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(

MANUAL

Practical Anatomy

The Late D. J. GUNNINGHAM

M.D. (EDIN. ET DUBL.). D.SC.. LL. D. (ST. AND. ET GLAS.), D.e.L. (0X0N.), F.R.S.,
LJiTE PROPESSOR 0F ANATOMY IN THE UNIYERSITY OF EDINBURGH

FIFTH EDITION

EDITED BY ARTHUR ROBINSON

PROPESSOR OF ANATOMY IN THE UNIYERSITY OF EDINBURGH

VOLUME SEGOND
THORAX; HEAD AND NECK

WITH 236 ILLUSTRATIONS

NEW YORK
WILLIAM WOOD AND GOMPANY

MDCCCCXII

PREFACE TO FIFTH EDITION

E main object of this preface is to thank those who have
kindly assisted me in the produetion of the booL At the
le time, it may be pointed out that the reasons for the
)ption of the Basle nomenelature were fully stated in vol. i.,
1 that the alterations whieh have been made in the plans
disseetion in vol. ii. are not less numerous than those made
vol. i. The alterations inelude ehanges in the method of
seeting the face, the posterior triangle, and the deeper
ts of the neek. Two plans of disseetion to display the
ddle ear and its surroundings are deseribed. They ean be
ried out on opposite sides of the head, and the steps of
i seeond method are those followed by the surgeon operat-
; for the relief of mastoid and middle ear disease. The
seetion of the thorax has been very largely re-arranged
h the object of giving the disseetor an opportunity of
dying the relative positions of the organs in the medi-
inum whilst they are praetieally undisturbed.
The various plans of disseetion deseribed were deeided
)n, ter many trials, as those best adapted to give the
dent a elear idea of the relative positions of important
letures ; and I am greatly indebted to my iirst and seeond
istants, Dr. E. B. Jamieson and Mr. T. B. Johnston, and
Professor R. B. Thomson of Cape Town, for the trouble
y have taken and the help they have given in devising,
difying, and testing new plans of work.
I am indebted also to Dr. Jamieson for disseetions of the
in and heart ; to Mr. Johnston for the disseetions of the
otid gland; to Mr. W. W. Carlowfo^"* '^'«seetion of the
diastinum ; and .to Messrs. M. B" "^. Rogers,

vi PREFACE TO FIFTH EDITION

and F. M. Halley for other disseetions upon whieh they
have expended time and skill, and whieh have been used
in the preparation of the new illustrations.

I wish also to thank Professor Arthur Thomson for per-
mission to use the illustrations of his beautiful disseetions of
the eye ; Professor A. M. Paterson for permission to use two
diagrams illustrating the eonneetions of some of the eranial
nerves ; and Dr. Logan Turner for the loan of the speeimens
from whieh the illustrations of the disseetion of the mastoid
region and middle ear were made.

All the new illustrations are from drawings made by Mr.
J. T. Murray. They are eharaeteristie of his excellent work,
and I am indebted to him for the eare and skill he has ex-
pended on their produetion.

The new indiees and the glossary are the work of Mr. J.
Keogh Murphy, F.R.C.S. I beHeve they will prove to be of
great service ; and I desire to thank him not only for the
time and trouble he has spent upon them, but also for many
useful suggestions whieh he has made during the progress of
the work.

ARTHUR ROBINSON.

Edinburgh, July 1912.

eONTENTS

Introdcctory,
Thoragig Wall,

THORAGie CaVITY,

Thoracic Joints,

THORAX-

1:2

HEAD AND XECK.
Face and Prontal Region of Head.

SlDE OF THE NeCK,

POSTERIOR TRIANGLE,

THE ScALP AND THE SUPERFICIAL STRCCn;RE5 OF THE

Temporal Region, ....
The DissEenoN of the Back, .
Remoyal of the Brain, ....
The Anterior Part of the Negk,
Temporal and Ineratemporal Regions,
Submaxillary Region, ....
Orie Ganglion and Tensor Palati, .
The Great Yessels and Neryes of the Neck,
The Lateral Part of the Middle Cranial Possa.
Dissegtion of the Orbit,
Preyertebral Region, .
The Joints of the Neck,
Mouth and Pharynx, .
Garotid Ganal, .
Neryus Makillaris,
Nasal Gayities, .

142

161
200

222

265

279

292

294
325

■^ ■* -^

330
356
364

385
386

389

VIII

eONTENTS

Spheno - Palatine Ganglion and Internal Makillary

ARTERYj .......

The Larynx, .......

The Tongue, . . . . . ■ .

PAGE

402
406

429

ENGEPHALON— THE BRAIN.

Membranes and Blood Vessels of the Brain,
Base of Brain, .....
The Gerebrum, .....
The Mesengephalon, ....
Basal Ganglia of the Gerebral Hemispheres,
The Parts of the Brain whigh lie in the Posterior
Granial Fossa, ......

439

452

459
506
512

520

THE AUDITORY APPARATUS.

EXTERNAL MeATUS, ....

Membrana Tympani,

Tympanig Gayity or Middle Ear,

AUDITORY OsSIGLES, ....

AUDITORY TUBE, .....

Intrapetrous Part of the Facial Nerve and the AeusTie

Nerve, . . ...

Yestibulum, .....

Ganales Semicirculares Ossei,
The Cochlea, .....

547
549

550

555
559

562

566
567
567

BULBUS OeULI.

General Strugture of the Eyeball, . . -571

The Sglera, .....

572

The Gornea, ....

573

TuNiCA Vasculosa OeuLi,

574

The Retina, ....

579

The Vitreous Body,

581

Lens Grystallina,

■ 583

Ghambers of the Eyeball,

. 584

DEX,

585

A GLOSSARY

OF THE

INTERNATIONAL (B.N.A.)
ANATOMIGAL TERMINOLOGY

GENERAL TERMS.
Terms indigating Situation and Direction.

Longitudinalis

Verticalis

Posterior

Yentral

Dorsal
Granial

Gaudal
Superior

Inferior
Proximalis

Distalis
Sagittalis

Frontalis

Longitudinal

Yertieal

Anterior 'i
Posterior /
Yentral

Dorsal
Granial

Gaudal
Superior'

Inferior .
Proximal

Distal
Sagittal

Prontal

}

Referring to the long axis of the lxxly.

{Referring to the position of the long
axis of the body in the ereet posture.
r Referring to the front and baek of the
^^ body or the limbs.

{Referring to the anterior and posterior
aspeets, respectively, of the body,
and to the flexor and extensor
aspeets of the limbs, respectively.
rRe^erring to position nearer the head
J or the tail end of the long axis.
1 Used only in reference to parts of
l the head, neek, or body.
Used in reference to the head, neek,
and body. Equivalent to eranial
and eaudal respectively.
rUsed only in reference to the limbs.
-! Proximal nearer the attaehed end.
l Distal nearer the free end.
'Used in reference to planes parallel
with the sagittal suture of the
skull, i.e, vertical antero-posterior
planes.

{Used in reference to planes parallel
with the eoronal suture of the skull,
ue. transverse vertical planes.

GLOSSARY

Horizontalis

Medianus
Medialis

Lateralis

Intermedius

Superiieialis

Profundus

Externus

Internus
Ulnaris

Radialis
Tibial

Fibular

Horizontal

Median
Medial ^

Lateral ,

Intermediate

Superficial 1
Deep /

External

Internal
Ulnar \

Radial/
Tibial \

Fibularj

{Used in reference to planes at right
angles to vertical planes.
/Referring to the median vertical
l antero-posterior plane of the body.
/'Referring to struetures relatively
nearer to or further away from the
median plane.
Referring to struetures situated be-
tween more medial and more
lateral struetures.

{Referring to struetures nearer to and
further away from the surface.
{Referring, with few exceptions, to the
walls of cavities and hoUow organs.
Noi to be used as synonymous with
medial and lateral.
{Used in reference to the medial and
lateral borders of the forearm,
respectively.
rUsed in reference to the medial and
J lateral borders of the leg, re-
[ spectively.

THE BONES.

B.N.A. Terminology.
YertebrsB

Fovea eostalis superior

Fovea eostalis inferior

Fovea eostalis transversalis
Radix areus vertebrae

Atlas

l?ovea dentis

Epistroplieas
Dens

Stemum

Gorpus sterni
Proeessus xiphoideus
Ineisura jugularis
Planum sternale

Ossa Granii.

Os frontale

Spina frontaIis
Proeessus zygomaticus
Facies eerebralis
Facies frontalis

Old Terminology.
YertebraB

Ineomplete facet for head of rib,

upper
Ineomplete facet for head of rib,

lower
Facet for tuberele of the rib
Pediele

Atlas

Facet for odontoid proeess

Axis

Odontoid proeess

Sternum

Gladiolus
Ensiform proeess
Supra-sternal noteh
Anterior surface

Bones of Skull.

Prontal

Nasal spine

External angular proeess
Internal surface
Erontal surface

GLOSSARY

B.N.A. Terminology.

Os parietale

Lineae temporales
Suleus transversus
Suleus sagittalis

Os oeeipitale

Ganalis hypoglossi
Foramen oeeipitale magnum
Ganalis eondyloideus
Suleus transversus
Suleus sagittalis
Clivus

Linea nuehse suprema
Linea nuehae superior
Linea nuehae inferior

Os sphenoidale

erista infratempora1is

Suleus ehiasmatis

Grista sphenoidalis

Spina angularis

Lamina medialis proeessus ptery-

goidei
Lamina lateralis proeessus ptery-

goidei
Ganalis pterygoideus [Vidii]
Fossa hypophyseos
Suleus earotieus
Gonehae sphenoidales
Hamulus pterygoideus
Ganalis pharyngeus
Tubereulum sellae
Fissura orbitalis superior

Os temporale

Ganalis facialis [Fallopii]
Hiatus eanalis facialis
Vagina proeessus styloidei
Ineisura mastoidea
Impressio trigemini
Eminentia areuata

Suleus sigmoideus
Fissura petrotympaniea
Fossa mandibularis
Semieanalis tubse auditivae

Os ethmoidale

Labyrinthus ethmoidalis
Lamina papyraeea
Proeessus uneinatus

Old Tkrmi.sdlogy.

Parietal

Temporal ridges
Groove for lateral sinus
Groove for sup. long. sinus

Oeeipital

Anterior eondyloid foramen
Foramen magnum
Posterior eondyloid foramen
Groove for lateral sinus
Groove for sup. long. sinus
Median part of up{>er surface ()f

basi oeeipital
Highest curved line
Superior curved line
Inferior cur\'ed line

Sphenoid

Pterygoid ridge
Optie groove
Ethmoidal erest
Spinous proeess
Internal pterygoid plate

External pterygoid plate

Vidian eanal
Pituitary fossa
Cavemous groove
Sphenoidal turbinal bones
Hamular proeess
Pterygo-palatine eanal
01ivary eminenee
Sphenoidal fissure

Temporal Bone

Aqueduct of P'alloi^ius

Hiatus P'allopii

Vaginal proeess of tympanie bone

Digastrie fossa

Impression for Gasserian ganglion

Eminenee for sup. semieireular

eanal
Eossa sigmoidea
Glaserian fissure
Glenoid cavity
Eustaehian tube

Ethmoid

Lateral mass
Os planum
Unciform proeess

X]l

GLOSSARY

B.N.A. Terminology.

Os laerimale

Hamulus laerimalis
Grista laerimalis posterior

Os nasale

Suleus ethmoidalis

Maxilla

Facies anterior
Facies infra-temporalis
Sinus maxillaris
Proeessus frontalis
Proeessus zygomaticus
Ganales alveolares
Ganalis naso-laerimalis
Os incisivum
Foramen incisivum

Os palatiham

Pars perpendieularis
Grista eonehalis
Grista ethmoidalis
Pars horizontalis

Os z7gomaticam

Proeessus temporalis
Proeessus fronto-sphenoidalis
Foramen zygomatico-orbitale
Foramen zygomatico-faciale

Mandibala

Spina mentalis
Linea obliqua
Linea mylohyoidea
Ineisura mandibulse
Foramen mandibulare
Ganalis mandibulae
Protuberantia mentalis

Old Terminology.

Laelirymal Bone

Hamular proeess
Laehrymal erest

Nasal Bone

Groove for nasal nerve

Saperior Ma^illary Bone

Facial or external surface
Zygomatic surface
Antrum of Highmore
Nasal proeess
Malar proeess
Posterior dental eanals
Laerimal groove
Premaxilla
Anterior palatine foramen

Palate Bone

Vertical plate
Inferior turbinate erest
Superior turbinate erest
Horizontal plate

Malar Bone

Zygomatic proeess
Frontal proeess
Tempora-malar eanal
Malar foramen

Inferior Masillary Bone

Genial tuberele or spine
External oblique line
Intemal oblique line
Sigmoid noteh
Inferior dental foramen
Inferior dental eanal
Mental proeess

The SkuU as a Whole.

Ossa suturarum

Foveol3e granulares (Paeehioni)

Fossa pterygo-palatina

Ganalis pterygo-palatinus

Foramen laeerum

Ghoanae

Fissura orbitalis superior

Fissura orbitalis inferior

Wormian bones
Paeehionian depressions
Spheno-maxillary fossa
Posterior palatine eanal
Foramen laeerum medium
Posterior nares
Sphenoidal fissure
Spheno-maxillary fissure

GLOSSARY

XIII

B.N.A. Tesmin'ology.

Claviciila

Taberositas eoiaeoidea
Taberositas eostalis

Seapola

Ineisura seapularis
Angulus lateralis
Angulus medialis

Hiunenu

Suleus intertubereularis
Grista tubereuli majoris
Grista tubereuli minoris
Facies anterior medialis
Facies anterior lateralis
Mai^o medialb
Margo lateralis
Suleus nervi radialis
Gapitulum

Epieondylus medialis
Epieondylus lateralis

Ulna

Ineisura semilunaris
Ineisura radialis
Grista interossea
Facies dorsalis
Facies Yolaris
Facies medialis
Margo dorsalis
Margo Yolaris

Badius

Tuberositas radii
Ineisura ulnaris
Grista interossea
Facies dorsalis
Facies volaris
Facies lateralis
Margo dorsalis
Margo Yolaris

Garpns

Os navicalare

Os Innatam

Os trignetmm

Os mnltangnlnm majns

Os mnltangnlnm minns

Os eapitatnm

Os hamatnm

Old Tlkminouigy.
Clavicle

Impressioo for eonoid ligament
Impression for rhomboid ligament

Seapnla

Supra-seapular noteh
Anterior or lateral angle
Superior angle

Hnmenu

Bieipital grooYe

Extemal lip

Intemal lip
Internal surface
£xtemal surface
Intemal border -
£xtemal border
Museulo-spiral groove
Gapitellum
Intemal eondyle
£xtcmal eondyle

Ulna

Greater sigmoid cavity
Lesser sigmoid cavity
£xternal or interosseous border
Posterior surface
Anterior surface
Internal surface
Posterior border
Anterior border

Radins

Bieipital tuberosity

Sigmoid cavity

Internal or interosseous border

Posterior surface

Anterior surface

External surface

Posterior border

Anterior border

Garpns
Seaphoid
Semilnnar
Cnneiform
Trapezinm
Trapezoid
Os magnnm
nnciform

XIV

GLOSSARY

Lower Extremity.

B.N.A. Terminology.

OS C0X8B

Linea glutsea anterior
Linea glutaea posterior
Linea terminalis
Spina isehiadiea
Ineisura isehiadiea major
Ineisura isehiadiea minor
Tubereulum pubieum
Ramus inferior oss. pubis
Ramus superior oss. pubis
Ramus superior ossis isehii
Ramus inferior oss. isehii
Peeten ossis pubis
Facies symphyseos

Pelvis

Pelvis major

Pelvis minor

Apertura pelvis minoris superior

Apertura pelvis minoris inferior

Femur

Fossa troehanteriea
Linea intertroehanteriea
Grista intertroehanteriea
Gondylus medialis
Gondylus lateralis
Epieondylus medialis
Epieondylus lateralis

Tibia

Gondylus medialis
Gondylus lateralis
Eminentia intereondyloidea
Tuberositas tibige
Malleolus medialis

Fibala

MalleoKis lateralis

Old Terminology.

Innominate Bone

Middle curved line
Superior curved line
Margin of inlet of true pelvis
Spine of the isehium
Great saero-seiatie noteh
Lesser saero-seiatie noteh
Spine of pubis
Deseending ramus of pubis
Aseending ramus of pubis
Body of isehium
Ramus of isehium
Pubie part of ilio-peetineal line
Symphysis pubis

Pelvis

False pelvis
True pelvis
Pelvic inlet
Pelvic outlet

Femar

Digital fossa

Spiral line •

Post. intertroehanterie line

Inner eondyle

Outer eondyle

Inner tuberosity

Outer tuberosity

Tibia

Internal tuberosity
External tuberosity
Spine
Tuberele
Internal malleolus

Fibala

External malleolus

Bones of the Foot.

Talas
Galeaneas

Tuber ealeanei

Proeessus medialistuberis ealeanei
Proeessus lateralis tuberis ealeanei
.Os caneifonne primam
Os caneiforme seeandam
Os caneiforme tertiam

Astragalas
Os ealeis

Tuberosity of
Inner
Outer

Inner caneiform
Middle caneiform
Onter caneiform

GLOSSARY

THE LIGAMENTS.
LigamentB of the Spine.

RN.A. Terminology. Old Tf.rminoi.(k;y.

Lig. longitndinale anterios

Lig. longitndinale posterius

Lig. flava

Membrana teetoria

Artieulatio atlanto-epistrophiea

Lig. alaria

Lig. apieis dentis

Anterior eommon ligament
Posterior eommon ligament
Ligamenta subflava
Posterior occipito-axial ligament
Joint between the atlas and the axis
Odontoid or eheek ligaments
Suspensory ligament

The Bibs.

Lig. eapituli eostae radiatum
Lig. stemo-eostale interartieulare
Lig. stemo-eostalia radiata
Lig. costoxiphoidea

Anterior costo-vertebral or stellate

ligament
Interartieular ehondro-stemal liga-

ment
Anterior and posterior ehondro-

stemal ligament
Chondro-xiphoid ligaments

Lig. temporo-mandibulare
Lig. spheno-mandibulare
Lig. stylo-mandibulare

The Jaw.

External lateral ligament of the jiiw
Internal lateral ligament of the jaw
Stylo-maxillary ligament

Upper £xtremity.

Lig. costo-claviculare

Labrum glenoidale

Artieulatio radio-ulnaris proximalis

Lig. eollaterale ulnare

Lig. eollaterale radiale

Lig. annulare radii

ehorda obliqua

Artieulatio radio-ulnaris distalis

Diseus artieularis

Reeessus sacciformis

Lig. radio-earpeum volare

Lig. radio-earpeum dorsale

Lig. eollaterale earpi ulnare

VOL. II — b

Rhomboid ligament

Glenoid ligament

Superior radio-ulnar joint

Intemal lateral ligament of elbow-

joint
External lateral ligament
Orbieular ligament
Oblique ligament of ulna
Inferior radio-ulnar joint
Triangular fibro-cartilage
Membrana sacciformis
Anterior ligament of the radio-

earpal joint
Posterior ligament of the

earpal joint
Internal lateral ligament of

wrist joint

radio-

the

XVI

GLOSSARY

B.N.A. Terminology.
Lig. eollaterale earpi radiale

Artieulationes interearpse
Lig. aeeessoria voIaria

Lig. eapitulorum (oss.

palium) transversa
Lig. eollateralia

metaear-

Old Terminology.

External lateral ligament of the

wrist joint
Garpal joints
Palmar ligaments of the metaearpo-

phalangeal joints
Transverse metaearpal ligament

Lateral phalangeal ligaments

The Lower Extremity.

Lig. areuatum

Lig. saero-tuberosum

Proeessus falciformis
Lig. saero-spinosum
Labrum glenoi<3ale
Zona orbieularis
Ligamentum iIiofemorale
Lig. isehio-eapsulare
Lig. pubo-eapsulare
Lig. popliteum obIiquum
Lig. eollaterale Abulare
Lig. eollaterale tibiale
Lig. popliteum areuatum
Meniseus lateralis
Meniseus medialis
Pliea synovialis patellaris
Pliese alares

Artieulatio tibio-fibularis
Lig. eapituli fibulae

Syndesmosis tibio-fibularis

Lig. deltoideum

Lig. talo-fibulare anterius

Lig. talo-fibulare posterius

Lig. calcaneo-fibulare

Lig. talo-ealeaneum laterale

Lig. talo-ealeaneum mediale

Lig. calcaneo-navicuIare plantare

Lig. talo-naviculare

Pars calcaneo-navicularis "1 lig.

-bifur-
Pars ealeaneo-euboidea I eatum

Subpubie ligament

Great saero-seiatie ligament

Falciform proeess
Small saero-seiatie ligament
Gotyloid ligament
Zonular band
Y-shaped ligament
Isehio-eapsular band
Pubo-femoral ligament
Ligament of Winslow
Long external lateral ligament
Internal lateral ligament
Areuate popliteal ligament
External semilunar eartilage
Internal semilunar eartilage
Lig. mueosum
Ligamenta alaria
Superior tibio-fibular artieulation
Anterior and posterior superior

tibio-fibular ligaments
Inferior tibio-fibular artieulation
Internal lateral ligament of ankle
Anterior fasciculus of external

lateral ligament
Posterior fasciculus of external

lateral ligament
Middle fasciculus of external lateral

ligament
External ealeaneo-astragaloid liga-

ment
Internal ealeaneo-astragaloid liga-

ment
Inferior calcaneo-navicuIar ligament
Astragalo-seaphoid ligament
Superior ealeaneo-seaphoid liga-

ment
Internal ealeaneo-euboid ligament

GLOSSARY

XVII

THE MUSGLES.
Masdes of the Baek.

Snperfici&l.

B.N.A. Terminology.
Levator seapulse

OLD Tf.KMINOU)GT.

Levator anguli scapulx

Serratus anterior

Masdes of the dhest,

Serratus magnus

Mnseles of Upper Ertremity.

Bieeps braehii

Laeertus fibrosus
Braehialis
Trieeps braehii

Caput mediale

Caput laterale
Pronator teres

Gaput ulnare
Braehio-radialis
Supinator

Extensor earpi radialis longus
Extensor earpi radialis brevis
Extensor indieis proprius
Extensor digiti quinti proprius
Abduetor pollieis longus
Abduetor pollieis brevis
Extensor pollieis brevis
Extensor pollieis longus
Lig. earpi transversum
Lig. earpi dorsale

Bieeps

Bieipital fascia
Braehialis antieus
Trieeps

Inner head

Outer head
Pronator radii teres

Goronoid head
Supinator longus
Supinator brevis
Extensor earpi radialis longior
Extensor earpi radialis brevior
Extensor indieis
Extensor minimi digiti
Extensor ossis metaearpi pollieis
Abduetor pollieis
Extensor primi internodii pollieis
Extensor seeundi internodii pollieis
Anterior annular ligament
Posterior annular ligament

Museles of Lower Eztremity.

Tensor fasciae latae

Ganalis adduetorius (Hunteri)

Trigonum femoraIe (fossa Searpae

major)
Ganalis femoralis
Annulus femoralis
M. quadriceps femoris —

Reetus femoris

Vastus lateralis

Vastus intermedius

Vastus medialis

M. artieularis genu
Tibialis anterior

Tensor fasciaj femoris
Hunter's eanal
Searpa's triangle

Grural eanal
Grural ring
Quadriceps —

Reetus femoris

Vastus externus

Grureus

Vastus internus

Suberureus
Tibialis antieus

XVIII

GLOSSARY

B.N.A. Terminology.

Tendo ealeaneus
Tibialis posterior
Quadratus plantae
Lig. transversum eruris
Lig. erueiatum eruris
Lig. laeiniatum
Retinaeulum museulorum

nseorum superius
Retinaeulum museulorum

naeorum inferius

pero-

Old Terminology.

Tendo Aehillis

Tibialis postieus

Aeeessorius

Upper anterior annular ligament

Lower anterior annular ligament

Internal annular ligament

External annular ligament

Axial Museles.
Museles of tlie Baek.

Serratus posterior superior
Serratus posterior inierior

Serratus postieus superior
Serratus postieus inferior

Splenius cervicis

Splenius eolli

Saero-spinalis
Ilio-eostalis—

Ereetor spinse
Ilio-eostalis —

Lumborum

Saero-lumbalis

Dorsi

Aeeessorius

Cervicis

Cervicalis aseendens

Longissimus —
Dorsi

Longissimus —

Dorsi

Cervicis

Transversalis cervicis

Capitis
Spinalis —

Dorsi

Traehelo-mastoid
Spinalis—

Dorsi

Cervicis

Colli

Capitis
Semispinalis —
Dorsi

Cervicis

Colli

Capitis
Multifidus

Complexus
Multifidus spinpe

Museles of Head and Neek.

Epieranius
Galea aponeurotiea
Proeerus

Pars transversa (nasalis)
Pars alaris (nasalis)
Aurieularis anterior
Aurieularis posterior
Aurieularis superior
Orbieularis oeuli
Pars laerimalis

Occipito-frontalis
Epieranial aponeurosis
Pyramidalis nasi
Oompressor naris
Dilatores naris
Attrahens aurem
Retrahens aurem
AttoUens aurem
Orbieularis palpebrarum
Tensor tarsi

GLOSSARY

XIX

B.N.A. Terminology.

Triangularis

Quadratus labii superioris —

Gaput zygomaticum

Gaput infraorbitale

Gaput angulare
Zygomaticus
Ganinus

Quadratus labii inferioris
Mentalis
Platysma
Stemo-thyreoid
Thyreo-hyoid

Old Tekminology.
I>epressor anguli oris

Zygomaticus minor

Levator labii su()erioris

Levator labii su()crioris alxt)uc nasi

Zygomaticus major

Levator anguli oris

Depressor labii inferioris

Levator menti

Plat}'sma myoides

Stemo-thyroid

Thyrohyoid

Moseles and Fascia of the Orbit.

Fascia bulbi Gapsule of Tenon

Septum orbitale Palpebral ligaments

Reetus lateralis
Reetus medialis

Reetus externus
Reetus internus

Museles of the Tongue.

Genio-glossus Genio-hyo-glossus

Longitudinalis superior Superior lingualis

Longitudinalis inferior Inferior lingualis

Transversus linguse Transverse fibres

Verticalis linguoe Yertieal fibres

Pharyngo-palatinus
M. uyulse

Levator veli palatini
Tensor veli palatini
Glosso-palatinus

Museles of the PhaiTni.

Palato-pharyngeus
Azygos uvul?e
Levator palati
Tensor palati
Palato-glossus

Deep Lateral Museles of Neek.

Sealenus anterior Sealenus antieus

Sealenus posterior Sealenus postieus

Longus eapitis Reetus eapitis antieus major

Reetus eapitis anterior Reetus eapitis antieus minor

Museles of Thorax.

Transversus thoraeis
Diaphragma pars lumbalis

Crus mediale

Crus intermedium

Crus laterale
Areus lumbo

(Halleri)
Areus lumbo

(Halleri)

eostalis medialis

Triangularis sterni
Diaphragm, lumbar part —

Crura and origins from areuate
ligaments

Ligamentum areuatum internum

eostalis lateralis Ligamentum areuatum externum

GLOSSARY

Museles of the Abdomen.

B.N.A. Terminology.

Ligamentum inguinale (Pouparti)
Ligamentum laeunare (Gimbernati)
Eibrae intererurales
Ligamentum inguinale reflexum

(Gollesi)
Annulus inguinalis subeutaneus

Crus superius

Crus inferius
Falx aponeurotiea inguinalis
M. transversus abdominis
Linea semieireularis (Douglasi)
Annulus inguinalis abdominalis

Old Terminology.

Poupart's ligament
Gimbernat's ligament
Intereolumnar fibres
Triangular fascia

External abdominal ring

Internal pillar

External pillar
Conjoined tendon
Transversalis musele
Fold of Douglas
Internal abdominal ring

Perineuin and Pelvis.

Transversus perinei superficialis
M. sphineter urethrae membranaeeae
Diaphragma urogenitale

Fascia diaphragmatis urogenitalis

superior
Fascia diaphragmatis urogenitalis

inferior
Areus tendineus fasciae pelvis
Ligamenta puboprostatiea

Fascia diapbragmatis pelvis superior
Fascia diaphragmatis pelvis inferior

Transversus perinei

Gompressor urethrge

Deep transverse musele and sphine-

ter urethrse
Deep layer of triangular ligament

Superficial layer of the triangular

Ugament
White line of pelvis
Anterior and lateral true ligaments

of bladder
Visceral layer of pelvic fascia
Anal fascia

THE NERYOUS SYSTEM.

Spinal Gord.

Fasciculus anterior proprius (FIech-

sig)
Fasciculus lateralis proprius
Nueleus dorsalis
Pars thoraealis
Suleus intermedius posterior
Golumnse anteriores, ete.
Fasciculus eerebro-spinalis anterior
Fasciculus eerebro-spinalis lateralis

(pyramidalis)
P'aseieulus eerebello-spinalis
Fasciculus antero - lateralis super-

ficialis

Anterior ground or basis bundle

Lateral ground bundle
eiarke's eolumn
Dorsal part of spinal eord
Paramedian furrow
Anterior grey eolumn
Direet pyramidal traet
Grossed pyramidal traet

Direet eerebellar traet
Gowers' traet

GLOSSARY

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XXII

GLOSSARY

Brain.

B.N.A. Terminology.

Rliombeneeplialon

Eminentia medialis

Ala einerea

Ala aeustiea

Nueleus nervi abdueentis

Nuelei n. aeustiei

Fasciculus longitudinalis medialis

Gorpus trapezoideum

Ineisura eerebelli anterior

Ineisura eerebelli posterior

Suleus horizontalis eerebelli

Lobulus eentralis

Folium vermis

Tuber vermis

Lobulus quadrangularis

Braehium conjunctivum eerebelli

Lobulus semilunaris superior

Lobulus semilunaris inferior

Gerebram

Peduneulus eerebri
GoUieulus superior
Gollieulus inferior
Aqueductus eerebri

Foramen interventriculare

Hypothalamus

Suleus hypothalamieus

Massa intermedia

Fasciculus thalamo-mammillaris

Pars opereularis

Thalamus

Pallium

Gyri transitivi

Fissura eerebri lateralis

Gyrus temporalis superior

Gyrus temporalis medius

Gyrus temporalis inferior

Suleus eentralis (Rolandi)

Suleus temporalis superior

Suleus temporalis medius

Suleus eireularis

Suleus temporalis inferior

Gyrus fusiformis

Suleus interparietalis

Suleus eorporis eallosi

Suleus einguli

Fissura hippoeampi

Gvrus einguli

Old Terminology.

Eminentia teres

Trigonum vagi

Trigonum aeustieum

Nueleus of 6th nerve

Auditory nueleus

Posterior longitudinal bundle

Gorpus trapezoides

Semilunar noteh (of eerebellum)

Marsupial noteh

Great horizontal fissure

Lobus eentralis

Folium eaeuminis

Tuber valvul3e

Quadrate lobule

Superior eerebellar pedunele

Postero-superior lobule

Postero-inferior lobule

Grus eerebri

Anterior eorpus quadrigeminum
Posterior eorpus quadrigeminum
Iter e tertio ad quartum ventri-

eulum, or aqued. of Sylvius
Eoramen of Monro
Subthalmie region
Suleus of Monro
Middle eommissure
Bundle of Vicq d'Azyr
Pars basilaris
Optie thalamus
Cortex eerebri
Anneetant gyri
PMssure of Sylvius
First temporal gyrus
Seeond temporal gyrus
Third temporal gyrus
Eissure of Rolando
Parallel suleus
Seeond temporal suleus
Limiting suleus of Reil
Oeeipito-temporal suleus
Oeeipito-temporal convolution
Intraparietal suleus
Gallosal suleus
Galloso-marginal fissure
Dentate fissure
Gallosal convolution

GLOSSARY

XXIII

B.N.A. Terminology.

Stria temiinalis

Trigonum eollaterale

Hippoeampus

Digitationes hippoeampi

Fascia dentata hippoeampi

edumna fomicis

Septum pellueidum

Inferior eornu

Gommissura hippoeampi

Nueleus Ientiformis

Pars frontalis eapsulae intemie

Pars oeeipitalis eapsulae intemae

Radiatio oeeipito-thalamiea

Radiatio eorporis eallosi

Pars frontaIis

Pars oeeipitalis

Old Termingldgy.

Taenia semieireularis

Trigonum ventriculi

Hippoeampus major

Pes hippoeampi

Gyms dentatus

Anterior pillar of fornix

Septum lueidum

Deseending horn of lateral ventricle

Lyra

Lentieular nueleus

Anterior limb (of internal eapsule)

Posteriorlimb(ofinternaIcapsule)

Optie radiation

Radiation of eorpus eallusum

Forceps minor

Forceps major

Membranes of Brain.

Gisterna eerebello-medullaris
eisterna interpeduneularis
Granulationes araehnoideales
Tela ehorioidea ventriculi tertii
Tela ehorioidea ventriculi quarti

eisterna magna
Gisterna 1)asalis
Paeehionian bodies
Velum interpositum
Tela ehoroidea inferior

Gerebral Nerves.

N. oeulomotorius
N. troehlearis
N. trigeminus

Ganglion semilunare (Gasseri)

N. naso-eiliaris

N. maxillaris

N. meningeus (medius)

N. zygomaticus

Rami alveolares superiores pos-
teriores

Rami alveolares superiores medii

Rami aWeolares superiores an-
teriores

Ganglion spheno-palatinum

N. palatinus medius

N. mandibularis

Nervus spinosus

N. alveolaris inferior
N. abdueens
N. facialis
N. intermedius
N. aeustieus

Third nerve

Fourth nerve

Fifth nerve

Gasserian ganglion
Nasal nerve

Superior maxillary nerve
Reeurrent meningeal nerve
Temporo-malar nerve
Posterior superior dental

Middle superior dental
Anterior superior dental

Meekel's ganglion
External palatine nerve
Inferior maxillary nerve
Reeurrent nerve
Inferior dental

Sixth nerve

Seventh nerve

Pars intermedia of Wrisberg

Eighth or auditory nerve

XXIV

GLOSSARY

B.N.A. Terminology.

Ganglion superius
N. reeurrens
Ganglion jugulare
Ganglion nodosum
Plexus oesophageus anterior 1
Plexus oesophageus posterior J
Nervus aeeessorius
Ramus internus

Ramus externus

Old Terminology.

Jugular ganglion of 9th nerve
Reeurrent laryngeal nerve
Ganglion of root "^ ^
Ganglion of trunk j ^^ ^

Plexus gulse

Spinal aeeessory

Aeeessory portion of spinal

aeeessory nerve
Spinal portion

Spinal Nerves.

Rami posteriores

Rami anteriores

N. eutaneus eoUi

Nn. supraclaviculares anteriores

Nn. supraclaviculares medii

Nn. supraclaviculares posteriores

N. dorsalis seapulse

Nn. intereosto-braehiales

N. thoraealis longus

N. thoraeo-dorsalis

N. eutaneus braehii medialis

N. eutaneus braehii lateralis

Fasciculus lateralis
Fasciculus medialis
N. eutaneus antibraehii lateralis

N. eutaneus antibraehii medialis

Ramus volaris

Ramus ulnaris
N. eutaneus antibraehii dorsalis

N. axillaris

N. interosseus volaris

Ramus palmaris N. mediani

Nn. digitales volares proprii

Ramus dorsalis manus

Ramus eutaneus palmaris

N. radialis

N. eutaneus braehii posterior

N. eutaneus antibraehii dorsalis

Posterior primary divisions
Anterior primary divisions
Superficial cervical nerve
Suprasternal nerves
Supraclavicular nerves
Supra-aeromial nerves
Nerve to the rhomboids
Intereosto-humeral nerve
Nerve of Bell
Long subseapular nerve
Lesser internal eutaneous nerve
Gutaneous braneh of circumflex

nerve
Outer eord (of plexus)
Inner eord
Gutaneous braneh of museulo-euta-

neous nerve
Internal eutaneous nerve
Anterior braneh
Posterior braneh
External eutaneous braneh of mus-

eulo-spiral
Circumflex nerve
Anterior interosseous
Palmar eutaneous braneh of the

median nerve
GoUateral palmar digital branehes

of median nerve
Dorsal eutaneous braneh of ulnar

nerve
Palmar eutaneous braneh of ulnar

nerve
Museulo-spiral nerve

Internal eutaneous braneh of

museulo-spiral nerve
External eutaneous branehes of
museulo-spiral nerve

GLOSSARY

XXV

B.N.A. Tekminology.

Ramus superHeialis
N. interosseus dorsalis

Nn. digitales dorsales

N. ilio-hypogastrieus

Ramus eutaneus lateralis

Ramus eutaneus anterior

N. genito-femoralis

N. lumbo-inguinalis

N. spermatieus extemus

N. eutaneus femoris lateralis
N. femoralis
N. saphenus

Ramus infrapatellaris

N. isehiadieus

N. peronseus eommunis

Ramus anaslomotieus pero-
nseus

N. peronseus superHeialis

N. peromeus profundus
N. tibialis

N. eutaneus surse medialis
N. suralis

N. plantaris medialis
N. plantaris lateralis
N. pudendus

Old Terminology.

Radial nerve

Posterior interosseous nerve
Dorsal digital nerves
IIio-hyp<^astric nerve

Iliae braneh of ilio-hypogastrie

ncrvc
Hypogastrie braneh of ilio-
hypogastrie nerve
Genito-erural nervc

Grural braneh of genito-erural

nerve
Genital braneh of genito-erural
nerve
External eutaneous nerve
Anterior erural nerve
Long saphenous nerve

Patellar braneh of long saph-
enous nerve
Great seiatie nerve
External popliteal nerve

Nervus eommunieans tibularis

Museulo-eutaneous nerve

Anterior tibial nerve
Internal popliteal nerve

Nervus eommunieans tibialis
Short saphenous nerve
Internal plantar
External plantar
Pudie nerve

THE HEART AND BLOOD-VESSELS.

Heart.

Atrium

Aurieula eordis
Ineisura eordis
Trabeeulse earneae
Tubereulum intervenosum
Suleus longitudinalis anterior
Suleus eoronarius
Limbus foss3e ovalis
Valvula venae cavge
Valvula sinus eoronarii

Auriele

Aurieular appendix

Noteh at apex of heart

Golumnae earneae

Intervenous tuberele of Lower

Anterior interventricular groove

Auriculo-ventricular groove

Annulus ovalis

Eustaehian valve

Valve of Thebesius

XXVI

GLOSSARY

Arteries.

B.N.A. Terminology.

Sinus aortse

A. profiinda linguse

A. maxillaris externa

A. alveolaris inferior

Ramus meningeus aeeessorius

A. bueeinatoria

A. alveolaris superior posterior

Aa. alveolares superiores anteriores

Ramus earotieo-tympanieus

A. ehorioidea

A. auditiva interna

Rami ad pontem

A. perieardiaeo-phreniea
Rami intereostales
Truneus thyreo-cervicalis
A. transversa seapulae
A. intereostalis suprema
A. transversa eolli
A. thoraealis suprema
A. thoraeo-aeromialis
A. thoraealis lateralis
A. circumflexa seapulae
A. profunda braehii
A. eollateralis radialis

A. eollateralis ulnaris superior
A. eollateralis ulnaris inferior
Ramus earpeus volaris
Ramus earpeus dorsalis
Aa. metaearpege dorsales
A. volaris indieis radialis
Areus volaris superficialis
Areus volaris profundus
A. interossea dorsalis
A. interossea reeurrens

A. interossea volaris

Ramus earpeus dorsalis

Ramus earpeus volaris

Aa. digitales volares eommunes

Aa. digitales volares propriae

Arteriae intestinales

A. suprarenalis media
A. hypogastriea
A. umbiliealis
A. pudenda interna
A. epigastrioa inferior

Old Terminology.
Sinuses of Valsalva
Ranine artery
Facial artery
Inferior dental artery
Small meningeal artery
Bueeal artery
Posterior dental artery
Anterior superior dental arteries
Tympanie braneh of int. earotid
Anterior ehoroidal artery
Auditory artery
Transverse arteries (branehes of

Basilar artery)
Arteria eomes nervi phreniei
Anterior intereostal arteries
Thyroid axis
Supraseapular artery
Superior intereostal
Transversalis eolli
Superior thoraeie artery
Aeromio-thoraeie artery
Long thoraeie artery
Dorsalis seapulge
Superior profunda
Anterior braneh of superior pro-

funda
Inferior profunda
Anastomotiea magna
Anterior radial earpal
Posterior radial earpal
Dorsal interosseous arteries
Radialis indieis
Superficial palmar areh
Deep palmar areh
Posterior interosseous artery
Posterior interosseous reeurrent

artery
Anterior interosseous artery
Posterior ulnar earpal
Anterior ulnar earpal
Palmar digital arteries
GoUateral digital arteries
Intestinal branehes of sup. mesen-

terie
Middle eapsular artery
Internal iliae artery
Obliterated hypogastrie
Internal pudie artery
Deep epigastrie artery

GLOSSARY

XXVII

B.N.A. Terminology.

A. spermatiea externa
Aa. pudendae estemse

A. circuinflexa femoris medialis

A. circumflexa femoris lateralis

A. genu suprema

A. genu superior lateralis

A. genu supenor medialis

A. genu media

A. genu inferior lateralis

A. genu inferior medialis

A. malleolaris anterior lateralis

A. malleolaris anterior medialis

A, peronsea

Ramus perforans

A. malleolaris posterior lateralis
A. malleolaris posterior medialis
Rami ealeanei laterales
Rami ealeanei mediales
A. plantaris medialis
A. plantaris lateralis
Aa. metatarsese plantares
Aa. digitales plantares

Old Terminology.

Cremasteric artery

Superficial and deep extemal pudie
arteries

Intemal circumflex artery

External drcumflex artery

Anastomotiea magna

Superior extemal artieular artery

Superior intemal artieular artery

Azygos artieular artery

Inferior external artieular artery

Inferior intemal artieular artery

Extemal malleolar artery

Intemal malleolar artery

Peroneal artery

Anterior peroneal artery
Posterior peroneal artery

Intemal malleolar artery

Extemal ealeanean artery

Intemal ealeanean artery

Intemal plantar artery

External plantar artery

Digital branehes

Gollateral digital branehes

Yeins.

V. eordis magna

V. obliqua atrii sinistri

Lig. venae cavge sinistrae

Vv. eordis minimae

Sinus transversus

Confluens sinuum

Plexus basilaris

Sinus sagittalis superior

Sinus sagittalis inferior

Spheno-parietal sinus

V. eerebri internae

V. eerebri magna

V. terminalis

V. basalis

V. transversa seapulae

V. thoraeo-aeromialis

Vv. transversae eolli

V. thoraealis lateralis

V. azygos

V. hemiazygos

V. hemiazygos aeeessoria

V. hypogastriea

V. epigastriea inferior

V. saphena magna

V. saphena parva

Great eardiae vein
Oblique vein of Marshall
Vestigial fold of Marshall
Veins of Thebesius
Lateral sinus
Toreular Herophili
Basilar sinus

Superior longitudinal sinus
Inferior longitudinal sinus
Sinus alae parv8e
Veins of Galen
Vena magna Galeni
Vein of the eorpus striatum
Basilar vein
Supraseapular vein
Aeromio-thoraeie vein
Transversalis eolli veins
Long thoraeie vein
Vena azygos major
Vena azygos minor inferior
Vena azygos minor superior
Internal iliae vein
Deep epigastrie vein
Internal saphenous vein
External saphenous vein

XXVIII

GLOSSARY

Lymphaties.

B.N.A. Terminology. Old Terminology.

Gisterna ehyli Reeeptaeulum ehyli

THE YISGERA.

Digestive Apparatus.

Areus glosso-palatinus

Areus pharyngo-palatinus

GI. lingualis anterior

Duetus submaxillaris

Gl. parotis aeeessoria

Duetus parotideus (Stenonis)

Dentes praemolares

Dens serotinus

Papillge yallatae

Reeessus pharyngeus

Tela submueosa

Plieae eireulares

Gl. intestinales

Valvula eoli

Golumnae reetales

Plieae transversales reeti

Valvula spiralis

Noduli lymphatiei aggregati

(Peyeri)
Intestinum jejunum
Intestinum ileum
Noduli lymphatiei lienales

(Malpighii)

Anterior pillar of fauces
Posterior pillar of fauces
Gland of Nuhn
Wharton's duet
Soeia parotidis
Stenson's duet
Bieuspid teeth
Wisdom tooth
Circumvallate papillae
Lateral reeess of pharynx
Pharyngeal aponeurosis
Valvul£e conniventes
Grypts of Lieberkuhn
Ileo-oeeal valve
Golumns of Morgagni
Valves of Houston
Valves of Heister
Peyer's patehes

Jejunum

Ileum

Malpighian eorpuseles

Bespiratory

Laryiix

Prominentia laryngea

Ineisura thyreoidea superior

M. ary-epiglottieus

M. Yoealis

M. thyreo-epiglottieus

Appendix ventriculi laryngis

Pliea Yoealis

Pliea ventricularis

Ligamentum ventriculare

Ligamentum vocale

Glottis

Rima vestibuli

Gartilago thyreoidea

Apparatus.

Adam's apple

Superior thyroid noteh

Aryteno-epiglottidean musele

Internal thyro-arytenoid musele

Thyro-epiglottidean musele

Laryngeal sae

True vocal eord

False vocal eord

Superior thyro-arytenoid ligament

Inferior thyro-arytenoid ligament

Glottis vera

Glottis spuria

Thyroid eartilage

GLOSSARY

XXIX

B.N.A. Terminology.

Membrana hyo-thyreoidea
Gartilago eomieulata (Santorini)
Tubereulum epiglottieum
Pars intermembranaeea (rimae

glottidis)
Pars intereartilaginea (rimse

glottidis)
Gonus elastieus (membranae

elastieae larynges)
Glandula thyreoidea
Glomus earotieum

Nose

Goneha nasalis suprema (Santorini)
Goneha nasalis superior
Goneha nasalis media
Goneha nasalis inferior

Old Termin<>l<k;y
Thyro-hyoid membrane
Gartilage of Santorini
Gushion of epiglottis
Glottis Yoealis

Glottis respiratoria

Grieo-thyroid membrane

Thyroid gland
Interearotid gland or body

Highest turbinate bone
Superior turbinate bone
Middle turbinate bone
Inferior turbinate bone

Urogenital Apparatns.

Gorpuseula renis

Paradidymis

Appendix testis

Duetus deferens

Gl. urethrales

Glandula bulbo-urethralis (Gowperi)

FoIlicuIi oophori vesicuIosi

Gumulus oophorus

Tuba uterina

Epoophoron

Appendiees vesiculosi

Duetus epoophori longitudinalis

Orificium internum uteri

Orificium externum

Proeessus vaginalis

Glandula magna vestibuli

Malpighian eorpuseles

Organ of Giraldes

Hydatid of Morgagni (male)

Vas deferens

Glands of Littr^

Cowper*s gland

GraaHan foIIicIes

Diseus proligerus

FalIopian tube

Parovarium

Hydatids of Morgagni (female)

Gartner's duet

Intemal os (of uterus)

External os

Ganal of Nuek

Bartholin's gland

Peritoneuin.

Bursa omentalis
Eoramen epiploieum
Lig. phrenieo-eolieum
Excavatio reeto-uterina (cavum

Douglasi)
Lig. gastro-lienale

Lesser peritoneal sae
Eoramen of Winslow
Costo-colic ligament
Poueh of Douglas

Gastro-splenie omentum

SENSE ORGANS.
Tlie Eye.

Selera Selerotie eoat

Lamina elastiea anterior (Bowmani) Bowman's membrane

XXX

GLOSSARY

B.N.A. Terminology.

Lamina elastiea posterior (Des-

eemeti)
Spatia anguli iridis
Angulus iridis
Zonula eiliaris
Septum orbitale
Fascia bulbi

Gommissura palpebrarum lateralis
Gommissura palpebrarum medialis
Tarsus superior
Tarsus inferior
Lig. palpebrale mediale
Raphe palpebralis lateralis
Tarsal glaiads

Old Terminology.
Descemet*s membrane

Spaees of Fontana
Irido-eomeal junction
Zonule of Zinn
Palpebral ligament
Gapsule of Tenon
External eanthus
Internal eanthus
Superior tarsal plate
Inferior tarsal plate
Internal tarsal ligament
Extemal tarsal ligament
Meibomian glands

The Ear.

Ganalis semieireularis lateralis
Duetus reuniens
Duetus eoehlearis
Reeessus spherieus
Reeessus elliptieus
Paries jugularis
Paries labyrinthiea

Eenestra vestibuli

Eenestra eoehleae
Paries mastoidea

Antrum tympanieum
Paries earotiea
Proeessus lateralis
Proeessus anterior

External semieireular eanal
Ganalis reuniens
Membranous eoehlea
Fovea hemispheriea
Fovea hemi-elliptiea
Floor of tympanum
Inner wall

Eenestra ovalis

Eenestra rotunda
Posterior wall

Mastoid antrum
Anterior wall

Proeessus brevis (of malleus)
Proeessus graeilis

MANUAL

PRACTICAL ANATOMY.

THORAK.

nPHE disseetion of the thorax is eommeneed on the thirteenth
-^ day^ after the subject has been plaeed in the disseeting-
room. By that time the upper limbs have been detaehed
from the trunk.

In form, the thorax resembles a truneated eone. Anteriorly
and posteriorly it is Aattened ; laterally it is full and rounded.
During Hfe the movements of the thoraeie walls produee
alterations in the eapaeity of the ehest cavity, and play an
essential part in the function of respiration ; these movements
the student should study upon himself and his friends.

The thoraeie cavity is bounded anteriorly by the sternum
and eostal eartilages ; it is bounded posteriorly by the twelve
thoraeie vertebrae and the intervening fibro-cartilages, together
with the portions of the ribs whieh extend laterally from the
vertebral eolumn as far as the angles ; the lateral boundaries
are formed by the bodies of the ribs, from their angles
posteriorly to their anterior extremities anteriorly. These
parts eonstitute the framework of the thorax, and ean be
studied on the skeleton as well as upon the part before
the disseetion is eommeneed.

The anterior wall of the thorax is shorter than the posterior
wall and, during expiration, the upper margin of the sternum

^ Saturdays and Sundays are not eounted.

a THORAX

lies opposite the iibro-eartilage between the seeond and third
thoraeie vertebra, whilst the lower end of the body of the
sternum eorresponds in level with the middle of the body of the
ninth thoraeie vertebra. The bodies of the thoraeie vertebrse
project anteriorly into the cavity of the thorax, and greatly
diminish its antero-posterior diameter in ihe median plane ;
but the baekward sweep of the posterior portions of the ribs
produees a deep hollow on either side of the yertebral eolumn,
for the reeeption of the most massive part of the lung.

The superior aperture, in/e/ of the ihorax, is a narrow
opening whieh is bounded by the first thoraeie yertebra, the

ieal Domes of ihe Pleural Saes, and parts in rt

iirst pair of eostal arehes, and the manubrium sterni. The
plane of this opening is very oblique ; it slopes from the tirst
thoraeie vertebra anteriorly and downwards. Through the
inlet of the thorax the apiees of the lungs project upwards
into the root of the neek, and, between them, the follow-
ing struetures pass through it : — the windpipe, the gullet, the
vagi, the phrenie nerves, the left reeurrent nerve, the ganglion-
ated sympathetie trunks, the thoraeie duet, and the great
arteries and veins whieh earry blood to and from the head
and neek and the upper limbs.

The base or inferior end of the thoras is very wide,
and is sometimes ealled the outlei. Anteriorly it is bounded
by the xiphoid proeess, and posteriorly by the twelfth thoraeie
vertebra. Between these points the lower margin of the
thorax presents a curved outline. Starting from the sternum,
it passes downwards, laterally, and posteriorly, as far as Ihe
tip of the eleventh eostal eartilage ; thenee it proeeeds up-

THORAGie WALL 3

wards, posteriorly, and medially to the vertebral eolumn. In
the iirst part of its extent it is formed by the eartilages of ihe
seventh, eighth, ninth, tenth and eleventh ribs, and in the
seeond part by the lower border of the twelfth rib.

The lower margin of the thorax gives attaehment to the
diaphragm, a highly vaulted or dome-shaped museulo-tendinous
partition, whieh intervenes between the cavity of the thorax
above and that of the abdomen below. It forms a convex
floor for the thorax, and a concave roof for the abdomen.
By its upward projection it greatly diminishes the general
vertical depth of the thoraeie cavity.

But the diaphragm does not form an unbroken partition.
It presents three large openings, by means of whieh struetures
pass to and from the thorax, viz. — (i) for the aorta, thoraeie
duet, and vena azygos; (2) for the oesophagus and vagi
nerves ; (3) for the inferior vena cava. Besides these there
are other smaller apertures whieh will be mentioned later.

THORAGie WALL.

Tkoo days at least should be devoted to the disseetion of
the thoraeie wall.

In addition to the osseous and eartilaginous framework,
the walls of the ehest are built up partly by museles, and
partly by membranes, and in eonneetion with these there are
numerous nerves and blood-vessels.

/ External intereostals.
^ I J Internal intereostals.

' Transversi thoraeis.

tSubeostals.
Anterior intereostal membranes.
Membranes, . . - Posterior intereostal membranes.

Pleural membrane (parietal part).

{Intereostal nerves.
Aortie intereostal arteries.
buperior intereostal arteries.
Internal mammary arteries.

Disseetion, — Portions of eertain of the museles of the upper limb and
of the abdominal wall are still attaehed to the thoraeie wall on eaeh
side. Antero-posteriorly the disseetor will meet with the peetoralis major,
the peetoreUis minor, and the serratus anterior, whilst towards the lower
margin oi\ the ehest he will reeognise the reetus abdominis anterior^^.
and the obtiquus extemus and latissimus dorsi upon its lateral aspeet. '.
rouDded tendon of the subclavius may also be seen taking origin fro'
the first eostal areh. These remnants must be removed so as to li
bare the eostal arehes and the intereostal museles. In detaehing

11 — \a

4 THORAX

serratus anterior and external oblique be careful not to injure the lateral
eutaneotis nerues whieh make their appearanee in the intervals between
their digitations. The anterior etUaneous nerues and perforating branehes of
the internal mammary artery must also be preserved ; they pieree the
origin of the peetoralis major in the intervals between the eostal eartilages,
elose to the margin of the sternum.

Intereostal Museles and Membranes. — These museles and
membranes oeeupy the eleven intereostal spaees on eaeh side.
In eaeh spaee there are two strata of museular fibres — a
superficial and a deep. The superficial layer of museular
fibres is ealled the extemal intereostal musele, and the deep
layer the intenial intereostal musele,

The extemal intereostal musdes are already exposed, and
very little eleaning is neeessary to bring out their eonneetions.
Note that entering into their eonstitution there is a large
admixture of tendinous fibres, and that these, as well as the
museular fibres, are direeted obliquely downwards and
anteriorly from the lower border of the rib above to the
upper border of the rib below. They do not extend farther
anteriorly, in the various spaees, than the region of union of
the bony with the eartilaginous parts of the eostal arehes. In
many eases, espeeially in the upper spaees, they do not
reaeh so far. When the museular fibres stop, the tendinous
fibres are prolonged onwards to the sternum in the form
of a membrane, whieh is ealled the anterior intereostal mem-
brane, The external intereostal museles of the two lower
spaees are exceptions to this rule. They extend anteriorly to
the extremities of the spaees. Posteriorly the museles ex-
tend as far as the tubereles of the ribs, but this is a point
whieh ean be satisfactorily demonstrated only after the thorax
has been opened.

Disseetion. — To bring the intemal intereostal musdes into view it is
neeessary to reflect the external intereostal museles, and also the anterior
intereostal membranes. Divide them along the lower border of eaeh
spaee, and throw them upwards. In effecting this disseetion, eare must be
taken of the intereostal vessels, whieh lie between the two museular strata,
and of the lateral branehes of the intereostal nerves.

The internal intereostal museles, thus laid bare, will be seen
to be similar in their eonstitution to the external museles.
The fibres, however, run in the opposite direetion — viz., from
above, obliquely downwards and posteriorly. Superiorly, eaeh
is attaehed to the inner surface of the upper rib, immediately
above the eostal groove ; inferiorly, it is attaehed upon the

THORAGie WALL 5

inner surface of the lower rib, elose to the upper margin.
The intemal intereostal museles are prolonged anteriorly
to the sternum. Posteriorly they extend to the angles
of the ribs. The posterior intereostal membranes extend from
the spine to posterior borders of the intemal intereostals
where they beeome eontinuous with the fascial layer hetween
the external and intemal intereostal museles. They will
be seen when the thorax is opened.

If the internal oblique musele of the abdomen has not been removed,
the disseetor should note that the anterior Hbres of the lowest two internal
intereostal museles beeome eontinuous with the tibres of that musele.

Sternum / / / i

M. transversus thoraeis / / ;

* « I
Intemal mammary artery ' /

Anterior intereostal membrane /

Anterior eutaneous nerve ■

Pleura/
Lateral eutaneous nerve

Anterior root.
Posterior root •

Internal iiiter-
eostal musele

Trunk of thoraeie nerve /')\ /\ ^"^mHSSM^T Anterior braneh of thoraeie

Posterior braneh ()'' /^ ^ I nerve (intereostal)

' / External intereostal musele

Anterior costo-transverse ligament ' . . , ,

Postenor mtereostal membrane

FiG. 2. — Diagram of one of the Upper Intereostal Nerves.

Intereostal Nenres. — The intereostal nerves are altogether
out of sight in the present stage of the disseetion. They are
hidden by the lower borders of the ribs whieh bound the
intereostal spaees superiorly. By gently pulling upon their
lateral eutaneous branehes they ean be drawn downwards,
and they are then seen to He between the two museular strata as
far anteriorly as a point midway between the vertebral eolumn
and sternum. There they sink into the substanee of the in-
ternal intereostal museles, amidst the fibres of whieh they may
be traeed to the anterior extremities of the bony parts
of the ribs, where they reaeh the deep surface of inter

6 THORAX

intereostal museles and are earried medially, iirst anterior
to the pleura, and then anterior to the transversus thoraeis
musele. Lastly, they eross anterior to the internal mammary
artery and turn anteriorly, at the side of the sternum, as the
anterior eutaneous nerues of the peetoral region. Eaeh nerve,
before it reaehes the surface, pierees — (a) the internal inter-
eostal musele ; (b) the anterior intereostal membrane ; (c)
the origin of the peetoralis major ; and (d) the deep fascia

(Fig. 2).

This deseription holds good for the upper five inter-
eostal nerves only. The lower six nerves leave the anterior
ends of the intereostal spaees and run into the abdominal
wall. As they leave the thoraeie wall the upper four of the
six pass posterior to the upturned eostal eartilages, and all six
pass between the interdigitating slips of the diaphragm and
the transversus abdominis museles.

The intereostal nerves are the anterior branehes of the
upper eleven thoraeie nerves. As they traverse the thoraeie
wall they give off — {a) the lateral eutaneous branehes, (S)
twigs to the intereostal, subeostal, and transversus thoraeis
museles. The terminal extremities of the upper five beeome
the anterior eutaneous nerves of the thorax. (For the
abdominal distribution of the lower six see Vol. I., p. 394.)

The lateral eutaneous branehes arise midway between the
vertebral eolumn and the sternum. They pieree the external
intereostal museles, and pass between the digitations of the
serratus anterior.

The first intereostal nerve does not give a lateral braneh,
and it does not beeome eutaneous anteriorly. The lateral
eutaneous braneh of the seeond intereostal nerve is the so-
ealled intereosto-braehial nerve.

It is not neeessary to make a disseetion of the intereostal nerves in more
than two or three of the spaees.

Intereostal Yessels. — The intereostal arteries should be
disseeted in spaees in whieh the nerves have not been
traeed, and in whieh, therefore, the internal intereostal
museles are still entire. It is only in a well-injected subject
that a satisfactory view of these vessels ean be obtained. In
eaeh intereostal spaee one artery is found passing dorso-ven-
trally \ and in eaeh of the upper nine intereostal spaees, two
anterior infcrcostal arteries run ventro-dorsally.

THORAGie WALL 7

In the upper two spaees the vessels whieh nin dorso-
yentrally are derived from the superiar intenostal division of the
costo-cervical braneh of the subclavian artery ; in the lower nine
spaees they spring direetly from the aorta, and are ealled the
aortie intereostal arieries,

The anterior intereostal arteries of the upper six spaees
proeeed direetly from the internal mammary, whilst those of
seventh, eighth, and ninth spaees arise from the museulo-
phrenie artery.

The intereostal vessels are distributed for the most part
between the two museular strata. From the angles of the
ribs onwards to a point midway between the vertebral eolumn
and stemum, the aortie intereostal arteries lie under shelter of
the lower margins of the ribs whieh bound the spaees superiorly,
and at a higher level than the eorresponding nerves. Then
eaeh divides into two branehes, whieh pass ventrally in
relation to the upper and lower margins of the intereostal
spaee. They give ofif small branehes whieh aeeompany the
lateral eutaneous nerves. The lower two aortie intereostal
arteries are earried onwards into the abdominal wall. The
branehes of the superior intereostal artery are disposed in a
manner similar to the aortie intereostal vessels.

The anterior intereostal arteries are two in number for eaeh
spaee, except the last two. At their origins they lie under
cover of the internal intereostal museles, and they run later-
ally in relation to the upper and lower margins of the ribs
bounding the spaees. After a short eourse they pieree the
internal intereostal museles, and end by anastomosing with
the aortie and superior intereostal arteries.

Dissedion, — ^The disseetor should next proeeed to remove the intereostal
museles. This disseetion must be done with great eare, for immediately
subjacent to the intemal intereostals and the ribs is the delieate pleural
membrane whieh lines the inner surface of the ehest wall. The membrane
must not be injured or detaehed from the deep surfaces of the ribs during
this stage of the disseetion. As the internal intereostal museles are removed,
the anterior perforating branehes of the internal mammary and museulo-
phrenie arteries, and the anterior eutaneous nerves must be preserved.

When the museles are removed the internal mammary artery with its
two accompan)ning veins will be seen behind the eostal eartilages, about
half an ineh from the side of the sternum. Glean these arteries in the
iritervals between the eartilages and note the small lymph glands
whieh lie beside them. Eaeh internal mammary artery ends by dividing
into superior epigastrie and museulo-phrenie terminal branehes in the
intenral between the sixth and seventh rib eartilages. Most likely this
spaee will be so narrow that a view of the bifurcation eannot be obtained.
If this is the ease, pare away the edges of the eartilages over the artery, or,

TT 1 h

THORAX

ore the medial part of the sixth eartilage eompletely. The
musele posleiioT to Ihe intema] mammaty artery is the transversus thoraeis
(O.T. triangulaiis stemi). Endeayout to define its slips in the inleivals
betweeu the eostal carli1:^es.

Tiie disseetor should note. as an importanl praetieal point, that towards
the lower margin of the thorax ihe pleural sae is nol prolonged downwards
to Ihe lowest limit of the reeess between the diaphragni and the eostal
aiehes. Indeed, in Ihe axillary tine, it will be Coani3 to fal1 eonsideiably

FiG 3 — Diss

short of this ConEequently the disseetoi will eome down direetly iipon
the diaphragm, when the mtetnal mtereostai museles are remoied from
this portion of the ehest wall The fibres of the diaphragm eorrespond
somewhal in their direetion with those of the mtemal intereostat museles,
and it ts no uneommon oeeurrenee for the sludent lo remove them and
thus expose the pentoneum undei the impiession ihat hc has simply laid
bare the pleuta. When the disseetion is propeily executed a strong fascia
will be seen It passes ftom the sutfice of Ihe diaphiagm to Ihe surface
of the eostal pteuia and holds the lattei in position. Preserve this mem-
brane for furthet esamination.

THORAGie WALL 9

Arteria MammaTia Intema. — This vessel arises, in the root
of the neek, from the first part of the subclavian. It enters
the thorax by passing downwards, posterior to the sternal end
of the clavicle and the eartilage of the first rib, and it deseends
to the interval between the sixth and seventh eostal eartilages,
where it ends by dividing into the superior epigastrie and the
museulO'phrenie branehes.

Plaeed anterior to the intemal mammary artery are the
upper six eostal eartilages, with the intervening intemal inter-
eostal museles and anterior intereostal membranes. The inter-
eostal nerves eross anterior to it before they turn forwards to
gain the surface. Posterior to the upper part of the artery is
the pleura ; and the transversus thoraeis intervenes between
the lower part of the artery and the pleural sae.

In addition to its two terminal branehes, a large number
of small eollateral twigs proeeed from the internal mammary —

I. The anterior intereostal,

2. The perforating,

3. The perieardio-phrenie,

4. Mediastinal and thymie,
' 5. Superior epigastrie,

6. Museulo-phrenie, .

\ to the thoraeie parietes.

> to parts in the interior of the thorax.

> the terminal branehes.

The anterior intereostal arteries are supplied to the upper six
intereostal intervals, and have been disseeted already (p. 6).
Two are given to eaeh spaee: frequently these arise by a
eommon trunk.

The perforating arteries aeeompany the anterior eutaneous
nerves, and reaeh the surface by piereing the internal inter-
eostal museles, the anterior intereostal membranes, and the
peetoralis major musele. One, or perhaps two, are given
ofif in eaeh intereostal spaee. In the female those of the
seeond, third, and fourth spaees attain a speeial importanee,
inasmueh as they eonstitute the prineipal arteries of supply to
the mammary gland.

The superior epigastrie artery passes between the sternal and
eostal origins of the diaphragm and enters the sheath of the
reetus musele of the abdominal wall.

The museulo-phrenie artery turns laterally and downwards,
along the eostal origin of the diaphragm and behind the rib-
eartilages. Opposite the eighth eostal eartilage it pierees the
diaphragm and terminates on its abdominal surface. It gives
off the anterior intereostal arteries to the seventh, eighth, and
ninth intereostal spaees (p. 7).

lo THORAX

Museulus Transyersus Thoraeis (O.T. Triangularis Sibemi).
— This is a thin museular layer plaeed on the deep surface of
the sternum and eostal eartilages. It is eontinuous below
with the transversus abdominis, and arises from the posterior
surface of the xiphoid proeess, the lower part of the body of
the sternum, and from the medial ends of the fifth, sixth, and
seventh eostal eartilages. Its fibres radiate in an upward and
lateral direetion, in the form of five slips, whieh are inserted
into the deep surfaces and lower borders of the seeond, third,
fourth, fifth, and sixth eostal eartilages, elose to their junction
with the ribs (Fig. 3).

In many eases the musele is feebly developed, and does not show
sueh wide eonneetions. Upon its anterior aspeet are plaeed the internal
mammary artery and some of the intereostal nerves.

It is only a partial view of the musele whieh is obtained in the present
disseetion, but it is not advisable to remove the eostal eartilages to expose
it further, as this would materially interfere with the subsequent display
of other more important struetures in their proper relations.

THORAGie CAVITY.

Before the disseetion of the interior of the thorax is eom-
meneed it is neeessary that the disseetors should have some
general knowledge of the cavity and its eontents. The shape
and the boundaries have been studied already (p. i), and it
must now be understood that the cavity is divided into two
lateral parts by a median septum ealled the mediastinum,
whieh extends from the sternum anteriorly to the vertebral
eolumn posteriorly, and from the upper aperture of the thorax
above to the diaphragm below.

The mediastinum is formed by the heart, enveloped in a
fibro-serous sae ealled the perieardium ; the great vessels
passing to and from the heart, i,e, the pulmonary artery and
veins, the aorta, and the vena cava superior ; the eesophagus ;
the traehea and the eommeneements of the bronehi; the
thoraeie duet ; the azygos, hemiazygos and aeeessory hemi-
azygos veins ; the vagi and phrenie nerves ; numerous lymph
glands ; and the areolar tissue in whieh these struetures are
embedded and by whieh they are bound together. For eon-
venience of deseription the mediastinum is divided into a
superior and an inferior portion^ by an imaginary plane
whieh passes from the lower border of the manubrium sterni
nteriorly, to the lower border of the fourth thoraeie vertebra

THORAGie CAV1TY ii

posteriorly ; and the inrerior mediastinum is .subdivided Inlo
anterior, middle, and posterior portions. Tho anUrior
mediasHnum is the part anterior to the perieardium, the
posterior mediastinum the part posterior to the perieardium,
whilst the perieardium and the heart wilh the great vessels
and the phrenie nerves with their aeeompanying vessels form
the middie mediasHnum. It is eustomary, howevcr, to speak o^
the mediastinum as if tt weie a spaee, and to say that the various
viscera, vessels, ete, lie in the mediastina (Fig. 19, p. 44).
- The lateral portions of the Ihoraeie cavity are known as

eostal pan of parklal plnira Cu>ial pan i)f parietal pkura

■Diagrammalie represenialion of a eross seetion ihrough

the pleural spaees; eaeh eontains the eorresponding lung
surrounded by an invaginated serous membrane ealled the
pleural sae. There are therefore two pleural saes, and eaeh is
so disposed that it not only lines the ehamber in whieh the lung
lies, but is also reAeeted over the surface of the lung, so as to
give it an external covering whieh is intimately eonneeted with
the pulmonary substanee. ConsequentIy, the wall of eaeh
pleural sae is separable into two portions, an invesling or
yiseeral part whieh covers the surface of the lung, and a lining or
parietal part whieh elolhes the inner surfaces of the boundary
of eaeh lateral part of the thoraeie cavity. It must be elearly
understood, however, that the two terms are merely applied
to indieate different portions of a eontinuous membrane.

12 THORAX

Eaeh lung lies free in the pleural spaee except along its
medial surface, where it is attaehed to the heart by the
pulmonary vessels, to the eorresponding bronehial tube, and
by a fold of pleura to the side of the perieardium.

The disseetion whieh has already been made shows the
pleura lining the deep surfaces of the eostal arehes and the
internal intereostal museles. This part is ealled the eostal
pleura^ and it is part of the parietal pleura^ but before it ean
be more fully investigated and before the remaining parts of
the pleurae and the lungs ean be examined, further disseetion
is neeessary.

Disseetion, — The pleural membrane previously exposed by the removal
of the eontents of the intereostal spaees must now be carefully separated
from the inner surfaces of the ribs by the gentle pressure of the iingers.
The separation should be earried anteriorly to the junction of the ribs
with their eartilages and posteriorly as far as possible. When this has
been done the ribs, from the seeond to the sixth inclusive, must be divided,
with bone forceps, at their junctions with their eartilages, and at the same
time any fibres of the transversus thoraeis whieh may be attaehed to them
must be eut. The first and the seventh and those below the seventh must
not be inter/ered with, Afterwards the ribs must be divided as far
dorsally as possible and the separated portions removed. After the separ-
ated parts of the ribs are detaehed, remove any sharp spieules of bone
from the eut ends of the remaining portions.

The outer surface of the eostal part of the parietal pleura will be exposed
in the area from whieh the ribs have been removed, and the disseetor
should notiee that it has the appearanee of a fibrous membrane with a
rough surface, the roughness being due to fragments of the connective tissue
(endothoraeie fascia) whieh eonneet it with the adjacent parts.

After he has examined the outer surface of the pleura, the disseetor
should divide it by a vertical ineision about midway between the anterior
and posterior borders of the area exposed. At eaeh end of the vertical
ineision a transverse ineision must be made. One of the two flaps so
formed must be thrown anteriorly, and the other posteriorly. The pleural
sae is now opened and the lateral surface of the lung, covered with the
visceral portion of the pleura, is exposed.

The cavity of the sae and its relations to the mediastinal septum, the
diaphragm, and the root of the neek ean be explored with the fingers ; and
the borders, surfaces, and the root of the lung ean be examined.

The Pleural Saes are two in number, a right and a left.
They are serous saes, and are therefore elosed. After
opening into the interior, the disseetor should notiee the
difference between the rough outer surface of the wall of the
sae and its smooth and glistening inner surface, and in order
that he may thoroughly understand the relationship of the
wall of the sae to the lung, the mediastinum and the wall of
the thoraeie cavity, he should follow the wall of the sae, with
his fingers, at three different levels — (i) at the level of the

THORAGie CAVITY 13

manubrium sterni; (2) at the level of the third intereostal
spaee ; and (3) at the level of the fifth eostal eartilage. He
must traee the wall of the sae in the vertical plane also.

Commencing at the level of the third intereostal spaee, he
should plaee his fingers on the surface of the lung and follow
it anteriorly and medially until, behind the sternum, he reaehes
the sharp anterior border, whieh should be pulled laterally ;
then, turning from the lung to the parietal pleura, he should
plaee his fingers on the inner surface of the anterior flap and
ibllow it medially. He will find, at a eertain point posterior
to the sternum, and to the left of the median plane, that his
fingers eease to pass towards the opposite side but are
earried posteriorly, along the lateral boundary of the medi-
astinum, until they eome to the big blood vessels and the air
tube of the lung whieh collectively form its root. Along the
front of the vessels his Aingers will now pass laterally, following
the reflection of the pleura on the front of the vessels, to the
medial surface of the lung, and then anteriorly to its anterior
border. Round the anterior border they will arrive at the
lateral surface of the lung ; along this they will pass to the
posterior border and thenee anteriorly along the posterior part
of the medial surface to the posterior surface of the root,
where they will feel, distinetly, the hard outline of the
bronehus. Following the posterior surface of the root medially,
they will reaeh the posterior part of the lateral boundary of
the mediastinum, along whieh they will pass posteriorly to the
vertebral eolumn, and thenee laterally along the posterior parts
of the ribs, and finally anteriorly along the inner surface of the
posterior flap to its anterior margin.

If the disseetor has followed the above instruetions he
eannot fail to have reeognised that the pleural sae is in-
vaginated by the lung, whieh in its growth laterally from
the mediastinal septum has invaginated and expanded a part
of the medial wall of the sae. The disseetor should now
examine a transverse seetion of a hardened thorax, or if
that is not available, the diagram on p. 11. The study of
either will convince him that the lung earrying the in-
vaginated part of the wall of the pleural sae on its surface
has expanded until it has praetieally obliterated thecavity of
the sae, and he will find that the invaginated pleura on the
surface of the lung, whieh is ealled the visceral pleura^
everywhere in elose apposition with the non-invaginatec

14 THORAX

portion whieh is termed the parietal pleura ; all that inter-
venes between the two portions being a thin stratum of fluid,
sufficient to lubrieate the surfaces and prevent friction during
the movements of the lung and the ehest wall.

After he has grasped the facts noted above the disseetor
should follow the inner surfac^of the pleura in the transverse
plane at tho level of the mth^eostal eartila^e, that is, below
the level of the root of the lung. At that level he will find
that the parietal pleura covering the lateral surface of the
mediastinal septum is eonneeted with the visceral pleura on
the medial surface of the lung by a thin fold, the pulmonary
ligament (O.T. ligamentum }atum pulmonis). This eonsists of
an anterior and a posterior layer, whieh eorrespond, respectively,
with the layers on the front and the baek of the root of the
lung, but are in eontaet with eaeh other at the level of
the fifth rib, on aeeount of the absenee of the great blood
vessels and air tube of the lung. The pulmonary li^^ament
extends laterally from the mediastinum to the medial surface
of the lung, and from the root of the lung above, to within
a short distanee from the diaphragm below. Its medial,
lateral, and upper borders are attaehed respectively to the
mediastinal septum, the lung, and the lower border of the
lung root, and are eontinuous with the pleura covering eaeh,
but its lower border is free. When he has satisfied himself
regarding the nature and the attaehments of the pulmonary
ligament, the disseetor should traee the pleura in the hori-
zoiital plane at the level Qf thp rnamihri]|m gtPYni, that is,
above the level of the root of the li^ng. Th^yg h^ will find
that the medial wall of the sae is not reAeeted on to the lung,
but that it passes posteriorly along the lateral surface of the
mediastinal septum from the sternum anteriorly to the vertebral
eolumn posteriorly, and thenee laterally and anteriorly to the
sternum in an unbroken eirele. In the same way he will
be able to traee the visceral pleura in a similar but smaller
unbroken eirele around the upper partof the lung.

Having traeed the pleura in three horizontal planes the
disseetor must next traee it in the vertical plane, first around
the lung, and then around the wall of the thorax. Gommeneing
with the lung, the fingers should be passeH along the anterior
border to the apex, thenee, down the thiek posterior border, to
the base, and anteriorly, aeross the concave base, to the anterior
border. By doing this he will again demonstrate to himself

THORAGie CAVITY

the fact that the lung is ensheathed in visceral pleura. N'ext,
plaelDg his hngera on the inner surface of the parietal pleura
behind the eostal eartilages, he should eany them upwards
towards the head, and he will find that they pass upwards into
the root of the neek for a distanee of from one to two inehes
above the level of the anteriot part of the first rib, but, on
aeeount of the obUque position of the rib, only to the level of
its neek posteriorly. The apex of the sae, therefore, lies in

the root of the neek, and by carefully palpating ils inner
surface,the disseetor will be able to distinguish the subclavian
artery whieh passes aeross its anterior surface below the highest
point, and, possibly, he may be able to loeate the interna!
mammary and costo-cervical arteries (O.T. superior inter-
eostal). The hrst deseends from the subclavian trunk
anterior eo the apex of the sae, and the seeond passes first
upwards to the apex and then posteriorly above it. Afler
disseetor bas examined the position and relations

1 6 THOR AX

apex of the sae he should follow its posterior wall downwards,
just lateral to the line of the vertebral eolumn, and, if he is
dealing with a subject in good eondition, he will iind that he
ean pass his fingers downwards to the lower border of the
twelfth rib, where they will be earried anteriorly on to the
diaphragm and over its surface to the anterior wall of the
thorax. If the disseetor earries out the examination of the
pleural sae in a thorough manner, and if he has appreeiated
the significance of the arrangements found at different levels,
he will have repeatedly convinced himself that the lung,
earrying the blood vessels and air tube with it, has invaginated
a portion of the lower part of the medial wall of the pleural
sae, and has then expanded anteriorly, posteriorly, upwards and,
to a eertain extent, downwards beyond the margins of the
aperture of invagination, whose position is indieated by the
root of the lung and the line of attaehment of the pulmonary
ligament. The portion of the wall of the pleura whieh is
invaginated by the lung is represented by (i) the visceral
pleura, (2) the layers covering the root of the lung, and (3)
the pulmonary ligament. .

Before eaeh lung is removed the disseetors should note
that its anterior margin does not extend so far anteriorly, and
the inferior margin does not extend so far downwards, as the
eorresponding part of the pleura. The portions of the
pleura unoeeupied by the lung are ealled the pleural sinuses.
The sinus along the anterior margin of the pleura is the
eosto-mediastinal sinus^ and that along the lower margin, the
phrenieo-eostal sinus, The walls of the sinuses are separated
by a eapillary spaee filled with pleural fluid, and the margins
of the lungs enter into the sinuses and reeede from them
during inspiration and expiration, respectively.

•

In the event of the lungs not having been hardened in situ by formalin
injection the disseetors may, with the eonsent of the disseetors of the head
and neek, introduee the nozzle of the bellows into the cervical part of
the traehea and inflate the lungs with air. A truer eoneeption of these
organs will thus be obtained, and a demonstration will be affbrded of their
high elastieity, and of their oonneetion with the wind-pipe.

After the disseetor has eompleted the general examination
of the walls of the pleural sae, he should pull the anterior
margin of the lung laterally to expose its medial surface,
the front of the root and the front of the pulmonary ligament ;
then he should divide the root and the pulmonary ligament,
from above downwards, elose to the medial surface of the

THORAGie CAVITY 17

lung. The lung, thus set free, is to be removed from the
thorax, wrapped in a eloth damped with preservative solution,

and plaeed aside for future study.

When the lung has been removed the margins of the
pleural sae must be examined, and their positions relative to
the ehest wall noted. This eannot be done to the best
advantage until both lungs have been removed. When this
has been done the dis-
seetor should introduee
one hand into eaeh
pleura, and plaeing an
index finger in eaeh
apex, he should note
that the apex issituated
about one_inch above
the jujiction of the
lateraL.two-thirds with
the medial third of the
elayiele, a fact whieh
he ean demonstrate
with the aid of his
partner on the opposite
side, who should hold
two maeerated clavicles
in their. proper posi-
""EToiis. The apiees of
opposite sides, there-
fore, are some distanee
apart, and are separ-
aled from eaeh other i
by the struetures oeeu-
pying the median part
of the neek; i'.e. the
air tube, ihe gullet, and the great arteries passing upwards to the
head. As the anterior margins of the pleurEe are traeed down-
wards from the apiees they will be found to converge, passing
behind the sterno-clavicular joints and eoming into apposition
at the lower border or the manubrium sterni, immediateiy to
the left of the median plane. Traeed further downwards the
anterior margins remain in apposition, the right frequently over-
lapping the left and both inelining sli|htly to the left, to the
Ievel of the fourth eostal eartilages. From the fourth eartilage
VOL. 11—2

6.— Diagram lo show the relation of ihe
asa aad Ihe pleural saes to Ihe nnterior
e depieled in

d ibe pleural s;

i8 THORAX

the anterior margin of the right sae eontinues to deseend, still
with a slight indination to the left, till it reaehes the xiphoid
proeess, where it beeomes eontinuous with the inferior margin.
This turns laterally, passing behind the xiphoid proeess and
the eartilage of the seventh rib ; it then erosses the junction

and heart

The

iitline of ihe heart

ted inred by a dotied

and ihe a

argins of Ihe pleura

saesa

e represented by blue

of the bone and eartilage of the eighth rib and reaehes
the level of the tenth rib in the mid-axillary hne; turning
posteriorly, it erosses ihe eleventh and twelfth ribs, and just
below the middle of the latter it beeomes eontinuous with the
posterior margin, whieh aseends along the line of the angle of
the ribs to the apex. On the left side, at the level of the
fourth eostal eartilages, the anterior margin of the ]eft pleura
turns away from the median plane, for a variable distanee,

THORAGie CAVITY 19

passing behind the fifth eosul eanilage ai the margln of the
sternum, or even an ineh more laterally ; il then deseends
to the lower border of the sixih eaitilage, where it beeomes

■;. a.— t^I Pleuial 5ac, of a subject b
opened imo by the removal of Ihe c
ba^ been renioYed so as to display the
along whieh ihe pleura is retleeted froni th
wall is uhibited.

liaphra

eontinuous with the lower maipn of the pleura, whieh p;
laterally and posteriorly along ihe lower border of the sl
eartilage, aeross the medial end of the sixih spaee, and aer
the seventb eartilage to the junciion of the eartilage a
11—2«

20 THORAX

bone of the eighth rib. The remainder of its eourse and the
positioti of its posterior margin are the same as on the right
side.

¥ia, 9. — The Righl Pleural Sae, in a subject hardeneil by forin.'>Jin iiyeetioii,
opened inio by the removal of the eostal parl of Ihe parietal pleura. The
riEhi lung also has been remoYed 10 display Ihe righi niediaslinal pleura.
Note Ihe line of diaphragmatie reHeetion of the pleura.

The student should mark out the margins of the pleural
saes on the living body, using himself and his friends for the
purpose, until he ean indieate them eorreetly, judging from
the eontour of the body alone and without feeling for the
skeletal points.

THORAGie CAVITY »i

After the disseetor has made himself thoroughly conversani

piG. lo, — The Right Pleural Chaniber opened up by ihe Temoval of its lf
wall. Tbe lung has been laken away so as lo expose (he media^
wall oT Ihe pleiu^ ebamber, 5everal of the siruetures in tbe me
[inal septum are seen shinitig tbrough the tnediastinal pleura.

2 2 THORAX

with the limits of the pleural saes, he should examine the eut
seetion of the root of the lung, and should endeavour to
reeognise, through the mediastinal part of the parietal pleura,
the positions of the main eonstituent parts of the mediastinum.
As these vary on the opposite sides, eaeh side must be eon-
sidered separately, and eaeh disseetor must make himself well
acquainted with the eonditions on both sides.

On the rightside^ in the posterior part of thefaceof the seetion
of the lung root, at least two parts of the bronehial tube will
be seen ; an upper, whieh is the so-ealled eparterial bronehus,
and a lower, the main stem of the right bronehus. Anterior
to and between the two bronehi is the pulmonary artery, and
more anteriorly, and at a slightly lower level, the upper pul-
monary vein. The lower pulmonary vein lies in the lowest
part of the root, below and slightly posterior to the main
bronehus. If the speeimen is well injected, branehes of the
right bronehial artery may be distinguished on the posterior
faces of the air tubes ; and anterior to and between the great
blood vessels, and between them and the bronehi, are a
number of bronehial glands, whieh are easily distinguished
by the blaek pigment deposited within them.

In the posterior part of the root of the lung, on the left side,
the disseetors will see the eut seetion of the left bronehus, .
and, in many eases, a seetion of its first ventral braneh also.
The left pulmonary artery is above the bronehus, and its
anterior wall is on a slightly anterior plane. The upper left
pulmonary vein is anterior to the bronehus, and the lower
left pulmonary vein is below the bronehus. In a well in-
jected speeimen the two left bronehial arteries may be seen
on the posterior wall of the bronehus, and a number of
bronehial glands will be found between and around the large
blood vessels and the bronehus.

Turning next to the mediastinal pleura on the right side,
the disseetors will note, anterior to and below the root of the
lung, a large bulging, due to the heart and perieardium, whieh
lie in the middle mediastinal area. Gontinuous with the
upper and lower ends of the posterior part of this bulging
they will see two longitudinal elevations. The upper, from
the level of the third eostal eartilage to the lower margin
of the lirst rib, is due to the superior vena cava and above
that level, to the right innominate vein. The lower elevation
is very short, and is eaused by the upper part of the inferior

THORAGie CAVITY 23

vena cava. A seeondary ridge, formed by the phrenie nerve
and the aeeompanying blood vessels, deseends along the
elevation eaused by the superior vena cava, erosses anterior
to the root of the lung, nins down along the posterior part
of the bulging due to the heart, and the anterior border
of the inferior caval elevation. Arehing over the root of
the lung is a curved ridge, due to the upper part of the
vena azygos, as it passes anteriorly to join the superior cava.
Above the vena azygos and posterior to the superior cava, the
right lateral surface of the traehea, or main air tube, may
be seen or felt in the superior mediastinal region, and,
deseending obliquely aeross it, from above downwards and
posteriorly, the right vagus nerve ean be palpated or seen.
Posterior to the root of the lung and to the bulging due to
the heart, the oesophagus may be reeognised in the posterior
mediastinal area, either by toueh or sight, or both. Somewhat
posterior to the oesophagus the margin of the aseending
portion of the vena azygos may be noted, and still further
posteriorly are the bodies of the vertebrae and the posterior
parts of the ribs. Grossing the bodies of the vertebrae trans-
versely the right intereostal vessels may be visible or they
may be felt, and, deseending along the line of the heads
of the ribs, the ganglionated trunk of the sympathetie ean be
reeognised by toueh, if not by sight.

The disseetors should examine next the mediastinum and
the posterior wall of the thorax on the left side (see Figs.
8, II, and 13).

By inspeetion and palpation they will easily reeognise the
positions of the larger and more important struetures. Below
and anterior to the root of the lung the mediastinal pleura is
bulged mueh more laterally on the left than on the right
side by the heart covered by the perieardium. Arehing
posteriorly and to the left, over the root of the lung, in the
superior mediastinal area, is the areh of the aorta, and from
its posterior end the deseending aorta runs downwards, in the
posterior mediastinal area, first posterior to the root of the
lung, and then posterior to the heart but separated, in part,
from the latter by the oesophagus, whieh diverges towards the
left side in the lower part of the thorax. Above the areh of
the aorta the left eommon earotid and subclavian arteries
and the oesophagus ean be distinguished in the above orde
antero - posteriorly. A long slender seeondary ridge, p

bone of Ihe eighth rib. The remainder of its eourse and the
position of its posterior margin are the same as on the right
side.

FiO. y. — The Right Pleural Sae, in a subject hardened by formalin iiijeclion,
opened inio by Ihe remoyal of Ihe eoslal part of Ihe parielal pleura. The
righi Lung also bas been removed lo display Ihe right mediastinal pleura.
Nole Ihe line of diaphraEmalie reHeelion of the pleura.

THORAGie CAVITV ii

After the disseetor has made himseir thoroughly conveTsant

fiG. lo.— The Right Pleural Chamber opened up by (he removal of its laleral
wall. Tbe lung has been laken away so as to expose ihe media5liDal
wall of tbe pleund ehamber. Sevenil of ihe sirueiures in Lhe medias-
linal septum are seen shining Ihrough the mediaslinal pleura.
11—26

20 THORAX

bone of the eighth rib. The remainder of its eourse and the
position of its posterior margin are the same as on the right
side.

(hyparlerialpail)

Kl<i. 9. — The kight Pleural Sae. in a subjecl hardened by fotmaUn injeclion,
opened into by the remova1 of the eoslal part of the parietal pleura. The
rig^t lung also has been removed to display Ihe right medlaslinal pleura.
Note the line of diaphragmalie reHedion of Ihe pleura.

THORACIC CAVITY
After the disseetor has made himself thoroughly

pie. lo. — The Righl Pleural Ghambet opened up by Ihe removaI of its laleral
wall. The lung ha^ been laken away so aE to e>:pc>se Ihe niediastlaal
wall of Ihe pleural ehaniber. Several of the slruelures In the medias-
tiual seplum are seen sbiniug Ihrougli Ihe mediaslinal pleura.

bone of the eighlh rib. The remainder of its eourse and the
posilion of its posterior margin are ihe same as on the right
side.

KiO. 9.— The Righl Pleural Sae, in a sabjecl hardened by formalin iiyeetion,
opened inlo bylhe removal of Ihe eostal part of the parietal pleura, The
ri£ht lung also has been remoyed lo display Ihe right mediaslinal pleura.
Nole the line of diaphragniatie reHeetion of the pleura,

THORAGie CAVITY ii

After the disseetor has made hiinself ihoroughly convcrsant

fIG. lO. — TbeRighlPleuraiehamberopenedupliy ll
wall. The lung has betn (aken away so as to i
wall of Ibe pleural etianiber. Several ot Ihe stn
liiial 9q>tuin aie seen shining ihrough the mediost

n— 2&

30 THORAX

at the level of the seeond eostal eartilage (see Fig. 12). As
it turns anteriorly the vein lies immediately to the right side
of the oesophagus, traehea and vagus nerve.

The tributaries of the vena azygos are : (i) The right
superior intereostal vein whieh drains blood from the
greater part of the seeond and third intereostal spaees.
(2) The eight lower intereostal veins and the subeostal vein
of the right side. (3) The vena hemiazygos, and frequently
(4) the vena hemiazygos aeeessoria. Both the latter enter it
from the left. In many eases the aeeessory azygos vein joins
the hemiazygos vein. (5) Two or more bronehial veins from
the right lung. (6) Some veins from the oesophagus. (7)
Some minute perieardial veins.

The vena azygos eommenees in the abdomen where it
anastomoses either with one of the upper lumbar veins or
direetly with the inferior vena cava. Thus it forms a more
or less direet anastomosis between the two venge cavae.

The intereostal veins and the aeeompanying arteries and
nerves, on both sides, and the hemiazygos and aeeessory
azygos veins will be studied at a later period of the disseetion
(see p. 108).

Contents of the Mediastiniun and the Struetures of the
Posterior Part of the Left Half of the Thorax seen irom the
Ijeft Side. — After the removal of the four pleural flaps deseribed
on p. 25 the following struetures are visible on the left side
of the thorax (see Fig. 13). Below and anterior to the root
of the lung is the perieardium, covering the left ventricle, the
left atrium, the eonus arteriosus of the right ventricle and the
pulmonary artery. Above the root of the lung is the areh of
the aorta. The areh of the aorta terminates posteriorly in
the deseending aorta, whieh passes downwards posterior to
the root of the lung and the perieardium, but it is separated
from the lower part of the posterior wall of the perieardium
by the oesophagus, whieh, at this level, is passing towards
the left side. On the left and anterior aspeet of the aortie
areh, from behind forwards, lie the left vagus nerve, the
superior cervical eardiae braneh of the left sympathetie
trunk, the inferior cervical eardiae braneh of the left vagus,
and the left phrenie nerve with its aeeompanying vessels.
Grossing the areh obliquely, from behind forwards and
upwards, is the left superior intereostal vein, whieh passes
lateral to the vagus and medial to the phrenie nerve. Above

THORAGie CAVITY 31

the areh or the aorta are the lower parts of the Ieft eommon

earotid and left subclavian arteries, and posterior to the latter
lies the oesophagus, with the thoraeie duet running along its
Ieft lateral border.

32 THORAX

Posterior to the deseending aorta are the left aortie inter-

eostal arteries, the aeeompanying veins, and the splanehnie

nerves ; and still more posteriorly and laterally lie the

sympathetie trunk of the left side and the left intereostal

,spaces and their eontents.

Dissedlon. — After the struetures exposed by the removal of the left
pleura have been loeated, the disseetors should direet their attention to the
sympathetie trunk and its branehes and eommunieations. The arrange-
ment of these is exactly similar to that already deseribed on the right side
(see p. 26). When the disseetors have confirmed this statement they
should turn to the left subclavian artery, whieh is the most posterior of the
three great branehes whieh spring from the areh of the aorta. Glean this
vessel without disturbing the vagus nerve, whieh deseends along its anterior
border. Afterwards elean the part of the aortie areh whieh lies posterior to
the vagus nerve, and the deseending aorta. Whilst eleaning the areh avoid
injuring the left superior intereostal vein, and, as the deseending aorta is
being eleaned, endeavour to preserve any of the aortie branehes of the
sympathetie whieh may have been found previously during the examination
of the sympathetie trunk.

As the aorta is eleaned the left border of the lower part of the
oesophagus will be brought more elearly into view, but the disseetor must
not attempt to elean the oesophagus at this stage.

After the deseending portion of the aorta is eleaned, the left aortie
intereostal arteries should be examined. They are nine in number ; they
emerge from the posterior aspeet of the aorta, and they all pass medial to
the sympathetie trunk as they approaeh the intereostal spaees. The upper
arteries aseend very obliquely to gain their proper spaees. Aeeompanying
the arteries are the eorresponding veins. The lower veins pass, posterior to
the aorta, to their terminations in the hemiazygos and aeeessory hemiazygos
veins, and will be more fully studied at a later stage ; but the veins from
the seeond and third spaees unite into a trunk ealled the left superior
intereostal vein.

The Left Superior Intereostal Vein. — This vein is formed
by the intereostal veins from the seeond and third intereostal
spaees of the left side, and it not uneommonly receives a
eommunieation from the first and fourth spaees. It deseends
along the medial border of the first left aortie intereostal
artery to the posterior end of the aortie areh, there it turns
anteriorly, along the left side of the aortie areh, and, passing
at the same time obliquely upwards, it erosses lateral to the
left vagus and medial to the left phrenie nerve. At a later
period of the disseetion it will be traeed to its termination
in the left innominate vein.

Disseetion. — After the left superior intereostal vein has been seeured
and studied, the disseetors should elean the region posterior to the left
subclavian artery, and expose thoroughly the left border of the oesophagus,
as that tube lies in the superior mediastinum, and the upper part of the
thoraeie portion of the thoraeie duet, whieh runs along the border of the
oesophagus.

THORAGie CAVITY 33

After this stage of the disseetion is eompleted, the disseetors
should exainine the triangular interval between the left phrenie
and left vagus neryes in the upper part of the thorax. Com-
meneing aboye, they should follow the vagus nerve down-
wards ; just before it reaehes the lower border of the aortie
areh, it gives off a very distinet braneh whieh turns round
the lower border of the areh. This is the important reeurreni
nerue whieh supplies the majority of the intrinsie museles of
the larynx of the same side. Immediately anterior and
medial to the point where the reeurrent nerve turns beneath
the areh, a very distinet fibrous eord must be defined. It
eonneets the areh with the upper border of the Ieft pulmonary
artery elose to its origin. This is the ligamentum arteriosum^
and it is the remains of the duetus arteriosus, through whieh
blood passed from the pulmonary artery to the aorta during
foetal life. When this has been seeured the areolar tissue
between the phrenie and vagus nerves must be carefully
removed. In this tissue two small nerves will be found
whieh run downwards, parallel with the vagus, aeross the areh
of the aorta. The one next the vagus is the superior cervical
eardiae braneh of the left sympathetie, and the one next the
phrenie is the inferior cervical eardiae braneh of the left
vagus. When these nerves are followed downwards they
will be found to end in the superficial eardiae plexus, whieh
lies in the areolar tissue below the aortie areh and to the right
of the ligamentum arteriosum.

Disseetion, — After the perieardium has been eleaned, ineisions should
be made through it on eaeh side, and the flaps formed should be turned
aside so that the disseetors may make themselves familiar with the relation-
ships of the heart to the mediastinal portions of the pleural saes. Two
longitudinal ineisions must be made on eaeh side, one anterior and one
posterior to the longitudinal strip of pleura Ieft on the lateral surface of the
phrenie nerve (see Figs. 12 and 13). On the right side the ineisions should
eommenee at the level of the upper pulmonary vein. On the left side
the anterior ineision should begin at the lower border of the aortie areh
and the posterior at the level of the left pulmonary arlery (see Fig. 13).
On both sides the longitudinal ineisions must deseend to the lower border
of the perieardium. On both sides ineisions should be earried anteriorly
from the upper and lower ends of the anterior longitudinal ineision to the
line aloDg whieh the mediastinal pleura was left attaehed to the anterior
surface of the perieardium (see Figs. 12 and 13). From the upper end of
the posterior longitudinal ineision on the right side a eut shoukl be made
downwards and posteriorly along the anterior aspeet of the root of the lung
to the upper end of the inferior vena cava (see P ig. 12).

From the upper end of the posterior longitudinal ineision on the left side
an oblique eut must be made downwards and posteriorly, along the line of

VOL. II — 3

34 THORAX

the anterior surface of the root of the left lung. When the ineisions have
been made, the anterior flaps ean be turned anteriorly and the posterior flaps
downwards. None of the flaps must be removed, for it will be neeessary
to replaee them in position at a later stage of the disseetion.

When the flaps marked out by these ineisions are turned aside the
disseetors will find that, on the right side, they have exposed the greater
part of the right atrium (see Fig. 12). They should note that the area of
the atrium whieh is exposed is separated into two parts by a vertical suleus,
the suleus terminalis^ whieh runs from the anterior face of the eardiae end
of the superior vena cava to the anterior aspeet of the terminal part of the
inferior vena cava. This suleus divides the atrium into a posterior part,
the sinus venosus, and an anterior part, the atrium proper, whose upper
and anterior part is prolonged medially to the anterior surface of the heart.
On the left side the greater part of the heart exposed by the reflection of
the perieardial flaps is the left ventricle, but in the upper part of the
area the auriele (O.T. aurieular appendage) of the left atrium is seen.
Anterior to it lie the stem of the pulmonary artery and the upper part
of the anterior portion of the right ventricle. A line of fat, in whieh lie
the interventricular braneh of the left eoronary artery and the aeeompany-
ing vein, indieates the position of the septum between the left and right
ventricles (Fig. 13).

After the disseetion is eompleted and the disseetors have carefully noted
the relative positions of the various struetures whieh have been exposed,
they should proeeed to study the phrenie nerves, whieh have been retained in
position by the strips of pleura on their lateral surfaces (see Figs. 12 and 13).

Nervi Phreniei. — Eaeh phrenie nerve arises in the neek
from the cervical plexus, receiving fibres from the third,
fourth, and fifth cervical nerves. It deseends on the sealenus
anterior musele and, at the root of the neek, passes anterior
to the subclavian artery and posterior to the eorresponding
vein, but on the left side, as it leaves the Sealenus anterior,
it lies anterior to the subclavian artery and posterior to the
eommeneement of the innominate vein. As it enters the
upper aperture of the thorax it erosses the internal mammary
artery, passing from its lateral to its medial side, then
it deseends along the lateral border of the mediastinum,
anterior to the root of the lung, to the diaphragm where
it breaks up into branehes. The majority of the branehes
pass between the museular fibres of the diaphragm and,
after eommunieating with the abdominal sympathetie nerve
fibres whieh form the diaphragmatie plexus, they are
distributed to the musele from its lower surface. The re-
lations of the phrenie nerves in the thorax are different
on the two sides, and the left phrenie nerve, as a whole, is
on a plane somewhat anterior to the right.

The right phrenie nerue deseends along the lateral borders
of the right innominate vein and the superior vena cava to
the point where the latter enters the perieardium, then along

THORAGie CAVITY 35

the side of the perieardium, whieh separates it from the
yenous sinus of the right atrium (see Fig. 12).

The Left Phrenie Nerue. — In the upper part of the thorax
the left phrenie nerve runs downwards between the left
eommon earotid and the left subclavian arteries and, whilst
lying between them, it erosses anterior to the left vagus and
posterior to the left innominate vein. In the lower part of
the superior mediastinum it passes lateral to the areh of the
aorta and the left superior intereostal vein, then, deseending
into the middle mediastinum, it lies at first anterior to the
root of the left lung, and afterwards it runs downwards along
the side of the perieardium, whieh separates it from the
anterior part of the left atrium and from the lateral part of
the left ventricle of the heart.

The left phrenie nerve is longer than its fellow of ihe right side, partly
on aeeount of the lower position of the diaphragni, and partly on aeeount
of the greater projection of the heart on the left side.

Branehes of the Phrenie Nenres. — The main distribution
of the phrenie nerves is to the diaphragm, but some minute
sensory twigs are given off by eaeh nerve to the perieardium
and to the pleura. The student should note the great import-
anee of the phrenie nerves. They are the nerves of supply
to the diaphragm, whieh is the chief musele of respiration.

Pulmones. — Before proeeeding to the further disseetion
of the eonstituent parts of the mediastinum, the disseetors
should study the lungs whieh they previously removed. The
lungs are two soft, comparatively light, spongy organs plaeed
one on either side of the mediastinum. The weight of the
right lung, when it is filled with an average amount of blood,
is 22 oz. and that of the left 20 oz. When the thorax is
opened the lungs eollapse to about one-third of their original
bulk (unless they have been hardened in situ\ and it is
difficult for the student to realise their proper size and
shape until they are distended to their original dimensions
with the aid of the bellows (see p. 16).

When healthy and sound, the lungs lie free within the
cavity of the ehest, and are attaehed only by their roots and
by their pulmonary ligaments. It is rare, however, that a
healthy lung is seen in the disseeting-room, for adhesions be-
tween the visceral and parietal portions of the pleura, due to
pleurisy, are generally present. Eaeh lung is aeeurately
adapted to the spaee in whieh it lies, and, when hardened

II— 3 a

36 THORAX

in sifu, it bears on its surface impressions and elevations
whieh are an exact eounterpart of the inequalities of the
struetures with whieh its surfaces are in eontaet at the
moment of fixation.

In the natural eondition eaeh lung resembles half a eone,
and il presents for examination an apex, a ^ase, a casfa/
surface, a medial sur/aee. An anterior and a posierior border
separate the medial from the lateral surface ; and an inferior
or basal border separates the base from the medial and lateral

LungB of a Child, hardened
in injeclion,

surfaces. The apex rises into the root of the neek for one
and a half inehes above the level of the anterior parl of the
Arst rib, and it is erossed by the subclavian artery, whieh
makes a groove upon the anterior border, a short distanee
below the summit, although the artery is separated from the
lung by the membranous cervical diaphragm (Sibson's fascia),
and by the pleura.

The base of eaeh lung has a semilunar outline and is
adapted to the upper surface of the diaphragm. Consequent]y
it is deeply hollowed out, and, as the right eupola of the

THORAnr rAyiTY

I diaphragm aseends higher than ihe lert. ihe basal concavity 1
I of ibe right lung is deeper than that of ihe !eft hing. The I
Ilateral and posterior parts of tbe basa! margin of ihe lung J
l.are thin and aharp and estend downwards into the phre
I eostal sinus of the pleura, whieh intervenes between the I
l.diaphragm and the wall of the lhorax. This margin reaehes a 1
I mueh iower position posteriorly and laterally ihan anleriorly, f
I but in all siluations it falls eonsiderably short of the bultom of I
>inus. The mediastinal part of the basal margin, whieh T
I Jies along the lower border of the peHeardium, is niore 1
irounded.

The diaphragm separates ihe base of the right lung from 1

the upper surface of the right lobe ol ihe iiver, and the base
Df the left lung from the left lobe of the iiver, ihe stomaeh,
the spleen, and, in some eases, from the left extremity of the
transyerse eolon.

The eostal sutface of tbe lung is very extensive and convex.
;It lies in relation witb the eostal pleura, whieb separates it,
from tbe ribs and intereostal museles, the transversus thoraei»^
and the sternum, and it bears the impressions of the eostal'
arehes.

Themedial surraee is separable into an antenoTOTnie/iias/im
portioH and a posterior or vertebral portion. The yerlebral
portion lies against the sides of tbe bodies of the vertebrK.
The mediastina! part is applied against the mediaslinal
partition and presents markings whieh are the exact eounter-
parts of the ine^ualities of Ihe eorresponding laleral surfar-
li— 3

lal

er-^li

38 THORAK

of the mediastinum. Thus, it is deeply hollowed out in
adaptation to the perieardium upon whieh it fits. The
perieardial concavity oeeupies the greater part of the
mediastinal surface, and, owing to ihe greater projection
of the heart to the left side, it is mueh more extensive in
the left lung than in the right lung.

'Medial of a Left Lung hardened it

At the upper and posterior part of the perieardial area is
the hilus of the lung. This is a wedge-shaped depressed area
through whieh the bronehus and the pulmonary artery enter
and the pulmonary veins and lymphaties leave the lung. It
is surrounded by the pleura whieh is ref!ected from its mai^in
on to the root of the lung, and the layer of reAeeted pleura
round the hilus is eontinuous, below, with the pulmonary
ligament. The portion of the perieardial area anterlor to the
upper part of the hilus of the left lung eorresponds with the

THORAGie CAVITY

position of the eonus arteriosus and the stem of ihe pulmonary
artery, and the same portion of the i>ericardial area on the
right side eorresponds with the position of ihe lower part of
the superior vena cava postetiorly and with the aseending
aorta anteriorly (Fig, 1 7). Below and poslerior to the lower

F:g. 17. — The Medial Surfaeeof a Righl Lung hardened

and posterior part of the perieardial area on the rigtit lung is a
seeondary depression due to the upper part of the inferior
vena cava. Posterior to the perieardial area and the hilus
there is a narrow strip of the mediastinal surfacc of the lung
whieh is in relation with the lateral wall of the posterior
mediastinum. On the right lung this portion of the
surface presents a longitudinal depression whieh eorresponds
with the right border of the oesophagus, and more posteriorly
at the upper part there may be a groove eaused by the vena

40 THORAX

azygos. The left lung in the eorresponding situation is
marked by a deep longitudinal groove whieh is produeed
by the eontaet of the lung with the deseending thoraeie
aorta ; and, elose to the base, a small triangular area, anterior
to the aortie groove, lies in relation with the left border of
the lowest part of the thoraeie portion of the oesophagus.

The portion of the mediastinal surface whieh lies above
the hilus and perieardial hollow is applied to the lateral
aspeet of the superior mediastinum and the markings upon
it are different on the two sides. On the left side a broad
deep groove, eaused by the aortie areh, curves over the hilus
and beeomes eontinuous posteriorly with the aortie groove
on the posterior mediastinal area. From this arehed groove
a sharply eut suleus, eaused by the left subclavian artery,
aseends on the medial side of the apex and, turning laterally
above, it erosses the anterior border of the apex a short
distanee below the summit. Immediately anterior to the
subclavian suleus the medial surface of the apex is oeeasion-
ally marked by a shallow suleus eaused by the lateral margin
of the left innominate vein, and more inferiorly its anterior
margin is depressed by the first rib. That portion of the
surface whieh lies posterior to the subclavian suleus is
separated by areolar tissue from the eesophagus.

On the right lung also a curved -suleus arehes over the
hilus. It is eaused by the vena azygos, as it passes anteriorly
to join the superior vena cava. This groove is mueh narrower
and less distinet than the suleus on the left lung due to the
aortie areh. From the anterior end of the suleus for the
azygos vein a broad shallow suleus passes upwards to the
lower and anterior part of the apex. This is produeed by
the superior vena cava and the innominate vein, and in some
eases it is prolonged to the upper part of the apex by a
slight longitudinal depression due to the pressure of the
internal jugular vein. Arehing laterally, aeross the upper
part of the anterior aspeet of the apex, there is a shallow groove
produeed by the right subclavian artery. Posterior to the suleus
for the innominate vein, the medial surface. of the apex lies in
relation with the right side of the traehea, and still further
posteriorly it is either in relation with the right lateral border
of the superior mediastinal part of the eesophagus, or it is
separated from it by a mass of areolar tissue.

The anterior and posterior borders of the lung are in

THORAGie CAVITY 41

marked eontrast with eaeh other. The anterior is eompara-
tively short and thin and it extends medially into the eosto-
mediastinal sinus of the pleura, whieh lies posterior to the
sternum and the eostal eartilages. It eommenees at the apex,
curves downwards, anteriorly and medially, posterior to the
sterno-clavicular artieulation, to the lower border of the
manubrium sterni, and then it deseends vertically to the base.
Immediately below the highest point of the apex it is grooved
by the subclavian artery on eaeh side, and on the left side it
presents a eardiae noteh at the leverof the fifth eostal eartilage.
The posterior border is rounded and indistinet. It deseends
from the apex to the base, along the line of the artieulations of
the heads of the ribs with ^ie bodies of the vertebrge, and
it is mueh longer than the anterior border.

Lobes of the Lniigs. — The left lung is divided into two
lobes by a long, deep obligue fissure whieh penetrates its
substanee to within a short distanee of the hilus. This fissure
begins above at the posterior border, about two and a half
inehes below the apex, at the level of the vertebral end of
the third rib, whieh eorresponds with the medial end of the
spine of the seapula. It is eontinued on the lateral surface,
in a somewhat spiral direetion, downwards and anteriorly till it
euts the inferior margin opposite the lateral part of the eostal
eartilage. The upper lobe of the lung lies above and anterior
to this cleft It is eonieal in form, with an oblique base.
The apex and the whole of the anterior border belong to it.
The lower lobe^ somewhat quadrangular, is more bulky than the
upper, and lies below and posterior to the Assure ; it eomprises
the entire base and the greater part of the thiek posterior
border.

In the right lung there are two fissures subdividing it into
three lobes. The obligue fissure is very similar in its position
and relations to the fissure in the left lung, but it is more
yertieal in direetion. It separates the lower lobe from the
upper and middle lobes. The seeond cleft, the horizontal
fissure^ begins at the anterior border of the lung at the level
of the fourth eostal eartilage and extends horizontally till it
joins the oblique fissure. The middle or intermediate lobe,
thus eut off, is wedge-shaped in outline. It lies between the
oblique and horizontal fissures.

i:dfrerences between the two Lungs. — The disseetors should
partieularly note the following differences between the two

4»

THORAX

lungs : — (i) The right lung is slightly larger than the left, in
the proportion of ii to lo. (2) The right lung is shorter
and wider than the left lung. This di^Terenee is due to
the great bulle of the right lobe of the Iiver, whieh eleyates
the right eupola of the diaphragm to a higher Ievel than
the Ieft eupola, and also to the heart and perieardium, whleh
project more to the !eft than the right, and thus diminish
the width of the left lung. (3) The anterior sharp
margin of the right lung is more or less straight; the
eorresponding margin of the left lung presents, in its lower
part, a marked angular' deficiency [ineisura eariiaed) for the

/"'■'•■"

reeeption of the heart and the perieardium. (4) The right
lung is subdiyided into three lobes, and the lcfi lung into two.
Ba>diz Pulmonis. — The root of the lung is formed by a
number of struetures whieh enter the lung at the hilus or
siit on its mediastinal suriaee, The struetures whieh form
the root are held together by an inrestment of pleura, and
they eonstitute a pediele whieh attaehes the lung to the
eontents of the mediastinum. The pleura has already been
remoyed from around them, and now a more detailed
examination of the eonstituent parts of the root and of its
relations must be made. The portion of the root still

THORAGie CAVITY 43

attaehed to the mediastinum should be used for this
purpose.

Disseetion, — Commence with the vagus nerve and follow it downwards
from a point just above the vena azygos on the right side, and from the areh
of the aorta on the left, looking carefully for small branehes whieh spring
from its anterior border and pass to the anterior surface of the root, where
they eommunieate with the twigs from the sympathetie ganglia, and from
the deep eardiae plexus, to form the anierior ptdmonary pUxus^ from
whieh branehes are distributed to the walls of the air tube and the blood
vessels. On the left side a few twigs may be found passing from the super-
ficial eardiae plexus to the anterior pulmonary plexus. After ihe branehes
of the vagus to the anterior pulmonary plexus have been identified, the
trunk of the vagus, on eaeh side, must be followed down to the posterior
surface of the root of the lung, where it breaks up into branehes whieh
unite with twigs from the eorresponding sympathetie trunk to form the
posterior pulmonary plexus (see p. 28). The posterior pulmonary plexuses
of opposite sides are eonneeted together by strong branehes, whieh pass
both anterior and posterior to the oesophagus, and eaeh gives branehes to the
walls of the bronehial lube and the blood vessels of the root of its own side.
These various branehes must be found and identified. After the posterior
pulmonary plexuses are satisfactorily displayed the bronehial blood vessels
should be found and deaned.

Arterise Bronehiales. — As a rule, two bronehial arteries are
distributed to the left lung and one to the right lung. The
two left bronehial arteries spring from the deseending aorta.
The right bronehial artery is a braneh either of the Arst right
aortie intereostal artery or of the upper left bronehial artery.
The bronehial arteries and their branehes run along the
posterior surfaces of the bronehi and their branehes, and
are the proper nutrient yessels of the lungs. Part of the
blood whieh they convey to the lungs is returned by the pul-
monary veins to the left atrium of the heart, but the remainder
is returned by bronehial veins, whieh open on the right side
into the vena azygos, and on the left side into the vena
hemiazygos aeeessoria, or into the left superior intereostal
vein.

Dissedion. — After the bronehial vessels have been traeed, the disseetor
should separate the great vessels and the air tube from eaeh other. Whilst
attempting this, he will find that his work is greatly impeded by the
hardened and pigmented bronehial glands. The relative positions of the
eonstituent parts of the roots of the lung have been noted already (p. 22).

The Belations of the Boots of the Limgs. — Anterior to the
root of eaeh lung are the phrenie nerve, with its aeeompanying
vessels, and the anterior pulmonary plexus ; behind it, the
posterior pulmonary plexus, and below it, the ligamentum
pulmonis. In addition, in front of the root of the right lui

THORAX

is the superior vena cava, aiid above and behind it, tlie vena
azygos. Whitst above the root of the left lung is the aortie
areh, and behind it, the deseending aorta (Figs. la and 13).
Bronehi. — There are two primary bronehial tubes, one
for eaeh lung. They spring froni Ihe lermination of the
traehea, and eaeh passes downwards and laterally, in the
root of the eorresponding lung, to the hilus, througb wbieh
it enters the lung. After passing through the hilus it deseends,
in the substanee of the lung, to ihe base, lying nearer the
posterior than the anterior border. In the root of the lung
the brouehus is erossed anteriorly by the pulmonary artery,

whieh afterwards deseends on the postero-lateral aspeet of the
intra-pulmonary part of the bronehial tube.

The relations of the bronebi are eonsidered later (p. 96).

The MediaBtmum and its Contents. — It has been pointed
out already that the raediastinum is the interval whieh
extends froni the sternum to the vertebral eolumn between
the two pleural saes ; that it is oeeupied by some of the
most important yiseera, vessels and nerves in the body,
i.e. the heart endosed in the perieardium ; the aorta and
its great branehes ; the great vessels whieh earry the blood
to and from the beart ; the eesophagus and traehea ; the
vagi and phrenie nerves; and ihe thoraeie duei. It was

THORAGie CAVITY

noted furlher that the nriediastinuiii is separated, for deserip-
tive purposes, into two main parts, the superior and the
inferior mediastinum, by an imaginary plane whieh passes
from the lower border of the tnanubrium anteriorly to the

in of the Anlerior P«tl
eostal eartilages were replaeed in posit
made. The rigtil sealenus ai
Ihe level of the upper border of Ihe !

away from il

lower border of the fourth thoraeie vertebra posteriorly ; it has
been noted also that the inferior mediastinum is separable
into three parts: (i) the anterior mediastinum, anterior to the
perieardium, (a) the posterior mediastinum, posterior to the
perieardium, and (3) the middle mediasttnum oeeupied by the
perieaidium, the heart, the great vessets immediately adjacent

46 THORAX

to the heart, and the phrenie nerves with their aeeompanying
yessels. These seetions of the mediastinum and their eon-
tents must now be examined in detail.

Disseetion. — The remains of the anterior part of the mediastinal pleura
must be divided longitudinally immediately posterior to the sternum, from
the lower end of the thorax to the apiees of the pleural saes. The sternal
extremities of the first ribs must be then eut through, elose to the manu-
brium sterni, and, at the same time, the sternal heads of the stemo-mastoid
museles must be separated from the manubrium, if that has not already
been done by the disseetor of the head and neek. After the sterno-
mastoid museles and the first ribs are divided, the sterno-hyoid and stemo-
thyreoid museles must be eut through transversely, as elose to the upper
margin of the manubrium as possible. Next, the body of the sternum must
be separated from the xiphoid proeess and the tips of the seventh eostal
eartilages. The sternum with the attaehed eostal eartilages may then be
removed and plaeed aside, but it must be carefully preserved for future use.

When the sternum is removed the mediastinum is exposed from the
front. As seen from the front, the superior mediastinum, whieh lies posterior
to the manubrium, is a relatively wide triangular area, with its apex below.
The anterior mediastinum, on the other hand, is merely a narrow cleft
between the adjacent anterior margins of the pleural saes, except opposite
the anterior end of the left fifth eostal eartilage where the left pleural sae
deviates slightly to the left and the anterior mediastinum beeomes slightly
wider (Fig. 20).

The anterior parts of both the superior and the anterior mediastina are
oeeupied by areolar tissue in whieh, as far down as the third or fourth
eostal eartilages, remains of the thymus gland niay be found.

Thymus. — The thymus gland is a bilobed organ, developed
from the third yiseeral clefts. It is well developed in the
foetus and in the ehild until the end of the seeond year.
Then it frequently undergoes atrophy, but it may persist even
until old age.

