissection of the muscles, with regard to their origin, insertion, action, and
relations, is of infinite importance to the student of human anatomy ; to the Veterinary Student
it is no less important, and more particularly with reference to the muscles of the limbs. A
correct knowledge of their situation, attachments, and functions is often the only guide the
Veterinary Surgeon can rely upon in the diagnosis of those apparently obscure cases of lameness
whicli are of such comparatively frequent occurrence. In the words of Mr. Henry Gray, we
may repeat that " an accurate knowledge of the points of attachment of the muscles is of great
importance in the determination of their action. By a knowledge of tiie action of the muscles,
the surgeon is able at once to explain the causes of displacement in the various forms of
fracture, or the causes which produce distortion in the various forms of deformities, and, con-
sequently, to adopt appropriate treatment in each case. The relations also of some of the
muscles, especially those in immediate apposition with the larger blood-vessels, and the surface
markings they produce, should be especially remembered, as they form most useful guides to
the surgeon in the application of a ligature to these vessels" (^Anatomy, Descriptive and
Surgical).
An accurate knowledge of the muscular system is also of great service to the Veterinary
Surgeon, in estimating the value to be placed upon the external conformation presented by
animals intended for diflferent kinds of labour.
" In dissecting," says Mr. Holden, " there are four principal objects to be constantly borne
in mind by the student : 1st, The impression on the memory of those facts of general anatomy
taught in tiie lectures. 2nd, Tlie study of those parts of the body more especially concerned
in surgical affections and operations. 3rd, The education of the sense of touch, and of the
hand in the use of instruments; and 4th, The education of the eye in the knowledge of the
several tissues of the body, in various positions, and varying circumstances. . . . The education
of the eye is a gradual and tedious process, but one which is pretty certain to be satisfactorily
accomplished if the student do but use his hands properly, and therefore a few words on the
manual part of dissection may not be out of place.
" First, as to the instruments requisite for dissection. A case, containing six or eight
scalpels, two pairs of scissors, a pair of dissecting forceps, a set of chain-iiooks, a blow-pipe,
and a probe, will enable the student to make all requisite dissections, supposing that he is
allowed the use of a saw and chisel in the dissecting-room. Great variety exists in dissecting-
cases, both as to form and expense, but so long as the instruments themselves are strong and
good, the simpler the case the better. Scalpels for dissection are made of two principal shapes ;
in one, the edge is bevelled to the point, the back being straight; in the other, both back and
edge are bevelled to a point midway between the two. The latter form is preferable for most
purposes. The blade should not be more than an inch and a half long, and never double
edged ; but the material of which the handle is constructed is a matter of indifference.
" For all ordinary dissection, it will be found most convenient to hold the scalpel like a
pen ; but for cleaning the fascia off muscles and following out small nerves, it is better to hold
it reversed, so that the back of the knife may be against the tissue which is to be preserved.
In making the first incision through the skin of a limb, or in any otlier position where a long
incision is required, the knife may, with advantage, be held under the hand, by which the
wrist has more play, and the student has the opportunity of practising a mode of holding the
knife which he will find very useful when operating on the living body.
" The forceps should be broad at the extremities and coarsely serrated, so that it may
retain a firm hold on small portions of tissue. It is very important that the forceps sliould not
MUSCLES OF THE TRUNK. 243
be too strong in the spring, for in that case it becomes so fatiguing to the hand that it is
impossible to continue its use for any lengtii of time. The forceps should be held lightly
between the thumb and the first and second fingers of the left hand, which may be steadied by
resting the little finger on a neighbouring part.
" The chain-hooks should be strong, and bent in the direction of the thickness and not of
the breadth of the steel, as is sometimes done. These Litter are very inferior, being liable to be
unbent under any considerable strain. Care should be taken that tlie chains are firmly linked,
and that the central ring is sufficiently stout to bear any force that may be applied. The
scissors should be large and strong, and it will be found advantageous to have one curved pair,
which is very useful in preparing the ligaments.
" The student will do well to bear in mind that he will probably be called upon in after life
to operate on the living body, the only preparation for which is careful dissection: he
should therefore, as far as possible, conduct all his dissections as methodically, and with as
much care, as if operating on the living body.
"The student should bear in mind that his manual labour is only a part of his duty, and
will be thrown away, unless he at the same time study the description of the part upon which
be is engaged ; he should not, therefore, carry the dissection further than he can learn the
description on the same day, and at the subject, and should, if possible, re-peruse the description
in the evening, and always on the next morning, before carrying the dissection any further.")
CHAPTEE II.
THE MUSCLES OF MAMMALIA IN PARTICULAR.
Article I. — Muscles of the Trunk.
Subcutaneous Region.
This only comprises a single muscle, the /leshi/ panniculus (panniculus cartiosus),
which moves the skin covering the trunk. Strictly speaking, however, we may
describe as dermal muscles all those which are attached to the inner surface of
the superficial integument — the muscles of the face, for example.
Fleshy Panniculus (Panniculus Carnosus).
Preparation. — Place the animal on its side, and carefully remove the skin, allowing the
panniculus muscle to remain on the subjacent muscles. It may also be easily prepared on
the subject placed in the first position.
Situation — Form — Extmt. — Situated on the inner surface of the skin covering
the sides of the thorax and abdomen, this is an immense wide muscle, UTegularly
triangular in shape, thin at its borders, and thicker in the middle than elsewhere.
The upper border corresponds to a curved line, convex superiorly, and
extending obliquely from the flank to the withers. The inferior border is carried
horizontally from the flank to the posterior border of the olecranian mass of
muscles, passing along the upper margin of the deep pectoral muscle, which it
covers, and to which it adheres somewhat closely. The anterior border descends
from the superior extremity of the shoulder on to the muscles of the forearm.
Structure — Attachments. — The fibres of this muscle are directed forwards
for its posterior two-tliirds ; but on arriving on the shoulder they gradually
become vertical. They are continued, on the margins of the muscle, by aponeu-
roses which attach it either to the internal surface of the skin, or the fibrous
fascia of the superficial muscles.
This muscle has, besides, a very remarkable insertion into the humerus, which
244 THE MUSCLES.
was noticed by G-, Cuvier, in his ' Le9ons d'Anatomie Comparee,' and which
appears to have been omitted, at least so far as SoHpeds are concerned, in every
treatise on Veterinary Anatomy. The following is what we have often observed
in this respect : On reaching the posterior border of the ulnar mass of muscles,
the panniculus divides into two superposed layers — one, superficial, is carried
to the muscles of the anterior limb ; the other, deep, soon terminates by an
aponeurosis, which is united to the deep pectoral muscle, and is bordered at
its . upper margin by a nacrous aponeurotic band that penetrates between the
thorax and the muscles of the arm, to be fixed to the small trochanter.
Relations. — By its superficial face, with the skin, to which it closely adheres ;
by its deep face, with the latissimus dorsi, the dorsal portion of the trajjezius, the
abdominal tunic, the great oblique muscle of the abdomen, the serratus magnus,
some external intercostals, the spur vein, and the superficial muscles of the
shoulder and arm.
Action. — The animal, in contracting this muscle, shakes the whole of the
cutaneous integument which covers it ; thus preventing insects from alighting on
the surface of the body, or tormenting by their bites or stings.
In the Dog, tlie panniculus carnosus is prolonsed over the croup, and is united along the
dorso-lumbar spine to that of the opposite side. It is very developed in the Cat.
Cervical Region.
This region comprises all the muscles grouped around the cervical vertebrae —
muscles which are conspicuous by their volume, and the important part they play
in the animal economy. There are described a superior and an inferior cervical
region.
A. SuPERioE Cervical, or Spinal Region of the Neck.
This includes seventeen pairs of muscles, arranged in four layers on each side
of the cervical ligament, as follows : —
First Layer.
Cervical portion of the Trapezius.
Second Layer.
Rhomboideus. Angularis scapulm. Spleniv^.
Third Layer.
Complexus. Trachelo-Mastoideus.
Fourth Layer.
Spinalis or Semispinalis Colli. Six Intertransversales Colli. Obliquus
Capitis anticus or inferioris. Obliquus Capitis posticus or superioris. Rectus
Capitis posticus major. Rectus Capitus posticus minor.
These occupy the triangular space circumscribed by the upper border of the
cervical hgament, the transverse processes of the vertebrae of the neck, and the
spinous process of the second dorsal vertebra.
Preparation. — Place the subject in the second position, and dissect in succession the four
layers of the region. To study the first layer, which is formed by the cervical portion of
tlie trapezius, remove the skin, connective tissue, and the fascia covering that muscle (see
Fig. 1.59). The preparation and study of the second layer, composed of tlie rhomboideus,
angularis, and splenius, is carried out in two stages. In the first, the trapezium and the
MUSCLES OF THE TRUNK.
245
mastoido-humeralis is removed, leaving only the cervical insertions of the latter muscle ; then
the limb is removed by sawing through the scapula beneath the insertions of the angularis
and serratus magnus, as in Fig. 162. But as neitlier the cervical or dorsal insertions
of the splenius are exposed, it is necessary to proceed to the second part of the operation by
removing the rhomboideus, angularis, and the superior extremity of the shoulder. To prepare
the third layer, which comprises the great and small complexus, it is sufficient to excise the
splenius, in following the direction of the neck, and to turn upwards and downwards the two
portions of the muscle (see Fig. 162). Lastly, the deep layer — the semispinalis and iutertrans-
versalis, oblique, and posterior straight muscles, as well as the cervical ligament — is
by removing the complexus and longissimus dursi muscles (see Fig. 162).
First Layer.
Cervical Portion of the Trapezius.
for description of this muscle, see
Region of the Back and Loins.
Second Layer.
Rhomboideus (Figs. 158, 6
162, 1, 2.)
Synonyms. — Described by Bourgelat as two muscles, the "proper elevator of the shoulder and
the rhomboideus, these were termed by Girard the cervico-subscapularis and dorso-subscapularis.
(This is the rhomboideus longus and brevis of Percivall, and the dor so- scapular is and cervico-
euhscapularis of Leyh.)
Form — Situation — Direction. — This muscle has the form of a very elongated
triangle, and is situated at the inner aspect of the cervical trapezius and the
Fig. 158.
LATERAL VIEW OF THE NECK; SUPERFICIAL MUSCLES.
1, 1, Parotid gland ; 2, sterno-maxillaris, and, 14, its junction with its fellow of the opposite side,
3, 4, mastoido-humeralis, or levator humeri; 5. splenius; 6, rhomboideus; 7, funicular portion
of the cervical ligament, or ligamentum colli; 8, angularis of the scapula; 9, supra- or antea-
spmatus; 10, trapezius; 11, infra- or postea-spinatus ; 12, jugular vein; 13, subscapulo-
hyoideiis; 15, trachea.
scapular cartilage, beneath the cervical ligament, the direction of which it follows.
Structure— Attachments.— It is composed of thick fleshy fasciculi, the anterior
of which are obhque downwards and backwards, the posterior passing directly
246 THE MUSCLES.
downwards. These fasciculi are fixed by their superior extremity to the funicular
portion of the cervical ligament and the summits of the spinous processes of the
four or five dorsal vertebrae succeeding the first— Jixed insertion ; by their inferior
extremity, to the inner aspect of the scapular cartilage, where the anterior
fasciculi are confounded with those of the angularis.
Relations. — Covered by the cervical portion of the trapezius, the scapular
cartilage, and the alponeurosis of the latissimus doi-si muscle, the rhomboideus
covers the sphenius, which is excavated near its superior border for its reception,
as well as the aponeurosis of the sen-atus auticus muscle through the medium of a
yellow elastic layer.
Action. — It draws the shoulder upwards and forwards.
2. Angularis Scapula (Levator Anguli Scapula) (Figs. 159, 4 ; 162, 3).
Synonyms. — Trachelo-subscapularis — Girard. Portion of the serratus ma.gnvis—Bourgelat.
Elevator of the scapula — Cuvier. (Anterior portion of the serratus magnus of Percivall. The
levator anguli scapulx of Man.)
Situation — Form — Structure. — This is a very strong muscle, situated in front
of the shoulder, triangular, flattened on both sides, thin at its superior border,
thick behind and below, and almost entirely fleshy.
Attachments. — It takes its origin from the transverse processes of the five last
cervical vertebras by five distinct portions, which are directed towards the scapula
in converging towards each other, and soon join to form a single muscular body,
which is inserted into the internal face of the scapula, on its anterior triangular
surface.
Relations. — This muscle is confounded at its inferior border with the serratus
magnus. It is covered by the cervical trapezius, the mastoido-humeralis, and the
small pectoral muscle. It covers the splenius, the inferior branch of the latissimus
dorsi, and transversalis costarum. Near its junction with the serratus magnus, its
internal face adheres very closely to the transverse processes of the three first dorsal
vertebrae .
Action. — It draws forward the superior extremity of the scapula, while the
humeral angle is carried backwards. If the shoulder becomes the fixed point, it
can act in the extension or lateral inclination of the neck.
3. Splenius (Figs. 162, 4, 5 ; 163, 10).
Synonyms. — Cervico-trachelian — Girard.
Form — Situation. — A considerable muscle, flattened on both sides, triangular,
and comprised between the cord of the cervical ligament, the inferior branch of
the latissimus dorsi, and the transvei-se processes of the four first cervical ribs.
Structure. — The splenius, aponeurotic only at its periphery, is composed of
thick fleshy fasciculi which are all directed forwards and upwards, to reach the
head and the first cervical vertebrae.
Attachments. — It is fixed, by its posterior border, to the lip of the cei*vical
ligament and the summits of the spinous processes of the first dorsal vertebrae,
by means of an aponeurosis which is continuous behind with that of the
serratus anticus, and confounded, by its inner surface, with that of the
complexus. Its anterior border is cut into four or five digitations, which
constitute the movable insertions of the muscle. The superior digitation is
the widest and thinnest, and terminates in an aponeurosis (Fig. 162, 5), which
MUSCLES OF THE TRUNK.
247
unites it to the mastoid tendon of the trachelo-mastoideus, and passes to the
mastoid crest. The second joins a very strong tendon common to the splenius,
the trachelo-mastoideus, and the mastoido-humeralis, which tendon is attached to
the transverse process of the atlas (Fig. 162, 9). The two or three others
are directly inserted into the transverse processes of the third, fourth, and fifth
cervical vertebras.
Relations.— ThQ splenius is related, outwardly, to the rhomboideus, the
Fig. 159.
StrPERFICIAL MUSCLES OF THE NECK AND SPINAL REGION OF THE BACK AND LCI
1, Dorsal trapezius; 2, longissimus dorsi ; 3, cervical trapezius ; 4, angularis scapulae; 5, spleniu
6, anterior, or superficial portion of the mastoido-humeralis; 7, its humeral iusertion ; 7', its
mastoid insertion; 8, the thin aponeurosis uniting this insertion to the sterno-maxillaris ; 8'
posterior portion of the mastoido-humeralis ; 9, its inferior aponeurosis inserted into the inter
stice of the long abductor of the arm; 10, sterno-maxillaris; 11, subscapulo-hyoideus ; 12
portion of the cervical panniculus; 13, portion of the great extensor of the forearm ; 14, posterior
belly of the long abductor of the arm ; 15, great pectoral muscle.
angularis scapulae, cervical trapezius, and mastoido-humeralis ; inwardly, to
the complexus and the two oblique muscles of the head ; by its inferior border,
to the superior margin of the inferior branch of the longissimus dorsi.
Action.— It extends the head and neck in inclining them to one side. If the
two act in concert, the extension is direct.
248 THE MUSCLES.
Third Layer.
4. CoMPLEXUS (CoMPLEXUS Major) (Fig. 163, 6, 7).
/Synoni/ms.— Durso-occipitalis — Ch'rard.
/Situation — Direction — Form. — A powerful muscle, included between the internal
surface of the splenius and the cervical ligament, the oblique direction of which,
forwards and upwards, it follows ; it is triangular, flattened on both sides,
elongated from before to behind, and divided longitudinally into two unequal
portions — a posterior and anterior.
Structure. — The posterior portion (Fig. 163, 6), the most considerable, is
aponeurotic at its origin, intersected by linear fibrous bands which obliquely
cross its direction, and is formed of fleshy fibres directed forwards. Those which
compose the anterior portion (Fig. 164, 7), intennixed with some tendinous
Fig. 160.
LATERAL VIEW OF THE NECK (MIDDLE LAYER OF MUSCLES).
1, Funicular portion of the cervical ligament; 2, complexus major; 3, complexus minor; 4, rectus
capitis posticus major; 5, rectus capitis posticus minor; 6, stylo-maxillaris ; 7, carotid artery;
8, pneumogastric nerve and branch of sympathetic; 9, longus colli; 10, recurrent nerve; 11,
inferior scalenus; 12, intertransversalis colli; 13, incision through rhomboideus and trapezius;
14, trachea.
fasciculi, are directed upwards, and appear to be inserted into the preceding.
It is this difference in the direction of the fibres of the two portions of the
complexus which allows them to be distinguished from one another ; the two
being only really separated by an interstice near their inferior extremity.
Superiorly, the muscle is constricted to form the summit of the elongated triangle
it represents, and terminates by a strong tendon.
Fixed insertions. — The posterior portion derives its origin : 1. From the
summit of the spinous processes of the first dorsal vertebrae, by a strong
aponeurosis which is confounded with that of the splenius and the serratus
anticus. 2. From the transverse processes of the four or five dorsal vertebrae
which follow the second, by as many aponeurotic digitations united by their
margins. The anterior portion is fixed : 1. To the transverse processes of the
two first dorsal vertebras, by two tendinous digitations analogous to those of
MUSCLES OF THE TRUNK. 249
the posterior portion. 2. To the articular tubercles of the cervical vertebrae,
by the inferior extremity of its fleshy fasciculi.
Movable insertion.— The movable insertion of the great complexus is effected
through its superior tendon, which is fixed to the posterior face of the occipital
protuberance, beside the cervical tuberosity.
Relations. — It is covered by the splenius and the trachelo-mastoideus. It
covers the cervical ligament, the upper branch of the longissimus dorsi, the semi-
spinalis colli, and the oblique and posterior straight muscles of the head. The
aponeurotic digitations which attach it to the dorsal transverse processes, are
comprised between the two branches of the longissimus dorsi. The interstice
which separates, inferiorly, the two portions of the muscle affords a passage to
the superior cervical artery.
Action. — It is a powerful extensor of the head.
5. Teachelo-Mastoideus (Complexus Minor) (Figs. 162, 6, 7 ; 163, 8, 9).
iSf/nonj/TKS.— Dorso-mastoideus— GiVard. {Trachelo-mastoideus— Percivall.)
Situation — Direction. — Situated at the internal face of the splenius, in an
oblique direction upwards and forwards, this muscle lies along the anterior border
of the complexus, and follows the inferior branch of the longissimus dorsi, wliich
it appears to continue to the head.
Form — Structure. — This is a long muscle, divided into two fleshy, fusiform,
and parallel portions — anterior and posterior — wliich we might strictly consider
as two distinct muscles. Both are composed of successive fasciculi, which become
longer as they are superficial, and terminate by a tendon at their superior
extremity. The tendon of the posterior muscle is flattened, and joins the
mastoid aponeui'osis of the splenius. That of the anterior muscle is funicular,
and receives, before its insertion, a digitation from the splenius (Fig. 163, 10),
and another from the mastoido-humeralis (Fig. 163, 11).
Fixed attachments. — The two fleshy portions have their fixed insertion in
common with the anterior portion of the great complexus : 1. On the transverse
processes of the two first dorsal vertebras, through the medium of aponeurotic
digitations which serve as an origin to the last-named muscle. 2. On the
articular tubercles of the cervical vertebrae, by the inferior extremity of their
component fasciculi.
Movable attachments. — The terminal tendon of the posterior muscle passes to
the mastoid process of the temporal bone. The anterior passes to the transverse
process of the atlas.
Relations. — Outwardly, with the splenius ; inwardly, with the complexus and
the oblique muscles of the head. The tendon of the posterior fleshy portion is
covered by the mastoid aponeurosis of the mastoido-humeralis.
Action. — The trachelo-mastoideus inclines to its side the head and upper part
of the neck. It also acts as an extensor of the head.^
' Bourgelat has described, by the name of long transversal, the anterior portion of this
muscle, and attached it to the posterior portion of the splenius. We do not know where to find
one or other of these in the crude description of Lafosse and Vitet. Girard considered them,
like ourselves, as a single muscle, which he designates the dorso-mastoideus. Rigot has united
them with the anterior portion of the great complexus and the foremost fasciculi of the short
transverse muscle (inferior branch of the longissimus dorsi), to make his long transversal; in
doing so he has only complicated their description. These two muscular fasciculi being, to
our view, exactly represented, the posterior, at least, by the complexus minor of authropotomists,
250 TBE MUSCLES.
Fourth Layer.
6. Spinalis oe Semispinalis Colli (Fig. 161, 4).
Synonyms.— ^hoxi spinous — Bourgelat. Dorso-spinalis— Gerard. (Spinalis colli— Percivall
Transversali* colli of Man.)
Situation. — Between the complexus and the cervical ligament, on the laminae
of the last five vertebrae of the neck.
Form — Structure — Attachments. — This muscle, a continuation in the cervical
region of that of the back and loins, is generally formed of five thick and short
fasciculi, strongly aponeurotic, directed forwards, upwards, and inwards.
These fasciculi, attached by their posterior extremities^^icff/ insertion — to
the five last articular tubercles of the cervical region, are fixed by their anterior
or superior extremities — movable insertion — into the sixth, fifth, fourth, third,
and second spinous processes of that region.
Relations. — Outwards, with the complexus ; inwards, with the superior branch
of the longissimus dorsi and the cervical ligament. By its anterior face, with
the laminae of the cervical vertebrae and the interlamellar ligaments.
Action. — An extensor and flexor of the cervical spine.
7. Intertransversales Colli (Fig. 162,. 9).
Synonyms. — Intercervicals — Girard. (The intertransversales of Man- Not mentioned by
Percivall.)
These are six small, short, and very tendinous fasciculi, each of which is
doubled into two secondary fasciculi, a superior and inferior. They are lodged
in the lateral excavations comprised within the transverse and articular processes
of the cervical vertebrse, and are carried from one vertebra to another, except
from the first to the second. Covered by the cervical attachments of the
majority of the muscles of the neck, they cover the vertebrae to which they
are attached, -as well as the vertebral arteries and veins, and the intervertebral
foramina. They incline the neck to the side.
8. Obliquus Capitis Anticus or Inferioris (Fig. 161, 7).
Synonym, — Axoido-atloideus — Girard,
Form — Direction — Situation. — A short, thick, and broad muscle, oblique
forwards and outwardly, and applied to the superior face of the two first vertebrae
of the neck.
Structure and Attachments. — Its fibres are nearly all fleshy, parallel to each
other, and longer as they become superficial ; they are attached by their posterior
extremityr-^cce^ insertion — to the external face of the spinous process of the axis,
and by their anterior extremity — movable insertion — to the superior surface of the
transverse process of the atlas.
Relatiotis. — Outwards, with the splenius, the complexus and trachelo-mas-
toideus ; inwards, with the atlas, the axis, and the atlo-axoid articulation ; above,
with the posterior straight muscles of the head ; below, with the anterior great
straight muscle.
we have thought it proper to give it that name. With regard to the muscle generally termed
the complexus minor by veterinary anatomists, following the example of Meckel we will describe
it as a portion of the rectus capitis anticus major.
(Percivall names Girard's axnido-occipitalis longus the " complexus minor," and his dorso-
mastvideus the " ti achelo-mastoideus." Leyh, following Girard, designates the latter muscle
the dorso-mastoideus.)
MUSCLES OF THE TRUNK.
251
j^ction. — It pivots the atlas on the odontoid process of the axis ; it is, there-
fore, the special rotator of the head.
9. Small Oblique, Obliquus Capitis Posticus oe Supekioris (Fig. 161, 8).
Synonyms. — Atloido-mastoideus — Girard. (Obliquus capitis superior — Percivall. Lateral
atloido-occipitalis of Leyh. Obliquus superior of Man.)
A short, thick, quadrilateral, and strongly aponeurotic muscle. Its fibres are
fixed posteriorly — origin — to the lip bordering the transverse process of the atlas ;
Fig. 161.
CERVICAL LIGAMENT AND DEEP MUSCLES OF THE NECK.
1, Lamellar portion of the cervical ligament; 2, funicular portion; 3, 3, semispinales muscles
of the back and loins ; 4, 4, spinales colli ; 5, rectus capitis posticus major ; 6, small ditto ;
7, great or inferior oblique muscle of the head ; 8, small ditto ; 9, 9, intertransversales colli ; 10,
anterior great straight muscle of the head ; 11, inferior portion of scalenus muscle; 12, superior
ditto.
they are carried from thence forward, upward, and inward, to be attached —
termination — 1. To the styloid process of the occipital bones. 2. To the external
surface of that bone, on the imprints which border the mastoid crest posteriorly.
3. To the mastoid crest itself. This muscle is covered by the mastoid tendon of
the trachelo-mastoideus, by the superior aponeurosis of the splenius, and that of the
252 THE MUSCLES.
mastoido-humeralis. It covers the occipito-atloid articulation, the occipital inser
tion of the posterior straight muscles of the head, and the origin of the occipito-
styloid and digastric muscles. It inclines the head on the atlas, and shghtlj
extends it.
10. Posterior Great Straight Muscle of the Head (Rectus Capitis
Posticus Major) (Fig. 161, 5).
Synonyms.— SmaU complexus and great posterior straight axuscle—Bourgelat. Long and
short axoido-occi pi talis— Gerard. (^Complexus minor and rectus capitis posticus major. —
Perdvall. Leyh gives this muscle the same designation as Girard. It is the rectus capitis
posticus major and medius of Man.)
Form — Structure — Situation. — Elongated, prismatic, easily divisible into two
fasciculi — one superficial, the complexus minor of Bourgelat (and Percivall) ; the
other deep, th.Q great posterior straight muscle of Bourgelat (and the rectus capitis
posticus major of Percivall) — entirely fleshy, and formed of parallel fibres, this
muscle is lodged, with the small posterior straight muscle, in a triangular space
circumscribed by the cord of the cervical ligament and the internal border of the
obUque muscles.
Attachments. — It is attached, by its superior extremity, to the whole extent of
the uneven lip which terminates the spinous process of the 2ix\s,-^fixed insertion.
Its anterior extremity is insinuated beneath the small oblique muscle, and is fixed
to the occipital bone, behind the superior insertion of the gi'eat complexus, the
tendon of which receives some of the fibres of the superficial fasciculus — movable
insertion.
Relations. — Above, with the complexus ; below, with the small straight
muscle ; inwards, with the cord of the cervical ligament and the analogous muscle
of the opposite side ; outwards, with the oblique muscles.
Action. — This muscle, a congener of the complexus, aids in extending the
head.
11. Posterior Small Straight Muscle (Rectus Capitis Posticus
Minor) (Fig. 161, 6).
Synonyms. — Atloido-occipitalis — Girard. {Rectus capitis posticus minor — Percivall. The
Atloido-occipitalis superior of Leyh. The rectus capitis posticus minor of Man.)
A very small, wide, and triangular muscle, flat above and below, and lying
immediately upon the fibrous capsule of the occipito-atloid articulation. It is
attached, posteriorly, to the superior face of the atlas — origin ; in front, to the
external surface of the occipital bone, below the preceding muscle, the action of
which it #iares.
Differential Characteus in the Muscles of the Cervical Region in the other
Animals.
1. Ruminants. — In the Ox, the angularis scapulas arises by six digitations from all the
cervical vertebr£e except the first ; the splenius is little developed, and is not attached to either
the tliird or fourth cervical vertebra.
In the Carnal, the angularis scaiiulae is very small, and does not go beyond the fifth cervical
vertebra in front. All the other muscles in this region are very much reduced in size. " If
the splenius exists in the Camel, it is so small that it often escapes dissection" (Cuvier).
2. Pig.— The muscles of tlie superior cervical region in this animal are generally very
developed. The rhomboideus is divided into two flesliy bodies, one of which proceeds to the
occipital protuberance, and the other to the rudimentary cervical ligament and the first dorsal
vertebrae. The angularis is attached, as in Ruminants, to the six oerviral vertebrae ; sometimes
it even shows a digitation that descends to the atlas. The splenius only terminates anteriorly
MUSCLES OF THE TRUNK. 253
by three fleshy portions ; but they are voluminous, and are inserted, one into the atlas, another
into the mastoid crest, and tlie third into the occipital protuberance. In the complexus, the
two portions are completely separated from each other, except at their upper extremity, by
the interspace lodging the superior cervical artery. The aponeurosis attaching the muscle to
the spinous processes of the first dorsal vertebrae is not confounded with that of the spleniua
or the serratus anticus respiratory muscle. The atloidean fleshy body of the trachelo-
mastoideus is scarcely distinct from the superior branch of the iongissimmo dorsi and the
intertransversales. Lastly, it is difficult to distinguish the small posterior straight muscle from
the deep fasciculus of tlie great straight muscle.
3. Camivora. — In these animals the muscles of the superior cervical region are nearly all
voluminous, as in the Pig. The rhomboidem is bifid at its origin, and its anterior branch arises
from the mastoid crest. The angularis is also attached to the last six cervical vertebrse. Very
thick and broad, the splenius only passes to the atlas and mastoid crest. The oblique and
$traight posterior muscles of the head are also remarkably thick.
B. Inferioe Cervical or Trachelian Region.
The muscles composing this region are situated in front of the cervical
vertebrae, and are, for the most part, grouped around the trachea, which they
envelop as in a kind of sheath. They are eleven in number, and are : the cervical
panniculus, mastoido-humeralis, sterno-maxillaris, sterno-thyro-hyoideus, suisca-
pulo-hyoideus, rectus capitis anticus major, rectus capitis anticus minor, rectus
capitis lateralis, scalenus, and the longus colli.
Preparation. — 1. Place the animal in the first position. 2. Remove the skin of this region-
in order to expose and study tiie cervical panniculus. 3. Remove that muscle and the parotid
gland to prepare the mastoido-humeralis,' the stylo-maxillaris, and sterno-thyro-hyoideus. 4.
Transversely cut through the mastoido-humeralis near the angle of the shoulder, and isolate it
from the subscapulo-hyoideua to expose this muscle ; taking care to preserve the jugular vein
and parotid gland, in order to study their relations with it. 5. Remove the fore limbs ; open
the thoracic cavity by sawing through the eight first ribs near their superior extremity'; take
out the viscera contained in tliis cavity, as well as the trachea, oesophagus, pharynx, and
larynx, to expose the longus colli, the scalenus, and the straight muscles of the head.
1. Subcutaneous Muscle of the Neck (Cervical Panniculus)
(Figs. 159, 12 ; 174, 1).
Synonyms.— It has been described by Bourgelat, and the majority of veterinary anatomists
who have followed him, as two muscles : the cuticularis of the neck and the face. (Percivall
includes this muscle in his description of tlie panniculus carnosus. It is the platysma myoide»
of Man.)
This is a membraniform expansion, partly fleshy, partly aponeurotic, which
covers the muscles of the neck, the submaxillary space, and the face.
The fleshy fibres form, in front of the neck, a thin band, which is united,
through the medium of a fibrous raphe, to that of the opposite side. This band
is in contact with the sterno-maxillaris, sterno-thyro-hyoideus, and subscapulo-
hyoideus, as well as the jugular vein — enveloping them all as in a sort of furrow.
It gradually becomes thinner from below upwards, in such a manner that around
the upper part of the throat it is only composed of some scattered fibres. In the
submaxillary space, and on the expanding borders of the inferior maxilla, the fleshy
fibres appear again of a certain thickness, but only to become attenuated on the
external surface of the cheeks.
• These fleshy fibres leave the carinif orm cartilage of the sternum ^ and inter-
' The mastoido-humeralis may be dissected at the same time as the trapezius, the subject
being placed in the second position. This conveniently permits the superior insertions of the
muscle to be studied (see Fig. 159).
* It will be seen, on referring to Fig. 159 and its legend, that we restore to the cervical
19
254 THE MUSCLES.
mediate middle raphe of the two muscles, and, directing their course outwards and
upwards, soon become confounded with the aponeurosis. The latter, extremely
thin, is spread over the mastoido-humeralis, the superior cervical muscles, the
parotid region, and the cheeks, and is finally attached to the zygomatic crest. On
an'iving near the commissure of the Ups, it is united to the buccinator muscle by
a fleshy fasciculus named, in Man, the risorius Santorini (Fig. 163)..
The cervical panniculus braces the muscles it covers, during their contraction,
and pulls backwards the commissures of the lips. We doubt very much whether
it has — in the cervical region at least — any action on the skin, for it adheres but
very slightly to its inner surface.
2. Mastoido-humeralis (Levator Humeri) (Figs. 158, 160, 162, 163).
Synonyms. — The muscle common to the arm, neck, and head — Bourgelat. Representing
the cleido-mastoid, and the clavicular portions of the trapezius and deltoid of Man, and the
trachelo-acromialis peculiar to quadruped Mammals ' — G. Cuvier, Lemons d'Anatomie Com-
par^e, 2iid edition. (This is the muscle which Percivall namts the levator humeri. The
above is the designation given to it by Girard and Chauveau. Leyh gives it the same designa-
tion as Bourgelat.)
Extent — Sitication — Direction — (Joynposition. — This muscle extends from the
summit of the head to the inferior part of the arm, and is applied to the scapulo-
humeral angle at the side of the neck, in an oblique direction downwards and
backwards. It is composed of two portions lying longitudinally, and somewhat
intimately united, and distinguished into anterior and posterior.
Form — Structure — Attachments. — A. The anterior or superficial portion (Fig.
159, 6) constitutes a long fleshy band, which appears to be united, by its anterior
border, to the cuticular muscle of the neck. Its superior extremity, thin and Avide,
is attached to the mastoid process and crest by an aponeurosis (Fig. 159, 71), which
is united, in front, to the tendon of the sterno-maxillaris by a very thin cellulo-
aponeurotic fascia. Its inferior extremity, thicker than the superior, is inserted
by means of a very short aponeurosis into the humerus, on the salient border
descending from the deltoid imprint, and which limits, in front, the musculo-
spiral groove on the body of that bone (Fig. 159, 7).
panniculus the sternal band attributed until now to the mastoido-humeralis. These are the
considerations which induce us to make this modification : 1. This band is not distinct from
the cervical panniculus ; a separation between the two muscles can only be artificially obtained.
2. In dissecting this band with care, we can see that its fibres, like those of the panniculus, are
not mixed with those of the mastoido-humeralis (superficial portion) ; they pass along the
external surface of that muscle, to which they intimately adhere, it is true, but they can easily
be separated, and are continuous with the aponeurosis of the first.
> At first sight, we might hesitate to admit that this muscle is formed of such varied and
complicated elements as are enumerated above. Nevertheless, it is a scientific fact ; and we
will give a demonstration, as simple as it is clear, that such is the case — the idea we owe to
J. F. Meckel. If we take the Dog, for example, and suppose it to be possessed of a clavicle
extending from the anterior extremity of the sternum to the acromion, this clavicle would bisect,
transversely, the inferior portion of the mastoido-humeralis, which would thus be divided into
two portions— a superior and an inferior. Tlie first, extending from the clavicle to the mastoid
process, on this side, and on the other to the mastoid crest, as well as to the cervical ligament,
where it is confounded with the trapeziiis, would exactly represent the clavicular portion of the
latter muscle, and the cJeido-mastoideus. With respect to the inferior portion, it perfectly
resembles, by its attachments, the clavicular portion of the deltoid. But, on the contrary, if
we suppose Man deprived of a clavicle, the three muscular fasciculi indicated, in becoming
confounded with each other, would form the mastoido-humeralis of the Dog, minus the posterior
portion, or the trachelo-acromialis, which is not represented in Man.
MUSCLES OF THE TBUNK. 255
B. The posterior or deep portion (Fig. 159, 9) is a second muscular band,
shorter and stronger than the preceding. It is attached, above, to the transverse
processes of the first four cervical vertebrae by as many fleshy bands (Fig. 159, 8),
which cover the superficial portion. The upper digitation, given off to the atlas,
is united to the tendon common to the trachelo-mastoideus and splenius (Figs.
162, 9 ; 163, 9, 10, 11). The inferior extremity of this portion of the muscle
widens on the scapulo-humeral angle, which it envelops in becoming closely united
to the anterior portion, terminating with it on the humerus. An aponeurosis,
which is confounded with that of the trapezius, and sends off a septum into the
interstice between the two portions of the long abductor of the arm, concurs to
fix this extremity by spreading over the muscles of the arm.
Relations. — It is covered, near its mastoid insertion, by the parotid gland and
the cervico-auricularis muscles ; for the remainder of its extent, by the aponeu-
rosis of the cervical panniculus, from which it is separated by a thin fascia con-
tinuous with that which extends over the trapezius. It covers the splenius,
trachelo-mastoideus, oblique muscles of the head, subscapulo-hyoideus (to which
it adheres intimately), the digastricus, long flexor of the head, the angularis,
scalenus, small pectoral, supra- and infra-spinatus muscles, the long abductor of
the arm, and the coraco-radialis.
Action. — When the superior is the fixed point, it carries the entire anterior
limb forward. This muscle, therefore, plays a very important part in locomotion,
as it is called into action when the animal raises the fore limb in getting over the
ground. If the fixed point of the muscle is the limb, it inclines the head and
neck to one side.
3. Steeno-maxillaeis (Figs. 159, 10 ; 174, 4).
Synonym. — The sterno-mastoideus of IVfon.
Form — Structure — Situation — Direction — Attachments. — ^A long narrow muscle,
almost entirely fleshy, and terminated at its upper extremity by a flattened tendon ;
situated in front of the neck, beneath the panniculus, and parallel to the anterior
border of the supei'ficial portion of the mastoido-humeralis, from which it is
separated by a space that lodges the jugular vein ; attached, inferiorly, to the
cariniform cartilage of the &ternnm—fix£d insertion; and superiorly — movable
insertion — to the curved portion of the posterior border of the maxiUaiy bone by
its terminal tendon.
Relations. — The muscle is covered by the panniculus, and the parotid gland.
It covers the trachea, the subscapulo-hyoideus, sterno-thyro-hyoideus, and the
maxillary gland. Its external border, parallel to the anterior border of the
mastoido-humeralis, forms with it a longitudinal depression termed the jugular
furroiv, because it lodges the vein of that name. Its inner border is intimately
united, in its lower third, to that of the opposite muscle.
Action. — It directly flexes the head, when acting in concert with its congener ;
but alone it turns it to one side. Lafosse and Rigot have wrongly considered
this muscle as a depressor of the lower jaw, Bourgelat has correctly stated that
it cannot move this jaw independently. (Percivall says that the pair will assist
in opening the mouth ; and Leyh asserts that when the mouth is closed, each
muscle will act as a flexor to the head.)
4. Steeno-thyeo-htoideus (Fig. 174, 6, 7).
Form — Structure — Situation — Attachments. — Small, ribbon-shaped, long, and
256 THE MUSCLES.
slender muscle in two portions ; digastric ; situated in front of the trachea ; con-
founded at their inferior extremity and united to those of the opposite side, so as
to form a single fasciculus which is attached to the cariniform cartilage of the
steTimm—flxed insertion ; isolated from each other above the tendon which makes
them digastric, and terminating by their superior extremity — movable insertion :
the first, on the inferior surface of the body of the hyoid bone in common with
the subscapulo-hyoideus ; the second, on the posterior border of the thyroid
cartilage.
Relations. — Covered by the sterno-maxillaris and the panniculus muscle, they
cover the anterior face of the trachea.
Action. — Depressors of the hyoid bone and larynx.
5. Subscapulo-hyoideus (Figs. 159, 11 ; 174, 5).
Synonyms. — Hyoideus — Bourgelat. (Subscapulo-hyoideiis — Percivall.)
Form — Structure — Situation — Direction. — This muscle forms a thin and wide
band, almost entirely fleshy, oblique forwards and upwards, extending from the
scapulo-humeral angle to the submaxillary space, and applied to the side of the
trachea, which it slightly crosses.
Attachments. — It derives its fixed insertion from the inner surface of the
subscapularis, by an aponeurosis which is detached from that covering the latter
muscle. Its movable insertion is into the body of the hyoid bone, in becoming
confounded with the sterno-thyro-hyoideus, and in being intimately united to the
muscles of the opposite side.
Relations. — Outwardly, with the subscapularis, supra-spinatus, small pectoral,
mastoido-humeralis — which closely adheres to it, the jugular vein, the sterno-
maxillaris, and the panniculus. Inwardly, with the scalenus, the large anterior
straight muscle of the head, the main trunk of the carotid artery and the nei^ves
accompanying it, the trachea, thyroid gland, and the inferior face of the larynx.
The jugular vein is entirely separated from the carotid artery by this muscle in
the upper half of the neck.
Action. — It is a depressor of the hyoid bone and its appendages.
6. Great Anterior Straight Muscle of the Head (Rectus Capitis
Anticus Major) (Figs. 161 and 162, 10 ; 163, 13).
Synonyms. — Long flexor of the head — Bourgelat. Trachelo-suboccipitalis — Girard. (Rectus
capitis anticus major — Percivall. Trachelo-occipitalis — Leyh.)
Form — Structure — Situation — Direction. — A long, flat muscle, fasciculated in
its posterior half, terminated in a tendinous cone at its anterior extremity, and
passing along the first cervical vertebrae in front.
Attachments. — Behind, to the transverse processes of the third, fourth, and
fifth cervical vertebrae by as many fleshy digitations, the most inferior of which
are the \oTige?,t— fixed insertion. In front, into the imprints on the body of the
sphenoid bone and the basilar process, by its terminal tendon — movable insertion.
Relations. — Outwardly, with the mastoido-humeralis, the subscapulo-hyoideus,
and the small anterior straight muscle. Inwardly, with the longus colH and
the muscle of the opposite side. In front, with the common carotid, the nerves
accompanying this arteiy, and the guttural pouch, which lines it near its movable
insertion. Behind, with the great oblique muscle of the head and the occipito'
atloid articulation.
MUSCLES OF THE TRUNK 267
Action. — It either directly flexes the head or carries it to one side, according
as it acts alone or with its fellow of the opposite side.
7. Small Anterior Straight Muscle of the Head (Rectus Capitis
Anticus Minor).
Synonyms. — Flexor capitis brevis — Bourgelat. Atloido-suboccipitalis— Girard. (Rectiis
capitis anticus minor — Fercivall. Atloido-oocipitalia inferior — Leyh.)
A small, entirely fleshy, prismatic fasciculus, lying to the external side of the
preceding muscle ; attached, posteriorly, to the inferior face of the body of the
atlas ; in front, to the body of the sphenoid bone and the basilar process, beside
the great anterior straight muscle. It is covered by the guttural pouch, and
covers the occipito-atloid articulation. It concurs in flexing the head.
8. Small Lateral Straight Muscle (Rectus Capitis Lateralis).
Synonyms. — Flexor capitis parvus — Bourgelat. Atloido-styloideus — Girard. (Obliqum
capitis anticus — Percivall. The rectus capitis lateralis of Man.)
Smaller than the preceding, and prismatic and entirely fleshy, like it, this
muscle lies on the side of the occipito-atloid articulation ; it is attached to the
atlas, outside the small anterior straight mu&cle— fixed insertion ; and to the inner
face of the styloid process of the occipital bone — movable insertion. It is the
congener of the two anterior straight muscles of the head.
9. Scalenus (Figs. 161, 162, 163).
Synonyms. — Costo-tracheleus — Girard. (Scalenus anticus and posticus of Man.)
Sitimtion — Direction — Composition. — Deeply situated at the inferior part of
the neck, in an oblique direction downwards and backwards, this muscle com-
prises two portions of unequal dimensions, placed one above another.
Form — Structure — Attachments. — A The superior portion {scalenus posticus
of Man), the smallest, is composed of three or four fleshy fasciculi, attached by
their extremities to the transverse processes of the last thi-ee or four cervical
vertebras. The last terminates at the superior extremity of the first rib.
B. The inferior {scalenus anticus of Man), the most considerable, is flattened
on both sides, thick and wide posteriorly, thin and naiTOw anteriorly, and is
composed almost entirely of fleshy fibres which are longest as they are inferior.
It is attached : 1. To the transverse processes of the last four cervical vertebrae
by short fasciculi scarcely distinct from one another, the first of which is crossed
by the last digitation of the great anterior straight muscle. 2. To the anterior
border and external face of the first rib, where all its fibres end.
Relations. — The scalenus responds : by its external face, to the subscapulo-
hyoideus, mastoido-humeralis, and the deep pectoral ; by its internal face,
to the longus colli, trachea, common carotid artery and its accompanying nerves,
and — on the left side only — to the oesophagus ; by its inferior border, to the
jugular vein. The two portions of the scalenus are separated from each other, in
front of the first rib, by an interspace traversed by the nei-ves of the brachial plexus.
Action. — When the first rib is the fixed point, this muscle either directly
flexes the neck or inclines it to one side. When the neck is the fixed point, it
draws forward the first rib and fixes it in this position dm'ing the dilatation of
the chest, in order to aid the inspiratory action of the external intercostal muscles.
THE MUSCLES.
10. Long Muscle of the Neck (Longus Colli).
Synonyms. — Flexor longus colli — Bourgelat. Subilorso-atloideus — Girard. {Longus colli
— Percivcdl. Dorso-atloideus — Leyh.)
Situation — Composition. — A single and considerable muscle, immediately
covering the inferior aspect of all the cervical and the first six dorsal vertebrae,
and composed of two lateral portions which are united on the median line, and
constitute, in certain animals, two distinct muscles.
Structure — Attachments. — Each lateral portion of the longus colli is composed
of a succession of veiy tendinous fasciculi. The most posterior of these is
attached to the inferior face of the bodies of the first six dorsal vertebrae, and
proceeds directly forward to reach the inferior tubercle of the sixth cervical
vertebra, into which it is inserted by a strong tendon. The other fasciculi, less
considerable, and confounded outwardly with the intertransversales of the neck,
are carried from one cervical vertebra to another, and are directed forwards,
upwards, and inwards, converging towards those of the opposite side. They are
attached successively : outwardly, to the transverse processes of the last six
cervical vertebrae ; inwardly, to the inferior ridge on the bodies of the first six.
The most anterior fasciculus passes to the inferior tubercle of the atlas, into
which it is inserted by a tendon common to it and the fasciculus of the opposite
side, and which receives the most superficial fibres of the tlii-ee or four preceding
fasciculi.
Relations. — Above and behind, with the vertebrae which it covere, as well as
their intervertebral discs ; below and in front, with the trachea and oesophagus,
and the vessels and nerves accompanying these two tubes ; on the sides, with the
great anterior straight and the scalenus muscles in its cervical portion ; and in
its intra-thoracic portion, with the pleurge, and important vessels and nei-ves.
Action. — It' flexes the whole neck, and the cervical vertebrae on one another.
Differential Characters in the Muscles of the Inferior Cervical Eegion in the
OTHER Animals.
A. Ruminants.— In the Ox and Sheep, the arrangement of the cervical pannicului< oflFers
a very considerable ditference from tliat observed in Solipeda. The fleshy portion is absent,
or appears to be absent, in the cervical region; tl:e anterior mnscles of the neck are only
covered by a thin fascia developed on the sides of tlie neck. When this fascia reaches tlie
face, it becomes continuous with the fleshy fibres ; a fasciculus of these fibres comporis itself
as in the Horse, and joins the buccinator: another is intercrossed in the maxillary space by
the analogous fasciculus of the opposite side.
The cervical panniculus in the Ox is also distinguished by an extremely remarkable
peculiarity, which it is necessary to allude to here: — The fleshy cervical band, altogether
absent in the Sheep, is not so in the Ox; wc have found it forming, beneath the above-
mentioned aponeurotic fascia, the hmg, thick strip which has been described by veterinary
anatomists as the analogue of the sterno-maxillaris in the Horse. This strip is attached, like
the muscular band which represents it in Solipeda, to the anterior point of the sternum. But
Us fibres, instead of being spread outwards over the mastoido-humeralis, ascend, perfectly
isolated from that muscle, to the posterior border of the inferior maxilla. There it terminates
(Fig. 172, 18) by a flattened tendon, which, after reaching the anterior border of the masseter,
is confounded with the aponeurosis of that muscle, and sends some fibrous bands over the
muscles of the face.
The two portions of the mastoido-humeralis of Ruminants are better defined, and more
oblique on one another, than in the Horse. The superficial partion receives, on its inner face,
a small, bright- red, funicular fasciculus, which proceeds from the cartilage of the first rib, and
which Meckel is inclined to consider as the vestige of the subclavius. It is divided, superiorly,
into two branches: one, the clavicular portion of the trapezius, very wide, passes to the mastoid
MUSCLES OF THE TRUNK. 259
process, the curved line of the occipital bone, and to the cervical ligament, in becoming con-
founded with the trapezium (Fig. 172, 22); the other, the cleido-mastoideus, terminates in a
tendon that joins the sterno-maxillaris, and is inserted into the basilar process, after
receiving the fibres of the long flexor of the head (Fig. 172, 21). The upper extremity of the
deep portion of the mastoido-humeralis is inserted into the atlas by a flattened tendon alone,
which is quite distinct from the atloid insertions of the splenius and the trachelo-mastoideus.
In the Sheep and Goat, the costal band that joins the superficial portion is absent. The
latter is divided at its inferior extremity into two branches, between which pass the biceps.
The upper branch passes to the epitrnchlea.
The sterno-maxillaris muscle, instead of being inserted into the inferior maxilla, is united
to the suboccipital branch of the mastoido-humeralis, to be attached to the basilar process. At
another time we will discuss" the determination of this muscle, and that of the fleshy band here
considered as belonging to the first (see Spinal Nerve).
The sterno-thyro-hyoid muscle is thicker than in the Horse, and not digastric.
The subscapulo-hyoideus of Ruminants is but slightly developed, and might be termed the
trachelo-hyoideus, as it proceeds to the transverse process of the tiiird or fourth cervical
vertebra. In its passage beneath the basilar branch of the mastoido-humeralis and sterno-
maxillaris, it contracts adhesions with the fibres of these two muscles.
The great anterior straight muscle of the head descends to the sixth cervical vertebra. Its
cervical insertions are covered by a very strong muscular fasciculus, which is annexed to it.
Like it, this fasciculus leaves the sixth cervical vertebra, and is attached to the transverse
processes of the four vertebrae preceding the last, by becoming confounded with the inter-
transversales, and finally terminating at the tracheal process of the atlas by fleshy and
aponeurotic fibres. This muscular fasciculus singularly strengthens the neck when it is
inclined to one side. In consequence of its attachments, it might be named the trachelo-
atloideus (Fig. 172, 24).
Lastly, in Ruminants the superior scalenus is very developed, being a flattened band which,
gradually expanding, is prolonged to tlie surface of the serratus magnus.
B. Pig. — In this animal, tlie cervical panniculus is in two portions : an inferior, which
comes from tiie point of tlie sternum ; and a superior, from the external capsular region. They
unite in front, and are prolonged in common on the muscles of the face, contracting adhesions
with the outer surface of the body and branebes of the inferior maxilla.
The other muscles of the inferior cervical region are not unlike those of Ruminants.
Of the two portions of the mastoido-humeralis, the superficial is bifid at its superior
extremity. The posterior branch, the clavicular portion of the trapezius, is attached to the
side of the occipital protuberance ; the anterior branch, the cleido-mastoideus, goes beneath
the external auditory hiatus, to the crest that replaces the mastoid process ; the deep portion
is attached above to the atlas only.
In the Pig, the fterno-maxillaris exactly represents that muscle in the Horse, as its tendon
passes directly to the mastoid process.
The sterno-thyro-hyoideus is double ; the supplementary branch going to the inferior face
of the thyroideus.
The subscapulo-hyoideus and great anterior straight muscle of the head, resemble those of
the Ox. The small straight lateral muscle is scarcely distinct from the small oblique. The
superior scalenus extends to the third rib. The two lateral portions of the longus colli are
separate, and form two distinct muscles.
C. Camivora. — In the Dog, each cervical panniculus is in two portions, as in the Pig.
The fibres from tbe breast are directed in a diveiging manner over the face, the submaxillary
space, and the parotid gland, where they form the parotido-auricularis muscle. The portion
coming from the external scapular region is thicker and wider; it covers the lateral parts of
the neck, the parotid gland, the parotido-auricularis, passes above the preceding, and termi-
nates on the face and in the submaxillary space, where its fibres join those of the opposite side.
The mastoido-humeralis comports itself somewhat as in Ruminants and the Pig. The
superficial portion is bifid superiorly ; one of its branches is fixed into the mastoid process —
the cleido-mastoideus ; the other into the mastoid crest and cervical ligament, in uniting by
aponeurosis with the trapezius— the clavicular portii.n of the trapezius. The deep portion
passes from the atlas to the scapular spine.
The tendon of the sterno-maxillaris goes to the mastoid process. The sterno-thyro-hyoideus
Is thick and not digastric, and commences from the cartilage of the first rib.
The Camivora have no subscapulo-hyoideus ; but they possess a very long scalenus, which
passes to the eighth rib, and a longus colli, which tends to become divided into two lateral
portions.
260 THE MUSCLES.
Spinal Region of the Back and Loins.
This offers for study seven pairs of muscles, nearly all of which have their
insertions extended over the dorso-lumbar spine, and are disposed in four layers
on each side of this long multifidious crest. These muscles are —
In the Fikst Layer.
Trapezim. Latissimm Dorsi.
In the Second Layee.
Serratus Anticus. Serratus Posticus.
In the Third Layer.
Longissimus Dorsi. Transversalis Costarum.
In the Fourth Layer.
lis of Back mid Loins.
Preparation. — 1. Place the animal in the second position. 2. Remove the skin with the
panniculus and the mass of olecranian muscles, to show, in a first operation, the trapezius and
latissimus dorsi (Fig. 159). 3. In a second operation, remove the entire fore limb, with
the latissimus dorsi muscle, the mode of termination of which may then be studied ; then pre-
pare the two smiiU serrated muscles. 4. Remove these two muscles, as well as the angularis
of the scapula and tlie splenius, to expose the transversalis costarum and longissimus dorsi
(Fig. 163). The superior branch of the latter remaining covered by the great complexus,
excise tliis muscle, leaving only its insertions into the transverse processes of the dorsal
vertebrae, to show how they are fixed between the two branches of the longissimus dorsi. 5.
Dissect the semispinalis by removing the longissimus dorsi and the internal angle of the ilium.
First Layer.
1. Trapezius (Fig. 159, 1, 3).
Synonym. — Dorso- and cervico-acromialis — Girard.
Situation — Form — Structure. — This is a superficial membraneous muscle,
situated on the sides of the neck and withers. Its shape is that of a triangle
base upwards. It is aponeurotic at its upper border and in its centre, which
allows it to be distinguished, especially in emaciated subjects, into a cervical and
a dorsal portion. The fleshy fibres of the first are directed downwards and back-
wards ; those of the second are oblique forwards.
Attachments. — By its superior aponeurosis, it is fixed to the cord of the cer-
vical ligament and to the summits of the transverse processes of the first dorsal
vertebrae, where it adheres to the external face of the latissimus dorsi. By its
central aponeurosis and that of its summit, it is attached to the tuberosity of the
olecranian spine and the external scapular aponeurosis.
Relations. — This muscle is covered by two aponeurotic planes, the fibres of
which cross its owti at a right angle. Inwardly, it responds to the rhom-
boideus, splenius, angularis, deep pectoral, the supra- and infra-spinatus, and
the latissimus dorsi.
Action. — It raises the shoulder, and carries it forward or backward, according
as one or other of its muscular portions contract.
2. Great Dorsal (Latissimus Dorsi) (Fig. 159, 2).
Synonyms. — Dorso-humeralis — Girard. (Latissimus dorsi — PercivaU.)
Form — Situation — Structure — Attachments. — A very broad triangular muscle^
MUSCLES OF THE TBUNK.
261
extended over the loins, back, and side of the thorax, and formed of an aponeu-
rotic and a muscular portion.
The aponeurosis is attached, by its superior border, to the summits of the
spinous processes of all the lumbar, and the last fourteen or fifteen dorsal
xeTtehrss—Jixed insertion of the muscle.
The fibres of the fleshy portion are detached from the inferior border of the
aponeurosis, at the twelfth or thirteenth ribs, to the cartilage of the scapula.
They are directed forwards and downwards, and all converge into a flat tendon
which is inserted into the internal tuberosity on the body of the humerus —
movable insertion. This tendon is remarkable, at its termination, for being
Fig. 162.
JBUSCLES OF THE SPINAL REGION OF THE NECK, BACK, AND LOINS (MIDDLE LAYER) ; AND OF THE
COSTAL AND ABDOMINAL REGION (SUPERFICIAL LAYER).
1, 2, Rhomboideus ; 3, annularis muscle of the scapula ; 4, splenius ; 5, its mastoid aponeurosis ;
6, mastoid portion of the trachelo-mastoideus ; 7, its tendon ; 8, cervical insertions of the
mastoido-humeralis ; 9, atloidean tendon common to the mastoido-humeralis, splenius, and
trachelo-mastoideus; 10, great anterior straight muscle of the head; 11, inferior scalenus;
12, superior scalenus ; 13, small anterior serratus ; 14, posterior ditto ; 15, serratus magnus ;
16, anterior fibres of the rectus abdominis, sometimes described as the traiisversalis costarum;
17, one of the external intercostals ; 18, great oblique ; 20, rectus abdominis; 21, stylo-maxillaris
portion of the digastric muscle.
placed at the external face of the teres magnus or adductor of the arm, from
which it receives fibres, and between it and the long extensor of the forearm ;
it then turns inwards, on the inferior extremity of the first, in such a manner
that this extremity is comprised within a duplicature of the membranous tendon
of the latissimus dorsi.
Relations. — This muscle is covered by the skin, panniculus carnosus, dorsal
portion of the trapezius, and the mass of olecranian muscles. It covers the
infra-spinatus ; the cartilage of the scapula ; the rhomboideus ; the anterior
and posterior serrated muscles, the aponeurosis of which is directly joined to its
own ; the longissimus dorsi ; the principal gluteal ; a portion of the external
surface of the last ribs, to which its aponeurosis strongly adheres ; as well as to
the corresponding external intercostals, and the serratus magnus. Between
the last rib and the external angle of the ilium, the aponeurosis unites with the
262 THE MUSCLES.
small oblique, but more particularly with the great oblique, muscle of the
abdomen : it is prolonged, posteriorly, on the muscles of the croup to constitute
the gluteal aponeurosis.
Action. — It carries the arm backwards and upwards ; and it may, according
to a great number of authors, serve as an auxiliary in inspiration when its fixed
point is the humerus. According to others, but in whose opinion we do not
share, it is an expiratory muscle.
Second Layer.
3. Small Anterior Serrated Muscle (Serratus Anticus) (Fig. 162, 13).
Synonyms. — Dorso-costalis — Girard. Anterior portion of the long serrated muscle —
Bourgelat. (Superficialis costarum — Percivall, Anterior serrated muscle of Leylj. Serratus
posticus superior of Man.)
Form — Situation. — This is a flat, thin, quadrilateral muscle, situated beneath
the rhomboideus and the latissimus dorsi.
Structure. — It is composed of an aponeurotic and a fleshy portion. The first
is confounded, in front, with the aponeurosis of the splenius, and is insinuated,
behind, underneath that of the posterior small serratus, with which it soon
becomes united. Its inferior border gives origin to the muscular portion, a little
above the interval which separates the transversalis costarum and the longissimus
dorsi. Narrow and elongated antero-posteriorly, the muscular portion is com-
posed of bright-red fibres directed obliquely backwards and downwards, which
form at the inferior border irregular, and sometimes but faintly marked, festoons.
Attachments. — It takes its fixed insertion, by the superior border of its
aponeurosis, from the summits of the anterior dorsal spines, with the exception
of the first, to the thirteenth inclusive. The movable insertion takes place on
the external surface and anterior border of the nine ribs succeeding the fourth,
by means of the digitations of the fleshy portion. This muscle is also attached
to the external surface of these ribs by a short fibrous band, which is detached
from the internal face of the aponeurosis, near its inferior border, and penetrates
the space between the longissimus dorsi and the transversalis costarum.
Relations. — Outwards, with the rhomboideus, serratus magnus, latissimus dorsi,
and the posterior small serratus, which covers its three last festoons ; inwards,
with the longissimus dorsi, the transversalis costarum, and the external
intercostals.
Action. — This is an inspiratory muscle, and it also serves as a check to the
deep spinal muscles.
4. Small Posterior Serrated Muscle (Serratus Posticus) (Fig. 162, 14).
Synonyms.— Jjumho-coHtalis— Girard. Posterior portion of the long serrated muscle —
Bou/gelat. (Superficialis costarum — Percivall. The posterior serrated muscle of Leyh. The
serratus posticus inferior of Man.)
Situation. — Situated behind the preceding, which it follows, and presenting
the same form and arrangement, this muscle also offers the following particular
features for study : —
1. Structure. — Its muscular portion, which is thicker and of a deep-red colour,
is cut into nine well-defined digitations.^ The fibres which compose it run in an
almost vertical direction.
' It frequently happens that only eight diiritations are found in each muscle.
MUSCLES OF THE TRUNK. 263
2. Attachmmts. — Its aponeurosis, closely united to that of the latissimus
dorsi, which covers it, is attached to the spinous processes of the dorsal vertebrse
succeeding the tenth, and to some lumbar vertebrae. Its digitations are fixed to
the posterior border and external face of the nine last ribs.
3. Relations. — Outwards, with the latissimus dorsi ; inwards, with the small
anterior serratus, the longissimus dorsi, transversalis costarum, and the external
intercostals. Some of its posterior digitations are partly concealed by those of
the great oblique muscle of the abdomen ; the last, indeed, is entirely covered by
that muscle.
4. Action. — This is an expiratory muscle, in consequence of its drawing the
ribs backwards and upwards.
Third Layer.
5. The Ilio-8pinalis Muscle (Longissimus Doesi) (Fig. 163).
Synonyms. — It represents the loug dorsal, short transversal, and long spinous of Bourgelat.
Cuvier and others have described it as consisting generally, in Mammalia, of five particular
muscles, designated as longissimus dorsi, transversalis cervicis, semispinalis dorsi, and semi-
spinalis colli. It corresponds to the longissimus dorsi, and transversalis cervicis of Man.
(Percivall designates this important muscle the longissimus dorsi — the name given to its
analogue in Man, By Girard, Leyh, and Oliauveau, it is styled the ilio-spinalis.)
Extent — Situation. — This, the most powerful and complex of all the muscles
in the body, extends along the dorso-lumbar spine, above the costal arches, from
the anterior border of the ilium to the middle of the cervical spine.
Form. — It is elongated from before to behind, and flattened above and below
in its posterior half, which represents the common mass in Man ; this mass is
prismatic in form, thick inwards, and thin outwards. Anteriorly, it is flat on
both sides, and bifurcates into two vohmiinous branches, a superior and inferior,
between which pass the insertions of the complexus to be fixed into the transverse
processes of the first dorsal vertebrae.
Attachments. — 1. Upon the lumbar border, the external angle and internal
smface of the ilium, the sacro-iliac ligament, and the sacrum. 2. To the spinous
processes of all the lumbar and dorsal, and last four cervical vertebrae. 3. To
the articular tubercles of the lumbar vertebrae and the transverse processes of all
the dorsal, and the last fom* cervical vertebrae. 4. To the costiform processes
of the lumbar vertebrae, and the external surface of the fifteen or sixteen last ribs.
Structure. — If this muscle is examined posteriorly, in the part which forms
the common mass, it wiU be found to be composed of very compact fleshy fibres,
covered in common by a thick aponeurosis. These fibres commence at the
posterior extremity of the muscle, and all proceed forward, stopping to make
successive insertions on the various bony eminences in its track, and forming
three diflferent orders of fasciculi, which are more or less tendinous at their
anterior or terminal extremity. These fasciculi are internal and superficial,
internal and deep, and external.
The internal and superficial, or spinal fasciculi, pass to the summits of the
spinous processes already noticed when speaking of the attachments. These
fasciculi are little, if at all distinct posteriorly ; but they become more so
anteriorly. About the sixth dorsal vertebras, they separate from the other
fascicuU to form the superior branch of the muscle (Fig. 163, 3).
The internal and deep, or transverse fasciculi, are those which attach the
muscle to the articular tubercles of the lumbar vertebrae and transverse processes
264
THE MUSCLES.
of the back and neck. They are well detached from each other, even posteriorly,
and are very tendinous. Anteriorly, they pass into the inferior branch of the
fongissimus dorsi, which they, in common with the external fasciculi, go to form.
From profound, they now become superficial ; and they are seen springing up be-
tween the others, which appear to separate to allow them to pass (Fig. 163, 4, 4).
MUSCLES OF THE TRUNK. 265
The external, or costal fasciculi, turn a little outwards to reach the ribs and
costiform processes of the lumbar region ; they are not very apparent in this
direction (%. 163, 2, 2).
It win be easily understood that all these fasciculi do not come from the
common mass, which would be expended long before its termination at the neck,
in consequence of the successive emissions of the fasciculi composing it. To
prevent this exhaustion, there are continually added to it numerous bimdles of
fibres, which arise either from its aponeurotic envelope, or from the bones on
which the primary fasciculi terminate, and comport themselves absolutely like
these, which they are charged to continue to the neck.
Relations. — It is covered by the pyramidal point of the principal gluteal
muscle, which it receives in a particular excavation, and by the aponeurosis of
the latissimus dorsi and the small serrated muscles. It covers the inter-
transversales of the lumbar region, the semispinalis of the back and loins, the
levatores costarum, and the external intercostals. Outwards, it is bordered by
the transversalis costarum.
The superior branch is covered by the complexus and the semispinaHs colli.
Inwardly, it responds to the cervical ligament and the analogous branch of the
opposite muscle.
The inferior branch responds, outwardly, to the angularis of the scapula ; it
covers some intertransversales colli, and the aponeurotic digitations which attach
the complexus to the transverse processes of the first dorsal vertebrse. From
these digitations it even detaches a number of muscular fasciculi, which go to
strengthen this branch of the longissimus dorsi.
Action. — It is a powerful extensor of the vertebral column, which, when it
acts singly, it inclines to one side. It may also take part in expiration.
6. Common Inteecostal Muscle (Teansversalis Costaeum (Fig. 163, 5).
Synonyms. — Trachelo-coatalis — Girard. The sacro-lumhalis of Man.
Form — Situation. — A long, narrow, and thin muscle — particularly at its
extremities — situated along the external border of the preceding muscle, with
which it is confounded behind the last rib.
Structure — Attachments. — This muscle, the structure of which has been
complicated by so many anatomists, is yet extremely simple. It is formed of
a series of fasciculi, directed obliquely forwards, downwards, and outwards,
tendinous at their extremities, and originating and terminating successively on
the external surface of the ribs. The most posterior leave the external border
and inferior face of the common mass. The tendinous digitation of the anterior
fasciculus is inserted into the transverse process of the last cervical vertebra, in
common with the inferior branch of the longissimus dorsi.
Relations. — Outwards, with the great and small serratus ; inwards, with the
external intercostals.
Action. — It depresses the ribs, and may extend the dorsal portion of the spine.
Fourth Layer.
Transverse Spinous Muscle of the Back and Loins (Semispinalis
OF THE Back and Loins) (Fig. 161, 3).
Synonyms. — Transverso-spinous — Girard. Dorso-lumbar portion of the semispinalis of Maa
(The spinalis and semispinalis dorsi — Percivall.)
Situation — Extent. — This is a very long muscle, directly applied to the super-
266 THE MUSCLES.
sacral and dorso-lumbar spine, and continuous, in front, with the semispinalis
colli ; these two muscles, therefore, measure nearly the whole length of the spine.
Structure. — It is formed by an assemblage of short fasciculi, which are
flattened on both sides, tendinous at their extremities, directed obliquely forwards
and downwards, and a little inwards, thus crossing at a right angle the spinous
processes they cover.
Attachments. — These fasciculi are attached, below, to the lateral lip of the
sacrum, the articular tubercles of the lumbar vertebrae, and the transverse
processes of the dorsal vertebrae — origin. They are fixed, above, to the spinous
processes of the sacral, lumbar, and dorsal vertebrae, and into that of the last
cervical vertebra — termination. It is to be remarked that they do not attain the
summits of these spinous processes in the first half of the dorsal region.
i^e/a^wws.— Outwards, with the lateral sacro-coccygeal and longissimus dorsi
muscles, which are confounded with it near its posterior extremity ; inwards,
with the sacral spine and the spines of the lumbar and dorsal vertebrae, and with
the interspinous ligaments of these three regions.
Action. — It is an extensor of the spine.
Differential Characters in the Muscles of the Spinal Region of the Back and
Loins in the other Animals.
A. Ruminants. — In the Ox, Slieep, and Goat, the trapezius is thick and very broad.
In the Sheep, only the posterior fasciculus of the muscle annexed to the latissimus dorsi is
seen. Some of its fibres are prolonged to the anterior border and external face of the latissimus
dorsi. In the Camel, the dorsal portion of the trapezius is remarkable for its size. The
latissimus dorsi has a thicker and wider body than that of the Hortse ; it descends low on the
ribs ; the aponeurotic portion passes beyond the boss or hump. In the longissimus dorsi, the
fasciculi are very distinct, even in the midst of the common mass, where the external fasciculi
can be clearly seen to become attached separately to the extremities of the transverse processes
of the lumbar vertebrae.
The anterior small serrated muscle is inserted, by its last digitation, into the ninth rib.
The posterior serrated is fixed into the four last ribs.
B. Pig.— Its trapezius is well developed. The latissimus dorsi is voluminous, and is attached
to the surface of the ribs, which it covers by digitations from its flesliy portion. It is fixed
near the small trochanter to the lip of the bicipital groove. The inferior branch of the
hngissimus dorsi of tbis animal is easily divided into two portions, traces of which are found
in the Horse : one is formed by the costal fasciculi, the other by the transversal fasciculi. The
latter constitutes the muscle to which Bourgelat has given the name of short transversal.
C. Camivora. — Several of the spinal muscles in tbe Bog resemble those of the Pig ; such
are the trapezium, the latissimus dorsi, and the longissimus dorsi. In animals of this group, it
is remarked that the anterior serrated is very tiiick and very developed, and that it is attached
to the eight ribs succeeding the second by as many well-marked festoons. The posterior has
only three digitations, which are attached to tbe three last ribs. The transversalis costarum
exactly resembles the sacro-lumbalis of Man ; behind the last rib, it constitutes a thick fleshy
body, separated by a fissure from the longissimus dorsi, with which it is attached to the coxa.
Lastly, the semispinalis of the back and loins is very strong in the lumbar region, and is
prolonged on the coccygeal vertebrae.
(According to Leyh, the semispinalis muscles are absent in the Horse and Ruminants;
they are found in the Pig between tlie spinous processes of the dorsal and lumbar vertebrae,
and in Camivora between the spinous processes of the cervical vertebrae.)
Comparison of the Mdscles of the Back and Neck in Man with the analogous
Muscles in the domesticated Animals (Fig. 164).
It is usual, in human anatomy, to describe by the name of muscles of the back and neck
those which correspond to the superior cervical region, and those of the spinal region of the
back and loins of the domesticated animals. The muscles of the inferior cervical region are
described in Man as muscles of the neck, with the hyoid muscles and the scalenus.
MUSCLES OF THE TRUNK.
267
1. Muscles of the Back and Cervix.
In the trapezius of Man, a cervical and a dorsal portion can no longer be distinguished.
Abo\ie, it is attached to the superior occipital curved line ; below, it is fixed to the external
third of the upper border of the clavicle, and to the acromion and scapular spine. The fibres
of the trapezius, which are fixed into the clavicle, represent a portion of the mastoido-humeralia
, of quadrupeds.
The latissimus dorsi resembles that of the Dog and Pig, its fleshy portion being very
Fig. 164.
FIRST, SECOND, AND PART OF THIRD LAYER OF MUSCLES OF THE BACK OF MAN; THE FIE8T
LAYER OCCUPIES THE RIGHT, THE SECOND THE LEFT SIDE.
Trapezius ; 2, tendinous portion, forming, with a corresponding part of the opposite muscle, the
tendinous ellipse on the back of the neck ; 3, acromion process and spine of scapula ; 4, latissimus
dorsi ; 5, deltoid; 6, muscles of dorsum of the scapula (infra-spinatus, teres minor, and teres
major; 7, obliquus externus; 8, gluteus medius ; 9, glutei maximi ; 10, levator anguli scapulae;
11, rhomboideus minor; 12, rhomboideus major; 13, splenius capitis, overlying the splenius,
above; 14, splenius colli, partially seen (the common origin of the splenius is attached to the
spinous processes below the origin of the rhomboideus major) ; 15, vertebral aponeurosis ; 16,
serratus posticus inferior; 17, supra-spinatus ; 18. infra-spinatus; 19, teres minor; 20, teres
major; 21, long head of triceps, passing between teres minor and major to the arm; 22, serratus
magnus, proceeding forwards from its origin at the base of the scapula ; 23, obliquus internus
abdominis.
developed ; it is attached to the external face of the four last ribs by muscular digitations, and
terminates on the border of the bicipital groove.
The rhomboideus is bifid, as in the smaller Quadrupeds. Less developed than in these
animals, the levator anguli scapulx is only fi.xed iu front to the four first cervical vertebrae.
In Man, the splenius is large, but by its insertions it resembles that of Solipeds. The
complexus, thick and broad above, is incompletely divided into two fleshy bodies, which are
268 THE MUSCLES.
attacher], superiorly, to the sides of tlie external occipital crest. The trachelo-mastoideus
is not fixed into the axis and atlas, its superior extremity passing directly to the mastoid
process.
There is nothing particular to note regarding the straight posterior and oblique muscles of
the head ; the differences they offer in their form are allied to the conformation of the bones in
this region.
Of the two small serrated muscles, that which corresponds to the anterior serrated or
animals rises very high ; for it is attached by an aponeurosis to the spinous processes of the
three first dorsal vertebrae, the seventh cervical, and the cervical ligament.
There are found in Man, lying along the vertebral furrows, several muscles which represent
the longissimus dorsi and the transversalis costarum of Solipeds. Thus tlie common mass
covering the lumbar vertebrae behind, is prolonged by two series of fleshy and tendinous
fasciculi ; one forms the sacro-lumhaiis, which resembles the transversalis costarum of animals ;
the other, the long dorsal, represents the inferior branch of the longissimus dorsi. The
superior branch of the latter is found in the semispinalis colli.
Lastly, there are also seen in Man semispinalis and intertransversalis muscles, which
correspond : the first, to the semispinalis of the back and loins and semispinalis colli ; the
second, to the intertransversales of the loins of the domesticated species.
2. Muscles of the Neck.
The mastoido-humeraUs is not present in Man, being peculiar to Quadrupeds; but we
should see a portion of its fasciculi in the cleido-mastoideus muscle, and in the clavicular
portions of the trapezius and deltoid.
The sterno-mastoideus corresponds to the sterno-maxillaris of animals; as in the Dog, it
is inserted into the external face of the mastoid process and the external two-thirds of the
superior occipital curved line. Below, it commences by two fasciculi — one from the sternum,
the other from the clavicle. We have already alluded to this clavicular fasciculus.
The sterno-lhyro-hyoideus is large and well developed, resembling in its disposition that of
the smaller animals. It is to be noted that the sterno-hyoideus portion leaves the sternum, tlie
first costal cartilage, and the internal extremity of the clavicle. The subscapulo-hyoideus is
digastric. The anterior great straight muscle of the head is attached to four cervical vertebrae,
as in Ruminants and the Pig. The anterior small straight, the lateral small straight, and the
longus colli, comport themselves as in the smaller animals. The anterior scalenus is very
developed, for it is attached to the six last cervical vertebrae.
Sublumbar, or Inferior Lumbar Region.
The muscles of this region are deeply situated at the inferior face of the
lumbar vertebrae and the ilium, concurring to form the roof of the abdominal
cavity, and are in more or less direct contact with the viscera contained in that
cavity. They are nine pairs. Three of these have received the generic name of
psoas, and are of large volume ; they are bound by a strong aponeurosis — the
iliac fascia, and are distinguished as the great psoas, iliac psoas (or iliacus),
and small psoas. A fourth is named the square muscle of the loins {quadratus
lumhorum). The other five, placed between the transverse processes of the
lumbar vertebrae, represent, in consequence of their connection with these kind
of fixed ribs, veritable intercostal muscles ; these are the intertransversales muscles
of the loins.
Preparation.— 1. Place the subject in the first position : open the abdominal cavity by
completely removing its inferior walls ; empty the cavity of the viscera it contains, and excise
the diaphragm, as that muscle prevents the anterior extremity of the great and small psoas
muscles being seen. 2. First study the iliac fascia, its form, relations with the long abductor
of the leg, its attachments, its continuity with the tendon of the small psoas, and the expansion
reflected from the aponeurosis of the ^reat abdominal oblique muscle. 3. Expose the three
psoas muscles by removing the iliac fascia, the two adductors of the leg, and the three
adductors of the thigh. 4. Remove the psoas muscles for the dissection of the quadratus and
intertransversales.
MUSCLES OF THE TRUNK. 269
1. Iliac Fascia, oe Lumbo-iliac Aponeurosis (Fig. 165, a).
This is a very resisting fibrous expansion, covering the great psoas and iliacus
muscles. Attached, inwardly, to the tendon of the small psoas, outwardly to
the angle and external border of the ilium, this aponeurosis, as it extends for-
•wards over the great psoas, degenerates into connective tissue. Behind, it also
becomes attenuated in accompanymg the two muscles it covers, until near their
insertion into the internal trochanter of the femur. Its external or inferior face
receives, posteriorly, the insertion of the crural arch, and gives attachment to
the long adductor of the leg ; for the remainder of its extent, it is covered by
the peritoneum.
2. Great Psoas Muscle (Psoas Magnus) (Fig. 165, 1).
i&j/nonj/ms.— Sublumbo-troclian t : n eus— Gi'rard. Psoas — Bourgelat. {Lumho-femoral — Leyh.)
Form — Situation. — This is a loug muscle, flattened above and below at its
anterior extremity, prismatic in its middle, and terminated in a cone at its
posterior extremity. It lies beneath the transverse processes of the lumbar
vertebrae.
Structure. — Almost entirely fleshy, this muscle is formed of very delicate
fasciculi, which are directed backwards, and long in proportion to their super-
ficial and deep situation. They all converge to a tendon which is enveloped by
the iliacus, and is confounded with it.
Attachments. — It is attached : 1. By the anterior extremity of its fleshy
fasciculi to the bodies of the last two dorsal and the lumbar vertebrae, except the
hindermost, and to the inferior face of the two last ribs and the transverse
processes of the lumbar vertebrae. 2. By its posterior tendon to the internal
trochanter, in common with the iliacus.
Relations. — Below, with the pleura, the superior border of the diaphragm,
and the lumbo-iliac aponeurosis, which separates it from the peritoneum and the
abdominal viscera situated in the sublumbar region ; above, with the two last
internal intercostals, the quadratus lumborum, and the intertransversales muscles ;
inwardly with the small psoas and the internal branch of the iliacus ; outwardly,
for its posterior third, with the principal branch of the latter muscle.
Action. — A flexor and rotator of the thigh outwards when its fixed point is
the loins, this muscle also flexes the lumbar region when the thigh is a fixed
point. It is, therefore, one of the agents which determine the arching of the
loins, and which operate, during exaggerated rearing or prancing, in bringing
the animal into a quadrupedal position again.
3. Iliac Psoas Muscle (Iliacus) (Fig. 165, 3).
Synonyms.— T\\o-irochaxiixnevii&—Girard. (Leyh divides this muscle into two portions,
which he describes as the great and middle ilio-femoralis.
Form — Situation — Direction. — This is a very strong, thick, and prismatic
muscle, incompletely divided into two unequal portions by the groove for the
reception of the tendon of the great psoas : an external portion, somewhat con-
siderable in size ; and an internal, small. These two muscular portions lie at
the entrance to the pelvis, on the inner face of the ilium, in an oblique direction
downwards, backwards, and inwards.
Structure. — It is almost entirely fleshy. The fasciculi forming it are spread
270
THE MUSCLES.
out in front, and collected behind, where they become slightly fibrous, and unite
with the tendon of the great psoas.
Attachments. — It has its fixed insertion on the whole of the iliac surface, on
the external angle of the ilium, the sacro-iUac hgament, and the ilio-pectineal
Fig. 165. I
MUSCLES OF THE SUBLUMBAR, PATELLAR, AND INTERNAL CRORAL REGIONS.
1, Psoas magnus ; 1', its terminal tendon ; 2, psoas parvus ; 3, iliacus ; 4, its small internal portion ;
5. muscle of the fascia lata ; 6, rectus femoris of the thigh ; 7, vastus internus ; 8, long adductor
of the leg ; 9, short adductor of the leg; 11, pectineus ; 12, great adductor of the thigh ; 12',
small adductor of the thigh; 13, semimembranosus; 14, semitendinosus. A, Portion of the
fascia i/iaca ; B, portion of the membrane reflected from the aponeurosis of the abdominal great
oblique muscle, forming the crural arch (Poupart's ligament) ; C, pubic tendon of the abdominal
muscles ; D, origin of the pubio-femoral ligament.
crest. Its movable insertion is into the small internal trochanter, in common
with the great psoas.
Relations. — Above, with the ilium ; below, with the iliac fascia and the long
adductor of the leg ; outwardly, with the muscle of the fascia lata and the origin
of the rectus femoris, from which it is separated by a space filled with fat ;
inwardly, with the crural vessels. It passes between the vastus internus and the
pectineus, to reach the trochanter.
Actions. — It is a flexor and rotator outwards of the thigh.
MUSCLES OF THE TRUNK.
271
4. Small Psoas Muscle (Psoas Parvus) (Fig. 165, 2).
according to Girard.
of the loins — 1
(^Psoaa parvus — Percivall.
Sublumbo-pubia
The lombo-iliacus
3, or sublumbo-iliacua,
Leyh.)
Situation — Form — Structure. Placed at the inner side of the psoas magnus,
very much elongated, and semipenniform in shape, this muscle is terminated
behind by a flattened tendon, and is composed of fleshy fibres, the longest of
which are anterior. These fasciculi are all directed backwards and outwards to
gain the tendon.
Attachments.— 1. To the bodies
of the three or four last dorsal, and
to all the lumbar vertebrse, by the
anterior extremity of its fleshy fibres.
2. To the ilio-pectineal line and the
lumbo-iliac aponeurosis, by the pos-
terior extremity of its tendon.
Relations. — By its inferior face
with the pleura, the superior border
of the diaphragm, the aorta or pos-
terior vena cava, and the great
sympathetic nerve ; by its upper face,
with the psoas magnus. It is tra-
versed, near its vertebral insertions,
by numerous vascular and nervous
branches.
Actions. — It flexes the pelvis on
the spine, when the loins are the
fixed point ; but should the pelvis be
fixed, it arches or laterally inclines
the lumbar region. It is also the
tensor muscle of the lumbo-iUac
aponeurosis.
Fig. 166.
DEEP MUSCLES OF THE SUBLITMBAR REGION.
1, Quadratus lumborum ; 2, 2, intertransversales ;
3, small retractor muscle of the last rib — a de-
pendent of the small oblique of the abdomen.
5. Square Muscle of the Loins (Quadratus Lumborum) (Fig. 166, 1).
Synonyms. — Sacro-costalis — Girard. (Sacro-lumbalis — Percivall. Quadratus lumborum of
Man.)
Situation — Form — Structure — Attachments. — This muscle is comprised between
the transverse processes of the lumbar region and the psoas magnus, is elongated
from before to behind, flattened above and below, and divided into several very
tendinous fasciculi. The principal fasciculus, situated outwardly, takes its origin
from the sacro-iliac ligament, near the angle of the sacrum, and extends directly
forward to gain the posterior border of the last rib, after being attached by its
upper face to the summits of the transverse processes of the lumbar vertebrse.
The other fasciculi are longer as they are anterior ; they leave the internal border
of the first, and are directed obliquely foi-ward and inward, to be fixed into the
transverse processes of the majority of the lumbar vertebrae, and the inner face
of the two or three last ribs.
Relations. — By its upper face, with the intertransversales, the small retractor
E72 THE MUSCLES.
of the last rib, and the fibrous fascia which unites that muscle to the small
oblique of the abdomen. By its inferior face, to the psoas magnus.
Actions. — It draws the last ribs backwards, and inchnes the lumbar spine to
one side.
6. Intertransveesales of the Loins (Fig. 166, 2, 2).
(^Synonym. — Litertransversales lumborum — Percivall. )
These are very small flat muscles which fill the intervals between the trans-
verse processes of the lumbar vertebrae. Their muscular fibres are mixed with
tendinous fibres, and are carried from the anterior border of one transverse
process to the posterior border of the other.
They respond, by their superior face, to the longissimus dorsi, and by their
inferior face to the quadratus, as well as the psoas magnus. They act by inclin-
ing the lumbar region to one side.
drpfebential characters in the muscles of the sublttmbar region in the otheb
Animals.
In Ruminants and the Pig, the muscles of this region so closely resemble those of
Solipeds, that a special description is unnecessary. It may be remarked, however, that the
quadratus lumborum in the Sheep is very developed, and throws fibres as far forward as tlie
four last ribs.
In the Dog, the psoas magnus is little developed, and only commences at the third, or even
the fourth lumbar vertebra ; the iliacus is very slender, particularly in its external portion ;
otherwise it is scarcely distinct from the psoas magnus, with which it may be said to form one
muscle ; the psoas parvus is relatively larger than the great ; it is not prolonged into tlie
pectoral cavity, and its anterior extremity is confounded with the quadratus lumborum, which
is longer and stronger than in all the other animals.
Comparison of the Subltjmbab Muscles of Man with those of Animals.
In human anatomy, by the names of psoas and iliacus are described the psoas magnum and
iliacus of animals. The psoas magnus of Man is distinguished from that of Solipeds by its
superior insertions, whicii do not go beyond the last dorsal vertebrae.
The psoas parvus is often absent : when present, it is attached, above, to the bodies of the
twelve dorsal vertebrae ; below, to the ilio-pectineal crest.
The intertransversales have been studied with the muscles of the back. The quadratus
lumborum, classed by anthropotomi.sts with the abdominal muscles, is distinctly divided into
three series of fasciculi : ilio-costal fasciculi, which pass from the upper border of the ilium to
the twelfth rib; lumbo-costal fasciculi, passing from the transverse processes of the three or four
last lumbar vertebrae to the twelfth rib ; and ilio-lumbar fasciculi, going from the iliac crest to
the posterior face of the transverse processes of all the lumbar vertebrae.
Coccygeal Region.
This region is composed of four pairs of muscles destined for the movementg
of the tail ; three, named the sacro-cocajgeal, are disposed longitudinally around
the coccygeal vertebrae, which they completely envelop ; the fourth is designated
the ischio-coccygeus {compressor coccygeus).
1. Sacro-coccygeal Muscles (Fig. 167, 1, 2, 3).
These three muscles are enclosed, with those of the opposite side, in a strong,
common aponeurotic sheath, which is continuous with the inferior ilio-sacral
and sacro-sciatic ligaments. They commence on the sacrum, are directed back-
wards and parallel with the coccyx, gradually diminishing in thickness, and are
formed by several successive fasciculi terminating in small tendons, which are
MUSCLES OF THE TRUNK.
273
inserted into each of the coccygeal bones. With regard to their situation, these
muscles are distinguished as sacro-coccygeus superior, sacro-coccygeus inferior, and
sacro-coccygeus lateralis.
A. Sacro-coccygeus Superior (Erector Coccygis). — The fasciculi which
form this muscle have their fixed insertion either in the summits and sides of the
three or four last processes of the supra-sacral spine, or from the coccygeal vertebrse
themselves. The tendons for their movable insertion into these vertebrae are
always very short.
This muscle, covered by the coccygeal aponeurosis, in turn covers the vertebrae
it moves. It responds : inwardly, to the analogous muscle of the opposite side ;
outwardly, to the lateral sacro-coccygeus, and, near its anterior extremity, to a
very strong aponeurotic expansion which separates it from the semispinahs
muscle. It directly elevates the tail, or pulls it to one side, according as it acts
in concert with its fellow or singly.
B. Sacro-coccygeus Inferior (Depressor Coccygis). — This muscle is
thicker than the precedmg ; its constituent fasciculi take their origin from the
Fi?. 167.
SACRO-ILIAC AND COXO-FEMORAL ARTICULATIONS, WITH THEIR SURROUNDING MUSCLES.
1, Sacro-coccygeus superior ; 2, sacro-coccygeus lateralis ; 3, sacro-coccygeus inferior ; 4, ischio-
coccygeus ; 5, deep gluteus; 6, crureus.
inferior surface of the sacrum, towards the third vertebra, and from the internal
face of the sacro-sciatic ligament and the coccygeal bones. It readily divides into
two parallel portions, which Bourgelat has described as two separate muscles.
The fasciculi of the internal portion are inserted, by their posterior extremity, into
the inferior face of the first coccygeal vertebrae. Those of the external portion
are furnished with strong superficial tendons, nearly all of which are for the
bones of the tail.
This muscle responds : outwardly, to the sciatic ligament, the ischio-coccygeus
{compressor coccygeus) and coccygeal aponeurosis ; inwardly, to the muscle of the
opposite side, and to the coccygeal attachment of the rectum ; above, to the
sacrum, the bones of the tail, and the lateral muscle ; below, to the rectum and
the coccygeal aponeurosis.
It either directly depresses the tail or inclines it to one side.
C. Sacro-coccygeus Lateralis (Curvator Coccygis). — This muscle may
274 THE MUSCLES.
be considered as the semispinalis of the coccygeal region ; indeed, it is confounded
with that muscle of the back and loins by its anterior extremity, and appears to
continue it to the inferior extremity of the tail.
The fasciculi composing it arise from the spinous processes of the last lumbar
vertebrfe, through the medium of the semispinahs, and from the coccygeal bones.
The tendons terminating these fasciculi are deep and not very distinct.
It responds : outwardly, at the posterior extremity of the longissimus dorsi,
to the inferior ilio-sacral ligament and the coccygeal aponeurosis ; inwardly, to
the semispinalis and the coccygeal vertebrae ; above, to the superior muscle ;
below, to the inferior muscle, from which it is nevertheless separated by several
small independent muscular fasciculi, which are carried from one coccygeal
vertebra to another. (Leyh designates these the intertransversales of the tail.)
It inchnes the tail to one side.
2. ISCHIO-COCCYGEUS (COMPRESSOR COCCYGIS) (Fig. 167, 4).
A small, thin, wide, and triangular muscle, situated against the lateral wall of
the pelvis, at the internal face of the sacro-sciatic Ugament.
It is attached, by an aponeurosis, to that Ugament and to the ischiatic ridge ;
it is then directed upwards to be fixed, by its muscular fibres, to the side of the
last sacral vertebra and the first two coccygeal bones.
It is related, outwardly, with the sacro-sciatic Ugament. and inwardly to the
lateral sacro-coccygeus and the rectum.
It depresses the entire caudal appendage.
Region of the Head.
The head has a large number of muscles disposed around the mouth, nostrils,
eyelids, the external ear, inferior maxilla, and os hyoides. They will be divided
into five secondary regions.
A. Facial Eegion,
This region includes those muscles of the head which form a part of the
framework of the lips, cheeks, and nostrils. Authors are far from being
unanimous with regard to the nomenclature and description of these muscles.
"We recognise eleven, which are enumerated below, chiefly according to the
nomenclature of Girard. They are : the labial {orbicularis oris) ; zygomaticus ;
supermaxillo-labialis (nasalis longus, or levator labii superioris proprius) ; maxillo-
labialis {depressor labii inferioris) ; mento-labialis, suspensor of the chin (levator
menti), which act on the lips ; alveolo-labialis {buccinator), which moves the
jaw ; super naso-labial is {levator labii superioris alcequi nasi), which moves lips
and nostrils ; great supermaxillo-nasalis {dilatator naris lateralis), small super-
maxillo-nasalis {dilatator naris superior), naso-transversalis {dilatator naris
transversalis), which dilate the nostrils and false nostrils only.
1. Labialis, or Orbicularis of the Lips (Orbicularis Oris) (Fig. 167, 27).
Preparation.— Remove with scissors the skin covering the two portions of this muscle ;
afterwards the buccal mucous membrane and subjacent glands within the lips, to expose its
internal face.
The orbicularis, disposed as a sphincter around the anterior opening of the
mouth, is regarded as the intrinsic muscle of the lips, and is composed of two
portions or fasciculi — one for the upper, the other for the lower lip. United to
MUSCLES OF THE TRUNK.
27$
each other at the commissures of the mouth, and confounded with the superficial
layer of the buccinator, which they appear to continue, these two muscular por-
tions also receive a large portion of the fibres belonging to the majority of the
extrinsic muscles, such as the dilatator naris lateralis and levator labii superioris
alfequi nasi.
The orbicularis is not attached to the neighbouring bone ; its component
fibres, affecting a circular form, have, consequently, neither beginning nor ending,
except in being continuous with other fibres.
The internal face of the superior fasciculus responds to a layer of salivary
glands, which in part separate it from the buccal mucous membrane. The external,
covered by the skin, adheres to it in the most intimate manner, and is found
isolated from it only on the median line, at first by the aponeurotic expansion of
Fig. 168.
SUPERFICIAL MDSCLES OF THE FACE AND HEAD.
1, Temporo-auricularis externus, or attollens maximus ; 2, levator palpebrae, or corrugator super-
cilii; 3, temporo-auricularis internus, or attollens posticus; 4, 5, zygomatico-auricularis, or
attollens anticus ; 6, orbicularis palpebrarum; 7, abducens, or deprimens aurem ; 8, parotid
gland; 9, temporal, or subzygomatic vein; 10, ditto, artery; 11, 12. superior and inferior
maxillary nerves- 13, fascia of the masseter muscle; 14, nasal bones; 15, supernasol-abialis, or
levator labii superioris alseque nasi; 16, supermaxillo-labialis, or nasalis longus labii superioris;
17, external maxillary or facial artery; 18, facial vein; 19, supermaxillo-nasalis magnus, or
dilatator naris lateralis ; 20, superior maxillary nerve ; 21, zygomatico-labialis, or zygomaticus ;
22, parotid, or Steno's duct ; 23, masseter ; 24, alveolo-labialis, or buccinator ; 25, super-
maxillo-nasalis parvus, or nasalis brevis labii superioris ; 27, labialis, or orbicularis oris ; 28,
maxillo-labialis, or depressor labii inferioris ; 29, mento-labialis, or levator menti.
the nasalis longus, then by a musculo-fibrous layer analogous to that which forms
the levator menti.
By its internal face, the inferior fasciculus likewise responds to the buccal
mucous membrane, and to some salivary glands. By its external face, it forms
an intimate union with the cutaneous integument, like the superior fasciculus.
This muscle plays the part of a constrictor of the anterior opening of the
mouth, and has complex functions to perform in suction, the prehension of food,
and in mastication.
2. Zygomatico-labialis (Zygomaticus) (Fig. 168, 21).
Synonyms. — Portion of the cuticularis of Bourgelat. The zygomaticus major of Man.
A very small, pale, and thin ribbon-like muscle, arising from the surface of
the masseter, near the maxillary spine, by an aponeurosis which is confounded
with the panniculus ; it terminates on the surface of the buccinator, at a short
276 THE MUSCLES.
distance from the commissure of the lips. Covered by the skin, it covers the
buccinator, and some of the superior molar glands, vessels, and nerves.
When this muscle contracts, it pulls back the commissure of the lips.
In SoJipeds there is also sometimes found a muscle resembling the zygomaticus
ininoi' of Man. It is a very small fasciculus situated under the preceding muscle,
near its superior extremity. It appears that this fasciculus is continued, above,
by the fibres of the lachrymal muscle, and is lost, below, on the buccinator sur-
face, a little beneath the carotid canal.
3. SUPERMAXILLO-LABIALIS (LEVATOR LaBII SuPERIORIS PrOPRIUS, OR NaSALIS
LONGUS) (Fig. 168, 16).
Synonyms. — Levator labii superioris of Bourgelat. The levator labii superioris proprii of
Man. {Nasalis longus labii superioris — Percivall.)
Situation — Direction— Form — Structure. — Lying vertically on the side of the
face, below the levator labii superioris alseque nasi, this muscle is a thick and
conical fleshy mass, terminated inferiorly by a tendon.
Attachments. — It is attached, by the upper extremity of its fleshy body, to the
external surface of the supermaxillary and zygomatic bones — origin. Its terminal
tendon passes over the transverse muscle of the nose, to unite with that of the
opposite side, and with it to form a single aponeurotic expansion, which dips by
small fibres into the subcutaneous musculo-fibrous tissue of the upper lip.
Relations. — Covered by the lachrymal and levator superioris alfequi muscles,
this muscle in turn covers the supermaxiUary bone, the bottom of the false nostril,
the dilatator naris inferioris, and the transversalis nasi.
Actions. — It raises the upper lip, either directly or to one side, as it acts singly
or in concert with its congener on the opposite side.
4. Maxillo-labialis (Depressor Labii Inferioris) (Fig. 168, 28).
Synonyms. — Depressor labii inferioris — Bigot. A dependency of the buccinator of Man.
(Depressor labii inferioris — Percivall. Inferior maxillo-labialis — Leyh. Depressor anguli oris
of Man.)
Situation — Direction — Form — Structure. — Situated along the inferior border
of the buccinator, and following its direction, this muscle forms a long narrow
fasciculus, terminating inferiorly by an expanded tendon.
Attachments. — 1. By its superior extremity, to the anterior border of the
lower jaw, in common with the deep plane of the buccinator— ^a;^c? origin. 2.
By its terminal tendon, to the skin of the lower lip — movat)le insertion.
Relations. — Outwardly, with the masseter and the facial portion of the cervical
panniculus ; inwardly, with the maxillary bone ; in front, with the buccinator,
with which it is directly united in its upper two-thirds.
Actions. — It separates the lower from the upper lip, and pulls it to the side
if one alone acts.
5. Mento-labialis, or Muscle of the Chin (Levator Menti) (Fig. 168, 29).
[Synonyms. — Percivall appears to describe this and the next muscle as one, the levator menti.
It is the quadratus menti of Man.)
This name is given to a musculo-fibrous nucleus, forming the base of the
rounded protuberance beneath the lower hp in front of the beard. This single
nucleus is confounded, in front, with the orbicularis of the lips, and receives into
its upper face the insertion of the two posterior middle muscles (levatores menti).
MUSCLES OF THE TRUNK. 277
6. Intermediate Posterior Muscle.
Synonyms.— M-eAins posterior — Bourgelat. (Levator menti — Percivall. Incisive muscle of
the lower lip — Leyh.)
Bourgelat describes, by this name, a small muscular fasciculus, analogous in
every respect to the medius anterior. This little muscle takes its origin from the
external surface of the body of the lower jaw, beneath the intermediate and
corner incisors ; from thence it descends into the texture of the lip, to unite with
that of the opposite side on the upper face of the mento-labialis. Several authors
have described it as a dependent of the last muscle.
7. Alveolo-labialis (Buccinator) (Fig. 168, 24).
Synonyms. — Molaris externus et internus — Bourgelat. {Buccinator — Percivall. Leyh
divides this muscle into two portions ; its superficial plane he designates the Buccinator, and
the deep plane the Molaris.)
Preparation. — Proceed to the ablation of the masseter ; dissect the external surface of the
muscle, taking care of the risorius Santorini and zygomaticus, which are confounded with it.
Then divide it in the middle, as far as the commissure of the lips ; turn down each strip on
the jaws, and remove the mucous membrane, in order to study the inner face of the muscle and
the attachments of the superficial plane to the maxillary bones.
Situation — Form. — Situated on the sides of the face, partly concealed by the
masseter muscle, and applied to the mucous membrane of the cheeks, the bucci-
nator is a flat, thin muscle, elongated in the direction of the head, and formed
of two superposed planes.
Extent — Structure — Attachments. — The deep plane, the longest and least wide,
is narrower at its extremities than its middle, and is formed of strongly aponeu-
rotic muscular fasciculi, which are attached, posteriorly : 1. To the alveolar
tuberosity. 2. To the external surface of the superior maxillary bone, above
the last three molar teeth. 3. To the anterior border of the inferior maxillary
bone, behind the sixth molar, in common with the depressor labii inferioris.
On reaching the commissure of the lips, this muscular layer appears to be
continued by small tendon's with the fibres of the orbicularis.
The superficial plane only begins about the middle of the deep one, the
anterior half of which it entirely covers. Its fibres, less tendinous than those of
the latter, extend from a median raphe which also divides the deep layer in its
length, and are directed, some forwards, some backwards, to terminate in the
following manner : the first are inserted into the external face of the super-
maxillary bone, above the first molar tooth and the superior interdental space ;
the second are attached to the inferior interdental space alone.
Relations. — Externally, with the masseter, zygomaticus, panniculus, dilator
naris lateraUs, levator labii superioris, the parotid duct, which crosses it to enter
the mouth, and the facial artery and veins ; internally, with the buccal mucous
membrane. The deep plane is accompanied and covered at its anterior border
by the upper molar glands ; its posterior border is margined by the inferior molar
teeth, which it partially covers. The superficial layer is distinctly separated from
the deep one in its anterior part, which is attached to the supermaxillary bone.
Behind, these two planes adhere more intimately to one another, though they
are found completely isolated by an interstice in which one or two large veins pass.
Actions. — The function of the buccinator is particularly related to mastication :
this muscle, in fact, pushes between the molar teeth the portions of food which
fall outside the alveolar arches : but it cannot aid in bringing the two jaws
together, as Lecoq has correctly observed.
278 THE MUSCLES.
8. SUPERNASO-LABIALIS (LEVATOR LaBII SuPERIORIS Al^QUI NaSI)
(Fig. 168, 15).
Synonyms. — The maxillaris of Bourgelat. The levator labii superioris alxque nasi of Man.
(Levator labii superioris alxque nasi — Percivall. Fronto-lahialis — Leyh.)
Situation — Direction — Form — Structure. — Situated on the side of the face, in
an obUque direction downwards and backwards, this is a wide muscle, flattened
on both sides, elongated from below to above, aponeurotic at its superior
extremity, and divided inf eriorly into two unequal branches, between which passes
the dilatator naris lateralis.
Attachments.— It has its origin, by its superior aponeurosis, from the frontal
and nasal bones, and unites on the median line with the muscle of the opposite
side. Its anterior branch, the widest and thickest, goes to the external ala of the
nostril and to the upper lip, where its fibres are confounded with those of the
orbicularis. The posterior branch terminates at the commissure of the lips.
Relations. — Outwards, with the skin ; inwards, with the levator labii superioris,
the posterior portion of the dilatator naris superioris, and vessels and nerves. Its
posterior branch covers the dilatator naris lateralis, and the anterior is covered
by that muscle.
Actions. — It elevates the external ala of the nose, the upper lip, and the com-
missure of the lips.
9. Great Supermaxillo-nasalis (Dilatator Naris Lateralis) (Fig. 168, 19).
Synonyms. — The pyramidalis-nasi of Bourgelat. The caninus of Man. (Dilatator naris
lateralis — Percivall.)
Situation — Direction — Form — Structure. — This muscle, situated on the side
of the face, between the two branches of the levator labii superioris, in an almost
vertical direction, is triangular in form, and slightly tendinous at its summit.
Attachments. — It has its origin, by the aponeurotic fibres of its summit, from
the external face of the supermaxillary bone, below its ridge. It terminates, by
its base, on the skin covering the external wing of the nostril, its most posterior
fibres being confounded with those of the orbicularis of the hps.
Relations. — Outwardly, with the skin and the inferior branch of the levator
labii superioris ; inwardly, with the anterior branch of that muscle, and with
vessels and nerves.
Actions. — It dilates the external orifice of the nasal cavity, by pulling out-
wards the external wing of the nostril.
10. Small Supermaxillo-nasalis (Dilatator Naris Superioris)
(Fig. 168, 25).
Synonyms.—The nasalis brevis, and portion of the subcutaneous muscle of Bourgelat.
(Nasalis hrevis labii superioris — Percivall.)
Girard has described, by the above name, a small, thick, and short muscular
fasciculus which covers the external process of the premaxillary bone, the fibres
of which, either originating from that, the supermaxillary bone, or the internal
face of the levator superioris muscle, terminate in the skin of the false nostril,
and the appendix of the inferior turbinated bone.
Rigot has attached to this muscle that described by Bourgelat as the short
muscle. The latter is composed of short, transverse fibres, applied to the
MUSCLES OF THE TRUNK. 279
expansion of the cartilaginous septum of the nose which projects laterally beyond
the nasal spine. These fibres abut, by their most eccentric extremities, against
the skin of the false nostril and the appendix of the inferior turbinated bone.
To this muscle we may attach the small muscular fasciculus which Bourgelat
has described as the anterior intermediate. To study it, it is necessary to raise
the upper lip and remove the mucous membrane lining it. It is then seen that
its fibres, attached to the inner side of the premaxilla, above the incisor teeth,
ascend to meet those of the dilatator naris superior, and to terminate with them
on the anterior appendix of the inferior turbinated bone ; some fibres become
lost in the lips.
The dilatator naris superior acts as an external dilator of the nostril and false
nostril. (Percivall names it the depressor labii superioris.)
11. Transversalis Nasi (Dilatator Naris Transversalis).
{Synonym. — Dilatator naris anterior — Percivall).
This muscle is in two parts : one, inferior, single, short, and quadrilateral,
flattened on both sides, lies on the wide part of the nasal cartilages, forming
transverse fibres ; the other, superior, pair muscle, formed of pale short fibres
passing from the thin portion of the septum nasi which is laterally bordered by
the nasal prolongation, to the skin of the false nostril and appendix of the upper
turbinated bone. Covered by the skin and the aponeurotic expansion of the two
elevator muscles of the upper lip, the transverse muscle of the nose covers the
cartilages to Avhich it is attached, and is confounded below with the orbicularis
of the lips.
Designed to bring together the two internal alte of the nose, this muscle
ought to be considered more particularly as the dilator of the nostrils ; and, in
addition, as an internal dilator of the false nostril.
B. Palpebral Region.
This region includes three muscles which act upon the eyelids or the sldn
in proxindty to the orbit ; these are the Orbicularis Palpebrarum, Fronto-
palpebral {Corrugator Supercilii), Lachrymalis.
1. Orbicularis of the Eyelids (Orbicularis Palpebrarum) (Fig. 168, 6).
This muscle is a thin wide sphincter common to the two eyelids, and lying
on the palpebral fibrous plate and the bones forming the margin of the orbit.
Its external surface is covered by the skin, to which it adheres very closely. A
small tendon wliich extends from the lachrymal tubercle to the nasal angle of the
eye, is considered as the origin of the fibres of this muscle ; some of these —
the most numerous— pass upwards and are distributed in a circular manner in
the upper eyelid ; the others reach the lower eyelid and rejoin the numerous ones
towards the temporal angle of the eye.
The contraction of this muscle determines the occlusion of the palpebral opening.
2. Fronto-Palpebral, or Corrugator Supercilii (Fig. 168, 2).
This is a short flat muscle, arising from the external surface of the frontal
bone, and passing downwards and outwards to mix its fibres with those of the
orbicularis at the supra-orbital foramen, which it covers, and the skin of the eye-
brow. It has been erroneously considered as an elevator of the upper eyelid. When
280
THE MUSCLES.
it contracts, it is limited to wrinkling the skin of the eyebrow in drawing it slightly
to the nasal angle — which it can do whether the eyelids are in contact or apart.
3. Lacheymalis Muscle.
((Synonym.— Not mentioned by Percivall. It is the inferior palpebral muscle of Leyh.)
A wide and very thin muscle, situated superficially below the eye. It is con-
tinuous, in front, with the panniculus ; behind, with the levator labii superioris ;
above, with the orbicularis of the eyelids. Its fibres, partly muscular and partly
aponeurotic, leave the external surface of the lachrymal and malar bones, are
directed do«Ti wards, and become
Fig- 169. lost in a connective tissue fascia
which covere the buccinator ;
some pass beneath the zygo-
maticus and form the zygoma-
ticus minor, when this is present.
This muscle is supposed to
corrugate and twitch the skin
below the eye.
c. aueicular, or conchal
Region.
The muscles of this region
move the concha, or pavilion
of the ear {concha auris). The
largest arise from the surface
of the cranial bones or cord of
the cervical ligament, and
terminate on the cartilages of
the external ear ; the medium-
sized pass from one cartilage to
another ; and the smallest are
found on the surface of the
concha, inside and out. The
latter are really intrinsic
muscles, but they are of so little
importance that we will not
describe them. The others are
ten in number.
In the first plane we find
the zijgomatico-auricularis {atto-
Ims anticus), temper o-auricu-
laris externus (attolens maxi-
mus), scuto-auricularis externus,
three cervico-auriculares (re-
trahens externum, medius, inter-
nus), and parotido-auricularis
(abducens) ; the second plane, the temporo-auricularis internus {attolens posticus),
scuto-auricularis internus, tympano-auricularis {mastoido-auricularis).
Before studying these muscles, it is indispensable to examine the pieces of
MUSCLES OF THE EXTERNAL EAR OF THE MULE.
1, 1, AttoUens maximus; 2, attoUens posticus; 3,. scuti-
form cartilage ; 4, scuto-auricularis externus. A, auri-
cular branches of the first cervical nerve ; B, anterior
auricular nerve (from the facial) ; C, terminal branches
of the superciliary nerve ; D, superficial or temporal
branch of the lachrymal nerve.
MUSCLES OF THE TRUNK. 281
cartilage which form the concha. These are three in number : 1. Conchal
cartilage. 2. Annular cartilage. 3. Scutiform cartilage.
1. Conceal Cartilage. — The principal portion of the pavilion, this cartilage
determines its general configuration. In shape it resembles a trumpet with a
wide opening on one side. Its entrance is elliptical, and elongated vertically,
being circumscribed by two thin borders which unite above at a point that
constitutes the summit (apex) of the organ. Its base, bulging in a cul-de-sac,
terminates in front by a constricted infundibulum ; it is attached to the margin
of the auditory hiatus by means of the annular cartilage, to the surface of
the guttural pouch by a pointed prolongation that descends outside this annular
cartilage, beneath the parotid gland, and terminates by several fibrous filaments.
This portion of the framework of the concha is a cartilaginous plate, rolled on
itself in such a manner as to circumscribe, between its borders, the entrance to
the ear, and to form, inferiorly, the complete infundibuliform canal just men-
tioned. (Externally, the integument of the ear is covered by ordinary hair, but
internally there are long fine hairs, especially near the entrance ; these prevent
the intrusion of foreign substances.)
In Ruminants, this cartilage is thin, inclined outwards, and largely open. In the Fig,
it differs slightly according to breed, but it is always much developed, sometimes erect, and
more frequently drooping forward. It is always short, pointed, erect, and open towards the front
in the Cat. In the Dog, it is sometimes short and straight ; in others broad and pendant.
2. AjraruLAR Cartilage. — By this name is known a little ring-shaped plate,
placed at the lower part of the conchal cartilage, intermediate between it and the
auditory canal. The internal integumentary membrane, with some yellow elastic
fasciculi, unites this cartilage to the other two portions between which it is situ-
ated. Its relations with these are such, that it receives within its lower border
the bony circular prominence forming the margin of the auditory hiatus, while it
may itself be received into the infundibuliform canal of the conchal cartilage —
an arrangement resembling the tubes of a telescope.
3. Scutiform Cartilage. — This is a small cartilaginous plate, situated in
front of the base of the concha, at the surface of the temporal muscle ; it is
irregularly triangular, is attached to the conchal cartilage by some muscular
fasciculi, and transmits to that cartilage the action of some other muscles which
are fixed on the cranial bones.
(The arteries of the concha proceed from branches of the external carotid,
and the veins pass to a trunk of the same name ; the nerves are divisions of the
facial and the first cervical pair.)
An adipose cushion, placed at the base of the ear, facilitates the movements of
the cartilages when they are acted upon by these muscles.
1. Zygomaticus-auricularis (Attollens Anticus) (Figs. 168, 4, 5 ; 170, 19).
This muscle is generally composed of two fleshy bands joined by connective
tissue, and rising from the zygomatic process of the temporal bone by means of an
aponeurosis common to it and the orbicularis palpebrae. The inferior of these
two bands is inserted into the outside of the base of the concha, its fibres mixing
with those of the abducens ; the superior band terminates on the outer border
of the scutiform cartilage.
Placed immediately beneath the skin, this muscle partly covers the superior
extremity of the parotid gland, and the zygomatic process.
It draws the ear forward.
282 TEE MUSCLES.
2. Temporo-auricularis Externus (Attolens Maximus) (Figs. 168, 1 ;
169, 1, 1 ; 170, 3, 4).
A very thin, wide muscle, covered by the skin, lying on the temporal muscle,
united posteriorly to the retrahens externus, in front and outwardly to the
attollens maximus. It arises from the whole of the parietal crest or ridge,^
mixing in its upper half or third with the muscle of the opposite side ; it termi-
nates, by one portion, on the inner margin of the scutiform cartilage, and by
another, on the inner side of the conchal cartilage, by means of a thin fascia that
covers part of the former cartilage and the external scuto-auricularis.
It acts as an adductor of the concha, drawing it inwards ; it also carries it
Fig. 170.
MUSCLES OF THE EAR.
1, Retrahens externus; 2, attollens posticus; 3, 4, attollens maximus; 5, scutiform cartilage;
6, scuto-auricularis externus; 7, posterior auricular artery; 8, portion of the zygomaticus-auii-
cularis; 9, orbital process; 10, temporo-auricularis internus ; 11, temporal muscle; 12, scutiform
cartila£;e ; 13, ditto ; 14, concha of the ear ; 15, scuto-auricularis externus ; 16, internal scuto-
auricularis; 17, abducens; 18, corrugator supercilii ; 19, zygomaticus-auricularis.
forwards, and concurs in making it pivot on itself,
the ear forward.
as to bring the opening of
3. Scuto-Auricularis Externus (Figs. 169, 4 ; 170, 6).
This muscle may be said to be a dependency of the preceding, the action of
which it transmits to the conchal cartilage, and renders it more complete.
Extending from the external face of the scutiform cartilage to the inner side
' Owing to this crest bordering the temporal fossa, Girard has thought proper to give to
the two muscles of the ear attached thereto, the name of temporo-auriculares ; but it would be
more appropriate to designate them the parieto auricularea.
MUSCLES OF THE TRUNK. 283
of the concha, and generally composed of two fasciculi, it is covered by the skin
and the conchal band of the attollens maximus, while it covers part of the internal
scuto-auricularis muscle.
When this muscle contracts, it principally participates in producing the
rotatory movement that carries the opening of the concha outwards.
4. Cekvico-auriculares (Retrahentes Aurem) Muscles (Fig. 168).
Three in number, and situated behind the ear, these muscles are broad, thin
bands, extending from the cervical ligament to the conchal cartilage. With
regard to their position at their origin, they may be distinguished as external^
middle, and internal ; the situation of their point of insertion in the concha also
permits their being classed as superior, middle, and inferior.
The retrahens externus, or superior or superficial cervico-auricularis, closely
united to the attollens maximus, and covered by the skin, covers the medius and
internus muscles. Attached by iis terminal extremity to the middle of the
posterior face of the concha, it draws that cartilage backwards and downwards.
The retrahens medius, or middle cervico-auricularis, comprised at its origin
between the other two, and intimately attached to them, especially the deep one,
is in relation with the skin for the greater part of its superficies. Its terminal
extremity is very wide and thin, and passes over the upper end of the parotid
gland, to be inserted outwardly into the base of the concha, after being slightly
insinuated beneath the abducens. This is a rotator muscle, turning the opening
of the ear outwards and backwards.
The retrahens internus, or inferior or deep cervico-auricularis, concealed beneath
the upper extremity of the parotid, to which it adheres closely, is inserted at the
base of the concha. Its action is similar to that of the middle muscle.
5. Parotido-auricularis (Abducens, or Deprimens Aurem)
(Figs. 168, 7 ; 170, 17).
Lying on the external face of the parotid gland, this is a long, thin, ribbon-
like band, narrower and thicker at its upper than its lower extremity. It arises
on the tissue of the gland, and terminates outside the base of the concha, below
the inferior commissure formed by the two borders of that cartilage.
Covered externally by a very thin portion of the cervico-facial panniculus,
the abducens is an abductor of the ear, inclining it outwards.
6. Temporo-auricularis Internus (Attollens Posticus) (Fig. 170, 2).
Situated beneath the superficial muscle of this name, and partly covered by
the retrahens externus, this muscle is long and triangular in shape, bright-red in
colour, and extending transversely on the surface of the temporalis ; it is attached,
inwardly, to the sagittal or spur-like ridge of the parietal bones, and outwardly,
by means of a small tendon, to the inner side of the concha, within the terminal
insertion of the retrahens externus auricularis. It is an adductor of the ear.
7. Scuto-auricularis Internus (Fig. 170, 16).
This is a muscle composed of two short, pale fasciculi, which cross each other
very obliquely, are concealed beneath the scutiform cartilage and the scuto-
auricularis externus, and lie directly on the adipose cushion of the ear. They
284 TEE MUSCLES.
arise from the inner face of the scutiform plate, pass backwards, and termi-
nate at the base of the concha, behind the infundibuhform cavity which that
cartilage forms at its root. This muscle is antagonistic to the external muscle
of this name, as it turns the opening of the ear outwards, and even backwards.
8. Mastoido-auricularis.
This name is given to a very thin fasciculus lying vertically on the inner
side of the cartilage, at the entrance to the ear. Arising from the margin of
the auditory external hiatus, and attached to the base of the concha, this little
muscle, in contracting, constricts the cartilaginous tube with which it is in contact.
D. Masseteric, or Temporo-maxillary Region.
This region comprises five pair-muscles for the movement of the lower jaw.
These are : the masseter, temporalis, pterygoidms internus, pterygoideus externuSy
and digastricus.
Preparation.— \. First study the digastricus and its stylo-maxillary portion, with the
internal pterygoid, in preparing the hyoid muscles as they are represented in Fig. 171. 2.
Expose the pterygoideus extemus, by removing in this preparation the hyoid bone and its
dependencies, as well as the two preceding muscles. 3. To dissect the temporalis, excise the
external pterygoideus from its inferior border, an operation which exposes the orbital fasciculus
of the temporalis ; then turn over the piece, saw oflF the orbital process at each end, and remove
the eye and auricular muscles. 4. Dissect the masseter, in clearing away from its external
surface the cuticularis and the vessels and nerves which cover it.
1. Masseter (Fig. 168, 23).
Synonyms. — Zygomatico-maxillaris — Girard.
Situation — Form — Structure. — Applied against the external face of the branch
of the lower jaw, the masseter is a short, wide, and very thick muscle, flattened
on both sides, irregularly quadrilateral, and formed of several superposed planes,
two of which are perfectly distinct towards the temporo-maxillary articulation,
by the somewhat different direction of their fibres. These are divided by a
considerable number of intersections, and are covered by a strong aponeurotic
layer, which becomes gradually thinner backwards and downwards.
Attachments. — The fasciculi of the masseter have their fixed insertion on the
zygomatic crest. Their movable insertion is on the imprints which cover the
upper half of the ramus of the inferior maxilla.
Relations. — It responds, by its superficial face, to the facial portion of the
cervical panniculus, to the nerves of the zygomatic plexus, and several venous and
arterial vessels ; by its deep face, to the inferior maxillary bone, the buccinator
and depressor labii inferioris muscles, the superior molar glands, and two large
venous branches ; by its inferior border, with the parotid duct, and the glosso-
facial artery and vein ; by its superior and posterior border, to the parotic gland.
Its deep plane responds, anteriorly, with the temporo-maxillary articulation, and
is so intimately confounded with the temporalis, that it is impossible to define
the respective limits of the two muscles.
Action. — This muscle, the special elevator of the lower jaw, plays an important
part in mastication. It always acts as a lever of the third class — the middle
Une, which represents the resultant of all its constituent fibres, passing behind
the last molar.
MUSCLES OF THE TRUNK. 285
2. Temporalis.
Synonyms. — Temporo-maxillaria — Girard.
Situation — Form — Structure. — Situated in the temporal fossa, to which it is
moulded, and which it fills, this muscle is flattened from above to below, divided
by strong tendinous intersections, and covered by a nacrous aponeurotic layer.
Attachments. — It takes its origin : 1. In the temporal fossa and on the bony
crests which margin it. 2. By a wide fasciculus, paler than the other portion of
the muscle, but not unconnected with it, from the imprints situated behind the
crest surmounting the orbital hiatus. It terminates on the coronoid process and
the anterior border of the branch of the lower jaw.
Relations. — This muscle covers the temporal fossa, and is covered by the
attoUens muscles, scutiform cartilage, internal scuto-auricularis, the fatty cushion
at the base of the ear, and by another adipose mass which separates it from the
ocular sheath. Its deep fasciculus responds, by its internal face, to the two
pterygoid muscles.
Action. — It brings the lower jaw in contact with the upper, by acting as a
lever of the first kind ; but the orbital portion of the muscle elevates the inferior
maxilla and moves it laterally by a lever of the third kindo
3. Pterygoideus Internus.
Synonyms. — Portion of the spheno-maxillaris of Bourgelat.
Sitimtion — Form — Structure.— Sit\ia.ted in the intermaxillary space, opposite
the masseter, the pterygoideus internus, although not so strong as that muscle,
yet so closely resembles it in form and structure as to be named by "Winslow the
internal masseter.
Attachments. — 1. To the palatine crest and subsphenoidal process— ;/?a;e^
insertion. 2. In the hollow excavated on the inner face of the branch of the
lower jaw — movable insertion.
Relations. — Outwardly, with the pterygoideus-externus, the orbital fasciculus
of the temporal, the maxillo-dental nerves, mylo-hyoideal, and lingual muscles,
arteries and veins, and the inner surface of the bone which receives its movable
insertion. Inwardly, with the tensors palati— external and internal, the
guttural pouch, the hyoideus magnus, hyoid bone, digastricus, the hypoglossal
and glosso-pharyngeal nerves, glosso-facial artery and vein, the hyoglossus longus
and brevis muscles, the laryngo-pharyngeal apparatus, the Stenonian duct, and
the submaxillary glands.
Action. — It is an elevator of the lower jaw, and also gives it a very marked
lateral or diductive motion. If the left muscle acts, this movement carries the
inferior extremity of the lower jaw to the right ; if it be the right muscle, then
in the contrary direction.
4. Pterygoideus Externus.
(Synoraj/w.— Portion of the spheno-maxillaris of Bourgelat.
Form — Situation — Strmture — Attachments. — A small, short, and very thick
muscle, situated within and in front of the temporo-maxillary articulation,
formed of shghtly tendinous fasciculi which leave the inferior face of the
21
286 THE MUSCLES.
sphenoid bone and the suhsphenoidal process, and are directed backwards and
upwards to be fixed to the neck of the inferior maxillary condyle.
Relations. — Outwardly, with the orbital fasciculus of the temporalis muscle
and the temporo-maxillary articulation. Inwardly, with the numerous nerves
emanating from the inferior maxillary branch, and with the internal pterygoid
and tensors palati.
Action. — When the two external pterygoids act in concert, the inferior
maxilla is pulled forward ; but if only one contract, the propulsion is accompanied
by a lateral movement, during which the extremity of the jaw is carried to the
opposite side.
5. DiGASTRICUS (StYLO-MAXILLARIS).
Synonyms. — Bourgelat has made two distinct muscles of this — the digastricus and stylo-
maxillaris. Girard lias described it as the stylo-maxillaris. (Percivall has evidently followed
Bourgelat's example, and divided the muscle into digastricus and stylo-maxillaris. Leyh
adopts the same course.)
Form — Structure — Situation — Direction. — Composed of two fleshy bodies
more or less divided by intersections, and united at their extremities by a median
tendon, this muscle is situated in the intermaxillary space, and extends from the
occiput to near the symphysis of the chin, describing a curve upwards.
Attachments. — It takes its origin from the styloid process of the occipital
bone, by its superior fleshy body. It terminates : 1. On the curved portion of
the posterior border of the lower jaw by a considerable fasciculus, which is
detached from the superior fleshy body.^ 2. On the internal face of the same
bone and the straight portion of its posterior border, by aponeurotic digitations
which succeed the muscular fibres of the inferior fleshy body.
Relations.— The superior belly of the muscle responds, superficially, to the
parotid gland and the tendon of insertion of the sterno-maxillaris ; deeply, to
the guttural pouch, the submaxillary gland, and the larynx and pharynx. The
median tendon passes through the ring of the hyoideus magnus. The lower
belly is in contact, outwards, with the ramus of the inferior maxilla ; inwards,
with the mylo-hyoideus muscle.
Action. — When this muscle contracts, it acts at the same time on the hyoid
bone, which it raises in becoming straight, and on the lower jaw, which it pulk
backwards and depresses at the same time.
E. Hyoideal Region.
This region includes six muscles grouped around the os hyoides, which they
move. Five of these are pairs : the mylo-hyoideus, genio-hyoideus, stylo-hyoideus,
kerato-hyoideus {hyoideus parvus), and the occipito-styloideus. The single one is
the hyoideus transversus.
Prepara(/on.— Separate the head from the trunk, and remove the muscles of the cheeks on
one side, with the parutid gland. 2. The branch of the inferior maxilla being thus exposed, it
is sawn through in two places; at first beliind the last molar, then in front of the first. 3.
After having separated the pterygoids and the stylo-maxillaris from the upper fragment or
condyle, and the coronoid process, it is torn off by pulling it backwards ; then the pterygoids
and digastricus are excised. 4. The inferior fragment of the jaw bearing the molar teeth is
1 This is the fasciculus which Bourgelat has described as a distinct muscle, and named the
ttylo-maxillaris.
MUSCLES OF THE TRUNK. 287
turned down by isolating the mylo-hyoideus from the mucous membrane. 5. Carefully remove
the tongue by separating its extrinsic muscles from the genio-hyoideus, the anterior appendix
of the hyoid bone, the transverse muscle, and the small hyoideus.
The dissection having been performed in this manner, the large hyoideal branch may Ijp
separated from the small, by sawing through the head longitudinally, leaving the symphysis
menti intact, and turning down the corresponding half to the side already dissected, as well as
the great hyoid branch, the pharynx, larynx, and soft palate.
1. Mylo-hyoideus.
jPorm — Situation — Structure. — A membranous muscle situated in the inter-
maxillary space, flattened from side to side, elongated in the direction of the
head, thinner and narrower below than above, and formed entirely of fleshy fibres
which extend transversely from its anterior to its posterior border. Inferiorly,
it is composed of a small fasciculus, which is distinguished from the principal
Fig. 171.
HYOIDEAL AND PHARYNGEAL REGIONS.
1, Neck of inferior maxilla ; 2, hard palate ; 3, molar teeth ; 4, buccal membrane ; 5, submaxillary
glands ; 6, soft palate ; 7, tendon of hyoideus magnus through which the tendon, 8, of the
digastricus passes; 9, lower portion of digastricus ; 10, stylo-hyoideus ; 11, buccal nerve; 12,
zygomatic arch; 13, orbital branch of fifth pair of nerves; 14, articular process of temporal
bone; 15, right cornu of hyoid bone; 16, hyo-glossus longus, or Kerato-glossus ; 17, lingual
nerve; 18, 18, tongue; 19, angle of left branch of inferior maxilla; 20, submaxillary gland,
left side ; 21, subscapulo-hyoideus ; 22, great hypoglossal nerve ; 23, hyo-thyroideus ; 24, sterno-
hyoideus ; 25, sterno-thyroideus ; 26, subscapulo hyoideus ; 27, thyroid gland ; 28, external
carotid artery ; 29, pneumogastric nerve ; 30, stylo-hyoideus ; 31, genio-hyoideus.
portion by the slightly different direction of its fibres, and which covers in part
the external surface of the muscle.
Attachments. — It originates from the mylo-hyoid line by the anterior
extremities of its fibres. Its movable insertion takes place on the inferior face
of the hyoid body, on its anterior appendix, and on a fibrous raph6 which extends
from the free extremity of this appendix to near the genial surface, and which
unites, on the median line, the two mylo-hyoidean muscles.
Relations. — By its external face, with the inferior maxilla, the digastricus,
and the submaxillary lymphatic glands. By its internal face, with the sublingual
gland, the Whartonian duct, the hypoglossal and lingual nerves, the genio-glossus,
hyo-glossus longus and brevis, and genio-hyoideus. Its superior border responds
to the internal pterygoid.
Action. — In uniting on the median line with that of the opposite side, this
288 THE MUSCLES.
muscle fonns a kind of wide band or brace on which the tongue rests. "When it
contracts, it elevates this organ, or rather applies it against the palate.
2. Genio-hyoideus.
Form — Strmture — Situation. — ^A fleshy, elongated, and fusiform body, tendinous
at its extremities, but especially at the inferior one, and applied, with its fellow
of the opposite side, to the mylo-hyoidean brace.
Attachments. — By its inferior extremity it is fixed to the genial surface —
origin ,- by its superior, it reaches the free extremity of the anterior appendix of
the hyoid body — termination.
Relations. — Outwards and downwards, with the mylo-hyoideus ; inwards, with
its fellow, which is parallel to it ; above, with the genio-glossus.
Action. — It draws the hyoid bone towards the anterior and inferior part of
the intermaxillary space.
3. Stylo-hyoideus.
Synonyms. — The hyoideus magnus of Percivall. The kerato-hyoidetis magnus of Leyh.
Form — Structure — Situation — Direction. — Thin and fusiform, this muscle,
smaller than the preceding, and, like it, tendinous at both its extremities, is
situated on the side of the laryngo-phaiyngeal apparatus and the guttural pouch,
behind the large branch of the hyoid bone, the direction of which it follows.
Attachments. — Above, to the superior and posterior angle of the styloid bone —
Hxed insertion ; below, to the base of the comu of the os hyoides — movable insertion.
Relations. — Outwards, with the pterygoideus intemus ; inwards, with the
gattural pouch, the pharynx, and hypoglossal nerve. Its anterior border is
separated from the posterior border of the styloid bone by the glosso-facial artery
and glosso-phaiyngeal nerve ; along the posterior border lies the upper belly of
the digastricus. Its inferior tendon is perforated by a ling for the passage of the
cord intermediate to the two portions of the latter muscle.
Action. — It is antagonistic to the preceding muscle, drawing the body of the
hyoid bone backwards and upwards.
4. Kerato-hyoideus (Hyoideus Paevus).
(Synonyms. — This is the hyoideus parvus of Percivall, and the small kerato-hyoideus of
Leyh.)
A very small fasciculus, triangular in shape, and flattened on both sides. In-
serted, on one side, into the posterior border of the styloid comu and the inferior
extremity of the styloid bone ; and on the other, to the superior border of the
thyi'oid cornu. It responds, outwardly, to the hyo-glossus brevis and the lingual
artery ; inwardly, to the buccal mucous membrane.
It approximates the cornua of the os hyoides to each other.
5. OCCIPITO-STYLOIDEUS.
Synonyms.— This is the muscle which, up to the present time, has been described by
veterinary anatomists as the stylo-hyoideus. This name has been given to the muscle named
by Girard the kerato-hyoideus magnus.
A small, flat, and triangular muscle hke the preceding, yet thicker and more
spread, filling the space comprised between the styloid process of the occipital
MUSCLES OF THE TRUNK, 289
and the horizontal portion of the posterior border of the styloid bone. Its
fasciculi become longer as they are situated posteriorly, are rather tendinous, and
are earned from one of these bones to the other. Outwardly, it responds to the
parotid gland ; inwardly, to the guttural pouch, which it covers for its whole
extent ; its posterior border is largely confounded with the superior insertion of
the digastricus. When this muscle acts, it causes the os hyoides to swing, caiTy-
ing its inferior extremity backwards and downwards.
6. Hyoideus Transversus.
By this name Bourgelat has described a short riband of parallel muscular
fibres, which unites the superior extremities of the styloid cornua, and approxi-
mates them to each other.
Differential Characters of the Muscles of the Head ik the other Animals.
1. Facial Region.
Ruminants. — There are found in the Ox :
1. An orbicular muscle of the lips, analogous to that in the Horse.
2. A buccinator of the same kind (Fig. 172, 5).
3. A zygomaticus, stronger and redder than in Solipeds. Its aponeurosis of origin, covered
by the panniculus, extends upon the surface of the masseter muscle as far back as the zygo-
matic arch, to which it is attached (Fig. 172, 7).
4. A levator labii superioris alsequi nasi, continued, above, with the inferior border of the
frontal or fronto-cuticularis muscle ; and divided, inferiorly, into two branches, which comprise
between them the levator labii superioris and the dilator naris lateralis. These two branches,
however, are not disposed as in Solipeds, the anterior covering the preceding muscles, and the
posterior, of but little importance, passing beneath them to lose itself in the substance of the
upper lip (Fig. 172, 3).
5. A levator labii superioris proprius, which gains the middle of the muzzle by passing
along the inner side of the nostrils (Fig. 172, 1).
6. Two additional levator labii superioris muscles to the above, considered as accessories to
the first, and which originate with it. Each terminates by a ramifying tendon that passes
under the nostril to mix in the tissue of the upper lip (Fig. 172, 1', 1').
7. A dilator naris lateralis, situated between the supermaxillo-labialis and its two accessory
muscles, and deriving its origin, in common with these three muscles, in front of the maxillary
spine (Fig. 172, 2).
8. A depressor labii inferioris, confounded with the buccinator, and having no terminal
tendon.
9. A levator menti, attached to the body of the inferior maxillary bone, as in the Horse,
by two middle posterior muscles. No anterior middle muscle has been found by us; and it is
certain that there is no dilator naris transversalis or dilator naris superioris present.
In the Sheep, the levator labii superioris does not exist ; apart from this peculiarity, there
is DO difference between the facial mu»cles of this animal and the Ox.
Pig. — This animal has no levator labii superioris, or dilator naris transversales muscles. The
dilator naris superior is present ; it is short, very thick, and situated near the margin of the
nostrils. The levator labii superioris proprius and the dilator naris lateralis are replaced by
three fleshy bodies, nearly parallel, lying on tiie side of the face. The superior originates in
the lachrymal fossa, and terminates by a tendon in the middle of the snout. The inferior, with
the middle, leaves the imprints in front of the zygomatic ridge, and is continued at its inferior
extremity by a tendon divided into several fibrillse, which pass below the nostril to be united
to the tendon of the superior portion : this is done in such a manner that the external opening
of the nose is encircled on the inner side by a kind of fibrous cravat, which, when these two
muscles contract, carries this opening outwards. It will also be understood that the superior
fleshy body, acting alone, ought to elevate the snout, while the inferior depresses it in drawing
it to one side. With regard to the intermediate fleshy mass, it is the representative of the
dilator naris lateralis of the Ox, and terminates in a great quantity of tendinous fibrillae at
the internal ala of the nose.
Camivora. — In the Dog and Cat the following peculiarities are found : —
The orbicularis oris is quite rudimentary.
290 THE MUSCLES.
The buccinator is very thin, and formed of only one muscular plane.
The zyijomaticus is continued, superiorly, with the attollens anticus.
The levator lahii superioris represents a wide, undivided, muscular expansion, united
superiorly to the panniculus of the forehead, and terminating inferiorly on the upper lip.
The levator lahii superioris and dilator naris lateralis constitute a single fleshy body formed
of several parallel fasciculi, which take their origin above the supra-orbital foramen, and
terminate together at the external wing of the nose and in the upper lip.
There is no dilator naris superioris, or dilator naris transversalis.
The middle anterior (depressor alx nasi) is perfectly developed.
The mento-labialis and its suspensory muscle, the middle posterior, are scarcely apparent.
2. Palpebral Region.
The lachrymalis in the Ox is more developed and thicker than in the Horse. Its most
anterior fibres glide under the zygomaticus, and are lost on the surface of the buccinator ; while
Fig. 172.
SUPERFICIAL MUSCLES OF THE OX'S HEAD.
1, Dilator naris superioris ; 1, 1', accessory fasciculi of the same ; 2, dilator naris lateralis ; levator
labii superioris ; 4, lachrymalis; 5, depressor labii inferioris ; 6, buccinator confounded with the
preceding; 7, zygomatico-labialis; 8, frontal, or cuticularis muscle of the forehead ; 9, orbicular
muscle of the eyelids; 10, zygomaticus; 11, attollens maximus; 12, scutiform cartilage;
13, external scuto-auricularis ; 14, mastoid process; 15, masseter ; 16, stylo-hyoideus ; 17,
digastricus ; 18, sterno-maxillary fasciculus belonging to the cervical panniculus; 19, subscapulo-
hyoideus; 20, sterno-maxillaris, or mastoideus; 21, anterior branch of the superficial portion of
the mastoido-humeralis ; 22, superior branch of ditto ; 23, deep portion of same muscle ; 24,
trachelo-atloideus, peculiar to Ruminants and Pachyderms ; 25, great anterior straight muscle
of the head.
the most posterior pass above the aponeurotic tendon of the zygomaticus and become confounded
with tiie panniculus. This muscle unites, above, with the orbicularis palpebrarum in a more
intimate manner than in the Horse, so that it is almost impossible to define the limits of the
two (Fig. 172, 4). The lachrymalis is absent in the Pig.
3. Masseteric or Temporo-maxillary Region.
In Ruminants, the masseter and temporalis are not so large as in Solipeds. In the
Camivora, however, they offer a remarkable development. The origin of the pterygoideus
MUSCLES OF THE TRUNK.
291
internus in Ruminants is nearer the middle line than in the Horse. Its obliquity is also
greater, and the movements of diduction it gives the lower jaw are more extensive. In all the
animals, other than Solipeds, the stylo-maxillaris fasciculus of the digastricus is entirely absent,
and the muscle has only a single belly extending directly from the occipital to the maxillary
bone. In the Ox is found a siball square muscle, formed of transverse fibres, which unites the
two digastric muscles by passing beneath the base of the tongue. This muscle, in contracting,
may raise the hyoideal apparatus, and in this way supplement the tendon of the digastricua
and the inferior ring of the stylo-hyoideus.
4. Hyoideal Region.
The two flesliy planes composing the mylo-hyoideus are more distinct in Ruminants than
in the Horse. The stylo-hyoideus of these animals commences by a long thin tendon. The
muscle has no ring for the passage of the digastricus.
a feature observed in all the domesticated animals
except Solipeds.
In the Carnivora, the stylo-hyoideus, formed by
a narrow, very thin, and pale fleshy band, commences
on the mastoid portion of the temporal bone by a
small tendon; the lerato-hyoideus is remarkable for
its relatively considerable volume; the occipito-
styloideus and the hyoideus transversus are absent.
COMPAEISON OF THE MOSCLES OF THE HuMAN HeAD
■WITH THOSE OF THE DOMESTICATED AnIMALS.
In Man, there are described as muscles of the
head, the epicranial muscles, muscles of the face, and
those of the lower jaw. The hyoid and digastric
muscles are reckoned in the region of the neck. Here
tliey will be placed in the region of the head.
1. Epicranial Muscles.
The middle portion of the human cranium is
covered by an aponeurosis that adheres closely to the
hairy scalp, but glides easily on the surface of the
bones. To the circumference of this epicranial
aponeurosis are attached four muscles, which move
it. One of them, attached behind to the superior
occipital curved line, is named the occipital muscle;
another, fixed in front of the forehead, is called the
frontal muscle ; the other two, double and lateral, are
inserted on the face of the temporal bone (ir the ex-
ternal ear, and are designated auricular muscles.
These epicranial muscles move the scalp forwards,
backwards, and sideways.
2. Muscles of the Face.
These are fourteen in number, ten of which are
found in the domesticated animals. We commence
by describing these common muscles (Fig. 170).
1. The orbicularis oris, which has a fasciculus that
passes to the skin from the columna of the nose; this
fasciculus is termed the depressor of the columna, or
moustache muscle (naso lahialis).
2. The buccinator, corresponding to the buccinator
of animals. Besides its oflSce in mastication, it takes
an important part in the blowing of wind instruments.
3. The superficial elevator of the wing of the nose and the upper Up. It resembles the
levator labii superioris, descends from the orbital margin of the supermaxilla, passes along the
wing of the nose, and is lost in the upper lip.
4. The deep elevator of the wing of the nose and the upper lip, the analogue of which is
found in the dilator naris lateralis.
muscles of the human head
(superficial layer).
, Frontal portion of the occipito-fron-
talis ; 2, its occipital portion ; 3, its
aponeurosis ; 4, orbicularis palpebra-
rum ; 5, pyramidalis nasi ; 6, com-
pressor nasi; 7, orbicularis oris; 8,
levator labii superioris alasque nasi ;
9, levator labii superioris proprius ;
10, zygomaticus minor; 11, zygo-
maticus major ; 12, depressor labii
inferioris ; 13, depressor anguli oris ;
14, levator labii inferioris ; 15, super-
ficial portion of masseter ; 16, its deep
portion ; 17, attrahens aurem ; 18,
buccinator; 19, attollens aurem; 20,
temporal fascia covering temporal
muscle ; 21, retrahens aurem ; 22,
anterior belly of the digastricus, with
tendon passing through pulley ; 23,
stylo-hyoid muscle ; 24, mylo-hyoi-
deus ; 25, upper part of sterno-mas-
toid ; 26, upper part of trapezius —
the muscle between 25 and 26 is the
splenius.
292 TEE MUSCLES.
5. The zygomaticus, the presence of which is constant in all species.
6. The small zygomaticus, represented in the Horse by only the small oblique fasciculus
sometimes found beueath the zygomaticus.
The small zygomaticus and the two elevators of the lips are lachrymal muscles; by their
simultaneous contraction they express discontent and melancholy. The zygomaticus, on the
contrary, is the muscle of laughter ; it draws the commissures of the lips outwards.
7. The caninus, or dilator naris lateralis of animals, is attached beneath the infra-orbital
foramen, and terminates in the skin of the upper lip.
8. The risorius of Santorini.
9. The muscle of the chin (jnento-lahialis).
10. The myrtiformis, or middle anterior of Bourgelat.
The other facial muscles of Man, whose analogues it is difBcult or impossible to find in
animals, are : —
11. The triangularis of the lips, which is inserted into the anterior face of the inferior
maxilla, and is carried upwards to the commissure of the lips. By its contraction it gives the
face an expression of melancholy or contempt.
12. The quadratus menti, which, after been attached to the maxilla within the mental
foramen, passes upwards on the skin of the lower lip, which it depresses, and thus contributes
to the expression of fear or dismay.
13. The transversalis nasi {comprei<sor nasi), a muscle which is fixed into the supermaxilla
and on the bridge of the nose, where it is confounded with the opposite muscle.
14. The dilator of the ala of the nostril, a very small triangular fasciculus applied to the
external part of the nostril, whicli, by contracting, it elevates.
3. Muscles of the Lower Jaw.
There is nothing remarkable to be noted in tlie masseter, temporal, or pterygoid muscles.
The upper belly of the digastricus is not attached directly to the inferior maxilla, as it is in
Solipeds.
4. Hyoideal Muscles,
These are only three in number : —
1. The mylo-hyoideus.
2. The stylo-hyoideus, which commences at the styloid process of the temporal bone, and
shows a ring for the tendon of the digastricus.
3. The genio-hyoideus.
We do not find in Man the occipito-styloideus, kerato-hyoideus, or the hyoideus-transversus.
Axillary Region.
This comprises two muscles, pairs, placed beneath the sternum, in the axilla
which terminate on the anterior limb. These are the superficial and deep
pectorals}
Preparation. — 1. Place the animal in the first position. 2. Unfasten one of the forelimbs,
and allow it to hang, so as to separate it from the opposite one. 3. Eemove the skin with
care, and dissect, on the side corresponding to the detached limb, the two muscles which form
the superficial pectoral. 4. Prepare the deep pectoral on the opposite side. To do this,
remove the panniculus cautiously, so as not to injure the muscle about to be examined ; divide
the superficial pectoral transversely, and turn back the cut portions to the right and left ; divide
also the mastoido-humeralis and cervical trapezius near their insertion into the limb, and
reflect them upon the neck.
1. Superficial Pectoral (Pectoralis Anticus and Transversus)
(Figs. 174, 9, 10 ; 175, 3).
Synonyms. — Muscle common to the arm and {orearm— Bourgelat. Pectoralis magnus of
Man. (Percivall and Leyh describe three pectorals, others four ; but, as will be seen in this
work, the two pectorals are each divided into two portions, which, for practical purposes, agrees
with those who describe four. This muscle is the Pectoralis transversus of Percivall. Leyh
For a justification of the employment of tliese new denominations, see the note at p. 230.
MUSCLES OF THE TRUNK. 298
divides this muscle into two portions, which he designates the sterno-radialis and small sterno-
humeralis.)
Situation — Composition. — This muscle is situated between the two anterior
limbs, occupies the inferior surface of the chest, and is formed by two portions
which adhere closely to each other, but are yet perfectly distinct. Following
the example of Girard, we will describe these as two particular muscles by the
names of sterno-humeralis, and sterno-aponeuroticus .
A. Sterno-humeralis (Pectoralis ksT\G\5^).— Form— Structure.— T\A% is
a short, bulky muscle, flattened above and below, contracted at its termination,
and composed almost entirely of thick parallel fibres.
Direction and Attachments. — It commences on the anterior appendage and
the inferior border of the sternum, and is directed obUquely backwards, down-
wards, and inwards, to reach the anterior ridge of the humerus, where it
terminates by an aponeurosis corumon to it, the mastoido humeralis, and the
sterno-aponeuroticus.
Relations. — Externally, to the skin, from which it is separated by connective
tissue, and to the inferior extremity of the cervical panniculus ; internally, to
the sterno-aponeuroticus and sterno-prescapularis. Its anterior border forms,
with the mastoido-humerahs, a triangular space occupied by the subcutaneous,
or " plate," vein of the arm.
Action. — It acts principally as an adductor of the anterior limb.
B. Sterno-aponeuroticus (Pectoralis Transversus). — Form — Structure
— Direction — Attachments. — A very wide, thin, and pale quadrilateral muscle
formed of parallel fleshy fibres, which arise from the entire inferior border of
the sternum, to pass at first outwards, then downwards, and terminate in the
following manner : the anterior fibres go to the aponeurosis which attaches the
mastoido-humeralis and pectoralis anticus to the anterior ridge of the humerus ;
the posterior fibres are also continued by a very thin fascia, which is spread
inside the limb to the external face of the antibrachial aponeurosis.
Relations. — By its superficial face, with the skin, which adheres intimately to
it by means of dense connective tissue, and with the pectoralis anticus, which
covers its anterior border. By its deep face, with the two portions of the other
pectoral, the flexor brachii, and the long extensor of • the forearm ; it also
responds, by this face, to the antibrachial aponeurosis and the subcutaneous vein
of the forearm, which it maintains applied against that aponeurosis.
Action. — It is an adductor of the anterior limb, and a tensor of the anti-
brachial aponeurosis.
2. Deep Pectoral (Pectoralis Magnus and Parvus)
(Figs. 174, 11, 13 ; 175, 1).
Synonym. — The pectoralis parvus of Man
Volume — Situation — Composition. — An enormous muscle, situated beneath
the thorax, and composed, like the preceding, of two perfectly distinct portions,
described by Girard as two muscles, and designated by him as the sterno-
trochineus and sterno-prescapularis.
A. Sterno-trochineus. — Pectoralis magnus of (Percivall, Rigot, and)
Bourgelat. (The great sterno-humeraUs of Leyh.)
Volume — Extent. — This muscle, the largest of the two, is considerable in
294
TEE MUSCLES.
Fiff. 174.
volume. Extending from the ninth or tenth rib to the upper extremity of the
arm, it at first lies beneath and against the abdomen, then beneath the chesty
and at last is comprised between the walls of
the latter cavity and the internal face of the
anterior limb.
Form. — It is thin and flat above and below
in its posterior third, thicker and depressed
from side to side in its middle third, and
narrow and prismatic in its anterior third.
Its general form may be compared to that
of a somewhat irregular triangle, elongated
from before to behind, which would have a
very short posterior border, a longer internal
or inferior border, and an external or superior,
still more extensive.
Structure. — It is entirely composed of
thick, parallel, fleshy fasciculi, all of which
leave the posterior or internal border of the
muscle to gain its narrow or anterior extremity.
These fasciculi, as they approach the superior
border, become longer, and those which proceed
from the posterior border commence by
aponeurotic fibres. Unfrequent intersections
of fibrous tissue exist towards the anterior
extremity of the muscle.
Attachments. — It originates: 1. From the
tunica abdominalis by the aponeurotic fasciculi
of its posterior border. 2. By its internal
border, from the posterior two-thirds of the
inferior border of the sternum. It terminates,
by its anterior extremity, on the internal
tubercle at the head of the humerus, the tendon
of origin of the coraco-humeralis, and the
„^^^ \ n«« fascia enveloping the coraco-radialis. Through
^W//// m ISlllllllllllill ^^® medium of this fascia, it is inserted into
Wmm ^^U ^^^ external lip of the bicipital groove formed
by the external trochanter, and is united to
the two terminal branches of the supra-spinatus
muscles (see Figs. 174, 12 ; 181, 5).
Relations. — Its deep face, which is suc-
cessively superior and internal, covers the ex-
ternal oblique and the straight muscle of
the abdomen, the serratus magnus, lateralis-
stemi, and pectoralis parvus, as well as some
thoraco-muscular nerves ; all these relations
are maintained by means of a loose and
abundant connective tissue. Its superior face,
which alternately looks downwards and out-
wards, responds : to the skin, from which it is separated by a slight cellulo-
fibrous fascia ; to the pectoralis transversus ; and to the muscles, vessels, and
MUSCLES OF THE AXILLARY AND
CERVICAL REGIONS.
1, Portion of the cervical panniculus ;
2, anterior portion of the mastoido-
humeralis ; 3, posterior portion of
ditto; 4, sterno-maxillaris ; 5, sub-
scapulo-hyoideus ; 6, 7, sterno-thyro-
hyoideus ; 8, scalenus ; 9, pectoralis
anticus ; 10, pectoralis transversus ;
11, pectoralis magnus; 12, portion
of the fascia- enveloping the coraco-
radialis, receiving part of the fibres
of the pectoralis magnus; 13, pec-
toralis parvus ; 14, its terminal
aponeurosis.
MUSCLES OF THE TEUNK. 295
nerves of the inner aspect of the arm, through the medium of the sub-brachial
aponeurosis of the panniculus and a considerable quantity of connective tissue.
Its upper border adheres in an intimate manner to the last-named muscle, and is
bordered by the spur (external thoracic) vein. The large vascular trunks which
leave the chest to reach the anterior limb, pass above its anterior extremity, in
crossing its direction.
Action. — It puUs the whole limb backwards, in pressing on the angle of the
shoulder.
B. Sterno-peescapulakis. — (The pectoralis parvus of Percivall and Bour-
gelat.)— Form — Situation — Direction.— A long prismatic muscle, contracted at its
two extremities, situated in front of the preceding, arising from the sternum,
directed forwards and outwards towards the scapulo-humeral angle, and after-
wards reflected upwards and backwards on the anterior border of the shoulder,
which it foUows to near the cervical angle of the scapula.
Structure and Attachments. — It is formed of very large fleshy fasciculi.
296 THE MUSCLES.
analogous to those of the pectoraUs magnus, which originate, by their inferioi
extremities, from the sides of the sternal keel and the cartilages of the first
three or four ribs. They follow the direction of the muscle, and terminate, one
above the other, on a short aponeurosis which covers the supra-spinatus, and is
confounded with the external aponeurosis of the scapula (Fig. 174, 14).
Relations. — In its axillary portion, this muscle responds, inwardly, to the
lateralis sterni, the first sternal cartilages, and the corresponding intercostal
muscles ; outwards, to the pectoralis magnus and transversus. In its prescapular
portion, it is in relation, outwardly, with the mastoido-humeralis and trapezius ;
inwardly, with the subscapulo-hyoideus, the scalenus, and the angularis of the
scapula ; behind, with the supra-spinatus, which is separated from it by the
external scapular aponeurosis.
Action. — This muscle is a congener of the pectoralis magnus, and pulls
the scapula backwards and downwards. It is also a tensor of the scap|j|ar
aponeurosis.
DiETERENTIAL ChABAOTERS IN THE MuSCLES OF THE AXILLARY REGION IN THE
OTHER Animals.
With regard to the pectoralis anticus and transversus, it is remarked that in the Ox,
Sheep, and Pig, the former is small and less distinct from the latter than in Solipeds ; and
that in the Dog and Cat, the latter is very thin and narrow.
In the Ox, the pectoraUs parvus is scarcely distinct from the pectoralis magnus, and
which does not extend beyond the inferior extremity of the supra-spinatus. In the Sheep,
this muscle is quite confounded with the pectoralis magnus. In the Pig, the pectoralis parvus
resembles that of the Horse. Its inferior extremity only covers the first clirondo-sternal
articulation ; the superior extremity is more voluminous. With regard to the pectoralis
magnus, it terminates on the summit of the external trochanter, after detaching a short branch
to the tendon of the coraco-humeralis. The pectoralis parvus of the Dog is very feeble, and
terminates with the principal muscle on the humerus.
Costal Region.
In each costal region we find fifty-three muscles, which concur, more or less
directly, in the respiratory movements. These muscles are : 1. The serrafus
magnus. 2. Seventeen external intercostals. 3. Seventeen internal intercostals.
4. Seventeen levatores costarum. 5. The triangularis sterni.^
Preparation. — 1. Place the subject in the second position. 2. Remove the fore limb and
all the muscles attaching it to the trunk, by sawing through tlie scapula as shown in Fig.
162, in order to expose the serratus magnus; finish the dissection by taking away all the yellow
fibrous tissue which covers its posterior dentations. 3. Study the external intercostals and
the levatores costarum, after removing the great oblique muscle of the abdomen, the serrati
muscles, the transversalis costarum, and the longissimus dorsi. 4. Excise some external
intercostals in order to show the corresponding internal ones. 5. The triangularis sterni is
dissected on another portion, wliich is obtained in separating the sternum from the thorax,
by sawing through the sternal ribs a little above their inferior extremity.
1. Sereatus Magnus (Fig. 162, 15).
Synonyms. — Costo-subacapularis — Grirard. Posterior portion of the serratus magnus of
Bourgelat. (A portion of Percivall's serratus magnus.)
Form — Situation. — A very wide muscle, disposed like a fan, split up into
' Veterinary anatomists describe in this region a muscle which they designate the costo-
gternalis, lateralis sterni, or transveralis costarum, but we consider it a fasciculus detached from
the rectus abdominis (see Inferior Abdominal Region).
MUSCLES OF THE TRUNK. 297
digitations at its inferior border, applied against the thoracic walls, and partly
concealed by the shoulder.
Structure.— It is composed of divergent fleshy fibres, all of which converge
towards the superior extremity of the scapula, and are covered by a very strong
aponeurosis that gradually diminishes from above to below, and only adheres to
the muscle in its inferior part.
Attachments.— \. To the external face of the eight sternal ribs. 2. To the
anterior triangular surface of the internal face of the scapula, behind the
angularis, with which it is confounded. 3. To the whole extent of the posterior
triangular surface of that bone.
On reaching the scapula, the aponeurosis separates from the fleshy fibres, and
is inserted alone into the fibrous plane which covers the muscular fasciculi of the
subscapularis.
i^eZaftows,— Outwardly, and through the medium of an abundant supply of
connective tissue, which facilitates the play of the limb against the lateral wall
of the thorax, to the subscapularis, supra-spinatus, adductor of the arm, latissimus
dorsi, and the mass of olecranian muscles ; inwardly, to the first seven external
intercostals, to the sides of the sternum, and to the anterior small serratus. Its
four posterior digitations cross the first five of the great oblique muscle of the
abdomen, and are covered by a prolongation of the abdominal tunic.
Action. — With that of the opposite side, this muscle constitutes a vast brace
or girth on which the thorax rests when the animal is supported on its anterior
limbs ; it therefore acts, in relation to the trunk, as a suspensory ligament.
When it contracts, its fixed point being the thoracic walls, it pulls the superior
extremity of the scapula downward and backward, and causes this portion of the
limb to perform a swinging movement which carries the inferior angle upwards
and forwards. If the limb is the fixed point, then it raises the thorax between
the two anterior limbs, and assists in the respiratory movements by elevating
the ribs.
2. External Intercostals (Figs. 161, 162).
Situation — Form. — These muscles fill the spaces between the ribs, but do not
descend beyond their inferior extremities ; they, therefore, do not occupy the
intervals between the cartilages. They are flattened, fleshy bands, gradually
diminishing in thickness from above to below.
StriKture — Attachments. — Each external intercostal muscle is composed of a
series of muscular fasciculi, intermixed with numerous aponeurotic fibres, both
of which pass obliquely backwards and downwards, from the posterior border of
the preceding to the external face of the succeeding rib.
Relations. — Outwardly, to the different muscles applied against the thoracic
walls ; inwardly, to the internal intercostals.
3. Internal Intercostals (Fig. 163, 16).
These are placed at the internal face of the preceding, which they exactly
repeat with regard to their general form, but from which they differ in the
following points : —
1. Very thick between the costal cartilages, these muscles are reduced at the
upper part of the intercostal spaces to a thin aponeurotic layer, supported only
by some fleshy fibres. They, therefore, gradually diminish in thickness from
below upwards.
298 THE MUSCLES.
2. Their fasciculi are less tendinous than those of the external intercostals,
and are carried obliquely forward and downward, from the anterior border of
the posterior rib to the posterior border and internal face of the rib in front ;
so that the fibres of the external and internal intercostals cross each other like
the letter X.
3. Outwardly, they respond to the external intercostals ; inwardly, to the
costal pleura.
Action of the intercostal muscles. — The function of these muscles has been for
a long time, and is even now, much discussed ; and it may be said that there
were never, perhaps, more diverse or contrary opinions given on any subject
than on this, Berard, who has summed up the elements of the discussion
with the greatest judgment, considers the external intercostals as inspiratoiy
muscles, and the internal ones also as inspiratory by those fasciculi which occupy
the spaces between the costal cartilages ; the remainder, the majority, are
expiratory.
4. Levatores Costarum.
Synonyms. — Transverso-costales — Girard.
Small, flat, triangular, muscular, and tendinous fasciculi, constituting, it
might be said, the heads of the external intercostals, from which they are
scarcely distinguishable in the first and last costal intervals.
They arise from the transverse processes of the doi-sal vertebras, and are
directed backwards and outwards, gradually expandmg, to terminate on the
external face of the one or two ribs which succeed their fixed insertion. Out-
wardly, they are in contact with the longissimus dor si ; inwardly, with the
external intercostals.
The levatores costarum draw the ribs forward, and are consequently inspu-atory
muscles.
5. Triangularis Sterni.
Synonyms. — Sternalis — Bourgelat. Sterno-costalis — Girard. (The sterno-costales of Per-
civall, and sterno-costalis of Leyh.)
Form — SitvMtion. — This muscle, flattened above and below, elongated from
before to behind, and dentated at its external or superior border, is situated in
the thoracic cavity, above the sternum and the cartilages of the true ribs.
Attachments. — It is fixed, by its internal border, on the superior face of the
sternum, to the ligamentous cord which circumscribes it outwardly. It has its
movable insertion on the cartilages of the sternal ribs, the first excepted, by
means of digitations from its external border.
Structure. — It is formed of strongly aponeurotic muscular fasciculi, which
are directed from the internal to the external border.
Relations. — Inwardly, with the pleura ; outwardly, with the cartilages to
which it is attached, the internal intercostals, and the internal thoracic vein and
artery.
Action. — The triangularis of the sternum concurs in expiration, by depressing
the costal cartilages. (Leyh asserts that if the fixed point be the sternum, this
muscle pulls the ribs forwards, and so widens the thorax ; but if the fixed point
is the ribs, the sternum will be raised and the thoracic space diminished.)
MUSCLES OF THE TRUNK. 299
Differential Characters in the Muscles of the Costal Region in the other
Animals.
The muscles of the costal region caunot be tlie same ia number in all the domesticated
animals ; the intercostals and levatores costarum, for instance, must vary in number with that
of the ribs. Beyond this, the differem^es are slight. In the Ox, the serratus magnus is very
extensive, and the portion which passes to the posterior triangular surface of the scapula is
readily distinguished from the anterior by its diminished thickness, the larger proportion of
aponeurotic iibres it contains, and the flattened tendon by means of which it is inserted. In
the Pig, it is remarked that the internal intercostals are prolonged— maintaining a certain
thickness — to near the vertebral spine.
Comparison of the Thoracic Muscles of Man with those of the Domesticated
Animals.
The muscles of the axillary and costal regions and the diaphragm, are named the thoracic
muscles in Man.
The pectoral muscles are distinguished into great and small. The pectoralis magnus corre-
sponds to the pectoralis anticus and trausversus of the Horse. It is attached, on one side, to
the inner two-thirds of the clavicle, the anterior face of the sternum, and the cartilages of the
first six ribs ; on the other, to the anterior border of the bicipital groove, and, by a fibrous
expansion, to the aponeurosis of the arm. The costal fasciculi are distinctly separated from
the clavicular atid sternal fasciculi
The small pectoral, which corresponds to tlie pectoralis magnus and parvus, is inserted, on
the one part, into the external face of the third, fourth, and fifth ribs ; on the other part, by a
tendon to the anterior border of the coracoid process.
In Man, there is found a muscle whicli does not exist in animals; this is the subdavius, a
very slender fasciculus situated beneath the clavicle, and attached to the cartilage of the first
rib and the external portion of the lower face of the clavicle (see Fig 164, 5).
The serratus magnus does not show any distinct aponeurosis on its surface ; it arises from
the eight first ribs, and its digitations are grouped into three princip;d fasciculi.
Lastly, in Man the internal intercostals are prolonged to the vertebral column by small
muscles, named intra-costals. •
INFERIOR ABDOMINAL REGION.
The lateral and inferior walls of the abdominal cavity are formed by a wide
musculo-aponeurotic envelope, which rests, by its periphery, on the sternum,
ribs, lumbar vertebrae, ilium, lumbo-iliac aponeurosis, and the pubis. This
envelope is concave on its superior surface, and results from the assemblage of
four pairs of large membraneous muscles aiTanged in superposed layers. Reckon-
ing them from without inwards, these are designated the (/reat, or external oblique,
the small, or internal oblique, the great straight, and the transverse muscle.
Covered outwardly by an expansion of yellow fibrous tissue — the tunica abdomi-
nalis — and separated from those of the opposite side by the linea alba — a medium
raphe extending from the sternum to the pubis — these muscles support the
intestinal mass, and by their relaxation or contraction adapt themselves to the
variations in volume which these viscera may experience.
Preparation.—Miex placing the animal in the first position, a wide opening is to be made
in the pectoral cavity by the ablation of a certain number of ribs, which should be divided
inferiorly, above the costal attachments of the great oblique muscle. The heart and lungs are
removed; then an incision is made in the diaphragm, to allow the digestive viscera contained
in the abdominal cavity to be taken away. It is not absolutely necessary, however, to empty
that cavity, and if its contents be allowed to remain, several punctures should be made in the
large intestine to prevent the accumulation of gas, and the too great distension of the abdominal
parietes.
These preliminary precautions having been adopted, then proceed in the following
manner : —
SOO TEE MUSCLES.
1. Remove the skin from tliis region, and with it the panniculus carnosus, in order to study
the external surface of the abdominal tunic. 2. The dissection of the great oblique muscle is
accomplished by removing the yellow fibrous envelope from the fleshy portion of the muscle,
together with the sterno-trochineus. The inguinal ring should be exposed by the ablation of
the dartos muscle, the sheath and penis, or the mammae. 3. On the opposite side, the small
oblique is uncovered by excising the great oblique, leaving, however, that portion of the
aponeurosis which is mixed up with that of the first muscle. 4. The latter having been
studied, dissect the great straight muscle of the abdomen on the same side, in separating from
the white line, by a longitudinal incision, the aponeurosis common to the two oblique muscles,
dividing this aponeurosis and the fleshy portion of the internal oblique by another incision
extending transversely from the umbilicus to the middle of the lumbar region, and laying back
one of the musculo-aponeurotic suctions on the thigh, the other on the ribs. 5. The transverse
muscle is dissected on the same side as the external oblique lias been. To expose it, nothing
more is necessary than to make two incisions similar to the foregoing, but including the two
oblique and the straight muscle, throwing back the two portions as above. 6. Lastly, open
the entire abdominal cavity by cutting through the transverse muscle in the same way; then
study the muscular digitations of that muscle, the internal orifice of the inguinal canal, and
the layer reflected from the aponeurosis of the great oblique muscle.
1. Abdominal Tunic (Tunica Abdominalis, Tunica Elastica).
The vast expansion of yellow elastic fibrous tissue spread over the two
external oblique muscles of the abdomen is so named.
Very thick towards the prepubic tendon of the abdominal muscles and in the
vicinity of the linea alba, this expansion gradually thins as it approaches the
sternum, and disappears near the abdominal insertion of the pectoralis magnus.
It also diminishes in thickness as it extends from the linea alba ; and when it
reaches the fleshy portion of the great oblique muscle it becomes reduced to an
extremely thin layer, the fasciculi of which separate more and more from one
another, until they completely disappear. Anteriorly, however, it is seen to be
prolonged on each side to the posterior digitations of the serratus magnus.
Posteriorly, it furnishes some bundles of fibres, which are detached from the
surface of the common tendon, and are carried between the thighs to be lost on
the internal crural muscles.
The abdominal tunic is covered by the skin and panniculus carnosus, from
which it is separated by an abundance of connective tissue. In the male, its
external surface gives attachment to the suspensory ligaments of the prepuce,
and to the dartos ; and in the female, to the elastic capsule which envelops each
mammary gland. By its internal face, it closely adheres to the aponeurosis of
the great oblique muscle ; though it is easily separated from the fleshy portion.
It is traversed by several openings, which aflford passage to the subcutaneous
vessels and nerves of the abdominal region.
Use. — The abdominal tunic acts as an immense elastic girth or bandage,
which aids the muscles in sustaining the weight of the intestines. As the
digestive organs increase in volume, this tunic increases in thickness.
In the Pig, Dog, and Cat, it is reduced to a simple cellulo-aponeurotic layer, owing to
the stomach and intestines in these animals exercising but a small amount of pressure on the
abdominal parietes.
2. White Line (Linea Alba).
The white line (lima albn) is a fibrous cord comprised between the internal
border of the two great straight muscles, and is considered as beiQg foiToed by
the intercrossing, on the median line, of the aponeuroses belonging to the oblique
and transverse muscles. Attached, in front, to the inferior sm'face of the xiphoid
MUSCLES OF THE TRUNK. 301
appendage, this cord is confounded, behind, with a large tendon, the fr&pubic or
common tendon of the abdominal muscles, which is fixed to the anterior border of
the pubis (Figs. 140, a ; 176, 10). This tendon, covered by the abdominal tunic,
contributes to form the internal commissure of the inguinal ring, and gives
origin to the pubio-femoral ligament.
Towards the union of its posterior third with its two anterior thii'ds, the
white line widens, so as to form a lozenge-shaped space, in the centre of which is
found the remains of the umbiHcus and the umbilical cord (Fig. 147, o).
3. Geeat Oblique, or External Oblique of the Abdomen (Obliquus
Abdominis Externus) (Figs. 162, 18 ; 176, 1).
Synonyms. Oosto-abdominalis— Girard.
Situation — Composition. — This muscle, the largest and the most superficial of
the four, is situated on the side and floor of the abdomen, and is composed of a
fleshy and an aponeurotic portion.
Form^ Structure, and Attachments of the fleshy portion. — This is composed of
fibres directed obliquely downwards and backwards, and presents itself as a wide
muscular band, narrower before than behind, applied to the inferior surface of
the last thirteen or fourteen ribs. Its superior border is concave, and attached :
1. To the external surface of the ribs just mentioned by as many slightly
aponeurotic digitations, the first four of which cross the dentations of the great
serratus. 2. To the aponeurosis of the latissimus dorsi, from the last rib to the
external angle of the ilium (Fig. 162, 18). Its inferior border, convex and
sinuous, is continuous with the aponeurosis ; it descends, in front, to the cartila-
ginous circle of the false ribs, which it projects beyond posteriorly, increasing in
this as it nears the lumbar region.
Form, Structure, and Attachments of the Aponeurosis. — This is narrow and
thin in front, wide and thick behind, of a triangular form, and composed of
white, nacrous-looking fibres passing in the same direction as the fibres of the
fleshy portion, with the inferior border of which it is continuous by its external
border. Its internal border is inserted into the white Une and the prepubic
tendon ; and its posterior border, extending from the external angle of the ilium
to the anterior border of the pubis, responds to the plicature of the flank,
embraces the corresponding crm-al muscles, and establishes the Une of demarcation
between the trunk and the abdominal limb.
The aponeurosis of the great oblique gives rise, at its posterior border, to two
very remarkable fibrous layers, which appear to be produced by the doubling of
this aponem'osis. One of these layers descends on the internal muscles of the
thigh to constitute the crural aponeurosis (Fig. 176, 4) ; while the other is
reflected upwards and forwards, to enter the abdominal cavity. This reflected
layer of the great oblique aponeurosis is named the crural arch {ligament of
Poupart or Fallopius) (Fig. 165, b).
Near the prepubic tendon of the abdominal muscles, and immediately before
its division into two layers, the aponeurosis of the external oblique is pierced
by a large oval aperture (the external abdominal ring) (Fig. 176, 5), the mferior
orifice of the canal through which passes the cord of the testicle in the male,
and the mammary vessels in the female. This channel has been named the
inguinal canal.
The description of the femoral aponeurosis, the crural arch, and the inguinal
302 THE MUSCLES.
ring — a necessary complement of the great oblique muscle — will be given here*
after.
Relations of the Great Oblique Muscle. — Externally, to the pectoralis magnus
and the abdominal tunic, which latter separates it from the skin and the panni-
culus. By its deep face, it is related to the ribs, into which it is inserted, as
well as with their cartilages, the corresponding intercostal muscles, the small
oblique, and the rectus abdominis. The latter even appears to be attached,
through the anterior moiety of its external border, to the fleshy portion of the
great oblique, by means of a sHght layer of yellow elastic tissue, which covers,
to a small extent, the deep face of the two muscles.
Action. — The external oblique, in contracting, compresses the abdominal
viscera, flexes the vertebral spine, and acts as an expiratory muscle. (By its
compression on the abdominal viscera, it concurs in the acts of defecation,
micturation, and parturition.)
Internal Crural Aponeurosis. — This fibrous layer descends from the
plicature of the flank on to the patella and the inner surface of the leg. Out-
wardly, it is confounded with the aponeurosis of the fascia lata ; inwardly, it
degenerates into connective tissue. It covers the long adductor of the leg, part
of the short adductor, the vastus internus, and the crural vessels at their exit
from the abdominal cavity.
Crural Arch. — As already mentioned, this is the reflected layer of the
great oblique aponeurosis, and is also named the ligament of FaUopius and
Poiqxtrfs ligament. It is a wide, flat band, attached by its extremities to the
external angle of the ilium and the anterior border of the pubis. Its anterior
face (Fig. 165, b) forms, inwardly, the posterior wall of the inguinal canal ; it
gives attachment, outwardly, to the posterior fibres of the small oblique muscle.
Its posterior face, applied against the superior extremity of the patellar muscles,
the long adductor of the leg, the pectineus, and the crural vessels on their
leaving the abdomen, embraces all these parts as in a vast arch, and from this
peculiarity it derives its name. Its superior border is inserted, for its external
half, into the lumbo-iliac aponeurosis. In its middle part it is much thinner,
and is prolonged to the external surface of the long adductor muscle of the leg
and the iliac fascia, to be at last mixed up with the latter. Within the pectineal
insertion of the small psoas muscle, it forms the anterior margin of the crural
ring : a triangular orifice circumscribed on the other side by the anterior border
of the pubis, the iliacus, and the long adductor of the leg, and through which
pass the crural vessels as they leave the abdomen by the crural arch.^ The
inferior border is continuous with the femoral aponeurosis and that of the great
oblique muscle.
Inguinal Canal. — This is an infundibuliform canal, compressed laterally,
through which the spermatic cord and external pudic artery pass from the
abdomen in the male, and the external mammary vessels in the female.
Situated on the side of the prepubic region, in an oblique direction do^vn-
wards, backwards, and inwards, and measuring from two to two and a half inches
in length, this canal lies between the crural arch, which constitutes its posterior
' This orifice is covered by a very thin aponeurotic layer, which is prolonged, above, on
the crural vessels, behind, into the pelvic cavity, and which appears to be continuous, inferiorly,
with the upper border of Poupart's ligament. This layer is perhaps only a dependency of the
subperitoneal aponeurosis ; and if so, it represents the only vestige of the fascia transversalis
It has been possible to discover in Solipeds.
MUSCLES OF THE TRUNK. 303
wall, and the fleshy portion of the small obUque muscle, which forms the anterior
wall.
Its inferior (external) or cutaneous orifice, also named the inguinal or external
abdominal ring, is much larger than the superior {^internal). Pierced in the
aponeurosis of the great oblique, in the angle formed by the union of the internal
border with the posterior border of the aponeurosis, this opening is oval in
form, directed obliquely backwards and inwards, which permits it to be described
as having tivo lips or pillars, and two extremities or commissures.
The pillars, distinguished into anterior and posterior, are composed of the
arciform fibres from the aponeurosis of the great oblique muscle.
The commissures, internal and external, result from the union of the two
pillars at their extremities. The internal is limited by the prepubic tendon of
the abdominal muscles.
The superior (internal) ov peritoneal orifice of the inguinal canal, is situated
in front of, and directly opposite to, the crural ring. It is a simple dilatable slit,
comprised, like the canal itself, between the crural arch and the small oblique
muscle. Not well defined at its extremities, this opening includes the neck of
the vaginal sheath.
4. Small or Internal Oblique Muscle of the Abdomen (Obliquus
Abdominis Internus) (Figs. 163, 17' ; 176, 6).
Synonyms. — Ilio-abdominalis — Girard.
Situation — Composition. — Situated beneath the preceding, which exactly covers
it, this muscle is, like it, composed of a fleshy and aponeurotic portion.
Form, Structure, Position, and Attachments of the muscular portion. — The
muscular portion is very thick, triangular, and flabelliform, and occupies the
region of the flank. Its superior border is united, by a thick, yellow, elastic
production, to the aponeurosis of the latissimus dorsi, and a peculiar small
muscle, named by the Germans the retractor costce, {retractor of the last rib),
which we consider as a dependency of the small oblique muscle. Its posterior
border is slightly raised, and lies against the crural arch, from which it separates,
inwardly, to form the inguinal canal. Its anterior and inferior border is convex,
irregular, and thinner than the other portions of the muscle, and is continuous
with the aponeurosis. All the fibres entering into the composition of this
muscular portion are spread like a fan, and leave the external angle of the ilium
and the external fourth of the crural arch, to be directed, the posterior fibres
backwards and inwards, the middle fibres downwards, and the anterior fibres
forwards to reach the antero-inferior border of the muscle.
Form, Structure, and Attachments of the Aponeurosis. — The aponeurosis is
irregularly triangular, and formed of nacrous-looking fibres, which are directed
like the muscular fibres, and cross in X fashion the aponeurotic fibres of the external
oblique. It succeeds the antero-inferior border of the muscular portion, and is
separated, superiorly, into several digitations which reach the internal face of the
last asternal cartilages. Throughout the whole extent of its internal border it is
fixed to the white line.
Relations. — Externally, with the external oblique. The aponeuroses of the
two muscles, which are merely superposed outwardly, are blended inwardly in
80 intimate a manner, that it might be considered their respective fasciculi were
301
THE MUSCLES.
Fig. 176.
M0SCLES OF THE INFERIOR ABDOMINAL REGION (ASS).
I, Abdominal tunic ; 0, umbilicus. 1, Panniculus camosus detached from the tunica abdominalii
and turned to the left ; 2, 3, portion of the great oblique turned over to the left ; 4, femoral
aponeurosis; 5, external abdominal ring; 6, muscular portion of the small oblique muscle;
7, aponeurosis of ditto; 8, strips of the tunica abdominalis and aponeuroses of the great and
small oblique muscles turned over to the right; 9, rectus abdominis; 10, prepubic tendon;
11, muscular portion of the transversalis abdominis; 12, aponeuroses of that muscle; 13, left
pectoi alls magnus ; 14, section of right ditto ; 15, pectoralis anf icus and transversus ; 16, inferior
extremity of the mastoido-humeralis ; 17, muscle of the fascia lata: 18, long adductor of the
leg; 19, 19', short adductors of the leg.
MUSCLES OF THE TRUNK. 305
woven into each other. The small oblique covers the rectus and transversalis
abdominis.
Action. — This muscle, a congener of the preceding, compresses the abdominal
viscera, depresses the last ribs, and causes the flexion — either direct or lateral — of
the vertebral column.
The retractor muscle of the last rib. — This small muscle, flattened on each side
and triangular in form, originates by aponeurotic fibres from the summits of the
first two or three transverse processes of the lumbar region. It terminates on
the posterior border of the last rib. Covered by the last digitation of the
posterior serratus and by the great oblique, it covers in turn the transversalis
abdominis. In contracting, it draws the last rib backwards, and fixes it in that
position, in order to permit the expiratory action of the internal intercostal
muscles. It therefore plays the same part, in regard to these muscles, that the
scalenus does to the external intercostal muscles (Fig. 162, 17).
5. Geeat Straight Muscle of the Abdomen (Rectus Abdominis)
(Figs. 162, 20 ; 176, 9).
Synonym. — Stemo-pubialia — Girard.
Situation — Extent — Form — Stricture. — This is a wide and powerful muscular
band, extending from the sternum to the pubis, included between the aponeurosis
of the internal oblique and that of the transversalis muscles, narrower at its
extremities than in its middle, and divided by numerous transverse and zig-zag
fibrous intersections. These strongly adhere to the aponeurosis of the small
oblique muscle, are nearer to each other, and more distinct, in front than behind,
and are produced by small tendons which are placed at certain distances on the
course of the muscular fasciculi, making it somewhat of a polygastric muscle.
Attachments. — In front : 1. To the prolonging cartilages of the last four
sternal and the first asternal ribs. 2. To the inferior face of the sternum.
Outwardly, by the anterior moiety of its external border, to the internal face of
the great oblique. Behind, to the anterior border of the pubis, through the
medium of the common tendon, which is a direct continuation of the rectus
abdominis.
Relations. — By its inferior face, and in front, with the pectoralis magnus and
great oblique ; for the remainder of its extent, with the aponeurosis of the small
oblique. By its superior face, with the transversalis muscle and the cartilages of
several ribs. By its internal border, with the white hue, which separates it from
the opposite muscle.
Action. — It draws the thorax backwards, and compresses the abdominal
viscera. It is also the principal flexor of the spine. (Leyh, remarking that
it shares in the functions of the preceding muscles, adds that it draws the pelvis
forwards during copulation.)
6. Transverse Muscle of the Abdomen (Transversalis Abdominis)
(Figs. 163, 18 ; 176, 12, 12).
Synonyms. — Lumbo-abdominalis — Girard. (The costo-abdoniinalis internus of Leyh.)
Sittmtion — Composition. — This muscle is situated immediately outside the
peritoneum, and forms the deep layer of the abdominal parietes. It is musculai
outwardly, and aponeurotic for the remainder of its extent.
306
THE MUSCLES.
Form, Structure, and Attachments of the muscular portion. — It presents a band
elongated from before to behind, extending from the sternum to the transverse
processes of the last lumbar vertebrae, following in its course the direction of the
cartilages of the ribs, and composed of parallel fibres passing from one border to
the other.
Its superior border, concave, is attached : 1. To the internal sm-face of the
asternal ribs by digitations placed opposite those of the diapliragm, but the
Fig. 177.
MUSCLES OF THE ANTERIOR ASPECT OF THE BODY OF MAN. ON THE LEFT SIDE THE SUPERFICIAL
LAYER IS SEEN; ON THE RIGHT, THE DEEPER LAYER.
1, Pectoralis major; 2, deltoid; 3, anterior border of the latissimus doi-si ; 4, serratus magnue ;
5, subclavius, right side ; 6, pectoralis minor ; 7, coraco-brachialis ; 8, biceps, with its two heads ;
9, coracoid process of the scapula; 10, serratus magnus, right side; 11, external intercostal
muscle of the fifth intercostal space; 12, external oblique; 13, its aponeurosis with the linea
alba ; 14, Poupart's ligament ; 15, external abdominal ring ; 16, rectus muscle of right side ;
17, pyramidalis muscle; 18, internal oblique; 19, conjoined tendon of internal oblique muscle
and Poupart's ligament.
majority of which do not mix with them. 2. To the extremity of the transverse
processes of the lumbar region by a thin fibrous layer. Its inferior border is
convex, and continuous with the aponeurosis.
Form, Structure, and Attachments of the aponeurosis. — This is triangular-
shaped, with the base behind, and with its fibres running in a direction trans-
verse to the median line. Closely laid one against another in front, these fibres
separate behind, and form only a very thin and incomplete layer.
By its external border, the aponeurosis is joined to the inferior margin of
MUSCLES OF THE TRUNK 307
the muscular portion. Its internal border is fixed to the xiphoid cartilage and
the white line. Its posterior border, badly defined, appears to join the crural
arch only on its outer aspect.
Relations. — Outwards, with the inferior extremity of the asternal ribs and
their cartilages, with the rectus abdominis, the small oblique, and the depressor
muscle of the last rib ; inwardly, with the peritoneum, from which it is separated
by the subperitoneal aponeurosis — an extremely fibrous layer which, in Man and
some animals, becomes much thickened towards the crural arch, where it forms
adhesions. It has been described, in human anatomy, as the fascia transversalis.
Action. — It compresses the abdominal viscera when it contracts, and presses
them against the vertebral column.
Differential Characters in the Muscles of the Abdominal Kegion in the otheb
Animals.
A. Ruminants. — The development of the tunica ahdominalis is in proportion to the
volume of the digestive viscera. This membrane is, therefore, very wide and thick in Rumi-
nants.
The obliquus externus has no femoral aponeurosis; its aponeurosis is therefore entirely
reflected in the abdominal cavity. The inguinal canal is very short ; its upper orifice is very
narrow, and it is situated near where the two portions of the long adductor of the leg unite
(Goubaux); its inferior opening is very elongated from before to behind, and without to
within.
The muscular portion of the small oblique occupies the entire space comprised between the
posterior border of the last rib, the extremity of the transverse processes of the lumbar vertebrae,
and the external angle of the ilium. The small retractor of the last rib is not distinct from the
principal muscle. The rectus abdominis is wide behind, with tendinous intersections more
marked at its superior than its inferior face ; the aponeurosis of the transversalis is much
thicker and more resisting than in Solipeds.
The prepubic tendon of the abdominal muscles is large, and attached to the inner face of
the short adductors of the leg by two ligamentous bands ; this attachment depresses the lower
part of the abdominal wall, and therefore it is that, in Ruminants, there is a concave depression
in front of the pubis.
B. Pig and Camivora. — The tunica ahdominalis is reduced to an insignificant layer.
The external oblique is remarkable for the enormous development of its muscular portion and
the narrowness of its aponeurosis. The internal oblique resembles that of Ruminants.
Comparison of the Abdominal Muscles of Man with those of Animals.
With the exception of some sligbt diff'erences, the abdominal muscles of Man resemble
those of the smaller animals. The tunica ahdominalis does not exist, but is represented by a
layer of connective tissue which separates the skin from the aponeurosis of the obliquus
externus. The muscular portion of this muscle has no attachment to the aponeurosis of the
great dorsal.
The aponeurosis of the obliquus internus is divided into two layers at the external border of
the rectus muscle; the anterior is consolidated with the external oblique, and passes in front
of the rectus; the posterior is united to the transversalis, and passes behind that muscle.
The aponeurosis of the transversalis is divitied into two layers, only one of which femains
behind the rectus; this is named the semilunar fold of Douglas.
The rectus offers three transverse fibrous intersections in its length (linem transversse). At
its upper extremity, it divides into three branches: the internal is attached to the xiphoid
appendage and the cartilage of the seventh rib; the middle, to that of the sixth rib; the
external, to the cartilage of the fifth rib.
" To the rectus is annexed a small triangular muscle, the pyramidalis, which is not
found in animals. This muscle is about 2^ inches long; is sometimes absent; most developed
in children ; is attached by its base to the pubis, between the spine and the symphysis ; and
by its summit is continuous with a tendon which is lost in the white line, and constitutes,
with that of the opposite siile, a fibrous cnrd whicii may be followed to the umbilicus"*
(Beaunis and Bouchard).
Lastly, at the inner aspect of all the abdominal muscles, beneath the peritoneum, is a fibrous
308 THE MUSCLES.
layer— the fascia traneversalis. Thi8 fascia is not distinctly limited upwards or outwards;
below, it is fixed to the crural arch, in the vicinity of the inguinal canal, and sends a layer to
the surface of the cord spermatic.
Diaphragmatic Region.
This is composed of a single muscle, the diaphragm.
Diaphragm.
Preparation. — Place the subject in the first position; open the abdomen and remove the
viscera it contains, as well as the large vascular trunks lying upon the sublumbar region ;
detach the peritoneum from the fleshy portion of the muscle, in order to show the digitationa
of the latter more distinctly, taking care not to allow the air to enter the thoracic cavity, as it
■would destroy the tense and concave form of tlie diaphragm.
Situation — Direction. — The diaphragm is a vast musculo-aponeurotic partition,
separating the thoracic from the abdominal cavity, between which it is placed in
an oblique direction downwards and forwards.
jTorm. — It is flattened before and behind, eUiptical, wider above than below,
concave posteriorly, and convex anteriorly.
Structure. — This muscle comprises : 1. A central aponeurotic portion desig-
nated the phrenic centre, which is incompletely divided into two leaflets by the
pillars or crura — fleshy columns which descend from the sublumbar region. 2.
A peripheral or circumferential portion, forming a wide muscular band around
the phrenic centre.
The phrenic centre (also named the speculum Helmontii^ or mirror of Hehnont)
is composed of white, glistening, radiating fibres which, originating from the
pillars, extend in every direction to join the muscular fibres of the peripheral
portion. It is pierced, in its right leaflet, by a large opening for the posterior
vena cava {foramen dextrum).
The crura ov pillars are two in number — a right and left. The right crus or
pillar, the most considerable, is a very thick, fleshy fasciculus which commences
under the loins by a strong tendon, united to the inferior common vertebral
ligament. It descends to the phrenic centre, to which it gives a heart-shaped
appearance. Near its inferior extremity, it presents an opening for the passage
of the oesophagus and pneumogastric nerves, in the abdominal cavity {foramen
sinistruni). The left pillar is a small triangular fasciculus, partly separated from
the preceding by an orifice {hiatus aorticus) for the transmission of the posterior
aorta, vena azygos, and thoracic duct. It also arises from the sublumbar
region by a tendon, which is confounded with that of its congener.
The peripheral muscular portion is continuous, by its concentric border, with
the central aponeurosis. Its eccentric border is divided into dentations. Above,
and on the left side, it nearly always joias the left pillar ; but on the right side it
stops at a certain distance from the corresponding pillar, so that towards this
point the phrenic centre is not enveloped by the peripheral portion, and is in
contact with the sublumbar region.
Attachments. — 1. To the bodies of the lumbar vertebrae by the tendons of its
two pillars, which tendons are confounded with the inferior common vertebral
Ugament. 2. By the external contour of its muscular portion, to the superior
face of the xiphoid cartilage ^ and the inner face of the last twelve ribs, near
' This sternal fasciculus sometimes shows a depression, in which the serous membranes of
the abdomen and thorax come into contact. If this fosette enlarges, it is converted into an
opening through which hernia of the intestine into the cavity of the chest may take place.
MUSCLES OF THE TRUNK.
309
their inferior extremities or cartilages. The digitations forming the last inser-
tions do not intercross, in Solipeds, with those of the transversalis muscle of the
abdomen, being separated by an interval which is wider behind than before.
Relations. — Anteriorly, it is covered by the pleura, and responds, mediately,
to the base of the lung. The posterior aspect, covered by the peritoneum, is in
contact with the greater part of the viscera contained in the abdominal cavity —
Fig. 178.
DIAPHRAGM OF THE HORSE (POSTERIOR FACE).
1, 1', The two portions of the right crus or pillar; 2, left crus or pillar ; 3, tendons of the pillars;
4, 4', peripheral muscular portion ; 5, left leaflet of the aponeurotic portion ; 5, 5', right leaflet
of the same ; 6, posterior vena cava ; 7, oesophagus passing through the opening in the right
pillar ; 8, posterior aoi-ta between the two pillars ; 9, cartilaginous circle of the ribs ; 10, 11,
section of the psoas muscle ; 12, section of a lumbar vertebra; 13, section of the common mass;
14, retractor muscle of the last rib ; 15, xiphoid appendage of the sternum.
the stomach, colon, spleen, and liver ; the latter is even attached to this surface
for a portion of its extent.
On each side of the pillars, the circumference of the muscle forms an arch
which passes over the great and small psoas muscles.
310 THE MUSCLES.
Action.— The diaphragm, in contracting, tends to become an inclined plane ;
its central portion is carried backwards, and the antero-posterior diameter of the
chest is increased. It is, therefore, essentially an inspiratory muscle. It may
also raise the ribs by making the mass of abdominal viscera its fixed point ;
it then acts as a reflected muscle, to which these viscera serve as a pulley. (The
diaphragm also aids the other abdominal muscles in expulsive efforts, and, when
affected with iiTegular spasmodic contractions, produces the peculiar phenomenon
in Man and some of the lower animals, known as hiccough.)
Differential Characters of the Diaphragm in the other Animals.
In the Ox, the pillars of the diaphragm are very lon<:]; and voluminous. " The attachments
of the muscular portion are much farther distant from the cartilaginous circle than in the
Horse, particularly at the superior part ; this disposition explains the innocuousness of puncture
of the paunch in the middle of the last intercostal space ; for in the Horse, when the instru-
ment is passed through this part, it penetrates the thorax " (communicated to M. Lecoq by
M. Tahourin).
In the Sheep, we have not remarked that the costal attachments were more forward than
in the Horse.
Rigot erroneously states that, in the Pig and Dog, the oesophagus passes between the two
pillars of the diaphragm ; on several occasions we have convinced ourselves that this tube
traverses the right pillar, as in tiie other animals.
Comparison of the Diaphragm of Man with that of Animals.
In the human diaphragm, the aponeurotic portion is divided into three leaflets, which has
caused it to be termed the aponeurotic trefoil. Between the middle and right leaflet is the
orifice through which the inferior vena cava passes. The openings for the passage of the
oesophagus and the aorta are situated between the two pillars. There are frequently met with,
in Man, one or two small accessory pillars, separated from the large pillars by an aperture that
afibrds a passage, on the right side, to the vena azygos and the sympathetic nerve, and on the
left side, to one of the lumbar veins and the other sympathetic nerve.
The peripheric muscular portion always joins, posteriorly, the central muscular portion.
Article II. — Muscles of the Anterior Limbs.
These are divided into four principal groups : the muscles of the shoulder,
arm, forearm, and foot.
Muscles of the Shoulder.
These muscles are grouped around the scapula, and all act upon the arm,
which they extend, flex, abduct, adduct, etc. They form two regions : an
external or supra-scapular^ and an internal or subscapular .
A. External Scapular Region.
This comprises four muscles : the long abductor of the arm {teres externus),
the short abductor (postea spinatus minor, or teres mitior), the supra-spinatus, and
infraspinatus. These muscles are applied to the external surface of the scapula,
aud are covered by an aponeurotic layer.
Preparation of the external scapular region. — Separate the limb from the trunk ; remove the
trapezius and mastoido-humeralis, to expose the external surface of the aponeurosis; take
away, also, the small pectoral muscle, after studying its mode of insertion into this fascia.
This being accomplished, next remove the latter muscle to show the supra-spinatus, the
infra-spinatus, and long abductor muscle of the arm ; leaving only the strip which attaches the
anterior portion of the latter to the tuberosity of the scapular spine.
To study the short abductor muscle, it is only necessary to cut the long abductor and supr»
MUSCLES OF THE ANTERIOR LIMBS.
311
spinatus across, and to throw back the sections : an operation requiring some care, because of
the intimate adherence of the short abductor to the infra-spinatus.
1. External Scapular Aponeurosis.
This aponeurosis, to which the pectoralis
parvus and long adductor of the arm act as tensors,
gives origin, by its internal face, to several septa
which penetrate between the scapular muscles,
and form around them more or less complete
contentive sheaths. Its external face is separated
from the skin by the panniculus carnosus, trape-
zius, mastoido-humeralis, and the aponeurotic
fascia which unites the last two muscles. It is
continuous, in front, with the thin fibrous ex-
pansion extended over the internal scapular
muscles ; behind and downwards, it is prolonged
over the muscles of the arm and insensibly de-
generates into connective tissues ; above, it is
attached to the fibro-cartilaginous prolongation
of the scapula.
2. Long Abductor of the Arm (Teres Ex-
TERNus), OR Scapular Portion of the
Deltoid (Fig. 179, 1, 1).
Synonyms. — Scapiilo-humeralis magnus — Girard.
(Teres major — Percivall. Great scapulotrochiterius — Leyh.)
Situation — Composition — Form — Direction . —
This muscle is situated beneath the scapular
aponeurosis, behind the infra-spinatus, and is
composed of two portions placed one above the
other, separated by a superficial interspace. The
posterior portion, the most considerable, is elon-
gated from above to below, bulging in its middle,
narrow at its extremities, plane on its external
and convex on its internal surface. It accompanies
the posterior border of the infra-spinatus, and is
lodged in a depression in the large extensor muscle
of the forearm.
The anterior portion, much shorter than the
preceding, extends over the infra-spinatus and
short abductor, by sUghtly crossing the direction
Fig. 179.
EXTERNAL MUSCLES OF THE
RIGHT ANTERIOR LIMB.
1, 1, Long abductor of the arm; 1',
its humeral insertion; 2, supra-
spinatus ; 3. infra-spinatus ; 3', its tendon of insertion ; 4, short abductor of the arm ; 5, biceps ;
6, anterior brachialis ; 7, large extensor of the forearm ; 8, short extensor of the forearm ; 9,
anconeus; 11, anterior extensor of the metacarpus; 11', its tendon; 12, aponeurosis separating
that muscle from the anterior brachialis; 13, oblique extensor of the metacarpus; 14, anterior
extensor of the phalanges ; 14', its principal tendon; 15, the small tendinous branch it furnishes
to the lateral extensor ; 16, lateral extensor of the phalanges ; 16', its tendon ; 17, the fibrous
band it receives from the carpus; 18, external flexor of the metacarpus; 19, .its metacarpal
tendon; 20, its supra-carpal tendon; ulnar portion of the perforans ; 22, tendon of the perforans,
23, its carpal ligament ; 24, its reinforcing phalangeal sheath ; 25, tendon of the perforatus.
312 TEE MUSCLES.
of these two muscles. Thick inferiorly, this portion diminishes considerably
towards its superior extremity.
Structure and Attachments. — The first portion is generally paler than the
second, and is composed of longitudinal fleshy fibres deeply intersected by tendi-
nous strips. It takes its origin, by its superior extremity, from the dorsal angle
of the scapula. The anterior portion is deeper-coloured and more tendinous
than the other. Its superior extremity, included within two fibrous folds
resulting from the duplicature of the scapular aponeurosis, is fixed, through the
medium of these, to the tuberosity of the scapular spine.
These two muscular bodies unite inferiorly, and terminate together on the
deltoid imprint or crest by tendinous and muscular fasciculi.
Relations. — Outwardly, to the scapular aponeurosis, with which it may be said
to form one body ; inwardly, to the infra-spinatus, the short abductor of the
arm, and the large and short extensors of the forearm.
Action. — It gives a very marked abduction movement to the humerus, and
also makes it pivot outwards. It acts, besides, as a flexor of that bone, when its
action is combined with that of the adductor of the arm. It should also be con-
sidered as a powerful tensor of the scapular aponeurosis.
3. Short Abductor of the Arm (Postea Spinatus Minor), or Teres
Minor (Fig. 128, 2, 3).
Synonyms. — Scapulo-humeralis minor — Girard. (Scapulo'trochiterim, medimi and parvum
^Leyh.)
Volume — Situation — Direction. — A small elongated muscle, situated below the
preceding and the subspinatus, along the posterior border of the scapula, the
direction of which it follows.
Form — Structure. — In its inferior half it is prismatic, muscular, divided by
fibrous intersections, and easily separated into several irregular fasciculi. In its
superior half it is flattened, entirely tendinous, and split into several digitations,
the longest of which are behind.
Attachments. — It originates : 1. Through the medium of its tendinous digita-
tions, from the posterior border of the scapula and the linear imprints in the
infra-spinous fossa. 2. From the small tubercle situated on the external side
of the margin of the glenoid cavity, by a short tendon. It tenninates on the
humerus, between the crest of the external tubercle and the deltoid imprint.
Relations. — Outwardly, with the infra-spinatus and the long abductor ;
inwardly, with the large extensor of the forearm, the short extensor, and the
capsule of the scapulo-humeral articulation.
Action. — Like the preceding, this muscle is an abductor and outward rotator
of the humerus.
4. Supra-spinatus (AfJTEA-SPiNATUS) (Figs. 179, 2 ; 181, 5).
iSi/Tioni/mg.—Supra-acromio-trocliiterius— Girard. (^Antea spinatus — Percivall. Anterior
spinatus — Leyh.)
Form — Situation. — This muscle is thick and prismatic, stronger below than
above, representing a very elongated pyi-amid, and completely filling, and even
projecting beyond, the supra-scapular fossa.
Structure — Attachments. — It is almost entirely formed of fleshy fibres, which
are attached, by their superior extremities, to the cartilage of prolongation of the
MUSCLES OF THE ANTERIOR LIMBS. 313
scapula, the inner face of the scapular aponeurosis, the supra-scapular fossa, and
the anterior border and cervical angle of the scaT^nlsi— fixed insertion. These
fibres, on reaching the inferior extremity of the muscle, form two very thick,
short, and slightly tendinous branches, united to each other by the enveloping
flexor brachii or biceps aponeurosis. The external branch reaches the summit of
the external trochanter of the humerus ; the internal is inserted into the corre-
sponding part of the internal trochanter — movable insertion.
Relations. — Outwards, with the scapular aponeurosis, to which its fibres adhere
in the most intimate manner ; inwards, with the scapula and the subscapularis
muscle ; forwards, with the small pectoral ; and behind, with the scapular spine
and the infra-spinatus. The two terminal branches cover and embrace the flexor
brachii tendon, and the capsule of the scapulo-humeral articulation.
Action. — This muscle is an extensor of the humerus, and a tensor of the
envelopuig flexor brachii aponeurosis. With regard to the articulation of the
shoulder, it plays the part of a powerful ligament — a function it shares with
the majority of the other scapular muscles.
5. Infra-spinatus (Postea-spinatus) (Fig. 179, 3, 3').
Synonym. — Subacromio-trochiterius — Girard.
Situation — Form. — Situated, as its name indicates, in the infra-spinatus fossa,
this muscle is wide, thin, and flattened on both sides at its superior extremity,
thick and prismatic in its middle, and conoid at its inferior extremity, which is
terminated by two short branches — an external and internal.
Structure. — The muscular fibres are directed, like the muscle itself, forward
and downward ; they are deeply mixed with strong aponeurotic layers. Of the
two branches in which it terminates inferiorly, the external is the strongest, and
is entirely constituted by a powerful tendon ; the internal is both muscular and
aponeurotic.
Attachments. — All the fleshy fasciculi of this muscle are fixed, either dii'ectly,
or through the medium of the internal aponeurotic layers : 1. To the whole
extent of the infra-spinatus fossa. 2. To the scapular spine and its tuberosity.
3. To the cartilage of prolongation of the scapula. 4. To the internal face of
the scapular aponeurosis— ^a;^^ insertion. The movable insertion of the muscle
takes place, on the external tuberosity, by its two terminal branches, the internal
passing within the convexity ; and the strong tendon constituting the external
branch (Fig. 179, 3') gliding, by means of a synovial bursa, over the surface of
this convexity, and attaching itself to the roughened facet which forms the crest
of the external tuberosity.
Relations. — It is covered by the anterior portion of the long abductor of the
arm, and by the scapular aponeurosis. It covers the scapula, its cartilage, the
fixed insertion of the large extensor of the forearm, and the short abductor, which
adheres to it in the most intimate manner at its superior or aponeurotic portion.
Its anterior border responds to the scapular spine and supra-spinatus muscle ; the
posterior is bordered by the long abductor of the arm. Its inferior extremity
protects, outwardly, the capsule of the scapulo-humeral articulation, and is con-
cealed beneath the mastoido-humeralis.
Action. — The infra-spinatus acts on the humerus as an abductor and outward
rotator.
314 TEE MUSCLES.
B. Internal Scapular REaiON.
This is composed of four muscles : thi*ee principal — the subscapularis, adductor
of the arm {teres internus), and the flexor hrachii — are situated on the internal
face of the scapula, and are covered by a very small fibrous fascia which is formed
of some scattered parallel fibres that run in a transverse direction. The fourth,
named the small scapulo-humeraUs, is a very slender fasciculus deeply lodged
behind the articulation of the shoulder.
Preparation. — Turn over the limb which has served for the dissection of the preceding
region, and remove the slight internal scapular fascia. Be careful to preserve the termina-
tion of the latissimus dorsi muscle, in order that its relations and adhesions with the adductor of
the arm may be studied ; leave also the humeral insertion of the pectoralis magnus, so that its
union with the tendon of the coraco-humeralis may be noted ; in a word, prepare the region ae
it is represented in Fig. 181. With regard to the small scapulo-humeral muscle, it ought to
be dissected at the same time as the short flexor of the forearm.
1. Subscapularis (Fig. 181, 3).
Synonym. — Subscapulo- trochineus — Girard.
Situation — Direction — Form. — This muscle, lodged in the subscapular fossa,
the name of which it bears, has the same oblique direction as the scapula. It is
wider above than below, and divides superiorly into three portions ; so that its
form exactly repeats that of the excavated surface it covers.
Structure. — The muscular fibres of the subscapularis slightly converge towardsi
its inferior extremity, and all end in a very strong, wide, and short tendon.
They are intermixed with deep and superficial tendinous fibres, which singularly
increase the tenacity of the muscle ; the superficial fibres are spread over the
internal surface in glistening, nacrous layers.
Attachments. — The subscapularis has its origin from the whole extent of the
fossa of that name. Its movable insertion takes place on the internal tuberosity
of the humerus, by means of a voluminous tendon it offers at its inferior ex-
tremity. A particular small synovial bursa facilitates the gliding of this tendon
over the eminence into which it is inserted.
Relations. — Externally, with the scapula. Its internal face is applied against
the serratus magnus, from which it is separated by a thick layer of connective tissue,
as well as by the rudimentary fascia covering the three muscles of the internal
scapular region in common. Its anterior border, margined by the supra-spinatus,
adheres closely to that muscle in its upper two-thirds, and forms with it, by its
inferior third, the intermuscular space that lodges the subscapular vessels and
nerves. Its posterior border responds to the adductor of the arm, with which it
also unites for the greater part of its extent ; it is isolated from this muscle, in its
inferior third, by the interspace lodging the subscapular vessels and nerves. Its
terminal tendon covers the capsule of the scapulo-humeral articulation, which it
powerfully binds ; it is in part covered by the tendon of origin of the coraco-
humerahs muscle, which ghdes over its surface as on a pulley, by means of a
synovial bursa.
Action.— This muscle is principally, and perhaps exclusively, an adductor of
the arm. It may be admitted, however, that it rotates the humerus inwards.
MUSCLES OF TEE ANTERIOR LIMBS. 315
2. Adductoe of the arm (Teres Internus, or Teres Major) (Fig. 181, 4).
%riom!/Tn8.— Subscapulo-humeralis— Girard. (Great scapulo-humeralis—Leyh.)
Form — Situation — Direction. — A long muscle, flattened on both sides, bulging
in its middle, contracted at its extremities, thick at its anterior, and thin at its
posterior border. It is situated behind the preceding, in the same oblique direc-
tion, and is parallel with the posterior portion of the long abductor, which it
appears to repeat in the internal scapular region.
Structure. — It is almost entirely muscular, showing only some tendinous fibres
at its external surface and upper extremity. Its inferior extremity is terminated
by a flat tendon, which also belongs to the latissimus dorsi, and which has been
already described (see p. 260).
Attachments. — It arises from the dorsal angle of the scapula, and the posterior
border of the subscapular muscle — origin ; it passes to the internal tuberosity of
the humerus, to be attached by its inferior tendon — termination.
Relations. — Outwards, with the aponeurosis of the latissimus dorsi and that
of the long extensor of the forearm, which isolates it from the large extensor
muscle ; inwards, with the sen-atus magnus, from which it is separated by the
fibrous and cellular layers mentioned in the description of the subscapularis. Its
inferior extremity covers the short flexor and middle extensor of the forearm ; it
is covered by the long branch of the coraco-humeralis, and by the vessels and
nerves which send their ramifications to the arm, forearm, and foot.
Action. — This muscle adducts the arm, and causes it to rotate inwards. If it
contracts at the same time as the long abductor, it du'ectly flexes the humerus.
3. Coraco-humeralis, Coraco-brachialis, or Omo-brachialis
(Fig. 181, 10).
Synonym. — Middle seapulo-humeralis — Leyh.
Volume — Situation — Direction. — A small elongated muscle, which appears to
belong to the arm rather than the shoulder, as it is situated at the internal face
of the humerus, which it slightly crosses. If it is described as in the subscapular
region, it is because of its attachments and action, which are, in every respect,
analogous to those of the other muscles of the shoulder.
Attachments — Form — Structure. — It commences on the beak of the coracoid
process by a small flat tendon, which is at first included between the supra-spinatus
and subscapularis, but afterwards leaves the interstice formed by these two muscles,
to be inflected and glide over the terminal tendon of the latter. This small
tendon is succeeded by two muscular branches — one deep, the other superficial.
The first is a wide, thin, and short band, almost entirely muscular, attached to
the body of the humenis above the internal tuberosity. The second forms a fleshy
body of a certain thickness, flattened on both sides, and strongly aponeurotic ;
the fasciculi composing it are longer as they are more posterior, and are inserted,
by their inferior extremities, into the imprints on the anterior face of the
humenis.
Relations. — This muscle is covered by the flexor brachii, and by the pectoralis
magnus, which is partly attached to its tendon. It covers the internal insertion
of the subscapularis, the humerus, the common tendon of the latissimus dorsi,
the adductor of the arm, and a small portion of the short flexor and middle
extensor of the forearm. Its posterior border is margined by the vessels and
316 THE MUSCLES.
nerves on the inner aspect of the arm. The anterior humeral nerve passes
between its two branches, along with an arterial and venous ramification.
Action. — It is an adductor of the arm, and makes it also pivot inwards. Its
direction and attachments do not permit it to produce rotation outwards, though
it has been stated to do so by several authors.
4. Small Scapulo-humeralis (Scapulo-humeralis Gracilis, vScapulo-
humeralis posticus).
(Synonyms. — Not mentioned by Percivall. Leyh, in addition to the above designation,
names it the tensor of the capsular ligament.)
The scapulo-humeralis gi-acilis is a very small cylindrical fasciculus, compiised
between the large extensor of the forearm and the capsule of the scapulo-humeral
articulation ; it derives its origin above the margin of the glenoid cavity of the
scapula, and tenninates below the head of the humerus by a thin tendon, which
insinuates itself between the fibres of the short flexor of the forearm. This
muscle appears to be peculiar to Solipeds, and has been regarded by Rigot as
intended to raise the capsule of the scapulo-humeral articulation during flexion,
so as to prevent its being pinched between the articular surfaces.
Differential Charactebs in the Muscles of the Shoulder in the other Animals.
The Carnivora are the only animals which oflPer somewhat notable differences in the
muscles of the shoulder.
Thus, the long abductor of the arm, very developed, has an anterior portion arising directly
from the acromion process, and a posterior portion which springs from the whole extent of the
scapular spine, by a short aponeurosis. The supra- spinatus is considerable, and terminates in
a single branch that goes to the great trochanter.
The infra- spinatus is not so large as the preceding, and is also undivided at its inferior
extremity : it is the inferior branch which is absent.
The coraco-humeralis is very short, and is composed of a single fasciculus, which terminates
above the humeral insertion of the adductor of tlie arm.
In the Pig, the disposition of this muscle is the same ; it is very tendinous.
In the Camel, on the external surface of the scapular region is an elastic layer which
extends over all the limb, and is worthy of notice. It arises from the borders of the cervical
ligament, covers the shoulder and arm, and is thickest behind the scapulo-humeral angle,
where the abductors and extensors of the forearm separate. It descends on the forearm in
front of the humero-radial articulation, and reaches the lower third of the anterior face of that
region, where it divides into two portions. The narrower and thinner of these go to the front
of the knee, where it gradually disappears in becoming thinner and lighter-coloured; the
largest division passes behind, and joins an equally elastic layer which comes from the inner
surface of the olecranian muscles and the elbow ; it reaches behind the knee, where it divides
into several strips, some of which are fixed into the inner border of the carpus and metacarpus,
and others on the flexor tendons of the phalanges, behind the metacarpo-phalangeal articulations.
This very remarkable elastic apparatus tends incessantly to flex the bone of the anterior
limb; and to its presence must certainly be attributed the characteristic locomotion of the
Camel — ^jerking and almost passive flexion of the metacarpus on the forearm, and the forearm
on the arm.
In the Camel, it is also remarked that the long abductor of the arm is entirely muscular, and,
superiorly, is only attaclied to the acromion spine.
Comparison of the Muscles of the Shoulder op Man with those of Animals.
As muscles of the shoulder, there are only described the deltoid, infraspinatus, teres minor
and major, and the subscapularis ; the coraco-brachialis being included in the region of the
arm, while the small scapulo-humeralis is absent (see Fig. 180).
The deltoid, represented in part by the long abductor of the arm of Solipeds, is a large,
triangular, flat muscle, that covers the articulation of the shoulder. Its fibres are inserted
into the external third of the anterior border of the clavicle, the external border of the aero-
MUSCLES OF THE ANTERIOR LIMBS.
317
mion, and the inferior border of the scapular spine for the whole of its width ; below, it i»
attached, through the medium of a tendon, to the deltoid imprint.
By their disposition, the supra-spinatus, infraspinatus, and subscapularis resemble the
muscles of Carnivora. The teres major, after establishing relations with the latissimus dorsi,
as in Solipeds, is fixed into the inner lip of the bicipital groove.
Muscles of the Arm.
These muscles, grouped around the humenis, are attached to the forearm by
their inferior extremities. Those situated in front flex this portion of the limb,
while those behind extend it. The first form the
anterior brachial region; the second, the posterior I'lg. 180.
brachial region.
A, Anterior Brachial Region.
This region is composed of only two muscles — the
lo7ig and short flexors of the forearm.
1. Long Flexor of the Forearm (Flexor
Brachii,or Brachial Biceps) (Figs. 128, 159, 181).
Synonyms. — Coraco-cubitalis, or coraco-radialis, according
to Girard. (Scapula- or coraco-radialis — Leyh.)
Preparation. — Place the limb on its internal face, throw
back the brachial insertion of the mastoido-humeralis, pectora-
lis auticus, and pectoralis transversus, over the external muscles
of the forearm ; excise, lengthways, the inferior extremity of
the supra-spinatus, to show the originating tendon of the muscle.
The inferior insertion may be studied with that of the short
flexor muscle.
Form — Situation — Direction — Structure. — A long,
cylindrical muscle, thick m its middle portion, bifid
inferiorly, situated in front of the humerus, in an
oblique direction downwards and backwards, tendinous
at its two extremities, divided by a great number of
strong fibrous intersections, one of which, nearly
central and much more considerable than the others,
is a veiy resisting cord that traverses the muscle
throughout its length, and becomes continuous with
the tendons at its extremities.
Attachments. — This muscle has its origin at the
base of the coracoid process by a superior, round, and
thick tendon (Fig. 128, 6) that reaches the bicipital
groove, on which it is moulded in becoming fibro-cartilaginous, and over which
it glides by means of a synovial sac, to be inflected backwards and confounded
with the body of the muscle. Its inferior tendon, extremely short and strong,
terminates on the superior and internal tuberosity of the radius — the bicipital
tuberosity — in becoming united to the capsular ligament of the elbow-joint, and
insinuating itself beneath the internal ligament of this articulation. At its
origin, this tendon gives off a somewhat resisting fibrous band, which is spread
over the surface of the anterior extensor of the metacarpus, and is confounded
with the antibrachial aponeurosis.
Relations. — It covers an adipose cushion, which separates it from the capsule
23
MUSCLES OF ANTERIOR ASPECT
OF man's upper arm.
1, Coracoid process of scapula ;
2, coraco-clavicular liga-
ment (trapezoid), passing up-
ward to clavicle ; 3, coraco-
acromial ligament, passing
to acromion ; 4, subscapu-
laris ; 5, teres major ; 6,
coraco-brachialis ; 7, biceps ;
8, upper end of radius ; 9,
brachiaiis anticus ; 10, in-
ternal head of triceps.
f
318
TEE MUSCLES.
of the scapulo-humeral articulation, the anterior face of the humerus, the coraco-
humeralis, and the articulation
Fig. 181,
INTERNAL ASPECT OF LEFT ANTERIOR LIMB.
1, Prolonging cartilage of scapula; 2, inner surface of
scapula ; 3, subscapulavis ; 4, adductor of the arm, or
teres internus ; 5, supra- or antea-spinatus ; 6, long
extensor of the forearm, or portion of the caput magnum ;
7, large extensor of the forearm, the other portion of the
caput magnum ; 8, middle extensor, or caput medium ;
9, humeralis obliquus, or short flexor of the forearm ;
10, coraco-humeralis ; 11, upper extremity of humerus;
12, coraco-radialis, or flexor brachii ; 13, lower extremity
of humerus ; 14, brachial fascia ; 15, anterior extensor
of the metacarpus, or extensor metacarpi magnus; 16,
belly and aponeurotic termination of the flexor brachii ;
17, ulna; 18, oblique flexor of the metacarpus; 19,
internal flexor of the metacarpus, or epicondylo-meta-
carpus; 20, radius; 21, tendon of the oblique extensor;
22, large metacarpal bone; 23, flexor tendons of the
foot ; 24, suspensory ligament ; 25, internal rudimentary
metacarpal bone; 26, extensor tendon of the foot; 27,
metacarpo-phalangeal sheath ; 28, lateral cartilages of
the foot ; 29, podophylla;.
ligrament of the ulnar articulation, and those muscles of
epicondyle.
of the elbow. It is covered :
1. By the supra-spinatus, be-
tween the two branches of
which it passes. 2. By a
special aponeurotic sheath, the
tensor of which is the above-
named muscle, with the pecto-
ralis magnus (see Fig, 179, 12,
in which this aponeurosis has
been partly preserved). This
sheath separates the flexor
brachii from the mastoido-
humeralis, the pectoralis trans-
versus, and from its congener
— the short flexor.
Action. — This muscle is a
flexor of the forearm, and a
tensor of the antibrachial
aponeurosis. It acts, besides —
through the cord which tra-
verses its entire length — as an
inextensible band that me-
chanically opposes the flexion
of the scapulo-humeral angle
while the animal is standing,
and when the forearm is main-
tained fixed by the contrac-
tion of the humero-olecranian
muscles,
2. Short Flexor of the
Forearm (Humeralis Ob-
liquus, Brachialis An-
Ticus, Humeralis Ex-
TERNUS) (Fig. 128, 12).
Synonyms. — Humero - cubitalis
obliquus, or liumero-radialis —
Girard. (Humero-radialis — Leyh.)
Preparation. — Lay the limb on
its internal face, and remove the
abductors of the arm, the infm-spi-
natus, and the large and shnrt ex-
tensors of the forearm, in urder to
expose the middle and upper ex-
tremity of this muscle. Tlien turn
the limb on its external face to
dissect the inferior extremity. To
study it in all its details, it is a good
plan to cut through the internal
the forearm which are attached to the
MUSCLES OF THE ANTERIOR LIMBS. 319
Form — Structure — Situation — Direction. — This is a very thick muscle, almost
entirely fleshy, voluminous in its superior part, and constricted inferiorly. It
is lodged in the musculo-spiral groove of the humerus, the direction of which it
exactly follows as it turns round the bone to cover, successively, its posterior
face, external face, anterior face, and the capsule belonging to the elbow
articulation, until it finally reaches the inner side of the radius.
Attachments. — The muscular fibres have their fixed insertion on the posterior
face of the humerus, below the articular head. They terminate, inferiorly, on
a flat tendon, which they almost entirely cover. This tendon ghdes in a trans-
verse groove situated on the inner face of the radius, below the bicipital tube-
rosity, and afterwards passing under the internal hgament of the elbow- joint,
it divides into two very short fasciculi ; one of these goes to the radius, and the
other to the ulna, where it is mixed up with the bundles of arciform fibres which
unite, on the inner side, the two bones of the forearm.
Relations. — We already know the parts this muscle covers. It is covered,
inwardly, by the adductor of the arm and the middle extensor of the forearm ;
posteriorly and externally, by the large and short extensors of that bone. Its
inferior extremity, comprised between the anterior extensor of the metacarpus
and the flexor brachii, passes below the antibrachial band of the latter, as under
a fibrous bridge.
Action. — It is simply a flexor of the forearm.
B. PosTERioE Brachial Region.
This is composed of four muscles, which have their movable insertion in
common on the summit of the olecranon, and are consequently designated
olecranian muscles. With reference to their action, they are also designated
extensors of the forearm, and are distinguished into long, short, middle, and small.^
The first three of these muscles resemble the triceps hrachialis (or triceps
extensor cuUti) of Man — the large extensor representing the long or middle portion,
the short extensor the external, and the middle extensor the internal. The small
extensor takes the place of the anconeus or elbow muscle of some authorities.
Preparation.— The muscles of this region ought to be studied before those of the preceding
■region. To dissect the large and short extensors, it is necessary to lay the limb on its inner
face, remove the slight fibrous layer wliich covers these two muscles, and raise the abductors
of the arm, which in great part conceal their origin. The limb is kept in the same position
for the dissection of the small extensor, which is not easily accomplished, as it is almost
entirely concealed by the short extensors, which, besides, closely adhere to it. To dissect the
long and middle extensors, it suffices to turn the limb on its external surface and cut away the
vessels, nerves, and lymphatics which partly cover the latter; care must also be taken to
isolate the muscle annexed to the latissimus dorsi.
1. Large Extensor of the Forearm (Caput Magnum), or Long Portion
OF the Triceps Brachialis (Figs. 179, 7 ; 181, 7).
5?/non«/ms.— Scapulo-olecranius magnus— G/rarfi. The long portion of the triceps brachi-
alis of Man. (Portion of llie caput magnum of the triceps extensor brachii— Percivall.)
Volume— Form— Situation.— An enormous, short, and triangular muscle,
> In veterinary -works, and in preceding editions of this work, there has been described in
this region a fifth muscle— the lonq extensor of the forearm. This has now been moved to the
region of the back and loins, wliere it is annexed to the latissimus dorsi, because of its relations
with that muscle.
320 THE MUSCLES.
occupying, with the short extensor, the space comprised between the posterior
border of the scapula and the humerus.
Structure and Attachments.— Th.Q fleshy mass constituting this muscle is
formed of very thick fasciculi, among which are found some aponeurotic bauds.
These fasciculi have their origin on the dorsal angle and the axillary border of
the scapula, either directly, or through the medium of two strong fibrous layers,
between which they are at first included. They are afterwards directed back-
wards and downwards, and converge towards a thick tendon which occupies the
posterior and inferior angle of the triangle represented by this muscle. The
tendon terminates by attaching itself to the summit of the olecranon, after
receiving a great number of fibres from the short extensor, and after gliding,
by means of a synovial capsule, over the eminence which serves for its insertion.
Relations. — The external surface is covered by a thin, fibrous, white-and-
yellow layer, which separates it from the panniculus ; it has near the upper
border an excavation into which is received the posterior portion of the long
abductor. Its internal face responds to the latissimus dorsi, the adductor of
the arm, and the long extensor. Its posterior border is margined by the latter
muscle ; the superior follows the axillary border of the scapula, and is attached
to it to constitute the fixed insertion of the muscle ; the inferior border responds
to the short and middle extensors.
Action. — It is an extensor of the forearm.
2. Short Extensor of the Forearm (Caput Medium), or External
Portion of the Triceps (Fig. 179, 8).
Synmym. — Humero-olecranius externus— GiVard.
Sittmtion — Direction — Form — Strmture. — This muscle is situated between the
humerus and the inferior border of the preceding muscle, and is directed
obliquely downwards and backwards. It is thick and short, flattened and
aponeurotic at its upper extremity, prismatic, and entirely formed of thick
parallel muscular fascicuU for the remainder of its extent.
Attachments. — One of its attachments is on the humerus, to the curved line
extending from the deltoid ridge to the base of the articular head (see for this
line Fig. 62, above 4), by the short aponeurosis of its superior extremity-^a^ei
insertion ; the other is to the olecranon, either directly, or through the tendon
of the large extensor — movable insertion.
Relations. — The prismatic shape of this muscle offers three faces, which
respond : externally, to the two abductors of the arm and to a slight fibrous
layer continuous ; above, with that which covers the large extensor ; and below,
with the antibrachial aponeurosis ; internally, to the small extensor — from which
it is difficult to separate it — to the short flexor of the forearm, and to the anterior
extensor of the metacarpus ; superiorly, to the large extensor, which closely
adheres to it.
Action. — An extensor of the forearm.
3. Middle Extensor of the Forearm (Caput Parvum), or Internal
Portion of the Triceps (Fig. 181, 8).
SyTWJij/m?.— Humero-olecranius intemus — Girard. (Caput parvum — PercivaU.)
Situation — Direction — Form — Structure. — This muscle is situated at the
internal face of the humerus, along the inferior border of the large extensor =
MUSCLES OF THE ANTERIOR LIMBS.
S21
^ig. 182.
It is oblique downwards and backwards, pyriform, enlarged at its superior
extremity, contracted inferiorly, where it terminates by two small flat tendons.
Attachments. — It originates, by its superior extremity, from the inner aspect
of the humerus, behind and above the tuberosity on its body. One of its
terminal tendons is attached to the summit of the
olecranon ; the other glides over a small convexity
on the inner side of that eminence, and goes to be
inserted a little lower than the first.
Relations. — Above, with the inferior border of the
large extensor ; outwards, with the humerus, the
short flexor, and short extensor of the forearm ; in-
wards, with the humeral insertion of the latissimus
dorsi and the abductor of the arm, the long branch
of the flexor brachii, the vessels and nerves on the
inner side of the arm, and the long extensor of the
forearm.
Action. — An extensor of the forearm.
4. Small Extensor of the Fokearm or
Anconeus (Fig. 128, 10).
Synonym. — Humero-olecranius minor — Girard.
Form — Structure — Situation — Relations. — This is
a small, thick, and prismatic muscle, almost entirely
fleshy, situated behind the elbow articulation. It
is applied against the synovial cul-de-sac which
ascends into the olecranian fossa, and to which it is
strongly attached ; it is hidden by the short extensor,
from which it is not easily distinguished.
Attachments. — It originates from the margin of
the olecranian fossa, chiefly above and outwards. It
terminates by being inserted into the anterior and
external part of the olecranon.
Action. — This little muscle, a congener of the
preceding, raises the articular capsule it covers, and
prevents its being pinched between the bony surfaces.
Differential Characters in the Muscles of the Arm
IN THE other Animals.
In all animals, the long flexor of the forearm, or flexor
brachii, is less thick and tendinous than in Solipeds.
In the Pig, Dog, and Cat, it comports itself in a
special manner at its inferior extremity ; it is attached at
first to the bicipital tuberosity, and also furnishes a small
tendinous branch which glides over the inner side of the
deep muscles on
ternal aspect
anterior LIMB.
THE EX-
)f right
1, Scapula; 2, coracoid process
of scapula ; 3, flexor brachii ;
4, superior extremity of humerus ; 5, external tuberosity of humerus ; 6, humeralis obliquus ;
7, body of humerus ; 8, biceps ; 9, anterior, or great extensor of the metacarpus ; 10, ulna ;
11, extensor pedis, or anterior extensor of the phalanges; 12, ulnaris accessorius, or ulnar portion
of the perforans ; 13, lateral extensor of the metacarpus, or extensor suffraginis ; 14, oblique
extensor of the metacarpus; 15, flexors of the foot; 16, trapezium; 17, annular ligament; 18,
carpal ligament of perforans tendon, 20; 19, perforatus tendon; 21, tendon of anterior extensor of
metacarpus; 22, small metacarpal bone; 23, suspensory ligament; 24, lateral band of metacarpo-
phalangeal sheath ; 25, perforans tendon ; 26, branch of the suspensory ligament joining the
extensor pedis, 27.
822 THE MUSCLES.
radius by means of a synovial bursa, and is fixed within the ulna, towards the base of the
olecranon.
The flexor brachii or biceps of the Camel, is manifestly decomposable iuto two muscular
portions, united above in a tendon. The inner portion is the largest and somewhat fusiform, and
is attached directly to the radius by its muscular fibres. The other portion, situated external
to and in front of the preceding, ends in a bifurcated tendon, one branch of which goes to the
bicipital tuberosity : the other, succeeded by a small fleshy fasciculis, joins the body of the
anterior extensor of the metacarpus.
The short flexor of the forearm, or humeralis ohliqum, is terminated in the Pig, Dog, and
Cat, by a small tendon which is fixed in the ulna, beluw the ulnar branch of the flexor
brachii.
The middle extensor of the forearm and anconeus of these animals are remarkable for their
volume.
Comparison of the Muscles of the Arm of Man with those of Animals.
In Man, three muscles are situated in front of tlie humerus — the biceps, coraco-humeralis,
and the humeralis ohliquus -, behind are found the triceps brachialis, and the anconeus.
The biceps, which corresponds to the flexor brachii of animals, commences on the scapula
by two heads, which unite towards the upper part of the humerus. The long portion is
detached from the upper part of the rim of the glenoid cavity ; the shortest commences from
the summit of the coracoid process. The inferior tendon of the biceps gives ofi", before fixing
itself on the bicipital tuberosity, a fibrous layer which is confounded with the antibrachial
aponeurosis.
The coraco-humeralis has only one fleshy body.
As in the Carnivora and Pig, the humeralis ohliquus terminates on the ulna, below the
coronoid process.
The triceps brachialis exactly represents, by its three heads, the large, middle, and short
extensors of the forearm of animals (see Fig. 180).
There is nothing particular with regard to the anconeus.
Muscles of the Forearm.
These muscles, nine in number, distributed in two regions — anterior and
posterior — envelop the bones of the forearm on every side except the internal,
where the radius is in mediate contact with the skin. They all terminate on
the different sections of the hand or anterior foot, which they flex or extend,
and are contained in a common fibrous sheath, which constitutes the antibrachial
aponeurosis.
Antibrachial Aponeurosis.
This retaining fascia forms a very strong and resisting envelope, which is
firmly fixed around the antibrachial muscles by the insertions it has on the bones
of the forearm, being attached to the olecranon, the internal aspect of the
radius, and to the inferior extremity of that bone, both inwards and outwards.
Its external face is covered by the superficial vessels and nerves, which are
separated from the skin by a very thin fibrous layer, more particularly observable
on the inner side, where it covers the antibrachial aponeurosis in a very evident
manner ; it is rendered tense by the pectoralis transversus. Up to the present
time, this fibrous layer has not been distinguished from the aponeurosis it covers.
The inner face of the latter gives rise to several septa, which penetrate the
interstices of the muscles to form around some of them special retention sheaths ;
it adheres to several of them very intimately. At its upper border, this aponeu-
rosis receives, inwardly, the insertion of the annexed muscle of the latissimus
dorsi ; in front, the accessory band of the flexor brachii ; outwardly, it is con-
tinuous with the fascia covering the external face of the olecranian muscles.
Inferiorly, it is prolonged around the knee to form the tendinous sheaths of that
MUSCLES OF THE ANTERIOR LIMBS. 323
The antibrachial aponeurosis is made tense by the contraction of the annexed
muscle of the latissimus dorsi, and that of the flexor brachii. With reference to
the pectorahs transversus, which has hitherto been regarded as intended to play
the same part, it can only act on the fascia which covers, externally, the anti-
brachial aponeurosis.
Preparation of the muscles of the forearm. — The preparation of these muscles is extremely
simple, as it suflBces to remove the antibrachial aponeurosis and the interstitial cellulo-adipose
tissue, to expose and to isolate them from each other. No special recommendations need there-
fore be given, as a glance at Figs. 179, 181, 182, and 183 will guide the student in his dissec-
tion, and supplement the manual details which would be superfluous here.
Nevertheless, as the terminal insertions of some of these muscles are enclosed witliin the
hoof, and as it is indispensable, in order to expose them, to remove this horny case, some
explanation will be given as to the manner in which this should be effected, particularly as
the apparent difficulty and labour too frequently cause this part to be omitted in the dissecting-
rooms.
1. The instruments necessary to remove the hoof are : a scalpel, toe-knife, hammer, and a
pair of pincers.
2. The limb siiould be in a vertical position, held by one or two assistants, and the foot
placed on a table, stool, or very soliti block of wood.
3. Pass the scalpel as deeply as possible around the coronet, to separate the wall of the
hoof from the organized tissues.
4. With the knife and hammer, split the wall into four or five pieces by vertical incisions.
5. When the wall is thus divided, it is sufficient to insert the knife under the fragments,
and, making it serve as a lever, tear them off; pincers may also be used for this purpose, each
of the pieces being twisted from the sole.
6. To remove the sole, the blade of the scalpel should be passed between its upper face and
the plantar stufuce of the third phalanx ; afterwards the toe-knife may be inserted in the
interval at the bulbs of the frog, so as to slightly raise the external border of the sole. This is
then seized by the pincers and pulled off, along with the frog, in a single piece, by a powerful
twisting movement, aided by the assistants, who press on the limb in a contrary direction.
A. Antekior Antibrachial Region.
In Solipeds, this region includes four extensor muscles. Two act on the
entire foot ; these are the anterior extensor and the oblique extensor of the meta-
carpus. Two others — the anterior and the lateral extensor of the phalanges—
terminate in the digital region.
1. Anterior Extensor of the Metacarpus (Extensor Metacarpi Magnus)
(Figs. 179, 11 ; 181, 15 ; 182, 9).
Synonyms — Epicondylo-premetacarpeus — Girard. It represents the two external radials
of Man. (Humero-metacarpeus — Leyh.)
Situation — Direction — Form — Structure. — This muscle, situated in front of
the radius, in an almost vertical direction, is composed of a muscular body and
a tendon. The first has the form of an inverted cone, is intersected by some
aponeurotic layers, and is composed of muscular fibres slightly arciform at their
superior extremities. The tendon, at first rounded, then flattened, commences
below the middle third of the radius, and succeeds the inferior extremity of the
muscular portion.
Attadiments. — This muscle has its fixed insertion : 1. By the upper extremity
of its fleshy fibres, on the crest that limits, behind and below, the musculo-spiral
groove of the humerus. 2. Above and in front of the inferior articular surface
of the humerus, by means of a strong fibrous band common to it and the
anterior extensor of the phalanges, and which expands on the deep face of these
324 THE MUSCLES.
two muscles in becoming intimately united with the capsular ligament of the
elbow articulation. Its movable insertion takes place on the anterior and
superior tuberosity of the large metacarpal bone, by the inferior extremity of its
tendon.
Relations. — The muscular portion is covered by the antibrachial aponeurosis
and the short extensor of the forearm. It covers the anterior face of the radius,
as well as the elbow articulation ; outwards and behind, it is in contact with the
inferior extremity of the short flexor of the forearm or humeralis obliquus, the
aponeurosis of which adheres intimately to the arciform portion of the fibres of
the anterior extensor of the metacarpus, and appears to attach this muscle to the
deltoid imprint. Its tendon covers a small portion of the anterior aspect of the
radius, and enters the internal vertical groove channeled in front of the inferior
extremity of that bone ; afterwards it passes over the capsular ligament of the
carpus, and is maintained against that membranous expansion by a wide fibrous
sheath, through which it glides by the aid of two synovial membranes (Fig. 183).
This tendon is crossed above the knee by that of the oblique extensor, which
passes to its surface.
Action. — The name of this muscle indicates its function ; it extends the
metacarpus on the forearm.
2. Oblique Extensor of the Metacarpus (Extensor Metacarpi
Obliquus) (Figs. 179, 13 ; 181, 21 ; 182, 14).
Synonyms. — Cubito-premetacarpeus, or radio-premetacarpeus — Girard. It is the repre-
sentative of the long abductor and short extensor of the thumb in Man. (Extensor metacarpi
obliquus vel parvus — Percivall. Badio-metacarpeus — Leyh.)
Situation — Form — Structure — Direction. — A small muscle situated at the
internal side of the radius, beneath the anterior extensor of the phalanges,
penniform in shape, strongly aponeurotic, and terminated by a tendon which
turns obhquely round the anterior aspect of the radius, in passing downwards
and inwards to reach the oblique channel on the inferior extremity of that bone,
and to pass thence to the inside of the knee.
Attachments. — It has its origin on the external side of the radius ; its
terminal tendon is fixed into the head of the internal metacarpal bone, by its
fibres becoming mixed with those of the internal ligament of the carpus.
Relations. — It is covered by the anterior extensor of the phalanges and
the antibrachial aponeurosis. It successively covers the anterior face of the
radius, the tendon of the anterior extensor of the metacarpus, the radial groove
lodging its tendon, and in which it glides by means of a small synovial bursa, as
well as the internal ligament of the carpus.
Action. — It extends the metacarpus, and may make it pivot from within
forwards.
3. Anterior Extensor of the Phalanges (Extensor Pedis)
(Figs. 179, 14 ; 181, 15 ; 182, 9).
Synonyms. — Epicondylo-prephalangeus — Girard. The extensor communis digitorum of
Man. (Eumero-prephalangeus — Leyh.)
Situation — Direction — Extent — For7n — Strticture. — This is a long vertical
muscle, situated external to and behind the anterior extensor of the metacarpus,
which it resembles in being composed of a fleshy and a tendinous portion. The
MUSCLES OF TEE ANTERIOR LIMBS. 325
muscular portion extends from the inferior extremity of the humerus to above
the lower third of the radius ; it is fusiform in shape, intersected by aponeurotic
layers, and bifid at its superior extremity.^ The tendinous portion forms two
unequal cords, which succeed the two terminal branches of the muscular part,
and lie closj to each other. These two cords enter the most external of the
three grooves in front of the inferior extremity of the radius, and reach the
anterior face of the carpal capsular ligament, against which they are maintained
by an annular ligamentous apparatus. After passing from beneath this ring, the
smallest, which is the most external, joins the tendon of the lateral extensor (Fig.
179, 15). The principal branch (Fig. 179, 14') continues its course on the
anterior aspect of the middle metacarpal bone and articulation of the fetlock,
until it arrives in front of the digit ; here it terminates on the os pedis, after
widening in a remarkable manner, and after receiving, laterally, at the middle of
the first phalanx, a reinforcing band which appears to be given off from the
inferior extremity of the suspensory ligament of the fetlock.
Attachments. — It has its fixed attachment by the superior extremity of its
muscular body. 1. Below the crest that limits, posteriorly, the musculo-
spiral groove of the humerus. 2. In front of the inferior extremity of the
humerus. 3. To the anterior border of the external ligament of the elbow-joint.
4. To the external and superior tuberosity of the radius. 5. To the external
border of that bone. Its principal tendon is inserted into the pyramidal process
of the third phalanx, after being successively attached to the capsular ligament
of the fetlock-joint and the anterior surfaces of the first two phalanges.
Relations. — The muscular portion, covered by the antibrachial aponeurosis,
covers the articulation of the elbow, the anterior face of the radius, and the
oblique extensor of the metacarpus ; it responds, in front, to the anterior
extensor of the same bone, to which it is intimately attached by its upper half •
behind, to the lateral extensor of the phalanges. The tendinous cords cover the
different parts already enumerated in describing the course of the muscle — that
is, the anterior face of the radius, the carpal joints, the principal metacarpal bone,
the articulation of the fetlock, and the first two phalanges. A vaginal synovial
membrane envelops them at the knee, to facilitate their gliding in the radial
groove and on the anterior aspect of the capsular ligament of the carpus ; while
the inner surface of the principal tendon is covered, in front of the fetlock, by a
small vesicular capsule, and, still lower, by the synovial membranes of the two
inter-phalangeal articulations.
Action. — This muscle extends the third phalanx on the second, that on the
first, and this again on the metacarpal bone. It may also concur in the extension
of the entire foot on the forearm.
(Two small muscles, which should be only considered as heads of this anterior
extensor, have been particularly described by Thiernesse and Phillips, and named
after these authors.
The 7nuscle of Phillips, according to Leyh, is long and thin ; it commences
on the lateral external ligament of the ulnar articulation and the external
superior tuberosity of the radius ; it is directed obliquely downwards and
forwards, lying beside the muscular portion of the common extensor. Towards
the middle and outer aspect of the radius, it gives off a small tendon, which
passes in the same sheath as the preceding, in front of the carpus, and continues
' This division, which has been noticed by several writers, has not been shown in Fig. 179
This is it mistake, us it is constantly present.
326 THE MUSCLES.
its course between the two tendons of the extensors of the phalanges to the near
fetlock, where it becomes mixed with that of the lateral extensor, a little above
the first phalanx.
The muscle of Thiernesse is smaller than that of Phillips, and situated at its
inner side. It arises, in front of the transverse ligament of the ulna, by a
muscular portion, becomes thinner as it descends, and terminates by a fine
tendon which is confounded with that of the common extensor, towards the
lower third of the forearm.)
4. Lateral Extensor of the Phalanges (Extensor Suffraginis)
(Figs. 179, 16 ; 182, 13).
Synonyms. — Cubito or radialis-prephalangeus, according to Girard. The extensor minimi
digiti of Man.
Direction — Situation — Extent — Form — Structure. — A small vertical muscle,
situated at the external side of the forearm, between the preceding and the
external flexor of the metacarpus, and formed of a fleshy body and a tendon.
The body, not very considerable, and flattened, extends from the upper extremity
of the radius to its lower fourth. The tendon (Fig. 179, 16'), at first rounded,
then flattened, reaches the gliding groove which divides the external inferior
tuberosity of the radius into two portions, passes to the external side of the
carpus, crossing the lateral ligament common to the articulations of this region,
and arrives at the anterior surface of the principal metacarpal bone, where it
receives the small tendinous branch detached from the anterior extensor, as well
as a strong fibrous band coming from the external side of the carpus (Fig. 179,
17). Afterwards, descending alongside the external border of the principal
tendon of its congener, and united to it by a fibrous fascia, it gains the articula-
tion of the fetlock, and expanding, terminates at the upper extremity of the first
phalanx.
Attachments. — 1. By its muscular body, to the external tuberosity of the
radius, the external ligament of the elbow articulation, and to the bodies of the
two bones of the forearm — origin. 2. By the inferior extremity of its tendon,
to the capsule of the metacarpo-phalangeal articulation, and in front of the
superior extremity of the first phalanx — termination.
Relations. — Its muscular portion, enveloped in a special aponeurotic sheath,
responds : in front, to the anterior extensor of the phalanges ; behind, to the
external flexor of the metacarpus, and the perforatus and perforans muscles ;
outwards, to the antibrachial aponeurosis. The tendon, surrounded by a vaginal
synovial sheath, in passing over the carpus, covers, beyond the knee, the anterior
aspect of the metacarpus and the anterior ligament of the metacarpo-phalangeal
articulation, over which it glides by means of a small vesicular synovial bursa.
It is covered by a slight fascia, which separates it from the skin, and which is
also spread over the tendon of the anterior extensor.
Action. — This muscle is an extensor of the digit, and also concurs in the
extension of the entire foot on the forearm.
In the Ass, this muscle is proportionately much smaller than in the Horse.
B. Posterior Antibrachial Region.
This is composed of five flexor muscles grouped vertically behind the bones
of the forearm. Three are situated superficially, and act on the whole of the
MUSCLES OF TEE ANTERIOR LIMBS. 327
foot ; these are the external flexor, oblique flexor, and the internal flexor of the
metacarpus. The other two, fixed to the digit by their inferior extremity, and
covered by the preceding, are designated the superficial and deep flexors of the
phalanges.
Superflcial Layer.
1. ExTEENAL Flexor of the Metacarpus (Flexor Metacarpi Externus),
OR Posterior UtNARis^ (Fig. 179, 18).
Synonyms. — Epicondylo-supercarpeus — Girard. (Humero-supercarpeus externus — Leyh.)
Situation. — The external flexor of the metacarpus is situated at the external
side of the forearm, between the lateral extensor of the phalanges and the
oblique flexor.
Form — Structure — Attachments. — This muscle is elongated from above to
below, flattened on both sides, thick in the middle, and intersected by very
strong aponeurotic bands. It commences on the summit of the epitrochlea by
a very powerful, but extremely short tendon. Inferiorly, it terminates by a
second tendon longer than the preceding, and divides into two branches, an
anterior and a posterior. The latter (Fig. 179, 20), short and wide, is inserted
into the pisiform bone in becoming mixed with the oblique flexor. The former
(Fig. 179, 19), roimded and funicular in shape, glides by means of a synovial
bursa in the channel excavated on the external aspect of the pisiform bone, and
which is converted into a canal by a little fibrous apparatus ; this branch is after-
wards fixed on the head of the external metacarpal bone, by being confounded
with the external hgament of the carpus.
Relations. — Covered by the antibrachial aponeurosis, this muscle covers the
two flexors of the digit. Its anterior border responds to the lateral extensor of
the phalanges ; the posterior to the oblique flexor. Its superior tendon lies
behind the external ligament of the elbow- joint, and is covered deeply by the
external cul-de-sac of the synovial capsule belonging to that articulation.
Action. — It flexes the foot on the forearm. (Leyh observes that it is more
particularly concerned in what is known as " high action.")
2. Oblique Flexor of the Metacarpus (Flexor Metacarpi Medius),
or Anterior Ulnaris (Fig. 180, 18).
Synonyms. — Epitrochlea supercarpeus — Girard. (Humero-metacarpeus internus — Leyh.)
Situation — Form — Structure. — This muscle, situated behind and within the
forearm, is an exact counterpart of the preceding in form and structure.
Direction. — Bourgelat has improperly named it an oblique flexor, for its direc-
tion is vertical like that of the other muscles of this region.
Attachments. — It has its origin : 1. On the base of the epitrochlea by the
tendinous fibres of its superior extremity. 2. On the olecranon, by a small, very
thin, and very pale fleshy band, which is annexed to the principal muscular body,
and soon unites with its posterior border. Its inferior tendon is undivided, and
' It is known that the bony eminences, hitherto termed in veterinary anatomy " epitrochlea "
and " epicondyle," correspond : the first, to the epicondyle of Man, the second, to the epi-
trochlea. It need excite no surprise, therefore, to see the denominations given by Girard to
the muscles of the posterior antibrachial region changed as above.
828 THE MUSCLES.
terminates on the pisiform bone, along with the external flexor, to which it is
intimately attached.
Relations. — By its superficial face, with the antibrachial aponeurosis, which
strongly adheres to its tendon ; by its deep face, with the flexors of the phalanges.
Its anterior border is covered by the internal flexor ; the posterior responds to
the external flexor.
Action. — It is a congener of the preceding.
3. Internal Flexor of the Metacarpus (Flexor Metacarpi Internus),
OR Palmaris Magnus (Fig. 181, 19).
Synonyms. — Epitrochlea metacarpeus — Girard. (Humero-metacarpeus internus — Leyh.)
Situation— Form — Structure — Attachments. — This muscle is situated within
the forearm, against the posterior face of the radius, and in its general features
resembles its congeners, the two preceding muscles. It is, however, not so wide,
is thinner, and less aponeurotic. Its upper extremity is fixed, by tendinous
fibres, to the base of the epitrochlea at the same point as the oblique flexor, with
which it is confounded — origin. Its inferior extremity terminates in a long, thin,
funicular tendon which passes through a fibrous sheath at the inner side of the
knee, and is inserted into the head of the internal metacarpal bone — movable
insertion.
Relations. — It is covered by the antibrachial aponeurosis, and covers the
oblique flexor, the perforatus and perforans, as well as important blood-vessels
and nerves. Its anterior border responds to the radius. A synovial sheath
envelops its terminal tendon, and facilitates its movements in the fibrous canal
through which it passes.
Action. — It is a congener of the preceding.
4. Superficial Flexor, Sublimis of the Phalanges, or Flexor Pedis
Perforatus (Figs. 179, 181, 182).
Synonyms. — Epitrochlo-phalangeus — Girard. (Humero-coronarls or humero-phalangeus —
Leyh.)
Situation. — The superficial flexor of the phalanges is situated, with its fellow,
the perforans, beneath the flexors of the metacarpus, which form around them a
kind of muscular envelope.
Form — Structure — Extent. — It is composed of a muscular and tendinous
portion. The first, long, thin, prismatic, and divided by a great number of
aponeurotic intersections, extends from the inferior extremity of the arm nearly
to the carpus. The tendon, continuous with the inferior extremity of the
muscular portion, receives at its origin an enormous fibrous production {superior
carpal or check ligam,ent), that arises from the eminence of insertion situated at
the posterior face of the end of the radius, and which contracts somewhat
intimate adhesions with the antibrachial aponeurosis, as well as with the
perforans.
After being thus reinforced, this tendon passes through the carpal sheath
and arrives behind the fetlock, where it forms a ring (Fig. 183, 21) for the
passage of the tendon of the deep flexor. To this peculiarity is owing the de-
signations of mrforatus and perforans., given to the two flexors of the phalanges.
MUSCLES OF THE ANTERIOR LIMBS.
Fig 183
Afterwards, it is inflected forwards over the sesamoid groove, and terminates by
two branches towards the middle of the digital region.
Attachments. — It takes its origin, in common with the perforans, at the
summit of the epitrochlea, and is inserted,
by the bifurcations of its tendon, into
the extremities of the pulley formed behind
the superior extremity of the second phalanx.
Relations. — The muscular portion,
covered by the external and the oblique
flexors of the metacarpus, may be said to
be embedded in the perforans, to which it
adheres in the most intimate manner. The
tendon covers that of the latter muscle, and
is in turn covered by the fibrous expansions
of the two metacarpal and metacarpo-
phalangeal sheaths, which are now to be
described.
Carpal sheath is the name given to a
very remarkable annular apparatus, formed
by the superficial face of the common pos-
terior ligament of the carpus, and by a thick
expansion of white fibrous tissue, together
constituting a perfect arch thrown across like
a bridge, from the pisiform bone to the inner
side of the carpus. This arch is continuous,
above, with the antibrachial aponeurosis,
and is prolonged, below, over the metacarpal
portion of the flexor tendons. An extensive
synovial membrane covers the internal aspect
of the carpal sheath, envelops the perforatus
and perforans in their passage through this
canal, ascends above the carpus, and descends
below the lower third of the metacarpal
region (Fig. 183, 4, 4), where it is insinuated
between the tendon of the perforans and its
carpal ligament. This synovial membrane
is strengthened in its middle portion by the
walls of the carpal sheath ; so that when
hypersecretion takes place in it, this is only
perceived by a swelling above the knee, ex-
ternally, between the posterior face of the
radius and the flexor muscles (Fig. 183, 3),
and another swelling at the tendons behind
the metacarpus.
The Metacarpo-phalangeal sheath is
formed by the sesamoid groove, the posterior
TENDONS AND SYNOVIAL SHEATHS OF THE
ANTERIOR LIMB OF THE HORSE.
M, Metcarpal bone ; El, lateral extensor of
the phalanges ; Ea, anterior extensor of
the phalanges ; Fs, tendon of the super-
ficial flexor of the phalanges (perforatus);
Fp, tendon of the deep flexor of the
phalanges (perforans) ; Ls, suspensory-
ligament of the fetlock. 1, Bursa for
the tendon of the anterior extensor of
the metacarpus ; 2, supero-external cul-
de-sac of the radio-carpal bursa; 3, superior cul-de-sac of the carpal bursa; 4, 4, inferior portion
of same ; 5, cul-de-sac of the capsule of the metacarpo-phalangeal articulation ; 6, 7, 8, superior,
middle, and inferior culs-de-sac of the sesamoid bursa; 9, inferior extremity of the same exposed
by excision of the reinforcing sheath of the perforans tendon.
330 THE MUSCLES.
face of the principal navicular ligaments, that of the glenoid fibro-cartilage of the
first interphalangeal articulaticn, and by the posterior pulley of the second
phalanx (Fig. 183, 5). It is completed by a very wide membranous expansion
applied against the flexor tendons, closely adherent to the perforatus on the
median line of the digit, and fixed, laterally, to the phalangeal bones by
the aid of three special fibrous bands (Fig. 184, 6, 7, 8). A very extensive
vaginal synovial membrane covers the internal walls of this passage, and is
reflected on the flexor tendons ; it ascends along these tendons to the inferior
extremities of the lateral metacarpals (Fig. 183, 6), and forms, inferiorly, a
somewhat large cul-de-sac which envelops the perforans tendon (Fig. 183, 9),
and behind the second phalanx lies against the posterior cul-de-sac of the
articular synovial membrane of the foot, and also against the superior cul-de-sac of
the navicular sheath (Fig. 137, 14). The metacarpo-phalangeal sheath is also
named the ffreat sesamoid sheath ; but this designation is more frequently
applied to the synovial membrane lining its walls. When this bursa is distended
by the fluid it secretes, it projects at all those points where it is not supported
by the fibrous walls of the metacarpo-phalangeal sheath. Then are formed above
the metacarpo-phalangeal articulation, and between the suspensory ligament of
the fetlock and flexor tendons, as well as below the fetlock — between the fibrous
bands which attach the sheath to the first phalanx — those small tumours named
"windgalls" (Fig. 183, 6, 7, 8). The inferior cid-de-sac (Fig. 183, 9) seldom
appears externally, as it is sustained by the reinforcing sheath of the perforans
tendon.
Action. — This muscle flexes the second phalanx on the first, that on the meta-
carpus, and the entire foot on the forearm. Its tendon, through the influence
of the fibrous band which attaches it to the posterior face of the radius, acts
mechanically as a stay while the animal is standing, by maintaining the meta-
carpo-phalangeal angle.
5. Deep Flexor of the Phalanges, or Flexor Pedis Perforans
(Figs. 179, 181, 182, 183).
Synonyms. — Cubito-phalangelis, or radio-phalangeus — Girard. (Humero-rndio-phdlangeus —
Leyh.)
Situation — Composition — Extent. — This muscle is situated immediately behind
the radius, and is composed of three portions which unite at the carpus, to be
continued to the inferior extremity of the digit by a long and powerful tendon.
Form, Structure, and Attachments of the muscular lioriion of the perforans. —
The three muscular portions may be distinguished, in regard to their origin, into
humercd, ulnar, and radial.
The humeral portion is the most considerable, and lies beside the perforatus ;
being three or four times the volume of that muscle, it is easily divided into
several very tendinous fasciculi, which leave the summit of the epitrochlea along
with the superficial flexor. The ulnar portion, situated between the external
flexor and the oblique flexor of the metacarpus, is very short and conoid, thick
at its superior extremity, contracted at its inferior, to which succeeds a long flat
tendon, united below to the principal tendon ; it has its origin on the summit
and the posterior border of the olecranon. The radial jwrtion (or radialis
accessorius) ^ is the smallest, and is deeply concealed beneath the epitrochlean
' It represents the flexor longus pollicis of Man.
MUSCLES OF THE ANTERIOR LIMBS.
muscular portion. The fibres composing it are fixed to the posterior surface of
the radius, where they are slightly divergent, and collect upon a small particular
tendon, which is confounded with the common tendon after contracting adhesions
with the radial band of the perforatus.
Course and Attachments of the tendon. — The tendon which succeeds these
three portions, enters the carpal sheath with that of the superficial flexor.
Towards the middle of the metacarpal region, it receives a strong fibrous band
from the great posterior ligament of the carpus (Figs. 179, 23 ; 182, 18),
traverses the sesamoid annular apparatus of the perforatus tendon
between the two terminal branches of that tendon, over
the pulley on the posterior face of the second phalanx,
and afterwards widens to form a large expansion desig-
nated the plantar aponeurosis.
This aponeurosis glides, by its anterior face, over the
inferior surface of the navicular bone, by means of a
particular synovial membrane — the navicular sheath —
and is covered, posteriorly, by a fibrous layer, noticed for
the first time by H. Bouley, who considered it a reinforcing
sheath for the perf orans tendon. It is finally inserted into
the semilunar crest of the os pedis, and the median
imprints situated behind this crest, becoming confounded
at its sides with the tissue of the lateral fibro-cartilages.
The navicular sheath is vesicular in form ; it covers
the navicular bone and the single ligament of the pedal
articulation, becomes reflected on the plantar aponeurosis
in front of this ligament, and ascends to the inferior cul-
de-sac of the sesamoid sheath, where it is again reflected
and continued by itself. It therefore forms two cids-de-
sac — one superior, the other inferior — which are readily
perceived in a longitudinal and vertical section of the digital
region (Fig. 137, 15, 16). The first is in contact with
the posterior cul-de-sac of the synovial membrane of the
pedal articulation, and is separated from the inferior sac
of the sesamoid sheath by a transverse layer of yellow
fibrous tissue, which attaches the perf orans tendon to the
posterior face of the second phalanx. The second is
situated beneath the interosseous ligament which unites
the navicular bone to the third phalanx.
The reinforcing sheath of the perforans tendon is
formed by a fibrous membrane, applied against the pos-
terior face of the plantar aponeurosis. This membrane
adheres intimately below, to the expansion it covers, and
ends in becoming entirely confounded with it. It is fixed,
at its borders, to the inferior extremity of the first phalanx, by means of two
lateral bands (Fig. 184, 3, 4), and to the metacarpo-phalangeal sheath by a small
median band. The latter passes on to the lower end of the great sesamoid
synovial sheath, and divides it into two lobes, which are very visible when the
sheath has been distended by injection.
Relations. — The epitrochlean muscular portion is covered, at its origin, by
the external cul-de-sac of the elbow-joint, which sac also covers the other muscles
FLEXOR TENDONS OF THE
PHALANGES IN THE HORSE.
I, Perforatus tendon ; 2,
tendon of the perforans
at its exit from between
the two branches of the
perforatus ; 3, 3, its in-
sertion in the semilu-
nar crest ; 4, 4, the two
lateral bands of its re-
inforcing sheath ; 5, 5,
fibrous expansion of the
metacarpo - phalangeal
sheath ; 6, 7, 8, its lateral
bands ; 9, 9, suspensory
ligament of the fetlock.
332 THE MUSCLES.
attached to the epitrochlea — the external and oblique flexors of the metacarpus.
It responds, anteriorly, with the radius and radial portion of the muscle ; pos-
teriorly, with the perforatus ; externally, with the external flexor of the meta-
carpus ; inwardly, with the internal and oblique flexors of the same ray.
The ulnar portion, covered by the antibrachial aponeurosis, covers the epi-
trochlean portion.
The radial division is comprised between the latter and the posterior face of
the radius.
The tendon is in contact, posteriorly, with that of the perforatus ; anteriorly,
with the posterior ligament of the carpus, the suspensory ligament of the fetlock,
and the sesamoid groove ; by its sides, with the vessels and nerves of the digit.
Its terminal expansion is covered by the plantar cushion, which adheres to it, in
front, in the most intimate manner ; it covers the navicular bone.
Admis. — This muscle flexes the phalanges on one another and on the meta-
carpus. It also concurs in the flexion of the entire foot on the forearm. The
band which attaches its tendon behind the carpus, as well as its phalangeal rein-
forcing sheath, gives it the mechanical power necessary to support the angle of
the metacarpo-phalangeal articulation and the digital region, while the animal is
in a standing posture.
(In the " Deep Flexor," of Chauveau's description, we find included two
portions which are separately named and described by Percivall and Gurlt.
These are the ulnaris accessorius and radlaUs accessorius of the former, and the
cuUto-ulnar and radial branches of the latter. These, in reality, are portions
of the perforans, and have been so designated in this treatise. Though arising
independently, they terminate in the perforans tendon before it leaves the carpal
sheath, and join with it in flexing the metacarpus and phalanges.)
DiFFEKENTlAL CHARACTERS IN THE MuSCLES OF THE FOREARM IN THE OTHER AnIMALS.
A. Ruminants. — In the Ox, Sheep, and Camel, the anterior extensor of thp. metacarpus
comports itself as in Solipeds.
The oblique extensor of the same region, terminates inside the upper extremity of the prin-
cipal metacarpus.
The anterior extensor of the phalanges offers a remarkable arrangement. It is divided
throughout its leugtb into two parallel portions: an external, which forms the common extensor
of the digits ; and an internal, the proper extensor of the internal digit.
a. The fleshy body of the common extensor (Fig. 185, 3) is a little more voluminous than
that of the second muscle. Its tendon (3') commences near the inferior third of the radius,
passes over the knee, tlie metacarpal bone, and the metacarpo-phalangeal articulation. On
arriving at tlie origin of the digits it bifurcates, and each of its branches goes to be inserted
into the pyramidal process of tlie third phalanx (3"). This muscle, in extending the digits, brings
them together, as Lecoq has judiciously remarked.
b. The proper extensor of the internal digit (Fig. 185, 4) much resembles the common
extensor in volume, form, and direction. Its tendon (4') passes, with that terminating the
latter muscle, into one of the inferior grooves of the radius and over the capsular ligament of
the carpus, where the two cords are enveloped by a common synovial sheath. Arrived at the
metacarpo-phalangeal articulation, this tendon is placed at the eccentric side of the internal
digit, and descends, gradually expanding, until it reaches the inferior extremity of this bone;
towards the middle of the first phalanx, it receives from the suspensory ligament of the fetlock
two constraining bands similar to those which, in Solipeds, bind the anterior extensor of the
phalanges on the same bone. This tendon bifurcHtes inferiorly ; one of its branches is attached
to the anterior face of the second phalanx ; tlie other, much wider than tiie first, covers the
common external lateral ligament of the two inter-phalaugeal articulations, and terminates on
the whole external side of the third phalanx. In the Sheep, this second branch is slender, and
is directed towards the heel, which it envelops by uniting its iibres with the perforans tendon
and the plantar cushion.
MUSCLES OF TEE ANTERIOR LIMBS.
Fig. 185.
The lateral extensor of the phalanges of Ruminants is thicker than in the Horse, and con-
stitutes tlie proper extensor of the external digit (Fig. 185, 5). Its terminal tendon (4', 6, 7)
comports itself exactly the same as thnt of the proper extensor of the internal digit, and, con-
sequently, does not merit special description. We may remark,
with Lecoq, that tiiese two muscles separate the digits from
each other in extending tliem; they are, therefore, to a certain
point, antagonists of the common extensor.
The oblique flexor of the metacarpus in the Camel has a
very thin ulnar portion, rather aponeurotic tliau muscular.
The inferior tendon of that muscle, at its insertion into the pisi-
form bone, detaches a baud to the internal border of the carpus.
In this animal, the internal flexor is attached to the superior
extremity <>f the internal border of the metacarpus.
The perforatus of the Ox and Sheep is composed of two por-
tions, the tendons of which unite towards the middle of tlie
metacarpal region. The single tendon (Fig. 186, 1, 2, 3) which
results from this union afterwards divides into two branches,
each of which comports itself, in regard to the digits, as the
single perforatus tendon does in the Horse, except tliat they
receive from the suspensory ligament a fibrous band analogous
to that which, in Solipeds, goes to the perforans tendon. This
band (Fig. 185, 13) concurs in the formation of the annular
ligament through which the latter tendon passes.
In the Camel, the muscular portion of tiie perforatus is not
present, but is represented by a tendinous band, the arrangement
of which is curious. It arises from the common posterior liga-
ment of the carpus, and at its origin adheres firmly to the branch
of the suspensory ligament of the fetlock which descends from the
pisiform bone ; it goes behind the perforans tendon, where it is
completely covered by a very strong white membrane, and about
the middle of the metacarpus it divides into two branches which
separate at a very acute angle. Each of these branches glides in
the sesamoidean sheath, the posterior wall of which is formed
by a strong layer that is attached to the sides of the suspensory
ligament and sesamoid bones. Below these bones, these two
branches bifurcate in their turn : whence results four branches,
which are inserted by pairs into the upper extremity of the two
secondary phalanges, as in the other Ruminants.
In the Ox, tlie terminal tendon of the perforans does not
receive any carpal band ; this goes to the perloratus. Above the
fetlock, it divides into two branches, one for each digit, which,
after traversing the perforatus, terminates behind the inferior
face of the third phalanx. There it is blended with the plantar
cushion, the inferior interdigital ligament, and a fibrous fascia
already noticeil in the description of that ligament. This layer
arises from the aponeurosis covering the flexor tendons in the
metacarpal region ; it descends on the heels, behind and outside
the digits, remains united to that of the other digit by an in-
termediate fibrous fascia, and is attached to the enveloping
sheaths of the flexor tendons, as well as to the superior inter-
digital ligament. Each terminates inferiorly, in becoming
united to the proper extensor of the digit, the plantar cushion,
the inferior digital ligament, and the deep flexor of the
phalanges.
There is not, properly speaking, a phalangeal reinforcing
sheath ; though we may consider as such the superior fasciculi
of the inferior interdigital ligament (Fig. 186, 6).
Of the three portions of the perforans in the Camel, the
MUSCLES OF THE FOREARM OP
THE OX (INTERNAL FACE).
1, Anterior extensor of the
metacarpus ; 1', insertion of
its tendon ; 2, oblique ex-
tensor; 3, common extensor
of the digits ; 3', its tendon ;
3", termmal bifurcation of
that tendon ; 4, proper ex-
tensor of the internal digit ;
4', its tendon ; 5, proper
extensor of the external
digit ; 5', its tendon ; 6, its
branch of insertion into the
second phalanx ; 7, branch
to the third phalanx; 8,
external flexor of the meta-
carpus ; 9, olecranian por-
tion of the perforans ; 10,
tendon of the perforans ;
11, tendon of the perforatus;
12, suspensory ligament of
the fetlock; 13, the band
it furnishes to the per-
foratus to form the ring through which the perforans passes ; 14, the external band it gives
off to the proper extensor of the external digit ; 15, flexor brachii ; 16, anterior brachial ; 17,
24
334
THE MUSCLES.
radial is the largest. The tendons of the three divisions become united in the carpal sheath,
and the resulting tendon is easily divisible into two as far as the middle of the metacarpus;
there it bifurcates, each branch passing into the terminal bifurcation of the band which repre-
sents the perforatus and goes to be inserted into the third phalanx, where it is covered by a
small reinforcing sheath.
B. Pig (Fig. 187). — In this animal, the anterior extensor tendon of the phalanges passes to the
superior extremity of the inner large metacarpal bone, and that of the oblique extensor to the small
internal metacarpal.
Instead of the anterior extensor of the -phalanges, four muscles are found —
1. The proper extensor of the great internal digit alongside the anterior extensor of the
metacarpus ; its tendon terminates in an expansion on the outside of the great internal digit,
after receiving, inwardly, a band from the corresponding interosseous muscle. It gives off,
towards the middle of the metacarpus, a very thin branch which
goes to the outside of the small internal digit.
2. The proper extensor of the great external digit, the largest
of tlie four, terminates in the same manner as the preceding, on
the outside of the great external digit.
3. The common extensor of the two internal digits, is con-
tinued by a tendon which bifurcates above the metacarpus, and
gives off a branch that reaches the pyramidal process of the small
phalanx of the internal digit, while the other branch — the most
important — passes into the space between the metacarpals of the
great digits, and bifurcates, in its turn, in front of the metacarpo-
phalangeal articulation, to terminate on the pyramidal process of
each of the great digits.
4. The common extensor of the two external digits, much
smaller than the preceding, is in great part concealed beneath the
proper extensor of the great external digit. Its somewhat thin
tendon bifurcates in front of the metacarpus, to give a branch to
the small external digit, going to the pyramidal process ; and a
second branch that goes to the principal tendon of the preceding
muscle, from which it soon becomes detached to gain the small
phalanx of the great external digit.
Lastly, there is in the Pig a representative of the proper
extensor of the thumb and index, but its tendon — the thickness
of a thread — is lost in that of the common extensor of the two
internal digits.
There is also a round pronator along the anterior border of
the internal ligament of the elbow-joint, as well as a short supi-
nator. The latter, extremely thin, has no humeral insertion ; it is
thrown diagonally on the anterior and upper face of the radius.
With regard to the tendon of the lateral extensor of the pha-
langes, or proper extensor of the external digit, this spreads out on
the outer face of that digit.
With regard to the muscles of the posterior antibrachial region,
it is remarked that : 1. The anterior branch of the terminal tendon
of the external flexor of the metacarpus passes to the head of
the outer metacarpal bone. 2. The internal flexor terminates on
the metacarpal of the great external digit. 3. The perforatus ia
formed by two muscular bodies, each terminated by a tendon in-
serted, inferiorly, into the second phalanx of one of the great digits. 4. The perforans is
divided into four terminal branches, which arrive at the last phalanx of the great and small
digits.
The external flexor of the metacarpus is almost transformed into a flat fibrous cord, extending
from the epitrochlea to the pisiform bone, and to the outer side of the carpus, where it expands.
The oblique flexor of the metacarpus is reduced to a thin muscular cord without an ulnar
insertion.
The internal flexor of the metacarpus, the most developed of the three, is inserted below on
the metacarpal of the small internal digit.
The muscular portion of the perforatus throws off a fasciculus to the perforans, and bifurcates
inferiorly ; the superficial branch passes out of the carpal slieath, and terminates by a tendon,
in the ordinary manner, on the second phalanx of the great external digit ; the deep branch
TENDINOUS AND LIGAMEN-
TOUS APPARATUS OF THE
POSTERIOR FACE OF THE
DIGITAL REGION IN THE
OX (POSTERIOR LIMB).
1, Perforatus tendon ; 2, 2,
its terminal branches ;
3,' 3, their bifurcation ;
4, 4, perforans ; 6, 6, su-
perior bands of the in-
ferior digital ligament
attached to the first pha-
lanx ; 7, inferior inter-
digital ligament ; 8, 8,
suspensory ligament of
the fetlock.
MUSCLES OF THE ANTERIOR LIMBS. 335
furnishes a fasciculus to tl,e perforans, after which it enters the carpal sheath with the latter,
ami terminates on the great internal digit.
The perforans presents an epitrochlean portion, divided into two fasciculi, between which
is interposed the perforatus— an ulnar portion very like that of the Horse, but inserted to
tlie inner side of the olecranon ; and an extremely rudimentary radial portion. These three
portions unite into a common tendon which, on reaching the middle of the metacarpus, quadri-
furcates to give a branch to each of the digits ; the two branches for the small digits pass
beneath a band which, from the sesamoid bones, is carried to the inner side of the second
plialanx, and takes the place of the ring of the perforatus.
Co Camivora.— In the Dog and Cat, the anttrior extensor of the metacarpus divides, at
Fig. 187.
ANTERIOR ANTIBRACHIAL REGION OF THE PIG (EXTERNAL AND INTERNAL FACES).
1, Anterior extensor of the metacarpus ; 2, oblique extensor of the metacarpus ; 3, proper extensor
of the great internal digit ; 3', its tendon, which gives off a thin branch to the small internal
digit; 4, proper extensor of the great external digit; 4', its tendon; 5, common extensor of the
two internal digits; 5', its tendon before bifurcation; 6, common extensor of the two external
digits ; 6', its tendon before bifurcation ; 7, proper extensor of the small external digit (lateral
extensor of the phalanges) ; 7', its tendon.
its lower extremity, into two branches, which exactly resemble those of the terminal tendons of
the two external radial muscles of Man : one is inserted into the metacarpus of the index, the
other into the metacarpus of the medius (Fig. 188, a, 5, 6, 7).
The oblique extejisor passes to the metacarpus of the thumb ; it furnishes, besides, a small
particular branch that glides, by means of a sesamoid, over the third bone of the inferior row
of the carpus, and is blended with the posterior ligament of the carpus (Fig. 188, a, 8 ; B, 4 ;
D, 8); it separates the thumb from the other digits, but we think it scarcely adapted for the
function of extensor.
The anterior extensor of the phalanges of Solipeds is replaced by a single muscle, the com-
mon extensor of the digits, terminated by a quadrifurcated tendon, whose branches are distributed
to the four great digits (Fig. 188, a, 9, 9').
The tendon of the lateral extensor is divided into three branches, which are inserted on the
anterior face of the three outer digits, and are blended with the tendons of the common
336 THE MUSCLES.
extensor, or with the fibrous bands furnishecJ to tliese tendons by the interosseous metacarpal
muscles.
The external flexor of the metacarpus comports itself as in the Pig. But tlie oblique flexor
is covered by the perfoiatus, and its olecranian portion, thicker than in tlie other animals, is
only united to the principal fleshy body altogether inferiorily. The internal flexor is slender
and conoid ; its tendon, thin and long, reaches the metacarpus of the index.
The 'perforatum of the Dog und Cat has a long, wide, and superficial body, separated from
the perforans by the oblique flexor of the metacarpus. Its tendon passes outside the carpal
sheath, and is divided into four branches, attached by their inferior extremity to the second
phalanx of the four principal digits.
For the perforans, it is noted :
1. That the radial portion of the muscle (the long flexor of the thumb in Man) commences
towards the superior extremity of the radius (Fig. 188, c, 4).
'2. That the ulnar division is a semi-penniform muscle, attached by the superior extremities
of its fibres to nearly the whole extent of the posterior face of the ulnar (Fig. 188, c, 3).
3. That the epitrochlean portion sends off, above tlie knee, a small particular fasciculus
terminating in a very thin tendon, which becomes lost in the fibrous arch of the carpal sheath
(Fig. 188, c, 6). This small muscle represents the palmaris brevis of Man.
The terminal tendon divides into five branches, one for each digit (Fig. 188, d, 4, etc.).
There have been already described in these animals :
1. Two external radial muscles, only distinct at their terminal extremity, and confounded
for the remainder of their extent. This is the anterior extensor of the metacarpus in Solipeds
(Fig. 188, A, 5, 6, 7).
2. A long abductor of the thumb, which appears to be the representative of the analogous
muscle, and the short extensor of the same digit in Man. It is the oblique extensor of the
metacarpus in the Horse (Fig. 188, a, 8).
3. A common extensor of the digits ; the anterior extensor of the phalanges in the Horse
(Fig. 188, A, 11).
4. A proper extensor of the three external digits, the proper extensor of the little finger in
Man, or lateral extensor of the phalanges in the Horse (Fig. 188, a, 10).
5. A posterior ulnar, or external flexor of the metacarpus in the Horse (Fig. 188, a, 13).
6. An anterior ulnar, or oblique flexor of the metacarpus in the Horse (Fig. 188, D, 6).
7. A great palmar, corresponding to the internal flexor of the metacarpus in the Horse
(Fig. 188, B, 8).
8. A small palmar, a dependency of the deep flexor of the phalanges (Fig. 188, c, 6).
9. A flexor suhlimis of the phalanges (Fig. 188, D, 1).
10. A deep flexor of the phalanges (Fig. 188, c. .5 ; D, 3).
11. A long flexor of the thumb, united to the preceding muscle (the radial portion of the
perforans (Fig. 18S, c, 4).
But in Carnivora there are five additional museles, which are not generally found in the
other animals. These are : the proper extensor of the thumb and index, long supinator, short
supinator, round pronator, and the square pronator. A special description will be given of these.
Muscles proper to the Forearm of Carnivora.
1. Proper Extensor of the Thumb and Index (Fig. 188, a, 11; b, 3).
Synonyms. — The extensor secundi internodii pnUicis and extensor indicts of Man.
This is a very small muscle, composed of a fleshy body and a tendon. The first is thin and
fusiform, and is situated under the lateral extensor; it has its origin with the oblique extensor
of the metacarpus at the external side of the radius. The tendon crosses the anterior aspect of
the knee, enveloped by the synovial sheath of the common extensor of the digits, under which
it passes. It divides into two branches, one of which goes to the thumb, the other to the index.'
2. Long Supinator (Fig. 188, a, 12; c, 8).
This muscle only exists in the rudimentaiy state in Carnivora. Its existence in the Dog
has even been denied, but this is an error; our researches have demonstrated that it is present,
in a more or less evident manner, in all breeds.
It is a very delicate baud, situated in front, and on the inner side of the anterior extensor
' In very powerful Horses, and more frequently in the Ox, we have met with traces of this
muscle in the form of a deep fasciculus situated in front of the lateral extensor.
MUSCLES OF THE ANTERIOR LIMBS.
Fig. 188.
B C.
337
MUSCLES OF THE FOREARM AND PAW OF THE DOG.
i. Anterior superficial region.— 1, Short flexor of the forearm (iinterior brachial) ; 2, long flexor of
the forearm (brachial biceps) ; 3, anconeus ; 4, round pronator ; 5, anterior extensor of the
metacarpus (external radial) ; 6, its tendon of insertion, destined for the lourth metacarpal l.one ;
7, that which goes to the third ; 8, external oblique of the metacarpus (long abductor and short
extensor of the thumb); 9, common extensor of the digits; 9', its terminal tendon at the point
where it divides into four branches ; 10, proper extensor of the three external digits, or lateral
extensor of the phalanges in the horse ; 10', its terminal tendon at the commencement of its
trifurcation ; 11, proper extensor of the thumb and index; 11', its terminal tendon; 12, 12, long
supinator ; 13, external flexor of the metacarpus (posterior ulnar).
B. Deep anterior region.— I, Round pronator ; 2, short supinator ; 3, proper extensor of the thumb
and index ; 4, oblique extensor of the metacarpus ; 5, superior insertion of the anterior extensor
of the metacarpus ; 6, ditto of the anterior extensor of the phalanges ; 7, proper extensor of the
three external digits; 8, internal flexor of the metacarpus (great palmar); 9, levator humeri;
10, 11, long and short flexors of the forearm.
C. Deep posterior region. — 1, Round pronator ; 2, square pronator ; 3, ulnar portion of the perforans ;
4, radial portion of the same (long flexor of the thumb) ; 5, terminal tendon of the same; 6,
tendon of the small palmar (division of the perforans) ; 7, anterior extensor of the metacarpus ;
8, long supinator ; 9, epicondyloid insertion of the perforatus, perforans, and oblique and internal
flexors of the metacarpus; 10, olecranian insertion of the oblique flexor; 11, supercarpal inser-
tion of the same; 12, terminal tendon of the internal flexor ; 13, proper extensor of the external
digits ; 14, coraco-radialis ; 15, tendon of the extensors of the forearm.
D. Superficial posterior region, and the special muscles of the foot or hand. — 1, Perforatus; 1', its
tendon divided at its passage behind the carpal sheath; 2. ditto, its terminal branches; 3, per-
forans ; 3', its tendon divided after its exit from the carpal sheath ; 4, ditto, its terminal branches ;
5, tendon of the internal flexor of the metacarpus ; 6, oblique flexor (anterior ulnar) ; 7, inferior
extremity of the long supinator; 8, terminal tendon of the oblique extensor of the metacarpus;
9, short abductor of the thumb; 10, opponent of the thumb; 11, short flexor of the thumb;
12, adductor of the thumb, transformed, in the dos, into the adductor of the index ; 13, short
flexor of the small digit; 14. adductor of the small digit; 15, opponent of the small digit;
16, 16 metacarpal interosseous muscles, a, a, a. Bands which maintain the flexor tendons on
the metacarpo-phalangean articulations, and limit the separation of the digits; collectively, they
represent, in a rudimentary state, the palmar aponeurosis of Man.
338 THE MUSCLES. '
of the metacarpus, taking its origin, along with that muscle, from the crest limiting the
musculo-spiral groove of the humerus, behind the ridge ; and terminating within the inferior
extremity of the radius by fleshy and aponeurotic fibres. This small muscle can have but a
very limited influence on the movements of the bones of the forearm, because of its trifling
volume. As its name indicates, it acts in supination.
3. Short Supinator (Fig. 188, b, 2).
A triangular and slightly divergent muscle, covered by the anterior extensor of the meta-
carpus and the common extensor of the digits. It has its origin in the soiall fossa situated
outside tlie humeral trochlea, by a flat tendon which is confounded with the external lateral
ligament of the elbow-joint. It terminates above the anterior face and the inner side of the
radius, by the inferior extremities of its fleshy fibres. Covered by the two preceding muscles,
it covers the elbow articulation and the bone receiving its insertion. It ought to be considered,
in Carnivora, as the principal supinator; it pivots the radius on the ulna, so as to turn the
anterior face of the first bone outwards.
4. Round Pronator (Fig. 188, b, 1 ; c, 1).
Situated on the inner and upper part of the forearm, between the great palmar or internal
flexor of the metacarpus and the mterior extensor of the same ray, the round pronator is a
thick and short muscle, which originates on the small, epicondyloid tuberosity of the humerus,
and terminates at the internal side of the radius by aponeurotic fibres.
5. Square Pronator (Fig. 188, o, 2).
This muscle is situated immediately behind the bones of the forearm, beneath tlie muscular
masses of the posterior antibrachial region. It extends from the insertion of the flexors of the
forearm to near the carpus, and is formed of transverse fibres which pass directly from the
ulna to the radius. It is, then, no longer, as in Man, a square muscle attached only to
the lower fourth of these two bones. The two pronators are antagonists of the short supinator,
turning forwards the anterior face of the radius and metacarpus.
Comparison of the Muscles of the Forearm of Man with those of Animals.
All the muscles of the forearm of Man are more or less perfectly represented in the forearm
of Carnivora.
In Man, these muscles are described in placing the forearm in a state of supination, and
are divided into three regions : anterior, external, and posterior.
1. Anterior Region.
This comprises eight muscles :
1. The round pronator, absent in animals except the Carnivora. This muscle forms the
internal oblique prominence in the bend of the elbow. It leaves the epitrochlea and the
coronoid process of the ulna, terminating on the middle third of the external face of the radius.
2. The great palmaris, which corresponds to the internal flexor of the metacarpus of the
Horse. Situated within the preceding, it is attached, above, to the epitrochlea ; below, to the
base of the second metacarpal. It is more especially a flexor of the hand.
3. The small palmaris, the presence of which is not constant, and is represented in the Dog
by a portion of the deep flexor of the phalanges.
4. The superficial flexor or perforatus has two planes of muscular fibres. The superficial
plane is destined to the tendons of the medius and annularis ; the deep plane to the tendons
of the index and little finger. These tendons are fixed into the secondary phalanges of the
above-named digits.
5. The anterior ulnar resembles the oblique flexor of the metacarpus of the Horse. It is
inserted, above, into the epitrochlea and the olecranon; below, in the pisiform bone. Its
action is transmitted, by a fibrous band, from this bone to the fifth metacarpal. It flexes the
hand by inclinin"; it inwards.
6. The deep flexor or perforans is resolved into two fasciculi : one, the internal, for the little
finger, the annularis, and the medius; the other, the external, for the index. The three first
tendons are at first united to each other by fibrous bands, and together pass through a sheath
formed by the perforatus.
7. The proper flexor of the thumb, represented in the Dog by the radial portion of the
perforans. It is attached, for one part, to the upper three-fourths of the anterior face of the
radius, the interosseous aponeurosis, and the coronoid process of the ulna ; on the other part,
to the second phalanx of the thumb.
MUSCLES OF THE ANTERIOR LIMBS.
8. The square pronator, a thick, quadrilateral muscle with transverse fibres, situated at the
deep and inferior portion of the forearm. This muscle in the Dog is much more extensive in
length.
2. External Region.
The muscles of this region are four in number, two of which, the supinators, are only
represented in Carnivorous animals : —
I. The long supinator forms a prominent mass at the bend of the elbow. It is attached to
Fig. 189.
Fig. 190.
BCPEBFICIAL MUSCLES OF HUMAN FOREARM.
1, Biceps, with its tendon ; 2, Vjrachialis an-
ticus ; 3, triceps ; 4, pronator radii teres ;
5, flexor carpi radialis ; 6, palmavis lon-
gus ; 7, a fasciculus of flexor sublirais
digitorum ; 8, flexor carpi ulnaris; 9,
palmar fascia; 10, palmans brevis ; 11,
abductor pollicis; 12, flexor brevis pol-
licis ; 13, supinator longus ; 14, extensor
ossis metacarpi, and extensor primi inter-
nodii pollicis.
DEEP LAYER OF SUPERFICIAL MUSCLES OF
HUMAN FOREARM.
1, Internal lateral ligament of elbow-joint ;
2, anterior ligament ; 3, orbicular ligament
of radius ; 4, flexor profundus digitorum ;
5, flexor longus pollicis ; 6, pronator quad-
ratus ; 7, adductor pollicis ; 8, dorsal in-
terosseous of middle, and palmar inter-
osseous of rmg, finger ; 9, dorsal inter-
osseous muscle of ring-finger, and palmar
interosseous of little finger.
the inferior third of the external border of the humerus, and to the base of the styloid procesB
of the radius. It is a flexor of the forearm, not a supinator, as its name indicates.
2. The first external radial is represented by a portion of the anterior extensor of the
metacarpus of animals. It commences at the inferior part of the external border of the humerus,
and terminates at the posterior part of the base of the second metacarpal.
3. The second external radial, also represented by a portion of the anterior extensor of the
metacarpus, terminates at the base of the third metacarpal.
4. The short supinator, a muscle bending round the upper third of the radius, is the
essential agent in supination.
340 THE MUSCLES.
3. Posterior Region.
The muscles of this region, divi8il)le into two layers, are:—
1. Tiie common extensor of the digits— &\denoT extensor of the phalanges of the Horse —
divided iiito four tendinous branches which pass to all the fingers, except the thumb.
2. The proper extensor of the little finger, whose tendon is joined to the brancli of the
common exlen^or tliat passes to the auricularis — the lateral extensor of animals.
3. The posterior ulnar, corresponding to the external iiexor of the metacarpus of tiie Horse.
It goes to the epicondyle at the upper extremity of the fifth metacarpal.
4. Tiie long abductor of the thumb, resembling a portion of the oblique extensor of the
metacarpus of animals. This muscle is attached to the posterior face of the ulna and radius,
and the upper extremity of the first metacarpal.
5. The short extensor of the thumb, which is also represented in animals by a portion of the
oblique extensor of the metacarpus.
6. The long extensor of the thumb, arising from the ulna, and inserted into the second
phalanx of the thumb. This muscle limits, inwardly, the excavation termed the anatomical
snuff-hox.
7. Tiie proper extensor of the index, whose tendon is confounded with the branch of the
common extencor passing to this digit.
These two latter muscles, blended in the Dog, exist only in a rudimentary state in the
other animals.
We will say nothing of the anconeus, placed in the antibrachial region by anthropotomists,
and which has been described in the posterior brachial region.
Muscles of the Anterior Foot or Hand
These will be studied successively in Carnivora, the Pig, Solipeds, and Ruminants.
A. Muscles of the Anterior Foot or Hand of Carnivora.
All the muscles of the human hand are found in that of Carnivora, tome perfectly developed,
others quite rudimentary. These muscles are: 1. The short abductor of the thumb. 2. The
opponent of the thumb. H. The short flexor of the thumb. 4. An adductor of the index— adductor
of the thumb in Man. 5. The cutaneous palmar. 6. The adductor of the small digit. 7. The
short flexor of the small digit. S. The opponent of the small digit. 9. The thvee lumbr id. 10.
Four interosseous metacarpals.
1. Short Abductor of the Thumb (Fig. 188, d, 9).
This is rudimentary, like the digit it is intended to move, and is situated behind the
metacarpal bone of the thumb ; it is composed of very pale fleshy fasciculi, which are continued
inferiorly by some tendinous fibres. It has its origin at the carpal arch, and terminates on the
metacarpal bone of the thumb, as well as at the external side of the superior extremity ' of the
first phalanx. It is a flexor and abductor of the thumb.
2. Opponent op the Thumb (Fig. 188, d, 10).
This vestige of the thick short muscle which bears the same name in Man is situated
beneath and within the preceding, in a slightly oblique direction downwards and outwards.
Pale and almost entirely muscular, it is attached to the posterior ligament of the carpus and
the metacarpal bone of the thumb. Owing to the conformation of this digit in Carnivora, this
muscle cannot act as it does in Man in producing the opposition of the thumb ; it only draws
it towards the axis of the hand, and is therefore merely an adductor of the thumb.
3. Short Flexor of the Thumb (Fi^'. 188, d, 11).
A very small muscle, deeper in colour than the other two, and situated between them, the
adductor of the index, and the fourth interosseous muscle. It is fixed, by its superior extremity,
in the mass of the posterior carpal ligament, and attached, below, to the internal side of the
first phalanx. It is a somewhat extensive flexor of the thumb.
4. Adductor op the Index (Fig. 188, d, 12).
Synonym.— The adductor of the thumb in Man.
Elongated, prismatic, compressed on each side, included between the third and fourth
' It is necessary to remember that the position of the digits is considered in relation to the
axis of the hand— that is, the median line separating the medius from the annularis.
MUSCLES OF THE ANTERIOR LIMBS. 341
interosseous muscles, and concealed by tlie tendinous portion of the common flexor of the
digits, this muscle is attached, superiorly, to the posterior carpal ligament with the third
interosseous muscle. It is fixed, inferiorly, by means of a small flattened tendon, along the
superior and internal side of the first phalanx of the index. It is regarded as the adductor of
the thumb in Man transformed into an adductor of the index, in consequence of the atrophy of
the fifth digit.
5. Cutaneous Palmar (Palmaris Brevis).
A thick, hemispherical, musculo-adipose body, forming the base of the exterior tubercle
placed behind the carpus. It adheres intimately to the skin by its superficial face, and deeply
to the aponeurosis covering the muscles of the hand.
6. Adductor of the Small Digit (Fig. 188, d, 14).
This muscle is superficially situated, external to, and behind the outer metacarpal bone, and
is composed of a thick, conical fleshy body, concave on its anterior surface, convex posteriorly,
and of a long, thin, and flat tendon, which succeeds tlie inferior extremity of the muscular
portion.
It is attached, by the superior extremity of the latter, to the pisiform bone; the tendon
terminates out»i le the superior extremity of tiie first phalanx of the small digit.
This muscle separates that digit from the axis of the hand, and is therefore an abductor
and not an adductor, as its name would indicate. That name has been given to it in Man,
because the hand has been considered in a state of supination, a position in which it is
effectively an adductor in regard to the median plane of the body. If this name has been
preserved here, it is owing to a desire not to import any new element of confusion into a
nomenclature already too complicated.
7. Short Flexor of the Small Digit (Fig. 188, d, 13).
Situated within the preceding, in a slightly oblique direction downwards and outwards,
flattened before and behind, triangular, and almost entirely muscular, this muscle derives its
origin from a ligament which unites the pisiform bone to the metacarpal region, and terminates
inferiorly on the tendon of the adductor, whose congener it is. It may also concur in the
flexion of the small digit, though to a very limited degree.