Disseetion. — All the remains of the mediastinal pleura and the thymus gland
should now be taken away, and the anterior surface of the perieardium and
the eontents of the superior mediastinum should be thoroughly eleaned.
When this has been done the right and left innominate veins and their
tributaries will be exposed. The innominate veins should be traeed to
their union with the superior vena cava. To the left of the superior vena
cava and below the left innominate vein lie the upper part of the aseending
portion of the aorta, and the anterior part of the aortie areh. When these
eontents of the upper part of the mediastinum have been thoroughly eleaned,
the various struetures found in the mediastinum must be studied in detail.

Venae Anonymse. — The innominate vein of eaeh side is
formed posterior to the sternal end of the eorresponding clavicle
by the union of the internal jugular and subclavian veins
of the same side, and it ends, at the lower border of the
right first eostal eartilage, by uniting with its fellow of the
opposite side to form the superior vena cava.

The right innominate vein is short and its eourse is

THORAGie CAVITY

almost vertical, It is aeeompanied on its medial side by the
innominate artery, on its lateral side by the righl phrente nerve,
and posterioriy by the right vagus nerve. Antero-laterally
it is in relation with the anterior margin of the right pleura.
The kft innominate vein is mueh longer than the right

\e nvemge adult.

It passes obliquely to the right and downwards, posterior to the
upper half of the manubrium sterni ; it lies posterior to the re-
inains of the ihymus glandandthe lower ends of the sterno-hyoid
and thyreotd museles, and anterior to the three great branehes
of the aortie areh and the left phrenie and vagus nerves.

Tributaries. — These are (i) the internal jugular vein, (2)
the subclavian vein, (3) the yertebral vein, (4) the internal
mammary vein, and frequently (5) the inferior thyreoid vein

THORAX

of the same side. In addition, the right innominate vem
receives the right lymph duet, or lymph vessels from the
head and neek, the upper extremity and the right half of
the thoras of the same side ; and the left innominate vein
receives (a) the lefi superior intereostal vein, (i) some peri-
eardiae and thymie veins, and (i^) the thoraeie duet.

Disue/iiin.—AtleT the innominate veins and their tributaries have been
studied the left vein may be pushed aside, or, ir neeessaiy, it may be eut

n order to display the thtee great branehes of the areh

^rsi'!

Arteria Anonyma, — The innominate artery is the largest
of the three great branehes of the aortie areh. It eom-
menees, from the upper border of the areh, posterior to the
eentre of the manubrium, passes upwards and to the right,
and terminates, posterior to the upper border of the right sterno-
clavicular artieulation, by dividing into the right eommon
earotid and ihe right subclavian arteries. Anterior to it are
the manubrium sterni, with ihe attaehments of the sterno-
hyoid and thyreoid museles, the right sterno-elayieular jo!nt,
the remains or the thymus gland, and the left innominate vein.

THORAGie CAVITY 49

Posterior to its lower part is the traehea, but as the artery passes
upwards and to the right it gains the side of the traehea and
has the upper part of the lung and pleura posterior to it.
To its left, at its eommeneement, is the left eommon earotid
artery, and at a higher level the traehea. On its right side
is the right innominate vein, whieh separates it from the right
phrenie nerve and the pleura. As a rule it gives off its
terminal branehes only, but oeeasionally a small artery, ealled
the thyreoidea ima^ springs from it

The Thyreoidea Ima.— This artery is frequently absent. When it is
present il springs from the innominate artery, or from the areh of the aorta,
and runs upwards, anterior to the traehea, to the thyreoid gland.

Arteria Oarotis Gominanis Sinistra. — The left eommon
earotid artery springs from the areh of the aorta immediately
to the left of, and slightly posterior to, the innominate artery.
It passes upwards, through the superior mediastinum and
posterior to the left sterno-clavicular joint, into the neek. Its
anterior relations in the thorax are similar to those of the
innominate artery. Posterior to it^ from below upwards, are the
traehea, the left reeurrent nerve, the oesophagus and the
thoraeie duet, and, on a plane somewhat more to the left, the
left phrenie and vagus nerves, and the subclavian artery. To
its right lie iirst the innominate artery, and then the traehea \
and to its left is the left pleura. It gives off no branehes in
the thorax.

Arteria Subclavia Sinistra. — The left subclavian artery
springs from the posterior part of the aortie areh, posterior to
the left eommon earotid. It passes vertically upwards, through
the superior mediastinum and posterior to the sternal end of
the clavicle, into the root of the neek. Anterior to it are the
left phrenie and vagus nerves, whieh separate it from the
left eommon earotid artery. Posterior^ and to its left side, it
is in relation with the left mediastinal pleura and the lung.
To its right side are the traehea and the left reeurrent
nerve, and, at a higher level, the eesophagus and the
thoraeie duet. It gives off no branehes in the thoraeie part
of its eourse.

Disseetion, — The lateral walls of the perieardium have already been
exposed and opened (see p. 33) ; the flaps then made should be replaeed
and fixed in position. When this has been done, the outline of the sae
will be fully displayed, and the disseetors ean then study its relations to
adjacent organs.

YOL. II — 4

So THORAX

The Perieardium. — This is a Abro-serous sae whieh oeeupies
the middle mediastinum. It surrounds the heart and the roots
of the great vessels whieh enter and leave the heart.

TTie Fibrous Perieardium, — The fibrous or outer part of
the perieardium is eonieal in form. Its base rests upon the
diaphragm, prineipally on the eentral tendon but also
upon the museular portion, partieularly upon the left side.
Near the median plane it is blended with the eentral tendon,
and ean be separated from it only by the aid of the edge
of the sealpel; more laterally the areolar tissue whieh
eonneets the perieardium and the diaphragm is easily broken
down by the handle of the knife. The diaphragm separates
the perieardium mainly from the upper surface of the liver, but
also, towards the left and anteriorly, from the fundus of the
stomaeh. The apex of the fibrous sae blends with the outer
eoats of the aorta, the pulmonary arteries and the superior
vena cava. The anterior su?face lies behind the body of the
sternum and the eartilages of the ribs from the seeond to the
sixth inclusive, but it is separated from them by the lungs and
pleurae, except (i) in the median plane of the anterior medi-
astinum, where eondensations of the areolar tissue of the medi-
astinum, ealled the superior and inferior sterno-perieardiae
ligaments^ eonneet the anterior surface of the fibrous sae to
the upper and lower ends of the body of the sternum
respectively, and (2) in the region of the sternal extremity of
the left fifth eostal dartilage, where the left pleura retreats
somewhat towards the left side, and the perieardium eomes
into direet relation with the sternum and the left transversus
thoraeis musele. This portion of the perieardium is the
so-ealled bare area. It is usually of small extent, and frequently
it does not extend beyond the margin of the sternum, but it is
of importanee beeause through it the surgeon attempts to tap
the perieardium when the sae is distended with fluid.

The lateral walls of the perieardium are in relation with
the mediastinal pleura, the phrenie nerve and the perieardiaeo-
phrenie vessels intervening (O.T. eomes nervi phreniei). The
posterior surface lies anterior to the deseending aorta and the
oesophagus medially, whilst laterally it is supported posteriorly
by the lungs and pleurae. At the junction of the upper parts of
the lateral and posterior surfaces, on eaeh side, two pulmonary
veins enter the perieardium and receive sheaths from its
fibrous wall.

THORAGie CAVITY

Dissediim. — When the relationa and prolongations of ihe tibrous peri-
eaidium have been studied, the two anterioi fUps already made in the
liteial walls oF the sae (see p. 33) shouhl be eonneeted ((^ethei and eon-
vetted into one large aDterioi flap. This ean be done by a liansverse eut,
passing aeioss the median plane jus( above (he diaphragm. The large

(riangulai tlap thus forn

Sould be (hrown upwards towards ihe apcx of

7(fe Serous Perieardium. — The serous perieardium is a
elosed and invaginated sae whieh iines the inner sutface of
the fibrous sae and envelops the heart and the roots of the
great vessels passing to and froin the heart.

The uninyaginated portion of the wall of the serous sae,

5»

THORAX

whieh lines the inner surface of the Abrous saCj is ealled the
parietal layer, and the invaginated portion, whieh enveiops the
heart, is the visceral portion. The inner surface of the sae is
lined by a iiat endothelium, and, during health, is smooth and

-The Perieardiiim ani
having been opened by ihe

if the Hearl. The thorade
injeclion, Ttie perieardium
lerior wall, the gteat yessels

glistening. The parietal and visceral layers are separated,
during health, merely by a thin layer of serous fluid, whieh
prevents friction between the two suriaees as they move over
eaeh other during the eontraetions and expansions Df the
beart.

THORAGie CAVITY 53

The Stemo-eostal 8iirilftce of the Heart. — B€fore the
disseetors disturb the heart, whieh- has been exposed by the
reflection of the anterior wall of the perieardium, they should
note carefully not only the parts of the heart whieh are visible,
but also their relations to the anterior wall of the thorax.
The latter they ean easily do by replaeing the sternum and
eostal eartilages in position from time to time.

They will find that the stemo-eostal surface is divided
into an upper, right, or atrial portion and a lower, left, or
ventricular portion by an oblique suleus, the eoronary su/eus
(O.T. auriculo-ventricular\ whieh is quite distinet below and
on the right, but is masked above and to the left by the
roots of the pulmonary artery and the aorta. The position
of this suleus ean be indieated on the surface by a line
extending obliguely downwards and to the right, from the
sternal end of the third left to the sternal end of the sixth
right eostal eartilage. Below and to the left of the suleus
is the ventricular part of the sterno-eostal surface, termi-
nating on the left and below in the apex of the heart, whieh
lies posterior to the fifth left intereostal spaee, three and a half
inehes from the median plane. The ventricular area of the
sterno-eostal surface is divided by the anterior longitudinal
suleus (O.T. anterior interventricular suleus) into a right
two-thirds, formed by the right ventricle, and a left third,
formed by the left ventricle. The anterior longitudinal
suleus terminates on the lower border of the sterno-eostal
surface, to the right of the apex, in a slight noteh, the ineisura
eordis. The apex, therefore, is formed entirely by the left
ventricle. The lower margin of the stemo-eostal surface lies
on the diaphragm. It is formed chiefly by the lower border
of the right ventricle, and only to a small extent by the apieal
part of the left ventricle.

The upper and right portion of the sterno-eostal surface is
formed by the atria, whieh are to a large extent eoneealed by
the pulmonary artery and the aseending part of the aorta.
Above and to the right is the right atrium, eontinuous above
with the superior vena cava and below with the inferior vena
cava, whilst its aurieular portion (O.T. aurieular appendage)
curves upwards and to the left, along the line of the eorona
suleus, to the root of the pulmonary artery.

Grossing the front of the right atrium, immediately b
the lower end of the superior vena cava, is a suleus, the s

THORAX

terminalis. If the heart is pulled a little over to the left this
suleus ean be traeed downwards, along ihe lateral aspeet of
the right atriuni) to the anterior aspeet of the upper end of
the inferior vena cava. It indieates the separation belween

KiBhlee

inunaa e.iiotid «rlery

L.ftcominoii(ar<

;<>rriEh[im

«mal iuEular vfln ,

BndoeitdiT

' Rigb. su

, U(. i<A«V

Righ,.ulxL

ivLiii>tin ;

L-:fli

FiG. 25. — Disseeti

ihe venous sinus of the atrium, into whieh the great veins
open, and the cavity of the atrium proper.

The whole of the right border of the heart is formed by
the right atrium. Its positton ean be indieated on the surface
by a line, convex to the right, whieh eommenees at the level
if the ihird right eostal eartilage, half an ineh from the

THORAGie CAVITY 55

sternum, and terminates opposite the sixth right eartilage at
the same distanee from the right margin of the sternum. At
the ugp^er and left eorner pf the atrial area is the apex of the
left auriele (O.T. aurieular appendage), and between the two
auncles~are the roots of the pulmonary artery and the aorta,
the former anterior to the latter. The rounded portion of
the upper part of the right ventricle, immediately below the
pulmonary artery, is the eonus arteriosus,

If a finger is introdueed into the cleft between the aorta
anteriorly and the superior vena cava posteriorly, it ean be
passed aeross, froni the right to the left side of the perieardial
cavity, through a passage, ealled the iransverse sinus of the
perieardium (Figs. 24 and 27). This sinus lies anterior to the
superior vena cava and the atria, and posterior to the aseending
aorta and the stem of the pulmonary artery. The upper border
of a finger plaeed in the sinus will indieate the position of the
upper border of the heart. This border is formed to a slight
extent by the upper border of the right atrium, but mainly by
the upper border of the Jeft atrium. Its position ean be in-
dieated, on the anterior surface of the body, by a line eom-
meneing half an ineh from the side of the sternum at the lower
border of the seeond left eostal eartilage, and ending at the
same distanee from the sternum on the upper border of the
third right eartilage. Whilst a finger is kept in the transverse
sinus a pointer should be introdueed into the right pulmonary
artery through its eut end in the root of the right lung. The
disseetor will note, as the pointer traverses the right pulmonary
artery, that it passes first posterior to the superior vena cava and
then along the upper border of the transverse sinus, that is
along the upper border of the heart where that border is
formed by the left atrium ; therefore the position of the right
pulmonary artery may be indieated, on the anterior surface
of the body, by the right two-thirds of the line whieh marks
the position of the upper border of the heart.

The left border of the anterior surface of the heart is
formed, to a slight extent, by the left atrium, but mainly by
the left ventricle. It is convex to the left and its position
is marked, on the surface of the body, by a line whieh eom-
menees above at the lower border of the left seeond eostal
eartilage, half an ineh from the sternum, and terminates b
at the apieal point in the fifth left intereostal spaee.

Before proeeeding further the disseetor should s»

56 THORAX

the information he has gained regarding the relationship of
the apex of the heart and the borders of the sterno-eostal
surface of the heart to the anterior wall of the thoraK, The
upper border is formed by the atria, and as the heart lies in
situ it is eoneealed to a great extent by the aorta and the

a C1avic1>
LA. Leftal
LV, Ltflw

Puloionary ot
Righlalrium.
lUehl venliic

pulmonary artery, Its position is marked on ihe surface
by a line extending frora the lower border of the seeond
left to the upper border of the third right eostal eartilage,
eommeneing and terniinating about lialf an ineh from the
border of ihe slernum. The righl bordtr is foriiied entirely
by the right atrium, and its position is indieated on the sur-

THORAGie CAVITY 57

face by a line, convex to the right, eommeneing above at the
lower border of the right seeond eostal eartilage, half an ineh
from the side of the sternum, and terminating below at the
sixth right eartilage half an ineh from its junction with the
sternum. More than two-thirds of the lower border are formed
by the right ventricle, and the remainder by the apieal portion
of the left ventricle, and the two parts may be separated by
a distinet noteh, the indsura eordis. This border is slightly
concave downwards, in eorrespondenee with the upward
convexity of the diaphragm on whieh it rests, and it has a
slight inelination downwards and to the left. It is marked,
on the surface of the body, by a line extending from the
sixth right eostal eartilage, near the sternum, to the apieal
point, whieh lies in the left fifth intereostal spaee from 3^
to 3I inehes from the median plane. The left border, whieh
is formed mainly by the left ventricle and only to a slight
extent by the left atrium, extends from the apex to a point
on the lower border of the left seeond eostal eartilage half
an ineh from the margin of the sternum.

The eoronary suleus, whieh indieates the plane of union

of the atria and ventricles and, therefore, the plane of the

atrio-ventricular and aortie and pulmonary orifices of the

heart, ean be indieated, on the surface, by a line extending

from the sternal end of the third left eostal eartilage to the

sternal end of the sixth right eartilage. Posterior to the left

extremity of this line, at the level of the upper part of the

third left eostal eartilage, is the orifice of the pulmonary artery.

The aortie orifice is a little lower and slightly to the right,

posterior to the sternum at the level of the lower border of the

third left eartilage. Immediately below the aortie orifice,

posterior to the left margin of the sternum, at the level of the

upper part of the fourth left eartilage, lies the mitral orifice ;

and the trieuspid orifice is situated posterior to the middle of

the sternum, opposite the fourth intereostal spaees. The

positions of the great orifices eannot be confirmed at this

stage of the disseetion, and they will be noted again at a

later period when the heart is opened.

After the sterno-eostal aspeet of the heart, the boundaries
of the transverse sinus, and the general position of the heart
have been studied, the disseetors should turn the apex of *'
heart upwards and to the right, and examine the in<
and posterior surfaces whilst the heart is still in situ.

56 THORAX

the mformation he has gained regarding the relationship of
the apen of the heatt and the borders of the sterno-eostal
surface of the heart to the anterior wall of the thoraK. The
upper bordtr Is formed by the atria, and as the heart lies in
situ it is eoneealed to a great extent by the aorta and the

pulmonary artery. Its position is marked on the surface
by a line extending from the lower border of the seeond
lert to the upper border of the third right eostal eartilage,
eommeneing and terminating about half an ineh from the
border of the sternum. The righi border is foriiied entirely
by the right atrium, and its position is indieated on the sur-

THORAGie CAVITY 57

face by a line, convex to the right, eommeneing above at the
lower border of the right seeond eostal eartilage, half an ineh
from the side of the stemum, and terminating below at the
sixth right eartilage half an ineh from its junction with the
sternum. More than two-thirds of the lower border are formed
by the right ventricle, and the remainder by the apieal portion
of the left ventricle, and the two parts may be separated by
a distinet noteh, the indsura eordis, This border is slightly
concave downwards, in eorrespondenee with the upward
convexity of the diaphragm on whieh it rests, and it has a
slight inelination downwards and to the left. It is marked,
on the surface of the body, by a line extending from the
sixth right eostal eartilage, near the sternum, to the apieal
point, whieh lies in the left fifth intereostal spaee from 3^
to 3j inehes from the median plane. The left border, whieh
is formed mainly by the left ventricle and only to a slight
extent by the left atrium, extends from the apex to a point
on the lower border of the left seeond eostal eartilage half
an ineh from the margin of the sternum.

The eoronary suleus, whieh indieates the plane of union
of the atria and ventricles and, therefore, the plane of the
atrio-ventricular and aortie and pulmonary orifices of the
heart, ean be indieated, on the surface, by a line extending
from the sternal end of the third left eostal eartilage to the
sternal end of the sixth right eartilage. Posterior to the left
extremity of this line, at the level of the upper part of the
third left eostal eartilage, is the orifice of the pulmonary artery.
The aortie orifice is a little lower and slightly to the right,
posterior to the sternum at the level of the lower border of the
third left eartilage. Immediately below the aortie orifice,
posterior to the Ieft margin of the sternum, at the Ievel of the
upper part of the fourth left eartilage, lies the mitral orifice ;
and the trieuspid orifice is situated posterior to the middle of
the sternum, opposite the fourth intereostal spaees. The
positions of the great orifices eannot be confirmed at this
stage of the disseetion, and they will be noted again at a
later period when the heart is opened.

After the sterno-eostal aspeet of the heart, the boundaries
of the transverse sinus, and the general position of the heart
have been studied, the disseetors should turn the apex o^
heart upwards and to the right, and examine the
and posterior surfaces whilst the heart is still in sit

6o THORAX

examination of the yense cavae will show that the lower ineh
of the superior vena cava lies within the fibrous perieardium
and that it is ensheathed, except along its postero-medial
border, by a covering of the serous layer, whilst the inferior
vena cava ean seareely be said to have any intra-perieardial
eourse, for it joins the lower and posterior part of the right
atrium immediately after piereing the fibrous layer, but the
margin of the orifice by whieh it enters is surrounded by the
serous layer except along a narrow Hne posteriorly. The
left pulmonary veins are covered by the serous layer on their
superior, anterior, and inferior aspeets, but not posteriorly;
and the right pulmonary veins, whieh enter the left auriele as
soon as they have piereed the fibrous perieardium, are in rela-
tion with the serous layer merely along the medial and lateral
borders of the orifices in the fibrous layer through whieh
they enter.

Disseetion. — After the examination of the reflections of the serous layer
of the perieardium is eompleted, the disseetors should study the vessels and
nerves whieh supply the walls of the heart. They are the eoronary arteries
and the eardiae veins and nerves, and they lie in the eoronary and longitudinal
sulei of the heart, whieh have been noted already. To display them the
visceral perieardium superficial to them must be eut and turned aside, the fat
whieh lies in the sulei around the vessels must be removed, then the main
vessels ean be traeed to their origins and terminations, and an endeavour
should be made to preserve the fine nerves whieh aeeompany the vessels.

ArteiisB Coronaxise. — The eoronary arteries are the nutrient
vessels of the heart. They spring from dilatations of the eom-
meneement of the aorta whieh are ealled the sinus aortee
(Valsalva). There are three sinuses of the aorta, an anterior
and two posterior, and only two eoronary arteries, a right and
a left ; the right artery springs from the anterior sinus, and
the left from the left posterior sinus.

The right eoronary artery passes anteriorly from the anterior
aortie sinus, between the pulmonary artery and the right
auriele ; turns downwards and to the right, in the eoronary
suleus, to the lower part of the right margin of the heart, round
whieh it curves. Then it proeeeds to the left, in the posterior
part of the eoronary suleus, till it reaehes the posterior end
of the inferior (posterior) longitudinal suleus, where it divides
into a small transverse and a large interventricular braneh.
The transverse braneh eontinues to the left till it anastomoses
with the circumflex braneh of the left eoronary artery. The
interuentrieular (deseending) braneh runs anteriorly in the

THORACIC CAVITY 6i

inrerior longitudinal suleus on the diaphragmatie surface of
the heart, and it anastomoses with the intcrvcntriculaT or
deseending braneh of the left eoronary artery at the eardiae
noteh on the lower margin of the heart. In addition to iis
terminal branehes, the right eoronary artery supplies branehes
to the roots of the pulnionary artery and ihe aorla, and to

of riahl eortpnary ortery

FiG. 28.— The Base of the Ventricular Pan of ihe Htarl from whieh the
Airia have been remoi«d. The detaehed atria are depieted in Fig.
31. The speeimen was hardered i'b sila.

the walls of the right atriuni and the right ventricle, the
larger and more nuinerous branehes being given to ihe
ventricle. One of the latter, the marginai braneh^ passes
along-the lower margin of the heart towards the apex of the
ventricle (see Fig. 29).

The , ltft eoronary artery, as it springs from the left
posterior aortie sinus (Fig. 28), lies posterior to the pulmonary
artery. For a short distanee it nins to the !eft, then it tums
anteriorly, between ihe pulmonary artery and the Ieft auriele,

62 THORAX

aiid diyides into a deseending or interyentrieular, and a
circumflex braneh. The inUrventricular branek passes down
the sterno-eostal surface of the heart, in the anterior longitudinal
suleus (Fig. 29), and turning tound the lower border, in the
eardiae noteh, it anastomoses with the inteTventricular braneh

ELghl_

of the right eoronary artery. The circumfiex braneh nins to
.theleft, in the eoronary suleus, turns round the left border
of the heart (Fig. 28) and anastomoses, on the posterior
surface, wilh the transverse terminal braneh of the light
eoronary. Prom the stem of the artery twigs are given to
the roots of tho pulmonary artery and the aorta, and its
terminal branehes 3u[)ply the walls of both ventricles and the_
walls of the left atrium.

Yeiue Goidis. — The eardiae veins are : (i) the eoronary;-

THORAeie CAvrry

<>>

ver

(i) the great eardtae vein ; (3) the inferior (posterior)
ventrkular vein ; (4) the iniddle eardiae vein ; (5) the obli(]ue
(6) the small eardiae vein; {7) the anterior eardiae
and (3) the venfe minimse eoniis.
The eoromry sinus lies at the base of the heart, in tlie
isterior part of the eoronaiy suleus, between the left atrium
'and the left ventride, It ean be displayed when the apex of
the heart is turned upwards and lo ihe righl. Its righl
eKtremity opens into ihe right atrium, immediately below and
to the left of the oriliee of tlie inferior vena cava, At its lefl

ihe Surtaee of the

extremily it reeeiyes the great eardiae vein. The greal eardiae
vein aseends along the anterior longitudinal suleus (Fig. 29),
where it lies in relation with the interventricular braneh of the
left eoronary artery. Al the upper end of the interventricu]ar
suleus it turns round the left border of the heart, with the
circuinflex braneh of the left eoronary artery, and it ends in
the left extremity of the eoronary sinus. The inftrior
(posterior) ventriatlar vein or yeins, from the diaphragmatie
surface of the left ventricle, and the middle (ardiae vein, whieh
mns posteriorly in Ihe inferior longitudinal suleus, end in the
T border of the eoronary sinus. The oblique vein deseends

l^^runs poste
l^^^bwer bord

THORAX

on the posterior wall of the left atriuni and ends in the upper
border of the sinus; and the small eardiae vtin (O.T. right
eoronary) runs along the lower margin of the heart with the
marginal braneh of the right eoronary artery, curves rourtd
the right border of the heart, in the eoronary suleus, ends in
the right extreniity of the eoronary sinus. The anterior eardiae

iHeeliun Df seruus perkardiun

FiG. 31.— The Amei

s depieled in Fig. 28. The speeini

veins are small vessels whteh aseend along the anterior surface
of the right ventricle and terminate direetly in the lower aod

anterior part of the right atrium. The ventt eordis minima are
small veins whioh pass from the substanee of the heart, and
more partieularly from the walls of the right atrium and
ventricle, and open, by small oriliees, into the cavity of the
right atrium. Tlie orifice through whieh the great eardiae
vein opens into the eoronary sinus is usually provided with a
valve ; the orifice of the small eardiae vein may be provided

Oardia-: N

T - .

*■ •;

» '_

_ -j' _i • >«

* ~ ■ ^ ■

r.r. r_'c:

XI •^.... ........

•^ -r • ^

l r '■■"'• -s ~ r»x ••--*-

.'. ■ ...■--. ^ * " i_r V * " • • • . ; . • .

'"•- ,_,..- ••.•r»*;v.*'"

a.,:.... .- ■ .-^ V-' ^ Tav *-. >:-- " V- * •

lir.: :-r:r "■ r.5 .■..-i-;"' . ■^- i •

■wr. So.

Atrium Dextrum ( O.T Bight Aunele . <.;...::
atrium bv means of the fo.^.wKig .n.:>: .... I.: :.:
a: the apex of the aune.e (0. 1. aur!..-^..ir u: :.-::: ■,

thesuleus terminalis and thruugh the Iatera;_w.:.. = ! :

to ihe posterior

border of the lower up.d nf ti.e
cavv then downwards, posterior to ihe sUi.:i> tcr::.:s... . •

■ .' : « r-rivi • and finallv anteriorlw aemsr, thv '. a •

mferior vena ca\a . "*,.,- . •' .

0' the .suleus terminahs and above the anterior a^pt. : : :
lower end of the inferior vena cava, to the o..r..:iary s,: r
Throw the Aap thus formed anteriorly, and elean the ::!ivr:.>r
of the cavity ^vith a sponge.

. , Aap is turned anteriorly a vertical museular ! i::Klle
will be noted on its inner surface. This is the eristn hrniituilis^
whieh eorresponds in position with the suleus tL-rnii^^a'.is un
the outer surface. It marks the boundary betweLU ihe

« ^ • «oi-t the atrium, and the posteriur part, whieh
anterior part, lh*- > ^ r i ,

is k own as the venous smus beeause the great vein.s ol
You n — 6

THORAK

the body and heart open into it. These two parts of the
cavity differ, however, not only in position and their relations
to the great yeins, but also in the eharaelers of their walls.
The whole of the interior of the atrium presents a polished
glossy appearanee, due to the endoeardial lining; but whilst the
wall of the venous sinus is smooth, the rest of the wall of the
atrium is rendered rugose by a large number of museular ridges

whieh eommenee at the erista terminalis and run anteriorly to
the right margin of the atrium. These bundles, on aeeount
of their somewhat parallel arrangement, are ealled the museuli
pietinali.

The veins whieh open into the right atrium are the (i)
superior vena cava, (2) inferior vena cava, (3) eoronary sinus,
(4) anterior eardiae veins, and (5) venK eordis minimte. The
aperture by whieh the blood leaves it is the trieuspid orihee.

The orijice of the superior vena (ava is in the upper and
posterior part of the atrium, at the Ievel of the tliird right eostal

THORAGie CAVITY

eartilage. It is entirely devoid of any valvular arrangenienl,
Immediateiy below it on the posterior wall of the atrium, in
a well-lixed heart, will be found a rounded prominenee,
t?u intervenous tubtrek (Lower), whieh tends to throw the

FiG. 33.— Sagittalst

stream of blood entering the atrium by Ihe superior vena
cava downwards and anteriorly into the atrio-ventricuIar orifice.
The orifice of the inferior vma cava is in the lower and
posteriorpartoftheatrium, at the level ofthesixth right eostal
eartilage and the lower border of the eighth thoraeie vertebra.
Running along its anterior margin, and intervening between it
and the atrio-ventricular opening, is the remnant of a valve,
the valve qf the vena cava (Eustaehian). It terminates, to the
left, in the lower end of a museular ridge, limbus fosne ova!is

(O.T. annulus malis), whieh lies on the inter-atrial septum
and forms the anterior and upper boundary of a shallow
fossa, the fossa twalis. At the upper end of this fossa there

was, during fcetal life, a forainen, the/e^

<ivak, through
whieh the two atria
eommunieatedwith
eaeh other, The
object of the valve
of the vena cava,
whieh in fcetal life
was mueh more
perfect, was to di-
reetthe oxygenated
inferior caval blood
through the fora-
men ovale into the
left atrium, whenee
it was passed into
the !eft ventricle,
and was then dis-
tributed, by the
aorta, throughout
the whole system.

During fcetal life it
would have been use-
less to pas5 the blood
through the lungs.

»hichw<

FiG. 34.

df:void of air. At the
een by ihe same time, had the
waii, or inat wall op- ox)^enated blood been
of ihe Yentrieles. This is passed through the
e speeimen ihal is depieled right atrium mto the
in pig. 31. tight ventricle, it would

have faileti to reaeh
the heod and the upper extremities, for, leaving the right ventricle liy Ihe
pulmonary artery, it would have enlered the aorta through the duetus
arteriosus beyond the origin of the left subclavian atlery and, thereibre,
beyond ihe innominate and leri eommon earolid a.rteries.

In many eases a small part of the foramen ovale persists
in the adult If it is present it will be found on the left of
the upper euryed end of the Umbus ovalis.

The opening of the eoronary sinus Hes to the left of the lower
end of the hmbus ovalis and direetly posterior to the trieuspid
oriliee. On its right margin lies a valvu]ar fold, the va!ve of

THORAGie CAVITV 69

the eoronary stnus (O.T, Thebesian)^ whieh tums ihe Mootl,
Aowing from lert to right in the sinus, anteriorly Inlo tht' atrio-
ventricular orifice. The venK minimae eordis and ihe anierior
eardiae veins open direetly into ihe alriuni hj- small orillees
seattered irregularly over the walls.

The Irieuspid orifice is in the lower and anterior lOTi of the
atrium. Il opens anteriorly inlo the lower and i>osicriur [lart iif
the cavity or the right ventricle, and is sufficieni1y large to
admit the tips of three Angei^ It is boundL-d by a fil>rous
ring to whieh the eusps of the righl atrio-vcntricular valve are
attaehed. These eusps will bc esamined when ihu righl
ventricle is opened.

■ough Ihe L'pper 1

Tlie Septnm Atriornin ajid the Fobu Oralis. — The inier-

atrial septum is a fibro-muscular partition whieh intervenes
between the right and ieft atria. In the fcetus it is piereed
by an obliquely direeted foramen, the foramen ovale, already
reterred to ; and in the adult it is marked on the lower and
posterior part of its right side by a shatlow depression, the/ossn
ovalis, whieh is bounded anteriorly and above by a museular
ridge, the limbus ovalis, whilst below and posteriorly it fades
away into the orifice of the inferior vena cava.

The floor of the fossa ovaIis is very thin ; it marks the
situation of the lower part of the foramen ovale of the fcetus,
and is formed by a portion of the inter-atrial wall whieh,
during fcetal life, aeted as a flap valve and prevented regurgi-
tation of blood from the lefl to the right atrium.

The Vena OaTO Saperlor. — The superior vena cava returns
to the right atrium the blood from the bead and neek, the

70 THORAX

upper extremities, the wall of the thorax, and the upper parts
of the walls of the abdomen. It eommenees, by the union
of the right and left innominate veins, at the level of the
lower border of the sternal end of the right first eostal
eartilage ; and it terminates, in the upper and posterior part of
the right atrium, at the level of the right third eostal eartilage,
about half an ineh from the right border of the sternum.
It lies partly in the superior and partly in the middle
mediastinum, and its lower half is within the fibrous perieardium
and is partly ensheathed by the serous perieardium.

Tributaries. — The tributaries of the superior vena cava are
the two innominate veins, by whose junction it is formed,
and the vena azygos, whieh enters it immediately before
it pierees the fibrous perieardium, at the level of the seeond
right eostal eartilage.

Relations. — The superior vena cava lies to the right of,
and somewhat posterior to, the aseending aorta. Posterior to
its upper part are the right pleura and lung on the right,
and the right vagus and the vena azygos on the left, and, at
a lower level, the right bronehus, the right pulmonary artery,
and the upper right pulmonary vein. Anteriorly and on the
left it is overlapped by the aseending aorta, and on the right
by the right pleura and lung. On its left side above is the
lower end of the innominate artery, and below is the aseending
aorta ; and on the right side is the right pleura, with the right
phrenie nerve and the aeeompanying vessels intervening.

The Thoraeie Part of the Iiiferior Vena Cava. — Only a
small portion, about three-quarters of an ineh, of the inferior
vena cava is found in the thorax. It aseends from the
diaphragm along the mediastinal surface of the right pleura
and lung, pierees the perieardium anterior to the lower
border of the right ligamentum pulmonis, and immediately
ends in the lower and posterior angle of the right atrium.

Relations. — Anterior to it is the diaphragm ; posterior to it
the vena azygos, the splanehnie nerves and the thoraeie duet ;
and to its right the phrenie nerve with its aeeompanying
vessels and the right pleura and lung (see Fig. 12).

Yentrieulus Dexter. — The cavity of the right ventricle
should be opened by three ineisions. The first should be
made transversely aeross the upper end of the eonus arteriosus,
immediately below the eommeneement of the pulmonary
artery. It should begin a little to the right of the upper

THORAGie CAVITY

end of the anterior longitudiiul suleus and terminate a
little to the left or the eoronary suleus. The seeond must
eommenee at the right end of the first and pass obliqucly
downwards and to the right, along the left margin of the
eoronary suleus, to the lower border of ihe heart, The third
eommenees at the lefl end of the first, follows the line of the
aiiterior tnter-ventricular suleus, lying a little to its right side.

FiG. 36.

ofthe Right Vtn

and also terminates at the lower margin of the heart. After
the triangular flap thus formed is turned downwards and lo
the right, the cavity of the ventricle should be eleaned with
the aid of sponge and forceps. If the moderator hand of
musele fibres, whieh eonneets the anterior wall of the ventricle
with the inter-ventricular septum, interferes with the neeessary
displaeement of the flap, it must be divided.

The cavity of tbe right ventricle has a triangular outline.
The atrio-ventricuiar orifice opens into the lower and posterior
angle, the pulmonary artery springs from the upper and

la THORAX

anterior angle, and between the two orifices is a strong and
rounded museular ridge, /Af supra-ventricular ridge. This
projects into the cavity eonyerting it into a U-shaped tube
whieh eommenees posterior to and below the supra-ventricular
ridge, runs anteriorly and to the left, towards the apex, and
turns upwards and anteriorly, along the anterior part of the
inter-ventricular septum and anterior to the supra-ventricular
rid^e, to the oriliee of the pulmonary artery.

On transverse seetion
the cavity of the right ven
tnele is semilunar in outline
in consequence of ihe thiek
I ' '^^^^^^ X.ik inter ventricular septum,

i^^^^H^ B^ ^^hii.h forms the left and
'^^■■pp' ^Kk. postenur wall bulging mto
■^ "^^^ ^ml. \\ the e-i^ity (Fig 37) Its

walls are mueh thieker
than the walls of the right
FiG 37 -Transierse seeiion thtoueh ^trium but much thinner

Ihe Yentrieular Pan of the Hearl than the walls of the left
seen froni ahove. ( Prom Lusehka, ) ventricle (Fig. 41). The

I. C»viiyofright™nrkk. reason for these differences

». Cavity of leik «nirieie. is obvious : the auride has

4! 'i^ick"w^rfwiveinrid= merely to force the blood

5. ThiDnerwaiiofrithtvemricie. through the wide atrio-

6. inisTior lungiiudinni (inisr.ven- ventricular orifice into the

v.in and inferior braneh of righi '"'g"^ ventricle, and the nght
eotonary attery. ventricle has only to send

j, Anler™ longiiudlnal (inWr-ven- (l,g blood thrOUgh the lungS

vein (uid anwtior btaneh "^or M '^ the left atrium ; but the

eoioraiy antry. left ventricle has to (oree

the blood through thewhole

of the body, the head and neek, aod the limbs ; and the

niuseular strenglh of the walls of the cavities of the heart is

proportiona! to the work they have to do.

The portion of the right ventricle whieh aseends to the
orifice of ihe pulmonary artery is the eonus arteriosus. Its
walls are smooth and devoid of projecting museular bundles,
but the inner surface of the walls of the remaining part of the
ventricle is rendered extremely irregular by the projeclion of
a laee-work of Aeshy ridges ealled irabeeula eamea. Some
of the trabeeulK are merely ridges raised in relief upon the

THORAGie CAVITY 73

surface; others are attaehed to the wall at eaeh extremity,
but are free in the rest of their extent. The cavity of the
ventricle is invaded, however, not only by the trabeeulse
earneae, but also by a number of eonieal museular projections,
the museuli papillares, These are attaehed by their bases to
the wall of the ventricle, whilst their apiees are eonneeted,
by a number of tendinous strands, to the margins and the
ventricular surfaces of the eusps of the atrio-ventricular valve.
As a rule there is one large anterior papillary musele attaehed
to the anterior wall, a large inferior papillar)* musele attaehed
to the inferior wall, and a number of smaller papillary museles
attaehed to the septal wall. Oeeasionally the anterior and
inferior museles are represented by a number of smaller
projections. It must be noted that the ehordae tendineae
from eaeh papillary musele, or group of papillary museles,
gain insertion into the margins and ventricular surfaces of
two adjacent eusps of the valve. The result of this arrange-
ment is, as the papillary museles eontraet simultaneously with
the eontraetion of the general wall of the ventricle, that ihe
ehordae tendineae hold the margins of the eusps together and
prevent them being driven baekwards into the atrium.

One of the trabeeulae earneae, whieh is usually strong and
well marked, passes aeross the cavity from the septum to the
base of the anterior papillary musele. This is the moderator
band, It tends to prevent over-distension of the cavity of
the ventricle, by fixing the more yielding anterior wall of the
ventricle to the more solid septum.

There is one opening of entranee into the right ventricle,
the atrio-ventricular, and one opening of exit, the pulmonary
orifice. Eaeh is guarded by a valve.

The right atrio-ventricular orifice lies at the lower and
posterior part of the right ventricle, its eentre being behind
the middle of the sternum at the Ievel of the fourth intereostal
spaee. It is about one ineh in diameter, and is surrounded
by a fibrous ring. It admits the tips of three hngers,
and it is guarded by a valve possessing three eusps, an
anterior, a medial, and an inferior. The anterior eusp
intervenes between the atrio-ventricular orifice and the eonus
arteriosus. The medial eusp lies in relation with the septal
wall ; and the inferior eusp with the inferior wall of the
ventricle.

The bases of the eusps are attaehed to the fibrous ring

THORAX

rouiid the margin of the orifice. Their apiees, margins,
and ventricular surfaces are attaehed to the ehord» tendineje.
Their aurieular suriaees, over whieh blood flows as it enters
the ventricle, are smooth, and their yentrieular surfaces are
more or less roughened by the attaehment of the ehordae
tendineae, but the roughening is less marked on the ventricular
surface of the anterior eusp over whieh the blood flows as it
passes through the eonus arteriosus to the pulmonary oriiiee.

Rue □f mediaTeusp <ff LrieuAiHd

Tht Alrio-vailricular Bundle. — The atrio-ventr[eulat bundle is 3. stnaU
bundle of peeuliai musele tibres, of pale eolour, whieh forms tlie only direet
museular eonneetion between the walls of tlie atria and Ihe ventricles (see
p. 92). To expose this bundle, the antetior part of the medial eusp of the
trieuspid vilve must be detaehed from the Sbrous atrio-ventricular ring.
When Ihis has been done, the pars membranaeea, or upper tibrous parl of
Ihe inter-ventricu1ar septum will be esposed, and ihe atrio-ventricular
bundle will be foun<i ninning alone ils posterior and lower border to the
upper end of the museular part 0' the septum, where it divides into right
and Ieft bcajiches. The right hraneh tuns along the rigbt side of the
septum lo the moderalor ^nd, along whieh it passes lo the anterior
papillary mltsele. The left braneh passes belween Ihe pars membranaeea

THORAGie CAVITY 75

and the upper end of the museular part of the septum, and then deseends
along the left side of the septum. Hoth branehes send oAT numerous rami-
fications whieh are distributed to the various parts of the walls of the

ventricles.

The pulmonary orifice lies at the upper, anterior, and left
part of the ventricle, at the apex of the eonus arteriosus. Its
eentre is behind the third left eostal eartilage immediately to
the left of the left border of the stemum, and its margin is
surrounded by a thin fibrous ring to whieh the bases of the
three semilunar eusps of the pulmonary valve are attaehed

Disseetton. — Note that immediately above its eommeneement the waJl
of the pulmonary artery shows three distinet bulgings ; these are the
pulmonary sinuses (Valsalva) of whieh two are anterior, and the third is
situated posteriorly. Make a transverse ineision aeross the wall of the
pulmonary artery immediately above the dilatations, and fr(>m eaeh end of
the transverse ineision make a vertical ineision upwards towards the areh
of the aorta ; raise the flap so formed and examine the eusps of the valve
from above.

Tke Pultnonary Valve, — Eaeh eusp of the valve is of semi-
lunar form. Its upper or arterial surface is concave, its
lower or ventricular surface is convex ; and it eonsists of a
layer of fibrous tissue covered, on eaeh surface, by a layer of
endothelium. The fibrous basis of the eusp is not equally
thiek in all parts. A stronger band runs round both the free
and the attaehed margin. The eentre of the free margin is
thiekened to form a small rounded mass — the nodulus o/ the
valve — ^and the small thin semilunar regions on eaeh side of
the nodule are ealled the lunulee of the valve. When the
ventricular eontraetion eeases, and the elastie reaetion of the
wall of the pulmonary artery forces the blood baekwards
towards the ventricle, the eusps of the valve are forced into
apposition ; the nodules meet in the eentre of the lumen ; the
yentrieular surfaces of the lunulae of adjacent eusps are eom-
pressed against eaeh other, and their free margins project
upwards into the cavity of the artery, in the form of three
vertical ridges whieh radiate from the nodules to the wall of
the artery. Regurgitation of blood into the ventricle is thus
effectually prevented.

The disseetor may readily demonstrate the general appear-
anee of the eusps and their relationship to eaeh other by
paeking the concavity of eaeh eusp with eotton wool.

Arteria Pnlmonalis. — The pulmonary artery lies within
the fibrous perieardium, and is enelosed, with the aseendii

76 THORAX

part of the aorta, in a eommon sheath of the serous
perieardium. It eommenees at the upper end of the eonus
arteriosus, posterior to the sternal extremity of the third left
eostal eartilage. It is about two inehes long, and it runs up-
wards and posteriorly into the concavity of the aortie areh, where
it bifurcates into two branehes. The bifurcation takes plaee
posterior to the sternal end of the left seeond eostal eartilage.
Relations, — At its eommeneement it is plaeed anterior to
the lower end of the aseending aorta, but as it runs upwards
and posteriorly it passes to the left side of the latter vessel,
and lies anterior to the upper part of the anterior wall of the
left atrium, from whieh it is separated by the transverse sinus
of the perieardium. Anterior to it is the upper part of the
anterior wall of the perieardium, whieh separates it from the
anterior part of the mediastinal surface of the left pleura and
lung. To its right side, below, are the right eoronary artery
and the apex of the right auriele, and above is the aseending
aorta. To its left side lie the left eoronary artery and the
anterior end of the left auriele.

Disseetion. — Cut away the anterior wall of the pulmonary artery up to
the level of its bifurcation and pass probes into its right and left branehes.
Note that the right braneh runs transversely to the right, and that the left
braneh runs posteriorly and to the left.

The right pulnionary artery eommenees at the bifurcation
of the pulmonary stem, below the areh of the aorta. As
it runs to the right, towards the hilus of the right lung, along
the upper border of the left atrium and the transverse sinus
(Figs. 2 1 and 27), it passes posterior to the aseending aorta
and the superior vena cava, and anterior to the eesophagus
and the stem of the right bronehus. It enters the hilus of
the lung below the eparterial braneh of the bronehus, above
and posterior to the upper right pulmonary vein, and it
deseends, in the substanee of the lung, on the postero-lateral
side of the stem bronehus, and between its ventral and its
dorsal branehes, where it will be disseeted at a later period
(p. 98).

Branehes. — As it enters the hilus of the lung it gives off a
braneh whieh aeeompanies the eparterial bronehus, and as-it
deseends in the substanee of the lung it gives off branehes
whieh eorrespond with the branehes of the stem bronehus
(see p. 98).

The left pulmonary artery runs posteriorly and to the

THORACIC CAVITY :;

left, aeross the anterior aspeet of tbe deseending aorta and tbe
kft bronehus, to the hitns of the left hiag. It is eoyened an-
terioriy and on the left by the anterior poit of the mediastinal
suriaee of the left pleuial sae As it deseends in the sub-
stanee of the lung it lies along ihe postero-UteTal asped
of the stetn bronehus and between its ventntl and donal
branehes (p. 98).

Branehes. — Except that it has no bianeh eorresponding
with that whieh aeeompanies the epanerial bronehus on the

right side, the branehes of the Ieft pulmonary artery are
similar to those given off by the right pulmonary artery.

Iiigajaentiim Arteriosiun. — The ligamentum arteriosum is
a strong Sbrous band whieh eonneels the eommeneement of
the Ieft pulmonary artery with the lower suriaee of the areh of
the aorta, It is the remains of the walls of a wide ehannel,
the duetus arteriosus, whieh united the Ieft pulmonary artery
with the aorta througbout the whole period of pre-nata! Iife.

During foeUl life (he lungs had no Eerating function ; tlierefore Ihe righl

pulraonaiy artery and the part of Ihe left pulmonary orlery beyond the

■igin of the duelus arteriosus were smill, for Ihey had merely to eonrey

" ■ ''" '' ''■"''"" life and growth oftne non-fiinctional lungs

su^eient blood to maintain Ihe life and growth

Al this period, therefoie, the blood whieh had entered the right

78 THORAX

through the superior vena cava and th^ right auriele (see p. 68), was ejected,
by the Yentriele^ into the pulmonary artery and the greater part of it passed
through the duetus arteriosus into the aorta, whieh it entered beyond the
origin of the left subclavian artery, and there mingled with the more
oxygenated blood from the plaeenta, the lower part of the body, and the
lower limbs, whieh passed from the inferior vena cava through the right
atrium and the foramen ovale to the left atrium, and thenee to the left
ventricle by whieh it was pumped into the aorta.

It is obvious that the passage of blood from the pulmonary artery into
the aorta oould take plaee only so long as the pressure in the pulmonary
artery was greater than the pressure in the aorta. At birth, when the
blood rushed through the rapidly enlarged right and left pulmonary arteries
into the lungs, as they expanded with the first respiratory efforts, the pres-
sure in the pulmonary artery and the duetus arteriosus was redueed below
that in the aorta, and the blood in the aorta would have Aowed into the
duetus arteriosus had it not been that the angle of union between the
duetus arteriosus and the aorta had beeome more and more aeute during
the latter part of foetal life, with the result that the upper and right margin
of the orifice of eommunieation attained a position overhanging the lower
and left margin (Fig. 39) ; and as soon as the blood pressure in the aorta
exceeded that in the duetus arteriosus, this margin, aeting as a flap valve,
was driven against the left and lower margin, elosing the orifice effectually.
After this oeeurred the utility of the duetus arteriosus terminated, and it was
converted into a fibrous eord — the ligamentum arteriosum.

Note that the left reeurrent nerve curves round the
lower surface of the aortie areh on the left side of the upper
end of the ligamentum arteriosum, and that the superficial
eardiae plexus lies below the aortie areh immediately to the
right of the ligament.

In a few eases the duetus arteriosus remains patent for
several years of life after birth, and oeeasionally it is patent
throughout the whole of life.

Disseetion. — Cut through the remains of the upper part of the eonus
arteriosus immediately below the bases of the eusps of the pulmonary valve,
and carefully disseet the upper part of the eonus and the lower part of the
pulmonary artery away from the front of the eommeneement of the aseending
aorta. When this has been done, turn the lower end of the pulmonary
artery upwards and pin it to the areh of the aorta (see Fig. 40). The
upper part of the anterior wall of the left ventricle and the eommeneement
of the aorta are now exposed, and the disseetor should note three bulgings
at the eommeneement of the aorta — the three aortie sinuses. One of the
three sinuses lies anteriorly, and the right eoronary artery springs from it.
The other two, a right and a left, lie posteriorly, and the left eoronary
artery springs from the left sinus.

Make a transverse ineision aeross the upper end of the left ventricle, a

hort distanee below the base of the anterior aortie sinus. On the right

de extend the ineision into the upper part of the inter-ventricular septum

nd earry it downwards and anteriorly in the septum to the apex of the

eart. From the left extremity of the upper transverse ineision earry an

iieision downwards and anteriorly through the left lateral border of the

interior surface of the left ventricle, parallel with the ineision already made

in the septum, towards the apex. As this ineision is made puU the anterior

THORAGie CAVITY 79

wall of the Ieft ventricle forwards till the base of a large papillary musele
whieh springs from its intemal surface is exposed ; earry the ineision
anterior to Uiis and then onwards to the apex, and rcmove the anterior
wall of the left ventricle and the anterior part of the interventricular
septum. The cavity of the left ventricle and the mitral valve, whieh guards
the left atrio-ventricular orifice, are now exposed (Fig. 40).

yentTieulus Sinister. — The cavity of the left ventricle is
longer and narrower than that of the right ventricle. It
reaehes to the apex, and when exposed from the front it
appears to be of eonieal shape. In eross seetion it has a
eireular or broadly oval outline, and its walls are very mueh
thieker than those of the right ventricle (Fig. 37). When
the interior has been eleaned with the aid of a sponge and
forceps, the disseetor will note that its walls are covered with
a dense mesh-work of trabeeulae earneae, whieh are finer but
mueh more numerous than those met with in the right
ventricle. The network is espeeially eomplieated at the
apex and on the inferior wall of the ventricle, whilst the
surface of the septum and the upper part of the anterior wall
are, comparatively speaking, smooth. But whilst the trabeeulae
earnese in the left ventricle are slighter and more numerous
than those in the right, the museuli papillares, on the other
hand, are less numerous and mueh stronger; indeed, as a
general rule there are only two papillary museles in the left
ventricle, an anterior and an inferior, the former attaehed to
the anterior wall and the latter to the inferior wall of the
cavity. The ehordse tendineae from the papillary museles
pass to the margins and to the ventricular surfaces of the two
eusps of the mitral valve, whieh guards the left atrio-ventricular
orifice, the ehordae tendineae from eaeh papillary musele
gaining attaehment to the adjacent margins of both eusps.

Disseetion. — Detaeh the anterior papillary musele from the anterior
wall of the ventricle and note that its ehordae tendinese go to the anterior
and left margins of the eusps of the mitral valve. Introduoe the blade of
a sealpel between the anterior margins of the eusps and earry it downwards
between the groups of ehordae going to the apex of the papillary musele ;
then split the papillary musele from its apex to its base leaving eaeh half
eonneeted with a eorresponding group of ehordse tendineae. The eusps of
the mitral ean now be separated from eaeh other, and the atrio-ventricular
orifice and the cavity of the ventricle ean be more eompletely examine(l.

The Orifices of ihe Left Ventrtcle. — There are two orifices
of the left ventricle — one of entranee, the left atrio-ventricular
orifice, and one of exit, the aortie orifice.

The Leit Atrio - ventricular OriAee. — The left atrio-

8o THORAX

ventricular orifice lies in the lower and posterior part of the
ventricle posterior to the left margin of the sternum at the
level of the fourth left eostal eartilage. It is somewhat smaller
than the right atrio-ventricular orifice and admits the tips of
two fingers only, a fact whieh will be better appreeiated when
the orifice is examined from the left atrium at a later period.
It is guarded by a bieuspid valve, ealled the mitral valve,
whieh prevents'regurgitation of blood from the left ventricle
into the left atrium.

The Mitral Valve. — The mitral or left atrio-ventricular
valve eonsists of two eusps, a large anterior and a small
posterior. Oeeasionally, however, as on the right side, small
additional eusps are interposed between the bases of the
main eusps. The bases of the eusps are attaehed to a
fibrous ring whieh surrounds the atrio-ventricular orifice and
their apiees project into the cavity of the ventricle. To their
apiees, margins, and ventricular surfaces are attaehed the
ehordse tendineae from the papillary museles, whieh hold the
margins of the eusps together and prevent the valve being
driven baekwards into the atrium during the eontraetion of
the ventricle. The disseetor should note, however, that the
ehordae tendineae spread less over the ventricular surface of the
anterior than over that of the posterior eusp, and he should
assoeiate this fact with the eireumstanee that bloodAows over
both surfaces of the large anterior eusp, whieh intervenes between
the atrio-ventricular and the aortie orifices. By means of
this large anterior eusp of the mitral valve the cavity of the
ventricle, whieh has, on the whole, a somewhat eonieal form,
is converted into a bent U-shaped tube, one Hmb of the tube
lying below and to the left, and the other anteriorly and to the
right. The blood enters the ventricle below and posteriorly
through the atrio-ventricular orifice. It runs anteriorly to-
wards the apex of the cavity along the inferior surface of
the anterior eusp of the mitral valve, then, as the ventricle
eontraets, it is driven upwards, anteriorly, and to the right, to
the aortie orifice, along the anterior surface of the large
anterior eusp of the mitral valve. The portion of the cavity
of the left ventricle whieh lies direetly below the aortie
orifice is known as the aortie vestibule (Fig. 40). Its walls eon-
sist mainly of fibrous tissue ; therefore they remain quiescent
during the eontraetion of the ventricle and, as a result, the
rapid elosure of the aortie valve is not interiTered with when

THORAC!C CAVITY

the ventricular eontraetion eeases and the elastie reaetion or
the walls of the aorta tends to force blood baele into the
ventricle.

The aoriie orifice Ues at the upper, right, and anterior
part of the cavity, posterior to the left margin or the sternum ax

the level of the third intereostal spaee. Its left and inferior
margin is separated from the atrio-yentrieular orifice by the
anterior eusp of the mitral valve. It is guarded by a valve,
the aortie valve, whieh prevents regurgitation from the aorta
into the ventricle. This valve, like the pulmonary valve,
eonsists of three semilunar eusps, but in eontradistinelion to

THORAX

the pulmonary valve, one of the eusps is plaeed anteriorly and
the other two posteriorly. The eusps of the aortie valve are
stronger than the eusps of the pulmonary valve deseribed on
p. 75, bot eorrespond with them in all details of strueiure.

Before terminating his examinalion of the left ventride

the disseetor should note thal the museular wall of the

'f cavity is thiekest a short dislanee from the atrio-ventricu)ar

oriiiee and thinnest at the apex, and he should exaniine the
inter-ventricular septuni.

T^ lHler-veHtriatIar Septum. — The inler-ventricular septum
is a museulo-membranous partition whieh separates the left
ventricle not only from the right ventricle, but also from the
lower part of the righl auriele. In ihe grealer pari of its
extent the .septum is thiek and museular, and is thiekesl below
and anteriorly, where it springs from ihe lower border of the
heart immediately to the righl of the apex and opposite the

THORAGie CAVITY 83

eardiae noteh. The museular part beeomes gradually thinner
as it passes upwards and posteriorly and, a short distanee
from the atrio-ventricular orifices, it terminates in a fibrous
membrane, the pars membranaeea septi^ whieh eonneets the
museular part of the septum with the fibrous rings whieh
surround the atrio-ventricular orifices and the orifices of the
pulmonary artery and the aorta. The pars membranaeea is
the thinnest part of the septum« Oeeasionally it is deficient
in whole or in part, and in sueh eases a eommunieation
exists between the two ventricles, and, in some rare eases,
between the left ventricle and the right auriele.

The pars membranaeea was exposed from the right side
when the anterior part of the medial eusp of the trieuspid
valve was removed during the disseetion of the atrio-ventri-
eular bundle (see p. 74).

Finally the disseetor should note that the inter-ventricular
septum is plaeed obliquely, so that its anterior border lies to
the left and its inferior border to the right; and that its
right lateral surface, whieh looks anteriorly and to the right,
bulges towards the cavity of the right ventricle (Fig. 37).

The Aorta. — The aorta is the great arterial trunk of the
body. It eommenees from the upper, anterior and right
portion of the left ventricle, at the level of the third inter-
eostal spaees and posterior to the left margin of the sternum.
It terminates at the level of the lower border of the fourth
lumbar vertebra, to the left of the median plane, where it
divides into the right and left eommon iliae arteries. It is
deseribed as eonsisting of three main parts : ( i ) the aseend-
ing part, (2) the areh, and (3) the deseending part. The
deseending part is divided into {a) thoraeie and (b) abdominal
portions. The first two parts and the thoraeie portion of the
third part are met with in the disseetion of the thorax.

The Aseending Part of the Aorta. — The aseending aorta
eommenees at the aortie orifice of the left ventricle and runs
upwards to the right and slightly anteriorly, posterior to the
first pieee of the body of the sternum, to the level of the sternal
end of the right seeond eostal eartilage, where it beeomes the
areh of the aorta. It lies in the middle mediastinum, is
enelosed in the fibrous sae of the perieardium, and is en-
sheathed by a covering of the serous sae whieh is eommon
to it and the stem of the pulmonary artery. The lumen of
this portion of the aorta is not of uniform diameter ; on the

THORAK

eontrary it presents four dilatations, three at the C
ment, the aortie sinuses (Valsalva), and one along the right
border, the grea/ sinus of the aorta. The latter is merely an
indefinite bulging along the right border of the vesse].

Relations. — The lower part of the aseending aorta lies
posterior to the upper part of the eonus arteriosus and the lower

Mediastinal Spaee al

part of the stem of the pulmonary artery ; but the upper part
is in direet relation with the anterior wall of the perieardium,
whieh separates it from the anterior part of the mediastinal
surface of the right pleura and lung. Posterior to the aseend-
ing aorta, from below upwards, are the left atrium, the right
pulmonary artery and the right bronehus. To the right are
the right auriele below and the superior vena cava above ; and

THORAGie CAVITY 85

to the left lie the left auriele below, and the upper part of the
stem of the pulmonary artery above.

Branehes, — Only two branehes are given off from the
aseending part of the aorta; they are the right and left
eoronary arteries. The right springs from the anterior
aortie sinus and the left from the left posterior sinus. Their
distribution has been deseribed already (p. 60).

The SnperAeial Gardiae Plexii8. — Before the areh of the
aorta is studied, the position, eonneedons and relations of the
superficial eardiae plexus should be detined. It lies below
the areh of the aorta, above the bifurcation of the stem of the
pulmonary artery, and between the aseending aorta on the
right and anteriorly, and the ligamentum arteriosum to the left
and p05teriorly. The positions of the superior cervical eardiae
braneh of the left sympathetie trunk, and the inferior cervical
eardiae braneh of the left vagus, on the left side of the
areh of the aorta, have been deiined already (p. T^Ti)-
Traee these nerves to the plexus, elear away the areolar
tissue from around the plexus, and traee branehes posteriorly
and upwards from it towards the deep eardiae plexus, whieh
lies posterior to the areh of the aorta. Other branehes whieh
spring from the superficial part of the eardiae plexus deseend
along the pulmonary artery and form the right eoronary
plexus, whieh is distributed with the right eoronary artery.

The Archof the Aorta, — The aortie areh eommenees at the
termination of the aseending part of the aorta, at the level of
the seeond eostal eartilage, and posterior to the right margin of
the sternum, from whieh it is separated by the anterior part
of the mediastinal portion of the right pleura and lung, or
by the remains of the thymus gland (see Fig. 43). It runs
posteriorly, to the left, and slightly upwards, through the middle
mediastinum and round the left margins of the traehea and
oesophagus (see Figs. 13 and 43), to the level of the lower
border of the left side of the fourth thoraeie vertebra, where it
beeomes eontinuous with the deseending part of the aorta. It
is curved in both the vertical and the horizontaI planes, and as
it passes posteriorly and to the left it forms a convexity
upwards, and also a convexity whieh is direeted anteriorly and
to the left. Its lower border is eonneeted with the left
pulmonary artery by the ligamentum arteriosum, and from its
upper border arise the three great vessels whieh supply the
head, neek, and upper extremities.

THORAX

Relations. — Ab(yve, the left innominate vein runs along its
upper border immediately anterior to the origins of the in-
nominate artery, the left eommon earotid artery and the left
subclavian artery, whieh spring from its upper border ; the first
arises from the apex of the convexity posterior to the eentre

of the manubrium sterni; the seeond arises elose to, and some-
times in eommon with the first, whilst the origin of the
subclavian is a little more posterior and to tiie left, separated
by adistinet intervalfrom the left eommon carotid(Figs. 2oand
34). Below the areh lie (i) the bifurcation of the pulmonary
artery and portions of its right and left branehes ; (2) the liga-

THORAGie CAVITY 87

mentum arteriosum, whieh eonneets the lcft pulmonar}- artery
with the areh ; (3) the superiieial part of the eardiae plexus
immediately to the right of the ligamentum arteriosum ; (4)
the left reeurrent nerve on the left side of the ligament ; and (5)
still further to the left, the left bronehus passes beneath the
areh on its way to the hilus of the left lung. To the right of the
areh are the traehea, the oesophagus, the left reeurrent nenre,
and the thoraeie duet The nerve lies in the angle between
the oesophagus and the traehea, and the thorade duet is pos-
terior to and to the left of the eesophagus (Fig. 43). The left
side of the areh is overlapped by the posterior part of the media-
stinal surface of the left pleura and lung, but intervening
between the pleura and the areh are (1) the left phrenie nerve,
(2) the inferior cervical eardiae braneh of the left vagus, (3)
the superior cervical eardiae braneh of the left sympathetie,
(4) the left vagus, and (5) the left superior intereostal vein.
The vein passes upwards and anteriorly, lying to the left of
the vagus and the eardiae nerves, and to the right of the
phrenie nerve (Fig. 13).

Disseetion, — Divide the right eoronary artery elose to its origin. Cut
through the anterior wall of the aseending part of the aorta on eaeh side of
the anterior aortie sinus ; extend the ineisions upwards to the eommeneement
of the aortie areh, and examine the aortie valve. Note that it is formed by
three semilunar eusps whieh are mueh stronger than the semilunar eusps of
the pulmonary valve (p. 75), but are exactly similar in stnieture and
attaehments. Note further that one eusp lies anteriorly, and the other two
posteriorly. £xamine the aortie sinuses and note that the right eoronary
artery springs from the anterior sinus, and the left eoronary from the left
posterior sinus. Note further that the orifices of the eoronary arteries, as a
rule, lie immediately above the level of the upper margins of the seniilunar
eusps. Replaee the stem of the pulmonary artery in position, and note the
relative positions of the pulmonary, aortie, and atrio-ventricular orifices.

Topography of the Great Orifices of the Heart. — Replaee
the sternum in position and note the relations of the eardiae
orifices to that bone. The pulmonary orifice is highest. It
lies to the left of the margin of the stemum at the level of the
third eostal eartilage. The aortie oriiiee is a little lower, and
more to the right, posterior to the left margin of the sternum,
at the level of the third left intereostal spaee. Below the aortie
orifice is the left atrio-ventricular orifice, posterior to the left
margin of the sternum at the level of the left fourth eostal
eartilage. Still lower and more to the right is the right atrio-
ventricular orifice, posterior to the eentre of the sternum at the
level of the fourth intereostal spaees (Fig. 44).

88 THORAX

Disstdion. — Divide the phrenie neives immediatelyabove thediaphiaem ;
then, with ihe handle and the edge of the sealpel, detaeh Ihe lower part
of Ihe perieardium frijm (he diaphragm. The altaehment of the peri-
eardium to the museular part of the diaphragm is not elose, and ean
easily be broken down. The altaehment to the eentral tendon is mueh
more iirni and, as the median plane is approaehed, the aid of the edge of
the knife will proliaLly be ileteSSary biifui:e a ?eparalion ean be effected.

ihe Anlerior

Divide the right innominale vein and the rlght phrenie nerve, immediately
above the upper end Df the superior ven3 cava, and as the di^ision is made
take eare nol to injure the right vagu5 posterior to ihe vein. Then divide
(he vena azygos just posterioi (o its entianee into the superior vena cava.
Cut the infeiior thyreoid veins, the innominate artery, and the Ieft eommon
earolid artery, immediately above (he upper boider of the !eft innt '
vein, and then divide the left innominate vein, in the interv3l belwe<
left eommon earotid and the left subclaviaii arteries. Cul the left p

THORAGie CAVITY 89

nerve, the superior eardiae braneh of the Ieft sympathetie, aml the inferior
cervical eardiae braneh of the left vagus, immediately above the upper
border of the aortie areh. Next divide the aortie areh. Enter the kniie at
the upper border of the areh, between the left eommon earotid and left
subclavian arteries and anterior to the left vagus and the left reeurrent
nerve, and eut from above downwards, eompleting the division of the
areh at the lower border, immediately to the left of the upper end of
the ligamentum arteriosum. The left superior intereostal vein will be
divided at the same time, but eare must be taken not to injure the left
reeurrent nerve, whieh is curving round the areh from the front to the
baek. When the ineisions are eompleted, pull the anterior part of the
aortie areh, with the superior vena cava and the lower parts of the innomi-
nate veins, anteriorly, and separate them irom the lower part of the
traehea and from the bronehL As the separation proeeeds, keep the edge
of the knife tumed towards the aortie areh, to avoid injury to the deep part
of the eardiae plexus, whieh lies anterior tp the bifurcation of the traehea.
When the lower border of the areh is reaehed, the twigs whieh eonneet the
superficial with the right half of the deep part of the eardiae plexus will
be exposed, and must be divided. When this has been done detaeh the
posterior surface of the perieardium from the front of the oesophagus and
the deseending aorta, taking eare to avoid injury to the plexus formed by
the vagi nerves on the anterior aspeet of the eesophagus. As soon as the
separation is eompleted, the heart, with the remains of the perieardium and
the lower parts of the phrenie nerves, ean be removed from the thorax, and
the investigation of the lefl atrium and the strueture of the heart ean
be proeeeded with ; but, before this is done, the disseetor should note that
the posterior wall of the perieardium intervenes between the posterior wall
of the left atrium and the anterior surfaces of the oesophagus and the
deseending part of the aorta, as the latter struetures lie anterior to the
middle four thoraeie vertebrse (Fig. 21).

After the heart and the roots of the great vessels have been removed from
the thorax, fasten the left vagus and the reeurrent nerve to the part of the
areh left in siiu by one or two points of suture ; then eut away the remains
of the perieardium from the heart, leaving only those portions of it whieh
mark the lines of reflection of the ()arietal to the visceral portions of the
serous sae. Note, as the posterior wall of the perieardium is removed, that
it forms the posterior boundary of the oblique sinus (p. 21).

The Left Atriuin. — The left atrium, like the right, is
separable into two parts — a larger main portion, the atrium
proper or body ; and a long narrow prolongation, the auriele
(O.T. aurieular appendage), whieh runs from the left margin
of the body anteriorly and to the right. The four pulmonary
veins, two on eaeh side, open into the left atrium. They enter
elose to the upper ends of the lateral borders of the posterior
surface, and not uneommonly the right or the left pair may
fuse into a eommon trunk at the point of entranee.

It has been noted previously that the left atrium forms
the greater part of the base of the heart, a small part of
anterior or sterno-eostal surface, and a still smaller ]
the left border. The only part whieh ean be seen fro
front, when the heart is in situ^ is the apieal portion

THORAX

auriele (appendage), for the portion whieh enters into the
formation of the sterno-eostal surface is hidden by the roots
of the aorta and the pulmonary artery (Fig. 35).

The posterior wall of the left atrium is of quadrangular
outhne. Along ils superior border lie the pulmonary arteries.
It is bounded inferiorly by the posterior part of the eoronary

FlO. 4S.

suleus, in whieh lies the ooronary sinus, and on the right by
an indistinet inter-atrial suleus, whieh indieates the position
of the posterior border of the inter-atrial septum. Deseending
obliquely aeross the posterior wall of the left atrium, from
the lower border of the left inferior pulmonary vein, down-
wards and to the right to the eoronary sinus, is the obIique
vein (Marshall), whieh is the remains of the left duet of

THORAGie CAVITY 91

Cuvier or the foetiis. Oeeasionally it beeomes the lower end
of a ]eft superior vena cava.

DisuelioH. — Open ibe left atrium by thiee iodsions— one boruonul «nd
wo vertical. The horizontal ineision must lun fiDni side lo &ide along ibe
T border oS tbe atrium, immedialeiy above the eoronary nileus : and
'erlieal ineisions must aseeod froin the eilremities of the horizontal to
he uppet border of the posteiioi 5urface, eaeh pusing lo tbe medial side
of the terminations of ibe eorresponding pulmonaiy Teins. When the
'ndsions have been made the poaterioi waTl of the atrium must be lurned
ipwards whilsl the ca.-n*j is b«i^ eKamined.

AorU 1.eft pulmoru

The inner surface of the wall of the left atrium is smooth
and generally devoid of museular bundles, but ihe inner
surface of the wall of its auriele (O.T. aurieular appendage) is
covered with museuli peetinati, a fact whieh ean be demon-
straled by earrying an ineision anteriorly into it. As this
ineision is made, the disseetors should note that, in a formalin
hardened heart, a strong museular ridge deseends along the
left border of the cavity anterior to the orifices of the lefc
pulmonary veins, entirely ooneealing them from view wh'
cavity is examine<i from the front.

On the right or septal wall of the left atrium the

92 THORAX

of the valve of the foranien ovale is marked by one or more
small semilunar depressions situated between slender museular
ridges. The portion of the septal wall whieh lies below and
posterior to these depressions forms the floor of the fossa
ovalis, and is the remains of the valve of the foramen ovale of
the foetus.

The Orifices of the Left Atrtum, — The oriAees of the left
atrium are the openings of the /our pulmonary veins^ whieh
convey to it the oxygenated blood from the lungs ; a number
of minute openings whieh are the mouths of the ven€e eordis
minimee] and the ieft atrio-ventricular orifice through whieh
blood passes from the left atrium to the left ventricle.

The openings of the pulmonary veins are situated in the
posterior wall, nearer the upper than the lower part, and elose
to the lateral borders, two on eaeh side. They are entirely
devoid of valves. The orifices of the venae eordis minimse,
whieh are seattered irregularly, are also valveless ; but the left
atrio-ventricular orifice, whieh lies in the lower part of the
anterior wall of the atrium, is guarded by a bieuspid valve, the
mitral valve^ whieh has been deseribed already (p. 79). This
orifice is smaller than the eorresponding orifice on the right
side, and admits the tips of two fingers only.

The Strueture ofthe Walls of the Heart. — The last step in the disseetion
of the heart eonsists in the examination of the strueture of its walls. On
the outside the walls are covered with the epieardiunty whieh is the visceral
part of the serous perieardium ; and on the inside they are lined with the
smooth and glistening endoeardium, whieh plays a large part in the
formation of the flaps of the valves, and is eontinuous, through the
oriAees, with the inner ooats of the arteries and veins. Between the
epieardium and the endoeardium lies the museular tissue of the heart,
whieh is termed the myoeardium, The museular fibres of the myo-
eardium are disposed in layers, in eaeh of whieh the fibres take a speeial
direetion.

The arrangement of the various layers of the myoeardium eannot be
displayed in an ordinary disseeting-room heart, in whieh the oontinuity of
the fibres has been destroyed by the ineisions made to display the cavities,
but the arrangement of the layers is praetieally the same in the hearts of
all mammals. Therefore, for the purpose of studying the layers, the
disseetor should obtain a sheep's heart. This should be filled with a
paste made of flour and water ; then it should be boiled for a quarter of an
hour. The boiling expands the paste, softens the connective tissue, and
hardens the museular fibres. After the boiling is finished the heart should
be plaeed for a time in eold water. After it has eooled, first the epieardium
and then the museular fibres should be gradually torn off".

The atrial fibres are difficult to disseet. They eonsist of three groups :
(i) A superficial group running more or less transversely and eommon to
both atria. They are best marked near the eoronary suleus. (2) A deep
group speeial to eaeh auriele. The extremities of these fibres are eonneeted

THORAGie CAVITY 93

with the iibrous atrio-ventrictilar rings, and tbey pa» orer tbe aorklei frc
front to baek. (3) The third groap eonsists of lets of aRnabr f.>>fcs
surrounding the onAees of the ▼eins whieh open into the atria.

The fibres of the Yentrieles are more easily dtsseeted. They a>f)si«t,
for the main part, of two groups — tbe saper6cial and the deep. Tbe f«r>ce»
of eaeh set are eommon to both ▼entrieles, aod tbe diMect'>ri «Jy>cld td^^.
the remarkable spiral or whorled arran^emesit of tbe wpcrfjaaJ ^ber»
whieh oeeurs at the apex, where tbey poss into tbe deeper paiti of tbe wall,

The superiieial fibres spring mainly from tbe fibroas a:ry>-Teii£ric?Iaj
rings. Those whieh are atta^ed to tbe right ring tom inwa/'ii 91 *.itit
apex and beeome eontinuous with the papiHarT moseles of tbe left reetriele,
whilst the fibres whieh spring from tbe leit ring poss in tbr tai&e way ":,
the papillary museles of the right ▼entride. Tbe deeper fir>ret ir^rm a£
OD-shaped layer, one loop of the C0 snrroanding tbe right ar^i !he ^y.h^ 'h^
Ieft ventricle.

The fibrous rings of the atrio-^entrieular orificcs interrene *^we«t tbe
atrial and the ventricalar mnsde fibres, bat tbe two grr/aps axe iroBj|^f
into assoeiation with eaeh other by tbe atrio-Tentrieolar baivJIe d^x.ri:^.
on p. 74. It has been assaroed that tbe impalses whieh r^^l^e^i th^
movements of the ventricles were coDveyed to tbem fr'^/ro !he atria ^jr
the fibres of this bundle, bat it has been sbown reeently tha: nzrr^rjti%
nerve fibrils are intimately intermingled witb tbe fihre% of th^ a/r/^-
ventricular bundle. It is possibie, tboeibre, tbat tbe cor*iiectir>6 berwei«i
the atria and the ventricles is nenro-mosenlar,

The Aetion of ihe Heart — The diderenees between tbe ▼ark^i para ^A
the heart, t.g. the thinness of tbe walls of tbe atria as eor/raiUiyi «;*h *>>^
thiekness of the walls of the ▼entrieles, and tbe greatitT rhirkr^t^ ^f *^^
walls of the left as eontrasted with tbose of tbe rigbt ▼entrir.le, ar<( awr u*"/:
with the functions of the varioas ehambers, and with rhe ar,ty>c 'm:,j'}, *r^
heart pla^rs in the maintenanee of the dreolatieA of the hWxi, 1':^. h^rarr
is a museular pump, prorided with receiving aitd ty:fj*'iT.^ r\ATt.''^\. \*
has three phases of aetion : (i) iipaiod of atrial comra/r*X/r. ; '2, a y^.fy'.
of ventricular eontraetion, whien immediately »uccwi% *ij: i*ijk. ryje,
traetion ; (3) a period of diastole or rest.

During the period of diastole or rest the chaLmT^\, j^'r>\/y.xly rr.:.-
traeted, £late, as the mosealar fibres of tbe beart relax. Th^ ^/lU^Aiy.r. .x
aided by the respiratory movements of tbe tborax. A* 'h^ 'iila*aV.r, ;>?',
gresses blood flows into the right atrinm £rom tbe »api»Tyyr T*T.a ca-.a, *:./-.
inferior vena cava, and the eoronary sinns ; and into tbt I<tft ^irl::.::. ♦r.r'/,j^h
the four pulmonary veins. The atrial eontraetion rrjr:.rr.*rr.f.frK 'm'.*}. *:.*■
eontraetion of the dreolar fibres whieh sarrr«nd the moa*h\ ^A ♦:,*: r*r.r.i
entering the atria, and thus tbe blood is prever.i^ frotri pei.V'..:.ii '^*'^
into the vdns. As the eontraetion extends to the g«»i<!Tal f.'^r^ '/ *':.*-. u*r.k.
the blood is forced onwards into ihe ▼entrieles, whir,h \j^r/A:.»: <'iX^ »rr.<*f'. .
Then the ventricular eontraetion eommenees, the a*rir/-v*T.T;', .ia/ va.v'-^
elose, and, as the eontraetion proeeeds, the 1/I/yyi u ^r;v'rr. v-* '/f *;.':
ventricles through the arterial orifices, that in th<r right v'-r-*r>'i': '/",:.;'
ejected into the pulmonary artery, and that in the I*rf? v^r.*r>,I«: ir.*.o *':■.*: a/,f *;»,

\Vhen the ventricular eontraetion is eomplet^d rh^ ;>^>y/: ^f <.ui.*r,i".
eommenees ; and, as long as tbe heart remains al;v«i, *Y,*: f:',f.\': '.% r'';ya*'/i.

The work of the atria is merely to force the h^y>^ rhr'/;^^r. *':.*: Wi'\*\/
open atrio-ventricular orifices into the ▼entrides aryl to *rx\/krA ♦h/: /lil»fir.^
walls of the ▼entrides, For this parpose no great Uifj: jh r'-r.r.Ut-A^ iU^-r*'
fore the walls of the atria are thin- The work of *he v'rr.rri/J/r* 'n rr*^^*
more se^ere, therefore their walls are thieker, l>at th^: right v/rritri/;l4f
only to exert soffident force to drive the blood thr//ugh i)%t: lung* im t)

94 THORAX

auriele, that is, through a comparatively short distanee and against a eom-
paratively small resistanee ; therefore its walls are thin as eompared with
the walls of the left ventricle, whieh has to be sufficiently strong to force
the blood through the whole of the trunk, the head and neek, and the upper
and lower limbs.

The Topography of the Heart. — Before proeeeding to the
study of the traehea, the disseetors should replaee the heart
in position and revise their knowledge of its relations to the
surface. Its position ean be indieated on the anterior wall
of the thorax by the following four lines : — (i) A line eom-
meneing at the lower border of the seeond left eostal
eartilage, half an ineh from the left border of the sternum,
and ending at the upper border of the third right eostal
eartilage, half an ineh from the right border of the sternum.
This line indieates the position of the upper border of the
heart, whieh is formed by the atria. (2) A line from
the upper border of the third right eostal eartilage to the
sixth right eostal eartilage. This line should eommenee
and end half an ineh from the border of the sternum, and
should be slightly convex to the right. It indieates the
right border of the heart, whieh is formed by the right atrium
alone. (3) A line from the sixth right eostal eartilage to the
apex, whieh lies behind the fifth left intereostal spaee three
and a half inehes from the median plane. This line marks
the position of the lower border of the sterno-eostal surface,
whieh is formed, in the greater part of its extent, by the
right ventricle, the left ventricle entering into its eonstitu-
tion only in the region of the apex. (4) A line from the
apex to the lower border of the seeond left eostal eartilage.
This line should be convex upwards and to the left ; the
point of greatest convexity should eoineide with the lower
border of the fourth left eostal areh, and the upper extremity
should be situated half an ineh from the left margin of the
sternum. It marks the position of the left border of the
heart, whieh is formed in four-fifths of its length by the left
ventricle and in the remaining fifth by the left atrium.

A line from the upper border of the sternal end of the
third left eostal eartilage to the lower border of the sternal
end of the sixth right eartilage indieates the anterior part
of the eoronary suleus. The points indieating the positions
of the arterial and atrio-ventricular orifices must be plaeed
below and to the left of the line of the eoronary suleus in
the following order from above downwards ; pulmonary orifice^

THORAGie CAVITY

aortie orifice, mitral orifice, triaisptd orifi(e. The eentrg of the
pulmonary orifice is posterior to the third leri eostal eartilage
at the margin of the sternum. The aortie onliee lies
posterioT tothelefthalf of thesteTnum opposite the ihirdinter-

Oriliee Df riehi ibienul iupiliir ™n | ■ .„Ui»tio

eostal spaees, The niitral oritiee is posterior to the Ieft border
of the stemum at the Ievel of the fourth Ieft eostal eartilage ;
and the eentre of the triouspid orifice is posterior to the middle
of the sternum at the level of the fourth intereosial spaees

Tlte Tltonele Portion of the Traeliea. — The thoraeie
poTtion of the traehea, like the cervical portion, is a wide

THORAK

lube kept eonstantly patent by a series Df eartilaginous rings
embedded in its walls. Posteriorly the rings are detieient
and in consequence the tube is Aattened behind (Fig. 43).
It enters the thorax at the upper aperture, posterior to the
upper border of the manubrium, and it tetminateSj, at the leyel
of the lower border of the maiiubrium and the'upper border
of tbe iifth thoraeie vertebra, by dividing into a right and a
left bronehus. It lies, therefore, in the superior mediastinum,

and its median axis is in the median plane, except at the
lower end where it deviates slightly to the right.

Relations, — Posteriorfy, it is in eontaet with the eesophagus,
whieh separates it from the yertebral eolumn ; and in the
angle between its left border and the anterior surface of
the eesophagus is the left reeurrent nerve (Fig, 43).

Anteriorfy, it is in relation below with the areh of the
aorta, the deep part of the eardiae plexus intervening ; and
at a higher level with the innominate and left eommon
earotid arteries, the left innominate vein and the inferior
thyreoid veins. More superficially lie the remains of the

THORACIC CAVITY

thymus, and still more superlieially the manubrium stemi
with the origins of the attaehed museles.

On ihe righi, it is in retation with the upper pan of the
mediastina! suriaee of the right pleura and lung (Fig. 43^

the right vagus nerve, and
the areh of the azygos
vein (Fig. 1 2). It is also
in relation, on its right
side, near its lower end
and more anteriorly, wiih
the superior vena cavn,
and at a higher level wi[h
the innominate artery.

Its left lateral relatiom
are the areh of the aorta
below and the left sub-
clavian and ]eft eommon
earotid arteries above.

Tho Bronelu. — Eaeh
bronehus ' passes down-
wards and laterally (irst
to the hilus of the eorre-
sponding lung and thenee
downwards in the sub-
stanee of the lung to itn
lower end. It ean,
therefore, be diyided
into an extra-pul-
monary and an intra-
pulmonary portion.
Theextra-pulmo nary
part, like thetraehea,
is kept permanently
open bythe presenee
of eartilaginous rings
in its walls; and as
the rings are defi-
oient posteriorly, the extra-pulmonary part of eaeh bronehus
presents a Aattened posterior surraee similar to that of the
traehea. The lumina of the intra-pulmonary parts of the
bronehi are kept patent by eartilaginous plates whieh are
irregularly distributed in the substanee of the walls.

98 THORAX

Relations of the Extra-pulmonary Part of the Right
Bronehus. — ^The right bronehus is mueh more vertical than
the left (Fig. 48), and, as the ridge whieh separates the oriiiees
of the two bronehi at their origins, lies to the left of the
median line of the traehea, the right bronehus is the
direet eontinuation of the traehea, and foreign bodies, whieh
have entered the windpipe, pass more frequently into it than
into the left bronehus. It passes downwards and laterally
from the upper border of the fifth thoraeie vertebra to the
level of the upper part of the sixth thoraeie vertebra, where
it enters the hilus. Anterior to the extra-pulmonary part of
the right bronehus are the aseending part of the aorta, the
lower part of the superior vena cava, and the right pulmonary
artery. Above it is the areh of the azygos vein ; z.n^ posterior to
it are the azygos vein, the posterior pulmonary plexus, and the
right bronehial artery. This part o.f the right bronehus gives
off one braneh, whieh arises elose to the hilus and is ealled
the eparterial bronehus, beeause it originates immediately
above the point where the right pulmonary artery erosses
anterior to the stem bronehus.

Relations of the Extra-puhnonary Part of the Left Bronehus,
— The extra-pulmonary part of the left bronehus eommenees
and ends at the same level as the eorresponding part of the
right bronehus, but it has further to go, beeause the hilus of
the left lung is further from the median plane than the
hilus of the right lung ; therefore it is longer and less vertical
than the right bronehus. It gives off no branehes.

Anterior to it are the left pulmonary artery, and the upper
and left part of the perieardial sae whieh separates the
bronehus from the left auriele. Above it is the arch.of the
aorta, and posterior to it are the deseending aorta, the posterior
pulmonaiy plexus, the left bronehial arteries, and the oeso-
phagus.

Disseetion. — The intra-pulmonary parts of the bronehi and the intra-
pulmonary parts of the pulmonary arteries and veins should now be
disseeted. The disseetors must eommenee at the hilus of the lung and
foIlow the bronehus and the vessels into the interior of the lung, eutting
away the lung substanee, but avoiding injury to the main branehes of the
bronehus and of the artery, and the main tributaries of the veins.

Relations of the Intra-pulmonary Parts of the Bronehi, the P11I-
monary Arteries and the Pulmonary Yeins. — After passing through the
hilus eaeh bronehus deseends, in the substanee of the lung, to the lower end
of the lung, lying nearer the medial than the lateral surface, and nearer the
posterior than the anterior border. As it deseends it gives off two sets of

THORAGie CAVITY 99

branehes : (i) ventral^ whieh ran towards the anterior border of the lung,
and (2) dorsaly whieh pass posteri<Mrly to the thiek posterior lx>riler. As
these branehes are given on below the point where ihe pulmonary artery
erosses anterior to the bronehus they are ealled hyparierial bramhes. The
hyparterial branehes arise altemately, first a ventral and then a dorsal
braneh, and, in addition, a number of small aeeessor)' branehes are piven
off from the stem bronehus in some of the intenrals l)etween the dorsal and
ventral branehes. On the right stde^ the eparterial bronehus, whieh is given
off from the extra-pulmonary part of the right stem bronehus, supplies the
upper lobe of the right lung. The first ventral hyparterial braneh supplies
the middle lobe, and all the remaining branehes are distributed to the lower
lobe. On the left side^ the first ventral braneh goes to the upper lobe of the
left lung, and all the other branehes go to the lower lobe.

The intra-pulntonary part of eaeh putnwnary artery deseends along the
postero-lateral aspeet of the intra-pulmonary part of the stem bronehus,
between the ventral branehes anteriorly and the dorsal branehes posteriorly,
and it gives off branehes whieh eorrespond with the branehes of ihe main
bronehus.

The vein from the upper lobe, on the right side, runs along ihe antero-
medial aspeet of the eparterial bronehus to the hilus, where it joins the
vein of the middle lobe, whieh lies along the antero-medial border of the
first ventral hyparterial bronehus, to form the upper right pulmonary vein.
The vein from the lower lobe aseends along the antero-medial border of
the intra-pulmonary part of the stem bronehus. On the left side, the upper
left pulmonary vein aeeompanies the first ventral bronehus, and the lower
aeeompanies the intra-pulmonary part of the stem bronehus ; eaeh vein
lies along the venlro-medial aspeet of the bronehus whieh it aeeompanies.

The Thoraeie Portions of the Vagi Nerres. — The thoraeie
parts of the vagi nerves, whieh are still in position, should
now be examined. Both yagi enter the thorax at the upper
aperture. The right vagus deseends, through the superior
mediastinum, posterior to the right innominate vein and the
superior vena cava, passing obliquely downwards and pos-
teriorly (Fig. 12) along the side of the traehea, and between
the traehea roedially, and the right pleura laterally, to the
areh of the azygos vein. Next it passes between the traehea
medially, and the areh of the azygos vein laterally, and reaehes
the posterior aspeet of the root of the right lung, where it breaks
up into a number of branehes whieh unite with branehes of
the sympathetie trunk to form the posterior pulmonary plexus.
It emerges from the plexus as a single trunk whieh runs
downwards and medially, in the posterior mediastinum, to the
front of the oesophagus. On the oesophagus it breaks up into
branehes whieh unite with branehes of the left vagus to form
the asophageal plexus (Fig. 47). At the lower end of the
thorax the right vagus again beeomes distinet ; it passes to the
posterior aspeet of the oesophagus and enters the abdomen
through the eesophageal orifice of the diaphragm.

TT — 7 n.

loo THORAX

Thoraek Branehes of the Right Vagus, — Whilst the right
vagus is in the superior mediastinum it gives off a thoraeie
eardiae braneh, whieh goes to the right half of the deep
eardiae plexus, and some anterior pulmonary branehes to
the front of the root of the right lung, where they join
with branehes of the eardiae plexus to form the anterior pul-
monary plexus. As it passes posterior to the root of the lung
it gives branehes to the bronehi and the lung ; and in the
posterior mediastinum it gives branehes to the oesophagus,
and to the posterior part of the perieardium and pleura.

The Left Vagus. — As the left vagus deseends through the
superior mediastinum it lies at first between the left eommon
earotid artery and the left phrenie nerve anteriorly, and the
left subclavian artery posteriorly, and then on the left side
of the areh of the aorta. In the latter situation it is erossed
laterally by the left superior intereostal vein. Below the
lower border of the aortie areh it passes posterior to the root
of the left lung, where it breaks up into branehes whieh enter
into the formation of the posterior pulmonary plexus. At
the lower border of the root of the left lung it emerges from
the plexus as two trunks, whieh deseend, into the posterior
mediastinum, to the oesophagus, where they unite with
branehes of the right vagus to form the oesophageal plexus.
At the lower end of the thorax the left vagus again beeomes
a single trunk whieh passes through the oesophageal orifice
of the diaphragm on the anterior aspeet of the oesophagus.

Thoraeie Branehes of the Left Vagus. — In the superior
mediastinum, whilst it lies against the left side of the aortie
areh, it gives off the left reeurrent braneh, branehes to
the upper and anterior part of the perieardium, and branehes
to the left anterior pulmonary plexus. Posterior to the root of
the left lung, it supplies branehes to the left bronehus and
the left lung; and during its eourse through the posterior
mediastinum, as it takes part in the oesophageal plexus, it
gives branehes to the oesophagus, to the posterior part of the
perieardium, and to the left pleura.

The Thoraeie Part of the Left Reeurrent Nerve. —
The left reeurrent nerve springs from the trunk of the
left vagus near the lower border of the left side of the
aortie areh. It curves round the lower border of the areh,
posterior and to the left of the ligamentum arteriosum, and
passes upwards, posterior and to the right of the areh.

THORAGie CAVITY loi

through the superior mediastinam, in tbe angle between the
left border of the traehea and the eesoi^iagus, and posterior to
the left eommon earotid artery. As it tums round the areh
it gives branehes to the deep eardiae plexus, and, as it aseends
along the left border of the traehea, it gives ofisets to the
traehea and to the oesophagus.

The Deep Gardiae Plens. — The deep eardiae plesus Hes
between the areh of the aorta and the bifurcation of ihe
traehea. It is more or less distinetly separable into rigbt and
left parts, and the right part is eonneeted with the super5cial
eardiae plexus. The right part of the plexus receives (i;
three eardiae branehes from the eenrieal part of the right
sympathetie trunk ; (2) the two cervical eardiae branehes of
the right vagus ; (3) the eardiae braneh of the right reeurrent
nerve ; (4) the thoraeie eardiae braneh of the right ^-agus.
It is eonneeted with the superficial eardiae plexus and gives
branehes to (i) the right anterior pulmonary plexus; (2)
the right atrium; (3) the right eoronary plexus. The left
part of the deep eardiae plexus receives (i) the middle and
lower cervical eardiae branehes of the left sympathetie trunk ;
(2) the upper cervical eardiae braneh of the left vagus ; /3)
the eardiae branehes of the left reeurrent nerve. It gives
branehes to (i) the left anterior pulmonary plexus; (2) the
left atrium ; (3) the left eoronary plexus.

Disseetion. — Cutthrough the right and lelt bronehi, elose to their origins
from the traehea ; then divide the traehea at the upper aperture of the
thorax and remove its thoraeie portion, but avoid injury to the vagi and
the left reeurrent nerves. The extra-pulmonary parts of the l^ronehi
will be retained in position by the bronehial arteries and ihe Lranehes
of the pulmonary plexuses ; and the thoraeie part of the ^irsophagus will be
fully exposed.

The Thoraeie Part of the (Esophagiis. — The thoraeie part
of the oesophagus enters the thorax at the upper aperture,
passes downwards, through the superior and posterior
mediastina, and leaves, at the level of the tenth thoraeie
vertebra, by passing through the eesophageal orifice of the
diaphragm into the epigastrie region of the abdomen. As it
enters the superior mediastinum it Hes somewhat to the left
of the median plane, but as it deseends it passes medially,
gains the median plane at the level of the fifth thoraeie
vertebra, and eontinues downwards in that plane to the level
of the seventh thoraeie vertebra. There it passes forwards

I02 THORAX

and to the left, aeross the anterior aspeet of the deseending
aorta and posterior to the perieardium (Figs. 12 and 21).

Posterior Relations. — In the superior mediastinum it is an-
terior to the left longus eolli musele and the vertebral eolumn.
In the upper part of the posterior mediastinum it is separated
from the vertebral eolumn by (i) the posterior part of the oeso-
phageal plexus, (2) the upper six right aortie intereostal arteries,
(3) the thoraeie duet, (4) the vena azygos, (5) the vena hemi-
azygos and the accessoryhemiazygos vein; and in the lower part
by (6) the oesophageal plexus and (7) the deseending aorta.

Anterior Relations. — Anterior to it, in the superior media-
stinum, lie the traehea, the left reeurrent nerve, the upper
part of the left eommon earotid artery, the left subclavian
artery, the areh of the aorta, and the struetures whieh lie
anterior to those already mentioned. As it passes from the
superior to the posterior mediastinum its anterior relations are
iirst the eommeneement of the left bronehus and then the
right pulmonary artery.^ In the posterior mediastinum^ the
eesophageal plexus is on its anterior surface, intervening
between it and the posterior wall of the perieardium, whieh
separates both the plexus and the oesophagus from the
posterior wall of the left atrium ; and at a lower level the
oesophagus lies posterior to the diaphragm (Fig. 21).

Right Laieral Relations. — In the superior mediastinum^ it is
in relation with the right pleura and lung and with the areh
of the vena azygos (Figs. 12 and 22), and in the posterior
mediastinum with the oesophageal plexus and right pleura
and lung, until it passes anteriorly and to the left, anterior to
the deseending aorta.

Left Lateral Relations. — In the superior mediastinum, it is
in relation on the left side with the thoraeie duet, the left
subclavian artery, the left pleura and lung, and the termination
of the areh of the aorta. From the fifth to the seventh thoraeie
vertebra its left lateral relations are the oesophageal plexus and
the deseending aorta ; and at its lower end^ as it lies anterior to
the deseending aorta, it eomes again into relation with the
left pleura and lung.

The disseetor should note (i) that, after death, the~
oesophagus is somewhat eompressed antero-posteriorly by
the struetures between whieh it lies. It probably has a
similar form during life when empty and flaccid, but beeomes

^ Verify this statement by replaeing the heart in situ.

THORAGie CAVITV

103

tnoie eireular when solids or Suids ue passing along it ; and
(2) that it is somewhat eonstrieted at the level of the Iefi
bronehus.

An ineh or more of the upper part of the posterior
mediastinal poition of tbe tube should be renioved and di»-
seeted under water in a eork-lioed tray. It will bc found to
possess from without inwards the following eoais : (■) an
extemal fibrous sheath; (a) a museular eoat ; (3) a sub-
mueous eoat ; and (4) a mueous intemal lining. The
submueous eoat forms a loose eonneetion between the
museular and mueous eoats ; consequent]y, when the museular

eoat is eontraeted the mueous lining is thrawn into longi-
tudinal folds. The museular eoat eonsists of an extemal layer
of longitudinal fibres and an intemal layer of eireular fibres.

Aorta DeBeendens. — The deseending aorta eommenees
at the termination of the aortie areh, at the lower border of
the left side of the fourth thoraeie yertebra. Il passes down-
wards, through the posterior mediastinum, and it leaves ihe
thorax by[iassingthrough theaortieaperture of the diaphragm,
opposite the lower border of the twelfth thoraeie vertebra.
Its length is about seven inehes, In the upper part of its
extent it lies to the left of the vertebral eotumn ; but in the
lower part it lies anterior to the eolumn, in the median plane.

Braruhes. — Branehes spring from both the anlerior and ihe
posterior aspeets of the deseending aorta. Those from the
anterior aspeet are the two left bronehial arteries, four
II— 7 e

104 THORAX

eesophageal branehes, and some small and iiregular media-
stinal and perieardial branehes. The posterior branehes are
nine pairs of aortie intereostal arteries and one pair of sub-
eostal arteries.

Relations. — Anteriorto the thoraeie part of the deseending
aorta, from above downwards, are the root of the ]eft lung ;
the upper part of the posterior wall of the perioardium,
separating the aorta from the left atrium ; the eesophagus,
separating the aorta from the lower part of the posterior wall
of the perieardium ; and the erura of the diaphragm, whieh
separate the lower portion of the thoraeie aorta from the

omental bursa of the peritoneum and from the posterior
surface of the eaudate lobe (O.T. Spigelian) of the Iiver,
Posteriorly are the vertebral eolumn, its own intereostal and
subeostal branehes, the hemiazygos and aeeessory hemiazygos
veins ; and it is overlapped posteriorly in the upper part of its
extent by the left pleura and lung. Along tts rigkt side, in its
whole length, are the thoraeie duet and the vena azygos, and
anterior to them, from the fiflh to the lower part of the
seyenth thoraeie vertebra, lies the eesophagus. At a lower
leyel a mass of areolar tissue separates the aorta from the
right pleura and lung. On its le/t side it is in relation with
the left pleura and lung.

Disseetiott. — Turn ihe remains of ihe lower parl of the ossophagus down-
wards lowards the diaphragm. Clean the ihoraeie duel, the right aortie
intereostal arteries. and the hemiazygos and aeeessory hemiazycos veins,
whieh lie postetior to the oesophagus. Then traee the thoraeie duet in the

THORAGie CA\nTY

FiG. 52- — The Thoraeie Duet and ils Tributaries.

io6 THORAX

whole of the thoraeie portion of its eourse, and arrange with the disse(;tor
of the head and neek to display the cervical portion of its eourse.

The Thoraeie Duet. — The thoraeie duet is a vessel of
small ealibre but of great importanee, for it conveys, to the
left innominate vein, the whole of the lymph from the lower
extremities, the abdomen (except that from part of the upper
surface of the liver), the left side of the thorax, ineluding the
left lung and pleura and the left side of the heart, the left
upper extremity, and the left side of the head and neek. It
is the upward prolongation of a dilated sae, the eisterna
ehyli, whieh lies between the right erus of the diaphragm and
the bodies of the first and seeond lumbar vertebrae. It
enters the thorax through the aortie orifice of the diaphragm,
lying between the aorta on the left and the vena azygos on
the right. It eontinues upwards through the posterior
mediastinum, lying between the deseending aorta and the
vena azygos, anterior to the right aortie intereostal arteries
and the hemiazygos and aeeessory hemiazygos veins, and
posterior to the right pleura below and the oesophagus above.
At the level of the fifth thoraeie vertebra it erosses to the left
of the vertebral eolumn, and then aseends, through the superior
mediastinum, along the left border of the oesophagus, in
eontaet, on the left, with the left pleural sae, and separated
posteriorly from the left longus eolli musele by the mass of
areolar tissue. Anterior to the thoraei'e duet, in the superior
mediastinum, are the termination of the aortie areh, the left
subclavian, and the left eommon earotid arteries, in that order
from below upwards. At the upper end of the thorax the
thoraeie duet enters the root of the neek, and, at the level of
the seventh cervical vertebra, it turns laterally, posterior to
the left eommon earotid artery, the left vagus nerve, and the
left internal jugular vein, and anterior to the vertebral artery
and veins, the thyreo-cervical trunk or inferior thyreoid artery,
and the phrenie nerve. Then, turning downwards, anteriorly
and medially, on the anterior aspeet of the sealenus anterior,
it erosses anterior to the transversa eolli and transversa seapulse
arteries, and terminates in the upper end of the innominate
vein, in the angle of junction of its internal jugular and sub-
clavian tributaries. Immediately before its termination it
receives the left eommon jugular and subclavian lymphatie
trunks, unless they end separately in one or other of the
three large veins. When the thoraeie duet is distended it

THORAGie CAVITY

107

bas 3 beaded or nodulated appearanee on aeeount or ihe
numerous valves whieh lie in its interior. The terminal
valve is usually situated a short distanee from the point of
entianee ot the duet into the lert innominate vein.

The lUght Irmphatie Dnet. — From the point where the
thorade duet tums from the front to the left of the
Tertebral eolumn a small lymphatie yessel, whieh frequently
eommunieates with the thoraeie duet, may be traeed upwar
along the ftom of the eolumn to the root of the neen,

io8 THORAX

where it ends in the eommeneement of the right innominate
vein. This is the right lymphatie duet. Immediately before
its termination it may be joined by the right eommon
jugular and right subclavian lymphatie trunks, but, as a
rule, the two latter vessels open separately into the sub-
clavian, the internal jugular, or the innominate veins (Parsons).
The right lymphatie duet conveys lymph from the upper part
of the right lobe of the liver, the right side of the thorax,
ineluding the right pleura and lung and the right half of the
heart, and, if it is joined by the jugular and subclavian trunks,
the lymph from the right upper extremity and the right side
of the head and neek also.

L^rmphoglandiilsB Thoraeales. — During the disseetion of the thorax
the disseetor will have noted eertain groups of lymph glands. These
are of eonsiderable importanee, for their enlargement in disease is not
infrequently the eause of serious thoraeie irouble ; but whilst some, sueh
as the bronehial glands, are quite obvious, others are frequently so
small that they eseape notiee. The following are the chief groups : — ( i )
Two ehains of minute glands wliieh are plaeed in relation to the anterior
thoraeie wall and follow the eourse of the internal mammary vessels. They
are termed stemal lymph glands, and are joined by lymphatie vessels from
the anterior thoraeie wall, the mammary glands, the anterior part of the
diaphragm, and the upper part of the anterior wall of the abdomen. (2) Two
ehains of glands on the posterior thoraeie wall — one on either side of the
vertebral eolumn in relation to the vertebral extremities of the ribs. These are
very minute ; afferents to them aeeompany the intereostal vessels ; therefore
they are ealled the intereostal lymph glandSi and they receive the lymphaties
of the posterior thoraeie wall. (3) Anterior mediastinal lymph glands,
two or three in number, whieh receive lymphaties from the diaphragm
and upper surface of the liver. They oeeupy the lower open part of
the anterior mediastinum. (4) Posterior mediastinal lymph glands, whieh
follow the eourse of the thoraeie aorta, and are joined by lymphaties
from the diaphragm, perieardium, and oesophagus. (5) Superior media-
stinal lymph glands, an important group, eight to ten in number, and
plaeed in relation to the aortie areh and the biiureation of the traehea.
The lymphaties of the heart, perieardium, and thymus enter these. (6)
Bronehial lymph glands, eontinuous above with the preeeding, and
massed chiefly in the interval between the two bronehi. They are also
prolonged into the roots of the lungs. The lymphatie vessels of the lungs
pour their eontents into them. In the adult, they are generally dark in
eolour, and sometimes quite blaek.

Dissedion. — Cut through the deseending aorta immediately above the
diaphragm. Detaeh its upper end from the left vagus and the left reeurrent
nerve whieh were previously fastened to it, then draw it forwards and
divide the intereostal and subeostal arteries, whieh arise from its posterior
surface, elose to their origins and remove it.

ArterisB Intereostales. — There are eleven pairs of inter-
eostal arteries. The upper two pairs are derived indireetly

THORAGie CAVITV 109

from the subclavian arteries; the remaining nine pairs are
branehes of the thoraeie part of the deseending aorta.

The Aortde Intereostal Arieries. — The nine pairs uf aortie
intereostal arteries spring from the posterior suHaee of the
deseending aorta, either separately or by a series (»f eomnion
trunks, one for eaeh pair. The right arteries are longer than
the left beeause the aorta lies to the left of the median plane :
and, sinee the deseending aorta eommenees only at the lcvel
of the lower border of the fourth thoraeie vertebra, the four
or five highest pairs have to aseend to gain the level of
the spaees to whieh they are distributed.

The right aortie intereostal arteries run aeross the anterior
aspeets of the bodies of the vertebra2, lying posterior to the
thoraeie duet and the vena azygos; then they turn posteriorly,
between the sides of the bodies of the vertebrai and the parietal
pleura ; and, finally, immediately before they enter the inter-
eostal spaees, they pass between the sides of the bodies of the
vertebrse medially and the sympathetie trunk laterally. The
shorter left aortie intereostal arteries run posteriorly, first
between the left pleura and the bodies of the vertebrae, and
then between the sympathetie trunk and the vertebral bodies.
As eaeh artery enters the spaee to whieh it belongs it gives oiT
a dorsal braneh^ whieh passes posteriorly, between the vertebral
eolumn medially and the anterior costo-transvcrse ligament
laterally ; it gives off a spinal twig, whieh enters the verte-
bral eanal through the eorresponding intervertebral foramen ;
then it divides into a medial and a lateral braneh whieh
aeeompany the medial and lateral divisions of the posterior
braneh of the eorresponding thoraeie nerve. After giving off
the dorsal braneh, the trunk of the artery runs laterally, along
the upper border of the spaee to whieh it belongs, at first
anterior to the posterior intereostal membrane, and then
between the internal and external intereostal museles. Its
further eourse has been deseribed already (p. 6). As it passes
along the upper border of the intereostal spaee, in the shelter
of the subeostal groove of the rib, it is situated between
the intereostal vein above and the anterior braneh of the
thoraeie nerve below.

The Subeostal Arteries. — The subeostal arteries are the
last pair of branehes whieh spring froni the posterior aspeet
of the thoraeie part of the deseending aorta. They enter
the abdomen, by passing beneath the lateral lumbo-eostal

iio THORAX

arehes, and they run, in eompany with the last thoraeie
nerves, along the lower borders of the last pair of ribs.

ArterisB Intereostales Supremse. — The superior intereostal
arteries, whieh supply the upper two intereostal spaees on
eaeh side, are derived from the costo-cervical branehes of
the subclavian arteries (Fig. 5). Eaeh superior intereostal
artery eommenees at the level of the upper border of the
neek of the first rib. It deseends anterior to the neek of
the rib, posterior to the parietal pleura and between the first
thoraeie ganglion of the sympathetie trunk medially and
the first thoraeie nerve; whieh is passing upwards to the
braehial plexus, laterally (Fig. 5). At the lower border of
the neek of the first rib it gives off the posterior inter-
eostal artery to the first intereostal spaee; then it erosses
anterior to the neek of the seeond rib, and, turning later-
ally, it beeomes the posterior intereostal artery of the seeond
spaee.

Nervi Intereostales. — The intereostal nerves are the
anterior branehes of the thoraeie nerves. They pass laterally
in eompany with the arteries. The twigs whieh eonneet
them with the sympathetie ganglia have been noted already
(p. 26). Eaeh nerve lies at a lower level than the eorre-
sponding artery, and is at first plaeed between the posterior
intereostal membrane and the pleura, and then between
the two museular strata. The further eourse of the nerves
is deseribed on p. 5.

The first thoraeie nerve runs upwards, anterior to the neek
of the first rib, to join the braehial plexus. It gives a small
braneh to the first intereostal spaee, but this nerve, although
it is disposed after the manner of an intereostal nerve, does
not furnish, as a rule, a lateral eutaneous or an anterior
braneh. The seeond intereostal nerue^ as a rule, sends a braneh
upwards, anterior to the neek of the seeond rib, to join that
portion of the first thoraeie nerve whieh enters the braehial
plexus. This eommunieating twig is usually minute and in-
significant, but sometimes it is a large nerve; when this is
the ease, the intereosto-braehial nerve (O.T. intereosto-
humeral), or lateral eutaneous braneh of the seeond intereostal
nerve, is very small or altogether absent.

YensB Intereostales. — The intereostal veins differ in their
arrangement upon the two sides of the body. On the right
side they terminate in three different ways : —

THORAGie CAVn Y 1 1 1

1. The intereostal vein of the first or highest s|>ace joins ihe right

innominate vein (sometimes the vertebral retM).

2. The intereostal veins of the seeond and third spaees (and sometimes

that of the fourth spaee) unite into a eommon trunk, termed the
rig'A/ superior intereosial vein^ whieh joins the upjK.'r part of the
vena azygos. '

3. The intereostal veins of the lower eight spaees join the vetta azy^s.

On the ie/i stde of the hoAy four modes of termination may
be reeognised : —

1. The intereostal vein of the first spaee joins the left innominate vein

(sometimes the vertebral vein).

2. The intereostal veins of the seeond and third spaees (and sometimes

that of the fourth spaee) converge and by their union form a single
trunk, termed the left superior intereostal vein^ whieh erosses the
areh of the aorta and joins the left innominate vein independently
of the first intereostal vein. The union with the left innominale
vein may be absent, and then ihe trunk formed by ihe veins of
the seeond and third spaees joins the aeeessory hemiazygos vein.

3. The intereostal veins of the fourth, fifth, sixth, seventh, and eighth

spaees terminate in the aeeessory hemiazygos vein (O.T. vena azygos
minor superior), whieh erosses posterior to the aorta and joins ihe
hemiazygos vein, or it ends direetly in ihe vena azygos.

4. The intereostal veins of the ninth, tenth, and eleventh spaees join the

hemiazygps vein (O.T. vena azygos minor inferior).

Vena Azyg08 (O.T. Vena Azygos Major). — This has
already been studied, but -should now be revised (p. 29),
and then the disseetor should examine the hemiazygos and
aeeessory hemiazygos veins.

Vena Hemiazygos Aeeessoria. — The aeeessory hemiazygos
vein is formed, on the left side of the body, by the union of the
intereostal veins of the fourth, fifth, sixth, seventh, and eighth
spaees. It eommunieates above with the left superior inter-
eostal vein, whieh earries the blood from the seeond and third
intereostal spaees to the left innominate vein ; and it receives
the left bronehial veins. At the level of the seventh thoraeie
vertebra it erosses to the right, posterior to the aorta and
thoraeie duet, and ends by joining either the hemiazygos vein
or the vena azygos. In addition to the intereostal veins it
receives the left bronehial veins.

Vena Hemiazygos (O.T. Vena Azygos Minor Inferior). —
This vein takes origin within the abdomen as the left
aseending iumbar vein. It enters the thorax by piereing
the' left erus of the diaphragm, and is eontinued upwards,
upon the vertebral eolumn, as far as the eighth or seventh
thoraeie yertebra. At this point it turns to the right, and,

iio THORAX

arehes, and they run, in eompany with the last thoraeie
nerves, along the lower borders of the last pair of ribs.

Arteriae Intereostales Supremse. — The superior intereostal
arteries, whieh supply the upper two intereostal spaees on
eaeh side, are derived from the costo-cervical branehes of
the subclavian arteries (Fig. 5). Eaeh superior intereostal
artery eommenees at the level of the upper border of the
neek of the first rib. It deseends anterior to the neek of
the rib, posterior to the parietal pleura and between the first
thoraeie ganglion of the sympathetie trunk medially and
the first thoraeie nerve; whieh is passing upwards to the
braehial plexus, laterally (Fig. 5). At the lower border of
the neek of the first rib it gives off the posterior inter-
eostal artery to the first intereostal spaee; then it erosses
anterior to the neek of the seeond rib, and, turning later-
ally, it beeomes the posterior intereostal artery of the seeond
spaee.

The first thoraeie nerue runs upwards, anterior to the neek
of the first rib, to join the braehial plexus. It gives a small
braneh to the first intereostal spaee, but this nerve, although
it is disposed after the manner of an intereostal nerve, does
not furnish, as a rule, a lateral eutaneous or an anterior
braneh. The seeond intereostal nerue, as a rule, sends a braneh
upwards, anterior to the neek of the seeond rib, to join that
portion of the first thoraeie nerve whieh enters the braehial
plexus. This eommunieating twig is usually minute and in-
significant, but sometimes it is a large nerve ; when this is
the ease, the intereosto-braehial nerve (O.T. intereosto-
humeral), or lateral eutaneous braneh of the seeond intereostal
nerve, is very small or altogether absent.

Venae Intereostales. — The intereostal veins differ in their
arrangement upon the two sides of the body. On the right
side they terminate in three different ways : —

THORAGie CAVn Y 1 1 1

1. The intereostal vein of the first or highest si^aee joins the ri^ht

innominaie vein (sometimes the vertebral vein),

2. The intereostal veins of the seeond and third spaees (and sometimes

that of thefourth spaee) unite into a eommon trunk, termed the
ri^A/ superior intereostal ^ein^ whieh joins the upiw i>art (>f the
vena azygos, '

3. The intereostal veins of the lower eight spaees juin the x'etta azy^s,

On the Uft side of the bodyy^r modes of termination may
be reeognised : —

1. The intereostal vein of the first spaee joins the left innominate vein

(sometimes the vertebral vein).

2. The intereostal veins of the seeond and third si)aces (and sometimes

that of the fourth spaee) converge and by their union form a single
trunk, termed the /e/t superior intereostal rein^ whieh erosses the
areh of the aorta and joins the left innominate vein independently
of the first intereostal vein. The union with the left innominate
vein may be absent, and then the trunk formed by ihe veins of
the seeond and third spaees joins the aeeessory hemiazygos vein.

3. The intereostal veins of the fourth, fifth, sixth, seventh, and eighth

spaees terminate in the aeeessory hemiazygos vein (O.T. vena azyg<)s
minor superior), whieh erosses posterior to ihe aorla and joins ihe
hemiazygos vein, or it ends direetly in thevena azygos.

4. The intereostal veins of the ninth, tenth, and eleventh spaees join the

hemiazygos vein (O.T. vena azygos minor inferior).

Vena Azyg08 (O.T. Vena Azygos Major). — This has
already been studied, but -should now be revised (p. 29),
and then the disseetor should examine the hemiazygos and
aeeessory hemiazygos veins.

Vena Hemia^ygos Aeeessoria. — The aeeessory hemiazygos
vein is formed, on the left side of the body, by the union of the
intereostal veins of the fourth, fifth, sixth, seventh, and eighth
spaees. It eommunieates above with the left superior inter-
eostal vein, whieh earries the blood from the seeond and third
intereostal spaees to the left innominate vein ; and it receives
the left bronehial veins. At the level of the seventh thoraeie
vertebra it erosses to the right, posterior to the aorta and
thoraeie duet, and ends by joining either the hemiazygos vein
or the vena azygos. In addition to the intereostal veins it
receives the left bronehial veins.

Vena Hemiazygos (O.T. Vena Azygos Minor Inferior). —
This vein takes origin within the abdomen as the left
aseending lumbar vein, It enters the thorax by piereing
the' left erus of the diaphragm, and is eontinued upwards,
upon the yertebral eolumn, as far as the eighth or seventh
thoraeie yertebra. At this point it turns to the right, and,

iio THORAX

arehes, and they run, in eompany with the last thoraeie
nerves, along the lower borders of the last pair of ribs.

Arteriae Intereostales Supremse. — The superior intereostal
arteries, whieh supply the upper two intereostal spaees on
eaeh side, are derived from the costo-cervical branehes of
the subclavian arteries (Fig. 5). Eaeh superior intereostal
artery eommenees at the level of the upper border of the
neek of the first rib. It deseends anterior to the neek of
the rib, posterior to the parietal pleura and between the first
thoraeie ganglion of the sympathetie trunk medially and
the first thoraeie nerve ; whieh is passing upwards to the
braehial plexus, laterally (Fig. 5). At the lower border of
the neek of the first rib it gives off the posterior inter-
eostal artery to the first intereostal spaee; then it erosses
anterior to the neek of the seeond rib, and, turning later-
ally, it beeomes the posterior intereostal artery of the seeond
spaee.

The first thoraeie nerue runs upwards, anterior to the neek
of the first rib, to join the braehial plexus. It gives a small
braneh to the first intereostal spaee, but this nerve, although
it is disposed after the manner of an intereostal nerve, does
not furnish, as a rule, a lateral eutaneous or an anterior
braneh. The seeond intereostal nerve, as a rule, sends a braneh
upwards, anterior to the neek of the seeond rib, to join that
portion of the first thoraeie nerve whieh enters the braehial
plexus. This eommunieating twig is usually minute and in-
significant, but sometimes it is a large nerve ; when this is
the ease, the intereosto-braehial nerve (O.T. intereosto-
humeral), or lateral eutaneous braneh of the seeond intereostal
nerve, is very small or altogether absent.

Venae Intereostales. — The intereostal veins differ in their
arrangement upon the two sides of the body. On the right
side they terminate in three different ways : —

THORAGie CAVn Y 1 1 1

1. The intereostal vein of the tirst or highest s{Kice joins the ri^ht

innominaie vein (sometimes the V€rteoral fein).

2. The intereostal veins of the seeond and third s|>accs (and sometimes

that of thefourth spaee) miite into a eommon trunk, termed the
rig'At superior intereostal yein^ whieh joins the upi^er {^rt (>f the
vena azygos. '

3. The intereostal veins of the lower eight s{)aces join the rena aty^s.

On the left stde of the \xAyfimr modes of terniination may
be reeognised : —

1. The intereostal vein of the first spaee joins the left innominate vein

(sometimes the vertebral vein).

2. The intereostal veins of the seeond and third s{)aces (and sometimes

that of the fourth spaee) converge and by their union form a single
trunk, termed the le/t superior intereostal rein^ whieh erosses the
areh of the aorta and joins the left innominaie i*ein inde{)endently
of the first intereostal vein. The union with the lt'ft innominale
vein may be absent, and then the trunk formed by the veins of
the seeond and third si^aees joins the aeeessory heniiazygos vein.