8. Opponent of the Small Digit (Fig. 188, d, 15).
A muscle elongated from above downwards, flattened before and behind, situated under the
perforans tendons, behind the second interosseous muscle, in a direction sliglitly downwards
and outwards. It originates from the posterior ligament of the carpus, and terminates within
the superior extremity of the first phalanx of the external digit by a small tendon. It acts as
an adductor by drawing the small digit towards the axis of the hand.
9. LuMBRicr.
These small muscles, which owe their name to the resemblance they bear to the lumbricales
or earthworms, are only three in number in Carnivora. They occupy the interval between the
four chief branches of the perforans tendon, from which they have their origin ; they terminate,
by a small fibrous digitation, on the extensor tendons of the three external digits. It is often
impossible to trace them so far ; for they are frequently observed to stop within and above the
first phalanx of tlie digits for which they are destined. Their functions cannot be rigorously
defined in Carnivora.
10. Metacabpa Interosseous Muscles (Fig. 188, d, 16, 16).
These are four thick and prismatic muscular fasciculi, elongated from above to below,
bifid at their inferior extremity, placed parallel to one another, in front of the flexor
tendons, from which they are separated by a thin aponeurotic layer, and behind the four large
metacarpals.
They have their origin on the posterior and lateral faces of these bones, as well as on the
posterior carpal and intermetacarpal lis;aments. Each terminates, by the two branches of its
inferior extremity, on the great sesamoids of the digit to which it corresponds. There they are
continued by a small tendon, which joins the chief extensor of the digit. These muscles
oppose undue extension of the digits while the animal is standing, flex them on the metacarpal
bones, and maintain the extt-nsor tendons on the anterior aspect of the plialanges.
342
THE MUSCLES.
B. Muscles of the Anterior Foot in the Pig.
In our notes on the myology of this animal, we find :
1. A muscle which originates in tlie substance of the metacarpo-supercarpal ligament, and
tenuiuates on tlie proper extensor of the small external digit by a librous strip joined to the
external fasciculus of the first interosseous muscle; it is also attached to the external sesamoid.
This is, no doubt, the representative of the short flexor of the small digit ia Man and the
Caniivora,
2. A single, but very voluminous lumhricus, fixed, at the one part, to the perforans tendon,
and at the other, to the proper extensor tendon of tlie small internal digit (index), as in the
preceding muscle.
3. Four interosseous metacarpal muscles, similar to those in the Dog, and whose terminal
digitations join the proper extensor tendons. The interosseous muscles of the two small digits
are not only divided at their inferior extremity, but
Fig. 191. throughout their whole length are observed to be two
veij- distinct fasciculi, one superficial and external, the
other deep and internal. The fibrous membraue cover-
ing these muscles, and which separates them from
the perforans tendons, is much thicker than in the
Carnivora.
C. Muscles of the Anterior Foot in
SOLIPEDS.
In Solipeds, only two liimbrici and two
interosseous metacarpal muscles have to be
described.
1. The lumhrici originate at the right and
the left of the perforans tendon, above the
sesamoid annular band of the perforatus. They
each terminate by a thin tendon, which is lost
in the fibrous layer enveloping the elastic
cushion of the ergot of the fetlock.
2. The interosseous muscles {anterior lum-
hrici— PercivaU) have been wrongly considered
by French veterinary anatomists as lumbrici
muscles, and are described by them as the
superior, or great lumhrici. Situated within the
rudimentary metacarpal bones, these two little
muscles are formed of a very delicate fleshy
mass embedded in the fibrous tissue surround-
ing the head of the metacarpal bones, and of
a long tendon which descends to the metacarpo-
phalangeal articulation, to be confounded with
the band furnished to the anterior extensor of
the phalanges by the suspensory ligament.
Sometimes this tendon is directly united to one of the extensors of the phalanges.
These two muscles represent the interossei of the lateral digits. With regard
to those of the median digit, they are transformed, as we have already seen, into
a fibrous brace which constitutes the suspensory ligament of the fetlock.
D. Muscles op the Anterior Foot in Ruminants.
These animals have no muscles, properly speaking, in the region of the foot ; in fact, we only
find in them the suspensory ligament of the fetlock, which is the interosseous of the two
complete digits.
Comparison of the Hand of Man with that op Animals.
The muscles of Man's liand are numerous and well-developed, in consequence of the extent
MUSCLES OF human HAND.
, Annular ligament; 2, 2, origin and
insertion of the abductor pollicis
muscle ; 3, flexor ossis metacarpi, or
opponens pollicis ; 5, deep portion of
flexor brevis pollicis; 6, adductor
pollicis ; 7, 7, lumbricales muscles
arising from the deep flexor tendons,
upon which the figures are placed ;
8, a tendon of deep flexor ; 9, tendon
of flexor longus pollicis ; 10, abductor
minimi digitii ; 11, flexor brevis
minimi digitii; 12, pisiform bone;
13, first dorsal interosseous muscle,
the abductor indicis.
MUSCLES OF THE POSTERIOR LIMBS. 343
and variety of the movements of its various parts. They are divided into three groups : the
external, or group of the thenar eminence, induce the movements of the thumb; the internal,
or group of the hypothenar eminence, those of the little finger ; and the middle group, occupy'
ing the metacarpal spaces, comprising the interosseous muscles. In addition, there is found in
the hand a cuticularis muscle, the cutaneous palmaris (palmaris hrevis).
The cutaneous palmaris occupies two-thirds of the hypothenar eminence; its fibres are
directed downwards and inwards. It corrugates the skin on the ulnar border of the hand.
A. Muscles of the Thenar Eminence.
The.>e muscles, nearly all present in the Dog, are :
1. The short adductor of the thumb, whose fibres, leaving the lower portion of the anti-
brachial aponeurosis, the process of the trapezius and the scaphoides, are succeeded by a
tendon which is inserted into tiie upper extremity of the first phalanx of the thumb.
2. The opponent (opponens) of the thumb, which passes from the anterior part of the
trapezium to the external border, and near the anterior face oi' the first metacarpal.
3. The short flexor of the thumb, a muscle adjoining the preceding, and which ia resolved
into two series of fibres— a deep and a superficial.
4. The short adductor of the thumb, a triangular muscle, occupying the outer half of the
hollow of the palm. It is attached to the os magnum, along the entire length of the third
metacarpal bone and, by a tendon, to the sesamoid and supero-internal tuberosity of the first
phalanx of the thumb.
B. Muscles of the Hypothenar Eminence.
These muscles are : 1. The abductor of the little finger, a small fusiform muscular body, which
is attached, above, to the pisiform bone, and below to the supero-internal part of the first phalanx.
2. The short flexor of the little finger, situated without the preceding, fixed in one part to
the process of the unciform bont , and in the other to the inner part of the first phalanx.
3. The opponent (opponens) of the little finger, a triangular muscle, situated below the
preceding. It is inserted into the process of the unciform bone, then into the inner border of
the fifth metacarpal and the adjacent portion of its anterior face.
C. Interosseous Muscles.
" The interosseous muscles are situated in each interosseous space, two for each space, and
are divided into dorsal and palmar. As there are four interosseous spaces, there ought to be
eight muscles; but it is usual to exclude the short adductor of the thumb, because (if its
special insertions ; this reduces the total number of interosseous muscles to seven — four dorsal
and three palmar.
"These small muscles arise from the lateral faces of the metacarpals to the lateral and
upper portions of the first phalanges. By their contraction, they incline these phalanges
laterally, and consequently carry the corresponding digit inwards and outwards."
It may be added that the lumbrici muscles are small muscular and tendinous fasciculi,
annexed to the tendons of the deep flexor of the phalanges ; their tendons terminate on the
external side of the four last digits, in becoming blended with the interossei.
Article III. — Muscles of the Posterior Limbs.
These form four principal groups : the muscles of the croup, thigh, leg, and foot.
Muscles of the Gluteal Region, or Croup.
This region is composed of three superposed muscles, which are applied
to the ilium, and are distinguished according to their relative situation as the
suf)erficial, middle, and deep gluteus.'^
They are covered by a thick fibrous fascia — a prolongation of the aponeurosis
of the great dorsal — which is continued backwards over the muscles of the
posterior crural region, where it is confounded with the superficial layer of the
fascia lata. This gluteal apotieurosis is fixed to the external angle of the ilium
and the supersacral spine. By its deep face it gives attachment to several
fasciculi of the superficial and middle glutei.
' For the justification of the employment of these new denominations, see note, p. 230
344
TEE MUSCLES.
Preparation. — 1. Place the animal on its side, or, better, in the second position. 2. Remove
the skin from this region in order to show the gluteal apoueurosis, and to study its extent,
attachments, and relations. 3. Cut away this aponeurosis to expose the anterior point of the
middle gluteus 'and the muscular portion of the superticial. To prepare the apoueurotic
portion of the latter muscle, the sacro-sciatic insertion of the long vastus must be detached by
the scalpel and thrown downwards. 4. Incise the superficial gluteus near its femoral insertion,
and reverse it on the sacral spine, so as to lay bare the external face of the middle or principal
^duteus. 5. Divide this muscle near its femoral insertions, taking care not to inj ure these, and
remove the whole of its mass, studying raeanwhUe the nature of its relations to the parts
it covers; the deep or small gluteus then becomes apparent, and may be conveniently
examined.
To render the dissection and study of these muscles easier, the hind quarters may be
arranged as in Fig. 192. A special upright support passes between the last ribs, and a
horizontal lever maintains the lumbar region fixed in a kind of metallic fork. By this
arrangement the croup and hips are
Fjg. 192. kept in a good direction, the mass
I/, ^ ^ C I being made tense, so that they can
be dissected nearly in their normal
relations.
1. SupEEFiciAL Gluteus
(Gluteus Exteenus)
(Fig. 193, 2, 4).
Synonyms. — Ilio-trochanterius
medius — Girard. Gluteus minor
— Boxirgelat. Gluteus medius —
Rigot and Lafosse. The gluteus
magnus of Man. (^Ilio-trochanterius
externus — Leyh.)
Coinposition — Situation . —
This muscle is composed of
two portions— one anterior,
the other posterior, closely
joined, and situated beneath
the gluteal fascia. They form
the most superficial portion of
the fleshy masses of the croup
and inner face of the thigh.
Form — Structure — Attach-
ments.— A. The anterior 'por-
tion (the mperflcial or middle
gluteal muscle of veterinary anatomists) comprises a muscular and an aponeu-
rotic division. The first is triangular in shape, deeply notched in its upper
border, so that it is sometimes divided into two parts — an external and an
internal. Its fasciculi are very thick and loosely united ; they all pass back-
wards and downwards, to converge in a flattened tendon which terminates the
inferior angle of the muscle. The aponeurosis, also triangular, is confounded
in front with the posterior border of the muscular portion and its terminal
tendon, and is insinuated behind, beneath the posterior portion ; it degenerates
into connective tissue at its inner and upper border. The anterior part of the
muscle has it?, fixed insertion : 1. On the internal aspect of the gluteal aponeu-
rosis, by the superior extremity of its muscular fasciculi. 2. On the postero-
external angle of the ischium, and the sciatic ligament, by the internal border
of its aponeurotic portion. It has its movable insertion, by means of its terminal
tendon, on the small external or third trochanter of the femur.
T, Table ; A, showing the principal support ; B, posterior
horizontal bar ; C, blunt point at the end of the branches
of the T placed at the extremity of the posterior branch;
D, anterior horizontal branch terminated by vertical
branches, E, on which the last pair of ribs rest ; L,
notched lever which keeps the animals hind quarters on
the support ad hoc.
MUSCLES OF THE POSTERIOR LIMBS
M5
B The posterior portion ^ (anterior portion of the long vastus of veterinary
anatomists), the largest of the two, is applied to the aponeuroses of the pre-
cedincr and extends from the sacral spine to the inferior extremity of the thigh.
It is ''prismatic, very broad at its upper end, and singularly contracted at the
opposite extremity. A wide and strong fibrous band, which becomes aponeurotic
towards the superior extremity of the muscle, covers the inner face in its inferior
portion. The muscular fibres appear to become longer as they are more pos-
terior ; all pass from the upper end to coUect on the tendinous layer.
The muscle arises, by the superior extremity of its fasciculi, on the gluteal
fascia sacral spine, sacro-sciatic ligament, the enveloping aponeurosis of the
coccygeal fascia, and the ischiatic tuberosity. It terminates : 1. On the circular
imprint situated behind the trochanter minor, by a branch detached from the
Fig. 193.
StJPERFICIAL MUSCLES OF THE CROUP AND THIGH OF THE HORSE.
1 Middle gluteus ; 2, anterior portion of the superficial gluteus; 3, tensor fascia latae ; 4, posterior
' portion of the superficial gluteal ; 5, biceps femoris ; 5', semitendinosus ; 6, semimembranosus.
deep tendon. 2. On the anterior face of the patella, along with the external
patellar ligament, by the inferior extremity of that tendon.
i?^/a^wws.— Externally, with the gluteal fascia, which, in being prolonged on
the posterior portion, increases in thickness, and becomes more or less elastic.
Inwardly, with the middle gluteus (gluteus maximus), the trochanter major, and
deep layer of the fascia lata, which isolates it from the vastus externus ; with
the anterior face of the patella, on which it glides by means of a synovial bursa
before being inserted ; with the sciatic nerves and great adductor of the thigh.
By its anterior border it is closely united to the muscle of the fascia lata ; by
» Lesbre proposes to name it the accessory of the superficial gluteus.
346 TTJE MUSCLES.
its posterior border it has relation, inferiorly, with the biceps femoris, and
higher, with the semiteudinosns, which slightly covers it.
Ad mi. — This muscle has been justly considered by Lafosse as an abductor
of the thigh. Bourgelat wrongly regarded it as an extensor, and Girard and
Rigot have repeated his error. Lecoq has proved that it rather produces flexion
than extension. The posterior portion is an abductor of the entire limb and an
extensor of the thigh, when the sacrum is its fixed point ; it plays a part in
rearing, when the fixed point is the leg.
2. Middle Gluteus (Gluteus Medius, Gluteus Maximus)
(Figs. 193, 1 ; 194, 1).
Synonyms. — Ilio-troclianterius magnus — Girard. Gluteus maximus — Bourgelat, Lafosse,
Bigot, etc. Gluteus medius of Man. (Superior portion of the great ilio-trochanterius — Leyh.)
Volume — Situation. — This muscle, the largest of the glutei, is of considerable
volume, and is applied against the iliac fossa, the sacro-sciatic ligament, and the
longissimus dorsi.
Form and Structure. — It is elongated from before to behind, wide and very
thick in its middle, prolonged forward by a thin point, and terminated behind
by three branches of insertion — two tendinous and one muscular. The muscular
fasciculi entering into its composition are generally very thick, and more or less
long ; all converge towards the posterior insertions of the muscle.
Attachments. — 1. By the superior or anterior extremities of the muscular
fasciculi, to the internal aspect of the gluteal fascia, the aponeurosis of the
longissimus dorsi, the superior face and the two anterior angles of the ilium,
the two ilio-sacral ligaments, and a small portion of the sacro-sciatic ligament.
2. On the trochanter major by its three posterior branches : the first, or median,
is a thick, round tendon fixed on the summit ; the anterior is formed by a
second wide, thin, and flat tendon, which is inserted into the crest, after gliding
over the convexity ; the posterior is a small, triangular, fleshy slip, aponeurotic
at its anterior border, by means of which it is attached behind the trochanter.
This slip corresponds to the pjramidalis muscle of Man.
Relations. — Covered by the gluteal fascia and the superficial gluteal muscle,
it covers the longissimus dorsi, which receives its anterior point, the iliac fossa,
the deep gluteal, the ilio-sacral and sacro-sciatic ligaments, the sciatic nerves,
and the gluteal nerves and vessels. Near the external angle of the ilium it is
bordered by the fascia lata and the iliacus, which are closely united to it.
Action. — When its fixed point is superior, this muscle extends and abducts
the thigh ; but when the femur is fixed, it causes the pelvis to rock on the
superior extremity of that bone, and assists in the act of rearing. In the first
instance it acts as a lever of the first order ; in the second, as one of the third order.
3. Deep Gluteus (Gluteus Internus) (Fig. 167, 5).
Synonyms. — Ilio-trochanterius parvus— GiVarcZ. Gluteus medius — Bourgelat. Gluteus
minimus — Lafosse and Bigot. The gluteus minimus of anthropotomists.
Form — Situation. — A small, short, thick, and quadrilateral muscle, flattened
above and below, situated beneath the preceding, and above the coxo-femoral
articulation.
Structure and Attachments. — It is composed of voluminous muscular and
tendinous fasciculi, which arise from the neck of the ilium and the supra -cotyloid
ridge, to be directed outwards and backwards, and terminate within the con-
vexity of the trochanter major.
MUSCLES OF TEE POSTERIOR LIMBS.
347
Belatiom.— Its upper face responds to the middle gluteus; the inferior
covers the coxo-femoral articulation, and strongly adheres to the fibrous capsule
of that joint. This face is also separated from the rectus parvus and the origin
of the rectus femoris by a very strong fibrous layer, which extends from the
external border of the ilium to the base of the trochanter major. Its posterior
border is in relation with the anterior gemellus of the pelvis.
fig. 194.
SUPERFICIAL MUSCLES OF THE CROUP AND THIGH. ^
1, Middle gluteus, or gluteus maximus ; 2, anterior spinous proce.ss of ilium; 3, muscle of the
fascia lata, or tensor fascia lata; 4, superficial gluteus, or gluteus externus ; *, great trochanter
of femur; 5, fascia lata; 6, patella, with insertion of rectus, 7, biceps femons, or adductor
magnus ; 8, superior and, 9, lateral coccygeal muscles; 10, semitendinosus and semimembranosus;
11, 12, triceps abductor femoris; 13, fascia of the thigh ; 14, vastus
vastus externus.
Action.— It is the special abductor of the thigh, and is also an accessory
rotator of the femur inwards.' (Leyh says it is a congener of the preceding
> Lesbre is of opinion that the middle gluteus, such as it has been described here, com-
prises two superposed muscles which are distinct at their troclianterian insertion : the super-
ficial is the middle gluteus of Man, and the deep the small gluteus of anthropotomists.
Therefore the muscle we have described as the deep gluteal in the Horse has no representative
in Man. Lesbre proposes to name it the abducens trochanter ius. It should be the homotype
of the inferior branch of the infra-spinatus, which is also absent in man, and which it would be
reasonable to describe, by analogy, as the abducens trochiterius.
348 THE MUSCLES.
muscb, and therefore an extensor of the thigh. It may also maintain the
capsular ligament tense.)
Differential Characters in the Muscles of the Gluteal Region in the other
Animals.
A. Ruminants. — In the Ox, Sheep, and Goat, the two portions of the superficial gluteus
are less distinct than in Solipeds (see Fig. 197). They form one muscle, remarkably de-
veloped, the inner face of which has no point of attachment on the femur; it glides behind the
trochanter by means of a vast bura;i, which is often the seat of pathological alterations —
synovial tumours which constitute the swellings or gout of the larger Ruminants. Another
synovial bursa, liable to tlie same malaiiies, covers the patellar tendon of the muscle on its
passage over the external condyle of the femur, and facilitates its gliding on that bony
eminence. Before joining the external patellar ligament, this tendon shows a very thick,
fibro-cartilaginous enlargement, and receives some of the fibres of the external vastus.
Another arrangement in this muscle, which it is essential to recognize in a surgical point
of view, is the union of the anterior border of the superficial gluteus oi the Ox with the /a«aaZato,
the two layers of which comprise that muscle between them, and closely adhere to each of
its faces. It very frequently happens tiiat, in emaciated cattle, this fascia is ruptured at the
trochanter, and the latter, instead of gliding on the inner face of the superficial gluteus, slips
before its anterior border to pass through tlie solution of continuity, where it is fixed so firmly
that it is sometimes necessary to cut across the fibres of the muscle in order to give the limb
liberty of movement.
The middle gluteus, not so thick as in the Horse, is not prolonged so far forward on the
longissimus dorsi ; and, on the contrary, the deep gluteus, more developed than in Solipeds, is
readily divisible into two portions, of which Rigot has made two distinct gluteals. In the
Camel, the middle gluteus does not go beyond the border of the ilium in front. The posterior
portion of the superficial gluteus has an attachment to the external border of the femur.
B. Pig. — The gluteal muscles of this animal resemble those of the Sheep, though the
posterior portion of the superficial gluteus does not always have a bursa for its passage over the
external condyle of the femur.
C. Carnivora. — The superficial gluteus, in its general arrangement, resembles that of
Man ; its posterior portion, which is scarcely distinct, arises from the sacrum, and terminates,
by an aponeurosis, below and behind the trochanter major. This aponeurosis receives, in front,
a small fleshy band, which arises by tendinous fibres from the surface of the middle gluteus,
next the external angle of the ilium. In these animals, also, the middle gluteus does not go
beyond the lumbar border of the ilium, and terminates behind by a single branch.
Comparison of the Gluteal Muscles of Man with those of Animals.
The gluteal muscles are distinguished, in regard to their volume, into great, medium, and
small (see note, p. 230).
The medium gluteus does not extend beyond the crest of the ilium in front.
With regard to the gluteus mazimus, it is inserted inwardly into the sacrum and the coccyx ;
below, into the external bifurcation of the linea aspera, from the trochanter major to the middle
third of the femur, as in Solipeds.
The gluteus parvus is proportionately more extensive than in the Horse.
•
Muscles of the Thigh.
These have been divided into three secondary regions, which are : the
anterior femoral or patellar, t\ie posterior femoral, and the internal femoral region.
A. Anterioe Femoral Region.
This region comprises three muscles situated in front of the femur : the
muscle of the fascia lata, the crural triceps, and the gracilis.
Preparation. — 1. Place the subject in the first position. 2. Study the fascia lata muscle
immediately after removing the skin from tliis region. 3. Take away this muscle and the
superficial gluteus, the semitendinosis and semimembranosis, the two adductors of the leg,
the pectineus, and the two adductors of the thigh, to expose the three portions of the triceps.
Separate these three muscular divisions from one another, commencing above where they
are scarcely adherent. Dissect the gracilis at the same time.
MUSCLES OF THE POSTERIOR LIMBS. 349
1. Muscle of the Fascia Lata (Tensor Fascia Lat^, Tensor Vagina
Femoris (Fig. 193, 3).
Synonyms. — Ilio-aponeuroticus — Girard. (Tensor vaginx — Percivall. Ischio-rotuleus ex-
ternus — LeyK).
Form — Situation. — A flat and triangular muscle, situated in front of the
superficial gluteus, and outside the external vastus.
Structure — Attachments. — It comprises : 1. A flabelliform muscular portion,
covered on its faces by tendinous fibres, and attached, superiorly, to the external
angle of the ilium. 2. An aponeurosis named the fascia lata, continuous with
the inferior border of the muscular portion, and soon divided into two super-
posed layers — one superficial, the other deep. The latter is insinuated between
the posterior portion of the superficial gluteus and the external vastus, joins the
terminal tendon of the anterior portion of that muscle, and is inserted into the
external border of the femur. The first, which also appears to divide into two
layers, is spread outwardly over the superficial gluteus, where it is confounded
with the gluteal aponeurosis ; and inwardly, over the internal crural muscles, to
become united to the femoral aponeurosis. Below, it is prolonged to the patella,
into which it is fixed ; it is even continued below that bone, to join the terminal
aponeurosis of the posterior branch of the long superficial gluteus.
Relations. — Outwards, with the skin ; inwards, with the external vastus, the
anterior rectus, and the iliacus ; behind, with the superficial and middle glutei.
In front, to a cluster of lymphatic glands, where it receives, on its aponeurosis,
the insertion of the panniculus carnosus.
Action. — It flexes the femur by raising the entire limb, and renders tense its
own terminal aponeurosis.
(In speaking of the uses of this muscle, Leyh states that — in addition to its
being a flexor of the thigh and an extensor of the leg through its action on its
aponeurosis — it maintains the position of the limb while the animal is standing,
and allows the other muscles to become relaxed.)
2. Crural Triceps.*
An enormous muscle lying against the anterior and lateral aspects of the
femur, composed of three portions which are not very distinct from each other
for the greater part of their extent, and which are separately described as the
anterior rectus or straight muscle, and the vastus externus and internus.
A. Anterior Straight Muscle of the Thigh (Rectus Femoris),
Middle Portion of the Triceps (Figs. 194, 6 ; 197, 16).
Synonyms. — The ilio-rotuleua of Girard. (Rectus— Percivall. Anterior ilio-rotuleus — Leyh.)
This muscle is embedded between the two lateral portions of the triceps, and
extends from the cotyloid angle of the ilium to the patella, in a direction slightly
obUque forwards and downwards.
Form— Structure. — Elongated, thick, and fusiform, the rectus femoris offei-s,
at its superior extremity, two short and flattened tendinous branches ; its middle
portion is formed of pale-red muscular fibres lying close to each other, and
' Following the example of M. Cruveilhier, we will describe by this name the triceps cruris
of the older anatomists, and the anterior rectus of the thigh.
25
850 THE MUSCLES.
marked by tendinous intersections : its inferior extremity is enveloped by a vast
aponeurotic cone.
Attachments. — It originates, by its two superior branches, from the imprints
which surmount, forwards and outwards, the lip of the cotyloid cavity. It
terminates, by its inferior extremity, on the anterior face of the patella.
Belations.—Extevnallj, internally, and posteriorly, with the two other portions
of the triceps ; anteriorly, with the tensor of the fascia lata. Its superior
extremity, included between the iliacus and the deep gluteus, is separated from
the coxo-femoral capsule by a little adipose cushion, which is insinuated between
its two branches.
Action. — An extensor of the leg and flexor of the thigh.
B. Vastus Externus (Fig. 201, 11).— Form— Extent— Sitimtion.— This is a
thick and wide muscular mass, flattened on each side, extending from the
superior extremity of the femur to the patella, and situated to the outer side of
the rectus femoris.
Structure and Attachments. — The fasciculi composing this muscle are inter-
mixed with strong aponeurotic layers, and originate from the whole outer surface
of the femur and the external half of its anterior face ; they are directed for-
wards and downwards, to terminate either on the anterior rectus, or on the
superior face and external side of the patella.
Relations. — Outwardly, with the fascia lata and superficial gluteus ; inwardly,
with the rectus femoris and the vastus internus, which is intimately confounded
with it except towards the superior extremity of the femur, where the two
muscles are distinctly separate ; behind, with the femur and the posterior portion
of the superficial gluteus.
Action. — It is an extensor of the leg.
C. Vastus Internus (Figs. 195, 7 ; 203, 17). — This muscle is not very
distinct from the preceding for the greater part of its extent, and forms with
it a deep and wide channel, in which the rectus femoris is lodged. It is a
repetition of the vastus externus, in so far as its form, structure, extent, attach-
ments, and action are concerned ; but it possesses the following peculiarities : —
The fibres entering into its composition arise from the whole internal face
and the inner half of the anterior face of the femur, and are inserted, some on
the aponeurosis of the rectus femoris, others on the internal patellar ligament, the
corresponding side of the patella, and on the superior face of the same bone, in
common with the vastus externus.
Relations. — By its external face, to the latter muscle and the rectus femoris ; by
its internal face, to the internal crural aponeurosis, the long adductor of the leg,
the iliacus, pectineus, and to the long branch of the great adductor of the thigh.
3. Anterior Gracilis (Crureus, Rectus Parvus) (Figs. 197, 6 ; 203, 15).
Synonyms. — Gracilis anterius — Rigot. Ilio-femoral gracilis — Girard. (Crureus vel cruralis
— Percivall.)
A small cylindrical muscle, situated in front of the capsule of the coxo-
femoral articulation, alongside the fibrous fasciculus that strengthens the anterior
portion of this membranous ligament.
Attachments. — It originates from the ilium, very near, and to the outside
of, the external branch of the rectus femoris; it afterwards insinuates itself
between the two vasti, and terminates on the anterior aspect of the femur by
aponeurotic fasciculi.
MUSCLES OF TEE POSTEBIOR LIMBS. 351
Belations. — This muscle is included between the three portions of the triceps
and the capsular ligament of the coxo-femoral articulation, to which it strongly
adheres.
Action. — It appears to raise (or render tense) the capsular ligament during
flexion of the femur.
B. Posterior Crural Kegion.
This region is constituted by three muscles situated behind the thigh. These
are the biceps femoris, the semitendinosus, and the semimembranosus.
Preparation. — Place the subject in the second position, allow one hind leg to lie unfastened,
and incline the body to the correspnniling side, leaving the other liinb attached to the sup-
porting bar, with the thigh slightly flexed to make these muscles tense. These preliminary
arrangements being adopted, proceed in the following manner : 1. Make a transverse incision
through the short adductor of the thigh, and turn back the two portions to the right and left,
so as to expose the whole of the semimembninosus, which is to he afterwards dissected from
the semitendinosus and the great adductor of the thigh. 2. After removing the aponeurosis
covering the biceps femoris and the semitendinosus, the latter is to be dissected by circum-
scribing as carefully as possible its two superior insertions. 3. The biceps is then to be
prepared. The biceps femoris and semitendinosus can be easily dissected in a limb arranged
as in Fig. 192.
1. Biceps Femoris (Triceps Abductor Femoris) (Figs. 193, 5 ; 194, 7).
'^ms. — Ischio-tibialis externus — Girard. A portion of the long vastus — Bourgelat,
Lafosse, Bigot. (The biceps abductor femoris of Percivall. Anterior pubio-ischio-tibialit —
Leyh.)
Situation — Extent — Direction. — This muscle is situated behind the thigh and
the glutei muscles, and extends from the sacral spine to the superior extremity
of the leg.
Form and Structure. — It is narrow at its upper extremity, and very wide and
thin inferiorly.
Its muscular fibres are partly attached, by their superior extremities, to a
longitudinal aponeurotic layer, which gives the muscle a penniform appearance ;
they terminate, inferiorly, in a strong aponeurosis united to that of the fascia
lata.
Attachments. — It arises, above, from the crest of the ischial tuberosity, where
the aponeurosis which gives it its penniform appearance is inserted.
Its terminal aponeurosis is spread over the tibial muscles to constitute the
fascia of the leg, and is inserted into the tibial crest.
Belations. — The gluteal aponeurosis, in the portion where it becomes semi-
elastic, adheres to the external surface of the biceps femoris. In front, the
muscle is related to the posterior portion of the superficial gluteus ; behind, to
the semitendinosus ; within, to the external muscles of the leg and the sciatic
nerves.
Action. — It flexes the leg and renders tense the tibial fascia, when its fixed
point is the pelvis. It rocks the pelvis on the femur when the leg is fixed.
2. Semitendinosus (Biceps Rotator Tibialis) (Figs. 193, 5' ; 194, 10).
Synonyms — Ischio-tibialis medius or posticus — Girard. (Posterior sacro-ischio-tibialis —
eyh. Percivall describes this and the next muscle by the name of adductor tibialis.)
Situation — Extent — Direction. — This muscle is situated behind the preceding
352 THE MUSCLES.
and the superficial gluteus, and extends from the sacral spine to the leg, describ-
ing a curv«, the convexity of which is posterior.
jTorm — Structure. — It is elongated from above to below, bifid at its superior
extremity, thick and prismatic, but nevertheless flattened on both sides. Its
muscular fibres are of a pale-red colour, are parallel to each other, and follow
the general direction of the muscle ; they terminate, inferiorly, on an aponeurosis,
by a flat tendon. In its middle portion, the body shows traces of the inter-
section which has obtained for this muscle the name — semitendinosus, in Man.
Attachments. — This muscle arises, above, by one of its branches, from the
sacral spine and the sacro-sciatic hgament, in common with the posterior portion
of the superficial gluteus, with which it exchanges some fibres ; ^ by the other
branch, which is the shortest, from the ischial tuberosity. Its inferior aponeu-
rosis is confounded with that of the tibia ; the tendon glides over the internal
surface of the tibia, and is inserted into its anterior crest.
Belations. — Its sacro-sciatic branch is covered by the gluteal aponeurosis, and
covers the superficial gluteus. For the remainder of its extent, it is related :
posteriorly, to that aponeurosis ; anteriorly, to the sciatic nerves ; externally, to
the superficial gluteus and gastrocnemius ; internally, to the semimembranosus
and the great adductor of the thigh.
Action. — It is a flexor of the leg, and tensor of the tibial aponeurosis, when
its fixed point is above ; when the leg is fixed, it becomes one of the active
agents in rearing.
3. Semimembranosus (Adductor Magnus) (Figs. 193, 6 ; 194, 10 ; 195, 13).
Synonyms. — Ischio-tibialis internua — Girard. (Great iscMo-femoralis—Leyh).
Situation — Volume — Extent — Direction. — Situated within the semitendinosus,
and shorter and thinner than it, the semimembranosus extends from the ischium
to the inferior extremity of the femur, and follows an oblique direction down-
wards and forwards.
Eorm — Structure. — Elongated vertically, flattened on each side, prismatic, thick
at its anterior, and very thin at its posterior borders. It is also voluminous at
its upper extremity, which has a small prolongation, the point of which ascends
to the base of the tail ; it is contracted, and terminated by a short tendon, at its
inferior extremity. It is formed of thick muscular fasciculi, which all terminate,
below, on the terminal tendon.
Attachments. — Above : 1. To the aponeurosis of the coccygeal muscles, by the
thin prolongation from its superior extremity. 2. To the ischial tuberosity, and
the inferior face of the ischium. Below, to the small eminence situated within
the internal condyle of the femur.
Belations.— lnwa,Tds, with a very thin prolongation from the gluteal aponeu-
rosis, and with the ischo-cavernous muscle and short adductor of the leg ; out-
wards, with the semitendinosus, the biceps femoris, and the sciatic nerves ; in
front, with the great adductor of the thigh, which is so intimately united to it
that some difficulty is experienced in separating their fibres.
Action. — It is an adductor of the limb and an extensor of the thigh, when
its fixed point is above ; but when the femur is fixed, it is an auxiliary in
rearing.
* The portion of this muscle whicli is attached to the sacral spine, certainly represents the
meet inferior part of the superficial gluteus of Man.
MUSCLES OF THE POSTERIOR L1MB8. S58
C. Internal Crural Region.
This region comprises nine muscles, applied in three superposed lasers against
the inner aspect of the thigh. These are : the lonfi and short adductor of the leff,
forming the superficial layer ; the pectineus and the small and great adductors of
the thujh, forming the middle layer. Those of the deep layer — that is, the quad-
rate crural {quadratus femoris), external obturator, internal obturator, and gemilli of
tlie pelvis — are not all situated on the inner face of the femur, one of them being
contained within the pelvic cavity. With these muscles — which do not present
a very considerable volume — another region might \)q formed and designated the
deep pelvi-crural, or coxo-femoral region.
Preparation. — 1. Place tlie subject in the first position. 2. Prepare on one side the two
muscles of the superficial layer, by removing the slight fibrous layer covering them, the internal
crural aponeurosis, and the inferior parieties of the abdomen. 3. To expose, on the opposite
side, the three muscles of the middle layer, cut through tlie two adductors of the leg, and turn
them back to the right and left; separate tlie semimembranosus from the great adductor of the
thigh ; it may be even useful, in order to study the latter muscle, to remove the entire mass of
the three ischio-tibial muscles. 4. Dissect the small deep muscles on a separate piece, as shown
in Figs. 195 and 197.
First Lager.
1. Long Adductor of the Leg (Sartorius) (Figs. 195, 8 ; 201, 15).
Synonymi. — Sublumbo-tibialis — Girard. {Internal ilio-rotuleus — Leyh.)
Form — Situation — Direction. — This muscle is long, thin, and flattened, narrow
at its inferior extremity, and situated at first within the abdominal cavity, at the
entrance to the pelvis ; afterwards, inside the thigh ; it is oblique from above to
below, behind to before, and within to without.
Structure. — It is formed of parallel muscular fibres., which extend from its
superior to its inferior border ; and it terminates, inferiorly, by an aponeurosis
which is confounded with that of the short adductor.
Attachments. — It originates, superiorily, from the inferior face of the iliac
fascia, near the tendon of the psoas parvus ; and it is inserted, by means of its
terminal aponeurosis, not on the supero-internal tuberosity of the tibia, but on
the internal patellar ligament, in common with the short adductor.
Relations. — It is covered by the crural aponeurosis and Poupart's ligament,
and covers the iliacus, psoas magnus, the anterior femoral nerve, and the vastus
internus. Superiorly, its inner border forms the limit — with the pectineus and
the anterior border of the short adductor — to a triangular space occupied by the
crural vessels ; below this space, the two adductors of the leg are closely adherent
to each other.
Action. — It adducts the leg, and flexes the femur.
2. Short Adductor of the Leg (Gracilis) (Fig. 195, 9).
Synonyms. — Subpubio-tibialis — Girard. (Pubio-tibialis — Leyh.)
Form — Situation — Direction. — A large quadrilateral muscle, thin at its
borders, situated inside the thigh in an oblique direction downwards and out-
wai-ds. It forms the base of what is called the Jf at of the thigh.
Structure. — Formed of parallel muscular fibres, which extend from its superior
to its inferior border, this muscle is tendinous at its origin, is covered by an
albugineous layer, and terminates inferiorly in a wide aponeurosis.
354
THE MUSCLES.
Attachments. — It originates, by the whole extent of its superior border, from
the under surface of the ischio-pubic symphysis, and is united to the muscle of
the opposite side — origin. Its terminal aponeurosis, united to that of the sar-
torious, is inserted on the internal patellar ligament and the internal face of the
tibia — movable insertion ; posteriorly, it is united to the aponeurosis of the semi-
tendinosus, and with it forms the tibial aponeurosis enveloping the tibial muscles.
Relations. — Its superficial face is covered by a cellulo-fibrous layer, and by
the saphena vessels and nerves. It covers, by its deep face the pectineus, the
MUSCLES OF THE STJBLUMBAR, PATELLAR, AHD INTERNAL CRURAL REGIONS.
1, Psoas magnus ; 1', its terminal tendon; 2, psoas parvus; 3, iliacus; 4, its small internal portion;
5, tensor of the fascia lata; 6, rectus femoris; 7, vastus internus ; 8, sartorius ; 9, gracilis; 11,
pectineus; 12, adductor magnus; 12', adductor parvus; 13, semimembranosus; 14, semitendi-
nosus. X, Portion of the iliac fascia ; B, portion of the layer reflected from the aroneurosis of the
obliquus abdominis externus, forming Poupart's ligament; C, pubic tendon of the abdominal
muscles ; D, origin of the pubio-femoral ligament.
adductors of the thigh, the semimembranosus and semitendinosus, and the
internal femoro-tibial ligament. It is traversed at its origin, and altogether in
front, by a very large vein.
Action. — An adductor of the limb and a tensor of the tibial aponeurosis.
MUSCLES OF THE POSTERIOR LIMBS. 355
Second Layer.
3. Pectineus (Fig. 195, 11).
Synonyms. — Superpubio-femoralis — Girard. Its anterior branch corresponds to the pectineus,
and the posterior to the middle adductor, in Man. (^Anterior pubio-jemoralis — Leyh.)
Situation — Direction — Form. — Situated beneath the preceding, in an oblique
direction downwards, forwards, and outwards, this muscle is conoid, thick, and
bifid at its superior extremity, contracted at its inferior extremity.
Structure and Attachments. — Its fasciculi arise either from the anterior border
and inferior surface of the pubis, or from the surface of the pubio-femoral liga-
ment, which passes between its two hranches—Jixed insertion. They are enveloped,
at their inferior extremity, by a tendinous cone, which is attached, on the inner
aspect of the femur, to the imprints surrounding the nutrient foramen — movable
insertion.
Belations. — Inwards, with the short adductor of the leg ; outwards and
forwards, with the femoral insertion of the psoas magnus and iliacus, the vastus
internus, the crural vessels, and the sartorius ; behind, with the gracilis, and,
near its superior extremity, with the obturator externus.
Action. — This muscle is an adductor and flexor of the thigh, and more par-
ticularly a rotator inwards of the same femur.
4. Small Adductor of the Thigh (Adductor Parvus, Adductor Brevis)
(Figs. 195, 12' ; 203, 14).
Synonyms. — The anterior portion of the biceps femoralis of Bourgelat, and of the subpubio-
femoralis of Girard.' (Middle pubio-femornlis of Leyh. A portion of the adductores femoris
of Percivall, and which he has named the adductor brevis.)
Situation — Direction. — Situated beneath the gracilis, between the pectineus
and the adductor magnus ; it passes in an oblique direction downwards and
outwards.
Form — Structure. — It is flat from before backwards, thick and narrow at its
upper extremity, thin and wide inferiorly. Its muscular fibres are of a pale-red
colour, nearly parallel to each other, and sometimes very indistinct — superficially,
at least — from those belonging to the adductor magnus ; inferiorly, they become
aponeurotic.
Attachments. — Above, to the inferior face of the pubis —origin ; below, to the
roughened quadrilateral surface on the posterior and middle aspect of the femur,
in common with the short branch of the adductor magnus — termination.
'Relations. — Inwards, with tlie gracilis ; outwards, with the obturator
externus ; in front, with the pectineus ; behind, with the adductor magnus.
5. Great Adductor of the Thigh (Adductor Magnus, Adductor Longus)
(Fig. 195, 12)
Synonyms. — Posterior portion of the biceps femoralis of Bourgelat, and of the subpubio-
femoralis of Girard. (Posterior pubio-femoralis — Leyh.)
Situation — Direction. — The great adductor is situated beneath the preceding
* After mature deliberation, we have decided on describing as two muscles the biceps
femoralis of Bourgelat. and to give to them the names of small and great adductors of the thigh,
by which Bichat has designated the corresponding muscles in the lower extremity of Man. We
have thought it our duty, in this instance, to follow the example given us by several German
authors.
356
THE MUSCLES.
muscle, between the small adductor and the semimembranosus, proceeding
obliquely downwards and outwards.
Form — Structure. — It is a long, thick, prismatic muscle, flat before and behind,
terminating, inferiorly, by two branches of unequal length, and almost entirely
composed of parallel muscular fibres, which are generally distinguished from the
fasciculi of the small adductor by their deeper colour.
Attachmmts. — Above, to the lower face of the ischium and to the single
tendinous band which at-
F'g- 196. taches the two muscles of
the flat of the thigh to the
pelvic symphysis — origin.
Below : 1. By its external
branch, the thickest and
shortest, to the quadrilateral
scabrous surface on the pos-
terior face of the femur, out-
side the small adductor. 2.
By its internal branch — the
longest and thinnest — to the
supero-internal condyle of
the femur, in conmion with
the semimembranosus and
the internal femoro-tibial
ligament —termination.
Relations. — Inwards, with
the short adductor of the leg ;
behind, with the semimem-
branosus ; in front, with the
small adductor, the external
obturator, and the inferior
extremity of the quadratus
femoris. Its external border,
thinner than the internal,
partly covers the superior ex-
tremity of the latter muscle, and is separated from the sciatic nerves and the
biceps femoris by an aponeurotic layer. The crural vessels pass between its two
branches, one of which, the internal, is related anteriorly and near its insertion to
the vastus internus.
Action. — This muscle is an adductor and extensor, as well as a rotator out-
wards of the femur.
Third Layer.
6. QuADEATE Crural (Quadratus Femoris, Ischio-Femoralis)
(Figs. 196, 14 ; 197, 10).
Synonyms. — The gracilis internus of Bourgelat, and the ischio-femoral gracilis of Girard.
(Not described by Percivall. Small ischio-femoralis of Leyh. The quadratus femoris of Man.)
Situation — Direction — Form — Structure. — Situated on the posterior face of
the femur, between the great adductor and external obturator, and oblique
downwards and outwards, the quadratus femoris is a small flat band, formed of
parallel muscular fibres, slightly tendinous at their inferior extremity.
DEEP MUSCLES OF THE COXO-FEMORAL REGION.
9, Deep gluteus, 10, origin of the rectus femoris; 11, rectus
parvus; 13, obturator externus , 14, quadratus femoris;
15, depressor coccygis.
MUSCLES OF THE POSTERIOR LIMBS. 357
Attachments. — Above, to the inferior surface of the ischium, in front of the
ischial tuberosity — oriffin ,- terminating, below, on the linear imprint on the
posterior face of the femur, a little below the trochanter internus (Fig.
197, 10).
Relations. — In front with the posterior face of the femur and external
obturator. Behind, and inwardly, with the adductor magnus. Outwards, with
the sciatic nerves and the gemellus posticus.
Action. — It is an extensor and adductor of the femur. In our opinion, its
mode of attachment will not permit it to rotate this bone either inwards or out-
wards— at least in Sohpeds.
7. Obtueator Externus (Fig. 196, 13).
Synonym. — Subpubio-trochauterius externus— (riVar^i.
Form — Structure — Situation — Direction. — A short, thick, flat muscle, tri-
angular, fasciculated, fleshy and aponeurotic, very delicate in texture, and
placed almost horizontally beneath the pelvis, at the margin of the obturator
foramen, which it covers, and from which it derives its name of obturator.
Attachments. — 1. To the inferior surface of the pubis and ischium, by the
internal extremities of its fasciculi— ^^a-^^/ itisertion. 2. To the trochanteric fossa,
by the external extremities of these fasciculi — movable insertion.
Eelations. — Inferior ly, with the pectineus, the two adductors of the thigh,
and the quadratus femoris ; superiorly, with the capsule of the hip-joint, and
the internal obturator.
Action. — An adductor and rotator outwards of the thigh.
8. Obturator Internus (Figs. 196, 197).
Synonym. — Subpubio-trochanterius internus — Girard.
Situation. — This muscle is situated in the pelvic cavity, above the oval
foramen, and is, consequently, opposite the external obturator.
Form — Structure — Attachnents. — It is formed of two portions. One is very
thin, and composed of slightly tendinous, divergent muscular fasciculi, which
arise from around the obturator foramen, are directed outwards, and terminate
in a tendon belonging to the other portion. The latter, elongated and penni-
form, is situated in the pelvis, and extends from the anterior angle of the
sacrum to the inferior extremity of the femur, following the direction of the
ischial border of the ilium, into which it is inserted. The tendon to which it
owes its penniform shape is inflected outwards, behind the supra-cotyloid crest
or sciatic ridge, joins the gemelli, and terminates in the bottom of the tro-
chanteric fossa.
Relations. — In its intra-pelvic portion, this muscle responds : outwards and
downwards, to the ilium, pubis, ischium, and external obturator ; inwards and
upwards, to the peritoneum, important vessels and nerves, and to a fibrous layer
that separates it from the bladder. In its extra-pelvic portion, it is in relation
with — behind, the middle gluteal muscle and the sciatic nerves ; in front, with
the gemelH. A synovial sheath facilitates the gliding of its tendon in the groove
in which it turns.
Action. — It is a rotator of the thigh outwards, and, contrary to the opinion of
the majority of authors, we believe it to produce abduction rather than adduc-
358 TEE MUSCLES.
tion, if at any time its position allows it to execute either of these two
movements.
9. Gemelli (Fig. 197, 8, 8, 9).
Synonyms. — Ischio - trochanterius — Girard. (Gemini — Percivall. Bifemoro - calcaneus —
Leyh.)
The two small muscles which receive this name are far from presenting the
same arrangement in every subject ; but we will describe that which appears to
be the most frequent. Two little elongated muscular fasciculi are usually found,
one above, the other below, the tendon common to the two portions of the
obturator internus. These two fasciculi (Fig. 197, 8, 8), arise from the external
border of the ischiiun, follow the direction of the above-mentioned tendon, and
are inserted into it by the external extremities of their fibres, exactly representing
the gemeUi of Man. But there is also a third (Fig. 191, 9), wide, flat, and often
Fig. 197.
COCCYGEAL AND DEEP MUSCLES SURROUNDING THE COXO-FEMORAL ARTICULATION.
1, Erector coccygeus ; 2, curvator coccygeus; 3, depressor coccygeus ; 4, compressor coccygeus; 5,
deep gluteus; 6, rectus parvus ; 7, tendon of the internal obturator; 8. 8, gemelli; 9, accessory
fasciculus of the gemelli; 10. quadratus femoris ; 11, sacro-sciatic ligament; 12, great sacro-
sciatic foramen ; 13, superior ilio-sacral ligament ; 14, inferior ilio-sacral ligament.
very voluminous, situated between the preceding and the obturator externus ; it
is attached, by its inner border, to the external border of the ischium, contracting
intimate adhesions with the other two and with the tendon of the obturator
internus, and becoming inserted by the whole extent of its external border into
the trochanteric fossa.
Relations. — Posteriorly, to the sciatic nerves ; anteriorly, to the capsule of
the hip-joint and the obturator externus, through the medium of an adipose
cushion.
Action. — Like the preceding muscle, these rotate the thigh outwards, and
perhaps tend to produce its abduction.
Differential Characters in the Muscles op the Thigh in the other Animals.
1. Anterior Crural Region.
In the Ox, Sheep, and Goat, the iensor of the fa»cia lata is much wider than in Sclipeds ;
that of the Camel is so developed that it completely euvelo| s the triceps cruralis. In the
MUSCLES OF TEE POSTERIOR LIMBS.
Dog and Cat, the same muscle shows, in front, a supernumerary fasciculus — a thick and long
strip mixed inwardly with the sartorius, and extending vertically from the external angle of
the ilium to the patella, into whicli it is inserted by a short aponeurosis.
The rectus femor is, in the Dog ami Sheep, has only one branch of origin.
The rtctus -parvus, that very thin muscle, does not exist in Solipeds and Carnivora.
2. Posterior Crural Region.
A. Ruminants. — In the Ox, Sheep, and Goat, the hiceps femoris is but little distinct
from tlie posterior portion of the superficial gluteus. It is longer and paler than in the Horse,
and its fibres are not penniform as in Solipeds.
The semitendinosus has no sacral prolongation: it arises only from the ischium.
The semimembranosus is divided, inferiorly, into two branches : one, very thick, passes to
the femur; the other, much smaller, termi-
nates by a tendon which is insinuated iieueath ''S° 1^^*
the internal lateral ligament of the femoro-
tibial articulation, to gain the superior ex-
tremity of the tibia.
In the Camel, an important peculiarity
should be noticed. In the posterior crural
region is found an elastic apparatus n sem-
bling that in the anterior limb of this animal.
This is in the form of a thick fascia, whicii
descends from the supra-spinous ligament and
the aponeurotic sheath of the coccygeal
muscles, is attached to the ischial tuberosity,
largely covers the space between the biceps
femoris and semitendinosus, crosses the sinus
of the femoro-tibial angle, and lies on the
retaining aponeurosis of the popliteus and
lateral extensor of the phalanges. Here it
divides into two portions : the smaller is com-
posed of fasciculi a little apart, which pass
backwards and mix with similar fasciculi from
the inner surface of the thigh, and become
attached to the tendon of tho gastrocnemius;
the larger portion descends in front of the
tarsus and metatarsus, and terminates towards
the lower third of that bone, on the surface
of the extensor tendons of the iligits. The
use of this elastic layer is to flex all the articu-
lations of the abdominal limb in a passive
manner.
The biceps femoris in the Camel resembles that of the Horse.
The semitendinosus is narrow in the middle, where it lias an aponeurotic tint.
The semimembranosus is thicker thnn the last-mentioned, but, like it, it is constricted in
the middle and expanded at its inferior extremity. It is attached, by its muscular fibres, to a
salient ridge above the internal condyle of the femur, and, by a short fibrous layer, to the
internal femoro-tibial ligament.
B- Pig. — The biceps femoris of this animal is arranged like that of the Sheep.
The semitendinosus and semimembranosus liave a small point that ascends towards the root
of the tail, and represents the sacro-sciatic branch of these two muscles in Solipeds.
C. Carnivora. — In these animals, the biceps femoris proceeds from the ischium, and
divides, inferiorly, into two unequal brandies: an anterior, the largest, terminates by an
aponeurosis which goes to the external patellar ligament and tibial crest; and a posterior,
attached to the tibial aponeurosis above and external to the gastrocnemius tendon.
The semitendinosus and semimemhranosus are as in the smaller Ruminants.
SUPERFICIAL MUSCLES OF THE CROUP AND
THIGH IN THE COW.
1, Middle gluteal ; 2, 2, biceps femoris, anterioi
portion ; 3, ditto, posterior portion ; 4, semi-
tendinosus ; 5, tensor of the fascia lata.
3. Internal Crural Region.
A. Ruminants. — The sartorius in the Ox and Sheep is traversed, near its origin, by the
femoral artery. In the Camel, the gracilis is bifid ; the anterior branch is the smallest. The
pectineus of the Ox, single at its upper extremity, is divided into two branches at its inferior
860 THE MUSCLES.
extremity. One of these branches, thin and pale, is prolonged to near the internal condyle of
the femur, while the principal stops, as in the Horse, on the posterior face of the bone.
The adductor parvus is scarcely distinct from the adductor magnus. The latter is undivided
at its inferior extremity, which stops at the posterior face of the femur, without going to the
inner condyle of that bone.
The obturator intemus has no upper portion; it is united to the obturator externus in
passing through the obturator foramen.
B Pig. In this animal, the internal crural muscles offer somewhat the same arrangement
as in the Ox.
C. Carnivora. — In the Dog and Cat, tlie sartorius arises from the external angle of the
ilium, and by its muscular portion is prolonged to the inner face of the tibia. The gracilis is
much thinner and narrower than in the other animals. The adductor parvus is a little, distinct
muscle, which begins on the inferior face of the pubis, and terminates at the posterior face of
the femur, below the quadratus femoris. The adductor magnus is, on the contrary, a wide,
thick, undivided muscle, attached to nearly the whole extent of the linea aspera of the femur.
There is nothing particular to note with regard to the quadratus femoris and the obturators;
the gemelli are always composed of two small, distinct fasciculi, which comport themselves as
in Man.
Comparison of the Muscles of Man's Thigh with those of the Thigh op Animals.
The muscles of the thigh in Man are divided into three regions, as in animals.
1. Anteeior Muscles.
The rectus parvus is not found in Man; nevertheless, there are reckoned three anterior
muscles of the thigh, because the sartorius, which corresponds to the sartorius of animals, is
included in this region.
The sartorius is a very long muscle, the width of which at most is about two fingers'
breadth. It is attached above, not to the lumbo-iliac aponeurosis, but to the anterior and
superior iliac spine; it is afterwards directed downwards and inwards, to pass round the
internal condyle of the femur, and terminate by an expanding tendon at the crest of the tibia.
The tensor of the fascia lata shows the same general arrangement observed in animals. It
is the same with the triceps femoris. The rectus femoris arises by two tendinous branches: one
is detached from the anterior and inferior iliac spine; the other from the brim of the cotyloid
cavity.
2. Muscles of the Posterior Region.
These are three in number : the femoral or crural biceps, semitendinosus, and semimembranosus.
The biceps femoris is represented in 8olipeds by the posterior portion of the biceps femoris. It
is an elongated muscle arising by two heads : tlie long head comes from the ischiatic tuberosity ;
the shortest from tlie middle of the linea aspera. After their union, these two heads give rise
to a tendon which is fixed into the head of the fibula, and sends an expansion over the tibial
aponeurosis.
The semitendinosus arises in common with the long head of the biceps ; its inferior tendon
lis reflected beneath the internal tuberosity of the tibia, to be fixed into the crest of that bone.
This tendon, with that of the sartorius, forms the aponeurotic expansion called the goose's foot.
The semimembranosus is voluminous in its lower portion, and arises, like the other two,
from the tuberosity of the ischium; its fibres pass to a tendon which, on reaching the inner
Bide of the knee, terminates in the three pieces composing that articulation (see Fig. 200).
3. Muscles of the Internal Region.
In books on human anatomy, these muscles are snmetimes designated, from their action, by
the generic name of adductors. They comprise : the internal rectus, peftineus. first or middle
adductor, second or small adductor, and third or great adductor. The square crural, the
obturators, and the gemelli are described among the posterior muscles of the pelvis. They
will, however, be briefly alluded to liere.
The internal rectus corresponds to the gracilis of animals. It is a thin muscle, bordering
the inner side of the thigh. It is attached, above, to the symphysis pubis ; below, to the crest
of the tibia, in common with the sartorius tendon.
MUSCLES OF THE POSTEBIOB LIMBS. 361
The pedineus repeats the anterior branch of the pectiueus of the Horse. It is inserted,
below, into the internal bifurcation of the linea aspera of the femur.
The first adductor corresponds to the posterior branch of the pectineus of Solipeds. It is
represented by a voluminous muscular mass, which arises from the spine of the pubis and
terminates on the middle third of the linea aspera.
The second or small adductor corresponds to the muscle of the same name in animals. It is
inserted into the same points as the preceding.
The third or great adductor is attached, above, to the ischiatic tuberosity and to the whole
Fig. 199. Fig. 200.
MUSCLES OF THE ANTERIOR FEMORAL
REGION IN MAN.
I, Crest of the ilium 5 2, its antero-
superior spinous process ; 3, gluteus
medius ; 4, tensor vaginse femoris ; 5,
sartorius ; 6, rectus ; 7, vastus externus ;
8, vastus internus ; 9, patella ; 10,
iliacus internus; 11, psoas magnus;
12, pectineus; 13, adductor longus;
14, portion of adductor magnus; 15,
gracilis.
MUSCLES OF THE POSTERIOR FEMORAL
AND GLUTEAL REGION IN MAN.
I, Gluteus medius ; 2, gluteus maximus ;
3, vastus externus, covered by fascia
lata ; 4, long head of biceps ; 5, short
head ; 6, semitendinosus ; 7, 7, semi-
membranosus ; 8, gracilis ; 9, portion
of inner border of adductor magnus ;
10, edge of sartorius ; 11, politeal
space; 12, gastrocnemius, with its two
heads.
of the lower branch of the ischium by aponeurotic fibres. It afterwards divides into two
branches : the external branch, entirely muscular, is fixed into the entire interspace of the
linea aspera ; the internal branch gives rise to a tendon which goes to the inner condyle of the
femur. Between these two branches is found, as in the Horse, the ring of the adductors, in
which pass the large vessels of the thigh.
The quadratus femoris of Man is nearly horizontal, as it is attached, inwardly, to the
external border of the ischium, and outwardly, between the great and small trochanters.
The obturator internus and gemelli resemble those of the Dog.
362 THE MUSCLES.
Muscles of the Leg.
These muscles, nine in number, are grouped around the two principal bonea
of the leg, so as almost to completely envelop them, leaving only the internal
face of the tibia uncovered. Like those of the forearm, they form two particular
regions : an anterior and a posterior ; and they are sheathed in common by the
tibial aponeurosis — a very solid fibrous covering, which in every respect corresponds
to the antibrachial aponeurosis.
Tibial Aponeurosis.
This aponeurosis is formed of several superposed layers which are intimately
united, and receives, superiorly, the insertion of the biceps femoris, the semi-
tendinosus, and the gracilis, which may be considered as its tensor muscles.
It is continued, inferiorly, over the tarsus and the metatarsal region, in
becoming singularly attenuated, and in covering the fibrous bands which bind
and retain the anterior tibial muscles in the bend of the hock. Its external
surface is separated from the skin by a very thin fibrous expansion ; its internal
face furnishes special and very firm sheaths around the majority of the tibial
muscles.
The tibial aponeurosis is attached to the internal surface and crest of the
tibia, as well as to the summit of the calcis. The latter attachment takes place
by a thick fibrous band, the singular and complicated arrangement of which
has not yet been exactly described. It is situated in front of the tendon of the
gastrocnemius, or between that tendon and the deep layer of the posterior tibial
muscles. By its borders, it is continuous with the tibial aponeurosis or fascia.
Superiorly, it adheres most intimately to the perforatus tendon, near the point where
the latter originates ; then it sends off a thick fasciculus that descends to the
gastrocnemius tendon. Below this, it appears to divide into two branches — an
external and internal — which are united to the calcanean cap of the perforatus
tendon, and are attached to the sides of the os calcis in such a manner, that
near its insertion the gastrocnemius tendon is found to be enveloped by a complete
fibrous sheath, formed partly by the perforatus tendon and partly by the band
just described. This latter, therefore, constitutes a strengthening apparatus for
the tendon of the gastrocnemius — a structure noticed by Girard, who made it a
branch of insertion of the semitendinosus ; and not without reason, perhaps,
because it arises from the tibial aponeurosis, which, in part at least, is itself
derived from the semitendinosus muscle.
Preparation of the Muscles of the tegr.— Separate the limb from the trunk by sawing through
the femur at its middle. Dissect the insertions of the superficial gluteus, the biceps femoris,
the gracilis, and the semitendinosus, to observe the continuity of these muscles with the
tibial aponeurosis : study the insertions of this aponeurosis, particularly that which it has on
the summit of the os calcis. To expose the muscles, remove their aponeurotic envelope, leaving,
however, the band it forms in front of the tendon of the gastrocnemius, as well as the bands
•which retain the tendons. Eemove the hoof in the manner already indicated for the anterior
extremity, and, finally, separate the muscles from one another — an operation so very simple
as not to require any special directions.
A. Anterior Tibial Region.
This is composed of three muscles : the flexor of the metatarsus, the anterior
extensor, and the lateral extensor of the phalanges. The first is deep-seated, the
other two are superficial.
MUSCLES OF THE POSTERIOR LIMBS 363
1. Anterior Extensor of the Phalanges (Extensor Pedis) (Fig. 201, 20).
Synonyms.— FemoTO-piepheilaugeus—Girard. The exten8or longus digitorum pedis of Man.
Situation — Direction— Extent. — This muscle, situated in front of the leg and
foot, follows the direction of these two sections for their whole extent.
Form — Strmture. — It is formed of a muscular body and a tendon. The first
Fig. 201.
EXTERNAL DEEP MUSCLES OF RIGHT POSTERIOR LIMB.
1, Crest of the ilium; 2, inferior sacro-sciatic ligament; 3, sacro-sciatic ligament; 4, obturator
ligament; 5, tuberosity of the ischium; 6. anterior tuberosity of the ilium; 7, deep gluteus,
8, its insertion into the great trochanter, 9 ; 10, iliacus; 11, vastus externus; 12, rectus femoris ;
13, great sciatic nerve; 14, gracilis; 15, sartorius; 16, patella; 17, lateral ligament; 18, oblique
flexor of the phalanges, or flexor pedis accessorius ; 19, peroneus ; 20, extensor pedis; 21,
soleus, or plantaris ; 22, gastrocnemius; 23, flexor pedis; 24, tendon of oblique flexor of the
phalanges; 26, perforatus tendon; 26, lateral ligament of perforatus tendon; 27, 28, annular liga-
ment ; 29, tendon of lateral extensor of the phalanges, or peroneus ; 30, external rudimentary
metatarsal bone
is fusiform, flat on each side, aponeurotic at its superficies in its superior moiety,
and tendinous internally in its inferior moiety. The tendon, at first round, then
flat, commences a little above the inferior fourth of the tibia, and reaches the
anterior face of the principal metatarsus, where it receives the extensor brevis,
364 TEE MUSCLES.
the tendon of the peroneus, and a funicular prolongation of the tibial aponeurosis.
It afterwards descends on the fetlock, where it comports itself exactly as the
corresponding tendon in the anterior extremity (see the extensor pedis in the
fore limb, p. 324).
Attachments. — Above, in the digital fossa between the trochlea and external
condyle of the femur, through the medium of the tendinous portion of the flexor
metatarsi— ^j-et? insertion. Below, on the capsular ligament of the metatarso-
phalangeal articulation, the anterior face of the two first phalanges, and the
pyramidal process of the os pedis.
Relations. — The muscular portion responds : outwardly, with the tibial
aponeurosis ; inwardly, to the flexor metatarsi ; posteriorly, to the peroneus.
The tendon successively covers : the anterior aspect of the tibia, the anterior
capsular ligament of the tarsus, the pedal muscle, the anterior face of the
principal metatarsal, the articulation of the fetlock, and the two first phalanges.
It is covered by the tibial aponeurosis, and by three annular fibrous bauds which
maintain the tendon in the bend of the hock. One of these bands — the superior
— is fixed by its extremities to the tibia, a little above the tibio-tarsal articulation ;
it is common to the muscle we are describing, and to the flexor metatarsi. The
middle band, attached to the cuboid branch of the latter muscle and the inferior
extremity of the os calcis, is for the anterior extensor of the phalanges. The
inferior maintains the two extensors against the superior extremity of the
principal metatarsal.
Action. — This muscle extends the digit and flexes the entire foot.
2. Lateral Extensor of the Phalanges (Peroneus) (Fig. 201, 19).
Synonyms. — Peroneo-prephalangeus— GiVard. The peroneus brevis of Man. (Tibio-
prephalangeus — Leyh.)
Situation — Form — Structure — Extent — Direction. — Situated on the external
side of the leg, between the preceding and the deep flexor of the phalanges, it is
composed of a muscular portion and a tendon. The fii-st, elongated, prismatic,
and slightly penniform, extends in the direction of the leg, from the superior
extremity of that region to beyond its inferior extremity. The tendon succeeds
the lower end of the muscular portion, and traverses the groove on the middle
of the infero-external tuberosity of the tibia, passing to the external side of the
tarsus, where it is enclosed in a very firm sheath, and is inflected forwards to
become united to the tendon of the anterior extensor, near the middle of the
metatarsal region.
Attachments. — It is attached, by the superior extremity of its muscular fibres,
to the external femoro-tibial ligament, to the whole extent of the fibula, and to
the fibrous partition which separates this muscle from the perforans — origin. It
terminates in the tendon of the anterior extensor.
Relations. — Its muscular body is enveloped in a special containing aponeu-
rosis, which separates it, in front, from the anterior extensor, and behind from
the perforans. The tendon covers the tibia, and margins the external and
superficial ligament of the tibio-tarsal articulation ; this ligament suppHes a
fibrous ring for the formation of its reflected sheath. A bursa facilitates its
motion in the interior of this sheath.
Action. — It acts Uke the preceding.
MUSCLES OF TEE POSTERIOR LIMBS.
3. Flexok of the Metatarsus (Flexor Metatarsi) (Fig. 202).
Synonyms. — Tibio-premetatarsus— GtVard. Its muacular portion represents the tibialis
anticus of autliropotomists.
This muscle is situated beneath the anterior extensor of the phalanges, on the
external surface of the tibia, and is composed of two distinct portions— one muscu-
lar, the other aponeurotic, not united from end to end,
but placed parallel one before the other.
A. Tendinous Portion (Fig. 202, 1). — Course —
Attachments. — This is a strong, pearly- white cord, com-
prised between the muscular portion and the anterior
extensor of the phalanges. It commences at the inferior
extremity of the femur, in the fossa between the trochlea
and the external condyle ; it afterwards passes through
the superior groove of the tibia, where it is enveloped
by a prolongation from one of the synovial membranes
of the femoro-tibial articulation, giving origin, below
this groove, to the muscular fibres of the anterior ex-
tensor of the phalanges. Lower, it receives some of
the fasciculi from the muscular portion, to which it
sends, in exchange, several aponeurotic layers ; it passes
under the superior annular band in front of the hock,
in company with the anterior extensor, and reaches the
level of the trochlea of the astragalus, where it is
perforated to form a ring for the passage of the inferior
extremity of the muscular portion. It finally terminates
in two branches : a large one, inserted in front of
the superior extremity of the principal metatarsus (Fig.
202, 4) ; the other, narrower, deviates outwards to reach
the anterior surface of the cuboid bone (Fig. 202, 3).
Relations. — In front, with the anterior extensor of
the phalanges ; behind, with the muscular portion and
the anterior capsular ligament of the tarsus.
Action. — This tendon enjoys the curious property of
bending the hock by an action altogether mechanical,
whenever flexion of the superior bones of the limb takes
place. It is, therefore, a conducting cord which regu-
lates the movements of flexion in the hock, and con-
forms them to those taking place in the other joints,
without requiring the intervention of an active agency
for the execution of these movements.
Another function has also been attributed to it —
that of passively opposing the flexion of the femur on
the tibia while the animal is standing, and in this
way serving as an adjunct to the muscular force which supports the weight of
the body. But, in our opinion, this is incorrect ; as, in order that it may perform
this task, it would be necessary for the foot to be maintained in a fixed position
by the contraction of its extensor muscles. But these muscles are really the
heads of the gastrocnemius, which have their origin behind the femur, and
which undoubtedly tend to flex that bone on the tibia — that is, to determine
FLEXOR METATARSI.
Tendinous portion ; 2, Ha
attachment to the femur;
3, its cuboid branch ; 4,
its metatarsal branch ; 5,
muscular portion ; 6, its
tendon passing through
the ring of the tendinous
portion ; 7, cuneiform
portion of this tendon;
8, its metatarsal branch ;
9, anterior extensor of the
phalanges drawn outwards
by a hook. A, Lateral
extensor; B, tibial inser-
tion of the middle patel-
lar ligament; C, femoral
trochlea
866 THE MUSCLES.
the movement it is supposed to prevent. And experiment clearly shows that we
are justified in this opinion ; for division of this tendon in the living animal
does not interfere in the slightest degree with its natural attitude, either when
standing at liberty or when compelled to stand.^
B. Muscular Portion. — Situation — Form — Structure. — Situated between
the tendinous cord and the tibia, this portion is elongated from above to below,
very wide at its superior part and narrow inferiorly, where it terminates in a
bifid tendon.
Attachments. — It originates, by the upper extremity of its muscular fibres,
from the tibia, below and on the sides of the groove through which the tendon
passes ; its most superficial fibres are even attached to the aponeurotic sheath
which envelops the lateral extensor. Its terminal tendon (Fig. 201, 6) traverses
the annular ligament which the tendinous portion forms at its inferior extremity,
and becomes inserted, by one of its branches, in front of the superior extremity
of the principal metatarsal bone, along with the analogous branch of the
tendinous division (Fig. 200, 8). The other ramification is directed to the
inside of the tarsus, to be attached to the second cuneiform bone (Fig. 202, 7).
Relations. — In front, with the tendinous portion of the muscle and the
anterior extensor of the phalanges ; behind, with the external face of the tibia.
The tendon, after traversing the annular ligament of the cord, covers the
metatarsal branch of the latter, and is in turn covered by the anterior extensor.
Action. — It is an active agent in flexing the foot on the leg.
B. Posterior Tibial Region.
This region includes six muscles, which are arranged in two superposed
layers behind the tibia. The superficial layer is formed by the gastrocnemii,
soleus or plantaris, and the superficial flexor of the phalanges. The deep layer is
composed of the popliteus, the deep flexor, and the oblique flexor of the phalanges.
• J. F. Meckel rightly considers this tendinous cord, not as a portion of the anterior tibial,
but as a dependency of tlie extensor longus digitorum. It would be wrong, however, to
describe it apart fioin the anterior tibial, properly so-called— that is, the muscular portion of
our flexor metatarsi, the two being, in their action, essentially one.
Is there anything in the human species analogous to this fibrous cord? After much
hesitation, we answer in the affirmative, and give it as our opinion that this tendon represents
the peroneus tertius in Man. These are our reasons tor making tliis assertion, hazardous as it
certainly is at first sight: In Man, the peroneus tertius cannot always be easily distinguished
from the extensor loiigus digitorum ; so that these two muscles may be regarded as a single
one until reaching the instep, where it extenda to the phalanges of the toes on the one part, nnd
the metatarsus on the other. Precisely the same arrangement is found in Solipeds ; the single
muscle divides into two fasciculi, one for the digital region (anterior extensor of the phalanges),
the other to the metatarsal region (tendon of our flexor metatarsi). This tendon, then, exactly
represents the fasciculus of the long common extensor of the toes (in Man), which goes to the
metatarsus, and is designated the peroneus tertius.
But to this it may be said : Your peroneus tertius in the Horse has no relation whatever to
the peroneus, and does not this prove that you are in error? No ; for if this muscle is attached
to the fibula in Man, it is because the principal muscle on which it depends is inserted there
itself. But as the anterior extensor of tlie phalanges of the Horse— that is, the common
extensor of the toes— is not inserted into the fibula, and has no connection with it in any way,
its metatarsal fasciculus— or rather its tendinous cord or peroneus tertius— ought to be absolutely
in the same condition. We repeat, however, that this opinion may be, perhaps, a little
hazardous ; and we give it with reserve, though we have some reasons for considering it to be
correct.
MUSCLES OF TEE POSTEBIOB LIMBS.
367
!. Gastrocnemius, or Gemelli of the Tibia (Gastrocnemius Externus)
(Figs. 201, 22 ; 203, 20).
Synonyms. — Bifemoro-calcaneus — Girard.
Situation— Comj)ositio7i—Extent.— The gemelli of the leg, situated behind the
Fig. 203.
MUSCLES ON INNER ASPECT OF LEFT POSTERIOR LIMB.
1, Crest of the ilium; 2, section through it; 3, sacro-sciatic ligament; 4, pyriformis; 5, posterior
portion of sacro-sciatic ligament ; 6, tuberosity of ischium ; 7, anterior portion of ischium, sawn
through; 8, pubis; 9, obturator foramen; 10, external iliac artery and vein, 11; 12, obturator
artery and vein (the figures are placed on the internal obturator muscle); 13, long adductor of
the leg, or sartorius; 14, small adductor of the thigh, or adductor parvus; 15, short adductor
of the leg, or gracilis; 16, rectus of the thish ; 17, vastus internus ; 18, patella, with insertion
of rectus; 19, upper extremity of tibia; 20, gastrocnemius; 21, popliteus ; 22, oblique flexor
of the phalanges, or flexor pedis accessorius, with its tendon, 34; 23, perforans muscle, with its
tendon, 35 ; 24, flexor metatarsi ; 25, anterior extensor of the phalanges, or extensor pedis ; 26,
annular ligament ; 27, tendon of flexor metatarsi, and its cunean branch. 28 ; 29, tendon of the
superficial flexor of the phalanges; 30, tendon of gemelli or gastrocnemius; 31, os calcis ;
32, astragalus; 33, perforatus tendon ; 34, tendon of oblique flexor joining the perforans
tendon, 35 ; 36, large metatarsal bone ; 37, extensor pedis tendon ; 38, terminal knob of small
metatarsal bone.
femoro-tibial articulation, below the ischio-tibial muscles, constitutes two thick
368 THE MUSCLES.
fleshy fasciculi distinct from one another only at their superior extremity, being
confounded for the remainder of their extent, and continued inferiorly by a
single tendon which extends to the point of the os calcis.
Form — Stnicture. — Both of these muscular masses are flattened on both
sides, thick in the middle, narrow at the extremities, and intersected by strong
tendinous bands. By their union they form a wide channel, open in front, which
embraces the femoro-tibial articulation and the muscles of the deep layer.
The tendon, at first fasciculated, then single and funicular, receives that of
the soleus, and is reinforced by a fasciculus from the fibrous band annexed in
front to the tendon of the perforatus (see the description of the tibial aponeurosis,
p. 362). An aponeurotic layer which covers the gastrocnemius, is continued
downwards, partly with the fibrous band, and partly with the tendon of the
muscle itself.
Attachments. — The external gemellus arises on the femur, from the rugged
lip which margins the supra-condyloid fossa in front ; the internal, from the
collection of tubercles which constitutes the crest of the same name. The
terminal tendon of the two bellies is fixed on the summit of the os calcis, not at
its anterior part, but posteriorly ; this being lubricated by a bursa that forms a
gliding surface on which the tendon rests during extreme flexion of the foot
(Fig. 101, 1).
Relations. — By their superficial face, to the three ischio-tibial muscles, and
the tibial aponeurosis ; by their deep face, to the perforatus — which adheres
intimately to the vastus externus — to the posterior ligament of the femoro-
tibial articulation, the popliteal muscle and vessels, the great sciatic nerve, and
the oblique and deep flexor muscles of the phalanges. The tendon lies beside
that of the perforatus, which is twisted around and completely envelops it at
its inferior extremity, in common with the fibrous band from the tibial aponeu-
rosis. The two tendons form what is usually termed the tendon of the hock, or
tendo Achilles.
Action. — The gastrocnemius extends the foot upon the tibia. It acts as a
lever of the first order when the limb is raised from the ground, and as one of
the second order when the hoof is placed on the ground. It maintains the
tibio-tarsal angle while the animal is standing, and in progression gives to the
hock that spring which carries the body forward.
2. Soleus (Plantaeis) (Fig. 201, 21).
Synonyms. — Bourgelat and liis successors have erroneously assimilated it to the plantaris of
Man. In regarding this little muscle as the soleus, we conform to the well-founded opinion
of Cuvier. It is the peroneo-calcaneus of Girard.
Form — Situation. — This is a thin, long, and riband-shaped rudimentary
muscle, situated at the external side of the leg, between the tibial aponeurosis
and the muscular portion of the perforans.
Attachments. — It is fixed, by its superior extremity, behind the supero-external
tuberosity of the tibia ; and terminates, inferiorly, by a small tendon, which joina
that of the gastrocnemius.
Action. — It is a feeble auxihary of the last-named muscle.
MUSCLES OF THE POSTERIOR LIMBS. 369
3. SuPEEFiciAL Flexor of the Phalanges (Flexor Perforatus,
Gastrocnemius Internus) (Figs. 201, 25 ; 203, 30).
fi'j/no/ij/ms.— Femoro-phalangeus — Girard. It is represented in Man by the plautaris and
flexor brevis digitorum, or perforatus. Tliese two, in the majority of Mammalia, are united
from end to end to form a single muscle.
Form — -Structure. — The perforatus of the posterior limb is only represented,
in reality, by a long tendinous cord that is somewhat muscular, slightly thickened,
and fusiform in its upper fifth, which forms the body of the muscle.
Origin — Direction and Relations — Termination. — It originates, by its upper
extremity, in the supra-condyloid fossa, descends between the two portions of the
gastrocnemius — to the external of which it is intimately related — on the posterior
face of the femoro-tibial articulation, and on the three posterior deep tibial
muscles. On reaching the inferior extremities of the muscular bellies of the
gastrocnemius, it becomes exclusively tendinous, and is directly united to the
fibrous band which reinforces the tendon of the hock. It afterwards disengages
itself below the gastrocnemius, and is placed at the internal side of its tendon,
then on its posterior surface, and in this position gains the summit of the os
calcis. There it becomes widened to form a fibrous cap, which is covered by a
large vesicular synovial membrane ; it is moulded to the posterior region of this
bony eminence, which it completely envelops in order to be fixed on its lateral
portions, and is united to the calcanean band from the tibial aponeurosis. From
this point the tendon of the perforatus is prolonged behind that of the perforans,
to the posterior face of the second phalanx, where it terminates in exactly the
same manner as the analogous muscle of the anterior limb.
Action. — It flexes the second phalanx on the first, and this on the metacarpus
It also concurs in the extension of the foot. Its principal office, however, is that
of a mechanical stay, destined to sustain the equilibrium of the body while the
animal is in a standing posture, by preventing the diminution of the angle of
the hock and that of the fetlock — the femur being fixed by the contraction of the
crural triceps and the gluteal muscles.
Beep Layer.
4. PoPLiTEUS (Fig. 203, 21).
Synonyms. — The abductor tibialis of Bourgelat, and femoro-tibialis obliquus of Girard.
Situation — Direction — Form — Structure. — Situated behind the tibia, below
the femoro-tibial articulation, this muscle is oblique downwards and inwards,
short and triangular, tendinous at its supero-external angle, and formed, for the
remainder of its extent, of divergent fleshy fibres, the longest of which are the
most inferior.
Attachments. — 1. In the lowest of the two fossae on the outside of the external
condyle of the femur, by its tendon — origin. 2. On the supero-posterior trian-
gular surface of the body of the tibia, by the inferior extremity of its muscular
fibres — termiyiation.
Relations. — Posteriorly, with the gastrocnemius and perforatus. In front,
with the posterior ligament of the femoro-tibial articulation, and the pophteal
vessels. Outwards, with the oblique and deep flexors of the phalanges. Inwards,
with the semitendinosus and tibial aponeurosis. The tendon, concealed at its
origin beneath the external femoro-tibial ligament, glides, by its deep face, over
370
TEE MUSCLES.
the contour of the external semilunar cartilage and the posterior portion of the
external facet on the tibia.
Action. — It flexes the tibia, and gives
^'S- 2^"*- it a slight rotatory movement outwards.
5. Deep Flexoe of the Phalanges
(Flexor Perforans, Flexor Pe-
dis) (Figs. 201, 23 ; 203, 23).
Synonyms. — Tibio-phalangeus — Girard.
The flexor perforans and flexor longus pollicis
pedis of Man. {Great tibio-phalangeus — Leyh.)
Extent — Situation — Direction — Com-
position.—Extending from the superior
extremity of the leg to the third phalanx,
and situated behind the tibia and foot,
the direction of which it follows, this
muscle is composed of a muscular body
and a tendon.
Form, Structure, mid Attachments of
the muscular portion. — This is thick and
prismatic, and incompletely divided into
two portions — an internal,^ and an ex-
ternal,^ which is the most voluminous.
It is attached : 1. To the posterior face
of the tibia, on the linear imprints which
occupy the inferior triangular surface.
2. To the supero-external tuberosity of
the same bone. 3. To the peroneus.
4. To the interosseous ligament uniting
that bone to the tibia.
Direction and Attachments of the
tendon. — The tendon commences above
the inferior extremity of the tibia,
where it is usually double, each muscular
portion being succeeded by a tendon,
the volume of which is in harmony with
the size of the muscle from which it
proceeds. The single tendon resulting
from the union of these two primary
ARTICULAR CAPSULES AND BURs^ IN THE ^^^s, cutcrs thc groovc f ormed by the
POSTERIOR LIMB OF THE HORSE. iuuer facc of thc OS calcis, where it is
I, Tibio-tarsal capsule (bulging anteriorly); 2, retained by a fibrOUS arch which
ibid, (bulging posteriorly); 3 superior cW-cfe- transforms this channel into a perfect
sac ot the tarsal bursa; 4, inferior cul-de-sac ^
of the same; 5, capsule of the metatarso
phalangeal articulation ; 6, 7, 8, superior, middle, and inferior culs-de-sac of the sesamoid bursa ;
9, posterior cul-de-sac of capsule of the first interphalangeal articulation ; 10, inferior part of the
sesamoid bursa completely exj)osed by excision of the reinforcing membrane of the perforans
tendon; 11, lateral cul-de-sac of the second interphalangeal or pedal articulation. T, Tibia;
M, matatarsus; C, lateral cartilage turneii outwards and forwards; Fs, perforatus tendon; Fp,
perforans tendon ; Ls, suspensory or superior sesamoid ligament.
The tibialis posticus of Man.
* The flexor longus pollicis of Man.
MUSCLES OF THE POSTERIOR LIMBS. 371
sheath, named the tarsal sheath. It glides in the interior of this canal by
means of a very extensive bursa, which extends upwards on the posterior liga-
ment of the tibio-tarsal articulation, and is prolonged inferiorly to the middle
third of the metatarsus. The tendon of the perforans afterwards descends,
vertically, behind the suspensory ligament, receiving from it a strong fibrous
band (the suhtarsal ligament), analogous to that of the fore limb, but less
voluminous ; it then passes through the annular portion of the perforatus, is
inflected with that muscle over the sesamoid groove, glides on the posterior
articulating surface of the second phalanx and that on the navicular bone,
thinning out into a plantar aponeurosis, which is provided with a phalangeal
reinforcing sheath, and finally terminates on the semilunar crest of the os pedis.
This tendon, therefore, on leaving the tarsus, comports itself exactly like that of
the anterior limb.
Relations. — Outwards, with the lateral extensor of the phalanges, the soleus,
and the tibial aponeurosis. Inwards, with this aponeurosis and the oblique flexor.
Behind, with the gastrocnemius, the perforatus, and the fibrous band of the tendon
of the hock. In front, with the tibia.
The tendon glides in the tarsal sheath by means of a very extensive bursa that
ascends on the posterior ligament of the tibio-tarsal articulation, behind which it
appears as a soft tumour (thoroughpin) when it is distended by synovia (Fig.
204, 3). The bursa descends to about the lower third of the metatarsal region.
Action. — This muscle flexes the phalanges on one another and on the meta-
tarsus. It may also extend the foot in pressing, during its contraction, behind
the tibio-tarsal articulation. In addition to this, its tendon acts, while the
animal is standing, as a mechanical support to the phalanges and the articular
angle of the fetlock.
In the Ass and Mule, the tendon of the perforans does not receive any sub-
tarsal ligament, this being absent in them.
6. Oblique Flexor of the Phalaijges (Flexor Accessorius)
(Fig. 203, '22)
Synonyms. — Peroneo-phalangeus— G/rard. The tibialis posticus of Man. (Small tihio-
phalangeua — Leyh.)
Situation — Direction — A muscle situated behind the tibia, between the pop-
liteus and the perforans, in a direction slightly oblique downwards and inwards.
Form — Structure. — It is composed of a fleshy fusiform body, intersected by
numerous fibrous bands, and provided with a funicular tendon inferiorly
Attcichments. — The superior extremity arises behind the external tuberosity
of the tibia — origin. The tendon is united, by its inferior extremity, to that of
the perforans towards the upper third of the metatarsal region — termination.
Relations. — The muscular portion responds : in front, to the perforans, the
popliteus, and the posterior tibial artery ; behind, to the gastrocnemius and the
perforatus. The tendon, at first lodged in a muscular channel in the perforans
and covered by the tibial aponeurosis, afterwards enters a tortuous sheath at the
inner side of the tai-sus, and which is formed by the groove that inchnes behind
the infero-internal tuberosity of the tibia.
Action. — It is a congener of the deep flexor.
872
THE MUSCLES.
Differential Characters in the Muscles of the Leg in the other Animals.
1. Anterior Tibial Region.
A. Ruminants.
Fi^. 205.
external muscles of the leg of
the ox.
1, Originating tendon of the muscle which
represents the anterior extensor of the
phal.inges and the flexor metatarsi in
the horse ; 2, its flexor fasciculus ; 5,
that which forms the common extensor
of the digits ; 5', the tendon of this
fasciculus ; 6, its terminal bifurcation ;
3, the long lateral peroneus; 3', its
tendon; 4, origin of the anterior tibial
(the muscular portion of the flexor
metatarsi in the horse) ; 7, proper ex-
tensor of the external digit (short
lateral peroneus); 8, its tendon ; 9, its
insertion into the second phalanx ; 10,
its insertion into the third phalanx ; 11,
external belly of the gastrocnemius ;
ir, its tendon ; 12, soleus; 13, tendon
of the perforatus ; 14, perforans ; 14',
its tendon; 15, suspensorj' ligament of
the fetlock; 16, the band it gives off
to the perforatus tendon ; 17, that
which it sends to the proper extensor
of the external digit
Among these animals, the Ox presents:
1. A complex muscle, which is represented in the
Horse by the anterior extensor of the phalanges, and
the tendon of the flexor metatarsi. Single at its
superior extremity, which begins by a tendon arising
from the digital fossa situated between the trochlea
and the external condyle of the femur (Fig. 205, 1),
this muscle comprises in its middle part three fleshy
divisions, which are terminated inferiorly by tendons.
One of these divisions, situated in front of, and
within the other two, has its tendon prolonged to the
extremity of the principal metatarsal bone, and is also
inserted into the cuneiform bones. It is a flexor of
the metatarsal region, and replaces the tendon which
performs this function in Solipeds (Fig. 205, 2).
The second, placed external to the preceding, con-
stitutes a common extensor of the digits, the tendon of
which cumports itself exactly like that of the anterior
limb (Fig. 205, 5, 5', 6).
The third, concealed by the other two, forms the
proper extensor of the internal digit, and resembles its
fellow in the fore extremity.
2. An anterior tibhd muscle (muscular portion of
the flexor metatarsi of the Horse). It is a triangular,
muscular body, lodged in the antero-external fossa
of the tibia, into the upper part of wliich it is in-
serted, and is succeeded by a tendon that commences
towards the middle of the tibia. This tendon passes
through a ring pierced iu the tendon of the muscle
that represents the tendinous portion of the flexor
metatarsi ; it then deviates inwards, and is fixed into
the cuneiform bones and superior extremity of the
principal metatarsal bone (Fig. 205. 4).
3. A proper extensor of the external digit (lateral
extensor of the phalanges in Solipeds, the peroneus
brevis lateralis in Man), the fleshy body of which is
altogether similar to that of the analogous muscle
in the Horse, and is terminated by a long tendon
which resembles that of the proper extensor of the
internal digit (Fig. 205, 7, 8, 9, 10).
4. A muscle which represents the peroneous hngtis
in Man, and of which in Solipeds there is not a trace.
This muscle commences by a short, conical, muscular
body in front of the supero-external tuberosity of the
tibia, and terminates by a long tendon, the direction
of which is as follows : included at first, like the
muscular portion, between the proper extensor of the
external digit and the triple muscular fasciculus
already described, it arrives on the outside of the
tarsus, passes through the fibrous groove of the proper
extensor, where it is enveloped by a special synovial
membrane, passes over the latter in slightly crossing
its direction, and is inflected at first backwards, then
outwards, by insinuating itself underneath the ex-
ternal tibio-tarsal ligament, and the calcaneo-meta-
tarsal and the posterior tarso-metatarsnl lijjaments,
which retain it in a chaimel on the inferior face of
18, the pedal
muscle ; 19, the insertion of the biceps femoris on the patella, and its external ligament.
MUSCLES OF THE POSTERIOR LIMBS. 373
the cuboido-scaphoid bone. It is finally inserted into the deep face of the second cuneiform
bone, and the external side of the superior extremity of the metatarsus, by a small branch
detached from the outer side of the principal tendon.
All these muscles are similarly disposed in the Sheep and Goat.
B. Pig.— The anterior tibial muscles of this animal resemble those of Ruminants, with the
exception of some peculiarities of secondary importance, among which the following may be
cited :
The muscular fasciculus which replaces the /e.cor metatarsi in the Horse, terminates on the
scaphoid and the second cuneiform bone. The common extensor of the digits has four tendons —
one for each digit. The proper extensors have two each — one for the small digit, and the other
for the great. The anterior tibial passes to the second cuneiform bone. The peroneus longus
lateralis is inserted, by its tendon, into the upper extremity of the internal metatarsus.
C. Camivora.— Four muscles are described in these animals : 1. An anterior tibial. 2.
A long common extensor of the digits. 3. A long lateral peroneus. 4. A short lateral
peroneus.
1. Anterior tibial. — Situated in front of the tibia, and more voluminous than tlie common
extensor of the digits, the superior extremity of which it covers, this muscle has its origin on
the crest and external tuberosity of the tibia. It receives, near the inferior third of this bone,
an extremely thin muscular baud which proceeds from the fibula, and which we may with
justice compare to the proper extensor of the big toe in Man. Then it terminates by a tendon
on the metatarsal bone of the internal digit; when this bone is connected with a digital
region, the third phalanx receives a particular branch from this tendon, which represents the
tendinous portion of the small proper extensor fasciculus annexed to the anterior tibial. This
muscle responds: in front, to the tibial aponeurosis; inwards and backwards, to tiie tibia;
outwards, to the common extensor of the digits. Its tendon is fixed in the bend of the liock
by a fibrous band, the arrangement of which is singular enough to deserve mention here.
Attached in front of the inferior extremity of the tibia, this band gives origin, by its internal
extremity, to a strong ligament which passes under the tendon of the anterior tibial muscle to
reach the anterior face of the tarsus, wliere it unites closely with the capsular ligament of this
region, and terminates on the superior extremity of tlie metatarsal bone of the middle digit.
This ligament binds the inferior extremity of the tibia to tlie metatarsus, and prevents undue
extension of the tibio-tarsal articulation. It is, perhaps, the representative of the tendon of
the anterior tibial reginn in the Horse.
2. Long common extensor of the digits. — This muscle is composed of a fusiform fleshy body,
and a quadrifurcated tendon. The flesliy body, situated beneath the tibial aponeurosis,
between the anterior tibial and the lateral peroneal muscles, covers the external face of the
tibia and the small fasciculus of tiie proper extensor of the thumb; it originates by a short
and strong tendon, from the inferior extremity of the femur, between the external condyle and
the trochlea. The tendon is continuous with the inferior extremity of the fleshy portion,
passes beneath the band of the anterior tibial, through another fibrous ring at the cuboid bone,
and is inserted, by its four terminal branches, into the four large digits, in the same manner
as the analogous tendon in the fore limb.
3. Long lateral peroneus. — This muscle is composed of a very short, conical, fleshy portion,
succeeded by a long tendon. Tlie former originates in front of the tuberosity of the supero-
external tuberosity of the tibia, and does not appear to have any connection with the fibula.
Included between the common extensor of the digits and the short lateral peroneus, it is
covered by the tibial aponeurosis, and covers the anterior tibial vessels. The tendon descends
parallel with tlie fibula to its inferior extremity, over which it glides in becoming inflected.
On reaching the cuboides, t enters a groove excavated on its external surface, gives off a short
isolated branch to the superior extremity of the first metatarsal bone, afterwards crosses trans-
versely the direction of the tarsus in passing behind the inferior row of bones, and terminates
on the metatarsus of the thumb. On its way, behind the cuboides, this tendon gives ofi" another
branch, which we have every reason to believe is constantly present ; it is a short, interosseous
fasciculus, that at first penetrates between the cuboides and the external metatarsal bone, then
between the latter and the second metatarsal.
This muscle carries the inferior extremity of the limb outwards, and when the foot Is much
extended it may act as a flexor.
4. Short lateral peroneus. — In Camivora, this muscle is formed by two fasciculi — a superior
and inferior, which may be described as two distinct muscles.
The superior fasciculus is a very weak muscular portion, attached to the upper third of the
anterior border of the fibula, and a funicular tendon succeeding its inferior extremity about
the middle of the tibia. Tiiis tendon glides over the inferior extremity of the fibula, behind
374 THE MUSCLES.
the long lateral peroneus, which it passes under ami crosses, in descending to the phalanges
of the external digit, where it is united to the tendinous branch of the common extensor
belonging to this digit.
The inferior fasciculus has its origin on the anterior border and external aspect of the
peroneus, by penniform fibres, which join a short, but more voluminous tendon than that of
the preceding fasciculus. This tendon, with tlie last, enters the posterior groove in the fibula,
and is attached, by its inferior extremity, to the upper end of the external metatarsus, outside
the branch furnished by the long lateral peroneus to that bone.
The superior fasciculus acts as a proper extensor of the external digit. The inferior is an
abductor of the foot.
2. Posterior Tibial Region.
A. Ruminants.— In the Ox, Sheep, and Goat, tlie muscular portion of the perforatum
is thicker than in Snlipeds. The portion of the per/oratis which represents the tibialis posticus
is also better defined than in them ; it is lodged in a depression on the principal portion, and
can easily be traced from the supero-external surface of the tibia, where it originates. The
tendon does not differ from that in the fore limb; but the bands which descend from the
metatarsus to the heels, to be united witli the two terminal branches of this tendon, are much
smaller than those in tiie metacarpal region.
In the Camel, the popliteus is altogether confined to the upper and posterior part of the
tibia. The perforatus is almost exclusively tendinous ; in its deeper portion there is a slight
expansion in which there are a few muscular fibres. The perforans has a very small fusiform
muscle ; its tendon glides on the internal face of the oscalcis, in a slight depres.sion representing
the tarsal bursa; it unites with the oblique flexor, and comports itself as in the anterior limb.
The oblique flexor of the phalanges is remarkable for its volume; instead of being an accessory
to the deep flexor, as in the other species, it alone forms the principal head of the perforans
tendon, the essential fleshy body of which is found, on the contrary, to be represented in the
majority of the other animals, by the analogue of the long flexor of the great toe.
B. Carnivora.— The soleus is absent in the Dog, but it is found in the Cat. The
muscular body of the perforatus is prismatic, voluminous, and entirely blended— in its upper
two-thirds at least— with the external head of the gastrocnemius; these two muscles have
therefore a common origin. The tendon is quadrifurcated, as in the anterior Umb ; it offers
on its surface, shortly before its division, several thin muscular bands, traces of the fleshy
portion of the common short muscle of the toes in Man. Several of these bauds come from
the perforans tendon, and all pass to the four terminal branches of the muscle. The terminal
tendon of the perforans is divided into four or five branches, one for each digit.
The posterior tibial is not united, inferiorly, to this tendon, but constitutes a perfectly
distinct muscle situated between the deep and oblique flexors of the phalanges. Formed by a
very small fleshy body and a long thin tendon, it arises above the peroneus, from the posterior
surface of the tibia. Its tendon lies beside that of the oblique flexor, and with it enters the
groove behind, and within the inferior extremity of, tlie tibia. Enveloped by a synovial mem-
brane proper to its passage through this groove, this tendon soon leaves it to pass to the free
surface of the posterior tarso-metatarsal ligament, with which it is blended towards the middle
of the tarsus.
Comparison of the Muscles of the Leg of Man with those of Animals.
In Man, the muscles of the leg are divided into three regions : an anterior, external, and
posterior.
1. Anterior Region (Fig. 20t5).
This includes three muscles :
1. The anterior tibial, which corresponds to the fleshy portion of the flexor of the meta-
tarsus, and the imperforate tendon of which is fixed into the first cuneiform.
2. The common long extensor of the toes, which represents the anterior extensor of the
phalanges of the Horse. This muscle is attached, above, to the external tuberosity of the
tibia and the upper three-fourths of the inner face of tlie fibula : its tendon divides into two
fasciculi, the internal of which furnishes a branch to the second, third, and fourth toes, and
tiie external goes to the fifth.
3. The proper extensor of the great toe, represented in the Dog by a small fasciculus
blended with the anterior tibial, is an elongated semi-penniform muscle that arises from the
inner face of the fibula and the interosseous ligament, and terminates on the second phalanx of
the great toe, after receiving the pedal tendon (extensor brevis digitorum).
MUSCLES OF THE POSTERIOR LIMBS.
375
2. External Kkgion (Fig. 206).
This region is only composed of two muscles : the long and short peroneus.
The first, which does not exist in Solipeds, is a penniform muscle attached to the upper
third of the fibula, the external tuberosity of the tibia, and the internal face of the tibial
aponeurosis, by the superior extremities of its muscular fibres. The flat tendon which termi-
nates it is fixed to the outer portion of the base of the first metatarsal.
The second corresponds to the lateral extensor of the phalanges of the Horse, and is found
Fig. 206.
Fi^. 207.
,5
SUPERFICIAL POSTERIOR MUSCLES OF THE
HUMAN LEG.
1, Biceps forming outer ham-string ; 2, ten-
dons forming ianer ham-string ; 3, popli-
teal space ; 4, gastrocnemius ; 5, 5, soleus ;
6, tendo-Achilles ; 7, posterior tuberosity
of OS calcis ; 8, tendons of peroneus longus
and brevis passing behind the outer ankle ;
9, tendons of tibialis posticus and flexor
longus digitorum passing into the foot
behind the inner ankle.
OF THE HUMAN LEG (ANTERIOR
TIBIAL REGION).
1, Quadriceps extensor inserted into the pa-
tella (the figure is on the tendon of the
rectus, the vastus internus and externus
being on each side) ; 2, subcutaneous sur-
face of the tibia ; 3, tibialis anticus ; 4,
extensor longus digitorum ; 5, extensor
proprius pollicis ; 6, peroneus tertius ; 7,
peroneus longus; 8, peroneus brevis; 9, 9,
borders of the soleus muscle; 10, part of
the inner belly of the gastrocnemius ; 11,
extensor brevis digitorum (the tendon in
front of the cipher is that of the peroneus
tertius ; that behind it, the peroneus brevis).
in all animals. It is penniform, and is attached above, by its fleshy fibres, to the lower two-
thirds of the external face of the fibula ; below, by its tendon, to the upper extremity of the
fifth metatarsal.
These two muscles determine very complicated movements in the region of the foot
3. Posterior Region (Fig. 207).
The posterior tibial muscles form two layers : a superficial and a deep.
876 TEE MUSCLES.
The first comprises the crural triceps and the plantarie. The triceps itself is composed ol
the gastrocnemius, of which we will say nothing, and the soleus. The latter is flattened from
before to behind, attached to the upper third of tlie fibula, the oblique line of the tibia, and
the middle tliird of the inner border of this bone, and terminated by an aponeurotic lamina
which is blended with the tendo-Achilles. The plantaris is formed by a small fusiform
muscular body, situated beneath the external gemellus, then by a long slender tendon, which
is confounded with the inner border of the tendo-Achilles, or is inserted into the os calcis.
The deep layer is composed of four muscles :
1. The popliteus, which in its attachments and position resembles that of animals.
2. The common long flexor of the toes, corresponding to the oblique flexor of animals. It is
an elongated penniform muscle, fixed above to the oblique line and middle third, of the
posterior face of the tibia. Its tendon is inflected beneath the external malleolus, passes in
front below the astragalus, receives the accessory of the long flexor, and then divides into four
branches for the four lesser toes.
3. The posterior tibial, represented by a portion of the perforans of animals ; its tendon is
reflected beneath the internal malleolus of the tibia, and is attached to the scaphoid process.
4. The proper long flexor of the great toe, also represented by a portion of the perforans.
This muscle is voluminous and prismatic, and is attached above to the lower two-thirds of the
posterior face of the fibula. Its tendon is reflected inwards on the astragalus and the groove
in the os calcis, crosses the tendon of the common long flexor, and terminates on the posterior
extremity of the third phalanx of the great toe.
Muscles of the Posterior Foot.
In Solipeds are found : 1. Tivo lumhrici and hvo ifiterosseous muscles,
corresponding to those of the anterior limb. 2. A pedal muscle.
Pedal Muscle (Extensor Pedis Brevis, Extensor Brevis Digitorum).
Synonym. — The tarso-prephalangeus of Girard.
This is a small riband-shaped fasciculus, situated in front of the principal meta-
tarsal bone, beneath the extensors of the phalanges. It is attached, by its inferior
extremity, to the internal surface of the tendon common to these two muscles, and
by its upper extremity to the lower end of the os calcis (and astragalus). It aids
in extending the digit (flexing the hock, and probably keeping the tendons tense.)
Differential Characters in the Muscles of the Posterior Foot in the other Animals.
A. Huminants. — This is the only muscle in the region of the foot met with in Rumi-
nants. It is attached, iiiferiorly, to the tendon of the common extensor and that of the proper
extensor of the internal digit.
B. Pig. — This animal possesses: 1. A pedal muscle attached, below, to the two branches of
the common extensor of the large digits. 2. Four interosseous metatarsal muxcles, whicli do not
appear to diff'er in their general arrangement from the metacarpal interosseous muscles.
C. Carnivora. — In the Dog and Cat there exist in the region of the posterior foot :
1. A pedal muscle, composed of three fasciculi which have their origin either fiom the
inferior extremity of the os calcis, or from the tendinous sheaths in the bend of the hock ; they
terminate on the second, third, and fourth digits, by small tendons joined to the branches of
the common extensor.
2. Tlie muscular digitations annexed to the tendon of the perforatus, traces of the fleshy
portion of the ^exor brevis digitorum of Man.
3. A flexor pedis accessorius, or perforans, a small undeveloped muscle commencing outside
the tarsus, and terminating by a very delicate aponeurosis on the posterior face of the perforans
tendon.
4. Two or three pale and rudimentary bands, situated inside the tarsus and near the
internal digit. These are *he vestiges of the muscles proper to the great toe in Man.
5. An adductor of the little toe (abductor minimi digit) is a thin, elongated muscle, carried
obliquely from the posterior tarso-metatarsal ligament to the internal side of the first phalanx
of that digit.
6. Four interosseous metatarsal muscles, resembling the analogous muscles of the metacarpal
region.
7. LxLmhrici similar to those of the anterior limb.
MUSCLES OF THE POSTERIOR LIMBS.
377
Comparison of the Muscles of the Foot in Man with those of Animals.
In Man, there are distinguished the muscles of the dorsal region, the plantar region, and
the interosseus muscles.
I. Dorsal Eegion.
This only contains one muscle, the pedal {extensor hrevis digitorum). It is attached,
behind, to the antero-external part of the upper face of the os calcis, by several aponeurotic
layers ; its fleshy fasciculi, four in number, are prolonged by as many tendons destined to the
first four toes ; three of them pass along with the tendons of the common extensor.
2. Plantar Region.
This is subdivided into three regions : a middle, internal, and external.
The first comprises : 1, The common short flexor of the toes, which is represeuted in Soli-
Fig. 209.
FIRST LAYER OF PLANTAR MUSCLES OF
HUMAN FOOT.
1, Os calcis ; 2, posterior part of plantar fascia
divided transversely ; 3, abductor pollicis ;
4, abductor minimi digitii ; 5, flexor
brevis digitorum ; 6, tendon of flexor
longus pollicis ; 7, 7, lumbricales.
THIRD AND PART OF SECOND LATER OF
PLANTAR MUSCLES OF HUMAN FOOT.
1, Incised plantar fascia ; 2, musculus acces-
sorius; 3, tendon of flexor longus digi-
torum ; tendon of flexor longus pollicis ;
5, flexor brevis pollicis ; 6, adductor pol-
licis ; 7, flexor brevis minimi digitii ; 8,
transversus pedis ; 9, interossei muscles,
plantar and dorsal ; 10, convex ridge
formed by the tendon of the peroneus lon-
gus in its oblique course across the foot.
peds by a portion of the perforatus. It is attached to the infero-internal tuberosity of the
03 calcis, and to the upper face of the middle plantar aponeurosis. It has four tendons, which
are inserted into the second phalanges of the first four toes, after forming rings through which
pass the tendons of the common long flexor.
2. The accessory of the long flexor, the fibres of which pass to the tendons of the common
flexor.
3. The lumbrici, four in number, and analogous to those of the hand.
The internal plantar region is composed of three muscles, which are found in a rudimentary
condition in the Dog.
L The short adductor of the great toe, which extends fiom the internal tuberosity of the os
calcis to the internal sesamoid and the first phalanx of the great toe.
878 THE MUSCLES.
2. The short flexor of the great toe, which arises from the third cuneiform and the tendon of
the posterior tibial, and terminates by two branches on the external sesamoid and the internal
Besamoid of the great toe.
3. Tlie short adductor of the great toe, a muscle formed by two fasciculi, and having a
common termination on the external sesamoid. One of these fasciculi arises from the inferior
face of the cuboides, the third cuneiform, and the base of the third and fourth metatarsal ; it
has been formerly described as the oblique adductor. The other has its origin from the
inferior face of the three last metatarso-phalangeal articulations : this has also been called
the transverse adductor.
The external plantar region likewise comprises three muscles, which are —
1. The short abductor of the little toe, which is detached from the internal tuberosity of the
08 calcis. and is inserted into the external portion of the first phalanx of the little toe.
2. Tlie short flexor of the little toe is attached, behind, to the sheath of the long peroneus
and to the process of the fifth metatarsal ; in front, to the external part of the first phalanx of
the little toe.
3. The opponens of the little toe, concealed beneath the preceding, is inserte 1 at one end to
the sheath of the long peroneus, and at the other to the external border of the fifth metatarsal.
3. Interosseous Muscles.
These are divided into dorsal and plaritar interoseei. Their disposition is nearly the same
as in the hand.
CHAPTER III.
THE MUSCLES IN BIRDS.
In Birds, we find the majority of the muscles already described ; though they
are appropriate by their form, volume, arrangement, etc., to the particular
conformation of the skeleton in these animals.
To undertake, in this essentially practical work, a special description of all
these muscles, would be to depart from the object aimed at ; and we therefore
confine ourselves to those points which present most interest, so far as animal
mechanics is concerned.
1. Tendons. — The tendons in birds present in the inferior limbs and at the
extremity of the wings an amount of ossification more or less extensive along
their course. This transformation of the fibrous tissue of the muscles is not the
effect of senility, for it is noticed in very young animals.
The tendons, in losing the greater part of their elasticity, doubtless gain in
tenacity ; and this allows them to transmit to the bony levers the muscular
efforts in a more integral manner.
It is also observed that the partial ossification of the tendons does not
exclusively belong to the limbs ; for it is not rare to meet with this change m
other regions, as in the neck of wading birds. In the museum of the Vetermary
School at Lyons is the skeleton of a heron which shows this peculiarity in the
highest degree ; the cervical vertebrae are roughened by a multitude of filiform
bony stylets, all directed backwards, and which have originated from the ossifi-
cation of the tendinoiLs fibrillae annexed to the muscles of the cervical region.
2. The Pectoral Muscles. — The two alternative movements which produce
flight — the elevation and depression of the wings — being due to the action of
the pectoral muscles, these merit special notice.
The superficial or great pectoral, " which alone weighs heavier than all the
THE MUSCLES IN BIRDS. 379
other muscles of the bird put together, is attached to the furculum, to the great
ridge of the sternum, and to the last ribs ; it is inserted into the very salient
rugged outline of the humerus. It is by this muscle that birds are able to give
those powerful strokes of the wings which are necessary in flight."
The deep or small pectoral is " placed in the angle formed by the body of the
sternum and its crest, and in the interval between the furculum and the coracoid
bone. Its tendon passes through the foramen formed by the union of the
furculum, the coracoid bone, and the scapula, as over a pulley ; it is inserted
above the head of the humerus, which it raises. It is by means of this arrange-
ment that nature has been able to place an elevator and depressor at the inferior
surface of the trunk so far from the centre of gravity, without which the bird
would have been liable to lose its equihbrium and tumble over head foremost in
the air." '
Cuvier, adopting the nomenclature of Vicq-d'Azyr, called this muscle the
middle pectoral, and he gave the name of small pectoral to a triangular fasciculus
which leaves the lateral angle of the sternum and the base of the coracoid bone,
to be inserted under the head of the humerus. In our opinion, this tendon does
not belong to the pectoral region, but to that of the shoulder ; and, with J. F.
Meckel, we are inclined to consider it as the curaco-humeralis, which has followed
the coracoid process in its development.^
3. The Diaphragm. — " In Birds, the diaphragm is so differently disposed
from what it is in the higher Yertebrata, that its existence has been successively
described and misunderstood, admitted and refuted, and is still looked upon as
problematical by a large number of anatomists. Nevertheless, this muscle exists,
and its development is in perfect harmony with the importance of its functions.
It is composed of two planes, which at their origin are confounded with each
other, but soon become separated and pursue, one a transverse, the other an
oblique direction. The transverse plane is triangular in form, and is carried
horizontally from the right to the left ribs against the inferior surface of the
lungs. The oblique plane is convex in front, concave behind, and extends from
the dorsal aspect of the spine to the sternum, dividing the cavity of the trunk
into two secondary cavities — the thorax and abdomen.
" In Birds, as in Mammals, the diaphragm is therefore intended to perform
two principal functions ; but to do this perfectly in the former, it is doubled.
So far, then, from this inspiratory muscle being absent in birds, or from its
existing in a rudimentary degree, they are really provided with two diaphragms :
1. A. pulmonary diaphragm, which presides in the dilatation of the lungs. 2.
A thoracic abdominal diaphragm, which partitions the great cavity of the trunk,
and concurs in the inspiration of the air by dilating the large aerial reservoirs
lying at its posterior surface. Of these two muscular planes, the first is analogous
to that portion of the diaphragm which, in Man and the Mammalia, is inserted
' Cuvier, Lemons d'Anntomie Compar^e.
* E. Geoffrey Saint- Hilaire, in his memoir on the bones of the sternum (Philonophie
Anatomique, vol. i. p. 89), in comparing the pectoral muscles of Fishes to those of Birds, also
employs the nomenclature of Vicq-d'Azyr, and recognizes three pectorals as well. We are,
however, obliged to confess ourselves as in opposition to the great master who has estal)lished
rules to follow in the classification of organs, in consequence of liis having limited his com-
parisons to the two classps of Vertebrata he had principally in view. If he had extended his
observations to the Mammalia, and in them sought for the analogue of the pectoralis parvus,
he wonkl have discovered it, as we have done, in the region of the shoulder, and not in that of
the sternum.
THE MUSCLES.
into the sternum and the ribs ; the second manifestly represents the pillars of
the diaphragm."
This description, taken from the work of Sappey, an observer as con-
scientious as he is talented, gives a perfectly exact idea of this muscle.
CHAPTER IV.
GENERAL TABLE OP THE ATTACHMENT OF THE
MUSCLES IN SOLIPEDS.
I. Vertebral Column.
A. Cervical Vertebrae.
1. Atlas.
The atlas gives attachment to nine pairs of muscles : —
a. By the surface representing the spinous process, to the —
Rectus capitis posticus minor.
6. By its transverse processes, to the —
1. Spleniua.
2. Trachelo-mastoideus.
3. Obliquus capitis anticua.
4. Obliquus capitis posticus.
5. Mastoido-humeralis.
c. By its body, to the —
1. Rectus capitis anticus minor.
2. Rectus capitis lateralis.
3. LonguB colli.
2. Axis.
The axis gives insertion to six pairs of muscles : —
a. By its spinous process, to the —
1. Semispinalis colli. ,
2. Obliquus capitis anticus.
3. Rectus capitis posticus major.
b. By its transverse processes, to the —
1. Intertransversales colli.
2. Mastoido-humeralis muscles.
A7id by the inferior face of its body, to the —
3. Lougus colli.
8. Third, Fourth, Fifth, Sixth, and Seventh Cervical Vertebra.
These vertebrae give insertion to the following muscles : —
a. By their spinous processes, to the —
1. Semispinalis colli.
2. Longissimus dorsi.
b. By their articular tubercles, to the —
1. Complexus.
2. Trachelo-mastoideuB.
3. Semispinalis colli.
4. Intertransversales colli.
GENERAL TABLE OF THE ATTACHMENT OF MUSCLES IN SOLIPEDS. 381
c. By their transverse processes, to the —
1. Angularis scapulae.
2. Splenius (3rd and 4th).
3. Mastoido-humeralis (3rd and 4th).
4. Tranaversalis costarum.
5. Semispinalis colli.
6. Longissimus colli (inferior branch).
d. And by the inferior faces of their bodies, to the —
1. Rectus capitis anticus major.
2. Longus colli.
B. Dorsal Vertebra.
The dorsal vertebrae give insertion : —
a. By their spinous processes, to the —
1. Splenius (1st to 5th or 6th).
2. Complexus (Ist to 6th).
3. Trachelo-mastoideus (Ist and 2ud).
4. Trapezius.
5. Latissimus dorsi (4th to 18th).
6. Rhomboideus (2nd to 7th).
7. Serratus anticus (2ud to 13th).
8. Serratus posticus (10th to 18th).
9. Longissimus dorsi.
10. Semispinalis of the back and loins.
6. By their transverse processes, to the —
1. Complexus.
2. Trachelo-mastoideus.
3. Longissimus dorsi.
4. Semispinalis of the back and loins.
5. Levatores costarum.
c. By their bodies, to the —
1. Longus colli (Ist to 6th).
2. Psoas magnus (17th to 18th).
3. Psoas parvus (16th to 18th).
C. Lumbar Vertebrae.
The lumbar vertebrae give insertion : —
a. By their spinous processes, to the—
1. Latissimus dorsi.
2. Serratus posticus (Ist to 3rd).
3. Longissimus dorsi.
4. Semispinalis of the back and loins.
b. By their articular tubercles, to the —
1. Longissimus dorsi.
2. Semispinalis of the back and loins.
c. By their transverse processes, to the —
1. Psoas magnus.
2. Quadratus lumborum.
3. Intertransversales of the loins.
4. Transversus abdominis.
5. Longissimus dorsi.
d. By their bodies, to the —
1. Psoas magnus.
2. Psoas parvus.
3. Crura of the diaphragm.
THE MUSCLES.
D. Sacrum.
The sacrum gives insertion to the —
1. Longissimus dorsi.
2. Semispinalis of the back and loina-
3. Erector coccygis.
4. Curvator coccygis.
5. Depressor coccygis.
6. Iscbio-coccygeal muscles.
7. Biceps femoris.
8. Semitendinosus.
9. Obturator internus.
E. Coccyx.
The coccyx gives insertion to the
1. Erector coccygis.
2. Depressor coccygis.
3. Curvator coccygis.
4. Ischio-coccygeal muscles (Ist and 2nd coccygeal vertebm).
II. Head.
A. Bones of the Cranium.
1. Occipital.
The occipital gives insertion to nine pairs of muscles : —
1. Complexus.
2. Obliquus capitis posticus.
3. Rectus capitis posticus major.
4. Rectus capitis posticus minor.
5. Rectus capitis aiiticus major.
6. Rectus capitis anticus minor.
7. Rectus capitis lateralis.
8. Digastricua
9. Occipito-styloid,
2. Paeietal.
The parietal gives attachment to one muscle : —
Temporalis.
3. Frontal.
The frontal gives insertion to the —
Levator labii superioris proprius.
4. Sphenoid.
The sphenoid gives attachment to four muscles : —
1. Rectus capitis anticus major.
2. Rectus capitis anticus minor.
3. Pterygoideus inteinus.
4. Pterygoideus externua.
GENERAL TABLE OF TEE ATTACHMENT OF MUSCLES IN S0LIFED8. 383
5. Temporal.
The temporal gives insertion to five muscles : —
1. Splenius.
2. Trachelo-mastoideus.
3. Obliquus capitis postioua.
4. Mastoido-humeralis.
5. Temporalis.
B. Bones of the Face.
1. Superior Maxilla.
The supermaxilla gives insertion to the following muscles x—
1. PanniculuB.
2. Buccinator.
3. Levator labii superioris propria.
4. Dilator naris lateralis.
5. Masseter.
2. Premaxilla,
The premaxilla gives insertion to the —
1. Dilator naris superior.
2. Levator menti.
3. Palatine.
The palatine gives insertion to the —
Pterygoideus intemus.
4. Malar.
The malar gives insertion to one muscle, the^
Levator labii superioris proprius.
5. Lachrymal.
The lachrymal gives insertion to one muscle, the—
Lacbrymalis.
6. Nasal.
The nasal gives insertion to one muscle, the —
Levator labii superioris proprius.
7. Inferior Maxilla.
The inferior maxilla gives insertion to the following muscles :-^
1. Sterno-maxillaris.
2. Buccinator.
3. Depressor labii iiiferiore
4. Levator menti.
5. Masseter.
6. Temporalis.
7. Pterygoideus intemu8.
8. Pterygoideus extemuB.
9. Digastricus.
10. Mylo-hyoideus.
11. Genio-hyoideus.
t THE MUSCLES.
C. Hyoid.
The hyoid gives insertion to the following muscles : —
a. By its body and its thyroid cornua —
1. Sterno-hyoideus.
2. Subscapulo-hyoideus.
3. Mylo-hyoideua.
4. Genio-hyoideus.
5. Stylo-hyoideus.
6. Hyoideus magnus.
7. Hyoideus transversus.
6. By its branches (styloid cornua aad styloid bones) —
1. Stylo-hyoideus.
2. Hyoideus magnus.
3. Ocoipito-styloideus.
III. Bones of the Thorax.
A. The Ribs and their Cartilages.
The ribs and costal cartilages give attachment to seventeen muscles :—
1. Scalenus (Ist).
2. Serratus anticus (5th to 9th).
3. Serratus posticus (9th to 18th).
4. Longissimus dorsi (3rd to 18th).
5. Transversalis costarum.
6. Psoas magnus (17th to 18th).
7. Quadratus lumborum (16th to 18th).
8. Serratus magnus (1st to 8th).
9. External iutercostals.
10. Internal intercostals.
11. Levatores costarum.
12. Triangularis stemi (2nd to 8th).
13. Obliquus abdominis extemus (5th to 18th).
14. Obliquus abdominis internus (asternal cartilages).
15. Eectus abdominis (asternal cartilages).
16. Transversalis abdominis.
17. Diaphragm (7th to 18th).
B. Sternum.
The sternum gives attachment to nine muscles : —
1. Panniculus cervicalis of the neck.
2. Sterno-maxillaris.
3. Sterno-thyro-hyoideus.
4. Superficial pectorals.
5. Deep pectorals.
6. Triangularis sterni.
7. Eectus abdominis.
8. Transversalis abdominis.
9. Diaphragm.
GENEBAL TABLE OF THE ATTACHMENT OF MUSCLES IN SOLIPEDS. 885
IV. Thoracic Limb.
A. Bones of the Shoulder.
Scapula.
The scapula gives attachment to seventeen muscles :—
a. By its external face, to the —
1. Supra-spinatuB.
2. Infra-spinatus.
3. Teres minor.
4. Teres externus.
5. Trapezius.
6. Mastoido-humeralie.
6. By its internal face, to the—
1. Rhomboideus.
2. Angularis scapulae.
3. Serratus magnus.
4. Subscapularis.
5. Scapulo-humeralis gracilis.
c. By its anterior border, comprised between the cervical angle and the coracoid process,
to the —
1. Sterno-prescapularis.
2. Biceps.
3. Coraco-humeralis.
4. Supra-spinatus.
d. By its posterior border, comprised between the dorsal angle and the corresponding
portion of the humeral angle, to the —
1. Caput magnum.
2. Scapulo-ulnaris.
3. Teres major.
4. Deltoid.
5. Teres minor.
B. Bones of the Arm.
Humerus.
The humerus gives attachment to twenty-four muscles :—
a. By its superior extremity, to the —
1. Supra-spinatus.
2. Infra-spinatuB.
3. Subscapularis.
4. Scapulo-humeralis gracilis.
5. Posterior deep pectoral.
6. Panniculus camosus.
b. By its body, to the^
1. Deltoid.
2. Teres minor.
3. Coraco-humeralis by two pointa
4. Teres major.
5. Brachialis anticus.
6. Caput medium.
7. Caput parvum.
8. Anconeus.
9. Extensor metacarpi magnus.
10. Extensor pedis.
386 THE MUSCLES.
11. Latissimus dorsi.
12. Mastoido-humeralis.
13. Anterior superficial pectoral.
e. By its inferior extremity, to the —
1. Extensor pedis.
2. Flexor metacarpi externus.
3. Flexor metacarpi obliquua.
4. Flexor metacarpi internua.
5. Flexor pedis perforatus.
6. Flexor pedis perforaus.
C. Bones of the Forearm.
1. Radius.
The radius gives attachment : —
a. By its upper extremity, to the —
1. Biceps.
2. Extensor pedis.
3. Extensor suflFraginia.
6. By its body, to the —
1. Brachialis anticus. «
2. Extensor metacarpi obliquas.
3. Extensor pedis.
4. Extensor suffraginis.
5. Flexor pedis perforans.
2. Ulna.
The ubia gives attachment to nine muscles : —
a. By its upper extremity {olecranon), to the—
1. Caput niagnus.
2. Scapulo-ulnaris.
3. Caput medium.
4. Caput parvum.
5. Anconeus.
6. Flexor metarcarpi obliquufl.
7. Flexor pedis perforans.
0. By its body, to the —
1. Brachialis anticus.
2. Extensor sufifraginis.
D. Bones of the Carpus.
PisiFOEM Bone.
The supercarpal bone, the only bone of the carpus which has muscular
attachments, gives attachment to two muscles : —
1 . Flexor metacarpi externus.
2. Flexor metacarpi medius.
E. Bones of the Metacarpus.
1. Principal Metacarpal.
The principal metacarpal gives attachment to a single muscle ^—
By its superior extremity, to the —
Extensor metacarpi magnus.
GENERAL TABLE OF THE ATTACHMENT OF MUSCLES IN SOLIPEDS. 387
2. External Rudimentary Metacarpal.
This gives attachment to a single muscle : —
Flexor metacarpi externizs.
3. Internal Rudimentary Metacarpal.
This gives attachment to two muscles : —
1. Extensor metacarpi obliquus.
2. Flexor metacarpi intemua.
F. Bones of the Digital Region.
1. First Phalanx.
This gives attachment to two muscles : —
1. Extensor pedis.
2. Extensor suflfraginis.
2. Second Phalanx.
This gives attachment to two muscles : —
1. Extensor pedis.
2. Flexor pedis perforatus.
3. Third Phalanx.
The third phalanx, or os pedis, gives attachment to two muscles : —
1. Extensor pedis.
2. Flexor pedis perforans.
V. Abdominal Limb.
A. Bones of the Haunch.
Coxa.
The coxa gives attachment to thirty-two muscles : —
a. By the ilium, to the —
1. Longissimus dorsi.
2. Iliacus.
3. Psoas parvus.
4. Quadratus lumborum.
5. Compressor coccygis.
6. Obliquus abdominis externus.
7. Obliquus abdominis internus.
8. Transversalis abdominis (through the medium of the crural arch).
9. Gluteals.
10. Tensor vaginae femoris.
11. Rectus femoris.
12. Rectus parvus.
13. Obturator internus.
b. By the pubis, to the —
1. Obliquus abdominis externus.
2. Rectus abdominis.
3. Transversalis abdominis (through the medium of the crural arch).
4. Gracilis.
6. Fectineus.
TEE MUSCLES.
6. Adductor parvus.
7. Obturator externus.
8. Obturator internus.
e. By the ischium, to the —
1. Superficial gluteus.
2. Biceps femoris.
3. Semitendinosus.
4. Semimembranosus.
5. Gracilis.
6. Adductor magnus.
7. Quadratus femoris.
8. Obturator extemus.
9. Obturator internus.
10. Gemelli of the pelvis.
B. Bones of the Thigh.
Femur.
The femur gives attachment to twenty-four muscles ;
a. By its upper extremity, to the —
1. Psoas magnus.
2. Iliacus.
3. Superficial gluteus.
4. Middle gluteus.
5. Deep gluteus.
6. Obturator extemus.
7. Obturator internus.
8. Gemelli of the pelvis.
b. By ite body, to the —
1. Superficial gluteus,
2. Fascia lata.
3. Vastus extemus.
4. Vastus internus.
5. Rectus parvus.
6. Pectineus.
7. Adductor parvus.
8. Adductor magnus.
9. Quadratus femoris, ^
10. Gastrocnemius.
11. Flexor pedis perforatus.
e. By its inferior extremity, to the —
1. Semimembranosus.
2. Adductor magnus.
3. Extensor pedis.
4. Flexor metatarsi.
5. Popliteus.
C. Bones of the Leg.
1. Tibia.
The tibia gives attachment to eleven muscles :—
o. By its upper extremity, to the —
1. Flexor metatarsi.
2. Soleus.
3. Flexor pedis perforans.
QENEBAL TABLE OF THE ATTACHMENT OF MUSCLES IN SOLIPEDS. 38?
4. Flexor accessorius.
5. Sartorius (through the medium of the internal patellar ligament).
b. By its body, to the —
1. Biceps femoris.
2. Semitendinosus.
3. Gracilis (in common with the long adductor).
4. Flexor metatarsi.
5. Popliteus.
6. Flexor pedis perforans.,
2. Fibula.
The fibula gives insertion to two muscles : —
1. Extensor suifraginis.
2. Flexor pedis perforans.
3. Patella.
The patella gives insertion to five muscles : —
1. Tensor vaginae femoris.
2. Rectus femoris.
3 Vastus externus.
4. Vastus internus.
5. Superficial gluteus (posterior portion).
D. Bones of the Tarsus.
Calcis.
The calcis gives insertion to the—
Gastrocnemius.
Cuboid.
The cuboid gives insertion to the —
Flexor metatarsi.
Second Cuneiform.
This gives attachment to one muscle, the —
Flexor metatarsi.
E. Bones of the Metatarsus.
The principal metatarsal gives insertion to one muscle, the
Flexor metatarsi.
F. Bones of the Foot.
1. First Phalanx.
The first phalanx gives insertion to one muscle, the —
Anterior extensor of the phalanges.
390 THE MUSCLES.
2. Second Phalanx.
The second phalanx gives insertion to two muscles t—
1. Extensor pedis.
2. Flexor pedis perforatus.
3. Third Phalanx.
The third phalanx gives insertion to two muscles ?—
Extensor pedis.
Flexor pedis perforans.
BOOK II.
THE DIGESTIVE APPARATUS.
CHAPTER I.
General Considerations on the Digestive Apparatus.
We have considered the animal as a machine composed of various levers and
capable of various movements ; but it will be easily understood that the working
of this machine will cause the wear or decomposition of the molecules which
enter into the construction of its organs, and that these springs or animated
wheels demand for their maintenance an incessant supply of new materials,
in order to repair their continual losses. Animals, therefore, are under the
necessity of taking aliment, from which they extract those reparative principles
that, distributed to all the organs, are assimilated to their proper substance.
The organs in which this work of preparation and absorption of the organiz-
able material is carried on, are collectively named the digestive apparatus — one of
the most important of those which, as we shall see, successively complicate and
perfect the animal machine. This apparatus does not, properly speaking,
constitute an essentially distinctive characteristic of animality, as there are
animals without a digestive cavity ; but it is yet one of the most salient
attributes, for the exceptions just mentioned are extremely rare. Considered in
the Vertebrata, this apparatus appears as a long tube, most frequently doubled
on itself many times, dilated at intervals, and provided along its course with
several supplementary organs, the majority of which are of a glandular nature.
This tube extends the whole length of the animal's body, and opens externally
by two orifices, one of these serving for the introduction of aliment, the other
for the expulsion of the residue of digestion. These openings are at the
extremities of the alimentary canal.
The conformation of this apparatus is not incidentally the same in all the
individuals composing the sub-kingdom of Vertebrata ; on the contrary, it
presents very numerous varieties, according to the habits and modes of life of
these individuals, and this makes its study interesting from two points of view :
in relation to the science of zoology, and to that of veterinary hygiene, which
derives from this study valuable indications concerning the regime of the
domesticated animals.
But this diversity of characters does not suffice to establish sharply defined
limits between the conformations that are distinguished by it. There is, in
reality, but one typical form of digestive apparatus, and the same principle
'prevails in its construction throughout the entire series. Thus, whichever of
the Vertebrata we may be studying, its alimentary tube will be found composed
392 GENERAL CONSIDERATIONS ON THE DIGESTIVE APPARATUS.
of a collection of dilatations or tubuliform cavities, which succeed each other
from before to behind in the following order : the mouth, jihari/nx, msophagm^
stomach, and intestine.
This system of cavities is divided, physiologically, into two principal sections.
The first comprises the mouth, pharjux, and oesophagus— the compartments
in which are carried on those digestive operations termed }yreparatory, because
they prepare the aUment for the subsequent modifications that constitute the
essential phenomena of digestion ; the second section is formed by the stomach
and intestines, where these phenomena take place.
Each of these two sections is furnished in its course with annexed organs,
which are present in the majority of Vertebrata ; these are the salivary glands
for the cavities of the first category, and the liver, immreas, and spleen for those
of the second.
In considering the general position of these various parts — principally in
Mammals and Birds— it is found that the first section of the digestive canal and
its appended organs are lodged beneath the upper jaw and the base of the
cranium, and under the cervico-thoracic portion of the vertebral spine. The
second section, with its annexes, occupies the great abdominal cavity.
In Man, these two sections are divided into supra-diaphragmatic and infra-
diaphragmatic regions, because of their relations to the diaphragm.
The constituent parts of the first category might be termed, by reason of
their functions, the preparatory organs of the digestive apparatus ; and those of
the second, or abdominal portion, the essential organs of digestion.
These various organs, with those of the respiratory and genito-urinary
apparatus, have received the name of viscera, and the term splanchnology is often
given to that branch of anatomy devoted to their study.^
These new organs differ so notably from those already described, that it is
necessary to enter into some generalities as to their nomenclature, arrangement,
form, structure, and physical or chemical characteristics.
Nomenclature in splanchnology does not rest on any scientific basis ; the
name of organs being sometimes derived from their form — as the amygdalm ;
sometimes from their direction — rectum- sometimes also from their uses — the
(esophagus, salivary glands ,- their length— duodenum ; the names of the anatomists
who have described them — the drnt of Stem, Fallopian tube ; and at times these
names are purely conventional, as the spleen.
They are distinguished as hollow and solid organs.
1. The HOLLOW ORGANS have a more or less considerable cavity, capable
of being increased or diminished, but they are not of a definite shape or size.
Their consistency varies with their state of plenitude or vacuity, and they are
single or double, symmetrical or asymmetrical.
In all cases, the walls of the hollow organs are composed of two or more
membranes, which we will now describe in a general manner.
• The deaignation viscera (from veseor, " I nourish ") has been given to the organs which aid
in nutrition, and the term Splanchnology (from ffn\a.yx>'ov, a " viecus " or " intestine ") has been
bestowed on that division of anatomy which treats of these organs. Splanchnology, thus
understood, comprises the study of the digestive, respiratory, urinary, and circulatory apparatus.
But the description of the latter forms a separate category, desiguated, in tlie language of tlie
schools, Angiology. On the other hand, however, several authorities include in Splanchnology
the organs of generation, and others even add the organs of sense. There is, therefore, no,
accord in the limits given to the definition of Splanchnology ; and this being the case, we have
thought it best to omit this expression and the distinction sought to be established by it.
GENERAL CONSIDERATIONS ON THE DIGESTIVE APPARATUS. 393
a. The innermost is called the mucous membrane, because of the mucus
with which its free surface is always covered. It is continuous with the skin at
the natural openings ; and from its similarity of organization, it has been named
the internal or re-entering skin, or internal tegumentanj membrane.
It should be remarked, however, that the comparison of the mucous membrane
with the skin only holds good at the two ends of the apparatus — anteriorly, from
the mouth to the stomach ; posteriorly, at the margin of the anus.
A mucous membrane comprises a superficial or epithelial layer and a deep
portion which constitutes the dermis, or chorion {corium).
The epithelium^ is a very thin, inert pellicle, entirely composed of epithelial
cells united by an almost insignificant quantity of amorphous matter {Mastema).
The cells are flat or polygonal, round or cylindrical, polyhedral, or very irregular
in shape. In consequence of these diverse forms, there is pavement (or flat,
simple, tesselated, or squamous), spherical (or spheroidal), and cylindrical or conical
(or columnar) epithelium. If the cells are furnished with small filiform appendages,
named vihratile cilia, the epithelium is then designated ciliated. When the cells
Fig. 210.
Fig. 211.
Fig. 212.
COLUMNAR EPITHELIUM.
1, Nucleus of the cell ;
2, membrane of the
cell raised from its
contents by the ab-
sorption of water.
COLUMNAR CILIATED EPITHELIUM
(magnified 310 DIAMETERS).
a, Nucleated cells resting on their
smaller extremities ; 6, cilia.
SQUAMOUS EPITHELIUM FROM
THE MOUTH.
The large scale is magnified
310 diameters, and exhibits
a nucleus with nucleolus in
the centre, and secondary
nucleated cells forming the
body of the scale.
are arranged in a single layer on the surface of the corium, the epithelium is said
to be simple ; it is stratified (or laminar) when the cells are arranged in strata
upon each other. In stratified epithelium, the shape of the cells is not the same
on the surface and beneath it, and it is named after the form of the superficial
layer : examples — stratified tesselated epithelium., stratified cylindrical epithelium.
The mucous dermis, or corium, is composed of connective tissue, the thickness,
elasticity, vascularity, and sensibility of which varies with the situation and the
function of organs. The corium is thin and almost destitute of elastic fibres
when applied to the bony walls of a cavity ; on the contrary, it is thick, elastic,
and slightly adherent when it lines organs which — like the stomach, oesophagus,
and intestines — are capable of increasing or diminishing in capacity. The fasciculi
of the connective tissue in the deeper layers of the corium are loosely united, but
nearer the surface they lie closer ; sometimes they form, under the epithelium,
an amorphous surface-layer, the basement (or limitary) membrane. In certain
places (intestine), the dermis has a layer of smooth muscular fibres which can be
resolved into two planes (the muscularis mucosce).
The sub-epithelial face of the corium is scarcely ever smooth, but offers
minute prolongations named villosities, or papillm, which are very varied in their
form and size ; it is more or less marked by depressions, named follicles. The
villi are observed on the deep-seated mucous membranes (intestine) ; they are
394 GENERAL CONSIDERATIONS ON THE DIGESTIVE APPARATUS.
Fig. 213.
CONICAL VILLI ON MUCOUS MEM-
BRANE OF SMALL INTESTINE
(MAGNIFIED 19 DIAMETERS).
a, Zone of follicles surrounding b.
solitary gland ; 6, apertures of
simple follicles.
Fig. 214.
more particularly the vascular and absorbent organs. The ^M_/?^7/fl? are found in
the vicinity of the natural apertures, and are rich in nerves ; they are more
especially the organs of sensibility. The follicles,
lined by one or other form of cell, are exclusively
organs of secretion.
b. The second membrane met with in the walls
of the hollow organs is of a muscular nature.
The mvsndar membrane is formed of unstriped
fibres, the slow contraction of which is involun-
tary. In certain organs — those adjoining the
natural apertures — the unstriped fibres are re-
placed by striped, which are under the influence
of the will, or have the same physiological and
reflex properties as the smooth fibres — as in the
oesophagus.
{Unstrijied or smooth bands of muscles are
composed of long fusiform cells with staff -shaped,
elongated nuclei, the cells varying from ttVs" ^^
-^ of an inch in length, and from s^^s ^^ ttW
of an inch in breadth.)
c. When the organs are lodged in one of the
great splanchnic cavities, such as the chest or
abdomen, they have a third membrane — a serous
layer, which lines the cavity, and is reflected
around the viscera contained in it, so as to
envelop them more or less completely. This
layer has, therefore, an adherent face, applied
either against the walls of the cavity or the
external surface of the splanchnic organs ; and
a free face, always in contact with itself.
A sei-ous membrane is composed of two layers :
a deep, connective portion, analogous to the
mucous corium ; and a superficial, which is only
tesselated epithelium. The free surface of this
epithelium is perfectly smooth, and lubricated by
a limpid serosity to facilitate the gliding of the
parts the membrane covers. (The epithelium is
a simple tesselated layer of flattened and poly-
gonal nucleated cells, about y^Vo- of an inch in
diameter.)
2. The SOLID ORGANS are either contained
in the splanchnic cavities or situated outside
them, in the midst of connective tissue, which,
in becoming more dense around them, often
forms a fibrous covering.
Like the hollow organs, they are single —
spleen, liver ; or in pairs — kidneys ; and sym-
metrical or asymmetrical in shape. They are
retained in their situation by their vessels and
nerves, by adherence to the neighbouring organs, or by particular serous bands.
FUSIFORM CELLS OF SMOOTH
MUSCULAR FIBRE.
Two cells in their natural state,
one showing the staff-shaped nu-
cleus ; 6, a cell with its nucleus,
c, brought distinctly into view by
acetic acid.
GENERAL CONSIDERATIONS ON THE DIGESTIVE APPARATUS. 395
With the exception of the lungs of animals that have respii;^d, all the solid
organs have a density greater than water. Their iveight and volume offer
numerous differences, which are individual, or peculiar to the species to which
they belong. Nevertheless, each organ possesses a certain volume and weight
which might be termed physiologic ; when the organ is above or below this
average, we are warranted in saying that it is in a pathological condition.
Solid organs are more or less round in form, and their surface is traversed
by a variable number of furrows, which indicate their division into lobes or
lobules.
Their colour is diverse ; they may be very pale — parotid gland ; or very dark
— liver, spleen ; or uniform, or of different shades — varieties which are most
frequently due to the mode of distribution of the vessels, or to the presence of
certain anatomical elements. The colour of organs is not always the same in
the deeper parts and at the surface, especially when they are enveloped by a
thick, opaque membrane — for instance, the testicle. Lastly, the coloration is less
intense after death than during life, and particularly if the animal to which the
organs belonged has been killed by effusion of blood.
The consistence of organs depends on their internal formation, and the nature
of their constituent elements ; there are soft organs — such as the lungs, and
resisting organs— as the testicles. As a general rule, the consistency of organs
diminishes after putrefaction has set in.
Cohesion is the resistance that organs offer to the forces which tend to tear
them ; it depends upon the texture of the organs, and the more or less abundance
of fibrous and elastic tissue in their structure. Cohesion is very different from
consistency ; thus, such an organ as the lung may be easily compressed, but may
be very difficult to tear.
If organs are examined with regard to their structure, it will be observed that
all have a thin or thick fibrous covering, which throws septa into their interior,
and which support their proper tissue ; this tissue varies with the nature of the
organs. It will also be found that they are traversed by a more or less considerable
number of blood-vessels — arteries and veins. These vessels expand into a capillary
network, the meshes of which have a shape closely allied to that of the elements
of the proper tissue. The number and volume of the vessels of an organ give
an exact idea of its importance, and of the activity of the physiological phenomena
taking place in it. Finally, into the composition of organs enter superficial and
deep lymphatic vessels and nerves, which generally follow the arteries. The
nerves show in their course small ganglionic enlargements.
All the solid organs are either glands, or are apparently glandular. The
function of glands is to elaborate or eliminate certain fluid or semifluid products,
which, thrown out in hollow organs, are absorbed by their internal surface, or
excreted.
The very simple (or tubular) glands consist of a straight or convoluted tube,
or of a small vesicular cavity opening on a tegumentary membrane ; they are
lined on their inner face by one or more layers of cells. As an example, there
may be cited the tubular glands of the stomach and intestines.
But there are also conglomerate glands — organs more complex, but which are
merely masses of simple glands. There are tubular glands, like the kidneys and
testicles ; racemose glands, such as the salivary gla7ids and pancreas ; or a
network of glands, like the liver. In these the essential anatomical element —
the polygonal, cylindrical, or spherical gland-cell — is situated on the inner face
396 THE DIGESTIVE APPARATUS IN MAMMALIA.
of a tube — as in. the kidney ; or a vesicle, as is seen in i\ie pancreas ; or deposited
without any order in the meshes of a plexus of canaliculi, as occurs in the liver.
The conglomerate glands are provided with a common excretory duct, that
commences in their mass by a great number of arborescent ramifications. The
walls of this duct are composed of an elastic, and sometimes contractile, connective
tissue membrane, covered on its inner face by an epithehum, which may or may
not be of the same character as that of the gland.
For a long time there have been classed as glands certain organs without
excretory ducts, and having only analogies to glands. The majority of these
belong to the lymphatic apparatus, and will be considered hereafter ; but it
may be mentioned here that they are all composed of masses of cells ; some are
small and simple — these are the closed follicles, solitary or agminated, and dis-
persed beneath the intestinal mucous membrane ; the others are more complex
and voluminous, and form lymphatic glands.
To the vascular system, but more particularly to the lymphatic apparatus,
are annexed other glandiform organs, the fundamental structure of which,
analogous in principle to that of the lymphatic glands, is, nevertheless, dis-
tinguished from them by certain peculiarities — such are the spleen, thymus
gland, and thyroid body.
This is the limit to which the generalities relating to the viscera that form
the object of splanchnology, must be confined. We will now pass to a descrip-
tion of the digestive apparatus in Mammals.
CHAPTER II.
THE DIGESTIVE APPARATUS IN MAMMALIA.
We will study, successively : 1. The preparatory organs, which include the
mouth, the salivary glands annexed to that cavity, the pharynx, and the otso-
phagus. 2. The essential organs, comprising the stomach and intestine, and their
annexes — the liver, pancreas, and spleen ; with the abdominal cavity, which
contains and protects these organs.
Article I. — Preparatory Organs of the Digestive Apparatus.
The Mouth.
The mouth — the first vestibule of the alimentary canal — is a cavity situated
between the two jaws, elongated in the direction of the larger axis of the head,
and having two openings : an anterior, for the introduction of food, and a
posterior, by which the aliment passes into the pharynx.
The mouth should be studied in six principal regions : 1. The lips, which
circumscribe its anterior opening. 2. The cheeks, forming its lateral walls. 3.
The palate, which constitutes its roof or superior wall. 4. The tongue, a muscular
appendage, occupying its inferior wall. 5. The soft palate {velum pendulum
palati), a membranous partition situated at the posterior extremity of the buccal
cavity, which it separates from the pharynx, and concurs in the formation — by a
portion of its inferior face and border — of the isthmus of the fauces, or posterior
opening of the mouth. G. The dental arches fixed on each jaw.
THE MOUTH. 3!9fJ
We will study each of these regions in particular, before passing to the
examination of the mouth in general.
Preparation. — The whole of the mouth ought to be examined in an antero-posterior and
vertical section of the head (see description of the soft palate).
1. The Lips (Fig. 168).
These are two membranous movable folds, placed one above the other belo-gf
the anterior opening of the mouth, which they circumscribe. There is, con-
sequently, a superior and an inferior lip, united at each side by a commissure.
Each lip offers for study an external and internal face, and a free and an
adherent border.
The external surface is convex, and presents, on the median line : in the upper
lip, a slight projection which divides it into two lateral lobes ; in the inferior hp,
and altogether posteriorly, the single prominence named the tuft of the chin.
This face, formed by the skin, is garnished with line, short hairs, amongst which
may be remarked long, coarse bristles, the roots of which are implanted per-
pendicularly in the integument, and pass beyond its deep surface, to be lodged
in the subjacent muscular tissue. These pilous tentacles ought to be considered
as real tactile organs, because several sensitive nerve-filaments penetrate to the
bottom of their follicles, and they have a very remarkable vascularization.
The internal surface, constituted by the buccal mucous membrane, and
moulded on the incisor teeth, is concave, smooth, rose-coloured, and often
stained with black spots. In the superior lip, particularly, may be remarked
numerous orifices opening on the summits of three small papillae ; these are the
openings of the excretory canals, by which the labial glands discharge their fluid
into the interior of the mouth.
The free border, thin and sharp, shows the line of demarcation that separates
the two teguments.
The adherent border is limited, in the buccal cavity, by a groove formed by
the mucous membrane in passing from the incisor arches to the inner side of the
lips. Beyond the mouth it is not indicated by any peculiarity of structure or
arrangement, the skin being continued directly from the neighbouring parts on
the lips.
The commissures mark, on each side, the point of union between the free
borders of the two lips. They are rounded in Solipeds, and offer nothing
remarkable otherwise.
Steuctuke.— Each lip is composed of two tegumentary layers : one cutaneous,
the other mucous, between which is found muscular tissue and glands, and the
general elements of every organization — vessels and nerves.
1. Tegumentary layers. — The skin adheres closely to the subjacent tissues,
and apart from the characters already indicated, there is nothing more to be sayi
at present with regard to its disposition, as it will be studied more completely
with the organs of sense. With regard to the mucous membrane, it may be
remarked that its dermis is thick and dense, and lies on a layer of salivary
glands ; it is provided with simple conical papillae, and is covered by stratified
tesselated epithelium. (It is sometimes streaked with pigment.)
2. Muscles. — These are : the labialis or orbicularis oris — the sphincter of the
buccal apertm-e, and common to the two lips ; in the upper lip, the aponeurotic
expansion of the levator labii swperioris propriu^, the musculo-fibrous tissue which
28
398 THE DIGESTIVE APPARATUS IN MAMMALIA.
separates this expansion from the cutaneous integument, and the terminal inser-
tion of the levator labii superioris alcBqui nasi and the dilator naris lateralis ; in
the inferior lip, the tuft of the chin and its suspensory muscles — the levatores menti.
All these muscles having been studied in detail in the Myology (p. 274), there is
no necessity for their being again described.
3. Labial glandules. — These form an almost continuous layer between the
mucous membrane and the orbicularis muscle. They are small secretory organs,
similar in their structure and uses to the salivary glands, and will be described
when these come under notice.
4. Vessels and nerves. — The blood is carried to the lips by the palato-labial,
and the superior and inferior coronary arteries. It is returned to the heart by the
satellite veins of the two last vessels. The lymphatics are very numerous, and
pass to the glands between the branches of the lower jaw. The nerves are of two
kinds : the motor, which are given off from the facial nerve, and are distributed
in the muscular tissue of the lips to cause its contraction ; the sensitive
nerves — from the maxillary branches of the fifth cranial pair — are distinguished
by their number and considerable volume, and are nearly all distributed to the
cutaneous integument, which they endow with an exquisite sensibility.
Functions. — The lips serve for the prehension of solid and liquid food ; they
retain it in the mouth after its introduction thereto, and they prevent the escape
of the saliva. They ought also to be regarded — especially the upper lip — as veiy
delicate tactile organs.
2. The Cheeks (Fig. 168).
These are two membranous walls, which enclose the molith laterally. In the
interior of the buccal cavity they are limited : behind, by the posterior pillars of
the tongue ; in front, by the lips, with which they are confounded around the
commissures ; above and below, by the furrow formed by the gingival mucous
membrane, where it is reflected from the molar arches on to the cheeks.
The greatest diameter of the cheeks is antero-posterior, like that of the cavity
it encloses. The vertical diameter is very small, especially behind ; anteriorly,
however, the cheeks assume a certain amplitude by the separation of the jaws.
Structure. — The cheeks are formed by the buccal mucous membrane, external
to which we find muscular tissue and glands. Vessels and nerves are supplied for
the conveyance of nutritive fluids, sensibility, or the stimulus to contractility.
1. Mucous membrane. — The external face of this membrane is closely attached
to the buccinator muscle, and to the inferior molar glands. Its free face presents,
at the level of the third upper molar tooth, the buccal opening of the parotid
duct, at the summit of a variably-sized tubercle. On the face of each dental
arch there is also remarked a linear series of little salient points, analogous to
the large parotideal tubercle ; these are the excretory orifices of the molar glands.
Its structure is the same as the mucous membrane of the lips. (It is of a pale
colour, and sometimes stained in patches with pigment.)
2. Muscular tissue. — This is the buccinator or alveolo-labialis muscle already
described. It may be remembered that the external face of this muscle is covered
by the masseter, the superior molar glands, and the skin ; while the internal
responds to the mucous membrane and the inferior molar glands.
3. Glands. — These are two masses of glandular lobules, known as the molar
glands. They will be described with the salivary glands.
THE MOUTH.
Is and nerves. — The external maxillary, coronary, and buccal arteries carry
blood to the cheeks. The veins empty them-
selves into the sateUite branches of these Fig. 21 o .
arteries.
The lymphatics proceed to the submaxillary
glands. The nerves are of the same kind, and
proceed from the same source, as those sup-
plying the lips : being the seventh pair of
cranial nerves for the muscular layer, and the
fifth pair for the integuments (with filaments
of the sympathetic for the blood-vessels and
labial glands.)
Functions. — The cheeks are very active
agents in mastication, by constantly pushing
the aliment, through the action of the bucci-
nator, between the dental grinding surfaces.
3. The Palate (Fig. 215).
Preparation. — Separate the head from the trunk ;
saw through the branches of tlie inferior maxilla above
the angle of the jaw, and from the crown of the last
molar tooth, so as to pass between the curtain of the
soft palate on the one part, and the base of the tongue
on the other, leaving the latter organ adherent to the
lower jaw. This last should be removed from the
upper jaw by cutting through the masseter and bucci-
nator muscles, and so, exposing the hard and soft
palates in such a manner as to render easy the special
dissections necessary for their study. For the palate,
these dissections are limited to the removal of the
mucous layer covering the deep venous network, and
to the partial excision of this, which allows the artery
and palatine nerves to be seen (see Fig. 215).
The palate (hard palate), palatine arch, or
upper luall of the mouth, is circumscribed, in
front and on the sides, by the superior dental
arch, and limited, behind, by the anterior
border of the soft palate. It is a parabolic
surface, exactly representing, in its configura-
tion, the bony palate (Fig. 50).
On its surface is remarked a median groove,
which partitions it into two equal divisions,
and which commences quite in front, at the
base of a small tubercle. Curved transverse
furrows, twenty in number (Leyh gives from
sixteen to eighteen), divide each of these
halves into an equal number of salient arches,
the concavities of which are turned backwards,
and which become narrower and less marked
as they are more posterior. (These arches and
furrows aid in retaining the aliment which the
tongue carries towards the palate during
deglutition.)
THE HARD AND SOFT PALATE OF THE
HOESE.
The mucous membrane has been removed
from the right side, and, with the
glandular layer, from the soft palate.
1, The ridges of the palatine mucous
membrane ; 2, venous network of the
deep layer, which is incised at the
external side to show the palatine
artery, 3, accompanied by the fila-
ments of the palatine nerve ; 4, car-
tilaginous digitation, over which passes
and is inflected the palatine artery ;
5, aponeurosis of the soft palate; 5',
terminal extremity of the tendon of
the tensor palati, forming by its ex-
pansion the staphyline aponeurosis ; 6,
the pharyngo-staphyhnus ; 7, the pa-
lato-staphylinus; 8, staphyline nerves.
400 THE DIGESTIVE APPABATUS IN MAMMALIA.
Structure. — The palate lies on the bony vault formed by the palatine and
supermaxillary bones. It includes in its structure :
1. A fibrous membrane, applied to the bone just mentioned, which sustains
a remarkably developed venous network, constituting a veritable erectile tissue,
and gives to the palate a greater or less degree of thickness, according to its state
of turgescence (Fig, 215, 2).
2. A mucous layer, extremely adherent, by its deep face, to the preceding
tissue, and of a whitish aspect in the horse. The corium, formed entirely of
connective tissue, shows numerous conical papillas, especially at the posterior
part of the palate. The epithelium fills up the depressions between the papillse ;
it is stratified, squamous, and remarkable for the great thickness of its horny
layer.
3. Two voluminous artmes — the palatine — are lodged in the bony fissures of
the palatine roof. These arteries proceed parallel to each other, and unite in
front by anastomosing to form a single trunk, which enters the incisive foramen.
It is of importance to know their disposition, from a surgical point of view, as care
ought to be taken not to wound them when abstracting blood from the palate.
The blood carried by these arteries arrives in the deep-seated erectile membrane,
and is finally removed by two very short venous trunks, which do not pass with
the palatine arteries into the palatine canal, but only into the palatine fissure.
4. Sensory nerves, which accompany the arteries, and are derived from the
superior maxillary branch of the fifth pair of cranial nerves.
Functions. — The palate has a passive, but important, share in mastication
and deglutition ; furnishing the tongue, as it does, with a firm basis in the
movements it executes when passing the food between the molar teeth, and in
carrying the ahmentary mass backwards to the pharynx.
4. The Tongue (Figs. 221, 223, 251, 306).
Preparation. — 1. By means of a strong saw without a back, make an antero-posterior and
vertical section of the head, in order to study the general disposition of the tongue. 2. From
another head remove the lower jaw, leaving the tongue in the intermaxillary space, to examine
the external conformation of the organ (see the dissection of the palate). On a third head,
kept for the study of the muscles, these parts are exposed in the following manner : The
masseter is entirely removed, and the cheek is detached from the lower jaw and turned over
on the upper jaw ; then the branch of the inferior maxilla is sawn through transversely, at
first behind, next in front of the molar teeth : the upper piece of bone should be detached by
disjointing it behind the temporo-maxillary articulation, after destroying the capsular liga-
ment and dividing the insertions of the pterygoid muscles. With resrard to the inferior piece,
it is reversed in such a way as to put the line of the molars downwards, and the inferior border
of the bone upwards in the bottom of the intermaxillary space. To do this, it is sufficient to
separate the buccal mucous membrane from the mylo-hyoideus muscle, proceeding from above
to below. Tiie dissection thus prepared, serves not only for the study of the muscles of the
tongue, but also for those of the deep salivary glands, the pharynx, larynx, guttural pouches,
the nerves and arteries of the head, etc. It is always better, in order to facilitate this dissec-
tion, to keep the jaws apart by fixing a piece of wood or bone between the incisor teeth
immediately after the death of the animal.
llie lingual canal. — The inferior wall (or floor) of the mouth, circumscribed
by the lower alveolar arches, forms an elongated cavity named the lingual canal
(or space), which lodges the organ designated the tongue. This canal occupies,
in its anterior third, the superior surface of the body of the inferior maxilla. For
the remainder of its extent, it is formed by a double groove in the floor of the
mouth, at the sides of the tongue. It exhibits the suhlimiiutl crest oxi^ the barhs^
of which we will speak when describing the sublingual and maxillary glands.
THE MOUTH. 401
Situation of the tongue. — The tongue occupies the whole length of this
elongated cavity, and thus extends from the back part of the mouth to the
incisor teeth, lying in the intermaxillary space, where it rests on a kind of
wide sling formed by the union of the two mylo-hyoidean muscles (see Fig.
307, 7).
External conformation. — It is a fleshy organ, movable in the interior of the
buccal cavity, and almost entirely enveloped by the mucous membrane which
lines that cavity. In Solipeds, it forms a kind of triangular pyramid, flattened
on each side, fixed to the os hyoides and the inferior maxilla by the muscles
which form the basis of its structure, or by the membrane that covers the
organ.
Its form permits it to be divided, for the study of its exterior, into three faces,
three borders, and two extremities.
The superior face, or dorsum of the tongue, narrower in front than behind,
is roughened by numerous papilla which give it a downy aspect. Two of these
papillae are remarkable for their enormous volume, their lobulated appearance,
and the situation they occupy at the bottom of two excavations placed side by
side, near the base of the organ — the lingual lacunce, or foramen ccecum of Mor-
gagni. This face corresponds to the palatine arch or roof, when the jaws are
together. The lateral faces, wider in the middle of the tongue than at its
extremities, are limited by the internal surfaces of the inferior maxillary branches.
On them are seen several large papillse, and the orifices of the lingual glandulce.
These two faces are separated from the former by two lateral borders, which
correspond to the superior alveolar arches when the mouth is exactly closed.
"With regard to the third or infeiior border, its existence may be said to be
fictitious ; by it enter the muscles which constitute the substance of the tongue,
and it is by it, also, that the organ is fixed at the bottom of the intermaxillary
space.
The posterior extremitg, or base of the tongue, is limited, in the interior of
the mouth, by a furrow which borders the base of the epiglottis. It presents
a thick, median, mucous fold, plaited in difl'erent ways, and carried over the
anterior aspect of the epiglottic cartilage. Two other folds, more anterior, also
formed by the buccal membrane, unite with the soft palate on each side of the
base of the tongue ; these are the posterior pillars of the organ (or the glosso-
epiglottic ligaments of Man), and comprise in their substance a voluminous
collection of glands. Behind these pillars are two triangular spaces, included
between the velum pendulum palati and the base of the tongue, each of which
has an excavation perforated with openings — a veritable amygdaloid cavity — which
represents the amygdalce (tonsils) of Man and the Carnivora ; it is a kind of
common confluent for the numerous glandulae accumulated outside the mucous
membrane that lines this excavation.
The anterior extremity of the tongue is quite free, from the middle of the
interdental space, and moves at liberty in the interior of the buccal cavity : it is
also termed the free portion of the tongue, in distinction to the remainder of
the organ, which is named the fixed portion. This free portion is flattened
above and below, and slightly widened or spatulated. Its superior face is
plane, or nearly so, and prolongs that of the fixed portion. The inferior,
slightly convex, and perfectly smooth, is continuous with the lateral faces of
the organ, and rests on the body of the inferior maxilla ; it is fixed to that bone
by a median fold of mucous membrane — the anterior pillar, or frcBuum lingvm.
THE DIGESTIVE APPARATUS IN MAMMALIA.
The borders, in joining each other in front, describe a parabolic curve which is
in contact with the incisive arches.
Structure. — The tongue offers for study, in regard to its structure : 1. The
mucous membrane enveloping the organ. 2. The muscular tissue which, in
reality, forms its mass. 3. The vessels and Jierves distributed to it.
1. Mucous membrane. — This membrane — a continuation of that lining the
mouth — is reflected at the bottom of the canal on the sides of the tongue, covers
the upper surface of the organ, and envelops the whole of its free portion.
Its dermis, or corium, has not the same thickness throughout, but is incom-
parably thinner and less dense on the sides of the fixed portion and the
inferior plane of the free part ; on the dorsum of the tongue it is difficult to
cut it. Its deep face receives the insertion of a large number of the muscular
fibres of the organ, and for the greater part of its extent it adheres in the most
intimate manner to these fibres, though its adherence is not so close at those
points where it is in contact with the labial glands.
Its superficial face is not smooth, but shows a prodigious quantity of minute
Fig. 216.
Fig. 217.
COMPOSITE PAPILLA FROM THE TONGUE
OF THE DOG.
1, Corium ; 2, epithelium.
SIMPLE FILIFORM PAPILLA FROM THE
POINT OF THE HOKSE'S TONGUE.
1, Corium ; 2, epithelium.
prolongations or papillce, which, accordmg to their shape, are distinguished as
filiform, fungiform, and calijciform papillce.
The filiform papillce (Fig. 217) are formed by thin prolongations terminating in
a point, each being covered by an epithehal sheath which greatly increases its
dimensions. They are simple or composite, having at their summit secondary pro-
longations, much smaller, and provided also with an epithelial covering. These
filiform papillfe are largest on the middle part of the dorsum of the tongue, where
they present a tufty appearance ; towards the point of the organ they are embedded
in epithelium, and are scarcely apparent in the minute elevations on its surface.
The fungiform pcqnllcB (p. capitatce) (Fig. 219, 2) are club or sponge-shaped
elevations of the derm, attached to the membrane by a short pedicle. Their
surface is convex and smooth, or studded with filiform papillifi. They are
scattered irregularly over the dorsum of the tongue, among the filiform papillae,
and are most numerous on the posterior third of its surface.
The calyciform papillcB (fossuJate, circumvallate, or Jetiticular pa^nllce) (Fig. 219)
are really f imgif orm, but instead of projecting above the free surface of the dermis,
they are placed in a depression in this membrane. They are surrounded by a
slightly elevated ring, within which is a narrow fossa around the pedicle of the
papilla ; several papiUae may be contained within one cup-shaped cavity. They
THE MOUTH.
403
only exist at the base of the tongue, where two of their number, very developed
and composite, correspond to the blind foramina of Morgagm (foramen ctecum).
At the base of a certain number of the fungiform and calyciform papillae is a
band of adenoid tissue.
It is generally beheved that these three kinds of papillae have each a distinct
function ; the filiform are to retain the alimentary and sapid substances on the
surface of the tongue, the fungiform are tactile organs, and the calyciform are
gustatory.
2. Muscles. — Beneath the mucous membrane, on the dorsal surface of the
tongue, is a cylindrical fibrous cord, which sometimes attains the thickness of a
large goose-quill. This cord is situated in the median plane, near the middle
part of the organ, and is from 2 to 3 inches long. It may be considered as a
fibrous support to the muscular tissue, and it sometimes directly adheres to the
deep surface of the mucous membrane. At other times, it is only connected
Fig. 218.
FORAMEN OF MORGAGNI IN
THE horse's tongue (SEEN
FROM above).
VERTICAL section OF A FORAMEN C^CUM OF THE
horse's TONGUE.
1, 1, Borders of the calyx ; 2, fungiform papillsc occupying
it ; 3, section of the ring of lymphoid tissue ; 4, racemose
glands ; 5, muscular fibres of the tongue.
with that membrane by a very short lamellar prolongation, and is then buried a
little deeper among the fibres of the superior muscular layer.
(The German hippotomists designate this the cartilage of the tongue. It is
only found in Solipeds, and was first described by Briihl, who gave it this desig-
nation. Leyh states that it is composed of dense fibro-cartilage, surrounded by
connective and adipose tissue ; that it is from 4 to 7 inches long, and f to 1 inch
in thickness ; and that it commences about an inch from the anterior appendix
of the hyoid bone.)
A similar cord, but not so strong or well-defined, is sometimes found at the
inferior surface of the free portion of the tongue.
Intrinsic muscles. — In studying the proper substance of the tongue in two
sections — one vertical and longitudinal, the other transverse — there is seen,
under the dorsal mucous membrane, a layer of red fibres, close in their texture,
and very adherent to that membrane. Amongst these fibres, there are some
which aifect a longitudinal direction, but the majority are vertical or transverse,
and all are interlaced in the most intimate manner. It appears as if this layer
(the lingualis superficialis of Man) were perfectly independent of the other
muscular fibres, the insertion of which it receives. It also forms a portion of
those which writers have named the intrinsic muscles of the tongue, and which
404 THE DIGESTIVE APPARATUS IN MAMMALIA.
comprise a superior and inferior, a transverse and a vertical linguaUs muscle,
found on the inferior aspect of the free portion of the organ. An attentive
examination, however, reveals that the fibres proper to this submucous layer are
continuous with those which, coming from a point situated beyond the tongue,
form the muscles named, in consequence, extrinsic, and that they are only the
prolongations of these. This division of the tongue into two orders of muscular
fasciculi does not, for this reason, possess the importance generally accorded
to it.
Extrinsic muscles. — If the muscular fibres of the tongue appear to be one
mass in the superior layer just referred to, it is not so when they are followed
beyond this layer ; on the contrary, we see them separate from one another, and
even admit between them — at least in the fixed portion — a certain amount of
adipose tissue, which is particularly abundant towards the base, where it forms
a mass called the fattij nucleus of Baur ; then they collect into fasciculi, or per-
fectly distinct muscles.
In Solipeds, these muscles number five pairs : 1. The stylo-glossus. 2. The
great hyo- or hasio-glossus. 3. The genio-glossus. 4. The small hyo-glossus
(the superior lingual of some authorities). 5. The pharyngo-glossus.
Stylo-glossus (Hyo-glossus Longus) (Fig. 220, 1).
Synonym. — Kerato-glossus externus — Leyh. The stylo-glossus of Man.
This is a very long riband-shaped band, formed of bright-red parallel fibres,
and extending from the styloid bone, or great cornu of the os hyoides, to each
side of the free extremity of the tongue.
It arises from the external surface of the large cornu, near its inferior
extremity, by a very thin aponeurosis ; it terminates near the tip of the tongue,
in expanding over the inferior surface and borders of the organ, and mixes its
fibres with those of the opposite muscle.
In the fixed portion of the tongue, this muscle is related : outwardly, to the
mylo-hyoideus, sublingual gland, hngual nerve, and the Whartonian duct ; m-
wardly, to the genio-glossus and great hyo-glossus muscles. The whole of its
free portion is covered by the buccal membrane.
In contracting, this muscle pulls the tongue towards the back of the mouth ;
it inclines it to one side when acting independently of its fellow on the opposite
side.
Great Hyo-glossus, Basio-glossus (Hyo-glossus Brevis) (Fig. 220, 2).
Synonym. — Hyo-glossus — Leyh.
A wide muscle, flattened on both sides, thicker than the preceding, and com-
posed of fibres passmg obliquely forward and upward, the longest of which are
anterior.
Its origin occupies the whole side of the body of the os hyoides, from the
extremity of the cornu to that of the spur process. Its fibres, after becoming
detached from this point of insertion, are insinuated beneath the preceding
muscle, spread out under the mucous membrane covering the lateral aspect of
the tongue, and for the most part are reflected inwards, nearly to the superior
face, to constitute the transverse fibres of the organ.
THE MOUTH.
405
It is in relation, outwardly, with the mylo-hyoideus, stylo-glossus, the great
hypo-glossal nerve, Wharton's duct, and the hngual mucous membrane ; inwardly,
with the small hyo-glossus, the small cornu of the os hyoides, the pharyngo-
glossus, genio-glossus, lingual artery, the terminal divisions of the glosso-pharyn-
geal nerves, and great and small hypo-glossals.
It retracts the tongue in depressing its base, according as it acts singly or
simultaneously with its fellow.
(In 1850, Briihl described as the middle descending sft/Io-glossus, a long,
narrow muscle arising from the lower extremity of the inner face of the styloid
bore, or large cornu of the os hyoides, and terminating near the tip of the tongue,
where it is covered by the hyo-glossus. It has since been described as the
internal or small kerato-glossus. Its action is the same as the stylo-glossus.)
Genio-glossus (Genio-hyo-glossus) (Fig. 220, 4).
This is a beautiful muscle, the fibres of which are disposed Uke a fan in the
vertical and median plane of the tongue.
It arises from the inner surface of the lower jaw, near the symphysis, by a
MUSCLES OF THE TONGUE, SOFT PALATE, AND PHARYNX.
1, Stylo-glossus ; 2, great hyo-glossus ; 3, the same, covered by the submucous layer formed by the
expansion of the small hyo-glossus ; 4, genio-glossus ; 5, pharyngo-glossus ; 6, palato-pharyngeus ;
7, hyo-pharyngeus ; 8, thyro-pharyngeus ; 9, crico-pharyngeus ; 10, oesophagus; 11, 12, tensors
palati ; 13, stylo-hyoideus ; 14, hyoideus magnus ; 15, genio-hyoideus ; 16, hyo-thyroideus [
17, sterno-thyroideus ; 18, crico-thyroideus.
tendon parallel to that of the genio-hyoideus. From this tendon are detached
a multitude of divergent fibres which pass backwards, upwards, and forwards, to
reach the upper surface of the tongue, and become continuous with the vertical
fibres of the submucous layer.
The two genio-glossi lie together on the median plane of the tongue, except
towards their origin, where they are constantly kept apart by adipose tissue.
Their inferior border responds to the genio-hyoid muscles, and their anterior
fibres are partly included between the two mucous layers of the frgenum linguae.
They are related, by their external face, to the great hyo-glossus, the stylo-glossus,
406
THE DIGESTIVE APPARATUS IN MAMMALIA.
the sublingual gland, the lingual artery, and the terminal branches of the three
lingual nerves.
The action of the genio-glossus is complex ; according to the portion of its
fibres which contract, it will carry the tongue forwards, pull it into the buccal
cavity, or draw it downwards into the floor of the mouth.
Small Hyo-glossus (Lingualis) (Fig. 220, 3).
Synonym. — Lingualia superior of Man.
Under this name is described a thin band, formed of parallel fibres, which is
exposed immediately on removing the mucous membrane, with the subjacent
glands, from the base of the tongue. This band arises from the inner side of
the articulation uniting the body of the os hyoides to its small cornu. It passes
Fig. 222.
Fig. 221.
ONE LOBE OF A RACE-
MOSE GLAND. FOLLICULAR GLAND FROM THE ROOT OF THE
1, Envelope of connec- tongue.
tive tissue; 2 excre- j^ Epithelium; 2, papilla of mucous mem-
tory duct ; 3, glandu- ^rane ; 3, cavity of the follicle ; 4, invest-
lar vesicle, or acini. j^g ^^s^t of the gland composed of connective
tissue ; 5, fibro-vascular matrix, forming its
parenchyma, and containing, 6, 6, the
closed capsules or follicles.
above the transverse muscle of that bone, which it crosses perpendicularly, is
surrounded at this point by a great mass of adipose tissue, and is prolonged
directly forward, beneath the lingual mucous membrane. Its fibres then vanish,
either on the superior aspect of the tongue or on its sides, or they descend
obliquely in crossing the direction of the hyo-glossus, to join the superior border
of the stylo-glossus.
(This muscle contracts and retracts the tongue.)
Pharyngo-glossus (Palato-glossus) (Fig. 220, 5).
A rudimentary muscle formed of parallel fibres, which, from their origin on
the lateral wall of the pharynx, pass outside the articular angle of the branches
of the OS hyoides, and between the hyo-glossus and genio-glossus, mixing with,
and intercrossing their fibres.
3. Labial glands. — The numerous glands of the tongue may be divided into
racemose (or lobulated) glands, and closed follicles (or follicular glands).
TEE MOUTH. 407
Th&racemose glands (Fig. 221) are spread on the sides and base of the tongue.
Near its upper border they form two rows, which are rendered visible by the
presence of a small tubercle placed beside each of them. At the base of the tongue
they are found beneath the fungiform and calyciform papillae, as well as beneath
the layer of closed follicles which lines the isthmus of the fauces.
At the entrance to this passage, the lingual mucous membrane is mammillated,
and each elevation has an orifice. This arrangement is connected with the
presence, at this part of the tongue, of the closed follicles (Figs. 222, 223), which
are more or less voluminous and aggregated, and separated from the muscles by
a continuous layer of racemose glands. They are composed of an envelope of
dense connective, and a mass of adenoid tissue, which has in its centre a
cavity that communicates with the orifice above the follicle, and is lined by the
lingual epithelium, minus its horny layer.
4. Vessels and nerves. — The tongue is supplied with blood by two arteries,
the lingual and sublingual; the blood is
removed by three large veins, two of which
enter the external maxillary, and the third
the internal maxillary vein. The lymphatics
constitute a very fine superficial network,
the emergent branches of which pass to
the submaxillary glands. The 7ierves are
the Ungual, the glosso-pharyngeal, and
the great hypo-glossal ; the latter is a
motor nerve, and consequently supplies the
muscles ; the others are exclusively sensi- ^
' T , -1 . 1 • , , SECTION OF AN AMYGDALOID FOLLICLE
tive, and are distributed more particularly of the horse's tongue.
to the mucous membrane. 1^ Follicle cut through the middle ; 2, follicle
Functions. — The tongue serves for divided beyond its centre ; 3, section of a
the prehension of liquids in all animals, '■"''°'°'' ^^"^'^ ' *' ^'''''•
and for solid ahment in the Ox. It concurs, with the jaws, in propelling the
substances to be crushed between the molar teeth during mastication ; and
it is, besides, one of the essential organs of deglutition. It is able to play this
important and complex part, through the varied movements it can execute in the
interior of the mouth ; and the extent of these movements demands a moment's
notice. They are of two kinds : those which influence only the form of the
organ, and those which cause it to submit to various displacements. They result
in either compressing it from side to side, above to below, or curving it longi-
tudinally, and even transversely. These movements are principally, but not
exclusively, due to the action of the intrinsic fibres ; they are perfectly indepen-
dent of the movements which, as a whole, produce the total displacement of the
tongue. With regard to these latter, they may result in carrying the tongue
beyond the mouth, or withdrawing it into that cavity, inclining it to one side,
raising it against the palate, depressing it on the floor of the mouth, or, finally,
lifting it towards the pharynx. It is worthy of remark that these movements
do not alone result from the action of the proper Ungual muscles above described ;
those belonging to the os hyoides, to which is attached the spur process,
concur also in producing them. But this process is not the only organ thus
attached to the hyoideal apparatus ; the larynx and, through it, the pharynx, are
placed in the same conditions, and are obliged to follow, like the tongue, the
movements of the bony framework supporting them.
408 TEE DIGESTIVE APPARATUS IN MAMMALIA.
There consequently results, between these three organs, a remarkable unity
of action, which is readily explained by the part they all take in the one common
act of deglutition.
5. Soft Palate (Figs. 215, 224).
Preparation.— Tihe soft palate is studied : 1. On the antero-posterior and vertical section of
the head (Fig. 220). 2. On the portion intended to show the interior of the pharynx (see the
preparation of this region). 3. On the portion represented in Fig. 215, the mode of dissecting
which has been indicated at page 399 ; in removing the mucous membrane and glandular
layer, the fibrous membrane and the two intrinsic muscles are exposed. The extrinsic muscles
should be studied with those of the pharynx.
Situatio7i — Form. — The soft palate {palatum molle, velum pendulum palati) is
suspended hke a partition between the mouth and the pharynx, and by its
posterior border circumscribes the orifice that establishes a communication
between these two cavities.
This partition, which continues the hard palate posteriorly, represents in its
external form a membranous valve, oblique downwards and forwards, much
longer than it is wide, and exhibiting for study two faces and /<??«• borders.
The inferior or anterior face, towards the mouth, shows longitudinal folds
and transverse ridges, with multitudes of orifices belonging to the submucous
glandulas. On its sides it is united to the base of the tongue by means of two
thick mucous columns, designated the posterior pillars of the tongue. The
superior or posterior face forms the anterior wall of the pharynx ; it only exhibits
some very shght longitudinal ridges.
The two latercd borders are inserted into the walls of the two cavities which
the soft palate separates. The anterior border, continuous with the palate, is
attached to the palatine arch, and follows the curve described by it. The
posterior border — the only free one — is concave, and closely embraces the base of
the epiglottis, which is usually found lying against the posterior surface of this
curtain. This border is continued at its extremities by two thin prolongations,
which can be followed on the lateral walls of the pharynx to the oesophageal
infundibulum, above which they unite in the form of an arch. These prolonga-
tions are the posterior pillars of the soft palate, in contradistinction to the two
mucous folds at the base of the tongue, which constitute, by their relation to
this partition, veritable anterior pillars. This posterior border concurs in cir-
cumscribing what is named the isthmus of the fauces— an aperture constantly
closed in Solipeds, in consequence of the great development of the soft palate ;
it is only dilated for the passage of the alimentary substances passing into the
pharynx. The isthmus of the fauces is, therefore, not merely an opening ; it is
a passage which has for its inferior wall the base of the tongue as far as the
epiglottis ; for its upper wall, the anterior face of the soft palate ; and for its
sides the posterior pillars of the latter.
Steucture.— To give the most simple idea of the structure of the soft
palate, it may be said that the mucous membrane of the palate, and that of the
floor of the nasal cavities, is prolonged behind the palatine arch, parallel to one
another, and become joined towards the free border of this curtain ; and it
might be further shown that, in the space between these two mucous membranes,
there is a fibrous membrane, muscles, a glandular layer, vessels, and nerves ;
besides these, there are no other elements in the organization of the soft palate.
THE MOUTH. 40S
They may be studied in the following order : 1. Fibrous membrane. 2. Muscles.
3. Mucous membranes. 4. Vessels and nerves.
1. Fibrous membrane (Fig. 215, 5). — This membrane, remarkable for its
power of resistance, forms a real framework for the soft palate, of which it only
occupies the anterior moiety. It is attached in front of the palatine arch, and is
prolonged posteriorly by a particular muscle, the palato-pharyngeus.
2. Muscles. — Of these muscles, which are all pairs, there are those which
constitute a layer situated in the middle of the soft palate itself, and represent
the intrinsic muscles ; these are the pharyngo-staphylinus {palato-pharyngeus)
and the palato-staphylinus {circumflexus palati). The others, the peristaphylinus
— external and internal {tensors palati external and internal), are only inserted
Fig. 224.
MEDIAN LONGITUDINAL SECTION OF THE HEAD AND UPPER PART OF NECK.
1, Upper lip; 2, premaxilla ; 3, hard palate; 4, tongue; 5, septum nasi; 6, nasal bone; 7, palatine
arch; 9, pterygoid bone; 10, epiglottis; 11, entrance to the Eustachian tube; 12, arytenoid
cartilage; 13, cricoid cartilage; 14, oesophagus; 15, frontal bone and sinus; 16, cerebrum;
17, corpus callosum ; 18, cerebellum; 19, sphenoid bone; 20, medulla oblongata; 21, cervical
ligament , 22, spinal cord ; 23, occipital bone ; 24, 24, atlas ; 25, 25, dentata ; 26, trachea.
into the organ by their terminal extremities, and therefore act as extrinsic
muscles.
Pharjmgo-staphylinus (Palato-pharyngeus) (Fig. 215, 6)
In removing the mucous and glandular layers which cover the anterior face
of the soft palate, there is exposed a wide and thin muscular fasciculus succeed-
ing the fibrous layer behind, and occupying the posterior half of the entire
organ. The fibres of which this muscle is composed, mixed in the median line
with those of the muscle of the opposite side, are directed backwards and
outwards, the most posterior following the curve of the free border of the
curtain. Arriving near the lateral border, they are reflected upwards, passing
between the pharyngeal mucous membrane and the middle constrictor of the
pharynx, with which it appears to be confounded posteriorly ; but with a little
attention it can be followed to the superior border of the thyroid cartilage, into
410 THE DIGESTIVE APPARATUS IN MAMMALIA^
which it is inserted, after making a somewhat long track mider the mucous
membrane of the pharynx.
This muscle stretches the curtain, and draws its free border from the
oesophageal inf undibulum, during pharyngeal deglutition.
Palato-staphylinus (Azygos Uvulae) (Fig. 215, 7).
(%nont;m8— Staphyleus— Gi'mrd. Circumflexm palati—Percivall. The azygos uvulas of
Man.)
A small, elongated, cyUndrical, bright-red muscle, opposed, in the median
line, to that of the other side, and extending over the inferior surface of the
preceding, from the palatine arch to the free border of the soft palate, which it
pulls forward and upward to dilate the isthmus of the fauces. It arises by a
small glistening tendon, not from the palatine, but from the staphyline aponeu-
rosis (Fig. 215, 7). The fascia which the two muscles form is for the most part
covered, in its middle portion, by the fibres of the tensores palati.
Sometimes, and especially in the Ass and Mule, the fibres of this muscle
are directly attached to the palatine arch, in becoming more or less insinuated
into the substance of the glandular layer.
Peristaphylinus Extemus (Tensor Palati) (Fig. 220, 11)
(Synonym. — The circumflexus of Man.)
This is a small, elongated muscle, flattened on both sides, bulging in its^
middle, thin and tendinous at its extremities, and extending obliquely forward
and downward from the styloid process of the temporal bone, where it has its
origin, to the pterygoid trochlea. Its terminal tendon glides and is inflected
inwards on this pulley, to be afterwards spread out and confounded with the
fibrous framework of the soft palate, which causes the framework to represent
an expansion of the tendon.
The muscle is covered, outwardly, by the pterygoidei muscles ; it is related,
internally, to the next muscle, which separates it from the Eustachian tube.
It is a tensor and depressor of the aponeurosis of the soft palate.
Peristaphylinus Intemus (Levator Palati) (Fig. 220, 12).
(Synonyms.— Stylo-pharyngeus—Percivall. The levator palati of Man.)
This is formed by a pale and thin band, which arises with the preceding
muscle, descends between it and the Eustachian tube, passes beneath the
superior constrictor of the pharynx, then below the mucous membrane of the
pharynx to reach the soft palate, where it expands on the anterior or posterior
surface of the palato-pharyngeus, beneath the glandular layer, its fibres becoming
mixed, on the median line, with those of its fellow.
This is an elevator of the soft palate.
3. Glandular layer.— Thh layer is comprised between the fibrous membrane
and the anterior mucous layer, becoming thinner as it is prolonged over the
intrinsic muscles ; it does not extend to the free border of the organ. It is
thickest on each side of the median plane, where it forms two lobes, which appear
on the anterior surface of the soft palate as an elongated ridge, much more
THE MOUTH. 411
marked in the Ass than the Horse. It is worthy of notice, that the glands
composing this layer throw all their secretion into the mouth — that is, on the
anterior face of the soft palate.
4. Mucous membranes. — The soft palate is covered on both its surfaces by two
mucous layere, one anterior, the other posterior, united, as has been remarked, at
the free border of the organ. The anterior is continuous, above, with the mucous
membrane of the hard palate ; on its sides, with that which covers the base of
the tongue. In stracture it is the same as the buccal membrane ; its epithelium
is stratified and tesselated. The other layer is nothing more than the pituitary
membrane extended over the posterior surface of the septum, and thence to
the lateral surfaces of the pharynx. It will be more fully described with the
latter.
5. Vessels and nerves. — The soft palate is supplied with blood by the
staphyline and pharyngeal arteries. The nervous filaments this partition receives,
emanate from the fifth pair of cranial nerves (superior maxillary branch), and
from Meckel's ganglion ; they form the staphyline or posterior palatine nerve
(Fig. 215, 8).
Ttie superior maxillaiy branch is entirely sensitive, and yet the staphyline
nerve goes to tegumentary, glandular, or contractile organs. How can it fulfil
this double function ? By receiving filaments from Meckel's ganglion, which has
motor fibres derived from the facial nerve.
Functions. — During the act of deglutition, the soft palate is raised to
enlarge the isthmus, and allow solids or liquids to pass through. The description
given of this septum, permits us to understand how it plays the part of a valve,
in rising freely while the alimentaiy bolus or mouthful of fluid passes from the
mouth into the oesophagus, across the pharyngeal vestibule, but never allowing the
matters which have once entered the oesophageal canal to return into the buccal
cavity. Also why, when any obstacle is opposed to the descent of aliment into
the oesophagus, after it has cleared the isthmus of the fauces, or even when the
animal vomits, the matters arrested in their passage or expelled from the stomach
are ejected by the nasal cavities, after flowing over the posterior surface of the
soft palate. This disposition of the pendulous curtain, in forming a complete
partition which hermetically seals the orifice of communication between the
mouth and pharynx, likewise sufficiently explains why, in normal circumstances,
Solipeds respire exclusively by the nostrils.
6. The Teeth.
Passive agents in mastication, the teeth are hard organs, bony in appearance,
implanted in the jaws, and projecting into the interior of the mouth, in order to
bruise or tear the solid alimentary substances.
Identical in all our domesticated animals, in their general aiTangement, their
mode of development, and their structure, in their external conformation these
organs present notable differences, the study of which offers the greatest interest
to the naturalist. For it is on the form of its teeth that an animal depends for
its mode of alimentation ; it is the regime, in its turn, which dominates the
instincts, and governs the diverse modifications in the apparatus of the economy ;
and there results from this law of harmony a striking coiTelation between the
arrangement of the teeth and the conformation of the other organs.
Compelled by the limits of our task to confine ourselves to the purely
descriptive part of the dental apparatus, we cannot stop to notice the interesting
412
TEE DIGESTIVE APPARATUS IN MAMMALIA.
Fig. 225.
physiological considerations on which this principal is founded ; but will begin at
once the anatomical study of the teeth, by indicating their general characters,
before examining them successively in all the domesticated species.
A. General Characters of the Teeth— General Arrangement.—
The teeth are fixed in the jaws, and ranged one against the other in such a way
as to form two parabolic arches opening behind, and interrupted on each side by
what is called the interdental space. Distinguished into superior and inferior,
like the jaws to which they belong, these arches come in contact with one another
in a more or less exact manner when the mouth is perfectly closed.
Those teeth which are placed together in front, at the
middle of the dental arches, are named incisors, or incisive
teeth ; the others, situated behind these, and always number-
ing two for each jaw, are called the canine teeth, or tusks ;
while the designation of molars is given to those which
occupy, in the more retired portion of the buccal cavity,
the lateral parts and extremities of the dental arches.
External Conformation. — Each tooth represents,
when completely developed, an elongated polyhedron, which
has sometimes a pyramidal form, and at others that of a
cone or parallelopiped.
A portion of the tooth is buried and solidly implanted
in one of the alveolar cavities of the maxillary bones ; this
is the root, or embedded jwrtion (or fang). The other por-
tion, circumscribed at its base by the gum, leaves the
alveolus to project into the mterior of the mouth, forming
the crown, oy free portion. The narrow constriction between
the crown and root is named the neck.
The fang is perforated at its inferior extremity by one
or more excavations (cavitaspulpcB), which penetrate deeply
into the substance of the tooth, and admit into their
interior the vasculo-nervous papilla, simple or ramified,
known by the name of the bulb, or dental pulp.
The crown, the portion submitted to friction during
mastication, and, consequently, to wear, offers the most
varied forms : sometimes it is shaped like a very acute cone ;
at others, it is divided into several tubercles more or less
salient ; and sometimes, again, it bears at the extremity of
the tooth a wearing surface more or less plane and regular.
Structure. — Three essentially different substances enter
into the structure of all the teeth — the ivory, enamel, and
cement; to which ought to be added the soft parts — ^the
pulp, gum, and alveolo-dental periosteum.
Ivory. — The ivory, or dentine, has the hardness of bone,
is of a whitish-yellow colour, and is rendered brilliant in places by its nacrous
reflection. It forms the principal mass of the tooth, enveloping everywhere the
pulp cavity.
Examined by aid of the microscope, this substance is found to be channeled
by a multitude of minute, undulating, and branching canals {dental canaliculi or
tubuli) embedded in amorphous matter (the fundamental substance).
The tubuli, or canaliculi, extend from the dental cavitv to the inner face of
MAGNIFIED SECTION OF
A CANINE TOOTH,
SHOWING ITS INTI-
MATE STRUCTURE.
1, Crown ; 2, 2, neck ;
3, fang, or root; 4,
cavitas pulpac ; 5,
opening by which the
vessels and nerves
communicate with
the pulp; 6, 6, den-
tine, showing fibrous
structure ; 7, 7,
enamel ; 8, 8, cement.
THE MOUTH.
413
the enamel ; single at their origin, they soon bifurcate, and again anastomose
several times during their slightly undulating course. They terminate in a
cul-de-sac, or in irregular cavities situated beneath the enamel, and named the
interglobular spaces of Gzermak (forming the interglobular or nodular layer).
These canals have a thin proper wall, and contain a dental fibre, which very
probably is a continuation of the pulp-cells. The fundamental substance (or
matrix) is amorphous, and not very abundant ; in its mass are deposited the
saline molecules which give the dentine its bony consistency. (These molecules
are deposited in lamellas, concentric with the pulp cavity. Nasmyth considers
the fibres to be rows of minute opaque points, arranged in a linear series
— baccated fibres — and to be merely the nuclei of the ivory cells, the interfibrous
substance being the remainder of the cell filled with calcareous matter.)
Its chemical composition much resembles that of bones. After remaining
Fig. 226.
SECTION THROUGH THE FANG OF A MOLAR TOOTH.
A, a, Dentine traversed by its tubuli ; 6, 6, interglobular, or nodular layer ; c, c, cementum.
in dilute hydrochloric acid for several weeks, it comports itself like them, by
giving up the calcareous salts with which it is impregnated to the acid solution,
and becoming soft like cartilage ; submitted to the action of boiling water, it
yields gelatine. The mineral matters of dentine differ from those of bone in
having a smaller proportion of carbonate of lime.
Enamel. — The enamel extends in a layer over the ivory of the free portion
of the tooth, the exterior of which it entirely envelops ; it is prolonged over
the fang in some animals, and in several kinds of teeth it dips, by the crown,
into the interior of the organ to a very great depth. It is brilliantly white, and
so hard that it strikes fire like steel.
Its microscopic structure is very interesting, the enamel being composed of
small prismatic hexagonal rods, s-^oo of an inch in diameter, and notched
on their faces. Owing to this notching, the prisms are intimately united to
each other. They form several layers which cross each other at an acute angle,
though in each layer they are exactly parallel to one another. By immersing
the enamel in dilute hydrochloric acid, there is detached from its surface a fine
amorphous membrane {cuticle of the enamel).
(The chemical composition of enamel appears to be 9 6 '5 per cent, of earthy
matter, and 3"5 of animal substance. The first consists of phosphate of lime,
with traces — 3 per cent. — of fluoride of calcium, carbonate of lime, phosphate
29
414 THE DIGESTIVE APPARATUS IN MAMMALIA.
of magnesia, and other salts. The rods are directed vertically on the summit
of the crown of the tooth, and horizontally at the sides.)
Cemext {cementum, substantia ostoidea, cortical substance, or criista
petrosa). — The cement is spread in a non-continuous layer over the external
surface of the enamel and dentine. It is accumulated in large quantity in the
substance of some teeth, as will be noticed when speaking of the incisors in
the Horse and the molars of the Herbivora.
The structure and properties of this substance differ in nothing from the
structure and properties of the spongy tissue of bone. In a physiological con-
dition, the cement does not contain any Haversian canals. (It contains,
sparingly, the lacunae and canaliculi which characterize true bone : those placed
near the surface have the canaliculi radiating from the side of the lacunae
towards the periodontal membrane ; and those more deeply placed join with the
adjacent dental tubuli. In the thicker portions of the crusta petrosa, the lamellae
and Haversian canals peculiar to bone are also found. As age advances, the
cementum increases in thickness, and gives rise to those bony growths, or
exostoses, so common in the teeth of
^ ig. 227. ^ ^YiQ aged ; the pulp cavity also be-
jj comes partially filled up by a hard sub-
J^^L 1;$4^ n B H stance, intermediate between dentine
^^^^£/^^^ fjt^^^BH ^^^ ^^^^ — osfeo-dentine, or secondary
^^W^^Jf^ i^^&r^nd <?(?»/w?e. It appears to be formed by
^7^> ■''V?'^^" ^^^ffrPf'Q ^ ^^^^^ conversion of the dental pulp,
^l^fr^^r^ Js^^S^^i which shrinks or even disappears.)
jj|^ -Mj/^ pg^^^^0 Dented pidp. — The jndp, or papilla,
C^^^ is formed by a fibrillar and nuclear
mass that fills the internal dental
A, TRANSVEKSE SECTION OF ENAMEL, SHOWING . t. • i i i i J
ITS HEXAGONAL PRISMS ; B, SEPARATED PRISMS, cavity. Itreccivcs blood-vcssels aud
nerves, and is enveloped in a very
thin membrane which is entirely composed of several layers of beautiful cyhn-
drical or prismatic cells, the most superficial of which send fibrillar prolonga-
tions into the dental tubuli. Towards the base of the papilla, this membrane
assumes the texture of connective tissue, and is reflected upwards on the fang of
the tooth to line the alveolus, and join the gum at the origin of the crown.
Gum. — The gum is a portion of the buccal mucous membrane surrounding
the neck of the tooth ; it concurs in consolidating it in the alveolar cavity.
Its structure is that of the membrane to which it belongs, being a thick dermis
furnished with papillae and tesselated epithehum. It does not contain any
Alveolo-dental periosteum. — This scarcely differs from ordinary periosteum,
except in being a little softer. It lines the alveolus and covers the cementum of
the fang.
Development. — Each tooth is developed in the interior of a closed sac named
the dented follicle or sac,^ and lodged in an excavation in the maxillary bones.
The sac presents, according to the species of animal and kind of teeth, numerous
variations, which we cannot stay to consider here : but must confine ourselves
merely to a brief sketch of the general and constant characteristics of its
' Two adjoining follicles and the papillae they contain, sometimes join each other, for we
have seen a two-years-old Ass in which the central and lateral incisors in the inferior maxilla
were united, so as to form only two teeth, instead of four.
THE MOUTE.
415
Fig. 228.
organization. (For details, see 'Embrjologj— Development of the Digestive
Apparatus.)
The dental follicle is constituted by an external enveloping membrane of a
cellulo-vascular nature (Fig. 228, a). It shows at its bottom the simple or
compound papilla, which at a later period is termed the dental pulp (b) ; this
organ, destined for the secretion of the dentine, then fills nearly the whole of
the follicle. In its upper part is observed the enamel organ, or germ {enamel
membrane), formed by a prolongation of the gingival epithelium, and connected
with the latter by a small mass of cells named the gubernaculum dentis. Most
frequently there is, opposite the bottom of the follicle, one or more papillae
which, in some cases, adhere by their whole length to one of the lateral walls
of the follicular sac, and the free extremities of which
cross those of the dentine papillse, or are buried in a
kind of cup on the summit of the latter appendages (c).
These are covered by the membrane of cyUndrical cells
mentioned above (d).
With regard to the enamel organ, its internal face
also presents a layer of cyhndrical cells.
It is in the interval between these two papillary
systems that the dental substance is deposited as in a
mould, consequent on a process of secretion and trans-
formation, the mechanism and progress of which are
somewhat comphcated. The dentine is produced by the
metamorphosis of the superficial cells of the dental germ.
These cells send out ramifying prolongations which con-
stitute the tubuli of the dentine, and those of the
middle layer secrete an intertubular amorphous substance,
in which the earthy salts are deposited from without
inwards. The enamel is deposited on the dentine, and
results from the transformation of the cylindrical cells
of the germ into enamel prisms. The cement is, in its
turn, deposited either on the enamel or the dentine after
their formation, and is produced, like the bony tissue, by
the internal face of this (periodontal) sac, which has be-
come alveolar periosteum.
When formed by the process above indicated, the tooth
pierces its follicle and appears in the interior of
the mouth, after having traversed the table of the
maxillary bones, if there is any, and the gingival membrane. (When the
calcification of the different tissues of the tooth is sufficiently advanced to enable
it to bear the pressure to which it will be afterwards subjected, its eruption
takes place, the tooth making its way through the gum. The gum is absorbed
by the pressure of the crown of the tooth against it, which is itself pressed up
by the increasing size of the fang. Concurrent with this, the septa between
the dental sacs, at first fibrous in structure, soon ossify, and constitute the
alveoli ; these firmly embrace the necks of the teeth, and afford them a solid
basis of support.) Though it has so far become estabhshed in its functions,
the process of growth in the tooth has not yet ceased. The pulp lodged in the
internal dental cavity, and charged with the formation of the ivory or dentine,
continues its functions — incessantly depositing new layers on those which were
THEORETICAL SECTION OP
THE DENTAL SAC OF A
PERMANENT INCISOR IN
THE HORSE.
A, Proper membrane of the
sac; B, dental pulp; C,
papilla of the external
cavity (pit) of the tooth,
a dependency of the ena-
mel membrane ; D, epi-
thelial layer of the den-
tme membrane ; E, cy-
lindrical cells of the
enamel membrane ; F,
dentine ; G, enamel.
The secretion of the ce-
ment is not supposed to
have commenced.
416 TEE DIGESTIVE APPARATUS IN MAMMALIA.
originally secreted. The dental cavity gradually diminishes in extent ; the
papilla becomes atrophied, and finishes by disappearing altogether at a period
of life more or less advanced, according to the kind of teeth and species of the
animal.
. In considering the entire dental apparatus, with regard to its development,
very interesting differences are remarked in the progress and period of evolution
— differences which have been made available for ascertaining the age of animals,
but the details of which would be out of place here. It may only be noted that
all animals have two successive dentitions : the first, composed of a certain
number of teeth designated the caducous (temporary, deciduous, or milk-teeth —
caduques, decaying or frail), because they are soon shed and give place to others
which are stronger and more solid (and also because they appear while the
animal is yet sucking) ; the second, comprising the latter, are named replacing
teeth, with new, non-deciduous teeth which are not replaced, and are therefore
named persistent teeth. (The replacing and persistent teeth are generally included
by us in the term permanent.)
The teeth of Solipeds are gradually pushed from their alveoH as they grow ;
^100
THIN SECTION OF THE INNER PORTION OF THE DENTINE AND OF THE SURFACE OF THE PULP
OF AN INCISOR TOOTH.
a, Portion in which calcification is complete, showing separate globular masses at the line of junction
with the uncalcified substance, 6 ; at c are seen oval masses of germinal matter (cells), with
formed material on their outer surface ; d, terminal portions of nerve-fibres.
and from this circumstance results deformity and thinning of the maxillae in the
regions which lodge the roots of the teeth.
B. Teeth of Solipeds. — The dentition of adult Solipeds is composed of
from 36 to 40 teeth, thus distributed in each jaw : male, 6 incisors, 2 canines,
12 molars ; female, 6 incisors, 12 molars.^ With regard to the first dentition,
it comprises the incisors and three anterior molars only, the canine teeth and
three posterior molars being persistent.
The latter teeth — those of the second dentition — offer in their development
a common, but very remarkable character, rarely met with in the other animals.
They are pushed up from the alveoli during the entire life of the animal, to
(' This is the number of persistent teeth given by all veterinary authorities, as well as
by Professor Owen. Huxley, however, gives the typical number in the adult horse as forty-four.
The first premolar is supposed to be a persisteut, and not a deciduous tooth, as it has no
successor.)
TEE MOUTH. 417
replace the surfaces worn off by friction ; so that the crown is formed suc-
cessively by the various portions of the fang, each of which issues m its turn
from the alveolar cavity.
Incisors. — These are so named because they serve, particularly in the
Herbivora, for the incision {mcido, to cut) of the food. They are arranged
in the segment of a circle, at the extremity of the jaw, and are distinguished
by the names of middle or central, intermediate or lateral, and corfier teeth. The
pincers are the two middle teeth, the intermediates the next, and the corners
occupy the extremities of the incisive semicircle.
The general form of these teeth is that of a trifacial pyramid, presenting
a curve with its concavity towards the mouth. The base of this pyramid,
formed by the crown, is flattened before and behind ; the summit, or ex-
tremity of the fang, is, on the contrary, depressed on both sides ; the shaft
of the pyramid offers, at different points of its height, a series of intermediate
conformations which are utilized as characteristics of age, the continual pushing
outwards of the teeth bringing each of them in succession to the frictional
surface of the crown (Fig. 232, 1).
Examined in a young tooth which has completed its evolution, the free
portion exhibits : an anterior face, indented by a slight longitudinal groove,
which is prolonged to the root ; a posterior face, rounded from side to side ;
two borders, of which the internal is always thicker than the external ; lastly,
the surface of friction (table). The latter does not exist in the tooth which has
not been used ; but in its stead are found two sharp margins circumscribing a
cavity named the external dental cavity (or better, infundibidum). This cavity
terminates in a conical cid-de-sac, which descends more or less deeply into the
substance of the tooth. The margins are distinguished into anterior and pos-
terior ; the last, less elevated than the first, is cut by one or more notches which
are always deepest in the corner teeth. It is by the wear of these margins that
the surface of friction is formed, and in the centre of which the infundibulum
persists during a certain period of time (Fig. 232, 2).
The fang is perforated by a single aperture, through which the pulp of the
tooth penetrates into the internal cavity (Fig. 231, 3, c).
In the composition of the incisor teeth is found the three fundamental sub-
stances of the dental organ. The dentine (Figs. 231, i ; 232, 3) envelops, as has
been shown, the pulp cavity. That which is deposited in this cavity after the com-
plete evolution of the tooth, to replace the atrophied pulp, has always a yellower
tint than the dentine of the first formation ; it forms on the table of the tooth
the mark designated by Girard the dental star (Fig. 232, 4, c). The enamel
covers the dentine, not only on its free portion, but also on the roots of the
incisors ; it is not prolonged, however, to their extremities, though it is more on
the anterior than the posterior face. It is doubled in the external dental cavity,
hning it throughout (Figs. 231 ; 232, 4, a) ; and when the surface of friction is
established, there can be perceived a ring of enamel surrounding that surface,
and an internal ring circumscribing the infundibulum : the first circle forms
what is called the encircling enamel ; the second, the central enamel (Fig. 232,
4, a, b).
In the virgin tooth, the latter is continuous with the external enamel, and
passes over the border which circumscribes the entrance to the infundibulum.
The cement is applied over the enamel, Hke a protecting varnish ; but it does
not exhibit the same thickness everywhere : on the salient portions it is
418
THE DIGESTIVE APPARATUS IN MAMMALIA.
extremely thin, and does not even exist when the tooth has been submitted
for some time to the friction arising from the contact of the aliment, the lips,
and the tongue. It is more abundant in depressed situations, as in the longi-
tudinal groove on the anterior face, and particularly at the bottom of the
infundibulum. Nevertheless, the quantity accumulated in this cul-de-sac is
not always the same ; we have seen it sometimes almost null, and on the
Fig. 230.
Fig. 231.
SECTION OF THE INCISOR TOOTH
OF A HORSE, SHOWING THE
ARRANGEMENT OF ITS DIF-
FERENT SUBSTANCES.
I, Dentine ; E, enamel ; 0, ce-
ment.
other hand we possess incisors unworn, or nearly
so, in which the cavity is almost entirely filled
by the crusta petrosa. We are not aware that,
up to the present time, any account has been
taken of these differences when calculating the
progress of wear; but it may be imagined that
they ought to influence in a sensible manner the
period at which effacement of the external dental
cavity takes place.
All the characteristics just indicated belong to
the deciduous teeth (Fig. 232, 5), except that they
are smaller than the permanent ; that they are of
a shining milky-white colour, due to the thinness
or absence of the crusta petrosa ; that they show
at the point of union between the free portion and
the root, a constriction named the neck ; that their
crown is finely striated, and not cannular, on the
anterior face ; that the external cul-de-sac (wfun-
dibulum) is shallow ; and that they are not constantly pushed outwards from
their cavities, their growth ceasing when they begin to be used. When the
replacing teeth appear, they do so a little behind the temporary ones, the shedding
of which they cause by gradually destroying their roots, these at last becoming
only a long and very thin shell of dentine.
The follicle in which the incisor teeth are developed shows only two papillae
DENTITION OF THE INFERIOR JAW
OF THE HORSE, THE TEETH SEEN
ON THEIR TABLES.
Consult Fig. 38 for the dentition
of the upper jaw.
THE MOUTH.
41&
one for the secretion of the dentine, lodged in the internal cavity of the tooth,
and hollowed into a cup-shape at its free extremity ; the other contained in the
external cul-de-sac (Fig, 228, a, b, c).
Tusks, Fangs, or Canine Teeth. ^ — " The tusks of Solipeds only exist in
the male ; it being quite exceptional to meet with them in the female, and even
then they are rarely so strong as in the male.
" These teeth are four in number, and are placed one at each side of the
jaws, a little behind the incisors, to which the lower canines are much nearer
Fie. 2"2.
INCISOR TEETH OF THE HORSE (DETAILS OF STRUCTURE).
1, A tooth in which is indicated the general shape of a permanent incisor, and the particular forms
successively assumed by the dental table in consequence of friction, and the continued pushing
outwards of these teeth. 2, A virgin tooth, anterior and posterior faces. 3, Longitudinal section
of a virgin tooth, intended to show the internal conformation and structure. Not to complicate
the figure, the external cement, and that accumulated in the infundibulum, has not been shown.
4, Transverse section for the same purpose : a, Encircling enamel ; 6, central enamel ; c, dental
star ; d, dentine. 5, Deciduous tooth.
than the upper. Between them and the first molar there is left a considerable
space, which constitutes the bar of the inferior jaw.
" The free portion of the tusk, slightly curved and thrown outwards, par-
ticularly in the lower jaw, offers two faces — an external and an internal — separated
from one another by two sharp borders inclined to the inner side, and meeting
in a point at the extremity of the tooth. The external face, slightly rounded,
presents a series of fine striae, longitudinal and parallel.
' The quotations included within inverted commas are from M. Lecoq's Traite de VExt€rieur
du Cheval et des Principaux Animaux Domestiques.
420 THE DIGESTIVE APPARATUS IN MAMMALIA.
" The internal face has a conical eminence in its middle, whose point is
directed towards that of the tooth, and is separated from each border by a
deep groove.
" The fang of the tusk, more curved than the free portion, has internally a
cavity analogous to that of the root of the incisors, and like it, this diminishes
and tinally disappears as it advances in age ; but it is always relatively larger,
because of the absence of the infundibulum in the canine teeth.
" The form we have described for the tusks, is that which they present while
still young. As the Horse grows older they lose their whiteness, and become
worn in an irregular manner, and this most frequently by the action of the bit
or snaffle ; for the difference in position of these teeth in the two jaws does not
allow of friction between them.
" The canine teeth are not shed, and grow but once. Some veterinarians,
and among them Forthomme and Rigot, have witnessed instances in which they
were replaced ; but the very rare exceptions cannot make us look upon these
teeth as liable to be renewed. We must not, however, confound with these
exceptional cases the shedding of a small spicula or point, which, in the majority
of Horses, precedes the eruption of the real tusks.
" The structure of these teeth is much simpler than that of the incisors ;
consisting, as they do, of a central mass of dentine hollowed by the pulp cavity,
and covered by an external layer of enamel, on which is deposited a little
cement.
" The arrangement of the developing folHcle is in harmony with the sim-
plicity of structure of the tusks ; at the bottom there is a simple and conical
papilla for the internal cavity ; on the inner wall, a double longitudinal ridge,
on which are moulded the ridge and grooves on the internal face of the tooth."
Molar Teeth. — " The molars are twenty-four in number — six in each side
of each jaw. There are also sometimes supplementary molars met with in front
of the true ones, and which may be four in number ; but these are small teeth,
having but little resemblance to the others, are most frequently shed with the
first deciduous molar, and are not replaced.
" Generally considered, the molar arches have not the same disposition in
both jaws. Wider apart in the superior one, they form a slight curve, with the
convexity outwards. In the inferior jaw, on the contrary, the two arches
separate in the form of a V towards the back of the mouth. Instead of coming
in contact by level surfaces, the molars meet by inclined planes, and in such a
way that the internal border is higher than the external in the inferior molars,
while the opposite is the case in the superior.
" Like the incisors, each molar presents for study a free and a fixed portion.
The free portion, nearly square in the upper molars, longer than wide in the
lower, shows at the external surface of the former two longitudinal grooves, the
anterior of which is the deepest, and which are continued on the encased portion.
This is not so with the inferior molars, which have but one narrow, and fre-
quently an indistinct, groove.
" The internal face in both jaws only shows one groove, and that but little
marked ; it is placed backwards in the upper molars, and is most apparent
towards the root.
" The anterior and posterior faces are in contact with the corresponding faces
of the adjoining molars, except at the extremities of the arches, where the
isolated face is converted into a narrow border.
THE MOUTH.
421
"With regard to the table of the tooth, it inchnes, as we have already
mentioned, outwards in the lower jaw, and inwards in the upper— a circumstance
which prevents the lateral movements of the jaws taking place without separa-
tion of the incisors, which separation removes them from friction." In the virgin
molar, this face is completely covered with enamel, and irregularly undulated.
In it may be recognized the two infundibular openings, which are prolonged in
the interior of the organ to the extremity of the root, and are almost entirely
tilled with cement at the period when the tooth has completed its evolution ;
they are only void before the secretion of this crusta petrosa. In the tooth
which has been worn, this frictional surface assumes a particular aspect, which
will be indicated with most advantage to the student by examining the structure
of the molar.
" The root, if examined a short time after the eruption of the free portion,
looks only like the shaft of the latter, without any appearance of fangs, and
Fig. 233.
PROFILE OF THE UPPER TEETH OF THE HORSE, MORE ESPECIALLY INTENDED TO SHOW THE
molars; the fangs have been EXPOSED.
a, Molai" teeth ; b, supplementary molar ; c, tusk ; d, incisors.
has internally a wide cavity. It is not until the tooth begins to be pushed from
the alveolus and its crown to become worn, that its fangs are formed ; these are
at first hollow, and afterwards filled, as well as the cavity of the tooth, by the
formation of a new quantity of dentine. From this time the fangs cease to
grow ; but the tooth, constantly projected beyond the alveolar cavity, allows the
walls which enclose it to contract ; so that, in extreme old age, it happens that
the shaft, completely worn away — instead of the tooth — leaves several stumps
formed by the fangs.
"The molars of the two jaws exhibit a variety of roots. In the molars
terminating the arches, either above or below, or at the extremities of these,
there are three ; while the intermediate molars have four fangs in the upper jaw,
and only two in the lower.
"The molars are separated from each other by their embedded portion,
particularly at the two extremities of the arch ; an arrangement which
strengthens them by throwing the strain put upon the terminal teeth towards
the middle of the line."
The structure of the molars resembles that of the incisors, though it is much
more complicated. The internal cavity is extremely diverticulated, and enveloped
by the dentine. The enamel is applied in a layer over it, and is doubled in its
external culs-de-sac exactly as in the incisors. There is also on the table of the
422 THE DIGESTIVE APPARATUS IN MAMMALIA.
tooth which has been worn, an external covering of enamel, and two circles, or
rather two irregular polygons, of central enamel circumscribing the two cavities.
In the superior molars, these bands of enamel represent a Gothic B, having a
small appendage on the loop nearest the entrance to the mouth. This hgure is
modified in the teeth of the lower jaw, the enamel of the infundibuli being con-
tinuous, on the inner side, with the external enamel. The cement is extremely-
abundant, and in the upper molars its total quantity nearly equals that of the
dentine ; it accumulates in the cuh-de-sac and on the external covering of enamel,
where it partially fills up the flutings on the faces of the crown. Prolonged
steeping of a molar tooth in hydrochloric acid, easily permits the isolation of
these elements.
Owing to the arrangement above described, the section of an adult molar
tooth, naturally represented by the surface of friction (Fig. 234), exhibits, out-
wardly, a layer of cement ; next, the external enamel ; between this and the
central enamel, the dentine, always yellower, and sometimes even black in the
middle ; lastly, the enamel bands of the infundibuli,
and the crusta petrosa filling them. As these enamel
bands are much harder than the other substances, they
are worn more slowly, and stand out in relief on them.
The table of the tooth has also, for this reason, the
appearance of a veritable mill-stone, and is admirably
disposed for the trituration of those fibrous substances
on which the animal usually feeds.
The follicle which develops these three elements of
_ i> ** the molar tooth, has at the bottom an enormous papilla
TRANS vKRsii SECTION OF A divided iuto SBVcral lobes, which lie too-ether for their
horse's upper molar ,11 ^, 1 J J • xi • X 1 J X 1
TOOTH. whole length ; lodged m the mternal dental cavity, it
A, External cement ; B, ex- gradually decreases, like the papilla in the other kinds
ternal enamel ; 0, dentine; of teeth, as the cavity bccomcs diminished by the
SmaTrrtt\°pTt'ro.a^' '"" formation of new dentine. Opposite to it are two long
papillae, which occupy the enamelled infundibuli.
"It Avas beheved for a long time that the molars of Solipeds were all
persistent teeth. This error, founded on the authority of Aristotle, was so
deeply rooted, that although Euini, towards the end of the sixteenth century,
had discovered the existence of two temporary molars, Bourgelat did not believe
it when he founded the French Veterinary Schools, and was only convinced
when Tenon had proved by specimens, in 1770, that the first three in each
arch are deciduous.
" The replacement of these twelve molars is not at all like what happens with
the incisors. The molar of the adult grows immediately beneath the temporary
one, and divides its two fangs into four, until its body is reduced to a simple
plate and falls off, allowing the contracted summit of the permanent molar to
appear ; and this grows up until it is soon on a level with the others in the row.
" The first replacing molar is always a little more elongated than that which
it succeeds, and it most frequently expels at the same time the supplementary
molar ; so that if forty-four teeth be developed in the male Horse, it is very rare
that they are all present at the same time."
Ruttimeyer has remarked that the tables of the first three molars are shorter
and wider in the Ass than in the Horse. The Gothic B the enamel forms is
consequently compressed, and the appendage to the anterior loop is wider in the
TEE MOUTH. 423
first than the second of these animals, and not so long. (Flower also observes
that the loop of enamel above the B is either absent, or scarcely perceptible in
the Asinine tribe.)
7. The Mouth in Geneeal.
We will now consider, as a whole, the cavity, the various parts of which have
been studied in detail ; and examine, successively, its general arrangement, '
capacity, and mucous membrane.
General disposition and capacity of the mouth. — The mouth, being elongated
in the direction of the head, offers a great antero-posterior diameter, and two
small diameters — one vertical, the other transverse. The first extends from the
base of the epiglottis to the anterior opening of the mouth ; the second, from
the palate to the floor of the mouth ; and the third, from one jaw to the other.
"When the jaws are in contact, the space included between these limits is divided
into two regions : one central, the other peripheral. The first is circumscribed
by the dental arches ; the second is comprised between these arches on the one
side, and the cheeks and inner aspect of the lips on the other. It may therefore
be remarked, that the capacity of the mouth is almost null in these regions. The
cheeks and lips, in reality, lie almost exactly against the alveolar arches, and the
tongue, in contact with the palate by its superior surface, almost entirely fills
the central region. If the jaws separate from one another, and the cheeks recede
from the dental arches, the cavity of the mouth becomes enlarged in proportion
as these movements are extensive. It must be remembered that the separation
of the jaws is effected in an angular manner, and that the dilatation produced in
the mouth by this movement is greater before than behind, the opening of the
angle comprised between the two jaws being directed towards the entrance to
the cavity.
Mucous memtrane. — The walls of the buccal cavity are covered by a tegu-
mentary membrane, which we have hitherto only examined in parts in the
different regions it covers ; but which, it is to be noted, forms here a single and
continuous layer — the mucous membrane of the mouth.
This membrane is continuous with the external skin around the margin of
the buccal opening ; from this point into the interior of the cavity, it extends at
first over the internal surface of the lips, then is prolonged backwards on the
cheeks as far as the posterior pillars of the tongue. If it is examined above and
below, to the bottom of the groove at the junction of the lips and cheeks, it is
seen to cover the maxillary bones and envelop the base of the teeth, where it
constitutes the gums. From the superior dental arch, it extends over the
palatine arch and the soft palate. And from the inferior arch, it descends to
the floor of the mouth, and is reflected over the tongue to form a covering for
that organ. At the isthmus of the fauces it is continuous with the pharyngeal
mucous membrane.
The organization of the mucous membrane of the mouth is perfectly in
harmony with the digestive acts performed in that cavity. It is there where
the alimentary substances, which are sometimes very hard, very resisting, and
covered with asperities, are crushed ; and to escape inevitable injury, this
membrane is protected by a very thick epithelium in those places which are
particularly exposed to the contact of these substances — such as the upper
surface of the tongue, the palate, and the cheeks ; even the corium, or sub-
epidermic layer, is also greatly thickened. But nature has not made this
424 THE DIGESTIVE APPARATUS IN MAMMALIA.
provision for the parts which are removed from the direct contact of alimentary
matters — as, for example, on the lateral aspects of the tongue, where the buccal
membrane is delicately organized.
This membrane also shows, in its lingual portion, small organs for the
perception of savours, which is one of the most important preparatory acts
of the digestive functions ; as the sensation resulting from this appreciation
constitutes an excitant to the desire for food, and also informs the animal of the
good or bad properties of the substances introduced into the mouth.
Differential Characters in the Modth of the other Animals
That the diflfL-rent regions of the mouth in the domesticated animals should offer some
diversities, will be leadily conceived, as all are not submitted to the same regime, nor do they
all live in tlie same manner.
Ruminants. 1. Lips.— The lips of the Ox are remarkably thick and rigid, and possessed
of little mobility, notwithstanding tlie great development of the muscles that move them; so
that they only concur indirectly in the prehension of food, the tongue being charged with the
largest share in this important task. The upper lip offers, in the middle of its external surface,
a large patch destitute of hair, variously coloured in different animals, always humid in health,
covered by small depressed eminences, and perforated by minute apertures, through which
tlie secretion of numerous thick, yellow, subcutaneous glandules passes to the surface. This
space, situated between the two nostrils, constitutes the muffle. (Around the muffle are some-
times a few hairs of the nature of tentaculse.)
In the Camel, Sheep, and Goat, the lips are thin and very mobile, and take an active
part in the prehension of food. The upper lip does not show any muffle, and is divided into
two portions by a median groove. In the Camel and Sheep, this groove is in reality a fissure ;
80 that each half of the lip can be readily moved independently of the other. (The upper lip
Is covered with hair in these animals. The Goat has a long tuft of hair appended to its lower
lip, the beard.)
2. Cheeks. — On the inner surface of the cheeks in the Ox, Camel, Sheep, and Goat,
from the commissure of the lips to the first molar tooth, is a multitude of long, thick, conical
papillsB directed backwards. Beyond, there are only small round elevations and a single row
of large papillae similar to the pn ceding, in a line with the upper molars. In the Sheep the
mucous membrane is sometimes spotted black ; in the Camel it is uniformly black.
3. Palate. — In the Ox, the palate is most extensive. Its posterior third is quite smooth,
and the transverse ridges (bars) only occupy the anterior two-tiiirds. (They are usually
sixteen in number.) They are not curved, but are cut into notches on their summit, which
is inclined backwards. In the Sheep and Goat, as also in the Ox, is remarked, in front
and in the middle, near the pad that replaces the upper incisor teeth, a kind of T, the stem of
which is directed forwards, and at the extremity of its branches is a very narrow aperture, the
buccal opening of Jacobson's canal (see the Nasal Cavities for a description of this canal).
On the palate of the Camel is a small salient crest that occupies the anterior two-thirds
of the middle line, and on each side are traces of transverse furrows, which are rather large
tubercles a little elongated from side to side.
4. Tongue. — The tongue of the Ox is distinguished hy the enormous development of the
muscles composing it. It is garnished with conical papillae which have a horny sheath, and
their summits, inclining backwards, give the tongue a very rough feel. In this animal it
serves for the prehension of food ; its mobility is very great, and it can be carried into the
nostrils with ease. (The body of the organ is rounder, and the point finer, than in the Horse.
The calyciform papillae are spread over the whole of its dorsal surface ; and at the root, on the
middle line, is a somewhat deep groove.)
The tongue of the Sheep, Camel, and Goat is smaller, proportionally, than that of
Solipeds.
That of the Camel has an extremely rich papillary development. On the borders of the
upper surface of the free portion are about half a dozen calyciform papillae, more or less large,
but some of them have a greater diameter than Morgagni's foramen. On the posterior half of
the same part are foliated papillae, which are less numerous and smaller as they proceed back-
wards. On the sides are small perforated prolongations analogous to the barbs of Wharton's
ducts.
5. Soft Palate. — It may be said, in a general manner, that the palatine prolongation is
shorter than in Solipeds. (The isthmus of the fauces is wider, however, and the amygdalae,
THE MOUTH.
426
very developed, are situated in the two large depressions formed on the sides of the soft palate
by the folding of the mucous membrane.)
In the Camel, however, the soft palate is very developed, and the channel between the
mouth and pharynx narrow and long. The anterior pillars ascend on the corresponding face
of the curtain, which has a pyramidal, soft, relaxed appendage, granular on the surface, very
movable, and with its base forwards ; on each side of its summit, tliis appendage has two
prolongations curving outwards, aud below them a small sinus or diverticulum; on the borders
Fig. 235.
Fig. 236.
0:^S INCISOR TOOTH.
a, Free portion, external face, outer
border ; a', ibid., internal face, outer
border ; b, root ; c, neck ; /, an-
terior border ; g, g', inner border.
are racemose glands, which raise the
mucous membrane. The latter is of
a dark colour, like the cheeks and
palate.
6. Teeth.— The teeth of the Ox are
thirty-two in number, twenty-f ur of
which are molars, arranged as in the
Horse, and eight incisors belonging
to the lower jaw. The latter are
replaced in the upper jaw by a thick
cartilaginous pud, covered by the
mucous membrane of the mouth ; this
pad forms the gum, and furnishes a
bearing for the incisors of the lower
jaw. Sometimes, as in the Horse,
1, Upper jaw, with'aTthe friction surface, and b, the there are found supplementary molars
\JL^J.Jr.f.... 9 Tnwpv i=,w. With a. the dental which, if four in number, will make
up the whole to thirty-six; though
they are never all present at one time
as the supplementary ones are shed before the molar dentition is completed.
The composition of the Ox's teeth is the same as those of the Horse, the only difference
being in the arrangement of the several substances. ,. x i.^
Incisors.-The incisors, eight in number, are placed en clavier (like a key-board) at the
extremity of the kind of rounded shoulder-bone by which the maxillary bone terminates,
forming around this point a perfect circle when they have acquired tlieir full development.
Instead of being fixed in the alveoli, as in Solipeds, they possess a certain degree of mobility,
sometimes mistaken for a diseased condition ; this is necessary, in order to prevent their wounding
the cartilaginous pad of the upper jaw against which they press. They are divided, accor. ling to
their position, into two centrals, tv^o first laterals, two second laterals, and two corner mcisors.
Each incisor offers for consideration two parts : one free, the other encased— the root, and
separated by a very marked constriction-the neck. This arrangement gives to the tooth the
form of a shovel, the root representing the handle (Fig. 236).
THE TEETH OF THE OX.
external" surface ; 2, Lower jaw, with
tables, and b, the external face.
426 THE DIGESTIVE APPARATUS IN MAMMALIA.
The free portion, flattened above and below, and thinnest and widest towards its anterior
extremity, presents two faces — an inferior or external, the other superior or internal , with
three borders, an anterior and two lateral.
The external face, slightly convex, and milk-white in colour, is covered with fine, undulat-
ing, longitudinal striae, which disappear with age, and leave the surface beautifully polished
(Fig. 236, a).
The internal face, flatter than the preceding, presents in its middle a slight conical
eminence, whose base widens and is terminated ne.tr the free extremity of the tooth, while its
sides are circumscribed towards each border by a well-defined groove (Fig. 236, a').
The two lateral borders (the internal slightly convex in its length, the external slightly
concave in the same direction) make the free portion appear as if thrown outwards. The
anterior border is sharp, and slightly convex from one side to the otlier ; it is the first part of
the tooth destroyed by wear.
The root is rounded, slightly conical, and implanted in an alveolus of the same form ; in
youth, it shows at its extremity an opening communicating with an internal cavity analogous
to that in tlie teeth of Solipeds, and prolonged into the interior of the free portion (Fig. 236, b).
In the virgin tooth, the enamel forms around the free portion a continuous layer, thinnest
on the internal surface, and extending very scantily over a part of the root.
The dentine forms the remainder of the organ, and the (pulp) cavity, which is originally a
large space of the same form as tlie tooth, is filled, as the animal grows old, by new dentine,
which, as in the Horse, has a yellower tint than the primitive ivory.
When the cavity is completely filled, the tooth ceases to grow, and is not pushed beyond
the alvenlu^f during wear, like the teeth of the Horse.
The incisor tooth has scarcely arrived at its perfect development, before it begins to be
worn. Its horizontal position, and its coming in contact with the pad on the upper jaw,
exposes the anterior border and superior face to friction, and consequent wear from before to
behind. The wear, therefore, chiefly aff"ects this upper face, which really forms the table of
the tooth, and which Girard designates the avale. When use has worn away the conical
eminence and the grooves bordering it, the tooth is levelled.
As wear goes on, there appears at first, and at the extremity of the tooth, a yellow band,
which is the dentine denuded of its enamel; and later, in this dentine a yellower transverse
band shows itself. With increase of wear, this contracts, then widens, and finislies by forming
a mark nearly square, and then round, which is nothing else tlian the recently formed dentine
that fills the pulp cavity of the tooth. It is a veritable dental star, analogous to that in the
Horse's tooth, and varying in form according to the incisor in which it appears.
In proportion as the teeth are used, they seem to separate from one another, although they
still remain in tlie same phices. This is because these teeth, in youth, only touched each other
by their extremities, and as they became worn they decreased in width, and were necessarily
separated to an extent varying with their degree of wear.
Finally, when the tooth has reached its last stage of wear, there only remains the root, the
upper poi-tion of which, becoming apparent by the retreat of the gum, stands as a yellow
stump— very distant from those which form with it the remains of the incisive arch.
The first incisors (or milk-Ueth) of the Ox, like those of the Horse, are all deciduous, and
differ from those which replace them by their smaller volume, less width, the transparency of
their enamel, and their being mere curved outwanls. Their roots are much shorter, nnd are
destroyed by the succeeding teeth. The two temporary centrals are always separated l)y a
marked interval, depending on the thickness of the fibro-cartilage in the maxillary symphysis
during youth.
Molars. — As in Solipeds, the molars are six in each side of the jaws, but they are much
smaller, and form a much shorter arch. Their reciprocal volume is far from being as uniform
as in the Horse, but goes on augmenting from the first to the sixth ; find to such a degree,
that the space occupied by the three anterior molars is only about one-half of that required
for the three posterior ones ; the last molar alone occupies nearly four times as much space,
lengthwise, as the first.
Their wearing surface, constructed on the same system as that of the Horse's molars,
present eminences a little more acute.
The arrangement of their three constituents is in principle the same as in the latter animal.
As in the Horse, the three front molars are deciduous.
The teeth of the Sheep and Goat are, like those of the Ox, thirty-two in number, divided
into eiglit incisors and twenty-four molars, to which are sometimes added supplementary
molars.
The incisors of the smaller Ruminants are not disposed like a key-board, as in the Ox, but
THE MOUTH. 427
stand up to form a grip, resting against the pad on the upper jaw much more by their extremity
than by their inner surface.
They are, besides, narrow, have scarcely any neck, and are fixed more solidly in the alveoli
(Fig. 237).
Their external face is white and polished, and is encased towards the gum in a kind of
black cement.
The internal face has two wide, longitudinal grooves, separated towards the middle of the
table by a simple ridge, wliich replaces the conical eminence of the Ox's incisor. These
grooves are nearly always lined with the black cement-like substance.
The incisors of the Sheep are, like the Ox's, dititinguished into temporary and replacing
teeth ; the first are known from the others by their smallness, and particularly by their
narrowness.
The wear of the incisors in the Sheep, from their position, ought to take place nearer the
anterior border than in the Ox; the dental star is observed
earlier, and always forms a narrower line from before to behind. pjg. 237.
The absence of a neck in these teetli is the reason why they
never appear to separate with wear, as has been remarked in
those of the Ox.
The molars have tlie greatest resemblance, in their general
form and relative proportions, to those of the Ox.
The teeth of the adult Camel are thirty-four in number —
six incisors in the lower maxilla, ten molars, and six teeth re-
sembling canines, two of which are fixed in the premaxilla. In incisor teeth of a sheep
the young animal, the incisors— the free border of whicii is sharp '^^^ years old.
as in the otiier Ruminants — are much inclined on the maxillary The second laterals and the
border, but become erect as the creature grows older, so as to corner incisors have not
resemble those of the Horse. yet been replaced.
The canines of the lower jaw are strong and pointed ; among
those of the upper jaw, the laterals only are greatly developed, and some authorities regard
them as premolars.
Tile proper molar teeth show the general arrangement and organization of the Ox's teeth.
They are covered by a dark cementum (Fig. 46).
Pig 1. Li'ps — In this animal the lips are widely cleft. The lower is pointed and little
developed; tlie upper is confounded with the snout, which will be described with the nostrils.
(The upper lip has little mobility.)
2. Cheeks. — Tliese are small and thin, and the mucous membrane smooth.
3. Palate. — Narrow and elongated, it is disposed as in the Horse. In front is seen the
orifices of Jacobson's canals. (The transverse ridges are twenty to twenty-two in number, the
anterior being larger than the posterior, and their free borders are united.)
4. Tongue, f^. Soft Palate. — These two organs are the same as in the smaller Ruminants,
except that the filiform papillae are perhaps less developed. (The isthmus of the fauces is
circular, and the posterior pillars are confounded with the mucous membrane at the upper part
of the oesophagu-^. Its anterior surface has several conical eminences in the middle, and the
amygdalae iire little rounded elevati(ms.)
6 Teeth. — The Pig has forty-four teeth, which are divided into twelve incisors, four
canines, and twenty-eight molars (Fig. 238).
The incisors, six in each jaw, exhibit very remarkable differences between each other.
The centrals and laterals of the upper jaw offer, by their form and the cavity they show on
their table, some analogy to those of the Horse. In the lower jaw, these teeth are straight,
directed forwards, and bear some resemblance to the incisors of rodent animals. The corner
incisors of botli jaws are isolated between the lateral and canine teeth, and are not nearly so
voluminous as the other incisors.
The tusks are very developed, particularly in the male, and cross each other during the
life of the animal ; ihey project from the mouth, and form a very dangerous weapon in the
wild boar. The primary canines are deciduous, like the incisors.
The molars, seven in each row, increase in volume from the first to the last, which Is very
strong. Their tables hold a middle place, with regard to arrangement, between that of the
Carnivora and Herbivora.
Carnivora. 1. Lips.— The Carnivora, like the Pig, do not use their lips to grasp their
food, and these are therefore thin, though movable. The upper lip of the Dog has a groove
in the middle line, and it covers the lower lip more or less at the sides according to the breed.
The lower lip is always scalloped on its free border near the commissures, which are very high.
428 THE DIGESTIVE APPARATUS IN MAMMALIA.
In the Cat, the hairy tentaculse are collected on the upper lip into two long lateral tufts the
moustaches ; they are very sensitive and movable.
2. Cheeks. 3. Palate. — The cheeks resemble those of the Pig; the palate that of small
Rumiuants. The mucous membrane is often stained by patches of pigment, especially on the
palate. (The latter is frequently quite black. The number of ridges on the palate varies from
seven to nine. Jacobsou's canal opens behind the incisors.)
4. Tongue. — This is thin and very movable. The papillae on its upper face vary somewhat
in the Cat and Dog. In the Cat, the filiform papillae on the anterior two-thirds of the tongue are
covered by a very strong horny sheath, the point of which is directed backwards. In the Dog
these papillfe are less developed, and there are observed, more particularly, a number of oomposite
filiform papillae, the divisions of which are very flexible. There also are found regularly disposed
among these, white shining epithelial particles which correspond to small fungiform papdlsB.
Fig. 238.
THE TEETH OF THE PIG.
1, Upper teeth, table surface ; 2, lower teeth, table surface ; 3, lateral view of the jaws.
At the base of the tongue of Carnivora, and within the anterior pillars of the soft palate,
are two elongated bodies with rounded extremities and a nodulated slippery surface ; these are
true amygdalse, formed by an agglomeration of closed follicles.
5. Soft Palate. — In the Dog and Cat, the soft palate is very short, and the istlimus of the
fauces wide. Consequently, these creatures breathe easily by the mouth, and expel matters
by it from the stomach during vomiting. At its free border, the soft palate shows a small pro-
longation, something like the uvula.
6. Teeth. — The teeth of the Dog are forty-two in number : twelve incisors, four canines,
and twenty-six molars.
The incisors, six in each side of the jaws, are more developed in the superior than in the
inferior maxilla, and are divided, as in the Horse, into centrals, lateials, and comer
incisors ; the last are much stronger than the preceding, and these again stronger than the
pincers.
THE MOUTH.
429
Their free part presents, in the virgin tootb, three tubercles : a middle, which is the
Btronc-est and two lateral; these, together, are not unlike a trefoil or the upper part of a ^ewr-
de-iis" especially those in the upper jaw. On the internal face is remarked a table or slope,
somewhat resembling that of the Ox and Sheep, and separated from the root by a very distinct
border, the extremities of which mark the lateral lobes. This table is of no advantage in
*^^ The°root, very developed, flattened oa both sides, and separated from the free portion by
Fig. 239.
GENERAL AND LATERAL VIEW OF THE DOG S TEETH.
a well-defined neck, is solidly encased in a deep alveolus. Its internal cavity is very promptly
obliterated.
When the tooth is submitted to wear, the middle lobe is the first to disappear ; so that it no
longer resembles a trefoil (Fig. 240).
The temporary incisors are much smaller and more pointed than the permanent ones ; yet,
like them, they show lateral lobes. At the period of their eruption these teeth are somewhat
wide apart.
The fangs, or canine teeth, two in each jaw, are very strong, elongated organs, conical in
form, curved backwards and outwards, and placed immediately after the incisors.
Fig. 240.
ANTERIOR VIEW OF THE INCISORS AND CANINE
TEETH OF A YEAR-OLD DOG.
LATERAL AND GENERAL VIEW OF THI
cat's TEETH.
The upper fangs are the thickest, and have a small space between them and the corner
incisors, in which the inferior canines are lodged.
These teeth are deciduous, like the incisors, and are distinguished from the replacing ones
by being thinner and more elongated.
3D
430
TEE DIGESTIVE APPARATUS IN MAMMALIA.
They are worn more or less quickly, according to tlie kind of food the animal obtains, and
are sometimes broken in fighting.
The molars are distributed in the two jaws, twelve being fixed in the upper and fourteen
in the lower. ' Nearly all of them are terminated by somewhat acute lobes, proper for tearing
animal food. The strongest in eacii jaw is, for the upper, the first back-molar or fourth in the
row, and iu the lower, the fifth. All in front of these are deciduous.
After iheir complete eruption from the alveolar cavities, the Dog's teeth are no longer
pushed outwards. They are remarkable
Fig. 242.
for their brilliant whiteness, which they
owe to the absence of cement on their
covering of enamel.
The Cat has thirty teeth . twelve in-
cisors, four tusks, and fourteen molars,
eight of which are in the upper, and six
iu the lower jaw.
All these teeth are constructed on the
same type as those of the Dog. The
canines are deeply striated on their ex-
ternal surface, instead of being smooth.
Rabbit. — It may be noted that in the
rabbit there are two incisors in the lower
jaw, and four in the upper, two of which
are placed behind the principal two.
I I \\:^?^s\ # V There are ten molars in the lower, and
\i \ \\ jl twelve iu the upper, which are, in prin-
'l \ l\ ciple, as in the horse.
H \ W /\ (The importance of a correct know-
f \ (\ I I I le<ige of the period of eruption, shedding,
* "^ ' ' replacing, and general wear of the teeth
of the domesticated animals, as a guide
to their age, induces me to give the table
on p. 431 (from Leyh), as indicating at a
glance the age at which the teeth appear,
are shed, and replaced in the diflferent
creatures.
Baumeister divides the successive
evolutions in the wear of the tables of
the horse's incisor teeth into four periods
— from six years to extreme old age.
The first, the transversely oval period,
extends from six to twelve years; the
round, from twelve to eighteen years ;
the triangular, from eighteen to twenty-
four years, and tlie antero-postHrior oval or triangular, from twenty-four years and upwards.
Girard an.l other Frencii authorities shorten these periods somewhat. Tlie triangular period,
for instance, only lasts from fourteen to seventeen years.)
Comparison of the Mouth op Man with that of Animals.
The shortness of Man's face influences the shape of the mouth ; therefore it is proportionately
shorter and wider than in the domesticated Mammals.
1. Lips. — The lips have a thick, free, everted border. They are lined by a rosy mucous
membrane, which is insensibly continued inwanls by the buccal membrane. The upper lip
is limited by the nose and the naso-labial furrow ; the lower is limited by the mentodabial
groove. The first has in its middle the subnasal furrow. Their structure is analogous to those
of animals.
2. C7/efi&«.— The cheeks are limited by the inferior border of the maxilla, the root of the
ear, the prominence of the chin, and the naso-labial furrow. Between the skin and the mucous
membrane, there is found — as in brutes— a glandular layer and muscles, chiefly the buccinator.
An adipose ball is always found near the anterior border of the masseter.
dentition of the rabbit : THE TEETH SEEN FROM
THEIR TABLES.
Upper jaw ; b, lower jaw.
' Toussaint has observed that, in breeds with short faces, the molars decrease in number,
or are placed transversely, so as to find room in the maxillae.
THE MOUTH.
431
i S
1 S-s
S OS •
I I I
■2 J §
•? -S ^ o
a> a r a
OJ c c s
c s I o o-^
■" -!- -S -" ■" ^..
o=r«
•^ lO lO
e .• I I I
I I I I
a g
05 ©O
: -Q C £ S
I >— I » c^ •>*l
II I I I
e 2
O 03 .S S § O
CZ2 H li( fe «} OD
Sfa
432
THE DIGESTIVE APPARATUS IN MAMMALIA.
3. Palate.— li does not possess a vascular membrane, as in the Horse, and its mucous
membrane shows a longitudinal and transverse furrow in its anterior two-thirds. It is pal©
and resisting.
4. Tonj/Me.— This is thick, short, and broad ; its base is almost vertical, and in the middle
is a perpendicular, fibrous, and semilunar lamina — the lingual septum — which gives insertion to
muscular fibres.
Authropotoruists distinguish intrinsic and extrinsic muscles. The first are : the lingualis
superior and inferior, transversus, and longitudinalis. The second are, as in Solipeds, the
stylo-glissus, genio-glossus, hyo-glossus, and pharyngo-glossus. There is also described a
palato-glossus, which partly belongs to the soft palate.
The mucous membrane shows the ditierent characters recognized in that of animals. That
Fig. 243.
MEDIAN ANTERO-POSTERIOR SECTION OF THE HUMAN FACE.
a, Septum of nose, with section of hard palate below it ; 6, tongue ; c, section of soft palate ; d, d,
lips; M, uvula; r, anterior arch, or pillar of fauces; i, posterior arch; t, tonsil; p, pharynx;
h, hyoid bone; k, thyroid cartilage; n, cricoid cartilage; s, epiglottis; v, glottis. 1, Posterior
opening of nares; 3, isthmus faucium ; 4, superior opening of larynx ; 5, passages into cesophagus ;
6, orifice of right Eustachian tube.
of the dorsal face is divided into two portions by two A-shaped rows of papillae, the summit ot
which abuts on the deep mucous follicle named the foramen csecum. The posterior portion presents
depressions which correspond to the closed follicles, and the fungiform and calyciform papillae ;
the anterior portion has a villous aspect, due to the great number of filiform papillae cowringit.
5. Soft Palate. — In Man, the soft palate is short and divided into two portions : an anterior,
horizontal, attached to the base of the tongue by the anterior pillars of the curtain ; a posterior,
movable and oblique, having a free portion, the uvula, and fixed to the lateral walls of the
pharynx by the posterior pillars. Tlie amygdalx, or mass of closed follicles, are lodged in the
triangular space between the anterior and posterior pillars. The fibrous structure is not
present, unless the small expansion of the external tensor of the palate represents it. The
muscles are the same as in animals, and, in addition, there are described two palato-glossal
muscles, included between the mucous folds tliat form the anterior pillars. The palato-
pharyngeus extends to the posterior nasal spine. The isthmus of the fauces is wider than in
the Carnivora.
THE SALIVARY GLANDS. 433
6. Teeth. — The teeth are thirty-two in number, sixteen in each jaw. They are distributed
in the foUowiug manner: four incisors, two canines, two small molars (bicuspidati), and three
large molars (multi-cuspidati).
The incisors, when viewed in profile or longitudinal section, have a wedge-shape» and their
free border is more or less sharp. The canines are irregularly conical; the molars have a
multiple fang, and the crown is studded with a variable number of tubercles : two on each
small molar and four on the large. In youth, there are only twenty teeth, ten in each jaw.
The Salivary Glands.
The salivary glands are secretory organs annexed to the buccal cavity, into
which they pour saliva — a recrementitious fluid that softens the food, favours its
mastication and deglutition, and has a chemical action upon it after its arrival
in the abdominal portion of the digestive tube.
Though very diversified in form, yet they present in their structure such
common characters, that, to obviate recurrence to their organization when
speaking of each gland, we will describe them here.
These glands are composed of a greyish-red or yellow spongy tissue, which is
divided into small, rounded, or polyhedral masses, called salivary lobules. These
extend in a layer beneath the adherent face of the mucous membrane, and
remain isolated from each other, or are agglomerated in a body to form a single
gland. In the latter case, they are united by close connective tissue, which
covers them as a very thin enveloping membrane, and throws into the lobular
interstices lamellar prolongations.
In studying the organization of one of these lobules, it will be observed that
it is made up of many very small secondary lobules, or acini, which are themselves
due to the agglomeration of minute elementary vesicles or follicles, the average
diameter of which is from 3-5-0^ to i^V^ of an inch; these open into the little
canal belonging to each of the secondary lobules, and which again joins those
of the other acini of the primary lobule, to form a single duct.
The minute elementary vesicles or follicles — the ghmdidar nds-de-sac (or
ultimate follicles) — are more or less completely filled with delicate cells, transparent
or slightly granular. They have for wall a thin amorphous membrane {membrana
propria), against which, towards the bottom of the caini, and beneath the glandular
epithelium, are cells having half-moon-like forms, a group of which constitutes a
mass called the crescent (or lanula) of Gianuzzi (or marginal cells) — example, the
submaxillary gland. (They are closely surrounded by a plexus of capillary
blood-vessels.)
"When the salivary lobules remain isolated, this canal — which is designated as
excretory, because it carries from the lobule the saUva secreted within the
elementary follicles — opens directly into the mouth. But when, on the contrary,
they all unite and form a single gland, their excretory canals finally converge
into one or more principal ducts, the termination of which, in every case, takes
place in the same manner — by opening into the mouth from the summit of a
more or less salient tubercle ; this arrangement renders the introduction of
particles of food into these excretory orifices somewhat difficult. The fibrous
and elastic walls of these ducts are lined by cylindrical epithelium.
To the fundamental tissue just described must be added arteries, veins, and
lymphatics, which convey the materials of secretion and nutrition ; as well as
the yierves which regulate the secretory and nutritive acts (excito-secretory and
vaso-motor nerves). According to many histologists, the excito-secretory nerves
remain between the acini, but others (Pfliiger, Gianuzzi, Paladino) assert that
434 TEE DIGESTIVE APPABATUS IN MAMMALIA.
they traverse the Avails of the nds-de-sac and come into direct relations with the
gland-cells.
The most voluminous of these glands— or those which comprise a very great
number of agglomerated lobules— will be first noticed. They are the parotid,
maxillarij, subUmjucd, and molar glands, which are all pairs, and are placed in
proximity to the mouth, when they do not lie immediately beneath the adherent
face of its mucous membrane. Secondly, the less important glands— those which
are spread in layers under that membrane, and including the labial, lingual, and
staphyhne glands — will be examined.
1. Parotid Gland (Figs. 168, 8 ; 247, 8).
Preparation.-T\xiB glaud, with its excretory canal, is seen after the removal of the cervico-
facial panniculus and parotido-aurieularis muscle. By injecting Steno's duct and the facial
artery and vein, the relations of these three vessels will be better seen at the maxillary fissure.
The parotid gland is situated in the space included between the posterior
border of the inferior maxilla and the transverse process of the atlas. It is
Fig. 244.
CAPILLARY NETWORK AROUND THE FOLLICLES
OF THE PAROTID GLAND.
LOBULE OF PAROTID GLAND, INJECTED WITH
MERCURY, AND MAGNIFIED 50 DIAMETERS.
elongated from above to below, flattened on both sides, and divided into two
faces, two borders, and two extremities.
The external face, nearly plane, is hollowed in its inferior part into a
longitudinal channel, which is sometimes transformed into a complete canal, and
lodges the jugular vein after it has traversed the glaud from below to its
superficies. This external face responds to the parotido-aurieularis muscle, the
panniculus, the atloidean loop, a cervical ramification of the facial nerve, and
the posterior auricular vein. The internal face is very uneven and moulded on
the subjacent parts. It covers the guttural pouch, the mastoid insertion of the
obliquus capitis superior, levator humeri, stylo-hyoideus, the tuberosity on the
posterior border of the os hyoideus, the digastricus, the tendon of the sterno-
maxillaris, and the submaxillary gland, which is separated from it by the thin
cellulo-aponeurotic layer uniting the latter muscle to the levator humeri ; also to
the external carotid artery and its two terminal branches, the posterior auricularis,
the muscles of the jaw, and, lastly, the facial nerve, which often passes
through the substance of the gland.
The anterior border of the gland is intimately united to the posterior border
of the maxilla ; it is related to the temporo-maxillary articulation, the sub-
zygomatic vessels and nerves, and the maxillo-muscular vessels. The posterior
THE SALIVARY GLANDS.
435
border is thicker than the preceding, and is separated from the transverse process
of the atlas by the terminal aponeurosis of the levator humeri, to which it is
only feebly adherent : it can also be easily separated from it, in order to raise
the parotid and pass through the stylo-hyoideus muscle, in the operation of
hyo-vertebrotomy.
The superior extremity is bifurcated, and embraces the base of the concha of
the ear. The inferior extremity is comprised in the angle formed by the union
of the jugular and glosso-facial veins.
Vessels mid nerves of the parotid gland. — This gland receives its blood by a
multitude of arterial branches from the large vessels it covers. Its nerves are
very numerous, and are derived from the facial and inferior maxillary nerves.
The excito-secretory nerve, says Moussu, is isolable on leaving the Gasserian
ganglion ; it is composed of four or five filaments which lie alongside the sub-
zygomatic or inferior maxillary nerve for about a centimetre, then on the surface
Fig. 246.
MODES OF TERMINATION OF THE NERVES IN THE SALIVARY GLANDS.
1, 2, Branching of the nerves between the salivary cells ; 3, termination of the nerve in the nucleus ;
4, union of a ganglion cell with a salivary cell ; 5, varicose nerve-fibres entering the cylindrical
cells of the excretory ducts.
of the guttural pouch until it reaches the posterior border of the inferior maxilla
and the internal maxillary vein, when it enters the gland. It is diificult to discover.
Small lymphatic glands are believed to have been seen in the substance of
the parotid.
Excretory canal. — The parotid gland is provided with a single excretory
canal — the duct of Steno or Stenon, so named from the anatomist who gave the
first good description of it. It is detached from the anterior border of the
gland, near its inferior extremity, where the eye may readily follow it between
the lobules to the three or four principal branches from which it originates (Fig.
247). At first in contact with the terminal tendon of the sterno-maxillaris,
it afterwards turns round the posterior border of the digastric muscle (stylo-
maxillaris portion), advances into the submaxillary space, creeps over the
pterygoid muscle, beneath the glosso-facial vein, and arrives at the maxillary
fissure, into which it enters with the aforesaid vein and corresponding artery,
but behind both. It then ascends externally along the anterior border of the
TEE DIGESTIVE APPARATUS IN MAMMALIA.
masseter muscle, to the level of the inferior molars, when it passes beneath its
two satellite vessels, obliquely crosses their direction, and pierces the cheek
towards the third upper molar tooth, opening into the mouth by a large tubercle.
The parotid duct is composed of two membranes : the internal, mucous, with
cylindrical epithelium ; and the external, made up of connective tissue, and
circular and longitudinal elastic fibres.
2, Maxillary or Submaxillary Gland (Figs. 247, 248).
Preparation. — To expose this gland, as well as the sublingual, divide the inferior maxilla,
as in preparing the muscles of the tongue for dissection (see p. 400).
This gland, smaller than the preceding, is situated in the submaxillary space,
on the side of the larynx, and
*'^S' '^^'^- within the parotid gland.
It is long and naiTow, flattened
on both sides, and describes a
slight curve with the concavity
turned upwards : a form which
allows it to be studied, with regard
to relations, on two faces, two
borders, and two extremities.
By its external face, it responds
to the internal pterygoid and digas-
tricus muscles, the sterno-maxil-
laris tendon, and the cellulo-apo-
neurotic layer separating it from
the parotid. Its internal face, ap-
plied to the side of the larynx,
responds, superiorly, to the guttural
pouch, to the carotid artery, and
to the nerves which accompany
that vessel in the upper part of the
neck.
The superior border, thin and
concave, is margined by the middle
part of the digastricus. The in-
ferior, thick and concave, is in con-
tact with the glosso-facial vein.
The posterior extremity is main-
tained beneath the transverse pro-
cess of the atlas, by an extremely
loose and abundant connective
tissue ; the anterior is insinuated
between the internal pterygoid and
the thyro-hyoideus muscle.
Vessels and n&rves. — The blood
is distributed to the maxillary
gland by various small innominate
arteries, like those of the parotid gland, and which are most frequently derived
from the external carotid and the glosso-facial. The nerves are principally
furnished by the carotid plexus.
INFERIOR ASPECT OF HEAD AND NECK.
1, Inferior border of lower jaw ; 2, genio-hyoideus ; 3,
mylo-hyoideus ; 4, submaxillary artery ; 5, ditto
vein ; 6, parotid duct ; 7, sterno-maxiilaris tendon ;
8, parotid gland ; 9, sterno-maxiilaris muscle ; 10,
11, 12, submaxillary glands; 13, sterno-thyro-
hyoideus and subscapulo-hyoideus muscles; 14,
thyroid gland; 15, ptery_e:oideus internus.
THE SALIVARY GLANDS.
437
Excretory/ canal. — Wharton'' s duct, as it is termed, is long and narrow ; has
very attenuated walls, and exists for nearly the whole length of the superior
border of the gland (sometimes on its internal face), where it receives the
ramifications from various lobules. At the anterior extremity of the organ it is
free, and passes forward between the mylo-hyoideus and hyo-glossus muscles.
After crossing, outwardly, the glosso-facial artery and great hypoglossal nerve,
and, inwardly, the tendon of the digastricus and the lingual nerve, it passes
between the great hyo-glossus muscle and the sublingual gland, lying closely to
the inner side of the latter ; thus it extends parallel to the lateral groove (or
channel) of the lingual canal on the floor of the mouth. It finally arrives near
Fig. 248.
MAXILLARY AND SUBLINGUAL GLANDS.
R, Maxillary gland ; S, Wharton's duct ; T, sublingual gland.
the frfenum of the tongue, but underneath the buccal membrane, and opens into
the mouth by a small, but very salient, floating tubercle, situated a httle in
advance of the frsenum, and vulgarly named the iarb {harhillon).
The structure of Wharton's duct is identical with that of Steno, but its
external tunic is extremely thin, and has not any circular elastic fibres.
3. Sublingual Gland (Fig. 248).
This is less in volume than the preceding, and is situated under the tongue,
in the submaxillary space.
Elongated from before to behind, and very flat laterally, it has, like the
438 THE DIGESTIVE APPARATUS IN MAMMALIA.
gubmaxillary gland, two faces, two borders, and two extremities, the relations
of which we will briefly indicate.
The external face is covered by the mylo-hyoideus muscle : the internal
responds to Wharton's duct and the genio-glossus and great hyo-glossus muscles.
The upper border projects beneath the mucous membrane on the floor of the
mouth, where it forms the sublingual ridge; the inferior, thin and sharp, is
comprised between the mylo-hyoideus and the genio-glossus muscles. The tivo
extremities are thin and tapering ; the posterior contains a branch of the lingual
nerve ; the anterior extends to the bottom of the angle formed by the union of
the two branches of the inferior maxilla.
Vessels and nerves. — This gland possesses a special, but small artery — the
suUiyigual. Its nerves come from the lingual nerve, and even from the carotid
plexus.
Excretory canals. — These number fifteen or twenty, and are named the ducts
of Rivinius. Flexuous and very slender, they are detached from the superior
border or internal face of the gland, ascend perpendicularly, and open into the
mouth on the sublingual crest or ridge, by a linear series of small orifices pierced,
as usual, in the centre of a tubercle.
4. Molar Glands.
These are so named, because they are disposed parallel to the molar arches.
There are two on each side.
The superior molar gland — the most considerable — appears as a narrow line of
salivary lobules placed outside, and along the upper border of, the buccinator
muscle. In its posterior part, where it is concealed beneath the masseter muscle,
this gland is thicker and more compact than in front, where the few lobules
which compose it scarcely come in contact with each other.
The inferior molar gland— less, lobulated and voluminous, and not so wide as
the preceding — is placed at the inferior border of the buccinator, immediately
beneath the mucous membrane of the mouth, and near the point where it is
reflected from the side of the cheek on to the inferior maxilla. It is bordered,
for the whole of its extent, by the buccal nerve.
Both glands pour their secretion into the mouth by numerous salient orifices,
which can be seen arranged in line on the buccal membrane, parallel to each
molar arch.
It may be remarked that these glands establish a transition between the
preceding and those yet to be mentioned. Their lobules are far from being so
compact as the parotid or sublingual lobules ; and they tend to separate from
each other, to become more independent. Therefore it is that many writers
regard them as distinct, and describe them as superior and inferior molar glands.
5. Labial, Lingual, and Staphyline Glands.
Tte lobules composing these glands are spread in layers, more or less thick,
on the inner face of the mucous membrane, instead of being agglomerated in
masses, as in the previous glands. Sometimes they are scattered, in consequence
of their small number. In general, the excretory duct of each glandule opens
independently into the mouth, without communicating with those of the neigh-
bouring lobules.
Labial Glandules. — These are more abundant in the upper than in the lower
THE SALIVARY GLANDS. 439
lip, and pass beyond the commissures, to be spread for a short distance over the
inner aspect of the cheeks. It is easy, in the Hving Horse, after turning up the
lip and carefully wiping it, to see the salivary fluid secreted by these small organs
escape from their excretory ducts.
Lingual Glandulce. — They form a layer under the mucous membrane at the
base of the tongue, and adhere very closely to the fibres of the small hyo-glossus
muscle, and, laterally, are continuous with the layer which covers the external
face of the amygdaloid mucous membrane. They are also found on the side of
the tongue, above the superior border of the great hyo-glossus muscle ; though
these are few and scattered, and look as if embedded in the substance of that
muscle.
Staphyline Glandulce. — The thick layer these form under the anterior mucous
covering of the soft palate, has been described with that organ. We have only
to observe here, that it is continuous, laterally, with the glands at the base of the
tongue, through the medium of the glandulce of the amygdaloid cavity ; and in
such a manner, that the part of the mouth inmiediately in front of the isthmus
of the fauces, and which might be justly considered as the isthmus itself, is
enveloped in a complete glandular zone. In the dead body, we always find in
this compartment a variable quantity of viscid fluid, which is certainly secreted
in this zone. It is here, then, that the alimentary bolus is enveloped in the
glutinous matter intended to favour its passage in the pharynx and oesophagus ;
and it is worthy of notice that the constricted canal in which this secretion is
poured out in the living animal, immediately precedes the canal traversed by
the bolus of food in the act of deglutition.
Differential Characters in the Salivary Glands of the other Animals.
The salivary system of the Herbivora is more extensive than that of the Omnivora, and
especially the Carnivora.
Ruminants. 1. Parotid gland. — The parotid glands of the Ox are distinguished by their
meagre development and red colour, whicli contrasts markedly with the pale yellow hue of the
maxillary glands. Tliose of the Camel have the same characters, and they are broader than
they are long. In tlisit animal, as well as in the Sheep and Goat, Steno's duct passes
through the mair^seter muscle. Moussu has seen the excito-motory nerve of the parotid, in the
Ox, become detached from the buccal nerve beneath the masseter muscle, become inflected on
the anterior border of that muscle, and pass backward and downward in the gland, following
Steno's duct. In the Sheep, the same origin and course ; consequently, the nerve passes on the
surface of the masseter, along with Steno's duct. It is often formed by two parallel filaments,
and is easily found and stimulated in order to produce the parotideal secretion. (In the Ox,
this gland offers, at the upper part of its anterior border, a round lobe lying on the masseter.
Steno's duct opens into the mouth at the fifth molar. It terminates in the Sheep and Goat
at the fourth molar.)
2. Maxillary gland. — In the Ox, this gland is much thicker than in Solipeds, its volume
being in inverse relation to that of the parotid. In its posterior moiety it enlarges into an oval
lobe which, below the larynx, lies against that of the opposite side. Wharton's duct follows the
same course as in the Horse; the papilla through which it opens is hard, resisting, and
notched, and is lodged in an elliptical fossette near the incisors.
The maxillnry gland of the Camel is slightly lobulated, and Wharton's duct docs not open
at the summit of the " barb," but at the base of the fraenum linguae by a kind of punched-out
opening.
3. Sublingual gland. — In the Ox, Sheep, and Goat, this gland comprises two portions: a
posterior, somewhat voluminous and lobulated, provided with a .special excretory duct, which
follows and opens near Wharton's duct (by the ductus Bartholinianus) ; and an anterior,
pouring out its secretion by many canals, and representing the gland proper. This arrange-
ment allows the saliva to be collected separately from this gland. In the Camel, this gland
is very small, its lobules being also loosely agglomerated ; it has only multiple ducts, as in the
Horse.
440 THE DIGESTIVE APPABATUS IN MAMMALIA.
4. Molar glands.— These are more developed in Kuminants than in Solipeds. The uppei
one is enlarged at its posterior extremity. Their nerves come from the buccal nerve.
Pig.— The parotid gland of this animal is little developed, as in Ruminants, and Steiio's
duct fullows the posterior border of tlie lower jaw. (Leyh says that it is, proportionately,
largely developed ; that its upper end does not reach the concha of the ear, and that Steno's
duct opens at the sixth molar.)
The sublingual gland is analogous in its disposition to that of the Ox. Cuvier, in his
Lecons d'A7iatomie Compar^e, indicates this :— " The Pig has two sublingual glands. One,
very long and narrow, accompanies, outwardly, the excretory canal of the submaxillary gland,
from the angle of the jaw to tiie second sublingual. It is composed of small lobules of a pale
red colour. Its excretory duct arises near the posterior third, and passes along with, but to
the outside of, the submaxillary duct. It terminates near the orifice of the latter by a small
opening; its diameter is equally small. The second sublingual gland is placid before the
first ; its' form is square and flattened, and the lobes of which it is composed are larger and
redder. It has from eight to ten excretory ducts." (In this animal the duct of Wharton does
not open into the mouth by a papilla ; consequently, there is no barb.)
Camivora.— The parotid of the Dog and Cat is small, and Steno's duct always passes
through the masseter. (It opens at the fourth molar in the Dog, and the third in the Cat.)
In the Dog, the mhmaxillary glands are larger than the parotids. " They even have in
front, along Wharton's duct, a small accessory gland, with a distinct excretory caiial opening
into the tame papilla as Wharton's." (Leyh states that the submaxillary duct does not project
into the mouth.) The supplementary gland is absent in the Cat.
The sublingual gland is not present in the Dog ; it is very .'<mall in the Cat, and carried
further back than in the other animals. (Leyh describes a sublingual gland as jiresent in tht
Camivora, which is divided into two portions, as in the Pig : the anterior being formed of
detached lobules that open into the mouth by several ducts ; and the posterior, larger above
than below, with two ducts, the s;i;aller opening into Wharton's duct, and the larger a little in
front of it.)
The upper molar gland of the Dog, scarcely noticeable for the greater part of its extent,
forms posteriorly, under the zygomatic arch, near the eye, an independent lobe, remarkable for
its large size and its single excretory duct. Duvernoy, who first described it, proposed to name
it the suhzygomatic gland. It is not present in the Cat. (This is doubtless the organ
described by Leyh as the orbital gland, which, he says, is only found in the Dog ; the superior
molar gland, according to him, not existing in that animal. This orbital gland is external to
the ocular muscles, has three or four excretory canals— the ductus Nuckiani — which converge
into one duct that opens into the month above the last molar.)
The labial, lingual, and staplnjUne glandulx are much less developed in the Camivora than
the Herbivora. This predominance of the salivary system in the latter is sufficiently
accounted for, when we consider the hard, fibrous, and coriaceous food these animals live upon,
and which must be ingested in large quantity, because of the small amount of nutrition
it contains. For its mastication and deglutition, a great amount of saliva is absolutely
necessary.
Bodents. — In the Rabbit, the inferior molar gland is very large. In addition to the
salivary glands already described, this animal has a small gland outside the buccinator muscle,
along the interior maxilla, at the mental foramen.
Comparison of the Salivary Glands of Man with those op Animals.
As in animals, the parotid is the most voluminous of the salivary glands. Its tissue is
reddish-grey and lobulated, the lobules adhering closely to each other. Its shape is irregular,
and it is moulded to the excavation behind the angle of the jaw. Steno's duct passes across
the masseter, and shows on its eourse some salivary lobules, forming what is named the
accessory parotid (or socia parotidis) ; it opens opposite the third upper molar.
The submaxillary gland weighs about half an ounce. It is partly situated beneath the
deep cervical fascia, and partly within the body of the lower jaw, between the mylo-hyoideus
and hyo-glossus muscles. Its lobules are more loosely united than those of the parotid.
Wharton's duct opens on the sides of the frjenum linguae by a small opening at the apex of a
round papilla (caruncida sublingualis).
The sublingual gland is analogous to that of the Ox and Pig. There are, in fact, two
sublinguals : an anterior about the size of an almond, and furnished with a single excretory
canal— the ductus Bartholini, that terminates near Wharton's duct; the other, posterior,
formed by several isolated lobules with multiple excretory ducts — the ductus Riviniani.
THE PHARYNX.
Fig. 249.
There are also labial, ataphyline, and lingual glands; with, besides, near the frsenum, a
small conglomerate gland — the gland of Nnhn — which has a special duct.
The Pharynx (Figs. 249, 250, 251).
Preparation. — 1. Study the general disposition and situation of this vestibule in the
antero-posterior vertical section of the head (Fig. 250). 2. In order to examine the interior
conveniently, the head should be separated from the neck, leaving attached to it a certain
portion of the trachea and oesophagus ; then by sawing across — either through or behind the
temporo-maxillary articulations — all that portion of the cranium is removed, and the posterior
parietes of the pharynx is exposed, and may be dissected to study the muscles (Fig. 251), or
opened in the middle line to reach the interior of the cavity (Fig. 249). 3. The muscles
should be dissected with those of the tongue, and in the same manner.
The 2jharynx is a membranous vestibule common to the digestive and air
passages, and situated behind the soft palate,
which separates it from the mouth ; above, it is
attached to the base of the cranium, and, be-
low, to the laryngeal apparatus.
Form and internal disposition. — In conse-
quence of the conformation of the soft palate,
which, in the domesticated animals, and par-
ticularly in Solipeds, is prolonged to the base
of the epiglottis, the pharynx forms a cylindro-
conical cavity, elongated from before to behind,
enclosed laterally and posteriorly by wide thin
muscles, and with the soft palate for an anterior
wall. Between the two Eustachian tubes, under
the base of the cranium, the pharyngeal cavity
presents a triangular diverticulum, the walls of
which are only mucous membrane. This diverti-
culum is much deeper in the Ass than in the
Horse.^ At the two extremities of this cavity
are openings which allow the pharynx to com-
municate with the other passages or cavities,
which we will at once begin to study.
At the upper extremity of the large axis of
the pharyngeal cavity, is to be remarked : 1. In
front, the two posterior openings of the nasal
cavities. 2. Behind, and directly opposite the
preceding, the two pharyngeal openings of the
Eustachian tubes, which are closed by a carti-
laginous kind of clap- valve. 2
At the inferior extremity of this axis is found :
1. In the centre, a vast gaping orifice project-
ing into the interior of the pharyngeal cavity,
like a tap into a cask : this is the entrance to the
larynx, the salient portions of which form, on the walls of the pharynx, two
PHARYNGEAL AND LARYNGEAL RE=
gion; the posterior part of
the head incised and thrown
FORWARD.
1, Base of the cranium ; 2, roof of
the pharynx ; 3, muscles of the
cheek ; 4, 4, walls of the pharynx ;
6, posterior nares ; 7, soft palate ;
8, entrance to the mouth ; 9, epi-
glottis ; 10, posterior pillars of soft
palate; 11, arytenoid cartilages;
12, opening of the oesophagus ; 13,
oesophagus ; 14, trachea.
' This pharyngeal cxcum was described for the first time by Verhsar of Utrecht.
* This region corresponds to the posterior nares (arriere fond) of Man, a diverticulum
which cannot be distinguished from the pharynx in the domesticated animals. Under the
designation of the posterior nares of the nasal fossx, it will be understood that we mean the
posterior extremities of these cavities.
442 TEE DIGESTIVE APPARATUS IN MAMMALIA.
lateral channels, limited superiorly by the posterior pillars of the soft palate.
2. In front of, and beneath this, is the isthmus of the fauces ; behind and above,
the oesophageal opening at the bottom of an infundibulum, which may be con-
sidered as a special region of the pharynx.
These seven openings into the pharyngeal cavity give it the appearance of
a cross road, into which abut different thoroughfares. It is necessary to note
that the air and digestive passages intersect each other here ; and in such a way
that, during deglutition, the bolus of food passes over the entrance of the larynx
to reach the cesophageal opening. This peculiarity is easily seen by referring to
Fig. 250.
Relations. — Viewed externally, for the study of its connections, it will be
found that the pharynx is related, posteriorly, to the guttural pouches, and
guttural or retro-pharyngeal lymphatic glands ; laterally, to the great cornu of the
Fig. 250.
MEDIAN LONGITUDINAL SECTION OF HEAD AND UPPER PART OF NECK.
1, Upper lip; 2, premaxilla; 3, hard palate; 4, tongue; 5, septum nasi; 6, nasal bone; 7, palatine
bone; 8, soft palate; 9, pterygoid bone; 10, epiglottis; 11, entrance to Eustachian tube: 12,
arytenoid cartilage; 13, cricoid cartilage; 14, oesophagus; 15, frontal bone ami sinus; 16, cere-
brum; 17, corpus callosum ; 18, cerebellum; 19, sphenoid bone; 20, medulla oblongata, 21,
cervical ligament; 22, spinal cord; 23, occipital bone; 24, 24, atlas; 25, 25, dentata; 26? trachea.
OS hyoides, the internal pterygoid and stylo-hyoid muscles, the glosso-pharyngeal,
great hypoglossal, and superior laryngeal nerves, and the glosso-facial artery.
Steucture. — The walls of the pharynx are composed of a mucous membrane^
external to which is a. fibrous and a muscular lager.
1. Murnvs membrane. — This membrane is covered, externally, by a thin
layer of yellow elastic fibres, and is much more delicate and less protected by
its epithelium than the buccal mucous membrane, of which it is a continuation ;
it is continuous with that of the oesophagus, the larynx, the nasal fossa?, and
the Eustachian tubes.
Its epithelium is stratified throughout ; but it is thin and ciliated in the upper
part, thicker and tes^elated on the inferior moiety, which more particularly
belongs to the digestive apparatus.
Everywhere there are rfwemose glands, though they are most numerous
towards the roof of the pharynx. There are also some follicular glands beneath
THE PHARYNX.
413
the mucous membrane, in the neighbourhood of the guttural opening, the nasal
cavities, and the Eustachian tubes. Lorge has described a lymphoid gland,
analogous to the pharyngeal amygdalae described by Kolliker, at the bottom of
the diverticulum between the Eustachian tubes.
2. Fibrous layer. — This is also named the pharyngeal aponeurosis. It com-
mences at the base of the cranium, is first seen on the posterior face of the
pharynx, then it passes beneath the muscular layer, where it gradually becomes
thinner. It is attached inferiorly to the cartilages of the larynx, and to a
fibrous cord that separates the pharynx from the oesophagus.
3. Muscular layer. — This is composed of six pairs of muscles, indicated in
Fig. 251.
PHARYNX OF THE HORSE (POSTERIOR VIEW).
T, Trachea; t, thyroid gland ; O, cesophagus ; e, e. Eustachian tubes, divided near their termination in
the pharynx. 1, Pterygo-pharyngeus, or superior constrictor ; 2, 2, stylo-pharyngeal muscles ;
3, 3, great cornua of the os hyoideus ; 4, hyo-pharyngeus, or middle constrictor; 5, 5, thyro-
pharyngeus, or thyroid fasciculus of the inferior constrictor; 6, crico-oesophageus ; 7, superior
longitudinal oesophageal muscle ; 8, origin of the oesophagus ; 9, posterior crico-arytaenoid muscle.
the following enumeration : the palato-pharyngeus, pterygo-pharyngeus, hyo-
pharyngeus, thyro-pharijngeus, crico-pharyngeus, stylo-phnryngeus.
Palato-pharyngeus {Pharyngo-staphyUnus). — This muscle, which has
already been described as belonging to the soft palate, is prolonged backwards
on the lateral wall of the pharynx, where its fibres are mixed with those of the
pterygo-pharyngeus, and go to be attached to the superior border of the thyroid
cartilage, by passing beneath the hyo-pharyngeus and thyro-pharyngeus muscles.
444 THE DIGESTIVE APPARATUS IN MAMMALIA.
It therefore also belongs to the pharynx, and in contracting diminishes that
cavity.
Pterygo-pharyngeus, or Superior Constrictor (the palato-pharyngeus
of Percivall). — This muscle is thin, wide, flat, and triangular. It arises from
the pterygoid process, whence its fibres diverge, some posteriorly, others in-
wardly. The former mis with those of the palato-pharyngeus, and comport
themselves like that muscle ; and the latter are united, on the median line, with
the analogous fibres of the opposite muscle, forming a kind of zone around the
origin of the Eustachian tube. This muscle is covered, externally, by a layer of
yellow elastic tissue, which is attached with it to the pterygoid bone : afterwards
it is fixed to the superior border of the great cornu of the os hyoides, and is
even prolonged on the external surface of the muscle it covers to the thyroid
cartilage.
The elasticity of this fibrous layer plays a certain part in the movements of
the hyo-laryngeal apparatus, in acting as a passive antagonist of its depressors.
This muscle is, and can only be, a perfect constrictor o'' the pharynx, as it
diminishes the diameter of that cavity in every directiuu — the longitudinal
diameter, by means of its posterior fibres, which draw the thyroid cartilage
forward ; and its transverse diameter, by the band thrown around the orifice of
the Eustachian tubes (Figs. 220, 6 ; 251, 1 ; 252, 8).
Hyo-pharyngeus, or Middle Constrictor ; Thyro-pharyngeus, or
First Middle Constrictor ; and Crico-pharyngeus, or Inferior Con-
strictor.— The two last of these muscles only form one in Man — the inferior
ronstrirtor of the pharynx. They are three muscular bands which terminate
above the pharynx, on a median fibrous fold, sometimes wide enough to look
like a triangular aponeurosis. The first band arises from the cornu of the os
hyoides ; the second, from- the external surface of the thyroid cartilage ; the
third, from the superficial face of the cricoid cartilage.
These are universally regarded as constrictors (Figs. 220, 7, 8, 9 ; 251, 4,
5, 5).
In attentively examining the crico-pharyngeus muscle of different authorities,
two fasciculi are recognized, which can be distinguished by the direction of their
fibres. The deep band passes to the origin of the oesophagus ; it will be described,
as well as the muscle hitherto npmed the arytaeno-pharyngeus, when the oesophagus
is referred to.
Stylo-pharyngeus. — A narrow band which descends from the inner surface
of the styloid bone on the side of the pharynx, where it is confounded with the
pterygo-pharvngens. It passes beneath the hyo-thyroid and crico-pharyngeal
muscles, and, spreading out like a fan, becomes attached to the upper border of
the thyroid cartilage and mucous membrane of the pharynx, above the posterior
pillar of the soft palate.
It narrows the longitudinal diameter, and it has been also regarded as a
dilator ; though the disposition of the parietes of the pharynx and the feeble
volume of this muscle, scarcely allow it to play any efficacious part in the
dilatation of that cavity. At most, it can only produce a very slight infundi-
bulum where it is inserted. The real dilating agent of the pharyngeal cavity is
the alimentary bolus, which is pushed into it by the action of the tongue and
soft palate (Fig. 251, 2, 2).
It is not rare to find a second stylo-pharyngeus muscle, terminating at the
same point as the first, but proceeding from the inferior extremity of the large
TEE PHARYNX.
445
cornu of the os hyoides, or styloid bone, instead of its upper part ; its fibres pass
beneath the hyo- and thyro-hyoideus muscles, and proceed upwards in crossing
the direction of the preceding muscle, terminating on the middle raphe on the
superior face. It pulls the upper wall of the pharynx backwards and downwards.
Certain anatomists designate it the inferior stylo-pharyngeus, and consider it
as a constrictor of the pharynx. It sometimes exist only on one side.
3. Vessels and nerves. — The blood sent to the pharynx comes from the
pharyngeal and thyroideal arteries. The nerves are supplied by the glosso-
pharyngens, pneumogastric, and great sympathetic.
Functions. — The pharynx plays a passive part in respiration, by servmg as
an intermediate canal between the nasal passages and the larynx.
Its principal function, however, is connected with the digestive phenomena,
by its being an active agent in the first stage of deglutition — a complex and
rapid movement, which is executed in the following manner : The bolus of food,
propelled by the tongue into the pharynx, is seized by the constrictor muscles,
Fig. 252.
MUSCLES OF THE PHARYNGEAL AND HYOIDEAL REGIONS.
1, Glenoid cavity of temporal bone ; 2, superior extremity of styloid bone ; 3, tensor palati with
its pulley, 5; 4, stylo-pharyngeus; 6, palato-pharyngeus ; 7, circumflexus palati; 8, pterygo-
pharyngeus; 9, sublingual gland; 10, portion of hyoid bone; 11, hyo-pharyngeus ; 12, thyro-
pharyngeus; 13, crico-pharyngeus ; 14, portion of stylo-pharyngeus; 15, hyo-thyroideus ; 16,
styloid bone; 17, crioo-arytenoideus lateralis; 18, oesophagus; 19, sterno-maxillaris and hyoideus,
and subscapulo-hyoideus ; 20, trachea; 21, hard palate; 22, tongue.
which come into action successively from before to behind, in a peristaltic and
involuntary manner, to carry the mass to the entrance of the cesophagus. The
food thus passes over the opening of the larynx during pharyngeal deglutition,
but it cannot enter it, becauses the bolus forces back the epiglottis on this
aperture, which it almost exactly closes ; because, also, the passage of the food
prevents pulmonary inspiration, which might, if allowed to take place, divert it
from its natural course, and throw it into the nasal air-passages. The applica-
tion of the walls of the pharynx to the pellet of food during its momentary
passage over the larynx, prevents all communication between the external air
and the lungs, and only permits the elevation of the ribs with the utmost
difficulty. The extreme rapidity of the act of deglutition is another reason for
the food escaping the larynx.
31
446 TEE DIGESTIVE APPARATUS IN MAMMALIA.
(Gray concisely remarks : "When deii-lutition is about to be performed, the
pharynx is drawn upwards and dilated in different directions, to receive the
morsel propelled into it from the mouth. The stylo-pharyngei, which are much
further removed from one another at their origin than at their insertion, draw
upwards and outwards the sides of this cavity — the breadth of the pharynx, in
the autero-posterior direction, being increased by the larynx and tono'ue being
carried forwards in their ascent. As soon as the morsel is received in the
pharynx, the elevator muscles relax, the bag descends, and the constrictors con-
tract upon the morsel and convey it gradually downwards into the a-sophagus.)
The deglutition of liquids is carried on in a similar manner.
It is curious to remark that, in Solipeds, the food does not come into direct
contact with the greater portion of the superior wall of the pharynx during its
passage through that cavity. When the alimentary mass is carried back by the
tongue, it raises the soft palate and bears the posterior border of this backwards
to the entrance of the oesophagus. The extreme development of this palatine
curtain, therefore, quite prevents this surface of the pharynx from being directly
applied to the food, and it is through the medium of this partition that the
constrictors exercise their peristaltic action on the morsel of aliment, until it
reaches the oesophageal orifice.
Differential Characters op the Pharynx in the other Animals.
The iiharynx nf Ruminants is elongated and very spacious. The hj-o-, thyro-, and crico-
pharyngeal muscles— the middle constrictor aud inferior constrictors— are less distinct from
each otiier tlian in the Horse: the inferior constrictor is very small, and the fibrous raphe on
which the constrictors unite is little developed. In the pharynx of the Ox and Sheep is
noticed a mucous fold that descends to the middle of the posterior wall, and appears to be a
continuation, posteriorly and inferiorly, of the nasal septum; whence results the formation of
two glanduhir pharyngeal caeca at their bottom.
In t ie Camel, this organ is remarkable for the large dimensions of its longitudinal direc-
tion and its relative narrowness. The posterior pillars of the soft i)aLite unite at a great
distance above the entrance to the cesophafrus, and the pharynx appears to be divided into two
compartments by a transverse mucous fold, which is detached from the posterior wall. The
superior compartment thus formed, shows, above, the guttural openings of the nasal cavities —
openings which are narrow and vertically elongated — and the orifices of the Eustachian tubes ;
while iit the bottom of the inferior compartment is the oesophageal infnndibulum and the
entrance to the larynx. The pharyngeal mucous membrane in this animal is black in colour.
In the Pig, the f)haryngeal caecum is sacculated, and its mucous membrane is very vascular,
and rich in closed follicles.
In the Dog, the infundibulum is very spacious. The posterior pillars of the soft palate
subside on the walls of the pharynx befce reaching the entrance to the oesophagus. The
pharyngeal mucous membrane, much finer than that of the oesophagus, is distinguished from
it by a sharp line of de:tnircation, and here it is very rich in glands. The crico-ph.tryngeal is
not very distinct from the tljyro-pharyngeal muscle; so that, in reality, only three constrictors
can be distinguished.
Comparison of the Pharynx of Man with that of Animals (Fig. 253).
In consequence of tlie smallness of the soft palate, the pharynx of Man is only a kind of
channel between the mouth and the larynx and oesophagus. It is usually divided into three
portions : a superior, the posterior nares, covered by ciliated epithelium ; a middle, or guttural,
and an inferior, or oesophageal. The two latter are covered with tesselated epithelium.
The muscles are almost the same as in the Dog, being a portion of the jialato-pharyngeus,
the superior, middle, and inferior constrictors, and a stylo-pharyngeal muscle.
Below the sides of the pharynx, and between the pillars of the soft palate, are the
amygdalae — almond-shaped organs, the surface of which shows the openings of the follicles
that, with the vessels and a little connective tissue, compose their substance.
TEE (ESOPHAGUS.
447
Fig. 253.
The (Esophagus (Figs. 254, 255).
PreparaUon. — Place the subject in the second or third position ; remove the cervical
panniculus from the left side ; take away the corresponding anterior limb, and proceed to the
excision of the ribs of this side, with the exception of the first. Afterwards dissect the vessels
and nerves in the neighbourhood of the oesophagus, taking care to preserve their relations with
each other.
Form. — The oesophagus is a long, cyhndrical, narrow, membranous canal, a
little wider below its commencement, easily dilated for the greater part of its
extent, destined to convey the food from the pharynx to the stomach, and
so to complete the act of deglutition.
Course. — It begins at the pharynx, and communicates with it by means of
the posterior opening situated above the glottis. It
is so narrow when not in use, that it admits with
diflficulty the tip of the finger. Behind, it is circum-
scribed by a fibro-mucous cord that is related to the
junction of the posterior pilhrs of the soft palate ;
in front, by the external surface of the arytsenoid
cartilages. It afterwards descends behind the trachea
to the middle of the neck, where it commences to
deviate towards the left side of that tube, and enters
the thoracic cavity by inclining towards the inner
aspect of the first left rib. It soon after regains its
situation above the trachea, passes over the base of
the heart, and reaches the opening in the right pillar
of the diaphragm, in passing between the two layers
of the posterior mediastinum. Traversing this open-
ing, it enters the abdominal cavity, and immediately
afterwards is inserted into the smaller curvature of
the stomach by an orifice designated the cardiac, which
will be studied at the same time as that viscus.
Relations. — The oesophagus in its course has the
following numerous relations : —
At its origin, it is comprised between the guttural
pouch and the posterior crico-arytenoid muscles.
In the cervical region, it is enveloped in a thick
layer of connective tissue, which unites it in a loose
manner to the surrounding organs, its relations with
these varying as we consider them superiorly or in-
feriorly. Superiorly, and in the median plane, it
occupies the space included between the trachea and
the longus-colli, being bordered on each side by the
common carotid artery, with its satellite nerves — the
trunk common to the great sympathetic and pneumogastric, and the inferior
laryngeal. Inferiorhj, it is related to the trachea on the inner side ; and, exter-
nally, to the inferior scalenus muscle, and the vessels and nerves in the left
cervical channel, which also includes the jugular vein.^
' It is not absolutely rare to find the oesophagus deviate to the right in the lower part of
the neck ; in this case its relations will be reversed. We have never seen this canal enter the
thorax in the median plane of the body.
In Horses with a flat trachea, the oesophagus is sometimes in the middle of the upper
HUMAN PHARYNX LAID OPEN
FROM BEHIND.
1, Section through base of
skull; 2, 2, walls of pha-
rynx drawn aside ; 3, 3,
posterior nares, separated
by the vomer ; 4, extremity
of one Eustachian tube ; 5,
soft palate ; 6, posterior
pillar of soft palate ; 7, an-
terior pillar ; 8, root of the
tongue, partly concealed by
the uvula ; 9, epiglottis
overhanging (10) the cordi-
forra opening of the larynx ;
11, posterior part of larynx ;
12, opening of oesophagus,
13 ; 14, trachea.
448 THE DIGESTIVE APPARATUS IN MAMMALIA.
At its entrance into the thoracic cavity, the oesophagus, still deviating to the
left, and lying on the side of the trachea, responds, externally, to the inferior
cervical gangUon, the afferent and emergent nerves of that ganglion, the ver-
tebral arteries and veins, and the superior cervical and dorso-muscular vessels,
which obliquely cross its direction. Beyond this it regains its position between
the trachea and the longus colli, passes above the left bronchus, to the right of
the thoracic aorta, until it reaches between the layers of the posterior mediasti-
num, which bring it into relation with the internal face of the limgs ; these are
channeled for its reception, and here it is accompanied by the oesophageal artery,
and the oesophageal branches of the pneumogastric nerve.
The very short portion lodged in the abdominal cavity is related, on the
Fig. 254.
TRANVERSE VERTICAL SECTION OF HEAD AND NECK IMMEDIATELY IN FRONT OF THE STYLOID
PROCESSES, AND BEHIND THE (ESOPHAGUS.
I, (Esophagus ; 2, inner surface of trachea ; 3, common carotid artery ; 4, recurrent nerve ; 5,
thyroid gland; 6, exterior of pharynx; 7, crico-pharyngeus muscle; 8, 9, 10, 11, guttural pouch
and objects in its interior ; 12, stylo-pharyngeus muscle ; 13, sphenoid bone ; 14, jugular ganglia;
15, internal carotid; 16, 17, pneumogastric nerve; 18, parotid gland; 19, great hypoglossal
nerve; 20, jugular vein; 21, subscapulo-hyoideus ; 22, stylo-maxillaris.
right, to a fissure in the superior border of the Hver, and is enveloped by the
peritoneum. It terminates about the upper third of the sixteenth rib.
Interior. — Internally, the oesophagus presents nothing of interest ; and it
only requires to be remarked, that its walls are always shrunken and in contact
when food is not passing between them. It appears narrower in consequence of
its inflections or relations with other organs : 1. Near its commencement. 2. At
its entrance to the thorax. 3. At its passage through the diaphragm.
Structuee. — The oesophagus has two tunics — a mucous and a muscular.
The mucous membrane is continuous with that of the pharynx and
stomach ; it is white, and shows numerous longitudinal folds, which allow the
surface of that tube ; in other cases it is drawn to the inferior face, below the sterno-maxillaris
muscles, along with the carotid artery and its satellite nerves, the jugular vein maintaining its
position.
THE (ESOPHAGUS.
449
canal to dilate. It adheres but loosely to the muscular coat, on which it can
glide with the greatest facility. It has a thick, resisting, stratified, tesselated
epithelium, an unstriped muscular layer, and some racemose glands.
(A third or middle coat is sometimes mentioned by anatomists ; it is com-
posed of the tissue connecting the latter tunic with the one to be next described.)
The muscular coat commences at the- posterior part of the pharynx by the
ari/teno-ossophageal and superior longitudinal casophageal muscles (Fig. 251). The
aryteno-msophageal muscle is an extremely thin, small band in Solipeds, situated
on the posterior border of the arytenoid cartilage, at the commencement of the
(esophagus, where its fibres disappear. To expose this muscle — which represents
the inferior longitudinal oesophageal of some authorities, the oesophagus should
be turned forwards on the upper surface of the pharynx.
The superior longitudiiial m^ophageal muscle is a small superficial band, the
Fig 255.
PECTORAL CAVITY AND MEDIASTINUM, SHOWING THE COURSE OF THE TRACHEA
AND (ESOPHAGUS.
A, Anterior mediastinum ; B, posterior mediastinum ; c, the heart and pericardium
part of the mediastinum; d, diaphragm; E, trachea; F, oesophagus.
the middle
fibres of which leave the base of the fibrous triangle that occupies the posterior
face of the pharynx, to disappear on the surface of the oesophagus, where some
of them form loops at different elevations.
To these muscles at the commencement of the oesophagus, must be added
the crico-obsofhagecd, which leaves the deep face of the crico-pharyngeus to pass
to the border of the oesophagus, where its fibres proceed above and below that tube,
in joining those of the muscle of the opposite side. This muscle compresses the
oesophagus at its commencement, in the same way as Wilson's muscle acts upon
the urethra.
The remainder of this muscular tunic is formed of superficial longitudinal
fibres, often assembled in fasciculi : and of a deeper series of spiral or circular
fibres, which, towards the inferior extremity of the canal, intercross in an almost
inextricable manner. This muscular layer in the cervical, and for a great part
of the thoracic portion of the oesophagus, has aknost the red colour of voluntary
450 THE DIGESTIVE APPARATUS IN MAMMALIA.
muscles ; but it becomes white, like the involmitary fibres, after the tube
enters the mediastinum, and acquires cousiderable thickness and marked rigidity
in the dead animal. It is to be noted that this arrangement of the muscular
tunic is especially evident towards the insertion of the oesophagus into the
stomach, and that the muscular tube is at this point so narrow, that it is almost
exactly occupied by the folds of mucous membrane it contains. For this reason
it is that, in this state of cadaveric rigidity, we may inflate a stomach by the
pylorus without applying a ligature to the oesophagus ; the aperture of the
canal being so perfectly closed that it does not allow a bubble of air to escape.
In describing the interior of the stomach, we will refer to the consequences
resulting from this interesting anatomical fact.
Vessels and nerves. — The oesophagus is supplied with blood by the divisions
given off by the common carotid artery, as well as the bronchial and oesophageal
arteries. The nerves are almost exclusively derived from the pneumogastric ;
the motor nerves are the superior oesophageal filaments — branches of the
external pharyngeal and laryngeal ; the sensitive filaments are derived from
the recurrent nerve. For the portion beyond the heart, the sensitive-motor nerves
are supplied by the oesophageal nerves of the pneumogastric, though in an
asymmetrical manner.
Functions. — This canal conveys nutriment from the pharynx to the
stomach ; it has no other uses.
Differential Characters of the (Esophagus in the other Animals.
In all the other domesticated animals, the muscular coat is red-coloured throughout its
whole extent, and everywhere offers the same degree of thickness and the same flaccidity. The
canal is also as wide towards the stomach as at the pharynx. In Rdminants and the Car-
NivoRA, it enters the stomach as a funnel-shaped (infundibuliform) tube.
In the Camel, the mucous membrane adheres more closely to the muscular tissue than in
Solipeds, according to Colin.
The dilatability of the oesophagus is very remarkable in these animals : Dogs swallow large
pieces of flesh ; and Cows and Oxen are able to ingest large turnips, or such voluminous foreign
bodies as shoes.
(In Ruminants and the Carnivora the oesophagus is, proportionally^, wider than in the
Horse and Pig.)
Comparison of the (Esophagus of Man with that of Animals.
The oesophagus of Man resembles that of Carnivora; its diameter is almost uniform. It
also inclines to the left below the neck, but in the thorax is in the median line, though it again
deviates to the left as it joins the stomach. As the thyroid in Man is very voluminous, it is
related to the oesophagus in the upper part of the neck. Two small accessory fasciculi, belong-
ing to the muscular tunic of the oesophagus, have been described : one is the broncho- oesophageal
muscle, which is detached from the left bronchus; and the other the pleuro -oesophageal muscle,
detached from the left layer of the posterior mt diastinum.
Article II.— The Essential Oegans of Digestion.
These organs being all contained in the abdominal cavity, this common
receptacle will first be studied ; afterwards the sfomach, intestines, and their
annexed organs — the liver, pancreas, and spleen — will be described.
The Abdominal Cavity.
In Mammalia, the interior of the trunk is partitioned by the diaphragm
into two great cavities, which lodge the majority of the organs so vaguely
TEE ABDOMINAL CAVITY. 451
termed the "viscera." The anterior, the smallest, is the pectoral or thoracic
cavity ; the posterior is named the ahdomen, or abominal cavity.
Form of the Abdominal Cavity. — The abdomen is a vast oval-shaped reservoir,
elongated from before to behind, having for its upper wall the muscles of the
sublumbar region, enclosed below and laterally by the muscles of the inferior
abdominal region, bounded in front by the diaphragm, and prolonged behind
between the bones and membranous hgaments of the pelvis.
The parts forming the walls of this cavity having been already described, we
will confine ourselves to an examination of its interior, in order to determine the
various regions into which it is possible to divide it — a matter of some impor-
tance, as it singularly facilitates the topographical study of the contained viscera ;
for to say that an organ is situated in the abdomen, is a very vague reference to
its precise situation, in consequence of the great extent of this cavity. It is
necessary, therefore, to divide the abdomen into a certain number of peripheral
regions which will correspond to the different parts of its wall, with a view to
define the situation of the organs lodged therein, yet without complicating
anatomical description. Six principal regions are recognized in the abdominal
cavity.
A. The superior, or sublumbar region, corresponds to the superior wall of the
abdomen ; that is, to the psoas muscles and the bodies of the lumbar vertebrae.
It extends from the opening between the two pillars of the diaphragm to the
entrance to the pelvis.
B. The inferior region, limited, laterally, by the hypochondriacs and the
flanks, commences, in front, at the xiphoid cartilage, and is prolonged to the
pubis ; it comprises all that portion of the abdomen which corresponds to
the linea alba and the two recti muscles. Its great extent necessitates its sub-
division into five secondary regions : The supra-sternal region, named the epigastric
in Man, placed above the xiphoid cartilage of the sternum ; the umbilical region,
situated behind the preceding, and so named in consequence of its including that
part of the wall which is pierced by the umbilicus ; the prepubic region — the
hypogastric or pubic of Man — occupies the space in front of the anterior border
of the pubis ; the tivo inguinal regions, diverticuli of the abdominal cavity, located
in the inguinal tracts, where they form the special reservoirs to be hereafter
described as the vaginal sheaths (or inguinal canals).
C. The lateral regions {right and left lumbar of Man) are limited : in front,
by the costal attachments of the diaphragm ; behind, by the entrance to the
pelvic cavity ; above, by the superior border of the small oblique muscle ; below,
by the interval comprised between the inferior border of that muscle and the
external border of the great rectus muscle. The designation of hypochondrific
is given to the sub-region which corresponds to the cartilaginous circle of the
false ribs. The flank is that section covered by the muscular portion of the
small oblique muscle.
D. The anterior, or diaphragmatic region, comprises the cavity formed by the
posterior face of the diaphragm. Like that muscle, it is divided into two regions,
a central and peripheral.
E. The posterior, or pelvic region, is a special diverticulum of the abdomen
described as the pelvic cavity. It is bounded, above, by the sacrum ; below, by
the superior face of the pubes, the ischia, and the internal obturator muscle ; on
the sides, by the constricted portions of the ossa innominata and the sacro-sciatic
ligaments. The entrance to this diverticulum is situated above the pubes and
THE DIGESTIVE APPARATUS IN MAMMALIA.
Fig. 256.
is of an oval form. Posteriorly, it is narrower, and is traversed by the rectum
and the e^enito-urinary organs, which open externally.
The Peritoneum. — The abdominal cavity is lined, internally, by a serous
membrane, the peritoneum, which will now be briefly described.
Like all the splanchnic serous membranes, the peritoneum is composed of a
parietal and a visceral layer, which together form a closed sac so arranged that the
organs contained in the abdomen are situated external to this sac. The adjoining
theoretical figure (256), representing a transverse section of the abdominal cavity,
will show at a glance this arrangement. Let a represent the section of the small
intestines floating at liberty in the interior of the cavity ; b, that of the aorta, at
the level of the great mesenteric artery : the
peritoneal membrane, c c, covers the walls of the
abdomen, and at the points D, D is folded around
the great mesenteric artery, in such a manner
as to form two layers, f, f, which come in con-
tact by their adherent faces, reach the intestine,
and then separate to envelop it. We then see
in this figure the parietal layer of the peritoneum
C C, the visceral layer, G g, and the two layers,
F, F, which establish the continuity of the
parietal and visceral portions ; the complete sac
formed by these is apparent, and it could be
rendered more so by the further separation and
development of the layers f, f ; so that there is
no difficulty in understanding how the small
intestine may be at the same time in the inferior of
the abdominal cavity, and outside the sac formed
by the serous membrane which lines that cavity.
This arrangemer.t is common to all the organs freely suspended in the abdo-
men. The serous folds which suspend them, in joining their peritoneal layer to
that which covers the parietes of the cavity, will be studied under the names of
ligaments, mesenteries, and omenta. Some organs — the kidneys, for example —
have no proper visceral layer, being contained between the abdominal wall and
the external face of the parietal peritoneum, and are invested with none of the
duplicatures just mentioned.
We will briefly study the duplicatures, ligaments, mesenteries, and omenta that
the peritoneum forms, starting from the umbilicus and passing forwards and
backwards (Fig. 2,')7).
On reaching t!ie supra-sternal region, the peritoneum forms a falciform dupli-
cature, extending from the umbilicus to the middle lobe of the liver, and which
is even prolonged between that lobe and the posterior face of the diaphragm ; at
the free border of this fold is a thickening, which is regarded as the remains of
the obliterated umbilical vein. In becoming doubled over the neighbouring
organs, the diaphragmatic portion constitutes : 1. The ligaments of the right and
left lobes of the liver. 2. The common ligament of that gland, which surrounds
the posterior vena cava. 3. The cardiac ligament that envelops the termination
of the oesophagus. Behind the liver is found the hepato-gastric ligament, which
fixes the stomach in the posterior fissure of the liver, and is, to the right and
backwards, attached to the duodenum at the lower face of the right kidney ; it
is then directed from right to left, and becomes continuous with the parietal
peritoneum of the sublumbar region and the mesentery proper.
THEORETICAL TRANSVERSE SECTION
OF THE ABDOMINAL CAVITY, TO
SHOW THE DISPOSITION OF THE
PERITONEUM.
THE ABDOMINAL CAVITY. 453
The two layers of the hepato-gastric ligament separate at the lesser curvature
of the stomach, to cover that viscus ; then join at its greater curvature, and pass
to the interior of the abdominal cavity. This fold receives the name of the great
or gastro-coUc omentum ,- it leaves the left tuberosity of the ventriculus, which it
suspends to the sublumbar region from the whole extent of the great curvature ;
to the right it goes beyond the pylorus, to be continued on the concave curvature
of the duodenum, as far as the cascum. By its posterior border, the great omen-
tum is extended around the termination of the large colon and the origin of the
floating colon, where it is confounded with the visceral peritoneum of these organs,
as well as with the parietal peritoneum. It results from this arrangement, that
the great omentum forms behind the stomach, and in front of the adherent portion
of the large colon, a space that communicates with the great peritoneal cavity
by a veiy naiTow opening — the foramen of WinslouK This aperture is included
between the vena portas, posterior vena cava, anterior extremity of the pancreas,
and the lesser cm-vature of the stomach. To the left of the latter viscus, on the
THEORETICAL LONGITUDINAL AND MEDIAN SECTION OF THE ABDOMINAL CAVITY, TO SHOW THE
REFLECTIONS OF THE PERITONEUM.
1, Liver ; 2, stomach ; 3, small intestine ; 4, origin of the floating colon ; 5, rectum ; 6, vagina and
uterus; 7, bladder; 9, posterior aorta ; 10, diaphragm; 11, posterior vena cava; 12, inferior
abdominal wall. Pp, Pp, parital peritoneum ; Pv, Pv, visceral peritoneum , L, gastro-hepatic
ligament ; M, mesentery ; Ge, great omentum.
external face of the great omentum, the spleen is suspended ; consequently, that
portion extending from the spleen to the ventriculus, is named the gastro-splenic
omentum.
The two layers composing the great omentum are very thin for the greater
part of theii' extent, and enclose the blood-vessels between them. In emaciated
animals, these vessels are distinctly seen, owing to the transparency of the mem-
branes, and they give the omentum a lacework appearance ; but in fat subjects
they are concealed by the adipose tissue deposited along their course, and which
may accumulate in considerable quantity.
In the sublumbar region, the parietal peritoneum forms several folds ; these
are : the hepatico-renal ligament., extending from the right lobe of the liver to the
anterior border of the right kidney ; the ligament of tJie lobus Spigelii, the mesen-
tery proper, the colic mesentery ; lastly, the greatly developed layers suiTOunding
454 THE DIGESTIVE AFPARATUS IN MAMMALIA.
the cfecum and the second flexure of the colon, which constitute the meso-coecum
and meso-colon.
The great mesentery is detached from around the large mesenteric artery, and
projects into the abdominal cavity to reach the small intestine at the lesser
curvature, and to envelop that viscus.
Its shape is that of an irregular triangle, the summit of which corresponds to
the mesenteric artery, the very short anterior border being continuous with the
duodenal frjenum, and the posterior border, the longest, with the meso-colon, its
convex festooned base being as long as the intestine itself. Between the two
layers that compose it, are the blood-vessels and lymphatics, as well as the nerves,
of the small intestine.
The colic mesentery is formed like the great mesentery. Its inferior border,
plane or plicated, is fixed to the small curvature of the floating colon and the
commencement of the rectum ; its upper border extends from the great mesenteric
artery, as far as the entrance to the pelvic cavity.
Around the cross of the ctecum, from the origin to the termination of the
great colon, the peritoneum is reflected to cover these viscera ; a layer passes
from the anterior border of the caecum on to the ileum and the second flexure of
the colon — this is the meso-ccmum ; another layer, comprised between the second
and third portion of the colon — the shape of which is that of a battledore, is
named the meso-colon.
If, again, the peritoneum is taken at the umbilical region and followed back-
wards, it will be found to insinuate itself into the inguinal canals, cover the
organs contained in the pelvis, and become reflected at the bottom of that cavity,
to be continued either with the peritoneum of the sublumbar region, or with that
on the lateral walls of the abdomen.
TMs serous membrane covers the fundus of the bladder, and at this point it
has three ligaments. The middle ligament, falciform in shape, leaves the large
extremity of the bladder, is attached to the anterior border of the pubis, and
insensibly disappears on the inferior abdominal wall ; on its free border is a small
fibrous cord, which is supposed to be the remains of the urachus. The two lateral
ligaments are more developed, and extend from the entrance to the pelvic cavity
to the vesical fundus ; they have on their free border the obliterated umbilical
arteries. In the male, the peritoneum is prolonged from the upper face of the
bladder to the enlargement of the deferent ducts, between which it sends a trans-
verse fold to the anterior extremity of the vesiculse seminales, and is then
reflected around the rectum.
In the female, it is carried from the bladder to the terminal portion of the
vagina, to the uterus, and to the cornua of that organ, where it forms three folds
named the broad ligaments, ligamefits of the ovary, and the round ligament ; then
it re-descends on the upper face of the vagina, and thence envelops the rectum,
around which it is reflected from behind forwards.
According to this arrangement, we see that the termination of the digestive
canal, and the parts of the genito-urinary organs situated altogether at the
posterior portion of the pelvic cavity, are placed outside the peritoneal serous
membrane.
Structuee. — Like all the serous membranes, the peritoneum is formed by a
membrane of connective tissue, rich in elastic fibres, and covered on its free face
by an endothelial layer (the cells of Avhich are flat and polygonal, and about ^-^
of an inch in diameter). Many blood-vessels are found on the adherent surface ;
THE STOMACH 465
while lymphatics are abundant in the visceral layer ; they are independent, or
form a sheath around the blood-vessels of the mesentery. Its nerves come from
the diaphragmatic, lumbar, and intercostal branches, and the great sympathetic.
Differential Characters in the Abdominal Cavity of the other Animals,
In the Carnivora. the abdominal cavity is very narrow; while in Ruminants it is very
vast, its capacity being in direct relation to the volume of the viscera it contains.
The general arrangement of the peritoneum varies but little in the different species, the
only notable diversities being remarixed in the great omentum. In the Ox, Sheep, and
Goat, this is detached from the middle of the lower face of the rumen, and envelops the right
sac of that organ, fixing the fourth compartment to its great curvature, and then passing upwards,
to become continuous with tiie mesentery. In the Dog and Pig, this fold descends in front
of the intestinal mass, until near the pelvis ; then it ascends in gathering on itself, and
ultimately spreads over the colon ; in the middle portion of the great omentum there are,
consequently, four layers laid against each other.
Comparison of the Abdominal Cavity of Man with that of Animals.
The abdominal cavity of Man is elongated vertically, and has an inferior cavity occupying
the entrance to the pelvis. There is nothing particular to note in its disposition, the differences
observed in it being allied to tlie external shape of the body. The peritoneum is spread over
its parietes nearly in the same manner as in the Carnivora ; the great omentum is formed by
four layers, and covers the intestines like an apron ; between its two layers is the lesser cavity
of the omentum, virtually in the adult.
The Stomach.
The stomach is a membranous sac placed between the oesophagus and
intestinea, and in which is completed the division of the alimentary matters.
The Stomach in Solipeds (Figs. 258, 259, 260, 261)
Preparation. — In order to study the relations of this organ, it suflBces to open the abdomen
and remove the intestinal mass in the following manner: Place the animal in the first
position, and very slightly inclined to the left side; make an incision througli the inferior
abdominal wall, or, still better, carry it away entirely by a circular incision, taking care not
to wound any part of the intestine. The entire viscera should then be withdrawn from the
abdominal cavity, and laid on the table which supports the subject ; for this mass cannot be
allowed to fall on the ground without risk of being pulled and torn, either in the intestine
itself, or those parts which it is desired to preserve intact in the abdomen. Incise the floating
colon where it joins the rectum, and the duodenum where it passes behind the great mesenteric
artery; the base of the caecum should now be detached from the sublumbar surface by the
rupture of the connective tissue which connects it to the right kidney and the pancreas; the
cellular connection between the latter gland and the terminal extremity of the fourth portion
of the large colon should also be broken ; after this, it is only necessary to divide the attach-
ment of the mesenteric bands to the sublumbar region, with the vessels contained between
them. The intestinal mass is then definitely expelled from tlie abdominal cavity. In this
way it is possible to expose, and conveniently prepare, not only the stomach, but also tlie
spleen, liver, pancreas, kidneys, ureters, etc. Nothing more remains than to make known the
procedure to be adopted in everting the stomach, in order to study its internal surface, or
dissect its deep muscular layer. It is recommended, first, to excise tiie stomach with at least
three inches of the oesophagus, and eight inches of the duodenum, and cleanse the interior of
the organ. This may be done in several way^, but the following is the simplest: a certain
quantity of water is introduced into the stomach by fixing the duodenum to a water-tap, the
right hand manipulating the organ while the left closes the duodenum to prevent the escape
of the liquid. The alimentary substances contained in it are in this way mixed with the
water, and may be expelled from the duodenum by pressing the stomach ; this operation, being
repeated four or five times, thoroughly cleanses the cavity of the organ. To evert the inner
surface, it is only necessary to introduce by the duodenum a loop of wire, and make it pass
through the cesophagus ; a strong waxed thread is fastened in the loop and firmly fixed around
456
THE DIGESTIVE APPARATUS IN MAMMALIA.
the oesophagus, when, in pulling back the wire, this extremity is drawn towards tlie pylorus,
and by careful traction the latter is so dilated as to allow the passage of the cardiac end, and
complete eversion of the stomach. Inflation will then give it its normal form and disposition?
with this difference, that the mucous membrane is external, and the serous tunic internal.
Lastly, to render the muscular layers of the stomach more evident, it is advisable to plunge
the organ into boiling water for some minutes, after which it should be put into cold water.
If it is desired to study the external and middle layers, the stomach should be inflated, and its
serous covering removed by strips with foiceps and the fingers; if the deep layer is to be
examined, the mucous membrane must be removed oy means of the forceps and scalpel from
a stomach previously everted.
Situation. — The stomach, also designated the ventriculus, is situated in the
diaphragmatic region of the abdomen, where it has a direction transverse to
the median plane of the body.
Dimensions. — Its average capacity, in an ordinary-sized Horse, is from 3 to 3^
gallons ; but it varies greatly according to the bulk of the animal, its breed, and
TEE STOMACH.
457
the nature of its food. Relatively, it is more considerable in common-bred
Horses, and in the Ass and Mule. When empty, its average weight is between
3 and 4 pounds.
Ji'orm. — Elongated laterally, curved on itself, often constricted in its middle,
and slightly depressed from before to behind, this reservoir presents, externally :
1. Ttvo faces — an anterior and posterior, smooth and rounded. 2. A great or
convex curvature, forming the inferior border of the organ, and giving attach-
ment, throughout its extent, to the great omentum — a membranous fold which
has been described as a dependency of the serous membrane. 8. A lesser or
concave curvature, into which the oesophagus is inserted, and which is united, to
the right of that canal, to the liver, by means of a fraenum known as the hepato-
Fig. 259.
STOMACH OF THE HORSE.
A, Cardiac end of the oesophagus ; b, pyloric end and ring.
gastric ligament. 4. A left extremity (the cardiac), dilated in the form of a large
conical tuberosity, and constituting the left cul-de-sac {or fundus) of the stomach.
5. A right extremity (the pyloric), narrower, curved upwards, and continued by
the duodenum, from which it is separated by a marked constriction — this is the
right cul-de-sac of the stomach.
Relations. — Studied in its connections with the neighbouring organs, the
stomach is related : by its anterior face, with the diaphragm and liver ; by its
posterior face, with the diaphragmatic curvature of the colon. Its inferior
border, margined to the left by the spleen, which is suspended from it by means
of the great omentum, is separated from the inferior abdominal wall by the
large anterior flexures of the colon ; its distance from this wall depends upon
458 THE DIGESTIVE APPARATUS IN MAMMALIA.
the fulness of the organ. The left extremity, suspended to the subliunbar region
by the aid of a very short serous ligament — a portion of the great omentum — is
related to the base of the spleen, the left extremity of the pancreas, and, less
directly, to the anterior border of the left kidney. The right extremity, lower
than the left, touches the right lobe of the liver and the above-mentioned
intestinal curvatures.
Interior. — When a stomach is opened to study its interior, one is at first
struck by the different aspect its internal membrane presents, according as it is
examined to the right or the left. To the left, it has all the characters of the
oesophageal mucous membrane, in being white, harsh, and even resisting ; it is
covered by a thick layer of epithelium. To the right, it is thick, wrinkled,
spongy, very vascular and follicular, has a reddish-brown tint that is speckled
by darker patches, loses its consistency, and is only covered by a very thin
epithelial pellicle. It is not by an insensible, but a sudden transition that the
mucous membrane of the stomach is thus
Fig. 260. divided into two portions ; and their separation
is indicated by a salient, more or less sinuous,
but sharply marked ridge. This ridge, then,
divides the stomach into two compartments —
a division already indicated externally, by the
circular depression observed in the majority
of subjects. The left sac or compartment is
considered as a dilatation of the oesophagus.
The right sac constitutes the true stomach of
Solipeds ; as on it alone devolves the secretory
function which elaborates the gastric juice, the
essential agent of digestion in this organ.
The interior of the stomach (Fig. 260)
iNTLRioR OF THE HORSLS STOMACH, o^^rs for study two apcrturcs : the cardiac and
A, Left sac ; b, right sac ; c, duodenal Py^oric. The cardiac, OT Oesophageal orifice, is in
dilatation. the Icsser curvature of the left sac of the
stomach. Its arrangement have given rise to
numerous discussions, as in it has generally been sought the reason why Sohpeds
vomit with such extreme difficulty. At one time there was described a semilunar
or spiroidal valve, which is opposed to the retrograde movement of the food ; and
at another time it was the oblique insertion of the oesophagus, resembling that
of the ureters into the bladder, and which, by a mechanism analogous to these,
proved an obstacle to the return of aliment into that oesophagus. Both suppo-
sitions are wrong. When we attentively observe the manner in which the
oesophagus comports itself at its termination, it will be noticed that it is inflected
downwards, after traversing the right pillar of the diaphragm, and is inserted
almost perpendicularly into the lesser curvature of the stomach. In opening
into this viscus, the oesophagus does not widen into an infundibulum, as in other
animals ; on the contrary, its calibre is here narrower than elsewhere, and its
cardiac or stomachal orifice, completely obstructed by the folds of mucous
membrane, only occupies an infinitely small portion of the internal surface of
the stomach.
With regard to the pylorus, it represents a large aperture formed at the
bottom of the right sac, and furnished with a thick circular ring ; this opening
can be completely closed through the action of the powerful sphincter surrounding
THE STOMACH. 459
it. It is furnished with a valve (the pyloric valve), formed by the union of the
cellular and mucous tunics, and the sudden disappearance of the circular muscular
fibres.
Structuee. — The parietes of the stomach are formed by three membranes :
an external, or serous ; a middle, or muscular ; and an internal, or mucom.
1. Serous membrane. — This membrane, derived from the peritoneum, adheres
closely to the muscular layer, except towards the curvatures. At the lesser
curvature, it is constantly covered by an expansion of yellow elastic tissue, the
use of which appears to be to maintain the two extremities of the stomach near
each other ; for when this is destroyed, the lesser curvature becomes considerably
elongated. Along the whole of the greater curvature is a triangular space
occupied by connective tissue ; this space disappears more or less completely as
the organ becomes distended.
It has three folds, which are detached from the stomach and carried on to
the adjacent parts, and are formed in the manner indicated in the general
description of the peritoneum. These folds constitute the cardiac ligament, the
gastro-hepatic ligament or omentum, and the great omentum.
The cardiac ligament is a short, serous band developed around the terminal
extremity of the cesophagus, and strengthened by fibres of yellow fibrous tissue.
It attaches the stomach to the posterior face of the diaphragm, and is continuous,
on each side, with the two folds about to be described.
The gastro-hqmtic (or lesser) ligament is a band composed of two layers,
which leave the lesser curvature of the stomach, and are inserted into the
posterior fissure of the liver. It is prolonged posteriorly, and to the right, along
the duodenum, where it constitutes a peculiar serous frsenum, which will be
studied with the small intestine.
The great or gastro-colic omentum, is detached from the whole extent of
the great curvature, from the cardia to the pylorus, beyond which it extends
to the duodenum. The portion surrounding the left cul-de-sac is excessively
short, and is carried to the sublumbar wall of the abdomen, to which it fixes the
stomach. For the remainder of its extent, this omentum is greatly developed,
and hangs freely in the abdominal cavity, among the intestinal convolutions.
The border opposed to the stomach is attached to the terminal portion of the
large colon, and to the origin of the floating colon. (For further details, see
the description of the peritoneum.)
These three ligaments fix the stomach in the abdominal cavity, m addition
to the oesophagus and duodenum, which are continuous with it.
2. Muscular memhrane. — This tunic, comprised between the serous and
mucous layers, is lined internally by a coveiing of condensed connective tissue
which adheres intimately to it, and may be regarded as the fibrous membrane of
the stomach. Dissection shows this muscular tunic to be composed of three
superposed planes.
The superficial plane envelops all the right sac, and the majority of its fibres
are spread in loops around the left ctd-cle-sac, their extremities being lost on
the surfaces of the organ. Some of them even extend over the great curvatm'e,
to the surface of the right sac ; while others are evidently continuous with the
superficial fibres of the oesophagus (Fig. 261, a).
The middle plane (Fig. 261, b) is formed of circular fibres spread over the
whole of the organ. In the right sac, they are placed immediately beneath the
serous membrane ; in the left sac, they pass beneath the fibres of the superficial
460 THE DIGESTIVE APPARATUS IN MAMMALIA.
plane, and finish by becoming mixed so intimately with these, that towards the
tuberosity formed by the left extremity it is impossible to distinguish them. By
their aggregation around the pylorus, they constitute the sphincter {ov pyloric
valve) which envelops that orifice.
The deep plane (Fig. 261, a), like the first, is specially destined for the left
sac, and cannot be properly studied except in an averted stomach deprived of its
mucous membrane. Much thicker than the superficial plane, it yet, in its
general arrangement, much resembles it. Thus, its fasciculi present loops which
embrace the left cul-de-sac, and the extremities of which are lost on the faces of
the organ, where some of them become continuous with the circular fibres. The
loops nearest the oesophagus embrace the stomachal opening of that canal like a
cravat. It is to be remarked that the fibres of this deep layer intersect those of
Fig. 261.
Fig. 262.
MUSCULAR FIBRES OF THE STOMACH
(external and middle LAYERS).
A, Fibres of the external layer enveloping
the left sac; B, fibres of the middle
plane in the right sac ; C, fibres of the
pylorus.
deep and middle muscular layer ex-
posed BY removing the MUCOUS MEM-
BRANE FROM AN EVERTED STOMACH.
A, Deep layer of fibres enveloping the left
sac ; B, fibres of the middle plane which
alone form the muscular layer of the
right sac ; C, fibres of the pylorus.
the superficial plane —the former passing from the left to the right sac, in
inclining downwards towards the great curvature, while the latter are directed
to the right and slightly upwards.
From this arrangement it results, as a glance at Figs. 261 and 262 will show :
1. That the right sac has only a singular muscular plane. 2. That, on the con-
trary, the left sac has three, all of which concur in propelling the ahment that
has accumulated in the left, or oesophageal reservoir, into the right, or true
stomach.
3. Mucous membrane. — Independently of the general characters noted in the
interior of the stomach, it has to be remarked that the gastric mucous membrane
is united to the preceding tunic by an expansion of connective tissue ; though it
adheres but feebly throughout the right sac, especially towards the greater
curvature, where it is thickest ; and that it has no ridges in the left sac, though
in the right they are always present, even when the organ is inflated.
On the surface of this membrane are seen microscopical apertures {alveoli) —
the orifices of the excretory ducts of glands ; these are rare in the left sac,
but extremely numerous in the right. In this region they are separated from
THE STOMACH.
461
each other by minute processes resembling papillae ; but the latter are only met
with in the vicinity of the pylorus.
The gastric mucous membrane is composed of an epithelial layer and a corium,
in which are distinguished a glandular and a muscular laijer. The epitheUum is
stratified and tesselated in the left compartment, simple and calyciform in the
right sac, where it covers the little mucous processes that separate the glandulae,
and penetrates more or less deeply into the interior of these, becoming
spheroidal.
In the left side, in the vicinity of the pylorus, there are found some
racemose glands analogous to those of the oesophagus ; but the real glandular
Fig. 263.
Fig. 264.
PEPTIC GASTRIC GLAND.
common trunk; 6, 6, its chief branches;
c, c, terminal caeca, with spheroidal gland-
cells.
PORTIONS OF ONE OF THE C^CA MORE
HIGHLY MAGNIFIED, AS SEEN LONGITUDI-
NALLY (a), and in TRANSVERSE SECTION
(B).
a, Basement membrane ; 6, large grandular
cell; c, small epithelial cells surrounding
the cavity.
layer is only to the right side. There are foun^ multitudes of parallel tubular
glands, united by a small quantity of delicate connective tissue which is very
rich in nuclei. They secrete the gastric fluid, or furnish the mucus that covers
the surface of the epithelium ; they are consequently distinguished as pepsine
{or peptic) and mucous glands, the former being much more numerous than the
latter.
They are composed of a simple straight tube at their origin (excretory duct),
which frequently divides into two or more flexuous tubes that terminate in
culs-de-sac (or glandular caca). The epithelium is not the same in the two
kinds of glands : the mucous glands (Fig. 265, a, h) are lined with cylinder-
THE DIGESTIVE APPARATUS IN MAMMALIA.
epithelium throughout their extent ; the peptic glands (Figs. 263, 204) are lined
with cylinder-epithelium at their origin (Fig. 263, a), but the secretory tubes
contain round peptic cells. (Each caeca, when highly magnified, is found to
consist of a delicate basement membrane (Fig. 265, a) inflected over a series
of nearly globular cells (b), which occupy almost the
whole cavity of the tube, and contain a finely granular
matter ; the narrow passage left vacant in the centre
is, however, still surrounded by a layer of epithelial cells
(c), the small size of which is in striking contrast to the
large dimensions of the gland-cells.)
The muscular layer (of the mucous membrane) is
immediately beneath the glandular structure, and con-
tains two planes of intersecting fibres. Lastly, the con-
nective tissue layer of the corium is thick and loose,
sustains the vessels (and nerves), and unites the mucous
to the muscular tunic of the stomach.
4. Vessels and nerves. — The stomach receives its
blood by the two branches of the gastric artery, the
sple7iic and its terminal branch — the left epiploic artery,
and by the pyloric and right epiploic arteries. The
principal arterial ramifications extend between the mucous
and muscular layers, where they furnish two capillary
reticulations to the glandular layer — a deep network that
sun-ounds the secretory tubes, and a superficial placed
between the alveoli. The blood is carried from the organ
to the vena portae by the satellite venous branches. The
MUCOUS GASTRIC GLAND WITH lymphatics form a subserous and two deep networks at
CYLINDER EPITHELIUM. ,, i /■ .1 i j i i 3 ■ .^ n-,
, , , . the base of the glandular layer and m the fibrous mem-
^' ' * appendage.' ' ^ ^^^^ brane. They enter small glands situated along the
curvatures, and from these to Pecquet's reservoir. The
nerves are derived from the pneumo-gastrics and solar plexus, and in accompanying
the vessels show microscopic ganglia in their course ; their mode of termination is
not known.
Fig. 266.
APPEARANCE OF THE PROPER GASTRIC MEMBRANE OF THE STOMACH IN AN INJECTED
PREPARATION (HUMAN).
A, From the convex surface of the folds, or rugcB ; B, from the neighbourhood of the pylorus, where
the orifices of the gastric follicles occupy the interspaces of the deepest portions of the vascular
network.
Functions. — In the stomach is begun those transformations by which
alimentary matters are rendered capable of being assimilated. There the food
THE STOMACH.
463
comes into contact with the gastric fluid, by the action of which its principal
elements, and particularly the albuminoid substances, become soluble and
absorbable.
Differential Characters in the Stomach of the other Animals.
The stomach is an organ that exhibits groat differences in the various domesticated
animals. In tlie study of these differences, we will proceed from the simple to the complex.
1. The Stomach of the Kabbit (Fig. 286).
The stomach of the Rabbit is described immediately after that of Solipeds, because of
the great resemblance between the two organs. Like the latter, the stomach of the Kabbit is
divided into two sacs— a right and left— and the oesophagus enters it at the middle of its
smaller curvature ; so that the organ shows a large tuberosity in cul-de-sac on the left of the
cardia. The sac is perhaps more elongated, narrower, and more curved than in that of the
Horse. The total capacity of the organ is from f of a pint to 1 pint.
2. The Stomach of the Pig (Fig. 289).
The Pig's stomach is simple, like that of the Horse, but it is less curved on itself, and
the cardia is nearer the left extremity ; the latter has also a small conical dilatation, which
has been compared to a cowl curved back-
wards. The cesophagua opens into the stomach pj^ 267
by a wide infundibulum, and the mucous mem-
brane of that tube is prolonged over the ga>tric
surface in a laiiius of from two to three inches
around the cardia. Here again we find a " tiace
of the division into two sacs," common to
Solipeds, and to nearly all Rodents.
The capacity of the Pig's stomach averages
from 1| to 2 gallons. (The muscular tunic is
thicker in the right than the left extremity ;
near the oesophagus, the serous tunic shows
some transverse folds.)
3. The Stomach of Carnivora (Fig. 267).
In the Dog and Cat the ventriculus is
but little curved, and is pear-shaped, the small
extremity corresponding to the pylorus. The
cardia is dilated like a funnel, and is nearer
the left extiemity of the organ than in other
animals. The oesophageal mucous membrane
is not continued beyond the margin of fliat
orifice. The simple stomach of Carnivora forms
only a single sac, whose internal mucous mem-
brane presents, throughout its whole extent,
the same organization as the membrane lining
the right sac of Solipeds. This membrane is
remarkable for the regular and undulated folds
it forms when the stomach is empty. Nothing
is more variable than tlie capacity of the Dog's
stomach, because of the great differences in the size of this animal, according to breed. Colin
has found the minimum to be 1^ pints, and the maximum If gallons; he calculates the
average to be about 2J quarts. In the Cat, the average is from 2 to 2i gills.
4- The Stomach of Ruminants (Fig. 268).
These animals are distinguished from the others by the faculty they possess of swallowing
their food after imperfect comminution, and causing it to return again into the mouth to
submit it to -a second mastication, previous to final deglutition. The gastric apparatus is
admirably arranged to effect this physiological finality, and is remarkable for its enormous
development, as well as its division into four separate pouches, which are regarded as so many
stomiichs.
stomach of the dog.
A, (Esophagus ; B, pylorus.
464
THE DIGESTIVE APPARATUS IN MAMMALIA.
These cavities represent a considerable mass that fills the greater part of the abdominal
cavity, and the medium capacity of which is not less than fifty-tive gallons ! One of them,
the Rumen, into which the oesophagus is inserted, constitutes nine-tenths of the total mass.
The other three, the Reticulum, Omasum, and Ahoruasum, form a short chain, continuous with
the left and anterior portion of the rumen. The abomasum alone should be considered as a
true stomach, analogous to that of the Dog, or the right sac of the ventriculus of Solipeds.
The other three compartments only represent, like the left sac in the latter animals, oesopha-
geal dilatations.
The description about to be given of each of these divisions more particularly applies te
the Ox; care will be taken, in the proper place, to note the special peculiarities in the stomach
of the Sheep, Goat, and Camel.
Rumen (Figs. 2G8, 271).— This reservoir, vulgarly designated the paunch, alone occupies
three-fourths of the abdominal cavity, in which it affects a direction inclined from above to
below, and from left to right.
External conformation. — Elongated from before to behind, and depressed from above to
Fig. 268.
OTOMACH OF THE OX, SEEN ON ITS RIGHT UPPER FACE, THE ABOMASUM BEING DEPRESSED.
A, Rumen, left hemisphere; B, rumen, right hemisphere; C, termination of the oesophagus;
D, reticulum ; E, omasum : F, abomasum.
below, it offers for study : 1. An inferior and a superior face, nearly plane, smooth, and divided
into two lateral regions by traces of fissures, which are only sensible at the extremities of the
organ. 2. A left and right border, smooth, thick, and rounded. 3. A posterior extremity,
divided by a deep notch into two lobes, described by Cliabert by the name of conical cysts. 4.
An anterior extremity, offering an analogous arrangement, and concealed, at first sight, by the
stomachs (or compartments) superadded to the rumen ; the notch on the right of this extremity
divides it into two unequal pouches, which will be referred to presently.
It is to be remarked that tliese two notches, which are prolonged on tl)e surface by furrows
that separate these into two lateral regions, divide the rumen into ttoo sacs— a rigid and left;
this division we shall find more manifest in the interior of the viscus. The right sac— the
shortest — is in great part enveloped by the serous covering which constitutes the great omentum.
The left sac surpasses the other by its two extremities, except in the Sheep and Goat (Fig.
271), in which the right conical cyst is longer than the left. The anterior extremity of this
left sac is tlirown back on the corresponding lobe of the right sac ; above, it receives the
insertion of the oesophagu.s, and is continuous, in front, with the reticulum.
THE STOMACH.
465
Eelations.— The external form of the rumen being determinerl, the study of its relations
becomes easy. By its superior surface, it is in contact with the intestinal mass ; its opposite
face rests on the inferior abdominal wall. Its left border, supporting the spleen, touches the
most elevated part of the flank and the sublumbar region, to which it adheres by cellular
tissue, as well as the vicinity of the coeliac trunk and the great mesenteric artery ; tlie right
border, margined by the abomasum, responds to the most declivitous portion of the right hypo-
chondriac and flank, as well as to the intestinal circumvolutions. Tlie anterior extremity,
bounded by the reticulum and omasum, advances close to the diaphragm; the posterior occupies
the entrance to the pelvic cavity, where it is more or less in contact with the genito-urinary
organs lodged there. In the pregnant female, the uterus is prblongeil forwards on the upper
face of the viscus just described.
Interior (Fig. 269). — In the interior of the rumen are found incomplete septa, which repeat
the division into two sacs already so marked externally These septa are two in number, and
represent large muscular pillars, which correspond inferiorly to the notches described at the
extremities of the organ. The anterior pillar (Fig. 269, g) sends to the inferior wall of
Fig. 269.
IKTERIOR OF THE STOMACH IN RUMINANTS, SHOWING THE UPPER PLANE OF THE RUMEN AND
RETICULUM, WITH THE (ESOPHAGEAL FURROW.
A, Left sac of the rumen; B, anterior extremity of that sac turned back on the riaiht sac; C, its
posterior extremity, or left conical pouch ; G, section of the anterior pillar of the rumen ; g, g, its
two superior branches; H, posterior pillar of the same; h, h, h, its three inferior branches; I,
cells of the reticulum; J, oesophageal furrow; K, oesophagus; L, abomasum.
the rumen a strong prolongation, directed backwards, and to the left ; it is continued on the
superior wall by two branches, which separate at an acute angle. The posterior pillar (Fig.
269, h), more voluminous than the preceding, has three branches at each of its extremities— a
middle and two lateral. The middle branches are carried forwards on the limit of the two
sacs, which they separate from one another ; that from above meets the corresponding branch
from the anterior pillar. The lateral branches diverge to the right and left in describing a
curve, and in circumscribing the entrance to the conical cysts, which they transform into two
compartments distinct from the middle portion of the sac of the rumen; the inferior go to
meet the superior br-inches, but do not altogether join them.
The internal surf;\ce of the rumen is covered by a multitude of papillary prolongations,
dependencies of the mucous membrane. To the right, and in the culs-de-sac, these papillae
are remarkable for their number, their enormous development, and their general foliated shape.
On the left side they are more rare, particularly on the superior wall, and only form very
466 THE DIGESTIVE APPARATUS IN MAMMALIA.
small mammiform tubercles; they are absent on the muscular columns. Tliis papillary
arrangement is still more developed in certain wild Ruminants, and it is BCarcely possible to
give an idea of their rlclmess in the stomach of Gazelles.
The interior of the rumen offers for study two openings, situated at the anterior extremity
of the left sac : one is the oesophageal orifice, pierced in the superior wall, dilated into an
infundibulum, and prolonged into the small curvature of the reticulum by a particular furrow
(or channel), which will be described after tlie latter compartment; the other, placed below,
and opposite the preceding, traverses tlie bottom of the cul-dv-sac from before to behind, and
forms the communication between the paunch and reticulum : it is a very large opening, cir-
cumscribed below and on the sides by a septum or semilunar valve, resulting from the junction
of the parietes of the rumen with those of the reticulum.
Structure. — Like all the hollow organs in the abdomen, the rumen has three tunics: a
serous, a muscular, and a mucous.
The iierous envelops the organ throughout, except above, in front, and to the left, the point
which touches the sublumbar region, and the pillars of the diapiiragm, as well us the bottom
of the notches which separate the cuh-de-sac from the extremities. This membrane gives
origin, like that of the stomach of the Horse, to a vast duplicature — the great omentum. The
arrangement of this, which is somewhat difficult to observe in the Ox, in consequence of the
enormous weight of the gastric mass, is readily seen in the smaller Ruminants. It begins at
the middle of the faces of the paunch and the fissure intermediate to tlie two conical cysts,
forming a wide envelope that contains the right sac and the abomasum ; it becomes attached in
passing over the great curvature of the last-named cavity, and is confounded, superiorly and
posteriorly, with the great mesentery.
The muscular coat is very thick, and forms the internal columns of the viscus. Its fibres
are disposed in several layers, whose arrangement is simple, and offers nothing really interest-
ing to study, except in the points where the serous tunic passes from one cul-de-sac to another,
or from the rumen to the reticulum; there it is often accompanied by thin and wide muscular
fasciculi which, like the latter membrane, stretch over the intermediate fissures, and thus
become real unitive or common fibres.
The muscular fibres of the rumen present an unmistakable transverse striation — a very
rare physical characteristic in the muscular tissue of organic life.
The mucous membrane offers some peculiarities, which deserve a few words. The corium
is very thick, and probably contains some glands, but they must be extremely few. The free
face of the membrane is excessively uneven, in consequence of the papillary apparatus mentioned
above.
The papillae of the rumen are foliaceous, conical, fungiform. Those of the first description
are much more numerous than the others; they have the shapeof an oval, elongated leaf; their
summit is wide and rounded, and the base narrow and apparently implanted in the corium.
On one face is a little rib that springs from the base and disappears on the widened portion,
resembling the principal vein or nervule of a leaf. On the other face, opposite the vein, is a
faint longitudinal groove.
These papillae are constituted by a layer of nucleated connective tissue, covered by epitlie-
lium; the former, in the principal papillfe, has on its faces and extremities minute prolonga-
tions, resembling on a small scale the secondary papillae described as existing on the lingual
mucous membrane. In the centre of the papillae are one or two main arteries, derived from the
network of the corium. These pass, in a slightly flexuous manner, to the summit, and break
lip into several branchlets, succeeded by veins, that descend along the surface of the papilla
into each of its secondary prolongations.
The conical and fungiform papillae are few in the left sac, and resemble the papillae of the
same name described on the tongue.
The epithelium of the mucous membrane of the rumen is remarkable for its strength and
cohesiveness. It belongs to the category of stratified tesselated epithelium, and forms a sheath
to each papilla, covering the corium in the interpapillary spaces.
There are frequently found, in opening the rumen of animals just killecl, large exfoliated
patches on the surface of this layer. This is a sufficient indication if the activity of the
secretion of the epithelium, and the rapidity of its renovation.
Reticulum (Honeycomb) (Figs. 268, 269, 270). Situation— Form— Relations.— Thia, the
smallest compartment, is elongated from side to side, slightly curved on itself, and placed
transversely between the posterior face of the diaphragm, in one direction, and the anterior
extremity of the left sac of the rumen in the other ; the latter only appearing, externally, to
be a prolongation, or a diverticulum of the rumen.
It has two faces, two curvatures, and two extremities. The anterior face adheres to the
THE STOMACH.
467
tendinous centre of the diaphragm by connective tissue. The posterior face lies against the
anterior extremity of the rumen. The great inferior or convex curvature occupies the supra-
sternal region. The lesser, superior, or concave curvature partly corresponds to the lesser
curvature of the omasum. The left extremity is only separated from the rumen by a fissure,
which lodges the inferior artery of tlie reticulum. The right extremity formp a globular
cul-de-sac, in relation with the base of the abomasum.
Interior (Figs. 269, 270). — The internal surface of the reticulum is divided by ridges of
the mucous membrane into polyhedral cells, which, in their regular arrangement, look like a
honeycomb ; tliey are widest and deepest in the cul-de-sac, and become gradually smaller in
approaching the superior curvature. The interior of these cells is divided into smaller spaces,
included one within the other, by secondary and successively decreasing septa. The principal
septa offer on their free border a series of conical prolongations, with a rough hard summit ;
while their faces are studded with minute, blunt, or pointed papillsB. The secondary septa
also show similar prolongations ; and those on their free margin are even more developed than
on the chief septa. Lastly, from the
bottom of the cells spring up a crowd of
long, conical, and very pointed papillae,
resembling stalagmites in their arrange-
ment.
It maybe noted that the foreign bodies
so frequently swallowed by Ruminants,
are usually lodged in the reticulum;
therefore it is that at the bottom of the
cells are found either small stones, at 1
needles or pins — often fixed in the inte
mediate septa — or nails, scraps of iron, et..
The interior of the reticulum communi-
cates with the left sac of the rumen by
the orifice already described, and with
the omasum by a particular opening
placed near the middle of the small curva-
ture, though a little more to the right
than the left. This opening — eight or
ten times smaller than the preceding — is
connected with the infundibulum of the
cardia by a remarkable groove (or chan-
nel)— the oesophageal — which will be de-
scribed separately, as it does not properly
belong to the reticulum.
Structure. — The serous membrane does not cover all the anterior surface of the organ, as
the latter adheres to the posterior face of the diaphragm. The muscular tunic is much thinner
than that of the paunch, and more fasciculated. The fibres pass in the same direction. The
corium of the mucous membrane sends a prolongation into each of the septa of the alveoli,
and into each of the conical papillse on tiuse septa, or to the bottom of these alveoli. The
stratified pavement epithelium is very thick, and its horny layer is very developed at the
summit of the papillae.
In tl)e Camel, the reticulum does not form a compartment distinct from the rumen, and its
existence is only indicated by some deep cells in the anterior part of that cavity. The
entrance of the oesophagus into the rumen is oblique from left to right. The oesophageal furrow
Ib limited by two unequal lips, the posterior being only slightly prominent, especially in its
middle portion.
(Esophageal Groove (Figs. 268, 270, 271).— This furrow is so named because it appears
to continue the oesophagus to the interior of the stomach. It extends on the lesser curvature of
tliC reticulum from the c.irdia to the entrance of the omasum ; commencing in the rumen, it
belonsrs to the reticulum for the remainder of its extent. Measuring from six to eight inches
in length, this demi-canal is directed fiom above downwards, and from left to right, between
two movable lips, which are fixed by their adherent border to the superior wall of the reti-
culum. These two lips are thickened at their free margins, which look downwards and to
the left. At their origin at the oesophageal infundibulum, they are thin and but slightly
elevated; but they become thick and salient on arriving near the orifice of the oma.sum, which
orifice they surround, though they neitlier meet nor become confounded with each other
The mucous membrane covering these two lips is much corrugated outwardly and on the
ANTERIOR VIEW OF THK OX'S STOMACH (THE AN-
TERIOR WALL OF THE RETICULUM HAS BEEN
REMOVED TO SHOW THE (ESOPHAGEAL GROOVE).
A. (Esophagus ; B, left sac of the rumen ; C, right
sac ; D, reticulum ; d', interior of ditto; E, omasum ;
F, abomasum ; x, oesophageal groove ; Y, its pos-
terior lip; z, its anterior lip; v, opening com-
municating with the reticulum and omasum ; R,
spleen ; O, opening between the rumen and reti-
culum.
468
THE DIGESTIVE APPARATUS IN MAMMALIA.
free border ; but In the interior of the groove it poasesses all the characters of the oesophageal
mucous membrane, in being smooth, white, and ridged longitudinally ; near the orifice of the
omasum it has some large conical papillae.
If this membrane be removed to study the subjacent tissue, the following arrangement is
observed : At the bottom of the channel, and in the space comprised between its two lips, are
transverse muscular fibres, which belong to the rumen or reticulum. The lips themselves are
entirely composed of longitudinal muscular fasciculi, particularly abundant towards the free
border ; these fasciculi are mixed with the proper fibres of the stomach, towards the extremities
of the canal, and are carried from one lip to the other in forming loops around the orifices
which communicate by this canal.
Omasum (Psalterium, Many-plies, Many-leaves, or Manyplus. Figs. 268, 270, 271).— In
the Ox, this compartment is larger than the reticulum, but in the Sheep and G-oat it is smaller,
Fig. 271.
stomach of the sheep (seen from the interior of the omasum).
O, (Esophagus; P, rumen; R, reticulum; c, abomasum ; F, omasum opened at its large curvature,
the two portions being reversed forward and backward. 1, Opening between the rumen and
reticulum, surrounded by the extremity of the lips of the oesophageal furrow ; 2, opening between
the omasum and abomasum. i, Commencement of the small intestine.
Situation — Form — Relations. — Situated above the cul-de-sac of the reticulum and tha
anterior extremity of the right sac of the rumen, this compartment, when distended, has an
oval form, is slightly curved in an opposite direction to the honeycomb division, and depressed
from before to behind. It has, therefore, an anterior face, applied against the diaphragm, to
■which it is sometimes attached by connective tissue ; a posterior face lying towards the paunch :
a great curvature, turned upwards, and fixed in the posterior fissure of tlie liver by an omental
frsenum which is continued on the lesser curvature of- the abomasum and duodenum; a lesser
curvature, which looks downwards and responds to the recticulum ; a left extremity, exhibiting
the neck, which corresponds to the orifice of communication between the reticulum and omasum ;
THE STOMACH. 469
a right extremity, continuous with the base of the abomasum, from wliich it is separated by
a constriction analogous to that of the anterior extremity, but much less marked.
Interior. — This compartment shows, in its interior, the two apertures placed at its extre-
mities. The right orifice, opening into the abomasum, is much wider than the left, which
communicates with the reticulum. The cavity which these orifices bring into communication
with tlie adjoining compartments, offers one of the most curious arrangements met with in the
viscera ; it being filled by unequally developed leaves of mucous membrane, which follow the
length of the cavity. These leaves have an adherent border attached either to the great
curvature or to the faces of the organ, and a free concave border turned towards the lesser
curvature. They commence at the side of the orifice of the reticulum by denticulated ridges,
between which are furrows, and which are prolonged from the base of the leaves to the entrance
of the abomasum. At the latter aperture they disappear altogetlier, after rapidly diminishing
in height. Their faces are studded by a multitude of very hard mamillary papillse, resembling
grains of millet, which are more developed and conical on some of the leaves than others.
All these lamellar prolongations are far from being of the same extent ; twelve to fifteen are
so wide that their free border nearly reaches the lesser curvature of the viscus, and between
these principal leaves are others which, thoui<h regularly enough arranged, are more or less
narrower. At first there is remarked a secondary leaf, half the width of the chief ones,
Fig. 272.
it - ^ ^ 'll
SECTION OF THE WALL OF THE OMASUM OF THE SHEEP (FROM THE GREAT CURVATURE,
SHOWING THE ORIGIN OF THE LEAVES).
P, peritoneum; m, the two musular layers; e, epithelium. I, 1, Principal leaves at their origin;
2, secondary leaf; 3, 3, leaves of the third order; 4, denticulated lamina; 5, 5, two planes of
muscular fibres ascending into the principal leaves, some issuing from the muscular layer of the
between which it is placed ; then, on each of its sides, another, one-half narrower ; and, lastly,
at the base of these, two denticulated laminae more or less salient. In a general way, the
leaves which are inserted into the great curvature are tlie longest and widest ; and those
attached to the faces of the viscus become shorter and narrower as they draw nearer the lesser
curvature. The space comprised between these prolongations is always filled by very
attenuated alimentary matters, which are usually impregnated by a very small quantity of
fluid, but are also often dry, and sometimes even hardened into compact flakes.
Structure. — The serous layer is a dependency of the peritoneum, and offers nothing par-
ticular; it does not completely cover the anterior face.
The muscular tunic is much fasciculated, and thin. It is formed by two layers of fibres
■which do not pass in the same direction, and dependencies of this tunic pass into the substance
of the leaves which fill the cavity of this compartment.
The mucous membrane is remarkable for the thickness of its stratified tesselated epithelium;
all the leaves are formed by two layers of this membrane, laid one against the other ; and
as their structure is interesting, we will notice it.
The principal leaves are composed of this duplicature of mucous membrane, and two
layers of muscular fibres between ; these layers are opposite each other at the commencement
of the leaf, and separated by a tr.msverse vessel; in the remainder of their extent they are
kept apart by the vessels that pass towards the border of the leaf. Their fibres are detached
from the surface of the muscular tunic and, at certain points, from its deep layer. In the
470
THE DIGESTIVE APPARATUS IN MAMMALIA.
smaller leaves there appears to be only one layer of muscular fibres ; on all the leaves are
various-sized papillae, the smallest of which are like a grain of millet, and have for base a
mass of condenser! connective tissue, the superficial fibres of which form a kind of shell (Fig.
273) ; the largest are club-shaped. They receive blood-vessels, and we have found in the
connective tissue which constitutes their basis, elements with a somewhat irregular outline,
provided with nuclei, which we considered to be nerve-cells (Fie;. 274).
The omasum in the Camel shows deep areolae instead of leaves, and the openijjg with
the abomasum is relatively very narrow.
Abomascm (Reed or Renxet. Figs. 268, 269, 270, 271). Situation— Form — Relations. —
The abomasum stands next to the rumen for capacity. It is a pyriform reservoir, curved on
itself, elongated from before to beliind, and situated behind the omasum, above the right sac
of the rumen. On the right it touches the diaphragm and the hypochondriac ; on the left it
is related to the rumen. The greater curvature, turned downwards, receives the insertion of
the great omentum. The lesser curvature, inclined upwards, gives attachment to the serous
band already noticed when speaking of the great curvature of the omasum. Its base is in
contact with the cul-de-sac of the reticulum, and is separated from the omasum by the con-
striction in tlie form of a thick neck, which corresponds to the communicating oritice of the
two stomachs. Its point, directed upwards and backwards, is continued by the duodenum.
Interior. — This being the true stomach of Ruminants, tlie mucous membrane lining its
interior acquires all the characters which distinguish that of the stomach of the Carnivora,
or that of the right sac of the Horse's stomach. It is soft, spongy, smooth to the touch,
vascular, red-coloured, covered by a thin epithelium, and provided with numerous glands for
SECTION OF A LEAF OF THE OMASUM.
1, 1, Muscular planes; V, vessel; 2, epithe-
lium; 3, 3, small-sized papillae, round and
hard.
LONGITUDINAL SECTION OF A LARGE PAPILLA
FROM THE OMASUM, SHOWING NERVE-CELM
IN ITS INTERIOR.
the secretion of the gastric juice. Thinner than in monogastric animals, this tenuity is com-
pensated for by a much greater extent of surface, which is still further increased by numerous
lamellar folds. These latter are analogous in constitution to tliose of the omasum, cross in a
very oblique manner the great axis of the abomasum, and altogether affect a kind of spiral
arrangement.
The abomasum has two openings : one, situated at its base, opens into the omasum ; the
other, placed opposite to the first, and much narrower, is the pylorus, which is circumscribed,
as in the other animals, by a muscular ring.
Structure. — The serous membrane is continuous with the omenta tiiat abut on the great and
lesser curvatures of the viscus. The muscular layer is of the same thickness as in the omasum.
The internal tunic has already been noticed.
Functions of the Stomach in Ruminants. — We cannot pretend to give here a complete
history of the phenomena of rumination, but must confine ourselves to describe in a few words
what are the principal attributes of each gastric dilatation.
The rumen is a sac where the aliment taken during feeding-time is kept in reserve, and
whence it is again carried into the mouth during rumination, after having been more or less
softened.
The reticulum participates in the functions of the rumen, to which it is only a kind of
diverticulum. But it is particularly with regard to liquids that it plays tlie part of a reservoir ;
the solid sub.stauces contained in it being always diluted by a large quantity of water.
The oesophageal groove carries into the omasum the substances swallowed a second time
after rumination, or even those which the animal ingests in very small quantity for the first
time.
THE INTESTINES. 471
The omasum completes the trituration and attenuation of the food, by pressing it between
its leaves.
The abomasum acts as a true stomach, charged with the secretion of the gastric juice ; in
this reservoir occur the essential phenomena of gastric digestion.
Comparison of the Stomach of Man with that op Animals.
In its form, the stomach of Man much resembles that of the Caruivora.
The insertion of tlie oesophagus, however, does not offer so large an infundibulum. The
organ is situated in the left hypochondriac, and is nearly horizontal.
Everywhere the mucous membrane is red and glandular; the muscular fibres are disposed
in three planes, as in Solipeds, but the third is found only in the middle portion of the stomach,
two alone being present towards the cardia and pylorus; where the stomach is largest the
contractile tunic is thinnest.
The Intestines (Figs. 275 to 283).
The alimentary canal is continued from the stomach, in the abdominal
cavity, by a long tube doubled on itself a great number of times, and which
terminates at the posterior opening of the digestive apparatus. This tube is
the intestine. Narrow and uniform in diameter in its anterior portion — which
is named the small intestine — it is irregularly dilated and sacculated in its
posterior part — the large intestine. These two portions of a whole, so markedly
defined in all the domesticated Mammals, are but imperfectly distinguished
from one another with regard to the digestive phenomena occurring in their
interior. We will study them in all the animals which interest us, and conclude
by a general and comparative examination of the entire abdominal portion of
the digestive canal.
Preparation. — The study of the intestines does not demand, properly speaking, any special
preparation; it being sufficient to incise the inferior wall of the abdomen to expose these
viscera. As their mass, however, is heavy and unmanageable, it is advisable to expel their con-
tents in a manner similar to that recommended for the preparation of the stomach : a puncture
at the point of the caecum allows the escape of the substances accumulated in that reservoir;
those which fill the large colon may be removed by an incision made towards the pelvic curva-
ture, and those in the floating colon by the rectum. The small intestine mny be evacuated by
three or four openings at about equal distances in the length of the viscus. Having done this,
inflate the intestines to somewhat of their natural volume ; this preparation then permits the
general arrangement of the intestinal mass in the interior of the abdomen to be easily studied.
It would be well to remove the entire mass altogether from the body, and lay it out on a
table, so as to isolate the various parts, study them in succession, and note their form.
In order to study the structure of a portion of the intestine, it si ould be treated as was the
stomach — plunged into boiling water for a few minutes, then the serous and mucous membranes
removed.
1. The Small Intestine (Figs. 282, 283).
Length — Diameter. — The small intestine is a long tube, which, in a horse of
ordinary height, may average about 24 yards in length, and from 1 to If inches
in diameter. This diameter is susceptible of variation, according to the state of
contraction of the muscular tunic of the viscus.
Form. — This tube is cylindrical, doubled on itself, and presents two cur-
vatures— one convex., perfectly free ; the other concave, named the small
curvature, which serves as a point of insertion for the mesentery that sustains
the organ. Removed from the abdominal cavity, freed from the serous folds
which suspend it, and distended by air or water, this disposition of the small
intestine naturallv causes it to twist in a spiral manner.
472 THE DIGESTIVE APPARATUS IN MAMMALIA.
Course and Relations. — The small intestine commences at the right cul-de-sac
of the stomach, from which it is separated by the pyloric constriction. At its
origin it presents a dilatation which, in form, closely simulates a small stomach,
the curvatures of which are the inverse of those of the proper stomach. Placed
at the posterior face of the liver, this expansion, or head, of the small intestine
begins the narrower portion, which at first is directed forward, then bends
suddenly backward — thus forming a loop investing the base of the cacum on
the right side ; then it is carried to the left in crossing, transversely, the sub-
lumbar region, behind the. great mesenteric artery ; here it is joined to the
origin of the floating colon by a very short serous frasnum. It then reaches the
left flank, where it is lodged, and where it forms numerous folds that are freely
suspended in the abdominal cavity among the convolutions of the small colon.
The terminal portion of this conduit, which is easily recognized hj the greater
thickness of its walls and its smaller diameter, disengages itself from these
convolutions to return to the right, and opens into the concavity of the caecum,
below, and a little to the inside of, the point where the large colon has its
commencement.
In the language of the schools, this terminal portion is named the ileum
(eiXetv, " to twist ") ; the part which is suspended in the left flank, and which forms
the principal mass of the intestine, is designated the jejunum {jejunas, " empty ") ;
and the curvature formed by this viscus at its origin, from the pylorus to the
great mesenteric artery, is termed the duodenum (twelve fingers' breadth).
This classical division is, however, altogether arbitrary, and scarcely deserves
to be retained. It would be better to divide the intestine into a Jixed or
duode7ial, a,nd a. free or Jloating portion.
Mode of attachment. — The small intestine is maintained in its position, at its
extremities, by the stomach and the ctecum. But its principal means of fixation
consists in a vast peritoneal fold, which, from its use, is named the mesentery
(jjLeaov, evrepov, " mediate " or " middle ").
This serous layer presents a very narrow anterior part which sustains the
duodenum, and fixes it in such a manner as to prevent its experiencing any
considerable displacement. Continuous, in front, with the gastro-hepatic
omentum, this portion of the mesentery is successively detached from the base
of the liver, the inferior aspect of the right kidney, or even from the external
contour of the base of the ctecum, and, lastly, from the sublumbar region, to
be soon confounded with the principal mesentery. This becomes wider as it
approaches the enseal extremity, and arises, as from a centre, from the outline
of the great mesenteric artery, to spread in every direction, and is inserted into
the small curvature of the floating portion of the viscus. The great length of
this insertion causes it to become extended in a spiral or screw-like manner,
around its point of origin. It may be remarked that the terminal extremity of
the intestine is retained between the two serous layers of the mesentery, to a
certain distance from its free border. This peritoneal fold consequently forms
at this point— at the side opposite to its insertion into the intestinal tube — a
particular fr^enum, which is observed to be carried to the anterior face of the
caecum.
Interior.— The interior of the small intestine shows longitudinal folds, which
are effaced by distension, except towards the origin of the duodenal portion^
Those met with in this situation possess all the characters of the ralvulce
connivenfes {valves of Kerkring) in Man ; they resist traction on the intestinal
THE INTESTINES. 473
membranes, and are formed by two mucous layers laid together, with a plentiful
supply of connective tissue between them.
The internal surface of the small intestine also oflfers for study a multitude of
villosities and glandular orifices, or follicles, which will be noticed hereafter. It
communicates with the inner surface of the stomach by the pyloric orifice, and
with that of the caecum by means of an opening which projects into the interior
of that reservoir, like a tap into a barrel. This projection, which is not very
marked, is formed by a circular mucous fold, strengthened externally by muscular
fibres, and is named the ilio-cmal valve or valvula Bauhini. Two additional
orifices open on the surface of the small intestine in its duodenal portion, from 5
to 8 inches from the pylorus : one is the orifice common to the biliary and
principal pancreatic duct, the other that of the accessory pancreatic duct.
Stkucture. — The wall of the small intestine, like that of the other hollow
viscera in the abdominal cavity, is composed of three tunics : —
1. Scrolls membrane. — This envelops the organ everywhere, except at its
small curvature, which receives the insertion of the mesentery ; it adheres
closely to its surfaces and the great curvature.
2. JIuscular membrane. — Covered internally by a layer of condensed connec-
tive tissue (which is sometimes considered a fourth tunic), this middle membrane
has two planes of fibres — one, superficial, is formed of longitudinal fibres
uniformly spread over the whole sui-face of the viscus ; the other, deep, is
composed of circular fibres, which are a continuation of those of the pyloric
ring.
3. 3Iucous membrane. — This tunic, extremely interesting to study, is soft,
spongy, highly vascular, very dehcate, and of a reddish-yellow colour. Its
external face is loosely adherent to the muscular membrane, and its free face
exhibits the villi, and the glandular or follicular orifices already noticed.
It comprises, in its structure, an epithelial lining, and a mucous dermis or
corium.
The epithelial layer is formed of a single row of spheroidal cells, implanted,
by their summit, which is often ramifying, in the surface of the dermis, and
lining the interior of the orifices which open on the inner face of the membrane.
The base of these cells has an amorphous cushion, which, when they are all
united, appears like a thin layer spread on the inner surface of the intestine.
Their protoplasm is frequently fenestrated or reticulated (Renaut) ; and among
the ordinary spheroidal cells, some calyciform cells are met with here and there.
The mucous dermis is thick and loose in its deeper portion, and is constituted
by fasciculi of connective tissue, mixed with elastic fibres, and lymphoid elements.
On its free surface it exhibits projections [villosities) and depressions (follicles),
which correspond to the glands. It has a muscular layer, the unstriped fibres of
which are arranged in a similar manner to those of the muscular coat of the
intestine. Lastly, it contains follicles, and vascular and nervous networks. "We
will study each of these.
The villi are the foliated or conical appendages, which are found to be
most developed in the shortest portion of the intestine. In Birds and the
Carnivora they attain their maximum length ; while in Ruminants they are in a
rudimentary state, though, whatever may be their dimensions, they are always
visible to the naked eye. Their number is considerable, and they have been
justly compared to the pile of velvet. In structure, they are each formed by a small
mass of connective tissue, in the centre of which is a chyliferous vessel or several
^4
TEE DIGESTIVE APPARATUS IN MAMMALIA.
vessels, with a magnificent network of peripheral capillary blood-vessels ; the
whole being enclosed in a complete epithelial sheath.
Fig. 275.
A. VILLI OF MAN, SHOWING THE BLOOD-VESSELS AND LACTEALS. B. VILLUS OF A SHEEP.
Fig. 276.
The orifices opening on the intestinal mucous membrane belong either to
Brunner's (duodenal) glands, or to those of Leiberkiihn (simple foil ides).
Brunner's glands form a continuous layer
beneath the duodenal mucous membrane.
They are tubular glands, ramifying and
fiexuous, which open on the surface of the
mucous membrane, either by a special ex-
cretory canal, or through the medium of a
Lieberkiihn's gland. (These glands secrete
a clear alkaline mucus, which contains no
formed elements, such as cells or nuclei.)
The glands {cryptce mucosa') of Lieher-
kiihn or Galeati are placed in the substance
of the mucous membrane, and are distin-
guished by their microscopical dimensions,
their considerable number, and their tubular
form, which has caused each of them to be
compared to the finger of a glove ; they
are implanted perpendicularly in the mem-
brane, and open on its free surface. They are found throughout the whole extent
of the intestine, and are lined with spheroidal epitheUum.
The solitary glands or follicles (glandulm solitarice, or lenticular glands) are
PORTION OF ONE OF BRUNNER S GLANDS.
THE INTESTINES.
475
round, salient bodies, visible to the naked eye. They are somewhat rare in the
small intestine, but are more abundant at the posterior portion of the large
intestine. They are formed by a mass of lymphoid elements, enveloped in some
condensed fasciculi of connective tissue. Around them the mucous membrane is
slightly umbilicated, and is destitute of villa and tubular glands, though these
are arranged in a circle around the follicles, to form the coronce tubulorum. (The
solitary glands usually contain a cream-Uke secretion, which covers the villi on
their free surface.)
The aggregated follicles (glandulce agminatce) are nothing more than solitary
glands collected together in a limited space, where they constitute what are
Fig. 277.
PERPENDICULAR SECTION THROUGH ONE OF PEYER'S PATCHES IN THE LOWER PART OF THE
ILEUM OF THE SHEEP.
a, a, Lacteal vessels in the villi ; h, b, superficial layer of the lacteal vessels (rete angustum) ; c, e,
deep layer of the lacteals {rete amplum); d, d, efferent vessels provided with valves; e, Lieber-
kiihn's glands ; /, Peyer's glands ; g, circular muscular layer of the wall of intestine ; h, longi-
tudinal layer ; i, peritoneal layer.
known as the glands of Pei/er or of PecMin, Peyer's patches, or the honeycomb
glands. Absent in the duodenum, and even at the commencement of the jejunum,
these glands are about a hundred in number, and are very irregularly placed on
the internal surface of the intestine at its great curvature, on the side opposite to
the mesentery. Their form is oval or circular, and the smallest scarcely measure
more than some few hundredths of an inch square, while the diameter of the
largest increases to 1| inch.
(Each of these patches is composed of a group of small, round, whitish
vesicles, covered with mucous membrane ; these vesicles consist of a moderately
thick external capsule, having no excretory canal, and containing a similar
secretion to that in the solitary follicles. They are surrounded by a zone or
band of simple follicles, and the spaces between them are covered with villi.
476
THE DIGESTIVE APPARATUS IN MAMMALIA.
The vesicles are usually closed ; though it is supposed they open at intervals to
discharge their secretion. The mucous and submucous coats of the intestine
are intimately adherent and highly vascular, opposite the Peyerian glands.)
Fig. 278.
Fig. 279.
PERPENDICULAR SECTION THROUGH THE INTESTINAL WALL TO SHOW A SOLITARY FOLLICLE.
a, Lieberkiihnian glands; 6, solitary follicle; c, lacteal vessels surroundiag, but not penetrating,
the follicles ; d, large efferent vessels, provided with valves.
4. Vessels and nerves. — The small intestine receives its arteries almost ex-
clusively from the great mesenteric artery. One, which goes to the duodenum,
comes from the coehac trunk. These arteries form a submucous network, from
which branches pass inwards and outwards, the first to
the muscular and serous tunics, the second to the glands
and the villi. A tubular network surrounds each
Lieberkiihnian gland, and is observed in each villus ;
while a spherical reticulation surrounds each solitary
follicle, loops being given off which penetrate nearly to
the centre of the follicle.
The veins have the same arrangement, and finally
enter the vena portse.
The lymphatics constitute three superposed networks
in the mucous membrane. The first is situated around
the glandular orifices ; it receives the central lacteal from
each villus ; the second is placed between the glandular
and the muscular layer of the mucous membrane ; the
third lies in the deep portion of the membrane, and
communicates with the meshes encircling the solitary
glands. The largest emergent vessels from these three
networks pass through the wall of the intestine, accom-
panying the blood-vessels between the layers of the mesentery, enter the mesenteric
glands, and terminate in the reservoir of Pecquet {receptaculum chyli). There
is another lymphatic network in the muscular tunic of the intestine.
'"^miiim
VILLI OF INTESTINE, WITH
THEIR CAPILLARY PLEXUS
INJECTED.
THE INTESTINES.
477
The nerves are from the solar plexus ; they form a submucous plexus
(Meissner's plexus) and a mtjenteric plexus {Auerbach's plexus), comi^vmed between
the two planes of jhe muscular tunic.
Numerous microscopic ganglia are found on the course of these plexuses.
Development. — The small intestine appears at an early period in the foetus,
and during the foetal existence of Ruminants preserves a very remarkable
predominance over the large intestine — a predominance equally marked in the
vessels it receives ; for in a foetus of five months, we have found the collective
arteries of the small intestine equivalent to about ten times the volume of those
of the caecum and colon.
Functions. — It is in the small intestine — under the influence of the hepatic,
pancreatic, and intestinal secretions — that are carried on those transformations
Fig. 280.
Fig. 281.
HORIZONTAL SECTION THROUGH THE MIDDr.E PLANE OP
THREE PEYERIAN GLANDS, SHOV?ING THE DISTRIBU-
TION OF THE BLOOD-VESSELS IN THEIR INTERIOR.
DIAGRAMMATIC REPRESENTA-
TION OF THE ORIGIN OF THE
LACTEALS IN A VILLUS.
e, Ceutral lacteal ; d, connec-
tive-tissue corpuscles with
communicating branches;
c, ciliated columnar epithe-
lial cells, the attached ex-
tremitins of which are di-
rectly contiguous with the
connective tissue corpuscles.
that constitute the digestive function. It is also in this intestine that the
absorption of the nutritive prmciples and fluids commences, and in which the
villi are the essential organs.
2. The Laege Intestine.
The large intestine commences by a vast reservoir in the form of a cul-de-sac^
named the cmcum. It is continued by the colon, the posterior extremity of which
is succeeded by the rectum. It is separated from the small intestine by the ileo-
cecal valve.
A. C^cuM (C^cuM Caput Coli) (Figs. 282, 283).
Situation — Direction. — This is a very wide and elongated sac, occupying the
right hypochondriac, where it affects an oblique direction downwards and back-
wards.
33
478 THE DIGESTIVE APPARATUS IN MAMMALIA.
Dimensions — Capacity. — Its length is ordinarily a little over three feet, and it
will contain, on an average, about 7^ gallons of fluid.
For)72 — External surface. — The elongated sac formed by the cfecum is conical
in shape, terminating in a point inferiorly, and bulging and curved like a crook
superiorly. Externally, it exhibits a great number of cii'cular furrows, interrupted
by longitudinal muscular bands, four of which are observed in the middle portion
of the organ ; they disappear towards its extremities. The bottom of these
furrows necessarily corresponds to the internal ridges, and these can be made to
disappear by destroying the longitudinal bands, which considerably lengthens the
caecum ; thus showing that these transverse puckerings are due to the presence of
the riband-like cords, and have for their object the shortening of the intestine
without diminishing the extent of its surface.
Relations. — To study its relations, the caecum is divided into three regions : —
1. The superior extremity., base, arch, or still better, the crook, shows in the
concavity of its curvature, wliich is turned forwards, the insertion of the small
intestine and origin of the colon. Placed in the sublumbar region, it is related,
superiorly, to the right kidney and the pancreas, through the medium of an.
abundant supply of connective tissue. Outwardly, it touches the parietes of the
right flank, and is encircled by the duodenum. On the inner side, it adheres by
connective tissue to the termination of the large colon, and is in contact with the
convolutions of the small intestine.
2. The middle portion is in contact, inwardly, with the same convolutions and
the large colon ; outwardly, with the cartilages of the false ribs, in following their
curvature.
3. The inferior extremity, ox point, usually rests on the abdominal prolongation
of the sternum ; but as it is free and can move about in every direction, it often
happens that it is displaced from this situation.
Mode of attachment. — The cfecum is fixed to the sublumbar region and the
terminal extremity .of the large colon, by a wide adherent surface. All around
this surface, the peritoneum^which constitutes the serous covering of the caecum —
is gathered into folds, and in passing from the caecum to the origin of the colon,
this membrane forms a particular short and narrow frsnum, designated the
meso-ccecum.
Interior. — Viewed internally, the caecum offers for study the mhndce, or
transverse ridges corresponding to the external furrows. "We have already seen
that these are due to simple circular folds, comprising in their thickness the
three tunics of the organ, and that they can be effaced by distension, to reappear
afterwards in varying number and position— differing widely, in this respect,
from the valvules conniventes of the small intestine.
Two orifices, placed one above the other, open on the internal surface of the
caecum, at the point corresponding to the concavity of the crook. The most
inferior represents the terminal opening of the small intestine at the centre of
the ilio-ccBcal valve, the presence of which in the domesticated animals has, in
consequence of a wrong appreciation of analogies, been denied ; it is nothing
more than the projection described as being made by the terminal portion of the
small intestine. The second opening, placed about 1| or 2 inches above the
preceding, and puckered around its margin, establishes a communication between
this viscns and the colon. If this opening be compared with the capacity of the
canal that begins from it, it will be remarked that it could scarcely be narrower.
Structure. — The serous tunic does not call for any notice, beyond that
THE INTESTINES.
479
already given when speaking of the attachments proper to the cgecum. The
muscular tunic is formed of circular fibres, crossed externally by longitudinal
bands, which maintain the organ in transverse folds. The mucous membrane is
thicker than that of the small intestine, and is also distinguished from it by the
absence of the Brumierian and agminated glands. It has, however, the solitary
follicles and crypts of Lieherkiikn, as well as some few intestinal villi. The blood-
vessels are the ccecal arteries and veins. The lymphatics pass to the sublumbar
receptacle ; the nerves are derived from the great mesenteric plexus.
Functions. — The csecum serves as a reservoir for the enormous quantities of
fluid ingested by herbivorous animals. The greater part of this fluid in its rapid
Fig. 282.
GENERAL V/EW OF THE INTESTINES OF THE HORSE (SEEN FROM THE RIGHT SIDE, WITH THE
PELVIC FLEXURE AND A PORTION OF THE SMALL INTESTINE CARRIED BEYOND THE
ABDOMINAL CAVITY).
a, CEsophagu'j; 6, right sac of the stomach; c, small intestine, showing its origin or duodenal por-
tion, encircling the base of the caecum ; d, caecum ; e, origin of the large colon ; /, first portion
of the large colon ; g. supra-sternal flexure ; h, second portion of the large colon ; i, pelvic flexure;
j, third portion of the large colon; k, diaphragmatic flexure; I, fourth portion of the large colon;
m, termination of the free colon; n, rectum; o, mesentery proper; p, colic mesentery (meso-
colon) ; q, anus ; r, internal inguinal ring ; s, spermatic vessels ; t, deferent canal ; u, bladder ; v,
vesiculse seminales; x, pelvic enlargement of the vas deferens; y, prostate; z, suspensory
ligament of the penis.
pastage through the stomach and small intestine, escapes the absorbent action
of the villi and accumulates in the Cfecum, into which it may be said to wash
the alimentary mass it comes in contact with ; it thus dissolves the soluble
and assimilable matters this mass may yet contain, and so favours their entrance
into the circulation, through the immense absorbing surface formed by the
mucous membrane of the large intestine.
The aliment undergoes still further change, and digestion is completed in
this viscus, principally in the Herbivora.
B. Colon.
The colon is divided into two portions, which differ from each other in
480
THE DIGESTIVE APPARATUS IN MAMMALIA.
volume, and in the disposition they affect in the abdominal cavity. The first
is the lame or double colon; the second, the small, single, ov floating colon.
A, The duodenum as it passes
behind the great mesen-
teric artery ; B, free por-
ti'in of the small intes-
tine; C, ileo-cascal portion ;
D, caecum ; E, F, G, loop
formed by the large colon;
G, pelvic flexure ; f, f,
point where the colic loop
is doubled to constitute
the supra-sternal and dia-
phragmatic flexures; 1,
posterior aorta; 2, 2,
arteries to the small in-
testines , 3, ileo-cascal
artery; 4, superior csecal
artery; 5, inferior csecal
artery ; 6, artery of the
arch of the csecum ; 7,
right colic artery , 8, left
or retrograde colic artery ;
9, first artery of the single
colon.
GEKERAL VIEW OF THE HORSE's INTESTINES (THE ANIMAL IS PLACED ON ITS BACK, AND THE
INTESTINAL MASS SPREAD OUT).
THB INTESTINES. 48i
The Laege or Double Colon (Figs. 282, 283, 284). — This intestine begins
at the caecum, and terminates by suddenly contracting at the origin of the small
colon.
Length — Capacity. — It is from about 10 to 13 feet in length, and has a
medium capacity equal to 18 gallons.
Form — General arrangement. — Removed from the abdominal cavity, and
extended on a table or on the ground, this portion of the intestine appears as
a voluminous canal, offering a succession of dilatations and contractions ; its
surface being traversed by longitudinal bands, and sacculated and furrowed
transversely for a great part of its extent, exactly like the caecum. It is also
doubled in such a manner as to form a loop, the two branches of which are of
equal length, and are held together by the peritoneum, which is carried from
Fig. 284.
THE COLON OF THE HORSE.
1, First portion ascending to form the supra-sternal flexure ; 2, second portion descending to form
the pelvic flexure, 7 ; 3, 6, longitudinal muscular bands; 4, point of the caecum, 5; 8, duodenum;
9, small intestine.
one to the other ; so that the terminal extremity of the large colon returns
towards the point of its origin.
But this colic flexure, owing to its length, could not be contained m the
abdomen ; and it is therefore doubled in its turn from above to below, and from
right to left (at the points f, f, in Fig. 283), forming curvatures which will be
noticed presently. From this circumstance, it results that the large colon,
studied in the abdominal cavity, is divided into four portions lying beside each
other in pairs ; so that a transverse section of that cavity, made in front of the
base of the csecum, would give for this intestine the results indicated in Fig. 285.
Course and Relations. — In following the course of the large colon from its
origin to its termination, in order to study its four portions in their normal
relations, the following is observed : —
Commencing from the arch or crook of the caecum, the colon is directed
forwards, above the middle portion of that reservoir, which it follows to its point.
Arrived at the posterior face of the diaphragm at its most declivitous part, it bends
downwards and to the left, forming its first sternal ox supra-sternal flexure, because
482 THE DIGESTIVE APPARATUS IN MAMMALIA
it rests on the xiphoid cartilage of the sternum (Fig. 282, g). Here begins the
second portion of the viscus, which is in immediate contact with the inferior
abdominal wall, and extends backwards into the pelvic cavity, where it is
inflected to the left to constitute the sigmoid or pelvic flexure. This curvature —
the centre of the colic loop — is in relation with the rectum and bladder, as well
as with the deferent canals, or the uterus and ovaries, according to the sex. It is
succeeded bj the third portion of the colon, which is carried forward, above, and
to the left of the preceding. Bound to the second division by peritoneum and con-
nective tissue, this new section reaches the tendinous centre of the diaphragm, and
is then doubled upwards and to the right. The flexure arising from this third
duplicature is called the diaphragmatic, because of its relations with the musculo-
aponeurotic membrane that partitions the great cavity of the trunk, or the gastro-
kepatic curvature, in consequence of its lying equally
Fig. 285. against the liver and stomach (it is also designated the
sigmoid flexure) (Fig. 282, k). To this flexure succeeds
the fourth and last portion of the large colon, bound to
the first portion, as the second is to the third. This
extends, posteriorly, to the base of the caecum, where it
terminates in a sudden contraction, and is continued by
the small colon ; it occupies the sublumbar region, and,
through the medium of connective tissue, is applied
against the inferior face of the pancreas and the inner
PLAN OF THE COLON. sidc 01 thc c^cal arcn.
Mode of attachment. — The large colon can be easily
displaced in the abdominal cavity. It is nevertheless fixed : 1 . By its origin, to
the cfficum and to the serous frsenum which attaches it to that receptacle. 2.
By the adherence of its terminal portion to the pancreas and arch of the caecum.
8. By the meso-colon. The latter ligament forms, in the concavity of the pelvic
flexure, a kind of racket, the handle of which is prolonged to a short distance
between the two branches of the colic flexure. Beyond this, these two branches
are directly placed side by side.
External surface. — "We have seen that the large colon does not offer the same
diameter everywhere, and that it is sacculated, plicated, and traversed by longi-
tudinal bands ; it is, however, important to study in detail this disposition of its
external surface in each of the regions already named.
At its origin, the large colon is extremely narrow, and scarcely equal to the
small intestine. But it soon dilates and assumes a considerable volume, which
it preserves beyond the pelvic flexure. It then becomes progressively constricted
to the middle of its third portion, where the diameter, reduced to its minimum,
is yet much greater than at the origin of the first portion. Near the diaphragmatic
flexure, it is again gradually dilated, and finishes by acquiring, near its
termination, the greatest volume it has yet exhibited. The muscular bands
which maintain its transverse folds throughout the whole extent of its first
dilated portion, are four in number. Three disappear in arriving towards the
pelvic curvature, and the only one remaining is that which is placed in the
concavity of that curvature. At the second dilatation there are three bands,
' "We have, in some instances, found the large colon doubled on itself in an inverse sense—
the second and third portions being placed above and in front of the first and fourth, with the
pelvic flexure touching the sublumbar region, in front of the caecum, and the point of the latter
directed back towards the pelvis.
THE INTESTINES. 483
two of which are prolonged to the floating colon. The transverse folds formed
by these flat bands are but faintly marked towards the pelvic curvature, and are
altogether absent in the narrow portion succeeding it ; it is only in the whole
extent of the first dilatation that they are deepest and most numerous.
Liternal surface. — This is exactly like that of the caecum.
Structure. — The serous membrane envelops the whole of the colon, except in
those places where it comes in contact with itself or with other viscera. So it
iiappens that the peritoneum, in passing from the sublumbar region to the last
portion of the colon, does not cover the surface, which adheres by connective
tissue to the inferior aspect of the pancreas and csecum ; neither, in being carried
from one branch of the colic flexure to the other, does it envelop their opposed
sides, except at the pelvic flexure, where it forms the meso-colon.
The muscular tunic does not differ in its arrangement from that of the
caecum ; neither does the mucous membrane. The arteries emanate from the
great mesenteric ; they are the two colic arteries. The two satellite veins soon
form a single trunk, which enters the vena portae. The lymphatics empty them-
selves into Pecquet's reservoir. The nerves emerge from the great mesenteric
plexus.
The Small, Single, or Floating Colon (Fig. 282). — This is a sacculated
tube, which succeeds the large colon, and is terminated in the pelvic cavity
by the rectum.
Length — Form — Course — Relations. — It is about 10 feet in length, and is
arranged in a similar manner to the small intestine, except that it is double the
size of that viscus, is regularly sacculated on its surface, and is provided with
two wide and thick longitudinal bands, one on the side of its great, the other on
its small, flexure. Arising from the terminal extremity of the large colon, to the
left of the cfficum, where it is related to the termination of the duodenum, and
where it receives the insertion of the great omentum, this intestine is lodged in
the left flank, forming folds which are mixed with the convolutions of the small
intestine. It afterwards passes into the pelvic cavity, to be directly continued by
the rectum.
Mode of attachment. — Floating like the small intestine, the small colon is
suspended by a serous layer, exactly similar to the mesentery proper, though
wider, and named the colic mesentery. This mesentery is detached from the
sublumbar region, not from around a central point, but from a line extending
from the great mesenteric artery to the interior of the pelvic cavity. It is
narrower at its extremities than in its central portion.
Interior. — The interior of the floating colon shows valvular folds, analogous
to those of the csecum and large colon. It is in the intervals between these that
the fgecal matters are moulded into balls.
Structure. — The serous membrane is without special interest, and the
muscular tunic is similar to that of the large colon. The mucous membrane is
also the same. These membranes receive their blood by the small — and a
branch of the gi'eat — ynesenteric artery. A venous trunk, passing between the
layers of peritoneum forming the mesentery, carries back the blood to the vena
portae. The lymphatics are nearly as fine and numerous as those of the small
intestine ; they enter the same confluent — the reservoir of Pecquet.
Functions of the Colon. — In this intestine is accomplished the absorption
of fluids, and of soluble alible matters. When the alimentary mass arrives in
the small colon, deprived of its assimilable principles and charged with excretory
484 TEE DIGESTIVE APPARATUS IN MAMMALIA.
substances thrown out on the surface of the intestinal tube, it loses its name and
receives that of excremejtt or J(eces. This excrement, compressed by the peri-
staltic contractions of the muscular tunic, is divided into httle rounded or oval
masses, which find their way to the rectum, where they accumulate, and whence,
in due course, they are expelled.
C. Rectum (Fig. 282).
The rectum extends, in a straight line, from the entrance to the pelvic
cavity to the posterior opening of the digestive canal, or amis. It is nothing
more, properly speaking, than the extremity of the small colon, the limit which
separates them being somewhat arbitrary ; it differs from that viscus, however,
in having no bulgings, and in its walls being thicker and more dilatable ; so that
it can be distended into an elongated pouch, and form a reservoir or receptacle
for the excrementitious matters until they are expelled.
Relations. — It is related, superiorly, to the roof formed by the os sacrum ;
inferiorly, to the bladder, the deferent canals, vesiculse seminales, prostate gland»
Cowper's glands, or to the vagina and uterus ; laterally, to the sides of the
pelvis.
Mode of attachment. — There ought to be considered as such : 1. The posterior
extremity of the colic mesentery, representing the meso-redum. 2. An orbicular
fold, constituted by the peritoneum in its circular reflection around this viscus
at the extremity of the pelvic cavity. 3. The suspensory ligaments of the penis,
which, joining under the rectum, form a ring encircling the posterior extremity
of the intestine (see Fig. 282 and the description of the penis). 4. A thick,
triangular band, comprising two lateral parts, and composed of white muscular
fibres ; this band, which is really a prolongation of the muscular tunic of the
viscus, is detached from the rectum above the anus, and is attached to the
inferior aspect of the coccygeal bones, between the inferior sacro-coccygeal
muscles, where its outline can be seen beneath the skin when the tail is elevated.
Stkuctuee. — The serous membrane does not envelop the whole of the
rectimi, that portion which traverses the bottom of the pelvic cavity being left
uncovered by it. The muscular layer is very thick, and composed of large,
longitudinal, and slightly spiral fasciculi, beneath which are annular fibres. The
mucous membrane, loosely attached to the muscular tunic, shows longitudinal and
transverse rugfe. The siuall mesenteric and the internal pvdic artery {artery of
the bidb) supply these membranes with blood. The nerves are derived from the
•pelvic or hypoyastric plexus.
Anus. — The anus, or posterior opening of the digestive tube, is situated
at the posterior extremity of the rectum, under the base of the tail, where, in
Solipeds, it can be seen forming a rounded prominence, which diminishes with
age. It is at the border or margin of this orifice, which is corrugated like the
mouth of a draw-purse where the intestinal mucous membrane meets with, and
is continued by, the external skin.
In proceeding from within outwards, there are found the following elements
entering into the structure of the anus : 1. The mucous membrane of the
rectum. 2. The prolongation of the circular and longitudinal fibres of the
muscular layer, forming what is named the internal sphinctei'. 3. A sphincter
muscle, composed of red fibres, which receives the insertion of a retractor. 4. The
fine, hairless, and closely attached skin, which covers the sphincter ; though
THE INTESTINES. 4S5
destitute of hair, it is rich in sebaceous follicles. "We will only notice the
The Sphincter of the Anus (sphincter ani) is formed of circular fibres,
some of which are fixed above, under the base of the tail, and are mixed, below,
with the muscles of the perineal region, especially the posterior constrictor of the
vulva in the female ; in the male, these fibres are lost on the surface of the
perineal aponeurosis. Comprised between the skin and the prolongation of
the muscular layer of the rectum, this muscle is (during life), owing to its
tonicity and natural shape, in a state of almost permanent contraction, in order
to keep the anal aperture closed ; it is only relaxed during the expulsion of
faecal matters or intestinal gases.
The Retractor of the Anus, or Ischio-anal muscle {retractor ani), is a
wide band, attached to the internal surface of the sacro-sciatic ligament, and even
to the supra-cotyloid crest, by aponeurotic fibres. The fasciculi composing this
band are all parallel to each other, while their posterior extremities are insinnated
beneath the sphincter, and are mixed wdth its fibres. This arrangement of the
retractor ani clearly indicates that it pulls the anus forwards, re-establishing it in
its normal position after expulsion of the f feces — an act that always results in
canying the posterior extremity of the rectum backwards.
These two muscles are of a red colour, and belong to those of animal life.
Their vessels are derived from the same sources as those of the rectum. The
Jmmorrhoidal nerve supplies them both with filaments.
Differential Characters of the Intestines in the other Animals.
In the domesticated auimals, the intestines vary as much in their dimensions, length, and
diametei-, as in their general arrangement.
1. The Intestines of the Rabbit (Fig. 286).
As for the stomach, so for the intestine we place the Ritbhit immediately after Solipeds,
'because the analogies are more marked in them than in the other animals.
The small intestine does not show any dilatation at its commencement, but it has an
enormous one at its termination in the caecum, and which has in its interior a fine Fever's patch ;
for this reason it is named the glandular pouch. The other agminated glands are equally
very developed, and are remarkable for their thickness, thougli they are not numerous — being
•only seven or eight. They are easily seen through the thin wall of the intestine, when this
has been washed and inflated. This intestine reaches the caecum in passing before the first
portion of the colon.
The cseciim is also proportionately more voluminous than in Solipeds. As in them, it has
the sliape of a cone suddenly attenuated towards its summit, and forming an arch or crook at
its upper part; but this crook is not very distinctly separated from the colon, and is continuous
witli it, without showing any constriction. Its internal surface is very curious, as it is
traversed by a spiral ridge of mucous membrane, which describes about twenty turns on the
wall of the intestine, and ceases about 4 inches from the point. This layer — the presence of
whicli is marked by a depression externally, that corresponds to its fixed border — may be about
\ of an inch or more in depth. The inferior cul-de-sac of tlie viscus, into which this fold does
not enter, forms, like the termination of the small intestine, a veritable glandular pouch. The
orifice of this latter intestine does not project into the interior of the caecum ; Bauhin's valve is
a disc, pierced like the iris, and fixed by its larger circumference around the margin of that
opening.
The colon also shows the division into two portions — the first, dilated and sacculated, and
even provided with rudimentary longitudinal bands on its external surface — is covered inter-
nally by round and regularly arranged prominences which resemble tliick villi, or traces of
tlie valvulae conniventes; the second, narrower and uniformly cylindrical, lies alongside tlie
duodenum, ascends into the diaphragmatic region in company with that intestine, and termi-
nates in the rectum, after describing several floating convolutions. On the sides of the rectum
nre two elongated glands which open into the perineal region.
486
THE DIGESTIVE APPABATUS IN MAMMALIA.
The total length of the Rabbit's intestines is nearly twenty feet, of which tl>e small intestine
takes about ten feet.
2 The Intestines of Ruminants (Figs. 287, 288).
The small intestine of the Ox floats at the extremity of a broad mesenteric layer, which is
narrower in front than behind, plane throughout, except at its intestinal border, which is of
considerable length, and is folded into a multitude of festoons. Twice the length of the small
intestine of the Horse — averaging about 49 yards — it is about one-half its diameter. The
Fig. 286.
INTESTINES OF THE RABBIT (GENERAL VIEW).
r, Liver; E, stomach. 1, Duodenum ; 2, 2', jejunum; 3, ilium ; 4, 4', 4", caecum; 5, point of tha
caecum (pushed to the right); 6, first portion of the colon; 6', second portion of the colon.
duodenum, at first sustained by the omentum, which attaches the small curvature of the fourth
compartment of the stomach to the posterior fissure of the liver, form- a particular loop, which
is in contact with the sublumbar region before it goes to be suspended by the large mesentery,
and to be continued by the convolutions of the floating portion. The ileum terminates as in
the Horse. The Peyerian glands are less numerous on the internal surface of the small
intestine than in Solipeds, though they are larger in size. In the Sheep and Goat, they
»re often more than eight inches in length, and extend to Bauhin's (ileo-csecal) valve.
The csecum is nearly cylindrical in form, without bulgings or longitudinal bauds. The
THE INTESTINES.
487
extremity of the cul-de-sac, rounded and globular, floats freely in the abdominal cavity, and is
directed backwards. At its opposite extremity, the caecum is continued directly with the
Fig. 287.
STOMACH AND INTESTINES OF THE SHEEP (GENERAL VIEW).
Ru, Rumen; Re, reticulum; F, omasum; C, abomasum ; E, great omentum; Fo, liver; R, right
kidney ; P, right e.xtremity of the pancreas ; M, mesentery. 1, Duodenum ; 2, floating portion of
the small intestine ; 3, terminal portion of the small intestine ; 4, extremity of the cul-de-sac of
the caecum ; 5, ellipsoid convolutions of the colon, seen through the right layer of the mesentery ;
6, last turn of the double colon ; 7, mesenteric glands.
488 THE DIGESTIVE APPARATUS IN MAMMALIA.
colon, without forming an arch, after having received the insertion of the small intestine. In
the Ox, in the vicinity of this insertion, there are traces of one of Peyer's patches. In the
Sheep and Goat, these patches are very numerous.
The colon, sustained between the layers of tlje great mesentery, on the margin of which is
suspended the small intestine, is coiled upon itself in such a way as to form u certain number
of elliptical convolutions, by at first maiiinj; several concentric spiral turns, which leave a
certain interval between them for the reception of the eccentric convolutions. The last spiral
turn is a little distant from the others ; in the smaller Ruminants, it is close to the insertion of
the mesentery in the small intestine, which it follows to near the duodenum, in describing
regular festoons. On arriving near the trunk of the great mesenteric artery, this convolution
passes to the right of that vessel, and is directed backwards, then forwards, thus forming a
flexure, and turns back in company with the duodenal flexure. The colon then continues in a
direct line to the rectum, attached to a short mesenteric layer, which, by its position, resembles
the large suspensory baml of the floating colon in Solipeds.
The calibre of this intestine is at first equal to that of the caecum ; but it soon becomes
constricted, and maintains a uniform diameter, which scarcely exceeds that of the small
Fig. 288.
OENERAL VIEW OF THE INTESTINES OF THE OX (RIGHT FACE).
A, Origin of the duodenum ; B, floating portion of the small intestine ; C, termination of the small
intestine ; D, caecum ; E, its point directed backwards ; f, flexure of the large colon at its termi-
nation ; G, H, terminal portion ot the intestine. 1, Insertion of the ductus choledochus ; 2,
insertion of the pancreatic duct.
intestine of the Horse. The muscular layer has the same arrangement as in the latter,
although it is not covered in all its points by the serous tunic, in consequence of the situation
of the colon between the two layers of the mesentery. In emaciated animals, however, it may
be remarked that the serous covering furnished by these layers to the muscular coat of the
colon is more extensive than at first we might be led to believe ; on tlie left side, the promi-
nences of the spiral convolutions are found to s-tand in relief on the surface of the mesentery,
and it is therefore more completely enveloped in the corresponding peritoneal layer.
From this description, it will be seen that in the large intestine of the Ox, Sheep, and
Goat, the cxcal division is well defined, but the division of the colon into a large or double,
and a small oi floating portion, can scarcely be made out; unless we regard as the large or
flexured colon, the spiral folds contained between the layers of mesentery, and see the floating
portion in the posterior extremity of the tube lying at first Rgainst the sublumbar wall of the
abdomen, and afterwards suspended by the short mesenteric frtenum which resembles tlie great
colic mesentery of Solipeds. It is worthy of remark that the great mesenteric artery goes to
the first, and the small mesenteric to the second portion, as in the Horse.
Measured throughout its whole extent, from the csecal cul-de-sac to the anus, the large
intestine of the Ox is from 33 to 39 J feet. It is, therefore, longer than that of the Horse;
but its capacity is much less, for it does not exceed from 6J to 7J gallons.
3. The Intestines of the Pig.
The average length of the Pig's intestines is about 72 feet, of whicli 56 go to the small,
and 16 to the large intestine.
THE INTESTINES.
489
In their general arrangement they bear some resemblance to those of the Ox. The small
intestine is suspended from the border of a mesenteric layer, which contains an elongated mass
of lymphatic glands. The duodenum forms an S curve in the convolutions of the colon. The
Fig. 289.
GENERAL VIEW OF THE INTESTINES OF THE PIG.
E, Stomach ; F, f', liver ; p, pancreas ; R, spleen ; M, mesentery ; v, bladder. 1, Duodenum ; 2,
jejunum ; 3, origin of the ileum ; 4, caecum, the end of which has been turned to the left ; 5,
principal mass of the colon; 5', last flexure of the colon emerging from the principal mass;
6, mesenteric gland.
THE DIGESTIVE APPARATUS IN MAMMALIA.
ileum occupies the posterior border of the mesentery, reaching the cjecum by keeping on the
right of the colon ; its insertion is oblique.
Among the peculiarities of the small intestine, may be cited the presence of an immense
Peyerian gland, which occupies the latter portion of the canal, where it figures as a band
measuring from 5 to 6^ feet in length.
The cmcum is directed backwards, and shows, on its internal surface, some Peyerian
patches ; it is sacculated, as in the
Fig. 290. Horse, and is furnished with three
longitudinal bands. The colon is
not comprised between the layers
of the mesentery, except in its
latter portion ; for the remain iler of
its extent it is on the left side of
the mesenteric layer, where it
forms a distinct mass. It describes
three turns from right to left, and
three turns from left to right; it
then passes forward, and, crossing
again from right to left, insinuates
itself between the duodenum and
pancreas. It has two of these
muscular bands in a portion of its
track, and even three towards the
csecum.
The rectum is situated above
the convolutions: of the colon, at
the border of a special mesenteric
layer.
4. The Intestines of Carnivoea
(Figs. 290, 291).
The intestines of the Caruivora
are remarkable for their shortness
and small volume. In a Dog of
ordinary size, they scarcely measure
more than 14 lectin length, of whicli
only from 24 to 28 inches are for
the large intestine. In the Cat,
the latter is about oue-half this
length, and the entire extent of the
viscus is equal to about 6 or 7 feet.
With regard to capacity, Colin gives
the following averages : for the
Dog's small intestine, 1 quart; tliat
of the Cat, ^ of a pint ; for the
large intestine in tiie Dog, nearly
1 quart, and in the Cat, a trifle more
than J of a pint.
The small intestine, suspended
at the extremity of a mesentery
similar to that of Solipeds, rests
on the inferior abdominal wall. It
is distinguished by the thickness
of its parietes, the length and
number of its \\\\i, which cover its
inner surface, and which are even
found accumulated on Peyer's
patches. These latter number about 20 in the Dog, and 5 or 6 in the Cat.
The csecum forms only a small, spirally twisted appendix, lined by a plicated and very
follicular mucous membrane, particularly in the Cat, and shows at the bottom of the cul-de-sac
a true Peyer's gland.
INTESTINES OF THE DOG.
a, Stomach ; h, duodenum ; c, jejunum ; d, ileum ; e, caecum ;
/, ascending colon ; g, transverse colon ; h, origin of de-
scending colon ; i, great omentum ; k, spleen ; I, mesentery :
m, pancreas. 1, Aorta ; 2, great mesenteric artery ; 3,
artery of the duodenum ; 4, artery of the large intestine ;
5, small mesenteric artery.
THE INTESTINES.
491
The colon is scarcely larger than the small intestine, and is neither sacculated nor furnished
with longitudinal bands. In its short course, it is disposed somewhat like the same intestine
in Man ; and, as in him, it may be divided into the ascending (Fig. 290, /), transverse (g), ancj
descending colon (ft), which is continued directly by the rectum.
Near the anus, this latter viscus presents on its sides two narrow apertures leading to
DIGESTIVE APPARATtrs OF THE CAT.
F, Liver; V, gall-bladder; E, stomach; R, spleen; R', right kidney; D, duodenum; Pa, pancreas;
C, caecum; In, small intestine (middle portion); I, ilium; M, M, mesentery; G, mesenteric
glands; Re, rectum; Ve, bladder; Di, diaphragm; PM, sublumbar muscles; P, left lung; P',
right lung.
two glandular pouches, which are filled with a brownish matter that has a strong and foetid
odour, and is secreted by the glands covering the internal wall of these diverticuli.
(Measurements of the intestines, always a subject of interest to comparative anatomists,
have been frequently made by different authorities. Leyh gives the length of the Horse's
intestines as from 10 to 12 times that of its body ; those of the Ox as from 20 to 22 times; the
THE DIGESTIVE APPARATUS IN MAMMALIA.
Sheep and Goat, from 26 to 28 times ; the Pig, from 15 to 17 times ; the Dog, from 4J to 5J times ;
and the Cat, from 4 to 5 times.
According to Hering, tlie entire length of the intestines of the Horse averages 100 Wurtem-
burg feet, 70 of which are for the small intestine, and 30 for the large. In the Ox they are
150 feet, 120 being for tiie small intestine, and 30 for the large; in the sheep they average 90
feet, from (>5 to 70 being allowed for the small intestine; those of the Goat measure 95, the
small intestine being 70 ; in the Pig they are 90 feet, 72 of which are for the small intestine,
and 18 for the large; large-sized Dogs averaged from 23 to 27 feet, from 20 to 22 of which were
for the small int. stine ; small dogs had only 6 feet in many instances. The Cat has from
4 to 5 feet.)
Comparison of the Intestines of Man with those of Animals.
Not unfreqnently the small intestine of Man is divided into duodenum and small intestine
proper. The duodenum is from 9 to 11
Fig. 292.
inches in length ; is dilated at its origin,
and firmly attached to the posteiior face
of the liver by a peritoneal fold, and to
the right of the sublunibar ngion by
connective tissue. It describes the arc of
a circle, in the concavity of which is
lodged the right extremity of tlie pan-
creas, and not the caecum, as in Solipeds.
Tlie small intestine proper is suspended
by a mesentery somewhat similar to that
of the Horse. Its length varies much —
from 13 to 26 feet. Its internal face has
a large number of transverse rugse, the
valvulae conniventes. It also shows from
20 to 25 Peyer's patches, particularly in
the ileo-csecal portion. Its structure is
like that already described.
In the large intestine are recognized
the caecum, colon, and rectum.
The caecum is a small reservoir placed
in the right iliac fossa, a little obliquely
downwards and to the left. It commences
at the ileu-csecal valve, has an average
length of about 2^ inches, and terminates
by a rounded extremity with a small
hollow prolongation, averaging 3 inches
in length — the ciecal or vermiform, appen-
dix. The mucous membrane is like that
of animals, and the muscular tunic is the
same.
The human colon is regularly saccu-
lated, like the small colon of the Horse ;
it begins in the right iliac fossa, above
the valvula Bauhini ; it ascends to the
lower face of the liver, passes abruptly
across from right to left, and, arriving
at the spleen, again changes its direction
downwards to the iliac fossa ; it then
again describes the iliac S, to reach the
mesial line, where it is continued by the
rectum. From this course, the colon has been divided into three portions : the ascending colon,
transverse colon, and descending colon. In the ascending and transverse colon are observed
three series of sacculi, separated by three muscular longitudinal bands; the descending colon
has only two.
There is scarcely anything special to note in the rectum and anus, except that they — and
especially the latter— are very rich, in arteries and varicnse veins, and that the anus is separated
from the rectum by small cavities open in front, and which are found in the Dog ; these are the
sinuses of Morgagni.
THE HUMAN INTESTINES AND SUPERIOR MESENTERIC
ARTERY.
1, Descending portion of the duodenum; 2, transverse
portion ; 3, pancreas ; 4, jejunum ; 5, ileum ; 6,
caecum and appendix vermiformis; 7, ascending
colon; 8, transverse colon; 9, descending colon;
10, superior mesenteric artery; 11, colica media;
12, the branch that inosculates with the colica
sinistra ; 13, pancreatico-duodenalis inferior ; 14,
colica dextra; 15, ileo-colica; 16, 16, vasa intes-
tmis tenuis.
the organs annexed to abdominal digestive canal. 493
Genekal aot) Comparative Survey of the Abdominal or Essential
Portion of the Digestive Tube.
We have terminated the description of the anatomical characters which
distinguish the essential portion of the alimentary canal in all the domesticated
animals, and what gradations has this study revealed ! Let us recapitulate and
compare them, before showing the admirable harmony which pervades these
diverse arrangements, and adapts them to the variations in general organization,
habits, and instincts.
In the Carnivora, which subsist on flesh (Do(/ and Oat), we have seen a
very ample stomach, secreting a gastric fluid throughout the whole extent of its
mucous membrane, and intestines (relatively) extremely short.
In the Omnivom, or Mammalia which live on a mixed diet (Fig), we have
found a small portion of the internal surface of the stomach occupied by a mucous
membrane unfitted to secrete gastric juice, and the intestines relatively of much
more considerable capacity than in Carnivora.
With the Herbivora, which derive their nourishment exclusively from the
vegetable kingdom (Ruminants, Rodents, and Solipeds), the surface for the pro-
duction of the gastric juice also singularly diminishes in extent, although the
stomach in some of these animals is remarkable for its extraordinary development.
But to compensate for this, the capacity of the intestinal canal assumes con-
siderable proportions, and, in the various species, is in direct inverse relation
to the area of the gastric surface. This surface being relatively more extensive
in Ruminants than in the Rabbit, and more also in that animal than in Solipeds,
all these animals ought to be classed in an inverse order, with regard to the
development of the intestinal surface.
Finally, in considering as the internal surface of the stomach (a point of view
quite rational) only those portions of the mucous membrane organized for the
secretion of the gastric juice, we are led to recognize that this surface is in
inverse proportion to that of the intestine ; that it reaches its highest develop-
ment in Carnivorous animals ; and that it is reduced to the smallest dimensions
in Solipeds — animals which, on the contrary, present a very great development of
the intestinal surface.
The nature of the aliment readily accounts for these remarkable differences.
The Carnivora, living on sul^stantial food, take it in very large quantity,
because they are exposed to frequent fastings ; it is, therefore, necessary that
they should have a stomach large enough to contain the ingested substances,
and to secrete the amount of gastric juice needed to transform them into
assimilable materials. If these animals have a short and narrow intestine, it is
because a small surface only is required to absorb the products of digestion, these
being mixed with but a minimum quantity of non-nutritive substances, and
readily come in contact with the absorbing membrane.
With regard to the Herbivora, their food contains a trifling proportion of
nutritive elements in an extremely large bulk of material, and being compelled to
ingest great quantities at short intervals, the stomach, properly called, can only
be a temporary receptacle for the aliment, which passes rapidly through it after
being impregnated by the gastric juice. The surface which secretes that fluid
is also singularly reduced, because if it has to perform its functions more frequently
than in Carnivora, it is not required to display so much activity in a given time.
If, on leaving the stomach, the alimentary matters encounter a vast intestinal
34
494 THE DIGESTIVE APPARATUS IN MAMMALIA.
surface, it is in order that the reparative materials dispei-sed in the alimentaiy
mass may not escape the absorbent action of that surface, and may be the more
effectually broughfinto contact with it. "We have this exemplified in Ruminants ;
owing to their double mastication, and the triturating action of the omasum,
their food arrives in the true stomach more comminuted and better attenuated
than in the Horse ; the mass, more finely broken up, retains less of the assimilable
and reparative matters, and these are more easily taken up by the absorbing
surface ; as a necessary consequence, the intestinal tube, although longer than
in Solipeds, is far from offering the same capacity.
Analogous considerations explain the reason for the intermediate conformation
of the digestive canal in Omnivorous animals.
There is, then, an admirable correlation between the conformation of the
digestive tube and the nature of the substances which form the basis of the
alimentation of animals ; and this harmony is equally apparent when the stomach
and intestines are compared with the other apparatus of the economy, and with
the natm-al habits and instincts of creatures. So it is that an animal furnished
with an ample stomach and narrow intestine, will have shai-p teeth and claws
to tear its prey, strength and agility to capture it, and will also possess sanguinary
instincts ; while another, with its gastric surface greatly diminished, will have
intestines as developed in their length as in their capacity, and be distinguished
by its peaceful habits, the absence of aggressive claws, and its dental apparatus
arranged for crushing and grinding its food — and so on.
Organs annexed to the Abdominal Portion of the Digestive
Tube.
These organs are three in number : two glands — the liver and pancreas, which
pour into the small intestine two particular fluids, the bile and pancreatic juice ;
and a glandiform organ, the splee?i, remarkable for its numerous vascular con-
nections with different organs of the digestive apparatus, and which for this
reason deserves to be studied with it, although it is doubtful, if not improbable,
that it has anything to do with digestion.
Preparation. — These three organs can readily be studied after removing tlie intestinal
mass, as indicated at page 471. In order to examine the details of their organization with
more fiicility, it would be well to detach them jtltogether, with the diaphragm and kidneys, and
to lay out the whole on a table. (To study the relations of these three organs with those of
the abdominal cavity, it is advisable to place the subject on its sternum, after removing the
intestines, and to detach the posterior part of the body at the loins.)
1. The Liver (Figs. 293 to 298)
Situation — Direction. — This organ is situated in the abdominal cavity, to the
right of the diaphragmatic region, and in an oblique direction downwards and
to the left.
Weight. — The weight of the healthy liver in a middle-sized horse, is eleven
pounds.
Form and External Surface. — Removed from its connections with the neigh-
bouring organs, and viewed externally, it is seen to be flattened before and
behind, irregularly elongated in an elliptical manner, thick in its centre, and thin
towards its borders, which are indented in such a manner as to divide the organ
into three principal lobes. Tliis configuration permits it to be studied in two
faces and a circumference.
THE ORGANS ANNEXED TO ABDOMINAL DIGESTIVE CANAL. 495
The anterior face is convex, perfectly smooth, and channelled by a wide and
deep fissure for the passage of the posterior vena cava. This fissure extends
directly from behind to before, and consequently slightly crosses the general
direction of the liver ; near the point where the vena cava leaves the gland
to pass through the diaphragm, are seen the openings of the principal sublobular
veins. The posterior face is equally smooth and convex, and has also a fissure
{the portal), by which the vena portse and the hepatic artery and nerves enter, and
by which the biliary ducts emerge from the liver. This groove is slightly con-
cave towards the left, and follows the direction of the liver in proceeding obliquely
downwards, backwards, and to the left.
The circumference may be divided into a superior or left, and an inferior or
rigid horder, united at both extremities by the ellipsis formed by the liver. The
superior hord"r presents, in proceeding from right to left : 1. The insertion of the
ligament of the right lobe. 2. The origin of the fissure for the vena cava. 3.
A notch for the oesophagus. 4. The insertion of the left ligament. The inferior
horder is sharp, and offers two deep notches, which divide the liver into three
lobes : a superior or right, an inferior or left, and an intermediate one. The
right lobe is usually of medium volume, and has above, on its posterior face, an
appendix in the shape of a small secondary lobule of a triangular form, the base
of which corresponds to the commencement of the portal fissure : this is the
ported lobe, or lobus Spigelii} The left lobe is nearly always the largest. The
middle lobe (lobus quadratus), the smallest of the three, is itself divided by
secondary notches into several digitations or lobules.
Relations. — ^Viewing the organ in position, in order to study its general
relations, it is found that the anterior face is applied against the diaphragm — a
disposition which increases its convexity, while diminishing that of its posterior
face ; and that the latter is in contiguity with the stomach, the duodenum, and
the diaphragmatic flexure of the colon.
The connections proper to each lobe are observed to be as follows : 1. The
middle lobe corresponds to the centre of the aponeurotic portion of the diaphi'agm.
2. The left lobe touches the left and inferior part of this aponeurosis, and is
prolonged to the corresponding point of the fleshy peripheral band of that muscle.
3. The right lobe is in contact with the right and superior part of the muscle ;
its upper border touches the right kidney ; the pancreas rests against its base, on
the posterior face.
Mode of attachment. — The liver is suspended to the sublumbar wall of the
abdomen, by the large blood-vessels which enter its fissures ; and it is also fixed
to the posterior face of the diaphragm by four particular bands. One of these is
carried from the anterior face of the Uver to the phrenic or tendinous centre,
and appears intended to prevent total displacement of the organ ; the other three
belong to each particular lobe.
A. The ligament of the anterior face of the liver (or coronary ligament) comprises
two series of very short aponeurotic fibres, which, arising from the two borders of
the vena cava fissure, go to be fixed to the posterior face of the phrenic centre.
The peritoneum is folded over it on each side, in passing from the diaphragm to
the liver. The adherence of these fibres to the walls of the vena cava is extremely
(' This, according to Flower, should be the caudate, not the Spirjelian lobe ; for he appears
to have proved that the free, ear-shaped lobe situated to the ris^ht of the vena portse in the
Horse, Rhinoceros, and Tapir, is not the lohus Spigelii, but the caudate lobe — the former being
represented by a long, attaclied, transverse ridge of hepatic tissue situated farther to the left.)
496 THE DIGESTIVE APPARATUS IN MAMMALIA.
close ; and the vena cava itself being thus in a manner united to the tissue of
the liver, it happens that the union of the anterior face of the viscus with the
phrenic centre could not be more solidly established.
B. The ligament of the left lobe is a wide peritoneal fold, between the two
layei-s of which are some fasciculi of white fibrous tissue. It is detached from
the aponeurotic centre, to the left of the oesophageal orifice, and is inserted into
the left part of the superior border of the liver.
C. The ligament of the right lobe is a fold analogous to the preceding, but
much shorter, and the origin of which, placed very high and near to the sublumbar
parietes, is partly covered by the right kidney. It is inserted into the superior
border of the viscus, and sends a small layer to the lobus Spigelii ; most frequently,
however, this lobule is sustained by a special peritoneal fraenum, given off from
the anterior border of the kidney.
D. The ligament of the middle lobe (the longitudinal^ broad^ falciform^ or
THE ORGANS ANNEXED TO ABDOMINAL DIGESTIVE CANAL. 497
suspensory ligament) is a falciform and vertical serous layer, the adherent border
of which is attached, almost in the median plane, to the posterior face of the
diaphragm, and even to the inferior abdominal parietes. At its free border is a
fibrous cord (the round ligament), the remains of the foetal umbilical vein. Its upper
part enters a secondary notch in the middle lobe, and is prolonged on the anterior
face of this to the point where the vena cava enters the diaphragm.
Structure. — As elements in its structure, the liver offers for study : 1. A
serous membrane. 2. A fibrous capsule. 3. The proper and fundamental tissue
of the organ.
1. Serous Membrane. — This membrane is only an expansion of the
peritoneal bands or ligaments already described, and of which the two, on arriving
at the organ, separate to become developed on its surfaces, and to completely
cover it except in the anterior and posterior fissures.
2. Fibrous (or Glisson's) Capsule. — This, the proper envelope of the
liver, is formed by a very fine fibrous membrane, closely adherent to the preceding
layer on the one side, and to the tissue of the liver on the other. It penetrates
the substance of that tissue in passing around the vessels lodged in the posterior
fissure, and from its inner face it sends a multitude of lamellar partitions, which
separate the hepatic lobules, and form a veritable framework in the interior
of the organ. The presence of this capsule has been denied, but its existence is
not to be doubted in all the domesticated animals ; it is particularly well developed
in Ruminants and the Pig.
3. Proper Tissue of the Liver.— The proper substance of the liver is
distinguished by its bluish-bro\\Ti or violet hue, the shades of which vary much
according to the subjects. It is heavy and compact, and so friable that it is crushed
by the most moderate pressure. It is composed of polyhedric masses from
■^ to -^Q of an inch in diameter, which are readily enough distinguished from one
another through the peritoneum on the surface of the organ, particularly when
the septa thrown in between them from Glisson's capsule are hypertrophied, from
some slight chronic irritation.
Sometimes the hepatic lobule is uniform in colour throughout ; often it shows
a red central point, with a yellow circle around it, and an interrupted red ring
circumscribing this again, and which communicates with a similar circle belonging
to the adjoining lobules, so as to compose a network on the surface of the gland ;
at other times the lobules are yellow in the centre and red at the circumference.
All these appearances, the study of which at one time was considered of much
importance, are uncertain, and may vary in a thousand ways, in combining with
one another ; so that they really demand but little attention, due as they are to
the greater or less degree of plenitude of the different vessels entering the lobule.
As the liver is composed of lobules placed beside each other, we will describe
one ; as, when its structure is well known, the organization of the entire organ
will be understood.
In a hepatic lobule we find : 1. Hepatic (or biliary) cells. 2. Biliary canaliculi
(or ducts). 3. Afferent vessels. 4. An efferent vessel. 5. Lymphatics. 6. Con-
nective tissue.
Hepatic cells. — These are polygonal or round, and much resemble squamous
epithehum ; their diameter varies from 3^ to 2^ of an inch. They have no
enveloping membrane, but contain one or two nuclei with nucleoli, granules
coloured by biliary matter, small masses of a substance which has been studied
by Bernard and Schiff, and named " animal amidon, or glycogen ; " and, lastly.
498
TEE DIGESTIVE APPARATUS IN MAMMALIA.
adipose granules, the volume and quantity of which vary with the condition
of the animals, or the period of digestion at which the liver is examined. The
hepatic cells are situated in the network formed by the vessels of the lobule, and
constitute its principal portion.
Hepatic Duds.— Bt&tmed to carry away the bile secreted in the interior
of the hepatic lobule, the biliary ducts form around it a kind of girdle that
accompanies the interlobular branches of the vena portae. Within and without,
this girdle sends off small prolongations ; the first bring it into communication
with the ducts of the neighbouring lobules ; the second pass to the centre of the
lobule, or they surround each cell.
The wall of the biliary ducts is a thin amoi-phous membrane, lined, near the
periphery of the lobule, by polygonal cells, smaller than the hepatic cells, and,
beyond, by a kind of endothelium or cuticle.
Afferent vessels. — These are the branches of the portal vein and hepatic artery.
The portal vein, after reaching the interior of the liver, divides into gradually
decreasing vessels, until it terminates in forming the interlobular reins. These
Fig 294
/■
Fig. 295.
, portion of a hepatic column, showing its compo-
nent secreting cells. B, Secreting cells detached :
a, In their normal state; b, a cell more highly
magnified, showing the nucleus and distinct oil-
particles ; c, in various stages of fatty degenera-
tion.
BILIARY CAPILLARIES OP
THE rabbit's liver.
PART OF A LOBULE,
SHOWING THE ARRANGE-
MENT OF THE BILIARY
DUCTS IN RELATION TO
THE HEPATIC CELLS.
a, Capillaries of the biliary
ducts ; 6, hepatic cells ;
c, biliary ducts ; d, ca-
pillary blood-vessels.
vessels surround the lobule, communicate with the neighbouring interlobular
veins, and give off a large number of twigs to the interior of the lobule, where
they anastomose, and constitute the hepatic capillary plexus. The hepatic artery
furnishes ramuscules, which mix with the ramifications of the portal vein in the
(vaginal) plexus. The principal branches of the latter are all directed from the
periphery towards the centre of the lobule, where they unite to form the afferent
vessel. It results from this arrangement that the hepatic cells which fill the
spaces between the vessels, are placed in radiating series.
Efferent vessel. — Situated in the centre of the lobules, this vessel receives all
the ramifications of the capillary plexus, and is named the intra-lohular or central
suhlohular vein. It is voluminous, and communicates with the other intra-lobular
veins. (These intra-lobular veins terminate in the larger trunks that run along
the bases of the lobules, and are named the suhlohular veins.)
Lymphatics. —In a hepatic lobule are found very fine lymphatic vessels that
THE ORGANS ANNEXED TO ABDOMINAL DIGESTIVE CANAL.
HORIZONTAL SECTION OF THREE SUPERFICIAL
LOBULES, SHOWING THE TWO PRINCIPAL SYS-
TEMS OF BLOOD-VESSELS.
a, a, Intra-lobular veins, terminating in the hepatic
veins; 6, 6, interlobular plexus, formed by
branches of the portal vein.
suiTOimd the branches of the hepatic plexus, where they form the lymphatic
vaginfe, or canals which contain the blood-vessels.
Connective tissue. — The intra-lobular connective tissue is scanty, the lobule
being almost entirely composed of cells
or capillaries ; some trabeculae, never- ^'S- ^^^•
theless, exist around the lymphatic
sheaths. There is, however, a larger
quantity in the interlobular spaces ;
and in some animals — especially the
Pig — Glisson's capsule sends somewhat
thick lamellae of connective tissue be-
tween these lobules.^
Excretory Apparatus (Fig.
298). — This is very simple in Solipeds,
and is composed of a vessel named
the ductus choJedochus, resulting from
the union of several trunks lodged in
the posterior fissure of the liver, and
which come from the three lobes.
Traced in the substance of the hepatic
tissue, these branches divide into more
and more attenuated vessels that arise
from the periphery of the lobules, and
are continuous with the biliary ducts
which envelop and penetrate these.
Course. — At its exit from the liver, the ductus choledochus lies between the
layers of the gastro-hepatic omentum, and ascends to the wall of the duodenum,
which it passes through at about six inches from the pylorus, along with the
principal pancreatic duct. The
orifices of these two canals are F'g- 297.
surrounded by a circular mucous
fold (ampulla of Vater), which is
usually very prominent, and acts
as a valve in preventing the
entrance of alimentary substances
into the apertures it encircles ;
this office it fills so well, that it
will not even allow the air with
which the duodenum may be in-
flated, to pass into the ducts.
There enter into the structure
of the ductus choledochus : 1. A
fibrous membrane, which some
anatomists believe contains un-
striped muscular fibres. 2. Sphe-
roidal epithelium. 3. Numerous
* The description of the hepatic lobule has been intentionally simplified to the utmost, to
treatises on histology being left the task of discussing the microscopical details wliich sometimes
cause a lobule to be considered as a collection of tubes placed at the end of the branches of the
biliary ducts, at other times as a portion of a conglomerate gland full of blood-vessels.
SECTION OF A SMALL PORTION OF THE LIVER OF A
RABBIT, WITH THE HEPATIC OR INTRA-LOBULAR
VEINS INJECTED
500 TEE DIGESTIVE APPARATUS IN MAMMALIA.
racemose glands, opening on the surface of the epithehum by very small
orifices.
Vessels and Neeves of the Liver. — The blood-vessels are the hepatic
artery, portal vein, and sublobular veins.
The hepatic arter// is a branch of the coeliac, and enters the gland by the
posterior fissure, in company with the portal vein and ductus choledochus. In
the liver it divides into very fine ramifications, which join the intra-lobular
plexus, anastomose on the surface of the biliary ducts, or are expended either on
the serous membrane, or in the walls of the portal vein.
The portal vein is the functional vessel of the liver. It reaches that organ by
the posterior fissure, and Glisson's capsule accompanies its ramifications as far as
the hepatic lobules, where they form the plexus of subhepatic veins.
The supra-hepatic (sublobular) veins are so named because they gain the
antero-superior face of the viscus, to open into the posterior vena cava. They
carry away the blood that has been brought by the portal vein and hepatic artery.
Their origm is due to the union of the intra-lobular veins, which make a passage
Fi?. 298.
EXCRETORY APPARATUS OF THE HORSE S LIVER.
1, left lobe of the liver; 2, middle lobe ; 3, right lobe ; 4, lobus Spigelii (caudate lobe) ; 6, posterior
vena cava at its entrance into the liver ; 7, vena portse ; 8, ductus choledochus ; 9, pancreatic
duct; 10, common entrance of these two ducts into the small intestine.
through the hepatic tissue with which their walls are immediately in contact,
gradually join each other, and enter the posterior vena cava on its way through
the anterior fissure of the liver. The number of trunks (hepatic) entering this
vessel is considerable, but the majority are very small ; the principal confluent
is placed at the anterior extremity of the fissure.
The lymphatics form a fine superficial plexus, easy to inject ; with deeper
networks placed around the vessels that penetrate by the posterior fissure. In
the lobules they are disposed as described above. Joined to the lymphatics
of the stomach, they constitute a single trunk that goes to the sublumbar
receptacle.
The nerves are more particularly derived from the solar plexus, although the
pneumogastric and diaphragmatic also supply filaments to the liver. They
interlace around the hepatic artery and portal vein ; their mode of termination
is unknown.
Functions. — The most important considerations are attached to the study
of the functions of the liver ; but we cannot enter into them in detail without
going beyond our subject.
THE ORGANS ANNEXED TO ABDOMINAL DIGESTIVE CANAL. 501
The liver more especially elaborates bile and sugar. It secretes the bile at
the expense of the blood of the portal vein, which comes from the intestinal
tunics charged with assimilable substances absorbed by the veins of the villi.
The bile is, therefore, in this respect an excrementitious secretion ; though
all its elements are not excreted, some of them acting on the alimentary
substances, and others being absorbed. From the most recent researches, it
would appear that it has a share in the purification of the blood, in digestion,
and in calorification — in the latter especially, as its absorbed elements are very
rich in carbon and hydrogen, bodies eminently fitted for the production of
animal heat.
The liver is also a glycogenetic gland, this function having been demon-
strated to pertain to it by Bernard. The sugar formed in the hver finds its way
into the blood, and leaves the organ by the sublobular veins. It is elaborated in
the hepatic cells, by the transformation of the substance known as " animal
amidon," which is brought into contact with a kind of diastaste that exists with
it in their interior.
It will thus be seen that the liver furnishes two very different products — bile
and sugar. The knowledge of this fact, combined with the internal arrangement
of the organ, has led some anatomists to consider the organ as two glands
reciprocally contained within each other. According to them, one gland is
tubular, and formed by the system of biliary ducts — this gland secretes the bile ;
the other gland is constituted by the hepatic cells, which produce the sugar. But
this hypothesis should be rejected, for it is probable that the sugar and bile are
produced in the large hepatic cells, and that the first passes into the veins, while
the second is poured into the biliary ducts.
In Solipeds, the secretion of bile, though most active during the digestive
period, yet goes on in a continuous manner.
(Certain deductions of a pathological kind are based upon the foregoing
anatomical facts, and have an important bearing with regard to comparative
pathology. They have been pointed out by Wilson, and are as follows : Each
lobule is a perfect gland ; its structure and colour are uniform, and it has the
same degree of vascularity throughout. It is the seat of a double venous
circulation ; the vessels of the one — hepatic — being situated in the centre of the
lobule, and those of the other — portal — at the circumference. Now, the colour of
the lobule, as of the entire liver, depends chiefly on the proportion of blood
contained within these two sets of vessels ; and so long as the circulation is
natural, the colour will be uniform. But the instant that any cause is developed
which will interfere with the free circulation of either, there will be an immediate
diversity in the colour of the lobule.
Thus, if there be any impediment to the free circulation of the venous blood
through the heart or lungs, the circulation in the hepatic veins will be retarded, and
the sublobular — or supra-hepatic — and intra-lobular veins will become congested,
giving rise to a more or less extensive redness in the centre of each of the
lobules ; while the marginal or non-congested portion presents a distinct border
of a yellowish white, yellow, or green colour, according to the quantity or quality
of the bile it may contain. " This is ^passive congestion ' of the liver, the usual
and natural state of the organ after death ; " and as it commences with the
hepatic vein, it may be called the first stage of hepatic venous congestion.
But if the causes which produced this state of congestion continue, or be from
the beginning of a more active kind, the congestion will extend through the
502 TEE DIGESTIVE APPARATUS IN MAMMALIA.
lobular venous plexuses " into those branches of the portal vein situated in th€
interlohuJar fissures, but not to those in the sjmces, which, being larger, and giving
origin to those in the fissures, are the last to be congested." In this second stage
the liver has a mottled appearance, the non-congested substance is arranged in
isolated, circular, and ramose patches, in the centres of which the spaces and
parts of the fissure are seen. This is an extended degree of hepatic venous
congestion ; it is " active congestion " of the liver, and very commonly attends
disease of the heart and lungs.
These are instances of partial congestion ; but there is sometimes general
congestiot of the organ. " In general congestion, the whole liver is of a red
colour, but the central portions of the lobules are usually of a deeper hue than
the marginal portions.")
Development. — The liver of the foetus is remarkable for its enormous
development. Its function commences early, for at birth the intestines are filled
with meconium — a product of the biliary secretion. A more detailed description
will be given when the general development of the foetus comes to be studied.
2. The Pancreas.
This organ has the greatest resemblance to the salivary glands in its structure
and physical properties ; and for this reason it has been named the abdominal-
salivary gland..
Situation — Weight. —It is situated in the sublumbar region, across the aorta
and posterior vena cave, in front of the kidneys, and behind the liver and
stomach. Its weight is seventeen ounces.
Form and Relations. — The pancreas is rather irregular and variable in form,
according to the kind of animal. Flattened above and below, traversed obliquely
from its inferior to its superior face by an opening for the passage of the portal
vein, and which is named the pancreatic ring, this gland is sometimes triangular,
sometimes oblong, and curved on itself ; it is under the latter form that we will
notice it.
Its fifces present the lobulated aspect of salivary glands. The superior
adheres by connective tissue to the aorta, posterior vena cava, coeliac trunk, solar
plexus, splenic vessels, and the right kidney and supra-renal capsule ; it is
covered by the peritoneum for a certain portion of its extent. The inferior is
related to the base of the caecum and the fourth portion of the colon, through
the medium of a thick layer of connective tissue. The anterior border, concave
and undulating, is in contact with the duodenum and the left extremity of the
stomach. The posterior is very convex, especially to the right, and near its
middle it presents a notch for the reception of the portal vein before its entrance
into the ring. The right extremity (or head) — the thinnest — adheres to the
duodenum, and shows the excretory ducts of the gland. The left is carried
towards the base of the spleen, in passing between the left extremity of the
stomach and the kidney of the same side.
Structure. — Superficially, it resembles the salivary glands, but in reality it is not
a racemose gland. It is an acinous gland in which the elongated culs-de-sac, filled
with polyhedral cells, have their axis occupied by a vessel and a cord of connective
tissue. The excretory vessels disappear on reaching these culs-de-sac, so that the
secreted products are infiltrated between the cells to reach the duct of Wirsung.
The gland receives its blood by the hepatic and great mesenteric arteries ;
the nerves come from the solar plexus.
THE ORGANS ANNEXED TO ABDOMINAL DIGESTIVE CANAL. 503
Excretory apparatus. — The pancreas has two excretory ducts — a principal,
described by "Wirsung, whose name it bears, and an accessory. The duct of
Wirsimg, lodged in the substance of the gland, but nearer the superior than the
inferior face, at first comprises two or three thick branches, which soon unite to
form a single trunk that emerges from the pancreas by the left extremity of the
organ. Larger than the ductus choledochus, it opens, as already stated, at
the same part of the duodenal surface. The accessory or azygos duct {ductus
vancreaticus minor) is much smaller ; it leaves the principal trunk, receives some
branches in its passage, and opens alone into the small intestine, directly opposite
the duct of Wirsung.
The ductus choledochus and the duct of "Wirsung do not pass directly through
the wall of the intestine, but obliquely, like the entrance of the ureters into the
bladder. They open in the middle of a circular valve — the ampulla of Vater.
This ampulla is limited by a thick primary mucous fold, and within this is a
second — thinner — beneath which the ductus choledochus opens ; at the bottom of
the space circumscribed by this second fold, beneath a free mucous lip, is seen
the duct of Wirsung. Such is the arrangement of the ampulla of Vater in the
Horse.
Functions. — From the researches of Bernard, it appears established that
the fluid secreted by the pancreas emulsifies fatty matters, and renders them
absorbable.
3. The Spleen (Fig. 299).
The spleen differs from glands, not only in the absence of an excretory duct,
but also in the other details of its organization. It has been considered as a
vascular gland, the uses of which are not yet determined in a precise manner.
Situation. — It is situated in the diaphragmatic region, close to the left
hypochondriac, and appears as if suspended in the sublumbar region, as well as
at the great curvature of the stomach.
Foryn — Direction — Relations. — The spleen is falciform, and directed obliquely
downwards and backwards. It has tivo faces, tvw borders, and a point.
The external face is in relation with the muscular portion of the diaphragm,
and is moulded to it. The internal, slightly concave, touches the large colon ; it
has sometimes a small lobule, or offers traces of lobulation. The posterior border
is convex, thin, and sharp. The anterior, thicker, concave, and bevelled at the
expense of the internal face, is channeled by a slight longitudinal fissure (or
hilus) that lodges the splenic vessels and nerves ; it receives the insertion of the
great mesentery, by which it is attached to the greater curvature of the stomach.
The base, or superior extremity, is thick and wide, and is related to the left
kidney and the corresponding extremity of the pancreas ; it shows the insertion
of the suspensory ligament. The point, or inferior extremity, is smooth and
thin.
Weight. — The average weight is 32 ounces ; but it is sometimes of enormous
dimensions — as much as three or four times its normal volume.
Mode of attachment. — The spleen is a floating organ, the displacements of
which are limited by a suspensory ligament, and the great (or gastro-splenic)
omentum. The first is a peritoneal fold which proceeds from the anterior border
of the left kidney and the sublumbar wall, and is strengthened by the elastic
fibrous tissue comprised between its two layers. It is fixed to the base of the
spleen, and is confounded, inwardly, with the great omentum. The latter is
504
THE DIGESTIVE APPARATUS J.V MAMMALIA.
already known as proceeding
to the splenic fissure, whence
serous covering.
Steucture. — The tissue
approaching to a red hue ; it
of the finger, and retains its
its substance includes a Jib:
vessels, and nerves.
Serous membrane. — This
in the fissure of the anterior
to the colon, and in its passage becoming attached
it extends over the surface of the organ to form its
of the spleen has a violet-blue colour, sometimes
is elastic, tenacious, and soft, yields to the pressure
imprint. Enveloped externally by the peritoneumr^
rous frameivork, splenic pulp, Malpighian corpuscleSy
is spread over the whole surface of the organ, except
border. Its internal face adheres most intimately
STRUCTURE OF THE SPLEEN (DIAGRAMMATIC).
A, Artery; V, vein. 1, Splenic trabeculse; 2, finer trabeculse; 3, reticulum of the splenic pulp;
4, lymphoid infiltration into the sheath of the arteries ; 5, its continuation with a Malpighian
corpuscle; 6, membrana propria; 7, sheath of the vein; 8, recticulum of the splenic pulp; 9,
termination of the fibrillar sheath of the capillaries; 10, tuft of arteries; 11, arterial capillaries;
12, their opening into the intermediate tracts of the pulp; 13, veins; 14, venous capillaries; 15,
part of the pulp containing the remains of cells; 16, Malpighian corpuscle attached to (17) an
artery, seen in a section perpendicular to the axis of the vessel.
to the proper tunic of the spleen. It is only an expansion of the serous bands
which limit the movements of the viscus.
Fibrous frameworJc. — Under the peritoneal membrane is a thick, resisting,
fibrous tunic, roughened and granular on its exterior, and sending from its deep
face into the interior of the mass a multitude of prolongations called trabeculce,
which cross in all directions, forming a cellular network, in the numerous naiTOW
meshes of which are the other elements of the organ. In washing out a morsel
of spleen in a jet of water, the latter are removed, and the outlines of this
fibrous structure are fully exposed. If a stream of water be passed through the
TEE ORGANS ANNEXED TO ABDOMINAL DIGESTIVE CANAL.
505
splenic artery, the same result will be arrived at. KoUiker has found in the
proper tunic of the spleen, and in its trabeculse, a particular contractile tissue —
the muscular cell-fibres — mixed with fasciculi of elastic or inelastic fibrous tissue.
(The proper coat, the sheaths of the vessels, and the trabeculse, consist of a dense
mesh of white and yellow elastic fibrous tissues, the latter considerably pre-
dominating. It is owing to the presence of this tissue that the spleen possesses
a considerable amount of elasticity, admirably adapted for the very great
variations in size that it presents in certain circumstances. In some of the
Mammalia, in addition to the usual constituents of this tunic, are found numerous
pale, flattened, spindle-shaped nucleated fibres, like unstriped muscular fibre. It
is probably owing to this structure that the spleen possesses, when acted upon by
the galvanic current, faint traces of contractility.)
Splejiic pulp. — This name is given to a reddish pultaceous material, which
partly occupies the alveolar network formed by the intersections of the trabeculae.
It is sustained by a very delicate reticulum of connective tissue, and is composed
Fig. 300.
Fig. 301.
A SINGLE SPr/.:NIC CORPUS-
CLE, FROM THE SPLEEN OF
THE OX.
1, External tunic, or mem-
brana propria; 2, granular
contents ; 3, part of a small
artery ; 4, its sheath, de-
rived from the external
tunic of the spleen, with
which the corpuscle is
closely connected.
BRANCH OF SPLENIC ARTERY WITH ITS RAMIFICATIONS
STUDDED WITH MALPIGHIAN CORPUSCLES.
of numerous elements, such as pigment granules, free nuclei, large cells with
several nuclei, lymphoid elements, and blood-globules in a state of decomposition
or transformation. These globules are free or enveloped in an albuminoid
membrane.
Malpighian corpuscles. — These are contained, like the splenic pulp, in the
meshes of the fibrous framework of the spleen, and are covered by that pulp.
Distributed on the course of the small arteries, these corpuscles, which are visible
to the naked eye, are little closed sacs of a wliitish colour. They are composed
of an adventitious tissue of arteries, in which are accumulated, at certain points,
lymphoid elements. They are, therefore, analogous to closed folHcles in then*
•structure. (The proper substance of the spleen consists of coloured and colourless
elements. The coloured are composed of red blood-corpuscles and coloured cor-
puscles, either free or included in cells. Sometimes unchanged blood-discs are
506 THE DIGESTIVE APPARATUS IN MAMMALIA.
seen included in a cell ; but more frequently the included blood-discs are altered
both in form and colour. Besides these, numerous deep-red, or reddish-yellow,
or black corpuscles and crystals, either single or aggregated in masses, are seen
diffused throughout the pulp substance ; these, in chemical composition, are
cksely allied to the haematine of the blood. The colourless elements consist of
r'anular matter ; nuclei, about the size of the red blood-discs, homogeneous or
granular in structure ; and nucleated vesicles in small numbers. These elements
iorai a large proportion of the entire bulk of the spleen in well-nourished
animals ; whilst they diminish in number, and occasionally are not found at all,
in starved animals. The application of chemical tests shows that they are
essentially a proteine compound. The splenic or Malpighian corpuscles are round,
whitish, semi-opaque bodies, glutinous in consistence, and disseminated through-
out the substance of the organ. They are more distinct in early than in adult
life or old age, and vary considerably in size and number. From the manner in
which they are appended to the sheaths of the smaller arteries and their branches,
they resemble the buds of the moss-rose. Each consists of a membranous
capsule, composed of fine pale fibres interlacing in all directions. The blood-
vessels ramifying on the surface of the corpuscles, are the larger ramifications
of the arteries to which the sacculus is connected, and also of a delicate capillary
plexus, similar to that surrounding the vesicles of other glands. These vesicles
have also a close relation vrith the veins, and fche vessels begin on the surface of
each vesicle throughout the whole of its cu'cumference, forming a dense venous
mesh in which each of these bodies is enclosed. It is probable that, from the
blood contained in the capillary network, the material is separated which is
occasionally stored up in their cavity ; the veins being so placed as to carry off,
under certain conditions, those contents that are again to be discharged into the
circulation. Each capsule contains a soft, white, semi-fluid substance, con-
sisting of granular matter, nuclei similar to those found in the pulp, and a few
nucleated cells, the composition of which is apparently albuminous. These
bodies are very large, after the early periods of digestion, in well-fed animals, and
especially those fed upon albuminous diet. In starved animals, they disappear
altogether.)
Arteries. — These emanate from the splenic artery at different elevations, and
plunge into the tissue of the spleen, preserving their reciprocal independence.
Their terminal ramifications do not open, as has been said, into venous sinuses,
but into minute tufts of capillaries, which traverse the splenic pulp, to be con-
tinued by the venous network.
Veins. — All the venous branches of the spleen open into the splenic vein, and
are lodged, with the con-esponding artery, in the fissm-e of the organ. Traced
from their commencement, they are seen to gradually lose their constituent
membranes, and to open into sinuses which are only lined by the endothelium
of the vessels. It is in these sinuses that the network of venous capillaries
which succeed the arterial capillaries, originates.
Lymphatic vessels. — These are found on the external surface of the organ,
and along the track of the blood-vessels. (There appear to be two systems of
lymphatics in the spleen of the Horse — one belonging to the trabecule, which
is in continuity with the lymphatics of the capsule ; and another accompanying
the branches of the splenic artery and its branches, investing these vessels like,
a sheath. These two systems may be named, respectively, the trabecular and
the perivascular lymphatics. Occasionally, the latter can be injected from the
THE ORGANS ANNEXED TO ABDOMINAL DIGESTIVE CANAL. 507
former. The perivascular lymphatics appear to arise in a delicate adenoid tissue
enclosing the smaller arteries, partly from a plexus, and partly from lymph-
cavities, the walls of which are formed by endothelial cells alone. The trabecular
system arises in a plexus lying between the muscle-cell fasciculi.
There is, according to Kyber, a distinct difference between the splenic pulp
and the adenoid tissue surrounding the artery, both histologically and patho-
logically. The latter he regards as performing the usual functions of the
lymphatic system ; while the former, he conceives, may exercise that digestive
action on the albuminoids of the spleen, which Schiff has demonstrated takes
place.)
Nerves. — They are derived from the solar plexus, and, enveloping the splenic
artery, with it enter the spleen. (They appear to be very large, but this
appearance is due to the great proportion of ordinary fibrous tissue investing
them.)
From what has- been said above respecting the arrangement of the splenic
arteries and veins, it will be perceived that the areolae formed by the trabeculag
of the fibrous framework contain the pulp, and are not in direct communication
with the arterial capillaries. Such an organization belongs to erectile tissues.
The arteries communicate with the veins proper by venous canals channeled in
the splenic pulp, and are lined only by an endothelium of elliptical cells. These
venous canals are extremely dilatable, especially in the Horse. When the splenic
vein is inflated, their walls separate and press back the pulp, they become con-
siderably enlarged, and distend the cells of the fibrous structure ; but the air
does not reach the interior of these cells.
Functions. — Nothing precise is known regarding the functions of the spleen ;
though they must be of very secondary importance, because animals in which the
organ has been extirpated, and which have recovered from the operation, have
continued to live in apparent good health. Numerous hypotheses have been
formed on this subject ; two of which, founded on the study of the anatomical
peculiarities of the spleen-tissue, and on exact physiological observations, are as
follows: 1. TTie spleen is a diverticulum for the portal vein. 2. The red corpuscles
of the blood are destroyed in the spleen.
With regard to the first hypothesis, it is evident that, owing to the presence
of the venous sinuses already mentioned, and their great dilatability, as well as
to the elasticity and contractility of the spleen-tissue, the organ is favourably
constructed to act as a blood-reservoir. Goubaux, on the other hand, has
demonstrated that there is always an augmentation in the spleen's volume when
an animal has ingested large quantities of water, the consecutive absorption of
which determines a certain tension in the portal venous system.
The second opinion, emitted by Kolliker, is founded on the existence in the
splenic pulp of blood- corpuscles in a state of decomposition, and in the analyses
.made by J. Beclard of the blood in the splenic vein, which have proved that
there is a notable diminution in the proportion of these. These analyses
have, however, been much questioned, and, recently, Malassez and Picard have
shown results which are in favour of the third hypothesis. They have found
that the red corpuscles increase in the blood of the splenic vein, while the
proportion of iron diminishes in the pulp ; and from this fact they conclude
that in the spleen there is a new formation of corpuscles, in which the iron
contained in the splenic pulp participates.
It is to be remarked that, in the researches undertaken to discover the
508
THE DIGESTIVE APPARATUS IN MAMMALIA.
functions of the spleen, account has not been taken of the connections existing
between this organ and the great omentum in the majority of Mammals, and
which testify that the spleen is only, properly speaking, a vascular appendage
placed on the course of this omentum. But the uses of this vast peritoneal fold
are themselves little understood. Might they not be included with those which
are presumed to belong to its appended organ ?
Differential Characters in the Organs Annexeti to the Abdominal Portion of
THE Digestive Canal in the other Animals.
Fig. 302.
The important diiferences these organs offer in the domesticated Mammals are more
particularly observed in the liver.
1. Liver. — In the domesticated Mammals other than Solipeds, the liver exhibits variations
in form, volume, and position, which have no influence on its organization : so that the study
of these possesses only a moderate amount of interest. This is not so, however, with regard
to the excretory apparatus, the arrangement of which is complicated, and becomes very inte-
resting. The biliary duct, in fact, on leaving the fissure
of the portal vein, and before reaching the intestine,
gives rise to a particular conduit which is detached at an
acute angle, and which, after a course of variable length,
according to the size of the animal, becomes dilated into
a vast sac, the so-called gall-bladder (Figs. 302, 303).
In all treatises on anatomy, the special conduit is
designated the cyxtic (or bile) duct, that portion which
precedes its origin being named the hepatic duct; while
the appellation of ductus communis choledochus is reserved
for the section which goes to the intestine. But these
distinctions are vicious, and we limit ourselves to the
recognition of: (a) A ductus choledochus exactly like
that of Solipeds, and like it extending from the pos-
terior fissure, where it originates by the union of several
branches, to the duodenum ; and (b) a cystic duct, which
branches suddenly into the choledic duct, and terminates
in the gall-bladder.
a. The gall-bladder (Fig. 302, 1) is a reservoir with
membranous walls, in which the bile accumulates during
the intervals of digestion. This sac, lodged wholly, or
in part, in a fossa on the posterior face of the liver, is
oval or pyriform, and presents a fundus and neck. Its
parietes comprise three tunics: an external, of peri-
toneum; a middle, formed of fibrous tissue; and an
internal, or mucous, continuous with that of the various
biliary ducts.
b. Tiie cystic duct (Fig. 302, 2) extends in a straight
line from the neck of the gall-bladder to the choledic
duct. It adheres intimately to the tissue of the liver,
and does not exhibit, internally, tiie spiral valves which have been described in Man. In
opening it longitudinally, tiiere are discovered, at least in Ruminants and the Carnivora, very
small orifices which pierce the wall adherent to the tissue of the liver: these are the openings .
of several minute, but special, biliary canals, named the hepatico-ctjstic ducts.
c. The ductus communis choledochus (Fig. 302, 3) comports itself exactly iis in Solipeds. It is
much wider than the cystic duct, and opens sometimes alone, sometimes with the pancreatic
canal, into the duodenum in a manner which, up to a certain point, reminds one of the moile
of termination of the ureters. Instead of passing perpendicularly across the intestinal parietes,
it first pierces the muscular layer, follows for a short distance between it and the mucous
membrane, and then opens on the internal face of the latter by an orifice which is encircled
by a valvular fold, as in the Horse.
Such is the excretory apparatus belonging to the liver in animals provided with a gall-
bladder. In these animals the biliary secretion is certainly continuous, as in the Horse; but
LIVER OF THE OX.
, Interior extremity of the liver;
B, superior extremity ; C, Spigelian
(caudate) lobe. 1, Gall-bladder;
2, cystic duct; 3, ductus chole-
dochus ; 4, root of that duct ; 5,
posterior vena cava ; 7, intestine ;
8, insertion of the pancreatic duct.
THE ORGANS ANNEXED TO ABDOMINAL DIGESTIVE CANAL.
509
in the intervals of digestion, the bile, instead of flowing directly on to the intestinal surface,
passes into the gall-bladder by the cystic duct, and there accumulates. When digestion
commences again, this reserve of bile is thrown into the ductus choledochus by the contraction
of the muscular fibres of tlie cyst, and by the pressure of the abdominal viscera; it meets that
which comes directly from the liver, and with it is carried to the duodenum.
We will now glance at the particular arrangement of this viscus in each species.
In the Ox, the liver is entirely confined to the right diaphragmatic region. It is thick,
voluminous, and scarcely notched at its periphery ; so that it is difficult, if not impossible, to
distinguish three lobes in it. In Fig. 302, this excretory apparatus is represented, the lobus
Spigelii alone being detached from the mass of the organ. The gall-bladder, fixed towards
LIVER OF THE DOG, WITH ITS EXCRETORY APPARATUS.
D, Duodenum and the intestinal mass ; p, pancreas ; r, spleen ; e, stomach ; /, rectum ; R, right
kidney 5 B, gall-bladder; ch, cystic duct; f f, liver; f', lobe of the liver, prepared to show the
distribution of the vena portse and hepatic vein ; vp, vena portsB ; vh, hepatic vein ; d, diaphragm;
VC, vena cava ; C, heart.
the superior extremity, is nearly always floating ; near its neck it receives the insertion of
several large conduits, which come directly from the upper part of the liver. The ductus
choledochus opens alone at a great distance from the pylorus; Colin has found it to be 24^
inches in one cow, and 29| inches in another. In the Sheep and Goat, the form and position
of the liver differs but little from that of the Ox. The ductus choledochus, however, unites
with that of the pancreas, and terminates at from 12 to 16 inches from the pylorus.
In the Camel, the liver has the same arrangement as in the other Ruminants, except that
Its posterior face is divided, lobulated, and much reticulated.
In the Pig, the liver has three well-marked lobes ; the middle carries the gall-bladder-
The ductus choledochus opens alone at 1 or 1§ inches only from the pylorus.
35
510
THE DIGESTIVE APPARATUS IN MAMMALIA.
In the Dog and Cat, the liver is very voluminous, is deeply notched, and is divided into
five principal lobes. The middle lobe has the gall-bladder attached to it, and gives it complete
lodgment in a fossa.
In the Dog, the ductus choledochus, joined to a small branch from the pancreatic duct,
enters the intestine at a variable distance from the pylorus, depending upon the size of the
animal, but usually between IJ and 4f incht s. In the portion comprised between the intestine
and the origin of the cystic duct, it receives several biliary canals of somewhat considerable
diameter. In the Cat, the ductus choledochus is most frequently inserted from about 1 to IJ
inches from the pyloric orifice; it opens immediately alongside the pancreatic duct, when it
does not join it. ■ u •
2. Pancreas.- In the Ox, the pancreas is not placed across the sublumbar parietes, but is
comprised between th.- layers of the mesentery, to the right of the great mesenteric artery.
The excretory duct is single, and opens into the small intestine at from 14 to 16 inches beyond
the ductus choledochus.
In the Sheep and Goat, there is the same general arrangement, but the excretory ducts
opens with that of the liver.
In the Pig, a portion of the pancreas is situated in the sublumbar region, between the
large tuberosity of the stomach and the last fiexure of the colon ; the other portion is lodged
in the duodenal fraenum. The duct of
Fig. 304.
UNDER SURFACE OF THE HUMAN LIVER.
1, Right lobe ; 2, left lobe ; 3, lobus quadratus ; 4,
lobus Spigelii; 5, lobus caudatus ; 6, longitudinal
fossa ; 7, pons hepatis ; 8, fossa of ductus venosus ;
9, inferior vena cava; 10. gall-bladder; 11, trans-
verse fossa; 12, vena cava; 13, depression corre-
sponding to the curve of the colon; 14, double
depression produced by right kidney and supra-
renal capsule.
Wirsung is inserteil at from 4 to 6 inches
behind the ductus choledochus.
The pancreas of the Dog is extremely
elongated, and included between the layers
of the mesentery which sustain the duo-
denum. It is curved at its anterior ex-
tremity, beliind the stomach, to one side
of tlie median line. Its excretory duct —
usually single — pierces the intestinal mem-
branes 2 inches beyond the hepatic duct
(Fig. 290, m). Except in the mode of
insertion of the excretory duct, which has
been described in noticing the ductus
choledochus, the pancreas of the Cat com-
ports itself exactly like that of the Dog.
3. Spleen.— In Ruminants, the spleen
is not supported by the great omentum, but
adheres to the left side of the rumen and
diaphragm. It is not falciform, and its
breadth is the same througliout its extent.
In the Camivora, it is suspended to the
great omentum at a certain distance from
the left sac of the stomach. It is irregu-
larly falciform, its point is less acute than
in Solipeds, and is directed upwards.
Comparison between the Annexed Organs of the Abdominal Portion of the
Digestive Canal in Man with those of Animals.
1. Liver.— hike that of Ruminants, the liver of Man is situated in the right excavation
of the lower face of the diaphragm. Its direction is nearly horizontal ; its shape is oval,
and its average weight from 49 to 53 ounces. The posterior border is thick and round;
the anterior border and extremities thin and sharp. The upper face, which in i-xpiration
ascends to the fourth rib, is divided into two portions or lobes— right and left, by the falciform
ligament : it is smooth and convex. The inferior face has three furrows, or fossae : two longi-
tudinal, united by a transverse, resembling altogether tlie letter H. The traiisverse furrow
represents that on the posterior aspect of the liver of animals, and its destination is the same.
The right longitudinal furrow lodges the obliterated umbilical vein ; the left, well marked
before and behind, lodges the gall-bladder in front, and the inferior vena cava behind. This
ftice has four lobes, the right and left, and two middle lobes. In front of the transverse furrow
is the lobus quadratus, and behind the same fissure is the lobus Spigelii.
TEE DIGESTIVE APPARATUS OF BIRDS. 511
Nothing is to be said of its structure, and the arraugeiBent of its excretory apparatus is
identical with that of the Ox.
On the lower face of the right lobe are three depressions: au anterior or impressw colica; a
deep middle one, impressio vesicse ; and a small posterior one, which receives the supra-renal
capsules, impressio renalis.
2. Pancreas.— This organ is very elongated transversely, like that of the Dog and Cat. It
is closely applied against the lumbar vertebrae, as in the Horse, bijt its anterior face is much
more enveloped by the peritoneum. Its right extremity rests on the duodenum, while the left
corresponds to the spleen and left kidney. Its texture is consistent, and of a greyish-white
colour. The duct of Wirsung terminates, along with the ductus choledochus, in the ampulla
of Vater.
3. Spleen. — This is not falciform, but quadrangular ; its inferior extremity is larger than
the superior. It is attached to the stomach by the great omentum, and its inner face is divided
into two portions by a salient ridge ; a little in front of this is a fissure — the hilum lienit —
by which vessels enter it.
CHAPTEK III.
The Digestive Apparatus of Birds.
Constructed on the same plan as that of Mammals, the digestive apparatus of
Birds nevertheless offers in its arrangement several important peculiarities,
which will be hurriedly noticed in reviewing, from the mouth to the anus, its
different sections.
Mouth. — The essentially distinctive character of the mouth of Birds consists
in the absence of lips and teeth, these organs being replaced by a horny production
fixed to each jaw, and forming the salient part termed the heak. In the Gallinam^
the beak is short, pointed, thick, and strong, the upper mandible being curved
over the lower. In Palmipeds, it is longer, weaker, flattened above and below,
widened at its free extremity, and furnished within the mouth, on the borders of
each mandible, with a series of thin and sharp transverse laminae to cut the
herbage.
The muscular appendage, or tongue, lodged in the buccal cavity, is suspended
to a remarkably mobile hyoidean apparatus. Covered by a horny epithelium,
and provided at its base with several papillae directed backwards, this organ
always affects the form of the lower jaw : in Poultry it is like the barbed head
of an arrow, the point being directed forwards ; in Pigeons this saggital form
is still more marked : in Geese and Ducks, on the contrary, and in consequence
of the wide shape of the beak, it has not this disposition, and is softer and more
flexible than in the GalKnacse,
With regard to the salivary glands annexed to the mouth, they are imperfectly
developed, the presence of the fluids they secrete being less necessary in Birds
than in Mammals, as the food is nearly always swallowed without undergoing
mastication ; consequently insaUvation is all but useless.
Gurlt ^ speaks of a parotid gland situated beneath the zygomatic arch, the duct
of which opens into the mouth behind the commissm-e of the jaws. Meckel names
this organ the angular gland of the mouth, and says that it is difficult to regard it
' GturM, Anatomie der Hausyogel. Berlin: 1849.
512 THE DIGESTIVE APPARATUS OF BIRDS.
as representing the parotids, any more than the glands of the cheeks and lips.
Duvernoy ^ categorically assimilates it with the latter.
The sublingual glands lie in the median line throughout nearly their whole
extent, and form an apparently single and conical mass, whose apex occupies the
re-entering angle formed by the union of the two branches of the lower maxilla.
According to Duvernoy, the submaxillary glands are represented by two very
small organs situated behind the preceding. Their existence, however, is far
from being general ; for among common poultry, the Turkey was the only bird
in which Duvernoy observed these submaxillary glands.
Pharynx (Fig. 305, 2). — This cavity is not distinct from the mouth, the
soft palate being entirely absent in Birds. On its superior wall may be remarked
the guttural orifice of the nasal cavities : a longitudinal slit divided into two
by the inferior border of the vomer. Below is another less extensive slit, the
entrance to the larynx, and which is remarkable for the complete absence of the
epiglottidean operculum.
(Esophagus. — This canal is distinguished by its enormous calibre and great
expansibility. Its walls are very thin, and contain in their substance lenticular
glands, easily seen in an inflated oesophagus, in consequence of the tenuity and
transparency of its textures.
At its origin, the oesophageal canal is not separated from the pharynx by any
constriction ; in its course it lies alongside the long muscle of the neck, and the
trachea ; its terminal extremity is inserted into the first compartment of the
stomach, or succentric ventricle, after entering the thorax and passing above
the origin of the bronchi, between their two branches.
In Palmipeds, the oesophagus is dilated in its cervical portion in such a
manner as to form, when its walls are distended, a long fusiform cavity.
In Gallinacce (Fig. 305, 3, 4, 5), this dilatation does not exist ; but the
oesophagus presents in its course, and immediately before entering the chest, an
ovoid membranous pouch named the crop (or iiigluvies). In the oesophagus of
these Birds, then, we find two distinct sections, joined end to end — one superior
or cervical, the other inferior or thoracic on the limit of which is the crop. The
latter does not differ in its structure from the oesophagus, and is a temporary
reservoir for the food swallowed by the animal during its meal, and where it is
softened by being impregnated with a certain quantity of fluid ; after which it is
passed into the succentric ventricle by the contractions of the external membrane
of the crop, aided by a wide subcutaneous cervicle muscle which covers that
reservoir.
In Pigeons, the crop is also present ; but it is divided into two lateral
pouches, and exhibits glandular eminences towards the common inferior opening
of these sacs into the oesophagus {aquiparous glands). Singular changes are
observed in the apparent structure of its walls in the male as well as lq the
female, from the eighth to the twentieth day of incubation, or during the first
weeks after hatching, which coincide with the appearance of a kind of secretion
which, when regurgitated, serves to nourish the young birds. At this period,
the membranes of the crop become thickened ; the vessels, more numerous and
more apparent, are redder, and the glands more developed ; the folds or ridges
of the mucous membrane become more marked, and in their interspaces are deep
depressions where an apparently milky fluid accumulates, and which is derived
from the active proliferation of the epithelium and its concomitant fatty
' Cuvier, Anatomie Cum,par€e. 2nd Edition. Paris : 1836.
THE DIGESTIVE APPARATUS OF BIRDS.
513
degeneration. There are no permanent glands for this secretion.^
exclusively nourish their yoimg with this fluid during the first three days of "their
existence.
F5g. 305.
GENERAL VIEW OF THE DIGES-
TIVE APPARATUS OF A FOWL.
The abdominal muscles have been
removed, as well as the ster-
num, heart, trachea, the greater
portion of the neck, and all
the head except the lower jaw,
which has been turned aside to
show the tongue, the pharynx,
and the entrance tn the larynx.
The left lobe of the liver, suc-
centric ventricle, gizzard, and
intestinal mass, have been
pushed to the right to exhibit
the diiferent portions of the
alimentary canal, and to ex-
pose the ovary and oviduct.
1, Tongue ; 2, pharynx ; 3, first
portion of the oesophagus ; 4,
crop; 5, second portion of the
(Esophagus; 6, succentric ven-
tricle ; 7, gizzard ; 8, origin
of the duodenum ; 9, first
branch of the duodenal flex-
ure ; 10, second branch of the
same; 11, origin of the float-
ing portion of the small in-
testine; 12, small intestine;
12', terminal portion of this
intestine, flanked on each side
by the two caeca (regarded as
the analogue of the colon of
mammals); 13, 13, free ex-
tremities of the caeca; 14,
insertion of these two culs-de-
sac into the intestinal tube;
15, rectum ; 16, cloaca ; 17,
anus; 18, mesentery; 19, left
lobe of the liver; '20, right
lobe; 21, gall-bladder; 22,
insertion of the pancreatic and
biliary ducts ; the two pan-
creatic ducts are the anterior-
most, the choledic or hepatic
is in the middle, and the cystic
duct is posterior; 23, pancreas;
24, diaphragmatic aspect of
the lung ; 25, ovary (in a state
of atrophy) ; 26, oviduct.
" Hunter, Observations on certain parts of the Animal Mconomy. London : 1792. Duvernoy,
inG. Q,\xyKX,Legons d'Anatomie Comparee. 2nd Edition. Paris: 1836. Charbonelle-Salle
and Phisalix, Sur la Secretion Lact€e de Pigeons en Incubation, in Comptes Rendu de I'Academie
des Sciences. 1886.
514 THE DIGESTIVE APPARATUS OF BIRDS.
Stomach. — The stomach presents numerous variations in Birds. Its simplest
form is seen in the Heron, Pelican, Petrels, etc., where it is a single sac provided
with a thick zone of glands around the entrance of the oesophagus, which secrete
the gastric juice. But in the majority of the other species, and particularly in
our domesticated Birds, the disposition of the stomach is modified and comphcated ;
the glandular zone destined for the gastric secretion forms a special compartment
— the surcentric ventricle, and this is followed by a second reservoir — the gizzard,
which is remarkable for the strong muscular constitution of its walls. The first
is also named the glandular stomach, and the second the muscular stomach.
Glandular stomach, or succentric ventricle {proventriculus) (Fig. 305, 6). — This
is an ovoid sac placed in the median plane of the body, between the two lobes of
the liver, and beneath the aorta. Its anterior extremity receives the insertion
of the oesophagus ; the posterior is continued by the gizzard. The volume of
this stomach is inconsiderable, and its cavity is very narrow ; the aliment does
not accumulate in it, but merely passes through, carrying with it the acid juice
which afterwards dissolves its protein elements. Its walls have three tunics : an
external or peritoneal ; a middle, formed of white muscular fibres, continuous
with those of the oesophagus ; and an internal, of a mucous nature, perforated
by orifices for the passage of the gastric juice. These are small cylinders placed
perpendicularly to the surface of the stomach, closely laid against one another,
like the microscopic glands of Lieberkiihn, and contained in the connective tissue
layer uniting the inner to the middle tunic. The glandular structure of this
receptacle caused it to be regarded as the true stomach in Birds ; but Jobert has
shown that the real gastric juice is secreted in the gizzard.
Gizzard or muscular stomach {ventricidus bulbosus) (Fig. 305, 7). — Much
more voluminous than the preceding, this stomach is oval in form, depressed on
each side, and situated behind the liver, being partly covered by the lateral lobes
of that gland. Above, and to the right, and at a short distance from each other,
are seen the insertion of the succentric ventricle and the origin of the duodenum.
The cavity of the gizzard always contains food mixed with a large quantity of
silicious pebbles, the use of which will be indicated hereafter.
This viscus is composed of the three timics which form the walls of all the
abdominal reservoirs. The internal, or mucous, is distinguished by the thickness
and extraordinary induration of its epidermic layer, which presents nearly all the
characters of horny tissue, and which results from the accumulation of the
products secreted by the epithelium. The latter is spheroidal, and is so easily
detached from the mucous chorium that it is often regarded as a special
membrane. On the adherent face of this corium are applied two powerful red
muscles — a superior and inferior, occupying the borders of the organ, and whose
fibres, disposed in flexures, pass from side to side, and are inserted into a strong,
nacrous aponeurosis on the lateral surfaces of the organ. Outside this contractile
apparatus is a thin peritoneal envelope.
The gizzard is the triturating apparatus of Birds. "When the aliment reaches
its cavity it has not yet submitted to any disaggregation, but here it meets with
all the conditions indispensable for the accomplishment of this act : two energetic
compressor muscles, a corneous layer spread over the internal surface of the
viscera, giving to it the rigidity necessary to resist the enormous pressure exercised
on its contents ; and silicious pebbles — veritable artificial teeth — which an
admirable instinct causes Birds to swallow, and between which, by the effort
of the triturating muscles, the food is bruised. This triturating action of the
THE DIGESTIVE APPARATUS OF BIRDS. 515
gizzard is only effected in Birds fed on hard coriaceous aliment, such as the
various kinds of grain. It would be useless in Birds of prey, in which the two
gizzard muscles are replaced by a thin fleshy membrane of uniform thickness —
showing that the presence of these muscles is subordinate to the kind of ahmentation.
Intestine. — The length of the intestine varies, as in Mammals, according to
the nature of the food : very short in Birds of prey, it is notably elongated in
omnivorous and granivorous Birds. Its diameter is nearly uniform throughout
its whole extent, and it is difficult to establish in Birds the various distinctions
recognized in the intestine of Mammalia. It begins by a portion curved in a
loop, which represents the duodenum, the two branches of which, lying side by
side, are parallel to each other, like the cohc flexure of Solipeds. Fixed by a
short mesenteric frsenum to the colon, this part of the intestine includes the
pancreas between its two branches. Its curvature floats freely in the pelvic
portion of the abdominal cavity (Fig. 305, 8, 9, 10).
To the duodenal loop succeed convolutions suspended to the sublumbar parietes
by a long mesentery, and which are rolled up into a single mass, elongated from
before to behind, occupying a middle position between the air-sacs of the
abdominal cavity. The analogy existing between this mass of convolutions, and
ths, floating portion of the small intestine of Mammals, does not require demonstration
(Fig. 305, 11, 12).
The terminal part of this floating intestine lies beside the duodenal loop, and
is flanked by the two appendages disposed like cceca. These, scarcely marked in
the Pigeon by two small tubercles placed on the track of the intestinal tube, do
not measure less than from 6 to 10 inches in the other domesticated Birds ;
they are two narrow culs-de-sac, slightly club-shaped at their closed extremities,
which are free and directed towards the origin of the intestine, while the other
extremity opens into the intestinal canal near the anus. There are always
alimentary matters in these sacs, these becoming introduced, in following a
retrograde course, by the same almost unknown mechanism which presides over
the accumulation of spermatic fluid in the vesiculae seminales. According to the
majority of naturalists, these two appendages, although described as cceca, do not
represent the reservoir bearing that designation in Mammals. This reservoir is
nothing more than a small special appendix placed on the track of the intestine,
in front of the free extremity of the above-mentioned culs-de-sac, and is only to
be found in a small number of Birds, and among these sometimes, as Gurlt^
affirms, is the Goose. According to this view, which appears to be a very
rational one, the portion of intestine comprised between the two blind tubes
annexed to the viscera (Fig. 305, 12') corresponds to the colon, and these tubes
themselves are only dependencies of this intestine.
The rectum (Fig. 305, 15) terminates the digestive canal ; it is the short
portion of intestine that follows the opening of the caeca. Placed in the
sublumbar region, this viscus is terminated by a dilatation, the cloaca (Fig. 305,
16), a vestibule common to the digestive and genito-urinary passages, which
opens externally at the anus, lodges the penis when it exists, and serves as a
confluent for the ureters, oviduct, bursa of Fabricius, and the deferent canals.
Abdominal Appendages of the Digestive Canal. — Lirer (Fig. 305, 19,
20). — This is a voluminous gland, divided into two principal lobes — a right and
left, the former always larger than the latter ; these incompletely include, on
each side, the gizzard and succentric ventricle. In the Pigeon, this gland is
» Gurit, Op. cit
516 TEE DIGESTIVE APPARATUS VF BIRDS.
provided with a gall-bladder (Fig. 305, 21) attached to the internal face of the
right lobe. But the arrangement of the excretory apparatus is not altogether
identical with that observed in Mammals which possess thi^ receptacle ; as two
biliary ducts open separately into the intestine towards the extremity of the
second branch of the duodenal loop. One proceeding directly from the two
lobes of the liver, is the hepatic or choledic dud; the other, the cystic duct,
remains independent of the latter, and opens behind it. It carries into the
digestive canal the bile accumulated in the gall-bladder, and which arrives there
by a particular duct belonging exclusively to the right lobe ; the cystic canal is
a branch of this duct (Fig. 305, 22).
Pancreas (Fig. 305, 23). — In the GaUinacce, this gland is very developed,
long, and narrow, and is comprised in the duodenal loop or flexm-e ; at the
extremity next the gizzard it has two principal excretory ducts, which separately
pierce the intestinal membranes, a little in front of the hepatic duct.
Spleen. — This is a small, red-coloured, disc-shaped body, placed to the right
of the stomachs, on the limit of the gizzard and succentric ventricle.
BOOK III.
Respiratory Apparatus.
The maintenance of life in animals not only requires the absorption of the
organizable and nutritive matters conveyed to the internal surface of the
digestive canal, but demands that another principle — the oxygen of the atmo-
sphere— should enter with these materials into the circulation. In animals with
red blood, this element, in mixing with the nutritive fluid, commences by
expelling an excrementitial gas — carbonic acid — and communicating a bright red
colour to that fluid, with which it circulates ; it is brought into contact, in the
general capillary system, with the minute structures of the various apparatuses,
exercising on the organic matter composing them a particular stimulating
influence, without which the tissues could not manifest their properties, as well
as inducing a combustible action which evolves the heat proper to the animal
body.
This new absorption constitutes the phenomenon of respiration. In the
Mammalia, this is effected in the lungs — parenchymatous organs chambered into
a multitude of vesicular spaces, which receive the air and expel it, after depriving
it of a certain quantity of oxygen, and giving, in return, a proportionate quantity
of carbonic acid. These organs are lodged in the thoracic cavity, the alternate
movements of dilatation and contraction of which they follow. They com-
municate with the external air by two series of canals placed end to end : 1. A
cartilaginous tube originating in the pharyngeal vestibule, and ramifying in the
lungs. 2. The nasal cavities, two fossae opening into that vestibule, and com-
mencing by two openings at the anterior extremity of the head.
CHAPTER I.
RESPIRATORY APPARATUS IN MAMMALIA.
In this apparatus we will first study the organs external to the thoracic cavity —
the nasal cavities, and larynx and trachea; then the chest and the organ it
contains — the lung.
To this study will be added that of the two glandiform organs, the uses of
which are unknown, but by their anatomical connections they belong to the
respiratory apparatus. These are the thyroid bodies and the thymus gland.
518
RESPIRATORY APPARATUS IN MAMMALIA.
The Nasal Cavities.
These cavities are two in number — a right and left — and offer for study : their
entrance, or nostrils — the fossce, properly called, which constitute these cavities ;
and the diverticuli named sinuses.
Preparation. — Remove the lower jaw from three heads. On the first of these make two
transverse sections, one passing between the second and third molar tooth, the other behind
the dental arch. Saw through the second head longitudinally and vertically, a little to one
side of the median line. On the third make a horizontal section in such a manner as to obtain
an inferior portion analogous to that shown in Fig. 41. On this the organ of Jacobson may
be studied.
Fig. 306.
1. The Nosteils.
The nostrils (or anterior or inferior nares) are two oblong, lateral openings,
situated at the extremity of the nose, circumscribed by lips or movable ivings
(alee) disposed in an obhque direction downwards and inwards, and slightly
curved on themselves, so as to present theu' concavity to the external side.
The lips or alee of the nostril are enveloped, inwardly and outwardly, by a
thin, delicate skin, covered by fine, short hairs. The external is concave on its
free margin ; the internal is convex. The commissure which unites these two
wings superiorly, fonns a slight arch curved inwards. When the finger is
introduced into this commissure it does not enter the nasal cavity, but the false
nostril — a conical pouch formed by the skin, extending
to the angle comprised between the nasal spine and the
ascending process of the premaxillary bone.
In the Ass, according to Goubaux, the false nostrU is
areolated at the posterior extremity, which ascends beyond
the summit of the re-entering angle formed by the nasal
and premaxillary prolongation.
The inferior commissure is round and wide, and, to-
wards the bottom, presents an opening, sometimes double^
which looks as if punched out ; this is the inferior orifice
of the lachrymal duct, which, in the Ass and Mule, is
carried to the inner face of the external wing, near the
superior commissure.
Steucture. — The nostril is composed of a carti"
laginous frameivorlc, muscles to move it, and shin, vessels^
and nerves.
Cartilaginous frameworlc (Fig. 306). — This framework
is formed by a cartilage, bent like a comma, and which, in
its middle part, lies against that of the opposite side, the
two making a kind of figure X. Fixed in a movable
manner to the inferior extremity of the middle septum
of the nose, by means of short intei-posed fibres, this cartilage offers : a wide upper
part, situated in the substance of the inner wing of the nostril, and covered by
the dilatator naris transversalis of the nose (Fig. 306, 1) ; and an inferior portion,
which, after passing into the lower commissure, is prolonged, in a blunt point, to
the external wing, where it receives the insertion of several fasciculi belonging to
the orbicularis muscle of the lips, the dilatator naris lateralis, and the levator
labii superioris (Fig. 306, 2). Each wing, therefore, possesses its cartilaginous
CARTILAGES OF THE
NOSTRILS
1, 1, Wide portion, forming
the base of the internal
wing of the nostril ; 2,
2, narrow extremity pro-
longed into the external
wing; 3, superior or an-
terior border of the nasal
septum.
THE NASAL CAVITIES. 519
skeleton ; but that of the external wing is very incomplete, in consequence of its
being only formed by the inferior extremity of the common cartilage.
These cartilages, it will be understood, sustain the alte of the nose, prevent
their falling inwards, and always keep open the external orifices of the respiratoiy
apparatus.
Muscles. — The motor muscles of the alae are all dilators in the domesticated
animals. They are : the trcmversalis dilatator naris, a single muscle placed on the
widened portions of the cartilages ; the dilatator naris lateralis, the insertion of
which occupies the whole extent of the external wing ; the dilatator naris superior,
fixed, by its two portions, to the skin of the false nostril ; the dilatator naris
inferior, which is confounded, superiorly, with the external fasciculus of the pre-
ceding muscle, it being attached to the inferior branch of the cartilaginous
appendix of the supermaxillary turbinated bone ; and, lastly, the levator labii supe-
rioris alaque nasi, the anterior branch of which is inserted, in part, into the external
wing. All these muscles, having been described in the Myology (p. 278), need
not be further alluded to here.
Skin of the nose. — The skin covering the alae of the nose, externally, is
doubled over their free margin to line their internal surface, being prolonged
over the entire extent of the false nostril, and is continued in the nasal fossae,
by the properly so called pituitary membrane. This skin is fine, thin, charged with
colouring pigment, often marked by leprous spots, and adheres closely to the
muscles included between its duphcatures, through the medium of a very dense,
resisting, connective tissue.
Vessels and nerves. — The nostrils are supplied with blood by the superior
coronary, the external nascd, and the palato-labial arteries ; it is returned by the
glosso-facial veins, and partly by the venous network of the nasal mucous
membrane. The lymphatics, large and abundant, receive those of the pituitary
membrane, and join the submaxillary glands by passing over the cheeks. The
nerves are very numerous, the sensory being derived from the maxillary branch
of the fifth pair, and the motors from the facial nerve.
Functions. — The nostrils permit the entrance to the nasal cavities, of the
air which is to pass to the lungs. Their dilatability allows the admission of a
greater or less volume, according to the demands of respiration. It is to be
remarked that, in Solipeds, the nostrils are the only channel by which the air can
gain access to the trachea, in consequence of the great development of the soft
palate, which is opposed to its entrance by the mouth ; these orifices are therefore,
for this reason, relatively larger than in the other domesticated animals, in which
the passage of air by the buccal cavity is easily accomplished.
2. The Nasal Foss^ (Figs. 306, 307, 308).
Channeled in the substance of the head, above and in front of the palate, and
separated from one another, in the median plane, by a cartilaginous septum which
does not exist in the skeleton, the nasal fossas extend from the nostrils to the
cribriform plate of the ethmoid bone, in a direction parallel to the larger axis of
the head. Their length is, therefore, exactly measured by that of the face (see
Fig. 308 for the whole of these cavities).
The nasal fossae are formed by two lateral walls, a roof or arch, di. floor, and
two extremities.
Walls. — The two walls are very close to each other, and the more so as they
are examined towards the ethmoid bone and the roof of the cavity. The space
520 RESPIRATORY APPARATUS IN MAMMALIA.
separating them varies, in proportion as it is measured at the turbinated bones or
at the meatuses.
Inner wall. — This is fonned by the nasal septum, and is perfectly smooth.
Outer vmlL — This is chiefly constituted by the supermaxillary bone ; it is
very rugged, and is divided into three meatuses, or passages, by the tui'binated
bones — the iiTegular columns applied against the inner face of the before-mentioned
bone.
The turbinated hones have already been described (p. 73), and we will only
now refer to the principal features in their arrangement. Each is a bony plate
rolled upon itself (Fig. 307, 2, 3), and divided, internally, into two sections, the
superior of which forms part of the sinus, and the inferior belongs to the nasal fossa ;
they are continued, inferiorly, by a fibro-cartilaginous framework, which prolongs
Fig. 307.
TRANSVERSE SECTION OF THE HEAD OF AN OLD HORSE, SHOWING THE ARRANGEMENT OF THE
NASAL CAVITIES AND MOUTH.
I, 1, Nasal fossae ; 2, superior turbinated bone , 3, inferior ditto ; 4, median septum of the nose ; 5,
central part of the buccal cavity (drawn more spacious than it really is when the two jaws are
brought together) ; 6, 6, lateral portions of the same ; 7, section of the tongue, showing it filling
the lingual canal.
their nasal section to the external orifice of the nose. The flexible appendage of
the ethmoidal turbinated bone is usually single, sometimes double, and disappears
before reaching the alfe of the nose. That of the premaxillary turbinated bone is
always bifurcated, and its antero-superior branch is directly continued by the
superior extremity of the internal wing of the nostril.
The meatuses are distinguished into superior, middle, and inferior, or into
anterior, middle, and posterior, as the head is inspected in a vertical or horizontal
position. The superior passes along the corresponding border of the ethmoidal
turbinated bone, and is confounded with the roof of the nasal cavity ; it is pro-
longed, behind, to near the cribriform plate of the ethmoid bone, and is the
THE NASAL CAVITIES. 521
narrowest. The middle, comprised between the two tui'binated bones, presents,
on arriving near the ethmoidal cells, the orifice that brings all the sinuses into
commmiication with the nasal fossa. This orifice is ordinarily narrow and
curved ; but we have seen it sometimes converted into a foramen sufiiciently
wide to permit the introduction of a finger-end. It is also by this meatus that
the inferior compartment of the turbmated bones opens into the nasal fossa, these
two bones being each rolled in a contrary direction. The inferior meatus, situated
under the maxillary turbinated bone, is not distinct from the floor of the nasal
cavity (see Fig. 307 for the arrangement of the turbinated bones and the
meatuses on the external wall of the nose).
Roof or arch. — This is formed by the nasal bone, and is only a nan'ow channel,
confounded, as has been said, with the superior meatus.
Floor.— Wider, but not so long as the roof, which is opposite to it, and from
which it is distant by the height of the cartilaginous septum, the floor is concave
Fig. 308.
LONGITUDINAL MEDIAN SECTION OF THE HEAD AND UPPER PART OF THE NECK.
1, 1, Atlas; 2, 2, dentata ; 3, trachea; 4, right stylo-thyroideus ; 5, guttural pouch ; 6, stylo..
pharyngeus; 8, palato-pharyngeus ; 9, sphenoidal sinus; 10, cranial cavity; 11, occiput; 12,
parietal protuberance; 13, frontal sinus; 14, ethmoidal turbinated bone; 15, premaxillary turbi-
nated bone; 16, entrance to nostril; 18, pharyngeal cavity; 19, inferior maxilla; 20, premaxilla;
21, hard palate.
from one wall to the other, and rests on the palatine arch, which separates .the
mouth from the nasal cavities.
In front of this nasal region is remarked the canal or or gem. of Jacohson — a
short duct terminating in a cul-de-sac in the middle of the cartilaginous substance
which closes the incisive foramen. • At the bottom of this ctd-de-sac opens a
second canal, longer, wider, and more remarkable, but which has not yet been
described. (It has been described by Steno, and is named " Steno's canal") It
has sometimes the diameter of a writing-quill, commences by a cul-de-sac at the
level of the second molar tooth, and accompanies the inferior border of the vomer
from behind to before, where it is enveloped in a kind of cartilaginous sheath —
a dependency of the nasal septum ; it terminates, as we have said, after a course
of about 5 inches.
The structure of Jacobson's organ resembles that of the excretory duct of
glands ; its walls are evidently composed of two tunics — an internal or mucous, very
522 RESPIRATORY APPARATUS IN MAMMALIA.
rich in follicles, and having longitudinal folds ; and an external, of a fibrous nature.
These membranes receive numerous vessels, as well as nerves emanating from a
long filament of the spheno-palatine ganglion, and which may be traced from
the external side of the canal to near the incisive foramen, where it is lost. Such
is the organ of Jacobson ; its uses are quite unknown. (It belongs to the
olfactory region, for between the ciliated cells of its mucous membrane are found
staff-like cells, which are connected with the ends of the olfactory nerve-filaments.)
Extremities. — The anterior or inferior extremity of the nasal fossa {regie vesti-
bularis) is formed by the nostril already described. The posterior or superior
extremity presents, above, a space occupied by the ethmoidal cells. Below £md
behind, this extremity communicates with the pharyngeal cavity by a wide oval
opening, which is circumscribed by the vomer and palate bones : this is the
guttural opening of the nasal fossa (or posterior nares).
Structure. — The nasal fossae offer for study : 1. The bony frameivork
by which these cavities are formed. 2. The cartilaginous septum, separating
them. ;3. The pitidtary membrane — the mucous layer lining their walls.
1. Bony Framework of the Nasal Fossae. — This comprises : 1. The
nasal., maxillary, frontal, and palate bones, which together form a vast irregular
wall circumscribing the nasal fossas. 2. The ethmoid bone, occupying the bottom
of this tubular cavity, and the turbinated bones applied against the lateral walls.
3. The vomer, placed in the median plane, and serving as a support for the
cartilaginous partition dividing this single cavity into two compartments. All
these bones having been already studied in detail, we confine ourselves to their
simple enumeration.
2. Middle Septum of the Nose {septum nasi) (Fig. 307, 4). — Formed of
cartilage susceptible of ossification, this partition is nothing more than the per-
pendicular lamina of the ethmoid bone prolonged to the extremity of the nose.
Its elongated form permits us to recognize in it tivo faces, two borders, and two
extremities. The faces are channeled by a multitude of furrows, which lodge
the anastomosing vessels of the magnificent venous plexus of the pituitary
membrane.
The superior border, united to the frontal bone and median suture of the
nasal bones, expands to the right and left on the inner faces of these, in forming
two lamina, thm at their free margin, the section of which is represented in
Fig. 307. These laminae are wide enough in front to project beyond the nasal
spine. The inferior border is received into the mortice of the vomer.
The posterior extremity is continued without any precise limitation, by the
perpendicular lamina of the ethmoid bone.
The anterior extremity, a little wider, supports the cartilages of the nostrils.
It is joined, below, to the premaxillary bones, and is spread out on the incisive
openings in a thick layer which exactly closes them.
This septum is covered by a thick perichondrium, which adheres intimately
to the pituitary membrane.
3. Pituitary Membrane. — This membrane — also designated the olfactory
mucous membrane, and Schneiderian membrane — is continuous with the skin lining
the inner face of the alas of the nose. Examined on the internal wall of the
nasal fossae, the pituitary membrane is seen to cover the cartilaginous septum
forming this wall, then spreads over the floor as well as the roof of the cavity,
reaching the outer wall, which it also covers in enveloping the external surface
of the turbinated bones, and is insinuated, by the middle meatus, into the cells
THE NASAL CAVITIES.
523
Fig. 309.
11/
of the inferior or anterior compartment of these osteo-cartilaginous columns. It
also penetrates, by the semicircular opening of this meatus, into the sinus, to give
it its mucous lining, and is likewise prolonged into the canal of Jacobson.
Behind, it is continuous with the lining membrane of the pharyngeal cavity.
Its deep face is separated by the periosteum or perichondrium, from the bony
or cartilaginous walls on which it is spread ; and it is united to the two precited
layers, this union being closest where it is thinnest, although it can always be
easily distinguished from them throughout the whole extent of the nasal fossa.
The free, or superficial face, presents numerous glandular orifices, and is constantly
covered by an abundance of mucus, that prevents the desiccation to which this
surface is exposed by the incessant movement of air over it.
Steuctuee. — The organization of the pituitary membrane resembles that of
other mucous membranes, but it also presents some difi'erences according as
it is examined near the nostrils or deeper in the cavities. It is also usual
to divide it into two portions — the olfactory mucous
memhrane, which covers the upper part of the ethmoidal
turbinated bone and cells ; and the Schneiderian mem-
brane, fining the inferior two-thirds of the nasal cavities.
The corium {tunica propria) of the Sclmeiderian mem-
hrane {regio respiratoria) is thick, soft, spongy, and rose-
coloured, and contains a large number of vessels and
glands. The latter are mucus or racemose glands, and
are extremely abundant in the layer covering the septum
of the nose, as well as at the inner face of the carti-
laginous appendages of the turbinated bones ; though
they are rare or altogether absent on the external face
of the latter. The epithelium is ciliated and stratified,
the deeper cells being spherical, those on the surface
cyhndrical.
The olfactory mucous memhrane {regio olfactoria)
differs from the preceding by its greater thinness, its
delicateness, its slightly yellow tint, and the character
of its epithelium. The corium {tunica propria) contains
straight or slightly convoluted tubular glands — the glands
of Bowman. The epithelium is columnar and stratified,
and readily alters ; in animals it is destitute of cifia.
The deeper cells contain some yellowish pigment granules.
Schultze describes as olfactory cells, certain fusiform
elements which he considers are concerned in olfaction,
prolongations — a deep one, which is connected with the fibres of the olfactory
nerve ; and a superficial, that enters between the epithelial cells, and tends to
approach the free surface of the membrane.
(The " olfactory cells " are thin, rod-like bodies (Fig. 309, b), presenting
varicose enlargements which are connected with processes of deeper-seated nerve-
cells. The epithelial cylinders proper {d, e) are related at their bases with the
septa of connective tissue belonging to the sub-epithelial glandular layer, and are
probably in communication with the olfactory cell. Schultze describes another
set of epithelial cells {a) as terminating externally by truncated flat surfaces, and
to all appearance not covered by any membrane, apart from the contents of the
cell, which are yellow, granular protoplasm, surrounding an oval nucleus lying
CELLS OF THE OLFACTORT
MUCOUS MEMBRANE.
a, b, c, After Schultze;
d, e, f, after Lockhart
Clarke.
These cells have two
524
RESPIBATORY APPARATUS IN MAMMALIA.
Fig. 310.
in colourless protoplasm. The extremity of these cells is thin, and they can be
traced inwards until they expand into a flat portion that sends off processes,
which appear to be continuous with the fibres of the submucous connective tissue.
Similar cells (c) are found towards the margin of the true olfactory region, but
these have a band at their free extremity, which is also provided with a circle
of cilia.)
The pituitary membrane receives its blood by the ophthalmic and nasal
arteries ; it is returned by the large anastomosing veins which form — in the deep
layer — a long, close, and magnificent plexus that terminates in the satellite vein of
the nasal artery. This plexuous arrangement is so marked at certain points — as
at the appendages of the turbinated bones — that it gives the mucous membrane
somewhat the appearance of erectile tissue. It will be understood that in
favouring the stagnation of the blood, this arrangement predisposes to hemor-
rhage.
The lymphatics of the pituitary membrane could not be injected for a long
time, neither in Man nor animals ; and this led several anatomists to deny their
existence. Nevertheless, they do exist, and form a fine super-
ficial network on the septum of the nose, the turbinated
bones, and the meatuses. The trunks passing from this net-
work go to the submaxillary glands.
The nerves of this membrane are numerous, and are
derived from the first and fifth pairs, and from Meckel's
ganglion. The ramifications of the olfactory nerve, on
emerging from the apertures of the cribriform plate of the
ethmoid bone, pass to the inner and outer walls of the nasal
cavities ; being destined for the olfactory mucous membrane,
they do not descend below the upper third of these cavities.
They form at first a close plexus, and afterwards terminate
in a manner not quite understood. Schultze admits that
they terminate on the olfactory cells mentioned above.
The branches derived from Meckel's ganglion and the
fifth pair, are specially destined for the Schneiderian mem-
brane, and are named the ethmoidal branches of the palpebro-
nasal and spheno-palatine nerves. They endow the nose
with an acute degree of sensibility, and it is believed that they render olfaction
more perfect.
(It is to be remarked that the filaments composing the olfactory plexus, differ
from ordinary cranial nerves in containing no white substance of Schwann, and
are nucleated and finely granular in texture, resembling the gelatinous form of
nerve-fibres. The surface to which they are limited is that covered with the
yellowish-brown epithelium.)
FIBRES OF ULTIMATE
RAMIFICATIONS OF
OLFACTORY NERVE
OF DOG.
3. The Sinuses.
The sinuses are very winding cavities, excavated in the substance of the bones
of the head, on the limits of the cranium and face, and around the ethmoidal
masses, which they envelop.
These cavities — diverticuli of the nasal fossae — are pairs, and are five on
each side, arranged in two groups: 1. The /rowto/, supermaxiUarij, sphenoidal,
ethmoidal sinuses. 2. The inferior maxillary sinus. The first four communicate ;
the last is usually perfectly isolated.
TEE NASAL CAVITIES. 525
First Group.
Frontal Sinus. — This cavity, situated at the inner side of the orbit, presents
very irregular walls, which are formed by the frontal nasal, lachrymal, and
ethmoid bones, and the superior portion of the ethmoidal turbinated bone. lb
communicates with the superior maxillary sinus by a vast opening, made in a
very thin bony partition. A thick vertical plate, often bent to the right or left,
but always imperforate, separates this sinus from that of the opposite side.
Superior Maxillary Sinus. — Channeled beneath the orbit, between the
maxillary, malar, ethmoid, and lachrymal bones, this diverticulum is the
largest of all, and is divided into two great compartments by the maxillo-dental
canal, which traverses it. The internal compartment is a kind of shallow cavity,
continuous with the sphenoidal sinus, and presents a narrow sht, which opens
into the ethmoidal sinus. The external compartment is separated, in front,
from the maxillary sinus, by a partition which Goubaux has, contrary to the
generally received opinion, demonstrated to be imperforate at all periods of life ;
though he has sometimes found it so thin as only to consist of two layers of
mucous membrane laid against each other. This compartment is prolonged
backwards into the maxillary protuberance, and the roots of the two last molars
project into its interior.
Sphenoidal Sinus. — This is the smallest, after that of the great ethmoidal
cell. Formed by the sphenoid and palatine bones, this cavity is very irregular,
and is subdivided by incomplete septa into several compartments, which may be
always reduced to two — an anterior, comprised between the palatine laminae ; and
a posterior, in the body of the sphenoid bone. In contact, on the median line,
with the sinus of the opposite side, it is separated from it by a twisted plate,
which is constantly perforated, even in young animals.
Ethmoidal Sinus. — This is a cavity in the large ethmoidal cell ; it consti-
tutes a real sinus, and has a narrow slit which brings it into communication with
the superior maxillary sinus.
Second Group.
Inferior Maxillary Sinus. — This last diverticulum is remarkable, because
of its not communicating with the others. Excavated in the super maxillary
bone, and separated from the superior sinus by the imperforate septum previously
mentioned, it is divided, like the latter cavity, into two compartments — an
internal, prolonged into the superior cavity of the supermaxillary turbinated
bones ; and an external — the smallest — showing the roots of the fourth molar,
rarely those of the third. It does not descend, as Rigot has asserted, above the
three anterior molars ; supposing the head to be vertical, it does not extend, in
the adult Horse, beyond the extremity of the maxillary ridge, in front of which it
would be necessary to trephine, in order to reach it. It is sometimes larger on
one side than the other.
The inferior maxillaiy sinus, in the Ass, communicates with the superior
maxillary sinus. " These two parts of the maxillary sinus, or the two maxillary
sinuses," says Goubaux, " always communicate largely with each other in the
Ass. I have never seen an exception to this ; and the peculiarity is due to the
fact, that the base or posterior extremity of the inferior turbinated bone is checked
in its development, and does not curve sufficiently to join the inner surface of
the supermaxilla, and become attached thereto,"
36
526 RESPIRATORY APPARATUS IN MAMMALIA.
Communicating Orifice of the Sinuses with the Nasal Fossa. — All
the sinuses of one side communicate with the corresponding nasal fossa, by the
curved slit at the bottom of the middle meatus. This slit penetrates the superior
maxillary sinus, under the septum that separates it from the frontal sinus ; it
also enters the inferior maxillary sinus, which thus communicates solely with the
nasal cavity, while the other diverticuli open in common into this cavity, through
the medium of the superior maxillary sinus.
Mucous Membrane of the Sinuses. — In entering the sinuses to cover
their walls, the pituitary membrane becomes extremely thin, and loses its great
vascularity ; it is applied immediately to the bones, and serves as a periosteum.
It has some nerves which terminate in small bell-shaped organs (Inzani).
Development of the Sinuses. — These cavities begin to be developed in
the foetus, and are gradually formed in the thickness of the bones they occupy.
They increase during the animal's hfetime, by the thinning of the bony plates
enclosing or partitioning them, and particularly by the growth of the superior
molar teeth, the roots of which project into them. The formation of the inferior
maxillary sinus is more tardy than the others ; though it is not so late as seven
or eight years, as the majority of Veterinary Anatomists have asserted. Goubaux
has proved that the sinus is already present in a six-months-old animal ; and in a
head which has been for several years in the museum of the Lyons School, and
which belonged to a foal of very small stature, about a year old, this sinus is
found, in its external part, to be already 1^ inches in depth, and -^ of an inch
in width.
Functions of the Sinuses. — Have the sinuses or diverticuli of the nasal
cavities, the same uses as these cavities ? It is probable, although not absolutely
certain. There is nothing to prove that they have anything to do with respira-
tion or olfaction ; and it would seem that their exclusive function is to give
increased volume to the head without increasing its weight, and in this way to
furnish wide surfaces of attachment for the muscles belonging to this region —
these cavities being all the more ample as the muscles are large and numerous.
DiFFEBENTIAL ChABACTERS IN THE NaSAL CaVITIES OF THE OTHER ANIMALS.
1. Nostrils. — In the Ox, the nostrils, placed on each side of the muffle, are narrower and
less movable than in the Horse. (The superior extremity of the ala is not horizontal ; the
inferior is divided into two branches.)
In the Pig, the end of the nose constitutes the snout (rostrum suis), the anterior surface of
which, plane and orbicular, shows the external orifices of the nostrils. This snout — a veritable
tactile organ employed by the animal to dig up the ground — is covered by a dark-coloured
skin, kept damp by a humid secretion, like the muffle of the Ox. It has for base tlie scooping-
hone—a, particular piece situated at the extremity of the nasal septum, and enveloped by a
layer of cartilage that extends around the nostrils. It is easy to distinguish two symmetrical
halves in this bone, which evidently represent the two cartilages in the nose of Solipeds.
In the Dog, the end of the nose forms a salient region, which is roughened, naked, usually
dark-coloured, damp, and sometimes divided by a median groove ; in this region the nostrils
are placed, their form resembling two commas opposed to each other by their convexities.
The cartilaginous framework sustaining these orifices is not composed of separate pieces, but
is only a dependency of the median septum and the appendages of the turbinated bones.
The same considerations apply to the nostrils of the Cat, with the exception of tlie colour
of the integument, which is nearly always of a rosy hue, like the mucous surfaces.
2. Nasal Cavities.— The nasal fossae of the Ox, Sheep, and Goat, are distinguished by
the presence of a third turbinated bone— the olfactory antrum, and by the communication
existing between them, posteriorly, above the inferior border of the vomer. We have already
seen that in these animals, as in those yet to be mentioned, the canal of Jacobson passes
completely through the palatine arch.
THE LARYNX. 527
In the Pig, the nasal fossae are long and narrow. They are, on the contrary, very short
in the Dog and Cat, and the internal cells of the turbinated bones, remarkable for their
number and complexity, all communicate with the proper nasal fossae, without concurring iu
the formation of the sinuses- The latter are divided by the vomer into two superposed com-
partments, very distinct from each other iu their posterior half; the superior is olfactory, the
inferior is respiratory.
3. Sinuses.— In the Ox, the frontal amuses are prolonged into the bony cores which support
the horns, and into the parietal and occipital bones ; they therefore envelop, in a most com-
plete manner, the anterior and superior part of the cranium, and form a double wall to this
bony cavity. They are extremely iiverticulated, and do not communicate with those of the
supermaxillary bones. They usually open, on each side, into the nasal cavities, by four
apertures at the base of the great ethmoidal cell. According to Girard, three of these orifices
lead to special compartments, isolated from one another, and grouped around the orbit, in
consequence of which these diverticuli of tlie frontal sinuses are designated the orbital sinuses.
This author lias denied the presence of sphenoidal sinuses; but they exist, although small,
and are in communication with the preceding.
The sinus of the great ethmoidal cell comports itself as in the Horse.
There is only one pair of maxillary sinuses, which are very large, and partitioned into two
compartments by a plate of bone ; this bears at its superior border the supermaxillo-dental
canal, like the superior maxillary sinus of Solipeds. The external or maxillary compartment,
is prolonged into the lachrymal protuberance; the internal occupies the substance of the
palatine arch. A wide orifice at the base of the maxillary turbinated bone aflbrds communica-
tion between this sinus and the nasal fossa.
In the Sheep and Goat, there exists a similar arrangement in the sinuses of the head;
but these cavities are much less spacious than in the Ox ; the frontal sinus, in particular, does
not extend beyond the superior border of the frontal bone.
In the Pig, these latter sinuses are prolonged into the parietal bones ; though they are far
from offering the same extent as in the smaller Ruminants. It is the same with the others;
they present an arrangement analogous to those of the Sheep and Goat.
In the Dog and Cat, there are only, on each side, a maxillary and a frontal sinus. The
first scarcely merits notice* and the second, a little more developed, opens into the nasal
cavity by means of a small aperture situated near the middle septum of the two frontal sinuses.
(Leyh states that the Carnivora have no maxillary sinus; consequently, the sphenoidal
sinus communicates below with the nasal fossae.)
Comparison of the Nasal Cavities in Man with those of Animals.
The external orifices of the nasal cavities of Man are called nostrils; these are flattened
transversely, and prolonged in front of the lobule of the nose; their external face, or ala,
is concave and movable. They are lined internally by a membrane that holds a middle
place between the skin and mucous membranes; it has a number of little hairs, eaUed
vibrissas.
The cavities or nasal fossas offer nothing particular ; as in animals, they show a superior,
middle, and inferior meatus. On their floor, in front, is seen the superior oriflce of the
incisive foramen, which corresponds to the commencement of Jacobson's canal. The pituitary
membrane has a squamous epithelium in its olfactory, as on its Schneiderian portion. At the
bottom of the nasal cavities and the upper part of the pharynx, is a kind of diverticulum
named the posterior nares; it has been already alluded to when speaking of the pharynx.
The sinuses are: 1. The sphenoidal sinus and the posterior ethmoidal cells, that open
beneath the roof of the nasal fossae. 2. The middle ethmoidal cells, opening into the superior
meatus. 3. The anterior ethmoidal cells, and frontal and maxillary sinuses, communicating
with the middle meatus. All these sinuses have a proper communicating orifice with the nasal
cavities.
The Air-tube succeeding the Nasal Cavities.
This single tube comprises : the larynx, which commences the trachea ; the
latter forms the body or middle portion, the bronchi terminating it.
1. Laeynx (Figs. 308, 311, 312, 313, 314).
Preparation.— 1. Make a longitudinal section of the head, in order to study the general
arrangement of the larynx (Fig. 308). 2. Isolate the cartilages, to examine their external
conformation. 3. Remove the muscles from a third larynx, to show the mode of articulation
RESPIRATORY APPARATUS IN MAMMALIA.
Fig. 311.
of the various cartilages (Figs. 312, 314). 4. Prepare the muscles in conformity with the
indications furnished by a glance at Fig. 314. 5. Remove a larynx as carefully as possible,
80 as not to injure the walls of the pharynx, in order to study the interior of the organ, and
especially its pharyngeal opening (Fig. 315).
Form — Situation. — The larynx forms a veiy short canal, which gives admis'
sion to the air during respiration, and is at the same time the organ of the voice.
It is a cartilaginous box, flattened on each side, and open from one end to
the other : the anterior orifice being situated at the bottom of the pharyngeal
cavity, and the posterior continuous with the trachea.
This apparatus, situated in the intra-maxillary space, is suspended between
the two cornua of the os hyoides, and
fixed to the extremities of these append-
ages by one of its constituent pieces. It
supports the pharynx, and by means of
the walls of the latter is attached to the
circumference of the posterior openings
of the nasal cavities.
In order to facilitate description, this
brief notice of its form, situation, general
relations, and mode of attachment will be
followed by a notice of its structure ;
afterwards, the study of its external and
internal surfaces will receive attention.
Structuee of the Larynx. — It
comprises in^its structure : 1. A cartila-
ginous framework, composed of five pieces.
2. Muscles, which move these pieces. 3.
A mucous membrane spread over the inner
surface of the organ. 4. Vessels and
nerves.
1. Cartilaginous fratneivorh of the
larynx. — In this we find : three single
median cartilages — the cricoid, thyroid,
and epiglottis ; and two lateral cartilages,
the arytcenoid. All are movable, one upon
the other.
Cricoid Cartilage (Fig. 311, c).
— This cartilage, as its name indicates
(xptKos, cTSos, " hke a ring "), is exactly
like a ring with a bezel placed upwards.
Depressed on each side, but all the less as
the animal has its respiratory apparatus
well developed, this ring offers ttvo faces, and ttvo borders or circumferences. The
internal face is smooth, and covered by mucous membrane. The external face is
provided, in the middle of the widened portion forming the bezel, with a little
eminence more or less prominent, elongated in the form of a crest, and separating
the two posterior crico-arytaenoid muscles (to which it gives attachment) from
each other. On the sides of this bezel are two small, articular, concave facets,
which coiTespond to the branches of the thyroid cartilage. Nothing remarkable
is to be noted for the remainder of the extent of this face. The superior circum-
CARTILAGES OF THE LARYNX DIS-
ARTICULATED.
C, Anterior surface of the cricoid: 1, facet
for the arytaenoid ; 2, facet for the thyroid.
A, External surface of the arytcenoid. a',
ibid., internal surface: 3, facet for the
cricoid. T, Thyroid, seen from above: 4,
4, posterior extremities of its wings; 5,
appendages for the hyoid cornua ; 6, body of
the thyroid. F, Epiglottis, supero-posterior
surface: 7, 7, prolongations forming the
supposed superior vocal cords.
THE LARYNX. 529
fermce, comprised laterally between the two branches of the thyroid cartilage, is
concave in the narrow part opposite the bezel, where it shows two lateral convex
articular facets for articulation with the arytgenoid cartilages. The inferior cir-
cumference is related to the first ring of the trachea ; it has a small notch, often
double, on the middle of the bezel.
Thyroid Cartilage (^vpco's, e'Sos, "like a shield") (Fig. 311, t).— This is
composed of two lateral plates, which have the form of an obliquangular parallelo-
gram, and are united at their anterior extremity to form a thick constricted part
which, in Veterinary Anatomy, is named the bodi/ of the thyroid. This body is
smooth on its inferior face, where it is covered by the terminal extremities of the
subscapulo-hyoideii muscles. On its superior face is an obtuse, rounded, and
irregular protuberance, on which the epiglottis articulates.
The plates, lateral branches, or alcB of the thyroid, present two faces, two
borders, and two extremities. The external face, slightly convex, is covered by
the hyo-thyroideus and thyro-pharyngeus muscles. The internal face, slightly
concave, is covered, near the superior border, by the pharyngeal mucous mem-
brane ; for the remainder of its extent it is in contact with the thyro-arytsenoid
and lateral crico-arytaenoid muscles.
The superior border is divided by a small prolongation into two parts — an
anterior, giving attachment to the thyro-hyoid membrane ; the other posterior,
into which is inserted the palato-pharyngeus muscle. This appendix — the great
thyroid cornu of Man — forms one of the obtuse angles of the parallelogram repre-
sented by each lateral plate of the thyroid cartilage ; it is united to the extremity
of the hyoid cornu ; and at its base is an opening, or deep notch, through which
passes the superior laryngeal nerve. The inferior border is also divided into two
parts by the second obtuse angle of the cartilage : the anterior part forms, with
that of the opposite plate, a receding angle occupied by the crico-thyi'oid mem-
brane (ligamentum crico-thyroideum medium) ; the posterior gives attachment to
the crico-thyroid muscle. The extremities constitute the acute angles of the
thyroid plate. The anterior joins that of the opposite branch, to form the body
of the cartilage. The posterior, slightly curved downwards, is terminated by a
small, convex, diarthrodial facet, which articulates with the concave facets on the
external face of the cricoid cartilage.
The thyroid cartilage is frequently partially, or even entirely, ossified.
Epiglottis (Fig. 311, e). — This is a soft and flexible appendage, shaped like
a sage-leaf ; inferiorly, it circumscribes the entrance to the larynx, and is bent
over it, so as to close it hermetically when the aUmentary bolus is traversing the
pharyngeal vestibule.
This cartilage has two faces, two latercd borders, a base, and a summit. The
anterior face is convex from side to side, concave from above to below, and covered
by the mucous membrane of the pharynx : it gives attachment to the hyo-epiglot-
tidean muscle.
The posterior face shows an inverse configuration, and is covered by the lining
membrane of the larynx, which is perforated by glandular orifices. The borders
offer a free portion, which aids in circumscribing the entrance to the larynx ;
as well as an adherent part fixed to the arytaenoid cartilage by means of a mucous
fold, and made irregular by the little cartilaginous bodies which are superadded
to it. (These are the cuneiform cartilages, or cartilages of Wrisberg, placed in the
arytaeno-epiglottidean fold of mucous membrane, which extends from the apex of
the arytgenoid cartilage to the side of the epiglottis.) The base is thick, and
530 RESPIBATORT APPABATUS IN MAMMALIA.
articulates with the middle part of the thyroid ; it gives origin, posteriorly, to
two lateral prolongations, which pass to the inferior border of the aiytasnoids,
but usually without joining these.
The summit unites the free portion of both borders, and is thi'own forwards
on the upper face of the soft palate.
Arytaenoid Cartilages (Fig. 311, a, a'). These two pieces have been so
designated from their resemblance, when approximated, to the mouth of a pitcher
(apvratva, £?8os, " like a pitcher "). They are situated in front of the cricoid,
above the entrance to the larynx ; each has an irregular quadrilateral form, and
presents for study tivo faces and four borders. The internal face is smooth,
almost flat, and lined by the laryngeal mucous membrane. The external face is
divided by a ridge into two portions : a superior, covered by the aryttenoid muscle ;
and an inferior, giving attachment to the thyro-arytasnoid and lateral crico-
arytsenoid muscles. The snpen-ior border is concave, and joined to that of the
opposite cartilage (by means of the ligamentum crico-ctrijtcenoideum). The inferior
border {processus voccdis) gives attachment, posteriorly, to the vocal cord. The
anterior border, thick and convex, and covered by the mucous membrane, circum-
scribes, superiorly and laterally, the entrance to the larynx ; it is in joining
above, with the homologous border of the other arytaenoid cartilage, that the
pitcher-beak already mentioned is formed. The posterior border projects into the
larynx by its inferior portion ; superiorly, this border is very thick, and is
hollowed by a small articular facet, which articulates with the anterior facet of
the bezel of the cricoid. Above, and to the outside of this facet, is a very promi-
nent tubercle {processus muscularis) that terminates behind the crest of the
external face, and gives attachment to the posterior crico-arytsenoid muscle.
Aeticulations of the Laryngeal Caetilages (Figs. 312, 313).— These
are of the simplest kind. They are as follows : —
A. The thyroid cartilage is joined to the os hyoides : 1. At the extremities
of the cornua, by means of a short ligament interposed between that extremity
and the appendix of the superior border of the thyroid. 2. To the whole extent
of the hyoid concavity, by an elastic membrane — the thyro-hyoid membrane,
attached to the body of the thyroid cartilage and the superior border of the lateral
plates of that cartilage (Fig. 313, 4).
B. The thyroid cartilage articulates with the cricoid by two small arthrodiae,
which unite the posterior extremities of the branches of the first cartilage to the
facets on the external face of the second. A thin external capsule encloses this
articulation (Fig. 312, 2). These two cartilages are also held together by means
of a membranous elastic ligament — the crico-thyroid membrane, which passes from
the angle comprised between the two branches of the thyroid to the anterior notch
of the cricoid (Fig. 313, 3).
C. The two arytaenoid cartilages are united, at their superior border, by the
arytenoid muscle and laryngeal mucous membrane.
D. The latter cartilages come in contact with the anterior facets of the cricoid
bezel, by means of the concave articular surface of their posterior border ; the
result is a small, but veiy movable, arthrodial joint, enclosed by a thin external
capsule and by the surrounding muscles (Fig. 312, 1).
E. These cartilages are also united to the thyi'oid, through the medium of
the vocal cords. These are two elastic bands which project within the larynx,
and between them include the triangular space termed the glottis ; their internal
face is covered by the mucous membrane of the larynx ; the thyro-hyoid muscles
TEE LARYNX. 531
envelop their external face ; their inferior extremity is fixed into the crico-thyroid
membrane, and the angle of the thyi'oid cartilage ; the superior is attached to the
inferior border of the arytaenoid cartilage, towards the angle which separates this
from the posterior border. The articulation of sounds is principally due to the
vibration of these cords (Fig. 313, d).
F. The epigloutis is attached by amphiarthrosis to the body of the thyroid
cartilage, by means of elastic fasciculi mixed with fat, which pass from the base
of the first to the upper face of the second. It is not rare to find among these
fasciculi small synovial bursas.
G. The epiglottis is united, laterally, to the inferior border of the arytsenoids,
through the medium of the two mucous folds already noticed, in the substance
of which are the cartilaginous prolongations annexed to the base of this fibro-
cartilage. These prolongations circumscribe, anteriorly, the ventricles of the
Fig. 313.
SUPERIOR FACE. INFERIOR FACE.
CARTILAGES OF THE LARYNX, HELD IN THEIR NATURAL POSITION BY THE ARTICULAR
LIGAMENTS.
a Cricoid cartilage; b, h, arytaenoid cartilages; c, body of the thyroid; c', c', lateral plates of the
thyroid; d, epiglottis; e, body of the hyoid bone; /, trachea. 1, Crico-arytsenoid articulation;
2, capsule of the crico-thyroid articulation ; 3, crico-thyroid membrane ; 4, thyro-hyoid mem-
brane ; 5, crico-trachealis ligament.
larynx, and are sometimes designated the superior vocal cords — a name rarely given
them, as they do not merit it.
H. Finally, the first ring of the trachea is attached to the cricoid cartilage by
a circular elastic membrane.
All of these articulations have neither the same importance nor mobility.
The kind of movements they permit is easily understood, and they are sufficiently
indicated in the description of the muscles which execute them.
It is sufficient here to state, that these movements may either produce the
shortening or elongation of the larynx, its dilatation or contraction in a transverse
direction, or the occlusion of its anterior opening.
2. Muscles of the larynx. — The laryngeal apparatus is elevated or depressed
with the hjoid bone, which it follows in all its movements. It is also moved
RESPntATOBT APPARATUS IN MAMMALIA.
by proper muscles, which either produce its total displacement, or cause the
several cartilages to play upon each other. Among these muscles there are three
extrinsic — the sterno-thyroideus, hyo-thyroideus, and the hyo-epiglottidem. The
others are intrinsic, or attached in their origin and termination to the different
pieces of the larynx ; they are — the crico-thijroid, posterior crico-arytmioid, lateral
crico-arytmwid, thyro-arytmnoid, and the arytCRnoideus muscles. All are pairs,
except the last and the hyo-epiglottideus.
Sterno-thyroideus.— (See p. 255.)
Hyo-thyroideus (Fig. 314, 3). — This is a wide, triangular muscle, formed
entirely of muscular fasciculi, wliich arise from the whole extent of the hyoid
cornu, and terminate on the external face of the thyroid ala ; the most inferior
are longest. This muscle covers the
Fig. 3U. thjToid cartilage and the thyro-
hyoid membrane. It is covered by
the maxillary gland.^
In contracting, this muscle
brings the thyroid cartilage within
the branches of the hyoid bone, and
in this way carries the larynx for-
ward and upward.
Hyo-epiglottideus. — This is
a small cylindrical fasciculus, the
fibres of which are buried in the
middle of a mass of adipose tissue,
and extend from the superior sur-
face of the body of the hyoid bone
to the antero-inferior face of the
epiglottis. Partly covered by the
mucous membrane of the pharynx,
this muscle concurs in restoring the
epiglottis to its normal position
after the passage of food or water
over it. But it is also necessary
to state that the epiglottis is
carried forward more particularly by its o^vn proper elasticity, as well as that of
the Ugamentous bands that attach it to the thyroid cartilage.
Crico-thyroideus (Figs. 314, 11 ; 315, 8). — This small muscle, applied to
the external side of the cricoid cartilage, is elongated from above to below, and
composed of somewhat tendinous fibres which cross, more or less, the general
direction of the muscle. They arise from the above-named cartilage, and pass
to the posterior border of the thyroid plate.
The crico-thyroideus shortens the laiynx, in bringing together the two
cartilages into which it is inserted.
Posterior Crico-arytenoideus (Figs. 314, 315, 5). — This is the most
powerful muscle in this region. Its fibres are directed forwards and outwards,
and arise from the bezel of the cricoid, which they cover, and from the median
crest of that part. They all converge, in becoming more or less tendinous,
towards the posterior tubercle of the arytenoid cartilage, on which they termi-
nate. Covered by the oesophagus and the crico-pharyngeal muscular band, this
(' This and the preceding muscle are usually described as one — the stvrno-thym-hyoideus.')
MUSCLES OF THE HORSE'S LARYNX.
Hyoideus transversus ; 2, kerato-hyoideus ; 3, hyo-
thyroideus ; 4, sterno-thyroideus ; 5, crico-arytae-
noideus posticus ; 6, crico-arytienoideus lateralis ;
7, aryteenoideus ; 8, posterior fasciculus of the
thyro-arytsenoideus ; 9, anterior fasciculus of ditto;
10, lateral ventricle of the larynx artificially dis-
tended and projecting between the two fasciculi ;
11, crico-thyroideus
TELE LARYNX.
533
Fig 315.
muscle is separated from that of the opposite side by the median crest of
the cricoid bezel.
The posterior crico-arytaenoid muscles dilate the entrance to the larynx, as
well as the glottis, in causing the arytsenoid cartilages to rotate or swing on the
cricoid cartilage, and in separating them from one another by their anterior and
inferior borders. They act as a lever of the first order.
Lateral Crico-arytsenoideus (Figs. 314, 6 ; 315, 5). A triangular muscle,
smaller than the preceding, situated between the thyroid and arytasnoid cartilages,
and formed of fasciculi longer in front than behind ; these arise on the side of
the anterior border of the cricoid cartilage, and are directed upwards, to
terminate outside the posterior crico-arytte-
noidens, on the tubercle of the arytaenoid
cartilage.
It is a direct antagonist of the last muscle,
and, consequently, a constrictor of the larynx.
Thyro-arytsenoideus (Figs. 314, 8, 9 ;
315, 6). — Lodged at the inner face of the thyroid
ala, this muscle comprises two fascicuh, sepa-
rated by the ventricle of the glottis.
The anterior fasciculus is a long and pale
band, arising from the internal surface of the
ala of the thyroid cartilage, near its receding
angle, and ascending to the arytasnoid cartilage,
bending round its external face to join on the
median line, the analogous fasciculus from the
opposite side, mixing its fibres with those of the
arytgenoideus. By its inner face, it covers the
superior vocal cord and the laryngeal mucous
membrane.
The posterior fasdeulus, wider than the
anterior, comports itself in a somewhat similar
manner. It commences from behind the same
point, and terminates on the external crest
(processus muscularis) of the arytfenoid carti-
lage ; but its most anterior fibres pass over this
crest, and join the arj^tenoid muscle. Its in-
ternal face is in contact with the vocal cord, and its posterior border is con-
founded with the fibres of the lateral crico-aryttenoideus.
Sometimes it happens that these fasciculi are not distinct from each other,
and exist only as a wide muscular band applied against the ventricle of the
glottis.
It is surmised that this muscle is a constrictor of the larynx. Its function
is particularly marked in phonation, when it modifies the length, separation, and
tension of the vocal cords.
Arytsenoideus.— Situated beneath the pharyngeal mucous membrane, above
the arytenoid cartilages, this, the smallest of the laryngeal muscles, is composed
of two lateral portions, the fibres of which arise from a median raphe and, diverg-
ing, pass to the superior part of the external face of these cartilages, where they
are inserted into the crest dividing that face, and unite with the thyro-arytaenoid
muscle.
POSTERO-LATERAL VIEW OF THE
LARYNX.
1, Epiglottis ; 2, arvtsenoid cartilages ;
3, thyroid cartilage ; 4, arytsenoi-
deus muscle ; 5, crico-arytsenoideus
lateralis ; 6, tliyro-arytaenoideus ;
7, crico-arytffinoideus posticus ; 8,
crico-thyroideus ; 9, ligament be-
tween the cricoid cartilage and first
ring of trachea, 10; 11, infero-
posterior extremities of crico-thyroid
cartilages.
534 RESPIRATOBY APPARATUS IN MAMMALIA.
The French works on Veterinary Anatomy cite this muscle — we do not know
why — as a dilator of the larynx. Its position in front of the crico-arytgenoid
cartilages sufficiently indicates that it cannot act otherwise than in bringing the
two arytenoid cartilages together. And the continuity of a large nimiber of its
fibres with those of the thyro-arytaenoideus, does not allow it to have any other
action than that of this muscle.
3. Mucous membrane of the larynx. — This membrane is only a continuation
of that of the pharynx, which, after covering the prominence formed by the
opening of the larynx, passes over the circumference of that opening, to be spread
on the posterior face of the epiglottis and the internal face of the arytaenoid
cartilages, to dip into the ventricles, pass above the vocal cords, line the inner
face of the cricoid cartilage, and, finally, to be prolonged into the trachea. Its
deep face adheres closely to the parts it covers, except in the lateral ventricles.
The free face is perfectly tense, and is covered with stratified tesselated epithelium
at the epiglottis and vocal cords, but only with ciliated epithelium elsewhere.
The superficial layer of its dermis is composed of reticulated tissue except at
the vocal cords, where it is closer and has some papillae (Coyne).
The glanduM of the larynx are racemose ; they are absent on the free border
of the vocal cords, but are numerous on the posterior face of the epiglottis, where
they are lodged in the minute depressions of the cartilage ; they are also found
on the arytfenoid cartilages and the arytteno-epiglottidean folds. There are
closed follicles also in the vestibule of the larynx, at the limit of the arytaeno-
epiglottidean folds and the epiglottis, on the posterior surface of the latter.
The mucous membrane of the larynx possesses an exquisite sensibility, owing to
which admission to the air-passage is denied to the solid or liquid alimentary
particles, which, dm'ing deglutition, might deviate from their normal course and
pass into this opening. The slightest touch brings into play this sensibility,
and determines an energetic reflex action of the constrictor muscles of the larynx
and chest ; from this results the almost complete occlusion of the larynx, and
a violent cough which expels the substances that have caused the irritation of the
membrane. Every one has experienced the effects of this reflex action, and knows
by experience the great sensibility of the larynx.
4. Vessels and nerves. — Blood is carried into the larynx by the laryngeal
arteries, which pass between the cricoid and the posterior border of the thyroid
cartilages. Their branches spread over the ventricle of the glottis and the thyro-
arytfenoid muscle, to be expended in the substance of the muscles and mucous
membrane. The terminal ramifications form red plexuses on the surface of cer-
tain parts of the larynx. The veins are satellites of the arteries. The lymphatics
foiTQ a superficial and a submucous network.
The pneumogastric fm'nishes the larynx with its principal nerves — the superior
and inferior laryngeal. The first is distributed to the upper part of the organ
and the entrance to the glottis, endowing the mucous membrane with that high
degree of sensibility which distinguishes it. The second is more especially a
motor nerve, and supplies all the muscles, except the crico-thyroid. A filament
of the recmTent nerve is distributed in the mucous membrane of the subglottal
portion, and to the inferior border and inner surface of the vocal cords. The
presence of nerve-filaments, analogous to those of the trachea, in the subglottal
part of the larynx may explain the difference, well known to physiologists, that
exists between the sensibility of the entrance to the glottis and that of the mf erior
border of the vocal cords.
THE LARYNX.
535
Fig. 316
External Surface of the Larynx. — It is divided into four planes : a
superior, inferior, and two lateral. The superior 'plane, formed by the arytaenoid
and posterior crico-arytasnoid muscles, is covered by the pharynx and oesophagus ;
in its anterior moiety, it is directly covered by the pharyngeal mucous membrane.
The inferior plane presents, from before to behiud, the thyro-hyoid mem-
brane, the body of the thyroid cartilage, the crico-thyroid membrane, the inferior
part of the cricoid cartilage, and the crico-trachealis ligament. There is remarked,
laterally, the inferior border of the thyro-hyoid muscle. This plane corresponds
to the scapulo-hyoideal muscles, which entirely cover it.
The lateral planes exhibit the external faces of the thyro-hyoid and crico-
thyroid muscles, that of the cricoid cartUage, and the alae of the thyroid. They
also show the opening through which passes the superior laryngeal nerve ; they are
related to the crico- and thyro-pharyngeal muscles, as well as the maxillary gland.
Internal Surface of the Larynx (Fig. 316). — This surface (or cavum
laryngis) is divided into three perfectly distiuct regions : a middle, named the
glottis; a s,ni^TioT,ca\]ed the supra-glottic portion ; and
an inferior, designated the infra- or sub-glottic flortion.
The glottis {rima glottic/is) is a naiTOw space in
the form of a very elongated isoscelated triangle, its
base being uppermost. This irregular fissure is com-
prised between the elastic structures known as the
vocal cords. It is the narrowest part of the larynx.
(The space between the vocal cords is designated
the glottis vocalis, pars vocalis, or interligamentous
portion ; that between the arytgenoid cartilages, the
glottis respiratoria, ^mrs respiratoria, or intercartila-
ginous portion.)
The supra-glottic portion {aditus ad laryngem,
introitus laryngis), wider than the glottis, but always
greatly depressed on each side, particularly in the
region comprised between the arytenoids, presents :
1. The two ventricles of the larynx {Morgagni's ven-
tricles), lateral excavations, dilated at the bottom,
which penetrate between the anterior border of the
vocal cords and the prolongations of the base of the
epiglottis, insinuating themselves even between the
fasciculi of the thyro-aryttenoid muscle (in the Ass
and Mule the ventricles are proportionately larger than in the Horse, and open
close to the base of the epiglottis). 2. The subepiglottic sinus, a deep depression
at the base of the epiglottis, which is provided, in the Ass and Mule, with a thin
membrane, capable of vibrating. 3. The entrance of the larynx, or pharyngeal
opening of the cavity, a vast, gaping aperture of an oval form, circumscribed by
the anterior border of the arytaenoids and the lateral border of the epiglottis, and
making a remarkable projection at the bottom of the pharyngeal space.
The subglottic portion of the larynx is the widest of the three ; it is directly
continuous with the canal of the trachea. In front is seen the prominence
formed by the posterior border of the vocal cords : above, a diffused and shallow
excavation, placed at the point of junction of the arytgenoid and cricoid car-
tilages, named the subarytcBuoid sinus.
Functions. — A« a tube intended for the passage of a column of air during
ENTRANCE TO THE LARYNX
OF THE HORSE.
i, Glottis ; B, epiglottis ; c,
entrance to the lateral ven-
tricle ; D, vocal cord ; E,
oesophageal infun^iibulum
opened ; f, f. posterior pil-
lars of the soft palate.
536 RESPIRATORY APPARATUS IN MAMMALIA
the act of respiration, the larynx does not give rise to any very interesting
physiological considerations. It is, nevertheless, worthy of remark that this
organ, like the nostrils, dilates or contracts, according to the volume of the
column of air introduced into, or expelled from, the lungs, and that its paralysis,
during rapid movements, causes an embarrassment in the respiration which
betrays itself in " roaring." But a physiological study of the larynx acquires a
real interest when it is examined with regard to the articulation of sounds, or as
an organ of phonation. This study, however, does not come within our province ;
though what has been said concerning the vocal cords will give a summary, but
satisfactory, idea of the mechanism which presides over this function, and the
part the larynx plays.
It may also be added, that nearly all the muscles of the larynx are concerned
in phonation, as by modifying the tension and the separation of the vocal cords,
they determine differences in the sounds. One only is concerned in respiration ;
this is the posterior crico-aryta^noideus, which is a dilator of the glottis.^
2. The Trachea (Figs. 317, 318).
Preparation.— FoWoy} the same procedure as for the dissection of the oesophagus.
The trachea is a flexible and elastic tube, formed by a series of incomplete
cartilaginous rings that succeed the larynx, and terminate above the base of the
heart by two divisions, which constitute the bronchi.
Form. — This tube is cylindrical, and (slightly) flattened above and below.
Its inferior face and two borders are regularly rounded, and offer transverse
grooves, which correspond to the intervals between the constituent pieces of the
trachea. The superior face, nearly plane, shows the thin and widened extremities
of these cartilages.
Course. — Leaving the posterior extremity of the larynx, the trachea descends
backwards to the entrance of the chest, in following the inferior border of the
neck below the longus colli muscle. It afterwards becomes inflected, superiorly,
to pass between the two first ribs, enters the chest, passes through the anterior
mediastinum, proceeds directly backwards, and finally arrives above the left
auricle of the heart, to the right of the posterior aorta, where it bifurcates.
Relations. — In its cervical portion, the trachea, surrounded by a loose and
abundant connective tissue, lies in a kind of muscular envelope which the
majority of the muscles of this region form around it, and which are : the
sterno-hyoid and sterno-thyroid, placed in front ; the sterno-maxillaries, situated
at first in front, and afterwards on the sides towards their termination ; the
subscapulo-hyoideii, above and in the middle of the lateral parts ; the scalenii,
altogether below and at the sides ; the longus colli, behind ; and outside all
these muscles, the superficial expansion of the cervical panniculus. This enve-
lope is thinnest in front of the middle portion of the neck ; and this is the part
where the operation of tracheotomy should be performed.
The trachea is also in relation, in its cervical portion : 1. "With the oeso-
phagus, which descends, as we know, at first in the middle of the posterior face,
then to the left side of the air-tube. 2. With the carotid arteries, which pass
along both sides of the tube, accompanied by their satellite nerves — the pneumo-
gastric, great sympathetic, and recurrent nerves.
(' For a special and detailed description of the anatomy and physiology of the Horse's
larynx, consult my work on Roaring in Horses {Laryngissimus paralyticus). London : 1889.)
THE TRACHEA.
537
After clearing the two first ribs, where it reaches its thoracic portion, the
trachea responds, superiorly, to the longus colli and the oesophagus ; below to
the brachial vessels, the anterior aorta which furnishes them, the anterior vena
cava, the cardiac and recurrent nerves, and to the base of the heart ; laterally,
to the inferior cervical ganglia of the great sympathetic, the vertebral vessels —
cervical and dorso-muscular — and to the two layers of the anterior mediastinum ;
Fig. 317.
THE RESPIRATORY ORGANS (INFERIOR, OR FRONT VIEW).
1, Trachea; 2, jugular vein; 3, rectus anticus major; 4, carotid artery ; 5, longus colli; 6, origin
of the common carotids; 7, vertebral artery; 8, section of first rib; 9, cephalic trunk of right
axillary artery; 10, anterior lobe of right lung; 11, middle, or supplementary lobe of ditto; 12,
posterior portion or lobe of ditto ; 13, heart; 14, cardiac artery ; 15, ventricular branch of cardiac
vein; 16, oesophagus.
to the right, the vena azygos ; to the left, the arch of the aorta and the thoracic
duct. The latter is sometimes carried to the opposite side.
Steuctuee. — The trachea comprises in its structure : the cartilaginous rings
which form its base ; the ligaments which unite these rings ; the mucous mem-
hrane spread over its inner face ; a muscular layer, which only lines that mem-
brane superiorly ; and vessels and nerves.
Cartilaginous rings of the trachea. — These are about fifty in number, and do
BESPIRATOEY APPARATUS IN MAMMALIA.
Fig. 31
TRACHEA, BRONCHI, AND LUNGS OF THE
HORSE (VIEWED FROM ABOVE).
not form perfect rings, being incomplete
on the upper side of the trachea. Each
is a kind of arc, composed of a cartilaginous
plate flattened and curved on itself ; the
extremities are turned towards each other,
and joined in the majority of the rings ;
they even overlap in some. These ex-
tremities are thin and wide, and some-
times bifurcate and unite with the adjoin-
ing rings.
In the middle part of the trachea,
these rings are generally larger than at the
origin or termination of the tube. The
last ring, in serving as a transition between
the trachea and bronchi, presents a more
complicated arrangement, being frequently
completed by isolated cartilaginous plates,
and always divided by a median spur or
bifurcation — directed towards the interior
of the trachea — into two lateral segments,
each of which corresponds to a bronchus.
Ligaments. — The rings of the trachea
are united at their borders by intermediate
ligaments, which are composed of elastic
tissue, and permit the lengthening or
shortening of the tube they concur to form.
Towards the extremities of the arcs,
they are confounded with a thin connec-
tive-tissue layer that unites these ex-
tremities. The fii-st cartilage is received
by its anterior border into the cricoid ring,
and joined to it by the wide annular
ligament mentioned at p. 531. Owing to
the elasticity of tliis ligament, the two
cartilages it binds together can move one
within the other, like two segments of
a telescope, and in this way vary the length
of the tube.
Muscular layer. — This layer only
covers the superior face of the trachea ; it
is formed of pale, rose-coloured, transverse
fasciculi, attached by their extremities to
the internal face of the cartilages. Its
action undoubtedly diminishes the diameter
A, Pharyngeal cavity, thrown open to show the entrance
to the oesophagus, B, and that of the larynx, c ; D,
oesophagus; E, left sac of the stomach; F, its risjht
sac ; G, duodenum ; H, trachea ; i, right bronchial
ramifications; K, left lung; L, anterior aorta; M,
common origin of the bronchial, oesophageal, and
first intercostal arteries.
THE BRONCHI. 539
of the trachea, by contracting the arcs composing this tube. (Kolliker has found
some longitudinal fibres passing across the transverse ones at the posterior
part of the trachea. Leyh describes longitudinal fibres in the anterior wall of the
trachea, between the mucous membrane and the cartilaginous rings, and which,
he states, diminish the length of the tube.)
Mucous membrane. — Continuous with that of the larynx, this membrane is
prolonged, through the medium of the bronchi, and in becoming modified in
character, into the air-cells. Its free or superficial surface is perforated by
glandular orifices, and exhibits longitudinal ridges which are ineflfacable by dis-
tension ; it is lined with ciliated epithelium. Its deep face is covered with yellow
elastic tissue disposed in longitudinal fasciculi, and ad-
Fig. 319. heres intimately either to the face of the cartilage and
" their intermediate ligaments, or to the posterior muscular
layer.
An essential characteristic which distinguishes this
membrane from that lining the larynx, is its slight
sensibility.
(The tracheal glands, the orifices of which are so
numerous in the mucous membrane, abound towards the
CILIATED EPITHELIUM . ^ {■ ^^ ^ ^ xi, 11 • 1 1, J •
FROM THE TRACHEA. postcrior part 01 the tube ; they are small, ovoid bodies,
3, External layer of longi- lying between the muscular and fibrous coats. Other
tudinal elastic fibres ; glands, Icss in size, are placed between the layers of fibrous
fayerofThr'mutus tissuc Uniting the Cartilages at the sides of the trachea,
membrane ; 3, round Their secretion is poured out upon the free surface of the
cells ; 4, oval and ob- jj^cous membrane, to lubricate and protect it.)
long cells: 5, ciliated ^^ , , m, /, , ■
cells. Vessels and nerves. — The small arteries emanating
from the vessels in the vicinity of the trachea — as the
carotid and the collateral branches of the brachial arteries — supply it with blood.
Its nerves come from the recurrent ; they show small ganglia on their track.
Functions. — Except as a tube for the passage of the inspired and expired air.
the trachea performs no other function.
3. The Bronchi (Figs. 318, 320, 327).
Preparation. — After removing the lung from the thoracic cavity, it ie filled with water by
fixing the trachea to a water-tap. The bronchi may then be dissected by tearing and triturating
the pulmonary tissue.
Each of the two bronchi — the terminal branches of the trachea — resembles
a tree embedded in the substance of the lung, and sending out a multitude of
branches.
Arrangement. — At a short distance from their origin, the bronchi enter the
lobes of the lung, and pass backwards and outwards towards the superior part of
the base of the organ, giving off in their course large collateral branches, until
they themselves are expended. These branches originate alternately above,
within, below, and outwards ; and thus extend in every direction. The first
forms an obtuse angle with the principal trunk, and is directed forwards, to
ramify in the anterior lobe of the lung ; the others are detached at an angle
more or less acute. All subdivide into gradually decreasing branches, which
soon become of a capillary diameter, and finally open into the infundibula of
the pulmonary air-cells (see Structure of the Lungs).
540
RESPIRATORY APPARATUS IN MAMMALIA.
Form. — The bronchial tubes are not flattened like the trachea ; a transverse
section shows them to be regularly cylindrical.
Volume. — The left bronchus is always smaller than the right, owing to the
left lung being the least ; and both are much inferior in volume to the aggregate
of their respective branches.
Relations. — Each bronchus enters the pulmonary lobe, or lung, along with
the blood-vessels, with which it forms what is called the root of the lung. The
divisions of this aborescent trunk are accompanied by the bronchial artery, vein,
and nerves, which ramify in the same manner.
Fig. 320.
A SMALL BRONCHIAL TUBE, WITH ITS BRONCHULES AND ULTIMATE RAMIFICATIONS.
Near their origin, the bronchi are related to the bronchial glands, above
which, and to the left side, passes the oesophagus.
Struct UKE. — The structure of the bronchial tubes resembles that of the
trachea ; their walls being formed by cartilages, a muscular layer, mucous
memhrane, and vessels and nerves.
Cartilages of the bronchi. — These only exist in tubes of a certain calibre, the
minute tubes being deprived of them, and having only membranous walls. As
in the trachea, there is for each tube a series of transverse rings joined border
to border ; though these are no longer formed of a single ring, but each results
from the union of several lozenge-shaped pieces, the extremities of which over-
lap ; they are united to each other, like the segments of the neighbouring rings,
by means of connective tissue, and also by the membranes spread over their
internal surface.
THE BRONCHI. 541
Muscular layer. — Extended in a very thin continuous layer over the entire
inner surface of the rings, this layer disappears in the smallest bronchial tubes.
3Iui'ous membrane. — This membrane is distinguished from that of the trachea
by its great sensitiveness ; it alone constitutes the
walls of the terminal bronchial divisions. (When the ^'g- 321.
cartilages terminate, the tubes are wholly mem-
branous, and the fibrous coat and longitudinal elastic
fibres are continued into the ultimate ramifications of
the bronchi. The muscular coat is disposed in the
form of a continuous layer of annular fibres, and
may be traced upon the smallest tubes ; it is com-
posed of the unstriped variety of muscular fibre.)
Vessels and nerves. — The vessels and nerves dis-
tributed in the tissue of the bronchial tubes, come
from the satellite vessels and nerves of these tubes „,,„„,,„
, , , . , . . ^ ^, MUCOUS MEMBRANE OF A BRON-
— the bronchial arteries, veins, and nerves. The chial tube, with the oapil-
lymphatics pass to the bronchial glands. laries injected.
Differential Characters in the Air-tube succeeding the Nasal Cavities in the
OTHER Animals.
Ruminants.— In the Ox, Sheep, and Goat, the interior of the larynx is simpler than in
the Horse, and the lateral ventricles and vocal cords are almost effaced. The most important
differences in its various pieces are a.s follows: 1. The thyroid cartilage has no anterior
appendices, but is provided, posteriorly, with two considerable prolongations that articulate
with the cricord cartilage (it has no excavation between the two wings, and is formed by a
single piece : its inner face, in the middle, near the lower border, has a small fossette to which
a round and very salient tuberosity on the external face corresponds). 2. The upper border of
the cricoid is not notched in front (neither is the bezel on its lower border). 3. The epiglottis
is wider, but not so pointed, than in Solipeds (Leyh says it is less extensive, but thicker).
4 A hypo-epiglottidean muscle bifid at its origin. (There is no arytseuo-epiglottidean
ligament.)
The trachea of these animals does not offer any important differences. The last ring is not
so developed as in tlie Horse, and tlie tube detaches a supplementary bronchus to a lobe of the
lung which does not exist in Solipeds. (The rings of the mid<lle portion are proportionately
narrow, and their extremities meet behind and form a salient ridge.)
In the Camel, the larynx is long and flattened before and behind, and the epiglottis is very
developed; the entrance to the larynx is triangular in shape, but its borders are convex
inwardly. In Ruminants there are some closed fuUicles at the base of the epiglottis.
Pig. — The larynx of the Pig is remarkable for its great mobility, suspended as it is to the
hyoid cornua by the base of a very developed epiglottis, rather than by the wings of the thyroid
cartilage. The epiglottis is in shape like an omega, is very high, and curved backwards in
such a fashion as to envelop the arytsenoids. There are wide, shallow, lateral ventricles, which
have a small oblong sinus that ascends between the thyroid cartilage and the mucous
membrane. These ventricles are not surrounded by the thyro-arytsenoideus muscle, which is
small and undivided; above and outwardly, tliey are margined by a thick cord — a kind of
superior vocal cord, considered by Duges as acting with the ventricles to modify the deep
grunting sounds. (Instead of a tuberosity on the external face of the thyroid cartilage, there
is a median crest, and its inferior border has a small point. The cricoid appears to be drawn
downwards and backwards, and its lower border is very prominent in the middle, and articu-
lates with one or two small cartilaginous plates which have been sometimes wrongly described
as belonging to the proper cartilages of the larynx. Tlie antero-sup(-rior angles of the arytse-
noid cartilages are united to a small cartilaginous piece which prolongs them ; their external
face has a spine, and the internal angles are separated by a small pisiform body called the
" interarticular cartilage.")
The trachea of this animal resembles that of Ruminants. (It has about thirty rings, and
has three bronchi.)
Cabnivora.— The larynx of the Dog and Cat is very like that of the Horse. In propor-
87
542 BESPIEATORY APPARATUS IN MAMMALIA.
tion, the epiglottis is shorter, wider at the base, and more triangular than in the other species;
the lateral ventricles are sliallow. (There is an interarticular cartilage, as in the Pig ; there is
no sub-epiglottidean ventricle, and the vocal cords appear to be nearer each other. The trachea
has about forty-two rings, the extremities of which do not meet ; the space between them is
less in the Cat than the Dog.)
The larynx and trachea of Man will be compared with that of animals, when we come to
describe the lungs.
The Thorax (Figs. 255, 322, 323, 324).
The thorax — also called the thoracic or pectoral cavity — lodges not only the
lungs, but also the heart and the large vessels that arise from or pass to that
organ, with a portion of the oesophagus and trachea ; as well as nerves, which
are as remarkable for their number as their physiological importance.
Situation. — We have seen that the thorax has for its base the bony cage
formed by the ribs, sternum, and bodies of the dorsal vertebrae. Suspended
beneath the middle portion of the spine, this cage is transformed into a closed
cavity by the intercostal muscles, which fill the spaces between the ribs ; and by
the diaphragm, that vast oblique partition which separates the thora.K from the
abdomen.
Internal conformation. — Considered as a whole, the thoracic cavity represents
a hollow cone placed horizontally, depressed on each side, and particularly in
front towards the summit ; with its base, formed by the diaphragm, cut very
obliquely, in consequence of the direction taken by that muscle. This obliquity
of the diaphragm renders the antero-posterior diameter of the cavity much
greater above than below ; the difference is more than double.
The internal surface of this conical cavity may be divided into six regions :
a superior, inferior, and tivo lateral planes, a base, a posterior plane, and &
summit.
The superior plane presents, on the middle Ime, a large projection resulting
from the union of the vertebral bodies ; and, laterally, two deep channels or
furrows — the vertehro-costal channels. These latter, wider behind than before,
are formed by the upper ends of the ribs ; they lodge the superior border of the
pulmonary lobes. The middle projection, or ridge, is comprised between these
two lobes. Covered in front by the posterior extremity of the longus colli, this
ridge is in relation with, for the remainder of its extent, the posterior aorta, the
thoracic duct, and the vena azygos ; on its sides are seen the subdorsal branches
of the great sympathetic nerve.
The inferior plane, much shorter than the preceding, is, like it, narrower in
front than behind ; it has for base the superior face of the sternum, the sternal
cartilages, and the triangularis sterni muscle. Posteriorly, it gives attachment to
the fibrous sac containing the heart.
The lateral planes, more extensive than the other two, are concave in both
their diameters. Formed by the internal face of the ribs and the deep intercostal
muscles, they are in contact with the external face of the lung,
The base, or posterior plane, formed by the convex face of the diaphragm, is
circumscribed on its exterior contour by the circle of asternal cartilages, and by
the last rib. In it we see the three openings in the diaphragm.
The summit, or entrance of the thorax, is an oval opening, elongated vertically,
comprised between the two first ribs and the longus colli muscle, and which is
partly closed by an enormous collection of lymphatic glands ; through this
TEE THORAX. 543
opening passes the trachea, oesophagus, axillary and carotid arteries, anterior
vena cava, and the pneumogastric, great sympathetic, inferior laryngeal, and
diaphragmatic nerves.
Such is the thoracic cavity. Like the abdomen, it is provided with a serous
lining, which will now be examined.
The Pleurae. — The serous lining of the thorax comprises two distinct
membranes, named the pleune, forming two sacs placed one against the other in
the median plane, and thus constituting a septum named the mediastinum, which
divides the thoracic cavity into two lateral compartments. Each pleura, there-
fore, covers one of the external or costal walls of the thorax, and the correspond-
ing moiety of the diaphragm ; it is afterwards reflected in the vertical and
antero-posterior plane of the cavity, to concur in the formation of the media-
stinum, whence it is carried over the lung. This arrangement exhibits the
pleura in four portions — a costal, diaphragmatic, mediastinal, together represent-
ing the parietal layer of the membrane, and a pulmonary or visceral portion.
The costal pleura is applied to the inner face of the ribs and the internal
intercostal muscles. Strengthened on its adherent face, at each intercostal space,
by a layer of yellow elastic tissue, this membrane is related, by its free face, to
the external surface of the lung, with which it does not, in a normal condition,
contract any adhesions. It is continued posteriorly, by the diaphragmatic layer ;
in front, above, and below, by the mediastinal pleura.
The diaphragmatic pleura adheres somewhat loosely to the fleshy portion of
the muscle, but the union is more intimate on the aponeurotic portion. This
layer is contiguous, by its free face, with the base of the lung ; it is confounded
with the mediastinum by the internal part of its periphery.
The mediastinal pleura is placed, by its adherent face, against that of the
opposite side, and in this way produce the middle septum that divides the thoracic
cavity into two portions. Several organs are comprised between the two layers
of this partition, but most important of all is the heart. In Veterinary Anatomy,
that part of the septum in front of this organ is named the anterior mediastinum
— the appellation of posterior mediastinum being reserved for the portion situated
behind it. These terms have not the same signification as in human anatomy,
though they are retained here to prevent misunderstanding.
The anterior mediastinum, thicker than the posterior, but much less extensive,
contains, superiorly, the trachea, oesophagus, anterior aorta and its divisions,
anterior vena cava, thoracic duct, and the cardiac, pneumogastric recurrent, and
diaphragmatic nerves ; it also includes the thymus gland in the foetus and veiy
young animal. ThQ posterior mediastinum is incomparably narrower below than
above, in consequence of the oblique position of the diaphragm. Its inferior
part, always deviated to the left, is extremely thin, and perforated by small
openings, which give it the appearance of fine lacework. Traversed altogether
superiorly by the posterior aorta, vena azygos, and thoracic duct, this mediastinum
gives passage, a little lower between its layers, to the oesophagus, oesophageal
branches of the pneumogastric nerves, and to the left diaphragmatic nerve. It
is these layers of this mediastinum which pass to the lung to constitute the
pulmonary pleura, in becoming reflected above and below, in a horizontal hne
extending from the root of the pulmonary lobe to the anterior face of the
diaphragm.
The pulmonary or visceral pleura — a continuation, as has been said, of the
mediastinal pleura — is in contact, by its free face, with the parietal layer of the
544
RESPIRATORY APPARATUS IN MAMMALIA.
membrane. Its deep face adheres intimately, in Solipeds, to the proper tissue of
the lungs.
Independently of these four serous layei-s, the right pleura furnishes a special
fold, which arises from the inferior wall of the thoracic cavity, and ascends to
envelop the posterior vena cava. This fold also sustains the right diaphragmatic
nerve.
In order to study the various portions of the pleurse collectively, with their
reciprocal relations, and their connections with the organs contained in the
thoracic cavity, we will suppose three transverse sections of this cavity : one
passing behind the heart ; the other at the roots of the lungs, and dividing the
left ventricle of the heart ; the third traversing the anterior mediastinum, a little
in front of the right ventricle.
If, in the first section (Fig. 322), we take the costal pleura at the point a,
and follow it up to b, we shall see it folded downwards to form the mediastmal
layer, to be applied to the aorta, c, and the oesophagus, d ; then reflected at e on
the lung, /, enveloping every part of the organ ; returning to the point e, it
Fig. 322
Fig. 323.
THEORETICAL SECTIONS OF THE THORACIC CAVITV, INTENDED TO SHOW THE DISPOSITION OF
THE PLEURA.
leaves the lung, is again reflected to achieve the formation of the mediastinal
septum, h g, and finally regains the point it started from. On the right side,
with only a slight variation, it has the same arrangement. After being carried
from the point a' to //, then to e', and after enveloping the lung, returning to e\
and being reflected in the median plane to the point g', the right pleura leaves
the inferior thoracic wall to pass around the posterior vena cava, and come back
to a', its point of departure.
The second section (represented by Fig. 323), shows the pleura arrived at the
point h, descending on the root of the lung, c, covering that organ and returning
to c, and reflected on the pericardium, d, to gain the point a.
In the third section (Fig. 324), we see the parietal pleura, a b, without any
points of continuity with the visceral pleura, c. It is at the level of this section
that the lung forms two perfectly free lobes, which are not attached to the
anterior mediastinum.
Structuee. — Like all the serous membranes, the pleurae have a free face
covered by a perfectly smooth endothehum, always in contact with itself, and
TEE THORAX. 545
constantly lubricated by a serous fluid which facilitates the gliding of the lung
on the parietes of the thoracic cavity. The deep face is united to the subjacent
parts by connective tissue destitute of fat ; the adherence of the visceral pleurae
is most intimate.
The pleura has plexuses of vessels— one, the subserous, has large meshes ; but
a second, the endothelial, has a finer network.
The nerves are from the sympathetic and pneumogastric for the pulmonary
pleura ; from the diaphragmatic and intercostal nerves for the parietal
pleura.
Functions. — The thorax is not a mere receptacle, but, on the contrary,
performs a very important part in the act of respiration. We know, in fact, that
it is dilated and contracted by the movements of the diaphragm and the ribs
(see pp. 193, 310). The limgs, being apphed immediately against the thoracic
walls, and never at any time separate from them, follow this cavity in then-
movements — dilating in inspiration and contracting in expiration, after a certain
quantity of the oxygen of the inspired air has been removed and replaced by an
equivalent amount of carbonic acid.
The movements of the thorax are, therefore, of capital importance, constitut-
ing, as they do, the initial phenomenon of respiration, and having dependent on
them all the other acts of this function.
Differential Characters in the Thorax of the other Animals.
In the Ox, the thorax is not so long, particularly in its superior part, as in Solipeds, by
reason of the slight obliquity of the diaphragm, and of its mode of attachment to the ribs.
The total capacity of this cavity is also certainly inferior to that of the Horse's chest. It is
the same, though relatively more extensive, in the Sheep, Goat, and Pig ; while the Dog
possesses in this respect an incontestable superiority over Solipeds. It is to be noted that all
these animals, without exception, are distinguished from the Horse, Ass, and Mule by the con-
formation of the posterior mediastinum. In them it is not open in its lower part, but as solid,
thick, and complete there as elsewhere. Therefore it is that the consecutive effusion of
pleuritis is readily localized in one of tlie pleural sacs in tiie first-named animals, while this
localization is impossible in the second. (This is an important observation, from a pathological
point of view ; but it is to be noted that exceptional instances have been recorded, in which
the posterior mediaotinum of the horse has been found imperforate.
The Lung (or Lungs) (Figs. 318, 321, 325, 326).
Preparation. — The disposition of the lung in the thoracic cavity is best studied by placing
the subject in the second position, opening the chest by excision of the ribs, as in Fig. 322,
and inflating the organ by the trachea. To study its external conformation, it should be
removed from the cavity, with the heart and large vessels, and inflated as before.
Situation — General disposition. — This essential organ of respiration is a spongy
viscus, lodged in the thoracic cavity, and divided into two lateral, but inde-
pendent, moieties, each of which occupies one of the two serous sacs formed by
the plurse. It is also described as fivo jnilmonary lobes, or tivo lungs — a right and
left, the latter a little less voluminous than the former.
Form and Relations. — Together, the lungs affect the outline of the thoracic
cavity ; each represents the moiety of a cone,^ and offers for study : an external
and internal face, a base and summit, and a superior, inferior, and posterior
border.
* This is not the natural shape of the lungs, and is only assumed when the chest is opened,
and their elasticity is no longer counterbalanced by the atmospheric pressure, except at the
external surface of the bronchi.
546
RESPIRATORY APPARATUS IN MAMMALIA.
The external or costal face is convex (and smooth), and moulded to the
external wall of the thorax.
The internal, or mediastinal face, forms a vertical plane, separated from the
opposite lung by the mediastinum. It shows : 1. A small anterior portion in
contact with the anterior mediastinum. 2. At the heart, an excavation in which
that organ is lodged. 3. Immediately behind this excavation, and a little above
it, the root of the lung {hilum-pulmonis) — a fasciculus formed by the air-tubes and
pulmonary vessels in entering the viscus. 4. A posterior portion, more extensive
than the other two put together corresponding to the posterior mediastinum,
LUNG OF THE HORSE, SUSPENDED BY THE TRACHEA (VIEWED BY ITS BASE AND INFERIOR BORDER).
T, Trachea; L, L', anterior lobes; E, E', cavity for the heart ; Ap, Ap, branches of the pulmonary
artery at their entrance to the heart; Vp, Vp, pulmonary veins at their emergence from the
lung ; F, F, external face of the lobes of the lung ; D, D, base of the lung, or diaphragmatic face
of the two lobes; H, internal lobule of the right lobe ; I, channel for the posterior vena cava;
0, oesophagus passing between the two lobes (a certain retraction of the organ appears to make
it pass between the lobe and lobule of the right lung).
and attached to that septum by means of a fold developed around the organ, to
form the pulmonary pleura ; this fold constitutes, posteriorly, a small serous
ligament {ligamentum latum pulmojiis), attached at once to the mediastinum and
the posterior face of the diaphragm. On this portion of the lung are remarked
two antero-posterior furrows : one, near the upper border of the organ, to
receive the thoracic aorta ; the other situated lower, but not so deep, more
marked in the left than the right, and lodging the oesophagus. In the right
TEE LUNGS. 547
lung, this mediastinal face offers a small particular lobule, which is absent in
the left.
The base, or diaphragmatic face of the lung, cut obliquely downwards and
backwards, is concave, and moulded to the anterior face of the diaphragm. On
the right lung is seen the posterior face of the small lobule noticed on the inner
side, and a deep fissure between it and the principal lobe, for the passage of the
posterior vena cava.
The summit of the viscus, situated behind the first rib, presents a kind of
detached appendix — the anterior lobule of the lung.
The superior border, thick, convex, and rounded, is lodged in the vertebro-
costal channel or concavity. The inferior, much shorter and thinner, is deeply
notched at the level of the heart, and more so on the left than the right side.
The posterior is elliptical, and everywhere circumscribed by the face of the
diaphragm, which it separates from the costal and mediastinal faces.
Structure. — An external serous envelope, proper fundamental tissue, functional
and nutrient vessels, lymphatics, and nerves : such are the elements which enter
into the organization of the lung.
Serous Envelope. — This is the pleura pulmonalis already described.
Lymphatic stomata are observed on its surface. (There has also been described
a subserous connective tissue, containing a large proportion of elastic fibres ; it
invests the entire surface of the lung, and extends between the lobules.)
Fundamental Tissue. Physical characters. — The pulmonary tissue in
the adult is of a bright rose-colour ; it has a deeper hue in the foetus which
has not respired. Although soft, it is yet very strong and resisting, and can
with difficulty be torn. Its elasticity is remarkable, and is the cause of the
collapse the lung experiences when air is admitted to the pleural sacs. It is
very light — plunged in water, if healthy, it floats ; this specific lightness is due
to the air imprisoned in the pulmonary infundibula. This may be proved by
what takes place when the lung of a foetus is inflated : heavier than water
before, it then becomes lighter, because, notwithstanding all the manipulation
that may be employed to expel the air introduced into the pulmonary vesicles, a
certain quantity always remains. On the other hand, the absolute weight of the
lung is relatively more considerable in the adult than in the foetus, the first
representing ^^ of the total mass of the body, while it is only ^V i^ the second.
A knowledge of these facts may be utilized in determining whether a given
lung has belonged to an animal which has respired, or has died before birth.
If the tissue is plunged in water, this test is called hydrostatic pulmonary
docimacy ; if its relative weight is to be ascertained, it is designated pulmonary
docimacy by weight.
These are the physical characters of the fundamental tissue of the lung ; we
will now study its anatomical characters.
Anatomical characters. — The pulmonary tissue is divided into a great number
of small polyhedral lobules by septa of connective tissue, which appear to be
prolongations of the corium of the enveloping serous membrane. This segmen-
tation into lobules is a common feature in the organization of the lungs in the
Mammalia, but it is more readily demonstrated in some than others : not very
evident in Solipeds, and less so in the Carnivora, it is well defined in Rumi-
nants and Pachyderms.
As the lobule constitutes the genetic unit of the lung, we will study its
organization in detail, as has been already done with regard to the hepatic
548
RESPIRATORY APPARATUS IN MAMMALIA.
lobule. It forms a small pyramid with a polygonal base, measiirins: about ^ of a
cubic inch, and is sm-rounded by a layer of connective tissue which unites it to
the neighbouring lobules, and in which are some lymphatics and the network
formed by the pulmonary vein. It appears to be suspended by its summit to a
very short pedicle consisting of : 1. A sublobular bronchiole of about 0'039 inch
in diameter. 2. A twig of the bronchial artery. 3. A branch of the pulmonary
artery. 4. A division of the pulmonary vein. While the first three elements of
the pedicle enter the lobule, the fom-th deviates suddenly and becomes a capillary
network on its outer surface.
In the lobule, the sublobular bronchule is named the intra-lobular bronchiole;
it gives off the lateral intra-lobular hi^onchioles in passing towards the base of the
lobule, where it throws off at last two terminal bronchioles. Each lateral bron-
chiole comports itself like the intra-lobular one, and terminates in the same
Fig. 326.
LUNG OF THE HORSE RESTING ON ITS DIAPHRAGMATIC SURFACE, AND VIEWED BY ITS ANTERIOR
EXTREMITY.
T, Trachea ; D, right lobe ; G, left lobe ; L, anterior lobule of the right lobe ; L', anterior lobule
of the left lobe ; Ap, branches of the pulmonary artery at their entrance into the two lobes ;
F, F', notch on the right and left of the inferior border of the lung, in face of the heart; E, notch
on the upper border for the passage of the aorta ; V, V, openings of the pulmonary veins ; La,
lobule of the right lung ; S, fissure for the passage of the posterior vena cava.
manner — by two short or acinous bronchioles, about ^^ of a millimetre in
diameter.
At the extremity of each of the terminal bronchioles — short or acinous — is
suspended a small pyramidal mass of 2 to 3 cubic millimetres — the acinus., which
at first showing an initial dilatation — the vestibule, afterwards gives off three,
four, or five divergent tubes of from ^ to f of a millimetre — the alveolar passages,
or, better, respiratory canaliculi. These are sacculated on their surface and
expanded at their termination, so as to resemble small bunches of grapes in
which the fruit is not very distinct from the stalk. The terminal dilatations are
named infundihnla, and the boss-like portions alveoli, or pulmonary vesicles.
The ramifications of the bronchial artery are expended in the tissue of the
bronchioles, and do not extend beyond the commencement of the alveoli and
infundibula ; while the branches of the pulmonary artery accompany the bronchi,
and become capillaries in the walls of the alveoli and infundibula. In this way
TEE LUNGS.
the conductive and the respiratory parts, properly speaking, of the lung have
an organic independence, just as they have a physiological and pathological
individuahty.
The elements of the pedicle, in ramifymg in the lobule, caiTy with them a
certain amount of connective tissue.
To demonstrate the structure of the lung,
and sections afterwards made to show
the pulmonary alveoli. But this
procedure has the inconvenience of
unduly distending these small cavities
by thinning, and even destroying,
their walls. A better method is the
following : leave the lung in the
intact thoracic cavity ; by the jugular
vein, pour into the right side of the
heart an injection of very hot tallow,
employing a certain amount of force
to propel it from the pulmonary
artery into the veins ; when this
injection has cooled, open the thoracic
cavity, and take out the lungs
These, being impregnated with solidi-
fied fat, do not collapse on contact
with the air, and sections made in
different directions then exhibit in-
numerable perfectly circular porosi-
ties, which are the open pulmonary
vesicles.
In this way it is easy to demon-
strate the presence of the air-cells ;
it may be inflated and dried,
Fig. 327.
CAST OF A PRETERIIIXAL AND TERMINAL BRON-
CHIOLE, FROM THE LUNG OF THE ASS.
I, Bronchiole of 1§ millimetre in diameter; 2, 2,
ramifications ^ a millimetre in diameter; 3, 3, 3, 3,
sublobular bronchioles ; 4, ramifications of an
intra-lobular bronchiole; 5, 5, infundibula ; 6, 6, 6,
respiratory canaliculi ; 7, pulmonary alveoli ; 8,
debris from the canaliculated part of a pulmonary
lobule; 9, acinus. A point has been chosen
where the moulding of a great number of alveoli
and acini failed, in order to show the divisions of
the bronchi better. Magnified 5 diameters.
but, in order to conveniently study
their arrangement, it is necessary to take a cast of them by means of a solidi-
fiable material introduced by the bronchi, and afterwards destroyed by the
maceration of the pulmonary tissue. The Darcet alloy, employed in this manner,
often gives very good results, as seen in figures 327, 328.
We will follow the preceding details on the interior of the lung, with some
words on the structure of its different parts.
The bronchiole, on entering the lobule, has all the elements of the larger
bronchi — cartilaginous rings, a layer of racemose mucous glands, muscular layer,
festooned mucous membrane, and ciliated epithelium ; but as it divides and
becomes smaller, its composition is modified. The intra-lobular bronchioles suc-
cessively lose their cartilages, the glandular layer, and the contractile layer, and
at last at the acini the mucous layer is reduced to its basement membrane, and
the epithelium becomes cubical. The walls of the infundibula are formed by a
thin amorphous membrane strengthened externally by some connective tissue and
an elastic network ; while the interior is lined by a row of flat cells, the outline
and nuclei of which can easily be made out in the adult animal. The capillaries
form an extremely rich network spread outside the proper membrane — though
sometimes they enter its substance, and push the epithelium towards the centre of
the alveolus.
550
RESPIRATORY APPARATUS IN MAMMALIA.
(The minute polygonal cells lining the air or pulmonary vesicles measure from
TffW to ^TD^ of an inch in diameter, and from ^winj <^o ^^5^ of an inch in thick-
ness. Between the vesicles is a tra-
p's- 328. becular tissue, mainly composed of
yellow elastic with a few muscular
fibres, some of which are united with
the lining membrane to strengthen it,
especially around the apertures of
communication between the adjoining
air-cells.
The capillaiy plexuses are so ar-
ranged between the two layers forming
the walls of two adjacent cells, as to
expose one of their surfaces to each,
in order to secure the influence of the
air upon them. These networks are
so close, that the diameter of the
meshes is scarcely so great as that of
the capillaries which enclose them.)
Vessels. — The lung is a very
vascular organ. The numerous rami-
fications it receives divide into two
orders — the functional and the nutri-
tive vessels.
Functional vessels of the lung. —
The blood is returned from all parts
of the body by the veins, after losing,
along with its bright red colour, the properties which render it fit to maintain
the vitality of the tissues. It thus arrives at the right side of the heart, whence
it is propelled into the lung, there to be regenerated by mediate contact with the
air. It is the pulmonary artery which conveys this fluid into the parenchyma of
the organ, and by the pulmonary veins it is carried back
to the heart. The artery is at first divided into two branches,
which ramify, and finally terminate in dense capillary plexuses
upon the walls of the infundibula. The veins — innumerable
and attenuated at their origin, like the arterial capillaries
— terminate in from four to eight principal trunks, which
open into the left auricle of the heart.
The branch of the pulmonary artery that enters each
lobule, is regarded as terminal — that is, it does not anas-
tomose directly with the arteries of the neighbouring lobules ;
on the contrary, the interlobular branches of the pulmonary
vein are in relation with the capillary network of the adjoin-
ing lobules.
These two orders of vessels, which necessarily participate
in the physiological functions of the lung — like the vena
port* with the liver — are very justly distinguished from the
other arteries or veins, by the designation o( functional vessels. But though they
are so named, it must not be inferred that they are excluded from all partici-
pation in the acts of nutrition.
CAST OF A PORTION OF THE BRONCHIAL DIVISIONS
AND SOME LOBULES AND ACINI, FROM THE LUNG
OF THE ASS.
1, Bronchiole, IJ millimetre in diameter; 2, 2, 2,
ramifications of 1 millimetre ; 3, 3, 3, 3, sub-
lobular bronchioles ; 4, 4, 4, intra-lobular
bronchial divisions ; 5, 5, acini ; 6, 6, respiratory
canaliculi ; 7, 7, infundibula; 8. 8, 8, mould of
complete lobules. It was necessary to break
away a number of lobules in order to show these.
Magnified 5 diameters.
Fig. 329.
PLAN OF A PULMO-
NARY LOBULE.
a, Bronchiole termi-
nating in a slight
dilatation, b ; c, air-
sacs, or infundibuli;
d, air or pulmonary
vesicles.
TEE LUNGS.
55]
Nutrient vessels. — By this name is designated the divisions of the bronchia]
arteries and vei7is, the terminal ramifications of which anastomose with the capil-
laries of the pulmonary vessels at the ultimate bronchules.
It is generally admitted that the
two arterial systems — bronchial and
pulmonary — are independent of each
other, and also of the general circu-
lation. Kiittner believes he has in
several ways demonstrated the exist-
ence of communications between
bronchial and pulmonary arterioles,
and between the latter and the sub-
pleural arterioles.
Lymphatics. — These vessels are
divided into superficial and deep. The
first form a network beneath the
pleura ; the second exist in large
numbers around the lobules. They
mix and terminate in the bronchial
glands ; but before doing so, they
enter the small lymphatic masses dis-
seminated in the texture of the lung,
in the neighbourhood of the bronchi.
There are also interlobular lymphatics
which follow the ramifications of the
bronchi and pulmonary artery. (Lym-
phatics of very small size have been
described as commencing in the
alveolar spaces, on leaving which they gain a proper coat or internal tunic, and
are subsequently supplied with valves.)
Nerves. —The nerves supplied to the tissue of the lung come from the same
source as those of the bronchial tubes —
the pneumogastric and great sympathetic
nerves. Their ramifications accompany
the pulmonary vessels and bronchi,
and they show small ganglia on their
course.
Functions. — To know that the lung
is the seat of the absorption of oxygen
and the expulsion of carbonic acid from
the nutritive fluid — phenomena accom-
panied by the transformation of the dark
into red-coloured blood, and the cooling
of the venous blood — is the only authen-
tic fact necessary to remember with
regard to the functions of this organ.
It must be added that the operations
from which all these phenomena result,
take place in the lung by the mediate contact of the atmosphere introduced
into the pulmonary alveoli during inspiration, with the blood traversing the walls
INFUNDIBULA OF LUNG, WITH INTERVENING
TISSUES.
a. Epithelium; b, elastic trabeculae; c, membranouB
wall, with fine elastic fibres.
Fig. 331.
ARRANGEMENT OP THE CAPILLARIES AROUND
THE INFUNDIBULA.
552 RESPIBATORY APPARATUS IN MAMMALIA.
of these spaces. With the intimate mechanism of these actions we have nothing
to do here, however.
Development. — Although the lung is in a state of inactivity in the foetus,
yet it is one of the early developed organs. During the whole period of foetal
existence, its lobular texture is much better defined than in the adult, and it
then appears to be formed exactly like a racemose gland. Sections of it prepared
for microscopical examination, distinctly show the vesicles and their arrangement.
We have already made known the differences in colour and density which dis-
tinguish the pulmonary tissue of the foetus and that of the adult. It only
remains to repeat what has been said as to the slight vascularity of the first,
and to note that the blood of the pulmonary artery passes almost entirely into
the posterior aorta by the arterial canal (or ductus arteriosus).
Differential Characteks in the Lungs of THii other Animals.
The form of tlie luugs of Ruminants does not diftVr from that of the Horse, except that
tie left is divided into two lobes, and the right into four — the anterior of tiiese being curved
in front of tlie heart. This is shown in Fig. 332.
The lungs of the Ox, Sheep, and Goat are remarkable for the distinctness with which
the lobules are deiined. They are, in fact, separated by loose connective tissue, which, by a
certain degree of traction, may extend 1 or 2 millimetres ; it forms a reticular and alveolar
system capable of being developed by insufflati<m. Kenant and Pierret have shown that the
dilatable tracts are lymph spaces, lined with a characteristically festooned epithelium ; so that
the pulmonary lobules in the lung of the Ox aie batheii in a lymphatic sac.
As a consequence of inflammation, tliese spaces, are gorged with fibrine and leucocytes, and
contrnst strikingly, by their pale tint, with the lobules ; therefore the lesions of pneumonia in
the larger Ruminants have an altogether special character — a fact to which Dietrichs drew
attention a long time ago.
In the Pig, the lungs comport themselves somewhat like those of Ruminants.
In the Dog and Cat, there is no well-marked fissure in either lung towards tlie heart,
which causes that organ to be almost completely enveloped by pulmonary tissue. Tlie left
lung has three lobes, and the right four, separated from one another by deep furrows, which
are generally prolonged to the root. The lobules are small, very close, and the pulmonary
tissue is exceedingly compact. (The pulmonary infundibula are proportionately larger than iu
Ruminants.)
Comparison of the Larynx, Trachea, and Lungs of Man with those of Animals.
1. Larynx. — The human larynx is proportionately shorter and wider than that of animals.
The principal cartilages are those which have been already studied ; but there are, besides,
small cartilaginous bodies, to which special names have been given : these are the cartilages of
Santorini and of Wrisberg. The facets on the cricoid for articulation with the thyroid are
placed on the small cornu detached from the external face of the cartilage. The thyroid is
wide, and protects the anterior face of the larynx ; the angle formed by the alse, which is more
marked in the male than the female, is very prominent, and is named the pomum Adami.
The epiglottis is short, broad in its middle, and rounded at its summit, something like that of
the Carnivora. The muscles are the same in number and disposition as in these animals; but
there is distinguished an oblique arytsenoideus — a fasciculus of the arytsenoid, wliich crosses its
f« How to form an X in passing from the upper border of one arytsenoid cartilage to the lower
border of tlie other.
Internally, the human larynx has no sub-epiglottic or sub-arytsenoid sinus like thnt of Soli-
peds, though it hiis lateral, or Morgagni's, ventricles that ascend a little to the outside of tlie
superior vocal cords.
2. Trachea. 3. Bronchi.— There is little difference to be remarked in these. Tiie trachea
is about four inches long and about one inch wide, and is composed of about twenty C-shaped
rings, which are closely united as in animals. It is situated iu thi^ median plane, in the upper
part of the neck, where it is embraced by the lobes of tlie thyroid gland ; at its entrance into
the chest it deviates slightly to the right. The two short canals between its lower extremity
GLANDIFORM BODIES CONNECTED WITH RESPIRATORY APPARATUS. 553
and the lungs are the bronchi; the right bronchus is the shortest and wiriest, and has an almost
horizontal direction, entering the right lung at the fourth dorsal vertebra ; the left is longer
and less voluminous, and reaches the corresponding lung at the tifth vertebra.
4. Lungs.— The lungs weigh about forty ounces. As in all animals, the right is more
voluminous than the left, and is divided into three lobes ; the latter has only two. The
inferior vena cava is not surrounded by pulmonary tissue : the principal lobes are partitioned
into lobules, which are visible on the surface, and on the limits of which are deposited, only in
Fig. 333.
LUNG OF THE SHEEP (INFERIOR VIEW).
1, Right lung; 2, left luDg; 3, trachea;
4, heart ; 5, carotid arteries ; (5, posterior
vena cava.
HUMAN LUNGS AND HEART (FRONT VlEW).
Right ventricle; 2, left ventricle; 3, right auricle;
4, left auricle ; 5, pulmonary artery ; 6, right pul-
monary artery; 7, left pulmonary nrtery ; 8, liga-
ment of ductus arteriosus; 9, arch of aorta; 10,
superior vena cava ; 11, arteria innominata ; 12, right
subclavian vein, with the artery behind it ; 13, right
common carotid artery and vein; 14, left vena in-
nominata; 15, left carotid artery and vein; 16, left
subclavian vein and artery; 17, trachea; 18, right
bronchus ; 19, left bronchus ; 20, 20, pulmonary
veins; 21, superior lobe of right lung; 22, middle
lobe ; 23, inferior lobe ; 24, superior lobe of left lung ;
25, inferior lobe.
the adult, a notable quantity of pigmentary matter, that gives the lungs the appearance of a
chess-board. There is nothing to be said respecting their intemul conformation and structure.
The Glandiform Bodies connected with the Respiratory
Apparatus.
1. Thyroid Body, or Gland (Fig. 334).
The thyroid body consists of two oval lobes of a reddish-brown colour,
and is situated close to, and behind, the larynx, beside the two first rings of the
trachea.
These two lobes, distinguished as right and left, appear at first sight to be
perfectly independent ; but close examination shows them to be united by an
intermediate portion (the isthmus), which passes across the anterior face of the
554
BESPIRATORY APPARATUS IN MAMMALIA.
GROUP OF GLAND VESICLES FROM THE THYROID
BODY OF A YOUNG SUBJECT.
a, Connective tissue ; 6, basement membrane of
the vesicles ; c, epithelial cells.
trachea. This connecting portion is far from being constant in the Horse,
while it is nearly always present in the Ass.
Each lobe of the thyroid body is related, inwardly, to the trachea ; outwardly,
it is covered by the subscapulo-hyoideus muscle.
Structuee.— The thyi-oid body is
Fig. 334. composed of a fibrous envelope, and a
proper tissue or parenchyma.
The fihrous envelope is composed of
slender, but strong connective tissue ;
it sends from its inner face a large
number of thin nucleated layers that
intersect each other, forming spaces in
which the proper tissue is contained.
The parenchyma is divided into
lobules, the presence of which is mani-
fested on the surface of the organ.
They are composed of vesicles communi-
cating with each other, the shape and
contents of which vary considerably
with age and situation. In the foetus,
or very young animal, they are round
or elliptical, and constituted by a thin
amorphous membrane, lined by poly-
gonal cells with a large nucleus, and
containing a granular fluid. In the
adult, these vesicles are misshapen, and, after being distended, several run to-
gether, while the epithelium is less evident, but uniform ; the contents have
become brown, and hold granules and nuclei in suspension ; and, finally, they
often assume the character of colloid matter, in becoming viscid and of a yellow
tint.
Vessels and nerves. — The thyroid body is remarkable for the relatively
enormous volume of its blood-vessels ; the arteries chiefly come from the thyro-
laryngeal branch — a collateral of the common carotid (they form plexuses on the
vesicle walls) -, the rei7is pass to the jugular. Its nervous filaments are from the
first and second cervical pairs, with twigs from the sympathetic. It has an
abundance of li/mphatics, which form a system of somewhat large cavities around
the alveoli.
Functions. — The thyroid body is one of the organs classed, in a somewhat
arbitrary manner, in the ill-defined category of ductless glands. Our knowledge
of its use is as uncertain at present as in the infancy of anatomical science.
So that we can say nothing more on this subject, except that the successive
or simultaneous excision of the two lobes in the Horse do not appear to cause
any derangement in the animal's health.
In those animals in which it is developed, it seems to have much importance,
and is said to play a part with regard to the brain, similar to that attributed to
the spleen in the abdominal circulation. Ha^mato-poietic functions have also
been ascribed to it, from the influence it exerts by means of the follicles placed
between its vesicular lobes ; these are supposed to destroy the mucme formed in
the body.
The study of its development does not throw any light on its functions.
GLANDIFORM BODIES CONNECTED WITH RESPIRATORY APPARATUS. 555
It is certainly relatively larger in the foetus and young animals than in adults ;
but the difference is not sufficiently marked to authorize us in drawing any
physiological inductions therefrom.
2. Thymus Gland (Figs. 335, 336).
The thymus gland is a transitory organ, being only present in the foetus and
very young animals, and in its nature closely resembles the thyroid gland. Like it,
it is divided into two lateral lobes, placed close together in the middle line, under
Fig. 336.
Fig. 335.
PORTION OF THYMUS GLAND
OF CALF, UNFOLDED.
a, Main canal ; h, glandular
lobules ; c, isolated gland
granules seated on the main
canal.
COURSE AND TERMINATION OF THE ABSORBENT DUCTS OF
THE THYMUS GLAND OF A CALF.
1, Internal jugular veins ; 2, superior vena cava ; 3, thoracic
duct, dividing into two branches, that again unite before
terminating in the root of the left jugular vein; 4, the two
thymic ducts : that on the left side opening into the thoracic
duct, and the right into the root of the corresponding jugular
the lower face of the trachea, partly without and partly within the chest, between
the two layers of the anterior mediastinum. It is elongated from before to
behind, of a whitish' colour, and uneven or lobulated on its surface like a salivary
gland.
Structure. — It owes its uneven aspect to its lobular structure ; for it is
effectively reduced by dissection into a multitude of granular lobules, in the
centre of which are found vesicular cavities containing a lactescent fluid. The
vesicles are larger than those of the thyroid gland, and have for walls a very
556 MESFIRATOtiJt APPARATUS IN MAMMALIA.
thin layer of delicate connective tissue ; they are filled by a mass of nuclei.
A wide, irregular cavity has been described as existing in the middle of each lobe
{j-eservoir of the thymus), and evidently communicating with the vesicles of the
lobules, as it contains a notable quantity of the same milky fluid. This cavity is
certainly not present at all periods ; for I have not met with it in two young
foetuses now lying before me as I write. But without dwelling on this particular
point, we may notice enormous blood-vessels, lymphatics, and nerves, as com-
plementary elements in the organization of the gland, the structure of which is
very similar to that of true glands, though differing from them in an important
feature — the absence of an excretory duct.
Nothing positive is known as to the functions of the thymus gland ; it is
only certain that they resemble those of the lymphatic glands, and that they are
exclusively related to the development of the young animal ; as it generally
disappears some months after birth, though it is sometimes found in the adult,
and even in very aged animals.
(Its functions are supposed to be the same as, or analogous to, those of the
thyroid. Structurally, the organ may be said to consist of an assemblage of
hollow glandular lobules joined together by connective tissue, each having a
cavity which opens into a central canal that has no duct, and being hned
externally by an almost amorphous membrane which divides it into "acini,"
or gland-granules. Separate acini are often observed on the main canal. Each
lobule is made up of its greyish-white, soft parenchyma composed of free nuclei
and small cells, and has a minutely distributed capillary plexus. The lymphatics
terminate in two large ducts that commence at the upper extremities of the lobes
of the gland — the thymic ducts — and pass downward to terminate at the junction
of the jugular and axillary veins at each side.)
Differential Characters in the Glandiform Bodies annexed to the Kespiratort
Apparatus in the other Animals.
The thyroid body, peculiar to Mammals, is more developed in Ruminants, Pacyderms,
and Carnivora, than in Solipeds. The two lobes are closer together, and are often united by
the thyroid isthmus. In the Pig this i^ very marked, and the gland well merits its name,
as it forms a veritable shield in front of the trachea, towards the lower part of the neck.
The thymus gland in young Ruminants is more voluminous than in tlie Foal, and is situated
higher up in the cervical region.' (In the Carnivora, it is divided into two brandies ; but it is
small, and completely lodged between the layers of the anterior mediastinum. It persists for
some time after birth, and seldom disappears in less than a year.)
(Comparison of the Glandiform Bodies annexed to the Respiratory Apparatus in
Man, with those of Animals.
In Man, the two lobes of the thyroid body are connected by an istlimus, and the upper
extremity of the lobe is carried up to the side of the thyroid cartilage. Tiie istlimus often gives
origin to a process of variable length and size, called the pyramid, or third lobe, which is
generally situated to the left. A muscle is sometimes found connected with the isthmus or
pyramid, and is attached above to tlie body of theos hyoidesor to the thyroid cartilage ; it has
been named the levator glandulas thyroidx.
The thymus gland is composed of two lobes, a right and left, only joined by connective tissue,
and having no structural communication. There is a cervical and a thoracic portion, the whole
extending from the fourth rib as higli as the thyroid gland. After birth it continues to enlarge
until the end of the second year, and begins to diminish between the eighth and twelfth
years.)
THE RESPIRATORY APPARATUS IN BIRDS. 557
CHAPTEE II.
The Respiratory Apparatus in Birds.
The organs composing- the respiratory apparatus of Birds offer conditions alto-
gether special, which have a remarkable influence on the mechanism of respira-
tion. The modifications in the performance of this function will be indicated
after an examination of the tubular apparatus which carries air into the Iwiff,
and the characters of that organ, as well as the air-reservoirs (or sacs) annexed
to it.
The Tubular Apparatus which carries Air to the Lungs.— When
this apparatus is compared with that of Mammals, no very sensible differences are
observed— at least, in domesticated Birds.
The nostrils, pierced through the upper mandible of the beak, have no mem-
branous and movable alse, and the nasal fossae open into the pharynx by a long,
narrow slit behind the bony palate. A transverse row of small, horny papillae,
placed at the anterior extremity of this aperture, represents the soft palate.
The larynx has no epiglottis : a defect which does not prevent the complete
occlusion of the glottis during the passage of food, as the laryngeal orifice is
circumscribed by two lateral lips, which then meet in the most exact manner.
The trachea is composed of complete cartilaginous rings, and not simple arcs.
In Song-birds, the last ring is a second larynx, the real organ which produces the
modulated voice of these creatures ; it only exists in a rudimentary condition in
Poultry, however, the last tracheal piece in them being slightly dilated, and
showing at the origin of the bronchi a membranous layer, from whose vibration
results cries or crowing. Other singular peculiarities belonging to the trachea
deserve to be described here, if they were not the exclusive appanage of some wild
fowl. "We are content to mention the presence of the bony drum found at the
terminal extremity of the trachea in the whistling Duck, and the remarkable con-
volutions that tube forms in the breast-bone of Cranes and male Swans.
The hrofichi only show incomplete rings in their structure. They pass into
the lung by its inferior face, towards the union of its anterior and two posterior
thirds. When describing this organ, their mode of ramification, and the nature
of the relations they bear to its proper tissue, will be considered.
The Lungs. — Sappey, in the remarkable memoir published by him in
1847,^ has described them as follows : " The lungs of Birds are situated on the
lateral parts of the vertebrse of the back — which separate them, and lying
against the arch of the thoracic cavity, to which they adhere. Their rosy colour
resembles that presented by these organs in Man and the Mammalia during
uterine life, and for some time after birth ; they are especially remarkable for
their restricted volume, which scarcely represents an eighth part of the thoracic
capacity. Their configuration is far removed from the conical form of the lungs
in Mammals, and the oval form of the same organs in reptiles ; they are semi-
elhptical, and if the two lungs of a Mammal were opposed base to base, their
hkeness would be produced : to obtain the same results with the limgs of a
reptile, it is necessary to divide them in the direction of their great axis.
" This shape enables us to distinguish in the lungs of a bird, two faces — a
' Sappey, Becherches sur I'Appareil Respiratoire des Oiseaux. Paris : 1857
38
558 THE RESPIRATORY APPARATUS IN BIRDS.
convex and concave ; two harder s — an external Hand an internal ; and tivo
extremities — an anterior and posterior.
" The convex face, also named the dorsal, costal, or superior face, corresponds
inwardly to the dorsal vertebras, and outwardly to the ribs and the intercostal
muscles ; it is exactly moulded on the walls of the thorax, and as the ribs pro-
trude on the internal face of these walls, it results that this surface of the lungs
is marked by transverse furrows which give it a lobulated aspect ; but these lobes
or lobules show nothing common with those composing the same organ in
Mammalia. In that class, the existence of lobes and lobules is an established
fact, and is caused by the dichotomous division of the bronchi ; in birds, it is
only apparent, and depends on the diminished thickness of the lung at each rib.
This face, quite imperforate, is covered by a thin layer of cellular tissue, which
unites it to the sides of the thorax.
" The plane or concave face looks downwards ; it is in relation with the
diaphragm, which separates it from the viscera of the thorax, and from the
abdomen ; from this arises its other names of inferior, diaphragmatic, or visceral
face. Like the preceding, it is covered by a very fine layer of cellular tissue,
which forms adhesions with the diaphragm ; but it differs from it by the orifices
it presents, which are five in number, and constitute veritable canals, through
which the air passes and repasses incessantly to and from the sacs, and from them
to the lungs.
" The herders are parallel to the axis of the body ; the internal is rectilinear,
thick, and rounded ; the external, convex, thin, and sharp.
" Of the two extremities, the anterior, which is very acute, occupies the
receding angle formed by the spine within the first rib without ; the posterior,
more considerable, has a rounded form."
In regard to structure, that which distinguishes the lung of Birds from that
of Mammals, is the mode of distribution and termination of the air-passages. In
Mammals, the large bronchial tubes, placed in the centre of the lung, send their
divisions towards the surface of the organ, or in a centrifugal manner ; in birds
they are disposed at the periphery of the lung, and direct their different ramifi-
cations towards the centre, or in a centripetal fashion. On the other hand, the
arboreal division of the bronchi in Mammals is replaced in birds by penniform
ramification. liastly, the terminal bronchial tubes instead of opening into a
series of closed vesicles, as in Mammals, anastomose with one another in birds,
so as to form an inextricable aerial network.
Sappey has further developed the knowledge acquired on this interesting
subject in the following terms : " Arrived in the puknonary tissue, it (the
bronchial trunk) dilates, divides, gradually contracts in following its primary
direction, and in this way gains the posterior extremity of the organ, where it
terminates by opening into the abdominal reservoir.
" This ferifying trunk, therefore, presents two very distinct portions, the one
extra-pulmonary, the other intra-pulmonary. The first offers the greatest analogy
to the bronchi of Mammalia ; it is membranous internally, elastic and fibrous
elsewhere, provided outwardly with cartilaginous rings, which embrace three-
fourths of its circumference, and is lined by mucous membrane characterized by
its pale rose-colour, and its marked adherence.
" The second differs from the preceding in its dimensions, form, and struc-
ture. Owing to its dilatation at its entrance to the lung, its dimensions are more
considerable, and may be stated as three to two of the extra-pulmonary portion.
THE RESPIRATORY APPARATUS IN BIRDS. 559
Beyond this enlargement, it diminishes in capacity by the emission of branches,
losing its cylindrical form to assume that of a cone with a trmicated summit.
Its walls are almost entirely destitute of cartilaginous rings, so that the origin of
the principal conduits is constantly membranous.
" The air-passages arising from this common trunk to constitute the frame-
work of the lung, are remarkable for their uniformity in number, form, and the
direction they olTer in all classes of birds. They are generally twelve, and their
origin is thus distributed : four arise from the internal wall of the trunk by a
series of orifices placed one after the other ; seven are detached from its external
wall by a second series of orifices also disposed in rows ; the twelfth springs from
its inferior wall, and immediately bends downwards and outwards to open into
the posterior diaphragmatic reservoir, which may be considered as a terminal
branch of the principal trunk.
" All the canals which have their origin from these linear series of openings
on the internal and external walls of the generating trunk, show this common
disposition : that from their commencement they pass towards the periphery of
the lung, that they divide and subdivide at this periphery, that they cover it
with their ramifications, and do not leave it to enter the pulmonary parenchyma
until their volume has been considerably reduced.