3. The intereostal veins of the fourth, fifth, sixth, seventh, and eighth

spaees terminate in the aeeessory hemiazygos vein ((J.T. vena a/ygos
minor superior), whieh erosses }x>sterior to the aorta and joins the
hemiazygos vein, or it ends direetly in thevena azygos.

4. The intereostal veins of the ninth, tenth, and eleventh sp>aces join the

hemiazygps vein (O.T. %>ena azygos ininor inferior).

Vena Azyg08 (O.T. Vena Azygos Major). — This has
already been studied, but should now be revised (p. 29),
and then the disseetor should examine the hemiazygos and
aeeessory hemiazygos veins.

Vena Hemiazygos Aeeessoria. — The aeeessory hemiazygos
vein is formed, on the left side of the body, by the union of the
intereostal veins of the fourth, fifth, sixth, seventh, and eighth
spaees. It eommunieates above with the left superior inter-
eostal vein, whieh earries the blood from the seeond and third
intereostal spaees to the left innominate vein ; and it reccives
the left bronehial veins. At the level of the seventh thoraeie
vertebra it erosses to the right, posterior to the aorta and
thoraeie duet, and ends by joining either the hemiazygos vein
or the vena azygos. In addition to the intereostal veins it
receives the left bronehial veins.

Vena Hemiazygos (O.T. Vena Azygos Minor Inferior). —
This vein takes origin within the abdomen as the left
aseending lumbar vein. It enters the thorax by piereing
the' left erus of the diaphragm, and is eontinued upwards,
upon the yertebral eolumn, as far as the eighth or seventh
thoraeie yertebra. At this point it turns to the right, and,

1 1 2 THORAX

erossing posterior to the aorta and the thoraeie duet, it joins
the vena azygos. Before it terminates it may receive the
aeeessory hemiazygos vein.

The thoraeie tributaries of this vein are the intereostal
veins of the lower three spaees of the left side and the left
subeostal vein. In the abdomen it receives the upper two
left lumbar veins.

The Anterior Intereostal Yeins. — The blood is drained
from the anterior part of the thoraeie wall by veins whieh
aeeompany the intereostal branehes of the internal mammary
arteries. They terminate in the internal mammary veins.

The veins of the thoraeie parietes are extremely variable, and the
deseription given above must be looked upon as representing merely their
more usual arrangement.

THORAGie JOINTS.

The disseetor should now eomplete the disseetion of the
thorax by an examination of the various thoraeie joints.

Disseetion. — When the portion of the sternum with the eartilages of the
ribs, whieh was laid aside, is studied, the following joints will be noted :
inter-sternal, eosto-sternal, and inter-ehondral. Very little disseetion is
neeessary. After the ligaments have been defined, the 4issector should
remove a thin sliee from the anterior aspeet of eaeh artieulation, in order
that the interior of the joint may be displayed.

Synehondrosis Stemalis. — The joint between the manu-
brium and the body of the sternum is a synehondrosis. The
opposing surfaces of bone are covered with a layer of hyaline
eartilage, and are united by intermediate fibro-cartilage. The
joint is supported by some anterior and posterior longitudinal
iibres whieh are developed in eonneetion with the strong and
thiek periosteum. The posterior ligament is the stronger of
the two. The joint between the body of the sternum and the
xiphoid proeess is also a synehondrosis till middle life, at
whieh period the two parts beeome ossiAed together.

Stemo-eliondral Artieulations. — Seven ribs artieulate with
eaeh side of the sternum by means of their eartilages.

The artieulations of the first and the sixth are peeuliar, inasmueh as
they artieulate with single pieees of the sternum, viz. with the manubrium
and the lowest pieee of the body, respectively ; whereas eaeh of the eartilages
of the other true ribs artieulates with two segments of the sternum. The
eartilage of the first rib is implanted upon the side of the manubrium

THORAGie JOINTS 113

without any s)movial membrane, or other material, intervening. The
seeond eostal eartilage is usually separated from the sternum by two
synovial cavities, between whieh an interartieular ligament is dcveloped.
In the ease of the other joints it is more eommon to hnd a single synovial
cavity and no interartieular ligament. There is, however, eonsiderable
variety in these artieulations, and a synoviaI membrane is very frequently
wanting altogether in the sterno-ehondral joint of the seventh eostal
eartilage.

With the exception of the first, whieh is a s^mehondrosis,
the sterno-ehondral joints belong to the diarthrodial variety.
They are provided with anterior and posterior ligaments, and
also, in those eases where the joint presents a double synovial
oayity, with an interartieular ligament.

Anterior and posterior stemo-eostal radiate ligaments, These
are strong, fiattened bands of fibres whieh radiate from the
extremities of the rib-eartilages and blend with the periosteum
on the anterior and posterior surfaces of the sternum. The
interartieular ligaments are feeble bands whieh pass from the
tips of the rib-eartilages to the stemum, and divide the artieu-
lations in whieh they exist into an upper and a lower eom-
partment, eaeh of whieh is lined with a synovial stratum.

Iiiter-eliondral Artienlations. — Interehondral joints are
formed between the adjacent margins of the ribs from the
sixth to the tenth. The joint cavities are surrounded by
ordinary eapsular ligaments, eaeh of whieh is lined internally
with a synovial stratum ; they are, therefore, diarthrodial
joints.

Costo-vertebral Artienlations. — The costo-vertebral joints
are separable into two groups, eapitular and costo-transverse.

The eapitular artieulations are the joints between the heads
of the ribs and the bodies of the vertebrae and the interverte-
bral fibro-cartilages ; they are diarthrodial joints. With the
exceptions of the first and the last three ribs, the head of
every rib artieulates with the bodies of two adjacent vertebrae
and the intervening intervertebral fibro-cartilage, and it is
eonneeted with them by an artieular eapsule and an inter-
artieular ligament. The interartieular ligament eonneets the
intervertebral fibro-cartilage with the ridge whieh separates
. the two facets on the head of the rib. It is united, anteriorly
and posteriorly, with the eapsule, and separates the joint cavity
into an upper and a lower eompartment. The anterior part
of the eapsule is speeialised into three radiating bands whie
form the radiate ligament, The upper and lower bands

VOL. II — 8

114 THORAX

to the eorresponding verlebr!e, whilst the intermedi.ite band
is attaehed to the intervertebral Hbro-eartilage. The eapilular
joints of the first, and the tenth, eleventh, and twelfth ribs are
eaeh formed between the head of the rib and the eorrespond-
ing vertebra. The interartieular ligament is absent; therefore
eaeh joint possesses only one cavity. The anterior parts of
the eapsules of these joints are not, as a rule, speeialised into
radiate bands.

Tlie Oosto-tianaTerse Artteulations are the joints fornied

between the neeks and the tubereles of the ribs and the trans-
verse proeesses of the vertebrEe.

The tuberele of eaeh rib, with the exception of the
eleyenth and tweUth, artieulates with the tip of the ttansyerse
proeess of the vertebra of the same number, by a eireular
artieular facet whieh is surrounded by an artieular eapsule
lined with a stratum synoviale. The joint is, therefore, a diar-
throdial joint and the upper and posterior part of the eapsule
is greaily thiekened, and is ealled the ligament of tke tubereh
(O.T. posterior eosto-transmrse liganieni). In addltion to the
eapsule and its posterior thiekening there are three aeeessory

THORAGie JOINTS 1 1 5

costo-transverse bands, the anterior and posterior eosto-trans-
yerse ligaments and the ligament of the neek of the rib.
The anterior eosto - transyerse ligament aseends from the
anterior margin of the upper border of the neek of the rib
to the lower border of the transverse proeess above. The
posterior costO'transverse ligament passes upwards from the
posterior part of the upper border of the neek of the rib to
the junction of the lamina and the transverse proeess of
the vertebra above ; and the ligament 0/ the neek of the rib
(O.T. middle costo-transverse iigament) eonneets the posterior
aspeet of the neek of the rib with the anterior aspeet of the
transverse proeess of the vertebra of the same number.

In the ease of the eleventh rib the costo-transverse liga-
ments are rudimentary or absent, and in the ease of the
twelfth rib they are usually entirely absent.

Intenrertebral Artiealations. — The bodies of the vertcbrae
are held together by a series of synehondrodial joints, sup-
ported anteriorly by an anterior longitudinal ligament, and
posteriorly by a posterior longitudinal ligament. The vertebral
arehes, by means of the artieular proeesses, form a series of
diarthrodial joints surrounded by eapsular ligaments, eaeh
eapsule being lined with a synovial stratum. Gertain ligaments
pass between different portions of the vertebral arehes and their
proeesses, viz., the ligamenta flava between adjacent laminse,
the inter-transverse, the inter-spinous, and the supra-spinous
ligaments.

The laminse and the spinous proeesses of the vertebrae have been
removed by the disseetor of the head and neek in opening up the vertebral
eanal to display the spinal meduUa. Consequently, the ligamenta flava,
the inter-spinous and supra-spinous ligaments, eannot be seen at present.

The anterior longiiudinal ligament (O.T. anterior eommon
ligament) is situated anterior to the bodies of the vertebrae,
and extends from the atlas vertebra above to the iirst pieee
of the saerum below. It eonsists of stout glistening fibrous
bands, whieh are firmly attaehed to the margins of the verte-
bral bodies and to the intervertebral fibro-cartilages. The
most superficial fibres are the longest, and extend from a
given vertebra to the fourth or fifth below it. The deeper
fibres have a shorter eourse, and pass between the borders
of two, three, or four adjacent vertebrae. The disseetor
eannot fail to notiee that the origin of the longus eolli musele
is inseparably eonneeted with this ligament.

II — 8«

ir6 THORAX

The posterior lon^tudinal ligament (O.T. posterior eommoti
ligammt) is plaeed on the posterior aspeets of the vertebral
bodies, and therefore within the vertebral eanal. It is Hrmly
eonneeted to the margins of the vertebral bodies and to the
intervertebral fibro-cartilages, but is separated from the eentral
parts of the bodies by some loose connective tissue and by a
plexus of veins, It is eonstrieted where it covers this venous
plexus, but widens out opposite the fibro-canilages. It there-
fore presents a sealloped or
dentieulated appearanee.
The interuertebral fibro-
' eartilages are a series of
dises of white fibro-car-
tilage, thieker anteriorly
than posteriorly, whieh are
interposed between the
bodiesofadjacentvertebrse.
The peripheral part of eaeh
dise, annulus fibroms, is
tough and Sbrous ; the
eentral portion, nudeus
pulposus, is soft and pulpy.
The dises inetease the
elastieity of the spine,
and tend to restore it to
its natural curvature after
it has been deflected by
museular aetion.

e intervettebral
:artilages eonstitute
the main bond of union
between the bodies of the vertebr£e, but, except in old people,
they are not direetly attaehed to the bone. A thin layer of en-
erusting hyaline eartilage eoats the opposing vertebral surfaces.

Fio. ss- — Posterior Longitiidinal Liga-
mem of liie Yeitebral Goliimn. The
yertebral arehes have been remored
froni Ihe veriebrEe,

The intertransmrse Kganunts are feeble bands whieh pass
between the tips of the transverse proeesses. In the lower
part of the thoraeie region they are intimately blended with
the intertransverse museles i in the middle and upper parts
of the thoraeie region they entirely replaee the museles.

FACE AND PRONTAL REGION 0F HEAD 117

HEAD AND NECK.

The disseetors of the Head and Neek begin work as soon
as the subject is brought into the room. During the first
three days, whilst the body is in the lithotomy posture, they
disseet the face, the anterior part of the eyelids, the superficial
part of the nose, and the anterior part of the sealp. During
the following five days, when the body is lying on its baek,
they disseet the posterior triangle, and eomplete the disseetion
of the sealp.

It is only by disseeting the face at this period, whilst
the parts are in good eondition, that the disseetor ean
gain any satisfactory idea of its eomponent parts ; and it is
essential that the eontents of the posterior triangle, whieh
is sueh an important surgieal region, should be displayed
before the disseetor of the arm has disturbed its posterior
boundary.

The first day should be devoted to the examination of the anierior part
of the frontal region of the head and the face, the study of the surface
anatomy of the oeular appendages, the reflection of the skin, and the elean-
ing of the superficial museles of the face and anterior part of the sealp.
On the seeond day the disseetors should display the superficial surface of
the parotid gland ; they should also find and elean the superficial vessels
and nerves, and traee them to their terminations. On the third day the
superficial museles must be reflected, and the deeper vessels and nerves
must be exposed and eleaned, and the auriele should be examined and
disseeted. On the fourth day, when the body has been plaeed upon its
baek, the disseetors should eommenee the disseetion of the posterior
triangle of the neek, and should eomplete that part of the disseetion in
three days. On the seventh day they should eomplete the examination
of the sealp. The eighth day should be devoted to a final study of the
braehial plexus in assoeiation with the disseetors of the upper extremity.

FACE AND FRONTAL REGION 0F HEAD.

The disseetors should eommenee the study of the face and
frontal region by an examination of the bony prominenees
and ridges in the area to be disseeted.

In the eentre of the facial area is the prominent outer
portion of the nose, eonsisting of a lower mobile part formed
mainly by skin and eartilage, and an upper rigid portior
formed by the nasal bones and the frontal proeesses

ii8 HEAD AND NECK

the maxill9e. On either side of the nose are the soekets
for the eyeballs, eaeh of whieh is bounded above by the
supra-orbital margin of the frontal bone and below by the
orbital margins of the maxilla and the zygomatic bone
(O.T. malar). The supra- and infra-orbital margins meet
laterally in the region of the eheek bone (zygomatic). From
the posterior part of the zygomatic bone, the zygomatic
areh, formed partly by the zygomatic and partly by the
temporal bone, extends posteriorly to the ear. Above the
zygomatic areh is the region of the temporal fossa, whieh
is bounded superiorly by the temporal line. The line
terminates anteriorly in the lateral part of the supra-orbital
margin. Above the medial part of the supra-orbital margin
the supereiliary areh ean be felt, and at a higher level,
above the lateral part of the supra-orbital margin, lies the
frontal tuber. The region above the nose and between
the medial ends of the supereiliary arehes is the glabella,

Below the zygomatic areh lies the ramus of the mandible
covered by the masseter musele; and extending anteriorly
from the lower end of the ramus is the body of the mandible.
A line dropped vertically through the junction of the medial
third with the lateral two-thirds of the supra-orbital margin,
will eut through the supra-orbital noteh of the frontal bone,
the infra-orbital foramen of the maxilla, and the mental foramen
of the mandible, all three of whieh may be felt if firm pressure
is made in the proper situations. The first, whieh lies in the
supra-orbital margin, transmits the supra-orbital vessels and
nerve. The seeond is plaeed about half an ineh below the
infra-orbital margin. It transmits the infra-orbital vessels and
nerve. The third lies midway between the seeond premolar
tooth of the mandible and the lower border of the mandible ;
it transmits the mental branehes of the inferior alveolar vessels
and nerve.

After the bony points of the region have been studied,
the surface anatomy of the oeular appendages should be
examined. Under this head are ineluded (i) the eyebrows;
(2) the eyelids; (3) the conjunctiva.

The eyebrows are two curved tegumentary projections
plaeed over the supra-orbital areh of the frontal bone ; they
intervene between the forehead above and the oeular regions
below. The short stiff hairs whieh spring from the eyebrows
have a lateral inelination.

FACE AND FRONTAL REGION 0F HEAl) 119

The eyelids (palpebne) are the semilunar eurtains ;>rovidcd
for the proteetion of eaeh eyebalL The upper lid is the
longer and mueh the more movable of the Iwo. \\'hen the
eye is open, the margins of the two lids are slightly concavc
and the interval between them, rima palptbranim, is elliptieal
in outline, When the eye is elosed, and ihe margins of the
lids are in apposition, the rima palpebrarum is redueed to a

Fia. 56. — Eyelid slighlly everled 10 shoH Ihe Coiijunciiva (enlarged).

nearly horizontal line. Owing to the greater length and
mobility of the upper hd, the rima, in this eondition, is piaeed
below the Ievel of the eomea or elear part of the eyeball.

At the extremities of the rima palpebrarum the eyelids
meet and form the palfebral eommissures, and immediately
lateral to the medial eommissure the rima expands into a
small triangular spaee ealled the laeiis laerimalis. If the
disseetor now esamines the free margins of the iids he will
note that to the lateral side of the laeus laerimalis they

I20 HEAD AND NECK

are flat, and that in eaeh ease the eyelashes project from
the anterior border, whilst the tarsal glands open along the
posterior border, a distinet interval intervening between the
eilia and the mouths of the glands. On the other hand,
the small portion of the margin of eaeh eyelid whieh bounds
the laeus laerimalis is more horizontal in direetion, somewhat
rounded, and destitute both of eyelashes and of tarsal glands.
At the very point where the eyelashes in eaeh eyelid eease,
and the palpebral margin beeomes rounded, a minute emi-
nenee with a eentral perforation will be seen. The eminenee
is the papilla laerimalis^ whilst the perforation, ealled the
punetum laerimak^ is the mouth of the laerimal duet^ whieh
conveys away the tears. Endeavour to pass a bristle into
eaeh of the orifices. The upper duet at first aseends, whilst
the lower one deseends, and then both run horizontally to the
laerimal sae.

The conjunctiva is the membrane whieh lines the deep
surfaces of the lids, and is reflected from them on to the
anterior aspeet of the eyeball. At the margins of the lids it
is eontinuous with the skin, whilst, through the puneta laeri-
malia and the laerimal duets, it beeomes eontinuous with
the lining membrane of the laerimal sae. The line of re-
flection of the conjunctiva from the lids on to the eyeball is
termed the fornix conjunctivce. Owing to the greater depth of
the upper lid, the conjunctival reeess between the upper lid
and the eyeball is of greater extent than that of the lower lid.
The conjunctiva is loosely eonneeted with the eyelids on the
one hand, and with the selera of the eyeball on the other.
Over the eornea the membrane beeomes thinned down to a
mere epithelial covering, whieh is elosely adherent.

In eonneetion with the conjunctiva, the pliea semiiunaris
and the earuneula laerimalis must be examined. The
earuneula is the reddish fleshy-looking elevation whieh
oeeupies the eentre of the laeus laerimalis. From its surface
a few minute hairs project. The pliea semilunaris is of interest
beeause in the human eye it is the rudimentary representative
of the membrana nietitans, or third eyelid, found in many
animals. It is a small vertical fold of conjunctiva, whieh is
plaeed immediately to the lateral side of the earuneula, and it
slightly overlaps the eyeball at this point.

Dissedion, — Distend the eyelids slightly by plaeing a little tow or eotton
wool steeped in preservative solution in the conjunctival sae ; then stiteh

FACE AND PRONTAL REGION OF HEAD 121

the margins of the lids together. Distend the eheeks and Iifis slightly by
plaeing tow or eotton wool steeped in preservative solution in the vesti)iule
of the mouth — that is, between the eheeks and lips extemally an<l the teeth
and gums intemally ; then stiteh the red margins of the lips together.

Reileet the skin by means of three indsions, a median longitudinal and
two transverse. Gommenee the median ineision midway belween the root
of the nose and the exiemal oeeipital protuberanee, eanry it anteriorly to the
forehead and then downwards aiong the median line of the forehea(l, the
nose and the lips, to the tip of the ehin. Gommenee the upper horizontal
ineision at the level of the rima palpebrarum ; carr>' it laterally from the
longitudinal ineision to the medial eommissure, then round the margins ot
the rima tothe lateral eommissure, and, Anally, posteriorly to the ear. The
lower horizontal ineision should run from the angle of the mouth to the
posterior border of the ramus of the mandible. Keflect the upper and
middle Aaps and leave them attaehed posteriorly. KeHeet the lower Hap
downwards to the lower border of the mandible. Note, whilst reflecting
the skin, that many of the superHeial Abres of the facial museles are
implanted into its deep surface. It is these fibres whieh tend to displaee
the margins of wounds of the face, and neeessitate the applieation of
numerous and firmly tied sutures in order to seeure quick and aeeurate
union. Whilst reAeeting the skin the disseetor must be careful to keep his
knife playing against its deep surface ; otherwise he is eertain to injure Ihe
sphineter musele of the eyelids, and the superficial extrinsic museles of the
ear whieh lie in the temporal r^on.

After the skin is reSeeted the superficial museles must be
eleaned. That whieh will first attraet attention is the orbieu-
laris oeuli around the orbit Above the orbieularis oeuli is the
frontalis belly of the epieranial musele. To the medial side
of the orbieularis oeuli he the museles of the nose, and below
it the museles of the upper lip pass downwards to the
orbieularis oris. Passing anteriorly and upwards, over the
posterior part of the lower border of the mandible, are the
upper and posterior fibres of the platysma, and more medially
are the museles of the lower lip.

Gommenee with the Orbieularis Oeuli (O.T. Orbieularis
Palpebranun). — Pull the eyelids laterally and note a prominent
eord-like band whieh extends from the frontal proeess of the
maxilla to the medial eommissure, where it beeomes eontinuous
with both eyelids ; this is the medial palpebral ligament
(O.T. intemal tarsal ligament). A somewhat similar band, the
lateral palpebral raphe (O.T. external tarsal ligament), extends
from the lateral eommissure to the zygomatic bone. After
the medial palpebral ligament has been reeognised, elean first
the thieker orbital part of the orbieularis oeuli, whieh covers
the superficial bony boundaries of the orbit, and then the
thinner palpebral portion^ whieh lies in the eyelids. The
palpebral part is not only thin but also pale, and its fibrf

122 HEAD AND NECK

eaeh eyelid, sweep in gentle curves from the medial palpebral
ligament to the lateral palpebral raphe, gaining attaehment to
both. They form a eontinuous layer of uniform thiekness in
eaeh eyelid, except near the free margins, where, elose to the
bases of the eyelashes, there is a more pronouneed fasciculus
termed the dliary bundie.

The orbital portion of the musele passes upwards to the
forehead, laterally to the temporal region and downwards into
the eheek. Its fibres are relatively dark and eoarse. They
all take origin medially from the medial part of the palpebral
ligament, the medial angular proeess of the frontal bone, and
the frontal proeess of the maxilla, and they sweep laterally
round the margin of the orbit in the form of a series of eon-
eentrie loops. The pars laerimalis of the orbieularis* oeuli
(O.T. tensor tarsi) will be deseribed when the eyelids are
disseeted (p. 140).

Museulus Epieranius (O. T. Oeeipito - Prontalis). — The
epieranius is a quadricipital musele possessing two oeeipital
heads, the oeeipitales museles, and two frontal heads, the
frontales museles ; they are all inserted into an intermediate
aponeurosis, the galea aponeurotiea (O.T. epieranial aponeur-
osis\ whieh extends from the frontal to the oeeipital region
(p. 158). The lower part of eaeh frontal head blends with the
orbieularis oeuli, and from its medial border a small museular
bundle, known as the museulus proeerus (O.T. pyramidalis
nast), deseends to the dorsum of the nose. At present only
the frontalis and the proeerus are to be displayed.

The Frontalis beeomes apparent immediately above the
upper border of the orbieularis oeuli. As it is eleaned eare
should be taken to avoid injury to the branehes of the supra-
orbital nerve whieh pieree it. It has little or no attaehment
to bone. Below, its fibres either blend with the fibres of the
orbieularis oeuli or they are attaehed to the skin of the eye-
brows. Above, they terminate in the galea aponeurotiea in the
region of the eoronal suture. The lateral border is attaehed
to the temporal ridge by aponeurotie fibres, and the medial
border blends with its fellow of the opposite side for a short
distanee above the root of the nose. Above the union the
medial fibres of opposite sides diverge, and below it they pass
downwards over the nasal bones as the proeeral museles.

Museulus Proeerus (O.T. Psrramidalis Nasi). — The proeeral
museles are often absent ; when present, eaeh springs from

FACE AND PRONTAL REGION OF HEAD 123

the lower and medial part of the eorresponding Trontalis.
It deseends over the nasal bone and ends on the dorsum
of the nose, where some of its fibres blend with the trans-
verse part of the nasalis and others are inserted into the skin.

Along the lower and medial border of the orbieularis oeuli
will be found the museles of the nose and the upper lip.

The proper museles of the nose are the museulus nasalis
and the museulus depressor septi, but the proeerus may also
be looked upon as partly a nasal musele, and the angular
head of the quadratus labii superioris has a nasal attaehment.

MtLseulus Nasalis. — The museulus nasalis eonsists of two
parts, the pars tranwersa (O.T. eomprtssor naris\ and the
pars alaris (O.T. dilator narii), The pars transversa springs
from the root of the frontal proeess of the maxilla, passes
aeross the eartilaginous part of the nose, above the ala, and
ends in an aponeurosis whieh eonneets it with its fellow of
the opposite side. The pars alaris springs from the maxilla,
at the side of the lower part of the anterior nasal aperture,
and it terminates in the posterior part of the ala and the
mobile part of the septum of the nose. The nasalis is partly
eoneealed by the medial fibres of the quadratus labii superioris.

MtLseulus Depressor Septi Nasi. — This small musele is
frequently difficult to display. It springs from the superficial
fibres of the upper part of the orbieularis oris, and is inserted
into the anterior part of the septum of the nose. It depresses
the septum and reduees the antero-posterior diameter of the
anterior nasal aperture.

After the museles of the nose have been examined elean
the superficial museles of the mouth and eheek.

Tlie Museles of the Mouth and Gheeks. — The museles of
this group form two layers, a superficial and a deep. Those
of the superficial group are the orbieularis oris, quadratus
labii superioris, zygomaticus, triangularis, risorius, quadratus
labii inferioris ; those of the deeper group are the bueeinator,
eaninus, incisivi and mentalis. All, with the exception of the
orbieularis oris, are bilateral. The members of the superficial
group must be examined first ; the deeper museles will be
displayed after the superficial vessels and nerves have been
disseeted.

Orbieularis Oris. — The orbieularis oris is the sphineter
musele of the oral aperture. It lies in the substanee of the
lips, and eonsists of a deeper layer of fibres whieh are arrange^'

124

HEAD AND NECK

in eoneentrie ellipsoidal rings, and a series of superficial fibres
into wliieh all tlie otlier museles of the lips and eheeks eon-
vet^e. The detaiis of its formalion eannot be understood
until the attaehments of the Other museles have been studied.

FiG. 57. — The Facial Museles.

MnseulnB Qiiadratns Labii SuperioriB.— The qiiadratus
labii superioris possesses three heads — a zygomatic, an infra-
orbita!, and an angular. As the musde is eleaned the
disseetor should seeure the upper part of the anterior facial
vein, whieh erosses ils superficial surface.

FACE AND FRONTAL REGION OF HEAI) 125

The zygomatic head (O.T. sygomatieus minor) springs
from the anterior part of the facia] surface of the zygomatic
bone, under cover of the lower lateral part of the orbieularis
oeuli. It runs downwards and anteriorly, and is inserted into
the lateral part of the upper portion of the orbieularis oris
and into the adjacent part of the skin of the upper lip.

The Infra-orbital Head (O.T. Levator Labii Suptrioris
Proprius). — This head springs from the whole length of the
infra-orbital border, under cover of the orbieularis oeuli. It
is inserted into the upper lateral part of the orbieularis oris
and the skin of the upper lip.

The angular head (O.T. levator iabii superioris alirque
nasi) springs from the frontal proeess of the maxilla. It
broadens as it deseends, and it is inserted into the ala of the
nose and into the upper part of the orbieularis oris.

MuseultLS Z7goiiiaticii8. — The zygomaticus (O.T. zygo-
matieus major) is a comparatively long, slender museular
band whieh springs from the facial suHaee of the zygomatic
bone, under cover of the lower lateral fibres of the orbieularis
oeuli and to the lateral side of the zygomatic head of the
quadratus labii superioris. Its fibres pass downwards and
medially to the angle of the mouth, where some blend with
the orbieularis oris and others are inserted into the skin.

The Bisorius. — This musele, when well developed, eonsists
partly of some of the uppermost fibres of the platysma musele
of the neek, whieh bend anteriorly to the angle of the mouth,
and partly of additional fibres whieh spring from the fascia
over the masseter musele and the parotid gland. Both
groups of fibres blend with the fibres of the orbieularis oris
at the angle of the mouth.

Museulus Triangularis. — The triangularis (O.T. depressor
anguli oris) springs from the oblique line on the lateral surface
of the body of the mandible. Its fibres converge as they
pass anteriorly and upwards, and, at the angle of the mouth,
they blend with the orbieularis oris, in whieh some of them
curve past the angle and terminate in the substanee of the
upper lip (Figs. 57, 58).

Museulus Quadratus Labii Inferioris (O.T. Depressor Labii
Inferioris). — ^This musele springs from the lower part of the
superficial surface of the mandible, between the mental
tuberele and the mental foramen, its posterior border h^^^^r-
overlapped by the triangularis. The fibres pass ^

126

HEAD AND NECK

and medially, some to blend with the orbieularis oris and
others to gairi attaehment to the slein of the lower lip.

PlatyBma. — Only the upper part of the broad, flat,
quadrangular subeutaneous musele of the neek is at present
visible. The posteriot fibrcs aseend over the lower border
of the ramus and the posterior part of the lower border of
the body of the maiidible, and they have already been seen
taking part in the formation of the risorius. The anterior
fibres gain direet insertion into the anterior part of the lower

border of the body of the mandible. The latter attaeh-
ment is the only bony attaehment whieh the musele possesses,
all its other attaehments being either to fascia or to skin.

DisseetiBn.
let

the masseter ; then tuin ihe risorius and ihe detaehed part of the platysma
lowaids Ihe angle Qf the mouth. Whilst doing this be cateful to avoid
inJHring the bianehes of the vessels and neives of the fiice.

As soon as the platysma and the risorias are reAeeted Seareh below the level
of the ear for bianehes of the great aurieular nerve whieh aseend over the
lower part of ihe parotid gland. Some of them pieree the parotid and
terminate in ils sulistanee, others end in Ihe akin of the masseterie legion.

Fin<l the anlerior faciat vein and the exteinat niaxillary artery at Ihe

FACE AND PRONTAL REGION OF HEAD 127

lower and anterior angle of the masseter as ihey eross ihe lower Iwirder <)f
the mandible. Clean them at this }X)int, but do nut traee them townnls
their terminations at present.

At the posterior border of the mandible note the fascia »>vcr the su|Xfr-
ficial surface of the parotid gland. It aseemls from the fascia of the neek,
and is attaehed above to the zygomatic areh. Note also that at the anterior
lx)rder of the parotid this fascia blends with the fascia on the sui>erticial
surface of the masseter musele. Cut through the fascia covcrmg the
parotid gland immediately anterior to the ear, extending ihe ineision from
the zygoma above to the angle of the mandil)Ie l)eIow ; then raise the
fascia from the gland, disseeting carefully anteriorly, upwards, and down-
wards. As the extremities and the anterior border of the gland are
approaehed, look carefully for nerves and vessels whieh einerge ^roin
beneath them, and also for the duet of the gland, whieh ap{x^ars from
under cover of the anterior border alK)ut a rtnger's breadth l)elow the
zygoma. The duet has thiek walls, is of eonsiderable size, and is easily re-
eognised. It runs anteriorly aeross the masseter and turns rt^und the anterior
border of the musele, bending at right angles to its original eourse. It
pierees, in turn, the fascia covering the bueeinator musele, the bueeinator
musele itself and the mueous membrane of the mouth ; and it opens into
the vestibule of the mouth, on a small papilla opposite the sec»)nd molar
tooth of the maxilla. Above the duet and below the /ygomatie areh find
(i) the aeeessory parotid, a small detaehed part of the parotid whieh
lies a short distanee anterior to the anterior border of the main mass
of the gland ; (2) the transverse facial vessels ; and (3) the zygoniatic
branehes of the facial nerve. Below the duet find the bueeal and the
mandibular branehes of the facial nerve. At the upi^er end of the parotid
seek for the superficial temporal vessels. Posterior to them lies the aurieulo-
temporal braneh of the third division of the trigeminal nerve, and an-
terior to them, the temporal branehes of the facial nerve. Kroni, or froni
beneath,'the lower extremity of the gland emerge (l) the cervical braneh ()f
the facial nerve, (2) the posterior facial vein ((3.T. anterior division of ihe
temporo-maxillary vein), and (3) the external jugular vein.

The Terminal Branelies of the Facial Nerve. — The dis-
seetor should note that there are five terminal branehes, or
groups of branehes, of the facial nerve : (i) temporal ; (2)
zygomatic ; (3) bueeal; (4) mandibular; (5) cervical. They
all emerge from under cover of the parotid gland, the
temporal branehes at its upper end, the cervical at its lower
end, and the remaining three groups of branehes at its
anterior border. The temporal branehes will be followed
when the temporal region and the sealp are being disseeted,
and the cervical braneh when the anterior triangle of the neek
is displayed; but the remaining three groups of branehes
should now be followed to their terminations.

The upper filaments of the zygomatic braneh or branehes run
anteriorly, aeross the zygomatic bone, and terminate, in both
the upper and the lower eyelid, in the fibres of the orbi-
eularis oeuli. If the branehes are carefully traeed, one of
them will be found to eommunieate with the zygomatico-

128

HEAD AND NECK

facial braneh of tbe seeond or maxillary diyision of the fifth
■ nerve. This small nerve pierees the ^ygomatie bone a short
distanee below ihe lateral border of the orbit.

The lower Slaments are larger. They run anteriorly along
the lower border of the zygomatic areh, under cover of the
museulus zygomaticus and the infra-orbital part o^ the

FiG. 59. — Nerve3 of Ihe Tae

3. ZyK™

quadratus labii superioris, and deep to the latter they eoni-
raunieate with the infra-orbital braneh of the maxillary diyision
0f the fifth nerve, forming wilh it the infra-orbitat plexus.

The bueeal braneh or branehes run towards the angle of
the mouth. At the anterior border of the masseter they eom-
munieate, around the anterior facial vein, with the bueeinator
braneh (O.T, ^long bneeal) of the third division of the fifth,
and they supply the bueeinator and the orbieularis oris.

FACE AND PRONTAL REGION 0F HEAI) 129

and the quadratus labii superioris immediately 1>elow their origins. and
turn them downwards towards the upper lip. When this has l^een done,
elear away the fatty tissue whieh lies on the deep asi^eet of the (|uadratus
labii superioris and seeure the infra-orbital vessels and nerve, as they emerge
from the infra-orbital foramen. The infra-orbital plexus lies deep to the
quadratus labii superioris, and on the superHeial as}XK:t (>f the museulus
eaninus. From the plexus three groups of branehes are distril)uted : ( i )
palpebral, whieh pass upwards to the lower eyelid ; (2) nasal, whieh run
medially to the nose ; and (3) labial, whieh deseend to the upper lip. Kither
by means of these branehes, or more direetly, the lower zygomatic twigs
of the facial nerve are distributed to the museulus zygomaticus, the museles
of the lower eyelid, museles of the nose, and tlie museles of the upper lip.

The mandibular braneh or branehes run anteriorly along the
mandible to be distributed to the museles of the lower lip.
As they pass anteriorly they lie deep to the triangularis, and
they eommunieate, under cover of it, with the mental braneh
of the inferior alveolar (O.T. dental) nerve. To display this
eommunieation the triangularis must be reflected, and the
mental vessels and nerves must be found as they emerge
from the mental foramen.

Arteria Maxillaris £xtema (O.T. Facial). — The ex-
ternal maxillary artery is a tortuous vessel whieh enters the
face at the lower and anterior angle of the masseter, after
turning round the lower border of the mandible and piereing
the deep fascia of the neek. From that point it runs
anteriorly and upwards to the angle of the mouth and then,
assuming a more vertical direetion, it is prolonged upwards,
as the angular artery, to the medial eommissure of the
eyelids, in the substanee of the angular head of the quadratus
labii superioris. Immediately after its entranee into the face
it is comparatively superficial, being covered by skin, super-
ficial fascia, and platysma, and it is easily eompressed against
the bone. More anteriorly it lies between the zygomaticus
superficially and the bueeinator deeply, then between the
quadratus labii superioris and the eaninus, and, as already
stated, its terminal part is usually embedded in the substanee
of the quadratus labii superioris.

Brandies, — The branehes of the external maxillary artery
form two groups, a posterior and an anterior. The branehes
of the posterior group pass posteriorly and are of small size.
They are distributed to the masseterie, bueeal, and malar
regions where they anastomose with the transverse facial, the
bueeinator, and the infra-orbital arteries.

The branehes of the anterior group run anterior'

VOL. II — 9

130

HEAD AND NECK

ccivc speeial naineii : ihey are Ihe inferior labial, the superior
bbiAl, ihe laieral iiawl, and the angular eontinuation.

Tlie inknW l.iN.i! (O.'l'. in/mor anwmry) arises below the
loYd of ilii' angle of ihe moulh and passes towards the

mediai

libno, uiulor eiiwr of the triangularis, the quadratU5

inreri.iris, and ihe orbicul;iris iiris. Iii the substanee of

) il lies immedialely adjacent lo ihe mueous membrane,

:iuast(inioses in tlu; mediaii plane with its feIlow of the

opposiie side.

riie superior lahial arises about the level of Ihe angle

the li;
and ii

FACE AND FRONTAL REGION 0F HEAl) 131

of the mouth and runs medially in the upi^er lip, between
the orbieularis oris and the mueous membrane. Before it
anastomoses with its fellow of the opposite side, it gives off
a braneh, the septal artery of the nose^ whieh passes upwards
and ramifies on the lower and anterior part of the nasal septum,
where it anastomoses with the septal braneh of the spheno-
palatine artery.

The Angular Artery, — ^This is the eontinuation of the
external maxillary beyond the point of origin of the lateral
nasal braneh. It runs upwards in the substanee of the
angular head of the quadratus labii superioris, and it
terminates at the medial eommissure of the eye by anastomos-
ing with the nasal braneh of the ophthalmie. The lateral
nasal braneh springs from the external maxillary at the point
where it beeomes the angular. It ramifies on the side of the
nose and anastomoses in the median plane with its fellow of
the opposite side.

In addition to the branehes already noted, a very definite
braneh is usually given off from the anterior aspeet of the
external maxillary artery immediately after it erosses the
lower border of the mandible. This braneh (O.T. inferior
labial) runs towards the median plane under covor of the
triangularis and the depressor labii inferioris, and it anasto-
moses not only with the inferior labial (O.T. inferior eoronary)
above, and its fellow of the opposite side in the median plane,
but also with the mental braneh of the inferior aIveolar artery.

Yena Facialis Anterior (O.T. Facial). — The anterior
facial vein is a less tortuous vessel than the external maxillary
artery to whieh it eorresponds, and it lies posterior, and on
a slightly more superficial plane. It eonimenees as the
angular vein^ whieh is formed at the medial eommissure
of the eyelids, by the union of the frontal and supra-orbital
veins, whieh deseend from the forehead. It passes down-
wards and posteriorly, in a comparatively straight line, to the
anterior inferior angle of the masseter, whieh it erosses
immediately behind the external maxillary artery ; then it
pierees the deep fascia of the neek, and enters the sub-
maxillary triangle. In the upper part of the face it lies on
the quadratus labii superioris ; then it is situated between the
zygomaticus and the risorius superficially and the bueeinator
deeply ; and as it erosses the anterior angle of the masseter
it is covered with the skin, superficial fascia, and the platysma.

II — 9a

132 HEAD AND NECK

Tributaries, — In addition to the frontal and supra-orbital
veins, it receives external nasal, palpebral, superior labial,
inferior labial, masseterie and superficial parotid tributaries.
As it erosses the bueeinator musele it is joined by the deep
facial vein, whieh eonneets it with the pterygoid plexus of
veins in the infra-temporal region.

Disseetion. — After the branehes of the facial nerve, the external maxillary
artery and the anterior facial vein have been studied, the disseetion of the
deeper museles and the deeper vessels and nerves must be proeeeded with ;
but the supra-orbital and supra-troehlear nerves, the supra-orbital vessels,
and the eorrugator supereilii musele may be left till the sealp is disseeted
(p. 156).

Museulus Ganinus (O.T. Levator Anguli Oris). — The

eaninus is eoneealed by the lower part of the orbieularis
oeuli, the quadratus labii superioris, and the zygomaticus, and
it is erossed superficially, near the angle of the mouth, by
the external maxillary artery. When the struetures superficial
to it are turned aside, the musele will be found springing from
the eanine fossa below the infra-orbital foramen. It passes
downwards to the angle of the mouth, where it blends with the
orbieularis oris, some of its fibres passing into the lower lip
(Fig. 57). It is an elevator of the angle of the mouth.

The Bueeinator. — This musele oeeupies the interval
between the upper and the lower jaws and forms a most
important part of the substanee of the eheek. Above, it
springs from the alveolar border of the maxilla, in the
region of the molar teeth. Below, it arises from the
alveolar border of the mandible, also in the region of the
molar teeth, and, posteriorly, it is attaehed to the pterygo-
mandibular raphe, whieh forms a bond of union between
the bueeinator and the superior eonstrietor of the pharynx.
This attaehment will be seen to better advantage when the
wall of the pharynx is stiidied (p. 373). Anteriorly, its fibres
converge towards the angle of the mouth, where they blend
with the orbieularis oris, of whieh they form a large part.
The manner in whieh the fibres enter the orbieularis must be
carefully noted. The upper and lower fibres pass direetly
to the eorresponding lips ; the middle fibres, on the other
hand, deeussate at the angle of the niouth, so that the lower
fibres of the series enter the upper lip, whilst the higher
fasciculi reaeh the lower lip (Fig. 61).

The Molar Glands. — The bueeinator is covered posteriorly

cia whieh must bc turcfullj renoTed. As tbb b bda^
ae Ihe disseaoi will iiDd. boih luperiiai] aoA deep m
; fascia, a number of bduH gUndt, the tmiar ssSet^ ,
nds. The duets or these gLuid» pietee tbe baeenutor aod I
^en into the restitnite t>r tbe momb. Oik oc t«o htteml \
wiph glands aiso are sometime* (utiod rtstii^ on tbe s

" J suriaee of the baeeinalor.
' DiistOiMi.—A!^ dK dineeikn ef llir liiiiiailiii ud ttm ■
b eompletnl, lenHHe ihe *tilcbes &tia tke Bft t c«cn ibe ^» m

'lie mueoui memlmni: ftom Ibe iict}> «otHei*. ia unleT ta e _, .

Miseuiar slios irliicliailai.-h ilw<>*tiiinilwki«talu ik >I>«uiU> RurKNM«flhB
pper aiui tlir Imrrr )iin, iihI Iu tlit{<iy Ibe niTMal» niaelr. A» tlir lip
re eveittd thr iltSKnrlor Umli) Bn|e lli*t ■ biU nl ■nieoin mrmbatK. ihe
pVH»/u'/f /j*iV, [aiits frtpni cic!i lip lo llir gBm i.f thr c. ^tr-pnniliog 'ytir in

le mediaD plaae ; and as thi
nall laiiai salivary giandi

They are leadily fell in tbe liiine wib}ecl by {iresine ihe tip ol II
angue againsl thf iniier surraees <jf the li[is.
UnBenli IneisiTi Labii SnperioiiB et IntnrioriB. — These |
; fou[ small museular bundles, two upper and two lower,
Sthieh attaeh ihe deepur pait of ihe orbieularis oris to the
~alveolar margins of the jaws in ihe regions of the upi^er and
lower lateral ineisor teeth.

Unaenlns Mentalis.— When the incisive musdes of the i
—lower jaw are detaehed from ihe bone and ihe lower lip j
£ Turther eyerted, a distinet museular bundle will be Tound c
leb side, springing f[om the ouler surface of the soeket of the I
line tooth, under cover of the quadratus labii inferioris. J
'he two bundtes eoni'erge and blend logether, between tbe i
le^al borders oT the museuli quadrali labii iiiferiuris, to I
a Btngle bundle whieh is inserled into [he skiii of the J
II is an elevator of the skin of the ehin
■9i

134

HEAD AND NECK

Nervus Bueeinatorius (O.T. Long Bueeal). — This nerve is
a braneh of the third division of the trigeminal nerve. It
passes anteriorly into the eheek from under cover of the
ramus of the mandible. It is a sensory nerve, and it supplies
branehes to the skin on the outer surface and the mueous
membrane on the inner surface of the bueeinator musele.
In order to display it at the present stage it may be neeessary
to make an antero-posterior ineision through the middle of
the anterior border of the masseter.

Eyelids. — The following strata will be exposed in eaeh
eyelid as the disseetion is earried from the surface towards
the conjunctiva.

Upper Lid.

LOWER LlD.

1. Integument.

2. Palpebral part of the orbieularis

oeuli.

3. The tarsus, the palpebral

fascia, and the expanded ten-
don of the levator palpebrae
superioris.

4. Conjunctiva.

1. Integument.

2. Palpebral part of the orbieularis

oeuli.

3. The tarsus and the palpebral

fascia.

4. Conjunctiva.

In addition to these struetures, two ligamentous bands,
named the medial palpebral ligament (O.T. internal tarsal
ligament) and the lateral palpebral raphe (O.T. external
tarsal ligament), will be notieed. They attaeh the tarsi to
the medial and lateral margins of the orbit.

Integument and Orbieularis Oeuli. — These strata have
been examined already, and the skin has been reiieeted.

Disseetion. — Separate the palpebral part of the orbieularis oeuli from the
remainder by a eireular ineision ; turn the palpebral part towards the
rima palpebrarum, and take eare, whilst raising the musele fibres, to preserve
the palpebral vessels and nerves, and at the same time to avoid injury to
the palpebral fascia. As the disseetion is eompleted the origin of the
musele from the medial palpebral ligament (p. 121) will be displayed.

Tarsi. — The removal of the palpebral part of the orbieularis
oeuli brings into view the palpebral fascia and the tarsi.
These lie in the same morphologieal plane, and they eonstitute
the ground-work of the eyelids.

The tarsi are two thin plates of eondensed librous tissue,
plaeed one in eaeh eyelid so as to oeeupy an area immediately

FACE AND ERONTAL REGION 0F HEAD 135

adjoining its free maigin. They differ very materially from
eaeh other. The superior tarsal plate is mueh the larger of
the two, and presents the figure of a half oval. Its deep
surface is intimately eonneeted with the subjacent conjunctiva,
whilst its superficial surface is elothed by the orbieularis musele,
and is in relation to the roots of the eyelashes. Its superior
border is thin, convex, and eontinuous with a tendinous
expansion of the levator palpebrse superioris. The inferior
border of the tarsal plate is thiekened and straight, and the
integument adheres firmly to it.

The inferior tarsal plate is a narrow strip whieh is similarly
plaeed in the lower lid.

Glandol» Tarsales (O.T. Meibomian rollieles). — At this
stage the student should examine the tarsal glands, whieh he
will display by everting the eyelids. They are plaeed on the
deep surfaces of the tarsi. To the naked eye they appear
as elosely plaeed, parallel, yellow granular-looking streaks,
whieh run at right angles to the free margins of the lids.
They are more numerous and of greater length in the
upper lid, and, being lodged in furrows on the deep surface
of the tarsal plates, they are distinetly yisible upon both
aspeets of these, even while the conjunctiva is in position.
Their duets open upon the free margin of eaeh lid posterior
to the eyelashes.

The Palpebral Fascia. — The palpebral fascia is a sheet of
fibrous membrane whieh oeeupies the interval between the
tarsi and the margins of the orbit, forming, with the tarsi, a
septum between the orbit and the exterior. Its peripheral
border is attaehed to the orbital margin, except at the medial
angle of the orbit, where it oeeupies a more posterior plane,
and is attaehed to the erista laerimalis, posterior to the medial
palpebral ligament and the laerimal sae. Its eentral border
in the lower lid is eonneeted with the lower border of the
lower tarsus. In the upper lid it blends with the expanded
tendon of the levator palpebrae superioris, and is attaehed
with it to the anterior surface of the upper tarsus. It is
piereed by the supra-orbital, supra-troehlear, and laerimal
branehes of the first division of the trigeminal nerve, and
by the terminal branehes of the ophthalmie artery.

Raphe Palpebralis Lateralis, — The lateral palpebral raphe
(O.T. extemal tarsal ligament) is merely a thiekening of the
palpebral fascia, between the lateral eommissure and thf
II— 9 c

136 HEAD AND NECK

medial border of the fronto-sphenoidal proeess of the zygomatic
bone (0-T. nialar), to whieh it eonneets both the tarsi.

Ligamentum PalpebraU Mediale (O.T. Internal Tarsal
Ligameni). — The medial palpebral ligament is a strong fibrous
band whieh eonneets the medial ends of both tarsi to the
frontal proeess of the maxilla. It lies between the skin
anteriorly, and the laerimal sae posteriorly. Byits upper and
lower borders it gives attaehment to fibres of the orbieularis

oeuli, and by the laieral part of its posterior surface, to the
pars laetimalis of the orbieularis oeuli (0-T. tensor tarsi).

Iievator Palpebne Superioris. — Only the anterior expanded
tendon of this musele ean be seen at the present stage of the
disseetion, and that, as a rule, in only a partially satisfactory
manner. The musele arises within the orbital eayity, ex[ends
forwards to the upper eyelid, and ends in an expanded tendon
whieh splits into three lamellEe; a superior lamella, whieh
blends with the upper part of the palpebral fascia and is
attaehed with it to the anterior surraee of the upper tarsus ;
an intermediate lamella, whieh is eonneeted with the upper

FACE AND PRONTAL REGION 0F HKAD

137

border of tbe upper tarsus; and an inrerior lamelb, whieh
gains insertion into the upper fomix of the conjunctiv3. It
raises the upper eyelid by pulling on the upi)ei larsus, and at
the same time elevates the upper fornix of the conjuncIiva.

Yessels uid Herries of the Eyelids. — At the niedial eoni-
missure two arteries, Mnt palpehral branehes of ihe ophthalmie,
pieree the palpebral fascia and run laterally, one in the upper
and one in the ]ower lid. At the lateral margin or the
orbit, one or more branehes of the laerimal dIvision of the
ophthalmie pieree the palpebral fascia and anastomose with

the palpebral arteries. An arterial areh, arats Uwseus, is thus
formed elose to the margin of eaeh eyelid, between the
orbieularis musele and the tarsus.

The veins nin medially towards the root of the nose and
open into the frontal and angular veins.

The neryes are more numerous and eome from a number
of different sourees. The motor Tilaments for the various
parts of the orbieularis oeuH are derived from the temporal,
and zygomatic branehes of the facial nerve. They enter
from the lateral margins. The sensory twigs for the upper
hd eome from the laerimal, supra-orbital, supra-troehlear, and
infra-trochlear branehes of the first or ophthalmie division of
the trigeminal nerve ; and the lower lid is suppHed by t'

138 HEAD AND NECK

infra-orbital braneh of the seeond or maxillary division of the
fifth nerve. The laerimal nerve will be found piereing the
palpebral fascia near the lateral part of the upper border of
the orbit ; the supra-orbital lies in the supra-orbital noteh at
the junction of the lateral two-thirds with the medial third of
the upper border ; and the supra- and infra-trochlear pieree
the palpebral fascia at the medial end of the upper border.
The branehes of the infra-orbital nerve pass to the lower lid
in the palpebral branehes of the infra-orbital plexus (p. 128).

Apparatus Laeriinalis. — The following struetures are in-
eluded under this head : (i) the laerimal gland and its duets ;
(2) the conjunctival sae ; (3) the puneta laerimalia ; (4) the
laerimal duets ; (5) the laerimal sae; (6) the naso-laerimal
duet ; (7) the laerimal part of the orbieularis oeuli.

Glandula Laeninalis. — This lies in the upper and lateral
part of the orbital cavity under cover of the zygomatic proeess
(O.T. external angular) of the frontal bone. It ean be exposed
by eutting through the palpebral fascia at the upper and lateral
angle of the orbit, and it will be found that the anterior part
of the gland projects slightly beyond the orbital margin and
rests upon the conjunctiva as the latter is reflected from the
lateral part of the upper lid on to the eyeball. If the anterior
border of the gland is raised and the point of the knife
earried carefully up and down in the fascia under it, several
exceedingly fine duets will be found passing from the gland
into the lateral part of the upper fornix of the conjunctiva.
The duets vary in number, and the seeretion whieh they
convey, whieh eonstitutes the tears, is earried, by the in-
voluntary movements of the upper eyelid, over the exposed
surface of the eyeball and is direeted towards the medial
eommissure ; there it passes through the puneta laerimalia
into the laerimal duets, and is earried by them to the laerimal
sae, whenee it passes by the naso-laerimal duet into the
inferior meatus of the nose. Under ordinary eireumstanees,
the amount of laerimal seeretion is merely suAieient for lubriea-
tion, and praetieally the whole of it is evaporated from the
surface of the eyeball ; consequently, when the laerimal duets
and the laerimal sae are extirpated, a proeeeding whieh is
neeessary under eertain eireumstanees, the patient suATers
little or no inconvenience from the overflow of tears, so long
as the seeretion is not excessive. If the amount of seeretion
is greater than ean be removed by evaporation, the excess,

FACE AND PRONTAL REr.lON 0F HKAD

under ordinaiy eireumstanees, pxsscs thri>iif;h ihe pniuta
the duets and thenee through ihe lacrtiii:il sa<- :ind ii
laerimal duet to the nose ; and ir the seeruiion beennK.-
abundlnt that it eannot be reniovcd liy i.v;iiiur;Ui(ni
drainage, p.irt fiows through the rima as tuars.

7'he Conjuncliml Sae. — 'l'he conjunctival sae is the potential
spaee between the eyelids and the eyebail. It opens exlernally
through the rima and eommunieates with the laerimal sae
through the puneta and the laerimal duets.

The Puneta Laerimalia. — It has been noted already that
the punetum laerimale of eaeh lid lies at the lateral ma
of tiie laeus laerimalis (p. iso). Smal! probes should n»

140 HEAD AND NECK

passed through the puneta into the laerimal duets and along
the duets into the laerimal sae (Fig. 64).

Saeeus Laerimalis. — The laerimal sae is the blind upper
end of a eanal whieh extends from the orbit to the inferior
meatus of the nose. It is lodged in the fossa laerimalis in
the anterior part of the medial wall of the orbit. It lies
posterior to the medial palpebral ligament, from whieh it
receives a iibrous expansion, and it is covered on its lateral
aspeet, and on the lateral part of its posterior aspeet, by the pars
laerimalis of the orbieularis oeuli. The laerimal duets open
into its antero-lateral aspeet, under cover of the medial
palpebral ligament ; and it is eontinuous below with the naso-
laerimal duet. The anterior wall of the sae should be ineised
and a probe passed down the naso-laerimal duet into the
nose. Note that as the probe passes along the duet it
inelines downwards, laterally. and slightly posteriorly.

Pars Laerimalis Orbieularis Oeuli (O.T. Tensor Tarsi). —
This small speeial portion of the orbieularis oeuli springs
from the posterior aspeet of the lateral part of the medial
palpebral ligament and passes posteriorly and medially, round
the lateral part of the laerimal sae, to the erista laerimalis of
the laerimal bone, to whieh it is attaehed. When it eontraets
it Gompresses the laerimal sae, and so tends to facilitate the
flow of the laerimal seeretion into the nose.

Duetus Naso-Laerimalis. — This duet will be seen at a
later period of the disseetion. It is a bony eanal, lined with
mueo-periosteum, whieh runs, in the lateral wall of the nose,
from the laerimal sae to the upper and anterior part of the
inferior meatus. It is about half an ineh long. At the medial
side of its lower end is a fold of mueous membrane, the pliea
laerimalis, whieh serves as a flap valve (Fig. 64).

The disseetion of the face should be eompleted by an
examination of the nasal eartilages and the external nasal
braneh of the ophthalmie division of the trigeminal nerve.
The nerve will be found emerging between the lower border
of the nasal bone and the lateral eartilage. After its
emergenee it deseends to the tip of the nose supplying
Alaments to the skin.

Dissedion. — The eartilaginous part of the nose should now be exainined
by stripping off the nasalis musele and Ihe remains of the integument.

Nasal Gartilages. — In addition to the septal eartilagei

FACE AND FR.ONTAL REGION OF HKAl) m

whieh will be more appropriately studied in ihe disseetion of
the nasal cavities, two eartilaginous plates will l>c found
upon eaeh side. These are : —

The l<^al earHiage is a triangular plate whieh, by ils
posterior margin, is attaehed to the lower border of the
nasal bone and the upper part of the sharp margin of the
nasal noteh of the maxilla. In the median plano this earlilage

FiG. 65.— C;\rlilagc5 of

beeomes eontinuous with its fellow of ihe opposile sidt', and
also with the subjacent anterior border of the seiUal eartilage
of the nose. Below, there is a slight intcrval between ihe
two lateral eartilages, in whieh is seen the margin of the
nasal septal earttlage. The inferior bordor of the lateral
eartilage is eonneeted with the lateral part of the alar
eartilage by some dense fibrous tissue.

The alar eartilagt is bent upon itself and folded round the
orifice of the nostril anteriorly and laterally. Posteriorly it
is deficient. The iateral part is ovaI, and does not reaeh
down to the margin of the nostril, nor postoriorly as far
as the nasal noteh of the maxilla. The interyal between
it and the bone is filled in by fibrous tissue in whieh one or
two small islands of eartilage (eartilagines minores vel sesa-
moideie) appear. Anteriorly, the bent part of eartilage eona
into eontaet with its neighbour and forms the point 0*"

142 HEAD AND NECK

nose. Medially^ the medial part of the eartilage is in the
form of a narrow strip whieh lies upon the lower part of the
septal eartilage, and projects slightly below it so as to support
the margin of the nostril upon this side. Its extremity is
turned slightly laterally.

SIDE 0F THE NECK.

On the fourth day after the body is brought into the room
it is plaeed upon its baek, and the disseetors of the head and
neek should examine the side of the neek and eommenee the
disseetion of the posterior triangle.

The side of the neek is bounded below by the clavicle,
above by the lower border of the mandible, the mastoid
portion of the temporal bone, and the superior nuehal line of
the oeeipital bone. Anteriorly it extends to the median plane,
and posteriorly to the anterior border of the trapezius musele.
It is divided into anterior and posterior parts, the anterior
and posierior triangles^ by the sterno-mastoid musele. If
the head is pulled over towards the opposite side, the sterno-
mastoid musele will be seen deseending from the mastoid
portion of the temporal bone and the superior nuehal line of
the oeeipital bone, to the upper border of the sternal third
of the clavicle and the anterior surface of the manubrium
sterni.

In the lower part of the posterior region, posterior to the
sterno ■ mastoid and above the convex middle third of the
clavicle, there is a depression ealled the fossa supraclavicularis
major, to distinguish it from the fossa supraclavicularis minor
whieh lies above the sternal end of the clavicle between the
sternal and clavicular heads of the sterno-mastoid. The
braehial plexus, the third part of the subclavian artery, and
the supra-clavicular lymph glands lie in the region of the
fossa supra-clavicularis major, and the fossa supra-clavicularis
minor indieates the position of the internal jugular vein near
its lower end.

POSTERIOR TRIANGLE.

Dissedion, — To expose the boundaries and eontents of the posterior
triangle make the following three ineisions through the skin. (i) From
the baek of the auriele along the upper border of the mastoid part of the

POSTERIOR TRIANGLE 143

temporal bone and the superior nuehal line to the external oeeipital pro-
tuberanee. (2) From the stemal to the aeromial end (>f the clnviclc.
following the line of that bone. (3) Join the anterior extrcmities of i and
2 by a vertical indsion passing along the baek of the external aeustie meatus
and then down the middle of the stemo-mastoid musele. Retleet the flap,
thus marked out, from before baekwards, and note that the skin is thieker
over the upper and posterior part of the triangle than ()ver the lower and
anterior part.

When the skin is reiieeted the superficial fascia and the lower |xirt ()f
the platysma musele will be exposed.

The 5uperficial fascia in the region of the posterior triangle
is comparatively thin, and embedded in its lower and anterior
part is the lower and posterior part of the platysma.

The Platysma. — The platysma is a thin sheet of musele
whieh eommenees in the superficial fascia of the infra-clavi-
eular region, whenee it aseends aeross the clavicle and through
the superficial fascia of the side of the neek, to the face where
its upper border has been examined already (p. 126). It
covers the lower and anterior part of the posterior triangle,
and the upper and posterior part of the anterior triangle ; and
it is supplied by the cervical braneh of the facial nerve,
whieh emerges from the lower end of the parotid gland.

Disseetion. — Make an ineision through the lower part of the platysma
along the line of the clavicle, and tum the part above the ineision upwards
and anteriorly. Whilst making the ineision and whilst reflecting the musele,
be careful not to injure the supraclavicular eutaneous nerves and the
external jugular vein, whieh lie direetly subjacent to it.

After the platysma is reflected, elean the external jugular vein, whieh
emerges from the lower end of the parotid and passes downwards, in-
elining posteriorly, to the lower and anterior angle of the posterior tri-
angle, where it pierees the deep fascia. Whilst eleaning the vein, avoid
injury to the nervus eutaneus eolli, whieh sometimes erosses superAeial
to the vein about the middle of its length. Seeure and elean the posterior
aurieular vein, whieh deseends behind the auriele and joins the external
jugular a little below the level of the angle of the mandible. Next, Hnd
and elean the superHeial branehes of the cervical plexus as they pieree the
deep fascia. They are (l) deseending branehes, the anterior, middle, and
posterior supra-clavicular nerves. (2) A transverse braneh, the nervus
eutaneus eolli (O.T. transverse cervical). (3) Aseending branehes, the
great aurieular and the small oeeipital.

The anterior and middle supra-clavicular nerues will be found piereing
the deep fascia immediately above the clavicle, the anterior at the posterior
border of the sterno-mastoid and the middle above the convexity of the
clavicle. They deseend into the peetoral region as far as the lower border
of the seeond rib and their lower portions will be displayed by the disseetor
of the arm. T\\!t posterior supra-clavicidar 7ierves pieree the deep fascia at
a somewhat higher level. They deseend aeross the lower and anterior part
of the trapezius to the aeromial region, and to the skin of the arm over the
upper part of the deltoid, where they will be exposed by the disseetor of
the arm.

HEAD AND NECK

The Deep Fascia. — The deep fascia fonns the superiieial
boundary or roof of the posterior triangle. It Is attaehed
below to the upper border of the middle third of the clavicle ;

FiG. 66. — The siiperlieial

above, to the superior nuehal Hne of the oeeipital bone;
anteriorly it is eontinuous with the fascia of the sterno-mastoid
and posteriorly with the fascia of the trapezius. It is piereed
by (i) the supra-clavicular branehes of the cervical plexus, (2)
the esternal jugular vein, (3) small eutaneous branehes of the

POSTERIOR TRIANGLE 145

transverse cervical, transyerse seapular (O.T. supraseapular),
and oeeipital arteries, and, oeeasionally, by the oeeipital artery
itself. It is not a very strong layer, and it is frequently dif)icult
to display it as a eontinuous sheet. Over the upper part of the
triangle it forms a single layer, but below, it splits into two
lamellse, a superiieial and a deep. The superficial layer whieh
is already displayed, is attaehed to the upper border of the
clavicle from the sterno-mastoid anteriorly to the trapezius
posteriorly. It is piereed by the external jugular vein and
the supraclavicular nerves.

Disseetion, — Traee the supraclavicular nerves upwards through the deep
fascia to the posterior border of the sterno-mastoid ; then, puUing theni aside,
eut through the superBeial layer of the deep fascia immediately above the
clavicle and along the posterior border of the sterno-mastoid, and turn it
upwards. Introduee the handle of the sealpel behind the claviclc and note
that it ean be passed downwards as far as the posterior border of the lower
surface of the bone. Its further progress is barred by the attaehment of
the seeond layer of the deep fascia to this border, where it blends with the
posterior lamella of the eosto-eoraeoid membrane. Pass the handle of the
knife forwards behind the stemo-mastoid and note that, without using any
great force, it ean be pushed medially until it erosses the median plane ;
therefore, the spaee between the two layers of deep fascia in the lower part
of the posterior triangle is eontinuous anteriorly with the spaee whieh lies
above and posterior to the manubrium sterni, between the first and the seeond
layers of the deep fascia of the anterior part of the neek. Laterally, this
spaee extends as far as the eoraeoid proeess, and upwards to a short distanee
above the posterior belly of the omo-hyoid musele. Clear away the areolar
tissue whieh lies between the two layers of the deep fascia, and expose a
further part of the external jugular vein, and the terminal parts of the
transverse cervical and the transverse seapular (supraseapular) veins, as
they join the posterior border of the external jugular. Pull the lower part
of the external jugular vein posteriorly and expose the termination of the
anterior jugular vein in its anterior border. Disseet carefully behind the
clavicle and find the transverse seapular (supraseapular) artery. Traee the
seeond layer of the deep fascia upwards and note that it is eontinuous with
the fascia whieh surrounds the posterior belly of the omo-hyoid musele ;
indeed it is the tension of this portion of the deep fascia whieh holds the
posterior belly of the musele down in its position.

Remove the remaining parts of the deep fascia, first from the upper,
and then from the lower part of the triangle, and expose the floor and the
remaining eontents of the triangle.

Gommenee above, in the region of the junction of the upper third and
the lower two-thirds of the posterior border of the sterno-mastoid, and
seeure the great aurieular, the small oeeipital, the aeeessory nerve, and the
nervus eutaneus eolli. The great aurieular is most easily found. It turns
round the posterior border of the sterno-mastoid, in the region indieated,
and runs upwards and anteriorly, parallel with and slightly above and
posterior to the external jugular vein. The small oeeipital will be found
hooking round the lower border of the aeeessory nerve a little above the
great aurieular ; and the nervus eutaneus eolli lies a little below the great
aurieular.

Follow the small oeeipital and the great aurieular nerves to their

VOL. II — 10

146 HEAD AND NECK

terminations, but the nervus eutaneus eolli must be traeed only to the
point where it erosses either superficial or deep to the external jugular vein.
It eventually divides into upper and lower terminal branehes, whieh will be
seen when the anterior triangle is disseeted.

Nervu8 Oeeipitalis Minor. — The small oeeipital is a sensory
braneh of the seeond cervical nerve. It emerges from under
cover of the sterno-mastoid, and aseends for a short distanee
along its posterior border, then it passes to the superficial
surface of the musele, pierees the deep fascia, and divides
into oeeipital, mastoid, and aurieular branehes. The oeei-
pital and mastoid branehes supply the skin in the regions
indieated by their names. The aurieular is distributed to the
skin of the upper third of the eranial surface of the auriele.

Nennis Anrieularis Magnus. — This eonsists of eutaneous
filaments derived from the seeond and third cervical nenres.
After turning round the posterior border of the sterno-mastoid
it runs upwards and anteriorly, towards the angle of the
mandible, in the deep fascia on the superficial surface of
the sterno-mastoid, and breaks up into three sets of terminal
branehes, mastoid, aurieular, and facial. The mastoid branehes
go to the skin of the mastoid region. The aurieular bramkes
supply the skin of the lower two-thirds of the eranial surface
and the lower third of the lateral surface of the auriele. The
facial branehes, whieh have already been seen, ramify in the
posterior part of the face, in the parotid and masseterie regions.
Some of the filaments enter the substanee of the parotid.

Disseetion. — The aeeessory nerve, previously found at the junction of
the upper third with the lower two-thirds of the posterior border of the
sterno-mastoid, must now be traeed downwards and posteriorly, through
the trian^^le, to the point where it disappears under cover of the trapezius,
at the junction of the upper two-thirds with the lower third of the anterior
border of that musele. As the nerve is eleaned, attempt to seeure twigs
from the third and fourth cervical nerves whieh eommunieate with it in
the posterior triangle.

Turn next to the posterior belly of the omo-hyoid musele, whieh
erosses the lower part of the triangle. Note that it divides the triangle
into a large upper or oeeipital portion, and a small lower or subclavian
portion. Cut through the fascia on the surface of the musele, parallel with
the musele fibres, and turn it upwards and downwards ; then turn the
upper border of the musele laterally and find the herve from the ansa
hypoglossi, whieh emerges from under cover of the sterno-mastoid and
enters the deep surface of the omo-hyoid to supply it.

Take away the remains of the superficial layer of deep fascia, and the
areolar tissue beneath it from the upper part of the triangle. Whilst
removing the latter note a number of lymph glands whieh lie embedded
in it along the posterior border of the sterno-mastoid, superficial to the
stems and branehes of the cervical nerves. At the apex of the triangle
look for the oeeipital artery, whieh either emerges between the adjacent

POSTERIOR TRIANGLE 147

borders of the trapedus and the sterno-mastoid, or pierees the trapezius a
little further posteriorly.

Between the aeeessory nerve above and the posterior belly of the omo*
hyoid below find (i) the upper part of the braenial plexus ; (2) its braneh
to the subclavius ; (3) its supraseapular braneh ; (4) its dorsalis seapuUe
braneh ; (5) its long thoraeie braneh ; (6) branehes from the third and
fourth cervical nerves to the levator seapulse ; (7) branehes from the third
and fourth cervical nerves to the trapezius, and others whieh eommunieate
with the aeeessory nerve in the posterior triangle ; and (8) the upper and
posterior part of the transverse eenrieal artery. Find the transverse cervical
artery as it appears from under cover of the upper border of the omo-hyoid.
It nins upwards and posteriorly. Next seeure the nerve to the sulx:lavius,
whieh lies under cover of the deep fascia above the omo-hyoid and a short
distanee behind the stemo-mastoid. Traee it upwards to its origin from
the trunk formed by the union of the fifth and sixth cervical nerves. Clean
the latter nerves and the upper part of the seventh cervical nerve, whieh
lies immediately below them. Then find the suprascaj)ular nerve, whieh
springs firom the lateral border of the trunk formed by the fifth and sixth
nerves. It lies immediately above the anterior part of the posterior l)elly
of the omo-hyoid, and disappears under cover of the posterior part.
Tum the trunk formed by the fifth and sixth cervical nerves anteriorly and
find, posterior to it, the upper roots of the long thoraeie nerve, whieh spring
firom the fifth and sixth nerves, and are emerging through the fibres of the
sealenus medius musele. The nervus dorsalis seapula: (O.T. nerve to the
rhomboids) lies at a slightly higher level than the supraseapular nerve. It
springs from the fifth cervical nerve, runs downwards and posteriorly, and
disappears, through the floor of the triangle, between the adjacent borders
of the levator seapulae above and the sealenus medius below. Above the
dorsal seapular nerve are the branehes firom the third and fourth cervical
nerves to the trapezius and the eommunieations to the aeeessory nerve.

When the struetures mentioned above have been found and eleaned,
proeeed to the disseetion of the subclavian portion of the triangle. Find
the transverse seapular artery (O.T. supraseapular), whieh lies behind the
clavicle, and therefore, strietly speaking, outside the limits of the triangle.
Then remove the seeond layer of deep cervical fascia whieh binds the
posterior belly of the omo-hyoid to the posterior border of the clavicle, and
find behind it (i) a further part of the external jugular vein ; (2) a further
part of the transverse cervical artery ; (3) the lower part of the nerve to the
subclavius ; (4) the upper portion of the third part of the subclavian artery ;

(5) the lowest root and the lower parts of the trunks of the braehial plexus ;

(6) a part of the long thoraeie nerve ; (7) supraclavicular lymph glands.
First elean the lower end of the external jugular vein and follow it

behind the clavicle to its termination in the subclavian vein. Note the
valves near its lower end. Next elean the transverse cervical artery and
the nerve to the subclavius. Follow the nerve to the subclavius aeross
the front of the third part of the subclavian artery ; and afterwards elean
the lower part of the subclavian artery and the adjacent part of the
braehial plexus, whieh lies behind and above the artery. Note that the
artery and the plexus are covered by a layer of deep cervical fascia, the
baekward prolongation of the prevertebral layer of fascia, whieh passes on
to them from the lateral border of the sealenus anterior, and is prolonged
along them to beeome eontinuous with the sheath of the axillary artery.

As the areolar tissue is eleared from the subclavian portion of the
triangle a number of supraclavicular lymph glands may be noted. They
receive lymph from the axillary glands, and they transmit it to the large
lymph vessels at the root of the neek.
II— lOa

t^S

HEAD AND NECK

Ader the eontents of Ibe lower part of the Iriangle are thoroughly eleaned,
remove the lemains of the fascia covering the niuseles whieh fono
the HooT of the Iriangle. Note Ihal this fa5cia is eontinuous anteriorly,
round the tips of the IransTerse proeesses of the cervica1 vertebr:e with the
prevertebral fascia. Posteiiotly it blends with the sheaths of the deeper

museles it the liaek of the neek ; above it is attaehed to the superior
nuehal line ; and below, as already stated, it is protonged inio the aidlla
along the axi11ary vesae1s and nerves.

BoimdarieB and Contenta of tlie Posterior Triangle. — The

disseetioii of the triangle should be eompleted in two days.
On the third day the disseetor should revise his knowledge
of the boundaries and the re!ative positions of the eontents.

POSTERIOR TRIANGLE 149

The triangle is bounded anUriarfy by the posterior border
of the stemo-mastoid ; posteriorly by the anterior border of the
trapezius; below by the upper border of the niiddle third
of the clavicle ; and abave by the superior nuehal line of the
oeeipital bone^ or by the meeting of the upper ends of the sterno-
mastoid and the trapezius. The roof is formed by the deep
cervical fascia, whieh is covered by superiieial fascia and skin,
and in its lower and anterior part by the platysma, whieh is
embedded in the superficial fascia. It is piereed by (i) the
extemal jugular vein at the lower and anterior angle ; (2) the
supraclavicular nerves, a short distanee above the clavicle ;
(3) small eutaneous branehes of the transverse seapular, trans-
verse eendeal, and oeeipital arteries ; (4) lymphatie vesscls
passing from the superficial struetures to the glands in the
triangle. It is frequently stated that the small oeeipital, the
great aurieular, and the cervical eutaneous nerves also
pieree the roof. As a general mle they turn round the
posterior border of the stemo-mastoid under cover of the
fascia, and pieree the fascia as it lies on the musele.

The floor is formed by the splenius eapitis, the levator
seapulae, the sealenus medius, and the sealenus posterior
musdes, with the addition, oeeasionally, of a small part of the
semispinalis eapitis (O.T. complexus) above, and the upper
serration of the serratus anterior below ; the latter appears
in the area of the triangle only when the clavicle is very
fully depressed. The museles of the floor are covered with
a layer of fascia whieh is the baekward eontinuation of the
prevertebral fascia of the anterior cervical region.

The eontents of the posterior triangle are : —

1. Fatty areolar tissue.

2. The posterior belly of the omo-hyoid musele.

3. Lymph T Post sterno-mastoid.

Glands, \ Supraclavicular.

{Third part of subclavian.
TransYerse cervical and its terminal branehes.
Oeeipital (sometimes).
f External jugular.
I Transverse cervical.
5. Yeins,'* \ Transverse seapular (O.T. supraseapular).
^Termination of anterior jugular.

^ The transverse seapular artery (O.T. supraseapular) lies posteribr to
the clavicle and is not, strietly speaking, in the triangle.

^ The subclavian vein is posterior to the clavicle 3Jid there^ore is not
eontained within the triangle.

11-10 6

^50

HEAD AND NECK

6. Nenres, ^

Branehes of cervical plexus.

' Aeeessory.
Small oeeipital.
Great aurieular.
Nervus eutaneus eoUi.
To levator seapulae.
,, trapezius.
,, sealenus medius.
, , , , posterior.
Supraclavicular.
To posterior belly of omo-hyoid from ansa hypoglossi.
Trunks of braehial plexus.
The nervus dorsalis seapulae. ^

long thoraeie. [^ Branehes of the braehial

supraseapular. j plexus.

})

»)

nerve to the subclavius.

Some of the eontents of the triangle whieh are now
displayed require further eonsideration.

The Posterior Belly of the Omo-hyoid Musele. — The
posterior belly of the omo-hyoid musele springs from the
upper border of the seapula and upper transverse seapular
ligament. It enters the posterior triangle, at its lower and
posterior angle, and runs upwards and anteriorly, at a
yariable distanee from the clavicle, to the posterior border
of the sterno-mastoid. Either immediately behind or
under cover of the posterior border of the sterno-mastoid it
joins the intermediate tendon whieh eonneets it with the
anterior belly. Its nerve has already been seen entering
its deep surface (p. 146) it divides the posterior triangle
into a lower or subclavian portion and an upper or oeeipital
portion.

The Aeeessory Nenre (O.T. Spinal Aeeessory). — The
portion of the aeeessory nerve whieh appears in the posterior
triangle eonsists of iibres whieh arise from the cervical part
of the spinal medulla and with them are ineorporated some
tilaments derived from the seeond cervical nerve. Before
appearing in their present situation the spinal iibres entered
the eranium through the foramen magnum and left it by pass-
ing through the jugular foramen ; then they passed downwards
and posteriorly, through the deeper Abres of sterno-mastoid,
where theyreceived theeommunieation from the seeond cervical
nerve. As already pointed out, the nerve usually enters the
posterior triangle at the level of the union of the upper third
with the lower two-thirds of the posterior border of the sterno-
mastoid. It runs downwards and posteriorly through the
triangle, along the line of the levator seapulae, and disappears

POSTERIOR TRIANGLE 1 5 1

under the trapezius at the junction of the upper two-thirds
with the lower third of its anterior border. As it enters the
triangle the smaU oeeipital nerve turns round its lower border,
and, as it erosses the triangle, it is joincd hy twigs from the
third and fourth cervical nerves.

The Branehes of the GerTieal Plenis. — Ihe disseetor
should note that whilst many of the branehes of the cervical
plexus lie within the area of the posterior triangle, the
plexus itself is under cover of the upper part of the sterno-
mastoid, where it will be exposed and studied when the
sterno - mastoid is reAeeted. The branehes whieh appear
in the triangle are the superficial branehes — the small oeeipital,
the great aurieular, the nervus eutaneus eolli, and the supra-
clavicular nerves; and the deep posterior branehes^ that is,
the nerves to the sealenus medius and posterior, the nerve
to the levator seapulae, the branehes to the trapezius and the
eommunieation to the aeeessory nerve.

The Third Part of the Sabclavian Artery. — Only a
portion of this part of the subclavian artery is in the triangle ;
the lower and lateral part is behind the clavicle. The part
in the triangle is situated deeply in the anterior inferior
angle and below the omo-hyoid musele. It is covered 7vith the
skin, superficial fascia, the platysma, deep fascia, the external
jugular vein, the ends of the transverse seapular, and trans-
verse cervical veins, and the nerve to the subclavius musele.
Behind it is the lowest trunk of the braehial plexus, whieh
separates it from the insertion of the sealenus niedius. Below^
it rests upon the first rib, against whieh it ean be eompressed,
and, more medially, on the cervical pleura.

The Braehial Plexus and its Supraclavicular Branehes. —
Only the upper portion of the braehial plexus lies in the
region of the posterior triangle, i,e. the roots, the trunks, and
some of the branehes ; the remainder lies either posterior to
the clavicle or in the axilla. The cervical portion lies in the
lower and anterior part of the posterior triangle partly in
the oeeipital and partly in the supraclavicular areas. The
detailed study of the plexus should be left till the fifth day
after the body has been plaeed upon its baek, when the
disseetor of the head and neek will assist the disseetor of the
upper extremity to disartieulate the clavicle and to lay bare
the whole of the plexus (p. 1 60).

The fourth day after the body ^'^" ^^en plaeed upon its

iSa HEAD AND NECK

baek should be deyoted to the study of the temporal region
and the anterior part of the sealp.

THE SGALP AND THE SUPERFTCIAL STRUGTURES
0F THE TEMPORAL REGION.

Under the term " sealp " are ineluded the soft struetures
whieh cover the vault of the eranium above the temporal
ridges and anterior to the superior nuehal line. Its eon-
stituent parts are arranged in iive layers : (i) skin; (2) super-
ficia] fascia ; (3) the epieranius, eonsisting of four museular

FiG. 68. — Seetion through the Sealp and Cranial WaU.

bellies, ihe two oeeipitales and the two frontales museles, and
the aponeurosis ealled the galea aponeurotiea, whieh eonneets
them together ; (4) a layer of ioose areolar tissue ; (5) tbe
periosteum, whieh is here ealled the perieranium. In the
teTiiporal region the wall of the eranium is mueh more thiekly
covered than m the sealp area, and it is possible to distinguish
eight layers of sofl tissues between the surface and the bone:
(1) skin; (2) superficial fascia ; {3) extrinsic museles of the
ear ; {4) the thin lateral extensions of the galeaaponeurotiea;
(5) a thin layer of fascia deseending from the temporal ridge
to the auriele ; (6) the strong temporal fascia ; (7)the temporal
musele; (8) periosteum.

TAe Sealp. — The sealp and the superficial temporal r^ion
are riehly supplied with biood vessels and nerves, whieh all

AURIGLE 153

enter froin tbe peripbery, passing into the superReial Taseia
afteT piereing tbe deep laseia of adjaccnt regions. As a
consequence of this arrangetnent lai^e flaps of ihe sealp may
be torn froin the eentre towards the margin, but, to long as
they remain attaehed at the periphery, their sourees of
vitality are not seriously interiered with, and if ihey are eleaned
and replaeed healing oeeurs rapidly and satisfac[orily.

Oineeliim. — The skin ha$ alteady been retnovnl Troin ihe Rnlerior
porls of the sealp and the teroporal region, A meilian longiludiiul in-
eision must now oe made Ibtough Ihe skin of the posleriot pan of (he
sealp as far as the exterQHl oeeipital proluberanee, and ihe Hap on eilher
side of Ihe ineision must be turned downwaids and posteriorly to ihe
superior uuehal line. When Ihis has been done Ihe dtsseetor should ex-
amine the auriele of the external ear, and fami1iarise himselC wilh ils yaeious
pans before he eommenees the disseelion of iU

FiG. 69.-Th(

Anriele or Pinna. — The auriele eonsists of a thin plate of
yellow Abro-eartilage, covered with integument. It is fixed in
position by eertain ligaments, and possesses two sets of feeble
museles — viz., one group termed the cxirinsic musdei, passing
to the eartilage from the aponeurosis of the epieranius and
the mastoid proeess, and a seeond group in eonneetion with
the eartilage alone, and therefore ealled the tntrinsie musdes.

The eotuha is the wide and deep fossa whieh leads into
tbe external meatus ; the antihdix is the curved prominenee
whieh bounds this posteriorly ; the helix is the folded or in-
curved margin of the auriele ; and the lobule is its soft
dependent part. The eoneha is partially subdivided into an
upper and a lower part by the eommeneement of the helix,
whieh curves upwards and forwards on its floor to beeome
eontinuous with the anterior border of the auriele. This
portion of the helix is ealled the erus heltm. A small pro-

154 HEAD AND NECK

minenee anterior to the meatus, and projecting posteriorly so
as to overshadow it, is termed the tragus, whilst a similar
eminenee posterior to and below the meatus receives the name
of the antitragus. The noteh between these two prominenees
is termed the indsura intertragiea. But it will be noted that
the upper end of the antihelix bifurcates, and in this way two
fossae are marked off from eaeh other; one — the fossa of the
helix, or seaphoid fossa — is plaeed between the helix and the
antihelix, and the other — thefossa of the antihelix, or triangular
fossa — is situated between the two diverging erura of the
antihelix.

Ligaments,

Anterior.
Superior.
Posterior.

r Aurieularis anterior.

Extrinsic museles,-! Aurieularis superior.

^Aurieularis posterior.

TMuseulus helieis major. ^

I Museulus helieis minor. I Upon the lateral face of the

T , . • 1 ! Museulus traedeus. { eaitilaee.

Intrmsie museles, ^, a/t i j?* • I

' ' Museulus antitragieus. )

Museulus transversus. \Upon the eranial face of

.Museulus obliquus. / the eartilage.

Dissedion. — When the disseetor has noted the various parts of the
auriele he should endeavour to display its extrinsic museles ; they are the
aurie ulares anterior [O.T. attrahens), superior{O.T. attollens)^ ?Lnd posterior
(O.T. retrahens). The two former spring from a lateral prolongation
of the galea aponeurotiea into the temporal region. The anterior is
inserted into the front of the heHx, and the superior into the eranial surface
of the auriele. To display them pull the auriele downwards and posteriorly,
and carefully remove the superficial fascia and, at the same time, avoid injury
to the aurieulo-temporal nerve, the temporal branehes of the facial nerve,
and the branehes of the superficial temporal artery whieh are aseending
through the superheial fascia of the temporal region to the sealp. The
aurieularis posterior arises from the outer surface of the mastoid part of
the temporal bone and passes anteriorly to its insertion into the eranial
aspeet of the eoneha. To display it puU the auriele anteriorly and remove
the fascia from the surface of the musele, at the same time seeure the
posterior aurieular artery and nerve as these aseend posterior to the e^ternal
meatus. As this is being done one or more mastoid lymph glands may
be seen, and eare must be taken to avoid injuring the braneh of the
posterior aurieular nerve to the oeeipitalis musele, whieh passes posteriorly
along the lower border of the aurieularis posterior or on its deep surface.

The aurieulares museles are supplied by the facial nerve ; the anterior
and the anterior part of the superior by its temporal branehes, and the
posterior and the posterior part of the superior by the posterior
aurieular braneh. After the aurieulares museles have been defined remove
the skin from the entire extent of the auriele to display the eartilage, the
ligaments, and the intrinsie museles.^ Great eare is required to make a
successful disseetion.

1 In niost eases it will be advisable to defer this part of the disseetion till
the body is turned on its baek for the seeond tirae (p. 200).

AURIGLE 155

The anrieiilar earillag^ extends throughout the entire auriele, with the
exception of the lobule and the portion between the tra^^us and tlie hclix.
These portions are eomposed merely of integument, fatty tissue, and
eondensed connective tissue. The shape of the eartilage corres{M)nils with
that of the auriele itself. It shows the same elevations and depressions,
and by its elastieity it serves to maintain the form of the auriele. But it
also enters into the formation of the eartilaginous or lateral iK>rtion of the
extemal aeustie meatus. By its medial margin this part ot the eartilage
is firmly fixed by Abrous tissue to the rough outer e<lge of the auditory
proeess of the temporal bone, but it does not form a eomplete tulK*. It is
deiident above and anteriorly, and here the tube of the meatus is eompleted
by tough fibrous membrane, whieh stretehes l^tween the tragus and the
eommeneement of the helix.

In a sueeessiul disseetion of the eartilage of the auriele, two other |K)ints
will attraet the attention of the student. The tirst is a deep slit, whieh
passes upwards so as to separate the lower |xirt of the eartilage of the
helix, termed the proeessus helieis eaudaius^ from the eartilage ()f the anti-
tragus ; the seeond is a sharp spur of eartilage whieh projects anteriorly
from the helix, at the level of the upper margin of the zygoma. This is
termed the spina helieis,

The LigamentB of the Anriole. — The ligaments are three bands of
fascia. The anterior passes from the spine of the lielix to the root of the
^goma. Thesuperior and p)osterior are both attaehed to the eartilage in
the region of the eoneha ; the former blends above with the temp<jral fascia,
and the latter is attaehed to the mastoid portion of the teniporal bone.

The Intrinsie MuBeleB of the Auriele. — The two museles of the helix,
the tragieus and the antitragieus, are plaeed upon the lateral face of the
eartilage. The transversus and the obliquus lie ujx)n the eranial surface of
the auriele.

The museu/us antitragieus is the best-marked member of the lateral
group. It lies upon the lateral surface of the antitragus, and its llbres pass
obliquely upwards and posteriorly. Some fasciculi ean be traeed to the
proeessus helieis eaudatus.

The museulus tragieus is a minute bundle of short vertical fibres
situated upon the lateral surface of the tragus. When well developed a
slender fasciculus may sometimes be observed to pass upwards from it to
the anterior part of the helix, where it is inserted into the spine of the helix.

The museulus helieis major is a well-marked band, whieh springs from
the spina helieis, and extends upwards upon the anterior part of the helix,
to be inserted into the skin whieh covers it.

The museulus helieis minor is a minute bundle of Aeshy fibres whieh is
plaeed upon the erus helieis as it erosses the bottom of the eoneha.

The museulus transversus auriculcB is found upon the eranial aspeet of
the auriele. It is generally the most strongly developed musele of the
series, and its fibres bridge aeross the hollow whieh, on this aspeet of the
auriele, eorresponds to the antihelix.

The museulus obliqtms au7-iculce is eomposed of some vertical fasciculi
bridging aeross the depression whieh eorresponds to the eminenee of the
lower limb of the antihelix.

After the aurieular museles and the auriele have l)ecn disseeted, traee
the temporal branehes of the facial nerve, the branehes of the super-
ficial temporal vessels, and the aurieulo-temporal nerve upwards, from
the point where they emerge from under cover of the upper end of the
parotid through the superficial fasciaof the temporal region to their termina-
tions in the superficial fascia of the seal»^ * ' ^ half an ineh behind the
zygomatic proeess of the frontal bone angular proeess) find

156 HEAD AND NECK

the zygomatico-temporal braneh of the maxillary nerve. Next pull the
auriele anteriorly and traee the posterior aurieular nerve to its termination
in the oeeipitalis musele, and in the intrinsie and extrinsic museles
of the auriele, and the posterior aurieular artery to its anastomoses with
the oeeipital and superficial temporal arteries. After this part of the
disseetion is eompleted, turn to the anterior part of the sealp and find
the medial and lateral branehes of the supra-orbital nerve. The medial
braneh pierees the fibres of the frontalis and the lateral braneh pierees
the galea aponeurotiea a little further posteriorly. Traee both branehes
baekwards through the superficial fascia as far as possible ; they extend to
the level of the lambdoid suture. Then seeure the supra-troehlear nerve,
whieh pierees the frontalis above the medial margin of the orbit, and traee
it upwards to its termination. With the branehes of the supra-orbital nerve
are branehes of the supra-orbital artery, and the supra-troehlear nerve is
aeeompanied by the frontal braneh of the ophthalmie artery.

When the nerves and vessels in the anterior region have been eleaned,
the head should be turned well over to the opposite side, and the branehes
of the oeeipital artery and the great oeeipital nerve should be sought for in
the posterior region ; they radiate upwards and anteriorly from the upper
extremity of the trapezius. After they have been seeured, the oeeipitalis
musele must be eleaned. It springs from the lateral part of the superior
nuehal line, and after a short eourse upwards and anteriorly it terminates in
the galea aponeurotiea. The remains of the superficial fascia should now
be removed from the surface of the galea aponeurotiea (O.T. epieranial
aponeurosis), and then the disseetor should make a survey of the vessels
and nerves whieh are met with in the sealp and the superficial fascia of the
temporal region.

Nenres and Yessels of the Sealp and the Saperficial
Temporal Begion. — Branehes of ten nerves are found, on eaeh
side, in the superiieial fascia of the region whieh lies above
the supra-orbital margin, the zygomatic areh and the superior
nuehal line. Of these, five He mainly anterior to the auriele
and five posterior to it ; and of eaeh group four are sensory
and one is motor. The four sensory nerves anterior to the
auriele are all branehes of the trigeminal nerve. They are
the supra-troehlear and supra-orbital branehes of the first or
ophthabnie division ; the zygomatico-temporal braneh of the
maxiUary or seeond division ; and the aurieulo-temporal braneh
of the mandibular or third division. The motor nerve is the
temporal braneh of the facial nerve.

The four sensory nerves, distributed mainly to the sealp
area behind the auriele, are the great aurieular and the small
oeeipital branehes of the cervical plexus ; the great oeeipital^
whieh is the medial division of the posterior braneh of the
seeond cervical nerve ; and the smailest oeeipital, not yet seen,
but whieh will be displayed when the body is tumed on its
face. It lies medial to the great oeeipital, and is the medial
division of the posterior braneh of the third cervical nerve.

NERYES AND YESSELS 0F SCALP 157

Tbe motor nerve distributed posterior to the auride is the
posterior aurieular braruh of the Taeial nerve.

The arteries distributed to the sealp are five in number on
eaeh side; they anastomose freely, and are derivcd, either
indireetly or direetly, from the internal and external earotid
arteries. Three are distributed mainly anterior to, and two
posterior to the region of the auriele. The three anterior to
the auriele are the /rontal and supra-orbital branehes of the
ophthalmie braneh of the intemal earotid, whieh aeeompany
the supra-troehlear and supra-orbital nerves, and the sup€rficial
temporal braneh of the external earotid. This braneh dividcs
into two main branehes, an anterior, whieh aeeompanies the
temporal branehes of the facial nerve, and is usually a very
tortuous vessel, and a posterior braneh, whieh aeeompanies the
aurieulo-temporal nerve, as it aseends anterior to the auriele
towards the vertex of the eranium. The two arteries posterior
to the auriele are both branehes of the external earotid. They
are the posterior aurieular^ whieh aeeompanies the posterior
aurieular braneh of the facial nerve to the mastoid region
and the posterior part of the parietal region, and the oeeipital^
whieh is distributed to the oeeipital area and posterior part
of the parietal area.

The terminations of the veins w^hieh drain the blood from
the sealp are as follows. The /rontal and supra-orbital veins
unite, at the medial border of the orbit, to form the angidar
vein^ whieh is the eommeneement of the anterior facial vein
abeady disseeted (p. 131). The blood it conveys passes
eventually to the internal jugular vein. The superficial
temporalvein aeeompanies the eorresponding artery. It unites,
immediately above the posterior root of the zygoma, with the
middle temporal vein, whieh pierees the temporal fascia at
that point. The trunk formed by the union of the superAeial
and middle temporal veins is the posterior /aeial vein, whieh
deseends through the parotid gland, emerges from under
cover of its lower end and terminates immediately below the
angle of the mandible by joining with the anterior facial vein
to form the eommon facial vein. Whilst in the gland, it gives
off the eommeneement of the external jugular vein. The
posterior aurieular vein deseends posterior to the external
meatus and terminates in the external jugular vein. The
oedpital vein aeeompanies the f 'ery into the sub-

oeeipital region, and ends in t' yenous plexus.

158 HEAD AND NECK

In addition to the arteries and veins there are numerous
lymph vessels in the sealp, but they eannot be displayed by
ordinary disseeting methods. Nevertheless, it is important
that the student should remember their usual terminations.
The lymph vessels of the anterior area end in small lymph
glands whieh are embedded in the superAeial surface of the
parotid gland. Those of the posterior area terminate either
in lymph glands whieh lie superficial to the mastoid part of
the temporal bone, or in oeeipital lymph glands, whieh lie in
the neighbburhood of the superior nuehal line.

Disseetion. — After the vessels and nerves of the sealp have been traeed,
the disseetor should eut through the fibres of the orbieularis oeuli and the
frontalis over the medial part of the supra-orbital eminenee and display the
eorrugator supereilii musele. It springs from the medial end of the
supra-orbital ridge of the frontal bone and passes anteriorly and laterally,
through the fibres of the orbieularis oeuli, to its insertion into the skin of
the eyebrow. It is supplied by the temporal braneh of the facial nerve.

Galea Aponeurotiea (O.T. Epieranial Aponeurosis). — The
galea aponeurotiea is fully exposed as soon as the superficial
fascia of the sealp is eompletely remoyed. It is a strong
layer of aponeurosis eonneeted anteriorly with the frontal
bellies of the epieranius, posteriorly with the oeeipital bellies,
and between the oeeipital bellies, with the external oeeipital
protuberanee and the medial parts of the superior nuehal lines,
or with the supreme nuehal lines wheh they are present.
Laterally it beeomes thinner, deseends over the upper part of
the temporal fascia, and gives origin to the anterior and
superior aurieulares museles. It is so elosely eonneeted
with the superjacent skin, by the dense superficial fascia,
that the two eannot be separated, except with the aid of
the eutting edge of the sealpel ; but above the supra-orbital
ridges, the temporal ridges, and the superior nuehal lines it
is only loosely eonneeted to the perieranium by the layer
of loose areolar tissue ; therefore the three elosely eonneeted
superficial layers, the skin, superficial fascia, and the galea
aponeurotiea, ean easily be torn from the perieranium, a
eireumstanee taken advantage of by the Indians who sealped
'their defeated foes. The looseness of the areolar tissue
beneath the galea aponeurotiea permits the latter to be
drawn forwards and baekwards by the alternate eontraetions
of the oeeipitalis and frontalis museles, and, as it moves, it
earries with it the skin and superficial fascia with whieh
it is so elosely blended.

SGALP 1 59

Disseetum, — The ditseetor, aftcr stud^ng the auaehments <if ihe galea
aponeurotiea, and after be has made himself thoroughly ronYersant with
the nenre and vasciilar sapply of the sealp, an<l has appreeiatetl the fact
that every part of its area is suppli^ by more than one ncrvc aml that the
blood vessels anastomose Yery treely together, should ncxt C(>nvincc hini*»clf
of the greater looseness of the areolar layer l)eneath the galea in the metlial
area and its greater denseness and eloser attaehment to the varii>us {larts
of the superjacent epieranius, and the subjacent perieranium at the mar);in>
of the sealp area. He may do this by introdueing the hamlle (>f a sealiirl
through a median ineision in the galea, aml {lassing it anteriorly aml
posteriorly and from side to side.

The Layer of Loose Areolar Tissue. — This is the f()urth
layer of the sealp. It is but slightly vascular and is ()f I(K)sc
texture, but is not §qually loose ovcr the whole area of iho
sealp; on the eontrary in the regions of the temporal and
supra-orbital ridges it beeomes mueh denser, and, at thesame
time, mueh more elosely eonneeted with the galea aponeurotiea
and the frontalis museles, whilst posteriorly it disappears
where the oeeipitalis museles and the galea beeonie attaehed
to the superior nuehal lines. It is on aeeount of these
peeuliarities that eATusions of blood or inAammatory exudations
in the areolar layer easily raise the greater part of the sealp
from the bone, but sueh eiTusions do not readily pass from
beneath the sealp into either the facial, temporal, or oeeipital
regions.

On the fifth day after the body has been plaeed upon its
baek, the eighth after it was brought into the room, the
disseetor of the head and neek must assist the disseetor of
the upper extremity to display the whole extent of the braehial
plexus and the origins of the branehes whieh spring froni it ;
and he should take the opportunity to revise his ow^n know-
ledge of the plexus. Detaeh the clavicular head of the
sterno-mastoid from the clavicle, and displaee the stemal
head towards the median plane. When this has been done
the anterior and upper parts of the sterno-clavicular joint
eapsule will be fully exposed, for the peetoralis major, whieh
covered the lower part of the anterior surface, has already
been reSeeted by the disseetor of the upper extremity.

Disseetion, — The sterno-cLavicular joint is deseribed on p. 28 of Vol. I.
After the disseetors have noted that the fibres of the eapsule run medially
and downwards from the clavicle to the sternum, the anterior, superior,
and posterior portions must be divided elose to the sternum, eare being
taken to avoid injury to the anterior jugular vein, whieh passes laterally
elose to the upper and baek part of the joint. When the division is
eompleted, elevate the sternal end of the clavicle by depressing the

i6o HEAD AND NECK

aeromial end, introduee the knife into the cavity of the joint, elose
to the sternum, and earry it laterally below the clavicle, to detaeh
the lower part of the interartieular eartilage from the sternum and
the eartilage of the first rib, and to divide the lower part of the eapsule
and the costo-clavicular ligament, whieh lies immediately lateral to it. If
the subclavius musele has not already been detaehed, it also must be divided,
and then the clavicle ean be displaeed laterally, and the whole extent of
the plexus will be exposed.

The Braehial Plexus. — The braehial plexus is fully deseribed on p. 28,
Vol. I., and only a brief resume of the main facts regarding it is given here.
The plexus is formed by the last four cervical nerves and the larger part
of the first thoraeie nerve ; it also receives a eommunieation from the fourth
cervical nerve and not uneommonly a small twig from the seeond thoraeie
nerve. These various nerves eonstitute the roots of the plexus. The roots
of the plexus emerge from between the sealenus medius and the sealenus
anterior, and unite to form three trunks^ upper, middle, and lower, whieh
lie superficial to the sealenus medius, the lowest of the three being wedged in
between that musele posteriorly and the third part of the subclavian artery
anteriorly. The upper trunk is formed by the fifth and sixth nerves and the
eommunieation from the fourth. The seventh nerve alone forms the mtddle
trunk ; and the lowest trunk is formed by the eighth cervical and first
thoraeie nerves and the eommunieation from the seeond thoraeie. Almost
immediately after their formation the trunks divide into anterior and
posterior divisions, and the divisions reunite to form three eords, lateral,
medial, and posterior. The lateral eord is formed by the anterior divisions
of the upper and middle trunks, the medial eord by the anterior divisi6n of
the lowest trunk, and all three posterior divisions unite to form the posterior
eord. The eords deseend behind the clavicle and subclavius musele,
through the cervico-axillary eanal, to the level of the eoraeoid proeess of
the seapula where the plexus terminates and eaeh eord divides into two
terminal branehes. The terminal branehes of the lateral eord are the
lateral head of the median nerve and the museulo-eutaneous nerve. Those
of the medial eord are the medial head of the median and the ulnar nerve,
and the posterior eord divides into the axillary (O.T. circumflex) nerve
and the radial (O.T. museulo-spiral). In addition to the terminal branehes,
eollateral branehes are given off from the roots, the trunks and the eords ;
and the roots are eonneeted with the middle and lower ganglia of the
cervical part of the sympathetie trunk by grey rami eommunieantes. The
branehes given off from the roots are twigs of supply to the longus eolli,
the sealenus anterior, the sealenus medius, and the sealenus posterior, the
roots of origin of the long thoraeie nerve, whieh supplies the serratus anterior
(O.T. magnus) and the dorsal seapular nerve (O.T. nerve to the rhomboids).
The roots of the long thoraeie nerve spring from the fifth, sixth, and seventh
nerves ; the upper two pieree the sealenus medius and the lowest passes
anterior to that musele. The three unite, behind the trunks of the plexus,
to form the stem of the nerve, whieh deseends behind the eords of the
plexus into the axilla. The dorsalis seapulse nerve arises from the lateral
border of the fifth nerve ; it disappears under cover of the levator seapulse
and supplies the two rhomboid museles, and, sometimes, the levator seapulae.

The branehes from the trunks of the plexus are the supraseapular nerve
and the nerve to the subclavius. They both spring from the upper trunk.
The eoUateral branehes of the three eords of the plexus, are ( i ) from the
outer eord : the lateral anterior thoraeie nerve ; (2) from the posterior eord :
the upper and lower subseapular nerves and the thoraeo-dorsal nerve
(O.T. long subseapular) ; and (3) from the medial eord : the medial anterior
thoraeie, the medial eutaneous nerve of the arm (O.T. lesser internal

iDISSECTION 0F THK BACK i6i

medial eataneoiis nenre of the foreann (O.T. iotenud
fA€ Braehiat Ptexus.—Tht plexu8 liet in the lower and
posterior triangle of the neek, partly abo^e and partly
Dellv of the omo-hyoid ; postenor to the elaTide ; and
tfe tke clavicle it is eoTered by the skin, the saperficial
fsma, branehes of the supraelaTieular nerTes, the Tirst
, the extemal jugular vein, and the terminal parts of the
and transverse (supra) seapular veins ; the seeond
eal fascia, the transverse eenrieal artery, the posterior
'oid, the nerve to the subclavius, and tne third part of
sry. Bekind the clavicU it is erossed superBdall^ b^
iilar artery (O.T. supraseapular). Belew the elanele it
skin and superficial fasda, the platysma, the middle
ires, the deep fascia, the peetoralis major, the |XK:toralis
: vdn, the branehes of the thoraeo-aeromial artery, the
ibrane, and the axillary artery and vein.
tions in the neek are the sealenus medius and the long
( the eueilla the serratus anterior, the fat in the interval
is anterior and the subseapularis, and linaUy the sub-
dal plexus has been examined, the clavicle must l)c
\ and the skin flap, reflected from the posterior triangle,
ad fixed in position by a few sutures.
i day after the body is brought into the room,
ixth day after it has been .plaeed on its baek,
. be tumed upon its face, with the thorax and the pelvis
»rted by bloeks. The body will remain upon its face for
ays, and during that period the disseetors of the head
eek must eomplete the disseetion of the posterior part
5 sealp ; disseet the museles, vessels and nerves of the
and the suboeeipital region ; and remove and examine
)inal meduUa.

THE DISSEGTION 0F THE BAGK.

seetion. — Make a median longitudinal ineision from the external
il protuberanee to the seventh cervical spine, and a seeond laterally
le seventh cervical spine to the aeromion, and throw the flap laterally.
this has been done the posterior triangle will be exposed from behind,
; disseetor should take the opportunity of noting the positions of the
:s and the eonstituent parts of the floor from this aspeet. Afterwards
5t look for the superficial nerves in the superficial fascia over the
part of the trapezius. If the great oeeipital nerve was not found
the disseetion of the sealp seeure it at onee, as it pierees the deep
:overing the upper end of the trapezius, about midway between the
il oeeipital protuberanee and the posterior border of the mastoid
. of the temporal bone ; traee it upwards through the dense superficial
)f the sealp and elean the branehes of the oeeipital artery whieh are
ited in the same region. The smallest oeeipital nerve will be found
L. II — 11

i62 HEAD AND NECK

in the superficial fascia between the great oeeipital and the median plane.
It is the medial division of the posterior braneh of the third cervical nerve,
and it supplies the skin of the medial and lower part of the posterior portion
of the sealp and the adjacent part of the skin of the baek of the neek.
Traee it upwards to its termination and downwards to the point where ii
pierees the deep fascia covering the trapezius. At a still lower level look
for the medial divisions of the posterior branehes of the other cervical
nerves. They are variable in number and position, but those whieh are
present will be found piereing the deep fascia over the trapezius, at a short
distanee from the median plane, and running downwards and laterally
towards the posterior triangle.

After the eutaneous nerves have been found remove the remains of the
superficial fascia and the deep fascia from the surface of the trapezius.

The Terminal Part of the Great Oeeipital Nerve. — The
great oeeipital nerve is the large medial division of the
posterior braneh of the seeond cervical nerve. It enters the
posterior part of the sealp, after piereing the upper part of the
trapezius and the deep fascia of the baek of the neek, and
ramifies in the superficial fascia of the sealp over the oeeipital
bone and the posterior part of the parietal bone, aeeompanying
the branehes of the oeeipital artery, and eommunieating with
the great aurieular and small oeeipital nerves.

Arteria Oeeipitalis. — After emerging from between the
trapezius and the sterno-mastoid, at the apex of the posterior
triangle, or piereing the upper part of the trapezius, the terminal
part of the oeeipital artery passes through the deep fascia of
the baek of the neek and enters the superficial fascia of the
posterior part of the sealp. It anastomoses with its fellow of
the opposite side, and with the posterior aurieular and the
superficial temporal arteries. As a rule, it breaks up into two
main branehes, a lateral and a medial. The medial braneh
gives ofF eutaneous twigs and a meningeal braneh, whieh passes
through the parietal foramen and anastomoses with a braneh
of the middle meningeal artery. Through the same foramen,
passes an emissary vein whieh eonneets the oeeipital veins
with the superior sagittal (longitudinal) sinus.

Mnseulus TrapeziiLS. — The trapezius and latissimus dorsi
eonstitute the first layer of the museles of the baek. Only
that part of the trapezius whieh lies above the level of the
seventh cervical spine belongs to the disseetor of the head and
neek ; the lower part and the latissimus must be eleaned by
the disseetor of the arm, but the disseetor of the head should
take the opportunity to revise his knowledge of the whole
origin and insertion of the musele. It arises from the medial
third of the superior nuehal line of the oeeipital bone,

THE DISSECTION 0F THE BACK

163

the extenial oeeipital protuberanee, the whole length uf the
ligamentum nuehie, the seventh cervical sptne, the tij>R of
all the thorade spines and the eorresponding supraspinous
ligaments.

Id Ihe r^on of the seventh eerriesl spne Iheorigin is miitt; aponeuiiitie
than elsewheie, and the line tendinous libtes of the miis<:li.-
fom an ovoid apmiearotie area some two inebes in lenpih.

Fic. 70, — SuperBeial disseetion of the Baek of the Neek,

The upper fibres of the musele deseend in obIique curves
and are inserted into the lateral tliird of the posterior border
and the adjacent part of the superior surface of the c!avicle ;
the interraediate fibres run horizontal!y, towards tlie shoulder,
and are inserted into the medial border of the aerotnion and
the upper lip of the posterior border of the spine of the
seapula. The lower fibres aseenH ""'' terminate in a small

i64 HEAD AND NECK

triangular tendon whieh plays over the smooth triangle at the
root of the seapular spine and is inserted partly into the lower
and partly into the upper lip of the spine. The mi^sele is
supplied by the aeeessory and the third and fourth cervical
nerves. It draws the seapula medially and braees theshoulder
baekwards, raises the tip of the shoulder, or depresses the
seapula and turns the glenoid fossa upwards aeeording to
whether the intermediate, the upper, or the lower iibres are
mainly in aetion.

Disseetim. — On the seeond day after the subject has been plaeed on its
face, the trapezius may be reAeeted. This must be done in conjunction
with the disseetor of the arm. First separate the musele from the oeeipital
bone, and then divide it about half an ineh from the spines of the yertebrse.
The musele ean now be raised and thrown laterally towards its insertion.
On its deep surface the aeeessory nerve, the twigs of supply from the third
and fourth cervical nerves and the superficial cervical artery will be notieed.
It is the duty of the disseetor of the upper limb to disseet these, but the
disseetor of the head and neek should traee the superficial cervical artery
to its origin from the transversa eolli.

The attaehments of the levator seapulae also must be defined. Two
twigs from the third and fourth cervical nerves, whieh lie on its surface
and finally enter its substanee, have already been seeured. Further,
passing downwards under cover of this musele, the dorsal seapular nerve
(O.T. nerve to the rhomboids) and the deseending braneh (O.T. posterior
seapular) of the transversa eolli artery will be found. Almost invariably
the dorsal seapular nerve gives one or two twigs to the levator seapulse.

The levator seapulae, the rhomboids, the posterior serrati and the splenius
are elassed as museles of the seeond layer. The rhomboids and the lower
part of the levator belong to the disseetor of the arm ; the remaining museles
are the property of the disseetor of the head and neek.

Mnseulus Levator Seapulse. — This musele arises by four
slips from the posterior parts of the transverse proeesses of
the upper four cervical vertebrae. These unite to form an
elongated musele whieh extends downwards and posteriorly to
be inserted into that portion of the vertebral border of the
seapula whieh is plaeed above the root of the spine. Its
nerve-supply eomes from the third and fourth cervical nerves,
and also from the dorsal seapular nerve.

The origin of the posterior belly of the omo-hyoid musele
may now be examined. It is attaehed to the upper transverse
ligament of the seapula and the adjacent part of the superior
border of the bone. The transverse seapular artery (O.T.
supraseapular) will be notieed passing over the upper trans-
verse ligament whilst the supraseapular nerve traverses the
noteh below it.

The seeond days work is now eompleted, and on the same day the

THE DISSECTION OF THE BACK

>6S

biek, :

i liiiuh hi* ihare or the disseetion of ihe
II lirgin Ihe
ion o( the deeper stiueluiei on the dorsal U|i«:t <>r ihi^ itunk.
Three days are allowed Hit Ihis disseetion, and lhfNC miy lie ilis]X)sed
of in the follomDg mannee : — Oit (hejlnt day, all ihe iiiu&c1l'S, fa<icin.',
neTYes, and blood vessels of the b&ek, wilh the cxci.'|>lii>n (>f Ihiise in
eonneetion witli the sub - oeeipilal tiiangle, should l>c sluiliiil : on ihe
stamd day, the sub-oeeipilal tiiangle musl be examined ; an<) un the thiid
day the medulla splnalis (O.T. s^mdaI eord) musl be displayeil.

Unseali Senati Posteriores. — These are two thin sheets
of Seshy iibres, whieh are plaeed upon the posterior aspeet

FiG. 71. — Diaigram 10 she

of the thoraeie wall. The serratus posterior superior is mueh
the smaller of the two ; it arises by a thin aponeurotie tendon
from the lower part of the ligamentum nuchje ; from the spinous
proeess of the seventh cervical.vertebra ; and from the spinous
proeesses of the upper two or three thoraeie vertebr£e. It
passes obIiquely downwards and laterally, and is inserted into
the outer suriaees of the seeond, third, fourth, and fifth ribs,
a short distanee anterior to theit angles.

The serratus posterior inferior will be brought into view by
raising and throwing medially that portion of the latissimus
dorsi whieh the disseetor of the upper limb has left altaehed
to the lumbo-dorsal fascia. It takes origin from the spinous
proeesses of the last two thoraeie and upper two lumbar

i66 HEAD AND NECK

vertebrae, and the supiaspinous ligaments between them.
The disseetor will note, however, that this is not an indepen-
dent and distinet attaehment, but that it is effected through
the medium of the lumbo-dorsal fascia, with whieh the
aponeurotie tendon of the musele blends. The musele
passes upwards and laterally and is inserted into the outer
surfaces of the lower four ribs.

Fascia Lumbo-dorsalis. — On the third day after the body
is plaeed upon its face the disseetor of the head and neek
should assoeiate himself with the disseetor of the abdomen
in the examination of the lumbo-dorsal fascia. It is an
aponeurotie layer, thin in the thoraeie portion of its extent,
but thiek and strong in the lumbar and saeral regions ; and
in all these regions it binds down the museles of the baek
to the sides of the spinous proeesses and to the transverse
proeesses of the vertebrae.

The Dorsal Part of the Lumbo-dorsal Fascia (O.T. Yertebrat.
Aponeurosis). — This part of the lumbo-dorsal fascia is a thin
transparent lamina whieh extends from the tips of the spines
and the supraspinous ligaments to the angles of the ribs.
At the upper end of the thoraeie region it dips beneath the
serratus posterior superior into the neek, and at the lower
end it blends with the aponeurosis of origin of the serratus
posterior inferior, and through that beeomes eontinuous with
the posterior layer of the lumbar portion.

Disseetion. — To display the lumbar part of the lumbo-dorsal fascia elear
away the remains of the origin of the latissimus dorsi, whieh springs irom
its posterior surface, and then reflect the serratus posterior inferior by
eutting through it at right angles to its fibres and turning it medially and
laterally towards its origin and insertion. As the lateral part is tumed
aside seeure its nerves of supply, whieh are derived from the lower inter-
eostal nerves, and enter its deep surface. Next remove the remains of the
origin of the serratus posterior inferior, and then the posterior layer of the
lumbar part of the lumbo-dorsal fascia will be eompletely exposed.

The Lumbar Part of the Lumbo-dorsal Paseia, — This portion
of the lumbo-dorsal fascia is separable into three lamellae, a
posterior, a middle, and an anterior. All three fuse together
laterally, where they beeome eonneeted with the internal
oblique and the transversus abdominis museles. Tht posterior
layer^ whieh is the strongest of the three, is a dense tendinous
aponeurosis. It is eontinuous above with the thoraeie part.
Below^ it is attaehed to the posterior part of the lateral lip of
the iliae erest, and to the dorsum of the saerum and the coccyx.

THE DISSEGTION OF THE HACK 167

MedieUly^ it is attaehed to the tips of the spines of the lumbar
yertebrae and the saerum ; and lattrally it blends ^ith the
posterior surface of the middle lamella (Fig. 71). The
aponeurosis of origin of the latissimus dorsi and the serratus
posterior inferior arise from its posterior surface.

Disseetion. — Make a longitudinal ineision through the {)ostcrior layer of
the lumbar part of the lumbo-dorsal fascia, midway tM.'twccn its medial
and its lateral borders. At eaeh end of the longitudinal ineision make a
transverse ineision extending from the spine medially to the lateral border
of the rounded mass of spmal museles lying under cover ()f the fascia.
Tum the medial part of the divided fascia towards the median plane, and
verify its attaehment to the vertebral spines and the supraspinous ligaments.
Pull the lateral part aside, and at the lateral border ot the mass of posterior
spinal museles it will be found to blend with a deeper layer, the middle
lamella. Push the mass of posterior spinal museles towards the median
plane, and follow the middle lamella of the fascia to its attaehment.

The middk lamella is attaehed medially to the tips of the
transverse proeesses of the lumbar vertebrae ; below to the
iliae erest, and above to the last rib. Laterally it blends
with the posterior and anterior lamellai, and immediately
lateral to its line of union with the posterior lamella the
internal oblique arises from its posterior surface. To expose
it thoroughly the mass of posterior spinal museles must be
pushed medially.

Disseetion. — After the middle lamella has been examined divide it
longitudinally, elose to its attaehment to the tips of the transverse proeesses,
and transversely along the line of the iliae erest, and turn it laterally. A
eonsiderable part of the posterior surface of the quadratus lumborum
musele will then be exposed. Displaee the lateral border of the quadratus
lumborum towards the median plane, and the anterior lamella of the
lumbar part of the lumbo-dorsal fascia will be brought into view.

•

The anterior lamella of the lumbar part of the lumbo-
dorsal fascia is attaehed medially to the anterior surfaces of
the roots of the transverse proeesses of the lumbar vertebrae ;
laterally it blends with the fused middle and posterior lamellae
to form the eommon aponeurosis of origin of the transversus
abdominis musele, and it is by means of the three lamellae
of the lumbar fascia that the latter musele arises from the tips
of the spines, and the tips and the roots of the transverse
proeesses of the lumbar vertebrse. The upper border of the
anterior lamella beeomes thiekened, and extends anterior to
the quadratus lumborum from the last rib to the trans-
verse proeess of the first lumbar vertebra as the areus
lumbo-eostalis lateralis (O.T. external areuate ligament); the

11—11 6

i68 HEAD AND NECK

lower border blends with the ilio-lumbar ligament. The
disseetor should verify these various attaehments by passing
his fingers over the posterior surface of the lamella from its
lateral to its mediai border, and from its upper to its lower end.

Disseetion. — After satisfying himself regarding the lamellae of the lumbar
part of the lumbo-dorsal fascia and their relations to the posterior spinal
museles, to the quadratus lumborum, and to the internal oblique and the
transversus abdominis museles, the disseetor should make a longitudinal
ineision through the anterior lamella, and the peri-renal fascia anterior to it ;
and, introdueing his finger through the opening into the extra-peritoneal
fatty tissue, he should serape away the latter until he exposes the kidney,
below the level of the last rib, and the adjacent part of the eolon, whieh
lies along the lower and lateral part of the kidney. After this has been
done he should reflect the serratus posterior superior and seeure its nerves
of supply whieh spring from the upper intereostal nerves and enter its deep
surface ; then he should remove the thoraeie part of the lumbo-dorsal fascia
and eommenee the study of the posterior spinal museles, beginning with
the splenius.