" The conduits leaving the orifices situated on the inner wall of the a3rial
trunk ramify on the inferior face of the lung ; those proceeding from the eche-
loned orifices on the outer wall are distributed on the opposite face. The first
constitute the diaphragmatic, and the second the costal bronchial tubes.
" The diaphragmatic hroiichial tubes, four in number, like the orifices from
which they originate, may be distinguished by the numerical names of first,
second, third, and fourth, in proceeding from before to behind ; the first bronchus
is carried forward horizontally, the second transversely inwards, the third
obliquely inwards and backwards, and the fourth directly backwards. In view
of their divergent direction, which resembles a fan, they might be designated as
the anterior, internal, and posterior diaphragmatic bronchial tubes ; and to dis-
tinguish the last two, the more voluminous one — which is directed backwards and
inwards — might be named the great posterior diaphragmatic bronchus, and the
one passing directly backwards, the small posterior diaphragmatic bronchus.
" The costal bronchial tubes, seven in number, may be also designated as first,
second, third, etc., in proceeding from before to behind. Parallel at their origin,
and in juxtaposition, like the pipes of an organ, they separate after following a
certain course, and affect, by their divergence, the fan-shape already observed in
the disposition of the diaphragmatic bronchi. Like the latter, they become
peripheral from their origin, and spread out from centre to circmnference. The
first is carried very obliquely upwards and inwards, to attain the anterior
extremity of the lung ; all the branches it furnishes arise from its anterior wall,
and those which are nearest its origin are inflected to gain the external border
of the organ. The succeeding tubes are directed forwards, the others forwards
and inwards ; while all proceed to meet those coming from the anterior dia-
phragmatic bronchus, though they do not anastomose with them. Coming in
contact, they plunge into the pulmonary tissue in such a way, that, when a lung is
inflated, we observe between these two orders of ramifications a very manifest
groove, which is perfectly distinct from those due to the protrusion of the ribs ;
this groove evidently represents, though in a rudimentary state, the inter-
lobular fissures in the lungs of quadrupeds.
560 THE RESPIRATORY APPARATUS IN BIRDS.
" The second, third, and fourth costal bronchi follow a transverse course,
and ramify on the inner border of the lung ; the fifth and sixth incline towards
the posterior extremity of the organ ; the seventh, very small, reaches this
extremity and disappears.
" The first costal bronchus is the most voluminous ; those succeeding it
gradually diminish in calibre. At their point of emergence they adhere closely
to the ribs ; all are imperforate, and this feature essentially distinguishes them
from those occupying the opposite face.
" The canalicuU furnished by these principal tubes do not sensibly differ in
calibre in the various bronchi ; all offer an equal diameter, and their dimensions
are only in relation to the total volume of the lung. All are detached at a right
angle from the pulmonary wall of each bronchus, and descend perpendicularly into
the lung ; and all, from their origin to their termination, preserve the same
diameter, and consequently the same cylindrical form. If this mode of ramifica-
tion be compared with that observed in Mammals, it will be seen to differ con-
siderably. In the latter class, the air-passages affect the dichotomous division
proper to the arteries and veins, the result of which is a series of arborescent canals
decreasing in capacity. In birds only two kinds of conduits are observed, the
primitive and peripheral, disposed around a generating axis like the barbs of a
feather on their stalk ; and the secondary and parenchymatous, implanted on the
pulmonary walls of the first, like the hairs of a brush on their common base.
These two arrangements are evidently similar, except that the peripheral canals,
which are few, only form a single row on each side ; while the canaliculi, very
numerous, form several. Consequently, it may be said that the mode of ramifica-
tion proper to Mammaha is essentially dichotomous, and that observed in birds
essentially penniform.
" Independently of the canaliculi arising from the pulmonary walls of the
diaphragmatic and costal bronchi, there are others which spring directly from the
generative trunk ; but in their dimensions, direction, form, and general disposi-
tion, they do not differ from the preceding.
" How do these canals terminate ? Notwithstanding the importance of this
question, it has been generally neglected ; though its solution alone may furnish
the analogies and differences necessary for the parallel which has always been
attempted to be established between the lungs of birds and those of other verte-
brates. Our special researches on this point have led us to the conclusion that
all the canaliculi open into one another, and by this anastomosis constitute an
extricable plexus the various parts of which communicate with each other."
Finally, it may be mentioned that " the walls of the pulmonary canaliculi
examined microscopically, appear to be covered internally with irregular septa
which circumscribe the areolae, and give them a cellular aspect."
The Aie-sacs.^ — " In birds, the pulmonary mucous membrane is continued,
at the level of the orifices in the lung, into the utriculiform cavities which are
developed between the walls of the thorax and the abdomen on the one side, and
the thoracic and abdominal viscera on the other. These air-reservoirs exist in
all the vertebrata of the second class. In all, they are situated at the periphery
of the viscera in the trunk, in such a manner that Cams has justly observed that
the lungs of Birds enclose all the other viscera ; so that when they are distended
by the entrance of air, they generally depress these viscera by pushing them
' What is said relating to these air-sacs is taken from the Memoir of M. Sappey, Recherchet
sur I'Appareil Respiratoire des Oiseaux. Paris : 1847.
THE RESPIRATORY APPARATUS IN BIRDS. 561
towards the median plane. In all, they are independent of each other, and
freely communicate either with the Imig by a single aperture, or with the bones
by one or more openings. Lastly, in all they are nine in number.
" These reservoirs are : the thoracic sac, situated at the anterior part of the
thorax ; two cervical reservoirs, situated at the base of the neck ; two anterior
diaphragmatic reservoirs, placed between the two diaphragms ; two posterior
diaphragmatic reservoirs, also between these two diaphragms, but behind the
preceding ; and, lastly, ttvo abdominal reservoirs, placed against the superior wall
of the abdomen. Of these nine reservoii-s, the first only is single and symmetrical ;
the others are pairs, and similarly arranged on each side of the median plane.
" The thoracic and cervical reservoirs are situated beneath, and in front of,
the lungs ; the abdominal reservoirs lie behind these organs, and the four
diaphragmatic sacs at their inferior part and between the preceding ; hence the
denomination of middle reservoirs sometimes applied to the latter, in opposition
to the first, which are named the anterior reservoirs, and to the second, called the
posterior reservoirs."
External Conformation of the Reservoirs. — 1. Thoracic reservoir
(Fig. 337, 2). — " It is situated above the clavicles and the inter-clavicular space,
in the cavity of the thorax, which it extends beyond on each side to the roots of
the wings, around the articulation of the shoulder. It is related with : above,
the trachea and oesophagus on the middle plane, the lungs and the origin of the
cervical reservoirs on the lateral parts ; below, with the sternum, the clavicles,
and the interclavicular aponeurosis ; behind, with the heart and anterior
diaphragmatic reservoirs, beneath which it is prolonged by forming on each a
long point ; in front, with the integuments of the neck, which it raises into
a hemisphere in Palmipeds, but which is angularly depressed in other classes ; on
the sides, with the sternal ribs, the two clavicles, and the membrane uniting them.
" The prolongations which arise from the lateral parts of these reservoirs, and
cross the walls of the thorax to pass around the articulation of the shoulder, are
three in number, and may be distinguished into inferior or subpectoral, superior
or subscapular, and middle or humeral.
" The subpectoral prolongation (Fig. 337, d) issues from the thoracic reservoir
by an orifice situated behind the posterior clavicle, and passes beneath the tendon
of the great pectoral muscle, where it spreads out as a lenticular cavity. The
relations it contracts with that muscle are remarkable : in Birds, still more than
in Man and a great number of quadrupeds, the tendon of the great pectoral is
formed of two parts, one direct, the other reflected ; it is between these two
portions that this small air-sac is insinuated, and where it forms a very firm
connection with them ; the effect of which is, that at the moment the great
pectoral muscle contracts, it dilates the subjacent cell and draws into it a greater
quantity of air.
" The subscapular and humeral prolongation communicate with the principal
reservoir by a common opening placed behind the small adductor muscle of the
humerus. After leaving this orifice, the subscapular sac spreads under the
scapular and subscapular muscle, which it separates from the ribs and corresponding
intercostal muscles ; it is developed more particularly in a longitudinal direction.
" The humeral prolongation occupies the axilla ; it is smaller than the
preceding, of a pyramidal form, and opens by its summit into an infundibular
fossa, which leads to the canal of the humerus.
" The thoracic reservoir differs from aU the others by the extremely numerous
562 RESPIRATORY APPARATUS IN BIRDS.
membranous folds which partition its cavity. The membrane forming it being
continued on itself, every organ traversing the thorax becomes the cause of a fold
in which it is imprisoned ; and as the thoracic cavity is traversed by the trachea
and the oesophagus, the muscles which move the inferior larynx, and the arteries
and veins, it will be understood how this reservoir should become irregular in
consequence of these various partitions, and also why the other serial sacs situated
between the viscera and the walls of the thorax, or the simple contiguous surfaces,
should preserve their regular and proper form.
"The thoracic reservoir communicates with the lungs by an infundibular
orifice, situated on the external side of the embouchure of each bronchus. This
orifice is dilated during inspiration, by the contraction of the two first fasciculi of
the pulmonary diaphragm."
2. Cervical reservoirs (Fig. 337, 1, 1). — "They are situated above the
preceding, and the inferior part of the neck and anterior part of the lung ;
inflated after removal from the neighbouring parts, they resemble two cones,
whose rounded base looks forwards, and whose pediculated summit is directed
backwards.
" Superiorly, these reservoirs lie against the cervical muscles ; inferiorly, they
correspond to the air-sac of the thorax, from which they are separated by the
trachea, the oesophagus, the pneumogastric nerves, and the jugular veins.
Inwardly, they are in juxtaposition, and consequently form a median septum
which includes in its substance the two common carotid arteries. Outwardly,
they are related to the origin of the cervical nerves, to each of which they furnish
a small sheath, and with the vertebral artery which they surround, but do not
contain in their cavity, as well as with a subcutaneous muscle and the skin. By
their summits, they communicate with the anterior diaphragmatic bronchus ; and
by their base they send out a prolongation which conducts the aii* into all the
vertebrse of the neck and back, into all the vertebral ribs, and, finally, into the
spinal canal,
" In their cervical portion, these prolongations present themselves in the f onn
of two canals extending from the base of the cervical reservoirs to the base of the
cranium, where they terminate ; parallel and contiguous to the vertebral arteries,
like them they are lodged in the canals excavated in the substance of the transverse
processes.
" From their external part arises, at the six last cervical vertebrae, as many
diverticuli, which, lying against each other, pass from each side in the muscles of
the neck, surrounded by a common fibrous envelope, and apparently form a kind
of canal at the inferior part of this region ; when, however, this fibrous membrane
is removed, it becomes easy to isolate them, and it is then seen that they are
completely independent, and resemble small cornua. Highly developed in
Palmipeds, they are only present in a rudimentary state in the other classes.
" On the internal side of these conduits, we see, at the level of each vertebra,
one or more orifices by which the air enters their interior ; and at the niter-
vertebral foramina another orifice, which allows it to pass into the spinal canal.
From the communication established by these orifices between the respiratory
apparatus and the spinal canal, it follows that in Birds the cervical region is
traversed by three atmospherical currents— two lateral or intertransverse, parallel
to the vertebral arteries ; the third median of interspinal, parallel to the spinal cord.
"Just as the medullary tissue is replaced by air in the bones of Birds, so
might it be imagined that the sub-arachnoidean fluid was also replaced by air
THE RESPIRATORY APPARATUS IN BIRDS. 563
around their spinal cord ; and observation justifies the correctness of this
prevision. The dura mater, whose capacity is so superior to the volume of the
marrow in Mammals, exactly measures the volume of that organ in Birds ; so
that there does not exist between the fibrous and nervous surfaces any space for
an accumulation of liquid : this anatomical fact is sufficient to demonstrate the
absence of sub-arachnoidean fluid in Birds. In denying the existence of this
fluid, it ought to be added that in this class of vertebrata, as in the preceding,
the spinal prolongation is covered by a triple envelope ; that in each, between the
pia mater and dura mater, is found a thin transparent membrane, which is
lubricated by a serous fluid ; but here this fluid does not collect, it only moistens
the arachnoid membrane.
"Considered in their dorsal portion, the prolongations springing from the
cervical reservoirs offer an entirely different arrangement to that already noticed.
The interspinal current, having entered the thorax, terminates by passing into
the first dorsal vertebra ; after coursing through every part of this vertebra, it
escapes by a lateral orifice into a small sac situated between the two first ribs, at
the origin of the first dorsal nerve ; from this sac, it passes into the second
vertebra by an opening placed on its antero-lateral part, then it flows back from
this into a new air-sac developed between the second and third ribs ; and passing
in the same manner into the third vertebra to sweep through a third intercostal
sac, it arrives nearer and nearer the last dorsal vertebra. In their dorsal portion,
the prolongations emanating from the cervical reservoirs thus form two currents,
though these are constituted alternately by the vertebrse and the small air-sacs
placed on their lateral aspect. At the same time that these sacs receive the air
from the vertebras preceding them, and transmit it to those which follow, they
communicate it to all the vertebral ribs.
" In no order of Birds do the terial currents leaving the cervical reservoirs
communicate with those which circulate in the cranium. Liquids injected either
by the serial portion of the vertebral canal or the lateral prolongations of the
neck, never enter the bones of that cavity. Thinking that the injection might
perhaps penetrate if passed in the opposite direction, we have perforated the
bones of the cranium, and to the aperture have adapted the extremity of a steel
syringe filled with mercury ; but the metal did not reach the aerial prolongations
of the neck. From this double experiment, we concluded that the cranial bones
have no communication with the respiratory apparatus."
3. Anterior diapkragmatic rese^-voirs (Fig. 337, 3). — " Placed between the
two diaphragms, they correspond : in front, to the thoracic reservoirs, against
which they stand ; behind, to the posterior diaphragmatic reservoirs ; outwardly,
to the ribs and intercostal muscles ; inwardly, to the thoraco-abdominal diaphragm
and oesophagus ; below, to the most distant part of the thoracic reservoir ; above,
to the pulmonary diaphragm, which separates them from the corresponding
lung. These air-sacs communicate with the lungs by a circular opening,
which originates from the great posterior diaphragmatic bronchus ; there is
often a second opening of communication beyond the embouchure of the trunk ;
this reservoir is the only one which receives air from the lung by a double
orifice."
4. Posterior diaphragmatic reservoirs (Fig. 337, 4). — " Oval-shaped like the
preceding, and situated like them in the interval which separates the two
diaphragms, these air-sacs are in contact, by their anterior part, with the
anterior diaphragmatic reservoirs, with which they form a vertical and trans-
564
BESPIBATOEY APPARATUS IN BIRDS.
Fig. 337.
verse septum. Sometimes this septum is carried a little more forward, and
then the anterior reservoir is smaller ; this is most frequent in Palmipeds.
At other times it inclines backwards, and the anterior reservoir is larger;
this arrangement is peculiar to the
Gallinacae. And, lastly, tliis partition
divides the intercepted space between
the diaphragms into two equal
cavities : rapacious Birds offer
numerous examples of this.
" Behind, these reservoirs stand
against the abdominal sacs, from
which they are separated by the
thoraco-abdominal diaphragm ; be-
low, they respond to the sternal ribs
and the lateral parts of the sternum ;
above, to the pulmonary diaphragm ;
inwards, to the thoraco-abdominal
diaphragm ; outwards, to the verte-
bral ribs and intercostal muscles.
" A parabolic opening, situated in
the middle part of the external border
of the lung, or a little more behind,
establishes their communication with
that organ. This orifice, which is
remarkable for its great dimensions,
occupies the extremity of a volumi-
nous bronchial tube which follows
the direction of the generating trunk,
and in such a manner that this
trunk appears to pass directly to-
wards the posterior diaphragmatic
reservoir, and to open as a canal."
6. Abdomimd reservoirs {Yig. 337,
5). — "The two air-sacs situated in
the abdomen present themselves,
when inflated, as two enormous
bladders, the capacity of each differ-
ing but little from the volume of
the trunk. Situated between the
superior and lateral parietes of the
abdomen on one side, and the abdo-
minal viscera on the other, they
cannot be dilated without driving
the intestinal mass downwards and
inwards.
" Their anterior extremity, con-
tinuous with the lung, is somewhat
inflected to pass under the fibrous arch extending from the spine to the pelvis.
" Their posterior extremity, dilated and voluminous, responds to the cloaca.
Outwardly, they adhere by cellular tissue to the thoraco-abdominal diaphragm,
6ENERAL VIEW OF THE AIR-RESERVOIRS OF THE
DUCK, OPENED INFERIORLY ; ALSO THEIR RELA-
TIONS WITH THE PRINCIPAL VISCERA OF THE
TRUNK.
1, 1, Anterior extremity of the cervical reservoirs ;
2, thoracic reservoir ; 3, anterior diaphragmatic
reservoir; 4, posterior ditto; 5, abdominal reser-
voir, a. Membrane forming the anterior dia-
phragmatic reservoir ; h, membrane forming the
posterior ditto. 6, Section of the thoraco-abdomi-
nal diaphragm, d, Subpectoral prolongation of
the thoracic reservoir ; e, pericardium ; /,/, liver;
g, gizzard; h, intestines; m, heart; n, n, section
of the great pectoral muscle above its insertion
into the humerus ; o, anterior clavicle ; p, pos-
terior clavicle of the right side cut and turned
outwards.
TEE RESPIRATOBY APPARATUS IN BIRDS. 565
the parietes of the abdomen, and those of the pelvis. Inwardly, they are in
contact with the intestinal mass and the testicles or ovaries. Below and in front,
they rest on a fibrous septum, which in all birds divides the abdominal cavity
into two smaller cavities : one anterior, which represents the abdomen and
lodges the liver, the other posterior, which represents the pelvis and contains
the stomach and intestines. This fibrous septum is extremely remarkable in
large birds, particularly the Ostrich, in which it has been described by Perrault
as a transverse diaphragm ; it is inserted into the entire circumference of the
pelvic bones, and sustains the stomach as well as the intestinal tube. Below and
behind, the abdominal reservoirs lie on the intestines. Above, these sacs cover
the inferior face of the kidneys, and there furnish three prolongations : 1. A
supra-renal prolongation. 2. Two femoral prolongations.
" The supra-renal prolongation leaves the principal reservoir at the postero-
external part of the kidneys ; from thence it passes obliquely upwards and
forwards, to spread over the superior surface of the kidney, which it depresses
when the abdominal sac is inflated. Arrived at the internal border of the
kidneys, these prolongations are introduced between the transverse processes of
the sacral vertebrae, and ascend from behind forwards to the height of the two
first dorsal vertebra, forming two triangular canals situated above the sacrum,
in the sacral channels, and separated from one another by a series of correspond-
ing spinous processes. The supra-renal prolongations are not present in all
birds ; they are particularly observed in the Gallinacas and diurnal rapacious
birds. In some Palmipeds— the Swan, for example — they are equally developed ;
in the Ostrich, they are replaced by the supra-spinal canals.
" The femoral prolongations' are two in number — an anterior small and a
posterior large ; they arise from the abdominal reservoir at the cotyloid cavities,
and leave the pelvis in traversing the bony opening through which the crural
vessels pass ; after clearing the limits of these cavities, they spread around the
coxo-femoral articulation, and terminate in a caecum in the majority of birds.
In diurnal birds of prey, they communicate with the femoral canal by an orifice
situated at the anterior part of the great trochanter.- These prolongations, very
developed in the Ostrich, also open in it into the femoral cavity ; it is not
without surprise that we see this arrangement, which is peculiar to birds remark-
able for their rapidity and power of flight, also present in those to which asrial
locomotion has been entirely denied. The abdominal reservoirs communicate
with the lung by an orifice situated beneath the fibrous arch of the diaphragm,
and disposed like the rose of a watering-can."
Communication of the Reservoirs with the Bones. — " The communi-
cations of the respiratory apparatus with the skeleton in birds are extremely
numerous. We will successively examine those belonging to each reservoir.
" The bones which receive air from the thoracic reservoir are : 1. The
anterior clavicle, which is perforated at its two extremities. 2. The posterior
clavicles, which are also perforated a little below their scapular extremity. 3.
The sternum which presents two series of openings — the middle ones that con-
duct the air into the sternal ridge, and the lateral ones, very small, six to eight
in number, corresponding to the intercostal spaces. 4. The scapulEe, which offer
one or more apertures at their anterior extremity, and receive the air for the
subscapular prolongation. 5. The humerus, which obtains the air for the
humeral prolongation by a fossa situated at the inferior and internal part of its
articular head. 6. The sternal ribs, which allow the atmosphere to penetrate
566 RESPIRATORY APPARATUS IN BIRDS
by small openings at their inferior extremities. To smn up, eight bones, without
reckoning the sternal ribs, whose number varies, receive the air which tills them
from the thoracic reservoir.
"The cervical reservoirs conduct the air. 1. To all the cervical vertebrae.
2. To all the dorsal vertebras. 3. To all the vertebral ribs. The vertebrae of
the neck are crated in their anterior part by the currents which accompany the
vertebral artery, and in their posterior part by the interspinal current. The
first obtain entrance to the anterior segment by one or more orifices made in
the inner wall of the intertransverse canals ; the median current penetrates the
posterior segment by two orifices, a right and left, situated on the inner and
medullary wall of that segment. The first vertebra of the back is provided
with air in the same manner, by the middle and lateral currents of the neck.
This air, after passing through the first vertebra, leaves by its lateral parts to
enter a small sac ; from this it goes into the superior part of the second
vertebra, escapes from this by its lower portion, to be received into a lateral sac,
and so on to the last dorsal vertebra. These sacs also supply the vertebral ribs
with air, which enters them by very small apertures situated at their spinal
extremity.
" The diaphragmatic reservoirs have no bony communications. The abdo-
minal reservoirs supply : 1. The sacrum. 2. The coccygeal vertebrae. 3. The
iliac bones. 4. The femurs. The air traversing the sacrum, coccyx, and ileum,
comes directly from the supra-renal prolongations, and that filling the femoral
cavity from the femoral prolongations. In this enumeration of the communi-
cations between the skeleton and the respiratory apparatus, we have taken as
a type the most aerated skeleton : that of diurnal birds of prey, like the eagle,
kite, hawk, etc. ; the bones which communicate with the air-sacs are not so
numerous in the other classes. In this respect, they may be ranged in three
categories : 1. Those which are serif erous in all classes. 2. Those in certain
classes only. 3. And those which are not so in any class. The bones always
aerated are the cervical and dorsal vertebrae, the sternum, and we may add the
humerus, though it is not s6 in the Ostrich. Those crated in some classes only
are : the furculum, clavicles, scapulae, vertebral and sternal ribs, the sacrum,
coccyx, and femurs. And the bones which are never aerated are those of the
forearm and hand, the leg and foot."
Structure of the Reservoirs. — The walls of these cavities are essen-
tially formed by a thin cellulo-serous membrane, strengthened in some places
by an external envelope of elastic fibrous tissue. Long, thin blood-vessels are
distributed to the substance of these walls ; they do not belong to the pul-
monary, but to the general circulation, the arteries being derived from the
aorta, and the veins opening directly or indirectly into the venae cava. No
lymphatics have been found in the air-sacs.
Mechanism of Respiration in Birds. — The anatomical arrangement
described above differs in so many respects from that existing in Mammals, that
it ought to bring about important modifications in the mechanism of respiration.
It does not come within our scope to write the history of these modifications ;
but we cannot dispense with indicating, in a summary way, their principal
characters, in order to make known in a general manner the signification of the
special organization this apparatus oifers in birds.
We remark, in the first place, that the slight mobility of the vertebral ribs,
and the adhesion of the lung to their inner face, only allows of a very slight
THE RESPIRATORY APPARATUS IN BIRDS. 567
dilatation of that viscus during inspiration. And the entrance of air into the
pulmonary tissue is not due to this dilatation ; it is due to the dilatation of the
diaphragmatic reservoirs ; the position of these effectively admits of their expan-
sion, by the play of the inferior on the superior ribs. The air is then drawn
into their cavity after traversing the larger bronchial tubes which open into
them, and also after passing across a certain region of the capillary network
formed by the canaliculi, where it comes into mediate contact with the blood,
and is submitted to the necessary transformations. The atmosphere, therefore,
arrives in the diaphragmatic sacs partly pure and partly altered by its contact
with the blood. During expiration, it again resumes the course it followed on
its introduction, traverses a second time the lung, and is thus respired once
more before being expelled from the body. It is, therefore, obvious that the
hasmatosic transformations accomplished in the lung take place during the two
acts of respiration — inspiration and expiration.
In studying the part that the other reservoirs play m this function,
Sappey has been able to prove that they act as antagonists to the first, by
contracting during inspiration and expanding in expiration. No doubt, at the
time of the contraction of the middle reservoirs, a small quantity of the air they
contain is driven back into the anterior and posterior sacs in passing across the
lung ; and without doubt, also, these latter give a part of their contents to the
diaphragmatic sacs at the moment of the expansion which draws the air into
these reservoirs. Sappey has also noted that these contents are always
formed of entirely vitiated air, while the air of the middle reservoirs has only
been partially respired.
It is necessary to add that the functions of the air-sacs do not cease here ;
for it has been demonstrated that they exercise a very marked influence : 1. On
locomotion, by diminishing the weight of the body, and, by their position,
rendering equiUbrium more stable. 2. On the voice, thfi range and power of
which they augment.
BOOK IV.
THE URINARY APPARATUS.
This apparatus, though simple, yet plays a very important part in the animal
economy, as it is charged with the duty of eliminating from the blood — along
with the superfluous water and other accessory substances — the excrementitial
nitrogenous products resulting from the exercise of the vital functions. These
products we find in the urine —the liquid secreted by the kidneys, and which
is carried by the iireters into a special reservoir— the bladder — where it accumulates,
and whence it is expelled from the body by the urethral canal, at periods more or
less distant, according to the requirements of the animal.
The kidneys, the essential organs of urinary depuration, will be first studied ;
then the excretory apparatus ; and, finally, a brief notice will be given of the
supra-renal c«jt?sM/es— small bodies annexed to the kidneys, the function of which
is not yet determined.
Preparation. — Place the animal in the first position, and remove one of the posterior limbs.
Take out the intestines, adopting the precautions indicated at page 455. Saw througli the
pelvic symphysis, as well as the neck of the ilium on the side opposite the remaining abdominal
limb, removing the coxal portion between these sections. The pelvic cavity being now
opened, the urinary apparatus is exposed, and to complete the preparation it is necessary to :
1. Remove the peritoneum, to show that the urinary apparatus is situated external to that
membrane. 2. Free the ureters and kidneys from the cellulo-adipose tissue surrounding them,
but retaining the vessels of the latter, and leaving undisturbed their relations with the pan-
creas and supra- renal capsules. 3. Inflate the bladder, and dissect its neck, taking care to
preserve the orbicular peritoneal fold which envelops its anterior cul-de-sac (or fundus).
In the male, the inflation of the bladder is very simple, and requires no directions. In the
female, however, it is requisite first to close the meatus urinarius, which is accomplished by
drawing its two lips towards the entrance to the vulva, by means of two chain-hooks, passing
two pins through their mucous membrane, and tying a ligature behind these ; the bladder is
then inflated by the ureter.
Independently of this dissection in situ, it is advisable to examine the urinary apparatus
when isolated, and laid arranged upon a table, as in Fig. 338. We can then study : 1. By
dissection, the structure of the kidneys and arrangement of the pelvis reualis. 2. The mode of
termination of th« ureters. 3. The interior of the bladder.
1. The Kidneys (Figs. 258, 338).
Situation. — These are two glandular organs situated in the abdominal cavity,
to the right and left of the sublumbar region, lying against the great psoas
muscles, and maintained in that position : 1. By an envelope of cellulo-adipose
tissue. 2. By the peritoneum, which passes beneath them. 3. By the pressure
of the digestive organs contained in the abdominal cavity.
Their situation is not absolutely alike, for the right comes forward to beneath
the two last ribs, while the left scarcely reaches beyond the eighteenth rib. The
latter is, therefore, more posterior than the former.
External conformation. — Studied externally, the kidneys present a special
THE URINARY APPARATUS.
569
form, which often serves as a term of comparison, and resembles more or less
that of a haricot bean, or the heart on a playing-card. The latter configuration
Fig. 338.
STTPERIOR AND GENERAL VIEW OF THK (il:;MTO-URIXARY APPARATUS IN THE MALE, WITH THE
ARTERIES.
A, Left kidney ; B, right kidney ; a, b, ureters ; C, C, supra-renal capsules ; D, bladder ; e, e, tes-
ticles; e, head of the epididymus ; e', tail of the epididymus ; F, deferent canal ; G, pelvic dilata-
tion of the deferent canal ; H, left vesicula seminales (the right has been removed, along with the
deferent canal of the same side, to show the insertion of the ureters into the bladder) ; i, prostate ;
J, Cowper's glands; K, membranous, or intra-pelvic portion of the urethral canal; L, its bulbous
portion ; M, cavernous body of the penis ; m, m, its roots ; N, head of the penis. 1, Abdominal
aorta; 2, 2, arteries (renal) giving off the principal capsular artery; 3, spermatic artery; 4,
common origin of the umbilical and arteries of the bulb ; 5, umbilical artery ; 6, its vesical branch ;
7, internal artery of the bulb; 8, its vesico-prostatic branch.
570 UBINABY APPARATUS.
is most frequently noticed in the right kidney, the left being generally like the
first.
Flattened on both sides, the kidneys show two perfectly smooth faces, the
inferior of which always exhibits a variable nmnber of fm-rows that lodge the
arteries ; the right kidney has always a special furrow for the ureter. Each
kidney has a circumference divisible into three borders, only the internal of
which offers a certain interest. This is deeply notched, to form the Jissure or
hilus of the kidney, which lodges the vessels and nerves of the organ, as well as
the origin of the ureter.
Weight. — The kidneys vary much in weight in individuals. The right is
always more voluminous and heavy than the left, its average weight being
27 ounces, while that of the last is 25 ounces.
Relations. — The relations of these two glands with the neighbouring parts
ought to be particularly examined. The right kidney is related, by its upper
face, to the great psoas muscle, the muscular portion of the diaphragm, and to
the last, or even the second-last rib. Its inferior face, incompletely covered by
peritoneum, adheres, for the greater part of its extent, either to the pancreas and
supra-renal capsule, or to the base of the caecum, by means of a loose and
abundant connective tissue. The internal border is in contact with the posterior
vena cava and the small psoas muscle ; the anterior, with the base of the right
lobe of the liver and the lobule of Spigel {lohus caudatus), through the medium
of the peritoneum ; the posterior border is enveloped in peritoneum. The left
kidney has, by its superior face, the same connections as the right, except in its
relation with the second last rib. Its inferior face is almost entirely covered by
peritoneum, and is related, in front and inwardly, to the supra-renal capsule.
The internal border is margined by the aorta ; the anterior touches the base of
the spleen and the left extremity of the pancreas ; the posterior is, like the
inferior face, in contact with the serous membrane of the abdominal cavity.
Internal conformation. — If a horizontal section is made of the kidney, it will be
found to possess a cavity called the rejial basin (or pelvis), into which the urine
secreted by the gland flows, and at which the ureter commences. Placed in the
middle of the kidney, near the hilus, the pelvis is elongated before and behind,
and depressed from above to below. Within it is remarked a wide infundibulum —
the origin of the ureter (the sinus renalis). Opposite to this funnel-shaped space
is a very prominent crest (;renal crest) that runs along the whole length of the
external side of the pelvis, and on which are noticed the orifices of the urinif erous
tubes ; these, by pressing the tissue of the kidney with the fingers, can be made
to pour out the urine accumulated in them. The renal cavity forms some very
small diverticuli opposite the infundibulum, the largest of which — situated before
and behind the latter — are named the arms of the pelvis.
This cavity is lined by a transversely plicated mucous membrane, continuous
with that of the ureter, and is covered with the epithelium of the uriniferous
tubes which open on the border of the crest. At these folds, the mucous mem-
brane contains small racemose glands lined by two layers of cells (Paladiuo and
Egli).
Structure. — The kidneys present for study in their structure : 1. An
enveloping tunic. 2. Than 2Jroper tissue. 3. Vessels and nerves.
1. Enveloping Tunic. — This is a fibrous membrane, intimately united to
the proper substance of the kidney, into which it sends a multitude of prolonga-
tions, and is folded around the blood-vessels in such a manner as to form sheaths,
THE VBINARY APPARATUS.
571
which enter with them into the organ. (Some authors— among them Leyh—
describe, in addition to this capsula propria, a thin layer formed by the condensed
areolar matrix of the kidney, from which it can be easily torn.)
Proper Tissue. — The glandular tissue of the kidneys {areola parmchijma, or
matrix) has, "externally, a reddish-brown colour, more or less deep in different
individuals. It is dense and friable, and easily torn when deprived of its fibrous
capsule. Its substance is not everywhere homogeneous : very dark-coloured
externally, where it forms the cortical layer, it becomes whiter around the pelvis,
where it constitutes the medullary layer ; where the latter comes in contact with
the former, and sometimes even near the pelvis, it assumes a tint like that of
wine.
These two portions are not well defined, but penetrate each other reciprocally,
so as to compose, at their point of junction, irregular festoons, very readily per-
ceived in a horizontal section of the kidney (Fig. 339).
The cortical is also distinguished from the medullary substance by its granular
Fig. 339.
HORIZONTAL LOXGITUDINAL SECTIOX OF THE HORSE'S KIDNEY.
a. Cortical (or vascular) portion ; b, medullary (or tubular) portion ; c, peripheral portion of the
latter ; d, interior of the pelvis ; d', d', arms of the pelvis ; e, border of the crest ; /, infundi-
bulum : a, ureter.
aspect, and the presence of minute, reddish spheres, readily visible to the naked
eye, and named Malpighian corpuscles ; while the medullary substance appears to
be composed of radiating fibres.
In the Horse, the tissue of the kidney cannot be divided into lobules or
pyramids ; to the naked eye it appears to be composed of fibres that start from
every part of its exterior, and converge towards the crest of the pelvis. A micro-
scopical examination demonstrates these fibres to be canals or tubes ; hence they
are designated tuhuU uriniferi, or Bellini's tubes. A delicate connective tissue — a
kind of stroma, which is very rare in the cortical, but more abundant in the
medullary substance, especially in the vicinity of the pelvis — sustains the vessels
and nerves, and unites the tubuh uriniferi to each other.
The tuhuli uriniferi are constituted by a proper amorphous membrane, very
572
URIXARY APPARATUS.
thin and elastic, the internal face of which is lined by simple epithelium that
readily alters -, the cells are polygonal in certain points, polyhedral in others, and
transparent or granular.
The uriniferous tube has not everywhere the same direction or diameter.
Taking it at its termination on the crest of the pelvis, and following it to its
origin in the Malpighian body, it is found that the tubule is at firet single,
straight, and voluminous, but that during its com'se across the medullary sub-
stance it divides into three or four tubes, which, in their turn, subdivide in a
dichotomous manner. These divisions are less voluminous and straight (col-
lected in bimdles, they are the pi/ramids of Ferrein), but their diameter is
uniform until they reach the cortical substance ; here they bifurcate, each branch
becomes flexuous, and is designated the uniting or junctional tube, and is con-
tinued in a kind of elongated U shape — the looped or ansiform tube of HenU —
which descends towards the centre of the kidney. The ascending branch of this
ansiform tube — the diameter of which is very small — suddenly dilates on entering
the cortical substance, describes several bends, contracts into a narrow neck, and
SECTION OF THE CORTICAL SL'lSSTASCt; OF THE KIDNEY.
, A, Tubuli uriniferi divided transversely, showing the spheroidal epithelium in their interior}
B, Malpighian capsule ; a, its afferent branch of the renal artery ; 5, its glomerulus of capillaries ,
c, c, secreting plexus formed by its efferent vessels , d, d, fibrous stroma.
then opens into a Malpighian body, after having taken the name of convoluted
tube.
The corpora Mcdpighicma (or capsides) are minute vesicles, the walls of which
possess the same structure as the uriniferous tubes ; each lodges a cluster of
arterial capillaries or renal glomerulus, and has two opposite openings : one com-
municating between the corpora and convoluted tubes, the other affording a
passage to the afferent and efferent vessels, which serve to irrigate a tuft of
capillaries forming the glomerulus of Malpighi. Between the membrane proper
and the glomerulus are two layers of epithelium — an external continuous with
that of the uriniferous tube, and an internal applied directly to the glomerulus
and forming a kind of hood over it (lining Bowman's capsuJe).
3. Vessels and Nerves. — a. The kidney possesses a special artery and vein,
remarkable for their enormous volume.
a. The artery (the renal) forms several branches that reach the kidney by its
inner border and inferior face, and divide into a certain number of principal
vessels, which are disposed in a wavy manner on the limits of the cortical and
medullary substances. From them are given off branches to each of these
THE URINARY APPARATUS.
573
snbstances, and among those distributed to the cortical are some regularly
disposed, which furnish, on each side, the glomerule ramifications ; these are the
afferent vessels, or Mcdpighian glonwi/les (or ti^fts) ; the others form a polyhedral
plexus around the convoluted tubes and corpora Malpighiana. The afferent vessels
of the renal glomerules enter this plexus.
The arterial branches of the medullary substance descend between and
parallel with the straight tubes (to form the arteriolar rectce), and anastomose by
transverse branches, so as to form a network with elongated meshes (around and
between the tubuli).
The (renal vein) issues from the kidney by the hilus, and succeeds the arterial
Fig. 341.
Fig. 342.
DISTRIBUTION OF THE RENAL VESSELS IN THE
horse's KIDNEY.
a, Branch of reaal artery; a/, afferent vessel;
m, m, malpighian tufts; ef, cf, efferent
vessels
tubes ;
vascular plexus surrounding the
st, straight tube ; ct, convoluted tube.
DIAGRAM OF THE COURSE OF THE URINI-
FEROUS TUBULE.
a, Orifice of tubule at pelvic crest ; 5, re-
current bj'anches which form loops, c, in
the medullary portion of the kidney, and
terminate in the Malpighian capsules in
the cortical portion.
capillaries. In the medullary substance,
there are straight veins as there are straight
arteries. On the surface of the organ,
beneath the fibrous envelope, are the stellate
veins of Verheyen — the junction of five or
six venules which converge towards a
central vein. The venules of the two
portions collect into more voluminous
vessels, which form complete arches at
their limits ; it is to the presence of
these vascular canals that the dark colour observed at this point of the renal
tissue must be attributed.
h. The lymphatics are abundant in tlie mass, but rare at the superficies of
the organ ; they form plexuses, the ultimate branches of which pass to the
sublumbar glands.
c. The nerves emanate from the solar plexus, and form a particular network
around the arteries, exhibiting, on their course, some microscopic ganglia. It is
not known how they terminate.
DevelopmenTo — The kidneys appear very early in the foetus, above and a
URINARY APPARATUS.
little behind the Wolffian bodies. They are then very distinctly lobiilated, but
the lobes gradually become fused, and have entirely disappeared at birth ; the
small irregularities on the surface are the only indications of their ever having
existed in Solipeds.
Functions. — The kidneys are the organs which secrete the urine ; but this
secretion does not take place to the same extent in all parts of their tissue. The
abundance of vessels in the cortical
Fig. 343.
TRANSVERSE SECTION OF THE KIDNEY.
1, Inferior border ; 2, cortical tissue ; 3, section of
blood-vessels; 4, pelvis; 5, ureter; 6, superior
border ; 7, renal artery ; 8, proper capsule.
of
substance, the presence of the Mal-
pighian corpuscles, and the flexuosi-
ties described by the uriniferous
tubes, sufficiently indicate that this
substance should be the principal, if
not the exclusive, seat of the secre-
tory function. But in what manner
does this secretion take place ? At
present it is generally agreed that
the urinary secretion is simply an
infiltration of the elements of the
urine contained in the blood, through
the walls of the vessels of the glome-
rulus. The difference existing be-
tween the diameter of the afferent
and efferent vessels of the Malpighian
glomerules — a fact the importance
of which was pointed out by Ludwig
the urine through the tissue of the
— sufficiently explains this filtration
kidneys.
The nutritive principles of the serum which leave the blood at the same time
as those of the urine, are taken up by the epithelium of the uriniferous tubes.
2. The Ueeteks (Fig. 338).
Form. — The ureter is a membranous canal, the diameter of a thick goose-
quill, which conveys the urine from the pelvis of the kidney into the bladder.
Its origin, course, termination, and structure, will be successively considered.
Orif/in. — It has been already shown that the origin of the ureter is at tKe
infundibulum of the pelvis of the kidney ; it leaves that organ by the internal
fissure or hilus, curves outwards, passes along its lower face, and is inflected
backwards in quitting the organ.
Direction. — The course it follows is almost in a straight line towards the pelvic
cavity, along with the posterior aorta or posterior vena cava, according to the side
to which it belongs ; it is in contact with the psoas parvus, and proceeds above the
peritoneum. After passing beyond the terminal branches of the posterior aorta,
which it crosses very obliquely, it becomes enveloped in a short peritoneal fold that
maintains it against the lateral wall of the pelvis ; it afterwards emerges from
this fold, and reaches the posterior and superior part of the bladder.
Termination. — Having reached that viscus, its termination takes place as
follows : instead of opening directly into the bladder by traversing at once, and
perpendicularly, the two membranes composing the organ, the ureter at first
pierces the muscular coat, between which and the mucous membrane it passes for
about an inch, and then opens on the surface of the latter. This arrangement
TEE URINARY APPARATUS. 575
prevents the "flowing back of the urine into the nreter during its expulsion, the
intermembranous portion of that canal being strongly compressed by the external
pressure then exerted by the muscular coat, and by the internal resistance which
the accumulation of urine in the bladder opposes to this pressure. So well are
Nature's intentions fuhilled in this respect, that we may inflate the bladder by
the ureter, after tying the canal of the urethra, and press vigorously on the dis-
tended organ, without being able to make a single bubble of air pass through the
perfectly pervious canal.
Steuctuee. — The excretory canal of the kidney is composed of three tunics :
1. An internal mucous tunic, continuous, in front, with that lining the pelvis
of the kidney, and behind, with that of the bladder. It is very tliin, pale,
plicated longitudinally, and has a stratified tesselated epithelium. (It has some
mucous follicles, but no villi.)
2. A middle inuscular layer arranged in two orders — a superficial, the fibres
of which are circular, and a deep set, passing in a longitudinal direction. (Leyh
and other authorities describe the arrangement of the muscular planes — which are
composed of smooth fibres — to be the reverse of this, the longitudinal being super-
ficial, and the deep circular.)
3. An external tunic, composed of connective tissue and elastic fibres.
The muscular tissue of the ureter, by contracting, accelerates the flow of the
urine.
3. The Bladdee (Fig. 338).
Position. — This is a membranous reservoir, lodged in the pelvic cavity, where
it occupies more or less space, according to the quantity of urine it contains ; it
may extend beyond the pubis, into the abdominal cavity.
Form. — Considered in a moderate state of plentitude, the bladder is ovoid in
figure ; its large extremity, being turned forward, forms a rounded cul-de-sac
{fundus), at the bottom of which is remarked a kind of cicatrice, caused by the
obliteration of the urachus. The other extremity terminates, posteriorly, by a
well-marked constriction — the neck (or cervix) of the bladder — which gives rise
to the urethral canal.
Weight. — The average weight of the empty bladder is about sixteen ounces.
Relations and mode of attachment. — The bladder is related : above, to the
vesiculae seminales, to the pelvic dilatations of the vasa deferentia, as well as to
the rectum ; below, to the inferior wall of the pelvis, on which it rests (by its
base) ; on the sides, to the lateral walls of that cavity. In the female, the upper
face of the bladder is in relation with the uterus and vagina, which entirely
separate it from the rectum. The posterior extremity or neck (cervix), flanked on
each side by the lobes of the prostate, is fixed below to the ischio-pubic symphysis,
by means of a particular ligament or fasciculus of elastic and contractile fibres,
which are detached from the muscular layer, and expanded over the lower face of
Wilson's muscle, to be carried backwards and downwards, and terminate on the
surface of the internal obturator muscle. The anterior extremity — or fundus —
is usually related to the pelvic flexure of the large colon.
This extremity is covered by a serous cap, which is prolonged backwards on
its body, further above than below. This covering is continuous with the
parietal layer of peritoneum, and adheres closely to the muscular tunic -of the
bladder, so that it constitutes its chief attachment ; its arrangement is precisely
similar, in principle, to that of the other serous visceral membranes.
576 V BINARY APPARATUS.
Thus the peritoneum, after covering the walls of the pelvis, is re/lected on the
organs contained in that cavity, and in particular on the bladder, around which
it forms an orbicular fold. This again gives rise to three secondary folds — a kind
of serous layers — which are usually termed the ligaments of the bladder. One of
these layers is single and vertical {broad ligament), and is fixed to the inferior
part of tlie fundus ; it is not rare to see it prolonged forward on the lower wall of
the abdomen, as far as the umbilicus ; on its free border it is said to have a thin
hem or cord — the last vestige of the urachus. If this cord exists — which appears
doubtful to us — it cannot possess the signification given to it ; for the urachus has
not. like the umbilical arteries, an abdominal portion ; it only commences at the
umbilicus to be prolonged in the cord to the allantois. The other two serous
layers {umbilical ligaments) — ^pairs and horizontal — are attached to the sides of the
fundus, and present, on their free border, a thick cord, the obliterated umbilical
artery.
(These are the so-called /a/se ligaments. There are true ligaments, formed by
processes of the pelvic fascia, which, in the male, are : the inferior, attaching the
prostate gland to the bladder ; the lateral, attached to the sides ; and a recto-
vesical, between the bladder and rectum. In the female, there are the vesico-
uterine and recto-uterine ligaments.)
Owing to this disposition of the peritoneum, tne bladder is divided into two
perfectly distinct regions : an anterior, enveloped by a serous layer ; the other,
posterior, is brought in contact with the surrounding organs through the medium
of the loose and abundant connective tissue of the pelvic region. This tissue —
constantly mixed with adipose masses around the neck of the bladder — submits,
with the serous membrane of the anterior region, to the changes in form and
continual displacements of the urinary sac.
Interior. — This pouch, studied internally, exhibits folds and ridges more or
less marked, according to its state of plenitude. It also shows, posteriorly, the
opening of the neck, which communicates with the urethral canal, and a little
higher, the orifices of the ureters. These three apertures circumscribe a smooth
triangular space — the trigone {trigonum vesicce).
Structuee. — The structure of the bladder is very simple. Two membranes
compose its walls, the internal of which is mucous, and the external muscular.
Anteriorly, the latter is covered by the peritoneum described above.
The mucous membrane is pale and thin, and is continuous with that lining
the ureters and the urethra. It shows some papilli« and some simple tubular
glands towards the neck. Its epithelium is stratified and tesselated, the super-
ficial cells being very irregular.
The musndar layer is composed of white fibres, the arrangement of which is
very complicated. Certain authorities describe three superposed planes, the fibres
of which pass in different directions. In the Horse, in which the walls of the
bladder are very thin, these planes are difficult to demonstrate. The fibres are
longitudinal, circular, oblique, spiral, and even twisted towards the fundus of the
bladder ; the deep fibres are reticulated. In the posterior region they do not
form a sphincter around the neck of the organ, as is generally beHeved : the real
sphincter is Wilson's muscle, which encircles the membranous portion of the
urethral canal.
{k' submucous layer, composed of vascularized connective tissue, has been
described ; it loosely connects the mucous and muscular layers.)
Vessels and nerves. — The parietes of the bladder receive their blood from
TEE URINARY APPARATUS.
577
several sources. The principal arteries come from the vesico-prostatic branch of
the internal pudic ; the umbilical artery also furnishes ramifications that reach
the fundus of the organ. The lymphatics pass to the sublumbar glands. The
nerves are furnished by the pelvic or hypogastric plexus, and the inferior branches
of the two last sacral pairs ; their twigs are spread more especially between the
muscular and mucous layers.
Development. — The study of the development of the bladder is very interest-
THE KIDNEYS AND BLADDER IN THE FCETUS OF SOLIPEDS.
A, Supra-renal capsules ; B, kidney ; b, ureter ; <;, bladder ; D, urachus. 1, abdominal aorta ; 2,
external iliac artery ; 3, umbilical artery ; 4, umbilical vein.
ing. It is narrower and more elongated in the foetus than the adult, and is
relatively more capacious during the whole period of intra-uterine life. It then
occupies the abdominal cavity as far as the umbilical opening, and is flanked by
the two umbilical arteries. Its posterior extremity alone enters the pelvis ; the
anterior extremity, forming a real neck, is continuous with the urachus, just as
578 URINARY APPARATUS.
the neck, properly so called, is continuous with the urethra (Fig. 344). At birth,
this anterior neck separates from the urachus, and is transformed into a free cul-
de-sac ; while the bladder is gradually withdrawn into the pelvic cavity, carrying
with it the umbilical arteries, and finishes by acquiring the position it definitively
occupies in the adult.
Functions. — The part played by the bladder is of incontestible utility. In
permitting the accumulation of the urine and the intermittent expulsion of that
excrementitial fluid, it spares animals the disagreeable condition in wliich they
would be placed if the hquid secreted by the kidneys was continually being dis-
charged as produced.
4. Urethra.
The description of this organ will be given with that of the genital organs,
as in the male it is common to the urinary and generative apparatus ; even in the
female it is intimately connected with the latter.
5. The Supra-renal Capsules (Fig. 338, 344).
Situation — Form. — The supra-renal capsules (or adrenals) are two small bodies
applied to the lower face of the kidneys, in front of the hilus, and close to their
inner border.
They are elongated from before to behind, flattened above and below, and
irregularly lobulated on their surface. Their length is from 2 to 23 inches, and
width from li to H inches. They have not the same volume, the right being
larger than the left.
delations. — A large amount of connective tissue, vessels, and nerve-filaments
attach these bodies to the neighbouring organs. The right is related, in front,
to the liver ; above, to the right kidney ; and inwardly, to the posterior vena cava
and the ramifications of the solar plexus. The left does not touch the liver or
spleen, but, by its inner border, is applied against the posterior aorta and great
mesenteric artery.
Structure. — At present, anatomists are not agreed as to the structure of the
supra-renal capsules. The following is what is probably most reliable in this
difficult point in normal histology.
These organs offer an enveloping membrane and parenchyma.
The enveloping membrane is fibrous, and sends off, from its inner face, prolon-«
gations which pass into the parenchyma and form cylindrical spaces, subdivided
by transverse bands. These spaces are named glandular cavities ; but the septa
soon become thin, and disappear almost completely, leaving nothing but some
very few trabeculse of connective tissue.
The parenchyma is divisible into two layers — the cortical and the medullary
substance. The first is of a dark-brown colour ; the second is yellow and soft,
and does not show any cavity in its centre ; that which has been described is the
result of the destruction of its proper elements, which soon change after death.
The glandular cavities of the cortical substance are filled with nucleated,
granular, and often fat cells, in the adult animal ; near the central substance
these cavities only contain a single cell.
The medullary substance has, for its basis, a very dehcate reticulum, support-
ing stellate cells analogous to those of nerve-tissue.
and nerves. — Like the kidneys, which are contiguous, the supra-renal
THE URINARY APPARATUS. 579
capsules receive a large quantity of blood, compared with their small volume.
The arteries are branches of the neighbouring vessels — the mesenteric and renal.
They form a very delicate plexus in the parenchyma. (They keep to the stroma
of the trabeculae ; consequently, their finest ramifications are found in the secou-
daiy septa of the cortical substance, where they form elongated plexuses, which are
rounder in the medullary portion. In the middle of the latter, the venous
ramuscules unite, and give rise to a considerable trunk — the vena supra-renalis — on
which the organ is placed as on a pedicle. It is this vein wliich constitutes the
debated cavity.)
The veins are satellites of the arteries in the tissue of the organ, and pass into
the renal vein or posterior vena cava. The lymphatics are scarce.
The supra-renal bodies receive many ganglionic nerves derived from the solar
plexus, but their mode of termination is unknown. (As mentioned by Chauveau,
the nerves of these organs are extremely numerous, they being more abundantly
supplied than any other structure of the kind in the body ; a large number of
small branches enter the cortical portion, to become developed in the medullary
tissue. As these nerves do not leave the medullary substance, and as, besides, its
cellular elements appear to be of the same nature as the multipolar ganghonic
cells, it is presumed that the nerve-fibres emerge from these globules, and that
the medulla acts as a ganglionic nerve centre. Though Leydig fully believed
the internal portion to be of a nei-vous character, he thought another function
might be attributed to the cortical, in consequence of its being most frequently
of a fatty nature. Bergmann was the first, in 1839, to class these organs with
the nervous system, and Remak, in 1847, by his researches in embryology, was led
to group them with the sympathetic ganglia, and named them nerve-glands.
Injm-y to the dorsal portion of the spinal cord, causes congestion and hypertrophy
of the supra-renal capsules. In a watery solution of the cortical portion, a rose-
tinted substance has been discovered, which changes to green with persalts
of iron.)
Development. — These bodies are relatively larger in the foetus than the adult,
though this difference does not influence their structure.
(Functions. — Their uses are still unknown ; they are ranked in the category
of blood-vascular glands, along with the spleen and thyroid body, the functions
of which are also not yet ascertained. Leydig is of opinion that these bodies
should be regarded as belonging to the nervous system ; but it is probable that
they are concerned in the processes connected with pigmentation.)
Differential Characters in the Urinary Apparatus of the other Animals.
1. Kidneys. — In the other domesticated Mammals, the renal glands are simple or multiple,
or, in other words, simple or lobulated. In the Ox, the kidneys liave an elongated shape
from before to beliind, which is altogether characteristic; and, in addition, they preserve
during life the lobulated form only seen in the other animals during intia-uterine existence.
Each agglomeration is composed of from fifteen to twenty secondary kidneys ; but the pelvis
is not formed in the centre of this agglomeration, being carried altogether outwards, and
occupying an excavation in the interior face of the organ, which represents the hilus. This
cavity is divided into as many short, wide prolongations — the calices — as there are principal
lobules ; the uriniferous tubes from each lobule open on a small papilla, which projects into
the bottom of the calyx. This papilla is, therefore, nothing more than the crest of the simple
pelvis in tlie kidney of Solipeds (Fig. 347).
In the Sheep and Camel, the kidneys are not lobulated, and the pelvis is carried to the
inner border, as in the Horse. In these animals, as well as in the Dog and Cat, there is an
arrangement which establishes a kind of transition between the pelvis of the Ox and that of
580
URINARY APPARATUS.
Solipeds. In them, this cavity is very large, and at the base of the crest shows deep diverticuli
that iMmity in the substance of the kidnev.
The kidneys of the Pig are simple externally, and voluminous; the hilus gives access to
a cavity in which are a number of papillae collected in twos or threes, and covered by calices.
The calices and the ureter have tiie same arrangement as in the Ox. (There are 10 or 12
papillse, and as many calices.)
2. Bladder.— The most important difference in the bladder of the domesticated animals,
consists in the extent of development of its peritoneal envelope. In nonsoliped animals this
covers all the organ to the neck ; the ligaments are also very short, and the viscus may be
easily projected into the abdominal cavity. The bladder is thin, and of considerable capacity
in Ruminants and the Pig ; in tJie Dog, on the contrary, it has a very thick muscular
layer, its fibres forming distinct fasciculi, especially when in a state of retraction. (In
Ruminants, the orifices of the ureters are near each other; at the fundus the mucous
membrane shows a small fossa, which is continued by a narrow canal that terminates in a
Fig. 345.
Fig. 346.
Fig. 347.
KIDNEYS OF THE OX.
Fig. 345. — Right kidney, viewed on its upper and external face. Fig. 346. — Left kidney, from its
internal and inferior face: a, Pelvis; b, b, b, branches of the pelvis terminating in calices; c,
ureter; (i, renal artery. Fig. 347. — The calices in the left kidney. The contents of the hilus,
including the branches of the pelvis, have been removed to show the tubercles at the bottom of
these calices. Only seven are visible, the others being beneath the borders of the renal fissure.
cnl-de-sac, and constitutes a free appendix about half an inch long, and of the thickness of a
goose-quill).
3. Supra-renal capsules. — These small organs are discoid in the Sheep and Pig, reniform
in the Dog. In the Ox, they are situated at a certain distance in front of the kidneys, and
their shape is like that of these bodies in the Horse ; though they are a little constricte i in
the middle, and slightly curved.
In Birds, the kidneys " are lodged at the same height, behind the peritoneum, imme-
diately pdsterior to the lungs, and in the lumbar and pelvic regions, where they occupy several
fossae excavated in the upper face of the pelvis. Their form is irregular and more or less
elongated, depending upon the hemes and other parts to which they are applied, and on which
they are moulded. In many Birds, nevertheless, three portions, more or less separated by
THE URINARY APPARATUS. 581
fissures, may be recognized. The ileo-lumbar portion— so named because of its constant
position in this region— is the most advanced; it is often the largest. Tlie middle is the
narrowest ; it is turned towards the ileo-sacral region, to enter the pelvis. The posterior is
contained in that cavity, and is again larger. These two latter portions are designated as the
anterior or superior pelvic, and the inferior or deep pelvic portions. Their internal and
superior border is often notched by a series of transverse fissures, produced by the protrusion
of the transverse processes of the sacral vert-^bras, as the lungs are furrowed by the projection
of the ribs." '
The excretory apparatus is incomplete, and is only formed by the ureters, which open into
the cloaca, where tlie urine is mixed with the fseces. Only one bird— the Ostrich— possesses
a bladder, which is disposed in a particular manner.
Comparison of the Urinary Apparatus of Man with that op Animals.
1. Kidneys. — The two kidneys of Man have, like those of tiie smaller domesticated animals,
the same shape — that of a haricot bean. The average weight is about from three to five ounces.
Contrary to what is observed in the Horse, the left kidney is more voluminous tiian the right,
and is higher.
The kidneys are simple externally, thougli their tissue is disposed in distinct lobes, which
number from eight to fifteen, and each is composed of a Malpighian pyramid and a superposed
pyramid of Ferrein ; they terminate, towards the hilus, by a cone or renal papilla, each
surrounded by a calyx, and are separated by small prolongations of the cortical substance —
the columnx Bertini.
2. Ureters. — These canals are disposed at their origin as in the Ox : they terminate as in the
other animals. In the hilus of the kidney are from eight to fifteen prolongations or calices,
■which unite into a larger cavity or great calyx, tliat finally opens into the renal pelvis ; this is
immediately followed by the ureter.
3. Bladder. — The large extremity of this organ is directed downwards in the bottom of the
pelvis, where it is continuous with the urethral can il ; its summit is directed upwards, and is
frequently pointed. Its mode of attachment and internal conformation are the same as in
animals ; and, as in the Horse, the peritoneum envelops it very incompletely. The muscular
fibres are arranged in three planes — -a superficial, which forms a band that is carried from
the anterior to the posterior face in passing over the summit ; a middle plane, the fibres of
which are circular; and a deep plane witii reticulated fibres.
Supra-renal capsules. — This name is quite appropriate to these bodies, as in Man — or at
least in the foetus — they form a kind of helmet that covers the upper part of the kidney.
There is nothing to add respecting their structure.
' Cuvier, Anatomie Compar^e, 2ud Edition. Paris : 1836-46.
BOOK V.
CIRCULATORY APPARATUS.
The animal economy is incessantly traversed by two fluids — hlood and lymph.
The hlood is a fluid, coloured bright red or brown by particular globules,
and from which the tissues derive not only the materials for nutrition and
secretion, but also the exciting principle which vivifies the organic matter. It
is named red or arterial, and dark-coloured or venous blood, according to its tint.
The lymph, or -white hlood, is a transparent, citrine-coloured fluid, which can
be obtained from most of the organs. That which comes from the abdominal
portion of the alimentary canal is charged, during digestion, with a portion of
the reparative materials elaborated in that apparatus, and is distinguished by its
lactescent aspect ; it is designated the chyle.
These fluids are carried by vessels — tubes continuous with one another.
When joined together, end to end, these tubes give rise to three principal canals :
Fig. 348.
THEORETICAL PLAN OF THE CIRCULATORY SYSTEM.
(H D 0 E, The canal for red blood ; E B A G, canal for dark blood. The arrows indicate the
course of the blood. Tlie two canals are represented in their middle portion, A B, CD, as isolated;
but in nature they are enveloped at this poiut in a common sac that concurs to form the heart.)
" One of these canals extend from the lungs to all parts of the body, and is
traversed by red blood.
" Tiie second extends from all parts of the body to the lungs, and carries
dark blood.
" The third passes from the majority of the organs towards the canal carrying
dark blood, in which it terminates ; it conveys the white blood, or lymph.
" The red-hlood and dark-hlood canals bear the greatest analogy to each other.
THE HEART. 583
Both are simple in their middle portion, which alternately dilates and contracts
to impress upon the blood the movement necessary to life. Both present at their
extremities innumerable ramifications, which ultimately join each other ; so that
the fluid they carry passes from one to the other in a constant and circular
direction. Both are composed, at their origin, of vessels in which the blood
moves in confluent columns — these are the veins ; and in their terminal portion,
of vessels in which the same fluid is spread in divergent columns — these are the
arteries (Fig. 3*49).
" The canal for ivhite blood is composed of a single order of vessels — the
lymphatics — converging tubes, the common trunk of which opens into the circu-
latory canal resulting from the junction of the red and dark blood vessels ; the
relation it affects with these latter, is that of a tangent with its circumference."
(Sappey.)
These three canals constitute the circulatory apparatus.
This apparatus therefore comprises: 1. The heart, a central organ, which
propels the blood. 2. A system of centrifugal vessels — the arteries — which carry
the blood from the heart into the different organs. 3. A system of centripetal
vessels — the veins — which bring the nutritive fluid to the heart. 4. The
lymphatics, an accessory centripetal system, for conveyance of lymph into the
blood-vascular circle.
In many anatomical works, the study of this apparatus — the heart, arteries,
veins, and lymphatics — is designated Angiology.
FIRST SECTION.
THE HEART.
The history of the heart comprises : 1. A general view of the organ. 2. The
study of its external conformation. 3. Its interior. 4. Its structure. 5. A
description of the pericardium, the serous cavity containing it. 6. A glance at
its physiology.
1. The Heart as a Whole (Figs. 255, 349, 350).
General sketch. — The heart — the central portion of the circulatory apparatus —
is a hollow muscle, the cavity of which is divided by a thick vertical septum,
into two perfectly independent chambers. Of these two contractile cavities, one —
placed on the track of the dark blood — propels it into the lungs ; the other —
situated on the course of the red blood — distributes it to all parts of the body.
Each of these is subdivided into two superposed compartments by a circular
constriction, at which is a membranous valve that, at certain fixed periods, is
elevated, and then forms a comple horizontal partition extended between the
two compartments.
The superior compartment receives the convergent or centripetal portion of
the blood-canal — that is the veins : it is named the auricle. The inferior gives
origin to the divergent or centrifugal part of the same canal, and is designated
the ventricle.
584 CIRCULATORY APPARATUS.
The cavities of the heart are distinguished into right or anterior, and left or
posterior, because of their relative positions. There are, then : a right auricle
and ventricle — the two dark-blood cavities ; and a left auricle and ventricle,
situated on the track of the red-blood canal.
Situation. — The heart is enclosed in a tibro-serous sac, named the jiei-icardium,
and is placed in the chest between the two layers of the mediastinum, opposite
the third, fourth, fifth, and sixth ribs ; in front of the diaphragm, which
separates it from the abdominal viscera ; above the sternum, which appears to
support it ; and beneath the vertebral column, to which it is suspended by means
of the large vessels. (Between the middle of the anterior border of the heart,
in front, and the entrance to the chest, is an interval of about four inches ; and
behind, at the same level, this organ is at a similar distance from the diaphragm.
It is distant from the fifth and sixth dorsal vertebrte — from which it is suspended
— about 4| or 5 inches in an average-sized Horse.)
Form and direction. — The heart presents the form of an inverted cone, slightly
depressed on each side, the axis of which, directed obliquely downwards and
backwards, deviates a little to the right at its superior extremity.
Volume. — In a medium-sized Horse, the greater axis of the heart is about lO^-
inches in length ; its antero-posterior diameter, measured near the base, is
equivalent to about 7^ inches. Its lateral diameter does not exceed from 5 to
5^ inches.
Ckimcitij. — It is very difficult, if not impossible, to obtain the exact capacity
of the heart's cavities. From reasoning, it might be supposed that the two hearts
have exactly the same capacity, and that this is equivalent to an average of from 1
to 1;^ pints. The amount obtained by measurement is much more considerable ;
but then the heart is distended to a greater extent than in its physiological state.
Weight. — The weight of the heart varies with the size of the animals, and
that to a considerable degree. Its average is about 6f pounds. (The volume
and weight of the heart are very much greater in well-bred than in common-bred
Horses. Its dimensions and capacity are greater in the living than the dead
animal ; as after death its cavities contract, particularly the aortic ventricle,
which has the thickest walls. This ventricle will then scarcely contain more
than from f to 1^ giUs ; the pulmonary ventricle, which is not so thick, and con-
sequently less contracted, may usually receive double that quantity ; while in
animals experimented on when expiring, it has been observed that these two
ventricles were much more capacious, and that each contained at least from
l^^ to 1| pints.)
2. External Conformation of the Heart (Figs. 349, 350).
Preparation. — Eemovethe heart, and with it a certain length of the vessels belonging to it;
fill its cavitied with tow, and free the furrows from tiie adipose deposited in them.
The cone represented by the heart is divided by a horizontal groove into two
unequal portions : the one superior, comprising the auricles or auricular mass ;
the other inferior or principal, formed by the ventricles or ventricular mass.
A. Ventricular Mass. — It is this which determines the conical shape of
the heart, and constitutes its largest portion. Owing to a slight flattening of the
organ in a lateral sense, it may be considered as having a right and left face, an
anterior and posterior border, an apex, and a base.
The right face, smooth and rounded, is traversed by a vascular furrow {right
TEE HEART.
585
ventricular groove) parallel to the axis of the heart, and which divides this face
into two sections — an anterior, belonging to the right ventricle ; and a posterior,
less extensive, forming part of the left ventricle (Fig. 350).
The lefi face, disposed in the same manner, also shows a groove (left ventri-
cular groove) on the limit of the two ventricles, which slightly crosses the large
diameter of the heart from behind to before, and above to below, and is much
nearer the anterior than the posterior border (Fig. 349).
Fig. 349.
THE HEART AND PRINCIPAL VESSELS (LEFT FACE).
a, Right ventricle ; 6, left ventricle ; c, right auricle ; c?, left auricle ; e, pulmonary artery ; «*,
obliterated ductus arteriosus; /, pulmonary veins; g, anterior aorta; h, left axillary artery;
», right axillary artery, or brachio-cephalic trunk; j, origin of the dorsal artery ; k, origin of the
superior cervical artery ; I, origin of the vertebral artery ; m, origin of the inferior cervical
artery; w, origin of the internal thoracic artery; o, origin of the external ditto; p, carotid
arteries ; q, posterior aorta ; r, anterior vena cava ; s, trunk of the axijlary vein ; t, trunk of the
internal thoracic vein ; u. trunk of the dorsocervical vein; v, posterior vena cava; exjunction
of the hepatic and diaphragmatic veins; x, vena azygos ; y, thoracic duct; z, embouchure of
that vessel, placed near the origin of the anterior vena cava. 1, Right cardiac artery ; 2, left
cardiac artery ; 3, auriculo-ventricular branch of the latter ; 4, its ventricular branch ; 5, cardiac
vein.
These two faces are related, through the medium of the pericardium, to the
plurfe and pulmonary lobes ; the latter separate them from the thorax, except
towards the middle and apex of the organ, where these faces come directly in
contact with the thoracic parietes through the notch at the inferior border of the
lung, and which is more marked in the left than in the right.
The borders are thick, smooth, and rounded. The anterior, formed by the
586
CIRCULATORY APPARATUS.
right ventricle, is very oblique downwards and backwards ; it niclines on the
sternum more or less, according to su])jects.
The posterior border, much shorter than the anterior, is nearly vertical.
Superiorly, it is separated from the diaphragm by the lung ; but, below, it is quite
close to that muscular septum.
The apex, or point of the ventricular cone, is blunt, slightly rounded, turned
to the left, and formed entirely by the left ventricle.
The base is related on the
Fig- 350. right, in front, and behind, to the
auricles ; it gives off on the left,
and a little in front, the two
arterial aortic and pulmonary
vessels.
B. Auricular Mass. — Elon-
gated from before to behind, dis-
posed like a crescent above the
right side of the base of the
ventricles, constricted in its middle
part, on the limit of the two
auricles, the auricular mass pre-
sents for study three faces, two ex-
tremities, and a base.
The superior face is divided by
a middle constriction into two
convex sections, each of which
corresponds to an auricle. The
anterior — or right section— shows
the entrance of the anterior vena
cava and vena azygos ; the pos-
terior— or left section — that of the
pulmonary veins. The trachea,
bronchi, and pulmonary artery pass
above this face (Figs. 349, 350).
The right face, the most ex-
tensive in the anteo-posterior
direction, is divided like the pre-
ceding, and disposed in a similar
manner. The right, or anterior
part, receives — behind and below —
the insertion of the posterior vena
cava, and the coronary and
bronchial veins (Fig. 350).
The left face, concave from
before to behind, includes the arterial trunks which leave the base of the heart.
Each of the extremities — anterior andposterior — constitutes a detached portion,
named the appendix auricularis ; these appendages are curved towards each other
in being flattened above and below. Their convex border is more or less
crenelated, like the margin of a cock's comb, and their culminating portion
advances nearly to the pulmonary artery, above the trunk of the cardiac
vessels (Fig. 349).
THE HEART AND PRINCIPAL VESSELS (RIGHT FACE).
o, Right ventricle ; 6, left ventricle ; c, right auricle ;
d, anterior vena cava ; e, vena azygos ; /, posterior
vena cava ; g, g, pulmonary veins ; h, h, divisions
of the pulmonary artery ; i, posterior aorta ; j, an-
terior aorta; k, thoracic duct; /, right cardiac
artery ; m, its vertical o*- ventricular branch ; n, its
horizontal or auriculo-ventricular branch ; o, ven-
tricular branch of the cardiac vein; p, auriculo-
ventricular branch of the same.
THE HEART.
587
The hase of the auricular mass, opposed to the base of the ventricles, is
separated from it at its periphery by the horizontal groove {aimculo-vmtricular
groove) of the heart.
3. Inteknal Conformation of the Heart (Figs. 351, 352, 358).
Preparation.— It sufBces to make a longitudinal incision before and behind the organ, in
order to expose its cavities. (I have followed Wilson's directions for many years when
examining the interior of the heart, and as a careful inspection of this organ is often necessary in
the course of an autopsy, I think the student should practise the best method of laying open
these cavities. The riglit auricle is prepared by making a transverse incision along its ventri-
cular margin, from the appendix tu its right border, and crossed by a perpendicular incision,
carried from the si<]e of the anterior to the pos-
terior cava. The right ventricle is laid open by Fig. 351
making an incision parallel with, and u little
to the right of, the middle line, from the
pulmonary artery in front, to the apex of the
heart, and thence by the side of the midille line
behind to the auric ulo- ventricular opening.
The interior of the left auricle is expn^ed by
a J_ -shaped incision, the horizontal section
being made along the border which is attached
to the base of the ventricle. The latter is
opened by making an incision a little to the left
of the septum ventriculorum, and coutiuuing it
around the apex of the heart to the auriculo-
ventricular opening behind.)
If the heart, when viewed externally,
appears to be a simple organ, it is not
so when examined internally. The
vertical septum which divides it into
two bil ocular cavities, in reality makes
two hearts of it — one for the dark, the
other for the red blood. We will suc-
cessively study these two cavities, by com-
mencing with the partition that separates
them.
A. Cardiac Septum. — The superior
part of this septum, between the two
auricles, is named the inter-auricular
partiUon {septum anricularum). The
inferior portion constitutes the inter-
ventricular partition {septum ventricu-
lorum). The first— thin and not exten-
sive— is perforated in the foetus by the
foramen of Botal {foramen ovale). The second, thick in its centre, thins a little
towards its borders.
B. Dark-blood (or Pulmonary) Heart. — The two superposed cavities
forming tliis portion are situated in front and to the right. They are indifferently
named the anterior or right cavities of the heart — the latter term being in general
use, though the first is much more convenient in Veterinary Anatomy.
Right Ventricle. — The right ventricle represents a hollow cone, a
horizontal section of which resembles a crescent, its posterior plane being pushed
into the cavity by the left ventricle.
RIGHT SIDE OF THE HEART LAID OPEN,
1, Cavity of right auricle ; 2, appendix auri-
culae, with musculi pectinati ; 3, anterior
vena cava opening into the upper part of
the right auricle ; 4, posterior vena cava ;
5, fossa ovalis, surrounded by the annulus
oralis ; 6, Eustachian valve ; 7, opening of
the coronary sinus ; 8, coronary valve ; 9,
entrance of auricular-ventricular opening.
a, Right ventricle ; 6, its cavity ; c, conus
arteriosus, or infundibulum ; d, pulmonary
artery ; e, f, tricuspid valve ; g, one of the
musculi papillares to which the curtains of
the tricuspid valve are attached by chordae
tending ; h, columnse carneue ; i, two mus-
culi papillares of valvular curtain ; /, I,
chord* tendinese; m, .semilunar valves of
pulmonary artery ; n, apex of left appendix
auriculae ; o, left ventricle.
588 CIRCULATORY APPARATUS.
It offers hvo ivalls, an apex, and a base.
Walls. — The anterior waU is concave ; its thickness is more considerable
above than below, and averages ^^ of an inch. The posterior ivall is convex, and
formed by the septum ventriculorum.
Both walls are uneven, from the presence of fleshy columns (columnce carnece),
which we will commence examining in a general manner, as they are found in
the four compartments of the heart. They are of three kinds : one kind, named
the pillars of the heart {musculi papiJlares) — thick and short, and fixed by their
base to the walls of the ventricles — have a free summit, into which are implanted
the tendinous cords {chordce tendincB) proceeding from the auriculo-ventricular
valve ; those of the second order (trabeculce carnce) are free in their middle part,
and attached by their extremities to the walls of the heart ; while the third
description {columned) adhere throughout their length to the cardiac tissue, on
which they stand as if sculptured in relief.
In the right ventricle, two columns of the first order, rarely three, are met
with — one on the anterior, the other on the posterior wall. The columns of the
second order number two or three principal ones, extending from one wall to the
other, or attached to two different points of the same wall. There also exist a
considerable number of small ones intermixed with those of the third order.
The latter are particularly abundant in the angles formed by the union of
the two faces, where they interlace and give rise to more or less complicated
areolae.
Apex. — The cipex of the right ventricle does not descend to the point of the
heart, being distant from it about H inches.
Base. — This has two large orifices — the auriculo-ventricular and the pidmonary
openings.
Auriculo-ventricular optening. — Placed on a level with the constriction that
divides the right heart into two superposed compartments, this orifice — widely
open and almost a regular circle in outline — forms the communication between
the auricle and ventricle. It is provided with a valvular fold that exactly closes
the orifice when the ventricle contracts to propel the blood into the lungs, and
which is termed the tricuspid (having three points) valve, in consequence of
its form. This valve offers : 1. A superior border, attached to the entire margin
of the auriculo-ventricular opening. 2. An inferior opening, free, cut into three
festoons by three deep notches, and fi-xed to the ventricular walls, principally
on the summits of the fleshy columns, by means of the tendinous cords which
ramify on reaching the valve. One of these festoons— more developed than the
others — is placed on the limit of the auriculo-ventricular and pulmonary
openings ; thereby constituting a kind of vertical partition that divides the
ventricular cavity at its base into two compartments — a right or auricular, and
a left or arterial. The other festoons are apphed to the anterior and posterior
walls of the ventricle. 3. An external face, which receives the insertion of a
great number of tendinous cords, 4. An internal face, which becomes superior
when the valve is raised to close the opening, when it constitutes the floor of the
auricular cavity.
Pulmonary opening. — This orifice represents the entrance of the pulmonary
artery. Situated in front and to the left of the preceding, but a little higher, it
occupies the summit of a kind of infundibulum (the conus arteriosus) formed by
the left compartment of the ventricle being prolonged upwards. It is perfectly
circular, smaller than the artery to which it gives origin, as well as the auriculo-
TEE HEART.
ventricular opening, from which it is separated by a kind of muscular spur, to
which is attached the principal festoon of the tricuspid valve.
The pulmonary opening is furnished with three valve^— the sigmoid (or semi-
lunar), suspended over the entrance to the pulmonary artery, and, as has been
ingeniously remarked (by Winslow), like three pigeons' nests joined in a triangle.
These valves are remarkable for their thinness— a circumstance which does not
interfere with their solidity. They present : an external, convex border, attached
to the margin of the orifice and to the walls of the puhnonary artery ; a free
border, straight when pulled tense, concave when left to itself, and sometimes
provided in its middle with a small, very hard tubercle, the nodule of Arantius
{nodulus, or corpus Arantii) ; a superior, concave face ; and an inferior, convex
one. The sigmoid valves are raised
and applied to the walls of the vessel ^S' ^'"'^*
at its entrance, when the ventricle
contracts and sends the venous blood
into the lung. "When this contraction
ceases, they fall back one against the
other by that part of their inferior
face next to their free border, so as
to oppose the reflux of the blood into
the ventricular cavity.^
Right Auricle. — The cavity of
the right auricle represents a very
concave lid or cover surmounting the
auriculo-ventricular opening, and is
prolonged, anteriorly, by a cm-ved
cul-de-sac. It offers for study this
anterior cul-de-sac, a, posterior, external,
and internal wall, as well as a superior
wall or roof, and the auricido-ventri-
cidar opening, which occupies the
whole floor of the cavity. This ori-
fice has been already described.
The anterior cul-de-sac is in the appendix auricularis ; it is divided by a great
number of muscular columns of the second and third orders {musculi pectinati),
into deep and complex areolae.
The posterior ivall responds to the interauricular septum ; it is smooth, and
usually marked by an oblique and more or less deep cvl-de-sar (or depression),
the remains of Botal's foramen. This depression is surrounded by the ring (or
isthmus) of Vieussens (anmdus oralis), and is named the fossa ovalis ; it is only
separated from the left auricular cavity by a thin membrane, a vestige of the
' It has been repeated, ad nauseam, that the occlusion of the arterial openings results from
the juxtaposition of the free harder of the sigmoid valves ; even the small tubercle in the
middle of this border, has been considered to play its part in closing the triangular central
space left when tliese valves meet. In passing the finger into the pulmonary artery of a living
animal, to explore the function of these membranous folds, it is readily perceived that they
come in contact by a large portion of their convex face, and not alone by their free border.
This arrangement is such, that we have with much diflSculty tried to produce an insufficiency
of contact by keeping one of the valves up ngainst the walls of the vessel with the finger; but
the others came down against the finger and applied themselves around it so as to exactly close
the orifice. ^
40 .. /-i
SECTION OF THE HEART AT THE LEVEL OF THE
VALVES.
p, Pulmonary artery; A, aorta; M, mitral valve;
T, tricuspid valve.
590 CIRCULATORY APPARATUS.
valve (Eustachian valve) circumscribing the interam-icular opening in the
foetus.^
In the wall are small orifices {foramina Thehesii) which lead to anastomosing
vessels {verice cordis minimce) in its substance.
The external ivall is areolated, and perforated behind and below by two
orifices, the largest of which is the opening of the posterior vena cava, the other
the opening of the large coronary vein. Both are destitute of valves, though
these are found at a short distance in the coronary vein. The bronchial vein
sometimes opens separately beside the latter.
The internal wall is smooth.
The superior wall, or roof of the auricle, shows the openings of the anterior
vena cava and vena azygos ; the latter only is provided with valves, which are,
however, not always present. On this wall are also remarked, in front, areolae
separated by muscular columns.
The thickness of the right auricular walls is very irregular, in consequence of
the reliefs sculptured on the inner face of that cavity. In some points it is
about ^ of an inch, and in others, particularly in the small culs-de-sac formed
by the reticulations, it is sometimes so thin as to appear exclusively formed
by the union of the external and internal serous membrane.
(When the vena azygos opens behind, there is between it and the orifice of
the anterior vena cava, a muscular layer with a free concave border, which forms
a kind of valve of very variable extent. Behind this vena cava is a thick
eminence — the tuberculum Loweri ; this has the form of a crescent, open in front,
and elongated from right to left at the superior border of the septum. The
anterior, or left border of the fossa ovalis, is thin and prominent, and constitutes
the Eustachian valve ^ — ^a musculo-membranous fold of a semilunar shape, with a
concave free border directed to the right and behind. It is of little use in
animals, because of their horizontal position. Immediately beneath the posterior
vena cava, and between it and the coronary vein, is a small membranous
crescent — the vcdve of Thehesius.)
C. Red-blood (or Aortic) Heart. — This is also called the posterior heart,
and more frequently the left heart, because it is situated behind and to the left of
the dark-blood heart. Its general disposition otherwise exactly resembles that
of the latter receptacle.
Left Ventricle. — This is a cylindro-conical cavity, the transverse section of
which is irregularly circular. Its walls attain a thickness of from 1-^ to 1| inches,
except towards the apex of the heart, where they are extremely thin. They are
less reticulated than those of the right ventricle, and exhibit several columns of
the second order, as well as two enormous muscular pillars — an external and
internal, for the attachment of the tendons of the auriculo-ventricular valve.
The apex of the cavity forms a reticulated cid-de-sac, which occupies the point
of the heart. The base is perforated by the auriculo-ventricular and the aortic
openings. The auricido-ventricidar opening— i^reckelj similar to that of the right
ventricle— is provided with a circular membrane, the mitral (or bicuspid) valve,
because it is cut into several festoons, of which two are the principal— the one
• Zangger and Zundel have observed instances of persistent foramen ovale in Foals, and
even in Horses. Goubaux has collected fifteen cases of this kind, thirteen of which occurred
in Bovines -aged from four mouths to twenty years— one in the Sheep, and another in the Dog.
This anatomist also met.with an abnormal communication between the two ventricles in an
adult Horse. Chatin has studied a similar anomaly in a young Hemionus.
' 2 The presence of a Eustachian valve in the Horse has been denied.)
THE HEART.
591
anterior, the other posterior, simulating in their outline the two faces of a
bishop's mitre. The anterior festoon is the largest, and is attached to the limit
of the two orifices, isolating from the ventricular cavity a diverticulum which
corresponds, in every respect, to the pulmonary infundibulum. The posterior
festoon is applied to the walls of the ventricle. Between these two there are
usually two secondary festoons, making up the total number to four ; frequently
there is an accessory fold, situated on the right side, and fairly developed ; the
valve is then tricuspid, like that of the right ventricle. Sometimes two of these
rudimentary folds are found on the left side — making five festoons in all. The
aortic opening — so named because it constitutes the origin of the aorta — is placed
in front and to the left of the auriculo-ventricular opening, from which it is only
separated by a thin muscular spur,
to which is attached the adherent ^"g- ^^'^■
border of the great festoon or curtain
of the mitral valve. It does not
differ in anything from the pulmonary
opening, and, like it, is provided with
three sigmoid (or semilunar) valves.
Left Auricle. — As in the right
auricle, this forms a kind of lid above
the auriculo-ventricular opening.
Smooth behind, in front, inwards and
outwards, its cavity presents a reticu-
lated cul-de-sac, which occupies the
auricula ; and a superior wall, also
reticular, having from four to eight
orifices — the openings of the pul-
monary veins. These orifices have
no valves. (Carnece columnce of the
third kind are also present, but chiefly
between the two posterior pillars ;
small ones are very numerous on the
borders and summit of the ventricle.
The columns of the second order are
simple or ramous, and pass from the
angles of union of the walls and the
point of the cavity ; others on the posterior wall go to the borders and the
interval between the two pillars. The most remarkable are bands extending from
one wall to the other, the two principal of which are long, strong, and ramous ;
they are fixed, on the one side, to the centre of the great posterior reliefs, and
ascend to be implanted, on the other side, into the middle of the anterior wall.)
LEFT CAVITIES OF HEART LAID OPE
1, Cavity of left auricle; 2, cavity of appendix
auriculae ; 3, opening of two right pulmonary
veins ; 4, sinus into which left pulmonary veins
open; 5, left pulmonary veins; 6, auriculo-ven-
tricular opening ; 7, coronary vein lying in
auriculo-ventricular groove ; 8, left ventricle ;
9, 9, cavity of left ventricle, a, Mitral valve,
its curtains connected by chordae tending to b, b,
columnce carnea; ; c, c, fixed columneae carnae on
inner surface of ventricle ; i, point of appendix of
right auricle.
4. Steucture of the Heart.
Preparation.— Bekre proceeding to dissect the muscular fibres of the heart, it is indis-
pensable to keep that viscus in boiling water for half or three quarters of an hour. It should
then be immediately immersed in cold water, to prevent the desiccation of the serous membrane
covering it, and which must be at once removed. The furrows should then be cleared of their
Vessels and fat ; this renders the superficial muscular fibres very apparent. The same result
may be attained by immersing the heart in vinegar or dilute hydrochloric acid. To isolate the
ventricles and unitive fibres from each other, the following procedure may be adopted : After
removing the auricular mass and dissecting the fibrous rings, the unitive fibres around these
S92 CIRCULATORY APPARATUS.
are divided with the point of the scalpel, care being taken not to injure the proper fibres. Then,
with the aid of the finger-nail or handle of the scalpel, follow the more or less artificial limit of
these two series of muscular planes in a spiral manner ; the vessels passing thiough the walls
of the heart must be cut through- The same course is fullowed in the substance of the inter-
ventricular septum, in order to separate tlie two sacs fiurmed by the proper fibres.
(It will be found that the simplest and best way to prepare the lieart for an examination
of its fibres, is to steep it in a very weak dilution of hydrochloric acid. Remove the serous
membrane, and tlie fibres can then be traced, layer by layer, from their origin to their
termination.)
The muscular tissue composing the heart rests on a fibrous framework, dis-
posed in rings around the auriculo-ventricular and arterial openings ; it receives
Fig. 354.
ArRICULO-VENTRICCLAR FIBRO-CARTILAGINOUS RINGS.
1, Pulnionary artery ; 2, superior border of the infundibulum ; 3, aorta ; 4, sigmoid or semilunar
valves; 5, bulgings of the aorta corresponding to the semilunar valves; ii, left auriclo-ventricular
opening; 7, right ditto ; 8, left fibro-cartilaginous ring ; 9, right ditto ; 10, the two rings meeting
together in the middle line.
vessels and nerves, and while covered in the internal cavities by two independent
serous membranes, it is enveloped, externally, by another membrane of the same
kind. An annvlar frameivork, muscular tissue proper, vessels and nerves, and
serous tunics — such are the elements entering into the structure of the heart.
A. Fibrous Rings, or Tendinous Rings of Lower. — These are also
named the fibrous zones of the heart, and are four in number : one for each of
the openings at the base of the ventricles.
The two arterial zones (the pulmonary and aortic) constitute two complete
rings, which are not disposed in a circular manner around the pulmonary aortic
openings, but are divided into three regular festoons with their concavities
THE HEART. 593
superior and internal, and corresponds to the insertions of the three sigmoid
valves. These zones are continuous, by their superior and external contour, with
the walls of the arteries, from which they are only distinguished by their whitish-
grey colour and slight elasticity, the arterial tissue being yellow and very elastic.
Their internal and inferior outline sends three thin prolongations into the serous
duplicatures of the sigmoid valves.
The auriculo-ventrkular zones do not completely suiTound the openings they
circumscribe. They are flat, brilliantly white tendons, laid one against the other
at the ventricular septum, and against the aortic ring ; they turn to the right
and left around the auriculo-ventricular openings, but without joining at their
extremities, which are dispersed as fibrillse in the muscular tissue of the ventricles.
Above, these zones give attachment to the muscular fibres of the auricles ; below,
to the ventricular fasciculi. Their internal and inferior border is prolonged into
the mitral and tricuspid valves, and is continuous, through these valves, with the
chordae tendinete of the ventricles. Some of these cords, generally the strongest,
are even directly inserted into the auriculo-ventricular zones.
It must be noted that, in Solipeds, there is constantly found, at the point
where the aortic and auriculo-ventricular zones lie against each other, a more or
less developed cartilaginous body, which, in the larger Ruminants, is transformed
into true bone. (Lavocat speaks of two cartilaginous points, one to the right, at
the junction of the aortic with the left auriculo-ventricular ring and the cardiac
septum ; the other, less developed, on the left, at the origin of the left ventricular
groove.)
B. Muscular Tissue (Fig, 355). — The muscular tissue of the heart is that of
organic life, as it contracts independently of the will. Nevertheless, it is formed of
red striped fibres, which differ from the striped muscles of the locomotory apparatus.
They are granular and dark under the microscope, and ramify and anastomose in
such a manner as to form an extremely fine network in the myocardium. From
the joining end to end of the segments of Weissmann, there result simple or
ramified prisms, the bases of which are notched like stairs. Each Weissmann
segment comprises : 1. In the centre, one or two nuclei with a nucleolus. 2. Con-
tractile cylinders of unequal length, around the nuclei. 3. A mass of protoplasm
enveloping the nucleus, extending 'between the contractile cyHnders, and forming
a kind of sarcolemma. Between the fibres of the myocardium there is very little
connective tissue, but there is a great number of blood-vessels and lymphatics.
The arrangement of the muscular fasciculi of the heart has been the object
of numerous investigations, which have only complicated what was already
known on the subject. We will endeavour to sum up, as simply as possible, this
arrangement, in examining it successively in the ventricles and auricles.
1. Fibres of the Ventricles. — According to the remark of Winslow, we
may compare the ventricles, in regard to the arrangement of the fibres composing
them, to " two muscular sacs included in a third ; " that is to say, each ventricle
is formed oi proper muscular fibres, covered externally by a layer of unitive fibres,
which envelop the two ventricles in common.
a. Proper fibres of the ventricles. — Taken altogether, these fibres represent,
for each cavity, a hollow cone, open at both its extremities — at the superior
extremity, by the auriculo-ventricular and arterial openings ; and at the inferior
extremity, by an aperture which admits the reflected fibres of the common layer.
All form loops, attached by their extremities to the outline of the superior
orifices, on the fibrous zones, and are rolled, more or less obliquely, around the
591 CIRCULATORY APPARATUS.
axis of the ventricles. It is from the apposition of the right and left systems
that the ventricular septum is formed.
b. Unitive fibres of the ventricles. — These are disposed as an external shell
enveloping the proper fibres. They leave the fibrous zones at the base of the
heart, and descend towards its apex : those of the right side, by inclining
forward ; the anterior, in following the direction of the great axis of the
ventricles ; those of the left face, by directing their course downwards and
backwards ; and the posterior, in roUing themselves from left to right around
the left ventricle. On arriving near the point of the heart, they turn from left
to right, and before to behind, in forming a spiral twist ; then they are reflected
from below upwards, to enter the inferior extremity of the ventricles, on the
internal face of the proper fibres of which they spread and ascend to the fibrous
zones at the base of the heart, where they terminate. Some of these reflected
fibres are disposed in relief, to constitute the columnse carnese, and reach the
Fig. 356.
Fig. 355.
ANASTOMOSING MUS-
CULAR FIBRES OP MUSCULAR WHORL AT THE POINT OF THE
HEART. HEART.
1, Vortex or whorl with small opening in the
middle; 2, auricle; 3, intercrossing of the
anterior and posterior unitive or uniting
fibres.
auriculo-ventricular zones through the medium of the chordfe tending that
directly connect these fibrous rings with the summits of the muscular pillars.
All the fibres do not reach the point of the heart to ascend to the fibrous
zones ; a certain number are reflected at different heights in the layer they form,
and Gerdy has compared them to a number of horns placed one within the
other, and flattened as are the walls of the ventricles.
Such is the general disposition of the unitive fibres of the ventricles : and it
will be seen that they form a superficial and a deep or reflected plane, between
which are comprised the fasciculi proper to each ventricular cavity.
The unitive fibres of the ventricles, therefore, form collectively a kind of
figure 8, the smallest loop of which is at the point of the heart ; there the fibres
are heaped together, leaving in the centre of the loop a very small space, through
which it is possible to pass a probe into the ventricle, without piercing anything
but the external and internal serous membranes of the organ.
2. Fibres of the Auricles. — The fibres of the auricles are either common
to the two cavities, or proper to each.
THE HEART.
595
The unitive fibres constitute two thin bands — a right and left, caiTied from
one auricle to the other.
The proper fibres are divided into several fasciculi, some of which are arranged
in rings around the auriculo- ventricular opening ; others in interwoven loops ;
and others, again, in sphincters, which suiTound the entrance of the veins.
These fibres are arranged in such a manner that, in contracting, they diminish
the auricles by their superior and lateral planes and extremities, and propel the
blood towards the auriculo-ventricular openings.
(The arrangement of the muscular fibres constitutes the most remarkable
Fig. 357.
POSTERIOR UNITIVE FIBRES, AND FIBRES OF THE POSTERIOR FACE OF THE AURICLES,
1, Posterior unitive fibres; 2, fibres of the right auricle; 3, fibres of the posterior vena cava.
feature in the anatomy of the heart. We have seen that the auricles, as well as
the ventricles, possess not only fibres proper to each compartment, but also
unitive or common fibres, which assure the simultaneousness in action of the
similar or homologous cavities. Besides, the fibres of the auricles and those of
the ventricles are distinct, and not continuous ; so that, from their independence
of each other, it results that these two sections of the heart may act separately,
and contract, not simultaneously, but alternately — a condition indispensable to
596 CIRCULATORY APPARATUS.
the free course .of the blood. The extremely fine and close connective tissue
uniting the muscular fibres, and the anastomosing of these, is another pecuharity
of structure that must be favourable to the solidarity of their action, which
ought to be simultaneous. In the healthy organ, adipose tissue is only found ir.
tlie grooves on its surface, around the vessels lodged in them, and particularly at
its base, between the large arterial trunks.)
C. Vessels and Nerves of the Heart. — Blood is carried to the muscular
tissue of the heart by two large vessels — the coronary arteries. They emanate
from the trunk of the aorta, at the sigmoid valves, and each divides into two
principal branches — one passing along the horizontal, the other in the vertical
furrow of the heart. Collectively, these arteries form two circles, which surround
the heart in intersecting it at a right angle in the auriculo-ventricular groove.
The blood is carried from the walls of the heart by a single but important
vein., which empties itself into the right auricle.
The li/mjjhatics follow the arteries, passing along the visceral layer of the
pericardium, and entering the cluster of glands situated near the base of the
heart. (The epicardium, as well as the endocardium — especially in the ventricles —
has a large network of fine lymphatics, the walls of which consist of only a
single layer of intimately adhering cells. Lymphatics are also numerous in the
myocardium, and amongst the muscular fibres there are lacunae or spaces lined
by endothelial cells — the origins of the lymphatics. The lymph passes into
lymphatic glands lying between the aorta and trachea, flowing thence into the
thoracic duct. No lymphatic vessels have been traced upon the chordge tendineaj,
and very few upon the auriculo-ventricular and semilunar valves.)
The nerves of the heart, furnished by the cardiac plexus, come from the
pneumogastric and sympathetic. The tubes are small, and show some cells in
their course. In addition to these, the heart is provided with a particular
ganglionic system, to which Remak, Bidder, and Ludwig have called attention.
It is believed that there exist three ganglia in different points of the cardiac
parietes, and that on these depend the movements of the organ. (Nerve-cells are
most numerous in the basal and middle parts of the ventricles of the heart of the
Dog, Sheep, Calf, and Pig, chiefly in the anterior and posterior inter-ventricular
grooves and on the left ventricle. According to Carpenter, the nerves of the
heart are : 1. Minute ganglia and fibres of the sympathetic, situated in the walls
of the cavities, and especially in the auriculo-ventricular furrow. 2. Fibres derived
from the cervical portion of the sympathetic, and passing to the cardiac plexus,
between the aorta and pulmonary artery. 3. Cerebro-spinal fibres entering the
inferior cervical or stellate ganglion, and proceeding to the same plexus, and
probably derived from a centre situated in the brain and spinal cord. 4. Fibres
coursing in the vagus — nervi cardiaci — and originating in a centre situated in
the medulla oblongata. The first three of these ganglia and fibres probably
collectively constitute the excito-motor system of the heart ; the fourth is an
inhibitory, restraining, or regulo-motor centre.)
D. Serous Membranes of the Heart. — These are three in number — two
internal, or endocardial, one of which occupies the right, the other the left cavity ;
and an external — epicardial — a dependency of the fibro-serous sac which contains
the heart.
1. Internal serous membranes^ or endocardia. — These two membranes, indepen-
dent, like the cavities they line, are spread over the auricular and ventricular
walls, covering the tendinous or muscular columns attached to these walls, and
THE HEART.
597
Fig. 358.
are prolonged into the veins and arteries, to form the internal tunic of these
vessels. At the auriculo-ventricular and arterial openings, they constitute a
duplicature for the valves situated there. These valves 'are, therefore, due to the
projection of a circular fold of the endocardium, between the two layers of which is
connective tissue mixed with elastic fibres in the auriculo-ventricular valves, and
a layer of connective tissue on each surface of the elastic fibres in the semilunar
valves. It is worthy of remark that the elastic fibres of the valves are more
abundant in the left than the right side of the heart.
The endocardium of the right heart has a red tint, which is deepest in the
ventricle. In the left heart, this tint is slightly yellow, especially in the walls of
the auricle, which may be attributed to the presence of a
thin layer of yellow elastic tissue that covers the adherent
face of the membrane.
The endocardium consists of two layers : 1. A thin bed
of connective tissue, connecting it to the muscular structure,
in which elastic fibres are pretty uniformly distributed, as
well as smooth muscular fibres, especially in the left heart.
2. An endothehum, consisting of a single or double layer
of somewhat elongated, polygonal, tesselated nucleated cells.
2. External serous membrane (epicardium). — This is the
visceral lining membrane of the pericardium, the description
of which follows
5. The Peeicardium (Fig. 255, c).
Preparation. — Place the auiinal in the second position, and remove
the sternal ribs by separating the cartilages and luxating their costo-
vertebral articulations. This procedure permits the study of the
situation and general disposition of the heart and pericardium. But
in order more easily to examine therecijirocal arrangement of these two
parts, it is necessary to extract them from the thoracic cavity by tearing
through the sternal insertion of the pericardium.
The pericardium, or proper serous covering of the heart, is a membranous sac
enclosing that organ, fixing it in ihe thoracic cavity, and favouring its movements
by its pohshed surface.
This sac is formed by a fibrous layer, within which is spread a serous
membrane, divided into two parts — one parietal, the other visceral.
The fibrous layer of the pericardium presents somewhat the general form of
the heart. Its internal surface is covered by the parietal portion of the serous
membrane. The external surface corresponds to the two layers of the mediastinum.
Its summit (or apex), depressed on each side, and elongated from before to behind,
is firmly attached to the superior face of the sternum, from the fourth rib to the
origin of the xiphoid cartilage. By its base, it is fixed to the large vessels going
to and leaving the heart, where it is continuous with their connective-tissue
sheath, and where it sends some fibres to the longus colli.
The serous membraiie of the 'pericardium has been well compared by Bichat to
a cotton nightcap, the external part of which would represent the parietal layer,
and the inverted part the visceral portion of the membrane. The parietcd layer
adheres in the most intimate manner to the internal face of the fibrous tunic,
and is reflected to form the visceral portion, around the pulmonary arteries and
the aorta for a certain distance from their origin, and on the pulmonaiy veins.
The viscercd layer envelops in common the two arterial trunks, covers a small
EPITHELIUM OF THE
ENDOCARDIUM.
1, Nucleated cells hs-
suming the fusiform
figure; 2, polygonal
nucleated cells.
598 CIRCULATORY APPARATUS.
part of the venae cavas — particularly the anterior — spreads over the insertion of the
pulmonary veins, and then descends on the auricles and ventricles. The free face
of this layer is in contact with that of the parietal layer ; the adherent face is
applied to the tissue of the heart or that of the large vascular trunks, except at
the horizontal and vertical grooves, where it rests on the coronary vessels, and on
the mass of adipose tissue constantly accumulated on their track.
In the living animal, the cavity of the pericardium is never entirely filled by
the heart, so that the movements of that organ are allowed much more liberty.
Othenvise, as it does not contain any gas, nor a sensible proportion of fluid,^
its walls are immediately applied to the surface of the heart.
The two layers of the pericardium are covered by a layer of endothelial
polygonal cells.
Blood reaches the pericardium by the mediastinal arteries. Its walls receive
some sympathetic nerve-fibres.
(The epicardium is composed of a fine network of connective tissue and elastic
fibres, as well as bundles of non-striped muscular fibres ; these resist the distension
that occurs when the heart contracts and a great strain is thrown upon the
endocardium. Gurlt, in 1867, described a thin muscle, niue inches long, situated
between the pericardium and the diaphragm of the Horse.)
6. Action of the Heart.
The function of the heart is to maintain the circulation of the blood, by the
rhythmical contractions of its two cavities. The right side propels that fluid
to the lungs, whence it returns to the left side, and from this it is thrown into
all parts of the body, after which it is brought back again to the right heart.
These contractions take place simultaneously in the two cardiac compartments.
In taking the heart at the moment when it is in a state of repose — that
is, in the intervals between the two contractions — we find that its two pouches
are being rapidly filled with the blood brought to it by the veins. When suffi-
ciently replete, the auricles slightly contract and push a portion of the fluid they
contain into the ventricles — these contracting irumediately after, to propel the
blood into the arteries. This passage of the blood into the arteries is a necessary
consequence of the contraction of the ventricles, as at the moment when this
occurs the auriculo-ventricular valves are raised, and so prevent the reflux of
the blood into the auricles. This fluid is then forced to enter the arterial orifices,
the valves of which are separated under the impulsive effort communicated to
the column of blood. When the heart returns to a state of repose, these valves
fall down, preventing the return of the blood into the ventricles ; while the
mitral and tricuspid valves subside against the walls of these cavities, and thus
again allow the passage of blood through the auriculo-ventricular openings.
By the term systole is designated the contraction of the heart's cavities, and
by diastole, the repose or relaxation of its tissue. For each revolution of the
heart there is, therefore : 1. The gmieral diastole of the organ, during which the
two cardiac cavities are filled by the afflux of venous blood. 2. The systole of
' With Horses in health, the fluid exhaled into the pericardium is barely sufficient to
moisten and lubrify the free surface of its serous membrane. But in those worn out and
enfeebled by age, privations, or disease, it is not rare to see it accumulated in greater or less
quantity. To verify this, however, an examination ought to take place immediately after
death, as tlie accumulation of fluid in the serous cavities by cadaveric exhalation is common in
all animals.
THE HEART.
599
the auricles, the effect of which is the repletion of the ventricles. 3. The systole
of the ventricles, propelling the blood into the arterial systems ; after which
comes another period of general diastole.
Differential Characteks in the Heart of the other Animals.
In the Ox, Sheep, and Goat, the ventricular mass of the heart is more regularly conical
than in Solipeds; it has three longitudinal grooves, one of which is accessory and passes
behind the (left) ventricle.
In the Ox two small bones, named cardiac bones, are found in the substance of the aortic
zone. The largest is in the right side, at the point where the arterial ring is approximated to
the auriculo- ventricular zones; the other, situated in the left, is perhaps not constantly
present. The first is triangular in shape, curved to the right, and its base is directed
upwards. The right face lies against the auriculo-ventricular opening; the left is covered by
the walls of the aorta at its commencement. It is about an inch in length. (The Ox's heart
averages from about 3^ to 4^ lbs. ; that of the Sheep, from 5J to 7 oz. It is more elongated and
pointed in Ruminants than in the Horse or Pig. The large bone in the Ox's heart is elongated
from before to behind, flattened laterally and curved to the left; its surface is roughened, and
its lengtii is sometimes about 2 inches.
The left, or small bone, is usually flat-
tened on each side and triangular, one
of its points is directed forwards, another
backward, and a third inferioriy; its
length is about three-quarters of an
inch when fully developed. Besides the
Ox, a small cross-shapeil bone is found
in the heart of the Sheep, Pig, Camel,
Deer, Giraffe, and sometimes in the
Horse. Remak found in the pericar-
dium of the Ox, at the border of the
left auricle, a row of villi similar to those
discovered in the border of the chicken's
heart.)
The heart of the Pig resembles that
of the Horse; its direction is a little
more oblique, and the pericardium is
fixed to the sternum from the third rib
to the xiphoid appendix, as well as to
the diaphragm. (The cartilage is not
ossified until a late period.)
In the Dog and Cat, the heart is
ovoid or nearly globular. It rests al-
most entirely on the upper face of the
sternum ; its anterior face has become
the inferior, and its point, directed
backwards, touches the anterior surface
of the diaphragm. The pericardium is
attached to the aponeurotic centre of the
diaphragm.
Comparison of the Heart of Man
with that of Animals.
Fig 35<^
HUMAN LUNGS AND HEART (FRONT VIEW).
1, Right ventricle; 2, left ventricle; 3, right auricle;
4, left auricle ; 5, pulmonary artery ; 6, right
pulmonary artery ; 7, left pulmonary arteiy ; 8,
ligament of ductus arteriosus; 9, arch of aorta;
10, superior vena cava; 11, arteria innominata; 12,
right subclavian vein, with the artery behind it ;
13, right common carotid artery and vein; 14, left
vena innominata; 15, left carotid artery and vein;
16, left subclavian vein and artery ; 17, trachea ;
18, right bronchus ; 19, left bronchus ; 20, 20,
pulmonary veins; 21, superior lobe of right lung;
22, middle lobe ; 2.S, inferior lobe , 24, superior lobe
of left lung ; 25, inferior lobe.
Tho human heart is ovoid, and
similar to that of Carnivora ; the ventri-
cular mass is not acute at its apex, as in Solipeds and Ruminants. Its direction is modified
in consequence of the antero-posterior flattening of tlie chest. It is situated across the median
plane of the thorax ; its right face in animals has become the anterior face in Man, and is
applied to the sternum ; the anterior border is in him the right border, and the posterior the
left border.
The organ is suspended obliquely downwards, forwards, and to the left ; consequently, the
right auricle is to the right of the sternum, between the third and fourth ribs, and the point
600 TEE ARTERIES.
on a level with the sixth left intercostal space. The auricular appendages, particularly the
right, are more rounded and bulging than in animals. The pulmonary veins, four in number,
open on the upper face of the left auricle.
There are no essential differences to be noted in its internal conformation. We may indi-
cate the presence of a fold that passes from the ring of Vieussens to the opening of the inferior
vena cava ; this is tlie Eustachian valve. We may also mention the Thebesian valve at the
entrance of tlie coronary vein.
The fibrous rings and muscular fasciculi are disposed as in the Horse.
The pericardium is a conical sac ; but instead of its base being presented upwards, it rests
against the tendinous centre of the diapliragm; its summit is lost among the large vessels;
and it adheres to the posterior face of the sternum.
SECOND SECTION.
The Arteries.
CHAPTER I.
GENERAL CONSIDERATIONS.
Definition. — The centrifugal vessels which carry the blood from the heart to
the various organs, are named arteries.
Division. — These vessels proceed from the heart by two trunks, wluch are
perfectly independent in the adult animal ; they originate, one in the right
ventricle, the other in the left.
The first of these trunks — which carries the dark blood — is the pulmonary
artery. The second conveys the red blood, and is named the aorta. There
exist, therefore, two groups of arteries — the pulmonary system, and the aortic
system.
General Form. — Single at their origin, the two arterial systems soon
divide into less voluminous trunks, which again subdivide into successively
decreasing canals, until at last their diameter becomes reduced to an extreme
degree of tenuity. In a word, the arterial trunks present the ramous disposition
of dicotyledonous plants. The total volume of the secondary trunks exceeds
that of the primary trunk, and the same relation exists between the respective
dimensions of the branches and their ramifications, to the ultimate divisions of
the artery. In tracing all the ramifications of one of these systems to a single
canal, it will be found that this canal is incessantly increasing, from its origin
to its termination, and that it represents a hollow cone with its apex at the
heart. ^
Particular Form. — Each artery is cylindrical in form, whatever its volume
may be. When the diameter of these vessels is measured at their origin and
' Berryer-Fontaine agaiij discusses this arrangement, and asserts that it is imaginary.
According to his calculations, the arterial blood in Man circulates in a cylinder, and not in a
cone. The measurements and the calculations we have made with ngard to the arteries of
Solipeds, have demonstrated once more that the volume of the terminal branches of an artery
Is greater than that of the latter. Consequently, we adhere to the old belief.
GENERAL CONSIDERATIONS. 601
their termination, between two collateral branches, no sensible difference is
perceived.
Mode of Origin. — The arteries are detached in &n angular manner from
the parent branches. Sometimes the angle of separation is more or less acute —
this is most frequently the case ; sometimes it is at a right angle, and at other
times it is obtuse. It will be readily understood that the degree of this angle
exercises a somewhat marked influence on the course of the blood. For example,
the blood from a principal vessel, in passing into the canal of a secondary one
which springs from it at an obtuse angle, must experience a notable check in its
impetus, because of the change in direction it has to encounter ; on the contrary,
the rapidity of the current is not modified to any appreciable degree in those
vessels which separate from them at a very acute angle. Towards the point of
separation, there is always remarked, in the interior of the vessel, a kind of spur,
the sharp border of which is towards the heart — thus dividing the current of
blood and diminishing the resistance. This spur resembles in its arrangement
the pier of a bridge, against which the waters are divided to pass on each side.
(When a short trunk divides abruptly into several branches, proceeding in
different directions, it is termed an axis. A very peculiar feature in the division
of arteries, however, and one which will be made amply conspicuous in the
following description, is their bifurcation or dichotoraous arrangement, which
prevails so largely.)
Course. — In the course pursued by an artery, it is necessary to consider the
situation occupied by the vessel, its direction, relations, and the anastomoses which
establish communication between it and the neighbouring vessels.
Situation. — The arteries tend constantly to recede from the superficial parts,
and to become lodged in the deeper regions ; in this way they are I'emoved from the
hurtful action of external causes — a tendency all the more marked as the arteries
are more considerable in volume, but which ceases to be manifested in the less
important ramuscules. These vessels, therefore, occupy either the great cavities
of the trunk, or the deep interstices on the internal face of the limbs ; when they
pass over an articulation, it is always on the side at which flexion occurs. But
in the limbs, for instance, the joints are flexed alternately in opposite directions,
and it then happens that the arteries in these regions have a slightly helicoid (or
spiral) arrangement. This is evident in the case of the femoral artery, which
passes round the inner face of the femur to become the popliteal artery ; and
also in the humeral artery, which is at first situated on the inner side of the
scapulo-humeral articulation, then winds around the humerus to be placed in
front of the elbow-joint.
Direction. — The arteries are sometimes rectilinear, and at other times more
or less flexuous. The latter disposition is evidently intended to prevent lacera-
tion of the vessels in organs capable of elongation and contraction, as may be
remarked in the tongue ; or to moderate the impetus of the blood, as in the
internal carotid arteries.
Relations. — In their course, the arteries may be in contact with the viscera,
nerves, muscles, bones, skin, and connective tissue.
a. In nearly every part of the body, the arteries maintain the most intimate
relations with the veins — sometimes with two of these vessels, when the artery is
placed between them ; sometimes with only one, which is always more superficial.
h. The arteries are usually accompanied by nerves belonging to the cerebro-
spinal or sympathetic systems. Those of the latter category are distinguished by
602 THE ARTERIES.
the reticular interlacing they form around the visceral arteries ; their structure
will be alluded to presently.
c. Lodged, for the most part, in the interstices of the muscles, the arteries
contract relations with these organs which it is very important to know, from
a surgical point of view. Some of these muscles lie parallel with important
arteries, and for this reason have been designated satellite muscles ; they serve to
guide the surgeon in searching for the arteries, by the more or less salient relief
their presence affords beneath the skin.
It is worthy of remark that the arteries are not included in the fibrous
sheaths enveloping the muscles ; these vessels nearly always occupy, with the
nerves wiiich accompany them, special lodgments from the approximation of
several aponeurotic sheatlis. When they pass through the substance of a muscle
— which sometimes happens — they are covered by a fibrous arch or ring, which
protects them from compression during muscular contraction — the arch or ring
receiving on its convexity the insertion of fibres from the muscle.
d. Nothing is more common than to see the arteries in direct relation with
the bones — as, for instance, the aorta, intercostals, etc. Neither is it very rare
to find a more or less thick layer of muscle between the arteries and portions of
the skeleton. In every case, a knowledge of the relations between the arteries and
bones is important to the surgeon ; as it enables him to interrupt the circu-
lation temporarily in these vessels, by exercising external pressure on the points
of their course which correspond to the several bones, and thus diminish their
calibre by flattening them.
e. In consequence of their deep situation, the arteries are, in general, distant
from the skin ; there are, nevertheless, some which course immediately beneath|
that membrane ; but these are only found about the head and in the extremities.
/. Lastly, all the arteries are enveloped by a layer of connective tissue, which
forms around them a kind of sheath, generally difficult to tear with the fingers,
and which isolates from the neighbouring parts, but chiefly the veins. This
connective tissue — more or less abundant according to the regions — is always loose
enough to allow the arteries to roll and be displaced with the greatest facility,
and thus to glide away from sharp bodies accidentally introduced into the tissues.
Anastomoses. — Very often the arteries are united to each other by communi-
cations, which have received the name of anastomoses, and which assure the
equable distribution of the blood in regulating its flow. There are distinguished :
1. Anastomoses hy convergence — formed by two vessels joining at their
terminal extremity in an angular manner, to form a third and more voluminous
trunk.
2. Anastomoses hy arches or hy inosculation — due to the junction of two
principal branches, which are inflected towards each other, meet, and unite to
form a single and curvilinear canal.
3. Anastomoses hy transverse communication — represented by ramifications
thrown transversely between two parallel arteries.
4. Mixed or composite anastomoses — in which are found a combination of the
different types enumerated above.
A knowledge of the anastomoses of vessels is of the highest practical interest ;
as these communications permit the surgeon, in extreme cases, to tie the principal
artery of a region without the latter experiencing any considerable nutritive
disturbance ; the blood continuing to amve by the collateral vessels which, at
first very small, gradually dilate from the eccentric pressure to which their walls
GENERAL CONSIDERATIONS.
are submitted. But these anastomoses, if they offer this immense advantage,
have also their inconveniences : we refer to the difficulties experienced in arresting
hfemorrhage in wounds of certain organs, owing to the relations of the principal
vessel with its communicating collaterals.
Mode of Distribution. — The branches an artery distributes in the neigh-
bouring organs are distinguished as terminal and collateral. The arteries, after
pursuing a certain course, divide into several branches — nearly always two, which,
as new arteries, continue the original vessel and take the name of terminal
Irojuches, because they really begin at the terminal extremity of that vessel.
The collateral vessels arise at various distances along the course of the arteries,
Fig. 360.
WEB OF frog's foot STRETCHING BETWEEN TWO TOES, SHOWING THE BL00D-VESSEI5
AND THEIR ANASTOMOSES.
a, a, Veins ; b, b, b, arteries, the capillaries being between.
and proceed in a lateral direction ; they increase in number as the arteries become
more supei-ficial.
The distinction between the terminal and collateral branches of arteries is not
always easy to establish, and is far from having an absolute value ; it possesses,
nevertheless, some importance, as it greatly facilitates description.
Termination. — Arteries terminate in the substance of the tissues by ex-
tremely fine and numerous ramuscules, which so frequently anastomose with each
other as to form a plexus or microscopical network, the meshes of which are very
close. These constitute the capillary sijstem, which again gives rise to ramifica-
tions of gradually increasing size — the veins. The capillary system is, therefore,
nothing more than a network of microscopical canals intermediate to the arteries
and veins.
In the erectile tissues, the mode of termination is different ; the small arteries
sometimes opening directly into the cells placed at the origin of the veins, without
passing through a capillary plexus. In describing the genital organs, we shall
notice, in detail, the termination of the arteries in the cavernous tissues.
Structure. — The walls of arteries offer a certain rigidity, which permits
601
THE ARTERIES.
these vessels to remain open when they are emptied of blood. The ancients
believed this was their normal condition, and that they were filled with air during
life. This was a grave error, as they contain nothing but blood. The gaping of
the arteries must be attributed solely to the physical properties of the tissues
composing their walls.
These walls comprise three tunics — an internal, middle, and external.
The internal tunic {tunica intima) is continuous with the endocardium of the
left heart on the one part, and on the other with the capillaries and veins. For
a long time it has been regarded as a serous membrane, but it has not absolutely
the same texture. It is composed of a simple endothelial layer which is in contact
with the blood, and is formed by fusiform cells that slightly bulge where their
nucleus is. The endothelium lies upon a layer of veiy fine elastic tissue (the
fenestrated membrane of Henle), perforated by openings which are occupied by
Fier. 3(33.
Fig. 361.
Fig. 362.
EPITHELIAL CELLS OP
BLOOD-VESSELS.
a, 6, From a vein ; c,
from an artery.
Magnified 350 dia-
meters.
FENESTRATED MEMBRANE
FROM THE CAROTID
ARTERY OF THE HORSE.
Magnified 350 diame-
ters.
NETWORK OF COARSE
ELASTIC TISSUE FROM
MIDDLE COAT OF PUL-
MONARY ARTERY OF
THE HORSE, THE FIBRES
BEING PIERCED WITH
CIRCULAR OPENINGS.
Magnified 350 diame-
ters.
a slightly fibrillated connective substance, and by ramifying and anastomosing
cells. Beneath this layer there is another, also composed of fine elastic and
connective fibres lying in a transverse direction, and which is attached to an
elastic layer (internal elastic layer) that determines the external limit of the deep
tunic of arteries in the aorta ; this layer is separated from the preceding by the
network of Langhans.
The middle tunic {tunica media) is remarkable for its thickness, its elasticity,
and its yellow colour in the principal vessels. It has for base several elastic parallel
layers, united by means of networks of fibres of the same kind, and having spaces
between them which are occupied by connective tissue and non-striped muscular
fibres ; these are arranged in a circular manner around the vessels. In the umbilical
and splenic (and also in the aorta, iliac, anterior mesenteric, and renal) arteries,
there are longitudinal muscular fibres. The proportion of these two elements
varies with the size and situation of the artery. In the large trunks— such as
the aorta, the elastic is more abundant than the contractile tissue ; in the
medium-sized vessels they are about equal : but in the small arteries, in which
the contractile force of the heart is lost because of their distance from it, the
muscular fibres almost exclusively compose the middle tunic.
GENERAL CONSIDERATIONS.
605
Fig. 364.
The external tunic (tunica adventitia) is only a layer of connective tissue, with
some longitudinal recticulated elastic fibres in its deeper part. Though this
tunic is very thin, yet it is strong ; as a ligature tied tightly around an artery
will rupture the other tunics, but not this.
The structure of the capillaries is not the same as that just described, but is
modified in proportion as they are fine. In the smallest capillaries, the walls are
formed by a thin amorphous membrane, in which (oblong) nuclei are somewhat
regularly disseminated ; in the finer arterioles, another layer external to this (the
contractile layer)^ and containing transverse nuclei, is
observed ; and in the larger arterioles — those imme-
diately succeeding the small arteries, these two nucleated
layers are enveloped by a thin tunic of connective tissue
{tunica adventitia).
(The most minute capillaries are merely tubes formed
by a single layer of transparent, thin, nucleated, endo-
thelial cells, joined by their margins. When perfectly
fresh, the capillary does not show the edge of the cells,
owing to the uniform refractive property of the wall of
the tube. The nuclei show an internuclear plexus of
fibrils. The cells are united by cement substance, and
here and there minute dots or slits may be seen, which
have been supposed by some authorities to be openings
— stomata, or stigmata. The narrojvest meshes of capil-
laries occur in the lungs and liver, and the wider in
muscle, beneath serous membranes, and in the organs of
sense. The widest capillaries are found in the liver, and
the narrowest in the retina and muscle.)
Vessels and nerves. — The arteries are provided with
vessels termed vasa vasorum, which are furnished either
by the arteries themselves, or by neighbouring vessels.
These vasa vasorum form a superficial network with
quadrilateral meshes, and a deep plexus, the principal
branches of which are helicoidal. The majority of
anatomists believe that this plexus does not extend be-
yond the external tunic.
The lymphatic vessels maintain intimate relations,
in certain regions, with the capillaries. In the brain
and spleen there has been discovered, Around the arterial
capillaries, a vessel that completely envelops them, and
which has been named the lymphatic sheath.
The nerves, designated vasa motors, accompany the
vessels and penetrate the muscular tunic, in which they
are distributed. These vasomotor filaments join the branches of the capillaiy
plexuses, and form, at the points where they meet each other, ganglionic enlarge-
ments ; from these arise the fibres of Remak, the termination of which is
unknown.
Anomalies in the Arteries. — In their arrangement, the arteries very often
present anomalies which the surgeon should be guarded against. These usually
are related to their number, their point of origin, and their volume. In a purely
anatomical and physiological point of view, however, these anomalies are of no
41
TRANSITION OF A MINUTE
ARTERY OF THE BRAIN
INTO CAPILLARY VES-
SELS.
1, Minute artery ; 2, tran-
sitional capillary; 3,
coarse capillary with
thick coat, represented
by a double contour line ;
4, fine capillary with
single contour. The
nuclei are seen widely
scattered in 4 and 3 ;
more closely congregated
in 2 ; and still more so
in 1, where they form an
epithelium. a, Trans-
verse elongated nuclei
of muscular cells, the
incipient muscular coat
of the artery.
606 THE ARTERIES.
moment ; as it matters little whether the blood comes from one source rather
than another, or that a collateral vessel becomes the principal at the expense of
the parent trunk, provided its relations are not altered, and the principle of
immutability of connections is maintained.
Preparation of the Arteries. — This requires two successive operations : 1. lujection.
2 Dissection.
Injection of the arteries. — The object to be attained in injecting these vessels, is to intro-
duce into their interior a solidifiable substance which will cause them to assume the volume
and f'onformation they presented during life, when they are filled with blood.
Tallow, coloured by lamp-black, is the most convenient and general injecting material.
Sometimes a solution of gelatine, with the addition of a certain quantity of plaster of Paris, is
used ; but this is seldom employed in the French scliools. A copper or brass syringe, and
a cannula witli a stop-cock to fit ou its extremity, are the only instruments necessary to propel
these matters into the arteries.
The following are the details of the operation, when it is desired to make a general injec-
tion : — The animal being placed ou a table, the carotid artery is exposed by an incision in the
jugular channel, and opened longitudiually. A ligature is applied above the opening, and the
tube, with the stop-cock, is firmly fixed in the cavity of the artery towards the heart by
a second ligature. The injection, previously prepared, is taken up by the syringe, which ia
fitted into the tube, and the piston pushed, in order to drive the contents of the instrument
into the arterial canals.
To perform the operation successfully, the following precautions are to be attended to:
1. Inject tlie vessels of an animal killed by effusion of blood, and yet warm. 2. If suet is
employed, and wiiich is always to be recommended, make it so hot that tlie finger can scarcely
endure it. When it is colder than this it solidifies too quickly, and when hotter it shrivels up
the sigmoid valves, passes into the left ventricle, and from thence into the auricle and pul-
monary veins — an acciilent generally attributed to the too-powerful force applied to the piston
of the syringe. 3. Do not make any undue pressure on the piston, though this does not strain
the sigmoid valves so frequently as is believed. 4. Cease injecting when the arteries react, by
their elasticity, on the piston, so as to drive it back in the syringe.
In order to ensure the retention of the injected matter in the arteries, and prevent the
sigmoid valves being forced, a cork may be introduced into the aorta through the left ventricle,
and firmly tied there by a strong ligature ; the cork should have a transverse notch for the
reception of the li<:ature.
Instead of injecting by the carotid, a long curved cannula may be fixed to the aorta itself,
after making an opening in the left side of the chest, on a level with the heart, by the ablation
of two segments of the ribs, and incising the pericardium and left auricle to introduce it. This
mode allows the tallow to be injected at a very liigh temperature, and gives the best results,
for it can then penetrate to the capillaries, if we only know how to manage it ; in certain organs
the injected matter may even be made to return by the veins.
But no matter what procedure may be adopted, there are several parts into which the
tallow can never be made to enter by a general injection ; these are the four extremities. So
that a special operation must be resorted to, in order to fill their vessels. After separating
them from the trunk, by sawing them through above the knees and hocks, tliey should be
allowed to steep for two hours in water, constantly kept up to a temperature of from 140° to
160° Fahr. at most; it is then easy to inject them, either by the posterior radial artery, or the
anterior tibial, after tying those branches which may be open at the cut extremity of the limbs.
If it is desired to make partial injections in other parts of tlie body, it will be better not to
sepaiate them from the trunk; but only to tie those vessels which anastomose between the
arteries to be filled and those which are not. For example, to inject the arteries of the head,
it suffices to push the mixture into one of the common carotids, after ligaturing the other in
the middle of the neck, and both vertebrals in the space between the two portions of the
scalenus muscle.
We may give the tallow more fluidity, and a higher degree of penetration, by mixing with
it a little spirits of turpentine ; or more consistence, in adding to it a small proportion of
beeswax.
The two following mixtures are borrowed from Oruveilhier's Anatomy : —
Tallow 9 parts.
Turpentine 1 part.
Ivory Black, mixed witli spirits of turpentine . . 2 parts.
PULMONARY ARTERY. 607
For preservative injections : —
Beeswax 1 part.
Tallow 3 parts,
Vermilion, indigo, or Prussian blue, previously
mixed in oil of turpentine A sufficient quantity.
Of course, it is well understood tliat these instructions are only intended for the dissecting-
room injections necessary for the study of descriptive anatomy. To inject the capillaries, it is
requisite to have recourse to other substances and other procedures. Suffice it to say that
these injections are made with cold fluids, such as varnish, alcohol, or spirits of turpentine,
holding ill suspension extremely fine colouring matter, gum arable dissolved and coloured by
a substance also in solution, etc., or, better still, colours rubbed up in oil, and mixed with oil
of turpentine.
Dissection of the arteries. — There are no general rules to be given for the dissection of
arteries.
CHAPTER II.
Pulmonary Artery (Fig, 349, e).
Preparation. — The pulmonary artery is not filled by tlie general injection mentioned above.
It is directly injected by propelling the tallow into the right heart by the anterior vena cava,
after tying the posterior vena cava.
The pulmonary artery arises from the infundibulum {conus arteriosus) in the
right ventricle, is directed upwards and then backwards, describing a curve the
concavity of which is infero-posterior ; on reaching the left auricle, it divides
into two secondary arteries — one for each lung. These arteries enter the pulmonary
tissue with the bronchi, and exclusively ramify in it.
The pulmonary artery accompanies the trunk of the aorta on the right side,
and is enveloped with it in a serous sheath, a dependency of the visceral layer of
the pericardium. At its origin, it is flanked before and behind by the auric ules
and the cardiac vessels. About the middle of its course, it is united to the
posterior aorta by means of a yellow elastic fibrous cord (the ligamentum arte-
riosum), the remains of the ductus arteriosus which, in the foetus, establishes a
large communication between these two vessels (*Fig, 349, e).
The w^alls of the pulmonary artery are much thinner than those of the aorta,
and are yellow and elastic, as in the other canals of the same order. We, how-
ever, have seen them in an Ass, formed almost entirely of red muscular fibres,
analogous to the fasciculi of the heart.
It may be repeated that the pulmonary artery conveys to the lungs the dark
blood carried to the right heart by the veins of the general circulation.
THE ARTERIES.
CHAPTER III.
THE AORTA.
If we take a general survey of the aorta, we shall find that it arises from the
base of the left ventricle, ascends to beneath the dorso-lumbar column, curving
backwards and downwards, and reaches the entrance to the pelvis, where it
terminates by four branches. It furnishes, besides, about from 2 to 2^ inches
from its origin, a secondary trunk, which soon divides into two new arteries, the
right and largest of which gives off a particular trunk — the common origin of
the two long vessels destined for the head.
This disposition permits us to recognize in the aorta seven principal sections :
1. The aortic trunk, or common aorta — the source of all the arteries, and
giving origin to the anterior and posterior aorta. It only furnishes blood
directly to the heart itself.
2. The ijosterior aorta — the real continuation of the common aorta — is distri-
buted to the posterior moiety of the trunk and to the abdominal limbs ; it
terminates by a double bifurcation.
3. The internal and, 4, external iliac arteries — branches of this bifurcation
which are almost entirely expended in the posterior limbs.
5. The anterior aorta — the smallest of the two trunks furnished by the
common aorta — is chiefly destined for the anterior moiety of the trunk and the
thoracic limbs.
6. The axillary arteries, or brachial trunks ; these arise from the bifurcation
of the preceding artery, and are continued by their terminal extremity into the
fore limbs.
7. The carotid arteries, or arteries of the head ; these emanate by a common
trunk from the right brachial bifurcation.
Article I. — Aortic Trunk, or Common Aorta.
The point of departure for all the arteries carrying red blood, the common
aorta, proceeds from the left ventricle by becoming continuous with the festooned
fibrous zone which circumscribes the arterial orifice of that cavity. It passes
upwards and a little forwards, bifurcating, after a course of 2 or 2^ inches, into
the anterior and posterior aortoe.
Its volume, inferior to that of its two terminal branches, is not uniform ; at
its origin, and opposite the sigmoid valves, it presents (an enlargement — the
buJbus a or fee— caused by) three dilatations, each corresponding to what is de-
scribed as the si7ius of the aorta (sinus aortici, sinus Valsah'ce).
Included, on the right side, in the crescent formed by the auricular mass ;
in relation, on the left side, with the pulmonary artery — which is joined to it by
means of cellulo-adipose tissue traversed by the cardiac nerves — the common
aorta forms, with the latter artery, a fasciculus enveloped by the visceral layer
of the pericardium, which is reflected as a sheath around these two vessels.
Two collateral arteries are given off directly from the aorta — the cardiac or
coronary arteries.
THE FOSTERIOR AORTA. 609
Cardiac or Coronary Arteries (Figs. 349, 350).
There are two cardiac arteries — a right and left — exclusively destined for the
tissue of the heart.
Right Coronary Artery (Figs. 349, 1 ; 350, V). — This originates from
the front and to the right of the aorta, at the free margin of the semilunar
valves, and proceeds perpendicularly, or at a right angle, from the trunk, passing
forwards to the right of the pulmonary artery, beneath the anterior auricle ;
then to the right and backwards, to reach the auriculo-ventricular groove, which
it follows till near the origin of the right ventricular groove. Here it divides
into two branches — one vertical, descending in this groove to the apex of the
heart, which it bends round to the front, and anastomoses with an analogous
branch of the left coronary artery ; the other is horizontal, smaller than the
first, and follows the original course of the artery in the auriculo-ventricular
groove, also inosculating with the artery of the left side.
Left Coronary Artery (Fig. 349, 2). — This arises opposite the preceding,
at the same angle of incidence, passes behind the pulmonary artery, and divides —
under the left or posterior auricle — into two branches similar in every respect to
those of the right artery. The vertical branch descends in the left perpendicular
groove ; the horizontal is lodged in the coronary groove ; and both anastomose
with the analogous branches of the opposite vessels.
From this arrangement, it results that the heart is surrounded by two arterial
circles — a vertical, or ventricular, which has been compared to a meridian ; and
a horizontal, or auriculo-ventricular, analogous to an equatorial circle.
In their course — which is more or less tortuous — the coronary arteries throw
out a considerable number of ramuscules, which enter the muscular tissue of the
heart. The vertical circle gives off branches that are entirely ventricular ; while
from the horizontal circle come the superior or auricular, and inferior or ventri-
cular branches. Among the latter there is one which, rising from the right
artery — where it bends at an angle beneath the auricle — enters the substance of
the right ventricle by passing round the puhnonary infundibulum ; its ramifica-
tions anastomose with those of a similar branch from the left artery, and in this
way establishes another communication between the two vessels.
Article II. — Posterior Aorta.
Course. — This artery (Fig. 349, 9) is a continuation of the aorta, which it
nearly equals in volume, and from which it passes upwards and backwards, de-
scribing a curve the convexity of which is antero-superior, and which is known
as the arch of the aorta. It thus reaches the left side of the inferior face of the
spine, about the seventh dorsal vertebra, behind the posterior extremity of the
longus cohi muscle, and is then carried directly backwards, following the bodies
of the vertebrte, though a little to the left at first ; it gradually inclines to the
right, however, and reaches the median plane at the pillars of the diaphragm.
Here it passes through the opening circumscribed by these two pillars {hiatus
aorticus), enters the abdominal cavity, and extends to the entrance of the pelvis,
under the spine, still preserving its median position. On reaching the last
intervertebral articulation, the posterior aorta terminates by a double bifurcation,
from which arise the external and internal iliac arteries.
610 THE ARTERIES.
Relations. — To facilitate the study of its connections, the posterior aorta may
be divided into two sections — one thoracic, the other abdominal.
a. At its origin or arch, the thoracic aoria is crossed to the right by the
trachea and oesophagus ; on the opposite side, it is related to the puhnonary
artery and the left lung. For the remainder of its extent, it is comprised
between the two layers of the posterior mediastinum, and through these is in
relation with the pulmonary lobes, which are fissured for its reception ; this
fissure is much deeper in the left than the right lung. Above, it is in contact
with the bodies of the last twelve dorsal vertebrae, and is accompanied on the
right by the large vena azygos and the thoracic duct ; the latter is often carried
to the left for the whole or a portion of its extent.
(Remak observed muscular fibres on the external face of the aortic arch and
thoracic aorta in the Horse, Sheep, and Pig ; the fasciculi they form are so large
as to be visible to the naked eye.)
h. The posterior or abdominal aorta, enlaced by the abdominal nerves of the
great sympathetic, is in relation, above, with the bodies of the luml)ar vertebrae,
the originating tendon of the diaphragmatic pillars, Pecquet's reservoir {recepta-
culum chyli), and the common inferior vertebral ligament ; it passes above the
pancreas and the peritoneum, the latter by its sublumbar layer covering the
posterior two-thirds of the vessel. On the right, it is accompanied by the posterior
vena cava, which perhaps it slightly pushes to the left of the median plane.
Collateral bra?iches. — The arteries emanating from the posterior aorta during
its long course, very naturally form two classes ; some are designated parietal,
because they are distributed to the parietes of the great splanchnic cavities ; the
others are the visceral branches, destined for the organs lodged in these cavities.
Among the parietal branches, may be noticed : —
1. The intercostal arteries, furnished by the thoracic aorta.
2. The diaphragmatic (or phrenic) arteries, the origin of which is placed on
the limits of the two portions of the vessel.
3. The lumbar arteries, and the middle sacral artery, arising from the abdo-
minal aorta.
The visceral branches are : —
1. The broncho-CBSophageal trunk, emitted by the thoracic portion of the
aorta,
2. The coeliac axis, great (or anterior) mesenteric artery, small (or posterior)
mesenteric artery, renal arteries, spermatic arteries, and small testicular (or artery
of the cord) or uterine arteries, which emerge from the abdominal portion.
Preparation of the posterior aorta and its collateral branches. — Immediately after injecting
according to one of the modes recommended at p. 606, place the subject in the first position,
the two posterior limbs being well extended backwards. Open the abdominal cavity, and
remove from it the intestines in the manner already indicated. Tlie tallow having become
perfectly solidified during these necessary manipulations, dissection may be proceeded with
at once. It is requisite, however, to remove the right and left walls of the thoracic cavity
beforehand, by suwing through the last fourteen or fifteen ribs at six or seven inches from their
superior extremity, and then separating them from the sternum by the saw, taking the pre-
caution of detaching the peripheral insertion of the diaphragm. It is recommended to prepare,
from before to behind, the various visceral branches of the vessel ; first, the hroiiclio-cesophageal
artery; then the coeliac axis; next, the anterior mesenteric artery and the renal arteries, after
spreading out the intestinal mass as in Fi?. 283 ; and, lastly, the small mesenteric and testicular
arteries, aftei- arranging the intestines as in Fig. 366.
THE POSTERIOR AORTA. 611
Parietal Branches of the Posterior Aorta.
1. Intercostal Arteries (Fig. 375).
The intercostal arteries, placed — as their name indicates — in the intervals of
the ribs, number seventeen pairs.
Origin, Course, and Distribution. — The last thirteen arise from the thoracic
aorta only ; the first comes from the cervical artery ; and the next three are
furnished by a special branch of the dorsal artery.
The aortic intercostals emerge at a right angle from the superior plane of
the trunk, on a level with the bodies of the dorsal vertebra, and at regular
intervals. Their origin is nearer that of the arteries on the opposite side as
they are more anterior, the first two or three arising in pairs from a common
trunk.
These aortic intercostals ascend to the vertebral bodies, beneath the pleura,
in crossing the direction of the sympathetic nerve-trunk and — the arteries of the
right side only — in addition, that of the vena azygos and the thoracic duct, to
the superior extremity of the intercostal spaces, where those of both sides divide
into two branches — the one inferior, or j^roper intercostal ; the other superior, or
dorso-spinal.
The inferior and superior branches of the first four intercostal arteries
emanate solely from the trunk that furnishes them, and which is the superior
cervical artery for the first intercostal, and the subcostal branch of the dorsal
artery for the succeeding three.
Inferior or intercostal branch. — This branch, the most considerable of the
two, placed at first beneath the pleura, then between the two intercostal muscles,
is lodged, along with a satellite vein and nerve, in the furrow on the posterior
face of the rib, and descends to the inferior extremity of the intercostal space,
where it terminates in the following manner : the first twelve or thirteen
branches anastomose with the intercostal ramifications of the internal thoracic
artery and its asternal branch ; the others are prolonged into the abdominal
muscles, where their divisions communicate with those of the anterior and
posterior abdominal arteries, as well as with the circumflex iliac.
In their course, these intercostal branches give arterioles to the pleurae, the
ribs, and the thoracic muscles, with the perforating ramuscules which cross these
muscles to ramify in the skin and the panniculus carnosus, but which, of course,
are absent where the pectoral wall is covered by the thoracic limb.
Superior or dorso-spinal branch. — This passes directly upwards to be dis-
tributed to the spinal muscles of the dorsal region and the integument covering
them, after giving off, when passing the intervertebral foramen, a branch which
enters the spinal canal by that opening, and is destined for the spinal cord and
its envelopes. An auxiliary of the middle spinal artery, this branch will be
studied at greater length when the cerebro-spinal artery is described.
Variations in origin. — Not unfrequently the first two pairs of aortic inter-
costal arteries proceed from a single trunk, thus giving rise to four branches ;
and this trunk is also often the source of these four intercostals and the bronchial
and oesophageal arteries, when its volume is very considerable. It is much
smaller when it only gives off the second pair of intercostals, which is sometimes
the case.
612 TEE ARTERIES.
2. Lumbar Arteries.
These are five or sLx in number, and do not differ in their general arrange-
ment from the intercostal arteries ; they having the same mode of origin, the
same division into two branches, and the same distribution. The superior, or
lumbo-spinal branch, is much larger than the inferior, and goes to the muscles
and integuments of the lumbar region ; it also furnishes a branch to the spinal
cord. The inferior branch passes above the large and small psoas muscles, giving
them numerous twigs, and extending to the muscular portions of the transverse
and small oblique abdominal muscles, where their ramifications anastomose with
those of the circumflex iliac artery.
The last, and sometimes also the second-last, lumbar artery arises from the
internal ihac trunk ; the others emerge directly from the iUac aorta.
3. Diaphragmatic (or Phrenic) Arteries.
These are two or three small vessels which spring from the aorta as it passes
between the two pillars of the diaphragm, and are destined for that muscle.
The left pillar receives a very insignificant branch, but the right has two, the
most considerable of which is alone constant ; it sometimes sends subpleural
ramuscules to the right lung.
4. Middle Sacral (Sacra Media) Artery.
This vessel is often absent, and when it exists is very variable in size, though
always extremely slender. It arises from the terminal extremity of the aorta,
in the angle comprised between the two internal iliac arteries, and is carried to
the inferior face of the sacrum, where it is expended in lateral ramifications
which go to the periosteum. It has been thought necessary to notice this artery,
as it attains a considerable volume in Man and some animals, and continues the
aortic ramifications beneath the sacral portion of the vertebral column.
Visceral Branches of the Posterior Aorta.
1. Broncho-cesophageal Artery (Fig. 318, m).
Destined for the lung, the visceral pleura, the mediastinum, and the oeso-
phagus, this artery arises, not, as is generally said, in the concavity of the arch
of the aorta, but opposite to it, and very near, but to the right of, the first pair
of intercostals ; often even in common with these arteries and with the second
pair.^ After leaving the aorta, it insinuates itself between that trunk and the
oesophagus, and above the bifurcation of the trachea divides into branches, the
bronchial arteries. In its short course, it gives off the two ascqyhageal arteries
and a certain number of innominate ramiiscuhs.
Bronchial Arteries. — The disposition of these two vessels is extremely
simple ; they enter the lung with the bronchi — one to the right, the other to
the left — and there break up into arborescent ramifications that follow the air-
tubes to the pulmonary lobules.
(Esophageal Arteries. — These two arteries are placed in the posterior
mediastinum, one above, the other below the oesophagus, which they accompany
for a short distance backwards, to the extremity of that canal.
' See Intercostals.
THE POSTERIOR AORTA. 613
The superior esophageal arter//, much more voluminous than the inferior,
inosculates with a branch of the gastric artery. In its course it gives descending
branches to the oesophagus, and ascending ones to the mediastinum.
The inferior oesophageal artery also anastomoses with a branch of the gastric ;
most frequently with that noticed above. Ifc likewises furnishes ascending and
descending divisions ; the latter, however, going to the mediastinum, and the
former to the oesophagus.
Innominate Ramuscules. — The innominate ramuscules of the broncho-
oesophageal trunk do not all proceed directly from it, there being always a
certain number which emerge from the bronchial or oesophageal arteries. They
are more particularly distributed to the trachea, to that portion of the oesophagus
which is in contact with the posterior extremity of that tube, to the bronchial
glands, the mediastinum, and the pulmonary pleura. Those destined for the
latter form on the surface of the lung — along with the divisions of the pleural
branch furnished by the gastric artery — a beautiful plexus.
2. CcELiAC Artery (or Axis) (Fig. 365, 2).
This artery arises at a right angle from the inferior face of the aorta,
immediately on the entrance of that vessel into the abdominal cavity. After
a course from half to three-fourths of an inch at most, in the middle of the solar
plexus, and beneath the superior face of the pancreas, this trunk separates into
three branches — a middle, the gastric artery ,- a right, the hepatic artery ; and a
left, the splenic artery.
1. Gastric Artery (the coronaria ventriculi of Man) (Fig. 365, 3). — This
artery descends on the large tuberosity of the stomach, extends to near the
insertion of the oesophagus, and then divides into two branches — the anterior
and posterior gastric. The first passes behind and to the right of the oesophagus,
and crossing the small curvature of the stomach, gains the anterior face of that
viscus, where it separates into flexuous and divergent branches that run beneath
the serous membrane, and are carried more particularly towards the left cul-de-sac
and around the cardia. The second vessel is distributed in the same manner to
the posterior wall of the organ, but chiefly to the right sac.
Independently of these two arteries, the gastric trunk gives off a third and
constant branch, which often comes from one of its two branches, and sometimes
also from the coeliac axis itself, or from the splenic. This branch accompanies
the oesophagus, along with the right pneumogastric, crosses the opening of the
right pillar of the diaphragm to enter the pectoral cavity, and then divides into
two branches, each of which anastomoses with one of the oesophageal arteries,
and is then thrown over the posterior extremity of a pulmonary lobe, which it
covers with a magnificent subpleural reticular arborization. This gastro-pulmo-
nary artery often anastomoses with the superior oesophageal branch only, and
goes exclusively to the right lung ; for the left lung and the inferior oesophageal
artery, in this case there is a special branch that emanates from the anterior
gastric. It is not rare to meet with varieties of another kind, but of which
it is not necessary to speak ; inasmuch as in these pleural ramifications we find
a disposition common to the whole arterial system — distribution almost invari-
able, origin very inconstant.
2. Splenic Artery (Fig. 365, 7). — The largest of the three branches of
the coeliac axis, this artery is directed downwards and to the left, lying beside
its satellite vein and the superior face of the left extremity of the pancreas. It
614
TEE ARTERIES.
reaches the anterior fissure of the spleen, in turning round the cardiac extremity
of the stomach, passes along the entire length of that fissure, and leaves it only
near the point of the organ to throw itself into the great omentum, where it is
named the left gastro-omeatal artery (or gastro-epiploica sinistra).
The splenic artery gives off, during its course, very numerous collateral
oranches. These are :
(1) External or splenic ramifications, which immediately enter the substance
of the spleen (Fig. 365).
Fig. 365.
ABDOMINAL OE POSTERIOR AORTA AND CCELIAC AXIS, IN THE HORSE.
1, Aorta; 2, cceliac axis; 3, gastric artery, 4, posterior gastric artery; 5, anterior gastric artery,
6, pleural brancii of the gastric artery; 7, splenic artery; 8, gastric ramuscules; 9, omental
rainuscules of the splenic artery ; 10, left gastro-splenic artery ; 10', one of the gastric branches
of that vessel; 11, hepatic artery; 12, pyloric artery; 13, right gastro-oniental artery; 14,
duodenal artery ; 15, trunk of the great mesenteric ; 16, first branch of the left fasciculus of that
artery, communicating with the duodenal ; 17, right renal artery. C, Oesophagus ; E, stomach,
lifted against the liver and diaphragm ; D, duodenum ; F, f', f", lobes of the liver; /, Spigelian
lobe (caudate lobe), S, spleen; R, r, kidneys and supra-renal capsules, s, s ; u, u, ureters; G,
posterior vena cava ; P, vena porta; ; p, p, crura or pillars of the diaphragm.
(2) Internal or gastric ramifications, also called the short vessels (vasa hrevia)
m Man, which are comprised between the two layers of the gastro-splenic
omentum, and go to the great curvature of the stomach, where they nearly
always divide into two branches — one which ramifies on the anterior wall of the
TBE POSTERIOR AORTA. 615
viscus, the other on its posterior wall. These vessels inosculate with those sent
to the membranes of the stomach by the proper gastric artery (Fig. 365, 8).
(3) Posterior or omental twigs of little importance, destined for the great
omentum (Fig. 365, 9).
Left gmtro-omental artery (Fig. 365, 10). — This artery follows the great
curvature of the stomach to a distance varying with the state of repletion of
that viscus, passing between the two layers of the omentum, and inosculating
with the right gastro-omental artery. The branches it sends off on its track are
descending or omenta}., and ascending or gastric; the latter being disposed
exactly like the analogous branches emanating directly from the splenic
artery.
3. Hepatic Artery (Fig. 365, 11). — Applied to the superior face of the
pancreas, and encrusted, as it were, in the tissue of that gland — the anterior
border of which it follows — the hepatic artery is directed from left to right,
passes under the posterior vena cava, which it crosses obliquely, reaches the
posterior fissure of the liver {foramen of Winsloiv), and enters it with the vena
portae to break up into several branches, the ultimate divisions carrying nutrient
blood to the lobules of the liver.
Before reaching that organ, however, the hepatic artery furnishes the
'pancreatic branches, the pyloric artery, and the right gastro-omental artery.
Pancreatic arteries. — Irregular and very numerous, these branches are
detached from the hepatic artery on its passage over the superior face of the
pancreas, and plunge into the tissue of that gland, the arterial blood of which
is chiefly derived from this source.
Pyloric artery. — This vessel arises at the dilatation towards the origin of the
duodenum, before the hepatic artery enters the posterior fissure of the liver, and
most frequently by a trunk common to it and the right gastro-omental artery.
It passes towards the small curvature of the stomach, and sends off branches
around the pylorus, which anastomose with the posterior gastric arteries and the
right gastro-omental artery.
Right gastro-omental artery {gastro-epiploica dextra) (Fig. 365, 13). — This
artery crosses the duodenal dilatation inferiorly and posteriorly, to place itself
in the substance of the great omentum ; in doing which it passes along the
large curvature of the stomach, and anastomoses by inosculation with the left
gastro-omental artery. In its course, it throws off omental and gastric branches,
which are analogous to those emanating from the latter vessel. Before crossing
the duodenum, it also emits a particular branch, designated in treatises on
Veterinary Anatomy the duodenal artery; this is a somewhat considerable
division, which follows the small curvature of the duodenum in the substance of
the mesentery, and joins the first artery belonging to the left fasciculus of the
great mesenteric, after furnishing some twigs to the pancreas, and numerous
branches to the duodenum (Fig. 365, 14).
In terminating the description of the right gastro-omental artery, it may be
remarked that the stomach— owing to the anastomoses uniting that vessel with
the artery of the left side — is suspended, as it were, in a vertical arterial circle,
formed by the splenic and left gastro-omental arteries on the one part, and the
hepatic and right gastro-omental arteries on the other — a circle the concavity of
which sends out on the stomach a great number of divisions that communicate
with the arterial ramuscules proper to that viscus.
616 THE ARTERIES.
3. Antekioe or Great Mesenteric Artery (Figs. 365, 306).
The anterior mesenteric arteri/, which ahnost entirely supplies the mass of
intestines with blood, is as remarkable for its volume as for its complicated dis-
tribution. This complexity, together with that of the intestine itself, gives rise
to some difficulty in the study of this vessel ; but this may be averted by adopting
the mode of description — as simple as it is methodical — resorted to in his lectures
by Lecoq.
The anterior mesenteric arises at a right angle from the posterior aorta, at
the renal arteries, and at 2 or 2^ inches behind the coeUac axis, from' which it is
separated by the pancreas ; it is directed immediately downwards, enlaced by the
anastomosing nerves of the solar plexus, and divides, after a course of from 1 to
1^ ^ inches, into three fasciculi of branches, which are distinguished as left, right,
and anterior. The left fasciculus goes to the small intestine ; the right is dis-
tributed to the terminal portion of that intestine, the cascum, and the first portion
of the flexure formed by the large colon ; the anterior is carried to the second
portion of that flexure, and to the origin of the small colon. The order in which
these three fasciculi have been indicated will also be that followed in their descrip-
tion ; this has, as will be observed, the advantage of recalling to the memory the
regular succession of the various parts of the intestine, and consequently the
passage of the food in this important portion of the digestive canal.
A. Arteries of the Left Fasciculus (Fig. 366, 2). — These arteries
number from fifteen to twenty, and are named the arteries of the small
intestine {vasa intestini tenuis), because of their destination. All spring at
once from the anterior mesenteric artery, either separately, or several in common,
and pass between the two layers of the mesentery to gain the intestine. Before
reaching the small curvature of that viscus, each divides into two branches, which
go to meet corresponding branches from the neighbouring arteries, and to anasto-
mose with them by inosculation ; from this arrangement- results a series of
uninterrupted arterial arches, the convexity of which is downwards, and which
exist for the whole length of the intestine, opposite, and in proximity to, its
concavity. From the convexity of these arches emanate a multitude of branches
that arrive at the inner curvature of the intestine, and the divisions of which pass
to each of the faces of that viscus, to rejoin and anastomose on its great curvature.
These divisions are situated beneath the peritoneum or in the muscular tunic,
and send the majority of their ramuscules to the mucous tunic, which is there-
fore distinguished by its great vascularity — a feature common to all the hollow
organs in the abdominal cavity.
Such is the general arrangement of the arteries of the small intestine ; and it
remains to indicate some of their special characters. These are as follows : 1.
The longest arteries of the small intestine are the most posterior, as they follow
the development of the mesentery, by which they are sustained. 2. The anterior
arteries generally form two series of superposed arches, before sending their
divisions to the intestine. 3. The first reaches the duodenum and anastomoses
with the duodenal artery — a branch given off by the coeliac axis. 4. The last
communicates with the ileo-caecal artery — one of the branches of the right
fasciculus.
' This trunk of the anterior mesenteric is usually, in old horses killed for dissection, the
seat of a more or less voluminous aneurism, whicii sometimes extends to the artery placed at
the origin of the branches of the right fasciculus, and it is not unfrequeutly met with in one
or the other section of the anterior mesenteric artery.
TEE POSTERIOR AORTA. 617
B. Arteeies of the Right Fasciculus. — The right fascicuhis of the great
mesenteric artery constitutes, at first, a single trunk some inches in length, which
soon divides into four branches. These are as follows : the ileo-ccecal artery, the
two ccecal arteries, and the right or direct colic artery.
Ileo-Caecal Artery (Fig. 283, 3). — This vessel often has its origin from
the internal csecal artery. It is placed between the two layers of the mesentery,
follows for a short distance, and in a retrograde manner, the ileo-csecal portion
of the small intestine, and wholly anastomoses with the last artery of the left
fasciculus, after emitting a series of branches, which are distributed to the
intestinal membranes.
Caecal Arteries. — Distinguished into internal or superior, and external or
inferior, these two arteries pass downward and a httle to the right, towards the
concavity of the caecal flexure, embracing between them the terminal extremity
of the small intestine, and lying at the middle part of the csecal sac, following
its direction.
The superior, or internal ccecal artery, is lodged in the most anterior of the
fissm-es formed by the longitudinal bands of the cscum, and extends beneath
the serous tunic to nearly the point of the viscus, where it terminates by
anastomosing with the external caBcal artery. The branches furnished by this
artery during its course escape in a perpendicular direction, and distribute their
ramifications on the walls of the caecum (Fig, 283, 4),
The external, or inferior ccecal artery, passes between the csecum and the origin
of the colon, to descend along the first-named organ by placing itself in one of
the external fissures, which is situated outwardly and posteriorly. Arriving at
the point of the organ, this artery bends over it to anastomose with the vessel
just described (Fig. 283, 7). It gives off on its track a series of transverse
ramifications, similar to those of the latter artery ; and besides these, a remarkable
branch which may be named the artery of the ccecal arch. This branch is detached
from the principal vessel near the origin of the colon, and ascends to the caecal
arch, following its concavity outwardly to pass forwards and downwards to the
first portion of the large colon, where it disappears after following a certain
com'se. The nimierous collateral branches detached by this artery are sent to
the walls of the latter portion of intestine, and the arch of the caecum
(Fig. 283, 6).
Right or Direct Colic Artery (Fig. 283, 7). — This is the largest of the
branches composing the right fasciculus of the anterior mesenteric artery.
Destined for the right portion of the flexure fonned by the large colon, it lies
immediately beside that viscus, beneath the peritoneal membrane, following it
from its origin to its pelvic flexure, where the artery anastomoses by inosculation
with the left colic or retrograde artery.
C. Arteries of the Ajstterior Fasciculus. — These are only two in
number : the left colic or retrograde, and the ^rs^ artery of the small colon, joined
at their origin to an extremely short trunk.
Left Colic or Retrograde Artery (Fig. 283, 8). — This is carried to the
left portion of the colic flexure, which it passes over, beneath the peritoneum,
from the terminal extremity of the viscus to the pelvic flexure, where it meets
the right artery ; in this manner it follows a course the inverse of that pursued
by the food, whence its name of retrograde colic artery.
Considered collectively, the two colic arteries represent a loop or flexure exactly
like that formed by the large colon itself. They proceed parallel to each other
618 THE ARTERIES.
and finish, after being slightly separated, by uniting to form a parabolic curve.
This arterial loop occupies a deep position on the intestinal loop, being found on
the inferior face of the first and fourth sections of the large colon, in the con-
cavity of the flexure which gives rise to the supra-sternal and diaphragmatic
curvatures, and on the superior plane of the second and third portions of the
vise us.
A considerable number of collateral branches escape perpendicularly from
this arterial loop, and pass into the membranes of the intestine ; some of them
establish a transverse communication between the two vessels. *
First Artery of the Small or Floating Colon (Figs. 283, 9 ; 366, 4).—
This branch, the calibre of which is often considerable, is inflected to the left,
downwards and backwards, to be placed in the colic mesentery, very near the
lesser curvature of the floating or small colon. It soon meets a branch of the
posterior mesenteric artery, with w^hich it anastomoses by inosculation.
D. Innominate Branches of the Great Mesentery. — These are the
twigs sent to the lymphatic glands, supra-renal capsules, mesentery, and pancreas,
the existence of which it is sufiicient merely to mention. Among those supplied
to the pancreas, there is one of somewhat considerable volume.
E. The Anastomoses of the Great Mesenteric Artery. — The multi-
plicity and calibre of these anastomoses assure, in the most favourable manner,
the circulation of the blood in the intestinal mass, which, by reason of its great
mobility, is exposed to displacements capable of inducing more or less extensive
compression. Not only do these anastomoses unite the diff"erent branches
destined to the same portion of the viscera — be it the small intestine, the csecum,
or the large colon ; but they also establish communications between the anterior
mesenteric artery and the neighbouring trunks, which in case of need can main-
tain the circulation — as, for example, when the two intestinal arteries are com-
pletely obstructed. The blood from the cceliac axis can really pass from the
duodenal artery into the branches of the left fasciculus of the anterior mesenteric ;
then by the ileo-ctecal artery into the branches of the right fasciculus, and
thence into the left colic artery, which, finally, transmits it to the first artery of
the small colon, as well as to the arches of the mesenteric artery. The communi-
cation existing between the broncho-oesophageal and the coeliac trunks, through
the medium of the oesophageal and gastric arteries, even allows a collateral
circulation to be formed, which would be capable of supplementing the posterior
aorta, supposing that vessel tied behind the trunk that distributes blood to the
bronchi and oesophagus.
4. Posterior or Small Mesenteric Artery (Fig. 366).
This artery carries blood to the small colon and rectum, and arises at a right
angle from the inferior face of the posterior aorta, from A^ to 6 inches behind
the anterior mesenteric. It descends between the two layers of the colic
mesentery, and is soon inflected back in describing a curve upwards, to pass
above the rectum ; when near the anus, its terminal divisions enter the walls
of that intestine.
In its course this artery gives off, at pretty regular intervals, thirteen or
fourteen branches, the foremost of which are the largest and longest ; they
originate from the convexity of the artery — that is from below, and either singly
or in clusters ; the latter disposition is the most common for the first four or
five. They descend into the mesentery, and arrive near the superior curvature
THE POSTERIOR AORTA.
619
of the intestine, where they are disposed in the following manner : The first
seven or eight bifurcate, and form arches like those of the arteries supplying the
small intestine, differing from them only in being nearer the small curvature of
the colon ; the other branches, which are destined for the terminal part of that
Fig. 366.
DISTRIBUTION OF THE POSTERIOR OR SMALL MESENTERIC ARTERY. THE SMALL COLON WITH ITS
MESENTERY IS SPREAD OUT AND THE SMALL INTESTINE THROWN BACK TO THE RIGHT, UNDER
THE DOUBLE COLON.
1, Trunk of the posterior mesenteric artery ; 2, anterior mesenteric artery ; 3, its anterior
fasciculus ; 4, first artery of the small colon, forming part of that fasciculus ; 5, retrograde colic
artery ; 6, right fasciculus of the anterior mesenteric; 7, branches of the left fasciculus; 8, renal
artery. 9, terminal extremity of the aorta; 10, external iliac artery; 11, circumflex iliac ai'tery;
12, internal iliac artery.
viscus and the rectum, ramify in the intestinal membranes without having
previously formed any arches.
The anterior ramuscule of the first branch anastomoses directly with the
artery sent to the small colon by the anterior mesenteric, and from this anasto-
mosis results the first colic arterial arch.
5. Eenal or Emulgent Arteries (Figs. 338, 2 ; 365, 17).
These are two arteries — one for each kidney — detached laterally, and at a right
angle, from the abdominal aorta, near the anterior mesenteric arteiy ; passing
620 THE ARTERIES.
outwards to the internal border of these organs, each divides into several
branches, which enter the gland either by its hilus or by its inferior face.
Reaching the interior of the kidney, these branches subdivide, and form a net-
work of large vessels placed on the limit between the cortical and medullary
portions, from which a multitude of ramuscules are given off, and pass almost
exclusively into the tissue of the cortical portion (see the description of the
Kidneys).
The right renal artery, longer than the left, passes between the small psoas
muscle and the posterior vena cava, to reach the right kidney. Both arteries
are in relation with the posterior extremity of the supra-renal capsules.
Remarkable for their relatively enormous volume, when compared with that
of the glands receiving them, these arteries, before penetrating the proper tissue
of the kidneys, give off only a few unimportant ramuscules, the principal of
which proceed to the supra-renal capsules (Fig. 365). Other twigs from the
anterior mesenteric artery, or even from the aorta itself, also supply these small
bodies. It is not unusual to find the kidneys receiving vessels from the arteries
in their vicinity. Thus, we have seen an artery from the external iliac pass into
a kidney by its lower face ; and we have also observed an artery, detached from the
aorta along with the anterior mesenteric, enter the kidney bv its anterior border.
6. Spebmatic Arteries.
These arteries differ in the male and female ; in the male they are also
named the great testicular arteries ; in the female they are exclusively designated
as the idero-ovarian arteries.
Spermatic or Great Testicular Artery (Fig. 338, 3). — This arises close
to the posterior mesenteric artery, either before, behind, or to one side of it, but
rarely on the same level as the artery of the opposite side ; it is then directed
backwards and downwards, sustained, with its satelHte vein, in a particular fold
of peritoneum, and reaches the entrance to the internal abdominal ring, into
which it is seen to pass with the other portions of the spermatic cord, and to
descend on the testicle by forming remarkable fiexuosities, which are united into
an elongated mass. Arrived within the head of the epididymis, this artery
insinuates itself beneath the tunica albuginea — becomes encrusted, as it were,
in its substance — and successively passes round the superior border, posterior
extremity, and the inferior border and anterior extremity of the testicle. In
this course it is very sinuous, and detaches at a right angle a large number of
equally flexuous branches, which creep over the faces of the organ while sending
numerous ramuscules into its structure. The epididymis also receives its blood
by this artery.
Utero-ovarian Artery. — The origin of this vessel is the same as that of
the preceding artery. It is placed between the two layers of the broad ligament,
and soon bifurcates into the ovarian and uterine arteries. The ovarian branch
describes numerous fiexuosities, like the corresponding artery in the male, and
comports itself on the ovary in the same manner as the latter vessel does on the
testicle. The uterine branch passes to the comu of the uterus, where its divisions
anastomose with the proper uterine artery.
7. Small Testicular Arteries (Male). Uterine Arteries (Fejiale).
Small Testicular Artery (Cremasteric Artery, Artery of the Cord). —
A pair, like the spermatic artery, this vessel is very slender, and originates
TEE POSTERIOR AORTA. 621
either from the aorta between the internal and external iUacs, or from the latter,
near its commencement. The last being the most common, it is usual to describe
it as a collateral branch of the external iUac trunk. We have regarded it as an
artery emanating directly from the posterior aorta, in order to include its descrip-
tion with that of the spermatic and the utero-ovarian arteries.
"Whatever may be its mode of origin, it gains entrance to the inguinal canal
with the spermatic vessels, to be distributed to the various parts constituting the
spermatic cord. Before penetrating the substance of this cord, it gives off several
ramuscules to the peritoneum, iliac glands, ureter, and vas deferens.
Uterine Artery. — This has the same point of origin as the preceding — its
analogue — but differs from it in its larger volume. It is placed between the two
layers of the broad ligament, and soon divides into two branches — ovarian and
uterine. The ovarian branch is flexuous, like the corresponding artery in the
male, and comports itself on the ovary as that vessel does on the testicle. The
uterine branch passes to the corini of the uterus, where its divisions anastomose
with the uterine artery proper.
Differential Chabacters in the Posterior Aorta and its Collateral Branches in
THE other Animals.
Posterior Aorta in Ruminants.
The artery pursues the same course as in Solipeds, and also terminates by four branches,
towards the entrance to the pelvic cavity.
Parietal Branches. — The intercostal arteries only differ from those of the Horse in their
number; as but twelve are met with, of which eight or nine are furnished by the posterior
aorta alone.
The lumbar and diaphragmatic branches are absolutely identical, in their disposition, with
the analogous arteries in Solipeds.
The middle sacral artery is more considerable in volume, particularly in the Sheep and
Goat. This will be referred to hereafter (see Internal iliac artery of Ruminants).
Visceral Branches. Broncho-cesophageal trunk. — This offers nothing particular.
Coeliac axis (Fig. 367, 1). — This artery descends on the rumen, a little behind the insertion
of the oesophagus, is directed to the right, and divides near the omasum into two terminal
branches — the stiperior and inferior arteries of the omasum and dbomasum.
The collateral branches given off from this trunk are : —
1. Several diaphragmatic arteries.
2. The splenic artery, almost exclusively destined for the spleen (Fig. 367, 8).
3. The superior artery of the rumen, always arising from a very short trunk common to it
and the preceding vessel, is carried backward to the superior face of the rumen, and from this
descends between the two conical vesicae, to anastomose with the artery of the inferior face of
the viscus (Fig. 3(;7, 2).
4. The inferior artery of the rumen, which is insinuated between the two anterior culs-de-sac,
and afterwards runs along tlie inferior face of the organ, passing towards the notch separating
the two conical vesicae, to meet the superior vessels (Fig. 367, 3).
5. The artery of the reticulum, has usually a common origin with the inferior artery of the
rumen, and passes forward on tlie left of the oesophagus, to be divided, near the insertion of
that conduit, into two branches — one, the superior, inclines to the right on the small curvature
of tiie viscus (Fig. 367, 5); the other, the inferior, occupying the fissure separating the great
curvature of the reticulum from the right sac of the rumen, and giving to the latter organ a
great number of branches (Fig. 367, 4).
6. The hepatic artery, whicli is not only distributed to the liver, but also furnishes a branch
for the gall-bladder, and a duodenal artery breaking up into two branches — the posterior
branch forming with the first artery of the small intestine an arching anastomosis; the anterior
communicating with the superior artery of the omasum and abomasum. Tliis hepatic artery
always originates between the trunk common to the splenic artery and the superior branch of
the rumen, and that which gives off the superior branch of the same viscus and the artery of
the reticulum.
42
THE ARTERIES.
The terminal branches of the coeliac artery comport fliemselves as follows :—
1. The superior artery of the omasum and abomasum passes successively to the great
curvature of the first of these reservoirs, and to the concave curvature of the second ; then it
goes beyond the pylorus to unite with the duodenal branch of the hepatic artery by inoscula-
tion (Fig. 367, 6). •
2. The inferior artery of the omasuin and abomasum, on the contrary, passes at first over
the small curvature of the omasum, afterwards the great curvature of the abomasum, and
disappears in the omentum, to which on its course it furnishes a great number of branches
(Fig. 367, 7).
In small Ruminants, the distribution of the arteries of the coeliac axis presents some
modifications. We will cite the principal, which belong to the mode of origin of the two
branches destined for the reticulum — these branches form two particular vessels which arise
singly from the coeliiic axis : the
Fig. 367. inferior artery at the same point as
. ; _ the superior artery of the rumen, the
'*^°^^ superior towards the terminal bifur-
cation of the axis.
Anterior mesenteric artery. — Its
origin approaches very closely that
of the coeliac axis. After a course
of from 6 to 8 inches, it divides into
two branches — an anterior and a
posterior. The first, for the small
intestine, creeps above it, between
the two layers of the mesentery, and
passes backward by describing a
curve which gives off from its con-
vexity— that is, below — a great num-
ber of branches, analogous in their
mode of termination to the arteries
of the small intestine in the Horse.
The posterior branch goes to the
large intestine, where it separates
into two principal branches: one
wliich passes to the colon, its di-
visions crossing to the right, to be-
hind and below, the convolutions
described by that viscus; another
which reaches the concave curvature
of the caecum, and anastomoses by
an arch with the terminal extremity
of the parent-branch of the arteries
supplying tlie small intestine.
Posterior mesenteric artery. — Very
short and narrow.
Renal, spermatic, and small spermatic arteries. — These do not differ in their essential
disposition from the analogous vessels in Solipeds.
2. Posterior Aorta in the Pig.
With the exception of the mesenteric vessels, the distribution of which resembles that
already indicated for Ruminants, and with the exception, also, of the middle sacral artery,
which will be alluded to when describing the internal iliac arteries, all the branches given off
by the posterior aorta comport themselves almost as in the Horse.
3. Posterior Aorta in Carnivora.
In these animals, as well as in the Pig, the denomination of posterior aorta is not justifiable,
because the arteries of the head and thoracic limbs spring directly from the aortic arch.
The branches of the aorta are distinguished as parietal and visceral.
A. Parietal Branches. — Beyond the fourth space, the intercostal arteries are furnished
by the aorta ; the first is voluminous, and throws off some considerable filaments to the musclee
of the withers. The first two lumbar arteries arise from the thoracic portion of the aorta,
because of the very backward insertion of the diaphragm ; the third is detached between the
arteries of the stomach in ruminants.
1, Coeliac axis ; 2, superior artery of the rumen ; 3,
inferior artery of the rumen ; 4, inferior artery of the
reticulum ; 5, superior artery of the reticulum ; 6,
superior artery of the omasum and abomasum ; 7,
inferior artery of ditto ; 8, splenic artery. A,
(Esophagus; b, left sac of the rumen; b', left conical
vesica; c, right sac of the rumen; c', right conical
vesica ; D, reticulum ; e, omasum ; F, abomasum ; G,
duodenum ; R, spleen.
THE INTEhNAL ILIAC ARTERIES. 623
two pillars of that rtrascle. In the abdominal cavity, close to the anterior mesenteric, the aorta
gives ciff a branch that soon divides into two: one is diaphragmatic, and descends on the
])Oaterior face ot that muscle; the other reaches the sublumbar region, passes over the psoas
muscle, and traverses the abdominal wall in the vicinity of the transverse processes of the
lumbar vertebrje. We will speak presently of the middle sacral.
B. Visceral Branches. — I have not found in the Dog any special bronchial arteries ; but
there are four or five oisophageal arteries that arise from different points of the tlioracic aorta ;
they descend into the mediastinum, to the right and left of the oesophagus, to which they are
distributed. They furnish branches that accompany the bronchi and enter the lungs.
The coeliac axis is again divided into three branches, as follows : The gastric, or stomachic
coronary artery, does not divide into two branches (anterior and posterior gastric) as in Solipeds.
Near its origin it furnishes a pancreatic branch ; then it expends itself in a great number of
filaments that are spreail over the posterior face and great tuberosity of the stomach, or over
its anterior face after crossing the small curvature.
The splenic artery reaches the spleen at the middle of its upper border. It gives on its
course : 1. A splenic branch that enters the upper extremity of that organ. 2. The left gastro-
omental. The hepatic artery provides the principal hepatic vessel at the posterior fissure of
the liver ; it is then continued by the right gastro-oraental artery. On the duodenum, the
latter gives origin to the pyloric and the pancreatico- duodenal branches ; the latter is volu-
minous, is lodged in the substance of the pancreas, and anastomoses by its last filaments with
the anterior mesenteric.
The anterior mesenteric artery arises in the vicinity of the coeliac axis ; it forms a curve
with the convexity backward, and anastomoses by its extremity with the pancreatico-duodenal
branch of the hepatic. From its convexity are detached several filaments (filaments to the
small intestine), that form arches towards the smaller curvature of that viscus. Behind, and
at a short distance from its origin, it gives a branch to the caecum and branches to the colon ;
the latter are sometimes large.
The posterior mesenteric commences near the termination of the aorta, and divides into two
branches— one passing forward, the other backward; they form the hsemorrboidal vessels
(see Fig. 290).
There is nothing special to note with regard to the renal ami spermatic arteries.
Comparison of the Aoeta of Man with that of Animals.
The aorta in Man offers the same general arrangement as in the Carnivora, the trunk
being inflected across, to be placed along the body of the dorsal and first lumbar vertebrai,
where it terminates in the iliac vessels.
It furnishes the coronary arteries, the arteries of the head and thoracic limbs — which will
be noticed hereafter ; ami the parietal and visceral branches to the chest and abdomen. At
first these are the intercostals, beyond the third space ; the diaphragmatic arteries, superior
and inferior according as they occupy one or other face of the diaphragm ; and, lastly, the
lumbar arteries.
Among the visceral branches are distinguished : 1. The bronchial arteries, two in number;
the left arises from the concavity of the aortic arch, and enters the lungs with the left bronchus ;
the right originates alone or in common with the preceding, and enters on the right bronchus.
2. The oesophageal arteries, disposed somewhat as in the Dog. 3. The coeliac trunk, tlie
distribution of which is nearly identical with tlmt of the Carnivora. 4. The superior or great
mesenteric, disposed in arches as in the Dog (see Fig. 292, 9). Its last branches pass to the caecum,
and the ascending and origin of the transverse portion of the colon. 5. The inferior or small
mesenteric, which arises from 1| to 2 inches from the bifurcation of the aorta ; this artery descends
into the meso-colon, and terminates on the sides of the rectum by the haemorrhoidal vessels ;
to the left, they emit branches to the large intestine ; the first ascend along the descending
colon, and anastomose on the transverse colon with the right colic brancli of the superior
mesenteric. 6. The renal and capsular arteries, which do not offer important differences. 7.
Lastly, the spermatic arteries, which are remarkable for the length of their course, commencing,
as they do, at the aorta, a short distance below the renal vessels.
Article IIL^-Internal Iliac Arteries, or Pelvic Trunks
(Figs. 338, 368, 370).
The two internal iliac arteries represent the middle or internal branches of
the quadrifurcatiou formed by the posterior aorta at its terminal extremity.
624 THE ARTERIES.
Extending from the body of the last lumbar vertebra, to near the terminal
insertion of the small psoas muscle, in an oblique direction downwards, outwards,
and backwards, the arteries are related -. in front, with the trunks of the common
iliac veins, which separate them from the external iliacs ; inwards, to the peri-
toneum ; above and outwards, to the sacro-iliac articulation and to the ilium.
In its course, the internal iliac artery emits the following branches : the
nmbilical artery, artery of the ImJh, ileo-lumbar yluteal, and subsacral arteries. At
its terminal extremity, it is divided into two branches which ride on the superior
border of the tendon belonging to the small psoas muscle — the one within, the
other without that tendon. The first is the ohturator artery, the second the
ileo-femoral artery. All these branches will be studied in the order of their
enumeration.
Preparation of the internal iliac artery. — Place the subject in the first position ; remove one
of the posterior limbs, leaving the rectum and bladder in the pelvis, and slightly inflating the
latter organ. Dissect, on the side from wliich the limb has been removed, the origin and
visceral ramifications of the branches furnished by the trunk of the artery. Follow, on the
opposite side, the ramifications given off by these branches to the muscles. To conveniently
prepare the coccygeal arteries, it is necessary, after removing the great sciatic ligament and
dissecting the internal artery of tlie bulb along with the subsacral trunk, to raise up the
rectum and bladder by means of the chain-hooks.
1. Umbilical Artery (Figs. 368, 5 ; 370, 3).
This artery forms a considerable vessel during foetal life, and carries the blood
of the foetus to the placenta ; it will be described in detail in the anatomy of the
foetus.
In the adult it is almost entirely obliterated, appearing only as a fibrous cord
extending from the internal iliac artery co the fundus of the bladder, and placed
at the free margin of the lateral serous fold detached from the fundus of that
organ. This cord throws off on its track one or more vesical branches, beyond
which its canal altogether disappears. These vesical branches also — though very
rarely — come from the internal pudic artery ; in which case the obliteration of the
umbilical artery is complete.
2. Internal Pudic Artery, or Artery of the Bulb (Figs. 368, 16 ; 370, 4)
This vessel differs in its distribution in the male and female.
Internal Pudic Artery in the Male. — It proceeds from the internal iliac,
near the origin of that vessel, by a trunk common to it and the umbilical artery ;
it is then directed backwards, following the superior border of the pyriformis
muscle, and placed either without or within the texture of the sacro-sciatic liga-
ment. Arrived at the neck of the bladder, it enters the pelvic cavity, lying beside
the prostate and Cowper's glands, and is finally inflected downwards, passing
round the ischial arch to reach the bulb of the urethra.
In its progress it furnishes :
1. Insignificant ramuscules to the muscle adjoining the sacro-sciatic ligament.
2. The vesico-prostatic artery (Figs. 338, 8 ; 368, 17). This is a branch con-
stant in its distribution, but variable in its origin. Destined to supply the pros-
tate gland, vesiculffi seminales, the pelvic dilatation of the vas deferens and the
canal itself, as well as the bladder, it usually commences near the prostate gland,
and passes backwards, in a flexuous manner, on the vesiculse seminales and the
vas deferens.
TEE INTERNAL ILIAC ARTERIES. 625
3. Slender ramifications for the pelvic portion of the urethral canal, Cowper's
glands, the anus, and the erector penis muscle.
The terminal extremity of the vessel is insinuated beneath the accelerator
urinaB muscle, and immediately divides into a multitude of ramuscules which
enter the erectile tissue of the urethral bulb, where they comport themselves as in
all tissues of this kind.
Varieties. — It is not rare to see this artery detach — before reaching Cowper's
gland — the cavernous artery., which then passes round the ischial arch along with
the nerve of the penis. Sometimes it only gives off the posterior dorsal artery of
the penis — a branch of the cavernous.
Internal Pudic Artery in the Female. (Fig. 370, 4.) — This artery ter-
minates, towards the vagina, by rectal, vulvar, vaginal, and bulbar branches ;
the latter are for the bulb of the vagina. As in the male, it does not
give off more than one important branch on its course ; this — the vaginal artery
(Fig. 370, .5) — is analogous in every respect to the vesico-prostatic artery ; its
terminal divisions go not only to the middle portion of the vagina, but also to
the body of the uterus, where they anastomose largely with the branches of the
uterine artery, and even pass to the bladder and rectum.
The internal pudic artery of the female, as in the male, is liable to numerous
variations. It may furnish the cavernous artery, or only the dorsal artery of the
clitoris. We have seen the vaginal artery come from the umbilical.
3. Lateral Sacral or Subsacral Artery (Figs. 368, 12 ; 370, 6).
Rising from the inner side of the internal iliac artery, at, or a little behind
the lumbo-sacral articulation, lying above the peritoneum, and beneath the
sacral foramina and the large nerves passing through them, this vessel is directed
backwards, and arrives near the posterior extremity of the sacrum, where it ends
in two branches : the ischiatic and lateral coccygeal arteries^ to which must be
added the middle coccygeal artery, usually given off by the vessel of the right
side.
Collateral Branches. — The lateral sacral artery sends off on its course
several insignificant ramuscules destined for the neighbouring parts, and four
spinal branches which enter the spinal canal by the inferior sacral foramina, and
leave it again by the superior, after throwing off some divisions to the posterior
extremity of the spinal cord and the cauda equina nerves ; these branches ramify
in the muscles lying along the sacral spine.
Terminal Branches. — 1. Ischiatic Artery.— It crosses the sacro-sciatic
ligament, to place itself under the superior extremity of the posterior portion
of the superficial gluteus, passes backwards and downwards, and divides into
several branches which descend into the substance of the semimembranosus and
semitendinosis muscles, to beneath the ischial tuberosity. These branches
anastomose, by their extremities, with the ascending branches from the femoro-
popliteal, as well as with the divisions of the obturator and deep femoral
arteries.
2. Lateral Coccygeal Artery.— This vessel represents the continuation
of the lateral sacral artery, though not by its volume — which is much less than
that of the ischiatic artery — but in its direction. It proceeds from before to
behind, for the whole length of the coccyx, between the rudimentary vertebra of
that region and the compressor coccygis, gradually diminishing in volume, and
626 THE ARTERIES.
detaching on its course a series of collateral ramuscules, which are expended in th(
muscles and integuments of the tail.
There has been described a superior lateral artery, a branch of the preceding,
and which passes between the erector coccygis and the superior face of the
coccygeal vertebrfe ; but this artery never exists : the superior coccygeal muscle
receives its blood by branches analogous to the spinal branches of the intercostal,
lumbar, and sacral arteries, and which emanate from the lateral coccygeal artery
at each of the vertebral bodies.
3. Middle Coccygeal Artery. — The origin of this vessel is liable to
numerous variations. Ordinarily, it is detached from the right lateral sacral
artery, in common with the lateral coccygeal of the same side. At other times,
it escapes from the lateral at 5 or 6 inches from its origin. In a specimen now
before us, it arises nearly from the middle of the lateral sacral artery. And it
may also proceed from either the left sacral or the corresponding lateral coccygeal
artery.
Whatever may be its point of emergence, this vessel is placed beneath the
inferior face of the coccygeal vertebrae, betvveen the two compressores coccygis,
crosses the suspensory ligament of the rectum, and extends to the extremity of
the coccyx, distributing ramuscules to right and left, and even downwards.
4. Ilio-lumbae or Ilio-muscular Artery (Figs. 368, 14 ; 370, 8).
Immediately after clearing the inferior face of the lateral angle of the sacrum —
and even often before — the internal iliac artery gives off from its external side,
and at a right angle, the ilio-lumbar artery, which passes directly outwards,
behind the sacro-iliac articulation, between the iliacus muscle and the bony
surface covered by it, and emits divisions that proceed to the above-named
articulation, as well as to the muscles of the sublumbar region. Near the angle
of the haunch, it terminates in several branches, which bend upwards on the
external border of the ilium, to penetrate the principal gluteal muscle, or the
tensor vaginte femoris.
5. Gluteal Artery (Figs. 368, 13 ; 370, 7).
This, the most voluminous of the branches emanating from the internal iliac,
arises opposite the preceding, and from -j^ of an inch to 1;^ inches behind the
lateral sacral. It is immediately reflected on the internal border of the ilium,
and emerges from the pelvis by the great sacro-sciatic foramen, along with the
anterior gluteal nerves, dividing into several branches which ramify in the texture
of the great and small gluteal muscles.
6. Obturator Artery (Figs. 368, 19 ; 370, 10).
This vessel, the origin of which has been already indicated, directs its coui-se
backward and downward, accompanied by a satellite vein and nerve, passes
between the peritoneum and ilium in following the inferior border of the pyri-
formis muscle, and finally insinuates itself beneath that muscle to make its exit
from the pelvis by creeping through the obturator foramen, after furnishing a
constant vesical twig. Placed between the external obturator muscle and the
inferior face of the ischium, it separates into several branches, the majority of
which descend into the internal crural and ischio-tibial muscles, anastomosing
with the ultimate divisions of the ischiatic and deep femoral arteries. Among
these branches there are two or three which go to the roots of the penis, and
TEE INTERNAL ILIAC ARTERIES. 627
enter the erectile tissue of the corpus cavernosum ; one of them, more important
than the others by its vohime, is designated the artert/ of the corpus cavernosum.
The obturator artery sometimes arises from the external iliac.
Artery of the Corpus Cavernosum (Fig. 368, 20). — This vessel passes
on the inferior face of the ischium, backwards and inwards, reaches the crus penis,
LATERAL VIEW OF THE GENlTO-URINARr ORGANS IN THE MALE.
1, Abdominal aorta ; 2, external iliac artery ; 3, common origin of the prepubic and deep femoral
arteries ; 4, prepubic artery ; 5, posterior abdominal artery ; 6, external pudic artery ; 7,
subcutaneous abdominal artery ; 8, anterior dorsal artery of the penis ; 9, 9, anterior and posterior
branches of that artery ; 10, internal iliac artery ; 11, last lumbar artery ; 12, subsacral artery ;
13, gluteal artery; 14, iliaco-muscular artery; 15, umbilical artery; 16, internal pudic artery;
17, its vesico-prostatic branch; 18, iliaco-femoral artery; 19, obturator artery ; 20, artery of the
corpus cavernosum; 21, posterior dorsal artery of the penis — a branch of the preceding; 22,
spermatic artery ; 23, posterior mesenteric artery, c, Termination of the small colon ; R, rectum;
S, sphincter of the anus ; I, suspensory ligament of the penis ; I', suspensory ligament of the
rectum ; V, bladder ; m, ureter ; T, testicle , E, epididymis ; D, deferent canal , v, vesiculae
seminales; p, prostate ; p, Cowper's gland; r, crus penis ; s, ligament of the corpus cavernosum.
and pierces it by several branches, after supplying some muscular divisions and
the posterior dorsal artery of the penis.
The latter is situated on the dorsal margin of the penis, passes forward
between the two ligaments attaching that organ to the symphysis pubis, and
proceeds to anastomose with the posterior branch of the anterior dorsal artery
(Fig. 368, 21).
7. Iliaco-femoeal Aetery (Figs. 368, 18 ; 370, 9).
Noticed as one of the terminal branches of the pelvic trunk, the iliaco-femoral
artery only exists as a vessel of a certain volume in SoUpeds. In other animals,
628 TEE ARTERIES.
as in Man, it is merely an insignificant and innominate branch of the obturator
artery. It proceeds outside the tendon of the small psoas muscle, between the
ihacus and the neck of the ilium, which it passes round obliquely, above the origin
of the rectus femoris muscle, to descend on the external side of the latter, and
plunge into the mass of the patellar muscles, entering them between the rectus
femoris and vastus externus, after sending some branches to the psoas and gluteal
muscles, and tensor vaginse femoris.
Differential Characters in the Internal Iliac Arteries of the other Animals.
1. Internal Iliac Arteries of Ruminants.
The terminal extremity of the aorta, after giving ofif the external iliac arteries, bifurcates
to constitute the internal iliacs, and in the angle of bifurcation throws out a very large branch
— the sacra media — from which emanate the arteries of the tail. This, however, is not the
only important peculiarity to be noted in the disposition of the pelvic arteries. The internal
iliac artery emits at its origin a very short, but very large branch, which divides to form the
umbilical artery, and an enormous uterine artery, that supplants, to a great extent, the utero-
ovarian artery ; it is then directed backwards, on the internal face of the great sacro-sciatic
ligament, crossing the direction of the lumbo-sacral plexus. In its course it furnishes branches
resembling the iliaco-muscular, the gluteal, and the ischiatic, and is continued about the middle
of the pelvis by the internal pudic artery, which terminates by forming the dorsal artery of the
clitoris, after distributing branchi s to the rectum and the genito-urinary organs lodged in the
pelvic cavity.
It will be seen from this description — which refers only to female animals, but is easily appli-
cable to males — that no mention is made (if an iliaco-femoral or obturator artery. This is
because these two vessels are entirely absent in the Sheep, and the last, though present in the
larger Ruminants, is yet in a very rudimentary state, butli lieing supplemented by the deep
femoral, the dimensions of which are considerable. Neitlier is the lateral sacral artery described,
as it is also absent, its ischiatic branch coming directly from the pelvic trunk, and its coccygeal
divisions being supplied by the middle sacral artery.
2. Internal Iliac Arteries of the Pig.
Two single branches, originating one above the other, arise from the extremity of the aorta,
between the two internal iliac arteries ; one divides almost at once into two lateral branches,
which go to right and left beneath the iliacus, and are the representatives of the iliaco-muscular
arteries of the Horse ; the other, or sacra media, placed in the midd'le line, proceeds backwards
on the inferior face of the os sacrum, and constitutes the coccygeal arteries after giving off, at
about 1^ inches from its origin, two lateral branches, traces of the lateral sacred arteries, which
furnish the spinal ramuscules of the sacral region.
The internal iliac artery, near its origin, sends off the umbilical artery, is directed back
towards the sacro-sciatic furamen, there detaches gluteal brandies, and is prolonged beyond
the foramen to the external surface of the sacro-sciatic ligament, in forming the internal pudic
artery.
The latter emits, before leaving the pelvic cavity, a long hemorrhoidal artery, that creeps
back by the side of the rectum, to be distributed to the posterior extremity of tliat intestine
and the adjoining genito-urinary organs. Outside the pelvis, it gives off some gluteal branches,
the most considerable and posterior of which represent the ischiatic artery of Solipeds. It then
re-enters the cavity of the pelvis, and terminates at the base of the penis by forming the
cavernous and dorsal arteries of that organ.
3. Internal Iliac Arteries of Carnivora.
The internal iliac a^-teries in the Carnivora result from tlie bifurcation of an arterial trunk
that prolongs the aorta beyond the origin of the external iliacs, as far as the first intersacral
articulation.
This pelvic trunk at first gives off the umbilical artery, wliich is remarkable for its small
calibre, and the flexuosities it describes before reaching the bladder.
Then the internal iliac artery courses for 1 or 1.^ inches behind, and to the inside of, the
pelvi-crural venous trunk, dividing into two branches at the entrance to the pelvis.
One of these branches goes towards the viscera contained in the pelvic cavity; this is the
inttrnal pudic artery. It passes backwards, turns round the ischial arch, and terminates in the
THE EXTERNAL ILIAC ARTERIES.
cavernous and dorsal arteries of the penis, after furnishing vesical, hsemorrhoidal, and urethral
branches, as well as the uterine artery (iu the female). The latter is very voluminous, and is
placed in the substance of the broad ligament, above the small curvature of the uterine cornu,
■whence it is directed forward to the ovary, where
it meets the utero-ovarian artery, after emitting Fig. 369.
numerous collateral branches, remarkable for
the ricliness of the vascular network they form
in the walls of the uterus.
The second branch of the internal iliac
artery resembles the lateral sacral artery and
its ischiatic branch in Solipeds ; it escapes from
the pelvic cavity with the great sciatic nerve,
which it accompanies to behind the thigh, where
it is expended, after giving off on its course
spinal and gluteal twigs. It is not this branch
which supplies the coccygeal arteries; these
come, as in the Pig and Ruminants, from the
middle sacral artery.
Comparison op the Internal Iliac Arteries
IN Man with those op Animals.
The aorta in Man bifurcates at the fourth
lumbar vertebra to form the common iliac arteries,
which descend to each side of the margin of the
pelvis, where they divide into two branches —
the internal and external iliacs.
The internal iliac, or hypogastric artery,
passes beneath the sacro-iliac articulation, and
breaks up into nine or eleven branches that go
to the walls of the pelvic cavity, or to the organs
contained in it. Their disposition somewhat
resembles that of Carnivora ; in their distribution
they represent the various branches of the in-
ternal iliac of Solipeds. Thus we find: 1. An
umbilical artery. 2. The vesico-prostafic artery,
resembling the branch of the same name given
off in tiie Horse by the internal pudic. 3. The
middle hcemorrhoidal artery, that passes to the
rectum like the branch of the internal pudic.
4. The ileo-lumhar artery, the iliaco-rnuscular
of Solipf'ds. 5. The lateral sacral artery, which,
behind, joins the middle sacral instead of divid-
ing, as in the Horse, into ischiatic and lateral
coccygeal. 6. The obturator artery. 7. Gluteal
artery. 8. Ischiatic. 9. Internal pudic, that
terminates, as in animals, by the cavernous,
dorsalis penis, and the transversa perinei arte-
ries. The arterial branches of the rectum, or
inferior hamorrhoidal, are furnished by the in-
ternal pudic artery.
Article IV. — External Iliac Arteries, or Crural Trunks (Fig. 370, 11).
These external branches of the terminal quadrifurcations of the posterior
aorta descend on the sides of the entrance to the pelvic cavity, in describing a
curve downwards and forwards, and an oblique direction downwards, backwards,
and outwards. Maintained within the psoas parvus and iliacus muscles by the
peritoneum covering them, they are bordered posteriorly and inwardly by the
iliac vein, which isolates them from the pelvic trunk. When they arrive at
the anterior border of the pubis, in the interstice separating the pectineus from
ABDOMINAL AORTA, WITH ITS BRANCHES, IN
MAN.
1, Phrenic arteries ; 2, coeliac axis ; 3, gastric
artery; 4, hepatic artery, dividing into right
and left hepatic branches; 5, splenic artery,
passing outwards to the spleen ; 6, supra-
renal artery of right side ; 7, right renal
artery longer than the left, passing outward
to right kidney ; 8, lumbar arteries ; 9,
superior mesenteric artery ; 10, the two
spermatic arteries; 11, inferior mesenteric
artery; 12, sacra media ; 13, common iliacs ;
14, right internal iliac; 15, e.xternal iliac;
16, epigastric artery ; 17, circumflexa ilii ;
18, common femoral artery, dividing into
superficial and deep femoral.
630
DISTRIBUTION OF THE EXTERNAL AND INTERNAL ILIAC ARTERIES IN THE MARE.
1, Posterior aorta ; 2, internal iliac artery ; 3, common origin of the internal pudic and tha
umbilical arteries (the latter is cut) ; 4, internal pudic artery ; 5, vaginal artery ; 6, lateral
I sacral artery ; 7, origin of the gluteal artery, which arises in this instance from the lateral
sacral — a circumstance most frequently observed in the Ass; 8, origin of the ilio-lumbar artery;
9, origin of the iliaco-femoral artery; 10, obturator artery; 11, external iliac artery; 12,
circumflex iliac artery (cut); 13, femoral artery; 14, common origin of the deep femoral and
prepubic arteries; 15, origm of the anterior great muscular artery; 16, origin of the saphena
artery (cut) ; 17, innominate branch ; 18, popliteal artery ; 19, femoro-popliteal ; 20, satellite
artery of the great femoro-popliteal nerve ; 21, posterior tibial artery ; 22, its communicating
branch with the saphena; 23, external plantar artery; 24, satellite artery of the internal plantar
nerve ; 25, digital artery.
THE EXTERNAL ILIAC ARTERIES. 631
the sartorius muscles, each is prolonged to the thigh, and takes the name of
femoral artery; and thence into the angle of the femoro-tibial articulation,
where it receives the designation of popliteal artery.
Before passing to the description of these two vessels — continuations of the
external iliac artery — we will indicate the collateral branches which emanate
from this artery itself. These are two principal — the small testicular, or
artery of the cord, or uterine, and the circumfiex iliac . The first having been
already described (p. 620), we have only to notice the second.
Circumflex Iliac Artery (Fig. 366, 11). — This artery commences at an
acute angle near the origin, and in front of, the external iliac ; it sometimes
emerges directly from the posterior aorta. It is directed outwards, passes
between the peritoneum and the lumbo-iliac aponeurosis, and arriving at the
external border of the psoas magnus muscle, or even beyond that, it bifurcates.
The anterior branch sends its ramifications into the transverse and small oblique
muscles of the abdomen, where they anastomose with the abdominal ramuscules
of the lumbar and intercostal branches ; the posterior Ufurcation, after giving
some vessels to the same muscles, traverses the abdominal wall a little below the
external angle of the ilium, in passing between the small oblique and iliacus
muscles, to descend within the anterior border of the tensor fascia lata muscle,
and expend itself in front of the thigh by subcutaneous divisions.
Femoral Artery (Fig. 370, 13).
The femoral artery, a prolongation of the external iliac, which changes its
name on leaving the anterior border of the pubis, at first lies beneath the crural
arch, beside a cluster of lymphatic glands, in the space comprised between the
pectineus, sartorius, and iliacus muscles. From this interstice it descends,
accompanied by its satellite vein, which lies behind it, and the internal saphena
nerve, along the pectineus and vastus internus, at the posterior border of the
sartorius. It soon leaves that muscle, however, to traverse the ring formed by
the two branches of the adductor magnus and the oblique concavity on the
posterior face of the femur, and reaches the superior extremity of the gastroc-
nemius, between which it is continued, and where it assumes the name of
popliteal artery.
On its course the femoral artery distributes a certain number of collateral
branches to the adjacent parts. These are : the prepuhic, deep muscular, super-
ficial muscular, the small muscular, and saphena arteries.
Preparation. — The animal being placed in the first position, and the limb raised, the skin
is carefully removed from the inner face of the thigh, the external generative organs in the
Inguinal region, and tlie inferior abdominal wall. The sapliena vein is first to be exposed, and
the branches of the artery of that name dissected ; next, the prepubic artery, which is to be
sought for in the inguinal canal, atid its branches prepared by dissecting from tlieir origin to
their termination. The excision of a portion of the adductors of the leg and the great
adductor of the thigh will sufficiently expose the femoral artery and its other collateral
branches.
1. Prepubic Artery (Fig. 368, 4).
This artery originates at the artificial line of demarcation separating the
external iliac from the femoral artery, at the superior extremity of the latter.
It therefore emerges from that vessel at the anterior border of the pubis, and
never alone, but always with the deep muscular branch, by means of a common
632 TEE ARTEBIES.
and generally very short trunk, which springs at an acute angle from uhe inner
side of the femoral artery.
The prepubic artery traverses the crural ring, opposite which it arises ; it lies
on the anterior face of Poupart's hgament, behind the neck of the inguinal canal,
and after a very short course separates into two branches — the posterior abdominal
and the external pudic arteries.
Posterior Abdominal Artery {Epigastric of Man) (Fig. 368, 5). — This
leaves the external pudic artery at an acute angle, enters the femoral ring by
crossing the direction of the spermatic cord, places itself between the small
oblique and transverse muscles of the abdomen, passes forward along the external
border of the rectus abdominis, and finally enters the substance of that muscle,
where its terminal divisions anastomose with those of the anterior abdominal
artery. The numerous collateral branches this artery throws off on its track
principally go to the rectus muscle, or the other parts composing the inferior
abdominal wall, the skin included ; the superior branches communicate with the
circumflex iliac.
The position this artery occupies at its origin, with reference to the abdominal
ring, is worthy of remark ; indicating, as it does, that in strangulated inguinal
hernia, division of the ring should be made outwards, to avoid wounding the
vessel.
External Pudic Artery (Fig. 368, 6). — This artery descends at first on
the posterior wall of the inguinal canal, behind, and a little to the inside of, the
spermatic cord ; then, having passed the external ring of the canal, it bifurcates
into the subcutaneous abdomincd artery, and the anterior dorsal artery of the penis.
The subcidaneons abdomincd artery is directed forward on the superficial
face of the abdominal fascia, bordering in its course the insertion of the sus-
pensory Hgament of the sheath. Arriving at the anterior extremity of that
ligament, it terminates in several subcutaneous divisions, one of which is
inflected beyond the umbilicus to anastomose in a circle with a similar branch
from the opposite artery. It gives off twigs to the scrotum, sheath, superficial
inguinal glands, skin, etc. (Fig. 368, 7).
The anterior dorsal artery of the penis gains the superior border of that
organ, after supplying one or two scrotal branches, and separates into two
portions ; one, posterior, meets the dorsal cavernous artery of the penis and
anastomoses with it ; the other, anterior, longer, more voluminous, and very
flexuous during retraction of the penis, follows the dorsal border of the organ
to its anterior extremity, where it enters the erectile tissue of this part. From
the two branches of this anterior dorsal artery, there are given off, as in the
posterior one, ramuscules which penetrate the corpus cavernosum and the walls
of the urethra ; they give, besides, some preputial twigs (Fig. 368, 8).
In the female, the external pudic artery offers a disposition which, if not
similar, is yet analogous to that just indicated. As in the male, this vessel
traverses the inguinal canal, and after leaving it divides into two branches :
one, the anterior, or suhcidaneous abdomincd artery ; the other, the posterior, or
mammary artery. The last — the most voluminous — represents -the dorsal artery
of the penis. It distributes several branches to the mammary tissue, and is
prolonged between the thighs by a perineal branch, which terminates in the
inferior commissure of the vulva, after giving off glandular and cutaneous
branches.
the external iliac arteries. 633
2. Profunda Femoris, Great Posterior Muscular Artery of thb Thigh,
OR Deep Muscular Artery (Fig, 370, 14)
Arising in common with the prepubic artery, the profunda femoris passes
backward, penetrates between the ihacus and the pectineus muscles, afterwards
between the latter and the external obturator muscle. In this way it arrives
beneath the deep face of the adductors of the thigh, when it becomes inflected
behind the femur, and disappears in the substance of the internal and posterior
crural muscles by ascending branches, which anastomose with the ischiatic artery,
and descending and internal branches, the terminal ramifications of which open
mto those of the obturator artery.
The principal twigs of the coxo-femoral articulation are derived from this
vessel.
3. SupERFicuLis Femoris, Superficial Muscular or Great Anterior
Muscular Artery (Fig. 370, 15).
Smaller than the preceding, and commencing opposite to it, but a little
lower, this artery passes downwards, outwards, and forwards, runs between the
sartorius and the musculo-tendinous cone which terminates in common the psoas
magnus and iliacus, furnishes some ramuscules to these muscles, dips into the
interstice separating the vastus internus from the rectus femoris, and is lost in
the mass of the triceps cruris.
This vessel, therefore, resembles the iliaco-femoral artery, which enters this
triceps by penetrating between the rectus femoris and the vastus externus.
4. Innominate or Small Muscular Arteries.
The femoral artery gives off on its course numerous small branches to the
neighbouring muscles, though too diminutive to merit particular description.
One of these furnishes the nutrieyit artery of the femur — the largest, perhaps,
of all the arteries supplying bones. Another (Fig. 368, 17) sends to the stifle
a long articular branch, analogous to the great anastomoticus of Man, which
descends along the vastus internus, beneath the adductors of the leg, at the
interstice separating these two muscles.
5. Saphena Artery (Fig. 370, 16).
This artery, remarkable for its small volume, the length of its course, and
its connections with the vein of the same name, supplies the skin on the inner
side of the thigh and leg.
It takes its origin, at an acute angle, from nearly the middle of the femoral
artery, either alone or in common with one of the principal innominate muscular
branches, and becomes superficial in passing into the interstice of the two
adductors of the leg, or in traversing one of these, usually the gracilis. It lies
on the surface of this muscle, beside the saphena vein, and bifurcates at the
angle of union of the two roots which constitute that vessel. One of the
branches accompanies the anterior vein to nearly the lower third of the leg ;
the other follows the posterior vein, and usually anastomoses in the hollow of the
hock, above the calcis, with a branch from the posterior tibial artery, and which
also communicates with one of uhe branches of the femoro-popliteal artery.
THE ARTERIES.
Popliteal Artery (Fig. 370, 18).
Preparation. — The preparation which has served for the study of the femoral artery being
nearly arranged as in Fig. 370, remove from it the internal head of the gastrocnemius and
the popliteus muscles.
The above name is given to the continuation of the femoral artery. This
vessel follows a descending direction behind the femoro-tibial articulation,
between the heads of the gastrocnemius muscle, insinuates itself l)eneath the
popliteus, and bifurcates at the tibio-fibular arch after a course of from 6 to 8
inches, to form the posterior and anterior tibial arteries.
The popliteal artery emits on its track : 1. The femoro-popJiteal artery.
2. Articular branches. 3. Muscular branches chiefly destined to the gastroc-
nemius muscle, of which it is necessary to particularize one long division that
descends within the peiioratus, in company with the great femoro-popliteal
nerve, to terminate superficially near the tendo-Achillis, where it anastomoses
with a recurrent branch of the posterior tibial artery (Fig. 370, 20).
The femoro-popliteal artery is the only one of these collateral branches
deserving particular mention. Its origin indicates the limit of the femoral
and popliteal arteries, as it is detached at a right angle below the ring of the
adductor magnus, at the intermediate point of these two vessels. Placed between
the semimembranosus and semitendinosus muscles on the one part, and the
biceps femoris on the other, this vessel is directed from before to behind, and
arrives at nearly the posterior border of the buttock, where it terminates in
subcutaneous branches, after emitting descending and ascending branches.
Among the first of these, which are principally destined to the gastrocnemius
muscle, sometimes exists the satellite branch of the sciatic nerve, and a thin
twig which descends with the external saphena nerve into the hollow of the
hock, where it meets, like the preceding, a branch of the posterior tibial artery.
Several of the ascending branches pass along the great femoro-popliteal nerve,
and all anastomose either with the deep femoral, or with the ischiatic arteries in
the substance or interstices of the ischio-tibial muscles (Fig. 370, 19).
Terminal Branches of the Popliteal Artery.
1. Posterior Tibial Artery (Fig. 370, 21).
Preparation. — Follow the indications furnished by Fig. 370.
At first situated deeply behind the tibia, beneath the popliteus, and the
oblique and deep flexors of the phalanges, tliis artery descends towards the hollow
of the hock, becoming gradually more and more superficial, and lying below the
tibial fascia, behind the tendon of the oblique flexor muscle, along with its
satellite vein. Arriving at the apex of the os calcis, it crosses the tibial fascia,
describes an S curve, and — along with the sciatic nerve — passes beneath the tarsal
arch ; at the astragalus it separates into two terminal branches — the plantar
arteries.
GoUatoral branches. — We cite : 1. Numerous branches destined to the posterior
deep tibial muscles. 2. The nutrient artery of the tibia. 3. The tarsal articular
arteries, a principal of which, along with a large venous arch, passes under the
perforans, near the inferior extremity of the tibia, to be distributed outside the
tarsus in descending ramuscules and ascending twigs, which extend as far as the
gastrocnemius and perforatus tendons. 4. A superficial ascending branch, arising
THE EXTERNAL ILIAC ARTERIES. 635
ordinarily from the second inflection of the S curvature formed by the artery
at its lower extremity, situated in the hollow of the hock, anastomosing with the
saphena artery, as well as with the satellite popliteal branch of the sciatic nerve,
the ramifications of which, nearly all subcutaneous, are scattered within and
without on the sides of the hock, and the inferior extremity of the thigh.
Terminal branches. — Tlie two terminal branches of the posterior tibial artery
are slender vessels— vestiges of the plantar arteries in Man. Lying on the outer
side of the synovial tendinous sheath lining the tarsal groove, they are placed —
one within, the other without, the perforans tendon, and descend along with the
plantar nerves to the upper extremity of the metatarsus, where they leave the
nerves, each to anastomose with the perforating pedal artery, forming a kind of
deep arch across the upper extremity of the suspensory hgament of the fetlock
— that is, from the post-metatarsal fibrous band that represents the interosseous
plantar muscles of tetradactylous or pentadactylous animals.
In their course, these plantar arteries only distribute some insignificant
ramuscules to the tarsal articulations.
From the convexity of the arch they form in uniting with the perforating
pedal artery, arise four long descending branches : 1. Two superficial,, innominate,
and veiy fine arterioles accompanying the plantar nerves, and passing by the side
of the flexor tendons to the sesamoid groove, where they inosculate with the
collaterals of the digit (Figs. 370, 23 ; 371, 8). 2. Two deep branches con-
stituting the plantar interosseous arteries, distinguished into external and internal.
The first is only an extremely fine vascular twig, very uncertain in its disposition,
and possesses no other importance in Solipeds than representing, in a rudimentary
state, an artery wliich is of considerable size in other animals. Placed within
the external metatarsal bone, it anastomoses, by its inferior extremity, with a
branch of the metatarso-pedal artery. The internal interosseous plantar artery
may be considered, if we disregard the study of analogies, as the continuation of
the perforating pedal artery, which it rivals in volume. It descends to the
external side of the internal metatarsal bone, beneath the margin of the suspen-
soiy ligament of the fetlock, and terminates a little above the tubercle of the
external metatarsal bone, in uniting at a very acute angle with the metatarso-
pedal artery. It gives off on its track : the nutrient of the large metatarsal bone ;
a small branch to the external interosseous artery ; several ramuscules which
cross the posterior border of the internal metatarsal bone to supply the connective
tissue, the skin, and the tendons on the large metatarsal bone.
2. Anterioe Tibial Artery (Fig. 371, 1).
Preparation. — Expose the artery by removing the anterior muscles of the leg.
The anterior tibial artery is the largest of the two branches terminating the
popliteal trunk. It traverses the tibio-fibular arch, and, with its satellite veins,
places itself on the anterior aspect of the tibia, down which it passes by following
the deep face of the flexor metatarsi. On reaching the front of the tibio-tarsal
articulation, it loses its name and takes that of the pedal (or great metatarsal)
artery.
The anterior tibial artery gives off a great number of collateral branches,
which are principally distributed to the tibial muscles. One of them, descending
along the fibula, beneath the lateral extensor muscle of the phalanges, clearly
represents a trace of the peroneal artery of Man.
636 TEE ARTERIES.
3. Pedal (or Great Metatarsal) Artery (Fig. 371, 2).
A continuation of the anterior tibial artery, the name of which changes on
reaching the region of the foot, the pedal artery courses downward over the
anterior face of the tibio-tarsal articulation, by bending shghtly outwards, and
passing beneath the cuboid branch of the flexor metatarsi. At the second row
of tarsal bones it divides into two branches, which we will designate the im-foraU
ing pedal (or perforating metatarsal), and the metatar so-pedal arteries,^ the latter
continued inf eriorly by the digital arteries, or collaterals of the digit.
The collateral branches emanating from this vessel are all articular or
cutaneous, and of no importance.^
Perforating Pedal (Arteria Pedis Perforans, Perforating Meta-
tarsal) Artery. — It crosses the tarsus from before to behind, by passing — with
a venous branch — into the canal between the cuboid, scaphoid, and great cunei-
form bones ; it then joins the arch formed by the anastomoses of the two plantar
arteries — terminal divisions of the posterior tibial (Fig. 371, 14).
Metatarso-pedal or Collateral Artery of the Cannon.^ — i\Iuch larger
than the preceding, this vessel (Fig. 371, 3) may be considered as a continuation
of the pedal (or great metatarsal) artery. It is lodged at first in the fissure
situated outside the large metatarsal bone, in front of the external metatarsal
bone, and afterwards passes between these two bones, above the tubercle termi-
nating the latter, reaching the posterior face of the first, between the two inferior
branches of the suspensory ligament, above the sesamoid groove, where the
vessel bifurcates to form the collateral arteries of the digit.
The collateral artery of the cannon receives, a short distance above this
terminal bifurcation, the internal plantar interosseous artery.
On its course it gives off : 1. Numerous anterior ramuscules for the connec-
tive tissue, tendons, Ugaments, and the skin on the anterior face of the meta-
tarsus and fetlock. 2. Some slender posterior divisions, one of which ascends
within the external plantar interosseous artery, after furnishing several liga-
mentous, tendinous, and cutaneous ramuscules in the posterior metatarsal region.
Digital Arteries, or Collateral Arteries of the Digit (Figs. 370, 25 ;
371, 5, 5 ; 377, 11). — Remarkable for their volume, these arteries carry blood
to the keratogenous apparatus enveloping the ungual phalanx, and from this
distribution derive such importance that they deserve a detailed study.
' The vessel we have here named the perforating pedal artery, is only the like termination
of tlie same artery in Man. The metatarso-pedal artery ought to be regarded as the represen-
tative of one of the dorsal iuterossei arteries, because of its position in the interstice of the
middle and external lateral metatarsal bones. The dorsal interstice of the inner side also
lodges an interosseous branch, usually supplied by the external plantar artery ; but its diameter
is so diminished tliat, in order to avoid complexity by introducing an almost useless element
into the didactic description of the posterior tibial artery, we have thought it our duty to
neglect its indication.
* One of these may be regarded as the analogue of the dormlis pedis of Man.
' Rigot has designated this artery — we do not know why— the superficial plantar artery.
It would have been better to have allowed it to retain the name given to it by Girard— the
lateral artery of the cannon. This is not the only instance in which the attempts of Rigot to
conform the nomenclature of the arteries to that of anthropotoraists has proved unfortunate, as
he has not always succeeded in finding in the Horse the real representatives of the arteries in
Man. The aim of this work does not allow us to discuss the vicious determinations and
denominations of Rigot every time we meet them. We are content to change them, purely
and simply, leaving to the judgment of the reader, should this matter interest him, the task
of deciding if we are right.
THE EXTERNAL ILIAC ARTERIES.
Origin. — The digital arteries succeed the terminal extremity of the collateral
of the cannon, and separate from one another in forming an acute angle below
the sesamoidean venous arch,
above the fetlock-joint, between
the two branches of the sus-
pensory ligament, behind the
inferior extremity of the large
metatarsal bone, and in front
of the flexor tendons of the
phalanges.
Course and Relations. — These
vessels descend — one to the
right, the other to the left, from
the lateral parts of the metacar-
po-phalangeal (and metatarso-
phalangeal) articulation to the
internal face of the basilar pro-
cess, where they bifurcate to
form the plantar and preplantar
ungual arteries.
"In the whole of this course,
it (the digital artery) follows the
track of the flexor tendons, rest-
ing on their margins, and main-
tained there by loose connective
tissue. Behind, it is flanked by
the plantar nerve, which covers
a portion of its surface, enlaces
it with numerous filaments, and
is so closely associated with it
in all its flexuosities, as to form
but a single cord with it.
" In front, it is margined,
though for a short distance, by
its satellite vein, which for the
whole of its track rests on the
lateral faces of the two first
phalanges.
" At its upper part, near
its origin, and on the lateral
PRINCIPAL ARTERIES IN THE POS-
TERIOR FOOT OF THE HORSE.
1, Anterior tibial artery; 2, pedal or
great metatarsal artery; 3, nieta-
tarso-pedal or perforating meta-
tarsal ; 4, arteria pedis perforans ;
5, 5, digital arteries ; 6, 6, arterioles of the ergot ; 7, perpendicular artery ; 8, artery of the plantar
cushion ; 9, anterior branch of the coronary circle ; 10, circumflex artery of the coronary cushion ;
11, preplanter ungual artery; 12, inferior circumflex artery of the foot; 13, collateral branch of
the posterior tibial artery distributed to the external surface of the hock ; 14, arteriole furnished
by the arch formed by the union of the two plantar arteries with the arteria pedis perforans, across
the superior extremity of the supensory ligament of the fetlock.
43
638 THE ARTERIES.
portions of the metacarpo-phalangeal articulation, the digital artery is crossed
from behind to before by the anterior branch of the plantar nerve, and it is
covered for the whole of its extent by the fascia that continues the proper tunic
of the plantar cushion, the lateral ligamentous band of which cuts its direction
obliquely downwards and forwards, at the middle portion of the first phalanx." ^
Collateral divisions. — These are: 1. At the fetlock, numerous fine branches
distributed to the metacarpo-phalangeal articulation, but particularly to the
sesamoid sheath and the tendons lodged in it.
2. To the environs of the upper extremity of the first phalanx, slightly
ascending and sometimes voluminous twigs, for the tissue of the ergot (the horny
tubercle behind the fetlock).
3. Towards the middle of the same bone, the vessel named by Percivall the
perpendicular artery, and correctly so, for it arises at a right angle from the
digital artery to divide almost immediately afterwards into two series of ramifi-
cations— anterior and posterior. The anterior branches are in nearly every
instance two principal : one ascending, passing beneath the check-band of the
extensor tendon, and climbing to the capsular ligament of the fetlock-joint to
meet the arterial divisions furnished directly to that ligament by the collateral
artery of the cannon ; the other descending, which reaches the side of the
second phalanx, Avhere its ramuscules anastomose with the coronary circle and
the circumflex artery of the coronary cushion. The posterior ramifications
consist most frequently of two principal branches— one ascending, the other
descending ; these insinuate themselves between the flexor tendons and the
sesamoid ligaments, to be distributed to these organs, but especially to the syno-
vial membrane of the large sesamoidean bursa. Sometimes it is seen to arise
alone from the digital artery. It must here be noted, that the divisions
furnished by the anterior branches of this perpendicular artery communicate
with those of the opposite side in front of the first phalanx, either above or
below the principal extensor of the digit ; and that the posterior branches
exhibit a series of analogous anastomoses. The body of the first phalanx is
therefore enveloped on every side by an arterial plexus,
4. At different elevations on the first and second phalanges, several tendmous
and cutaneous twigs, which are of no importance.
5. The artery of the plantar cushion, which arises at the superior border of
the lateral cartilage, is directed obMquely backward and downward, and placed
within the posterior border of that cartilage, to be distributed to the middle
portion of the complementary apparatus of the third phalanx, as well as to the
villous tissue and the coronet. The branch expended in the latter sometimes
proceeds directly from the digital artery; it is a very remarkable vessel, is
inflected from before to behind, crossing the posterior border of the pedal carti-
lage, creeping on the internal face or in the texture of the skin, a little above the
coronet, parallel with that portion of the keratogenous apparatus, and terminates
by anastomosing with a branch of the artery now to be noticed.
6. The coronary circle,'^ formed by two transverse branches — one anterior, the
other posterior, springing at a right angle from the digital artery, under the
cartilaginous plate of the os pedis— passes around the coronary bone to meet
the analogous branches of the opposite artery, to anastomose with them directly
and by inosculation. The coronary circle therefore presents two distinct por-
' H. Bouley, Traite de V Organisation du Pied du Cheval. Paris, 1851.
* So named because it encircles the coronet.
THE EXTERNAL ILIAC ARTERIES. 639
tions : one posterior, placed above the superior border of the small sesamoid,
beneath the perforans tendon ; the other anterior, more extensive and volmniaous,
covered on the sides by the lateral cartilages of the foot, and in its front or
middle part by the expansion of the anterior extensor tendon of the phalanges.
The collateral ramuscules furnished by the posterior part of the circle are
small, few, and of no interest.
Among the branches arising from the anterior portion, there is only a single
pair of arteries to be noted, which are remarkable for their mode of distribution
and their volume. They originate near the border of the extensor tendon, and
immediately divide into two divergent branches : one the internal, which passes
across that tendon to anastomose with the homologous branch of the opposite
side ; the other, external, passes backward to meet the cutigeral branch furnished
by the artery of the plantar cushion, and joins that vessel. From this disposi-
tion results a very fine superficial vascular arch around the coronet, which is well
named the circumflex artery of the coronary cushion ; it is situated a little above
the cutidural artery, beneath the skin of the coronet, and looks as if encrusted in
that membrane ; by its two extremities it rests on the arteries of the plantal
cushion, and is fed by the two principal vessels of the coronary circle ; while it
furnishes ascending anastomosing ramuscules to the inferior divisions of the per-
pendicular artery, as well as numerous descending branches passing into the
coronary cushion and the laminal tissue of the foot.
Such is the ordinary disposition of the coronary circle and its superficial arch
— the circumflex artery of the coronary substance ; though it varies much in
different animals, and even in the feet of the same animal. To attempt to
describe here the variations we have seen would be supererogatory, and we may
hmit ourselves to saying that these varieties were almost exclusively confined to
the origin of the branches composing these two circular vessels and their manner
of arrangement, without modifying in any way the general disposition of the
circles.'
Terminal divisions. — These are, as has been ah-eady mentioned, the plantar
and preplantar ungual arteries.^
a. The preplantar ungual artery is the smallest of these two terminal branches.
Situated at first inside the basilar process of the third phalanx, it turns round
this to traverse the notch which separates this process from the retrossal eminence,
is lodged with a satellite nerve in the preplantar fissure, which it crosses from
before to behind, and terminates near its anterior extremity by several divisions
that bury themselves in the os pedis. In its course, it distributes : 1. Before
passing into the sub-basilar notch, a deep retrograde branch destined to the bulb
of the heel and the villous tissue. 2. Immediately after leaving that notch, a
second retrograde branch, whose divisions pass backward, behind the great
circumflex artery of the pedal bone. 3. During its passage in the preplantar
fissure, several ascending and descending branches which ramify iu the laminal
tissue ; the firet anastomose with the descending divisions of the coronary circle
and the circumflex artery of the coronary cushion.
* We may notice here one of these variations, which is somewhat frequently met with in
the anterior limb. This consists in the anterior descending branch of the perpendicular artery
uniting at its terminal extremity with the circumflex artery of the coronary substance, which
it concurs to form.
* In all treatises on anatomy, these vessels are simply designated the plantar and preplantar
arteries. We have added the epithet ungual to distinguish these arteries from the properly
so-called plantar bmnclies— the terminal divisions of the posterior tibial artery.
640 TEE ARTERIES.
b. The plantar ungual artery ou,2:lit to be regarded as a continuation of the
digital arterj, because of its vokime and direction. Lodged at first, with a fine
nervous branch, in the plantar fissure, it afterwards enters the canal of the same
name, and thus penetrates into the semilunar sinus of the os pedis, where it
anastomoses by inosculation with the opposite artery, forming a deep vascular
arcade which we designate the plantar arcade or circle, or, after M. H. Bouley,
the semilunar anastomosis (Fig. 377, 12)!
Two orders of branches emanate from the convexity formed by this' anasto-
motic loop. The (tscencUng order " irradiate in the spongy framework of the
third phalanx, and like so many hair-roots, escape by numerous openings from
its anterior face, where they form a very intricate plexus by anastomosing, in the
texture of the laminal tissue, with the extreme divisions of the anterior branch
of the digital artery and those of the coronary circle. ... It is to these divisions
that Spooner has given the name of anterior laminal arteries " (H. Bouley).
The descending order, much more considerable, named by Spooner (W. C, of
Southampton) the inferior communicating arteries, arise at a right angle from the
anterior circumference of the semilunar anastomosis, traverse in a divergent
manner the tissue of the phalanx, and make their exit by the large foramina
situated a little above the inferior border of the bone, where they furnish a mul-
titude of ascending ramuscules which Concur to form the arterial network of the
laminal tissue. " Then they anastomose transversely* by a succession of little
arcades which are thrown from one to the other, and in this way give rise to a
great circumflex canal which follows the contour of the parabolic curve exhibited
by the thin border of the os pedis, on its inferior face" (H. Bouley). This
vascular arch, which we pui^pose naming the inferior circumflex artery of the foot
(Fig. 377, 12), to distinguish it from the circumflex of the coronary cushion, is
joined by its extremities to the preplantar artery, in the same manner that the
latter circumflex is united to the artery of the plantar cushion. From its con-
cavity it throws off some fourteen or fifteen convergent branches, which are
destined to the villous tissue of the sole.
Differential Characters of the External Iliacs in the other Animals.
1. External Iliac Arteries of Ruminants.
In the Ox, apart from the considerable vohime of the great muscular arteries of the tliigh,
the external iliac, as well as the femoral and popliteal arteries continuin": it, comport themselves
almost the same as in the Horse. It is only when we reach the posterior and anterior tibial
arteries that we find some peculiarities worthj^ of notice.
Posterior tibial artery. — Much more voluminous than that of Solipeds, this artery follows
the same course, and terminates iu an analogous manner : forming at its lower extremity two
plantar branches, which anastomose witli the perforating pedal artery behind the superior ex-
tremity of the principal metatarsal bone, and beneath the suspensory ligament. But these two
branches are far from possessing the same volume ; the internal is incomparably the largest,
and appears to be the direct continuation of the posterior tibial artery.
From this anastomosis results, as in tiie Horse, two series of metatarsal branches — a deep
and a superficial.
The deep branches, two or three in number, form on the posterior face of the metatarsal
bone, below the suspensory ligament, the posterior interosseae, mixed with two or three reticu-
lated venous branches ; they anastomose by their inferior extremity with a perforating branch
of the collateral of the cannon.
The superficial branches, similar to those which accompany the plantar nerves in the Horse,
are of very unequal calibre ; the external is so rudimentary that it often escapes dissection ;
the internal in reality continues tlie plantar artery of the same side. Both are united to the
perforating branch already noticed.
TEE EXTERNAL ILIAC ARTERIES 641
Anterior tibial artery. — After passing dowu along the leg on its antero-external face, as in
Solipeds, this vessel arrives on the hock, where it takes the nume of pedal artery, and furnishes
the per/orating-pedal artery ; it is continued by the metatarao-pedal or collateral artery of fht
cannon.
a. The perforating pedal artery does not differ from that of the Horse.
h. The metatar so- pedal, or collateral of the cannon, descends, flanked by two satellite veins,
in the channel on the anterior face of the metatarsal bone, giving off towards the inferior
extremity of that channel, the perforating branch already spoken of, and is continued into the
digital region as the common digital artery.
The perforating branch of the collateral of the cannon passes into the foramen pierced from
before to behind, across the inferior extremity of the metatarsal bone, arriving beneath the
suspensory ligament, and then divides into several ascending and descending branches. The
first join the deep and superficial posterior metatarsal arteries furnished by the plantar and
pedal perforating arteries. Among tiip second, we notice three digital arteries, facsimiles in
miniature of those which will be described in the anterior limb : two lateral, descending on the
eccentric side of the phalanges ; a median, turning within the flexor tendons to place itself
behind them on the middle line of the digital region, and prolonged into the interdigital space,
where it anastomoses with a branch of the principal artery of the digits.
The latter artery — the common digital — descends into tlie space between the digits, after
passing beneath the capsular ligament of the metatarso-phalangeal articulations, in the notch
between the two articular surfaces of the metatarsal bone, and terminates above the inferior
extremity of the first phalanx by two ungual arteries, the description of which will be reserved
until describing the arteries of the anterior limb. In the number of collateral branches
emanating from this vessel, there may be particularly remarked a large offshoot which arises
a little before the separation of the two ungual arteries, and is directed from before to behind,
dividing at the posterior part of the interdigital space into several divisions, the principal of
which are ; 1. Two transverse branches passing between the flexor tendons and tlie phalanges,
to be joined to the lateral digital arteries. 2. A single ascending branch, joining with the
posterior median digital artery. 3. A descending branch, also single, dividing into two por-
tions which reach the heels, to be distributed to the plantar cushion and tlie villous tissue.
These branches represent the arteries of the plantar cushion in the Horse, and will be noticed
more in detail in the description of the arteries of the anterior limb, where in principle tliey are
found to be exactly like these.
2. External Iliac Arteries of the Pig.
The distribution of these vessels in the Pig is remarkably like that we have described as
existing in Ruminants, even in the terminal portions of the limbs, notwithstanding the com-
plete development of the two lateral digits. It may be noted, however, that the posterior tibial
artery is somewhat slender, and that it is singularly increased by its anastomosis with tlie
saphena artery, the dimensions of which are relatively considerable.'
3. External Iliac Arteries of Carnivora.
The external iliac is divided in tlie Carnivora, as in the other animals, into three sections :
the proper iliac artery, the femoral artery, and the popliteal artery, terminated by the tibial
branches.
Proper iliac artery. — Tiiis vessel does not give rise to any branch, as the circumflex iliao
comes directly from the posterior af)rta.
Femoral artery. — As in the Horse, this gives off: 1. Several muscular innominate branches.
2. Two great muscular arteries, the posterior of wliich furnisiies the prepubic artery. 3. A
saphenal branch.
In the Bitch, the external pudic artery, emanating from the prepubic division, presents
Bome peculiarities in its distribution. It gives off a long branch which is placed in the texture
of the mainmse, and passes forwanl to meet and unite with the mammary branch furnished by
the internal thoracic artery ; it then runs between the two thighs in a flexuous manner, and
reaches the lips of the vulva, where it ends in numerous ramuscules that anastomose with the
vulvar divisions of the internal pudic artery.
The saphena artery is as remarkable for its large volume as for its destination. It descends
' In small Ruminants, the posterior tibial artery, properly speaking, is equally rudimentary;
the saphena artery constitutes tlie principal vessel. From a note which we made a long time
ago, it appears the first vessel is altogether absent sometimes, and that the plantar divisions
come exclusively from the saphena, as in the Carnivora.
612
THE ARTERIES.
on the internal face of the leg, furnishing numerous subcutaneous divisions, and terminates at
the hock by several slender plantar twigs, which accompany tlie flexor tendons. Among the
branches given oif by this vessel in its course, it is necessary to distinguish two — one which
follows the anterior branch of the saphena vein to the hock, where it communicates by its
terminal divisions with the tarsal artery ; the other arises a little lower, passes beneath the
Fig. 372.
Y\z. 373.
ANTERIOR ASPECT OF HUMAN LEG AND FOOf.
1, Tendon of insertion of the quadriceps ex-
tensor muscle ; 2, insertion of the ligamen-
tum patellre ; 3, tibia ; 4, extensor lungus
digitorum ; 6, peronei ; 7, inner belly of
gastrocnemius and soleus; 8, annular
ligament; 9, anterior tibial artery; 10,
its recurrent branch inosculating with (2)
inferior articular and (1) superior articular
arteries, branches of the popliteal; 11,
internal malleolar artery; 17, external
ditto, inosculating with anterior peroneal
artery, 12; 13, dorsalis pedis artery; 14,
tarsea and metatarsea ; 15, dorsalis hal-
lucis artery ; IR, continuation of dorsalis
pedis into sole of foot.
POSTERIOR ASPECT OF HUMAN LEG.
1, Tendons of inner hamstring; 2, ditto of
biceps; 3, popliteus muscle ; 4, flexor
longus digitorum; 5, libiilis posticus;
6, fibula; 7, peronei muscles; £>, Jowcr
portion of flexor longus pollicis, v/itl". itc
tendon ; 9, popliteal artery, sivlng off
articular and muscular Viranchcs; 10, an-
terior tibial artery; 11, posterior tibial
artery; 12, relative position of tendons
and artery; 13, peroneal artery; 14, pos-
terior peroneal.
phalangeal flexor muscles, and is expended on the hock in articular and malleolar branches. In
the latter branch we see a trace of the 'peroneal artery of Man. The saphena itself, considered
as a whole, and particularly towards its inferior moiety, supplements the posterior tibial
artery.
THE EXTERNAL ILIAC ARTERIES.
643
Popliteal artery. — This artery gives an iimportant femoro-poiiliteal branch, and enters the
tibio-peroneal arch to constitute the anterior tibial artery, after distributing on its course
muscular ramuscules — rudiments of the posterior tibial artery of other animals.
The anterior tibial artery, arriving in front of the hock, detaches the tarsal artery — a
voluminous branch, divided near its origin into several superficial superior and inferior branches.
It continues to descend, traverses from before to behind the superior part of the third inter-
metatarsal space, and terminates by an arterial arch situated beneath the flexor tendons ; from
this arch emanate ascending divisions, that anastomose with the plantar arteries, and three
large descending or digital branches, which affect the same disposition as three analogous
principal arteries emanating from the superficial palmar arch of
the anterior limb.
Fig. 374.
Comparison of the External Iliacs of Man witk those of
Animals.
In Man, the external iliac forms the external branch of the
bifurcation of the common iliac ; it extends to the crural arch,
where it takes the name of femoral artery. It furnishes the cir-
cumflexa ilii and epigastric : the latter resembling, in its distribu-
tion, the posterior abdominal branch given off by the prepubic
artery in the Horse.
Tlie femoral artery has the same general disposition as in
animals, and almost the same collateral branches. There is no
prepubic artery ; the divisions furnished by this trunk in Solipeds
originate separately from the femoral artery ; these are : the
abdominal tegumental artery (superficial epigastric), and the exter-
nal pubic arteries — the one resembling the subcutaneous abdominal
artery, and the others the branches of the external pudic artery
of animals.
The popliteal artery is a superficial vessel situated at the
posterior face of the knee-joint, in a lozenge-shaped space limited
by the muscles of tlie region, and named the popliteal space. At
the tibio-peroneal arch it bifurcates, and constitutes the anterior
til'ial and the tibio-peroneal trunks.
The tibio-peroneal artery does not exist in animals in which
tlie peroneal artery is in a rudimentary state, in consequence of
the feeble development of the peroneus. This trunk is short, and
furnishes the nutrient artery of the tibia, then divides into the 1
peroneal and posterior tibial artfries. The first descends to the
external malleolus, along the inner f ice of the tibia, and terminates
in two branches, one of which, the anterior peroneal, communicates
with the dorsal artery of the tarsus — a branch of the pedal. The
posterior tibial, on reaching the concavity of the caleis, constitutes
the internal and external plantar arteries. The internal plantar
is directed forwards, beneath the sole of the foot, and is lost in the
muscles of the great toe, or forms the collateral of the latter vessel.
Beneath the tarsal articulations, the external plantar describes a
curve, having its concjtvity backwards, and anastomoses, at the
fourth intermetatarsal space, with the termination of the dorsalis
pedis; from this results a plantar arch, which gives off, from
without to within: 1. The external collateral of the little toe;
2, 3, 4, 5, the interosseous plantar (or digital) arteries of the first, second, third and fourth
intermetatarsal spaces ; these arteries, at the root of the toes, bifurcate to furnish collaterals
to these organs.
The anterior tibial artery, situated on the anterior face of the interosseous ligament that
unites the tibia to the peroneus, extends to the annular ligament of the tarsus, where it is con-
tinuerl by the dorsalis pedis, which descends along the dorsum of the foot to gain the summit
of the fourth interosseous space.
The dorsal artery of the metatarsus (metatarsea) is almost nil in Solipeds. In Man it is
directed transversely to the tarsus, from within to without ; its terminal branches unite on the
dorsum of the tarsus, and the arch itWrns gives off the dorsal interosseous arteries of thetliree
first spaces. These communicate above and below, in the intermetatarsal spaces, with the
arteries of sole of
human foot.
, Under surface of os cal-
eis ; 2, musculus aoces-
sorius ; 3, long flexor
tendons ; 4, tendon of
peroneus longus ; 5, ter-
mination of posterior
tibial artery; 6, internal
plantar ; 7, external
plantar ; 8, plantar arch
giving oft' four digital
branches, three of which
are seen dividing into
collaterals for adjoining
644 THE ARTERIES.
plantar interosseous arteries by the anterior and podfrinr perforating arteries ; finally, at the
base of the toes they bifurcate to form the collateral arteries of the toes.
The dorsal collateral artery of the fourth space represents the vessel described in the Horse
by the name of metatarso-pedal artery, or collateral of the cannon ; it forms the internal
coUaterrtl dorsal of the fourth toe, and external collateral of the great toe.
The dorsalis pedis, after giving off tlie last-named vessel, dips into the fourth space and
reaches the lower surface of the foot, where it anastomoses with the internal plantar artery.
In this last portion of its course it resembles the vessel we have named the perforating pedal
in Solipeds.
Aeticle v.— Anterior Aorta (Fig. 375, 1).
This vessel, the smallest of the two trunks succeeding the common aorta, is
no more than 2 or 2^ inches in length at the most. It leaves the pericardium
to pass between the two layers of the mediastinum in an oblique direction from
below upwards and behind forwards, above the right auricle, below the trachea,
and to the left of the anterior vena cava. After furnishing some insignificant
twigs to the pericardium and mediastinum, it divides into two branches which
constitute the brachial trunks or axiUary arteries.
In Pachyderms, Carnivora, and Rodents, the anterior aorta does not exist,
and the axillary arteries arise directly from the common aorta, towards the point
from which the anterior aorta arises in other animals.
Article YI. — Brachial Trunks, or Axillary Arteries (Fig. 375, 2, 3).
The brachial trunks — terminal branches of the anterior aorta — are distinguished
into left and right. The latter is much larger than the former, because it fur-
nishes arteries to the head. It is also named the arteria innominata.
Origin. — They separate from one another at an acute angle, the left being
a little more elevated than the right.
Course and direction. — Both branches are directed forwards, between the layers
of the anterior mediastinum and beneath the trachea ; gaining the entrance to
the chest, and leaving it by turning round the anterior border of the first rib,
under ttte insertion of the scalenus, they become inflected backwards and down-
wards, to be placed, one to the right, the other to the left, at the internal face of
the anterior limb, in the middle of the nerves of the brachial plexus, and continue
within the arm, assuming the name of Mimeral artery on leaving the interstice
which separates the subscapularis muscle from the adductor of the arm.
In its thoracic course, the left trunk describes a curve — the convexity being
upwards — the right taking a rectilinear direction.
Relations. — In studying the relations of the brachial trunks, we recognize two
principal portions — one thoracic, placed in the chest ; the other axillary, situated
within the limb. In their thoracic portion, the brachial trunks, at first lying
beside each other, separate slightly in front to reach the internal face of each of
the two first ribs. They are accompanied by the cardiac, pneumogastric, inferior
laryngeal, and diaphragmatic nerves, and are included, as already noticed, between
the two layers of the anterior mediastinum. The right occupies nearly the
middle line beneath the inferior face of the trachea, to the left and above the
anterior vena cava. The left slightly rises on the side of the trachea, and
generally corresponds inwardly to the thoracic duct.
In their axillary portion, these vessels accompany the coiTesponding venous
trunks, cross the terminal tendon of the subscapularis muscle in passing below
the humeral insertion of the deep pectoral, and among the branches of the
THE BRACHIAL OR AXILLARY ARTERIES. 645
brachial plexus, but embraced more particularly bj the median, anterior humeral,
and uljiar nerves.
Distribution. — The axillary arteries give off, on their course, eight collateral
branches. Four arise from the thoracic portion : three upper — the dorsal,
superior cervical, and vertebral arteries ; and an inferior — the internal thoracic.
Two are detached at the first rib — one downwards, the other forwards ; these are
the external thoracic and superior cervical arteries. Two originate from the axil-
lary portion of the trunk and pass upwards : they are the supra- and subscapular
arteries. After furnishing the latter vessel, the brachial trunk is continued by the
humeral artenj.
Independently of all these branches, the right axillary artery gives off, near
its origin, the common trunk of the two carotid arteries, which will be studied in
a separate article.
Preparation. — The subject being placed on the right side, remove the skin and the left
anterior limb, in order to make the dissection at two periods.
First period. — Dissect all the intra-thoracic portion of the left axillary artery and its col-
lateral branches, as in Fig. 375, taking care to leave the inferior cervical artery (which has
been cut in the figure to render the drawing more distinct) attached by its superior extremity
to the middle portion of the mastoido-humeralis, which has not been disturbed.
Second period. — Prepare, on the separated limb, the extra-thoracic portion of the vessel and
all the arteries it furnishes, in taking as guides Figs. 376, 377.
Collateral Branches of the Axillary Arteries.
1. DoESAL, DoRSO-MUSCULAE, OE Teansveese Ceevical Aetery (Fig. 375, 4).
Chiefly directed to the muscles of the withers, this artery — the first given off
by the brachial trunk — crosses outwardly the trachea, thoracic duct, oesophagus,
great sympathetic nerve, and the longus colli, in proceeding beneath the media-
stinal layer ; it reaches and passes over the second intercostal space, bends slightly
backwards, and places itself in the interstice separating the angularis scapulse
and serratus magnus from the inferior branch of the longissimus dorsi, where it
separates into several divergent branches. The majority of these ascend towards
the superior border of the withers, neck, and shoulders, by gliding between the
latter muscles, the splenius, and the serratus anticus on the one part, and the
serratus magnus and rhomboideus on the other, to be distributed to those
muscles and the integuments covering them. The most anterior of these
branches passes between the splenius and complexus muscles, parallel with
the superior cervical artery, which is in front of it, and communicates by its
ramuscules with the latter vessel, as well as with the vertebral and occipito-
muscular arteries. The last-named branch is sometimes long and voluminous,
and partly supplements the superior cervical, as is exemplified in the specimen
which served for Fig. 375.
Before leaving the thorax, the dorsal artery gives off some unimportant
ramuscules and the subcostal artery {superior intei-costal of Man). This branch
(Fig. 375, 5) curves backwards and, with the sympathetic chain, places itself
beneath the costo-vertebral articulations, against the longus colli, furnishing the
second, third, and fourth intercostal arteries and the corresponding spinal branches,
and terminating at the fifth intercostal space by either forming the artery which
descends into that space, in anastomosing by inosculation with a branch emanat-
ing from the first posterior intercostal artery, or by expending itself in the spinal
646 THE ARTERIES.
muscles. Frequently, the second intercostal and its spinal branch come directly
from the doi*sal artery ; the fifth also often arises from the posterior aorta.^
On the right side, the dorsal artery always proceeds from a trunk common to
it and the superior cervical artery — a circumstance sometimes observed in the
left. This trunk has no relation with the oesophagus.
2. Superior Cervical, Cervico-muscular, or Deep Cervical Artery
(Fig. 375, 6).
This vessel arises in front of the preceding artery, has the same relations in
the thoracic cavity, which it leaves by passing between the two first ribs, behind
the last costo-transverse articulation ; ^ it is then directed upwards and forwards,
passing beneath the inferior branch of the longissimus dorsi and complexus
muscles, courses in a flexuous manner through the space comprised between the
latter muscle on one side, and the superior branch of the longissimus dorsi and
cervical ligament on the other, and aiTives at the second vertebra of the neck,
where its terminal divisions anastomose with the branches of the occipito-
muscular, vertebral, and even the dorsal arteries.
The superior cervical artery distributes in its course : 1. The first intercostal
arteiy and the first spinal branch. 2. Very numerous branches which are
expended in the muscles and integuments of the cervical region, as well as in the
large hgament occupying the middle plane of that region ; among these branches,
one longer than the others traverses the complexus muscle to place itself between
it and the splenius, and is sometimes supplemented in great part by the dorsal
artery.
3. Vertebral Artery (Fig. 375, 7).
Arising at an acute angle from the axillary artery at the first intercostal space,
and covered at its origin by the mediastinal layer, the vertebral artery proceeds
forward and upward, within the first rib, outside the oesophagus,^ the trachea,
and the inferior cervical ganglion, and is situated at the bottom of the interstice
separating the two portions of the scalenus, with the fasciculus of branches
arising from the brachial plexus, which is a little above the vessel. It then
passes beneath the transverse process of the seventh cervical vertebra, and
traverses the series of cervical foramina, hidden beneath the iutertransversahs
colli, to anastomose in full canal with the retrograde branch of the occipital
artery, at the atlo-axoid articulation, underneath the obliquus capitis posticus
muscle.
In its track, it detaches at each intervertebral space numerous branches,
which may be divided into inferior, superior, external, and internal. The first
chiefly pass to the scalenus, longus colli, and rectus capitis anticus major. The
second, which are incomparably larger and more numerous than all the others,
are destined to the complexus and trachelo-mastoideus, semispiualis, and longis-
simus dorsi muscles ; they anastomose with the divisions of the superior cervical
and occipito-muscular arteries. The external branches are very small, and pass
to the intertransversalis muscle. The internal branches enter the intervertebral
foramina to join the middle spinal artery.
' For the description of these arteries, see p. 611.
» We liave seen it escape, along with the dorsal artery, by the second intercostal space.
* On the right, these relations with the oesophagus are not present.
THE BRACHIAL OR AXILLARY ARTERIES.
647
4. Internal Thoracic (Pectoral), or Internal Mammary Artery
(Fig. 375, 9).
The internal thoracic artery emerges from the brachial trunk at the first rib,
Fig. 375.
DISTRIBUTION OF THE ANTERIOR AORTA.
I, Anterior »orta ; 2, left axillary artery ; 3, right axillary artery ; 4, dorsal artery ; 5, subcostal
artery ; 6, superior cervical artery ; 7, vertebral artery ; 8, 8', inferior cervical artery ; 9, origin
of the internal thoracic artery ; 10, origin of one of the external or intercostal branches of this
artery; 11, one of its inferior ramuscules; 12, external thoracic artery; 13, origin of the supra-
scapular artery; 14, common carotid artery ; 14', accessory thyroid artery ; 14", thyro-laryngeal
artery; 15, atloido-muscular artery; 16, occipito-muscular artery; 17, posterior aorta. A,
Pulmonary aorta ; B, trachea ; C, oesophagus ; D, cervical ligament ; E, superior branch of the
longissimus dorsi muscle ; F, inferior branch of the same ; G, complexus muscle : H. splenius
muscle ; i, J, originating aponeurosis of the splenius and the serratus anticus muscles ; K, section
of the obliquus capitis major ; L, rectus capitis posticus major ; M, rectus capitis anticus major }
N, sterno-maxillaris ; O, P, deep and superficial pectoral muscles turned downwards.
648 THE ARTERIES.
and immediately descends along the inner face of that bone to the sternum,
remaining covered by the pleura. It then bends backwards, passes under the
triangularis sterni muscle and above the sternal cartilages, which it crosses near
the chondro-sternal articulations, and reaches the base of the xiphoid cartilage,
where it ends in two branches — one abdominal, the other thoracic, and which
have been named the anterior abdominal and asternal arteries.
In its course, the internal thoracic artery sends off collateral branches, which
may be distinguished into superior, inferior, and external. The superior are
always very slender, and proceed to the pericardium and mediastinum. The
inferior (Fig. 375, 11) are very large, and traverse the intercostal spaces to enter
the pectoral muscles, where they meet the ramifications of the external thoracic
artery. The external branches (Fig. 375, 10) follow the intercostal spaces ;
each generally divides into two branches, which finally anastomose by inoscula-
tion with the terminal divisions of the first seven intercostal arteries.
Terminal branches of the interned thoracic artery. 1. Anterior abdominal
artery. — This vessel separates from the asternal artery at an acute angle, and
passes directly backward to escape from the chest by coureing beneath the xiphoid
cartilage ; it then places itself on the superior face of the rectus abdominis,
which it enters, after detaching lateral branches to the abdominal walls, and
anastomoses by its terminal ramifications with the posterior abdominal artery.
2. Asternal artery. — This vessel glides within the cartilaginous circle formed
by the false ribs, in crossing the digitations of the transversalis alxlominis, and
terminates at the thirteenth intercostal space, in which it ascends to anastomose
with the corresponding intercostal artery. It supplies in its track intercostal
branches, which comport themselves like the analogous branches of the internal
thoracic artery ; fine diaphragmatic arterioles : and abdominal divisions, which
particularly ramify in the transversahs abdominis.
5. External, Inferior Thoracic, or External Mammary Artery
(Fig. 375, 12).
Principally distributed to the deep pectoral muscles, this artery commences
at an acute angle in front of, but close to, the preceding, turns the anterior
border of the first rib, and then passes back against the internal face of the deep
and superficial pectoral muscles, in which are extended its collateral and terminal
divisions. It gives off a fine branch which accompanies the spur vein, and
ramifies in the panniculus carnosus.
This artery sometimes rises from the supra-sternal vessel ; its volume is
subject to great variations, and we have seen it entirely absent.
6. Inferior Cervical or Trachelo-muscular Artery (Fig. 375, 8, 8').
Arising opposite the two preceding vessels, sometimes near the external, and
at other times near the internal mammary arteries, this vessel is at first situated
in the gulf between the jugulars, within the anterior superficial pectoral muscle,
and above the glands at the entrance to the chest ; it divides after a short course
into two branches, which separate at a very acute angle. One of these, the
superior {ascending cervical of Man), rises between the mastoido-humeralis and
subscapulo-hyoideus muscles, to which it is distributed, as well as to the glands
at the point of the shoulder, and the anterior superficial pectoral and angularis
scapulae muscles.
THE BRACHIAL OB AXILLARY ARTHBIES. r^ 649
The inferior branch (thoracica acromialis of Man) descends in the interspace
comprised between the mastoido-humeralis and the anterior deep pectoral muscles,
accompanying the cephalic vein ; it is distributed to these two muscles, and super-
ficial and anterior superficial pectorals.
7. SuPEA-scAPULAE OE Peescapulae Aeteey (Fig. 375, 13).
This is a small and slightly tortuous vessel, which arises from the axillary
artery, a little before it reaches the tendon of the subscapularis muscle. It is
directed upwards, and enters the space included between that muscle and the
supra-spinatus, after sending off some divisions to the anterior superficial pectoral
muscle. Its terminal branches are expended in the inferior extremity of the
supra- and infra-spinati muscles, the tendon of the biceps, and in the articulation
of the shoulder.
8. Infea-scapulae oe Subscapulae Aetery (Fig. 376, 2).
This artery is remarkable for its considerable volume ; it arises at a right
angle from the axillary artery, at the space separating the subscapularis from the
teres major muscles. Its origin indicates the limit artificially fixed between the
brachial trunk and the humeral artery. It is seen to proceed upwards and back-
wards in this interspace, within the caput magnima, until near the dorsal angle
of the scapula, where it terminates.
It gives off on its track :
1. An artery which, following the inferior border of the latissimus dorsi
muscle, ascends to its inner face, throwing off twigs into the substance of the
muscle, as well as into the panniculus carnosus.
2. The scapulo-humeral, or posterior circumflex artery of the shoulder, which
passes from within that articulation, beneath the caput magnum, to reach its
external face. After giving off some collateral branches, it arrives, with the
circumflex nerves, underneath the abductors of the arm, where it breaks up, like
its sateUite nerve, into several divergent branches destined to the three muscles
above named, the oblique flexor and short extensor of the forearm, and to the
mastoido-humeralis and panniculus carnosus.
3. Muscular hranches, which escape at intervals during the course of the
vessel, and are sent forwards and backwards. The anterior pass either to the
internal or external side of the scapula, or to both sides of that bone, the posterior
border of which they embrace in their bifurcation. The internal divisions creep
in the fissures on the deep face of the bone, throwing their ramuscules into the
subscapularis muscle, and even reaching the supra-spinatus, as well as the inser-
tion of the angularis scapulte and serratus muscles. The external divisions
traverse the caput magnum, to be distributed to the supra- and infra-spinati and the
abductor muscles of the arm — one furnishing the nutrient arteiy of the scapula.
Y\xQ posterior branches supply the abductor of the arm, and the caput magnum.
Humeral Artery, or Terminal Artery of the Brachial Trunk (Fig. 376).
Course. — This vessel is a continuation of the axillary artery, which changes
its name after giving off the subscapular branch. At first it describes a slight curve
forwards to descend almost vertically to the inside of the thoracic Umb, by
crossing obliquely the direction of the humerus, and terminates above the
650 p-i THE ARTERIES.
inferior extremity of that bone by two branches, which constitute the anterior
and posterior radial arteries.
Relations. — In its course, the humeral artery is related : in front, to the
median or ulno-plantar nerve, and to the posterior border of the coraco-humeralis
muscle, which it closely follows ; behind, to the vein of the arm, and through it
to the ulnar nerve ; outwardly, to the common tendon of the latissimus dorsi and
the teres major, to the caput parvum, and to the humerus ; inwardly, to the
sheath of the biceps muscle, which separates the posterior deep pectoral from the
artery of the arm, and in which this vessel is enclosed, in common with its satellite
vein, the lymphatic glands and vessels of the arm, as well as with the nerves of
the fore limb.
Collateral branches. — Among these may be distinguished four, which merit
particular mention. They are the prelmmeral, external and internal collateral
arteries of the elboiv, and the principal artery of the flexor brachii muscle. "We
need only indicate, besides these, several irregular ramuscules which go to the
latter muscle, to the coraco-humeralis, and to the caput parvum.
1. Prehwmral, or anterior circumflex artery (Fig. 376, 4). — This arises at a
right angle, is directed forward, passes between the two branches of the coraco-
humeralis, turns round the anterior face of the humerus, beneath the bicipital
groove, and terminates in the mastoido-humeralis muscle. During its progress it
gives off branches to the coraco-humeralis and biceps muscles, as well as to the
articulation of the shoulder. Among the articular ramifications, there is one
which ascends outwardly on the tendon of the infra-spinatus ; the ultimate
divisions anastomose with the ramuscules of the posterior circumflex artery.
2. Deep humeral (humeralis profunda), or ext&rnal collateral artery of the
elbow (Fig. 376, 5). — A very large branch which emerges from the humeral
trunk, by forming with that artery an almost right angle at the common
terminal tendon of the latissimus dorsi and the teres major. After a very short
course, it divides into two principal branches ; one of these sends its ramuscules
into the caput magnum and medium ; the other passes under that muscle in
turning round the humeralis obliquus, along with the radial nerve, and reaching
beneath the caput medium, descends — still with its satelhte nerve — in front of
the articulation of the elbow, where this branch anastomoses with the anterior
radial artery. It supplies all the olecranian muscles — except the caput magnum —
as well as the humeralis obliquus and the extensor metacarpi magnus.
3. Epicondyloid, internal collateral of the elbow {cubital), or ulnar artery (Fig.
376, 7). — Smaller than the external collateral, this artery arises at the nutrient fora-
men of the humerus, and proceeds backwards on the internal face of that bone, to
pass beneath the caput magnum, by following in a more or less flexuous manner
the inferior border of the caput parvum ; it then descends, at first behind the
epicondyle, then on the forearm, which it passes along for its whole length,
underneath the aponeurotic sheath of this region, between the flexor metacarpi
medius and externus, accompanied by the ulnar vein and nerve of the same
name, and the tendon of the ulnar portion of the perforans muscle. Arriving
near the carpus, this long branch anastomoses by inosculation with a branch from
the posterior radial artery.
In its antibrachial course, this artery only gives off very attenuated branches,
the study of which is of little importance. But before attaining the forearm, it
furnishes : 1. The nutrient artery of the humerus. 2. Articular ramuscules.
3. More or less voluminous muscular branches, particularly for the caput
THE BRACHIAL OR AXILLARY ARTERIES.
651
magnum and medium, and superficial pectoral muscles. Those which arrive in
the latter muscle traverse it only to become subcutaneous alternately ; one of
them accompanies the principal superficial vein of the forearm, and sends
ramuscules into the bend of the elbow.
Regular in their distribution, these
different arteries present numerous
varieties of origin, among which it is
difficult to distinguish the most con-
stant disposition. The last-mentioned
vessel and the nutrient artery of the
humerus, often emanate directly from
the humeral trunk.
4. Principal artery of the biceps, or
coraco-radialis artery (Fig. 376, 6). —
This arises a little below or above the
preceding ; opposite to, or in front of
it, it usually divides into two branches
— one ascending, the other descending,
which enter the substance of the
muscle.
1. Anterioe Eadial (or Spiral)
Artery (Figs. 376, 377).
The anterior radial artery, the
smallest of the two terminal branches
of the humeral, separates at an acute
angle from the posterior artery, above
the articular condyle of the humerus.
It descends on the anterior face of the
ulnar articulation, passing beneath the
inferior extremity of .the flexor muscles
of the forearm and the superior ex-
tremity of the extensor metacarpi,
where it meets the radial nerve ; in
company with this nerve, it extends ■
on the anterior face of the radius,
below the extensor metacarpi magnum,
to the knee, where it becomes very
thin and breaks up into several
ramuscules, which are continued on
TERMINATIONS OF THE AXILLARY ARTERY
IN THE HORSE.
A, Axillary portion of the brachial trunk. 1,
Supra-scapular artery ; 2, infra-scapular artery;
3, branch to the latissimus dorsi from the latter ;
4, prehumeral or anterior circumflex artery ;
5, humeralis profunda ; 6, principal artery of
the biceps; 7, internal collateral or cubital artery; 7', the point where it becomes the ulnar;
8, nutrient artery of the humerus, c, Posterior radial artery at its origin. 9, Muscular branch
of the posterior radial artery; 10, 10, collateral of the cannon, one of the terminal branches of
the posterior radial ; 11, vessel common to the interosseous metacarpals, another branch of the
posterior radial artery.
652 THE ARTERIES.
the capsular ligament of the carpal articulations, after anastomosing on the
inner side with the divisions of a branch furnished by the posterior radial artery,
and on the outside with the ramifications from the interosseous artery of the
forearm.
These terminal ramuscules are distributed to the carpal articulation, or the
sheaths of the extensor tendons, and communicate with the dorsal interosseous
metacarpal arteries.
The collateral branches given off by this artery are very numerous, the
majority of them being detached from the superior portion of the vessel, near
the elbow ; they are intended to supply that articulation, but more especially the
muscular masses lying in its neighbourhood, or covering it.
Such is the usual disposition of the anterior radial artery ; though it is liable
to numerous variations — principally in the manner in which it comports itself
with the interosseous artery of the forearm, which may even supplement it for
the whole of the middle and lower part of its course. This will be noted in
describing the next artery.
2. Posterior Radial Artery (Fig. 377, 1).
This vessel, in its volume and direction, represents the continuation of the
humeral artery. It descends, along with the ulno-plantar nerve, on the internal
ligament of the humero-radial articulation, behind the terminal extremity of the
biceps ; then under the internal flexor of the metacarpus, its satellite muscle.
Arriving at the inferior extremity of the radius, it divides into two terminal
branches -, these are the common trunk of the interosseous metacarpal arteries, and
the collateral (large metacarpal) artery of the cannon.
The following are the principal collateral branches furnished by the posterior
radial artery : —
1. At the superior extremity of the radius, articular ramuscules which anasto-
mose with analogous branches from the ulnar artery.
2. A little lower, large divisions destined for the muscles of the posterior
antibrachial region, some of them arising from the next artery.
3. The interosseous artery of the forearm, a considerable vessel which arises at
the same point as the preceding — the radio-ulnar arch, and crosses this from
within to without, after traversing the posterior face of the radius, beneath the
perforans muscle, to descend along the extensor suffraginis, in the channel
formed outwardly by the union of the two bones of the forearm. This inter-
osseous artery furnishes, immediately after its exit from the radio-ulnar arch,
several branches to the articulation of the elbow and the antibrachial muscles.
At its terminal extremity it usually divides into a number of branches, the
majority of which join the branches sent to the carpus by the anterior radial
artery. It is rare that it does show some fine anastomoses with one of the
divisions of the latter artery in front of, or outside the articulation of the
elbow ; sometimes it directly joins that vessel ; and we have seen it, on the con-
trary, receive the anterior radial artery, which it in part supplanted.
4. Several muscular and musculo-cutaneous ramuscules without any fixed
arrangement, arising from different points of the course of the parent artery,
below the preceding divisions.
5. A deep branch, also liable to very numerous variations, having its origin
at the radial insertion of the perforatus muscle, descending on the posterior face
of the radius, chiefly destined to the carpus, and remarkable for the anastomoses
THE BRACHIAL OB AXILLARY ARTERIES.
653
that its internal divisions form with the anterior radial artery, and for those
which occasionally unite its external ramifications to the ultimate branches of
the interosseous artery of the forearm or the ulnar artery
(I'ig- 377, 2).
1. FiEST Terminal Branch of the Posterior Radial
Artery (Radio-palmar), or Common Trunk of the
Interosseous Metacarpal Arteries^ (Figs. 376, 5;
377, 3).
This arterial branch separates at a very acute angle from
the collateral artery of the cannon. It descends inside and
behind the carpus, accompanied by the principal subcutaneous
vein of the limb, and with it is included underneath a super-
ficial fascia, which maintains them in a channel hollowed on
the external face of the carpal fibrous sheath. It thus arrives
within the head of the inner metacarpal bone, where it is
inflected to the outer side by crossing the superior extremity
of the suspensory ligament, and between it and th^ metacarpal
ligament the latter furnishes to the perforans tendon ; it
anastomoses by inosculation with a descending branch which
emanates from the superficial arch that, above the carpus,
unites the ulnar artery to the origin of the collateral artery of
the cannon (Fig. 376). The loop-like anastomosis thus formed
by the radio-palmar artery exactly corresponds to the deep
palmar arch of pentadactylous animals, particularly to that of
Man. We propose to name it also the infra-carpal arch, by
reason of the position it occupies with regard to the carpus ;
reserving the appellation of supra-carpal arch for the superficial
palmar arch, which is represented by the anastomosis established
between the collateral artery of the cannon and the ulnar artery.
Four principal branches emanate from this infra-carpal
arch : these are the metacarpal interosseous arteries, distin-
guished as posterior or palmar, and anterior or dorsal.
a. The posterior interosseous arise, one on the right, the
other on the left, at the head of the lateral metacarpal bones,
each descending on its own side and in a flexuous manner,
along these rudimentary bones, in the angular groove formed
7-
ARTERIES OF THE FORE FOOT, SEEN FROM BEHIND,
The muscles and tendons have been removed, only a small portion of the
perforans tendons being left ; the os pedis has been chiselled away on its
plantar face to expose the semilunar anastomosis.
1, Posterior radial artery; 2, innominate carpal branch; 3, supra-carpal
arch; 4, ulnar artery; 5, radio-palmar artery, or common trunk of the
Interosseous metacarpal arteries; 6, infra-carpal arch; 7, 7, posterior
interosseous metacarpal arteries; 7', 7', anterior interosseous metacarpal arteries; 8, 8, their
origin; 9, collateral artery of the cannon; 10, its communicating branch with the interosseous
arteries; 11, U, digital arteries; 12, semilunar anastomosis in the os pedis; 13, emergent
branches of this anastomosis; 14, plantar imgual artery, forming the anastomotic arch; 15, origin
of the preplantar ungual artery; 16, origin of the plantar-cushion artery; 17, origin of the
anterior branch of the coronary circle; 18, posterior branch of the same.
' This vessel corresponds to the radio-palmar artery ofiMan, by which uame it is sometimes
Jesignated. Rigot has improperly named it the deep plantar artery.
654 TBE ARTERIES
by their inner face and the posterior face of the principal metacarpal bone,
terminating- at the inferior extremity of the lateral bones, by anastomosing in
full canal with a branch of the collateral of the cannon. They furnish some
ramifications to the suspensory ligament which covere them, and several tendinous
and cellulo-cutaneous twigs ; one supplies the nutrient aitery of the large meta-
carpal bone (Fig. 377, 7).
b. The anterior interosseous arteries arise from nearly the same point as the
preceding — one outwards, the other inwards — turning back round the head of
the lateral metacaqjals to place themselves in the groove which separates these
from the large metacarpal bone, on their external or dorsal face, after having
thrown off several anastomosing ramuscules that communicate between the two
arteries in front of the upper extremity of this bone, or with the terminal
branch of the anterior radial and the interosseous arteries of the forearm. By
their terminal extremity, these two arteries anastomose with a branch of the
collateral of the cannon — that which receives the posterior interosseous arteries
(Figs. 376, 7; 377, 11).
The doi-sal interosseous arteries, although much finer than the palmar — in
Solipeds these arteries are qiyte rudimentary — nevertheless furnish collateral
divisions for the anterior tendons of the metacarpus, the periosteum, the con-
nective tissue, and the skin. They often communicate with the posterior arteries
by deep branches, which cross the intermetacarpal ligaments.
Variations. — The existence of the interosseous metacarpal arteries, their
position, and their anastomoses with the inferior extremity of the collateral of
the cannon, are constant ; though this is not the case with regard to their origin,
or the source whence they are derived. In the tyjiical description given, we have
considered them all as being furnished by the radio-palmar artery ; but it is
necessary to add that one of the four — the external dorsal — often comes directly
from the arterial branch that, from the siqjra-carpal arch, descends along the
carpus to concur in forming the infra-carpal arch, by anastomosing with the
radio-palmar, or rather with a branch of the interosseous of the forearm. It is
also necessary to add that these metacarpal arteries sometimes arise together
from one large branch furnished by the collateral of the cannon, at the superior
extremity of the metacarpus (Fig. 377), and which receives the now rudimentary
radio-palmar artery, as well as that given off by the supra-carpal arch ; so that
we may have two superposed supra-carpal arches. We have met other anomalies
which need not be noticed here, as they are without interest.
2. Second Terminal Branch of the Posterior Radial, or Collateral
Artery of the Cannon ^ (Figs. 376, 9 ; 377, 2).
The collateral artery of the cannon (or large metacarpal artery) (Fig. 376, 9)
continues by its volume and direction, the posterior radial artery. It passes,
with the flexor tendons, under the carpal arch, and descends on the inner side of
these tendons, accompanied by the internal plantar nerve, to above the fetlock
and near the sesamoid bones, where it bifurcates into the digital arteries.
Collateral branches. — We observe :
1. Near the origin of the artery, and very often from the posterior radial
artery itself, a branch which anastomoses above the pisiform bone with the ulnar
artery, forming an arch, the convexity of which is inferior (Figs. 376, 10 ; 377,
> This artery, the mperficial plantar of Rigot, represents one of the metacarpal palmar
hranches furnished by the superficial palmar arcli in Mau and other pentadactylous animals.
THE BRACHIAL OR AXILLARY ARTERIES.
6.55
11), and which has been ah-eady noticed as the supra-carpal or superficial palmar
arch, in contradistinction to the
infra-carpal or deep palmar
arch — the source of the inter-
osseous arteries of the meta-
carpus. This ramification fur-
nishes one or more muscular
arterioles that usually anas-
tomose with the other branches
of the posterior radial artery ;
and an inferior division/ which
descends in the carpal arch,
within the pisiform bone, to the
superior extremity of the meta-
carpus, where it inosculates
with the radio-palmar artery,
after detaching several carpal
ramuscules, the principal of
which winds round the inferior
border of the pisiform bone.
2. On its course, numerous
and fine synovial, tendinous,
and cutaneous divisions.
3. A trunk springing from
the terminal extremity of the
vessel, between the two digital
arteries, sometimes even from
one of these, which is placed
at the posterior face of the
principal metacarpal bone,
within the two branches of
the suspensory ligament, and,
passing upwards, soon divides
into two branches ; these anas-
tomose by inosculation with
ARTERIES OF THE ANTERIOR FOOT
OF THE HOUSE.
1, Posterior radial artery; 2, 2, col-
lateral of the canuou ; 3, trunk
common to the interosseous meta-
carpals ; 4, ulnar artery ; 5, supra-
carpal arch ; 6, descending branch
from the arch to form the infra-
carpal arch ; 7, arteriole for the
ergot from the trunk common to
the interosseous metacarpals ; 8,
infra-carpal arch ; 9, branch of the collateral of the cannon concurring, in this preparation, in the
formation of the interosseous metacarpals; 10, a dorsal interosseous metacarpal artery: 11, com-
municating branch of the collateral of the cannon with the interosseous metacarpals ; 12, 12,
digital arteries ; 13, 13, arterioles of the ergot; 14, perpendicular artery — one of its branches to
the circumflex artery of the coronet, has been excised on removing the lateral cartilage ; 15, 15,
arteries of the plantar cushion; 16, anterior part of the coronary circle; 17, posterior part of
ditto; I 18, prej)lantar ungual artery ; 19, inferior circumflex arterv of the foot.
■ Analogous to the radio-ulnar artery of Man.
656 THE ARTERIES.
the posterior interosseous arteries of the metacarpus, after giving off on each side
two other ramuscules that wind round the borders of the large met;) carpal bone,
receiving the dorsal interosseous arteries, and ramify in front of the fetlock, on
the anterior face of the cannon bone, and in the texture of the capsular ligament
of the metacarpo-phalangeal articulation (Figs. 376, 10 ; 378, 11).
Terminal branches. — These are, as we said, the digital arteries, which almost
exactly repeat the disposition of these vessels in the posterior limb, and which
have been described at p. 036.
Differential Characters in the Axillary Arteries of the other Animals.
1. Axillary Arteries of Ruminants.
Thf se vessels comport themselves in their origin, course, and relations, as in Solipeds.
The special characters they present in their distribution are as follows : —
1. Dorsal artery. — This arises from a trunk common to it and the vertebral artery, and
usually leaves the thorax by passing above the first costo-vertebral articulation. Its subcostal
branch proceeds directly from the above-named trunk.
2. Superior cervical artery. — This is absent, and is replaced by a branch of the dorsal artery,
but particularly by the superior muscular divisions of the vertebral artery.
3. Vertebral artery. — Extremely voluminous, and terminates in the muscles of the neck,
after passing through the foramen of the axis ; it is remarkable for the considerable size of its
spinal branches.
4. Inferior cervical, and internal and external thoracic arteries. — Tiiese do not present
anything worthy of special consideration, except that the last is very voluminous in the Ox
and very slender in the Sheep, and supplies the satellite arterial branch of tlie ceplialic vein,
which, in Solipeds, arises from the inferior cervical artery.
5. Supra-scapular artery. — This vessel appears to us to be absent in the Sheep, and its place
supplied by the divisions of the inferior cervical artery.
6. Subscapulary artery. — The scapulo-humeral branch gives off the majority of the branches
for the posterior brachial muscles.
7. Humeral artery. — The muscular arteries are of small size, particularly the deep humeral,
which is largely replaced by the scapulo-humeral branch.
8. Anterior radial artery. — This comports itself similarly to that of the Horse, and is liable
to as frequent anomalies.
9. Posterior radial artery. — This artery follows the same course as in Solipeds; only
instead of furnishing the radio-palmar artery near the carpus, at the point where it becomes
the collateral artery of the cannon, it gives off that vessel much higher, and near the upper
third or middle of the forearm. Its interosseous branch, lodged in the deep channel on tho
outside of the bones of this region, where the radius and ulna join, is separated into two
branches near the inferior extremity of that groove. The anterior of these ramifies on the
dorsal face of the carpus, and anastomoses with the division of the anterior radial artery; the
posterior traverses the inferior radio-ulnar arch, to distribute the majority of its branches
behind the carpal articulations.
10. Radio-palmar artery.— Anaing, as we have already seen, from the posterior radial
artery, towards the upper third of the forearm, this branch descends to the superior extremity
of the metacarpus in following, as in the Horse, a superficial course, and ends in four meta-
carpal interosseous arteries : three posterior or palmar, and one anterior or dorsal. The posterior
interosseous arteries are very irregular and inconstant in their disposition; they communicate
witli each i)ther by several branches, and anastomose, inferiorly, either with the lateral digital
ftrteries, the collateral of the cannon, or, as is most commonly the case, with a brancli of the
latter vessel. These interosseous arteries are distinguislied into external, middle, and internal ;
the first two are comprised between the posterior face of the metacarpus and the suspensory
ligament ; the third, placed at the inner border of that ligament, is more considemble than
the others, and by its volume and direction represents the continuation of the radio-palmar
artery. The anterior interosseous artery passes through the foramen at the superior extremity
of the metacarpus, and, arriving at the dorsal face of the bone, bifurcates, its ascending branch
reaching the capsular ligament of the carpal articulations, where it anastomoses with the
divisions of the anterior radial and interosseous arteries of the forearm ; the descending is
lodged in the anterior groove of the metacarpal bone, and joins a perforating branch of the
THE BRACHIAL OR AXILLARY ARTERIES. 657
collateral artery of the cannon — a branch that crosses the foramen towards the inferior ex-
tremity of the bony diaphysis. If it is desired to ascertain the signification of these interosseous
arteries, in their relation to the elements composing the foot of Ruminants, we readily recognize:
in the posterior median artery, the interosseous palmar of the two great digits ; in the posterior
lateral arteries, the interosseous palmar, intermtdiates to these middle digits, and the rudi-
mentary lateral digits represented by the ergots, or dew claws ; and in tlie single autfrior
artery, the dorsal interosseous of the two great digits. We may even prove, by a more minute
examination, the existence of dorsal interosseous arteries corresponding to the lateral palmar
interosseous vessels.
11. Collateral artery of the cannon. — This artery follows the same track as in the Horse, as
far as the lower third or fourth of the metacarpus. Arrived at this point, it gives off — as in
the Horse — a branch the divisions of which communicate with the interosseous arteries, and
are continued by the digital arteries, three in number— a middle and two lateral.
a. The communicating branch with the metacarpal interosseous arteries, very often arises
from the internal digital artery.
It is insinuated between tiie divisions of the suspensory ligament, and ascends on the
posterior face of the metacarpus, breaking up into a number of branches which nearly all join
the precited arteries, or even the lateral digital, in having a variable and complicated arrange-
ment which it is neeilless to notice here. One of tliese branches — a true perforating artery,
traverses the inferior extremity of the cannon bone, and ascemls in its anterior groove to join
the anterior interosseous artery, after detaching ramuscules to the metacarpo-phalangeal
articulation.
h. The middle digital artery represents, in its dimensions, the continuation of the collateral
artery of the cannon, and is a very voluminous vessel. It is at first inflected backwards and
outwards, to be placed on the posterior face of the perforatus tendon ; then it descends into
the interdigital space by passing behind the sesamoid bursa, beueatli the ligament uniting the
two claws. Reaching the inferior extremity of the first phalanx, it divides into two ungual
arteries — one for each digit, which are inflected forwards, pass beneath the internal ligament
common to the two interphalangeal articulations, and enter by the foramen at the inner side
of the pyramidal process, into the internal sinus of the third phalanx, where each ramifies in
the same manner as the plantar ungual arteries of the Horse.
Several collateral branches, remarkable for the richness of their arborizations, escape from
this median artery of the digits and its terminal divisions. The most important of these are:
1. At the middle of the first phalanx, two short transverse branches— a right and left, passing
beneath the flexor tendons, and going from the median digital artery to the lateral arteries of
the digits. 2. Nearly at the same point, a single artery which traverses the interdigital space
from behind to before, to pass between the two tendons of the common extensor of the phalanges,
■whence it ramifies on the anterior face of the digits by ascending alongside the anterior median
vein, and anastomosing with a descending branch of the perforating artery which crosses the
inferior extremity of the metacarpus. 3. A double branch analogous to the artery of the
plantar cushion of the Horse, having its origin at the terminal extremity of the digital artery,
often arising from the ungual artery, either on one side or b"th, ami communicating, by a
transverse branch, with its homologue ; it is directed backward and downward on the bulb of
the heel, where it forms an anastomotic arch with the lateial digital aitery ; from the convexity
of this arch, which is turned downwards, there escapes a large number of reticulating ramus-
cules, which go to the keratogenous membrane and the plantar cushion.
c. The lateral digital arteries are distinguished into internal and external. The first has
its origin at the bend formed by the collateral of the cannon, when that vessel is inflected on
the posterior face of the perforatus tendon to become the median digital artery, most frequently
in common with the branch the divisions of which join the metacarpal interosseous aiteries.
The second commences a little further ofl", after having received a branch from eitner this
communicating artery, or from the external interosseous palmar ; it is not rare to see it
entirely formed by one of these branches, or by the two together. Whatever may be their
point of origin, the lateral digital arteries descend on the eccentric side of the digits, outside
the flexor tendons, and terminate in anastomosing by inosculation with the artery of the
plantar cushion. Among the collateral branches emanating from these arteries, there ought to
be distinguished that which goes to the ergot, and the transverse branch thrown across between
each, as well as the median digital artery.'
' In several instances, we have seen the lateral digital arteries stop at this transverse
anastomosis, which then received them entirely-
THE ARTERIES.
2. Axillary Arteries of the Pig.
Both spring separately from the arch of the aorta : consequently, there is no anterior aorta.
The right uxillari/ artery, ot brachio cephalic trunk, &Tat arises; the left comes immediately
after.
0. The right axillary artery is directed forwards, under the inferior fiice of the trachea, and
leaves the thorax to reach the inner face of the anterior limb, as in other animals.
It furnishes successively : —
1. At tht! first rib, an 1 below, the two carotid arteries, rising singly from nearly the same
point.
2. Directly opposite to these vessels, a trunk remarkable for the complexity of its dis-
tribution ; it is directed upwards and backwards, on the side of the trachea and longus cnUi,
crosses the interval between the second and third ribs, and rises to the deep cervical muscles
to terminate in the vicinity of the nape of the neck. It evidently represents the deep or
superior cervical artery. Near its origin it gives off the vertebral artery, the termination of
wliich is exactly the same as in the Horse. Beyond this, it detaclies the dorsal artery, which
ascends into the muscles of the withers, after passing into the first intercostal space. Lastly,
it supplies, before leaving the thorax, the subcostal or superior intercostal artery, placed across
the superior extremities of the third, fourth, and fifth ribs.
y. Always within, but a little more forward than the first rib, a voluminous inferior cervical
orteri/, divided into several ascending branches; and the two thoracic arteries, which offer
nothing particular for description.
4. Outside the thorax, on the internal face of the scapulo- humeral articulation, the humeral
or subscapular arteries. The first, less voluminous than the other, presents, from its origin to
the distribution of its branches in the foot, a disposition essentially resembling that observed
in this ve.'<sel in Ruminants ; the second courses upwards in the space between the sub-
scapularis and the teres major, and soon divides into two terminal branches, one of which
continues the course of the vessel, while the other passes beneath the subscapularis muscle to
carry its ramifications into the autero-external muscles of the shoulder, furnishing in its
course: (1) The great dorsal artery, throwing a part of its ramifications into the olecranian
muscles. (2) A voluminous branch that provides the greater number of the divisions given off",
in the Horse, by the deep humeral and prehumeral arteries. (.S) Two articular branches, one
of which closely represents the supra-scapular artery.
b. The left axillary artery only differs from the right in the disposition of the superior
cervical, dorsal, and vertebral arteries, which have distinct origins ; the two last are very close
to each other, and the first furnishes the subcostal branch.
3. Axillary Arteries of Carnivora.
These arise separately from the convexity of the arch of the aorta, as in the Pig, and
furnish successively, besides the carotids, special branches of the axillary artery trunk : —
1. A voluminous trunk, the common origin of the dorsal, superior cervical, and subcostal or
superior intercostal arteries. The first passes between the two anterior ribs ; the second in
front of the first ; the third across the internal face of the first, second, and third ribs, near
their cartilages, where it emits ascending and descending intercostal branches.
2. The vertebral artery, anastomosing, as in Solipeds, with a retrograde branch from the
occipital artery ; it supplements, in very great part, the superior cervical, the volume of which
is diminutive ; it is only distributed to the superior part of the neck.
3. The inferior cervical artery, giving off" the pectoral branches.
4. The internal thiracic artery, remarkable for its large volume, and for a superficial
division cliiefly destined to the mammae, which joins an analogous branch from the external
pudic artery.
5. An external thoracic branch, the origin of which more resembles that of the supra-
scapular artery, which appears to be absent.
6. The subscapular artery. — After furnishing this vessel, the axillary is continued by the
humeral artery, which we will now examine in detail.
Humeral Artery. — Placed at first immediately behind the biceps muscle, this vessel
descends beneath the pronator teres, and divides at the superior extremity of the radius into
two terminal brunches— the ulnar and radial arteries.
It detaches on its course collateral branches, analogous to those which have been described
for Solipeds, and among which is a thin vessel — a vestige of the anterior radial artery, that
passes beneath the terminal extremity of the biceps to supply the muscles covering, anteriorly,
the articulation of the elbow.
THE BRACHIAL OR AXILLARY ARTERIES. 659
Ulnar artery.— 'Much smaller than the radial, this vessel gives off, near its origin, the
interosseous artery, wliich sometimes proceeds directly from the humeral artery, and the calibre
of which always exceeds, in animals, that of the ulnar artery. The latter is directed obliquely
outwards and downwards, passing under the perforans, and gains the internal face of the
anterior ulnar or oblique flexor of the metacarpus, where it lies beside the ulnar nerve, to
descend with it inside the unciform bone, and join the posterior interosseous artery, or one of
its terminal branches. On its track it gives off a number of muscular or cutaneous branches,
several of which anastomose with the internal collateral artery of the elbow, as well as with
divisions of the radial artery.
Interosseous artery — This artery is placed between the ulna and radius, underneath the
pronator quadratus, and is prolonged to the lower third of the forearm, where it separates
into two branches — the anterior and posterior interosseous arteries, after throwing off on its
way several branches, mostly anterior, which enter the antibrachial muscles by traversing the
space comprised between the two bones of the forearm, the principal escaping by the radio-
ulnar arch.
The anterior interosseous artery, after passing between the radius and ulna, descends on
the anterior face of the carpus, where its divisions meet, inwardly, the collateral rauiuscules
of the radio-palmar artery, and outwardly, the arborizations of a branch from the posterior
interosseous artery, forming with these vessels a wide-meshed plexus, from which definitely
proceed several filaments that join the dorsal interosseous metacarpal arteries.
The posterior interosseous artery may be regarded, by its volume and direction, as the
continuation of the interosseous trunk. After emerging from beneath the pronator quadratus,
it detaches an internal flexuous branch anastomosing with the radio-palmar artery, then
several external musculo-cutaneous branches; after which it is placed within the pisiform
bone, where it divides into two branches, after receiving the ulnar artery. The smallest of
these branches anastomoses by inosculation with the superficial palmar arch ; the other, larger
and deeper seated, is carried in front of the flexor tendons, beneath the aponeurosis covering
the interosseous muscles, across the superior extremity of these, and so forming the deep
palmar arch, which unites with a thin filament from the radio-palmar artery. This arch
supplies, with some ramuscules destined to the muscles of the hand (or paw), eight inter ossf.ous
metacarpal arteries— four posterior or palmar, wliich are united by their inferior extremity
with the collaterals of the digits, after giving several divisions to the muscles of the hand ; and
four anterior or dorsal, traversing the superior extremity of the intermetacarpal spaces, like
the perforating arteries in Man, joining the anterior interosseous branches of the forearm, and
descending afterwards into the intermetacarpal spaces, to unite with the collateral arteries of
the digits at the metacarpo-phalangeal articulations. •
Radial artery — the posterior radial of the other animals. Lying alongside the long flexor
of the thumb and the perforans muscle, this artery follows the inner face of the perforatus
muscle, and curving outwards to be united to a branch from the posterior antibrachial inter-
osseous artery, formg the superficial palmar arch, from which escape four branches — the
palmars or collaterals of the digits. Tliese are at first situated between the perforatus and
perforans tendons, and reach tlie superior extremity of the interdigital spaces, where they
receive the metacarpal interosseous arteries, and comport themselves in the following manner :
the internal goes to the thumb ; the second — counting from within outwards— gains the con-
centric side of the index; the third, the largest, divides into two branches which lie alongside
the great digits ; the last goes to the external digit.
Comparison of the Axillary Arteries in Man with those of Animals.
The arteries of the thoracic limbs and liead arise separately from the arch of die aorta ;
consequently, in Man there is no anterior aorta.
The vessel of the liinb that represents the axillary of animals is here resolved into two
portions : the subclavian artery and axillary artery.
The Subclavian Artery has not the same origin on both sides; on the right it arises
from the aorta by a trunk common to it and the carotid of that side — the arteria innominata;
while the left is detached separately from the most distant part of the aoriic aruh. The
subclavian vessels extend to the inferior border of the clavicles, and furnish seven important
collateral branches, wliich are present in the domesticated animals. They are —
1. The vertebral artery, situated in the vertebral foramina of the cervical vertebrae, as far
as the axis ; there it anastomoses, as in Solipeds, with a branch of the carotid, enters the
spinal canal by the ioramen magnum, and unites with its fellow at the lower border of the
pons Varolii to form the basilar artery which, in the Horse, comes from the cerebro-spinal
artery of the occipital.
660
THE ARTERIES.
Fig. 379.
2. The inferior thyroid, the origin of which, and some branches, we find in the ascending
branch {ascending cervical) of the inferior cervical artery in the Horse.
3. The internal mammary artery divides into two branches
at the xiphoid cartilage of tiie aterauni.
4. The superior intercostal artery, the analogue of which we
866 in Solipeds, in the subcostal branch of the dorsal.
5. The supra-scapular artery, present in all animals and dis-
posed in the same manner.
6. The transcerse cervical (transversa colli), represented by
the extra-thonicic branches of the dorsal artery.
The Axillary Artery, or extra-thoracic portion of the
subclavian trunk, extends to the external border of the pectoral
muscle, where it is continued by the humeral artery. The
axillary gives off: the thoracica acromialis, resembling tlie de-
scending branch of the inferior cervical artery of large quad-
rupeds; the external mammary ; subscapular; and posterior and
anterior circumflex, branches of the preceding in Solipeds.
Humeral (Brachial) Artery, — This artery extends from
the external border of tlie pectoral muscle to the bend of the
elbow : here it divides into two terminal branches — the ulnar
and radial.
In its course it gives off several muscular braiches, and an
external and internal collateral of the elbow (coUuteralis ulnaris
superior and inferior). In the lower third of the arm, the
brachial artery is comprised between the brachialis anticus and
inner border of the biceps ; so that, during flexion, and especially
active and forced flexion, of the forearm on the arm, in vigorous
sulijects, the circulation is arrested in the vessels of the hand.
The radial artery oi Man is represented in the Horse by the
posterior radial artery. It is directed downward and a little
inward, supposing the hand to be in a state of pronation ; it
crosses the carpus in front of the trapezium and scaplioides, at
the bottom of the anatomical snuft-box, and beneath tlie flexor
tendons of the phalanges forms the deep palmar arch, finally
anastomosing with a branch of the ulnar at the hypothenar
eminence. Along its course it furnishes muscular branches :
the carpea anterior ; radio-palmar, which passes outwards, and
unites with a branch of the ulnar artery to form the superficial
palmar artery ; the dursalis pollicis ; the carpea posterior, which
concurs in the formation of the dorsal arch of the carpus, that
gives origin to the dorsal interosseous branches.
The ulnar artery, formed, in Solipeds, by the anterior radial,
passes downward and outward; it is at first covered by the
great pronator muscles, great and small palmar, and superficial
flexor ; lower, it is only protected by the antibrachial aponeurosis
and the skin. On the anterior face of the carpus, it passes
within the pisiform bone, and anastomoses with the radio-palmar
artery ; whence results the superficial palmar arch. It gives
rise to two recurrent arteries that ascend to receive the collateral
vessels of the elbow, then to a trunk seen in animals, and which
divides into the anterior and posterior interossece.
The three arches in the vicinity of the carpus, the constitu-
tion of which has been already given, are distributed in the
following manner : —
The superficial palmar arch is situated at the surface of the
flexor tendons ; from its convexity it emits four or five meta-
carpal branches: the first reaches the external border of the
little finger as the external collateral of that organ ; the other
four are lodged in the interosseous spaces, and when they reach
the roots of the fingers they bifurcate and form the external
or internal collateral arteries of the five fingers. The deep
palmar arch furnishes: articular branches to the wrist, the
AbTKRIES OF THE HUMAN
FOREARM.
., Lower part of biceps; 2,
inner condyle of humerus ;
3, deep portion of pronator
radii teres; 4, supinator
longus ; 5, flexor longus
pollicis ; 6, pronator quad-
ratus ; 7, flexor profundus
digitorum ; 8, flexor carpi
ulnaris ; 9, annular liga-
ment ; 10, brachial artery ;
11, anastomotica longus
magna, inosculating above
with the inferior profunda,
and below with the anterior
ulnar recurrent; 12, radial
artery; 13, radial recurrent,
inosculating with the supe-
rior profunda ; 14, super-
ficialis vohx ; 15, ulnar ar-
tery ; 16, superficial palmar
arch, giving off digital
branches to three fingers
and a half; 17, magna
pollicis and radialis indicis ;
18, posterior ulnar recur-
rent; 19, anterior inter-
osseous; 20, posterior inter-
osseous.
THE COMMON CAROTID ARTERIES. 661
perforating tranches which cross the interosseous spaces to unite with the dorsal interossese ;
the palmar interossea;, which join the superficial interossese before their division into collateral
branches. Lastly, the carpal dorsal arch gives off the dorsal interossea, which receive per-
forating filaments above and below tlie metacarpus, and are expended in the articulations and
skin of the fingers.
Article VII. — Common Carotid Arteries (Figs. 375, 14 ; 381, 1).
These two vessels (named from Kdpa, the head) ^ arise from the right axillary
artery, at a short distance from its origin, by a common trunk— the cephalic
artery — which is detached at a. very acute angle, and is directed forward beneath
the inferior face of the trachea, and above the anterior vena cava, to terminate
near the entrance to the chest by a bifurcation that commences the two common
carotids — right and left.
Each of these arteries afterwards ascends in a sheath of connective tissue,
along the trachea, at first beneath that tube, then at its side, and finally a little
above its lateral plane. Each carotid arrives in this way at the larynx and
guttural pouch, where it divides into three branches.
In its course, this vessel— independently of the connection between it and the
trachea — has the following relations : —
Throughout its entire length, it is accompanied by the cord that results from
the union of the pneumogastric nerve with the cervical portion of the sympa-
thetic, and by the recurrent nerve ; the latter is placed below or in front of the
vessel, from which it is somewhat distant in the lower part of the neck ; the
first is situated above or behind the artery, and lies close to it.
It is also related : behind, in its upper two-thirds, to the longus colli and the
rectus capitis anticus major ; outwardly, to the scalenus towards the inferior
extremity of the neck, and to the subscapulo-hyoideus, which separates the
artery and jugular vein in the middle and upper part of the neck. But near the
entrance to the chest these two vessels are in direct relationship — the vein below
and the artery above.
It is also to be noted, that the glands at the entrance of the chest are in
contact with the carotids, and that the left artery is related, besides, to the
oesophagus.
Collateral Branches. — The branches furnished by the common carotid
on its course are somewhat numerous, but they are of such inconsiderable
diameter that their successive emission does not sensibly vary the calibre of the
vessel from which they emanate ; so that the carotids represent, from their origin
to their termination, two somewhat regular cylindrical tubes. These collateral
branches are destined either to the muscles of the cervical region, or to the
oesophagus and trachea. Two of them — the thyro-laryngeal and accessory thyroid
arteries — will occupy us in a special manner.