Mnseulus Splenius. — The splenius has a eontinuous origin
from the lower half of the ligamentum nuehae, and from the
spines of the seventh cervical and upper six thoraeie vertebrae.
Its fibres pass obliquely upwards and laterally, forming a thiek
flat musele, whieh soon divides into a cervical and a eranial
portion, termed respectively the splenius cervicis and the
splenius eapitis.

The splenius eeruids turns anteriorly and is inserted by
tendinous slips into the tubereles of the transverse proeesses
of the upper two or three cervical vertebrse, medial to the
levator seapulae.

The splenius eapitis passes under cover of the upper part
of the sterno-mastoid musele, and gains insertion into the
lower part of the mastoid portion of the temporal bone and
into the lateral portion of the superior nuehal line of the
oeeipital bone. To see this insertion, the sterno-mastoid
musele may be divided along the superior nuehal line, but
it must not be detaehed from the temporal bone.

Disseetion. — The deeper spinal museles must now be disseeted. B^n
by reflecting the splenius musele. Detaeh it from its origin and throw
it laterally and upwards towards its insertion. Whilst doing this, preserve
the eutaneous branehes of the cervical nerves whieh pieree it.

When the splenius eapitis is fully reflected, a small triangular spaee
will be notieed elose to the superior nuehal line of the oeeipital bone.
Anteriorly, it is bounded by the longissimus eapitis (O.T. traehelo-mastoid) ;
posteriorly, by the lateral border of the semispinalis eapitis (O.T. eom-
plexus) ; and above, by the superior nuehal line of the oeeipital bone.
The floor of this little spaee is formed by the superior oblique musde of

THE DISSECTION 0F THE BACK 169

the head, and it is travened by the oedpital artery, whieh in thii part of
its eourse gives off its deseending braneh (O.T. arteria prineeps eenrids),
and its meningeal braneh.

The Third Layer of MnidM.— Under this head are ineluded a series
of museular strands whieh streteh with a greater or less degree of eontinuity
along the entire length of the dorsal aspeet of the vertebral eolumn. In the
lumbar region they eonstitute a bulky Aeshy mass whieh niay l>c eonsidered
the main starting-point. This mass is the miiaoiiliiB ■ftcro-tpiiudii whieh
has the following origins : — (i) from the spines of all the lumbar Yertebne ;

(2) from the supraspinous ligaments whieh bind the lumbar spines togelher ;

(3) firom the dorsum of the saerum and from the posterior saeroiliae liga-
ment ; (4) from the posterior fifth of the iliae erest ; (5) from the deep
surface of the posterior layer of the lumbo-dorsal fascia. In great part the
superficial suriaee of this museular mass is covered l)y and is adherent to
the posterior layer of the lum1x>>dorsal fascia.

Superiorly the saero-lumbalis divides into three eolumns. The lateral
eolumn first separates from the general mass, and to it the name (>f ilio-
eostalis b given ; the middle eolumn is termed the longissimuSy and the
medial eolumn, whieh beeomes quite distinet only as the upper part of the
dorsal region is approaehed, is ealled the spinalis. The semispinalis musele
is also ineluded in the third layer.

The Ilio-eoatalis is a eolumn of museular bundles whieh extends from
the lumbar to the cervical region. It is separable into three segments
known, from below upwards, as the ilio-eostalis lumborum, the ilio-eostalis
dorsi, and the ilio-eostalis cervicis.

Ilio-eostalis Lumborum. — This musele and the longissinius dorsi beeome
distinet at the Ievel of the last rib, and the interval l)etween them is marked
by the exits of the lateral divisions of the posterior branehes of lower
thoraeie nerves,

The musele ends above in a series of six or se^ren slender tendons, whieh
are inserted into the angles or the eorresponding parts of the lower six or
seven ribs.

The Ilio-eostalis Dorsi (O.T. Museitlus Aeeessorius) arises by six or seven
slender tendons from the angles of the lower ribs, on the medial sides of the
tendons of insertion of the ilio-eostalis lumborum, and it is inserted by a
series of similar tendons into the angles of the upper six ribs and to the
transverse proeess of the seventh cervical vertebra.

The Ilio-eostalis Cervicis (O.T. Cervicalis Aseendens). — This highest
segmeht of the ilio-eostalis arises, on the medial side of the ilio-eostalis
dorsi, by four slips whieh spring from the third, fourth, fifth, and sixth ribs ;
it is inserted into the transverse proeesses of the fourth, fifth, and sixth
cervical vertebrge.

To display the ilio-eostalis properly, the disseetor should first evert the
lowest segment, and then in turn the middle and upper segments, but
whilst doing this he must take eare to preserve the lateral divisions of the
posterior branehes of the spinal nerves.

The Longplssimus is the middle and largest of the three musele eolumns.
It extends upwards, through the thoraeie and cervical regions, to the head,
and it also is separable into three segments : longissimus dorsi, longissimus
cervicis, and longissimus eapitis. The interval between the longissimus
and the spinalis is frequently diflficult to define, but if the fascia is carefully
eleaned from the lateral to the medial border of the longissimus in the
upper thoraeie region, the separation will beeome apparent, and after it
has been found the attaehments of the longissimus must be defined.

Longissimus Dorsi. — The dorsal part of the longissimus possesses two
rows of slips of insertion : a medial row of tendinous slips whieh are

lyo HEAD AND NECK

attaehed to the tips of the transverse proeesses of the thoraeie and the
aeeessory proeesses of the lumbar yertebrse, and a lateral row of museular
slips whieh are inserted into the lower ten ribs, on the lateral sides of their
tubereles, and to the transverse proeesses of the lumbar vertebrse, and to
the posterior surface of the middle lamella of the lumbar fascia.

Longissimus Cervicis{O.T. Transversalis Cervicis). — This portion of the
longissimus springs from the transverse proeesses of the upper four thoraeie
vertebroe, and is inserted into the posterior tubereles of the transverse
proeesses of the cervical vertebr3e from the seeond to the sixth inclusive.

Longissimus Capitis (O.T. Traekelo-mastoid). — The longissimus oapitis
lies in the neek under cover of the splenius. It arises in oommon with the
longissimus cervicis from the transverse proeesses of three or four of the upper
thoraeie ^ertebrse, and, in addition, from the artieular proeesses of a like
number of the lower cervical vertebr3e. The narrow Aeshy band whieh results
is inserted into the posterior part of the mastoid portion of the temporal
bone, under cover of the splenius eapitis and sterno-mastoid museles.

The Spinalis. — This is the most medial, shortest, and weakest of the three
eolumns, and the most difficult to define. Below, it is intimately blended
with the longissimus dorsi, but it may be regarded as taking origin by four
tendons from the spines of the upper two lumbar and lower two thoraeie
vertebr£e. These end in a small museular belly, whieh is inserted by a
series of slips into a very variable number of the upper thoraeie spines.
It is elosely eonneeted with the subjacent semispinalis dorsi.

Spinalis Cervicis. — This upward prolongation of the spinalis is not
always easy to define. It springs from the si^ines of the lower four cervical
^ertebrte and is inserted into the spines of the seeond, third, and fourth
cervical vertebrae.

Disseetion. — The oeeipital artery has already been seen erossing
the apex of the posterior triangle (p. 149), and its terminal branehes have
been disseeted as they ramify in the sealp (p. 157). The seeond part of
the vessel, whieh extends from under shelter of the mastoid proeess, along
the superior nuehal line of the oeeipital bone, to the point where it pierees
the trapezius to beeome superficial, ean now be exposed fully. To efFect
this, the longissimus eapitis (O.T. traehelo-mastoid) must be divided a
short distanee below its insertion, and, along with the splenius eapitis,
thrown upwards as far as possible.

Arteria Oeeipitalis. — The seeond part of the oeeipital
artery is now displayed. In the region of the mastoid proeess
it is very deeply plaeed ; indeed, no less than five struetures
lie superficial to it. These are (enumerating them in order
from the vessel to the surface) — (i) the origin of the posterior
belly of the digastrie musele ; (2) the mastoid proeess; (3)
the longissimus cervicis ; (4) the splenius eapitis ; and (5)
the sterno-mastoid.i As the artery runs posteriorly, it very
soon emerges from under cover of the first three of these
struetures, and a little farther on it leaves the shelter of the
splenius, and is then covered by the sterno-mastoid alone.
Issuing from under cover of the posterior border of that musele,

^ It is not uneommon to find the artery at this point of its eourse between
the splenius and the longissimus eapitis.

THE DISSECTION OF THE BACK 171

the artery erosses the apex of the posterior triangle, and
disappears under the trapesius, whieh it finally ()ierces near
the extemal oeeipital protuberanee, to reaeh the sealp. Two
museles eonstitute its deep relations — y\z^ the insertions of
the superior oblique and the semispinalis eapitis (O.T.
complexus).

The following brafuhes may be traeed from this portion of
the ooeipital artery : (i) deseending (O.T. arteria p)rince|>s
eeryids) ; (2) meningeal ; (3) museular.

The ramus deseendens (O.T. arteria prirueps eerrids) is a
twig of some size, whieh passes medially to the lateral border
of the semispinalis eapitis (O.T. complexus) ; there it divides
into a superficial and a deep braneh. The fonner ramities on
the surface of the semispinalis eapitis, whilst the latter sinks
under that musde, where it will be followed to its anastomosis
with the deep eendeal artery at a later stage in the disseetion.

The small meningeal hraneh enters the posterior eranial fossa
through the mastoid foramen, and supplies the dura mater
and eranial wall in this region.

The museular twigs go to the neighbouring museles.

The ffeins eorresponding to the oeeipital artery are two,
or perhaps three, in number. They drain the blood from the
oeeipital portion of the sealp, and open into the sub-oeeipital
plexus, whieh is drained by the vertebral and deep cervical
yeins. The most lateral of the oeeipital veins frequently
eommunieates with the transverse sinus (O.T. lateral) through
the mastoid foramen.

Disseetion, — The semispinalis eapitis, whieh has been exposed by the
reflection of the splenius and the turning aside of the longissimus cervicis
and longissimus eapitis, must now be eleaned, and whilst this is being done
and its attaehments are being defined, eare must be taken of the medial
divisions of the posterior branehes of the seeond, third, fourth, and fifth
cervical nerves. The first of these — or, in other words, the great oeeipital
— from its great size, runs little risk of injury, but the others are liable to
be overlooked. They all emerge from the substanee of the musele elose to
the median plane.

Semispinalis Capitis (O.T. Complexus). — The semispinalis eapitis is the
uppermost part of a museular eolumn eonsisting of three segments, whieh
are spoken of collectively as the semispinalis, and individually as the semi-
spinalis dorsi, the semispinalis cervicis, and the semispinalis eapitis. It
belongs to the third layer of museles, of whieh the greater number have
been disseeted already. The two lower segments will be disseeted subse-
quently, but it is convenient to examine the semispinalis eapitis at onee.
It is a thiek Aeshy mass whieh springs by tendinous slips from the transverse
proeesses of the upper six thoraeie vertebrae and the artieular proeesses of
the fourth, fifth, and sixth cervical vertebr3e. Its massive upper extremity

172

HEAD AND NECK

U inserted into a somewhat oval area on the oeeipital bone, between the
superior and inrerioi nuehal lines elose to the eKtemal oeeiintal erest. It is
sepaiated tioin its fellow musele of Ihe oppo^le side by the ligamentum
nuehii; ; and its most medial part, whieh is to a eettain extent distinet from
the genetal mass, is divided into two bellies by an inlermediale tendon and
is freqiiently spoken of as Ihe bhieuter eemieis. Oeeasionally the remainder
of the musele is also interseeted by a tendinous septum.

eate, not only on aeeount of the nerves whieh have been seen to peribrate
the musele to reaeh the surface, but also on aeeount of the stnietures
whieh it covers. In its upper part it lies over the sub-occipilal triangle
and the museles bounding it, whitst below it eoyers the semispinuia
ceivicis. A thiek dense fascia isplaeed over these subjacent parls, and iil
this lie eerlain of the cervical nerves and the anastomosis between the
deseending braneh of the oeeipital artery and the arteiia profunda eemdE.
The disseelor must speeially look fDr a smal! Iwig fiom the posterior
braneh of the sub-oeeipital nerve whieh enleis the deep suiface of the uppei
part of Ihe semispinalt^ eapitis, and foi a larger bianeh to the same musele
rroni the greal oeeipital netve.

LigamAiitum Hnelue (Fig. 72). — This is a strong fibious
partition plaeed in the median plane between the museles on

THE DISSECTION 0F THE BACK 1 73

eaeh side of the baek of the neeL It represents a |K)wcrful
elastie strueture in guadrupeds, whieh helps to sustain the weight
of tbe dependent head. In man, however, there is nut niu(*h
elastie tissue developed in eonneetion with it, and it ap|>cars
to be a eontinuation upwards of the supraspinous liganient
from the spine of the seventh cervical vertebra to tlie cxtcrnal
oeeipital protuberanee. In shape it is soniewhat triangular.
By its base it is attaehed to the external oeeipital erest ; by
its anterior border it is fixed by a series of sli|)s to the
posterior tuberele of the atlas, and to the bifid spines of the
cervical vertebrae, in the intervals between their tubereles. Its
apex is attaehed to the spine of the seventh cervical vcrtebra,
whilst its posterior border is, in a measure, frec, and givcs
origin to the traj>e2ius, rhomboid, serratus i>osterior superior,
and splenius museles.

Arberia ProAmda GenrieiB. — The deep eeruieal artery springs
from the costo-cervical braneh of the subclavian, and reaehes
the dorsum by passing posteriorly between the transvcrse
proeess of the last cervical vertebra and the neek of the first
rib. At the present stage of the disseetion it is seen aseend-
ing upon the semispinalis cervicis musele and anastomosing
with the deseending braneh of the oeeipital. Both vesscls
anastomose with twigs from the vertebral artery.

The arteria profunda cervicis is aeeompanied by a large
vein — the vena profunda eeruieis, This vessel begins in the
sub-oeeipital plexus, and it ends in the yertebral vein elose to
its termination. It reaehes this point by turning forwards
under the transverse proeess of the last cervical vertebra.

Posterior Branelies of the Spinal Nenres. — The nerves of
the baek must now be examined. They are the posterior
branehes of the spinal nerves. With four exceptions (viz.,
the first cervical, fourth and fifth saeral, and the eoeeygeal
neryes), eaeh posterior division will be found to divide into a
lateral and a medial division,

Examine these nerves successively in the cervical, dorsal, and lumbar
regions. It is well, however, to defer the disseetion of the saeral and
eoeeygeal nerves until the multifidus musele has been studied.

Cervical Begion. — In this region the posterior branehes
of the spinal nerves are eight in number. The posterior
braneh of the sub-oedpital or first nerue fails to divide into a
medial and a lateral division. It lies deeply in the sub-

174 HEAD AND NECK

oeeipital triangle, and will be examined when this spaee is
disseeted.

The posterior braneh of the seeond eeruieal nerue is very
large. It appears between the vertebral arehes of the atlas
and epistropheus vertebr3e. The posterior branehes of the
sueeeeding six eeruieal nerues arise from the eorresponding
spinal nerve-trunks in the intervertebral foramina. They turn
dorsally on the medial sides of the posterior intertransverse
museles, and appear in the intervals between the transverse
proeesses.

The lateral divisions are of small size, and are entirely
devoted to the supply of adjacent museles.

The medial divisions are not all distributed alike, nor
indeed do they present the same relations. Those from the
seeond^ third^ /ourth^ and fifth nerues run medially towards the
spinous proeesses, superficial to the semispinalis cervicis
musele, and under cover of the semispinalis eapitis. When
elose to the median plane they turn posteriorly, pieree the
semispinalis eapitis, splenius, and trapezius museles, and
beeome superficial. In their eourse to the surface they give
numerous twigs to the neighbouring museles.

The medial division of the seeond nerve is remarkable for
its large size. It receives the speeial name of great oedpitaL
It will be notieed turning round the lower border of the
inferior oblique musele, to whieh it supplies some twigs. In
passing to the surface it pierees the semispinalis eapitis (O.T.
complexus) and trapezius. To the former it gives several
twigs. The distribution of this nerve on the oeeiput has
been notieed already (p. 156).

The medial division of the third nerve also sends an oiTset
to the oeeipital portion of the sealp (p. 156).

The medial divisions of the lower three posterior branehes
of the cervical nerves resemble the preeeding, in so far that
they take a eourse medially towards the spinous proeesses.
They difFer from them, however, in running deep to the semi-
spinalis cervicis, and in being, as a rule, entirely expended
in the supply of museles.

Dorsal Begion. — The posterior branehes of the thoraeie
nerves make their appearanee in the intervals between the
transverse proeesses. The lateral divisions proeeed laterally,
under cover of the longissimus musele, and appear in the
interval between the longissimus dorsi on the one hand and

THE DISSECTION OF THE BA(K 17^

the ilio-eostalis on the other. The ufper stx or snrm ui these
nerves are exhausted in the supply of the mtdille ami Ijtcral
eolumns of the saerospinalts ; the lawtr^rt or stx, hiiwi:vrr.
are eonsiderably larger, and eontain both onotdr and scn9«ir\'
fibres. After giving up their motor fibres to the niuv Icv
they beeome superlieial, by piereing the serratus (Kisterinr in
ferior and the latissimus dorsi, in a line mith the angles (if
the ribs. The eutaneous distribution of these mnt-s hxs
already been examined by the disseetor of the up|H.*r linih.

The tnedial divisions also are distributed diHerently in ihe
upper and lower portions of the dorsal region. The lowtr
five or six are very small, and end in the multifidus
musele. The upper six or seven pass medially l)etwcen the
multifidus and semispinalis, and after supplying the museles
between whieh they are situated, they beeome suj)erficial. In
passing towards the surface they pieree the splenius, rhom-
boids, and trapezius museles, and thus gain the su{)erficia]
fascia, where they have been disseeted already.

Ltimhar B^on. — The medial dirisions of the [)osterior
branehes of the five lumbar nerves are small, and, like the
eorresponding twigs in the lower dorsal region, they havc
a purely museular distribution. * They end in the multifidus.

The iateral divisions sink into the substanee of the saero-
spinalis, and are eoneemed in the supply of that musele, and
also of the lumbar intertransverse museles. The upper three
of these nerves are of large size, and beeome eutanoous by
piereing the superficial lamella of the lumbo-dorsal fascia.
They have already been traeed by the disseetor of the lower
limb to the skin of the gluteal region. The lowest lateral
division eommunieates with the eorresponding braneh of the
first saeral nerve.

Blood Vessels of the Baek. — In the eeruieal region the
disseetor has already notieed the arteria profunda cervicis,
and the deseending braneh of the seeond part of the oeeipitai
artery. Deep in the sub-oeeipital region he will subsequent]y
meet with a small portion of the vertebral artery. In addition
to these, however, minute twigs may be discovered, in a well-
injected subject, passing posteriorly from the vertebral artery
in the intervals between the transverse proeesses, and also in
the sub-oeeipital spaee. These supply the museles, and
anastomose with the other arteries in this region.

In the dorsalregion \ht posterior branehes oi the aortie inter-

176 HEAD AND NECK

eostal arteries make their appearanee between the transverse
proeesses. Eaeh of these vessels reaehes this point by .*
passing dorsally in the interval between the body of a vertebra ^
and the anterior costo-transverse ligament. It is assoeiated
with the eorresponding posterior braneh of a spinal nerve^
and is distributed with it to the museles and integument of
the baek.

In the lumbar reglon similar branehes are derived from the
lumbar arteries. They are distributed in the same manner.

In both dorsal and lumbar regions these vessels, before
reaehing the baek, furnish small spinal branehes whieh enter !
the vertebral eanal through the intervertebral foramina. ■■[
These will be traeed at a later period. \

The veins aeeompanying the dorsal branehes of the lumbar
and intereostal arteries pour their blood into the lumbar
and intereostal veins. They are of large size, being joined
by tributaries from the posterior vertebral venous plexus, and
also by others from within the vertebral eanal.

Disseetion. — The remains of the third layer of spinal museles must now
be disseeted. They are the semispinalis dorsi and semispinalis cervicis.

The semispinalis cervicis is already exposed ; but to display the
semispinalis dorsi it is neeessary to remove the spinalis dorsi musele.

The semispinalis dorsi is eomposed of a series of museular slips, with
long tendons at either end, whieh arise from the transverse proeesses of the
sixth to the tenth thoraeie vertebr£e. It is inserted into the spines of the
upper four thoraeie and lower two cervical vertebr9e. The semispinaUs
cervicis lies under cover of the semispinalis eapitis. It springs from the
transverse proeesses of the upper five thoraeie ^ertebrse, and is inserted into
the spines of the seeond to the fifth cervical vertebrae. The slips eomposing
the semispinalis museles streteh over five or more ^ertebrse.

Disseetion. — The fourth layer of museles must now be examined. It
ineludes the multifidus, the rotatores, the interspinales, theintertransversales,
and the reeti and oblique museles of the sub-oeeipital region. The latter have
already been exposed by the reflection of the semispinalis eapitis (complexus).
To display the other members of the group the semispinalis dorsi and
cervicis must be detaehed from the spines and drawn aside, and the
saerospinalis must be separated from the lumbar and saeral spines and
turned laterally, if this has not already been done in traeing the nerves.

Museulus MultiAdus. — In the lumbar and saeral regions the multi-
fidus will be seen to eonstitute a thiek Aeshy mass, whieh elings elosely
to the vertebral spines. In this situation it has a very extensive origin —
viz., (i) from the deep surface of the aponeurotie origin of the saerospinalis ;

(2) from the posterior surface of the saerum as low as the fourth aperture ;

(3) from the posterior saero-iliae ligament ; (4) from the posterior superior
spine of the ilium ; and (5) from the mammillary proeesses of the lumbar
vertebr8e. In the thoraeie region it takes origin from the transverse proeesses
of the vertebr3e, and in the cervical region from the artieular proeesses of at
least four of the lower cervical vertebr8e. The bundles whieh eompose the

THE DISSECTION OF THE H.\(K 177

maldfidus pass over two, three, or four vertc)tr.r. an*! .irt* inMitt-il ti:(M-s iif thr iiii>v.il>Ii \i-iti>^r r .10
high up as the epistropheus <f ).T. axis).

Muenli Sotatorei. — These are a series uf mii.iII iiiu<h-1< h %«)ui Ii iiu\ l>r
exposed by raising the multiAdus. In the (lor^.il rt-f;i>>ii 1-31 )i iiiu<» li* Hpriii^'»
from the root of a transverse proci>ss, and is in'4-rt(-<l iiit>t tlu- I.1111111.1 ur ihe
vertebra immediately a)K>ve, elose to ihi* ri>«»i i»f !)i»' H|in"U-» iriKi-*x.
Somewhat similar museles have lieen desrrilK-il in thir t (-rvi( .il .iiirr ^uiie-rtiei.il olips \«hi« h «-..ihm 1 1
altemate vertebne with eaeh otner.

MoBeiili IntenpiiialM aad IntartraiiiTtnarii. 'rin- n:/^^ /^in .-<

museles ean hardly be said to exist in the dor'^1 n-i^ion. i-xi-r|it in it<. ui ;« i

and lower piarts, where the}' are present ina ruiliiiu*nt.iry « ••ii'hii>>M. l:i

the neek they are arranged in pairs, oeeupyini; eaeh inirrN|.in..iiN iii:.i\ I,

with the exception of that between the opistropluus :in<i ,111.1-«. In ili«-

lumbar region also they are well marked and in |>;ur< : Ihti- ihey ait-

attaehed to the whole length of the spinous procc>sc>. rht- ////<-/■// i/;/..-v; e

mtisdes are strongly develoi)ed in the luint>ar rcj;i«»n. an! iK."t u]y tlu- mtire

length of the intertransverse inlervals. AddititMial ri»un'!iii t'.i««ii<'uli niay

be observed passing between ihe access«iry prtK\s««iN. TIu-ni- an- ttTnu<i

Wit interaeeessorii. In the dorsal ref^on inttTtransvtT«»o nuiM l. s ]mmii1\

developed — are found only in the lower three or ft)ur >]ia(\N. In iIk- •,r:u-,i:

region they are present in pairs and will Ik: c\aniiiuti -^ulisi-<juintly.

Leyatores eostamm. — These eonstituie a suries ()f twtUe
fan-shaped museles, whieh are classifiecl as niiisrks()f ihe ihoraN,
but they are exposed when the longi.ssimus aiid ilio eostalis
are removed, and therefore should bc cxanHnod now. 'i'lu y
pass from the transverse proeesses to the ril)s. The firsi
musele of the series springs from the tip of the transversc
proeess of the last cervical vertcbra, and, exi)anding as
it proeeeds downwards and laterally, it is inserted int(; the
outer border of the iirst rib, immediately beyond the
tuberele. Eaeh of the sueeeeding museles takes origin from
the tip of a thoraeie transverse proeess, and is inserted into
the outer surface of the rib immediately below, along a line
extending from the tuberele to the angle.

Posterior Branehes of the Saeral Nerves. — These are
very small. The upper four will be found emerging from
the posterior saeral foramina ; the fifth appears at the lower
end of the saeral eanal.

To expose the upper three the multifidus covering the
upper three saeral apertures must be carefully removed.
Eaeh of these three nerves will be found to divide in
the usual manner into a medial and lateral division.

The medial dwtswns are very fine, and end in the
multifidus.

The lateral dwisions are somewhat larger, and join

voL. II — 12

178 HEAD AND NECK

together so as to form a looped plexus upon the dorsum of the
saerum. This eommunieates above with the lateral division
of the last lumbar nerve and below with the posterior braneh
of the fourth saeral nerve. Branehes proeeed from the loops
to the surface of the saero-tuberous ligament (O.T. great saero-
seiatie). Einally they beeome superficial by piereing the
glutaeus maximus musele, and they supply a limited area of
skin over the glutaeal region. They have already been
examined by the disseetor of the lower limb.

The lowest two posterior branehes of the saeral nerves
do not separate into medial and lateral divisions. They
are very small, and, after eommunieating with eaeh other,
and also with the eoeeygeal nerue^ they distribute filaments to
the parts on the posterior aspeet of the lower portion of the
saerum and on the dorsal aspeet of the coccyx.

Twigs from the lateral saeral artery aeeompany the saeral
nerves and anastomose with twigs from the glutseal arteries,

Posterior Braneh of the Goeeygeal Nerve. — ^This is a
slender twig whieh emerges from the inferior opening of the
saeral eanal, and, after being joined by a filament from the
last saeral nerve, is distributed on the dorsum of the coccyx.

Posterior Vertebral Venous PlexiLS. — A plexus of veins is
situated upon the superficial aspeet of the vertebral arehes
subjacent to the multifidus musele. This plexus eolleets
blood from the integument and museles of the baek, and
in the thoraeie and lumbar regions pours it into the posterior
tributaries of the intereostal and lumbar veins. In the neek
it is espeeially well marked, and its blood is emptied into the
vertebral veins. Not many of these venous ehannels will be
seen in an ordinary disseetion. They are, however, a souree
of serious trouble during operations upon the vertebrae.

Disseetion. — The fourth day after the body is plaeed upon its fece
must be devoted to the disseetion of the sub-oeeipital triangle, and the
fifth day to the display of the meduUa spinalis (O.T. spinal eord), its
membranes, nerve-roots, and blood yessels.

If the disseetor is pushed for time, it is better that he should proeeed at
onee to expose the spinal medulla, and defer the disseetion of the sub-
oeeipital region until the head and neek have been removed from the body.

Sub-Occipital Spaee. — The sub-oeeipital spaee is a small
triangular area, exposed by the reflection of the semi-
spinalis eapitis (O.T. complexus) and the splenius musele.
It is bounded by three museles — (i) the reetus eapitis

THE DISSEGTION OF THE BUK .79

posteiior ma}or fonns its uppei and medial IwundaTy ;
(1) the obliquus iDferior limits it below ; and (3) ihe oblitiiius
niperior bounds it above and lo Ihe lateral side. /A
^oer eonsists of tvo Btmettires — viz. Ihe posterior areh of
Ibe atlas and the thin posterior atlanto-oeeipiial membrane.

It eontains a portion of the vertebral artery and the posterior
braneh of the sub-oeeipital or first cervical nerve.

Z>/!/«/i(>H.— Before eleaning the museles bounding Ihe Iriangle, the

poslerior braneh of the sub-oeeipitaL nerve muBl be seeuted. Tlus ean

best be done by Iraeing inlo the spaee Ihe minule twig whieh it has been

seen to give lo the deep suriaee of the semispinalis eapitis, or, if this has

II— 12«

i8o HEAD AND NECK

not been retained, by endeavouring to fmd the twig whieh it gives to the
reetus eapitis posterior major. The tissue in whieh the nerve lies is very
dense, and the disseetion is in consequence somewhat difficult.

Eeetus Gapitis Posterior Major. — This musele springs by a
pointed origin from the spine of the epistropheus (O.T. axis),
and, expanding as it passes upwards and laterally, it is inserted
into the oeeipital bone along the lateral portion of the inferior
nuehal line and the surface immediately below.

Eeetus Oapitis Posterior Minor. — This is a small fan-
shaped musele, plaeed to the medial side of, and overlapped
by, the preeeding musele. It takes origin from the tuberele
on the posterior areh of the atlas, and is inserted into the
medial part of the inferior nuehal line of the oeeipital bone
and the surface between this and the foramen magnum.

Obliquus Oapitis Iiiferior.— This musele extends from the
extremity of the spine of the epistropheus to the posteridr
border of the transverse proeess of the atlas. The great
oeeipital nerve will be seen hooking round its lower border.

Obliquus Oapitis Superior. — This musele springs from
the transverse proeess of the atlas, and is inserted into
the oeeipital bone in the interval between the nuehal lines,
below and to the lateral side of the semispinalis eapitis.

Posterior Braneh of the Sub-Oeeipital Nerve. — The
posterior braneh of the sub-oeeipital nerve does not divide
into medial and lateral divisions. It enters the sub-oeeipital
triangle by passing dorsally, between the posterior areh of
the atlas and the vertebral artery, and at onee breaks up
into branehes whieh go to supply five museles — viz. the two
posterior reeti, the two oblique museles, and the semispinalis
eapitis. In addition to these museular twigs it gives a eom-
munieating, and sometimes a eutaneous filament.

The eommunieating braneh generally proeeeds from the
nerve to the obliquus eapitis inferior, and joins the great
oeeipital nerve. The eutaneous braneh, when present, aeeom-
panies the oeeipital artery to the integument over the oeeiput.

Arteria Vertebralis. — Only the third portion of this vessel
lies in the sub-oeeipital triangle. Emerging from the foramen
in the transverse proeess of the atlas, it runs posteriorly and
medially in the groove upon the posterior areh of the same
bone. In this eourse it lies immediately posterior to the lateral
mass of the atlas and above the sub-oeeipital nerve. It leaves
the spaee by passing anterior to the thiekened lateral ex-

THE DISSECTION OF THE BACK 181

tension of the posterior atlanto-oeeipital membrane, whieh
nins from the posterior areh of the atlas to the i^osterior lip
of its artieular proeess and is ealled the obIi()ue ligamont
of the atlas ; then it pierees the dura mater and entors the
vertebral eanaL

Small branehes proeeed from the vertebral arter>- in this
situation to supply the parts in its immediate neighbourhood,
and to anastomose with the deseending braneh of ihe oeeipital
artery and the arteria profunda cervicis.

DiBseetioii to op«ii the Yerielnral Ganal.— The first step eonsists in
thoroughly eleaning the laminae and spinous proeesses u{K>n iHith sides.
The multitidus must be eompletely removed froni the tU^rsuni of the
saerum. At the same time the posterior branehes of ihe ncrves niust
be retained, so that their eontinuity with the various spinal nerve-trunks
may be afterwards established. The posterior wall of the vertehral eanal
should now be remoyed in om pieee by sawing through the laniin;ir on
either side, and diyiding the ligamenta flava, froni the third cervical
yertebra down to the lower opening of the eanal on the baek of the saerum.

In making this disseetion the student must attend to the following
points : — (i) the eut should be direeted through the laminiv elose to the
medial sides of the artioular proeesses ; (2) the saw must be used in an obli(jiie
plane, so that the eut through the laminx slants slightly medialwards ;
(3) in eutting through the cervical laminae the head and neek should hang
oyer the end of the table, and be flexed as mueh as }X)ssil)le, whilst the
saw is worked from below upwards ; (4) in the ease of the lumbar region,
where, indeed, most difficulty will be met, a high bloek must be plaeed
under the abdomen of the subject, whilst the bloeks supporting the ehest
and pelvis are removed. It will probably be neeessary at this }X)int to
have reeourse to the hammer and ehisel.

The laminse and spinous proeesses whieh are thus removed are eonneeted
with eaeh other by the ligamenta flava and the suprasi^inous and inter-
spinous ligaments. They should be laid aside for the present. A de-
seription of these ligaments will be found on p. 358. When the speeimen
is firesh, however, the disseetor should test the high elastieity or the
ligamenta flava by stretehing the sp>ecimen.

Between the dura mater and the walls of the eanal, the disseetor will
notiee a quantity of loose areolar tissue and soft fat. The latter is
espeeially plentiful in the saeral region, where it somewhat resembles the
marrow in the meduUary cavity of a long bone. Great numbers of large
veins and minute arteries ramify in this areolo-fatty material.

Arterise Spinales. — In a well-injected subject a minute
spinal artery will be seen entering the yertebral eanal through
eaeh intervertebral foramen. These arteries are derived from
different sourees in the different regions of the spine. In the
eeryieal region they eome from the yertebral artery, and in
the thoraeie region from the posterior branehes of the inter-
eostal arteries ; in the lumbar region from the dorsal branehes
of the lumbar arteries. They supply the spinal medulla and its

11—12 6

i82 HEAD AND NECK

meninges, the bones, the periosteum, and the ligaments ; and
their arrangement is very mueh the same in eaeh of the
three regions.

Eaeh spinal artery may be looked upon as giving off three
main twigs: of these, one, termed the pre-laminar braneh^
a very small twig, ramifies upon the deep surface of the
vertebral arehes and ligamenta flava ; another, the neural
braneh^ ean be followed to the dura mater, whieh it pierees
immediately above the point of exit of the eorresponding
spinal nerve; whilst the third, \ht post-eentral branehy is earried
medially, anterior to the dura mater, towards the posterior
surface of the vertebral bodies, and divides into an aseending
and a deseending twig. These anastomosewith the eorrespond-
ing twigs above and below, and in this manner a eontinuous
series of minute arterial areades is formed, from whieh
branehes pass medially to form a series of eross anastomoses
with the eorresponding vessels of the opposite side.

In the eeruieal re^on small branehes from the aseending
cervical artery also find their way into the vertebral eanal ;
whilst in the saeral portion of the eanal the disseetor will find
branehes from the lateral saeral arteries.

Intemal Yertebral Venoiis Plexus. — This plexus extends
along the whole length of the vertebral eanal, and eonsists
essentially of four subsidiary longitudinal plexuses, two
anterior and two posterior, whieh anastomose freely with
eaeh other.

The posterior plexuses are united by many eross branehes,
whieh run along the deep aspeet of the vertebral arehes and
ligamenta flava. Above, they eommunieate with the oeeipital
sinus, whilst all the way down they are eonneeted with the
posterior vertebral venous plexus by wide ehannels whieh pieree
the ligamenta flava. Laterally they send branehes through
the intervertebral foramina to join the posterior branehes of
the intereostal and lumbar veins.

The anterior pleoeuses eannot be disseeted whilst the medulla
spinalis (O.T. spinal eord) and its membranes are in situ^ but
it is convenient to deseribe them at this stage. Ihdeed, the
disseetion is one of eonsiderable difficulty, even under the
most advantageous eireumstanees. They form two main
longitudinal venous ehannels plaeed one upon either side of
the posterior longitudinal ligament of the vertebral bodies, and
they are joined by transverse branehes whieh eross the median

THE DISSECTION 0F THE BACK 183

plaue anterior to that ligament opposite eaeh vertcbral body.
Eaeh trarisverse vem receives large tributaries from the in-
terior of the vertebra. Superiorly, eaeh of the niain longitudinal
ehannels eommunieates with the oeeipital sinus or the basilar
plexus within the eranium ; and eaeh of the posterior ehannels
gives off a braneh whieh emerges above the posterior areh of
the atlas to join the eommeneement of the vertebral vein.
Opposite the various intervertebral fibro-cartilages the anterior
plexus sends off branehes whieh run towards the inter-
vertebral foramina, where they join with eorresponding branehes
of the posterior plexus, to form the intervertebral veins whieh
aeeompany the eorresponding spinal nerves.

Memnges of the Medulla Spinalis (Fig. 74). — The medulla
spinalis, like the brain, with whieh it is eontinuous, is enveloped
bythree membranes termed memnges, The most external
investment is a strong fibrous membrane ealled the dura
fnater\ the seeond, in order from without inwards, is a non-
vascular tunie termed the arachnoid\ whilst the third and
most internal is the pia mater, These membranes are
direetly eontinuous with the eorresponding investments of
the brain.

Disseetion. — Theouter surface of the dura mater must now be eleaned.
This is effected by removing the loose areolar tissue, soft fat, and posterior
intraspinal veins from the yertebral eanal. It is neeessary, also, to define
earelully the numerous lateral prolongations whieh the membrane gives to
the spinal nerves.

Dura Mater Spinalis (Fig. 74). — In the vertebral eanal the
dura mater eonstitutes an exceedingly dense and tough fibrous
tube, whieh extends from the foramen magnum above, to the
level of the seeond or third pieee of the saerum below. It is
separated from the walls of the vertebral eanal and its lining
periosteum by an interval, whieh is filled by loose fat and areolar
tissue, and the internal vertebral venous plexus. Even
before the membranous tube is laid open, the disseetor ean
readily satisfy himself that it forms a very loose sheath around
the spinal medulla and the nerve-roots whieh form the eauda
equina ; in other words, it is very eapaeious in eomparison
with the volume of its eontents. Its ealibre, moreover, is by
no means uniform ; in the cervical and lumbar regions it is
eonsiderably wider than in the thoraeie region, whilst in the
saeral eanal it rapidly eontraets and>finally ends by blending
with the filum terminale, a fibrous thread whieh is prolonged
II— 12c

i84 HEAD AND NECK

downwards through the saeral eanal from the extremity of the
medulla spinalis (O.T. spinal eord),

The eylindrieal tube of spinal dura mater does not lie
free within the vertebral eana!, although its attaehments are
of sueh a nature that they do not in any way interfere wilh
the free movement of the yertebral eolunin. Above, the dura
mater is firmly attaehed to the seeond and third cervical

vertebr£e, and around the margin of the foramen magnum ;
below, the tilum terminale, on whieh it terminates, ean be
traeed as far as the dorsal aspeet of the coccyx, where it is
lost by blending with the periosteum. On either side the
spinal nerve-roots, as they pieree the dura mater, earry with
them into the intervertebral foramina tubular sheaths of the
membrane, whieh are attaehed to the margins of the foramina,
whilst, anteriorly, loose librous prolongations — more numerous
above and below than in the dorsal region — eonneet the tube
of dura mater to the posterior longitudinal ligament of the

THE DISSEGTION 0F THE BA(:K 185

vertebral eolumn. No eonneetion of any kind cxists lM.*twccn
the dura mater and the vertebral arehes or ligamenta flava.

Disseetion. — The tube of dura mater may now l»c u|ii'nct! with the
seissors. The ineision should 1)e earrieil through the nunilirane in the
median plane. Care, however, must 1)C taken not to injurc the delieate
araehnoid, whieh is subjacent.

Caviim SaMunde. — The subdural cave (O.T. spaee) is the
eapillary interval between the dura niater and the araehnoid
(Fig. 74). The deep surface of the dura, whieh is lurned
towards this spaee, is smooth, moist, and polished. The
disseetor will notiee, upon either side, the series of apertures
of exit for the roots of the spinal nerves. These are ranged
in pairs opposite eaeh intervertebral foramen. The subdural
spaee is prolonged laterally, for a short distanee, upon eaeh
of the nerve-roots, and has a free eommunieation with the
lymph paths present in the nerves.

Viewed from the inside of the tube of dura niater, eaeh of the two
nerve-roots belonging to a spinal nerve is seen to earry wiih it a s])ecial
and distinet sheath. When examined, however, on the outside of the tube
of dura mater, they appear tobe envehiped in one sheath, beeause the two
sheaths are elosely held together on the outside hy intervening connective
tissue, whioh ean be removed with a little careful elisseetion. When this is
done, the two tubular sheaths will be seen to remain distinet as far as the
ganglion on the posterior root of the nerve. At that point they blend
with eaeh other.

Araehnoidea Spinalis (Fig. 74). — The araehnoid resembles
the dura mater in forming a loose, wide inyestment for
the spinal medulla. Unlike the dura, however, it is remark-
able for its great delieaey and transpareney. The sae whieh
it forms is most eapaeious, and ean be demonstrated most
easily towards its lower part, where it envelops the extremity
of the spinal medulla and the eoUeetion of long nerve-roots
whieh eonstitute the eauda equi?ia. Make an ineision into it,
and insert the handle of the sealpel, or, better still, inflate the
sae with air by means of a blowpipe. Above, the araehnoid
beeomes eontinuous, at the level of the foramen magnum, with
the araehnoid membrane of the brain, whilst, laterally, it is
prolonged upon the various nerve-roots, thus eontributing
to eaeh a tubular sheath. It terminates blindly below at the
level of the seeond or third saeral vertebra.

Cavum Subaraehnoideale (Fig. 74). — This term is applied
to the wide spaee between the araehnoid and pia mater. It
is oeeupied by a variable amount of eerebro-spinal fluid, and

i86 HEAD AND NECK

is direetly eontinuous with the eranial sub-araehnoid spaee.
Three ineomplete septa partially subdivide the spinal sub-
araehnoid spaee into eompartments. One of these septa is a
median partition ealled the septutn subaraehnotdeale^ whieh eon-
neets the pia mater covering the posterior aspeet of the spinal
medulla with the araehnoid. In the upper part of the cervical
region the subaraehnoid septum is represented merely by a
number of strands passing between the two membranes ; in the
lower part of the cervical region and in the thoraeie region it is
almost eomplete. The two other septa are formed by the liga-
menta dentieulata. These spread outwards from eaeh side of
the medulla spinalis, and will be studied with the pia mater.

Disseetion. — Take away the araehnoid mater from a portion of the spinal
meduUa, and proeeed to the study of the pia mater.

Pia Mater Spinalis. — This is a firm vascular membrane,
elosely adherent to tl^e surface of the medulla spinalis (O.T.
spinal eord). It is thieker and denser than the pia mater
of the brain, largely owing to the addition of an outer layer
of fibres whieh run chiefly in a longitudinal direetion. The
pia mater sends a fold into the antero-median fissure of the
medulla spinalis, and the septum whieh oeeupies the posterior
median fissure of the medulla spinalis is firmly attaehed to
its deep surface. Anteriorly, in the median plane, the pia
mater is thiekened to form a longitudinal glistening band,
whieh receives the name of the linea splendens, Of eourse,
this ean be seen only after the medulla spinalis (O.T. spinal
eord) has been removed from the vertebral eanal. The blood
vessels of the medulla spinalis lie between the two layers of the
pia mater before they enter the substanee of the spinal medulla,
and the various spinal nerves receive from it elosely fitting
sheaths whieh blend with their connective-tissue sheaths.

Ligamentum Dentieulatum (Figs. 74 and 75). — ^This is a
remarkable band, whieh stretehes laterally from either side
of the meduUa spinalis, and eonneets it with the dura mater.
Its pial or medial attaehment extends in a eontinuous line,
between the anterior and posterior nerve-roots, from the level
of foramen magnum above to the level of the body of the first
lumbar vertebra below. Its lateral margin is widely serrated or
dentieulated. From twenty to twenty-two dentieulations may
be reeognised, and the highest is attaehed to the margin of
the foramen magnum. They oeeur in the intervals between the

THE DISSECTION OF THE BACK

1S7

spinal nerves, aod, pushing the aiaehnoid bcfore them, they
are attaehed by their pointed extremttics to ihe inner surraee
of the dura mater.

The ligamenta dentieulau maintain Ihe meduUa 5[iina]is
(O.T. spinaleord) in the middleof the tubeotdura materand
partially subdivide the sub-araehnoid spaee into an anterior
and a posterior eompartment In the anterior c(im[»artment
the anterior nerve-roots pass latetally ; the posterior eomparl-
ment eontains the posterior nerve-roots, and is imperfectly
subdivided into two lateral subdivisions by the septum
postieum.

Medulla Spmalis
(O.T. Spinal Gord).
— The spinal meduUa
itself may now be
studied in sifu. It is
aeylindrieal strueture,
slightly Aattened an-
terior-ly and pos-
teriorly,whichextends
from the foramen
magnum, where it is
conti!iuous with the
meduUa oblongata of
the brain, to t
lower border of the
body of the first or
the upper border of the body of the seeond lumbar vertebra.
Its lower end rapidly tapers to a point, and is termed the
iemus medullaris. From the extremity of this, a slender fila-
ment, termed the filum krminak, is prolonged downwards to
the dorsal surface of the coccyx.

In the female the average length of the meduUa spinalis is
43 cm. ; in the male it is 45 cm.

Throughout the greater part of the thoraeie region of the
spine the meduUa spmalis presents a uniform girth, but in the
cervical and lower thor-ieie regions it shows marked swellings,
termed respectively the inlumesuntia cervicalis and intumeseentia
lumbalis. From these enlargements proeeed the nerves whieh
supply the upper and lower limbs The eeniieal swelling is the
more evident of the two It begins at the upper end of the
meduUa spinalis (O.T. spmal eord) and attains its greatest

FiG. 75.— Lalenilviewof Ihe Medulla Spinali
Dura Maier, and Liganieolum Denlieulatur
(Hirschfeldand Lenill^)

iS8

HEAD AND NECK

breadth (13 to 14 mni.) opposite the fifth or sixth cervical
vertebra. Below, it subsides opposite the seeond . thoraeie
yertebra. The lumbar swelling begins at the level of the tenth
thoraeie yertebra, and attains its maximum transverse diameter
(11 to 13 mm.) opposite the last thoraeie vertebra. Below, it
rapidly tapers into the
eonus medullaris.

Filnm Teminale. —
This delieate thread-like
hlament lies amidst the
numerous long nerve-roots
whieh oeeupy the lower
[lart of the vertebral eanal,
but it ean readily be de-
teeted from these (i) by
its silvery glistening ap-
pearanee, and (z) by its
eontinuity with the ex-
tremity of the eonus
meduUaris.

Although the eentral

eanal of he medulla

nd spnals sp olonged

^ down n s nteno

fo nea ly half ts

leng h and neryous

^ ^ elemen s ean be

a m raeed n s sub-

s an e fo a 1 ke

d stan e he filum

e m n le s ch efly

eomposed of p a

ma e The Inea

^^gh h P "//«:/ n and the

lowe ends of he

u a a m y also be ons de ed o be eon nued

the level of he seeond o h d a al veneb a

ape ed end of he ube of du a ma er and

and finally ea h ng he lowe

s by blend ng t '

it pierees

receives an n e n en f 1

end of the sa al eanal

periosteum on he do sal surfa e of he coccyx o the last

pieoe of the saerum

THE DISSECTION 0F THE BACK 189

In length it measures about six inehes. The part within
the tube of dura is termed the fiium terminaU intemum^ the
portion outside is \h^filum terminale extemum.

Spmal Nerve8. — Thirty-one spinal nerves take origin from
eaeh side of the medulla spinalis (O.T. spinal eord). These
are classified into five groups, aeeording to the yertebrae with
whieh they are assoeiated. The thoraeie, lumbar, and saeral
neryes eorrespond in number with the yertebrae in eaeh of
those regions — thus, there are twelve thoraeie, five lumbar,
and five saeral nerves, eaeh of whieh issues from the vertebral
eanal below the vertebra with whieh it numerieally eorresponds.
In the cervical region, however, there are eight nerves, the
first of whieh eomes out between the oeeiput and the atlas,
and is therefore distinguished by the speeial name of the si^b-
oedpital neroe, There is only one eoeeygeal nerve on eaeh
side.

Spinal Nerve-Boots (Figs. 75 and 77). — Eaeh spinal nerve
springs from the side of the spinal medulla by tivo roots — an
anterior 2in6. 2iposterior. Except in the ease of the sub-oeeipital
nerve (where the posterior root is sometimes absent), the
posterior nerve-root is the larger of the two. In addition,
the posterior root is distinguished by possessing an oval
ganglion, termed the spinal ganglion. There is, also, a
wide physiologieal difference between the two roots — the
posterior root is eomposed of afferent fibres, the anterior root
eonsists of efferent fibres. Immediately beyond the ganglion
the two roots unite to forni the spinal nerue-tnmk, whieh
eontains a mixture of both efferent and afferent nerve-fibres.

The mode of attaehment of the two nerve-roots to the side of
the medulla spinalis is somewhat different in the two eases.
In eaeh instanee they are attaehed by several separate fila
radieularia^ whieh spread out from eaeh other as they approaeh
their attaehments. In the ease of the posterior root the
fila enter the spinal medulla consecutiveIy along a eontinuous
straight line and at the bottom of a slight furrow. The fila
of the anterior root, on the other hand, are not so regularly
plaeed. They emerge from the medulla spinalis over an area
of some breadth. The portion of the medulla spinalis whieh
stands in eonneetion with a pair of nerves receives the
name of a " neural segment."

It will be noted that the size of the nerve-roots differs greatly.
The lower lumbar and upper saeral nerve-roots are mueh

igo HEAD AND NECK

the larger, whilst the lower saeral and the eoeeygeal roots
are the smaller. In the cervical region the roots inerease in
size from above downwards, but more rapidly in the lower
members of the group ; in the thoraeie region the roots of the
iirst nerve are large, but those whieh sueeeed it are small and
of uniform size.

In relaliye length, and in the direetion whieh they follow in
the vertebral eanal, the nerve-roots also show great differences,
This is due to the medulla spinalis being so mueh shorter than
the eanal in whieh it lies. In the upper part of the cervical
region the nerve-roots are short, and proeeed laterally in a
more or less horizontat direetion. Below the upper cervical

region the nerve-roots beeome more oblique, and the lower
the origin of the nerve the longer is its eourse in the eanal.
The arrangement of the lower thoraeie, the lumbar, saeral, and
eoeeygeal nerve-roots is partieularly eharaeteristie. They are
exceedingly long, and deseend vertically from the lower
portion of the meduUa spinalis, forming a bundle whieh is
ealled the eauda equina.

Mode of Ezit of Spinal Neires ftom Vertebral OanaL —
The lower six cervical nerves, the thoraeie nerves, and the
lumbar nerves make their exit through the intervertebral
foramina ; whilst eaeh of the two branehes of the upper four
saeral nerves finds its way out by a saeral foramen. The
upper two cervical neryes, the fifth saeral nerve, and the
eoeeygeal nerve, however, fo]low a diAerent eourse, The
sub-oeeipital emerges by passing over the posterior areh of

THE DISSEeriON 0F THE BACK

191

the atlas, and the seeond cervical nerve by passing over the
yertebral areh of the epistropheus {O.T. axis). The fifth
saeral aud the eoeeygeal nerve leave ihe saeral eanal through
its lower aperture (Fig. 78).

1] Cana1

This ean be easily done by snipping away ihe artieular proeesses with the
bone-forceps. The posilion of Ihe ganElion on the poslerior toot, the
eonneetions of the sheath of dura mater, the union of the two loots to form
the spinal nerve-trunk, and the dirision of ihe lattet into the anterior
and posleriot btanehes ean thus be studied. An attempt should also
be made at the same time to discovet the minute ranius meningeas.
This is a tine twig whieh is formed by the union of a small fi1ament ftain
thespinal nerve-trunk with a minule braneh ftom the sympathetie trunk.

192 HEAD AND NECK

It takes a reeurrent eourse through the intervertebral foramen to end in
the bones and periosteum of the vertebral eanal.

Ganglia Spinalia. — These ganglia are oval swellings de-
veloped upon the posterior nerve-roots, just before they unite
with the anterior roots to form the spinal nerve-trunks. They
are found upon the posterior roots of all the nerves, except,
oeeasionally, upon those of the sub-oeeipital and the eoeeygeal
nerves.

The spinal ganglia are formed upon the posterior nerve-
roots as they lie in the intervertebral foramina, except in the
eases of the lirst two cervical and the saeral and eoeeygeal
nerves. The ganglia of the Arst two cervical nerves lie upon
the posterior areh of the first and the vertebral areh of the
seeond cervical ^ertebrae respectively ; the ganglia of the
saeral nerves are plaeed within the saeral eanal, but out-
side the tube of dura mater. The ganglion on the posterior
root of the eoeeygeal nerve is inside the tube of dura mater.

Spinal Nerve-Trunks. — These are formed by the union
of the anterior and posterior nerve-roots immediately beyond
the spinal ganglia. This union takes plaee in the ease of the
eoeeygeal and saeral nerves in the saeral eanal; in the
lumbar, thoraeie, and lower six cervical nerves, in the inter-
vertebral foramina; and in the ease of the first two cervical
nerves, on the arehes of the atlas and epistropheus.

The nerve-trunk is exceedingly short; indeed, it divides
almost immediately into its anterior and posterior branehes,, In
the ease of the saeral and eoeeygeal nerves, this subdivision
takes plaee in the saeral eanal, and the spinal nerve-trunks
of these nerves are distinetly longer than in the ease of the
nerves whieh oeeupy a higher level.

The distribution of the posterior branehes has already
been examined (p. 173).

Disseetion, — At this stage the disseetor may adopt one of two methods
in the further treatment of the medulla spinalis and the nerves whieh spring
from it. If the medulla spinalis is fresh and in sueh a eondition that it may be
successfully hardened, it is best to transfer it at onee to the preservative iluid.
If, on the other hand, it is soft and not fit for proper preservation, it should
be removed with all its membranes and nerve-roots, and plaeed in a eork-
lined tray filled with water. There is no method by whieh the araehnoid,
the pia mater, the ligamenta dentieulata, and the nerve-roots ean be so
well studied as this.

In removing the medulla spinalis, the spinal nerves should be divided as
they lie in the intervertebral foramina, and in sueh a manner that as
long a pieee as possible of eaeh nerve remains attaehed to the dura

THE DISSEGTION 0F THE BACK 193

mater and the spinal medulla. Wherever it is possible the ganglia should
be taken with the nerves. The same rule applies to the saeral nerves also.
The medulla spinalis and its membranes should then be eut aeross at the
highest limit of the vertebral disseetion. By pulling upon the dura mater
the whole spedmen may now be lifted from the vertebral eanal and trans-
ferred to the water-bath. The dura mater should then be slit down
the median plane, and the edges of the ineision must be tumed aside.
By fixing the dura mater with pins to the eork at the bottom of the tray,
the iurther disseetion ean be eondueted with great advantage.

Aiteries of the Mednlla Spinalis (O.T. Spinal Oord). — It

is only when the arterial injection is partieularly good that
the spinal arteries ean be made out satisfactorily.

A large number of small arteries are supplied to the
meduUa spinalis. These are the anterior and posterior spinal
arteries whieh spring from the vertebral in the eranium, and
a series of lateral spinal arteries whieh reaeh the side of the
medulla spinalis and are derived from di^Terent sourees in
eaeh region. In the neek they eome from the vertebral,
aseending cervical, and deep cervical arteries; and in the
thorade and lumbar regions from the posterior branehes of
the intereostal and lumbar arteries. By the anastomoses of
these arterial twigs, five longitudinal trunks are formed upon
the surface of the medulla spinalis. One of these lies in
the median plane anteriorly, and may be termed the antero-
median artery. The other four are plaeed in relation to the
sulei along whieh the posterior nerve-roots enter the medulla
spinalis. One runs downwards anterior to the line of entranee
of these roots, and the other posterior to it on eaeh side of
the meduUa spinalis. These slender arterial trunks may there-
fore be termed the postero-lateral longitudinal vessels,

The antero-median vessel is formed above by the union of the two
anterior spinal branehes of the vertebral arteries. One of these is larger
than the other, and takes a mueh greater share in the formation of the
median trunk. Below the level of the fifth pair of cervical nerves the
eontinuity of the median vessel depends upon the reinforcements whieh
it obtains from the lateral spinal vessels. The number of lateral spinal
arteries whieh join the median vessel is very variable. The majority
of these arteries end on the nerve-roots ; only five to ten reaeh the median
vessel. The antero-median artery runs downwards, under cover of the
linea splendens of the pia mater. Its ealibre is uniform throughout,
and where the medulla spinalis ends it proeeeds onwards for some distanee
upon the filum terminale.

Th^ postero-lateral arteries on eaeh side of the medulla spinalis are formed
in the upper part of the cervical region by the bifurcation of the eorre-
sponding posterior spinal braneh of the vertebral artery. Lower down
their eontinuity is maintained by twigs whieh reaeh them on the posterior
roots of the spinal nerves from the lateral spinal arteries. It may be

VOL. II — 13

194

HEAD AND NECK

regarded as a rule, that where a lateral spinal artery gives a braneh to
one of the postero-lateral arterial trunks, it does not furnish another
to the antero-median arterial trunk. In this way diflferent lateral spinal
arteries are in eonneetion with the longitudinal trunks on the anterior
and posterior aspeets of the medulla spinalis. The postero-lateral vessels
end at the lower extremity of the meduUa spinalis.

From the five main arterial ehannels whieh thus extend along the spinal
medulla numerous anastomosing twigs ramify in the pia mater.

Yeins of the Medulla Spinalis. — These veins are small and
numerous, and their disposition eannot be said to eorrespond
with that of the arteries. They are very tortuous, and form
a plexus with elongated meshes. Six more or less perfect
longitudinal venous trunks may be notieed on the surface of
the medulla spinalis in eonneetion with this plexus ; two of
these are median, and are plaeed respectively on the anterior
and posterior aspeets. The anterior trunk runs upwards
under cover of the antero-median spinal artery. The other
four are lateral, and are situated two on either side, in
relation, respectively, to the anterior and posterior nerve-roots.

Upon eaeh side, the veins of the medulla spinalis effect
eommunieations with the veins in the vertebral eanal by means
of small twigs whieh run laterally on the nerve-roots.

How to distinguish the anterior from the posterior surface of

the medulla spinalis.

Anterior Surface.

1. Linea splendens.

2. Single anterior spinal artery in

median plane.

3. Anterior nerve - roots smaller

than posterior, and springing
by fila whieh emerge from
the medulla spinalis, not in a
eontinuous straight line, but
irregularly over an area of some
width.

POSTERIOR SURFACE.

1. The postero - lateral arteries in

relation to the posterior ncrve-
roots.

2. Fila of origin of posterior

nerve-roots entering themeduUa
spinalis along a straight and
eontinuous line, and at the
bottom of a distinet suleus.

3. Posterior nerve-roots larger than

the anterior, and provided with
ganglia.

Preseruation of the Mediilla Spinalis. — If the medulla spinalis is in a
fit state for preservation, it should be immersed for a few weeks in
methylated spirit, to whieh a small amount (4 per eent) of formalin has been
added. When sufficiently firm, the disseetor should endeavour to learn
something of its internal strueture by making transverse seetions aeross
it at different levels, and inspeeting the eut surface elosely with the naked
eye, or with the aid of a magnifying glass.

Intemal Strueture of the Medulla Spinalis. — A good deal
ean be learned by a naked-eye inspeetion of eross seetions of

THE DISSECTION 0F THE BACK 195

tbe tnedulla spinalis iaa.de in diSerent r^ions and at different
levels.

In sueh seetions the arUero-median fissure ond the postero-
median stptum and suleus, whieh pariially divide it along the
whole of its length into right and left halves, beeome obvious.

The antero-median fissure is mueh shorter than the posterO'
median septum. IC dips dorsally to a eommissure of white
matter, anterior while eommissure, whieh eonneels the two
halyes of the medulla spinalis ; and il eontains a Told of pia
mater and branehes of the anlerior spinal vessels. The
postero-median suleus is a shallow furrow whieh runs along

the posterior surface of the medulla spinalis in the median
plane, and the postero-median septum extends from the
bottom of the suleus to a transverse grey eommissure ealled
the posterior eommissure.

The two halves of ihe medulla spinaUs, thus marked oiT
from eaeh other, are to all intents and purposes symmetrieal,
and they are joined by a more or less broad band or eom-
missure whieh intervenes between the anterior fissure and the
posterior septum.

An inspeetion of the surface of eaeh lateral half of the
medulla spinalis brings into view a groove or furrow at some
little distanee from the postero-median suleus ; it is ealled
the poslero-lateral sulms. Along the bottom of this groove

196 HEAD AND NECK

the fila of the posterior nerve-roots enter the medulla spinalis
(O.T. spinal eord) in aeeurate linear order. There is no
eorresponding furrow on the anterior part of eaeh lateral half
of the meduUa spinalis in eonneetion with the emergenee of
the fila of the anterior nerve-roots ; and it should be noted
that these fila emerge over a broad area, whieh eorresponds
in its width to the thiekness of the subjacent anterior eolumn
of grey matter.

The medulla spinalis is eomposed of an inside eore of grey
matter whieh is surrounded on all sides by an external eoating
of white matter.

Grey Matter of the Medulla Spinalis. — The grey matter in
the interior of the medulla spinalis has the form of a Auted
eolumn. When seen in transverse seetion, it presents the
shape of the letter H. In eaeh lateral half of the medulla
spinalis there is a eomma-shaped mass of grey matter, the
concavity of whieh is direeted laterally. The ereseents of
opposite sides are eonneeted aeross the median plane by a
transverse band, whieh is ealled the grey eommissure, The
postero-median septum passes from the surface of the medulla
spinalis to the grey eommissure. The bottom of the antero-
median fissure is separated from it by an intervening strip
of white matter whieh is termed the anterior white eommissure,
In the grey eommissure may be seen the eentral eanal of
the spinal medulla. It is just visible to the naked eye as a
minute speek. This eanal tunnels the entire length of the
spinal medulla, and opens above (after having traversed the
lower half of the medulla oblongata) into the fourth ventricle
of the brain. The portion of the grey eommissure whieh lies
posterior to the eentral eanal is ealled ih^ posterior eommissure^
the portion anterior to it receives the name of anterior grey
eommissure,

In eaeh ereseentie mass of grey matter eertain well-defined
parts may be reeognised. The projecting portions whieh
extend posterior and anterior to the eonneeting transverse grey
eommissure are termed the posterior and the anterior grey
eolumns, They ean be distinguished from eaeh other at a
glanee.

The anterior grey eolumn is short, thiek, and very blunt at its
extremity. Eurther, its extremity is separated from the surface
by a tolerably thiek eoating of white matter, through whieh
the fila of the anterior nerve-roots pass on their way to the

THE DISSECTION 0F THE BACK 197

surface. The thiekened end of the anterior eolumn is termed
the eaput eolumna anteriorts^ and the eonstrieted part elose to
the grey eommissure is ealled the ceroix eolumna anterioHs.
The posterior grey eolumn in most loealities is elongated and
narrow. Further, it is drawn out to a fine point, whieh almost
reaehes the bottom of the postero-lateral suleus. This
pointed extremity receives the name of the apex eolumme
posterioris] the slightly swollen part whieh sueeeeds it is
the eaput eolumnae posterioris ; whilst the slightly eonstrieted
part adjoining the grey eommissure goes under the name of
the cervix eolumnee posterioris,

Covering the tip of the posterior eolumn there is a substanee
whieh differs in its eomposition from the general mass of grey
matter, and presents a translueent appearanee. It is termed
the substantia gelatinosa {Rolandt).

The grey matter is not present in equal quantity through-
out the entire length of the meduUa spinalis. Therefore it is
neeessary that it should be eonsidered in different regions, and
it must be understood, when the terms cervical, lumbar, saeral,
ete., are applied to different portions of the spinal medulla,
that these terms apply to the regions to whieh the nerves of
the same name are attaehed.

Wherever there is an inerease in the size of the nerves
attaehed to a partieular part of the medulla spinalis, there a
eorresponding inerease of the grey matter may be notieed. It
follows from this that the distriets in whieh the grey matter
bulks most largely are the lumbar and cervical swellings.
The great nerves whieh go to form the limb plexuses enter
and pass out from those portions of the medulla spinalis. In
the intermediate thoraeie region there is a reduetion in the
quantity of grey matter, in eorrespondenee with the smaller
size of the thoraeie nerves.

The shape of the ereseentie masses of grey matter is not
the same in all regions. In the thoraeie region both eolumns
are narrow, although the distinetion between the anterior grey
eolumn and the more attenuated posterior grey eolumn is still
sufficiently manifest. In the cervical region the eontrast
between the grey eolumns is most marked ; the anterior grey
eolumn is very thiek in eomparison with the posterior grey
eolumn. In the lumbar region, on the other hand, the
difference in the thiekness of the two grey eolumns is not
nearly so apparent, owing to a broadening out of the
11—13 h

HEAD AND NECK

Fk;. 8o.— TranEverse seelions Ihiough Ihe Medulli
Spinalis in different regions. A. Cervical Region
B. Mid-lhoraeie Region; C. Lower Thoraeii
Region ; D. Lumbat Region,

posterior grey
eolumn. A see-
tion taken rrom
the eentre o£ eaeh
region ean very
readily be reeog-
nised by the
featuies men-
tioned.

In the thoTaeie
region of th e spinal
medulla, more
espeeially in the
upper part, there
is another ehar-
aeter whieh is very
distinctive. A
pointed an d promi-
nent triangular
projection juts out
from the lateral
aspeet of the eres-
eentie mass of
grey matter nearly
opposite the grey
eommissure. This
is ealled the laieral
grey eolunm (Eig.
80, B and C).
It disappears in
the cervical and
lumbar swelhngs,
but again heeomes
evident both in
the upper cervical
and in the lower
saeral regions,
Below the

thoraeie region
the postero-med-
ian septum dimin-
ishes and the antero-median iissure inereases in depth, until,

THE DISSEGTION 0F THE BACK 199

m the saerat region they are almost equal in depth and the
eentral eanal oi.cupies the eentre of the medulla spmalis

White Matter of the Mednlla Spliudu — The white matter
rorms a thiek eoat ng on the outside of the Huttd eolumn of
grey matter It is marked oS mto three funicuh The
postertor funiciilus is wedge shaped in transverse seet on and
hes between the postero median st.ptun and the postenor
grey eolumn The laieral /unieuius oeeupies Ihe concavity of
the grey ereseent Postenorly it ts bounded by ihe posterior
gre} eolumn and the postero lateral suleus v^hilst anteriorly tt
e\tends as far as the most laieral fila of the anterior nerve
roots The antmor /unieulus ineludes the white matter

FiO. 81, — Tran5verse seelioii through Ihe upper cervical part of Ihe MeduUa
Spinalis of a (ull-time l'uitus, irealed by the Pal-Weigerl proeess.

betweeti the antero-median Assure and the anterior eolumn
of grey matter, and also the white matter whieh separates
the thiek extremity of the anterior grey eolumn from the
surface of the spinal medulla and is traversed by the emerging
fi]a of Ihe anterior nerve-roots.

In the cervical region a faint longitudinal groove nins
downwards on the surface of the posterior funiculus of ihe
medulla spinalis. This indieates the position of a septum
whieh passes into the funiculus from the deep surface of the
pia mater and divides it ineompletely into two unequal strands.
The groove is termed the intermediale posterior suleus. The
strand on its medial side is the /aseimlus gradlis (Goll's),
whilst the lateral and larger strand receives the name of the
/aseieulus euneatus (Burdaeh's).

II— 13c

200 HEAD AND NECK

The white matter of the medulla spinalis inereases steadily
in quantity from below upwards.

The fasciculi graeilis and euneatus, whieh form the posterior funiculus
of the medulla spinaiis, are eomposed of iibres whieh enter the spinal medulla
as the fila of the posterior nerve-roots. In the lower portion of the medulla
spinalis the two fasciculi are not marked off from eaeh other.

In the lateral and anterior funiculi of the adult spinal medulla it is not
possible with the naked eye to distinguish the different strands of fibres of
whieh they eonsist, but the student should remember that sueh strands or
traets are present. The three l)est-defined traets in the antero-lateral part
of the spinal medulla are, (i)the fasciculus eerebello-spinalis (O.T. direet
eerebellar traet) ; (2) the fasciculus eerebro-spinalis lateralis (O.T. erossed
pyramidal traet) ; (3) the fasciculus eerebro-spinalis anterior (O.T. direet
pyramidal traet).

The fasciculus eerebello-spinalis aseends to the eerebellum, but, traoed
in the opposite direetion, it is found to disappear in the lower thoraeio region
of the medulla spinalis. The /aseieulus eerebro-spinalis lateralis oeeupies
a larger distriet of the medulla spinalis. It is plaeed in the lateral iunieulus
anterior to the posterior eolumn of grey matter and immediately medial to the
fasciculus eerebello-spinalis. As the fasciculuscerebello-spinalis disappears in
the lower part of the medulla spinalis the fasciculus eerebro-spinalis lateralis
eomes to the surface, and it ean be traeed as low as the fourth saeral nerve.
T\it fasciculus eerebro-spinalis anlerior {orms the narrow strip of the anterior
funiculus, whieh lies immediately adjacent to the antero-median fissure. It
reaehes down to about the middle of the thoraeie r^on of the meduUa
spinalis and then disappears.

After the body has been five days on its face it will be
replaeed upon its baek with the thorax and pelvis supported
by bloeks, and the disseetors of the head and neek should at
onee proeeed to elean the temporal fascia, and afterwards to
remove the brain and study the interior of the eranium.

Disseetion. — Take away the anterior and superior aurieular museles and
remove the thin layer of fascia subjacent to them whieh deseends from
the lower border of the galea aponeurotiea to the zygomatic areh. When
this has been done the strong temporal fascia will be exposed. Note that
it is attaehed above to the temporal ridge and below to the upper border
of the zygomatic areh. The details of its eonneetions will be studied at
a later period.

REMOYAL 0F THE BRAIN.

After the superficial attaehments of the temporal fascia
have been noted the disseetors of the head and neek should
proeeed to remove the brain.

Disseetion. — The head being supported upon a bloek, extend the median
ineision, already made in the galea aponeurotiea, to the nasion anteriorly and

REMOVAL 0F THE BRAIN loi

to the extenial ocd[MtaI protuberanee posteriorly, and eul through the loose
areoiar tissue and the perieranium in the same line down to Ihe bone.
With the handle of the sealpel, or with a ehisel, detaeh the perieianium from
Ae bone on eaeh side and turn it posteriorly and downwards to the temporal
ridges, leaving the bone perreetly bare. Nolelhatalthough ihe perieranium
is loosely altaehed over Ihe surface of the various bones of the vault, it
is finnly attaehed along the lines of ihe erania! sutures by proeesses thal
dip in belween the bones and separate theit edges. Delaeh the galea
aponeutotiea and the lemporal fascia from the lemporal lidge on eaeh side
withthe edge of theknife; then eairyingtheedgeot the knifeanleriorly and
posteriorly between ihe temporal musele and the bone delaeh the upper
partof themusclefrom theskull. When this has been done, eaeh halfof the
seah' ean be tuined down over the ear.

The disseetors should next obtain a saw, a ehisel, and a mallet, and

proeeed to remove the eaUaria. The line along whieh the saw ia to be
used may be marked out on the skull by eneirding it wilh a pieee of string,
and then marking the eranium with a peneil along the line of the strbg.
Anterioily, the eut should be made fully three-quatters of an ineh above the
marginsoftheorbits ; postetiotly, it should be earried tound at lhelevel of a
point midway between the lambda' and the extemal oeeipital proluberanee.
The saw shouid be used to divi(ie the outer table of the skull only. When
the diploe is teaehed, the sawdust will beeonie red and moist, and the saw
shouid then be abandoned, The hammerand ehisel ate now btought into

iequisition, and by shoit shaip
readily be split along the line in i
divided. When this has been <Io
cio5s-bar of the ehisel into the lissu
Dnia Mater Eneephali.—
distinet membranes, whieh ;

ilh these the
'hieh the outer table of the eranium is
le, insinuale the hook at the end of the
e in fionl, and wteneh off the skull-eap.

-The brain is elothed by three
re termed the meninges. These

ieapex

inital bone, or Ihe point

202 HEAD AND NECK

are from without inwards — (i) the dura mater; (2) the
araehnoid ; and (3) the pia mater.

When the skull-eap is detaehed, the outer surface of the
dura mater, as it covers the upper surface of the eerebral
hemispheres, is exposed It is rough, and dotted over with
bleeding points. If a portion is plaeed in water, its roughness
beeomes still more manifest, and is seen to be due to a multi-
tude of fine fibrous and vascular proeesses by whieh it is
eonneeted with the deep surface of the bones. These have
neeessarily been torn asunder in the removal of the skuU-
eap. The bleeding points are most numerous along the
median line, or, in other words, along the line of the superior
sagittal sinus (O.T. longitudinal) ; and if the handle of the
knife is run from before baekwards, so as to make pressure
along this line, a eonsiderable quantity of blood will ooze out.
This shows that a number of small veins from the eranial
bones have been ruptured. The degree of adhesion between
the dura mater and the inner surface of the eranial bones
varies in different subjects and in different loealities. In all
eases it is strongly adherent along the lines of the sutures, like
the perieranium externally; and, further, it is mueh more firmly
attaehed to the base than to the vault of the eranium. In the
ehild — indeed, as long as the bones of the eranium are grow-
ing — it is more adherent than in the adult ; and it is more
firmly bound to the bone again in old age.

The disseetors should now elean the outer surface of the
dura mater with a sponge. They will then reeognise the middle
meningeal artery upon eaeh side, aseending in the substanee
of the membrane, and sending off its branehes in a widely
arboreseent manner. It stands out in bold relief from the
membrane. If the skull-eap is examined, its inner surface
will be observed to be deeply grooved by the branehes
of the artery and the veins whieh aeeompany and lie external
to them (Wood Jones). The meningeal arteries are not
intended for the supply of the membrane alone, as the name
might lead one to imagine. They are also the nutrient
vessels of the inner table and diploe of the eranial bones.

Granulationes Araehnoideales (O.T. Paeehionian Bodies).
— These granulations are almost invariably present, and, as a
rule, are best marked in old subjects. They are small granular
bodies, ranged in elusters on either side of the superior
sagittal (O.T. longitudinal) sinus, into whieh many of them

REMOYAL 0F THE BRAIN

»03

protnide (Fig. 83), As a general rule, they are most evident
towards the postenor part of the par etal reg on At first s ght
they appear to be protrus ons from the dura mater but this
is not the ease They spnng from the araehnoid and the sub.
araebnoid t ssue, and are enlai^ements of ihe normal v Ih of
the membrane (F g 84)

Two Layerg of the Dnr» Mater — Hav ng noted these
prel m nary deta Is from an exam na on of he outer surface
of the dura n ater the student s n a pos t on to understand
that th s membrane does not belong ent relj lo the broin.
It performs a double functon (i) t aets as an intemal
penosteum to the bones forming the eran al cavity and (a)

FlG. B3.— Median seetion IhrouE'i t
the Superior Sagillai Blood Si
s«n prolruding into the sinus.

(E.I:

rontal Bone and eorresponding part of
The araehuoideal granulationa are
:d.)

it gives support to the dilTerent parts of the brain. Gonse-
quently, it eonsists of two strata, whieh, in most loealities, are
firmly adherent, but they ean usually be easily demonstrated
in the disseeting-room, These strata may very appropriately
be termed the endoeranial and the supporttng layers. Along
eertain lines these two layers sepatate from eaeh other. In
some eases they separate so as to form blood ehannels, termed
sinus dura matris, for the conveyance of venous blood; in
other eases they separate in order that the inner supporting
layer may form strong folds or partitions, whieh pass in
between eertain parts of the brain ; and by these partitions the
eranial cavity is divided tnto eompartments eommunieating
freely with one another, and eaeh holding a defioite sub-
division of the brain (Fig. 87).

Disstetiim. — These points mlist now be ¥erified. Begin I"

204

head fbrwards. Support
the dura miter m an ant
guperior saeiltal slnus, aod along

HEAD AND NECK

this position, and make

; two ineisions Ihiough
iireeiion— one on eaeh side of the
; whole iength. From the mid-
it of eaeli of these ineisions another eut must be made Ihrough eaeh
lateral portion of the dura mater downwards to the eut mai^in of (he skull
immediately above Ihe eat (rig. 85). The dura maler covering the upper
aapeet of the brain is thus divided inlo a eentral strip eontaining the
superior sagittal sinus, and four triangular flaps. The llaps should
now be tuined downwaids Dvet the eut matgin of the skull, and in this
position Ihey preserve the brain, during its removal, fiom laeeration by the
sharp bony edge.

CaTiim Subdnrale. — The subdural spaee is the term applied

to the interval between the dura mater and the araehnoid —
Figs. 83 and 84. It eontains a very small quantity of serous
fluid, whieh moistens the opposed surfaces of the membranes.
A striking eontrast between the two suriaees of the dura
mater ivill be noted. The external surface is rough and
Aoeeulent ; the internal surface is smooth and glistening.

Veiue Oetebri. — The eerebral veins whieh return the blood
from the surface of the eerebral hemispheres will be seen
shining through the araehnoid. They are lodged for the
most part in the sulei between the gyri, and run upwards
to the median plane. When they reaeh the superior sagittal
sinus they turn anteriorly, and lie against the wall of the sinus,
for some distanee, before they open into it.

REMOVAL 0F THE BRAIN

ao5

Sinns Sagittalis Snperioi (O.T. Superior Longitndisal). —
Open into this venous ehannel by ninning the knife through
its upper wall froni behind forwatds (Pigs. 85 and 86). It
begins anteriorly at the erista galli of the ethmoid bone,
where it not iiifrequently eommunieates with the veins in
the nasal cavity through the foramen cjecum. It extends

posteriorly, grooying the eranial vault in the median plane, to
the internal oeeipital protuberanee, on the right aspeet of
whieh it beeomes eontinuous with the right transvetse sinus
(O.T. lateral). Its lumen, whieh is triangular in eross-seetion,
is very small anteriorly, but expands greatly posteriorly. On
either side of the sinus, and opening into it, are a number of
clefts between the two layers of the dura raater ; thi

2o6

HEAD AND NECK

the lateral laeuna. The inferior angle of the ehannel is
erossed by a number of minute bands, named elwrda WilUsii;
and araehnoideal granulations bulge into it. The mouths of
the superior eerebral veins open into the sinuSj or into the
lateral laeunse, pouring their blood into the sinus in a diree-
tion eontrary to that in whieh the blood flows within tbe

VII. FacU1 Titrv

ehannel — that is, the terminal portions of the veins are direeted
anteriorly, whilst the blood in the sinus flows posteriorly.

Th« Belation o[ the ArBelmDideal GiauulationB to the Snpeilor
SoKittal Sinus and tha Lateral Laenn». — When the granulations push
themselves inlo the sinus or the lateial laeuna: they push before (hetn a
thin eontinuous covering of the floot Df the spaee, and when they project
still further and eneroaeh upon the bones of Ihe skuU they a.re coveied also
liy B thin expansion of the roof of the spaee.

Falx Gerebri (Figs. 86, 87). — This is a siekle-shaped redupli-
eation of the inner layer of the dura mater, whieh deseends
in the median plane, between the two eerebral hemispheres.

REMOYAL 0F THE BRAIN 207

In order to expose it, the eerebral veins must be divided as
they open into the superior sagittal sinus, and ihe hemisphere
gently pulled lateraily. Anteriorly, the falx eerebri is narrow,
and attaehed to the erista galli of the ethmoid bone. Ii
inereases in breadth as it passes baeltHards, and posteriorly
it is attaehed in the median plane to the upper surface of
ihe tentorium eerebelli. The anterior part of the falx is
frequently cribriform, and is sometimes perforated by aperlures
to sueh an extent that it almost resembles laee-work. Along

FlC. 87. — Fronial seetion Ihrougli ihe Craniiil Civity in a plane whieh passes
through the posterioi' part of Ihe foranien magnum. The poslerior
parl of Ihe eranial cavity, from whieh the brain has been removed, is
depieted.

eaeh border its two layers separate to enelose a blood-sinus.
Along its upper convex margin runs the superior sagittal
sinus ; along its concave free border eourses the mueh smaller
in/erior sagittal sinus ; whilst along its attaehment to the
tentorium is enelosed the straight sinus. Its inferior concave
margin overhangs the eorpus eallosum, with whieh, however,
it is not in eontaet, eseept to a very slight extent, posterlorly.

KBmoTal ot the Brain,— The disseetors should now proeeed lo remove
the brain. IIaving divided Ihe attaehment of the falx eerebri lo Ihe
erista galli, puU it posleriorly. Next, removing the bloek upon whieh
the head rests, and siipporting. the oeeiput and poslerior lobes of the bruti
with the left hand, let the head drop well downwards. In all probaWlit'
the frontal lobes will fall away by thelr own weight from the anter^'

2o8 HEAD AND NECK

of the base of the eranium, and perhaps earry with them the olfactory
bulbs. Should they remain in position, however, gently raise them with
the fingers, and at the same time separate the olfactory bulbs from the
cribriform plate of the ethmoid with the handle of the knife. As the
olfactory bulbs are raised the minute olfactory nerues whieh spring from
them and perforate the cribriform plate of the ethmoid bone are torn aeross.
The large round and white optie nerues (seeond pair of eerebral nerves) now
eome into view, as they leave the eranial cavity through the optie foramina.
When these are divided, the intemal earotid arteries will be exposed, and
more posteriorly, in the median plane, the infundibulum will be seen ; it
is a hollow eonieal proeess whieh extends from the tuber einereum at the
base of the brain to the hypophysis (O.T. pituitary body), whieh lies in
the fossa hypophyseos (O.T. pituitary fossa). Divide the earotid arteries
and the infundibulum. Posterior to the infundibulum is the upper
border of the dorsum sellae, terminating on eaeh side in the rounded posterior
elinoid proeess. Passing anteriorly on eaeh side of the dorsum sellse is the
eorresponding third eerebral nerve, whieh must not be touehed at present.
A little more laterally, and on a slightly lower plane, is the medial or free
border of the tentorium eerebelli, a fold of the inner layer of the dura mater
whieh lies above the eerebellum and forms the roof of the posterior fossa
of the eranium.

Carefully displaee the temporal pole of the brain from under cover of the
posterior border of the small wing of the sphenoid, whieh lies to the lateral
side of the optie nerve and the eut end of the internal earotid artery ; then
raise the temporal lobe from the floor of the middle fossa, and from the
upper surface of the tentorium eerebelli. Pass the knife posterior to the
dorsum sellae, immediately above the level of the third eerebral nerve, and
eut through the midbrain, as it aseends from the posterior fossa, from its
lateral surface inwards to the median plane. Repeat the operation in the
same way on the opposite side, and remove the eerebrum and upper part of
the midbrain from the eranium.^

Plaee the removed eerebrum in the vault of the eranium and lay it aside.
Then note the relative positions of the parts exposed. Anteriorly lies the
floor of the anterior fossa of the eranium ; behind it, on a more depressed
plane, the middle fossa, and still more posteriorly the sloping tentorium
eerebelli.

In the median plane anteriorly is the projecting erista galli, partially
dividing the anterior fossa into lateral halves. On either side of the erista
galli is the depression from whieh the olfactory bulb was dislodged, and still
more laterally are the portions of the floor of the anterior fossa whieh form
the roofs of the orbits ; they bulge upwards as well-marked convexities.
Eaeh lateral part of the floor of the anterior fossa terminates posteriorly in
a sharp margin, formed by the posterior border of the small wing of the
sphenoid. This margin overhangs the anterior part of the middle fossa.
It is covered with a thiekening of dura mater in whieh runs the spheno-
parietal blood sinus, and it terminates medially in a projecting proeess,
the anterior dinoid proeess. On the medial side of eaeh anterior elinoid
proeess lie the eorresponding optie nerve and internal earotid artery, and
springing from the upper surface of the artery is its ophthalmie braneh,
whieh runs anteriorly under cover of the optie nerve. Posterior to the
divided ends of the internal earotid arteries, and in the median plane, is the
infundibulum deseending into the hypophyseal fossa, and more posteriorly,
on either side, are the projecting posterior elinoid proeesses. The area
between the four elinoid proeesses is covered by a fold of the inner layer

* For alternative method see p. 217.

REMOYAL 0F THE BRAIN

109

(J tbe dara niatet, lenned the dia^hragma sMr. In ils epntte is nn
apeitaie Ibioogh whteh the ioiiindibuluni pusses lo join Ihe hypophysis
(O.T. pitoilaiy bod;) ; and it binds down Ihe h) ;»ph]-sis in ihe Tossa. In ils
antoioe and posterior margins, respeclively, are loilged the sinus inter-
-- lior and Ihe anus inlereayetnosus posterior (O.T. eiieuliu

FlG. 88.— Interior of the Cranium afler the rcmova1 of the eerebtum. The
iransYerse, stratght, and superior petrosal sinuses have been openedn and
ihe dura maler has been removed from Ihe tloor of the middle tossa,

In the dura mater, on eaeh side of the hypophyseal
(pituitary) fossa, lies the eorresponding cavernous sinus, whieh
will be disseeted later, and slill more kierally are the de-
pressed lateral portions of the middle eranial fossa, lined with
dura mater, in whieh the trunk and sonn<" "*■ the branehes of

VOL, n — 14

2IO HEAD AND NECK

the middle meningeal artery are visible. Posterior to the
middle fossaliesthe tentorium eerebelli coveringthecerebellum.
The peripheral margin of the tentorium is attaehed, on eaeh
side, to the posterior elinoid proeess, the upper margin of the
petrous part of the temporal bone, the posterior inferior angle
of the parietal bone, and to the transverse ridge on the inner
surface of the oeeipital bone. The eentral or free margin
erosses the attaehed margin behind the posterior elinoid
proeess on eaeh side, and is attaehed anteriorly to the apex
of the anterior elinoid proeess. It bounds an oval opening,
the door of the tent, through whieh pass the midbrain sur-
rounded by the araehnoid and the pia mater, and the posterior
eerebral arteries. Piereing the midbrain nearer its posterior
than its anterior border is the aqu8eductus eerebri (O.T.
aqueduct of Sylvius). Posterior to the aqueduct is the lamina
quadrigemina of the midbrain and anterior to it the pedun-
euli (O.T. erura) eerebri. Eaeh pedunele eonsists of an
anterior part, the basis peduneuli (O.T. crusta\ and a posterior
part, the tegmentum^ the two being separated by a lamina of
dark eoloured tissue, the subsiantia nigra, The bases pedun-
euli are entirely free from eaeh other, but the tegmental
portions are united together anterior to the aqueduct.

Running anteriorly and laterally from the medial side of
eaeh pedunele to the angle between the anterior ends of the free
and the attaehed borders of the tentorium, is the third eerebral
nerve. Glose to the midbrain the ner\'e passes between the
posterior eerebral artery above and the superior eerebellar
artery below; and between the free and attaehed borders
of the tentorium it pierees the dura mater, in the middle
fossa, and enters the wall of the cavernous sinus. Between
the posterior ends of the third nerves lies the upper end of
the basilar artery, dividing into the two posterior eerebral
branehes; and the disseetors should note that the arteries
lie in an enlargement of the subaraehnoid spaee whieh is
known as the dsterna interpeduneularis. In the median plane
posterior to the midbrain is the divided vena eerebri magna
(O.T. great vein of Galen). It passes posteriorly and upwards,
and pierees the apex of the tentorium to enter the straight
sinus, whieh lies in the angle of union between the falx
eerebri and the tentorium eerebelli.

Curving posteriorly around the midbrain and ending
posteriorly in the great eerebral vein on eaeh side is the vena

REMOYAL OF THE BRAIN 211

basalis^ and immediately above it, running anteriorly, is the
slender fourth eerebral nerve. If the free border of the
tentorium is turned laterally, at the point where it is erossing
the attaehed border, the fourth nerve will be seen perforating
the inner layer of the dura mater to enter the wall of the
cavernous sinus.

When the disseetors have verified the facts noted above,
they should examine the lower free border of the falx eerebri,
in whieh they will find the small inferior sagittal sinus, whieh
terminates posteriorly, at the apex of the tentorium, in the
straight sinus. The straight sinus must now be opened by
earrying the knife posteriorly through the falx eerebri along
its line of union with the tentorium. Then the falx eerebri
must be eut away from the oeeipital bone, and as this is done
the posterior part of the superior sagittal sinus will be opened
up. After the falx has been removed the right and Ieft
transverse and the right and left superior petrosal sinuses must
be opened by ineisions earried along the attaehed border of
the tentorium (Fig. 88). The disseetors will probably find
that the superior sagittal sinus turns to the right and beeomes
eontinuous with the right transverse sinus, whilst the posterior
end of the straight sinus turns to the left and joins the left
transverse sinus. In a eertain number of eases this arrange-
ment is reversed, and not uneommonly, as in the speeimen
shown in Fig. 88, there is a eommunieation between the
right and left transverse sinuses aeross ihe front of the internal
oeeipital protuberanee. Oeeasionally the superior sagittal,
the two transverse sinuses, the straight sinus, and the oeei-
pital sinus unite anterior to the internal oeeipital protuber-
anee in a eommon dilatation, the confluens sinuum (O.T.
toreular Herophili). The transverse sinus, on eaeh side, runs
from the internal oeeipital protuberanee to the lateral end of
the superior border of the petrous part of the temporal bone,
where it dips downwards into the posterior fossa, and at the
same point it is joined by the superior petrosal sinus, whieh
runs postero-laterally along the superior border of the petrous
part of the temporal bone from the cavernous sinus to the
transverse sinus, eonneeting the two together.

Disseetion. — With the point of the sealpel open the spheno-parietal
sinus, whieh runs along the posterior border of the small wing of the
sphenoid, and traee it medially to the cavernous sinus, but do not open the
latter. Then remove the dura mater ii^^^ ^^^» ^"«^eral part of the middle
fossa on one side to expose the semilur 'an) ganglion of the

II — 14 a

212 HEAD AND NECK

fifth nerve, the middle meningeal artery and its two terminal branehes, the
aeeessory meningeal artery, if it is present, and the great superficial petrosal
nerve. Gommenee immediately to the lateral side of the anterior part of
the free border of the tentorium, where a eut through the inner layer of the
dura will open into a spaee (O.T. Meekel's cave) between the two layers of
the dura, in whieh lies the semilunar ganglion. From the postero-medial
border of the ganglion \ht posierior braneh or sensory root passes baekwards
into the posterior lossa to enter the pons ; and from its anterior-lateral border
the ophthalmie braneh passes upwards and anteriorly in the lateral wall of
the cavernous sinus, the maxillary braruh runs anteriorly to the foramen
rotundum, and the mandibular braneh passes downwards into the foramen
ovale. By theside of the mandibular nerve the aeeessory meningealartery may
befound entering the eranium ; and a little further posteriorlythe middle men-
ingeal artery will be seen passing into the middle fossa through the foramen
spinosum. After entering the eranium the middle meningeal artery runs
anteriorly and laterally, aeross the floor of the middle fossa, towards the
lateral wall and divides into an anterior and a posterior braneh ; the former
aseends on the anterior part of the lateral wall to the anterior inferior angle
of the parietal bone, and the latter runs posteriorly and laterally, and then
aseends on the inner surface of the squamous part of the temporal bone.
The g}'eai superjicial petrosal nerue appears on the anterior surface of the
petrous part of the temporal bone through the hiaius nerui /aeialis^ whieh
lies to the medial side of the eminentia areuaia. It runs anteriorly and
medially and disappears beneath the semilunar ganglion.

After the struetures mentioned above have been found
and eleaned, the disseetors must remove the tentorium eere-
belli. Cut through the free border immediately posterior to
the point where it erosses the attaehed border; the fourth nerve
also will be divided by this ineision. Repeat the ineision on
the opposite side, and then eut through the membrane elose
to its attaehed border, but to the medial sides of the superior
petrosal and transverse sinuses ; next divide the ven8e basales
at their points of junction with the vena eerebri magna
(O.T. vein of Galen); then raise the anterior part of the
tentorium and, passing the knife beneath it, separate it from
the falx eerebelli, whieh is attaehed to its lower surface in the
median plane. The tentorium may now be Hfted out and the
araehnoid covering the upper surface of the eerebellum will
be exposed.

After the upper surface of the eerebellum has been eleaned,
eut through the third eerebral nerves, and then press baek-
wards the peduneuH eerebri and the pons (Yarolii), whieh lies
immediately below them, to expose the fifth and the sixth
nerves. Cut the fifth nerves as they eross the upper borders
of the petrous parts of the temporal bones, and then divide
the small sixth nerves, whieh lie more medially and at a
shghtly deeper level. Press the pons and eerebellum still

REMOYAL 0F THE BRAIN 213

further baele and divide the seventh and eighth nerves as
they enter the internal aeustie meatus. Below the eighth
neives lie the ninth, tenth, and eleventh nerves. These also

must be eut ; and the roots of the twelfth nerves, whieh lie
deeper and more medially, must be identified and divided.
The pons ean then be displaeed still furthe' ' -ly and

the front of the meduUa oblongata wil' into

11—14 h

ai4

HEAD AND NECK

view. Pass the knife downwards, anterior to the meduUa
oblongata, into the vertebral eanal, and, eutting firmly baek-
wards and laterally, on eaeh side, divide the medulla spinalis
and the vertebral arteries. Withdraw the knife, pass two
fingers downwards anterior to the medulla oblongata and lift
it and the pons and the eerebellum out of the posterior fossa.
Plaee these iower parts of the brain, whieh collectively
eonstitute the hind brain, with the bemispheres previously

1 ihrougb Ihe Head a little lo ibe tight or ihe Median
hows Ihe posterior erania.1 lossa and the upper part or tbe
lal afier the removaI o( Ihe brain ajid the medulla spinalis.

removed, and tben examine the eut ends of the eerebral nerves
and the blood sinuses whieh lie in the region of the posterior
fossa.

In the upper end of the vertebral eanal iies the
upper extremity of the severed meduila spinalis, attaehed
on either side to the margin of the foramen magnum by
the uppermost dentation of the ligamentum dentieulatum.
Anterior to the ligamentum dentieulatum, on eaeh side, is
the verlebral artery, and still more anteriorly, on a slightly
deeper plane, the fi!a of ibe anterior root of the first cervical

REMOYAL 0F THE BRAIN 215

nerve may be distinguished. At a higher level on eaeh side
the two rootlets of the hypoglossal nerve pieree the dura, as
they pass into the hypoglossal eanal (O.T. anterior eondyloid
foramen). The spinal root of the aeeessory nerve passes
through the foramen magnum into the eranium, posterior to
the ligamentum dentieulatum, and, turning laterally over
the margin of the foramen magnum, it joins the eerebral
fibres of the aeeessory and the tenth nerve, with whieh it
passes through an aperture in the dura opposite the jugular
foramen. Immediately above the eleventh and tenth nerves
the smaller trunk of the ninth nerve pierees the dura. Above
the ninth nerve the eighth nerve and the motor and sensory
roots of the seventh nerve pass into the internal aeustie
meatus, aeeompanied by the small auditory braneh of the
basilar artery and the auditory vein. The two roots of the
seventh nerve lie in a groove on the upper and anterior
aspeet of the eighth, the small sensory root (O.T. pars
intermedia) being situated between the motor root and the
eighth nerve. The small motor and the large sensory root
of the fifth nerve pass through an opening in the dura whieh
lies above and medial to the internal aeustie meatus ; and the
sixth nerve pierees the dura mater below and to the medial
side of the opening for the fifth nerve, opposite the side of
the base of the dorsum sellae. The small fourth nerve
pierees the under surface of the free border of the tentorium
at the point where it is erossing the attaehed border.

After the disseetors have familiarised themselves with the
positions of the eerebral nerves as they pieree the dura mater,
they should examine the falx eerebelli and eomplete the
display of the eranial blood sinuses.

The Falx Oerebelli is a small sagittal fold of the inner
layer of the dura mater whieh projects anteriorly, between the
lateral lobes of the eerebellum, from the internal oeeipital
erest (Figs. 87, 89).

Sinus Transversus (O.T. Lateral). — The horizontal part of
the transverse sinus has already been traeed from the internal
oeeipital protuberanee to the superior border of the petrous
part of the temporal bone, where it turns downwards to
the jugular foramen. At first the deseending portion runs
downwards, on the inner surface of the mastoid part of the
temporal bone, and then anteriorly and again downwards
aeross the upper and anterior surfaces of the juc

II — 14 c

2i6 HEAD AND NECK

of the oeeipital bone. On aeeount of the sinuosity of its
eourse this part is ealled the sigmoid portion of the transverse
sinus, Open this part of the sinus and find the mouth of the
mastoid emissary vein in its posterior border about half-way
down.

The disseetors should now obtain the basal part of a
maeerated skuU and should note the relation of the transverse
sinus to the outer surface. They will find that the position
of the sinus ean be indieated on the external surface, by a line
whieh eommenees at the external oeeipital protuberanee, passes
forwards, with a slight upward convexity, along the superior
nuehal line to the upper part of the mastoid part of the
temporal bone and then deseends to the level of the lower
margin of the external meatus.

Sinus Oeeipitalis. — The oeeipital sinus is not uneommonly
absent. When it is present it eommenees in the right or left
transverse sinus or the eonAuens sinuum, and deseends for a
short distanee in the posterior border of the falx eerebelli. It
terminates below in two lateral branehes, whieh leave the falx
eerebelli and run along the borders of the foramen magnum
between the layers of the dura mater, to terminate anteriorly
in the lower ends of the transverse sinuses.

Sinus Petrosus Inferior. — The inferior petrosal sinus lies
along the posterior angle of the petrous part of the temporal
bone extending from a point lateral to the opening for the
sixth nerve to the medial side of the opening in the dura
for the ninth nerve of the same side. Lay the sinus open.
It opens anteriorly into the cavernous sinus, from whieh it
receives blood, and it passes posteriorly through the jugular
foramen to join the upper end of the internal jugular vein.

Plexus Basilaris, — The two inferior petrosal sinuses are
eonneeted together aeross the upper surface of the basilar
part of the oeeipital bone by a plexus of small venous ehannels,
to whieh the term basilar plexus is applied. Unless these
ehannels happen to be distended with blood the disseetors will
probably be unable to display this plexus.

The disseetors should note that the dura mater is mueh
more firmly attaehed to the bones of the base than it was to
the bones of the vertex, a fact whieh should have attraeted
their attention as they removed the membrane from the floor
of the middle fossa. They should note also that it gives
sheaths to the nerves whieh pieree it, and that at the margins

REMOYAL 0F THE BRAIN 217

of the yarious foramina its outer layer beeomes eontinuous
with the periosteum on the outer surface of the eranium,
whilst at the margin of the foramen magnum the inner layer
beeomes eontinuous with the single layer of dura mater whieh
surrounds the medulla spinalis ; and that at the same level the
araehnoid and pia mater of the brain beeome eontinuous with
the araehnoid and pia mater of the spinal meduUa (O.T. spinal
eord). Before terminating the survey of the interior of the
eranium the disseetors should revise their knowledge of the
blood vessels, and their relations to the dura mater ; and they
should remove the hypophysis (O.T. pituitary body) and in-
vestigate its naked-eye strueture.

Siniis Darse Matris. — Four blood sinuses lie iti the median
plane\ (i) the superior sagittal sinus in the upper or attaehed
border of the falx eerebri ; (2) the inferior sagittal sinus in the
free part of the lower border of the falx eerebri ; (3) the
straight sinus along the line of attaehment of the falx eerebri
with the tentorium eerebelli; (4) the oeeipital sinus in the
upper part of the attaehed border of the falx eerebelli.

Two sinuses lie in a Mgher horizontal plane : these are the
spheno-parietal sinuses, whieh run along the posterior borders
of the small wings of the sphenoid bone.

Six sinuses lie in a lower horizontal plane\ (i) the two
cavernous sinuses at the sides of the body of the sphenoid ;
(2) the two superior petrosal sinuses along the upper angles
of the petrous parts of the temporal bones, in the anterior
parts of the attaehed border of the tentorium eerebelli ; (3)
the horizontal parts of the transverse sinuses in the posterior
parts of the attaehed border of the tentorium. The terminal
parts of the transverse sinuses deseend along the anterior parts
of the lateral walls of the posterior fossa.

Two sinuses run obliquely dowmuards, posteriorly^ and later-
ally : these are the two inferior petrosal sinuses.

Three sinuses run transversely eonneeting paired sinuses of
opposite sides : (i) the anterior intercavernous sinus in the
anterior border of the diaphragma sellae ; (2) the posterior
intercavernous sinus in the posterior border of the diaphragma
sellae; and (3) the basilar plexus whieh eonneets together the
inferior petrosal sinuses aeross the upper surface of the basilar
part of the oeeipital bone.

Alternatiye Method of Remoying the Brain. — Ifit j«-^^ ^*
desirable to remove the brain entire by the more rapid but le*'

2i8 HEAD AND NECK

method usually adopted in the post-mortem room, then the following steps
should be taken after the falx eerebri has been detaehed from the erista
galli and the dura mater lining the vault of the eranium has been thrown
aside (see p. 204).

Remove the bloek upon whieh the head has been resting, and, support-
ing the oeeiput and the posterior part of the brain with the left hand, let
the head drop well downwards and in all probability the weight of the
frontal lobes will draw them away from the floor of the anterior fossa of
the skuU, and possibly the olfactory lobes may be earried with them. If
the olfactory bulbs remain in position on the cribriform plates of the
ethmoid at the sides of the erista galli, gently raise them with the handle
of the sealpel and press them baekwards on to the under surfaces of the
frontal lobes. As the olfactory bulbs are raised the ol/adory nerue fila-
ments whieh pass from their lower surfaces through the cribriform plates
are torn. As the frontal lobes are pressed baekwards the large round
and white optie nerues eome into view as they are leaving the eranial cavity
through the optie foramina. When these are divided the intemal earotid
arteries will be exposed, and more posteriorly in the median plane lies the
in/undibulum^ a hoUow eonieal proeess whieh eonneets the hypophysis
eerebri (O.T. pituitary body) with the tuber einereum at the base of the
brain, and more laterally are the oeulo-motor nerues. Sever eaeh of these
struetures in turn. On the lateral side of eaeh third nerve lies the medial
or free border of the tentorium eerebelli passing anteriorly to be attaehed to
the anterior elinoid proeess. Turn this margin aside with the point of the
knife, and the minute troehlear nerve (fourth eerebral nerve) will be brought
into view. It lies under shelter of the free border of the tentorium, and
should be divided at this stage. The head must in the next plaee be turned
forcibly round, so that the face is direeted over the left shoulder. Raise
the posterior part of the right eerebral hemisphere with the fingers, and
note that it rests upon the tentorium eerebelli — a broad horizontal proeess
of dura mater whieh intervenes between it and the eerebellum. Divide
the tentorium along its attaehed border, and take eare whilst doing this
not to injure the subjacent eerebellum. Now turn the head so as to bring
its left side uppermost, and treat the tentorium on that side in the same
manner. The two parts of the trigeminal nerue (fifth eerebral nerve) per-
forating the dura mater near the apex of the petrous portion of the temporal
bone ; the abdueent nerue (sixth eerebral nerve) piereing the dura raater
behind the dorsum sellae of the sphenoid bone ; the facial nerue and the
aeustie nerue disappearing into the internal aeustie meatus ; the glosso-
pharyngeal, the vagus, and the aeeessory nerues leaving the skull through
the jugular foramen ; and the two slips of the hypoglossal nerue piereing tne
dura mater over the hypoglossal eanal (O.T. anterior eondyloid foramen),
will eaeh in turn eome into view upon either side, and must be divided in
sueeession. In the ease of the three nerves passing out of the eranium
through the jugular foramen, the disseetor should endeavour to leave the
aeeessory of the right side intaet within the eranium, by dividing its roots
of origin from the meduUa oblongata, whilst on the other side he should
remove it with the brain. This nerve is readily reeognised beeause it
aseends from the vertebral eanal into the eranial cavity through the foramen
magnum. Now thrust the knife into the vertebral eanal, and divide the
medulla spinalis and the vertebral arteries, as they turn anteriorly upon
the upper part of the meduUa spinalis (O.T. spinal eord) ; then sever the
aeeessory nerve of the left side, and the roots of the first pair of spinal
nerves. When this has been done let the head fall well downwards, gently
dislodge the medulla oblongata and eerebellum, and the whole brain ean
be removed. The vena eerebri magna (Galen), as it passes from the

REMOYAL 0F THE BRAIN 219

interior of the brain to enter the straight sinus, is ruptured by this
proeeeding.

Meniiigeal Yeins. — In addition to the named blood sinuses, venous
ehannels aeeompany the meningeal arteries and more partieularly the
trunks and branehes of the middle meningeal artery. These vessels are
of wider ealibre than the eorresponding arteries, and lie external to them
in the grooves on the inner surfaces of the eranial bones. When the
arteries are distended they eompress the middle parts of the veins and
drive the blood into their anterior and posterior margins. When this
oeeurs eaeh artery appears to be aeeompanied by two veins, a eireumstanee
whieh is probably responsible for the statement that some of the meningeal
arteries have venae eomites.

Emissaria. — Emissary veins are blood ehannels whieh
eonneet the sinuses of the dura mater with the veins whieh
lie outside the eranium. They are : (i) Emissary veins eon-
neeted with the superior sagittal sinus — {a) from the anterior
extremity of the sinuses an emissary vein passes through
the foramen eaeeum. This vein divides below and either
beeomes eontinuous with the veins of the nasal foss8e, or its
branehes pass through foramina in the nasal bones and join
the angular veins; {b) two parietal emissary veins, whieh
pass through the parietal foramina and eonneet the superior
sagittal sinus with the oeeipital veins. (2) Emissary yeins
eonneeted with the transverse sinuses — {a) two mastoid
emissary veins, one on eaeh side, pass through the mastoid
foramina and eonneet the sigmoid parts of the transverse
sinuses with the posterior aurieular veins ; {b) two post-
eondyloid veins, one on eaeh side, pass through the eondyloid
eanals and eonneet the lower ends of the transverse sinuses
with the plexuses of veins in the suboeeipital triangles. (3)
Emissary veins eonneeted with the cavernous sinuses— («) a
vein whieh traverses the foramen ovale, or the foramen Yesalii,
and eonneets the cavernous sinus with the plexus of veins
around the external pterygoid musele ; {b) a plexus of veins
whieh passes through the temporal bone with the internal
earotid artery and eonneets the cavernous sinus with the
pharyngeal venous plexus; {c) in a sense the ophthalmie
vein may be eonsidered an emissary vein, for although under
ordinary eireumstanees it is a tributary of the sinus, blood ean
flow through it in the opposite direetiori from the sinus into
the orbit, and then along the tributaries whieh eonneet t^
ophthalmie vein with the angular vein, and along the c r
whieh eonneet the ophthalmie vein through the 1
orbital fissure with the veins in the infratemporal regioi

220 HEAD AND NECK

The Arteries of the Oranial Cavity. — (i) The vertebral
arteries ; {2) the internal earotid arteries ; (3) the meningeai
arteries,

Arteria Yertebrales. — The vertebral arteries pieree the
spinal dura mater below the foramen magnum, through whieh
they enter the eranium. As eaeh artery passes through the
foramen it lies anterior to the highest dentation of the liga-
mentum dentieulatum, and it passes between the hypoglossal
and first cervical nerves. It was divided when the hind brain
was removed, and its eut extremity lies near its point of
entranee into the eranial cavity.

Arteria Oarotides Intemse. — Eaeh internal earotid artery
enters the eranium at the laeerate foramen between the apex
of the petrous part of the temporal bone and the body of the
sphenoid, where it pierees the outer layer of the dura mater.
Then it runs anteriorly in the cavernous sinus to the medial
side of the anterior elinoid proeess, where it turns upwards,
pierees the inner layer of the dura mater and the araehnoid,
and gives off its ophthalmie braneh, whieh runs anteriorly below
the optie nerve to the orbit. The artery was eut immediately
behind its ophthalmie braneh during the early stages of the
removal of the brain.

Meningeal Arteries. — These are the nutrient arteries of
the dura mater, and of the inner table and diploe of the eranial
bones. They are derived from a great number of diSerent
sourees, but the only one of any size is the middle meningeal
braneh of the internal maxillary artery. The others are
small twigs, and, except in a well - injected subject, will
not be easily made out. They are: (i) anterior meningeal
from the anterior ethmoidal artery ; (2) the aeeessory meningeal
from the internal maxillary artery; (3) some small branehes from
the aseending pharyngeal, oeeipital, and vertebral arteries.

Eaeh middle meningeal artery is a braneh of the eorre-
sponding internal maxillary artery. It enters the eranium
through the foramen spinosum of the sphenoid, and divides
upon the inner surface of the great wing of that bone into two
large terminal branehes. Of these, the anterior braneh aseends
upon the great wing of the sphenoid, and the anterior
inferior angle of the parietal bone, grooving both deeply,
whilst the posterior braneh turns posteriorly upon the
squamous portion of the temporal bone. The branehes
whieh proeeed from these trunks spread out widely and,

REMOYAL 0F THE BRAIN

221

with the aeeompanying venous ehannels, oeeupy the arbor-
eseent grooves on the inner surface of the eranial vault.

The vein whieh aeeompanies the middle meningeal artery
passes through the foramen spinosum and ends in the plexus
around the external pterygoid musele.

Eaeh anterior meningeal artery proeeeds from the anterior
ethmoidal artery as it aeeompanies the anterior ethmoidal
nerve aeross the cribriform plate of the ethmoid bone.
It supplies a limited area of dura mater and bone in the
anterior fossa of the eranium.

The aeeessory meningeal arteries (O.T. small meningeat) are
somewhat ineonstant; they arise either direetly from the

FiG. 91. — I, Hypophysis ; 2, in median seetion ;
3, in horizontal seetion. (Sehwalbe. )

cu Anterior lobe.
b. Posterior lobe.
em. Gorpus mamillare.

i. Tuber einereum.
ch. Optie ehiasma in seetion.

ro. Optie reeess of the third ventricle.
o. Optie nerve.
a'. Infundibulum with projection from

anterior lobe upwards anterior

to it.

internal maxillary or from the middle meningeal. Eaeh
enters the eranium through the eorresponding foramen ovale,
but it should not be looked for at the present stage, as it
is best examined along with the semilunar (O.T. Gasserian)
ganglion and the three divisions of the trigeminal nerve.

The meningeal branehes from the aseending pharyngeal arteries
are the terminal twigs of those vessels. They enter the
eranium through the laeerate and jugular foramina, and
through the hypoglossal eanal (O.T. anterior eondyloid
foramen). The braneh whieh passes through the jugular
foramen is the largest.

The meningeal branehes of the oeeipital and 'uertebral arteries
are small, and are distributed in the posterior eranial fossa.
The former enter through the jugular, mastoid, and parietal
foramina, the latter through the foramen magnum.

222 HEAD AND NECK

The meningeal veins may be regarded as being arranged in
two sets : one set eonsists of small ehannels whieh pour their
blood into the blood sinuses; the other set is eomposed of
veins whieh aeeompany the meningeal arteries and earry
their blood to venous trunks on the exterior of the eranium.

Hypophysis Oerebri (O.T. Pituitary Body) (Fig. 91). —
The over-hanging margin of the diaphragma sellae should be
eut away and the hypophysis carefully dislodged from the
fossa hypophyseos (O.T. pituitary fossa) of the sphenoid bone.
It is an oval strueture, slightly Aattened from above down-
wards, and with its long axis direeted transversely. It eonsists
of a large anterior lobe, and a smaller posterior lobe. The
anterior lobe is hollowed out posteriorly so as to form a
concavity for the lodgment of the posterior lobe. If a sagittal
seetion is made through the body, the line of separation
between the two lobes is seen very distinetly. The infundi-
bulum, whieh eonneets the hypophysis with the tuber einereum
of the brain, is attaehed to the posterior lobe only (Fig. 91, i).
Thus, even in the adult, there is a elue to the different modes
of development of the two lobes. The posterior lobe is derived
from the brain, whilst the anterior lobe is an off-shoot from
the primitive bueeal cavity.

When the inspeetion of the interior of the eranium is eompleted the
disseetors must fill the eranial cavity with tow steeped in preservative solu-
tion ; replaee the skull-eap in position and retain it by bringing the sealp flaps
over it, and stitehing them aeeurately together. The brain must be put in
a jar in a 5 per eent solution of formaIin and plaeed aside till the disseetion
of the remaining parts of the head and neek is finished.

THE ANTERIOR PART 0F THE NEGK.

After the skull-eap has been replaeed and the sealp has
been stitehed over it let the head hang down over the end of
the table, pull the ehin as far from the sternum as possible
and fix it in position with hooks. Then examine the region of
the front of the neek. It is a large triangular area, bounded
laterally by the anterior borders of the sterno-mastoid museles,
above by the lower border of the mandible, and below by the
middle part of the upper border of the manubrium sterni ; and
it is divided by the median plane into two smaller subsidiary
triangles, the anterior triangles of the neek^ eaeh of whieh is
bounded above by the mandible, posteriorly by the stemo-

THE ANTERIOR PART 0F THE NECK 223

mastoid, and anteriorly by the median plane. Pass the iridex
finger from the ehin to the sternum along the median line and
loeate in sequence the body of the hyoid bone, the angular
anterior border of the thyreoid eartilage, the rounded areh of
the erieoid eartilage and the rings of the traehea. The latter
are partly masked by the isthmus of the thyreoid gland.
Plaee the thumb and the forefinger on the body of the hyoid
bone and earry them posteriorly, one on eaeh side, along its
great eornua. Note that the posterior ends of the eornua lie
immediately in front of the anterior borders of the sterno-
mastoid museles. Above the body of the hyoid bone lies the
submental triangle roofed in by the mylo-hyoid museles, whieh
form the diaphragm of the mouth ; and above eaeh great eornu
is the eorresponding submaxiUary region, Between the body
of the hyoid bone and the upper margin of the thyreoid
eartilage is the thyreo-hyoid spaee, bounded posteriorly by the
middle part of the thyreo-hyoid membrane, whieh lies anterior
to the upper part of the pharynx and the middle of the
epiglottis (Fig. 159). Traee the upper border of the thyreoid
eartilage posteriorly and note that it terminates on eaeh
side in a pointed projection, the superior eornu, whieh lies
immediately in front of the anterior border of the sterno-
mastoid. Between the lower margin of the thyreoid eartilage
and the upper border of the erieoid eartilage lies the erieo-
thyreoid ligament, forming part of the anterior wall of the
lower portion of the larynx.

The disseetors should make themselves thoroughly familiar
with the landmarks mentioned above, both on their own neeks
and on the neeks of their friends, and they should note that
whilst in the dead subject there may be some difficulty in
palpating the isthmus of the thyreoid gland, as it erosses
anterior to the seeond, third, and fourth rings of the traehea,
they will have no difficulty in loeating the small soft eushion-
like mass in the living subject.

Disseetion.—The skin was eut along the lower border of the mandible
at the eommeneement of the disseetion of the face ; now, make a median
ineision through it ftom the ehin to the sternum and turn the triangular
flap, thus marked out, posteriorly and laterally, to a short distanee beyond
the anterior margin of the sterno-mastoid. When this is done the super-
ficial fascia covering the anterior triangle on eaeh side will be eKpos'^H • i*f
is thiekest and most laden with fat in the submental region. Ir
part of it lie the fibres of the platysma, running upwards ar
towards the mandible. The anlerior fibres of the musele
to the anterior part of the lower border of the mandible, ana .

THE ANTERIOR PART OF THE NECK 225

of the dee > a about half-way between the sternum and
tlie thyteoi oart e. The altaehments of the seeond layer
of deep fascia of the lower part of the neek may be summarised
as Tollows. Il is attaehed below to the posterlor surface of
the manubrium sterni and to the posterior border of the
clavicle, to whieh it binds the posterior belly of the omo-hyoid
(p. 145). Above, it fuses with ihe more superficial layer, along
an oblique line whieh aseends fTom the level of the eoraeoid
proeess to the level of the upper end of the traehea. Above
that level it forms, with the superficial layer, a eommon lamella,
whieh aseends on the infra-hyoid museles to gain attaehment
to the body and great eomu of the hyoid bone. The spaee
between the two layers eontains, in the region of the anterior
triangle, ihe lower parts of the anterior iugular veins, the
anastomosis between them, and the areolar tissue in whieh
they are embedded. In the posterior triangle its eontents are
the lower end of the extema! iugular vein, the terminations of
the transverse cervical and transverse seapular veins, the
transverse seapular artery, and areolar tissue. Note that the
anterior iugular vein on eaeh side lies superficial to the deep
fascia in ihe upper part of the neek ; then it pierees the first
layer of deep fascia and lies between the two layers, where it
anastomoses with its fellow of the opposite side ; finally it tums
laterally deep to the stemo-mastoid, and terminates in the
external jugular vein at the anterior boundary of the sub-
clavian part of the posterior triangle.

J}iss£ciion. — Make two ineisions througU the deep faseia cif the upper
patt or the anterior triangle, one along the lower bonler of the mandible
ftom the angle to half an ineh from the ehin, and a seeond at right angles
to the (irst, Trom its middle to the great eornu of Ihe hyoid bone. Whilst
making the horizontal ineision avoid injuiiiig Ihe eieteinal maxillaiy arteiy
(O.T. Taeial) and the anterior facial vein, whieh pieree the deep faseia at
the le¥el or the anteriot bordet of the massetet. Keflect the two triangular
ilaps of iasaa. matked out by the ineisions and expose the lowet surface of
the submaj:illary gland, the submaxillaty lymph glands, Ihe anterior and
posterioi bellies of the digastrie musele, the lower part of the stylo-hyoid
musele, and a fuithei pait of the anterior facial vein.

The maiority of the submaxillary lymph glands lie
the lower border of the mandible on the superfidal
the submaxillary gland. The anterior facial vein ci 1

posterior part of the submaxillary gland su i

external maxillary artery dips deeply betv
of the mandible and the submaxillary j
VOL. II — 16

2 26 HEAD AND NECK

and lower part of the submaxillary gland usually overlaps the
stylo-hyoid and the posterior belly of the digastrie museles,
and not infrequently it overlaps the great eornu of the hyoid
bone also. Its anterior border may overlap the anterior
belly of the digastrie. Raise the lower border of the gland
and expose another layer of deep fascia covering the museles
whieh lie deep to it. Plaee the handle of the knife on this
fascia and push it gently upwards. Note that it passes
upwards to the level of the mylo-hyoid line on the inner surface
of the mandible, to whieh the mylo-hyoid musele is attaehed.
The fascial sheath in whieh the submaxillary gland is enelosed
eonsists, therefore, of a superlieial layer of deep fascia whieh
extends from the great eornu of the hyoid bone to the lower
border of the mandible, and a deeper layer whieh passes from
the great eornu of the hyoid to the mylo-hyoid line of the
mandible. The two layers blend in front of the anterior
belly of the digastrie, and posteriorly they unite, behind the
posterior belly of the digastrie, with the connective tissue in
whieh the earotid vessels are embedded.

Disseetion, — Remove the deep fascia in the region of the anterior
triangle and expose the divisions and the eontents of the triangle.

The Divisions of the Anterior Triangle. — After the deep
fascia is removed, the disseetor will reeognise that eaeh
anterior triangle may be divided into three subsidiary areas
whieh are ealled the digastrie, the earotid, and the museular
triangles, by means of the two bellies of the digastrie musele
and the anterior belly of the omo-hyoid musele.

The digastrie triangle is bounded by the two bellies of the
digastrie musele and the lower border of the mandible.

The boundaries of the earotid triangle are, above and in
front, the posterior belly of the digastrie ; below and in front,
the anterior belly of the omo-hyoid ; and, behind, the anterior
border of the sterno-mastoid.

The museular triangle is bounded, above and behind, by
the anterior belly of the omo-hyoid; below and behind,
by the anterior border of the sterno-mastoid ; and in front,
by the middle line of the neek.

An additional triangle eommon to the two sides lies between the hyoid
bone below, the two anterior bellies of the digastries laterally, and the
mandible above. This is ealled the submenidl triangle.

The Middle Line of the Neek. — Before eommeneing the

THE ANTERIOR PART OF THE NECK

disseetion of the eontents of the subsidiary parts of the
anterior triangle the disseetors of both sides should, together,
study the struetures whieh lie in the middle line of the neele
and immediately to either side of it ; for this region is of the
highest importanee to the surgeon. The area is diyided by
the hyoid bone into supra-hyoid and infra-hyoid portions,

In the supra-hyoid part lie struetures whieh are eoneerned
in the eonstruetion of the floor of the mouth. The disseetor

will have notieed already that the fatty superficial fascia ts
more fully deyeloped here than elsewhere in the neek, and
that the anterior margins of Ihe two platysma museles meet
and deeussate iii the median plane, for about half an ineh
or so, below the ehin. The anterior belHes of the two
digastrie museles are attaehed to tbe mandible, one on either
side of the symphysis. From this they deseend towards the
hyoid boiie, and diverge slightly from eaeh otber so as to
leave a narrow triangular spaee, the submental triangU, be-
tween them (Fig. 93). The floor of this spaee is formed by
: portions of the two mylo-hyoid museles, whilst

2 26 HEAD AND NECK

Disseetion, — Remove the deep fascia in the region of the anterior
triangle and expose the divisions and the eontents of the triangle.

The digastrie triangle is bounded by the two bellies of the
digastrie musele and the lower border of the mandible.

An additional triangle eommon to the two sides lies between the hyoid
bone below, the two anterior bellies of the digastries laterally, and the
mandible above. This is ealled the submental triangle,

The Middle Line of the Neek. — Before eommeneing the

THE ANTERIOR PART 0F THE NECK 23J

disseetion of the eontenls of the subsidiary parts of the
anterior triangle the disseetors of both sides should, together,
study the struetures whieh lie in the middle line of the neek
and immediately to either side of it ; for this region is of the
highest importanee to the sui^eon. The area is divided by
the hyoid bone into supra-hyoid and infra-hyoid portions.

In the supra-hyoid part Ue struetures whieh are eoneemed
in the eonstruetion of the floor of the mouth. The disseetor

FlG, 92.— Diagram 10 show the Boundaries of the Triangles of the Neek.

will have notieed already that Ihe fatty superlieial fascia is
more fully developed here than elsewhere in the neek, and
tbat the anterior margins of Ihe two platysma musdes meet
and deeussate in tbe median plane, for about half an ineh
or so, below tbe ehin. The anterior bellies of the two
digastrie museles are attaehed to tbe mandible, one on either
side of ihe symphysis, From this they deseend towards tbe
hyoid boiie, and diverge shghtly from eaeh other so as to
Ieave a narrow triangular spaee, the submentai triangk, be-
tween them (Fig. 93). The floor of this spaee is formed by
the anterior portions of the two mylo-hyoid iri> '"s. wbilst
II— 15a

2 26 HEAD AND NECK

and lower part of the submaxillary gland usually overlaps the
stylo-hyoid and the posterior belly of the digastrie museles,
and not infrequently it overlaps the great eornu of the hyoid
bone also. Its anterior border may overlap the anterior
belly of the digastrie. Raise the lower border of the gland
and expose another layer of deep fascia covering the museles
whieh lie deep to it. Plaee the handle of the knife on this
fascia and push it gently upwards. Note that it passes
upwards to the level of the mylo-hyoid line on the inner surface
of the mandible, to whieh the mylo-hyoid musele is attaehed.
The fascial sheath in whieh the submaxillary gland is enelosed
eonsists, therefore, of a superficial layer of deep fascia whieh
extends from the great eornu of the hyoid bone to the lower
border of the mandible, and a deeper layer whieh passes from
the great eornu of the hyoid to the mylo-hyoid line of the
mandible. The two layers blend in front of the anterior
belly of the digastrie, and posteriorly they unite, behind the
posterior belly of the digastrie, with the connective tissue in
whieh the earotid vessels are erabedded.

Disseetion. — Remove the deep fascia in the region of the anterior
triangle and expose the divisions and the eontents of the triangle.

The digastrie triangle is bounded by the two bellies of the
digastrie musele and the lower border of the raandible.

The boundaries of the earotid triangk are, above and in
front, the posterior belly of the digastrie ; below and in front,
the anterior belly of the omo-hyoid ; and, behind, the anterior
border of the sterno-mastoid.

An additional triangle eommon to the two sides lies between the hyoid
bone below, the two anterior bellies of the digastries laterally, and the
mandible above. This is ealled the submental triangle,

The Middle Line of the Neek. — Before eommeneing the

THE ANTERIOR PART 0F THE NEGK

237

disseetion of the eontents of the subsidiary parts of the
anterior triangle the disseetors of both sides should, together,
study the struetures whieh lie in the middle line of the neek
and immediately to either side of it ; for this region is of the
highest importanee to the surgeon. The area is diyided by
the hyoid bone into supra-hyoid and infra-hyoid portions.

In the supra-hyoid part tie stnietures whieh are eoneerned
in the eonstruetion of the floor of the mouth. The disseetor

FlG. 92, — DiagTam to show Ihe Boundaries of the Triangles of (fae Neek.

will have notieed already that the fatty superficial fascia is
more fully developed here than elsewhere in ihe neek, and
that the anterior margins of the two platysma museles meet
and deeussate iri the median plane, for about half an ineh
or so, below the ehin. The anterior bellies of the two
digastrie museles are attaehed to the mandible, one on either
side of the symphysis, From this they deseend towards the
hyoid bone, and diverge slightly from eaeh other so as to
leave a narrow triangular spaee, the submenlal triangk, be-
tween them {Fig. 93). The floor of this spaee is formed by
the anterior portions of the two mylo-hyoid museles, whilst

2 26 HEAD AND NECK

and lower part of the submaxillary gland usually overlaps the
stylo-hyoid and the posterior belly of the digastrie museles,
and not infrequently it overlaps the great eornu of the hyoid
bone also. Its anterior border may overlap the anterior
belly of the digastrie. Raise the lower border of the gland
and expose another layer of deep fascia covering the museles
whieh lie deep to it. Plaee the handle of the knife on this
fascia and push it gently upwards. Note that it passes
upwards to the level of the mylo-hyoid line on the inner surface
of the mandible, to whieh the mylo-hyoid musele is attaehed.
The fascial sheath in whieh the submaxillary gland is enelosed
eonsists, therefore, of a superiieial layer of deep fascia whieh
extends from the great eornu of the hyoid bone to the lower
border of the mandible, and a deeper layer whieh passes from
the great eornu of the hyoid to the mylo-hyoid line of the
mandible. The two layers blend in front of the anterior
belly of the digastrie, and posteriorly they unite, behind the
posterior belly of the digastrie, with the connective tissue in
whieh the earotid vessels are embedded.

Disseetion, — Remove the deep fascia in the region of the anterior
triangle and expose the divisions and the eontents of the triangle.

The digastrie triangle is bounded by the two bellies of the
digastrie musele and the lower border of the raandible.

An additional triangle eommon to the two sides lies between the hyoid
bone below, the two anterior bellies of the digastries laterally, and the
mandible above. This is ealled the submental triangle.

The Middle Line of the Neek. — Before eommeneing the

THE ANTERIOR PART 0F THE NECK 227

disseetion of the eontents of the subsidiary parts of the
anterior triangle the disseetors of both sides should, K^ether,
study the struetures whieh lie in the mlddle line of the neek
and immediately to either side of it ; for this region is of the
highest importanee to the surgeon. The area is divided by
the hyoid bone into supra-hyoid and infra-hyoid portions.

In the supra-hyoid part lie struelures whieh are eoneemed
in the eonstruetion of the floor of the mouth. The disseetor

of the Triangles of ihe Neek.

will have notieed already that the fatty superlieial fascia is
more fully developed here than elsewhere in the neek, and
that the anterior margins of the two platysma miiseles meet
and deeussate iii the median plane, for about half an ineh
or so, below the ehin. The anterior bellies of the two
digastrie museles are attaehed to the mandible, one on either
side of the symphysis. From this they deseend towards the
hyoid boue, and diverge slightly from eaeh other so as to
leave a narrow triangular spaee, the submtnlal triangle, be-
tween them (Fig. 93). The floor of this spaee is formed by
the anterior portions of the two mylo-hyoid museles, whilst

228

HEAD AND NECK

biseeting the floor of the triangle, in the median plane, is the
fibrous raphe into whieh these museles are inserted. Not
infrequentiy the medial margins of the digastrie museles send
deeussating fibres aeross the interval. Within the subraental
triangle are the submental glands, whieh receive lyroph from

FlG, 93. — Disseetion of the Kront of the Neek. The Righl Sterno-masloid

the median part of the lower lip and ehin and the anterior
part of the tongue.

In ihe median area of the infra-hyoid part there is a
narrow interrauseular interval, bounded on eaeh side, above,
by the medial margins of the sterno-hyoid museles, and to a
smaller extent, below, by the medial margins of the sterno-
thyreoid museles (Fig. 93); raore lateraily lie the anterior bellies

THE ANTERIOR PART 0F THE NECK 229

of the omo-hyoid museles. In this median intermuseular
interval the following struetures will be found : (i) the median
part of the thyreo-hyoid membrane ; (2) the anterior border
of the thyreoid eartilage with the projecting prominentia
laryngea (O.T. pomum adami) at its upper end ; (3) the
areh of the erieoid eartilage ; (4) the erieo-thyreoid ligament
with the anastomosis between the erieo-thyreoid arteries, and
the anterior ends of the erieo-thyreoid museles; (5) the first
ring of the traehea with the anastomosis between the medial
terminal branehes of the superior thyreoid arteries ; (6) the
isthmus of the thyreoid gland ; (7) the inferior thyreoid veins,
and (8) the lower cervical rings of the traehea. Oeeasionally
the third or middle lobe of the thyreoid gland and the
levator glandulae thyreoidea,*or one or other of them, is found
extending upwards from the isthmus of the thyreoid gland.
When it is present the middle lobe either terminates above
in a pointed extremity or beeomes eontinuous with a fibrous
eord, the remains of the thyreo-glossal duet, whieh disappears
posterior to the hyoid bone. The levator extends from the
isthmus or from the third lobe, and is attaehed above to the
lower border of the hyoid bone.

Disseetion. — To display these struetures fully the fascia whieh covers and
binds together the infra-hyoid museles of opposite sides must be removed.
When this has been done the anterior part of the thyreoid eartilage will be
exposed, and, above it, in the thyreo-hyoid interval, lies some loose areolar
tissue. If an ineision, direeted upwards and posteriorly, is made into this
tissue, behind the lower border of the hyoid bone, the infra-hyoid bursa
will be opened, and when this and the areolar tissue are removed, the
thyreo-hyoid membrane will be exposed. Note that the membrane extends
from the upper border of the thyreoid eartilage posterior to the body of the
hyoid bone to its upper border. When the areolar tissue in the lower part
of the intermuseular interval is removed the inferior thyreoid veins will be
displayed ; they disappear, below, behind the sternum where they join tbe
innominate veins. Oeeasionally also a small unpaired artery, the thyreoidea
ima^ will be found aseending, in the median plane, to the isthmus of the
thyreoid gland. Behind the inferior thyreoid veins lies another layer of
deep cervical fascia, the pretraeheal layer. It covers the front of the
traehea,' envelops the isthmus of the thyreoid gland, and is attaehed above
to the lower border of the thyreoid eartilage. The part whieh extends
from the isthmus of the thyreoid gland to the tbyreoid eartilage aets as a
suspensory ligament of the isthmus. The disseetors will find that, so long
as the attaehments of this part of the pretraeheal fascia are not interfered
with, they eannot displaee the isthmus of the thyreoid gland downwards.
On the other hand, if they eut through the attaehment of the fascia to the
thyreoid eartilage, introduee the handle of the knife through the ineision,
and press downwards, they will be able to displaee the isthmus of the
thyreoid gland to a lower level and expose the upper rings of the traehea.
At the root of the neek the pretraeheal fascia deseends into the thorax,
11—15 6

2 30 HEAD AND NECK

along the anterior surface of the traehea, and it blends below with the
fibrous perieardium.

Remove the pretraeheal fascia from the region of the intermuseular
interval, first above and then below the isthmus of the thyreoid gland. As
the fascia is disseeted away the following struetures will be displayed.
Immediately below the thyreoid eartilage is the erieo-thyreoid ligament,
overlapped on eaeh side by the anterior part of the erieo-thyreoid musele.
Grossing anterior to the ligament, transversely, is the anastomosis
between the erieo-thyreoid branehes of the superior thyreoid arteries.
It lies nearer the lower than the upper border of the ligament. Below
the erieo-thyreoid ligament is the convex anterior part of the erieoid
eartilage ; then follows the erieo-traeheal ligament, uniting the erieoid
eartilage to the first ring of the traehea. The isthmus of the thyreoid
gland lies at a lower level opposite the seeond, third, and fourth rings of
the traehea. Along its upper border is the anastomosis between the
medial terminal branehes of the superior thyreoid arteries, and below it
are the lower cervical traeheal rings.

The superficial layers of the deep fascia must now be removed from the
whole area of eaeh anterior triangle, and for this purpose and for the
satisfactory disseetion of the eontents of the triangles, it is neeessary that
the head be turned well over to the opposite side ; therefore the disseetors
must arrange to work alternately.

Commence with the digastrie triangle. Its boundaries are
the lower border of the mandible and the two bellies of the
digastrie musele.

Its eontents are: (i) the lower part of the submaxillary
gland; (2) the submaxillary lymph glands; (3) part of the
external maxillary artery ; (4) part of the anterior facial vein ;
(5) the mylo-hyoid nerve; (6) the mylo-hyoid artery; (7) a
small part of the hypoglossal nerve ; (8) a small part of the
lingual vein.

Disseetion. — Remove the deep fascia whieh was previously turned aside
(p. 225) and elean the submaxillary lymph glands. Most of these glands
lie immediately below the mandible in the angle between it and the sub-
maxillary gland, but some may be found on the superficial surface of the
gland. Turn the gland upwards and fix it with hooks ; then seeure the
mylo-hyoid nerve and artery as they enter the posterior border of the
anterior belly of the digastrie about the middle of its length. Define the
band of fascia whieh surrounds the intermediate tendon of the digastrie and
binds it to the great eornu of the hyoid bone. Note that the tendon is em-
braeed by the cleft lower end of the stylo-hyoid musele. Glean the posterior
belly of the digastrie and the stylo-hyoid musele whieh deseends along its
anterior border. Note that the posterior belly of the digastrie and the
stylo-hyoid disappear, postero-superiorly, under cover of the angle of the
mandible. Clean the anterior belly of the digastrie, and then examine
the floor or medial boundary of the triangle. Immediately behind the
anterior belly of the digastrie it is formed by the posterior fibres of the
mylo-hyoid musele ; and more posteriorly and on a deeper plane it is
formed by the hyoglossus.

eiean the portion of the mylo-hyoid whieh is exposed and, at its
posterior border, immediately above the great eornu of the hyoid bone,

THE ANTERIOR PART 0F THE NECK 231

seeure the hypoglossal nerve and the lingual vein, the vein lying l^elow
the nerve. Displaee the lingual vein and the hypoglossal nerve upwards ;
eut through the fibres of the hyoglossus, immediately alx)ve and parallel
with the great eornu, and display the Ungual arter}', whieh in this }x>silion
lies immediately above rhe great eornu, parallel with the lingual vein but
separated from it by the hyoglossus musele.

All the struetures whieh have been mentioned above will be met with
in the disseetion of other regions, when a full aeeount of them will lje given.

Turn next to the earotid triangle, so ealled beeause it
eontains parts of the eommon, internal, and external earotid
arteries. It is bounded posteriorly by the anterior border of
the sterno-mastoid ; above and anteriorly by the posterior
belly of the digastrie ; and below and anteriorly by the anterior
belly of the omo-hyoid.

Disseetion. — Traee the anterior facial vein from the digastrie triangle
aeross the superficial surface of the posterior belly of the digastrie to its
posterior border, where it unites with the posterior facial vein, whieh is
deseending from under cover of the lower end of the parotid gland. The
trunk formed by the union of the anterior and posterior facial veins is the
eommon facial vein. Traee the eommon facial vein downwards and
posteriorly to its union with the intemal jugular vein, at or under cover
of the anterior border of the sterno-mastoid. Remove the deep fascia
and the areolar tissue, and the lymph glands whieh he in the angle belween
the posterior belly of the digastrie and the anterior border of the stemo-
mastoid, below the lower end of the parotid gland ; seeure the lingual
vein, whieh passes baekwards from the tip of the great eornu of the hyoid
bone to join the intemal jugular vein ; and the hypoglossal nerve as it
erosses anteriorly at a higher level, superficial to the internal and extemal
earotid arteries. As the nerve turns anteriorly aeross the large arteries it
is itself erossed, superficially, by the sterno-mastoid braneh of the oeeipital
artery, and it gives oflf its deseending braneh. Traee the deseending
braneh downwards, in the fascia whieh lies superficial to the lower part
of the internal and the upper part of the eommon earotid arteries, to
the point where it disappears under cover of the anterior belly of the
omo-hyoid, avoiding injury to the lingual, eommon facial, and superior
thyreoid veins ; ^ and seeure the eommunieating braneh, from the seeond
and third cervical nerves, whieh joins its posterior aspeet The latter
nerve may eross either superficial or deep to the intemal jugular vein.
Return to the hypoglossal nerve at the point where it gives oflf its deseending
braneh, and traee it anteriorly to the upper aspeet of the posterior end
of the great eornu of the hyoid bone, wnere it gives ofF the braneh of
supply to the thyreo-hyoid musele. Traee the braneh into that musele
below the level of the great eornu, then follow the trunk of the hypoglossal
anteriorly to the digastrie triangle. Note that as it runs anteriorly it
passes deep to the posterior belly of the digastrie and the stylo-hyoid
musele, and superficial to the hyoglossus, whieh aseends to the tongue from

^ The lingual vein may join the eommon facial vein, in whieh ease the
latter usually enters the internal jugular opposite the interval between the
hyoid bone and the th^rreoid eartilage, as in the speeimen depieted in Fig. 93.
The superior th^rreoid vein joins the interaal jugular or the eommon facial
vein opposite the th3n*eo-hyoid interval.

II — 15 c

232 HEAD AND NECK

the upper border of the great eornu. Remove the fascial sheath from the
superficial surfaces of the lower parts of the internal and external earotid
arteries, and from the upper part of the eommon earotid artery. Note that
the latter divides into the two former at the level of the upper border
of the thyreoid eartilage, and that the external earotid is at first medial
and anterior to the internal earotid.

Five branehes may spring from the external earotid in the earotid
triangle, three from its anterior surface : the superior thyreoid, the lingual
and the external maxillary ; one from its medial surface, the aseending
phar)nigeal ; and one from its posterior surface, the oeeipital ; but not un-
eommonly the oeeipital and the external maxillary arise beyond the limits
of the earotid triangle under cover of the posterior belly of the digastrie.
The superior thyreoid springs from the front of the lower part of the ex-
ternal earotid below the level of the great eornu of the hyoid and runs
downwards to the lower angle of the earotid triangle, where it disappears
under cover of the anterior belly of the omo-hyoid. The lingual arises
immediately above the level of the tip of the great eornu. It runs an-
teriorly above the level of the eornu, forming a loop, convex upwards,
whieh lies deep to the hypoglossal nerve ; and it disappears under cover
of the posterior border of the hyoglossus musele. The aseending pharyngeal
braneh, whieh springs from the medial surface of the lower end of the ex-
terpal earotid, aseends on a deeper plane, between the external and in-
ternal earotids and the wall of the pharynx, and will be followed at a later
stage of the disseetion. The external maxillary and the oeeipital arise
immediately below the posterior belly of the digastrie and almost at
onee disappear under cover of the musele ; not uneommonly they
arise under cover of its lower border. Before proeeeding to elean the
branehes of the external earotid seeure the internal and external laryngeal
branehes of the superior laryngeal braneh of the vagus nerve. The internal
braneh will be found in the posterior part of the thyreo-hyoid interval below
the great eornu of the hyoid b.one and behind the posterior border of the
thyreo-hyoid musele, beneath whieh it disappears. It is aeeompanied by
the laryngeal braneh of the superior thyreoid artery. The external braneh
is more difficult to find ; but, if the superior thyreoid artery and the upper
part of the eommon earotid are displaeed posteriorly, the nerve will be
Ibund, lying deep to them, in the fascia whieh covers the anterior part of the
inferior eonstrietor musele. Remove the fascia from the surface of the in-
ternal jugular vein, whieh overlaps the posterior borders of the eommon
and internal earotid arteries. Disseet in the interval between the vein and
the arteries and seeure the vagus nerve, whieh Hes deeply. Remove the
remains of the fascia from the earotid arteries and the internal jugular vein,
but avoid injury to the hypoglossal nerve and its branehes ; and note the
presenee of the upper deep cervical lymph glands whieh lie on the superficial
surfaces of the great arteries and the internal jugular vein. The glands are
sometimes very large, and the disseetors should remember that they receive
lymph from the face, the mouth and tongue, the posterior part of the nose
and the upper part of the pharynx. After the large vessels are eleaned,
remove the fascia from the branehes of the external earotid artery and the
twigs they give off, so far as they lie in the region of the earotid triangle.
Gommenee with the superior thyreoid. Immediately after its origin it gives
off a small infra-hyoid braneh, then a laryngeal braneh whieh aeeompanies
the internal laryngeal braneh of the superior laryngeal nerve ; and, just
before it disappears under cover of the anterior belly of the omo-hyoid, a
sterno-mastoid braneh arises from its posterior border and runs downwards
and posteriorly, along the upper border of the omo-hyoid, aeross the super-
ficial aspeet of the eommon earotid artery and the internal jugular vein.

■ THE ANTERIOR PART 0F THE XECK 233

Next, dean the luigual artety and note its smil] $apn-hyi-t-! tinnkrh. Tbe
extemal maiillary artery giresoS no branehes in the eW'-ti'i iriaogle. l-ul »
stemo-niastoid braneh of the oeeinUil arteiy «ill usually \< liian-i [ouing
downwards and posteriorly, Euperheial to Ihe loop or ibe hrpngkiHal ncrve.
Push ihe lower border of the parotid gtand upwards. and immwliately under
cover [>f it, at Ihe level of the aikgle of Ihe mandiUe, seeure (he aeeeHoor

of the sealenus anlerior m

ts it emerges trom under covei of the posterior belly or (he digastrie
O'inastoid rioin the oeeipital

The floor or medial boundary of the earotid triangle is
forraed by the upper part of the thyreo-hyoid musele, the

234

HEAD AND NECK

posterior part of the hyoglossus and the middle
eonstrietors of the pharynx. The two latter mi
be displayed at present, but the thyreo-hyoid is e:
the great eornu of the hyoid bone, and part of th<
ean be seen in the angle between the great eomu
and the lower part of the posterior belly of the dij

The MuseiiLar Triaiigle. — When the deep
covers the museular triangle is removed port
three museles are brought into view. Posten
the anterior belly of the omo-hyoid, more antei
the same plane is the sterno-hyoid, and below anj
the latter, but on a deeper plane, is a small part
thyreoid.

The museles mentioned may be eonsidered
floor or medial boundary of the triangle, and ii
taken the struetures they cover, whieh lie mor^
under cover of the floor. These struetures
exposed.

Disseetion. — Divide the anterior belly of the omo-h]
anterior border of the sterno-mastoid and tum it upwards |
into the hyoid bone. As this is done its twig of supply froi
glossi will be eut. Divide the stemo-hyoid as low down
it upwards to its insertion into the body of the hyoid bone
of supply from the loop whieh is ealled the etnsa hypeglos
by the union of the deseending braneh of the hypogk
eommunieating braneh from the cervical plexus. Seeure
sterno-thyreoid from the ansa h)rpoglossi ; then remove the :
the lower part of the thyreo-hyoid musele, the greater
thyreoid and the anterior part of the thyreoid eartilage.
sterno-thyreoid is inserted into an oblique line on the oiit<
lamina of the thyreoid eartilage and that the thyreo^hyoid a
same line and is inserted into the great eomu of tne hy^
erieo-thyreoid braneh of the superior thyreoid artery may "
downwards and anteriorly along the upper end of th<
aeeompanied by the external laryngeal nerve ; or the n€
may lie deep to the upper end of the musele.

Divide the sterno-thyreoid as low down as possible and
to its insertion ; remove the fascia under cover of it and ej
lobe of the thyreoid gland, and below it a small part of
traehea.

The disseetor should note that whilst the stemo-mastoi<
turbed the posterior part of the lateral lobe of the thyreoi<
lower extremity are not exposed, but if the sterno-mast<
posteriorly the whole of the lateral surface of the lobe is br<
The disseetor should note also that until the stemo-mast<
posteriorly only a small portion of the upper end of the eomi
the lower parts of the internal and external earotid artei
indeed, the eommon earotid may be entirely eoneealed.
of the anterior border of the internal jugular vein projects

THE ANTERIOR PART 0F THE NEGK 235

sterno-mastoid in the upper and posterior angle of the earotid triangle ; and
it also is not uneommonly hidden when the sterno-mastoid is well developed.
During life, however, when the musele is soft and pliable the struetures
eoneealed by it are readily exposed, for the musele is easily displaeed
posteriorly after the fascia has been divided along its anterior border. In
the disseeting-room it is not possible to obtain a proper view of the eourse
and relations of the eommon earotid artery and the internal jugular vein, or
to appreeiate the relations of the tirst part of the subclavian artery and the
relations of the sealenus anterior musele, until the sterno-mastoid has
been reflected. Divide the external jugular vein immediately below the
point where it is joined by the posterior aurieular tributary and turn it
downwards. Divide the great aurieular nerve at the level of the angle of
the mandible and turn it posteriorly ; and turn posteriorly the neryus
eutaneus eolli, whose two terminal branehes have been eut already. The
clavicular head of the sterno-mastoid was eut when the clavicle was
removed ; now divide the sternal head, turn the musele upwards towards its
insertion. As the musele is turned upwards, sterno-mastoid branehes of the
transverse seapular, superior thyreoid, and oeeipital arteries will be exposed ;
and if they interfere with the reflection of the musele they must be divided.
Slightly above the level of the sterno-mastoid braneh of the oeeipital artery
the aeeessory nerve will be found passing through the deeper fibres of the
musele, and eare must be taken to avoid injury to it ; but it may be disseeted
out of the musele and left in position on the lateral surface of the internal
jugular vein.

Deep Cervical Fascia. — When the sterno-mastoid has been
reflected a deep fascial plane of the neek is exposed in whieh
lie many lymph glands. Before earrying the disseetion further
the disseetor should reeonsider the arrangement of the deep
cervical fascia. He has already seen that it forms a eomplete
sheath enelosing the museles of the neek and the struetures
whieh lie between and under cover of them. The general
arrangement of the fascia is studied best on transverse
seetions of the neek made at the level of the isthmus of the
thyreoid gland and a short distanee above the sternum. At
the former level it is possible to reeognise (i) a superficial
layer; (2) a pretraeheal layer ; (3) a prevertebral layer; and (4)
a fascial sheath whieh eneloses the eommon earotid arteries,
the internal jugular vein and the vagus nerve, as they lie in
the angular interval between the sterno-mastoid laterally, the
thyreoid gland, the traehea, eesophagus medially, and the
prevertebral museles posteriorly. ThQfirst or superficial layer,
as it is traeed posteriorly, splits to enelose the sterno-mastoid
musele. Beyond the sterno - mastoid it passes posteriorly
to the anterior border of the trapezius musele, forming the
roof of the posterior triangle, then splits again to enelose the
trapezius, along the surfaces of whieh it is prolonged till it
blends with the suprasDinons ligaments and the ligamentum

236

HEAD AND NECK

nuehse. The lamella whieh covers the deep suriaee of the
stetno-mastoid is blended with the lateral surface of the earotid
sheath. The pretraeheal layer, whieh has been disseeted
already in the median plane, ensheaths the thyreoid gland
and ble ds po tero-late ally wth the medial suriaee of the
ca ot d heatb The prevertebral layer covers the anterior
su faces of he preverteb al museles and passing laterally,
blends V tb the poster or aspeet of tbe ca otid sheath ; then,

turn ng round the tips

,^^^^*g^pp U of the transverse pro-

— ~ . I ^ eesses of the vertebrse,
t I asses posteriorly,
co er ng the museles
wh ch form the floor of
the posterior triangle ;
and t beeomes eontinu-
ous ith the sheaths of
the deep museles of the
posteriorpartoftheneck.
Laterally and pos-
te orly, the superficial
la>e of the deep fascia
pa ses upwards over the
sterno-mastoid and the
trapezius to be attaehed
to the superior nuehal
1 nes and the mastoid
port ons of ihe temporal
bones In the anterior
cerv eal reg on t s attaehed to the bod) and the great eomua
of the hyoid bone, and then, as t is prolonged further upwards,
it sptits anteriorly to endose the submaKillary gland, and
posteriorly to enelose the parotid. It bas been noted already
that the lamella whieh passes superficial to the subma^illary
gland is attaehed to the lower border of the mandibte, and
tbat whieh passes deep to the gland is eonneeted above to
the mylo-hyoid line on the inner surface of the mandible. The
layer whieh passes superficial to the parotid gains attaehment
to the zygoma and is prolonged forwards to blend with the
fascLa covering the masseter. The lamella whieh passes deep
to the parotid covers its postero-medial and antero-medial
surfaces ; the posterior part is attaehed above to the lower

THE ANTERIOR PART 0F THE NECK

237

border of the tympanie plate and the anterior part to the
posterior border of the petro-tympanie fissure (O.T. Glaserian).
It also gains an intemediate attaehment to ihe styloid
proeess and to the posterior border of the angle of the
mandible. This partieular portion is relalively thiek ; it lies
in relation with the lower part of the antero-medial surface of
the parotid and is known as the stylo-mandibular ligament.

When the supirficial layer is traeed downwards it is found
to split, between the erieoid eartilage and the sternum, irito two
lamellae. The more superficial of the two lies superficial to
the sterno-mastoid and is at- Yitsi layn ordeip fa5cui

taehed below to the upper
border of the sternum and the
upper border of the clavicle.
In the anterior region the
deeper lamella deseends upon
the anterior surfaces of the
intra-hyoid museles and is at-
taehed below to the posterior
surface of the manubnum ;
laterally it passes deep to the
stemo - mastoid and is fused
with the lateral border of the
earolid sheath. In the posterior
triangle the deeper lamella
ensheaths the posterior belly
of the omo-hyoid and binds it
down to the posterior border
of the elayiele. The spaee ■
between the two lamellas has
been ealled the supra-sternal
spaee. Its boundaries and eontents have been fully deseribed
already {p. 224).

The upper atlaehment of the pretraeheal layer is to the
erieoid eartilage and to the laminEe of the thyreoid eattilage
below the insertion of the sterno-thyreoid musele. At its
lower end it blends with the fibrous perieardium in the
middle mediastinum.

The pr^ertebral layer ean be followed upwards to the
base of the skull, where it is attaehed, in the anterior cervical
region, to the posterior and medial raargins of the jugular
foramen and to the basilat part of the oeeipital bone, anterior

;. 96. — Diagram of deep cerv
leve1 of ibe ibyteoid gland.

338 HEAD AND NECK

to the insertions of the prevertebral museles and posterior to
the superior eonstrietor of the pharynx. Below, it blends
with the fascia on the anterior aspeet of the vertebral eolumn
in the posterior mediastina! region.

The Garotid Staeath. — The term earotid sheath is applied
to the fascia whieh surrounds and embeds the earotid arteries,
the internal iugular vein, and the vagus nerve. Part of it has
been removed already, and the disseetor will have noted that
it is in no sense a membrane, but merely the fibro-areolar
tissue whieh fills the interval between the transverse proeesses
of the yertebrae posteriorly, the traehea, Iaryrx, pharynx,
eesophagus, and the lateral lobe of the thyreoid gland medially,
and the sterno-mastoid laterally ; that it is eontinuous with
the fascial planes in its immediate neighbourhood, and that

FiG. 97.

through it run the earotid arteries, the internal jugular vein,
and the vagus nerve, eaeh in its own speeial eompartment.

Disseetisn. — Remove the areolar lissue and the glands whieh lie under
cover of the stemo-mastoid ; stiteh ti^ether Ihe two parls of the divided
anlerior belly of the omo-hyoid musele and ltx the musele to the eommon
earotid arte^ and the internal jugular vein with one or two stitehes ; Ihen
proeeed lo display the struetuies whieh lieunder cover of thesterno-masloid.
A glanee at the followii^ list will convince the disseetor that (hey are
extremely numerous.

Struetures heneath the Stenio-Uastoid

MuseleB. — The upper part of the splenius eapitis ; the
upper and posterior part of the posterior beliy of the digastrie;
the origins of the levator seapulEe, the sealenus medius, the
longus eapitis {O.T. reetus eapltis anlieus major), the reetus
eapitis lateralis and the sealenus anterior ; the intermediate

THE ANTERIOR PART 0F THE NECK 239

tendon of the omo-hyoid, and the lower and posterior part of
the stemo-hyoid and sterno-thyreoid.

Arteries. — The upper part of the eommon earotid (the
lower part is still eoneealed by the lower parts of the omo-
hyoid and the lower parts of the stemo-hyoid and sterno-
thyreoid museles) ; the transverse seapular and its sterno-
mastoid braneh ; the transverse cervical ; the stemo-mastoid
braneh of the superior thyreoid ; the oeeipital and its stemo-
mastoid branehes.

Vems. — The greater part of the internal jugular vein ; a
part of the lower transverse portion of the anterior jugular
vein ; and, oeeasionally, the lower end of the extemal jugular
vein when that vessel dips anteriorly to its termination.

Nerves. — The cervical plexus and its branehes, ineluding
the phrenie nerve ; part of the aeeessory nerve.

If the lower parts of the divided stemo-hyoid and sterno-
thyreoid museles are displaeed downwards, the lower part of
the eommon earotid and the eommeneement of ihe first part of
the subclavian artery will be exposed. Grossing the front of
the latter are the lower portion of the cervical part of the vagus
and a strand of sympathetie iibres ealled the ansa subclavia ;
on the left side, the subclavian artery and the ansa are eon-
eealed by tlie eommeneement of the innominate vein. At
the same time the middle thyreoid vein will be exposed,
and the posterior border of the lateral lobe of the thyreoid
gland also.

Disseetion. — Commence by eleaning the anterior branehes of the eenrieal
nenres from the seeond to the eighth, as they emerge between the museles
attaehed to the tubereles of the transverse proeesses of the cervical
yertebrse. The first nerve, whieh tums downwards anterior to the trans-
yerse proeess of the atlas, will be exposcd later. As the upper nerves are
eleaned the disseetors will find that the seeond is eonneeted to the third,
and the third to the fourth, by looped strands, convex posteriorly, whieh
eonstitute the two lower loops of the cervical plexus. The seeond nerve is
eonneeted with the first also by a loop, convex anteriorly, whieh passes
upwards anterior to the transverse proeess of the atlas and posterior to the
upper part of the internal jugular vein. It ean be exposed if the vein is pulled
anteriorly ; and the disseetor must at the same time seeure the twigs of
eonneotion whieh pass from the medial side of the loop to the hypoglossal
nerve and to the superior cervical ganglion of the sympathetie trunk, whieh
lies behind the upper part of the intemal earotid artery.

After he has defined the loops of the plexus he should traee the remains
of the small oeeipital, the great aurieular, the transverse eutaneous nerve of
the neek and the supraclavicular branehes, whieh he displayed in the
posterior triangle, to their origins from the roots of t|ie plexus. The
eommunieating branehes whieh pass anteriorly to the deseendens h^rpe^lossi
from the seeond, and s^* — ** — " also from the third cervical nerve, must be

240

HEAD AND NECK

followed ; they may eross either superficial or deep to the internal jugular
vein. Then the phrenie nerve, whieh springs from the fourth cervical
nerve, and receives additional twigs from the third and fifth nerves, must
be followed downwards and anteriorly till it disappears under cover of the
lower part of the internal jugular vein. It lies upon the surface of the
sealehus anterior and passes deep to the omo-hyoid musele and the trans-
verse cervical and transverse seapular arteries. Running parallel with,
and anterior to it, is the aseending cervical braneh of the inferior thyreoid
artery.

Small occipitalj R
H

Great aurieular

Hypoglossal

Nervus eutaneus eolli

Braneh to levator
seapulae

Deseending trunk

To genio-hyoid

Thyreo-hyoid nerve
Deseendens h^rpoglossi

Ansa hypoglossi

eatin^ to
fifth cervical

Phrenie

FiG. 98. — Diagram of the Cervical Plexus and the Ansa

Hypoglossi.

I, II, III, IV.— Anterior branohes of the upper four cervical nerves.

R. Branehes to reeti and longus eapitis.
S. M. Branehes to the sterno-mastoid.
C.C. Rami eommunieantes cervicales.

C.H. Communicating braneh to hypo-
glossal.

This diagram shows that the deseendens hypoglossi, the braneh to the
thyreo-hyoid, and in all probability the branehes to the genio-hyoid, are
eomposed of fibres given to the hypoglossal by the eommunieating twigs
it receives from the first cervical nerve.

Plexiis Cervicalis. — This is a looped plexus formed by
the first four cervical nerves. It lies in the upper part of
the side of the neek under cover of the sterno-mastoid. The
upper loop of the plexus, whieh eonneets the first and seeond
nerves together, is direeted forwards and lies between the
internal jugular vein anteriorly, and the transverse proeess of
the atlas posteriorly. The seeond and third loops, whieh

THE ANTERIOR PART 0F THE NECK 241

unite the seeond and third and the third and fourth nerves
are direeted posteriorly ; and they lie on the superficial surface
of the upper p'art of the sealenus medius musele. The first
loop is eonneeted with the upper ganglion of the sympathetie
trunk and with the hypoglossal nerve ; and the roots of the
seeond, third and fourth nerves also are eonneeted, by grey
rami, with the upper cervical sympathetie ganglion.

The branehes of the plexus are divisible into two main
groups, the superficial and the deep. The deep branehes are
separable into two groups : the anterior, whieh run forwards
and the posterior, whieh run baekwards ; and the superficial
branehes are classified as aseending, transverse and deseending.

The anterior group of deep branehes ineludes : (i) the ramus
eommunieans cervicalis, and (2) the phrenie nerve.

The posterior group of deep branehes is formed by : (i) The
eommunieating branehes to the aeeessory nerve. (2) Branehes
of supply to (a) the sterno-mastoid from the seeond nerve;
(p) the levator seapulse from the third and fourth ; (c)
the trapezius from the third and fourth ; (d) the sealenus
medius from the seeond, third, and fourth. (3) Less im-
portant museular branehes from the first loop to {a)
the reetus eapitis lateralis; (^) the reetus eapitis anterior
(O.T. reetus eapitis antieus minor); {c) the longus eapitis
(O.T. reetus eapitis antieus major). (4) Museular branehes
from the third and fourth nerves to the longus eolli.

The aseending group of superficial branehes is formed by the
small oeeipital and great aurieular nerves. The transverse
braneh is the nervus eutaneus eolli, and the deseending
branehes are the supraclavicular nerves. All the superficial
nerves have already been traeed in the earlier stages of the
disseetion (pp. 145, 146), but the phrenie nerve requires
careful eonsideration.

Nennis Phrenieus. — The importanee of the phrenie nerve
depends upon the fact that it is the nerve of supply to the
chief musele of respiration, the diaphragm. The majority of
its fibres spring from the fourth cervical nerve, but it receives
twigs from the third and, not uneommonly, from the fifth
nerve also. It deseends from the neek through the superior
and posterior mediastinal regions of the thorax, and, after
piereing the diaphragm, it is distributed on its lower surface.
Only the cervical portion of the nerve belongs to the dis-
seetor of the neek ; the remainder is displayed by the disseetor

VOL. II — 16

242 HEAD AND NECK

of the thorax (p. 341). In the neek the nerve runs down-
wards and anteriorly, on the superiieial surface of the sealenus
anterior, whieh forms its deep relation. In this part of its
eourse it is covered by skin, superficial fascia and platysma,
deep fasciaandsterno-mastoid; and, deep to the sterno-mastoid,
it is oyerlapped by the internal jugular vein, and it is erossed
by the omo-hyoid, the anterior jugular vein, and the transverse
cervical and transverse seapular arteries on both sides ; on the
left side by the thoraeie duet, and on the right side by the
right lymph duet. At the root of the neek it passes from the
medial border of the anterior sealene to the anterior surface
of the first part of the subclavian artery ; and it is covered
anteriorly by the clavicle on both sides, by the subclavian
vein on the right side, and by the eommeneement of the in-
nominate vein on the left side, and it erosses either anterior
or posterior to the internal mammary artery. It gives off no
branehes in the neek, but it sometimes receives a eommuniea-
tion from the nerve to the subclavius.

After the disseetor has eompleted the examination of the formation, tbe
relations, and the branehes of the cervical plexus, he should replaee the
divided ihfra-hyoid museles in position and study their attaehments and
relations.

The Infra-hyoid Museles are a series of flat, band-like
museles whieh lie upon the traehea, thyreoid gland, and
larynx. They are disposed in two strata — viz., the omo-hyoid
and the sterno-hyoid eonstituting a superficial layer; and
the sterno-thyreoid and thyreo-hyoid a deep layer.

Museulus Omohyoideus. — This is a two-bellied musele. The
posterior belly springs from the upper border of the seapula
and the upper transverse seapular ligament. It erosses the
posterior triangle of the neek, dividing it into oeeipital
and subclavian portions, and terminates under cover of the
sterno-mastoid musele in an intermediate tendon ; and it is
superficial to the phrenie nerve and the sealenus anterior.
The tendon is held in position by a strong proeess of cervical
fascia whieh is firmly attaehed below to the sternum and the
first eostal eartilage. The anterior belly emerges from under
cover of the anterior border of the sterno-mastoid, and takes
an almost vertical eourse through the anterior triangle. It is
inserted into the lower border of the body of the hyoid bone,
at the lateral side of the sterno-hyoid. In the anterior
triangle of the neek it forms the boundary between the

THE ANTERIOR PART OF THE NEGK 343

earotid and the museular subdivisions, and it lies supertieial
to the internal jugular vein, the eommon earotid artery, the
deseendens hypoglossi, the superior thyreoid artery, the ex-
ternal laryngeal nerve, the attaehments of the sterno-thyreoid
and Ihyreo-hyoid museles to the lamina of the thyreoid

eartilage; and immediately below its insertion it covers part
of the thyreo-hyoid membrane, Both bellies are supplied by
branehes from the ansa hypoglossi.

Museulus Stemokyoidtus. — This arises from the posterior
aspeet of the medial end of the clavicle, the posterior
sterno-clavicuIar ligament, and the posterior surface of the
manubrium. It is inserted into the lower border of the body

244 HEAD AND NECK

of the hyoid bone, between the median plane and the insertion
of the omo-hyoid. A short distanee above the sternum an
oblique tendinous interseetion frequently divides it into two
portions. The lower part of the musele is covered by the
sterno-mastoid, and it is erossed by the anterior jugular vein.
Its prineipal deep relations are the lower part of the eommon
earotid artery and the sterno-thyreoid musele, whieh separates
it from the lateral lobe of the thyreoid gland. It is supplied
by branehes from the ansa hypoglossu

Museulus Stemothyreoideus, — This musele lies under cover
of the preeeding and is both broader and shorter. It springs
from the posterior aspeet of the manubrium sterni and from
the eartilage of the first rib. Diverging slightly from its
fellow as it aseends, it is inserted into the oblique line on
the lateral face of the lamina of the thyreoid eartilage. An
ineomplete tendinous interseetion may sometimes be notieed
interrupting its museular fibres. The nerve supply is derived
from the ansa hypoglossi, In the neek it is covered in the
greater part of its extent by the sterno-hyoid ; but the posterior
part of its insertion is covered by the anterior belly of the
omo-hyoid ; and the lower and anterior part is covered by skin
and fascia only. The nerve supply is derived from the ansa
hypoglossi.

Museulus Thyreohyoideus. — This musele lies on the same
plane as the sterno-thyreoid, and may be regarded as its
upward eontinuation. It takes origin from the oblique line
on the outer surface of the lamina of the thyreoid eartilage,
and is inserted into the lower border of the great eornu of
the hyoid bone under cover of the omo-hyoid musele. It
eoneeals part of the lamina of the thyreoid eartilage and
the lateral part of the thyreo-hyoid membrane, and the
aperture in the membrane through whieh the laryngeal braneh
of the superior thyreoid artery and the internal laryngeal
nerve enter the pharynx. It is supplied by a twig from the
hypoglossal nerue.

Disseetion. — The disseetors of the head and neek should now proeeed to
study the relations of the eommon earotid and subclavian arteries, the
cervical part of the thoraeie duet, and the dome of the pleura, before these
are disturbed by the disseetors of the thorax. Whilst this is being done,
the omo-hyoid must be retained in position, but the upper and lower portions
of the other infra-hyoid museles may be turned upwards and downwards
respectively.

Remove the remains of the fascial sheath from around the oommon

THE ANTERIOR PART 0F THE NECK 245

earotid artery and the adjacent part of the internal jugular vein. Separate
the vein from the artery and elean the portion of the vagus nerve whieh
lies between them on a posterior plane. Note that on the right side the
nerve erosses the anterior surface of the subclavian artery, and there gives
off its reeurrent braneh ; and that on the left side it lies medial to the sub-
clavian artery on an anterior plane.

After the lower parts of the vagi have been eleaned, look for the terminal
part of the thoraeie duet on the left side and for the right lymphatie duet on
the right side. In seeking for the thoraeie duet pull the lower end of the
left internal jugular vein aside and displaee the eommon earotid artery
anteriorly ; then look for the duet as it turns laterally from the border of
the oesophagus a little below the level of the erieoid eartilage ; traee it
posterior to the internal jugular vein to its termination in the eommenee-
ment of the innominate vein. On the right side look for the right lymphatie
duet entering the innominate vein in the angle of union of the internal
jugular and subclavian veins. Next look for the cervical portion of the
sympathetie trunk, whieh deseends posterior to the eommon earotid. Glean
the nerve trunk carefully and elean also the inferior thyreoid artery, whieh
erosses anterior or posterior to it, at the level of the erieoid eartilage. Dis-
plaee the eommon earotid laterally, and in the angle between the borders
of the traehea and the oesophagus find the reeurrent braneh of the vagus ;
traee it upwards to the point where it disappears under cover of the lateral
lobe of the thyreoid gland, and downwards to the subclavian artery.

Arteria Oarotis Ooiniimnis.— The eommon earotid arises
diATerently on the two sides. On the right side it springs
from the termination of the innominate artery, behind the
sterno-clavicular joint, and on the left side from the aortie
areh in the superior mediastinum. The left artery aseends
to the baek of the left sterno-clavicular artieulation. From
the sterno-clavicular joint eaeh eommon earotid artery runs
upwards, posteriorly, and slightly laterally to the upper border
of the thyreoid eartilage, whieh lies opposite the dise
between the third and fourth cervical ^ertebrse ; and there it
ends by dividing into its two terminal branehes — the internal
and the external earotid arteries.

Superficial Relations, — Above the level of the anterior
belly of the omo-hyoid the eommon earotid artery is covered
by the skin, the superiieial fascia and the platysma, the deep
fascia and the anterior margin of the sterno-mastoid. It is
erossed immediately above the omo-hyoid by the sterno-
mastoid braneh of the superior thyreoid artery and, at a higher
level, by the superior thyreoid vein ; and it is overlapped by
the anterior margin of the internal jugular vein. In the
lower part of its extent it lies more deeply : its superiieial
relations are the skin and superiieial fascia, the deep fascia
and the sterno-mastoid ; the anterior jugular vein, erossing
transversely, deep to the sterno-mastoid and above the upper

246

HEAD AND NECK

border of the clavicle ; the omo-hyoid, the sterno-hyoid, and
the sterno - thyreoid museles. Deep £o the museles, the
branehes of the ansa hypoglossi deseend in front of its
sheath; and the middle thyreoid vein erosses it to ioin the
internal jugular vein.

Postenor to it lie the transverse proeesses of the cervical
vertebr£e and the origins of the longus eolH, longus eapitts
(O.T. reetus eapilis antieus major), and the sealenus anterior.
The inferior thyreoid artery erosses posterior to it at the level
of the erieoid eartilage ; and the vertebral artery lies between
it and the transverse proeess of the seventh cervical vertebra.
On the right side, the reeurrent braneh of the vagus erosses

posterior to it, iramediately above its origin ; and on the Ieft
side the thoraeie duet turns laterally behind it, between it
and the vertebral artery.

To its medial side, below, lie the traehea and eesophagus,
with the reeurrent nerve in the angle between their adjacent
borders ; and to the medial side of its upper part are the
larynx and pharynx. The lateral lobe of the thyreoid gland
lies either medial to the artery, separating it from the
eesophagua, pharynx, traehea, and larynx, or it forms a direet
anterior relation (Figs. 97, loi). Between its upper extremity
and the inferior eonstrietor musele of the pharynx lies the
earotid body. As a rule, the terminal divisions are the only
branehes of the eommon earotid, but oeeasionally the
superior thyreoid or ihe aseending pharyngeal artery arises

THE ANTERIOR PART 0F THE NECK 347

{rom it, instead of from the extema.l earotid. Thls is more
espeeially the ease when the division of the eomnion earotid
takes plaee at a higher levei than usual.

earotid Body. — This is a liltU oval, reddish-brown body, plaeed upon
Ihe deep aspeel of the eommon eaiotid aiteiy at the point where it
birureales. To eitpose it, thererore, the vessel must he twisled lound ia
siieh a manner thal its posteiior surraee eomes to look roiwBids. It is
elosely eonneeted with (he sympathelie tiUments wbieh twine around the
eatotLd vessels ; and in strueture it is similar in its natute lo ihe minule
eoeeygeal body, whieh rests upon the antetiot aspeel or ihe coccyx. It ii
ineluded, thererore, in the group or duetless glands. Entenng it ale
numeious minule arterial (wigs, whieh take oiigin rrom ihe teimination of
the eommon eaiotid and the eommeneemenl of ihe exletnal earolid. The
runetion of this remarkable liltle body is quite unknown. MoM likely it

Arteria SnbelaTiA. — The relations of the third part of the
subclavian artery were exainined during the disseetion of the
posterior triangle (p. 1 5 1 ). Those of the first and seeond parts
must now be studied. On the right side a small portion of the
iirst part is already exposed between the lower ends of the
internal iugular vein and the eommon earotid artery ; the
remainder ean be seen if the intemal jugular vein is drawn
aside. On the Ieft side the first part of the artery is eoneealed
by the eommeneement of the innominate vein, whieh must be
pushed aside. On both sides the seeond part of the artery
lies posterior to the sealeniis anterior, whieh must be left in
position.

The subclavian artery is the first portion of the great
arterial trunk whieh earries blood for the supply of the upper

248 HEAD AND NECK

extreiTiity. It arises ditTerently on the two sides of the body.
On the right side it takes origin behind the sterno-clavicular
artieulation from the bifurcation of the innominate artery.

FiG. loa,— DeepDis5ectionof theKooiofthe Neek on the Left Side lo show
Ihe Dome of the Pleura and the relations of the Terminnl Pnrt of the
Thoraeie Duet. The slerno-niasloid and tlie depressors of the hyoid and
larynji have been remoyed,

On the Uft side it arises from the aortie areh in the superior
mediastinum. In both eases it takes an arehed eourse
laterally aeross the root of the neek, posterior to the sealenus
anterior and on the anterior surface of the cervical dome of -.

THE ANTERIOR PART 0F THE NECK

'49

pleura, a short distanee below its summit \.t the outer
border of the first nb it beeomes the axilkrj artery.

For descriptive purposes the artery is divided into three
parts. The _^rst part extends from the ongin of the vessel

to the medial margin of the sealenus anterior; the seemd
portion lies posterior to that musele ; and the tkird part
extends from the lateral border of the sealenus anterior to
the outer border of the first rib.

First /'ar/.—Omng to the dilTerenee of origin, the relations
of the first portion of the subclavian artery are not the same

250 HEAD AND NECK

on the two sides of the body. The first part of the right
subclavian extends obliquely upwards and laterally, and at its
termination at the medial margin of the sealenus anterior
it has reaehed a point above the level of the clavicle. It is
plaeed very deeply. Anteriorly, it is covered by the skin,
superficial fascia, platysma, deep fascia, and three museular
strata — viz., the clavicular origin of the sterno-mastoid, the
sterno-hyoid, and the sterno-thyreoid. Three veins and some
nerves are plaeed anterior to it. At the medial margin of
the sealenus anterior it is erossed by the internal jugular
and vertebral veins, whilst the anterior jugular vein, as it
passes laterally under cover of the sterno-mastoid, is separated
from it by the sterno-hyoid and sterno-thyreoid museles. The
nerves whieh eross anterior to it are the vagus, a loop from
the sympathetie (ansa subclavia), and in some eases eardiae
branehes of the vagus and sympathetie as they run to the
thorax. At the lower margin of the artery the vagus nerve
gives off its reeurrent braneh.

The cervical dome of the pleura is both below and posterior
to the artery, and the reeurrent braneh of the vagus nerve
hooks round below and aseends posterior to it.^

On the left side^ the first part of the subclavian aseends
almost vertically from its origin from the aortie areh, and,
reaehing the root of the neek, it curves laterally aeross the
dome of the pleura to the medial margin of the sealenus
anterior. The relations of the cervical part are somewhat
different from those on the right side. The same fascial
and museular layers, and the same nerves and veins, are
anterior to it. Owing to its different direetion, however, the
neryes and veins are plaeed more or less parallel to it. Three
additional relations are established — viz., the phrenie nerve and
the left innominate vein lie anterior to it ; and the thoraeie
duet first passes upwards in relation to its medial or right
side, and then arehes over it to reaeh the angle of junction
between the subclavian and internal jugular veins.

The reeurrent nerve on the left side hooks round the areh
of the aorta, and lies to the medial side of the subclavian
artery.

Seeond Part. — The seeond portion of the subclavian artery

^ If the liing has been removed by the disseetor of the thorax the lower
and posterior relations should be verified by examination from the thoraeie
side.

THE ANTERIOR PART 0F THE NEGK 251

forms the highest part or summit of the areh, and rises from
half an ineh to an ineh above the level of the clavicle.

In this part of its eourse the vessel is not so deeply
plaeed. Anteriorly it is covered by — (i) skin ; (2) superiieial
fascia and platysma ; (3) deep fascia ; (4) clavicular head
of the sterno-mastoid ; (5) sealenus anterior. The phrenie
nerve on the right side is also an anterior relation, but it is
separated from the artery by the medial margin of the
sealenus anterior. Posteriorly and inferiorly^ the vessel is in
relation with the pleura, Sibson's fascia intervening. The
subclavian vein lies at a lower level than the artery and on
an anterior plane, and is separated from it by the sealenus
anterior.

The third part of the subclavian artery is deseribed on
p. 151.

Branehes of the Subclavian Artery. — Four branehes
spring from the subclavian trunk (Fig. 103). Three take
origin, as a general rule, from the iirst part of the artery
elose to the sealenus anterior, and one from the seeond part.
They are —

Yertebral,
2. Thyreo-cervical

Inferior thyreoid
Transverse cervical
Transverse seapular.

From the J ,
first part. \

V3. Internal mammary.
From the i ^ . . f Superior intereostal.

seeondpart. [ Costo-cervical. [Deep cervical.

In a great number of eases a braneh of eonsiderable size will be
observed springing from the third part of the subclavian artery. This,
in all probability, is the deseending braneh of the transverse cervical,
arising direetly from the subclavian. It is so eommon an oeeurrenoe that
the disseetor must always be prepared to meet it.

Arteria Yertebralis. — This is the first braneh whieh is
given off by the subclavian. It springs from the upper and
posterior aspeet of the trunk about a quarter of an ineh from
the m.edial margin of the sealenus anterior on the right side,
and from the point where the vessel reaehes the root of the
neek on the left side. Only a small portion of it is seen in
the present disseetion. It proeeeds upwards in the interval
between the longus eolli and the sealenus anterior museles,
posterior to the eommon earotid, and disappears into the
foramen transversarium of the transverse proeess of the sixth
cervical vertebra. It is plaeed very deeply, and is covered

252 HEAD AND NECK

anteriorly by its eompanion vein and the eommon earotid
artery. Numerous large sympathetie twigs aeeompany it.

The yertebral artery on the left side is posterior to the
internal jugular vein and the eommon earotid artery, and it
is erossed by the thoraeie duet.

The vertebral vein issues from the aperture in the transverse
proeess of the sixth cervical vertebra. It passes downwards,
antero-lateral to its eompanion artery, and posterior to the
internal jugular vein, to open into the posterior aspeet of the
eommeneement of the eorresponding innominate vein. Near
its termination it erosses the subclavian artery. It receives
the deep eeruieal and the anterior vertebral veins,

Tnineus Thyreocervicalis (O.T. Thyroid Axis). — This is
a short wide trunk, whieh arises from the anterior aspeet
of the subclavian artery, elose to the medial margin of the
sealenus anterior, and under cover of the internal jugular vein.
It lies between the phrenie and vagus nerves, and almost
immediately breaks up into its three terminal branehes — viz.,
the inferior thyreoid, the transverse seapular, and the transverse
cervical.

Arteria Thyreoidea Inferior. — This vessel takes a sinuous
eourse to reaeh the thyreoid gland. At first, it aseends for
a short distanee along the medial border of the sealenus
anterior, and under cover of the internal jugular vein ; then,
at the level of the erieoid eartilage, it turns suddenly medial-
wards and passes posterior to the sympathetie, the vagus, and
the eommon earotid artery, to the posterior border of the
thyreoid gland, where it gives off branehes to the larynx and
then deseends along the posterior border of the gland, dis-
tributing branehes to its substanee and to the traehea and the
oesophagus.

The following branehes will be notieed arising from the
inferior thyreoid artery : —

1. Aseending cervical.

2. Inferior laryngeal.

3. Traeheal.

4. Pharyngeal.

5. GEsophageal.

6. Glandular.

7. Museular.

Arteria Cervicalis Aseendens. — This small but eonstant vessel
runs upwards in the interval between the sealenus anterior
and longus eapitis, and gives branehes to the museles in
front of the vertebral eolumn. It also gives o^ spinal branehes^
whieh enter the vertebral eanal upon the spinal nerves, and

THE ANTERIOR PART 0F THE NECK 253

anastomose with branehes from the vertebral artery. The
ultimate distribution of the spinal branehes has been notieed
already (p. 193).

Arteria Laryngea Inferior, — This small vessel aeeompanies
the inferior laryngeal nerve to the larynx. The traeheal^ eesopha-
geal, and pharyngeal branehes supply the traehea, the gullet,
and the pharynx. They are of small size, and anastomose
with the bronehial and oesophageal branehes of the thoraeie
aorta. The glandular branehes are usually two in number.
One aseends upon the posterior aspeet of the lateral lobe of
the thyreoid gland, whilst the other is given to its base or
lower end. They inoseulate with the eorresponding vessels
of the opposite side, and also with the branehes of the
superior thyreoid artery. The museular branehes are a series
of irregular twigs given to the various museles in the
neighbourhood.

Vena Thyreoidea Inferior — The inferior thyreoid vein does
nbt run in eompany with the artery of the same name. It is a
comparatively large vessel whieh eomes from the lateral lobe
and the isthmus of the thyreoid gland, and deseends upon
the traehea under cover of the sterno-thyreoid musele. The
veins of both sides enter the thorax, and frequently unite to
form a short eommon stem, whieh opens into the left in-
nominate trunk. In other eases, however, the right vein
will be observed to open separately into the angle of union
between the two innominate veins. Both veins, as they
proeeed downwards, receive tributaries from the larynx,
traehea and oesophagus.

The anterior vertebral vein aeeompanies the aseending
cervical artery, and opens into the vertebral vein as it issues
from the foramen transversarium of the sixth cervical vertebra.

The Transyerse Seapular and Transverse Gervical Arteries.
— Both of these arteries have already been examined in the
greater part of their eourses (p. 147). After taking origin
from the thyreo-cervical trunk, they both pass laterally aeross
the sealenus anterior musele and the phrenie nerve under
cover of the clavicular head of the sterno-mastoid. The
transverse seapular erosses the anterior sealene musele elose
to its insertion, immediately above the subclavian vein ; the
transverse cervical is plaeed at a slightly higher level.

The transverse seapular and transverse eeruieal veins have
already been seen joining the external jugular vein.

2 54 HEAD AND NECK

Arteria Mammaria Intema. — The internal mammary artery
springs from the lower and anterior aspeet of the subclavian,
direetly below the thyreo-cervical trunk. It passes downwards
upon the anterior surface of the pleura, posterior to the medial
end of the clavicle and the medial end of the subclavian vein,
to reaeh the thorax. As it lies posterior to the subclavian
vein the phrenie nerve passes from the lateral to the medial
side, either anterior or posterior to it. In the neek the in-
ternal mammary artery is not aeeompanied by a vein.

Truneus Costocervicalis. — This braneh takes origin from
the posterior aspeet of the seeond portion of the subclavian
artery, elose to the medial border of the sealenus anterior.
On the left side, however, it proeeeds, as a rule, from the
first part of the parent trunk. To bring it into view the
subclavian artery must be dislodged from its position. It
is a short trunk whieh passes upwards and posteriorly over
the apex of the pleura to the neek of the first rib, where it
divides into the deep cervical artery and the superior intereostal
artery.

If the lung is removed from the thorax the disseetor
should take the opportunity of examining this artery from the
thoraeie aspeet.

Arteria Cervicalis Profunda. — This braneh passes dorsally
and disappears from view between the transverse proeess of
the seventh cervical vertebra and the neek of the first rib.
It has been already notieed in the disseetion of the baek
of the neek (p. 173).

The deep eeruieal vein is a large vessel. It joins the
vertebral vein.

Arteria Intereostalis Suprema. — The superior intereostal
artery turns downwards anterior to the neek of the first rib,
between the first thoraeie nerve and the first thoraeie ganglion
of the sympathetie. It gives a posterior intereostal braneh to
the first spaee and ends as the posterior intereostal artery of
the seeond spaee (Fig. 5).

Vena Subclavia. — The subclavian vein is the eontinuation
of the axillary vein into the root of the neek. It begins
at the outer border of the first . rib, and arehes medially
on the anterior surface of the lower end of the sealenus
anterior. At the medial margin of this musele, and posterior
to the sternal end of the clavicle, it joins with the intemal
jugular to form the innominate vein. In eonneetion with

THE ANTERIOR PART 0F THE NECK 255

the subclavian vein note: (i) that the areh whieh it forms
is not so pronouneed as the areh of the eorresponding
artery; (2) that throughout its whole eourse it lies at a
lower level, and upon a plane anterior to the artery; and
(3) that it is separated from the artery by the sealenus
anterior and the phrenie nerve. In the whole of it§ eourse
the vein lies posterior to the clavicle.

The sheath of the subclavian vein is attaehed to the posterior surface of
the eosto-eoraeoid membrane. This is a relation of some praetieal import-
anee ; for, on aeeount of it, a forward movement of the clavicle drags upon
the vein, and in eases where the vessel is wounded there is always a danger
of air being sueked into the vein by sueh a movement.

. The tributary of the subclavian vein is the external jugular
vein, whieh joins it at the lateral margin of the sealenus
anterior.

Duetus Thoraeieus et Duetus Lsrmphatieus Dexter. — The
thoraeie duet is the vessel by means of whieh the ehyle and
the lymph, derived from by far the greater part of the body,
are poured into the venous system on the left side (p. 106).
Its terminal or cervical portion is displayed in the disseetion of
the neek. It is a small, thin-walled vessel, frequently mistaken
for a vein, whieh enters the root of the neek at the left
margin of the oesophagus. It is there that it should be
sought. At the level of the seventh cervical vertebra it
arehes laterally and anteriorly, and then downwards, above
the apex of the pleura, and it enters the innominate vein in the
angle of the union of the internal jugular vein with the
subclavian. As the thoraeie duet eourses laterally it lies at
a higher level than the subclavian artery, and passes posterior to
the eommon earotid artery, the vagus nerve and the internal
jugular vein, and anterior to the vertebral artery and vein
and the thyreo-cervical artery or its inferior thyreoid braneh ;
and as it runs downwards to its termination it is separated
from the sealenus anterior by the transverse cervical and
transverse seapular arteries and the phrenie nerve. Eurther,
as it approaehes the point at whieh it ends, it erosses the
first part of the subclavian artery.

A valve eomposed of two segments guards its entranee
into the innominate vein.

Duetus Lymphatieus £>exter. — The right lymph duet is
the eorresponding vessel on the right side, but it is a eom-
paratively insignificant ehannel whieh conveys lymph from a

256 HEAD AND NECK

mueh more restrieted area. It eommenees in the posterior
mediastinum, where it not uneommonly eommunieates with
the thoraeie duet : and it aseends to the root of the neek

FlG. 104-— DeepDisseetionof IheRoot of1he Neek oti the Lefl Side lo show
the Dome i>f ihe Pleura and the relations of the Terminal Parl of the
Thoraeie Duet. The sterno-mastoid and the depressors of the hyoid and
larynx have been removed.

the right side, where it terminates in the eommeneement of
the innominate vein by opening into it in the angle of union
of the subclavian and internal jugular veins. As in the ease of
the thoraeie duet, its orifice is guatded by a double valve,
Lymph passes to it from the intereostal giands wbieh lie in

THE ANTERIOR PART 0F THE NECK 257

the upper interspaees of the right side, and from the thoraeie
yiseeral glands of the right side. About half an ineh from
its tennination it is sometimes joined by the right subclavian
and jogular lymph trunks, whieh convey lymph from the
right upper extremity and the right side of the head and
neek, respectively. Under these eireumstanees it eonstitutes
the main lymph drain for the following distriets : ( i ) right
upper hmb ; (2) right side of the head and neek ; (3) upper
part of right thoraeie waD; (4) right side of diaphragm
and upper surface of liver; (5) thoraeie viscera on right
side of median plane, viz. right side of heart and peri-
eardium and the right lung and pleura. But not uneommonly
the right jugular and subclavian lymph trunks open
separately into the internal jugular, the subclavian, or the
innominate vein.

Oendeal Plenra. — The pleural sae of eaeh side, with the

apex of the eorresponding lung, projects upwards into the

root of the neek, and the disseetor should now examine the

height to whieh it rises, and the eonneetions whieh it estab-

lishes (see Figs. i and 5). Its height with reference to the

first pair of eostal arehes varies in diiTerent subjects. In

some eases it extends upwards for two inehes above the

stemal end of the first rib ; in others for not raore than one

ineh. These diATerenees depend on the degree of obliquity

of the thoraeie inlet. Posteriorly, in the majority of eases,

the apex of the pleura eorresponds in level with the neek

of the first rib. It forms a dome-like roof for eaeh side of

the thoraeie cavity, and is strengthened by a fascial expansion

(frequently termed Sibson' s fascia\ whieh covers it eompletely,

and is attaehed on tbe one hand to the transverse proeess

of the seventh cervical vertebra and on the other to the inner

margin of the first rib.

Note that it is in relation with : (i) the sealenus anterior ;
(2) the sealenus medius; (3) the subclavian artery; (4) the
yertebral artery ; (5) the costo-cervical trunk; (6) the superior
intereostal artery; (7) the internal mammary artery; (8) the
innominate vein ; (9) the vertebral vein ; (10) the subclavian
vein; (11) the vagus nerve; (12) the phrenie nerve; (13) the
reeurrent nerve on the right side; (14) the first thoraeie
nerve; (15) the first thoraeie ganglion of the sympathetie ;
(16) the ansa subclavia (Yieusenii).

The sealenus anterior covers the antero-lateral part of the

V0L. 11—17

35»

HEAD AND NECK

dome, separating h from the subclavian vein, whieh ends at
the medial border of the musele. Immediately above the
vein the subelayian artery erosses the dome below its apex.
The internal mammary artery deseends from the subclavian,
passes posterior to the subclavian vein, and is erossed, as it
hes behind the vein, by the phrenie nerve, whieh .passes in
some easesanterior to, and in others posterior to the artery.

Iltary, and Sublingual Gland

The costo-cervical arlery aseends from the subclavian and
erosses the apex of the dome ; its superior intereostal braneh
deseends, posterior to the apex, between the Arst intereostal
nerve on the lateral side, and the first ihoraeie sympathelie
ganglion on the medial aide. The vagus nerve deseends
anterior to the medial part of the subclavian artery, and, on
the right side, its reeurrent braneh turns round the lower
border of ihe artery; the ansa subclavia lies to the lateral
side of the reeurrent nerve.

PASDTED GLiSrr'

u>d liie bnn ^kt. i^ He: ii

elanu aittiT, ^e&irt jBi«j!rJu^ u Ite n

GlsndnlA Puotu. — Hie parodd gland is «edged into a
raore or less triangular inlerval, the parolid s/tut, whieh is
bounded anteriorly by the posterior borders of the masseter,
the ramus of the roandible, and the intemal ptetygoid, and
postero-medially by the anterior border of the stemo-mastoid,
the mastoid proeess, the posterior belly of the digastrie, the
styloid proeess, and the stylo-hyoid musele. The spaee
extends upwards to the estemal ac ic meatus, and it >s
prolonged downwards into t 'riangle, into whieh

26o HEAD AND NECK

the lower extremity of the gland deseends for a short
distanee beyond the angle of the mandible. The gland,
however, is more extensive than the spaee and passes for a
yarying distanee forwatds beyond its anterior border over ihe
superheial surface of the masseter.

In aeeordanee with the position whieh it oeeupies the
gland tnay be deseribed as possessing three surfaces, two
extretnities, and four borders. The surfaces are superficial
or laleral, postero-medial, and antero-medial ; the extremities,
upper and lower ; the borders, anterior, posterior, medial, and

FiG. 107.— Pari

superior. The medial border separates the antero-medial
from the postero-medial surface. The anterior and posterior
borders separate the lateral surface from ihe antero-medial
and postero-medial surfaces, respectively. The upper border
interyenes between the upper siirface and the other three
surfaces.

The superficial surface is triangular in outline (Fig. 1 05). It
is covered by skin, superficial fascia, platysma and risorius, and
deep fascia. Embedded in it are a few superficial parotid
lymph glands, whieh receive lymph from the anlerior part of
the sealp, the face above the !evel of the mouth, and froni
the lateral surface of the auriele. Posteriorly, it is in
relalion with the mastoid proeess and the anterior border of

PAROTTD GLAXP rti

the stemo-mastoid mosekL Aberrt. :t z'jD'.rjtSr ±»t T«:si*r-i:ir
part of the lower border of tbe zy^'j:iii. LZii u^ ^i'Ter sirii;::^
of the extemal meatus^

From beneath the pait zzi eeeiiae: "wtit. ii.'t r"r'-»iiii. tnntnr-t
ihe aurieulo-temporal nerre. ibe t£z:i»:rLl iirLnLrji:f :c mt
facial nerve, and the super^eiil lempiril ^^t:ry. in. iirsr vr3 i:
the sealp ; and the posterior far:?.' Tt^i. CJ5L.t«p»f:ir* iriiDir in.'^tr
of it. Its lower eitremitT, wbiei is we^irei 'iteriet:*::! li**: ^rieiir
of the mandible and the anterior bieDrr :c lii*: s:*r:i:-ii;2siinc-
is usually in eontaet with ocke ti ir.e '^^^K^ 6t?t-: Krratil
glands, whilst the posterior fajcial Ttdr. irit -'r-^ -^^r-.*^^' 'x
the extemal jugu]ar Tein, and the oerTS-:aZ 'iirij:i±. :c
nerve emerge from it : the forn:er ys^^kr^ orjwz:
posteriorly, and the two latter dowewsLrdr irjC ir.i*ri:r}T-

From beneath the ^Lnttnor bOTOer, TLi"^ rt?s:i tC'CJc: dbe
masseter, the duet of the gland /Seernierii^ ±rf: trsssrsrse
facial artery, and the zygoma2k:. b!XX2LL ^riid ^g^ierr/iugr
branehes of the laeial nerre pass rorwards : irid tie tstaspen*
facia] vein disappears under eorer ^A ii,

The due^ of t?ie parotid j^md 4Ste:i5er.'i t, '^Js 2g.9SEriasr
from under cover of tbe anteiior border oc tryt gui^wi nra
anteriorly aeross the masseter. at tiiC krrcC 'A sl lisae criwx
from the lobule of the anriele to a j»c3t sbtoLreid aaaewT
between the red margin of the rs^^ '^ 2sc ia>t ala of
the nose. At the anterior border of tlt: ixj2JMfx: :t rsr»
inwards, at right angles to its fonner eoer^ aa: ii» yjK^je:^
the sueking pad of fat, the hueeinaior iasda, di«t 'T>3cjcarjat<w'
musele and the mueous membrane rX tbe Tt$tix«it *:/ ti*t
mouth, it opens into the restibale, on the a;« <rj a yst^l^
opposite the seeond molar tooth of tbe maxi]b,

Immediately anterior to the 3nxenoT \^/rdtT ^A t3>t ?5aw3,
below the zygoma and above the daet, lies a saaaH «r^OMsS^S
portion of the gland substanee ealled the aeeesu^ par^^^ 3t%
duet opens into the main duet.

£>£ssectum.—The gland mnst bc remored ytau:ssja^ « •-ii^: trru!r.i^*a
whieh pass through it are diweeted oot. The fuiaJ BitTre asri iU 'mw^
are the most superficial struetiires io the satAta&ee 'A ihn \at'f:A ? ti-er^^^
they must be disseeted first. Traee the termaal lnajcha yjifjtTjr^n ^^-'^
the gland until they j<Mn the main dirisioos, v1dca axe ibt u^r -^ Um;^^'^
facial and the lower or eermeo'^aeiai. The tem|wrai ajyi tr^x:^x, 'x^r^
spring from the temporo-£u3al dirisioo, theUioeal, a&a£*f:':^iifer, i'^ o^i-^i
from the cervico-fecial divisioii. FoIlaw the ^amifXA yM^*x,j ^'ff^
the posterior isieial vein-to their mnoD with the tnmk 'A t^ r>tnr% »?/xi
pierees the postero-medial sm^Mre of tbe g^and ; then tra<:^ tbs: tr«.ii ^:i'm

11—17 6

262 HEAD AND NECK

the root of the styloid proeess to the stylo-mastoid foramen and seeure the
braneh whieh springs from it to supply the posterior belly of the digastrie
and the stylo-hyoid museles, and the posterior aurieular braneh. As the trunk
of the nerve is being eleaned the posterior aurieular braneh of the external
earotid artery will probably be exposed, passing upwards and posteriorly
along the upper border of the posterior belly of the digastrie to the baek of
the external meatus, and erossing either superAeial or deep to the nerve.
Next, remove the deeper parts of the gland and expose^the posterior facial
vein, deseending towards the angle of the mandible. It receives the trans-
verse facial and the internal maxillary veins, and it gives off the eommenee-
ment of the external jugular vein ; and then it passes out of the lower end of
the gland and unites with the anterior facial vein to form the eommon facial
vein. Deep to the veins will be found the upper end of the external
earotid artery dividing into its superficial temporal and internal maxillary
branehes ; and the transverse facial and middle temporal offsets of the
superficial temporal will also be displayed.

When the remains of the deeper part of the gland have been removed,
the styloid proeess with the origin of the stylo-hyoid musele, and the
posterior belly of the digastrie will be exposed ; and the internal jugular vein
and the internal and external earotid arteries will be seen disappearing
under cover of the digastrie. If the oeeipital artery lies at its lower level,
it also will be noted as it runs upwards and posteriorly, along the lower
border of the digastrie, erossing superficial to the two large vessels, and
to the aeeessory nerve, whieh emerges from under cover of the digastrie and
passes downwards and posteriorly aeross the internal jugular vein.

The disseetor should now obtain a gland whieh has been
removed uninjured from the parotid spaee, or a east of a
gland, and proeeed to study the relations of the upper end
and the postero-medial and antero-medial surfaces.

The upper extremity presents a deep concavity whieh is
usually separable into a larger lateral part whieh lies in
eontaet with the eartilaginous part of the external meatus,
and a smaller medial part whieh touehes the bony wall of the
meatus (Fig. 109). The anterior boundary of the upper
end forms a sharp ridge, whieh lies in the narrow interval
between the eapsule of the temporo-mandibular artieulation
and the front of the external meatus.

Tht postero-medial sufface is marked by a series of depres-
sions whieh eorrespond with the struetures in the postero-
medial boundary of the parotid spaee. Above is a shallow
depression eorresponding with the anterior border of the
mastoid proeess, and below the latter a groove eaused by the
anterior border of the sterno-mastoid. More medially is a
shallow depression due to the posterior belly of the digastrie
and the stylo-hyoid, and, still more medially and at a higher
level, a suleus whieh eorresponds with the position of the
styloid proeess. Below the level of the digastrie groove the
postero-medial surface covers portions of the internal jugular

PAHOTID GLAXD ri;

vein and the intemal a«i ensmil ci-:oz irisns. Tri
eoiiimeneement of the eiterru; ."^^^ii-r ^r. :rt ;«:!s;iri:r
facial vein, aod the eerrieal b*5i>cr. :?' :!■; ir^ t-tn-i -.irtrrt
from this part of the sDTface. Iic=:*cii:=.'; i.ZK-- zzk :,-si=r^z
groove, elose to the medu] t'itee. lii-t o.:t^=i:- xir:c.i; =Ci=»
the gland ; and direetly U:era! :c :r* =7«- =■! :t tr-t ir:':'^
for the styloid proeess the facil :*rre ^a^^^s =:: :i>t e^rii
substanee. The disseetor shocJc :xr^ iLii :bt j<'jKE-:-2:*fi
surface of the gland is sepaiated ^-e ii ;; t« ^ura :c '^ut
internal jugular vein and the interr-a^ eario: ir^sry. i-e T-jn

PDslen>Hiwi]u} bcnlrrvf ^po'a^^

the last four eerebral nerves by the posteiioT beily ol ti^
digastrie, the styloid proeess and the mnseks aiatiitd t& n.

The medial border of tbe gland lies in tke an^ hetwttn
the postero-medial and the anterim bonntlaiies of tbe ;a;rx3d
spaee, where the styloid proeess, the stylo.|iyoid mm'^ a.-jd
the posterior belly of the digastrie disppear tmder eorer ol
the posterior border of the intemal pterygoid mnsde: and
from it a proeess, ike pterygind khe, nsitally proieets zi'jmj^,
for a short distanee, between the intemal pttrygoid arai tbe
inner surface of the lamus of the mandible Tlirough the
base of this proeess tbe exienial earotid passes fr'ym the
postero-medial to tbe antero-medial mi&ee of the gland.

Tke AnUro-meMal Snr/aee.- — Tbe medial pait <A the

264 HEAD AND NECK

antero-medial surface is direeted anteriorly and Hes in relation
with the lower part of the posterior border of the internal
pterygoid, the stylo-mandibular ligament, and tbe posterior
border of tbe ramus of the mandible. The more lateral part is
direeted medially and rests against the lateral surface of the
masseter. This surface is piereed (i) by the external earotid
artery, {2) ihe posterior facial and the internal maxil!ary veins,
{3) all the terminal branehes of the facial nerve except the
cervical, and (4) by tbe duet of the gland.

As the disseetor examines the parotid spaee he will note
that as the external earotid disappears under cover of ihe

FiG. 109.— ParotidGland, amero-medial aspeet.

posterior belly of the digastrie it is plaeed so far anteriorly
that it is also under cover of tbe posterior border of the
mandible ; and it does not emerge from under cover of the
mandible until it reaehes the level of the neek of the bone,
wbere it appears on the antero - medial surface of the
gland and divides into its two terminal branehes. Purther,
he will now readily reeognise tbe impossibility of studying
the upper end of the cervical part of the internal earotid,
the upper part of the internal jugular vein, and the last
four eerebral nerves, until he is in a position to reflect the
posterior belly of the digastrie and the styloid proeess ; and
as both of them are, to a eertain extent, under cover of the

TEMPORAL AND INPRATEMPORAL REGIONS 265

mandible it is obvious that the mandible must be removed.
This will be done during the disseetion of the temporal and
infratemporal regions, whieh must now be proeeeded with.

TEMPORAL AND INPRATEMPORAL REGIONS.

Fa£cia Temporalis. — The temporal fascia is a strong
glistening membrane whieh is stretehed over the temponU
fossa, binding down the temporal musele. Its upper margin
is attaehed to the upper of the two curved lines whieh
eonstitute the temporal ridge on the lateral aspeet of the
skull, and anteriorly to the temporal line of the fronta]
bone. As it approaehes the zygomatic areh, it splits into
two laminae, whieh are separated from eaeh other by a narrow
interval filled with fat. The two laminae are attaehed one to
the upper border of the zygomatic areh and the posterior
border of the zygomatic bone, and the other to the medial
surfaces of these two portions of bone. They ean readily
be demonstrated by dividing the superficial layer elose to its
attaehment, and throwing it upwards ; by the handle of the
knife the attaehment of the deep layer ean then be made out
In the upper part of its extent, the temporal fascia b eom-
paratively thin and the fibres of the subjacent musele may
be seen shining through it ; below, it is thieker, and owing
to the fat whieh is interposed between its laminae, it is
perfectly opaque. It is piereed immediately above the
posterior part of the zygomatic areh by the middle temporal
braneh of the superficial temporal artery and by the middle
temporal vein (p. 157).

Museulus Masseter. — The masseter is a massive quadrate
musele whieh covers the ramus of the mandible. Its
fibres are arranged in two sets — a superficial and a deep.
The superficial part of the musele arises A-om the anterior two-
thirds of the lower border of the zygomatic areh, and its
fasciculi are direeted downwards and posteriorly. The deep
part springs from the whole length of the medial aspeet of the
zygomatic areh, and also from the posterior third of its lower
border. Its fibres proeeed downwards and anteriorly. Only
a small pieee of the upper and posterior part of this portion
appears on the surface. The masseter is inserted into the
lateral surface of the ramus of the mandible, over an area

266

HEAD AND NECK

whieh extends downwards to the angle, and upwards
inelude the lateral aspeet of the eoronoid proeess.

Disseetim. — To display the temporal musele, and at the
expose the nerve and artery of supply to the masseter, make the foI
disseetion. Divide the deep part of the temporal fascia along the
border of the zygomatic areh and remove it. The middle temporal
and the ^Ygomatirn-^^rpp^yal "^gy^i whieh pieree it, must be dis ^
from it ana preserved. The zygomatic areh, with the attaehed i
must next be thrown down by dividing the bony areh anterior and
to the origin of the musele. First make use of the saw, and then
the division by means of the bone forceps. The posterior eut sh<
made immediately anterior to the mandibular (O.T, glenoid)
the head of the lower jaw ; the anterior eut must extend obliquely
the zygomatic bone, from the extreme anterior end of the upper mi
the areh, downwards and anteriorly to the point where the lower
meets the zygomatic proeess of the maxilla. When the division
pleted, and the nerve and artery to the masseter are divided, the
areh and the attaehed masseter may be readily thrown downwards
the angle of the mandible. The Aeshy origin of the deep
the masseter from the medial surface of the zygomatic areh ean
seen. The disseetion is frequently eomplieated by a number of fibi
the temporal musele joining this part of the masseter. In turi
masseter down, its nerve and artery of supply must first be cl<
they pass laterally through the ineisura mandibulse (O.T. sigmend
posterior to the tendon of the temporal musele. Leave the
attaehed to the angle of the jaw and elean the temporal musele.

Museulus Temporalis. — The temporal musele is fan-
It arises from the whole extent of the temporal fossa,
lower of the two lines whieh eonstitute the temporal ri<
the infratemporal erest on the great wing of the sphi
It receives additional fibres also from the deep si
the temporal fascia. From this broad origin the
converge towards the eoronoid proeess of the man<
The anterior fibres deseend vertically, the posterior fil
iirst pursue a nearly horizontal eourse, whilst the intemu
fasciculi proeeed with varying degrees of obliquity.
approaehes its insertion, a tendon is devel8ped u]
superficial aspeet, and this is inserted into the summil
anterior edge of the eoronoid proeess. The deep part
musele remains Aeshy, and gains insertion to the
surface of the same bony prominenee by an attaehment
reaehes as low down as the point where the anterior m\
the ramus merges into the body of the mandible. The
tion eannot be fully examined at present ; it will be dealtj
later.

Disseetion. — Detaeh the eoronoid proeess from the mandible,
it upwards with the attaehed temporal musele. A very oblique

TEMPORAL JkXI> I

nnelei eora di ibe ^b9- pMe •■ Ac SH^

tetnpotst ioBsa. 11»

anrGme to Iblkrar the
give brondUB to ihe M
□f the tempanl beae.
tiaeed to tiw \riaL a

d SOTfaoeirf thg j|;fifl8

iif the temponl

The iDRatimpanl n^
opened ap by leidantng* )«
lontal euu Dnssi be iB»ik ^mt An^^ I
Dthei imnudmelT alM*e ik leHd «f tte
rorsDien. Tolnd tlielc:Mla<tk>
thruu between Ibe

a]veolai

Parts diqliTel br tt* akom DiMetta.— When tbe &i

ajid areobr tissae are nniKrml, tbe pleiygtMl attielei wID
eome iDto riew. The t^irrmU ptrrygaid exlcnd* tutrieontall;
to the oeek «r the maDdilile. Tbe imttrmd ptrryg/id, «nbrae-
ing the antenor pait of th^: eUtanal plerygtitd intuiele betwern
its two heads of oi^n, proeeetb doirnwards and ptMleriarly ■
upon the deep sur&ee uf ibe nuous uf tbe mandible. It I
bears ver7 mud) ihe sain« relatko [£> the mnlial atpeirt »f the
ramus tbat the masaeter preseuls to its lotetal lurbei^ The
greal btood iressel of the spac« — Ibe inttrmU maxi!lary trttry
— proeeedi anteriorly tipoa (frequc»t]y under cover <rf> ihe
estemal pter):goid mnsele. Thc ttertts tif ihe rt^giiin obo will
be found in elose tebtionsbip to llie >ufnc tnusdr. Thm,
emei^ng froia between itt Upper border and thi: i:ninLil wiill,
at the levei of die tnfratt;tnpofaJ iwsi, are ihe masi/ttrie and
the two dtt/ tempora/ ruroa ; appeaiio]; fn>ai iindtr t?oTer of
its iower ttorder are llte in/erior ahMtiar and the Sngnai
Herves; whilsi the auriewi^ee>i^ft>ral nnrr ts nilaied lo iu
medial sutfacc posierkrly and Uii: bttidnater iurtx anienori^. i

368

HEAD AND NECK

The fonner appears posterior lo the temporo-mandibular joint,
and the bueeinator nerve either pierees it or emerges from
between its two heads of origiii. The spheno-mandibulM-
ligament also will be seen. It is the thin strip of membraiie
whieh lies medial to the inferior alveolar nerve.

MnseulaB Pterygoidens EAeniiis. — The extemal pterygoid

arises ir the infratemporal fossa by two heads, an upper and
a lower. The upper head springs from the infratemporal
ridge and surface of the great wing of the sphenoid; the
lower head takes origin from the lateral surface of the laieral
pterygoid lamina (O.T. external pterygoid plate). The
musele diminishes in width as it passes posteriorly, and it is
inserted into the fovea pterygoldea on the anterior surface
of the neek of the mandible, and also into the anterior margin
of the diseus artieularis of the temporo-mandibular artieulation.

TEMPORAL ANi' :n57l-.ti::: ! }_^

Mnsenlns PteiTSOide^ IrT«Erc£ — T'* . -.. - :
also is bieip::^: i: i'.s -r '.:-::- -v • . :.
origin of ihe "..-^t: r.'r.i ' :: . • "-
superficiai and sn:i:!tr : --• . ' :■ - ■.".:. - . . - ^
from the io'A-er ar.d y^-t^ .' -.^. *■. . ■

maxilla, and :i:s-^ :.':zi ir.t .----:--: : ■• . " ...

proeess 'O.T. :u':.-er::::; .: :-t ::..::- ■• ■-. ■ - - - . ..^
hidden bv tl':e e.x:trr-2^ ::-:^.z: i Lr.:-r: • ■-:--: .
fossa from ihe r:.t:i.\2L :">r:i:-: :■:■-. ..-.-. : -. - . . .:.:. -

and from ihe surt'aee :■: :r.r :_■*:":_•-. :* -'r ■ -. : -

bone whieh apr-ear? 'r.n'.'^rir. :i- :v " :~ : : ..— ■.■
The two heads c: ihe rr.-^5.:.i -.-:.:z i- :■ -. v:- ■/..-:.- -
anterior part of ihe tir.tT"^ y.-—z'. - :." : ■ : ■ * :- ■ •••:
downwards wiih a ;■:?:-:: -!::■:': - -.: - :.* : :.. "
insertion into ihe ar.r^e :: :.":■= ::\:.-^. -.. l* i .• .• -. v ■-
and posterior par: :f \:.t :: t i-i Lne." :•' ■.:•: -:.r: l: t:
high as the manGib--:i: f:ri:::t.'-

Arteria MaTillaris Intena. — T-.-i -r; .- .. .:«-. i:-:r \
the two lerminal brar.er.ts :f :it ti't^.i. ji.-:':i1 i.^--.—
takes origin in:mecia:t:y p':--':tr. : - :: -_:-: •.-.-; ::#-

mandible andproeeeds c.r,:tr.:r;; :: '-i-: l-:--^!:' :;l.- ' ::i-
infratemporal fo55a- where :: disipi'tri--: '":'r -■^-•v '■ «-^r -;
between the two heads of irigi.-: :c i^t tir.tr-.;*. y.^j . ii
musele and enterins :r.t '•-•^r'-'i=iA'^ "-* '.':-:-i- l ;.
divided into three ps-ns f:r •::r.-.t--.:::.'::t :' v.:»:':rr.r. T':»^
first part runs horizonia::v '>::Trtf.': *.::■: "..r:!. :-" ::i- r^i.-i:;: n-
and the spheno-mar-dii'.::^^ ii'Lnt.-.: Z: r:: i.r.r^ ::,-.
lower border of ihe pos^en^r ;.;i.-: :f v_t ti^t-T.i. :-.t^-::'i:
musele, and usually erosses :Le :.i:*ri:r s--.t;:.i/ -.itnt :.:::rr
ficially. The sec(md part tr:tz.Zi :•:.:-. i^-i; ::'Vi.--.: i.-i:
anteriorly upon the Ia:enil s'^kr^t 'A '^xi •::-.-:^*.i. ^r.rry.u',
musele, under cover of ir.t \zj^rL'.z. "A "L-^t '.rr: :•:'-*. :: -t .1-.
The third part dips hti'Kttri ^r.t :t^ bts.ii :>•' -.^rt *r:.-tr-;i.
pterygoid into the pierygo-p&Ji:;r-e f-.Aii-

This is the most htrrutr.i ATrs.r.^rfZj^r- 'js. r. .■: -r.r
uneommon to find the seeone par: :f ::-jt ir:tr;. -r.-i :: •
deeper plane, viz. between t:^.t i.':*jtrr-a: ir-i t-r--rr-:i.. :r.*r;;:«.:
museles. In that ease the ves5<t: r- ?*■*;■ i -^r^ii .i.:— i. ■
between the heads of tbe exterr-il ^etri^'-'^i .:- ^y.r- * -.:
appears on its surface before er.itrir-s: V..* ^»:*r;T>Vii ■'"''•-
fossa.

The branehts of the intemal maxi:'-^'~* antr irt :iS.-j-. 'r--:

270

HEAD AND NECK

aeeording to the portion of the vessel from whieh they spring.
Only one braneh of the third part, viz. the posterior superior
alveolar artery^ ean be studied in this disseetion. Those
arising from the first and seeond parts are : —

From the First Part.

1. Arteria aurieularis profunda.

2. Arteria tympaniea.

3. Arteria meningea media.

4. Ramus meningeus aeeessorius.

5. Arteria alveolaris inferior.

From the Segond Part.

1. Arteria masseteriea.

2. Rami pterygoidei.

3. Arterise temporales profundae.

4. Arteria bueeinatoria.

The Deep Aurieular Artery, — This small vessel pierees
the anterior wall of the external aeustie meatus to supply
the skin whieh lines it, and also the superficial part of the
tympanie membrane.

The Meningeal and Tympanie Branehes proeeed upwards
under cover of the external pterygoid musele, and, therefore,
eannot be fully studied until that musele is reflected.

The In/erior Aheolar Artery arises opposite the middle
meningeal, and runs downwards, upon the spheno-martdibular
ligament, to enter the mandibular foramen. It is generally
aeeompanied by two ven8e eomites, and it is plaeed posterior to
the inferior alveolar nerve. Just before entering the foramen,
the inferior alveolar artery gives off the slender mylo'h^oid'
braneh, whieh is earried downwards and anteriorly, with the
eorresponding nerve, upon the deep aspeet of the mandible,
to the digastrie triangle of the neek.

The branehes from the seeond part are given off for the
supply of the neighbouring museles. The Masseterie passes
horizontally, posterior to the temporal musele, with the nerve
of the same name, and has been seen entering the masseter
musele. The Ptery^oid Branehes^ are irregular twigs to the
pterygoid museles. The Deep Tempgral JSranches are two in
number — anterior and posterior\ they pass upwards in the
temporal fossa, between the bony wall of the eranium and the
temporal musele. They supply twigs to the temporal musele,
and they anastomose with the middle temporal artery. The
Bueeinator Braneh aeeompanies the bueeinator nerve, and

-| II ■! I ■■ I I II I •• '' '

is distributed to the bueeinator musele and the mueous

TEMPORAL AND INPRATEMPORAL REGIONS 271

membrane of the eheek. It anastomoses with the external
maxillary (O.T. facial) artery.

The PosUrior Su1>erior Alyeolar Braneh, from the third part
of the internal maxillary artery, deseends upon the posteriolr
aspeet of the maxilla, and sends branehes through the alveolay .
eanals of the maxilla for the supply of the upper molar
and praemolar teeth (Fig. iio). Some small twigs go to the
gum and others supply the lining membrane of the maxillary *
sinus.

Pterygoid and Intemal Maxillaxy Yeins. — The veins in
this region are very numerous, but they eannot be studied
satisfactorily in an ordinary disseetion. They eonstitute a
dense plexus, termed the ptery^oid pleoeus^ around the external
pterygoid musele. Tributaries eorresponding to the branehes
of the internal maxillary artery open into this network,
whilst the blood is led away from its posterior part by a short
wide trunk, ealled the internal maxillary^vein. This vessel
aeeompariies the first part of the internal maxillary artery
into the parotid gland, and joins the posterior facial vein
behind the neek of the mandible.

The pterygoid venous plexus is eonneeted with the
cavernous sinus by an emissary vein. It eommunieates with
the inferior ophthalmie vein, through the inferior orbital fissure,
and with the anterior facial vein by an anastomosing ehannel
ealled the deep facial vein whieh deseends aeross the external

surface of the bueeinator musele.

Artic\ilatio Mandibularis. — Before the external pterygoid
musele is thrown anteriorly, the temporo-mandibular joint
must be examined. It is a diarthrodial joint of the ginglymus
type, and its cavity is separated into an upper and a lower
part by a diseus artieularis. In eonneetion with it there are
the following ligaments : —

LlGAMENTS PROPER.

ACCESS0RY LlGAMENTS.

[. Cfl.psnle. I. Spheno-mandibular.

5. Temporo-mandibiilar. | 2. h)iylo-mandibular.

I. Cai^

nporo-mandil

Diseus Artigularis.

The eapsule eneloses the joint cavity. Above, il is attaehed
• posteriorly, laterally, and mf ' ** margin of the man-

212 HEAD AND NECK

dibular fossa, and anteriorly to the anterior margin of the
artieular luberde. Below, it is attaehed to the neek of the
mandible ; and between its uppsr and lower attaehments it is
eonneeted with the margins of the diseus artieularis.

The Umporo-mandibular Itgament {O.T, txtemal laterat) is
a strong triangular band whieh is attaehed above to the
lateral surface of ihe posterior part of the zygoma aryd to the
tubeteie at the root of the zygoma. Its fibres run down-
wards.and posteriorly to the neek of the mandible.

The spheno-mandibular ligament {O.T. internal lateral) is a
long membranous band whieh extends from the spine of the
sphenoid to the lingula and to the sharp medial margin of the

Styloid pr..a

\ ""'"'"■^'
FiG. III. — Seetion Ihrough Temporo-mandibular Jomt,

mandibular foramen. It is not in direet relationship with the
joint. Above, it lies medial to the external pterygoid musele
and the aurieulo-temporal nerve; lower down, the intemal
maxillary yessels intervene between it and the neek of the
mandible ; whilst, still lower, the inferior alveoIar vessels and
nerve are interposed between it and the ramus of the mandible.

The stylo-maniibular ligament has been notieed already. It
is a fibrous band, derived from that portion of the deep
cervical fascia whieh forms a part of the eapsule of the
parotid gland. It is attaehed above to the styloid proeess,
and below to the angle and posterior border of the ramus of
the mandible, between the internal pterygoid and masseter
museles.

An examination of these ligaments will show that veiy

TEMPORAL AND INPRATEMPORAL REGIONS 273

«* — ^^'•»

little is added to the strength of the joint by their presenee.
The seeurity of the joint depends not so mueh upon its liga-
ments as upon the strong museles of mastieation, whieh keep
the head of the mandible in its plaee.

The diseus artieularis is an oval plate of fibro-cartilage, with
its long axis direeted transversely. It is interposed between
the eondyle of the mandible below and the mandibul^r fossa
(O.T. glenoid) and the artieular tuberele (O.T. eminentia
artieularis) above, and it divides the joint cavity into upper
and lower parts, eaeh of whieh is provided with a separate
synovial lining. To expose the eartilage, the temporo-man-
dibular ligament must be removed. The dise will then be
seen to be adapted to the
two bony surfaces between
whieh it lies. Above, it is
concavo - convex in eorre-
spondenee with the tuber-
eulum artieulare and the
mandibular fossa of the tem-
poral bone; whilst below, it
is concave, and fits upon
the upper aspeet of the eon-
dyle of the mandible. In
the eentre it is thin, and in

SOme eases it is perforated. p^. 112.— Diagram of th^ different
ItS circumference is thiek, positions oeeupied by the head of the
more espeeially pOSteriorly. niandible and the diseus artieularis
xx 1 u i_ \. j 1 ^\\ as the mouth is opened and elosed.

It should be noted also that

the external pterygoid musele is partly inserted into its

anterior border.

The synovial stratum whieh lines the eapsule enelosing the
upper cavity of the joint is of greater extent and looser than
that of the lower eompartment. This is in assoeiation with
the larger size of the artieular surface of the temporal bone
as eontrasted with the eondylar surface.

Moyements. — The movements whieh the mandible ean perform at
the temporo-mandibular joint are the following : — (i) depression ; (2)
elevation ; (3) protraetion ; (4) retraetion ; (5) lateral or ehewing move-
ments. When the mandible is depressed the diseus artieularis and the
eondyle move anteriorly on the mandibular fossa, and the eondyle finally
takes up a position on the tubereulum artieulare. This forward gliding
of the dise and eondyle in the upper eompartment of the joint is aeeom-
panied by another movement ''^wer eompartment of the joint,

VOL. II — 18

2 74 HEAD AND NECK

whieh eonsists in a rotation of the eondyle of the mandible on the
lower surface of the artieular dise. Elevation of the mandible or elosure
of the mouth is brought about by a reverse series of ehanges in both
eompartments of the joint. Whilst these movements are going on, the
mandible rotates around a transverse axis whieh traverses the bone in
the neighlwurhood of the mandibular foramen. This is the point, there-
fore, of least movement, and consequently in opening and shutting the
mouth the inferior alveolar vessels and nerves are not unduly stretehed.
In protraetion and retraetion the movement is chiefly eonBned to the
upper eompartment of the joint, and the eondyle of the mandible with
the artieular dise glides anteriorly and posteriorly upon the temporal
artieular surface. In the lateral movements of the jaw the mandible is
earried alternately from side to side, as in the proeess of ehewing.

The museles on eaeh side whieh are chiefly engaged in produeing these
movements are the following : — (i) depressors — the platysma, the mylo-
hyoid, and the anterior belly of the digastrie ; (2) elevaiors — the masseter,
internal pterygoid, temporal ; (3) protraetors — the external pterygoid, and
to some extent the internal pterygoid and the superlieial fibres of the
masseter ; (4) retraetor — the posterior fibres of the temporal and the deep
iihres of masseter ; (5) lateral fnovement is produeed by the museles of
opposite sides aeting alternately.

BeAeetion of Ezternal Pterygoid. — The eondyle of the mandible must
now bc disartieulated and thrown anteriorly with the attaehed external
pterygoid musele. It is well to detaeh the diseus artieularis with the
head of the bone, in order that it may be more thoroughly examined.
Care niust be taken not to injure the aurieulo-temporal nerve, whieh lies
in elose proximity to the medial asp'^t ol Tli^^Sint. When the dis-
artieulation is eomplete, the musele may be displaeed anteriorly by gently
pushing the eondyle under the internal maxillary artery.

The rcflection of the external pterygoid musele brings into view, after
a little disseetion, the mandibular division of the trigeminal nerve,
emerging from the foramen ovale, and breaking up into its branehes of
distribution. The slender diorda tympani will be found proeeeding down-
wards and anteriorly to join the lingual nerve ; and the middle meningeal,
tyuipauie^ and aeeessory meningeal arteries may be traeed to the points
where they leave the infratemporal region.

ArteriaB Meningea Media et Tympaniea and Bamus Menin-

geus Aeeessorius. — The middle ineningeal artery has already
heen seen arising froni the first part of the internal maxillary
artery. It proeeeds upwards, medial to the external ptery-
goid musele and lateral to the tensor palati, and disappears
from view through the foramen spinosum, by whieh it enters
the eranial cavity (p. 212). It is usually embraeed by the
two roots of the aurieulo-temporal nerve.

The aeeessory meningeal artery and the tympanie artery generally arise
Trom the mieklle meningeal. The aeeessory meningeal inelines anteriorly and
upwards, and enlers the eranial cavity by passing through the foramen
ovale ; the tympanie runs upwards and posteriorly, and reaehes the
lympanum by passing through the petro-tympanie fissure (O.T. Glaserian).
In the tympanie cavity it anastomoses with the styloid-mastoid braneh of
the posterior aurieular artery.

TEMPORAL AND INPRATEMPORAL REGIONS 275

Hemis MtuidibiilariB. — The mandibular braneh of the
trigeminal nerve arises within the eranium from the semilunar
(O.T. Gasserian) ganghon, and enters the infratemporal
region through the foramen ovale. It is eomposed of
sensory fibres, but it is aeeompanied through the foramen
by the small ntotor root of the ttigeminal nerve ; and by the
union of the sensory and motor parts, immediately after
they gain the exterior of the eranium, a mixed nerve-trunk

TiG. 113.— Diagram of Mandibular Nerve. By Prof. A. M. Paterson.

resuits. This nerve-trunk lies medial to the external pterygoid
musele and lateral to the tensor palati, and after a very short
eourse (not exceeding 5 mm.) it ends by dividing into
two parts, named the anterior and posterior dmsions of the
mandibular nerve (Fig. 113).

The trunk of the mandibuiar nerve gives off two branehes
before it divides, va., (1) nersus spinosus (O.T. reeurrent nerae),
3"d (z) the nerve to the internal ptpryi-piH nm'mplp

The neruus spinosus is a very slender twig whieh enters

2 76 HEAD AND NECK

the eranium by aeeompanying the middle meningeal artery
through the foramen spinosum. It supplies the dura mater.

The neroe to the internal pterygoid will be found passing
under cover of the posterior border of the internal pterygoid
musele at its upper end. In elose relation to the root of
this nerve is the otie ganglion,

From the two terminal diyisions of the mandibular
trunk the chief branehes of distribution arise. The anterior
diyision is mueh the smaller of the two, and is eomposed almost
entirely of motor iibres derived from the motor root of the
trigeminal nerve. The only sensory iibres whieh it eontains
are those whieh form the bueeinator nerve, It gives off the
following branehes : —

i;__Mass£teiic.

2. Two deep temporal.

3. External pterygoid.
4.nBuccinator.

The large posterior division is chiefly sensory. It eontains
only a very few fibres from the motor root, and these are
prolonged into its inferior alveolar braneh, and afterwards
eome off in the form of the mylo-hyoid nerye, The branehes
of the posterior division arel ( i ) aurieulo-temporal ; (2)
inferior alveolar ; (3) lingual.

Neruus Masseterieus, — The masseterie nerve runs hori-
zontally above the external pterygoid musele, and, passing
through the ineisura mandibulse (O.T. sigmoid noteh)
posterior to the temporal musele, it enters the posterior and
upper part of the deep surface of the masseter. Before
reaehing the masseter it gives one or two twigs to the
temporo-mandibular joint.

Nerui Temporales Profundi, — There are usually two
deep temporal nerves, anterior and posterior, The posterior
nerve is the smaller of the two ; it frequently arises by a
eommon root with the masseterie. Both deep temporal
nerves pass laterally above the external pterygoid, and then
turn upward on the medial wall of the temporal fossa. They
supply the temporal musele.

Neruus Buednatorius. — The bueeinator nerve (O.T. long
bueeal) is the largest of the branehes arising from the
anterior division of the mandibular nerve. It proeeeds
laterally between the two heads of the external pterygoid
musele, and then runs downwards and anteriorly under
cover of the temporal musele, and under cover of the anterior

TEMPORAL AND INFRATEMPORAL REGIONS 277

border of the masseter also, to reaeh the outer surface of the
bueeinator musele. There it unites with branehes of the
facial nerve to form the bueeal plexus^ from whieh branehes are
distributed to the mueous membrane and skin of the eheek.

The bueeinator nerve is a sensory nerve, and all the sensory
fibres in the anterior diyision of the mandibular nerve
enter into its eomposition. A few motor fibres, however,
are also prolonged into it; these eome off from it in two
branehes, viz., (i) in the nerye to the extemal pterygoid.
whieh, as a rule, arises in eommon with the bueeinator nerve ;
and(2) in a third twig of supplv to th^ tpmpnral mnsHe. This
temporall)ranch springs from the bueeinator nerve, after it has
reaehed the lateral surface of the external pterygoid, and
proeeeds upwards to supply the anterior part of the temporal
musele (Fig. iio). In some eases the bueeinator nerve
pierees the temporal musele instead of passing under cover of it.

Nervus Aurieulo - Temporalis. — The aurieulo - temporal
nerve springs by two roots from the posterior division of
the mandibular nerve, under cover of the external pterygoid.
The two roots are eomposed of sensory fibres and eaeh
receives a eommunieation from the otie ganglion, by means of
whieh it is brought indireetly into assoeiation with the glosso-
pharyngeal nerve. The roots embraee the middle meningeal
artery, and unite posterior to it to form a stem whieh runs
posteriorly between the neek of the mandible and the
spheno-mandibular ligament. At the interval between the ear
and mandible it turns upwards, in relation to the deep surface
of the parotid gland, erosses the zygoma in eompany with
the superficial temporal artery, and enters the sealp, where it
breaks up into terminal branehes.

Its branehes are : (i) one or two strong branehes of
eommunieation t^ thf r^"npr^r/yfani<ii nprv^; (2) a few slender
filaments whieh enter the posterior aspeet of the temporo-
mandibular joint ; (^ some twigs to the parotid gland ; (4'
terminal filaments to the skin over the temporal regiori ant
summit of the head ; (5) aurieular branehes.

The aurieular branenes are usually two to the skin lining
the interior of the external meatus, and iwo to the integument
over the upper and anterior part of the auriele. The former
gain the interior of the meatus by passing between the osseous
and eartilaginous portions of the eanal.

Nennis Alveolaris Iiiferior. — The inferior alveolar nerve

II— 18t

2 78 HEAD AND NECK

(O.T. inferior dental) is the largest braneh of the mandibular
nerve. Emerging from under cover of the external pterygoid,
at the lower border of the musele, it passes downwards upon
the spheno-mandibular ligament and enters the mandibular
foramen. The inferior alveolar artery runs downwards
posterior to it, whilst the lingual nerve is anterior to it
and upon a somewhat deeper plane. The inferior alveolar
is a sensory nerve, but a few iibres from the motor root
are prolonged downwards within its sheath as far as the
mandibular foramen. At this point they eome oflf as the
slender mylo-hyoid nerve.

The mylo-hyoid nerue, aeeompanied by the artery of the
same name, pierees the spheno-mandibular ligament and
proeeeds downwards and anteriorly in a groove upon the
inner surface of the mandible to the digastrie triangle. A
narrow prolongation of the spheno - mandibular ligament
bridges over the groove and holds the nerve and vessel in
position. In the digastrie triangle the mylo-hyoid nerve has
been disseeted already (p. 230). It breaks up into numerous
branehes for the supply of two museles, viz., (i) the mylo-
hyoid, and (2) the anterior belly of the digastrie.

Nennis Lmgualis. — The lingual nerve is entirely sensory.
In the iirst part of its eourse, like the other branehes of the
mandibular nerve, it lies medial to the external pterygoid
musele. As it deseends it appears at the lower border of
the musele. Then it proeeeds downwards and anteriorly,
between the internal pterygoid musele and the mandible, and
enters the submaxillary region, where it will afterwards be
traeed to the tongue. It lies anterior to and on a slightly
deeper plane than the inferior alveolar nerve. It gives off
no branehes in the infratemporal region, but, whilst still
under cover of the external pterygoid, it is joined at an aeute
angle by the ehorda tympani braneh of the facial nerve. Not
infrequently, also, a eommunieating twig passes between it
and the inferior alveolar nerve.

Ghorda Tympani. — This is a slender nerve whieh arises
from the facial in the eanalis nervi facialis (O.T. aqueduct of
Fallopius). It gains the infratemporal region by traversing
the tympanie cavity and appearing through the medial part
of the petro-tympanie Assure (O.T. Glaserian), whenee it runs
downwards and anteriorly, medial to the spheno-mandibular
ligament. It is joined by a slender filament from the otie

SUBMAXILLARY REGION 279

ganglion, and it unites with the lingual nerve a short distanee
below the upper end of the latter.

Disseetion. — The student should now endeavour, by means of a Hey's
saw, a ehisel, and the bone forceps, to remove the outer table of the mandible,
and thus open up the mandibular eanal.

Straetures within the Mandibular GanaL — The mandibular
eanal is traversed by the inferior aheolar vessels and nerue^
whieh give oflf twigs to the roots of the molar and praemolar
teeth. Both the artery and the nerve terminate by dividing
into a mental and ineisor braneh.

The mental artery and nerue appear on the face through
the mental foramen, and have been examined already ; the
ineisor artery and nerve pass anteriorly to the symphysis and
send up twigs to the eanine and ineisor teeth. The vessel
anastomoses in the bone with the eorresponding artery of
the opposite side.

SUBMAXILLARY REGION.

The superficial area of the submaxillary region has been
disseeted already, under the name of the anterior part of the
digastrie triangle (p. 230). It is now neeessary to earry the
disseetion to a deeper plane, in order to expose a number
of parts in eonneetion with the tongue and floor of the
mouth. The struetures thus displayed are : —

1. Submaxillary gland and its duet.

2. Sublingual gland.

3. Side of the tongue, and the mueous membrane of the mouth.

Mylo-hyoid.
Digastrie.
Stylo-hyoid.
Hyoglossus.
Stylo-glossus.
Genio-hyoid.
Genio-glossus.

{Mylo-hyoid.
Hypoglossal.
Lingual.
Glosso-pharyngeal.

6. Submaxillary ganglion.

7. Lingual artery and veins.

8. Part of the external maxillary artery.

9. Stylo-hyoid ligament.

4. Museles. H

Disseetion. — To prepare the part for disseetion, it is neeessary to throw
baek the head to its full extent, and turn it slightly to the opposite side.
II— 18c

28o HEAD AND NECK

If the stufi&ng in the mouth has not been previously removed, it should
be taken out now. When this has been done, divide the external maxillary
artery and the anterior facial vein at the point where they eross the lower
border of the mandible. Next detaeh the anterior belly of the digastrie from
its attaehment to the anterior part of the medial aspeet of the lower border
of the mandible ; and then, with the saw, eut through the mandible lateral
to the median plane.^ It is essential that thedivision of the anterior part
of the mandible should be slightly lateral to the median plane on eaeh
side, in order that the median part of the bone, with the attaehments
of the genioid museles, may be left intaet.

After the division of the bone has been eompleted the lower border of
the lateral part of the mandible must be everted, turned slightly upwards,
and fixed in position with hooks. When this has been done the boundaries
and eontents of the submaxillary region ean be examined.

Part of the region has already been seen as the digastrie portion of the
anterior triangle of the neek, but it will now be obvious that the region
oeeupied by the submaxillary gland is mueh more extensive than the
digastrie triangle ; for, although both are bounded anteriorly and posteriorly
by the anterior and posterior bellies of the digastrie musele, the upper
boundary of the digastrie triangle is the lower border of the mandible,
whilst the submaxillary region extends upwards to the level of the mylo-
hyoid ridge on the inner surface of the mandible.

After the mandible has been turned upwards the disseetor should
proeeed, in the first plaee, to examine the relations of the digastrie and
stylo-hyoid museles, then the mylo-hyoid musele, and afterw£yrds he must
study the submaxillary and sublingual glands and the deeper struetures
whieh are found in the medial boundary of the submaxillary region.

Museuliis Digastrieus. — This musele limits the sub-
maxillary region inferiorly and separates it from the earotid
and submental triangles.

The anterior belly of the digastrie springs from the inner
surface of the lower border of the mandible elose to the
symphysis ; and the posterior belly arises from the mastoid
noteh of the temporal bone on the medial side of the mastoid
proeess. The two bellies converge upon the upper border of
the hyoid bone, where they are united by an intermediate
tendon, whieh is attaehed to the hyoid bone at the junction
of the body with the great eornu, by a strong loop of fibrous
tissue developed from the deep cervical fascia. Posterior to
the loop, through whieh it plays, the intermediate tendon
passes through the cleft lower end of the stylo-hyoid musele.

Relations, — The anterior belly is covered by the skin,
superficial fascia and the platysma, and the deep fascia. It
is overlapped by the anterior border of the submaxillary gland,
and its deep surface is in eontaet with the mylo-hyoid musele.
Its anterior border is the posterior boundary of the submental

^ If the part is soft and pliable there may be no neeessity to make this
diyision of the bone.

SUBMAXILLARY REGION 281

triangle, and its posterior border is the anterior boundary of
the digastrie triangle.

The relations of the posterior belly are more numerous
and important. Posteriorly, it is covered by the mastoid
proeess and the attaehments of the sterno-mastoid and
splenius eapitis museles. Between the mastoid proeess and
the angle of the mandible it forms part of the postero-medial
boundary of the parotid spaee and is covered by the parotid
gland ; next it is covered by the angle of the mandible and
the insertion of the internal pterygoid musele. As it lies in
the anterior triangle it is covered by the skin, the superficial
fascia and platysma, and the deep fascia; it is erossed by
the anterior facial vein, and is overlapped by the posterior
part of the submaxillary gland.

It is superficial to the internal jugular vein, the internal
and the extemal earotid arteries, the external maxillary artery,
the middle eonstrietor of the pharynx, and the lower and
posterior part of the hyoglossus musele. The aeeessory
nerve passes posteriorly and downwards between it and the
internal jugular vein, and the oeeipital artery passes upwards
and posteriorly under cover of its lower border, superficial
to the aeeessory nerve. The hypoglossal nerve deseends
vertically on its deep 8urface in the angle between the
internal jugular vein and the internal earotid artery, and
the glosso-pharyngeal nerve passes anteriorly and downwards
between it and the internal earotid. The posterior aurieular
artery runs upwards and posteriorly along the posterior part
of its upper border under cover of the postero-medial surface
of the parotid, and the stylo-hyoid musele deseends along the
same border.

The posterior belly is supplied by the facial nerue^ and the
anterior belly by the mylo-hyoid braneh of the inferior alveolar
nerve.