Thyro-laryngeal Artery (Fig. 381, 14"). — This vessel, which corresponds
exactly to the superior thyroid artery of Man,^ arises from the common carotid at
a short distance from its termination, a little behind the larynx or above the
thyroid body ; it passes on that organ, into which it enters by two principal
branches that turn round its superior extremity and anterior border, after sending
two branches to the larynx — a superior, also for the pharyngeal walls ; and
' Baillet has remarked that the two common carotid arteries have not the same calibre In
the Horse.
* We would have given it the same name if we could have found the true representative of
the inferior thyroid artery.
662 THE AETERIES.
an inferior, much more considerable, exclusively distributed to the laryngeal
apparatus. The latter passes between the cricoid and the posterior border of
the thyroid cartilage, on the internal surface of which it sends off several
ramuscules, some of which pass forwards, others backwards — the latter spreading
over the ventricle of the glottis and the thyro-arytfeuoid muscle, to become
expended in the arytenoid muscle. The superior branch for the pharynx, also
supplies the crico-arytjenoideus.
It sometimes happens that the thyro-laryngeal artery is found divided at its
origin into two quite distinct branches, each furnishing a laryngeal and a thyroid
division, as in Fig;. 381, 3.^
We have already remarked on the disproportion existing between the con-
siderable calibre of the branches sent by this artery to the thyroid body, and the
slender volume of that organ ; so that it will at present suffice to remind the
student of this peculiarity.
Accessory Thyroid Artery (Figs. 375, 14' ; 381, 2).— The origin of this
vessel precedes that of the first ; it is much smaller, and enters the thyroid body
by the posterior or inferior extremity of this glandiform lobe.
This artery often sends only some excessively fine ramuscules to the thyroid
body, and expends itself almost entirely in the cervical muscles.^
Tebminal Branches. — The three branches which terminate the common
carotid are the occipital, and infernal and extermd carotid arteries ; the latter is
incomparably larger than the other two, which only appear to be collateral
offshoots from the principal vessel. It is these branches which distribute the
blood to the various parts of the head. We will devote three special paragraphs
to their study ; but 'their preparation will previously demand some notice.
Preparation of the arteries of the head. — After carefully removing the skin, dissect the
superficial arteries of one side — that is, the externul maxillar}-, maxillo-muscular, the temporal
trunk, and the posterior auricular arteries — excising the parotid gland to expose the origin of
the three last-named vessels. On the opposite side, the deep arteries are prepared, after dis-
posing of the branch of the inferior maxilla, as in the preparation of the muscles of the
TONGUE ; tlie orbital and zygomatic processes being removed in three sections with the saw, as
in Fig. 381, which will serve as a guide in the dissection of all these arteries.
It is possible to prepare all the arteries on one side ; and in order to do this, a commence-
ment should be made by dissecting the superficial branches; after which, these are cut in the
middle of tlieir course and the first half thrown back on the parotid. The facial is left intact.
Tiie deep arteries are reached by dividing and disposing of the inferior maxilla, as was directed
in the second procedure in preparing the muscles of the tongue and pharynx.
Occipital Artery (Fig. 381, 6).
The occipital artery is a slightly flexuous vessel, lying alongside the upper
third of the internal carotid. It ascends beneath the transverse process of the
atlas, in passing behind the guttural pouch, between the maxillary gland and
the straight anterior muscles of the head. It then insinuates itself between the
rectus capitis lateralis and the inferior arch of the above-named vertebra, to pass
through its anterior foramen, and terminate by two branches, after coursing
along the short fissure that unites this foramen with the superior foramen. In
' It was doubtless a case of this kind that Rigot had before him when he described the
above vessel, and made two arteries of it — tlie thyroid and laryngeal. But, we repeat, this is
only an exceptional instance, and does not authorize its being supposed to be the rule, and
cause the creation of a distinct thyroid and laryngeal artery; since each branch of the vessel
is distributed to the larynx and thyroirl borly at the same time.
* We regard it as the analogue of the middle thyroid of Man.
THE COMMON CAROTID ARTERIES. 663
its track, this artery is crossed, outwardly, by the pneumogastric and spinal
nerves, and the occipital nerve of the great sympathetic, and is accompanied by
the divisions of the inferior branch of the first pair of cervical nerves.
The two terminal branches of the vessel are the occipito-muscular and cerebro-
spinal arteries.
The collateral branches are three in number, and in the order of their
emission are named : 1. The prevertebral artery. 2. The mastoid artery. 3.
The atloido-muscular {ramus anastomotims, or retrograde) artery.
Collateral Branches. — 1. Prevertebral Artery (Fig. 381, 9). — The
smallest of all the branches emanating from the occipital, this artery is detached
at a very acute angle, and immediately divides into several filaments, some
muscular, the others meningeal. The majority of the first pass between the
occipito-atloid articulation and the rectus capitis anticus minor muscle of the
head, and expend themselves either in that muscle, or in the rectus capitis anticus
major ; the second, generally two in number, are always very slender, and reach
the dura mater by entering, one through the foramen lacerum basis cranii, the
other by the condyloid foramen.
Sometimes the prevertebral artery arises from the common carotid, near the
occipital and internal carotid.
2. Mastoid Artery (Fig. 381, 8). — This vessel arises at an acute angle
above the preceding, and goes towards the mastoid foramen by creeping on the
external surface of the styloid process of the occipital bone, beneath the obliquus
capitis anticus. It enters the parieto-temporal canal by this foramen, to anasto-
mose by inosculation with the spheno-spinous branch of the internal maxillary
artery.
In its course it describes a curve downwards, and throws off a large number
of collateral branches. Among these are some which originate before the artery
enters its bony canal, and which are destined for the muscles of the nape of the
neck. Others arise in the interior of this canal, and escape from it by the
orifice in the temporal fossa, to expend themselves in the temporal muscle.
Some ramuscules reach the dura mater.
"We have seen the mastoid artery arise directly from the common carotid,
and furnish a parotideal branch. We have also found it passing over the
surface of the obliquus capitis anticus, and curve suddenly to enter the parieto-
temporal canal.
3. Atloido-muscular (Ramus Anastomoticus) or Retrograde Artery
(Fig. 381, 7). — This branch is not constant, and when it does exist it presents
a variable volume. It is detached from the occipital, underneath the transverse
process of the atlas, by forming with the parent branch a right, or even an
obtuse angle ; it is directed backwards, traverses the inferior foramen in the
transverse process of the atlas, places itself beneath the atlo-axoid muscle, and in
a flexuous manner advances to meet the vertebral artery, which it directly joins,
after giving off some branches to the great oblique and neighbouring muscle.
This anastomosis is the means of establishing a collateral communication between
the vertebral artery and the divisions furnished by the common carotid ; so that
these two arteries can mutually assist or supplant each other.^
Terminal Branches. — 1. Occipito-muscular Artery (Fig. 381, 10). —
Covered at its origin by the obUquus capitis inferior, the occipito-muscular artery
' In a Mnle we have found a large anastomosis between the retrograde and mastoid
arteries, beneath the ala of the atlas.
664 THE ARTERIES.
is directed transversely inwards to the surface of the rectus capitis posticus major,
and soon separates into several branches — ascending and descending : these are
mixed with the divisions of the first superior cervical branch, all of which go to
the muscles and integuments of the occipital region. The descending branches
anastomose with the terminal divisions of the superior cervical artery.
2. Cerebro-spinal Artery. — This vessel enters the spinal canal by the
anterior foramen of the atlas, traverses the dura mater, and divides into two
branches on the inferior face of the spinal cord. Of these two branches, the
anterior is united, by convergence, with the analogous branch of the opposite
artery on its arrival at the middle of the inferior surface of the medulla oblongata,
and so forms the basilar artery ; the other passes backwards, and constitutes the
origin of the middh spinal artery, by anastomosing, after a short course, with the
corresponding branch of the other cerebro-spinal artery. There results from this
distribution a kind of vascular lozenge, situated at the lower face of the medulla
oblongata, which receives in its middle the two cerebro-spinal arteries. This
regular arrangement is not, however, always observed ; these arteries may unite
at the posterior extremity of this lozenge, as is shown in Fig. 889.
Basilar Artery. — This is a single vessel that creeps in a somewhat flexuous
manner on the inferior face of the medulla oblongata, beneath the visceral arach-
noid membrane, and, passing over the pons Varolii, terminates at the anterior
border of this portion of the isthmus, by anastomosing with the two posterior
cerebral arteries (Fig. 380, 11, 11).
On its course it gives off :
1. A multitude of plexuous ramuscules, which enter the substance of the
medulla oblongata and the pons Varolii, or are distributed to the roots of the
nerves emanating from the medulla oblongata.
2. The posterior cerebeUar arteries — vessels liable to numerous anomalies in
their origin. They usually arise from the basilar artery at a right angle, behind
the posterior border of the pons Varolii, and bend outwards — one to the right,
the other to the left — by passing along the surface of the medulla oblongata, the
external border of which it thus reaches ; they are then inflected backwards
beneath the cerebellar plexus choroides, whence they spread their ramifications on
the lateral and posterior parts of the cerebellum.
3. The anterior cerebeUar arteries — two or three on each side, only one of
which is constant. These vessels are very variable in their disposition, and arise
from the terminal extremity of the basilar artery, in front of the pons Varolii,
and sometimes even from the posterior cerebral arteries. Usually united in
fasciculi, they are directed outwards and a little backwards in turning roimd the
crura cerebri, and plunge into the anterior part of the cerebellum.
4. Two branches anastomosing with the internal carotid artery. These
branches are not constant, and are most frequently met with in the Ass. They
begin at the basilar artery in front of the posterior border of the pons Varolii,
traverse the dura mater to enter the cavernous sinus, and join the carotid arteries
at their second curvature.
Middle Spinal Artery. — A very long vessel, lodged in the inferior fissure
of the spinal cord, and measuring the whole extent of that organ, which it
follows from before to behind. It is from this artery that are given off the
branches that cover with their arborizations the medullary tissue, or penetrate its
substance. This emission, which ought soon to exhaust the artery, does not,
however, sensibly diminish its diameter : as it receives on both sides, during its
THE COMMON CAROTID ARTERIES. 665
course, numerous additional vessels. Two series of ramuscules, in fact, emanate
either from the vertebral, intercostal, lumbar, or sacral arteries, enter the spinal
canal by the intervertebral foramina, and join this artery. Generally, however,
they do not pass to the spinal cord until they have anastomosed with each other
outside the dura mater, so as to form on the floor of the vertebral canal two
lateral vessels placed beside the venous sinuses, and united by transverse anasto-
moses ; this disposition is most evident in the cervical region of the Ox
(Fig. 382).
Internal Carotid Artery (Figs. 380, 7 ; 381, 5).
One of the terminal branches of the common carotid, the internal carotid
ascends at first to beneath the base of the cranium, outside the anterior straight
muscles of the head, and bends forward to reach the foramen lacerum basis
cranii. In this primary portion of its course, it is suspended in a particular
fold of the guttural pouch, margined by the superior cervical ganglion, ac-
companied by the cavernous branch of the sympathetic nerve, and crossed in
various directions by the nerves that form the guttural plexus. On arriving at
the middle of the occipito-spheno-temporal hiatus, it enters the cavernous sinus,
and in the interior of that cavity, where it is bathed in venous blood, describes
two successive and opposite curvatures — the first, looking forwards, occupies the
carotid fossa in the sphenoid bone ; the second, with its convexity posterior, at
which the internal carotid receives an anastomosing branch from the basilar
artery — which branch is voluminous and nearly constant in the Ass; but is
rare and, when present, very slender in the Horse. After the last inflection, the
two internal carotids communicate by a very large transverse branch, which is
always flexuous, often reticulated, and leave the cavernous sinus in crossing the
dura mater, to gain the cranial cavity.
These arteries are then placed at the sides of the pituitary gland, within the
superior maxillary /nerve, proceed from behind forward, and terminate in two
branches before reaching the optic nerve. One of these branches constitutes
the posfcrior communicating artery ; the other soon bifurcates to form the middle
and anterior cerebral arteries.
Posterior Cerebral Artery. — This vessel is inflected from before to
behind, to one side of the pituitary gland (Fig. 380, 14), and anastomoses behind
it, forming on the crura an arch which is often reticulated, and which receives
the basilar artery in the middle of its convexity.
A multitude of hair-like ramuscules escape from this artery and enter the
substance of the crura ; but the principal branches it emits proceed in a flexuous
manner inwards and backwards, towards the great cerebral fissure, and terminate
either on the posterior extremity of the cerebral hemisphere or in its interior —
in the plexus choroides, or even in the cerebellum. The disposition and number
of these branches are very variable, but there is one which may be regarded as
constant ; this is the largest of all, and certainly merits the designation of
posterior cerebral artery (Fig. 380, 11).
Middle Cerebral Artery. — This vessel separates itself from the anterior
cerebral artery, external to the optic commissure, is lodged in the fissure of
Sylvius, passing through it in a flexuous manner, and at its extremity separates
into several branches which ramify on the lateral and superior faces of the brain,
and anastomose by their terminal divisions with the posterior and anterior
cerebral arteries.
THE ARTERIES.
Anterior Cerebral Artery. — This enters immediately above the optic
commissure, and proceeds inwards to unite, in the middle line, with the opposite
artery, forming with it a single vessel. This middle artery (or arteria corporis
ARTERIES OF THE BRAIN.
B, Medulla oblongata; p, pons Varolii; L, mastoid lobule; o, olfactory lobule; C, chiasma of the
optic nerves; m, mammillary or pisiform tubercle (corpus albicans); h, pituitary gland (three-
fourths have been excised). 1, 1, Cerebro-spinal arteries; 2, middle spinal artery; a, loxenge-
shaped anastomosis of the two cerebro-spinal arteries, from which result, in front — 4, the basilar
artery (usually the cerebro-spinal arteries arrive in the middle of the lozenge); 5, 5, posterior
cerebellar arteries ; 6, anterior ditto ; 7, internal carotid artery, with the sigmoid curve it makes
in the cavernous sinus ; 8, internal carotid on the sides of the pituitary gland ; 9, transverse
reticulated anastomosis thrown between the two internal carotids behind the pituitary gland ;
10, biiurcation of the internal carotid; 11, 11, posterior cerebral arteries anastomosing behind
the corpus albicans, receiving in the middle of this anastomosis the two terminal branches of the
basilar artery; 12, middle cerebral artery; 13, anterior cerebral artery; 14, posterior com-
municating artery.
callosi) enters the longitudinal fissure of the brain by bending round the anterior
extremity of the corpus callosum, and, after a short course, divides into two
branches which pass from before to behind, one to the right, the other to the
THE COMMON CAROTID ARTERIES. 667
left, on the internal face of the hemispheres, a short distance from the corpus
callosum, and near the posterior extremity of that great commissure. The
branches emitted by these arteries— either in their track or at their termination —
anastomose with those of the posterior and middle cerebral arteries, as well as
with the lobular branch of the ophthalmic.
Before uniting in a common trunk, the two anterior cerebral arteries receive
the meningeal branch of the ophthalmic, the calibre of which often even sur-
passes that of these vessels.
From the anastomosis of the anterior cerebral arteries and the posterior
cerebral with the terminal branches of the basilar artery, there results on the
inferior surface of the pons Varolii an irregular arterial circle— the circle or
polygon of Willis, which surrounds the pituitary gland. From this circle are
detached six groups of arterioles, which are destined to supply the principal grey
masses in the brain — the corpus striatum and optic thalami.
External Carotid Artery (Fig. 381, 12).
This artery ought to be considered, because of its volume and direction, as
the continuation of the common carotid. It is directed forward, arrives at the
posterior border of the great cornu of the os hyoides, passes between it and the
stylo-hyoid muscle, and is inflected so as to form an elbow which is turned
forward, and afterwards ascends vertically to near the neck of the condyle of
the inferior maxilla, at the posterior angle of the hyoid branch. There it
bifurcates to give rise to the superficial temporal and internal maxillary arteries.
In the first part of its course — that is, from its origin to the hyoid bone — the
external carotid artery is related : inwardly, to the guttural pouch and the
glosso-pharyngeal and superior laryngeal nerves ; outwardly, to the outer belly
of the digastric muscle, and the hypoglossal nerve.
In its second portion, it is comprised between the guttural pouch, the parotid
gland, the great cornu of the os hyoides, and the inner side of the posterior
border of the inferior maxilla.
The collateral branches this artery furnishes are three principal — the glosso-
facial, maxillo-muscular, and posterior auricular. But it also gives off others
of less importance, which are distributed to the guttural pouch, the guttural
glands, and the parotid gland.
Collateral Branches of the External Carotid.
1. Submaxillary, Facial (or Glosso-facial) Artery (Fig. 381, 13).
This arises from the external carotid, at the point where that vessel passes
beneath the stylo-hyoid muscle, and is immediately inflected downwards on the
side of the pharynx, between the posterior border of the large cornu of the hyoid
bone and the above muscle. It passes in proximity to the anterior extremity of
the maxillary gland, crossing Wharton's duct outwardly, and leaves the deep
situation it at first occupied, to become more superficial in the submaxillary
space, where it rises on the surface of the internal pterygoid muscle, and is
directed forwards to the maxillary fissure. Turning round this fissure, it climbs
on the cheek, in front of the masseter muscle, to above the maxillary spine,
where it terminates in two small branches.
THE ARTERIES.
In its long and complicated course, the submaxillary artery describes a semi-
circle upwards, and is very naturally divided, for the study of its relations, into
Fig. 381.
ARTERIES OF THE HEAD.
1, Common carotid artery; 2, accessory thyroid artery, 3, 4, thyro-laryngeal artery, divided into
two branches ; 5, internal carotid artery ; 6, occipital artery ; 7, atloido-muscular artery at its
exit from the inferior foramen of the atlas; 8, mastoid artery; 9, prevertebral artery; 10,
occipito-musciilar artery; 11, terminal extremity of the vertebral artery joining the atloido-
muscular branch ; 12, external carotid artery ; 13, submaxillary artery ; 14, pharyngeal
artery; 15, lingual artery; 16, sublingual artery; 17, coronary, or inferior labial artery; 18,
THE COMMON CAROTID ARTERIES. 669
three portions — a deep, an intermaxillary, and a facial. The first, or deep
portion, accompanied in its superior moiety by the glosso-pharyngeal nerve, is
related, outwardly, to the internal pterygoid muscle ; inwardly, to the guttural
pouch, the hyo-pharyngeus, hypoglossal nerve, middle tendon of the digastricus,
the hyo-glossus brevis, Wharton's duct, and the subscapulo-hyoideus. The inter-
maxillary, or middle portion, is bordered by the glosso-facial vein, lies against
the pterygoideus internus, and is in contact with the submaxillary glands. The
facial, or terminal part, is lodged at its commencement in the maxillary fissure,
in front of the glosso-facial vein and the parotid duct ; it ascends with these
two vessels along the anterior border of the masseter, on the depressor labii
inferioris and buccinator muscles, beneath the subcutaneous and zygomaticus
muscles and the ramifications of the facial nerve, which perpendicularly crosses
the direction of the artery.
Terminal Branches. — The external maxillary artery terminates in two
small branches which separate from each other at an obtuse angle, one being
directed upwards, the other downwards. The ascending branch passes to the
surface of the orbicularis palpebrarum, below the lachrymalis, and anastomoses
with the divisions of a palpebral branch emanating from the supermaxillo-dental
artery (Fig. 381, 19). The descmding branch goes to the false nostril and the
entrance to the nasal cavities, by creeping beneath the levator labii superioris
(Fig. 381, 20).
Collateral Branches. — These are five principal branches : 1. The pharyn-
geal. 2. Lingual. 3. Sublingual ; all of which arise from the first portion of
the submaxillary artery. 4. The inferior and superior coronary arteries, emanat-
ing from the facial portion. Besides these, there are a great number of inno-
minate branches of secondary importance, which proceed to the neighbouring
parts, and principally to the maxillary gland, submaxillary glands, the masseter
muscle, and the muscles and integuments of the face. We will content ourselves
with merely noting the existence of these latter branches.
1. Pharyngeal Artery (Fig. 381, 14). — This arises from the submaxillary,
at a variable distance from its origin, and sometimes even in the angle formed
by that vessel and the external carotid artery. Whatever may be its commence-
ment, it is always directed forwards, passes between the hyo-pharyngeus muscle
and the great cornu of the hyoid bone, and, describing some flexuosities, goes
towards the pterygoid process, beneath the elastic layer which covers the pterygo-
pharyngeus muscle. It terminates in the soft palate, after giving off on its
course ascending and descending branches, which expend themselves in the walls
of the pharynx.
2. Lingual Artery (Fig. 381, 15). — As considerable in volume as the
parent branch, this artery is detached at an acute angle from it, at the extremity
of the hyoid cornu. With the glosso-pharyngeal nerve, it passes beneath the
hyo-glossal muscle, crossing the small branch of the os hyoides, and extends to
the extremity of the tongue by gliding in the interstice between the genio-glossus
coronary, or superior labial artery ; 19, superior terminal branch of the external maxillary
artery; 20, inferior terminal branch of ditto ; 21, maxillo-muscular artery; 22, 23, posterior
auricular artery; 24, superficial temporal artery; 25, subzygomatic artery; 26, inferior auricular
artery; 27, internal maxillary artery; 28, inferior dental artery; 29, fasciculi of pterygoid
arteries; 30, tympanic artery; 31, spheno-spinous artery; 32, deep posterior temporal artery;
33, deep anterior temporal artery; 34, ophthalmic artery; 35, supra-orbital artery; 36, lachrymal
artery ; 37, buccal artery ; 38, palatine artery ; 39, superior dental arteri 40, orbital branch of
that vessel,
45
670 TEE ARTERIES.
and hyo-,dossns muscle, whera it meets the branches of the lingual and hypo-
glossal nerves.
Flexuous in its course, in order to adapt itself to the elongation of the tongue,
the lingual artery emits a very great number of collateral branches, which escape
perpendicularly from the entire periphery of the vessel ; but chiefly above, below,
and on the inner side, to ramify in the muscles and integuments of the tongue.
Running parallel to each other, the two lingual arteries communicate by five
transverse ramuscules, and join at their terminal extremity, which becomes very
slender.
3. Sublingual Artery (Fig. 381, 16). — This artery has its origin at the
anterior extremity of the submaxillary gland, and runs forward along the external
surface of the mylo-hyoideus muscle, which it afterwards crosses towards the
posterior extremity of the sublingual gland. It then follows the inferior border
of this gland, sending into it numerous branches, and after giving some filaments
to the genio-glossus and genio-hyoideus muscles, is prolonged on the sides of
the frtenum linguae, where it ends by fine ramuscules in the buccal mucous
membrane.
Among the branches this artery detaches before attaining the sublingual
gland, it is necessary to distinguish those which are destined to the mylo-hyoideus
muscle, some of which — the descending — are thin and irregular : the others —
ascending — being long, thick, and parallel to each other.
Sometimes this artery does not reach the sublingual gland ; it then remains,
for the whole of its extent, external to the mylo-hyoideus muscle, and sends its
terminal divisions to the vicinity of the symphysis of the inferior maxilla. In this
case, the gland receives a special branch from the lingual artery, a circumstance
which is usual in Man, in whom this artery is named the submental.
4. Coronary or Inferior Labial (Fig, 381, 17). — Springing from the
glosso-facial artery at an acute angle, shortly before that vessel arrives at the
depressor labii inferioris, the inferior coronary artery passes under that muscle,
and following its direction, descends into the texture of the lower lip, where it
is mixed up with the ramifications of the mental nerve, and where it terminates
by forming a very fine anastomotic arch with the vessel of the opposite side.
In its track, it gives branches to the buccinator and depressor labii inferioris
muscles, and to the tissues of the lower hp, to which it is chiefly destined. In
its passage near the mental foramen, it receives the inferior dental artery as it
leaves that opening.
5. Coronary or Superior Labial Artery (Fig. 381, 18). — Smaller than
the preceding vessel, and often altogether rudimentary, this artery is detached
from the principal trunk at nearly a right angle, above the origin of the dilator
naris lateralis, and sometimes below that muscle. It subsequently gains the upper
lip, along with the infra-orbital branches of the superior maxillary nerve, by
passing between the levator labii superioris proprius and the dilator naris
lateralis : it then terminates in forming an arch by inosculation with the palato-
labialis artery.
The branches it gives off pass to the external ala of the nose and the textures
of the upper Up. Some are expended in the muscles just named, and in the
buccinator.
2. Maxillo-muscular Artery (Fig. 381, 21).
The maxillo-muscular artery is a vessel that does not appear to have its
THE COMMON CAROTID ARTERIES. 671
representative in Man. It emerges from the external carotid, above the point
where it is inchided between the large cornu of the os hyoides and the
stylo-hyoideus muscle. Remarkable for the very obtuse angle it forms at its
origin with the principal vessel, it descends behind the posterior border of the
inferior maxilla, covered by the parotid gland. It then divides into two branches
— a deep one, which goes to the internal pterygoid muscle, after furnishing some
ramuscules to the neighbouring organs ; and a superficial one, which turns round
the posterior border of the maxiUa, and emerging from beneath the parotid
gland, above the insertion of the stemo-maxiUaris muscle, plunges into the
masseter, and expends itself in the body of that muscle by several branches which
anastomose with the divisions of the subzygomatic artery.
3. PosTEEiOR AuEicuLAR Artery (Fig. 381, 22).
Third collateral branch of the external carotid, the posterior auricular artery
arises at a very acute angle above, and a little behind, the preceding vessel. It
ascends beneath the parotid gland, behind the base of the concha of the ear,
crosses the cervico-am-icular muscles, and reaches the extremity of the cartilage
by passing underneath the skin which covers its posterior plane.
In its course, it emits several ascending auricular branches, which arise at
different elevations and cover the concha with their divisions. Among these we
ought to distinguish the first (Fig. 381, 23) ; this has its origin at the temporal
trunk, and soon divides into two branches — one, profound, after sending a very
thin filament into the middle ear by the stylo-mastoid foramen, passes between
the external auditory canal and the mastoid process to enter the subconchal
adipose tissue and the internal scuto-auricular muscle ; the other, superficial,
embedded in the parotid tissue, proceeds to the external side of the concha, and
buries itself in the interior of that cartilage, along with the middle auricular
nerve, after abandoning some external ramuscules.
From these auricular branches there also escape a multitude of parotideal twigs.
Terminal Branches of the External Carotid.
1. Superficial Temporal Artery or Teaeporal Truxe: (Fig. 381, 25).
This is the smallest of the two terminal branches of the external carotid.
After a short ascending course between the parotid gland, the guttural pouch,
and the neck of the maxillary condyle, behind which it is situated, this arteiy is
divided into two branches : the anterior auricular and the suhzygomatic.
Anterior Auricular Artery (Fig. 381, 26). — This vessel appears to be,
not only by its voltune, but also by its direction, the continuation of the temporal
artery. Embraced, near its origin, by the facial nerve and subzygomatic branch
of the inferior maxillary nerve, it rises behind the temporo-maxillary articulation
and supra-condyloid process, beneath the parotid gland, to the temporal muscle,
into which it passes after emitting parotideal twigs and auricular branches, one
of which penetrates to the interior of the concha, while the others are expended
in the anterior muscles of the ear and the integuments covering these muscles.
Subzygomatic Artery (Fig. 381, 25 ). — More considerable than the anterior
atiricular, this artery disengages itself from beneath the parotid gland by turning
round the posterior border of the maxilla, along with the nervous anastomosis
which gives rise to the subzygomatic plexus, and is placed above that anastomosis,
672 THE ARTERIES.
beneath aud to the outside of the afore-mentioned condyle. There it ends in
two branches of equal volume — a superior or superficial, and an inferior or deep,
both of which ramify in the substance of the masseter muscle, and anastomose
with the divisions of the maxillo-muscular, or with the masseter branches of the
external maxillary arteries.
The superior branch, or transverse artery of the face, goes towards the anterior
border of the masseter muscle in a fiexuous manner, close to the zygomatic ridge.
At first lying on the superficies of the masseter, it afterwards buries itself in that
muscle.
The inferior branch, or masseteric artery, dips in among the deep fasciculi of
the masseter muscle, to which it is distributed, along with the masseteric nerve.
Near its origin, it communicates with the deep posterior temporal artery by a
fine ramuscule, which passes into the sigmoid notch. In Man and some animals,
this artery comes from the internal maxillary.
2. Inteenal Maxillary or Gutturo-maxillary Artery (Fig. 381, 27).
Situated at first immediately within the maxillary condyle, below the articu-
lation of the jaw, this artery passes to the inner side, towards the entrance of the
subsphenoidal canal, by describing two successive curvatures — the first backwards,
the other forwards. After being tnus shaped like an S, it travels forward along
the subsphenoidal canal to the orbital hiatus, and then reaches the maxillary
hiatus, where it is designated the palato-labial artery.
In order to study its relations, the course of this artery may be divided into
three portions — a posterior or guttural, a middle or sphenoidal, aud an anterior
or infra-orbital. The postei-ior portion hes on the internal face of the external
pterygoid muscle, covered inwardly by the guttural pouch, and crossed outwardly
by the inferior maxillary nerve and some of its branches. The middle division
is enveloped by the bony walls of the subsphenoidal canal. The anterior portion,
along with the superior maxillary nerve, passes across the space separating the
orbital from the maxillary hiatus, by creeping along the palatine bone, beneath a
considerable mass of fat.
Collateral Branches. — The arteries given oflp by the internal maxillary
on its course are eleven principal. Five arise from the first portion of the
vessel : two below, the inferior dental and the group of the pterygoid arteries ;
three above, the tympanic, spheno-spinous (great meningeal), and posterior deep
temporal.
Two escape from the superior portion of the interosseous or sphenoidal
division. These are the anterior deep temporal and ophthabnic arteries. Four
commence from the third section of the artery : two inferior, the buccal and
palatine ■ and two upper, the superior dental and the 7msal.
1. Inferior Dental Artery (Fig. 381, 28). — This vessel — also named the
maxillo-dental artery — is detached at a right angle from about the middle of
the first curvature described by the internal maxillary. It travels forward and
downward between the two pterygoid muscles, afterwards between the internal
one and the maxillary bone, entering with the inferior maxillary nerve into the
dental foramen, through the whole extent of which it passes. Arrived at the
mental foramen, it separates into two branches — a deep one, which continues
the interosseous course of the vessel, to be distributed to the roots of the tusk or
tush, and the three adjoining incisor teeth ; the other superficial, generally very
slender and even capillary, issuing by the mental foramen with the terminal
TEi: COMMON CAROTID ARTERIES. 673
branches of the maxillary nerve, and anastomosing with the inferior coronary
artery.
Before penetrating the maxilla, this artery furnishes divisions to the internal
pterygoid and mylo-hyoid muscles.
In the interior of the maxillo-dental canal, it gives off diploic branches, as
weU as twigs, to the roots of the molar teeth and the alveolar membrane.
2. Pterygoid Arteries (Fig. ;381, 29).— It maybe said, in a general manner,
that the two pterygoid muscles receive their arteries from all the vessels passing
near them ; though there are two, and sometimes three, branches more especially
intended for them. These branches — or, properly speaking, pterygoid arteries —
arise from the middle of the second curvature of the internal maxillary, either
at an acute or right angle, and enter the pterygoid muscles, after a short course
forward and downward on the external tensor palati muscle— this, and its fellow,
the internal muscle, also receiving some branches.
3. Tympanic Artery (Fig. 381, 30). — A very thin and small, but constant
artery, gliding along the surface of the guttural pouch, accompanying the
tympano-lingual nerve, and penetrating the tympanic cavity by a foramen
situated at the base of the styloid process of the temporal bone (the fissura
Glaseri). It throws off ramuscules to the wall of the guttural pouch and the
trigeminal nerve ; these often arise directly from the trunk of the internal
maxillary artery, beside the tympanic branch.
4. Spheno-spinous or Great Meningeal Artery (Fig, 881, 31). — Com-
mencing at an obtuse angle, opposite the pterygoideal vessels, this artery lies
against the sphenoid bone, near the temporal insertion of the tensor palati
muscles, is directed backwards and upwards, enters the cranium by the foramen
lacerum basis cranii, outside the inferior maxillary nerve, passes beneath the dura
mater, and soon after engages itself in a particular foramen in the parieto-
temporal canal, where it anastomoses by inosculation with the mastoid artery.
Before penetrating this canal, the spheno-spinous artery gives off a meningeal
branch, the ramifications of which, destined to the dura mater, stand in relief on
that membrane, and creep along in the small grooves channeled on the inner
surface of the cranium.
The volume of this vessel is subject to the greatest variations, and is always
in an inverse proportion to that of the mastoid artery.
5. Posterior Deep Temporal Artery (Fig. 381, 32). — This arises at a
right angle, immediately before the entrance of the internal maxillary artery into
the subsphenoidal canal. It ascends on the temporal bone, in the temporal
muscle, passing in front of the temporo-maxillary articulation, which it turns
round to be inflected backwards. Tliis vessel communicates with the masseteric
artery by a fine division, which traverses the sigmoid notch in the maxillary
bone.
6. Anterior Deep Temporal Artery (Fig. 381, 33). — Springing at a
right angle, like the preceding, in the interior of the subsphenoidal canal, this
artery escapes by the superior branch of that conduit, ascends against the bony
wall of the temporal fossa, along the anterior border of the temporal muscle,
in which it is almost entirely expended. It gives some ramuscules to the adipose
tissue of the temporal fossa. Its terminal extremity arrives beneath the internal
parieto-auricularis muscle, and ramifies in it and in the skin of the forehead.
7. Ophthalmic Artery (Fig. 381, 34). — This vessel has a somewfiat
singular arrangement. After being detached from the internal maxillary in the
674 TEE ARTERIES.
subsphenoidal canal, in front of the deep anterior temporal artery, with which
it is sometimes united, it penetrates by the orbital hiatus to the bottom of the
ocular sheath ; it then enters the cranium by the orbital foramen, after describing
a loop opening backwards and downwards, which passes between the muscles of
the eye, beneath the superior rectus, and abov^e the optic nerve and the sheath
formed around it by the retractor.
Entering the cranium, the ophthalmic artery passes inward along a groove
in the ethmoidal fossa, and terminates by two branches — a meningeal and a
nasal.
Collateral tranches. — In its orbital track, the ophthalmic artery emits
numerous collateral branches, which arise from the convex side of the loop
described by this vessel. These are : the muscular arteries of the eye, the ciliary,
mitral artery of the 7-etina, supra-orbital, and lachrymal arteries.
In its cranial portion, it furnishes the cerebral branches.
The muscular arteries of the eye have a destination sufficiently indicated by
their name. Their number and mode of origin vary. They are usually two
principal, which arise directly from the ophthalmic artery, and others of a smaller
size furnished by the lachrymal and supra-orbital branches.
The ciliary arteries — destined to the constituent parts of the globe of the eye,
but chiefly to the choroid coat, the ciliary processes, and the iris — are long thin
branches, emanating, for the most part, from the muscular arteries.
"We only mention the centralis retince artery here ; as it and the ciliary
arteries will be described when we come to study the visual apparatus.
The supra-orbital artery ascends, with the nerve of the same name, against
the inner wall of the ocular sheath, to gain the supra-orbital foramen ; passing
through that orifice, it is distributed to the frontal and supra-orbital muscles,
the orbicularis palpebrarum, external temporo-auricularis muscle, as well as to
the integument of the frontal region (Fig. 381, 35).
The lachrymal artery creeps upwards and forwards, between the muscles of
the globe of the eye and the superior wall of the ocular sheath, to terminate
in the lachrymal gland and the upper eyelid (Fig. 381, 36).
The cerebral branches of the ophthalmic artery vary in number, and frequently
there is only one, of somewhat considerable volume. They pass to the anterior
extremity of the cerebral lobe, and anastomose with the divisions of the anterior
cerebral artery.
Terminal branches. — The meningeal branch, after detaching ramuscules to the
dura mater, and particularly to the falx cerebri, anastomoses in the middle line,
below the process of the crista galli, with that of the opposite side, and after-
wards joins the anterior cerebral artery.
The nasal branch traverses the cribriform plate of the ethmoid bone, and
divides into a number of ramuscules, which descend either on the ethmoidal cells,
or on the middle septum of the nose, where their ramifications form arterial tufts
of a pleasing aspect.
8. Buccal Artery (Fig. 381, 37). — The buccal artery emerges at an acute
angle from the internal maxillary, a short distance in front of the orbital hiatus,
and descends obliquely between the maxillary bone and the superior insertion
of the internal pterygoid muscle, terminating in the posterior part of the molar
glands, and in the buccinator and depressor labii inferioris muscles.
In its course it gives some insignificant ramuscules to the pterygoid muscles,
as well as to the masseter, and a long branch to the adipose cushion in the temporal
THE COMMON CAROTID ARTERIES. 675
fossa. The latter branch sometimes comes directly from the internal maxillary
artery.
9. Staphyline Artery (Fig. 381, 38).— A very thin filament, which accom-
panies the staphyline nerve in the groove of the same name, and is distributed
to the soft palate.
10. Superior Dental Artery (Fig. 381, 39).— This vessel— which is also
named the supermaxillo-dental artery — enters the superior dental canal, arrives
near its inferior or infra-orbital opening, and then divides into two thin branches.
One of these continues in the same course in the supermaxillary bone, to supply
arterial blood to the alveoli of the foremost molars, the tusk, and the incisor
teeth ; the other {infra-orbital branch) passes out of the canal with the terminal
divisions of the superior maxillary nerve, and communicates on the forehead
with a ramuscule from the external maxillary artery.
On its way, the superior dental artery emits several collateral branches, the
majority of which commence in the interior of the dental canal, and pass either
to the alveoli of the posterior molars, the tissue of the bone, or the membrane
lining the sinuses. One of these branches — the orbital, and the largest — escapes
from the principal artery before its entrance to the superior dental canal, creeps
along the floor of the orbit towards the nasal angle of the eye, whence it descends
on the forehead, after giving off some divisions to the caruncle of the eye, the
lachrymal sac, and the lower eyelid.
11. Nasal or Spheno-palatine Artery.— Situated, at first, at the bottom
of the maxillary hiatus, this artery, springing at a right angle from the parent
trunk, traverses the spheno-palatine foramen, and divides into two terminal
branches — an external and an internal — in ramifying on the walls of the nasal
cavity.
Terminal Beanch of the Internal Maxillary Artery. Palato-
Labial or Palatine Artery (Fig. 215, 3).— A continuation of the internal
maxillary, this vessel at first traverses the palatine foramen, follows the palatine
groove to near the superior incisors, is then inflected inwards above a small
cartilaginous process (Fig. 215, 4), and vmites on the middle hne with the artery
of the opposite side, forming an arch with its convexity forwards, from which
proceeds a single trunk that passes into the incisive foramen.
The palatine arteries, in their advance, furnish a series of branches to the
anterior part of the soft palate, the membranes on the roof of the mouth, and
the gums and upper teeth.
The single trunk resulting from their anastomoses is placed, immediately
after its exit from the incisive foramen, directly beneath the buccal mucous
membrane, and at once divides into two principal branches — a right and left ;
these are lodged in the tissue of the upper lip, and pass back to meet the coronary
arteries, with which they anastomose by inosculation, after throwing off on their
track a great number of branches to the muscles and integuments of the lip and
nostrils.
Differential Characters in the Carotid Arteries of the other Animals.
1. The Carotid Arteries in Carnivora.
In the Dog, the carotids arise singly frona the axillary artery, and ascend beneath the
transverse process of the atlas, along the trachea, following a course exactly like that pursued
by these vessels in the Horse.
Among the collatt ral branches furnished by them, maybe distinguished the thyro-laryngeal
676 TEE ARTERIES.
artery, remarkable for its enormous calibrt', its descending in front of the lateral lobe of the
thyroid gland, and its termination in the median isthmus of that ghmd.
The terminal branches of the carotid are, as in Solipeds : 1. The occipital. 2. The in-
ternal carotid. 3. The external carotid, the continuation of the common cardtid.
Occipital Artery. — Inconsiderable in volume, this vessel arises in front of the anterior
border of the transverse process of tlie atlas, passes into the notch on its border, and divides into
two brandies — the occipito-muscular and the cerebrospinal arteries.
In its course, it gives off braticiies analogous to those which emanate from the prevertebral
artery of tlie Horse. It also gives a mastoid artery, which only sends one very small branch
into the paricto-temporal canal, and is destined almost exclusively to the deep muscles of the
neck. In aildition, the occipital throws off a retrograde artery, which directly joins the vertebral.
The arrangement of the occipital artery in Oarnivora is, therefore, almost identical with
what has been described in Solipeds.
Internal Carotid Artery. — This vessel reaches the posterior opening of the carotid
canal, along which it passes forward, then describes a very curious flexure which leaves the
cranium by the carotid foramen (see p. 59), theu re-enters that cavity after receiving a
particular branch from the external carotid. It afterwards anastomoses on the side of the
pituitary fossa, with the divisions of the spheno-spinous artery and the returning briinches of
the ophtiialmic artery, forming a kind of plexus which appears to be a trace of the rtte mirabile
of Ruminants and Pachyderms, and from which proceed tlie cerebral arteries.
External Carotid Artery. — This arterial branch terminates, as in Solipeds, by the
superficial temporal and the internal maxillary arteries.
It gives off on its course : 1. An artery representing the meningeal branch of the pre-
vertebral of the Horse, and which ascends in a flexuous manner on the side of the pharynx to
join the carotid flexure.
2. A laryngeal artery, entering the larynx with the superior nerve of that organ, after
giving ramuscules to the maxillary gland.
3. The lingual artery, a vt ry large tortuous branch, the course of which resembles that of
the same vessel in the Horse.
4. A facial or external maxillary artery, divided into two branches above the inferior inser-
tion of the digastricus. One of these branches — analogous perhaps to the submental of Man-
passes within this insertion, and is prolonged to the chin, after furnishing ramuscules to the
parts lodged in the intermaxillary space. The other branch winds round the inferior border of
the maxilla, in front of the masseter muscle, and is expended on the face by ascending and
descending branches, among which we can readily perceive the two coronary arteries, and the
two twigs which we have noticed in Solipeds as terminal branches of the vessel.
.5. The posterior auricular artery, after detaching parotideal and musculo-cutaneous vessels,
is situated on the middle of the external face of tlie concha, and is directed towards the terminal
extremity of the cartilage, where it separates into two branches, which are inflected en arcade^
and return, in following the borders of the concha, towards the base of the latter, where they
anastomose with other branches, either from the posterior or anterior auricular, and which
come to meet them.
Superficial temporal artery. — After a brief course behind the tempore i-maxillary articulation,
this vessel bifurcates : its posterior or auricular branch anastomosing with a division of the
posterior auricular, but not before it has sent ramuscules to the interior of the concha, and
furnished some uiusculo-cutaueous twigs. The other, the anterior or temporal branch, glides
beneath the aponeurosis of the temporal muscle, above the upper margin of the zygomatic arch,
and winds upwards and inwards around the outline of the orbit, to terminate on the face by
anastomosing ramuscules, either with the infra-orbital branch of the superior dental artery, or
with the facial. In its sub-epoueurotic course, it gives divisions to the temporal muscle.
Above the orbital arch, it emits several superficial ascending and internal twigs, one of the
principal of which communicates by ramuscules with the posterior auricular artery, the
auricular branch of the superficial temporal, and with the homologous ramuscules from the
opposite side.
Internal maxillary artery. — The course pursued by this vessel is similar to that which it follows
in the Horse. After describing an S curvature between the condyle of the maxillary bone and
external pterygoid muscle, it traverses the subsphenoidal canal, and passes outside the internal
pterygoid towards the maxillary hiatus, where it is continued by the superior dental artery.
a. The following are the principal collateral branches emitted by this vessel :
1. The inferior dental artery.
2. The deep posterior temporal artery, which furnishes a masseteric branch that traverses the
sigmoid notch in the maxillarv bone, to enter the masseter muscle.
THE COMMON CAROTID ARTERIES. 677
8. A fine tympanic arteriole.
4. The spheno-spinous artery, almost entirely destined to the formation of the plexus of the
cerebral arteries.
5. Several pteryynid arteries.
6. The ophthalmic artery, which, before entering the ethmoidal fossa by the orbital foramen,
gives, independently of the branches noted in Solipeds— except the supra-orbital, which is
absent— a fasciculus of particular branches. These penetrate the cranium by the great sphe-
noidal fissure, accompanying the motor and sensory nerves of the eye, to join the internal
carotid and spheno-spinous arteries.
7. The anterior deep temporal artery.
8. A staphyline artery, more voluminous than that in the Horse.
9. The palatine artery.
10. A buccal and an alveolar artery, the principal divisions of which enter Duvernoy's
gland.
b. The superior dental artery, which terminates the internal maxillary, and furnishes an
orbital and an infra-orbital branch, as in Solipeds. The latter, remarkable for its volume,
emerges from the superior dental canal with the infra-orbital nerves, to join the divisions of the
external maxillary artery on the face, and in the tissue of the upper lip.
2. Carotid Arteries in the Pig.
There is nothing particular to notice regarding the course of these vessels, which we know
arise separately from the axillary artery.
Occipital Artery. — In its (listiibution,it greatly resembles the same vessels in the Horse
and Dog. Its most important branches are the following : 1. A very small retrograde artery,
anastomosing with tlie vertebral. 2. A branch which ascends into the muscles of the neck,
representing the mastoid artery. 3. Several occipital arterioles, which pass, with the principal
artery, by the anterior foramen of the atlas. This artery is expended in a complete manner in
the muscles of the neck, and without sending a cerebro-spinal branch to the interior of the
spinal canal.
Internal Carotid Artery. — After furnishing a large meningeal artery, this vessel enters
the cranium by the foramen lacerum basis cranii, and there divides to form a rete mirabile, analo-
gous to that of Ruminants, and of which a description will be given hereafter. The cerebral
arteries arising from this r^seau differ but little from those of Solipeds ; these are the posterior
cerebral arteries, which give rise to the basilar artery and originate the middle spinal artery.
External Carotid Artery.— This artery is seen to pass between tjje pterygoid muscles and
the branch of the maxilla, in describing several inflections, and arrives in the maxillary hiatus,
without exhibiting in its course any sensible distinction between the external carotid, properly
called, and its continuation, the internal maxillary artery.
Among the branches it supplies, we notice :
1. The lingual artery, more voluminous, perhaps, than in the other animals.
2. A branch analogous, in its origin at least, to the glosso-facial artery of the Horse, and
•which distributes its ramuscules in the submaxillary space, and particularly to the salivary
and lymphatic glands.
3. The posterior auricular artery, noticeable for its great length and considerable volume.
4. The transverse artery of the face and the anterior auricular artery, arising separately
beside each other, and extremely slender.
5. Several deep temporal and masseteric arteries.
6. Pterygoid branches.
7. An enormous buccal branch.
8. The ophthalmic artery, concurring to form the rete mirahile.
9. A small orbital branch, coming from the superior dental artery in Solipeds and Carnivora.
10. The nasal, palatine, and superior dental arteries.
3. Carotid Arteries of Ruminants.
A. In the Sheep, which will serve as a type for this description, the carotid arteries arise
by a common trunk from the right axillary artery, as in Solipeds. Arriving in the cephalic
region, towards the upper part of the neck, they furnish a thyroid and a laryngeal branch, then
give off a very slender occipital artery, and are continued from this point by the external
carotid.
The internal carotid, properly called, is absent, and we shall see immediately how it is com-
pensated for.
Occipital Artery.— Having given some ramuscules to the anterior straight muscles of the
OT8 THE ARTERIES.
head, and a small meningeal branch whicli enters the cranium by the foramen lacerum basis
cranii, this vessel passes into the condyloid furamen, which also affords a passage to the hypo-
glossal nerve, places itself beneath the dura mater, and is inflected backward to open into the
anterior extremity of the collateral artery of the spine, at the superior foramen of the atlas.
The branch resulting from this junction emerges by that foramen, to be distributed in the
muscles of the neck, where its divisions resemble those of the occipito-muscular and atloido-
muscular branches in the Horse.
In traversing the condyloid foramen, the occipital artery sends into the parieto-temporal
canal, by a peculiar bony conduit (see p. 50), a very small filament which is distributed to
the dura mater, in anastomosing with a branch of the posterior auricular.
It communicates, after its entrance into the cranial cavity, with the rete mirabile.
External Carotid Artery. — Terminated, as in the Horse, by the superficial temporal and
internal maxillary arteries, this vessel sends off on its course :
1. A pharyngeal artery, the origin of which is nearly confounded with that of the occipital
artery.
2. The lingual artery, furnishing a collateral branch which exactly represents the sub-
Fig. 382.
THE RETE MIRABILE OF THE SHEEP, SEEN IN PROFILE.
1, Carotid artery ; 2, occipital artery; 3, lingual artery, 4, maxillo-muscular artery; 5, posterior
auricular artery ; 6, superficial temporal artery; 7, anterior auricular artery ; 8, middle temporal
artery; 9, transverse artery of the face; 10, internal maxillary artery; 11, inferior dental
artery; 12, spheno-spinous artery ; 13, deep posterior temporal artery ; 14, deep anterior temporal
artery; 15, commencement of the originating arteries of the rete mirabile; 16, encephalic rete
mirabile; 17, trunk of the encephalic arteries arising from the rete mirabile; 18, ophthalmic
artery ; 19, ophthalmic rete mirabile ; 20, common origin of the arteries of the eye ; 21,
supra-orbital artery; 22, buccal artery; 23, superior dental artery; 24, orbital branch of the
latter ; 25, palatine artery ; 26, nasal artery.
mental of Man, and is divided into two branches that resemble the sublingual and ranine
arteries.
3. A large division for the maxillary gland.
4. The posterior auricular artery, from which proceeds : 1. The stylo-mastoid arteriole,
which penetrates the aqueduct of Fallopius. 2. Concho-muscular branches. 3. A large
branch, resembling the mastoid artery of the Horse. This enters the temporo-parietal canal
by a small foramen between the occipital and petrous portion of the temporal bone, and forms
two branches : an external, emerging from this canal by the wide orifice in the temporal fossa,
and expending itself in the temporal muscle, after anastomosing with the two deep temporal
arteries; smd an internal — a considerable meningeal artery — destined principally to the falx
cerebri and the tentorium cerebelli.
THE COMMON CAROTID ARTERIES. 679
5. A small maxillo-muscular artery, ramifying eutirely in the internal pterygoid and the
subcutaneous muscles.
Superficial temporal artery.— This vessel divides, almost at its origin, into three branches :
1. A posterior, supplying the anterior arteries of the ear.
2. An anterior, forming the transverse facial, and terminating by the coronary or labial
arteries, after giving some ramuscules to the masseter and the muscles of the forehead.
3. A median artery, representing the middle temporal of Man. This vessel detaches some
divisions to the temporal muscle, gives off the lachrymal artery, as well as a palpebral branch
rising from the same point, and terminates near the base of tlie cranium by two particular
arteries that are developed around the base of the horn, and form a real arterial circle from
which inferior and superior divisions are given off. The latter are tlie most considerable,
and glide on the bony core of the frontal appendage, where they are distributed almost
exclusively to the generating membrane of the horny tissue, only throwing some filaments into
the sinuses.
Internal maxillary artery.— It does not traverse the subsphenoidal canal, as that bony
passage does not exist.
The following are its principal branches : —
1. The inferior dental artery, which emits some pterygoid ramuscules.
2. The spheno-spinous artery, arising from the same point as tlie preceding, often in common
with it, giving also bome pterygoid branches, and entering the cranium by the oval foramen to
aid in the formation of the rete mirabile, in a way to be indicated hereafter.
3. The po»terior deep temporal artery, which detaches a masseteric artery.
4. The interior deep temporal artery.
5. The buccal, principally sent to the masseter muscle.
6. The ophthalmic artery, longer than in the other animals, forming a loop before traversing
the orbital foramen, and giving a supra-orbital branch and a fasciculus of muscular and ciliary
arteries. Near the point where the originating trunk of this fasiculus is detached, the ophthalmio
artery shows on its course a very curious arrangement which lias not yet been noticed ; we
believe this is a veritable arterial plexus, in a ganglionic form, in principle exactly disposed as
that about to be described (Fig. 382, 19).
7. The originating arteries of the rete mirabile, usually consisting of two principal vessels,
arising with the ophthalmic, passing backward through the supra-sphenoidal canal, and rami-
fying in a special manner to form a mass of reticular twigs, designated the rete mirabile
(Fig. 382, 16).
This network is a small ovoid mass, elongated from before to behind, placed beneath the
dura mater, on the side of the sella Turcica, within the superior maxillary nerve, and composed
of a multitude of fine arterial divisions which anastomose with each other in an extremely
complicated manner. Its inferior extremity, passing into the supra-sphenoidal canal, receives
the generating arteries. The posterior extremity, covered by the clinoid process, is in com-
munication with the spheno-spinous artery, which there expends itself. Towards its middle
part, and above, the twigs forming it reconstitute themselves into a single trunk analogous
to the intercranial portion of the internal carotid of Solipeds (Fig. 382, 17), and which traverses
the dura mater, dividing into three branches. These are the anterior, middle, and posterior
cerebral arteries ; the latter anastomoses, by convergence, with the homologous artery of the
opposite side, behind the pituitary gland, to form the basilar artery and the middle spinal artery,
■which continues it.
This singular disposition of the arteries of the encephalon well deserves the name of rete
mirabile (wonderful network), by which it is known. If we were desirous of giving a summary
idea of this network, we might compare it to a lymphatic gland, the efferent vessels of which
would be represented by the originating arteries with the spheno-spinous, and the efferents by
the originating trunk of the encephalic arteries.
8. Next comes the superior dental, the orbital branch of which presents a considerable
volume, and terminates on the anterior surface of the head by long superficial divisions.
Some of these — the ascending — anastomose with the inferior branches of the arterial circle
situated amund the base of the horn ; while others, the descending, communicate with the
infra-orbital branch of the same vessel, and with the superior coronary artery.
9. The last to be given off are the nasal and palatine arteries, which terminate the internal
maxillary: the nasal artery is disposed as in the Horse; the palatine goes entirely to the
palate.
B. In the Ox, we find all the peculiarities just enumerated, except with the following
differences : —
1. A little above the origin of the lingual artery, the external carotid gives rise to ao
THE ARTERIES.
Fig. 383.
external maxillary artery, which turns round the inferior border of the maxilla, in company
with its satellite vein, and terminates on the forehead, as in the Horse, after supplying the
coronary arteries.
2. The maxillo -muscular artery is distributed to the two masseters — to the external, as well
as the internal.
3. The transverse artery of the face does not form the coronary arteries, as these come from
the external maxillary ; it is altogether expended in the masseter muscle.
4. The anterior auricular artery sends an enormous branch into the temporo-parietal canal,
by the orifice situated behind the supra-condyloid process.
5. The ophthalmic artery and the generating arteries of the rete mirabile proceed from a
common trunk.
6. The rete itself shows some diflferences. We do not find, as in the Sheep, two lateral
elongated lobes, almost independent of each other, but a circular mass surrounding the sella
Turcica. Besides, the occipital arteries concur in its
formation, and pass into its posterior part (Fig. 383).
(This rete mirabile of Galen would appear to be
formed on the carotid and vertebral arteries of animals,
which, in a state of nature, feed from the ground; the
object being to furnish an equable and prolonged supply
of blood without tiie risk of check or hindrance, and
thus to obviate the tendency to congestion of tlie brain
during the dependent position of the head. This
minute subdivision and subsequent reconstitution of
an artery, with a like intention, is also observed in
other creatures besides grazing animals. The vessels
in the arm of the sloth are so disposed that the animal
can remain suspended by it for long periods; and a
similar arrangement is noted in the legs of birds — such
as the Swan, Goose, etc., which stand for a long time.
Around the Horse's foot the arteries break up into
numerous divisions, and we know that this animal can
remain in a standinir attitmle for months, and even
years. The rete ophthahnicum of birds is arranged like
the rete mirabile. The same object is sometimes
attained by great tortuosity, as we have already seen
in the description of several of the arteries. Perhaps
the most marked example, however, is to be found in
the carotid artery of the Seal, which is nearly forty
times longer than the space it has to traverse.
But it may be remarked that there is no rete mira-
bile in the Horse— though it is also a grazing animal
— at all to be compared with that of Ruminants, the
circle of Willis being its only representative.)
THE RETE MIRABILE OF THE OX
(POSTERIOR face).
1, Rete mirabile; 2, trunk of the
originating arteries of the rete mi-
rabile; 3, .spheno-spinous artery; 4,
trunk of the encephalic, or internal
carotid arteries ; 5, branches of the
occipital passing to the rete mira-
bile; 6, interspinal arterial canal,
formed by the intervertebral spinal
branches.
Comparison of the Carotid Arteries of Man
with those of animals.
The common carotids of Man have a different origin,
the right arising from the arteria innominata, the left
from the arch of the aorta. At the inferior border of the
thyroid cartilage, they terminate by only two branches — the external and internal carotids ; the
occipital artery is but a division of the former.
Internal Carotid Artery. — Contrary to what is observed in animals, the internal
carotid is a little larger than the external, a difference which is explained in Man by the
predominance of the cranium over the face. This vessel describes a flexuous course until it
reaches the carotid foramen in the petrous bone ; it forms two curves in the cavernous sinus,
penetrates the dura mater, and divides at the fissure of Sylvius into four branches, which are,
as in Solipeds: the posterior communicating, anterior cerebral, middle cerebral, and artery of
the choroid 'plexus. The internal carotid has an important collateral branch— the ophthalmic
artery — that arises from the convexity of the curve the carotid makes inside the anterior clinoid
process, at the bottom of the orbit. If it differs at its origin, yet this vessel has a distribution
analogous to that already described.
TEE COMMON CAROTID ARTERIES. 681
External Carotid Artery. — In its origin, course, and termination, the external carotid
comports itself as in animals. It gives rise to six branches :
1. The superior thyroid, resembling in its distribution the thyro-laryngeal of Solipeds.
2. The lingual artery, which furnishes a sublingual, and takes the name of ranine at its
termination.
3. The facial artery, which gives off the palatina ascendens, analogous to our pharyngeal,
and the submental.
The two last-mentioned arteries arise separately ; consequently, there is not a glosso-facial
in Man as we have seen it in the Horse.
4. The posterior auricular artery.
5. The inferior pharyngeal artery.
6. The occipital. — This vessel represents the occipital of the Horse minm its cerebro-spinal
ARTERIES OF THE FACE AND HEAD OF MAN.
1, Common carotid; 2, internal carotid; 3, external carotid; 4, 4, occipital artery 5 superior
thyroid artery ; 6, trapezius ; 7, lingual artery ; 8, sterno-mastoid ; 9, facial artery ; 10, temporal
artery, dividing into anterior and posterior branches; 11, submental branch; 12, transverse
facial artery; 13, inferior labial branch ; 15, inferior coronary, and, 17, superior coronary branch;
19, lateral nasal branch ; 21, angular branch.
branch. It gives off a mastoid artery, and terminates in the muscles of the neck and on the
posterior aspect of the cranium. The cerebro-spinal branch is replaced by the termination of
the vertebral artery, which forms on the inferior face of the medulla oblongata the basilar
artery, the disposition of which is identical with that already described.
The superficial temporal artery, and the internal maxillary artery, constitute the termination
of the external carotid.
The internal maxillary is directed towards the spheno-palatine or nasal foramen, into
which it passes and terminates by the spheno-spinous artery. It does not give off the
682 THE VEINS.
ophthalmic artery, that vessel coming from the internal carotid ; but it furnishes all the other
branches we have studied in animals. There are, therefore: a tympanic artery; a meningeal,
middle, or spheno-spinous ; an anterior and posterior deep temporal ; an inferior dental ; a
buccal; a masseteric; pterygoideans ; and a descending palatine or palato-labial artery.
THIRD SECTION.
THE VEINS.
CHAPTER I.
GENERAL CONSIDERATIONS.
Definition. — The veins are the centripetal vessels of the circulatory system.
They bring back to the heart the blood which has been carried from that viscus
to the organs.
Division. — Some proceed from the lungs, carrying red blood, and converge
towards the left auricle of the heart : these are the pulmonary veins, or veins of
the lesser circulation. Others emerge from the mass of all the organs, transport
the dark blood, and open into the right auricle : these are the veins of the
general circulation.
There are, therefore, two venous systems commencing by a capillary network,
opposite an arterial network. Sometimes a third system of veins has been
described for the intestines ; indeed, the vena portse offers a certain indepen-
dence in the midst of the veins of the general circulation, as it terminates in a
capillary plexus in the interior of the liver, and by this plexus it communicates
with the posterior vena cava.
General Disposition. — The veins, after succeeding the capillary networks
which terminate the arteries, or the spaces in the erectile tissues, form a series of
convergent ramifications which repeat, in a general manner — but in an inverse
gense— the arterial ramifications, the course of which they for the most part follow.
A certain number, nevertheless, are placed at some distance from the arterial
trunks, beneath the external tegumentary membrane, where they are disposed in
a vast network that constitutes the superficictl veins of the body. Apart from
this peculiarity, we have nothing more to say with regard to the situation,
direction, relations, and anastomoses of the veins than has been already made
known in studying the arteries. It is only to be remarked, that the anastomoses
of the venous system are more numerous, larger, and more complex than those
of the arterial system ; that they also communicate with more voluminous
trunks ; and that they very often join the deep to the superficial veins. At
certain points— external genital organs, bladder, rectum— the anastomoses are so
numerous as to constitute veritable venous plexuses. These are more especially
met with in regions where the circulation is liable to be more or less hindered,
either from the displacement of organs or variations in their volume. Fenwick
has made known some important communications with regard to the mainte-
nance of the circulation ; for instance, those between the subcutaneous veins,
the laro-e veins of the limbs, and the substance of the thoraco-abdominal
GENERAL CONSIDERATIONS. 683
parieties ; and between the vena portse and the deep epigastric and vesical
veins.
Form. — "With regard to form, the veins represent cyhndrical tubes, sHghtly
knotted on those parts of their course which correspond to their valves, but they
are rarely distended as the arteries are ; the only exceptions are found in the
venous polyhedral spaces or sinuses in the dura mater. Veins offer the same
collective form as the arteries, the general volume of the venous ramifications
being as much more developed as they are distant from the heart, so that all the
branches collected at last into an imaginary single canal would form a hollow
cone, the apex of which would correspond to the auricles.
Number and Capacity. — In comparing the two orders of vessels with
reference to their number and capacity, we discover notable differences. The
veins are more numerous than the arteries, as a great number of the latter are
accompanied by two of the former, and the subcutaneous veins have no repre-
sentatives in the arterial system. All the veins being, besides, much more
voluminous than the corresponding arteries, it follows that the total capacity
of the venous system much surpasses that of the arterial system, and that we may
consider the relation of two to one as being the approximate expression of this
difference.
When the veins are compared with the arteries, it is remarked that the
relations between the length of the trunks and branches are reversed. In
the arteries, the trunks are large and the branches short ; in the veins, on the
contrary, the branches are relatively much longer than the trunks. This dis-
position favours the flow of the blood in the veins, at the commencement of
which we do not find, as in the arteries, a propelling organ.
Another arrangement to answer the same end, in opposing the influence that
atmospheric pressure might have on the veins, is the attachment of these vessels
to the walls of the cavities they pass through ; this is observed, for instance, at
the entrance to the thorax.
This disposition, so favourable to the circulation of the blood, becomes a
constant source of danger to the surgeon, by its permitting the introduction of
air into the circulatory system — especially during inspiration — when a vein is
opened.
Internal Conformation. — The interior of the veins is remarkable for the
presence of valvular folds, the arrangement of which resembles, in principle, that
of the sigmoid valves of the heart. These valves offer : an adherent border
attached to the walls of the vessel ; a free, semilunar border ; a concave surface
towards the heart when the valves are tense ; and a convex surface which, on
the contrary, looks towards the roots of the veins.
These valves are most frequently single, but they are sometimes joined in
twos or threes ; according to some authorities, there are even found four or five
together, arranged in a circular manner. They are distinguished as parietal and
ostial valves, the latter being placed at the entrance of one vein into another.
All the veins are not provided with them, however, and where they exist they
may be more or less numerous. They are absent in the pulmonary system, and
in the trunks of the venaB cava ; absent or quite rudimentary throughout the
extent of the vena portae ; rare and sUghtly developed in the vena azygos, the
veins of the testicle, uterus, and ovary ; and very numerous, very large, and
very complete in the veins of the limbs.
The function of these valves is to favour the onward course of the blood,
681 THE VEINS.
and to oppose its reflux from the heart towards the organs. Applied, as they
are, to the walls of the veins by their coucave face during the regular and
normal circulation, they are disposed as a transverse valve to sustain the column
of blood when any strain or pressure gives that column a retrograde movement.
Structure. — The walls of the veins are thin, semi-transparent, and elastic,
and collapse when the vessels are empty. Compared with the arteries, they have
only two distinct tunics.
The internal tunic is composed of an endothelial layer of irregular and poly-
gonal cells, lying on a layer of connective tissue, limited by an elastic layer
— analogous to the internal elastic layers of arteries.
The external tunic is composed of connective tissue, elastic fibres, and
smooth muscular fibres — the first predominating.
The muscular fibres are transversal, longitudinal, or oblique, their aiTange-
ment varying with the vessels. Lorge states that the vena porta? and intra-
lobular veins in the Horse have only longitudinal muscular fibres.
In some veins or portions of a vein they may be absent. In the veins of
the bones, and in the sinuses of the dura mater, the walls are reduced to a layer
of endothelium laid on a layer of connective tissue.
The venules differ from the arterioles in the dissemination of their muscular
fibres, which form a continuous layer in the latter.
The veins have very numerous vasa vasorum, which form a complete net-
work around them. The vena portae alone is accompanied by nerve filaments
from the great sympathetic.
(As remarked, the superficial veins are generally unaccompanied by arteries ;
they usually pass between layers of superficial fascia, and at the most convenient
situations — generally those best protected — pass through the underlying fascia
to terminate in the deep veins. These are most frequently accompanied by
arteries, being often enclosed in the same sheath with them, particularly in the
extremities. With a large number of arteries there are two veins, one on each
side, the venm comifes, though the largest arteries have only one venous trunk.
The large and frequently repeated communications are undoubtedly intended to
compensate for the thinness of their parietes, which expose to obstruction and
dilatation ; this they cannot overcome, because of the slowness with which the
blood passes through them. The valves are accessory to these inosculations ;
upon the cardiac face of each valve the vein is expanded into two sinuses, which
correspond to the extent of the valve ; these pouches give the distended vessel
its nodulated appearance. Remak found longitudinal muscular fibres in the
adventitia of the large veins of the Ox and Sheep, but chiefly in the hepatic
portion of the posterior vena cava and the veins of the liver.
It is also stated that these longitudinal fibres are found in the inner part of
the middle coat — for some authorities still describe three tunics— of some veins
— ihac, femoral, umbilical ; and the veins of the pia mater, brain, and spinal
cord, retina, and placenta, as well as those of the bones and dura mater sinuses,
have no muscular tissue at all. Valves are absent in the veins of the viscera,
of the cranium and vertebral canal, and umbilical vein, in addition to the precited
vessels. The endothelial cells on the side of the valves over which the blood
passes, are more elongated than on the cardiac side of the valves, where the
long axes of the cells are placed transversely — an arrangement which diminishes
friction.)
THE CARDIAC OR CORONARY VEINS. 685
Injection of the Veins. — To render the dissection and study of the veins more easy, they
ought to be filled with tallow or any other solidifiable matter, like the arteries. But to attain
this result the same mode of procedure cannot be employed as for them. Instead of causing
the injecting material to flow from the trunk into the branches, it is necessary to propel it
from the branches towards the trunk, because of the presence of the valves ; this is to be done
by successively fixing the cannula into several venous brandies.
Four injections generally sufiice to fill the whole venous system in a satisfactory manner.
The first is made from the alveolar vein, beneath the masseter muscle; the second from a
digital vein of one or both anterior limbs, or from tlie side of the foot, after having destroyed
by a stylet the few valves which are sometimes found towards the point of union in this vein;
or from the side of the heart. The third, from the posterior digital veins, in the same way ;
the fourth, by an intestinal vein. If any important veins are empty after these four injectiona —
a case of frequent occurrence — they can be directly injected.
CHAPTER II.
Veins of the Lesser Circulation, or Pulmonary Veins (Fig. 349,/).
The pulmonary veins comport themselves in a similar manner to the correspond-
ing arteries. They are lodged in the substance of the lung, and collect in from
four to eight trunks, which open into the roof of the left auricle, after emerging
from the pulmonary organ immediately above the origin of the bronchi. As
they are destitute of valves, they readily allow the blood to flow towards their
roots. It is they which carry to the left heart the blood thrown into the lungs
by the right ventricle, to be submitted to the revivifying action of the
atmosphere.
CHAPTER III.
Veins of the General or Systemic Circulation.
These vessels bring to the right auricle the blood which has been dispersed in
the texture of organs, by the ramifications of the great arterial tree.
They open into the auricle by forming three groups — the coronary or cardiac
veins, the anterior vena cava, and the posterior vena cava.
The diaphragm establishes the exact limit between the domains of the
anterior and posterior vena cava.
Aeticle I. — Caediac oe Coeonaey Veins.
There are several small, and one large or great coronary vein.
Small Cardiac Veins. — These are the almost insignificant vessels, un-
determined in number, which come from the walls of the right ventricle and
open directly into the corresponding auricle at the coronary groove. (Among
these may be included the debatable ve^ice Thehesii — a multitude of minute
venules said to arise in the structure of the heart, and open directly into its
cavities.)
, Great Coronary Vein (Figs. 349, 5 ; 350, o, p). — This vein is formed
by two roots : one is lodged in the right ventricular groove, and accompanies
the cardiac artery of the sajne side ; the other follows, at first, the left ventricular
46
686 THE VEINS.
groove, ascends nearly to the pulmonary artery^ and is then inflected backwards
by placing itself in the coronary groove, along with the horizontal branch of the
left cardiac artery. Turning round the base of the posterior ventricle, it joins
the right root, near the upper extremity of its groove. The common trunk
resulting from this junction, after a short course opens into the right auricle,
below and within the entrance of the posterior vena cava.
In their course, the two branches of the coronary vein receive branches from
the auricular and ventricular walls.
The bronchial veins, ramifying on the bronchi Uke the arteries, the satellites
of which they are, also open into the great coronary vein, very near its entrance,
after becoming a single vessel, which sometimes passes directly into the auricular
cavity.
Article II.— Anterior Yena Cava (Figs. 349, r ; 350, d ; 389).
This is a voluminous trunk, which ought to be considered as the correspond-
ing vein of the anterior aorta. It extends from the entrance of the chest to
the right auricle, into the roof of which it is inserted. It is comprised between
the two layers of the anterior mediastinum, and lies below the trachea, to the
right of the anterior aorta.
Four large vessels — the ftao jugular and tico axillary veins — opening in
common in the space comprised between the two first ribs, constitute the roots
of this vessel.
Collateral Affluents. — The affluent vessels which the anterior vena cava
receives in its course are : the internal thoracic, vertebral, superior cervical, and
dorsal veins, and the great vena azygos.
Internal Thoracic or Internal Mammary Vein. — A satellite of the
artery of the same name, this vein opens into the anterior vena cava, at its
origin (Fig. 389).
Vertebral Vein. — It accompanies the corresponding artery in the canal
formed by the foramina in the transverse processes of the cervical vertebra, and
joins the vena cava at the origin of that artery (Fig. 389).
Superior Cervical Vein. — Exactly resembles the artery the name of which
it bears.
Dorsal Vein. — This vessel follows the dorso-muscular artery, and, like it,
presents a subcostal branch. On the left side, this branch is designated the
small vena azygos, and is often prolonged to the eleventh or twelfth rib ; it
receives the intercostal veins of the spaces it crosses.
It may be remarked that the vertebral, superior cervical, and dorsal veins
of the right side, are nearly always thrown separately into the vena cava, while
on the left side they constantly unite to form a single trunk (Figs. 349, w ; 389).
Great Vena Azygos (Figs. 349, x ; 350, e ; 389).— This is a long single
vein, which commences at the first lumbar vertebra, and extends forward on
the right of the anterior aorta, beneath the bodies of the dorsal vertebrae to
about the sixth, when it is inflected downward to terminate in the anterior vena
cava, near the entrance of that vessel, or even directly into the right auricle.
In its course, the great vena azygos is maintained against the bodies of the
dorsal vertebra by means of the parietal pleura ; it runs alongside the outer
border of the thoracic duct, which separates it from the aorta. ^ The terminal
' Sometimes the azygos is situated between the aorta and the thoracic duct. When the
latter lies to the left side, it is in direct contact with the posterior aorta.
THE ANTERIOR VENA CAVA. 687
extremity of its inflection crosses the oesophagus and trachea to the right, and
is included between these two tubes on the one side, and the right layer of the
mediastinum on the other.
Its roots are some branches emerging from the spinal and psoas muscles, and
which are not usually in direct communication with the posterior vena cava, aa
in Man and the other animals.
During its progress, it receives the first lumbar and the satellite veins of all
the aortic intercostal arteries, right and left. But when the small vena azygoa
is prolonged backwards beyond the posterior extremity of the subcostal artery,
that vessel, as we have already seen, forms the confluent of a certain number of
left posterior intercostals.
Jugular Veins (Figs. 386, 389).
The jugular is a satellite vein of the carotid artery.
Origin. — It commences behind the inferior maxilla, below the articulation
of the jaw, by two large roots — the superficial temporal vein and the internal
maxillary vein, which correspond to the two terminal branches of the external
carotid artery.
Situation—Direction. — This vessel passes downward and backward, lodged
at first in the substance of the parotid gland, afterwards in the muscular inter-
space designated the jugular furrow, which is comprised between the adjacent
borders of the mastoido-humerahs and sterno-maxillaris muscles. Reaching the
inferior extremity of the neck, it terminates in the following manner : —
Termination. — On arriving near the entrance to the chest, the two jugulars
unite in forming a vessel named the confluent of the jugulars. This confluent,
into which open the two axillary veins, is comprised between the two first ribs,
and situated below the trachea, in the middle of the prepectoral lymphatic glands.
Fixed by fibrous bands to the neighbouring parts, and particularly to the two
first ribs, the walls of the jugular confluent do not collapse when the venous
system is in a state of vacuity — an anatomical peculiarity which it is necessary
to understand, in order to explain the manner in which air obtains entrance into
the circulation when the jugular or axillary veins are opened, as well as affording
an indication how to prevent this serious accident.
Relations. — At its upper extremity, the jugular vein is surrounded by the
parotideal tissue. For the remainder of its extent, it is covered externally by
the cervical panniculus, and by the branches of the cervical plexus which creep
on the external surface of that muscle. Inwardly, its relations vary as we
consider its situations, above or below : above, it is related to the subscapulo-
hyoideus muscle, which separates it from the common carotid and its satellite
nerves ; in its inferior moiety, it is in direct relation with that vessel, which is
above it, as well as with the trachea, and even, though only on the left side,
with the oesophagus.
CoLLATEEAL AFFLUENT VESSELS.— The Collateral veins which go to the
jugular from its origin to its termination, are : 1. MaxiUo-muscular veins. 2.
Posterior auricular vein. 3. Occipital vein. 4. Suhmaxillary or facial vein.
5. Thyroid vein. 6. Cephalic vein. 7. Parotideal and innominate muscular
branches.
A. MaxiUo-muscular Veins.— Two in number, corresponding to the
branches of the artery of the same name, and entering the jugular close to its
origin, either separately or after forming a common trunk.
688 THE VEINS.
B. Posterior Auricular Vein. — A voluminous vessel which commences
on the concha, and descends on the external face of the parotid gland, near its
posterior border, where it is joined by numerous divisions from the parotid
lobules. It opens into the jugular vein, generally a little below, and opposite to,
the maxillo-muscular vessels, though it is sometimes lower — often even after the
occipital vein (Fig. 385, 13).
C. Occipital vein. — The occipital vein corresponds, in every respect, to its
fellow-artery. It has two roots — an anterior, which originates at the posterior
extremity of the subsphenoidal confluent ; and a posterior, commencing beneath
the transverse process of the atlas, and formed by three principal branches.
Among the branches of the latter root, one passes with the retrograde artery
through the posterior foramen of the atlas, and constitutes, as it were, the origin
of the vertebral vein ; the second communicates with the occipito-atloid sinuses,
by traversing the atlas near its middle ; the third — satellite of the cerebro-spinal
artery — comes also from these sinuses, and receives the venules which accompany
the ramifications of the occipito-muscular artery.
D. Sub-maxillary or Facial Vein. — A satellite of the artery of the same
name, this vessel begins on the forehead by two roots — a superior and inferior,
analogous in every point to the terminal branches of the artery. It descends
along the anterior border of the masseter muscle, gains the maxillary fissure,
into which it is inflected, placing itseK between the artery and Steno's duct ; then
proceeds backwards and downwards on the internal pterygoid muscle, always
accompanied by the glosso-facial artery until near the anterior extremity of the
maxillary gland, when it leaves it to follow the inferior border of that gland, and
enters the jugular vein, after crossing the sterno-maxillaris muscle outwardly, and
forming with the latter vein an angle which is occupied by the inferior extremity
of the parotid gland (Fig. 385).
Branches of origin. — Of the two branches which, by their union, constitute the
origin of the submaxillary vein, the inferior {dorsalis nasi) — a satellite of the
nasal branch of the corresponding artery — possesses no interest. The superior,
or angular vein of the eye, merits particular notice, as venesection is sometimes
practised on it. It arises near the nasal angle of the eye, and creeps to the
external face of the elevator muscle of the upper lip, below the lachrymalis
muscle.
Collateral branches. — In its progress, the submaxillary vein receives a great
number of affluents, the principal of which are the alveolar vein, the labial or
coronary veins, the buccal vein, and the sablinguaJ vein.
a. Alveolar vein (vena varicosa). — This is a considerable vessel lodged beneath
the masseter, and lying against the supermaxillary bone, between the zygomatic
crest and the aveoli of the upper molar teeth (Fig. 385).
The arrangement of this vessel is most singular ; its anterior extremity opens
into the submaxillary vein, and its posterior extremity traverses the ocular
sheath, receives the ophthalmic veins, and passes, with the ophthalmic nerve of
the fifth pair, into the foramen lacerum orbitale, to open into the cavernous sinus
in the interior of the cranium.^
Before traversing the ocular sheath, and towards the maxillary hiatus, this
vein receives the superior dental and the confluent of the tiasal veins — vessels
' We have also seen it send into the subsphenoidal canal, to the inner side of the internal
maxillary artery, a slender branch that joined the anterior extremity of the subsphenoidal con-
fluent. But we cannot say that this disposition is constant.
THE ANTERIOR VENA CAVA. 689
which emerge from the bony orifices traversed by the arteries of the same name
— that is, the maxillo-dental canal and the nasal foramen. It also receives the
confluent of the palatine veins, which pass by the palatine groove, instead of
coursing along the palatine canal with the corresponding artery. In general,
these three branches do not join the alveolar vein separately, but rather by a
common trunk.
The alveolar vein does not present a uniform volume. It increases until
it reaches the alveolar tuberosity, where it forms a kind of large reservoir ; but
in traversing the ocular sheath it suddenly becomes constricted, and maintains a
small diameter until its entrance into the cavernous sinus. (The reservoir is
supposed to prevent congestion of the cavernous sinus.)
This vein may be considered as an affluent of the sinuses of the dura mater,
as well as of the external maxillary vein.
b. Labial or coronanj veins. — Satellites of the labial arteries. The superior
is often rudimentary. The inferior, always voluminous, is constituted by the
union of several anastomotic branches lying against the external face of the
mucous membrane of the cheek.
c. Buccal vein. — Among the affluents of the external maxillary vein, we cite
this, because it opens into the latter by its anterior extremity, opposite the inferior
coronary vein, with which it sometimes communicates by a particular branch.
But the buccal vein, properly speaking, constitutes the root of the internal
maxillary, and we will describe it as such.
d. Sublingual vein. — A large vessel, formed of two branches, which arise in
the substance of the tongue, and pass sometimes separately into the internal
maxillary vein. This sublingual vein passes through the mylo-hyoideus muscle,
from within to without, and joins the principal vessel at the lymphatic glands
lodged in the submaxillary space.
E. Thyroid Vein. — This is a voluminous trunk, resulting from the union
of the venous divisions which accompany the laryngeal and thyroid branches
of the thyroid or thyro-laryngeal artery. It joins the jugular beside the sub-
maxillary vein, and most frequently above it.
F. Cephalic or Plate Vein. — A superficial vessel, which represents one of
the terminal branches of the principal subcutaneous vein of the forearm. It is
lodged in the interspace of the mastoido-humeralis and anterior superficial
pectoral muscles, and enters the inferior extremity of the jugular vein (Fig. 389).
G. Innominate Veins. — A certain number come from the parotid gland,
but the principal arise in the muscles of the neck and withers. One of the latter
accompanies the superior branch of the cervico muscular-artery.
Roots of the Jugular Vein.
These are constituted by the superficial temporal and internal maxillary veins,
which are chiefly supplied by the sinuses of the cranial dura mater.
1. Superficial Temporal Vein.
Corresponding in the most exact manner to the temporal vein, this vessel is
lodged behind the posterior border of the maxilla, near the articulation of the
jaw, beneath the parotid gland, and is embedded in its tissue.
From the union of these two roots, there results :
1. The anterior auricular vein — a very large, often multiple, and reticulated
690 TEE VEINS.
branch, anastomosing with the pterygoid branches of the internal maxillary artery.
This vein issues from the parieto-temporal conduit, behind the supra-condyloid
eminence ; it receives one or two branches which escape from this conduit by
the foramina in the temporal fossa, crosses the temporalis muscle, and is charged
with venules which arise in the interior of that muscle, as well as in the textures
of the external ear (Fig. 385, 8).
2. The subzygomatic vein, a satellite of the homonymous artery, and, like it,
is divided into two branches— one accompanying the transverse artery of the
face, the other the masseteric artery. The latter branch communicates by its
inferior extremity with the external maxillo-muscular vein ; it joins, by its other
extremity, an enormous branch which comes from the temporal muscle, and
which passes into the sigmoid notch, after anastomosing largely with the deep
temporal branches of the internal maxillary vein (Fig. 385, 6).
2. Internal Maxillary Vein.
Remarkable for its enormous volume, this vein creeps between the internal
masseter muscle and the maxilla, in an oblique direction upwards and backwards.
Arriving within the articulation of the jaw, a little below the maxillary condyle
and the external pterygoid muscle, it joins the temporal vein after being slightly
inflected downwards. It therefore runs its course at a certain distance from the
corresponding artery.
The internal maxillary has for its radicle the hmcal vein, which it succeeds
near the superior extremity of the buccinator muscle.
Satellite of the artery and nerve of the same name, this buccal vein,
remarkable for its volume, is situated beneath the masseter muscle, near the
inferior border of the buccinator muscle ; by its anterior extremity it com-
municates directly with the internal maxillary vein, nearly opposite to the
junction of the inferior coronary vein ; its posterior extremity is continued
directly with the internal maxillary vein. The collateral branches it receives in its
course, come from the masseter muscle and the parietes of the cheek.
On its way it receives a great number of affluents ; these are :
1. A large lingual vein, accompanying the small hypoglossal nerve.
2. The inferior dental vein.
3. The trunk of the deep temporal veitis — a large vessel situated in front and
to the inside of the temporo-maxillary articulation, where it communicates with
the masseteric vein. This vessel arises in the texture of the temporalis muscle, but
particularly in the parieto-temporal confluent, with which it joins through the
foramina in the temporal fossa.
4. The pterygoid veins, numerous branches, only a portion of which come
from the pterygoid muscles. The others, arising from the subsphenoidal con-
fluent of the sinuses of the dura mater, form, on the superficial face of the
external pterygoid muscle, a wide-meshed network which communicates pos-
teriorly with the temporal vein, and anteriorly with the confluent of the deep
temporal veins. But as these two vessels are bound together, outside the
temporo-maxillary articulation, by means of the masseteric artery, it results that
this articulation is enlaced on every side by one of the richest venous plexuses in
the whole body (Fig 386, 10).
3. Sinuses of the Dura Mater.
We will here describe not only the sinuses of the cranial dura mater
THE ANTERIOR VENA CAVA.
which supply the radicles of the jugular vein, but also those of the spinal dura
mater, although these empty themselves into other veins ; in order that we may
Fig. 385.
RADICLES AND COLLATERAL BRANCHES OF THE JUGULAR VEIN IN THE HORSE (EXTERNAL VIEW).
M, Inferior maxilla ; A, buccinator ; Mo, superior molar gland ; Ma, masseter muscle (the greater
portion has been removed); R, elevator of the upper lip; S, Steno's duct; C, carotid artery; 0,
subscapulo-hyoideus muscle ; St, sterno-maxillaris muscle ; P, termination of the two previous
muscles. 1, Radicles of the facial vein ; 2, superior coronary vein ; 3, inferior coronary vein ;
4, 4, 4, facial vein; 5, alveolar vein; 6, 6, transverse facial vein communicating in front with
the facial vein ; 7, buccal vein ; 8, anterior auricular vein ; 9, masseteric vein ; 10, deep network
of the masseteric veins ; 11, maxillo-muscular vein ; 12, 12, jugular vein ; 13, posterior auricular
vein; 14, occipital vein and its various branches; 15, laryngeal vein.
be able to consider, in their entirety, all the vessels of the nervous centres which
carry dark blood.
692 THE VEINS.
The Sinuses of the Dtjea Matee m General. — These are vascular spaces
in the texture of the dura mater, or situated between that membrane and the
bones which form the walls of the cerebro-spinal sheath, or are even excavated on
the inner surface of these bones. These spaces differ more particularly from
the veins, by their being generally of a prismatic form, by being continually open,
by the absence of valves in their interior, and by the presence, in some of them, of
lamellfe {traheculce), or intersecting filaments {chordce WUlisii) which stud their
inner surface, and make them look reticulated.
Their walls are reduced to an epithelial layer that lies either on the dura
mater, or on the osseous tissue.
It is into these sinuses that the veins of the brain and spinal cord disgorge
themselves.
The Sinuses of the Cranial Dura Mater in Particular. — Four prin-
cipal will be described : the superior longitudinal sinus of the falx cerebri, or
median sinus, the ttvo cavernous or sphenoidal sinuses, and the group of occipito-
atloid sinuses.
1. Sinus of the Falx Cerebri, Superior Longitudinal or Median
Sinus. — Channeled in the substance of the falx cerebri, and becoming wider
as it extends backwards, this sinus commences near the crista galli process, and
terminates on the internal parietal protuberance by bifurcating. The two
branches resulting from this division form the origin of the parieto-temporal
confluent, or winepress of HerophiJus (torcidar Herophili, Fig. 386, 1, 4).
2. Cavernous or Supra-sphenoidal Sinuses. — These are two in number
— a right and a left. They occupy, on the internal face of the sphenoid bone,
at each side of the sella Turcica, the so-called cavernous fissures. Bordered
outwardly by the superior maxillary nerve, they receive at their anterior
extremity the insertion of the alveolar vein. Posteriorly, they join each other,
and in doing so form a kind of arch, open in front, around the pituitary gland
(Fig. 386, 8). Each opens widely at the foramen lacerum basis cranii, into the
subsphenoidal confluent.
3. Occipital or Occipito-atloid Sinuses. — By this name is designated a
network of large irregular veins, situated beneath the external face of the dura
mater, on the sides of the occipital foramen, and on the entire internal surface
of the atloidean ring. Anteriorly, these venous reservoirs communicate, through
the condyloid foramen, with the posterior extremity of the subsphenoidal con-
fluent. Posteriorly, they are continuous with the spinal sinuses, of which we
may consider them to be the origin (Fig. 386, 6).
4. Rudimentary Sinuses of the Cranial Dura Mater. — Independently
of the above-described reservoirs, there exists, on the mner wall of the cranium,
some rudimentary venous sinuses which should be indicated ; these are : 1. One
or two veins lodged in the structure of the tentorimn cerebelli, designated the
petrosal or transverse sinuses, communicating, below, with the cavernous sinuses,
and entering, above, into the parieto-temporal confluent.^ 2. Some small,
irregular, and reticulated cavities, very variable in their disposition, situated
beneath the dura mater, on the sides of the cerebellar cavity, and which generally
empty themselves into the subsphenoidal confluent by traversing the posterior
part of the foramen lacerum basis cranii, and also opening sometimes into the
petrosal sinus ; these cavities may be regarded as the representatives of
• More frequently, perhaps, these veins arise directly from the substance of the brain, and
do not communicate, below, with the cavernous sinuses.
THE ANTERIOR VENA CAVA.
the lateral sinuses in Man (Fig. 386, 5). 3. In some instances, an inferior median
sinus, channeled near the free border of the face of the brain, passes behind
into the torcular Herophili (Fig. 386, 2).
Fig.
SINUSES OF THE DURA MATER AND RADICLES OF THE JUGULAR VEIN OF THE HORSE, SEEN IN
A MEDIAN AND LONGITUDINAL SECTION OF THE HEAD.
i., Atlas ; Ax, axis ; V, third cervical vertebra ; C, nasal septum ; P, pharynx ; E, Eustachian tube ;
M, interior maxillary nerve — coinu of the ns hyoideus ; La, tongue; L, larynx; T, trachea; G,
submaxillary salivary gland; F, falx cerebri. 1, Sinus of ditto; 2, middle inferior sinus; 3,
venae Galeni ; 4, torcular Herophili; 5, small sinuses of the cerebellar cavity ; 6, occipito-atloidean
sinus ; 7, spinal sinus ; 8, communicating branch of the cavernous sinuses ; 9, internal maxillary
vein receiving above; 10, 10, 10, the pterygoid veins; 11, trunk of the temporal veins; 12,12,
jugular vein; 13, posterior auricular vein; 14, occipital vein; 15, radicle of the occipital vein
arising from posterior extremity of the subsphenoidal confluent; 16, 16, facial vein.
The Spinal Sinuses in Particular. — We thus designate in Veterinary
Anatomy — and with good reason — two series of venous reservoirs which are found
694 THE VEINS.
throughout the whole extent of the vertebral column, on the sides of the roof
of the spinal canal. Lodged in the lateral depressions on the superior face of
the vertebral bodies, at the side of the common superior vertebral ligament, and
covered by the dura mater, these reservoirs, continued from one vertebra to the
other, are like two large, irregular, parallel veins, which commence at the atlo-
axoid articulation, terminate on the first coccygeal vertebrae, where their presence
is yet well defined, and communicate with one another during their course by
transversal anastomoses (Fig. 386, 3).
Affluent Veins that open into the Sinuses of the Dura Mater. —
These are the vessels which carry blood either from the dura mater itself, or
from the substance of the nerve-centres : those of the first category are rare, but
the second are numerous. Although we are unwilling to make a detailed study
of the latter, we must nevertheless notice what is most remarkable in their
disposition.
a. On the brain, the veins form a much richer and closer network than that
of the arterial ramifications ; from this network proceed a certain number of
principal branches, which throw themselves into the sinuses of the cranial dura
mater. The veins of the cerebrum, for the most part, gain the median and
transverse sinuses ; a few only pass into the cavernous sinuses. Those of the
medulla oblongata and cerebellum go to the petrosal and occipital sinuses.
With regard to the internal veins of the brain — those which, by their inter-
lacing, constitute the choroid plexus — they unite into a large trunk — the great
vein of the brain, or vena Galeni, which bends round the superior extremity of the
corpus callosum, reaches the interlobular fissure, and enters the falciform or
middle sinus, near its posterior end, after receiving the superficial veins from
the inner face of the hemispheres.
b. The venules arising from the spinal cord are also very remarkable for the
fine network they form on the surface of the organ. They collect into a common
trunk — the median spinal vein, which runs from before to behind, throughout
the whole extent of the superior groove in the spinal cord ; thus occupying an
analagous, though opposite, position to that of the artery of the same name.
From this vein escape, at intervals, emergent branches which open into the spinal
sinuses.
Effluent Canals of the Dura Mater Sinuses. — We have to notice,
under this designation, the veins which carry the blood from the sinuses, and
will consider in succession those which commence at the cranial sinuses, as
well as those that emerge from the interspinal canals.
a. To be carried from the cranial sinuses, the blood flows into two kinds of
double gulfs, known as the parieto-temporal or subsphenoidal conff vents.
The parieto-temporal confluents are lodged in the canals of the same name,
along with the mastoid artery. Each commences at the base of the internal
parietal protuberance, and terminates behind the supra-condyloid eminence. The
median and transverse sinuses are confounded with the superior extremity of
these reservoirs, and empty into them the blood coming from the encephalic
mass. This fluid is subsequently taken away by the superficial and deep temporal
veins, which have their principal radicles in these confluents.
In Ruminants, the parieto-temporal confluent opens into the temporal veins, and has in
front a branch that passes to the foramen lacerum basis crauii. In the Pig and Cat, it is
lodged in the two grooves which open, one at the anterior foramen lacerum, the other at the
posterior.
THE ANTEEIOR VENA CAVA.
Fig. 387.
The suhsphmoidal confluents (Fig. 387) extend on the sides of the body of
the sphenoid bone and basilar process, from the base of the subsphenoidal
process to the condyloid fossa, concurring in the closing of the occipito-spheno-
temporal hiatus. They open at their middle portion into the corresponding
cavernous sinus, by an oval aperture which the
internal carotid artery traverses in penetrating
into the cranium. The anterior extremity
terminates in a cul-de-sac. Posteriorly, they
communicate through the condyloid foramina
with the occipital sinuses. The vessels which
carry off the blood from these confluents are
the pterygoid veins, and the anterior radicle of
the occipital vein. "We know that the posterior
branch of the latter vessel removes the blood
directly into the occipital sinuses.
h. The emergent veins of the spinal sinuses
present a more simple disposition. At each
intervertebral space arise several branches,
which more particularly make their exit by the
intervertebral foramina to join the neighbour-
ing veins ; in the cervical region, the vertebral
veins serve as a receptacle in this way for the
venous branches from the spinal sinuses ; in
the dorsal region, it is the spinal branches of
the intercostals ; in the loins, the analogous
branches of the lumbar veins ; and in the sacral
region, the lateral sacral vein.
As a whole, the venous system of the
cerebro-spinal centres presents a special physi-
ognomy. The veins arising from the nerve
substance or the meninges, instead of passing
immediately into the veins of the neck or head,
open at first into irregular cavities {sinuses)
established between the cranium and the mem-
branes enveloping the nervous centres, or ex-
cavated in the cranial walls. The blood collects
in certain of these cavities, named confluents,
whence the vessels go which finally open into
the deep or superficial veins of the cervical
region. There are, therefore, two stages be-
tween the veins of the brain or spinal cord
and the veins of the neck and face — the sinuses
and confluents.
SUBSPHENOIDAL CONFLUENTS IN
THE HORSE.
1, Middle part of the subsphenoidal
confluent (right side); 2, anterior
extremity of ditto ; 3, posterior
extremity in the subcondyloid cavity
of the occipital bone ; 4, one of the
pterygoid veins, discharging from
the confluent ; 5, 6, anterior radicles
of the occipital vein, discharging
from the confluent ; 7, posterior
radicle of the left occipital vein; 8,
occipital vein ; 9, 9, temporal veins,
discharging from the parieto-tem-
poral confluents ; 10, temporal
condyle; 11, tuberosity of the
temporal bone; 12, styloid process
of the occipital bone ; 13, condyle
of ditto; 14, atlas; 15, axis; 16,
rectus capitis anticus muscle.
Axillary Veins.
A general confluent of all the veins of the thoracic limb and of some from
the trunk, the axillary vein commences beneath the scapulo-humeral articulation,
towards the terminal extremity of the corresponding arterial trunk, accompanying
696 THE VEINS.
the latter to the entrance of the chest, and joining the confluent of the jugulars
to constitute, with these two vessels, the inferior vena cava (Fig. 389, 18).
In studying, from their origin to their termination, the numerous branches
which concur in the formation of this venous trunk, we recognize : —
1. That they form in the foot a very rich network, from which proceed the
digital reins, satellite vessels of the homonymous arteries.
2. That to these digital veins, which are united in an arch above the
sesamoids, succeed three metacarpal branches, or collaterals of the cannon — two
superjjcials, placed on each side of the flexor tendons, and a deep vein, situated
underneath the suspensory ligament, along with the interosseous arteries.
3. That the metacarpal veins also open into each other, in the superior and
posterior region of the carpus, to form, on again separating, two groups of anti-
hrachial veins : one group comprising the idnar and the posterior or interned
radials, which accompany the arteries of the same name ; the other, constituted
by a single subcutaneous branch — the median veiii — which receives at its superior
extremity the anterior superficial radial vein.
4. That at the ulnar articulation, these two groups of antibrachial veins join
the satellite vessel of the anterior radial artery, and communicate by a very
complicated system of anastomoses, from which results a principal trunk — the
humeral rein.
0. That the humercd vein, after receiving on its course several muscular
branches and the subcutaneous thoracic vein, unites near the shoulder- joint with
the brachial or subscapular trunk, to form the axillary vein.
We will study all these branches in the inverse order of their enumeration.
1. Brachial oe Subscapular Vein.
A very considerable vessel, the arrangement of which resembles that of the
subscapular artery, though presenting some special peculiarities which do not
merit much attention ; for example, it most frequently receives the satellite vein
of the prehumeral artery.
2. Humeral Vein.
Placed behind and to the inner side of the humeral artery, this vessel com-
mences above the articulation of the elbow, being formed at this point by the
anastomosing system of veins from the forearm, and terminates below the shoulder-
joint in opening into the subscapular vein.
Independently of the subcutaneous thoracic vein, which will be studied in
a special manner, the humeral vein receives on its way several collateral satellites
of the branches emanating from the humeral artery. One of these, the epicondy-
loid, is only a continuation of the ulnar vein.
Very often we find a second humeral vein in the deep region of the arm ;
this is an accessory vessel, parallel to the preceding, and situated opposite it, in
front of the artery.
3. Subcutaneous Thoracic or Spur Vein.
This vein, which is important to know, as bleeding is sometimes practised
from it, commences on the flank and belly by numerous superficial divisions,
which unite in two principal radicles and afterwards become a single trunk,
placed in the substance, or on the external surface of the panniculus carnosus,
THE ANTERIOR VENA CAVA. 697
where it is directed forwards in following the superior border of the posterior
superficial pectoral muscle, accompanied by an arterial ramuscule and a thick
nerve. It insinuates itself beneath the olecranian muscles, and finally terminates
in the humeral vein by joining the branch that follows the deep muscular artery.
4. Deep Veins of the Forearm.
A. Anterior Radial Vein. — This follows the same track, and affects the
same variations, as the corresponding artery.
B. Posterior Radial Veins. — The posterior radial artery is always accom-
panied, and, as it were, enveloped, by a fasciculus of three or four venous
branches, which frequently anastomose with each other, and are reinforced by
collateral branches, among which the interosseous vein must be noted.
These radial branches commence above the carpus, by continuing the meta-
carpal veins. They concur to form the humeral vein, in joining the other
antibrachial veins at the inferior extremity of the arm.
C. Ulnar Vein. — This vessel is lodged, with the nerve and small artery of
the same name, in the interspace between the oblique and internal flexors of the
metacarpus. A number of muscular and subcutaneous branches enter this vein.
It has the same origin as the posterior radial veins. Its superior or terminal
extremity bends forward, close to the trunk of the ulnar artery, and goes to the
inferior extremity of the humeral vein. Frequently the ulnar vein is double in
the latter portion of its track, and between these two branches lies the artery.
It always communicates at this point, by one or more branches, with the deep
muscular vein.
5. Superficial Veins of the Forearm.
Placed outside the fibrous sheath formed by the antibrachial aponeourosis,
these veins, which are principally two in numlber, are maintained against the
external face of that membrane by a thin fascia that separates them from the
skin.
A. Median or Internal Subcutaneous Vein (Fig. 389, 31). — This is
also one of the vessels selected for the operation of phlebotomy. It is the
continuation of the internal metacarpal vein, ascends from the inner face of the
carpus to the superior extremity of the forearm, by crossing the radius in a very
oblique manner, and terminates in two very large branches, the posterior of
which is the basilic vein, and the anterior the cephalic vein.
The basilic vein traverses the superficial pectoral muscle, to aid in forming
the humeral trunk (Fig. 389, 34).
The cephalic, or plate vein, crosses the superficial band of the biceps muscle, is
lodged in the space comprised between the mastoido-humeralis and anterior
superficial pectoral muscles, and afterwards opens in the jugular vein (Fig.
389, 35).
B. External Subcutaneous or Anterior Radial Vein (Fig. 389, 32).
— Less considerable than the preceding, this vein arises at the carpal region, in
its course occupies the anterior face of the forearm, and terminates in uniting its
superior extremity either to the internal subcutaneous, or the cephalic vein ; the
last is most frequently the case.
TEE VEINS.
6. Metacarpal Veins.
Three in number, these veins are distinguished into internal and external
metacarpals or collaterals of the cannon, and deep or interosseous metacarpal or
collateral.
A. Internal Metacarpal Vein. — More voluminous than the others, this vein
passes from the vicinity of the fetlock along the flexor tendons, accompanied by
the principal artery of the cannon and the external plantar nerve, places itself in
the special sheath which envelops the common trunk of the interosseous arteries
to the inside of, and behind the carpus, to be continued in the antibrachial
region by the internal subcutaneous vein, after communicating with the other
metacarpal veins (Fig. 389, 30).
B. External Metacarpal Vein. — Situated opposite the preceding — to the
external side of the flexor tendons, in company with the corresponding plantar
nerve — this vessel follows that nerve to near the supra-carpal, and then separates
into several reticulate branches which anastomose with the internal vein, from
which proceed the ulnar and internal or posterior radial veins.
C. Interosseous Vein. — A tortuous, irregular, and sometimes multiple
vessel, lodged with the plantar interosseous arteries between the suspensory
ligament and the posterior face of the principal metacarpal bone. Reaching the
superior extremity of that bone, it unites largely to the right and left with the
external and internal metacarpals, sending upwards one or two small branches
which traverse the carpal sheath along with the collateral artery of the cannon,
and enter into the posterior radial branches above the knee.
7. Digital Veins.
These veins occupy, on the sides of the digital region, the samo position as
the homonymous arteries in front of which they are placed They arise from
the network formed on the lateral cartilages by the veins of the foot, and termi-
nate in uniting above the fetlock, between the flexor tendons of the phalanges
and the suspensory ligament, so as to form an arch (the sesamoidecai) from which
proceed the three metacarpal veins (Fig. 389, 37).
8. Veins of the Foot oe Ungual Eegion.
The importance of the region to which these vessels belong, requires that
they should be described more fully than the other veins, and as has been
already done with the arteries of this part of the body. We will, therefore,
borrow the exact and minute description given by M. H. Bouley.^
This venous apparatus may be divided into external and internal or intra-
osseous.
a. External Venous Apparatus.
" The external venous apparatus of the digital region is very remarkable for
the nmnber, development, superficial distribution, and reticulated disposition of
the canals composing it. To give an idea of this, we cannot do better than
compare its general form to a net whose irregular meshes are extended over, and
moulded on, the two last phalanges which are contained in it.
" This intricate reticulation of the venous apparatus of the foot is marvel-
lously displayed in specimens injected after maceration, and then dried.
' TraiU de V Organization du Pied du Cheval, p. 65.
TEE ANTERIOR VENA CAVA. 699
" To facilitate its description, we recognize in it three parts distinct by their
situation, though they only form a continuous one. They are :
" 1 . The solar plexus.
"2. ThB podophyllous plexus.
" 3. The coronary plexus.
" A Solar Plexus. — The veins of the solar plexus are remarkable for the
equaUty of their calibre throughout the whole extent of the plantar surface, and
by the almost absolute absence of anastomotic communications with the deep
parts.
" Sustained in a special fibrous web {plantar reticulum), which replaces the
periosteum at the lower surface of the phalanx, and is a continuation of the
corium of the villous tissue, these veins appear indeed to have so little commu-
nication, except with each other, that it is possible to detach the plantar reticu-
lum from the superior face of the third phalanx without disturbing them.
" The general disposition of the veins in the texture of the reticulum
supporting them, closely resembles that of the secondary ribs of the limb (or
laminar meritliaX) of certain asymmetrical leaves. In their course they follow an
irregularly broken Hne, intercepting each other by joining at short intervals, so
as to form unequal-sized, unsymmetric, polygonal spaces.
" These veins discharge themselves by a double canal — a central, the least
considerable and least constant ; the other, peripheral or circumflex, correspond-
ing to the artery of the same name,^ and of which it is the satellite vein.
" Central canal. — The central canal is formed by the simultaneous anasto-
moses of a crowd of venous ramifications converging towards the centre of the
digit. It is of a parabolic shape, and embraces in the concavity of its curvature
the point of the pyramidal body, whence it throws its two branches in a parallel
manner on the sides of that body, into the bottom of the lateral lacunas as far as
the cartilaginous bulbs, where it proceeds to the external coronary plexus. This
disposition is not constant, however, as specimens are frequently met with in
which this central canal is replaced by multiple veins, which are more consider-
able than those forming the whole of the plexus, and which serve them as over-
falls towards the superficial coronary plexus.
" Circumflex or peripheral vein. — This vein is of large calibre, and formed by
divergent ramifications from the solar plexus, as well as the descending veins
of the podophyllous plexus ; it margins the external border of the villous tissue,
in following a slightly undulous hne within the circumflex artery, of which it is
the satellite. It is sometimes broken up, at certain points of its course, into
several smaller canals which are continuous with its trunks.
" In its circular route, all the divergent solar and descending podophyllous
veins are discharged into it, and it terminates, at the extremities of the crescent
formed by the third phalanx, in several large branches which pass beneath the
podophyllous tissue to the lateral cartilage, where they concur to form the
superficial coronary plexus.
"B. Podophyllous Venous Plexus or Network. — The veins of the
podophyllous plexus exhibits a disposition analogous to those of the solar plexus ;
like them, they are sustained in the meshes of a fibrous texture (the reticulum
processigerum of Bracy Clark, the suhpodophtjlJous reticulum of French Veteri-
narians) spread on the anterior surface of the bone, in the same way as the
periosteum is on other bones, and continuous with the corium of the laminal
' The inferior circumflex artery of the foot.
700
THE VEINS.
tissue. Communicating largely between each other by multiple anastomoses, like
the solar plexus, they appear to be completely isolated from the deeper parts,
from which it is commonly believed they emanate.
" Tortuous and split up into branches in their course, the podophyllous veins
wind in a serpentine manner along the length of the laminfe they cover, very
close to each other, and forming narrow elongated meshes. Their confluence is
such, that at certain points they appear bound together by their external walls.
" The calibre of these vessels is tolerably uniform throughout the extent of
the podophyllous plexus, except towards the posterior parts, where their principal
canals empty themselves into the coronary plexus,
" The podophyllous veins are in anastomotic communication, below, with the
circumflex vein of the solar plexus,
Fig. 388. which they concur to form, and
above, with the coronary plexus,
which is only a continuation of them.
" C. Coronary Venous Plexus.
— The coronary venous plexus (Fig.
388, 2, 4) is arranged like a ramose
garland around the second phalanx
to the origin of the third, and on the
surface of the cartilaginous apparatus
which completes the latter.
"It is supported, Uke the other
venous networks of the digit, by a
fibrous texture immediately subjacent
to, and continuous with, the corium
of the coronary substance, and is
juxtaposed, as well as adherent, to
the expansion of the extensor tendon,
the lateral cartilages, and to the
bulbous enlargements of the plantar
cushion.
" This plexus proceeds from the
intra-osseous, podophyllous, and solar
networks. To facilitate its descrip-
tion, we recognize it in three parts :
one central and anterior, situated between the two cartilaginous plates, and two
lateral, corresponding to these cartilages.
"Central Part of the Coronary Plexus. — The central part of the
coronary plexus (Fig. 388, 2), immediately subjacent to the substance or cushion
of that name, constitutes a very close network formed by innumerable venous
radicles, which rise in a tortuous manner from, and are continuations of, the
podophyllous plexus, until they reach a large anastomotic vein thrown across
from one cartilaginous plexus to the other, and into which they open by from
ten to twelve principal mouths (Fig. 388, 3').
" These veins of the central part of the coronary plexus gradually increase in
calibre, and diminish in number, from the podophyllus plexus, where they take
their origin, to their superior and terminating canal, which itself only apjDears to
be the result of their successive anastomoses.
" Cartilaginous Plexus, or Lateral Parts of the Coronary Plexus.
THE VEINS OF THE FOOT.
THE ANTERIOR VENA CAVA. 701
— The cartilaginous plates serve to support, by their two faces and the canali-
culi by which they are traversed, a mass of very close, anastomosing, and con-
verging veins, which, from its situation, may be designated the cartilaginous
plexus.
" This cartilaginous plexus is formed by two layers of vessels — a siqjerficial
and deep.
" Superficial cartilaginous layer or plexus. — The superficial layer (Fig. 388,
3, 4), extended over the external surface of the cartilaginous plates and bulbs,
has its origin by innumerable radicles from the veins of that part of the podo-
phyllous plexus corresponding to the superficies it occupies. These roots, massed
in a very dense network, converge towards the superior portions by diminishing
in number and augmenting in volume, and terminate in forming themselves, by
the aid of successive anastomoses, into ten or twelve principal branches which
again unite into two considerable vessels (Fig. 388, 6), situated at the superior
limit of the plexus. These vessels, finally, by their last fusion at the inferior
extremity of the first phalanx, constitute the digital vein, the satellite of the
artery of the same name (Fig. 388, 5).
" Considered from below upwards, in a foot previously prepared by injection,
the digital vein, divided into two branches, subdivides itself into secondary
branches and ramuscules which diverge and spread over the convex surface of
the cartilage and coronary cushion, resembling somewhat the disposition of trees
trained as espaliers, whose spreading branches are fixed to the walls on which
they ramify.
" The two peripheral branches of the superficial cartilaginous plexus establish
communications with the opposite cartilaginous plexus, in contracting direct
anastomoses with the branches of the plexus which are symmetrical to them.
" The anterior anastomosing canals are double and superposed.
" The most inferior and superficial is constituted by the large vein (Fig 388,
3') thrown slantingly across from one plexus to the other in the median plane,
and on the external surface of the extensor tendon ; this receives a considerable
multitude of venous ramuscles, which emerge from the anterior part of the podo-
phyllous plexus.
" This first communicating vein joins the anterior branches of the carti-
laginous plexus.
" The second communicating vein, situated three-quarters of an inch above
the first, and beneath the tendon, is thrown transversely from one anterior
branch of the plexus to the other. They open into each other on each side, at
the same point where the first communicating vein enters.
" Sinuous in the whole of its track, sometimes double, and sometimes formed
of several confluent veins — as in Fig. 388 — this anastomosing canal serves as an
outlet for several deep veins.
" The anastomosis between the posterior peripheral branches of the cartila-
ginous plexus is formed by an irregularly curved and long vein of large calibre,
sinuous or broken in its course, but always considerably longer than the distance
from the two cartilaginous plates between which it is extended.
" This posterior communicating vein acts as a confluent to the canals emerging
from the cartilaginous bulbs, and to the posterior part of the solar plexus, which
throws into it five or six well-developed afferent veins.
" Deep cartilaginous layer or plexus. — The deep layer of the cartilaginous
plexus is formed :
47
702 TEE VEINS.
"1, By somewhat large ascending branches from the posterior part of the
podophyllous and solar plexuses.
"2. By the deep internal venous apparatus of the third phalanx.
" 3. By the deep veins arising from the coronary bone and the ligaments
and tendons surrounding it.
" The ascending branches of the podophyllous tissue are introduced by the
numerous foramina which traverse the base of the cartilaginous plate and the
inferior fibrous covering of the plantar cushion ; they follow the canals which
continue those foramina in the substance of the cartilage, and reach its internal
face, along with the branches proceeding from the intra-osseous venous system
and those coming from the tendons and ligaments, forming a fasciculus of five
or six thick converging veins which unite in two large ascending branches.
These anastomose with each other before their definitive junction with the two
peripheral branches resulting from the superficial cartilaginous plexus, with.
which they concur in constituting the digital vein."
b. Internal or Intra-osseous Venous Apparatus.
" Girard, junior, and Rigot have denied that the plantar artery had, in the
interior of the phalanx, a satellite venous system. These two able anatomists
committed an error.
" The disposition of the venous apparatus in the interior of the phalanx is
absolutely identical with that of the arterial.
" The satellite radicular venules of the terminal arteries converge, by forming
successive anastomoses, towards the semilunar sinus, into which they enter by
the anterior interosseous canals, ascending and descending, and by which the
emergent arteries from the semilunar anastomosis pass outwards. There they
join into a semicircular canal, the satellite of that anastomosis, which is con-
tinued backwards by two efferent veins that follow the posterior canals of the
semilunar sinus, emerge by the plantar foramina, pass into the fissure of the
same name, ascend within the basilar process, He at the internal face of
the cartilaginous plate, in one of the infractuosities with which it is sculptured,
and concur in the formation of the deep layer of the cartilaginous plexus.
"Beside these veins converging towards the cartilaginous plexus, there is
a small number of divergent ones which follow the track of the arteries, and
pass into the podophyllous plexus through the anterior porosities of the phalanx.
" The dissection of specimens injected by the veins puts this arrangement of
the venous apparatus in the interior of the os pedis beyond a doubt.
" But is this internal venous system limited to the group of vessels which
are satellites of the arteries, or is it not rather extended over a vaster surface,
and may not all the areolae of the spongy tissue of the bone be considered as a
dependency of it ?
" This way of viewing it would seem to be supported by the result of certain
injections, in which the material introduced by the neighbouring veins has filled
all the internal spongiolae of the bony tissue ; though this was probably due to
an accident in the operation, and it is presiunable that the direct passage of the
venous injection into the areolae of the spongy tissue arose from a rupture in the
vascular walls. If the tissue of the phalanx formed a kind of diverticuliun for
the venous system, as the opinion just given would admit, operations performed
on this part during life, when the texture of the bone is deeply involved, ought
THE POSTEBIOR VENA CAVA. 703
to be followed by haemorrhage from the open orifices of these areolae — a circum-
stance which does not take place.
" It does not appear, therefore, that there is, in the structure of the third
phalanx, any departure from the general plan on which bones are constructed,
and we think that its internal venous system is hmited to the vessels — very
numerous as they are — which accompany the arterial divisions."
Akticle III.— Posteeior Vena Cava (Figs. 349, v ; 350,/; 389).
This vein, the volume of which is not equalled by that of any other vessel
in the body, commences at the entrance to the pelvis by two large roots, the
common iliac veins.
From this point it is directed forward, beneath the bodies of the lumbar
vertebrae, soon reaches the superior border of the liver, where it leaves the
lumbar region to lodge itself in the fissure on the anterior face of that gland ;
passing through this, it traverses the foramen dextrum of the diaphragm, and
opens into the postero-external part of the right am'icle of the heart.
In this course, the posterior vena cava is naturally divided into three
portions — a sublumbar, hepatic, and thoracic.
The sublumbar portion, placed to the right of the posterior aorta and to the
left of the right kidney and supra-renal capsule, is maintained against the
common inferior vertebral hgament and the left psoas parvus muscle by
the peritoneum and the pancreas. It is related, besides, to the right renal
artery, which crosses its face perpendicularly, as well as the corresponding great
splanchnic nerve and the nerve divisions of the right renal and lumbo-aortic
plexuses.
In its hepatic portion, the posterior vena cava is only related to the liver and
diaphragm, which form a complete canal around it.
The thoracic portion is lodged between the right lung and its internal acces-
sory lobule, and is enveloped by a particular serous fold — a dependency from the
right pleura, and which has been already described (p. 543).
Collateral afferents. — Those vessels which, as considerable as they are nume-
rous, open into the posterior vena cava, are, enumerating them from before to
behind :
1. ThQ phrenic or diaphragmatic veins.
2. The vena ported, a trunk into which are collected the majority of the
abdominal visceral veins ; instead of opening directly into the vena cava, it is
divided in the liver like an artery, reconstituting itself into a certain nmnber of
thick branches — the hepatic veins, which enter the vena cava on its way through
the anterior fissure of the liver.
3. Renal veins.
4. Spermatic veins.
5. Lumbar veins.
All these vessels will be studied, in the order above indicated, before the
radicles or common iliac veins of the vena cava.
Phrenic or Diaphragmatic Veins.
These are two, sometimes three, enormous vessels lodged in the texture of
the tendinous centre, commencing by several branches in the fleshy portion of
the muscle, and entering the vena cava as it passes through the diaphragm.
GENERAL VIEW OF THE VEINS IN THE HORSE.
1, Anterior vena cava; 2, 2, posterior vena cava; 3. right common iliac vein, divided at the ilio-
sacral articulation ; 4, left common iliac vein ; 5, femoral vein ; 6, obturator vein ; 7, subsacral
vein; 8, left spermatic vein; 9, posterior abdominal vein; 10, renal vem : 11, 11, ascending
branches of the asternal vein; 12, vena azvgos, with itsjntercostal tranche^, and in hjnt the
subdorsal venous branch, 13; 14, oesophageal vein: " ' ' ' "■
15, dorsal or dorso-muscular vein; 16,
TEE POSTEBIOR VENA CAVA. 705
Vena Portse (Figs. 389, 390).
The manner in which this vessel comports itself gives it an altogether
peculiar physiognomy, and has caused it to be considered as a separate vascular
system.^ After what has been already said concerning the structure of the
liver, it must be admitted that the vena port^e is distributed in that gland
exactly like an artery.
It begins in the sublumbar region, at the anterior mesenteric artery, by the
union of three large radicles ; it is then directed forwards and a little to the
right, traversing the pancreatic ring, below the vena cava, and is afterwards
lodged in the great posterior fissure of the liver, where it ramifies by forming
the interlobular veins, the capillary divisions of which give rise to the sublobular
vessels.
Interlobular and sublobular veins (Fig. 303, YP, \h). These vessels having
been already studied in the description of the liver, we need not again occupy
ourselves with them, but refer only to a peculiarity incompletely noticed in that
description, with reference to the sublobular veins.
We know that these vessels are divided into two categories, according to
the arrangement of their openings. The majority enter the vena cava in
forming a single confluent placed at the anterior extremity of the fissure in
the liver, at the phrenic veins ; the others open separately over the whole
extent of the hepatic portion of the venous trunk. In carefully examining
the confluent towards which all the veins of the first group converge, we
recognize the junction of three principal veins, one coming from each of the
hepatic lobes, and furnished with three very isolated, incomplete valves. With
regard to the vessels of the second group, Claude Bernard^ considers them
to come, for the most part, directly from the sublobular veins, and not from
the capillary network formed by these veins in the lobules of the liver. It is
true that injections readily penetrate from the vena portse into the vena cava,
but they do this quite as much by passing along the large sublobular vessels
as the canals of which we now speak ; and, besides, if the material forced into
the vena ports is mixed with some imperfectly powdered colouring matter,
the injection will arrive colourless, or but shghtly tinged, in the sublobular
vessels and the vena cava. These facts, we see, do not miUtate in favour of
' Nevertheless, there are communications between the portal system and the general
circulation, through the medium of the oesophageal and haemorrlioidal veins. These com-
munications become very evident when the circulation in the liver is obstructed.
* Legons de Physiologie Expcrimentale. Paris : 1856.
cervical or cervico-muscular vein ; 17, vertebral vein ; 18, right axillary vein, cut at the
anterior border of the first rib; 19, supra-sternal or internal mammary vein; 20, left axillary
artery; 21, termination of the left cephalic vein; 22, left jugular; 23, right jugular; 24,
external maxillary or glosso-facial vein; 25, coronary vein; 26, angular vein of the eye; 27,
subzygomatic vein ; 28, posterior auricular vein ; 29, maxillo-muscular vein ; 30, internal meta-
carpal vein; 31, internal subcutaneous vein; 32, radial subcutaneous vein; 33, posterior radial
vein; 34, basilic vein; 35, plate or cephalic vein; 36, coronary venus plexus; 37, digital vein;
38, internal metatarsal vein ; 39, anterior root of the internal saphena vein ; 40, posterior root of
ditto; 41, internal saphena; 42, great coronary vein; 43. small mesaraic vein; 44, different
branches of the great mesaraic vein ; 45, trunk of the vena porta in its sublumbar portion,
lodged in the pancreas; 46, the same in the posterior fissure of the liver— below it is seen entering
the substance of the gland, il, Subscapulo-hyoideus muscle cut obliquely in the direction of the
trachea ; p, cervical panniculus turned down to expose the jugular furrow ; o, right auricle of the
heart ; A, posterior aorta ; G, section of the right lung ; f, left lobe of the liver behind the section
of the diaphragm; R, right Ijidney carried up and forward; l, oesophagus; v, bladder; s, rectum;
T, thoracic duct ; t'. termination of that duct in the confluent of the j'ugulars.
706 THE VEINS.
Bernard's opinion ; and there is every reason to believe that the system of
the vena ports and that of the vena cava do not communicate, in the adult,
otherwise than by the capillary network which is intermediate to the interlobular
and sublobular vessels. If any other means of communication exist, they must
be extremely small.
(Ligature of the portal vein causes distension of all the abdominal vessels,
and a highly congested state of the abdominal viscera ; whilst the blood-pressure
quickly falls, and the animal dies. So distensible are the abdominal vessels,
that they can contain nearly all the blood in the body. The ventricular systole
may send a pulse down the valveless posterior vena cava, and cause a pulse in
the liver. That gland swells with each systole, and relaxes with each diastole of
the heart.)
Constitumt vessels of the vena portm. — The three roots of this vein are the
anterior and posterior mesenteries and the splenic vein.
The collateral affluents it receives on its course are principally two : the
right gastro-epiploic or gastro-omental veins and anterior gastric.
We will make a rapid survey of all these vessels.
1. Roots of the Vena Port^.
A. Anterior Mesenteric or Anterior Mesaraic Vein (Figs. 380, 44 ;
390, 2, 7). — This is an enormous venous canal into which flows the blood that
has passed through the walls of the small intestine, caecum, large colon, and
the origin of the small colon, the divisions of which con-espond exactly to
the different branches furnished by the anterior mesenteric artery.
When traced from its opening to its origin, in an inverse direction to the
course of the blood, it is observed to lie between the two colic arteries, and
proceed beyond the flexure formed by the supra-sternal and diaphragmatic
flexures, beyond which it divides into two satellite branches for the colic
arteries, which anastomose in arcade towards the pelvic flexure, like the arteries
they accompany.
It is therefore by the union of two colic veins (Fig. .390, 8, 9) that the
anterior mesenteric vein is constituted, and in this formation numerous collateral
affluents concur ; among these may be noticed the two cceecd veins (Fig. 390,
5, 6), the ilio-ccecal vein (Fig. 390, 4) coming from the origin of the floating
colon, and the veins of the small intestine — vessels arranged so exactly like the
corresponding arteries, that we may dispense with any further description of
them.
B. Posterior Mesenteric or Posterior Mesaraic Vein (Figs. 389, 43 ;
390, 12). — This vessel commences above the rectum, near the anus, by large
hcmiorrhoidal branches which communicate with the homonymous ramuscules
of the internal pudic. It is directed forwards, between the two layers of the
second mesentery, along the small mesenteric artery, which it passes, and extends
to the great mesenteric artery, on the left side of which it unites with the splenic
vein, before opening into the anterior mesenteric to form the vena portfe. In
its course it receives all the satellite venous branches of the divisions of the
artery of the same name, the arrangement of these being similar to that of the
arterial ramifications.
C. Splenic Vein (Fig. 390, 13). — This is an enormous canal which
accompanies the splenic artery, and comports itself exactly like it. It begins
by the left gastro-omental vein (Fig. 390, 14) anastomosing in arcade with the
TEE POSTERIOR VENA CAVA.
707
Fig. 390.
right gastro-omental, receiving on its track gastric, splenic, and omental hranches^
and joining the posterior mesenteric after passing above the left extremity of
the pancreas, and obtaining the posterior gastric vein (Fig. 390, 16).
2. collateeal affluents of the
Vena Port^.
A. Right Gastro-omental or Gas-
tro-epiploic Vein (Fig. 390, 15).— We
already know that the hepatic artery, be-
fore entering the liver, gives off pancreatic
branches, a pyloric branch, and a gastro-
omental division, which in turn detaches
a small duodenal artery ; the vessel de-
scribed as the right gastro-omental vein
corresponds, in every respect, to all these
collateral ramifications of the hepatic artery.
This vein, then, has its origin from
around the great curvature of the stomach,
but at an undetermined point, as it forms
an anastomotic arch with the left gastro-
omental vein. Posteriorly, it crosses the
dilatation at the origin of the duodenum,
receives the pyloric, duodenal, a.nd pancreatic
veins, and opens into the vena portJB after
traversing the pancreas.
B. Anterior Gastric Vein. — Satel-
lite of the homonymous artery, this vein
joins the vena portae separately, after the
entrance of that vessel into the great pos-
terior fissure of the liver, and when very
near the terminal extremity of that fissure.^
Renal Veins.
Two in number, like the arteries they
accompany, these veins are distinguished
by their enormous volume and the thin-
ness of their walls. The left, having to
cross the abdominal aorta before entering
the vena cava, is longer than the right.
They receive the majority of the veins from
the supra-renal capsules (Fig. 389, 10).
Spermatic Veins.
These vessels correspond to the sper-
matic arteries in the male, and the utero-
ovarian arteries in the female.
the vena portie and its roots (partly
theoretical).
1, Trunk of the vena poi-tse ; 2, its origin;
3, veins of the small intestine ; 4, ilio-
caecal vein ; 5, external caecal vein ; 6,
internal coecal vein; 7, anterior mesenteric
vein ; 8, 9, colic veins forming the roots
of that vessel ; 10, collateral vein some-
times continuing the left colic, and
joining the anterior mesenteric vein near
its origin ; 11, common confluent of the
posterior mesenteric and splenic veins ;
12, posterior mesenteric vein and its
collateral branches; 13, splenic vein; 14,
left gastro-omental vein ; 15, right ditto;
16, posterior gastric vein, a. Stomach ; b,
duodenum; c, small intestine; d, caecum;
e, large colon; /, floating colon; g, rectum;
h, portion of the great omentum ; i,
spleen ; j, mesentery ; k, colic mesentery.
• Among these collateral affluents of the vena portse, it is necessary to mention the biliary
veins which Claude Bernard has injected in the Dog. These vessels, whicli correspond to the
hepatic artery, pass from the posterior surface of the liver, and open into the portal vein at a
short distance from th;it j;l,ind.
708 TEE VEINS.
Testicular vein. — The radicles which constitute this vein present, at their
emergence from the superior border of the testicle, a flexif orm and very com-
plicated arrangement, enlacing, turning, and inflecting themselves in a thousand
ways around the convolutions of the great spermatic artery, and ascending in
this manner towards the neck of the abdominal ring, which they pass through,
usually after joining to form two trunks. These rise towards the sublumbar
region, beneath the peritoneum, in a fold of which they are at first included ;
they communicate with one another in their course by anastomosing branches,
and are generally united into a single spermatic vein, which opens into the vena
cava near the renal vein (Fig. 389, 8).
Utero-ovarian vein. — This vein — which is very voluminous — enters the vena
cava at the same point as the corresponding vessel in the male, and proceeds,
as its name indicates, from the ovaries and uterus by flexuous and reticular
branches, the fusion of which into a single trunk only takes place near the vena
cava.
Lumbar Veins.
Satellites of the arteries of the same name, these vessels enter the vena cava
separately. The most anterior often open into the vena azygos.
Common Iliac Veins.
This appellation is given to two enormous vessels, into which are collected
all the veins of the abdominal limb and the posterior part of the trunk — very
short vessels, that, by their junction, form the posterior vena cava (Fig. 389,
3, 4).
The common iliac vein is lodged in the angle of separation comprised between
the external and internal iliac arteries, and is a continuation of the two satellite
veins of these vessels. The right — shorter than the other — passes above the
external iliac artery to join the vena cava at its origin. The left — longer —
insinuates itself between the body of the second last lumbar vertebra and the
terminal extremity of the posterior aorta, to open into the other.
If we trace — as was done with the veins of the anterior extremity — from the
ungual region to the pelvis, all the branches which concur in the formation of
these two trunks, we shall find, as the common point of departure for each, a rich
subungual, plexus, from which spring two digital veins. To these succeed three
metatarsal veins, the common origin of all the vessels of the leg. These latter
are distinguished as superficial and deep, and are four in number — -two saphena
veins in the first group, and two tibial veins in the second — continued by the
poplitecd vein. This vessel is itself continued by the femorcd and extermd iliac
veins, which finally form the common iliac, by opening into the interned diac vein.
All these vessels will be studied in an inverse order to that in which they
have been enumerated, and as follows : —
1. Internal iliac vein.
2. Extermd iliac vein.
3. Femorcd vein.
4. Poplitecd vein.
5. Deep veins of the leg.
6. Superficial veins of the leg.
7. Metatarsal veins.
8. Veins of the digital region.
THE POSTERIOR VENA CAVA. 709
1. Internal Iliac Vein.
This vessel is formed by the satellite veins of the branches furnished by
the homonymous artery : these are the iliaco-femoral, obturator, iUaco-muscuIar,
gluteal, lateral sacral, and internal pudic, the distribution of which does not differ
from that of the corresponding arterial divisions.
The trunk resulting from the union of these different branches is usually
very short ; it may even be altogether absent, and we then see the veins which
should form it, open into the common ihac vein by forming two or three separate
groups, situated very close to each other.
2. External Iliac Vein.
This vein constitutes the principal root of the common iliac, which is but
a continuation of it — the internal iliac being only, properly speaking, a collateral
affluent of the single canal represented by the external and common iliac veins.
Situated behind the iliac artery, this external iliac vein commences at the
anterior border of the pubis, where it is directly continued, without any line of
demarcation, liy the femoral vein.
The only important vessel it receives on its course is the iliac circumflex vein,
which, however, opens more frequently into the common than the external iliac.
3. Femoral Vein.
Continuous by its superior extremity with the external iliac vein, and
inferiorly with the popliteal, the femoral vein is remarkable for its large volume ;
it closely follows the artery of the same name throughout its extent (Fig.
389, 5).
The collateral affluents it receives in its course are distinguished by their
number and considerable volume. They are : — •
1. The satellite veins of the miiscidar arteries.
2. The internal saphena vein, which will be again referred to in describing
the superficial veins of the leg.
3. The preiyubic vein, formed by the posterior ahdominal and the branches of
the internal piidic. The latter are very numerous and large, and anastomose
with each other, forming between the thighs, in the texture of the scrotum and
sheath, and above the penis, a very rich network which communicates behind
with the cavernous veins. This network only sends a small trunk into the
inguinal canal, along the external pudic artery ; in its middle part it opens into
an enormous branch which passes through the ring in the sartorius muscle, and
is lodged in the inferior groove of the pubis to join the femoral vein.
One of these external pudic veins represents the subcutaneous abdominal
vein, and communicates with the subcutaneous thoracic vein.
All these branches in the female show an analogous disposition.
4. Popliteal Vein.
Satellite of the -popliteal artery, this vein is formed by the union of the
anterior and posterior tibial veins.
Among the branches it receives on its course, the femoro-popliteal vein may be
particularly noted ; this accompanies the artery of the same name, and joins the
external saphena before opening into the popliteal vein.
710 TEE VEINS.
5. Deep Veins of the Leg.
These are two in number : the anterior and posterior tibial.
A. Anterior Tibial Vein. — Placed beside the homonymous artery, often
double, always very ample, this vein originates on the anterior face of the tarsal
articulations by means of several anastomosing roots, the principal of which is
formed by the deep metatarsal vein, that passes through the cuboido-cuneo-
scaphoid canal from behind to before. After crossing the fibular arch with the
artery, it joins the posterior tibial to constitute the popliteal vein.
B. Posterior Tibial Vein. — This commences near the hollow of the hock,
in front of the calcis, by radicles which principally come from the two saphena
veins. It then ascends along its satellite artery, to open into the anterior vein
beneath the popliteal muscle.
6. SuPEEFiciAL Veins of the Leg.
These are the internal and external saphena.
A. Internal Saphena Vein. — This vessel shows two roots — an anterior
and posterior (Fig. 389, 39, 40).
The first proceeds from the internal metatarsal vein, the second from the
external. Both ascend, in converging towards each other, on the internal face
of the tibia, uniting into a single branch before reaching the thigh.
This single branch — always very voluminous — glides upwards on the sartorius
muscle, and terminates in a variable manner on reaching the groin : sometimes
it is insinuated into the interstice between the gracilis and sartorius, to join the
femoral vein, and at other times it ascends to the ring of the gracilis, to open
into the external pudic veins.
B. External Saphena Vein. — It rises, by a short branch, outside the os
calcis, communicates, even at its origin, with the posterior root of the internal
saphena by means of a large reticular anastomosis thrown transversely in front
of the apex of the calcis ; and with the posterior tibial, by a large branch that
passes between the tibia and the flexor pedis perforans muscle. It follows the
external saphena nerve outside the gastrocnemius tendon, behind the external
head of the gastrocnemius muscle, and enters the popliteal vein, after joining the
femoro-popliteal vessel.
7. Metataesal Veins.
These veins are three in number, and are distinguished as internaL external^
and deep ; they proceed from the sesamoidean arch, which is formed by the
anastomosis of the two digital veins.
A. Internal Metatarsal Vein. — This vessel, the most considerable of the
three, appears more particularly to continue the digital vein of the same side.
For the greater part of its extent it is placed with the internal plantar nerve,
along, and a little in advance of, the flexor tendons. Arriving near the tarsus,
it deviates slightly to reach the anterior face of the tarsal articulations, and
there communicates — by a very large transverse branch — with the origin of the
anterior tibial vein ; afterwards it rises on the internal face of the leg, where it
constitutes the anterior radicle of the internal saphena vein.
B. External Metatarsal Vein. — It occupies, outside the flexor tendons, a
position analogous to the preceding. Towards the superior extremity of the
THE POSTERIOR VENA CAVA. 711
metatarsus, it communicates, by a short, thick branch, with the deep vein. It
then continues its ascending course by entering the tarsal sheath along with the
plantar arteries, and is prolonged in the hollow of the hock, passing along the
femoro-popliteal nerve, forming the posterior root of the internal saphena.
C. Deep Metatarsal Vein. — This is placed beneath the suspensory liga-
ment, at the inner side of the principal interosseous plantar artery. Near the
tarsus, it receives a very large branch from the external vein, and then passes
through the cuboido-cuneo-scaphoid canal, to form the largest root of the anterior
tibial vein.
8. Veins of the Digital Region.
As these resemble, in every respect, those belonging to the anterior limb, the
same description will suffice for both (see p. 698).
Differential Characters in the Veins of the other Animals.
It does not come within our plan to give a complete description of the venous system in
these animals, because of the small utility of such a study. To remain faithful to our object,
we confine ourselves to tlie indication of the special characters of the veins on which
bleeding is usually practised, and those which may be interesting in a surgical point of view —
such as tlie digital veins of Ruminants.
A. Angular Vein of the Eye. — This vessel is remarkable for its large volume in the
Sheep ; and as it is well defined beneath the skin, in consequence of the fineness of that
meml>rane, it is more frequently selected for phlebotomy than in other animals.
B. Jugular Vein. — Very large in all animals, and particularly in the Ox, this vein
deserves the preference given to it when it is proposed to abstract a certain quantity of blood
from the system.
In all non-soliped animals there is found an accessory jugular, which sometimes exists in
tlie Horse — but is much less in size — alongside the common carotid artery. It arises from the
occipital vein, and therefore extends the whole length of the neck. Sometimes its diameter
is small; but it is often so large as to receive a very notable quantity of blood from the
principal jugular, when compression is applied to the latter to favour the flow of blood after
opening it — a circumstance that explains the difliculty sometimes experienced in obtaining a
voluminous jet of blood.
C. Abdominal Subcutaneous Vein.— In the Bovine species, this vessel has an enor-
mous volume, especially in the Milch-cow, in contradistinction to the subcutaneous thoracic
vein, which is always very small.
This vein is prolonged forward on the wall of the abdomen, to near the xiphoid cartilage,
where it passes through to join the internal thoracic vein.' Behind, it is formed by multiple
branches, which anastomose with each other, or with those of the opposite vein, and are in
communication with the proper external pudic veins.
D. Internal Saphena Vein. — This is always smaller than in Solipeds, and is rarely
selected to extract blood_from.
E. External Saphena Vein.— This vessel is, on the contrary, more voluminous than in
the Horse, and at the same time more superficial ; consequently, it is more favourably situated
for phlebotomy, as well in Pigs and the Carnivora, as in Ruminants. It arises from the union,
in the hollow of the hock, of the two principal roots furnished by the metatarsal veins.
F. Veins of the Posterior Foot in the Ox. — As in the Horse, they commence in the
subungual network of the digital region, which is double, like the region itself.
a. Three digital veins leave this reticulum : 1. A median or anterior one, arising by two
roots from the anterior part of each network, passing between the two digits, and joining the
anterior .superficial metatarsal vein above the fetlock. 2. Two laterals, communicating with
one another, behind, by a transverse anastomosis which receives several venules from the
ungual plexus, and with the anterior vein by an iuterdigital branch, united by an arch in front
of the flexor tendons, above the sesamoid groove.
b. These digital veins are continued by five metatarsal veins : two deep and one superficial
anterior, and two posterior.
' The openings through which these vessels pass in the abdominal parietes, are commonly
named the milk fountains or doors.
712 THE VEINS.
The two deep anterior veins are small vessels which accompany the collateral artery of the
cannon, wliich is placed between them. They arise in the interdigital space from the anterior
digital vein, communicating, by the inferior metatarsal foramen, with the sesamoid arch,
sending off on their way transverse anastomoses, and being continued above the tarsus by the
two anterior tibial veins, whose roots they constitute.
The anterior superficial vein is very voluminous. It proceeds from the sesamoid arch,
receives near its origin the middle digital vein, rises in front of, and a little to the outside of,
the tarsus, communicating at this point with the anterior tibial veins ; it divides above the
tibio- tarsal articulation into two branches : a posterior, forming the anterior root of the external
saphena ; the other anterior, joining the anterior tibial vein of tlie external side.
The two posterior veins spring from the sesamoid arch. Situated at first between the sus-
pensory ligament of the fetlock and the posterior face of tiie metatarsus, and communicating
there by several anastomoses, tiiese two veins are continued along the tarsus — the one within,
the other without. The internal follows the corresponding plantar artery, and is prolonged in
the tibial region by tlie posterior tibial and internal saphena veins. The external ascends
within the calcis, and is united to a branch of the anterior superficial metatarsal, to form the
external saphena vein. Before leaving the deep situation they occupy below tlie suspensory
ligament of the fetlock, these two vessels — but especially the internal — concur to form a perfo-
rating branch which traverses the cuboido-scaphoid canal to join the anterior tibial veins.
G. Veins of the Anterior Foot in the Ox. — Four digital veins escape from the two
subungual plexuses : an anterior, posterior, and two lateral.
a. The anterior digital vein, which is very slender, is lodged superficially between the
two digits, and comports itself at its origin like the analogous vein of the posterior limb, in
rising by two roots. In being prolonged above the fetlock, it constitutes a subcutaneous meta-
carpal brand), which occupies the anterior and internal plane of the cannon, and is united
above the knee to the principal cutaneous vein of the forearm.
b. The posterior digital vein — often doubled by a small accessory branch — accompanies the
common digital artery, and extends along the collateral artery of the cannon, to constitute one
of the posterior radial veins.
c. The internal digital vein, after passing the digital region, is lodged between the cannon
bone and tlie internal border of the suspensory ligament, proceeds outside the carpal sheath
■with the radio-palmar artery, and divides above the knee into two branches— an anterior, the
origin of the internal subcutaneous vein of the forearm; the other posterior, forming one of
the posterior radial veins.
d. The external digital vein occupies, on the outer side of the external digit and the cannon
bone, a po.-ition analogous to the internal vein. It gives rise to several deep metacarpal veins
which anastomose, and are mixed with the interosseous palmar arteries; the principal vein and
its accessory branches are joined, below the carpus, to the internal vein.
It is to be remarked that these four digital veins communicate, in the interdigital space,
by anastomoses resembling those of the posterior limb; and that the last three, or principal
veins, anastomose above the fetlock in forming a complicated and variably arranged sesamoid
arch, on leaving which these digital veins become metacarpal vessels.
Comparison of the Veins in Man with those of Animals.
In Man, as in animals, the veins are grouped into those of the lesser circulation — m pul-
monary veins— and those of the greater circulation. The latter open* into the heart by three
trunks— the cardiac veins, and superior and inferior vena cava.
The superior vena cava represents the anteri<jr vena cava of animals, and receives the blood
from the veins of the head, thoracic limbs, and a portion of the chest. It extends from the
first costal cartilage to the heart, and commences after the junction of the two brachio-
cephalic trunks or innominate veins.
The superficial veins of the thoracic limb at first form, on the back of the hand, a plexus
of elongated meshes from which the median, radial, and ulnar veins spring. Near the bend of
the elbow, the median bifurcates and gives rise to the median ce^ihalic and median basilic.
Blood is abstracted from one or other of these branches. At the arm, all the superficial veins
constitute but two trunjcs — the cephalic and basilic veins. The deep vessels join these to form
the axillary vein, which becomes the subclavian below the clavicle, then the brachio-cephalic
trimk (vena innomlnata) when it receives the internal jugular.
The venous sinuses of the cranial dura mater are proportionately more developed than in
Solipeds, though they have the same arrangement. There is constantly present a middle or
inferior longitudinal sinus.
The jugulars, which carry the blood from the cranium and face to the heart, are four in
THE LYMPHATICS. 713
number. The anterior jugular — the smallest — descends beneath the superficial cervical aponeu-
rosis, in front of the sterno-mastoideus muscle, and enters the subclavian vein. The external
jugular commences by the union of the facial and temporal veins ; in its disposition it resembles
the jugular of the Horse, and would be a complete representative if deprived of the branches
from the cranial sinuses. The internal jugular arises at the posterior foramen lacerum, at a
dilatation of the lateral sinus named the bulbus venoe jugularis, and passes to the subclavian
vein. Lastly, the posterior jugular (or vertebral vein) situated beneath the complexus muscle,
and in relation with the cervical vertebrae, carries the blood from the spinal sinuses in this
region, and which, in Solipeds, is received by the occipital and vertebral veins.
The inferior vena cava corresponds to the posterior vena cava of animals, and receives the
blood from all the sub-diaphragmatic veins. It originates from the union of the two common
iliac veins, at the third lumbar articulation, and terminates in the right auricle. In its course
it receives the median sacral, lumbar, renal, supra-renal, inferior phrenic, and right spermatic
veins. The latter forms on the surface of the testicle, and at the origin of the cord, a rich
network — the spermatic plexus; on the abdominal portion of the cord it constitutes the
pampiniform plexus.
The vena cava also receives the vena portce, which has the same disposition as in animals.
It begins by three branches — the great and small mesenteric and splenic veins. For affluents,
it has the pancreatic and duodenal venules, and the right gastro-omental vein. It passes
behind the pancreas, and not through that gland, as in the Horse.
The veins of the abdominal limb are divided into deep and superficial. The first terminate
by forming the femoral vein, which, in joining the vessels of the pelvis, constitutes the common
iliac vein. The superficial veins commence by a network on the dorsum of the foot, which
gives origin to the two saphenas— external and internal.
FOURTH SECTION.
THE LYMPHATICS.
CHAPTER I.
General Considerations.
Charged with the absorption and transport of the chyle and lymph, the
lymphatic or absorbent vessels are convergent canals with thin and transparent
walls, which originate in the texture of organs by fine reticulated radicles ; these,
after passing through one or more glands — glandiform bodies placed on their
course — enter the venous system by two trunks — the thoracic duct and the great
lymphatic vein.
Lymphatic Vessels.
These vessels resemble veins in so many points, as to merit the name of ivhite-
blood veins. Like these vessels, the lymphatics are directed from the periphery
to the centre of the circulatory apparatus ; hke them, they are nodulated cylin-
drical tubes ; internally, and at those points where they outwardly appear to
be constricted, they show numerous valves which look towards the heart. Like
the veins, again, they separate into two orders of canals — the ones deep-seated,
lodged in the vasculo-nervous intermuscular sheaths ; the others superficial,
situated on the surface of containing aponeuroses. Like the veins, also, the
lymphatics terminate in two principal trunks resembling the venas cavEe ; and,
714 THE LYMPHATICS.
finally, as the veins have three tunics, so have the lymphatics, these not differing
in any respect, except in being very much thinner.
If we pass into the domain of physiology, it is also easy to observe characters
which are common to the two anatomical systems under comparison. They, in
fact, almost equally divide the absorbent function between them — a function
which is accomplished in the radicular network of each ; and the dynamical
process which gives impulsion to the fluids they carry, if it is not quite identical
in both, is at any rate very similar in many points.
We may, nevertheless, observe numerous differences between the veins and
the lymphatics, and chiefly in their form, number, capacity, and structure.
The form of the lymphatic canals is, as we have said, nodulated and cylin-
drical ; but their nodosities are much less marked, and are closer together than
in the veins, owing to the larger number and greater development of the valves.
Besides, as these vessels proceed for considerable distances, and preserve their
regularly cylindrical form with undiminished capacity, if we mentally bring all
the divisions of the lymphatic system to a single canal, we no longer have a
hollow cone the apex of which corresponds with the heart — although the capacity
of the lymphatic vessels augments from the trunk towards the branches ; for
this canal only represents a series of cylinders joined end to end, and successively
decreasing from its origin to its termination.
The number of lymphatic vessels in a certain region is always much greater
than that of the veins. But as the lymphatics are much smaller than the veins,
Fig. 391.
A LYMPHATIC VESSEL WITH ITS VALVES.
there is not, as might at first be supposed, a proportional increase in their total
capacity. Observation, indeed, demonstrates that the relation between the
capacity of the lymphatics and the corresponding veins of a region does not
exceed one to two.
The structure of the lymphatics differs from that of veins, in that there exists,
in those of average dimensions, smooth muscular fibres in the adventitious tunic.
The presence of muscular fibres in the external tunic of these vessels is rendered
necessary by the absence of an impelling organ at the origin of the lymphatic
system — such an organ being, in reality, disseminated throughout the extent of
the vessels, and aids the vis a tergo that causes tiie lymph to cu'culate in their
interior.
We terminate this short parallel, to notice in detail several points connected
with the general history of the lymphatics, and which merit particular attention ;
we allude to the origin, course, and termination of these vessels.
Origin. — For a long period after the discovery of the lymphatic vessels, a
state of profound ignorance existed as to their origin. Nevertheless, the
importance of the solution of the problem was well appreciated, as it was really
the key to the theory of absorption ; numerous hypotheses, therefore, sprang
into existence. The anatomists who occupied themselves with the question,
were hindered in their investigation by the imperfect means of research at their
disposal. Beyond the larger branches, the lymphatics escaped attention, owing
THE LYMPHATICS. 715
to their transparency and tenuity. Thanks, however, to the patient and minute
researches of Hunter, Cruikshank, Mascagni, Fohmann, Panizza, Cruveilhier,
and Sappey, the lymphatics were injected by colouring matters or by mercury,
and thus rendered visible to their finest ramifications.
It is now known that the lymphatics arise from ccqnllaries, which form net-
works or terminal culs-de-sac.
These terminal culs-de-sac exist in the intestinal villi ; and it is no longer
maintained that the ends of these small appendages have an opening by which
the lymphatic vessels receive the chyle that bathes the mucous membrane of the
intestine.
The plexuses are composed of more or less irregular meshes, and their form
and volume often vary with the arrangement of the tissues or organs in which
they are studied. They may be superficial or deep, and exist together or sepa-
rately. In many membranes the two networks are found, but then the superficial
is thinner than the deep. They are mixed with, or placed above, the blood-vessel
plexuses, but never communicate with them.
Do these lymphatic plexuses exist in all the tissues, properly speaking ? Here
is another question of incontestible importance, the solution of which for a
long time occupied the attention of anatomists. Judging by analogies, one is
tempted to reply in the affirmative — why, in fact, should the lymphatics not
«xist everywhere throughout the organism, when the blood-capillaries are con-
stituent parts of the framework of each tissue ? Nevertheless, direct observa-
tion has not revealed lymphatic plexuses in all organs ; there are even tissues in
which theii- existence has been absolutely denied — though prematurely, it is well
to say, because we may always ascribe the non-success of a lymphatic injection
either to the imperfection of the instruments employed, the insufficiency of the
measures adopted, or to certain peculiar conditions as yet unknown and attach-
ing to the species of animals selected for the demonstration of the lymphatic
networks in a certain region. In support of this last assertion, we may observe
that Sappey has not yet been able to inject the pituitary plexuses in Man or the
Calf, and that he looks upon their existence as being at least doubtful ; while
in the Horse, this lymphatic apparatus is as remarkable for its richness, as for
the facility with which it may be filled with mercury.
It may be asserted that they do not exist in the epidermis, or in epithelial
layers.
The following are the most trustworthy notions available on this subject.
The lymphatic vessels of the sMn are very numerous, and form two networks :
one, with extremely fine meshes, occupies the most superficial layer of the dermis ;
the other, placed beneath the deep face of the integument, includes vessels more
voluminous than the first, and communicates with it by multiple ramuscules.
These lymphatic plexuses are far from being equally developed in every region,
though it is unanimously agreed that no part is entirely destitute of them.
In the mucous membranes, an analogous arrangement of these vessels is met
with. It is more than probable that they exist throughout the whole extent of
these membranes, though their positive demonstration has yet to be made in
some regions. In other regions, the injection of these networks is, on the
contrary, very easy, and gives the most magnificent results ; we particularly
mention the lingual, intestinal, and pituitary mucous membranes. The
lymphatics belonging to the latter membrane assume so beautiful an aspect
in the Horse, that we would advise anatomists who desire to inject lymphatics
716 THE LYMPHATICS.
always to choose that animal. The operation is simple and always successful,
and we are astonished that in the hands of some mdividuals it should fail. Not
only can the two networks of the membrane be filled, but also the trunks
arisin<i: from them, and which are directed towards the entrance of the nasal
cavities, collect in several thick branches around the nostril, and curve up
towards the face to reach the submaxillary space, where they enter the glands
situated to the right and left of that region.
The majority of anatomists admit the presence of lymphatic plexuses in the
splanchnic or synovicil serous memhranes. Sappey, however, denies this ; he con-
siders the vessels that can be so easily injected by pricking the external surface
of a viscus, as belonging to its proper tissue, and not to the serous membrane
covering it. Those on the inner face of the walls of the splanchnic or synovial
cavities, and which are sometimes filled with mercury, do not, according to him,
come from the serous tunic, but from the subjacent tissues.
The lymphatics do not exist in vessels. The lymphatic sheaths discovered by
His, Robin, and Tomaso, around the blood-capillaries of the Frog, and those
of the brain and spleen of Man, and recognized by Rusconi, Milne-Edwards, as
well as demonstrated by Ranvier around the vessels of the mesentery, ought not
to be considered as the lymphatics of vessels ; they merely surround the ultimate
vascular ramifications, and do not arise in the substance of their walls.
In the nerve tissue lymphatics have not been discovered, though they are
present in the meninges.
Their existence is doubtful in hone tissue and in the muscles ; but they are
abundant in the glands and glandiform organs of the animal economy, forming
the finest, richest, and most easily demonstrated plexuses, Sappey admits that
they are exceeded by smaller capillary networks and spaces.
It has been stated above that the lymphatics commence by capillaries arranged
in networks. Are these networks the real, or only the apparent origin of the
lymphatics ? This is a question that has been, and is still, warmly discussed.
It is, however, believed that the plexuses are fed by very minute radicles lodged
in the substance of the tissues.
But how do these radicles originate ? In the epithelium, says Kiiss ; in the
plasmatic cells of the connective tissue, asserts Virchow ; in the serous membranes,
states Recklinghausen, since he observed fatty matters penetrate the lymphatics
by the abdominal surface of the diaphragm. The opinion of Yirchow is upset
at present by the researches of Ranvier, which have modified the descriptions
given of the connective tissue. According to this authority, plasmatic cells do
not exist in that tissue ; and what have been described as such by Virchow, have
been only radiating spaces hmited by the fascicuh of connective-tissue fibres, in
which elements analogous to lymph corpuscles circulate. The researches of
Ranvier tend to support the hypothesis of Recklinghausen, and show that in the
connective tissue of the economy there is an infinite number of minute serous
cavities into which the lymphatic vessels open, in which the lymph circulates,
and which are in communication, on the other hand, with the great splanchnic
cavities.
Course of the Lymphatic Vessels. — The lymphatics follow the course
of the veins, and are divided, exactly like them, into superficial and deep vessels.
The latter, running parallel to each other, are grouped immediately around the
corresponding veins, on which they generally lie. The first, although situated
in proximity to the superficial veins, are widely spread on each side and on
TEE LYMPHATICS.
717
the surface of the superficial aponeuroses, in forming parallel fasciculi, like the
deep lymphatics.
The direction followed by the lymphatics m their course, is nearly always
somewhat rectilinear ; they never show the flexuosities which are so marked
in the course of certain arteries, and even some veins. Neither do they com^
municate with one another by transverse or arching anastomoses, Uke those so
commonly met with in the other two orders of vessels belonging to the circulatory
apparatus. They frequently, however, in their parallel course, bifurcate and
join the neighbouring vessels. (At certain situations— as at some of the articula-
tions, and in other parts — the larger trunks suddenly break up into a close
interlacing plexus of small vessels or capillaries — Fig. 392 — which in their
arrangement greatly resemble the refe mirahiU of the blood-vessels. This plexus
F>K. 392.
A SECTION OF A SIMPLE LYMPHATIC RETE MIRABILE, VIEWED FROM THE SURFACE.
a, a, Afferent vessels ; h, b, efferent vessels only partially visible (from the popliteal space).
is surrounded by condensed connective tissue, and is penetrated by blood-vessels,
though no communication takes place between them and these, the only points
at which communication occurs being where the great lymphatic trunks empty
themselves into the vena cava. This refe would appear to be the first step
towards the formation of a lymphatic gland.)
But of all the considerations relative to the course of these vessels, the most
interesting are those which belong to the glandiform bodies placed along their
track, the abridged history of which we shall give immediately.
Termination. — We have already mentioned the thoracic duct and the right
great lymphatic vessel as being the receptacles of all the absorbent vessels of
the body, and we have also stated that these two trunks enter the general venous
system ; this union of the blood with the lymphatic system takes place at the
origin of the anterior vena cava, and this vessel may be considered as the
general confluent for all the absorbents of the body. The researches of Haller,
Cruikshank, and Mascagni first threw light on this important fact ; and it is to
those of Fohmann, Panizza, Rossi, etc., that we owe the realization of this
discovery.
48
718
THE LYMPHATICS.
Nerves. — Bert and Laffont have demonstrated the existence of vaso-motar
nerves in the chyliferous vessels of the Dog. Galvanization of the solar plexus
or the great splanchnic nerve, causes contraction of the wall of these lymphatics.
(The lymphatic spaces surrounding vessels are designated })erivasciilar canals.
Lymphatics originate in lacunte, or spaces between the fibres of the connective
tissues, and these are lined by endotlielial cells ; they are drained by lymphatic
vessels — the arrangement presenting an analogy to the vascular system of insects
and Crustacea. Masses of protoplasm — the connective-tissue corpuscles — abound
in many tissues, occupying some of the interstitial spaces ; the latter communicate
freely with each other, the communication being tubes in the form of small
pores or canals. The fluid drained off is the lymph, which passes into gradually
enlarging canals.)
Lymphatic Glands.
The lymphatic glands are ovoid, spherical, or discoid bodies of medium
consistency, grey, rosy, or red-coloured, and sometimes quite black, and which
at several points intercept the course of the lymphatic vessels.
Their number is considerable, and they are rarely single, but most frequently
Fig. 394.
Fig. 393.
SEOriUN OF A LYMPHATIC GLAND.
O, a, The fibrous tissue that forms its exterior ;
6, 6, superficial vasa inferentia ; c, c, larger
alveoli, near the surface ^ d, d, smaller alveoli
of the interior , e, e, fibrous walls of the alveoli.
SIMPLE LYMPHATIC GLAND.
, The capsule with sections of lym-
phatics, d, d, passing through it ;
6, lacunar and intercommunicating
passages, permeated by the lymph,
and forming the superficial lymph-
path of Frey ; c, nucleus, or me-
dullary portion, with section of
blood-vessel in the centre.
are collected in groups along the blood-vessels. They are always larger in youth
than in old age.
All the vessels of the lymphatic system are provided with at least one gland
on their course, and some even pass through two or three before opening into
the thoracic duct or great lymphatic trunk. On reaching these glands, they
plunge into their substance by ramifications, appearing on the opposite point
after being reconstituted into several principal canals, which are generally larger
and less numerous than the original vessels. The latter take the name of
afferents {vasa inferentia or afferentia) ; the others are named efferents {vasa
vfferentia), because they leave the gland to reach the central canal.
Structure. — The structure of the glands is extremely complex.
They have an envelope of connective tissue (continuous with the tunics of the
THE LYMPHATICS.
719
Fig. 395.
afferent and efferent vessels) that surrounds their proper substance, which is
composed of two layers of a different aspect — one cortical, the other medullary.
The first appears to be granular, the second somewhat fibrous. This proper
tissue is sustained by connective laminse (or trabeculce. septa — continuations of
the capsule) which contain smooth muscular fibres. The trabeculge form alveoli
in the cortical layer, and a sort of minute tubes in the central layer. These
alveoli — or follicles — are in their turn divided by fine reticular connective
tissue into secondary spaces, which become smaller as they lie nearer the centre ;
at the periphery, where they are most
voluminous, they are named lymph sinuses.
Everywhere these sinuses are filled with
lymph corpuscles. The arrangement is
identical in the medullary substance; in the
interior are seen a great number of arterial
capillaries or lymphatic cords. The nerves
are derived from the sympathetic system.
The afferent lymphatics, where they
■enter the gland, communicate with the
alveoli in the cortical substance ; these
alveoli are connected by the cords of the
central layer, and the latter are united,
in their turn, to the alveoli of the op-
posite side of the cortical substance, from
which the efferent ramuscules spring. The
lymph, therefore, traverses every part of
the gland, and during this very tortuous
course becomes charged with lymph-cells.
Certain glands have a much simpler
structure, being entirely composed of
lymphatic capillaries rolled up on them-
«elves in clusters, and anastomosing in
networks. These capillaries arise from
the divergent arborization of the afferent
vessels, and are continuous with the con-
vergent branches which, by their union,
form the efferent lymphatics. The organs
have received the name of fcdse ylctnds,
though they are really lymphatic glands.
In support of this assertion, it may be
said that " in descending the animal series,
we see the glands becoming more and
more simplified, and transformed at a
great number of points into an interlacing of vessels. In birds, they only occupy
the base of the neck and the entrance to the chest, forming in all the other
regions simple plexuses ; in reptiles and fishes, the lymphatic glands disappear
altogether, and the plexuses that replace them are themselves not at all compli-
cated" (Sappey).
(The cortical part of the gland contains the round masses of adenoid tissue —
sometimes called secondary nodnles — which are continuous with the oval masses,
also adenoid tissue, found in the medullary portion ; and both oval and round
PORTION OF THE MEDULLARY SUBSTANCE OP
THE MESENTERIC GLAND OF AN OX, THE
ARTERY OF WHICH IS INJECTED WITH
CHROMATE OF LEAD (MAGNIFIED 300
DIAMETERS).
a, Medullary substance with capillary net-
work, fine reticulum of connective tissue,
and a few lymph corpuscles ; b, b, super-
ficial lymph-path, traversed by a reticulum
of nucleated cells (c, c), with numerous
anastomosing prolongations. The lymph
corpuscles have for the most part been
removed ; d, d, trabeculae composed almost
exclusively of unstriped muscular tissue ;
g, a small medullary cord, or bridge, con-
taining a blood-vessel and numerous lymph
corpuscles.
720 THE LYMPHATICS.
masses are surrounded by the lymph sinuses. In the centre of the meshes of
the adenoid tissue is a dark portion filled with cells showing karyokinetic division
— this is a germ centre, which is more particularly the seat of the formation of
leucocytes which pass into the lymph sinuses, and thence into the vasa efferentia.
The sinuses are lined by a single layer of flat endothehal cells, a similar layer
covering the surface of the round masses in the cortex, the strands in the
medulla, and the surface of the trabeculse — these cells being even found in the
bands of reticular connective tissue passing from the trabecule.
Lymphatic glands are richly supplied with blood-vessels, either entering the
hilum or distributed over the surface. Those on the surface ramify on the
capsule, and penetrate the gland by running along the centres of the trabeculae.
The large vessel entering the hilum divides into branches, surrounded by con-
nective tissue, and these also run along the trabeculae. From these minute
branches spring, which pass through the lymph sinuses, and are ultimately dis-
tributed to the round masses in the cortex and to the strands in the medulla,
ending in a very fine-meshed capillary network. The veins pass out of the gland
at the hilum. Nerves also penetrate lymphatic glands, and medullated and non-
medullated fibres have been traced, but their mode of ending is unknown.
It is important to observe that adenoid tissue containing leucocytes is not
limited to lymphatic glands, but is found in many mucous membranes some-
times diffused in a stratum, and sometimes in sharply defined masses ; small
nodules or follicles are also found in mucous membranes, containing germ
centres, and resembling the round masses in a lymphatic gland. These are
seen in the solitary and agminated glands of Peyer in the intestinal canal ;
they vary much in different species of animals, and even in individuals of the
same species ; and they differ from ordinary lymphatic glands, chiefly in the less
intimate connection existing between them and lymphatic vessels. The leucocytes
originating in them probably do not enter the lymphatic system directly, but
wander through the epithelium covering the surface of the mucous membrane.
Amphibia have no lymphatic glands, but, as may be seen in the Frog, there are
large lymphatic spaces beneath the skin, which are traversed by very delicate
bands of connective tissue.
Preparation of the Lymphatic Vessels. — The lymphatic networks can only be studied
after having been filled with mercury by means of injection; but as this operation is not
usually practised by the pupils for whom this book is written, the mode of performing it will
only be traced in a few words.
The apparatus in use consists of a glass tube continued by a flexible one, which carries at
its inferior extremity an iron tap and a fine cannula, also of iron, or (better) glass. To apply
this apparatus, the tube ought to be suspended and then filled with mercury ; the cannula is then
seized by the right hand, keeping it parallel to the membrane we wish to inject, and burying
it in the most superficial layer of that membrane. The extremity of the cannula is thu&
introduced into th*: midst of the meshes of the lymphatic network, and necessarily wounds
some of the capillaries which compose it. In opening the tap, the mercury is allowed to flow
into the capillaries by the solutions of continuity they present, and fills them in the most per-
fect manner. The lymphatic plexuses being always superposed on the capillary blood-vessels,
one is always certain of injecting them only, in taking the precaution to penetrate the membrane
as superficially as possible. If the point of the cannula enters too deeply, the mercury will
pass into the veins, and the operation will be unsuccessful, and must be commenced again.
To study the branches and lymphatic trunks, it will sufiice to inflate them from their origin
towards their termination. This procedure, properly conducted — and it was almost exclusively
the only one adopted by the older anatomists — gives the most satisfactory results, and is even
suificient to demonstrate the texture of the glands. Or the trunks may be filled, from their
termination to their origin, by some solidifiable substance.
THE THORACIC DUCT. 721
CHAPTER II.
THE LYMPHATICS IN PARTICULAR.
We will commence with the examination of the thoracic duct and all its affluents,
and terminate by studying the great lymphatic vein {ductus lymphaticus dexter').
In this description the glands and principal lymphatic vessels will be only
referred to, the arrangement of the networks being already noticed when speak-
ing of the different organs, and they will be further alluded to when treating of
the nervous system, the organs of sense, and those of generation.
Article I. — The Thoracic Duct (Fig. 389, t t).
Preparation. — Tie the jugulars and axillnry veins near their termination, as well as the
anterior vena cava about the middle of its length ; expose the thoracic duct by removing the
ribs on the right side ; open that vessel near the pillars of the diaphragm, and throw into its
interior two injections of tallow, one forward, the other backward from the incision. The first
injection will lill the canal and the venous reservoir which is intersected between the ligatures
applied to the above-named vessels; the second, although directed in opposition to the valves,
overcomes the resistance oftVred by them, and passes into Pecquet's cistern and the principal
branches which open into that confluent.
Or we may seL-ct one of these branches in the abdominal cavity — for example, one of those
which lie beside the colic arteries near tlieir origin — and inject the entire thoracic duct from
its origin to its termination. But this proceeding requires more practical ability than the first,
in order to find the vessel which is to receive the cannula ; if the animal is very fat, it is
impossible.
The thoracic duct is the general confluent for all the lymphatics of the body,
with the exception of those which come from the right anterior hmb and the
right moiety of the head, neck, and thorax.
Extent. — It extends beneath the vertebral column, from the first lumbar
vertebra to beyond the entrance to the thorax.
Origin. — Its origin is marked by a very irregular dilatation, described as the
suUumhar reservoir, or cistern of Pecquet {receptacuhim or cysterna chyli), into
which open the principal affluents of the canal.
This reservoir is divided, internally, by lamellfe into several incomplete com-
partments, and may be more or less voluminous and circumscribed, as well as
very variable in shape.
It is placed above the abdominal aorta and the posterior vena cava, at the
anterior mesenteric artery, or more frequently a little behind it.
Course. — To this receptacle succeeds a tube, the calibre of which is very
irregular, and appears singularly slender when compared with the diameter of
the commencing dilatation, or that of the affluent vessels composing it. This is
the thoracic duct. It enters between the two pillars of the diaphragm (hiatus
aorticus), along with the posterior aorta, deviating more or less to the right side
of that vessel, and accompanies it to about the sixth dorsal vertebra, in passing
to the outside of the right intercostal arteries, which it crosses, and beneath the
vena azygos, beside which it lies. Sometimes, however, we find it carried in this
first part of its course directly above the thoracic aorta, between the double
series of intercostal arteries, and to the left of the vena azygos, which is then
found immediately in contact with the right side of the aorta ; or it may even
722 THE LYMPHATICS IN PARUCULAM.
pass to the right of that vein, concealing the greater part of it from sight.
Leaving the above-mentioned dorsal vertebra, the thoracic duct abandons the
aorta and crosses the flexm-e of the vena azygos to the left, to extend itself
forward on the left, but often also on the right side of the trachea. It after-
wards places itself between the two axillary arteries, crosses the interval between
the pre-pectoral glands, emerges from the chest, and terminates in a manner to
be indicated hereafter.
Termination. — The terminal extremity of the thoracic duct has always a dila-
tation analogous to that which exists at its origin, though much smaller, better
circumscribed, and less irregular — a dilatation which opens into the anterior
vena cava sometimes by a single orifice furnished with valves, at other times by
two very short branches, the length of which cannot be estimated at more than
the fifth part of an inch, and which are also valvular at their entrance. The
point where this entrance takes place is nearly always at the summit of the vena
cava, and precisely at the point of junction of the two jugulars. The thoracic
duct rarely opens elsewhere ; though the fact that it does so at times is exempli-
fied in a specimen in the museum of the Lyons School, in which the opening of
the duct is placed between the termination of the left jugular and that of the
corresponding axillary vein.
Varieties in Solipeds. — " The thoracic duct is far from always showing itself
in Solipeds as I have described it, but in its course and insertion it presents a
great number of variations which we w^ill now pass in review.
" The single canal is sometimes divided into two branches, which, after pro-
ceeding parallel to each other, soon unite to form a single vessel. This division
usually takes place at the base of the heart, where the lymphatics of the
bronchial and a-sophageal glands enter ; it forms a ring the diameter of which
is often not more than f of an inch, or an ellipse whose larger axis is from §
to f of an inch. We see this happen once, twice, and even thrice in the anterior
half of the canal, which becomes single at its termination as it was at its origin.
The spaces circumscribed by the bifurcations constitute what have been termed
the insuhe.
" The duct, instead of remaining single, very often becomes double from its
commencement (Fig. 397). Then the two canals are sensibly equal, or one is
larger than the other. If they are unequal, it is usually the right which has the
advantage, though the contrary sometimes occurs. In any case, the two ducts
are isolated — one being to the right, the other to the left of the aorta. In
advancing towards the entrance to the thorax, they remain completely separated,
or communicate with each other by one or two — more or less voluminous, trans-
verse anastomosing branches. Reaching to ten, eight, and sometimes even to
two inches from their opening into the jugular gulf, the two ducts approach
each other, and become at last a single vessel. Their fusion generally takes
place at the base of the heart, and I have never seen them remain distinct
throughout their whole extent, to enter the vena cava separately.
" Sometimes (Fig. 39k) there emanates from the gland, at the entrance to the
thorax, a long canal which proceeds parallel to the first, and joins it after a
retrogade course, near the crura of the diaphragm.
" The thoracic duct, double for the greater part of its extent, from the time
it leaves the receptaculum chyli, occasionally ends by becoming triple. In this
case, the largest of the two canals is divided into tAvo branches ; then the three
canals, after pursuing a certain course, all join at the same point, or two are first
THE THORACIC DUCT
Fig. 396,
Fig. 397.
Fig. 398.
DIFFERENT VARIETIES OF THE THORACIC DUCT IN THE HORSE.
A, Receptaculum chyli ; b, sublumbar branches ; c. anterior mesenteric branch ; d, posterior mesen-
teric branch. In Fig. 396 the duct is single, the usual condition, and enters the summit of the
anterior vena cava by two short branches. It is double in Fig. 397 ; and in Fig. 398 it has a
long branch that arises at the entrance to the thorax and joins the duct, by a retrograde course
near the pillars of the diaphragm.
724 TEE LYMPHATICS IN PARTICULAR.
united into a single vessel, into which the third opens at a variable distance from
the confluent of the first." ^
The affluents of the thoracic duct. — The lymphatic vessels which enter the
thoracic duct are as remarkable for their number as their volume. Some empty
themselves into the receptaculum chyli ; a few vessels open into the great
lymphatic vessel of the thorax, and the others terminate in that canal near its
entrance into the venous system.
The first, variable in their number — particularly the largest — are more espe-
cially regarded as the roots of the thoracic duct.
Ordinarily three are found, with a certain number of small accessory trunks.
One of the largest branches enters the posterior part of the receptaculum chyli.
Very often double, and even multiple, it arises from an enormous group of glands
in the sublumbar region, around the posterior extremity of the abdominal aorta
and vena cava, and into which are collected all the vessels of the posterior limbs,
the pelvis, abdominal walls, and the pelvi-inguinal viscera. The other two trunks
reach the left side of the receptaculum, and result from the union of the lym-
phatics which come from the abdominal digestive organs ; among these
lymphatics, however, there are some belonging to the parietes of the stomach
and the parenchyma of the liver and spleen, and which reach the right side of
the receptaculum, to open singly into that cavity.
The affluents the thoracic duct receives on its course, proceed from the viscera
contained in the thoracic cavity, and from the walls of that cavity.
Those which terminate at the anterior extremity of the duct are formed by
the lymphatics of the left anterior Hmb, and the left half of the thorax,
diaphragm, neck, and head.
We will now examine rapidly all the radicles of these affluents.
Article II. — The Lymphatics which foem the Affluents of the
Thoracic Duct.
These lymphatic vessels are divided into five groups : 1. Those of the
abdominal limb, the pelvis, the abdominal parietes, and the pelvi-inguinal organs.
2. Those of the abdominal digestive viscera. 3. Those of the organs contained
in the chest. 4. Those of the thorax. 5. Those of the head, neck, and anterior
limb.
Lymphatics of the Abdominal Limb, Pelvis, Abdominal Parietes,
and the Pelvi-inguinal Organs.
All these vessels converge towards an immense group of glands — the sub-
lumbar. Besides these, there are other groups on different parts of their course,
constituting the deep inguinal, superficial inguinal, popliteal, iliac, and precrural
glands. The successive description of these glands, and their afferent and
efferent vessels, will complete the study of this apparatus.
1. Sublumbar Glands (Fig. 399).
This group, which occupies, as its name indicates, the sublumbar region,
comprises : 1. A small single mass situated in the sinus of the angle formed by
the two internal iliac arteries, and is often only a single large gland. 2. Another
' G. Colin, Traite de Physiologie Comparde det Animauz Domestiques, 2nd Edition, vol. ii
Paris; 1871.
THJiJ AFFLUENTS OF THE THORACIC DUCT.
Fig. 399.
725
THK LYMPHATIC SYSTEM OF THE HORSE.
Facial and nasal ple.xus the branches of which pass to the subglossal glands ; B, c, parotid
lymphatic gland, sending vessels to the pharyngeal gland; d, E, large trunks passing towards
726 THE LYMPHATICS IN PARTICULAR.
mass lodg^ed between the two iliac arteries, and a third placed without, and to
the front of, the common iliac ; these two are double. 3. A single agglomera-
tion of glandular lobules dispersed around the origin of the posterior mesenteric
and spermatic arteries ; these are separate from one another.
The different masses receive the lymphatics of the pelvis, the emergent
branches of the deep inguinal glands, those which come from the iliac glands,
some ramuscules from the rectum and large colon, and those from the spermatic
cord.
They are bound to each other by communicating branches, and give rise to
several series of emergent branches, which soon collect into one or more trunks
that enter the receptaculum chyli.
2. Deep Inguinal Glands.
This is a considerable mass of glandular lobules lodged beneath the crural
aponeurosis and arch in the interstice between the adductor muscles of the leg,
along with the iliac vessels, within which they are placed.
The form of this group is elongated, and its length may be six to eight
inches, or even more ; its superior extremity extends as high as the anterior
border of the pubis. It is composed of from fifteen to twenty lobules, which
rarely have a uniform colour— some being grey and others brown, or nearly
black.
The afferents are formed by the superficial lymphatics that accompany
the internal saphena vein — the radicles of which may be traced beyond the fet-
lock- and by the deep satellite vessels of the iliac artery and vein. The efferents
proceed to the sublumbar glands, by ascending in the abdomen along the
external iliac artery and vein.
3. SuPEEFiciAL Inguinal Glands.
These are placed in front of the inguinal ring, at the side of the sheath, on
the track of the subcutaneous abdominal artery, where they form a small
elongated mass from two and a haK to three inches in length, and are composed
of a dozen principal lobules.
Their afferents, which are very numerous, come from the inner aspect of the
thighs, the sheath, scrotum, and the inferior abdominal wall. The efferent
vessels, much larger, but less numerous — there are only five or six — ascend in
the inguinal canal, accompanying the external pudic artery and the inguinal
nerves. They enter the deep inguinal glands, after traversing the inguinal canal
in company with the prepubic artery.
the thorax ; F, G, H, glands receiving the superficial lymphatics of the neck, a portion of those
of the limbs, and those of the pectoral parietes ; i, junction of the jugulars; j, axillary veins;
K, summit of anterior vena cava ; L, thoracic duct ; M, lymphatics of spleen — N, of stomach — 0,
of large colon — S, of small colon ; R, lacteals of small intestine — all joining to form the two
trunks, p, Q, which open directly into the receptaculum chyli ; T, trunk which receives the
branches of the sublumbar glands, u, to which the vessels of the internal iliac glands, V, the
receptacles of the lymphatics of the abdominal parietes, pass ; w, precrural glands receiving
the lymphatics of the posterior limb, and which arrive independently in the abdomen; X, super-
ficial inguinal glands into which the lymphatics of the mamma:, external generative organs, some
superficial trunks of the posterior limb, etc., pass ; Z, deep inguinal glands receiving the super-
ficial lymphatics, z', of the posterior limbs.
THE AFFLUENTS OF THE THORACIC DUCT. 727
4. Popliteal Glands.
These are a very small mass of from three to five independent lobules,
situated behind the great sciatic nerve and gastrocnemius muscle, between the
biceps femoris and semitendinosus muscles, and near the femoro-popliteal artery.
They receive some of the lymphatics from the neighbourhood of the hock,
and those coming from the posterior and inferior part of the gluteal region.
Their efferents join the deep inguinal glands, by followmg the muscular inter-
stices of the thigh.
5. Iliac Glands.
Slightly yellow in colour, and of a soft consistence, these glands are five
or six in number, and form a group which is situated in the triangular space
between the two branches of the circumflex iliac artery. They receive the
emergent branches of the precrural glands, and a great number of deep
lymphatics from the abdominal wall. Their efferent branches, four or five in
number, follow the circumflex iliac artery to pass to the sublumbar glands.
6. Precrural Glands.
Placed within the anterior border of the tensor fascia lata, on the course of
the circumflex iliac artery, these glands form a small elongated mass, composed
of a dozen lobules lying close to each other. To this group come afferent
vessels from the anterior and internal part of the thigh. It gives origin to
three or four large efferent vessels, which ascend the internal face of the fascia
lata muscle, accompanying the circumflex iliac artery, and entering the abdominal
cavity near the angle of the haunch, to join the iliac glands.
Lymphatics of the Abdominal Viscera.
1. Glands and Lymphatic Vessels of the Rectum and Floating Colon.
The glands in this portion of the intestinal tube are : at flrst, two or three
lobules placed at the base of the tail and on each side of the sphincter ani ; in
the second place, a very numerous series of small glandular bodies situated along
the small curvature of the viscus ; thirdly, some rounded lobules comprised
within the tAvo layers of the mesentery, and placed on the course of the arterial
and venous divisions.
Originating in the texture of the mucous and muscular tunics, the lymphatic
radicles gain the glands of the small curvature of the colon, and escape from
them as efferent branches, which pass in great numbers into the mesentery.
These efferents — or at least some of them — pass through the lymphatic glands
placed on the course of the blood-vessels, and collect, near the origin of the
posterior mesenteric artery, into several somew^hat luminous branches, which
join the divisions of the sublumbar glands, or those of the large colon.
2. Glands and Lymphatic Vessels of the Double Colon.
There is seen on this enormous viscus ^ double chain of glands, lying beside
the colic arteries, and numerous small lobules disseminated at a short distance
from the principal glands, and on the track of the collateral branches furnished
by these two vessels.
728 THE LYMPHATICS IN PARTICULAR.
Received at first, for the most part, by these lobular bodies, the lymphatics
which have emanated from the tmiics of the double colon afterwards join the
principal glands, from which they emerge in forming several large satellite
branches for the colic vessels. Only two or three in nimiber at the pelvic
flexure, these branches are increased to ten or twelve on arriving near the origin
of the colic arteries. It is from the union of these vessels with those of the
small intestine, tli^it the two large mesenteric trunks (Fig. 896, a, c) arise,
which, with the branches emanating from the sublumbar glands (Fig. 396, b),
form the receptaculum chyli.
3. Glands and Lyjiphatic Vessels of the C^cu:\r.
There exists, on the track of each ca^cal artery, a moniliform series of glands,
farther apart from one another than those of the double colic chnin, to which
the vessels coming from the caecal membranes are directed, cind from which
several long satellite branches of the blood-vessels, that proceed to the r^ame
trunk as those of the small intestine, depart.
4 Glands and Lymphatic Vessels of the Small Intestine.
The glands which receive the lymphatic vessels from the email intestine
are very large and abundant. About thirty in number, of a grey colour, very
compact, fusiform, often bifurcated at their superior extremity, these glands
are placed in the substance of the mesentery, near the origin of the anterior
mesenteric artery, from which those belonging to the portion of intestine
nearest the end of the viscus are most distant. The latter also possess, in
addition, fifteen special small glandular lobules, dispersed on the track of the
ileo-cffical artery.
We have already noted the richness of the vascular apparatus which rises
from the wall of the small intestine, towards the mesenteric glands. It must
be added that these glands give off, at their superior extremity, large l>ranches,
two or three for each, which soon coalesce to form more voluminous branches,
that concur in the formation of the two intestinal roots of the receptaculum
chyh.
5. Glands and Lymphatic Vessels of the Stomach.
There are two classes of lymphatic glands for the stomach : 1. Several large
glands situated on the small curvature of the organ. 2. A series of small
lobules disseminated along the great curvature to the attachment of the gastro-
colic omentum.
The vessels which emerge from them " gather on the course of the gastric
arteries and veins, and ascend to the great tuberosity, near the trunk of the
coeliac artery ; there they anastomose with the lymphatics from the spleen and
liver, and unite into several flexuous branches, some of which open directly into
the thoracic duct, to which the others pass, after joining the anterior trunk of
the intestinal lymphatics " (Colin).
6. Glands and Lymphatic Vessels of the Spleen and Liver.
" The lymphatic vessels of the spleen, rising some from the interior of the
viscus, others from its surface, pass towards the splenic artery and vein : they
traverse several groups of glands on the track of these vessels, commencing from
THE AFFLUENTS OF THE THORACIC DUCT. 729
the middle of the fissure, ascend, five or six in number, towards the origin of
the artery in forming a sinuous mass, the divisions of which, anastomosing with
those of the stomach and liver, open, on the one hand, with the latter in the
anterior trunk of the intestinal lymphatics, and, on the other, into a magnificent
plexus communicating directly with the thoracic duct.
" Finally, the lymphatics of the liver form a very close network on the
surface, and another in the interior of the gland. They collect towards the
posterior fissure, and first dip into a primary and very small glandular group,
then into a second group of voluminous round glands, which are concealed
between the trunk of the vena portas and the pancreas. They open in common
with the vessels of the stomach and spleen " (Colin).
Glands and Lymphatic Vessels of the Organs contained in the
Thoracic Cavity.
We find annexed to these organs three groups of lymphatic glands : 1. A
series of small granular masses in the posterior mediastinum, on the course of
the oesophagus. 2. The bronrhial glands, situated in the angle of bifurcation
of the trachea, around the origin of the bronchi, which they follow for a short
distance into the pulmonary tissue. 3. Two long strings of lobules extended
on the sides of the inferior face of the trachea, from the base of the heart to
near the first rib.
The first group receives the posterior lymphatics of the oesophagus, the
second those of the lung, and the third those of the pericardium, heart, and a
portion of the trachea and oesophagus. Their efferents, uniting into some large
trunks, enter the thoracic duct at different distances.
Glands and Lymphatic Vessels of the Thoracic Walls.
These glands form three series : 1. A double chain of small rounded glands,
situated on each side of the dorsal column, above the intercostal spaces, and
beneath the costal pleura. 2. A frequently voluminous mass, lodged at the
base of the xiphoid cartilage, behind the heart, and in front of the inferior
part of the diaphragm. 3. Some rudimentary glands lying beside the internal
thoracic vessels.
The lymphatics of the diaphragm, after receiving those from the convex
face of the liver, pass to the glands placed at the base of that muscle, whence
they escape in the form of several vessels that accompany the internal thoracic
vessels, and open into the anterior extremity of the thoracic duct or the great
lymphatic vein, the majority of them through the medium of the prepectoral
glands. These vessels receive, on their course, those which are brought from
the inferior part of the intercostal spaces into the supra-sternal glands.
The other lymphatic vessels of the thoracic wall ascend between the two
muscles which close these spaces, and go to the subdorsal glands, which after-
wards eject them, near the origin of the thoracic duct, in the form of one or
two long vessels proceeding in a retrograde manner on each side of the dorsal
vertebrae.
Lymphatic Vessels of the Head, Neck, and Anterior Limb.
These vessels are aU directed towards the entrance to the chest, and ai-e
gathered into a group of glands, called the frejpectoral, which, with regard to
730 TEE LYMPHATICS IN PARTICULAR.
the lymphatics of the anterior part of the body, play the same part as the
sublumbar glands do to the vessels of the posterior region.
Before arriving at this common point of convergence, they are intercepted
on their course by other glands, which form four principal groups : 1. The
guttural or p?iaryngeal glands. 2. The submaxillary gkmds. 3. The prescapular
glands. 4, The brachial glands.
In studying these different glandular groups in succession, with their afferent
and efferent vessels, a sufficient idea will be afforded of the entire lymphatic
apparatus in the region which remains to be examined.
1. Pkepectoral Glands.^
These form, on each side of the terminal extremity of the jugular, within
the inferior border of the scalenus muscle, a very large mass which extends into
the chest by passing beneath the axillary vessels, and asosnds to the inner face
of the first rib on each side.
Into these glands pass the lymphatic vessels emerging from the prescapular
and axillary glands, those which descend along the trachea with the common
carotid, and which come from the pharyngeal glands, as well as the majority of
those which follow the internal thoracic vessels.
They give rise to several short and voluminous branches : those from the
glands of the right side form, by their junction, the great lymphatic vein ; and
those from the left side join the thoracic duct, or enter separately beside the
latter, at the summit of the anterior vena cava.
2. Pharyngeal Glaot)S.
Very numerous, soft, and loosely united to one another, these glands are
disposed in an elongated mass that occupies the lateral plane of the pharynx,
below the guttural pouch, and is prolonged backwards, even beyond the thyroid
body.
They receive all the lymphatics from the head ; some come directly from
the base of the tongue, the soft palate, the pharyngeal walls, and the larynx ;
the others are derived from the submaxillary glands, and from a lobule lodged
in the substance of the parotid gland.
The efferent branches which leave it are four or five in number. Always
voluminous, they descend along the trachea, some separately, but the majority
are united in a fasciculus which follows the carotid artery. They have on their
course several elongated glands, to which the lymphatic radicles that arise from
the cervical portion of the trachea nnd oesophagus pass. On arriving near the
entrance to the chest, they are generally lost in the prepectoral glands ; though
some of them traverse these without dividing, and directly enter — on the left —
the thoracic duct, and on the right, the great lymphatic vein. It has been even
possible for us to inject the latter vessel by one of these vessels exposed on the
right side.
3. Submaxillary or Subglossal Glands.
They represent a fusiform mass situated at the bottom of the submaxillary
space, in the receding angle comprised between the digastricus on the one side,
' These are glands, we believe, which ought to be regarded as the representatives of the
axillary glands of Man.
TEE GREAT LYMPHATIC VEIN.
731
and the mylo-hyoideus and subscapulo-hyoideus muscles on the other, above and
near to the facial artery. The lymphatics of the tongue, cheeks, lips, nostrils,
and nasal cavities join these glands. Their efferents reach the pharyngeal or
guttural glands.
4. Prescapular Glands.
By their union these form a kind of chain, at least twelve inches in length,
placed on the course of the ascending branch of the inferior cervical artery,
beneath the internal face of the mastoido-humeralis muscle, and descending
close to the attachment of the sterno-maxillaris muscle.
The majority of the lymphatics of the neck, and those of the breast and
shoulder, open into these glands. Their efferents, short and volummous, enter
the prepectoral glands.
5. Brachial Glands.
Situated beneath the anterior limb, inside the arm, these vessels are divided
into two groups — one placed near the ulnar articulation, within the inferior
extremity of the humerus ; the other disposed in a discoid mass behind the
Fig. 400.
Fig. 401.
THE GREAT LYMPHATIC VEIN AKD ENTRANCE OF THE THORACIC PVCT.
A, Thoracic duct; B, great lymphatic vein, or right lymphatic trunk; C, D, anastomoses estab-
lished between them near their insertion.
brachial vessels, near the common insertion of the teres major and latissimus
dorsi.
The first group receives the vessels from the foot and the forearm, wnich
accompany the superficial veins, or pass with the deep arteries and veins into
the muscular interstices. It sends nine or ten flexuous branches to the second
group, into which open directly the lymphatics of the arm and shoulder, and
from which emerge a certain number of efferents that pass, in company with the
axillary vessels, to the prepectoral glands.
Article III. — Great Lymphatic Vein.
The second large receptive trunk of the lymphatic vessels, this great vein
(the dtfchis h/mphaficus dexter) leaves the prepectoral glands of the right side,
and therefore becomes the general confluent of the lymphatics from the right
anterior limb, the right axillary and superficial costal regions, as well as the
right half of the head, neck, and diaphragm.
This trunk is only from three-fourths of an inch to two inches in length.
732 THE LYMPHATICS IN PARTICULAR.
" It usually opens at the junction of the jugulars, at the side of the vessels, by
an orifice furnished with a double semilunar valve. Sometimes one or two of
the branches which concur to form it, describe circumvolutions around the
corresponding brachial trunks or some of its divisions, before joining the others.
Lastly, it is not rare to see this lymphatic trunk anastomose with the thoracic
duct by voluminous collateral branches, then unite with it in such a way as to
be inserted together by a single orifice above the confluent of the jugulars "
(Cohn)
Differential Characters in the Lymphatic System of other than Soliped Animals.
The lymphatic system, glaiiJs aud vessels, is more developed in Ruminants and the Pig
than in the Carnivora.
In this respect the domesticated animals may be classified in the following order: Ox,
Sheep, Horse, Pig, Dog, Cat.
Kusiinants. — " The thoracic duct of large Ruminants, when it has entered the thorax by
a special opening in the diaphragm, almost distinct from that of the aortic liiiitus, is placed
above and to the right of the aorta, between it and the spine. There, although outside the
corresponding intercostal arteries, it is completely concealed by a thick layer of adipose tissue,
in which are numerous subdorsal glands. Towards the fifth dorsal vertebrr^ ii receives a large
lymphatic vessel from the enormous gland on the track of the oesophagus in the posterior
mediastinum ; it then crosses the direction of the aorta and the oesophagus, passes to the left,
gains entrance to the thorax, anil upens in front of the first rib, above the junction of the left
jugular with the anterior vena cava." '
" The varieties it presents in the Ox are numerous and very common. The rarest dis-
position is that of a canal, single throughout its
Fig. 402. entire length, such as it has been described^ and
sucii as it is usually found to be in small Ruminants
(Fig. 406). This canal (Fig. 403), single at its
origin aud for the greater part of its extent, often
bifurcates towards the base of the heart, or at a
short distance from its insertion. Of these two
branches, one passes to the rigiit of the oesophagus
and trachea, th<i other to the left of these, in follow-
ing the ordinary direction ; and, at the entrance
to the thorax, they either terminate separately, each
entrance of the thoracic duct in in the angle formed by the union of the jugular and
the ox. corresponding axillary vein, or together at the samo
point — the confluent of tlie two jugular veins.
"It happens tliat one of the branches of the bifurcated canal is, in its turn, subdivided Into
two smnller branches, and that the other experiences at the same time a similar subdivision;
so that the trunk of the canal, at first single, becomes double, then quadruple, and con.-jequently
opens into the venous system by four distinct orifices. If the branches of the canal, instead of
remaining isolated, send oflf transverse anastomoses, there results a complication of which
Solipeds do not offer an example (Fig. 402).
" The tlioracic duct is often double throughout its extent. The two canals are then detached
separately from the receptaculum chyli ; one follows the right side, the other the left side of
the aorta, describing an arch with concavity downward at the base of the heart, on the lateral
parts of the trachea, terminating either very near one another, and on the same transverse line,
at the junction of the two jugulars ; or one to the right, the other to the left, in each of these
two veins, and not far from their junction with the axillaries (Fig. 404).
" When the two canals arise from the receptaculum, they sometimes repeatedly anastomose
with each other by sinuous and curved branches, as sliown in Fig. 405.
" Then all the branches collect in the antejior mediastinum, and constitute a single canal
0 Zundel has pointed out the curious fact, that in Ruminants, the long, special, lymphatic
gland situated between the layers of mediastinum and above the ojsophagus, sometimes becomes
so voluminous that its weight impedes rumination, especially wlien the animal is lying. The
bolus of food is prevented from ascending into the oesophagus, and this may become a frequent
and periodic cause of indigestion.)
THE GREAT LYMPHATIC VEIN.
733
which, near its termination, again subdivides into four vessels that open separately, two to the
right and two to the left, in the usual place.
" This variety Is the most remarkable and complicated of all those observed in the domesti-
cated animals.
Pig.— "The thoracic duct of the Pig, usually single throughout its whole extent, ia
Fig: 405.
VARIETIES IN THE THORACIC DUCT OF THE OX.
sometimes divided, at from 1 to 1| inches from its entrance, into two branches which soon
reunite m an oval dilatation ; this, after receiving the vessels from the head, neck, and limbs
opens towards the extremity of the left jugular. '
Carnivora.— "In the Dog, the receptaculum chyli is enormous; in shape it is ovoid, and
49
734 THE CIRCULATORY APPARATUS OF BIRDS.
is prolonged between the pillars of the diaphragm into the thoracic cavity. Tlie thoracic doct
of this animal generally resembles that of the Pig. Yet it sometimes offers in its course and
termination very numerous variations; Rudbecky has noticed a bifurcation above the heart,
and another bifurcation the branches of wliich anastomose with each other several times.
Swammerdam and Steno have figured numerous irregular anastomotic divisions towards the
middle of a single canal, to its point of departure. These old authors have indicated and
Fig. 406.
THORACIC DUCT OF SMALL RUMINANTS.
represented double and triple junctions of different forms. Lastly, Bilsius has shown an arch,
or rather a very remarkable ring, at the entrance of the vessel, at its junction with the
lymphatic vessels of the neck and anterior limbs, and which is more or less analogous to that
which I have observed on several occasions in the Horse, Pig, and Cat." •
CHAPTER III.
THE CIRCULATORY APPARATUS OP BIRDS.
We will briefly examine the characteristics of the different portions of the
circulatory apparatus — the heart, blood-vessels, and lymphatic vessels — of Birds.
Article I. — The Heart.
The heart, in Birds, is situated quite at the entrance to the chest, in the
middle line, and is contained in a pericardium that adheres to the posterior
diaphragmatic septum and the cervical reservoir. In the domesticated species,
it has the form of an acute cone, the base of which is surmounted by a less
distinct auricular mass than in the Mammalia.
Internally it has four cavities. The right ventricle is more crescent-shaped
than in Solipeds, and in a manner envelops the left ventricle in front and to the
right ; it does not reach the point of the heart. The auricular valve is not
tricuspid, and offers a very remarkable arrangement. " This valve, in fact,
instead of being formed as usual by membranous curtains, with margin retained
by cords fixed to the walls of the ventricles, is composed of a wide muscular leaf
which appears to be a portion of the inner wall of the ventricle detached from
the interventricular septum. This septum is convex, and the auriculo-ventricular
orifice is situated in the space comprised between it and the muscular valve in
' G. Colin, op. cit.
TEE CIRCULATORY APPARATUS OF BIRDS. 735
question ; so that when the latter contracts at the systole, it is applied against
this septum and closes the passage." ^
There is nothing particular to note with regard to the left ventricle, the walls
of which are likewise thicker than those of the right.
The auricles have a kind of diverticulum or sinus, where the veins that open
into each of these cavities unite.
Article II.— The Arteries.
The aorta of Gallinaceous Birds ascends beneath the lower face of the right
lung, then turns abruptly backwards and a little to the left. It attains the
middle line towards the anterior extremity of the kidneys, and in this situation
it reaches the sacral vertebrae, where it divides into three branches — the arteries
of the pelvic limbs, and the middle sacral artery.
Close to its origin, the aorta gives off the hrachio-cephalic (or innominate)
trunks. With the Fowl this name is perfectly correct, as they both furnish
vessels to the wings and head. The right passes upwards and forwards, is
inflected backwards at the first rib, and continued on the lower face of the wing
by the humeral artery. It throws off a thoracic artery, the volume of which is
in relation with that of the pectoral muscles ; this artery emits superficial
branches that form in the skin of the abdomen, with other vessels, a very rich
plexus named by Barkow the rete mirabile of incubation. It afterwards gives
off a cephalic trunk, from which arise the ascending cervical, vertebral, and right
carotid artery. The left brachio-cephalic trunk has the same distribution as the
right, a slight difference only being observed in its direction ; on leaving the
thoracic cavity it describes a small S curvature.
The carotid arteries exhibit a somewhat curious arrangement. Each springs
from a corresponding brachial trunk ; and, placed at first on the sides of the neck,
they make a curve, with convexity anterior, and gain the middle line by passing,
the right above the oesophagus, the left above the trachea. They remain beside
each other, beneath the longus colli, from the second last to the second cervical
vertebrae, where they separate at an acute angle and reach the border of the jaw,
terminating there in two branches— the internal and external carotid arteries.
The other collateral branches furnished by it are : 1, The intercostal arteries.
These may arise from the subcostal branches which are parallel to the aorta ;
thus, in the Fowl, there is a common descending intercostal which proceeds from
the vertebral, and a common ascending intercostal that leaves the aorta as it passes
into the abdomen. 2. The codiac trunk, which commences at the middle of the
lower face of the lung, and, descending obliquely backward, reaches the posterior
aspect of the liver. It divides into several ramuscules, of which there are three
principal vessels ; a very fine one goes to the spleen ; a left or middle one passes
to the gizzard along the proventriculus ; the third, more voluminous, is directed
to the right side, gives a twig to the liver, and is continued by a long pancreatico'
duodenal branch that joins the extremity of the loop which the intestine forms
at its origin. 3. The anterior or superior mesenteric, which arises at a short dis
tance behind the coeliac trunk, enters the mesentery, and is directed backwards,
describing a curve with convexity antero-inferior, and which emits twigs to the
intestine. 4. The spermatic or ovarian arteries. The inferior or posterior mesen-
' Milne-Edwards, Lemons sur la Physiologie et V Anatomic Comparee de VEomme et det
Animaux, vol. iii.
736 THE CIRCULATORY APPARATUS OF BIRDS.
teric leaves the subsacral artery, and, by some ramuscules, reaches the rectum and
cloaca.
Shortly before its termination in three branches, the aorta gives off an artery
that crosses the middle portion of the kidneys, leaves the abdominal cavity, and
becomes distributed to the anterior muscles of the thigh, after detaching the
qngastrk artery. The latter proceeds forward, beneath the skin of the abdomen,
and anastomoses with the ramifications of the thoracic artery.
The arteries of the pelvic limbs — the femoral or iliac, in passing above the
kidneys, furnish the renal arteries ; they then leave the pelvis by the sacro-sciatic
foramen, immediately behind the coxo-femoral articulation. Placed beneath the
muscles on the posterior face of the thigh, in following the branches of the
lumbo-sacral plexus as far as the femoro-tibial articulation, they are then con-
tinued by the popliteal vessels. These arteries throw off articular ramuscules,
the nutrient artery of the tibia, and a long branch to the muscles on the posterior
aspect of the leg ; they are placed in the groove resulting from the junction of
the tibia and fibula, and pass through the osseous interspace to form the anterior
tibial arteries.
The yniddle sacral continues the aorta to the bottom of the pelvis ; when it
arrives below the last coccygeal vertebra, it forms a kind of arch, the ramifications
of which are distributed among the muscles and quills of the tail.
Aeticle III. — The Veins.
As in Mammals, the veins are distinguished as belonging to the great and
lesser circulation.
The veins of the great circulation are collected into three trunks that open
into the right auricle of the heart ; there are two anterior vena, cavm and one
posterior vena cava. They enter a particular compartment — a kind of sinus — in
the auricle.
The anterior vence, cavce collect the blood from the subclavian arteries and
those of the head. The jugular veins, which are their principal branches, are
not the satellites of the carotid arteries, as in the larger domesticated animals ;
they are superficial and situated on the sides of the trachea ; while the carotids
are placed in the middle line, beneath the longus colli. They are not of the
same calibre in all species, the right jugular being more voluminous than the
left ; there is always, however, a transverse anastomosis between the two jugulars,
below the base of the cranium.
The posterior or inferior vena cava commences at the anterior extremity of
the kidneys, and passes forwards, traversing the right portion of the liver,
receiving the hepatic veins, and enters the right auricle.
Among the branches forming it may be cited the femoral or iliac veins.
These vessels do not accompany the corresponding arteries, and therefore do
not enter the pelvic cavity by the sacro-sciatic foramen, but pursue a course
analogous to that described for these vessels in Solipeds, in passing beneath the
crural arch.
In Birds furnished with a crest and mandibles, the skin of the head is provided
wit"h an excessively rich vascular plexus.
Article IV. — The Lymphatics.
Birds possess lymphatic vessels and glands. The latter are few, and are scarcely
THE CIRCULATORY APPARATUS OF BIRDS. 737
met with elsewhere than in the cervical region ; the former are abundant in
the viscera, and unite in such a manner as to form tivo thoracic ducts. These
ducts commence at the coeliac trunk, and pass along the lower face of the lung,
receiving the lymphatics of that organ and those of the wings, and finally open
into the jugular veins, a little in front of their union with the axillary veins.
A transverse branch forms a communication between the two thoracic ducts,
towards their termination.
BOOK YI.
APPARATUS OF INNERVATION.
FIRST SECTION.
THE NERVOUS SYSTEM IN GENERAL.
The functions of the instruments which we have just described, suffice in them-
selves to maintain nutrition — the locomotory acts which permit the animal to
seek its food and to introduce it into its organism, the elaboration and absorption
of the assimilable materials of the alimentary mass in the interior of the digestive
cavity, the circulation of the reparative fluids in the economy, and the depuration
and revivification of these fluids by the action of the lungs and the kidneys ;
so that nothing more is required to constitute the conditions necessary for the
manifestation of the nutritive phenomena.
Besides the apparatus necessary to carry on the functions of nutrition, how-
ever, there is needed an excitory system which will move them from their inertia,
and a regulating system to direct their special activity. These two systems are
found in the apparatus of innervation. Stimulated by the nervous system, the
properties of the apparatuses of nutrition no longer remain in a latent state,
but manifest themselves by their usual results.
Thanks to the nervous system, the animal acquires all the attributes of what
it has become habitual, after Bichat, to term animal life — that is, sensibility,
volition, instinct, and intelligence.
The perceptive centre which receives the stimuli developed at the periphery
of organs, or in their substance ; the excitatory centre which induces motion in
all the other tissues ; the seat of the instinctive and intellectual faculties, charged
with numerous and important functions — the apparatus of innervation presents
itself as a most attractive study. We will commence by giving a general and
succinct idea of its conformation, structure, properties, and functions, before
undertaking the special description of the different parts composing it.
General Conformation of the Nervous System.
The apparatus of innervation comprises a central and a peripheral portion.
The first represents a very elongated mass lodged in the spinal canal, and
expanded at its anterior extremity, which occupies the cranial cavity. This is
named the cerebrospinal axis or centre.
The second consists of a double series of ramescent branches, which are given
off laterally from the central mass, to be distributed to all parts of the body ;
these branches are the nerves.
The Cerebko-Spinal Axis. — The axis, properly so called, lodged in the
THE NERVOUS SYSTEM IN GENERAL. 739
vertebral canal, forms the spinal cord. It is a large white cord, terminating in
a point at its posterior extremity, and giving off, at each intervertebral foramen,
one of those nerve-branches which, collectively, represent the peripheral portion
of the apparatus of innervation.
The expanded extremity enclosed in the cranium is named the encephalon (or
brain). More complicated in its conformation than the spinal cord, this portion
is divided, as we shall see, into four parts : 1. A white peduncle, the continuation
of the spinal cord. 2. Three grey-coloured ovoid masses, one of which is posterior,
the other two being anterior, and placed symmetrically side by side. This
medullary prolongation gives off, right and left, like the cord itself, nerve-
branches destined almost exclusively to the head.
The Nerves. — The nerves are in the form of fasciculated cords, issuing
from the orifices at the base of the cranium, or through the intervertebral
foramina, and passing into all the organs by ramifying like arteries, which they
generally accompany.
All the nerves arise from the medullary axis, or from its encephalic pro-
longation, by radicles more or less apparent. They are divided, according to
the relative position of their point of emergence, into two great categories — the
superior, arising from the corresponding face of the spinal axis ; the others,
inferior, escaping from the lower face — a distinction which is perfectly appre-
ciable with regard to the cord itself, but which is more difficult to estabhsh in the
encephalic peduncle, as it is less distinct.
At their emergence from the bony canals which give them passage, the
radicles of each nerve always unite into a thick common trunk.
In the majority of cases, there enter into the composition of this trunk the
nerves or fibres of the two orders ; only a few nerves are composed of fibres of
the one kind, and these all belong to the brain.
At the origin of the trunk into which the nerve roots are collected, there is
a greyish enlargement termed a ganglion ; but this peculiarity belongs exclusively
to the superior fibres.
After a variable course, which is generally short, this trunk divides into
branches, the point of departure for all the nerves of the body. Among these
branches, those which are expended in the apparatuses of animal life are pairs,
and perfectly alike on both sides of the body. Those of the organs of nutrition
are composed at first of an almost symmetrical double chain, placed beneath the
spinal column, the elements of which are borrowed from nearly all the nerve
trunks issuing from the cerebro-spinal axis ; in proceeding to their destination,
their distribution is most irregularly complicated. As they offer on their course
& great number of ganglia similar to those we have already mentioned, they are
called ganglionie nerves ; they are also designated the net'ves of organic or vegetative
life, while the others are named the nerves of animal life or of relation.
Structure of the Nervous System.
Two particular substances — one greg, the other white — enter into the organi-
sation of the nervous apparatus. These two substances are formed, the first of
nerve-tubes and united nerve-cells ; the second of tubes alone.
The nerve-tubes are microscopic elements, composed of sections or segments
about a millimetre in length, joined end to end. Each segment {inter anyiular
segment) is formed of a sheath {Schivann's sheath) — a thin, homogeneous mem-
740
TEE NERVOUS SYSTEM IN GENERAL.
Fig. 407.
DIAGRAM OF STRPC
TURE OF XERVE
FIBRE.
1, Sh
lary
th; 2, medul-
substance of
Schwann ; 3, axis-
cylinder, or primi-
tive band.
brane, within which is a layer of protoplasm containing a nucleus. The axis of
the segment is occupied by a slender cylindrical stalk {(ixis-cyUnder of PurTcinjey
or bund of Remak ), the space between it and the protoplasm
being filled by a viscid opatjue substance {nvjeJin, medidla,
white substame of Schwann, or sheath of the marrow), which
is stained black by osmic acid, and is quickly coagulated
by cold.
The axis-cylinder is not interrupted at the points of con-
tact of the segments, btit passes through the annular con-
strictions, and runs from beginning to end of the nerve.
When the medulla is solidified, it is seen to be bordered
by two dark lines, parallel to the walls of the nerve-tubes ;
this aspect has caused the latter to be named '• double-con-
totired tubes (or nerve-fibres)."
All the nerve-tubes do not possess, at the same time,
these three parts, for the medulla may be absent : so that
there are distinguished medidlated and non-meduUated nerve-
fibres. The first, more or less thick, are met with in the nerve-centres, and at
the origin and middle portion of the nerves ; the second are found at the termi-
nation of nerves, and in the great sympathetic.
There are also observed in the nerves of organic
life, elongated elements, designa,ted fibres of Iiemak,grei/
fibres, and nucleated nervous fibres. These are pale,
flattened fibres, with parallel borders, and furnished
with elliptical nuclei. Some authorities consider these
to be bands of connective tissue, and not nerve elements.
The nerve-cells, or corpuscles, are voluminous, and
formed by a mass of protoplasm without any enveloping
membrane, but in the midst of which are numerous
fibrillar. In the ganglia they are covered by a layer of
fibrillar connective tissue, provided with nticlei, which
appear to furnish them with a very thick enveloping
membrane. The nucleus, with one or two nucleoli, is
often surrounded by granules of a brown colour.
The nerve-cells have prolongations or jwles, the
nmnber of which varies from one to five. Cells with
only one prolongation are named unipolar ; those which
have two are bipolar ; and those which have a greater
number are designated multipolar. In Mammalia, one
of these prolongations — nerve prolongation, prolongation
of Deiters — in the spinal cord establishes relations be-
tween a cell and nerve-tube ; the others are of a proto-
plasmic nature, and ramify — these ramifications joining
those of neighbouring cells.
Such are the anatomical elements that enter into the
structure of the nervous system.
In the white substance of the cerebro-spinal axis,
only medullated nerve-tubes of every size are found ; in
the grey substance are tubes, and a more or less con-
siderable number of nerve-cells are situated alons: their course.
NERVE-TUBE.
A, Nerve-tube slightly mag-
nified : a, annular con-
striction ; 6, nucleus of
the interannular segment;
c, axis-cylinder. B, An-
nular constriction and por-
tions of the interannular
sesments highly magnified
(prepared with osmic acid,
which colours the myelin
black) : a', annular con-
striction, or node of Ran-
vier ; h', nucleus of the
interannular segment ; c',
external nucleus of the
sheath.
THE NERVOUS SYSTEM IN GENERAL.
741
To these two elements is added a large quantity of blood-vessels, which are
incomparably more abmidant in the grey than in the white substance. It must
Fig. 409.
MULTIPOLAR OR STELLATE GANGLIONIC NERVE-C^-LL, WITH ONE OP ITS PROLONGATIONS
a, Becoming continuous with the axis-cylinder of a double-coutoured nerve-fibre, 6.
Fig. 411.
Fig. 410.
SEVERAL MULTIPOLAR NERVE-CELLS.
be added that in the grey substance the chief ele-
ments are these ganglionic cells, supported or bound
together by neuroglia, distinct from connective tissue.
In the nerves, the elementary tubes are alone met
with ; they are disposed in long bundles, which are
collected into successively increasing fasciculi. A
cellulo-vascular envelope — the neurilemma (or peri-
neurium)— binds all these fasciculi into a single cord,
and forms a special sheath around each of them.
The details of their organization will be referred to
hereafter.
It is admitted that the ganglionic nerves, or
PYRAMIDAL CELL OF THE GREY
SUBSTANCE OF THE BRAIN
CORTEX.
N, Nucleus; a, a, small ramified
protoplasmic prolongations ;
c, prolongations of the base
of Deiters (bringing the cells
into communication with the
axis-cylinder of the nerve-
fibre).
742
TEE NERVOUS SYSTEM IN GENERAL.
nerves of organic life, possess a greater quantity of slender tubes than the others.
These tubes are commonly designated as the organic nerve-fibres. They also
contain fibres of Remak.
In the spinal ganglia^ the cells are joined to the nerve-tubes. It has been
Fig. 412.
Tig. 413.
MICROSCOPIC GANGLION PROM HEABT
OF FROG.
BIPOLAR GANGLIONIC CELLS AND NERVE-
FIBRES, FROM 6ANGLI0N OF FIFTH PAIB
IN LAMPREY.
shown, by dissection and microscopical observation, that the corpuscles com-
posing the ganglia or expansions at the origin of the nerves, are all attached ta
the superior fibres. The other tubes have none.
In the cerebrospinal axis, the two substances are equally associated, and
Fig. 415.
STELLATE NERVE-CELL, FROM THE NUCLEUS
CERVICIS CORNU (POSTERIOR VESICULAR
column) OF A FCETUS OF SIX MONTHS.
MAGNIFIED 420 DIAMETERS.
STRUCTURE OP GANGLIONIC NERVE-CELL.
A, According to Beale ; B, according to Arnold.
a. Straight fibre ; 6, double spiral fibre ; c,
capsule of connective tissue.
connected with each other by a prolongation (or single pole) which is inflected
in such a manner as to resemble a T or Y (cells with T-shaped fibres), but in a
variable manner, according to the region. In the spinal cord and its prolonga-
tions into the encephalon, the grey substance occupies the interior ; while it is
spread over the exterior of the encephalic lobes, and envelops the white substance.
. THE NERVOUS SYSTEM IN GENERAL. 743
Properties and Functions of the Nervous System.
It would require a long chapter to do justice to this subject, and we could
not venture on it here without going beyond our domain. We will, however,
offer some remarks on those notions connected with the properties and functions
of the nervous system, which are strictly necessary for the comprehension of the
anatomical facts to be hereafter dealt with.
And first as to the properties of the nerves.
"We will suppose the spinal canal to be opened in the lumbar region, and the
cord laid bare in a living animal. If we cut across the inferior roots of one of
the spinal nerves, and compress with a pair of forceps one or more of these roots
by the end remaining attached to the cord, nothing results to denote that this
irritation has had any influence on the organism. But if, instead of operating
on the central or attached end of these divided roots, we excite the peripheral
end which is continued by the trunk of the nerve, contraction of the muscles of
the limb which receives the fibres coming from the irritated roots is produced.
The muscular tissue comports itself as if the irritation were directly applied
to it ; so that the nerve has served as the medium of communication. It has
received the stimulus, it has been excited by it, and it has conducted this to the
muscles to which the nerve is distributed. This double reaction produced by
the nerve-tubes is their special attribute, their essential property. With Vulpian,
we might designate it collectively by the term neurility ,- but it is necessary to
distinguish the two modes it affects, by naming the property of being impressed
by stimuli as the excitahility of the nerve, and nervous conductibility its aptitude
to convey the excitations which have impressed it.
The same experiment may be repeated on the upper roots. It is then per-
ceived that the pinching, which produces no effect at the peripheral extremity,
causes pain when applied to the central end. The animal testifies immediately,
by cries and movements, that it feels the touch of the forceps. But, as will be
mentioned in a moment, the impression resulting from this touch has only been
perceived by the brain ; it has therefore been conducted to the spinal cord by the
stimulated nerve-fibres, and then to the brain by the fibres of this medullary axis.
In putting to one side, for the moment, the part played by the latter in the
phenomenon now analyzed, it will be seen that the superior fibres of the spinal
nerves enjoy the same attributes as the inferior ; neurility is their appanage, and
this property is apparent in its two qualities — excitahility and conductiMlity .
Only here the latter property is exercised in a centripetal sense ; while in the first
instance it acted in a centrifugal sense. But it must not be assumed that these
two conductibilities are essentially distinct. The physiological differences by
which they appear to be distinguished, seem to belong to the difference in the
relations of the nerve-fibres with the organs to which they are distributed. In
one case (that of the centrifugal nprves), the organs of reaction — the muscles —
are placed at the peripheral extremity of the nerves ; in the case of the centripetal
nerves, the organs of reaction — the brain and spinal cord — are found at the
central extremity of the nerve-fibres. This theory of the unity of nervous
conductibiUty has, moreover, been proved to be correct by the researches of
Philipeaux and Vulpian, who have utihzed the experiment of Gluge and Thier-
nesse on the union of the central end of the lingual (centripetal), with the
peripheral end of the hypoglossal nerve (centrifugal) ; and recently by Bert, in
grafting the tail of the Rat into that animal's back.
744 THE NERVOUS SYSTEM IN GENERAL.
It is easy to demonstrate that this double property of conduction belongs to
all the nerve-fibres arising from the cerebro-spinal axis — centripetal conductihility
being peculiar to the superior fibres, and centrifugal conduct ibility to the inferior
ones. It is also demonstrated that this conduction acts in either one sense or
the other, whatever may be the part of the nerves so stimulated ; as the nerve-
tubes possess, throughout their whole length, the property of excitability and
conductihility.
The fibres with centrifugal conductihility are the motor nerves ; those with
centripetal conductihility are the sensitive nerves. But sensibiUty does not exist
only in the filaments of the superior roots ; it has also been remarked in the
lower roots, and these owe it to the filaments which are given off from the roots
with centripetal conductihility, and which return to the nervous centres by the
motor roots. The sensitiveness evinced by these motor roots is named recurrent
sensibiUty. This sensitiveness has also been demonstrated on the peripheral end
of the sensory nerves of the limbs and face (xlrloing and Tripier).
The anatomical and physiological characters of the nerves persist as long as
they are in communication with the centres. If they are divided at any part of
their course, the portion attached to the spinal axis still preserves its properties ;
but that situated beyond the section — the peripheral end, as it is named —
degenerates, and becomes incapable of conducting the sensitive impressions, or
of transmitting the voluntary motor stimuli.
Now as to the spinal cord.
Does the medullary axis, which has apparently, in great part, the structure of
a nerve, possess, like the latter, excitahility and conductihility — those two essential
properties of the peripheral nervous system ?
Excitability is entirely absent in the grey substance. On the surface of a
section of the cord, the slightest, or even the most intense irritation of this por-
tion, produces no reaction. In the white substance, this excitability can only be
easily rendered evident on the surface of the upper bundles or fasciculi, where
it is exquisite. With regard to the always limited reactions observed when the
stimulations are made on the deep part of the fasciculi, it is difficult to say if
they result from the excitability of the spinal cord, or that of the nerve-roots
which traverse the white substance.
Nervous conductihility is certainly one of the attributes of the spinal cord ;
the transmission of stimuli of the sensitive nerves to the brain, and the voluntary
movements that result from stimulation of the motor nerves, demonstrate that
the necessary medium between the nerves and brain — the spinal cord — possesses
conductihility. But the spinal cord may act as a nerve-centre, and the
foUowin^f experiment irrefutably demonstrates it.
I will suppose that an animal has had its spinal cord cut across in the lumbar
region, and I excite, by pinching, one of the superior roots remaining intact on
the caudal portion. The stimulus cannot be conducted to the brain, as this
part is isolated from it ; and yet movements take place in the muscles of the
posterior limbs. Does it happen that, after section of the medulla, the conductive
property of the nerve-fibres which arise superiorly, is interverted and changed
into centrifugal conductihility ? No ; for after the transverse section of these
roots, the irritation of their central end produces exactly the same effects. It
must be, therefore, that the stimulation had first reached the medulla, and was
then transmitted by it to the muscles by means of the centrifugal-current fibres.
And this is really what occurred ; section of the whole of these fibres of the
TEE NERVOUS SYSTEM IN GENERAL. 745
spinal cord hindered the manifestation of all movement in the muscles, when the
superior roots were touched. There is, as has been said, reflexion in the substance
of the cord, on to the inferior roots, from the UTitation due to this pinching ;
the property which permits the medullary axis to act in this manner is named
the reflex power. It may be remarked that, if we suppose for a moment the
superior and inferior nerve-roots to be united in an arch in the substance of
the spinal cord, this reflex property would be nothing more than the nervous con-
ductibility itself operating precisely in the direction special to each kind of nerves.
This union really exists ; only the nerve-roots are not in communication,
except through the medium of the cells in the grey substance, in which the
sensitive is changed into motor excitability.
The reflex power is extinct immediately after death occurs in Mammals,
but it may last for several hours, or even for a day, in a decapitated animal in
which asphyxia has been averted by pulmonary insufflation. The extent of the
movements it determines is in relation to the intensity of the stimulus which is
the primary cause of it ; — merely local when they result from a slight irritation,
these movements may take place in all the muscles of the body after powerful
stimulation.
Let us now inquire into the attributes of the encephalon.
Excitability has been determined in several points of the medulla oblongata,
and in the interior of the cerebellum. Physiologists have long denied it to the
surface of the latter, and to the substance of the cerebral hemispheres ; but
within the last twenty years, Fritsch and Hitzig, Ferrier, Carville and Buret, and
others, have demonstrated that several points of the cerebral and cerebellar cortex
are excitable by electricity. The brain possesses conductibility, because the grey
substance composing it is the receiver of, and the point of departure for, all the
excitations. In fine, the encephalic mass should possess neurility like the nerves,
but this general property is more or less modified. What more particularly dis-
tinguishes the encephalon, is its action as a sensitivo-motor centre ; in it arrive
the stimuli from the sensitive nerves, and there they are felt and considered.
In the brain arise the motor excitations which result in spontaneous voluntary
movements.
In an animal paralyzed by division of the cord at the occipito-atloid articu-
lation, and in which death has been prevented by artificial respiration, observation
demonstrates that sensibility and spontaneous motricity are preserved in the
head, the nerves of which are in direct communication with the brain. Pinch
the upper lip, and the creature testifies by the movements of this part that it feels
pain. Pass the finger to\^ards the eye, and the eyelids are twinkled and closed —
a proof that the animal sees objects, appreciates the distance which separates it
from them, and tries to remove tlie eye from their contact. More striking still,
the animal feels hungry, and endeavours to satisfy this craving by seizing the
food within its reach, and masticating and swallowing it. After this demon-
stration, it is no longer possible to doubt that, if an animal feels, it is by the
brain, and if it wills., it is also by the brain.
But sensibility and volition do not constitute the only attributes of the brain ;
for it is the seat of other manifestations not less interesting — those of the instincts
and inteUigence.
The brain also contains several special motor and sensory centres, the exist-
ence of which modern physiology and pathology have completely established.
These centres are situated in or on the surface of different parts of the organ.
746 TEE NERVOUS SYSTEM IN GENERAL.
To sum up, the nerves possess a single physiological property— nmrt/^.
This is manifested by excitability and by centripetal conductibility in the nerves,
the roots of which are uppermost, centrifugal conductibiliti/ in the nerves with
inferior roots.
The spinal cord is inexcitable in its grey substance, but is excitable on the
surface of its superior fasciculi, and with difficulty so in the remainder of its
white substance. It serves as the organ of transmission between the brain and
the nerve-roots ; and is, in addition, endowed with rejlex power.
The brain is endowed with a special activity, to which is due sensibility^
motUity, and volition, and the manifestations of instinct and intelligence.
It remains to examine the nature of the influence the nervous system exer-
cises on the other apparatuses, through the properties we know it to possess. But
here again we must limit ourselves to principles.
Since Bichat's time, it has been agreed to divide into two great classes those
functions which maintain the life proper of the individual — those of animal life
or relation, and those of organic or vegetative life.
The first, which are exercised with consciousness, comprise the sensorial
functions and voluntary movements ; the latter are induced by the impulsion
originating in the brain, and transmitted to the muscles by the nerve-fibres with
centrifugal conductibility ; the former have for their object the appreciation, by
the brain, of tactile sensations — of heat, light, taste, and smell, by means, or
through the instrumentality, of the nerve-fibres possessed of centripetal con-
ductibility, which transmits to the brain the stimulus developed at their
terminations by these diverse physical agents.
The functions of vegetative life — those which are executed unconsciously, we
may say, in animals, and which are not the result of physio-chemical forces — are
placed under the influence of the reflex power of the spinal cord. For example,
the stomach is empty, and its mucous and muscular membranes remain altogether
passive — there being no contractions in the first, nor secretion of gastric fluid
in the second. Food arrives in its interior, and immediately its activity is
developed ; the muscular tunic executes movements which produce mixture of
the food, and propel it towards the pyloric orifice ; while from the surface of the
mucous membrane is poured an abundant solvent secretion. This change is due
to the stimulus exercised by the alimentary particles on the extremity of the
centripetal nerve-fibres, and which has been transmitted by them to the medullary
axis, there reflected on the centrifugal fibres, and carried by these to the tunics
of the stomach, the special functions of which are thus brought into play.
It is worthy of remark that the properties of the nervous system, which act
in so important a manner on the organs of vegetative life, have no direct influence
on nutrition itself. Destruction of the nerves in a certain region will certainly
derange the nutrition of its tissues, in consequence of the paralysis of the vessels,
but it is not destroyed. There is a very large category of organized beings —
vegetables, for instance — in which nutrition is very active, and in which there
is no nervous system. So that the property which determines the essential
phenomena of nutrition is an attribute of living matter.
TEE CEBEBBO-SPINAL AXIS. 747
SECOND SECTION.
THE CENTRAL AXIS OP THE NERVOUS SYSTEM.
The cerehro-spinal axis is resolved, as we have said, into two principal sections —
the spinal cord and the brain. "We will study these two portions in succession —
the spinal cord first, in order to facilitate description, although that organ only
holds the second place, from a physiological point of view. The protective parts
of these two apparatuses will, however, be examined before we proceed further.
CHAPTER I.
The Enveloping and Protecting Parts of the Cerebro-spinal Axis.
The cerebro-spinal apparatus is lodged, as has been already mentioned, in a bony
case — ^the spinal canal — which is prolonged anteriorly by the cranial cavity ; but
it is protected more immediately by three envelopes, which have received the
names of chari mater, arachnoid, andjsia mater.
The Bony Case containing the Cerebro-spinal Axis.
A knowledge of the bones which enter into the formation of this protective
case cannot be acquired without also knowing the case itself ; so that we dispense
with its special study here. We will allude, however, to the succinct terms already
employed in describing the spijial canal, and in the same spirit of concision will
also describe what has hitherto been deferred — the cranial cavity.
1. The Spinal Canal.
This canal communicates, anteriorly, with the cavity of the cranium. Very
wide at the atlas — to receive the odontoid process, and allow those rotatory move-
ments of the head which prevent the medulla being injured — the spinal canal
suddenly contracts at the axis : it expands again at the end of the cervical and
commencement of the dorsal region, where the medulla presents a greater volume,
and the movements of the spine are very extensive. Towards the middle of the
back, the spinal canal has its smallest diameter ; but on leaving this portion, and
as far as the lumbo-sacral articulation, it widens again ; after which it rapidly
decreases, and altogether disappears towards the fourth or fifth coccygeal ver-
tebra. The lumbo-sacral dilatation coincides with the expansion the cord shows
at this point, and with the enormous volume of the nerves lying beside it.
2. The Cranial Cavity (Figs. 41, 42).
This is a very irregular, ovoid-shaped box, the walls of which are formed by
the frontal, parietal, occipital, ethmoidal, and temporal bones.
It presents for consideration four planes and two extremities.
The superior plane offers on the middle line, and towards its superior third,
the parietal protuberance, the two lateral crests of which concur with that
eminence in dividing the cranial cavity into two compartments : one posterior,
7« THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
destined to contain the cerebellum ; the other anterior, incomparably larger,
lodging the cerebral hemispheres, and divided by the single rudimentary crest
which begins at the falciform process, and joins the crista galli, into two lateral
sections — one for each hemisphere. Hereafter we shall see that the folds of the
dura mater are attached to this parietal protuberance, and to the ridges detached
from it, thus rendering much more perfect the partitioning of the cranial cavity.
On the hiferal planes there is also noticed the division into a cerebellar and
cerebral compartment, due to the lateral crests of the falciform process, which are
prolonged obliquely to near the sphenoid bone ; the first section is formed by the
occipital and the inner face of the petrous bone ; the second by the squamous
portion of the temporal, the frontal, and the great wing of the sphenoid bone.
Both are concave, and marked by digital impressions, as they also are on the
superior plane.
The inferior plane, very irregular, offers from behind forward : 1. On the
middle line, the basilar channel, into which the greater portion of the medulla is
received ; the pituitary fossa, made deeper by a circular fold of the dura mater,
and lodging the gland of that name ; the optic fossa, where the chiasma of the
optic ner\-es is situated. 2. On the sides, the foramen lacerum, partly closed by
cartilaginous substance, and by the dura mater ; the cavernous sinuses and
maxillary fissures, outside which is remarked a deep and wide digital impression
for the reception of the mastoid or inferior lobe of the brain.
The posterior extremity of the cranial cavity shows the occipital foramen, by
means of which this cavity communicates with the spinal canal.
The anterior extremity offers, in the median plane, the crista galli process, or
superior border of the perpendicular plate of the ethmoid bone ; on the sides,
the two ethmoidal f oss« —deep depressions containing the olfactory lobes, and at
the bottom of which is observed the cribriform plate of that bone.
The Envelopes of the Cerebro-spinal Axis.
Preparation. — In order to study the cerebro-spinal axis, the same preparation as for the
spinal cord — to be alluded to hereafter - should be followed. When the centres are freed from
their bony covering, the membranes miiy be incised, dissected, and separated from each other
— the arrangement of the sub-arachnoid spaces being rendered apparent by insuffliition.
The arrangement of the cranial dura mater can be studied by making an antero-posterior
section of the cranium beyond the middle line, and a transverse section in front of the internal
occipital protubprance. On the first is seen the falx cerebri and pituitary fold, and on the second
the tentorium cerebelli.
The three membranes which cover the cerebro-spinal axis, and separate it
from the walls of the bony cavity enclosing it, are thus designated. Generally
termed meninges, and distinguished as external, middle, and infernal meninge,
these membranes are better known as the dura mater, arachnoid, and pia mater
— names which will be employed in our description.
The dura mater, or external meninge, is a strong fibrous membrane in contact
with the walls of the cranium and the spinal canal.
The arachnoid, or middle meninge, is a tunic of a serous nature, which resolves
itself into two layers — an external, applied to the inner face of the dura mater ;
and an internal, spread, through the medium of the pia mater, over the cerebro-
spinal axis, from which it is again separated at a great number of points by a
particular fluid, the suh-aruchnoid (or liqvx)r cerebro-spinalis).
The pia mater, or internal meninge, is the proper envelope of the central
TEE CEREBROSPINAL AXIS. 749
nervous mass ; it is cellulo-vascular, closely adherent to the external surface of
the mass, attached to the visceral layer of the arachnoid by more or less dense
connective tissue, between the meshes of which is the sub-arachnoid fluid.
This arrangement of the cerebro-spinal envelopes permits the cerebro-spinal
axis to be assimilated, to a certain extent, to a viscus, and the bony case contain-
ing them to a splanchnic cavity, the serous membrane of which — the arachnoid
— is covered outside its parietal layer by a fibrous expansion — the dura mater, and
within its visceral layer by a cellulo-vascular tunic— the pia mater, or internal
meninge.
This collective view of the envelopes belonging to the nerve-centres will
now be followed by a special description of each, in which their spinal and cranial
portions will be successively considered, after glancing at them in a general
manner.
1. The Duea Matee.
•
This is the most external and the strongest of the cerebro-spinal envelopes,
and lines the walls of the cerebro-spinal cavity, exactly repeating its shape. It
is, therefore, a second protective covering, which is dilated at its anterior
extremity into an ovoid cavity that lodges the brain, and terminates in a pro-
longed point at the coccygeal vertebrae.
It has two faces — an external, in contact with the walls of the cranium ; and
an internal, adhering in the most intimate manner to the external layer of the
arachnoid.
In several parts of its extent it is traversed by the nerves that proceed from
the cerebro-spinal axis, and by the vessels for this portion of the nervous
Stkuctuee. — The dura mater possesses the texture of all white fibrous mem-
branes. It is composed of parallel longitudinal fasciculi of connective tissue,
mixed with some fine elastic fibres. Bourgelat thought they formed two distinct
layers — an external and internal ; but nowhere is it possible to demonstrate this.
It receives hlood-ve^seh ; the arteries are derived — for the spinal portion, from
the vertebral, intercostals, lumbar, and lateral sacrals ; for the cranial portion,
meningeal ramuscules, such as the ethmoidal branch of the nasal, the spheno-
spinous, and tympanic, mastoideal, and cerebro-spinal arteries. Nerves have been
seen passing to its cranial portion ; these have been divided into anterior, middle,
and posterior. The first are furnished by the ethmoidal filament of the nasal
nerve : the second from the Gasserian ganglion ; and the third, by the ophthal-
mic branch of Willis. The nerves of the spinal portion are very fine and have
no myeline ; at first they accompany the vessels, then leave them to be dis-
tributed in the middle part of the membrane. The existence of lymphatic
vessels has not yet been clearly demonstrated.
Spinal Dura Mater (Theca Vertebkalis, Dura Mater Spinalis). —
This is a very elongated sheath, continuous at the occipital foramen with the
cranial dura mater, and terminated behind by an attenuated point lodged in the
narrow channel which, in the middle coccygeal vertebrae, represents a trace of
the spinal canal. As it is in shape exactly like the latter, its largest diameter is
at the atlas, and at the brachial and lumbo-sacral enlargements of the spinal
cord. Its capacity depends greatly on the volume of the latter, and in some of
its parts it can allow accumulation of the cerebro-spinal fluid ; this is impos-
sible, however, for nearly the whole extent of the cranial region.
50
750 THE CENTRAL AXIS OF TEE NERVOUS SYSTEM.
The external face of the dura mater is very slightly adherent— especially above
— to the walls of the spinal canal ; and it is even separated from them, at the inter-
vertebral spaces, by a certain quantity of adipose tissue which is never absent,
though the animals be ever so emaciated. This face covers, inferiorly, the com-
mon superior ligament, and the veins we have described as spinal sinuses.
(It does not form an endosteum for the vertebrae as it does for the cranial
bones.)
The interrwl face gives attachment, between each pair of nerves, to the
festoons of the dentated membrane, a dependency of the pia mater. It is
rendered smooth and polished by the external layer of the arachnoid, to which it
is so firmly united that it is needless to attempt their separation. Here the
external layer of the arachnoid is reduced to a simple row of cells with flattened
nuclei.
On each side, the substance of this meninge is completely traversed by a
double series of orifices for the passage of the spinal nerves, around which it sends
small special sheaths as far as the intervertebral foramina.
Cranial or Encephalic Dura Mater (Dura Mater Cerebralis). —
This membrane forms a sac which is exactly moulded by its external face to
the cranial parietes, and by its internal face to the surface of the brain. The
latter, therefore, completely fills the cavity of the cranium, a circumstance that
explains why an accumulation of fluid is impossible in this region.
External surface. — It adheres strongly, by cellulo-vascular bands, to the cranial
walls, the undulations on which it follows. This adhesion is not, however, equally
marked everywhere, for on the sides of the roof of the cerebral compartment it
is least intimate, and it is closest on the middle plane of this roof, on the crista
galli, around the parietal protuberance, on its crests, and towards the lateral faces
of the cerebellar compartment at the petrous bones, where the membrane is very
thin.
This face gives rise to a number of prolonged sheaths, corresponding to the
nerves leaving the base of the cranium. The principal are found around the
ethmoidal filaments, the optic nerves, and the two thick branches furnished by
the Gasserian ganglion.
Internal surface. — The internal surface of the cranial dura mater is covered
by the parietal layer of the arachnoid, which is firmly attached to it only in the
spinal region. It sends into the cranial cavity three prolongations, which are
distinguished as the falx cerebri {falx, " a sickle "), tentorium cerebelU {tentorium,
" a tent "), and the pituitary fold. These processes complete the partitioning of
the cranial cavity, isolate the various external bulgings of the encephalic mass,
and protect them from the compression they might exercise on each other.
a. The Falx Cerebri is a vertical middle layer comprised between the two
cerebral hemispheres, and owes its name to its sickle-like form.
Its antero-superior border is adherent and very convex, and corresponds to
the crista galli process, as well as to the median ridge on the inner face of the
frontal and parietal bones. This border is very thick, and hollowed internally
by a prismatic and triangular venous canal — the middle sinus.
Towards its inferior border, which is free and concave, and rests on the
corpus callosum, the falciform process is extremely thin, and cribbled like
lacework.
The posterior extremity, or base of the falx, rests on the parietal protu-
berance.
THE CEREBROSPINAL AXIS. 75l
The anterior extremity advances in a curve to near the optic fossa.
In aged animals, there are sometimes found on the faces of the falx cerebri,
especially towards its posterior extremity, small yellow granulations, known as
the Pacchionian bodies. They are little nuclei of connective tissue that arise
from the sub-arachnoideal tissue ; meningeal granulations would be a better
designation than that of glands, which is sometimes given to them.
b. The Tentorium Gerebelli is composed of two lateral layers, which form a
transverse partition between the cerebellum and the posterior extremities of the
cerebral lobes.
Each layer, coursed internally by one of the transverse sinuses, ofifers : an
adherent convex border, attached to the parieto-temporal crest ; a free concave
border, turned inwards and a little forwards, remarkable for its thickness and
solidity, and, with the second lamina, circumscribing an oval opening through
which the medulla oblongata passes ; a superior extremity, attached to the parietal
protuberance ; an inferior extremity, which disappears above the Gasserian
ganglion, near the fold that surrounds the pituitary gland.
Of the two faces of these layers, the anterior corresponds to the cerebral lobes,
the posterior to the cerebellum.
c. The supra-sphenoidal or pituitary fold, is a thick, slightly salient, and
almost circular pad, channeled internally by the cavernous sinus, and circum-
scribing the sella Turcica by enveloping the pituitary gland laterally and posteriorly.
2. The Arachnoid Membrane.
The arachnoid has the same arrangement as all the splanchnic serous
membranes, in being composed of two layers — a parietal and a visceral, both
constituting a perfectly closed sac, outside of which the cerebro-spinal axis is
contained. The cavity of this sac is traversed by the roots of nerves, the vessels
of the brain and cord, and filaments and cellular layers which pass from the pia
mater to the dura mater ; around all these its layers form sheaths, by becoming
continuous with one another.
Each of these layers exhibits an adherent and a free face. The adherent
face of the parietal layer is attached, as we have already seen, to the dura mater.
That of the visceral layer covers the nervous axis, in spreading itself over the
pia mater, but without accompanying it into the convolutions of the central
mass ; it is beneath this face of the visceral layer that the cerebro-spinal (or
sub-arachnoid) fluid is confined in spaces which will be studied hereafter. By
their free face, which is smooth and moist, like that of all serous membranes, the
arachnoid layers are in contact with each other.
Structure. — The structure of this membrane resembles that of all others of
the same nature. The meshes of elastic fibres are most abundant in the cranial
portion. Everywhere the parietal layer is only composed of a single layer of
epithehum. The arachnoid has no proper vessels or nerves ; those which pass
through it only accompany each other.
Spinal Arachnoid Membrane. — The parietal layer presents nothing of
interest. The visceral layer is separated from the spinal cord, throughout its
extent, by a somewhat considerable space (the sub-arachnsid), in which the
sub-arachnoid fluid is collected ; this space is greatest posteriorly, around the
terminal extremity of the cord and the nerves of the cauda equina.
The adherent face of this membrane is only connected with the external
surface of the spinal cord by thin filaments detached from the pia mater.
752 THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
Cranial or Encephalic Arachnoid.— There is nothing special to note in
the iiarietal Jayer.
If the visceral layer be traced from the occipital foramen— where it is
continuous with the spinal arachnoid— to the anterior extremity of the cerebral
lobes, it is seen to be prolonged infer iorly on the lower face of the medulla
oblongata, as far as the pituitary stem, to which it furnishes a covering : the
pituitary gland itseK is not covered by the arachnoid, except on a portion of the
superior or deep face ; from the medulla oblongata it is carried forward, and
extends on each side of the cerebellum and cerebral lobes. Superiorly, this
internal layer spreads over the surface of the cerebellum, and is reflected at the
bottom of the fissure between that organ and the cerebral hemispheres, over the
posterior extremity of the latter, enveloping them separately by descending into
the interlobular fissure as far as the corpus callosum. Reaching the anterior
extremity of the cerebrum, it gains the olfactory lobes, is principally prolonged
on their super o-posteri or face, and doubles around the ganglion of grey substance
on their inferior face, to be continued with the parietal layer.
In covering the external sm-face of the brain, the cranial arachnoid does not
adhere everywhere to the nurve substance, but is only slightly connected with it,
through the medium of the pia mater, at such salient points as the summits of
the cerebral convolutions. Neither does it dip down to enter the sulci existing
between these parts, but passes over them, and in this way forms a large number
of sub-arachnoid spaces {epi-cerehral spaces) analogous to that developed over the
whole extent of the spinal cord.
These spaces, which are filled by the sub-arachnoid fluid, differ widely in
form and dimensions. In Man, three principal have been described, and these
are also found in animals ; Magendie has named them the confluents of the sub-
arachnoid fluid. Of these three confluents, the antwior is situated in advance of
the chiasma of the optic nerves, between the two cerebral lobes : the inferior,
the largest, is comprised between the pituitary stem and the pons Varolii to the
surface of the peduncles of the cerebrum ; while the third, or posterior confluent,
lies behind the cerebellum, at the calamus scriptorius.
None of these spaces communicate with the internal cavities of the brain,
and, consequently, the sub-arachnoid fluid cannot enter them. Magendie has
nevertheless described a communication between the posterior confluent and the
ventricle o^ the cerebellum ; though the opening he described towards the
calamus scriptorius has not been found in the Horse by Renault, and we may
affirm, with Lavocat, that it does not exist in the other animals.
The Sub-arachnoid Fluid. — The fluid contained in the sub-arachnoid
spaces is slightly yellow or colourless, and perfectly limpid and transparent.
Some authorities assert that it is secreted by the visceral layer of the arachnoid,
and others by the pia mater. According to the remark made by Cruveilhier, the
nerve-centres are immersed in it, like a foetus in the liquor amnii ; and this
remark, which is particularly applicable to the spinal cord, gives the key to the
use of this fluid, which keeps the organ away from the walls of the spinal canal,
deprives it of the greater part of its weight (Foltz), and thus diminishes every
kind of injury to which it might be exposed— whether from without (concussion),
or within (intermittent afllux of blood) — in a word, the cerebro-spinal fluid
constantly maintains an equilibrium in pressure around the central nervous axis.
(This fluid, so necessary for the support and protection of the cord and brain,
is alkaline, and contains but a small quantity of albumen ; it varies in quantity.
THE CEREBROSPINAL AXIS. 753
according to the relative size of the cerebro-spinal axis and its containing cavity,
or with the amount of blood sent to this region. By affording, under all
circumstances, an equable pressure on the brain and spinal cord, and the nerves
emanating from these, its importance as a hydrostatic agent is greatly enhanced.)
3. The Pia Mater.
The pia mater — the proper envelope of the cerebro-spinal axis — is a thin
membrane, the framework of which, essentially connective tissue, sustains on its
external face a very abundant network of blood-vessels and nerves.
Applied immediately to the surface of the brain and spinal cord, it adheres
firmly to that surface and follows all its inequalities — penetrating between the
cerebral or cerebellar convolutions, and forming in each intermediate sulcus two
layers that lie against each other.
The external face of the pia mater, bathed in part of its extent by the sub-
arachnoid fluid, adheres to the visceral layer of the arachnoid by means of a
more or less dense and close connective tissue. From it arise the cellular
coverings that constitute the neurilemma of the nerves. It detaches a multitude
of filamentous and lamellar prolongations to the internal face of the dura mater,
which traverse the arachnoid cavity in the same manner as the nerves and
vessels, by being enveloped, like these, in a sheath furnished by the arachnoid
membrane. Always very short, these prolongations resemble the adhesions
between the two layers of that membrane.
The internal face is attached to the nerve substance by multitudes of arterial
and venous radicles or connective filaments, which leave the pia mater to plunge
into that substance.
The vessels of the pia mater form a very close network, from which are
detached branches that reach the medulla oblongata and brain. They are
accompanied by nerve-filaments, and are surrounded hj perivascular canals, which
are now believed to be lymphatics. Certainly, in their interior a colourless fluid
circulates, which contains lymph-corpuscles.
Spinal Pia Mater. — Less vascular than the cranial pia mater, with which
it is continuous towards the medulla oblongata, this membrane is remarkable for
the arrangement of the prolongations that arise from its two faces.
The internal prolongations form longitudinal layers at the fissures of the cord,
and enter these fissures.
The external prolongations attach, as we have said, the pia mater to the
external meninge. A very large number are filamentous in form, and are
dispersed over the superior and inferior surfaces of the cord. Others constitute,
on each side of the organ, a festooned band named the dentated ligament
{ligamentum denticulatum or dentata). These ligaments exist throughout the
entire length of the spinal cord, between the superior and inferior nerve-
roots : their inner border is confounded for its whole length with the pia mater ;
and their outer margin, cut into festoons, attaches itself to the dura mater by
the summit of the angles separating these festoons.
To complete this description of the spinal pia mater, there may be noticed
a posterior or coccygeal 2)rolongation {filum termijiale) — a very narrow process
formed by this membrane at the posterior extremity of the cord, situated in the
midst of the cauda equina nerves, and attached to the bottom of the conical
cul-de-sac at the termination of the dura mater.
(This ligament, or memhrana dentata, serves to maintain the position of the
754 THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
spinal cord in its hydrostatic bed, and so prevents the nerves proceeding from
it being dragged during flexion of the spine.)
Cranial or Encephalic Pia Mater. — The vascular element predominates
in this portion of the internal meninge.
This membrane sends scarcely any prolongations to the dura mater, except
at the medulla oblongata, though it projects remarkably large ones into the
cerebral mass and the sides of the cerebellum. The description of the velum
interpositum, and the cerebral and cerebellar plexus choroides, belongs to the brain.
(The pia mater is extremely vascular on the surface of the cerebrum, and
forms remarkable anastomosing loops in the intermediate spaces of the conr
volutions, which chiefly supply the grey substance. It is the nutrient membrane
of the brain and spinal cord. Its nerves accompany its arterial branches, and are
minute filaments from the sympathetic.)
"Differential Characters in the Enveloping and Protective Parts of the Cerebro-
spinal Axis in the Other Animals.
The bony space that protects the spinal cord and brain does not present any noteworthy
diflferences in the domesticated animals, and the subject has been already sufficiently studied
in the osteology of the head and vertebral column.
With regard to the meninges, their number and general disposition are nearly the same in
all the species. In the Sheep, however, the cranial dura mater appears to be absent, or is
only represented by a mere thickening in which is the middle sinus ; the falx cerebri is only
indicated towards its two extremities. The vestige of this septum is more developed in the Goat.
Comparison of the Enveloping and Protective Parts of the Cerebro-Spinal
Axis of Man with those of Animals.
There is nothing particular to be said respecting the cranial cavity and spinal canal, nor
yet the arachnoid and pia mater. The dura mater has tlie folds described in Solipeds, and,
in addition, a falx cerehelli, that extends from the tentorium of the same name to near the
foramen magnum. The meningeal granulations, or Pacchionian glands, are nearly constant
in aged individuals, and their volume is sometimes so considerable, that by compression they
thin away, and even perforate, the cranial bones at corresponding points.
CHAPTER II.
THE SPINAL CORD.
Preparation. — Isolate the cranium and vertebral column from all the other parts of the
body ; open the spinal canal and the cranial cavity by their superior surface, as in Fig. 416,
by, raising with a chisel (or rogne-pied — the farrier's " toe-knife ") and hammer, the roof of the
skull and annular portion of all the vertebrae. The organ may tlien be studied in situ in its
bony case, and surrounded by its membrane; afterwards extract the whole spinal cord
enclosed in the dura mater, and open up the latter along the course of the cord, so as to
completely expose that portion of the nervous system.
On a cord hardened by water to which a tenth part of nitric acid has been added, the
arrangement and distribution of the grey and white matter may be studied; the different
cords composing it may be also more or less exactly separated.
(The saw and farrier's pincers, or spine ratchet, will be found useful auxiliaries in the
tedious and delicate operation of exposing the brain and cord, and particularly in laying open
the cranial cavity. An easy mode of obtaining access to the spinal canal and its contents, is
to saw through the laminae of the vertebrae on each side, at the roots of the transverse processes,
and raise the arches with the chisel or toe-knife.)
ExTEENAL Conformation of the Spinal Cord.
General view. — The spinal cord is that portion of the nervous centres which
occupies the spinal canal. It is a thick, white, and irregularly cylindrical cord,
TEE SPINAL CORD.
7M
756 THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
commencing at the occipital foramen, where it continues the medulla oblongata,
and terminating in a point at the upper third of the sacral canal, or a little
beyond that, giving off at each side, during its course, the superior and inferior
roots of the spinal nerves.
Weight. — In medium-sized animals, the weight of the cord is represented by
the following approximate numbers : for the Horse, 10^ ounces ; the Ass, 5i
ounces ; Cow, 7| ounces ; Sheep and Goat, If ounces ; Pig, 2^ ounces ; Dog, li
ounces ; Cat, 4^ drams ; and Rabbit, 3i drams.
Shape and volume. — The spinal cord is slightly flattened above and below,
throughout its whole length ; in whatever part we examine a transverse section
of it, we shall always find the lateral diameter greater than the vertical, and that
this section appears regularly elliptical.
The flattening is more marked in the lumbar than in any other region.
Its volume is far from being uniform. In following it from before to behind,
we at first remark that it presents the same dimensions to the fifth cervical
vertebra, and that between this point and the second dorsal vertebra it forms
an oblong enlargement, designated the brachial cei'rical e}ilargement (or bulb).
Beyond this, it assumes its original volume, and even becomes gradually smaller
than in the cervical region. Towards the middle of the loins, it again enlarges
to constitute the lumbar enlargement (or bulb), which extends to the entrance of
the sacral canal. After this dilatation comes a conical prolongation (conus
meduUaris), the point of wliich represents the terminal extremity of the cord.
If we compare the diameter of this cord with that of the spinal canal, we shall
observe, as has been already said, that the capacity of the containing cavity
is generally related to the volume of its contents, and that the former is, as a
rule, most capacious at the cervical and lumbar enlargements. It will even be
noticed that the dilatation the spinal canal offers at these two points, is relatively
more considerable than the increase in volume of the cord. This is because the
mobility of the spine, which is very great in these two regions, requires this
difference to secure the spinal axis from injury during the movements executed
by the vertebral column. This protective combination is also found elsewhere —
at the atlas, for example, where we know motion is considerable ; and throughout
the entire extent of the cervical region, which in this respect greatly exceeds the
dorsal region.
Means of fixture. — The cord is relatively fixed in its envelopes by : 1. Its
continuity with the brain. 2. The coccygeal ligament. 3. The dentated
ligaments.
E.tternal surface of the cord. — Covered by the pia mater, this surface presents
an extremely simple disposition. On its superior and inferior planes, at each
side, we remark the double series of sensitive and motor roots of the spinal
nerves, which are implanted in the same longitudinal line to right and left of
the middle plane, and are collected in fasciculi opposite the intervertebral
foramina.
In the middle line, and throughout the entire length of the cord, there are
two deep and narrow fissures : one superior {fissura longitudinaUs superior), the
other inferior {fissura longitudinaUs infei'ior), into which the pia mater enters.
Four other fissures have been described at the point of emergence of the nerve-
roots, by the names of suferior and inferior collateral fissures (or sulci) ; but the
two superior alone exist, and even these are often scarcely noticeable, being
rather indicated by the origin of the nerve-roots.
TUE SPINAL COED.
757
Inteenal Conformation and Structure of the Spinal Cord.
In making a transverse section of any portion of the cord, we may convince
ourselves that it has an internal cavity. This central canal is elliptical, and
lined by a simple layer of columnar ciliated epithelium, resting on a thin con-
nective membrane — the ependymis of Virchow. (The cilia of these cells are only
to be seen in early life ; in advanced age the canal may be closed, the cells then
becoming much altered in form from pressure. The canal is immediately sur-
rounded by spongy horny matter.) This section also shows the two median
fissures mentioned in describing the exterior of the cord, the inferior of which is
wider and deeper than the superior, the situation of the latter being scarcely
perceptible.
These two fissures lie one before the other, and do not meet so as to com-
pletely divide the cord into two lateral halves, but remain separated by two
thin horizontal and superposed bands
of nerve matter, that pass from one
end to the other of the medullary axis.
The inferior, formed of white sub-
stance, corresponds to the bottom of
the inferior fissure ; while the superior,
composed of grey matter, meets the
superior fissure.
These bands are named the white
and grey commissures of the spinal cord
(Figs. 418, 419, 420).
Notwithstanding the presence of
these two commissures between the
lateral halves of the spinal axis, these
latter do not the less constitute two
symmetrical systems, the structure of
which will now be studied.
Each medullary cord represents a
semi-cylinder of white substance, in the
centre of which is a mass of grey matter,
that varies somewhat in quantity in
different regions, but the arrangement of which is everywhere the same. Thus,
inwardly, this grey matter joins the grey commissure ; above, it sends off a thin
prolongation that traverses the substance of the medullary cord {superior grey
cornu), to reach the bottom of the superior collateral fissure ; below, it gives rise
to an analogous, though a thicker and a more irregular, prolongation (inferior
grey cornu), which is directed well in front of the inferior roots, but does not
reach the surface of the cord. In consequence of this arrangement, the grey
substance of the cord forms altogether a kind of capital H, the horizontal
branch of which is perforated in the middle by the central canal.
This arrangement of the grey substance causes the white matter to be
divided, in each lateral moiety of the spinal axis, into three cords or secondary
columns ; the superior of these is perfectly isolated, and is comprised between
the middle superior fissure and the origin of the sensitive roots ; another, the
inferior, united to that of the opposite side by the white commissure, is limited,
inwardly, by the inferior median fissure, and outwardly by the line of origin of
SECTION OF THE SPINAL CORD OF THE HORSE
AT THE LUMBAR REGION. MAGNIFIED TWO
DIAMETERS.
1, Superior median fissure ; 2, infei-ior median
fissure ; 3, 3, superior collateral fissures ; 4, 4,
inferior ditto ; 5, grey commissure ; 6, white
commissure , 7, 7, superior grey cornua; 8, 8,
inferior grey cornua , 9, central canal.
758
THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
the motor nerve-roots ; while a third — the lateral or intermediate — thicker than
the others, is confounded supei-ficially with the inferior, and formed by all that
portion of the cord situated between the lines of origin of the superior and
COAi-
TRANSVERSE SECTION OF THE SPINAL CORD IN THE LUMBAR REGION. (AFTER DEITERS.)
.a., Inferior root ; R.p., superior root ; R.i.p., internal portion of the superior root ; C.p., superior
commissure ; C.a.a., inferior commissure ; C.c, central canal. The network of myeline fibres
in the grey substance, as well as those in the infei'ior grey commissure, are not indicated.
inferior roots. Of these three columns, the first is sensory
which in reaUty are only one — are not.^
the other two-
' The existence of so-called " systematic lesions " in Man has led anthropotomists to dis-
tinguish, iu the white substance of the cord, a great number of regions. Thus, the innermost
portion of the anterior column (inferior in animals) is designated Tiirck's fasciculus ; the corre-
sponding portion of the posterior column (superior) in tiie cervical region is GolVs column ; the
lateral column is rigorously limited by the grey cornua ; while the regions around these latter
are named the anterior and posterior radicular zones.
In adhering to the facts of normal anatomy, it must be admitted that some of these dis-
tinctions are in great part artificial. Nevertheless, there are found on the limits of certain
THE SPINAL CORD.
759
Steucture. — Independently of the epithelium mentioned when describing
the ependymis, neuroglia, nerve-fibres, nerve-cells, and vessels enter into the
structure of the spinal cord.
The neuroglia has been compared to a kind of sponge (the so-called spongy
matter), in the spaces of which are the other elements of the cord. It exists in
the white and the grey matters, but it is more abundant in the superior grey
cornua than in the inferior cornua. It surrounds the upper extremity of the
former, in becdning softer and more transparent, and is here designated the
gelatinom substance of Rolando (substantia gelatinoso Rolandi). It constitutes,
TRANSVERSE SECTION OF SPINAL CORD THROUGH THE MIDDLE OF THE I,UMBAR REGION, SHOWING
ON THE RIGHT SIDE THE COURSE OF THE NERVE-ROOTS, AND ON THE LEFT THE POSITION OF
THE PRINCIPAL TRACTS OF VESICULAR MATTER.
A, A, Inferior columns ; p, p, superior columns ; L, L, lateral columns ; a, inferior median fissure ;
p, superior median fissure; 6, 6, 6, h, inferior roots of spinal nerves; c, c, superior roots;
d, d, tracts of vesicular matter in superior column ; e, tracts of vesicular matter in inferior column
/, central canal ; g, substantia gelatinosa.
in great part, the grey commissure, and can be deeply stained by the carminate
of ammonia.
The neuroglia is associated with a small quantity of connective tissue, which
enters the cord along with the vessels. It is formed of a mass of cells, the mem-
regions either a depression on the surface of the cord, or on its substance a fasciculus of
connective tissue, or a vessel larger than in other points.
The systematic lesions of the cord not having yet been observed in the domestic animals, it
cannot be stated at what point the distinctions established in the human spinal cord are justified,
so far as that of the Horse is concerned. In some sections of the cord of that animal, it would
appear that the fasciculus of Tiirck is distinct from the other parts of the anterior column ;
but in a great number the separation is extremely vague. The columns of Goll alone are very
distinct in the superior portion of the cervical region. They are especially visible in the Dog.
In fact, at the present time the topography of the human spinal cord cannot be without
uncertainty when applied to that of animals ; but the efforts of pathologists and anatomists
should be directed to dissipating this uncertainty.
760
THE CENTRAL AXIS OF THE NEBVOUH SYSTEM.
TEK SPINAL CORD.
761
branous bodies of which, irregularly stellate, send
numerous prolongations between the nerve-tubes
and cells.
(In the substantia gelatinosa on the superior
surface of the cord is a network of fine fibrils,
epithelial in its nature, and consisting of cuticiilar
matter ; this is known as the granular matter,
or spongy horn-substance.)
The fibres and cells form, with the neuroglia,
the whole of the grey substance.
The cells have a more or less large number
of protoplasmic prolongations which ramify and
anastomose, or have a process — the prolongation
of Deiters — which puts them in communication
with a nerve-tube. They are more or less
voluminous.
The fibres of the grey substance are all very
fine, and some have a sheath of myeline ; the
others are reduced to an axile filament.
In the Horse, the cells are not universally
distributed throughout this substance, but are
collected in small masses Avhich form longitudinal
columns. The largest are grouped in three small
masses around the inferior cornu — one external,
another internal, and the third at the extremity ;
the latter is the most considerable. They are
in relation with the motor roots of the nerves.
Some are spread in the middle part of the
grey substance, and principally opposite the point
where the grey commissure joins the cornua.
There they form Lochhart Clarke''s column.
A small number are placed on the margin
of the superior grey cornu, and these, as well as
the cells of Clarke's column, receive radicular
filaments from the spinal sensory nerves.
Finally, some form an external column
{column of Burdach) at the junction of the two
cornua, whence emerges, above, the small nerve
of Wrisberg. They are probably connected with
the vaso-motor phenomena.
The nerve-tubes (or tubules) affect longi-
tudinal, transversal, oblique, and vertical direc-
tions. They bring the cells of one lateral moiety
of the medulla into communication with : 1.
The tubes of the white substance which pass
towards the brain. 2. Each other. 3. The cells
of the opposite moiety, by passing into the com-
missures. 4. The tubes of the white substance
of the opposite moiety, by following the same
course.
Fig. 422.
LONGITUDINAL SECTION THROUGH
CERVICAL ENLARGEMENT OF SPINAL
CORD OF CAT.
AC, Inferior white columns ; Ac', por-
tion showins the arrangement of
the longitudinal fibres ; PC, pos-
terior white columns ; G, grey sub-
stance between them (the vesicles
being omitted to avoid obscuring
the course of the fibres); A, anterior
roots of the nerves ; p, posterior
roots, consisting of three kinds :
the first, a, crossing the posterior
columns horizontally, and then
passing obliquely downwards,
across the grey substance, into the
anterior columus ; the second, 6,
traversing the posterior columns
horizontally, and then losing them-
selves in the grey substance ; the
third, c, for the most part becoming
continuous with the longitudinal
fibres of the posterior column ; all,
or ne:irly all, ultimately entering
the grey substance.
762 TEE CENTRAL AXIS OF THE NERVOUS SYSTEM.
The neuroglia and nerve-tuhes constitute the ivhite substance, which Is
arranged, as we know, into three columns at least. All the tubes of this sub-
stance do not ascend to the brain, as was believed for a long time ; the opinion
that the tubes of the spinal nerves formed the medulla and extended to the brain,
has been abandoned since Volkmann measured, comparatively, the section of all
these nerves and that of the nervous spinal-axis.
The tubes or fibres of the white substance have not always the same com-
position, nor the same size. Many have no enveloping membrane, and those
which possess one have not a nucleus ; so that it is difficult to regard this as a
true sheath of Schwann. Certain anatomists, however, consider them to be so,
but without the constriction (Ranvier) ; while others admit that they are so
provided, like the elements of the nerves (Tourneur and Legoff ).
These tubes are thick in the inferior columns, and uniformly smaller in the
superior ones. A mixture of fine and thick tubes is observed in the lateral
columns, but the finest are always generally towards the grey substance.^
(Volkmann has established the fact, that the size of the medulla corresponds
with the number of nerve-tubes given off at any point. He gives the weight of
four segments, each 2f inches in length, from the spinal cord of the Horse, and
the relative extent of the grey matter in square lines ; these are as follows : —
Area
Area
of grey
of white
Grains.
matter.
matter.
rom below 2nd spinal nerve, 219 .
. . 13 .
. 109
„ 8th „ „ 293 .
. . 28 .
. 142
„ „ 19th „ „ 163 .
. . 11 .
89
„ 30th „ „ 281 .
. . 25 .
. 121)
In the white substance the tubes are longitudinal, oblique, or transversal ;
the latter arise from the cells of the grey substance, and form the roots of the
nerves emerging either by the superior or inferior collateral fissure.
The tubes of the inferior columns pass to the cells of the grey substance, or
reach the brain by remaining in the corresponding moiety of the cord — the
fibres of the right half of the medulla gaining the brain without passing into
the left half. Those of the lateral columns decussate, each sending to, and
receiving from, the other, tubes which cross in the white commissure. The
superior columns contain fibres that extend directly to the brain ; these are
sensorial. There are also found transverse fibres that enter the cells of the
superior grey cornua, and others that pass into the cells of the inferior or motor
cornua.
Such is, in a few words, the arrangement of the nerve-elements in the spinal
cord. The subject is a very long and complicated one, which cannot be dealt
with in a more detailed manner in an elementary work on descriptive anatomy.
Vessels. — In the spinal cord the grey is richer in vessels than the white sub-
stance. The capillary networks are finer in the former than the latter, and chiefly
in the vicinity of the nerve-cells.
Arterial blood entere the cord by three orders of vessels : 1. The median
arteries, which pass into the inferior and superior middle fissures. 2. The radi-
cular arteries, which follow the roots of the spinal nerves. 3. The peripheral
arteries, which arise from the vascular ramifications of the pia mater (Duret).
The vessel which furnishes these divisions is the middle spinal artery.
' There is a tendency now to the belief that these slender tubes serve for the conveyance
of sensory impressions. An alteration in tliem is coincident with deranged sensibility.
THE BRAIN. 763
The veins are proportionately large. Two are lodged in the grey commissm-e ;
and a third, which is voluminous, lies in the middle superior fissure.
All the vessels arc accompanied by the slender nerves disposed in plexuses
issuing with the communicating veins, or the superior radicles which they follow
into the substance of the cord.
In the cord there are perivascular lymph spaces^ which probably open into the
deep layer of the pia mater.
Differential Chaeacters in the Spinal Cord of the otoee Animals.
In all the species, the white aud grey substances affect the disposition above described ;
only some slight differences in the reciprocal volume of each have been remarked. As in the
Horse, the spinal cord does not extend beyond the sacral region. Its length has no relation to
that of the coccygeal region, as certain anatomists would, in principle, establish ; in the Rabbit,
for example, the tail of which is very short, the spinal cord is prolonged into the coccygeal
Tertebrse.
Comparison of the Spinal Cord of Man with that op Animals.
The spinal cord of achilt Man does not reach beyond the first lumbar vertebra, though in
the foetus it is in the coccyx. It is rounder than in the Horse, and the grey substance is,
relative to the white, more abundant than in the spinal cord of the domesticated animals. The
posterior grey cornua are also larger and less elongated, than the superior cornua in the Horse ;
and the roots of the nerves are also more voluminous than in that animal.
No nerve-cells are found in the posterior coiuua, and Clarke's column is limited to the
dorsal region; so that the sensitive nerves of the back and loins arise in the dorsal region.
The nerves of the cervical region arise from a series of nuclei arranged in the medulla
oblongata.
CHAPTER III.
THE BRAIN, OR ENCEPHALON.
Article I. — The Brain as a Whole.
The hrain is that portion of the nervous system which is lodged in the cranial
cavity. It succeeds, without any line of demarcation, the spinal cord, of which
it may be considered, with regard to its figure, as a kind of efflorescence.
General form and composition. — In shape it is an ovoid mass, elongated from
before to behind, and very slightly depressed above and below.
When it is viewed on its superior face (Fig. 423), we first see, behind, a white
pedicle — the prolongation of the spinal cord — and a single lobe of a grey colour
designated the cerebellum. In front of this is remarked two other lobes, separated
from the first by a deep transverse fissure, into which the tentorium cerebelli
passes. Isolated from one another on the middle line by a shallower fissure, these
two lobes constitute the brain, and are usually named the cerebral hemispheres.
In turning over the brain to examined its inferior face, we see that the posterior
peduncle of the organ — a continuation of the spinal cord — is prolonged beneath
the cerebellum, which is joined to the lateral parts of its superior face ; this por-
tion then enters the cerebral hemispheres by their inferior face, behind two thick
white cords — the optic nei-ves — which mark the anterior limit of this prolongation
(Fig. 424). This is the isthmus of the brain — ^a name given to it because it
764
THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
actually forms an intermediate bond between the three enlargements which form
the principal mass of the organ.
The cranial portion of the central nervous mass is, then, composed of three
Fig. 423.
BRAIN OF THE HORSE (UPPER SURFACE). THREE-FOURTHS THE NATURAL SIZE.
1, Great longitudinal or inter-hemispherical fissure; 2, 2, crucial fissure; 3, 3, fissure of Rolando;
4, 4, its anterior branch ; 5, 5, its posterior branch ; 6, 6, plaits of the ascending frontal convolu-
tion ; 7, 7, the two plaits of the external parieto-occipital convolution ; 8, 8, internal parieto-
occipital convolution; 9, 9, first frontal convolution; 10, 10, second frontal convolution; 11, 11,
sigmoid gyrus, often concealed by the annectent gyrus of 12, which joins the ascending frontal convo-
lution of the second frontal ; 13, lobule of the curved plait ; 14, 14, annectent gyrus uniting the two
parietal convolutions to the sigmoid gyrus, and through it to the frontal convolutions, o, 0,
Olfactory bulbs; B, medulla oblongata; c", middle lobe of the cerebellum; c*, lateral lobes of
ditto.
apparatuses : the isthmus of the brain — a prolongation of the spinal cord ; and the
cerebellum and cerebrum — bulbous lobes grafted on the superior face and anterior
extremity of this peduncle. These three divisions are very well seen in their
THE BRAIN, OB ENCEPRALON. 765
entirety and reciprocal relations in Fig. 424. "We will study them separately and
in succession.
Volume of the brain. — Contrary to what is found in the spinal cord, the
dimensions of the brain closely represent those of the cavity containing them :
the visceral layer of the arachnoid lying everywhere immediately on the proper
envelope of the nervous mass — the pia mater — except at the sub-arachnoid spaces ;
and, on the other hand, the arachnoid cavity can scarcely be said to exist while
the dura mater is, as it were, glued to the cranial walls, and in reality constitutes
their internal periosteum.
The brain has, therefore, no room to move in its receptacle, but is maintained
in it in an almost absolutely immovable condition, which coincides exactly with
that of the sutures or cranial articulations.
Weight. — The total weight of the brain, in average-sized animals, may be
inferred from the following figures : Horse, 22 oz. 15 drams ; Ass, 12 oz. 11
drams ; Ox, 16 oz. 15 drams ; Sheep and Goat, 4 oz. 9^ drams ; Pig, 5 oz. 10
drams ; Dog, 6 oz. 5i drams ; Cat, 1 oz. 1 dram ; Rabbit, 5i drams.
Cornevin has remarked that the cranial capacity, if not the weight of the
brain, is greater in the female than in the male of the domestic species and breeds
of animals.
In comparing these figures with those of the spinal cord, it will be seen that
the relative weight of the latter to that of the encephalic mass differs notably in
the several animals, being highest in the Dog, and lowest in the Rabbit. The
relations in each species, between the two divisions of the nervous system, are the
following : Dog, 1 : 5-14 ; Cat, 1 : 3-75 ; Sheep and Goat, 1 : 2'60 ; Ass, 1 :
2-40 ; Pig, 1 : 2-30 ; Horse, 1 : 2-27 ; Ox, 1 : 2-18 ; Rabbit, 1 : 2. We give
these numbers, as it has always been attempted to establish, in the predominance
of the brain, the cause of the development of intelligence, and that the best
measure of this predominance is really the relation of the spinal cord to the brain.
It has also been attempted to measure this predominance of the brain by compar-
ing its weight with that of the entire body ; but it is sufficient to cast one's eye
over the tables drawn up with this view in several anatomical and physiological
works, to be convinced that this basis does not possess all the value desirable.
Preparation of the train. — To study the brain, it is necessary to extract it from its bony
receptacle ; a result achieved in two ways. The first consists in opening tlie roof of the
cranium by hammer and chisel, after removing from its exterior all the parts covering it, or
which are in its vicinity. The dura mater is then excised with scissors, and the brain, which is
thus directly reached, is completely isolated by raising its posterior extremity, and cutting from
behind to before all the nerves passing through the foramina at the base of the cianium, with
the pituitary stem, as well as the extremity of the olfactory bulbs. This method is very ex-
peditious, but it sacrifices the pituitary gland, which remains firmly embedded in the sella
Turcica — an inconvenience we obviate by resorting to the second procedure. In this, the
cranium is opened by its base or floor, after separating tiie head from the trunk, cutting away
the lower jaw. tongue, and os hyoides. and excising all the soft parts so as to expose the bony
surfaces. The head, thus prepared, is held by an assistant, the roof of the cranium resting
on a table or block. Armed with a chisel and hammer, the operator first removes the
zygomatic arches and the styloid processes of the occipital bone, then the condyles of this bone,
the basilar processes, and the sphenoid, palatine, and ethmoid bones, returning to the lateral
portions of the cranium, which are chiselled away in succession from the occipital to the eth-
moid bones. The brain, being suflBciently exposed, is relieved from its dura mater as in the
first method, and raised in the left hand to destroy, by means of scissors held in the right hand,
the attachments which yet fix it to the cranial roof, and which are chiefly the veins that open
into the sinuses of the dura mater. In afterwards excavating the ethmoidal fossae with the
point of a scalpel, the olfactory bulbs are detached and the mass is free. This procedure
51
766 TEE CENTRAL AXIS OF TEE NERVOUS SYSTEM
is more diflScnlt than the first, bnt possesses several advantages over it; for not only do we
preserve the pituitary gland, but have the ethmoidal lobes more intact, and may also have,
if desired, the ganglia of the cranial nerves, with a more or less considerable portion of the
nerves themselves.
After indicating the methods for extracting the brain from its bony case, we ought to say
some words as to tlie course to be pursued in order to study it successfully. To do this it is
advantageous to have two brains ; one of these should be hardened by steeping it for some
weeks in alcoliol (or methylated spirit), or in water to which has been added a tenth part of
nitric acid. This hardening contracts the nerve substance, and causes the cavities and reliefs
to appear more manifest. (It is a good plan to place the brain, base uppermost, in a suitable
vessel, and if a piece of cloth be spread beneath it, its removal therefrom will subsequently be
greatly facilitated.)
We commence by examining rapidly the whole apparatus, and pass immediately to the study
of the isthmus, of which it is necessary to have at first a well-defined idea. We therefore take
a hardened specimen, and isolate this portion of the brain in the manner represented in Fig.
425 ; to do this, it suffices to cut through tlie peduncles of tbe cerebellum, and excise the cere-
bral liemispheres upwards and backwards; the remains of these and the cerebellum should be
preserved for an analysis of their structure. The isthmus thus isolated is fitted for an examina-
tion of its external conformation and its internal cavities — the ventricle of the optic layers and
the aqueduct of Sylvius — into which we may penetrate by a superior longitudinal incision.
After the isthmus, the cerebellum is to be studied — in its external conformation — on an
intact specimen ; and in its internal conformation and structure on the incised piece.
We terminate with the cerebrum, the superficies of which is soon examined ; its interior
should be studied in the following manner: It is necessary to begin by demonstrating the
. existence of ventricles in the olfactory lobes, and their communication with all the other in-
ternal cavities of the brain, which can easily be done by the inflation of one of these organs by
means of a straw (or dissecting-case tube), which raises the pituitary gland, the cerebrallobes
and the cerebellum. Tiien we pass to the corpus callosum, which is exposed, as in Fig. 434,
by a horizontal section of the hemispheres across the centrum ovale. The corpus callosum of
each side is afterwards excised in the middle line to reach the interior of the lateral ventricles,
and this great commissure of the brain ought, after studying the septum lucidum, to be cut
across in the middle and turned over, as in Fig. 435, so as to show the fornix. The foramen
of Monro is next examined; then the corpus striatum, hippocampi, taenia semicircularJB,
choroid plexus, and velum interpositum. which are exposed by the ablation of the hippocampi
and fornix Lastly, we return to the foramen of Monro to study its communication with the
ventricle of the (jptic thalanii ; it will be well, also, to again examine the latter, as well as the
aqueduct of Sylvius and the ventricle of the cerebellum, which we arrive at in dividing
that organ through the middle and separating the halves.
Two longitudinal and vertical sections, one median (Fig. 428), the other at the side (Fig.
431), will not be without utility in the study of these particulars. They may be made by
means of a saw, the brain remaining enclosed in the cranial cavity.
(A useful implement I have employed for removing the bony casing of the brain without
risk of injuring the latter, is a chisel with a thin cutting edge which is slightly concave, the
corners being smooth and rounded, and projecting beyond the cutting edge.)
The brain may be preserved for an indefinite time when it has undergone the following
preparation : 1. Place it for from twelve to fifteen days in a solution of nitric acid (10 to 100).
2. Then leave it for a week in a solution of bichromate of potassium (20 to 1000). 3. Afterwards
sleep it for three or four days in alcohol at 40° 4. Take it from the alcohol, allow the latter
to evaporate, then put it in a paraffin bath for from ten to fifteen minutes, not allowing it to boil.
5. Withdraw it from the paraffin and allow it to dry. After this series of preparations the
brain shrivels, but it preserves its shape, and will not putrefy.
Article II. — The Isthmus (or Medulla Oblongata).
We will study in succession the external and internal conformation of this
part, and its structure.
External Conformation of the Isthmus.
The isthmus, or medulla oblongata, is a prismatic prolongation of the spinal
cord supporting the cerebellum, and terminating in the cerebral hemispheres ;
TEE ISTHMUS. 767
it increases in size from behind to before, and may be considered as having
ioxiT faces and ttvo extremities.
The inferior face (Fig. 424), on which we can distinctly, and without any
preparation, perceive the natural limits of the isthmus, is crossed nearly in its
middle by a thick fasciculus of arciform fibres, which constitute the annular pro-
tuberance {protulerantia annularis), pons Varolii, or mesocephalon (or nodus
encephali). All the portion lying behind this fasciculus belongs to the medulla
oblongata. That in front forms the cerebral peduncles {crura cerebri).
The superior face (Fig. 425), covered by the cerebellum and the posterior
extremity of the cerebral lobes, is more mammillated than the preceding. Passing
from behind to before — on the superior face of the medulla oblongata — there is
remarked the section of the peduncles of the ce^-ebellum, the vcdve of Vieussens, the
corpora quadrigemina, and the thalami optici.
The lateral faces (Fig. 426), concealed in their anterior part by the hemi-
spheres of the brain, exhibit the profile of the medulla oblongata, pons Varolii,
peduncles of the cerebellum (crura cerebelli), cerebral peduncles (crura cerebri),
corpora quadrigemina, and thalami optici.
The posterior extremity of the isthmus belongs to the spinal bulb, and
continues the spinal cord, from which it is only distinguished artificially.
The anterior extremity is enveloped below, and on each side, by the oblique
fasciculi which form the two optic nerves, and beneath which are insinuated the
fibres of the isthmus before they pass into those parts of the cerebral hemispheres
which bear the name of corpora striata.
After this enumeration of all the parts which constitute the isthmus of the
brain, we will examine them in detail, and in the following order : 1. Medulla
oblongata. 2. Po7is Varolii. 3. Crura cerebri. 4. Crura cerebelli. 5. Valve
of Vieussens. 6. Corpora quadrigemi?ia. 7. Thalami optici. After these we
will describe the pineal and pituitary glands — small appended lob^s placed, one on
the superior, the other on the inferior face of the isthmus.^
1. Medulla Oblongata (Figs. 424, 425, 426).
The medulla oblongata constitutes the posterior portion of the encephalic
isthmus ; it succeeds the spinal cord, and extends forward as far as the pons
Varolii. It is a thick peduncle of a white colour, wider before than behind, flat-
tened above and below, and having four faces — an inferior, superior, and two lateral.
Inferior face (Fig. 424). — This face rests in the channel of the basilar process.
Convex from side to side, and limited anteriorly by a transverse fissure which
separates it from the pons Varolii, posteriorly it does not offer anything to
distinguish it from the spinal cord.
' There is far from being any agreement ms to the number of parts which ought to compose
the encephalic isthmus, some authorities making more, some less. The limits of this small
apparatus will, nevertlieless, be found perfectly circumscribed if it be examined in the lower
animals, and particularly in the Horse. An antero-posterior section of the brain, made to one
side of the middle line, appears to us all that is needed to definitely settle the point. This
section, seen in Fig. 428, shows in the clearest manner that the encephalic prolongation of the
spinal axis extends to the corpora striata, and that it comprises the medulla oblongata, pons
Varolii, cerebral and cerebellar peduncles (or crura), the corpora quadrifremina. and the thalami
optici. All these, then, belong to one and the same system— the medullary prolongation, which
serves as a bond of union between the three principal masses of the brain, and which we havu
designated the isthmus. It may be added, that this manner of considering the encephalic
isthmus perfectly agrees with the teachings of physiology.
768
THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
On the middle line there is a well-marked fissure — a continuation of the
inferior fissure of the cord — which lies between two very elongated prominences
that are sometimes but Uttle apparent, and which, from their form, are named
the corpora pyramidalia (Fig. 424, p, p). The base of these pyramids touches
Fig. 424.
GENERAL VIEW OF THE HOESE'S BRAIN (INFERIOR FACE).
B, Medulla oblongata; p, p, pyramids of ditto. 1, Internal root of the spinal accessory nerve; 2,
external roots of ditto ; 2', roots of the pneumogastric nerve ; 3, root of the auditory nerve ; 4, root
of the facial nerve ; 5, sixth nerve ; 6, root of the fifth nerve ; 6', 6", motor and sensory roots of
the fifth nerve. P.c, P.c, crura cerebri. 7, Third nerve ; 8, optic commissure ; 10, fissure of
Sylvius; 11, pituitary gland ; 12, extra-venti'icgilar nucleus of the corpus striatum ; 13, external
root of the olfactory bulb; 14, internal root of ditto; 15, olfactory bulb; 16, 16, grey nuclei
from which proceed the olfactory nerves ; 17, lateral lobe of the cerebellum ; 18, temporal lobe
of the brain ; 19, first temporal convolution ; 20, lobule of the curved plait ; 21, gyrus rectus ;
22, frontal lobe (antero-external face).
the pons Varolii, and their apex is insensibly lost, posteriorly, on reaching the
spinal cord.
Outwardly is an almost plane surface, bordered anteriorly by a transveree
band (Fig. 330) which lies immediately behind the pons Varolii ; sometimes it is
covered for the greater part of its extent by a very thin expansion of arciform
THE ISTHMUS. 769
/ibres, between the anterior border of which and the transverse band — and
particularly in pieces that have been hardened by alcohol or acidulated water — is
seen a slight oblong prominence which corresponds to what in Man is designated
the corpus oUvare} This is isolated from the pyramid by a longitudinal groove,
whence emerge, in front, the roots of the sixth cranial pair, and behind, those of
the twelfth pair ; outwardly, it is limited and separated from the restiform body
by the origin of the majority of the roots belonging to the glosso-pharyngeal and
pneumogastric nerves.
Superior face. — Covered by the cerebellum, it is channeled in its middle by an
excavation (Fig. 424, 5), which constitutes the floor of the fourth ventricle.
This cavity is prolonged forward above the pons Varolii, between the crura
cerebelli, and from its forming an angle behind, resembling the point of a pen,
it has been named the calamus scriptorius?
Two thick cords, prolongations of the superior fasciculi of the medulla
spinalis, border the calamus scriptorius on each side ; these are designated the
corpora restiformia.^ Lying together at their posterior extremities, they separate
anteriorly, so as to represent the branches of a V (Fig. 425, 1).
Lateral faces. — Much narrower than the other two, and showing two thick
borders, these faces give the profile of the corpora restiformia (Fig. 426, 2),
corpora pyramidalia (4), and the fasciculus between these two.
2. The Pons Varolii (Figs. 425 ; 426, 5).
TliQpons Varolii — also named the tuber annulare, or mesocephalon — is- that part
of the brain which stands out prominently across the isthmus, between the
medulla oblongata and the crura cerebri, and which is lodged in the anterior
depression of the basilar process.
It is a semicircular band of white transverse fibres thrown across, like a
bridge, from one side to the other of the cerebellum. It has two faces. The
superior face is adherent to the fasciculi of the medulla oblongata, which is
prolonged to form the crura cerebri.^ The infeiior face is in every sense convex,
wider in its middle than in its lateral portions, and crossed from behind to before
by a shallow median groove for the basilar artery. It offers for consideration
two borders and two extremities.
The posterior border, sUghtly convex, is separated from the medulla oblongata
by a slight groove.
* This prominence corresponds to the corpus olivare of Man only in its position, as it has
not its structure ; for the former has a grey nucleus in its substance, which is divided into two
email masses, the superior of whicli is found in Ruminants.
* In the bulbar portion of the calamus gcriptarius, are seen the diversely coloured prominences
which correspond to the origin or course oi' some cranial nerves. These are— viewing them
from behind to before, and within to without, commencing at the middle fissure — the internal
white alu, corresponding to the nucleus of the hypoglossal nerve; the grey ala, corresponding
to the nuclei of the pneumogastric, spinal, and glosso-pharyngeal nerves ; the external white
ala, situated above the auditory nucleus; lastly, the eminentia teres, placed between the
middle fissure and the crura cerebelli, lodging the bend in the root of the facial nerve.
The point of the calamus scriptorius is covered by a small white layer extending from one
border to the other, named the holt, flie cavity beneath this being designnted the ventricle of
Arantius, at the bottom of which is usually seen the opening of the central canal of the spinal cord.
* The posterior pyramids are formed by the bulbar prolongation of the grey column of the
epinal cord ; they pass to the right and left, and disappear towards the posterior crura cerebelli ;
they expand near the summit of the calamus scriptorius, and at this point possess very great
excitability.
* Some authorities carry the superior face of the pons to the floor of the fourth ventricle.
THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
The anterior border — also convex, but indented in its middle — largely overhangs
the crura cerebri, which are limited on this side by a well-marked fissure.
The extremities are bent upwards to enter the substance of the cerebellum, in
the form of tAVo thick cords, which constitute the middle crura cerebelli (Fig.
425, 6). They exhibit the apparent origin of the trifacial nerves.
The pons Varolii does not exist in Birds.
Kig. 425.
3. The Crura Cerebri (Figs. 425,
426).
These are two very large white fasci-
culi, visible at the inferior surface and
sides of the isthmus, covered superiorly
by the corpora quadrigemina and thalami
optici, and continuous — above the pons
Varolii — with the fibres of the medulla
oblongata ; while their anterior extremi-
ties enter the cerebral hemispheres.
These peduncles are separated from
each other by a middle fissure — the inter-
pedunndar — which bifurcates in front to
circumscribe the fisiform tubei'de {corpus
albicans, hidhi fornicis) — a small, single,
and rounded elevation of a white colour
like the peduncles, covered by the
pituitary gland (Fig. 423, 4), the root
of which is represented by the tuber
cinereum, and which is situated in front
of this body (see Description of the pitui-
tary gland on p. 773).^
Behind, the crura cerebri are limited
by the anterior border of the pons
Varolii. In front, they are circumscribed
by the optic nerves, which pass ob-
liquely around their anterior extremity
and join on the middle line before the
tuber cireneum, to form a commissure
called the chiasma (or commissure) of the
optic nerves (Fig. 424, 8). On the sides,
their tissue is confounded with that of
the corpora quadrigemina and thalami
optici, which are superposed on the crura
cerebri. It may be remarked that the
part of their lateral face situated below
• The inferior fHce of the crura cerebri offer some more interesting details. Tlius, behind
the corpus albicans is a triangular space— ^/se interpedunmlar perforated layer (locust perforatus
posticus, pons Tarini) pierced by a large number of openings for the posterior group of arterioles
given off from the circle of Willis. On each crus is seen, near the middle line, a longitudinal
fissure from which issues the nerve of the third pair ; outside tliis is another groove that
separates a fasciculus of white fibres from a mammilated surface of a grey colour. There are
also observed some fasciculi of transverse fibres which proceed from the band of Reil. The
crura cerebri represent two stages, separated by a mass of grey substance named the locus niger.
SUPERIOR VIEW OF THE ENCEPHALIC ISTHMUS.
1, 1, Corpora restiformia ; 2, section of the
middle cerebellar peduncle ; 3, section of the
posterior cerebellar peduncle ; 4, anterior
cerebellar peduncle ; 5, floor of the postt^rior
ventricle ; 6, valve of Vieussens ; 7, 7, tuber-
cula testes ; 8, 8, tubercula nates ; 9, 9,
thalami optici; 10, corpus geniculatuin in-
ternum; il, corpus geniculatum externum;
12, corpus striatum ; 13, taenia semicircularis;
14, pineal gland; 15, its peduncle; 16, com-
mon anterior opening ; 17, 17, anterior pillars
of the trigonum or fornix ; 18, trifacial
nerve; 19, facial nerve; 20, auditory nerve;
21, glosso-pharyngeal nerve ; 22, pneumo-
gastric nerve ; 23, spinal nerve.
TEE ISTHMUS. 771
the tubercula testes, forms a well-defined triangular space, designated the band of
Eeil, lateral triangular fasciculus, and lateral oblique fasciculus of the isthmus.
4. The Crura Cerebelli.
The cerebellum is attached to the upper face of the isthmus, by two short and
thick lateral funiculi of white substance, between which is comprised the posterior
ventricle ; these constitute the crura cerebelli.
Three distinct fasciculi enter into the composition of each of these cords — an
anterior, a posterior, and a middle.
The latter, or middle cerebellar peduncle (crus cerebelli ad pontem), is the
largest of the three. It is formed by the prolongation of the extremities of the
pons Varolii (Figs. 425, 2 ; 426, 6).
The posterior cerebellar peduncle (crus ad medullam oblongatum) — the most
slender— is formed by the restiform body, one portion of which is reflected below
the posterior root of the auditory nerve to reach the substance of the cerebellum.
It is closely united to the preceding, from which it is with difficulty distinguished
(Fig. 425, 3).
The anterior cerebellar peduncle {processus e cerebello ad testes) (Fig. 425, 4) is
a fasciculus very distinct from the other two, related by its inner border to
the middle peduncle, which it obliquely crosses, loses itself in the cerebellum by
its supero-posterior extremity, arriving behind the testes, and passing beneath
these small organs by its antero-inferior extremity, along with the band of Reil
or supero-lateral fasciculus of the cerebral peduncles.
In studying the structure of the cerebellum, we will see how these peduncles
comport themselves in its interior.
5. Valve of Vieussens (Fig. 425, 6).
This designation is given to a very thin, white layer which unites, on each
side, the two anterior cerebellar peduncles. In shape it is nearly a parallelogram.
Its superior face is covered by the cerebellum ; the inferior concurs in forming
the roof of the cerebellar {fourth) ventricle. The two lateral borders are joined
to the peduncles which this valve unites ; the anterior is attached behind the testes ;
while the posterior adheres to the anterior vermiform process {linguetta laminosa)
of the cerebellum.
Gall has considered this layer as a commissure of the anterior cerebellar
peduncles, and we think rightly ; for we see it formed almost exclusively of
transverse fibres which run from one of these peduncles to the other. These
fibres are most apparent in front, where the membrane is much thicker ; behind,
they are mixed with some longitudinal fasciculi.
6. Corpora Quadrigemina or Bigemina (Figs. 425, 7, 8 ; 426, 8, 9).
These are four round eminences, placed in pairs, which surmount the cerebral
peduncles behind. The two posterior, the smallest, are also named the tubercula
testes, and the anterior pair the tubercida nates.