Museulus Stylohyoideus. — The stylo-hyoid musele is a
small museular bundle whieh springs from the posterior
border and lateral surface of the middle third of the styloid
proeess and deseends along the upper border of the posterior
belly of the digastrie. It divides below into two slips whieh
embraee the intermediate tendon of the digastrie and are then
inserted into the hyoid bone, at the junction of the great
eornu with the body. Its main relations are praetieally the
same as those of the posterior belly of the digastrie, but it is

2 82 HEAD AND NECK

not under cover of the mastoid proeess, the sterno-mastoid,
and the splenius museles. It is supplied by \ht /aeial nerue,

Dissedion, — Turn the anterior part of the submaxillary gland posteriorly,
and elean the posterior part of the mylo-hyoid musele, whieh lies deep to
it. Note that a proeess, the deep part of the gland, springs from the
medial surface of the superficial part and passes anteriorly, deep to the
mylo-hyoid. Disseet the external maxillary artery out of the deep suleus in
the posterior part of the gland, without injuring its submental braneh
whieh runs anteriorly along the lower border of the mandible ; then displaee
the posterior part of the gland anteriorly and expose the hypoglossal nerve
immediately above the great eornu of the hyoid bone, and, at a higher
level, the lingual nerve. Both nerves lie on the lateral surface of the
hyoglossus musele. Hanging from the lower border of the lingual nerve is
the small submaxillary ganglion, from whieh several branehes pass to the
gland. Note again the deep part of the gland, springing from the medial
surface of the superficial part, and also the duet of the gland emerging
from the superficial part of the gland and passing anteriorly, with the
deep part, between the mylo-hyoid musele laterally and the hyo-glossus
medially. Then study the position and relations of the superficial portion
of the gland. The relations of the deep part will be seen after the mylo-
hyoid is reflected.

Glandula Submaxillaris. — The submaxillary salivary gland
eonsists of a superficial larger portion and a deep smaller
portion. The superficial portion is lodged in a spaee whieh
is bounded anteriorly by the anterior belly of the digastrie ;
posteriorly by the posterior belly of the digastrie, the stylo-hyoid,
and the stylo-mandibular ligament ; below by the deep fascia
of the neek ; and laterally by the inner surface of the body
of the mandible and the lower part of the medial surface of
the internal pterygoid musele. The fascial relations of the
gland have been deseribed already (p. 226). The disseetor
should note now that, in aeeordanee with the eontour of the
spaee in whieh it lies, he ean reeognise that the superficial
part of the gland possesses an anterior and a posterior
extremity, and three more or less well-defined surfaces,
inferior, lateral, and medial. The posterior extremity abuts
against the stylo-mandibular ligament, whieh sepa^^tes it from
the parotid, and it overlaps the stylo-hyoid and posterior
belly of the digastrie. It is cleft by a groove in whieh
lies the external maxillary artery. The anterior extremity
rests on the anterior belly of the digastrie.

The inferior surface is covered by the layer of deep
cervical fascia whieh extends upwards from the great eornu
of the hyoid bone to the lower border of the mandible ; it
is erossed posteriorly, under cover of the deep fascia, by tbe

SUBMAXILI.ARY REGION

283

anterior facial vein. Along its upper border lie the majority
of the subniaxillary lymph glands ; the external ima^illary
artery turns round between it and the lower border of the
mandible at the anterior border of the masseter ; and the sub-
mental braneh of the external maxillary artery runs anteriorly
in the angle between it and the bone,

The lateral surface is in relalion posteriorly with the lower

part of the medial surface of the internal pterygoid, and
anteriorly with the inner surface of the body of the mandible
below the mylo-hyoid ridge. The external maxillary artery,
after it emerges from the groove in the posterior end of the
gland, and beforo it turns round the lower border of the
mandible, riins anteriorly and downwards between this surface
and the internal pterygoid ; and the ,my]o-hyoid artery and
nerve lie between it and the body of the mandible before
they pass, more ant' ' "^ the medial surface of the gland.

284 HEAD AND NECK

The medial surface is in relation with the mylo-hyoid and
hyoglossus, the lingual nerve and the subniaxillary ganglion,
and the hypoglossal nerve. It overlaps the stylo-hyoid
musele, both bellies of the digastrie, and the great eornu of
the hyoid bone ; and the deep part of the gland and the duet
both spring froni this surface before they pass anteriorly
between the mylo-hyoid and the hyoglossus museles.

The nerve supply of the gland is derived from the lingual
nerve, the submaxillary ganglion, the sympathetie plexus on
the external maxillary artery ; and its vascular supply eonsists
of small submaxillary branehes from the external maxillary
artery.

The relations of the deep part of the gland and the duet
will be investigated after the mylo-hyoid has been reflected.

Disseetion. — Displaee the superficial part of the gland and the submental
braneh of the external maxillary artery posteriorly ; eut the mylo-hyoid
vessels and nerve, and turn the anterior belly of the digastrie downwards ;
then elean the mylo-hyoid musele and examine its attaehments.

Museulus Mylohyoideus. — This is a thin sheet of
museular fibres, whieh arises from the mylo-hyoid ridge
upon the inner surface of the body of the mandible, by
an origin whieh extends from . the last molar tooth to the
symphysis. Its fibres are direeted downwards, medially,
and anteriorly, and present two different modes of insertion.
The posterior fibres are inserted into the body of the hyoid
bone; these, however, form a comparatively small part of
the musele. The greater number of the fibres are inserted
into a median raphe, whieh extends between the symphysis
of the lower jaw and the body of the hyoid bone. The
two mylo-hyoid museles, therefore, streteh aeross from one
side of the body of the mandible to the other, in front of the
hyoid bone, and eonstitute a floor for the anterior part of the
mouth. This floor is frequently termed the diaphragma oris,
The mylo-hyoid musele is supplied by the mylo-hyoid braneh
of the in/erior alveolar nerue.

Disseetion. — Cut the mylo-hyoid musele a little below its origin from the
mylo-hyoid ridge and turn it downwards and anteriorly. Whilst doing
this be careful not to injure the mueous membrane of the mouth whieh
lies in eontaet with it above.

Parts exposed by the ReAeetion of the Mylo-hyoid (Fig.
115). — The side of the tongue is now brought into view,
with a number of struetures in eonneetion with it. First

SUBMAX1LLARY REGION 285

note the mueous rnembrane stretehing from the tongue lo
the gum of the lower jaw ; then identify the various museles.
The hyoglossus, a portion of whieh was previously visible
behind the mylo-hyoid, is fully exposed. It is a quadranguiar
sheet of Aeshy iibres whieh extends from the hyoid bone to
the side of the tongue. Mark its position, beeause all the
struetures in this region have a more or less intimate relation-
ship to it Thus, posterior and also superiieial to its upper
part, the stylthglossus musde will be reeognised, whilst anterior

.,_ Slylo-EloKus

to it are the gento glossus and the genio-kyoid. The genio-
hyoid musele oeeupies the antero-inferior part of the region,
whilst the anterior part of the genio^lossus is seen in the
interval between it and the hjoglossus. Upon the surface of
the hyoglossus, the lingual and hypoglossal nerves, the eon-
neeting loop between them, the deep portion of the sub-
maxillarygland with the submasillary duet, and the submaxillary
ganglion are to be disseeted. The lingual nerve oeeupies the
highest leve!, and passes anteriorly upon the musele near its
insertion into the tongue. The kypogiossal nerve, with its
vena eomitans, err p to the hyoid bone, whilst the

286 HEAD AND NECK

deep part of Ihe submaxillary gland and the submaxtUary duet
(Wharton's) oeeupy an intermediate plaee Although the
mbmaxiltary gangltm is very minuie, its relations are so
preeise that it is very easily found By seizing the hngual
nerve and disseeting carefully in the interval between it
and the deep part of the submaxillary gland, the ganghon
will be exposed, and tts roots and branehes of distnbution
tnade out Upon the genio glossus, antenor to the

laterior nasal eoneha (O T iof«ior turbm»!)

Eitemil
DuxILUry artety
Sup«£dal parl or
ibmakiUaiy Bland

submuillaiy gk
Hypogle- -'

hyoglossus, the disseetor will note the sublingual gland with
its artery of supply. If the stylo-hyoid and the posterior
belly of the digastrie are displaeed posteriorly, eertain
struetures wiil be seen passing under cover of the posterior
margin of the hyoglossus musde. These are:— ^i) the
glosso-pharyngeal nerve immediately below the stylo-glossus
musele; (2) the stylo-hyoid ligament a little lower down ;
and (3) the lingual artery elose to the hyoid bone,

Museulus HyogloSBua.— This isa quadrate, flat musele whieh
arises from the whole lengih of the greater eomu, and also from

SUBMAXILLARY REGION 287

the body of the hyoid bone, Its (ibres pass upwards to the
posterior part of the side of the tongue, mediaj to the stylo-
gloBSUS. The hyoglossus is supplied by ihe hypoglossal

Muaeulns Stylo-glossus. — The stylo-glossus musele is an
elongated Aeshy sHp whieh takes origin from the anterior aspeet
of the styloid proeess near its tip, and, lo a slight extent, from
the upper part of the stylo-hyoid ligament also. Passirig down-

wards and anteriorly its fibres may be traeed upon the side
of the tongue as far as the tip. Some of them deeussate
with the fasciculi of the hyoglossus «lusele. The nerve of
supply to the stylo-glossus eomes from the hypoglossal.

MuseuluB Geniohyoideus. — The genio-hyoid musele is
plaeed elose to the median plane, in eontaet with its fellow of
the opposite side, It is a short musele whieh arises from
the spina mentalis upon the posterior surface of the symphysis
of the m; ' extends downwards and posteriorly to

gain insi anterior aspeet of the body of the

hyoid bq 'ossal rterve supplies the genio-hyoid.

2 88 HEAD AND NECK

The Deep Part of the Submaodllary Gland. — It has been
noted already that the small deep part of the submaxillary
gland springs from the medial surface of the superficial part at
the posterior border of the mylo-hyoid musele. It will now be
obvious that it passes anteriorly and upwards, between the
mylo-hyoid laterally and the hyo-glossus and genio-glossus
medially, until it eomes into eontaet with the sublingual gland.
It is aeeompanied by the lingual nerve and the submaxillary
duet, both of whieh lie on its medial surface.

Duetus Subinaxillaris. — The duet of the submaxillary
gland (O.T. Wharton's duet) emierges from the medial surface
of the main part of the gland, and proeeeds, with the deep
part of the gland, anteriorly and upwards upon the hyo-
glossus musele. At first it lies between the lingual nerve
above and the hypoglossal nerve below. Reaehing the
surface of the genio-glossus musele, it is erossed laterally,
and then below and medially, by the lingual nerve. Then it
passes to the medial side of the sublingual gland, and gains the
floor of the mouth, where it opens by a small orifice plaeed
on the summit of a papilla whieh lies elose to the side of the
frenulum linguae.

The wall of the duet is mueh thinner than that of
the parotid duet. If a small opening be made in it, the
disseetor will experience little difficulty in passing a fine probe
or bristle along it into the mouth.

Glandula Sublingualis. — ^The sublingual gland lies in the
floor of the mouth, and is the smallest of the larger salivary
glands. It is almond shaped, about one ineh and a half
long ; and its relations are very dehnite. Its prominent upper
border ean be seen within the mouth, beneath the anterior
part of the tongue, where it is covered by a fold of mueous
membrane termed the pliea sublingualis (Fig. 146). Medially
it rests upon the genio-glossus musele, whilst laterally it is
lodged in a fossa on the inner aspeet of the mandible,
immediately lateral to the symphysis and above the mylo-
hyoid ridge. Below^ it is supported by the mylo - hyoid
musele. Its anterior extremity reaehes the median plane,
above the anterior border of the genio - glossus, and is in
eontaet with its fellow of the opposite side. The duet of
the submaxillary gland and the lingual nerve are prolonged
anteriorly medial to the sublingual gland.

Numerous small duets (the number varying from eight

SUBMAXILTJVRY REGION 289

to twenty) proeeed from the sublingual gland. These, as a
rule, open into the mouth on the summit of the pliea sub-
lingualis (Birmingham).

Nervus Tiingnalls. — In the disseetion of the infratemporal
region, the lingual nerve was seen passing downwards between
the ramus of the mandible and the internal pterygoid musele.
As it deseends it inelines anteriorly, and, after passing
over the attaehment of the superior eonstrietor musele of
the pharynx to the posterior end of the mylo-hyoid ridge,
it lies below and posterior to the last molar tooth between the
mueous membrane of the mouth and the body of the mandible.
At this point it is in danger of being hurt by the elumsy
extraction of one of the lower molars, and here also it may
be divided by the surgeon, from the inside of the mouth.
In its further eourse the nerve keeps elose to the side of
the tongue, erossing the styloglossus and the upper part of
the hyoglossus, and, beyond that, the submaxillary duet.
Its terminal branehes are plaeed immediately under the
mueous membrane of the mouth, and it ean be traeed as
far as the tip of the tongue.

The branehes whieh proeeed from the lingual nerve in the
submaxillary region are of two kinds — (i) twigs of eom-
munieation ; (2) branehes of distribution.

{I. Two or more to the submaxillary ganglion.
2. One or two whieh deseend along the anterior
border of the hyoglossus musele to unite with
the hypoglossal nerve.

T, 1 r I. Slender filaments to the mueous membrane of the

Branehes I ^^^^^ ^^^ ^^^

T\' ^ ^u *• I 2. A few twigs to the sublingual gland.
Distribution. I^t> i-?*u* •&&

\, 3. Branehes to the tongue.

The lingual branehes pieree the substanee of the tongue,
and then ineline upwards to supply the mueous membrane
with the papillae over the anterior two-thirds of this organ.

Ganglion Submaiillare. — This is a minute ganglion whieh
lies upon the upper part of the hyoglossus musele in the interval
between the lingual nerve and the deep part of the sub-
maxillary gland. In size, it is not larger than the head of a
large pin; and, when freed from the connective tissue surround-
ing both it and its branehes, it will be seen to be suspended
from the lingual nerve by two short branehes, whieh enter its
upper border, and are separated by a distinet interval. Of these,
the posterior eonneeting twig is frequently in the form of two

VOL. II — 19

I
I

HEAD AND NECK

< or three Rlaments, whieh convey to the ganglion its sensory
and seeretory roots, whilst the anterior eonneeting braneh miist
be looked upon as a twig given by the ganglion to the lingual
Derye.

In eommon with the other ganglia developed in eonneeiion
with the branehes of the trigeminal nerye, this ganghon has
three roots — viz. (i) a sensory root from the lingual nerve ; (3)
, a seerelory root from the ehorda tympani ; and {3) a sympathetie
rool from the plexus around the external maxillary artery.

From its lower border seyetal minute twigs proeeed, and
these are distributed — (1) to the submaxil]ary gland and
duet; {2) to ihe sublingual gland froru the braneh whieh
it gives to the Hngual nerve ; and (3) to the mueous mem-
brane of the mouth.

Norrus HypoglosBUs. — This nerve has been traeed in the
disseetion of the anlerior triangle to the point where it
disappears under cover of the mylo-hyoid musde (p. 231).
It is now seen passing anteriorly upon the hyoglossus musele,
ahove the hyoid bone and below the level of the deep
part of ihe submax!llary gland. At the anterior border of
the hyoglossus it gains the surface of the genio-glossus
musele, into the substanee of whieh it sinks; and (inally
it breaks up into branehea whieh supply the museular sub-
stanee of the tongue. Upon the hyoglossus musele it is
aeeompanied by a vena eomitans.

The branehes whieh spring from the hypoglossal nerve in
this region are very numerous, and are entirely distributed to
museles. It supplies — (i) ibestylo-glossus; (2) thehyoglossus;
(3) the genio-glossus ; (4) the genio-hyoid ; and (5) the
intriiisie museles of the tongue,

In addition, it eommunieates freely with the lingual
nerye. The more apparent of these eonneetions take plaee
in the form of one or more loops in relation to the anterior
border of the hyoglossus. Other eommunieations with the
same nerve are effected in the substanee of the tongue.

BaAeetion of tJie Hyaslo'HnE. — The hyoglossus should now bc
earerully delaehed from Ihe hyoid bone, and Ihrown upwnrds towards
tbe tongue. In doing thls there is no need to divide the slnielures
whieh lie upon its surraee. By the reAeetion of this musele Ihe follQw-
ing stnietures will be (iilly displayed— (i) the profunda linguie artery
and the veiiis whieh aeeumpany it ; (2) the dorsales lingu^ arteries and
L vrans; (3) the posterior poit of the genio^lossuE ; (4) the origin ai the
middle eonstrieloi of Ihe phaiynx ; and (5) the attaehment of the slylo-
hyoid ligAment,

SUBMAXILLARY REGION 291

Museulus Gtenioglossns. — This is a flat triangular musele,
the medial surface of whieh is in eontaet with its fellow of
the opposite side in the median plane. It arises by a short
pointed tendon from the upper mental spine on the posterior
aspeet of the symphysis of the mandible, and from this its
Aeshy fasciculi spread out in a fan-shaped manner. By far
the greater part of the musele is inserted into the tongue by
an insertion whieh extends throughout the whole length of
the organ from the tip to the base; below the tongue, a
few iibres reaeh the side of the pharynx. The genio-glossus
is supplied by twigs from the hypoglossal nerue,

Axteria Lingualis. — As the lingual artery is now fully
exposed, it ean be conveniently studied at this stage.
It springs from the anterior aspeet of the external earotid,
and is separable into two parts — viz. (1) a part extending
from its origin to the posterior border of the hyoglossus
musele ; (2) a part lying in relation to the upper border of
the hyoid bone and extending to the anterior border of the
hyoglossus, where it divides into two terminal branehes, the
sublingual and the deep artery of the tongue.

The first part has been fully examined in a previous
disseetion. It lies in the earotid triangle of the neek, and
is therefore comparatively superficial. It is erossed by the
hypoglossal ner\'e, and lies, medially, against the middle
eonstrietor. The seeond part proeeeds anteriorly along the
upper border of the great eornu of the hyoid bone, and
is covered by the hyoglossus musele, whieh intervenes
between it and the hypoglossal nerve. The nerve, how-
ever, is plaeed at a slightly higher level. The deep or
medial relations of the artery in this stage of its eourse
are the middle eonstrietor of the pharynx and the genio-
glossus.

The branehes of the lingual artery are : —

1. Suprahyoid from the^r^/ part (p. 233).

2. Dorsalis linguae from the seeond part.

3. Sublingual.

4. Profunda.

Rami Dorsales Linguee. — The dorsalis ^linguse is generally
represented by two or more well-marked branehes, whieh
pass upwards, under cover of the hyoglossus musele, to end
in twigs to the mueous membrane covering the pharyngelal#
part of the dorsum of the tongue. Some twigs are supplied

II— 19a

292 HEAD AND NECK

also to the museular substanee of the organ, and a few may
be traeed baekwards into the tonsil.

Arteria SubUngualis, — This springs from the termination
of the seeond part and emerges from under cover of the
anterior border of the hyoglossus, and then aseends upon the
genio-glossus to reaeh the sublingual gland, whieh it supplies.
It gives branehes to the surrounding museles also ; and
it anastomoses with its fellow of the opposite side and with
the submental braneh of the external maxillary artery.

Arteria Profunda Linguee, — The deep artery of the tongue
aseends almost yertieally upon the genio-glossus, overlapped
by the anterior border of the hyoglossus ; when it reaehes
the under surface of the tongue, it runs towards the tip and
ends in terminal branehes. It ean easily be exposed by
dividing the mueous membrane along its eourse, when it will
be seen to lie elose to the attaehment of the frenulum of
the tongue, and to be eontinued forwards in the interyal
between the genio - glossus and the inferior longitudinal
musde. Its eourse is tortuous to allow of the protrusion or
elongation of the organ, and it gives off numerous branehes.

Lingnal Veins. — The lingual artery is aeeompanied by
two small venae eomites whieh lie with it under cover of
the hyoglossus ; but the main vein of the tongue erosses
the lateral surface of the hyoglossus, and another smaller vein,
the vena eomitans hypoglossi^ aeeompanies the hypoglossal
nerve. The ven8e eomites of the artery and the vena eomitans
hypoglossi unite with the main vein to form the lingual vein,
whieh opens into the eommon facial vein or into the internai
jugular vein.

Stylo-hyoid Ligament. — This is the last strueture to be
examined in this disseetion. It is a iibrous eord whieh
springs from the tip of the styloid proeess and passes
antero-inferiorly to be attaehed, under cover of the hyo-
glossus musele, to the lesser eornu of the hyoid bone. It is
not uneommon to find it partially ossiiied; in other eases
it may assume a ruddy hue and eontain museular iibres.

OTie GANGLION AND TENSOR PALATI.

During the disseetion of the submaxillary region the
disseetor has noted a nerve ganglion, the submaxillary gangiion^
eonneeted with the lingual braneh of the mandibular nerve,

OTie GANGLION AND TENSOR PALATI 293

and when he was examining the infratemporal region refer-
enee was made to the otie ganglion, whieh is assoeiated
with the tnink of the mandibular nerve and the braneh whieh
it supplies to the internal pterygoid musele. This ganglion
and its eonneetions should now be displayed, and afterwards
the tensor palati musele should be eleaned and followed from
its origin to the hamulus of the medial pterygoid lamina.

Disseetion. — Cut the lingual and inferior alveolar nerves immediately
below their origins ; evert the upf)er part of the mandibular nerve and
examine the otie'ganglion ; then divide the intemal pterygoid, along the
posterior border of the lateral pterygoid lamina, depress the lower part of
the musele and elean the tensor palati, whieh forms the medial relation
of the middle meningeal artery, the otie ganglion and the mandibular nerve,
separating them from the lateral surface of the auditory tube (Eustaehian).

Gkmglion Otieuin. — This is a minute oval body about
4 mm. in length. It lies immediately below the foramen
oyale, between the mandibular nerye laterally, the tensor veli
palatini medially, and the middle meningeal artery posteriorly ;
and it is intimately assoeiated with the origin of the nerve to
the internal pterygoid.

The otie ganglion is usually deseribed as receiving motor, sensory, and
sympathetie roots. The motor root is supplied by the nerve to the intemal
pterygoid musele ; the sympathetie root eomes from the plexus around the
middle meningeal artery. In addition to these, the small superficial petrosal
nerue enters the posterior border of the ganglion, and conveys to it sensory
fibres.

The following are the branehes whieh proeeed from the otie ganglion : —

(A twig whieh passes downwards and anteriorly to the
tensor veli palatini. (Tensor palati.)
A twig whieh proeeeds upwards and posteriorly to
supply the tensor tympani.
{One or more fine filaments to one or both of the roots
of the aurieulo-temporal nerve.
A minute eommunieating filament to the ehorda
tympani.

Museulus Tensor Veli Palatini.— This flat and band-like
musele is elosely applied to the deep surface of the internal
pterygoid musele. It arises from the seaphoid fossa at the
rbot of the medial pterygoid lamina, from the posterior
border of the lower surface of the great wing of the sphenoid,
from the spine of the sphenoid, and from the lateral aspeet of
the auditory tube (O.T. Eustaehian). It deseends to the
lower end of the medial pterygoid lamina and ends in a
tendon whieh turns horizontally under the hamulus into
the soft palate, where its attaehments will be seen later.
11—19 h

294 HEAD AND NECK

THE GREAT YESSELS AND NERYES

0F THE NECK.

As soon as the disseetion of the infratemporal and the
submaxillary regions is eompleted the disseetor should tum
to the study of the external earotid artery and its relations.

Arteria Gaxotis Eztema. — The external earotid is one
of the two terminal branehes of the comm6n earotid. It
eommenees therefore at the level of the upper border of the
thyreoid eartilage, opposite the dise between the third and
fourth cervical ^ertebrae; and, after running upwards and
posteriorly to the level of the neek of the mandible, it
terminates, between that portion of bone and the upper part
of the antero-medial surface of the parotid gland, by dividing
into two terminal branehes, the superAeial temporal and the
internal maxillary. At its eommeneement it lies anterior and
medial to the internal earotid ; and it is ealled external not
on aeeount of its relation to the internal earotid, but beeause
it is distributed mainly to the parts on the exterior of the
skull. It is at first comparatively superficial in the upper
part of the earotid triangle ; next it passes under cover of the
lower part of the postero-medial surface of the parotid and the
posterior belly of the digastrie and the stylo-hyoid musoles.
At the upper border of the stylo-hyoid it enters a groove in
the medial border of the parotid, through whieh it passes to
the upper part of the antero-medial surface of the gland,
posterior to the neek of the mandible, where it terminates.

Relations. — As it lies in the earotid triangle it is covered
by the skin, superficial fascia and platysma, branehes of the
nervus eutaneus eoUi and the cervical braneh of the facial
nerve, and the deep fascia. Beneath the deep fascia it is
erossed superficially by the eommon facial and lingual veins
and the hypoglossal nerve ; and, at the upper end of the
triangle, it is eoneealed by the lower end of the parotid gland
and it is erossed from behind forwards by the posterior facial
vein. After it leaves the earotid triangle it is overlapped by
the angle of the mandible, and is erossed by the posterior
belly of the digastrie and the stylo-hyoid. At its termina-
tion it is eoneealed by the upper part of the parotid and is
erossed by branehes of the facial nerve.

GREAT VESSEI^ AND NERVES 0F NECK 295

To tts medial side lies tlie wall of the pharynx, rrom whieh
tt is separated, in the region of ihe earotid triangle, by the
external and internal laryngeal branehes of the superior

laryngeal nerve. The medial relations at a higher level will
be seen to greater advantage at a later stage when the styloid
proeess is detaehed and displaeed. They are the pharyngeal
braneh of the yiigii^, the stylo-pharyngeus, the glosso-pharyngeal

296 HEAD AND NECK

nerve, and the styloid proeess or the stylo-hyoid ligament.
These struetures lie to its medial side after they have passed
obliquely between it and the internal earotid, whieh has
gradually attained a plane posterior and medial to that in
whieh the external earotid lies.

In the whole of its extent the extemal earotid is aeeom-
panied by numerous sympathetie nerve libres, derived from
the upper cervical sympathetie ganglion ; they eonstitute the
external earotid plexus^ whieh distributes offsets along all the
branehes of the artery.

Bratiehes, — The branehes of the external earotid artery are
the superior thyreoid, the lingual, and the external maxillary
from its anterior aspeet; the oeeipital and the posterior
aurieular from its posterior aspeet ; the aseending pharyngeal
from its medial side ; and the superficial temporal and the
internal maxillary are its terminal branehes.

Arteria Thsrreoidea Superior. — This vessel arises within
the earotid triangle, from the anterior aspeet of the extemal
earotid elose to its origin. It runs downwards and anteriorly,
under cover of the omo-hyoid, sterno-hyoid, and sterno-thyreoid
museles, to the apex of the lateral lobe of the thyreoid gland,
where it ends by breaking up into three terminal branehes.

The following branehes proeeed from it : —

1. Hyoid.

2. Superior laryngeal.

3. Sterno-mastoid.

4. Grieo-thyreoid.

5. Glandular.

Rarnus Hyoideus. — This is a minute twig, whieh springs
from the superior thyreoid in the earotid triangle. It runs
along the lower border of the hyoid bone, under cover of the
thyreo-hyoid musele, and anastomoses with its fellow of the
opposite side, and with the hyoid braneh of the lingual
artery.

Arteria Laryngea Superior — This is a larger vessel. It
springs from the superior thyreoid in the earotid triangle,
and, assoeiating itself with the internal laryngeal nerve, it
enters the pharynx after piereing the thyreo-hyoid mem-
brane.

Arteria Sternodeidomastoidea. — The sterno-mastoid braneh
is a small vessel whieh runs downwards and posteriorly, aeross
the earotid sheath along the upper border of the anterior
belly of the omo-hyoid musele, to reaeh the deep surface of
the sterno-mastoid musele, into whieh it sinks. It gives,

GREAT YESSELS AND NERVES OF NECK 297

in addition, minute twigs to the depressor museles of the
larynx.

Ramus Cncothyreoideu5. — The erieo-thyreoid artery runs
medially upon the erieo-thyreoid ligament, and anastomoses
with its fellow of the opposite side. It has already been
notieed in the disseetion of the middle line of the neek
(p. 229).

Rami Glandulares. — The glandular rami are the three
terminal branehes. They spring from the main trunk at
the apex of the lateral lobe of the thyreoid gland. The
largest is distributed on the medial surface of the lateral
lobe; the smallest ramifies on its lateral suriaee; whilst
the third runs downwards upon the anterior border of the
lateralj lobe, and then along the upper border of the isthmus
towards its fellow of the opposite side. The anastomosis
between the thyreoid arteries of the two sides is by no means
free.

Ven(B Thyreoideee Superiores. — The superior thyreoid veins
emerge from the gland and form a trunk whieh receives
tributaries eorresponding in a great measure with the branehes
of the artery. It erosses the upper part of the eommon
earotid and joins the internal jugular vein.

Arteria Lingualis. — The lingual artery springs from the
external earotid at the level of the great 'eornu of the
hyoid bone in the earotid triangle. It runs along the upper
border of the great eornu. As its name indieates it is
the artery of supply to the tongue. It has already been
disseeted in the earotid triangle and the submaxillary region,
and the details of its eourse and relations are given on

PP- '^ZZ^ 291.

Arteria Maxillaris Extema (O.T. Facial Artery). — The ex-
ternal maxillary artery ean be studied, at the present stage of
the disseetion, from its origin up to the point where it mounts
upon the mandible to reaeh the face. This is termed the
cervical part oi the artery. It springs from the anterior aspeet
of the external earotid, immediately above the lingual, in
the upper part of the earotid triangle, and passes vertically
upwards, on the lateral surface of the middle eonstrietor
musele of the pharynx, to the angle of the mandible, where
it disappears under cover of the posterior belly of the
digastrie and the stylo-hyoid musele. At this point the
«uperior eonstrietor is medial to it and separates it from the

2gS HEA.D AND NECK

lateral surface of tlie tonsil. At the upper border of the
stylo-hyoid it enters a deep groove in the posterior end of
the submaxillary gland. Emerging from this it turns down-
wards and anteriorly between ihe laleral surface of the gland

iperneiol CEapDnJ

and the intotnal pterygoid musele, and turning round the lower
border of the mandible at the anterior border of the masseter
it enters the face. For details of its facial eourse see p. 129.
l'our named brnnehes spring froni the e.vtcrnol niaxillary
artery in the ccrvical part of its eourse :■ — ■

GREAT YESSELS AND NERYES 0F NECK 299

Arkria Palatina Asemdms. — The aseending palatine

braneh is given off for the supply of the soft palate, but

il distributes branehes to the tonsil and auditory (O.T.

Eustaehtan) tube also. It aseends between the stylo-

'su

yLanw

Hy«;

bone

Ihftr

)rhi-o

=r.

pharyngeus and stylo-glossus museles, and wiU be seen when
the styloid proeess is reiieeted.

Ramus Tonsi//aris.~The tonsillar braneh runs upwards
between the internal pterygoid and stylo-glossus museles, then
turns medially, pierees the superior eonstrietor, and enters
the lonsil.

The glandu/ar branehes are given to the submaxillary
gland as the external maxillary artery passes through it.

300 HEAD AND NECK

Arteria Submentalis, — This is a braneh of some size. It
arises elose to the base of the mandible, and nins towards
the ehin upon the mylo-hyoid musele. Near the symphysis
it ehanges its direetion, and is earried upwards over the border
of the mandible, to end in branehes for the museles and
integument of the ehin and lower lip. In the submaxillary
region it gives numerous twigs to the surrounding museles
and glands, and anastomoses with the sublingual artery by
branehes whieh pieree the mylo-hyoid musele. It anasto-
moses, in the face, with the inferior labial braneh of the
external maxillary and the mental braneh of the inferior
alyeolar.

Vena Facialis Anterior. — The eeroieal porHon of the
anterior facial has already been seen (p. 231) passing posteriorly
and downwards, superiieial to the submaxillary gland. After
receiving tributaries eorresponding to the branehes of the
similar part of the external maxillary artery, it joins the
posterior facial vein. The short trunk thus formed is termed
ih^ eommon /aeial vein, and it pours its blood into the intemal
jugular at the level of the hyoid bone.

Arteria Oeeipitalis. — The oeeipital artery springs from the
posterior aspeet of the external earotid at the same level as
the external maxillary. It takes the lower border of the
posterior belly of the digastrie musele as its guide, and runs
upwards and posteriorly, under cover of the sterno-mastoid
musele, and generally under cover of the lower border of the
posterior belly of the digastrie, to reaeh the interval between
the mastoid portion of the base of the skuU and the transverse
proeess of the atlas. Thenee onwards it has been studied
in the disseetion of the sealp and the baek of the neok
(pp. 162, 170). The first part of the vessel erosses the internal
earotid artery, the vagus nerve, the aeeessory nerve, and the
internal jugular vein, whilst the hypoglossal nerve hooks
round it.

The only branehes whieh spring from this portion of the
oeeipital are : (i) museular twigs; and (2) a meningeal
braneh.

The museular twigs are given to the neighbouring musoles,
and one of them, larger than the others and very eonstant, is
termed the sterno-mastoid braneh, runs parallel with the
aeeessory nerve, and sinks with it into the substanee of
the sterno-mastoid musele.

GREAT YESSELS AND NERVES 0F NEGK 301

A tneningeal braneh assoeiates itself with the internal
jugular vein, and ean be followed upwards upon it to
the jugular foramen, through whieh it passes into the
eranium.

Arteria Aurieiilaris Posterior. — The posterior aurieular
artery will be found above the level of the posterior belly of
the digastrie, and, like the oeeipital, it takes origin from the
posterior aspeet of the external earotid artery, In the first
part of its eourse it is plaeed deeply, and runs upwards and
posteriorly between the styloid proeess of the temporal bone
and the postero-medial surface of the parotid gland to reaeh
the interval between the mastoid proeess and the baek of
the auriele. Then it joins the posterior aurieular nerve.
Its further eourse has been studied in the disseetion of the
sealp (p. 157).

This portion of the posterior aurieular artery gives off
(i) museular twigs ; (2) a few branehes to the parotid gland ;
and (3) the stylo-mastoid artery.

Arteria Stylomastoidea. — This is a slender vessel whieh
enters the stylo-mastoid foramen. In the interior of the tem-
poral bone it has an extensive distribution. It supplies twigs
to the mastoid eells and to the tympanie cavity and is earried
onwards in the eanalis facialis (O.T. Eallopian) to anastomose
with the petrosal braneh of the middle meningeal.

Arteria Maxillaris Intema. — The eommeneement of the
internal maxillary artery, from the termination of the external
earotid, between the neek of the mandible and the antero-
medial surface of the parotid gland, has been seen already, and
the artery has been traeed through the infratemporal region
to the pterygo-palatine fossa, where its terminal branehes will
be disseeted at a later period.

Arteria Temporalis Superficialis. — Like the internal
maxillary, this artery eommenees between the neek of the
mandible and the antero-medial surface of the parotid gland.
It passes upwards and, as it emerges from under cover of
the upper end of the parotid, it erosses the posterior end
of the zygomatic areh and enters the superficial fascia of the
sealp, in whieh it aseends on the superficial surface of the
temporal fascia, and anterior to the auriele it breaks up
into two branehes, /rontal and parietal. These anastomose
with eaeh other and with their fellows of the opposite
side. The frontal anastomoses with the supra-orbital and

302 HEAD AND NECK

frontal branehes of the ophtlialmie also, and the parietal
with Ihe posterior aurieular and the oeeipital arteries. Whilst
it is still undet cover of the parotid it gives branehes to the

eiior ihyreoU Brtety
Thyreo-hyoid muKle

gland ; anterior aurieuiar branekes i.0 t\\.^ i\ir\c\& ; the transverse
facial, whieh passes along the lower border of the zygoraatic
areh aeross the masseter. As ihe superficial temporal erosses
the zygoma it gives off a zygomatico-orbital bramh, whieh runs
to the lateral border of the orbit, and a niiddle temporal

GREAT YESSELS AND NERYES 0F NECK 303

branehy whieh peHbrates the temporal fascia and anastomoses
in the temporal fossa with the deep temporal branehes of the
internal maxillary. The eourse of this braneh and also the
distribution of the terminal branehes have been followed in
earlier stages of the disseetion (pp. 266, 267).

Disseetion, — Divide the posterior belly of the digastrie immediately
below its origin, and tum it downwards and anteriorly towards the hyoid
bone ; then examine the stylo-pharyngeus musele. It may be neeessary to
eut the oedpital and posterior aurieular arteries in order to gain free aeeess
to the deeper parts, but this should not be done unless it is neeessary.
Care must be taken whilst eleaning the stylo-pharyngeus to avoid injuring
the glosso-pharyngeal nerve, whieh turns round its posterior border and
erosses its superiieial surface.

MtLsenliis Stylopharyngeus. — This is the longest of the
three slender museles whieh spring from the styloid proeess.
It arises from its deep or medial surface elose to its root, and
extends downwards and anteriorly to gain the side of the
pharynx, where it disappears under cover of the upper border
of the middle eonstrietor musele. Whilst under cover of
the middle eonstrietor its fibres blend with those of the palato-
pharyngeus, and, with these, are inserted into the posterior
border of the eorresponding lamina of the thyreoid eartilage.
Some of the fibres, however, are lost in the wall of the pharynx.
If the disseetor removes the fascia at the posterior part of
the thyreo-hyoid spaee he will expose the lower fibres of the
middle and the upper fibres of the inferior eonstrietor, and
in the interval between them, on a deeper plane, the lateral
surface of the lower part of the stylo-pharyngeus.

Disseetion. — Snip through the base of the styloid proeess with the bone
forceps, and throw it and the attaehed museles downwards and anteriorly.
The upper parts of the internal earotid artery and the internal jugular vein
are now exposed, and the aseending pharyngeal artery ean be followed to
the base of the skull.

Arteria Pharyngea Aseendens. — To expose this vessel the
disseetor must push the external earotid anteriorly and elean
the interval between it and the internal earotid. The
aseending pharyngeal springs from the medial surface of the
external earotid elose to its lower end and is its smallest
braneh. It aseends along the lateral border of the pharynx,
lying between the stylo-pharyngeus laterally and the eon-
strietors of the pharynx medially, first in a plane between the
external and internal earotid arteries, and then to the medial
side of the internal earotid. As it passes upwards it gives

304 HEAD AND NECK

pharyngeal branehes to the wall of the pharynx and
prevertebral branehes to the prevertebral museles. At
the base of the skull it gives off meningeal branehes, whieh
enter the eranial cavity through the hypoglossal canaV the
jugular foramen, and the foramen laeerum; and palatine
branehes, whieh pieree the pharyngeal aponeurosis above the
upper border of the superior eonstrietor and deseend, along
the levator palati, to the soft palate. Offsets from these
branehes are given to the auditory tube (O.T. Eustaehian)
and to the tonsil.

Disseetion. — After the aseending pharyngeal artery has been examined,
the iniernetl earotid artery^ the glosso-pharyngeal^ ^agus, aeeessory, and
hypogLossal nerues, and the superior cervical ganglion, with their various
eonneetions and branehes, must be disseeted. A dense and tough fascia
envelops these struetures, and a great amount of patienee is required to
traee the branehes of the nerves through it. One nerve — the pharyngeal
braneh of the vagus — whieh proeeeds downwards and anteriorly upon the
superficial or lateral aspeet of the internal earotid, is espeoially liable to
injury, and must thereibre be borne in mind from the very outset of
the disseetion. The intemal laryngeal and the extemal laryngeal nerves
have been previously displayed in the anterior triangle of the neek. These,
if traoed upwards, will lead to the superior laryngeal braneh of the vagus,
whieh lies in relation with the deep aspeet of the internal oarotid artery.
Near the base of the skull all the nerve-trunks will be found making
their appearanee, elose together, in the interval between the intemal
jugular vein and the internal earotid artery ; whilst posterior to the vein
the reetus lateralis musele and the Jirst loop of the eeruieal plexus will be
seen.

Arteria Oarotis Intema. — The internal earotid artery is
one of the two terminal branehes .of the eommon earotid,
and it eommenees at the level of the upper border of the
thyreoid eartilage. From this point it proeeeds upwards
in the neek, in a vertical direetion, until it reaehes the
base of the skull; there it disappears from view by entering
the earotid eanal of the petrous portion of the temporal
bone, through whieh it reaehes the interior of the eranium.
The internal earotid artery ean therefore be very appropri-
ately divided into three parts — viz. (i) a cervical ; (2)
a petrous ; and (3) an intraeranial. The cervical part
alone eomes under the notiee of the student in the present
disseetion.

In the first part of its extent the internal earotid artery
lies in the earotid triangle, and is therefore comparatively
superficial. It is covered by the integument, platysma, and
fascia, and is overlapped by the sterno-mastoid musele and

GREAT YESSELS AND NERYES 0F NECK 305

the anterior border of the internal jugular vein ; it is erossed
by the hypoglossal nerve and the sterno-mastoid braneh of the
oedpital artery, the lingual and eominon facial veins ; and the

deseendens hypoglossi deseends on its superiieial suri'aee. As
it proeeeds upwards, it eomes to lie under cover of the lower
end of the parotid gland, and then at a bigher level under
cover of the posteriot belly of the Hitrastrie, the stylo-hyoid,
VOL. II — 20

3o6 HEAD AND NECK

the stylo-pharyngeus, and the styloid proeess, whieh separate
it from the postero-medial surface of the parotid gland. It
wlll be noted also that three neroes and two arteries eross the
vessel superficia]ly, viz. : —

The hypoglossal, as already noted, erosses it in the eaiotid
triangle ; the other nerves eross it under cover of the posterior

belly of the digastrie. The oeeipital arlery erosses it at the
level of the lower border of the posterior belly of the digastrie,
and the posterior aurieular at the level of its upper border.

The relationship of the external earotid artery to the
internal earotid is a varying one. At first the external
earotid hes antero-medial to it ; but soon, owing to its in-
elination posteriorly, it eomes to he direetly superficial to the
internal earotid. The fo]lowing struetures intervene between
the two vessels i — ■

1. Slyloid proeess. I 4. l'haiyngeal 1jranche$ of vagus

2. .Stylo-pharyngeus musele. ani) syuipnthetie.

3. Glosso-pharyngeal nfrve. | 5. A |)orlion of Ihe parolid gland.

Posterior to the internal earoiid is the longus eapitis (O.T.
reetus eapitis aniieus major) and the sympathetie trunle;
postero-laterally are the glosso-pharyngeal, the vagus, the
aeeessory and the hypoglossal netve ; and still more laterally

GREAT YESSELS AND NERVES 0F NECK 307

and posteriorly is the internal jugular vein. On its tnedial
asped the intemal earotid is related to the pharynx, the
aseending pharyngeal artery and the levator veli palatini.

Before leaving this vessel, note that near the base of the
skull four nerves appear in the interval between it and the
internal jugular vein ; these are the glosso-pharyngeal, the
vagus, the aeeessory, and the hypoglossal.

Vena lugularis Intema. — The internal jugular vein is the
largest venous ehannel of the neek. It enters the neek through
the postero-lateral eompartment of the jugular foramen, where
it is direetly eontinuous with the transverse sinus of the eranial
cavity. From the jugular foramen it proeeeds downwards,
until it reaehes the posterior aspeet of the medial end of
the clavicle, where it joins the subclavian vein to form the
innominate vein. Its eommeneement in the jugular foramen
shows a slight dilatation, termed the bulb^ the lumen of whieh
remains at all times patent owing to the eonneetion of its
walls to the margins of the foramen. The skull eap should
be removed and a probe should be passed from the trans-
verse sinus into the internal jugular vein, to demonstrate the
eontinuity of the two ehannels.

Reiations. — At its eommeneement the internal jugular
vein lies postero-lateral to the upper end of the cervical
part of the internal earotid artery, from whieh it is partially
separated by the last four eerebral nerves. As it deseends
it assumes a more direetly lateral relationship, first to the
internal and then to the eommon earotid, overlapping eaeh
vessel to a slight extent anteriorly ; and it is enelosed with them
and the vagus nerve in a eommon sheath of deep cervical
fascia, the nerve lying in its own eompartment of the sheath
between the arteries medially and the vein laterally, and in a
posterior plane.

The superficial or lateral relations of the vein in the upper
part of its extent are the styloid proeess, with the stylo-
pharyngeus and stylo-hyoid museles, and the posterior belly
of the digastrie, whieh separate it from the upper part of the
postero-medial surface of the parotid gland. In this part
of its extent it is erossed superficially, along the upper border
of the posterior belly of the digastrie, by the posterior
aurieular artery, and at the lower border of the digastrie
by the aeeessory nerve, passing downwards and posteriorly,
and by the oeeipital artery passing upwards and posteriorly

11—20 a

3o8

HEAD AND NECK

superficial to the nerve. At a slightly lower Ievel it js eon-
eealed by the lower part of the postero-medial surface of the
parotid, and il is erossed by the sterno-mastoid braneh of the
oeeipital artery. After it emerges frotn under cover of the
parotid, it lies under cover of the anterior border of the
sterno-mastoid, eseept in the region of the upper part of the
earotid triangle, where it may project anteriorly, beyond the
anterior border of the musele, for a short distanee. It is
separated from the sterno-mastoid by numerous deep cervical
lytnph glands ; and under cover of the rausele it is erossed
superlieially, at the level of the upper part of the thyreoid

eartilage, by the eommunieans cervicalis from the cervical
plesus, and, at the level of the erieoid eartilage, by the
intermediate tendon of the oino-hyoid, the sterno-mastoid
braneh of the superior thyreoid artery and the nerve to the
posterior belly of the omo-hyoid. Below the omo-hyoid it
is covered by the posterior border of the sterno-hyoid, and is
erossed by the anterior jugular vein ; and at its termination
it lies posterior to the sternal end of the clavicle.

Posteriorly, it is in relation with the reetus eapitis lateralis ;
the reetus eapilis anterior (O.T. andeus minor) ; and the loop
between the iirsl and seeond cervical nerves. At a lower
level its posterior relations are the Iransyerse proeesses of the
cervical vertebrffi and the museles attaehed to their anterior
tubereles, viz., the longus eapitis (O.T. reetus eapitis antieus

GREAT YESSELS AND NERVES 0F NEGK 309

major) and the sealenus anterior. Between its posterior
surface and the sealenus anterior are the aseending cervical
artery, the phrenie nerve, and, erossing superiieial to the latter,
the transyerse cervical and the transyerse seapular arteries.
On the left side the terminal part of the thoraeie duet also
erosses the phrenie nerve posterior to the internal jugular vein.
At the medial border of the sealenus anterior the thyreo-
cervical artery is posterior to it, and at a lower level, the
first part of the subclavian artery and the dome of the pleura.

The right vein is usually the larger of the two; and as
they approaeh the root of the neek both veins ineline slightly
to the right, with the result that, on the right side, the lower
part of the vein is separated from the eommon earotid artery
by a small triangular interval bounded below by the subclavian
artery, whilst on the left side the vein overlaps the anterior
aspeet of the eommon earotid artery.

Tributaries, — Immediately below its eommeneement the
internal jugular vein is joined by the inferior petrosal sinus,
and then, successively, by offsets from the pharyngeal plexus,
by the lingual vein, the eommon facial vein, the superior and
middle thyreoid veins. In some eases it is joined near its
upper end by a vena eomes whieh runs with the oeeipital
artery; and, oeeasionally, near its lower end, it receives the
lymph trunks whieh usually open into the eommeneement
of the innominate vein.

Disseetion. — Slit open the lower part of the vein and examine the valve
whieh lies elose to its extremity. It eonsists of two or three semilunar
flaps whieh prevent regurgitation of blood from the innominate vein into
the internal jugular.

Nervi Glosso-pharsrngeus, Yagus, Aeeessorius. — After
the removal of the brain these nerves were seen leaving
the eranial cavity through the middle eompartment of the
jugular foramen in the interval between the eommeneement
of the internal jugular vein postero-laterally and the inferior
petrosal sinus antero-medially (p. 215, and Fig. 125, p. 31 o).
The disseetor should again examine the interior of the eranial
cavity and refresh his memory as to the manner in whieh
they enter the foramen. The glosso-pharyngeal oeeupies
the most anterior position, and it is eut off from the others
by a separate tube-like sheath of dura mater. The aeeessory
is plaeed posterior to tlie vagus^ and both are ineluded
within the same sheath of dura mater. They therefore

11—20 1

31«

HEAD AND NECK

traverse the foramen in elose eontaet with eaeh other.
Reaehing the exterior of the skull, the three beeome
assoeiated with the hypoglossal nerve; and the four nerves
lie for a short distanee in the interval between the internal
jugular vein and the interiial earotid artery, but soon they
ehoose different routes. The lueessory inelines posteriorly,
superlieial or deep to the intemal jugular vein ; the glosso-
pharyngeal runs anteriorly, supertieial to the intemal earotid.

■etion through Ihe H&id a
II stiows Ihe posterior eranial fos£a and the upper part ot the vertebral
eanal afier the removal of the brain and the medulla spinalis,

and under cover of the posterior belly of the digastrie ; at
a lower level the hypoglossal turns anteriorly aeross the
external and internal earotld arteries ; and the vagus proeeeds
vertically downwards, lirst between the internal jagular vein
and the internal earolid, and then between the vein and the
eommon earotid (Fig. loo).

In &a ordinary disseetion it i<i imposslble 1o follow out many ai the
minule twigs whieh lake origin ftom these nerves in the region of the
basis eratiii. To do so it is neeessary lo possess a perfeclly fresh part
whieh has been speeially prepared by having ihe soft parts toughened with
spirit and Ihe bone softened by immersion in a wealt solution of aeid.

GREAT YESSELS AND NERYES 0F NEGK 311

Even then the disseetion is a difficult one, although it should eertainly be
undertaken by the advanced student, in the event of his being able to obtain
a part for the purpose.

In the following deseription of these nerves the aeeount
of the branehes whieh ean in all eases be traeed is printed in
ordinary type^ whilst that of those requiring speeial disseetion
is printed in small type,

Nennis Glosso-phaiTiigeus. — The glosso-pharyngeal nerve
inelines downwards and anteriorly and erosses the internal
earotid artery superiieially. At iirst it lies medial to the
styloid proeess and the stylo - pharyngeus musele, then it
hooks round the lower border of the musele and eunres
anteriorly upon its superlieial surface to gain the base of
the tongue. In the disseetion of the submaxillary region,
its terminal part was seen disappearing under cover of the
hyoglossus musele, where it ends in lingual branehes,

In the present disseetion the following branehes should be
made out : —

1. Communicating braneh from

the facial.

2. Nerve to the stylo-pharyngeus.

3. Pharyngeal.

4. Tonsillitie.

5. Lingual.

The eommunieating braneh from the facial springs from the nerve to
the posterior belly of the digastrie, and, as a rule, emerges from midst the
(ibres of that musele to join the glosso-pharyngeal elose to the lower part of
the jugular foramen.

The stylo-pharyngeal nerue is a small twig whieh enters the
musele of the same name. The greater part of its fibres,
however, are eontinued through the musele to the mueous
membrane of the pharynx.

Tht pharyngeal branehes eonsist — (i) of one or two small
twigs whieh perforate the superior eonstrietor to reaeh the
mueous membrane of the pharynx ; and (2) a larger nerve
whieh eomes off higher up and passes with the pharyngeal
braneh of the vagus to the pharyngeal plexus. It frequently
divides into two or more branehes.

The tonsillitie branehes proeeed from the glosso-pharyngeal
near the base of the tongue. They form a plexus over the
tonsil, termed the eireulus tonsiilaris, and give twigs to the
mueous membrane of the isthmus faucium and the soft
palate.

The terminal or lingual branehes will be followed in the
disseetion of the tongue.

11—20 c

313

HEAD AND NECK

Tbere are still olher points in eonneetion with the glosso-pl
nerve wbieh Tei|uiie tnenllon. A( the lowei part of the jugula[
two small gai^lia ore fornied upon its trunk, and froin the lower
eertain mlnute branehes are given off. The upper BMglior "" "
gaitglion supeHm ; the luwer one Is teimed the gtmgheit feriv.

The superior gangiioH \% a. small ganglionie swdlin^, wl
only a portion of the tibres of the nerve trunk. It 'k plaeed i
upper part of the bony gioove in whieh the nerve lies os il proeeeds ti
the jugular foramen. No branehes arise from it.

The petrmis ganglien is a larger swelling, whieh invoIves the e
nerve-trunk, and lies at the opening of the jugulai forlinen, betnee
vagus oerve and the inferior petrosal sinus (whieh in
and the anteiior Irarder of the foramen). Its length is
or three lines. Thiee hianehes of eommunieation entei oi pioeeed fiai
These eonneet It with — (i) the supeiior eerrieal sympathEtie ganglion
the auiieular bianeh of the vagus ; and (3) the jugulai gangLoo ol

In addilion to these twigs the lympanie ntme tak^ origin troia
petious ganglion.

T;nipuiie Nmw.— The ullimate destinalion of this
r^aided as the olie ganglion, but it takes a veiy dreuito'
thal strueture an<l it gives olTliranehes on the way, It enters s small ^oran
on the lidge whieh sepaiates the jugular fossa fiom the earotid foraiJ
on the lower surface of Ihe petious Irane, and it is eondueted by a
eanal to the tympanie cavity. It erosses the innei wall of this chantfl
giooving the piomontoiy. Having gained the anterior part of W
tympanum, it enteis the bone a seeond time, and runs in a mimite eal
whieh tunnels the petrous bone below the upper end or the ehanneS

whieh is lodged the tensoi tympani musele. In this pail of i'-

tympanie neive is ioined by a braneh fiom the ganglian genieuli
facial neive, and, anei the junciion is eileeted, it is teimed the s/'ial
Jicial ptlrosal iierue.

The eanal in whieh the nnall !uperjkial petrosal Berve is lodged c
into the eranial cavity upon the anleiior surface of the petious 1:
immediately lateial to the hiatus eanalis faciatis (O.T. Pallopii). Thr
this the neive emerges, and soon Ieaves the interior of the eranium 1
passing downwards in the inleryal between the gieat wing of the sphenoB
and tlie petious nart oi the lemporal bone, 01 Ihtough Ihe esnalieul^
innuininatus, oi thiou^h Ihi' forameo ovaIe. Outside the aku
joimng the olie ganglion.

In Ihe tympanie cavity Ihe lynipanie nenie giveE biandies of tiipM
— (I) to Ihe mueous membiane of the tymponum j {2) to the litud
memlHane of the mastuid eells ; and (3) to the mueous membtane nt lh|
audiloiy tube (Kustaehian). It is eonneeled with the sympathetie plw

n the mternal enrotid arteiy by the sttperii

bramhe

ind inferi

:e ihe siibslanee of Ihe petrous parl ot the ti

NsiTUA Vagus. — The vagus passes through the niid<
eonipartment of the jugu]ar foramen in eompany with the I
aeeessory — both being induded within the same shealh of \
dura mater. In the neek it pursues a vurtica! eourse,
lying, at lirst, between the internal jugular vein and the
internal earotid arlery, and afterwards between the same '

^msS!^

■ ^

CLES

artery. It arises I

proeesses of the tl

K, and, tapering si

the sealene tubi

and also into

n ihe two subela

rib,

facg is eoneeakd by

• the clavicle,
king its medial boi
ihe intemal juf
o-hyoid ; ihe phi
illy ; and the trans^
rteries passing pos!
ierve. Belween it

above, with the tip
ind below, with
f the subclavian arl
t/era! boriir touehes
he medial border is
ry, its inferior thyn

raore powe
ngs from the poste
; proeesses (with
iiid it is inserted i
the upper surfact
he rib and the gro

iterior triangle of

lation with the brae

Hibelayian artery.

pulie ; aod the dc

ineh ot the transv

musele. The k

Itioo with the ape

()f ihe li)ng thoi

|:k.

; sealenus posterit

; sealenus me

Iprings by two or l

HEAD AND NECK

of the eranium. Stroi^ bran'

between it and the first
and the superior eendoal gan
r'urther, the bypoglossal ncrve
to it by fibrous attaehment,
erehange of nerve filaments takes d
it Distribntion of tlie Oeirieal ]
branehes whieh spring from the
neek are the foliowing: (i)
aryngeal; {3) reeurrent; (4) cardia3
hairngenB. — The pharyngeal branl
pper part of the ganglion nodosumB
and anteriorly, superheial to tiie interB
;nd in the pharyngtal plextii, It
two branehes, of whieh the upper ii
Laryneeus Snpeiior. — This, a niueh largH
. the middle of the ganglion nodosum.
s and anteriorly, but differs rrom the
passing deep to the intemal eari
tion it ends by dividing into the tn/emaim
rnal laryngeal nerves ; both of these '.
ly seen in the disseetion of the anteriorl

it divide5, Ihe supetior laryngeat eATtets eos
fine twigs with the superiot cervical ganglion of the s>
) receives one ot two rilaments from the phaiyiigeal pleJ

intemal laryngeal nerve runs to the interyal t
»id bone and the thyreoid eartilage ; therJ
iring under cover of the posterior border 1
hyoid musele, it pierees the membrane of thl
uid enters the pharynx, and then deseends W

exkmal laryngeal nenie is a very slender braneh.l
downwards and anteriorly to reaeh the erieo-tl
in whieh it ends.

ng braneh from the superior cervical gangB

na BeeniTe&s. — The reeurrent nerve arisea
1 the two sides. On the right sidt, after spri

HEAD AND NECK

:ion, and one or more mirute

1 eonneetion with it. Its termina! twigs are

;]es and mueous membrane of the pharynx,

(the ramits lingualis vagi) eoniieets the pl_
■poglossal nerve.
HypoglossaB. — The hyp<^lossal nerve makes 1
the eranium through the eanalis hypoglJ
;rior eondyloid foramen). It pierees the dura ti
jaraCe parts, whieh unite into one s
my eanal, As it issues from the eanai it lies dee
3 the internal iugular vein and the internal ca
immediately afterwards it inelines laterally,
. half spiral turn around the ganglion nodosuni of t;
t appears between the two vessels, and deseends betwel
o the lower border of the posterior belly of the d
j, where it passes into the earotid triangle. Its cl<4
etion with the ganglion nodosum of ihe yagus 1
noted already (p. 314). In the earotid triangle it hQo|
1 the lower end of the oeeipital artery, telo^
oid braneh, and, turning anteriorly, it ereiisses the oeeipita
nternal and external earotid arteries and the loop of t"
ual artery superlieially. Then it passes on ihe med
:s of the posterior belly of the digastrie and the slylo-hyoi^
l enters the digastrie triangle, where it disappears medial
be mylo-hyoid, and at the anterior border of the hyoglossuM
nters the base of the tongue.

iramheso/eommunkaliiHi.—'Sei.iKhe baaeoT fhe skul! Ihehype^los
■oughl inlo eonneetioo wilh— (l) Ihe superior cervi(.-a1 ganglion ; (a) tl .
is ; and (3) the firEt eenrieal nerve ; as it lurns loHnd the ociijMtBL
ry it receives {4) the ramus Uiigualis vagi from Ihe pharyngeal pleitusa
on the surface oi the hyoglossus it eommunieate'i witli (5) the linr"'"™
-e (|). 290).

Branekes of Dislribution. — (i) The meningeal braneh a
he upper part of the eanalis hypoglossi, and, regaining E
;rior of the eranium, it is distributed to the dura 1
und the foramen magnum. (2) Yasmlar twigs are sajtd t
supplied to the deep aspeet of the intemal jugular x
The deseetidens kypoglosst, whieh conveys fibres of I
t cervical ncrve to the infra-hyoid museles. (4) Tti«fr
'Ae thyreo-hyoid, whieh also eonsists of first cervical E
es. (5) The terminal branehes, whieh ^'inuly the |
lid and ail the intrinsie and extrinsic m
ept the palato-glosstis.

3i8 HEAD AND NECK

Nerms Caroticus Internus, — This braneh has been noted
passing from the upper end of the ganglion into the earotid
eanal. Its distribution will be eonsidered later.

Nervi Garotiei Extemi, — Two to six iilaments, ealled
external earotid branehes, run to the external earotid artery,
and form a loose interlaeement around it and its branehes.
From this extemal earotid plexus b, braneh is given to the
earotid body, and prolongations are eontinued on all the
branehes of the artery. The part eontinued upon the extemal
maxillary artery supplies the sympathetie root to the sub-
maxillary ganglion, whilst the subdivision upon the middle
meningeal artery furnishes the eorresponding root to the otie
ganglion, as well as the external superficial petrosal nerve whieh
runs to the ganglion genieuli of the facial nerve.

Rami Laryngo-pharyngei, — The laryngo-pharyngeal branehes
pass between the two earotid arteries to join the phar^oigeal
plexus, and some join the superior laryngeal nerve.

Neruus Gardiaeus Superior, — This is a long slender braneh
whieh springs by several roots from the ganglion, and then
proeeeds downwards, posterior to the earotid artery. At
different stages of its eourse it is joined by other branehes of
the sympathetie, by a braneh from the vagus, and also by
Alaments from the external laryngeal and reeurrent nerves.
The right superior eardiae nerue is eontinued into the thorax
by passing posterior or anterior to the subclavian artery, and it
ends in the deep eardiae plexus. The lefi superior eardiae neroe
follows the left eommon earotid artery in the thorax, and,
erossing the left side of the areh of the aorta, ends in the
superficial eardiae plexus.

Ganglion Cervicale Medium. — This ganglion is the
smallest of the three ganglia of the neek. It is plaeed
opposite the sixth cervical vertebra in elose proximity to
the inferior thyreoid artery, upon whieh it not infrequently
rests. Its branehes are: {^i) grey rami eommunieantes^ ^ibieh
pass between the eontiguous margins of the sealenus anterior
and longus eolli museles and eonneet it with the fifth and
sixth cervical nerues ; (2) thyreoid branehes, whieh run to the
thyreoid gland, along the inferior thyreoid artery, and form
eonneetions with the external laryngeal and reeurrent nerves ;
(3) the middle eardiae nerve.

On both sides the middle eardiae nerue enters the thorax
and is lost in the deep eardiae plexus. On the right side

THYREOII) (;LANI) ^ir;

it passes posterior or anterior to tho sul>claviari ariery ; (m
the /e// side it is eontinued downwards !)etwccn tlie r «iiiiinon
earotid and subclavian arteries.

Gkmglion Gervicale Iiiferiiis. — The infcri(}r(;crvir.i] ^'an^Mion
is lodged in the interval between the transvcrsc \i\uiK^^. of th»;
seyenth cervical vertebra and the neek of the Tirst rib. In thi^
position it lies posterior to the vcrtcbral ariery. It ii by u*,
means uneommon to find it more or less i:u\\.\i\*:\*-\\ fi] ■*■'],
over the neek of the first rib, with the fii:»t thora' i'. '^\\u'^\v,u.
The eonneetion between it and the middle fcrvi';i] \l;a\.'^\.'.u \.
generally in the form of two or more >lcr:d'-r u*:x\k 'sr«! . *,{
whieh one passes anterior to the sulx:lavian ,kn*:\'y 'W.*-.
latter loops round the subclavian nrlery nr.d i-! N.r:;*/! th'-
ansa subclavia (Yieussenii).

The branehes of the infcrior ccrvira! i:ari''i:^r: .ir';

1. (}rey rami eommunieantes to ihe :»cV'.Ti'ri a:.': • -,;:.":. ' ■ : : .-

2. Kami vasculares.

3. Inferior eardiae nerve.

The rami vasctilares are fmc brai 1 '. h •: -. -a ;. ; ^ : , \',:\\. :i ;,]''.,
around the subclavian artery and its fyr'j.'y ;.■ .. '].'...•:
around the vertebral artery are rerriari-ia'.!'; :'or i;,»:;r .;';;' ../• .

The neruus eardiaeus in/erior on b-^^ \\i -.y:-: . • ; r , r ♦: r . ' : . * : ':-';/
eardiae plexus.

After the vcssels and ner\es of •.,-,•: :.-:'.'/. :.-i.;*: -,':*■:. .*.#:.*':
ihe disseetors should exani:,''jj *.:.■: *.:,}. -.'.;': ;;..;,';,

Glandula Thyreoidea. — Th-: tr.yr':'.;c ;.:;:.': i. o :..'/:..,
vascular solid body, whieh elas;.-. \:.': ;.;.; *:r \/^r. 'A ?;,#;
traehea-and extends upv.ard-. for ':;^r/i'; «'ii'/a. '.'.'; ■.]/,:. *::it\.
side of the larynx. It vari'js greatiy :n ■.iz'; ;.'. (i'Ai».:'::/. m
dividuals ; and in femaIo-s and (,r.:yirf:u it ;•, aiv.a)'; r';iat;v':i)
larger than in adult nr-ale?;. I*. ^/jr.\'. .*.. 'A \:.T*:t: '*•«;;! ;/.ark':d
subdinsions, viz., two latei-a! io'^e-h '//.:. f:*\ a^r/.h th'; u.t.rA^itt
plane by the isthmus. Ea'.r. lattral loU ':\ •■,orr.';v.;ja*. ^.oni^al
in form ; its base lies at '.he i';v-:i ^A \:.*: fifth or iu*: f>jxtli
traeheal ring, whibt its a:y:.x T'sW'i ii'ti/^lr/.i tfiC bide ^^ the
thyreoid eartilage. Its lupir/idal or lateral mr/au is fuU ai
rounded. and is elothed r^y the \trf:\rdJAi*:'d\. biy4:r t
fascia, from whieh it derive.s a hTA^sairt ; and it is c
sterno-th)Teoid, stemo-hyoid, and orr. r>-hyoid mu
the anterior border of the sterno-mastoid (f ij
Its deep cr medial sur/aet is adapted to the 9

HEAn AND NF.CK

lies, viz., to ihe side of the traehea, the erieoid eartilage,
and the thyreoid eartilage. Its postertor bttrder is in telation
' with the lateral margins of the eesophagus and the lateral

^^K margin or the pharj-nx, and in many eases it overlaps the
^^V eommon earotid artery. Its anterior border is eonneeted with

V* My

ispondiiig border of the opposite lateral lobe by the
isthmus. Above the isthmus it is in relation with the anterior
termiaal braneh of the superior thyreoid artery, and below the
isthmus with the eommeneement of the inferior thyreoid vein.
The isthmui of the thyreoid glaiid has already been seen
in the disseetion of the middle line of the neek. It is a
'i band of varying width whieb lies anterior to the seeond, third,

TRAGHEA AND CESOPHAGUS 321

and fourth rings of the traehea, and, therefore, nearer the
lower than the upper ends of the two lateral lobes.

An additional lobe, the pyramidal or middle lobe^ is
frequently present. It is an elongated slender proeess whieh
springs from the isthmus, on one or other side of the median
plane (more usually on the left side), and extends upwards
towards the hyoid bone. To this it may be eonneeted by
fibrous tissue, or by a narrow slip of museular fibres ealled
the levator glandulee thyreoideee, In some eases this little
musele has an attaehment to the thyreoid gland independ-
ently of the pyramidal proeess. The thyreoid gland is firmly
eonneeted to the parts upon whieh it lies, and therefore
follows the larynx in all its movements.

The disseetor should note the great vascularity of the thyreoid gland.
Four large arteries, and oeeasionally a fifth smaller vessel, convey blood to
its substanee. The two superior thyreoid branehes of the external earotid
arteries divide at the apex of eaeh lateral lobe into three branehes for its
supply ; the two inferior thyreoid branehes^ from the thyreo-cervical trunks
of the subclavian arteries, distribute their terminal branehes to the basal
portion and deep surface of eaeh lateral lobe. The oeeasional artery is
the thyreoidea ima^ a braneh of the innominate or, more rarely, of the
eommon earotid or the aortie areh. It aseends upon the anterior aspeet
of the traehea to reaeh the isthmus of the thyreoid gland. These thyreoid
arteries anastomose with eaeh other.

The veins whieh drain the blood away from the thyreoid gland are still
more numerous. They arise in part by tributaries whieh spring from a
venous network on the anterior face of the strueture, but chiefly by branehes
whieh emerge from its substanee. They are three in number on eaeh side
— viz. the superior thyreoid, the middle thyreoid, and the inferior thyreoid.
The superior and middle t hyr,eo i d veins eross the eommon earotid artery and
join the internal jugular ; the inferior thy^-eeid vein deseends on the traehea.
At the root of the neek it usually joins its fellow of the opposite side to
form a eommon stem whieh opens into the left innominale.

Traehea and (Esophagus. — The windpipe and the gullet
in the cervical portion of their eourse may now be studied.
Both begin at the level of the erieoid eartilage, anterior to
the sixth cervical vertebra. From this point they extcnd
downwards, anterior to the vertebral eolumn, to the thoraeie
cavity.

The traehea, or windpipe^ is a wide tube whieh is kept
eonstantly patent by the eartilaginous rings embedded in its
walls. These rings do not form eomplete eireles ; posteriorly
they are deficient, and, in consequence, the posterior surface
of the traehea is Aattened. Above, it is eontinuous with the
larynx, and, throughout its eourse in the neek, it is plaeed in
the median plane of the body. The anterior relations of the

voL. II — 21

HEAD AND NECK

tiaetiea have already been rully diseussed in eonneetioii with
the deseription of the parts oeeupying the middle line of the 1
neek {]). aig). Posteriorly, it rests upon the guUet. Upor
«V(fer«flfe is tlieeommon earotid artery; whilst elosely applied '
to it in its upper part is the lateral lobe of the thyreoid
gland. The reeurrent nerve aseends, on eaeb side, in the i
angle between the traehea and eesophagus.

IThe eesophagus or gulkt is a narrow tube, with thiek
, museular walls, whieh extends frora the pharynx to the
stomaeh. In the cervica! part of its eourse it lies between the
\ traehea and the longus eolli rausdes, and as il deseends

' Vsgu

it inelines, shghtly to the left, so that t eomes n ore elosely -I
into relation with the lat ra! obe of the h) eo d gland and I
the earotid sheath upon the left s de tban w th the same J
struetures on the oppos te s de

The disseetor n ay erm a e h s d sseet on of the neek byl
an examination of the sealene n useles and the reetus eap tts'l
lateralis.

Museuli Sealeoi. — These museles eonstitute the Aeshy mass I
whieh is seen extending from tbe transvcrse proeesses of the I
cervical vertebr3e to the upper two eostal arebes. They are I
three in number, and are named, from tbeir relative positions, f
anterior, ttttdius, aad postrrior.

Afusculus Sealettus Anlerior. — ^Tbis is a well-defined musclej
whieh is separaled from ihe sealenus medius by the rool

SGALENE MUSGLES 323

the braehial plexus and the subclavian artery. It arises froin
the anterior tubereles of the transverse proeesses of the third,
fourth, fifth, and sixth cervical vertebrae, and, tapering some-
what as it deseends, it is inserted into the sealene tuberele
on the inner margin of the first rib, and also into the
superior surface of the same bone between the two subclavian
grooves.

The upper part of its anterior surface is eoneealed by the
sterno-mastoid and the lower part by the clavicle. The
eommon earotid artery deseends along its medial border.
Between it and the sterno-mastoid lie the internal jugular
vein ; the intermediate tendon of the omo-hyoid ; the phrenie
nerve, passing downwards and medially; and the transverse
cervical and transverse seapular arteries passing postero-
laterally, superficial to the phrenie nerve. Between it and
the clavicle lies the subclavian vein.

Its posterior surface is in relation, above, with the tips of
the lower cervical transverse proeesses, and below, with the
apex of the pleura, the seeond part of the subclavian artery,
and its costo-cervical braneh. The lateral border touehes the
roots of the braehial plexus, and the tnedial border is in
relation with the thyreo-cervical artery, its inferior thyreoid
braneh, and with the vertebral artery.

Museulus Sealenus Medius, — This is a more powerful
musele than the preeeding. It springs from the posterior
tubereles of all the cervical transverse proeesses (with the
exception, in some eases, of the first), and it is inserted into
a rough oval impression whieh marks the upper surface of
the first rib between the tuberele of the rib and the groove
for the subclavian artery.

It forms part of the floor of the posterior triangle of the
neek. Its superficial surface is in relation with the braehial
plexus and the third part of the subclavian artery. Its
posterior border touehes the levator seapulse ; and the dorsal
seapular nerve and the deseending braneh of the transverse
cervical artery pass between it and that musele. The lower
part of its anterior border is in relation with the apex of
the pleura, and the upper two roots of the long thoraeie
nerve pieree the substanee of the musele.

Museulus Sealenus Posterior. — The sealenus posterior is
generally inseparable, at its origin, from the sealenus medius.
It is the smallest of the three, and springs by two or three

II— 21«

3i8 HEAD AND NECK

Nerms Caroticus Iniernus, — This braneh has been noted
passing from the upper end of the ganglion into the earotid
eanal. Its distribution will be eonsidered later.

Nervi Carotici Extemi. — Two to six filaments, ealled
external earotid branehes, run to the external earotid artery,
and form a loose interlaeement around it and its branehes.
From this extemal earotid plexus a braneh is given to the
earotid body, and prolongations are eontinued on all the
branehes of the artery. The part eontinued upon the external
maxillary artery supplies the sympathetie root to the sub-
maxillary ganglion, whilst the subdivision upon the middle
meningeal artery furnishes the eorresponding root to the otie
ganglion, as well as the external superficial petrosal nerue whieh
runs to the ganglion genieuli of the facial nerve.

Rami Laryngo-pharyngeL — The laryngo-pharyngeal branehes
pass between the two earotid arteries to join the pharyngeal
plexus, and some join the superior laryngeal nerve.

Nerous Cardiacus Superior — This is a long slender braneh
whieh springs by several roots from the ganglion, and then
proeeeds downwards, posterior to the earotid artery. At
different stages of its eourse it is joined by other branehes of
the sympathetie, by a braneh from the vagus, and also by
filaments from the external laryngeal and reeurrent nerves.
The right superior eardiae nerue is eontinued into the thorax
by passing posterior or anterior to the subclavian artery, and it
ends in the deep eardiae plexus. The lefi superior eardiae neroe
follows the left eommon earotid artery in the thorax, and,
erossing the left side of the areh of the aorta, ends in the
superficial eardiae plexus.

Ganglion Cervicale Medium. — This ganglion is the
smallest of the three ganglia of the neek. It is plaeed
opposite the sixth cervical vertebra in elose proximity to
the inferior thyreoid artery, upon whieh it not infrequently
rests. Its branehes are: {i) grey rami eommunieantes, whieh
pass between the eontiguous margins of the sealenus anterior
and longus eolli museles and eonneet it with the fifth and
sixth eeruieal nerues \ (2) thyreoid branehes^ whieh run to the
thyreoid gland, along the inferior thyreoid artery, and form
eonneetions with the external laryngeal and reeurrent nerves ;
(3) the middle eardiae nerve.

On both sides the middle eardiae nerue enters the thorax
and is lost in the deep eardiae plexus. On the right side

312 HEAD AND NECK

There are still other points in eonneetion with the glosso-pharyngeal
nerve whieh require mention. At the lower part of the jugular foramen
two small ganglia are formed upon its trunk, and from the lower of these
eertain minute branehes are given off. The upper ganglion is ealled the
ganglion superius ; the lower one is termed the ganglion petrosum,

The superior gangiion is a small ganglionie swelling, whieh involves
only a portion of the fibres of the nerve trunk. It is plaeed in the
upper part of the bony groove in whieh the nerve lies as it proeeeds through
the jugular foramen. No branehes arise from it.

The petrous ganglion is a larger swelling, whieh involves the entire
nerve-trunk, and lies at the opening of the jugular foramen, between the
vagus nerve and the inferior petrosal sinus (whieh intervenes between it
and the anterior border of the foramen). Its length is not more than two
or three lines. Three branehes of eommunieation enter or proeeed from it.
These eonneet it with — (i) the superior cervical sympathetie ganglion ; (2)
the aurieular braneh of the vagus ; and (3) the jugular ganglion of the
vagus.

In addition to these twigs the tympanie nerue takes origin from the
petrous ganglion.

Tympanie Nerye. — The ultimate destination of this nerve may be
regarded as the otie ganglion, but it takes a very eireuitous route to gain
that strueture and it gives off branehes on the way. It enters a small foramen
on the ridge whieh separates the jugular fossa from the earotid foramen
on the lower surface of the petrous bone, and it is eondueted by a narrow
eanal to the tympanie cavity. It erosses the inner wall of this ehamber,
grooving the promontory. Having gained the anterior part of the
tympanum, it enters the bone a seeond time, and runs in a minute eanal,
whieh tunnels the petrous bone below the upper end of the ehannel in
whieh is lodged the tensor tympani musele. In this part of its eourse the
tympanie nerve is joined by a braneh from the ganglion genieuli of the
facial nerve, and, after the junction is effected, it is termed the small super-
ficial petrosal nerue.

The eanal in whieh the small superficial petrosal nerue is lodged opens
into the eranial cavity upon the anterior surface of the petrous bone,
immediately lateral to the hiatus eanalis facialis (O.T. Fallopii). Through
this the nerve emerges, and soon leaves the interior of the eranium by
passing downwards in the interval between the great wing of the sphenoid
and the petrous part of the temporal bone, or through the eanalieulus
innominatus, or through the foramen ovale. Outside the skull it ends by
joining the otie ganglion.

In the tympanie cavity the tympanie nerve gives branehes of supply
— (i) to the mueous membrane of the tympanum ; (2) to the lining
membrane of the mastoid eells ; and (3) to the mueous membrane of the
auditory tube (Eustaehian). It is eonneeted with the sympathetie plexus
on the internal earotid artery by the superior and inferior earotieo-tympanie
branehes whieh pieree the substanee of the petrous part of the temporal
bone.

Nennis Vagus. — The vagus passes through the middle
eompartment of the jugular foramen in eompany with the
aeeessory — both being ineluded within the same sheath of
dura mater. In the neek it pursues a vertical eourse,
lying, at first, between the internal jugular vein and the
internal earotid artery, and afterwards between the same

GREAT YESSELS AND NERYES 0F NECK 313

vein and the eommon earotid artery, enelosed within the
sheath whieh envelops the vessels, but on a plane posterior
to them. Its posterior relations, therefore, are similar to
those of the internal and eommon earotid arteries. At the
root of the neek it enters the thorax, and has different
relations on the two sides. On the right side it erosses
the first part of the subclavian artery ; on the left side^ after
erossing anterior to the thoraeie duet, it proeeeds downwards
between the eommon earotid and left subclavian arteries,
posterior to the left innominate vein. For its thoraeie
relations see p. 99.

The vagus, like the glosso-pharyngeal, has two ganglia in
eonneetion with its upper part. These are the ganglion
jugulare and the ganglion nodosum,

Ganglion Jugulaxe (O.T. Ganglion of Root).— This is situated within the
jugular foramen. It is a rounded swelling whieh is eonneeted by eom-
munieating twigs with several of the nerves in the neighbourhood, and
it gives off two branehes of distribution.

Branehes of Communication. — (i) With the facial nerve ; (2) withthe
petrous ganglion of the glosso-pharyngeal ; (3) with the aeeessory ; (4) with
the superior ganglion of the sympathetie.

Branehes of Distribution. — (i) Meningeal ; (2) Aurieular nerve.

The meningeal braneh is a minute twig whieh runs upwards through
the jugular foramen, and, dividing into two branehes, is distributed to
the dura mater in the posterior eranial fossa.

The aurieular nerue (O.T. Arnold's nerve) obtains a filament of eom-
munieation from the petrous ganglion of the glosso-pharyngeal, and passes
posteriorly upon the lateral surface of the bulb of the internal jugular vein
to enter a minute aperture on the posterior part of the lateral wall of the
jugular fossa. A narrow eanal then eonduets it through the substanee
of the temporal bone, and, on its way, it erosses the eanalis facialis a
short distanee above the stylo-mastoid foramen. It is thus brought into
elose relation with the facial nerve and is eonneeted with it by an
aseending and a deseending braneh of eommunieation. Finally, it appears
on the surface of the skull, in the interval between the mastoid proeess and
the external aeustie meatus, where it eommunieates with the posterior
aurieular braneh of the facial. It supplies the skin on the posterior aspeet
of the outer surface of the walls of the meatus, the skin covering the lower
half of the inner surface of the wall of the meatus, and the lower half of
the tympanie membrane.

Ganglion Nodosum. — After emerging from the jugular
foramen, the vagus nerve is joined by the eerebral portion of
the aeeessory nerve^ and swells out into the ganglion nodosum
(O.T. ganglion of trunk).

The ganglion nodosum is an elongated reddish-eoloured
swelling of about three-quarters of an ineh in length, whieh
is developed upon the stem of the vagus half an ineh

322 HEAD AND NECK

traehea have already beeti fully diseussed in eonneetion with
the deseriplion of the parts oeeupying the middle line of the
neek (p. 229). Posteriorly, it rests upon the gullet Upon
eiiher side is the eommon earotid artery ; whilst elosely applied
to it in its upper part is the lateral lobe of the thyreoid
gland. The reeurrent iierve aseends, on eaeh side, in the
angle between the traehea and eesophagus.

The «sophagus or gullet is a narrow tube, with thiek
museular walls, whieh extends Trom the pharynx to the
stomaeh. In the cervical part of its eourse it lies between the
traehea and the longus eoUi museles, and as it deseends

it inelines slightly to the left, so that it eomes more dosely
into relation wiih the lateral lobe of the thyreoid gland and
the earotid sheath upon the left side than with the same
struetures on the opposite side.

The disseetor may terminate his disseetion of the neek by
an examination of the sealene museles, and the reetus eapitis
lateralis.

Museuli Sealeni,— -These museles eonstitute the Aeshy mass
whieh is seen extending from the transverse proeesses of the
eeryieal vertebrK to the upper two eostal arehes. They are
three in number, and are named, from their relaliye positions,
anterior, medius, 2.nA posierior.

Miiseulus Sealenus Anterior. — This is a well-delined musele
whieh is separated from the sealenus medius by the roots of

SGALENE MUSGLES 3« 3

the braehial plexus and the subclavian artery. It arises frotn
the anterior tubereles of the transverse proeesses of the third,
fourth, fifth, and sixth eenrieal yertebrse, and, tapering some-
what as it deseends, it is inserted into the sealene tuberele
on the inner margin of the first rib, and also into the
superior surface of the same bone between the two subclavian
grooyes.

The upper part of its anterior surface is eoneealed by the
sterno-mastoid and the lower part by the clavicle. The
eommon earotid artery deseends along its medial border.
Between it and the stemo-mastoid lie the intemal jugular
vein ; the intermediate tendon of the omo-hyoid ; the phrenie
nerve, passing downwards and medially; and the transverse
cervical and transverse seapular arteries passing postero-
laterally, superficial to the phrenie nerve. Between it and
the clavicle lies the subclavian vein.

Its posterior surface is in relation, above, with the tips of
the lower cervical transverse proeesses, and below, with the
apex of the pleura, the seeond part of the subclavian artery,
and its costo-cervical braneh. The lateral border touehes the
roots of the braehial plexus, and the medial border is in
relation with the thyreo-cervical artery, its inferior thyreoid
braneh, and with the vertebral artery.

Museulus Sealenus Posterior, — The sealenus posterior is
generally inseparable, at its origin, from the sealenus medius.
It is the smallest of the three, and springs by two or three

11—21 a

3»4

HEAD AND NECK

slips from the transverse proeesses of a eorresponding number
of the lower cervical vertebr£e in eommon with the sealenus
medtus. It is inserted into the upper border of the seeond
rib, immediately anterior to the insertion of the levator
eostse.

The sealene museles are supplied by twigs from the
anierior branehes of tht cervical nerves, partiatlarly the lower

Dhseelion.—Tbs liltle muEele termed (he reelus eapilis lateralis should
now be eieaned, and its attadiments detined. It lies in the inlerral
between the transverse proeess of the alks and Iheiueular proeess of the
oeeipital bone, posterior lo Ihe eommeneement of the inlernal jugular
veiD. Tbe anterior braneh of the (irsl eenrieal nerve wiU t>e seeo emerging
from under cover of its medial mai^in.

LATERAL PART OF MIDDLE GRANIAL EOSSA 325

Beetns Oapitis Lateralis. — ^The reetus lateralis arises from .
the anterior part of the upper surface of the extremity of the
transverse proeess of the atlas, and is inserted into the under
surface of the jugular proeess of the oeeipital bone. It is
supplied by a twig from the anterior braneh of the first
cervical nerve.

BemoTal of the Head and Neek from the Tnmk.— By the time that
the disseetors of the head and neek have arrived at this stage of their work,
the disseetors of the thorax have in all probability finished their disseetion.
If this is the ease, the head and neek may be removed from the tnink by
eutting through the vertebral eolumn at the level of the intervertebral fibro-
eartilage between the third and fourth thoraeie vertebrae. By this pro-
eeeding the upper three thoraeie ^erte'brse, with the attaehed portions of the
first, seeond, and third pairs of ribs, are removed with the neek. The
sealene museles and the longus eoUi are therefore preserved intaet.

THE LATERAL PART 0F THE MIDDLE

GRANIAL FOSSA.

The struetures eontained within the middle eranial fossa
may now be examined. In earrying out this disseetioii, the
head should be supported on a bloek so that the floor of
the eranial cavity looks upwards. The following are the
struetures whieh must be displayed : —

1. Cavernous venous sinus.

2. Internal earotid artery.

3. Middle meningeal artery.

4. Aeeessory meningeal artery.

5. The two roots of the Trigeminal nerve, with the Semilunar

ganglion and the three main divisions of the trigeminal
nerve.

6. Oeulo-motor nerve (3rd eerebral). . .

7. Troehlear nerve (^th eerebral).

8. Abdueent nerve (6th eerebral).

9. Internal earotid plexus of the sympathetie.

10. Greater superficial petrosal nerve.

11. Smaller superficial petrosal nerve.

Disseetion. — ^The dura mater has already been removed from one half of
the middle eranial fossa, and on that side it is only neeessary to differentiate
the stnietures whieh lie in the cavemous sinus ; on the other side the dura
mater must be stripped from the medial part of the lateral portion of the
middle eranial fossa. Enter the knife at the anterior elinoid proeess, and
earry it posteriorly to the apex of the petrous bone. This ineision must go
no deeper than is neeessary to divide the dura mater, and must be made
immediately to the lateral side of the openings in the membrane through
whieh the oeulo-motor, the troehlear, and tngeminal nenres pass.* It is

6 HEAD AND NECK

f important to preserve these apertures inlaet, so ttia.t the prenumal
5 of the nerve9 may be held in position duiing the disseetion. The
n thiDUgh the daea. matei may now be earried postero-Iaterally along

the upper border of the petrous bone ii

the li

if ihe supeiioi petrosal

sr with great

eare, for it is intimately eonneeted with the netve» whieh lie subiaeent to
it. Tbus, where il forms the latera! watl of the cava^oiis sinus, it
is elosely applied to the oeulo-motor and tioehlear nerves, and tirmly
attaehed to tbe ophthalmie division of Ihe tiigeminal nerve, whilst over
the petrous bone it is united to the surface of tbe semilunai gajiglion.
The edge of tbe knire, theTefole, musl be kept elose to the membrane, and
> small portion of the membrane may be left upon ihe neryes. This ean
be removed afterwa.rds as Ihe neryes are delined.

Sinns CavenioBtt8. — The cavernous sinus has been opened

by the above disseetion. It is a short, wlde venous ehannel,
whieh extends along the side of the body of the sphenoid bone,
from the lower and medial end or the superior orbital Sssure
(O.T, sphenoidal lissure} to the apex of the petrous pbrtion
of the temporal bone. Anteriorly, blood is eondueted into it
by the ophthalmie veins and the spheno-parietal sinus ; whilst
posteriorly the blood is drained away by the superior and
inferior petrosal sinuses. But it has still other eonneetions.
Thus, it receives blood from the lower part of the lateral
surface of the brain by the superficial middle eerebral vein
and some small inferior eerebral veins. It is united with
the eorresponding sinus of the opposite side by means of the
anterior and posierior intercavernous sinuses (p. 2 1 7). Lastly,
one or more emissary veins Ieave its lower aspeet ; one passes
out of the eranium by the foramen ovale, or it may be

SGALENE MUSGLES 323

the braehial plexus and the subclavian artery. It arises froin
the anterior tubereles of the transverse proeesses of the third,
fourth, fifch, and sixth cervical yertebrie, and, tapering some-
what as it deseends, it is inserted into the sealene tuberde
on the inner margin of the first rib, and also into the
superior surtaee of the same bone between the two subclavian
grooves.

The upper part of its anterior sur/aee is eoneealed by the
stemo-mastoid and the lower part by the elayiele. The
eommon earotid artery deseends along its medial border.
Between it and the stemo-raastoid lie the internal jugu!ar
vein ; the intermediate tendon of the omo-hyoid ; the phrenie
nerve, passing downwards and medially; and the transverse
cervical and transverse seapular arteries passing postero-
laterally, superficial to the phrenie nerve. Between it and
the clavicle lies the subclavian vein.

Its posterior sur/aee is in relation, above, with the tips of
the lower cervical transverse proeesses, and below, with the
apen of the pleura, the seeond part of the subckvian artery,
and its costo-cervical braneh. The lateral border touehes the
roots of the braehial plexus, and the medial border is in
relation with the thyreo-cervical artery, its inferior thyreoid
braneh, and with the vertebral artery.

Museulus Sealenus Medii/s.—Tius is a inore power^nl
musele than the preeedlng. It springs from the posterior
tubereles of all the cervical transyerse proeesses (with the
exception, in some eases, of the first), and it is inserted into
a rough oval impression whieh marks the upper surface of
the first rib between the tuberele of the rib and the groove
for the subclavian artery.

It forms part of the floor of the posterior triangle of the
neek. Its superficial surface is in relation with the braehial
plexus and the third part of the subclavian artery. Its
posterior border touehes the !evator seapulas ; and the dorsal
seapular nerve and the deseending braneh of the transverse
cervical artery pass between it and that musele. The lower
part of its anterior border is in relation with the apex of
the pleura, and the upper two roots of the !ong thoraeie
nerve pieree the substanee of the musele.

Musmlus Sealenus Posterior. — The sealenus posterior is
generally inseparable, at its origin, from the sealenus medius.
It is the smallest of the three, and springs bytwo or Ihree

328 HEAU AND NECK

Nerva8 Trigemiiius. — The two roots of this nerve have
already been seen piereing the dura mater at the apex of
the petrous portion of the temporal bone under the anterior
margin of the tentorium. Now that the dura mater has been
raised from the lateral part of ihe middle eranial fossa, the
further relations of these nerve-roots within the eranium may
be studied, It will be noiieed that the loosely eonneeted

■ned lalerally.

and parallel funiculi of the portio major, or sensory root, at
onee begin to divide and join with eaeh other so as to
form a dense plexiform arrangement, whilst, at the same time,
the nerve-root inereases somewhat in breadth. The interlaee-
ment, thus brought about, oeeupies the smooth depression
whieh marks the anterior aspeet of the apex of the petrous
portion of the temporal bone, and it sinks into the semilunar
ganglion (O.T. Gasserian).

LATERAL PART 0F MIDDLE GRANIAL POSSA 329

The Ganglion Semilunare (O.T. Gasserian) is somewhat
ereseentie in form. It lies upon the sutural junction between
the apex of the petrous bone and the great wing of the
sphenoid bone, where it is enelosed within a reeess or spaee,
ealled the cavum Meekelii^ formed by a separation of the two
layers of the dura mater. The concavity of the ganglion is
direeted postero-medially, and it is upon this aspeet that it
receives the interlaeing libres of the sensory root of the
trigeminal nerve ; the convexity of the ganglion is direeted
antero-laterally and from it emerge the three main divisions
of the trigeminal nerve. These are — (i) the lirst, or
ophthalmie division ; (2) the seeond, or maxillary division ;
and (3) the third, or mandibular division. The medial
border of the ganglion is eonneeted with the internal
earotid sympathetie plexus by filaments of eommunieation.

The/or/io minor or motor root of the fifth nerve should now
be followed. Before the nerve pierees the dura mater the
motor root lies along the medial side of the large sensory root,
but it soon ehanges its position and eomes to lie beneath
the sensory part. To display this relationship, draw the
eut ends of the two roots through the aperture in the dura
mater whieh leads into the cavum Meekelii, and, gently
dislodging the semilunar ganglion from its plaee, turn it
antero-laterally so as to expose its deep surface. The small
and firm motor root ean readily be reeognised lying in a
groove upon the deep surface of the ganglion ; and if it* is
displaeed from this, it will be seen to have no eonneetion with
the ganglion, but to be eontinued onwards towards the foramen
ovale. It ultimately joins the mandibular division of the
trigeminal nerve. This junction may take plaee within the
eranium, in the foramen ovale, or immediately outside the
skull.

The three prineipal divisions of the trigeminal nerve may
next be examined. Begin with the mandibular division,
whieh is the largest. This proeeeds direetly downwards, and
almost immediately leaves the eranial cavity through the
foramen ovale.

-• Whilst isolating this large nerve-tnink and defining the bony aperture
through whieh it makes its exit, look eareiiilly for the aeeessory meningeal
artery, whieh enters the eranium through the same foramen. If the
injection has been forced into this vessel it ean easily be deteeted. An
emissary vein whieh eonneets the cavemous sinus with the pterygoid
venous plexus also passes through the foramen oyale.

330 HEAD AND NECK

The maxillary division is eomposed entirely of sensory
Abres. It runs anteriorly in relation to the lower and lateral
part of the cavernous sinus, and, after a short eourse within
the eranium, makes its exit through the foramen rotundum.
Near its origin it gives off a fine meningeal braneh to the dura
mater of the middle fossa of the eranium.

The ophthalmie division is the smallest of the three branehes
of the trigeminal nerve, and, like the maxillary, it is eoni-
posed entirely of sensory fibres. It passes anteriorly in the
lateral wall of the cavernous sinus, and ends, elose to the
superior orbital fissure, by dividing into three terminal branehes.
As it traverses the sinus it is aeeompanied by the oeulo-
motor and troehlear nerves, both of whieh oeeupy a higher
level. Like the other two divisions of the trigeminal nerve,
the ophthalmie nerve gives off a meningeal braneh, This
small twig passes into the tentorium eerebelli.

The terminal branehes of the ophthalmie division of the
trigeminal nerve are the naso-eiliary, the laerimal, and the
frontal. The naso-eiliary^ as a rule, takes origin first ; the
laerimal is given off soon after; and then the stem of the
nerve is eontinued onwards as the /rontal. These three
nerves enter the orbit through the superior orbital fissure.

Neryus Oeulomotorius (Third), Nervus Troehlearis (Foiirtli),
and Nennis Abdueens (Sixth). — It has been noted already
that the oeulo-motor nerve pierees the dura mater within the
small triangular area, in the middle eranial fossa, whieh
lies immediately anterior to the erossing of the attaehed
and free margins of the tentorium (p. 210). It has been noted
also that the troehlear (fourth) nerve pierees the dura mater
in the posterior fossa under the free margin of the tentorium.
Both now proeeed anteriorly in the lateral wall of the cavern-
ous sinus. The oeulo-motor nerve oeeupies the highest
level, then eomes the troehlear nerve, and immediately
below that the ophthalmie division of the trigeminal nerve.
They therefore present a numerieal order from above down-
wards. The abdueent nerue^ whieh pierees the dura mater
in the posterior fossa, at the lower and lateral part of the
dorsum sellas, curves round the lateral side of the internal
earotid artery, and then passes anteriorly more direetly within
the cavernous sinus than the others (Fig. 130).

The oeulo-motor, troehlear, and abdueent nerves during
their eourse in the cavernous sinus receive eommuniea-

LATERAL PART OF MIDDLE GRANIAL FOSSA 331

tions from the earotid plexus and froni the ophihalmie
nerve, and they al] enter the orbit by passmg through
the supenor orbital fissure Before domg so, the oeulo
motor nerve dmdes into an upper and a lower division
As they pass through the supenor orbital fissure the vanous

nerves undergo a ehange in their relative positions. This,
howeyer, will be studied in the disseetion of the orbit.

Arteria Garotis Interna. — The intraeranial portion of the
intemal earotid artery may now be examined. It Hes upon
the bteral aspeet of the body of the sphenoid, and, for the
greater part of its eourse, it traverses the cavernous sinus. It
emerges from the earotid eanal into the foramen laeenim
at the apex of the petrous bone ; then it passes through the
upper part of the foramen laeerum, pierees the outer layer

332 HEAD AND NECK

of dura mater, and enters the middle eranial fossa at the root
of the posterior elinoid proeess ; there it bends at right angles,
and passes anteriorly to the lower root of the small wing of
the sphenoid, where it turns abruptly upwards and pierees
the inner layer of the dura mater, immediately posterior to
the entranee of the optie nerve into the optie foramen, and
on the medial side of the anterior elinoid proeess. It was
severed at this point during the removal of the brain ; but it
will be afterwards seen to end on the basal aspeet of the
brain, at the eommeneement of the Assura lateralis (O.T. Sylvian
fissure), by dividing into the anterior and middle eerebral
arteries. Throughout its whole eourse it is surrounded by
sympathetie Alaments, and soon after its entranee into the
eranium the abdueent nerve erosses its lateral side.

The intraeranial portion of the internal earotid artery giyes
off the following branehes : —

These are minute twigs
whieh arise in the
cavernous sinus.

1. Branehes to the hypophysis,

2. Branehes to the semilunar ganglion,

3. Branehes to the dura mater,

4. Ophthalmie, ^

5. Posterior eommunieating, I These will be studied at a later

6. Anterior eerebral, \ terminal j stage.

7. Middle eerebral, / branehes. J

8. Ghoroidal.

Plexiis Oarotieus Intemus. — The sympathetie filaments
whieh form this plexus ean be satisfactorily disseeted only in
a subject whieh has not been injected ; and even then, the
disseetion is an exceedingly difl5cult one. The intemal earoHd
plexus is plaeed in the cavernous sinus and is chiefly massed
upon the lower and medial aspeet of the internal earotid
artery, at the point where it makes its bend upwards. It
supplies filaments to the hypophysis, to the third and fourth
nerves, and to the ophthalmie division of the trigeminal nerve,
and gives the sympathetie root to the eiliary ganglion (O.T.
lentieular ganglion).

Nervus Petrosus Superficialis Major. — ^This small nerve,
along with a small arterial twig from the middle meningeal
artery, ean readily be exposed in the groove on the anterior
face of the petrous bone whieh leads from the hiatus eanalis
facialis to the foramen laeerum. It is plaeed under the semilunar
ganglion, whieh must therefore be turned antero-laterally.
In the eanalis facialis it joins the ganglion genieuli of the
facial nerve. When traeed in the opposite direetion, it will

DISSEenON OF THE ORBIT 333

be foiiiid to mtor the foiamen laeennn, where it joins the
nenms fetrosus pra/undus firoin the earodd plexus. The tnink
formed by the union of these two fi1aments is the nerms
eanalis ^aygoidei {pjT, Vidian neroey,

NenmB Petoosus SuperAeialiB Idior appeais upon the anterior face
of the petrous bone, throogh an apertnre whieh is plaeed immediately
lateral to the hiatns eanalis ^aieialis. It leaves the eramal cavity by passing
down¥Fards between the great wing of the sphenoid and the petrous part
of the temporal bone, or through the eanalieulus innominatus or through
the foramen ovale, to reaeh the otie ganglion. This minute nerve, as
has been mentioned already (p. 312), is formed by the union of the
tympanie braneh of the glosso-pharyngeal with a braneh from the ganglion
genieuU of the &cial.

Ertomal Saperficial Petrosal Nerre. — It is convenient at this stage to
take note of a fourth petrosal nerve — the extemal supcrficial petrosaL It
takes origin from the sympathetie plexus whieh aeeompanies the middle
meningeal artery, and, entering the petrous bone, is eondueted to the
ganglion genieuU of the facial nenre.

Middle and Aeeessory Menmgeal Arteries. — The entranee
of the middle meningeal artery through the foramen spinosum
should now be examined. It gives minute twigs to the
semilunar ganglion, and one — the petrosal artery — whieh
aeeompanies the great superficial petrosal nerve into the
hiatus eanalis facialis. The further eourse of the middle
meningeal artery has been deseribed already (pp. 220).
The neryus spinosus of the mandibular nerve also enters
the eranium through the foramen spinosum (p. 275).

The aeeessory meningeal artery enters the eranium through
the forameh ovale, and is distributed chiefly to the semilunar
ganglion.

DISSEGTIGN 0F THE ORBIT.

Within the orbital cavity the following struetures are
grouped around the eyeball and the optie nerve : —

'Reetus superior.
Reetus inferior.
Reetus lateralis.
Museles, . ,\ Reetus medialis.
Obliquus superior.
ObUquus inferior.
. Levator palpebrae superioris.
I Ophthalmie artery and its branehes.
Yessels, . . ^. Ophthalmie veins (superior and inferior) witb their tribo-
\ taries.

334 HEAD AND NECK

Nerves,

''Oeulo-motor (^rd eerebral).
Troehlear (^th eerebral).
Abdueent (6th eerebral).
Prontal,

j . j I from ophthalmie division of the trigeminal

XT -i-' 1 or fifth eerebral nerve.
Naso-eihary, j

Zygomatic braneh of the maxillary division of the tri-

geminal nerve.

Giliary ganglion.

Laerimal gland.

Fascia Bulbi.

Dtsseetion. — The roof of the orbit must be removed with the aid of the
saw, the ehisel, and the bone forceps. Begin by removing the thiek eranial
wall above the orbital opening, leaving only a thin portion eorre-
sponding to the superior orbital areh. Whilst this is being done,
eare should be taken to preserve the soft parts of the forehead and the
upper eyelid. It is of great advantage to retain, throughout the whole
examination of the orbital cavity, the bony ring whieh eonstitutes its opening
on the face. The thin roof of the orbit may next be removed with the
ehisel and bone forceps. The lesser wing of the sphenoid, where it forms
the upper boundary of the superior orbital fissure, should be taken away
by the bone forceps, but the disseetor should carefully preserve intaet the
ring of bone around the optie foramen. The superior orbital fissure is
now fully opened up, and the various nerves, as they enter the orbit from
the cavernous sinus, may be followed out. Lastly, the anterior elinoid
proeess may be taken away with advantage.

Periosteum. — If the disseetion has been successfully
earried out, the periosteum elothing the under surface of the
orbital roof will be exposed uninjured. The periosteum of
the orbit forms a funnel-shaped sheath, whieh eneloses all the
eontents of the cavity except.the zygomatic nerve, and is but
loosely attaehed to its bony walls. Posteriorly it is direetly
eontinuous, through the superior orbital fissure, with the
dura mater. Expanding with the cavity, it beeomes eon-
tinuous anteriorly, around the orbital opening, with the
periosteum whieh elothes the exterior of the skull. Here
also it presents important eonneetions with the palpebral
fascia.

BeAeetion of the Periosteum and the subse^uent DiBseetion. — The

periosteum should be divided along the middle line of the orbit, and then
transversely elose to the orbital opening. It ean now be thrown medially
and laterally. When this is done, the laerimal gland will be exposed in the
antero-lateral part of the cavity. Further, the large frontal nerve, lying
upon the upper surface of the levator palpebroe superioris, will be seen in the
middle line of the orbit ; as it approaehes the anterior part of the cavity
it is joined by the supra-orbital artery. The other superficial struetures
are usually more or less obseured by the soft pliable fat, whieh every-
where fills up the interstiees between the different orbital eontents. On
carefully separating this, along the medial wall of the orbit, the superior
oblique musele will be more fully displayed, and lying upon and entering

DISSEGTION OF THE ORBIT

335

the posterior part of this musele the small Itoehleai or fourth eeiebtal nerve
will be discovered. The disseetor often fails to find this nerve, beeause as
a geneial nile he looks for il too lat fotwatd5. Lastly, the Inerimal ncrve
aod attery will be found, running along the lateta! wall of the orbit, above
the level of the uppei margin of the lateral reetus musele.

These struetures must be thoioughly eleaned and isolaled by the removal
of ihe .fal from around them. As the superior ohUque musele is
followed anteriorly it will be found to end in a slender tendon, whieb
passes through a ring-like pulley attaehed to the medial angular proeess of

;. 133— The Ophtha

delined, and the tendon of tbe
musele followe<l lalerally from it to its inseition inlo Ihe eyeball. Nole that
the levator paipebia; superioiis lies upon tbe upper suiface of the supeiiot
reetus, and, if it is laised, a nerve twig will be notieed emerging ftom the
substanee of Ihe reetus superiot for the supply of ibe levator palpebrs
musele. This is a braneb of ehe supeiioi division of the third netve. .

The disseetion of the above parts wiU be facilitated by grasping the
anterior part of the eyeball wilh Ihe foiceps and drawing it forwards. It
may be retained in this position by running a line needle and thiead through
the oeulat conjunctiva and stitehing it to the nose. In doing ibis, however,
take eate that the needle does nol penetrale Ihe eomea, beeause this might
lender the subsequenl inilation of tJie eyeball impos^ble.

336 HEAD AND NECK

Nennis Prontalis. — The frontal nerve is the eontinuation
of the stem of the ophthalmie division of the trigeminal
nerve, after it has given off its laerimal and naso-eiliary
branehes. It enters the orbit through the superior orbital
fissure, above the museles, and runs anteriorly upon the upper
surface of the levator palpebrse superioris, immediately sub-
jacent to the periosteal lining of the orbital cavity. It ends
at a variable distanee from the orbital opening by dividing
into the supra-orbital and supra-troehlear branehes.

The supra-iroehlear nerve is the medial and smaller of the
two terminal branehes of the frontal. It runs towards ihe
troehlea of the superior oblique musele, above whieh it pierees
the palpebral fascia, leaves the orbit, and turns round the
orbital areh to reaeh the forehead. Its further eourse has
been deseribed already (p. 156). In the orbit it gives off
one small twig elose to the pulley of the superior
musele. This passes downwards to join the infra-trochlear
braneh of the naso-eiliary nerve.

The supra-orbital nerue is eontinued onwards, in the line
of the parent stem, and, passing through the supra-orbital
noteh or foramen, it turns upwards on the forehead (p.
156). In the disseetion of the sealp this nerve has been
seen to divide into a lateral and a medial division. Some-
times the separation takes plaee within the orbit, and in
that ease the larger lateral part oeeupies the supra-orbital
noteh.

Neryus Laerimalis. — This is the smallest of the terminal
branehes of the opKlhalmie division of the fifth. It enters
the orbit through the superior orbital fissure, above the level
of the museles, and runs anteriorly, along the lateral wall of
the cavity, above the upper margin of the lateral reetus
musele. At the anterior part of the orbit it eontinues its
eourse, under cover of the laerimal gland, until it reaehes
the lateral part of the upper eyelid, in whieh it ends (p. 137).
Within the orbital cavity it gives numerous twigs to the deep
surface of the laerimal gland, and sends downwards a filament
whieh eonneets it with the zygomatic braneh of the maxillary
nerve.

Nervus Troehlearis. — The small fourth nerve is destined
entirely for the supply of the superior obligue musele. Having
entered the orbit through the superior orbital fissure, above the
museles, it passes antero-niedially, under the periosteum, and

DISSEGTION 0F THE ORBIT 337

finally sinks into the upper or orbital surface of the superior
oblique musele not far from its origin.

GlandulaLaerimalis. — Thelaerimalglandis asmall, flattened
and distinetly lobular strueture of oval form, whieh is plaeed
transversely in the antero-lateral part of the orbit. It eon-
sists of two parts or groups of lobules — a superior and an
inferior — imperfectly separated from eaeh other. The glandula
laerimalis superior^ whieh eonstitutes the main mass of the gland,
lies in the orbital cavity. Its lateral convex surface is lodged
in a hollow upon the medial aspeet of the zygomatic proeess
of the frontal bone, and it is bound to the lateral part of the
orbital areh by short fibrous bands whieh proeeed from the
periosteum. The deep or medial surface is slightly concave,
and rests upon the levator palpebrse superioris and lateral
reetus, whieh intervene between it and the eyeball. The
glandula laerimalis inferior lies below and anterior to the
superior part, from whieh it is partially separated by the ex-
panded tendon of the levator palpebrae superioris. It projects
into the base of the upper eyelid, and rests upon the eon-
junctiva whieh lines the under aspeet of the lid. This portion
of the gland has been already examined in the disseetion of
the eyelids (p. 138). Even in the undisseeted subject it ean
be seen through the conjunctiva when the upper eyelid is
fully everted.

The laerimal gland seeretes the tears, and its duets
(three to five from the superior part and three to nine from
the iii!enoi^part) open upon the under snrfarfi nf thp upper
evelid in The neighhnnrhond nf tl^ fornix (Fig. 64).

Museulus Leyator Palpebrse Superioria. — This_muscle rests
upon the upper surface of the rer.tns snpprinr. Posteriorly,
it is narrow and pointed, but it expands as it passes above
the eyeball to reaeh ihe upper eyelid. ItJiises from the under
surface of the rQof of the orbit immediately anterior to-the
optie fQramen. and in the anterior part of the orbital cavity
it widens out int^ a hm^r] Tpemhrannnt; t^ypansion, the Con-
neetions of whieh have been deseribed already (p. 136). The
lateral and medial margins of this expansion are fixed to the
rim of the orbital opening, in elose proximity to the liga-
mentum palpebrale mediale and the raphe palpebralis lateralis.
By these attaehments excessive aetion of the musele upon the
upper eyelid is in a measure eheeked.

• Dissedion. — Divide f ^ throw the ends anteriorly and

V0L. II — 22

338

HEAD AND NECK

posteriorly. The levator palpebrae superioris also may be eut midway
between its origin and insertion. On raising the posterior portion a
minute nerve twig will be seen entering its deep or oeular surface.
This eomes from the superior division of the third or oeulo-motor nerve.

The eyeball should now be indated. This may be done from the
front or from behind. If the latter method is seleeted, gently separate
the fat under cover of the superior reetus musele, and push the eiliary
vessels and nerves away from the optie nerve. Next make a small ineision
through the sheath of the nerve. Pass a ligature round the nerve anterior
to the opening, and then pass a blowpipe, provided with a stylet, through
the ineision and along the nerve into the interior of the eyeball. When the
globe of the eye is fully inAated, the ligature may be tightened as the blow-
pipe is withdrawn. A very mueh better plan, however, is to inflate the

eyeball from the front. For this
purpose make an oblique valvular
aperture in the selero-eorneal junc-
tion, with the point of a sharp
narrow-bladed knife. Through
this the blow-pipe may be intro-
duoed, and on its withdrawal after
the inAation of the eyeball the
valvular eharaeter of the opening
is sufficient to prevent the eseape
of the air.

Posterior to the eyeball the dis-
seetor will notiee a quantity of
loose bursallike tissue. Thi? is
the fascia bulbi (O.T. eapsule of
Tenon). Seize the upper part of
this with the forceps, and remove
a small portion with a pair of
seissors. An aperture is thus
made into the fascia, and the
handle of the knife ean be intro-
dueed into the spaee between it
and the eyeball. In favourable
eases the extent of the fascia ean be gauged, and perhaps even the pro-
longations or sheaths whieh it gives to the tendons of the oeular museles
may be made out. The deseription of the fascia bulbi is given on p. 347.

Museulus Reetus Superior.— The reetus superior, whieh
lies under cover of the levator palpebrse superioris, is now
fully exposed. It arises from the upper marp;in of the optie
foramen, passes anteriorly above the <^p^^^ nprvp, and ends.
upoiTthe upper asp^r^ nf thp pyphall in a thin, delieate tendon.
whieh expands somewhat to be inserted into the selera about
three or four lines posterior to the selero-enrneal jnnrtinn,
It is supplied by a braneh from the suj>erior diyision of the
oeulo-motor nerue.

Museulus ObliaUUS Superior. — This mnsrl^ arisps frnm the
rOOf^' 0f the Orbit immediately nntprinr_ ^(^ fhp npppr anH

medial part of the nptir fnrampn. It passes ^anteriorl^^-along

FiG. 134. — Diagram of the Superior
Oblique Musele. (From Hermann
Meyer. )

a. Troehlea and synovial sheath.

DISSEGTION 0F THE ORBIT 339

the medial wall of the cavity above the medial reetus. At

the anterior part ot the orbit it enas in a siender tendon,
whieh enters the troehlea and at onee ehanges its direetion.
prnrppHing pngtprn-latprally^ upon the upper surface of the
eyeball, under cover of the superior reetus. Beyond the
lateral edge of the superior reetus the tendon expands some-
what, and is inserted into the selera midway between the
entranee of the optie nerve and the eomea.

The troehlea ox pulley through whieh the tendon passes is
a small fibro-cartilaginous ring, whieh is attaehed by hbrous
tissue to the troehlear fossa — a depression in the frontal bone
elose to the medial angular proeess. The puUey is lined with
a synovial sheath whieh facilitates the movement of the
tendon, and from its lateral margin it gives a hbrous invest-
ment to the tendon.

Disseetion. — Divide the superior reetus midway between its origin and
its insertion, and reAeet the eut ends. On raising the posterior part of
the musele the superior division of the oeulo-motor nerve is brought into
view, as it sinks into the deep or oeular surface of the musele.. It
sends a twig to the levator palpebrse superioris. The removal of some
fat will bring the optie nerve more fully into view. At the posterior part of
the orbit three struetures will be seen erossing the optie nerve — viz., (i) the
naso-eiliary nerve ; (2) the ophthalmie artery ; and (3) the superior
ophthalmie vein. These should be carefully eleaned and their branehes
followed out. From the naso-eiliary nerve one or two delieate thread-
like branehes — the long eiliary nerues — will be found passing along the
optie nerve to reaeh the eyeball. The shoTi eiliary nerves, mueh more
numerous, aeeompany the long eiliary branehes, and ean readily be dis-
engaged from the fat whieh surrounds the optie nerve. A strong member
of this group should be seleeted and followed posteriorly ; it will lead the
disseetor to the eiliary ganglion. This is a minute body whieh is situated
upon the lateral side of the optie nerve in the posterior part of the orbit.
With a little patienee and eare the roots whieh the naso-eiliary nerve and
inferior division of the oeulo-motor nerve give to this gangUon ean be
isolated, and perhaps even the sympathetie root from the internal earotid
plexus will be found.

Nervus Optieus. — The optie nerve enters the orbit through
the optie foramen. It earries with it a strong loose sheath
of dura mater, and also more delieate investments from
the araehnoid and pia mater. The ophthalmie artery, whieh
aeeompanies it, lies on its infero-lateral aspeet. Within the
orbit the nerve ihelines antero - laterally, and at the same
time somewhat downwards, to the baek of the eyeball, where
it pierees the selera a short distanee to the medial side of
its eentre. The disseetor has noted already that the
ophthalmie artery and vein and the naso-eiliary nerve eross

340 HEAD AND XECK

above ihe op::c r.er^e, ar.d thar it is elosely aeeompanied by
ihe de'.:oji:e c:::.in- nerves and vessels. The optie nerve is
sl:4:h:';v lo::£:er :hap. :he disMnee whieh it has to nin from the
opiio ioran:en :o :he i^'.obe o! the eve. so that the movements
ot the eyelur. may ::o: be :r.:erfered with. Within the eye-
ball ihe optio nen-e spreads ou: in the retina.

Nerms Naso-ciliaxi& — The naso-eiliar}- nerve (O.T. nasal)
arlses irom the oph:hai:r.:c di^'ision of the trigeniinal in the
anterior j>an of :he cavernous sinus. Ii passes through the
superior orb::al nssure a:id er.iers ihe orbital eayity, between
the two heads of :he la:eral rec:'.:s musele and between the
two divisions of :ho ihird ::erve. It then indines antero-
mediar.y, and, croi^i:'ii: the op:ic nerve obliqueIy, it runs
be:wee:i the ir.edial rec:us and superior oblique museles to
the medial waU of :he orbi^ whero it di^ides into two ter-
minal branehes — \i-\, :he i::fra-:roch!ear and the anterior
e:h:iioidal nerves. In .iddi:ion :o :hese ii gives off in the
orbi: :he fo'lowi::g bra::ches: ^i^ long root to the eiliary
ga:iglion : ^^^ long ci'.iar\- ::er\os : ^3^ posterior ethmoidal
nerve.

A\:,:;".v /..■•;^c-: u,:\c-:: C:\':\:r:s. — This is a very slender
tV.amen: whieh s'ori::^* fro:r. :he n.iso-ci:iarN- as it enters the
orbit bo:ween :he hoads of :he '..r.eral reetus. It runs along
iho lateral side of :he op::c nor\e, and enters the upper and
pos:orior par: of ihe oiliary g.\;:glion.

.\Vr:/ Ci':\:r^s .'.."•:,<t'. — The two long eiliary branehes
spri:ig fro:ii ihe naso-ciliar\- as i: erosses the optie nenre.
They pass an:oriorly. upon :he mov:ia'. side of the optie
nerve. :o roaoh ihe globe of :he eye where they pieree the
selora. One of the lo:^.g ei'iary ::or\es very eonstantly
u:i::os wi:h one of :he shor: ci'.'..iry ::'..; :::en:s.

^A Vr: ;. y £: ': ":.•;-". :.';> / ' s:: • ;'. • '■ p.- ssos : h rough the posterior
e:h:v.oidal foramen :o tho o:h:::oid.'.l oo'ls and the sphenoidal
air si::us.

.Wr: ■;. .% A' v-.j.'/\v ^■.V.; rs. — Tho in: ra- ; roohloar bnineh runs

aloiig :he medi.il wall of :ho orbi: bo'.ow iho superior oblique

muso'e. Afior passi:ig u::dor :ho :roch!oa of that musele it

emorgos from iho orbi: and appoars upo:i the face, where it

^as boen dissoc:od alroady ^p. i^S^. Noar the pulley it

eei ves a co m m ;: :i i oa t i n e i w i e * ro :u t h. 0 s u 'ora • t r^H'hlear nerve.

AVr:v/j: Z''V".\vJ.:.';> .:/»;.vr;.'r — This is the lar^r of the

' terminal branohes of the naso-oiliarv ner\*e. Il lea^'es

DISSEGTION 0F THE ORBIT 341

the orbit by the anterior ethmoidal eanal, and is eondueted to
the interior of the eranium, in whieh it appears at the lateral
margin of the cribriform plate of the ethmoid. The eanal
in whieh it luns ean readily be opened up with the bone-
forceps to expose the nerve. Upon the cribriform plate it
turns anteriorly, under the dura mater, and almost immedi-
ately disappears, through a sHt-like aperture at the side of the
erista galH, into the nasal cavity. There it gives intemal
nasal branehes to the mueous membrane, and is eontinued
downwards upon the posterior aspeet of the nasal bone.
EinaHy, it emerges upon the face, as the external nasal nerue^
by passing between the lower margin of the nasal bone and
the lateral eartilage of the nose. Its terminal iilaments have
been deseribed already (p. 140).

Ganglion Oiliare (Fig. 138). — The eiHary gangHon is a
smaH quadrangular body, not mueh larger than the head
of a large pin. It is plaeed in the posterior part of the orbit,
between the optie nerve and the lateral reetus musele, and
very eommonly on the lateral side of the ophthalmie artery.
At its posterior border it receives it5 three roots ; whilst from
its anterior border the short eiHary nerves are given off.

The sensory root eomes from the naso-eiHary, and is eaHed
the long root. The short or motor root is a short, stout trunk ;
it eomes from the braneh of the oeulo-motor nerve whieh
goes to the inferior obHque musele. The sympathetie root
eomes from the internal earotid plexus, it joins the ganglion,
elose to the entranee of the long root from the naso-eiliary
nerve. In some eases it joins the long root before it reaehes
the ganglion.

Nervi Ciliares Breves. — The short eiliary nerves are from
four to six in number. They eome off in two groups, superior
and inferior. The lower nerves are generally more numerous
than the upper. As these fine nerves pass along the optie
nerve they divide and thus inerease in number ; at the baek
of the eyeball from twelve to eighteen may be eounted.
Finally they pieree the selera by a series of apertures whieh
are plaeed around the entranee of the optie nerve.

Arteria Ophthalmiea. — The ophthalmie artery is a braneh
of the internal earotid. It aeeompanies the optie nerve
into the orbit through the optie foramen. At first it lies
below the optie nerve, but soon winds round its lateral side,
and, erossing above it, passes anteriorly along the medial

II— 22a

340 HEAD AND NECK

above the optie nerve, and that it is elosely aeeompanied by
the delieate eiliary nerves and vessels. The optie nerve is
slightly longer than the distanee whieh it has to run from the
optie foramen to the globe of the eye, so that the movements
of the eyeball may not be interfered with. Within the eye-
ball the optie nerve spreads out in the retina.

NeiYUS Naso-eiliaris. — The naso-eiliary nerve (O.T. nasal)
arises from the ophthalmie division of the trigeminal in the
anterior part of the cavernous sinus. It passes through the
superior orbital fissure and enters the orbital cavity, between
the two heads of the lateral reetus musele and between the
two divisions of the third nerve. It then inelines antero-
medially, and, erossing the optie nerve obliquely, it runs
between the medial reetus and superior oblique museles to
the medial wall of the orbit, where it divides into two ter-
minal branehes — viz., the infra-trochlear and the anterior
ethmoidal nerves. In addition to these it gives ofF in the
orbit the following branehes: (i) long root to the eiliary
ganglion ; (2) long eiliary nerves ; (3) posterior ethmoidal
nerve.

Radix Longa Ganglii Ciiiaris, — This is a very slender
filament whieh springs from the naso-eiliary as it enters the
orbit between the heads of the lateral reetus. It runs along
the lateral side of the optie nerve, and enters the upper and
posterior part of the eiliary ganglion.

Nerui CiUares Longi. — The two long eiliary branehes
spring from the naso-eiliary as it erosses the optie nerve.
They pass anteriorly, upon the medial side of the optie
nerve, to reaeh the globe of the eye where they pieree the
selera. One of the long eiliary nerves very eonstantly
unites with one of the short eiliary filaments.

Neruus Ethmoidalis Posterior passes through the posterior
ethmoidal foramen to the ethmoidal eells and the sphenoidal
air sinus.

Neruus Infratrochlearis. — The infra-trochlear braneh runs
along the medial wall of the orbit below the superior oblique
musele. After passing under the troehlea of that musele it
emerges from the orbit and appears upon the face, where it
has been disseeted already (p. 128). Near the puUey it
receives a eommunieating twig from the supra-troehlear nerve.
Neruus Ethmoidalis Anterior. — This is the larger of the
two terminal branehes of the naso-eiliary nerve. It leaves

DISSEGTION 0F THE ORBIT 341

the orbit by the anterior ethmoidal eanal, and is eondueted to
the interior of the eranium, in whieh it appears at the lateral
margin of the cribriform plate of the ethmoid. The eanal
in whieh it runs ean readily be opened up with the bone-
forceps to expose the nerve. Upon the cribriform plate it
tums anteriorly, under the dura mater, and almost immedi-
ately disappears, through a slit-like aperture at the side of the
erista galli, into the nasal cavity. There it gives intemal
nasal branehes to the mueous membrane, and is eontinued
downwards upon the posterior aspeet of the nasal bone.
Finally, it emerges upon the face, as the external nasal neroe^
by passing between the lower margin of the nasal bone and
the lateral eartilage of the nose. Its terminal Alaments have
been deseribed already (p. 140).

Ganglion Giliare (Fig. 138). — The eiliary ganglion is a
small quadrangular body, not mueh larger than the head
of a large pin. It is plaeed in the posterior part of the orbit,
between the optie nerve and the lateral reetus musele, and
very eommonly on the lateral side of the ophthalmie artery.
At its posterior border it receives its three roots ; whilst from
its anterior border the short eiliary nerves are given off.

The sensory root eomes from the naso-eiliary, and is ealled
the long root, The short or motor root is a short, stout trunk ;
it eomes from the braneh of the oeulo-motor nerve whieh
goes to the inferior oblique musele. The sympathetie root
eomes from the internal earotid plexus, it joins the ganglion,
elose to the entranee of the long root from the naso-eiliary
nerve. In some eases it joins the long root before it reaehes
the ganglion.

Nerui Ciliares Breves. — The short eiliary nerves are from
four to six in number. They eome off in two groups, superior
and inferior. The lower nerves are generally more numerous
than the upper. As these fine nerves pass along the optie
nerve they divide and thus inerease in number ; at the baek
of the eyeball from twelve to eighteen may be eounted.
Finally they pieree the selera by a series of apertures whieh
are plaeed around the entranee of the optie nerve.

11—22 a

34» HEAD AND NECK

wall of the orbit, below the superior obHque musele. At the
medial side of the oebit it ends hy dividing into two terminal
branehes — viz., the frontal and the dorsal nasal (Fig. 136).

The branehes of the ophthalmte artery are very numerous,
and they ean seldom be 5atisfaclorily displayed, unless a
speeial injection has been made. They are : —

1. Laerimal. 1

4. Giliary.

1 7. Palpebral.

2. Museular. 1

5. Supta-orbital.

8. Dorsal nasal.

3. Arleria eenlralis letin^. |

6. Ethmoidal.

1 9. Piontal.

Arteria Laerimalis. — The laerimal braneh aeeompanies
the laerimal nerve, and supplies the gland ot that name and

the conjunctiva. In eaeh eyelid an arlerial areh, the areiis
tarseus, is formed by the anastomoses of the two lateral
palpebra! branehes of the laerimal with the two medial
palpebral branehes of the ophthalmie.

Jiami Museulares eome off at variab!e points, not only
from the main artery, but also from eerEain of its branehes.
They supply the museles eontained in the orbital cavity.

The Arteria Centralis Retinee is a minute but important
artery. It pierees the infero-medial surface of the optie
nerye, about half an ineh posterior to the eyeball, and
passes, in its substanee, to the interior of the globe of
the eye.

Arteria Ciliares are very numerous. Two groups are

DISSEGTION 0F THE ORBIT

343

reeognised — y\z., a posterior and an anterior. The posierior
eiliary arieries run with the eiliary nerves. They arise as
two trunks whieh spring from the ophthalmie whilst it lies
below the optie netve. These divide into several slender
branehes, whieh pieree the selera around the entranee
of the optie nerve. Two members of this group of vessels
enter the eyeball on eithet side of the optie nerye, soraewhat

apart frora the others. They are termed arteria diiares
posteriores longie (Fig. 135). The arterim eiltares anleriores
eome off, in the anterior part of the orbit, from the laerimal
and museular branehes. They vary in number from six to
eight, and run to the anterior part of the eyeball, where they
form an arterial eirele under the conjunctiva. Pinally, they
pieree the selera inimediately posterior to the eornea.

Arteria Supraorbilalis. — This aeeompanies the supra-orbital
nerve to the forehead, where it was disseeted at a previous
stage(p. 157).

344 HEAD AND NECK

■ Arteri(B Ethmoidales, — There are two ethmoidal branehes,
an anterior and a posterior ; they pass through the anterior
and posterior ethmoidal foramina on the medial wall of the
orbit. The arteria ethmoidalis posterior supplies the mueous
lining of the posterior ethmoidal eells, and sends twigs to the
upper part of the nose. The arteria ethmoidalis anterior is
a larger braneh. It runs in eompany with the anterior
ethmoidal nerve, and gives off minute twigs at eaeh stage of
its eourse. Thus in the anterior ethmoidal foramen it gives
branehes to the mueous lining of the anterior ethmoidal eells
and the frontal sinus ; during its short sojourn in the eranial
cavity it gives off a small arteria meningea a?iterior] in the
nasal cavity it gives twigs to the mueous membrane. Its
terminal braneh appears on the face and supplies the side of
the nose.

Arteria Dorsalis Nasi, — The dorsal artery of the nose is
distributed at the root of the nose, and anastomoses with
the angular braneh of the external maxillary artery.

Arteria Brontalis. — This aeeompanies the supra-troehlear
nerve to the forehead, where it has been disseeted already

(P- 157).

Vense Oplitlialimese. — As a general rule there are two

ophthalmie veins, superior and inferior. The superior

ophthalmie vein is the larger of the two and it aeeompanies

the artery. It takes origin at the root of the nose, where

it eommunieates with the angular vein. The inferior

ophthalmie vein lies below the level of the optie nerve, and

it is brought into eommunieation with the pterygoid venous

plexus by an offset whieh passes through the inferior orbital

fissure. The two ophthalmie veins receive numerous tribu-

taries during their eourse through the orbit ; finally they

pass between the two heads of the lateral reetus musele, and

through the superior orbital fissure to open into the cavernous

sinus, either separately or by a eommon trunk.

Museuli Reeti Oeuli. — The four straight museles of the

eyeball diverge from the apex of the orbit. They form the

sides of a four-sided or pyramidal spaee in whieh are en-

elosed the optie nerve and the greater part of the globe of

the eye. The reetus superior^ whieh has been refiected, has

been studied already. The reetus medialis springs from the

medial side of the optie foramen, and the reetus inferior takes

origin from a fibrous band whieh bounds the medial end of the

DISSEGTION 0F THE ORBIT 345

superior orbital fissure. The reetus lateralis is distinguished
from the others by arising from a iibrous areh, the extremities ■
of whieh are termed its two heads of origin. The lower
htad arises iti eommon with the reetus inferior from the
body of the sphenoid, where tbis bounds the media! end of
the superior orbital fissure ; the upptr head is attaehed above
the superior orbital tissure upon the lateral side of the optie
foramen, where its origin beeomes eontinuous with the
superior reetus. Through the arebway whieh intervenes
between the two beads of the lateral reetus pass the two

divisions of the oeulo-motot nerve, the nasoeiliaiy nerve, the
abdueene nerve, and fbe ophtbalmie veins (Fig. 137).

A belter view of these attaehments may be obtained by dWiding Ihe
optie ni;rve dose to the optie fotamen and turning the eyeball anteriorly.

Tbe manner in wbieb the reeti museles ate inserted into
tbe eyeball should next be studied. Eaeh ends in a deheate
meinbranous tendon, wbieh is inserted into tbe selera, about
a quarter of an ineb posterior to tbe selero-eorneal junction.

NerTus Ooulomotoriua. — Tbe two divisions of tbis nerve
enter the orbit through the saperior orbital fissure, between
tbe two heads of the lateral reetus. Tbe superior dwision bas

346 HEAD AND NECK

been traeed to the reetus superior and the levator palpebrae
superioris. The inferior division is larger. It almost im-
mediately divides into three branehes for the supply of the
reetus medialis, the reetus inferior, and the obliquus inferior.
The nerves to the two reeti enter the oeular surfaces of the
museles ; the nerve to the inferior oblique is prolonged
anteriorly, in the interval between the reetus inferior and
reetus lateralis, and enters the posterior border of the inferior
oblique musele. Soon after its origin this braneh giyes the
shori motor root to the eiliary ganglion.

Neryus Abdueens. — The sixth nerve will be found elosely
applied to the oeular surface of the lateral reetus. It enters
the orbit through the narrow interval between the heads of
lateral reetus musele and it supplies this musele only.

Arrangement of the Nerves in the Superior Orbital
Pissure. — When the orbit is disseeted, and the various nerves
met with in the disseetion of the cavernous sinus are traeed
into the cavity, the disseetor will note that the arrangement of
the nerves in the superior orbital fissure is somewhat different
from that in the sinus.

The laerimal, frontal, and troehlear nerves enter the orbit
above the museles on very mueh the same plane (Fig. 137).
The other nerves enter between the heads of the lateral
reetus. Of these the superior division of the oeulo-motor
nerve is the highest, next eomes the naso-eiliary nerve, then
the inferior division of the oeulo-motor nerve, and the
abdueent nerve oeeupies the lowest level.

Disseetion. — The inferior oblique musele is plaeed very diflferently from
the other museles of the orbit. It is situated below the eyeball, running
below its inferior surface to gain its lateral surface. It must be disseeted
from the front. It is neeessary, therefore, to restore the eyeball to its
natural plaee. Next, evert the lower eyelid and remove the conjunctiva
from its deep surface as it is reflected on to the globe of the eye. A little
disseetion in the floor of the anterior part of the orbit and the removal of
some fat will reveal the inferior oblique musele.

Museulus OblioLuus Inferior. — This musele arises from a
small depression on the orbital surface of the maxilla,
immediately lateral to the opening of the naso-laerimal duet.
It passes laterally, below the inferior reetus musele, and,
inelining slightly posteriorly, ends in a thin membranous
tendon, whieh gains insertion into the lateral aspeet of the
selera of the eyeball under cover of the reetus lateralis. The
insertion is not far from that of the superior oblique, but

DISSEGTION OF THE ORBIT

347

is plaeed more posteriorly. It is supplied by the in/erior
division of the third nerw.

Taseia Bnlbi (O.T. Gapsole of Teson). — The eonneetions
of the iibrous sheath of the eyeball are somewhat eom-
plieated, and they eannot be satisfactorily displayed, in every
detail, in an ordinary disseetion. The fascia may be studied

Lcvalor [olpebtrEiiupPrioii'i--

from a threefold point of view — (i) in its eonneetion with
the eyeball; (z) in its eonneetions with the museles inserted
into the globe of the eye ; and (3) in its eonneetions with
the walls of the orbit.

The relation whieh the fascia bulbi beats to the eyeball
is very simple. The menibrane is spread over the posterior
five-sixths of the globe — the eornea alone being free from it.
Anteriorly, it lies in relation with the oeular conjunctiva, with
whieh it is ir nneeted, and it ends by bleoding

348 HEAD AND NECK

with the conjunctiva elose to the margin of the eornea.
Posteriorly^ it fuses with the sheath of the optie nerve where
the nerve pierees the selera. The internal surface of the
membrane (i.e, the surface towards the globe of the eye) is
smooth, and is eonneeted to the eyeball by some soft yielding
and humid areolar tissue, the interval between them eon-
stituting, in fact, an extensive lymph spaee ealled the spatium
inter/asdale. Its external surface is in eontaet posteriorly
with the orbital fat, to whieh it is loosely adherent ; and it is
iirmly attaehed to the oeular conjunctiva more anteriorly. It
obviously, therefore, forms a membranous soeket in whieh
the eyeball ean glide with the greatest freedom.

The tendons of the various oeular museles are inserted
into the eyeball within this fascia, and they gain its interior
by piereing the membrane opposite the equator of the globe
(Fig. 139). The lips of the openings through whieh the four
reeti museles pass are prolonged posteriorly upon the museles,
in the form of sheaths, very mueh in the same manner that
the infundibuliform fascia is prolonged upon the spermatie
eord from the abdominal inguinal ring. These sheaths
gradually beeome more and more attenuated, until at last
they blend with the perimysium of the museular bellies. In
the ease of the superior oblique musele the eorresponding
prolongation is related only to its reflected portion ; when it
reaehes the pulley it ends, by beeoming attaehed to its
margins. The sheath of the inferior oblique may be traeed
upon the musele as far as the floor of the orbit. The medial
or oeular edge of eaeh of the four apertures through whieh
the reeti museles pass is strengthened by a slip of fibrous
tissue (Loekwood), and as the fascia bulbi is firmly bound to
the bony wall of the orbit at various points these slips aet as
pulleys, and proteet the globe of the eye from pressure during
eontraetion of the museles. The aperture for the superior
oblique is not furnished with sueh a slip, and it is doubtful
if the opening for the inferior oblique musele possesses one.

Disseetion. — An admirable view of the relations whieh the fascia
bulbi presents to the eyeball and the tendons of the oeular museles ean
be obtained by the following disseetion : — Divide the lateral eommissure of
the eyelid to the margin of the orbital opening. PuU the eyelids widely
apart, so as to expose as mueh as possible of the anterior face of the
eyeball. Next divide the conjunctiva by a eireular ineision just beyond
the eornea. At this point the fascia bulbi is so intimately eonneeted
with the conjunctiva that it is divided at the same time. Now raise eare-

DISSECTION 0F THE ORBIT

The openings in the fascia bulbi foT the tendons of the oeular museles
and the thiekened matgins of these apertures ate well seen. Note also the
sheaths whieh are given to the ^nuseles.

Check and Snspansory Lig&ments.-— The eonneetions of
the Taseia bulbi to the walls of the orbital cavity are
somewhat eomplieated. The susptnsory ligament (Loekwood)
plays an important part in this respeet. It stretehes aeross
the anterior part of the orbit, after the fashion of a hammoek,
and gives support to the eyeball, Its two e^tremities are

FiG. 139.— Dlsseelion of Ihe Paseia Bulbi from Ihe fronl.

narrow, and are attaehed respectively to the zygomatic and
laerimal bones. Below the eyehall it widens out and blends
with the fascia bulbi. The lateral and medial eheek ligamenls
also eonstitute bonds of union between the fascia bulbi and
the orbital wall. They are sttong bands whieh pass from
the sheaths around the lateral and medial reeti museles
to obtain attaehinent to the zygomatic and laerimal bones
respeetiyely, where they are brought into assoeiation with
tbe entremities of the suspensory ligament. The function
of the eheek ligaments is to Hmit the eontraetion of the
media] and lateral reeti museles, and thus prevent excessive
rotation of the eyeball in a lateral or medial direetion.
There is a similar but iess direet provision by means of whieh
the aetion of the auperior and inferior reeti musdes is limited.

350 HEAD AND NECK

The aetion of the former musele is eheeked through an
intimate eonneetion with the levator palpebrae superioris in
the anterior part of the orbit ; the aetion of the inferior reetus
is eheeked through a eonneetion with the suspensory ligament.

Disseetion. — In order that the zygomatic braneh of the maxillary
division of the trigeminal nerve may be displayed in its eourse through the
orbit, the orbital eontents must be removed. The nerve will then be
found in the midst of a little soft fat in the angle between the floor and
lateral wall of the orbit.

Nervus Zygomaticus (O.T. Temporo-MaIax). — This small
nerve arises, in the infra-temporal fossa, 'from the maxillary
diyision of the trigeminal nerve. It enters the orbit by
passing through the inferior orbital iissure and almost
immediately diyides into two terminal branehes — the
zygomatico-temporal and the zygomatico-facial.

Ramus Zygomaticotemporalis. — This braneh runs antero-
superiorly upon the lateral wall of the orbit, under cover of the
periosteum, and, after receiving a eommunieating twig from
the laerimal nerve, it enters the zygomatico - orbital eanal
of the zygomatic bone. This eonduets it to the anterior part
of the temporal region, where it has been examined already
(pp. 155 and 156).

Ramus Zygomaticofacialis. — The zygomatico-facial braneh
also enters a zygomatico-orbital eanal, and is linally eon-
dueted to the face by the zygomatico - facial eanal whieh
traverses the zygomatic bone (p. 127).

PREYERTEBRAL REGION.

The following are the struetures to be displayed in this
disseetion : —

Prevertebral museles.
Intertransverse museles.
Cervical nerves.
Yertebral artery.

Yertebral vein.

Yertebral and cranio-vertebral
artieulations.

Disseetion. — To separate the anterior part of the head with the pharynx
from the posterior part and the vertebral eolumn a somewhat eomplieated
disseetion is neeessary. Plaee the head upside down, so that the eut margin
of the skuU rests upon the table ; divide the eommon earotid artery, me
internal jugular vein, the vagus nerve, and the sympathetie tnink, on
eaeh side, at the level of the neek of the first rib ; puU the traohea
and oesophagus, together with the great blood vessels and nerves, away
from the anterior surface of the vertebral eolumn. The separation must

PREYERTEBRAL REGION 351

be effected right up to the base of the skull. At this point great eaution
must be observed, otherwise the pharyngeal wall or the insertions of the
prevertebral museles will be damaged. The base of the skull having been
reaehed, the point of the knife should be earried aeross the basilar portion
of the oeeipital bone, between the pharynx and the prevertebral museles,
to divide the thiek investing periosteum.

The basilar portion of the oeeipital bone must now be divided by means
of a ehisel. Still retaining the part upside down, plaee the skull so that its
floor rests upon the end of a wooden bloek. Then apply the edge of the
ehisel to the under surface of the basilar portion of the oeeipital bone,
adjust it aeeurately in the interval between the pharyngeal wall and the
prevertebral museles, and with a wooden mallet drive it through the base
of the skull, inelining it, at the same time, slightly posteriorly.

The next step in the disseetion eonsists in making two saw-euts through
the eranial wall. The head having been plaeed upon its side, the saw
must be applied to the lateral aspeet of the skull, half an ineh posterior to
the mastoid proeess, and be earried obliquely antero-medially to reaeh a
point immediately posterior to the jugular foramen. A similar saw-eut
must be made upon the opposite side of the head.

To eomplete the disseetion the disseetor must again have reeourse to the
ehisel. Plaeing the preparation so that the floor of the eranium looks
upwards, divide the base of the skull, on eaeh side, in the interval between
the petrous portion of the temporal bone and the basilar portion of the
oeeipital bone. Anteriorly, this eut should reaeh the lateral extremity of
the ineision already made through the basilar portion ; whilst posteriorly,
it should be earried to the medial side of the jugular foramen to reaeh
the medial end of the saw-eut. When this has been done upon both sides
of the basilar portion, the anterior part of the skull earrying the phar)mx and
the great blood-vessels and nerves ean be separated from the pwsterior part of
the skull and cervical portion of the vertebral eolumn. The only large
nerve whieh will be divided is the hypoglossal, but, as it is eut elose to the
basis eranii, and above its eonneetion with the ganglion nodosum of the
vagus, it retains its position.

The pharynx and anterior portion of the skull should now be covered
with a pieee of eloth soaked in preservative solution, and the whole
enveloped in an oil-eloth wrapper. It ean then be laid aside until the
disseetion of the prevertebral region and the ligaments of the cervical
vertebr3e and the oeeiput have been eompleted.

Returning to the posterior part of the skull and the cervical
portion of the vertebral eolumn, the disseetor should proeeed
to define the attaehments of the museles whieh lie anterior
to the transyerse proeesses and the bodies of the yertebrae.
These are three in number on eaeh side, viz. : —

1. The longus eolli.

2. The longus eapitis (O.T. reetus eapitis antieus major).

3. The reetus eapitis anterior (O.T. antieus minor).

Museulus Longus CoIIi. — This is the most powerfuI of the prevertebral
museles, and it lies nearest to the median plane. Its eonneetions are some-
what intrieate, but when it has been thoroughly eleaned it will be seen to
eonsist of three portions — viz., upper and lower oblique parts, and an
intermediate vertical part.

The lower oblupie division arises from the lateral aspeet of the bodies of

aHA~ .OT? N^eS

ihrw! tpri'liri'iu» slips froin the anteriot tubereles of the Iransrerse pioeesses
<>f the thir'I, foutth, an'l fifth ceTvical Teriebr.t ; ii iat<eTi somewliat as it
pr'ieeR'lt iipH'arr]) anii inedially to obtoin a poinled anA tendinous insetlion
Hil'i Ibe Biitnri'ir lulitrele of Ihe atlas. The :,rn\ii/ (ari of the musele is
niueh Ibe bree^t 'if Ihe ihiee divisions. It lies along the medial side of the
iiUi'jiin i^irti'iTis, aiirl is iDtimately eonneeied witb tuih of them. It arisei
in C(>mni'in with tln: inferioi obIique part by two oi ibree slips fioin the
niilntnT thu iMitliet 'if the upper two or three thoraei): yertebrK ; above

PREYERTEBRAL KKr,UA

» \ «

this it derives additional slipK of orijjin froin ihe U».lu> ..| ili. ;. «. .,
cervical reriebr^E- : lastly, its lateral l»>n]t.'r is iiiiiluii • «I \^\ n|;j.x ■,.
transrerse proeeises (.•£ ihe l'iwer lhri.-c i»r l-.ur «ii\n,>l \.i;.i. \
stretehes vcr::cally ::- w:iri>. arj'l i- inN.;it..i ii]>i>ii ih> iii.«liil .|.i, . • .-.
upper obli'j-j- yi.n ■.■f iLt :: us !•.■ "••y thn.- t. n.hi.Mi, |.|.., .^.. .. «Ii. ■.

obtain a:i2:h2-irr.: :: ih-. ■•.•Jj-_-- ■ :' :•,-. v.-..-rri, •!..i-!. .ui.l i tii , , n i. ,|

vertebr;<:.

LoD^nB Gapiids '.T. £eeciiiCa.pLUi Asti(nullajor I !.• I -ni: i .i| ihh
is aa tl:i^h.iiri n.Uriiiit v:.ill L.rii'!:.- :•; ir^r ■— . •. •- !.;• fi .rn !).. .niii m>>i
tiriierrles :■:' uit --'Lii---- trri.-. :r )•.•_-.-*-.- *''•,: " ■.- . '•?".. J.f'li. ;ii.-l ntli

£.-=zriz7l ~:=r.-'.'Cji. 1: ir iL-.—.r: u:.:-.ri •• ■■ •:,» ', ;••■'". "i'n

*J:e :iiji-T L^in'r. -.»:' Ui-: :,:::.*l.- :■ r-.i : ■" .:.- »• :.; = .■ • ■ ]■. i. •• h
•Jiis •JL5.trL.:c Ur-. n:*-Ls.:^: ::.•.:::.•- -':;:■:: • i: • ■ .; ■ ; ...■•■ ;.. .. di.
Aii^inr iiiiirr: '" iiit * -^'.-i t^l , .::i;::. : ; :• •;■ v- •/■ (t *>.>

£&rSLJ *^-*T*''--" *^T=.*"^i| " in.'<nr.kw^t§ KsiSi?

ii. " L- 1 : 1 i.:!'-!;^-:': i" -:i ii iLs'r^ ■.". — ._.-,.. , . . . .....

— »m— - ._.... . .- ^. .. ..« y^» .... ^'■P ■■*

- .-T ■r-etr' ••::. .■-

■i-

3^2r^ >^^^2Si«^t — " .?"■ ■-«■^•t "^ '".^":.i. .-*~ *^ '«e-

. ^*__^^" ^ ..... ^^

»• « r - « - * . ^^

(-«t «.«.1» .^— ... » • ' ■■ ■ ~

over :!i=: j:.'r.-rr'".' .-s^' -^ --*■-

t-jranii^ju -T. -•*^ _'Sii-"^^^^s*^'

354 HEAD AND NECK

the infeTior obliqne, and the superior oblique. The anterior tubereles and
the eostal porlions of the transverse proeesses of the Ihird, fourth, fifih,
and sixth cervical vertebrie should then be snipped oS with the bone forceps.

Arteria VertebraJia. — ^This is an artery of great importanee,
for te^ether with its fellow of the opposite side and the basilar
artery, whieh is formed by their union, it supplies the hind-
brain, the mid brain, and the postenor parts of the eerebral
hemispheres, and it helps to supply the spinal medulla. It

of the Vertebra]

eommenees at the root of the neek, as a braneh of the first
part of the subclavian artery, and it runs upwards, through the
transyeree proeesses of the cervical vertebrfe, to the base of
the skuU. It enters the skuU through the foramen magnum
and unites in the posterior fossa of the eranium, at the lower
border of the pons, with its fellow of the opposite side to
form the basilar artery. On aeeount of its varying relations
it is divided into four parls. Tbe iirst part, whieh extends
from the subclavian artery to the transverse proeess of the
sixth cervical yertebra, has been seen already (p. 251). It lies
between the longus eolli medially, the sealenus anterior

PREYERTEBRAL REGION 355

laterally, the transverse proeess of the seventh cervical
vertebra and the inferior eendeal ganglion of the sympathetie
posteriorly, and the vertebral vein and the eommon earotid
artery anteriorly.

The seeond part, now exposed, eommenees where the
artery enters the transverse proeess of the sixth cervical
vertebra. It passes vertically upwards, through the series
of foramina transversaria, till it reaehes the foramen in the
transverse proeess of the epistropheus. In that it runs
laterally as well as upwards to gain the foramen in the
more laterally plaeed transverse proeess of the atlas ; and, as
it emerges upon the upper aspeet of the atlas, the third
part eommenees and curves round the lateral and posterior
aspeets of the upper artieular proeess of that bone, in a
groove upon the upper surface of the posterior areh. As
soon as it has passed under cover of the lateral margin of the
posterior atlanto-oeeipital membrane it beeomes the fourth
part. The fourth part turns upwards, pierees the dura mater
and passes into the skull through the foramen magnum,
anterior to the uppermost digitation of the ligamentum denti-
eulatum; then, turning antero-medially, between the h)^po-
glossal nerve above and the first cervical nerve below, it
passes to the anterior surface of the medulla oblongata, and,
as already stated, joins its fellow of the opposite side at the
lower border of the pons.

Relations, — The relations of the first part have already
been sufficiently eonsidered. The seeond part lies in and
between the transverse proeesses of the cervical vertebrae,
medial to the intertransverse museles, lateral to the bodies
of the vertebrge, and anterior to the anterior branehes of the
cervical nerves as they pass laterally. It is surrounded not
only by the sympathetie nerve plexus derived from the
inferior cervical ganglion, whieh aeeompanies all parts of
the artery, but also by a venous plexus whieh terminates below
in the vertebral vein or veins. The third part of the artery
lies on the posterior areh of the atlas in the anterior boundary
of the sub-oeeipital triangle. As it turns posteriorly from the
foramen in the transverse proeess of the atlas the anterior
braneh of the first cervical nerve lies to its medial side,
between it and the lateral mass of that bone ; and, as it tums
medially, posterior to the upper artieular facet, the trunk of
the first cervical nerve lies below it on the posterior areh, and

11—23 a

356 HEAD AND NECK

the posterior braneh enters the triangle from beneath its
lower border. For the relations of the fourth part see above
and p. 443.

Branehes. — No braneh of importanee is given off from
the first part. The seeond part gives off lateral spinal
(p. 193) and museular branehes. The branehes from the
third part are museular twigs, and branehes to anastomose
with twigs from the oeeipital and the deep cervical arteries.
The fourth part gives off a meningeal braneh before it
perforates the dura mater and, afterwards, a series of branehes
to the eentral nervous system (see pp. 443, 444).

Vena Yertebralis. — Only the first part of the vertebral
artery is aeeompanied by a definite vertebral vein. There
are no aeeompanying veins with the fourth part of the artery,
but a plexus is formed round the eommeneement of the
third part, by the union of tributaries from the venous plexus
in the vertebral eanal and from the plexus of veins in the
sub-oeeipital triangle. This plexus aeeompanies the seeond
part of the artery through the transverse proeesses of the
cervical ^ertebrae ; it anastomoses with the venous plexuses in
the vertebral eanal ; and it terminates below in one or two
vertebral veins ; these aeeompany the first part of the artery
and end in the posterior aspeet of the eommeneement of the
innominate vein.

Disseetion. — The museles must now be eompletely removed, in order
that the vertebral and cranio-vertebral joints, and the ligaments in eon-"
neetion with the cervical portion of the vertebral eolumn may be examined.

The Joints of the Negk.

The epistropheus, atlas, and oeeipital bone present a series
of artieulations in whieh the uniting apparatus is very different
from that of the ^ertebrae below.

Artieulations of the Lower Five Cervical Vertebr8B. — The
lower five cervical vertebrae are united together very mueh
upon the same plan as the vertebrae in other regions of the
vertebral eolumn. Both the bodies and the vertebral arehes
are eonneeted by distinet artieulations and speeial ligaments.

Three separate joints may be said to exist between the
opposed surfaces of the bodies of two adjacent cervical
vertebrae — viz., a eentral synehondrosis and two small lateral
diarthrodial joints.

JOINTS OF THE NECK 357

The synehandrosis oeeupies by far the greatest part of
the interval between the vertebra} bodies, and it presents
the usual eharaeters of sueh an artieulation. The opposed
bony surfaces are eoated with a thin layer of hyaline or
enerusting eartilage, and are brought into direet union
by an interposed dise of fibro-cartilage. The intervertebral
fibrD-cartiiages are distinetly deeper anteriorly than posteriorly,
and upon this eireumstanee the cervical cuivature of the
eolumn in great measure depends,

The two diarthrodial joinis are plaeed one on eaeh side
where the dise of fibro-cartilage is absent. They are of stnall
extent, and are confined entirely to the interva]s between the
projecting lateral lips . of the upper surface of the body

and the bevelled-off lateral margins of the lower surface of
the yertebral body immediately above. The bony surfaces
are eoated with enerusting eartilage, and are separated by
a synovial cavity proteeted by a feeble eapsular ligament

The ligaments whieh bind the bodies of the lower five
cervical vertebr£e together are the direet eontinuation upwards
of the anterior and the posterior longitudinal ligaments of
the vertebrje. When the medulla spinalis was removed,
the lamina of the vertebrse, below the epistropheus, were
taken away so that very little disseetion will be required to
make out the eonneetions of both of these hgaments. The
anterior longitudinal ligament is a strong band plaeed on the
anterior faces of the vertebral bodies, It is mpre firmly fixed
to the intemning intervertebral fibro-cartilages than to the
bones. The posterior longitudinal ligament, whieh lies on

358 HEAD AND NECK

the posterior aspeets of the vertebral bodies, eonstitutes the
anterior boundary of the vertebral eanal. In the cervical
region it eompletely covers the bodies and does not present
the dentieulated appearanee whieh is so eharaeteristie lower
down. It is attaehed ehieiiy to the fibro-cartilages and
the adjacent margins of the bones.

The vertebral arehes of the lower five cervical vertebrae are
bound together by (a) the artieulations between the artieular
proeesses; (S) ligamenta flava; (c) interspinous ligaments;
and {d) intertransverse ligaments ; (e) ligamentum nuehse.

The yoints between the opposing artieular proeesses are of
the diarthrodial variety. The surfaces of bone are eoated
with eartilage; there is a joint cavity surrounded by a
distinet eapsular ligament lined with a stratum synoviale.
This ligament is more laxly arranged in the neek than in
the lower regions of the vertebral eolumn.

The Ugamenta fiava may be examined on the laminse whieh were
removed for the display of the spinal meduUa, and whieh the disseetor was
direeted to retain. They fill up the gaps between the laminse of the
yertebrae, and ean be best seen when the anterior aspeet of the speeimen
is viewed.

Ligamenta Flava, — These ligaments are eomposed of yellow
elastie tissue. Eaeh is attaehed superiorly to the anterior
surface and inferior margin of the lamina of the vertebra
above, whilst inferiorly it is fixed to the posterior surface
and superior margin of the lamina of the vertebra next
below. In this way they form with the laminae a smooth,
even, posterior wall for the vertebral eanal. Eaeh ligament
extends from the posterior part of the artieular proeesses to
the median plane, where its free thiekened median border is
in eontaet with its fellow of the opposite side. The median
slit between them, in the spaee between eaeh pair of
vertebral arehes, is filled with some lax connective tissue,
whieh allows the egress from the vertebral eanal of some
small veins. The width of the ligaments in the different
regions of the vertebral eolumn depends upon the size of
the vertebral eanal. Therefore they are widest in the neek
and in the lumbar part of the eolumn. The ligamenta flava,
by virtue of their great strength and elastieity, are powerful
agents in maintaining the curvatures of the vertebral eolumn ;
they also give valuable aid to the museles in restoring the

JOINTS 0F THE NECK

3S9

vertebral eolumn to its original position afteT it has been bent
in a ventral direetion.

The interspinous Hgamnis are most strongly developed in
the lumbar region, where they fill up the intervals between
the adjacent margins of eontiguous spinous proeesses. In
the thoraeie region, and more so in the neek, they are very
weak,

The supraspin&us ligaments are thiekened bands whieh
eonneet the summits of the spinous proeesses. In the neek
they are replaeed by the ligamentum nuehs (p. 172).

FlG, 143. — The Ligamenta Flava ia the Lumbar RegiOD of the SpiM,

The intertrans7}<rse Ugaments are feebly marked in the
cervical region and extend chiefly between the anterior bars
of the transverse proeesses.

Artienlations of ttie Epistropheiu, Atlas, and Oedpital
Bone. — The artieulations whieh exist between these three
bones all belong to the diarthrodial eiass, Between the atlas
and epistropheus (O.T. axis) ihere are three sueh joints —
viz., a pair between the opposed artieular proeesses, and a
third between the anterior face of the dens and the posterior
face of the anterior areh of the atlas, Between the atlaa
and oeeipital bone there is a pair of joints — viz., between
the oeeipital eondyles and the elliptieal cavities upon the
upper aspeets of the lateral masses of the atlas.

36o HEAD AND NECK

The ligaments eonneeting these three bones together may
be divided into three main groups, as follows : —

Ligaments eonneeting atlas
with epistropheus, . . .

Ligaments eonneeting oeei-
pital bone with atlas, . ,

Ligaments eonneeting oeei-
pital bone with epistro-
pheus,

' Anterior longitudinal.
Ligamenta flava.
Gapsular.
Transverse portion of erueiate ligament

with inferior erus.
Aeeessory ligaments of the atlanto-epis-
tropheal joints.
' Anterior longitudinal ligament.
Anterior oeeipito-atlantal membrane.
Posterior oeeipito-atlantal membrane.
Transverse part of erueiate ligament with
superior erus.
^ Gapsular.

^' Membrana teetoria.
Superior and inferior erura of the erudate

ligament.
Alar.
Apieal.

Anterior Longitudinal Ligament (Fig. 144). — This is a
eontinuation upwards of the eommon anterior longitudinal
ligament. Below, it is attaehed to the anterior aspeet of
the body of the epistropheus, whilst above, it is fixed to the
anterior areh of the atlas. It is thiek and strong in the
middle, but thins ofif towards the sides.

Ligamenta Flava. — These iill the interval between the
laminae of the epistropheus and the posterior areh of the
atlas, to the eontiguous margins of whieh they are attaehed.
They are broader and more membranous than the ligamenta
fiava at lower levels.

Oapsulse Artieulares. — These are somewhat lax, and are
attaehed to the margins of the artieular proeesses.

Membrana Atlanto-Oeeipitalis Anterior (Fig. 144). — This
membrane extends from the upper border of the anterior areh
of the atlas to the under surface of the basilar portion of the
oeeipital bone, anterior to the foramen magnum. On eaeh
side of the median plane it is thin and membranous, and
stretehes laterally so as to abut against the atlanto-oeeipital
eapsular ligament. In the median plane it is strengthened
by the upper part of the anterior longitudinal ligament.

Membrana Atlanto-Oeeipitalis Posterior. — This is a thin and
weak membrane whieh oeeupies the gap between the posterior
areh of the atlas and the posterior border of the foramen
magnum, to both of whieh it is attaehed. It is very finnly

JOINTS 0F THE NECK

361

eonneeted with the dura mater, and oti eaeh side it reaehes
tbe atlanto-oeeipital eapsular ligament. Eaeh of its kteral
borders fontis an areh over the groove, posterior to the upper
aitieular facet of the atlas, tn whieh the vertebra] artery and
the lirst cervica1 nerve are lodged. It is not uneommon to
find these &brous arehes ossiSed.

AtUmto-Oeeipital eapsnlar Ligamenta. — These eonneet
the oedpital eondyles with the lateral masses of the atlas.

iUe of eanihe

ween xht body of Ihe e[

They eompletely suiround the joints, and are eonneeted
anteriorly with the anterior atlanto-oeeipital membrane, and
posterioriy with the posterior atlanto-oeeipital membrane.

The oeeipital bone, therefore, around the foramen magnum
is attaehed by speeial ligaments to eaeh of the four portions
of the atlas — viz., to the anterior areh, to the two lateral
masses, and to the posterior areh.

362 HEAD AND NECK

is neeessary therefore to remove, with the bone forceps, the laminse of the
epistropheus and the posterior areh of the atlas. The squamous part of
the oeeipital bone also must be taken away by sawing it through, on
eaeh side, imraediately posterior to the jugular proeess and the eondyle,
earrying the saw eut into the foramen magnum. The upper part of the
tube of dura mater, whieh still remains in the vertebral eanal, must
next be carefully detaehed. A broad membranous band stretehing upwards
over the posterior aspeet of the body and dens of the epistropheus
is displayed. This is the membrana teetoria.

The Membrana Teetoria (O.T. Posterior Occipito-axial
Ligament). — This is a broad ligamentous sheet whieh is
attaehed below to the posterior aspeet of the body of
the epistropheus, where it is eontinuous with the posterior
longitudinal ligament of the vertebrae. It extends upwards,
covering the dens and the anterior margin of the foramen
magnum, and is attaehed above to the superior grooved
surface of the basilar portion of the oeeipital bone.

Dissedion. — Detaeh this membrane from the epistropheus and throw
it upwards upon the basilar portion of the oeeipital bone. By this pro-
eeeding the aeeessory ligaments of the atlanto-epistropheal joints and the
erueiate ligament are brought into view, and very little further disseetion
is required to define them.

Aeeessory Atlanto-epistropheal Ligaments (Fig. 145). —
These are two strong bands whieh take origin from the
posterior aspeet of the body of the epistropheus elose to the
base of the dens. Eaeh band passes upwards and laterally,
and is attaehed to the medial and posterior part of the
lateral mass of the atlas. To a eertain extent they assist the
alar ligaments in limiting the rotary movements of the atlas
upon the epistropheus.

Ligamentum Orueiatum (Fig. 145). — The erueiate ligament
is eomposed of a transverse and a vertical part. The liga-
mentum transversu?n atlantis is by far the most important eon-
stituent of this apparatus. It is a strong band whieh stretehes
from the tuberele on the medial aspeet of the lateral mass of
the atlas on one side to the eorresponding tuberele on the
opposite side. With the anterior areh of the atlas it forms
a ring whieh eneloses the dens — the pivot around whieh the
atlas bearing the head turns. It is separated from the
posterior aspeet of the dens by a loose synovial membrane
whieh extends anteriorly on eaeh side until it almost reaehes
the synovial membrane in eonneetion with the median joint
between the dens and the anterior areh of the atlas. Indeed,

JOINTS 0F THE NECK 363

in Eotne eases a eommunieation exists between the two synorial
cavities.

The vertical part of the enieiate ligament eonsists of an
upper and a lower limb, whieh are termed the enira. Both
are attaehed to the dorsal surface of the transverse ligament.
The erus superius is the longer and Aatter of the two, and
extends upwaids on the posterior aspeet of the dens to be
attaehed to the upper aspeet of the basilar part of the
oeeipital bone immediately beyond the anterior margin of

the foramen magnum. The erus it^erius, mueh shorter,
extends downwards, and is fixed to the posterior aspeet of

the body of the epistropheus.

Disstdim. — Detaeh the superioi eras froiii the oedpital boDe, ind
(hrow it downwards. The apieal ligament is Ihus displayed, and a bettei
view of the alar ligamenis is obtained.

Ligamentum Apieis Dentis.— The apieal ligament of the
dens eonsists of two parts — an anterior and a posterior. The
posterior part is a rounded eord-like ligament whieh is attaehed
below to the summit of the dens, and above to the anterior
margin of the foramen magnum. This ligaraene, inasmueh

364 HEAD AND NECK

as it is developed around the eontinuation of the ehorda
dorsalis from the dens to the basis eranii, is a strueture of
eonsiderable morphologieal interest. The anterior part of
the apieal ligament is a flat and weak band whieh is
attaehed above to the anterior margin of the foramen magnum
at the same point as the posterior portion. Below, the two
portions are separated by an interval filled with eellular tissue,
and the anterior part is attaehed to the dens immediately
above its artieular facet for the anterior areh of the atlas.

Ligamenta Alaria (Fig. 145). — These are very powerful
bands whieh spring, one from eaeh side of the summit of
the dens. They pass laterally and slightly upwards to be
attaehed to the medial aspeet of the eondyloid eminenees of
the oeeipital bone. They limit rotation of the head, and
in this they are aided by the aeeessory atlanto-epistropheal
ligaments.

Moyements. — Nodding movements of the head are permitted at the
atlanto-oeeipital artieulations. Rotatory movements of the head and atlas
around the dens, whieh aets as a pivot, take plaee at the atlanto-
epistropheal joints. Excessive rotation is eheeked by the alar ligaments.

MOUTH AND PHARYNX.

The disseetors must now return to the anterior part of the
skuU, whieh had been laid aside while the disseetion of the
prevertebral region was being earried on. The mouth and
pharynx should engage their attention in the first instanee.

Mouth. — The mouth is the expanded upper part of the
alimentary eanal whieh is plaeed in the lower part of the
face, below the nasal ehambers. Its cavity is eontrolled by
museles whieh are under the inAuenee of the will, and it
is separable into two parts : a smaller external part, termed
the vestibule, whieh is bounded externally by the lips and
eheeks, and internally by the teeth and gums; and a large
part, the moutk proper^ whieh is plaeed within the teeth.

The mueous lining of the mouth should be thoroughly eleansed, and
the two subdivisions of the cavity examined through the oralfissure,

Yestibulum Oris. — The vestibule of the mouth, whieh
passes round the teeth and gums, is a mere fissure-like spaee,
except when the eheeks are inAated with air. It is into this
part of the mouth that the parotid duets open (p. 261).

MOUTH 365

Above and below^ it is bounded by the reflection of the
mueous membrane from the lips and eheeks on to the
alveolar margins of the maxilla and mandible. Anteriorly^
it opens upon the face by means of the oral fi§sure ; whilst
posieriorly^ it eommunieates, on eaeh side, with the cavity
6f the mouth proper through the interval between the last
molar tooth and the anterior border of the ramus of the
mandible. The existence of this eommunieation is of import-
anee in eases of spasmodie elosure of the jaws when all the
teeth are in plaee, beeause through it Auids may be introdueed
into the posterior part of the mouth proper.

In paralysis of the facial museles the lips and eheeks fall away from the
dental arehes and food is apt to lodge in the vestibule.

Oayum Oris Proprium. — The mouth proper is bounded
anteriorly and laterally by the gums and teeth, whilst posteriorly
it eommunieates by means of the i^hinus_fqudufn with the
pharynx. The floor is formed by the tongue and the mueous
membrane whieh eonneets it with the inner aspeet of the
mandible ; the root is vaulted, and is formedby the hard
an(i the soft palates. Into this pairt of the bueeal cavity the
duets of the submaxillary glands and the duets of the sub-
lingual glands open (p. 288). When the mouth is elosed
the dorsum of the tongue is usually applied more or less
elosely to the palate and the cavity is almost eompletely
obliterated.

The various parts whieh bound the oral cavity may now
be examined in turn.

Labia Oris. — The strueture of the lips has in a great
measure been examined already in the disseetion of the face
(P' ^'^'h)' Eaeh lip is eomposed of four layers : (i) Cuta-
neous; (2) museular; (3) glandular; and (4) mueous. The
skin and mueous membrane beeome eontinuous with eaeh
other at the free margin of the lip. From the inner aspeet
of the upper lip the mueous membrane is reflected to the
alveolar margin of the maxilla and from the inner aspeet of the
lower lip to the mandible. In eaeh ease it is raised in the
median plane in the form of a free fold termed the /renulum,
The museular layer eonstitutes the chief bulk of the lips. It
is formed by the orbieularis oris and the various museles
whieh converge upon the oral Assure. Numerous laUal
glands lie in the submueous tissue whieh intervenes between

366 HEAD AND NECK

the mueous membrane and the museular Abres. The duets
of these glands pieree the mueous membrane and open into
the vestibule. In eaeh hp there is an arterial areh formed
by the eorresponding labial arteries (p. 130).

The lymph vessels of both lips join the submaxillary
lymph glands, but some of the lymph yessels of the upper
lip pass to the supertietal parotid glands.

Buees. — Six layei5„enter into the eonstruetion of the
eheeksLa.lL of_wliich_haYe-]i£

FiG, 1+6, — The Sublingual Regioii in Ihe Inlerior of the Moulh.

of the faee_- (i) Skin ; (2) a fatty layer traversed by some of
the facial museles and the external m3xi!lary artery; (3)
the bueeo-pharyngeal aponeurosis; (4) the bueeinator musele;
(5) numerous bueea! glands, similar in eharaeter to the labial
glands, lie in the submueous tissue between the mueous mem-
brane and the bueeinator musele ; (6) the mueous membrane.
Four or five mueous glands of larger size, termed the tnolar
glands, oeeupy a more superficial position. They Iie either
external or internal to the bueeo-pharyngeal aponeurosis, elose
to the point where this is piereed by the parotid duet, and
their duets open into the vestibule of the mouth. The
buuo-pharyngeal aponeurosis is a dense fascia whieh covers the
bueeinator musele. Above and below, it is attaehed to

MOUTH

367

the alveolar portions of the maxilU and mandible, whilst
posteriorly it is eontinued over the pharyn». The museles
whieh traverse the fatty layer are chiefly the zygomaticus,
the risorius, and the posterior fibres of the platysma. The
parotid duet pierees the inner three layers of the eheek, and
opens into the vestibule of the mouth opposite the seeond
molar tooth of the maxilia.

aingiTie et Dentes. — The mueous membrane of the gums
is smooth, vascular, and firmly bound down to the subjacent

FlG. 147.- — Isihmus of the Fauces as seen through Ihe widdy opened Monlh.
The tonsils in the subject rrom whieh ihis drawing wiu made were
somewbat enlarged.

periosteum of the alveolar portions of the jaws by a stratum
of dense connective tissue. It is eontinuous on the one
hand with the mueous membrane of the lips and eheeks,
and on the other with the mueous membrane of the mouth
proper. The gums elosely embraee the neeks of the teeth.

In the adult the teeth in eaeh jaw number sisteen. From
the median line posteriorly, on eaeh side, they are the two
ineisors, the eanine, the two prasmolars, the three molars.

Hoor of the Uonth. — Tbe mueous membrane ts reflected
from the inner aspeet of the mandible to the side of the
tongue, but in the anterior part of the mouth the tongue lies

^ \

\~^

z: -r r --- r— :: .:.- : u -:_ ::i'~r-. inii iners rre miieoiis
T..-v. -..: - :r- .: - . - 7- ;:= i: r Tzm lee aee Qf the
::...: L ::. - " r-. :: T-iiie n ±:s rf*^on the

■ ■: : ":. - . - ::l- -:j :::^i:.. r^ii- "/t /'i-'r -'a^'Al-'t^Tui/u^
— : - L :".::.:■.::.:: L 7 ir*:: -r. i' :::»: 1: esrie s palled
1:: V ..-:_-. . r. :-.:._: : i: : . .li^ zic::iJ:rL.z^ ▼lI :e 5een to

■ \:=: iuiT^ 221 '^"7 virc3. £ach

: ..:-_: :-:sr TE ^Ee""?Sfi& ot the
:c-v-:::i rie siie :c ±e u

:j:c ^ ' :f :ze paj

--■T— -^- ^- - - -;■"■ -V^ :." :::e fu.:-:zg^vr:i:!3.
3mzct :f "ue 3£^a:i2. — 7i r i*ir-i i::«i ±:e ser: ralates fonii
::= :::-._:: ..t ::'.^:.it :-ic -ii.:*^ r:i:c :c rre moath (Fig.
: . . . 7? ; :•: : "^ r":3: :z.-: —-«iile :£ iie ri:scericr eee maigin
::' :ir :•: "■: z^j^iz. lz i r.ie^-::; -Tee :z.e iersm c£ the toi^e,
:-~.r *r. j -*--_ :«, fce.i 7.; :-* . ?^iz — g il.rng the median
.-.iz'"r! :■: :_: iTT .■Li.-i i_-'i ir-r 5.:i^ ruiiies is a raphe
■V _-..:_-. -.tri' ..:»:::: iz:ir.:r-- :-:j«::r::z ±.e ir:cL5ive ^oramen,

Ir. ±i^ i::::r. ;: y^:: ::" ::.i i^-ri r»ilj.:e lie nueeas membrane,
:r. ej.:.i ?.ie :f :ir riyir. :? ii::-5-=. in:o three or foiir
:7.ir.?v:r5c 11: i ::~i^i:::r? :: r.i^rs : =::re posteriorly it is
::.T.rj.ri::.e. ^r::::!. 7;. :irr:illv r^r^idsg the postero-
'.j.:rril i::^".f*? ::' :ir :ili:f :ie i:55o::jr s^i'.l be able to feel
:ir iir:i-: :f :i: r:ri:il ::rryg::i ljz:in:e.

Isihniis Fa::ci:iixL — rr.:? r.ii::e is ziven :o the eommuni-
c:i:::r. ■r-:-:vTrtr :ir ri:i:i yr:yer ir.d r:e pharyiut (Fig. 147).
To cb:i:r. 1 g::i v:r-v :: i: :r.e rieurh must be well opened
and :he ::r.i:-ie iryressed The isihn^us taudum and the
parrs whlih i :i::i :: ear. be exarii::ed best in the Iiving
subject«F> 147'. I: :s bvur.ded above by the soft palate,
below by :he d:rsiri of the rongue, a:id on eaeh side by two
curved tolds of mueous merr.brane, remied respectively the
areus glossopalatinus (O.T. anrerlor pillars of the fauces) and
the areus phar)-ngopalatinus (O.T. posterior pillars of the
fauces).

The areus palatini spring from the base of the uvula, and
areh laterally and then downwards. The areus glossopalatinus
inelines anteriorly as it deseends ; it ends upon the side of
tln: posterior part of the tongue, and it eneloses the glosso-

PHARYNX 369

palatinus musele. The areus pharyngopalatinus^ more strongly
niarked, inelmes posteriorly, and is lost upon the side of the
pharynx ; it eneloses the pharyngo-palatinus musele.

In the triangular interval whieh is formed by the divergence
of these two folds lies the tonsiL

Strietly speaking, the term isthmus /atieium should be confined to the
interval between the two glosso-palatine arehes, as the tonsil and the
pharyngo-palatine arehes belong to the lateral wall of the pharynx.

Pliax3rnz. — The pharynx is a wide museulo-aponeurotie
eanal, about 5 inehes long, whieh extends from the base of
the eranium to the level of the body of the sixth cervical
vertebra. There, at the lower border of the erieoid eartilage,
it beeomes eontinuous with the eesophagus. Plaeed posterior
to the nasal cavities, the mouth and the larynx, it serves as
the passage whieh eonduets air to and from the larynx, as well
as the food from the-mouth to the eesophagus.

Under ordinary eonditions it is expanded from side to
side and eompressed antero-posteriorly, so that it possesses
anterior and posterior walls and two lateral borders. Above the
level of the orifice of the larynx there is always sufficient
spaee for the passage of air to the lungs, but below the
orifice of the larynx the anterior and posterior walls are in
eontaet, except when separated by the passage of food.

It is widest above, at the base of the eranium, posterior
to the orifices of the auditory tubes (O.T. Eustaehian).
Thenee it narrows to the level of the hyoid bone. It widens
again at the level of the upper part of the larynx and then
rapidly narrows to its termination.

To obtain a proper idea of the eonneetions of the pharynx, the disseetor
should distend its walls moderately by stuffing it with tow. This may be
introdueed either from above, through the mouth, or from below, through
the oesophagus.

The pharynx will now present a somewhat ovoid form.
Posteriorly^ its wall is eomplete, and, when in position, it lies
anterior to the upper six cervical vertebrae, the prevertebral
museles, and the prevertebral fascia. To these it is bound
by some lax connectiv^ tissue whieh offers no impediment to
the movements of the eanal during the proeess of degluti-
tion. Laterallyy the pharynx is related to the great vessels
and nerves of the neek, as well as to the styloid proeess and
the museles whieh take origin from it. Upon this aspeet of

VOL. II — 24

370 HEAD AND NECK

the pharynx also is plaeed the pharyngeal plexus ot nerves,
whieh supplies its walls with motor and sensory twigs. An-
teriorly^ the pharyngeal wall is interrupted by the openings of
the nasal cavities, mouth, and larynx; and it is from the
struetures whieh lie in proximity to these apertures that it
derives its prineipal attaehments. Thus from above down-
wards it is attaehed on eaeh side — (a) to the medial pterygoid
lamina; (b) to the pterygo-mandibular raphe; (^)to the side
of the tongue ; (d) to the inner aspeet of the mandible ; (e)
to the hyoid bone ; (/) to the thyreoid eartilage ; (^) to the
erieoid eartilage. Above^ it is attaehed to the basis eraniL
These various attaehments will be studied more fully when
the eonstituent parts of its walls are disseeted.

It should be noted that an altogether false idea of the natural fonn of
the pharynx is obtained when it is examined in its present stuffed eondition,
and removed from the vertebral eolumn. When seen in transverse seetions
of the frozen body it will be noted that, with the exception of its upper or
nasal part, whieh remains patent under all eonditions, the anterior wall is
more or less nearly approximated to the posterior wall, and below the
opening of the lar^m^ it presents the appearanee of a simple transverse
slit.

Pharsmgeal Wall. — The wall of the pharynx eonsists of
four well-marked strata. These are from without inwards:
(i) bueeo-pharyngeal fascia; (2) pharyngeal museles ; (3)
pharyngeal aponeurosis; (4) mueous membrane. The
museular layer, whieh is eomposed of the three eonstrietor
museles, with the stylo-pharyngeus and pharyngo-palatinus
on eaeh side, must now be disseeted.

For this purpose plaee the preparation so that the ehin rests upon a
bloek and the pharynx hangs downwards with its posterior surface
towards the disseetor. The eonstrietor museles should now be carefully
eleaned, in the direetion of the museular fibres, by removing the bueeo-
pharyngeal fascia, whieh covers them.

Bueeo-pharyngeal Fascia. — This is a eoating of fibrous
tissue whieh ensheaths both the bueeinator and the pharyn-
geal museles.

Yenae Pharynge». — Upon the posterior wall and lateral
borders of the pharynx the disseetor should notiee numerous
veins joined together in a plexiform manner. These eon-
stitute the pharyngeal venous plexus^ whieh eolleets blood
from the pharynx, soft palate, and prevertebral region. It
eommunieates with the pterygoid plexus and the cavernous
sinus. Two or more ehannels lead the blood from it to the

PHARYNK

371

intemal jugular vein. This venous plexus, together with the
phar^mgeal plexus of neTves, will iequire to be remoyed in
order to display the museles properly,

OonstrietoT Unseles. — The eonstrietor museles are three
curved sheets of museukr iibres whieh are so arranged that
they overlap eaeh other from below upwards ; thus, the

t. Middie eonstrietor.

g. Thyteo-byoid.

^. Hyoglouus.

i- Stylo-hyind.

/. Mylo-hyoid.
tn. Crico.tbyreoid.

j*. Stylo-hymd Ligameni

1. Si

laryngeal ne

14S.-

inferior eonstrietor overlaps the lower part of the middle
eonstrietor, whilst the middle eonstrietor, in tum, overIaps the
'lower part of the superior eonstriotor, The three museles are
inserted, in the median plane, into the median raphe whieh
deseends from the basilar portion of the oeeipital bone along
the posterior aspeet of the pharynx.

MusmIus Constrictor Pharyngts Inferior (Fig. 148, f). —

372 HEAD AND NECK

The inferior eonstrietor musele is relatively short anteriorly
at its origin, and relatively long posteriorly, where it blends with
the fellow of the opposite side in the median raphe of the
posterior wall of the pharynx. It arises from the posterior
part of the side of the erieoid eartilage, and from the
inferior eornu, the oblique line, and the upper border of
the thyreoid eartilage. The musele curves posteriorly and
medially around the pharyngeal wall to meet its fellow of
the opposite side in the median raphe. The lower fibres take
a horizontal direetion, but the remainder aseend, with inereas-
ing degrees of obliquity, until the highest fibres reaeh the raphe
at a point a short distanee below the basis eranii. The lower
margin of the inferior eonstrietor overlaps the eommeneement
of the oesophagus, and the inferior laryngeal nerve and the
laryngeal braneh of the inferior thyreoid artery pass upwards,
under cover of it, to reaeh the larynx.

Museulus Constrictor Pharyngis Medius, — This is a fan-
shaped musele (Fig. 148, e\ It arises from the great and
small eornua of the hyoid bone and from the lower part of
the stylo-hyoid ligament. From this origin its fibres pass
round the pharyngeal wall, to be inserted with the eorre-
sponding fibres of the opposite side into the median raphe.
As they pass postero-medially, the lowest fibres deseend,
the highest aseend, and the intermediate fibres run horizontally.
The lower portion of this musele is overlapped by the
inferior eonstrietor, and in the interval whieh separates the
margins of the museles anteriorly, opposite the thyreo-hyoid
interval, the internal laryngeal nerve and the laryngeal braneh
of the superior thyreoid artery will be seen piereing the
thyreo-hyoid membrane to gain the interior of the pharynx.

Dissedion. — The superior eonstrietor possesses a somewhat eomplieated
origin, and to bring this fully into view it will be neeessary to eut through
the internal pterygoid musele about its middle, if this has not already been
done (p. 293), and turn the upper and lower portions aside.

Museulus Gonstrietor Pharyngis Superior (Fig. 148, d\ —
The superior eonstrietor has a weak but eontinuous line
of origin from the following parts : {a) the lower third of
the posterior border of the medial pterygoid lamina and its *
hamulus ; (b) the pterygo-mandibular raphe, whieh is eommon
to it and the bueeinator musele; {e) the posterior end of the
mylo-hyoid ridge on the inner aspeet of the mandible ; (i) the
mueous membrane of the mouth and side of the tongue.

PHARYNX 373

From tliis somewhat extensive origin, the fibres curve postero-
medially to reaeh the median raphe, whilst, as a rule, some
of the highest gain a distinet insertion into the pharyngeal
tuberele on the under surface of the basi-oeeipital bone.

The lower part of the superior eonstrietor is overlapped
by the middle eonstrietor, and the stylo-pharyngeus passes into
the interval between the two as it deseends to its insertion
(Fig. 148, «). The upper border of the musele, whieh is
free and ereseentie, falls short of the basis eranii.

Baphe Pterygo-mandibularis (Fig. 148, q). — This is a
strong, narrow, tendinous band, whieh extends from the
hamulus of the medial pterygoid lamina to the posterior
part of the mylo-hyoid ridge of the mandible. It aets as
a tendinous bond of union between the bueeinator and
superior eonstrietor museles, and its eonneetions ean be
appreeiated best by introdueing the finger into the mouth
and pressing laterally along the eourse of the raphe.

Sinus of MorgagiiL — This name is applied to the semi-
lunar spaee whieh intervenes between the upper ereseentie
margin of the superior eonstrietor and the basis eranii.
The deficiency in the museular wall of the pharynx in this
region is eompensated for by the inereased strength of the
pharyngeal aponeurosis, whieh, in this situation, is ealled the
pharyngo-basilar fascia. In eontaet with the outer surface of
the aponeurosis are two museles belonging to the soft palate
— viz. the ievator veli palatini and the tensor veli palaiini (Fig.
1 48, c and S). The levator, whieh is rounded and Aeshy, lies
posterior to the tensor, whieh is flat and more tendinous.
The tensor ean readily be reeognised from its position in
relation to the deep surface of the internal pterygoid musele
and from its tendon turning medially under the hamulus of
the medial pterygoid lamina. In the upper part of the spaee,
elose to the basis eranii and between the origin of the two
museles, will be seen the auditory tube (O.T. EustaeMan tube).

Phaiyngeal Aponeurosis. — The upper part of the pharyn-
geal aponeurosis, the pharyngo-basilar /asda^ is strong, and it
maintains the integrity of the wall of the pharynx where the
museular fibres are absent. As it is traeed downwards it
gradually beeomes weaker, until it is ultimately lost as a
disjtinct layer. It lies between the musdes and mueous mem-
brane and eomes to the surface only where the museles are
absent It is the prineipal means by whieh the pharynx is

II— 24a

374 HEAD AND NECK

attaehed to the base of the skull, and it is united also to the
auditory tubes and the bony margins of the ehoana.

extreniity of Ihis eul, the knife should be C!
biisis eranii. The stuffing should be remo'
the phatyns eleansed.

Interior of tlio Pharysi. — The mueous membrane is now
exposed, and it should be noted that it is eontinuous,

PHARYNX 375

through the various apertures whieh open into the pharynx,
with the mueous membrane of the nasal cavities^ the auditory
tubes and tympanie cavities, the tnouth proper^ the larynx, and
the oesophagus,

Raeemose glands^ whieh lie immediately subjacent to the
mueous membrane and seerete mueus, are present in great
numbers. There are also numerous lymph /ollieles^ and
in eertain loealities these are aggregated together into large
masses (the tonsils and the pharyngeal tonsil). These will
be studied with the regions of the pharynx in whieh they
are plaeed.

The soft palate projects into the pharynx, posterior to
the isthmus faucium, and divides the cavity of the pharynx
into an upper and a lower part. The upper part^ ealled
the naso - pharynx^ eommunieates with the nasal cavities
and the tympanie cavities by four apertures, viz. the two
ehoanae (O.T. posterior nares) and the two auditory tubes
(O.T. Eustaehian tubes).

The lower portion of the pharynx may be regarded as
eonsisting of an oral part^ whieh lies posterior to the
mouth and tongue, and a laryngeal part^ plaeed posterior
to the larynx. Below the soft palate there are three
openings into the pharynx, viz. the opening of ihe mouth or
isthmus /aueiumy the opening of the larynx, and the opening of
the oesophagus,

Pars Nasalis. — The naso-pharynx is situated immediately
posterior to the nasal cavities and below the body of the
sphenoid and the basilar part of the oeeipital bone. It is the
widest part of the pharynx. Its walls, except the soft palate,
are not eapable of movement, and, consequently, its cavity
always remains patent, and presents under all eonditions very
mueh the same form.

In its anterior boundary are the ehoanae, through whieh it
opens into the nasal cavities. The ehoanee are two oblong
orifices whieh slope from the base of the eranium downwards
and anteriorly to the posterior border of the hard palate.
Eaeh is an ineh long and half an ineh wide, and it is separated
from its fellow by the posterior part of the septum nasi, whieh
in this region is formed by the vomer. By looking through
the ehoanae a partial view of the lower two meatuses of the
nose and of the posterior ends of the middle and inferior
eonehae may be obtained.
11—24 h

376 HEAD AND NECK

On the lateral wall of the naso-pharynx, on eaeh side, is
seen the orifice of the auditory tube, and posterior to it the
pharyngeal reeess. The ostium pharyngeum of the auditory
tube lies immediately posterior to the lower part of the
eorresponding ehoana, at a level whieh eorresponds elosely
with the posterior end of the inferior eoneha. It is bounded
above and posteriorly by a prominent and rounded margin
termed the torus tubarius^ whieh is altogether deficient below
and anteriorly. A fold of mueous membrane, termed the
salpingo-pharyngeal fold^ deseends upon the lateral wall of the
pharynx from the posterior lip of the orifice of the auditory
tube. As this is traeed downwards it gradually disappears.

The disseetor should pass a Eustaehian eatheter through the nose into
the auditory tube. Hold the eatheter with the point downwards. Pass it
posteriorly through the right nasal cavity, along the septum of the nose, to
the posterior wall of the pharynx. Pull it towards the palate till the bent end
of the eatheter eatehes against the baek of the hard palate. Turn the point
through a quarter of a eirele to the right side of the head and it will enter
the right auditory tube. If it is desired to eatheterise the left auditory tube
pass the eatheter through the left nasal cavity, and in the final stage tum the
point to the left side.

In the natural eondition of parts there is a deep reeess
on the lateral wall of the naso-pharynx immediately posterior
to the prominent posterior lip of the orifice of the auditory
tube. This is termed the lateral reeess of the pharynx.

The roof and posterior wall of the naso-pharynx are not
marked off from eaeh other. They form together a eontinuous
curved surface. The upper portion of this surface looks
downwards and may be regarded as the roof ; the lower portion,
whieh looks anteriorly, eonstitutes the posterior wall. The roof
is formed by the basilar part of the oeeipital bone, and
also by a small part of the under surface of the basi-sphenoid,
covered with a dense periosteum and a thiek eoating of mueous
membrane. The posterior wall is supported posteriorly by
the anterior areh of the atlas and the anterior surface of the
epistropheus. In that part of the roof whieh lies between the
two lateral reeesses of the naso-pharynx there is a marked
eolleetion of lymphoid tissue, the pharyngeal tonsil, Over its
surface the mueous membrane is thiekened and wrinkled, and
in its lower part a small median pit, termed the pharyngeal
bursa, may usually be found ; it is just large enough to admit
the point of a fine probe.

The fioor of the naso-pharynx is formed by the curved,

PHARVNX

377

sloping upper surface of the soft palate. Between the posterior
border of the soft palate and the posterior wall of the pharynx
there is an interval, termed the pharyngeal hihmus, through
whieh the naso-pharynx eonnmunieates with the oral pharynx.

Il is imporlant to nole that the posterior wall and rixtf or the naso-
pharynx ean be explored by the tinger introdueed through the mouth and
the pharyngeal isthmus.

When the naso-pharynx is illuminated. by lighl reAeeled froin a mirror

introdueed thtough the mouth, a view of the four oritiees whieh open into
this patt of the pharynn may be obtained. Owing to the mitror being
plaeed obliquely, and lielow the level of the bard palate, only the posterior
parts of the infeiior eoneha; are risible through the ehoanEe, and the inferior
meatuses of the nose are aitogether out of sight. The mitidle and superior
meatuses of the nose and the middle and superior eonehEe, however, ean
be btought into view and their eondition aseertained. The lateral walls
of the naso-pharynx and the oriiiees of the auditory tubes ean also be fu11y
inspeeted.

Pars Oralis. — The oral pharynx hes posterior to the mouth
and tongue. The pharyngeal part of the tongue, whieh looks

378 HEAD AND NECK

more or less direetly posteriorly, forms its anterior wall in its
lower part. Above this is the isthmus of the fauces, or
the opening into the mouth, limited on either side by the
glosso-palatine areh. These arehes may be regarded, there-
fore, as the lateral boundary lines between the mouth and the
pharynx. On the lateralwall of the oral pharynx the pharyngo-
palatine areh forms a prominent fold whieh is gradually lost
as it is traeed downwards. Within this fold is the pharyngo-
palatine musele. This is an important relation, beeause the
posterior palatine arehes form the lateral boundaries of
the pharyngeal isthmus, and by the eontraetion of the
pharyngo-palatine museles the two posterior arehes ean be
approximated until the opening of the isthmus is obliterated ;
the passage of food and Auids from the oral pharynx into
the naso-pharynx is thus prevented.

The areus glosso-palatinus and the areus pharyngo-palatinus
form, on eaeh lateral wall of the oral pharynx, the anterior and
posterior limits of a triangular interval in whieh is lodged the
tonsil. The upper part of this area, above the level of the
tonsil, presents a small depression termed the supra'tonsillar
fossa,

In the ehild, and not uneommonly in the adult, a triangular
fold of mueous membrane, the pliea triangularis^ extends
posteriorly from the lower part of the glosso-palatine areh
and the base of the tongue aeross the surface of the tonsil.
The upper border of the fold may be free or it may beeome
attaehed to a greater or less extent to the surface of the
tonsil.

Pars Larsmgea. — The laryngeal portion of the pharyngeal
cavity diminishes rapidly in width to the level at whieh it be-
eomes eontinuous with the oesophagus. In its anterior wall, from
above downwards, may be seen : (i) the epiglottis; (2) the
superior aperture of the larynx with the reeessus piriformis on
either side ; and (3) the posterior surfaces of the arytaenoid
and erieoid eartilages, covered with museles and mueous
membrane.

Aditus Laryngis. — The superior aperture of the larynxy
situated below the pharyngeal part of the tongue, is a
large, obliquely plaeed opening whieh slopes rapidly from
above downwards and posteriorly. It is somewhat triangular
in outline, and the basal part of the opening, plaeed above and
anteriorly, is formed by the free border of the epiglottis.

PHARVNX 379

Posteriorly, the opening rapidly narrows, and tinally ends in
the interval between the two arytsenoid earlilages. The
sides of the aperture are formed by two sharp and prominent
folds of mueous membrane, termed the ary-epiglottie fo/ds,
whieh eonneet the lateral margins of the epiglottis wiih the
aryt£enoid eartilages. Two small nodules of eartilage, in the
posterior part of eaeh ary-epiglottie fold, give rise to two
rounded eminenees, of whieh the anterior is the cuneiform
tuberde, and the posterior the eornieulate tuberde.

On either side of the lower part of the laryngeal open-
ing there is a small three-sided or pyramidal depression,
ealled the reeeisus piriformis. On the lateral side it is

bounded by the posterior part of the lamina of the thyreoid
eartilage and the thyreo-hyoid membrane ; on the medial side _
by the aryttenoid eartilage and the ary-epiglottie fold ; whilst its
posterior wall is formed by the posterior wall of the pharynx,
when ihis is in plaee. The reeessus piriformis presents a
wide entranee, whieh iooks upwards ; but it rapidly narrows
towards the bottom (Figs. isoand 151); and it is important to
the surgeon beeause in this little poeket foreign bodies intro-
dueed into the pharynx are liable to be eaught.

Below the opening of the Iarynx, the anterior and posterior
walls of the pharynx are always elosely applied to eaeh other,
except during the passage of food.

;/ opening is plaeed opposite the lower border

38o HEAD AND NECK

of the erieoid eartilage. This is the narrowest part of the
pharynx.

Velum Palatinum. — The soft palate is a movable eurtain,
whieh projects downwards and posteriorly into the pharynx.
During deglutition it is raised, and helps to shut off the
nasal part of the pharynx from the portion below. Anteriorly^
it is attaehed to the posterior margin of the hard palate ; on
eaeh side it is eonneeted with the lateral wall of the pharynx ;
whilst posteriorly it presents a free border. From the eentre
of this free margin the eonieal proeess, termed the umla^
projects ; whilst the sharp concave part of the border, on either
side of the uvula, beeomes eontinuous with the pharyngo-
palatine areh, whieh deseends on the side wall of the pharynx.
The upper surface of the soft palate is convex and eontinuous
with the floor of the nasal cavities; the inferior surface is
concave and forms part of the vaulted roof of the mouth.
From the posterior part of this surface on eaeh side a glosso-
palatine areh curves downwards ; and along its median plane
may be seen a slightly marked median ridge or raphe.

The soft palate is eomposed of a fold of mueous membrane,
between the two layers of whieh are interposed museular,
aponeurotie, and glandular struetures, together with blood
vessels and nerves.

(The two levatores veli palatini.
The two tensores veli palatini.
The two glosso-palatini.
The two pharyngo-palatini.
The museulus uvul8e.
Palatal aponeurosis.
Palatal glands.

{Aseending palatine from external maxillary.
Palatine braneh from aseending pharyngeal.
Twigs from the deseending palatine braneh of the internal
maxillary.
Middle palatine, . . . ^

• I

T^, J Posterior palatine, . . I from the spheno - palatine

JNerves, . \ T^ranehes ^— ->.o,„«™i X ^.«„i;^«

plexus,

Branehes from pharyngeal \ ganglion.

The raeemose mueous glands in the soft palate form a very
thiek layer, immediately subjacent to the mueous membrane
whieh elothes its inferior surface. Glose to the posterior
border of the hard palate the soft palate eontains very few
museular fibres; there it is eomposed chiefly of the two
layers of mueous membrane enelosing the glands, and the
palatal aponeurosis.

PHARYNX 381

Disseetion. — The disseetion of the soft palate is difficult, and it is only
in a fresh part that the preeise relations of the different museular layers
ean be made out. Begin by rendering it tense by means of a hook, and
then remove carefully the mueous membrane from its upper and lower
surfaces, and also from the glosso- and pharyngo-palatine arehes. The
latter proeeeding will expose the glosso - palatine and the pharyngo-
palatine museles on eaeh side.

Museulus Glosso-palatinus. — The glosso-palatinus is a
delieate museular slip, whieh arises from the side of the
posterior part of the tongue and curves upwards and medially
to reaeh the under surface of the soft palate, above the
glandular layer. There its iibres spread out and beeome
eontinuous with the eorresponding fasciculi of the opposite
side. It forms the lowest museular stratum of the soft
palate.

Museulus PhaoTngo-palatinus. — The pharyngo-palatinus
forms two museular strata in the soft palate whieh enelose,
between them, the museulus uyulae and the levatores palati
museles. The upper layer is very weak and confined to the
posterior part of the velum. It eonstitutes the most super-
ficial museular stratum on the upper aspeet of the soft palate,
and beeomes eontinuous with the eorresponding portion of the
musele of the opposite side. The deeper layer takes origin
from the posterior margin of the palate bone and from the
palatal aponeurosis, and some of its fibres mingle with those
of the eorresponding musele of the opposite side. Lateral to
the soft palate the two strata eome together, and are joined
by one or two delieate museular slips whieh spring from the
lower border of the eartilage of the auditory tube. These
slips are sometimes deseribed as the salpingo-pharyngeus museie,
The pharyngo-palatinus, thus formed, arehes downwards and
posteriorly in the posterior areh of the fauces, and spreads
out into a thin sheet of fibres in the wall of the pharynx.
Blending to some extent with the stylo-pharyngeus, it is inserted
into the posterior border of the thyreoid eartilage. Some of
its fibres, however, ineline posteriorly and are inserted into
the pharyngeal aponeurosis.

Museulus UvulsB. — This delieate musele is plaeed on the
upper aspeet of the soft palate, and, posteriorly, it is covered
by the superficial fibres of the pharyngo-palatinus. These
must be removed to expose it fully. It eonsists of two
minute slips whieh, as a rule, arise from the posterior nasal
spine of the hard palate, and lie one on either side of the

382 HEAD AND NECK

median plane. As they pass posteriorly into the uvula they
unite into a single rounded museular bundle.

Disseetion, — The levator palati musele has been seen already on the
outer aspeet of the pharynx in the sinus of Morgagni. To display it from
the inside it is neeessary to remove the wall of the pharynx between the
auditory tube above and the upper border of the superior eonstrietor
below, and then follow its fibres into the soft palate. In a well-injected
subject the disseetor will observe the aseending palatine artery in rela-
tion to this musele.

Museulus Levator Veli Palatini. — The levator palati is a
rounded Aeshy musele whieh arises from the lower and medial
border of the eartilage of the auditory tube, and from the
rough surface on the under aspeet of the apex of the petrous
part of the temporal bone. It passes downwards and an-
teriorly, erosses the upper border of the superior eonstrietor,
pierees the pharyngeal aponeurosis, passes below the orifice of
the auditory tube and enters the soft palate. There its fibres
spread out below the uvular musele and above the anterior
or deep portion of the pharyngo-palatinus. Anteriorly, some
of the fibres are inserted into the palatal aponeurosis; but
more posteriorly, the majority of the fibres beeome eontinu-
ous with the eorresponding fasciculi of the opposite side.

Museulus Tensor Veli Palatini. — The origin of the tensor
veli palatini and the relations of its museular belly were noted on
p. 293. The musele deseends from the base of the skuU along
the lateral surface of the medial pterygoid lamina, and ends
in a tendon whieh turns horizontalIy towards the median plane,
below the hamulus, where a bursa mueosa facilitates the play
of the tendon on the bone. In the soft palate the tendon ex-
pands below the lower layer of the pharyngo-palatinus, and some
of its fibres blend with the palatal aponeurosis whilst others
gain attaehment to the horizontal part of the palate bone.

Palatal Aponeurosis. — The palatal aponeurosis extends
posteriorly from the posterior margin of the hard palate to
give strength and support to the soft palate. At first it
is strongly marked, but it weakens rapidly as it passes
posteriorly. The small portion of the soft palate whieh it
supports eontains few museular fibres, and remains always
more or less horizontal in position. The mueh more extensive
posterior museular part of the soft palate eonstitutes the
movable sloping portion. The tensor palati operates upon
the anterior aponeurotie portion of the soft palate.

PHARYNX 383

Yessels and Nerve8 of the 8oft Palate. — The aseending
palatine braneh of the extemal maxillary artery is, as a rule,
the prineipal art^ry of supply to the soft palate. It has
already been traeed on the wall of the pharynx (p. 299),
where it lies in the sinus of Morgagni, in relation to the
levator palati musele, whieh it aeeompanies into the soft palate.
Th^palatine braneh of the aseending pharyngeal artery may
also be traeed into the soft palate. In eases where the
preeeding artery is small, this twig will be found enlarged
so as to take its plaee (p. 304). The deseending palatine
braneh of the internal maxillary artery also sends small twigs
to the soft palate and tonsil.

Two nerues enter the soft palatie from the spheno-palatine ganglion — viz.
the posterior palatine and the middle palatine nerue. It would appear,
however, that they do not supply the museles, but are distributed to the
mueous membrane. The levator palati, the museulus uvul3e, the glosso-
palatinus, and the pharyngo-palatinus are supplied by twigs from the
pharyngeal branehes of the vagus, whieh convey to them fibres whieh are
originally derived from the eerebral part of theaeeessory nerve {v. p. 315)
(W. Aldren Tumer). The tensor palati is probably supplied by the
braneh whieh it receives from the otie ganglion, whieh conveys to it fibres
originally derived from the motor part of uie trigeminal nerve.

Tonsillae Palatinse. — The mlatine tonsils are two prominent
masses of lymphoid tissue, plaeed one on* eaeh lateral wall
of the pharynx, in the triangular interyal between the two
palatine aret^es and immediately above the pharyngeal'part
of 4h£_J;pngue. The pharyngeal or internal surface of the
tonsil is eoyered with mueous membrane and presents a
number of oriiiees whieh lead into erypts or reeesses in its
substanee. The deep or external surtaee is embedded in the
pharyngeal wall and is supported by the superior eonstrietpr
musele of the pharynx (see p. 2q8). It is covered by a^layer
of fibrous tissue whieh forms an ineomplete eapsule for the
organ. It is important to note that between the tonsil and
the superior eonstrietor there is some lax connective tissue, so
that the organ ean be pulled forwards by the volsellum with-
out dragging the wall of the pharynx with it

The tonsils have a rieh blood-supply, They derive arterial
twigs from the tonsillar and aseending palatine branehes of
the external maidllary. the deseending palatine braneh of the
internal maxillary, the aseending phaiyngeal, and the dorsalis
linguae.

Tuba Auditiva (O.T. Enstaehiaii Tube). — ^This is the

384 HEAD AND NECK

■

eanal whieh conveys air from the pharynx to the tympanie
cavity. It is divided into two portions, aeeording to the parts
whieh enter into the eonstruetion of its wall. Thus, in the
lateral part of its eourse, as it nears the tympanie cavity, its
wall is bony, and it runs in the interval between the tympanie
and petrous portions of the temporal bone. The medial part
eonsists mainly of eartilage. It is plaeed on the base of the
skull, and is lodged in the gutter or groove between the
petrous part of the temporal bone and the great wing of the
sphenoid. This is the subdivision of the tube whieh eomes
under the notiee of the disseetor at the present stage, and
he should first note its direetion and then study its relations
and the eonstruetion of its wall.

The direetion of the eanal ean be readily aseertained by
passing a probe into it through its pharyngeal orifice. It runs
postero-laterally with a slight inelination upwards and passes
first above and then to the lateral side of the levator palati,
and along the medial side of the upper part of the tensor palati.
It lies, therefore, in a eonsiderable part of its extent between
the two museles.

Before removing the mueous membrane from the
pharyngeal part of the tube the disseetor should note that at
the lower margin of the orifice there is a prominent rounded
eminenee, the levator eushion^ due to the subjacent levator veli
palatini. The removal of the mueous membrane will reveal the
fact that the wall of the tube is formed, in great part, by a
triangular plate of eartilage, whieh is folded upon itself so
as to proteet the tube on its upper and medial aspeets. The
eartilage is deficient below and laterally, its plaee being
taken by dense fibrous tissue, whieh eonneets the margins
of the eartilage and eompletes the wall of the eanal. The
projecting free base of the eartilage gives rise to the torus
tubarius already examined on the lateral wall of the naso-
pharynx (p. 376). A museular slip, whieh deseends from the
lateral margin of the eartilage, in relation to the outer un-
proteeted side of the tube, has been termed the dilatator tubee
(Rudinger). It joins the tensor palati. The interior of the
tube is lined with mueous membrane eontinuous with that
of the pharynx and the tympanie cavity ; and its ealibre varies
eonsiderably in different parts of its eourse. It is narrowest
at a point termed the isthmus^ situated at the junction of
the osseous and eartilaginous parts. As the tube is traeed

CAROTID CAXAL -5?

thenee to the phaiyni it gradually inerease? ir. c::2:':'re:. mi
attains its greatest widlh at its opening in:o the liasr-TeunTL]

GAROTID GANAU

The earotid eanal, whieh traverses the interieir of tbe
petrous part of the temporal bone, oontains tbe internal
earotid artery, the intemal earotid eondnuation of the oerrkaLl
sympathetie and a plexus of veins,

Disseetion, — The earotid eanal may be opened np br retoaraa^ its
inferior wall with the bone forcep6. In doing this, it is x>oii Deeessair to
interfere with the auditory tube, whieh lies in dose proadmiir. The dis-
seetion must be made on one side only.

Arteria Garotis Intema. — The intemal earotid artei>- in
this part of its eourse is about three-quarters of an ineh long.
At first it aseends yertieally ; then, bending suddenly, it nins
horizontal]y antero-medially. It emerges from the eanal at
the apex of the petrous bone and enters the foramen laeeram,
where it turns upwards, pierees the extemal layer of the duia
mater^ and enters the middle fossa of the skulL From this
point onwards the internal earotid artery has been examined
already (p. 331). Whilst within the earotid eanal it lies
below and anterior to the eoehlea and the tympanie cavity.
The great superficial petrosal nerve and the semilunar
ganglion are plaeed above it, but are separated from it by a
thin plate of bone, whieh is, however, sometimes absent

Nenrus Garotieus Intemus. — The disseetor has already
noted this large braneh proeeeding from the upper end of
the superior cervical ganglion and entering the earotid eanal
with the internal earotid artery. It divides almost im-
mediately into two parts, whieh are plaeed on either side of
the artery. Eaeh of these soon divides into a number of
branehes whieh eommunieate together around the internal
earotid artery forming the intemal earotid piexus. The
further disseetion of these branehes is a matter of some
difficulty, and ean be satisfactorily eflfected only under
speeially favourable eireumstanees.

At the posterior end of the cavemous sinus a ganglion is sometimes
found in the plexus, and where the sixth nerve erosses the internal earotid
artery the plexus is very dense. This part is known as the eauemous
plexus. At the anterior end of the cavemoas sinus the earotid plexus

YOL. 11 — ^25

386 HEAD AND NECK

breaks up into branehes whieh aeeompany the anterior and middle eerebral
arteries.

The internal earotid plexus eommunieates with the tympanie plexus by
means of superior and inferiorcarotico-tympanic branehes given off in the
earotid eanal, and with the spheno-palatine ganglion by the great deep
petrosal braneh, whieh unites with the great superBeial petrosal of the facial
nerve to form the nerve of the pterygoid eanal (O.T. Vidian). It gives
branehes also to the semilunar ganglion, the third, fourth, sixth and the
ophthalmie braneh of the fifth nerve, and a braneh whieh aeeompanies the
naso-eiliary nerve into the orbit and joins the eiliary ganglion.

NERYUS MAXILLARIS.

As the maxillary nerve passes anteriorly, from the semilunar
ganglion to the face, it traverses the foramen rotundum, the
upper part of the pterygo-palatine fossa, the pterygo-maxillary
fissure, the inferior orbital fissure and the infra-orbital eanal.
The disseetor should therefore proeeed to expose the nerve
in these loealities.

Disseetion. — Remove the temporal musele and the upper head of the
external pterygoid musele, and, plaeing the saw upon the eut margin of the
skull at a point immediately above the external meatus, earry it obliquely
downwards and anteriorly through the squamous part of the temporid
bone and the great wing of the sphenoid, towards the medial end of the
superior orbital fissure. This saw-eut should enter the superior orbital
fissure immediately to the lateral side of the foramen rotundum. A
seeond saw-eut should then be made from the eut margin of the eranial
wall, immediately above the anterior margin of the great wing of the
sphenoid bone, downwards into the superior orbital fissure to meet the first
saw-eut. The wedge-shaped pieee of bone ineluded between these euts
ean now be removed. Additional spaee may be obtained, and the pterygo-
palatine fossa may be more fully opened up, by removing what remains of
the great wing of the sphenoid upon the lateral side of the foramen rotundum,
but the circumference of this aperture must be carefully preserved. Proeeed,
in the next plaee, to open up the infra-orbital eanal. In its posterior part
its upper wall is usually so thin that it ean easily be removed by a pair
of disseeting forceps, but anteriorly it sinks deeply under the lower part of
the rim of the orbital opening, and here the ehisel must be employed.
The maxillary nerve ean now be defined and its branehes displayed.
The infra - orbital artery and vein, whieh aeeompany the nerve in the
infra-orbital eanal, will be exposed at the same time.

Nennis Maxillaris. — The maxillary nerve springs from the
semilunar ganglion within the eranial cavity (p. 330). It is
eomposed entirely of sensory fibres, and passes anteriorly,
outside the dura mater and in relation to the lower part of the
cavernous sinus, to the foramen rotundum through whieh it
enters the pterygo-palatine fossa. It erosses the upper part
of this fossa, curves laterally through the pterygo-maxillary

NERVUS MAKILLARIS

387

fissure into the infra-teinpora! fossa, and, near the middle
of the inferior orbital fissure, enters the infra-orbital eanal,
where it receives the name of infra-orbital. The infra-
orbitat eanal traverses the floor of the orbit, whieh, it should
be remembered, forms the roof of the masillary sinus
also, Finally, the nerve emerges upon the face through
the infra-orbital foramen, and breaks up, under cover of the
quadratus labii superioris, into numerous branehes whieh
form a dense plexus with twigs from the facial nerre. Its

F[G. 152. — Diagiam i>f (he Maxillary Nerve.

termina] fitamen[s are distributed to the lower eyelid, the
nose, and the upper lip. The eourse of the maxillary nerve
may be separated into five stages, in eaeh of whieh branehes
are given ofF. These are : —

c (already deseribed).
superior alTeolat.
. In the inlia-OTbital TMiddle supeiioi B]veolar.
eanal, . . . \ Anlerior superior alveolaj'.
CPalpebraI,\
5. In the laee, . . \ Nasal, l- alteady deseribed.
|.Ubial, )

3SS HEAD AND NECK

The z\^t>'nti/:\- m^rre, whieh has already been disseeted
in ihe orbii, ean now be traeed to its origin from the
maxillary ner>-e in the int'ra-temporal fossa. The spheno-
palatiiu hranekis are two stout twigs whieh arise from the
under aspeet of the maxillary ner>-e, and proeeed vertically
downwards, in the pter\-go-palatine ^ossa, to the spheno-palatine
ganglion. of whieh ihey eonsiirute the s^nsery roots,

Xerri A!:eo'ans Su/rn'i^rts. — These are usually three in
number, and are distinguished as posterior, m^ddle, and
anterior. The middle superior alveolar ner\-e is sometimes
absent as a separate trunk, in whieh ease it arises in eommon
with the anterior superior alveolar braneh.

The p^sUrier su/^W a/z't\\\ir naree takes origin in the
infra-temporal fossa, and almost immediately diN-ides into
two branehes, whieh proeeed downwards upon the posterior
aspeet of the body of the maxilla. They eontribute a few
fine filaments to the mueous membrane of the eheek and
to the gum, and then disapp>ear into the minute posterior
dental foramina to supply the three molar teeth and the lining
membrane of the maxillar\' sinus.

The middU superior aJzY.'/ar mrre supplies the two
premolar teeth. It arises from the infra-orbital nerve, and
ean be easily deteeted (when present) by gently raising the
parent trunk from the floor of the infra-orbital eanaL It
deseends in a minute eanal whieh traverses the lateral wall
of the maxillan* sinus.

The anterior su/<rrior a/reo/ar «irrcv, mueh the laigest of
the three alveolar branehes, springs from the infra-orbital as it
approaehes the anterior j\irt of the eanal. It ean be brought
into view by raising the j>arent trunk from the floor of the
eanal, and it will then be seen to enter a speeial bony tunnel
whieh traverses the maxilla in the anterior wall of the
maxillary sinus. The disseetor should endeavour to open
up this eanal with ihe ehisel. After supplying a braneh to
the mueous membrane of the lowor and anterior part of
the nasal cavity, the anterior superior aheolar nerve diyides
into branehes for the ineisor and the eanine teeth.

WTiile traversing the ma\illa. ihe ihree superior aIveolar branehes
eommunieate wiih eaeh oihor. ami form iwo nerve-loops (Fig. 152).
Numerous twigs proeeed from these, and ioin in a tine plexus. It is from
this plexus that the terminal tilamonts to the toeih and gum take origin.

Arteria Infi:a-orbitali3. — The infm-orbital artery is a

NASAL CAVITIES 389

braneh of the intemal maxillary. It arises in the pterygo-
palatine fossa and aeeompanies the infra-orbital nerve. In
the face its terminal twigs anastomose with branehes of the
external maxillary, transverse facial, and bueeinator arteries ;
in the infra-orbital eanal it gives some fine branehes to the
eontents of the orbital cavity, and also the anterior superior
alveolar artery whieh aeeompanies the nerve of that name,
and supplies the ineisor and eanine teeth, and the lining
membrane of the maxillary sinus.

The in/ra-orbttal vein joins the pterygoid plexus.

NASAL CAVITIES.

Disseetion, — The portion of the mandible whieh still remains, te^ether
with the tongue and larynx, must now be removed from the upper part of
the skuU. From the angle of the mouth on eaeh side earry the knife
posteriorly, through the bueeinator and the mueous membrane of the eheek,
the pterygo-mandibular raphe, and the lateral wall of the pharynx. The
internal pterygoid musele has been divided already, but it will be neeessary
to eut the intemal earotid artery, the smaller vessels whieh are still un-
divided and the nerves whieh still eonneet the pharynx with the skull. The
larynx and tongue must be laid aside for iuture disseetion.

The anterior part of the skull should next be divided into two lateral parts
by sawing through it in the sagitta]* direetion elose to one side of the nasal
septum. As a general rule the nasal septum is not vertical, but deviates
more or less to one or other side of the median plane. This deviation is
more frequently direeted to the right than to the left side. Endeavour to
determine the direetion whieh it takes in the skuU under observation,
by passing a probe into the nasal cavity through the ehoanae. The
seetion through the skuU should be made elose to the concave side of the
septum. Begin anteriorly by introdueing a knife into the nostril of that side,
and earry it upwards through the eartilaginous part of the nose to the nasal
bone. Then plaee the speeimen so that the face rests upon the table, and
divide the sort palate in the median plane. The seetion may now be
eompleted by sawing through the hard palate and bony roof of the nasal
cavity to the side of the median plane. The disseetor should make every
effort to preserve the septum of the nose intaet. As a general rule the
upper eoneha is partially injured. This is not a very serious matter, as
the lateral aspeet of the nasal cavity ean be studied upon the opposite side
when the septum of the nose has been removed.

Septum Nasi. — The nasal jeptum 4^^^^^^ the cavity of
the nose into two t\'^tccv» eh^mhers — ^the "gl^t ^"^ ^^^^ naeai
eayities. It is not plaeed aeeurately in the median plane,
but" almost invariably shows a bulging or deviation to one
or other side (more frequently to the right side). Im-
mediately above the orifice of the nostril or anterior aperture
of the nasal cavity, the septum shows a slight depression,

39°
whieh

HEAD AND NECK

eorresponds to the vestibule of the nose, and forms
the raedial wall of this subdivision ot the nasal cavity.
The vestibular part of the partition is elothed with skin,
eontinuous with the external integument ; from this a
number of sti£f hairs, termed vibriua, project. Over the
rest of its extent the septum nasi is covered with mueous
membrane, whieh is elosely adherent to the subjacent peri-
osteum forming with it a mueo-periosteum; and it is

separable into two distriets, viz., a lower or respiraiory
area, and a mueh smaller upper or olfactory area, eomprising
noi more than the upper third of the septum, in whieh
branehes of the olfactory nerve spread out. The respiratory
mueous membrane is very ihiek and spongy. It is highly
vascular and eontains numerous mueous glands. The minute
oriRees of the gland duets ean be deteeted by the naked
eye. Over the olfactory distriet of the septum the mueous
membrane is softer and more delieate, and not so Ihiek. In
the fresh state it presents a yellowtsh eolour, and the glands
are smaller.

NASAL CAVITIES 391

In favourable eases a minute orifice may be deteeted in the mueous
membrane, on the lower and anterior part of the nasal septum, immediately
posterior to the vestibular area. It is plaeed above the anterior end of a
well-marked elongated projection whieh passes obliquely posteriorly and
upwards, and eorresponds to the thiekened lower margin of the septal
eartilage. This aperture varies in diameter from ^ mm. to ij mm.
(Sehwalbe). It leads into a narrow eanal, whieh passes posteriorly for
a short distanee, and then ends blindly. It is of interest beeause it
represents in the human subject the rudiment of the vomero-nasal organ
(O.T. ormn of Tacohpn\. a tubular strueture whieh is highly developed in
some of tne lower animals.

Constnufbion of the Nasal Septum. — Strip the mueo-
periosteum from the exposed surface of the septum nasi and
the parts forming the septum will be rendered visible. The
bulk of the partition is eomposed of the perpendieular lamina
of the ethmoid and the vomer posteriorly, and of the septal
eartilage anteriorly. Small portions of other bones take a
minor part in its eonstruetion. Thus, ^bo^^ apd posteriorly
there are the erest and rostnim of the sphengid ; above and
anteriorly is the nasal spine of the frontal bone : whilst below
there is the erest of bone formed hy the apposition of tlie
palatSTproeesses of the palate and maxillary bones of opposite
sides.

Gartilago Septi Nasi. — The septal eartilage fills up the
wide angular gap whieh intervenes between the perpendieular
lamina of the ethmoid and the vomer, and it projects anteriorly
towards the point of the nose. It is a broad irregularly
quadrilateral plate. Its upper and posterior border is in ap-
position with the anterior border of the perpendieular lamina
of the ethmoid ; its lower and posterior border^ mueh thiekened,
is received into the groove in the anterior border of the vomer
and the nasal erest of the maxillse. The angle between these
two borders is prolonged posteriorly, for a varying distanee,
in the form of a tongue-shaped eartilaginous proeess, whieh
oeeupies the interval between the two plates of the vomer.
The upper and anterior border of the septal eartilage is in
eontaet above with the suture between the two nasal bones ;
below this it is related to the two lateral eartilages of the
nose, whilst still lower down it is seen in the interval between
the two larger alar eartilages.

Its eonneetion with the lateral eartilage on eaeh side is a very intimate
one ; indeed, below the nasal bones, the three eartilages are direetly
eontinuous, but lower down they are separated by a fissure whieh runs
upwards for some distanee on eaeh side. The lower and anterior border is
very short ; it is free, and extends posteriorly to the anterior nasal spine.

392 HEAD AND NECK

The anterior angle of the septal eartilage is blunt and rounded, and does not
reaeh to the point of the nose, whieh is fonned by the alar eartilages.

The deyiation of the septum nasi from the median plane will now (in all
probability) be seen to be due to a bulgiiTg to one side of the yogier and
perpendieular lamina ot tiie ethmoid along their line of unionl It is not
deveIoped until after the seventh year.

Disseetion. — The septal eartilage and thin bony part of the septum
must now be removed pieeemeal. This must be done very carefully, as
it is neeessary to preserve intaet the mueo-periosteum whieh elothes the
opposite side of the septum. It is in this mueo-periosteum that the nerves
and blood vessels must be examined.

Yessels and Nenres of the Septum Nasi. — The following
is a list of the nerves : —

Nervesof Smell, . OIfactory.

[ I. Naso-palatine.

Nerves of Gommon

2. Medial nasal braneh of the anterior eth-
moidal nerve.

sensation, . . | 3. Nasal branehes from spheno-palatine

I ganglion and from the nerve of the

l, pterygoid eanal (O.T. Vidian).

The Medial Group of Olfactory Nerues, — These nerves are
distributed in the mueo-periosteum of the upper part of the nasal
septum and are barely distinguishable, except in a fresh part ;
further, they are so soft that it is hardly possible to isolate
them. They enter the nasal cavity through the medial series
of apertures in the cribriform plate of the ethmoid, and pro-
eeed downwards in grooves on the surface of the perpen-
dieular lamina of the same bone.

Neruus Naso-palatinus, — The naso-palatine nerve is a
long slender twig whieh ean easily be deteeted upon the deep
surface of the mueo-periosteum of the septum. It springs from
spheno-palatine ganglion, and enters the nasal cavity through
the spheno-palatine foramen. In the first part of its eourse
it runs medially upon the inferior surface of the body of the
sphenoid. Having gained the nasal septum, it ehanges its
direetion and passes downwards and anteriorly, in a shallow
groove on the surface of the vomer under cover of the mugo-
periosteum. Finally it enters the foramen of Searpa, and,
where the two foramina of Searpa open into the eommon
incisive foramen, the neryes of opposite sides unit^ in a plexus
from whieh branehes are given to the mueous membrane
covering the anterior part of the \y^xc{ palatp, The naso-
palatine nerve is aeeompanied bv the posterior nasal septal
artery; and, as it hes on the surface of the vomer^ it supplies
Rpmp sir?\)l twigg to the mueo-periosteum of the septum nasi.

NASAL CAVITIES 393

A few nasai brgnehts froin the spheno-palatine ^an^lion^ and
also from the nerye of the pterygoid eanal^ reaeh the mueo-
periosteum over the superior and posterior part of the septum.
They are very minute, and it is questionable if the disseetor
will be able to discover any traee of them in an ordinar}- part.

The medial nasal branehes of the anterior ethmoidal nerye
will be found deseending over the anterior part of the nasal
septum. They may be traeed as far as the vestibule.

The arteries whieh convey blood to the septum nasi are :
(i) the posterior nasal septal, whieh aeeompanies the naso-
palatine nerve ; (2) a braneh of the anterior ethmoidal aeeom-
panying the medial branehes of the anterior ethmoidal nerve ;
(3) some minute twigs to the upper part of the septum from
the posterior ethmoidal artery ; (4) the septal braneh of the
superior labial artery, whieh is distributed upon the eolumna
nasi.

Disseetion, — The mueo-periosteum of the septum may now be divided,
by the seissors, along the roof of the nasal cavity. Before doing this,
disengage from its surface the naso-palatine nerve and the medial branehes
of the anterior ethmoidal nerve, in order that they may be aiterwards traeed
to their origins. When the layer of mueo-periosteum, thus detaehed from
the roof of the nose, is thrown down the nasal cavity is expo6ed.

Cava Na.si. — The nasal cavities are two ehambers plaeed
one on eaeh side of the septum nasL They are narrow, but
the vertical depth and antero-posterior length of eaeh cavity
is very eonsiderable. The width inereases somewhat from
above downwards; thus, in the upper part, the superior
eoneha is separated from the septum by an interval of only
2 mm., whilst lower down a spaee of 4 or 5 mm. intervenes
between the inferior eoneha and the septum. £ach nasal
cavity presents a medial wall formed by the septum, a lateral
wall, a roof, a floor, and an anterior and a posterior aperture.

The anterior apertures of the nasal cavities, or nostrils, are
two oval orifices whieh open upon the face and look down-
wards. The posterior apertures^ or ciestf^i open into the naso-
pharynx and look posteriorly and downwards.

The narrow roo/ of the nasal cavity eonsists of an inter-
mediate horizontal portion formed by the cribriform plate of
th£_ethmoid bone, and of an anterior and a posterior sloping
part. The anterior part is formed by the narrow grooyed
nasal surface of the irontal spine of the ^rontal bone^ the
nasal bone, and the angle between the lateral eartilage and

394 HEAD AND NECK

the septal eartilage. The posUrior pari of the roofJs_COffi-
posed (>f the aniprifir and iinder siirfaces of the bodv of the
SEhenoid, and also of the ala of the yornei, tIie_S2henoidaJ
proeess of the palale bone, and the. vaginal proeess of the
medial pterygoid lamina, all of whieh are apphed to the under
suitaee of the sphenoidal body.

The^^r of the nasal cavity is of eonsiderable width. It is
formed by the palatal proeesses of the maxilla and the palate
ljones, and is concave from side to side. Purther, it presents
a. gentle antprn-pnstprior slnpp, being slightly higher anteriorly
tlpn posteriorly. On the anterior part of the iioor, and elose
n(; the septum nasi, the disseetor may see a minute funtiel-
shaped depression of the tniiro-perinstpum into Ihe ineisiye
tbramen. This is of interest ftom a developmental poTnt ol
view ; for it is a vestige of the extensive eommunieation whieh

NASAL CAVITIES 395

existed injlie_enibryo between the ea^UkS-OLllie-^iose and the
mouth.

Lateral Wall of the Nasal Gayity. — The lateral wall of
the nasal cavity is rendered uneven and eomplieated by the
projection of the threeeonehae (O.T. turbinal bones).

The part whieh the different bones take in the formation of ihe lateral
wall of the cavity of the nose must in the first plaee be studied in a
sagittal seetion through the maeerated skull, and the disseetor should
eonstantly refer to sueh a preparation during the disseetion. Anteriorly, il
is formed by the lateral earlilage, the alar eartilage, the nasal bone» andthe

is lormea Dy tne laterai eariiiage, tne aiareartugge, tne nasai Done» anu tne
frontal^rocess of the maxijjg. MorejStl5orly the laerimal» the *;thninid-
and the mfenor concha,'with a small portion of the bo^y of the msueilla,

enter into its eonstruetion ; whilst still more posteriorly are the perpen-
dieular part of the palate bone and the medial pterygoid lamina 01 the
sphenoid. Plaeed in relation to the lateral aspeet of this wall are the
ethmoidal air-eells, whieh intervene between the upper part of the nasal
cavity and the orbit, whilst, at a lower level, the great air sinus of the
maxilla, the maxillary sinus, is situated immediately to the lateral side of
the nasal cavity (Fig. 154).

Tuming now to the disseetion, the disseetor will see that
the lateral wall is separable into three areas or' distriets.
These are — (i) the vestibule; (2) the atrium meatus medii ;
(3) the repion of the eonehas and theinteryening meatuses.

Yestibulum Nasi-^^he vestibular part (Fig. 155, 6, 6')
of the lateral wall is a depression of a somewhat oval form
plaeed immediately above the aperture of the nostril. It is
partially divided into anjipper and lower portion by a short
ridge, whichj)rojects anteriorly from its posterior boundarv :
and it is HnthpH throughout with integument enntini^^^ns with
the_skin. From this anumber of stout, stiff hairs^ termed
yibrissa^ project (Fig. 155, 5). The vibrissae whieh spring
from the anterior part of the region ineline posteriorly, whilst
those wEiehare implapted into tbe posterior part are direeted
anteriiirly ; in this manner a sieve-likearrangement is proyided
at the_aiiterior aperture of the n^e. The vestibular part of
the lateral wall is plaeed opposite the eorresponding area on
the septum nasi, and the two together eonstitute an ampullated
entranee to the nasal cavity. The eapaeity and shape of this
seetion of the cavity is inAueneed to a eertain extent by the
eontraetion of the nasal museles.

Atr^Tim Meatns Medii — ^This part of the lateral wall of the
nasal cavity (Fig. 155, s) is plaeed above, and slightly posterior
to the vestibular distriet, and it receives its name from the
fact that it lies immediately anterior to the middle meatus.

39« -

HEAD AND NECK

It is slightly hoUowed out and concave, and at its upper pait,
near the nasal bone, a feeble eleyation termed the agger nasi
may be notieed ; this begins elose to the anterior part of the
attaehed margin of the middle eoneha, and runs obliquely

FiG. 155.— Laleral Wall of ihe Left Nasal Cavity. (From Sehwalbe.)

,. PronlalairsLnus.

11. Keeessus sphcni>4Ihn]oidiilis.

0. Fr«borderorihcnssslbonc.

4. Sphenadal air >JTiiis.

S. Vibrisaa.

16. Pliea naso-phaiyngea.

7. Elerad™ inl«v«,mg belwesn fhe

ij. Moalus naso-phaiyogms.

yeslibular disiriei aiid ihe atrium.

18. Oriiiee of auditory lube.

19. Posteriot lip oF audilory lulie.

ao. LaleralrteessoTpharynK.

0. eoneha suprenm. ^

a, i, c. Fr« border of ibe niiddle lonehs

down.ffiardajjii?nteriorly. It represents an additional eoneba
whieh is present in some mammals. A slight depression
above the agRer nasi. whieh leads posteriorly to the nlfart(irv
distriet of the lateral wall of the nasal cavi ty, is the sukus
olfactorius.^^ ^

Coiiclfe (O.T. turtinal bones). — Posterior to theyestibule

'*'«)U!a..

NASAL CAVITIES 397

and the atrium are the eonehae with the intervening meatuses.
The superior egneha (Fig. 155, 12), whieh projects from the
labyrinth of the ethmoid bone, is very short, and is plaeed
on the upper and posterior part of tht^ lateral wall of the
cavity. Its free border begins a short distanee below the
centre^of the cribriform plate, and passes obliguely down-
wards^ and posteriorly to a point immediately below the
body of the sghenoid, where it ends. The middle eoneha
(Fig. 155, 14) also is a part of the ethmoid. Its free border
begins a short distanee below the anterior end of the eribri-
forna42laJ:e, and at first takes a vertical eourse downwards ; then,
bending suddenly^ it passes posteriorly. and it ends midway
between the body of the sphenoid and the posterior border
of the hard palate. The inferior eoneha (Fig. 155, 15) is an
independent bone ; it extends posteriorly upon the lateral
wall ^f the nasal cavity, midway between the middle eoneha
and the tloor of the npse. Its lower free margin is some-
what convex downwards.

Meatus Nasi. — The superior meatus (Fig. 155, 13) is a short
narrow fissure between the superior and middle eonehae.
The posterior ethmoidal eells open into its upper and anterior
partbyone, or, m some eases, by several apertures.

To bring these orifices into view, the superior eoneha should be
turned aside by introdueing the blade of a pair of forceps under its entire
length, and forcing it upwards. Care should be taken not to injure the
mueous membrane more than is neeessary.

The middle meatus is a mueh more roomy passage whieh
extends posteriorly fram the atrium, between the middle and
inferior eonehae.

The middle eoneha should be forcibly tilted upwards and posteriorly,

The upper and anterior part of the middle meatus leads into
a funnel-shaped passage whieh runs upwards into the eorre-
sponding frontal sinus. This passage, the intundibulum^ eon-
stitu1;es th^rhannel of eommunieation bet^een— the-iroiltal
sinus, and the nasal cavi ty .

Upon the Jateral wall of the middle meatus a deep curved
groove or gutter, whieh eommenees at thp infnnHihnhim and
runs frgm_ abo:ye downwards and post^norly. will be_seen.
In this grooye, whieh is termed the hiSS^ semilunaris (Fig.
156), are the openings of the anterior ethmoidal eells and

39» HEAD AND NECK

the ojaxillary. sinus. The upper boundary of the hiatus
semilunaris is prominent and bulging. It is termed the bulla
eihnwidalis. On or above the bulla is the aperture of the
niiddle "ethmoidal eells (Fig. 156). The sUt-like opening of
the maxillary sinus lies in the posterior part of the hiatus
semilunaris.

Tbe disseetoi should now open up the niaxillary sinus by remoTing
its laleral wall. This may be done by sawing upwards Ihrough the toot of
the lygoiUBlie proeess of the maxilla.

means of whieh this great air s

munieates with the middle meatus lies in the medial wall
of the cavity mueh nearer the roof than the iioor — a position
highly unfavourable for the eseape of Auids whieh may
eolleet in it. Sometimes, however, a seeond orifice, eireular
/ in outline, will be found. This is situated lower down ; when
it is present it opens into the middle meatus, immediately
above the middle point of the attaehed margin of the inferior
eoneha.

The diaseetor should note Ihat, on aeeount of the relationship of the
intundibulum to Ibe hiatus seiniluna.ris and of the lallei lo the opening
of the mixillaiy sinus, there is a tendeney, in some eases, for the » ' '
of the frontal sinuses lo flow into the masillary sinus.

NASAL CAVITIES 399

The inferiQr_jumius is the horizoniaL_passage whieh lies
between the inferior eoneha and the floor and lateral wall
of the nasal cavity. It is plaeed-pDsterior to the yestibule,
and the fre£__hQrder of the iiiferior_concha turns downwards
and limits it anteriorly (Fig. 156). On this aeeount, and
beeause its floor slopes downwards and posteriorly, the in-
ferior meatus is more aeeessible to the eurrent of expired
air than to the eurrent of inspired air. In the anterior part
of this meatus will be found the opening of the naso-laerimal
duet whieh conveys the tears to the nasal cavity (Fig. 156).

To bring the aperture of the naso-laerimal eanal into view, remove
a small portion of the anterior part of the inferior eoneha with the
seissors.

The orifice of the naso-laerimal duet varies in form,
aeeording to the manner in whieh the mueous membrane is
arranged around it. Sometimes it is wide, patent, and eireular ;
at other times the mueous membrane is prolonged over
the opening, redueing its size and aeting as a flap valve to
the orifice. In some eases, indeed, the orifice may be so
minute that it is difficult to find. Its eontinuity with
the laerimal sae should in all eases be established by passing
a probe from above downwards through the naso-laerimal
eanal (Fig. 64).

Kfourth meatus is generally present on the lateral wall of
the nasal cavity. This is due to the partial subdivision of
the superior eoneha into an upper and lower part by a short
groove whieh proeeeds anteriorly from the anterior aspeet
of the body of the sphenoid. This additional meatus is
termed the reeessus si)heno-ethmoidalis^ and in its posterior
part is the aperture ot the sphenoidal air sinus (Fig. 156).
This orifice may be eireular or slit-like, aeeording to the
manner in whieh the mueous membrane is disposed around
it.^ The upper portion of the superior eoneha whieh
is plaeed above this additional meatus is ealled the eoneha
suprema (Fig. 155, 10).

To the narrow cleft-like portion of the nasal cavity whieh
extends from the roof to the floor between the septum
medially and the eonehae laterally the term meatus eommunis
is applied; and the part of the cavity whieh lies posterior

^ When the reeessus spheno-ethmoidalis is absent, the sphenoidal air siniis
opens into the intenral between the roof of the nasal cavity and the superior
eoneha.

4oc HEAD AND NECK

to ihe einehal repon, i::id herween ii and the ehoans,
is tbe nasc-fi*in^^^' y-^'v> *F^. 155. -.-l

11 neo-periosteum of the lAtoil Wall of tlie GaTnm NasL
— Ii has been noted tha: iher^iibele :s lined with integument
The remainder of the Latera] wall ^s well 35 the roof and floor
of the naal tossa. is T.ned with muiyr^ Tn^mhran^* wKlrh j«^
so eloselY blended with the yiiSpripnt ppn'rwai^nnn that the
two ^are inseparable and form a nmeo-periosteum. This
is eonnnuous throuj:h the naso-!acr:n:al duet with the oeular

conju|xcti\-a, through the ^]}ri.-^^I^^~J!p^!I!lI!^ ^^^ ^^^ dp1itratf*
lining membrane oi :he air>ctel]s whieh open into the nas^
cavity, and through^ ih^ ^hnany ir^T}^ the phar)-pgf>al rnnnnTta
membrane. On the lateral wall. as on the septum, the
mueo-periosteum is^ mapped out into an upp^r nlfa^t»ry aP<3l
a lower resp:ratorv ponion. This subdivision eannot be
appreeiated by the naked eye. for the one distriet passes
into the other wi:hout any sharp line of demareatioiu The
olftutory rigion eomprises merely the upper eoneha; the
respiratory n^.en ineludes the middle and inferior eonehse, the
middle meatus, the lower meatus. and the atrium. In the lower
pait of the lateral wall the mueo-periosteum is thiek and
spongy. This is partieularly notieeable over the lower borders
and posterior extremities of the middle and inferior eonehae,
where the membrane presents an irregular surface and forms
soft bulging eushions. This eondiiion is largely due to the
presenee of a rieh venous ple^us, the vessels of whieh nin
for the most part in an antero-posterior direetion. In the
ease of the lower eoneha, the veins are so numerous
that the mueo-periosteum assumes the eharaeter of cavemous
tissue, andJg^ometimes spoken of as the *'yectile body."
When turgiawith blood it swells out and obliterates the
inter\'al between the eoneha and the septum. The mueo-
periosteum oi the floor, meatuses, and the atrium, is
smoother than, and not so thiek as, that over the eonehse.
Ever)'where numerous mueous glands are embedded in it,
and the minute punctiform orifices of the duets are yisible to
the naked eye. In the olfactor}' region the lining membrane
of the nose, in the fresh state, is of a yellowish eolpur, and
it is softer andmore delicatg..ihati_in_ths^resjniratory part

The great yaseularity of the mueous membrane Qf the pose
is doubtless (or^the purpose of moistening and raising the
temperature of the inspired^dr.

NASAL CAVmES 401

Nerve8 and Ves8el8 on tlie Lateral Wall of the Hasal

Cavity : —

Nerves of Smell, . 01factory nenres. »±jAM

fi, Lateral nasal branehes of anterior ethmoidalA / ^^^
2. Nasal braneh oF anterior supenpr alveolar.C^' ^^**
Nerves of Gommon 3. Posterior superior nasal branehes from spheno-^
Sensation, . / palatme ganglion and from the nerve ot the

pterygoia eanal.
,4. Two postenor inferior nasal branehes frqm the
antenor palatine nerve.

The olfactory neroes are from twelve to twenty fine filaments
whieh spring from the lower surface^n(i' llie eAtiemity Of the
olfactofy„bulb, and, passing through the apertures in the eribri-
form plate of the ethmoid Jnto the nasal cavity, they separate
into a lateral and a medial grmip. To eaeh nerve an inyest-
mentTrom the eerebral membranes is given. The niedMot
sei>tal neryes were deseribed on p. ,^q 2 . The lateral nerues
deseend in the mueo-periosteum on the lateral wall of the nasal
cavitY. At first lodged in shallow grooves or minntp bogy
eai^als, they SOOn diyide into bunehes of hranrheg^whir^isprpari
out over the upper eoneha and the region immediately below.
The disseetion of these neryes is exceedingly difficult, butjn
a well-preserved part ^hpy r^n gpn^rally be partially displayed.