The posterior corpora quadrigemina, or tubercula testes, are related, in front,
to the anterior eminences ; behind, to the anterior cerebellar peduncles and the
valve of Vieussens, from which they are separated by a transverse groove, at
the bottom of which arise the pathetici nerves. An oblique band unites them,
772 TEE CENTRAL AXIS OF TEE NERVOUS ST8TEM.
outwardly, to that portion of the optic layer named the corpus geniculatum
internum ; while they limit, externally, the bands of Reil.
The anterior corpora quadrigemina, or tubercula nates, are distinguished from
the preceding not only by their larger volume, but by their colour, which is grey,
that of the testes being white. They are also rounder, nearer each other, and
covered by the cerebral hemispheres ; while the posterior rather lie beneath the
cerebellum. A curved groove isolates them, in front, from the thalami optici.
7. Thalami Optici (Fig. 425, 9).
This name is given to that part of the upper face of the isthmus which is
situated in front of the corpora quadrigemina. These thalami are, therefore,
placed above the anterior part of the cerebral peduncles.
Larger altogether than the corpora quadrigemina — and more so before than
behind— each exhibits a grey, slightly convex, and very irregularly quadrilateral
surface, covered by the velum interpositum, which separates it from the cornu
Ammonis {pes hippocampi), and from the posterior pillars of the fornix, beneath
which they are placed.
Imvardlij, they incline towards each other in forming on the middle line
a somewhat deep fissure, in which runs, from before to behind, two white
longitudinal bands that will be noticed hereafter as the anterior peduncles of the
pineal gland. This fissure enters, behind, the common posterior opening {foramen
commune posterius) ; in front, into the common anterior opening {forammi commune
anterius) — orifices which will be described with the interior of the isthmus.
Outwardly, each thalamus opticus shows two prominences called the corpora
geniculata, from which arise the second pair of nerves ; placed one before the
other, the posterior nearer the middle line than the anterior, these two projections
are distinguished as external and internal. The corpus geniculatum externum is
• always more voluminous, better defined, and situated on a more elevated plane
than the corpus geniculatum internum, which is united to the posterior corpora
quadrigemina by an oblique band (Figs. 425 ; 426, 10, 11).
Behind, the thalami optici appear to be notched to receive the nates, which
they slightly enclose.
In front, they are separated from the coi-pus striatum by a groove, at the
bottom of which is a narrow strip named the semicircular band {taenia semi-
circularis).
8. Pineal Gland, or Conarium (Epiphysis Cerebri) ^ (Fig. 425, 14).
This name has been given to a small tubercle of a reddish-brown colour, in
the form of a pine-cone, enveloped by a duplicature of pia mater from the velum
interpositum, with its apex upwards, and its base resting on the common
posterior opening {foramen of Monro), which it closes, and around which it is
attached by a circular ridge.
From this lamella is detached, in front, two fibrous cords — the anterior
peduncles of the conarium (or habence). These (Fig. 425, 15) are two narrow
' This organ, and the next to be described, do not really belong to the isthmus system, but
rather — as has been already mentioned — to the appended glands which should receive separate
description. The first is probably the vestige of a rudimentary eye, the second that of a
lymphatic gland. (It appears to be now conclusively established that the pineal body is the
representative of an ancestral form of eye — most clearly demonstrated in certain lizards.)
THE ISTHMUS. 773
white bands, which commence at the base of the pineal gland, and are directed
forward parallel to each other, in the bottom of the fissure of the thalami optici,
to which they firmly adhere. On arriving at the anterior common opening, they
become attached to the anterior pillars of the crura of the fornix. Sometimes
they are very narrow, and separated by an interval ; but more frequently they are
relatively wide, and immediately in contact on the median line.
The conarium is far from always offering the same volume ; it has been
shown in its usual dimensions in Fig. 425, and in Fig. 429 it is shown as
incomparably larger.
The tissue of the pineal gland is greyish in colour, and coiii-ains more or less
numerous calcareous granules. In the midst of its connective tissue are vesicles
Fig. 426.
LATERAL VIEW OF THE ISTHMUS.
1, Medulla oblongata; 2, corpus rectiforrae ; 3, lateral fasciculi of the medulla oblongata ; 4, inferior
fasciculus, or corpus pyramidale; 5, pons Varolii; 6, middle peduncle of the cerebellum; 7,
cerebral peduncle (crus cerebri); 8, testis; 9, natis ; 10, corpus geniculatum intesnum ; 11,
corpus geniculatum externum; 12, optic nerve; 13, fourth nerve resting on the band of Reil ;
14, sensitive root of the trigeminal nerve; 15, its motor root; 16, facial nerve; 17, auditory
nerve.
filled with polyhedral cells ; it is in the centre of these vesicles that are found — in
old animals — mineral concretions (brain sand — acervuJus cerebri). Many anatomists
consider this body a vascular gland ; while others regard it as a nervous organ,
which has relations with the brain through the medium of its anterior peduncles.
9. Pituitary Gland (Figs. 424, 11 ; 429, 19).
The pituitary gland — also named the hypophysis cerebri and supra-sphmioidal
appendage — is a small disc-shaped tubercle, fixed to the anterior extremity of
the interpeduncular fissure by the pituitary stem {infundibulum) and the tub&r
a. The tuber cinereum is a little eminence of a grey colour, situated in the
middle line, between the corpus albicans and the chiasma of the optic nerves, at
the anterior limit of the isthmus. This eminence is hollow, and its cavity is
nothing more than a diverticulum of the middle ventricle.
774 THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
h. The infimdihulum is only a short conical prolongation, with its base attached
to the tuber cinereum, and its apex to the superior face of the pituitary gland.
The cavity of the tuber cinereum is continued into the infundibulum, and termi-
nates in a cul-de-sac towards its summit. This prolongation, also formed of grey
substance, is distinguished by its great fragility ; so that it requires some care to
preserve it intact when opening the cranium at its base.
c. The pituitary gland is lodged in the sella Turcica, where it is enveloped by
the supra-sphenoidal duplicature of dura mater. It is a small, nearly circular
body, flattened above and below, and more or less thick, according to the subjects.
Its inferior f me rests on the sphenoid bone through the medium of the dura
mater, to which it is strongly adherent ; the nqjerior covers the corpus albicans,
with a portion of the cerebral peduncles, and in front receives the insertion of
the pituitary stem. Its circumference is related to the supra-sphenoidal duplicature,
the interior of which forms the cavernous sinus.
There is no cavity in the pituitary gland.
The matter composing it is yellow in the anterior half of the organ, and
brown in its posterior portion. Its structure resembles that of the supra-renal
capsules, and there is a tendency to regard it as a lymphatic organ (though it
has been surmised that it may have a function in connection with the blood-
supply to the brain).
Internal Conformation of the Isthmus (Figs. 427, 428).
The isthmus is hollowed at the thalami optici by a central cavity, named the
middle (or thvrcV) ventrich, which is extended backwards beneath the corpora
quadrigemina by a canal — the aqueduct of Sylvius ; this opens, below the valve
of Vieussens, into the posterior (or fourth) ventricle — another cavity comprised
between the cerebellum and medulla oblongata. These three diverticuli will be
studied in succession.
1. Third or Middle Ventricle, or Ventricle of the Thalami Optici
(Fig. 429, 13).
The middle ventricle is an irregular cavity, elongated from behind to before,
depressed on each side, and offering for study two ivalls, a floor, a roof and two
extremities.
The two walls are smooth, nearly plane, or very slightly concave from above
to below.
The floor is extremely narrow, and only forms a channel, the bottom of which
corresponds to the interpeduncular fissure — which is nearer in front than behind—
and to the corpus albicans and tuber cinereum. The cavity of the latter (Fig.
429, 20), prolonged into the pituitary stem, communicates with the middle
ventricle, and assists in its formation.
The roof, as narrow as the floor, and, like it, nothing but a channel, is con-
stituted by the two thalami optici, which are joined to one another above the
ventricle, forming a thick grey commissure (Fig. 429, 16). It is terminated at
its extremities by the two orifices already noted as the posterior and anterior
common foramina. The posterior common foramen (Fig. 429, 15) commences
behind the grey commissure, and terminates at the base of the pineal gland by
an irregularly expanded cid-de-sac. It is Hmited behind by the posterior tvhite
THE ISTHMUS.
775
commissure — a thin fasciculus of transverse fibres placed in advance of the corpora
quadrigemina, above the entrance to the aqueduct of Sylvius (or iter a tertio ad
quartum ventrindum), the extremities of which are lost in the substance of the
thalami optici (Fig. 427, 9). The anterior common foramen, also designated the
foramen of Monro (and iter ad infundibulum) (Fig. 429, 14), is the medium of
communication between the middle and lateral ventricles, and affords a passage
to the vascular cord which unites the two choroid plexuses. It is pierced in
front of the grey commissure, beneath the summit of the fornix, the two pillars
of which concur to circumscribe it, and between which is seen the anterior ivhite
commissure. This is a small band of white transverse fibres, analogous to that
which constitutes the posterior commissure, but thicker, and passing in front of
the anterior pillars of the fornix, its extremities entering and becoming lost in
the corpus striatum on each side.
The posterior extremity of the middle ventricle — narrower than the anterior,
and placed on a more elevated
plane— is continuous with the aque- F'i? ■iS?
duct of Sylvius, the entrance of
which (Fig. 427, 10) is beneath the
posterior commissure, towards the
common foramen.
The anterior extremity, more
dilated than the posterior, is situ-
ated immediately above the optic
chiasma, and is only separated from
the bottom of the great interlobular
fissure of the brain by a small and
very thin grey lamina attached to
that chiasma, and for this reason
named by writers the grey root of
the optic nerves. This lamina
(lamina cinerea) is readily seen when
the optic commissure is turned back
on the pituitary gland ; it is suf-
ficient to traverse this to enter the
middle ventricle.
The ependymis, which forms the
wall of the central canal of the
spinal cord, also lines the walls of
this cavity ; through the aqueduct of Sylvius, it is prolonged into the posterior
(or fourth) ventricle ; by the foramen of Monro it passes into the lateral
ventricles, and thence into the spaces in the middle of the olfactory lobes.
TRANSVERSE SECTION OF THE BRAIN AT THE
POSTERIOR COMMON FORAMEN.
White substance of the hemisphere, or centrum
ovale of Vieussens ; 2, 2, grey substance forming
the external layer of the convolutions; 3, section
of the corpus callosum ; 4, 4, interior of the lateral
ventricles ; 5, section of the great vena Galeni ;
6, 6, cerebral peduncles ; 7, 7, section of the
isthmus ; 8, posterior common foramen ; 9, pos-
terior white commissure ; 10, entrance to the
aqueduct of Sylvius.
2. Aqueduct of Sylvius (Fig. 429, 6).
This is a longitudinal median canal, passing beneath the corpora quadrige-
mina, and above the crura cerebri.
It is prismatic in shape ; its anterior extremity communicates with the
middle ventricle, and the posterior opens below the valve of Vieussens into the
fourth ventricle.
776
THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
3. The Posterior or Cerebellar Ventricle (Fig. 429, 5).
This ventricle^ (or sinus rhomboidalis), situated beneath the cerebuUum,
between its peduncles, and above the medulla oblongata and pons Varolii, is a
cavity elongated from before to behind, and ahnost entirely occupied by the
vermiform processes.
Its superior ivall is formed by these two processes, the valve of Vieussens,
and that of Renault. The inferior, or floor of the cavity, is represented by the
depression on the upper face of the medulla oblongata, and which is prolonged
in front, above the pons Varolii, to near the testes.^
The anterior extremity communicates with the aqueduct of Sylvius. The
posterior occupies the summit of the calamus scriptorius.
Structure of the Isthmus.
The isthmus, being only a prolongation of the spinal cord, ought to resemble
it in its structure ; and this is, in
Fig. 428.
fact, what is observed, particularly
in its posterior part, the common
features in their organization, how-
ever, disappearing as we approach its
anterior extremity.
We will follow the distribution of
the white and grey substance in the
isthmus.
The white substance includes the
longitudinal tvhite fibres, as well as the
transverse white fibres. Among the
first may be mentioned the infero-
lateral columns. These decussate at
the neck of the medulla oblongata, in
DISSECTION OF THE MEDULLA OBLONGATA, SHOW-
ING THE CONNECTION OF ITS SEVERAL FASCI-
CULI, OR STRANDS.
A, Corpus striatum ; B, thalamus opticus ; C, D,
corpora quadrigemina ; E, commissure connecting
them with the cerebellum ; F, corpora resti-
formia ; P, P, pons Varolii ; st, st, sensory tract ;
mt, mt, motor tract ; g, olivary tract ; p, pyra-
midal tract ; og, olivary ganglion ; op, optic
nerve ; 3m, root of third pair (motor) ; 5s, sen-
sory root of the fifth pair.
successive layers ; afterwards they
pass along the inferior middle fissure,
where they constitute the motor por-
tion of the pyrafnids of the medulla
oblongata, and, traversing the pons
Varolii, they then form the upper
stage of the crura cerebri, finally
entering the corpora striata.
The posterior columns also decus-
sate a little in front of the antero-lateral columns. When this intercrossing of
fibres has terminated, they form the deep or sensitive portion of the pyramids, pass
beyond the pons Varolii, constitute the upper stage of the crura cerebri, and pass
into the substance of the thalami optici.
With regard to the inferior columns of the spinal cord, they do not decussate
on entering the isthmus, but they are displaced by the infero-lateral. We then
find them in the centre of the medulla, beneath the grey substance in the floor of
' As the cerebellum concurs in the formation of this cavity, it would perhaps be better to
defer its study until that organ has been described.
* For the features of this region, see the description of the upper face of tiie medulla
oblongata.
THE ISTHMUS. ITl
the fourth ventricle. After passing through the pons Varolii and the upper stage
of the crura cerebri, they enter the thalami optici.
To the longitudinal fibres which continue those of the spinal cord, must be
added the fibres of the corpora restiformia and those of the anterior cerebellar
The corpora restiformia proceed from the cerebellum, of which they form the
posterior peduncles, and go to be lost on the surface or in the mass of the
medulla oblongata, under the surface of the white transverse tractus.
The anterior cerebellar peduncles descend from the cerebellum, approach the
middle line, concur in the formation of the upper stage of the crura cerebri, and
terminate in the thalami optici.
To this important system of white longitudinal fibres — a prolongation of those
of the spinal cord — are found annexed as complimentary elements in the organi-
zation of the isthmus, several systems of transverse fibres and masses of grey
substance. The following is a summary account of the arrangement of these
new elements.
In proceeding from behind to before, we notice, among the white transverse
fibres —
1. The expansion of arciform fibres which sometimes covers the inferior face
of the medulla oblongata (Fig. 456,/) : their superior extremity is lost on the
corpus restiforme ; the inferior passes into the intermediate fissure of the pyramid
and the lateral fasciculus. It is derived from the column of GoU (Fere).
2. The proper fibres of the pons Varolii : they constitute a very thick semi-
circular fasciculus, the extremities of which form the middle cerebellar peduncles
and enter the cerebellum. A portion of this fasciculus envelops, inferiorly and
laterally, the longitudinal fibres of the isthmus ; the other passes between the
two portions of the anterior pyramids.
3. The transverse fibres of the valve of Vieussens and those of the white
commissure, which have been already noticed.
The grey substance of the isthmus, which now remains to be mentioned, is far
from being so abundant as the white substance, and — as in the spinal cord — it is
principally situated deeply in the substance of the organ — at least in the greater
number of points.
If the grey matter of the cord is traced into the medulla oblongata, it will be
found that it undergoes modifications in its distribution, with regard to the course
and displacement of the columns of fibres. The inferior cornua are divided into
two portions, in consequence of the decussation of the infra-lateral columns. Their
bases are spread along the middle fissure on the floor of the fourth ventricle,
where they form the fiuclei of the cranial motor nerves. The heads, carried
backwards and outwards, constitute the motor nuclei of the mixed cranial nerves.
The superior cornua are also divided into two portions on entering the medulla
oblongata, by the decussation of the superior columns. The base, which accom-
panies the central canal of the spinal cord, is spread on the floor of the fourth
ventricle, and forms — to the outer side of the nuclei of the motor nerves — the grey
mass known as the sensitive nuclei of the mixed cranial nerves. The head is
abruptly thrown outwards, and constitutes the sensitive nucleus — the origin of
the large branch of the trigemini.
To these grey formations must be added the masses alien to the spinal cord.
We mention : the pyramided nuclei, which occupy the inner border of the
pyramids ; the olivary nuclei, that are found in other than Soliped animals ; the
778 THE CENTRAL AXIS OF TEE NERVOUS SYSTEM.
small protuberential masses, disseminated between tlie transverse fibres of this
region ; and the locus niger — a grey mass that separates the two stages of the
crura cerebri. Finally, there is a small mass of this grey substance which con-
stitutes each of the corpora quadrigemini, and which is covered by a thin pellicle
of white matter, scarcely visible in the anterior eminences.
The fhalami optici is a similar mass, though more volummous, darker coloured,
and without a layer of white substance on its superficial face.
Lastly, nerve-cells exist between the various layers of transverse fibres of the
pons Varolii, and between the tubes which constitute the valve of Vieussens.
Differential Characters in the Isthmus op the other Animals.
Apart from its volume, the isthmus does not present any sensible differences in Rumi-
nants and the Pig. In the Ox, it is remarked tliat : 1. The inferior pyramids of the medulla
oblongata are more prominent, and the transverse cords parallel to the pons Varolii more
voluminous than in Solipeds. 2. The crura cerebri are short. 3. The optic nerves are larger
than in Solipeds. 4. Tliere is a large developed pituitary gland, excavated by a wide cavity,
and flattened above and below. 5. Lastly, the testes are more conical, and less distinct from
the nates than in the animals already studied.
In the Carnivora, the fourth ventricle is very wide and deep, and bordered by salient
and detached corpora restiformia. Its floor is marked by some white transverse striae, more
apparent than in the Horse. The pons Varolii is large ; the columns of the medulla oblongata,
parallel to its posterior border, are as developed as in the Horse, without taking into con-
sideration the difl"erence8 in size of the two species. The pyramids are voluminous, and the
olivary bodies well defined. The testes are larger than the nates.
Asa general rule, the development of the pons Varolii is in relation to that of the lateral
lobes of the cerebellum.
Comparison of the Isthmus of Man with that of Animals.
In human anatomy, the medulla oblongata and isthmus are described separately.
The first shows on its lower face a well-marked groove — a continuation of that of the spinal
cord. It terminates anteriorly in a deep fossa, named the foramen cascuin of Vicq-d'Azyr.
The pyramids are well marked. The olivary bodies are much more prominent than in animals,
and are also distinguished by the presence of a grey nucleus in tlieir interior. The medulla
oblongata of Man has not the transverse band, behind the pons Varolii, which we have found
in the Horse (Fig. 424).
With regard to the isthmus proper, it contains the parts in front of the medulla oblongata
already studied in the domesticated animals. Tlie pons Varolii is very large ; the crura cerebri
are separateil from each other by a groove, at the bottom of which are several small openings.
The fourth ventricle is deep, is bordered by well-developed corpora restiformia, and enclosed
posteriorly and laterally by the valves of Tarini (velum medullare posterius). On its floor are
remarked transverse strise (lineas transversae) named the barbs of the calamus scriptorius, which
are also found in the Dog. The testes are smaller than the nates; but the diflerence in their
volume is less considerable than exists between Solipeds and Ruminants. Their structure is
identical with that already described.
Article III. — The Cerebellum.
The cerebellum, or posterior enlargement of the brain — is the single mass
supported by the isthmus, separated from the cerebrum by the transverse parti-
tion constituting the tentorium cerebelli, and lodged in the posterior compart-
ment of the cranial cavity, which almost exactly gives the measure of its volume.
Leuret has ascertained the weight of this organ. On the average it weighs
2i ounces in the entire Horse and Mare, and 2| ounces in the castrated Horse.
This weight is to that of the brain as 1 : 7"07 in Stallions ; as 1 : 6-59 in
Mares ; and as 1 : 5'97 in Geldings.
THE CEREBELLUM. 779
1. EXTEENAL CONFOKMATION OF THE CEREBELLUM (FigS. 423, 433).
The cerebellum — isolated by dividing its lateral peduncles from the medulla
oblongata on which it is fixed — is almost globular in form, slightly elliptical, and
elongated transversely ; while its external surface is furrowed by a great number
of sulci, the two principal of which {sulci horizontalis) pass in a circular manner
on each side of the middle line around the organ, dividing it into three lobes — a
middle and two lateral.
The three lobes of the cerebellum are not always readily distinguished from
each other, in consequence of the shallowness and irregularity of the two sulci
separating them. We will, nevertheless, study them in succession, and afterwards
examine— in a general manner — the furrows on their superficies.
lliddle lobe (Fig. 423, c^).— This has been compared to a silkworm rolled
in a circular manner around the middle portion of the cerebellum, with its two
extremities joined— without being confounded — below the inferior face of the
organ.
This vermicular disposition is not well defined in the middle and superior
portions of the cerebellum, where this lobe is always more or less subdivided into
large multiple and irregular lobules ; but it is better marked before and behind,
in those points which correspond to the two extremities of the creature selected
as a term of comparison. There may be remarked two longitudinal eminences
transversely annulated on their surface, and curved beneath the cerebellum in
such a way as to come in contact with each other. These eminences constitute
the anterior and posterior vermiform processes. Their extremities are lodged in
the fourth ventricle, the roof of which they concur in forming.
On the anterior vermiform process the posterior border of the valve of
Yieussens is inserted.
The posterior vermicular process also receives the insertion of a valve already
mentioned, and which must be again briefly referred to. This valve described
for the first time by Renault— forms a lamina of a certain thickness stretched
above the calamus scriptorius. It has exactly the triangular form of this space,
and presents a superior face covered by the posterior vermiform process ; an
inferior face, studded in some points with small vascular loops ; a base fixed to
the vermis, near the free extremity of that prominence, and to its lateral parts ;
two lateral borders, attached to the corpora restiformia on each side of the
calamus scriptorius ; and a summit corresponding to the receding angle of the
excavation. This lamina is, doubtless, nothing more than a septum formed by
the external pia mater, and on which is extended the internal membrane that
lines the walls of the cerebellar ventricle. Otherwise, it is in direct continuity,
towards its base, with an evident dependency of the pia mater — the plexus
choroides}
Lateral lobes (Fig. 423, c^, c^).— These are shaped like two irregular seg-
ments of a sphere. Their surface, fissured and lobulated in every direction,
presents nothing interesting externally, superiorly, or posteriorly. It is by
their inferior part that the peduncles enter the substance of the cerebellum ;
and behind this point, beneath their lateral parts, lies the cerebellar plexus
choroides.
The cerebellar choroid plexuses. — This name is given to two small reddish
granular masses, formed of vascular loops, elongated from before to behind,
> This septum is represented in the rudimentary state in Man, by the valvulx Tarini.
780
THE CLNTBAL AXIS OF THE NERVOUS SYSTEM.
flattened above and below, and comprised at their internal borders between the
corpora restiformia and the inferior face of the lateral lobes of the cerebellum,
to which they are strongly adherent by their superior face. These two plexuses
are joined by means of Renault's valve, which is united to them towards its
base.
Sulci and lobules of the cerebellum. — On examining, in a general manner, all
the sulci which intersect the external surface of the cerebellum, we see that they
penetrate to very unequal depths in the substance of the organ, and that they
Fig. 429.
MEDIAN AND VERTICAI, SECTION OF THE BRAIN.
1, Section of the medulla oblongata ; 2, ditto of the pons Varolii ; ditto of the crura cerebri ; 4,
ditto of the cerebellum, showing the arbor vita; 5, posterior ventricle covered by the cerebellum ;
6, aqueduct of Sylvius; 7, section of the valve of Vieussens (the figure and the line proceeding
from it are too much forward) ; 8, natis ; 9, internal extremity of the hippocampus ; 10, section
of the pineal gland (it is as voluminous as it was in the specimen from which this drawing was
taken) ; 11, great vena Galeni, proceeding from the velum interpositum and choroid plexus, 12 ;
13, middle ventricle; 14, foramen of Monro; 15, common posterior foramen; 16, grey com-
missure; 17, anterior white commissure; 18, section of the corpus albicans; 19, ditto of the
pituitary gland; 20, interior of the pituitary stem communicating with the middle ventricle;
21, section of the optic chiasma ; 22, ditto of the fornix; 23, ditto of the corpus callosum ; 24,
septum lucidura; 25, cerebral convolutions; 26, olfactory lobule.
divide it into successively decreasing segments, of which Figs. 429 and 482 may
furnish a sufficient idea.
There is at first a certain number of principal lobules, which are divided
into secondary lobules ; and these, again, are in their turn separated into short
lamellae, representing the extreme limits of cerebellar lobulation.
Leuret has counted 178 lamellae in a section of the middle cerebellar lobe of
the Horse. In this animal he found the largest number.
2. Internal Conformation and Structure of the Cereb"ellum.
The cerebellum concurs — by its inferior plane and the internal face of its
peduncles— to form the cavity already described as the posterior or cerebellar
TEE CEREBELLUM.
781
ventricle ; but in the mass of the organ itself there is no trace of excavation or
other peculiarity. This is demonstrated in the most evident manner by sections
of its substance made either in an antero-posterior or in a transverse direction.
"We only see in these, traces of the sulci which divide the organ into lobules ; and
they also afford evidence as to the structure of the cerebellum, showing that —
like all the other parts of the cerebro-spinal axis — it is formed of white and grey
substance.
The latter — spread over the entire surface of the organ — constitutes the
cortical layer of the different segments of which it is composed. It is even
prolonged into the convolutions, which increase the surface-extent of the cere-
bellum. In each lobule it may be resolved into
superposed layers, parallel to the layer of white
substance that forms the nucleus of the lobule ;
between these layers of grey substance is a very
thin mass of white matter.
The white substance, enveloped on every
side by the grey, forms two thick nuclei
occupying the centre of the lateral lobes, and
which are united and confounded on the median
line in the texture of the middle lobe.
These two nuclei — in continuity on each
side with the cerebellar peduncles — are only
their prolongations or intercerebellar portions.
They send into the middle of each principal
lobule a long and thick branch, which gives off
smaller divisions that ramify in the secondary
lobules, and from which escape a new series of
ramuscules that enter the smallest segments ;
this gives to the cerebellum a beautiful arboreal
aspect, justly designated by the older anatomists the arbor vitcR (see Figs. 429, 432,
for representations of the arbor vitce, cerebelli).
In the interior of these nuclei a little in front, there sometimes exists a
small, slightly grey streak ; this is the trace of the corpus rhomboideum (or corpus
dentatum of Man).
Stilling has noted two small grey nuclei, which are symmetrical, and are
situated in the inferior layers of the middle lobe.
The nuclei of the white substance of the cerebellum are constituted by nerve-
tubes, which are intermixed with numerous nuclei, and are continuous on one
side with the crura cerebelh, and on the other tenninate in the cells of the grey
substance.
In the grey streak that forms the corpus rhomboideum, is a great number of
large nerve-cells.
With regard to structure, the grey matter of the cerebellum is made up of
three layers ; the superficial is very rich in blood-vessels, has a greyish tint, and
is composed of rounded elements, indeterminate in their nature, lying in an
amorphous substance ; the middle layer, is composed of Purkinje's cells — large
elements disposed in a single row, and provided with ramifying prolongations
which are at first directed to the preceding layer, and are then reflected downwards
into the deep layer, where they are perhaps continuous with the axis-cylinder of
the nerve-tubes of the white substance. The latter — also named the rust-coloured
52
ARRANGEMENT OF THE LAYERS AND
CELLS OF THE CENTRAL GREY MAT-
TER OF THE CEREBELLUM.
A, White matter. 1, Granular or rust,
coloured layer (substantia ferruginea) •
2, layer of Purkinje's cells ; 3, super-
ficial amorphous layer.
782
THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
layer (substantia ferrugineu) — has a yellow tint, and a mass of nuclei pressed
against one another.
If the direction of the white substance fibres is traced,
Fig- ■*3i- it will be found that some form an intra-cerebellar com-
missural system, while others constitute a radiation system
fy-i/r'i^^ that unite the cerebellum to the other parts of the brain.
The first extend from one corpus rhomboideum to the other,
across the cerebellum, or in following the middle cerebellar
peduncles. The second represent the anterior and posterior
cerebellar peduncles and a part of the middle peduncle.
The anterior peduncles, after intercrossing, pass into the
thalami optici (red nmlei of Stilling) ; the posterior enter
the nuclei of the restiform bodies and ohvary body, where
they become united to the sensory system of the spinal
cord ; lastly, the middle ones, after intercrossing, disappear
in the grey nuclei of the pons Varolii.
The prolongations of the large cells in the cortex cere-
belli — also named the cells of Purkinje — are continuous with
the fibres of the white substance.
SECTION OF THE COR-
TICAL SUBSTANCE OF
THE CEREBELLUM.
a,Medullary substance,
showing its fibres;
6, substantia ferru-
ginea, composed of
fibres and cell-nu-
clei ; c, grey surface,
granular at the sur-
face, and contain-
ing large multipolar
branching cells near
the substantia fer-
ruginea.
Differential Characters in the Cerebellum of other than
SoLiPED Animals.
The external and internal conformation of the cerebellum offers
the closest analogies in the domesticated Mammalia. In all, its
volume, compared with that of the other encephalic lobes, is not in-
variable. Thus, while the relation between the weight of the cere-
bellum and that of the brain of the Horse is as 1 to 7 ; in the Ox it is
as 1 to 9 ; the Dog 1 to 8 ; the Cat 1 to 6 ; and the Sheep 1 to 3. The
cerebellar cortical convolutions are less numerous than in the Horse.
Leuret has found 175 lamellae in the middle cerebellar lobe of the
Ox, 77 in the Sheep, 66 in the Cat, and 32 in the Rabbit. These
are the only differences to be noted.
Comparison of the Cerebellum op Man with that of Animals.
In Man, the encephalic mass being enormous, the cerebellum is
absolutely more considerable in volume than in the larger domesticated
animals ; though, in proportion to the cerebral hemispheres, it is
smaller than in the Ox, its relation to the latter lobes being as 1 to 8.
It is covered by the occipital lobes of the brain ; is wider than
it is long, and projects much beyond the medulla oblongata. It has
three lobes ; but these are only visible on its lower aspect ; on the opposite face, the median
lobe is depressed and concealed beneath the lateral lobes, which are so large tiiat they have
been named the cerebellar hemispheres. The fissure which separates these hemispheres is
named the great middle fismre of the cerebellum ; it lodges the falx cerebelli. The inferior
vermis forms a free projection in which is the fourtli ventricle ; this is termed the uvula of the
cerebellum. The uvula is connected at each side with the valves of Tan/w'— laminae of nerve-
substance lodged for the most part in the fourth ventricle, and hidden by the lower face of the
cerebellar hemispheres. Tlie latter constitute, on the sides of the medulla oblongata, two
prominences situated one below the other, above the crura cerebelli; the first is designated the
amygdala or tonsil, the second the pneumogastric lobule (oi flocculus).
Article IV. — The Cerebrum.
The cerebrum, the principal portion of the brain, comprises the two anterior
THE CEREBRUM.
783
lobes or hemispheres of that apparatus — enlargements which are elongated in the
direction of the great diameter of the head and cranial cavity, lie beside each
other in the middle line, and are united at their central part by a transverse
commissure, and by the isthmus, the anterior extremity of which penetrates
their substance inferiorly (see Figs. 424, 429, 432 for a good idea of this
penetration).
These two lobes together represent an ovoid mass, having its larger extremity
adjacent to the cerebellum ; it is depressed above and below ; deeply divided
above, in front, and behind by a median antero-posterior tissure, and receives in
the middle of its inferior face the insertion of the crura cerebri.
This mass — seven to nine times more voluminous than the cerebellum — fills the
anterior compartment of the cranial cavity, and thus occupies the greater portion
of that space.
Leuret has found that, on the average, it weighs in the Stallion, 15^ ounces ;
in the Mare, 14i ounces ; and in the castrated Horse, 14 ounces 12i drams.
Fiff. 432.
ANTERO-POSTERIOR AND VERTICAL SECTION OF THE BRAIN, TO ONE SIDE OF THE MEDIAN LINE.
1, 1, Isthmus; 2, medulla oblongata; 3, pons Varolii; 4, crus cerebri; 5,6, corpora bigemina;
7, optic thalamus; 8, pituitary gland; 9, pituitary stem; 10, optic nerve; 11, cerebellum;
12, 12, cerebral hemisphere; 13, ventricle of the hemisphere; 14, corpus striatum; 15, cornu
Ammonis; 16, olfactory bulb; 17, ventricle in the olfactory bulb.
It offers for study its external conformation, its internal conformation, and its
structure.
ExTEENAL Conformation of the Cerebrum.
Instead of examining the organ in mass, with regard to its external conforma-
tion, we will first consider the great longitudinal fissure which divides it length-
ways ; and afterwards study its two lateral halves, or cerebral hemispheres, which
in reality constitute two symmetrical organs.
1. The Longitudinal Fissure (Figs. 423, 424),
This fissure exists throughout the entire vertical and antero-posterior circum-
ference of the cerebrum, but does not everywhere offer the same arrangement.
784 THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
On the superior aspect of the organ it is very deep, and when the two hemispheres
are separated to discover its extent, we see that it reaches to the upper face of the
great commissure — the coi-pus callosum. Behind, it curves between the posterior
lobes of the hemispheres, but without corresponding directly with the posterior,
thick, rounded margin of the coi-pus callosum, above which there is a feeble
adhesion between the two halves of the cerebrum, forming a kind of bridge. But
in front it passes to the anterior margin of this commissm'e, and is prolonged in
the interval between the anterior lobes of the hemispheres, to reach the inferior
face of the brain.
Examined inferiorly, this interlobular fissure is well defined in front, where it
reaches the anterior border of the coi-pus callosum ; but behind, on leaving the
optic commissure — and which marks the anterior limit of the isthmus — this fissure
appears suddenly to stop. This is because it becomes considerably enlarged, and
is changed into a vast notch which admits the anterior extremity of the isthmus
— or rather, it bifurcates to pass on each side between the hemisphere and the
anterior extremity of the spinal prolongation, at first crossing the optic nerve,
then turning round the crara cerebri and corpora bigemina, above which its
branches unite, and are confounded with the undivided part of the fissure that
separates the posterior lobes of the hemispheres (Fig. 424).
There exists, then, around the point of entrance of the isthmus into the cere-
brum a well-marked Une of demarcation, which constitutes — above and laterally — ■
a very deep fissure, in which is embedded the vascular expansion known as the
velum interpositum ; this space is designated the fissure of Bichdt, or great {trans-
verse) cerebral fissure.
The longitudinal fissure receives the longitudinal septum of the dura mater,
or falx cerebri. It also lodges arteries and veins, among which it is necessary to
distinguish the great vena Galeni, which ascends from the bottom of the fissure,
after passing round the posterior border of the corpus callosum.
2. The Cerebral Hemispheres.
Preparation. — To see the fissures, sulci, and convolutions of the brain, the organ should be
macerated for some days in a solution of nitric acid (5 or 10 to 100 of water). On removing
it from this, the pia mater and vessels (ire carefully taken away and the brain gently dried,
when the grooves and fissures widen, and the lobes and lobules can be distinctly seen.
Each hemisphere — or lateral moiety of the cerebrum — represents an ovoid
segment, in which we may consider four /aces and two extremities.
The supei-ior face is convex, and is covered by the roof of the cranium, which
is formed by the frontal and parietal bones.
The external — equally convex and insensibly confounded with the adjacent
faces — corresponds to the lateral walls of this cavity — that is, with the squamous
portion of the temporal bone, the parietal and frontal bones, and the ala of the
sphenoid.
The inferior — irregularly mammillated — rests on the sphenoid bone. The
intm-nal is plane, and for the greater part of its extent is related to the other
hemisphere through the medium of the falx cerebri ; it is in its central and
inferior portion that the union of the two halves of the cerebrum takes place, by
means of the great cerebral commissure and the anterior extremity of the
isthmus.
The posterior extremity of the hemisphere corresponds to the cerebellum, which
THE CEREBRUM. 785
slightly depresses it, and from which it is separated by the transverse septum of
the dura mater (tentorium).
The anterior extremity — or late — is lodged in the fossa formed on each side of
the crista galli by the frontal and sphenoid bones.
The most important peculiarities to be noted on the surface of the hemi-
spheres, are the convolutions, which we will now describe.
Cerebral Convolutions.^ — These are the portions of the cerebral cortex
which are disposed in the form of more or less sinuous ridges, separated from
each other by deep grooves or fissures {sulci).
A convolution (or gyrus) may include several plaits or folds — that is, several
parts separated or merely indicated by shallow grooves ; so that convolutions
should not be confounded with plaits.
The convolutions are not independent, strictly speaking, but are often united
to those adjoining by more or less concealed reliefs, called passage plaits (annec-
tent or bridging gyri) ; sometimes two or more are very ostensibly connected in
this way.
The convolutions in Solipeds are very sinuous, and limited by deep sulci ;
some of these latter — more important than the others by their depth and constancy
— are named ^sswres. Notwithstanding an apparent great irregularity, the cere-
bral convolutions are somewhat constant in their aiTangement ; so that it is
possible to describe them one by one.
a. Fissure and grooves. — On the inferior face of the brain is seen a transverse
depression at the optic commissure (Fig. 424, 10). This depression — named the
fissure or vcdley of Sylvius — passes from within to without, and, on arriving at the
side of the brain, divides into two or three branches, of which one — the principal
— is inflected backwards, reaches the posterior extremity of the hemisphere, and
forms the superior limit of a lobe named the temporal or sphenoidal lobe (Fig. 433,
7). The other one or two branches remain slightly buried in the middle part of
the hemisphere ; they lodge the divisions of the middle cerebral artery.
In glancing over the superior surface, there will be perceived a deep groov^e
coming from the great longitudinal fissure, which it intersects at nearly a right
angle. This groove — which Leuret has named the crucial fissure (Fig. 423, 12)
— is surrounded by a more or less apparent convolution, designated the sigmoid
gyrus (Fig. 423, 11). The crucial fissure divides the superior face of the hemi-
sphere into two parts — the anterior belonging to the frontal lobe, the posterior to
the parieto-occipitcd lobe.
On the external face of the hemisphere is seen a deep groove, which, com-
mencing between the middle and posterior branch of the fissure of Sylvius, is
directed upwards in a curve, the concavity of which is inferior, and ends in the
vicinity of the crucial fissure (Fig. 433, 8, 8). This curved groove resembles the
fissure of Rolando. If looked at in the other direction — from before to behind
— it appears to bifurcate in its middle part, and the upper branch {interparietal
' Leuret believes that the cerebral convolutions of animals are arranged after a certain
type (longitudinal type) essentially different from the human type. We think the difference
is not so great as has been imagined ; and it appears possible to discover in the brain of brutes
if not the longitudino-transverse type, at least the tendency to this type observed in the human
brain. In the description given above, the value of this assertion can be judged. We ought
to state that our conclusions are based on the comparative examination of the brains of adults
and foetuses, on tlie distribution of the blood-vessels, and on the physiological experiments
which enabled us to fix the position of the excitable zones of the cerebral cortex in the larger
Quadrupeds.
786 TEE CENTRAL AXIS OF TEE NERVOUS SYS 1 EM.
fissure) passes back to disappear in the posterior extremity of the hemisphere (Fig.
423, 5). The fissure of Rolando separates the frontal from the parietal lobe, and
the portion of the brain comprised between its bifm-cation and the posterior
branch of the fissure of Sylvius, forms a quadrilateral lobe (Figs. 423, 13 ; 433,
10), which resembles the lobule of the curved plait in the brain of Man.
Lastly, on the internal face of the hemispheres is found the inner portion of
the frontal and parieto-occipital lobes, and a long convolution that accompanies
the coi-pus callosum (Fig. 429), named the caUosal convolution, or crested con-
volution {gyrus fornicatus), because of the notches on its upper border in Man.
It is separated from the frontal and parieto-occipital lobes by a deep groove
— the calloso-maryinal fissure.
The crested convolution commences, in front, beneath the genu of the corpus
callosum ; behind, it is inflected downwards, is continuous with the liippocampal
convolution, and by some annectent gyri is in relation with the posterior
extremity of the hemisphere.
In fine, a cursory examination of the surface of the hemispheres denotes the
presence of some principal grooves Hmiting three lobes and a lobule ; these are the
frontal, 2)arieto-occi]ntal, and spJienoidal lobes, and the lobule of the curved plait}
We will now describe the convolutions of these lobes and lobule.
b. Frontal lobe. — This lobe presents three faces.
The inferior face {orbital lobe) is triangular (Fig. 424), and its base is occupied
by the fissure of Sylvius, in front of which is remarked the extra- ventricular nucleus
of the corpus striatum (Fig. 424, 12), which has a portion of itssm'face perforated
by vascular openings — the locus perforatus. Near the summit it detaches the
olfactory or ethmoidal lobide (Fig. 424, 15), which arises by two white-coloured roots
that margin the extra- ventricular nucleus ; the external root (Fig. 424, 13) is con-
tinuous with the convolution that is prolonged on the temporal lobe ; the internal
root (Fig. 424, 14), which is shorter, arises from the inner face of the hemisphere,
in front of the optic commissm-e. This appendicular lobule is directed forwards,
and terminates by an oval expansion — the optic bulb (Fig. 424, 16) — which
extends beyond the anterior extremity of the brain to be lodged in the ethmoid
fossa. The olfactory lobule has a cavity in its interior — a diverticulum of the
lateral ventricle — and is received into a depression of the frontal lobe, named
the olfactory fissure, that extends to the summit of the orbital lobule, and
separates two convolutions, the internal of which is named the yyrus rectus (Fig.
424, 21).
The external face of the frontal lobe shows a great fissure almost parallel with
that of Rolando, and between these two fissures is a long convolution that usually
describes three curves (Figs. 423, 6, 6 ; 433, 11, 11) ; this limited convolution
takes the place of the ascending frontal convolution in Man. In front, it is
always united to the other frontal convolutions, and the fusion is more or less
apparent.
On the same face is perceived another great fissure, that commences in the
vicinity of the crucial fissure, where it sometimes appears to be continuous with
» In the domestic animals, the occipital lobe— already so difficult to circumscribe in Man —
iB not more distinct in his neighbour. The posterior extremity of the hemispheres is, as it were,
pushed forward by the internal occipital protuberance and the cerebellum. We make of the
posterior region of the hemisphere a parieto-occipital lobe, implying by this term the fusion of
the two parietal and occipital lobes. The latter is certainly very small, but we cannot admit
its disappearance. We do not find in the brain of the Horse, the lobule of the insula or island
of Heil, which in Man is concealed at the bottom of the fissure of Sylvius.
THE CEREBRUM.
787
that of Rolando : it is directed forwards, outwards, and downwards — that is to say,
it turns round the anterior extremity of the hemisphere to terminate near the
fissure of Sylvius. Within this fissure is a triangular convolution, with its
summit directed backwards ; it is generally divided into two folds at its inferior
part — this is the first frontal convolution (Figs. 423, 9 ; 433, 15, 15).
Another convolution is included between this fissure and that which margins
the ascending frontal convolution ; it is doubled into two wide flexuous folds
which pass into the latter in front, and represents the second frontal convolution
(Figs. 423, 10, 10 ; 433, 14, 14).
Fig. 433.
BRAIN OF THE HORSE (LATERAL FACE).
■, Medulla oblongata; Pr, pons Varolii ; Pc, cei-ebral peduncle (crus cerebri). 1, Middle lobe of the
cerebellum; 2, lateral lobe of ditto; 3, medullary root of the spinal accessory nerve; 4, internal
roots of ditto and roots of the pneuraogastric ; 5, transverse fasciculus of the medulla oblongata,
at the extremity of which the facial nerve appears to arise ; 7, fissure of Sylvius ; 8, 8, 8,
fissure of Rolando; 9, posterior branch of ditto; 10, lobule of the curved plait; 11, 11, 11,
limiting frontal convolution; 12, 12, parieto-temporal convolution (analogous to the ascending
parietal convolution); 13, second parieto-temporal convolution; 14, 14, the two principal folds
of the second frontal convolution; 15, 15, folds of the first frontal convolution; 17, fiarieto-
occipital lobe; 18, inferior tempoi-al convolution (2nd and 3rd of Man) ; 19, superior temporal
convolution (1st of man); 20. intra-ventricular nucleus of the corpus striatum ; 21, external root
of the olfactory lobule; 22, olfactory nerves.
The third convohition seen in Man is not defined in the Horse by an impor-
tant fissure, and if it exists in this animal it is probably represented by the origin
of the inferior fold of the second convolution, which is sometimes separated from
the rest by a shallow sulcus.
The internal face of the frontal lobe shows the internal part of the first
frontal convolution, and a portion of the calloso-marginal fissure and crested
convolution.
c. Temporal or sphenoid(d lobe. — Also named the mastoid lohde by Veterinary
Anatomists, the temporal lobe in Solipeds is a large pyrif orm eminence occupying
788 THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
the posterior part of the inferior face of the hemisphere (Figs. 423, 18, 19 ; 433,
18, 19). It is curved on itself, the convexity being outwards, and its inner
border is related to the crus cerebri. It concurs in forming the great longi-
tudinal fissure, its large extremity being turned forwards and margins the fissure
of Sylvius, while the posterior extremity disappears in the posterior lobe of the
hemisphere.
The surface of the temporal lobe is almost smooth, and shows scarcely more
than one slight fissure, parallel to the posterior branches of the fissure of Sylvius
(Fig. 433). This fissure (the parallel fissure) terminates more or less directly
behind, between the branches of a ^ convolution — the curved j^lffit- The
external branch of the latter is continuous with the superior temporal convolution
(Fig. 433, 19), which is comprised between the parallel fissure and the fissure of
Sylvius. The part situated below the parallel fissure (Fig. 433, 18) represents
the second and third temporal convolutions of Man. The temporal lobe is very
simple in Solipeds, and is hollowed internally by a cul-de-sac cavity that consti-
tutes the bottom of the posterior or reflected portion of the lateral ventricles.
d. Lobule of the curved plait. — Nearly quadrilateral in shape (Figs. 423, 13 ;
433, 10), this lobule is included between the fissure of Sylvius, the inferior part
of the fissure of Rolando, and the interparietal fissure. It is formed by a large
convolution, confounded at its commencement with the ascending frontal convo-
lution, and which soon divides into two undulating plaits that unite, behind,
with the superior temporal convolution, the curved plait, and sometimes with
the convolutions of the parieto-occipital lobe.
e. Parieto-occipital lobe. — The limits of the occipital lobe — so difficult to
establish in the human brain — cannot be determined in that of the Horse ; for
this reason it is that we now describe a parieto-occipital lobe resulting from the
fusion of the parietal with the occipital lobe.
This lobe offers three faces. The external face is almost entirely occupied
by a large convolution — the parieto-temporal — formed by two folds, the outer of
which (Figs. 323, 7, 7 ; 433, 12, 12) margins the interparietal fissure and the
anterior part of the fissure of Rolando ; in front, it is continuous with the plait
that surrounds the crucial fissure and — through the medium of the latter — the
first frontal convolution ; behind, it is inflected downwards to be continued on
the posterior face of the lobe.
The internal face shows the parieto-occipital portion of the corpus callosum
convolution, and of the second parieto-occipital convolution ; these two being
separated by the calloso-marginal fissure, from which is detached a branch that
rides on the superior border of the hemisphere and forms the crucial fissure.
The second parieto-occipital convolution (Figs. 423, 8, 8 ; 433, 13) has the
form of a wedge, the summit of which is directed forward ; here it is single,
and is confounded with the first convolution of the same lobe, and with the
plait that surrounds the crucial fissure ; but it afterwards divides into two
principal, almost straight plaits, which are continued on the posterior face of the
lobe.
The latter is occupied by the posterior extremity of the parieto-occipital
convolutions. It is oblique downwards and forwards, and is separated from the
cerebellum by the transverse duplicature of the dura mater. On this face are
seen three or four undulating plaits which join each other, and pass on to the
convolutions of the hippocampus.
TEE CEREBHUM.
Inteenal Conformation of the Brain.
In separating the cerebral hemispheres by their upper face, we discover the
great commissure known as the corpus callosum — the first object that presents
itself for study in the internal conformation of the brain.
If we afterwards remove, with a sharp instrument, and by a horizontal
section, all that portion of the hemispheres which covers this commissure, and
also if the latter be excised to a certain extent to the right and left of the middle
line, we shall penetrate two symmetrically disposed cavities in the centre of each
hemisphere. These cavities are the lateral or cerebral ventricles.
They are separated on the middle plane by a thin partition — the septum
lucidum — which is attached to the corpus callosum by its upper border, and
fixed by its inferior border into the fornix^ a kind of middle arch, beneath which
is the foramen of Monro, or orifice communicating with the two ventricles. On
the floor of these cavities is observed two large eminences— the corpus striatum
Fig. 434.
Fig. 435.
THE CORPUS CALLOSUM OF THE HORSE, AFTER
REMOVAL OP THE UPPER POKTIOM OP THE
CEREBRAL HEMISPHERES.
I, Centrum ovale of Vicq-d'Azyr ; 2, 2, trans-
verse fibres of the corpus callosum ; 3, 3,
tractus longitudinales; 4,4, cornua, or angles
of the posterior extremity ; 5, 5, ditto of
anterior extremity.
ANTERIOR PORTION OF THE LATERAL VENTRI-
CLES OF THE DOG, EXPOSED BY REMOVAL OF
THE ROOF.
1, Corpus callosum; 2, anterior part of the
corpus callosum, turned forward after de-
stroying the septum lucidum, to show the
fornix, 3, 3 ; 4, 4, hippocampi ; 5, 5, taeniae
semicircularis ; 6, 6, choroid plexus ; 7, 7,
corpora striata.
and the hippocampus ; with a vascular and apparently granular cord forming the
cerebral choroid plexus — a dependency of the velum interpositum.
It now remains to enter into some detail with regard to the anatomical
characteristics of all these parts.
1. The Corpus Callosum (Figs. 434, 435).
The corpus callosum is a kind of arch thrown over the two lateral ventricles,
while at the same time it is a commissure uniting the two hemispheres. It
belongs exclusively to Mammalia.
Composed entirely of white substance, this arch is of an elongated, quadri-
lateral sliape, being elongated in an antero-posterior direction ; it thus presents
for study two faces, two boi-ders, and two extremities.
790 THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
The superior face, free in the middle, and corresponding to the bottom of the
interlobular fissure, is covered right and left by the substance of the hemispheres.
It is traversed from before to behind by two white, and generally very delicate,
cords— the tradus longitudinalis (the chonlm lonyitudinalis of Lancisi) of the
corpus callosum — which lie together on the middle line. The inferior face is
divided — by the insertion of the septum lucidum — into two lateral portions, each
of which forms the roof of one of the cerebral ventricles. Behind, it rests on
the middle part of the fornix.
The two lateral borders of the corpus callosum disappear in the central sub-
stance of the hemispheres, where it is almost impossible to distinguish their
limits.
The posterior extremity appears at the bottom of the interlobular fissure —
after destroying the adhesion usually established above it between the two hemi-
spheres— in the form of a thick, rounded enlargement {splenium) doubled below,
and confounded with the middle part of the fornix. It is prolonged, laterally,
above the ventricular cavities, in forming two angles {linece transversm) which
are soon lost in the white central substance of the cerebrum.
The anterior extremity comports itself in a similar manner between the
anterior lobes of the hemispheres. It is named the genu of tJie corpus callosum,
and is doubled more abruptly than the posterior end, terminating by a thin
narrow portion — the rostrum.
2. The Lateral or Cerebral Ventricles (Figs. 429, 435).
The lateral veyitricles are two large elongated cavities excavated in the hemi-
spheres, lying against each other in their anterior moiety, and divergent in their
posterior part, which is very much curved backwards, outwards, and downwards,
to open into the substance of the sphenoidal lobe.
This disposition permits the division of the cerebral ventricles into two
regions — an anterior, and a posterior or reflected.
The anterior region — anterior cornu, or frontal diverticulum — is separated in
the median plane from the opposite ventricle, by the septum lucidum and the
summit of the fornix, beneath which is the foramen of Monro establishing a
communication between the middle and the two lateral ventricles, and between
these latter. Above, it offers a smooth wall formed by the corpus callosum.
Below, on its floor, there is first remarked, in front, the corpus striatum ; behind,
the internal portion of the hippocampus ; in the middle, an oblique groove
running backwards and inwards, at the bottom of which floats the choroid
plexus. The anterior extremity of this region, occupied by the base of the
corpus striatum, is continued by a narrow opening into the interior of the
olfactory lobe. The posterior is prolonged, without any Hne of demarcation, by
the reflected portion of the ventricular cavity.
The latter region (posterior or descending cornu, or sphenoidal diverticulum)
occupies the most declivitous portion of the posterior lobe of the hemisphere,
and is a much-curved canal with its concavity forward ; this canal terminates
in a cul-de-sac in the substance of the sphenoidal lobe. On the floor of this
canal is marked the posterior portion of the hippocampus and the choroid plexus.
A very fine membrane — the ventricular arachyioid — plays the part of a serous
membrane and covers the walls of these cavities, being spread everywhere over a
layer of white substance, prolonged into the ethmoidal diverticulum, and con-
tinuous, through the foramen of Monro, with that of the middle ventricle. This
TEE CEREBRUM. 791
membrane secretes a limpid and transparent fluid, analogous to the cerebro-
spinal fluid, though in health it is always in small quantity.
3. The Septum Lucidum (Fig. 429, 24).
This appellation is given to a thin middle band, standing vertically between
the two lateral ventricles, elongated from before to behind, widened considerably
at its anterior extremity, terminating in a point at its posterior extremity, and
inserted above into the corpus callosum, below into the back of the fornix.
On the faces of this partition, which is formed of white substance, is spread
the proper membrane of the lateral ventricles. In the human species, a narrow
ventricle has been described as found in its substance ; but this does not appear
to exist in the domesticated animals.
4. The Fornix, or Trigonum (Fig. 435, 3).
Also named the vault of three or four pillars, the fornix {arch) is a single
middle body in the interior of the brain, concurring to separate the two ven-
tricles, and serving to support the septum lucidum. It is depressed below and
above, and is of a triangular form ; its apex, looking downward, stands in the
median plane above the foramen of Monro and the thalami optici, though sepa-
rated from the latter by the velum interpositum and the hippocampi, and
receives on its upper face the insertion of the septum lucidum. Behind, at its
base, and in the middle line, the fornix is confounded with the corpus callosum,
which it supports ; it is prolonged on each side by a lamina extending to the
surface of the hippocampus, forming the cortical layer of this deep convolution
of the brain, and with its congener constituting the posterior pillars ( posterior
crura, tmnice hippocampi, or corpora fimhriata) of the fornix. These two pillars
are united by some white transverse fibres, which form what has been named
the lyre.
In front, at its apex, the fornix is also attached to the corpus callosum, and
divides into two cords or anterior pillars {crura) — (Figs. 425 ; 429, 17), which
pass in front of the anterior cerebral commissure, are inflected downwards and
backwards, in traversing the optic thalamus, on the sides of the middle ventricle,
and finally have their extremities confounded with the mammillary process
{corpus albicans).
These two crura limit, in front, the foramen commune anterius, or foramen of
Monro (Fig. 425, 16), over which the apex of the fornix is thrown across like an
arch (Fig. 425).
The fornix is white throughout its whole extent, with a greyish tint towards
its summit.
5. The Hippocampi (Fig. 435, 4).
The hippocampus, or cornu Ammonis (from its resemblance to a ram's horn,
the crest of Jupiter Ammon), is an elongated projection, a veritable internal
convolution of the brain (is, in fact, the internal sm-f ace of the ffi/rus fornicatus,
or convolution lying upon the corpus callosum, and which terminates at the
fissure of Sylvius). It occupies the floor of the anterior part of the lateral
ventricle, and is prolonged throughout its reflected portion, the curvature of
which it exactly follows. Considered together, the two hippocampi somewhat
closely resemble the uterine cornua of the Cow.
By their internal extremity, they are in contact with each other beneath the
middle portion of the fornix, and above the optic thalamus, which is separated from
792 TBE CENTRAL AXTS OF THE NERVOUS SYSTEM.
them by the velum interpositum (Fig. 429, 9). Their external extremity occupies,
in the sphenoidal lobe, the cul-de-sac of the reflected portion of the lateral ventricle.
The central mass of this projection is formed of a nucleus of grey substance,
covered on both faces by a layer of white substance. The layer that covers its
inferior face is named the subicidum, and that which extends over its surface is
designated the alreiis ; it is a kind of prolongation of the posterior pillars of the
fornix.
Towards the concave border of the hippocampus, this white layer offers a
kind of wide hem, beneath which the choroid plexus passes ; this hem constitutes
a small curved band, like the cornu Ammonis, wider in its middle part than at
its extremities, and is named the corpus fimbriatum, or tcBnia hippocampus.
The grey layer comprised between the two white bands also makes a slight
projection at the inner border of the hippocampus, and forms the fascui dentata}
6. The Corpora Striata (Fig. 435, 7).
The corpus striatum is a mass of grey matter interposed on the course of the
crura cerebri. It includes the entire thickness of the floor of the lateral ventricle,
and projects outwards, on the lower face of the hemisphere, between the two
roots of the olfactory lobule.
The corpus striatum owes its name to its structure : the thick nucleus of
grey matter composing it is, in fact, traversed by white fibres from the crura
cerebri, which pass into the hemispheres ; these fibres appear at several points
in the form of sharply defined white strias.
It is divided into two portions by these fibres, which collectively constitute
the internal capsule (Fig. 436, Ci). The external portion is the extra-ventricular
niccleus of the corpus striatum, so named because of its position, and lenticular
nucleus, in consequence of its shape ; just as the internal portion is most
frequently designated the intra-ventricular nucleus of the corpus striatum, or
caudate nucleus (Fig. 436). The caudate or intra-ventricular nucleus occupies the
anterior region of the lateral ventricle (Fig. 435, 7)
This eminence is pyriform in shape, and obHquely elongated forward and
inward. Its surface is smooth, and regularly convex. Its base, or anterior
extremity, corresponds to the anterior cid-de-sac of the ventricle. The simamit,
or posterior extremity, disappears at the commencement of the reflected portion
of the ventricular cavity. Outwardly, the corpus striatum is limited by a groove
that forms the angle of union between the floor and roof of the ventricle.
Inwardly, it is separated from the optic thalamus and cornu Ammonis by another
groove, in which the choroid plexus floats, and which is oblique inwards and
forwards, and shows at the bottom the tcenia semicircularis (Fig. 432, 13). This
is a flattened white cord, which disappears inwardly towards the foramen of
Monro, and bends outwards along the optic nerve to within about | of an inch
from the optic commissure ; in this way it forms a kind of circular band around
the anterior extremity of the isthmus, beneath which all the fibres of the latter
pass to reach the cerebral hemispheres.
7. The Velum Interpositum and Choroid Plexus (Fig. 435, 6).
The velum interpositum (velum vasculosum, tela choroidea) is a vascular
expansion derived from the pia mater, which penetrates the brain by the great
' Sabatier, taking comparative anatomy and embryology as his guide, regarded the hem of
the hippocampus as a ganglion spread along the origin of tlie optic nerve.
THE CEREBRUM.
793
transverse fissure, and insinuates itself between the thalamus opticus and the
convolution of the cornu Ammonis. The velum, on arriving beneath the taenia
hippocampus, terminates in the choroid plexus — a red, granular-looking cord,
which is suspended by its antero-external border, and projects into the interior of
the lateral ventricle.
The choroid plexuses of the brain (plexus choroidece) extend from the anterior
extremity of the corpus striatum to the bottom of the cul-de-sac, or sphenoidal
diverticulum. In the anterior part of the ventricle, they occupy the oblique fissure
which traverses that part, to the inner side of the caudate nucleus. In the posterior
region, they float in front of the cornu Ammonis. Their anterior or internal
extremity, more voluminous than the external, always forms a small appendage
Fig. 436.
1 i
CA L
DIAGRAM OF A TRANSVERSE SECTION OF THE HUMAN BRAIN AT THE MIDDLE PART OP
THE CORPUS STRIATUM.
CO, Corpus callosum ; CA, intra-ventricular (or caudate) nucleus of the corpus striatum ; L, extra-
ventricular, or lenticular nucleus of the corpus striatum ; ci, ci, internal capsules placed between
these two nuclei.
which remains quite free. They are united to each other, near this extremity,
by an intermediate cord, which goes through the foramen of Monro in passing
l)eneath the fornix.
Like the velum interpositum, the choroid plexuses are formed by a network
of arteries and veins. They are often incrusted in calcareous matter, and may
be the seat of more or less voluminous cysts.
The veins proceeding from this vascular apparatus are very voluminous, and
by their union form the great vena Galeni, which bends round the splenium of
the corpus callosum to reach the interlobular fissure, and proceeds to the sinus
of the falx cerebri.
The Steucture of the Brain.
The structure of the brain is certainly one of the most interesting points in
7M
THE CENTRAL AXIS OF TEE NERVOUS SYSTEM.
the study of the nerve-centres ; for on a perfect knowledge of it depends the
sokition of the most difficult problems in the physiology of the nervous system.
Numerous attempts have been made to elucidate its intimate organization ; but
we must here omit the multitude of secondary details revealed by these researches,
and limit ourselves to the essential and fundamental facts.
The tu'o nerve-suhstances enter into the texture of the cerebral hemispheres,
and both are exactly disposed as in the cerebellum.
The grey substance extends over the entire external surface of the brain, and
is prolonged into the plaits — thereby augmenting the extent of that surface, and
so forming the cortical layer of the cerebral convolutions. Gratiolet has compared
this layer to a ring-purse opening on the internal face of the hemisphere, having
for its rings the convolutions of the hippocampus and corpus callosum, in which
is included the white medullary substance.
The grey matter projects into the lower face of the olfactory lobes and
Fig 437
COURSE OF ONE PORTION OF THE ASSOCIATION NERVE-FIBRES IN A HEMISPHERE. (DIAGRAMMATIC.)
interior of the hemispheres, where it forms the central ganglia known as the
claustrum, lenticular nucleus, and caudate nucleus.
In order to study the distribution of the central grey masses, horizontal and
vertical sections must be made of the brain, through the corpora striata. In
a vertical section by the optic commissure (Fig. 436), will be seen the caudate
nucleus limiting outwardly the lateral ventricle, and separated from the lenticular
nucleus by a layer of white substance — the internal capsule; between the
lenticular nucleus and the cerebral cortex there is a certain amount of white
matter. If the section is made a little more behind, there will be observed,
between the grey matter and tlie lenticular nucleus, a small greyish band named
the claustrum ; this is separated from the lenticular nucleus by the external capsule.
To sum up, it is easy to perceive that the distribution of the central grey
masses Qenticulo-striated bodies) is subordinate to the internal capsule. Otherwise,
this plays a considerable part in the physiology of the hemispheres.
THE CEREBRUM.
795
In the middle of each hemisphere, the white substance constitutes a consider-
able nucleus, which, from its form, is named the centrum ovale (Vicq-d'Azyr)
(Fig. 427, 1 ; 434, 1), and which is united to that of the opposite side by the
great cerebral commissure, or corpus callosum, sending a prolongation into each
convolution ; thus exhibiting the exact disposition of the lateral white masses of
the cerebellum, with which the nuclei of the hemispheres have also another point
of resemblance, in that they are attached to the cerebral peduncles, as the first
are to the cerebellar. But the latter peculiarity is less evident than the others —
which are at once obvious in horizontal and transverse sections of the brain —
and can only be clearly demonstrated by the manipulations necessary to unravel
the intimate texture of the white substance.
In studying this texture in brains hardened by nitric acid, washed in pure
water, and exposed to dry air for a day or two, we perceive that the white
cerebral substance is entirely composed of fine fibrous lamellae, diverging in every
Fig. 438.
Fi£r. 439.
DIAGRAM OF THE COURSE OF THE ASSOCIATION
NERVE-FIBRES OF THE CORPUS CALLOSUM AND
OF THE ANTERIOR COMMISSURE.
DIAGRAM OF THE COURSE OF THE RADIAT-
ING NERVE-FIBRES OF THE CORONA
RADIATA, AND THE RELATIONS OF THE
CORPORA STRIATA WITH THE CORTICAL
GREY SUBSTANCE.
direction, corresponding by their concentric extremity to the centre of the
hemisphere, and abutting, by their peripheral extremity, on the inner face of the
grey covering of the convolutions.
With regard to the relations between the centrum ovale and the cerebral
isthmus, and those the fibres of the former have with the other parts of the brain,
it is found that the fibres of the lower stage of the peduncles attach the
isthmus to the cerebral hemispheres, in passing through the corpora striata, and
radiate in the centrum ovale. Here these fibres form a kind of fan — the radiant
crown {corona radiata) of Reil. The internal capsule is the point of departure
of these fibres, and is therefore designated t\iQfoot {pes) of the radiant croivn.
In the centrum ovale, the nerve-fibres form two great apparatuses — an
apparatus of association and an apparatus of radiation (Pitres).
The first comprises a system of intra-hemisphere commissures, and a system of
inter-hemisphere commissures.
The fibres of the first system unite the neighbouring convolutions, and those
more or less distant from each other.
796
THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
The second system comprises the fibres of the corpus callosum. It was
formerly believed that these fibres arose from the cerebral peduncles, but now it
is thought they pass merely from one hemisphere to another. The anterior com-
missure belongs also to this system ; but great uncertainty exists as to the
connections of its fibres.
The radiation apparatus is formed by the fibres of the corona radiata. Among
them a great number should proceed, according to Meynert, to the caudate
nucleus, the lenticular nucleus, and the optic thalamus {cortico-striated, cortico-
lenticular, and cortico-optic fihres). The others form two direct peduncular
fasciculi — one, occupying the anterior two-thirds of the corona radiata, going
from the motor convolutions of the cortex to the infero-lateral fasciculi of the
Fig. 440.
Fig. 441.
ARRANGEMENT OF THE LAYERS AND CELIiS
OP A FRONTAL CONVOLUTION.
1, Hyaline layer; 2, layer of the small
pyritmid cells ; 3, thick layer of the great
pyramid cells ; 4, granular layer ; 5, 6,
layer of so-called volition cells (beneath
this layer is the white fibrillated
substance).
CORTICAL SUBSTANCE
OF THE CEREBRAL
HEMISPHERES.
a, Medullary .sub
stance ; b, reddish
grey layer ; c, clear
white streak, com-
posed of horizontal
fibres; d, grey layer;
e, external white
layer.
spinal cord ; the other occupies the posterior part of the corona radiata, and
passes from the lateral and posterior convolutions of the hemisphere to disappear
in the cerebral peduncle. This fasciculus is sensitive.
The white substance of the brain is formed of very fine nerve-fibres. The
grey substance of the cortex is made up of five or six superposed layers. In the
frontal region there are six layers, as follows : 1. A granular layer, with very
small stellate cells. 2. A stratum containing numerous small pyramidal cells.
3. A very thick layer with large cells — great pyramidal, or giant cells. 4. A
granular layer formed of numerous small and uniform cellular elements. 5 and
6. Two layers having for their principal elements stellate or fusiform cell^
{volition cells).
In the occipital region, the third layer is absent ; but in the cornu Ammonia
it is very developed. Lastly, the giant pyramid cells are more particularly found
in the cortical regions in the vicinity of the crucial fissure.
THE CEREBRUM.
797
The grey substance forming the corpora striata has, for its essential elements,
cells analogous to the medium cells of the cerebral cortex.
Vessels. — The arteries of the brain come from the three cerebral arteries (see
the internal carotid). The branches of these vessels form two systems which
have a common origin, but which remain distinct at the periphery. The cortical
Fig. 442.
BRAIN OF THE OX (UPPER FACE). THREE-FOURTHS NATURAL SIZE.
, Neck of the medulla oblongata; Pj, posterior pyramid of the medulla oblongata; S, inter-hemi-
spherical fissure. 1, Middle lobe of the cerebellum; 2, 2, lateral lobes of the cerebellum; 4,4,
anterior part of the fissure of Rolando interrupted by an annectent gyrus uniting convolutions 9
and 6 ; 4', inferior part of ditto ; 4", posterior branch ot ditto ; 5, second parietal convolution with its
plaits , 6, first parietal convolution with its plaits ; 7, 7, crucial fissure (the sigmoid gyrus surround-
ing it is hidden beneath the before-mentioned plait); 8, first frontal convolution; 9, union of the
second frontal with the limited frontal convolution ; 10, limiting front convolution ; 11, lobule of
the curved plait.
si/stem furnishes blood to the pia mater and the grey cortex. The central system
leaves the circle of Willis, and is distributed to the ganglionic centres. The
arterioles of this system form groups which are generally independent of
each other (Duret).
The venous blood from the centre of the hemispheres issues by the vena
53
798
THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
Galeni. On the surface of the hemispheres are large veins which enter the
sinuses of the dura mater.
The lymphatics form sheaths around the small blood-vessels.
Development. — See " Embryology," for the development of the brain.
Differential Characters in the Brain of the other Animals.
In the animals which interest us, the brain presents differences with regard
to volume, as might be sur-
mised from what has been stated
in our general remarks, when
dealing with the cerebrum and
cerebellum ; in the arrange-
ment of the convolutions there
are also important differences.
Ruminants (Figs. 442,
443). — In these creatures, the
brain is more globular than in
Solipeds. The hemispheres are
wider behind than in the Horse
and Ass, but they are narrower
in the frontal region ; there they
are a little flattened on each side,
and curved downwards. The
fissure of Sylvius is deeper at
its commencement ; its middle
branch, much more developed,
ascends to near the upper face
of the hemisphere ; at the
bottom of the latter is a V-
shaped plait, which unites the
ascending frontal convolution
to the second frontal convolu-
tion. This plait is concealed in
Solipeds.
The large fissures are dis-
posed nearly as in the Horse ;
but it should be noted that the
fissure of Rolando is interrupted,
near its origin, by an annectent
gyrus which is thrown from
the curved plait on to the as-
cending frontal convolution,
and, in front, by another plait
that unites the first parietal
convolution to the limited fron-
tal convolution.
The sigmoid gyi'us, or its
analogue, is concealed between
the passage plait that joins the parietal to the frontal convolutions.
In the Sheepy the convolutions and the sulci on the surface of the brain are
brain of the sheep (upper face), natural size.
B, Medulla oblongata : 1, posterior pyramiil of ditto. Ce,
Cerebellum: 2, 2, lateral lobes of ditto; 3, middle lobe
of ditto. C, Right hemisphere of the brain. 12, Inter-
hemispherical fissure ; 13, 13, upper end of the fissure
of Sylvius; 14, 14, fissure of Rolando; 15, 15, postero-
inferior branch of ditto ; 16, 16, posterior branch of
ditto ; 4, external parietal convolution ; 5, internal
parietal convolution; 6, lobule of the curved plait; 7,
annectent gyrus uniting the frontal lobe to the lobule
of the curved plait, above the fissure of Sylvius ; 8,
second frontal convolution ; 9, first frontal convolution ;
10, annectent gyrus uniting the first frontal convolution
to the second parietal convolution ; 17, 17, crucial fissure.
G, G, Sigmoid gyrus.
TEE CEBEBRUM.
799
arranged in exactly the same manner as in the Ox, as may be seen in comparing
Figs. 442 and 443.
Pig. — The cerebellum is flattened before and behind, against the base of the
brain. The latter is much more elongated than in Ruminants. The convolutions
are much more simple and less undulating than in the brain of the Ox and Sheep,
and in this respect they establish a kind of transition between Kuminants and
the Carnivora. In front of the
crucial fissure there is a deep ^'8- *"**•
incision on the upper border of
the hemisphere, and which is
continued by a fissure between
the two frontal convolutions to
the anterior extremity of the
brain (Fig. 444).
The gyri fissures — those
which separate the convolutions
of each lobe — are larger than in
the Horse.
T\iQ convolutions of the frontal
lobe are here also three in num-
ber. The ascending frontal and
first frontal show scarcely any
differences. On the contrary,
however, the second frontal
passes almost directly backwards,
instead of being oblique up-
wards and forwards, as in Soli-
peds. Simple in front, it bifur-
cates behind, and its two branches
pass into the ascending frontal
convolution.
There is nothing worthy of
remark with regard to the tem-
poral lobe, nor to the lobule of
the curved plait.
The first par ieto-occipital con-
volution is less distinctly divided
into two plaits than in the
Horse ; it joins, in front, the
first frontal and the ascending
frontal convolution. The second
offers nothing in particular.
Dog. — The hemispheres are much more elongated than in the preceding
species, except in the Bulldog ; the convolutions are very slightly flexuous. At
first sight, it is difficult to find on the brain of the Dog the sulci and lobes dis-
tinguished in Solipeds ; but an attentive examination allows it to be approximated
to the brains of these animals.
It is to be noted that the middle branch of the Jissure of Sylvius (Fig. 445, 3)
is very oblique backwards, which causes the fissure of Rolando to commence
much further back than in Solipeds and Ruminants. This fissure at first ascends
BRAIN OF THE PIG (UPPER FACE).
B, Medulla oblongata. C, Cerebellum
NATURAL SIZE.
1, middle lobe of
ditto ; 2, 2, lateral lobe of ditto. S, Inter-hemispheri-
cal fissure : 3, 3, crucial fissure ; 4, 4, deep fissure
separating the first frontal convolution, 9, from the
second; 12, 13, 5, fissure of Rolando; 6, first parietal
convolution; 7, second ditto; 8, limited frontal convo-
lution ; 10, annectent gyrus between the limiting fron-
tal convolution and frontal convolutions (probably the
sigmoid gyrus) ; 11, lobule of the curved plait.
800
THE CENTRAL AXIS OF THE NERVOUS SYSTEM.
backwards, describes a marked curve with concavity antero-inferior, then returns
forwards, and terminates by two branches at some distance from the sigmoid
gyrus, from which it is separated by a plait that unites — as in Ruminants — the
first parieto-occipital convolution to the anterior convolutions. The result of
this arrangement is that the frotital lobe extends well backwards on the external
face of the hemisphere. On the other hand, the convolution that occupies the
position of the lobule of the curved plait is much reduced ; it communicates by an
annectent gyrus with the parieto-occipital lobe. The latter occupies two-thirds of
the upper face of the hemisphere ; it is limited in front by a very evident crucial
LATERAL FACE OF THE DOG S BRAIN.
BULLDOG.
1, Inter-hemispherical fissure; 2, crucial fissure; 3, fissure of Sylvius; 4, fissure of Rolando; 5,
olfactory bulb ; 6, temporal lobe; 7, 7, sigmoid gyrus ; 8, 9, the two convolutions of the parieto-
occipital lobe; 10, convolution of the curved plait; 11, 12, the two plaits of the ascending frontal
convolution ; 13, 14, frontal convolutions ; 15, annectent gyrus uniting the ascending frontal to the
frontal convolutions ; 16, plait uniting the external parietal to the frontal convolutions ; 17,
annectent gyrus uniting the internal parietal convolution to the sigmoid gyrus. C, Cerebellum ; Bu,
medulla oblongata ; P, Pons Varolii.
fissure and a sigmoid gyrus. The temporal lobe is well defined ; its parallel sulcus
is completely effaced.
To sum up : in the Dog, the lobes and lobules observed in Solipeds and Rumi-
nants are found ; their relative extent alone is changed. A word has to be said
with regard to the frontal and parieto-occipital lobes. The fii-st is enveloped by
an ascending frontal convolution that describes a very sudden flexuosity, and
enters the sigmoid gyrus. The second frontal convolution immediately surrounds
the middle branch of the Sylvian fissure ; behind, it has the same relations with
the ascending convolution as in the Horse ; in front, it passes into that convolu-
tion. Lastly, the first frontal convolution is, like the orbital lobe it surmounts,
TEE CEREBRUM.
80]
suddenly and greatly flattened on each side ; it is nearly smooth, and is joined,
behind and downwards, to the second frontal convolution and external root of
the olfactory lobe ; it is confounded, above, with the convolution surrounding
the crucial fissure. The upper face of the parieto-occipital lobe forms a longer
triangle than in Solipeds and Ruminantl.
^\\Q first parieto-occipital convolution, double as in the other animals, bifurcates
in front ; its internal branch runs into the extremity of the second convolution
and the sigmoid gyrus, while its external branch, as in the Ox, passes on to the
ascending frontal convolution. If we supposed this branch interrupted by a
notch, the fissure of Rolando would be disposed, in front, in the same way as in
Solipeds.
Cat. — The brain of the Cat is more regularly ovoid, and more flattened than
Fig. 446.
Fig. 447.
BRAIN OF THE CAT (NATURAL SIZE).
B, Medulla oblongata. c, Cerebellum : 1,
middle lobe of ditto ; 2, 3, lateral lobes of
ditto. S, Inter-hemispherical fissure ; 4, 4,
crucial fissure ; 5, second parietal convolu-
tion; 6, first parietal convolution; 7, limiting
frontal convolution ; 8, sigmoid gyrus.
BRAIN OF THE DOG (UPPER FACE).
NATURAL SIZE.
B, Medulla oblongata. C, Cerebellum : 1,
middle lobe of ditto ; 2, 3, lateral lobes of
ditto. S, Inter- hemispherical fissure; 4,4',
crucial fissure ; 5, sigmoid gyrus ; 6, second
parietal convolution ; 7, first parietal con-
volution; 8, limiting frontal convolution;
9, first and second frontal convolutions.
that of the Dog. The convolutions, less flexuous than in that animal, also afifect
the longitudinal type, as may be seen in Fig. 447. The crucial Assure is placed
quite in front, near the anterior extremity of the hemispheres, which is occupied
by a very short, first frontal convolution. The occipital portion of the parieto-
occipital lobe is very reduced, and the region it occupies is indented to receive a
part of the cerebellum.
Comparison op the Cerebrum op Man with that op Animals.
The cerebrum of Man (Fig. 448) is distinguished by its regularly ovoid shape, and its great
development, particularly behind, where it covers the cerebellum — a feature never observed
in animals.
802 TKE CENTRAL AXIS OF THE NERVOUS SYSTEM.
Viewed superiorly, it shows the upper part ot the frontal, parietal, and occipital lobes. The
frontal lobe is separated from the parietal by the fissure of Rolando, which is very deep, and
almost transversely intersects the middle portion of the hemisphere. The parietal lobe is
separated from the occipital by the external perpendicular fissure.
The fissure of Rolando is separated by two large convolutions — the frontal ascending and
parietal ascending. %
The inferior face of the hemisphere is intersected by a deep fissure of Sylvius, at the bottom
of which is found the lobule of the insula, when the temporal lobe, situated in front of it, is
separated from the frontal lobe, situated behind it.
The internal face presents, besides the parts described in animals, two fissures — the internal
perpendicular and vertical branch of the calloso-marginal fissure. Between these two fissures
is the central or quadrilateral lobule — a dependency of the parietal lobe ; in front, the paracentral
lobule that surrounds the termination of tlie fissure of Rolando, and the internal face of the
frontal lobe ; behind, the cuneiform lobule, the internal portion of the occipital lobe.
Its convolutions are larger, and separated by deeper sulci than in the domestic aoimals.
Fig. 448.
THE BASE OF THE HUMAN BRAIN.
1, Longitudinal fissure ; 2, anterior lobes of cerebrum ; 3, olfactory bulb ; 4, lamina cinerea ; 5, fis-
sure of Sylvius ; 6, locus perforatus anticus ; 7, optic commissure ; 8, tuber cinereum ; 9, third
nerve; 10, corpus albicantium ; 11, fourth nerve ; 12, locus perforatus posticus ; 13, fifth nerve;
14, crus cerebri ; 15, sixth nerve ; 16, pons Varolii ; 17, portio dura of seventh nerve ; 18, middle
lobe of cerebrum; 19, portio molliss of seventh nerve; 20, anterior pyramid; 21, glosso-pharyn-
geal nerve; 22, olivary body; 23, pneumogastric nerve; 24, lateral tract; 25, spinal accessory
nerve; 26, digastric lobe; 27, hypoglossal nerve; 28, cerebellum; 29, amygdala; 30, slender
lobe ; 32, posterior inferior lobe.
'Yhe frontal convolutions are three in number; the third, or external, indistinct in animals,
is situated on the externo-inferior part of the lobule, immediately above the fissure of Sylvius;
it is named the language convolution, or convolution of Broca, to signify that this surgeon
demonstrated that it was the seat of language. These convolutions, all proceeding backwards,
pass into the ascending frontal convolution.
The temporal lobe, which is very developed, shows three undulating convolutions on its
surface, distinguished as first, second, and third.
The convolutions of the lobule of the curved plait are incomparably more developed than in
animals.
Lastly, the occipital lobe has three convolutions— ^rs<, second, and </jt>d— joined to those of
the parietal lobe by two annectent gyri.
THE NERVES. 803
It may be added that the olfactory lobes arise, as in animals, from two orders of roots, but
they are small and entirely hidden beneath the inferior face of the frontal lobes.
Examined internally, the brain of Man offers the following principal differences :—
The corpus callosum is very developed, and, above the ventricle, forms, from before to
behind, a salient angular prolongation named the frontal cornu and occipital prolongation,
ov forceps major.
There is nothing to note concerning the fornix and septum lucidum, except that there is
a ventricle in the latter which communicates with the middle ventricle by a small aperture —
the vulva.
The lateral ventricles offer remarkable differences. They are not prolonged into the
olfactory lobes, but possess a diverticulum that enters the occipital lobe, below the forceps
major. This space is more or less developed, and terminates in a point; it is named the
ancyroid or digital cavity, and shows on its floor a small convolution which has been designated
the ergot of Morand (pes hippocampi). The diverticulum and convolution do not exist in
animals. The cornu Ammonis is slightly uneven on its surface ; it is limited, inwardly, by
a band, and belnw this by a grey denticulated lamina— the gyrus fornicatus.
The optic thalamus forms an enormous prominence on the floor of the lateral ventricle,
between the caudate nucleus and tlie cornu Ammonis, while it is entirely covered by the latter
in the brain of animals.
THIRD SECTION.
THE NERVES.
The n&rves represent the peripheral portions of the apparatus of innervation.
They are cords ramifying in every part of the body, having their origin in the
spinal cord or its prolongation — the brain. Before commencing their special
study, it is necessary to possess a summary notion of the principal distinctions
of which they are susceptible, with regard to their origin, distribution and
termination.
Structure. — The nerves are formed by an aggregation of the nerve-tubes
already described. These are grouped in primary fasciculi, which are rectilinear
or slightly undulating, and enveloped in a sheath of delicate connective tissue — •
the perineurium {internum). These primary fasciculi are again collected into
bundles to form secondary fasciculi, which are maintained by a layer of fibrillar
connective tissue thicker than the perineurium {perineurium externum). Finally,
these secondary bundles by their union constitute the nerve, around which the
connective tissue becomes condensed, and constitutes the neurilemma.
(Extremely small septa pass into the secondary bundles of nerves, consti-
tuting the endoneurium ; from this delicate folds or lamellae are given off around
each nerve-fibre, corresponding to the perimysium of individual muscle-fibres.
The coverings of the nerves are anatomically continuous with the connective
tissue coverings of the brain and spinal cord. The perineurium consists both of
ordinary connective tissue and elastic tissue ; and it is hned by two, and in
small nerves by one, layer of endothelial cells, forming the sheath of Henle.)
Vessels traverse the connective tissue separating the fasciculi from each
other ; they anastomose in a network with elongated meshes which are parallel
with the nerve-tubes, and they are also surrounded by the tiervi nervorum.
(Lymph-spaces exist between the layers or lamellse of the perineurium, and it
would also appear that each individual nerve is surrounded by a lymphatic
space, which is continuous with the subdural and subarachnoid lymph-spaces
804 TEE NERVES.
of the spinal cord and brain, while it has no communication with the lymphatics
in the vicinity of the nerve. It follows that any increase of pressure in the
lymphatic spaces of the central organs, will afPect the nerve-ramifications
throughout the body.)
On the track of certain nerves is observed a greyish enlargement, or ganglion.
This is composed of a mass of nerve-cells situated on the course of the tubes.
All the upper roots of the spinal nerves are provided with a ganglion. In these
spinal ganglia in Mammalia, the nerve-cells are unipolar, and the single prolon-
gation is directed towards the periphery. Ranvier has demonstrated that this
prolongation is united to the nerve-tubes of the roots of the nerves at an
annular constriction, and that from this arrangement there result T or Y-shaped
tubes.
Division. — Nerves are divided, with reference to their destination, into two
principal groups : 1. The cerehro-spinal nerves, or nerves of animal life ; 2. The
ganglionic nerves^ or nerves of organic life.
Cerehro-spinal nerves. — These emanate directly from the cerebro-spinal axis,
and are divided into two secondary groups : 1. The cranial or encephalic nerves^
which arise in the brain, and make their exit by the foramina at the base of the
cranium, to be distributed almost exclusively in the head. 2. The spinal or
rachidian nerves, arising in the spinal cord, and passing to the muscular or
tegumentary parts of the trunk and limbs, through the intervertebral foramina.
After what has been said with regard to the apparatus of innervation, we
know that the fibres composing these cords are distinguished — by their point
of origin and their properties — into fibres of superior origin or of centripetal
conduct ihility, and fibres of inferior origin or of centrifugal conductibility. The
first have a ganglion on their course.
The cerebro-spinal nerves are exclusively formed of the first description of
fibres, and are named sensitive nerves, as they conduct the stimulus which brings
into play the sensibility of the brain. They are distinguished as nerves of general
sensibility and nerves of special sense. The first are destined to convey all
stimuli except those produced by light, sounds, or odoriferous particles ; the
second exclusively conduct the latter.
The nerves which are composed only of fibres of the second kind are called
motor nerves, because it is they which carry to the muscles the spontaneous
stimulus to motion originated by the will.
Those which are composed at once of motor fibres and fibres of general
sensibility, constitute the mixed nerves ; these form the largest category.
Ganglionic Nerves. — These nerves — collectively representing the great sympa-
thetic system — form below and on the sides of the spine, two long cords, rendered
moniliform by the presence of ganghonic enlargements. In the constitution of
these cords nearly all the cerebro-spinal nerves concur ; their ramifications —
frequently ganglionic also — are sent to the viscera of the neck, the thorax, and
the abdomen.
In these nerves of organic life are found the two kinds of nerve-tubes — fibres
of centripetal and fibres of centrifugal conductibility. But these tubes appear to
have only very indirect relations with the brain, for the will has no influence
over the organs which receive their nerves from the great sympathetic ; and
besides this, in health the excitations developed in these organs are all reflected by
the spinal cord, and do not provoke in any way the special activity of the brain
— they are not felt.
THE NERVES. 805
However this may be, it must be remarked that the special anatomical and
physiological characteristics of the sympathetic nerves, should not cause them to
be considered as a system independent of the first, or cerebro-spinal nerves. The
fibres composing both have, in fact, a common origin in the spinal cord — or,
rather, those of the ganglionic nerves emanate from the nerve-cords of animal
life. In the considerations which follow, we will therefore omit this distinction
of the nerves into two groups.
(The nerve-fibres in the sympathetic system of nerves are chiefly non-medul-
lated, and form the preponderance of this kind of nerve-fibre. Syrnpathetic
nerves are whiter than cerebro-spiift,! nerves, or have a pale-grey hue.)
Origin of the Nerves. — We ought to distinguish in these cords their
real or deep origin, and their superficial or apparent origin.
The latter is represented by the point of issue of the roots of the nerves,
which are ordinarily spread in a fan-shape, then united — generally after a very
brief course — into a single trunk, which offers at its commencement a ganglionic
enlargement, if fibres of general sensibility enter into its constitution. The
inferior spinal roots issue from the bottom of the inferior collateral furrow of the
spinal cord ; the superior roots from slightly within the superior collateral furrow.
Their real origin is the point of departure of these roots in the substance of the
cerebro-spinal axis. The nuclei of the nerves have been the object of much
investigation during recent years, and we therefore know the majority of them.
It may be remarked that the cells of the nuclei of the spinal nerves are larger
than those of the grey matter of the medulla oblongata. Otherwise, the motor
cells diminish in volume from below upwards — that is, from the lumbar region
to the medulla oblongata (Pierret).
Distribution of Nerves. — The nerve-trunks, formed by the radicles of
which we have just spoken, issue in pairs from the foramina at the base of the
cranium or in the walls of the spine, to be distributed to all parts of the body by
dividing into successively decreasing branches.
Those among these branches which ramify in the organs of animal life,
generally follow the track of the deep vessels or the subcutaneous veins, and are
always found most superficial. Their ramescence is effected in a very simple
manner, by the successive emission of the fasciculi composing the principal
trunks, until these are completely expended. These branches pursue their
course nearly always in a direct line ; only some — as the ramifications of the
two principal nerves of the tongue — describe very marked flexuosities, with
the same protective intention as the arteries of that organ. Anastomoses some-
times join these branches to one another ; and anastomoses — frequently compli-
cated - unite many nerves together, forming what are called plexuses. But in
these anastomoses, no matter how comphcated they may be, there is never any
fusion of the nerves, but merely aggregation of their fibres, which always pre-
serve their independence, characters, and special properties. These anastomoses,
then, differ essentially from those of arteries, and never permit two trunks to
mutually supplement each other when the course of one is inteiTupted.
The nerves sent to the organs of vegetative life, and which arise from the
two subspinal chains in the formation of which nearly every pair of nerves
concurs, comport themselves in their distribution in a slightly different manner.
They are enlaced around arteries, forming on these vessels very complicated
plexiform networks, and yet the fibres composing them are as absolutely inde-
pendent as in the anastomoses above described.
806 THE NERVES.
Termination of the Nerves. — This point should he examined separately
in the case of the motor and the sensitive nerves — that is, in the muscles and
the integumentary membranes. The distinction, however, is not quite so abso-
lute as this, for the muscles always receive some sensitive tubes, with their motor
filaments.
In entering the muscles the 7notor nerves divide their branches, still appearing
as double-contoured tubes. It was at one time believed that these fibres formed
loops (Valentin) in the interior of the muscle, and retm'ned to their starting-
point. This opinion has become obsolete since the ultimate termination of the
nerves has been studied by Rouget, Krause, Kiihne, Kolliker, Engelmann, Ranvier,
and others. What is kiaown of this subject is as follows : The voluminous,
double-contoured nerve-tubes which, more or less, cross the direction of the
muscular fibres, soon divide and form pale tubes, with nuclei disseminated on
their course. These tubes contain an axis-cylinder and a medullary layer. They
pass on to a muscular fibre in the following manner : the nucleated sheath of
the nerve-tube spreads, and is confounded with the sarcolemma ; the medulla
suddenly stops when it has reached the ?notor end-plate, which is granular and
Fig. 449.
MUSCULAR FIBRES, WITH TERMINATION OF MOTOR NERVE (FROM THE GASTROCNEMIUS
OF THE RANA ESCULENTA).
«, Terminal pencil of a dark-bordered nerve-fibre ; b, intramuscular naked axis-cyliuder ; c, nucleus
of the neurilemma ; d, clavate extremities of the neive ; e, spaces of the muscle-nuclei ; /, terminal
knob of nerve, with central fibres and vesicular dilatations of the nerve.
has small nuclei. The axis-cylinder enters this little plate, and breaks up into
fibrillae, which terminate in a manner unknown on coming into contact with the
contractile fibrillfe.
(When the ultimate nerve-fibre approaches the muscular fibre, the former
loses the white substance of Schwann, while the axis-cylinder pierces the sarco-
lemma and terminates in the motor end-plate. These plates vary much in form
and general appearance. Sometimes they seem to consist of very minute fibres,
formed by the splitting up of the axis-cylinder, anastomosing so as to form a
network, but usually they take the form of irregularly shaped granular masses
or discs, containing numerous vesicular nuclei.)
The mode of termination of the sensitive nerves varies, according as they are
sensorial or general sensibility nerves.
It appears to be demonstrated that the tubes of the sensorial nerves have at
their extremity an elongated cell, analogous to that from which they started.
An idea has been given of this arrangement in describing the olfactive portion of
THE CRANIAL OB ENCEPHALIC NERVES. Sffl
the pituitary mucous membrane. Other examples will be given when studying
the organs of the senses.
The other sensitive nerves — the cutaneous nerves, for example — have been
supposed to terminate by peripheral loops, and again by free extremities passing
into a kind of cell elements. It is certain that these two modes exist simul-
taneously ; recurrent sensibility, which Claude Bernard demonstrated in some
cranial nerves, proves that certain nerves have pre-terminal peripheral loops.
Our own experiments have shown :^ 1. That this recurrent sensibility is a
general phenomenon belonging to the sensitive nerves of the limbs, and even to
all the sensitive ramifications of the spinal nerves and those of the face. 2. That
the recurrent anastomotic loops are formed at different parts along the course of
the nerves, either beneath the integuments or in their texture. It may be added
that there are found in the papillae of the skin, in certain regions — hand, foot,
lips, tongue, glands, clitoris — the corpuscles of Meissner, or tactile corpuscles.
These are composed of condensed connective tissue, and are conical, like a pine-
cone, the summit towards the periphery. By their base they enter one or more
nerve-tubes, which terminate in enlargements. In the conjunctiva, lips, etc.,
are also found rounded bodies analogous in their structure to the tact corpuscles,
and which are named the corpuscles of Krause. Lastly, on the course of the
collateral nerves of the fingers and in the mesentery of the Cat, are the Pacinian
corpuscles., or corpuscles of Vater — small globular or ovoid bodies, formed of
several concentric layers of tissue, and with a central cavity or canal into which
penetrates and terminates — by one or more enlargements — a filament from the
nerve-trunk (reduced to the axis-cylinder only).
CHAPTEE I.
The Cranial or Encephalic Nerves.
The cranial nerves leave the brain in pairs, regularly disposed to the right and
left, and designated by the numerical epithets of first, second, etc., counting
from before backwards.
Willis, taking for a basis the number of cranial openings through which
the nerves passed, divided them into nine pairs, with which he described the
first spinal pair, making it the tenth in the series of cranial nerves. This
division being faulty in some respects, it was sought to perfect it. Haller com-
menced by removing the first spinal or suboccipital pair of nerves to their
proper region ; then followed Soemmering and Vicq-d'Azyr, who doubled the
seventh pair of Willis, and reduced his eighth into three distinct pairs, according
to considerations derived from the destination and uses of these nerves. The
number of pairs of cranial nerves, their order of succession, and their nomen-
clature were then estabhshed in the following manner : —
' Arloing and Tripicr, " Recherches sur la Sensibility des Teguments et des Nerfs de la
Main" {Archives de Physiologie, 1869).
THE NERVES.
Ist pair, or olfactory nerves . . corresponding to the 1st pair of Willis.
2nd pair, or optic nerves 2nd pair „
3rd pair, or common motores oculorum nerves 3rd pair „
4th pair, or pathetici nerves 4th pair „
5th pair, or trigeminal nerves 5th pair ,
6tii pair, or abducentes nerves 6th pair „
7th pair, or facial nerves \
8th pair, or auditory nerves / ^^^ "
9th pair, or glosflo-pharyngeal nerves ......)
10th pair, or pneumogastric nerves > 8th pair „
11th pair, or accessory or spinal nerves )
12th pair, or great hypoglossal nerves 9th pair „
In the following table, these nerves are classed according to their properties :—
, ^^ „ . , ( olfactory nerves or Ist pair.
1. Nerves of special ) *• „ o„-i
*^ s optic nerves 2na „
sense . . . ( auditory nerves 8th „
2. Mixed nerves /" trigeminal nerves 5th „
with double < glosso-pharyngeal nerves 9th „
roots . . . ( pneumogastric nerves 10 th „
/ common motores oculorum nerves .... 3rd „
9 M t. „^,^„o i pathetici nerves 4th „
8. Motor nerves \ '^i , , ^^,.
with single I abducentes nerves 6th „
, ^ j facial nerves 7th „
" r accessory or spinal nerves Uth „
^ great hypo-glossal nerves 12th „
(Sir Charles Bell considered the fourth, seventh, and eighth nerves as form-
ing a separate system, and to be allied in the functions of expression and respira-
tion. In consonance with this view, he termed them respiratory nerves, and
named that portion of the medulla oblongata from which they arise, the
respirator 1/ tract.)
One of the characteristics of the cranial nerves being their diversity, it is
scarcely possible to study them as a whole, and it is only in their origin that
they resemble each other in some points. A good idea of their origin is given
in Fig. 452.
Preparation of the cranial nerves. — Four preparations are necessary for the study of the
cranial nerves :
1. A brain extracted after opening the cranium by its base, and hanlened by prolonged
immersion in alcohol or very diluted nitric acid. This piece permits the origin of the nerves
to be studied (Fig. 424).
2. The superficial nerves of the head : these are the auricular nerves, and the divisions of
the subzygomatic plexus, with the infra-orbital and mental branches, as well as the superficial
ramuscules of the three nerves of the ophthalmic branch of the fifth pair (Fig. 168).
3 A piece disposed as in Fig. 454, for the study of the maxillary nerves. To prepare it,
the greater part of the masseter muscle should be removed in dissecting the masseteric nerve;
the globe of the eye must be extirpated, the orbital and zygomatic processes excised, the two
maxillary sinuses opened, and the branch of the inferior maxillary bone chiselled off as in the
figure. Lastly, the anastomosis of the facial with the subzygomatic nerve is dissected, by
cutting away the parotid gland.
4. The deep nerves, including those of the globe of the eye ; this preparation should be
made by following exactly the instructions given for dissecting the arteries of the head. Figs.
450 and 454 will serve as guides for details.
The pneumogastric and spinal nerves, which are not included in these considerations,
should be prepared and studied at the same time as the great sympathetic. When treating of
the latter, we will refer to them.
Preparations 2. 3, and 4 may be made on one head, and simultaneously. With this object,
the head is skinned, and the facial panniculus, beneath which the branches of the subzygo-
matic plexus lie, is removed. The parotid gland is carefully dissected off, to expose the sub«
TEE CRANIAL OR ENCEPHALIC NERVES. 809
parotideal branches of the facial nerve ; then proceed as if preparing the muscles of the tongue
and pharynx and the arteries of the eye. Finally, the branches of the fifth pair, hypoglossal,
glosso-pharyngeal, and ocular nerves are exposed by freeing them from the tissues surround-
ing them.
To follow more easily the ramifications of the cranial nerves in their intra-osseous course,
the head may be macerated in a bath of diluted nitric acid. The bones being softened, are
more easily cut and chiselled, while at the same time the nerves themselves are rendered more
firm and apparent by the dissolution of the connective tissue.
1. FiEST Paik, or Olfactory Nerves (Figs. 423, 424).
The first cranial pair is constituted by the olfactory lobules, the anterior
extremities of which give off a great number of nerve-filaments ; these pass
through the cribriform foramina to ramify in that part of the pituitary mem-
brane lining the bottom of the nasal fossae.
Each olfactory lobule is connected with the brain by two roots — an external
and an internal — both composed of white substance (Fig. 424). The external
commences by a grey-coloured convolution which borders, externally, the tempo-
ral lobe of the hemisphere. The internal, followed from before backwards, turns
round in the interlobular fissure, in front of the optic commissure, to mix with
the cerebral convolutions. These two roots circumscribe a triangular space
occupied by the extra-ventricular nucleus of the corpus striatum, which they
embrace. In brains which have been macerated for a long time in alcohol, it is
easy to see that the fibres of these roots are continuous, in very great part, with
those of the corpus striatum, and leave with the fasciculi of the isthmus, which
radiate and spread through the grey matter of the corpus striatum.
According to Meynert and Luys, a portion of the radicular fibres of the
olfactory nerves intercross in the substance of the white commissure of the
encephalic isthmus.
After the union of its two roots, the olfactory lobule is constituted by a wide
white band that passes forward on the inferior face of the hemisphere, and soon
terminates in a very elongated oval dilatation lodged in the ethmoidal fossa.
This bulb is formed by grey substance on its inferior face, and white substance
on the superior. It is said to be a flattened ganglion laid on a band of white
substance, which at first represents in itself the olfactory lobule.
We have already seen that this lobule is hollow, and that it communicates
with the lateral ventricles of the brain. This peculiarity, added to the special
features of its external physiognomy, might, it appears to us, give rise to doubts
as to the real nature of the lobules in question. It is evident that they are not
nerves, but rather dependencies of the brain ; and it is only conformable to
custom that we describe them here as the first pair of cranial nerves.
The real olfactory nerves are the filaments which arise from the inferior face
of the ganglion or oJfactory bulb, and which traverse the cribriform plate to reach
the mucous membrane of the nose. Their number corresponds to the ethmoidal
foramina. At first very soft, delicate, and easily torn, they are enveloped on
their passage through these apertures by a very strong neurilemma, which gives
them great solidity. Some, in ramifying, descend on the septum nasi ; others —
and these are the most numerous — divide on the ethmoidal cells, where they form
fine and more or less plexuous tufts among the no less interesting divisions of
the ethmoidal branch of the ophthalmic artery. Their terminal extremities do
not descend below the upper third of the nasal fossae, but remain confined to the
bottom of these cavities.
810 THE NERVES.
These are the special nerves of smell. They receive the impression of odours
and transmit it to the brain ; this function, which has been accorded and refused
them time after time, appears to be now definitively accepted.
2. Second Pair, or Optic Nerves (Fig. 424).
The nerves of vision present for consideration in their interesting study, their
origin, course, termination, andi properties.
There has been much dispute — and there will probably be much more — with
regard to the origin of the second pair. But without confining ourselves to an
appreciation of the opinions which have pervaded science on this matter, we will
describe what we have observed in the domesticated animals.
When the isthmus is isolated from the brain (Fig. 426, 12) and examined
laterally, we recognize on its anterior limit the white band that constitutes the
optic nerve. Studied at its origin, this band is continuous, in the most evident
manner, with the external side of the thalamus opticus, where it forms the two
enlargements known as the corpora geniculata. This thalamus ought, therefore,
to be regarded as the point of departure of the nerve that bears its name. But
as the external corpus geniculatum is in contact with the natis, and as the
internal is united to the testis by a band of white fibres, it is almost certain,
according to several authorities, that the corpora quadrigemina concur in furnish-
ing the constituent fibres of the optic nerves.^
At first wide and thin, the optic band (tractus opticus) is rolled round the
cerebral peduncle downwards and forwards, and gradually narrows. Arrived at
the inferior surface of the brain, it is changed into a funicular cord, which unites
with that of the opposite side to form the commissure or chiasma of the optic
nerves ; this is only a temporary fusion, as beyond it the two nerves reappear,
each passing into the optic foramen, to reach the interior of the ocular sheath
and the bottom of the globe of the eye.
We will enter into some details on the relations of the optic nerves in the
different points of the course we have indicated.
In their flat portion, or origin, they are comprised between the cerebral
peduncles and the hemispheres. From the point where they arrive free, at the
inferior face of the brain, to the commissure, they are covered by the pia mater,
and adhere by their deep face to the superior extremity of the peduncles.
The commissure is lodged in the optic fossa, and receives on its deep face the
insertion of the small grey lamina which bounds the third ventricle in front ; for
which reason this is generally described as the grey root of the optic nerves. But
of all the proper connections of the commissure, the most important are certainly
those which each nerve maintains with its congener at their junction. What
becomes of the fibres of each nerve in this anastomosis ? Do they cross one
another to reach the opposite eye ; or do they merely lie together, and afterwards
separate, in order to go to the eye on their own side ? Anatomy demonstrates
that the fibres of the commissure do not exclusively affect either of these arrange-
' To the optic nerve has been attributed two roots, which are two portion8 of the small band
of that name. The external root arises in the optic thalamus, the external corpus geniculatum,
and the anterior corpora quadrigemina ; the internal leaves the internal corpus geniculatum.
According to certain authorities, the two roots pass to the game points ; but others assert that
they reach the four corpora (juadrigemina.
THE CRANIAL OR ENCEPHALIC NERVES. 811
ments ; for in studying them in a specimen that has been macerated for some
days, it is found that the majority cross each other in a very evident manner,
but that a part regain the nerve corresponding to the side from which they came.
It is therefore seen that the nerves of the second pair are composed of one kind
of fibres on this side of the commissure, while beyond it they show two kinds —
the fibres from the right and left sides. The majority, we have said, cross each
other ; and the proof of this is afforded in certain facts observed in pathological
anatomy, which are of sufficient interest to be mentioned here. In the cases so
frequently occurring in the Horse, when an eye is lost from the ravages of
periodic ophthalmia {fiuxion periodique), the consecutive atrophy of the optic
nerve nearly always stops at the commissure, though it sometimes happens that
it gets beyond this ; and it is observed that it is usually the nerve opposite to
the diseased eye which suffers the most. Otherwise, the arrangement just de-
scribed is only a degree less advanced than that remarked in certain species — in
the osseous fishes, for instance — in which the optic nerves entirely cross each
other without confounding or mixing their fibres.
But behind the ganglionic centre of these nerves, contained in the corpora
geniculatum and quadrigemina, the direct fibres of the optic nerves cross each
other, and reach — along with those that crossed at the commissure — the sensitive
centre spread in the grey substance of the posterior lobe of the brain. This is
the opinion of Gudden, Nicati, Charcot, Landolt, etc. ; they compare the optic
nerves to the other cranial nerves.
Beyond their commissure, the nerves of the second pair are in relation with
the walls of the optic foramina ; then with the posterior rectus muscle {retractor
ocuJi), which envelops each nerve as in a sheath. In the orbital cavities they
are also related to some other nerves and vessels.
"With regard to its termination, the optic nerve enters the globe of the eye
by piercing the sclerotic and choroid coats, towards the most declivitous part of
its posterior surface, and expands in the form of a membrane, which is described
in the apparatus of vision as the retina. Before traversing the bottom of the
eye, this nerve always becomes markedly constricted.
The study of the structure of the optic nerve reveals some peculiar facts
which it is well to know, though they are more curious than interesting. The
upper part is entirely destitute of envelope, while the inferior — that in front of
the commissure — has a double neurilemma. The external layer of this is only
a dependency of the dura mater— a kind of fibrous sheath attached at one end
to the margin of the optic foramen, and at the other to the sclerotica. The
internal, which is analogous to the neurilemma of the other nerves, emanates
"from the pia mater, and shows a multitude of septa (forming the lamina cribrosa),
which keep the fibres of this nerve apart from each other. To make this
organization manifest, the nerve should be steeped in an alkaline solution for
some days, and then washed in a stream of water to remove the softened nervous
matter ; the nerve is to be afterwards tied at one of its extremities, inflated, tied
at the opposite end, and dried. By means of some sections, all the canals that
lodge the fasciculi of nerve-tubules, and which are formed by the internal
neurilemma, are visible.
Concerning the properties of the optic nerve, we will say nothing ; though
they are analogous to those of the other nerves of special sense. It transmits to
the brain the impressions f m'nished by the sense of vision, and mechanical irrita-
tion of it does not cause pain.
812
THE NERVES.
3. Third Pair, or Common Oculo-motor Nerves (Figs. 424, 450).
The nerves of the third pair emanate from the cerebral peduncles, near the
interpeduncular fissure, and at an almost equal distance between the corpus
albicans and the pons Varolii, in front of the loats niger. Their roots, seven
or eight in each, penetrate the texture of these peduncles, pass backwards, traverse
the red nuclei of Stilling, and may be traced to their nucleus, placed aV)ove the
anterior border of the pons Varolii. This nucleus is united, in the middle line,
to that of the opposite side.
From the union of these roots results a flattened trunk, which is at first
carried outward, and is almost immediately inflected forward, to enter — along
with the sixth pair and the ophthalmic
Fig. 450. branch of the trigeminal nerve — the
smallest of the great supra-sphenoidal
foramina — the sphenoidal fissure
{foramen lacerum basis cranii). The
common oculo-motov nerve afterwards
arrives, by the orbital hiatus, at the
bottom of the ocular sheath, where
it separates into several branches
destined to the following muscles of
the eye : the elevator of the upper
eyelid, superior rectus, internal rectus^
inferior rectus, posterior rectus — ex-
cept its internal fasciculus — and the
small oblique. The branch to the
latter is remarkable for its great
length ; it reaches its destination in
passing to the outside of, and then
below, the inferior rectus. The
motor roots of the ophthalmic gang-
lion furnished by this nerve, are given
off from the same point as the branch
or the small oblique muscle.
The nerves of the third pair are
purely motor, as is shown by their
connections with the inferior plane
of the cerebral peduncles, and their^
exclusive distribution to contractile organs. They excite all the muscles lodged
in the ocular sheath, except the external rectus, the great oblique, and posterior
rectus. They also innervate the constrictive muscular fibres of the iris ; the dilating
fibres are supplied with nerves by the sympathetic.
4. Fourth Pair, or Pathetici (or Trochlearis) (Fig. 450, 6).
The pathetic or internal oculo-motor (or trochlearis) nerve is the smallest of all
the cranial nerves. Its description is extremely simple. It arises from the band
of Reil, immediately behind the coi-pora quadrigemina, by two short roots, which
reach the anterior border of the valve of Vieussens, where are some cells, and from
there — their real nucleus, which is confounded with that of the conunon oculo-
motor— after intercrossing on the middle hue with the pathetic of the opposite
KERVES OP THE EYE.
I, Ophthalmic branch of the fifth pair ; 2, palpebro-
nasal br nch; 3, lachrymal nerve; 3', temporal
branch of that nerve ; 4, frontal nerve ; 5, ex-
ternal oculo-motor nerve ; 6, trochlear nerve ;
8, 9, 10, 11, branches of the common oculo-motor
nerve; 12, superior maxillary nerve; 13, its
orbital branches.
THE CRANIAL OB ENCEPHALIC NERVES. 813
Bide, it is directed outwards, downwards, and forwards, to disengage itself from
the deep position it at first occupies, and lies beside the superior branch of the
trigeminus, accompanying it to the supra-sphenoidal foramina, the smallest of which
it enters (pathetic canal). This opening is exclusively intended for it, and carries
it to the bottom of the ocular sheath, when it gains the deep face of the great
oblique muscle, in which it ramifies.
The physiological study of this nerve gives rise to some very interesting
remarks, which we will sum up here in a few words. The two oblique muscles of
the eye pivot the ocular globe in the orbit, without causing the slightest deviation
either upwards, downwards, or otherwise, of the pupillary opening. But this
rotatory movement is altogether involuntary, and is only accomplished in certain
determinate conditions. " Guerin, Szokalski, Hueck, and Helie have remarked,
that when the head is alternately inclined to the right or left, while the vision is
fixed on any object, the ocular globes describe around their antero-posterior axis
an inverse rotatory movement that has the effect of preserving a constant relation-
ship between the object from which the luminous rays proceed and the two
retinae. In this rotatory motion, the great oblique muscle of one side has for its
congener the small oblique of the other side : thus, when the head is inclined on
the right shoulder, the right eye revolves inwards and downwards on its axis,
under the influence of the superior oblique muscle, while the left eye turns on
itself outwards and downwards, through the action of the inferior oblique ; when
the head is inclined on the left shoulder, an inverse movement takes place in the
two eyes. This simultaneous rotation of the eyes around their antero-posterior
diameter, when the head is inclined to one side or the other, is necessary for the
unity of perception of visual objects ; if one of the two eyes remained fixed while
the other turned on its axis, we should perceive two images — a superior corre-
sponding to the healthy eye, and an inferior to the diseased one. These two
images are visible when the head is vertical, and particularly when it is inclined
to the affected side ; they are merged in one when the head is carried to the
healthy side." ^
The involuntary action of the oblique muscles of the eye in this rotatory
movement, strongly attracts attention to the nerves which these muscles receive,
and stimulates a desire to learn the particular conditions which permit them to
act as excito-motors independently of the will ; although they, as well as the
muscles which they supply, belong to those of animal life. In the present state
of science, nothing positive can be affirmed on so delicate a subject. There are,
nevertheless, two interesting remarks to make : the pathetic nerve is excliisively
destined to the superior oblique muscle, and the long branch sent by the common
oculo-motor nerve to the inferior oblique does not give any filament to the neigh-
bouring parts. This branch is, therefore, also the exclusive nerve of the inferior
oblique, and may be considered as a second pathetic.
(Sir Charles Bell designated the fourth nerve the " respiratory nerve of the
eye," and asserted that it was large in all animals capable of much expression.)
5. Fifth Paie, or Trigeminal Nerves (Figs. 451, 452, 453, 454).
The nerve we are about to describe has also been named by Chaussier the
trifacial nerve. It is distinguished among all the cranial nerves by its enormous
volume, the multiplicity of its branches, the variety of its uses, and its connections
with the great sympathetic system. It therefore requires to be described as com-
' Sappey, Anatomie Descriptive.
54
814
THE NERVES.
pletely as possible ; and in this description we will include the study of the cephalic
ganglia of the great sympathetic system, which ought to be regarded as annexes
of the fifth pair.
Origin. — The trigeminus belongs to the category of mixed nerves, as it
possesses two roots — ^one sensitive, the other motor.
Sensitive root (Fig. 426). — This is the largest root. It emanates from the
outside of the pons Varolii, near the middle cerebellar peduncle, and is directed
forward and downward to gain the anterior portion of the foramen lacerum,
where it terminates in a very large semilunar enlargement — the Gasserian ganglion.
Flattened above and below, and wider in front than behind, this root on the
outer side is about | of an inch in length, but the inner side is double that
measurement, because of the oblique position of the gangUon which continues it.
If it be traced into the substance of the pons Varolii, it will be found that the
fibres of the latter separate for its passage from the deep plane it at first occupies.
Fig. 451.
DIAGRAM OF A SECTION OF THE PONS VAROLII OF MAN, AT THE ISSUE OF THE FIFTH PAIR
OR TRIGEMINAL NERVE.
PP, Pyramids ; Pr, transverse fibres of the pons Varolii, with stratification of the grey substance ; TT,
grey substance in the floor of the fourth ventricle (locus cceruleus) ; CP, gelatinous substance of
Rolando; T, ascending roots of the trigeminus, curving to emerge from the pons — great or
sensitive root of the trigeminus ; MA, motor nucleus of the trigeminus ; M'A', small root or motor
root of the trigeminus (masticator nerve) ; T', fifth pair at its emergence ; x, x, raph^.
The following is the manner in which it comports itself in this plane : This root is
separated into two orders of fibres — posterior and anterior. The first pass beneath
the arcif orm fasciculi of the pons VaroHi, to be continued with the grey mass in the
medulla oblongata (Fig. 451, CP), which here represents the superior grey cornu
of the spinal cord ; the others, anterior, separate from each other, and soon
become confounded with the mass of cells in the interior of the isthmus, on the
walls of the aqueduct of Sylvius. Others, finally, reach the locus cmrulms (TT) —
a portion of the grey substance on the floor of the fourth ventricle. The sensi-
tive nucleus of the trigeminus extends from the pons Varolii to the neck of the
medulla oblongata ; it is very long (Fig. 452, F, F', F')- The fibres of the
trigeminus — or the cells which receive these fibres — are in communication with
several cranial nerves, particularly the pneumogastric, glosso-pharyngeal, facial,
and auditory (Fig. 452).
Semilunar or Gasserian ganglion (Fig. 425, 18).— This ganglion, which receives
the sensitive root of the trigeminus, is crescent-shaped, its concavity being turned
backwards and inwards. It may be said to be embedded in the fibro-cartilaginous
THE CRANIAL OR ENCEPHALIC NERVES.
815
substance which in part closes the occipito-spheno-temporal hiatus, and divides it
into several particular foramina. Its superior face is covered by the dura mater,
and sends a number of filaments to that membrane.
The Gasserian gangUon is not continued by a single trunk, but immediately
divides into two thick branches, one of which leaves the cranium by the foramen
ovale — an opening formed by the above-named hiatus ; while the other is lodged
in the external fissure in the intra-cranial surface of the sphenoid bone, and passing
along it as far as the entrance to the supra-sphenoidal foramina, bifurcates.
Hence it results that the trigeminus is divided — even at its origin — into three
branches : two superior — the oph-
thalmic branch of Willis, and the
superior maxillary nerve, commenc-
ing by the same trunk ; and an
inferior, which constitutes the in-
ferior maxillary nerve.
Motor or small root (Fig. 426,
8). — This is a flattened band which
emerges from the pons Varolii, at
the inner side of the principal root.
Its fibres may be easily followed to
the interior of the pons Varolii
(Fig. 451, M'A') ; they disappear
in the nucleus of grey substance
situated inside the nucleus of the
principal sensitive root, near the
floor of the fourth ventricle (MA).
Leaving the pons Varolii, this root
passes forwards on the inferior face
of the Gasserian ganglion, which it
crosses in a diagonal manner out-
wards, and beyond which it inti-
mately unites with the fibres of the
inferior maxillary nerve. The
superior maxillary nerve and the
ophthalmic branch do not receive
any fibres from it. In the fifth
pair, then, it is only the inferior
maxillary nerves which are at the
same time sensitive and motor, and
are real mixed nerves.
A, Ophthalmic Branch (or
Nerve of Willis) (Fig. 450, 1).— This is the smallest of the three divisions
furnished by the Gasserian ganglion ; it proceeds by a trunk common to it and
the maxillary nerve, which will be described hereafter. This branch enters the
smallest of the large supra-sphenoidal foramina, along with the common and ex-
ternal oculo-motor nerves, and in the interior of this bony canal it divides into
three ramuscules, which reach the bottom of the ocular sheath by the orbital hiatus.
These ramuscules are :
1. The frontal or supra-orbital {supra-trochlear) nerve.
2. The lachrymal nerve.
LATERAL VIEW OF THE MEDULLA OBLONGATA, SHOW-
ING THE ARRANGEMENT OF THE FIFTH PAIR, AND
RELATIVELY OF THE MOST IMPORTANT NUCLEI.
Py, Pyramidal tract ; Gf, genu facialis, or bend of the
facial nerve ; Os, superior olivary body ; 0, inferior
ditto ; Py.Kr, decussation of pyramids. The nuclei,
situated near the middle line, are darker tinted.
The numerals represent the roots of the cranial
nerves, according to their number.
816 • TEE NERVES.
3. The nasal or palpebro-nasal nerve.
1. Frontal or Supra-orbital Nerve (Fig. 450, 4). — This is a flat, volu-
minous branch placed on the inner wall of the ocular sheath, and proceeding
nearly parallel with the great oblique muscle of the eye to the supra-orbital fora-
men, into which it passes along with the artery of the same name. Undivided
before its entrance into this orifice, immediately after its exit from it, it separates
into several ramuscules, which meet the anterior auricular nerve, and are expended
in the skin of the forehead and upper eyelid.
2. Lachrymal Nerve (Fig. 450, 3). — This is composed of several filaments,
which ascend between the ocular sheath and the elevator muscle of the eyelid and
superior rectus, to enter the lachrymal gland. One of these (Fig. 450, 3')
traverses the occular sheath behind the orbital process, and places itself — from
before to behind — on the external surface of the zygomatic process, where it
divides into a number of ramuscules, some of which mix with those of the anterior
auricular nerve to form the plexus of that name, while the others pass directly into
the anterior muscles and integuments of the ear.
3. Nasal or Palpebro-nasal Nerve (Fig. 450, 2). — This describes a curve,
like the ophthalmic artery, and passes with that vessel into the cranium by the
orbital foramen. After coursing through the ethmoidal fissure that lodges the
artery, it traverses the cribriform plate, and divides into two filaments — an
internal and external, which ramify in the pituitary membrane on both sides of
the nasal fossa. Before entering the orbital foramen, this nerve gives off a long
branch {infra-trochlear) that glides over the floor *of the orbit, to reach the nasal
angle of the eye, where it is distributed to the lachrymal apparatus lodged there,
as well as to the lower eyelid ; it also detaches a long filament to the membrana
nictitans and the sensitive roots of the ophthalmic ganglion, which will be noticed
hereafter.
B. Superior Maxillary Nerve (Figs. 425, 19 ; 458, 15). — This nerve is
the real continuation of the superior trunk given off by the Gasserian ganglion,
where we will begin to follow it to its termination, examining briefly the ophthal-
mic branch already described as a collateral division of this trunk.
Remarkable for its volume, and its prismatic and funicular shape, the superior
maxillary nerve proceeds from the inner and upper section of the semilunar gang-
lion, and at first occupies the fissure on the internal face of the sphenoid bone,
outside the cavernous sinus, and is covered at this point by the dura mater.
After sending the ophthalmic branch into the smallest of the great supra-
sphenoidal conduits — the great sphenoidal fissure — it enters the most spacious of
these openings — the foramen rotundum — arrives in the orbital hiatus beneath the
ocular sheath, and, with the internal maxillaiy artery, passes along the space filled
with fat which separates that hiatus from the origin of the infra-orbital foramen,
which it follows to its external orifice on the face. There it terminates in a
number of branches named the infra-orbital ramuscules (or pes anserinus, from
their resemblance to the claws of a goose's foot).
In its course, this nerve gives off a large number of collateral divisions, among
which may be more particularly distinguished :
1. An orbital branch.
2. The great or anterior palatine nerve.
3. The staphyline or posterior palatine nerve,
4. The nasal or spheno-palatine nerve.
5. The dental nerves.
THE CRANIAL OR ENCEPHALIC NERVES. 817
In addition to which are described :
6. The infra-orhital, or terminal branches of the superior mazillary nerve.
1. Orbital Branch (Fig. 450, 13). — This ramuscule arises in the interior of
the supra-sphenoidal canal, and enters the ocular sheath with the divisions of
the ophthalmic branch. It almost immediately breaks up into two or three
very slender filaments, which ascend to the temporal angle of the eye, passing
between the fibrous lining of the orbit and the outer surface of the motor
muscles of the eye, and are distributed to the eyelids and neighbouring
integuments.
2. Great or Anterior Palatine Nerve (or Palato-maxillary) (Fig.
215, 3). — It arises from the superior maxillary nerve at the orbital hiatus, from
a trunk common to it and the nasal and staphyline branches ; it passes into the
palatine canal with the palato-labial artery, which it follows to the foramen
incisivum, where it stops.
During its course in the palatine canal, this nerve throws off two or three
small filaments, which escape by particular foramina to the anterior part of the
soft palate — median palatine nerve. Freijuently they arise from a common trunk
before the palato-maxillary nerve enters its canal, and -pass to their destination
by particular openings. For the remainder of its extent on the roof of the
palate, this nerve forms, around the arteries it accompanies, a plexiform network
similar to that of the ganglionic nerves ; the filaments escaping laterally from it
are sent to the soft parts of the palate, as well as to the gums.
3. Staphyline or Posterior Palatine Nerve (Fig. 215, 8).— The fila-
ments composing this nerve are very easily separated, and frequently anastomose
with those of the preceding nerve. They accompany the palatine artery in the
canal of that name, bend in front of the pterygoid process to penetrate the soft
palate between the glandular layer and the tunica albuginea. They then become
inflected backwards, and ramify either in the mucous and glandular tissues of the
velum pendulum, or the palato-pharyngeal and circumflexus-palati muscles. This
destination, therefore, indicates in this nerve the presence of motor fibres ; we
shall see hereafter whence they come.
4. Nasal or Spheno-palatine Nerve. — Springing from the same trunk
as the two preceding nerves, thicker than the staphyline, and nearly of the same
volume as the anterior palatine, the nasal nerve passes with its artery into the
nasal or spheno-palatine foramen, to penetrate the cavity of the nose, where it
separates into two branches — external and internal, which are distributed to the
pituitary membrane.
5. Dental Branches. — These are destined to the roots of the upper teeth,
and proceed from the superior maxillary nerve during its intra-raaxillary course ;
some even arise before the entrance of that nerve into the bony conduit which
it passes through to reach the face. These latter — analogous to the posterior
dental nerve of Man — enter the canal with the parent branch, and throw their
divisions into the roots of the last molar tooth, and sometimes also into the
second last. One portion of them plunges directly into the maxillary protu-
berance, to be expended in the mucous membrane lining it, after furnishing
some filaments to the periosteum.
Among the dental branches given off from the maxillary nerve during its
interosseous course, some pass to the molars, and others to the canine and incisor
teeth. The first — or middle dental nerves — separate in groups from the maxillary
trunk on its passage above the roots of the molar teeth ; they penetrate these
818 ■ TEE NERVES.
roots after a brief forward course, and give some thin filaments to the membrane
lining the maxillaiy sinuses.
The second is only at first a single branch — the anterior dental nei-ve — which
rises from the maxillary trunk shortly before it leaves its bony canal. After a
somewhat long course in the substance of the maxillary bones, this branch becomes
expended in ramuscules for the canine tooth and the incisors ; it is always accom-
panied by a very slender aiterial twig.
6. Infra-orbital or Terminal Branches of the Superior Maxillary
Nerve. — These ramuscules spread on the side of the face in a magnificent
expansion, which may be looked upon as one of the richest ner\ous apparatuses
Fig. 453.
GENERAL VIEW OF THE SUPERIOR AND INFERIOR MAXILLARY NERVES.
The eye has been excised, after sawing through and removing the orbital and zygomatic processes.
The maxillary sinuses have been exposed by means of a gouge or chisel, the masseter muscle
removed, and the inferior maxilla opened to show the nerve in its interosseous course.
1, Facial nerve; 2, origin of the posterior auricular nerve ; 3, filament distributed to the stylo-hyoid
muscle; 4, digastric branch; 5, trunk of the anterior auricular nerve; 6, origin of the" cervical
filament; 7, plexus formed by the union of the facial and superficial temporal nerve; 7', branch
of that plexus united to the infra-orbital nerves, 15'; 11, inferior maxillary nerve; 8, superficial
temporal nerve; 9, masseteric nerve; 10. gustatory nerve; 12, 12, dental branches; 13, mylo-
hyoidean nerve; 14, buccal nerve; 15, superior maxillary nerve; 16, spheno-palatine ganglion;
17, staphyline (or palatine) nerve; 18, common carotid ai^tery ; J 9, trunk of the occipital; 20,
trunk of the internal carotid; 21, external carotid; 22, trunk of the posterior auricular artery
embraced by a loop of the facial ; 23, trunk of the superficial temporal ; 24, internal maxillary
artery ; 25, trunk of the deep anterior temporal artery ; 26, orbital branch of the superior
dental; 27, buccal artery; 28, inferior dental artery.
in the animal econon.y. Covered at its emergence from the infra-orbital foramen
by the levator labii superioris proprius muscle, this fasciculus descends beneath
the levator labii superioris alaeque nasi and lateral dilator of the nostril towards
the nostrils and upper lip, which receive the terminal extremities of its consti-
tuent branches in the substance of their muscular and tegumentary tissues ;
these branches are slightly divergent and flexuous, and for the most part
anastomose with a large motor trunk furnished by the facial nerve (Fig. 453, 15').
C. Infeeior Maxillary Nerve (Figs. 168, 12 ; 453, 11). — At its exit from
the cranium, this branch is situated immediately within the temporo-maxillary
articulation, and thence is directed forward and downward, passing at first
THE CRANIAL OR ENCEPHALIC NERVES. 819
between the two pterygoid muscles, then between the inner and deep face of the
maxilla, arriving at the inferior dental foramen, through which it passes and
runs along the whole couree of the canal, escaping at last by the mental foramen
to form an expansion of terminal branches similar to those of the superior
maxillary nerve, and named the mental nerves.
For the first third of its extent, the inferior maxillary nerve is a flattened
band ; but beyond this it becomes thicker, and acquires a funicular shape.
At its origin it gives rise to four branches —
1. The masseteric nerve.
2. The buccal nerve.
3. The /lerve of the internal pt&rygoid muscle.
4. The superficial temporal or suhzygomatic nerve.
After its emergence from between the two pterygoid muscles, it furnishes —
5. The gustatory nerve.
6. The mylo-hyoidean nerve.
In its intermaxillary course, it detaches —
7. The dental branches.
Also a triple series of collateral nerves, which we will study before describing
the terminal branches ; these are —
8. The mental nerves.
The trunk of the inferior division of the fifth pair represents a mixed nerve,
because it is formed of sensitive and motor fibres. Is it the same for each of the
branches just enumerated : this is, do they all contain fibres of the two orders ?
This is a question on which the dissection of the two roots has taught us very
little, for their fibres soon become confounded so intimately that it has always
been found impossible to follow them separately into each nerve. But the study
of the distribution of these branches, corroborated by physiological experiments,
has greatly enlightened us in this inquiry. We see among them nerves destined
to the muscles, and others to glandular or integumental structures ; the first are
therefore chiefly composed of motor fibres, like all other muscular nerves ; and
the second exclusively contain sensitive fibres, or at least are destitute of voluntary
motor fibres. In describing each branch in particular, we shall notice their
special properties.
1. Masseteric Nerve (Fig. 453, 9 ; 459, 2). — It is detached from the prin-
cipal trunk, in front of, though close to, the base of the cranium, bends round the
anterior face of the temporo-maxillary articulation, and passes through the
sigmoid notch of the inferior maxilla to descend into the texture of the masseter
muscle and there ramify.
At its origin, this nerve furnishes two filaments which often proceed from
one very short trunk, and ascend to and expend themselves in the temporal
muscle ; this trunk is, then, the deef posterior temporal nerve.
Before crossing the corono-condyloid notch, it detaches to this same temporal
muscle a small branch which represents the deep middle temporcd nerve.
The destination of all these branches sufficiently proves that they are
motor.
2. Buccal Nerve (Figs. 453, 14 : 459, 4). — This nerve, which is twice the
size of the preceding, arises from the same point, though slightly below it. It
is directed forwards, traverses the external pterygoid muscle, and reaches the
posterior extremity of the superior and great molar gland ; leaving this, it is
placed beneath the buccal mucous membrane, and descends to the commissure of
820 THE NERVES.
the lips, along the inferior molar gland and the inferior border of the buccinator
muscle.
It gives some very fine filaments to the external pterygoid, in its passage
across that muscle. Beyond this, it furnishes a very slender ramuscule to the
orbital portion of the temporal muscle — the analogue of the anterior deep temporal
nerve of Man.
On the superior molar gland, it emits a fasciculus of branches to this organ
and the buccinator muscle. In its submucous track it throws off, at certain
distances, ramuscules of various sizes which go to the inferior molar gland and
the buccal membrane ; while its terminal filaments are expended in the lining
membrane and glands of the lips, near the commissure.
The majority of the filaments given off by this nerve to the external pterygoid
and temporal muscles are doubtless motor, but the other ramuscules are sensitive ;
even those distributed to the buccinator muscle are no exception, for its sub-
masseteric portion is supplied by the facial, as well as the superficial or anterior
part.
3. Internal Pterygoid Nerve. — It forms, with the preceding nerves, a
single fasciculus, which leaves the anterior part of the inferior maxillary nerve.
After crossing, outwardly, the internal maxillaiy artery, it descends between the
nervous trunk from which it emanated, and the external layer of the tensor
palati muscle, to go to the inner side of, and become expended in, the internal
pterygoid muscle.
This nerve is the smallest branch of the inferior maxillaiy trunk, after the
mylo-hyoidean, and excites the contraction of the muscle receiving it.
4. Superficial Temporal, Temporo-auricularis, or Subzygomatic
Nerve (Figs. 453, 8 ; 459, 3) — This arises from the inferior maxillary nerve,
at the opposite side of the fasciculus formed by the three preceding branches, or
posteriorly. Placed at first at the inner side of the temporo-maxillary articu-
lation, and between it and the guttural pouch, it is afterwards directed down-
wards and outwards, passes between the parotid gland and the posterior border
of the inferior maxilla, and below the condyle ; it then bends round the neck of
that bony eminence to arrive beneath, and to the outside of, the precited articu-
lation, where it terminates by anastomosing with the facial nerve.
In its course it sends off numerous fine filaments to the guttural pouch, the
parotid gland, and the integuments of the temporal region. Among the latter,
it is necessary to notice more particularly those which accompany the superficial
temporal artery.
This nerve appears to be exclusively sensitive. Section of it, before it anas-
tomoses with the facial nerve, does not really prevent contraction of the muscles
which receive the divisions of the plexus formed by this anastomosis.
5. Lingual or Gustatory Nerve (Figs. 453, 10 ; 459, 5). — The gustatory
nerve — the principal branch of the inferior maxillary trunk, which it almost
equals in volume — is detached at an acute angle from the anterior border of
that nerve shortly after its exit from the pterygoid muscles. To accomphsh
its course, which it effects in describing a slight cm-ve with concavity antero-
posterior, it is directed forwards and downwards, passing between the internal
pterygoid muscle and the branch of the inferior maxillary bone, and gaining the
base of the tongue, where it is situated beneath the buccal mucous membrane.
It afterwards descends more deeply, between the mylo-hyoid and hyo-glossua
longus muscles, turns round the inferior border of the latter — including also
THE CRANIAL OR ENCEPHALIC NERVES. 821
"Wharton's duct — to enter the space separating the genio-glossus from the hyo-
glossus longus and brevis muscles. From this point it continues to near the free
extremity of the tongue, proceeding in a veiy flexuous manner, and giving off,
on its course, divisions equally tortuous, which traverse the organ, but without
detaching any ramuscules to the lingual muscles ; these divisions terminate in
the middle and anterior portions of the lingual mucous membrane.
Before penetrating the mass of the tongue, this nerve furnishes : 1. At, and
in front of, the posterior pillars of that organ, some small ramuscules which are
sometimes plexiform, and are distributed to the mucous membrane at the base of
the tongue. 2. Lower, and behind, one or two thin filaments which are carried
to Wharton's duct, and ascend with it to the maxillary gland. 3. A sublingual
branch, the divisions of which enter the gland of that name, as well as the
mucous membrane covering the sides of the tongue.
The gustatory nerve receives, near its origin, the tympano-lingual filament or
chorda tympani — a branch of the facial nerve soon to be described. Its terminal
divisions mix and anastomose with those of the great hypoglossal nerve, in the
deep muscular interstice which lodges both.
Physiology teaches us that the gustatoiy nerve gives to the anterior two-thirds
of the lingual mucous membrane ordinary sensation, and, in addition, that
special sensibility (or gustatory power) by virtue of which that membrane enjoys
the property of appreciating savours. This is its exclusive function. With
regard to the tympanic filament from the facial nerve, and which is joined to the
gustatory, Bernard is of opinion that it participates in the exercise of this sense
of taste. Its radiating fibres extend to the submucous muscular layer of which
we have spoken, and on which the lingual papillse rest, and endow it with the
property of acting on these papillse by adapting them, we may say, to the sapid
substances brought into contact with them. Lussana goes further than this,
and, basing his statement on observations made on Man and on experiments,
asserts that the nerve of the tympanum passes to the mucous membrane, and
endows it with the sense of taste. It may be added that Yulpian did not at one
time agree to either of these opinions, because, according to his experience, this
nerve did not go to the tongue, but stopped at the submaxillary ganglion ; now,
however, he admits that some of its fibres pass into the lingualis muscle, and may
aid in causing movement of the tongue. Prevost, of Geneva, believes that the
chorda tympani joins the internal branch of the Ungual nerve.
6. Mylo-hyoidean Nerve (Fig. 453, 13). — The designation of this nerve
indicates its destination and uses. It goes to the muscle bearing its name, and
excites its contractility ; it arises opposite to the preceding, and, like it, descends
between the internal pterygoid muscle and the inferior maxillary bone, adhering
somewhat closely to the latter. But arriving at the posterior border of the mylo-
hyoideus muscle, it passes to the outside of it, and, meeting the sublingual
artery, ramifies with it on the external face of that muscle.
7. Dental Branches (Fig. 453, 12). — These are of two orders : some
passing to the molar, the others to the canine and incisor teeth. Their description
does not merit any special indication.
8. Mental Nerves, or Terminal Branches of the Inferior Maxillary
Nerve. — Perfectly analogous to the infra-orbital ramuscules, these nerves form
a fasciculus by diverging and flexuous branches, which leave the mental foramen
to be distributed to the textures of the lower lip, after receiving a branch from
the facial nerve (Fig. 453, 11').
822 THE NERVES.
D. The Sympathetic Ganglia annexed to the Fifth Pair. — These
ganglia, joined by filaments of communication to the anterior extremity of the
great sympathetic nerve, in reality belong to the special system formed by that
nerve-chain, as they possess the structure and properties of the other ganglia
composing it. It is therefore necessary that we should have a motive sufficiently
powerful to induce us to move them from their natural category, and mix up
their description with a nerve so different to them in its nature and functions.
This motive we find in the intimate relations of contiguity and continuity which
these ganglia manifest towards the branches of the trigeminus ; in the fact that
we sometimes find them united to these branches, and deeply mixed up with their
fibres ; and also because, in certain cases, they seem to disappear entirely, and
then their filaments of emission or reception are directly received or emitted by
the fifth pair.
The study we are about to undertake of each of the ganglia, will fully justify
what we have advanced. We will precede it by a few words of introduction, as
to the general facts relating to these small organs.
The number of sympathetic ganglia annexed to the fifth pair is susceptible of
variation, not only in different species, but also with individuals of the same species.
In the domesticated Mammifers, we somewhat constantly — though not
invariably — find three principal ganglia placed on the course of the branches
emanating from the Gasserian ganglion. These are : 1. The ophthalmic ganglion,
belonging to the nerve of the same name. 2. The spheno -palatine ganglion,
annexed to the superior maxillary branch. 3. The otic ganglion, which lies
beside the inferior maxillary nerve. Anatomists describe other two — the sub-
maxillary ganglion and the' naso-palatine (or Cloquefs) ganglion ; but we have
not yet dissected them in Sohpeds, though they should exist. The submaxillary
ganglion has been found in the Dog at a short distance from the point where the
lingual nerve gives off a branch to the maxillary gland. It receives sensitive
roots from the lingual, and motor roots (vaso-motor or excito-glandular) from
the chorda tympani.
These small bodies possess those common charactere which have been so
clearly indicated by Longet, and to which we will briefly refer. All are in
communication with the superior cervical ganglion by one or more generally very
slender filaments, and all receive one or more ramuscules from a sensitive and
a motor nerve ; these ramuscules — the afferent branches of the ganglia — are
considered as their roots. All, finally, emit from their periphery a more or less
considerable number of emergent branches or ramifications, which share the
properties, more or less modified, of the two orders of roots. The description of
each ganglion therefore includes, independently of its form, situation, etc., an
indication of all these ramuscules — ramuscules of communication with the superior
cervical ganglion ; afferent ramuscules or roots ; and emergent ramuscules. This
rule can be applied to all the ganglia, and renders their study perfectly methodical.
1. Ophthalmic (Ciliary or Lenticular) Ganglion. — This ganglion is
readily discovered, as it is always in contact with the common oculo-motor nerve,
and united to it near the point where the branch passing to the inferior oblique
muscle arises. It rarely exceeds the volume of a grain of millet, and is sometimes
so minute that it would altogether escape observation, did we not know exactly
where to look for it.
Its motor root is generally formed of two very short ramuscules coming from
the third pair. Its sensitive root, much longer, proceeds from the palpebro-nasal
THE CRANIAL OR ENCEPHALIC NERVES. 823
nerve ; it is usually through the medium of this root that the ophthalmic
ganglion communicates with the superior cervical ganglion, by means of a thin
filament it receives from the cavernous plexus.
The emergent filaments leave the anterior part of the ganglion, and arrange
themselves in a flexuous manner around the optic nerve to reach the sclerotica,
bearing the name of ciliary nerves. Some emanate directly from the palpebro-
nasal nerve, especially when the ganglion is rudimentary. Their number is
uncertain, though it is usually from five to eight.
Reaching the sclerotica at the bottom of the eye, they traverse that membrane,
and pass between its inner surface and choroid coat to the ciUary circle (or
ligament), where each divides into two or three ramuscules that anastomose with
those of the adjacent ciliary nerves, and in this manner they form a circular
plexus. From the concavity of this nerve-circle arises a series of plexuous
divisions, which are spread over the iris, influencing its contractile property.
2. Spheno-palatine, or Meckel's Ganglion. — The largest of the cranial
ganglia, nothing is more variable than its arrangement. The following appears
to be the most constant : in raising the superior maxillary nerve in its course
across the space separating the orbital from the maxillary hiatus, we discover,
lying on the upper border of the spheno-palatine nerve, a long, grey-coloured
enlargement ; this is the gangUon we are about to describe.
It is elongated and slender, irregularly fusiform, constricted at different
points of its extent and dilated in others ; it is not attached to the spheno-
palatine nerve by simple cellular adhesions or by some branches tin-own from one
cord to the other, but is intimately united to it by means of a most complicated
intercrossing of fibres, in such a way that the spheno-palatine ganglion really
forms part of the nerve of that name.
Affere?it branches. — It receives, posteriorly, the Vidian nerve — a composite
ramuscule which constitutes its motor root, and connects it with the superior
cervical ganglion. This nerve will be described with the facial, as that trunk
furnishes ins principal portion. Its sensitive roots naturally come from the
spheno-palatine nerve ; they are as remarkable for their number as their volume,
and also enter the posterior part of the ganghon.
Emergent branches. — Four series of these are recognized :
(1) A very numerous series which is detached at a right angle from the
superior border of the ganglion, and proceeds towards the ocular sheath. The
majority appear to be lost in that fibrous membrane, but we have seen some pass
through it, creep on the lower and inner wall of the orbit, and arrive at the
margin of the orbital foramen. There they were manifestly united to the other
filaments coming from the palpebro-nasal nerve, and formed a small plexus, the
divisions of which seemed destined to the ophthalmic vessels, and even to some of
the muscles of the eye — more especially the oblique ones. Among these divisions,
we have observed some which went to join the nerve of the membrana nictitans.
(2) A second series proceeding from the opposite border, and establishing a
union between the ganglion and the spheno-palatine nerve, or passing to the
palatine nerves in a more or less complicated plexiform manner, to increase them.
(3) A group arising from the anterior extremity and immediately passing to
the spheno-palatine nerve.
(4) A last fasciculus detached from the posterior extremity, to enter the two
great supra-sphenoidal canals.
Such is the usual aiTangement of the spheno-palatine ganglion. "We have
824 THE NERVES.
found it divided into three small masses, connected with each other by numerous
filaments of a deep grey colour, and free from all connection with the spheno-
palatine nerve. The small posterior mass in this case received the Vidian nerve
and the sensitive roots from the fifth pair. The distribution of the emergent
branches was unaltered.
Among the anatomo-physiological facts pertaining to the study of this
ganglion, we may remark that the staphyline, or posterior palatine, nerve derives
from it the motor property which permits it to cause contraction of the muscles
in the soft palate.
3. Otic or Arnold's Ganglion. — It appears to us that the presence of
this gangUon is not constant ; for we have sometimes found it replaced by a small
plexus, provided with some ahnost microscopic ganghonic granules.
When it does exist, it presents itself as a small fusiform enlargement placed
within the origin of the inferior maxillary nerve, beneath the insertion of the
Eustachian tube. To discover it, we have only to look for the commencement of
the buccal nerve, to which it is joined by some filaments that are so short and
thick, that we might imagine it to be fused on that trunk.
Its sensitive roots are represented by the preceding filaments. The small
superficial petrosal nerve, coming from the facial, constitutes its motor root.
From the sympathetic ramuscule accompanying the internal maxillary artery, it
receives \i^ filament of communication with the superior cervical gangUon.
Among its efferent ramuscules must be cited a superior filament, which enters
the petrous portion of the temporal bone to disappear in the internal muscle of
the malleus (tensor tympani) ; and two inferior filaments of a more considerable
volume, which separate in numerous ramuscules for the pterygoid muscles, the
Eustachian tube, and the tensor and levator palati muscles.
PHYSiOLoaiCAL R6suMi6 OF THE FiFTH Pair. — The trigeminus conveys
sensation to the skin covering the head, to the eyelids, the soft and hard palate,
the nasal fossae and sinuses, the nostrils, the greater portion of the tongue, the
saUvary glands and cheeks, and the upper and lower lips. The enormous tuft
formed by the terminal branches of the superior maxillary nerve, endow the
upper lip with the attributes of an organ of very exquisite tact.
The gustatory branch is, for the anterior two-thirds of the tongue, the essential
instrument of the sense of taste.
By its motor root, the inferior maxillary nerve produces contraction of the
muscles that bring the jaws into apposition — all those composing the masseteric
region, except the digastricus. This root is often designated, in consequence of
this function, the masticatory nerve.
The fifth pair also influences — as is demonstrated by vivisections and the
observation of pathological facts — the secretion of the mucous membranes and
glands receiving its filaments. Moussu believes he has experimentally proved
that the excito-secretory fibres of the inferior molar and the parotid gland— in the
Horse and Ruminants — proceed from the fifth pair, and not from the facial nerve.^
Finally, it is admitted that the nutrition of the tissues in which the
trigeminus ramifies depends upon this nerve.
' He says, with regard to the Horse : " The excito-secretory nerve of the parotid can be
isolated from the Gaeserian ganglion. It is composed of from four to five filaments, which lie
beside either the subzygomatic or the inferior maxillary nerve for a very short distance; then
it is placed on the surface of the guttural pouch, and reaches the posterior border of the inferior
maxilla and internal maxillary vein, to enter the parotid gland."
THE CRANIAL OR ENCEPHALIC NERVES.
The ramuscules sent by the sympathetic chain to the Gasserian ganglion, are
perhaps not foreign to the part the lifth pair seems to play in the secretory acts —
nutritive and vaso-motor.
Jolyet has found in the superior maxillary nerve, vaso-dilator filaments for
the mucous membrane of the nasal fossae, the skin on the wings of the nostrils
and lips, and the mucous membrane of the latter and the gums.
6. Sixth Paie (Abducentes), oe External Oculo-motor Nerves (Fig. 450, 5).
The external oculo-motor arises from the medulla oblongata, immediately
behind the pons Varolii, by from five to eight converging roots, which appear
to issue from between the
inferior pyramid and the Fig- ^54.
lateral fasciculus of the me-
dulla oblongata (Fig. 424, 9).
Its nucleus is confounded with
the anterior or superior nu-
cleus of the facial, which will
be described presently (Fig.
454, ME).
It is directed immediately
forward, leaves the pons
Varolii in lying close to the
inner side of the superior
maxillary nerve, and traverses
the foramen lacerum orbitale
— which already lodges the
ophthalmic branch of the
fifth pair and the common
oculo-motor nerve — to pierce
the bottom of the orbit. It
is entirely expended in the
external rectus (or abductor)
muscle of the eye, after giving
off a small ramuscule to the
external portion of the re-
tractor muscle.
DIAGRAM OF A SECTION OF THE MEDULLA OBLONGATA AND
PONS VAROLII OF MAN, AT THEIR JUNCTION.
PP, Pyramids ; Pr, Pr, transverse fibres of the pons Varolii
(between the various layers of these fibres are irregular
strata of masses of grey substance) ; ME, ME, roots of the
external motores oculorum ; M, nucleus common to the
external motores oculorum and facial nerve; FT, fasciculus
teres (vertical portion of the genu facialis) ; Fi, inferior
nucleus of the facial, in which arise the radicles that
form the fasciculus teres; GP, gelatinous substance of
Rolando (head of the posterior cornu); T, ascending or
sensitive root of the trigeminus; A'C, grey substance on
the floor of the fourth ventricle (nucleus of the auditory
nerve); AG, auditory nerve; e, external root of ditto;
», internal root of ditto ; xx, raphe ; GR, restiform body.
7. Seventh Pair (Portio Dura), or Facial Nerves (Figs. 453, 454).
The facial is a nerve exclusively motor at its origin,^ but it becomes mixed,
during its course, by the addition of several sensitive branches.
Origin. — It emanates from the medulla oblongata, immediately behind the
pons Varolii, and appears to originate at the external extremity of the transverse
band that margins the posterior border of that protuberance. But if we attempt
to trace its origin in the substance of the medulla oblongata, we see the single
fasciculus it constitutes, at its point of emergence, descend into the groove
between the pons Varolii and the above-mentioned band ; it then traverses
nearly the whole thickness of the medulla, passing between the lateral cord or
• See hereafter the description of the great petrosal nerve, for an account of the constitution
of the facial nerve.
826 THE NERVES.
column, and that portion of the restiform body which is continuous with the
large root of the fifth pair. Arrived near the floor of the foui'th ventricle, the
facial nerve separates into two fasciculi. The less important goes to a nucleus
confounded with that of the external motores oculorum ; the other passes back-
wards, and forms a prominence (fasciculus teres) on the floor of the fourth
ventricle ; then it is suddenly inflected outwards and forwards, forming a bend
(the geniculate ganglion, genu facialis (Fig. 452, TT) described by Deiters,
Vulpian, etc., and terminates in a nucleus {posterior or inferior nucleus) situated
in the lateral parts of the medulla oblongata, on the prolongation of the inferior
cornua of the spinal cord (Fig. 452, Fi). The cells of the nucleus are multi-
polar, pigmented, and larger than those of the anterior nucleus. In the Cat,
the principal fasciculus has no bend or genu.
Course. — Scarcely has the facial nerve left the medulla oblongata, than it is
directed outwards, to pass into the internal auditory meatus, along with the
auditory nerve, which lies in contact with it behind. It afterwards enters the
aqueduct of Fallopius, courses along it, and follows its inflections, which results
in its forming a bend forward at a short distance from the internal opening of
the canal, and a curve with concavity anterior, on its passage behind the cavity
of the tympanum. On leaving the aqueductus Fallopii by the stylo-mastoid
foramen, it is hidden beneath the deep face of the parotid gland, and continues
to be inflected forward — passing between that gland and the guttural pouch — and
reaches the posterior border of the inferior maxilla, where it issues from beneath
the anterior margin of the parotid to become superficial and place itself on the
masseter muscle, immediately beneath the temporo-maxillary articulation. There
it terminates in two or three branches, which anastomose with those of the super-
ficial temporal nerve from the fifth pair, thus forming the facial or subzygomatic
plexus {pes anserinus) (Fig. 168).
Distribution. — a. In its interosseous course, the facial nerve successively
furnishes —
1. The, great superficial petrosal nerve {nervus petrosus superficialis major).
2. The small superficial petrosal nerve {nervus petrosus superficialis minor).
3. The filament of the stapedius muscle {tympanic branch).
4. The chorda tympani.
It communicates, besides, with the pneumogastric nerve, by means of a
voluminous filament described as — \
5. The anastomotic branch of the pneumogastric.
b. The branches it emits on its course beneath the parotid gland arise either
from its superior or inferior border ; they are —
6. The occipito-styloid nerve.
7. The stylo-hyoid nerve.
8. The digastric nerve.
9. The cervical ramuscule.
10. Filaments to the guttural pouch and parotid gland.
The superior branches comprise : —
11. The posterior auricular nerve.
12. The middle auricular nerve.
13. The anterior auricular nerve.^
■ It Is necessary to add to these branches, those which go to the parotid gland, the
stimulation of which excites its secretion. Moussu believes at present, that these excito
secretory branches do not really come from the seventh, but from the ninth pair.
TEE CRANIAL OR ENCEPHALIC NERVES. 827
c. To this collection of collateral ramuscules are added the terminal branches,
formed by their anastomoses with the superficial temporal nerve —
14. The subzf/gomafic plexus.
A. CoLLATBEAL BRANCHES. — 1. Great Superficial Petrosal Nerve. —
This is a very remarkable ramuscule, which is detached from the bend of the
facial nerve to proceed to Meckel's ganglion. The importance of the peculiarities
attaching to the study of this nerve requires us to call special attention to its
origin, course, and termination ; though the details into which we are about to
enter may be omitted by the student.
Origin. — Ganglion geniculare. — The manner in which the great superficial
petrosal nerve comports itself at its origin is yet an obscure and disputed subject,
on which, however, light is beginning to be thrown. The following is the most
general opinion : This nerve arises from a small grey enlargement, the geniculate
ganglion (or intumescentia gangliformis), placed on the course of the facial nerve,
at the summit of the angle which that trunk describes after its entrance into the
aqueduct of Fallopius. The presence of this small ganglion on the seventh
pair should assimilate the facial to a mixed nerve, the sensitive root of which
would be represented by the -portio intermedia of Wrisherg — a thin filament com-
prised between the seventh and eighth pairs, and which emanates directly from
the medulla oblongata to pass into the posterior part of the ganglion geniculare.
We have constantly found this ganglion in the domesticated animals. There
exists, in fact, on this angle or elbow of the facial nerve, a very slight, grey,
conical prominence, composed of ganglionic cells which a microscopical examina-
tion readily reveals, and giving origin on its apex to the great superficial petrous
nerve. This prominence, which, we repeat, is very small, forms part of the facial
nerve, on which it only presents a kind of swelling. We have never seen the
sharp and precise limitation of its base that is figured in the majority of icono-
graphies of human anatomy.
On the other hand, when, on portions steeped for several weeks in water
acidulated by nitric acid, we have studied the constitution of the great petrosal
nerve, even at its origin, we have found it formed of two fasciculi very easily
separated — one internal, the other external. The latter alone is continuous with
the geniculated ganglion; the other^ traverses the facial nerve from before to
behind, then it is suddenly inflected inwards to ascend to the origin of the nerve,
and mix with its fibres. But this fasciculus very often maintains its independence
as far as the medulla oblongata, into which its fibres penetrate separately ; they
then appear as a small particular trunk beside that of the principal nerve, and
comprised between it and the auditory nerve. The great petrosal nerve does not,
therefore, proceed exclusively from the ganglion geniculare, as considerable por-
tions of its fibres — entirely destitute of ganglionic cells — ^emerge directly from the
facial nerve. With regard to the external fasciculus, the separation of its fibres by
the action of the acid shows very plainly that the grey substance of the ganglion
is found almost exclusively on their track ; and if we trace these fibres — like
those of the preceding fasciculus — into the substance of the facial nerve, we shall
find that, instead of proceeding towards its origin, they appear to be directed to
its termination — a remarkable circumstance, which we believe may be explained
by admitting that they come from the anastomosing branch of the pneumogastric
nerve, of which we will speak hereafter.
From this arrangement, it results that the great petrosal nerve arises from
the facial by two real, though intimately connected, roots : the internal is
828 THE NERVES.
evidently motor ; the external possesses the ganglionic cells of a sensitive root ;
and the trunk they both form may be regarded as a mixed nerve.
As will be observed, our view of the ganglion geniculare differe from the
general opinion held with regard to it, inasmuch as we make it belong exclusively
to the great petrosal nerve, and not to the whole of the facial fasciculi. On the
other hand, the portio intermedia of Wrisberg is not, in our opinion, the sensitive
root of the facial, the fibres of which we only look upon as motor ; it is not even
that of the great superficial petrosal nerve, of which it might, at the most, be con-
sidered as only an accessory filament. In the Horse, this ramuscule is extremely
attenuated, and can scarcely, if at all, be distinguished at its origin from the
filaments of the lateral root of the auditory nerve ; it is seen to enter the aqueduct
of Fallopius, and divide on the bend (or gangliform enlargement) of the facial
nerve into several gradually diminishing filaments, which are confounded with
the proper fibres of this nerve, or the ganglion geniculare. What a difl'erence
there is between this arrangement, and that of the real sensitive roots opposite
the ganglia placed on their track !
The opinion which regards the nerve of "Wrisberg as the sensitive root of the
facial has, we beheve, been more particularly accredited by the apparent impos-
sibility of otherwise accounting for the sensibility this nerve possesses, even at
its exit fi'om the stylo-mastoid foramen — that is, before contracting any anasto-
mosis with the fifth pair ; but this sensibility belongs exclusively to the fibres of
the communicating branch sent by the pneumogastric nerve, and not to the
fasciculi of the facial, as is proved by stimulating the latter outside the aqueduct
of Fallopius, after destroying the pneumogastric at its origin. If it is sought to
regard the intermediate nerve absolutely as a branch distinct from the original
filaments of the auditoiy, and if it be determined to make it a sensitive nerve,
then it must at least be admitted that it does not caiTy its sensibility beyond
the stylo-mastoid foramen, and that all its filaments disappear in the ramuscules
furnished by the facial in its interosseous coui-se. Otherwise, it is known that
Longet considers this nerve as forming the small superficial petrosal branch and
the nervous filament of the stapedius muscle ; but he makes it a motor branch,
destined to supply the muscles of the middle ear. His idea is very ingenious,
and would assuredly be feasible if it werf possible to follow the intermediate
nerve from its origin to the lateral column of the medulla oblongata ; but,
unfortunately, this is not the case, as the small ramuscule only appears to be
an offshoot of the fibres proper to the auditory nerve.
To sum up, the great superficial petrosal nerve proceeds from the facial by
two roots — one motor, the other sensitive — assimilable, to a certain point, to the
roots of the spinal nerves. The first is furnished by the filaments of the seventh
pair ; while the second probably comes from the pneumogastric nerve, and has
annexed to it on its course the ganglion geniculare. The nerve of Wrisberg
perhaps concurs in the formation of this ganglion, but it is certainly not its
principal source. We ought to add, that a study of microscopical sections of the
isthmus has caused Mathias Duval to regard this nerve as an en-atic portion of
the glosso-pharyngeal ; and Pierret has assimilated it to the vaso-motor filaments
which leave the lateral column of the spinal cord, to form the rami communicantes
of the great sympathetic, while the nucleus from which the branch proceeds
constitutes the anterior extremity of this column. A good deal of obscurity
still prevails with regard to the intermediate nerve, and Sapolini has proposed
to make it a thirteenth cranial nerve.
THE CRANIAL OR ENCEPHALIC NERVES. 829
Course and Termination. — The great petrosal nerve, after being detached from
the facial, and forming with it an obtuse angle opening outwards, enters the
aqueduct of Fallopius — a small passage running from behind forward, in the
substance of the petrous bone, above the fenestra rotunda and cochlea. Arriving
at the interior of the cavernous sinus — which it passes through, immersed in the
blood that sinus contains — it receives a branch from the ganglionic plexus there,
is lodged in the Vidian fissure, then in the Vidian canal, and in this manner
gains the orbital hiatus, where it separates into several branches — most frequently
two — which join the posterior part of Meckel's ganglion. It constitutes the
motor root and sympathetic filament of that ganghon.
2. Small Superficial Petrosal Nerve. — A very thin filament detached
from the facial to the outside of the preceding, and likewise traversing the
petrous bone from behind to before, to enter the otic ganghon, as its motor root.
3. Filament of the Stapedius Muscle (Tympanic). — The facial nerve,
in its passage above and in front of the stapedius muscle, closely adheres to it,
and gives it one, perhaps several, extremely short filaments.
4. Chorda Tympani (Fig. 459, 6). — This filament — also named the tympano-
lingual nerve — arises at a very obtuse angle from the facial, near the external
orifice of the aqueductus Fallopii ; but in reality it comes from the trigeminus.
It penetrates the cavity of the tympanum by a particular opening, courses from
its posterior to its anterior wall in describing a curve downwards, and passes
among the chain of auditory bones, between the handle of the malleus and long
branch of the incus. Escaping from the middle ear by a canal {fissura Glaseri)
on the hmits of the mastoid and petrous portions of the temporal bone, it proceeds
foi-wards and downwards, and finally joins the gustatory nerve after a short course
beneath the external pterygoid muscle, outside the guttural pouch.
It is distributed with the lingual in the mucous membrane of the anterior
portion of the tongue, and even, according to Vulpian, in the muscles of that
organ ; as stimulation of the chorda tympana causes movement of the tongue
several days after division of the great hypo-glossal nerve. That physiologist
attributes to it all the phenomena that Claude Bernard had observed in the
submaxillary gland, after stimulation of the ganglion of that name — vaso-dilating
and excito-secretory effects. Consequently, the choroda tympanum should throw
a certain number of fibres in that ganglion, and from it into the gland.
5. Anastomosing Branch of the Pneumogastric Nerve. — {See the
description of the tenth pair.)
6. Occipito- Styloid Nerve (Fig. 453, 3).
7. Stylo-hyoid Nerve.
8. Digastric Nerve (Fig. 453, 4). — These three spring from a common
fasciculus at the stylo-mastoid foramen, and ramify in their respective muscles,
after a certain course beneath the parotid gland.
9. Cervical Branch (Figs. 453, 6). — This nerve has its origin almost in
the middle of the subparotideal portion of the facial, near a particular loop
thrown by that nerve around the posterior auricular artery, and often from this
loop itself.
It afterwards traverses the parotid gland from within to without, and above
to below, to descend at first on its external face — beneath the parotido-auricularis
muscle — then into the jugular channel, where it is lodged below the deep face or
in the substance of the panniculus muscle, which receives its terminal divisions
near the anterior appendix of the sternum.
55
830 THE NERVES.
In its course this nerve communicates with the inferior branches of the
second, third, fourth, fifth, and sixth cervical pairs by branches from them ; it
sends numerous collateral filaments into the texture of the panniculus.
10. Filaments of the Guttural Pouch and Parotid Gland. — Re-
markable for their number and tenuity, these filaments do not otherwise deserve
particular mention.
11. Posterior Auricular Nerve (Fig. 453, 2). — It commences at the
stylo-mastoid foramen, is directed upwards beneath the parotid gland, accom-
panying the posterior auricular artery, and is distributed to the posterior muscles
of the external ear. It sometimes has at its origin a loop analogous to that
embracing the posterior auricular artery.
12. Middle Auricular Nerve. — Most frequently this arise from the same
point as the preceding nerve — it might be said in common with it — ascends
towards the base of the concha in traversing the parotid gland, and pierces the
cartilage to supply the interconchal integument, and the muscular fibres which
cover its adherent face in some parts.
13. Anterior Auricular Nerve (Fig. 453, 5). — This is the largest of the
three auricular nerves. After being detached from the facial nerve, opposite
the cervical branch, and after ascending across the parotideal tissue, it gains
the external face of the zygomatic process, where it meets the superficial
divisions of the lachrymal nerve ; it continues forward beneath the external
pariefeo-auricular muscle, reaches the base of the orbital process at the supra-
orbital foramen, there crossing the terminal branches of the nerve of that name ;
it then descends vertically within the orbit to below the nasal angle of the eye,
where it mixes with the superficial divisions of the palpebro-nasal nerve, and
finally terminates on the face of the lachrymalis and levator labii superioris
alaequi nasi muscles.
In its progress, it gives off numerous ramuscules to the anterior muscles of
the ear, the levator palpebrse superioris, and the orbicularis of the eyelids.
This nerve is remarkable for the relations it maintains with the terminal
ramuscules of the three branches of the ophthalmic nerve, or fifth pair.
Although there do not exist any real anastomoses between it and these various
branches, it is customary to designate the reticular mass they form in front of
the ear and on the side of the face, as the anterior auricular plexus.
Terminal Branches of the Facial Nerve, or Subzygomatic Plexus
(Fig. 168, 11, 12). — The facial nerve, as we have seen, terminates in several
branches — usually two, on arriving beneath the temporo-maxillary articulation,
where they join the superficial temporal nerve. After becoming sensori-motor,
they are continued on the external face of the masseter, covered by the panni-
culus muscle of the head, to which they give some ramuscules, and are united
to each other by anastomosing branches of variable disposition. It is always
observed, with regard to this arrangement, that the branches of the subzygo-
matic plexus, on arriving near the anterior border of the masseter, are divided
into a series of divergent ramuscules which pass to the surface of the vascular or
glandular canals situated in front of the masseter, to enter the tissues of the
lips, cheeks, and nostrils.^
' The following is an extract from a memoir by Arloing and Tripier. " On the Conditions
of Persistency of Sensibility in the Peripheral Extremity of Cut Nerves " (Archives de
Physiologie, 1876), relating the differences observed in the arrangement of the subzygomatic
TEE CBANIAL OR ENCEPHALIC NERVES. 831
Among: these ramuscules, the superior is remarkable for its great volume ;
it passes beneath the zygomaticns muscle, lies close to the inferior border of
the dilator naris lateralis, beside the superior coronary artery, and afterwards
runs below that muscle, where it joins the terminal ramuscules of the superior
maxillary nerve, with which it is distributed to the textures of the upper lip and
alje of the nose (Fig. 453, 7')-
A second ramuscule — the inferior, smaller than the preceding — follows the
inner aspect of the depressor labii inferioris muscle, to mix by its anterior
extremity with the terminal fasciculus of the inferior maxillary nerve, and
ramify— with the proper filaments of that fasciculus — in the tissue of the lower
lip.
Between these two principal branches is a series of smaller ramifications
destined to the buccinator muscle. Among these are some which become
inflected on the inner face of the masseter, and reach the deep portion of the
buccinator, where they anastomose with the filaments of the buccal nerve.
Other ranuiscules— situated below the principal inferior branch— are expended
in the panniculus on the face ; one of them, after bending round the lower
border of the inferior maxilla, reaches the submaxillary space.
Functions of the Facial Nerve. — This nerve excites contraction of the
muscles of the middle ear, external ear, the cheeks, lips, nostrils, orbicularis of
the eyelids, and the cervico-facial panniculus. By its great superficial petrosal
filament, it influences the movements of the muscles of the soft palate, and it is
admitted — as already noticed when speaking of the gustatory nerve — that its
tympano-lingual ramuscule acts on the submucous muscular layer of the tongue.
The facial nerve, also, without doubt, exercises its influence on the parotid
gland.
It serves as a medium for the passage for vaso-motor and excito-secretory
filaments.
It is to be remarked that the facial nerve has no influence over the masseter
plexus of Soliptids. It is useful to know these differences in accounting for the phenomena
that accompany accidental or experimental lesions in this plexus.
As a general rule, the facial nerve divides into two branches close to the parotid gland.
The auriculo-temporal nerve divides into three unequal branches when it reaches the max-
illary condyle ; the upper branch — slender, single, or bifurcated — follows the superficial
temporal artery and disappears in the skin of this region, or rejoins in part the temporo-facial
plexus. The other branches lie close beside the two branches of the facial nerve — the two
nerves being confounded with each other as they proceed to their terminations. This type,
■which we consider very rare, is modified in various Witys : —
1. The sensitive and motor filaments, instead of being confounded suddenly at the anterior
border of the parotid gland, may proceed side by side. This separation is generally less
marked in the superior temporo-facial branch ; when it exists in the inferior branch, the motor
filament is situated between the masseter and the panniculus, the sensitive filament between
the latter and the skin.
2. Separation of the sensitive and motor portions is complete. The inferior facial branch
especially may proceed alone to the lips; the sensitive branch for it follows at first the
superior branch of the plexus, and only leaves it about the middle of the masseter, to pass on
the cheek and rejoin its satellite motor filament in the lower lip only. In this case, the
inferior branch has only filaments from the facial.
3. Instead of a prompt separation between the branches of the temporo-auricular and the
facial nerve, tliere is sometimes observed fusion of the four branches, whicli may be pro-
longed some distance beyond the parotid gland. We have seen dispositions of this kind, in
which the inferior branch (tiien always mixed) was detached from the fasciculus, at the
level of the eye, in forming a very acute angle.
Sometimes marked differences are observed in the two plexuses in the same animal.
832 THE NERVES.
muscle : notwithstanding their intimate relations, it does not detach the smallest
filament to it.
Its anastomoses with the various branches of the trigeminus and pneumo-
gastric nerves, endow some of its branches with great sensibility.
8. Eighth Paie, or Auditory Nerves (Figs. 424, 455, 456).
This is the nerve of hearing ; it has a very simple disposition, which we will
sum up in a few words.
Origin. — The auditory nerve {portio mollis) proceeds from the medulla
oblongata by two roots — an anterior or lateral, and a posterior. The latter
(Fig. 425, 20) commences on the floor of the fourth ventricle by some con-
vergent strise (limce transverse^ stricB medullares), as is admitted in the majority
of treatises on human anatomy — though we have never been able to discover
these strise in the domesticated animals ; it is afterwards directed outwards,
round the posterior cerebellar peduncle, and unites with the anterior root on
the side of the medulla oblongata. The latter root (Fig. 456, g), consists of
a single fasciculus joined with that of the facial, and escapes from between the
fibres of the restiform body. The nucleus of the auditory nerve has been dis-
covered by Schroeder Van der Kolk, a little below that of the facial nerve.
Course and Termination. — These two roots immediately unite into a single
soft cord, situated behind that of the seventh pair, with which it is directed
outwards to reach the internal auditory meatus. There it divides into two
branches — an anterior and posterior — the fasciculi of which traverse the fora-
mina at the bottom of the meatus : the former to gain the axis of the cochlea
(the cochlear branch), and the latter the semicircular canals {vestibular branch).
The description of these two branches will be deferred until we come to study
the sense of hearing.
9. Ninth Pair, or Glosso-Pharyngeal Nerves (Figs. 456, 3 ; 459, 10).
The glosso-pharjTigeal is a mixed nerve, which conveys general sensation,
with gustative sensibility, to the posterior third of the tongue, and excites
contraction of the pharyngeal muscles.
Origin. — This nerve originates on the side of the medulla oblongata, behind
the eighth pair, by eight or ten fine roots, some of which are implanted in the
restiform body ; while the others — the smallest number— escape, like the fila-
ments of the facial nerve, from the interstice between that body and the lateral
column of the medulla oblongata.^ The roots of this nerve pass into two
diflPerent nuclei. The sensitive fibres reach a nucleus (Fig. 455, pn) situated near
the floor of the fourth ventricle, in the prolongation of the superior cornu of the
medullary axis ; while the motor fibres enter another nucleus (Fig. 455, s)
belonging also to the hypo-glossal, and which lies in the direction of the inferior
cornua of the spinal cord. At their exit from the medulla oblongata, these
' This disposition— which is readily exposed in the Horse— appears to us sufficient to remove
all the doubts existing iu the minds of a large number of anatomists, as to tiie nature of the
glosso-pharyngeal nerve. It evidently possesses at its origin, as motor filaments, those arising
from the same part as the facial nerve, and as sensitive filaments those from the restiform
body. Besides, we may object to the opinion whicii would also attribute the motor property
of the glosso-pharyngeal nerve to the anastomosing branches passing between it and the
seventh pair, on the ground that tliese anastomoses are far from being constant, and that in
Bome species they are always totally absent.
THE CRANIAL OR ENCEPHALIC NERVES.
roots soon unite in a single cord, which issues from the cranium by a particular
orifice in the posterior part of the foramen lacerum, and at this point it exhibits
a grey oval-shaped enlargement — the ganglion petrosum or ganglion of Andersch,
in which it is somewhat difficult to distinguish the motor filaments of the nerve
from those which arise between the lateral and superior columns of the medulla
(Fig. 456, 2).
Course a?id Termination. — Scarcely has the glosso-pharyngeal nerve escaped
from the cranium, than it descends, in describing a curve with concavity
forward, behind the large branch of the os hyoides, included at first between
a fold of the guttural pouch, then between the latter and the internal pterygoid
muscle. Lying beside the ex-
ternal carotid artery in the F'S- "^55.
latter part of its course, it x'-*"''**\ ^^^ ^
passes with it along the pos- "^^^ ^ ^ \f ^ V^'
terior border of the great cornu ^/^Vpys>^-^^<lX^->^^^^7^^^^^
of the hyoid bone, and gains
the base of the tongue with
the lingual artery, by coursing
beneath the hyo-glossus brevis
muscle. The papillae on the
posterior portion of the lingual
mucous membrane receive the
terminal ramuscules of this
nerve. (See the Sense of Taste. )
Collateral Branches. — On
its course it furnishes —
1. Jacobson's nerve {tym-
fanic hranch), a very thin fila-
ment springing from An-
dersch's ganghon, proceeding
upwards, and entering a par-
ticular foramen in the petrous
portion of the temporal bone, to
be distributed more especially
to the tympanum ; sending
also to the superficial petrosal nerves two branches, which are designated the
great and deep small petrosal nerves.
2. Filaments of communication with the superior cervical ganglion, two or three
in number, though sometimes replaced by a single ramuscule.
3. A brafich to the carotid plexus, which passes back on the guttural pouch
to reach the terminal extremity of the common carotid, whence its filaments
are sent, with those of the sympathetic nerve, either to the external carotid,
occipital, or even to the common carotid artery itself. This branch communi-
cates, by several anastomoses, with the numerous sympathetic branches which
pass from the superior cervical ganglion to the surface of the guttural pouch,
and which are either expended in that membrane, or join the posterior border of
the great hypoglossal nerve.
4. A pharyngeal branch (Fig. 459, 11), which is generally detached close
to the pharyngeal artery, and forms — along with the pharyngeal filaments of
the pneumogastric nerve — a remarkable intricate plexus {^pharyngeal) on the
Aft
DIAGRAM OF A SECTION OF THE MIDDLE PORTION OF THE
MEDULLA OBLONGATA OF MAN.
PP, Pyramids ; CC, floor of the fourth ventricle : H, radicular
fibres of the great hypoglossal nerve ; nh, classical
nucleus of ditto; n'h', accessory nucleus of ditto; S,
accessory (motor) nucleus of the mixed nerves ; pn,
sensitive nucleus of the mixed nerves (glosso-pharyngeal,
pneumogastric, spinal accessory) ; nr, nucleus of the
restiform bodies; GP, gelatinous substance of Rolando
(head of the posterior cornu) ; T, ascending root of the
trigeminus ; M, radicular fibres of the pneumogastric ;
01, grey layer of the olivary body ; R, internal juxta-
olivary nucleus ; T, external ditto ; xx, raphe.
834 THE NERVES.
upper wall of tne pharynx, below the guttural pouch. This plexus receives
a filament from the hypoglossal nerve.
10. Tenth Paie, Vagus, or Pneumogastric Nerves (Figs. 452, 455,
458, 480).
The pneumogastric nerve is as remarkable for its extent, as for the multi-
plicity of physiological uses ascribed to it.
It is prolonged beyond the stomach, after distributing to that viscus, the
oesophagus, pharynx, lung, bronchi, trachea, and larynx a large number of
filaments on which depend the movements, secretory functions, and purely
sensory phenomena of which all these organs are the seat.
Origin. — The pneumogastric is a fixed nerve, and consequently arises from
two kinds of roots ; these we will successively describe before passing to its
distribution, though it must be remarked that this subject has not yet been fuhy
determined.
Sensitive roots. — These arise from a nucleus of grey substance situated near
the floor of the fourth ventricle, a little behind the glosso-pharyngeal nucleus —
sensitive nucleus of the mixed nerves (Fig. 455, pn) — and in which the fibres of
the antero-lateral columns of the medulla oblongata, or respiratory tract of Bell,
appear to be lost. In leaving the medulla, they form from four to ten bundles,
which describe a shght curve with convexity upwards ; the highest middle fibres
coi-respond to the groove that limits, superiorly, the respiratory fasciculus, the
posterior and anterior fibres bending downwards to the pyramids — the second
more than the first.
These roots proceed transversely outwards, mixed with connective tissue
and some fine muscular ramifications, and leave the cranium by one of the
openings (jugular foramen) in the posterior part of the foramen lacerum,
uniting in their passage through that aperture into a somewhat voluminous
ganglion, called in Man the jugular ganglion {iqiper ganglion, or ganglion of the
root).
Motor roots. — Several anatomists and physiologists consider these as a portion
of the accessory nerve of Willis, and give them the name of internal or bulbar
root of the spinal nerve. They are situated a little behind the preceding, and
arise, in the middle of the respiratory tract, from a mass of grey substance which
also emits the motor fibres of the glosso-pharyngeal {motor nucleus of mixed nei'ves
— Fig. 455, s) ; consequently, they are not so elevated as the whole of the sensitive
fibres. They are separated from the latter by a comparatively large vein, and are
distinguished from them by their anastomotic tendency. Becoming longer as
they are more posterior, and frequently anastomosing with each other, the fila-
ments forming these motor roots converge, and gain the posterior part of the
foramen lacerum ; this they pass through by one or two special openings to join
the jugular ganglion, beneath and behind which we find them applied. A certain
number of the most posterior of these filaments lie beside the medullary root of
the spinal accessory nerve ; but they are soon detached to pass with the others to
the jugular ganglion.
Jugidar or Ehrenritter's ganglion. — Elongated from before to behind, and
flattened above and below, the jugular ganglion is embedded in the cartilaginous
substance that fills the foramen lacerum. When it has been macerated for some
time in dilute nitric acid, it may be resolved into two portions — one correspond-
ing to the sensitive, the other to the motor roots. Some white nerve-filamentiS
THE CRANIAL OR ENCEPHALIC NERVES 835
appear to pass to its surface without becoming confounded with it. It is in
relation, in front, with the ganglion of Andersch ; behind, it crosses somewhat
obliquely the medullary root of the spinal accessory nerve.
The jugular gangUon is also in relation with the spinal, glosso-pharyngeal,
and facial nerve. It communicates with the external root of the spinal accessory
nerve by the few radicular filaments indicated above. With the glosso-pharyn-
geal it IS connected by : 1. An afferent filament coming from the highest roots
of the ninth pair, and which meets it at its antero-internal angle. 2. By an
efferent branch it sends to the ganglion of Andersch. 3. Lastly, it is united to
the facial by a branch we have named the anastomosing branchy extending from
the pneumo gastric to the facial nerve.
This anastomotic branch, on leaving the jugular ganglion, is somewhat con-
siderable in volume, and it has appeared to us that, at times, among its radicles
there were some in direct continuity with the sensitive roots of the pneumogastric
nerve. This branch is directed forward, above the ganglion of Andersch, crosses
Jacobson's branch, traverses the petrous temporal bone, and arrives in the
aqueduct of Fallopius ; here it meets the facial nerve, at the point where the
latter gives off the chorda tympani. A small number of fibres then lie beside the
nerve of the seventh pair in ascending towards the origin of that nerve, where,
in our opinion, they constitute a large portion of the great petrosal nerve— that
which has at its origin the ganghon. Other fibres descend, on the contrary, in
following the proper fibres of the facial nerve, and are lost among these ; but the
largest number cross that nerve and continue their course in the substance of
the temporalis muscle, to be chiefly distributed to the membrane lining the
internal auditory canal.
Course and relations. — Beyond the jugular ganglion, the trunk of the
pneumogastric remains intimately allied with the spinal accessory for about f
of an inch ; these two nerves then separate to allow the great hypoglossal nerve
to pass between them ; after which the pneumogastric nerve descends alone
behind the guttural pouish, in proximity to the superior cervical ganglion.
Near the origin of the occipital artery it crosses to the inner side of that
vessel, and beyond this it is joined in the most intimate manner to the cervical
portion of the sympathetic chain ; the single cord resulting from this fusion
follows the common carotid artery, above which it is situated, to near the entrance
of the thorax. The two nerves then resume their reciprocal independence, the
pneumogastric penetrating the thorax a little below the sympathetic, in passing
among the lymphatic glands lying between the two first ribs.
In this course, the two pneumogastrics have nearly the same relations ; though
there is something special connected with the left, which is related to the
cesophagus towards the lower part of the neck.
Within the chest, however, these two nerves comport themselves a little
differently. The right passes round the axillary artery very obliquely, upwards,
outwards, and backwards beneath the mediastinal pleura, to follow the external
face of the trachea to above the origin of the bronchi, where this nerve termi-
nates. The left also passes below the brachial trunk ; but instead of turning
round the trachea, it merely lies beside that tube, and reaches the root of the
lung, after crossing, outwardly, the origin of the two aortae.
When these nerves arrive above the bifurcation of the trachea, they terminate
by forming the bronchial plexus and cesophogeal nerves — the latter being prolonged
to the stomach and the solar plexus.
836 TEE NERVES.
Beneath the jugular ganglion, but in the upper part of the neck, the pneumo-
gastric receives iilaments from the spinal accessory, ganglion of Andersch, sympa-
thetic, hypoglossal, and the two first cervical. These different nerves cross each
other in a very complex manner on the surface of the guttural pouch, the
pharynx, and divisions of the carotids, and form the guttural, pharyngeal, and
cartoid plexuses.
Distribution. — The branches furnished by the pneumogastric on its course
are
Fig. 456.
^
^^^fi;
'^*^
^^^5^8!!""'
il-
(MUGIN OF THE NERVES ARISING FROM THE MEDULLA OBLONGATA, AND PARTICULARLY THAT OF
THE PNEUMOGASTRIC, SPINAL ACCESSORY, HYPOGLOSSAL, AND GLOSSO-PHARYNGEAL.
a, Medulla oblongata ; 6, pyramids ; c, enlargement simulating the olivary body ; c?, latei'al posterior
fissure ; e, fissure limiting, superiorly, the respiratory tract of Ch. IJell ; /, corpus restiforme ;
g, auditory nerve ; h, external oculo-motor ; «", trigeminus ; j, arciform fibres of the medulla
oblongata. 1, Pneumogastric ; 2, spinal accessory, inner root ; 3, glosso-pharyngeal ; 4, spinal
accessory, medullary column; 5. inferior, or anterior, root of the great hypoglossal; 5', its
ganglionic root; 6, facial nerve; 7, jugular ganglion; 8, anastomosis of the pneumogastric with
the facial ; 9, ramuscule from the external branch of the spinal accessory passing to the pneumo-
gastric. (From Toussaint's Thesis on the Anatomie Compare'e du Nerf Pncumogastrique.
Lyons: 1869).
1. Communicating filaments tvith the sup&rior cervical ganglion^
2. Pharyngeal branch.
3. Superior laryngeal nerve.
4. Communicating filaments ivith the infe^'ior cervical ganglion.
5. Inferior laryngpal nerve.
6. Cardiac filaments.
We will pass in review these collateral divisions before studying the terminal
branches, which are :
THE CRANIAL OR ENCEPHALIC NERVES.
887
1. Those forming the bronchial plexus.
2. Those constituting the esophageal nerves.
COLLATEEAL BRANCHES OF THE PnEUMOGASTRIC
Nerve. — 1. Filaments of the Inferior Cervical
Ganglion. — Always very slender, these sometimes
come from the pharyngeal ramuscule.
2. Pharyngeal Nerve (Fig. 459, 15). — Originat-
ing from the pneumogastric nerve at the middle part
of the superior cervical ganglion, the pharyngeal passes
forwards and downwards on the side of the guttural
pouch, and gains the upper face of the pharynx, where
it terminates in forming a plexus with the pharyngeal
branch of the ninth pair. This is a sensory-branch.
It gives off a large division that passes backwards to
the surface of the middle and posterior constrictor
muscles, to which it gives branches, and, throwing off
a filament to the external laryngeal nerve, reaches the
commencement of the oesophagus ; it descends on the
outside of that tube, by becoming distributed in its
muscular tunic. This division — which w^e have named
the cesopjhageal branch of the pharyngeal nerve — may be
traced on the oesophagus to the lower part of the neck,
and in some subjects even into the thoracic cavity.
3. Superior Laryngeal Nerve (Fig. 458, 1). —
More voluminous than the preceding, and arising a
little lower, this nerve follows an analogous course to
reach the side of the larynx, where it enters the aperture
below the appendix of the superior border of the thyroid
cartilage, to be almost, entirely expended in the laryngeal
mucous membrane, which it endows with a very
exquisite degree of sensibility.
At the inner face of the thyroid cartilage, it has
several branches that are directed forward, upward,
and backward. The first pass to the mucous membrane
at the base of the tongue and the two surfaces of the
epiglottis. The second are distributed in the lateral
walls of the pharynx. Of the third, some go to the
mucous membrane of the arytenoid cartilages and that
of the oesophagus ; while others descend on the thyro-
arytfenoid and lateral crico-arytgenoid muscles, to unite
with the branches coming from the recurrent, and
form an anastomosis analogous to the anastomosis of
Galien (Fig. 458, 5).
Before, penetrating the larynx — and even very near
its commencement — it furnishes a motor filament to
ORIGIN AND DISTRIBUTION
OF THE EIGHTH PAIR OP
NERVES IN MAN.
1, 3, 4, Medulla oblongata;
1, corpus pyramidale of
one side ; 2, pons Varolii ;
3, corpus olivare; 4, corpus
restifbrme ; 5, facial nerve ;
6, origin of gloss^^-pharyn-
geal nerve ; 7, ganglion of
Andersch ; 8, trunk of the
nerve ; 9, spinal accessory ;
10, ganglion of pneumo-
gastric; 11, its plexiform ganglion; 12, its trunk; 13, its pharyngeal branch, forming the
pharyngeal plexus, 14, assisted by a branch from the glosso-pharyngeal, 8, and one from the
superior laryngeal, 15; 16, cardiac branches; 17, recurrent laryngeal branch; 18, anterior
pulmonarv iiranches ; 19, posterior pulmonary branches; 20, oesophageal plexus; 21, gastric
branches ;' 22. origin of the spinal accessory nerve; 23, its branches distributed to the sterno-
maxillaris and mastoido-humeralis ; 24, its branches to the trapezius muscle.
TEE NERVES.
the crico-pharyngeal and crico-thyroid muscles. This filament either arises directly
from the pneumogastric nerve, or— as is most frequently the case — from the
pharyngeal ramuscule ; this is the external laryngeal nerve of anthropotomists
(Fig. 458, 8).
The external laryngeal
Fig. 458.
DISTRIBUTION OF THE NERVES IN THE LARYNX
OF THE HORSE,
s, Base of the tongue ; h, epiglottis ; c, arytenoid
muscles ; c?, section of the thyroid cartilage to
show the parts it covers; e, cricoid cartilage;
/, trachea; g, oesophagus; h, thyro-arytaenoid
muscle ; i, lateral crico-arytaenoid muscle ;
j, posterior crico-aryiaenoid muscle ; k, arytse-
noid muscle. 1, Superior laryngeal nerve ;
2, inferior laryngeal ; 3, br:iuches of the
superior laryngeal passing to the epiglottis
and tongue; 4, branches of the superior laryn-
geal passing to the oesophagus ; 5, very rine
multiple anastomoses between the two laryn-
geals ; 6, tracheal branches ; 7, branch to the
posterior crico-arytfenoid muscle (a portion is
distributed, tlirough the muscles, to the
subjacent mucous membrane); 8, branch to
the lateral crico-arytaenoid muscle; 9, branch
to the thyro-arytfenoid muscle ; 10, branch
passing to the arytaenoid muscle; 11, (Esopha-
geal branch of the pharyngeal nerve (it some-
times comes from the external laryngeal).
(From Toussaint's work.)
receives accessory branches from the
superior cervical ganglion, the oesopha-
geal branch, and the pharyngeal nerve,
and is then distributed to the muscular
tunic of the oesophagus. It is to the
union of this branch with the oesopha-
geal branch of the pharyngeal nerve,
that we have given the name of ^mperior
(Bsopliageal nerves}
4. Communicating Filaments
with the Inferior Cervical Gang-
lion.— These do not always directly
enter this ganglion, for when the middle
cervical ganglion exists they pass to it.
They are not similarly disposed on both
sides. The filaments of the right pneu-
mogastric, two or three in number, are
extremely short, though voluminous.
The left pneumogastric usually only
furnishes a single, long, thin ramuscule,
which is detached in the region of the
neck near the point where the pneumo-
gastric commences to separate from the
cervical branch of the sympathetic, and
reaches the inferior cervical branch of
the sympathetic, and reaches the inferior
cervical ganglion by remaining along-
side the principal nerve.
5. Inferior Laryngeal Nerve
(Figs. 458, 2; 480, 27, 28).— Also
named the recurrent, or tracheal re-
current, because of its disposition. It
begins in the thoracic cavity, and
ascends along the trachea to the larynx,
the intrinsic muscles of which it stimu-
lates, with the exception of the crico-
thyroid.
The two recurrent nerves are not
quite symmetrical at their origin. That
of the right side is detached from the
pneumogastric below the axillary artery,
near the dorso-cervical artery. It is
immediately reflected forward in em-
bracing the origin of that vessel,
asrainst the trachea, in the middle
which it crosses inwards to be placed
• Toussaint has seen this branch leave the oesophagus to lie beside the recurrent ; but its
filaments always return to that tube as ascending twigs.
TEE CRANIAL OR ENCEPHALIC NERVES. 839
of the principal cardiac nerves, with some of which it contracts intimate
relations.
On the left side, it is only when the pneumogastric nerve arrives near the
root of the Imig that it gives off its recurrent. To be reflected forward, the
latter turns from left to right behind the arch of the aorta, and arrives beneath
the inferior face of the trachea, among the cardiac nerves, with which it com-
municates, like the right.
The inferior laryngeal nerves are in this way mixed, at a greater or less dis-
tance from their commencement, with those branches of the sympathetic (see
the description of the si/mpathetic) which collectively constitute the tracheal
plexus. They are soon disengaged, however, and leave the chest, but always in
proceeding along the inferior face of the trachea, then ascending on its sides,
below the carotid arteries, which they gradually approach, and finally attain the
larynx in penetrating beneath the crico-pharyngeal muscle.
According to Goubaux, the left recurrent must be situated more superficially
than the right in the lower part of the neck, and for this reason should be more
exposed to compression. He thus explains why, in chronic "roaring," the
alterations observed are nearly always in the left muscles of the larynx.
The terminal divisions of the recurrents are distributed to the posterior and
lateral crico-aryttenoid, and the arytainoid and thyro-arytasnoid muscles, as well
as to the subglottic mucous membrane.
In their long course, they emit collateral ramuscules that also ascend, and
are distributed to the mucous membrane and muscular layer of the trachea, as
well as to that of the oesophagus.'
The recurrent msophageal ramuscules are all sensitive, and form five groups :
the first and second arise, on the left side, close to the arch of the aorta, ascend
on the sides of the trachea, and pass to the portion of the oesophagus lying
between that tube and the thoracic section of the longus colli muscle. The
third, more considerable, springs from a branch given off at the brachial trunks ;
it is markedly recurrent, and forms on the side of the trachea, with the second,
a small plexus, and then lies closely alongside the oesophagus, which it accom-
panies for a distance of eight inches from the first rib. The branch constituting
the fourth group is the longest of all ; it is detached about two or two and a half
inches in front of the first rib, and after emitting several long tracheal filaments,
it ascends on the side of the trachea, close to the border of the oesophagus, where
it generally disappears at about six or eight inches from the pharynx. The fifth
group is composed of a branch detached from the recurrent, about the point
where the preceding terminates ; it goes entirely to the origin of the tube.
6. Cardiac Filaments. — These will be alluded to when describing the
sympathetic nerves.
Terminal Branches of the Pneumogastric Nerves. 1. Bronchial
Plexus (Fig. 480, 29). — The bronchial plexus is formed by several branches
from the pneumogastric, on the arrival of that nerve above the roots of the
lungs ; these interlace into a network and ramify around the bronchi, following
these into the texture of the lungs. It is these branches which give to the
mucous membrane its great sensibility, and which provoke those evident con-
tractions of which the bronchioles are the seat.
2. (Esophageal Branches (Fig. 480, 30, 31).— After emitting the ramus-
(' For a detailed description of the superior and inferior laryngeal nerves, see my treatise
on "■Roaring in Horses." London : 1889.)
840 TEE NERVES.
cules of the bronchial plexus, each pneumogastric is continued along the
oesophagus by two branches — a superior and inferior — making four branches
for the two nerves. The two superior lie together, and form a single cord,
either immediately or after a certain course : the two inferior comport them-
selves in the same manner with one another — making a double anastomosis, from
which arise the two nerves we are about to describe, and which are designated
the oesophageal nerves, because of their situation. The right nerve forms a large
portion of the superior cord ; the left, especially, gives ramuscules to the inferior.
Placed between the layers of the posterior mediastinum, these two nerves
follow the oesophagus for a certain distance — one above, the other below — giving
off some ramuscules to that muscular tube, detaching one or two communicating
branches, and traversing the foramen sinistrum in the diaphragm to enter the
abdominal cavity.
The inferior terminates in the parieties of the stomach, by forming on the
small curvature, to the right of the cardia, a very rich pre-stomachal plexus,
which throws the majority of its ramuscules on the right sac of that viscus.
The superior passes to the left of the oesophageal insertion, along with the
gastro-pulmonary artery, and is lost in the solar plexus, after giving off numerous
divisions on the left sac of the stomach, mixing with the sympathetic ramuscules
that encircle the gastric artery, and anastomosing around the cardia with those
of the inferior cord. It is very difficult to follow the filaments of this cord from
the pneumogastrics after their arrival at the solar plexus ; we nevertheless observe
some of them passing to the liver, others accompanying the sympathetic branches
that come from the solar to the posterior mesenteric plexus in following the
small mesenteric vein ; and no doubt others find their way among the filaments
of the trisplanchnic nerve, which proceed with the anterior mesenteric artery.
Functions of the Pneumogastric. — Formed by the two orders of fibres,
the pneumogastric is a sensory-motor nerve, and the seat ot reflex currents which
make it play a very important part in several acts of vegetative life, and bring it
into relationship with the great sympathetic nerve, with which we have seen that
the tenth pair maintains anastomotic connections in several points of its course.
It is the pneumogastric nerve that gives to the mucous membrane of the
larynx the exquisite sensibility it enjoys.
It stimulates the motor muscles of the larynx to movement.
To it is also due the sensibility of the broncho-pulmonary mucous membrane.
It causes contractions of the muscular fibres in the broncho-tracheal passages
— contractions which are involuntary, and due to reflex influence.
It also causes movements of the oesophagus and the stomach, which are
involuntary and due to reflex currents.
Perhaps it acts in an analogous manner — by reflex action — in the secretion of
the gastric fluid and the functions of the Hver ; but these are points which science
has not yet determined.
It appears proved that it exercises an influence on the essential phenomena of
respiration (liaulanie), as it participates in the centripetal stimulation which
brings the respiratory mechanism into play.
It transmits to the heart the influence of the moderating centre of that organ
which is situated at its roots in the meduUa oblongata.
After its section in the region of the neck, the movements of the heart
become very precipitate, and we may diminish the force of these movements, or
even completely arrest them, by galvanizing the peripheral end of the nerve. In
TEE CRANIAL OB ENCEPHALIC NERVES. 841
this action on the heart, one nerve, usually the right, plays a predominant part
(Arloing and Tripier).
It also transmits to the bulbar vaso-motor centres, through the medium of
the depressor nerve of the circulation — Cyon's nerve — which forms part of it, a
stimulus that leaves the heart and produces a general vaso-dilatating effect —
chiefly, however, in the abdominal cavity.
11. Eleventh Pair, Spinal Accessory Nerves, or Accessory Nerves of
THE Pneumogastrics (Fig. 456, 2, 4).
The spinal accessory is an exclusively motor nerve, which, at its exit from
the cranium, is so intimately connected with the pneumogastric, that we might
perhaps follow the example of Miiller, and describe the two as forming one and
the same pair.
Origin. — This nerve exhibits a singular disposition, in that it arises from the
"whole extent of the cervical spinal cord, and ascends in the spinal canal to near
the pneumogastric, with which it leaves the cranium by the posterior part of
the foramen lacerum. It is also described as a cranial nerve, in consequence
of the latter peculiarity ; but from its origin it is rather a spinal nerve, a fact
which is sufficiently indicated by the name generally given to it.
In the interior of the spinal canal, it is a long cord measuring from 27 to 31
inches in middle-sized animals. It commences, by a very fine point, at the
cervical or brachial enlargement of the spinal cord, follows that organ in an
ascending course, lying close to its lateral column, and passing between the roots
of the two orders of cervical nerves until it arrives at the medulla oblongata,
where it is inflected outwards at the foramen lacerum posterius, into which it
passes to leave the cranium.
In this ascending course it gradually increases in volume, as it at intervals
receives additional filaments from the lateral column of the spinal cord, like the
radicular extremity of the nerve itself. Traced into the spinal cord, the radicular
filaments are found to arise from a nucleus situated outside the base of the
inferior cornua. Before making its escape from the cranium, it receives, besides,
some of the posterior or motor roots of the pneumogastric nerve. In the fora-
men lacerum, it becomes applied against the ganglion (jugular) of that nerve, in
the manner of motor fibres of mixed nerves, and gives it some of its own filaments,
while it also receives others.
The long cord here described as the root of the spinal accessory, is considered
by some authorities as only a portion of this nerve, to which they give the name
of external or medullanj root of the spinal accessory. They designate as the
internal or bulbar root of that nerve, the anastomosing filaments already described
as the motor roots of the pneumogastric. According to them, this internal root
only lies beside the pneumogastric for a very short distance, ultimately leaving
it and forming the superior laryngeal and pharyngeal nerves, which seem to arise
from the vagus rather than from the accessory of Willis.
Distribution. — Beyond the ganglion of the pneumogastric, the spinal accessory
nerve remains beside the trunk of the pneumogastric for scarcely an inch ; it
then separates from it at an acute angle, the sinus of which is occupied by the
great hypoglossal nerve, is directed backwards, passing beneath the superior
extremity of the maxillary gland and mastoido-humeralis muscle, gains the
supero-posterior border of that muscle, and follows it to the front of the shoulder.
842 TEE NERVES.
Here it slightly ascends, crosses that region below the inner face of the cervical
trapezius, and is distributed to the dorsal trapezius.
On its passage it emits : 1. One or two thick filaments to the superior cervical
ganglion, proceeding from the spinal accessory by a small plexiform network,
where the nerve separates from the pneumogastric. 2. Near the maxillary gland,
a thick branch to the sterno-masillaris muscle. 3. Slightly beyond this, another
branch destined to the anterior portion of the mastoido-humerahs, 4. A series
of ramuscules to the cervical trapezius.
In its course, the spinal accessory traverses the anterior part of the superficial
cervical plexus, and receives additional ramuscules from the first, second, third,
fourth, fifth, and sometimes even from the sixth cervical nerves.
Reduced to its medullary root, as has been described, the spinal accessory
stimulates the muscles to which it is distributed, and through them has a share
in expiration. By the contraction of these muscles, the ribs may be maintained
raised for a certain period, and cause the air to be slowly expelled ; also allowing
the sounds or voice produced by its passage through the larynx to be modulated.
Crowing is no longer possible in Birds when the medullary root of the spinal
accessory has been divided, as has been demonstrated by Bernard.
12. Twelfth Paie, ok Hypoglossal Neeves (Figs. 171, 22 ; 456, 5; 459, 10).
The hypoglossal nerve is exclusively motor, and stimulates the muscles of the
tongue.
Origin. — It apparently arises from the lower face of the medulla oblongata,
on the prolongation of the line of origin of the inferior spinal nerves, by a dozen
converging filaments. Traced into the medulla, these filaments are found to pass
into a principle nucleus situated near the point where the central canal of the
spinal cord enlarges to form the floor of the fourth ventricle, inside the pneumo-
spinal nucleus, and in the small masses of grey substance placed below and out-
side the preceding, named the accessory nucleus.
The roots of the hypoglossal nerve pass through the dura mater in two or
three bundles, which enter the condyloid foramen of the occipital bone, where
they unite to form a single cord. The hypoglossal has also a ganglionic root
which Toussaint constantly found in the Ass, Mule, Ox, and Bog, and which
had been previously seen by Meyer and Yulpian. The ganglion of the hypo-
glossal in the Horse is fusiform, and the size of a small lentil (Fig. 456, 5'). It
is sometimes absent.
Distrihution. — The hypoglossal nerve, thus constituted, immediately after its
departure from the condyloid foramen, communicates with the first cervical pair
by means of a transverse ramuscule ; it then passes between the spinal accessory
and pneumogastric nerves, descends on the external face of the guttural pouch,
where it is connected with the superior cervical ganglion of the sympathetic by
numerous filaments, which in great part form the plexiform network called the
" guttural plexus." The nerve afterwards crosses to the outside of the external
carotid artery, in proceeding forward and downward on the side of the pharynx
and larynx, receiving at that point a slender ramuscule from the first cervical ;
it then passes within the inferior extremity of the stylo-hyoid muscle and the
submaxillary artery, which it crosses very obliquely, is prolonged between the
mylo-hyoid and great hyo-glossus muscles, sends numerous small filaments to
the latter and a ramuscule to the genio-hyoideus, and finally terminates in a
THE CBANIAL OR ENCEFEALIC NERVES,
843
series of branches analogous to those of the gustatory nerve, and which mix
with them. , , ^ •
These branches are therefore reflected upwards, bendmg round the posterior
Fig. 459.
DEEP NERVES OF THE HEAD IN THE MULE.
1 Superior maxillary nerve at its exit from the foramen lacerum ; 2, masseteric nerve; 3, sub-
' zygomatic nerve ; 4, buccal ; 5, lingual or gustatory nerve ; 6, chorda tympani ; 7, inferior
maxillary nerve, cut near where it enters the maxillo-dental canal; 8, mylo-hyoideus nerve
maxiuary ueive, uui. ncai «iicic ii, c.cio x..^ ............ ..., „„....., _,..._,-. -j -■_ ,.
pterygoid nerve; 10, glosso-pharyngeal nerve; 11, its pharyngeal branch; 12, its lingual branch;
13, pneumogastric nerve; 14, superior laryngeal branch of that nerve; 15, its pharyngeal
branch; 16, spinal accessory of Willis; 17, hypoglossal nerve; 18, origin of the cervical cord of
the great sympathetic; 19, the same after its union with the pneumogastric. A, Common
carotid artei-y ; B, accessory thyroid artery ; C, thyro-laryngeal artery ; D, origin of the internal
carotid artery (the vessel is concealed by the guttural pouch) ; E, occipital artery ; F, external
carotid artery; G, internal maxillary artery; JI, pharyngeal artery (drawn too large); /, sub-
maxillary artery; J, lingual artery; A', origin of the maxillo-muscular artery; L, posterior
auricular artery ; M, trunk or origin of the superficial temporal artery ; 0, inferior dental artery ;
F. posterior deep temporal artery; Q, anterior deep temporal artery; ^, maxillary gland; S,
Wharton's duct ; T, sublingual gland. The letter N placed at the upper end of the large cornu
of the hyoid bone has no signification.
border of the great hyo-glossus, and pass into the interstice between that muscle
and the genio-glossus. They are distributed to all the muscles of the tongue.
The hypoglossals, being motor nerves, cause the contraction of the muscles
of the tongue during the movements proper to mastication and the production
of the voice. Though they most frequently act together, yet they may do so
separately, as in the unilateral movements of the tongue.
Differential Characters in the Cranial Nerves of the other Animals.
In the domesticated Mammals, the cranial nerves offer the greatest analogies; their origin
is the same in all, and it is only in their distribution that we find some variety, due to the
844 THE NERVES.
difference in the form of the head. Consequently, in this comparative analysis we shall not
discover any fundamental differential characters.
Ruminants. — There is no difference to note in the four fimt pairs.
Trigeminal nerve. — Divided into three branches as in Solipeds. It has been stated that in
Ruminants the ophthalmic branches are distributed to the majority of tlie muscles of the eye;
in the Sheep, we have only seen the palpebro-nasal nerve offering this relationship to the
motor organs of that part. Tiie anterior palatine nerve is relatively voluminous.
In the Ox and Sheep, the buccal nerve furnishes the excito-secretory nerve of the parotid
gland; it is inflected on the anterior border of tlie masseter, and follows Steno's duct, iu both
species, to reach the gland. It is often formed by two parallel filaments (Moussue). A filament
of the inferior branch of the buccal nerve which goes to the molar gland, is also excito-secretory
(Moussu).
Facial nerve. — Towards the middle of its subparotideal course, tliis gives off a large
anterior auricular nerve ; when it arrives at the middle of the posterior border of the masseter
muscle, it divides into two branches. The inferior branch passes obliquely downwards and
forwards, towards the mental foramen, where it terminates as in the Horse; it furnishes an
anastomotic branch to the superior. The latter crosses the middle portion of the masseter, and
becomes mixed with the suborbital ramuscules of the fifth pair; about the midille of its
course it receives a filament from the superficial temporal nerve. We need not allude to the
auditory and glosso-pharyngeal nerves, except to say that the latter communicates with the
pneumogastric soon after its exit from the foramen lacerum.
Pnenmogastric nerve. — This offers numerous differences in its roots and distribution.
In the Ox and Sheep, the sensitive roots arise from an irregularly elliptical surface com-
prising the whole of the respiratory tract. They are from fifteen to twenty in number, and
often join each other; they may divide into three principal fasciculi arising at slight distances.
The Tnotor roots are a little larger than in the Horse ; before joining the sensitive roots they
are confounded in a small ganglion that pertains to them.
The jitgular ganglion is voluminous, but apart from this it presents the same features as in
the Horse, receiving all the proper roots of tlie pneumogastric and internal root of the spinal
accessory, and even those which are united in their own ganglion. The portion of the
ganglion that is more especially formed by the roots of tlie spinal accessory is rather an intri-
cation of nerve-fibres than a real ganglion ; it is impossible by the most minute dissection to
separate it from the rest of the ganglion.
The jugular ganglion also receives a division of the glosso-pharyngeal, and it gives one to
this nerve and the external branch of the spinal accessory.
The pneumogastric nerve, in the guttural -portion, is much larger than in the Horse. This
peculiarity is noticeable throughout its whole extent, and is indicated at its roots.
The ganglionic plexus is absent in the Ox. The course and relations of the nerve in this
portion, are analogous to those observed in Solipeds.
The pharyngeal nerve is voluminous, and the branch it sends to tlie oesophagus is the
largest of its divisions: this branch passes backwards to the surface of the constrictors of the
pharynx, joins the external laryngeal, gives a large branch to the thyro-pharyngeus, and is
insinuated on the sides of the oesophagus, between it and the thyroid gland ; there it divides
into two portions, one of which descends on the sides of the oesophagus, where it forms a very
rich plexus with the l)ranche8 from the inferior laryngeal, wliile the other is lost immediately
in the recurrent nerve at the thyroid gland.
The external laryngeal arises at a short distance above the superior laryngeal, where it
receives a large branch from the glosso-pharyngeal and another from the sympathetic, and
immediately passes alongside the oesophageal branch of the pharyngeal nerve. With a little
attention, we may dissect a fasciculus coming from the external laryngeal and passing to the
crico-thyroid muscle, and the thyroid gland and its vessels, after receiving a branch from
the superior laryngeal. In the Sheep, the external laryngeal sometimes gives a branch to
the oesophagus, and whicli anastomoses with the inferior laryngeal, or descends on the side
of the tube, conjointly with the oesophageal branch of the pharyngeal.
The superior laryngeal rises below the preceding ; it is very voluminous, and communicates
with the sympathetic, either directly or through the medium of the guttural plexus, and with
the pharyngeal nerves and external laryngeal. Beneath the thyroid cartilage, a large division
anastomoses with the inferior laryngeal, and is finally lost in that nerve below the larynx. It
is easily seen that this brancli gives, in the cervical region, a great number of filaments to the
oesophagus and trachea.
With the exception of some insignificant peculiarities, the pneumogastric comports itself In
the cervical and thoracic regions as in the Horse.
THE CRANIAL OR ENCEPHALIC NERVES.
The recurrente arise as in Solipeds, but their relations are somewhat different in the cervical
region. They are placed in the channel formed by the trachea and oesophagus, and are
Fig. 460.
NERVES OF THE GUTTURAL REGION IN THE OX.
fl, (Esophagus ; 6, trachea; c, common carotid artery; c?, glosso-facial artery. 1, Pneumogastric
nerve; 2, spinal accessory; 3, glosso-pharyngeal ; 4, great sympathetic and cervical ganglion;
5, pharyngeal nerve; 6, external laryngeal; 7, superior laryngeal; 8, inferior laryngeal; 9,9,
oesophageal branches of tiie pharyngeal and external laryngeal.
56
846 THE NERVES.
separated from the carotid artery and the cord common to the sympathetic and pneumog;a8trifl
by the very great width of the CESophagus. Their distribution to the muscles of the larynx
takes place as in the Horse ; the only noteworthy feature is the anastomosis of the nerve, end
to end, witli the superior laryngeal. In the wliole of its cervical portion, the branches to the
oesophagus are more numerous and voluminous than in Solipeds, although they all have the
same physiological oflSce, except those that are derived from the branch of tlie superior laryngeal,
which are motor.
The differences remarked in the nerve in the abdominal cavity, are in relation to the volume
and form of the stomach and its compartments.
The following is what we have observed in the Sheep : —
After receiving a large filament from the superior cord, the inferior oesopJiageal nerve
divides into three principal branches : one passes to the left, furnishing nerves to the anterior
face and greater curvature of the reticulum and the upper border of the rumen ; a median,
which is distributed to the anterior face of the psalterium, reaches the substance of the
mesentery, follows the abomasum, to which it sends some filaments, and finally anastomoses
with the retrograde nerves coming from a rich plexus that exists on the posterior face of the
liver and gall-bladder ; it forms, conjointly with the divisions of tiie solar plexus and superior
oesophageal nerve, a rich plexus, from which arise branches to the liver, abomasum, and
duodenum.
The superior cesophageal nerve is chiefly distributed to the rumen. Before reaching the
stomach, it gives several divisions to the plexus already mentioned — and which might be
named the " hepatic plexus" — receives a large branch from the solar plexus, and sends to it a
smaller one. It afterwards divides into two principal branches, the largest of which passes
along the superior fissure of tije rumen, along with the vessels of that organ. According to
Lavocat, this branch forms a large plexus there, which has in its centre a guuglionic enlarge-
ment, whence emanate the ramuscules that go to the whole of the upper face, sides, and lower
surface of the rumen. In the Sheep we have not found a ganglion, but this does not prevent
this branch from being distributed to all the parts indicated by Lavocat.
The other branch is very large, and situated in the omentum until it arrives at its convex
border, when it leaves it to be distributed to the left side of ti e abomasum; while the analo-
gous nerve fiom the inferior oesophageal passes more especially to the right face.
In the Camel, the pneumogastric gives off, near the point where it joins the cervical
branch of the sympathetic, a very remarkable branch. This is somewhat plexiform at its
origin, and directly furnishes a certain number of pharyngeal filaments, the superior laryngeal
nerve, and, a little lower, the inferior laryngeal nerve, forming a slight arch where it curves to
ascend; it tiien descends along the oesophagus into the thorax, giving filaments to that tube
and to the trachea. When it reaches the second dorsal vertebrae, this branch unites, below
the oesophagus, with that of the opposite side. The single branch resulting from this union
runs between the trachea and oesophagus, and ends by dividing into several filaments that
enter the bronchial plexus.
For the whole of its cervical course, the pneumogastic lies close beside the sympathetic
and does not give off any ramuscles worthy of note. After separating from the sympathetic
at the entrance to the chest, it passes into that cavity alongside the trachea to the commence-
ment of the bronchi ; there it forms, with its congener of the opposite side, the hroncho-oesopha-
geal plexus, which is extremely remarkable, and is prolonged behind by the oesophageal nerves
— similar to those in the Horse. The pneumogastric does not appear to directly furnish
filaments to the inferior cervical ganglion.
Spinal accessory.— The origin of this nerve offers slight differences, which we have indicated
in speaking of the motor roots of the pneumo.i^astric. With regard to its distribution in the
Ox, it offers the following features : At the inferior extremity of the transverse process of the
atlas, it divides into two branches— a superior and inferior. The first is a little larger than
the spinal accessory of the Horse, and comports itself as in that animal. The inf. rior branch
is directed downward and backward, traverses the muscle we have named the sterno-sub-
occipital (see Myology), beneath a tendon that runs across the muscular fibres, and arrives
letween that muscle and the sterno-maxillaria. At this point it separates into a certain
number of ramuscules, the first three or four of which are slightly recurrent, and enter the
upper part of the sterno-maxillaris ; the others are large and directed towards the sternum,
to be distributed to the latter muscle, or to it and the sterno-suboccipitalis.
These branches ot the spinal accessory represent the branch which, in the Horse, passes
exclusively to the sterno-maxillaris. In reflecting' on the distribution they offer in the Ox, we
are biought to the conclusion that the sternal hand, which has been described as belonging to
the first, forms, with the sterno-suboccipitalis, one and the sacre muscle— the analogue of the
THE CRANIAL OR ENCEPHALIC NERVES. 847
sterno-maxillaris or sterno-mastoideus of Solipeds. These two muscular fasciculi are, other-
wise, closely attached to each otlier, if not cunfouuded near their origin at the anterior pro-
longation of the sternum.
Lastly, the hypoglossal nerve, before crossing the pneumogastric, communicates with the
first cervical by a considerable brancli ; lower, it gives off a long ramuscule that descends on
the carotid artery.
Pig. — We need not refer to the olfactory, optic, or motores oculorum, neitlier to the glosso-
pharyngeal, as what has been siiid about them in Solipeds holds good in this animal.
Trigeminal werye.— This also divides into tliree principal branches. The palpebro-nasal
ramuscule of the ophthalmic branch, anastomoses with a motor nerve of the eye on the deep
face of the external rectus muscle. The superior maxillary nerve leaves the cranium by the
great sphenoidal slit, and immediately enters the superior dental foramen ; its orbital course is
therefore very short.
Its spheno -palatine branch passes at once below the alveolar tuberosity, where it divides
into several ramuscules: one, entering the palatine fissure, forms the posterior palatine nerve;
the others pass into the palatine arch at various distances, to cont^titute the middle palatine
nerves ; some of them even enter the palatine canal with the anterior palatine or palato-labial
nerve.
Facial. — Beneath the parotid gland, this divides into several branches, of which there are
three principal. One is directed upwards, and passes in front of the ear ; this is the smallest.
The second jiroceeds forward, crosses the masseter near the zygomatic process, unites with the
inferior branch, and is expended among the suborbital ramuscules of the superior maxillary.
The third passes downward and forward, under the parotid gland, arrives in the intermaxillary
space, is inflected in front of the masseter to become superficial, and terminates with the
middle branch. Towards the maxillo-labialis muscle, this inferior branch gives off a ramuscule
.to the lower lip.
Pneumogastric. — This joins the sympathetic near the upper third of the neck, and at its
point of union offers a greyish enlargement resembling the gaugliform plexus of Man. As far
as the origin of the oesophageal nerves, the pneumogastric of the Pig resembles that of the
Horse. The latter is voluminous, and does not divide into two branches immediately beyond
the bronchial plexus, but at some distance from it. Numerous anastomoses exist between the
two oesophageal nerves — superior and inferior. At their termination they differ much from
each other in volume ; the inferior is very small, and terminates on the anterior face of the
stomach; the superior, much larger, partly remains at the stomacii, and partly crosses the
small curvature of that viscus to enter the solar plexus.
Spinal accessory. — This nerve commences and terminates as in Solipeds. After being
inflected backward on the anterior border of the raastoido-humerali.-<, it divides into two
ramuscules — a deep and superticial. The first is confounded with a cervical nerve, near the
intervertebral foramen through which the latter passes; the second goes to the trapeziug
muscle, in which it is expended.
Near the base of the tongue, the hypoglossal gives off a filament that passes to the genio-
hyoideus muscle.
Carnivora. — In these animals the majority of the cranial nerves do not offer any important
differences. We will, therefore, say nothing concerning the first two pairs, or of the motores
oculorum, spinal accessory, and glosso-pliaryngeal, except that the motor nerves of the eye are
mixed with the filament of the ophthalmic branch among the muscles of the orbit.
Trigeminal nerve. — When the branch constituting the superficial temporal nerve, reaches
the posterior border of the maxilla, it divides into several ramuscules ; one portion lies beside
the middle branch of the facial, the other accompanies the anterior auricular nerve by becoming
intimately united to it. We have also found, in the Dog, a branch that is detached from the
inferior maxillary, almost immediately after its exit from the cranium. It descends into the
intermaxillary space, in company with the facial artery. At the posterior border of the mylo-
hyoideus muscle it separates into two ramuscules: one is applied to that muscle, and follows
it to near the symphysis of the jaw; the other is inflected outwards and upwards, in front of
the masseter muscle, and joins the inferior branch of the facial. Owing to this arrangement,
each of the branches of the facial is provided with a sensitive ramuscule from the fiftli pair.
The lingual nerve furnishes vaso-motor and excito-secretory nerves to the submaxillary
and sublingual glands, as is shown in Fig. 461, borrowed from Bernard.
Facial, — At its exit from the external auditory hiatus, it divides into four branches, three
of which appear to form its termination. The first — the smallest — is directed downwards
across the parotid gland, and constitutes the cervical ramuscule. The other three are dis-
tinguished as superior, middle, and inferior.
THE NEEVES.
The superior branch, the largest, ascends towards tlie forehead, and describes a curve with
convexity upwards, turns round the orbit, and terminates near its nasal angle. In its course it
furnishes: 1 An anterior auricular ramuscule. 2. Above the insertion of the masseter, several
muscular filaments. 3. It is crossed, above the eye, by the superciliary filaments of the
ophthalmic nerve. The middle branch accompanies Steno's duct to the surface of the cheek ;
reaching the anterior border of the masseter, it anastomoses in a very flexuous manner with
the ramuscule of the inferior branch, and ti-rminatps in the upper lip and the end of the nose.
The inferior branch pas&es towards the maxillary fissure; there it receives the sensitive
5 .jtf m
^ IT t
ramuscule sent to it by the fifth pair, gives off filaments to the middle branch, and is then
continued into the lower lip.
Pneumogastric. — The sensitive roots closely resemble, in their disposition, those in the Ox.
The motor roots are separated into two series of filaments ; the anterior unite in a small ganglion
then pass into the jugular ganglion ; the posterior lie beside the medullary root of the spinal
accessory, but leave it to become united with the jugular ganglion.
Below the foramen lacertim, the pneumogastric nerve gives off tlie pharyngeal nerve before
forming the analogue of the plexifnrm ganglion of Man. This plexus is better defined than
in him, and is a real fusiform elongated ganglion, at the grey basis of which some white
e seen. It is situated a little farther from the cranium than the superior cervical
THE CRANIAL OR ENCEPHALIC NERVES. 849
ganglion. The ganglion itself furnishes the superior laryngeal nerve, which gives off, as in
Man, the external laryngeal nerve.
There is nothing to indicate in the pharyngeal nerve, its disposition being absolutely the
same as in the Ox.
In the Dog, the superior laryngeal nerve has a curious disposition, whicli has not yet, to
our knowledge, been described. Reaching the inner face of the thyroid cartilage, it gives off,
as in the other animals, filaments to the glottis, epiglottis, liase of the tongue, and oesophagus;
but the ramuscule of Galien, which nearly equals the superior laryngeal in volume, does not
anastomose with the inferior laryngeal ; it gives a large branch to the crico-arytaeiioid muscle
in passing to its surface, and then leaves the larynx to the inside of the recunent, descending
on the trachea as far as the entrance to the chest. In that cavity, the descending branch of
the superior laryngeal forms two divisions that communicate with the ramuscules of various
other nerves passing into this region. On the right side, the largest division receives a
voluminous branch from the inferior cervical ganglion; then the two divisions unite, and join
the pneumogastric after it has turned round the brachial trunk, a little behind the point of
emergence of the inferior laryngeal.
On the left side the same arrangement is found; the anastomoses are larger and more
numerous than on the right siie; the branch follows, in an inverse direction, the course
pursued by the recurrent nerve, to join the pneumogastric at the part where the recurrent
originates from the latter.
In this course, the branch gives large ramuscules to the oesophagus and trachea ; those
distributed to the former either pass along the muscular tunic and return again to the nerve,
or continue along the surface of that tube. In all cases, there is found on the sides of the
oesophagus a rich plexus formed by these filaments, as well as by those coming from the
pharyngeal nerve.
• This branch also offers other peculiarities. Thus, it is very often found alongside tlie
laryngeal nerve for some distance, and sometimes at several points. When this happens in
the upper part, at tiie larynx, as occurs in many cases, it appears to have an anastomosis as
in the Ox ; but it is always easy to separate the two nerves, even in fresh specimens, and this
separation is greatly facilitated if the piece lias been steeped in water acidulated by nitric acid.
In the cervical portion, the pneumogastric nerve is closely united to the sympathetic, the
separation of the nerves being no longer possible as in the Horse and Ox.
We have already described a portion of the inferior laryngeal nerve, in speaking of the
tracheo-oesophageal branch of the superior laryngeal. Comparison with otiier animals requires
that we should transfer the latter to the recurrent. In the Dog, the inferior laryngeal rises by
two distinct branches, a short distance from each other, on the right and left aides; these may,
or may not, lie together for some distance, but they never become fused. The external part of
the nerve receives at intervals filaments proceeding from the superior laryngeal branch, and it
rarely gives very fine twigs to tiie trachea and oesophagus. The conimunicatious with the
cardiac and tracheal nerves are also chiefly made by the tracheo-oesophageal branch.
The bronchial nerves are large and numerous.
The oesophageal plexus, which is furnished by the nerves of the same name, is larger and
finer than in the Horse.
There is nothing to note particularly in the termination of the nerves in the stomach.
The hypoglossal gives a long branch that passes to the sides of the larynx, and enters the
muscles on the anterior face of tlie trachea.
Rabbit. — We shall only notice some differences in the facial and pneumogastric nerves.
The facial gives two or three fine branches to the temporo-auricular nerve, on its sub-
parotideal course. When these two nerves reach the anterior border of the parotid, they are
parallel to and superposed on each other, and it is only on the middle of tht; masseter that the
temporn-facial plexus is formed. Sometimes the branch for the risorius of Santorini is detached
before the formation of the plexus.
The pneumogastric has a gangliform plexus, like that of Carnivora. In the cervical region,
it is isolated from the filament of the sympathetic. The Rabbit has a sensitive heart-nerve,
discovered by Ludwig and Cyon, and named by them the depressor nerve of the circulation. It
usually begins by two roots — one furnished by the pneumogastric, the other by the superior
laryngeal nerve. It descends along the neck, beside the cord of the sympatlietic, receives — on
entering the thorax — ramuscules from the first thoracic ganglion, and is soon lost in the substance
of the heart. The root from the superior laryngeal should be the largest, as Toussaint has
always found it, while he has rarely seen that which is detached before the formation of the
plexus.
THE NERVES.
Comparison of the Cranial Nerves of Man with those of Animals.
The few modifications offered by the cranial nerves of Man, when compared with those of
animals, are dictated by the dispositiou of tlie [larts and organs to which tliey are distributed.
We have spoken of the ulfactury lobes when studying the brain, so that we need not again
refer to them. The three succeeding nerves offer nothing worthy of mention.
Trigeminal nerve. — This has the same origin and divisions as in animals.
The frontal nerve of the ophthalmic portion divides into two branches; these are inflected
upwards on the margin of the orbit, and distributed to the skin of the forehead. These two
branches— well developed in the Dog— are distinguished as internal and external. The latter
anastomoses with a brancli of the facial. TJie nasal nerve, after spreading over the surface of
the turbinated bones and tiie meatus, gives off a ramuscule that becomes subcutaneous in
Fig. 462.
NERVES OF THE FACE AND SCALP.
, Attrahens aurem muscle; 2, anterior belly of occipito-frontalis ; 3, auriculo-temporal nerve;
4, temporal branches of facial; 5, attolens aurem muscle; 6, supra-trochleav (5th); 7, posterior
belly of occipito-frontalis ; 8, supra-orbital ; 9, retrahens aurem muscle; 10, temporal branch of
temporo-orbital ; 11, small occipital ; 12, malar branches of facial ; 13, posterior auricular (7th) ;
14, malar branch of temporo-malar (5) ; 15, great occipital ; 16, infra-orbital branches of facial ;
17, facial; 18, nasal; 19, cervico-facial division of 7th ; 20, iufra-orbital ; 21, branches of digastric
and stylo-hyoid ; 22, temporo-facial division of 7th ; 23, great auricular ; 24, buccal branches of
facial; 25, trapezius muscle ; 26, buccinator (5th) ; 27, splenius capitis ; 28, masseter; 29, sterno-
mastoideus ; 30, superma.xillary branches of facial nerve ; 31, superficial cervical ; 32, mental ;
33, platysma muscle ; 34, submaxillary branches of facial nerve.
passing between the inferior border of the nasal bone and cartilage of the nostril ; this is the
naeo-lobular nerve.
The superior maxillary nerve leaves the cranium by the foramen rotundum. reaches the
suborbital furrow, and spreads over the face by suborbital branches. Like thnt of animals, it
gives rise to an orbital ramuscule, and posterior and anterior dental branches. Differences
appear in the other branches which are furnished, in animflls, by the superior maxillarv nerve;
in Man these branches leave Meckel's ganglion. The filaments leaving this ganglion are;
1. The pharyngeal nerve of Bock, which is distributed in the upper portion of the mucous
membrane of the pharynx, in that of the Eustachian tube, and the posterinr orifice of the
nasal cavities. 2. The palatine nerves — great or antenor— sent to the mucous membrane of
THE CRANIAL OR ENCEPHALIC NERVES.
851
the anterior portion of the palate; middle palatine, distributed to that of the soft palate, and
posterior palatine, tliat goes to the two faces of the soft palate and its muscles. 3. The nasal
or spheno-palatine nerve.
DISTRIBUTION OF THE EIGHTH PAIR OF NERVES ON LEFT SIDE.
1, Gasserian ganglion of 5th nerve ; 2, internal earotid artery ; 3, pharyngeal branch of pneumo-
gastric ; 4, glosso-pharyngeal nerve ; 5, lingual nerve ; 6, spinal accessory ; 7, middle constrictor
of pharynx; 8, jugular (internal) vein (cut); 9, superior laryngeal nerve; 10, ganglion of trunk
of pneumogastric ; 11, hypoglossal nerve on hyoglossus ; 12, ditto communicating with 8th and
1st cervical nerve; 13, external laryngeal nerve ; 14, second cervical looping with the first; 15,
pharyngeal plexus or inferior constrictor; 16, superior cervical ganglion of sympattietic ; 17,
superior cardiac nerve of pneumogastric ; 18, third cervical nerve; 19, thyroid body ; 20, fourth
cervical nerve; 21, 21, left recurrent laryngeal nerve; 22, spinal accessory communicating with
cervical nerves; 23, trachea ; 24, middle cervical ganglion of sympathetic; 25, middle cardiac
nerve of pneumogastric; 26, phrenic nerve (cut); 27, left carotid artery; 28, brachial plexus;
29, phrenic nerve (cut); 30, inferior cervical ganglion of sympathetic; 31, pulmonary plexus of
pneumogastric; 32, thoracic aorta; 33, oesophageal plexus ; 34, vena azygos superior ; 35, vena
azygos minor ; 36, gangliated cord of sympathetic.
The inferior maxillary nerve closely resembles that of animals, the only differences consisting
in: 1. The deep middle temporal nerve rising direct from the maxillary. 2. The lingual
852 THE NERVES.
nerve is detached near the base of the cranium. 3. The superficial temporal uerve fumishea —
independently of the filaments uniting it to the facial — an auriculo-temporal branch that
ascends iu front of the ear, and terminates in the skin of the temporal region.
In Man, there is annexed to the fifth pair the submaxillary ganglion, which receives a
sensitive branch from the lingual, a motor filament from the chorda tympani, and sympathetic
filaments; it gives off several emergent filaments, nearly all of which pass into the maxillary
gland. There is nothing to say of the internal motores ocuhrum.
Facial. — In its collateral branches, the facial nerve of Man is absolutely the same as in
animals. It has, however, a brunch not described in them — the ramuscule of Hirsch/eld, which
reaches the base of the tongue, where it is distributed by mixing with the glosso-pharyngeal.
The termination much resembles that of the Dog. Two principal brandies have been named
the temporo-facial and the cervico-facial. The first receives the superficial temporal nerve, and
describes an arch from which are detached the temporal, frontal, palpebral, suborbital, and
buccal ramuscules, which form the subparotideal plexus. The second, lodged in the parotid
gland, passes towards the angle of the jaw, where it anastomoses with the cervical plexus ; it
furnishes the inferior buccal, mental, and cervical branches.
Glosso-pharyngeal. — This nerve commences and terminates as in Solipeds, and has the same
relations. It furnishes tlie branches of the digastric and stylo-hyoid muscles, the filament of the
stylo-glossus muscle, and, finally, the tonailitic ramuscules that form, around the amygdala, the
tonsilar plexus.
Pneumogastric. — Formed by the union of the sensitive roots, the pneumogastric leaves the
cranial cavity bj' the posterior foramen lacerum ; in the interior of that foramen it, shows the
jugular ganglion ; a little lower, it has a second fusiform enlargement— the gangliform plexus—
which is found in the Dog. Here it receives the internal branch of the spinal accessory, or
otherwise its motor roots. Beyond this gangliform enlarjjement, the pneumogastric is placed
a little within the sympathetic, descends along the neck, enters the chest, and terminates on
the stomach and in the solar plexus. The relations of the two pneumogastrics in the thoracic
cavity are the same as in animals. In terminating in the semilunar ganglion, the two pneu-
mogastrics unite and form an arch named the memorable loop of Wrisberg.
The Viirious anastomoses of the pneumogastric iu Man cflfer nothing particular.
The pharyngeal branches leave the gangliform plexus, and are constituted by the filaments
carried to the pneumogastric by the internal root of the spinal accessory. They are two, three,
or four in number, and form the pharyngeal plexus.
The superior laryngeal nerve also arises from the gangliform plexus, and oflfers, as in
Ruminants, a Galien branch that anastomoses, end to end, with a branch of tiie inferior
laryngeal. The external laryngeal is furnished by this nerve; it is distributed to the inferior
constrictor muscle of the pharynx, the crico-thyroid muscle, and the mucous membrane of the
subglottic portion of the larynx and the ventricle of the glottis.
The recurrent nerves aflfect a distribution analogous to that already made known.
The pneumogastric also gives cardiac, pulmonary, and oesophageal branches. The cardiao
lie beside those coming from the sympathetic and recurrents, and enter the ganglion of
"Wrisberg, situated at the base of the heart. The oesophageal branches are remarkable for
their number and complexity, and form a veritable oesophageal plexus. The gastric branches
are also very numerous.
Spinal accessory, — It presents bulbous roots which are well known, and medullary roots
which usually extend to the fifth cervical, and sometimes to the first dorsal. After its exit
from the posterior foramen lacerum, it divides into two branches— an internal and externaL
The internal branch, formed by the bulbous roots, enters the gangliform plexus of the pneu-
mogastric. The external branch comports itself as in animals.
The hypoglossal resembles that of Carnivora, and, like it, possesses a branch for th«
hyo-thyroideus and genio-hyoideus.
SPINAL NERVES. 853
CHAPTER II.
SPINAL NERVES.
"We designate as spinal, vertebral, or rachicUan nerves, those which emanate from
the spinal cord, and leave the vertebral canal by the intervertebral foramina to
proceed to the various organs.
They are estimated at 42 or 43 pairs, and are apportioned as follows in the
five regions of the spine : cervical, 8 pairs ; dorsal, 17 pairs ; lumbar, 6 pairs ;
sacral, 5 pairs ; and coccygeal, 6 to 7 pairs.
They differ from the cranial nerves in closely resembling each other in the
fundamental points of their constitution. All proceed from the lateral aspects
of the spinal cord by two orders of roots : one motor, the other sensitive. In all,
these two roots unite into a very short trunk in passing through the intervertebral
foramen ; and this mixed nerve divides almost immediately into two terminal
branches — a superior, destined to the spinal muscles and the integuments
covering them ; the other, inferior, passes to the lateral and lower parts of the
trunk or to the limbs. All send, from their inferior branch, one or more
ramuscules to form the great sympathetic.
The roots of the spinal nerves olfer everywhere the same disposition ; each
nerve is formed by two fasciculi of converging filaments — superior and inferior —
which are naturally more numerous and large when they belong to voluminous
trunks, as may be remarked in those proceeding from the two bulbous enlarge-
ments of the spinal cord. The common axis of these two fasciculi affects a
transverse direction in nearly all the spinal pairs ; but that of the posterior
nerves inclines more backwards, as they reach the terminal extremity of the cord.
The filaments of the superior fasciculi — or sensitive roots — are larger than the
others, and emerge from the collateral groove on the spinal cord. They may be
followed, in animals, to the cells of the superior grey cornua. But these cells are
not sufficiently numerous to receive all the fibres of the superior roots, and some
of these pass into the cells of Clarke's columns.
The filaments of the inferior fasciculi — or motor roots — arise opposite the pre-
ceding, on the lower face of the cord, at a short distance from the middle line,
and on the limits of the inferior and lateral columns. They may also be traced
to the interior of the cord, as far as the inferior grey cornua.
These filaments do not unite to form their common trunk until after they
have passed through the dura mater. This is an extremely short trunk that
occupies the corresponding intervertebral foramen, and presents on its upper
face a ganglionic enlargement, which is exclusively placed on the course of its
sensitive fibres ; the motor filaments being simply laid beside them, and do not
mix with them until beyond the ganglion. Immediately after this union, a small
filament is given off that enters the spinal canal to be distributed to the sinuses
and the bodies of the vertebra.
After leaving the meningeal sheath, the radicular fasciculi of the nerves,
furnished by the terminal extremity of the spinal cord, run a somewhat long
course in the sacral canal, before finally uniting and passing into the tissues.
The common fasciculus they collectively form at the posterior extremity of the
spinal canal is named the cauda equina.
The distributive branches of the spinal nerves cannot be considered in a
854
THE NERVES.
general manner, because of their diversity,
each region of the spine.
We will study them successively in
Fig. 464.
Article I. — Cervical Nerves (8 Pairs).
Superior Branches. — The Jirst (the suboccipital of Willis) passes through
the superior foramen of the atlas, in company with the cerebro-spinal artery.
It arrives in the space between the small oblique muscle of the head and the
posterior straight muscles, and divides immediately into several divergent
branches, which are distributed to the three above-named muscles, the anterior
extremity of the complexiis, and the cervico- and temporo-
auricular muscles. The ramuscule sent to the latter
ascends within the concha, and breaks up into several
filaments that supply the skin of the external ear.
The second immediately furnishes some ramuscules
to the obliquus capitis posticus muscle, beneath which it
is placed, as well as to the anterior oblique. It is after-
wards directed backwards, comporting itself like the suc-
ceeding ones.
These diminish in volume from the third to the eighth.
All pass through the intertransversales muscle, and
divide into several branches, which are distributed to the
muscles and integuments of the superior cervical region.
Among these, the superficial, which are almost rudimentary
in the two last pairs, reach the inner face of the splenius.
The others, deep and more voluminous, cross the semi-
spiiialis colli, and, dividing, ascend between the complexus
and cervical ligament, to near the superior border of that
large elastic layer. They generally intercommunicate by
several filaments, and in this way form a network on the
inner face of the complexus, which Girard named the deep
cervical plexus.
Inferior Branches. — These branches augment in
size from the first to the last, and separate into two
perfectly distinct groups. The divisions of the first six
cover the lateral and anterior parts of the neck, as well
as the muscles of the breast. Usually anastomosing with
each other by long communicating branches, they in this
waj form a vast nervous network traversed by two important nerves — the spinal
accessory and cervical filament of the facial ; this is the superficial cervical plexus.
The other two are united with the preceding by a filament passing between the
sixth and seventh, soon l)ecoming confounded with each other, as well as with
the two first branches of the dorsal region ; they constitute — in common with the
latter — the brachial plexus.
Without saying any more as to the disposition of this double plexus, we will
pass to the particular description of each cervical pair of nerves.
First. — Deeply situated beneath the transverse process of the atlas, this nerve
leaves the anterior foramen of that vertebra, and accompanies the occipital artery
and vein to place itself immediately between the rectus capitis anticus minor and
rectus lateralis muscles. It then crosses the rectus capitis anticus major and the
spinal accessory nerve, which it separates ; and arrives, after describing a slight
GANGLION OF A SPINAL
NERVE FROM THE LUM-
BAR REGION OF A
POPPY.
a, Superior root ; 6, in-
ferior root; c, ganglion
on the superior root;
d, e, junction of the
fibres from the inferior
and superior roots with
those comins; from the
ganglion ; d, superior
trunk of spinal nerve ;
e, its inferior trunk.
CERVICAL NERVES. 855
curve forward, near the thyroid gland, finally entering the subscapulo-hyoideus
by several terminal divisions.
Near its origin, this inferior branch of the first cervical nerve furnishes
collateral ramuscules to the three recti muscles of the head. Lower, it is in
commimication with the superior cervical ganglion and the spinal accessory
nerve by several filaments. At the carotid artery, it sends forwards, to the side
of the larynx, a very fine branch that quickly divides into two ramuscules, one
of which joins the hypoglossal nerve, and the other goes to the thyro-hyoid
muscle. It then throws off, from its convex side, several small descending
nerves, all of which are destined to the subscapulo-hyoid, sterno-hyoid, and
thyroid muscles.
One of these filaments, joined by a ramuscule from the second pair, is dis-
tinguished for its great length ; it may be followed to near the sternum, where
it is expended in the fleshy mass common to the four mnscles that extend from
that bone to the larynx and os hyoides. Its constant disposition should obtain
for it the name of pre-cprviml 7ierve.
Second. — This descends beneath the obliquus posticus, crossing the direction
of the rectus anticus major, and ramifying therein by numerous branches. We
specially indicate : 1. Those furnished to the latter muscle, and which are the
shortest and deepest 2. The atloid loop, a long, thick superficial branch, which
enters the anterior portion of the levator humeri, and is directed forward and
upward on the parotid gland, bending round the transverse process of the atlas ;
this ramuscule gives off filaments to the parotido-auricularis, as well as to the
panniculus of the face, and terminates in two branches of unequal volume, the
largest of which ascends on the outer side of the concha, and the other, situated
behind, reaches the cervico-auricular muscles. 3. Another superficial branch,
which passes over the jugular, near the junction of the glosso-facial, and divides
into two ramuscules ; these proceed forward with the submaxillary facial vein to
the submaxillary space, where they are distributed to the skin and subcutaneous
muscle. 4. Anastomosing filaments, which unite it to the two branches of the
spinal nerve. 5. Accessory ramuscules to the cervical filament of the facial
nerve. 6. Two communicating branches which pass beneath the rectus anticus
major : one going to the first, the other to the third pair of nerves. 7. A deep
branch going to join the pre-cervical filament of the first pair, and directly
throwing off some fine divisions to the subscapulo-hyoideus muscle. 8. A last
branch that arises at the intervertebral foramen, and passes at first — with the
vertebral artery — into the posterior foramen of the second vertebra, and after-
wards those of the succeeding vertebrte, to enter the inferior cervical ganglion
of the sympathetic nerve, receiving on its course filaments from the third, fourth,
fifth, sixth, and seventh pairs.
Third, fourth, fifth, and sixth. — Each of these crosses the intertransversales
colli by a different interstice to that through which the corresponding superior
branch passes. They gain the inner face of the mastoido-humeralis, where they
divide into deep and superficial ramifications.
The first are distributed to the deep muscles of the sides, and anterior part of
the neck and shoulders. Among them ought to be distinguished those which
form a communication between the four pairs, and the third with the second.
Veiy long and thin, these filaments lie on the side of the large muscular mass
formed in front of the cervical vertebrae by the rectus anticus, longus colli, and
scalenus muscles. There they form sometimes arches, and at other times
856 THE NEBVE8.
anastomoses by convergence. Those of the fifth and sixth pairs, uniting at the
anterior border of the scalenus with a branch of the brachial plexus, constitute the
diaphrngmatic {phrenic) nerve, which will be noticed hereafter.
The superficial ramuscules gain the external surface of the mastoido-
humeralis by traversing its substance, or passing between its two portions.
Much more numerous and larger than the preceding, they are distributed — in
front — to the cervical panniculus ; behind, to the trapezius ; or below, to the
mastoido-humeralis and pectoralis anticus and transversus. Those passing to the
two last muscles are very long and voluminous ; they represent the acromial and
clavicular branches of the cervical plexus of Man. It may be remarked that the
posterior filaments generally communicate with the spinal accessory, while the
anterior ones, in meeting the cervical branch of the facial nerve on the jugular,
often give it some anastomosing fibres.
Seventh. — An enormous branch comes from the interstice between the two
portions of the scalenus, to pass entirely into the brachial plexus. It usually
receives an anastomosing twig from the diaphragmatic filament furnished by the
sixth pair.
Eighth. — This is thicker than the preceding, and comports itself like it. It
directly furnishes its anastomotic branch to the inferior cervical ganglion.
Aeticle II. — DoESAL Nerve (17 Paies).
These nerves, numbering seventeen pairs, comport themselves in an extremely
simple and almost identical manner ; so that their description is not nearly so
complicated as that of the nerves of the cervical region.
Superior Branches. — They present two principal ramuscules for the spinal
muscles and the skin of the dorso-lumbar region. One ascends towards the summit
of the spinous processes of the dorsal vertebrae, by passing between the semi-
spinalis and longissimus dorsi ; the other is directed outwards, in traversing the
substance of the latter muscle.
Inferior Branches. — These are more considerable in size than the pre-
ceding, and descend into the intercostal spaces, between the pleura and the
internal intercostal muscles, or even in the texture of these. With the exception
of the first, the arrangement of which is different, they all pass at first over the
head of the posterior rib to reach the convex border of the anterior one, and
follow it to the extremity of the intercostal space.
There they terminate in the following manner : those of the sternal ribs
traverse the pectoral muscles, giving filaments to these, and are expended in the
skin of the subthoracic region. Those of the asternal ribs enter the abdominal
muscles, passing between the transversalis and rectus abdominis ; they also give
cutaneous filaments to the skin of the abdomen.
Near their origin, the inferior branches communicate with the sympathetic,
for the most part, by several filaments.
In their course they furnish numerous fine ramuscules to thf^ intercostal
muscles, and, in addition, give off — about the middle of their length — a very thick
division — the perforating intercostal hranch, which traverses the costal muscles
and descends beneath the panniculus carnosus, ramifying partly in that muscle
and partly in the skin. The most anterior perforating branches generally anas-
tomose with the subcutaneous thoracic branch of the brachial plexus.
With regard to the first dorsal pair, its inferior branch enters the latter
plexus ; but it nevertheless furnishes an intercostal branch, always extremely
LUMBAR NERVES. 857
slender, which passes over the external intercostal muscle to be expended in its
substance, before aiTiving at the sternum. The second pair also concurs in the
formation of the brachial plexus, though only by a small branch.
Article III. — Lumbar Nerves (6 Pairs).
Superior Branches. — Distributed to the spinal muscles and the integu-
ments of the loins and croup, these are larger than the corresponding branches
of the dorsal region, but present an analogous disposition. They give superior
ramuscules to the muscles of the spine, and very long external divisions which
pass through these muscles, to be distributed to the skin of the croup.
Inferior Branches. — The /rs^— comprised in the interval separating the
last rib from the first lumbar transverse process, between the quadratus lumborum
and the psoas magnus — passes downwards and backwards until it arrives between
the transverse and internal obUque muscles of the abdomen, to which it gives
filaments, and is finally distributed in the rectus abdominis muscle.
Above the superior border of the internal obhque muscle, it furnishes a per-
forating branch to the skin of the flank and the posterior part of the panniculus
carnosus.
The second, disposed in the same manner as the preceding, follows an analogous
course, and breaks up into several divisions which are lost in the internal oblique
muscle. From one of these sometimes emanates a slender filament, which joins
one of the inguinal nerves of the third pair. We must not overlook, in the
enumeration of the branches emitted by this second pair of lumbar nerves, the
two perforating branches which descend in front, and on the inside, of the thigh,
to be distributed to the skin of the flank and the internal crural region.
The third ^ also passes outwards, above the psoas muscles, which receive
from it several divisions, and ramifies in the muscles of the flank. It has also
perforating nerves, destined to the inguinal region, and these comport them-
selves in a sufficiently interesting manner to merit particular mention. They
are usually three in number — an internal and two external inguinal nerves.
The three pass at first beneath the peritonemn, and are directed backwards,
downwards, and outwards, towards the inguinal canal, which they enter — one
to the inside, the other to the outside of the spermatic cord. They give off
some filaments to the cremaster and abdominal muscles, and at last ramify
in the envelopes of the testicle, the sheath, and the skin of the inguinal region.
The two external nerves are often confounded in a single trunk, on their arrival
at the cremasteric muscle. The disposition they affect at their origin is
extremely variable ; sometimes they have each a distinct commencement, and
separately traverse either the small or large psoas muscle, or the space between
these ; and, at other times, the internal and one of the external inguinal nerves
proceed from a common trunk at the intervertebral foramen, the second external
nerve then arising alone towards the external border of the psoas magnus
muscle. Most frequently, the internal nerve receives a branch from the fourth
pair, and it is even sometimes entirely formed by that branch. This variation
in arrangement is not, however, the exclusive appanage of the inguinal nerves ;
we have seen the third pair alone furnish these three nerves and the filaments
to the psoas muscles, without being prolonged into the muscles of the flank.
The fourth ^ pierces the psoas parvus muscle, and enters the space separating
' Representing the ahdomino-gen>tal B.n(i femoro-genital branches of Man.
* The femoro-cutaneous branch of the lumbar plexus of Man.
858 THE NERVES.
it from its congener — the psoas magnus. After passing between the peritoneum
and the lumbo-iliac aponeurosis, it arrives below the angle of the haunch, and
makes its exit from the abdomen ; it then descends within, and in front of, the
tensor fascia lata muscle, and, accompanying the divisions of the circumflex
iliac artery, it is prolonged to the stifle, where it is expended in the skin. At
its origin, it gives : 1. A thick, short branch to the psoas magnus muscle.
2. A large anastomosing branch which concurs in the formation of the lumbo-
sacral plexus. 3. A filament that joins the internal inguinal nerve furnished bj
the third pair. We have already mentioned that this nerve sometimes emanates
entirely from the fourth pair.
The fifth and sixth — much more voluminous than the preceding — unite, and,
with the three first sacral pairs, form the plexus of the abdominal limb.
All the inferior lumbar branches communicate with the sympathetic by
several filaments, which pass across the fasciculi of the psoas parvus muscle ;
and all communicate with each other — the two last by fusion of their fibres,
and the first five by means of more or less voluminous anastomotic branches,
which are far from being constant.
Aeticle IV. — Sacral Nerves (5 Pairs).
We describe, as sacral nerves, not only the four double cords which escape
by the lateral foramina of the os sacrum, but also the nerve that passes through
the intervertebral foramen between that bone and the last lumbar vertebra.
Superior Branches. — These are small ramuscules that pass through the
supra-sacral foramen, reach the muscles lodged on the sides of the sacral spine,
and terminate in the skin of the croup.
Inferior Branches. — Thick nerves, which diminish in volume from the
first to the fifth, and leave the sacral canal to pass downwards and backwards on
the sides of the pelvic cavity.
The first, second, and third are directed towards the great sciatic opening,
and are united into a wide nervous band that constitutes the pelvic portion of
the lumbo-sacral plexus, to be described at another time.
The fourth and fifth course along the side of the pelvic cavity — in the
texture of the sacro-sciatic ligament, or even within it ; united at their base by
an anastomosing filament, they do not usually communicate — at least, in a direct
manner — with the fasciculus formed by the three first pairs.
The fourth constitutes the internal pudic nerve, which passes between the
two roots of the corpora cavernosa in bending round the ischial arch, where
it lies nearly alongside its fellow of the opposite side. This nerve afterwards
descends on the dorsal border of the penis, in the midst of the magnificent
venous plexus of that organ, describing flexuosities which allow it to adapt
itself to the elongation of the penis. Arriving at the extremity of the organ,
it terminates in numerous divisions in the proper erectile tissue of this part,
or in the mucous membrane covering it. On its course it emits very long
flexuous branches, the ultimate ramifications of which enter the corpora caver-
nosa, or go to the urethral canal. Before leaving the pelvis, it gives off", behind,
two thin ramuscules to the muscles and skin of the perineo-anal region. These
ramuscules, like the principal trunk, receive anastomotic filaments from one of
the ischio-muscular branches of the lumbo-sacral plexus.
The fifth is the anal or hcemorrhoidal nerve. It passes backward, above
DIAPHRAGMATIC NERVE. 859
the preceding, and is distributed to the sphincter ani muscle and the surround-
ing integuments. Before quitting the pelvis, it gives a ramuscule to the
levator ani.
The five inferior sacral branches emit, near their origin, a more or lesa
slender filament that proceeds to the pelvic or hypograstic plexus. The anasto-
mosing divisions, through which they communicate with the sympathetic chain,
are generally thick, short, and multiple.
Aeticle v.— Coccygeal Neeves (6 to 7 Paies).
In the coccygeal region are found two pairs of nerves — one placed beneath
the compressor muscle of the tail, the other below the curvator muscle. These
two nerves extend to the extremity of the tail, throwing off on their track some
muscular and cutaneous filaments. They are formed by the superior and inferior
branches of the coccygeal nerves, which gradually amalgamate to form the two
nerves.
These coccygeal branches are six or seven in number, and very distinct ; they
diminish in volume from the first to the last. The first only gives a slender
filament for the formation of each coccygeal trunk ; it is chiefly expended in the
integuments and muscles at the base of the tail.
Aeticle VI. — Composite Neeves foemed by the Infeeioe Beanches op
THE Spinal Neeves.
We already know that these nerves represent three groups : 1. The dia-
vhragmatic nerve. 2. The brachial plexus. 3. The lumbosacral plexus. They
will be studied in this order.
Diaphragmatic (or Phrenic) Nerve.
The diaphragmatic nerve (the internal respiratory nerve of Bell) is formed by
two principal branches, and a small accessory ramuscule, the presence of which
is not constant. The latter comes from the fifth cervical pair ; the two others
proceed, one from the next pair, the other from the brachial plexus. The branch
from the sixth pair pierces the inferior scalenus muscle from within to without,
gives off a filament to the brachial plexus, and descends obliquely backAvards to
the surface of the muscle it passes through, to unite — at the entrance to the
chest — with the branch of that plexus. This latter branch, generally shorter and
thicker, comes exclusively from the seventh cervical pair.
The trunk of the diaphragmatic nerve, formed in this manner, passes into the
thorax after receiving the branch of the fifth pair — when it exists — passes within
the axillary artery, along with the pneumogastric nerve, and often at this point —
if not always — obtains a filament from the sympathetic. It then gains the side
of the base of the heart, passing beneath the pleura, and finally attains the tendi-
nous centre, after a course of at least eight inches between the two layers of the
posterior mediastinum — the left nerve being in the mediastinum proper,^ while that
of the right side lies in the special serous partition for the posterior vena cava.
' Lesbre has found, in an Ass, an anomaly in the course of the left diaphragmatic nerve.
It passed directly from the base of the heart to the anterior face of the diaphragm, being sus-
tained in the middle of the corresponding portion of the pleural cavity by a special fold,
analogous to that of the posterior vena cava in the right pleura.
SCO TEE NERVES.
Even before its aiTival at the tendinous centre, this nerve divides into
several branches, the ramifications of which pass to the sides of the crura of the
diaphragm.
Brachial Plexus.
This plexus comprises an enormous fasciculus of nerves, situated between
the thoracic parietes and the inner face of the anterior limb, formed by the
inferior branches of the sixth, seventh, and eighth cervical, and the two first
dorsal pairs ; they are principally sent to the muscles and integuments of that
limb.
Mode of constitution. — The sixth cervical pair only assists in the fomiation
of this plexus, by the slender filament from its diaphragmatic branch ; but the
next two are entirely devoted to it, as well as the first dorsal, with the exception
of a very thin ramuscule, which constitutes the first intercostal nerve. The root
furnished by the second dorsal pair only represents a very small part of its
inferior branch, the other portion forming a somewhat voluminous intercostal
nerve.
The various branches converge towards each other, and gain the space
between the two portions of the scalenus muscle (if we consider it as one), where
they unite, and become confounded into a single fasciculus by sending filaments
and ramuscules to each other ; this fasciculus soon separates into a certain
number of divisions, the disposition of which will be referred to presently. It
will be remarked that the intercrossing of the branches composing the brachial
plexus does not occur in a confused and irregular fashion, and if the reticulation
of the ramuscules passing from one to another does not take place in a constant
manner, it is, at any rate, far from being inextricable. It is easy to follow the
filaments from any pair of nerves for a certain distance in the divisions given
off by the brachial plexus, especially after maceration in dilute nitric acid. This
originating fasciculus of the brachial plexus is very wide and short. It is at
first comprised between the superior portion of the scalenus (or superior scalenus)
and the longus colU. In its course between the two portions of that muscle,
it bends round the first rib by its posterior border, and is related inwardly to the
vertebral artery and vein, as well as to the vertebral nerve-filament proceeding
to the sympathetic, and accompanying these vessels.
3Iode of distribution. — Immediately after leaving the interspace in the
scalenus, the brachial plexus arrives beneath the shoulder, near the scapulo-
humeral angle. There it divides into a certain number of branches, amongst
which it is impossible to distinguish the terminal divisions and collateral
ramuscules. Without noticing this distinction, however, we will describe them
in succession, commencing with those that pass to the trunk, and afterwards
those which are destined for the limb. The latter will be examined in the
following order : first, the shortest branches, or those which proceed to the
upper parts of the member; and next, the longest branches, or those passing
to the foot.
All these divisions are named and classified in the following enmneration : —
BRACHIAL PLEXUS.
861
Name.
Origin.
A. Branches to the Body.
1. Diapliragmatic (phrenic) branches.
2. Levator anguli scapulae and rhoniboideus branch.
3. Serratus magims, or superior thoracic branch.
4. Pectoral or inferior thoracic branches.
5. Subcutaneous thoracic branch.
6. Latissimus dorsi branch.
5th, 6th, and 7tii cervical pairs.
6th cervical pair.
6th and 7th cervical pairs.
6tii and 7th cervical pairs.
1st and 2nd dorsal pairs.
8th cervical pair.
B. Branches to the Shouldeb.
7. Circumflex or axillary nerve.
8. Teres major branches.
9. Subscapular branches.
10. Supra-scapular nerve.
8th cervical pair.
8th cervical pair.
7th cervical pair.
6tii and 7th cervical pairs.
C. Branches to the Arm and Fore-arm.
11. Anterior brachial or musculo-cutaneous nerve.
12. Musculo-spiral or radial nerve.
7th and 8th cervical pairs.
1st dorsal nerve.
D. Branches to the Forearm and Foot.
13. Ulnar or cubito-cutaneous nerve.
14. Median or cubito-plantar nerve.
Ist and 2nd dorsal pairs.
8th cervical, and 1st and 2nd
dorsal pairs.
Preparation of the Brachial Plexus. — The animal is placed in the first position, and
slightly inclined to one side by allowing one of the anterior limbs to hang unrestrained. The
pectoral muscles are then excised close to their insertion in the unfixed limb, and turned
upwards, maintaining them in this position by the chain tentacula which are attached
superiorly to a band that unites the extremities of the two suspensory diagonal bars. Care
should be taken to separate the pectoralis magnus from the panniculis, in allowing the latter
to fall on the table along with the limb. By tearing through the considerable mass of con-
nective tissue surrounding the nerves of the brachial plexus, these soon appear, and may be
isolated with the greatest facility. It is advisable, in this dissection, to preserve the arteries;
and it is also of importance to leave the perforating intercostal branches intact, in order to
observe the anastomoses of these with the subcutaneous thoracic division.
In this operation, the anterior limb is very much separated from the trunk, and the
relations of the nerves are necessarily more or less changed; but it exhibits the whole of
the plexus in the most perfect manner.
To trace the divisions of the principal nerves from tiiis plexus, a limb enti|gly removed
from the body is made use of, and, if possible, with the arteries injected. The ne^es are then
found in their natural relations, and can be more readily dissected. Figs, 465, 466 will
guide the student in looking for these nerve-divisions.
1. Diaphragmatic Branches.
See the description of the diaphragmatic nerve above.
2. The Levator Anguli Scapula and Rhomboideal Branch (Fig. 465, 7).
Entirely furnished by the sixth cervical pair, this branch is directed upwards
to the surface of the levator anguli scapulge. It soon divides into several fila-
ments, which are wholly expended in the substance of that muscle, the serratus
magnus, and the rhomboideus. The filament supplying the latter is slender
and very long, and, to reach its destination, passes through the levator anguli
scapulas.
3. Serratus Magnus, or Superior Thoracic Branch (Fig. 465, 8).
This very remarkable branch proceeds, by two principal portions, from the
fasciculus common to all the divisions of the brachial plexus — one emanating
57
862 THE NERVES.
from the sixth cervical pair ; the other from the seventh, and always traversing
the last fasciculus of the superior scalenus before joining the first. The single
branch resulting from the union of these two roots is thin and very wide. It
passes back to the surface of the serratus magnus, crossing the direction of its
fibres, and is expended in its substance, sending regularly arranged ramifications
upwards and downwards.
This is the respiratory nerve of Bell.
4. Pectoeal, or Inferior Thoracic Branckes.
Five principal are distinguished : —
1. One emanating from the sixth and seventh cervical pairs — particularly the
former — and passing to the internal face of the anterior deep pectoral muscle,
to ramify exclusively among its fibres, after dividing into two branches : an
anterior, short and thick, and a posterior, long and slender (Fig. 465, 10).
2. A second branch, arising from the anterior brachial and cubito-plantar
(or median) nerves, by two roots, which join in forming an arch beneath the
axillary artery.
It passes between the anterior and posterior deep pectoral muscles, and
terminates in the superficial one, after furnishing some ramuscules to the
posterior deep pectoral by means of a long thin filament, which is carried back
to the external surface of that muscle (Fig. 465, 11).
3. The other three, passing to the posterior deep pectoral muscle, generally
come from the trunk that constitutes the subcutaneous thoracic branch. Com-
prised between the serratus magnus and posterior deep pectoral, they are
directed downward and backward, and enter the latter muscle. One of them —
longer and thicker than the other — follows the course of the spur vein.
5. Subcutaneous Thoracic Branch (Fig. 465, 9).
This is a very remarkable nerve, arising from the brachial plexus by a trunk
common to it and the ulnar nerve. Placed at first to the inside of that nerve,
it soon leaves it to pass backward to the internal face of the caput magnum and
the panniculus carnosus. In its long com'se, it acts as a satellite to the spur
vein, above which it is situated. It may be followed to the flank, where its
terminal divisions are lost in the substance of the panniculus muscle. Those it
gives off are also destined to that muscle ; they anastomose with the majority of
the perforating intercostal nerves, forming an elaborate network on the inner
face of the panniculus.
One of its branches, along with a voluminous perforating nerve, bends round
the inferior border of the latissimus dorsi, and passes forward to enter the
scapulo-humeral portion of the panniculus.
6. Latissimus Dorsi Branch (Fig. 465, 6).
Formed of fibres, the larger portion of which come from the eighth cervical
pair, this branch proceeds backwards and upwards to the internal face of the
latissimus dorsi, and is soon expended in that muscle. It is long and thick.
7. Circumflex or Axillary Nerve (Fig. 465, 13).
Somewhat considerable in voliune, this nerve is furnished directly by the
eighth cervical pair. It passes backward and do^vnwa^d on the internal face of
;ig. 465.
NERVES OF THE BRACHIAL PLEXUS.
1, Diaphragmatic branch of the sixth cervical pair,
^ branch to the brachial plexus ; 2, seventh cervical pai
eio-hth cervical pair ; 4, first dorsal pair ; 5, second dorsal pair ;
6, great dorsal branch; 7, levator anguli scapulae and rhom-
boideal branch ; 8, superior thoracic branch ; 9, subcutaneous
thoracic branch, giving rise, near its origin, to the three in-
ferior thoracic branches; 10, 11, two other inferior thoracic
branches; 12, nerve of the teres major; 13, axillary nerve;
14, subscapular nerves ; 15. supra-scapular nerve ; 16, radial
nerve; 17, anterior brachial nerve; 18, ulnar nerve; 19, its
internal cutaneous branch ; 20, median nerve ; 21, its mus-
culo-cutaneous branch ; 22, 22, 22, superficial ramuscules of
iiuit branch. A, Humeral artery ; b, posteripr radial artery.
EXTERNAL NERVES OF THE ANTERIOR LIMB.
Supra-scapular nerve ; 2, axillary nerve ; 3, radial
nerve; 4, superficial ramuscuJe of the musculo-
cutaneous nerve ; 5, ulnar nerve ; 6, its terminal
cutaneous branch. A, Anterior radial artery.
864 THE NERVES.
the subscapularis muscle, to the intei-stice between it and the teres major, where
it crosses the subscapular artery. It proceeds behind the scapulo-humeral
articulation, along with the circumflex artery, entere between the teres minor
and the caput magnum and medium, and, arriving beneath the deltoid, it
divides into several diverging branches, destined to the teres minor, deltoid,
mastoido-humeralis, and even to the integuments covering the anterior region
of the arm.
Before entering the space that lodges the subscapular artery, it sends filaments
to the scapulo-humeralis and gracilis muscle.
8. Nerve of the Teres Major (Fig. 465, 12).
This arises from the eighth cervical pair — like the preceding — by the one
trunk, and passes backward, at first on the subscapularis muscle, then on the
adductor, in the substance of which it disappears by numerous filaments.
9. Subscapular Branches (Fig. 465, 14).
These branches are two in number, and are generally derived from the trunk
of the seventh pair. After a short course backwards, they divide into several
ramuscules, which pass among the fibres of the subscapularis muscle.
10. Supra-scapular Nerve (Fig. 465, 15).
Very short and thick, this nerve is formed by the sixth and seventh cervical
pairs. After a brief course backwards, between the levator anguli scapulae on
the one side, and the anterior deep pectoral, prescapularis, and supra-spinatus on
the other, it gains the space between the latter muscle and the subscapularis,
and enters it a little above the supra-scapular artery. It is then carried to the
external face of the scapula, after bending round the anterior border of that
bone, passes across the acromion spine, and ascends to the infra-spinous fossa, to
expend itself in the muscle occupying this space. On its passage beneath the
supra-spinatus muscle, it gives it several ramuscules.
11. Anterior Brachial or Musculo-cutaneous Nerve (Fig. 465, 17).
This nerve proceeds from the seventh and eighth cervical pairs, descends to
the internal face of the scapulo-humeral articulation, and meets the axillary
artery, which it crosses outwardly, at an acute angle. It then joins the median
nerve by a large short branch, that passes beneath the artery and forms a loop
around it ; descending in front of the median nerve, to the bifurcation of the
coraco-humeralis, it insinuates itself between the two branches of that muscle,
and, breaking up into several ascending and descending ramuscules, enters the
substance of the biceps. It also furnishes filaments to the coraco-humeralis,
before its passage between the two branches of that muscle. Besides this, it
concurs, by a small branch, in the formation of one of the anterior thoracic nerves.
12. Radial (or Musculo-spiral) Nerve (Figs. 465, 16 ; 466, 3).
This is certainly the largest nerve furnished by the brachial plexus. It arises
chiefly from the first dorsal pair, and is directed backwards and downwards, on
the inner face of the subscapularis and teres major muscles, crossing their
direction. In this portion of its course, it proceeds parallel to the humeral
TEE BEACH I AL PLEXUS. 865
artery, from which it is separated by the ulnar nerve. Arriving at the deep
humeral artery — which it leaves on the outside — it passes behind the humerus with
the divisions of that artery, and enters between the caput magnum and brachialis
anticus. After creeping along the posterior border of the latter muscle, it gains
the anterior face of the ulna-radial articulation, where it is covered by the two
principal extensors of the metacai-pus and the phalanges, and, meeting the radial
artery, accompanies it on to the oblique extensor of the metacarpus. There it
terminates by two branches, which enter the texture of that muscle.
In its course, it successively gives off —
1. Before leaving the internal face of the limb, to pass beneath the mass of
extensor muscles of the forearm, a very thick fasciculus, composed of several
branches — descending and ascending. The latter bend round the terminal
tendon common to the latissimus dorsi and teres major, to become lost in the
body of the great extensor ; the others reach either the long and middle
extensors, or the inferior portion of the principal muscle — the large extensor.
2. Behind the arm, filaments to the caput medium and anconeus, and
several cutaneous ramuscules, disengaged from beneath the former muscle,
that descend beneath the skin on the anterior face of that part.
3. In the antibrachial region, branches to the extensor metacarpi magnus
and flexor metacarpi externus, and the two extensors of the digit.
In brief, we see that the radial nerve is distributed to, and therefore
stimulates, the whole mass of the extensor muscles of the forearm and foot,
besides a flexor of the latter ; and that it endows the integument of the anterior
antibrachial region with sensibility.
13. Ulnar or Cubito-cutaneous Nerve (Figs. 465, 18 ; 466, 5).
Chiefly formed by fibres from the dorsal pairs, this nerve — less considerable in
volume than the preceding — passes backward and downward, and places itself
behind the humeral artery, which it accompanies to below the origin of the deep
humeral. After crossing the latter vessel, it passes between the scapulo-ulnaris
and caput parvum, and gains the inner side of the elbow, running over the
epicondyle, below the ulnar band of the oblique flexor of the metacarpus. It
follows the posterior border of that muscle to near the pisiform bone, where it
terminates by two branches. In the latter part of its course, it lies beneath the
antibrachial aponeurosis, accompanied by a division of the epicondyloid artery.
One of the two branches — the cutaneous (Fig. 466, 6) — crosses the space
between the terminal tendons of the external and obhque flexor muscles of the
metacarpus, as well as the antibrachial aponeurosis, to expend itself in several
ascending horizontal and descending filaments, beneath the skin of the forearm,
the anterior face of the knee, and the external side of the cannon. The other
branch, with a ramuscule from the median nerve, constitutes the external plantar
nerve.
In its course, the ulnar nerve gives off two fasciculi of collateral branches.
The first (Fig. 465, 19) is detached from the principal trunk a little above the
epicondyloid artery, and passes backward and downward between the scapulo-
ulnaris and the anterior superficial pectoral — supplying some filaments to the
latter — traverses it to become subcutaneous, and to be distributed to the skin of
the forearm, beneath the elbow {internal brachial cutaneous). The second arises
at the epicondyle, and is destined to all the muscles of the posterior antibrachial
region, except the external and internal flexors of the metacarpus.
866 THE NERVES.
14. Median or Cubito-plantar Nerve (Fig. 465, 20).
This nerve is composed of fibres coming from the dorsal and eighth cervical
pairs. It is detached from the posterior part of the trunk of the plexus and
proceeds towards the axillary artery, where it forms an anastomosis with the
anterior brachial nerve, through the loop already noticed when describing that
nerve as being formed by filaments passing from one cord to the other, x
Leaving this point, it is placed in front of the humeral artery, and accom-
panies it to its terminal bifurcation ; then it continues to descend on the inner
face of the limb, along with the principal branch of that artery — the posterior
radial — until it reaches the ulnar articulation, where it lies against the internal
ligament of that joint, and crosses — at a very acute angle — the direction of its
satelUte vessel to become posterior. This position it inverts below the articu-
lation, when it assumes, and preserves for the greatest part of its extent, its
antibrachial course, remaining always a little more superficial than the artery.
Above the lower third of the forearm, it bifurcates to form the plantar nerves.
In its course, this nerve successively furnishes —
1. Before its arrival on the axillary artery, one of the originating branches of
the thoracic nerve passing to the anterior superficial pectoral muscle.
2. At the middle of the humerus, a long branch, represented in Man by that
portion of the musculo-cutaneous nerve which proceeds to the anterior brachial
muscle and the skin of the forearm. This branch enters beneath the biceps,
and forms two divisions ; one of these is expended in the brachialis anticus
while the other passes between that muscle and its congener — the long flexor — to
become superficial and gain the internal aspect of the limb, when it breaks up
into two principal filaments, which pass to the external face of the antibrachial
aponeurosis, and accompany with their divisions the two subcutaneous veins of
the forearm to below the carpal region (Fig. 465, 21, 22).
3. In the antibrachial region, and at various elevations — but particularly below
the ulnar articulation — ramifications to the internal flexor of the metacarpus and
the two flexors of the phalanges.
Plantar Nerves. — These nerves, two in number, are distinguished as
internal and external.
The internal plantar nerve — one of the terminal branches of the median nerve —
lies beside the large metacarpal artery, and follows that vessel along the perforans
tendon to near the fetlock, where it ends in several digital branches. In its
track it furnishes a number of cutaneous metacarpal ramuscules, and an anasto-
mosing branch, which, after being detached from the principal trunk, about the
middle of the cannon, bends obliquely behind the flexor tendons to join the
external plantar nerve. This is formed by the union of two branches— one
coming from the ulnar nerve, the other from the median, and joining the first
at the upper border of the pisiform bone, after passing beneath the inferior
extremity of the oblique flexor of the metacarpus. This nerve, which accom-
panies the external metacarpal vein for its entire length, descends with it, and
with an arteriole that concurs in forming the subcarpal arch, outside the flexor
tendons, in a special fibrous channel of the carpal sheath. Near the superior
extremity of the cannon, within the head of the external metacarpal bone, it
sends on the posterior face of the suspensory ligament of the fetlock a deep
plantar branch, chiefly destined to the fleshy portion of the interosseous muscles.
It is the analogue of the deep palmar branch of the ulnar nerve in Man. Con-
THE BRACHIAL PLEXUS.
867
tinuing its descending course along the perforans tendon, it throws off some
superficial metacarpal ramuscules, receives the accessory branch supplied by the
internal nerve, and terminates, like the latter, in a number of digital branches
on aiTiving at the fetlock ; these it now remains for us to examine.
NERVES OF THE DIGIT.
P, Plantar nerve ; B, median branch ; C, anterior branch ; d, digital artery ; H, inconstant division
given off to the cartilaginous bulbs; i, i, branch to the plantar cushion ; K, transverse coronary
branch ; m, podophyllous branch ; 0, preplantar branch ; Q, descending ramuscule to the fissure
of the patilobes ; R, ramuscules accompanying the digital artery in the plantar fissure ; v, vein
which is not constant, and which sometimes accompanies the plantar nerve throughout its
phalangeal course.
The digital branches are the terminal branches of the plantar nerves ; they
are three in number on each side, and accompany the digital artery and vein.
868 TEE NERVES.
which, at some points, they cover with their divisions. They separate from one
another nearly at the insertion of the suspensory hgamerit into the sesamoid
bones. One of them descends in front of the vein ; another passes between the
two vessels ; while the third follows the artery behind. They may, therefore,
be distinguished, according to their position, into anterior, middle, and posterior
(Fig. 467, M, 0, r).
The anterior branch distributes its collateral divisions to the skin on the
anterior face of the digit, and its terminal ramuscules in the coronary cushion.
The middle branch frequently anastomoses with the other two, particularly
with the anterior, and to such a degree as to be scarcely distinguished from it ;
it enters the coronary cushion and the podophyllous tissue.
The posterior branch — much more considerable than the preceding, and a real
continuation of the plantar nerve — is at first superposed on the digital artery^
then it is placed immediately behind that vessel. It descends with it to near
the basilar process of the third phalanx, follows the preplantar ungual artery into
the lateral fissure of that phalanx, and, like that vessel, expends itself in the
midst of the podophyllous tissue, as well as in the osseous structure. This branch
gives off numerous ramuscules on its course. Of these there may be more par-
ticularly noticed : 1 . Some posterior divisions, distributed behind the flexor
tendons, especially at the fetlock. 2. A satellite branch to the artery of the
plantar cushion. 3. A filament arising below the lateral cartilage, passing for-
ward, in proximity to the anterior branch of the arterial coronary circle, and
becoming lost in the meshes of the deep venous network of the cartilage. 4. A
small podophyllous division, the origin of which is placed at the same height as
the preceding filament, but opposite it, and which descends on the retrossal
process, where it traverses the cartilaginous tissue to pass to the podophyllous
reticulation, after distributing posterior ramuscules to the plantar cushion. 5.
Several extremely fine filaments enlaced around the plantar ungual artery, and
with it passing to the interior of the os pedis ; some of these filaments ascend to
the nerve of tlie opposite side.-^
Differential Characters in the Brachial Plexds of the other Animals.
In the domesticated Mammals, the nerves of the brachial plexus do not offer any very
important differences in the upper part of the limb ; these only become apparent in the nerves
of the last section.
Ruminants.— The brandies of the plexus— the same in number as in the Horse— are rela-
tively more voluminous than in that animal. In the Ox they are often tiexuous in tiieir upper
part. In the Sheep, the diaphragmatic nerve is formed by a single filament, detached from
the branch the sixth cervical nerve gives to the brachial plexus, and whicii passes over the surface
of the scalenus; and a second branch which comes from the fifth pair, runs beneath the
scalenus, and joins the first on the inner surface of the first rib (Toussaint). There are no
' It is because we conform to established usages, and are unwilling to force analogies, that
we preserve the designations of " plantar nerves " and " digital branches," as well as the above
manner of describing them. Comparative anatomy desires other names and a different descrip-
tion ; for it demonstrates that the external plantar nerve corresponds to the interosseous palmar
of the second space in pentadactylous animals ; and the internal plantar to the interosseous palmar
of the third space. It also shows that the digital branches are the exact representatives of the
collaterals of the digits which result, in the pentadactylous species, from a bifurcation of each
interosseous nerve.
According to this description, it will be seen that the terminal branches of the meiiiau
nerve are not only distributed over the posterior face of the digit, hut that a good number of
fiilaments are sent to tiie dorsal face— a remark which has been made in recent years, with
leference to the distribution of the collateral palmar neives of the human fingers.
THE BRACHIAL PLEXUS.
diflferences in the branch of the angularis and rhomboideus, in the branches of the pectoral
muscles, the subcutaneous thoracic branch, or the anterior brachial or musculo-cutaneous nerve.
The nerve of the serratus magnus does not sliow the branch which, in the Horse, arises from
the sixth nerve and passes tlirough the scalenus; but on the surface of the serratus magnus it
receives a filament from the branch of the angularis. The latter is detached from the sixth.
The branch of the latissimus dorsi muscle and the axillary nerve are confounded at their
origin, and also adhere fo one of the two
branches of the siibscapularis nerve. The
second branch of the latter is free through-
out its extent, and distributed in the mus-
cle of the same name, along with some fila-
ments furnisiied by the supra-scapularis.
The radial nerve, when it reaches the
teres major, divides into three branches :
one is buried in the long extensor of the
forearm ; the other traverses the middle
extensor ; and the third is inflected on the
tendon of the latissimus dorsi, and passes
between the middle and large extensor
of the forearm. "When the radial nerve
turns outwards around the arm, and is
placed between the anterior brachial and
the mass of the olecranian muscles, it
furnishes : 1. Muscular branches that pass
immediately beneath the extensors of the
metacarpus and phalainges. 2. A sensitive
branch that leavesthis muscular interstice
to become subcutitneous. This cutaneous
branch of the radial nerve gains the inner
face of the forearm, and divides in two
branches that descend parallel to the
median subcutaneous vein. One of these
is distributed around the carpus ; the
other is placed a little in front of the meta-
carpus, and reaches the mctacarpo-plialan-
goal articulation, where it terminates by
two principal filaments that constitute the
dorfiol collaterals of the difjits ; there is
a third which crosses the interdigital to
anastomose with the palmar collaterals.
The ulnar and median nerve of Kuuii-
nants lie beside each other, as far as the
middle of the arm. This double cord is
situated at the surface of the humeral
artery ; at the carpus the two nerves otfer
the same distribution as in the Horse, but
beyond tliis there are some differences.
The ulnar does not receive a branch
from the median at the carpus, and it
forms the external plantar nerve or iiiter-
os.seous palmar of the second space, placed
at the external border of t h e flexor tendons.
This nerve is reinforced by a filament de-
tached from the external plantar, that
joins it a little above the fetlock -joint ; it
gives ramuscules to the ergot, and is then
continued by the external collateral nerve
of the outer digit, into the toe.
The median is continued by the internal plantar, or interosseous palmnr of the third space.
Towards the inferior third of tlie metacarpus, it divides into three branches : the third passes
to the external plantar ; the second proceeds to the interdigital space, where it bifurcates to
form the internal collateral palmar nerves of the external digit, and external collateral of the
NERVES OF THE DIGITAI; REGION OF RUMINANTS
(POSTERIOR face).
M, Internal plantar nerve, a continuation of the
C, internal plantar nerve, a continuation
of the ulnar. 1, Branch of the plantar, furnishing,
2, the internal collateral nerve of the internal
digit ; 3, branch giving otF the internal collaterals
of the digits ; 1', branch of the internal plantar
that joins the e.\ternal plantar ; 4, external col-
lateral of the e.'cternal digit.
870 THE NERVES.
internal digit; the third gives some filaments to the ergot, and passes along the digital region,
where it constitutes the internal collateral of the internal digit.
Pig. — Three fasciculi are detached from the brachial plexus; the posterior is the most
voluminous, and furnishes the radial, median, and ulnar.
The branches of the plexus that pass to the trunk and the first segments of the anterior
limb much resemble those of Ruminants; the branch of the serratas magnus is remarkable for
its length and size.
The median nerve is disposed like that of Solipeds and Ruminants, as far as the carpus*,
from this point it passes beneath the flexor tendons of the phalanges, gives filaments to the
interosseous palmar muscles, and at the two rudimentary digits divides into four branches:
the two upper are the smallest, and forms the collaterals of the rudimentary digits; tlie
inferior two are tiie longest, and reach the principal interdigital space, forming the collaterals
of the two great digits.
The ulnar gives off, towards the middle of the arm, a branch that passes to the ulna ; at
the ulnar it furnishes several muscular branches. The nerve then bend round to the outside
of the forearm, and on arriving above the pisiform bone, bifurcates : one branch goes along
the outer border of the flexor tendons, and is continued by the collateral of the external digit;
the other is placed on the anterior face of the metacarpus, and also bifurcates to give the
external digits their dorsal collateral nerves.
Caknivoba. — The four last cervical and first dorsal compose the brachial plexus in the
Caruivora ; the fifth cervical gives an insignificant filament. When the plexus is unravelled,
its principal brandies are observed to send fibres to each other.
The number of the distributive branches is the same as in Solipeds, and the disposition ol
the superior branches is so analogous as to call for no remark ; so we will only describe the
anterior brachial, radial, median, and cubital nerve.
The anterior brachial, or muscnlo-cutaneous, is constituted by a filament from the sixth
cervical and the more voluminous branches coming from the seventh. Placed in front of the
axillary artery, this cord arrives at the scapulo-humeral articulation, where it bifurcates : one
of the branches passes forward to the biceps ; the other remains alongside the anterior border
of the humeral artery, and terminates by a slightly recurrent branch that is buried in the
anterior brachial muscle, and by a very fine filament that becomes subcutaneous at the elbow,
and descends on the inner border of the forearm to be lost in the vicinity of the carpus. The
anterior brachial is, therefore, in these animals, a muscnlo-cutaneous nerve. The branch
uniting it to the median nerve is situated a little below the middle of the humerus, instead
of being beneath the axillary artery, as in Solipeds.
The radial nerve, in the 35og, is exclusively formed by the eij;hth cervical ; it receives
filaments from the median, ulnar, and axillary nerve, and gives branches to these three. When
it reaches tlie interstice of the triceps and anterior brachial, it crosses the limb above the outer
face of the elbow, and divides into two series of terminal branches.
The muscular branch enters beneath the muscles on the anterior face of the forearm.
The cutaneous bifurcates immediately : the smallest branch, passing inwards, extends beyond
the bend of the elbow, lies at the inner border of the median subcutaneous vein, and is dis-
tributed to the lower moiety of the forearm, the thumb, and internal border of the index digit.
The largest lies at the outer side of the median subcutaneous vein ; it sends a recurrent
ramuscule to the bend of the elbow, and, at the elbow, detaches three filaments to the first,
second, and third dorsal intermetacarpal spaces ; these filaments bifurcate at the dorsum of the
digits to constitute the collateral dorsal nerves. The first metacarpal nerve anastomoses, by a
fin transverse brancli, with the ulnar ramuscule that constitutes the external dorsal collateral
of the small digit.
To resume : the radial of the Dog gives branches to the dorsal face of all the digits, except
the external border of first digit, or auricularis.
In the Cat, there are some differences. The internal branch of the radial sometimes
lies with the external branch; it is placed at the inner border of the metacarpus, gives off a
filament to the dorsal face of the thumb, and afterwards forms the internal dorsal collateral
nerve of the index. The external branch leaves the anterior face of the carpus, and is situated
at the origin of the third interosseous space, where it divides into three metacarpal branches;
the external of these is very fine, and directed obliquely outwards, anastomosing with the
dorsal branch of the ulnar, between the first and second digits.
The median of the Dog is united to the ulnar as far ns the lower fourth of the arm ; it is
situated behind the humeral artery, and the filament it receives from the musculo-cutaneous
joins it at a short distance from the elbow-joint. Placed beside the radial artery, tlie median
is, towards the lower third of the forearm, immediately below the posterior border of the
THE BRACHIAL PLEXUS.
871
great palmar tendon : it afterwards passes through the carpal sheath, siving a branch that
constitutes the internal palmar collaterals of the thumJt, and external of the index; it finally
forms three branches, the first of whicli anastomoses with the ulnar, at the surface of the palmar
arcli, and is lost on an artery ; the other two, receiving a filament from the ulnar at the origin
of the digits, bifurcate to form the internal palmar collateral of the annularis, and collaterals of
the medius and index. The second gives, in addition, a slender branch, that is lost in the
Fig. 469.
¥vi 4-70,
NERVES OF THE PALMAR FACE (DOG).
A, Trunk of the median dividing into six branches;
Bl, branch of the superficial nervous arch; b2,
branch disappearing on a vessel ; b3, b4, branches
uniting with the corresponding ramuscules of the
ulnar; b5, branch forming the internal collateral
of the index ; b6, rudimentary branch passing to
the thumb; C, collateral given off by the median;
Cl, C2, C3, c4, collaterals furnished by the median
and ulnar, a, Palmar branch of the ulnnr; 6,
superficial branch giving off a filament to the hypo-
thenar, and a second that forms the superficial
nervous arch ; 61, deep branch passing to the
muscles of the skin ; in, not anastomosing with the
median ; ml, m2, anastomosing with the correspond-
ing branch of the median ; the innermost passes to
the muscles of the thumb; c, c, c, collaterals fur-
nished by the ulnar.
NERVES OF THE PALMAR FACE (CAT).
A, Trunk of the median dividing into
two branches; B, internal branch,
giving a rudimentary filament to the
thumb, Bl, external branch, receivmg
a filament, /, from the ulnar; c, C, C, C,
collaterals furnished by the median.
a, Palmar branch of the ulnar divid-
ing into three branches ; h, internal
branch, detaching the filament, /, to
the median; 61, external branch;
62, deep branch ; c, c, c, collaterals
furnished by the ulnar.
internal and middle lobe of the large cushion of the paw. In fine, the median of the Dog
furnishes to all the digits, except the auricularis and external border of the annularis.
In the Cat, the median traverses the bony canal at the lower extremity of the humerus,
and separates below the carpal arch into three branches. The internal branch is destined to
the rudimentarv thumb, and the internal palmar border of the index. The middle branch
872
THE NERVES.
descends in the third interosseous space, furnishes a filament to the large cushion of the paw,
and divides to form the external palmar collaterals of the index and internal of the medius.
Finally, the external branch is placed in the second intermetacarpal space, and gives the
following palmar collaterals : the external of the medius and internal of the annularis.
The ulnar nerve of the Dog, below the elbow, lies beside the ulnar artery to the lower third
of that vessel ; there it forms two branchLS— a dorsal and palmar. The dorsal branch becomes
subcutaneous, passes along the external border of the forearm, metacarpus, and small digit, and
constitutes the external dorsal collateral nerve of the latter.
The palmar branch leaves the carpal sheath, gives otf, at the trapezoides, a ramuscule that
passes to the surface of the palmar muscles to form the external collateral palmar of the
auricularis, and then, at the surface of the deep palmar arch, divides into eight terminal
t
Fig. 471.
THE NERVES OF THE AXILLA. OF MAN.
1, Scalenus medius; 2, scalenus anticus; 3, cord formed by 5th and 6th cervical nerves; 4, 7th
cervical nerve ; 5, superscapular nerve ; 6, subclavian avteiy (cut) , 7, insertion of subclavius ; 8,
cord formed by 8th cervical and 1st dorsal nerves ; 9, pectoralis major (reflected); 10, internal
anterior thoracic nerve ; 12, origin of subclavius ; 13, pectoralis minor (reflected) ; 14, internal
cutaneous nerve; 15, axillary artery (cut); 16, posterior thoracic nerve ; 17, musculo-cutaneous
nerve; 18, origin of pectoralis minor; 19, median nerve; 20, nerve of Wrisberg ; "21, coraco-
brachialis ; 22, intercosto-humeral nerve; 23, ulnar nerve; 24, subscapularis ; 25, brachial
artery ; 2'i, lateral cutaneous branch of 3rd intercostal nerve ; 27, middle subscapular nerve ; 28,
short subscapular nerve; 29, pectoralis major (cut); 31, basilic vein; 32, serratus magnus; 33,
latissimus dorsi.
ramuscules. The smallest of these is expended in the rudimentary muscles of the thumb, the
small digit, and interosseous muscles ; the largest, three in number, lie on the interosseous
arteries, and bifurcate at the digits to form the palmar collaterals ; the two internal ramuscules
are previously confounded with the corresponding branches of the median. From this arrange-
ment, it results that the ulnar nerve supplies the palmar surface of all the digits, except the
internal border of the index.
The ulnar of the Cat also divides into a dorsal and a palmar branch, but the distribution
of these is not the same as in the Dog.
The dorsal branch bifurcates at the carpus : one of the filaments forms the external dorsal
collateral of the small digit; the other reaches the first interosseous space, receives a branch
THE BRACHIAL PLEXUS.
878,
from the radial, and afterwards gives off the internal dorsal collateral of the small digit, and
external of the auricularis.
The palmar branch does not extend to all the digits as in the Dog. Passing within the
pisiform bone, it divides into several filaments ; some of these are distributed to the muscles of
the small digit and thumb ; another follows the external border of the small digit, and con-
stitutes its external palri)ar collateral ; one of the longest
is lodged in the first intermetacarpal space, giving a fila- _Zi?i *'^2-
ment to the large cushion of the paw, and the internal
palmar collaterals of the small digit and external of the
annularis.
Comparison of the Brachial Plexus in Man with
THAT of Animals.
The brachial plexus of Man, like that of the Dog, is
constituted by the anterior branches of the four last cervi-
cal, and the last dorsal nerves. The few variations ob-
served are very slight, and are to be ascribed to the differ-
ence in form of the regions to which the nerves are dis-
tributed.
The shoulder of Man being short, and the other seg-
ments of the limb long and well detached, the branches
of the brachial plexus can be divided into collateral and
terminal.
Tlie coZiafem? branches are: 1. The subclavian branch,
whicii is not found in our animals, they having no sub-
clavian muscle. 2. The nerve of the levator anguli
tcapulx. 3. Nerve of the rhomhovhus. 4. Supra-scapular
nerve. 5. The serratus mngnus (posterior ihnracic) nerve.
6. Subscapular, which is divided at its origin into two
branches as in the Sheep and Cainivora. 7. The nerves of
the great and small pectorals (anterior thoracic). The
accessory nerve of the internal cutaneous, reprpsented in
quadrupeds by the subcutaneous thoracic. 9. The nerve
of the latissimus dor si. 10. The nerve of the teres major.
The terminal branches go to the arm, forearm, and hand.
They iire :
1. The internal cwtoneoMg, which in tije Horse is fur-
nished by the ulnar nerve. It becomes subcutaneous at
the upper third of the arm, and a little above the elbow
bifurcates ; the anterior is spread on the anterior aspect of
the arm to the wrist ; the posterior passes backwards, and
is expended in the skin of the lack, and inner part of the
forearm.
2. The musculo-cutaneous, or perforans Casserii, the
disposition of whicli is analogous to that of Carnivnra.
3. The axillary nerve, regarding which there is nothing
to say.
4. The radial nerve (musculo- spiral) passes as in
animals, lies in the musculo-spiral groove of tiie humerus,
gives off an internal and external cutaneous branch, and
reaches the antero-external part of the arm. in the space
between the anterior brachial and long supinator, where
NERVES OF THE FRONT OF FORE-
ARM AND HAND OF MAN.
1, Supinator longus (cut) ; 2, ulnar
nerve ; 3. brachialis anticus ; 4,
biceps; 5, musculo-spiral nerve;
6, median nerve ; 7, posterior
interosseous nerve; 8, pronator
teres and flexor carpi radialis
(cut) ; 9, extensor carpi radialis
longior (cut) ; 10. brachial artery; 11, supinator brevis ; 12, flexor sublimis digitorum (cut);
13,13, radial nerve; 14, 14, flexor carpi ulnaris ; 15, extensor carpi radialis brevier; 16, ulnar
artery; 17, radial origin of flexor sublimis digitorum (cut); 18, flexor profundus digitorum; 19,
tendon of pronator teres; 20, 20, dorsal branch of ulnar nerve; 21, 21, radial artery; 22, 22,
deep branch of ulnar nerve; 23, flexor longus pollicis; 24, abductor minimi digiti ; 25, anterior
interosseous nerve; 26, digital branches of ulnar nerve; 27, tendon of supinator longus; 28, one
of the lumbricales muscles; 29, pronator quadratus ; 31, tendon of flexor carpi radialis; 33,
digital branches of median nerve ; 35, adductor pollicis.
874 TEE NERVES.
it terminates by two brauches. The anterior of these reaches the back of the liand, and gives
off three rainuscules there, which are distributed as follows : the first forms the external dorsal
collateriil of the thumb ; the second bifurcates, and constitutes the internal dorsal collateral
of the thumb and external collateral of the index ; lastly, the third supplies the internal
collateral of the index and external of the medius. This brancli always anastomoses with the
dorsal branch of tlie ulnar. Tlie posterior branch — motor — is expended in the muscles on the
posterior and external aspect of the forearm.
5. Thti median nerve commences by two branches. One arises in common with the musculo-
cutaneous or anterior brachial, and corresponds to the anastomosis found around the axillary artery
of the Horse; tiie other is detached from the trunk common to the ulnar and internal cutaneous.
The median runs along the biceps, passes in front of the elbow, and lies beneath the annular
Ijo-ament of the carpus, where it terminates in furnishing: 1. A filament to the short abductor
of the thumb. 2. Palmar ramuscules to the thumb, index, and medius, and external border of
the annularis. This disposition of the medius, therefore, much resembles that of the Cat.
6. The ulnar nerve passes along the inner border of the arm and forearm, and divides, a
little above the inferior extremity of the olecranon, into tNvo terminal branches— a dorsal and
palmar. The first is directed on the back of the hand, and separates into three metacarpal
branches, which, in their course, furnish the dorsal collaterals of the auricularis and annularis,
and internal collateral of the medius ; the otiier parts of the hand are supplied by the radial.
The second, or palmar branch, is superficial, and detaches the palmar collaterals of the little
finger and internal collateral of the annularis, as well as a deep ramuscule that lies across the
interosseous muscles, and is a motor nerve. To resume, we see that this distribution of the
terminal branches of the brachial plexus of Man much resembles that described lu Carnivora,
and especially in the Cat.
Lumbo-sacral Plexus.
The last two lumbar pairs, and the three first sacral, in becoming fused
together, form the lumbo-sacral plexus, which corresponds in every respect — by its
constitution, as well as by its mode of distribution — to the plexus of the thoracic
limb.
It is usual, in human anatomy, to describe a lumbar and a sacral plexus, each
formed by the inferior branches of all the spinal pairs, the names of which they
bear. In our opinion, this course has two inconveniences. At first, it apportions
into two fasciculi the nerves of the abdominal limb, and, besides in including in
the description of these nerves the first lumbar pair and the last sacral, elements
are introduced in this description which are altogether foreign to it. It may be
remarked, that the four first lumbar pairs, when they anastomose with each other,
do so by very slender filaments ; that they only send some subcutaneous filaments
to the posterior limb ; that the two last sacral branches— principally for the genito-
urinary organs and the posterior extremity of the digestive tube— are usually with-
out any direct communication with the others ; that the two last lumbar pairs
and the three first sacral are alone fused in the same manner as the brachial plexus,
and comport themselves like that plexus in the distribution of their branches.
It is with some reason, then, that we have described, in a special manner, the
inferior branches of the four lumbar pairs and the two last sacral, reserving the
fasciculus formed by the five intermediate pairs for a special description, under
the name of the lumbo-sacral plexus.
Mode of constitution.— In glancing at this plexus, we may perceive that it is
divided into two portions— an interior and posterior, each having a thick trmik
in the centre.
The first of these trunks is formed by the two above-named lumbar pairs,
which join each other after a short course, and after receiving an accessory branch
from the fourth pair. The second— wider and thinner than the preceding— com-
prises the fibres of the three sacral pairs which escape from beneath the subsacral
vessels, and unite in a smgle fasciculus. These two trunks are connected with
THE LUMBOSACRAL PLEXUS. 875
each other by one or two branches proceeding from the first sacral pair to the
obturator nerve — one of the distributive branches of the first.
Relations. —The anterior portion of the lumbo-sacral plexus is concealed
beneath the psoas parvus muscle, and separated by the internal iliac artery from
the posterior portion. The latter, placed above and on the side of the pelvis, at
the sacro-sciatic foramen, corresponds, inwardly, to the subsacral vessels ; out-
wardly, and in front, to the gluteal vessels.
Mode of distribution.— The anterior portion of the plexus at first gives off
several small branches to the psoas muscles, and particularly to the iliacus — these
branches were designated by Girard the iliaco-muscular nerves ; it then termi-
nates in two large branches— the crural and obturator nerves. The posterior por-
tion is continued by two important trunks— the great and small femoro-popliteal
n&rves. At the base of the latter, it emits the anterior and posterior gluteal
nerves. These branches and their ramifications will be successively studied.
Preparation of the lumbo-sacral plexus.— After removing the skin and abdominal viscera, the
hind quarters are isolated by sawing through the vertebral column behind the last rib ; then, by-
means of a section almost in the middle of the pelvis, one of the limbs is cut off, and the pieces,
disposed as in Fig. 473, should be maintained iu the first position— that is, with the croup
resting on the dissecting-table near one of the bars, and the limb suspended vertically, the foot
upwards, by a cord attached to the ring of the bar.
Afterwards, the preparation is executed in two stages. In the first, after the excision of
the pelvic organs and the psoas parvus muscle, the whole of the plexus and its formative
branches are dissected, taking Fig. 373 as a guide. In the second, the posterior part of the
plexus, with the nerves it gives off, are exposed on the external side, by excising the greater
portion of the principal gluteal muscle and the anterior portion of the biceps femoris, as in
Fig. 474.
To follow the various divisions of the nerves emanating from the plexus, to their termma-
tioas, it is well to use the other limb, which, not being fixed, can be laid on a table, and in this
way is uiore convenient than the first for this part of the operation.
A. Anteeior Portion.
1. Iliaco-muscular Nerves.
These nerves are of little importance. The principal one accompanies the
iliaco-muscular artery across the iliacus muscle.
2. Crural or Anterior Femoral Nerve (Fig. 473, 2).
This is the largest of the branches arising from the anterior portion of the
plexus. It descends between the psoas magnus and parvus, to the common conical
extremity of the latter muscle and the iliacus, where it is covered by the sartorius ;
there it terminates in a wide tuft of branches, which, pass to the rectus femoris
and vastus internus.
Below the sartorius, it successively emits two long branches, which deserve a
particular description.
The first represents the fasciculus which, in Man, includes the crural musculo-
cutaneous branch. We have named it the accessory branch of the internal saphenic
nerve. It reaches the interstice between the sartorius and gracilis muscles, in
crossing the crural vessels very obhquely forward. Leaving this space, it becomes
subcutaneous, in forming numerous divisions which surround the saphena artery
and vein.
The second, or internal saphenic nerve, passes at first between the sartorius
and vastus internus, and parallel to the first, which is situated more inwardly and
876
THE NERVES.
posteriorly. Near the inferior extremity of the interstice separating the sartorius
and gracilis, it escapes and becomes subcutaneous, dividing into a number of
filaments which meet those of the accessory nerve.
Fig. 473.
LTJMRO-SACRAL PLEXUS AND INTERNAL NERVES OF THE POSTERIOR LIMB.
i, 1, Lumbo-sacral plexus ; 2, anterior femoral nerve ; 3, internal saphena nerve ; 4, obturator
nerve; 5, originating fasciculus of the great and small femoro-popliteal nerves; 6, superficial
ramuscules of the posterior gluteal nerves; 7, great femoro-popliteal nerve; 8, internal pudic
nerve ; 9, haemorrhoidal or anal nerve ; 10, internal plantar nerve ; 11, 12, its digital ramifications.
Note. — In the above figure is seen tlie posterior part of the plexus formed by the nerve- branches which pass
through the three first subsacral foramina. That which escapes from the foramen between the sacrum and last
lumbar vertebra, only gives a fine branch to this part of the plexus, and sends the greater portion of its fibres, in
two cords, to the anterior part. This arrangement is not rare, and is generally seen, we believe, when there are
only five lumbar vertebra : as is remarked in the Ass and Mule, and sometimes in the Horse. It will, therefora,
be understood that ttie nerve deecribed by us as the first sacral pair becomes a lumbar pair.
THE JjUMBO-SACRAL PLEXUS. ST!
These two branches communicate by deep or superficial anastomosing loops.
Before leaving the space between the sartorius and gracilis, they give some
slender filaments to these two muscles, particularly to the latter. Near their
origin, they even distribute some to the iJiacus. Becoming subcutaneous, theii
ramuscules cover the inner face of the thigh and leg ; the longest of these accom-
pany the saphena vein to the anterior aspect of the hock.
It sometimes — indeed, most frequently — happens that the internal saphena
nerve and its accessory form only a single branch, the muscular or cutaneous divi-
sions of which otherwise comport themselves exactly like the above. This is
exemplified in the dissection represented in Fig. 473.
3. Obturatoe Nerve (Fig. 473, 4).
Situated underneath the peritoneum, to the inner side of the iliac vessels — which
it accompanies to the origin of the obturator artery — this nerve follows the latter
to the upper face of the pubes, and passes with it beneath the internal obturator
muscle, to traverse the obturator foramen. In this way it arrives outside the
pelvis, where it nevertheless remains deeply concealed by the muscular masses on
the internal aspect of the thigh. Its terminal ramification are expended in the
obturator externus, adductors of the thigh, pectineus, and gracilis. The branch
to the latter muscle is the longest ; it leaves the space between the pectineus and
graciUs, and descends backwards on the internal face of the muscle to which it is
distributed.
B. Posterior Portion.
4. Small Sciatic or Anterior and Posterior Gluteal Nerves.
The small sciatic nerve of the Horse is composed of several cords that issue
from the pelvis by the upper part of the great sciatic notch, and which have been
for a long time described as the anterior and posterior gluteal nerves.
The anterior gluteal or ilio-musmlar nerves (Fig. 474, 2, 3, 4, 5) are four or
five in number, and arise either separately or in groups from the posterior portion
of the lumbo-sacral plexus. They appear to be more particularly furnished by
the two first sacral branches. All leave the pelvic cavity by the gi-eat sciatic
opening, along with the anterior gluteal vessels. The principal branches are lost
in the middle gluteal muscle. One of them (Fig. 474, 4) crosses the neck of
the ilium above the superficial gluteal muscle, and passes outwards to be dis-
tributed to the tensor vaginae femoris. The last, which is the most slender,
descends to the external surface of the superficial gluteus, and is distributed in
its substance (Fig. 474, 5).
The posterior gluteal, or isrhio-muscular nerves (Fig. 474, 6, 6', 8), are usually
two in number — a superior and inferior.
The first escapes through the great sacro-sciatic notch, along with the femoro-
popHteal nerves, and is situated on the external surface of the sciatic ligament.
It passes backward, between this ligament and the middle gluteus, to beneath
the anterior or croupal portion of the biceps femoris, in which it is distributed
by several filaments. Besides these, it gives : 1. In passing beneath the gluteus
middle, a slender, but constant filament to the posterior portion of that muscle.
2. Another, and more considerable branch, which bends round the posterior
border of that muscle, to be directed forward and outward to the superficial
gluteus
58
g78 THE NEEVES.
The second nerve, situated beneath the preceding, appears to be detached
from the posterior border of the great sciatic nerve. It is placed on the external
surface of the sciatic Ugament, is directed backwards in passing below the croupal
portion of the rectus femoris, and vastus externus and internus, passes through
those muscles above the ischial tuberosity, descending underneath the sacral
portion of the semitendinosus, soon to leave its deep track and become superficial.
It escapes from between the latter muscle and the three just named, and is lost
beneath the skin covering the posterior part of the thigh. Its deep portion gives
POSTERIOR PORTION OF THE LUMBO-SACRAL PLEXUS.
t Conioining fasciculi of the three first sacral nerves ; 2, 3, 4, 5, anterior gluteal nerves ; 6, 6', 8,
posterior gluteal nerves; 7, 9, branches which traverse the great sciatic ligament, and com-
municate between the posterior gluteal branches and the divisions of the internal pudic nerve ;
10 11 12 13, great sciatic nerve and its crural branches; 14, small femoro-popliteal nerve; 15,
its cutaneous or peroneal-cutaneous branch.
off collateral branches which reinforce the divisions of the internal pudic nerve,
as well as filaments to the long branch of the semitendinosus muscle.
5. Geeat Sciatic or Great Femoro-popliteal Nerve (Figs. 201, 13 ;
475, 1, 2).
This enormous nerve (the largest in the body), issues by the great sciatic
opening in the form of a wide band, which is applied to the external face of the
sciatic ^Hgament. Comprised at first between that ligament and the middle
gluteus, it is directed backwards in passing over the fixed insertion of the
gluteus internus, and arrives behind the gemelli and quadratus femoris muscles.
On leaving this point, it is inflected to descend behind the thigh, where it is
lodged in the muscular sheath formed for it by the biceps, the semitendinosus
THE LUMBO-SAURAL PLEXUS. 879
and membranosus, and the great adductor of the thigh. Arriving towards the
superior extremity of the leg, it enters between the two bellies of the gastroc-
nemius muscle, passes along the posterior aspect of the perforatus muscle, and
descends in the channel of the hock, beneath the tibial aponeurosis, following
the internal border of the fibrous band that reinforces the tendon of the hock.
It finally terminates at the calcis by two branches — the external and internal
plantar nerves.
From the point at which the great sciatic enters between the bellies of the
gastrocnemius muscle, and as far as the furrow of the calcis, this nerve corre-
sponds to the branch named in Man the " internal popliteal " — a branch that is
continued by the posterior tibial, which terminates in the plantar filaments.
In its long course, this nerve successively gives off : 1. The external popliteal
nerve, 2. A branch to the muscles of the deep pelvi-crural region. 3. Another
to the posterior crural muscles. 4. The external saphenous nerve. 5. A
voluminous fasciculus to the muscles of the posterior tibial region. All these
branches will be studied, more especially the external popliteal — which is so
disposed in Solipeds, that Veterinary authorities have described it as a special
trunk, by the name of the " small femoro-popliteal," and even as the " small
sciatic nerve." We will afterwards pass to the terminal branch.
Collateral Branches of the Great Sciatic Nerve.
1. EXTEENAL POPLITEAL OR SmALL FeMORO-POPLITEAL NeRVE. — This
nerve separates from the great sciatic at the gemelli muscles of the pelvis. It
is then directed forward and downward, proceeds between the biceps and the
gastrocnemius muscles, and arrives outside the superior extremity of the leg,
behind the lateral ligament of the femoro-tibial articulation, where it terminates
by two branches — the musculo-mtaneous, and the anterior tibial nerve.
In the long course it follows from its origin to its bifurcation, the external
pophteal nerve only furnishes a single collateral branch — this is the cutaneous
nerve which is detached from the parent trunk above the gastrocnemius, and
traverses the inferior extremity of the biceps to terminate by divergent ramuscules
to the skin of the leg. It might be named the peroneal-cutaneous branch. Before
becoming superficial, this cutaneous nerve gives off a small descending filament
which goes to reinforce the external saphenous nerve, after creeping over the
aponeurotic layer of the external portion of the gastrocnemius. This branch —
which might be designated the accessory of the external saphenous — sometimes
proceeds directly from the popliteal, as may be remarked in Fig. 475.
Terminal Branches. — These two branches stimulate the muscles belonging to
the anterior tibial region, and endow the skin on the anterior surface of the foot
with sensation.
The musculo-cutaneous nerve is situated beneath the tibial aponeurosis ; it
first sends a bundle of ramuscules to the lateral extensor of the phalanges, and
continues to descend between that muscle and its congener — the anterior extensor
— to the middle of the tibia. It then traverses the fibrous envelope of the tibial
muscle, becomes subcutaneous, and gains the anterior face of the metatarsus,
where it is lost in the skin. Some of its terminal filaments may be followed to
the fetlock, and even beyond it (Fig. 475, 6).
The anterior tibial nerve passes in front of the preceding, to one side of the
superior extremity of the leg, and then plunges beneath the anterior extensor of
THE NERVES.
the phalanges, giving to that muscle and the flexor of the metatarsus short, but
thick, ramuscules. It descends to the front of the tarsus, always covered by the
anterior extensor of the phalanges, and placed at the external side of the anterior
tibial vessels. When it arrives below the tibia, it lies immediately alongside the
pedal artery, and follows it, in its metatarsal portion, to near the fetlock. It
then separates from its satellite vessel — and
passes on the side of the digit, where it ends
in cutaneous filaments (Fig. 375, 5).
Among the ramuscules this nerve gives
off in its course, are cited those to the pedal
muscle.
2. Branches of the Muscles of the
Deep Pelvi-crural Regiox. —This region
comprises the obturator internus, gemelli,
and quadratus femoris muscles. The nerve
sent to them is long and attenuated ; it is
detached from the sciatic nerve at the middle
of the supra-cotyloid ridge, and descends
with that trunk behind the coxo-femoral
articulation, to distribute its terminal di-
visions to the above-named muscles. The
longest and thickest of these goes to the
quadratus femoris. That passing to the
obturator internus re-enters the pelvic cavity
by the small sacro-sciatic notch, and ascends
to the vicinity of the ilio-sacral articulation.
3. Branch to the Ischio-tibial, or
Posterior Crural Muscles. — This branch
is thick and short. It arises from the bend
formed by the great femoro-popUteal nerve
at the gemelli muscles, and soon divides
into several ramifications which are distri-
buted to the short portion of the biceps, the
middle and inferior parts of the semitendi-
nosus, and into the semimembranosus. Some
of the filaments for the latter muscle pass
between it and the adductor magnus, in
which they partly terminate (Fig. 474, 12).
4. External Saphenic Nerve. — This
branch commences at from 2 to 6 inches
from the point where the great sciatic nerve
dips between the two portions of the gastroc-
nemius muscle. It is placed on the external
portion, and descends beneath the special
aponeurotic layer covering that muscle, to
the origin of the tendon of the hock. It then receives its accessor!/ nerve — the
reinforcing filament which comes from the cutaneous branch of the small femoro-
popliteal nerve, and is prolonged beneath the tibial aponeurosis into the channel of
the hock, accompanying the external saphenic vein, and following the external
border of the fibrous band that goes to strengthen the tendo-Achillis. In this
EXTERNAL NERVES OF THE POSTERIOR
LIMB.
1, 2, Great sciatic nerve ; 3, external saphenic
nerve; 4, external popliteal nerve; 5,
anterior tibial nerve; 6, musculo-cuta-
neous nerve; 7, origin of the peroneal-
cutaneor.s branch ; 8, accessory branch
of the external saphenic nerve; 9, ex-
ternal plantar nerve with its divisions,
which cover the digital artery and vein.
THE LUMBOSACRAL PLEXUS. 881
way, it occupies the same situation outside the hock that the great sciatic does
on the inner side. It afterwards passes over the tarsal region, and is expended
on the outside of the metatarsus in several filaments, some of which descend
to the outer aspect of the digit (Figs. 473, 11, 12 ; 475, 9).
5. Fasciculi to the Posterior Tibial Muscles.— This fasciculus is
composed of numerous branches, which are detached together from the sciatic
nerve on its passage between the two portions of the gastrocnemius muscle, in
the form of a thick short trunk. The muscles of the superficial layer — the
gastrocnemius, perforatus, and the thin fleshy band, improperly designated the
" small plantaris " by Veterinarians — receive ramuscules which are remarkable for
their large number and their shortn 'ss. Those of the deep layer are supplied
by filaments from a single long and thick branch, which descends between the
perforatus and the internal portion of the gastrocnemius. It may be remarked,
that the filament going to the so-called small plantaris muscle passes underneath
the external division of the gastrocnemius, outside the perforatus, and that, by
its position, it exactly represents the soleus ramuscule in Man. We are, therefore
— with Vicq-d' Azyr, Cuvier, and others — justified in naming this little muscle the
soleus, instead of continuing to designate it the small plantaris, which appellation
is given to another muscle.
6. In its course along the tendo-Achillis, the sciatic nerve emits some slender
cutaneous filaments, which we do not consider worthy of further notice.
Terminal Branches.
Plantar Nerves (Fig. 473, 10, 12). — These two nerves enter the tarsal
sheath, behind the perforans tendon, along with the plantar arteries. Towards
the superior extremity of the cannon, they definitively separate from each other ;
the external is carried outwards between the precited tendon and the rudimentary
metatarsal bone ; the internal is placed with that tendon, and follows the
posterior border of the inner metatarsal bone. Both afterwards descend on the
fetlock, where they comport themselves like the analogous nerves of the anterior
limb.
Differential Characters in the Lumbo-sackal Plexus of the other Animals.
As was tlie case with the brachial plexus, so with this; the diflferences observed being
trifling in the upper part of the limb, but more numeious and important in the region of the
foot, the complexity ot arrangement varying with the species.
Ruminants. — The lumbo-sacral plexus of these animals is constituted by two lumbar and
tl\ree sacral nerves, as in Solipeds ; but tlie third sacral only gives a very fine filament, which
reaches the second in passing downward and forward.
At the femoro-tibial articulation, the branches of the plexus are similar to those in the
Horse. Below that articulation, the following disposition has been observed in the Sheep.
Tlie muscido-cutaneous branch of the popliteal is long and thick. It descends on the
anterior face of the metatarsus, and at the metatnrso-phalangeal articulation bifurcates, the
branches forming the dorsal collaterals of the digits. The anterior tibial nerve presents two
branches parallel to the tibial vessels; one passes along the metatarsal region, and when it
arrives at the bottom of the groove between the condyles of the metatarsus, it divides into two
branches that constitute the deep collaterals of the digits ; these collaterals furnish filaments
to the posterior face of the digital region.
The great sciatic resembles that of Solipeds. Its terminal branches — or plantar nerves —
differ from those of the Horse, in the absence of the transverse anastomosis that unites the two
cords in the region of the tendons.
Pig. — The lumbo-sacral plexus of this animal Is composed of two lumbar and three sacral
nerves; reckoning, of course, as a sacral nerve, the trunk that escapes from between the last
882 TEE NERVES.
lumbar vertebra and the sacrum. The plexus may be divided into two povtinns. the first
furnishing a femoral and an obturator nerve. The internal saphenic branch of the femoral nerve
is lone and voluminous; at its origin it is as large as the branch }ia8sinK to the anterior
muscles of the thigh, and it descends on the inner face of the metatarsus, forming the dorsal
collateral of the internal digit.
The great sciatic is voluminous and round. The branches it gives to the muscles of the
pelvis and femur are disposed nearly as in Solipeds and Kuminants ; but differences are
observed in the external popliteal and the terminal branches.
The musculo-cntaneous nerve reaches the metatarsal region, where it separates into three
branches, which form the dorsal collaterals of the digits.
Tlie anterior tibial nerve descends between the two principal metatarsals, and at the root
of the middle digits divides to anastomose with the plantar nerves. Of these the external is
small, and gives collaterals to the two external digits; the internal, the largest, descends
between the two principal digits, where it bifurcates; above, it gives a branch to tiie internal
digit.
Carnivora. — In these animals, the lumbo-sacral plexus is formed by the last four lumbar
and the first two sacral.
The crural and obturator nerves, which arise from the fourth, fifth, and sixth lumbar nerves,
offer nothing particular in their disposition.
The internal saphenic branch is as long as in the Pig; it passes to the internal face of the
tarsus, lies alongside the fourth metatarsal bone, and forms the internal dorsal collateral of
the fourth toe.
The great sciatic may be described as having, as in Man, two terminal branches which
separate a little above the posterior face of the femoro-tibial articulation. The external
popliteal nerve passes to the surface of the external gastrocnemius, enters between the common
long flexor of the toes and the long lateral peroneal muscle, where it bifurc;ites. The musculo-
cutaneous branch descends beneath the latter muscle to the lower third of the leg, when it
becomes superficial, and, accompanied by a vein, is lodged in the interspace between that
muscle and the anterior tibial ; it passes in front of the tarsus, and reaches the upper part of
the metatarsus, where it divides into three divisions. It must be mentioned that at the tibio-
tarsal articulation is thrown off a very fine cord, which is directed outwards, and forms the
external dorsal collateral of the first toe. Each of its three terminal branches courses
along an intermetatarsal space, and at the metatarso-phalangeal articulations separates into
two filaments, whence results the following distribution: the external branch forms the
internal dorsal collaterals of the first toe and external of the second ; the middle constitutes
the internal dorsal collaterals of the second toe and. external of the third; lastly, the internal
furnishes the internal dorsal collaterals of the third toe and external of the fourth. The
anterior tibial nerve accompanies the artery of that name, descends along the external face of
the tibia, and terminates in two branches at the tarsus. Of these, one is distributed to the
tarsal articulations and the pedal muscle: the other, internal, enters the intermetatarsal
space, and at the corresponding metatarso-phalangeal joints anastomoses with the internal
branch of the musculo-cutaneous nerve, and is lost in the same parts. Tiie internal popliteal
forms the second terminal branch of the great sciatic nerve, and in the Dog and Cat repre-
sents that portion of the latter which, in the Horse, is situated behind the femoro-tibial
articulation. It is continued by the posterior tibial nerve, which terminates by the two
plantar nerves. During its course, the external popliteal furnishes articular and muscular
filaments, as well as cutaneous twigs subsequently ; among the latter may be mentioned the
external saphenic, which arises by two brandies, and is expended behind the malleolus, at the
outer side of the tarsus. The plantar nerves are external and internal ; the latter lies at the
inner border of the tendon of the superficial fiexor muscles of the phalanges, and when it
joins the middle of the metatarsus, it detaches a fine filament that forms tlie internal plantar
collateral of the fourth toe ; it then passes obliquely towards the first toe, at the deep face of
the above-named tendon, and successively gives off three filaments— one for each intermetar
tarsal space. These filaments anastomose with the terminal branches of the external plantar,
at the metatarso-phalangeal articulations; the first two filaments supply the large cushion
of the paw.
The external plantar nerve passes between the two flexor tendons of the toes, where it
gives a filament that constitutes the external plantar collateral of the first toe. It is after-
wards placed outside the deep flexor, then enters beneath the short flexor and divides into
several branches— muscular and digital. Each of the latter— three in number— passes into a
corresponding interosseous space and bifiurcates at the metatarso-phalangeal articulations,
receiving filaments from he internal plantar, and forming the following plantar collaterals :
THE LUMBOSACRAL PLEXUS
Fig. 476.
the internal of the first toe, internal and external of the second, internal and external of the
third, and external of the fourth digit.
Comparison of the Lumbo-sacral Plexus in Man with that of Animals.
It is usual, in human anatomy, to describe a lumbar and a sacral plexus.
The lumbar plexus is constituted by the anastomoses of the anterior branches of the five
lumbar nerves ; > these are united by fine filaments, which are not intricately associated. The
divisions of this plexus are distinguished as collateral and terminal branches. The first,
destined to the upper part of the limb and the skin covering the external genital organs, are
represented in Solipeds by the ramifications of the lumbar nerves, which have been separately
described. The terminal branches are
the obturator crural, and anterior
femoral (or anterior crural). There is
nothing to be said respecting the ob-
turator nerve ; it leaves the pelvis by
the obturator foramen, as in all the
animals mentioned. The crural has
been described as having four terminal
branches: the internal and external
musculo-cutaneous, the nerve of the
triceps crureus {muscular branch), and
the internal saphenous. The two
musculo-cutaneous branches have their
analogue in the Horse, in the filament
we have named the accessory branch
of the internal saphenic. The nerve
of the triceps is expended in the an-
terior rectus, and the vastus intern us
and externus. The saphenic de-
scends between the muscles of the
inner aspect of the tliigh, beneath the
aponeurosis, and becomes superficial
at a short distance from the condyle
of the femur, giving a patellar branch
that divides in the skin of the knee,
and a tibial branch that is expended
on the inner face of the tarsal articula-
tions and the foot.
The sacral plexus comprises the
first three sacral nerves, to which is
added a lumbo-sacral branch furnished
by the lumbar nerves, and a fine fila-
ment that ascends from the fourth
eacral.
Ten collaterals and a terminal
branch arise from this plexus.
The collateral branches are divided
into intra-pelvic and extra-pelvic:
they are five in each group. The first
are destined to the muscles of the
inner aspect of the pelvis, and to those
of the perineum and the skin of this
lumbar plexus of man.
1, Right gangliated cord of .sympathetic ; 2, abdominal
aorta ; 3, 3, last dorsal nerves ; 4, psoas parvus ; 5,
quadratus lumborum ; 6, psoas magnus; 7, 7, ilio-
hypogastric nerves; 8. iliacus iuternus; 9, 9, ilio-
inguinal nerve; 10, lumbo-sacral nerve; 11, genito-
crural nerve; 12, gluteal nerve; 13, iliac branch of
ilio-hypogastric nerve; 14, sacral plexus; 15, 1.5, 15,
external cutaneous nerves; 17, transversalis abdomi-
nis; 19, obliquus internus ; 21, obliquus externus;
23, 23, anterior crural nerves ; 25, 25, obturator
nerves ; 27, 27, crural branch of genito-crural nerve ;
2>, genital branch of genito-crural nerve; 31, external
iliac artery ; 33, external abdominal ring.
region. The second are distributed to
the muscles on the outer aspect of the pelvis, and the skin on the posterior face of the thigh.
They are —
1. Visceral branches that descend on the sides of the rectum and are lost in the hypogastric
plexus. 2. Nerve of the elevator of the anus. 3. Exmorrhoidal or anal nerve. 4. Nerve of the
internal obturator that apptars to arise, in the Horse, from the sciatic trunk. 5 Internal
fudic, which has been described with the sacral nerves. In Man this nerve leaves the pelvis
(' Wilson says the four upper lumbar nerves and the last dorsal ; Heath gives the same
constitution.)
884 THE NERVES.
by the great sciatic notch (or foramen), and retuma to it by the lesser ; within the iachiatio
F'g- 477. Fig. 478.
ITERVES AT THE POSTERIOR ASPECT OF
HUMAN LEG.
1, Popliteal artery ; 2, great sciatic nerve ;
3, adductor magnus; 4, biceps; 5, superior
internal articular artery; 6, external pop-
liteal nerve; 7, gastrocnemius (cut); 8,
anterior tibial artery ; 9, tendon of semi-
membranosus ; 10, peroneus longus ; 11,
sural arteries and nerves ; 12, peroneal
artery ; 13, internal popliteal nerve ; 14,
tibialis posticus; 15, portion of soleus;
16, peroneus brevis ; 17, popliteus; 18,
flexor longus pollicis; 19, posterior tibial
nerve ; 20, calcanean branch of posterior
tibial nerve ; 21, posterior tibial artery ;
22,tendn-Achillis ; 23, flexor longus digit-
orum; 25, tendon of tibialis posticus; 27,
plantar nerves; 29, plantar arteries.
NERVES AT THE FRONT ASPECT OF HUMAN
LEG.
1, External popliteal nerve ; 2, anterior
tibial artery; 3, musculo-cutaneous nerve;
4, anterior tibial nerve; 5, peroneus
longus; 6, tibialis anticus; 7, extensor
longus digitorum ; 8, anterior annular
ligament; 9, peroneus brevis; 10, tendon
of extensor proprius pollicis; 11, extensor
proprius pollicis; 12, dorsal artery of foot;
13, point at which the musculo-cutaneous
nerve pierces the fascia and bifurcates; 14,
tendon of tibialis anticus ; 15, internal
branch of musculo-cutaneous nerve; 16,
cutaneous branch of anterior tibial nerve;
17, external branch of musculo-cutaneous
nerve; 19, deep branch of anterior tibial
nerve; 21, external saphenic nerve; 23,
extensor brevis digitorum.
THE GREAT SYMPATHETIC NERVOUS SYSTEM. 885
tuberosity it divides into two branches — an inferior or perineal, and a superior or dorsalis penis
nerve. The latter is placed on the dorsum of the penis, and reaches tlie mucous membrane of
the glans and prepuce; the former does not go beyond the muscles and integuments of the
perineum. 6. The superior gluteal nerve. 7. Nerve of the pyramidalis. 8. Nerve of the
superior gemellus. 9. Nerve of the inferior gemellus and quadratus cruralis. 10. The small
sciatic, or inferior gluteal nerve, the inferior or femoral branch of whicii is very long, descend-
ing, as it does, to the middle of the posterior face of tlie thigh, beneath the crural aponeurosis,
to the popliteal space, where it becomes superficial, and terminates in the skin of the upper
portion of the leg.
The terminal branch of the sacral plexus forms the great sciatic nerve, the distribution of
which is the same as that of Carnivora. The collateral ramuscules of the great sciatif are the
branch of the long portion of the biceps ; the semitendinosus and semimeiubranosus branch ; the
branch to the great adductor; and, lastly, tliat to the short portion of the biceps. It terminates
by the external and internal popliteal.
Tiie musculo-cutaneous and anterior tibial, continuations of the external popliteus, comport
themselves almost the same as in the Dog. They form dorsal collaterals to the third, fourth,
and fifth toes, as well as to tlie second.
The internal popliteal presents an external saphenous nerve that passes along the external
border of the foot, and has, in addition, a branch that ascends on the dorsum of that organ.
The external saphenous furnishes the dorsal collaterals to the first toe, and the external
collateral to the second. Tlie posterior tibial nerve continues the internal sciatic in the leg; it
terminates in the plantar nerves. The internal plantar furnishes the collateral nerves to the
fifth, fourth, and third toes, and the internal collateral of the second toe. The external
divides into three branches : the two superficial branches form the collaterals of the first toe,
and the external collateral of the second ; the deep branch passes inwards, behind the inter-
osseous muscles, and is expended in those of the fourtii space, after giving filaments to the
oblique abductor of the large toe, transverse abductor, last two lumbricales, to the interosseous,
and very fine filaments to the articulations of the tarsus with tlie metatarsus.
It will therefore be seen, that, in Man, the brandies of the deep trunk of the external
plantar join those of the internal plantar, to form the collateral nerves.
CHAPTER III.
THE GREAT SYMPATHETIC NERVOUS SYSTEM.
Preparation of the Great Sympathetic— 7%e same subject ought to suffice for the prepara-
tion of this as well as for the pneumogastric and spinal nerves. After placng the animal in
the first position, the intestines are remuved, one of the posterior limbs cut off, and the greater
portion of the os innominatum cleared away by sawing through the symphysis pubis and the
neck of the ilium ; the dissection of all the abdomino-pelvic portion of the system, and that of
the terminal branches of the pneumogastric nerve, is then proceeded with. The anterior limb
of the same side should be afterwards detached, the scapula having been previously sawn
across its middle part, and tlie thorax thrown open by the ablation of the entire costal wall, in
sawing throu^di the sternal cartilages below, and the ribs above, at their superior extremity.
All the thoracic portion of the ganglionic nervous apparatus, and the pneumogastric nerves,
may then be prepared, Notliing more remains to be accomplished except the dissection of
tlie sympathetic and the vagus nerve in the cervico-cephalic region, with that of the spinal
nerve ; this operation is not attended with any difficulty, and should be preceded by the extir-
pation of a branch of the inferior maxilla. It is useful to inject the arteries previously ; as
then the filaments of the sympathetic that lie alongside the vessels of the different organs in
the abdominal cavity can be more easily followed.
The great sympathetic, also named the trisplanchnir system ((nrXavxvov, an
intestine or viscus), because of its position and destination, is the nervous appa-
ratus of the organs of vegetative life.
THE NERVES.
As has been already shown in the general consideration of the nerves and
the whole nervous system, this apparatus has for its base two long cords extend-
ing from the head to the tail, underneath the vertebral column, and to the right
and left of the mesian line. Towards the last sacral vertebra, a portion of these
two cords converge towards each other, and lie beside the mesial coccygeal
artery. ' Some anatomists think that the great sympathetic does not stop at this
point, but is prolonged beneath the coccygeal vertebrae, where it enters a gan-
glion that has been described of late years as the " coccygeal gland " {Luschka's
gland) ; this, however, is not a nerve-ganglion.
Each cord presents on its course numerous ganglia, to which it owes its
chain-like aspect ; they are usually elliptical in shape, though
they may also be round or semilunar ; some are studded with
prolongations at their borders. Beneath each of the regions
of the spine, these ganglia are equal in number to the
vertebrse, with the exception of the cervical region, in which
there are only two — one at the top, the other at the bottom,
of the neck.
To this chain arrive afferent branches, by the union of
which it is constituted ; these branches are furnished by the
nerves of the medulla oblongata and the inferior spinal
branches, except those of the coccygeal region. The ajfferent
branches join the sympathetic at each ganglion ; but as there
are only two ganglia in the region of the neck, the afferent
filaments of the cervical nerves are grouped in such a manner
as to reach the superior and inferior ganglion.
Those nerves which are given off from the ganglia to be
distributed to the viscera, are named the effei-ent or emergent
branches. They are interlaced around the arteries to reach
their destination, forming plexuses on the surface of these
STMPATHETIC GAN-
GLION FROM A
PUPPY.
a, a, Trunk of the
sympathetic nerve ;
b, communicating
branches from a
spmal nerve; these
diviJe into two fas-
ciculi which pass
upwards and down-
wards in the trunk;
c, c, the ganglion
composed of gan-
glion cells; d, small
branch, probably
destined to accom-
pany an artery ; e,
visceral branch.
This general idea of the disposition of the great sym-
pathetic is sufficient to show that its double ganglionic chain
does not represent two particular nerves arising at one
determinate point, and ending at another. Properly speak-
ing, they have neither origin nor termination : they are
always giving off branches, which are as frequently replaced
by others. In this way they might be compared to the median
spinal artery, which offers somewhat the same mode of con-
stitution— with its afferents supplied by the spinal branches
from the intervertebral foramina, and its efferents destined to the substance of
the spinal cord.
Structure. — The ganglia of the great sympathetic differ but little in their
structure from the spinal gangha, which have been already described. They
have an envelope of connective tissue, which sends very fine septa into their
interior. In the spaces are cells a little smaller and paler than those of the
spinal ganglia ; they are round, or furnished with poles that bring them into
communication with the afferent and efferent nerve-tubes ; there are also, in the
ganglia, tubes which only pass through it, and merely lie beside the cells.
The afferent branches of the ganglia have not the white tint of the cerebro-
spinal nerves ; they are named the greij nerves. They owe their colour to the
THE GREAT SYMPATHETIC NERVOUS SYSTEM. 887
fibres of Remak, which they contain in large quantity. With these nucleated
fibres are associated fine double-contoured fibres — myelin fibres — which proceed
from the communicating rami, or afferent filaments supplied by the spinal nerves ;
these fibres often leave the ganglia to pass directly to organs.
In describing the sympathetic chain, it is divided into five sections : a cranial^
cervical, dorsal, lumbar, and sacral.
1. Cranial Portion of the Sympathetic.
This is composed of the spheno-palatine, ophthalmic, and otic ganglia, all of
which communicate with the superior cervical ganglion. Their description has
been given with that of the fifth cranial pair of nerves.
2. Cervical Portion of the Sympathetic.
The cervical section of the ganglionic chain is formed by two large ganglia
placed one at the top, the other at the bottom, of the neck, and united to each
there by an intermediate cord.
A. Superior Cervical or Guttural Ganglion (Fig. 480, 1). — This
ganglion is a very elongated fusiform body, lying beside the internal carotid
artery, comprised with it in a particular fold of the membrane forming the
guttural pouch, and therefore situated in front of the transverse process of
the atlas, in proximity to the glosso-pharyngeal, pneumogastric, spinal, and
hypoglossal nerves, as well as the inferior branch of the first cervical pair. All
these nerves communicate with the ganglion by slender filaments, and in this
way form around it a veritable plexus, which has been designated the guttural
plexus by Veterinary Anatomists.
Afferent Branches. — These are communicating filaments belonging to the
nerves already enumerated. They do not possess sufficient importance to merit
particular mention. We may notice the existence of the filaments supplied by
the inferior branches of the first four cervical nerves.
Efferent Branches. — These are : 1. Branches accompanying the internal
carotid arteiy into the cranium. 2. A thick fasciculus which reaches the origin
of the three terminal divisions of the common carotid. 3. Small filaments to
the membrane of the guttural pouch and the wall of the pharynx.
The following are the principal anatomical characters of these three orders
of branches : —
a. The satellite branches of the internal carotid artery arise at the superior
extremity of the ganglion. They may vary in number. Two are generally
found, of unequal volume — a posterior, and an anterior, which is the smallest.
They interlace around the internal carotid in anastomosing with each other, and
with that vessel enter the cavernous sinus, where they form, by their divisions,
a little plexiform apparatus named the cavernous plexus, the various branches of
which connect it with several of the cranial nerves. Among these branches are
remarked : 1. Some filaments joined to analogous filaments from the opposite
side, on the transverse anastomosis which unites the two internal carotids in the
cavernous sinus. 2. A branch lying beside the great petrosal nerve, and
concuiTing in the formation of the Vidian nerve, which enters the spheno-palatine
ganglion. 3. A ramuscule going to the ophthalmic ganglion, in company with
fibres from the ophthalmic branch of the fifth pair. 4. Several filaments passing
to the Gasserian ganglion. 5. Branches which mix with the fibres of the three
motor nerves of the eye.
TEE NEBVES.
THE GREAT SYMPATHETIC NERVOUS SYSTEM. 889
b. The inferior carotid fasciculus, sent to the terminal extremity of the
sommon carotid, escapes from the inferior part of the guttural ganglion.
Frequently at its origin it is only a thick cord, but ordinarily it is composed,
from its commencement, of several branches bound to one another by com-
municating filaments. Reaching their destination, these branches meet ramuscules
emanating from the glosso-pharyngeal and pneumogastric nerves, and anastomose
with them to form, around the origin of the three terminal branches of the
common carotid, the so-called carotid plexus, the ramifications of which almost
exclusively follow the external carotid, the greater part being distributed to the
glands and salivary lobules. In Man, the division which follows the spheno-
spinal artery passes to the otic ganglion ; the same takes place, no doubt, in
animals.
c. The guttural or pharyngeal filaments, arising from the anterior border of
the ganglion and the inferior carotidean fasciculus, are generally very delicate.
Those which reach the superior wall of the pharynx concur, with the glosso-
pharyngeal and the pneumogastric, to form the phan/ngeal plexus.
B. Intermediate Cord of the Two Cervical Ganglia. — This cord
leaves the inferior extremity of the superior cervical ganglion, lies close beside
the pnemnogastric nerve, which always exceeds it in volume, and descends to the
entrance of the thorax, where it separates from the vagus nerve, and joins the
inferior cervical ganglion. It neither receives nor gives off any branch in its
course.
G. Inferior Cervical Ganglion (Fig. 480, 2). — Generally thicker than
the superior, this ganglion is placed within the costal insertion of the inferior
scalenus. The right, always a little more anterior than the other, is applied
immediately against the side of the trachea. That of the left side is separated
from it by the oesophagus. Both are related, externally, to the vertebral artery.
The inferior cervical ganglion is very liable to vary, and become irregular in
form. It is sometimes lenticular, at others more or less elongated, always
stellate, and not unfrequently double. In the latter case — which is perhaps more
frequent in the left than the right — its two portions are distinguished into anterior
and posterior. The last forms the inferior cervical ganglion, properly called (Fig.
480, 2) ; the former is much smaller, and is bound to the other by a wide and
short greyish band, constituting what has been designated in Man the middle
cervical ganglion (Fig. 480, 3).
In front, the ganglion which we are describing receives the cord intermediate
to 2, Cervical portion of the sympathetic chain; 1, superior cervical ganglion, in the middle of the
guttural plexus ; 2, inferior cervical ganglion ; 3, middle cervical ganglion ; 4, intermediate
cervical cord, intimately united at its middle portion with the pneumogastric nerve; 5, cardiac
nerves; 6, dorsal portion of the sympathetic chain; 7, great splanchnic nerve; 8, lesser splanchnic
nerve; 9, semilunar ganglion, centre of the solar plexus; 10, portion of the hepatic artery
encircled by its splexus ; 11, the splenic artery, ditto ; 12, the gastric artery, ditto ; 13. the
anterior mesenteric artery, ditto; 14, kidney, elevated, receiving the renal plexus ; 15, the supra-
renal capsule with its plexus; 16, lumbn-aortic plexus; 17, lumbar portion of the sympathetic
chain; 18, posterior mesenteric plexus; 19, branches from it passing to the anterior mesenteric
plexus : 20, spermatic plexus ; 21, branches going to the pelvic plexus ; 22, sacral portion of the
sympathetic chain ; 23, pelvic plexus; 24, afferent brauches furnished to the sympathetic by the
spinal pairs; 24', the cord which receives six of the cervical ra.m\xs,cxx\e%\ 2h, pneumogastric
nerve; 26, superior laryngeal (the pharyngeal branch is seen to be detached from the pneumo-
gastric a little below); 27, inferior laryngeal nerve of the right side; 28, that of the left side at
the point where it bends round the arch of the aorta; 29, nerves of the bronchial plexus ; 30,
superior oesophageal branch; 31, inferior ditto; 32, spinal nerve; 33, hypoglossal nerve; 34,
glosso-pharyngeal nerve (represented too thick).
890 THE NERVES.
to the two ganglionic enlargements in the region of the neck, either directly, or
through the medium of the middle cervical ganglion, when that is present. It is
continued backwards with the dorsal portion of the sympathetic chain.
Afferent Branches. — These are two, proceeding from the cervical pairs.
One is a thick nerve, satellite to the cervical vertebral arteiy (sometimes
named the vertebral plexus), and lodged with it in the foramina of the cervical
vertebrae ; it is formed by filaments emanating from the second, third, fourth,
fifth, sixth, and seventh pairs of cervical nerves, and thus carries in a mass, to
the sympathetic, the contingent of afferent nerve-fibres of the majority of these
nerves (Fig. 480, 24').
The other branch is an isolated one, proceeding from the eighth cervical pair.
Besides these afiferents, there ought to be noticed the filaments sent by the
pneumogastric nerve, and which join the middle cervical ganglion, when it is
present (see the description of the pneumogastric nerve).
Efferent Branches. — These are detached from the posterior and inferior
parts of the ganghon, and for the most part proceed to the heart. Some extremely
fine filaments go to the anterior mediastinum, or pass on to the collateral arteries
of the brachial trunk.
The cardiac nerves (Fig. 480, 5) cross the base of the pericardium, alongside
the common aorta, and are then distributed to the tissue of the auricles and
ventricles. Some follow the divisions of the pulmonary artery, and concur in the
formation of the bronchial plexus.
To arrive at the heart, these nerves accompany the axillary arteries and the
trachea, giving origin, on the inferior face of the latter, to a very large fasciculus,
named, in Veterinary anatomy, the tracheal plexus ; this is single, and is travereed
from behind to before by the two recurrent nerves, which give or receive from it
numerous filaments.
The cardiac nerves come from the right and left sides. In the Horse they
usually have the following disposition : —
a. On the left side are four nerves, two of which — very fine — proceed from
the middle cervical ganglion and disappear on the vessels whicli arise from the
convexity of the brachial arteiy. Of the other two, one is superficial, the second
deep. The former — the most voluminous — begins as a filament from the middle
cervical ganglion, and passes backwards and downwards, forming an arching
anastomosis below the brachial artery with a branch detached from the inferior
cervical ganghon, then lies beside the following. The deep nerve is at first
formed of three elements : 1. Medullary fibres furnished by the spinal pairs.
2. A ramuscule from the cervical cord of the sympathetic. 3. A slender filament
which leaves the left pneumogastric, near the entrance to the thorax. It places
itself in the direction of the heart, adheres to the superficial nerve, is inflected on
the concavity of the brachial artery, margins that vessel on the left, and insinuates
itself between the aorta and the pulmonary artery. At this point, these nerves
are distributed to the heart and large vessels, a branch passing beneath the
right auricle and entering the cardiac muscle ; a second branch ramifies on the
commencement of the pulmonary artery and on the right ventricle ; two other
grey, plexif orm branches anastomose more or less between the aorta and pulmonary
arteiy, and unite beneath the arch of the aorta, with a nerve from the right side,
then descend in the vertical groove on the heart, to be expended in the left
ventricle ; lastly, other ramuscules, parallel to the pneumogastric, go to the
pulmonary artery and aorta.
THE GEE AT SYMPATHETIC NERVOUS SYSTEM. 891
5. On the right side are two principal cardiao nerves, and four secondary
filaments. The first cardiac nerve is a long branch that arises at fhe middle
cervical ganglion. It is formed by fibres from the sympathetic, and by a
fasciculus furnished by the right pneumogastric, at the entrance to the thorax ;
it also probably receives medullary fibres through the medium of a communicating
branch between the middle and inferior ganglion. This nerve is reinforced by
two filaments that proceed from the inferior cervical ganglion, and sometimes
from the second middle ganglion, one of which — the posterior — is itself reinforced
by a left sympathetic filament that reaches its destination in passing along the
recurrent nerve. When it is entirely constituted, the first nerve creeps on the
base of the heart, turns round the arch of the aorta, and mixes its terminal fibres
with those of the left cardiac nerves. The second right cardiac nerve is formed
by the union of tkree branches that arise successively from the corresponding
pneumogastric, behind the dorsal artery, along the right side of the trachea.
This nerve attaches itself to the sympathetic in the dorsal region, by three
branches that approach the latter below the first, fourth, and sixth ribs.
When the second right nerve arrives above the termination of the anterior
vena cava, it divides into two branches ; one of tnese goes to the roof of the
auricles, and the other — joined by a filament from the pneumogastric — is
expended by numerous ramuscules, on the surface of the left ventricle ; some
even extend to the right ventricle.
The four secondary filaments are echeloned on the portion of the pneumo-
gastric included between the entrance to the thora'x and the division of the
bronchi, These filaments go to the large vessels, and into the walls of the heart.^
3. Dorsal Portion of the Sympathetic.
The cord represented by this portion of the sympathetic chain leaves the
inferior cervical ganglion, and extends from before to behind, towards the
diaphragm, passing beneath the superior extremities of the ribs — or rather, below
the vertebro-costal articulations, against which it is maintained by the pleura —
and crossing the intercostal arteries. It is continued in the abdominal cavity by
the lumbar portion, after passing through the arch in the superior border of the
diaphragm, along with the psoas parvus.
Along its course, this cord exhibits, at each intercostal space, a small fusiform
ganglionic enlargement — seventeen in all. The two or three first are most
frequently absent ; but then the anterior extremity of the nerve has for some
extent the appearance of a ribbon-shaped ganglion, which seems to be due to the
elongation, posteriorly, of the inferior grey mass of the cervical portion.
Afferent Branches. — Furnished by the inferior branches of the dorsal
nerves, these ramuscules number from one to three for each ganglion. In
proceeding from the intervertebral foramina to the sympathetic, they traverse the
superior extremity of the intercostal space, passing sometimes behind, sometimes
before, the arteries of that name.
Efferent Branches. — A very few delicate branches pass to the pleurae ;
those which demand notice are the great and lesser splanchnic nerves.
• To sum up — the cardiac nerves contain fibres from the pneumogastrics. The rifjht
pneumogastric furnishes a greater number to them tkan the left. Perhaps to this circumstance
is due the predominance of the right vagus in the phenomena attending arrest of the heart's
action (Arloing and Tripier, " Contribution a la Physiologie des Nerfs Vagues," in Archiv. de
Phyeiologie Nor. et Path. 1872).
892 THE NERVES.
a. Great splanchnk nervps (Fig. 480, 7). — This commences to be detached
from the doreal chain towards the sixth or seventh ganglion, is directed backwards
bj the external side of that chain, receives an accessory branch from each of the
enlargements it passes by, except the last two or three, and enters the abdominal
cavity through the arch of the psoas parvus, where it usually looks like a small
ganglionic mass ; after which, it is inflected inwards, and terminates on the
side of the aorta, between the coeliac and mesenteric trunks, by a second and
enormously developed mass — the solar ganglion.
The two solar., or semilunar ganglia, as they have also been designated, and
which are the largest in the body, are elongated from before to behind, and
flattened above and below. They communicate with one another by means of
a wide and thick greyish cord, which encircles, posteriorly, the trunk of the great
mesenteric artery, and by a multitude of filaments which pass from the left to
the right, in front of that vessel. From this arrangement results a single plexus,
situated at the inferior face of the aorta, between the origin of the two precited
arterial trunks.
This plexus, named the solar plexas, receives some branches from the superior
oesophageal cord of the pneumogastric nerve. It subdivides on its periphery
into several secondaiy plexuses, which leave, as from a centre, the principal
network : the ramifications of this— very large and numerous — proceed to the
neighbouring organs in accompanying the arterial divisions, around which we see
them interlacing and anastomosing in a very complicated manner. It is for this
reason that there have been described separately: 1. A gastric plexus, going to
the stomach, on the parietes of which its branches anastomose with those of the
pneimiogastrics. 2. A hepatic plexus, for the liver, duodenum, pylorus, and
pancreas. 3. A splenic plexus, one part of which passes to the spleen, the other
to the stomach. 4. An anterior mesenteric plexus — the most considerable of all —
is distributed to the same organs as the artery of that name. 5. A renal and a
supra-renal plexus — double, and scarcely distinct from each other — send their
terminal divisions to the kidneys and supra-renal capsules. The terminations of
the filaments of these plexuses have been already described in the Splanchnology.
It is necessary to add to this rich nervous apparatus, the lumbo-aorfic plextis,
formed by the large and numerous branches which spring from the solar plexus
behind the great mesenteric artery, creep along the sides and the inferior face of
the aorta, frequently anastomose with each other, and reunite at the posterior
mesenteric plexus.
h. Lesser splanchnic nerve (Fig. 480, 8). — This branch is composed of two
or three filaments that emanate from the last subdorsal ganglia, and which,
instead of joining the great splanchnic nerve like the others, with which they
communicate by one or two fine divisions, collect in a short thin cord, the rami-
fications of which pass directly into the solar plexus, or are confounded with the
nerves of the kidney and the supra-renal capsule.
4. Lumbar Portion of the Sympathetic.
This is a cord similar to that of the dorsal portion, and provided with fusi-
form ganglionic enlargements equal in number to the pairs of lumbar nerves.
This cord is applied against the psoas parvus, near the common inferior vertebral
ligament, and is covered on the left by the aorta, on the right by the posterior
vena cava. It is directly continued by the sacral portion of the sympathetic
chain, at the lumbo-sacral articulation.
THE GREAT SYMPATHETIC NERVOUS SYSTEM. 893
Afferent Branches. — Furnished by the inferior branches of the lumbar
nerves, tliese raujuscules comport themselves exactly like those of the dorsal region.
Efferent Branches. — These are short filaments, analogous to those which,
by their union, constitute the splanchnic nerves. Their number is not constant,
and is generally less than that of the ganglia. Two or three join the lumbo-
aortic plexus ; the others reach the origin of the small mesenteric artery, anas-
tomose around it with the posterior extremities of the branches of that plexus,
and thus form another single network, designated the posterior mesenteric plexus
(Fig. 480, 18).
This plexus, in the centre of which is a more or less voluminous ganglion,
sends to the various branches of the small mesenteric artery ramifications for the
walls of the small colon and the rectum.
It supplies besides : 1. Two or three large branches which follow the posterior
mesenteric vein, and join the anterior mesenteric plexus, after throwing some
divisions into the colic mesentery (Fig. 480, 19).
2. Satellite branches to the two spermatic arteries, constituting the plexus of
that name (Fig. 480, 20).
.3. Two or three long divisions (Fig. 480, 21) which enter on each side of
the pelvis, by passing beneath the external face of the peritoneum, and reach
the lateral plane of the rectum, where they meet the filaments emanating
directly from the inferior sacral nerves. From the anastomosis of these divisions
results a rich nervous network, called in Man the hypogastric plexus, and which
we have designated the pelvic plexus ; this network supplies all the organs con-
tained in the pelvic cavity (Fig. 480, 23).
5. Sacral Portion of the Sympathetic.
A continuation of the lumbar cord, this portion of the sympathetic chain is
situated beneath the sacrum, to the inner side of the inferior sacral nerves. It
offers four very elongated ganglia, which communicate with these nerves by one
or more filaments, and which give rise to several very fine ramuscules that are
lost in the connective tissue on the inferior face of the sacrum.
Its posterior extremity, which terminates behind the great sympathetic, does
not always comport itself in the same manner. We sometimes see it become
attenuated to a very delicate ramuscule, which passes on to the mesian coccygeal
artery, and anastomoses with that of the opposite side. But sometimes, also,
this ramuscule cannot be distinguished, and the sub-sacral cord seems to be
abruptly terminated by the filament of communication from the last sacral pair.
Functions. — The functions of the sympathetic are as yet incompletely
known, notwithstanding the labours of many physiologists, at whose head must
be placed Claude Bernard. In a physiological condition, this nerve possesses
an extremely obscure sensibility, but which may, nevertheless, become very acute
in pathological states. It conveys to organs the unconscious, motor excitations
originating in the spinal cord or its ganglia ; and through the filaments it
furnishes to the vessels — the vaso-motor nerves — it holds under its control the
circulatoiy phenomena, especially in the capillary plexuses, causing these canals
to suddenly dilate or contract, and thus diminish or accelerate the flow of blood
in them. By this action on the blood-vessels, it may have a secondaiy influence
on the nutrition of the organs to which these vessels are distributed.^
' Francois Franck has published, in the Travaux du lahoratoire de M. Marey, pour VAnn€e
1875, a long memoir on the " Nerfs Vasculaires de la tete." The author passes in review the
59
894 THE NERVES.
Differential Characters in the Great Sympathetic of the other Animals.
In all the domesticated Mammals, the general disposition of the great sympathetic is very
similar ; so that there are but few and slight differences to note.
In the Ox, the cervical filament of the sympathetic does not arise from the lower extremity
of the superior ganglion, but behind, from its middle portion ; it is divisible into two or three
filaments for a certain distance, after which it lies beside the pneumogastrio. The ramuscule
that leaves the lower end of the cervical ganglion is very large, and reaches the division of the
common carotid ; that which accompanies the iuternal carotid artery is also of considerable
size. (Kuminants have 13 thoracic and 6 lumbar ganglia.)
In tlie Dog, the cervical sym[)athetic cord is closely united with the pneumogastric, and
it is not possible to separate them from each other, as can be done in Solipeds and Kuminants.
(In the Carnivora, there are 13 thoracic and 7 lumbar ganglia.)
In the Rabbit, there are two cords which are independent along the whole length of the
neck.
The Pig has a superior cervical ganglion, which is fusiform and very long ; at its lower
extremity it gives oli" several filaments, one of which lies beside the pneumogastric in the
cervical region, but separates from it to join tlie middle cervical ganglion ; the others pass to
the tenth nerve, and are confounded with it at the ganglionic enlargement it shows behind
the pharynx. At the entrance to the chest, a branch separates from the pneumogastric, passes
along with tlie axillary arteries, and finally enters the lieart. This brancli is perhaps formed
by the filaments of the sympathetic that joined the pneumogastric at the upper part of the
neck. (The inferior cervical ganglion, according to Leyh, is completely isolated from the
thoracic ganglion. The Pig has 14 thoracic and 7 lumbar ganglia.)
In the other domestic animals other than Solipeds, the number of ganglia in the dorsal,
lumbar, and sacral portions depends upon the number of vertebrae in these several regions in
the different species. In them, the first subdorsal ganglion is more voluminous and detached
than in the Horse.
Comparison of the Great Sympathetic in Man with that of Animals.
It is divided and disposed as in animals. The cervical portion is composed of a superioi
fusiform ganglion, from which emerge many branches that have been studied with the greatest
care. Tliere are described: 1. Superior or intercranial branches. 2. External or anastomosing
branches with the first four spinal nerves. 3. Internal or visceral branches, which mix witli
the pharyngeal and laryngeal filaments of the pneumogastric. 4. Anterior or external
carotideal branches, which pass to the common carotid and the middle of a small ganglion,
the intercarotid. 5. Posterior, muscular, or osseous branches. All these are present in the
Horse. A cervical filament and two inferior ganglia— middle and inferior— complete this
region, of which there is nothing more to be said.
The thoracic portion is absolutely identical in its disposition with that of animals ; it gives
rise to a great splanchnic nerve, and terminates in the semilunar ganglia.
There are no diflferences to note in the lumbar and sacral portims, which we have described
as the pelvic.
CHAPTEK IV.
THE NERVOUS SYSTEM IN BIRDS.
Pkotective Parts of the Cerebro-spinal Axis.— The protective parts of
tlie nerve-centres are the same in all vertebrate animals ; consequently, there
works of his predecessors, and makes known the new results he has obtained in associating
anatomy with physiology, summing them up in the following principal conclusions: 1. The
vessels receive their nerves from the free filaments of the sympathetic, and trom filaments of
the same kind contained in the mixed spinal nerves obtained by the latter from tlie spinal cord
and the ganglia. 2. The superficial and deep vessels of the face are nmervated by the free
sympathetic filaments from the superior cervical ganglion and the pre-vertebral cord, and by the
branches of the facial and the trigeminus. 3. The vessels of the ear receive their nerves from
the free sympathetic, the facial, and the trigeminus, as well as the cervical plexus. 4. The
encephalic vessels are innervated by the carotid and vertebral plexuses.
THE NERVOUS SYSTEM IN BIBD8. 895
is nothing to remark regarding those of Birds, beyond what has been said at
p. 158. The envelopes or meninges are three in number, and disposed as in
Mammals.
''Thefalx cerebri is found in Birds ; in the Turkey it has the form of the
segment of a circle, and extends from the middle of the interval of the openings
for the olfactory nerves to the tentorium cerebelli. The falx cerehelli is absent ;
the tentorium is small and sustained by a bony plate, and there are, in addition,
two particular folds, one on each side, that separate the hemispheres from the
tubercula quadrigemina " (Cuvier). Owing to the absence of the falx cerebelli,
Fig. 481.
A B
BRAIN OF A BIRD. A, INFERIOR FACE ; B, SUPERIOR FACE.
HH, Medulla oblongata ; Med, spinal cord ; HE, cerebellum ; MH, optic lobe ; VH, cerebral
hemisphere ; L.ol, olfactory lobe ; Hyp, hyopophysis. Tr. opt, optic tract ; /, olfactory nerves.
The cranial nerves are indicated by the corresponding numerals.
the meninges of Birds are closer together than those of Solipeds or Man.
According to Leydig, the falx cerebri is partially ossified in birds.
Spinal Cord. — In Birds, the spinal cord is perforated by a central canal,
and also offers, as in Mammals, two enlargements — a cervico-dorsal and lumbar.
It is prolonged into the coccygeal vertebrae, and thus furnishes another proof
against the assertion of certain naturalists, who desire to establish a relation
between the length of the spinal cord posteriorly, and the development of the
coccygeal region. The two fasciculi of the medullary axis are separated from
one another at the lumbar enlargement, and afterwards join in the sacral region.
Between them is an elliptical space — the rhomboidal sinus — which is filled by
transparent gelatinous connective substance — a kind of efflorescence of the
ependymis of the central canal.
Encephalox. — In a medium -sized Fowl, the brain weighs about 2^ drams,
and comprises the three portions present in MammaHa.
896 THE NERVES.
The encephalic isthmus is not divided into two sections by the pons Varolii,
which is absent in birds ; the crura cerebelli are immediately connected with
the corpora restiformia. The lower face of the isthmus is very convex posteriorly ;
in front, the tubercula bigemina are united to each other by a comparatively
large transverse cord, formed by the optic nerves intercrossing in the median
line. The superior face is depressed above the cerebellum, so as to constitute a
fourth ventricle, the floor of which is also shaped like the point of a pen ; in
front of this ventricle are the tubercula bigemina {optic lobes) — two voluminous
tubercules separated from each other above, where they embrace the cerebellum,
and salient on the sides of the lower face. They are hollow internally, and
communicate with the aqueduct of Sylvius. The thalami optici are little developed.
The cerebellum is almost reduced to the median lobe, the lateral lobes — situated
behind and below it — being very small and conical. By its anterior extremity,
this cerebral ganglion passes between the corpora bigemini, and touches the
cerebral hemispheres. The cerebellum is annulated transversely to its surface,
and between the principal fuiTows are secoj^dary ones, as in Mammals. The
white substance forms, in its interior, an arborization in relation, by the number
of its branches, with the simplicity observed on the surface of the organ. In
the centre of the cerebellum of birds is a small cavity communicating with the
fourth ventricle.
The cerebrum, divided into two hemispheres by a shallow fissure, has the
shape of the heart on a playing-card, more particularly when viewed on its lower
face. The convolutions are absent on the upper and lateral faces of the organ,
and on the inferior is a vestige of the fissure of Sylvius, which is directed obliquely
forward and outward. The olfactory lobes are little developed, and are placed
together in the mesian line.
The two ventricles are confounded, there being no corpus callosum nor
septum lucidum. There is no reflected portion in the ventricle ; consequently
the hippocampi and mastoid lobules are absent ; the corpora striata are, on the
contrary, large, and occupy nearly the whole floor of the ventricles.
Cranial Nerves. — These are twelve pairs, as in Mammals ; and their origin
is analogous, if not identical ; the only trifling differences observed are due to
the absence of the pons VaroUi, and the convexity of the lower face of the
isthmus.
Olfactory nerve.— We have mentioned above how this is formed at the anterior
portion of the cerebral hemispheres.
Optic nerve.— It appears to be detached from the tubercula bigemini, and,
after a very short course, to intercross with that of the opposite side. In certain
Birds, and especially in the diurnal rapacious kind, the optic nerves are con-
stituted by fasciculi of undulating nerve-tubes.
Common motores oculonm. Pathetici. External motores oculor urn. -There is
nothing particular to remark respecting these.
Trifieminal nerve.— Th\^ nerve divides into three principal branches, as in
the domesticated animals. The op)hthahnic branch has a nasal ramuscule that
becomes superficial, and extends to the extremity of the beak, as well as a third
filament that is lost around the inferior orifice of the nasal cavities.
The superior maxillary issues from the cranium by the opening through which
the lower maxillary nerve passes, creeps below the orbit, traverses the maxillary
bone, and terminates on the sides of the beak by filaments that resemble the
infra-orbital ramuscules of the Horse.
THE NERVOUS SYSTEM IN BIRDS. 897
The inferior maxillary furnishes two bi*anches : one passes through the dental
canal, and arrives at the extremity of the Lower mandible ; the other is spread in
the subcorneus integuments of the same.
Facial nerve. — This is small in Birds. " It is distributed to the muscles
of the jaws and the small muscles which erect the feathers of the crest"
(Cuvier).
Glosso-pharyngeal nerve. — This calls for no remark.
Pneumogastric nerve. — There are few differences observed in this ; it is as
extensive as in Mammals, and its anastomoses and relations are nearly the same.
It is not entirely formed at its exit from the cranium, and always offers two or
three constituent filaments that join it, and are confounded at some distance
from the point of emergence. The recurrents furnish ramuscules to the crop.
Spinal accessory nerve. — This likewise has a medullary root that appears at
the third cervical vertebra ; it runs along with the vagus nerve to become
superficial.
Hypoglossal nerve. — The same origin as in Quadrupeds. Where it crosses the
pneumogastric, it detaches a long filament that passes along with the jugular
vein towards the chest. On the sides of the larynx it bifurcates ; one branch
proceeds forward beneath the tongue, the other follows in the same direction, but
on the upper surface of that organ.
Spinal Nekves. — We need only notice the nerves of the wing and pelvic
limb, the others being disposed in a similar manner to those above described.
Brachial plexus. — Three principal branches — the last cervical and first two
dorsal — form this plexus in Palmipeds ; in the Gallinaceae there are four —
the last three cervical and first dorsal. These branches anastomose beneath the
deep face of the scapulo-humeral articulation. When fully constituted, the
plexus gives off some collateral ramuscules, and terminates by two fasciculi of
branches. The first collateral goes to the deep pectoral muscle ; another is dis-
tributed to the muscles surrounding the head of the humerus, as well as to the
articular capsule. The fascicuh of terminal branches may be distinguished,
after their situation, as anterior and posterior. The latter represents the internal
brachial, cutaneous, and radial nerves ; it gives off muscular and cutaneous ramus-
cules that extend to the digits at the extremity of the wing. The anterior
fasciculus is larger, and is also extended to the whole of the limb, being expended
in motor and sensitive filaments ; near its origin it furnishes ramuscules to the
superficial pectoral muscle. This fasciculus represents the median, ulnar, and
anterior brachial, or musculo-cutaneous of Mammals.
Lumbo-sacrcd plexus. — Two lumbar and four sacral nerves constitute this
plexus. In the Fowl it is distinctly divisible into two portions, an anterior and
posterior, considerably wide apart.
The anterior portion is composed of the lumbar branches and a portion of the
first sacral ; their fusion takes place on the salient bony ridge that separates the
lumbar from the sacral regions. It gives origin to four or five branches, among
which are clearly discernible : 1. A. filament to the tensor fascia lata muscle. 2.
A crural or femoral nerve. 3. An internal saphenic nerve that descends to the
leg. 4. An obturator nerve. The latter is very slender, and directed down-
wards and backwards, passing into the muscle that closes the obturator
foramen.
The posterior portion comprises a portion of the first sacral, and the whole of
the three succeeding nerves. These are directed outwards, towards the sciatic
898 THE NERVOUS SYSTEM IN BIRDS.
notch, where they unite ; during their course in the interior of the pelvis, they
are surrounded by the tissue of the kidney. The distribution of this portion of
the plexus resembles that of the Horse. Thus, in leaving the great sciatic notch,
it gives off the anterior and posterior gluteal nerves, then two long branches that
lie together as far as the gemelli. These branches are : 1. The great sciatic, with
a ramuscule for the gemelli and the posterior tibial muscles. 2. The external
popliteal, which, outside the superior extremity of the leg, divides into the musculo'
cutaneous and anterior tibial nerve.
BOOK VII.
THE SENSORY APPARATUSES.
Among the nerves described in the preceding book, those which have been
designated sensory nerves have for their principal, or even exclusive function, the
transmission to the brain of the impressions derived from the surrounding
physical world. These nerves are, therefore, the essential instruments of sensa-
tion, and the organs to which they are distributed constitute the sensory
apparatuses. These are admirably disposed for the reception of the cerebral
•stimuli, and are five in number— the apparatuses of touch, taste, smell, vision, and
hearing. The principal characteristics of these will be briefly enumerated.
CHAPTER I.
APPARATUS OP TOUCH.
The sense of touch is destined for the appreciation of tactile sensations, and,
incidentally, those resulting from variations of temperature. The apparatus
which ministers to it, is formed by the peripheral radicles of the nerves of general
sensibility distributed in the skin — the resisting membrane closely investing the
entire body, and continuous, at the margin of the natural openings, with the
mucous or internal membrane.
The entire skin, therefore, represents the organ of touch ; but, as in Man,
this membrane has certain privileged regions which are more active than others
in the exercise of this faculty — these are the limbs and the lips.
The structure of the skin, though pertaining to general anatomy, will be
•studied here somewhat in detail, and then the arrangement of its appendages—
the hair and horny productions — will be examined.
Article I. — The Skin.
Preparation. — See treatises on histology.
The skin, properly speaking, is composed of two layers : the derma and
epidermis.
The Derma. — The derma or coriiim (corium cutis, cutis vera), forms nearly
the entire thickness of the membrane. Its inner face (stratum subcutaneum)
adheres more or less closely to the subjacent parts, through the medium of a
cellulo-adipose expansion {panniculus adiposus). Its external face, covered by
the epidermis, is perforated by openings through which the hairs pass, or through
which the secretion of the sudoriparous and sebaceous glands is thrown out upon
900
THE SENSORY APPARATUSES.
the surface of the skin ; this external face also shows a multitude of little eleva-
tions termed papilJce, in which the majority of the nerves terminate.
The derma is not of the same thickness everywhere, being much thinner
where it is protected from external injury — as on the under-surface of the belly,
the inner side of the legs, thighs, etc. ; it is also thin around the margin of the
SECTION OF horse's SKIN (FROM WING OP THE NOSTRIL).
E, Epidermis ; D, derma. 1, Horny layer of the epidermis ; 2, stratum mucosum ; 3, papillary layei
of the derma ; 4, excretory duct of a sudoriparous gland ; 5, glomerule of a sudoriparous gland ;
6, hair-follicle ; 7, sebaceous gland ; 8, internal sheath of the hair-follicle ; 9, bulb of the hair ;
10, mass ot adipose tissue.
natural openings, to permit the transition between the two membranes, and
to endow these apertm-es with theu- necessary dilatability.
Structure. — The derma is composed of fasciculi of connective tissue inter-
woven and matted in a solid manner, and in the meshes of which are some
smooth muscular fibres, which, by their contraction, produce the condition of
the skin known as the cutis anserina (goose-skin). Somewhat loosely woven in
its deepest part to form the reticular layer {stratum
Fig- -193. reticulare), the derma contains the roots of the hair-
follicles, the sudoriparous (or sweat) glands, and
small masses of adipose tissue ; superior, its
structure is very condensed, to constitute the papil-
lary layer {stratum papilJare), the superficial Umit
of which forms an amorphous layer {basal membrane).
The papilke are of two kinds — vascular and
nervous, and are regularly arranged in parallel series.
They are most numerous in those parts of the skin
especially destined for the exercise of touch— as at
the lips, in the keratogenous membrane (of the
foot), and other parts where sensibility is very acute — such as the scrotum, sheath,
and integuments of the penis. The papillary prolongations of the derma are
conical or fungiform, and pediculated ; their dimensions are very variable ;
measuring from -j--^ to -^ of an inch in length, and from y-^ to ^^ of an inch
CAPILLARY LOOPS IN THE CUTA-
NEOUS PAPILLA OF THE UPS.
TBE APPENDAGES OF THE SKTN.
901
in width at their base. The nerve-papillse are the organs of touch, and con-
tain either the corpuscula tactus (or axile bodies) of Meissner or those of Kraiise.
The sebaceous glands He beside the hair-follicles, each hair being flanked by
two glands. These small organs are composed of a very granular epithelium,
and are usually oval in shape.
(They are embedded in the upper j^ ^*S- *84. ^
stratum of the derma, and present
every degree of complexity — from
the simplest follicle to the com-
pound lobulated gland. In some
situations, their excretory ducts
open independently on the surface
of the epidermis. Those asso-
ciated with the hairs are raceiform
and lobulated, consisting of glan-
dular vesicles, which open by short
pedunculated tubuli into a common
excretory duct, and the latter,
after a short course, into the hair-
follicle. In some parts the ducts
are short and straight ; in others,
where the skin is thick, they are
spiral. They are lined by an in-
version of the epidermis, which
forms a thick and funnel-shaped
cone at its commencement, but soon becomes soft and uniform. Sebaceous glands
are met with in all parts of the body, but are most abundant in those parts which
are naturally exposed to the influence of friction, or require to be supple. The
sebaceous glands of large hairs are appendages of the follicles ; but where there
are soft woolly hairs, they are rather appendages of
the glands. The secretion — sebum — is a fatty
matter mixed with the debris of broken-down cells.
The glands are very large and numerous in the
sheath — preputium penis, where they are designated
Tyson's glands. Miiller found in the Pig a special
cutaneous gland, somewhat resembling the sebaceous
glands. It is situated on the inner and posterior
aspect of the knee, and is from | to ? inches in
TACTILE PAPILLA FROM THE SKIN, SHOWING THE
tactile corpuscles, OR " axile bodies."
A, In the natural state ; B, treated with acetic acid.
Fig. 485.
length, and from
to
inch in width. In the
Sheep, there is found, in the skin between the claws,
a particular inversion of the integument that f onus
a small elongated pouch, curving upwards, and
terminating in a cul-de-sac. This is the inter-
digitalpouch, interungulate gland, sinus, or biflex canal
— sinus cutaneus unguJarum ,- it secretes a viscid
matter from glands which, according to Ercolani,
are analogous to the sebaceous glands. The pouch is lined with very fine hairs,
and often contains foreign substances, such as sand ; it sometimes becomes in-
flamed and its orifice occluded, when it is transformed into a retention cyst.)
The sudoriparous glands are deeper situated than the last (passing even into
INTERUNGULATE SINUS OF SHEEP.
Inner aspect of first phalanx ; b,
hoof, or claw; c, interungulate
gland ; d, ori6ce of its duct.
902
THE SENSOBY APPARATUSES.
the subcutaneous connective tissue, where they are surrounded by adipose cells).
They consist of a convoluted tube (or several tubuli produced by dichotomous
subdivision) embedded in the reticular layer of the derma, and form an elliptical
glomerule, generally lying obliquely to the surface of the skin in the Horse. The
Fig. 486.
Fig. 487.
d
VERTICAL SKCTION OF THE SKIN TREATED WITH
A SOLUTION OF CAUSTIC SODA, showing the
branches of cutaneous nerves, a, b, inosculate
incr to form a terminal plexus, of which the
ultimate ramifications pass into the papillae,
excretory canal is a continuation of this glomerule,
and passes through the derma and epidermis in a
spiral manner. (The tube is lined with a single
layer of cubical cells containing pigment and
fat-granules, while its wall is formed of a delicate
ynembrana propria. In large glands, smooth muscu-
lar fibres are found between the memhrane propria
and the gland cells.)
The blood-vessels form a very rich network in
the papillary layer of the derma, and also surround
the sebaceous and sudoriparous glands. The li/m-
phatirs are disposed like the capillaries.
(The arteries arise from vessels in the underlying
fasciae, and pass vertically towards the surface,
forming three sets of capillaries — the deepest to the
adipose tissue, the next run round the sweat-glands,
the last — the terminals — form a net-work in the
stratum papiUare, which sends loops into the papillae
and small twigs into the hair-follicles and sebaceous
glands. The veins arise in the stratum papillare
from the loops in the papillse, and from the follicles
and sebaceous glands.
The lymphatics form two capillary networks
— one of fine vessels forming narrow meshes in
the stratum papillare, below the blood-capillary
network ; and one with wider meshes, in the subcutaneous tissue. Minute
lymphatics are also found outside the hair-follicles and the two sets of glands.)
The nerves are aiTanged in two layers : one loosely distributed in the derma ;
SUDORIPAROUS GLAND (MAGNIFIED
40 diameters).
a, a, Contorted tubes composing
the gland, and uniting in two^
excretory ducts, 6, 6, which join
into one sjiiral canal that per-
forates the epidermis at c. and
opens on its surface at d; the
gland is embedded in fat vesi-
cles, e, e.
TEE APPENDAGES OF TEE SKIN. 903
the other very close, and lodged in the papillary layer, which is traversed by
recurrent fibres giving off tubes that pass into the nerve-corpuscles of the papillae.
The superficial network detaches the terminal fibres that pass into these
papillge or into the stratum mucosum of the epidermis. The intra-epidermic
nerve terminations have been particularly observed in the snout of the Pig.
Epidermis. — The epidermis is a thin pellicle, covering the superficial face of
the derma ; it is destitute of blood-vessels, and is formed of cells which are being
continually deposited on the derma ; these cells become flattened in layers as they
are pushed up from the latter, and are destroyed by friction on the surface of the
skin. The deep face of the epidermis is moulded on the upper surface of the
derma ; consequently, it lodges the papillae, and dips into the follicles and ex-
cretory ducts of the glands of the skin ; its external face is not a very exact
repetition of the surface of the derma, and is covered with hair. The epidermis
tends to equalize, and to fill up, the depressions existing between the papillse.
Structure. — The epidermis comprises two layers, which are not very distinct
from each other in the Horse. The deep layer, or rete Malpighi {stratum mucosum),
is composed of soft, nucleated, pigmented, denticulated
cells, which are sometimes attached by their fine pro- ^'s- '*^^-
longations {prickle-cells) to other ceils more or less
distant ; there are spaces between them filled with an ^^
amorphous semifluid substance. The superficicd or horny
layer {stratum corneum), is constituted by hard, horny,
flattened cells, which still contain some pigment-granules, -^^^^^
and are insensibly confounded with those of the rete ^^^t-S-^.
mucosum. ^ "^ ^ ""^-S
(Where the epidermis is thick, there is seen between ^.j'^ 9 n%j^--p
the two layers just mentioned, a third — the stratum ^ <3> ^ g,; 'C®#-<*
lucidum — the nature of which has not yet been defined. p^g^j©^^'
It is transparent, and apparently amorphous. The theory "^^^S:,:^^^^^
of growth of the epidermis is believed to be as follows : o^^ic^^j^ section of epi-
5 1 , • 1 J- o DERMIS, SHOWING THE
a layer of plastic lymph is thrown out on the surface ot progressive develop-
the derma, and is converted into granules, which are ment of its compo-
termed cell-germs, or cytoblasts. These imbibe serum ^^'^^ cells.
from the lymph and adjacent tissues, so that the outer- «' ^",tl ^flKra,') •
most covering of the cytoblast is gradually distended ; these nuclei are giadu-
the latter becomes a cell, and its solid portion, which ally developed into cells
. /• . . at 0, c, and a, and the
always remains adherent to some point of the inner sur- cells are flattened into
face of the cell membrane, forms the nucleus of the cell. lamellae, forming the
Within this nucleus one or more nuclei are developed ; epiderm^i^l e^^
these are named nucleoli. The process of imbibition
continuing, the cell becomes more or less spherical ; so that, after a certain time,
the papillary layer of the demia is covered by a thin stratum of spherical cells
pressed closely together, and corresponding with every irregularity of the papillae.
New cells being continually produced before the formation of the others has
been quite completed, these are removed in layers further and further from the
surface of the derma, and, becoming subjected to the influence of physical laws,
their fluid contents evaporate ; they collapse, flatten, and gradually assume an
elliptical shape ; then they are a mass of completely flat cells, with an included
nucleolated nucleus, and finally become a thin membranous scale, in which the
nucleus is scarcely apparent.)
904 THE SENSORY APPARATUSES.
In Solipeds and other animals, the epidermis is generally dark-coloured, from
the presence of pigment-corpuscles, the number of which increases with their
depth in the membrane. This coloration is perhaps intended to prevent the
rubefacient effects of the heat of the sun's rays, by augmenting the absorbing
and dispersing power of the cutaneous surface. In the majority of cases, this
coloration is absent in the Sheep, whose skin is protected by a thick fleece ; and
also in tlie Pig, whose habits in a wild, as in a domesticated condition, keep it
out of the direct action of the sun.
(In some regions of the body of all animals, the skin forms folds, as at the
junction of the fore limb with the body, the flank, and between the thighs. In
the Cow, it forms the large pendulous layer at the throat and breast, known as
the " dewlap ; " and in the Goat and Pig, it not unf requently constitutes teat-
like prolongations depending from the throat, which nearly always contain a
small cartilaginous nucleuc and some muscular fasciculi. The thickness of the
epidermis is sometimes greatly increased by wear and friction, as we frequently
see in the skin covering the knees of Sheep, etc.)
(The functions of the skin are, as we have seen, tactile and secretory ; m
addition, it is eminently protective. Its secretory action is always more or less
active, but the production of perspiration is greatest when the body is at a high
temperature, as during active exertion ; at other times the perspiration is
insensible. In this respect, the skin has intimate sympathetic relations with
other organs which have somewhat analogous functions, such as the lungs,
kidneys, intestines, etc., and when its function is disordered or checked, it
induces alterations in the secretions of one or all of these organs. The skin is
also the seat of a constant and important respiratory action, as it absorbs oxygen
and throws off carbonic acid, and any interruption to this process is injurious.)
The skill of Ruminants shows, at certain points, depressions destitute of hair, but extremely
rich in sebaceous glands. Such is the tear fossa situated on the face, and tl biflex canal
between the digits— as in the Sheep, and particularly in the Goat. (It should be remarked
that sioeat-glanih are found in the skin of the Ox, and in tl. ; pads of the feet of Dogs and Cats.
They attain a great size in the pig's snout. The nos; and upper lip of Ruminants, and that of
the Dog an<i Cat, contain racemose glands that secrete : clear, watery, alkaline fluid.)
Article II.— Appendages of the Skin.
Preparation. — See treatises on histology.
The appendages of the skin are hairs and horny productions^ dependencies of
the epidermic layer.
Hairs.
The hairs are the filaments which, collectively, form the external covering of
the skins of animals.
In the Horse, the bristly appendages known as horsehair should be dis-
tinguished from the hairs proper ; the latter are fine and short — particularly
in the regions where the skin is thin — imbricated on each other, and spread
over the entire surface of the body in c continuous layer which is designated
the coat. The former are long and flowing, occupy the summit of the head,
where they constitute the forelock ; the upper border of the neck, where they
form the mane ; and cover the caudal appendage with a splendid tuft — the tail.
Some of these also form special organs on the free margin of the eyelids, and
are termed eyelashes ; while others, inserted about the lips and below the eyes,
are named tentacula. (The eyelashes are chiefly implanted in the upper lid.
TEE APPENDAGES OF TEE SKIN.
905
The hairs of the tail are the longest and strongest in the body. These par-
ticular hairs also grow on the posterior aspect of the limbs, generally from
about the knees and hocks to the hoofs ; at the sesamoid bones they constitute
a long tuft — the fetlock — which surrounds the horny growth named the " ergot."
These " foot-locks " are peculiar to the Horse, and vary in length and coarseness
with the breed of the animal.)
"When the hair is fine, long, and wavy, it f onus ivool ,- and when straight and
rigid, as in the Pig, it is known as bristles.
In the Ass and Mule, the forelock and mane are rudimentary or absent,
and the hair of the tail is
limited to a small tuft at the
extremity of the organ in the
former animal ; while in the
latter it is much less abundant
than in the Horse.
In the Ox, these hairs
are not present, except at the
extremity of the tail, as with
the Ass.
There are no other animals
which have other hair than
that composing the coat.
(The ordinary hair of the
coat is soft and elastic, in-
clined in particular directions,
and varies in length not only
according to the regions of
the body on which it grows,
but also according to the
season or climate. In the
Horse, the direction of the
hair of the coat gives rise to
curiously fonned waves, lines,
and circles, the most constant
of which is on the forehead.
In the Cow, the hair is
frizzly on the forehead ; on
the posterior part of the thighs
it has a particular direction,
while on the outer side it passes downwards, and from the posterio" part of the
mammae it ascends as high as the vulva ; this characteristic disposition forms
what the French have termed ecussois, by which some have pretended to recognize
the lactiferous qualities of the animal.
In the Sheep, real hair — not wool — is found on the lower part of the face,
and the extremities of the limbs.
In the Goat, the hairs of the beard are veiy long, and compose a distinc-
tive tuft ; this animal has also a fine crisp duvet or dotvn beneath the ordinary hair.
In the Pig, the bristles are very strong in the region of the back ; in old
animals they are usually bi- or trifurcated at their free extremity ; there also
exists a fine soft hair on this animal. It has no tentacular hairs.
HAIR-FOLLICLE.
1, External dermic layer of the follicle ; 2, internal dermic
layer; 3, amorphous lininr of the follicle; 4, external
epidermic layer ; 6, hair-bulb ; 7, vascular papilla ; 8,
cells of the medullary substance.
906 THE SENSORY APPARATUSES.
In the Dog, the length, fineness, and consistency of the hair depends on the
breed.
In the Cat, the hair in some breeds — as in the Angora— is remarkable for
its length and softness. This creature has the tentacula enormously developed
as a moustache.
In "none of these animals is there a " foot-lock.")
Steucture. — The hairs are implanted in the texture of the derma, and
sometimes even in the subjacent tissues, their base being enclosed in a follicle,
at the bottom of which their elements are developed. It is therefore necessary
to study : 1. The structure of the hair. 2. Thaf. of the hair-folHcle.
1. The hair presents a free portion — the shaft (scapus), and another con-
cealed in the follicle — the root (radix pili) ; the latter widens at its base — the
hulh {bulbus pili) of the hair — to embrace the papilla or hair-germ.
There are three superposed layers in a hair. The epidermis (cuticle) is a thin
lamella of homy flattened cells, imbricated like tiles on a roof. Its elements
are marked on the surface of the hair by shaded lines anastomosing to form
a network ; they enlarge, and become more apparent under the influence of an
alkali. The epidermis belongs to the shaft and a portion of the root ; near the
bulb it is replaced by soft nucleated cells, which are implanted vertically.
The cortical substance (cortex) forms the largest part of the thickness of the
hair. It is striped longitudinally, and provided with pigment granules, the
number of which varies with the colour of the coat. In white hairs these
granules are absent, but there are found in them, as well as in coloured hairs,
small spaces containing air, and which exhibit a dark colour under the micro-
scope. Treated by potassium or sulphuric acid, the cortical substance is reduced to
elongated spindles, which again may be decomposed into slender epithelial
lamellte without nuclei. On arriving at the root, the cells change their cha-
racter, becoming polyhedric, filled with fluid, and exhibit a perfectly distinct
nucleus and more or less pigment. The meduUary substance (mechdla) occupies
a narrow irregular cavity in the centre of the hair, extending from the bulb
or termination of the root, to the point. It has for its base rectangular, rarely
circular, cells, which, according to Kolliker, contain fat-granules and air-
globules. (Many hairs show no medulla, and even in thick hairs it does not
always extend the entire length of the hair.)
2. The hair-follicle is a narrow cavity, slightly contracted at its orifice and
dilated at the bottom, where the hair-papilla is placed. It is a simple involution
of the skin, as its structure demonstrates. It presents, from without to within :
1. A loose conjunctival layer, analogous to the reticular layer of the derma.
2. An internal dermic layer, dense and close hke the papillary layer of the skin.
3. An amorphous limiting membrane. 4. An epidermic zone — the external sheath
of the hair — formed by cells, similar to those of the stratum mucosum. 5. A
second epidermic zone — the interned sheath of the hair — which repeats the horny
layer of the epidermis, and is confounded with the termination of the epidermis
of the hair towards the lower third of the follicle.
The papilla, or hcdr-germ, is a small, conical, vascular, and nervous prolonga-
tion rising up into the hair-bulb. It furnishes the hair with nutrition and the
elements of growth.
The walls of the follicles of the enormous hairs — or tentacula — which garnish
the lips of the Horse, or bristle from those of the Cat (moustaches), are pro-
vided with nerve-ramifications which endow these appendages with a high
TEE APPENDAGES OF THE SKIN. 907
degree of sensibility, and enable them to play an important part as organs
of touch.
The follicles of these large hairs show, between the second and third layers of
their wall, a vascular dilatation — a kind of erectile tissue — that probably plays a
part also in the exercise of touch (Leydig, Odenins, Paladino, etc.).
Two sebaceous glands, and a smooth muscular fasciculus, are annexed to the
pilous follicle. The sebaceous glands — which have been already described —
open into the sheath of the hair by a small excretory canal, which traverses
the fibrillar walls of the foUicle. The muscular fasciculus {musculus arrector
pill) is situated on the side to which the hair and its foUicle are inclined ; it
arises from the superficial face of the deima, and terminates at the bottom of
the foUicle, which it erects by contracting. When the fasciculi contract over a
wide surface, the extent of the skin is diminished, and the hairs are erected and
partially ejected from their follicles — producing the cutis anserina.
(Next to the innermost layer of the corium of the hair is a layer of stratified
epithelium — the external root-sheath ; and lining this, in the upper part of the
follicle, is the internal root-sheath, representing the stratum corneum. This
inner root-sheath divides, near the orifices of the sebaceous glands, into two
layers — Henle's sheath being the outer, and Huxley's sheath the inner.
The formation of a hair is identical with the formation of the epidermis
by the papillary layer of the derma. The capillary plexus of the follicle throws
out plastic lymph which is converted into granules, then into cells, which become
elongated into fibres. The cells that are to form the surface of the hair, are
converted into flat scales that enclose the fibrous structure of the interior. As
these are successively produced, they overlap those previously formed, and give
rise to the waving lines seen on the circumference of the hair ; this overlapping
also causes the roughness experienced in drawing a hair between the fingers from
its point to the bulb. The latter is the newly formed part of the hair, its
expanded form being due to the greater bulk of the fresh cells.
The colour of the hair is very varied in animals, ranging from black to
white, red and brown, with all the intervening shades. The tint also changes
at different periods of life, being sometimes altogether altered between the
juvenile and adult periods ; dark-coloured Horses becoming light-coloured as
age advances. Besides, it is never uniform in the same animal ; black Horses
not unfrequently having white patches and diverse tints, with other dissimilari-
ties. The disease termed " melanosis " is very common in old white Horses
which were previously grey, and is supposed to be due to the localization of the
black pigment at certain limited points. The hair grows according to the
climate, seasons, food, etc., and varies with the species and breed. The coat in
every animal is shed at certain times, and is replaced by new hairs.
The hair preserves the skin from unhealthy external influences — wet and
cold for example. It is a bad conductor of heat, and therefore keeps the body
warm. The tentacula are very useful as tactile organs ; while the mane, fore-
lock, and tail keep away insects, and the long hairs of the fetlock and pastern
protect these parts from the injurious effects of cold and wet, and the action of
foreign bodies.)
Homy Productions.
The horny tissues form several groups. The first comprises the horns of
Euminants ; the second, the so-called chestnuts of Solipeds ; the third, the pro-
THE SENSORY APPARATUSES.
tective layer enveloping the digital extremities, and constituting the claws of
Garni v'ora, the Pig, Ox, Sheep, and Goat, and the hoofs of the Horse, Ass, and
Mule. These latter productions, ranking as they do among the most important
organs of the locomotory apparatus of Solipeds, will fii-st receive notice.
1. The Hoof of Solipeds.
The hoof of Solipeds is an extremely important study, because of the
numerous diseases which affect this region. Consequently, it has been the
subject of several voluminous works, to which the student must be referred
for a more complete description of
Fig. 490.
LONGITUDINAL MEDIAN SECTION OF THE FOOT.
1, Anterior extensor of the phalanges, or extensor
pedis; 2, literal extensor, or extensor suffraginis;
3, capsule of metacarpo-phalangeal articulation ;
4, large metacarpal bone ; 5, superficial flexor of
the phalanges, or perforatus ; 6, deep flexor, or
perforans ; 7, sheath ; 8, bursa ; 9, sesamoid
bone; 10, ergot and fatty cushion of fetlock; 11,
crucial ligament; 12, short sesamoid ligament;
13, first phalanx; 14, bursa; 15, second pha-
lanx ; 16, navicular bone ; 17, plantar cushion ;
18, third phalanx; 19, plantar surface of hoof;
20, sensitive or keratogenous membrane of tliird
phalanx.
its organization ; ^ as we cannot do
more here than give some essentially
descriptive details, necessary to fill
up the outline that we have traced
out.
We will at firet glance at the parts
contained in the hoof, returning after-
wards to a description of the homy
case itself.
a. The Pabts contained in the
Hoof.
Proceeding from within to with-
out, we find, in the interior of the
horny box : 1. The third phalanx,
navicular bone, and lower part of
the second phalanx, forming the
articulation of the foot. 2. The four
ligaments that bind this articulation.
3. The tendon of the common ex-
tensor of the phalanges which covers
the articulation in front, and that of
the perforans which supports it be-
hind, in becoming inserted into ' the
pedal bone, after gliding over the
posterior surface of the navicular
bone. 4. The complementary ap-
paratus of the third phalanx. 5.
The matrix of the hoof, or kerato-
genous membrane— a continuation of the derma covering the digital region. To
these parts must be added the vessels and nerves of thi» region.
The description of the bones has been given at pp. 114, 150 ;
Of the articulation and its ligaments, at p. 209 ;
Of the tendon of the anterior extensor of the phalanges, at p. 325 ;
Of the perforans tendon, at p. 331 ;
* Pee particularly, among the French works, the Traite de VOrgnnisation du Pied du
Cheval, by M. H. Bouley. (See nlso the still more recent work by Leis<ring, Der Futz det
Pferdeg Dresden : 1870. Also a long series of papers by me on this subject in the Veteri-
narian for 1871-2.^
TEE APPENDAGES OF TEE SKIN. 909
Of the arteries, at pp. 636, 654 ;
Of the veins, at pp. 698 to 703.
Of the nerves, at pp. 865, 881.
It remains to notice the complementary apparatus of the third phalanx, and
the Tceratogenous memhrane.
Preparation. — The dissection of the fibro-cartilages is made at the same time as that of the
articulation of the foot. A good idea of the shape of the plantar cushion can be obtained in a
longitudinal and median section of the digital region (Fig. 493), and on the piece prepared to
show tlie subcorneal tissue. This is obtained by two proce<lures. In the fiist, we wait until
decomposition has softened the cells between the hoof and the keratogenous membrane, when
the hoof can be easily pulled off. In the second, the foot is kept for several hours in boiling
water, then held in a vice by the pastern while the tissues around the coronet are slightly cut
through ; a pair of shoeing pincers is now employed at the heels in pulling the hoof up and
down until it comes off. The foot is then washed to free it from tlie debris. (The hoof can
also be removed by prolonged maceration, or l>y roasting on a fire, when it may be cut and torn
off by the farrier's knife and pincers).
Fig. 491.
A. Complementary Apparatus of the Pedal Bone. — In the indication
we gave of this apparatus at p. 117, it was mentioned that it was composed of
two lateral pieces — thejibro-cartilages of the pedal
bone, united behind and below by the plantar
cushion — a fibrous, elastic mass, on which the
navicular bone rests, through the medium of the
perforans tendon. We will take this distinction
as the basis of our study.
1 . Pibro-cartilages of the Pedal Bone.
— Each of these pieces represents a plate flattened
on both sides, having the form of an oblique-
angled parallelogram, and prolonged behind the
third phalanx. The external face is convex, and
pierced with openings for the passage of veins ;
it sUghtly overhangs that of the pedal bone. The
internal face is concave, channeled by vascular
furrows, and covers, in front, the pedal articula-
tion, and the synovial cul-de-sac that projects
between the two lateral Ugaments of that joint ;
below and behind, it is united to the plantar
cushion, either through continuity of tissue, as
at the inferior border, or by fibrous bands passing
from one to the other. The upper harder, some-
times convex, sometimes rectilinear, is thin and
bevelled like a shell ; it is separated from the
posterior margin by an obtuse angle, in front of
which this border is often broken by a deep notch that gives passage to the vessels
and nerves of the digital portion. The inferior border is attached, in front, to
the basilar and retrossal processes ; behind the latter, it is reflected inwards to
become continuous with the tissue on the lower face of the plantar cushion.
The posterior border is oblique from before to behind, and above to below, and
joins the preceding two. The anterior border is oblique in the same direction,
and is united so intimately to the anterior lateral ligament of the pedal articula-
tion, that it cannot be separated from it except by an artifice of dissection. It
60
horizontal section of the
horse's foot.
1, Front, or toe of the hoof; 2, thick-
ness of the wall ; 3, laminae ; 4,
insertion of the extensor pedis ; 5,
OS pedis; 6, navicular bone ; .7,
wings of the os pedis; 8, lateral
cartilage: 9, flexor pedis tendon;
10, plantar cushion; 11, inflection
of the wall, or " bar; " 12, horny
frog.
THE SENSORY APPARATUSES.
sends to this ligament, and to the tendon of the anterior extensor of the
phalanges, a fibrous expansion that becomes fused with that of the opposite
side.
The fibro-cartilages comprise in their structure a mixture of fibrous and
cartilaginous tissue, though the mixture of these is far from being perfectly
homogeneous, or everywhere in the same proportions.
The cartilages of the fore feet are thicker and more extensive than those of
the hind ones.
(The lateral fibro-cartilages are peculiar to Solipeds.)
2. Plantar Cushion. — The plantar cushion is a kind of wedge, situated
in the space between the two cartilaginous plates of the third phalanx, and
between the perforans tendon and the lower part of the hoof. Its shape allows
it to be considered as having an antero-superior and
an infero-posterior face, a base, summit, and two lateral
borders.
The antero-superior face is moulded on the aponeu-
rotic expansion of the perforans tendon, and is " covered
by a cellulo-fibrous membrane, the proper tunic of the
plantar cushion, which is continuous, on its inner face,
with the fibrous septa by which this organ is traversed,
and adheres by its external or anterior face to the
reinforcing sheath interposed between it and the per-
forans tendon " (Bouley). This expansion is prolonged,
above, to the fetlock, where it is confounded with the
superficial fascia of the metacarpal region ; it is mar-
gined, laterally, by two small, very strong' ligamentous
bands which, at their middle portion, cross in a very
oblique manner the fasciculus formed by the vessels
and nerves of the digit. Each of these bands is fixed,
superiorly, to the base of the rudimentary digit known
as the ergot, and to the knob of the lateral metacarpal
bone ; their inferior extremity is attached within the
retrossal process.
The infero-posterior face of the cushion is covered
by the keratogenous membrane, and presents at its
middle the pf/rcmidal body, a prominence exactly like
that of the frog, to which it corresponds. It shows,
then, in front, a single conical prolongation, and be-
hind, two divergent prominences separated by a median excavation.
The base of the apparatus lies behind, and is inclined upwards ; it is divided
by a depression into two lateral masses— the bulbs of the plantar cushion— on the
inside of which the posterior prominences of the pyramidal body reach, and
which become confounded, outwardly, with the posterior and inferior angle of
the cartilaginous plates. This portion of the cushion is, like the anterior face,
covered by a cellulo-fibrous expansion, which separates it from the skin of the
pastern ; this expansion is attached, by its lateral margins, to the posterior
border of the cartilages, and continued, superiorly, on the surface of the anterior
expansion, with which it soon unites.
The summit (jjoint or apex) forms a sharp border, more or less regularly
convex ; it is fixed into the plantar face of the pedal bone, in front of the semi-
LOWER FACE OF THE HORSE's
FOOT, THE HOOF HAVING
BEEN REMOVED.
1, Heel ; 2, coronary cushion;
3, branch of the plantar
cushion ; 4, median lacuna,
or commissure; 5, laminsc
of the bars ; 6, velvety
• tissue of the sole.
THE APPENDAGES OF THE SKIN. 911
lunar ridge and the insertion of the perforans tendon, with which the plantar
cushion mixes its fibres at this part.
The lateral borders are wider behind than before, in consequence of the
wedge-like shape of the whole organ ; they are continuous with the inner face
of the lateral cartilages, as already indicated in describing the latter.
The organization of the plantar cushion differs much from that of the carti-
lages. It has for its base a fibrous structure, continuous with that which consti-
tutes the fundamental framework of these ; this structure is very dense towards
the infero-posterior part of the organ, and becomes gradually looser as it leaves
this region ; the meshes it contains are filled with a yellow pulp composed of
fine, elastic, and connective fibres, in the midst of which some adipose cells are
found. (I have attentively examined this yellow pulp, and can perceive that it
is essentially constituted by adipose tissue). Numerous blood-vessels and nerves
complete this structure.
B. The Keratogenous or Subcorneus Membrane.— The keratogenous
membrane envelops the extremity of the digit, by spreading over the terminal
■expansion of the tendon of the extensor pedis, through the medium of a fibrous
fascia — a dependency of the lateral cartilages ; and also over the inferior moiety
■of the external face of these cartilages, the bulbs of the plantar cushion, pyramidal
l)ody, anterior part of the plantar face of the third phalanx, and over the anterior
•surface of the same bone. It covers all these parts like a sock, and the hoof
■encloses it, as a shoe does the human foot.
This membrane becomes continuous with the skin of the digital region, at a
circular liue that intereects the middle portion of the second phalanx, and in-
clines obliquely downward from behind to before. Below this line, in front and
laterally, the subungular tissues form a semi-cylindrical protuberance, covered
with vilH, and designated the " bouiTelet." (This elastic prominence has received
several most inappropriate names from English farriers and hippotomists, such
as " coronary ligament," " coronary substance," " cutiduris," etc. From its
function, structure, situation, and its analogy to the plantar cushion, I have
designated it the " coronary cushion.")
On the plantar cushion and the lower face of the pedal bone, this membrane
becomes a villous tunic — the velvety tissue — which is continuous, towards the
bulbs, with the extremities of the coronary cushion.
The portion spread over the anterior face of the third phalanx constitutes the
laminal {podophyllous) or "leafy tissue," so called because of the laminae or
parallel leaves seen on its surface.
The three regions of the keratogenous apparatus will be successively studied.
1. Coronary Cushion. — This part is the matrix of the wall of the hoof,
and is lodged in a cavity excavated at the upper border of this part of the horny
case. It forms, according to the expression employed by M. Bouley, a rounded
prominence, which projects like a cornice above the podophyllous tissue.
Its inferior border is separated by a white zone from the upper extremity of
the laminae, which constitute this boundary.
The superior border is limited by a slightly projecting margin named the
perioplic ring, because it secretes the horn of the periople. Between this margin
and the cushion is a sharply defined groove.
The extremities, narrower than the middle portion, on arriving at the bulbs
of the plantar cushion, bend downwards into the lateral lacunae of the pyramidal
body, where they become confounded with the velvety tissue.
912
TEE SENSORY APPARATUSES.
The surface of the organ shows filiform prolongations, a little constricted at
their base, and named papiJlcE, viUo-papiUcB, villi, and villous loops, the size of
which is greatest towards the lower part of the cushion ; those of the perioplic
ring are smallest. Contained within the minute apertures at the upper part
of the hoof -wall, these papillaB— considered as a whole, and when the hoof has
been removed by maceration — form a tufty surface most perfectly seen when the
foot is suspended in water.
The structure of the coronary cushion resembles that of the derma, of which
it is in reality only a continuation. It comprises a fibrous framework, remark-
able for its thickness and density, with a considerable number of vessels and
nerves, the ramifications of which may be followed to the extremity of the villi.
Fig. 493.
LATERAL VIEW OF THE HORSE'S FOOT,
AFTER REMOVAL OF THE HOOF.
1, Perioplic ring, divided by a narrow
groove from the coronary cushion,
2, which is continuous with the
plantar cushion, 4, and join= the
vasculnr laminae, 3, through the
medium of the white zone.
HIGHLY MAGNIFIED HORIZONTAL SECTION OF A HORSE'S
HOOF, SHOWING THE RELATIONS BETWEEN A KERA-
PHYLLOUS AND A PODOPHYLLOUS LAMINA.
1, Principal podophyllous lamina; 2, secondary ditto
{laminella) \ 3, elliptical cells (analogous to the generat-
ing layer in the rete Malphigii) ; 4. cells of the same,
but already keratinized, and colourable by carmine ; 5,
ke)ai>hyllous lamina.
To its great vascularity is due the bright red colour it shows on its surface ;
this colour is sometimes masked by black pigment.
(I have found a notable quantity of adipose tissue in the cushion).
2. Velvety Tissue. — Much thinner than the plantar cushion, the velvety
tissue— the formative organ of the sole and frog — extends over the whole of the
plantar region of the third phalanx, as well as the plantar cushion, the bulbs of
which, and the pyramidal prominence it covers, by adapting itself exactly to the
irregularities of this elastic mass.
Its surface, which altogether resembles the general configuration of the
plantar surface of the hoof, is divisible into two regions — a central, correspond-
ing to the pyramidal body and the frog, and continuous on the bulbs of the
cushion with the extremities of the coronary cushion and the perioplic ring, but
chiefly with the latter ; the other, peripheral, is covered by the horny sole.
THE APPENDAGES OF THE SKIN. 913
separated from the podophyllous tissue by the plantar border of the foot, some-
what encroached upon posteriorly by the laminae corresponding to the bars, and
is continuous, above these laminaB, with the plantar cushion.
The surface of the velvety tissue is studded with villi similar to those of the
coronary cushion, and about the same size. The longest are towards the cir-
cumference of this surface, and the shortest in the median lacuna of the pyra-
midal body ; all are lodged in the porosities on the inner surface of the horny
sole and frog.
This tissue shows the same organization as the coronary cushion. The
vascular corium, forming its base, is thickened at its peripheral portion by a
fibrous network named the plantar reticulum, in the meshes of which are sustained
the veins of the inferior surface of the foot.
3. Laminal Tissue. — This part of the keratogenous membrane is also
very frequently designated the podophyllous tissue (and still more frequently, in
this country, as merely the lamiyim). It is spread over tlie anterior face of the
third phalanx, occupying the interval between the plantar border of that bone
and the lower margin of the coronary cushion ; its width is, therefore, greater
at the anterior portion of the phalanx than on its sides, where the extremities of
the membrane are reflected below the bulbs of the plantar cushion on to the
velvety tissue.
This membrane owes its name to the leaves it exhibits on its superficies ;
these are from five to six hundred in number — we have counted 560 — run
parallel to each other, and are separated by deep channels, into which are dove-
tailed analogous leaves from the inner side of the wall of the hoof ; they extend
from the white zone that hmits the inferior border of the coronary cushion —
where they are not so salient — to the plantar border of the foot, where they
each terminate in five or six very large villous prolongations, which are lodged
in the horny tubes at the circumference of the sole.
The leaves {lamina) of the podophyllous tissue increase in width from above
to below ; their free margin is finely denticulated, and, under the influence of
any inflammatory cause (laminitis, ablation of the horny wall), these denticulse
become largely developed, and transformed into veritable papifla^. Their sides are
traversed by folds, about sixty in number, which pass uninterruptedly from top
to bottom. These secondary leaves, or lamellae, are fixed obliquely on the sides
of the lamiufe, as the barbules of a feather are attached to the barbs (Figs. 494,
4 ; 496, f," c!')
The podophyllous tissue is not in immediate contact with the keraphyllous
tissue, or horny laminge ; between the two there is a mass of soft, elHptical cells,
always destitute of pigment, easily stained with carmine, and appearing to stud
the ramifications of the vascular laminse (Fig. 494, 4). A transverse section of
the union of the hoof with these laminae, when treated with carmine, presents a
very fine aspect, appearing as so many fern or acacia-of-Judsa leaves placed
between the keraphyllous laminae — the principal nerves and the secondary
nervules of the leaves, being represented by the lamina and its lateral ridges, the
limb of the leaves by the young cells spread around the latter.
The structure of the podophyllous membrane resembles that of the other parts
of the keratogenous apparatus. Its corium is, like that of the peripheral portion
of the velvety tissue, separated from the os pedis by a fibrous reticulum, which
supports the veins, and forms, to some extent, the periosteum of the third
phalanx.
914
TEE SENSORY APPARATUSES.
The leaves of the podophyllous membrane are immense lamellar papillae, which
should be included among the principal instruments concerned in the tactile
sensibility of the Horse's foot, and which play a really mechanical part, in con-
curring— by their dovetailing with the keraphyllous (or horny) laminae — to assure
the solidity of the union of the hoof with the living parts. The cells which
Fig. 495.
be d
HORIZONTAL SECTION OF THE JUNCTION OF THE WALL WITH THE SOLE OF THE HOOF.
a, Wall, with its horn-tubes; 6, 6, horny laniinse projecting from the wall; c, c, horn-tubes formed
by the terminal villi of the vascular laminae, the horn surrounding them and occupying the spaces
between the horny laminae, constituting the " white line ; " d, horny sole, with its tubes.
multiply on their surface have usually but little share in the formation of the
horn. This will, however, be alluded to hereafter.
h. Description of the Hoof.
The hoof of the Horse — considered as a whole — represents a kind of box that
envelopes the inferior extremity of the digit, by fitting closely on the keratogenous
HORIZONTAL SECTION OF THE WALL, AND HORNY AND VASCULAR LAMINA, TO SHOW THE
JUNCTION OF THE LATTER AND THE LAMINELLjE.
a, Inner portion of the wall with the laminae arising from it ; 6, vascular laminae ; c, horny lamina
of aver.ige length ; c', c', unusually short lamina;; c", c", laminellae on the sides of the horny
laminae ; d, vascular lamina passing between two horny ditto ; d', vascular lamina passing
between three horny laminje ; d", lateral laminellae ; e, e, arteries of vascular laminae which
have been injected.
membrane, to which it is united in the most intimate manner by a reciprocal
penetration of prolongations into cavities that exist on the surfaces in contact.
Its general shape is, as was demonstrated by Bracy Clark, that of the moiety
of a cylinder cut obliquely across its middle, and resting on the surface of this
section. In nearly all feet, however, it is slightly conical.
THE APPENDAGES OF THE SKIN.
915
Prolonged maceration separates it into three portions — the tvall, sole, and
frog.
Wall. — The wall — also named the crust — is that part of the hoof which is
apparent when the foot rests on the ground. This thick plate of horn covers
the anterior face of the foot, and, gradually narrowing in width and diminishing
in thickness, passes round each side until it reaches the bulbs of the plantar
cushion, when its extremities are sharply inflected inwards, between the frog and
internal border of the sole, becoming confounded with the latter about its middle
or anterior third, after being greatly reduced in breadth and substance.
The middle— or anterior part — of this horny envelope is popularly known as
the toe ; its two sides are designated outside and inside toe ,- the lateral regions con-
stitute the quarters ; the heels are formed by the angles of inflection of its
extremities ; while these extremities themselves, passing along the inner border
of the sole, are termed the bars.
Examined with regard to the direction it follows in its relations with the
ground, this envelope is seen to be much inclined in its middle region or toe, and
this obhquity gradually diminishes until the
posterior part of the quarters is reached ; at
this point the wall is nearly perpendicular.
The following are the characters it offers
in the conformation of its faces, borders, and
extremities : —
The external face, convex from side to side,
and perfectly straight from the upper to the
lower border, is smooth, polished, and shining :
an appearance it owes to a thin horny layer,
independent of the wall proper, designated the
periople.
This periople forms, on the upper part of the
wall, a kind of ring, continuous with the bulbs
of the plantar cushion, and with the frog, of
which it is only a dependency ; responding, by
its upper margin, to the perioplic ring, which
secretes it ; towards the lower part of the wall
it is gradually lost, friction incessantly thinning
and destroying it.
The inner face presents, over its entire ex-
tent, the white parallel leaves which dovetail with the laminae of the podophyllous
tissue. Collectively, these are named the Iter aphyllous tissue.
The superior border is bevelled off, on its inner aspect, into a circular con-
cavity, into which the plantar cushion is received. This excavation is named
the cutigercd cavity, because of its relations ; it offers on its surface a multitude
of minute openings — the commencement of the horny canaliculi which receive
the villosities of the cutiduris.
The inferior border, in contact with the ground, and subjected to wear in
unshod animals, is united inwardly, and in the most intimate manner, with the
circumference of the sole.
The extremities, constituted by the reflected and re-entering prolongations
known as the bars,iorm, outwardly, the external side of the lateral lacunge of the
frog ; they are provided, inwardly, with laminas like the rest of the wall. The
HOOF JUST REMOVED FROM THE
FOOT (SIDE view;.
Inner surface of periople, or coronary
frog-band, with some hairs passing
through ; a', outer surface of same
at posterior part of foot ; a", a
section through the wall to show
its thickness; 6 to c, quarter of the
hoof, from b to the front is the out-
side (or inside) toe ; from c to d the
outside (or inside heel) ; e, frog ; /,
bevel on upper margin of wall for
reception of coronary cushion ; g,
keraphylla, or horny laminae.
916
THE SENSORY APPARATUSES.
upper margin of these prolongations is confounded with the frog and sole ; the
lower appears between these two parts, and is effaced at a certain distance from
the point of the frog.
Sole. — The sole is a thick horny plate comprised between the inner border
of the wall and its reflected prolongations ; thus occupying the inferior face of
the hoof. It offers two faces and two borders or circumferences.
The inferior, or external face, forms a more or less concave surface, according
to circumstances. The superior, or internal face, corresponds to the peripheral
portion of the velvety tissue ; it shows a multitude of little apertures analogous
to those of the cutigeral cavity, into which are inserted the papillae of the kerato-
genous membrane.
The external border, or large circumference, is united, throughout its extent, to
the inner contour of the lower border of the wall, by means of its denticulae,
HOOF, WITH OUTER PORTIOV OF THE WALL
REMOVED TO SHOW ITS INTERIOR.
a, a, Periople, or coronary frog-band; 6,
cavity in upper part of wall for coro-
nary cushion ; c, upper, or inner, surface
of "bar;" d, vertical section of wall;
d', the same at the heel ; e, horizontal
section of ditto ; /', horny laminae of
bar; /", ditto of wall ; /"', lateral aspect
of a lamina; g, upper, or inner surface
of the horny sole ; A, junction of the
horny iHminae with the sole (the " white
line"); i, toe-stay at the middle of the
toe; k, upper, or inner surface of the
horny frog; I, frog-stay; m, cavity
corresponding to a branch of the frog;
n, ditto corresponding to the body of
the frog.
PLANTAR OR GROUND SURFACE
OF A HOOF (right FOOT).
The interval from a to a repre-
sents the toe ; from a to 6, 6,
outside and inside quarters;
c, 0, commencement of bars;
d, d, inflections of wall at the
heels, or "buttresses;" e, La-
teral lacuna ; /, /, /, sole ; g,
white line ; g,' g', ditto be-
tween the sole and bar; h,
body of frog ; », branch of
frog; k, k, glomes, or heels of
frog; /, median lacuna.
which are reciprocally dovetailed into those on the inner face of the wall near its
inferior border. The internal border, or small circumference, is a deep, V-shaped
notch, widest behind, which corresponds to the bars, and at the bottom of which
the point of the frog is fixed.
Frog. — This is a mass of horn, pyramidal in shape, and lodged between two
re-entering portions of the wall. It offers four planes (or sides), a base, and a
summit (or point).
The inferior and the two lateral planes constitute the external surface of the
organ. The first is hollowed by a longitudinal excavation, which is shallow in
well-formed hoofs, and is named the median lacuna of the frog, separating the
two salient portions, or branches, which diverge posteriorly find join the heels.
The other two planes are directed obliquely downwards and inwards ; they adhere
TEE APPENDAGES OF THE SKIN. 917
closely, at their upper third, to the external side of the bars, and anteriorly to the
inner border of the sole. " This union is so close that no line of demarcation is
apparent between these parts, and their separation can only be obtained by pro-
longed maceration. The non-adherent, or free portion, forms the inner side of
the cavities know as the lateral lacunce, or commissures of the frog, whose external
side is constituted by the inferior face of the bars " (Bouley).
The superior plane, forming the internal face of the frog, is cribbled with
holes like that of the sole, and is exactly moulded on the pyramidal body of
the plantar cushion. It also offers a triangular excavation, divided posteriorly
into two latter channels by a prominence directed from before backwards, to
which Bracy Clark gave the name of frog-stay, but which M. Bouley prefers to
designate the stay {arete — spine or ridge) of the frog.
The hase or posterior extremity of the frog, constituted by the extremities of
its branches, forms two rounded, flexible, and elastic eminences separated from
each other by the median lacuna ; they cover the angles of inflection of the wall,
and are continuous at this point with the perioplic band. Bracy Clark named
them the glomes of the frog.
With regard to the summit — or anterior extremity of the organ — it is a point
wedged in the re-entering angle comprised between the two portions of the inner
border of the sole.
In the Ass and Mule, the hoof is always naiTower, laterally, than that of the
horse ; the wall is always higher and thicker, the sole more concave, the frog
smaller and deeper seated at the bottom of the excavation formed by the sole,
and the horn is much more hard and resisting.^
(The angle of the wall of the hoof in front varies from 50° to 56°, though
usually eiToneously stated to be 45°. The inner face of the wall— at the middle
of the toe, and in a line with the frog-stay — frequently shows a more or less salient
and conical prominence — base towards the lower margin of the wall — which
corresponds to a vertical depre'fesion in the os pedis. Vallada imagined that this
projection served to unite the wall and sole more closely, but it is far more pro-
bable that its function is the same as that of the frog-stay— to maintain the
position of the os pedis, and prevent its rotation within the hoof. I have, there-
fore, named it the " toe-stay.")
Structure of the Hoof-horn.— The structure of the horn has been the
subject of a great number of researches ; Gurlt, Delafond, Bouley, Gourdon, and
Ercolani ^ have given descriptions of it, and we have also some details to add to
the labours of these authorities.
The hortiy substance constituting the hoof of Solipeds, has a fibrous appearance ;
this is most conspicuous in the wall, less apparent in the frog and deeper portions
of the sole, but impossible to distinguish in the superficial layer of the latter,
where the disintegration continually taking place separates the horn in scaly
fragments of varying thickness and extent. The consistence of the horn is
always less in the frog than in the sole and wall. Its tint is in some hoofs black,
in others white, and in others, again, a mixture of these two. The inner face of
the wall, however, is never black ; and when the lower part of the limb is partially
' The third phalanx of the anterior limb of these animals has the same shape as in the
Horse, notwithstanding the lateral flattening of the hoof covering it.
* (The researches of Professor Kawitsch must be omitted. They will be found in vol.
xxviii of the Marfazin fur Thierheilliiinde, and also in a little brorhure entitled Ueber den
feineren Ban und das Wnchdhum des Hufhorns— Berlin : 1863. Leisering must likewise be
referred to. My own researoht s are published in the Veterinarian for 1871.)
918 THt: SENSORY APPARATUSES.
or wholly white, we may be sure that all the thickness of the wall will either be
white at corresponding points in the former, or entirely so in the latter.
Except in the keraphyllons tissue, the minute structure of the hoof-horn
always exhibits the same characters. Everywhere it is perforated by cylindrical
canals, the upper end of which is funnel-shaped, and these contain the papillae of the
matrix, whether they belong to the coronary cushion or velvety tissue ; while the
lower end reaches the inferior border of the wall, or lower face of the sole and
frog, according to their situation. It is rare to find them in the horny laminae.
All are rectilinear, with the exception of those of the frog, which are somewhat
flexuous ; and all have the same oblique direction downward and forward,
following the inclination of the anterior portion of the wall. They are, therefore,
almost exactly parallel to each other, not only in the same, but in two different
regions. Their diameter varies considerably, though the smallest are always those
of the periople ; in the wall, they are smaller as they approach the outer surface.
These tubes are not mere canals hollowed out of the horny substance ; on the
contrary, they have very thick walls which are formed of numerous concentric
layers, one within the other, and the horny tissue connecting them has not the
same apparent stratiform disposition. Filled by the papillte of the keratogenous
membrane at their superior extremity, these canals are not empty for the remainder
of their extent : but contain a particular white substance, which is so opaque
that it appears of a fine black hue when examined as a transparency in the micro-
scope. This matter is not deposited in a uniform manner in the canals, but
irregularly, looking like a knotted cord or a necklet of beads ; and where it does
exist, it does not always exactly fill the calibre of the tube, an interval being
observed between the inner face of the latter and the intra-tubular deposit.
Sometimes it is seen outside the canals, among the concentric lamellae, and even
in the horny intertubular substance
If we are desirous of completing our knowledge of the minute organization
of the hoof -horn by studying the anatomical elements constituting it, we shall find
that it is formed of epithelial cells belonging to the kind most widespread in
the economy — pavement epithelium. These horn epithelial cells are very thin,
pale, polygonal, and generally oblong, have sharply defined borders and finely
granular faces, sometimes showing a nucleus containing a single or multiple
nucleolus. The nuclei sometimes occupy the centre, at other times another part
of the cells — even their margins ; and they also contain pigment-granules more
or less coloured and numerous. Acetic acid acts very slowly on them, and is
limited to making them more transparent. Potassium and soda at first softens,
then distends them, causing their granulated aspect to disappear, and rounding
their contours ; afterwards, they become quite diaphanous, and finish by being
completely dissolved
Examined in their reciprocal relations, these epithelial cells are seen not to
be agglomerated comfusedly together, but are, on the contrary, disposed in a
regular manner, forming a real framework that wonderfully concurs in assuring
solidity and flexibility. In the walls of the tubes we see them arranged
horizontally around the canal, and stratified from within to without, so as to
form successive concentric layers. In the intertubular horn they are disposed
differently, their stratification being no longer parallel to the direction of the
tubes, but perpendicular to it, and piled upon each other in the intervals
separating the latter. This change of direction does not occur suddenly ; at
the limits of the tubes epithelial cells are seen lying obliquely.
THE APPENDAGES OF THE SKIN.
919
In a transverse section of the wall, there are observed around the tubes, in
the intertubular substance, as well as in the horny laminae, small irregularly
elliptical spaces containing a solid denticulated mass of a brownish tint, which is
easily stained with carmine. These bodies are more elongated in the inter-
tubular substance than in the walls of the tubes, and have a certain resemblance
to the cartilaginous capsules, but especially to the bone cavities filled by their
contents.
Independently of the hard, dry, and flattened cells, there is found an opaque
substance that partly fills the tubes, and which is also sometimes met with in
their walls. This material does not differ from the last in its nature ; it is also
formed, as has been asserted by Gourdon and Ercolani, of irregular granular
cells which are stained by the carminate of • ammonia.
Figment-corpuscles are found in the substance of the coloured horn, and are
disposed singly, or in small masses, in the epithelial cells of the inter-tubular
Fig. 501.
HORN-CELLS FROM THE SOLE
OF THE HOOF.
a, Young cells from the upper
surface of the sole; b, cells
from the lower surface, or
dead horn of the sole.
CONSTITUENT ELEMENTS
OF THE WALL.
a, Horn-cells ; 6, horn-
fibre from the hoof of a
new-born foal, showing
the vertical disposition
of the cells.
substance. The presence of these corpuscles has been denied, and the coloration
has been attributed to a greater condensation, at certain points, of the epithelial
elements. Fine pigment-granules are disseminated in the cells, but it is evident
that beyond these there are at different points pigment-corpuscles ; for, after
treating a section of coloured horn with soda, the epithelial elements are distended,
become pale, and disappear, leaving, however, here and there, masses of black
granulations. These pigmentary corpuscles are absent in white horn.
Development of the Hoof. — The hoof being a dependency of the epidermis,
is developed like it — that is, by the incessant formation of cells in the layer that
corresponds to the stratum mucosum. The velvety tissue forms the sole and
frog ; the perioplic ring the periople, and the coronary cushion the wall. In
these different parts, the epithelial cells multiply, and become flattened in layers
parallel to the surface that secretes them, and in proportion as they recede from
920 THE SENSORY APPARATUSES.
that surface ; so that the wall grows from its superior to its inferior border, and
the other two parts of the hoof from their internal to their external face.
The villi of the coronary cushion and the velvety tissue are the organs
around which the epithelial lamellae are grouped, and their presence determines
the tubular structure of the horn ; their function is completed by the exhalation
of a particular fluid that maintains the flexibility of the hoof, and, probably,
by the development on their surface of the irregular cells which cluster in the
interior of the tubes.
The laminal tissue, in a normal condition, does not concur to any extent in
the development of the wall. The cells covering it are multiplied in describing
a downward and forward movement ; and though they are certainly applied to
the inner face of the wall, yet they do not constitute the horny lamiuis. The
latter are formed on the coronary cushion, at the commencement of the vascular
laminae, and they descend with the wall in gliding along the surface of the layer
of cells separating them from the latter ; this downward movement is facilitated
by the multiplication, in the same sense, of these cells. This opinion as to
the function of the vascular laminae is based on comparative anatomy, on the
presence of some longitudinal tubes in the horny laminae, and on pathological
observations.
When the podophyllous tissue is inflamed — whether or not it be exposed — its
latent activity is quickly manifested, and it rapidly throws out a large quantity
of hard consistent horn, traversed by tubes which, according to Gourdon, are
directed obliquely backwards. These tubes are more irregular than those of the
normal wall, are disposed in parallel series, and are formed around the villo-
papillae developed on the free border of the laminae. In this horn, produced by
the vascular laminae only, there are never observed between these latter the
horny plates of cells — sharp and distinct in the midst of the other cells, as in
those of the wall formed by the coronary cushion.
The horn thrown out on the surface of the podophyllae, immediately after
the removal of a fragment of the wall, is not a definitive horn, but must
be replaced by that from the coronet. This substitution is complete ; as a
microscopical examination proves that the wall which descends from the cushion,
and is furnished with horny laminas, passes beneath the provisional wall, and
glides downward — by the combined action already mentioned — over the surface
of the soft cells of the vascular laminae. As soon as the latter are covered by
the proper wall, their marginal papillae become atrophied, and they again assume
the limited function pertaining to their physiological condition.
(The description of the disposition of the epithehal cells given by Chauveau
does not quite coincide with my own observations. As he correctly states, these
cells are formed in planes parallel with the surface that secretes them ; conse-
quently, around the papillae they are more or less vertical, while between them they
are horizontal. The walls of the tubes, or fibres, are therefore composed of cells
disposed in a vertical manner ; while in the inter-fibrous horny matter they
are arranged in the opposite direction. The loose nodulated contents of the
tube is composed of cells thrown off from the termination of the papilla, and
corresponds to the pith of feathers. The soft cells interposed between the
vascular and horny laminas are carried down to the lower margin of the wall,
where — with the elastic horn secreted by the papillae which terminate the former —
they constitute the peculiar light-coloured band, or " white line," which marks
the junction of the sole with the wall (Fig. 499, g). This intermediate band of
THE APPENDAGES OF THE SKIN. 921
soft flexible horn at this point obviates tearing of the sole from the wall, and
fracture of the former. The cells of the horny laminae are more or less fusiform.
The beautiful lateral leaflets on the sides of the horny laminte — corresponding
to those on the vascular leaves — were observed by me in 1858 ; in 1862 they
were described by Rawitsch and Ercolani, and, at a later period, by Colin of
Alfort and Leisering of Dresden. They are very conspicuous in a well-prepared
section — Fig. 496, c", c", d".
It should be observed that the growth of the wall of the hoof is indefinite,
but that the sole and frog, after attaining a certain thickness, exfoliate. For
complete details as to the physiology of the Horse's foot, the student is referred
to the Veterinarian for 1871.
It may here be noted that hairs and horn-tissue contain a substance named
keratin, which is remarkable for the large proportion of sulphui' existing in it in
a loose or free state.)
2. The Claws of Rumikants and Pachyderms.
In the Ox, Sheep, and Pig, the plantar cushion covers the bulb of the heel of each digit,
wliere it furms a convex mass ; it extends to the insertion of the deep flexor tendons of the
phalanges, in becoming triangular in shape, and thinner.
In the Camel, the foot rests on the ground by the lower face of the two last phalanges.
These are protected by a double elastic cushion, but covered behind by a single horny sandal.
Tlie third phalanx is continued in a short and very convex claw, resembling somewhat a Dog's
claw.
The keratogenous membrane has the same regions as in the Horse. The periople is separated
from the coronary cushion by a well-marked groove, and has very large papillae. The parietal
coronary cushion is wide and flat, of a brownish tint in its upper moiety, white iuferiorly ; it
blends behind with the velvety tissue of the plantar cushion, and ends in a point inwardly.
The papillae covering it are smaller than those of the periople and velvety tissue. The laminae
of the podophyllous tissue are nearer each other, and proportionately wider than in Solipeds;
they are furnished with somewhat atrophied laminellse.
The liorny envelope enclosing the extremity of the digits of the Ox, Sheep, and Pig,
is a kind of copula, having almost the form of the third phalanx ; it is usually named the claw.
The claw of the Ox has an outer face resembling the wall of the Horse's hoof, and an inner
face which is slightly concave, and marked by undulating grooves ; owing to this concavity
the two claws of each foot only touch at the extremities of their adjacent faces. The plantar
region of the claw is slightly depressed, and but little developed ; it is chiefly made up of the
plantar cushion, which is covered by a thin layer of supple tubular horn. On the interior of
the claw is seen a wide shallow cutigeral cavity, perforated by very fine openings, and laminae
thinner and more numerous than in the Horse's hoof. The tubes of the claw-horn are very
small, being surpassed in diameter by those of the periople and sole.
Above and behind each claw are two little rudimentary horny capsules, which are named
ergots. They are absent in the Camel. (Each ergot contains a small bone, which is not
attached to the skeleton in Ruminants. In the Pig, these rudimentary claws are larger, and
are connected with the bones of the leg. In this animal the horn of the claws is altogether
thinner, softer, and less resisting than in Solipeds. The ergot is the representative of those
digits which are apparently absent in the solid and cloven foot.)
3. The Claws of Caenivora.
In these animals, the third phalanx of the digits is enveloped in a conical horny sheath
that curves downwards like the bone itself. This covering is designated the claw, or nail, and
off'ers somewhat the same organization as the horns of Ruminants ; it is developed, and grows
in the same manner, as the hoof of Solipeds, its matrix being a prolongation of the corium
which extends over the third phalanx, after dipping into the circular furrow at the base of that
bone.
Placed at the extremity of the digital region, the claw in these animals is not utilized in
locomotion, as the foot does not rest on the ground by the extremities of the digits, but by the
whole plantar surface. Therefore it is, that we find on this face a kind of epidermic sandal
covering five fibro-adipose tubercles— four small ones placed along the four principal digits
922 TEE SENSORY APPARATUSES.
(the fifth or thumb not being sufficiently developed to reach the ground), and a large central
one, circumscribed in front by the others. This arrangement diffuses the pressure caused
by the weight of the body (and, doubtless, ameliorates the concussion arising from the
exertions these animals make, as well as ensures their footsteps being noiseless when
approaching their prey).
In the Cat, the claws are very sharp and retractile ; being capable of erection and depression
in the interdigital spaces, by means of a small yellow elastic ligament passing from the second
to the third phalanx. This animal's claws constitute its most powerful weapon of attack and
defence.
In the Rabbit, the claws enable it to burrow in the ground : and the Dog can also employ
them in this manner.
4. The Frontal Horns.
These are conical horny sheaths, more or less large and curveil, and annulated transversely ;
they are formed by concentric layers of epithelial cells and some pigment-corpuscles. The
horns grow in the same manner as the wall of the Horse's hoof. The kerato^enous membrane
covering the core arising from the frontal bone, like that covering the last phalanx of the
Horse, has a papillary coronary portion at the base, and a laminer portion lor the remainder
of its extent. The coronary base fijrms the matrix for the horn.
(The length, direction, and general form of the horns varies in Ruminants, not only with
regard to species, age, and race, but also sex. The Bull, in the Bovine species, generally has
short, thick, powerful horns; the Cow, long and slender ones; and the Ox, Lirge, long, and
strong ones. Some breeds have no horns at all. It is the same with the Goat species,
though generally the horns in these are long, flattened, and curved backwards and downwards.
With the Ram, the horns are sometimes immense and very powerful, being of a spiral form.
They are usually less, or altogether absent, in the Ewe. In the Bovine species, the transverse
rings on the horns serve to indicate the age, the first appearing after two years.)
5. The Chestnuts.
This name is given to a little horny (oval or round) plate found, in the Horse, on the inner
face of the forearm — in the lower third of the region, and at the upper extremity of the inner
face of the metatarsal bone. It is composed of a mass of epithelial cells, arranged in tubes
like the horn of the hoof. In Solipeds, the chestnut is the representative of tlie thumb.'
That on the posterior limbs is absent in the Ass ; in the Mule it is very small.
(In fine-bred Horses, this horny production is much less developed than in the coarser
breeds. It is always smaller in the hind limbs.
6. The Ergots.
In the hind and fore legs, we also find a similar, but smaller corneous mass, growing from
the skin of the fetlock, and named the ergot. Like the chestnut, it bears the same relative
development in fine and coarse-bred horses.)
CHAPTER II.
APPARATUS OP TASTE.
The sense of taste permits the appreciation of savours, or the sapid properties of
bodies.
Two nerves — the chorda tympani and the lingual branch of the ninth pair —
appear at present to be the only sensory filaments endowed with the exercise of
this function. They ramify in the lingual mucous membrane, which is thus
made the organ of taste. (Three nerves are usually mentioned : 1. The glosso-
(' This is very doubtful, particularly for any member of the class Ungulata ; and from the
fact that in the Rhinoceros and Tapir the second digit is perfectly developed, these epidermic
appendages would be most probably larger in them than in the Horse, if they represented the
pollex and hallux; however, they are altogether absent. Besides, in the anterior limb of
the Horse and Ass they are above the carpus.)
TEE APPARATUS OF TASTE. 923
pharyngeal, distributed to the superior third of the tongue. 2. The lingual
branch of the fifth, distributed to the anterior two-thirds. 3. Filaments from
the chorda tympani.)
The tongue and its investing membrane having been described at p. 400,
their anatomy need not again be referred to ; but we must glance at the organi-
zation of the latter, in considering it as the special apparatus of gustation. This
will necessitate a few words with regard to the free surface of the membrane
which comes into contact with the sapid bodies, and some considerations on the
terminations of the nerves wliich transmit the impressions produced by these
bodies to the brain.
Free Surface of the Lingual Mucous Membrane. — This surface is
studded by a multitude of papillary prolongations, which are nearly all Kmited
to the upper surface of the tongue, to which they give a tufty appearance.
Their form and volume, as mentioned at p. 402, are very variable, according to
their situation : some are microscopic, while others form voluminous caruncles ;
others, again, are long, conical, and fihform ; another variety is round or
depressed, representing a hemispherical tubercle scarcely projected beyond the
general surface, or placed at the bottom of an excavation in the mucous mem-
brane. The latter constitute the circumvallate papillcB {p. circumvalatce, p.
letiticulares), and are considered the true organs of gustation ; the others are
the fungiform {p. capitat(c) and filiform papilke, which play a mechanical part on
the surface of the tongue.
The circumvallate papiUce in the Horse are two in number, and situated near
the base of the tongue ; their diameter is so considerable that they have been
named the blind or caecal openings (taste-pores). They are the principal, but
not the only organs of taste. Their surface is mammillated, each prominence
corresponding to a single papilla, and being placed below the level of the raised
border encircling them. A deep fossa surrounds them, and limits at their base
a pedicle, which unites them to the other portions of the mucous membrane (see
Figs. 218, 219).
The circumvallate papillae show, around their peduncle, a band of adenoid
tissue ; and in their substance conglomerate glands, as in other parts of the
mucous membrane. They are covered by an epithelium containing some
scattered pigment-granules, the thickness of which is much diminished at the
bottom of the fossa circumscribing them.
Termination of the Gustatory Nerves. — The hypoglossal is the motor
nerve of the tongue, the lingual the nerve of general sensibility, and the chorda
tympani and glosso-pharyngeal the filaments of special sensibility : this appears
to be clearly ascertained from the recent experiments and observations of Lussana,
The lingual branch of the glosso-pharyngeal nerve gives gustatory sensibility to
the posterior third of the tongue ; the chorda tympani to the anterior two-thirds.
The gustatory nerves present— as do all those of the organs of sense — a par-
ticular mode of termination. First indicated by Axel Key, their special manner
of terminating has been carefully studied by Lowen, Schwalbe, and Ranvier.
According to these anatomists, the terminal nerve-tubes lose their medullary
envelope, and, reduced to their axis-cylinder, are thrown out in small oval masses
which might be termed gmtative huJbs (taste-buds, or taste-goblets). Sartoli and
Ranvier have seen some directly enter the epithelium around the bulbs. The
gustatory bulbs are more particularly placed around the pedicles of the calyciform
papillae, in the substance of the epithelium. They are fusiform, their inner
924 THE SENSORY APPARATUSES.
extremity rests on the mucous derma, where they receive the terminal nerve-
tubes ; and their external extremity reaches the epithelial layer, where they are
seen either between two cells, or in an orifice pierced in a single pavement cell.
Each taste-body is composed of a small cluster of cells, which are distinguished
from each other by their character and position ; those occupying the axis of
the organule are the gustative cells ; they are in communication with the nerve-
tubes on one side, and on the other are furnished, for the most part, with rods
which attain the free surface of the tongue. The superficial, or protective cells,
completely envelop the preceding ; they are a kind of epithelial-cells, imbricated
hke the skins of an onion.
These sensitive organs are very numerous in the walls of the circumvallate
papillae, Schwalbe reckoned their number at 35,000 in the papillas of the Ox.
(As many as 1760 have been counted on one circumvallate papilla of the Ox. In
the papillm foliatcB of the Rabbit there are from 14,000 to 15,000 taste-bulbs ; in the
papillae of the Sheep and Pig about 9500). They are not met with in these papillae
only ; Lowen has found them in a large number of fungiform papillae, if not in
all. There is nothing extraordinaiy in this, as the whole surface of the tongue
may, in various degrees, appreciate savours. (Szabadfoldy has described small
oval or pyriform bodies, lying with their long diameter parallel to the surface.
The axis-cylinders of the gustatory nerves enter these, and terminate at their
lower part in a slight swelling ; so that they resemble small Paccinian bodies.)
Differential Characters in the Apparatus of Taste in the other Animals.
In the domestic Manimifera, the differences in this apparatus are found in the number and
variety of forms of the papillae of the tongue.
In Ruminants, the circumvallate papillae are disposed in two rows at the base of the
tongue ; they are smaller than in the Horse, but more numerous— about a dozen being counted
in each row. In the Ox, the filiform papillae are covered by a homy sheath, which renders
them hard to the touch.
In the Camel, there are only seen five or six circumvallate papillae, surrounded by papillsb
foliatae.
The Pig, like Solipede, has only two circumvallate papillae.
In the Dog and Cat, there are two principal papillae, and in their vicinity some smaller
calyces. The filiform papillae are composite, and covered by a thick homy layer. Between
them, regularly placed, are seen the fungiform papillae, which have a brilliant aspect when
looked at obliquely on the surface of the tongue.
In the Rabbit, the gustatory nerve-endings are buried in special papillary organs, situated
on the limits of the upper surface and sides of the tongue, near its base, and named the foliated
organs.
Comparison of the Apparatus of Taste in Man with that of Animals.
This has been already alluded to at p. 432.
CHAPTER III.
APPARATUS OF SMELL.
Preparation. — See directions for the preparation of tiie nasal cavities.
The sense of smell gives the appreciation of odorous emanations to animals.
The active instruments of this sense are the filaments of the first pair of cranial
nerves, which ramify in the upper part of the pituitary membrane ; this becomes.
TEE APPARATUS OF SMELL. 92$
with the cavities it lines, the olfactory apparatus. These parts having been already
referred to at p. 523, we will pass to the other senses.
(The olfactory filaments, passing down from the olfactory ganglion, form a
plexus upon the surface of the pituitary membrane. These filaments, as already
noted (p. 523), differ widely from those of the ordinary cranial nerves, in containing
no white substance of Schwann, but are nucleated and finely granular in structure,
and resemble greatly the gelatinous form of nerve-fibres. Their distribution is
limited to the membrane at the upper third of the nasal septum, the upper part
of the turbinated bones, and the wall of the nasal cavities adjoining the cribriform
^late of the ethmoid bone ; all this surface being covered with an epithelium of
a rich sepia-brown hue. As has also been mentioned, Schultze divides these cells
into two sets — supporting cells and olfactory cells. The first (Fig. 309, a) are
described as terminating externally by truncated flat surfaces, which cannot be
observed to be covered by any membrane separate from the contents of the cell.
These contents appear to consist of protoplasma with a yellow granular aspect
externally, wliile at the lower part an oval nucleus embedded in transparent
protoplasm can be easily seen. At their attached end, these cells become
attenuated, and may be traced inwards for a considerable distance until they
expand into a broad flat sheet or plate, which is never coloured, though it
frequently presents a granular appearance. The processes passing off from this
appear to be continuous with the fibres of the submucous connective tissue.
Towards the margin of the true olfactory region, cells perfectly analogous to
these are met with, the only difference being that they present a well-defined
band or seam at their free extremity, which is surrounded by a circle of ciha
{Fig. 309, c). The cells of the second set (Fig. 309, b) are continuations of the
nerves, and have been named olfactory cells. They are thin, fibrous, or rod-like
bodies, terminating at the same level as the proper epithelial cells, and presenting,
when traced inwards, a series of varicose swellings directly continuous with the
prolongations of deeper-seated nerve-cells. Clarke states that the nerve-fibres,
on reaching the base of the epithelial layer, divide into finer and finer branches,
to form a network with numerous interspersed nuclei, through which they are
probably connected with the olfactory cells (Fig. 309,/). The proper epithelial
cylinders {d, e) are connected at their bases with the septa formed of the connec-
tive tissue belonging to the subepithelial glandular layer.)
CHAPTER IV.
APPARATUS OP VISION.
Designed for the perception of external images rendered visible by the luminous
rays, the sense of sight depends upon the excitability of the optic nerve, the
terminal extremity of which is expanded as a thin membrane at the back of
each eye. The latter is a globular organ lodged in the orbital cavity, attached
to muscles which can move it in various directions, and protected by membranous
and movable screens known as the eyelids, the play of which over the surface of
the eye is facilitated by the lachrymal fluid ; this keeps their inner surface
constantly moist.
61
926 THE SENSORY APPARATUSES.
The essejitml organ of vision, or glohe of the eye, will be first described ; then,
Tinder the designation of the accessory portion of the visual apparatus, we will
notice the receptacle for this globe, or orbital cavity ; the muscles that move the
eye ; the protective membranes, or eyelids ; the membrana tiictitans, or accessory
eyelid ; and, lastly, the lachrymal apparatus, which concurs in the protection of
the ocular globe by the fluid it incessantly throws out upon its surface.
Aeticle I. — The Essential Organ of Vision, or Ocular Globe (Fig. 502).
Preparaticm. — The eye is removed ftom the orbit, and freed from the muscles and fat on it»
posterior surface. Its membranes may then be dissected by means of delicate instruments, and
an idea formed of the structure of the eye. But in order to study the form and relations of the
diflFerent membranes and media of the eye, the globe should be hardened in gradually con-
centrated solutions of chromic acid. When it is so hardened, sections can be made in every
direction, at any distance from the axes, as the shell of the eye does not become deformed. It
it is very easy to study the organization of the eye on such preparations.
The globe, or ball of the eye, is a spherical shell, the interior of which is filled
with fluid or semifluid parts, named the humours or media of the eye. The wall
of this shell {tunica externa) is formed of a continuous, very resisting, colourless
envelope, limpid and translucid in its anterior portion, which constitutes the
transparmt cornea ; and white and opaque for the remainder of its extent. It is
known as the sclerotica.
On the inner face of the sclerotica is a second tunic (tunica media) — the
choroid : a black membrane that lines the posterior face of the retina {tunica
interna), and which, near where the two constituent portions of the external
envelope unite, throws into the interior of the eye an elliptical diaphragm with
a large opening in its centre — the iris. Immediately behind this disc is suspended
or set, like a rose-brilliant, in the centre of a circular zone depending from the
choroid, a biconvex body — the crystcdline lens, one of the media of the eye, and
which divides the interior of its cavity into two compartments : a posterior, very
laro-e, occupied by the vitreous humour ,• and an anterior, itself divided by the
iris into two chambers of unequal dimensions, which contains the aqueous
humour.
Viewed externally, and as a whole, the organ resulting from the union of all
these parts represents a globular body, the anterior region of which corresponds
to the cornea, and is more convex than the other points : a circumstance that
tends to increase the antero-posterior diameter of the eye. But as this ocular
sphere— to which is added, in front, this segment of a smaller sphere— is sensibly
depressed from before to behind, it results that the other two principal diametere
the vertical and transversal — offer about the same dimensions as the first;
Girard has even stated that the latter is the least. With an eye hardened by
chromic acid, we have found that the transverse diameter measured 0-036 m., and
the vertical 0-040 m. (1-417 X 1-575).
Two paragraphs will be devoted to the description of the constituent parts of
the globe — one for the membranes, the other for the ynedia.
The membranes (or tunics) of the eye are of three kinds. Two are exclusively
fibrous, and form the framework ; these are the sclerotica and cornea. The second
is characterized by the association in its interior of the contractile element and
of vessels; and the third is represented by the retina, which is nervous in
structure.
TEE GLOBE OF THE EYE.
927
The Membranes of the Eye.
A. FiBKOus Membranes.
1. The Sclerotic (Fig. 502, h).
The sclerotic is a white, very solid membrane, forming in itself about four-
fifths of the external shell of the eye.
Its external face., in relation with the recti muscles and adipose tissue, receives
posteriorly — though lower than the middle — the insertion of the optic nerve,
Fig. 502.
THEORETICAL SECTION OF THE HORSE S EYE
1, Orbital arch ; 2, lachrymal gland, a, Optic nerve ; 6, sclerotic ; c, choroid ; d, rptina; e, cornea,
/ /, iris ; ^, A, ciliary ligament and processes given off by the choroid, though represented as
isolated from it, in order to indicate their limits more clearly; i, insertion of the ciliary processes
on the capsule of the crystalline lens ; jy crystalline lens ; k, crystalline capsule ; I, vitreous
humour ; ?«, n, anterior and posterior chambers ; o, theoretical indication of the membrane of
the aqueous humour ; p, p, tarsi ; q q, fibrous membrane of the eyelids ; r, elevator muscle of
the upper eyelid; s s, orbicularis muscle of the eyelids; t t, skin of the eyelids; u, conjunctiva;
V, epidermic layer of this membrane covering the cornea ; x, posterior rectus muscle ; y, superior
rectus muscle; z, inferior rectus muscle; w, fibrous sheath of the orbit (or orbital membrane).
which passes through it and the choroid to form the retina. Its internal face is
loosely united to the choroid by vessels, nerves, and connective tissue.
In front, the sclerotic shows an elliptical opening, the greatest diameter of
which is transversal, while its border — bevelled on the inner side — is closely
united to the circumference of the cornea. The substance of this membrane is
traversed by numerous vessels ^and nerves, and is not of the same thickness
throughout ; at the back, around the entrance of the optic nerve, it is thickest ;
it then diminishes gradually towards the larger axis of the organ, and afterwards
increases until it meets the cornea.
Structure. — The sclerotic is wholly composed of fasciculi of connective
928 THE SENSORY APPARATUSES.
tissue interwoven in a very close manner, with some elastic fibres and little masses
of pigment between, especially at its posterior part. Among these fasciculi, a
large number pass from before to behind, and these are intersected by others
which are placed in a circular manner around the globe. The superficial fibres
are continuous with the neurilemma of the optic nerve. (Delicate elastic fibres
are mixed with the others, and in the lacunae of the network are some connective
tissue corpuscles. Between the choroid and sclerotica is loose connective tissue
containing numerous elastic fibres, and branched pigment-cells and non-pigmented
fiat endothelial cells ; this forms the lamina supra-choroidea, or lamina fusca
sclera. The optic nerve, at its entrance into the sclerotic, is very much con-
stricted, and passes through a funnel-shaped, porous mesh of fibrous tissue
named the lamina cribrosa, in the centre of which is a larger opening than the
others, for the passage of the arteria centralis retinae — the pones opticus.)
The arteries of the sclerotic are derived from the anterior and posterior
ciliary arteries ; the veins pass into trunks lying parallel to the ciliary arteries.
Nerves have been found in the sclerotic of the Rabbit, but Leydig could not find
any in the Calf. Lecoq has remarked that in the Ass, particularly when it is
old, the back part of the sclerotic is encrusted with an unmistakable layer of
bony matter. (In Birds, bony plates are found in this region, and some Reptiles
also have them.)
2. The Coknea (Fig. 502, e).
(Preparation. — The cornea should be removed with the sclerotic coat, by immersing the
eye under water, and making a circular incision with scissors about a quarter of an inch from
the margin of the membrane.)
The cornea is a transparent membrane forming the anterior part of the eye,
to the interior of which it allows the light to pass. It closes the anterior opening
of the sclerotic, and thus completes the external envelope or shell of the globe, of
which it forms about a fifth part.
Elliptical— like the opening it closes — the cornea presents : 1. Two faces,
perfectly smooth — one external, convex ; the other internal — concave, forming
the external wall of the anterior chamber, 2. A circumference, bevelled on its
outer edge, and received into a similar bevel around the sclerotic opening, like
the glass of a watch into its case.
Structure. — Three layers enter iuto the composition of the cornea — an
external, internal, and middle.
Middle layer. — This, the proper cornea, is remarkable for its thickness. When
pressed between the fingers, its two faces can be easily made to glide over each
other — a proof that its tissue is disposed in superposed and parallel planes ; it is
indeed possible to decompose the cornea into several lamina and laminellae.
These layers are formed by chondrigenous amorphous matter and connective
fibrillse, which may be disassociated by pyrogallic acid. They are perforated by
more or less irregular openings, and lacunae (spaces of Fontana) occupied by cells,
the prolongations of which anastomose through these slits. The cornea contains
in its substance a regular network of stellate cells, and of migratory cells wander-
ing through the slits and in the lacunae. Lecoq a long time ago remarked that
this layer became opaque when the eye was strongly squeezed, and attributed
this change to expression of the fluid it contained. Dubois has observed the
same opacity in the cornea of the Dog, as a consequence of ansesthesia by chloride
of ethylene.
,THE GLOBE OF TEE EYE. 929
In the normal condition, the transparency of the cornea results from the
equal refraction of the connective tissue fibrillae, and the chondrigenous substance
surrounding them.
The external layer is only the conjunctival epithelium spread over the anterior
face of the cornea. This epithelium in the Horse measures '014 mm. in thick-
ness ; it is stratified, flattened on its surface, but cyhndrical below, where it
rests on the middle layer, and from which it is not separated — as in many other
species of animals — by a proper limitary membrane.
The m?ier layer is a portion of the membrane of the aqueous humour. It is
composed of : 1. A hmitary membrane — the posterior elastic lamina (or nmnbrane
of Descemet) — •002 mm. in thickness, which becomes slightly fibrous at the peri-
phery of the cornea, where it forms, in passing on to the iris, the pectinated
ligament. 2. A lining of polygonal (flat) epithelial cells {endothelium), which
are provided with a large nucleus.
(Some authorities give five layers to the cornea, the first being the corneal
epitheUum, and the second the anterior elastic lamina, or Boivmaii's membrane.
The third consists of a very elastic tissue, perfectly structureless, and possessing
a remarkable tendency to curl up ; but boiling, or the action of acids, does not
render it opaque, as with the other layers. Very fine fibres— ;^&roe arcuatoe — pass
obliquely between it and the next layer — the substantia propria, or cornea proper
— consisting of a large number of strata with branched fusiform cells. The fourth
layer is the posterior elastic lamina ; and the fifth layer consists of the epithelial
cells already mentioned.)
Vessels. — The cornea has Httle vascularity in the adult. The vessels form
loops around its borders, but in the foetus they advance to near its centre.
Nerves. — These were discovered by Schlemm. They penetrate by the peri-
phery of the cornea, and form a network on its surface. According to Kiihne,
Hoyer, Conheim, and Poncet, the ultimate nerve-ramifications pass into the
epithelium on the anterioir surface, and arrive between the most superficial cells.
(The nerves of the eyeball perforate the sclerotic in the region of the
optic nerve, and run between it and the choroid anteriorly. During their
course, they give off branches provided with ganglion cells, to the choroid, and,
finally, they form a ring-like plexus in the ciliary region, termed the orbiculus
gangliosus ciliaris. From this plexus branches go to the ciHary muscle, the iris,
and the cornea. The nerves for the cornea pass first into the sclerotic, and form
a plexus round the margin of the cornea — the plexus cmtmlaris — from which
branches run into the conjunctiva and the cornea. The fibres entering the
substance of the cornea lose their white substance, and run on as naked axis-
cylinders to form networks in the different layers.)
B. Musculo-Vascular Membranes.
3. The Choroid Coat (Figs. 502, c ; 503).
(Preparation. — If the cornea has not yet been removed, it and the sclerotic may now be
dissected away from the choroid or second tunic. The connections between them are closeet
at the circumference of the iris, and at the entrance of the optic and ciliary nerves and arteries.
Fine blnnt-pointed scissors are necessary. A small portion of the sclerotic, near its anterior
circumference, is pinched up and clipped off, the edge of the incision is raised, the circum-
ference of the sclerotic divided, and that tunic removed piecemeal ; a gentle pressure with the
edge of the knife will remove it from its attachments around tlie circumference of the iris.
This dissection is best conducted under water. The ciliary nerves and long ciliary arteries
will be seen passing forward, between the sclerotic and choroid, to the iris.)
930 THE SENSORY APPARATUSES.
The choroid is a thin, dark-coloured membrane spread over the inner face of
the sclerotic, the general conformation of which it repeats. It is divided into
two zones by the ora serrata — a denticulated line which corresponds to the point
where the retina changes its characters.
Posterior or choroid zone. — Throughout the whole of this zone the choroid is
uniformly thin, and corresponds, by its externa} face {superjicial layer, or stratum
of the larger vessels), with the sclerotic ; by its interned face, it is in contact with
the retina, but does not adhere to it. Posteriorly, it shows an opening through
which the optic nerve passes. In front, at the anterior opening of the sclerotic,
it is continuous with the anterior zone.
The inner face (or lai/er — the membrana-chorio-capillaris) of the choroid is
not uniform in colour, being perfectly black in the lower part of the eye ; this
is abruptly terminated at a horizontal line that passes about the eighth or ninth
part of an inch above the optic papilla. From this line, on the segment of a
circle from f to f of an inch in height, it shows most brilliant colours — at first
blue, then an azure-blue, afterwards a brownish blue, and beyond this an intense
black. The bright portion is the tapetum {lucidwn, or tapetum fibrosiim).
The background of the colour is green with bluish shades, that vary slightly
according to the tint of the animal's coat. In black or dark grey Horses, the
tapetum has a deeper blue tint than in others ; and in white Horees it is some-
times yellowish brown.
(This beautiful iridescent layer is composed of numerous undulating bundles
of connective tissue, contained in another layer of fine elastic fibres — the houndary
stratum of the ground substance — placed between the two layers of the choroid.)
Anterior or ciliary zone. — This includes two parts— the " ciliary muscle "
and the " ciliary body." The ciliary muscle {annulus albidus, or musculus
ciliaris) varies in width from one to two millimetres ; its external face adheres
closely to the sclerotic, and its internal is continuous with the ciliary body ; the
posterior border is continuous with the choroid zone, near the canal of Fontana,
The anterior border gives attachment to the greater circumference of the iris.
Its structure and uses will be referred to hereafter.
The ciliary body {corpus ciliare) forms a kind of zone or ring, wider than the
ciliary muscle, and consequently overlaps the latter before and behind. It
extends, on one side, on the inner face of the choroid, and on the other, on the
posterior face of the iris. When the cornea and sclerotic are removed so as to
expose the ciliary muscle, this zone is not seen ; and to discover it, it is necessary
to excise all the posterior part of the shell of the eye by a circular incision, and
evacuate the vitreous humour. We then observe, around the crystalline lens,
a wide, black circle, forming very regular radiating folds, projecting inwards by
their inner extremities, and appearing in the posterior chamber of the eye, after
cutting away the iris ; all abut by these extremities on the circumference of the
lens, which they do not quite reach, although the latter is sustained by, and
" set " in, the centre of the ciliary body.
These radiating folds, named the ciliary processes (Fig. 503, 4), are from
110 to 120 in number in the Horse, and are constituted by little parallel leaves,
wider at their inner than their outer extremity ; the furrows that separate them
posteriorly are partly concealed by the prolongation of the retina that constitutes
the zonula of Zinn. The coronet formed by the ciliary processes is usually
asymmetrical — that is, narrower on the inner than on the outer side.
(The elements of the ciliary muscle run in three directions : 1. Meridional
THE GLOBE OF THE EYE.
931
Fig. 503.
fibres — numerous bundles near the sclerotic, and extending to the choroid,
forming the tensor choroideoe. 2. Radial fibres, next the meridional, radiating
towards the centre of the eye. 3. Circular or equatorial fibres, constituting the
sphincter or ciliary muscle of Miiller.
The ciliary muscle originates on the inner wall of a minute circular canal — •
named the ciliary canal, canal of Schlemm, sinus
circularis iridis, circulus venosus orbicuU ciliaris,
or camd of Fontana, from its discoverer. It is
surmised to be a venous sinus, as it can always
be injected from the arteries.)
Structure. — The choroid zone is composed
of four superposed layers : 1. The external is
formed by a network of connective elastic
fibres, among which are disseminated a great
number of pigment-cells. 2. The second layer is
constituted by a network of large arteries and
veins — the posterior ciliary — and a plexus of
nerves (ciliary) accompanied by ganglia and
some (stellate) pigment-cells. (The veins are
arranged with great regularity in drooping
branches, to form the vasa vorticosa — Fig. 505,
2, 4 ; these are chiefly on the outer surface of
the layer, the arteries ramifying on the inner
surface.) The veins open into the ophthalmic
vein. 3. The third layer, or tunica Ruyschiana,
has for its basis an amorphous substance con-
taining a network of exceedingly fine capillaries
(extending to the ciliary processes). 4. The interned layer is composed of hexagonal
cells, regularly placed one upon the other on the surface of a limitary membrane ;
the cells are provided with a nucleus, and contain pigment-granules which ex-
clusively occupy their anterior moiety. (On the choroid
this cell-formation is single, but on the iris and ciliary
processes there are several layers. A very delicate mem-
brane— membrane of Bruch, or vitreous membrane — has
been described as lining the inner surface of the choroid,
and retaining the pigment in its place ; this membrane
may be seen on the posterior surface of the iris, and it
probably prevents the pigment being removed by the
aqueous humour.) The use of the choroid membrane
is to convert the ocular globe into a veritable darkened
chamber, and to constitute for the retina a calefactory
apparatus. (The pigment absorbs the rays of light which
pass through the retina, and thus prevents their becoming
reflected and confusing the vision. The brilliant metallic-
coloured layer named the tapetum is more particularly
observed in nocturnal animals, and especially in the Carnivora. By reflecting
the rays of light a second time through the retina, it probably enables the animal
to see better at night. It is the cause of the glare perceived in the eyes of
Cats and other creatures, in the dark.)
The ciliary circle is a contractile body, being composed of unstriped musculai
ANTERIOR SEGMENT OF A TRANSVERSE
SECTION OF THE GLOBE OF THE EVE
(human), SEEN FROM WITHIN.
I, Divided edge of the three tunics —
sclerotic, choroid (the dark layer),
and retina ; 2, pupil ; 3, iris (the
uvea) ; 4, ciliary processes ; 5, den-
ticulated anterior border of the
retina.
Fig. 504.
CELLS FROM THE CHOROID
COAT.
a, Pigmentary granules
concealing the nucleus ;
6, the nucleus distinct.
TEE SENSORY APPARATUSES.
fibres which are arranged in orbicular fasciculi, or extend backwards (and are
lost in the choroid, behind the ciliary processes). These fibres are mixed in the
plexus of ciliary nerves, on the track of which small ganglia are formed. By its.
contractions, the ciliary circle (or muscle) plays an important part in accommo-
dating the eye to the perception of objects at different distances. (In Birds, the
muscular fibres are striped.)
The ciliary body ox processes are formed by intercrossed fasciculi of (fibrillated)
connective tissue, vessels, and some unstriped muscular fibres ; their inner
surface is covered by pigment, like that of the choroid zone.
4. The Ieis (Figs. 502,/"; 505, 6).
The iris forms in the interior of the eye — at the anterior opening of the
sclerotic, and in front of the crystalline lens — a veritable diaphragm pierced with
a central opening — the pupil — which contracts or dilates according to the
intensity of the light and the distance of the objects to which the vision i&
Fig. 505.
THE EYE (human) WITH THE SCLEROTIC COAT REMOVED.
1, Sclerotic coat ; 2, veins of the choroid ; 3, ciliary nerves ; 4, veins of the choroid, or vena
vorticosa ; 5, ciliary ligament ; 6, iris.
directed. This diaphragm divides the space between the cornea and the anterior-
face of the lens, and internal extremities of the ciliary processes, into two-
compartments or chambers of unequal size ; the anterior space is the largest, the
posterior having only a virtual existence, as the iris is close to the crystalline lens.
In shape, the iris is elliptical, like the cornea and the sclerotic aperture.
Its anterior face is flat or very slightly convex, and has very marked circular
furrows and radiating striae, noticeable only at the outer circumference of the
membrane. It is diversely coloured, not only according to species, but also in
individuals. In Solipeds, it has nearly always a brownish yellow tint ; though
sometimes it is nearly white or bright grey, when the animal is said to be " wall-
eyed."
The posterior face, in relation with the lens and ciliary processes, is covered
by a very thick layer of pigment named the uvea. Portions of this pigment,
supported by a small pedicle, frequently pass through the pupillary aperture and
appear in the anterior chamber of the eye, where they are known as " soot-balls,"'
or corpora nigra. (There are frequently several of these black spongy masses^
TEE GLOBE OF THE EYE.
•which are generally attached to the upper border of the pupil ; on the lower
margin, when present, they are much smaller. Their colour is a brownish black.
They are sometimes so large as to give rise to apprehensions of injury to the
vision.)
The larger circumference of the iris is attached to the ciliary muscle, which
unites it to the choroid ; it is also related to the margin of the cornea, as well as
to that of the sclerotic opening.
The lesser, or internal circumference, is elliptical, and circumscribes the
pupillary opening.
Structure. — The organization of the iris has been much discussed ; but at
present it is admitted that its principal element is unsfcriped muscular fibre. A
proper membrane and two epithelial layers enter into its formation.
The proper membrane has, for its framework, circular or radiating fasciculi of
wavy connective tissue, with pigment-
•cells. Between the fasciculi are placed f'g- 5^^-
the unstriped fibres ; these are disposed
in a circular manner around the pupil
to constitute the pupiUary sphincter, and
■others radiate from the lesser circum-
ference towards the ciliary ligament to
form the dilator of the pupil. Very fine
radiating vessels are disseminated among
these fibres, and pass to the anterior
ciliary trunks. The nerves supplied to
the iris are from the ophthalmic gang-
lion— which has afferent nerves from
the ophthalmic nerve of Willis — the
common oculo-motor nerve, and the
■sympathetic. These nerves regulate
the reflex movements of contraction
and dilatation of the pupil.
(Behind the proper membrane has
teen described a clear, homogeneous one,
■composed of dense elastic substance.)
The anterior epithelial layer is composed of the polygonal cells of the aqueous-
humour membrane, already described as existing on the posterior surface of the
•cornea.
The posterior epithelial layer, or urea, is constituted by pigment-cells analogous
to those of the choroid, but less regular in shape. (This pigmentary stratum —
or pars iridica retincB — in addition to the cells, has a fine covering — the limitans
iridis — the continuation of the limitans interna retince.)
In the foetus, the pupil is closed by a very thin transparent membrane — the
membrana pupillaris. (It is identical with the anterior layer of the capsule of
the crystalline lens.)
^ C. Nerve-Membrane.
5. The Retina (Figs. 502, d; 507 ; 508).
(Preparation. — The choroid must be removed under water by means of forceps and scissors,
after the lens and vitreous humour have been evacuated. A good view of the retina is to be had
hy looking through the vitreous humour, after the lens and iris have been excised from an eye.)
MUSCPLAR STRUCTURE OF THE IRIS OF A
WHITE RABBIT.
Sphincter of the pupil ; 6, b, radiating fasciculi
of dilator muscle ; c, c, connective tissue, with
its corpuscles.
984 TEE SENSORY APPARATUSES.
The retina, the essential portion of the eye — considered as the terminal
expansion of the optic nerve — extends over the internal face of the choroid,
from which it is easily separated, and lies between that membrane and the
vitreous humour. On arriving at the cihary body, it is exactly moulded on
the radiating folds of its posterior face, and with them is prolonged to the
circumference of the crystalline lens, on the capsule of which it appears to
become lost, after being closely united to it. It also adheres so firmly to the
ciliary processes that, in the fresh eye, it is impossible to detach it. When the
eye has been kept some time, however, the two are easily separated ; the cornea
is removed with a portion of the sclerotic ; then, dividing the iris into several
pieces by diverging incisions, each is turned outwards by a slight traction that
ruptures the ciliary zone and the choroid. The retina, being thus divested of
the parts which cover it anteriorly, is seen to form around the lens a kind of
Elizabethan ruff, dovetailing with the ciliary processes. This plaited collar ha&
been named the zonula of Zi?in {zonula ciliaris, and ora serrafa). This zonula —
the origin of which has been so much discussed — probably belongs to the vitreous
humour.
At the point where the optic nerve enters the eye, there is found on the
retina a small oval elevation, the larger axis of which is about ^ inch ; this little
prominence is the optic papilla, or punctum ccecum {papilla conica). From its
centre emerge the vessels of the retina.
At some distance above the punctum cmcum — on the antero-posterior axis of
the eye — is the yellow spot {macula lutea), in the centre of which is an oval
depression — ila.Q fovea centralis. This region is the most sensitive part of the retina.
Structuee. — The retina is the most important of the three tunics of the
eye, and it is also the thinnest and most delicate. It forms a soft, pulpy,
transparent expansion when quite fresh, but becomes white and opalescent soon
after death. Boll has discovered that, during life, the retina becomes purple
in the dark, but regains its normal tint when again exposed to light. This
coloration resides in the inner segment of the rod portion. Kiihne has observed
that the modification in the retinal purple also occurs when the eye is extirpated.
The author has obtained permanent pictures of luminous objects on the retina in
treating it with a 5 per cent, solution of alum. The retina-red is regenerated at the
expense of the oil drops between the pigmentary layer and the retina. Capranica
studied the chemical and spectroscopic characters of these drops in 1876-77.
The retina is composed of connective tissue and nerve-elements, which are
arranged to form nine or ten superposed layers.
Connective Tissue. — This is very delicate and nucleated, and forms two
thin layers, named the external and internal limitary memhranes ; these are
connected by radiating fibres which pass through the nerve-elements, and
anastomose very closely in the molecular layer.
Nerve-elements. — These are distributed in seven layers, which present
the following characters : —
1. Layer of rods and cones (Fig. 507, 1). — This is also termed the memhrana
JacoU {hacillary or columnar layer). It is situated between the inner face of
the choroid and the external limitary membrane.
Rods and cones, regularly mixed, make up its structure. Each of these
comprises two portions or segments (separated by a bright transverse line). The
outer segment (or shaft) is brilliant and refractive, and consists of a small stalk
terminating in a point for the cones : with a shorter stalk than the inner seyment
THE GLOBE OF THE EYE.
985
2. External granular
Fig. 507.
between the external
Fig. 508.
for the latter, and equal in length to this segment for the rods. The inner seg-
ment is a small granular shaft for the rods, and an enlargement, the base of
which is towards the centre of the eye for the cones. The elements of this layer
quickly alter after death
layer (2). — This is comprised
limitary and the intermedi-
ate membrane. It is formed
by the granules of the cones
and those of the rods — small
cells with an oval nucleus
{vision cells), furnished with
an external prolongation
that joins them to the base
of the cones and rods, and
an external varicose prolon-
gation which often enlarges
on arriving at the inter-
mediate layer.
3. Intermediate lager
(3). — This is very thin, and
composed of flexuous fi-
brillte, which are connected
with the adjoining elements.
4. Inner granular layer
(4). — In this we find cells,
the membrane of which is
in immediate contact with
the nucleus. These cells
have minute prolongments
analogous to those of the
external granular layer,
which connect them with
the surrounding layers,
5. Molecular layer (5).
layer (the grey vesicular) presents a granulous aspect ;
in its mass, the connective tissue forms a close mesh,
in the midst ot which are seen fine fibrillae passing in
every direction.
6. Ganglionic layer (6). — This is composed of a single
stratum of ramifying nerve-cells, the prolongations of
which pass into the molecular layer, where they join the
filaments of the next layer.
7. Layer of the optic-nerve fibres (7).— The fibres
(ultimate fibrils) of the optic nerve, in passing through the sclerotic and choroid,
anastomose with each other, and arrange themselves in a cone shape, the apex
of which corresponds with the papilla conica ; at this point they suddenly spread
out in every direction, between the ganglionic layer and the internal limitary
membrane.
To sum up, the retina comprises the following layers, reckoning from before
to behind : 1. Internal limitary membrane. 2. Layer of optic-nerve fibres. 3.
VERTICAL SECTION OF RKTINA.
I, Bacillar layer; 2, outer grau-
ular layer; 3, intermediate
fibrous layer; 4, inner granular
layer; 5, finely granular grey
layer; 6, layer of nerve-cells;
7, layer of fibres of optic nerve;
8, limitary membrane.
-One of the thickest, this
DIAGRAM OF THE STRUC-
TURE OF THE RETINA.
p, Pigment -cell of the
retina connected with a
rod ; n, cone seated on
the raembrana limitans
externa, the inner seg-
ment containing a cone
ellipsoid, and a needle ;
inf, proper fibre con-
necting rod and cone
with one of the cells of
the membrana fenestra,
the cells of which are
in communication with
the membrana limitans
interna, mli, by means
of a thick radial fibre
with an oval nucleus
attached ; gg, multi-
polar ganglion of nerve-
elements ; op, optic
fibrilla; gri, supposed
connectionof the nucleus
with prolongation of a
ganglion-cell.
936 TEE SENSORY APPARATUSES
Layer of ganglion-cells. 4. Molecular layer. 5. Inner granular layer. 6. In-
termediate layer. 7. Outer granular layer. 8. Outer limitary membrane. 9.
Layer of rods and cones. 10. Pigmentary layer of the choroid, if this be attached
to the retina, as Schultze proposes.
It is to be remarked, that at the ora serrata all the nerve-elements of the
retina disappear.
Pigment Layer. — This is represented by a row of cells spread on the posterior
face of the rod-and-cone stratum. These cells have
F'g- 509. many small prolongations, which are insinuated be-
tween the rods and cones, and the elongated or
rounded pigmentary granules of a more or less dark
colour.
(At the papilla conica, all the other elements than
the nerve-fibres are entirely absent ; hence this is
presumed to be a " blind spot.")
Blood-vessels. — The retina possesses a particular
vascular distribution. The arteria centralis retinae,^
with its vein, enters the optic nerve at a short
distance from the globe, and with it passes into the
eye ; they traverse the papilla, and immediately
CAPILLARIES IN THE VASCULAR ,•{.,., ^ i i r i • i • j- x J
LAYER OF THE RETINA. dividc Hito two branchcs, one or which is directed
upwards, the other do\vnwards. Close and fine
anastomoses unite the vessels of the retina with the ciliary vessels at the back
of the sclerotic.
The distribution of the vessels in the different strata of the retina is variable.
They are only found in the layer of nerve-fibres, in the retina of the Horse, Rabbit,
and Guinea-pig ; but they are seen in all the layers — that of the rods excepted —
of the retina of the other animals.
THE MEDIA OP THE EYE.
1. The Crystalline Lens (Fig. 502,/).
The lens, as its name implies, is a (solid) transparent body, sustained at the
smaller circumference of the zone formed by the ciliary processes (behind the
pupil, and partially embedded in the vitreous humour). It is biconvex in shape,
and flatter on its anterior than its posterior surface. We have measured the lens
of the Horse's eye, and find the following dimensions : vertical diameter ^^
and transverse diameter -y^ of an inch. The posterior face is evidently more
convex than the anterior, for we found the transverse diameter of the last to be
^, and that of the first -^ of an inch.
Structure. — The lens is enveloped in a transparent membrane — the capsule
— which is not adherent to it. Its thickness is uniform in the Horse, and its
tissue is slightly striated transversely ; its internal face is lined by a layer of
pavement epithelium. (It is a homogeneous elastic membrane, partly of cuticular
formation by epithelial cells, and partly an altered product of the embryonic
connective tissue.)
The proper tissue {substantia propria) of the lens is disposed in concentric
layers, the outer of which are almost fluid (gelatinous), but their consistence
gradually increases towards the centre. These layers are composed of hexagonal
TEE MEDIA OF THE EYE. 937
prismatic bands (the fibres of the lens, themselves extremely long epithelial cells)
denticulated on their borders, and provided with one or more nuclei.
The epithelium on the inner face of the capsule becomes dissolved soon after
death, and forms the liquor Morgagni^ which is, consequently, nothing more
than a, post-mortem product.
The lens has neither vessels nor nerves.
In the foetus, it receives the central artery of the retina— a branch which
passes forwards through the vitreous humour and enters the posterior face of the
lens ; but this vessel disappears a long time before birth.
(It should be noted that the fibres of the lens pass in a meridional direction,
but none go beyond the entire half of the lens — as the nearer a fibre starts
from the anterior pole, the further it is removed from the posterior pole at its
termination.
To examine the structure of the lens, it is best to boil it, or to immerse it in
alcohol ,or very diluted nitric acid, which renders it hard and opaque. It is then
found to be divided into three equal parts by three lines, which radiate from the
centre to within one-third of the circumference ; so that each of these portions
is composed of hundreds of concentric layers, arranged within one another, like
the coats of an onion. If any single layer is examined with the microscope, it
is found to be made up of these parallel fibres, which measure about :5^oW of
an inch in thickness, and are united to each other by finely serrated or scalloped
borders that dovetail in the most beautiful manner.
The lens is nourished by means of the extremely delicate layer of nucleated
cells on its surface, which absort nutriment from the capsule.
The use of the lens is to bring the rays of light to a focus upon the retina,
they being greatly refracted in passing through it.)
2. The Vitreous Humoue (Fig. 502, 1).
The vitreous hody, or humour, occupies all the cavity of the eye behind the
lens (about two-thirds of the interior of the eye).
It appears to be a colourless, transparent jelly, much more fluid than the
lens, and is formed of a fluid amorphous substance contained between layers of
extremely delicate connective tissue, anastomosing with each other, in every
direction. On the surface these layers join a thicker one, contiguous to a thinner
that envelops the whole mass, and named the hyaloid membrane. Beneath this
membrane, in front, are bundles of connective tissue which gradually diverge
widely forward, and become attached to the front and posterior circumference
of the capsule of the lens, to constitute the zonula of Zinn,
(This humour also contains round cells like leucocytes, and stellate and
spindle-shaped cells, sometimes showing vacuoles in their protoplasm. The
spaces in the humour communicate freely, and are rendered apparent by freezing
the eye or steeping it in chromic acid, when it is found that the humour is inter-
sected by a large number of delicate partitions, with a cylindrical space — canalis
hyaloideus, or the canal of Cloquet — in the axis, for the passage of the central
artery in the foetus. The menibrane is firmer on the surface than elsewhere, so
that it serves as a capsule for the humour, and suffices to keep it in shape after
the outer envelopes of the eye are removed. As mentioned, the lens is maintained
in situ by the zonula of Zinn.
This humour concurs in refracting the rays of light.)
THE SENSORY APPARATUSES.
3. The Aqueous Humour.
This is a liquid that owes its name to its great fluidity ; it is contained m
the anterior and posterior chambera of the eye, in front of the lens. It is
secreted by a particular membrane — the membrane of the aqueous humour, or
membrane of Descemet or Demours — an extremely thin serous layer, easily dis-
tinguished on the posterior face of the cornea, and admitted to exist on the two
surfaces of the iris, the ciliary processes, and anterior face of the capsule of the
lens (Fig. 502, o), where it is reduced to epithelium only.
Schwalbe has observed the glandular appearance of the epithelium on the
ciliary processes ; and Ehrlich has shown that when flourescene is injected beneath
the skin, it is eliminated by the anterior chamber of the eye when the aqueous
humour is evacuated by puncture of the cornea. From these facts, conclusions
have been drawn as to the analogy between this epithelium and a gland. Tliis
gland is completely innervated (Schaler and Uthof, Nicati) ; the Gasserian
ganglion is its moderator centre.
(The eyeball has no proper lymph-vessels, but it has numerous small inter-
communicating spaces which are related to larger spaces — such as Schlemm's
canal, the canal of Petit, the canalis hi/aloideus, Tenon's space on the dural
sheath of the optic nerve ; and this arrangement allows the lymphatic system
of the eye to be divided into two regions — an anterior and a posterior.
The chief function of the aqueous humour appears to be to maintain the
convexity of the cornea, and to facilitate the movements of the iris and lens ; as
well as to assist, to some extent, in refracting the light that passes through it
to the lens and retina. The rapidity with which this fluid can be regenerated
is very striking ; absorption also takes place very rapidly in the anterior chamber
of the eye. The frequency of adhesions between the iris and lens, after attacks
of ophthalmia, is accounted for by the minute quantity of this fluid that exists
between them, as, owing to the smallness of the posterior chamber, this is reduced
to a mere film.)
Article II. — Accessory Organs of the Visual Apparatus.
ORBITAL CAVITY.
Preparation. — The ocular cavity is prepared by clearing the temporal fossa of its musc'es
and adipose tissue, and removing the eyelids, also the eye and its muscles.
Situated at the side of the head, at the point corresponding to the union of
the cranium and face, the orbital cavity is circumscribed by a bony margin, in
the formation of which the orbital process, frontal, lachrymal, malar, and a small
portion of the zygomatic process of the temporal bone, concur. Posteriorly,
however, there are no bony walls, and the cavity— in the skeleton— is continuous
with the temporal fossa. But a fibrous membrane completes this cavity in the
domesticated animals, and keeps it distinct from the fossa.
Designated the ocular sheath {ocular membrane, or periorbita), this fibrous
structure is attached, posteriorly, to the border of the orbital hiatus, and
anteriorly to the inner face of the orbit ; being prolonged beyond the external
lip of this osseous rim to form the fibrous membrane of the eyelids. Strong
externally, the ocular sheath is thin where it is in contact with the bones of the
cavity. It is traversed by vessels and nerves, and is composed of a mixture of
THE ACCESSORY ORGANS OF VISION. 939
elastic and inelastic fibres. (Unstriped muscular fibres have also been described
as existing in this orbital periosteum.)
Thus completed, the orbital cavity has the form of a regular hollow cone,
open at its base, and closed at the apex, which corresponds to the orbital hiatus.
In the ordinary position of the head, the opening of this cone is directed
forwards, downwards, and outwards.
Independently of the globe of the eye. the orbital cavity lodges the muscles
that move it, the membrana nictitans, and the lachrymal gland.
(Unstriped muscular fibres have been found in this ocular sheath in Sheep
and other animals, also in Man.)
Muscles of the Globe of the Eye (Fig. 510).
These are seven in number : five termed recti muscles, and distinguished as
posterior, superior, inferior, external, and internal; two named oblique — a large
and small.
{Preparation. — Detach the eyelids from the margin of the orbit, cutting away the lower,
but leaving the upper. Saw through the zygomatic process of the temporal bone, in front of
the temporo-maxillary articulation, also through the temporal process of the malar, and the
base of the orbital process of the frontal bone ; remove the excised piece of bone, and the
temporal fossa and ocular sheath are exposed. Cutting through the latter, the muscles of
the eye are seen disposed in a conical manner around the globe ; dissect away the fat lodged
among them, in order to isolate them.)
L Posterior Rectus or Suspensory Muscle {retractor oculi, retractor
bulbi).— This, muscle completely envelops the extra-cranial portion of the optic
nerve, being a muscular sheath resembling in shape the fibrous lining of the
orbit. Its fibres are disposed longitudinally, arise around the optic foramen, and
are inserted into the posterior part of the external face of the sclerotic. It is
always more or less fasciculated, and may be frequently separated into four
portions — superior, inferior, external, and internal.
In contracting, it draws the globe towards the back of the orbit. The
physiological result of this movement will be noticed hereafter.
2. Superior, Inferior, External, and Internal Recti Muscles. — These
four muscles are placed longitudinally on the preceding, and repeat, on a large
scale, the disposition of its four bundles. As their borders are in contact, they
constitute a fleshy sheath around it, analogous to that which it forms around the
optic nerve. Exactly resembling each other, these four muscles compose so
natural a group, that they may be described together. Each is a fiat band,
formed of parallel fibres, firmly attached by its posterior extremity to the back
of the sheath, and to the interior of the subsphenoidal canal ; anteriorly, it is
inserted by a thin aponeurosis into the sclerotic, at the margin of the cornea.
Isolated from one another, and from the retractor by the mass of fat belonging
to the membrana nictitans, these small muscles are related, externally, to the
ocular sheath.
There is nothing particular to be noted regarding them, their position being'
sufficiently indicated by their names. Their function is to bring the pupillary
opening into contact with the rays of light, by inclining the cornea towards them,
either upwards, downwards, inwards, or outwards ; or into intermediate positions,
which happens when two adjacent muscles — the inferior and external rectus, for
instance — combine their action at the same moment.
940
THE SENSORY APPARATUSES.
3. Great Oblique Muscle (trocMearis, or ohliquus superior oculi). — Lying-
to the side of the internal and superior rectus, and formed, like them, of a fleshy^
band terminated by a thin aponeurosis, this muscle differs from the preceding in
its interrupted course. Arising from the back of the orbit, and passing forward
against the inner wall of that cavity, it reaches a strong fibro-cartilaginous,
pully-like process — a dependency of the aponeurosis of the orbit — attached by
its extremities to the frontal bone, at the base of the orbital process ; it passes
through this loop, and then bends outwards, to insinuate itself below the terminal
extremity of the superior rectus, and become inserted into the sclerotic, between
the latter muscle and the external rectus.
This muscle pivots the eye inwards and upwards in the orbit, carrying the
outer aspect of the globe upwards,
P'g- ^1^' and its lower part outwards ; this
faculty it owes to its reflection in
the cartilaginous loop, as it acts as
if its insertion were at the angle it
forms there.
4. Small Oblique Muscle
{ohliquus inferior oculi). — Much
thicker, though very much shorter
than the preceding, and almost
entirely fleshy, this muscle is placed
in a transverse direction on the
globe of the eye, being nearly
parallel to the reflected portion of
the great oblique. It arises in the
lachrymal fossa, passes outwards,
and terminates in the sclerotic, be-
tween the external and inferior recti
muscles.
It is an antagonist of the great
oblique, pivoting the eye in a con-
trary direction.
It is to be noted that the double
rotatory movement executed by the
oblique muscles is altogether involuntary, and that it is constantly produced when
the animal inclines its head to one side— doubtless to maintain the visual axis
always in identical relations with the same point of the retina. This movement
is well seen in Man when the head is brought round to either shoulder : the eye
then pivots in the orbit in an inverse direction to that to which the head inclines,
so that a mark placed at the upper part of the iris when the head is straight
would occupy the same position after the lateral movement. Simultaneous in
both eyes, this pivoting is executed by certain muscles in each ; the great oblique
for one, the small oblique for the other, according to the direction in which the
head is turned.
(A third, or middle oblique muscle, has been mentioned by Strangeways, as
sometimes, if not always, found between the superior and inferior oblique muscles.
It has been described as arising by a fine tendon from a small depression in
the upper part of the orbital process of the frontal bone, between the origin of
the inferior oblique and the puDey of the superior oblique muscle. This tendon
MUSCLES OF THE EYEBALL (VIEWED FROM ABOVE).
1, Section of orbital process of frontal bone to which
the fibro-cartilaginous pulley, 4, of the superior
oblique muscle, 5, is attached; 2, zygomatic
process of the temporal bone; 3, portion of sphe-
noid bone into which the recti and superior oblique
muscles are implanted ; 6, pathetic! nerve ; 7,
internal rectus ; 8, superior rectus ; 9, levator
palpebrae muscle; 10, external rectus; 11, eye-
ball; 12, upper eyelid; 13, lower eyelid; 14, inner
canthus of eye.
THE ACCESSORY OBGANS OF VISION. 941!
is succeeded by a fusiform fleshy mass, about three lines in diameter and an inch
long, embedded in adipose tissue ; it passes obliquely upwards and outwards on
the external face of the rectus muscle, and terminates in a thin flat tendon which
accompanies the upper belly of the superior oblique for a short distance, and
becomes confounded with the tendon of that muscle as it runs beneath the
superior rectus. It is supposed to be an accessory of the superior oblique, and
to regulate and facilitate the gliding of that muscle through the acute angle
formed by its pulley.)
Protective Organs of the Eye.
1. The Eyelids (Figs. 502, 510).
Preparation. — There is no difiBculty in studying the eyelids. Removing the skin carefully
allows the orbicularis to be seen ; in turning this up, the fibrous layer is found ; and if the
orbital process be removed by means of the saw, the levator palpebrse superioris is discovered
in cutting away the upper part of the ocular sheath. Lastly, on an eye extracted along with
the eyelids, the mode of union of these with the globe will be readily demonstrated.
The surface of the eye is covered and protected in front by two movable
membranous curtains — the eyelids {palpebral) — one superior, the other inferior.
Attached to the circumference of the orbit by their external border, the eye-
lids have a convex external face formed by the skin, and a concave internal face,
moulded on the anterior surface of the eye, and lined by the conjunctiva, which
is reflected above and beiow on the eyeball — the duplicatures constituting the-
superior and the inferior conjunctival {ox palpebral) sinuses.
Each lid has also a free border opposed to that of its fellow, with which it-
unites at an angle by its extremities, so as to form two commissures (or canthi).
This border is shghtly bevelled on the inner side, and shows a series of small
openings — the excretory orifices of the Meibomian glands ; as well as a row of
erect hairs^ — the eyelashes. These wiU be described presently.
When the two lids are closed by the approximation of their free borders, they
completely cover the eye, and form a narrow fissure comparable to a closed
button-hole. When they are separated, they circumscribe an oval space {fissura
palpebrarum), the greater axis of which is directed obliquely downwards, forwards^
and inwards. The upper contour of this space — formed by the free margin of
the superior eyelid — is always more curved than the lower. The superior com-
missure (or canthus) has also been named the temporal angle of the eye. The
nasal angle, constituted by the inferior commissure, is always rounder than the
other ; it lodges the caruncula lacrymalis (in the lachus lachrymalis).
Structure of the Eyelids. — A fibrous plate, terminated towards the free
border of the lid by a small tendinous arch named the tarsus ,• a sphincter muscle —
the orbicularis palpebroe — in contact with the fibrous membrane ; the levator pal-
pebrcB — a muscle partly lodged in the ocular sheath, and terminated anteriorly by
a very thin and wide expansion placed beneath the superior fibrous plate ; a
cutaneous envelope in two layers — an external, the skin, and an internal of
mucous membrane, the conjuncMva, joining at the free border of the lid ; — these
are the elements which enter into the composition of the protective coverings of
the eye.
1. Fibrous Membrane. — Usually thicker in the lower than the upper lid,
this membrane is attached, by its adherent border, to the rim of the orbit, where
942 THE SENSORY APPARATUSES.
it is continuous with the periosteum and the fibrous wall of the ocular sheath.
Its free border is margined by the tarsus.
2. Tarsus. — This is a fibrous lamella that forms a solid frame for the free
border of the lid. It is elongated, narrow at its extremities, thin at its fixed
border — where it is confounded with the fibrous membrane — and channeled on its
inner face by several transverse parallel grooves which lodge the Meibomian
glands. This small fibrous arc regulates the contraction of the orbicularis
muscle, and prevents the lid being drawn into wrinkles ; by the rigidity it bestows
on the eyelids, it allows these to meet — border to border — without puckering,
when the muscle is in action.
3. Orbicular Muscle of the Eyelids (orbicularis palpebrarum, musculm
ciliaris Riolani). — For a description of this muscle, see Myology, p. 279.
4. Elevator Muscle of the Upper Eyelid, or Orbito-palpebralis
{Levator palpebrce superioris). — When the ocular sphincter ceases to contract, the
lower eyelid droops from its own weight ; the upper lid, however, requires some
special muscular agency to raise it, and this it finds in the levator palpebrae.
This is a very thin, narrow, fleshy band, lodged in the ocular sheath with the
other muscles of the eyeball, and is related to the superior rectus, the com-se of
which it follows. On reaching the lachrymal gland, it expands into a wide
aponeurotic membrane that passes between the conjunctiva and the fibrous plate
of the eyelid, and terminates on the tarsus. (Besides ending in the fascia jjalpe-
bralis, some of the fibres — enclosing smooth muscular fibres — pass on to the upper
margin of the tarsus to constitute Miiller's muscle — or palpebralis superior.
Similar smooth fibres in the lower lid, form a palpebralis inferior.)
It will be seen that this muscle is inflected on the eyeball in a pulley-like
manner, and it is owing to this disposition that it has the power of raising the
lid. If the eyeball were not present, the muscle would draw the free margin of
the hd towards the back of the orbit, instead of elevating it.
5. Integuments of the Eyelids. — The different layers enumerated are
comprised between two tegumentary folds— the skin and conjunctiva — which are
continuous at the border of the eyelids. We will examine these, with their
appendages — the eyelashes and Meibomian glands.
a. Skin. — Intimately adhering, by its inner face, to the orbicularis muscle,
this membrane is thin (smooth), and covered with numerous fine short hairs. In
the foetus, it shows at the orbital arch — when the skin everywhere else is nude —
a well-marked semicircle of hairs — ^the eyebrow. Fat is never found beneath it.
b. Conjunctiva. — The conjunctiva, as its name indicates, joins the eyelids to
the eyeball. Very fine and highly vascular, this mucous membrane is a continua-
tion of the skin at the border of the lids, lines the inner face of each of them,
envelopes the anterior portion of the membrana nictitans in a particular fold,
covers the caruncula lachrymalis, and enters the puncta ; it is then reflected, at
the adherent border of the eyelids, on to the eyeball, extending over the sclerotic
and terminal aponem-otic expansion of the recti muscles. On arriving at the
margin of the cornea, it is impossible to trace it further ; though it is represented
by the thin layer of pavement epithelium already described. At the surface of
the lachrymal caruncle, it shows some very fine hair-bulbs. It possesses some
papillae (on the palpebral portion only, the ocular reflection being thinner, and
having none of these nervous processes), and tubular and aggregate glands, as
well as closed follicles. We have found large numbers of the latter, the volume
of which was considerable ; they form a corona around the cornea.
THE ACCESSORY ORGANS OF VISION. 943
c. Eyelashes. — These are two rows of hairs {cilia) implanted in the free
border of the lids, and destined to prevent the entrance of dust and small
particles of foreign matter into the eye. They are much longer, and more
abundant and stronger, in the upper than the lower lid, their presence there
being more necessary, as extraneous particles are most likely to enter the eye when
falHng. But if the eyelashes of the lower lid are few and rudimentary, this is
compensated for by the presence on its surface of some long bristly hairs,
scattered here and there, and exactly like the tentacula of the lips.
Like all hairs, without exception, the eyelashes are flanked at their base by
two or three small sebaceous glands, the duct from which opens into their
follicle.
d. Meibomian glands. — These are little acinous bodies, analogous to sebaceous
glands, which open alternately into a common, and very long excretory canal.
They are lodged in the transverse grooves observed on the inner face of the tarsal
ligaments. The unctuous matter they secrete is thrown out on the free border
of the lids, and enables these to retain the tears more easily within the ocular
cavity. In sick animals, this secretion accumulates at the canthi and base of the
lids. (Each gland consists of a central tube, with a number of openings round
its sides leading to short caecal dilatations. The secretion also facilitates the
movements of the lids.)
6. Vessels and Nerves of the Eyelids. — These membranous curtains
receive their blood, for the most part, by the supra-orbital and lachrymal
arteries, and the orbital branch of the superior dental artery. The terminal
extremities of the three sensitive nerves of the eye, formed by the ophthalmic
branch of the fifth pair and the orbital filaments of the superior maxillary
branch, ramify in them. The anterior auricular nerve causes the orbicularis
muscle to contract. The motor filaments of the levator palpebrse are derived
from the third pair.
(The blood-vessels of the eyelids proceed from those which pass from the
outer and inner angle of the eye ; they form an arch on the inner margin of the
eyelid — the arcus tar sens externus. After supplying the tissues, some of these
vessels anastomose with the arteria ciliaris antica. The ocular conjunctiva has
generally few blood-vessels visible in health ; when inflamed, however, it becomes
intensely red and vascular.
The lymphatics form a dense network in the tarsal conjunctiva ; those in
this membrane in front of the sclerotic and around the margin of the cornea,
probably join the small canals of the latter. The tunica propria of the eyelid
has many lymph-cells, and in some animals — as Ruminants — they form small
lymphoid glands.
The nerves of the conjunctiva form a rich plexus on the margin of the eyelid,
and terminate in small oval enlargements or end knobs — the corpuscles of Krause
— which are more particularly observed beneath the corneal epithelium.)
2. Membrana Nictitans.
This organ, which is also named the third eyelid, winking eyelid, etc., is placed
at the greater (inner) angle of the eye, whence it extends over the eyeball to
reheve it from foreign bodies which may fall upon it.
It has for its framework a fibro-cartilage — reticulated or elastic — irregular
in shape, thick and nearly prismatic at its base, and thin anteriorly, where it is
covered by the conjunctiva ; it is continued, behind, by a strong adipose cushion,
944 THE SENSORY APPARATUSES.
which is insinuated between all the muscles of the eye, and to which it is loosely^
attached. No muscle directly concurs in the movements of this body : they are
entirely mechanical. When the eye is in its usual position, there is only per-
ceived the fold of conjunctiva that terminates it in front ; the remainder is
concealed in the fibrous case of the eye. When, however, the latter is with-
drawn into the orbit by the contraction of its recti muscles, the globe compresses
the fatty cushion belonging to the cartilage ; this cushion, pressing outwards,
pushes the membrana before it, and the latter then entirely conceals the whole
front of the globe. This movement is instantaneous, but it may be momentarily
checked by pressing gently on the eye when the animal retracts it within the orbital
cavity.
The use of the membrana is— as will be seen from the above — to maintain the
healthy condition of the eye, by removing any matters that have escaped the
eyelids ; and what clearly demonstrates this function, is the inverse relation that
always exists between the development of this body, and the facility with which
animals can rub their eyes with their anterior limbs. So it is that, with the-
Horse and Ox, the thoracic limb of which cannot be applied to this purpose^
the membrana is very developed ;' in the Dog, which may use its paw to somfr
extent when it requires to brush its eye, it is smaller ; in the Cat it is still less ;
while in the Monkey and in Mankind, whose hands are perfect, it is rudimentary.
In Tetanus, the membrana nictitans often remains permanently over the eye, in
consequence of the continued contraction of the recti muscles.
(Towards the middle of the outer face of the membrana is a small yellowish-
red, acinous gland — the glandula Harden, firmly bound by a strong fibrous
membrane to the cartilage, and surrounded by adipose tissue ; it secretes a thick
unctuous matter, which escapes by two or three small apertures on the inner face
of the membrana.)
LACHRYMAL APPARATUS.
Preparation. — The lachrymal gland is prepared at the same time as the levator palpebrarum
(see above). To dissect its excretory apparatus, melted tallow should be injected into the
lachrymal canals by the nasal opening of the duct. The lachrymal bone should be chiselled
away, iu order to see the canal ; the nasal portion can be shown in a longitudinal and vertical
section of the head, made outside the median plane.
This apparatus comprises : 1. A gland which secretes the tears. 2. A series
of canals that carry the superfluous fluid to the external orifice of the nasal
cavities.
Lachrymal gland. — This gland, situated between the orbital process and the
upper part of the eyeball — from which it is separated by the superior rectus and
levator palpebrae muscles — is convex on its upper face, and concave inferiorly, in
accordance with the parts it adjoins. Only little developed, it is formed of very
small granules, united by fine connective tissue ; from these arise minute radicles,
the junction of which forms a certain number of very narrow ducts, that open
on the inner face of the temporal (outer) angle of the eyelids. These are the
hygrophthalmic canals.
The lachrymal gland secretes the tears that lubrify the anterior surface of
the eye. This fluid escapes upon the organ at the temporal angle of the lids,
and is carried between them and the eyeball towards the nasal angle. Its>
secretion is incessant, but it js increased by anything that irritates the con-
junctiva, and its character may even change under the same influences.
THE ACCESSORY ORGANS OF VISION. 945
The lachrymal gland belongs to the category of conglomerate glands ; con-
sequently, it IS analogous to the salivary glands. (The gland is maintained in
situ by a capsule formed by the fascia of the orbit.)
The hygrophthalmic canals have a thin fibrous membrane for their walls ;
.this is covered by cyUndrical epithelium.
Caruncula lachrymalis. — This name is given to a small round (or fusiform)
body, frequently entirely, or partially black (or brown), slightly uneven, and
situated in the nasal angle of the eye ; it is nothing more than a small fold of
conjunctiva covering some agglomerated follicles, and the bulbs of several fine
hairs, which are readily seen on its surface. It may be regarded as designed to
•direct the tears towards the puncta, or to separate any extraneous particles that
this fluid may carry towards it.
It has for its base a small mass of connective tissue, in the midst of which
are some hair-roots, and some rather large glandules, lined by an epithelium
■charged with fat-granules. Nerve-tubes ramify around the hair-bulbs.
Puncta lachrymalia. — These are two little openings, situated one in each
eyelid, a short distance from the nasal commissure, by which the tears pass from
the oculo-palpebral surface into the lachrymal 'ducts.
Lachrymal ducts. — These are continuations of the last, and, like them, are
very narrow ; they carry the tears into the lachrymal sac. The superior is
longer than the inferior duct, and arrives at the sac behind it. The mucous
membrane lining these ducts is thin, and covered by a stratified pavement
epithelium, similar to that of the conjunctiva.
Lachrymal sac. — This little reservoir— lodged in the indifundibulum that
precedes the lachrymal foramen in the bone of that name — receives the tears
from the two ducts, and passes them into the lachrymal canal. Its mucous
membrane only differs from that of the ducts in being covered with ciliated
epithelium.
Lachrymal canal (nasal duct). — The tears accumulated in the sac flow into
this long duct, which extends to the lower aperture of the nostril. About one-
half of its course is in the canal of the lachrymal bone, which protects it, and
which terminates between the two turbinated bones. The remainder of the canal
is beneath the nasal mucous membrane, whence it passes to the inner surface of
the outer wing of the nostril ; there it terminates by an orifice — sometimes two
— that looks as if punched out of the membrane, towards the lower commissure,
near the point where there is a line of demarcation between the dark colour of
the skin and the rosy tint of the mucous lining.
This aperture constitutes the " nasal outlet."
The epithelium of the membrane lining the canal is ciKated in its bony,
■stratified in its nasal, portion. On the surface of the membrane are to be seen
the openings of the secretory ducts of some racemose glands, which are lodged
in the walls of the canal. Throughout its extent, the canal is lined by a con-
tinuation of the mucous membrane of the lachrymal sac. In Solipeds, this canal
•opens on the cutaneous surface at the entrance to the nostrils ; it therefore
happens that in these animals the conjunctiva, with it prolongations, forms a
particular mucous membrane, independent of the great gastro-pulmonary
membrane.
In the Ass and Mule, the orifice of the lachrymal canal is situated at the
inner face of the outer wing of the nostril, and not near the inferior conmiissure,
as in the Horse.
946 THE SENSORY APPARATUSES.
(Sometimes this outlet is double. The lachrymal secretion is not only useful
in facilitating the movements of the eyelids over the eyeball, but it washes away
dust and hurtful matter from off the surface of the cornea, keeping the epithelium
clean, moist, and healthy.)
Differential* Characters in the Visual Apparatus of the other Animals.
t
Essential Organ of "Vision.— In the Ox, the eyeball resembles in shape that of tlie
Horse ; but in small animals, particularly the Dog, it is much more spherical. In Birds it
is very convex in front ; its largest diameter is the antero-posterior.
Sclerotic— This is the same in all the domesticated quadrupeds. In Birds, however, it
has some curious features. Posteriorly, it has for base a cartilaginous layer, covered on both
sides by fibrous tissue ; this layer frequently ossifies around the optic nerve, where it forms
the posterior sclerotic ring. Around the cornea, there is the anterior sclerotic ring, composed
of small bony imbricated scales, capable of moving on each other, and modifying the shape of
the globe of the eye.
Cornea. — In the Dog and Cat, the structure of the cornea is similar to that of the Horse.
In the Ox, Sheep, and Pig, there are two limitary membranes ; one, consequently, beneath
the epithelium of the anterior face. In Birds, this limitary membrane is thickest in front.
Choroid. — In Mammifers, there are some sliglit differences in the coloration of the tapetum.
Thus, in the Ox, it is golden green, wliich becomes blue at the circumference; iu the Sheep,
it is a pale golden green ; a golden yellow in the Cat ; and white, bordered with blue, in the
Dog. (It is absent in the Pig.) In Birds, it is uniformly black ; this membrane has also a
network of non-striped muscular fibres, and, in addition, " Crampton's muscle, which arises from
the inner face of the osseous ring, and is inserted into the cornea " (Leydig). (According to
Hassenstein, in rapacious animals there is, behind the tapetum, a layer of corpuscles composed
of lime salts ; to this is owing the brilliancy of their eyes in the dark.)
Jris. — In all animals the iris is muscular. In Mammifers, the contractile fibres are non-
striped; in Birds, they are striped. (In the Ox, its anterior face has a brighter colour than
in the Horse. In the Sheep, it is a brownish yellow ; in the Goat, blue.) In the Dog, its
colour is a more or less bright golden yellow; in the adult Cat, green ; and in young animals,
a bright blue. The pupil is elliptical iu the Ox, as iu Solipeds (in the Sheep and Goat, it
is more elongated) ; in the Dog, it is circular, and, when very much diluted, it is the same in
the Cat; but, when contracted, it becomes elliptical vertically, and may be so narrow as to
represent nothing more than a thin perpendicular slit. (In the Pig, it is round.)
There are no differences worthy of note in the other parts of the eye.
Accessory Organs of the Visual Apparatus. — The motor and protective organs
are nearly the same in all the other animals.
Muscles. — Birds have only six muscles — four recti, and two oblique. The latter arise from
the anterior wall of the orbit ; consequently, the great oblique does not pass through a pulley.
(The posterior rectus, or retractor muscle, is most developed in Ruminants, which, during
their whole time of feeding, have the head in a dependent position. In most of the Carnivora,
instead of this muscle forming a complete hollow cone, as in Ruminants, there are four distinct
strips, almost resembling a second set of recti muscles, but deep-seated, and inserted into the
posterior, instead of the anterior, portion of the globe.)
Eyelids. — The disposition of these is the same in all Mammifers. In Birds, the lower lid
is the largest, and is furnished with a particular depressor muscle ; there are no Meibomian
glands. There is a third eyelid, corresponding to the membrana nictitans of Quadrupeds; it
is suflBciently extensive to cover the entire front of the eye, and is moved by a curious little
apparatus.
Glands.— In Ruminants, the Pig, and in Birds, there is found annexed to the membrana
nictitans, Earder's gland— & conglomerate gland, with adipose epitlielium in Mammifers, and
cylindrical and granular in Birds. It secretes a thick white matter, which is thrown out on
the membrana by one or two orifices. Its use is, doubtless, to favour the movements of that
organ over the surface of the eye, as well as those of the eyelids. (In the Ox, this gland is
voluminous; it has two large and several small ducts. The lachrymal gland is also voluminous,
and its nasal opening is situated liigher in the nostril than in the Horse. In the Sheep, there
are found, near the lachrymal fossa, several adipose follicles, which do not properly belong to
this apparatus, and which secrete a consistent, unctuous, yellow matter In the Pig, the
lachrymal ducts are separated, by a bony partition, into two sets, as far as the lachrymal sac.)
TEE AUDITORY APPARATUS. 947
Comparison of the Visual Apparatus of Man with that of Animals.
Essential Organ of Vision.— The eyeball of Man is almost spherical, as in the
carnivora.
The sclerotic does not differ much. The cornea has two limitary membranes, and is much
less elliptical than in Solipeds. The choroid has the same zone as in animals ; it is uniformly
brown. The ciliary processes, seventy to eighty in number, are a little longer than in the
Horse, and do not exceed, in front, the ciliary ligament, to the inner face of which they adhere
throughout their external border. The pupillary opening of the iris is always round. The
retina is the same in structure as already described. A little above the optic papilla, there is
a circular or oval patch, about 5', of an inch in diameter, in the centre of which is a transparent
spot ; this is the yellow spot (macula lutea), with the fossa centralis of the retina (fovea centralis,
foramen of Soemmering).
At this patch, the tissue of the retina is slightly modified, especially at the fossa ; there are
only cones in the columnar layer, and all the other layers appear to be confounded into one
granular mass. (This spot only exists in animals which have the axes of the eyeballs parallel
with each other, as in Man, the Quadrumana, and some saurian Reptiles.)
There is nothing particular in tlie aqueous humour, lens, or vitreous humour.
Accessory Organs of the Visual Apparatus. — The orbital cavity in Man is entirely
enclosed by bony walls, and there is no fibrous sheath. (A fold of the orbital fascia has been
described as separating the eye from its surrounding adipose tissue, and which, like a "tunica
vaginalis," enables the globe to roll with rapidity and precision.) The muscles are six in
number — four recti, and two oblique; the great oblique is the same as in animals. Only the
rudiment of a caruncula lachrymalis is present. The nasal duct opens at some distance up on
the surface of the inferior meatus.
CHAPTER V.
AUDITORY APPARATUS.
The sense of hearing — destined for the perception of sounds produced by the
vibration of bodies — has for essential agents the auditory or eighth pair of
cranial nerves, the terminal fibrillae of which ramify in the membranous walls
of a system of cavities forming the internal ear. These cavities are excavated in
the substance of the petrous bone, and communicate, externally, by means of
two other systems of diverticuli, which constitute the middle and external ear.
Article L — Internal Ear, or Labyrinth.
The cavities which, together, compose this part of the auditory apparatus,
being entirely channeled within the petrous portion of the temporal bone, have
their walls — forming the osseous labyrinth — constituted by that bone. They
contain the soft parts, named the membranous labyrinth, and fluids {endolymph).
The Osseous Labyrinth.
This is composed of three portions : the vestibule, semicircular canals, and
cochlea.
Preparation.— These cavities can be seen by making sections through the petrous bone, in
different directions. But it is better to expose them by cutting away this bone, after it has
beeu softened by prolonged steeping in dilute nitric acid.
948
THE SENSORY APPARATUSES.
1. The Vestibule (Fig. 515, /).
This is a small, somewhat oval cavity, in the centre of the bone, and outside
the perforated bony plate that forms the bottom of the internal auditory hiatus.
It is a real vestibule, with regard to the other parts of the labyrinth, which all
open into it.
On its external ivall is the fenestrn ovalis (fenestra vestibuli), an opening
closed by the stapes. The inner wall shows the foramina through which the
filaments of the vestibular branch of the auditory nerve pass. Below., and in
front, is a large orifice, the commencement of the scala cochleae ; above, are five
little apertures, the openings of the semicircular canals.
2. The Semicircctlar Canals (Fig. 513).
Three in number, and very narrow, these canals owe their name to their
•form. They are placed above the vestibule, like three semicircular arches
Fig. 511.
;^--e^
DIAGRAM OF THE LABYRINTH IN FISHES, BIRDS, AND MAMMALS
I. FISH; n. bird; III. mammal.
JT, Utricle; S, saccule; US, utricle and saccule; Cr, canalis reuniens; R, recessus of the labyrinth;
VC, commencement of the cochlea ; C, cochlear canal ; L, logenulus ; R', cupola, forming the
summit of the cochlear canal ; V, caecum of the vestibule of the cochlear canal.
united in a triangular manner at their base, and are distinguished as superior
or anterior, posterior, and external. The first two open together, by their adjacent
extremities, into the vestibule ; consequently, there are only five orifices of the
semicircular canals in this cavity. In addition, the adjoining openings of the
posterior and external canals are so close to each other, that they appear to be
sometimes united at the bottom of a short common canal.
3. The Cochlea (Fig. 514).
Situated behind, and below the vestibule, at the inner wall of the cavity of
the tympanum, the cochlea (snail-shell) is well named, as it presents exactly the
form of certain molluscs' shell. It is a spiral conical canal, twisting downwards,
forwards, and upwards, around a central conical axis (the modiolus, or columella) ;
TEE AUDITORY APPARATUS.
SO that its centre nearly corresponds to the inner wall of the tympanum. A
partition — the lamina spiralis, spiral like the cavity — divides it into two distinct
sections, or scales — a superior and inferior. This partition is attached by its inner
border to the central axis of the cochlea, but is free at its external margin, whick
does not quite reach the periphery of the cavity. The two scalse, therefore^
Fig. 512.
SECTION THROUGH ONE OF THE COILS OF THE
COCHLEA.
ST, Scala tympani ; SV, scala vestibuli ; CC, canalis
cochleae ; membrana of Reissner ; lis to Isp, lamina
spiralis membi-anacea; Us, limbus laminae spiralis;
ss, sulcus spiralis ; gs, ganglion spirale situated
on nc, the nervous cochlearis indicated by the
black line ; Iso, lamina spiralis ossea ; t, mem-
brana tectoria; 6, membrana basilaris ; Co, organ
of Corti; Isp, ligamentum spirale; Cc, cells of
Claudius. 1, Rod of Coiti of the first order ; 2,
rod of Corti of the second order.
communicate, in the skeleton, by means of an
opening (the helico-trema) that follows the free
border of the lamina spiralis throughout its
extent.
The inferior scala (or scala vestibuli) enters
the vestibule ; the commencement of the
superior scale, or scala tympani, is formed by
the fenestra rotunda {fenestra cochleae), which
brings it into communication with the middle
ear, without the presence of a membrane ex-
actly closing that aperture.
Fig. 513.
SECTION OF THE COCHLEA PARALLEL T0»
ITS AXIS, THROUGH THE CENTRE OP-
THE MODIOLUS.
1, Modiolus ; 2, infundibulum in which
the modiolus terminates ; 3, 3, coch-
lear nerve, sending its filaments
through the centre of the modiolus ;
4, 4, scala tympani of the first turoi
of the cochlea ; 5, 5, scala vestibuli
of the first turn; the septum between
4 and 5 is the lamina spiralis; a.
filament of the cochlear nerve is
seen passing between the layers of
the lamina to be distributed in thfr
membrane investing the lamina ; 8,
loops formed by the filaments of the
cochlear nerve on the lamina spiralis;.
9, 9, scala tympani of the second
turn of the cochlea ; 10, 10, scala
vestibuli of the second turn ; the-
septum is the lamina spiralis; 11,
the remaining half turn of the scala.
vestibuli ; tlie dome above is the-
cupola, the line passing thi-ough it
leads to the remaining half turn of
the scala tympani. The osseous
lamina forming the floor of the scala
vestibuli curves spirally round to-
constitute the infundibulum, 2; 14,
the helicotrema through which a
bristle is passed ; its lower extremity
issues from the scala tympani of the-
middle turn of the cochlea.
The Membranous Labyrinth.
The membranous labyrinth comprises three parts, corresponding to the threfr
cavities of the osseous labyrinth. 1. The vestibule. 2. The semicircular canals.
3. The cochlea.
1. The Membranous Vestibule (Fig. 513).
This is composed of two sacs with thin, soft walls, lodged in the osseous;
labyrinth. The supei'ior is the largest, is oval-shaped, and is named the utriculus ;
it communicates with the semicircular canals, of which it is a confluent. The
950
THE SENSORY APPARATUSES.
infmor is smaller, spherical in shape, and forms the sacculus ; it appears to be
perfectly closed, though in contact with the utriculus.
The membranous vestibule is composed of two distinct layers— an external,
of connective tissue ; and an internal, epithelial, resting on an amorphous mem-
brane. At the expansion of the nerve-filaments, the latter is absent, and is
replaced by a white calcareous substance (minute crystalline particles of carbonate
and phosphate of lime) which, in the domesticated animals, appears as a powder,
and is named the calcareous powder of the vestibule, ear-dust, or otoconites
(otoliths),
(Some authorities give four layers : an external or serous, derived from the
lining membrane of the laby-
^ig- 51*- rinth ; a vascular, with multi-
tudes of vessels ; a nervous,
_ _^ formed by the expansion of the
^1^^ ^'^ .|^P2^'^--^^^^gt^l|| , filaments of the vestibular nerve ;
//f '^""^ / jtV\'^^^^p^^*^^K^pff|ffif^ and an internal serous membrane,
r/U P'S,'%^^mmmj^^»!m\\n\mM,/ ^^.^^^Yi secretes the limpid fluid
contained in its interior. Spots
of pigment are constantly found
in the tissue of the membranous
labyrinth.)
2. The Membranous Semicir-
cular Canals (Fig. 513).
These are three thin tubes,
which correspond exactly with,
though they are of smaller
diameter than, the osseous semi-
circular canals ; they open into
the utriculus in the same manner
as the latter do into the bony
vestibule. Each has one of its
two extremities dilated into a sac
or ampulla (sinus-ampullaceus) ;
for the two superior and external
canals it is the anterior extremity,
and for the posterior canal the
outer extremity.
In structure they resemble
the vestibular sacs.
THE COCHLEA OPENED, TO SHOW THE ARRANGEMENT
OF THE TWO RAMPS AND DISTRIBUTION OF THE
AUDITORY NERVE.
a, Cochlea ; b, auditory nerve ; c, blood-vessel ; d, d',
vascular ramifications ; e, posterior part of facial
nerve turned upwards; /, intermediate nerve of
Wrisberg ; g, summit of tiie cochlea ; h, common
trunks of the petrosal nerves.
3. The Membraj!I0us Cochlea (Fig. 514).
The membranous cochlea is represented by two membranes, which complete
the lamina spiralis ; they continue the osseous laminse of the latter, and are
inserted into the external wall of the cochlea.
They give rise to three cavities, or scalse, in the interior of this portion of
the ear — an inferior, or tj/mpanic scala ; a superior, or vestibular scala ; and a
middle, or auditive scala, in which the organ of Corti is lodged. The vestibular
scala is itself divided by the membrane of Reissner into two canals — the jrroper
THE AUDITORY APPARATUS. 95I
vestibular scala, and Lowenherg's, or the collateral scala ,- so that, m reality, there
are four cochlean scalae (Fig. 512).
We do not, therefore, find in the cochlea — as in the other regions of the
labyrinth — a system of membranous cavities included in osseous cavities.
The structure of the membranes that limit the auditive scala is not perfectly
known, and is still disputed by anatomists ; but connective, epithelial, and nerve
elements appear to form their base.
With regard to the organ of Corti, it is a very curious and interesting portion
of the auditory scala, being formed of a series of solid and elastic arches resting
by their extremities on the membrane — the basilar — that separates the auditory
from the tympanic scala, their convexity being towards the superior, or membrane
of Corti. These arches number about three thousand in Man, and are composed
of two portions or articles — an external and an internal, united by a thickening
in the vicinity of the membrane of Corti. To these elastic arches are added
conical or fusiform ciliated cells, the function of which is to increase and transmit
to the terminations of the auditory nerve, the slightest vibrations of the organ
of Corti. (For fmther details, see works on Histology.)
Fluids of the Labyrinth.
These liquids are of two kinds — one is contained in the membranous labyrinth,
the other in the osseous labyrinth.
The fluid of the membranous labyrinth — or endo-lymph of Breschet — is con-
tained in the sacs and tubes constituting the membranous vestibule and semi-
circular canals. It is limpid and fluid like water. The fluid of the osseous
labyrinth, or peri-lymph of Breschet, fills the two scalfe of the cochlea, and
bathes the external surface of the vestibule and membranous semicircular canals,
which it separates from the corresponding walls of the osseous labyrinth.
Distribution and Termination of the Auditory Nerve in the
Membranous Labyrinth.
This nerve (the i^ortio mollis of the seventh pair) divides, as we have said,
into two branches — a cochlear and a vestibular.
The cochlear branch, the largest, reaches the base of the cochlea, where it
breaks up into a large number of fasciculi, one portion of which expands over
the first turn of the lamina spiralis, the other on the second, and a third on the
third ; the latter ramifications penetrate to the auditory scala, and terminate on
the organ of Corti. This anatomist has seen, on the primary fibres of these
ramifications, a gangUonic cell {ganglion spiral), at the point where they leave
the lamina spiralis ossea. The primary fibres finally lose their myelin sheath,
and, reduced to their axile filament, they terminate in the cells accompanying the
arches of Corti.
The vestibular branch divides into three portions, their terminal filaments
passing through the openings of the perforated spots (foramina 7iervina)^ and
ramify in the wall of the sacculus, utriculus, and the ampulla; at the extremities
of the three semicircular canals.
Article II. — Middle Ear, or Case of the Tympanum.
Excavated in the substance of the petrous portion of the temporal bone, on
the limit of the petrous and mastoid sections — but chiefly in the latter — the middle
952 THE SENSORY APPARATUSES.
ear constitutes an irregular cavity, which we may consider as composed of two
walls and a circumference.
The external ivall is principally constituted by the membrane of the tympanum.
The internal wall, formed by the petrous bone, offers two openings — the fenestra
ovalis a,nd fenestra rotunda — the one situated behind the other, and separated by
a small eminence named the promontory. The circumference is occupied for
nearly the whole of its extent by the mastoid cells — large open cavities in the
tympanum.
Internally, the tympanum contains a chain of small bones named the malleus,
incus, OS orbiculare, and stapes ; these bones form the medium of communication
between the tympanum and the fenestra ovalis —from one wall to the other of
the cavity of the tympanum.
This cavity is lined by a fine mucous membrane, which is continuous with.
that lining the pharynx, by means of a cartilagmous canal — the Eustachian tube^
that conveys the external air to the middle ear.
"We will glance briefly at the anatomical characters of the parts enumerated,
and which enter into the formation of the middle ear.
1. The Membrana Tympani (Fig. 515, 5).
Situated on the external wall of the middle ear, which it separates from the
bottom of the auditory canal, this membrane is oval in shape ; its greater axis
measures 11 mm. It is thin and capable of vibrating. Its inner face, inclining
inwards and slightly convex, is adherent to the handle of the malleus. Its.
external face — forming the bottom of the auditory canal — is slightly concave
(towards the meatus). The circumference is fixed in a bony frame named the
tympanal circle, which is sharply defined, but incomplete at its upper part, and
enveloped by the mastoid cells, the cavities of which radiate around this circle.
Although very thin, this membrane is composed of three layers — a middle^
of a fibrous (and muscular) character (fibres radiating towards the centre, and
also circular) ; an external — epidermic ; and an internal — the mucous membrane
of the middle ear. It has vessels and nerves, but not in the external and middle
layers. The nerves are numerous," and extend to the epithehum. (This-
membrane receives those vibrations of the air which set in movement the chain
of bones in the ear, and thus propagates them to the fenestra ovalis and labyrinth.)
2. The Promontory, Fenestra Ovalis, and Fenestra Rotunda (Fig. 515).
Placed in the upper part of the tympanic wall, the promontory is only a very
small eminence separating the fenestra rotunda from the fenestra ovalis. (It is
marked by grooves in which lie the branches of the tympanic nerves.)
Th.Q fenestra ovalis {fenestra vestibuli), situated in front of the promontory,,
is an opening the form of which is sufficiently indicated by its name. It is the
opening between the tympanum and osseous vestibule, and is closed by the base
of the stapes. In the Horse, its average diameters are '004 by -002 mm.
The fenestra rotunda {fenestra cochlece) is separated from the preceding by
the promontory, and, behind this small projection, it is closed in the fresh state
by a thin membrane (m. tympani secundaria), that forms a kind of diaphragm
between the middle ear and the tympanic scala of the cochlea. Its dimensions
are about the same as those of the fenestra ovalis. (The aqueduct of Fallopius
is a canal commencing at the internal ear, passing above the fenestrfea and
THE AUDITORY APPARATUS.
953
promontory, and terminating at the mastoid foramen. It contains the facial
nerve which passes through the tympanic cavity.)
3. The Mastoid Cells (Fig. 515, G).
These cells occupy all the circumference of the tympanic cavity, except above.
They are small, more or less irregular, deep spaces, separated by thin partitions
Fig. 515.
RIGHT TYMPANIC CAVITY OF THE HORSE'S EAR (ANTERIOR PLANE, VERTICAL AND
TRANSVERSE SECTION).
At Auditory canal; B, membrana tympani; C, malleus; D, incus; E, os orbiculare; F, stapes; G,
mastoid cells ; H, fenestra ovalis ; I, vestibule ; /, K, L, outline of the semicircular canals ; i/,
cochlea ; N, commencement of the tympanic scala.
radiating around the tympanic circle, their free margin being turned towards the
centre of the cavity.
In several animals, and particularly the Carnivora, the mastoid cells form a
special compartment in the tympanic case, communicating with the latter by
a single opening. The largest are situated at the inferior part of the tympanic
oavity, below the vaginal process of the temporal bone. (In the Sheq) and
-Goat, the mastoid cells and their bony septa are entirely absent.)
4. The Bones of the Middle Ear (Fig. 516).
Four articulating bones (the ossicula auditus), named the malleus, incus, os
954
TEE SENSORY APPARATUSES.
orliculare, and stapes, compose the bony chain of the middle ear ; this chain
extends in a broken course from the external to the internal wall of the
tympanum. The pieces are movable on each other, and are joined by ligaments
and moved by muscles.
1. Malleus {hammer). — This is the longest of the bones — average length,
•Oil mm. — and offers a handle and a head, which almost equally divide it. The
ha?idle (manubrium) is placed almost vertically, and is firmly fixed to the inner
face of the membrana tympani. The head, directed upwards, has a diarthrodial
facet for articulation with the incus. The neck, or upper part of the handle,
Fig. 516.
BONES OF THE MIDDLE EAR OP THE HORSE.
M, Malleus: 1, handle; 2, head. E, Incus: 1, inferior branch; 2, superior branch; 3, body. L|
Os orbiculare. Et, Stapes: 1, summit; 2, 2, branches; 3, base. Me, Muscle of the stapes; o,
bony nucleus in the terminal tendon.
shows two small processes for insertion (processes gracilis and hrevis), the inner-
most of which is very developed.
2. Incus (anvil). — This bone presents a body or middle portion, and two
branches. The body is channeled externally by a diarthrodial facet, corresponding
with that on the malleus. Of the two branches, the superior terminates in a
blunt point ; while the other, inferior, is united at its extremity to the os orbiculare.
3. Os Orbiculare. — This is a little, circular, discoid bone, included between
the inferior branch of the incus and stapes.
4. Stapes (stirrup). — Remarkable for its shape, which is exactly that of a
stirrup, this bone is placed almost horizontally. Its summit (or head) articulates
with the OS orbiculare ; its middle part is divided into two branches, having
between them an aperture that is closed by the tympanic mucous membrane.
Its base is received into the fenestra ovalis, and resembles that cavity in shape ;
and it is maintained in its position by the mucous lining of the tympanum, which
TEE AUDITORY APPARATUS. 955
passes over the stapes, after being reflected around the margin of the fenestra
ovalis.
(These bones transmit the vibrations of the membrana tympani to the fluid
in the labyrinth.)
5. Ligaments of the Auditory Bones. — We need only mention the
existence of these here, as they are too small and unimportant to merit a
particular description.
6. Muscles of the Auditory Bones. — Four muscles have been described :
three for the malleus, and one for the stapes. But two of these being extremely
small, and their muscular character doubtful to many anatomists, we will only
notice the internal muscle of the malleus and that of the stapes.
a. The internal muscle of the malleus {tensor tympani, musculus internum
mallei). — This is a little elongated fasciculus, lodged in a particular groove in
the mastoid portion of the temporal bone. It arises near the superior extremity
of the Eustachian tube, and passes downwards and backwards, to terminate by
a tendon which is reflected outwards, in front of the fenestra ovalis, and is
inserted into the neck of the malleus.
h. Muscle of the stapes {stapedius). — Lodged in an excavation in the inner
wall of the tympanum, near the fenestra vestibuli, on the course of the aquaeductus
Fallopii, this muscle is remarkable for its brevity, its relatively considerable
thickness, and its conical shape. It terminates by a small tendon in front of the
head of the stapes. In the Horse, Ox, and Sheep, a small bony nucleus is found
in the tendon (Fig. 516, o).
(The tensor tympani retracts the bones of the ear inwards. In contracting
it draws the handle of the malleus towards the cavity of the tympanum, and
this brings the membrane with it ; consequently, the convexity of the latter is
increased and its tension is augmented. In addition, while the handle of the
malleus is carried inwards, its head is turned outwards by a pivoting motion, and
this pulls the body of the incus also, the long process of which is raised and
inclined inwards, pushing the os orbiculare and stapes towards the fenestra
ovaHs. The base of the latter bone being in contact with the fluid in the
vestibule, this is stirred ; so that this muscle likewise acts indirectly in producing
the undulations in this fluid. The muscles of the tympanum are classed as
tensors and laxators. It is well to know that all are tensors, and none of them
act as relaxors ; relaxation of the membrane occurring when the muscles are not
in action.) '
5. The Mucous Membrane of the Tympanum.
Very fine and vascular, this membrane covers all the angularities of the
middle ear, is reflected on the chain of bones, and is continued into the mastoid
cells. It is continuous with that lining the Eustachian tube, and therefore
should be considered as a prolongation of the tegumentary membrane spread
over the walls of the pharyngeal vestibule. It is covered by a simple pavement
epithelium.
6. The Eustachian Tube.
The Eustachian tuhe is a fibro-cartilaginous canal between the cavity of the
middle ear and the pharynx.
« Extending in a straight line beneath the base of the cranium, from the
tympanic case to the upper and lateral part of the pharyngeal cavity, this canal
956 THE SENSORY APPARATUSES.
i« also named the guttural duct of the tympanum. It is nearly four inches long
in Solipeds, is flattened on both sides, and bordered by the stylo-pharyngeus
muscle. Its upper or tympanic orifice is narrow ; the inferior, guttural, or
pharyngeal orifice, situated near and behind the guttural openings of the nasal
cavities, is wide, and represents a great slit extending obliquely downwards
and outwards ; the contiguous borders of this aperture are sustained by a
cartilaginous plate — a kind of pavilion formed by the expansion of the tissue
•constituting the base of the tube.
Throughout its length, the guttural duct is cleft inferiorly, and by this
long aperture the mucous membrane escapes and descends to form the large sac
peculiar to Monodactyles, known as the guttural pouch.
7. The Guttueal Pouches.
The mucous membrane lining the Eustachian tube is continuous, forward,
with that of the pharynx ; above and behind, it is prolonged into the tympanic
cavity, which it lines. Below, it is dilated, and forms the guttural pouch.
Two in number — one being on each side — the guttural pouches lie against each
other in the median plane, and descend to the larynx, where they terminate in a
cul-de-sac constituting their fu7idus. Before and behind, they extend from the
anterior part of the pharynx to the inferior face of the atlas. The capacity of
«ach is about f of a pint ; but in consequence of the extensibility of the mucous
membrane, the extent and capacity of the guttural pouches are particularly variable.
Irregular in shape, like the space which it occupies, the guttural pouch
corresponds, behind and above, with the base of the occipital and sphenoid bones.
When this reservoir is distended, its lower part, or fundus, descends on the
lateral portions of the pharynx and larynx, to the lower extremity of the parotid
gland, in the loose connective tissue of that region.
Externally, the guttural pouch contracts numerous different relations in the
intermaxillary and parotideal regions, and in its j^osterior portion.
a. In the intermaxillary region, it is in relation with the tensor palati,
pterygoideus and hyo-pharyngeus muscles, as well as with the internal maxillary
artery and lingual nerve ; it envelops the large cornu of the hyoid bone, and
covers the inner face of the internal pterygoideus muscle.
b. In the parotideal region, the guttural pouch responds, above, to the inner
face of the parotid gland, from which it is separated by the auricular vessels and
nerves ; a httle lower, at the posterior angle of the hyoid bone, to the stylo-
hyoideus muscle and the styloid process of the occipital bone ; here the auricular
artery passes obliquely upwards and backwards, and the membrane of the pouch
is more closely united to the parts covering it.
Below this, the guttural pouch is in relation with the stylo-maxillaris muscle,
external carotid, and the nerves forming the guttural plexus such as the ninth
and twelfth pairs, the sympathetic, etc. Lower, it is related to the parotid gland,
to the inferior extremity of which it may be prolonged.
c. Posteriorly. — The guttural pouch is in relation with the atlas, flexor
muscles of the head, occipital artery, etc. ; it forms a fold that envelops
principally the pneumogastric and sympathetic nerves, and, anteriorly, another
fold that encloses the internal carotid.
The mucous membrane of the guttural pouches is thicker and stronger than
that hning the Eustachian tube and the cavity of the tympanum. Only slightly
adherent to the adjacent parts, except at the branch of the hyoid, the inner face
THE AUDITORY APPARATUS. ■ 957
of the stylo-hyoideus, etc., it is smooth internally, and lubriiied by the mucus it
secretes. It may become the seat of purulent collections, which compress the
larynx and obstruct the respiration, and it is in such cases that the pouch is
punctured.^
This membrane receives numerous fine vascular and nervous ramifications
from the neighbouring branches.
The guttural pouches communicate with the pharynx and cavity of the
tympanum, and usually contain air ; the quantity of this may vary in health,
according to the degree of dilatation of these membranous sacs. Their dilatation
is chiefly produced by the palato-pharyngeus muscle, several fibres from which
extend to their mucous membrane ; and, besides, when the ear is erected this
membrane is thrown into a state of tension, through the adhesion of the lower
prolongation of the concha to its surface.
The functions of the guttural pouches are far from being well known. It
cannot be affirmed that they increase phonation ; indeed, their use appears to be
rather related to audition, if it be considered that these annexes of the guttural
duct of the tympanum coincide, in Sohpeds, with a less development of the
mastoid cells than in the other animals.
With regard to the Eustachian tube, it serves to renew the air in the tympanic
cavity, this renewal being indispensable to the perfect accomplishment of hearing.
The epithelium lining the guttural pouches is cylindrical and vibratile.
(It is essential that the equilibrium between the external air and that in the
cavity of the tympanum should be maintained, in order to avert irregular tension,
or even rupture, of the membrana tympani. Perosino states that the guttural
pouches are filled with warm air during expiration, and that this is partly changed
for cold air in inspiration.)
Aeticle III. — The Exteenal Eae.
The external ear comprises the external auditory canal, and a widened appen-
dage opening outwardly, designated the concha, or imvilion.
The External Auditory Canal.
This canal {meatus auditorius externus), described in the Osteology, is, in the
Horse, of a cylindro-conical shape, and has an average width of '020 to '022 m.
It has at the bottom the membrana tympani, which separates it from the middle
ear. Its axis forms with the surface of that membrane an angle of about 30°.
Its entrance — the external auditory hiatus — gives attachment to the infundi-
bulum of the conchal apparatus. It is lined by a thin integumentary membrane,
intermediate in character between the skin and mucous membrane, and has
in its substance a large number of glands and convoluted tubes, analogous to
the sudoriparous glands — but here named ceruminous glands, as they secrete an
unctuous matter — the cerumen.
The Concha, or Pavilion.
The external trumpet-shaped appendage named the concha (concha auris)
varies much in shape in the different animals, though in all it offers the same
details in organization — a cartilaginous framework composed of three pieces,
' Bartheleray, sen., and Goubaux, have found, in the guttural pouches, solid masses formed
of mucus and epithelial cells.
63
958 TEE SENSORY APPARATUSES.
muscles to move these, an adipose cushion to ensure liberty of movement, and
integuments covering the whole.
1. Caetilages of the Concha (see p. 281).
2. Muscles of the Exteenal Eae (see p. 281).
3. Adipose Cushion of the Exteenal Eae.
This cushion, which is never absent — even in the most emaciated animals-
envelops the base of the concha in front, inwardly, and posteriorly. It facilitates
the movements of that organ.
4. Integuments of the Exteenal Eae.
The skin covering the concha is covered with fine close hairs. That lining
its interior is very thin and vascular, adheres closely to the cartilage, and is
furnished with long silky hairs, to prevent the entrance of dust into the ear.
Differential Chakactebs in the Auditory Apparatus of other than Soliped Animals,
In the various kinds of animals we study, there are no notable differences in the internal ear.
In the middle ear, there are some modifications, either in the bones or accessory parts. Id
Ruminants, the auditory bones are like those of the Horse, except that the handle of the
malleus is more curved, and the body of the incug is longer. In the Dog, the handle of the
malleus is covered with small, pointed processes, and the branches of the stapes are long and
thick. In the Pig, the branches of the latter are slight and inflected, and the base is wide
and thin; in a word, the stapes of this animal bears no resemblance to a stirrup; the malleua
is very much inflected forward. In the last two animals, no osseous nucleus is found in the
tendon of the stapedian muscle.
It is needless to say that the fenestra ovalis varies with the base of the stapes. (The
absence of the mastoid cells in the Sheep and Goat has been already noted.)
The Eustachian tube exists in all the animals, but tiie guttural pouches are only found in
Solipeds.
In the external ear, the conchal cartilage varies much in shape. It is thin, inclined out-
wards, and widely open in Ruminants. In the Pig, it differs a little, according to breed,
though it is always much developed, sometimes erect, but most frequently drooping. In the
Dog, it is sometimes short and erect, sometimes broad and pendulous. It is always short,
pointed, erect, and open in front, in the Cat. (In this animal a small duplicature of the
external margin of the concha is often seen.) In Birds, the external ear is limited to the
auditory canal.
Comparison between the Auditory Apparatus in Man and that op Animals.
There is nothing to be said regarding the internal ear. The middle ear comprises the
same parts as that of Mammifers other than Solipeds. Tlie handle of the malleus is straighter,
the incus more voluminous, and the stapes thinner, proportionately, than in animals. There
is no bony nucleus in the stapedian muscle. The muscle of the malleus is lodged in a distinct
canal belonging to the Eustachian tube.
The external ear is composed of only two cartilages : one, forming the base of the concha,
represents that cartilage in animals ; the other, belonging to the auditory canal, resembles the
annular cartilage in the Horse. The concha is very irregular in shape, and stands at an angle
of from 15° to 45° from the temporal bone ; it is convex superiorly, and terminates inferiorly
by a small lobe. On its anterior face it presents prominences and depressions; the former are
four in number: the helix, a fold encircling the ear behind and above; the antihelix, a con-
centric prominence, almost parallel with the preceding; the tragus, a triangular, pointed
process, covered with hair, situated in front of the auditory canal (meatus); the antitragus,
opposite the tragus, behind the canal, and above the lobule. The depressions are : the concha,
a wide cavity, limited by tlie antihelix ; the scaphoid fossa (fossa innnminata) situated above
the latter; and the/o88a triangularis comprised between the helix and antihelix.
The pavilion of the ear is traversed by several muscular fasciculi, which can have no
influence on its movements. The concha has also extrinsic muscles — the anterior auricu-
htris (attrahens aurem), auricularis superioris (attolens aurem), and the auricularis posteriores
(retrahens aurem). The action of these on the concha is very slight.
BOOK YIII.
GENERATIVE APPARATUS.
Individuals in the organic kingdom possess the faculty of reproduction, and
thus they perpetuate the species to which they belong. In Mammifers, the
generation of a new being demands the concurrence of two individuals — a male
and female— y^ho have intercourse under certain determinate circumstances.
The female furnishes a germ — the ovum, and the male a fertilizing fluid — the
semen, which vivifies the ovum, and renders it capable of development.
We have, therefore, to study separately the generative, or genital organs of the
male, and those of the female.
CHAPTER 1.
GENITAL ORGANS OP THE MALE.
The semen is elaborated in the structure of the two testicles. These are lobular
glands, each of which is provided with an excretory duct, doubled a great number
of times on itself at its commencement, to form the epididymis, and destitute of
convolutions for the remainder of its extent, which is named the vas deferens.
This canal carries the fecundating fluid into vesiculm seminales — reservoirs with
contractile walls — where it accumulates, and wnence it is expelled during copu-
lation, by passing through the ejaculatory ducts and the urethral canal. The
latter is a single canal common to the two apparatuses of generation and urinary
depuration ; it is provided in its course with three accessory glands — the prostate
and Coivper's glands, and is supported by an erectile body (the corpus cavernosum),
with which it forms an elongated organ — the penis, which, in the act of copu-
lation, is introduced into the vagina, to the bottom of which it carries the
spermatic fluid.
We will successively consider the secretory organs or testicles, and the excretory
apparatus, comprising all the other organs.
Preparation. — To see the arrangement of the male generative organs properly, it is necessary
to dissect them in situ, and then remove them from the pelvis in order to examine them
thoroughly.
The subject in which the organs are to be examined in situ should have the skin removed
from it, except at the parinseum, scrotum, a portion of the inner face of the thighs, and the
inferior surface of the abdomen, from a transverse line passing from one haunch to the other.
The intestines are taken from the abdominal cavity, by dividing its walls in front of that line;
the left posterior limb is removed, leaving the sacro-sciatic ligament which is behind it.
Finally, after distending the rectum and bladder, which have previously been emptied — the
first with tow, the second with air introduced by the ureter, wiiich is then tied on itself— the
dissection of the internal genital organs can be proceeded with. This dissection is carried
960 GENERATIVE APPARATUS.
out as for as the bladder and anus, the cellulo-adipose tissue being removed from the bottom
of the pelvis, taking care to leave the peritoneum, where it passes on to the pelvic organs. The
portion of the ischium to which no organ required tor this study is attached, may be sawn off.
In detaching the skin from the inner surface of the thigh, and as far as the middle line,
the fixed portion of the penis and one of the dartos sacs are exposed. The separation of the
scrotum from the dartos is a laborious operation, because of the fineness and the adherence of
the skin; it ought to be effected by means of a good scalpel, and with every precaution. Tlie
preparation is completed by dissecting the suspensory ligaments of the corpus cavernosum, the
penis, and the prepuce (sheath), about which tiiere is no difficulty.
(The dartiis and other layers within tlie scrotum are more easilly dissected, if the skin be
drawn tight over the testicle and tied between tlie latter and the abdomen, so as to keep it
tense on the surface of the organ.)
The Testicles, or Secretory Organs of the Semen.
The testicles (testes) are two glands suspended on each side of the penis,
between the thighs, where each occupies a particular serous pouch — the tunica
vaginalis. We will commence by describing this cavity, and afterwards the
organ it contains.
1. Tunica Vaginalis.
The tunica vaginalis, in the domesticated animals, is only a diverticulum of
the abdominal cavity, the serous membrane of which — the peritoneum — becomes
hernied in the inguinal canal — passing, as it does, through the upper (internal)
inguinal ring, and prolonged belov\^ the inferiui (external) ring, so as to form a
serous sac, which is enveloped by membranous walls.
We have to study, in the tunica vaginalis : 1. Its interior. 2. The enveloping
memhranes which form the external wall, and to which we give the common
name of scrotum.
Interior. — The serous sac constituting the tunica vaginalis is vertically
elongated, and slightly inclined downwards, inwards, and backwards. Its
inferior extremity, forming the bottom, or cul-de-sac, is pear-shaped, and lodges
the testicle and its epididymis. Its middle portion, contracted into a narrow
canal, contains the spermatic cord. The superior extremity, or entrance, is open,
to maintain communication with the abdominal cavity ; through it pass the
spermatic vessels and vas deferens.^
As has been said, the peritoneum forms this vaginal sac. As in the abdomen,
it is divisible into two hjers— parietal and visceral. The latter {tunica vaginalis
propria) covers the testicle and the cord ; while the former {tunica vaginalis
communis, or reflexa) lines the innermost of the membranous coverings which
serve as a wall to the tunica vaginalis. These two layers are made continuous
by a serous frsenum, analogous to the mesentery which sustains the floating
colon ; like it, it is formed by the junction of the two layers. Flat, elongated
from above to below, and extending vertically from one end of the sac to the
other, this fraenum is attached, by its upper border, behind the spermatic cord ;
its lower extremity passes over the epididymis, and from it on to the testicle ;
above, it is continued into the abdominal cavity, in accompanying the different
vessels composing the cord.
(A small quantity of serous fluid is usually present in the tunica vaginalis.
When in excess it gives rise to hydrocele.)
Enveloping Membranes. — The stratified layers that form the external walls
' If this opening be abnormally dilated, a loop of intestine may enter it, and lie alongside
the testicle in the sac, constituting inguinal hernia.
TEE GENITAL ORGANS OF TEE MALE. 961
of this vaginal membrane — and which are generally described in anatomical
treatises, with the two serous layers, as the envelopes of the testicle — are four in
number. Reckoning them from within to without, they are the fibrous tuny,,
cremaster muscle, dctrtos, and scrotwn.
Fibrous Tunic {infuadibulform fascia). — This forms the most complete
covering to the tunica vaginalis, extending, as it does, over the whole surface
of the parietal serous layer, to which it is closely adherent. Very thin, especially
at the points corresponding to the cremaster, this membrane is continuous,
around the upper inguinal ring, with the transversalis fascia, of which it is only
a dependency ; its external face is in relation with the cremaster and dartos.
Cremaster (or cremasteric fascia). — This .muscle is usually described as an
envelope of the testicle, by the name of tunica erythroides. In the domesticated
animals it is a bright-red band, attached, above, to the inner or peritoneal sur-
face of the ilio-lumbar aponeurosis ; it descends into the inguinal canal, envelops
outwardly only the middle portion of the tunica vaginalis, and expands below on
the ctd-de-sac, where its fibres terminate by small tendons, which are inserted
into the external surface of the infundibuliform fascia. Therefore it is that
the envelope the cremaster forms is very incomplete — the greater portion of the
testicle, and the inner side of the cord, being left unprotected by this muscular
tunic. It is in relation, inwardly, with the fibrous membrane, to which it is
united by a plentiful connective tissue ; externally, it is related to the posterior
wall of the inguinal canal and the dartos. (It is a connective dependency of
the internal oblique muscle.)
It is the contraction of the cremaster that causes the sudden ascent of the
testicle.
Dartos. — The tissue composing this tunic is contractile ; it is constituted by
a mixture of elastic tissue and unstriped muscular fibres. The dartoi'c tunic
does not reach the inguinal canal ; consequently, it does not cover that part of
the tunica vaginalis. It forms a pouch below the inguinal ring, and is spread
from around the margin of this on to the neighbouring parts, to which it adheres
somewhat closely ; it is prolonged, gradually thinning, into the sheath of the
penis, and even on to the penis itself, and to the tunica abdominalis, as well as
between the thighs. The two pouches it forms are quite independent of each
other, never becoming confounded, though placed in contact on the mesial line
to form a double partition (septum scroti), the leaves of which are separated
above for the passage of the penis. The dartos is in relation, inwardly, with
the fibrous and erythroid tunics, from which it is isolated by an abundance of
lamellar connective tissue,^ which is very condensed towards the globus major
epididymis, and forms at this point a kind of cord that passes from the fibrous
tunic to the dartos, adhering strongly to each. Externally, the dartos is covered
by the scrotum.
This tunic determines the vermicular movements of which the scrotum is
the seat. It wrinkles the skin of the scrotum, and makes it firm and dense, thus
aiding the cremaster in raising the testicle. When it is not in a state of con-
traction, the skin of the scrotum is smooth and even, and the testicle pendulous.
Scrotum. — The different membranes enumerated above are double, one
being for each tunica vaginalis ; but the scrotum constitutes a single pouch,
enveloping the two testicles at the same time. It is merely the portion of skin
' The testicle is disengaged by tearing tlirough this tissue, in castration by the " covered
operation."
962 GENERATIVE APPARATUS.
covering this region, and is thin, and so closely adherent to the dartos that it
can only with difficulty be separated from it. It is covered by very short fine
hair, and the extremely nmnerous sebaceous follicles in its texture secrete an
unctuous matter that renders its surface soft to the touch.
(There are also numerous sudoriparous glands, and these, with the sebaceous
glands, keep the skin soft and pUable, and modify the effects of friction during
progression. On its surface it shows a 7-aphe or seam in the middle, which is a
trace of its primary division, and corresponds to the median septum separating
the testicles.)
2. The Testicles (Figs. 517, 518, 519, 521).
External Conformation. — Each testicle is oval in shape, flattened on both
sides, lodged in the cul-de-sac of the tunica vaginalis,^ and suspended at the
extremity of the spermatic cord. The description of this organ is extremely
simple ; it offers for study two faces, two borders, and two extremities.
The faces, external and internal, are smooth and round. The inferior border
is convex and free, like the faces ; the supeiHor, ahnost straight, is related to the
epididymis, which adheres to it by its head and tail.
Means of Attachment. — The testicle is freely pendent in the lower part of the
tunica vaginalis, where it cannot readily be displaced, because of the narrowness
of the space containing it. It is suspended, by its upper border, to the testicular
or spermatic cord -."^ a thick funiculus contained in the middle portion of the
vaginal sheath, and formed by the aggregation of the spermatic vessels with
the vas deferens.
This cord is itself sustained in the tunica vaginalis by the frsenum that unites
the two serous tunics of that cavity.
Steucture. — Independently of the serous tunic that covers the exterior of
the testicle, there enter into its structure a fibrous membrane, tissue proper, and
vessels and nerves. The excretory duct will be studied separately.
Fibrous Membrane. — This membrane, designated the tunica albuginea, forms
a strong, resisting, thick shell around the testicle, and its texture is channeled
by sinuous spaces which lodge the large spermatic vessels. It is covered by the
visceral layer of the tunica vaginalis, to which it closely adheres ; its inner face
sends thin septa into the proper substance of the gland, which divide the latter
into the spermatic lobules. Towards the upper border of the testicle, and in
front, the tunica albuginea is slightly thickened ; this part is named the corpus
Higmorianum (or mediastinum testis), and at this point the seminal ducts pass
through it to reach the epididymis.
(This membrane is dense and inelastic, being composed of white fibrous
tissue interlacing in every direction.)
Tissue proper. — The proper substance of the testicle resembles a greyish-
yellow pulp, contained in the tunic albuginea ; it is divided by the prolongations
which that tunic sends into its interior, into small, conical, distinct lobules {lobuli
' One or both testicles may be retained in the constricted portion of the tunica va^nalis,
or remain in the abdomen ; animals in ■which this occurs are named monorchids or cryptorchids.
The absence of one or two testicles (anorchidism) is extremely rare. Ectopix of the testicles
is the designation applied to these organs when they are found elsewhere than in the ordinary
situation.
* III surgical anatomy, there is sometimes included in the spermatic cord the middle
portion of the tunica vaginalis and ail its envelopes — the serous, fibrous, and erythroid tunics.
THE GENITAL ORGANS OF THE MALE.
testis), independent of each other. These lobules vary in number, from two to
three hundred, and all have the same organization, each being constituted by
two or three extremely convoluted filiform tubuli, about from one to two yards
in length. These tubes — the tubuU seminiferi — anastomose frequently with each
other, are intertwined, and can be unwound like a ball of thread. One of their
extremities terminates in a cul-de-sac ; the other is detached from the lobule,
and enters a central system of excretory ducts which will be referred to im-
mediately.
When we cut through a testicle vertically and lengthways, so as to divide
the corpus Highmorianum into two lateral portions, there is seen in its substance
a whitish framework, sometimes not very apparent, which, curving upwards at
both extremities, extends from that body to the posterior extremity of the testicle
Fig. 518.
Fig. 517.
DIAGRAM OF THE TESTICLE.
t, Mediastinum testis, containing
the rate testis ; 2, 2, trabeculi ;
3, one of the lobules ; 4, 4, vasa
recta; 5, globus major; 6, globus
minor ; 7, vas deferens.
A TESTICLE INJECTED WITH MERCURY.
, a, Lobules formed of seminiferous tubes ; 6, rete
testis; c, vasa etferentia; d, ilexures of the efferent
vessels passing into the head, e, e, of the epididy-
mis ; /, body of the epididymis ; g, appendix ; h,
Cauda ; i, vas deferens.
{Fig. 518), where it disappears ; from this are given off a large number of
fibrillae (trabeculce testis), which diverge in all directions. A mercurial injection
by the vas deferens, shows that this part of the testicle is chiefly formed by a
ramifying system of rectilinear canals with very thin walls, which open into each
other, and unite, on reaching the corpus Highmori, into about twenty principal
trunks, from 'S mm. to '6 mm. in diameter. These are named the straight canaliculi
{vasa or tuhuli recti), to distinguish them from the convoluted tubuli (tubuU
contorti) ; they receive the latter at their exit from the lobules, are surrounded
by numerous blood-vessels, and are sustained by the fibrous septa of the tunica
albuginea, which appear to converge towards the point they occupy. At the
corpus Highmorianum, the tubuli recti pass through that body, forming in its
texture an anastomosing network — the rete testis — and are contmued into the
epididymis as the efferent canals (vasa efferentia).
964
GENERATIVE APPARATUS.
Fig. 519.
The seminiferous tubes in the lobules are from -20 mm. to -25 mm. in diameter.
Their walls are composed of two membranes — an internal, which is thin, amor-
phous, and formed of cells joined border to border as in an endothelium ; and
an external, thicker, lamellar, and containing nuclei. The walls are lined by a
stratified epithelium, which is constantly undergoing evolution in the adult.
The external layer is named the basal epithelium. It contains two kinds of cells :
ordinary, indifferent cells, named the " cells of Sertoli ; " and thin, round,
granular cells (^spermatogonia) mixed with,
these. The latter are the male ova of
Robin, and it is they alone which exhibit
the phenomena of spermatogenesis. Before
the manifestation of this process, the male
ova proliferate, join the cells of Sertoli, and
form on the face of each of these elegant
radial series.
Spermatogenesis is the name given to
the epithelial evolution which leads to the
formation of spermatozoids. In spermato-
genesis, there are two periods : 1. The
period of the proliferation of the tubular
epithelium resulting in the production of
the spermatoblasts. 2. The period of dif-
ferentiation, in which the spermatoblasts
are transformed into spermatozoids. This-
change involves the nucleus of the sperma-
toblast, which becomes the head of the
spermatozoid ; then the protoplasm, from
which is produced the tail of the sperma-
tozoid.
Between the seminiferous tubules is a
stroma composed of somewhat peculiar
connective tissue, in which are numerous
cells filled with yellowish granules. Blood-
vessels and lymphatics course through this
stroma.
Vessels and nerves. — The blood is carried
to the testicle by the spermatic arteryy
which is almost exclusively appropriated ta
it ; this vessel, after describing a great
number of very remarkable flexions, enters the upper border of the gland, a
little behind the epididymis. It does not immediately plunge into its sub-
stance, however, but passes within the texture of the tunica albuginea, along the
borders of the testicle, and forms a complete circle around it. From this circle
it sends oif divisions, which spread over the sides of the organ, detaching fine
arterial ramifications that penetrate its proper tissue in accompanying the inter-
lobular septa. (There is generally described a tunica vasctdosa., which forms one
of the coverings of the testicle. This, in reality, is not a distinct coat, but
merely the fine ramifications of the spermatic artery spreading beneath the
tunica albuginea, and held together by delicate connective tissue.)
The veins are very voluminous and frequently varicose ; they comport them-
VERTICAL SECTION OF THE TESTICLE
(horse's), passing THROUGH THE CORPUS
HIGHMORIANUM.
1 Spermatic cord, with its serous covering;
2, sections of the flexuous vessels of the
cord; 3, head of the epididymis, or globus
major ; 4, tail of the epididymis, or globus
minor; 5, vas deferens; 6, corpus High-
morianum ; 7, rete testis ; 8, tunica
albuginea sending prolongations from its
inner face, and which divide the testicle
into lobules , 9, surface of the tunica
albuginea.
TEE GENITAL ORGANS OF THE MALE.
965
selves like the arteries, and unite in a single trunk that enters the posterior vena
cava, near the renal veins. (On the cord, in addition to their sometimes varicose
condition, the spermatic veins have been observed to form a network, named
the pampiniform plexus.)
The lymphatics are most numerous beneath the serous layer and the tunica
Fig. 520.
THE INTERNAL GENITO-URINARY ORGANS, WITH THE STOMACH, LIVER, AND SPLEEN, IN
THE F<ETUS OF A MARE
R, Left kidney ; V, bladder ; T, testicle ; at, spermatic artery ; G, gubernaculum testis ; e,
epidiiiymis (the letter is placed in the centre of the serous layer which suspends the testicle and
spermatic vessels from the subiumbar resion, and after the descent of the gland, forms the
frtenum between the two layer.s in the vaginal sheath); E, stomach; F, liver; /. lobus Spigelii ;
P, vena portse ; C, umbilical cord ; 0, umbilical vein ; 0', intra-hepatic course of that vein,
indicated by a double dotted line.
albuginea. They commence by lacunae in the interstitial connective tissue, and
form a very rich network, in the meshes of which are seminiferous tubules. They
pass into the network of the tunica albuginea, and thence they follow the sper-
matic cord to terminate in the sublumbar glands.
The nerves of the testicle are derived from the sf athetic (and pass from
966 GENERATIVE APPARATUS.
the abdomen with the blood-vessels) ; they form a small particular plexus around
the artery. (The nerves pierce the membrana propria of the tubuli semiuiferi,
and end in a more or less pyramidal mass of protoplasm, in which lie clear
elliptical nuclei. The ends of the fibres, therefore, lie in close proximity to the
outer layer of the secreting cells.)
Development. — In the foetus, at an early age, the testicle floats in the
abdominal cavity, being suspended from the sublumbar region, near the flank,
by a wide peritoneal fold, at the anterior border of which are the spermatic
vessels (Fig. 520, e) ; the tunica vaginalis is not yet present. The mechanism
of the formation of this is very simple, and easy to understand. The visceral
layer of the tunica vaginalis, Avhich envelops the testicle and the cord, being
already formed, as well as the serous frienum that establishes continuity between
this and the parietal layer in the adult animal, it only remains to explain how nature
proceeds to construct the vaginal sac in which the gland is afterwards contained.
We have remarked that to the posterior extremity of the testicle is attached
a thick round funicle, the other end of which passes into the internal inguinal
ring ; this is enveloped by the peritoneum, and fixed to the posterior border of
the serous layer that suspends the testicle. This funicle is the guhernaadum
testis, and is continuous by its inguinal extremity with the dartos, the structure
of which it apparently shares, and which alone acts as the scrotal sac to it.
The serous layer covering it has on its outer adherent face the cremasteric muscle,
which is attached to the ilio-lumbar aponeurosis in the vicinity of the inguinal
ring, enters the serous tube formed by the peritoneal envelope of the guberna-
culum, and advances by its terminal extremity to near the testicle. To this
organ is due the principal share in the formation of the vaginal pouch.
When the progress of development in the foetus pushes the testicle towards
the inguinal region, the gubernaculum acts as a guide, as its picturesque name
sufficiently indicates. It is the first to descend into the inguinal opening, draw-
ing the testicle after it. But in performing this movement it also carries along
its peritoneal covering, which gradually leaves it to become related, by its
adherent face, to the walls of the inguinal canal ; and thus this membrane
becomes reflected, just as would a sock everted or turned down from the leg ta
the foot, the latter being supposed to represent the testicle.
The parietal layer of the vaginal sac is, then, nothing more than the serous
tube that, in the foetus, enveloped the gubernaculum testis while it was in the
abdomen, and which is reversed on the testicle and cord after their descent into
the scrotum, the cremasteric muscle on its adherent face having become external.
In all species, the descent of the testicle commences before birth : in the
Bovidfe it is even completed in the early months of intra-uterine existence. In
Solipeds, however, the testicle most frequently remains in the inguinal canal
until the animal is from six to ten months old.
Function. — The testicles secrete the spermatic (or seminal) fluid. Pure semen,
such as is derived from these glands, is a white, viscid, odourless, and slightly
alkaline fluid. It contains a small quantity of liquid matter (Uqiior seminis),
in which is an innumerable mass of spermatozoids. After the semen has passed
through the genital canals, it is made much more watery by the addition of
the fluids secreted by the walls of these excretory ducts, or by the glands annexed
to them.
The spermcdozon, zoosperma, spermatozo'ides, or spernwtic filaments, are little
elongated bodies from gio to sU of a line in length. They have a pyriform,
THE GENITAL ORGANS OF THE MALE.
flattened, or lancet-shaped head, and a filiform tail terminating in a point ; this
tail is often furnished at its origin with an enlargement, or unilateral or bilateral
alae. Their form is slightly modified during their course through the excretory
ducts. (In the different species, though possessing certain fixed characters, the
spermatozoa yet offer some curious diversities. Some of these are well exhibited
in the annexed representations of
these particles, found in the semen Fig. 521.
of very dissimilar animals.)
The spermatozoa move by undu-
lations of the tail (Grohe attributes
the motion to the contractile pro-
toplasm contained in the head) ;
ihey can traverse '004 m. in a
minute. Their movements persist
for several days in the genital
organs of the female ; they are
suddenly arrested by water, acids,
and the electric spark ; on the
contrary, they are animated by
alkaline fluids. (The movements
cease when the spermatozoa are ex-
posed to a temperature of 120°
Fahrenheit.) These bodies are de-
veloped in the cells of the tubuli
seminiferi by a modification of
their contents. Their development has been already described above.
1, Spermatozoon of the fro^ ; 2, of the triton ; 3, of
the finch ; 4, of the field-mouse ; 5, of the hedge-
hog ; 6, sheep, a, Head with nucleus ; b, body ; e,
tail.
Excretory Apparatus of the Semen.
1. The Epididymis and Deferent Canal (Figs. 368, 517, 518, 519).
Epididymis. — The organ thus named commences the excretory canal of the
testicle. It is a body elongated from before to behind, placed against the upper
border, and a little to the outside, of the testicle. It has a middle portion and
two extremities.
The middle is contracted, flat on both sides, and free outwardly ; it is related,
inwardly, to the spermatic vessels and the testicle, to which it is attached by a
very short serous layer. The extremities are expanded, and adhere closely to the
testicle. The anterior — the largest — is named the head of the epididymis, or globus
major. The posterior, the tail of the epididymis, or globus minor, is more detached
from the testicle, and is curved upwards to be continued by the deferent canal
{vas deferens).
Structure. — The epididymis results from the union of from twelve to twenty
small tubes — the efferent ducts — which, arising from the rete testis, open together,
at a variable distance, into the globus major. Towards the globus minor there
is only one duct, which is more voluminous and less flexuous, and ends by becom-
ing detached from the posterior lobe of the epididymis to constitute the vas
deferens.
The organization of the walls of these ducts is not the same throughout.
Thus, in the efferent ducts it comprises a simple ciliated epithelium, resting on a
proper amorphous membrane, which again is placed on unstriped circular fibre,
968 GENERATIVE APPARATUS.
lying on a thin fibrous tunic ; while beyond, there is observed a stratified ciliated
epithelium, a proper membrane, two layers of unstriped fibres — circular and
longitudinal — and also a fibrous tunic. The thickness of the muscular layers
increases from before to behind.
The epididymis is enveloped by a fibrous membrane and the tunica vaginalis
propria. It receives its arteries and nerves from the same sources as the
testicle.
Vas Deferens. — This duct is about the thickness of a goose-quill, and is at
first flexuous, then straight. It lies parallel with, but behind and to the inner
side of, the spermatic vessels, as far as the opening of the internal ring ; passing
through this opening, it enters the pelvic cavity, and crosses obliquely the ureter
and obliterated cord of the umbilical artery. It is then inflected backwards above
the bladder, suddenly dilates {bulbous portion), and is prolonged as far as the
neck of that reservoir, where it terminates, after having penetrated beneath the
prostate gland by a sudden constriction, at the origin of which, and outwardly,
the vesicula seminalis opens, and is continued by the ejaculatory ducts.
It may, therefore, be divided into four portions— a testicular, funicular,
inginual, and pelvic.
The vas deferens is sustained in the vaginal canal by a very short serous fold
— a dependency of the fraenum — the two layers of which envelop the spermatic
vessels, within and behind which this duct is situated. In the abdominal cavity,
it is fixed by the prolongation of this serous duplicature. Its dilated or pelvic
portion is in contact, superiorly, with the vesiculte seminales, and is finally united
to its dilated homologue of the opposite side — which it has been gradually
approaching — by means of a triangular peritoneal fold, that comprises between
its two layers a small club-shaped cavity — the prostatic utricle, which will be
alluded to again.
The calibre of the vas deferens is very small in its vaginal and abdominal
portions, but is greater towards the pelvic dilatation, where the wall of the duct
offer a well-marked areolated disposition (ampullce).
Structure. — The vas deferens is formed, internally, by a very fine mucous
membrane covered with cylindrical epithelium, and to this is added, externally, a
contractile and a, fibrous tunic. The contractile layer is formed of three planes of
smooth muscular fibres ; the deep and superficial planes have longitudinal, and
the middle circular fibres. It is, proportionately, very thick at the dilated por-
tion of the duct, and it is to its great density that the vas deferens owes its con-
sistence as a hard, rigid cord. The mucous membrane of the pelvic dilatation
offers a large surface, being inflected into all the depressions, but it has no
follicles ; the cells of its epithelium have special granules which give a dark
colour to the membrane.
2. The Vesicula Seminales and Ejaculatory Ducts (Fig. 522).
The vesiculce seminales are two oval pouches, the volume of which varies with
their contents ; they are placed in the pelvic cavity, above the bladder and the
vas deferens.
Each vesicula has a middle portion and tivo extremities. The middle portion
is enveloped by a loose abundant connective tissue, and is in relation with the
rectum above, and below with the bladder and vas deferens.
The anterior extremity is the largest, and forms a rounded cul-de-sac, covered
THE GENITAL ORGANS OF THE MALE.
Fig. 522.
in almost the same manner as the bladder by the peritonemn, which at this
point furnishes a very small triangular frifinum (the recto-vesical fold) that
unites the two vesiculae. The posterior extremity tapers to a narrow neck or
gullet, which passes beneath the prostate gland, and joins at a very acute
angle the terminal extremity of the vas deferens, to constitute the ejaculatory
duct.
The walls of this pouch are composed of three membranes : an internal
mucous, a middle muscular, and an external
fibrous. The mucous layer is contmuous with
that of the ejaculatory ducts, and is very thin,
dehcate, and follicular. It shows numerous
folds, which disappear with distension of the
duct. The middle layer evidently belongs to the
class of muscular membranes. At the bottom of
its cul-de-sac it gives off several fasciculi, which
radiate on the external surface of the peritoneum.
(In addition to these, the vesiculae and vasa
deferentia have a muscular covering with fibres
arranged in longitudinal and transverse direc-
tion, the latter being the most superficial. This
muscular layer, being continuous over the vesi-
culae seminales and vas deferens, when it contracts
will compress and shorten these ; consequently,
it has been named the compressor vesiculcB et ductus
semincdis. The fibroiis coat of the vesiculse is
merely condensed connective tissue.) The mucus
and muscular coats are supplied with blood by
the vesico-prostatic artery {inferior vesical) ; their
nerves are derived from the pelvic plexus.
The richness in glands of the mucous mem-
brane of the vesiculas seminales, has led several
anatomists to consider them as organs of secre-
tion, and not as reservoirs for the semen. But
the large cavity that each forms, appears to
demonstrate that they serve as reservoirs and
secretory organs at the same time. Their fluid
is added to the semen, as is the secretion of the
prostate and Cowper's glands.
The ejaculatory duct is very short, and succeeds
the narrow canal of the vesicula after the latter
opens into the vas deferens. The two ducts pass
between the prostate gland and urethra, and,
after 'a brief course, terminate in the latter, on
the side of the verumontanum — a tubercle which
will be noticed presently.
Near to, and in front of this tubercle, is a third very small orifice — the open-
ing of the third pouch included between the serous duplicatures joining the vasa
deferentia. (This is the siims pocidarls or utriculus prostatio, the protometra, or
vesicula seminalis tertia or media of Gurlt.) Improperly designated the third
vesicular, or masculine uterus (Weber), this pouch (sometimes double) secretes a
SUPERIOR VIEW OF THE PELVIC POR-
TION OF THE VASA DEFERENTIA,
VESICULA SEMINALES, PROSTATE
GLAND, cowper's GLANDS, AND THE
INTRA-PELVIO PORTION OF THE
URETHRA.
1, Left vas deferens; 1', its pelvic
dilatation; 2, 2, the same on the
right side ; 3, 4, vesiculae seminales;
5, the third vesicula; 6, serous
layer uniting the vasa deferentia ;
7, that comprised between the two
vesiculae ; 8, prostate gland ; 9,
bladder seen through the serous
fold of the vasa deferentia; 10,
membranous or intra-pelvic portion
of the uremral canal, covered by
Wilson's muscle; 11, 11, Cowper's
glands enveloped by that muscle;
12, 12, ischio-cavernosus muscle;
13, accelerator urinae muscle.
970 GENERATIVE APPARATUS.
fluid which is thrown into the urethra.^ (This third vesicula is present in all the
domesticated animals.)
The ejaculatory ducts may become obliterated ; then the secretion of the
vesiculae seminales accumulates in their interior, and gradually distends them
until they attain enormous dimensions. We found, in a Gelding, a vesicula
which was nearly as large as the bladder ; it contained a brownish, adhesive fluid,
holding in suspension epithelial cells and free nuclei.
(The vesiculae seminales, in addition to tiieir own secretion, receive the semen
conveyed by the spermatic ducts, and keep it in reserve until copulation ; when
the contraction of its muscular apparatus expels it into the ejaculatory ducts,
and from these into the urethral canal.)
3. The Urethra.
The urethra is a canal with membranous and erectile walls, commencing at
the neck of the bladder, and terminating at the free extremity of the penis.
Course. — When followed from its origin to its termination, it is seen to
proceed at first horizontally backwards, then bend downwards at the ischial arch
to leave the cavity of the pelvis, placing itself between the two roots of the
corpus cavernosum, and passing forward in the channel formed at the lower
border of these, until it arrives at the head (glans) of the penis, where it termi-
nates by forming a small (cylindrical) prolongation, named the urethral tube.
In its track, the urethra is divided into two very distinct portions : the intra-pelvic
— the shortest, and the extra-pelvic — the most extensive, and which is supported
by the corpora cavernosa. The latter division, being alone enveloped by the
erectile tissue that enters into the formation of the urethral walls, has been also
named the spongy portion, the first being designated the membranous (and pro-
static) portion.
Interior. — Internally, this canal has not the same width throughout. Very
constricted at its origin, towards the neck of the bladder, it expands somewhat
suddenly at the prostate gland ; its dilatation, improperly named in Man the
cul-de-sac of the bulb (bulbous portion), or, better, the ventriculus, extends to its
curve over the ischial arch, where it gradually contracts. After this it preserves
the same reduced dimensions throughout its course, though these dimensions may
be increased during the passage of the urine or semen. There is, however,
behind the urethral tube a small oval dilatation, named the fossa navirularis
(Fig. 524). Smooth throughout its extra-pelvic portion, the inner surface of the
urethra offers, near the neck of the bladder, and on its upper wall, the excretory
orifices of the prostate gland, which form two lateral lines of minute perforated
tubercles. Between these two lines is found the urethral ridge or verumontanum
{caput galUnaginus), a httle eminence elongated from before to behind, on the
sides of which the ejaculatory ducts open. Behind this are the excretory orifices
of Cowper's glands.
Relations. — The intra-pelvic portion of the urethra is in relation, above, with
the prostate, which adheres closely to it, and with the rectum, to which it is
' In some Asses, we have found this pouch bifurcated at its anterior extremity, and there-
fore bearing a distant resemblance to the female uterus.
(Though Chauveau states that the protometra is improperly named the male uterus, it would
appear, nevertheless, that the designation is correct ; as this pouch is not a gland in the
ordinary sense of the term, and is certainly the rudiment of the duct which develops into the
uterus in the female.)
TEE GENITAL ORGANS OF THE MALE. 971
united by the abundant loose connective tissue in this part of the pelvis ; below,
it lies on the internal obturator muscle ; laterally, it is related to the muscles
and ligamentous or aponeurotic expansions that close in the sides of the pelvis.
Outside the pelvic cavity, the urethra is united in the most intimate manner
to the corpora cavernosa, which embrace its anterior border. By its posterior
border, it is related to the suspensory ligament of the penis.
Structuee. — The urethra is composed of : 1. Mucous membrane. 2. An
srectile envelope. 3. Muscles. 4. Vessels and nerves. 5. The perineal aponeuroses,
which are in immediate relations with this canal.
1. Mucous Membrane. — This is rather delicate, and forms the lining of
the canal. It is continuous, posteriorly, with that of the bladder, and in front
with the integument enveloping the head (glans) of the penis ; it is also
prolonged into the excretory ducts of the glands annexed to the urethra, and the
€Jaculatory ducts. It has longitudinal folds, and is always in contact with
itself, except during the passage of urine or semen ; it has scarcely any papillae,
only a few being found near the anterior extremity of the canal ; and its tissue
is very rich in elastic fibres.
The epithelium of this membrane is stratified and cylindrical, but at the
portion furnished with papilla it becomes pavemental.
2. Erectile Envelope. — This envelope, lying outside the mucous membrane,
does not cover the intra-pelvic portion of the canal. It commences a little above
the ischial contour, behind Cowper's glands, by a very thick bulging portion,
named the bulb of the urethra. In front, it terminates by another bulbous
enlargement, into which the anterior extremities of the corpora cavernosa enter,
named the head of the penis (glans penis).
The tissue composing this envelope has the same organization as other
erectile apparatuses, being a network of communicating cavities separated by
elastic septa, the latter showing in their structure some contractile elements (see
Corpora Cavernosa).
3. Muscles. — Behind the prostate gland, the mucous membrane of the
urethra is covered by a fleshy layer of circular fibres, forming a sphincter.
Another muscular envelope, constituting the bidbo-cavernous or accelerator urinoe
muscle, also covers the erectile tissue of the urethra, accompanying it to near
the glans, where it gradually disappears. To these two principal muscles of the
urethra are added two pairs of secondary fasciculi — the compressor of Cowper's
glands and the transversus perincei. The following is a resume description of
the muscular apparatus : —
a. Urethral sphincter.^ — This may be described as a single muscle composed
of two portions — an inferior and a superior. Both are formed by transverse
fibres thrown over the membranous portion of the urethra, and both— the
superior and inferior — are united at their extremities, which are not attached to
the walls of the pelvis. Behind, the superior fibres are mixed with those of the
compressor of Coivper's glands.
b. Accelerator urince. — Composed of transverse fibres encircHng the urethra
' Up to the present, this organ has been described in books on Veterinary Anatomy as
Wilson's muscle. In a work entitled Recherches sur VAnatomie compare'e du Perine'e, published
in Professor Robin's journal, Paulet riglitly objects to this designation, which perpetuates an
error of interpretation. We adopt this opinion, not only with regard to this muscle, but also
the ischio-urethral, which, with him, we more exactly designate aa the compressor of Cowp&i'$
glands.
972 GENERATIVE APPARATUS.
from the ischial arch to the free extremity of the penis, this will also be studied
as a single organ, separated into two lateral portions by a median raphe passing
along the whole posterior face of the urethra. The fibres pass from this raphe
to the right and left, enter the furrow of the corpora cavernosa, and reach the
upper surface of the urethra, where they advance towards each other, but do not
join in the middle line ; so that the circle formed by this muscle is necessarily
incomplete.
c. Compressor muscle of Comperes glands. — This muscle is composed of two
layers of fibres — a superior and an inferior — confounded on the periphery of
Cowper's glands. The superior layer is continuous, it may be said, with the
upper part of the urethral sphincter. The inferior layer is attached, posteriorly,
by some aponeurotic fibres to the ischial arch.
d. Transversus perincei. — This is a very thin ribbon-like fasciculus, often
scarcely distinguishable from the ischio-anal muscle {retractor am). It extends
transversely from the ischial tuberosity — to which it is attached through the
medium of the sacro-sciatic ligament — to the mesial line of the perineum, where
its fibres — confounded with those of its homologue on the opposite side — appear
to be inserted in the accelerator urin^e muscle at its origin.
e. Action of the urethral muscles. — 1. The urethral sphincter, when it contracts,
compresses between its two layers the membranous portion of the urethra. It is
a veritable sphincter, and opposes the escape of the urine ; when the semen is
thrown from the vesiculae seminales into the urethra, it also prevents that fluid
entering the bladder, by permitting the accelerator to empty, from before to
behind, the initial dilatation of that canal. 2. The accelerator urince is correctly
named, from the part it plays in ejecting the semen from the urethra — it being
the chief agent in this act. 3. The compressor of Coivper'^s glands pulls back the
membranous portion of the urethra, along with Cowper's glands, and acts as a
compressor to these. 4. The transversus perincei dilates the bulbous portion of
the urethra, by drawing it out laterally.
4. Vessels and Nerves. — The urethra is supplied with blood by the bulbo-
urethral arteries and the two pairs of arteries — the dorsals of the penis. Voluminous
veins — frequently varicose, and satellites of the arteries — carry it away. The
Igmphatics form a very rich plexus beneath the mucous membrane ; their trunks
pass to the inguinal, and some to the sublumbar, glands. The nerve-Ma.ments,
are from the internal pudic and great sympathetic.
5. Aponeuroses of the Perineum. — In the perinaeal region, the urethra
is covered by two superposed fibrous layers.
The superficicd aponeurosis is fibro-elastic, and appears to arise from the inner
surface of the thighs, where it is mixed with the dartos ; it covers the piirinteum,
and its fibres, becoming disassociated, disappear on the sides of the sphincter ani.
This membrane is in relation, externally, with the skin, and, internally, with the
deep aponeurosis. On the middle of its external face, it receives the insertion of
a muscular fasciculus, which is detached from the sphincter.
The deep or perinatal aponeurosis, formed of white inelastic fibrous tissue,
adheres to the preceding by its outer face, and to the accelerator urinte and
ischio-cavernous muscles by its inner face. Above, it is lost around the termina-
tion of the rectum ; below, it expands between the thighs. To the right and
left, it insinuates itself between the erector penis and semimembranosus muscles,
to be attached to the ischiatic tuberosity ; it is prolonged in the pelvic cavity
between the bladder and rectum, where it hmits two independent spaces : 1. A
THE GENITAL ORGANS OF THE MALE. 978
superior — defecatory — space. 2. An inferior— genito-urinary— space. Below
it is confounded with the fibrous envelope of the penis.
4. The Glands annexed to the Urethra.
A. Prostate (Fig. 522, 8). — This single and symmetrical gland is situated
at the commencement of the urethra, and lies across the neck of the bladder. A
constriction in the middle divides it into two voluminous lateral lobes, inclining
slightly forward. Its upper face corresponds to the rectum, through the medium
of the connective tissue at the bottom of the pelvic cavity. Its inferior face,
moulded on the neck of the bladder, embraces it above and laterally, and is
closely attached to it ; it covers the terminal extremity of the vas deferens and
ejaculatory ducts, and the neck of the vesiculae seminales.
Structure. — The tissue composing this gland forms a number of com-
municating cells, which are larger in the Ass than the Horse ; in these is
collected a quantity of viscid fluid {succus prostaticas) secreted by their walls,
and which is ejected into the urethra by the two rows of orifices arranged on the
sides of the verumontanum. These communicating cells are nothing more than
conglomerate glands, which are distributed in a stroma of connective tissue and
uustriped muscular fibres. The epithelium of the glandular culs-de-sac is formed
of two layers of cells ; those of the excretory ducts are ciliated.
B. Cowper's Glands. — In Veterinary anatomy, these are frequently named
the small prostates. They are two globular bodies, denser in texture than the
prostate gland, but otherwise the same in organization, except in their
epithelium, which is cylindrical. They are situated on each side of the urethra,
in the perinseal region, above the ischial arch, and are completely enveloped by
a somewhat thick fleshy covering, formed by the fibres of the compressor muscle
(Fig. 522, 11).
The fluid they secrete is thrown into the urethral canal by numerous orifices
in several rows, near the middle line of the superior plane. It has the same
physical properties as that of the prostate, and both are poured into the urethra
in abundance immediately before ejaculation ; the expulsion of the semen is by
this means facilitated.
5. The Corpus Cavernosum.
The corpus cavernosum is an erectile body, which forms the base of the penis
and supports the urethra ; it is situated between the thighs, prolonged beneath
the abdomen, attached behind to the ischial arch, and terminates in front by a
free extremity, which is received into the erectile enlargement named the glans
penis.
External conformation. — Flattened on both sides, this body offers for study
two lateral faces, two borders, and two extremities.
The faces are plane, and present no features of interest. The superior, or
dorsal border, is the thickest, and is rounded on both sides. The inferior is
channeled throughout its extent by a deep furrow which lodges the urethra.
The posterior extremity is bifurcated, the two branches constituting the roots
(corpora or crura) of the penis ,• they are fixed to the ischial arch, one to the
right, the other to the left, and are covered by the two ischio-cavernosus
{erector penis) muscles — short, thick, and strong masses intersected by numerous
64
974 GENERATIVE APPARATUS.
tendinous fibres, and partly concealed by the semimembranosus muscles. These
erector penis muscles arise from the inferior ischiaic spine, and terminate on the
membrane enveloping the crura of the penis, which they cover posteriorly and
externally.
The anterior extremity of the corpus cavernosum forms a blunt point, and is
surrounded by the spongy tissue of the glans.
Mode of attachment of the corpus cavernosum. — The chief attachment is
constituted by the insertion of the two crura into the ischiatic arch. There is
also a double suspensory ligament proceeding from the ischio-pubic symphysis,
where it is confounded with the superior attachments of the short adductor of
the thigh, and passes to the dorsal border of the corpus
Fi|^3. cavernosum, a little in front of the point of union of its
crura.
Structuee. — This erectile organ is composed, ex-
ternally, of a white, elastic, fibrous envelope, remarkable
for its thickness, especially on the dorsum ; it gives off,
from its inner face, a certain number of lamellar trabe-
culge which partition the interior of the cavity it forms.
One of these septa {septum pectiniforme) is directed
vertically from the upper to the lower border, and di-
TRANsvERSE~%ECTioN OF vldcs thc corpus cavcmosum into two lateral portions
THE PENIS, SHOWING THE {corfora cavemoso)^ which would indicate that the crura
URETHRr WITH THE ^^® "^^ ^^^ °^^^^ ^^ ^^^^^ P^^^^^ ^^ ^^0°' ^^^ ^^^^^^^
CORPUS CAVERNOSUM. joiuod to each other. In the Horse, this septum is
1, Erectile tissue of the generally Very incomplete, and rarely extends the whole
corpus caveruosum ; 2, length of the Organ.
urethral canal ; 4, e^rectile The lamellar prolongations sustain other elastic and
tissue of the urethra ; 5, contractile bands, which circumscribe the cavities in
secttnlf'theTspensory ^^^^ch is lodged the essential portion of the erectile
ligament of the penis. tissue. According to Legros, the latter is composed of
a network of capillaries interposed between the arterial
and venous twigs ; this network shows abrupt or regular dilatations of a diameter
varying from •0001 m. to '0015 m. These successively dilated capillaries have
very thin walls, which are adherent to the contractile prolongations of the
envelope, and are lined by a very delicate pavement endothelium. In the areolae
of the cavernous tissue, particularly towards the base of the organ, the arteries
offer a special arrangement ; their walls are very thick, and they soon divide
into a bouquet of branches which enter the areolae, where they terminate either
by a cul-de-sac, or — which is most frequent — give off small free branches convo-
luted in a spiral manner. These are the arterim helkince described by Midler and
Rouget. (The walls of the cells are composed of white and yellow fibrous tissue,
and unstriped muscular fibres. The cells themselves are in reality venous sinuses.
KoUiker found a minute artery to proceed from each of the caecal terminations
of the helicine arteries, and terminate, like the other capillaries, in the veins.
The dilated vessels have been regarded by some anatomists as only vascular loops.
The cells, during the erection of the penis, are distended with blood.)
The arteries of the corpus cavernosum and dorsales penis pass into the
erectile structure, and supply this organ with blood. The collateral veins of
these arteries arise near the surface. The nerves are from the internal pudic
and great sympathetic.
THE GENITAL ORGANS OF THE MALE.
975
6. The Penis.
The penis is the male organ of copulation, and results from the union of the
corpus cavernosum and the spongy portion of the urethra. These parts have
already been described ; so it now remains to consider the organ in its entirety.
The penis commences at the ischial arch, passes between the thighs and the
two dartoid sacs containing the testicles, and is prolonged beneath the belly,
where it terminates in a free extremity.
All the portion comprised between the ischial arch and the scrotum is
maintained and deeply covered by the sm'rounding textures, and is named the
fixed portion of the penis. The remainder of the organ — its anterior moiety —
is, on the contrary, its free p)ortion, as it forms a detached appendage sustained
by a cutaneous fold — the sheath (or prepuce).
The Fixed Portion occupies the perinasal region and that between the
thighs, where it is enveloped by
the arteries, veins, and nerves ^'g- ^24.
already known, as well as by a
large quantity of connective tissue
(and the skin).
The Free Portion is lodged
in the prepuce during the inactive
condition of the organ, but pro-
trudes from it when in a state of
erection. It is then seen to be
covered by a smooth, unctuous,
tegumentary membrane with
numerous papillae, and of variable
colour, though most frequently it
is black or variegated. Its base
presents a slight circular enlarge-
ment, due to the accumulation,
beneath the mucous membrane, of
a small annular mass of elastic
and contractile tissue. Its ex-
tremify or glans is also a circular enlargement, lunited behind by a salient ridge
— the corona glandis — which is notched inferiorly, and at the moment of ejacu-
lation assumes a considerable development, its shape being then not unlike
the rose of a watering-can. This enlargement has for its basis the terminal
expansion of the urethral erectile tissue, and presents on its anterior face : 1. In
the centre, a rounded prominence due to the anterior point of the corpus cavern-
osum. 2. Beneath this, the urethral tube encircled by a fossa. 3. At the
bottom of the fossa, and below the urethra, the orifice of a double cavity —the
urethral sinus, which widens at the bottom, and in which accumulates sebaceous
matter that sometimes becomes so hard as to prevent the flow of the urine, by
compressing the tube. 4. Inferiorly, the suburethral notch.
The dermis covering the extremity of the penis is rich in nerves which,
according to Kraiise, have round dilatations which he designates as " terminal
genital corpuscles."
To complete the description of the penis, there only remain to be described :
1. Two suspensory and retractile ligaments which concur, with the natural elasti-
LONGITUDINAL SECTION OF THE FREE EXTREMITY OF
THE horse's penis IN A RELAXED STATE.
1, Erectile tissue of the corpus cavernosum ; 2, urethra;
3, fossa navicularis ; 4, urethral tube ; 5, erectile
tissue of the urethra; 6, ditto of the glans; 7,
corona glandis ; 8, urethral sinus.
976 GENERATIVE APPARATUS.
city of the fibrous envelope of the corpus cavernosum, to return the organ to ita
ordinary position when the phenomenon of erection has ceased. 2. The tegu-
mentary fold, or sheath, which envelops the free portion of the penis when in
its ordinary state of repose.
A. Suspensory and Retractile Ligaments of the Penis. — Two in
number, these ligaments arise from the lower face of the sacrum, descend as
flat bands in front of the sphincter ani, between the retractor muscle of the anus
and the rectum, to which they give numerous short fasciculi from their posterior
border ; they then unite at the mesial line, below the anal opening, thus forming
around the terminal extremity of the rectum a real suspensory ring. Lying
together, and intimately united, they are continued on the accelerator urinae,
which they follow at the raphe, and are eventually lost in its texture, near the
free extremity of the penis.
These cords are composed of unstriped muscular fibres.
B. Prepuce. — The prepuce, or sheath, is a cavity formed by a fold of the
abdominal skin, and lodges the free portion of the penis ; it is entirely effaced
at the moment of erection, when the copulatory organ is lengthened and enlarged.
The skin at the opening of the prepuce enters its cavity, and, on arriving at the
free portion of the penis, forms a circular cul-de-sac in becoming reflected over
the organ, which it envelops.
This lining integument of the prepuce is fine, and is very irregularly plicated ;
it is destitute of hair, and holds a middle place, with regard to organization,
between the skin and mucous membranes. It contains in, or beneath, its sub-
stance a considerable number of sebaceous or prceputial glands that secrete an
unctuous fatty matter (exhaling a peculiar odour, and dark grey in colour — the
smegma praputii), which is spread over the free surface of the membrane.
Above, the inner integument of the sheath is applied to the tunica abdomin-
alis. Below, and on each side, tlie cutaneous fold constituting this cavity con-
tains between its layers an expansion of yellow elastic fibrous tissue, the lateral
portions of which, attached to the abdominal tunic, are named the suspensory
ligaments of the prepuce.
In the Ass, there exists, near the entrance to the prepuce, and on each side,
a small tubercle which may be looked upon as a rudimentary teat of the female.
(The prepuce protects the penis, and sustains it when in a flaccid state. In
certain Horses, a gurgling sound is produced in trotting, from the air brusquely
entering and leaving this sheath.)
Differential Characters in the Male Genital Organs of the other Animals.
Ruminants.— Farina? sheath.— Go\\h&\x\ has remarked that, in the Bull, the internal
inguinal ring is very small when compared with that usually seen in the Horse. It is situated
nearly at the point of union between the two originating branches of the sartorius muscle.
Testicles— In these animals tiie testicles are very voluminous, oval, and vertically elongated.
Thev, with their envelopes, form a pendant mass that occupies the inguinal region. The
scrotum is always of a pale colour. In the interior of the testicle, the corpus Higlimorianum
and the rete testis nre very marked. (The proper tissue is yellow, and the septa formed by
the prolongations of the tunica albuginea are not very distinctly seen.)
Epididymis.— Vas deferens.— T!\\e head of the epididymis is wide and flat, and partly covers
the ant.rior border of the testicle. The miildle portion, smaller than in Solipeds, represents a
narrow cord lying outside the posterior border of the seminal gland. The tail is a little free
appendage, inflected inwards and upwards to become continuous with the vas deferens. The
latter is dilated, as in the Horse, when it arrives above the bladder, and lies beside the duet
of the opposite side. The two, thus joined, increase from before to behind, leave the neck of
THE GENITAL ORGANS OF THE MALE.
OT7
the bladder in passing above the vesiculse seminales, then go beneath the prostate, and
terminate in tlie uretlira— on the summit of a ridge— by two elliptical orifices.
Vesiculee seminaUs.—In the BuU, the vesiculae seminales have not the same appearance aa
Fig. 525.
INTERNAL GENITAL ORGANS OF A YOUNG BULL (UPPER FACE).
Bladder ; U, ureter ; C, penis enveloped by the corpus cavernosum. 1, Testicle in its fibrous
envelope; 2, cremaster; 3, testicle exposed; 4, head of the epididymis; 5, tail of the epididymis,
6, vas deferens; 7, dilatation of the vasa deferens; 8, vesiculae seminalis; 9. prostate; 10, intra-
pelvic portion of the urethra surrounded by its sphincter; 11, ischio-urethral muscle; 12, accele-
rator urinse ; 13, transversus perinaei.
in the Horse, and they have not so large a cavity in their interior. They are two elongated
masses, lobulated on their surface, yellow in colour, and possessing quite a glandular aspect.
They have sometimes been designated the lateral prostates. They are composed of aciniform
978
GENERATIVE AFPABATUS.
glands, enclosed in a mass of connective tissue and unstriped fibres ; they open into a commoa
central canal, which terminates in tlie vas deferens.
Urethra. — This canal is inflected like the letter S. Its diameter regularly diminishes from
its commencement to its termination, wliich is not provided with a urethral tube, as iu
Solipeds. Internally it presents : 1. Immediately beyond the neck of the bladder, a short, but
very salient verumontanum, which divides into two mucous columns that gradually subside
posteriorly. 2. Towards the ischial arch, a
valve the free border of which — directed down-
wards— covers a cul-de-sac from about three-
fourths to one inch deep.
The structure of the urethra is also dif-
erent. The walls of the membranous portion
are tliicker than in the Horse ; they have a
layer of erectile tissue, and a sphincter muscle,
very thick below and laterally, the fibres of
which are inserted in the middle of the upper
surface, into an aponeurotic rapiie'.
At the ischial arch, when the canal bends
downwards, the spongy tissue becomes more
abundant to form the hulh of the urethra ; but
the prominence at this point is chiefly due to
the accelerator urinas, as is shown in Fig.
526, C 4, This muscle is extremely powerful,
but it soon ceases beneath the ischial arch.
The trausversus perinasi is as strong as in
Solipeds.
Glands annexed to the urethra. — Cowper's
glands are absent. Tlie prostate gland is not
voluminous, and forms, at the commencement
of the urethra, a little transverse yellow, bilo-
bate mass, beneath which pass the vasa
deferentia ; it also lies beneath the sphincter
muscle, and is prolonged for some distance on
the membranous portion of the urethra.
PfMis. — In the Bull, the penis is long and
thin, and carried well forward beneath the
belly. It is enclosed at the perinseum in an
aponeurotic sheath, which is covered by the
iscbio-tibial muscles. This sheath is double,
its superficial layer being continuous with the
dartos, and it has the same physical cha-
racters; the deep layer is thin, white, and
inelastic.
In front of the pubis, the penis describes
two successive curves — the S of the penis — the
first with its convexity forward;*, the second
backwards. It is at the second curve that
the suspensory ligmnents join tlie penis, and
continue along its sides to its extremity.
The free portion of the organ — very taper-
ing— is covered by a fine, papillated, very
sensitive, rose-coloured mucous membrane.
It is lodged in a narrow prepuce that ad-
vances much more forward beneath the ab-
domen than in Solipeds, and has at its opening a bunch of long stiff hairs. This cutaneous
sheath is moved by four subcutaneous muscles: two posterior or retractors (Fig. 527, 2) which
draw the sheath backwards, and concur in exposing the penis at the moments of its erection ;
and two anterior or protractor muscles (Fig. 527, 1) which carry the prepuce forward to its
former position. The latter are found in the Cow, and do not appear to be of any use.
The two constituent portions of the copulatory organ are not joined in the same manner as
in Solipeds, the channel for the lodgment of the urethra being transformed into a complete
canal, by a narrow layer of the fibrous envelope of the corpus cavernosum. The latter is little
J 1
SECTIONS OF THE URETHRA OF THE OX AT
DIFFERENT POINTS.
Af Intra-pelvic portion: 1, Urethral sphincter; 2,
erectile tissue ; 3, urethral canal ; 4, prostate
gland. B, The middle of the penis : 1, Fibrous
cord of the corpus cavernosum ; 2, urethral
canal ; 3, its erectile tissue ; 4, envelope of
the corpus cavernosum. C, At the crura of the
penis : 1, 1, Crura of the corpus cavernosum ;
2, urethral canal ; 3, its erectile tissue ; 4,
accelerator urinae ; 5, erector penis muscle.
TEE GENITAL ORGANS OF THE MALE.
979
developed, and presents, internally, a longitudinal fibrous cord; it is not much dilated during
erection. In this act, the penis is elongated by the straightening out of its curvatures, rather
than by any real lengthenings; when erection ceases, the organ is retracted into the preputial
cavity by the contraction of the suspensory ligaments, which reform its double inflection behind
the scrotum.
In the Ram, the disposition of the testicles and vasa deferentia is somewhat similar. The
membranous portion of the urethra has no prostate, but quite posteriorly it has two small
Cowper's glands, the upper face of which is covered by a red muscular layer that leaves the
origin of the bulbous portion and is lost on this surface. Tl)e muscles are disposed as in the
Bull. But the spongy portion of the urethra is not enveloped by the corpus cavernosum,
which is channeled, as in Solipeds, by a furrow that lodges the urethra. The head of the
penis is remarkable for two lateral folds, disposed like wings at the base of the glans. One
of these is only slightly developed, so that the head of the penis looks asymmetrical. The
Fig. 527.
PENIS AND MUSCLES OF THE PREPUCE OF THE BULL.
1, Protractor muscle of the prepuce; 2, retractor of ditto; 3, testicles in the scrotum ; 4, the S o(
the penis; 5, suspensory ligaments of the penis attached to the second curve; 6, subcutaneous
abdominal vein.
urethra is also prolonged by a vermiform appendix from 1 to Ij inches long. (In the Ram, the
extremity of the urethra has tlie form of a narrow cylinder curved backwards, its opening being
a longitudinal slit. In Ruminants, towards the extremity of the prepuce are small teats;
these, in the He-goat, are sometimes glandular, and secrete a fluid analogous to milk.)
Pig. — The testicles of this animal are round, and placed in the perinseal region. The
scrotum is narrow, and but little detached : the pouches of which it is composed appearing
simply as two hemispherical prominences on the surface of the perinseum. There is nothing
particular to be remarked in the epididymis and vas deferens; (the tail of the first is very-
voluminous; the latter has no pelvic dilatation.)
Tlie vesiculsB seminales, with regard to disposition, are intermediate between those of the
Horse and Ox. Their walls are thick and very glandular, and their interior is diverticulated.
(They are, proportionately, very large, and, in structure, closely resemble those of Ruminants;
980 GENERATIVE APPARATUS,
indeed, iu these animals they rather appear to be organs for the secretion of a milky liquid
that is mixed with the semen, than reservoirs for the fecundating material, as that fluid never
coataius any spermatozoa.) There are two prostates: one disposed as in the Ox; the other
placed across the neck of the bladder, as in Solipeds. The penis resembles that of Ruminants,
except in tlie absence of the muscles of the prepuce ; it has also a particular preputial sheath,
which lias been studied by Lacauchie. (When flaccid, the penis of the Pig is twisted in a
spiral manner at the extremity. The prepuce is narrow, and longer than in Ruminants. At
the upper part of its opening is the special poucli mentioned by Chauveau, and which is formed
by a fold of the skin. It opens into the prepuce, and secretes, in the Boar, an unctuous fluid,
possessing a particularly disagreeable smell, and which is mixed with the urine. The odour
of the secretion even taints tlie flesh of this creature.)
Carnivora. — The testicles of the Cat are formed like, and placed in the same situation as,
those of the Pig ; those of the Dog are more oval, and are pendent.
The Carnivora have no vesicals seininales. Tlie prostate gland surrounds the neck of the
bladder; it is of a yellow colour, concave on its upper surface, and divided into two lateral
lobes on its lower face. Cowper's glands are absent in tlie Dog ; they exist in the Cat (in
which they are very small, and excrete their secretion by separate efferent canals). The urethra
(in its pelvic portion) is very long; towards the ischial arch it shows an enlargement or bulb,
though this is less, proportionately, than in the Ox; the accelerator urinae muscle is continued
for a longer di-stance around it. (The spongy portion is thinner in the Cat than iu the Dog.)
" In the Dog, the jjents is long and pointed. The posterior half is constituted by the
corpus cavernosum, which is little developed, and has not a complete middle septum. The
anterior moiety has for its base a bone, found in several other manimifers, which is intended to
favour the introduction of the penis into the genital organs of tiie female.
" The penien or penial bone is elongated, conical, and incurvated, so as to constitute a furrow
inferiorly, in which is lodged the urethra when it leaves the fibrous chaimel of the corpus
cavernosum; its apex, anteriorly, partly forms the point of the penis; its base is intimately
united to the anterior portion of the corpus cavernosum; the median septum, which is very
dense, is fixed in this bone, as is the fibrous envelope which mixes with its periosteum.
" The penial bone almost entirely constitutes the base of all that portion of the penis
Included within the sheath ; in addition, this part possesses two distinct erectile enlargements —
an anterior and posterior. The first is analogous to that of the glans penis of the Horse, and
is formed by an expansion of the erectile tissue of the urethra ; club-shaped at its anterior
base, it has there a point suddenly bent downwards, beneath which is the urethral orifice ;
posteriorly it is thin, and partially covers the other erectile mass. Tlie latter is supplementary ;
it begins at the base of the free portion of the penis, where the integument of the sheath is
folded in a circular manner around it. From 1 to 1^ inches long, it embraces the upper border
and sides of the bone ; pyramidal in shape, its base, which is posterior, is from \ to l\ inches
thick; in front, it thins away beneath the erectile tissue of the head.
"Such are the two erectile masses, the summits of which overlap, so that the free portion of
the penis, bulging in front, and still more so behind, is narrowest in the middle. Although
contiguous, these two vascular dilatations are independent of each other ; the posterior has,
likewise, no communication with the corpus cavernosum, and possesses two particular veins
which pass backward in the lateral groove. Each is erected separately during copulation,
when they assume a large size ; the great volume of tlie posterior enlargement prolongs the
duration of this act, until flaccidity ensues. This peculiarity is a consequence of the absence
of the seminal reservoirs (the vesiculae seminales).
" In the Dog, two small muscles are found which appear to be destined to elevate the penis
and direct it during its introduction into the sexual parts of the female, as its erection is always
feeble. These are two fasciculi which proceed from the crura of the penis, and pass forward
to unite in a common tendon implanted on the dorsal border of the organ ; they thus resemble
the cord of a bow.
" The Bubpenial muscular cords exist as in the other animals. The prepuce is narrow and
long, and, as in the didactyles, has protractor muscles ; the integument is thin and rose-coloured,
like that covering the free portion of the penis.
" In the Cat, the penis is short, and directed backwards ; but in a state of erection it is in-
elined forwards for copulation. Its free portion presents some peculiarities. It is conical, and
its summit, near which is pierced the urethral opening, has for its basis a small incomplete
penial bone, that encloses a layer of erectile tissue — an expansion of that of the urethra. This
free portion is covered by an integument studded with somewhat rigid papillae directed back-
wards, and capable of being made erect during copulation. These points, which are met with
in nearly all the feline species, are analogous to the hairs, scales, strong spines, and even the
TEE GENITAL ORGANS OF THE MALE. 981
cartilaginous saws, of certain other animals, and which appear to be related to the degree
of sensitiveness of the female sexual organs " (A. Lavocat).
Glaiids annexed to the genital orgam.—Chatm has studied the anal glands in the Dog.
These are two oval masses about half an inch long, situated on the sides of the rectum, at its
teriuination. They are covered by a tunic of striped muscular fibres, and are formed by acini
measuring from -05 mm. to -07 mm. and -10 mm., whicli are lined by polyhedral cells of -009
mm. In the centre of the gland is a small reservoir that communicates by a short and dilatable
canal with the definitive excretory duct; this opens on the margin of the anus by an opening
partially concealed by a told of skin. The secretion is brownish and foetid.
In the young Dog, the general disposition is the same, the constituent anatomical elements
only being a little smaller.
In the Cat, the disposition of the glands differs but little from wliat is observed in the Dog.
Roj)Ems.— Vaginal sheath.— In the Rabbit, the internal inguinal ring is very elongated,
and placed horizontally below the inferior fiice of the pelvis ; the bottom of the scrotal cavity
— pyriform — hangs beneath the ischium.
The cremaster muscle completely envelops the fibrous tunic ; the dartos is only represented
by a few scattered fibres ; the scrotum is covered by long and fine hairs.
Tes^'c/es.— Tliese are ellipsoid in shape and relatively voluminous. They are lodged som'e-
times in the scrotum, at other times in the abdomen ; in tiie latter case, they are attached to
the bottom of the scrotal sac by a gubernaculum testis. The seminiferous ducts are very
developed, and easily separated.
Epididymis— Vas de/trens.—The head of the epididymis is flattened, and the tail forms a
conical and very much detached appendix. The vas deferens is isolated from the vessels of
the testicle in the scrotal cavity, so as to form two spermatic cords. When the deferent canals
arrive above the bladder, they remain free and without dilatation, and open at difl'erent places
in the urethral canal, beneath a small valve.
Vesicula seminalis.— There is only one— the male uterus— Vfith thin walls, lying on the
cervix and part of the upper face of the bladder. This vesiculus terminates, posteriorly, by
a very short canal placed in the prostate, and opening on the surface of the urethra, above a
Talve situated between those which cover the termination of the deferent canals.
Urethra. — This canal is very dilatable, and has thin walls exclusively membranous in its
terminal moiety. It has no erectile enlargement at its extremity.
Glands. — The prostate of the Rabbit is oblong and voluminous ; it lies across the com-
mencement of the urethra, but is prolonged forward in such a manner as to cover the deferent
ducts and a great part of the vesicula semiualis. There are two Cowper's glands, which are
oval and enveloped in the sphincter of the urethra.
Penis. — When this organ is relaxed, it has a horizontiil direction, parallel to the coccygeal
region. Its total lengtli is about 8 inches— 4 for the fixed, and 4 for the free portion. The
dorsal border is thin, and the other border has a groove in which is lodged the urethra.
The penis is contained in a prepuce or sheath, the outer surface of which is garnished with
longer hairs than those on the neighbouring parts ; it is also provided with a retractor muscle,
which is fixed around the penis.
The other muscles tliat act on the penis are : 1. Two enormous erectores penis. 2. A
rudimentary accelerator urinse that seems to disappear towards the extremity of the organ. 3.
A long, flat muscle, the fibres of which are directed obliquely downwards and backwards,
commencing, as they do, on the borders of the coccyx, and terminating on the sides of the deeper
portion of the corpus caveruosum ; in contracting, this muscle draws the penis from the inferior
face of the coccygeal vertebrse. 4. A muscle formed of two bellies, attached to the ischiatic
arch, and prolonged behind by a tendon which is fixed on the dorsum of tlje penis. This
muscle — which we propose to name the subischio-cavernous (suberectores penis) — plays an
important part in copulation. We have observed, while injecting the penis, that the organ in
a state of erection is vertical ; but this position is unfavourable for sexual intercourse, and then
it is that the muscle intervenes, for when it contracts it raises the penis towards the abdomen,
and renders coition possible.
Glands annexed to the genital organs. — Below the root of the tail, on each side of the anus
and prepuce, are two large shallow cavities lined by white skin, moist and destitute of hair.
In the centre of these cavities is a papilla with an opening in its summit ; this papilla corre-
sponds to the anal gland.
The anal glands are conical, and formed of two little superposed masses — one brown in
colour, the other yellow-tinted. They are constituted by a number of glandular acini, that
secrete a fatty unctuous matter. At the bottom of these cavities also open the excretory duct
of two other undescribed glands. These are situated deeply on each side of the rectum ; they
982 GENERATIVE APPARATUS.
are yellow in colour, and are formed — like the preceding — of acini, the cells of which contun
much fat. Because of their situation, we have named these the rectal glands.
We have also studied tlie generative organs of the Leporide — a new or hybrid species
which has been the subject of much discussion ; and have remarked that there is a perfect
resemblance between these organs in a male Leporide and those of the Rabbit. The testicles
found in the abdomen have furnished a fluid rich in very vivacious spermatozoids. These
Leporides have, therefore, all that is necessary for reproduction inter se.'
Comparison of the Genital Organs of Man with those op Animals.
Coverings of the testicles. — The scrotum, dartos, tunica erythryoidea,&nd tunica vaginalis have
the sume organization as in Solipeds. The scrotum is rich in sebaceous glands, and the tunica
vaginalis is separated by a serous layer from the peritoneal cavity.
Testicles. — These are ovoid, and situated in an oblique direction downwards and inwards ;
their largest curvature is forwards.
The epididymis ofl'ers the same arrangement as already noticed, except that the vm
Fig. 528.
16
SECTION OF PELVIS TO THE LEFT OF THE MEDIAN LINE AT THE PUBES, AND THROUGH
THE MIDDLE OF THE SACRUM.
1, Section of left pubic bone; 2, peritoneum on bladder; 3, left crus penis; 4, pelvic fascia
forming anterior ligaments of bladder ; 5, part of accelerator urina; ; 6, posterior layer of
triangular ligament forming the capsule of the prostate ; 7, anterior layer of triangular
ligament; between 6 and 7 are seen the membranous urethra, deep muscles of urethra (insertion),
and Cowper's gland of the left side; 8, vas deferens; 9, bulb of urethra; 10, rectum; 11, cut
edges of accelerator urinse and transversus perinaei ; 12, left ureter; 13, reflection of deep layer
of superficial fascia round transversus perinaei ; 14, left vesicula seminalis ; 15, cut edge of
levator ani ; 16, rectum ; 17, prostate gland.
deferens, in being detached from the globus minor, is bent somewhat suddenly to reach the
abdominal cavity. There are several diverticuli annexed to the epididymis, named the pedicu-
lated hydatid of Morgagni, non-pediculated hydatid aberrant vessels, and corpus innominatum of
Giraldes.
The hydatid of Morgagni is a little projection at the head of the epididymis, filled with a
serous fluid which is never mixed with the semen. The non-pedicidated hydatid is a small
white mass which rises from the testicle at some distance from the globus major ; it has a
cavity that communicates witli the duct of the epididymis. The aberrant vessels are fine
flexuous ducts given off" from the globus minor, and soon terminate in a cul-de-sac. The corpus
innominatum of Giraldes is a small mass of ramifying tubes included in the connective tissue
uniting the globus majnr to the testicle. All these anpendages of the testicle or epididymis,
are the remains of the Wolffian body.
For further details, see Arloing, " Etude Comparative sur les organes genitaux du Lifevre^
du Lapin et du Leporide," in Robin's Journal de I'Anatomieet de la Physiologie for 1868.
THE GENITAL ORGANS OF THE FEMALE. 983
Vas deferens. — This is not united to its fellow by a peritoneal fold ; it is slightly dilated on
arriving at the neck of tlie bladder, as in the Horse. The vesiculse seminales are elongated,
and lobulated on their surface, as in Ruminants.
Urethra. — Tliis canal has a fixed and a free portion : the first is sliglitly inclined downwards
and forwards ; the second is suddenly inflected, and, with the preceding, forms the prepubio
angle, which disappears with erection. Its diameter increases a little at the bulb, and again
at the meatus, to form the fossa navicularis. Its erectile envelope forms a considerable enlarge-
ment at its commencement — the 6mZ6, and this is covered, as in the Ox, by the accelerator
urinaB; it also composes another, the glans, that constitutes the head of the penis. Oii its inner
surface are some valvular folds, and some depressions — the lacunm of Morgagni, the verumon-
tanum — and towards the summit of this a email poucli — the male uterus {sinus pocularis)
which, on a very reduced scale, represents the third vesicula df Solipeds. The muscles of the
urethra are the ischio-cavernosum^ accelerator rsinir;, Wilson's muscle, and the transversus
perinaei— superficial and deep. On emerging from the pelvic cavity, the urethra traverses an
aponeurotic membrane named the ligament of Carcassonne.
Corpus cavernosum. — This oflfers nothing particular in its disposition.
Penis. — This organ is free, and is suspended in front of the pubis. It is enveloped by a
fibrous covering — the superficial fascia, and a cutaneous cylinder — the prepuce. It is attached
by two suspensory ligaments: the superficial is elastic, and arises from the linea alba; the
deep is inelastic, and is detached from the symphysis pubis and the anterior pillar of the
inguinal ring. (It is usual to describe only one ligament — the Ugamentum suspensorium penis,
separating to form two layers which give passage to the dorsal vessels, and nerves of the penis.)
The glans is separated from the rest of the organ by a constriction designated the cervix, and
around this the skin forms a (circular) fold — the prepuce, which covers the glans more or less
completely. It is attached to the middle of its lower face by a thin fold — ihefrsenum prssputii.
The inner surface of the prepuce has a large number of sebaceous glands.
CHAPTER IL
GENITAL ORGANS OF THE FEMALE.
Preparation. — In dissecting the female generative organs, their normal relations should be
preserved as much as possible by preparing the subject as in Fig. 536.
1. Place the subject in the first position, carefully removing the skin covering the perinaeum
and mammae, the [lart of the abdominal walls on v/hich the latter rest being left, but the intes-
tines removed according to the usual procedure — a portion of the floating colon being only
allowed to remain, i'inally, the posterior part of the trunk is cut away by sawing through
the spine at the sixteenth dorsal vertebra.
2. Before proceeding to dissect, it is well to inject the bulb of the vagina by the internal
pudic artery near its origin, and the uterus and bladder c^ould be inflated.
To inflate the uterus, the following is the procedure : tlio cervix is made to project through
an incision in the middle line of the wall of the vagina; then a straw or inflating tube is
introduced into the uttrus, and air injected thereby ; when sufliciently distended, the cervix is
firmly tied with a waxed thread. The bladder fr: distended by injecting air through a ureter,
after closing the urethra; this is done by finding the meatus urinarius with the index finger
of the left hand ; a hook is then placed on the orifice, which is drawn to the vulva, where two
pins are pushed crossways through its mucous menibrane and a ligature of waxed thread tied
behind these; the points of the pins are cut ofi", and the parts allowed to resume their natural
position.
Finally, the vagina and rectum are slightly distended by means of bundles of tow.
3. When these preparations are completed, one of the posterior limbs is disarticulated;
the upper part of the gluteal and posterior crural muscles, as well as a portion of the sacro-
Bciatic ligament, are cut away. In removing the cellulo-adipose tissue from the pelvic cavity,
the neok of the bladder, the rectum, and the vulva are freed ; care should be taken not to
injure the peritoneal fold that surrounds the nn'ddle region of the vagina. The constrictor
muscle of the vulva is exposed in removing the skin by shreds with scissors, as was done with
the orbicularis muscle of the lips. Afterwards, the portion of the ischium which conceals some
portions of the details of the preparation is removed by the saw.
984 GENERATIVE APPARATUS.
4. When the organs have been studied in situ, tliey are removed — the broad ligaments
being preserved— and sprciid on a table, in order to study their interior.
5. An injection into the galactopliorous sinus allows a good idea to be formed of the
general disposition of the mammary gland.
These organs resemble those of the male in their general disposition. Thus
we find in the female : 1. Two secretory organs — the ovaries — analogous to the
testicles, in which the germ is elaborated. 2. The uterine (Fallopian) tube,
disposed — like the epididymis and vas deferens— as a flexuous canal, through
which the ovum passes on leaving the ovary. 3. The uterus, a single reservoir
formed of two lateral moieties which may be compared to the vesiculte seminales,
as it is there that the germ remains until it is fully developed. 4. The vagina,
a membranous canal analogous to the urethra, and giving passage to the foetus
after it has been formed in the uterus : this canal, which receives the penis
during copulation, also shows, at its exterior opening, the vulva — an erectile
apparatus — and the clitoris, which is nothing more than a rudimentary corpus
cavernosum of the male. The female has also certain glands, which, in many
species, exist in a rudimentary form in the male : for instance, the mammae,
organs for the secretion of milk, the first nourishment of the young animal.
(The glands of Duverney, in the female vagina, seem to be analogous to
Cowper's glands in the male, as they are present in the females of all animals
where the latter exist in the male, and their secretion appears to be of the same
character.)
It may be remarked, after this observation, that the male and female genital
apparatuses are constructed on the same type — a circumstance which is most
clearly demonstrated at an early period of intra-uterine life, when it is impossible
to distinguish the sexes.
1. The Ovaries (Figs. 529, 535).
Situation — Form — Relations. — The ovaries (testes muliehres) — the essential
organs of generation in the female — are two ovoid bodies, smaller than the
testicles, though of the same shape, situated in the abdominal cavity,^ and
suspended from the sublumbar region — where they correspond with the intestinal
convolutions — a little behind the kidneys. Smooth on the surface, these organs
present, in the middle of their upper face, a deep and more or less oblique
fissure, resembling the hilus of the kidney ; this gives attachment to the paviUon
of the tube.
Means of attachment. —The ovary floats at the anterior border of the broad
ligament ; it is also sustained by the vessels that enter it, and by a small cord of
unstriped muscular fibres — the ligament of the ovary — which attaches it to the
uterus.
Structure. — The organization of the ovaries comprises a serous membraney
a tunica albuginea, proper tissue, and the Graafian vesicles embedded therein.
Serous membrane. — This is a continuation of the broad ligaments ; it covers
the whole organ (except at the hilus), adhering closely to the tunica albuginea.
Tunica alhwjinea. — This is similar to that enveloping the testicle, being a
very resisting fibrous covering which sends prolongations into the substance of
the ovary.
» Tlie ovaries sometimes leave this situation. Thus Dupont, of Plazac, has observed them,
in four swine, occupying little cavities, analogous to those of the male scrotum, in the perinseaj
region {Journal des Vet^rinaires du Midi, December, 1869).
THE GENITAL ORGANS OF THE FEMALE.
985
On the surface of this fibrous membrane is found a complete layer of
cylindrical cells, which was at one time regarded as a dependency of the peritoneal
serous membrane ; but it differs widely from it in an anatomical point of view.
It is named the germ-epithelium, in order to indicate the share it takes in the
production of ova during the early period of their development.
Proper tissue. — The proper tissue, or stroma, of the ovary is more consistent
than that of the testicle ; it is hard, grates on being cut into, and is greyish-red
in colour. It is divisible into two layers, distinguishable by their aspect and
structure (Fig. 529).
1. The medullar^/ layer — that nearest the hilus— is slightly red and spongy ;
SECTION OF THE OVARY.
1, Cortical vesicles; 2, larger vesicles; 3, vesicles surrounded by the granular membrane; 4, 5. 6,
7, 8, follicles in various stages of development; 9, membrana granulosa; 10, ovum; 11, cumulus
proligerus; 12, non-ruptured follicle surrounded by a capillary network; 13, follicle with its
contents partly escaped ; 14, stroma of the cortical zone ; 15, vessel entering by the hilus of the
ovary; 16, stroma of the hilus; 17, external membrane of a corpus lutea ; 18, arteries of a
corpus lutea ; 19, its central vein.
it is formed by an interlacing of the connective fibres, unstriped muscular fibres,
and a large number of vessels that radiate from the centre towards the peripheiy.
2. The cortical layer has the elements of connective tissue for its base ; it is
but little vascular, and contains in its substance the Graafian vesicles or follicles
{ovisacs), and is consequently often named the ovigenous layer. These ovisacs
are in various stages of development ; the smallest are situated beneath the
tunica albuginea, and gradually increase as they lie deeper. When fully
developed, they are filled with a transparent, citron-coloured fluid ; the
ovigenous layer can then no longer contain them, and they protrude more or less
from the surface of the ovary.
A Graafian vesicle, in its perfect state, is composed of an envelope and its
contents. The envelope comprises : a fibrous membrane {tunica fibrosa), which
is confounded with the stroma of the ovary, and in it we may recognize two
layers, the internal of which is rich in vessels ; an epithelium, or membrana
GENERATIVE APPARATUS.
granulosa, consisting of round or polygonal granular cells. At the bottom of
the ovisac, this epithelium forms a small mass — the cumulus proUgerus (oi
germinal eminence), in the centre of which is the ovulum or eo^or of the mammal.
The rontejits {liquor folliculi) is a clear yellow fluid, which becomes red on
admixture with blood when the vesicle ruptures.
The ovulum, or ovum, is a cell about -j^^ of an inch in diameter, enclosed in
the discus proUgerus, or cumulus proUgerus. The ovum is invested by a thick
membrane — the zona pellwida {membrana vitellina), formed of cells traversed by
radiating canals — the porous canalicuU (ova-tubes) ; its granular contents are
named the viteUus, or ijolk ; and its (vesicular nucleated) nucleus, designated the
germinal vesicle, or vesicle of Purkinje, and lying at a certain point on the zona
pellucida, has in its centre a white patch — the germinal spot, or spot of Wagner.
Balbiani has discovered, alongside the germinal vesicle, another, which he has
named the embryogenic vesicle.
Vessels and nerves. — The thick, flexuous, arterial divisions are given off by
• the utero-ovarian artery; they
^'-- ^^^- ramify in the spaces formed by
the tunica albuginea, before
reaching the proper tissue by
entering the hilus. The veins.,
are of large calibre, and form a
very rich network around the
gland — the bulb of the ovary ;
they terminate in the vena cava,
near the renal veins. The lym-
phatics are very abundant in the
medullary substance, and anas-
tomose in a network around the
follicles before they pass to the
sublumbar glands. The nerves
emanate from the small mesen-
teric plexus.
Development. — The ovary
of Solipeds is of great size in the
foetus, being often nearly as large
as in the adult animal. Fig.
530 exhibits the proportion between its volume and that of the uterus in a six
months' foetus. It becomes atrophied in aged animals.
Functions. — The productive organs of the germ, or ovum, the ovaries are
the testicles of the female. They form the ova, and then at certain periods set
them at liberty. As the ova are contained in the Graafian vesicles, it is necessary
to study : 1. The development of these vesicles. 2. Their rupture, or dehisence.
3. The phenomena occurring in them after rupture.
Development of the Graafian vesicles. — The use of the Graafian vesicles is to
remove the ova from the ovary — to prepare their dehiscence ; consequently, the
development of these vesicles is subordinate to the presence of ova. The latter
begin to form among the cells of the germ-epithelium covering the surface of
the ovary ; then they become deeply embedded in the organ by means of Pfliiger's
cords, thrown out by the germ-epithelium.
When the ovum is thus buried in the stroma of the ovary, the epitheUum
OVARIES, OVIDUCTS, AND UTERUS OF A FO^.TCS
(EQUINE).
TEE GENITAL ORGANS OF THE FEMALE.
Fig. 531.
accompanying it proliferates and forms two layers — membrana granulosa — around
them. The surrounding connective tissue, pressed out, accommodates itself to
the surface of the mass, and gradually constitutes a spherical shell-^the fibrous
envelope ; then the Graafian vesicle is formed. Soon the two layers of the
membrana granulosa separate at one part to form a cavity — the cavity of the
vesicle (Fig. 529, 5, 6, 7) ; but as the separation is not complete, the ovum,
encircled by the internal membrane, lies beside the external membrane. As the
cavity of the vesicle enlarges, the tissue of the ovary becomes more condensed,
and constitutes the fibrous wall, which soon receives a network of vessels.
(This description does not altogether agree with what is taught by physiologists.
It would appear that, in the course of development, groups of cylindrical cells
grow up from the stroma of the ovary so as to enclose the primordial ova.
These may even form tubular-like structures, called by some German writers the
ova-tubes. By-and-by, each ovum is surrounded by cells, forming a httle round
body called the primary follicle, which consists of the
ovum and of epithelial cells surrounding it. The forma-
tion of this follicle around each ovum is for the purpose,
in due time, of ejecting the ovum from the ovary. The
size of the follicle increases by the multiplication of
epithehum-cells, and soon a space exists round the ovum
which is filled with a fluid — the liquor follkuU. This
liquid may be formed by transudation from the surround-
ing blood-vessels, and, as some have suggested, by the dis-
integration and melting away of some of the epithelial
cells. We have now a vesicle filled with fluid — the
Graafian vesicle — having a diameter of from '5 to 5 mm.
The connective tissue forms the wall of the vesicle. It
consists of : 1. A connective tissue covering the them folli-
cuU, which is formed of two strata — an outer of fibrous
tissue, tunica fibrosa ; and an inner, tunica propria, rich
in cells and vessels. 2. A lining of stratified folHcular
epithelium, sometimes called the membrana granulosa.
This lining of epithelium-cells forms a prominence at one
side, called the cumulus ovigerus, or discus proligerus, and
the layer surrounding the ovum has been termed the
tunica granulosa. The space is occupied, as already men-
tioned, by the liquor folliculi. When the ovum reaches
maturity, the Graafian vesicle is full of fluid, and bluges out from the surface of
the ovary. It may be mentioned that the primordial ovum is a large round cell,
provided with a nucleus and nucleolus ; it originates from a single cell of the
germ-epithelium.
In the Cow, at puberty the stroma of the ovary is crowded with follicles so
minute, that it has been computed that a cubic inch would contain two hundred
millions of them.
Puberty occurs earlier in small than in large animals. In the Rabbit,
Guinea-pig, Rat, and Birds, it is reached during the first year ; in the Dog and
Cat, in the second year ; in the Ox, Horse, and Lion, in the third year ; in the
Camel, in the fifth year ; and in the Elephant, between the twentieth and thirtieth
year. Menstruation — or a series of phenomena resembling this function in
Woman — occurs in many animals, and is known as the rut, or heat. Cows and
OVARItTM OF THE RABBIT
AT THE PERIOD OF
CESTRUM, SHOWING
VARIOUS STAGES OP
THE EXTRUSION OP
OVA.
988 GENERATIVE APPARATUS.
Sheep rut twice ; the Cat, Bitch, and Sow, two or three times ; and the Rabbit
and Guinea-pig, eight or twelve times, in the course of the year. The condition
lasts in the ^lare and Cow from two to four days, and in the Sow and Bitch
from six to ten days. During this period the females have a peculiar smell, by
which the males are attracted, even from long distances.)
Rupture of the Graafian vesicles. — After puberty the ovary becomes vascularized,
and a certain number of Graafian vesicles increase in volume. At the period of
oestrum, one or more of these, according to the species, participate in the change
in the ovary, become vascular and distended, and finish by rupturing and
evacuating the discus proligerus and ovum. The latter is received into the
Fallopian tube and conveyed towards the uterus.
Corpus luteum. — After the rupture of a Graafian vesicle, its cavity is filled
by a clot of blood, which gradually contracts and loses its colom* ; at the same
time the tunica fibrosa becomes hyDertrophied, and the membrana granulosa is
wrinkled and transformed into cylindrical epithelium. To this period of
progression succeeds one of regression, during which the cylindrical cells become
infiltrated with fat and are graduall absorbed. The term corpus luteum is
given to the cicatrix resulting from the rupture of a Graafian vesicle.
Fig. 532.
Fig. 533.
CONSTITUENT PARTS OF A KAMMALIAI
Fig. 532, Entire ovum. Fig. 533, Ovum ruptured, with the contents escaping: mv, vitelline
membrane ; _/, yolk ; vg, germinal vesicle ; tg, germinal spot.
The progress of the phenomena of hypertrophy and regression is much slower
when the escape of the ovum has been followed by impregnation ; so that we
have false corpora lutea (those which are independent of pregnancy), and true
corpora lutea, those of gestation, and which do not disappear until several weeks
after parturition. (The true corpora lutea are recognizable, after parturition,
as small white or dark-coloured masses — the corpora albicans vel nigrum. The
yellow colour, to which they owe their name, is due to the infiltration of the
cylindrical cells with fat.)
During early life the Graafian follicles are not inert, as has been believed, but
are active ; only instead of rupturing and throwing their contents into the
Fallopian tubes, after attaining their full development they shrivel, become
atrophied, and eventually nothing is left of them except a very small yellow
body.
Such are, very briefly, the functions of the ovary.
(Beneath the hilus of the ovary, and between the layers of the broad liga-
ment and the round ligament, is found a small body, usually described as the
'parovarium or epoophoron, consisting of a number of fine tubes or tortuous canals
THE GENITAL ORGANS OF THE FEMALE. 989
with blind extremities lined with ciliated cylindrical epithelium. It is considered
as the remains of the Wolffian body - a foetal structure that forms the epididymis
in the male, and has been named the orga?i of Rosenmiiller in the female.
Chauveau does not mention its existence in the domesticated animals, though
Leyh does. There is also the paroophoron, likewise found in the broad ligament,
and formed of small canals lined with cylindrical cells. This is supposed to be
a relic of the urinary portion of the Wolffian body.)
2. The Fallopian or Uterine Tubes, or Oviducts (Fig. 535, 2).
The Fallopian tube is a little flexuous canal, lodged in the broad ligament,
near its anterior border. It commences at the ovary by a free, expanded
extremity — the pavilion of the tube (or ostium abdominah), and terminates in the
cul-de-sac of the uterine cornu by opening into it (the ostium uterinum). Its
Fig. 534.
9
SUCCESSIVE STAGES IN THE FORMATION OF THE CORPUS LUTECM IN THE GRAAFIAN
FOLLICLE OF A SOW (VERTICAL SECTION).
a, The follicle immediately after the expulsion of the ovum, its cavity being filled with blood, and
no ostensible increase of its epithelial lining having yet taken place; at b, a thickening of this
lining has become apparent ; at c, it begins to present folds, which are deepened at d, and the clot
of blood is being absorbed and decolorized ; a continuance of the same process, as shown at e,f, g, h,
forms the corpus luteum, with its stellate cicatrix.
canal at the middle is so narrow as scarcely to admit more than a very thin
straw, and its calibre is still less towards the uterine extremity ; near the ovary,
however, it is wide enough for the passage of a thick goose-quill.
The orifice of the uterine extremity opens in a small and very hard tubercle.
The ovarian extremity, in all Mammalia, offers a very remarkable arrangement.
It opens into the peritoneal cavity, near the fissure of the ovary, and in the
centre of the expansion named the pavilion of the tube, which is also designated
the fimbriated extremity (or morsus diaboli). This pavilion is attached to the
external side of the ovary, and has a very irregular outline — notched, as it is,
into several lancet-shaped, unequal prolongations {fimbria), which float freely in
the abdomen. Here are, then, two important anatomical facts — the discontinuity
between a gland and its excretory duct, and the communication of a serous cavity
fvith the exterior.
Structure. — The Fallopian tube is formed of a serous, a muscular, and a
mucous tunic. The serous {external) is furnished by the broad ligament, and is
derived from the peritoneum. The middle is formed of unstriped muscular fibres,
which extend into the pavilion. (They are arranged as circular — internal, and
65
990 GENERATIVE APPARATUS.
longitudinal — external fibres, and are continuous with those of the uterus ; they
are mixed with embryonic nucleated connective tissue.) The mucous membrane
is arranged in longitudinal folds in the tube, but in the pavilion these folds are
radiating ; it is covered by a ciUated cylindrical epithelium (the vibrations of the
cilia being towards the uterus). (It has very few glands and no villi.) At the
margin, or fimbriae, of the pavilion it suddenly ceases, and is continued by
the peritoneum (a serous cyst is frequently found in this situation ; at the other
extremity the mucous membrane is continuous with that of the uterus).
Functions. — The excretory duct of the ovary, the Fallopian tube seizes the
ovum expelled from the Graafian vesicle, and carries it to the uterus. It is there-
fore necessary that, at the moment of rupture of the vesicle, the fimbriae should
be applied to the ovary, in order to receive the germ and bring it to the abdominal
orifice of the tube. The application of the pavilion to the ovary is brought about,
either by the contraction of the muscular fibres it contains, or through the dis-
tension of the bulb of the ovary. Sometimes this mechanism is insufficient, and
the ovum falls into the abdominal cavity, becomes fixed there, and is developed
if it has been previously fecundated ; this occurrence constitutes the most
remarkable variety of extra-uterine gestation.
The oviduct also conveys the seminal fluid of the male to the ovum.
3. The Uterus (Figs. 535, 536).
The uterus is a membranous sac to which the ovum is carried, and in which
it is developed.
Situation. — It is situated in the abdominal cavity, in the sublumbar region,
at the entrance to the pelvic cavity, where its posterior extremity is placed.
Form and relations. — In its posterior moiety, the uterus is a single cylindrical
reservoir, slightly flattened above and below ; this is the body of the uterus. Its
anterior moiety is bifid, and gives rise to two cornua, which curve upwards.
The bod// is related, by its upper face, to the rectum, which lies on it after
passing between the two cornua ; it receives, on the sides of this face, the attach-
ment of the broad ligaments ; its lateral and inferior faces are related to the
intestinal convolutions. (Inferiorhj, it is in relation with the bladder.) Its
anterior extremity (or fundus) is continuous, without inten'uption, with each of
the cornua ; thQ posterior extremity is separated from the vagina by a constriction,
named the neck {cervix) of the uterus.
The cornua, lying among the different portions of intestine which occupy the
same region, offer : a free and convex inferior curvature ; a superior curvature, to
which the suspensory ligaments are attached ; a posterior extremity, or base, fixed
to the body of the organ ; and an anterior extremity or summit — a rounded blind
pouch looking upwards, and showing the entrance of the Fallopian tube,
3Ieans of attachment. — Floating in the abdominal cavity, like the intestines,
the uterus is also, like them, attached by bands which suspend it to the sub-
lumbar region, and which for this reason have been named the suspensory or
broad ligaments of the uterus.
These bands are two in number, are irregularly triangular in shape, and are
more developed before than behind. Close to each other posteriorly, and
separating in front like the branches of the letter V, they leave the sublumbar
surface and descend towards the uterus, to be attached by their inferior border
to the sides of the upper face of the body and the small curvature of the cornua.
Their anterior body is free ; they sustain the Fallopian tubes and ovaries, th»
THE GENITAL ORGANS OF TEE FEMALE. 991
former being placed between the two serous layers of the ligament, and the latter —
also within this ligament — receives a band detached from the principal layer,
forming with it, beneath the ovary, a kind of small cupola.
Fig. 535.
15 19
GENERATIVE ORGANS OF THE MARE, ISOLATED AND PARTLY OPENED.
1, 1, Ovaries; 2, 2, Fallopian tubes; 3, pavilion of the tube (external face); 4, ditto (inner face,
showing the opening in the middle); 5, ligament of the ovary; 6, intact cornu of the uterus- 7
a cornu thrown open; 8, body of the uterus (upper face); 9, broad ligament; 10, cervix, with its
mucous folds; 11, cul-de-sac of the vagina; 12, mterior of the vagina, with its folds of mucous
membrane; 13, urinary meatus, and its valve, 14; 15, mucous fold, a vestige of the hymen; 16,
interior of the vulva; 17, clitoris; 18, 18, labia of the vulva; 19, inferior commissure of the
vulva.
There is also another little naiTow long band outside the broad ligament, and
which can be traced as far as the upper inguinal ring. Anteriorly, it has a small
992 GENERATIVE APPARATUS.
enlarged appendix ; between the two layers forming this fold is found a thin
muscle, altogether like the male cremaster before the descent of the testicle into
the scrotum. This may be looked upon as the analogue of the round ligament of
Woman.
The uterus is also fixed in its situation by its continuity with the vagina.
Interior. — The inner surface of this organ shows mucous folds, which exist
even in the foetus ; they are arranged in a longitudinal series, and are not
effacable by distension ; though they disappear during gestation, consequent on
the enlargement that takes place in the uterine cavity.
This cavity has three compartments : the cariti/ of the body, and those of the
cornua. The latter are pierced, at their extremity, by the uterine orifice of the
Fallopian tube ; while the former communicates with the vagina by a narrow
canal that passes through the posterior constriction of the uterus (cervix),
and which is, in Human anatomy, named the cavity of the cervix (os uteri, os
externum, os triccB). In all the domesticated animals, except the Rabbit, this
canal is prolonged to the bottom of the vagina, in something the same fashion
as a tap is into the interior of a barrel ; and in this way it always forms a very
marked projection in the vaginal cavity. Around this projection, the utero-
vaginal mucous membrane is raised in transverse folds disposed in a circular
manner, which give it the appearance of a radiated flower ; in Veterinary
anatomy, this projection of the cervix is consequently named the "expanded
flower "—fleur epanouie ; it is the tench's nose of the Human being.
Structure. — The walls of the uterus are composed of three membranes—
an external, serous ; a middle, muscular ; and an internal, mucous ; with vessels
and nerves.
The serous tunic envelops all the organ ; it is an expansion of the broad
ligaments, which are prolonged backwards on the posterior extremity of the
vagina, and are afterwards doubled in a circular fashion around that canal, to
pass over either the rectum, the bladder, or the lateral walls of the pelvis.
Between the two cornua this membrane forms a particular fraenum, which is only
slightly developed in Solipeds.
The muscular layer comprises longitudinal (superficial), and circular (deep)
fibres, analogous to those of the small intestine. Near the insertion of the broad
ligaments, they give off a series of fasciculi which are prolonged between the
two layers of these ligaments. These are not the only smooth muscular fibres
met with in the ligaments, however ; for Rouget has found others throughout
their whole extent, but particularly in the vicinity of the ovaries.^ (Around the
cervix uteri, the circular fibres are most dense and numerous.)
In the pregnant animal, the number of fibres composing this layer is much
more considerable than in ordinary circumstances ; this increase has for its object
to permit the dilatation of the uterus, without allowing its parietes to become
too attenuated ; they do become more or less thin, notwithstanding, according
to the species. It has also been remarked that, during pregnancy, the muscular
fibres present a manifest striation. (The elements of these fibres are short fusi-
form cells with long oval nuclei, mixed with a large quantity of embryonic,
nucleated connective tissue.)
The mucous membrane is very rich in cellular elements, and is thin, delicate,
and raised into folds. It is covered by ciliated epithelium, which becomes
> Unstriped contractile fibres are also found, iu the male, along tlie spermatic cord, beneath
the visceral layer of the tunica vasinalis.
THE GENITAL ORGANS OF TEE FEMALE. 993
cylindrical in the os uteri, and pavemental around the cervix ; here also are
found calyciform cells — a kind of unicellular glands which secrete the thick mucus
found in this part. (The cilia vibrate towards the fundus of the organ. The
membrane is closely connected with the muscular tunic, and is composed of
embryonic, nucleated, connective tissue, without elastic fibres.) The uterine
mucous membrane is destitute of papillae except at the cervix (where there are
many highly vascular papillas) ; but it lodges numerous simple or ramified
glands, which are straight or slightly flexuous at their extremities. At the
cervix, these glands enlarge at the bottom, and assume something of the
appearance of acinous glands.
(These mucous glands are designated simple and cylindrical. The first are
most numerous towards the cervix ; some, here and there, with their orifices
closed, are enlarged, and form small vesicular tumours— the ovida, cysts, or glands
of Nahothi ; they secrete the peculiar transparent mucus found here. The
cylindrical, uterine, or utricular glands are closely clustered together, sometimes
bifurcated, often twisted in a spiral fashion, and terminating in a cul-de-sac in
the substance of the membrane. In structure they resemble other mucous
glands, consisting of a membrana propria, an epithelium of spheroidal cells at
the bottom of the tube, and of columnar cells in its duct. During gestation
they are much enlarged, and receive the cotyledonal processes of the placenta.
At the period of oestrum, the glandular secretion of the uterus is more active
than at other times.)
Vessels — Nerves. — The blood is brought to the uterus by the uterine and utero-
ovarian arteries, and is conveyed from it by veins corresponding to the latter.
In animals which have been pregnant several times, the vessels are remarkable
for their enormous volume, their tortuousness, and the adhesion of the veins
to the neighbouring tissues. (The arteries freely anastomose ; they ramify
through the muscular and mucous tunics, constituting coarse and fine networks,
which ultimately end in the veins. These are very large, and have no valves ;
the plexuses they form are considerable.)
The lymphatics that proceed from the uterus are as remarkable for their
number as their size ; they pass to the sublumbar region.
The nerves supplying the organ come from the small mesenteric and pelvic
plexuses. (In the uterus there are several important nerve-gangha ; and during
gestation it has been ascertained that the nerves, like the vessels, enlarge, and
after parturition return to their former size.)
Development. — Narrow in the foetus, and in the adult which has not been
impregnated, the uterus increases in size in animals which have had young
several times.
Functions. — The uterus is the sac in which the embryo is developed. The
ovum grafts itself upon the mucous membrane of the organ by its placental
apparatus, in order to draw indirectly, from the maternal blood, the materials
for its development. This function of the uterus gives rise to most interesting
anatomical and physiological considerations, which will be referred to when
giving the history of the ovum.
4. The Vagina (Figs. 535, 536).
The vagina is a membranous canal with thin walls.; it succeeds the uterus,
and terminates posteriorly by an external opening — the vulva.
Situation and Relations. — Situated in the pelvic cavity, which it passes
994 GENERATIVE APPARATUS.
across horizontally, the vagina is in relation with the rectum above, below with
the bladder, and laterally with the sides of the pelvis and the ureters. Con-
nective and adipose tissues suiTOund it posteriorly.
Internal conformation.— The inner surface of the vagina is always lubricated
by an abundance of mucus, and is ridged by longitudinal folds {columnce rugosce).
c o •
2%.
° d s 3
O O (M
o £ ..-5
n, 3 M
^ O 3 ■—
In front, at the bottom of the canal, is observed the projection formed by the
cervix uteri ; posteriorly, this surface is continuous with that of the vulva.
Structure. — The vagina is formed of two tunics — an inner, mucous, and
nn external, muscular. The mucous membrane (pale red in colour) is continuous
with that Uning the vulva and the uterus (and bladder) ; it is provided with
TEE GENITAL ORGANS OF •THE FEMALE. 995
papillae, and is lined by stratified squamous epithelium. It contains some closed
follicles. (It consists of connective and elastic tissues, to which its extensibility
and firmness are due.)
The muscular coat is rose-coloured, and traversed by a large number of
vessels ; it is surrounded, for the greater part of its extent, by an abundance
of connective tissue, which unites it to the organs contained in the pelvic cavity ;
in front, however, it is enveloped by the peritoneum, which surrounds the vagina
before passing to the uterus. (This connective tissue is sometimes designated
the third or fibrous tunic of the vagina. The muscular fibres are unstriped, and
arranged in circular and longitudinal series ; towards the posterior portion of
the canal they are redder than in front.)
Vessels and nerves. — The vagina is supplied with blood by the internal ptcdic
artery ; this fluid is carried from it by numerous veins, which are disposed in a
plexus around the canal, and enter the satellite of the artery. The nerves come
from the pelvic plexus. (The lynrphatics accompany the veins, and pass to the
pelvic glands.)
Function. — The vagina receives the male organ during copulation, and
through it the foetus passes during parturition.
5. The Vulva (Fig. 535).
The external orifice of the vagina, the mdva is situated in the perinseal region,
immediately below the anus. We will consider in succession its external opening^
its cavity., and its structure.
External Opening. — This is a vertical elongated slit, presenting two lips
and tuw commissures. The lips (labia vulvae) are covered externally by a fine,
smooth, unctuous, and (almost) hairless skin, rich in colouring pigment, and
lined internally by mucous membrane ; on their free margin, the limits of these
two membranes are well marked. The superior commissure is very acute, and
almost meets the anus, from which it is nevertheless separated by a narrow space
— the perinceum. The inferior commissure is obtuse and rounded ; it lodges the
clitoris.
Cavity op the Vulva. — By all Veterinary authorities, this cavity is de-
scribed as belonging to the vagina, to which it forms the entrance ; but consider-
ing the analogies that exist between the genital parts of Woman and those of
animals, this cavity must be distinguished from that of the vagina. It offers
for study the hymen, which separates the two cavities, the meatus urinarius and
its valve, and the clitoris.
The Clitoris — Exactly like the corpus cavernosum of the male — which it
represents in miniature — and from 2 to 3 inches in length, the clitoris commences
by two crura fixed to the ischiatic arch, and covered by a rudimentary erector penis
muscle. After being attached to the symphysis by means of a suspensory liga-
ment analogous to that of the male, it passes backwards and protrudes into the
vulvular cavity, towards the inferior commissure. Its free extremity, lodged in
that cavity, is enveloped by a mucous cap — the prepuce of the clitoris {prceputium
clitoridis), which is folded in various directions, and excavated about the centre
of the tubercle by a small follicular cavity that represents the extremity of the
male penis. The organization of the clitoris resembles in every particular that
of the corpus cavernosum of the penis — a fibrous framework, erectile tissue, and
•cavernous vessels. It is the contact of the penis with this organ during copula-
tion, that chiefly occasions the venereal excitation.
996 Gh.,t.tiATIVE APPARATUS.
The Meatus Urinarius and its Valve.— The urethral canal in the
female is very short. It passes immediately beneath the anterior sphincter
muscle of the vulva, and after a brief course in the texture of the floor of the
vagina, it opens into the vulvar cavity by an orifice covered by a large mucous
valve : this is the meatus urinarius and its valve. The urinary opening, placed
at the bottom of the cavity, at frc- : S^ to 5 inches from the external opening,
is wider than the male urethn",, and will admit sounds of somewhat large size,
for the catheterism of the bladaer. The valve has its free border inclining
backwards, to direct the flow of r.riEe towards the exterior, and prevent its reflux
into the vagina.
(The female urethra is composed of two tunics : a mucoi/s, continuous with
that of the bladder and vagina ; and a muscular coat, also a continuation of
that belonging to these organs, and chiefly made up of circular fibres ; some
flat fasciculi attach it to the periosteum of the ischial bones. The urethra is
not suiTounded by a corpus spongiosum, as in the male.)
The Hymen. — This membrane, when it exists, distinctly separates the
vulvar from the vaginal cavity. It is rarely present, however ; though we
have observed it several times in the adult Mare.^ It forms a circular partition,
fixed by its margin to the vulvo-vaginal walls, as w^ll as to the valve of the
meatus urinarius, and is perforated by one or more openings which establish a
communication between the vulva and vagina. On many occasions we have
found, in old brood-mares, pediculated appendages— the remains of this septum.
It is usually represented by a transverse fold of mucous membrane, notched on
its free border, which lies above the meatus urinarius.
Structure of the Vulva. — The vulva offers for study in its structure :
1. The mucous membrane lining its interior. 2. An erectile body lying on that
membrane, and named the vaginal bulb. 3. Tivo constrictor muscles — anterior
and posterior. 4. Two muscular ligaments. 5. The external skin.
1. Mucous membrane. — Continuous with that of the vagina and bladder, this
membrane has a rosy colour, which may become a bright red at the period of
oestrum. It often shows, near the free border of the labia — and especially on the
mucous cap of the clitoris — black pigment patches, which give it a speckled
appearance. It has in its substance a great quantity of mucous follicles and
sebaceous glands. The latter exist near the free border, particularly about the
clitoris, and especially in the space between that erectile body and the inferior
commissure of the vulva, where they meet in several small sinuses. (These
glands secrete an unctuous matter possessing a special odour ; they are most
active during oestrum.)
Where the mucous membrane is furnished with papillae, it is covered by a
stratified pavement epithelium.
2. Vaginal (or vestibular) bulb. — This is an organ entirely formed of erectile
tissue with wide areolae ; it is divided into two branches {bulbi vestibuli), which
arise from the vicinity of the crura of the clitoris and pass on the sides of the
vulva, where they terminate in a round lobe. Covered by the posterior con-
strictor of the vulva, the vestibular bulb conununicates, inferiorly, with the
veins of the corpus cavernosum. The influx of blood into the cells of its tissue
contracts the vulvar cavity, and concurs to render the coaptation of the copu-
latory organs more perfect during coition.
• Goubaux gives several instances, in an article on " Purturitiou in the Domestic Animals,*
published in the Bectieil de M^d. V^te'rinaire for 1873.
THE GENITAL ORGANS OF THE FEMALE. 991
3. Muscles of the vulva. — Imperfectly described and determined in books on
Veterinary Anatomy, these belong to the category of voluntary muscles. We
recognize two, which will be described as the posterior and anterior constrictors.
Posterior Constrictor of the Vulva. — AnalogouL to the constrictor
vagince of Woman, this muscle — included in the labia of the vulva — forms a veri-
table sphincter. Above, its fibres are mixed with those of the sphincter ani, and
are attached to the sacrum through the medium of the suspensory ligaments.
Inferiorly, the most anterior are fixed to the base of the clitoris ; the middle
are prolonged between the thighs, and are inserted into the inner surface of
the skin.
Inwardly, it is in relation with the vestibular bulb and the mucous membrane
of the vulva. Its external face is separated from the skin of the labia by a very
vascular cellulo-fibrous tissue capable of tonic contraction, and in the midst
of which are always found isolated red fasciculi — dependencies of the principal
muscle.
This muscle, in contracting during copulation, constricts the aperture of the
vagina and compresses the penis ; and as, in consequence of its attachment to
the clitoris, it cannot act without raising that erectile body, it appHes this to
the male organ and causes a greater degree of excitement. With animals in
<Estrum, the movements of the clitoris are frequently observed to propel that
organ outwards, especially after micturition ; in this case, the fibres of the
constrictor attached to the clitoris erect it by its base, while those which are
fixed into the skin between the thighs depress the inferior commissure of the
vulva. This double action necessarily exposes the erectile tubercle lodged in
that commissure.
Anterior Constrictor of the Vulva. — This muscle is formed of arciform
fibres which envelop — below and laterally — the vaginal walls at the entrance of
the canal ; its extremities are continued, by means of aponeurotic fascia, to the
sides of the rectum, where they are lost ; some even pass tc the inferior surface
of the sacrum. By its posterior border, this muscle is mixed with the preceding.
4. Muscular ligaments of the vulva. — Traces of the suspensory ligaments of
the male penis, these are disposed in the same manner at their origin. After
becoming united beneath the rectum, they descend in several fasciculi into the
labia of the vulva, and disappear among the fibres of the posterior constrictor.
5. External skin. — This is fine and black (or hght-coloured), destitute of
hair, smooth and unctuous, and adheres closely to the subjacent tissues.
6. The Mamm^.
The mammce are glandular organs ; they secrete the fluid that should nourish
the young animal during the early months of its life. They are rudimentary in
youth, and become developed with the advent of puberty, assuming their greatest
development towards the end of gestation ; they are most active after parturi-
tion, and cease their function, as well as diminish in volume, when the period of
lactation has terminated.
Situation. — These glands are two in number, placed beside each other in the
inguinal region, where they occupy the situation of the scrotum in the male.
Form. — They are two hemispherical masses, separated from each other by a
shallow furrow, and showing in their centre a prolongation called the teat, nipple,
or mammilla, which is pierced at its free extremity by several orifices for the
998 GENERATIVE APPARATUS.
escape of the milk ; it is by this prolongation that the young animal effects
suction.
The two glands are fixed in their position by the skin which covers them,
and which is thin, black, covered with a line down, and altogether destitute of
hair in the vicinity of, or on, the teat, where the cutaneous surface is smooth,
greasy, and supple. They are also attached to the tunica abdominalis by several
wide, but short, elastic bands, which resemble the ligaments of the prepuce in
the male.
Structure. — Structurally, the mammary glands offer for study : 1. A yellow
(elastic) fibrous envelope. 2. Glandular tissue. 3. The (jalactophorous (or lactiferous)
reservoirs or sinuses. 4. The excretory canals, or mammary (or milk) ducts.
The elastic envelope, placed in the middle line, beside its fellow of the opposite
side, is mixed with the suspensory bands that descend from the abdominal tunic,
and sends into the substance of the gland a number of septa, which are inter-
posed between the principal lobules.
The glandular tissue is a compound of gland-vesicles or acini, clustered in
groups around the lactiferous ducts. (The gland-vesicles are made up of an
amorphous membrane — membrana propria — lined with spheroidal nucleated cells.
Fig. 537. Fig. 538.
GLAND-VESICLES, WITH THEIR EXCRETORY ULTIMATE FOLLICLES, OR GLAND-VESICLES,
DUCTS TERMINATING IN A DUCTUS LAC- WITH THEIR EPITHELIUM OR SECRETING
TIFEROUS: FROM A MERCURIAL INJECTION CELLS, a, a, AND NUCLEI, 6, 6.
(magnified FOUR TIMES).
They are -^ of an inch in diameter.) The lactiferous ducts commence by
blind extremities, and run into each other to constitute a certain number of
principal canals ; these open into the galactophorous sinuses (each a saccidus vel
sinus lactiferus). The glandular culs-de-sac are lined with a polyhedral epithe-
lium when the gland is inactive ; but during lactation the alveoli enlarge, their
walls become thickened by a regular epithelial layer, and their cavities filled with
spherical cells which are infiltrated by a great quantity of fat.
Placed at the base of the teat, the galactophorous sinuses or reservoirs are
generally two in number, but sometimes there are three, and even four. They
nearly always communicate with each other, and are continued into the mam-
milla by an equal number of independent excretory canals — the definitive dmtSy
the orifices of which are very small, and are seen beside each other at the free
extremity of the teat. A fine mucous membrane lines the inner face of this
excretory apparatus ; it is doubled in the teat by a thick layer of tissue, which,
again, is covered by the skin that adheres closely to it. (Between the external
and internal tunic of the teats are found numerous fasciculi of unstriped
muscular fibres, arranged in a circular and longitudinal manner around these
ducts.)
Connective and adipose tissue, vessels, and nerves complete this organization.
The arteries are from the external pudic trunk ; the veins are very numerous.
TEE GENITAL ORGANS OF THE FEMALE. 999
and pass to the abdominal subcutaneous vein ; capillaries form a rich network
around the alveoli. The lymphatics are very developed. (The nerves are
derived from the first lumbar pair.)
Functions. — The mammte secrete the milk ; they undergo remarkable
modifications at puberty and at the end of each gestation — modifications which
are related not only to their volume and secretion, but also to their minute
structure. After gestation, the gland-vesicles shrink — become, as it were,
atrophied, and have only a polygonal epithelium. At the termination of gesta-
tion, they are enlarged, new vesicles are developed, and the epithelium changes
its character — filling the gland cavities,
assuming a spherical shape, and becoming Fig. 539.
charged with fat-granules. The period of .. fvo°o^°''°9<'
lactation being completed, the mamms - '- - ^ - ^ ^
assume their former character. (In Mares
which have not been bred from, the
mammte are hard and small, the teats only
slightly prominent, and the glandular _oo„^-„ 6„ ^
tissue scanty. In old brood-mares, on the 0°° o, ®g^ Opo°o 0°^° o o p» o°Oo*o °?°°. ©
contrary, they are flaccid and pendent, and ^ ^5 ^o o ^j^ ^ 0-0 ^
the teats somewhat lengthened. The milk "^% 0° °|o ^ o ®0°^.
secreted by the mammary glands is a white ''g'>°°so° °So 00°^"
fluid, possessing a sweet taste, and com- . ''W0'$^°o'^ ^ ■
posed of an albuminous water containing ^^^''P°!6Bp°
caseine in solution, milk sugar, salts, and
fatty matter in globules — the butter.
TTsnallv a small nnantitv i<5 '^pfrptprl snmp microscopical appearance of milk, with
usual y a small quantity is secreted some ^^^ intermixture of colostric corpus-
days before parturition ; that which is cles at a, a, and elsewhere.
yielded for a short time after that period
— the colostrum — is rich in white corpuscles, and has purgative properties. The
colostrum is of a rich yellow colour, less fluid than the milk of a later period,
of a higher specific gravity, sUghtly acid, and containing large oil-globules, a few
irregular flakes — probably epithelium-scales — a little granular curd-like matter,
and a small number of granular corpuscles.)
Differential Characters in the Female Genital Organs of the other Animals.
Certain organs offer some differences worthy of notice, while others are formed as in
Solipeds.
Ruminants. — Ovaries. — In the Cow, the ovaries are relatively much smaller than in the
Mare, but tlieir form and structure are identical. (The Graafian vesicles are visible through
the tunica albuginea.)
Uterus. — The uterus of the Co"w, compared with that of the Mare, offers but few differ-
ences with regard to its general disposition in the pelvic and abdominal cavities, except that
it is not so advanced in the latter. Supposing the uterus to be perfectly horizontal, a trans-
verse line drawn through the plane of the abdomen, before the external angle of the ilium, is
exceeded by the extremity of the cornua from about 1 J to 2 inches ; so that if the animal were
on its back, the uterus would only be prolonged to the fourth or fifth lumbar vertebra.
With regard to form, the uterus of the Cow presents a very remarkable disposition, which
it is necessary to note. The concave curvature of the cornua looks downwards, while in the
Mare it looks upwards ; though in both the sublumbar ligaments are attached to this con-
cavity. Therefore it is that in the Cow — if we consider the uterus as freely suspended in the
abdomen — the extremity of tht) cornua is twisted outwards and upwards, while the base,
although drawn in the same direction by these ligaments, maintains its direction, because it
is in a manner fixed by the body of the uterus. The latter receives, like the cornua, the
1000 GENERATIVE APPARATUS.
insertion of the broad ligaments on its lower plane, so that it overlaps them, while the utema
of the Mare projects below them. Otherwise, these lijjaments are very ample, especially at
their anterior border; they are wide apart in front, towards their lumt«,r attachment, wliich
is prolonged even on the parietes of the flank. The ligaments may be altogether compared to
a triangular cravat, one angle of which is attached to the bottom of the pelvic cavity, and the
other two to the tuberosities of the ilium. On this cravat lies the body and part of the cornua
of the uterus.
The uterine cornua are thin and tapering at their anterior extremity. The body is short
and narrow.
The interior of the utenis of the Cow is less ample tlian that of the Mare. Its surface is
studded with rounded tubercles, known as cotyledons, which will be studied iiereafter. It is
only necessary to say here that they are numerous ia the cornua, but small and few in the
body of the organ.
The cervix uteri, about from 2f to 3 J inches long, is narrow and irregular. The "ex-
panded flower," more finely plicateil than in the Mare, is almost cartilaginous. Three other
plicated rings, eafh smaller than the other, are e'chelonned in the cavity of the cervix, from
the external orifice to the body (corresponding to the pHcae palmatx, or arbor vitm uterina, of
Woman.)
In structure, the muscular layer is generally thicker than in Solipeds.
In the Sheep and Goat, the arrangement is the same as in the Cow, except that the
cotyledons are hollowed like a cup in their centre, and deserve their name. (The cornua are
longer and more pendent than in the Cow.)
In the Camel, the cervix uteri is very long, and is encircled by six corona of superposed
mucous folds, hard and rigid on their surface. The cavity in the body is divided in two for
the greater part of its extent, by a septum formed by the junction of the two cornua.
Vagina. — In the Cow, the sides of the vagina are traversed, for a certain distance, by a
mucous canal tliat opens into the vulvar cavity, beside the meatus urinarius. These ducts,
the use of which is unknown, are designated the canals of Gxrtner. They are not present in
the Sheep or Goat. (In Ruminants, the vagina is longer, and its external tunic thicker,
than in the Mare. Leyh describes the canals of Gaertner as present in the Mare, though
rarely.)
Vulva. — This has thick labia in the Cow. The inferior commissure is acute, and furnished
with a tuft of hair. (The corpus cavernosum of the clitoris is longer, thinner, and more
flexuous, and the glans much smaller, than in the Mare.) The meatus urinarius is disposed
as in the Mare; but there exists, on the floor of the urethra, a valve the free border of which
is directed backwards. This valve surmounts a small cul-de-sac, which it is necessary to avoid
in catheterism of the bladder. At about an inch from the entrance to the vulva, there are
found in the texture of the labia the vulvo-vaginal glands (glands of Bartholine). Discovered
by Duverney, described by Bartholine, and recently by Colin, these glands (two in number)
are about the size of a large almond ; their wide extremity is directed upwards, and the
narrow end, situated in the vicinity of the iscMo-clitoridis muscle, gives origin to the excretory
canaliculi. They are yellow racemose glands, and their ducts unite to form a kind of sinus,
which at length opens in the vaginal cavity, about 4 inches from the labia of the vulva.
(These glandulse vaginie are supposed to be analogous to the prostate glands, and are covered
by muscular fasciculi. They are composed of pyriform glandular vesicles, lined by squamous
epithelium, and surrounded by a dense nucleated connective tissue ; the excretory ducts are
invested by columnar epithelium, and surrounded by a thin layer of smooth muscle-cells, dis-
posed longitudinally. Their secretion is a clear, yellowish, viscid mucus.)
(In the Sheep and Goat, the labia of the vulva have several folds externally, and the
inferior commissure terminates in a point.)
Mammx. — In the Cow, eacli lateral mammary mass — although enclosed in a single fibrous
capsule — is composed of two distinct glands, each having its teat; so that this animal really
has four mammx and four teats. There are also frequently found behind these, two rudi-
mentary imperforate (sometimes, though very rarely, perforate) teats.
In the centre of each gland, at the base of the teat, is a single galactophorous sinus, the
general confluent of all the lactiftrous ducts — a wide cavity opening at the extremity of the
teat by a definitive excretory canal.' (The mammse of the Cow occupy the same region as
those of the Mare, and the teats are longer and thicker.)
' Sanson has seen, at Grignon, a Cow with seven teats, all giving milk. He has also seen
*wo teats communicating with the same galactophorous sinus, and he believed that there are
•nly two mammae, no matter how many teats there may be. Goubaux is of opinion that
' ^
THE GENITAL OliGANS OF THE FEMALE. 1001
In the Sheep and Goat, there are only two mammae, as in the Mare and Ass, though they
are formed as in the Cow. The Goat has frequently two posterior rudimentary mammse.
Pig. — The ovary of the Bow has a lobulated aspect, like the ovary of Birds. This appear-
ance is due to the ovisacs which, when they are well developed, project beyond the surface of
the ovarium, instead of remaining encysted in its stroma. The oviduct is less flexuous, but
its length is proportionately greater than in the other species. The body of the uterus is sliort,
but the cornua are very long and folded, and float amongst the intestinal convolutions. (Its cervix
does not project into the vagina, and the two cavities — vagina and uterus — are continued into
each otlier without any marked limit between them. The mucous membrane is very loose,
soft, and fine to the touch, and its surface is gathered up into numerous folds of various forms.
The broad ligaments resemble the mesentery, and the cornua join the Fallopian tubes without
any very perceptible limit.)
The vagina shows Gsertner's canals, as in the Cow. (Its mucous membrane has numerous
longitudinal folds anteriorly ; and in front a multitude of fine points, wliich are the excretory
ducts of small glands analogous to the prostates. On the sides of the meatus urinarius are two
small fossettes surrounded by a ring. There is no vaginal valve.) Tlie inferior commissure
of the vulva is more acute than in Ruminants. The mammae are ten in number, disposed in
two rows, extending from the inguinal region to below the chest. They have no galacto-
phorous reservoirs, as in the larger Ruminants — the lactiferous ducts uniting directly into a
variable number of definitive canals that pass through the teat, to pierce its extremity by
from five to ten orifices. (There are, of course, five or six glands in each row, each with its
teat.)
Carnivora.— In the Dog and Cat, the ovaries and uterus are disposed as in the Pig; the
ovaries (are situated behind the kidneys, and) are lodged in a particular fold of the broad liga-
ments, which forms a kind of cup. There are no Gaertner's canals in the vagina. The vulva
of the Dog is triangular, and acute at its inferior commissure. The Cat has a small bone in
the clitoris. The mammx are ten in number in the Dog, and eight in the Cat ; they are
distinguished, as in the Pig, into inguinal, abdominal, and pectoral. (Each teat has from eight
to ten orifices. The vagina is long, and wider at the vulva than towards the uterus. Beside
the smooth muscular fibres of its external coat, it has wliite fibres which give it greater thick-
ness and resistance. The mucous membrane forms longitudinal, intersected by transverse,
folds ; the valve of the meatus urinarius scarcely exists. Tiie cervix of the uterus projects
into the vagina, and is even more voluminous than the body, which is short ; it is hard to the
loucli.)
Rodents.— Otz-aries. — In the Rabbit, these organs are about from J to i inch in length,
and from 1| to 2 inches in breadth ; they are faintly rose-tinted, and the Graafian vesicles
and corpora lutea — extremely numerous— are scattered over the entire surface of the glands.
Fallopian tube. — The pavillion of the tube is very developed, and exceeds the ovary in
front ; it is bent downwards and backwards, in order to be fixed on the ovary.
Uterus.— In the Rabbit, the uterus is double, there being really two distinct organs lying
beside each other at their origin, but diverging for the remainder of their extent. Their
average length is from 4 to 5 inches ; each is cylindrical and slightly flexuous, and opens at
the bottom of the vagina by a small " expanded flower." The broad ligaments are fixed in
the uterus as in the Cow, and the uterus is drawn outwards.
Vagina. — This is flattened above and below, and sustained by the borders of its inferior
face ; it is from about 2 to 3 inches long, but its origin is not well defined, as the meatus
urinarius is more or less crossed by Gaertner's canal, which naturally belongs to the vagina.
That canal lies to the left of the meatus, but it soon disappears there, to reappear in the
vicinity of the left uterine canal.
Vulva. — Rather more than two inches long, the vulvar cavity is almost entirely situated
beyond the ischiatic arch, and is attached, witir the rectum, to the inferior surface of the
coccygeal region. Its orifice shows labia majora and minora. The first is garnished, near
the inferior commissure, with a tuft of long fine hairs ; the second commence towards the
superior commissure, and are attached inferiorly to the clitoris. The latter organ hRS for its
base a corpus cavernosum 1| inch long; its free portion is flattened and tapering, and it may
become so very salient, when the labia of the vulva are drawn forward, as to resemble a small
penis.
The muscles of the vulva are : 1 . A posterior constrictor. 2. An anterior constrictor — very
Sanson has met with anomalies. For ourselves, we have found that each teat has a special
galactophorous sinus. In this Cow, therefore, there were five mammary glands, one of which
1002 GENERATIVE APPARATUS.
large, commencing at the coccygeal vertebrae, and inserted into tlie borders of the clitoris. 3,
Two erectores penis muscles. 4. A subischio-cavernous muscle, less voluminous than in the
male, but of the same shape.
Mammse. — They are disposed as in the Sow and Bitch.
Glands. — The female Rabbit possesses, like the male, a pair of rectal and a pair of anal
glands.
In the female Leporide, it is remarked tliat the external genital organs resemble thosd
of the Rabbit, and that the internal ones hold a middle place between those of the Rabbit and
doe-Hare; otherwise these organs show everything necessary for reproduction.
Comparison of the Generative Organs of Woman with those of Animals.
Ovaries. — These organs are oval, about 1^ inches long and i of an inch broad, and are
lodged in the posterior layer of the broad ligaments. They are attached to the uterus by the
ligament of the ovary, and united to the Fallopian tubes by the Fallopio-ovarian ligament.
Their structure is the same as in animals. A Graafian vesicle usually ripens every month ; its
rupture corresponds with the menstrual period. Annexed to tiie human ovary is found the
organ of Rosenmiiller, composed oi" from fifteen to twenty tortuous tubes opening into a transverse
Fig. 540.
II
uterus of the human female, with its appendages (viewed from the front).
1, Body of the uterus; 2, fundus; 3, cervix; 4, os uteri; 5, vagina, with its colurana and
transverse rugae; 6 fi, broad ligament of the uterus; 7, convexity of the broad ligament formed
by the ovary; 8, 8, round ligaments of the uterus; 9, 9, Fallopian tubes; 10, 10, their
fimbriated extremities; 11, ovary ; 12, utero-ovarian ligament; 13, Fallopio-ovarian ligament;
14, peritoneum of anterior surface of uterus fit is removed at the left side, but on the right is
continuous with the anterior layer of the broad ligament).
branch ; these tubes are lined by ciliated epithelium, and filled with a yellow fluid ; they form
a closed system included in the broad ligament, between the ovary and oviduct.
Oviduct. — Placed at the upper border of the broad ligament, it is nearly straight, and
terminates by a pavilion notclied into about fifteen unequal fringes.
Uterus.— The human uterus is situated between the bladder and rectum, being inclined
slightly downwards, from before to behind. Its form is very difl'erent from the uterus of the
animals we have described, being that of a flattened gourd ; its volume varies with age and the
number of gestations ; it weighs about two ounces. It is described as having a body and
cervix. The body is triangular, and at the extremities of its upper border the Fallopian tubes
open into it. The cervix is fusiform ; the projection it makes at the bottom of the vagina is the
tench's nose — a transversal slit bordered by two unequal lips. The inner face of the cervix
shows the plicas paZmate— arborizations formed by the mucous membrane.
There is not! ling special to be noticed in its structure.
The broad ligaments comprise a quantity of muscular fibres between their layers, and which
accumulate at certain points to form accessory folds ; among tliese the most important are the
round ligaments. These leave the anterior face of the uterus, pass forward and outward, enter
the inguinal canal, and terminate in the connective tissue of the mons Veneris.
Vagina. — This canal is about 2| inches wide : it is in contact with the rectum, and responds
in front, by connective tissue, to the bladder and urethra. Its internal face has longitudinal
folds— the columnas of the vagina — which are intersected by transverse folds. Below the orifice
of the urethra is the entrance to the vagina, a circular opening partially closed by the hymen in
virgins. Rarely complete, this membrane may afl'ect different shapes, and consequently receive
^
GENERATIVE APPARATUS OF BIRDS. 1003
various names— as horse-shoe, bilabial, semilunar, annular, and fringed hymen. When ruptured,
it retracts very much, but there always remain some vestiges of it, which are designated
carunculse myrtiformes.
Vulva.— Thin presents a cavity and an orifice, as in the domesticated animals ; but the
cavity is not so deep, and is named the vestibule; it extends to the hymen or its debris. The
entrance to the vulva occur in the middle of a cuneiform prominence that is confounded, above, with
a kind of eminence— the mons Fe?iem— wliich appears to protect the pubic symphysis. It is
margined by two folds on each side : one cutaneous— the labia majora ; the other mucous— the
labia minora (or nymphse). The labia majora are convex externally, continuous above with
the mons Veneris, and unite below to form an acute angle, named the fourchette ; they are
covered externally with hair. The labia minora, more or less developed, leave the fourchette,
and extend around the entrance to the vagina, uniting above the clitoris, and forming the prepuce
of that organ.
The clitoris is lodged in the superior commissure of the vulva ; its point is directed down-
wards, especially during erection ; its base is attaclied, on each side, to the two erectile lobes
which constitute the bulb of the vagina (bulbi vestibuli).
Two racemose glands— the vulvo-vaginal, or glands of Bartholine—pout their secretion over
the walls of the vestibule.
Marnrn^.— These are pectoral, and two in number. In their centre, they present an
enormous papilla— the 7iipple— into which the excretory canals open ; it is surrounded by a
brown circle, the areola of the nipple.
CHAPTER III.
Generative Apparatus of Birds.
1. Male Generative Organs.
The generative organs of the male are the testicles, and an excretory apparatus
much simpler than that of Mammals.
Testicles. — These organs are placed in the sublumbar region of the abdominal
cavity, behind the lungs, and below the anterior extremity of the kidneys, in front
of the three last ribs. Their form is usually oval, and their volume varies with
the different species, as well as at different seasons ; at the breeding-season they
are greatly developed.
E.ccretory afparatus. — In Birds there is not, properly speaking, an epididymis.
The vas deferens passes from within the posterior extremity of the testicle,
is directed in a flexuous manner backwards, draws near to the ureter on its own
side, going along the kidney with it, and arriving at the cloaca, where it termi-
nates by an orifice to be alluded to hereafter. In the Duck, it has near its
termination a small oval vesicle, always filled with spermatic fluid.
Organ of copvlation. — This varies with the species. In the Gallinacge, it is
only a small papilla, placed below, near the margin of the cloacal opening, and
between the two orifices of the deferent canals. This papilla is traversed by a
furrow, through which the semen flows.
In the Palmipedes, this organ is much more developed, and is peculiar.
Contained within a tubular cavity in the cloaca, it is protruded externally at the
moment of copulation by the eversion of this cavity, like the finger of a glove ;
it then appears as a long pendent appendage, twisted like a corkscrew.
1004
GENERATIVE APPARATUS OF BIRDS.
2. Generative Organs of the Female.
The development of the young animal taking place external to the female,
the generative organs are hmited to that producing the ovum, and the duct
through which it passes on leaving the ovary.
Ovari/. — In birds there is only one ovary, which is situated on the left side,
the right one becoming atrophied very early in nearly all species. This ovary is
situated, hke the testicles, in the sublumbar region of the abdominal cavity, and
constitutes a more or less voluminous body, composed of a variable number of
ova in process of development— some
Fig. 541.
OVAKY OF THE BIRD.
a, c, c. Ova (eggs) in the various stages of develop-
ment ; 6, stieak without vessels, indicating the
point where the vesicle is about to rupture to
allow the ova to escape; d, ruptureil vesicle;
e, very small ovum showing tl^# cicatriculus.
very young, little, and white ; others
more advanced in age, being larger and
yellow in colour. The ova are en-
veloped in a very vascular cellular
membrane, which, when they are ripe,
splits in a circular manner, following
an equatorial line, and permits the
escape of the essential part of the egg
— the i/elloiv (yolk), or vitellus.
Oviduct. — This duct is long, very
wide and dilatable, and very flexuous.
It begins, near the ovary, by an un-
fringed pavilion, and terminates in the
cloaca by a somewhat narrow orifice,
which is considerably widened when
the Qgg passes through it.^ The egg
— composed, on entering the oviduct,
of the fundamental part named the
yolk, or vitellus— h enveloped in an
albuminous covering during its pro-
gress towards the cloaca, and after-
wards with a protecting shell. The oviduct of birds is, therefore, something
more than an excretory canal, as it participates in the formation of the ovum.
It is composed of three membranes — an external serous, maintains the tortuous
tube ; a middle, muscular ; and an internal, mucous.
In the two sexes, above the cloaca there is a diverticulum named the pouch
of Fabricius, which is extirpated in Brittany, in order to render the hen birds
sterile.
• Instances of abdominal " egg-laying " have been observed. Reul gives examples in
which it was due to atresia of the oviduct {Annales de Med. Veterinaire de Bruxelles, 1887>
BOOK IX.
EMBRYOLOGY.
Embryologij has for its object the study of the modifications which the ovum
undergoes, from the moment it is fecundated until it is transformed into a new
being capable of living in the external world.
The points of this subject, belonging to the domain of anatomy, will be
divided into three chapters. In the first, the transformations of the ovum which
produce the embryo will be examined. In the second, the various portions of
the ovum — the annexes of the foetus — will be studied ; and the third will deal
with the development of the foetus.
CHAPTER I.
The Ovum and its Early Embryonic Developments.
Aeticle I. — The Ovum.
The ovum of the domestic mammifers is a vesicle about y^Vtr of an inch in
diameter (the germinal spot being from ^-^ to tt^Vtt of an inch), contained in
the Graafian follicle, in the midst of the cumulus proUgera.
It possesses : 1. An amorphous, transparent enveloping membrane, '01 mm.
thick, named the vitelline membrane, or zona pellucida. 2. A hazy viscid fluid,
holding in suspension a large number of dark-coloured granules and fat-globules :
this is the vitellm, or yolk. 3. The germinal vesicle, a spherical transparent
nucleus lying to one side of the vesicle, and readily altered. The germinal spot,
a kind of very brilliant nucleolus seen in the centre of the nucleus.
According to Balbiani, there also exists in the ovum of all animals — from
insects up to Mammals — beside the germinative vesicle, a second nucleus— named
Balbiani'' s or the embrgogenous vesicle — which plays a very important part in the
nutrition of the ovum and the phenomena succeeding fecundation.
Article II. — First Embryonic Developments.
These include three important events — the segmentation of the viteUus, the
formation of the blastoderm, and the appearance of the embryo.
These phenomena have been particularly studied in the ovum of the Rabbit,
and it is to the researches of Van Beneden on this subject that science owes the
most important information on the first phenomena that occur after fecundation
in the Mammalia.
1. Segmentation of the Vitellus. — This takes place immediately after
1006
EMBRYOLOGY.
fecundation ; and although we have not to treat of fecundation itself, yet it ia
well to bring forward the essential fact resulting from modern investigations
on this point, showing that this great act consists in the fusion of two germs
— the female pronucleus, arising from the division of
the germinal vesicle ; and the male pro)iucleus, due to
the transformation and migration of the spermatozoid.
These two elements, by their fusion, originate the i/olk-
nucleus which, by its double origin, contains the material
elements of hereditary continuity.
The division of the yolk-nucleus begins and deter-
mines the segmentation of the yolk — equivalent to cell-
proliferation.
Before becoming segmented, the yolk separates from
its enveloping membrane, retracts, and leaves around it
a space occupied by a transparent fluid.
The segmentation of the yolk is total, the entire
mass undergoing proliferation, and the first effect of
this is the production of two cells resulting from the
division of the yolk. These two primary cells, or
segmentation globes, in their turn divide and give rise
to two generations which have different destinies to
fulfil. This specialization is already naturally contained
in the two primary globes of segmentation, and is
marked by particular characters. The two globes are,
in fact, unequal in size. The largest — the edodermic
globe — is transparent ; the second — the endodermic globe
— is charged with granules which are readily stained by osmic acid.
The proliferation of the ectodermic and endodermic globes continues, and in
Buch a manner that the segmentation globes issuing from the first proceed towards
A GRAAFIAN VESICLE, FROM
A WOMAN THIRTY-TWO
YEARS OF AGE.
In this is seen the epithelial
covering formed of poly-
gonal cells, and an ovum
in which there is at a the
germinal vesicle with its
spot, and at h the embryo-
genous vesicle, much
smaller, and surrounded
by numerous granules
which are disseminated in
the vitellus; c is the
zonula pellucida.
OPTICAL SECTIONS OF THE OVUM OF A RABBIT IN TWO STAGES
AFTER SEGMENTATION.
ep, Epiblast, or ectoderm ; hy, hypoblast, or entoderm ; hp, blastopore. The ectoderm and endoderm
are differently shaded.
the periphery, and tend to envelop the mass of those which arise from the division
of the endodermic globes. Finally, in about seventy hours after fecundation, in
the Rabbit, the envelopment is complete.
EARLY EMBRYONIC DEVELOPMENTS.
1007
The yolk is formed of a peripheral layer of clear transparent cells— the
ectoderm, or epiblast— lining the vitelline membrane, and embracing a central
mulberry mass (morula) of polyhedral and granular cells— the endoderm, or hypo-
llast. The ectoderm shows at one of its points an aperture— the hlastopore, or
anus of Rusconi— into which penetrates and closes it, but without overlapping it,
a prolongation of the endoderm— the cork of Ecker. At this phase in its evolu-
tion, the yolk constitutes what is termed in comparative embryology, the meta-
gastnda.
2. Passage of the Metagastrula to the Uterus, and Formation op
THE Vesicle and Blastodermic Layers. — As soon as the metagastrula has
reached the uterus, it commences to be transformed into a clear and transparent
vesicle, which grows rapidly, attaining in four or five days a diameter of from
8 to 9 mm., and constituting the blastodermic vesicle, or blastoderm.
The appearance of the blastoderm is marked by the appearance of a fissure
that separates the ectoderm from the endoderm, leaving them only adherent at
a point corresponding to the blasto-
pore, which was already formed
towards the end of the third
day.
Owing to the pressure of the
fluid that fills it and tends to ac-
cumulate, the ectoderm becomes
distended and fissures ; its cells
multiply, and it fiattens so as to
embrace a layer that, towards the
ninetieth hour, attains from '15 to
•17 mm. The endoderm, pressed
upon by the fiuid, is deformed and
spread over a point beneath the
ectoderm, where it becomes the
gastrodisc. The vesicle, formed at
this part of two superposed layers,
is still monodermic everywhere else
(Fig. 544) ; nevertheless, the cells
of the gastrodisc change in charac-
ter, becoming flattened, and in an
ovum of from 105 to 115 hours,
having a diameter of from -9 to 2
mm., they form an endothelial
lining to the ectoderm to an extent which increases with the marginal growth of
the internal layer.
But all the cells of the endoderm are not so transformed. In ova of five
days old, having from 2 to 4 mm. to the centre of the gastrodisc, some are
found which have preserved their primary characters of segmentation spheres,
and remain interposed between the ectoderm and endoderm— between the
external and internal layers. This residual cellular mass, which has escaped
the endodermic transformation, is the point of depr.rture of a third layer— the
mesoderm {mesoblast), or middle lager, which is already marked at this period by
a circular spot at the pole of the gastrodisc. It is this spot that has been known
since the time of Bischoff and Coste as the germinal area or streak. The germijial
—also named the embryonal— area is only at first the optical signification of the
OVUM OF THE RABBIT, NINETY HOURS AFTER
FECUNDATION.
br, Cavity of the blastodermic vesicle; ep, epiblast, or
ectoderm, forming a complete sac ; hy, hypoblast,
or endoderm, forming the gastrodisc; zp, zonula
pellucida.
1008 EMBRYOLOGY.
appearance of the middle layer, and although the embryo at a later period reveals
its first outlines in this part of the blastoderm, it must not be forgotten that it
is not yet traced ; so that the qualification of embryonal area cannot be accepted
in a literal sense.
In the following days, the internal and middle layers continue to grow. By
multiplication of the elements of the mesoderm, the germinal area increases in
thickness and in surface, pushing up the ectoderm, which becomes salient like a
shield, and has a well-defined circular outline. The germinal area at this moment
reveals the thickening of the central region of the mesoderm (mesoblast), which
extends by its borders at the same time as the endoderm, so that the walls of the
vesicle are soon composed of three layers throughout.
From the seventh to the eighth day, the blastoderm figures as an elliptical
vesicle, somewhat flattened, from 7 to 8 mm. in diameter, filled with a trans-
parent albuminous fluid, and formed of three superposed layers. It does not yefc
exhibit any traces of morpliological differentiation except the germinal area, or
Fig. 545.
VIEWS OF THE BLASTODERMIC VESICLE OF A RABBIT ON THE SEVENTH DAY.
A. FROM ABOVE; B, FROM THE SIDE.
ag, Embryonal area ; ge, limit of the gastrodisc or endoderm (hypoblast).
central thickening of the mesoderm. It is true, however, that the outline of the
embryo soon becomes apparent, and the three layers of the blastoderm play a
distinct part in its formation, which it is necessary to indicate beforehand.
a. The external layer — ectoderm, epiblasf — is also named the sensorj/ or
smsitive layer, because it gives rise to the epidermis or epidermic formation, and
to all the nerve-elements of the sensory terminations — retina, organ of Corti,
etc. ; it also furnishes the outline of the central nervous system.
h. The internal layer — endoderm, ht/jwblast — also merits the name of mucous
layer, as it originates — not the mucous membranes, as is often said — but the
epithelium of the post-diaphragmatic portion of the digestive apparatus and the
glands annexed thereto —liver and pancreas.
c. The middle layer — mesoderm, mesohlast — serves as a centre for all the other
tissues — connective, muscular, blood-vessels and lymphatics, serous membranes,
sexual glands, etc. The multiplicity of its future specializations does not, there-
fore, authorize a particular denomination, though it is at times designated as the
EARLY EMBRYONIC DEVELOPMENTS. 1009
serous or germinal layer. The qualification of vascular layer should not be given
to it, as it belongs to a special formation which will be alluded to hereafter.
3. Appearance and Formation of the Embryo.— The place in which the
embryo is developed is prepared by a differentiation in the germinal area. At
first opaque throughout its extent, it becomes clear in Ids central region, and is
thus divided into two concentric and circular zones— the transjmrent and the
ofaque zone. The phenomena which follow are easily studied in the Chick, and
it is in it that we will observe them. But it is necessary at first to examine the
composition of a Bird's q^;^ ; though its complexity is due to the circumstance
that the development of the embryo takes place externally, and that the germ
must therefore carry with it its nutriment and its protective envelopes.
Essential parts. — The Qgg of Birds — like that of Reptiles and all the Oviparous
Vertebrates — is, then, only a germ provided with an enormous quantity of aliment,
and it is this mass that constitutes the yolk. The germ itself — that which is the
physiological equivalent of the ovum of Mammals— is represented by a small,
circular, white spot — the cicatricula — situated on the surface of the yolk, beneath
the vitelline membrane ; in this, exclusively, resides the evolutionary force, and
it is this spot which undergoes segmentation. It corresponds, then, to the whole
of the vitellus of the ovum in Mammalia, and merits the name of plastic vitellus, to
distinguish it from the nutritive vitellus represented by the yolk. Although there
is no marked line of demarcation between the two masses, and although from the
plastic vitellus there emanates a kind of protoplasmic atmosphere that penetrates
the nutritive vitellus, it might be maintained that the latter does not participate
to any extent in the segmentation, which remains exclusively localized in the plastic
vitellus. In this sense it may be said that the segmentation is partial in the ova
of the type named meroUastic. The ova of Mammalia and those of the same type
are, on the contrary, holoblastic — ova in which segmentation involves the whole
of the yolk.
In the Fowl, whether or not fecundation has taken place, segmentation occurs
during the passage of the Q^g in the tube, and is nearly completed at the moment
of laying. The cicatricula visible in the vitelline membrane therefore represents,
in the new-laid Qgg, not the primary and simple germ, but the germ segmented
and ready to form the blastoderm. To see this properly, a fresh egg, sliould be
opened in water ; the centre of gravity of the yolk being eccentric, the vitellus
passes in a certain direction, bringing the cicatriculus to the highest pole of the
yolk, in the centre of the visible hemisphere.
Accessory parts. — In passing through the oviduct, the ovum — reduced, as we
have seen, to the mass of the vitellus — is surrounded successively by : 1. A layer
of albumen. 2. A testaceous membrane. 3. A shell.
The albumen — or " white " — forms three layers of different densities. As, in
its progression, the egg is submitted to a rotatory mo\'ement on its greater axis,
so the albumen undergoes a twist and a particular condensation along this axis ;
in this way are formed two kinds of coverings, that can be seen floating and
adhering to the yolk of eggs opened in water, and which are named the chulazm.
The shell membrane (jnemhrana putaminis), fibroid in appearance, at the
thick pole is doubled into two layers to form a cavity — the air-chamber. This
cavity increases as development goes on, in order to meet the respiratory demands
of the embryo, or fcetus ; while the yolk and albumen become progressively
expended as the foetus grows.
The shell is an organic framework impregnated with lime salts ; but it is
1010
EMBRYOLOGY.
unnecessary here to enter into a consideration of the very complex details of its
structure and mode of formation.
The above description shows the fundamental identity between the holoblastic
DIAGRAMMATIC SECTION OF A FOWL'S UNHATOHED EGG.
I., Blastoderm; w.y., white vitellus, consisting of a pyrit'orm central mass and a certain number of
concentric layers ; y., yellow vitellus, in alternate layers with the preceding ; v.t., vitelline
membrane; x., layer of albuminous fluid surrounding the vitellus; w., consistent albumen ; ch.L,
chalazae; a.ch., air-chamber; i.s.m., inner layer of the testaceous or shell membrane; s.m.,
external layer of ditto ; s., shell.
Fig. 547.
and meroblastic ova ; they only differ in the enormous predominance of the
nutritive vitellus in the latter. This predominance has the mechanical effect of
localizing the phenomena of segmentation to
one pole of the egg — that in which is the plastic
vitellus ; and we have seen that this is com-
pleted at the moment of laying. The blastoderm
that issues from this centre of proliferation
necessarily assumes the shape of a disc — the
germinal disc ; then of a spherical cap lying on
the yolk by its concavity, and tending to em-
brace it by the progressive extension of its
circular border. This investment is only com-
pleted towards the sixth day of incubation, and
the blastoderm is therefore late in assuming
the vesicular form. Notwithstanding differences
of the same kind, arising from another manner
of proceeding than that observed in Mammals,
the successive formation of the germinal area,
and its doubling into an opaque and a trans-
parent zone, take place.
The appearance of the embryo is manifested
by a temporary formation known as the primitive trace — embryonal rudiment, or
axile layer. The primitive trace is marked on the blastoderm by two dark streaks
pr.s
AREA PELLUCIDA IN THE VERY EARLY
BLASTODERM OF THE CHICK, SHOWING
THE PRIMITIVE LINE AT ITS FIRST
APPEARANCE.
pr.s, primitive trace ; ap, transparent
or pellucid area.; a.op, opaque area.
EAKLY EMBRYONIC DEVELOPMENTS 1011
close together, separated by a bright line (primitive streak), but continuous with
each other in front. All the transparent zone in front of the primitive line has
been designated by Duval as the tergal zone, and we adopt this correct and
convenient term. The growth of the primitive line takes place at its posterior
extremity, and to this circumstance is due the change in shape of the transparent
area, which becomes pyriform.
It is indispensable to see, on transverse sections, the arrangement of the
blastoderm and its layers at the primitive trace. The ectoderm, formed of a
layer of cubical cells, is curved in the middle, and its deep face becomes con-
founded with the mesoderm. The latter, formed of small angular cells, is placed
between the two layers, and enters the substance of the opaque zone. The
endoderm, formed of a single layer of fiat cells throughout the extent of the trans-
parent zone, suddenly becomes thicker at the opaque zone, by the stratification
of its cells still filled with vitelline granules. These marginal thickenings have
been named by Kolliker the endodermic ridges ; it is to them that the opaque
zone owes its optical characters.
This transverse section enables us to see, for the first time, the three super-
Fig. 548.
TRANSVERSE SECTION OF A BLASTODERM OF THE SAME AGE AS FIG. 547.
pos., Primitive trace ; ep., epiblast, or ectoderm ; hy., endoderm ; yk., above, the endodermic ridge.
The section passes nearly through the middle of the primitive trace.
posed layers of the germinal disc ; and it exhibits, between the ectoderm and the
mesoderm, a curious and characteristic continuity of the primitive trace, which has
for a long time exercised the wisdom of embryologists, and given rise to debates
now terminated. We will say nothing of the solution arrived at, as it would lead
us too far from the scope of this work ; and only refer to the primitive trace,
because for a long time it passed for what it was not, and also because there was
seen in it a trace of the central nervous system, which only appeared morpho-
logically towards the twentieth hour. Destined to retrograde and disappear,
the primitive trace is only on the threshold of the embryonal development — an
atavic episode, the significance of which cannot be given here, but of which it
is necessary to speak, and to point out, in order not to confound it with the
origin of the nervous system.
Article III.— General Direction of Development.— Vertebral Type.
The ulterior modifications in the three layers of the blastoderm— inflections,
invaginations, doublings— tending to the realization of this type, and from the
end of the first day, furnish very interesting indications.
We will study these in a blastoderm from the twentieth to the twenty-fourth
hour (Fig. 547).
1012
EMBRYOLOGY.
The outline of the embryo distinctly appears as a very elongated ellipse.
At its inferior extremity is seen (Fig. 549) a very slender crescent, the per-
spective of which does not give so good an idea of its disposition as longitudinal
sections do. This appearance of the blastoderm seen on the surface, is due to the
inflection of its margins downwards and inwards. The elliptical disc represented
by the embryo, and which is lying flat on the yolk, gradually has its borders
curved downwards, and converging towards the middle on its ventral face. This
inflection of the embryo brings about the formation of the walls of the body
and its cavities. In their progressive incurvation, the borders circumscribe an
aperture, which contracts and becomes the umbilicus. The inflection proceeds
from before to behind, and is constituted by successive folds, which have been
Fig. 550. .
AREA PELLUCIDA OF THE BLASTO-
DERM OF A CHICK SOON AFTER
THE FORMATION OF THE PRIMI-
TIVE GROOVE.
pr, Primitive trace with the primitive
groove ; af, amniotic fold. The
shaded part around the primitive
trace shows the extension of the
mesoblast.
AREA PELLUCIDA IN A BLASTODERM OP
EIGHTEEN HOURS, SHOWING THE
MEDULLARY GROOVE.
pr, Primitive trace; m.c, medullary groove,
or dorsal furrow; A, medullary fold.
designated, from their situation, as the cephalic fold, lateral fold, and caudal
fold.
Fig. .549 shows precisely the commencement of the cephalic fold — that is,
the first trace of that grand phenomenon which leads to the formation of the
great splanchnic cavities. It may be remarked that, throughout, the three layers
of the blastoderm engaged in forming the embryo are continued by their borders
with the other parts of the blastoderm. It may also be stated that the embryo
is only a morphological specialization of the blastodermic vesicle, and that there
is reason to distinguish the embryonal blastodermic layers from the extra-
embryonal layers. "We shall soon see the why and wherefore, by reason of the
continuity of the two regions of the blastoderm, of the modifications in the
embryonal layers bringing about correlative modifications in the extra-embryonal
layers.
GENERAL DIRECTION OF DEVELOPMENT. lOlS
The tergale zone is occupied by a new formation, which appears to be the
continuation of the primitive trace, but is in reality altogether distinct. This is
a furrow formed by a longitudinal excavation in the ectoderm, and which com-
mences the trace of the central nervous system ; it is named the medullary
groove, or dorsal furrow. At the bottom of this groove a dark line betrays
the presence of the chorda dorsalis, or notochord — a provisional skeletal stalk
that sustains the medullary groove.
The presence of the medullary groove leads to the division of the embryo
into two perfectly distinct zones — the spinal zone, corresponding with the
medullary groove, and the marginal zone comprising all the other part to the
borders of the embryo. These facts become very intelhgible in a transverse
section through the middle of the medullary groove (Fig. 551). It is seen how
the latter is formed by the thickening and median inflection of the ectoderm,
Fig. 551.
TRANSVERSE SECTION OP A BLASTODERM AFTER THE FORMATION OF THE MEDULLART GROOVE
AND THE NOTOCHORD.
A, Ectoderm ; B, mesoderm ; c, endoderm : mc, medullary groove ; mf, medullary fold ; ch, noto-
chord. The figure represents the left half of the section.
which resembles a V widely open, the two branches of the V constituting the
medullary folds (Fig. 550). By their inflection and union they ultimately form
a closed tube — the neural canal, perhaps better designated as the neuraxis
(Fig. 552).
The endoderm does not offer any other modification, but the mesoderm
undergoes transformations of the highest interest. The interposition of the
chorda dorsalis divides it into two symmetrical moieties. The thickened parts,
which, in the two moieties, are subjacent to the corresponding medullary fold,
form the lateral layers (or plates). Beyond, the mesoderm shows, in certain
embryos at this time, a very marked indication of a decisive event in the evolu-
tion of the embryo and the realization of the vertebral type ; but it is more
convenient to study this in a more advanced embryo.
In transverse sections, the mesoderm can be seen undergoing cleavage into
two layers (Fig. 552). The space between these — and which is really a fissure
of no importance — grows to a great extent ; this is the pleuro-peritoneal fissurSy
which at a later period becomes the pleuro-peritoneal cavity.
The two layers resulting from the splitting of the mesoderm, perform very
difl'erent functions. The superficial layer, which furnishes materials for the
parieties of the body — including the dermis of the skin — has been named the
musculo-cutaneous layer ; the deeper one is designated the fibro-intestinal layeTy
which sufficiently indicates the direction of its approaching evolution.
In their ulterior modifications, the two layers remain closely allied to the
ectoderm and endoderm ; and by this association they constitute formations
akeady complex, which it is necessary to note and to qualify. The musculo-
1014
EMBRYOLOGY.
cutaneous layer lining the ectoderm constitutes the somatopUure ; and the fibro-
intestinal layer lining the endoderm constitutes the splanchnopleure.
But it is essential to remark that phenomena of the same order occur pro-
gressively in the extra-embryonal mesoderm, which, throughout its extent,
undergoes delamination, and becomes two layers equally alhed with the
ectoderm and endoderm. It is sufficient to add that the somatopleure and
splanchnopleure are continued beyond the embryo by two identical formations,
which it is convenient to designate as the extra-embryonal somatopleure and
splanchnopleure.
We have given all the facts and adopted the language which, up to the
present, can be embraced in a preliminary view of the general direction of the
development and the manner in which the vertebral type is realized, as well as
TRANSVERSE SECTION OF THE DORSAL REGION OF AN EMBRYO CHICK OF FORTY-FIVE HOURS.
A, Ectoderm ; B, mesoderm ; M.c, neuraxis ; P.v., lateral layer, or mesoblastic limit ; p.p., pleuro*
peritoneal cavity ; c.h., notochord ; S.o., somatopleura ; S.p., splanchnopleura ; W.d., Wolffian
canal; a.o., aorta; v, blood-vessels; w, mesodermic ridge, or germinal wall; op, limit of the
opaque area and area pellucida. The figure represents the right half of the section.
the correlations between the embryonal and extra-embryonal blastoderms. The
study of these correlations allows us to trace the origin of the envelopes which
protect the foetus, and are known as the annexes of the foetus.
In Fig. 553 is given a series of sections of an embryo more or less advanced.
In sections F and I the embryonal somatopleure and splanchnopleure are already
iucurvated downwards and inwards. In passing from F to I, we see how the
splanchnopleure of each side advance towards each other, and tend to form a
tube opened inferiorly at each section — this is the intestine. Its walls, not
joined at this point, are continuous with the extra-embryonal splanchnopleure,
which is really the umbilical vesicle ; in Birds, the latter contains the mass of
the yolk. Above the intestine are seen the superposed sections of the notochord
and neural canal ; and it is the order of this superposition that is characteristic
GENERAL DIRECTION OF DEVELOPMENT.
1015
—-w
FROM A TO N IS A SERIES OF DIAGRAMMATIC FIGURES SHOWING THE MANNER IN WHICH THE
EMBRYO AND ITS ENVELOPES ARE FORMED.
ttt, Vitelline membrane; e, embryo; pp, pleuro-peritoneal cavity; af, folds of the amnion; a,
amnion proper ; ae or ac, cavity containing the liquor amnii ; al, allantois ; a' digestive tabe ; 9
or ys, vitellus, or vitellin sac.
1016 EMBRYOLOGY.
of the vertebral type. The alliance of the embryonal and extra-embryonal
blastoderms has, at the commencement, a form that allows us to understand the
origin and mode of formation of the foetal annexes — umbilical vesicle, amnion,
chorion, aUantois. Before proceeding to the description of these organs, we will
examine precisely their origin.
It has been already shown that the umbilical vesicle is nothing more than
the whole of the extra-embryonal splanchnopleure. The amnion is derived from
the extra-embryonal somatopleure ; from F to I this derivation may be followed.
Around the embryo the somatopleure undergoes a double inflection — one that
establishes the limits between its two embryonal and extra-embryonal parts,
and passes up towards the back of the embryo ; and another — C— which is
continued over the inner face of the vitelline membrane, and is named the fold ;
the amniotic layer comprised between the two inflections constitutes the amnion.
This membrane is made complete by the union of the amniotic folds (I) ; the
embryo is entirely enclosed in the amnion. The union of the amniotic folds
entails, at the same time as the occlusion of the amnion, the occlusion of the
remainder of the extra-embryonal somatopleure, which lines the whole of the
internal face of the vitelline membrane, and forms a continuous and independent
membrane — the serous layer, or, better, the chorion.
The umbilical vesicle, the amnion, and the chorion, circumscribe a space
named the external calome, and communicating freely with the pleuro-peritoneal
cavity.
In Figs. E and H, showing longitudinal sections, are seen the general
relations of all these parts. At al, Fig. Gr, is observed the origin of the aUantois,
which appears to be only a diverticulum of the last portions of the intestines.
The allantoid sac soon passes into the ccelome, and there develops in size and
shape according to the species of the animal.
In the preceding chapter, we have seen by what evolutive modes the foetal
envelopes or membranes are derived from the intra-embryonal part of the somato-
pleure and splanchnopleure. These envelopes or membranes are represented in
the diagrammatic figure, 553. To them are joined the cord of vessels and the
capillaries that establish the relations between the mother and progeny. The
whole receive the name of annexes of the foetus.
CHAPTER II.
THE PCETAL ENVELOPES OP SOLIPEDS.
Preparation. — The dissection of the annexes of the foetus is a delicate operation ; but a
good idea of their arrangement may be obtained in several ways.
1. The embryo should be first removed from the uterus. This is very easily effected in
Solipeds, as the adhesions between the placenta and the uterus are nearly always destroyed when
dissection is undertaken. With the foetus of Ruminants, it is necessary to open the uterus
from the cervix to the summits of the cornua, the incision passing between the cotyledons. la
order to accomplish this, the point of the branch of a pair of scissors is passed between the
chorion and uterus, in raising the wall of the latter. The cotyledons are then sought for.
With the foetus of the Cow, the chorion is carefully pulled from the uterine cotyledon in order
to separate the placentas ; with that of the Sheep and Goat, the cotyledons are pressed between
two fingers, in order to expel the chorial villi from their interior.
THE FOSTUS. 1017
2. The foetus being isolated, the chorion is studied with regard to shape and external
aspect. To scl- the relations of its internal face with the other annexes, we may resort to a
plan which gives good results with the foetus of Ruminants. This consists in tilling tlie
allantois and amnion by small openings with diflferent-coloured fluids. The limits of the two
sacs can then be very well made out through the cliorion, while their reciprocal relations can
also be observed. With Solipeds, the allantoid cavity must necessarily be opened ; the mem-
brane of that name is partially separated from the inner surface of the chorion by blowing in
air along the principal divisions of the vessels of the cord, by means of a straw or blow-tube.
3. To complete the study of the amnion and the allantois of Ruminants, it is best to blow
in air beneath the chorion, after removing the contents. The chorion is then carefully taken
away, in breaking through — by means of the fingers and forceps — the laminal tissue uniting
these two membranes; in the same way are destroyed the fasciculi which bind the allantois
to the amnion. In Solipeds, notliing is more easy than to inflate the amnion, and to study
its shape and relations. The chorial layer of the allantois is demonstrated as already de-
scribed ; a similar procedure is employed to show the existence of the amniotic layer, which is
more easily done than with the other.
4. The vessels of the umbilical cord and placenta should be injected, and to make an
injection penetrate satisfactorily, tlie placental vessels, with the foetus and chorion, should be
placed in tepid water for some time.
The annexes of the fcetus comprise : 1. A membranous envelope exactly
Fig. 554.
DIAGRAM OF THE FCETAL MEMBRANES OF A MAMMAL.
pc. Zona pellucida with villi, and sz, the remainder of the extra-embryonal somatopleure con-
stituting the chorion; am, amnion; AC, cavity of amnion; UV, umbilical vesicle; al, allantois;
ALC, cavity of the allantois ; e, ectoderm, or outer layer of the embryo (epiblast) ; m, mesoblast
(or middle layer) ; H, endoderm of the embryo (alimentary canal).
moulded on the uterus, and known as the chorion. 2. A second ovoid sac in-
cluded in the first, and containing the foetus — the amnion. 3. The allantois— o.
membrane formed of two layers spread over the inner surface of the chorion
and the external face of the amnion, as well as covering the parts between these
two envelopes. 4. A small pyriform bladder constituting the umbilical vesicle.
5. The placenta — a collection of vascular tufts which graft the young creature
to the mother. 6. The umbilical cordy composed of vessels that attach the foetus
J018 ~^ EMBRYOLOGY.
to the envelopes sniToundiiig it, and which ramify in the placental tufts (Fig.
556).
1. The Chorion (Figs. 554, 555).
The outermost envelope of the ovum, the chorion is a vast membranous and
perfectly closed sac, the shape of which exactly corresponds with that of the uterus.
It has a hodij and two cornua. The latter, when inflated, are plicated and
sacculated like the caecum, and are always unequal in volume — that in which
the foetus is developed having by far the largest dimensions.^
The external face is studded with small red tubercles, formed by the placental
tufts. It adheres to the internal surface of the uterus. Between the two
membranes there is found a small quantity of sanguinolent fluid ; but on one
occasion, in the Ass, it had the appearance of milk.
The internal face, lined by the external layer of the allantois, is united in
the closest manner to that membrane, except at the umbilical cord, where there
Fie. 555
EXTERIOR OF THE CHORIAL SAC (MARE).
A, Body ; B, C, cornua.
exists a kind of conical infundibulum occupied by the umbilical vesicle. Ad-
hesion is established by means of the vessels of the umbilical cord passing into
the texture of the chorion, and by very delicate, laminal, interannexial connective
tissue.
Structure and Development. — The external covering of the ovum is at
first formed by the vitelline tunic, itself constituted by the transparent membrane,
covered externally by a layer of cells derived from the Fallopian tube or uterus.
This primitive chorion is replaced by a portion of the extra-foetal somatopleure,
which becomes the secondary or definitive chorion. It is destitute of vessels until
the allantois is developed.
When the chorion is complete, it is composed of three layers : 1. An external
epithelial covering, formed of a single layer of uniform cylindrical cells, contain-
' When there is only one foetus, it is always more particularly developed in one comu,
which consequently has an enormous volume when compared with the other. When there
are two foetuses— as often happens in the Ewe — there is one in each cornu; and then the
cornua develop in the same manner.
THE FCETUS. 1019
ing at some points fat-granules. 2. A chorial stroma of embiyonic connective
tissue — fibres, stellate cells, and round and migratory cells in the midst of a
large quantity of albuminous fluid. Dastre has observed in this layer opaque
plates — chorial plates — composed of irregular particles of tribasic phosphate of
lime, which ultimately serves for the ossification of the foetal cartilages. The
chorial deposit in Solipeds has the appearance of a network, the meshes and
spaces in which are badly defined. 3. A layer of mucous connective tissue that
unites it to the allantois.
From this description, it will be seen that the chorion does not play a merely
mechanical part in protecting the foetus and supporting the placental blood-
vessels, but that it holds in reserve the materials that will serve for rapid
nutritive changes at a given moment.
2. The Amxion (Figs. 556, A ; 557, C).
The second sac enveloping the foetus — the amnion — floates freely in the interior
of the chorion, to which it is only united at one point through the medium of
the umbilical cord. It contains the young creature, which is also attached to
its inner face by the vessels of the cord. It has the shape of an ovoid pouch
depressed around the umbilical vessels, around which it forms a sheath as it goes
to be confounded with the skin of the foetus. It has thin transparent walls.
Its external face is covered by the inner layer of the allantois, to which it
adheres slightly. A large number of flexuous vessels, enveloped by a thick layer
of mucous tissue, course over this surface. The internal face is perfectly smooth,
and is applied more or less directly to the skin of the foetus. It exhales a fluid
in which the latter floats — the liquor amnii.
Structure. — As the amnion is derived, hke the chorion, from the somato-
pleure, it is not surprising to find in it three superposed layers : 1. A very thin
connective-tissue membrane that adheres to the allantois. 2. A proper membrane
— also of connective tissue — but containing some muscular fibres, which explains
the contration of the amnion observed in the chick. 3. An epithelial lamina
lining the latter. There are sometimes met with, at certain points on the inner
surface of the amnion, small, white, opaque masses, composed of glycogenic ceUs,
which become brown when treated with iodine.
Liquor amnii. — Enclosed with the foetus in the cavity of the amnion, this
fluid is more or less abundant, according to the period of gestation ; its relative
quantity being always less as the foetus is advanced in development. At an
early period it is somewhat milky in appearance, but later it assumes a citrine or
slightly reddish tint. It has a salt taste, and contains 99 per cent, of water,
with albumen and salts, the principal of which are chloride of sodium and the
sulphate and phosphate of lime.
3. The Allantois (Fig. 556).
The allantois is a membrane that covers the inner face of the chorion, and
is folded around the insertion of the umbilical cord, to spread itself over the
whole external surface of the amnion. It thus transforms the chorial sac into
a kind of serous cavity, in which the amnios is enclosed as a viscus.
The inner, or amniotic lamina, is attached to the amnion " so shghtly, that
dissection, and especially insufflation, easily destroys its adhesion. When the
second of these measures is resorted to, in order to separate the two membranes.
1020
EMBRYOLOGY.
the allantoid surface assumes a sacculated or blistered appearance, due to the
numerous cellular bands that attach it to the amnion. These bands rupture
when the inflation is forced, and a noise is heard analogous to that produced by
the rumpling of parchment. With a little care, the whole of this portion of
the allaiitois — the extent of which equals that of the amnion — may be entirely
detached.
" The degree of adhesion of the chorial allantois is more marked. Ordinary
dissection — which is easy along the first divisions of the cord — is much more
difficult towards the chorion, and soon becomes, if not impossible, at least very
arduous, if we desire to separate it. But here, again, inflation demonstrates the
existence of the membrane, and its continuity with the portion so easily dissected
from the amnion. If, after opening the allantoid sac by cutting through the
DIAGRAM OF THE DIFFERENT PARTS OF THE FCETAL HORSE, TOWARDS THE MIDDLE OP GESTATIOIT.
P P, Placenta ; Ch Ch, chorion ; Al', external lamina of the allantois ; Al, internal lamina of
ditto ; o, urachus; e, cavity of the allantoid ; A, amnion ; B, cavity of the amnion; Vo, remains
of the umbilical vesicle ; V, vessels of the umbilical cord ; F, foetus.
chorion and the lamina lining it, a tube is introduced between the two membranes
— which is readily done near a large vessel — by a slight inflation the air enters
between the allantois and chorion, though it only follows the track of vessels of
a certain size, to the sides of which there is but little adherence. If the inflation
is pushed, the air — following the smallest vascular ramifications— renders the
membrane more apparent, though without detaching it from the points where
the vessels have almost become capillaries.
" If, instead of injecting the air towards the ramifications, it is propelled in
the opposite direction, it will soon be perceived to extend towards the allantoid
portion of the umbilical cord, and insinuate itself between the amnion and the
allantois covering it — an evident proof of the continuity of the two layers which
THE F(ETUS. 1021
have been separated for the purpose ot studying them, but which are, in reaUty,
only two portions of the same membrane that forms a complete sac." ^
The cavity of this sac communicates with the bladder by means of a canal
divisible into two portions : 1. The infutuUbulum — a wide canal continued in
the amniotic portion of the umbiUcal cord, the walls of which are continuous, on
the one part, with the amniotic lamina of the membrane, and on the other part
with the chorial lamina, after being prolonged as a sheath around the cord.
2. The urachus, a musculo-membranous canal that extends from the umbilicus
to the summit of the bladder, with the umbihcal arteries on each side (Figs. 556 ;
557, A B).
Structure and Development. — The allantois has the structure of a serous
membrane. It possesses : 1. An endothelial lining, the cells of which are thin
and polygonal, leaving between them, here and there, stomata that permit the
blood-serum to transude through its texture ; these cells contain the glycogen.
2. A middle layer or stroma, of the nature of connective tissue, little vascular,
and the fibres of which are parallel. 3. An external layer of loose connective
tissue, rich in vessels, and resembling subserous tissue ; this layer is continuous
with the parietal fibrous tissue of the foetal peritoneum, through the medium of
Wharton's jelly.
The allantois, as we have described it, passes beneath the mucous membrane
of the bladder instead of being confounded with it.
The blastodermic laminae — internal and middle — concur in the formation of
the allantois ; but the middle one has the largest share in this. There is a
tendency to beHeve that the extra-foetal portion of this vesicle is a cavity formed
in the intra-annexial connective tissue, and that this cavity is at a later period
transformed into a serous one. In any case, it serves as a support to the vessels
passing between the foetus and placenta.
Allantoid Fluid. — This cavity contains a fluid, the quantity of which
increases with age. Colourless and transparent at first, it afterwards becomes
amber-tinted, and this gradually deepens ; at the same time it grows turbid, and
flocculent masses form in it. Its reaction is alkaline, and it has the property of
emulsifying fats. It contains albumen, urea, various salts, and sugar — 2*5 per
1000 average. The proportion of the latter does not vary much during
gestation.
The presence of urea in this fluid, as well as the communication of the urachus
with the bladder, has led to the supposition that the urinary secretion of the
foetus contributes to its formation. But this is not demonstrated, and the mere
presence of urea is not sufficient to attribute this origin to the allantoid fluid ;
for the blood, lymph, cerebro-spinal fluid, as well as all other serous fluids, contain
a proportion at least as considerable.
Hippomanes. — This name is given to small brown masses, more or less
numerous — though often there is only one — which float in the allantoid fluid.
"These bodies, of the consistency of gluten, and elastic like it, are flattened,
thinner at the borders than towards the centre, oval or irregularly circular, and
about the diameter of a five-franc piece. It is difficult to explain the presence of
the hippomanes in the allantoid sac. Nothing in its appearance indicates that it
may be formed at the expense of the liquid contained in this membrane. Some-
times pediculated hippomanes are found, and these may assist in explaining the
formation of the free hippomanes. Bourgelat speaks, in his Anatomic, of pedicu-
• F. Lecoq, Bes Annexes du Foetus.
67
1022
EMBRYOLOGY.
lated hippomanes, and I have been able to make the following observationB,
through having met with a large number on a foetus : —
" Besides the free hippomanes found floating in the allantoid fluid, there were
remarked, on the outer wall of the sac, a great number of small tear-shaped bodies
of variable size, adhering by a pedicle which was more or less narrow as the mass
was more developed. Their colour was the same as that of the principal hippo-
manes, and if pressed between the fingers, the brown matter contained in a thin-
Fig. 557.
FCETUS OF THE MARE, WITH ITS ENVELOPES.
, Chorion; (7, amnion removed from the allantoid cavity, and opened to expose the foetus; 2),
infundibulum of the urachus; B, allantoid portion of the umbilical cord ; b, point of the external
surfare of the chorion, destitute of placental villi, and corresponding to the part where the three
pediculated hippomanes are attached.
walled sac escaped by the pedicle, and spread itself over the external surface of
the chorion. There the villosities of the placenta were absent at the margin of
the opening, which was surrounded by a whitish areola (Fig. 557, b).
"Might it not be admitted, from this disposition, that the hippomanes is
developed between the placenta and the uterus, and is carried inward, by pushing
before it the chorion and layer of the allantois covering it, until, on reaching the
TEE FCETUS.
1023
allantoid cavity, it becomes detached, like certain fibrous or cartilaginous bodies
in the synovial or serous cavities ? " (F. Lecoq).
According to Dastre, the hippomanes arise between the chorion and the
allantois, and they are formed by the phosphatic matter of the chorion, which
collects in masses at certain points, where it is enveloped by a mass of the sub-
jacent mucous connective substance of this membrane.
4. The Umbilical Vesicle.
The umbilical vesicle is a small fusiform or pyriform pouch, lodged in the
infundibulum at the extremity of the umbilical cord. Its fmidus adheres to
the chorion ; the opposite extremity is prolonged to a variable depth in the
substance of the cord, and is even continued — in the very young foetus — to the
abdominal cavity, by a narrow canal that communicates with the terminal
portion of the small intestine.
This pouch has a red colour, due to its great vascularity. Its walls receive a
special artery derived from the anterior mesenteric, its corresponding vein passing
to the portal vein. These are the two omphalo-mesenteric vessels.
In the last months of foetal life, the umbiUcal vesicle is always more or less
atrophied ; its cavity has disappeared, and it is nothing more than a thin reddish-
brown cord. Its vessels also become
atrophied in the same manner, and nearly Fig- 558.
always nothing else is found than the
artery, reduced to the dimensions of a
thread.
PORTION OF THE ULTIMATE RAMIFICATIONS
OF THE UMBILICAL VESSELS, FORMING THE
FCETAL VILLI OF THE PLACENTA.
5. The Placenta (Figs. 556, 558, 559).
The placenta is the organ which
establishes relations between the foetus
and the uterus of the parent. It ad-
heres to the chorion, of which it is only
a kind of dependency.
In Solipeds, the placenta is composed of a multitude of small tubercles
{placentce), spread uniformly over the external surface of the chorion, which they
almost completely cover. Their number and development are greatest in the
middle portion of the chorion — in the zone where the principal divisions of the
umbilical cord lie beside this membrane. Thence they diminish towards the ex-
tremity of the uterine cornua and body. In front of the openings of the uterus —
Fallopian tubes and os uteri — they are rare. These small tubercles are formed by
an aggregation of extremely vascular vilU, which implant themselves in the follicles
of the uterine mucous membrane. The terminal ramifications of the vessels of
the cord constitute the vascular apparatus of these villi (Figs. 558, 559, 560).
The parts of the uterine mucous membrane which are related to the foetal
placentae, are named the uterine or maternal placentce. They are constituted by
follicular cavities, which are formed beside permanent glandular follicles in the
mucous membrane during gestation, but they disappear after parturition
(Ercolani).
This Italian anatomist compared the cavities of the maternal placentae to
glands which secrete a kind of uterine milk. Laulanie, from a study of the
maternal placenta of the Guinea-pig — and which he regards as a colossal multi-
1024 EMBRYOLOGY.
nucleated cell, the protoplasm in which is intersected by vessels — is of opinion
that the placental cavities in the Mare are of the same character, except that
there are several giant cells. There is nothing glandular in the epithelium
lining these cavities ; on the contrary, they are often confounded with the cells
of the deeper part.
These cavities are, then, sinuses lined with blood-vessels, and are not glands.
Besides, as may be seen in examining Fig. 559, they are quite distinct from the
proper tubular glands of the uterine mucous membrane.
Structure and Development. — The villi of the placenta have for their
base a tissue similar to that of the chorion, their stroma being formed by bundles
of connective tissue mixed with cells. They are covered by a simple cylindrical
epithelium placed immediately on the connective stroma (Fig. 56oi Their
Fig. 559.
VERTICAL SECTION OF THE INJECTED PLACENTA OF A MARE.
ck, Chorion, with its villi partly m situ, partly torn out of the uterine sinuses, cr ; g, uterine
glands ; V, blood-vessels ; E, epithelium.
interior is occupied by a capillary network, the finest divisions of which are
subjacent to the epithelium ; the network itself is supplied by a branch from the
umbilical arteries, and the blood is returned by a vein nearly in the centre of
the villus.
The vessels pre-exist in the villi ; consequently, the latter do not develop
from the chorial tissue, but rather, it might be said, the chorion is pushed back
by the pressure of the vessels-. The placenta succeeds, then, the development of
the allantois, the use of which is to convey the umbilical vessels from the
umbilicus to the chorion.
The villi penetrate the uterine mucous membrane, in such a way that the
capillary systems of the mother and foetus are only separated by the thin walls
of the vessels, and the epithelium of the villi and follicles.
The fusion of these two systems has never been observed, and all the inter-
changes between the female and its young take place through the capillaries by
osmotic force only.
TEE FCETUS.
1025
6. The Umbilical Coed (Figs. 556, 557).
The cord is formed by the vessels which, in the foetus, caiTj the blood to the
envelopes, and chiefly to the placenta. It is divided into two portions — an
amniotic, the longest, which is always twisted on itself like a cord, and covered
externally by the amnion that is prolonged on its surface, to be continued with
the skin around the umbilicus ; the other — the allantoid portion (Fig. 557, B) —
much shorter and less twisted, is enveloped by
the sheath that continues the two layers of the
allantois, and is inserted into the superior wall
of the chorion, between the two cornua.^
Three vessels compose the cord — two arteries
and a vein; these are covered by a layer of
embryonic tissue — the gelatine of Wharton —
which makes them appear much larger than
they really are.
The Umbilical Arteeies ^ arise from the
internal iliac, and pass along the sides of the
bladder ; escaping by the umbilicus, they arrive
at the terminal extremity of the amniotic portion
of the cord, and giving off some branches to
the amnion, they are continued to the extremity
of the allantoid portion, where they end in an
expansion of placental ramifications. These
arteries run parallel to the median plane of
the body of the foetus, to the umbilicus ; they
are perpendicular at the infundibulum, which
proves that the allantois undergoes a twist in
the early period of development. The amniotic
divisions of these arteries are few, and extremely
flexuous ; they are included between the allantoid
layer and the amniotic membrane, within which
they may be seen projecting.
The placental or cliorial divisions — infinitely
larger and more numerous — leave the end of
the cord, and pass in every direction between the chorion and external lamina
of the allantois, beneath which they are very prominent. By their anastomoses
they form a very rich network, from which proceed the capillary twigs that
enter the villosities of the placenta. Observation demonstrates that these twigs
do not communicate with the maternal vessels, and that they are continued by
venous radicles, the origin of the vessel now to be described.
The Umbilical Vein commences by these capillary radicles of the placental
villi, which unite between the chorion and amnion to form a network of more
voluminous divisions and complexity than that of the arteries. Two principal
PORTION OF ONE OF THE FOETAlj
VILLI, ABOUT TO FORM PART OP
THE PLACENTA (HIGHLY MAGNI-
FIED).
a, a, Its cell covering; 6, 6, 6, its
looped vessels; c, c, its basis of con-
nective tissue.
' Goubaux has remarked that the relations between these two portions are not constant.
In a six months' foetus, the amniotic part measured -40 m., and the allantoid part -24 m. In a
foetus of ten months, the first was -30 m. long, and the second -20 m.
2 The -walls of the umbilical artery are very rich in muscular fibres, which are longitudinal
and transversal, but are irregularly distributed. There is no internal elastic tunic in any of tha
branches external to the umbilicus.
EMBRYOLOGY.
Fig, 561.
FtETUS OPENED ON THE LEFT SIDE TO SHOW THE COURSE OF THE UMBIUCAL VESSEI;S
IN THE BODY.
A, Umbilical cord ; B, umbilical vein ;
6, spleen ; H, liver ; /, intestine ;
arteriosus ; N, thymus gland.
C, umbilical artery; £>, bladder; ^.testicle; J", kidney;
/, lung; K, heart; L, pulmonary artery; if, ductus
Fig. 562.
BIX)OD-VESSELS IN THE LIVER OF AN EQUINE F<ETUS AT MID-TERM.
A Umbilical vein; B, its anastomoses with the portal vein, C] D, ductus venosus; E, posterior
rena cava.
THE FCETUS.
1027
Fig. 563.
branches are, finally, the result of the coalescing ; and these soon unite into a
single trunk, which accompanies the two arteries in the cord. On reaching the
umbilicus, this, the umbilical vein (Fig, 561), bends forward on the inner face of
the abdominal parietes, where it
is covered by the peritoneum,
and arrives at the liver, into
which it enters and opens di-
rectly into the vena portae ; the
junction of the two vessels
giving rise to a single canal,
from which proceed the sub-
lobular veins (Fig. 562). In
other animals than Solipeds, this
single vessel gives off a par-
ticular trunk of somewhat con-
siderable volume, which passes
directly to the posterior vena
cava, and forms what is named
the ductus venosus of Arantius
(Figs. 562, 563).
Such are the umbilical
vessels, and it will be seen that they form a part of the circulatory system of
the young creature, which will be more completely studied hereafter.
LIVER OF A LAMB AT BIRTH.
, Posterior vena cava ; B, vena porta ; C, umbilical
vein; Z), anastomosis of the umbilical vein with the
vena portae.
Differential Characters in the Annexes of the Fcetus of the other Animals.
1. Rdminants. — Placenta. — The placental apparatus of the Cow is not uniformly spread
over the outer surface of the chorion, but is constituted by a variable number of vascular
bodies— about sixty on an average — disseminated here and there, and dovetailed by reciprocal
penetration of prominences and cavities, into analogous bodies on the inner surface of the
uterus, designated cotyledons. These are only thickened points of the mucous membrane, the
follicles of which are enormously enlarged. They exist, we have seen, before gestation ; but
observation demonstrates that they may be afterwards formed or entirely renewed, especially
in those cases in which accidental circumstances have rendered those present insufficient for
their oflSce. The largest are found in the body of the uterus ; in the cornua they are smaller
as they are nearer the extremity. Their form i& generally elliptical, and they are attached to
the uterine surface by a wide mucous peilicle; their surface is convex, and perforated by
numerous openings, into which the placental tufts pass. They have always a yellowish
colour, which, added to their external characteristics, gives them the appearance of a moril
mushroom.
With regard to the placentie, they repeat, on the surface of the chorion, the disposition of
the cotyledons on the uterus. They are vascular, concave patches, closely embracing the
cotyledous, and showing on their surface a multitude of long ramifying papillae, which bury
themselves in the cotyledonal cavities. They are attached to the chorion by a very thick,
short, vascular pedicle.
In the Sheep and Goat, the arrangement is the same, except that the cotyledons are
hollowed out in their centre, like a cup, and into this cavity the placentae are inserted (Fig. 565)
Chorion. — The primary chorion disappears at the same time that the amnion is formed, and
it is completely replaced by the definitive chorion towards the twentieth day, in tlie foetus of
the Sheep. The general form of this sac is an exact repetition of that of the uterine cavity.
This membrane responds to the inner face of the uterus, in the iuterplacental points. These
points constitute the chorion (or decidua) serotina, and the part carrying the placentae is named
the chorion frondosum. The inner face of the chorion is united to the amnion and the allaatoia
by means of inter-annexial laminated tissue.
Allantois. — Very diflerent from that of the Mare, and otherwise much less complicated,
the allantois of Ruminants is a very elongated cavity, the middle portion of which receives
the insertion of the urachus, and its extremities are prolonged into the two cornua of the
1028 EMBRYOLOGY.
chorion. This sac, which is an expansion of the urachus, is always reversed on one of the
sides of tlie amnion ; its two braiicbes are sacculated on their surface like the large intestine
ami the greatest forms a cul-de. sac. or conical diverticulum. *
The extremities of the allantoid coraua appear to have pierced the cliorion ; they form a
point covered with a yellow, mucus substance, and separated from the rest of the membrane
by a circular constricticu. This part is beneath the chorion, like the remainder of the
membrane, only the vessels do not extend beyond the constriction ; so that the elements of
the chorion and allantois here undergo a kind of murtiticati(jn. The allantoid infundibulum
is encircled by a vascular network that accompanies it throughout tue umbilical cord.
The epithelium of the allantois is every wliere colourable by iodine reagents, in Kuniiuants.
At times the hippomanes is Ibund floating in the liquid it contains.
Jmntow.— Altogether like that of Solipeds, tiiis membrane is readily resolved into two
Fig. 564.
FCETUS OP THE SHEEP, FREED FROM ITS CONNECTION WITH THE UTERUS.
AL AL, Allantois slightly inflated, seen beneath the chorion ; Am Am Am, amnion slightly dis-
tended with fluid underneath the chorioa ; P, P, P, placentae on the surface of the chorion ; C,
umbilical chord ; al, al, extremities of the allantoidean cornua, looking as if protruding through
the chorion.
laminae, and presents on its inner surface a great number of little, yellowisii-white, epidermic
patches, more especially visible on the amniotic covering of the cord. The epithelium is only
stained by iodine at these patches, or villi. These productions are surrounded at their base
by a girdle of glycogenic cells. In the foetus of the Cow, at a late stage of gestation, the
amniotic fluid is not abundant, and becomes white and viscid ; in one instance we found it
stringy, like a solution of gelatine.
Umbilical cord. — This comprises two arteries and two veins ; the latter forming one trunk
on their entering the abdomen. To reach the chorion, tiiese vessels only traverse the amniotic
cavity. Tliey are accompanied by tlie urachus, which at their extremity presents the dilatation
that results in the allantoid sac.
Unihilical vesicle. — This pouch disappears at an early period, and not a vestige of it is to be
found after the formation of the abdominal parietes.
TEE FCETUS. 1029
2. Pig.— The placenta is formed by an expansion of the villous tubercles, as in Solipeds.
The chorion is not entirely covered by these tubercles, but here and there it shows bright little
patches, where its tissue is merely covered by an epithelial layer ; it is also glabrous at those
points wliere it is in cont:ict with the chorion of neighbouring foetuses.
The chorion has not a body and two coruua, but is merely an elongated sac, the two
extremities of which are in relation with the adjacent foetuses. The inner face corresponds,
as in Ruminants, with the amnion and allantois. The latter is the same as in the Cow, tliough
it is very much shorter ; the inner covering of this membrane contains the glycogenic matter,
but that of the amnion has none.
The umbilical vesicle, amnion, and cord, are also the same as in Ruminants.
3. Carnivora.— Tlie placenta is a thick gir<lle, surrounding the middle portion of the
chorion. It has a Uvid colour in its middle, green on its borders. When the green-coloured
matter is isolated, and treated with alcohol and chloroform, then submitted to certain reagents,
it appears to be identical with the colouring matter of the bile, and derived, as that is, from
the haemoglobin of tlie blood.
The allantois is disposed, in principle, as in Solipeds.
The chorion is quite like that of the Pig with regard to form, but it is diflferent with regard
Fig. 565.
SEMI-DIAGRAMMATIC VERTICAL SECTION OF A MATERNAL COTVLEDOX OF THE SHEEP.
(^cr, Uterine sinus; e, epithelial lining of the sinus; V, veins, and c, flexuous arteries of the sub-
epithelial connective tissue.
to structure, as it hac no chora plates v/ith mineral granules. Nothing is known as to the
organ which fulfils the function of these deposits.
The umbilical vesicle— yfhidi remains VQvy developed at all periods of foetal life — resembles
in shape the allantois of the Pig, being a transversely elongated sac included between the
amnion and the inner allantoid lamina, and provided at its middle portion with a narrow
pedicle, which is prolonged into the umbilical cord ; its walls are extremely vascular.
•The amnion is lined, internally, by the inner lamina of the allantois.
The umbilical cord has, as in Solipeds, an allantoid portion; but it is extremely short, and
enveloped in a wide fold of the allantois.
Results.— The comparative examination of the disposition of the placenta may furnish
valuable indications as to the procedure to be adopted in practising artificial delivery; as the
surgical manoeuvres should necessarily vary with the extent and disposition of the points of
union existing between the uterus and the foetal envelopes.
With this practical object in view, we believe that it is useful to divide the ilomesticated
animals into two groups : those which have a simple, and those which have a multiple placenta.
The first group may be subdivided, according as the simple placenta is general or local.
1030 EMBRYOLOGY.
This division is summed up in the following table : —
I_,._ ( Mare.
Diffuse < g
Local and circular . | ^' ^ '
I Oat.
,,,,., , ^ ( Convex cotyledons . oi. '
Multiple placenta | Concave cotyledons . f'^
[ (jrOitt.
Comparison of the Annexes of the Human Fcetds with those of Animals.
The human foetus, like that of the domesticated Mammals, is enveloped by an amnion and
chorion, which are generally identical in disposition with those already described. The umbilical
vesicle submits to the same change as in the Mare, becoming so quickly atrophied that scarcely
any traces of it can be found at birth. It is impossible to isolate the aUantois from the inner
face of the amnion and chorion ; so that some anatomists only admit its presence by analogy
witli what is observed in animals.
The umbilical cord offers nothing particular. The placenta is circular ; its diameter at the
termination of pregnancy being from 6 to 8 inches, and its thickness from 1 to H inch. There
is distinguished the foetal placenta, to the midst of which the umbilical cord reaches; and the
maternal placenta, the villi of which dovetail with those of the former.
The insertion of the placenta takes place towards the fundus of the uterus, near one of the
Fallopian tubes. When there are more than one foetus, there is a corresponding number of
placentas.
Independently of those annexes — which are the same in all — there is described for the
human foetus a special envelope, external to the chorion — this is the membrana decidua. This
is formed by the hypertrophied mucous membrane, which is doubled around tlie ovum, when
the latter is lodged in the uterine cavity. Consequently, there results the division of the
decidua into two parts— the true decidua (decidua vera) which covers the uterus, and the
reflected decidua (decidua reflexa) which envelops the chorion. These present the characters
of the hypertropliied uterine mucous membrane.
CHAPTER III.
DEVELOPMENT OF THE FCETUS.
In the two preceding chapters, we have seen how the fecundated ovum is modified
to furnish the earliest lineaments of the foetus and the organs annexed to it ;
this chapter will be deveted to an examination of the manner in which the foetus
is developed, though this subject more properly belongs to physiology.
The young creature is designated an embryo during the early period of gesta-
tion, before it has assumed any definite shape ; but as soon as it exhibits the
form of the species to which it belongs — and particularly when the placental
circulation is established — it is named /a^ws.
Grurlt has divided the duration of gestation into seven periods, the length
of which varies according to the species. He has also measured the dimensions
of the ovum, the embryo, and the foetus of each of them. We may, therefore,
accept the figures he has given in order to learn the age of the foetus. They are
shown in the two following tables : —
THE FCETUS.
1081
^^
M
1
week,
h wei k
h week
week.
th an.l
ks.
1
'H-s -s
■S £ ®
—
:5§ §
.a s ^
B
Hfa fa
CC OQ
;z;
ja 4=
M J3
ja
week
to t
to t
s s
s
1
fourth
fourth
ek
sixth
eek
eighth
ek
levent
week
II
rd and
m the
xtli we
m the
ghth w
m the
nth we
m the fc
fteenth
a s
1= £« 2 «
2- P«
2 S
Hfa fa
fa fa
fa
^ 35
® 03
3
th week
li to t
eventh
and nin
H
th to
•ek
enth to
eek
II
2
^
jtc 5 .a
g^l^
s«
g
5
o
[lird and
rom the
seventh
rom the
the eigl
weeks
rom the
thirti^ent
rom the t
eighteen
^1
Hfa fa
fa fa
fa
^ ^
rom tlie thirteenth to
the twentieth week
rom the twenty-eighth
to the thirty -second
s
1
hird and fourth week
rom the ^Ith to t
eighth week
rom the ninth to t
twelfth week
T-2
ill
EHfa fa
fa fa
fa
2 2
S^Sj,
c
II
i
1
fourth week
fifth to t
eek
ninth to t
hweek
fourteenth
ty-second we
wenty-tliird
y-fourth wee
hird and
rom the
eighth w
rom the
thirteent
the
twen
the t
thirt
II
i^ i-S
C 03
1-
Hfa fa
fa fa
fa
^
•
ill 1
i i
fe!»H fa
fa CB
:k
Ills
i a a^
i a 35
' lO 05 CO
I CO » ■*!
:i a a i I i
o a a s ° ""
o '*« ^ » 53 sn
i-i CO 03 rt CC •*!
a fi a a a a
X iaa aa
g «0500N
V X ■* oa «o -H
CC -^ W iO »o —
f- O rt ?^ -X -H
faajHfafaoQcc
1032
EMBRYOLOGY.
The following are the weights of the completely developed foetuses.
The iveight of the foetus of the Mare, at birth, varies according to breed. It
has been found to be 35 pounds in a Corsican Mare, and 135 pounds in a Suflfolk-
Boulonnaise Mare ; and between these extremes are many intermediate weights.
In Cattle, the weight of the Calf is, on an average, 2*31 parts that of the Cow.
According to Leuckart, the weight of the Puppy at birth is about one
pound ; that of the Lamb, ten or eleven pounds ;
that of the Pig, five pounds ; that of the Chick,
about one and a half ounce.
The transition between the embryonic and the
foetal condition being inappreciable, we will study
the first phases of development under the heading
of formation of the embryo, and the last under
that of the development of organs.
Article I. — Formation of the Embryo.
When the embryo has assumed the form of an
elongated streak, and shows in its centre the
primitive groove, there appear in the middle
lamina of the blastoderm the chorda dorsalis, the
vertebral lamince, and the lateral lamince,.
Development of the Chorda Dorsalis and
Vertebral Laminae.
The chorda dorsalis is a cylindrical cord,
slightly attenuated at both extremities, which is
developed beneath the primitive groove. On its
sides is a series of small, opaque, quadrangular
masses — the vertebral /«mw««— which are nothing
more than the jjrotovertebrce, or first traces of the
foetal vertebrae. They appear in the embryo, on
each side of the neural axis, in the form of dark
quadrilateral spots, and are developed in a series
in the spinal zone.
They are hollowed by a central cavity, to-
wards which converge a radial series of cells. On
their lateral surfaces they are continuous with the
musculo-cutaneous and fibro-intestinal lamina, by
means of an intermediate part — the intermediate cellular lamina.
At the third day they give rise, by differentiation, to the muscular lamincB
(Fig. 567, m.s.). The protovertebrse afterwards become fused, and invest all the
neural tube and the chorda dorsalis ; and it is in this homogeneous matrix that
an ulterior segmentation marks the traces of the definitive vertebrae. The articular
intervals in the latter correspond to the middle portion of the proto-vertebrae.
The muscidar lamince, in augmenting in volume, are inflected upwards, and
unite in the middle line of the back. They form, in great part, the muscles of
the vertebral furrows ; they also give off, below, prolongations which concur in
the development of the intercostal and abdominal muscles, as well as those of the
extremities.
EMBRYO OF THE CHICK AGED
ABOUT THIRTY-SIX HOURS (IN-
FERIOR face).
FB, Anterior brain, on the sides of
which are seen the optic vesicles.
op; s.o, posterior limit of the fold
of somatopleure ; HB, posterior
brain ; MB, middle brain ; p.v.
and v.pl, protovertebrae ; ch, an-
terior extremity of the notochord ;
pi, outline of the area pellucida;
pv, primitive trace.
TEE FCETUS.
Article II.— Development of the Various Organs in the Animal
Economy.
Development of the Nervous System.
We will at first glance at the development of the nervous centres — the Irain
and spinal cord ,■ then their peripheral parts — the tierves.
1. First differentiations of the neuraxis. — The trace of the central nervous
system or neuraxis, resides, or has been seen, in the primitive groove, resulting
from an inflection of the thickened ectoderm (Fig. 551). The complete invagina-
tion of the ectoderm brings about the formation of a tube— the neural canal
(Fig. 552). From the thirty-sixth hour, the medullary laminae are close to
each other in front in the middle line, but are not yet fused together. From
Fig. 567.
TRANSVERSE SECTION OF THE BODY OF AN EMBRYONIC DUCK, THREE DAYS OLD. (AFTER BALFOUR.)
om., Amnion ; so., somatopleure ; sp., splanchnopleure ; wd, Wolffian canal ; st, segmentary tube ;
ca.v,, cardinal vein ; m.s., muscular lamina, or plate ; sp.g., spinal ganglion ; sp.c, spinal cord ;
ch., notochord ; ao., aorta ; hy, endoderm.
the fortieth hour, the neural canal is closed as far as the rhomloidal sinus — the
lozenge-shaped space where the primitive groove is widest.
Towards its anterior part, the neural canal shows three successive dilatations
— tracts of the brain, and constituting the three primitive cerebral vesicles. The
remainder of the neural canal forms the spinal cord.
2. Development of the brain.— The cerebral vesicles— at first three in number, and
distinguished as anterior, middle, and posterior — soon undergo an increase to five.
The anterior cerebral vesicle throws out two hollow prolongations which
become the cerebral hemispheres, and now constitute the anterior brain. On the
other hand, the anterior cerebral vesicle itself becomes the vesicle of the optic
thalami, or intermediate brain (see Fig. 568).
1034
EMBRYOLOGY.
The middle cerebral vesicle gives origin to the cerebral crura, the corpora
quadrigemina, and the aqueduct of Sylvius or middle ventricle. It deserves to
be named the vesicle of the corpora quadrigemina of the middle brain.
The third vesicle becomes doubled, forming the cerebellar vesicle, or posterior
brain, from which arises the cerebellum, and the vesicle of the medulla oblongata
which originates that body.
The middle vesicle is that which, at first, increases most rapidly in volume ;
it soon, however, ceases to grow, in
order to allow the anterior cell to
become developed, when the brain
assumes its ovoid form, with a pre-
dominance of the anterior part.
Towards the end of the first
third of intra-uterine life, nearly all
the parts of the brain are distinct :
the two hemispheres have become
isolated by the development of the
septum lucidum ; the convolutions
appear on their surface ; and the cor-
pora quadrigemina and cerebral cura
are distinctly defined. It is not until
a little later that the cerebellum is
distinguishable, as well as the pons
Varolii, medulla oblongata, corpora
restiformia, and corpora pyramidalia.
3. Development of the spinal cord.
— The neural canal is the first trace
of the spinal cord ; it occupies the
whole length of the vertebral spine,
and its cavity communicates, in
front, with the fourth ventricle.
"When the spine is developed, the
cord does not increase proportion-
ately in length, and appears to ascend
in the vertebral canal ; it stops about
the middle of the sacrum in the
equine foetus, but ascends higher
in the other species. During this
apparently ascensional movement is
developed the Jilum terminate, and
the nerves of the cavda equina.
The walls of the neural canal, at first very thin, increase in thickness by the
appearance of the nerve of the cord. Soon they divide into two layers — an in-
ternal, the epithelium of the central canal ; the other external — the (jrey substance
of the cord. Gradually the canal contracts, and the marrow is seen, with its
longitudinal furrows.
At the end of the first month, the inferior roots are in existence, as well as
the spinal ganglia ; the latter are developed at the expense of the protovertebrie,
afi will be shown presently. The superior roots are formed some time afterwards.
The envelopes of the cerebro-spinal centres are furnished by the protovertc
EMBRYO OF THE CHICK AT FROM THIRTY TO
THIRTY-SIX HOURS.
/.o, Anterior bvaiu; m.6, middle brain ; A.6, posterior
brain ; op.v, optic vesicle ; du.p, olfactory fossa ;
o.f, vitelline vein; p.v, protovertebrse, or meso-
blastic somite ; m./, line of junction of the
medullary laminae above the neuraxis ; s.r,
rhomboidal sinus ; t, caudal fold ; p.r, remains of
the primitive groove ; a.p, area pellucida.
THE F(ETUS.
1035
bral laminfe ; they are developed after the sixth week, progressing with the
growth of the parts they are destined to cover.
4. Dn'elopmmt of the nerves. — 'The development of the nerves is somewhat
obscure. The motor roots seem to arise from the cord ; but the spinal ganglia
are formed separately in the protovertebrte, and perhaps originate the sensitive
roots. The nerve-branches begin by elongated ramifying cells, which
become fused to each other by their extremities — the nuclei of the cells lying at
the periphery becoming the nuclei of the white substance of Schwann, the proper
nerve-tissue being afterwards gradually deposited between the axis-cylinder and
the envelope.
Fig. 570.
Fig. 569.
TRANSVERSE SECTION OF THE EMBRVO
OF A FOWL AT THE BEGINNING OF
THE THIRD DAY OF INCUBATION, X
90-100.
ch, Chorda dorsalis ; wwh, position of a
thinning, or cavity in the protoverte-
bral mass, dividing it into an anterior
and posterior portion ; hp, parietal
lamina; df, intestinal fibrous lamina;
dd, intestinal glandular lamina ; dr,
primitive intestinal groove; A, corneal
lamina j mr, medullary tube (spinal
cord); m, muscular lamina; /), pleuro-
peritoneal cavity ; af, fold of the
amnion ; ao, primitive aorta ; t)C, vena
cardinalis ; un, Wolffian body ; ung,
duct of the Wolffian body.
LONGITUDINAL SECTION OF THE EYE OF EMBRYO
FOWL.
1, From an embryo at about the sixty-fifth hour of
incubation ; 2, from an embryo a few hours
older; 3, from an embryo at the fourth day of
incubation, h, Corneal lamina; /, lens in fig. 1,
still connected with the corneal lamina, and
possessing a small cavity, o, in its interior (in
figs. 2 and 3 it is seen detached, but still
hollow) ; r, introverted portion of the primitive
optic vesicle, subsequently becoming the retina ;
a, posterior j>art of the optic vesicle, which,
according to Remak, probably becomes the
choroid coat, ciliary processes, and iris, and in
figs. 1 and 2 is still connected with the brain
by the hollow optic nerve ; x, thickening of the
corneal lamina around the spot from which the
lens has detached itself; gl, vitreous body, or
humour.
The great sympathetic is early seen as a nodulated cord. It is probably de-
veloped in the same manner as the other nerves.
Development of the Organs of Sense.
The principal portion of the organs of sense belong to the dependencies of
the nervous system, and are developed with it ; the other parts belong to the
external epithelial lamina, the skin, and the germinative lamina.
1. Visual Apparatus. — From the anterior cerebral vesicle are given off two
tubular prolongations, which are directed forward, and terminate by the primitive
eye-vesicles, traces of the ocular globes. The hollow protrusions form the optic
nerves ; the vesicles furnish the retina and choroid. The crystalline lens,
vitreous humour, cornea, and sclerotica arise from the external blastodermic
layer. These modifications take place in the following manner : —
The external integument of the foetus passes over the front of the primitive
eye-vesicles. Here it shows a slight depression on its outer surface, and on its
inner face a cellular protrusion (Fig. 570, 1 o), which, becoming developed,
1036 EMBRYOLOGY.
surrounds the external depression, completely closes it, and constitutes the com-
mencement of the crystalline lens (Fig. 570, 2 /). The latter, thus formed,
presses on the primitive eye-vesicle, pushes it backwards (2), and gives rise to a
secondary eye-vesicle, the anterior wall of which becomes the retina, and the
posterior wall the choroid. The lens is, therefore, a dependency of the epithelial
lamina ; the cells composing it become elongated into fibres in the centre, and
are disposed at its circumference as a primary amorphous envelope — the crystalline
capsule — and afterwards as a secondary envelope rich in vessels.
The portion of the integument which is not doubled to form the lens envelops
the globe, and gives rise to the sclerotica and cornea ; the epidermis furnishes the
epithelium of the latter, which becomes distinct from the sclerotica in the course
of the fourth month.
An aperture — the sclei-otic cleft — is made at the lower part of the fibrous
envelope of the eye ; this is connected with the development of the vitreous body —
a prolongation of the derm — a kind of conjunctival bud passing through this
opening, and placing itself between the crystalline lens and the anterior wall of
the secondary eye-vesicle (3 gl), where it is developed and transformed into the
vitreous body. At first it is encircled by vessels like the lens, but these disappear
before the termination of gestation.
The optic nerve is developed in the pedicle uniting the eye-vesicle to the
anterior cerebral vesicle. The retina is formed by the inner lamina of the
secondary eye-vesicle ; it extends to the lens in changing its character anteriorly.
According to Remak, the choroid is constituted by the posterior lamina of the
eye-vesicle ; it advances at first to the lens, and then becomes inflected in front
to form the iris. The borders of the pupil are attached to the vascular envelope
of the lens, and this gives rise to the pupillary diaphragm, which disappears before
birth.
The motor and protective organs of the eye are gradually developed around
the globe. The eyelids are small cutaneous folds that appear towards the first
third of uterine life ; they increase, and unite at their margin until immediately
before, or soon after birth, when they separate.
The lachrymal gland is a dependency of the epithelial lamina which is pushed
in above the globe. At first solid, it gradually becomes channeled out by cavities,
from which arise the excretory ducts.
2. Auditory Apparatus. — The internal ear, auditory nerve, and middle ear,
are developed separately. The labyrinth appears in the shape of a vesicle, which
is not in direct relation with the posterior cerebral cell ; it is constituted by
a depression of the epidermic lamina — the auditory fossa— which is gradually
developed, and at last becomes a closed cavity. At this time, the wall of the
labyrinth is only a simple epithelial membrane ; this is soon covered, outwardly,
by a vascular connective membrane that separates into three layers — an internal,
joined to the epithelium to form the membranous labyrinth ; an external, that
lines the cartilaginous labyrinth ; and a middle, the soft, embryonic, connective
tissue of which disappears, and is replaced by the perilymph. At the same time that
these changes of structure are occurring, the vesicular form of the labyrinth is
modified, and shows the cochlea, semicircular canals, utriculus, and saccidus.
The middle and externcd ear arise from the first pharyngeal (branchial) cleft,
which is never completely closed, while the others disappear. At first, then, we
find a cavity communicating externally with the pharynx ; this cavity contracts,
and is separated into two portions by a partition that spreads across its middle,
THE FCETUS.
1037
and which becomes the membrana tympani ; the internal portion is the middle
ear and Eustachian tube ; the external portion is the external auditory canal.
The ossicula auditus appear in a cartilaginous state towards the third month ;
they gradually ossify, and have scarcely acquired their definitive volume at birth.
The external ear {concha) is developed beneath the integument after the second
month.
3. Olfactory apparatus. — This commences by two depressions of the epider-
mic lamina, analogous to the auditory fossa and that of the lens. These two
olfactory fossas appear below the ocular vesicles, and become more and more dis-
tinct, being margined by small projections which increase their depth. Behind,
they communicate with the pharynx. The appearance of the palate separates
them in front from the buccal cavity, and from
this period the nasal fossae are constituted. They
are completed by the development of the bones
of the face.
The olfactory hidbs and nerves are primarily
hollow, and joined to the anterior cerebral cell.
The nostrils are formed, in the young foetus, by
a mass of mucus and epithelium ; towards the
middle of gestation they are open.
4. Gustatory apparatus. — See, subsequently, I
the development of the tongue^ in digestive ap-
AN EMBRYO (HUMAN) OF FOCB
WEEKS, ENLARGED ABOUT THREE
TIMES.
a. Vesicle of corpora quadrigemina ;
6, vesicle of cerebral hemispheres;
c, vesicle of third ventricle ; d,
vesicle for cerebellum and medulla
oblongata ; e, auditory vesicle ; /,
olfactory fossa ; h, liver ; **,
caudal extremity.
5. Tactile apparatus. — The skin and its de-
pendencies.— The skin is developed at the expense
of the epidermic lamina of the middle layer of
the blastoderm. The cutaneous laminfe — by the
modification of their elements — form the derma,
in which the blood-vessels are very apparent at
the third month. In the epidermis, the mucous
and the horny layers are soon distinguished ; in
the first, the pigment is visible at the commence-
ment of the fifth month in the larger Quad-
rupeds. When the foetus increases in volume, the epidermis exfoliates, and its
debris floats in the liquor amnii.
In the third month, the hairs are seen in the foetus of the Mare and Cow ;
they appear at first on the eyebrows, lips, and the joints of the limbs ; at the sixth
or seventh month they cover the body. They may be shed and renewed before
birth. They are developed in a prolongation of the epidermic lamina, which is
embedded in the substance of the derm ; it is shaped like a httle bottle, and is
composed of a mass of cells ; in its centre, these cells are modified and collected
together to form a small cone, the base of which covers the growing papilla. This
cone becomes elongated, touches the surface of the epidermis, doubles under the
effort to push through it, and finally makes its exit, after which it can grow freely.
The sebaceous and sudoriparous glands are developed in the same manner,
towards the middle period of uterine existence.
" The horny productions — the claics, hoofs, ergots, chestnuts — begin to show
themselves early. Towards the end of the second month, in the fcetus of the
Cow, there is perceived, at the extremity of each limb, a small pale, translucid,
conical tubercle, which is the rudiment of the hoof. At the commencement of
1038
EMBRYOLOGY.
the fourth montli, or thereabouts, the hoof, better defined, has become firm and
opaque, and has assumed a fine yellow tint. At mid-term, brown or black
patches are manifest if the coronet is provided with pigment ; it is only about
the end of gestation that the hoof towards the coronet begins to have the
greenish hue peculiar to horn destitute of pigment, but the remainder of this
production — especially at the inferior part — preserves its yellow colour uutil birth.
In Solipeds, the ' chestnuts ' are shown at mid-term, in the shape of thin brown
plates, which are soon darker-coloured." *
The horn of the hoof is not at first tubular ; after birth it is shed, and is
succeeded by a more consistent tubular horn, which had been forming beneath it.
Development of the Locomotory Apparatus.
1. The Skeleton. — ^We have seen at p. 19 how the development and growth
of the bones take place ; it is therefore needless to recur to this subject here ; so
we will limit ourselves to an examination of the mode of development of the
principal sections of the skeleton.
A. Development of the vertebra. — The vertebral spine is the first portion of
the skeleton manifested in the embryo ; it is represented by the chorda dorsalis
Fig. 572.
Fig. 573.
DIAGRAM SHOWING THE POSITION OF THE
CHORDA DORSAUS IN THE BODY OF THE
VERTEBRA, AND THE FORMATION OF THE
DIAGRAM SHOWING THE ATTENUATION OF NEURAL ARCHES.
THE CHORDA DORSALIS IN THE MIDDLE OF
THE BODIES OF THE VERTEBRA, WHILST c^> Chorda dorsalis ; cv, body of the verte-
PRESERViNG ITS ORIGINAL DIAMETER IN bia ; a, ueural arch, or neurapophysis ; c,
THE INTERVERTEBRAL SPACES. "b ; ^w, transverse process.
ch, Chorda dorsalis; v, body of vertebra ; U,
intervertebral spaces.
— a stalk constituted by a mass of cells situated in the interior of a transparent
sheath. The protovertebrce. appear on each side of the chorda dorsalis ; in becom-
ing developed, these parts encircle the latter and the medullary canal ; from this
results the external theca of the cord, and the superior uniting membrane. From
this time, the vertebral column exists in the shape of a membranous axis.
Soon this membranous spine is segmented to give rise to the vertebrae, and
its various portions gradually become cartilaginous. Each persistent vertebra
does not exactly correspond to a protovertebra. In reality, the latter takes a
share in the formation of two vertebrge, and divides into two portions — an
inferior, which constitutes the posterior moiety of a permanent vertebra ; and
a superior, which forms the anterior moiety of the persistent vertebra imme-
diately behind the preceding and the intervertebral disc.
' Colin, Trait€de Fhysiologie Compar^e des Animaux, 2nd Edition. Paris, 1873.
THE FCETUS.
1039
The bodies of the vertebras are developed more rapidly than their spinal
portion : thus, towards the end of the second month, all the vertebral bodies
are already cartilaginous, while the vertebral laminae are yet membranous. It
is only in the third month that ossification begins in the vertebral column. The
number of osseous nuclei — primary and complementary — is not the same in all
species ; they have been enumerated at p. 20. In a large number, the spinous
process is regarded as the result of the joining together of the two moieties of
the vertebral arch ; in the Sheep, on the contrary, the spinous process forms a
nucleus altogether independent of the vertebral arches. Thomas has noted this
disposition, and he considers it as peculiar to animals the anterior dorsal
vertebrae of which are furnished with a long spinous process.
During ossification, the chorda dorsalis disappears, except between the
vertebrae, where it is developed to form the intervertebral substance or discs.
B. Development of the cranium and face. — The brain is enveloped by a
membrane formed at the expense of the protovertebral laminae. This cranial
membrane becomes partly cartilaginous, partly fibrous ; the cartilage exists at the
base of the cranium, and seems to prolong the bodies of the vertebrse into this
region ; indeed it is known that the skull may be resolved into four portions,
each corresponding to a vertebra. The cartilage is insensibly transformed into
bone ; while the fibrous part — comprising the roof of the skull and its lateral
walls — passes directly into an osseous state.
The bones of the face are developed at the expense of the pharyngeal arches.
This designation is given to four laminae (or lamellce) which spring from the
anterior extremity of the chorda dorsalis, and double downward and inward to
join those of the opposite side. They are also named the branchial and visceral
Fig. 574.
arches, and the spaces between
them are called the pharyngeal
clefts. The upper jaw, mouth,
nasal cavities : i.e. the nasal,
maxillary, and palatine bones,
are furnished by the first arch.
Meckel's cartilage, which arises
from the handle of the malleus
to pass towards the inferior
maxilla, is also a dependency of
this branchial arch ; it disap-
pears towards the sixth or
seventh month. It is to be
remarked that, at the com-
mencement, the mouth com-
municates with the nasal cavi-
ties ; the palate is developed in
two moieties which advance
towards each other, though they
remain a long time apart ; so
that at this time the young
animal really has a hare-lip. The second pharyngeal arch forms the stapes, the
pyramidal process of the temporal bone, the styloid arch, and the branch of
the hyoid. The third develops the hyoid bone, with its cornua ; while the
fourth arch only constitutes the soft parts of the neck.
THE HEAD OF A FCETAL LAMB DISSECTED TO SHOW
MECKEL'S CARTILAGE.
M, Meckel's cartilage; wi, the malleus; t, incus ; Zy, th*
tympanic; H, the hyoid; Sg, the squamosal; Vt,
pterygoid ; pi, palatine ; L, lachrymal ; pmx, pre-
maxilla ; N, nasal sac, Em, Eustachian tube.
1040 EMBRYOLOGY.
The integument covering the pharyngeal bones is sometimes imprisoned at
some points, when fusion of the bones of these arches occurs. There then result
small dermoid cysts that slowly enlarge, and which the surgeon is sometimes
called upon to remove from time to time, as they disfigure the face — if they have
no other inconvenience.
C. Development of the Thorax. — The ribs are dependencies of the protoverte-
bral laminte, which curve towards the lower face of the vertebral column. The
true ribs are most rapidly developed, and before attaining the middle line are
united by their internal extremity, and form a moiety of the sternum. A fissure
separates the costal arches of the right side from those of the left : this gradu-
ally contracts, and finally disappears, and the sternum is then formed. The ribs
are, after the petrous bone, the parts of the skeleton which are most promptly
ossified, ossification commencing in the middle ribs.
The costal arches do not belong exclusively to the dorsal vertebrae, but have
a tendency to form along the whole length of the spine ; and it is not rare to
see— attached to the lumbar vertebrae— a small cartilaginous nucleus, which is
soon lost in the texture of the abdominal walls. This nucleus assumes large
dimensions on the last cervical vertebrae of Birds.
The form of the thorax varies with the species ; in some it is circular, in
others it is flattened laterally ; and in all cases it is less developed in the foetus
and young animal than in the adult. It is in the latter that the thoracic cavity
presents, proportionately, its greatest dimensions.
D. Development of the Limbs. — The limbs do not show themselves until after
the formation of the spinal column, the pharyngeal arches, and the thoracic
parietes. They appear as four little prolongations from the thorax and pelvi^
and are slightly enlarged at their origin and constricted in the middle. Their
free extremity is flattened, and either divides or remains single, as the animal
has one or more apparent digits. It is in these prolongations that the carti-
laginous segments are developed, which, at a later period, become the bones of the
limbs. For the manner in which ossification is carried on in each bone, reference
must be made to Osteology, Articles IV. and V., pp. 97 and 127.
2. Muscles. — The muscles are developed around the bones when these have
become perfectly distinct. They may be divided into four groups — the vertebral
muscles, which come from the muscular laminae of the protovertebrae ; the
visceral muscles — thoracic and abdominal cavities, neck and jaw — having the
same origin ; the cutaneous muscles, which are developed at the expense of
the cutaneous laminae of the middle layer of the blastoderm ; and the muscles
of the hmbs, the development of which is not yet perfectly known.
It was at one time believed that the muscular fibres were formed by the
junction — end to end — of several elongated cells ; but it is now known that
they are constituted by a single cell which lengthens, and the nuclei of which
multiply and lie at the surface, while its contents are transformed into a substance
that offers the characteristics of contractile tissue. The sarcolemma is formed
after the fibre, by a modification of the connective tissue surrounding it.
Development of the Circulatory Apparatus.
During the first days which follow the appearance of the embryo in the
substance of the blastodermic layer, there is no trace of vessels in the area
germinativa. It is not long, however, before the heart and some blood-vessels
THE FCETUS.
1011
ifh-:'
are seen in the middle layer, the vessels extending to the surface of the um-
bilical vesicle, which gradually shows itself. While the contents of the vitel-
line vesicle are undergoing absorption by the embryo, the heart is being completed,
the vessels are developing, the allantois is formed, and the placental circulation —
which continues until birth — is established. From this time the circulatory
apparatus has acquired its definitive
disposition. Fig. 575.
1. Appearance of the heart. — Circu-
lation in the umbilical vesicle. — The
pleuro-peritoneal cavity of the embryo
presents, anteriorly, a diverticulum —
the cardiac cavity — in the interior of
which the heart is developed.
From what has been already said,
it will be understood that the circu-
latory apparatus is adapted to take the
part, successively, of the umbilical
vesicle and the placenta ; and from this
two great systems arise — the umbilical
or omphalo-mesenteric circulation, and
the allantoid circulation.
As Dareste has it, the heart is
primarily double. Its two portions are
formed on each side by a folding in-
wards of the fibro-intestinal lamina
and its endothelial lining. The two
cardiac cavities open into each other
by the absorption of the walls joined
as a septum, and the simple heart
assumes the form of a looped tube
inclined to the right, as in Fig. 577.
As soon as it shows itself, the
heart contracts and dilates alternately,
the movements being very slow, though
they gradually become quicker. To-
wards the twelfth day, the central
organ of the circulation has the
form of a contractile cylindrical tube.
From its anterior part spring two
branches — the aortic arches {arcus
aortce) — which are directed towards
the head of the embryo, and are
afterwards inflected downwards and
backwards.
The aortic arches join together to constitute the single aorta, which, in its
turn, divides into two trunks— the arterice vertebralis, or primitive aortcp. These
vessels pass along the lower surface of the embryo, parallel to each other, and
furnish during their course four or five divisions— the omphalo-mesenteric arteries
—which ramify in the area germinativa, and open into a limitary vein named
the sinus (or vena) terminalis. From the network of the area and the sinus
DIAGRAM OF THE FORMATION OP THE VENJE
OMPHALO-MESENTERICiE AND UMBILICALES.
1, At the time of the first appearance of the um-
bilicales, and the commencement of the om-
phalo-mesenteric£e ; 2, at the time of the first
appearance of the branches to and from the
liver, and the diminution of the omphalo-
mesenteric vessels ; 3, 4, at the period of com-
plete fcetal circulation in 1, omphalo-mesenteric
trunk ; in 2, 3, remains of it ; in 4, vein of the
yolk-sac alone ; om', right, and om", left vena
omphalo-mesentericse ; u, trunk of the um-
bilical vein ; u', right, and u", left vena um-
bilicalis; c?c, ductus Cuvieri ; y, jugularis; c,
cardinalis ; /, liver; ha, hepatica advehentes;
hr, hepaticffi revehentes ; m, mesentericae ; da,
ductus venosus Arantii ; ci, cava inferior; p,
vena portee ; I, lienalis ; m, mesenterica su-
perior.
1042 EMBRYOLOGY.
arise two vessels — the vence omphalo-mesentericce — which enter the posterior
extremity of the heart.
In Birds there are only two omphalo-mesenteric or vitelline arteries.
The circulation in the umbilical vesicle is somewhat ephemeral in several
species, and it has been already stated that the vesicle is atrophied at an early
jieriod of f cetal life. In Birds it is most extensive ; and its presence may be noted
in the Carnivora during the whole term of uterine existence.
2. Development of the heart and vessels. — Placental circulation. — The hearty
which, until now, was a cylindrical tube, is considerably modified before it attains
its complete development. In its different phases, it successively offers all the
forms known to exist in vertebrate animals. The first change consists in an
inflection ; the tube curves in an S-shaped manner, so that its inferior part becomes
superior ; it then dilates at three points : the anterior and superior dilatation
situated at the origin of the aorta is named the aortic bulb {bulbus aortce) ; the
middle dilatation, the ventricular cavity; and the posterior dilatation, the auri-
Fig. 576.
HEART OF THE EMBRVO OF A RABBIT, THE SAME, SEEN FROM BEHIND.
SEEN FROM BEFORE. g^ Venae omphalo-mesentericae ; d. right
ta, Truncus arteriosus; I, left ventricle; r, auricle; e, bulbus aortfe ; /, the six aortic
right ventricle; a, auricle; u, venous sinus. arches; c, atrium ; 6, auriculae.
cidar cavity. Haller's passage is the name given to the constriction between the
auricle and ventricle, which at this time are single. They do not remain long so,
however. The ventricular cavity is the first to be divided into two compartments,
and the division is marked externally by a groove which appears on the surface
of the heart of the Ovine embryo towards the nineteenth day, and on the twenty-
fifth in the Equine foetus. This groove coiTesponds to an interventricular
septum, which insensibly rises from the bottom of the ventricles ; when it reaches
the auricles, it concurs in forming the auriculo-ventricular openings.^ The
margins of these openings are provided with a small slightly salient lip, which
afterwards, in developing, originates the mitral and tricuspid valves. The heart
has now three cavities — two ventricles and an auricle ; but in a brief period the
latter is doubled, and the compartments are then four in number. Externally,
there is observed a depression which shows the division in the auricles ; at a point
corresponding to it, a septum is developed in their interior which remains incom-
plete during the whole of foetal life, being perforated by the foramen of Botal.
With regard to the aortic bulb, it contracts and divides into two vessels — the aorta
and pulmonary artery.
' This septum is sometimes arrested in its development, whence results an abnormal com-
munication between the ventricles. Some instances have been given when describing the
heart.
TEE FCETUS.
1043
The arteries are developed partly at the expense of the vessels
primary circulation, and partly in the vascular lamina of the
Fig. 578.
of the
mbryo.
The heart, when it was only a simple
cylindrical tube, presented at its
anterior extremity two aortic arches,
which curved backwards and united
to form the single aorta, then the
vertebral or common aortte. The
aortic arches are situated at the inner
face of the two first pharyngeal
arches ; afterwards more are de-
veloped, which are placed within the
other pairs of arches, until the num-
ber is increased to five, though they
never all exist at the same time.
Some atrophy, while others are being
developed : the two first entirely
disappear ; the third form the caro-
tids ; the fourth the axillary arteries
and the arch of the aorta ; the fifth
atrophies on the right, and on the
left originates the pulmonary artery,
the ductus arteriosus, and the aorta.
The latter is continued along the
spine by the fusion of the two
primitive aortae. They present, at
their posterior extremity, the pelvic
vessels — which are very small — and
the umbilical arteries, which are, on the contrary, remarkable for their volume
HEART OF AN EQUINE FCETUS. . THE RIGHT AURICLE
AND PUbXERIOR VKNA CAVaWaVE BEKN OPENED
TO SHOW THE FORAMEN OF BOTAL.
1, Left ventricle ; 2, right ventricle ; 3, interior of
the right auricle ; 4, posterior vena cava ; 5,
foramen of Botal.
PLAN OF THE AORTA AND ITS ARCHES AT AN EARLY PERIOD.
1 Truncus arteriosus, with one pair of aortic arches, and dotted lines indicating the position of the
' second and third pairs ; 2, the same, with four pairs of aortic arches, and indications of the fifth ;
3, the same, with the three posterior pairs of aortic arches, from which the permanent vessels of
the embryo are developed, with dotted outlines showing the position of the two (now) obliterated
anterior arches ; 4, permanent arterial trunks in their primitive form, the obliterated portions
still shown in dotted outline, 1-5, primitive aortic arches, a. Aorta ; p, pulmonary artery ;
p', p", branches to the lungs ; aio', root of thoracic aorta (ad) on leit side ; aw, obliterated root
springing from right side ; s". s', subclavian artery ; v, vertebral ; ax, axillary ; c, common
carotid ; c', external carotid ; c", internal carotid.
The peripheral arteries arise, independently of the central vessels, on the
interior of the vascular lamina. They appear in the form of solid cellular
1044
EMBRYOLOGY.
DIAGRAM OF THE CIR-
CULATION AT THE
COMMENCEMENT OF
THE FORMATION OF
THE PLACENTA
(seen FROM THE
front).
a, Venous sinus re-
ceiving all the sys-
temic veins; b, right
auricle ; 6', left
auricle; c, right
ventricle ; c', left
ventricle ; d, bulbus
aorticus,sub(iividing
into, e, e', e", bran-
chial branches ; /,
/', arterial trunks
formed by their con-
fluence; g, g', vena
azygos superior ; h,
h', confluence of the
superior and inferior
azygos ; j, vena cava
inferior; k, k', vena
azygos inferior ; m,
descending aorta ;
n, n, umbilical arte-
ries proceeding from
it ; 0, o', umbilical
veins; g, omphalo-
mesenteric vein ; r,
omphalo-mesenteric
artery distributed
on the walls of the
vitelline vesicle, t;
V, ductus venosus;
y, vitelline duct; z,
chorion.
branches, which are hollowed in the centre by a cavity in
which the cells become free. In proportion as these new
vessels are developed, the omphalo-mesenteric vessels dis-
appear, until at last there only remain one or two ducts
that pass to the umbilical vesicle.
The umbilical veins are developed immediately after the
formation of the omphalo-mesenteric veins ; they enter the
common trunk of the latter, and when its ramifications
diminish in volume, the umbilical veins increase rapidly ;
when the liver is formed around them, they throw into it
branches, which are the rudiments of the hepatic network.
Between the hepatic and sublobular veins, the umbilical
vein communicates with the vena cava by the ductus venosits
of Aranzi, which, according to M. Colin, does not exist in
the foetus of Solipeds in the last moiety of uterine life.
The veins of the embryo form four principal trunks at
first — two anterior, the anterior cardinal veins ; and two
posterior — the posterior cardinal veins. The veins of the
same side unite in twos, from which result the Cuvierian
ducts ; these open transversely into the omphalo-mesenteric
trunk, close to the auricular cavity.
The anterior cardinal veins issue from the cranium ;
they form the jugular veins, and communicate by an anasto-
mosis that extends transversely from left to right. Below
this anastomosis, the left vein gradually atrophies, as does
the Cuvierian duct of the same side ; but the canal on the
right side increases, and becomes the anterior vena cava.
The posterior vena ca,va appears behind the liver towards
the fifth month ; it receives the veins of the kidneys and
Wolffian bodies, and, behind, it anastomoses with the cardinal
veins. The latter disappear in their middle portion, and are
replaced by the vertebrcd, veins, the right of which forms the
vena azygos. There only remain the two extremities of the
cardinal veins ; the anterior enters the Cuvierian duct, and
the posterior constitutes the hypogastric and crural veins.
From this disposition, it will be seen that at first the venous
system of the foetus is perfectly symmetrical, but that in the
adult animal it becomes asymmetrical.
In consequence of these successive developments, the
placental circulation is instituted, and continues the same
until the termination of intra-uterine life. The heart is
always the organ that propels the blood, and this passes
into the arteries, reaches the umbilical arteries, and is carried
to the placenta. There it is renewed — becomes ^r^^rm? through
contact with the maternal blood — and is returned by the
umbilical veins. In the substance of the liver it is mixed
with the venous blood of the intestines and posterior ex-
tremities, through the medium of the ductus venosus. and at
last arrives at the right auricle, then passes into the right
ventricle, from which it is propelled by a contraction.
THE FCETUS.
1045
Instead of going to the lungs — which do not yet act as respiratory organs — the
blood, being pressed by the contraction of the right ventricle, passes into the
aorta by the ductus arteriosus.
To sam up, the foetus never receives pure arterial blood into its organs, this
being always mixed with venous biood — the mixture taking place at several
points : 1. By the foramen of Botal. 2. In the aorta by the ductus arteriosus.
3. In the liver by tlie ductus venosus. The head and neck are the parts which
receive the purest arterial blood — a fact that explains the predominance of the
anterior over the posterior portion of the body of the foetus.
At birth, the conditions of existence being suddenly changed, marked modifi-
cations take place in the circu-
latory apparatus. The lungs ^'S- ^^l-
become the organs of respira-
tion, and rapidly increase in
capacity ; the pulmonary artery
dilates to give passage to the
blood that flows to them ;
while the ductus arteriosus is
obliterated, in order to isolate
the arterial from the venous
blood. This separation of the
two fluids also takes place in
the liver by the atrophy of the
ductus venosus, and in the
heart by the occlusion of the
foramen of Botal ; though,
according to Goubaux, that
orifice frequently remains open
in young animals. Its persis-
tence has also been noted in
the human adult. Notwith-
standing the presence of this
foramen, the circulation can-
not be much disturbed ; as
when the heart contracts, the
auricles become isolated by the constriction of the opening and the raising of a
valve.
(Lymphatic vessels and glands are found at an early period of foetal life, after
the blood-circulation has been fully established. In connection with these
should be mentioned the prevertebral hmno-lymph glands, which are best observed,
however, in the adult animal — and particularly in the Sheep and Ox. They are
small oval or lenticular bodies, about the size of a mustard-seed, and are found
in the abdominal and pelvic cavities among the fat and connective tissue, between
the vertebral column and peritoneum, as well as in the thorax, in the middle and
posterior mediastinum. They are larger in Oxen than Sheep ; there are from
three to four hundred in the latter. They are supposed to be the source of
some, at least, of the lymphoid cells and non-nucleated and multi-nucleated
corpuscles which occur in the blood.)
TRANSVERSE SECTION OF THE ADVANCED EMBRYO OF A
RABBIT, SHOWING THE RELATIONS OF THE HEART WITH
THE LUNGS AND DIGESTIVE TUBE.
ht, heart ; pc, pericardial cavity ; pl.p, pleural cavity ; Ig,
lungs ; al, digestive canal ; ao, aorta ; ch, notochord ; rp,
ribs; st, sternum; sp.c, spinal cord.
1046
EMBRYO LOQT.
Fig. 582.
A9 0
FIRST APPEARANCE OF THE LUNGS.
In a Fowl at four days ; b, at six days ; c,
termination of bronchus in a very young
Pig-
Development of the Respiratory Apparatus.
Observers -are not unanimous as to the development of the lungs. According
to Reichert and BischoflF, they arise from two small solid cellular masses lying on
the surface of the anterior portion of the intestinal canal. These become
channeled out into numerous ramifying- cavities (by the deliquescence or fusion
of the internal cells), which communicate
with the trachea. Costa states that they
commence by a median, bud-like, hollow
process that opens into the oesophagus.
The walls of the communicating aperture
elongate considerably, and at a later period
form the trachea and larynx ; while the
hollow bud divides into two pyriform sacs,
each of which becomes broken up into a
multitude of subdivisions to constitute
the pulmonary lobes, with their vesicles
and infundibula.
The trachea is completed by the development of the cartilaginous rings in the
tube that binds the lungs to the oesophagus. They appear at the commencement
of the third month.
The larynx is developed in the
^''g- 583. same manner at the pharyngeal open-
ing. It is always somewhat unde-
fined during youth, and its definitive
I* volume is not acquired until the
period of puberty.
The thymus gJand appears as a
process of the respiratory mucous
membrane. It seems to be formed
at the larynx, and gradually descends
along the trachea to the entrance of
the thorax.
Development of the Digestive
Apparatus.
In this paragraph, the develop-
ment of the alimentary canal will
be first studied, then that of the
organs annexed to it.
A. Alimentary Canal. — We
have seen how the embryo, in be-
coming incurvated, divides the blasto-
dermic vesicle into two parts which
communicate by a large pedicle. The
external portion is the umbilical
EMBRYO OF DOG, rWENTV-FIVE DAYS AFTER LAST
COPULATION.
0, a, Nostrils ; h, b, eyes ; c, c, first visceral arches,
forming the lower jaw ; d, d, second visceral
arches ; e, right auricle ; /, left auricle ; g, right
ventricle; h, left ventricle; i, aortic bulb; k k,
liver, between the two lobes of which is seen the
divided orifice of the omphalo-mesenteric vein; I,
stomach ; m, intestine, communicating with the
umbilical vesicle, n n ; o o, corpora Wolffiana; pp,
allantois ; q, q, anterior extremities ; r, r, posterior,
extremities.
vesicle ; the pedicle is the omphalo-
mesenteric duct, and the inner part the intestinal cavity.
The latter may be resolved into three portions : the anterior intestine, which
TEE F(ETU8. 1047
forms the pharynx and oesophagus ; the posterior intestine, that gives rise to
the rectum ; and the middle intestine, which becomes the stomach and in-
testines.
The middle intestine appears at first as a uniform cylindrical tube, the
diameter of which is afterwards modified to constitute the organs comprised
between the oesophagus and rectum.
1. Mouth. — It begins by a depression limited by the maxillary buds. This
blind pouch gradually enlarges inwardly, and proceeds to meet the pharynx,
from which it is only separated, at a certain period, by a thin membrane ; this
is at last absorbed, and the two cavities then communicate. Until the third
month, the mouth is confounded with the nasal cavities ; at this time the palate
appears, and this eventually isolates them.
2. Tongue. — Appearing at first as a small prominence on the maxillary
buds, the tongue is completed by the addition to it of a bud from the second
branchial arch. Its epithelium and glands come from the external blastodermic
lamina ; they are developed in the third and fourth months.
3. Pharynx and (Bsophagus. — These two organs become enlarged and
elongated as the foetus grows. The oesophagus communicates at first with the
trachea ; but it slowly closes, and finally separates completely from that canal.
4. Stomach. — This is formed by the dilatation of the anterior part of the
middle intestine. The dilatation is fusiform, and its largest axis longitudinal ;
it soon incurvates, and its longest axis is then transversal. In Ruminants, the
stomach is at its first appearance simple ; but before long it shows grooves on
its surface, and in its interior septa, as in the normal state. During foetal life
this organ is small ; but after birth, when solid food begins to be taken, it
augments rapidly in volume. During lactation in Ruminants, there is remarked
a predominance of the fourth over the other gastric compartments ; but im-
mediately the young animal commences to consume fibrous aliment, the rumen
quickly increases in size, and it is not long before it becomes the most consider-
able division.
5. Intestines. — The intestinal tube is primarily of a uniform calibre, though
in a short time there can be distinguished the various regions of which it is
composed. According to A. Baer, the cfecum is early seen in hoofed animals,
and is situated in the vicinity of the omphalo-mesenteric duct. This duct
detaches itself from the extremity of an intestinal loop, which is drawn towards
the umbilical ring ; when the latter is becoming atrophied and progressing
towards complete obliteration, this loop reascends into the abdominal cavity.
The intestines are smooth on their inner face during the first two months ;
but during the third they show their villosities and the glands of Lieberkuhn.
The Brunnerian and solitary glands are a little later in showing themselves.
6. Rectum. — This is derived from the posterior intestine, and is developed
like the other portions.
7. Anus. — Towards the caudal extremity of the foetus is observed a depres-
sion, analogous to the buccal cid-de-sac. This gradually deepens, and is joined
to the rectum and genito-urinary organs. Later, it is separated from the latter,
and then belongs exclusively to the alimentary canal.
B. Annexes of the Alimentary Canal. — These are the salivary glands,
teeth, liver, pancreas, and spleen.
1. Salivary glands. — These are developed in a solid cellular bud, which is
related to the epithelium at the commencement of the digestive apparatus. This
1 048 EMBR YOLOG Y.
bud increases, and at the same time is hollowed into glandular pouches. The
submaxillary gland is the first to appear ; according to Bischoff, it is entirely
formed in the foetus of a Cow only an inch in length. The parotid gland is the
last to be formed.
2. Teeth. — These organs are developed in the interior of a cavity, named the
dental folJich or sac, by means of the elements of three germs — one belonging to
the ivory, another to the enamel, and a third to the cementum.
Follicle. — The dental follicle is an oval cavity, with walls composed of two
layers ; the external is fibrous and complete ; the internal — soft or gelatinous — is
allied at the bottom to the ivory germ. The latter is a prominence which is
detached from the bottom of the follicle, and has the exact shape of the tooth.
Its structure comprises, in the centre, delicate connective tissue provided with
vessels and nerves, and on the surface a layer of elongated cells. At the summit
of the follicle, facing the ivory germ, is the enamel germ ; it is exactly applied
to the dental pulp, which it invests like a cap, and is composed of a small mass
of mucous connective tissue covered by a layer of cylindrical cells — the ada-
mantine tissue of Renaut — joined to the buccal epithelium by the gubernaculum
dentis. The cementum organ manifestly exists in the Foal, according to M.
Magitot. The base of the ivory germ has been found, but it disappears rapidly
after having performed its function.
How are the different parts of the dental follicle developed ? When the
maxillary arches are formed, the alveolar borders show a ridge which enters
the embryonal tissue of the jaws. On the inferior border of this epithelial ridge
are formed buds (enamel organs), in number equal to that of the temporary teeth
— these are the primitive buds.
While these buds — dependencies of the octoderm — are developing towards
the interior of the jaw, there appear the dental bulbs (ivory organs), which arise
from embryonic tissue ; these grow outwards and bury themselves in the summit
of the enamel organs, so as to form a cap over them. Afterwards the wall of
the dental follicle is detached from the base of the bulb, rises, and envelops the
two germs in an oval sac.
Magitot and Legros have remarked in the embryo of a Mare that : 1. At
the hundredth day, the enamel organs of the incisiors are distinct, and are detached
from the epithelial layer ; the follicles of the molars are in a slightly more advanced
state. 2. At one hundred and ninety days, the incisor follicles are closed ; the
molars are almost in the same state. 3. At two hundred days, the follicles have
attained their complete development— which precedes by some days the appear-
ance of the dentine cap ; the permanent incisor follicles are visible, but not yet
closed. 4. At two hundred and twenty days the temporary follicles are very
voluminous ; the dentine cap is already considerable ; and the two coronary and
radicular cement organs are in place and quite developed.
Formation of the ivory, enamel, and cementum. — The ivory and enamel are
developed by the modification of the elements situated at the surface of their germ.
It has been shown that the germ of the ivory, or dental pulp, had exactly
the form of the future tooth ; consequently the ivory which arises from its
periphery offers the shape of this tooth. The ivory {dentine) is constituted by
the cells of the germ, which elongate, send out prolongations — the dental fibres
— that ramify and anastomose, and by an intercellular substance which is im-
pregnated with calcareous matter, is moulded around these fibres, and forms the
dental canaliculi.
THE FCETUS. 1049
The enamel is derived from the deep cells of its germ, which are elongated
and prism-shaped, and are calcified on becoming applied to the surface of the
ivory.
The cementum is developed at the expense of the walls of the follicle, accord-
ing to the mode of ossification of the connective tissue.
Eruption. — As the ivory is formed, the tooth increases in length and presses
the enamel germ upwards ; the latter, constantly compressed, becomes atrophied,
and finally disappears when the tooth has reached the summit of the follicle.
In the same way the young organ pierces the dental follicle and gum, and makes
its eruption externally.
Such is the mode of development of the deciduous teeth. The permanent
ones are formed in the same manner.
The enamel organ proceeds from a point adjoining the summit of the follicle
of the temporary tooth, and buries itself beneath the latter, where it forms the
dental bulb and the walls of the new follicle. The follicles of the three last
molars — which are permanent — arise independently of those of the temporary
teeth. The bud of the first of these molars springs from the epithelial ridge on the
border of the jaws, the buds of the other two being derived from the first,
3. The liver. — This gland commences to be developed very early in all the
species. It appears on the surface of the duodenum in the form of two or more
buds, according to the number of lobules in the adult liver. To these external
buds are corresponding internal ones, arising from the intestinal epithelium —
that is, the inner lamina of the blastoderm. The first are contained in a layer of
the mesoblast that separates the anterior
aditus of the pericardium ; they grow and ^^^^^^^^|^^
envelop the omphalo-mesenteric vein ;
the second ramify in their interior, and
form the system of biliary canals.
The liver grows rapidly, and, towards
the third month, almost entirely fills the
abdominal cavity ; at a later period its
growth is less marked, although at birth
it is yet proportionally larger than in origin op the liver from the intestinal
adult life wall in the embryo of the fowl, on the
„ ■ „i £ X fourth day of incubation.
4. Pancreas. — The pancreas first ap- „ , . . ..
,., ,, ,. 1 T • ii ,- a,Heart; ft, intestine; c, everten portion, giving
pear, hke the salivary glands, m the form oHgin to liver; d, liver; e, portion of vitel-
of a solid cellular bud, which afterwards line vesicle.
is channeled into ramescent cavities.
5. Spleen. — According to Bischoff, this body is developed — during the second
month — on the large curvature of the stomach. Arnold states that it is formed
at the same time as the liver, in a strip extending from the stomach to the
duodenum. It subsequently separates from the pancreas and becomes fixed to
the stomach, where its elements assume the character of spleen-tissue.
Development of the Genito-Urinary Apparatus.
The development of the genital organs is related to that of the urinary organs,
as the apparatus they form have some parts in common.
Immediately after the formation of the intestines, the genito-urinary organs
are furnished by the Wolffian bodies. These — also named i[\Q primordial kidneys
1050
EMBRYOLOGY.
Fig. 585.
and bodies of OTcen — are glandular in structure, and extend in front of the vertebral
column from the heart to the pelvis. They are composed of small transverse
canals, filled with a whitish fluid, which enter a common excretory duct that lies
parallel to the spine, and opens inferiorly into that portion of the allantois which
becomes the bladder.
The Wolffian bodies are placed behind the peritoneum, and are attached by
two serous folds : an anterior — the diaphragmatic liyament — and a posterior — the
lumbar ligament of the corpora Wolffiana. The organs furnish a liquid analogous
to the urine ; though it is not long before their secretion undergoes great modi-
fications ; indeed, these bodies soon atrophy, and disappear more or less rapidly,
according to species. One portion serves for the development of the genital
organs ; the other gives rise to organs the signification of which is unknown —
such as the organ of Rosenmiiller — which is very developed in the Mare, and the
canals of Gaertner, visible in the Cow and Rabbit (Mare and Pig).
A. Urinary Organs. — We have seen above how the allantois is derived
from the blastodermic lamina ; it has now to be stated that the bladder is derived
from the allantois. This reservoir is the result of the dilatation of the abdominal
portion of the allantois. During foetal life, the bladder is extended, by the
urachus, to the umbilical ring ; but after birth the urachus is obUterated, and
the bladder is withdrawn into the pelvic cavity. Hereafter we shall study the
urethra.
The kidneys appear a long time after the Wolffian bodies, in the shape of two
blind pouches constituted by a pushing back of the wall
of the excretory duct of that body. These little cids-de-
sac ramify, and are afterwards replaced by solid buds, in
the interior of which are developed the uriniferous tubes
and Malpighian bodies. According to certain observers,
the kidneys subsequently communicate with the ureters,
which are developed separately in the middle layer of
the blastoderm (for further details, see Book IV., p. 573).
(In the female, the Wolffian bodies do not entirely
disappear ; the canals of Gaertner and the bodies of
Eosenmiiller, situated in the broad ligaments, between
the ovaries and Fallopian tubes, are their remains in
adult life ; traces of them are also found in the male, near
the head of the epididymis, where they constitute the vasa
aherrans of the testicles. The supra-renal capsules are
very large in the Equine foetus, being nearly one-half the
size of the kidneys.)
B. Genital Organs. — The genital apparatus of the
male and female are at first very much alike ; indeed,
during a certain period it is impossible to distinguish
the sexes ; so that some authorities have proposed to term
this period of development the " indifferent state of the genital organs." Later,
the sexes are defined ; and this period of development may be studied in the
internal and external organs.
1. Indifferent state of the internal genital organs. — Towards the sixth week,
there is observed on the lower face, and near the inner border of the Wolffian
bodies, a little white cord, which increases in volume and maintains almost the
same position. This new organ is the genital gland, which is attached to the
STATE OF THE GENITO-
URINARY APPARATUS IN
THE EARLY EMBRYO OF
THE BIRD
a, Corpora Wolffiana ; 6, 6,
their excretory ducts;
c, kidneys; d, ureter;
e, e, testes.
TEE FCETU8. 1051
Wolffian body by serous folds, and is formed by a mass of young cells sustained
by an enveloping membrane.
The development of this gland is accompanied by the formation of the
genital or MuUer''s duct, which is seen to the inside, and in front of, the "Wolffian
duct. Miiller's duct is at first a solid cellular column, which afterwards becomes
a canal ; it terminates above in a blind pouch, and opens, below, into the bladder,
near the Wolffian duct, which is formed at the same time.
The stroma of the genital glands in the two sexes, is the seat of a differentia-
tion that gives rise to a system of reticulated solid cords, called the sexual
cords. Its surface is covered by an epithelium, which is continuous with that
of the peritoneum, but so specialized here as to merit the name of f/erm-
epithelium.
The sexual specialization is produced in the following manner : — ^
a. In the male, by the evolution of the sexual cords, or tubuli seminiferi.
The testicle is completed by the annexation of the anterior region of the
Wolffian body, which forms the head {globus major) of the epididymis, while
the tail (or globus minor), vas deferens^ and ejaculatory duct, are derived from
the Wolffian duct. Lastly, the vesiculce seminales and the origin of the urethra
are formed by the posterior extremity of Miiller's ducts, which join and open
into the uro-genital sinus, as the very short canal is named which communicates
between the bladder and cloaca.
The developed testicle remains in the abdominal cavity, or descends through
the inguinal canal into the scrotum. The mechanism of this descent has been
already explained.
(It may be necessary here to state that, in the Equine species, the testicles
do not usually descend into the scrotum until some time after birth — about six
months ; while in other animals they reach that sac during foetal life. In the
Bovine species, the testes are in the scrotum about the twentieth week of gesta-
tion, and in the Sheep and Goat about the fifteenth week ; indeed, it has been
observed that in all Ruminants their descent is effected before the skin is covered
with hair. In the Carnivora, they are usually in the scrotum a few days before
birth.)
b. In the female, the sexual specialization is produced by a process of the
germ-epithelium, which results in the establishment of an ovigenous layer. The
Fcdlopian tube and its pavilion are formed by the anterior part of Miiller's duct,
the extremity of which shows a small linear orifice. The uterus and vagina arise
from the posterior part of Miiller's ducts. These lie beside each other, and
end by joining behind to constitute a single canal ; the two divergent portions of
these canals comprised between the point of fusion and the Fallopian tubes form
the uterine cornua.
The uterus and vagina are at first placed end to end, without any apparent
> At the same time that the sexual specialization of the genital gland is affirnfed in the
ovary and testicles, the glands themselves afford exact evidence of the opposed sexualities. In
the testicles, the germ-epithelium is the seat of an evolution that gives rise to the primordial
ova which Laulanie has observed in the fcetus of the Cat, measuring from -7 to -12 m. In the
same animal species, this author has noted — with regard to the fcetal ovary — the connections
between the primitive sexual cords and the tubes of the "Wolffian body, establishing the
homology of the first tubuli seminiferi. A demonstration has therefore been given for the first
time, of a real organic hermaphrodism of the sexual glands, and from this arises tlie interesting
notion that the sexuality of the individual has been preceded by a period of indifference and
a period of bisexuality.
1052 EMBRYOLOGY.
separation ; but towards the sixth month the neck of the uterus commences to
be defined.
2. Indifferent state of the external genital organs. — The intestine is terminated
by the cloaca — a cavity into which the digestive canal and bladder open by the
uro-genital sinus. This confusion quickly ceases by the development of a trans-
verse septum that divides the cloaca into two compartments — the anal opening
and the uro-genital aperture. At the inferior end of the latter appears the genital
tubercle — the rudiment of the penis or clitoris, and wliich is surrounded by
cutaneous folds — the genital folds. This tubercle increases in volume, and has
a furrow passing from betind to before. Up to this moment it is impossible to
distinguish the sexes.
Development of the external genital organs of the male. — The male sex is marked
by the rapid development of the genital tubercle, which becomes the penis — its
extremity enlarging to constitute the glans. The genital furrow closes posteriorly,
and forms the urethra. The genital folds draw towards each other below the
penis, unite in the middle line, and thus produce the scrotum. Owing to these
modifications, the digestive apparatus is completely separated from the genito-
urinary organs, and the urethral canal is connected with the bladder and the
excretory ducts of the testicle.
Development of the external genital organs of the female. — The indifferent state
of the genital organs is readily succeeded by the feminine type. The uro-genital
sinus forms the vulvar cavity or vestibulum of the vagina, which is so marked
in the lower animals. The genital tubercle becomes the clitoris ; the genital
furrow closes at a certain part to constitute the perinasum ; while the genital
folds form the labia of the vulva. The mammae — dependencies of the generative
organs— appear after the first month of uterine life.
INDEX.
PAGE
PAGE
Abdomen
. 450
Anatomy, comparative
I
Abdominal aorta .
609
ib.
cavity
450
descriptive
ib.
. 455
ib.
differential characters ii
I . lb.
general
ib.
divisions of
450
ib.
. 299
ib.
form of
451
physiological
ib.
lining membrane of
. 452
regional
ib.
. 451
ib.
reservoirs .
565
surgical .
ib.
rings of
. 303
typographical
ib.
. 450
ib.
Abdominal salivary gland
. 555
ib.
Abomasum
470
Ancyroid cavity
803
interior of.
*.
Andersch's ganglion
833
structure of
ib.
Aneurism
. 616
Absorbent vessels
713
Angiology
'. '. C
J92, 583
Accessory portion of visual appara
tus . 938
Animal amidon .
. 497
Acervulus.
. 773
Annular cartilage
281
Adipose cushion of ear . ,
. 958
protuberance
769
Adrenals ....
. 578
Annul us albidus
930
Affluents of thoracic duct
. 724
589
Aggregate follicles
475
Anomalies in arteries
. 605
Air-cells of lungs
549
Anorchidism
. 962
Air-chamber ot egg . .
. 1009
Ansiform tube of Henl
572
Alimentary canal
447, 455
Anterior antibrachial i
egion
323
Allantoid fluid .
. 1021
aorta
^
d44
Allantois . . . .101
6, 1017, 1019
biachial region
\
317
chorial
. 1020
771
. 1021
femoral or crural region
. 348
Alveoli of glands
460
mediastinum
. 543
lymphatic .
. 719
patellar ....
348
Alveolo-dental periosteum .
. 414
peduncles of conarium
772
Alveus ....
792
tibial region
362
Amnii, liquor .
. 1019
white commissure of brain .
774
Amnion ....
1017, 1019
Anus .....
. 484
Amniotic lamina
. 1019
1047
Amphiarthroses .
. 177
of Rusconi
. 1007
*.
Aorta
608
Ampulla of Vater
499, 503
anterior ....
. 644
Amygdalae
. 401
common ....
608
Amygdaloid cavity
ib.
— : — comparison of . . ,
623
Anastomoses . .
. 602
644
by arches .
ib.
differential characters in
621
ib.
carnivora' .
622
ib.
pig . .
ib.
convergent
ib.
621
ib.
611
transverse communicating
ib.
posterior ....
609
. 805
preparation of .
610
Anatomical elements
3
612
Anatomy
1
Aortae, primitive
1041
anthropotomy .
.•6.
Aortic heaiT ....
590
69
1054
INDEX.
PAGE
Aponeurosis
232
Arteries, relations ....
322
structure ....
containing . . . .
239
termination
crural
301
302
abdominal, anterior
349
posterior ....
gluteal
243
972
accessory thyroid
ih.
anterior cerebellar
superficial
ib.
plantar .... 3
31, 371
mesenteric ....
tibial
362
radial . . . .
Apparatus ....
6
tibial ....
circulatory, in mammalia
582
arteria corporis callosi. .
734
396
asternal
511
atloido-muscular
generative
959
738
posterior . . . .
924
axillary
respiratory, in mammalia
517
in birds .
557
899
949
basilar
taste, of .
922
brachial
899
urinary . • . .
568
vision, of .
925
buccal
Appendix auricularis .
586
bulb
Aqueduct of Fallopius
952
caecal
of Sylvius ....
775
Aqueous humour
938
left
membrane of
ih.
right . . . .
Arachnoid membrane .
751
carotid, common
752
collateral branches
751
structure .
ib.
790
external . . . .
Arantius, nodule of .
589
internal . . . .
duct of . . . .105
7, 1044
Arbor vitae cerebelli .
781
cavernous
Arciform fibres of bulb
777
centralis retinae . . . .
Arch of aorta ....
609
hamal ....
167
ischial ....
. 133
ischiatic ....
ib.
cerebral, anterior
neural ....
167
middle . . . .
pharyngeal
. 1039
Arcus aortse ....
. 1041
cerebro-spinal . . . .
Arm, bones of .
. 101
cervical, deep . . . .
Arms of pelvis of kidney
. 571
Arnold's ganglion
824
Arterial zones of heart
. 592
cervico-muscular
Arteriae helicinae
974
transverse ...
vertebralis
. 1041
ciliary
Arteries .....
600
. 602
anomalies .
. 605
posterior, of shoulder .
. 601
direction
ib.
. 607
division
. 600
middle . . . .
form, particular .
ih.
ccEliac ....
general considerations .
ih.
form . . .
ih.
left or retrograde
■ injection .
. 606
collateral of the cannon . 6
. 603
branches . . . .
. 601
of the digit
preparation .
. 6«>6
colon, first of small colon
INDEX.
1055
Arteries, coraco-radialis . ,
PAGE
651
Arteries, internal mammary
PAGE
647
620
maxillary .
672
coronary .... 6
09, 670
pudic
624
638
625
627
of male
624
cremasteric
620
interosseous, of forearm
652
629
anterior
654
cubital ....
650
metacarpal.
653
dental, inferior .
672
ib.
superior
675
intestinal, small .
616
612
ischiatic ....
625
digital ....
636
labial, inferior .
. 670
direct colic
617
ib.
dorsal ....
645
lachrymal ....
674
anterior of penis
632
640
625
652
615
lateral coccygeal
625
elbow, external collateral
650
ib.
internal collateral
ib.
ib.
619
middle
612
epicondyloid
650
terminal branches
625
epigastric ....
632
left colic ....
617
67, 671
lingual ....
669
collaterals .
ib.
612
external pudic .
632
632
facial ....
667
648
femoral ....
631
internal .
647
femoro-popliteal .
634
672
first artery of floating colon .
618
mastoid ....
663
613
maxillary, external
667
gastro-epiploica dextra
615
internal
672
14, 615
maxillo-muscular
670
667
673
gluteal ....
626
mesenteric, great
616
great meningeal .
673
anastomoses
618
616
616
posterior of thigh
633
617
testicular . ...
620
616
672
of right fasciculus
617
974
innominate branches
618
hepatic ....
615
small
ib.
44,649
636
650
middle cerebral .
665
deep ....
ib.
—coccygeal .
626
humeralis profunda .
650
612
629
664
643
muscular, deep .
633
differential characters ii
1 640
great anterior .
ib.
623
ib.
629
ib.
differential characters ii
1 628
nasal ....
675
617
626
627
occipital ....
662
626
collateral branches
663
ib.
occipito-muscular
ib.
dental
672
612
cervical
648
omental ....
615
640
omphalo-mesenteric .
1041
ib.
673
infra-scapular .
649
ovarian ....
621
labial
670
palatine ....
675
969
palato-labial ... 6
72, 675
innominata
644
615
innominate branches of great mesen
pectoral ....
647
teric ....
618
pedal ....
636
613
perforating
ib.
intercostal
611
638
665
pharyngeal
669
iliac.
623
phrenic ....
612
1056
INDEX.
PAGE
Arteries, plantar .... 635
Arteries, thoracic, internal teiminal
cushion
638
branches
635
640
popliteal .
634
transverse-cervical
posterior abdominal
632
transverse of face
671
communicating .
665
ulnar . . .
deep temporal
672
umbilical .
625
652
utero-ovariaa
tibial
634
vaginal
.•6.
vasa brevia
ib.
intestini tenuis .
650
preplantar ungual
639
vertebralis
prepubic .
631
vesico-prostatic .
prescapular
649
Arthrodia .
prevertebral
663
Arthrology
633
Articular cartilages .
673
pulmonary
607
Articulations
preparation of
.•6.
in general .
pyloric
615
radial, anterior .
651
nomenclature
posterior .
652
anterior limbs, of
radio-palmar
653
atlo-axoid .
. 663
renal
. 619
reticulum, artery of
621
17, 663
carpo-metacarpal
right colic
617
rumen, superior of
621
ib.
sacral, lateral .
625
costo-vertebral .
sacra media
612
coxae
saphena .
. 633
scapulo-humeral
649
small mesenteric
618
femoro-tibial
intestine .
. 616
foot .
small testicular
. 620
head
ih.
675
spinous
. ID —
. 673
interchrondral .
spiral
. ■■». •
. 651
interhyoideal
splenic
. 613
675
. 645
first .
subcutaneous abdomim
[l
. 632
second
. 670
third
667
subsaci'al .
. 625
intervertebral •
subscapular
. 649
ischio-pubic
subzygomatic .
. 671
laryngeal cartilages, ol
633
671
occipito-atloid .
superior dental .
. 675
pedal
supermaxillo-dental
ib.
pelvic
supra-scapular .
. 649
posterior limbs .
674
temporal .
671
deep anterior
. 673
sacro-iliac
posterior
ib.
scapulo-humeral
superficial
. 671
tarsal
. 620
small
ib.
thoracic, external
. 648
inferior
t6.
i
■ internal .
. 647
tibio-fibular
.
INDEX
1057
PAGE
Articulations, tibio-tarsal .
221
Bones, nerves . . . .
Arytsenoid cartilages .
530
number
Ascending frontal convolution
786
nutrition
Auditive scala ....
950
Auditory apparatus .
947
regions
Auricles .... 583, 5
86, 589
relative form
Auricular or conchal region
280
Auricular facet ....
128
situation
586
Auriculo-ventricular openings . 5
88, 590
in birds
zones . r
593
anterior maxillary
Axile bodies ....
901
astragalus
Axillary region ....
292
atlas
Axis, cceliac ....
613
axis ,
cylinder . . . , .
740
calcaneus .
of arteries .
601
calcis
capitatum
Baccated fibres of tooth
413
Bacillary layer of retina
934
carpus
Balbiani's vesicle
1005
cervical vertebrae
BandofReil ....
771
Barbs 4
00, 437
coccyx
Bars of hoof ....
915
costa;
Bartholine, glands of .
1000
Basement membranes . . . .
5,393
cuboid
Basilar membranes .
951
cuneiform .
process of os pedis
116
Bauhini, valvula
473
dorsal vertebra
Bellini's tubes ....
571
ethmoid
Bichat, fissure of . . .
784
Bicipital tuberosity .
317
fibula
Bicuspid valve ....
590
first metacarpal
Biflex canal ....
901
Biliary ducts ....
498
great cuneiform
Bipolar nerve-cells
740
hamatum .
Bizzero's cells ....
18
Bladder . . ...
575
humerus .
attachments
ih.
hyoid
7, 1050
■ form ....
575
incisive
• functions ....
578
incus
interior ....
576
inferior maxillar
575
-; relations ....
ib.
576
lachrymal .
575
large cuneiform
Blastema
393
lumbar vertebrae
Blastoderm, formation of .
1007
lunare
ih.
magnum .
Blastodermic vesicle .
1007
malar
Blastopore ....
ib.
malleus
Blind spot ....
936
maxillary, inferi
)r
Blood
583
superior
Bones, in general
7
metacarpals
13
metacarpus
blood-vessels
18
metatarsus
cavities
15
middle cuneiform
cells of
16
conformation, internal .
15
navicular .
development
19
occipital .
13
OS coronae .
eminences .
14
innominatum
*.
orbiculare
• general principles
11
imprints
14
penis .
■ internal conformation .
15
palatine .
lymphatics .
18
parietal
medulla . . .
ih.
patella
,
names
12
pedal
.
1058
INDEX
Bones, pelvic
penial
peroneus
pisiform
premaxilla.
prominens
pterygoid
pubis
pyramidal ,
radius
ribs .
sacrum
scaphoid of carpus
of tarsus
scooping-bone
second phalanx
sesamoids .
small cuneiform
small sesamoid
sphenoid .
stapes
sternum
styloid
supercarpal
• superior maxillary
supermaxilla
tarsus
temporal •
. third phalanx
tibia.
■ trapezium.
trapezoides
tricuspid .
. turbinated
■ ulnar
■ unciform .
vertebra dentata
prominens
tricuspid
vertebse
cervical
coccygeal
dorsal
lumbar
^— vomer
zygomatic .
Botal, foramen of
Bourrelet .
Bowman's capsule
Brachial bulb .
Brachio-rachidian bulb
Brain (see Encephalon)
Bristles .
Bronchi .
cartilages .
disposition. .
form
glands
relations ,
structure .
volume . .
Bronchial cartilages .
glands
tubes
Bruch, membrane of .
Brunner's glands
Buccal mucous membrane
Bulbi fornicis
vestibuli .
FACE
127
980
142
108
65
30
69
128
110
103
94
39
110
147
526
115
ib.
148
117
56
954
92
79
108
63
ib.
144
59
115
140
110
ib.
30
73, 520
105
110
28
30
i6.
24
27
41
32
36
74
69
589, 1042
911
572
756
ib.
763
905
539
540
359
540
729
540
ib.
ib.
ib.
729
540
931
471
398
770
Bulb of ovary .
of plantar cushion
of urethra .
Bui bus aortae
olfactorius.
Burdach, column of
Bursse, serous .
Caducous teeth ,
Caecum
of Morgagni
pharyngeal
Calamus scriptorius
Calcareous powder of
Calices
Calyciform papillae
Callosal convolution
Calloso-marginal fissure
Canal, biflex
ciliary
Cloquet, of
Font ana, of
Ga;rtner, of
Haversian .
hygrophthalmic
inguinal
Jacobson, of
perivascular
Schlenim, of
spinal
Steno, of .
Sylvius, of
Canalis hyaloideus
Canine teeth
Canthi of eyelids
Capillaries
Capillary system
Capsular ligaments
Capsule of brain.
of Glisson .
of lens
Capsules, supra-renal
Ca))ut gallinaginus
Cardiac cavity .
ligament .
oririce
septum
Carpal sheath
Carpus
articulations
bones
movements
Cartilage .
of the tongue
Cartilages, complementary
incrustation
interarticular
interosseous
stratiform
annular
cariniform
conchal
costal
ensiform .
mterarticular of
scutiform .
semilunar .
Wi-isberg, of
xiphoid
estibule
jaw
fibro-
INDEX.
1059
PAGE
PAGE
Caruncula lachrymalis
. 945
Chordae vocales 530
sublingualis . . .
. 440 :
Willisii .
eaij
Cauda equina . . . .
. 853 !
Chorial plates .
1019
Caudate nucleus.
792,794 !
Chorion .
1018
Cava, vena, anterioi- . . .
. 686
definitive .
t6.
posterior . . . .
703
development
ib.
Cavernous sinus.
. 692
frondosum
1027
Cavities
15
primitive .
1018
Cell-germs . . . .
. 903
ib.
Cells
3
serotina .
1027
multiplication of .
»6.
structure .
1018
16
Choroid membrane or
coat .
929
connective . . ,
4
anterior
930
great pyramid .
. 796
posterior
ib.
lb.
931
hepatic . . . .
497
plexus, cerebral
779,7
89, 793
medullary
4
930
4.740
Chyle
582
olfactory .
523, 925
Cicatricula
1009
prickle . . . .
. 903
Cilia
943
. 782
Ciliary body
30, 932
Sertoli, of .
964
canal
931
small pyramid .
. 796
ib.
supporting
. 925
ligament .
30, 931
Cementum . . . 4
14, 415, 1048
processes .
ib.
Central canal of spinal cord .
. 757
930
Central sublobular veins
. 498
Ciliated epithelium
393
Centres of ossification
20
Circulation, adult
582
Centrifugal conductibility .
744
foetus
1042
nerves . . . .
ib.
Circulatory apparatus
582
Centripetal conductibility .
ib.
in birds
734
ib.
Circulus venosus orbiculi ci!
iaris
931
Centrum ....
. 167
Circumvallate papillae
02, 923
ovale of Vic-d'Azyr .
. 795
Cistern of Pecquet
721
Cerebellar crura
. 771
Clark, vesicular column of
761
peduncles .
767
Claws
921
ventricle .
771, 776, 781
Clefts, pharyngeal
1039
. 1034
Clitoris .
995
Cerebellum
763, 778
ib.
external conformation .
. 779
Closed follicles .
407
. 781
Coat
<
)05, 907
Cerebral hemispheres .
785
Coccygeal gland
886
767, 770
272
trigonum .
. 791
nerves
859
790
vertebras .
41
vesicles
. 1033
Cochlea .
948
Cerebro-spiiial axis
. 747
. 950
. 804
Cceliac axis
. 613
Cerebrum ....
. 783
Cohesion .
. 395
convolutions
. 785
Colic mesentery
.
1:54. 483
external conformation .
. 783
Collateral scala.
. 951
783, 784
vessels
. (i03
structure .
. 793
Colon
479
Cerumen ....
957
double
. 481
Ceruminous glands
ib.
attachments
. 482
Cervical ganglia
887
481
ib.
ib.
vertebrae .
27
ib.
Cervix of bladder
575
functions .
. 483
of uterus .
990, 992
length
481
Chambers of the eye .
. 926
ib.
Cheeks ....
. 398
483
. 399
small
ib.
. 398
attachment
ib.
Chestnuts ....
907, 922
lb.
Chiasma of optic nerves
770
ib.
Chorda dorsalis .
. 1013, 1032
interior
ib.
Chordae longitudinales
790
ib.
tendinae
. 588
1 relations
.
iO'
1060
INDEX.
PAGE
PAGB
Colon, small, structure
483
Comparison of, nerves, great sym
Colostrum ....
999
pathetic
886
Columella ....
948
881
Columnae carnse . . . . f
88, 591
oesophagus
450
588
pancreas ....
510
rugosae ....
994
446
Columnar epithelium .
393
salivary glands .
440
Columns of spinal cord . . 7
57, 761
scapulo-humeral articulation
195
Commissures of frog . . .
917
510
of inguinal canal.
303
spinal cord
763
397
stomach ....
471
of nostril ....
518
119
of optic nerves .
810
97
757
thymus gland .
556
of vulva ....
995
thyroid gland . , .
.•6.
Common aorta ....
608
trachea ....
552
Comparison of abdominal cavity .
458
urinary apparatus
581
of abdominal limb
151
veins ....
712
of annexes of foetus . .
1030
45
623
947
of apparatus of taste . . 4
32, 924
Complementary apparatus of pedal bone
909
articulations, coxo-femoral .
216
Composite nerves
804
humero-radial
197
Compressor vesiculae .
969
interphalangeal .
212
Conarium ....
772
metacarpo-phalangeal .
207
Concha auris ....
280
199
281
scapulo-humeral
195
16.
auditory apparatus
958
Conchal cartilage
*.
axillary arteries.
659
Confluent of jugulars . . .
687
552
Confluents of subarachnoid fluid .
752
carotid arteries . . .
680
Congestion of liver
501
782
Conglomerate glands .
395
cerebro-spinal axis
754
Conjunctivae ....
942
cerebrum ....
801
Connective cells . .
4
197
»6.
enveloping membranes
754
5
external iliac arteries .
643
Contractile cells . . .
4
. 983
fibrillffi . . 0 .
231
male . . .
. 989
Convoluted tube of kidney o
572
great sympathetic . .
. 894
Coracoid process . . .
98
head ....
90
Corium cutis . . . . S
99, 900
heart . . .
. 599
Cork of Ecker ....
1007
. 629
Cornea .....
928
— — intestines ....
492
,b.
isthmus of brain
778
Cornu Ammonis
791
larynx ....
552
Cornua of spinal cord .
757
liver ....
510
990
lumbo-sacral plexus . .
883
of ventricles . .
790
. 553
Corona glandis ....
975
mouth ....
430
radiata ....
795
307
Corona; tubulorum . . .
475
arm ....
. 322
Coronaria ventriculi . . .
613
• back ....
266
Coronary cushion . .
911
costal region ,
299
. ligament ....
ib.
310
ib.
foot .'.'.'.
377
structure .
912
338
Corpora albicans vel nigrum
988
gluteal region .
348
cavernosa ....
973
hand
342
791
head
291
772
leg .
374
Malpighiana
572
neck ....
268
nigra ....
932
316
68, 776
sublumbar . .
272
quadrigemina ... 7
67, 771
thigh . . . .
360
restiformia ... 7
69, 777
thoracic . . .
299
Corpus albicans ... 7
70, 791
nasal cavities . . . .
527
Arantius . . . . .
589
872
callosum . . . .
789
cranial . . . .
849
973
INDEX.
10(Jl
Corpus cavernosum, external confoima
Cuticle
903
tion ......
973
Cutiduris ......
911
structure .
974
Cutigeral cavity ....
915
932
Cutis anserina .... 900. 907
781
Cuvierian ducts .....
1044
fimbriatum
792
Cysterna chyli
721
geniculatum, externum
772
Cytoblasts
903
internum .
ih.
Czermak, interglobular spaces of .
413
962
luteum
988
Dartos
961
false .
»6.
Deciduous teeth . . . 416, 426
ih.
Deferent canal .... 963,967
olivare
769
structure of
ih.
• rhomboideum .
781
Deglutition ....
445
89, 792
Demours, membrane of
938
(Jorpuscula tactus
901
Dental follicle .... 414, 1048
Corpuscles of Krause .
807,9
01, 943
germ .... 415,921
ih.
pulp .... 414,415
Pacinian . .
807
414
terminal genital .
975
Dentated membrane .
750
of Vater .
807
Dentine
412
Corti, membrane of .
951
Derma 899,900
organ of .
Costae
ih.
900
94
Descemet, membrane of . . 929, 938
Costal cartilages
95
Development of annexes of alimentary
543
canal ....
1047
region
296
of auditory apparatus .
1036
Cotyledons
1027
of brain ....
. 1033
Cotyloid cavity .
127
. 1032
Cowper's glands
973
of circulatory apparatus
1041
Cranial arachnoid
752
of cranium and face . .
1039
cavity
747
of digestive apparatus
1046
dura mater
750
1030
1039
of genital organs
. 1050
807
of genito-urinary apparatus .
1049
• origin of .
808
of gustatory apparatus
1037
pia mater .
. 754
of heart and vessels .
1042
Cranium, bones of .
46
of lateral laminae
. 1032
Cremaster
961
of limbs ....
. 1040
Cremasteric fascia
ih.
of locomotory apparatus
. 1038
Crested convolution ,
786
. 1045
Cricoid cartilage
528
of muscles ....
. 1040
Crico-thyroid membrane
529
. 1032
530
. 1035
Crown of tooth .
412
of nervous system
. 1033
Crucial fissure .
785
. 1013
Crura cerebelli .
711
of olfactory apparatus
1037
cerebri . .
r67, 770
of respiratory apparatus
1045
of fornix .
791
of skeleton
. 1038
of penis
. 973
of spinal cord
1034
Crural aponeurosis
501, 302
1037
arch
ih.
1040
internal region .
353
of urinary organs
1050
posterior region .
351
1038
ring .
302
1032
Crus ad meduUam oblongati
im
771
of visual apparatus
1035
cerebelli ad pontem
ih.
Dewlap
904
Crusta petrosa .
414
Diaphragm ....
308
Cryptae mucosae .
474
Diaphragmatic pleura
543
Cryptorchids
962
region ....
308
Crystalline lens .
i
26, 936
Diarth roses ....
171
development of
936
Diastole of heart
598
1036
Dieters, prolongation of
761
structure of
£
36, 937
Differential characters in abdomina
Cumulus ovigerus
987
cavity .
455
Cuneiform cartilages .
529
air-tube
541
curved plait
788-
1027
Cutaneous gland of Pig
901
apparatus of taste
923
lamina
1032
1062
INDEX.
PAGE
Differential characters in articulation
.^
Differential characters in forearm .
atlo-axoid ....
. 186
— gluteal region
. 203
head
. 192
hyoid region
. 215
leg .
. 220
• masseteric region
humero-radial
. 197
palpebral .
. 203
panniculus carnosus
209
210
207
spinal region
. 188
198
thigh
scapulo-humeral
195
193
nasal bones
225
temporo-maxillary
189
220
958
palatine bone
axillary arteries
656
brachial plexus .
866
parietal bone
798
carotid arteries .
675
pharynx . . . .
111
-cerebellum
782
limb . . . .
798
premaxillary bone
cervical vertebrae
30
pterygoid bone .
■ coccygeal bones .
41
sacral vertebra; .
cranial nerves
843
salivary glands .
118
scapula . . . .
— dorsal vetebra?
35
envelopes of cerebro-spinal axi
, 754
spinal cord
56
• external iliac arteries
640
femur
139
sternum . . . .
106
52
superior maxillary bone
genital organs of female
999
976
great sympathetic system
894
thorax
heart
599
thymus gland
103
hyoid bone
79
76
urinary apparatus
628
intestines .
485
778
lachrymal bone .
70
vomer . . . .
144
Digestive apparatus ... 3
liver
508
of Birds . . . .
lumbar vertebra
37
Dilator of the pupil . . . .
lumbo-sacral plexus
881
Dissection of arteries . . . .
lungs
552
Discus proligerus . . . .
lymphatic system
732
Dorsal nerves
malar bone
69
furrow . . . . .
metacarpal bones
113
groove . . . . .
■ metatarsal bones
149
424
Double-contoured nerve-fibres
muscles.
Duct of Steno
307
of Wharton . . . .
342
of Wirsung . . . .
arm .
321
Ducts, accessory pancreatic
axillary region .
296
biliary . . . . .
252
Cuviei-ian . . . . .
258
genital
• superior
244
guttural . . . . .
299
mammary . . . . ,
310
Miiller's
facial region
289
parotid
INDEX.
1063
Ducts, perspiratory
salivary
thymic
Ductus ad nasum
arteriosus
choledochus
couise
structure
cysticus
ejaculatorius
galactophorus
hepaticus .
lactiCerus .
lymphaticus dexter
pancreaticus minor
pi-ostaticus
Riviniani .
— — thoracicus .
venosus of Aranzi
Duodeual glands
Duodenum
Dura mater
structure
Duverney, glands of
Ear, external
internal, nerves
middle
Ear-dust
Ectoderm .
Ectoderraic globe
ridges
Ectopias of testicles
Effluent canals of dura
Ejaculatory ducts
Elastic fibres
Embryogenous vesicle
Embryology
Embryonal area
Emergent veins of spi
Eminences
Eminentia teres .
Enamel
germ
Enarthrosis
Encephalic arachnoid
dura mater
pia mater .
Encephalon
as a whole
constitution
general form
isthmus
volume
weight
Endocardium
Endoderm
Endodermic globe
Endolyraph
Ensiform cartilage
Envelopes of cerebro-:
Ependymis of spinal
Epiblast .
Epicardium
Epidermis
growth of .
structure .
Epididymis
■ structure .
nal
spinal
PAGE
. 902
435, 437
556
945
b2,
1043
499
ib.
ib.
508
969
998
499
998
731
503
973
438
721
1027, 1044
471
472
749, 751
749
984
957
948, 951
957
950
1007
1006
1011
962
694 '
568, 969
4
1005
ib. I
1007 :
695
14
796 I
413, 1048
415, 1048 i
176 I
752 :
750 I
754
763 j
ib.
ib.
ib. I
766
765
ib. :
596
1007
1006
948, 951
93
474
757, 775
1007 i
597
903
Epiglottis
Epithelial cells
tissue
Epithelium
ciliated
columnar
cylindrical
pavement
simple
spherical
squamous
stratified
Epoophoron
Erectile tissues
Ergot
of Morand
Essential organ of vision
Ethmoidal lobe ,
sinus
Eustachian tube
valve
External auditory hiatus
Eye ...
Eyelashes .
Eyelids
commissui-es
integuments ,
structure .
Eye-vesicles, primitive
I Falciform ligament
j Fallopian tubes .
i functions
structure
False glands
nostril
Falx cerebelli .
j cerebri
■ Fang of tooth .
Fascia infundibuliform
lata .
trausversalis
Fasciculus, primitive
Fatty nucleus of Baur
Fauces
isthmus of
Female pronucleus
Femoral region .
Fenestra cochlea
ovalis
rotunda .
vestibuli
Fenestrated membrane
Ferrein, pyramids of
Fetlocks .
Fibres
of Remak .
Fibro-cartilages, complementary
intervertebral
pedal bone
Fibro-intestinal lamina
Fibrous tissue .
Fibrous zones of heart
Filiform papillae
Filum terminale
Fimbria of Fallopian tube
j6. Fimbriated extremity of oviduct
967 Fissura Glaseri .
ib. i longitudinalis, inferior
PAGE
529
4
th.
393
«5.
ib.
ib.
ib.
ib.
ib.
ib.
ib.
988
518
905, 910, 922
803
926
785, 786
525
952, 955
590, 600
957
925
943
925, 941
941
942
941
1031
452
989
990
989
719
518
754
750
412, 417
961
349
303, 307
231
404
408
ib.
1006
348
950
948, 951, 952
949, 951, 952
948, 952
604
572
905
4
740, 887
117
179
909
1013
4
592
402, 923
753, 1034
. 989
ib.
. 673
. 756
1064
INDEX.
Fissura longitudinalis, superior .
PAGE
. 756
Fossulate papillae ....
. 941
Fourchette ....
Fissure of Bichat
784
Fourth ventricle of brain .
calloso-marginal
. 786
Fovea centralis ....
interlobular
. 783
Fracinum linguae
. 785
praeputii ....
interpeduncular .
. 770
Frog of hoof . ,
parallel .
. 788
Frog-stay . . ,
. 116
Frontal diverticulum .
pleuro-peritoneal
. 1013
horns
Rolando, of
785
lobe
785, 786
*5
Flocculus ....
. 782
Functional vessels of lungs .
Fluid of labyrinth
. 953
Fundus of bladder , .
Foetus, development of .
. 1030
Fungiform papillae . .
40
circulation in . .
. 1041
Funicular ligaments . . ,
17
Follicles, aggregated .
. 475
396, 407
Galactophorous ducts .
hair . . .
906
sinuses . . .
. 474
Galeati's glands . .
mucous .
393, 461
Ganglia ....
72
simple . . ,
. 374
structure .
396, 474
Andersch's . .
8S
structure of
396, 473
Arnold's .
ultimate .
. 433
Follicular glands . .
. 406
intermediate
. 995
superior .
Fontana, canal of
. 931
spaces of .
. 928
Cloquet's .
Foramen of Botal . .
589, 942
Ehrenritter's
caecum of Morgagni .
401
of Vicq-d'Azyr .
. 778
geniculate
commune anterius
772, 775
posterius . .
. 772
hypoglossal
condyloid . . .
47
inferior cervical
infra-orbital
63
intumescentia
26
57
47
Meckel's .
posterior ,
ib.
middle cervical
Monro, of
775, 789, 790
naso-palatine
. 951
nutrient . , .
18
otic .
obturator .
129
petrosum .
occipital .
47
semilunar .
\ 8
58, 587
58
Soemmering, of .
. 947
spinal
spinal . . ,
24
submaxillary
spinosum . . ,
58
61
Ganglion cells .
subpubic . . .
. 129
Ganglionic nerves
subsphenoidal . .
58
Gasserian ganglion
superciliary
51
Gastro-colic omentum .
4.
40
Gastrodisc
supra-orbital . .
51
Gastro-hepatic omentum
trachelian
47
Gastro-splenic omentum
vertebral .
»6.
Galatine of Wharton .
Vidian
56
Gelatinous substance of Rolando
Winslow .
. 453
Gemmation
Forceps major .
. 803
Generative apparatus .
Forearm, bones of . ,
. 103
of Birds .
Fore foot, bones of
107
Genital duct
Forelock ....
. 904
gland
Formation of embryo .
. 1032
organs of female
Fornix ....
789, 791
Fossa centralis retinae
947
. 589
Genu of corpus callosum
— — navicularis . .
. 970
Germ epithelium
.
INDEX.
1065
Germ of hair .
PAGE
906
Glands, popliteal
PAGE
727
Germinal area .
. 1007
pra;putial .
! 901, 976
disc . . , ,
. 1010
. 727
986
prepectoral
730
spot . . .
lb.
. 731
streak
. 1007
prostate .
. 973
vesicle
. 1004
racemose .
395, 407
Gianuzzi, "lanula of . ,
. 433
727
Ginglymus
176
salivary .
. 433
Glandulae agminatae .
. 475
sebaceous .
. 901
ib.
simple
. 395
Glands ....
395
socia parotidis
441
agminated
. 475
solitary
396, 474
anterior limb, of
. 729
. 728
. 1000
staphyline
. 438
brachial .
. 731
stomach, of
. 728
Brunner, of . .
. 474
. 730
caecum, of .
728
sublingual
437, 439
ceruminous
. 957
sublumbar
724
cheeks, of. . ,
398, 438
436,
439, 730
886
subzygomatic
. 440
colon, of .
. 727
sudoriparous
901
conglomerate
. 395
. 729
. 973
thymus .
. 555
cutaneous, of Pig .
. 901
thyroid .
553
duodenal . . ,
. 474
tracheal .
539
. 984
tubular .
. 395
follicular .
. 406
Tyson's .
. 901
Galeati's .
. 474
uterine
993
gastric
. 461
utricular .
ib.
genital
105
vulvo-vnginal
. 996
guttural .
. 730
Glandular cuts-de-sac
433
944, 946
tissue
5
head, of .
. 729
Glans clitoridis .
995
honeycomb
. 475
. 975
. 727
Glenoid cavity .
98
inguinal, deep .
726
Glisson, capsule of
497
.6.
Globus major epididyE
ais
967
. 728
ib.
interungulate of Sheep
. 901
Glomes of frog .
917
labial
398, 406, 438
Glomeruli of kidney
572
■ lachrymal .
. 944
Glottis .
535
laryngeal .
. 534
Gluteal aponeurosis
543
lenticular .
474
region
ib.
Lieberktihn's
474,479 ;
Glycogen .
497
400,438
Goll's column .
758
liver
494, 728
Goose-skin
900
lobulated . . . .
. 395
Graafian vesicles
985
. 886
Granules, fat .
3
lymphatic . . . .
. 718
pigmentary
ib.
mammary . . . .
. 997
proteic
ib.
maxillary . . . .
436, 440
Great lymphatic vein
721
943
sympathetic system .
885
molar . . . .
398, 438
structure .
886
■ mucus of stomach
. 461
transverse cerebral fissi
ire .
784
. 729
Grey nerve-fibres
740
Nuhn's .
441
root of optic nerves
810
odoriferous . .
. 523
777
Pacchionian
. 751
Gubernaculum dentis .
41
5, 1048
palate, soft
411, 439
testis
966
pancreas . . . .
. 502
Gum
414
parotid . . > ■^
134, 439, 450
Gustative bulbs .
923
Pecklin, of . , .
475
cells .
924
peptic . . . .
. 461
Guttural pouches .
596
perspiratory
. 901
Gyri
785
Peyer's ....
475
annectant .
ib.
, 730
Gyrus fornicatus
791
■ pineal ....
772
rectus
786
pituitary ....
522, 773
Habenae .
772
1066
INDEX
FAOK 1
PAGE
Haemal arch 167 ;
Hypochondriac region.
451
Hsematies.
3
Hypogastric region . . . .
ih.
Hairs ....
904 :
Hypophysis cerebri . . . .
773
follicles .
906
formation of
907
Ileo-csecal valve. ... 4
73, 478
ih.
Ileum
472
germ of . •
906
Imprint
14
horse, of .
904
Incisor teeth . . 412r, 4
17, 425
sheath of .
906
Incus ......
954
Haller's passage . .
1042 ■
Infundibula of lungs . . . .
548
Hand . . . .
121
Infundibuhform fascia .
961
Harder, glands of
s
44, 946
Infundibulum . . . . .
773
Harraonia suture . <
177
Inguinal canal
302
Haversian canals , ,
16
hernia
632
Head, bones of .
46
302
in general .
80
Injection of arteries . . . .
606
Heart .
583
of veins
685
action
598
Inosculation ....
602
capacity .
584
Insulae ......
722
ih.
Integuments of external ear.
958
external conformation
ih.
Intel-articular meniscii
216
ih.
Intel-auricular partition
587
general sketch . ,
583
Intercarotid ganglion . . . .
894
interior .
587
Interglobular spaces of Czermak .
413
■ nerves and vessels of
596
Interlobular fissure
783
serous membrane .
ih.
veins
498
situation .
584
Internal crural region.
3.53
591
ear .....
947
volume
584
nerves of .
951
weight
ih.
Interosseous cartilages
173
Helicine arteries . ,
. 974
Interpeduncular fissure . .
770
Helico-trema
949
Interstitial substance .
232
Hemispheres, cerebral
784
Interungulate gland .
901
Henle, ansiform tube of
. 572
Interventricular septum
587
sheath of .
. 803
Intervertebral fibro-cartilages
179
Henson, streak of .
232
foramen ....
26
Hepatic cells
497
Intestines .....
471
ducts
. 498
development
1047
497
large ....
477
Hernia, inguinal
632
attachment
478
Herophilus, wme-press of
692
capacity .
ih.
Highmorianum, corpus
963
dimensions.
lb.
Hilum pulmonis.
546
ih.
Hilus of kidney .
570
functions .
479
Hippocampus
89, 791
mterior
478
Hippomanes
1021
ih.
Hollow organs ,
392
i6.
ih.
structure .
.•6.
Holoblastic type
1009
small ....
471
Honeycomb glands
475
attachment
. 472
Hoof
. 908
ib.
ih.
. 477
description of
914
form.
. 471
development of .
919
. 477
structure of
. 917
472
wall of .
. 915
•6.
Hoof-horn . . .
917
structure .
. 473
ih.
Intra-lobular veins
498
Horn cells.
. 918
Ins
. 932
Horns, frontal .
. 922
. 933
Horny productions
907
Ischiatic spine ....
. 128
Horsehair
. 904
Island of Reil ....
. 786
Humours of eye .
926, 936
Isthmus of brain . . 763,
766, 767
Hyaloid membrane
. 937
. 766
Hydatid of Morgagni .
. 982
internal conformation of
774
Hygrophthalmic canals
. 944
structure of
776
Hymen
. 996
. 408
Hyoideal region .
. 286
Iter ad infundibulum .
. 775
Hypoblast.
. 1007
quartum ventriculum .
ib.
INDEX
1067
PAGE
PACK
Ivory
412, 1048
Lateral ventricles
789, 790
Left auricle of heart .
. 591
Jacob's membrane . •
934
ventricle of heart
590
Jacobson, nerve of . . .
. 833
Leg, bones of . .
140
Jejunum . . . . .
Jugular channel
. 521
. 472
Lens, crystalline
362
. 936
. 687
ib.
ib.
structure of
ib.
Lenticular ganglion .
822
Keraphyllous tissue .
. 915
. 471
Keratogenous membrane
Kidneys . . . . »
. 911
. 568
papilla
792
402, 923
.■6.
Lenticulo-stnated bodies
794
internal .
. 570
Leucocytes
4
development
573, 1050
Lieberkiihn's follicles .
474
ib.
574
. 1041
Ligaments
173
proper tissue
571
174
570
funicular .
ib.
. 568
interosseous.
ib.
structure •
. 570
ib.
ib.
peripheral .
%b.
. 570
white.
. 173
Krause, corpuscles of .
806, 943
174
. 975
202
arteriosum
607
Labia vulva . . . .
. 995
224
Labial glands .
398, 438
atlo-axoid, inferior
186
Labyrinth.
. 947
ib.
superior .
auditory .
t6.
954, 955
membranous
949
bladder, of
576
Lachrymal apparatus .
. 944
454, 990
. 945
calcaneo-astragaloid
223
ducts
ib.
calcaneo-metatarsal
224
gland
944
capsular of atlo-axoid
articulation. 188
. 816
of carpal
. 202
. 945
„ . 192
Lachus lachrymalis .
941
of coxo-femoral
• 215
Lacteal vessels .
. 473
r „ . 218
Lactiferous ducts
. 998
„ . 196
sinuses . . •
ib.
„ . 190
Lamella of foot .
. 913
langeal „ . 206
Lamina cinerea .
. 775
„ . 188
cribrosa
811, 928
al „ . 194
. 928
of temporo-maxil
lary „ . 188
spiralis
Laminae of foot .
. 949
913
cardiac
„ . 180
. 452
Laminal tissue .
ib.
carpo-metacarpal
201
Lancisii, chorda longitudinalis of
. 790
carpal, anterior .
201, 202
Large intestine .
Larynx ....
477
cervical .
180
. 527
193
articulations
. 530
ciliary
931
. 1046
colli .
180
. 535
201
external surface .
ib.
. 180
. 528
179
functions ,
. 535
ib.
i6.
supra-spinous
180
. 531
coronary of liver
495
nerves
534, 837, 838
192
. 528
ib.
ib.
lor . . 191
ventricles .
535
ib.
. 534
214
Lateral columns of spinal cord
. 757
. 215
fibro-cartilages .
. 909
. 830
. 917
crico-trachealis .
531
. 1032
. 187
triangular fasciculus of isthr
nus . 771
. 223
1068
INDEX.
PAGE
PAGE
Ligaments, cuboido-scaphoid
223
Ligaments, uterine, suspensory . . 990
denticulated . . . .
753
vesico-uterine
576
diaphragmatic . . . .
1049
997
Fallopii
302
Wolffiani, of corpora .
1049
femoro-patellar . , . .
218
Limbs in general
154
glosso-epiglottic
401
155
hepatic . . . . .
495
Limitans iridis .
933
453
Limitary membranes .
5, 393
humero-radial, external lateral
195
Linea alba
299, 300
internal lateral .
196
Linea; transversse
. 790
212
Lingual canal
400
ib.
438
interannular
182
glandula .
398
190
lacunse
401
intercarpal
200
mucous membrane
923
interlamellar
182
Linguetta laminosa
771
00, 201
Lips
397,4
23, 424
198
functions of
398
interphalangeal, first .
208
397
second
ib.
Liquor amnii
1019
204
folliculi .
986
interspinous
182
labyrinth! .
951
intervertebral .
179
937
206
seminis
966
546
Liver
494
lobus Spigelii, of
453
attachments
495
lumbar of corpora Wolffiani .
1049
development
5C
2, 1049
metacarpo-phalangeal .
204
direction .
494
nuchse ....
180
ib.
odontoid ....
186
functions .
500
ovarian . . . . 4
154, 984
proper tissue
497
patellar ....
217
relations .
495
929
494
peripheral, inferior
191
structure .
497
Poupart's ....
302
494
pubio-femoral .
214
Lobes of liver .
495
radio-carpal
200
Lobular bronchial tube
. 547
198
Lobulated glands
395
ib.
Lobule, anterior of lung
. 547
external transverse
ib.
of curved plait .
86, 788
recto-uterine
. 567
Lobuli testis
. 962
recto-vesical
ib.
Lobulus pneumogastricus
. 547
round, of uterus . . . 4
154, 992
Lobus Spigelii .
. 495
. 212
Lockhart's columns .
761
ib.
Locomotory apparatus
7
ib.
Locus coeruleus .
. 814
scaphoido-cunean
. 224
perforatus
786
sesamoid ....
. 204
posticus .
ib.
inferior
ib.
Longitudinal fissure of brain
. 783
lateral
ib.
Lowenberg's scala
. 951
ib.
Lumbar nerves .
857
spleen, of .
. 503
vertebrae .
36
stellate . . . . ]
91, 192
Lumbo-rachidian bulb
. 756
ib.
Lumbo-sacral plexus .
. 874
subflava ....
182
Lungs
545
supra-dorso-lumbar .
. 180
development
". 5
J2, 1045
supra-spinous cervical .
ib.
. 545
206
. 551
of penis . . 975, <
J76, 978
fundamental tissue
. 547
of sheath .
. 976
general disposition
. 545
of uterus .
. 990
t6.
tarsal ....
221
serous envelope .
. 547
225
situation .
545
teres ....
. 215
structure .
. 547
. 217
Luschka's gland
. 886
• tracheal ....
538
Lymph
. 582
umbilical ....
576
Lymphatics, course of
. 716
154, 990
. 714
round . . ,
ib.
glands
. 718
INDEX.
1069
Lymphatics, numbei- .
origin
plexuses
preparation of
rete mirabile
structure
termination
vessels
Lymphatics
Birds, in .
bladder, in
bone, in
brachial .
bronchial .
caecum, in .
colon, large, in
small, in
guttural .
heart, in .
hepatic lobules, in
iliac
inguinal, deep
superficial
intestines, in
kidneys, in
laryngeal .
lips, in
liver, in .
lungs, in .
mucous membranes, in
muscle, in .
nerve-tissue, in
nostrils, in
ovary, in .
penis, in .
peritoneum, in
pharyngeal
pia mater, in
pituitary .
popliteal .
precrural ,
prepectoral
prescapular
rectum, in .
serous membranes, in
skin, in
small intestines,
spleen, in .
stomach, in
subglossal .
sublumbar
submaxillary
supra-renal capsules, in
testicle, in
thorax, in .
thymus gland, in
thyroid gland, in
urethra, in
uterus, in .
vagina, in .
vessels, in .
Lymphatic sheaths
Macula lutea
Male pronucleus
Malleus .
Malpighian corpuscles
glonierules
70
PAGE ]
PAGE
715
Mammae . . .
997
. 714 i
form . . . .
ib.
715, 717
functions . . . .
. 999
. 714
situation . . . .
. 997
717
structure . . . .
998
714, 718
Mammary ducts
ib.
. 717 !
glands . . . .
ib.
713 I
Mammilla . . . .
997
. 713 1
Mammillary tubercle ■
. 780
736
Manubrium . . . .
. 954
577
Manyplies . . . .
. 468
18, 716
Marginal zone . . . .
. 1013
731
Masculine uterus
. 969
551, 729
Mastoid cells of ear
952, 953
. 728
lobule of brain .
787, 788
727
Matrix of hoof .
908, 911
ib.
Maxillary gland
. 436
. 730
Meatus auditorius externus
. 957
. 596
nasal
. 520
500
. 995
. 727
valve of .
ib.
. 726
Meckel's cartilage
. 1039
ib.
ganglion .
823
479, 727
Meconium
502
. 573
Median lacuna of frog
. 916
. 534
sinus
. 692
. 398
Mediastinal pleura
. 543
500, 728
Mediastinum, anterior
ib.
. 551
posterior .
ib.
715
testis
962
235, 716
Medulla of bones
18
. 716
Medulla oblongata
766, 767
. 524
Medullary cells
. 4,18
. 906
groove
. 1013
972
layer of kidney .
. 571
. 458
Medullated nerve-fibres
740
. 730
Medullo-cells .
. 4,18
. 753
Meibomian glands
941, 942, 943
524, 525
Meissner, corpuscula tactus of
. 901
. 727
Membrana chorio-capillaris .
930
ib.
dentata
753
730
granulosa .
985, 987
. 731
. 934
. 727
nictitans .
. 943
. 716
pupillaris .
. 933, 1036
715, 902
. 1009
. 426
tympani .
. 952
506, 728
ib.
462, 728
. ■ 986
. 730
Membrane of aqueous humour
. 938
. 724
basilar
951
. 730
Bruch, of .
. 931
. 579
choroid
. 930
. 965
conjunctival
942
729
Corti, of .
. 951
. 556
. 938
. 554
dentated .
753
972
Descemet, of
. 938
. 993
eye, of . . .
927
. 995
604
716
hyaloid
. 937
605, 716
keratogenous
. 911
. 719
. 393
Reissner, of
950
947
. 394
. 1006
vitreous
. 931
. 954
Membranous cochlea .
950
504, 572
ib.
. 573
. 970
1070
INDEX.
PAGE
PAOE
Membraneous vestibule . . . 949
Mucous membrane of ureters
575
Meningeal granulations
751
of uterus .
992
Meninges of cerebro-spinal axis
748
994
Meniscii, interarticular
173
of vulva
996
Meroblastic type
1009
Muller's duct ....
1050
Mesenteric glands
728
Multipolar nerve-cells
740
Mesentery.
452, 472
Muscle-plasma ....
235
colic .
452, 454, 483
Muscles: — striped in general
227
. 452
action
237
Meso-caeoum
452, 478
attachments
229
Mesocephalon .
767, 769
appendages
238
Mesoblast .
. 1007
239
Meso-colon
452
containing aponeuroses, of
i6.
Mesoderm
1007
contractility
236
Meso-rectum
484
development . . 23
6, 1040
Metacarpo -phalangeal sheath
329
228
Metacarjius
111
form ....
•6.
Metagastrula .
1007
380
Metatarsus
148
in Birds
378
Middle cerebellar peduncle
771
229
951
lymphatics
. 716
septum of nose .
522
239
774
nomenclature
229
Milk
999
physico-chemical properties
235
Milk-fountains .
711
physiological properties
236
Mitral valves .
590
preparation of
239
Mixed nerves
804
preservation of
. 242
Modiolus .
948
. 229
Molar glands
398, 438
serous bursse of
239
teeth
420, 426, 430
situation
. 228
Monorchids
962
227
Monro, foramen of
75, 789, 790
. 231
Mons veneris
. 1003
Morgagni, caecum of .
401
membranes of .
. 239
hydatid of
982
tendons and aponeuroses
. 232
937
tissue
. 231
ventricles of
535
. 237
Morsus diaboli .
989
vessels and nerves
235
Morula
. 1007
volume
227
Motor end-plate
235
unstriped . . . S
127, 394
Motores oculorum nerve
812
283
Mouth
. 396
accelerator urinae
. 971
development of .
1046
adductor of arm
315
in general
. 423
brevis
. 355
Mucous derma .
393
magnus
335
corium
.'6.
parvus
. 355
membrane
ib.
. 351
of bladder .
. 576
. 355
541
magnus
. 352
479
277
of cheeks .
398
321
of Fallopian tubes
990
246
of guttural pouches
956
annulus albidus
930
952
antea-spinatus .
312
479
997
small
473
323
of larynx .
534
of phalanges . C
24, 363
of lips
397
gracilis
. 350
lymphatics in
715
. 349
of mouth .
423
327
of oesophagus
448
907
olfactory .
523
533
of pharynx
442
arytasno-oesophageal .
449
526
attollens anticus
281
of soft palate
411
282
of stomach
460
posticus
283
of tongue .
402
azygos uvulae
410
539
basio-glossus
404
of tympanum
955
351
INDEX.
1071
PAGE 1
PAGB
Muscles, biceps rotator tibialis . . 351 |
Muscles, flexor brachii
317
317
metacarpi externum
327
brachialis anticus
318
internus
328
bronchial
541
327
277
metatarsi . . . .
365
bulbo-cavernous
971
pedis ... 3
30, 370
319
accessor i us .
371
320
30, 370
parvum
ib.
perforatus . . 3
28, 369
253
fronto-palpebral
279
cervico-auriculaies
283
gastric ....
459
ciliaris
930
gastrocnemius .
367
409
gastrocnemius exlernus
ib.
265
369
complexus major
248
gemelli of pelvis
358
249
of tibia
367
S
73, 274
358
972
genio-glossus
405
ib.
hyo-glossas
ib.
969
288
middl
J 444
gluteus externus
344
ib.
346
second middle
ib.
*.
ib.
gracilis . . • .
353
995
great adductor, of thigh
355
vulvae, anterior .
997
256
ib.
complexus ,
248
315
. 260
ib.
. 404
corrugator supercilii .
279
. 301
961
of head
. 250
ciico-arytsenoideus lateralis
533
. 269
posticus
532
. 305
449
serratus
. 296
pharyngeus
444
supermaxillo-nasalis .
. 278
• thyroideus
532
heart, of .
. 593
349
humeralis externus
. 318
350
obliquus .
ib.
curvator coccygis
273
. 532
961
404
deep flexor of phalanges
330, 370
longus
ib.
gluteus
. 346
pharyngeus
. 444
pectoral .
293
hyo-thyroideus
. 532
deltoid
311
hyoideus magnus
. 288
depressor coccygeiis
273
parvus
ib.
labii inferioris .
276
289
283
iliac psoas ....
. 269
diaphragm
308
iliacus ....
t6.
digastricus
286
ilio-spinalis
263
. 278
. 313
»6.
intermediate posterior.
. 277
transversalis
. 279
internal flexor of metacarpus
. 328
erector coccygeus
. 273
297
penis
973
. 303
. 323
obturator .
. 357
obliquus
. 324
285
pedis
324, 363
vastus
. 350
. 376
interossei ....
342
digitorum
ib.
250
suffraginis .
. 326
. 272
external flexor of metacarpu
327
ib.
. 297
. 250
. 301
intestinal . . . 473,
183, 484
. 357
intrinsic of tongue
. 403
pterygoid .
. 285
. 485
. 350
ischio-cavernosus
973
extrinsic of tongue
404
. 274
. 349
. 356
■ fleshy panniculus
.
. 243
. 973
1072
INDEX.
Muscles, kerato-hvoideus
288
Muscles, pericardium
labiahs . ' .
274
peristaphyleus externus
280
in tern us
large extensor of forearm
319
peroneus .
533
extensor of phalanges . C
26, 364
4
lateralis sterni .
296
Phillips, of
260
levator anguli scapulae
246
popliteus ....
humeri
254
labii superioris alaequi nasi
278
minor
propnus .
276
posterior constrictor of vulv£
menti
277
palati . .
410
942
ulnaris
levatores costarum
298
protractor of sheath .
lingualis ....
406
403
parvus
311
pterygoideus externus .
adductor of leg .
353
internus
extensor of forearm
319
317
pterygo-pharyngeus .
258
quadratus cruralis
263
lumborum .
longus colli
258
lumbrici ....
. 342
oculi
masseter ....
284
of sheath .
«6.
rectus
humeralis .
. 254
maxillo-labialis .
276
capitis anticus major
mento-labialis .
ib.
minor
middle constrictor of pharynx
444
extensor of forearm
. 320
gluteus
. 246
lateralis
mylo-hyoideus .
. 286
femoris
nasalis brevis labii superioris
. 276
oculi externus .
i6.
oblique extensor of metacarpus
. 324
. 327
posterior .
of phalanges
. 371
superior
250
parvus
inferior
ib.
retraheutes aurem
superior
. 251
. 301
sacro-coccygeal .
. 303
coccygeus inferior
oculi inferior
940
superior
ib.
obturator externus
. 357
lumbalis .
ib.
sartorious .
. 288
oesophageal
449
scapulo-humeralis gracilis
orao-brachialis .
. 315
oris ....
274
scuto-auricularis externus
. 279
internus .
orbito-palpebralis
942
panuiculus carnosus .
. 243
seraispinalis of back and loin
palato-glossus .
. 406
colli .
t09, 443
dorsi.
staphylinus
. 410
palmaris magnus
. 328
parotido-auricularis .
. 283
pectineus ....
. 355
posticus .
pectoralis anticus . . '
292, 293
short abductor of arm .
magnus
. 293
1-6.
extensor of forearm
transversus . . '
292, 293
pedal ....
. 376
perforans . . . . '
530, 370
perforatus . . . i
528, 369
anterior serrated.
INDEX.
1073
Muscles, small complexus
extensor of forearm
hyo-glossus
lateral rectus
oblique of abdomen
of head
posterior rectus
serrated
psoas
. scapulo-humerahs
supermaxillo-nasalis
soleus
sphincter ani
vaginae
spinalis colli
splenius
of loins
stapedius .
sterno-aponeuroticus
costales
humeralis .
hyoideus
maxillaris .
prescapularis
thyro-hyoideus
trochineus .
stomach, of
stylo-glossus
hyoideus
maxillaris .
pharyngeus
subcutaneous of neck
sublimis of phalanges
subscapularis
subscapulo-hyoideus
superficial gluteus
flexor of phalanges
pectoral
superior constrictor of pharynx
superior longitudinal oesophageal
supermaxillo-labialis
supei-naso-labialis
supra-spiuatus .
suspensory, of «ye
temporalis.
tempoi-o-auricularis externus
internus
tensor fascia latae
palati
tympani
vaginae femoris
teres externus .
internus
major
minor
thyro-arytsenoideus
pharyngeus
tracheal
transversalis abdominis
costarum
hyoidei
nasi .
transverse of abdomen
spinous of back and loins
transversus perinaei
trachelo-mastoideus
trapezius .
triangularis sterni
PAGE
249
321
406
257
303
251
252
262
271
316
278
368
485
995
250
265
246
271
955
293
298
293
225
255
295
255
293
459
404
410, 444
253
328
314
256
344
328, 369
292
444
449
276
278
312
939
285
282
283
349
410
955
349
311
315
.•6.
312
532
444
538
305
265
289
279
305
265
972
249
260
Muscles, triceps abductor femoris
brachialis .
extensor brachii
femoris
trochlearis
tympani secundaria
ureters, of
urethral sphincter
uterus, of .
vagina, of .
vastus externus .
internus
vulva, anterior constrictor
posterior .
Wilson's muscle .
zygomatico-auricularis
zygomatico-labialis
zygomaticus
Muscular cell-fibres .
fibre
insertions, table of
lamina
tissue
non-striped
striped
of heart
Musculi papillares
pectinati .
Musculus ciiiaris
Riolani
Myeloplaxes
Myolemma
Myosine .
Nasal cavities
duct
meatuses .
Navicular sheath
Nerve-cells
corpuscles
fibres
tubes
Nerves : — animal, of .
cerebro-spinal
cranial
distribution
division
ganglionic .
general sensibility
mixed
motor
organic life, of
origin
preterminal peripheral loops of
special sense
structure
termination
vegetative life, of.
in Birds .
abducentes
accessory of external saphenous
of internal saphenoui
of pneumogastric
acromial .
anal .
angularis .
anterior brachial
femoral
PAGB
351
319, 320
319
349
940
952
575
971
995
350
ib.
997
ib.
576, 971
281
275
ib.
505
4,231
380
1032
231
lb.
ib.
592
589
930
942
4, 18
231
236
519
945
519
520
331
740
740
4
740
804
ib.
ib.
805
804
804
804
ib.
ib.
ib.
805
807
804
518,
804
894
825
879
875
841
856
858
861
864
875
1074
INDEX.
PAGE
Nerves, anterior gluteal . , .877
Nerves, latissimus dorsi branch
palatine .
817
levator anguli scapulae
tibial
879
832
lumbar
auricular, anterior
830
lumbo-sacral
middle
ih.
ib.
862
brachial .
860
superior .
ib.
buccal
819
cardiac
891
mental.
cervical
829, 854
musculo-cutaneous
8
821, 829
ciliary
. 823
862
nasal
clavicular .
856
obturator .
coccygeal .
859
occipito-styloid ,
32, 951
collateral-dorsal .
869
crural
875
internal .
cubito-cutaneous
865
866
Cyon's
841
superior .
dental
17, 821
olfactory ,
anterior
818
ophthalmic of Willis
817
optic
posterior .
ib.
orbita»
841
palatine, anterior
diaphragmatic .
56, 859
digastric .
829
digital .
867
palmar
856
palpebro-nasal .
collateral .
869
pathetic! .
825
popliteal .
879
saphenic .
880
facial
25, 830
petrosal, great deep
875
superficial
femoro-popliteal, great
878
small deep .
small
879
frontal
815
pharyngeal
8
832
phrenic
8
gluteal, anterior
877
8
posterior .
ib.
external
878
ib.
internal
il
827
pneumogastric .
gustatory ,
820
popliteal, external
858
hypoglossal
842
875
mollis
ilio-muscular
877
posterior palatine
inferior maxillary
818
iufra-orbital
ib.
816
pudic, internal .
857
rachidian .
357
tibial
internal
ib.
radial
861
recurrent .
877
oesophageal
internal pterygoid
820
pudic
858
respiratory
859
rhomboideal
833
sacral
— lachrymal
816
saphenous, external
laryngeal, external
837
accessoiy
8
838
internal
superior ,
837
INDEX.
1075
Nerves, sciatic, great .
PAGE
. 878
1 Nostrils, functions of .
PAGE
. 519
small
877
Notochord
. 1013
. 861
Nucleated nerve-fibres
740
small sciatic
. 877
Nuclei of corpus striatum .
792
superficial petrosal
829
740, 762
. 817
spinal ....
. 853
Obturator foramen
129, ISO
841
Occipito-atloid siuus .
. 692
splanchnic, great
. 892
Ocular membrane
938
lesser
ib.
sheath
ib.
817
(Esophageal groove
. 467
stylo-'hyoid
. 829
(Esophagus
447
subclavian
. 873
course
ib.
862
form
ib.
. 821
450
suboccipital
. 854
448
864
relations .
447
subzygomatic
. 820
structure .
. 448
superficial temporal
ib.
Oken's bodies .
. 1049
. 837
Olfactory apparatus .
523, 924
maxillary .
315, 816
cells
523, 925
supra-orbital
. 816
786
864
lobules
785, 786, 809
. 820
nerves
809
middle deep
. 819
Omasum ....
468
ib.
structure .
. 469
. 820
Omentum, gastro-colic
453, 459
temporo-auricularis .
ib.
452, 459
teres major
864
453, 503
. 862
great
453, 459
ib.
Omphalo-mesenteric vessels .
1023, 1042
superior
. 861
Ophthalmic nerve
815
tibial, anterior .
. 879
Optic bulb . ■ .
. 786
. 881
770, 810
tracheal, recurrent
. 838
ib.
trifacial ....
813
nerves
ib.
ib.
934
trochlearis
. 812
thalami
772
829
Ora serrata
930, 934
tympano-lingual
B21, 829
Orbiculare, os .
. 954
ulnar ....
. 865
Orbital cavity .
926, 938
vagus ....
834
Organ of Corti .
. 951
. 853
of Jacobson
521
vestibular . . . . :
m, 951
989, 1050
Vidian .
823
Organic life, nerves of
739, 746, 804
Wrisberg, of . , .
827
Organs ....
5
Nerve-tubes of spinal cord .
761
392
Nerve colline ....
235
ib.
glands ....
579
solid
. 394
740
394, 395
sheath ....
739
Os externum
992
Nerve-tissue ....
5
. 954
Nervous system ....
738
ib.
ib.
uteri . . . .
ib.
of Birds .
894
Osseous labyrinth
947
Nervi cardiaci . . . . .
596
Ossicula auditus
. 953
803
Ossification, centres of
20
Neural arch ....
167
Osteo-dentine . . . .
414
Neuraxis ......
1033
167
Neurilemma .... 7
41, 803
Osteogeny . . . .
19
Neurility
743
Osteology . . . .
7
Neuroglia . . . . 5, 7
41,759
Ostium abdominalis .
. 923
Nodule of Arantius . . , .
589 i
ib.
Nodus encephali . . . .
767
Otoconites . . . .
. 950
Nomenclature in myology .
229
Otoliths
tb.
392 j
Ova of Birds . . . .
. 1009
Non-medullated fibres
740
Ovaries
. 984
Nostrils 5
18, 519
986, 1050
framework of .
518
986
1076
INDEX.
Ovaries, situation
. 984
Pelvis, in general
»6.
Penis
Oviducts
. 989
Peptic glands . . . .
Ovisacs ....
. 985
Perforans tendon, sheath of
development
986
Pericardium . . . .
rupture .
ib.
muscle of .
. 985
Perilymph . . . .
Ovula Nabothi .
. 993
Perimysium . . . .
Ovulum ....
986, 1004
Perinseum
. 1004
aponeuroses of .
Ovum , . . .
986
Perineurium . . . .
Periople . . . . .
74
Pacchionian glands
. 751
Perioplic ring . . . .
Pacinian corpuscles
. 807
Periorbita . . . .
Palate . . . 396,
424, 427, 428
Periosteum . . . .
hard . . 334.
424, 427, 428
Peritoneum
. 400
structure of
structure .
ib
Perivascular canals .
71
soft . . . . 408,
424, 427, 428
Perspiration
411
Perspiratory ducts
. 409
glands
structure .
. 408
Pes anserinus .
Palatine glands .
438
Palatum molle .
. 408
Petrosal sinuses
Palmar arch
660
Peyer's glands ,
Palpebrae ....
. 942
Phalanges
Palpebral sinuses
. .-6.
Pharyngeal arches
Pampiniform plexus .
. 965
Pancreas ....
. 502
clefts
development
. 1049
Pharynx ....
excretory apparatus .
503
502
functions .
. 503
. 502
functions .
situation .
ib.
structure .
ib.
relations .
Pancreatic ring . .
ib.
Panniculus adiposus .
. 899
Phillip's muscle
Papilla conica ,
934
Phrenic centre .
Papilla ....
. 393
Pia mater ....
of foot
. 912
cranial
of skin
900, 902
spinal
of tongue .
. 402
Pigment cells .
calyciformes
402, 923
Pigmentary corpuscles of horn
capitata .
ib.
circumvallatse .
ib.
granules .
filiformes .
ib.
Pigmentum nigrum
fossulate .
402
Pillars of diaphragm .
fungiformes
402,, 923
ib.
posterior .
Parieto-occipital lobe .
. 788
of heart .
Parielo-temporal confluents .
. 694
of inguinal canal
lobe .
. 788
of rumen .
Paroophoron
. 989
of soft palate
Parotid duct
. 435
434, 439, 440
Parovarium
. 988
of tongue, anterior
Pars iridica retinae
. 933
Passage plaits .
. 785
Pineal gland
Paihetici nerves
. 812
Pisiform tubercle
Pavilion of Fallopian tube .
. 989
Pituitary fold of dura mater
Pecklin's glands
475
gland
Pecquet, cistern of
. 721
Pectinated ligament .
. 929
Pectoral cavity .
. 542
nerves of .
Pedunculi cerebelli .
767, 771
stem
cerebri
767, 770
Placenta ....
." 101
Pelvis ....
. 127
structure of
difference in sexee
. 134
multiple .
INDEX.
1077
PAGK
Placenta, simple .... 1030
Precrural glands
Plantar arcade or arch
•
640
Preparation :— arteries .
910
anterior tibial .
lb.
structure of
911
axillary
910
brachial .
866
reticulum .
6
99, 913
head, of .
Pleurae
543
iliac, internal
544
structure .
ib.
popliteal .
Pleuritis, effusion of .
545
posterior tibial ,
Pleuro-peritoneal cavity
1013
fissure
ib.
tibial, anterior .
Plexus, general anatomy
fi
05, 886
annularis .
929
articulations
anterior auricular
830
atlo-axoid ,
892
brachial .
854, 860
chondro-costal
837, 839
chrondo-sternal .
carotid .
. 889
capillary, of lungs
550
costo-vertebral .
887
coxo-femoral
cervical, deep .
854
ib.
fii-st interphalangeal
choroides .
792
humero-radial .
cerebellar .
779
coronary (venous)
699, 700
interphalangeal, first .
facial
826, 830
. 892
guttural .
887
hepatic
892
pelvis
893
lumbo-aortic
892
second interphalangeal
. 874
spine, of .
. 715
mesenteric, anterior
892
. 893
vertebrae .
myenteric .
. 477
. 965
• pelvic
. 893
bronchi ....
• pharyngeal
i
533, 889
cerebro-spinal axis, envelopes of
699
choroid coat
renal
. 892
solar, nerve
ib.
cranial nerves .
699
eye
892
subzygomatic .
'. i
$26, 830
genital organs, male .
superficial cervical
854
892
great sympathetic nervous system
sympathetic
. 886
heart ....
tracheal .
. 890
498
hoof
682
intestines ....
vertebral .
. 890
lachrymal apparatus .
Plicae palmatae .
. 1000
larynx ....
Pneumogastric lobule .
782
liver ....
Podophyllous tissue .
. 913
lumbo-sacral plexus .
Pons Tarini
. 770
lungs ....
Varolii .
?67, 769
lymphatics
Popliteal glands
. 727
maxillary gland .
Portio dura
. 825
mouth ....
832
muscles ....
Porus opticus .
. 928
abdominal region, inferior
Pouches, guttural
. 956
alveolo-labialis .
Poupart's ligament
302
Praeputial glands
976
crural region
Praeputium clitoridis .
. 995
Precervical nerve
885
brachial region, anterior
584,
1078
INDEX..
PAGE 1
PAGE
Preparation, muscles, brachial region,
Primitive groove . . • .
1013
posterior
buccinator . . . .
319 I
1011
277
trace
1010
cervical region, inferior
253
Primordial kidneys . . . .
1049
superior
244
Processes e cerebello ad testes
771
costal region
296 1
Promontory of ear . . . .
952
crural region
848
Pronucleus, female . . . .
1006
anterior
»6.
male . . . . .
ih.
353 !
Properties of nervous system
743
351 1
Prostate gland .
973
308 1
«6.
external scapular region
310 i
Protometra
969
eye
939 :
Protoplasm
3
941 !
Protuberantia annularis
767
facial . . . .
274 i
Pro toverte brae .... 103
2, 1038
femoral region, anterior
348 !
Pulmonary artery
607
351 j
heart ....
587
flexor, short, of forearm
318
lobes ....
545
323 1
547
gluteal region .
344
opening of heart
588
286 1
pleura ....
547
299
tissue ....
ih.
cervical
253
vesicles ....
548
268
Puncta lachrymalia .
945
314
Punctum caecum
934
274
Pupil
932
leg . ......
362
Pupillary membrane .
933
268
sphincter
' ib.
284
Purkinje's axis-cylinder
740
243
cells ....
782
posterior brachial region
319
Pylorus A
t57, 458
scapular region, external
310
Pyramidal eminence of os pedis
. 116
314
Pyramids of the bulb .
. 768
spinal region of back an
loins
260
Racemose glands . . . .
595, 407
sublumbar region
268
Rachidian bulb
. 767
. 244
Radiant crown of Reil
. 795
284
Raphe of scrotum
. 962
518
Receptaculum chyli
. 721
447
Recto-vesicle fold
969
orbital cavity
. 938
Rectum .....
. 484
osseous labyrinth
947
attachment
ib.
palate ....
399
. 1047
soft ....
. 408
484
. 494
ib.
parotid gland
. 434
Recurrent sensibility
744
pericardium
597
Red nuclei of Stilling
. 782
pharynx ....
. 441
Reflex power ....
. 746
. 933
Reil, band of ... .
771
soft palate
. 408
radiant crown of
. 795
spinal cord
. 754
Reissner, membrane of
. 950
spleen ....
494
Remak, band of ...
740
455
Renal glomerules
. 572
. 436
pelvis ....
. 570
• sympathetic nervous system
. 885
Reservoir of thymus gland .
. 556
thoracic duct
721
Respiratory apparatus
. 517
tongue ....
trachea ....
400
of Birds
557
. 536
of Mammifers
. 517
. 568
nerves
808
veins ....
685
Retemirabile . . 676,677,679,
680, 717
Prepuce
. 976
Malpighi ....
. 903
of clitoris ....
. 995
680
Preservation of muscles
. 242
testis ....
. 963
Prickle-cells ....
. 903
Reticular layer of the derma
. 900
Primitive aortae
. 1041
Reticulum ....
. 466
band of Remak .
. 740
467
chorion ....
. 1018
processigerum
699
eye-vesicles
. 1035
Retina
933
fasciculus o . .
. 231
Retrossal process of os pedis
. 116
INDEX.
1079
PAGE 1
PAGE
Rhomboidal sinus .... 1033 1
Sheaths, lymphatic .
. 716
Ribs ....
94
329
Right auricle of heart
.
589
. 331
ventricle „
587
ocular
82, 938
Rima glottidis .
535
penis, of .
975, 976
Ring, inguinal .
303
perforans tendon, of .
. 331
pancreatic
.
502
. 739
589
tarsal
371
Rings of trachea
537
Shell, egg, of . . .
. 1009
Rivinian ducts ,
438
ib.
Rolando, gelatinous substance
of
759
Shoulder, bones of
98
Root of lungs
540, 546
Sigmoid gyrus .
785
Rosenmiiller, organ of
989, 1050
valves
589, 591
Rudimentary sinuses of dura
matei
. 692
Simple follicles .
. 474
Rumen
464
glands
. 395
structure of
466
Sinus ampuliaceous
. 1030
. 950
Sacculus of ear
952
aortici
608
Sacral nerves
858
circularis iridis .
. 931
Sacrum
39
901
Salivary glands
. 433
lactiferus .
. 998, 1000
development of
1047
. 969
433,
435,^
t37, 438
renalis
. 570
lobules
433
rhomboidalis
776, 1033
Saphena veins .
710
, 1042
Sarcolemma
231
Valsalva .
. 608
Sarcous elements
f
231, 236
Sinuses, structure of .
. 683
Scala, auditive .
. 950
affluents of
. 694
collateral .
951
aortic
. 608
ib.
. 692
tympanic .
i
)50, 951
dura mater, of .
690
vestibular
ib.
. 692
proper
. 951
ib.
Schindylesis
. 177
effluents of
694
Schneiderian membrane
. 523
692
925
ib.
Schwann, white substance oi
740
ib.
Sclerotica
. 927
petrosal .
ib.
Sclerotic cleft .
. 1036
ib.
Scrotum .
. 961
. 525
Scutiform cartilage
. 281
693
Sebaceous glands
901
ib.
Secondary dentine
414
transverse
. 692
Segments of Weismann
. 593
galactophorous .
998
Segmentation of vitellus
. 1004
head, of .
524
. 1006
. 526
Semen
. 966
functions of
ib.
Semicircular anastomoses
. 640
525
band
772
ib.
canals
. 948
maxillary, inferior
ib.
. 814
ib.
589
mucous membrane of
526
Semilunar crest of pedal bon
. 116
sphenoidal
ib.
fibro-cartilages .
. 216
lymphatic
. 719
Seminiferous tubes
963
I)alpebral .
. 941
Sensitive-motor centre
745
renal
. 570
Sensorial functions
. 746
. 776, 1033
Septum auricularum .
587
535
.
789, 791
subepiglottic
ib.
pectiniforme
. 974
terminalis
. 1042
scroti
. 961
Valsalva, of
608
— ventriculorum
587
Skeleton ....
8
Serous bursse
. 239
Skin ....
. 898
membrane
. 394
904
Sertoli, cells of
964
. 898
Sesamoid bones
. 115
epidermis .
898, 903
Sharpey's perforating fibres
17
foetus, of .
. 1037
Sheaths, arteries of
602, 605
definitive . .
ib.
hair of
. 907
functions .
. 904
1080
INDEX.
PAGE
Skin, structure . . . 900, 903
Stomach in orifices . . ,
PAGB
. 458
Small intestines
. 471
situation .
456
Smegma piaeputii
. 976
. 459
Smell, apparatus of
. 924
Carnivora
. 463
Socia parotidis .
441
Pig . . . .
t6.
Soemmering, foramen
of '.
. 947
Rabbit
ib.
Soft palate
.408,
424, 427, 428
Ruminants
ib.
Sole of hoof <r^
Solid organs ■ 4V
916
470
. 394
Subarachnoid fluid
. 752
f \
394, 395
Subarytaenoid sinus
. 535
Solitary glands .
474, 479
Subcorneous integument
911
Somatpleure
. 1014
Subcutaneous region .
. 227
Speculum Helmontii
308
Subepiglottic sinus .
. 535
Spermatic cord .
9
62, 965
Subhepatic veins
. 498
Spermatogonia .
964
Subiculum
792
Sphenoidal lobe .
785
Sublingual crest
. 400
Sphincter ani .
485
gland
437, 439
933
Sublobular veins
498, 500
vaginse
995
Sublumbar reservoir .
721
Spinal arachnoid
751
Submaxillary gland .
436, 439, 440
canal
747
Subpodophyllous reticulum .
. 913
754
Subsphenoidal confluents
. 694
external conformation (
f
ib
Substantia ferruginea .
782
general view of .
754
. 759
757
ostoidea .
. 414
756
Suburethral notch
. 975
structure
759
Succus prostaticus
. 973
volume
756
Sudoriparous glands .
. 901
weight
ib.
Sulci horizontalis
. 779
749
bupra-renal capsules .
. 578
marrow
739
development
. 579
nerves
853
. 578
constitution
ib.
functions .
. 579
854
. 578
pia-mater .
753
situation .
ib.
1013
ib.
Spine, the, in general
42
Supra-sphenoidal appendage
. 773
Splanchnology .
392
Suspensory ligament of fetlock
206
Splanchnopleure
1014
penis
974, 976, 983
Spleen
503
. 976
attachment
ib.
uterus
. 990
development
1049
Sylvius, fissure of
. 785
direction .
503
Sympathetic nervous system
. 885
form
ib.
. 886
507
structure .
ib.
relations .
503
Symphyses
. 177
ib.
Synarthroses
. 176
structure .
. 504
. 177
503
Synovia ....
175, 239
Splenic corpuscles
505
Synovial capsules
»6.
pulp
.'6.
fossae
172
Spongy horn-substance
761
. 175
portion of urethra
971
membranes
. 239
Spontaneous voluntary movement.
745
sheaths
ib.
Stapes ....
954
villi
lib
Staphyline glands
438
Systole of heart
. 598
Stars of Verheyen
573
Steno's duct
435
Tactile corpuscles
. 807
canal
521
Taenia hippocampi
. 791
Stilling, red nucleus of
782
semicircularis .
772. 792
Stomach in Solipeds .
455
Tail
. 904
1047
Tapetum lucidum
930, 931
456
fibrosum .
t6.
form
ib.
Tarin, valves of
778, 779
462
Tarsal sheath .
. 371
interior
458
Tarsi ....
942
ligaments .
459
Tarsus ....
144
mucous membrane
460
Taste, apparatus of
. 922
muscular n
membrane
459
Teats ....
. 997
INDEX.
1081
PAGE
PAGE
Teeth ....
411
Thoracic, affluents, termination . . 722
characters of
. 412
: varieties in
ib.
414, 1047
Thorax ....
92, 542
412
190, 193
eruption of
. 1048
. 544
external conformation
. 412
in general .
193
structure .
ib.
internal conformation ^^
542
. 427
ib.
Pig .
»6.
Thymic ducts ^^T
556
Ruminants
. 424
Thymus gland .
555
Solipeds .
416
1046
Tegumentary membranes
5
556
Temporal fossa .
83
structure .
ib.
lobe . . .
785, 787
Thyroid cartilage
529
Tela choroidea .
. 792
Thyro-hyoid membrane
. 530
Tendinous centre
. 308
Thyroid gland .
553
592
554
. 239
ib.
synovial membranes .
ib.
Tibial aponeurosis
362
Tendo-Achilles .
. 368
Tissues .
4
Tendons ....
. 232
Toe- stay .
917
anterior extensor of metacar
pus . 323
Tongue
400,
424,4
128, 432
es . 301
401
330
development of .
. 1046
extensor pedis .
. 324
functions of
. 407
s . 327
muscles of.
. 403
. 365
pillars of .
. 401
hock
. 367
ib.
ib.
structure of
. 402
. 261
Tonsils
401
large extensor of forearm
. 319
. 782
lateral extensor of phalange
326
Torcular Herophili .
692
320
Trabeculae of spleen .
504
oblique flexor
. 327
testis
. 963
perforatus
328, 369
Trachea .
536
330, 370
course
ib
prepubic .
. 301
development
. 1046
Tentorium cerebelli . .
. 750
536
Tentacula
904, 906
relations .
ib.
Tergal zone
. 1011
structure .
537
Terminal genital corpuscles .
. 975
Trace, primitive
1010
motor plate
235, 806
Tracheal glands ,
539
vessels
. 603
Tractus longitudinalis.
790
Testaceous membrane .
. 1009
810
Testes cerebelli .
771
respirator! us
808
. 984
Transverse sinuses
692
tubercula .
. 771
Tricuspid valves
588
Testicles ....
960, 962
Trifacial nerve .
813
attachment of .
960
Trigeminii
ib.
descent of .
. 966
Trigone
576
. 966, 1051
Trigonum vesica
ib
ectopise of
962
Trisplanchnic system .
885
. 960
Trochlea .
176
. 962
Trochlearis nerve
812
. 966
Tuber annulare .
769
structure of
962
cinerium .
773
Testicular cord .
ib.
Tubercula nates
771
Thalami optici .
'. 767, 772
ib.
'i'hebesius, valve of
• 590
testes
ib.
Theca vertebralis
. 749
Tuberculum Loweri .
590
Thiernesse's muscle .
. 326
Tubular glands .
395
Third ventricle of brain
. 744
Tubuli seminiferi
963
Thoracic aorta .
. 610
uriniferi .
571
cavity
. 542
Tuft of chin
397
duct.
. 721
Tunic of plantar cushion
911
. 724
Tunica abdominalis
99, 300
. 721
adventitia .
605
extent
ib.
albuginea of ovary
984
ib.
of testicle .
962
1082
INDEX.
PAGE
Tunica, erythroides .
961
Vaginal synovial membrane
granulosa ....
. 987
Valsalva, sinus of . . .
. 604
Valves, Bauhin, of
.•6. 1
Ruyschiana
. 931
Eustachian
. 960
ilio-caecal .
communis .
»6.
(6.
lymphatic
t6.
vasculosa testis .
. 964
mitral
Tiirc's fasciculus
758
Renault, of
Tympanal circle
. 952
semilunar .
Tympanic scala . . . .
949
sigmoid
Tympanum . . . .
952
Tyson's glands . . . .
. 901
Thebesius, of
Ultimate follicles
. 433
veins, of .
Umbilical cord . . . .
1017, 1025
Vieussens, of
arteries . . . .
. 1025
vulvo-vaginal .
region . . . .
451
. 1025
Valvulae conniventes .
Varolii, pons
vesicle . . . 1014
, 1016, 1023
Vasa afferentia .
Unipolar nerve-cells .
. 740
etferentia .
Uniting tube of kidney
. 572
Unitive fibres of heart
594, 595
recta
Unstriped muscular fibres .
394
Urachus. ....
1021, 1050
of veins
Ureters . . . •
. 574
ib.
Vascular blood glands
ib.
Vas deferens
structure .
ib.
structure of
. 575
Vegetative life, nerves of
. 574
Veins : — definition
Urethra ....
. 578
disposition .
970
course
ib.
form .
interior
ib.
ib.
injection of .
structure .
. 971
female, of ,
996
abdominal, subcutaneo
us
Urethral ridge .
970
alveolar .
. 975
Urinary apparatus
. 568
Uro-genital sinus
. 1051
vena cava .
Uterine glands .
. 993
auricular, anterior
tubes .
. 989
. 990
structure .
. 989
basilic
Uterus ....
990
basium vertebrarium
attachment
ib.
. 993
form.
. 990
buccal
functions .
. 993
caecal
interior .
. 992
cardiac
masculine .
. 969
. 990
structure .
. 992
Utricular glands
993
central of foot .
Utriculus of ear.
. 949
of retina .
Uvula of cerebellum .
. 969
. 782
colic.
Vagina ....
. 993
collateral, of cannon, e
xternal
. 995
internal conformation .
. 994
coronary .
situation .
993
great
structure .
994
small
Vaginal bulb
sheath
. 996
of foot
. 960
INDEX.
1083
PAGE 1
PAGE
Veins, dental, inferior . . .690
Veins, portal . . . . .
705
688
posterior cardinal
1044
703
701
digital
dorsal
90, 698
vena cava ... 70
3, 1044
686
prepubic
709
688
690
ductus venosus .
1044
pulmonary . . . .
685
707
pyloric
707
facial . . .
688
radial, anterior ... 6
96, 697
femoral
709
posterior . . . .
967
ib.
697
Galeni
694
707
gastric, anterior
707
saphena, external
710
ib.
internal
ib.
gastro-epiploic, left
706
solar ....
699
right
707
spermatic ....
707
706
splenic . . . . .
706
right
707
spur. „ . „ . .
696
gluteal
708
subcutaneous, abdominal
711
709
internal . . . .
697
haemorrhoidal .
706
696
humeral .
696
sublingual.
689
. 709
705
common .
. 708
submaxillary
688
709
696
ib.
690
ilaco-femoral
ib.
superficial temporal . . 6
87, 689
iliaco-muscular .
ib.
686
. 706
690
. 689
superficial . . 6
87, 689
interlobular of liver
705
708
686
Thebesii ....
685
maxillary .
. 687
thoracic, external
686
thoracic .
686
internal .
ib.
709
thyroid ....
689
. 697
710
intra-lobular, of liver
. 495
posterior .
ib.
intra-osseous, of foot
702
697
. 687
1044
588, 689
. 698
709
708
690
Vena azygos ....
. 686
lumbar
. 708
Galeni .
. 694
mammary, internal
. 686
portae
705
maxillary, internal
387, 690
. 1042
maxillo-muscular
. 687
ib.
. 694
vertebral .... 6
id, 1044
697
cava, anterior
686
. 706
posterior . . . 7(
)3, 1044
ib.
: Velum interpositum . . . '
f'84, 792
meseraic, anterior
ib.
pendulum palati
. 408
metacarpal, external
ib.
vasculosum
792
.
696, 698
Velvety tissue of foot .
912
internal .
ib.
Vena azygos, great
. 686
metatarsal
. 710
small
ib.
. 711
ib.
710
posterior .
. 703
ib.
! Galeni ....
394, 789
^^ nasal
. 688
portae ....
705
709
Venae comites ....
. 684
occipital .
palatine
pancreatic
peripheral
phrenic
plate
ib.
. 931
. 1042
Ventricles of brain . .771,774,
?76, 790
689
cerebellar .
. 776
, 707
. 699
fourth
790
774
703
lateral
789, 790
689, 697
middle
774
699
. 776
.
. 709
i third
. 774
1084
INDEX.
PAGE
PAGB
Ventricles of thalami optic . . 774
Vitreous humour . . .
. 937
of heart .
587, 590
Viscera
392
535
Visceral 'pleura . . . .
543
^'entricular arachnoid
790
Vision, apparatus of .
. 925
584
Vocal cords . . . .
. 530
Vermiform appendix .
492
superior .
. 531
processes of cerebellum
779
Voluntary movements
746
ib.
Vulva
995
posterior
ih.
cavity of .
.•6.
Vermis of cerebellum .
ib.
external opening of .
«6.
Vertebrae .
24
structure . . . .
. 996
ib.
Vulva of brain .
. 803
proper to .
26
Vulva, labia .
. 995
development
2
6, 1038
26
Wall of hoof .
. 915
Vertebral column
24
angle of .
. 917
development of
1038
structure of
•6.
167
Weismann, segments of
593
1032
Wharton's duct .
. 437
Vertebro-costal channels
512
gelatine of
. 1025
Veru montanum
969
White line of hoof .
. 920
Vesicle, serous .
1016
substance of Schwann .
740
ib.
. 759
Vesicles, Graafian
i
m, 986
longitudinal fibres of brain
. 776
548
ib.
Vesicula seminalis tertia
969
Wilson's muscle
971, 983
Vesiculae seminales
968
Winepress of Herophilus
. 692
Vestibular scala
950
Winslow, foramen of .
. 453
Vestibule of ear
949
Wirsung, duct of
. 503
Vibratile cilia .
393
Wolffian bodies .
1049, 1050
Vibrissa .
527
Wrisberg, nerve of
. 827
Vicq-d'Azyr, caecum of
778
centrum ovale of
. 795
Xiphoid appendage of sternum
93
Vidian canal
829
nerve
Villi, intestinal .
»6.
823
473
Yolk of egg
Yolk nucleus .
. 1009
. 1006
Villosities
393
Villo-papillae of foot .
912
Zona pellucida ...
. 1005
Villous loops of foot .
ib.
Zonula ciliaris .
930, 931
Vitellus .
986, 1003
of Zinn
930, 934
Vitreous body .
. 937
Zoiisperma
. 966
(4)
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