The posterior superior nasal nerves^ whieh eome from the
spheno-palatine ganglion and from the nerve of the pterygoid
eanal, are minute filaments, but the disseetor should nevertheless
endeavour to traee them to their distribution upon the lateral-
wall. Theyenter the nose through the spheno-palatine foramen,
whieh is situated at ttie posterior end of the superior meatus.

The best plan to adopt for their display is to traee the largest of the
group, the naso-palatine nerve, whieh has already been exposed on the nasal
septum, laterally aeross the roof of the nasal cavity. This will lead the
disseetor to the foramen, and by carefully disseeting the mueo-periosteum
in its neighbourhood the other nenres of the group may be deteoted as they
enter the nasal cavity.

They are distributed to the mueo-periosteum over the upper
and middle eonehse, and the posterior part of the Aeptum.

The inferior nasal nerues are two in number; they both
arise from the anterior palatine nerve.

Make a vertical ineision, through the mueo-periosteum over tbe posterior
part of the medial pterygoid lamina, and carefully raise the membrane
from the posterior part of the lateral wall of the nasal cavity.

The upper of the two inferior nasal nerves will be found
emerging through a small aperture in the perpendieular part
YOL. II — 26

402 HEAD AND NECK

of the palate bone, at a point between the posterior extremities
of the middle and inferior eonehge. It divides into an aseend-
ing and deseending braneh. Both nin anterioriy ; the former on
the middle eoneha, the latter on the inferior eoneha. The lawer
of the two inferior nasal nerves appears through a foramen
in the perpendieular part of the palate bone, immediately
posterior to the inferior eoneha, upon whieh it is distributed.

The anterior ethmoidal nerue (O.T. nasat) should be ex-
posed as it deseends in the groove upon the deep surface of
the nasal bone (p. 393). It gives medial branehes to the
septum, and lateral branehes to the mueo-periosteum over the
anterior part of the lateral wall, and to the anterior parts of
the middle and inferior eonehae.

The main artery of supply to the nasal mueo-periosteum
is the spheno-palatine^ a braneh of the internal maxillary. It
gains entranee to the nasal cavity through the spheno-palatine
foramen, in eompany with the posterior superior nasal neryes.
The septal braneh of this vessel aeeompanies the naso-palatine
nerve, whilst others are distributed upon the lateral wall of the
cavity. Several twigs are given also by the deseending palatine
braneh of the internal maxillary and the two ethmoidal arteries^
but these are small and will be seen only in eases where the
injection of the subject has been unusually successful.

SPHENO-PALATINE GANGLION AND INTERNAL

MAXILLARY ARTERY.

The spheno-palatine ganglion is situated in the pterygo-
palatine fossa on the lateral side of the spheno-palatine fora-
men ; and at this stage it ean be exposed best by disseeting
from the medial or nasal side.

Disseetion. — The mueo-periosteum has already been removed irom
the posterior part of the lateral wall of the nasal cavity, and the inferior
nasal branehes of the anterior palatine nerve have been found piereing the
perpendieular part of the palate bone. The disseetor eannot fail to notiee
the eourse taken by the trunk from whieh these filaments arise. The lamina
of bone whieh forms the medial wall of the pter^'go-palatine eanal is so
thin that the nerve ean bc distinetly seen through it. By carefully opening
up this eanal with a ehisel, and following the anterior palatine nerve upwards,
the disseetor will be led to the ganglion in the pterygo-palatine fossa.
The naso-palatine nerve should at the same time be traeed to its origin.
The ganglion is so hemmed in by the bony walls of the fossa that it is very
difficult to display it thoroughly ; but by removing the orbital proeess of the

SPHENO-PALATINE GANGLION 405

palate bone, and a portion of the body of the sphenoid, with the bone
forceps, it may be more or less satisfactorily exposed. In the same
restrieted spaee will be found the terminal portion of the internal maxillary
artery, from whieh numerous branehes are given off.

Ganglion Spheno-palatinum. — This is a small, triangular
Aattened body, whieh is lodged in the pterygo-palatine fossa.
It is embedded in soft fat, and is surrounded by the ter-
minal branehes of the internal maxillary artery. Two stout
spheno - palatine branehes deseend from the maxillary nerve
and join it from above, but only eertain of their fibres
are involved in the ganglion ; the remainder are eontinued
direetly into the nasal and palatine nerves whieh proeeed
from the ganglion. The spheno-palatine branehes may be
regarded as eonstituting the sensory roots of the ganglion.

From the splieno-palatine ganglion branehes are given oflf
whieh radiate in four direetions — viz., medially to the nose ;
downwards to the palate ; posteriorly to establish eonneetions
with the facial nerve and earotid plexus, as well as to supply
the mueous membrane of the pharynx ; and anteriorly to the
orbit.

Medial branehes, . Posterior superior nasal nerves.

'Anterior palatine.
Middle palatine.
Posterior palatine.
Nerve of pterygoid eanal.
Some lateral posterior superior nasal
branehes.
Anterior branehes, . Orbital.

Deseending branehes,
Posterior branehes, .

From the internal maxillary artery twigs are given oflf
whieh aeeompany these nerves.

Posterior Superior Nasal Nerues, — There are two groups of
the posterior superior nasal nerves, a medial and a lateraL
The medial branehes pass through the spheno - palatine
foramen and aeross the roof of the nasal cavity to the posterior
part of the septum. The largest of them, the naso-palatine
nerve, runs downwards and anteriorly in a groove on the
surface of the vomer (p. 392). Some of the branehes of the
lateral posterior group also pass through the spheno-palatine
foramen and are distributed to the superior meatus, to the
superior and middle eonehae, and to the posterior ethmoidal
air eells. Other branehes of the lateral group pass posteriorly,
some in the mueo-periosteum of the upper and posterior part
of the nasal cavity, and one in the pharyngeal eanal (O.T.

II— 26«

404 HEAD AND NECK

pterygo-palatine or pharyngeal nerve). They are distributed
to the mueo-periosteum of the posterior part of the roof of
the nasal cavity, to the adjacent parts of the wall of the
pharynx, to the sphenoidal air sinus, and to the pharyngeal
part of the auditory tube.

The deseending branehes are the palatine nerves, and with
them are ineorporated the posterior inferior nasal nerves.
The palatine nerves are three in number, anterior (O.T. great
or posterior palatine), middle, and posterior. As a rule these
spring by a eommon trunk from the lower aspeet of the
ganglion. The trunk deseends in the pterygo-palatine eanal,
whieh has been opened up already, but to expose the
nerves a dense iibrous investment must also be removed.
The nerve-trunk will then be seen breaking up into its eon-
stituent parts.

Disseetion, — Traee, in the first instanee, the two smaller nerves — viz.,
the middle and posterior palatine branehes. These leave the main eanal
and enter the small palatine eanals, whieh eonduet them through the
pyramidal proeess of the palate bone. Before opening these up it is well
to seeure the nerves as they emerge from the lower openings of the eanals.
This ean very readily be done, by disseeting posterior to the hamulus of
the medial pterygoid lamina and gently separating the soft parts from
the under aspeet of the pyramid of the palate bone. As the disseetion
is being made from the inside, the middle palatitte nerve will be first en-
eountered, and it will be seen to pass posteriorly into the soft palate,
under cover of the tendinous expansion of the tensor veli palatini.^ This
must be divided, in order that the nerve may be followed to its distribu-
tion. The posterior palatine nerue will be found issuing from its eanal a
short distanee to the lateral side of the preeeding nerve. It is distributed
to the soft palate in the neighbourhood of the tonsil. It is smaller than
the middle palatine nerve, and is sometimes absent. The large anterior
palatine nerue should now be followed onwards to the hard palate. To
do this the lower part of the palatine eanal must be opened up by removing
a small portion of the posterior and lateral part of the horizontal plate of
the palate bone.

The a?iterior palatine nerue is the largest braneh of the
spheno-palatine ganglion. It deseends through the pterygo-
palatine eanal, aeeompanied by the great palatine braneh of
the internal maxillary artery ; it enters the palate through the
great palatine foramen and runs anteriorly, in a groove on the
lower aspeet of the hard palate, towards the incisive foramen.
It supplies the gum, the mueous membrane, and the glands
of the vault of the mouth ; and, in the neighbourhood of the
incisive foramen, it eommunieates with the naso-palatine

^ The present is a good opportunity to observe the eomigated or wrinkled
appearanee of the tendon of the tensor palati, as it passes under the hamulus.

SPHENO-PALATINE GANGLION 405

nerve. As it passes down the pterygo-palatine eanal the
posterior inferior nasal branehes, whieh were enelosed in
its sheath, leave it and enter the nasal cavity (p. 401).

In traeing the anterior palatine nerve in the palate,
the disseetor should note the numerous glands whieh are
plaeed under the mueous membrane of the vault of the
mouth, and the manner in whieh these indent the bone.^

Disseetion. — Gonsiderable difficulty will be experienced in exposing the
nerves in the pharyngeal and pterygoid eanals^ whieh are very inaeeessible.

To open up the pharyngeal eanal the sphenoidal proeess of the
palate bone must be eautiously removed with the bone forceps, and then
the disseetor should proeeed to open up the pterygoid eanal (O.T. Vidian),
whieh traverses the root of the pterygoid proeess. As the bone is very
hard and brittle at this point, the disseetion must be effected very carefully.

The neroe of the pharyngeal eanal belongs to the posterior
superior nasal group (p. 403).

Neruus Canalis Pterygoidei (O.T. Vidian), — The nerve
of the pterygoid eanal is formed by a junction between the
great superficial petrosal braneh of the laeial and the great
deep petrosal braneh of the earotid plexus. It traverses the
pterygoid eanal, and joins the posterior aspeet of the spheno-
palatine ganglion, of whieh it may be eonsidered to repre-
sent both the motor and sympathetie root, In the eanal it
is invested by a strong iibrous envelope, and when this is
removed it may sometimes be notieed to break up into a
fine plexus whieh surrounds the aeeompanying artery. It
has already been seen to give some fine filaments to the
mueo-periosteum of the nose.

The Rami Orbitales, — The orbital branehes of the ganglion
are exceedingly minute ; they pass anteriorly through the
inferior orbital fissure to supply the periosteum of the orbit.

Termination of Intemal Maxillary Artery. — The intemal
maxillary artery breaks up into its terminal branehes in the-
pterygo-palatine fossa. They are —

1. Posterior superior alveolar (p. 271).

2. The infra-orbital (p. 388).

3. The deseending palatine.

4. The spheno-palatine.

The Deseending Palatine Artery, — The deseending palatine

^ An equally good method of traeing the anterior palatine nerve is to
remove the palatal proeesses of the palate and maxilla with the bone
forceps, and then to display the nerve and artery on the upper surfaces of
the mueous membrane and glands.

4o6 HEAD AND NECK

artery is a terminal braneh of the internal maxillary artery.
As it deseends in the pterygo-palatine fossa it gives ofr, usually,
the artery of the pterygoid eanal, and as it enters the pterygo-
palatine eanal several small palatine arteries spring from it ;
then it beeomes the great palatine artery, The great palatine
artery deseends through the great palatine fQtamen into the
hard palate; there it runs anteriorly to reaeh the incisive
foramen, through whieh it passes into the nasal cavity to
anastomose with the posterior artery of the septum, whieh is
an offset of the spheno-palatine artery.

The stnall palatine arteries^ whieh spring from the deseend-
ing palatine, immediately before it beeomes the great palatine
artery, in the upper part of the pterygo-palatine eanal ; they
deseend through the small palatine eanals, and are distributed
to the soft palate, the palatine arehes, anti to the tonsil.

The Spheno-palatine Artery. — The spheno-palatine artery
enters the nasal cavity through the spheno-palatine foramen.
It gives off (i) a braneh to the sphenoidal air sinus, (2) a
braneh whieh passes posteriorly to the upper part of the
pharynx through the pharyngeal eanal (O.T. pterygo-palatine
artery) to be distributed to the roof of the posterior part of
the nasal cavity and to the roof of the pharynx ; this braneh
anastomoses with the aseending pharyngeal artery. Then the
spheno-palatine artery divides into lateral and septal posterior
nasal branehes. The lateral branehes are distributed to the
lateral wall of the nasal cavity, where they anastomose with
the branehes of the posterior and anterior ethmoidal arteries,
and with the lateral nasal braneh of the external maxillary.
They supply not only the mueo-periosteum of the lateral
wall of the nasal cavity, but also the mueo-periosteum of
the air sinuses whieh open into the cavity. The posterior
septal braneh of the spheno-palatine artery aeeompanies the
posterior nasal septal nerve along the surface of the vomer ;
it anastomoses with the great palatine artery, and with the
septal braneh of the superior labial artery.

THE LARYNX.

The lateral portions of the mandible, whieh are still
attaehed by mueous membrane to the sides of the tongue,
should be removed, and the disseetion of the larynx eom-
meneed.

THE LARYNX 407

Gtoneral Constraction and Position. — ^The larynx eon-
stitutes the upper expanded portion of the air-passage whieh is
speeially modiiied for the produetion of the voice. Its walls
are eomposed of eartilages, museles, ligaments, and an in-
ternal lining of mueous membrane. Before proeeeding with
the disseetioh 'Skhe student should study the form and eon-
neetions of the nine laryngeal eartilages in a permanent speei-
men (v, p. 422).

The jarvnx_is plaeed -in the upper and anterior part of
th^ neek, where it forms a marked projection. It lies below
the hyoid bone and tongue, and is direetly eontinuous with
the traehea inferiorly. Anteriorly it is covered by the
integument and fasciae, and, on either side of the median
plane, by two thin strata of museles — viz., the sterno-hyoid and
omo-hyoid ; the sterno-thyreoid and the thyreo-hyoid. As a
general rule a narrow proeess of the thyreoid gland, termed
the pyramidal lobe^ is also eontinued upwards on its anterior
surface. On eaeh side the lateral lobe of the thyreoid gland is
prolonged upwards upon it ; and it is related to the great
vessels of the neek. Posteriorly it is in relation to the pharynx,
whieh separates it from the prevertebral museles. If the
tip of the epiglottis is taken as its upper limit, the larynx in
the adult may be regarded as being plaeed anterior to that
portion of the vertebral eolumn whieh extends from the lower
>rder of the second-to the lower bnr<j[pr ^r thp sixth r.pryjy^1
vejtebrg.s; but its position alters somewhat with the movements
of the head and also during deglutition.

Interior of the Larsmi. — The cavity of the larynx is
smaller than might be expected from an inspeetion of its
exterior. On looking into its interior from above it will be
seen to be subdivided into thr^^ pnrrinns by two eleyated
folds of mueous membrane whieh extend antero-postenoHy^
and project inwarSs fr6m eaeh side of the cavity. ^The upper
folds are termed the plie^R m^irieulares (O.T. false vocalcords) ;
the lower pair receive the name of the p/iea vocales (O.T.
true vocal eords), The latter are the chief agents in the
produetion of the voice, and the larynx is so eonstrueted
that ehanges in their relative position and in their degree of
tension are brought about by the aetion of the museles and
the reeoil of the elastie ligaments.

Yestibulum Laryngis. — ^The vestibule is the upper sub-
division of the laryngeal cavity (Fig, 150); it extends from the

4oS

HEAD AND NECK

Thyreoid -earUlsgr

superior aperture (aditus laryngis) of the larynn down to the
plic£e ventriculares. In its lower part it exhibits a marked
lateral eompression. Its width, therefare, diminishes froni
above downwards, whilst owing to ihe obliquity of the aditus
the anterior wall is longer than the posterior. Anteriorly it
is bounded by the posterior surface of the epiglottis and the
thyreo-epiglottie ligament, both covered with mueous mem-
brane. This wall
deseends obIiquely
from above down-
wards and anteri-
orly, and beeomes
narrower as it
approaehes the
anteriorends of the
plicEe ventriculares.
Eaeh lateral wall
of the vestibule is
formed by the
medial surface of
the ary-epiglottie
fold. For the most
part it is smooth
and slightly eon-
cave, but in its
posterior part the
mueous membrane
bulges medially in
the form of two
elongated vertical
elevations plaeed
one posterior to
the other. The
r elevation is formed by the cuneiform eartilage and
a mass of glands assoeiated with it, enelosed within, the
ary-epiglotiie fold; the posterior elevation is due to the
anterior margin of the aryt.tnoid eartilage and the eor-
nieulate eartilage. A shallow groove deseends between these
rounded elevations and terminates beiow by running into ihe
interval between the ventricular and the vocal folds. The
posterior wallo{\.\^& vestibule is narrow, and eorresponds totbe
interval between the upper parts of the two arytsenoid eartilages.

Fra 157.-

0 show ihe eompattii

ough ihe Larynx

THE LARYNX 409

The aditus laryngis has already been examined in the
disseetion of the pharynx (p. 378). The parts whieh bound
it should again be carefully studied.

The epiglottis projects upwards posterior to the root of the
tongue. Its lingual or anterior surface is free in the upper
part of its extent only, and is attaehed to the pharytigeal
part of the tongue by a prominent median fold of mueous
membrane, termed the glosso-epiglottie fold, Two lateral folds
are also present; they eonneet its margins with the lateral
walls of the pharynx at the side of the tongue and are
ealled the pharyngo-epiglottie/olds, Between the two layers pf
mueous membrane whieh eonstitute eaeh of these three folds,
there is a small amount of elastie tissue. The depression on
eaeh side between the tongue and the epiglottis whieh is
bounded by the glosso-epiglottie and the pharyngo-epiglottie
folds is termed the vallecula (Fig. 150). The posterior free
surface of the epiglottis forms the greater part of the anterior
boundary of the vestibule of the larynx. The upper part of
this surface is convex, owing to the manner in whieh the
upper margin is curved towards the tongue ; below this
convexity there is a slight concavity, and still lower a marked
bulging over the upper part of the thyreo-epiglottie ligament.
This last projection is ealled the tuberde of the epiglottis\ it
forms a eonspieuous object in laryngoseopie examinations of
the larynx.

The ary-epiglottie folds of mueous membrane enelose
between their two layers some connective tissue, the ary-
epiglottie museles, and, posteriorly, the cuneiform and the
eornieulate eartilages, whieh surmount the arytaenoid eartilages.
As already mentioned, these small nodules of eartilage raise
the posterior part of the ary-epiglottie fold in the form of
two rounded eminenees or tubereles whieh are easily seen
when the larynx is examined by the laryngoseope.

The Middle Subdivision of the Larsoigeal Cavity (Fig. 157)
is the smallest of the three. Above it is bounded by the
ventricular folds, below by the vocal folds ; it eommunieates
with the vestibule above and the inferior eompartment of the
larynx below.

Plieee Ventriculares {O.T.false vocal eords). — The ventricular
folds are two prominent mueous folds whieh extend antero-
posteriorly on the lateral walls of the laryngeal cavity. They
are soft and somewhat flaccid, and their free borders are

410 HEAD AND NECK

slightly arehed, with the concavities looking downwards.
Within eachfold are eontained — ( i ) a ligamentum ventriculare ;
(2) numerous glands whieh are chiefly aggregated in its middle
part ; and {3) a few musele hbres. The interval between the
ventricular folds is termed the riTna vestibuU\ it is eonsider-
ably wider than that between the vocal folds. It foUows,
therefore, that the four folds are distinctively visible when
the cavity of the laryns is examined from above, but when
examined from belaw, the vocal folds alone ean be seen.

Plieee Vocahs (O.T. Thte vocal eords). — The vocal foIds are
plaeed below the ventricular folds, and extend from the angte
between the laminie of the thyreoid eartilage, anteriorly, to the

vocal proeesses of the arytsenoid eartilages posteriorly. E^eh
Yoeal fold is sharp and prominent, and its mueous membrane is
thin and is hrmly bound down to the subjacent vocal ligament.
In eolour it is pale, almost pearly white, whiist posteriorly
the point of the vocaI proeess of the arytsenoid eartilage,
whieh stands out in relief, presents a yellowish tinge. In
frontaI seetion eaeh vocal fold is somewhat prismatie in form,
and the free border looks upwards and medially (Fig. 157).

The vocal foIds are the agents by nieans of whieh the voice
is produeed. The ventricular foIds are of little importanee
in this respeet ; indeed, they ean in great part be destroyed
without any appreeiable difference in the voice resulting.

The rima glottidis is the elongated lissure by means of
whieh the middle eomparlment of Ihe Iarynx eommunieates
with the iower subdivision. It is plaeed somewhat below

THE LARYNX 411

the middle of the laryngeal cavity, of whieh it eonstitutes
the narrowest part. Anteriorly it eorresponds to the interval
between the vocal folds ; posteriorly it eorresponds lo the
interval between the bases and vocal proeesses of the ary-
tienoid eartilages (Fig. 160). It is eomposed, therefore, of
two very distinet parts — (i) a narrow anteriior portion, be-
tween the vocal folds, involving less than two-thirds of its
length, and ealled

Hyo-tpteloa

the pa.

membranaeea ; (2) a

broader, shorter por-

tion, between the

arytsnoid eartilages,

termed the pars in-

tereartilaginea. The

form of the rima

glottidis undergoes

frequent aiterations

in the living person.

During ordinary

quiet respiration it is

laneeolate in outline,

and the intermem-

branous part has

the form of an elon-

gated triangle with

the base direeted

posteriorly. When

the giottis is widely

opened the broadest

part of the hssure

lies between the ex-

tremities of the vocal

proeesses of the arytsenoid eartilages, and there eaeh side

of the rima presents a marked angle. The two vocal folds,

on the other hand, may be approximated so elosely to eaeh

other, as in singing a high note, that the intermembranous

parl is redueed to a linear ehink, The length of the entire

fissure diiTers eonsiderably in the two sexes. In the male

its average length is 23 mm. ; in the female, 17 mm.

The laterai wail of the !arynx, in the interyal between the
ventricular and the vocal foids, shows a poeleet-like depression

□f epiglotlit

byaryt.-PDDid enniillEe

.ttilage

412 HEAD AND NECK

or reeess, termed the ventriculus laryngis (O.T. laryngeal
sinus). The disseetor shouid endeavour to gauge the
extent of this, by means of a probe bent at the extremity.
The reeess passes upwards, undermining the ventricular fold,
and its mouth or orifice is narrower than its cavity. Under
cover of the anterior part of the ventricular fold a slit-like
aperture will be deteeted. This leads into the appendix
ventricuK (O.T. laryngeai saeeuie), a small diverticulum, whieh
aseends between the ventricular fold and the lamina of

the thyreoid eartilage. This sae is of variable extent, but
as a rule it ends biindly at ihe level of the upper border of
the ihyreoid eartilage.

The Lowost Sn1>divisioa of the Laryngeal Cavity (Fig. 1 57)
leads direetly downwards into the traehea. Above, it is
narrow and laterally eompressed, but it graduaOy widens out
until in its lowest part it is eireular. It is bounded by the
sloping inner surface of the eonus elastieus, and by the irmer

THE LARYNX 413

aspeet of the erieoid eartilage. It is through the anterior wall
of this eompartment that the opening is made in the operation
of laryngotomy.

Mueous Membrane of the Laryiue. — This is eontinuous
above with that lining the pharynx, and below with the
mueous lining of the traehea. Over the laryngeal or posterior
surface of the epiglottis it is elosely adherent, but elsewhere,
above the level of the vocal folds, it is loosely attaehed by
submueous tissue. As it passes over the vocal folds it is very
thin and tightly bound down, and in inAammatory eonditions
of the larynx, attended by oedema, this attaehment usually
prevents the iniiltration of the submueous tissue from extend-
ing downwards below the rima glottidis.

The mueous membrane of the larynx has a plentiful supply
of raeemose glands whieh seerete mueus. Over the surface
of the vocal folds these are eompletely absent.

Disseetion. — Plaee the larynx upon a bloek so that its anterior surface
looks upwards, and fix it in that position with pins. The branehes whieh
the external laryngeal nerve gives to the erieo-thyreoid musele should in the
first plaee be followed out ; and, carefully preserving the superior and inferior
laryngeal vessels and the internal and inferior laryngeal nerves, the dis-
seetor should in the next plaee proeeed to remove the thyreoid gland, and
the omo-hyoid, sterno - hyoid, sterno-thyreoid, and thyreo-hyoid museles.
The fibres of origin of the inferior eonstrietor musele also should be
eleared away from the thyreoid and erieoid eartilages. The broad thyreo-
hyoid membrane, the erieo - thyreoid ligament, and the erieo-thyreoid
museles are now exposed, and their attaehments may be defined.

Membrana Hyo-thyreoidea. — This is a broad membranous
sheet, whieh oeeupies the interval between the hyoid bone
and the thyreoid eartilage. It is not equally strong throughout,
but shows a eentral thiek portion, the median thyreo-hyoid
Ugament^ largely eomposed of elastie fibres, and eord-like
right and left margins, the lateral thyreo-hyoid ligaments,
whilst in the intervals between the eentral part and the
lateral margins it is thin and weak. The median ligament is
attaehed above to the posterior aspeet of the upper margin of
the body of the hyoid bone ; below, it is fixed to the sides of
the deep median noteh whieh interrupts the superior border of
the thyreoid eartilage. The upper part of its anterior surface is,
therefore, plaeed posterior to the posterior hollowed-out surface
of the body of the hyoid bone ; a mueous bursa is interposed
between them, and in eertain movements of the head and
larynx the upper border of the thyreoid eartilage is allowed
to slip upwards posterior to the hyoid bone. On eaeh side of

414

HEAD AND NECK

the strong eentral part the thyreo-hyoid membrane is attaehed
below to the upper margin of the lamina of the thyreoid
eartilage, and above to the deep aspeet of the great eornu of
the hyoid bone. It is piereed by the internal laryngeal nerve
and superior laryngeal vessels. The lateral thyreo-hyoid
ligament, whieh forms the posterior border of the membrane,
on eaeh side, is rounded and eord-lilee, and is eomposed chiefly
of elastie fibres. It extends from the tip of the great eornu
of the hyoid bone to the extremity of superior eomu of the
thyreoid eartilage. In this ligament there is usually developed
a small oval eartilaginous
or bony nodule, whieh is
termed the eariilago tritieea.
MuseuluB Grieo-
tliTTeoideus. — The erieo-
thyreoid musele is plaeed
on the side of the erieoid
eartilage, and bridges over
the lateral portion of the
erieo - thyreoid interval.
Taking origin from the
lower border and outer
surface of the areh of
the erieoid eartilage, its
fibres spread out in an
upward and posterior
direetion, and are inserted
into the inner aspeet of
the lower margin of the
thyreoid lamina, and also into the anterior border of its
inferior eornu. As a general ruie, it is divided into two parts.
The anterior or obUque pari is eomposed of those iibres whieh
are attaehed to the lamina of the thyreoid eartilage; the
posterior or straight part is formed of those fibres whieh are
inserted into the inferior eornu of the thyreoid earlilage. It
is elosely assoeiated with the inferiOr eonstrietor musele. The
erieo-thyreoid musele is supplied by the extemal laryngeal
braneh of the superior iaryngeal nerve.

eonuB Elastieus. — Extending upwards, from the upper
border of the anterior and lateral parts of the erieoid eartilage
to the thyreoid and arytasnoid eartilages, is a strong elastie
membrane, the eonus elastieus, whieh is separable into a

— The Crico-thyr

THE LARYNX 415

median and two lateral parts. The median part is the erko-
thyreoid ligament whieh extends from the upper border of the
anterior part of the erieoid areh to the lower border of the
thyreoid eartilage. Eaeh lateral part (O.T. lateral part of
erieo-thyreoid membrane) runs upwards and medially and
terminates in a free thiekened border, the ligamentum loeale^
whieh lies in the substanee of the pliea vocalis and is
attaehed posteriorly to the vocal proeess of arytaenoid, and
anteriorly to the angle of union of the two laminae of the
thyreoid eartilage. The inner surface of the eonus elastieus
is covered with the mueous membrane of the lowest seetion of
the cavity of the larynx, and the outer surface is in relation
with the lateral erieo-arytaenoid and the vocalis museles.

Dissedion. — The position of the laiyme mnst now be rerersed- Fix
it upon the bloek in sueh a manner that its posterior aspeet is direeted
upwards. The oesophagus should then be siit open bj a median iDeisioo
through its posterior wall. Next remove the maeoos membraDe vliicfa
covers the posterior aspeet of the erieoid and arytaeiK»d eartilages. In
doing this, bear in mind that the inferior laryi^eal artery and the infenor
laryngeal nerre pass upwards, between the thyreotd and erieoid eaitilages,
and must be presenred.

Upon the posterior aspeet of the broad lamina of the erieoid eaitilage
the disseetor will now note the two posterior erieo-arytaEnoid mtueles, aod
the attaehment of the tendinous band throagh wlueh tbe longitiidinal fifarcs
of the oesophagus are fixed to the erieoid eartilage. Tbe haod takes or%in
from the prominent median ridge on the posterior aspeet of tbe eriooHl
eartilage. On the posterior surface of the ar^rtaenoid eartilages, and bridg-
ing aeross the interval between them, are the transverse and oldiqise ports
of the ar^rtsenoid musele. Espeeial eare mnst be taken in deanii]^ tlns
musele in order that the eonneetions of the saperficial deenssatii^ fibres
may be aseertained fully.

The lateral layer of the right ary-epglottie fold of moooas membraDe
should now be eautiously removed. This will ex]x>se the aiy-epigiottie
musele, the cuneiform eartilage, and the eomiealate eaitilage 6f that side.
This is perhaps the most difficalt part of the disseetion, beeanse the
disseetor has to establish the eontinuity of the sparse fibres, wlueh oom-
pose the pale ary-epiglottie musele, with the deenssaring fibres of tbe
aryt^enoid musele.

Museulus erieo-Arytaenoideiis Posteiior. — The posterior
erieo-arytaenoid musele is somewhat fan-shaped (Fig. 162).
It springs by a broad origin from the depression whieh marks
the posterior surface of the erieoid eartilage, on eaeh side of
the median ridge, and its fibres conveige to be inserted into
the posterior surface of the museular prouss or projecting
lateral angle of the base of the arytaenoid eartilage.

In pursuing this npward and lateral eoarse, tbe fibres run with different
degrees of obbqaity. The appennost fibres are short and nearly borizoDial ;

HEAD AND NECK

MuseuluB ArTttanoidens. — The aiytsenoid tnusele eonsists
of two portions — a superficial part, tenned the arylxnoideus
t?bliquus, and a deeper layer, ealled the aryteBnoideus transversus.

The arytanoideus obliquus is eomposed of two bundles of
museular (ibres, eaeh of whieh springs from the posterior aspeet
of the museular proeess of the eorresponding ar}tsenoid

Ary-tpigloHie B)ld
ThyreD-hyniil Dwmbrane.

PiG. 162. — Museles of the Poslerior Aspeet of Oie Lat7nx.

eanilage (Fig. 162). From these points the two Aeshy slips
proeeed upwards aiid medially, and eross eaeh other in the
median plane like the limbs of the letter X. Reaehing the
summit of the arytienoid eartilage of the opposite side, some
of the fibres are inserted into it, but the greater proportion
are prolonged, round the base of the eomieulate eartilage,
into the ary-epiglottie foId. There they receive the
name of the aty-epighttieus musde, and as they approaeh
the epiglottis they are joined by the fibres of the thyreo-
epiglottieus musele. The oblique arytsenoid museles may
be eonsidered as eonstituting a ■ ' -"hineter musde

THE LARYNX 417

for the superior aperture of the larynx, £ach bundle

starting from the base of one of the aryteenoid eartilages
is prolonged into the ary-epiglottie fold of the opposite
side, and along this to the margin of the epiglottis.

The arytanoideus iransversus is an unpaired musele. It is
eomposed of transverse tibres whieh bridge aeioss the interval
between the two arytienoid earlilages, and are attaehed to
the posterior aspeet of the lateral border of eaeh arytsenoid
eartilage. Many of the libres tum round the arytaenoid

FlG. 163. — Laleral view of ihe Museles of ihe ILarynK. The filH™ passing
poatero-Euperiorly froni the upper border of the museulus vocaIis are the
Hbres of the Ihyreo-epiglollieus. Ihey blend above wilh the ary-

eartilage and beeome eontinuous, on eaeh side, with the fibres
of the thyreo-arytEenoid musele.

Disseelien. — The further disseetioti of the laiyngeal museles should be
eontined to the right side of the latyrui. The lelt side should be teserved
for the study of the net^es and vessels. Plaee the Iarynx on its lell side,
and, having fixed it in this position, Temove the right eneo-thyieoid musele.
The light lateral pait of the thyreo-hyoid membrane should next be divided,
and the light inlerior eotnu of the thyieoid eaitilage disartieulated from ils
facet on the side of the erieoid earliUge. An indsion should now be made
through the right lamina of the tbyieoid eartilage, a shoit distanee to the
VOL. II — 27

41 8 HEAD AND NECK

right side of the median plane, and the detaehed pieee must be earelully
removed. Three museles are now exposed, and must be eleaned.
They are named from below upwards : —

1. The lateral erieo-arytoenoid.

2. The th)nreo-aryt0enoid.

3. The th)nreo-epiglotticus.

Museulus eheoarytsenoideus Lateralis. — The lateral erieo
arytoenoid musele is triangular in form,-and smaller than the
posterior erieo-arytaenoid (Fig. 163). It springs from the
upper border of the lateral part of the erieoid eartilage, ex-
tending to the facet on the lamina whieh supports the base of
the arytaenoid eartilage ; a few of its fibres take origin from
the eonus elastieus also. From this attaehment its fibres run
posteriorly and upwards, and converge to be inserted into the
anterior surface of the proeessus museularis of the arytaenoid
eartilage. The superficial or lateral surface of this musele is
covered by the lamina of the thyreoid eartilage and the upper
part of the erieo-thyreoid musele ; its deep surface is appHed
to the eonus elastieus.

Museulus Yoealis. — The museulus vocalis is a sheet of
museular fibres whieh springs, anteriorly, from the angle of
union of the two laminae of the thyreoid eartilage. It runs
posteriorly, along the ligamentum vocale and the upper part
of the eonus elastieus, and is inserted into the lateral surface
of the body and the anterior surface of the museular proeess
of the arytaenoid eartilage. Its lower fibres blend with the
upper margin of the lateral erieo-arytaenoid musele and the
medial fibres, whieh run along and to a eertain extent are
attaehed to the ligamentum vocale,^ form a bundle, triangular
in frontal seetion, to whieh the term internal thyro-arytaenoid
musele was formerly applied. The vocalis musele protraets
the arytaenoid eartilage, and adduets and relaxes the vocal
ligaments.

Museulus Thyreoepiglottieus. — The thyreo - epiglottie
rnusele springs from the thyreoid eartilage, immediately above
the museulus vocalis, with the upper border of whieh it is more
or less blended. Its fibres run posteriorly and upwards, into
the ary-epiglottie fold, where they blend with the ary-epiglot-
tieus, and they are inserted into the lateral border of the
lower half of the epiglottis.

^ The fibres whieh are attaehed to the ligamentum vocale are ealled
collectively the ary-vocalis musele.

THE LARVNX

419

Mnseiiliis ThrreoarytonoidenB (O.T. TliyTo-uTteiioideiu

EitemuB). — This musele also springs froin the angle of union
of the two laminEe of the thyreoid eartilage, in elose assoeia-
tion with the vocalis. Its fibres pass posteriorly, and are
inserted into the lateral surface of the arytanoid eartilage.
It protraets the arytainoid eartilage, and adduets and relaxes
the vocal fold.

FiG. 164. — Promal seelion of Laryni showing Museles.

DineslioH. — The la.leta.1 erieo-arytsenoid mnsele should now be csiefutly
reinove<l, and a.t the same time the disseetor shouid endeaYoui to disengage
Ihe libTes or the thyreo-arylsnoideus fiom the deeper museulus vocaliB,
in order that the relation of the Ia.ttei to the vocb1 liguaent ma; be
stndied. Fina.lly remoye the museulus vocalis. This will display the outer
surraee of the eonus elastieus, the vi>ch1 ligament, and the wall ol the laiyn-
geal ventric1e. By careful]y disseeting between the two layers of mueous
membrane whieh form the ventticular fold, the weak ventricular ligament,
whieh gives it support, may be discovered, as well as a number of raeemose
glands whieh Ue in telation lo it.

Lisamentum Vocale. — This ligament is the thiekened
free border of the lateral part of the eonus elastieus, and it
eonstitutes the support of the vocal fold. It is attaehed,
anteriorly, elose to its fellow of the opposite side, to the
middle of the angular depression between the two laminie of

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THE LARYNX 421

Disseetion. — Remove the remains of the ary-epiglottie fold, the ventricular
and the vocal folds, and the lateral part of the eonus elastieus on the
right side of the larynx, but be eareiul not to injure the arytaenoid eartilage
or the eornieulate eartilage. Should the cuneiform eartilage be present
in the ary-epiglottie fold it should be detaehed and preserved. By this
disseetion a eloser view of the side wall of the laryngeal cavity ean be ob-
tained. The undisseeted vocal fold of the left side should be examined
again, the laryngeal ventricle and appendix explored, and their preeise
eonneetions and extent determined. When the disseetor has satistied
himself upon these points he ean proeeed to display the vessels and nerves
of the larynx. The superior laryngeal artery and the internal laryngeal
nerve reaeh the pharynx by piereing the lateral thin part of the thyreo-hyoid
membra'ne, and they deseend along the lateral wall of the reeessus piriformis
to the larynx. By applying traetion to the nerve, and at the same
time dividing the mueous membrane upon the medial surface of the thyreo-
hyoid membrane, they ean easily be discovered. In following the branehes
into whieh they divide, the mueous membrane must be gradually removed
from the wall of the larynx. The inferior laryngeal artery and nerve enter
from below and proeeed upwards, under cover of the lamina of the
thyreoid eartilage. They ean be satisfactorily displayed only by the
removal of this pieee of eartilage, but the disseetor is not reeommended
to adopt this method unless another larynx is available for the examination
of the eartilages and joints. By drawing the thyreoid eartilage laterally
the more important branehes ean be studied.

Bamus Intemus of the Nervus Lax3riigeus Superior. —

In the disseetion of the neek the internal laryngeal nerve was
seen springing from the superior laryngeal braneh of the
vagus. It is a sensory nerve, and its branehes are distributed
chiefly to the mueous membrane of the larynx. After piere-
ing the lateral part of the thyreo-hyoid membrane, it divides
into three branehes. The uppermost of these sends Alaments
to the ary-epiglottie fold, to the mueous membrane whieh
covers the epiglottis, and to the three folds anterior to it.
The twigs whieh go to the epiglottis ramify on its posterior
surface, but many of them pieree the eartilage to reaeh the
mueous membrane on its anterior surface. The intermediate
braneh of the internal laryngeal nerve breaks up into iilaments,
whieh are given to the mueous membrane lining the side wall
of the larynx. The lowesi braneh deseends and gives filaments
to the mueous membrane whieh covers the lateral and
posterior aspeets of the arytaenoid and erieoid eartilages. A
fairly large twig, whieh proeeeds from this braneh, runs down-
wards upon the posterior aspeet of the erieoid eartilage to join
the laryngeal braneh of the reeurrent nerve.

Nervus Beeurrens. — The reeurrent nerve has previously
been seen arising from the vagus, and it has been traeed, in
the neek, up to the point where it disappears under cover of

11—27«

42 2 HEAD AND NECK

the lower border of the inferior eonstrietor musele and beeomes
the i?iferior laryngeal nerue^ whieh aseends upon the lateral
aspeet of the erieoid eartilage, immediately posterior to the
erieo-thyreoid joint. There it is joined by the eommunieating
twig from the intemal laryngeal nerve, and almost immediately
afterwards it divides into two branehes. The largeroi the two
proeeeds upwards, under cover of the lamina of the thyreoid
eartilage, and breaks up into filaments whieh supply the lateral
erieo-arytaenoid, the thyreo-arytsenoid, the vocalis and the
thyreo-epiglottie museles; the smaller ox posterior braneh inelines
upwards and posteriorly, upon the posterior aspeet of the
erieoid eartilage, and under cover of the posterior erieo-
arytaenoid musele. It suppUes twigs to that musele, and is
then eontinued onwards to end in the arytaenoid museles.

The inferior laryngeal nerve is, therefore, themotor nerve
of the larynx. It supplies all the museles with the exception
of the erieo-thyreoid, whieh obtains its nerve-supply from the
external laryngeal. The inferior laryngeal nerve, however,
eontains a few sensory fibres also. These it gives to the
mueous membrane of the larynx below the rima glottidis.

Laiyngeal Arteries. — The superior laryngeal artery^ a
braneh of the superior thyreoid, aeeompanies the internal
laryngeal nerve ; the inferior laryngeal artery^ whieh springs
from the inferior thyreoid, aeeompanies the inferior laryngeal
nerve. These two vessels ramify in the laryngeal wall and
supply the mueous membrane, glands, and museles.

Laryngeal Oartilages and Joints. — The eartilages whieh
eonstitute the skeleton of the larynx and give support to its
wall are the following : —

n--A^ I 4- Ar^'lrenoid, \

3'. Gar'tilage of the \ ^^^g^^* 5- Corniculate, paired.

^ epiglottis, J 6- Cuneiform, J

They are eonneeted by eertain ligaments.

Dissedion. — The mueous membrane and museles must be carefuily
removed from the eartilages, and the ligaments must be defined. Great
eaution must be exercised in eleaning the arytoenoid eartilages and the
eornieulate eartilages, in order that the latter may not be injured.

Oartilago Epiglottiea. — The epiglottie eartilage is a thin,
leaf-like lamina of yellowfibro-cartilage whieh is plaeed posterior
to the tongue and the body of the hyoid bone, anterior to
the upper aperture of the larynx. When divested of the

THE LARYNX 423

mueous membrane whieh covers it posteriorly and also, to
some extent, anteriorly^ the epiglottie eartilage has the form
of an obovate leaf and is indented by pits and piereed by
numerous perforations. In the pits glands are lodged, and
through the foramina vessels and, in some eases, nerves
pass. The broad end of the eartilage is direeted upwards
and is free; its margins are to a large extent enelosed within
the ary-epiglottie folds. The anterior surface is free only in
its upper part. This part is covered with mueous membrane
and looks towards the base of the tongue. The posterior
surface is covered throughout its whole extent with the
mueous membrane of the larynx. The pointed lower end
of the eartilage, the petiolus^ is eonneeted by a stout fibrous
band, termed the thyreo-epiglottie ligament, to the angle
between the laminae of the thyreoid eartilage.

Epiglottie Ligaments. — The epiglottis is bound by
ligaments to the base of the tongue, to the side wall of the
pharynx, to the hyoid bone, and to the thyreoid eartilage.
The glosso-epiglottie fold and the two pharyngo-epiglottie folds
have been studied already. In eaeh there is a small quantity
of elastie tissue. The hyo-epiglottie ligament is a short,
broad elastie band whieh eonneets the anterior face of the
epiglottis to the upper border of the body of the hyoid bone.
The thyreo-epiglottie ligament is strong, elastie, and thiek. It
proeeeds downwards, from the lower pointed extremity of the
epiglottis, and is attaehed to the angular depression between the
two laminae of the thyreoid eartilage, below the median noteh.

The triangular interval whieh is Ieft between the lower
part of the eartilage of the epiglottis and the median part of
the thyreo-hyoid membrane eontains a pad of soft fat, and is
imperfectly elosed above by the hyo-epiglottie ligament.

Oartilago Thyreoidea. — This is the largest of the laryngeal
eartilages. It is eomposed of two broad and somewhat quadri-
lateral plates, termed the laminee^ whieh meet anteriorly at an
angle, and beeome fused along the median plane. Posteriorly,
the laminae diverge from eaeh other and enelose a wide
angular spaee. The anterior borders of the laminae are fused
only in their lower parts. Above they are separated by a
deep, narrow V-shaped noteh ealled the ineisura thyreoidea
superior. In the adult male the angle formed by the meeting
of the anterior borders of the two laminae, espeeially in the
upper part, is very projecting ; and, with the margins of the

434

HEAD AND NECK

Buperior thyreoid noteh, whieh lies above, it eonstitutes a marked

subeutaneous prominenee in the neek, whidi receives the
name of the laryngeal prorninenee {O.T. pomum Adamt^ The
posUrior border of eaeh lamina is thiek and rounded, and is
prolonged beyond the superior and inferior borders of the
lamina in the form of two slender eylindrieal proeesses,
termed the eomua. The superior eomu, longer than the

HyoU

Liganieiits of l.aTyiii.

infcrior eornu, givcs attaehment to the lateral thyreo-hyoid
ligament. The shorter, stronger inferior eornu curves sl^htly
medially. On the medial aspeet of its lip there is a facet
whieh artieulates with the side of the erieoid eartilage. The,
superior border of the lamina is for the most part slightly
convex, and anteriorly it dips down lo beeome eontinuous
with the mai^in of the superior thyreoid noteh. The in/erior
border is to all intents and purposes horizontaIj but it is
divided by a projection, termed the in/erior tuberde, into

THE LARVNX

425

a short posterior part and a longer anterior part. The outer
sur/aee of the lantina is relatively flat. Immediately below
the posterior part of the upper border, and anterior to ihe root
of the superior eornu, there is a distinet prominenee ealled the
superior iuberele. From this an ohlique ridge deseends towards
the inferior tuberde on the lower border of the lamina. This
ridge gives attaehment to the sterno-thyreoid, thyreo-hyoid
and the inferior
eonstrietor museles,
and divides the
outer surface of the

r and a pos-
terior part. To the
latter, whieh is mueh
the smaller of the
two, is attaehed the
inferior eonstrietor
musele of the
pharyns, The inner
surface of the lamina
is smooth and slight-
ly concave. To the
angular depression
hetween the two
lamin^ are attaehed
the thyreo-epiglottie
iigament, the ven-
trieular andthevocal
ligaments.

erieo-thyreoid
Joiiits. — The artieu-
lation, on eaeh side,
between the tip of the inferior eornu of the thyreoid ear-
tilage and the side of the erieoid eartilage, belongs to the
diarthrodial variety. The opposed surfaces are surrounded
by a eapsular ligaraent whieh is lined with a synoyial stratum.
The raovements whieh take plaee at these joints are of a
twofoId eharaeter — viz., (i) gliding; (z) rotatory. In the
first ease the erieoid facets glide upon the thyreoid surfaces in
different direetions. The rotatory movement is one in whieh
the erieoid eartilage rotates around a transverse aitis whieh

436 HEAD ANt) NECK

passes thtOTigh the eentre of the two joints. Eaeh eapsular
ligament is strengthened by stout bands on the posterior
aspeet of the j'oinL

eartUago Cricoidea. — This is shaped like a signet ring.

aspeLt of Cart liges and Ligamenls of Laryny.

The broad postenor part, iie lamtna, is somewhat quadrilateral
in form. Its superior border presents a Taintly marked
median noteh, and on eaeh side of this there is an oval
convex facet whieh artieulates with the base of the arytEenoid
eartilage. The posterior suriaee of the laniina is divided, by
an eleyated median ridge, into two slightly hollowed-out
areas whieh give attaehment to the posterior erieo-arytaenoid
museles. The median ridge itself gives origin to a tendinous

THE LARYNX 427

band whieh proeeeds upwards from the longitudinal fibres of
the oesophagus. The anterior part of the erieoid eartilage
is the areh, The lower border of this is horizontal, and is
eonneeted to the first traeheal ring by membrane, the erieo-
traeheal ligament The areh is narrow anteriorly, and is
attaehed to the lower border of the thyreoid eartilage by
the erieo-thyreoid ligament. Posteriorly, the upper border
rapidly aseends. Upon the posterior part of the lateral
surface of the erieoid eartilage there is a eireular, slightly
elevated, convex facet, whieh looks laterally and upwards,- for
artieulation with the inferior eornu of the thyreoid eartilage.
Internally the erieoid eartilage is lined with mueous membrane,
and its lumen is eireular below, but elliptieal above.

The narrow band-like part of the anterior areh of the
erieoid eartilage lies below the lower border of the thyreoid
eartilage, whilst the lamina is received into the interval
between the posterior portions of the laminae of the
thyreoid eartilage.

Oartila^ines Comiculatse. — Before proeeeding to the study
of the arytsenoid eartilages the disseetor should examine the
eornieulate eartilages and the manner in whieh they are
held in position. They are two minute pyramidal nodules
of yellow elastie eartilage whieh are plaeed on the summits
of the, arytsenoid eartilages, and are direeted posteriorly and
medially. Eaeh eornieulate eartilage is enelosed within the
eorresponding ary-epiglottie fold of mueous membrane, and
is joined to the apex of the arytaenoid eartilage by a
synehondrodial joint.

Oartilagines ArsrtaBnoideae. — In dealing with the arytaenoid
eartilages it is well to remove one in order that its external
form may be studied; the other should be retained in
position, for the purpose of examining the erieo-ar^rtaenoid
joint and the movements whieh ean be performed at that
artieulation.

The aryteenoid eartilages are pyramidal in form, and sur-
mount the upper border of the lamina of the erieoid-
eartilage. The apex of eaeh is direeted upwards, and is
curved postero-medially. It supports the eornieulate eartilage.
Of the three surfaces, one looks medially, towards the eorre-
sponding surface of the opposite eartilage, from whieh it is
separated by a narrow interval; another looks posteriorly;
whilst the third is direeted antero-laterally. The medial

428 HEAD AND NECK

surface is narrow, vertical, and even, and is elothed with
mueous membrane. The posterior stirface is concave; it
lodges and gives attaehment to the arytaenoideus transversus
musele. The antero-lateral surface is the most extensive of
the three, and is uneven for museular and ligamentous attaeh-
ments. Upon this aspeet of the arytsenoid eartilage the
museulus vocalis and the thyreo-arytaenoid museles are in-
serted. The surfaces of the arytaenoid eartilage are separated
by three borders, viz., an anterior, a posterior, and a lateral.
The lateral border is the longest, and, at the base of the'
eartilage, it is prolonged postero-laterally in the form of a
stout prominent angle or proeess, termed the proeessus museu-
laris, It gives attaehment anteriorly to the erieo-arytsenoideus
lateralis musele; and posteriorly to the erieo-arytsenoideus
posterior. The anterior border of the arytaenoid.eartilage is
prolonged into the projecting anterior angle of the base.
This is ealled the proeessus vocalis, It is sharp and pointed,
and gives attaehment to the vocal ligament (O.T. true yoeal
eord). The base of the arytaenoid eartilage presents an
elongated concave facet, on its under aspeet, for artieulation
with the upper border of the lamina of the erieoid eartilage.

Crico-arytsenoid Joiiits. — These artieulations are of the
diarthrodial variety. There is a distinet joint cavity sur-
rounded by a eapsular ligament, whieh is lined with a S)movial
stratum. The erieoid artieular surface is convex, that of
the arytaenoid concave ; both are elongated in form, but they
are plaeed in relation to eaeh other so that the long axis of
the one interseets or erosses that of the other, and in no
position of the joint do the two surfaces aeeurately eoineide.
The movements allowed at this joint, as the disseetor ean
readily determine, are of a twoibld kind — (i) giiding, by
whieh the arytaenoid is earried medially or laterally, or, in
other words, a movement by whieh the arytaenoid advances
towards or retreats from its fellow ; (2) rotatory^ by whieh the
arytaenoid eartilage revolves round a vertical aMS. By this
movement the vocal proeess is swung laterally or medially, so
as to open or elose the rima glottidis.

The disseetor should note that the eapsule of this joint
is strengthened posteriorly by a strong band whieh plays a
most important part in the meehanism of the artieulation.
It restriets movement of the arytaenoid eartilage.

eartilagines Cuneifonnes. — These are two little rod-shaped

THE TONGUE 429

nodules of yellow elastie eartilage, whieh are plaeed one in
eaeh ary-epiglottie fold near its posterior end. They are not
always present.

Aetion of the Laryngeal Museles. — The disseetor should now eonsider
the manner in whieh the museles of the larynx operate upon the vocal
ligaments in the produetion of the voice. Tension Qf the vocal eords is p^o-
dueed by the eontraetion of the e^r.o-t^yr^gi^ ^^^.^u^ tKo oblique parts
of the niuseles puU the upper border of the erieoid earlilage upwards,
whilst the straight portions, through their insertions into the inferior eornua,
draw the erieoid eartilage posteriorly, thereby inereasing the distanee
between the angle of the thyreoid eartilage and the vocal proeesses of the
arytrenoid eartilages. When the erieo-thyreoid museles eease to eontraet,
the relaxation of the eords is brought about by the elastieity of the
ligaments. The vocalis. and the thyreo-arytoenoideus must be regarded
as antagonistie to the erieo-thyreoid museles. When they eontraet they
approximate the angle of the thyreoid eartilage to the arytsenoid eartilages,
and still further relax the eords, and when they eease to aet, the elastie
ligaments of the larynx again bring about a state of equilibrium.

The width ofthe rit?ia glottidis is regulated by the arytoenoideus musele,
whieh draws together the arytaenoid eartilages. The lateral and posterior
erieo-arytaenoid museles also modify the width of the rima glottidis. When
they aet together they assist the arytaenoid musele in elosing the glottis,
but when they aet independently they are antagonistie museles. Thus the
crico-arytcBnoidei posteriores^ by drawing the museular proeesses of the
arytsenoid eartilages postero-laterally, swing the proeessus vocales and the
vocal folds laterally, and thus open the rima. The erieo-arytanoidei
laierales aet in exactly the opposite manner. By drawing the museular
proeesses in an opposite direetion they elose the rima.

But the museles of the larynx have another function to perform besides
that of vocalisation. It was formerly thought that the superior aperture
of the larynx was elosed, during deglutition, by the folding baek of the
epiglottis ; that in fact the epiglottis, during the passage of the bolus of
food, was applied like a lid over the entranee to the vestibule of the larynx.
The investigations of Prof. Anderson Stuart have slinwn ^hi^f; t)^f^ «;ypf;i;inr
aperture of the larynx is elosed during swallowingLUY^the elose apposition
and the for war3" pr^^ (IT^ two *afy tienoid cartjlages, wnien are

Toreeoagainst t£eXubercle"^'fflee|5iglotHs. The muscleTchiefly eoneemed
in this movement are the~t"liy7eo-arytsenoid museles and the transverse
aryteenoid musele. These museles form a true sphineter vestibuli. The
ary-epiglottieus musele also assists in the elosure.

THE TONGUE.

The tongue is a museular organ plaeed on the floor of
the mouth. It has important duties to perform in eonneetion
with the functions of mastieation, deglutition, and artieulation,-
Moreover, the mueous membrane whieh covers it is speeially
modified, in eertain loealities, in eonneetion with the peripheral
terminations of the nerves of taste. The root of the tongue
is attaehed to the hyoid bone ; the pointed anterior extremity

430 HEAD AND NECK

is free ; the upper border of the base forms the lower boundary
of the isthmus faucium.

Mueous Membrane. — The lingual mueous membrane is
a part of the general mueous lining of the bueeal cavity.
The dorsum of the tongue^ when the mouth is elosed and
the organ is at rest, is strongly arehed antero-posteriorly,
and, for the most part, is moulded into the vaulted roof of
the mouth. The tongue eonsists of two developmentally
distinet parts, termed oral and pharyngeal. These are
marked off from eaeh other, even in the adult, by a V-shaped
groove ealled the sukus terminalis, The apex of this suleus
points posteriorly, and eoineides with a median blind pit
whieh receives the name of the /oramen eeeeum, From this
the two limbs of the suleus diverge antero-laterally, and they
reaeh the margins of the tongue at the attaehments of the
glosso-palatine arehes.

The oral part of the tongue, by its upper or dorsal
surface, stands in relation to the hard palate, and to some
extent to the anterior part of the soft palate also. The
pharyngeal part of the tongue looks posteriorly, and forms
the anterior wall of the oral portion of the pharynx. In its
upper part it is related to the soft palate, whilst below it is
intimately related to the epiglottis. On the lateral wall of the
pharynx, immediately above this portion of the tongue, is
the tonsil.

The mueous menfbrane whieh envelops the tongue
presents very different appearanees in different loealities.
That portion whieh is spread over the pharyngeal part of
the tongue, and is prolonged upwards over the surface of
the tonsil, is smooth and somewhat glossy and presents no
visible papillae. It is from this distriet that the glosso-
epiglottie fold takes origin, and every here and there the
surface is studded with low projections, whieh are produeed
by lymph follicles plaeed subjacent to the mueous membrane.
Eaeh of these small elevated areas, as a rule, presents in the
eentre a minute pit, visible to the naked eye.

Anterior to the foramen eaeeum and suleus terminalis the
mueous membrane whieh covers the dorsum, sides, and tip
of the oral part of the tongue is beset with papillae of
different kinds. As these are individually visible to the naked
eye the mueous membrane presents a very eharaeteristie
appearanee. Purther, a median groove or suleus extends

THE TONGUE 431

posteriorly from the tip of the tongue to Ihe foramen eseeom,
and divi<ies the atiterior two-thirds of the dorsum into two
halves.

On the under suriaee of the tongue the mueous mem-
brane is smooth and comparatively thin. In the median
plane it forms Ihe/renulum lingua^ whieh has been studied
at an earlier stage. On eithet side of the median line the
deep lingual vein may be notieed, in the liying subject, ex-
tending anteriorly towards the tip. To the lateral side of this,

Tipo^n«^.

and, therefore, somewhat nearer the border of the tongue, is a
delieate and feebly marked foId of mueous membrane, from
the free border of whieh a row of fringe-like proeesses or
fimbrije project. It is termed xhe pliea Jimbriala ; as it extends
anteriorly, towards the tip of the tongue, it inelines towards
the median plane. On the side of the tongue, immediately ■
anterior to the lingual attaehment of the glosso-palatine
arehes, five short vertical fissures in the mueous membrane,
separated by interyening folds, may be notieed. These are
ikiit papilla /oliatm. They are the representatives of Ieaf-Iike
foIds of the mueous membrane, whieh are mueh more highly
developed in eertain of the lower animals (hare and rabbit).

432 HEAD AND NECK

and whieh are speeially eoneemed in receiving the impressions
of taste.

Papill» Linguales. — These are of four kinds, and differ
in size, shape, and in the position they oeeupy on the
surface of the tongue. They are termed the vallate, the
fungiform, the eonieal, and the filiform.

Papillee VaUat(B, — The yallate papillae (O.T. circumvallate),
seven to twelve in number, are the largest, and are plaeed
immediately anterior to the suleus terminalis, in two rows
whieh diverge from eaeh other in an antero-lateral direetion,
like the two limbs of the letter V. The foramen eaeeum
lies immediately posterior to the median vallate papilla, whieh
forms the apex of the V. In form, a vallate papilla is
broad and somewhat eylindrieal, slightly narrower at its
attaehed than at its free extremity, arid it is sunk in a pit.
It is thus surrounded by a deep treneh, the outer wall of
whieh, termed the vallum, is slightly raised beyond the general
surface of the mueous membrane, and forms an annular eleva-
tion whieh eneireles the free extremity or summit of the
papilla.

Papillee Fungiformes. — The fungiform papillae are mueh
smaller, but are present in mueh greater numbers. They are
found chiefly on the tip and sides of the tongue, but they are
seattered at irregular intervals over the dorsum also. Eaeh
papilla presents a large, full, rounded, knob-like extremity,
while it is greatly eonstrieted at the point where it springs
from the mueous surface. In the living tongue the fungiform
papillae are distinguished by their bright red eolour.

Papillee Conicce, — The eonieal papillae are present in very
large numbers. They are smaller than the fungiform variety,
and although they are quite visible to the naked eye they
ean be more conveniently studied by the aid of an ordinary
poeket lens. They are minute eonieal projections whieh
taper towards their free extremities, and they oeeupy the
dorsum and sides of the tongue anterior to the suleus
terminalis. They are arranged in parallel rows whieh are
plaeed elose together, and in the posterior part of the dorsum
these diverge from the median suleus in an antero-lateral
direetion. Towards the tip of the tongue the rows of eonieal
papillae beeome more or less transverse in direetion, and on
the sides of the tongue they are arranged perpendieularly.

Papillee Filiformes. — The filiform papillae are similar in

THE TONGUE

433

general eharaeters to the eonieal papillte, but the epithelial
eap at the apex of the eone is broken up into thread-like
proeesses.

Hnselea of the Tongne. — The tongue is eomposed almost
entirely of museular hbres, with some adipose tissue inter-
miKed. It is divided into two lateral halves by a median
septum, and the musdes in eonneetion with eaeh of these

PoMeriDr Mly

FiC 170 — Museles of

eonsist of an mtnnsie and an extnnsic group Th
follows :—

GeniO'glossus.

Hyo-e[os5U5.

ehondro-glossus.
l Stylo-glossus.
- Palato-glossus.

Superior longitudinal,

Interior longitudinal.

Vertical.

Transverse.

Intrinsie Museles,

The extrinsic musdes take origin from parts outside the
tongue, and thus are eapable not only of giving rise to ehanges
in the form of the organ, but also of produeing ehanges in
its position. The intrinsie museles, whieh are plaeed entirely
within the substanee of the tongue, are, for the most part,
eapable of giving rise to alterations in its form only.

voi,. 11—28

434 HEAD AND NECK

Wilb the exception of Ihe ehondeo-glossus, the extiinsic moseles haye
been studied already, hut the disseetor should take this opportuDity of
examining more lulty theii insertions, and ihe manner in whieb ibeir tibres
ire related to one another and lo Ihose of the intrinsie museles. For this
putpose caiefu11y teileet the mueous membiane from the light half of the
tongue, and follow the museles into that side of the organ. At the same
time the lingual nerve and the piofunda linguse aitery should be preserved.
On Ihe undet suiface of the tongue, near the tip, the removal of the mueotis
membiane will expose a group of glands, ag^regated togelber so as to form
a small oval mass on eaeh side of ihe median plane. This is known as the
apieal^andat \iu: ^and o/ NiiAn.

The st}!oglossus will be seen running along the side of
the tongue to the tip where the museles of opposite sides
beeome to a eertain extent eontinuous The hyo-glossus
extends upwards to the side of the tongue, and its fibres pass,

.^ i

e posteiior part

for the tnost part, under eoyer of those of the stylo-glossus to
reaeh the dorsum, over the posterior part of whieh they spread
out, beneath the mueous membrane. The genio-glossus sends
its fibres vertically upwards into the tongue on eaeh side of
the median septum, and its insertion stretehes from the tip
to the base. The fibres of the palato-glossus beeome eon-
tinuous with those whieh form the stratum transyersum.

The ekoiidro-glessus is not always pieaenl. Il is sepaiated fiom the
deep suiface of the hyo-glossus hy the lingual vessels, and by the pbaiyn-
geal slip of the genio-glossus. It is a alender museular band whieh lakes
oiigin fiom the medial aspeet of the loot of Ihe smaller eornu, and the
adjoining pait tiS ihe hody of ibe hyoid hone. Its tihres aseend, to entei
the tongue and linally spiead oul on tbe dorsum under cover of the
superior longitudinal musele.

Musailus Longituiiina/is Superior. — This is a eontinuous
layer of longitudinal Abres whieh covers the entire dorsum
linguK, from the root to the tip, immediately beneath the
mueous membrane. Towards the base of the tongue it is

THE TONGUE 435

thinner than in front, and there it is overlapped by the trans-
verse fibres of the hyo-glossus, and is intermixed with the
fibres of the ehondro-glossus.

Museuli LongitudiKales In/eriores. — The inferior longi-
tudinal museles are two rounded Aeshy bundles plaeed upon
the inferior aspeet of the tongue, one on eaeh side. Pos-
teriorly, eaeh inferior longitudinal musele lies tn the interval
between the hyo-glossus and the genio -glossus, and is
attaehed to the hyoid hone; anteriorly, it is prolonged
to the apex of the tongue hetween the medial border of
the stylo-glossus and the genio^lossus ; with the former it is
more or less blended.

Museulus Transversus Lingua. — The fibres of this musele

Inrer DT odgiluduui]

lie under the superior longitudinal hbres, and eonstitute a
thiek layer whieh extends laterally from the lateral face of
the septum linguje, to the side of the tongue. The fibres
of the genio^lossus aseend through this transverse stratum
and break it up into numerous lamellse (Fig, 172). It is
joined by the fibres of the palato-glossus (Henle) {Fig. 171).

Museulus Yertiealis Zingu(e.—The vertical fibres extend in
a curved direetion from the dorsum to the under aspeet of
the tongue, and deeussate with the fibres of the transverse
musde.

Nerres and YesBelB of the Toiijn& — The nerve5 of the
tongue are — (i) the glosso-pharyngeal ; (2) the lingual; (3)
the hypoglossal ; and (4) a few twigs from the internal
laryngeal. These should be traeed on the left side of the
tongue, where the mueous membrane is still in position.

Tihe g/osso-piaryngea! nerveh&s been traeed up to the point

436 HEAD AND NECK

where it disappears under cover of the byo-glossus e
There it divides into two branehes. The smaller of these
extends anteriorly, upon ihe side of ihe tongue, and may be
traeed as far as a point midway between ihe root and the tip.
The larger braneh tums upnards, and is distributed to the
mueous membrane «hieh invests the posterior third of the
dorsum linguae. It gives twigs to the rallate papillse, and
some line tilaments may be followed to the anterior surface
of the epiglotlis. The glosso-phaiyngeal nene is a nerre of
taste and of eommon sensibility.

The tingual and hypogloaal nerves are deseribed on pages
289 and 316, and their terminal branehes should aow be
traeed as far as is possible.

Hyoid lone Genio'hyoid
PiG. 173. — TransYerse Beeiion ihrough Ihe Tongue. (Prom Aely.)

The intemal laryngeal nerse gives a few delieate filaments
to the glosso epiglotiie and pharyngo-epiglottie folds and the
mueous membrane of the root of the tongue.

The arteria pro/unda lingua should be followed to the tip
or the tongue, where it Ibrms a small loop of anastomosis with
its feIlow of the opposite side.

Septniii Lingna.— The septum of the tongue ean be seen
best by making a transverse seetion through the organ. This
will display, in a measure, the transverse and vertical museular
fibres also. The septum is a median tibrous partitionl It
is strongest posteriorly, where it is attaehed to the hyoid
bone. It does rot reaeh the dorsum of the tongue, being
separated from it by the superior longitudinal musele.

GENERAL APPEARANGE 0F BRAIN 437

ENGEPHALON— THE BRAIN.

Diredions. — If the brain was divided into two parts, when it was
removed, they should be fixed together with large pins passed through the
eerebellum into the eerebral hemispheres ; the brain should then be plaeed
on a disseeting-room platter, with its superior surface uppermost. It is
neeessary to keep it moist, during the whole disseetion, by means of a
eloth dipped in water. Unless this is done the membranes are apt to
beeome dry, and then they are exceedingly difficult to remove.

General Appearanee of the Brain. — When viewed from
above, the brain presents an ovoid Agure, with the broad end
direeted posteriorly. Its greatest transverse diameter is in
the neighbourhood of the part whieh lies between the two
parietal tubers of the eranium. The only portions whieh are
visible when the brain is in this position are the two convoluted
hemispheres of the eerebrum. These are separated from eaeh
other by a deep median cleft, ealled the longitudinal fissure^
whieh extends from the anterior to the posterior end of the
brain.

The position of the brain should now be reversed. Turn it so that it
rests on its superior surface.

The inferior aspeet of the brain is usually termed the
"base." It presents an uneven and irregular surface, whieh
is more or less aeeurately adapted to the inequalities on the
floor of the eranium. On this surface the main subdivisions
of the organ may be reeognised. Thus, posteriorly is seen the
short eylindrieal portion, ealled the medulla oblongata^ through
whieh, at the foramen magnum, the brain beeomes eontinuous
with the spinal meduUa. The meduUa oblongata rests on
the under surface of the eerebellum, being received into the
vallecula or hollow whieh intervenes between the two eere-
bellar hemispheres. The eerebellum is a mass of eonsiderable
size whieh lies under the posterior parts of the eerebral
hemispheres. It ean be easily reeognised on aeeount of the
elosely set, curved and parallel fissures whieh traverse its
surface. Above the medulla oblongata, and in direet eonnee-
tion with it, is a prominent white elevation ealled the pons,
The basilar artery extends upwards in a median groove on
its surface. Immediately anterior to the pons there is a
deep hollow or reeess. This is bounded posteriorly by the

II— 28«

43» THE BRAIN

pons, on either side by the proieeting temporal lobes of
the eerebrum, and anieriorly by the orbital portions of the
frontal lobes of the eerebrum. At the present stage of the

examination of the brain, the bottom of this hollow is hidden
from view by the araehnoid, whieh stretehes over it like a
veii ; but the hypophysis will be seen within its iimits if it has
been removed wiih the brain. Passing laterally from either
side of the anterior part of this reeess will be seen Ihe deep

MEMBRANES AND BLOOD YESSELS 439

Assura lateralis (O.T. Sylvian fissure), whieh intervenes between
the pointed and projecting extreniity of the temporal lobe and
the frontal lobe of the eerebrum ; whilst in the median plane,
anteriorly, the longitudinal fissure will be seen between the
frontal portions of the eerebral hemispheres. On either side
of the longitudinal fissure, and separated from it by a narrow
gyrus, the olfactory traet and bulb may be reeognised.

MEMBRANES AND BLOOD YESSELS 0F

THE BRAIN.

Araelmoidea Eneephali. — The araehnoid forms the inter-
mediate covering of the brain. It is plaeed between the dura
mater and the pia mater, and is direetly eontinuous with the
araehnoid of the spinal medulla. It is an exceedingly thin
and delieate membrane, whieh ean be seen best on the base
of the brain, as in that loeality it is not so elosely applied to
the pia mater as elsewhere. Unlike the pia mater it does
not (except in the ease of the longitudinal and the lateral
fissures) dip into the sulei or fissures on the surface of the
eerebrum and eerebellum. It bridges over the inequalities on
the surface of the brain and it is spread out in the form of a
very distinet sheet over the medulla oblongata, the pons, and
the hollow on the base of the brain whieh lies anterior to the
pons. The eut ends of several of the eerebral nerves will be
seen passing through this sheet ; whilst, anteriorly, immedi-
ately to the lateral side of the optie nerve, the internal earotid
artery will be notieed piereing it.

Gavum Subaraelmoideale. — The interval between the araeh-
noid and the pia mater receives the name of the subaraehnoid
spaee. It eontains the subaraehnoid Auid, and is broken up
by a meshwork of fine filaments and trabeeulae, whieh eonneets
the two bounding membranes (viz., the araehnoid and the pia
mater) in the most intimate manner, and form a delieate
sponge-like interlaeement between them. Where the araeh-
noid passes over the summit of a eerebrd gyrus, and is eon-
sequently elosely applied to the subjacent pia mater, the
meshwork is so elose and the trabeeulae so short that the
two membranes eannot be separated from eaeh other. To
the disseetor they appear to form a single lamina. In the
intervals between the rounded margins of adjacent gyri distinet

44°

THE BRAIN

angular spaees exist between the araehnoid and the pia
mater. In these the subaraehnoid tissue ean be studied, and
it will be seen that these intervals on the surface of the
eerebrum serve as eommunieating ehannels for the free
passage of the subaraehnoid fluid from one patt of the brain
to another. The larger branehes of the arteries and veins
of the brain traverse the subaraehnoid spaee ; their walls are
direetly eonneeted with the subaraehnoid trabeeulse and are
bathed by the subaraehnoid iluid.

eutenua Subaraehiioidaales. — In eertain situations the
araehnoid is separated from the pia mater by interval5 of

eonsiderable depth and extent. These expansions of the
subaraehnoid spaee are termed oisternas subaraehnoideales. In
them the subaraehnoid tissue is relatively redueed. There
is no longer a elose meshwork ; the trabeeulae oonneeting the
two bounding membranes lake the form of long tilamentous
interseeting threads whieh traverse the spaees. A beautiful
demonstration of these may be obtained by dividing in the
median plane, with the seissors, the sheet of araehnoid whieh
is spread over the medulla oblongata and pons, and tuming
the two pieees gently aside.

Gertain t>( the eistern^ [equire speeial mention. The la[^est and most
eonspieuous is ealled the (isUrna (ertbetlo-mtdullai-is (O.T. magna). Il is
a ilireel upwitd eontinuation of the posteriot pait of the subaraehnoid spaee

MEMBRANES AND BLOOD YESSELS

441

ofthespinal meninges into the posterior partof theeranium. It is formcd
by the araehnoid membiane bridging ovei the wide interval belween the
postetioi pait of Ihe undei £uiface af the eeiebellum and the medulla
oblongata.

The eistema poittis is the name given to another of these leeesses. It is
the eontinuation upwards, on Ihe noor of the eranium, of the snterior part
of Ihe subaraehnoid spaee of Ihe spinal meninges. In ihe r^on of ihe
medulls oblongata it is eontinuoiis on eithei ^de with the eeiebello-medul-
hiry eistem, 50 that this subdivi^on of ihe biain is eompletely sunounded
bya wide subaiaehnoid spaee. Wilhin theeisteina pontis aie the veTtebia1
and basilar aiteiies

An o o he pon he a a hno d memb ane osse be ween Ihe pro-

I dd e pordon of the
ibranei of tbe brain

jecling temporai lobes, and covers in the deep hollow in this legion of tbe
base of the biain. This spaee is eailed the eistema ittitrpedmuularit,
and within it aie plaeed the laige arteries whieh take pait in the fonna-

thiasmatis, whieh lies ante
eeiebral arteries.

AII the subaiaehnoid c
one anothei, and also with the nariow intervals 01
bium. The subaiaehnoid spaee does n
the subduial spaee. In eeitain toeatities, however, il
the ventticiilar system of the brain. Three sueh apertures are deseribed in.
eonneetion with the fourth ventiicle, whilst anothei slit, on eaeh side, is said
(o lead fiDm Ihe eisleina interpeduneulaiis into the lower end of the eoiie-
sponding infctior horn of the lateral ventricle,

Extending laterally from the eistema interpeduneularis, on eaeh side,
is the eislerna fossie lateralis eeiebri, wbieh exlcnds along the stem of the
lateial tissure into the lateial fbssa, aiound the middle eerebial aiteiy.
Anterioily (be eisteina ehiasmatis is eontinuous wilh a piolongation whidi

the freeEt manner with
the surface of tbe eeie-
any way wlth

442 THE BRAIN

extends into the longitudinal- iissure with the anterior eerebral arteries.
A dilatation of the subaraehnoid spaee over the dorsum of the mid-brain
round the great eerebral vein (O.T. vena magna Galeni) is eailed the
eisterna veme magme eerebri,

Granulationes Araelmoideales (O.T. Paeehionian Bodies).

— The eonneetion of the araehnoideal granulations with the
araehnoid has been referred to already (p. 202).

Pia Mater Eneephali. — The pia mater forms the immediate
investment of the brain. It is finer and more delieate than
the eorresponding membrane of the spinal medulla, and it
follows elosely all the inequalities on the surface of the brain.
Thus, in the ease of the eerebrum, it lines both sides of every
suleus and forms a fold within it. On the eerebellum the
relation is not so intimate ; it is only the larger fissures of
the eerebellum whieh eontain folds of pia mater.

It has been noted that the larger blood vessels of the
brain run in the subaraehnoid spaee ; the finer twigs enter the
pia mater and ramify in it before passing into the substanee
of the brain. As they enter they earry with them sheaths
derived from the pia mater. Consequently, if the disseetor
raises a portion of this membrane from the surface of the
eerebrum, a number of fine proeesses will be seen to be with-
drawn from the eerebral substanee. These are the blood-
vessels, and they give the deep surface of the membrane a
rough and Aoeeulent appearanee.

The pia mater is not confined to the exterior of the brain.
A fold is earried into its interior. This will be exposed in
the disseetion of the brain, and will be deseribed under the
name of the tela ehorioidea (O.T. velum interpositum) of the
third ventricle.

Disseetion. — The blood vessels of the brain should now be followed out
as far as it is possible to do so without laeeration of the brain substanee.
Begin by stripping the araehnoid from the base of the brain. This will
bring into view the main trunks. As the vessels of the brain are deseribed,
many parts whieh have not yet eome under the notiee of the disseetor must
be mentioned.

Arteries whieh supply Blood to the Brain. — Four main

arterial trunks earry blood into the eranium for the supply
of the brain — viz., the two internal earotid arteries and the
two vertebral arteries. The vertebral arteries enter through
the foramen magnum, whilst the internal earotid arteries gain
admittanee through the laeerate foramina after traversing the
earotid eanals. These vessels have been divided in the

MEMBRANES AND BLOOD YESSELS 443

removal of the brain. The eut ends of the internal earotids
will be seen, on the base of the brain, immediately to the
lateral sides of the optie nerves ; the yertebral arteries lie
on the sides of the meduUa oblongata. A very remarkable
and eomplete anastomosis takes plaee at the base of the
brain by the inoseulation of branehes whieh spring from
the internal earotid and vertebral arterial systems. This is
termed the dreulus arteriosus (Willis), and the branehes
whieh take part in its formation lie in the eisterna inter-
peduneularis and the eisterna ehiasmatis.

Two systems of branehes, both going to the eerebrum but
differing greatly in their mode of distribution, proeeed from
the vessels forming the arterial eirele. One system eonsists
of very numerous slender twigs, whieh, as a rule, eome off in
groups in eertain loealities, and at onee pieree the substanee
of the eerebrum so as to gain its interior. These are the
eentral or basal branehes, The other system is eomposed of
branehes whieh ramify over the surface of the eerebrum, and
is termed the system of eortieal branehes. The eentral parts
of the brain, ineluding the basal ganglia, receive their blood-
supply from the basal system, and the vessels whieh eon-
stitute this group do not anastomose with eaeh other. The
eortieal vessels supply the eerebral cortex and the finer
branehes, whieh ramiiy in the pia mater, anastomose with
one another ; therefore, the neighbouring vascular distriets of
the eerebral cortex are not sharply eut oif from eaeh other.

Arteria Vertebralis. — The vertebral artery enters the sub-
araehnoid spaee in the upper part of the vertebral eanal by
piereing the dura mater and the araehnoid. Gaining the
interior of the eranium, through the foramen magnum, it is
eontinued upwards on the side of the medulla oblongata.
Soon it inelines to the anterior aspeet of the medulla
oblongata, and, meeting its fellow of the opposite side in
the median plane, it unites with it, at the lower border of
the pons, to form the basilar artery.

During this part of its eourse the vertebral artery gives off
the following branehes : —

1. Posterior spinal.

2. Posterior inferior eerebellar.

3. Anterior spinal.

4. Bulbar.

Arieria Spinalis Posterior, — This is the first braneh that
is given off after the vertebral artery pierees the dura mater.

444

THE BRAIN

It passes downwards on the spinal medulla along the line of
the posterior nerve-roots (p. 193)-

Arteria CertbelH In/erior Posterior. — The posterior inferior
eerebellar artery is the largest braneh of the vertebral artery,
It takes origin immediately above the posterior spinal artery,

FlG. 177. — Floor of the eranium afler the removal of the btf
Tenlorium Gerebelli. The blood vessels forming the Gireulu!
have been left in plaee. \^ 'A,UC> *"

and pursues a tortuous eourse posterioriy, on the side of the
upper part of the medulla oblongata, among the Ala of the
hypoglossal nerye, and then among the iila of the yagus.
pinally, turning round the resttform body, it gains the yalleeula
of the eerebellum, where it ends by dividing into two terminal
branehes. Of these, one turns j)osteriorly, in the vallecula,
between the inferior vermis and the lateral hemisphere of
the eerebellum, whilst the other ramifies on the posterior

MEMBRANES AND BLOOD YESSELS 445

part of the inferior surface of the eorresponding eerebellar
hemisphere.

Arteria Spinalis Anterior. — The anterior spinal artery arises
near the lower border of the pons, and it is rare to find the
vessels of the two sides of equal size. They converge on
the anterior surface of the medulla oblongata and unite,
forming the eommeneement of the median vessel whieh
extends downwards on the ventral face of the spinal medulla.

The bulbar arteries are minute vessels whieh enter the
substanee of the medulla oblongata ; they spring both from the
vertebral artery itself and also from its branehes.

Arteria Basilaxis. — The basilar artery, whieh is formed by
the union of the two vertebral arteries, is a short trunk. It
extends, in the median plane, from the lower to the upper
border of the pons. At the latter point it ends by dividing
into the two posterior eerebral arteries. The basilar artery
lies in the middle part of the eisterna pontis and oeeupies
the median groove on the ventral or anterior surface of the
pons. Anteriorly it is supported by the basilar portion of
the oeeipital bone and the dorsum sellae of the sphenoid.

The branehes whieh spring from the basilar artery proeeed
laterally for the most part from either side of the vessel.
They are : —

1. Pontine.

2. Internal auditory.

3. Anterior inferior eerebellar.

Rami ad Pontem. — The pontine branehes are numerous
slender twigs whieh run laterally on the surface of the pons
and enter its substanee.

Arteria Auditiva Intema. — The intemal auditory artery
will be seen amongst the pontine branehes. It aeeompanies
the aeustie nerve into the internal aeustie meatus, and is
distributed to the internal ear.

Arteria Cerebeili Inferior Anterior. — This artery inelines
postero-laterally to reaeh the anterior part of the inferior
surface of the eerebellum.

Arteria Gerebelli Superior, — The superior eerebellar artery
is a large vessel whieh springs from the basilar elose to its
termination. It winds laterally and posteriorly, along the
upper border of the pons, to reaeh the upper surface of the
eerebellum, upon whieh it spreads out in a number of large
branehes.

4. Superior eerebellar.

5. Posterior eerebral.

446 THE BRAIN

Arteria Cerebri PoBterior. — Iminediately beyond the origin

of the two superior eerebellar arteries the basilar tmnk
bifurcates into the two posterior eerebral arteries. These
diverge from eaeh other, and, curving laterally and posteriorly,
eneirele the meseneephalon. Then ihey nin posteriorly towards
the under sufface of the splenium of the eorpus eallosum.
In this eourse eaeh posterior eerebral artery lies deeply in
the interyal between the eorresponding peduneulus eerebri
and the hippoeampal gyrus, and, tinally, passing on to the
tentorial surface of the eerebral hemisphere it disappears

FlG. 178. — Medial and Tentorial Surfaces of Ihe lefi Cerebral Hemispliere.
Tlie dislriel siipplieii by Ihe anterior eerebtal anery is linted psrpU ; hy
the middle eerebral artery, itut ; and Uy the posterior eerebral nrtery,
red. (Senii-diagraninintie.}

from yiew, by sinking into the anterior extremity of the eal-
earine fissure. In this fissure the artery ends by diyiding into
two terminal branehes, viz., the ealearine and the parieto-
oeeipital (Figs. 178 and 180).

The oeulo-motor nerve passes anteriorly in the interval
between the posterior eerebral and the superior eerebellar
arteries, elose to the plaee where they arise from the basilar ;
and the small troehlear nerye winds round the peduneulus
eerebri below the posterior eerebral artery.

The following liranehes spring from the posterior eerebral artery ;—

{Postero-tnedian. 1 [ Tetnporal.

rostero-laleral. Corlical < CHlcatine.

Posterior ehoiioidal. ] I, l'arieto-oeeiiMtaL

MEMBRANES AND BLOOD YESSELS 447

The postero-median eentral arteries arise elose to the origin of the parent
trunk. They proeeed upwards, in the interval between the peduneuli eerebri,
and, piereing the substantia perforata posterior (O.T. posterior perforated
spaee), they supply the thalami and the medial parts of the peduneuli
eerebri.

The postero-lateral eentral arteries are a group of small slender twigs
whieh arise on the lateral surface of the peduneulus eerebri, and go to the
eorpora quadrigemina and the thalamus.

The posterior ehorioidal artery^ somewhat larger, goes to the tela
ehorioidea of the third ventricle and the ehorioid plexus of the lateral
ventricle (Figs. 178 and 179).

The temporal branehes, two or three in number, turn laterally, over the
hippoeampal gyrus, and ramily on the under surface of the temporal lobe
of the eerebrum (Figs. 178 and 180).

The ealearine braneh follows the ealearine fissure to the oeeipital pole
of the eerebral hemisphere, round whieh it turns to reaeh the lateral surface
of the oeeipital lobe. It is the chief artery of supply to the euneus and the
lingual gyrus, and is therefore speeially eoneerned in the nutrition of the
visual eentres of the eerebral cortex (Fig. 178).

The parieto-oeeipital artery is the smaller of the two terminal branehes
of the posterior eerebral. It runs upwards in the parieto-oeeipital fissure,
and reaehing the upper margin of the eerebrum it turns round it to
reaeh the lateral surface of the oeeipital lobe. It supplies branehes to the
euneus and prseeuneus (Figs. 178, 180).

Arteria Oarotis Intema. — The eut extremity of this great
vessel lies on the lateral side of the optie ehiasma, in the
angle between the optie nerve and the optie traet. At the
substantia perforata anterior, elose to the eommeneement of
the lateral iissure, it ends by dividing into the anterior and
middle eerebral arteries (Fig. 1 79). The middle eerebral artery
is the larger of the two terminal branehes, and, as it enters the
lateral (O.T. Sylvian) iissure, it appears to be the eontinuation
of the parent trunk. The anterior eerebral artery^ on the
other hand, proeeeds medially from the internal earotid at
almost a right angle. This explains how it is that emboli
pass more frequently into the middle eerebral than into the
anterior eerebral artery. From the internal earotid artery,
after it has emerged from the cavernous sinus (p. 331), the
following branehes arise : —

1. Ophthalmie (already studied,

P- 341)-

2. Posterior eommunieating.

3. ehorioidal.

4. Middle eerebral.

5. Anterior eerebral.

Arteria Communicans Posterior. — This, as a rule, is a
slender braneh whieh passes posteriorly to join the posterior
eerebral between its postero-median and postero-lateral groups
of basal twigs (Fig. 181).

Arteria Ghorioidea, — The ehorioidal artery enters the

448

THE BRAIN

inferior eornu of the lateral yentriele, and passes into the
ehorioid plexus in that cavity (Fig. 179).

Arteiia Oerebri Anterior. — The anterior eerebral runs first
horizontally, above the optie ehiasma, towards the median plane
(Figs. 178, 179). Then, bending sharply upon itself, it tuma
upwards in the anterior part of the longiludinal (issure, anterior

FiG. 179. — Iiiferior Surface of Ihe Cerebral Hemisphere. The dislriets sup-
pliod by the three eetebral arleries are linted differeQlly ; poslerior lerebt^
Mtery, reii; middle eerebial arlery, i/ue ; aoleritir eerebral artery, /iir]«Jlr.

Co the laniina terminalis, and along the rostrum to the genu
of the eorpus eallosum, round whieh it bends ; then it passes
posteriorly along the medial face of the hemisphere, on the
upper surface of the eorpus eallosum, to the parieto-oeeipital
Assure (Ftg. 1 78). As it lies anterior to the lamina terminalis
it is eonneeted with the opposite anterior eerebral artery by
the ankrior eonimunieating artery, and as it passes along the
longitudinal fissure, between the hemispheres, it lies elose to
its fellow of the opposite side.

MEMBRANES AND BLOOO YESSELS 449

Numerous branehes proeeed from the anletioT eerebial artery : —
Basal or eentral { Antero-median.

l Medkl orbital.
Cortical J ■^"""O' medial fronlal.

I Intermediate medial froiital.

l. Posterior medial frontaL

The anlero-mediaii arteries pieree the base of the brain anterior lo the
optie ehiasma. They supply the rostrum of the eotpus eallusum, the
lamina teiminalis, and the septum pellueidum.

The medial erbital branehes are two or Ihree in numlier. They turn
round the matgln of the longitudinal lissure to reaeh ihe medial pait of the

=■1

i dislrielssupplied
(Semi-diagram-

orbital sutfaceoflhefrontal lobe. Theysuppiylhegytustcelus,theolfacloiy
traet and bulb, and the medial orbital gyrus (Figs. 17S and 179)-

The anlerisr medial /ronlal artery tamifies upon (he anterior part of the
inedial surbee of Ihe fronlal lobe, and its terminal Iwigs turn lound the
uppet mai^in of the eerebtal bemispbeie, aad supply the upper part or (he
lateral surSee of the frontal lobe (Fig. 178)-

The intermediate inedial /rontal ariery ramifiei oa Ihe medial surfice
of tbe frontal lobe postetiot to the preeeding braneh. Its (erminal pait
■ ■ ■■ - -' mof (he

passes ovet the paraeetittal lobule, and leaehes Ihe adjac

I porlKm 01

Arteria Oerebri Media. — At 6rst the middle eerebral artery
passes laterally and then upwards in the lateral fissure. It

VOU II— -28

■^- ■/'- \-' ■':•'',/' ."-• /-«- •-j, j— •^■5^15. -r *--f» ■ —^^^-'rT Tt=^":rP- i^^w*

Tr>» ',rtrj--rj« »rJi'i: ^^rir^g fr:ci iie z:3i'il'; isrs-rml ir-irT 3xaj be
'r,T4rj'.r.*--..

' >',T* : 'j« » r.r ir.er.'t't.

Fr'-t:*.5.I - Inrtri^r lii-inl ^irTrr:!'
* Aseesin^ 5r::ci2l_

T*n:pcraL

'I h': ar ^rr:*--! '.,5 tr.t arUin'lTiir-il -aiil /»"-"»/ are Trar n
\h*rt'^. *!:**-, v:->.*i.''.*.l.i r^rtora.*^ an*-er:or *-•£ =^??^7 ^ Iei:ii5jcm rrneleiis,
•r.': iT^.^.rr^l ar.'i '.h* eiternal eap.'^^I-^. rhe ca-ii:i ^.^rl'eTii. ind a portiaD of
*c.^, *hal;irr.j-..

17»*: /ronial a.'.i pKiri'tial hranehe: t^im r^en-i :he iipeer Iip of the
f/'/%*.*Tior rirnit of th^ \z.\tT2X rjszzt zzA aseend oc :be Lneril sartKe of the
h':rr,:*ph-rr*;. Th»: /r'yntal hrart'^'m: are : ■!■ laieril :-r^i:^ to tbe laeenl
;Ar: of •h'i ^rhi''jal 'Ts-rraee of '.r,t (Trtr.isl I:be : 2 in^irirr ljxeral fnmeal
*o 'h': i.'.f':r:'^r a.'.'-i rr.M'ile it'-^r.'.^l gyri ; -3. a:cir^inz f^^7n:zl^ «-hieh nns
ijp*Aar'i'- ir» T*-A'a.\v»r: to the ar.terior eer.u^ gy^^-

Tfi': a:rendini^ parieiil hrineh eitends :n an upwnrd and posterior
«'Jir':/'/iori ir; rf:Iati^r* to :he p^^steer.tral g^TU.^. ar:i 13 :errnin.il twigs snpply
^h': j.^r':aV:r ;.ar: ^/the c^.r.-:x of :he 5-jper::r par:e:al iobele.

'I he pririetotemporal hraneh ii a very large anery whieh issaes fiK>iii
rh': \/>\*-.x'v>x :>ar: of :he ^r^terior hraneh of :he Ia:eral nssure : it sends
hrar.'-h':'-. ■.i:jW^x'1- to the infer:or parietal lobwle. an-i others vhich indme
'!o'Anwari-, ov':r the :/>s:-rr:or par of the :en:poraI I?l-e. Its twigs, as
;t rjl';, '■iO not ':r.':roach u;/jn the Ia:eral 5urface 01 ihe oeeipital lobe.

Th': temporal hran^he:, two or three in riUinb"er. issue troai the posterior
rrifr.j . of th'; la*':ral fis=ure, and, tuming downwaris and posteriorly, over
if '. low:r lip '/.-?. the 5u;y:rior temp^oral g>TU>., they ramit}- apon the
I;i*':ral '-.:irf;i''y; of the terri[Xjral lo:^.

eireulus Arteriostis CO.T. Girele of Willis). — This re-

rnarkable anastomosis is plaeed beneath the base of the brain
in th^; deep hollow anterior to the pons. It takes the fonn
of a heptagonal or hexagonal figure, and the vessels whieh
eorripos/; it lie in the eisterna interpeduneularis and the eistema
^:hiasrriatis. .\nteriorlv it is elosed bv the anterior eommuni-
(:nut\pr artery whieh links together the two anterior eerebral
artf ries. ()n either side is the posterior eommunieating
;jrtery eonneeting the internal earotid (from whieh the anterior

MEMBRANES AND BLOOD YESSELS 451

eerebral springs) with the posterior eerebraL The arterial
ring is eompleted posteriorly by the bifurcatibn of the basilar
artery into the two posterior eerebral vessels (Fig. 181). As
a rule the eireulus arteriosus is not symmetrieal. One posterior
eommunieating artery is almost invariably larger than its fellow
of the opposite side. .

Dissedion. — The brain being plaeed with its base uppermost, the
disseetor should proeeed to remove the blood vessels and membranes from

nterior eerebral artery

Anterior eommunieating
earotid
Middle eerebral

Antero-lateral basal arteries
Posterior eommunieating

Postero-median basal arteries
Posterior eerebral artery

Superior eerebellar artery

FiG. 181. — Diagram of the Gireulus Arteriosus.

its surface. This must be done with the forceps and a pair of seissors.
It is a disseetion whieh requires very delieate manipulation, beoause the
eerebral nerves, at their points of attaehment to the brain, are so intimately
eonneeted with the pia mater that any undue traetion applied to the
membranes will tear the nerves away. Indeed, in the ease of the
medulla oblongata, the disseetor is advised to. leave the pia mater in
position until the nerve roots have been studied. The relation of the pia
mater to the fourth ventricle also renders this desirable.

In removing the araehnoid and pia mater from the lateral surface of
the eerebrum, it is well to raise it first from the margins of the hemisphere,
and then to work towards the lateral fissure (Sylvian). By this method, the
membranes and vessels within this great fissure and in relation to the
insula ean be withdrawn without damage to the brain substanceC Of
eourse, at the present stage, the membranes eannot be removed from
every part of the brain ; but as the disseetion proeeeds, opportunities for
eompleting the proeess will arise.

11—29 a

452 THE BRAIN

BASE 0F BRAIN.

Fossa Interpeduneularis. — ^When the membranes are re-
moved from the base of the brain, the peduneuli eerebri (O.T.
crura\ two large rope-like strands, will be seen issuing from the
upper aspeet of the pons. Plaeed elose together as they
emerge from the pons, they diverge as they proeeed upwards
and anteriorly, and, fmally, eaeh pedunele disappears into the
eorresponding half of the eerebrum. Turning round the
lateral aspeet of eaeh pedunele, where it passes into the
eerebrum, will be seen a Aattened band, ealled the optte traet.
These bands converge as they pass anteriorly, and are Anally
joined together by a short transverse eommissural portion,
termed the optie ehiasma. This ehiasma is plaeed below the
posterior end of that portion of the longitudinal fissure whieh
intervenes between the inferior surfaces of the frontal lobes
of the eerebrum. The optie nerues run antero-laterally from
the ehiasma.

The eerebral peduneles, the optie traets, and the optie
ehiasma enelose a deep rhomboidal or lozenge-shaped interyal
on the base of the brain, whieh is termed the interpeduneular
/ossa. Within the limits of this area the following parts may
be seen. The substantia perforata posterior bounded an-
teriorly by the eorpora mamillaria] anterior to the eorpora
mamillaria is the tuber einereum, and attaehed to it is the
infundibulum of the hypophysis. These struetures take part in
the formation of the floor of the third ventricle of the brain.

The oculo-7?iotor nerues issue from the brain within the
interpeduneular fossa. Eaeh nerve emerges from the medial
side of the eorresponding peduneulus eerebri.

Substantia Perforata Posterior (O.T. Posterior perforated
spaee). — At its posterior angle, immediately anterior to the
pons, the interpeduneular fossa is very deep, and is roofed
by a layer of grey matter in whieh are numerous small
apertures. This is the substantia perforata posterior. From
the apertures whieh are dotted over its surface the postero-
median basal branehes of the posterior eerebral artery have
been withdrawn.

Oorpora Mamillaria. — These are two small, white, pea-
shaped eminenees plaeed, side by side, anterior to the sub-
stantia perforata posterior. At a later stage of the disseetion

BASE 0F BRAIN

453

their eonneetions with the eolumns of the fornix will be
displayed.

Tnber emereiun. — This is a slightly raised field of grey
matter whieh oeeupies the interval between the eorpora

mamillaria posteriorly, the optie ehiasma anteriorly, and the
optie traets laterally. Springing froiii the anterior part of the
tuber einereum, immediately posterior to the optie ehiasma,
is the inrundibulum or stalk of the hypophysis. In the

RASE 0F BRAIN

ral prominenee ealled the olive. A distinet suleus or grooye,
^ieh passes downwards anterior to this body, separates it
elongated strand, termed ihe pyraniid of the medulla
fc]ongata. From the bottom of this suleus and its prolonga-
n downwards issue a series of nerve fila whieh belong to two
t nerves. Those whieh issue from the lower part of
3ve, below the level of the olive, belotig to the anlerior
vot of the firit eemkal nerve ; those whieh emerge from the

Optic.hL-iir,,n_ _

^^br^

Mesi-'iieeplialo» of a full-l!

e Fo:lus.

upper part of the groove, in the interval between the olive
and the pyramid, form the hypoglossal ntrve.

OIoaso-phaiynKeal,'Va^,aiidAcceasoiyNeiveB. — Posterior
to the olive, in the postero-laleral suleus of the meduUa
oblongata, is atiolher eontinuous Tow of nerve fila. These
fxtend downwards, beyond the level of the olive, and are
:ittached to ihe whole lenglh of the medulla oblongata in
linear ordor. They lielong lo three nerves, but it is im-
•ipossible at present (seeing that the nerve-trunks whieh

454 THE BRAIN

removal of the brain its eonneetion with that body was
severcd.

Snbstantiae Perforat» Anteriores. — These are small
iriangular distriets of grey matter, one on eaeh side. Eaeh
is bounded posteriorly by the uneinate extremity of the hippo-
eampal gyrus; anteriorly by the diverging striae of the
olfactor)- traet : and medially by the optie traet. I^terally
it passes into the roof of the lateral iissure, and is perforated
by the antero-lateral basal arteries. The grey matter in this
area is eontinuous above with the grey matter of the lentiform
nueleus (O.T. lentieular).

TiamiTia Terminalis. — If the anterior border of the optie
ehiasma is displaeed posteriorly a thin lamina will be notieed.
It passes upwards from the ehiasma into the longitudinal
fissure, to beeome eonneeted with the rostrum of the eorpus
eallosum. This is the latnina terminalis, It eloses the third
ventricle anteriorly, and is eontinuous on either side with the
grey matter of the substantia perforata anterior.

Superficial Origins of the Oerebral Nerves. — Twelve
eerebral nenes are enumerated arising from the brain on either
side of the median plane. They are the olfactory or first ;
the optie or seeond ; the oeulo-motor or third ; the troeh-
lear or fourth ; the trigeminal or fifth ; the— abdueent or
sixth ; the facial or seventh ; the aeustie or eighmT^e
glosso-pharyngeal or ninth; the vagus or tenth ; the aeeessory
or eloventh ; and the hypoglossal or twelfth.

Eaeh of these nerves is said to have a " superficial " and a
" deep " origin. By the term " superficial origin " is meant
the region where its fibres enter or leave the brain surface ;
the term ** deep origin " indieates the eonneetions whieh are
established by the fibres of the different nerves with nuelei or
elusters of nerve-cells within the substanee of the brain. These
nuelei are of two kinds : ( i ) those in eonneetion with whieh
the afiferent or entering nerve fibres end ; and (2) those from
whieh the efierent or emerging ner\'e fibres arise. It is the
superficial attaehments only whieh eome under notiee of the
disseetor at the present time.

No fewer than eight of the eerebral ncr\*es have a superficial
attaehment to the ventral part of the hind brain whieh is
formed by the meduUa oblongata and the pons.

Hypoglossal Nerve. — Upon the lateral aspeet of the
medulla oblongata, in its upper half, is a very eonspieuous

BASE 0F BRAIN

455

oval prominenee ealled the olive. A distinet suleus or groove,
whieh passes downwards anterior to this body, separates it
from an elongated strand, termed ihe pyramid of the medulla
oblongata. From the bottom of this suleus and its prolonga-
tion downwards issne a series of nerve fi]a whieh belong to two
different nerves. Those whieh issue from the lower part of
the groove, below the level of Ihe olive, belong to the anlerior
root of the first cervical nerve ; those whieh emerge from the

upper part of the groove, in the interval between the olive
and the pyramid, form the hypoglossal nerse.

GlosBO-phairngeal, YaguB, and AeeessoryHorres.— Posterior

to the olive, in the postero-lateral suleus of the medulla
oblongata, is another eontinuous row of nerve Pila. These
estend downwards, beyond the Ievel of the olive, and are
attaehed to the whole length of the medulla oblongata in
linear order. They belong lo three nerves, but it is im-
possible at present (seeing ihat the nerve-trunks whieh they

45^

THE BRAIN

build up are divided) to determine preeisely the number of
fila whieh belong to eaeh. From below upwards the nerves
whieh they (orra are the aeeessory, the vagus, and the glosso-
pharyngeal. The fila of the vagus and the glosso-pharyngeal
are mueh more elosely erowded together than those of the
aeeessory,

The roots of the aeeessory, whieh spring from the medulla
oblongata, eonstitute only one part of the nerve. The spinal

part springs from the spinal medulla, as low down as the sixth
cervical nerve, by a series of roots whieh issue from the lateral
funiculus, posterior to the attaehment of the ligamentum
dentieulatum.

Aenatie and Fiu:ial Nerres. — These issue elose together
at the lower border of the pons, and imraediately above the
restiform body. The aatsHe nerve is the larger of the two,
and it lies on the lateral side of the facial. Its two roots,
termed the eoehlear and the vestibular, embraee the restiform
body.

BASE 0F BRAIN

457

The facial neme issues from the poiis elose to its lower
border, and just to the medial side of the aeustie nerve,
by two roots, a large motor root, and a small sensory root
(O.T. pars intermedia), The two roots unite in the internal

Abdueant Nerve. — This is a small nerve whieh emei^e's
from the groove between the iower border of the pons and the
lateral part of the pyramid.

Trigemuial Nerve, — This is the largest of all ihe eere^
nerves. It appears at the side of the pons, nearei^ts'^per

eerebelluni.
MKemephale

i.phen^

;

Itraehium poniis.
. RBlirLirn, liody.

in whieh thi
(From Sehi

«albe.)

part5of

than its lower border and in a line with the facial and aeustie
neryes. It eonsists of two roots — a large sensory root, portio
major, eomposed of a great number of lila loosely held together,
and a smali, more eompaet motor root, portio minor, whieb
emerges antero-medial to the point at whieh the sensory root
enters the pons.

Troehlear Nerve. — The superficial origin of the troehlear
or fourth nerve eannot be seen at presenL It emerges from
the anterior medullary velum, on the dorsal aspeet of the
brain-stem. It is a delieate little nerve whieh has a long
intraeranial eourse. It winds round the lateral side of the
peduneulus eerebri, between the eerebrum and eerebellum.

458 THE BRAIN

Oeulo - motor Nerve. — This may be seen within the
interpeduneular fossa. It issues by several fila from the
suleus oeulomotorius on the medial face of the eerebral
pedunele.

Optie Nerve. — This is a large round nerve whieh passes
antero-laterally from the optie ehiasma.

01factory Nerves. — These arise from the olfactory bulb
and enter the nasal cavity through the foramina in the
cribriform plate of the ethmoid bone,

Gteneral Oonneetions of the Several Parts of the Brain. —
Before proeeeding to the more partieular study of the different
parts of the brain the student should acquire a general
eoneeption of the manner in whieh these are eonneeted with
eaeh other. In the posterior eranial fossa, below the ten-
torium, are plaeed the medulla oblongata, the pons, and
the eerebellum, whieh eonstitute collectively the Rhomben-
eephalon or hind-brain. They surround a cavity whieh is
ealled the fourth ventricle of the brain, and all stand in
intimate eonneetion with one another. The upper end of
the medulla oblongata terminates chiefly in the pons, but two
large strands on its posterior or dorsal aspeet, termed the
restiform bodies, pass posteriorly into the eerebellum (Fig.
185, d). The transverse fibres of the pons are gathered
together on either side in the form of a large rope-like strand,
the braehium pontis. This disappears into the eorresponding
hemisphere of the eerebellum (Fig. 185, c\

The great mass of the brain is termed the eerebrum.
This oeeupies the anterior and middle eranial fossse, and
extends posteriorly into the oeeipital region above the
tentorium eerebelli. The greater part of the eerebrum is
formed by the eerebral hemispheres, whieh are separated
from eaeh other, in the median plane, by the longitudinal
fissure. At the bottom of this fissure may be seen the corfus
eallosuin^ a broad eommissural band whieh eonneets the two
eerebral hemispheres with eaeh other. Eaeh hemisphere is
hollow — the cavity in its interior being termed the lateral
ventricle of the brain. Between and below the eerebral
hemispheres, and almost eompletely eoneealed by them, is
the thalameneephalon, The prineipal parts forming this portion
of the brain are the two thalami, between whieh is the third
ve?itricle of the brain — a deep, narrow cavity oeeupying the
median plane. The third ventricle eommunieates with the

THE GEREBRUM 459

lateral ventricles through the foramen interuentrieulare (O.T.
/oramen qf Monro),

The eerebrum is eonneeted with the parts in the posterior
eranial cavity (pons, eerebellum, and medulla oblongata) by
a narrow stalk ealled the mid-brain^ or meseneephalon. The
mid-brain is built up of a ventral portion, the peduneuli
eerebri, passing between the pons and the eerebrum (Fig.
185, a\ and a dorsal portion, the lamina quadrigemina.
It is tunnelled by a narrow passage — the aquceductus eerebri
(O.T. agueduet of Sylvius) — ^whieh eonneets the fourth and
the third ventricles.

THE GEREBRUM.

Gerebral Hemispheres. — Eaeh eerebral hemisphere presents
a lateral, a medial, and an inferior surface, whieh are separated
from one another by more or less distinetly marked borders.
The lateral surfa£e is convex, and is adapted to the concavity
of the eranial vault. The medial surface is flat and perpen-
dieular, and is more or less eompletely separated from the
eorresponding surface of the opposite hemisphere by the falx
eerebri, whieh oeeupies the longitudinal fissure. The inferior
surface is irregular, and is adapted to the anterior and middle
eranial foss3e, and also to the upper surface of the tentorium
eerebelli. Traversing this surface, in a transverse direetion,
nearer the anterior than the posterior end of the hemisphere,
is the stem of the lateral fissure (O.T. Sylvian) (Fig. 182).
This deep cleft divides the inferior surface into an anterior
or orbital area^ whieh rests upon the orbital plate of the frontal
bone and is, consequently, concave from side to side, and a
more extensive posterior or tentorial area^ whieh lies on the
floor of the lateral part of the middle eranial fossa and the
upper surface of the tentorium eerebelli. The tentorial
portion of the inferior surface is arehed antero-posteriorly,
and looks medially as well as downwards.

The borders whieh separate the surfaces from eaeh
other are the supero-medial, the supereiliary, the infero-
lateral, the medial oeeipital, and the medial orbital. The
supero-77iedial border, convex antero-posteriorly, intervenes
between the medial and lateral surfaces. The superdliary
border is highly arehed, it separates the orbital surface

46o THE BRAIN

from the lateral surface. The infero-lateral'harder marks off
the tentorial part of the inferior surface from the lateral
surface. The medial oeeipital border is not very distinet,
except in eases where the brain has been hardened in situ,
It extends from the posterior extremity of the hemisphere to
the posterior end of the eorpus eallosum, and intervenes
between the medial surface and the tentorial part of the inferior
surface. The medial orbital margin extends from the frontal
pole to the lamina terminalis and separates the orbital from
the medial surface.

The most projecting part of the anterior end of the
eerebral hemisphere is ealled the frontal pole^ whilst the
most projecting part of the posterior end is termed the
oeeipital pole, On the under surface of the hemisphere, the
prominent rounded portion of eerebral substanee whieh ex-
tends anteriorly below the lateral iissure receives the name of
the temporal pole. In a well-hardened brain a broad groove is
usually present on the medial aspeet of the oeeipital pole of
the right hemisphere. This eorresponds to the termination
superior sagittal venous sinus.

Longitudinal Fissure. — This great median cleft is oeeupied
by the fold of dura mater termed the falx eerebri. Anteriorly
and posteriorly, it eompletely separates the eerebral hemi-
spheres from eaeh other, but the intermediate part is Aoored
by the eorpus eallosum — the eommissural band whieh passes
between the hemispheres and eonneets them together. The
upper surface of the eorpus eallosum ean be displayed by
gently drawing asunder the two sides of the longitudinal
fissure.

Dissedion. — If two brains are available, the disseetor is adyised, at this
stage, to separate the eerebrum from the eerebellum, pons and medulla
oblongata in one of them, by eutting transversely through the mid brain if
this has not been done already. The eerebrum may then be split in the
median plane by plaeing a long knife in the longitudinal iissure and divid-
ing, with one sweep, the various parts whieh eonneet the two sides to eaeh
other. By this proeeeding, the three surfaces of eaeh eerebral hemisphere
are exposed, and the gyri and sulei ean be studied fully and satis£Eu:torily.
If only one brain is at the disposal of the student, he should not, at this stage, .
separate the eerebral hemispheres from eaeh other, but should endeavour
to follow out the gyri and sulei with the various parts of the brain in
position. No doubt he studies the hemisphere in this way at a dis-
advantage, but as the disseetion proeeeds, opportunities will oeeur whieh
will enable him to examine those distriets of the surface whieh he ean see
only imperfectly at present.

Gerebral Gyri and Sulei. — The surfaces of the eerebral

THE GEREBRUM 461

hemispheres are rendered highly irregular by the presenee of
gyri, separated from one another by intervening furrows,
termed sulei and fissures. The surface pattern whieh is pre-
sented by these gyri and sulei is, in its general features, the
same in all human brains; but when the eomparison is
pushed into more detail many di^Terenees beeome manifest,
not only in the brains of different individuals but also in
the two eerebral hemispheres of one individuaL

Of the furrows two yarieties must be reeognised, viz.,
eomplete and ineomplete. The eomplete fissures are few in
number and they eonsist of inwardly direeted folds whieh
involve the whole thiekness of the eerebral wall. They eon-
sequently show in the interior of the eerebral cavity or lateral
ventricle in the form of elevations on its walls. In this
eategory are ineluded (i) the hippoeampal fissure ; (2) the
anterior portion of the ealearine fissure ; and (3) a portion of
the eollateral fissure. The ineomplete fissures and the suki are
merely furrows of varying depth whieh do not produee any
effect on the surface of the ventricular walls.

O-eneral Strueture of the Gerebral Hemispheres. — Eaeh
eerebral hemisphere is eomposed of an outside eoating of
grey matter, spread in a eontinuous and uninterrupted layer
over its surface, and an internal eore of white matter. The
grey eoating is termed the eerebral cortex^ whilst the white
internal part is ealled the medullary eentre, Eaeh gyrus
shows a eorresponding strueture. It has an extemal
covering of grey matter supported upon a eore of white
medullary matter. But, in addition to the grey matter on the
outside, there are eertain large deposits of grey matter em-
bedded in the substanee of eaeh hemisphere in its basal part,
These eonstitute the basal nuelei, and although to a eertain
extent they are isolated from the grey matter on the surface,
nevertheless, at eertain points, they are direetly eontinuous

with it.

By means of the gyri and sulei the grey matter on the
surface of the hemisphere is inereased, and its elose
assoeiation with the vascular pia-mater is maintained without
any unneeessary inerease of the bulk of the organ. The
vascular pia-mater dips into every fissure and suleus, and
opportunity is therefore afforded for the eortieal vessels to
break up into twigs of exceeding fineness before they
enter the substanee of the hemisphere. The distribution

46j

THE BRAIN

of the blood to the grey cortex is in this way rendered
uniform.

Oerebral Lobes and Inteiloliar FiBBtireB. — Cenain of the
fissures whieh traverse tbe surface of the eerebnini are
arbitrarily ehosen for the purpose of subdividing the surface
into distriets, termed lobes. These fissures, whieh receive
the name of interhhar, are the following — (i) the lateral
fissure (O.T. Sylvian); (j) the eentral (O.T. fissure of
Rolando); (3) the parieto-oeeipitai ; (4) the eollateral; and
(5) the eireular suleus (O.T. limiting suleus of Reil).

— Gyri and Sulei on Ihe Latenil Surface of Ihe Gerebral Hemisphere.

The lobes whieh are mapped out by these fissures are —
(i) the frontal; (2) the parietal ; {3) the oeeipital ; (4) the
temporal ; (5) the insula. To these may be added a sixth
lobe, in no way related to the interlobar Rssures, viz., the
olfactory lobe.

Lateral Pissnre (O.T. Sylvian). — This is the most eon-
spieuous lissure on the surface of the eerebrum. It is
eomposed of a short main stem, from the lateral extremity of
whieb three branehes tadiale. The stem is plaeed on the
inferior surface of the eerebrum (Fig. i8z). It begins at
tbe substantia perforata anterior. Thenee it passes laterally,
forming a deep cleft between the temporai pole and the
orbital surface of the frontaI lobe. Appearing on the lateral

«;t -■

(3' :■■-■- ■■

T.-.-: /

1 r»-* -■ - ^- - - -

u:.''v:.:^

I - .i ^» '

464 THE BRAIN

the insula to meet the temporal opereulum. Its margin
forms the upper lip of the posterior braneh of the latend
iissure.

The /rontal opereulum (Fig. 186) is the small triangular
pieee of eerebral cortex between the anterior aseending and
horizontal branehes of the lateral lissure. It is sometimes
termed the/ar^ triangularis,

The orbital opereulum (Fig. 186) is for the most part on
the under surface of the hemisphere. It lies below the
anterior horizontal limb of the lateral lissure, and passes
posteriorly from the orbital aspeet of the frontal lobe over
the anterior part of the insula.

Suleus Oentralis (O.T. Fissure of Bolando). — The eentral
suleus takes an oblique eourse aeross the lateral surface
of the eerebral hemisphere (Fig. 186). Its upper end in
many eases euts the supero-medial border of the hemisphere
a short distanee posterior to the mid-point between the
frontal and oeeipital poles, whilst its lower end terminates
above the middle of the posterior braneh of the lateral iissure.
When its superior extremity turns round the supero-medial
border of the hemisphere it is eontinued posteriorly,
for a short distanee, on the medial surface (Fig. 187).
Although in its general direetion the suleus eentralis is
oblique, it is far from being straight. Nearer to its upper
than to its lower end it is bent posteriorly so as to form a
bay, within whieh is aeeommodated a portion of the eerebral
cortex whieh represents the motor area of the opposite upper
limb. The upper and lower limits of this bay are termed
the upper and lo%ver genua of the fissure.

Pissura Parieto - oeeipitalis. — The greater part of this
fissure is situated on the medial surface of the eerebral hemi-
sphere (Fig. 187); only a very small part appears on the
lateral face (Fig. 186).

The lateral part of tJie parieto-oeeipital fissure (O.T. extemal
parieto-oeeipiiat) euts the supero-medial border of the hemi-
sphere, in a transverse direetion, from one and a half to two
inehes anterior to the oeeipital pole. It is usually not more
than half an ineh in length, and it is brought to an abrupt
termination by an arehing convolution whieh winds round its
extremity, and receives the convenient name of areus parieto-
oedpitalis (Fig. 186).

The medial part of the parieto-oeeipital fissure (Fig. 187)

r-'x

i downwards, in a :w.' :■* •^\-.; \'f. / %'', . .*. • .. - - ■• ••.•.- -
•»re of the hemisrKt*-.';'. ^.> >. ,v..'.v.v.. . .. •■ - -.'. ,•■.%■.- . . V
**1:, at its lower onr.. ^' ■'> i>'r ,-;;\;;-. .■/.- .■.v.. .v

^■.;sura Oollateralis i^y.s: *. S-^ V''.r .\..;. v ■.;.■..---. ■•. ■= •.
■nely marked fis$uro o.'; ',:\c ',c\\uk\.V, \\--..\ »v; •.:•.. .•.•..; •.•.,-.x
*^''C of the eerobni'i ho',v.:>;^l*.<'iv" 1; ^.e •,■.♦.■: •.♦., ■.» \*\w
Iial pole, and ONtoiu'.s ;;?*.;or.iMl\ (im>:;\\;-. \\\x- -., i\>jsm »1
Posteriorly il lios ^oIonn a\u\ \\\\i\\\i-\ i«« U». . »l. \tiiw.

I .-1111 >l ai«li »..'

/ * . \ I ...l.i . ...|».U

^ 1 ■ A •

• *^ »

• •i |P.

»..

, ry*-*-v:. •*- — ^ -1j/

^i^ eallosuiu
Keptuiii peUueiduni

Anterior com[i]is.tui*.:

li \»-nv

.^ tllllll>il< > ir>/{. •

^ i''icj. 187. — The J'jvri 1»'' \mIi«. ••»» ^to .■'.\,':i..". .n.< * v,»i. -...■.».

"* "^, whilst anterioriv it .k ;»»::.'i*.''.v.'.«/. v.*.'v. :•..*. •.•.•.\«-r^ i.u-.yi.
7 by the hippoeamn'ii v"'.x«: i-'-.n:'. 1: :-..* •.•.^/.\..v iv..\
"lodial convolution >fi tu» i^nuM'u. ;.•••.' -.«* ".-..^ t '.-.;>. «*,*..•
f the hemispher»' 'j'*q. -<' .

ior tO the eollat'^riil Il^imIi ^ :h'.illi\it* .ul.».u, .w \t

ic anterior end of ^*-' ••iiii)/vi->..i i\)'j* iwt', ni,\.^ •*.»*».
the temporal \)'''^*<^. i*"*^! ^»'* iiu»iu!c.»* \» w\/\)'.'Ji'.»
'\ of the hippocf*rrTrj.^J j\T*i* .' ««t t- 'w» .',•;. -,^1
'//> or eeto-rhinal fi^^urt ^Y\%. ro8^,
^eus Oinguli (O.T. -^* ] > -' 'i. ^•.

;.'.is is a stroi ^ m» t -atlterior' jiftr*. >r

. n — 30

.Ji

466

THE BRAIN

the medial surface of the hemisphere. It eommenees on the
lower portion of the anterior part of the medial surface, curves
Tirst upwards and then posteriorly. Finally, tuming upwards,
it euts the supero-medial border of the hemisphere a short
distanee behind the upper end of the suleus eentralis, and
terminates on the lateral surface of the parietal lobe. It
separates the anterior portion of the medial surface into a
marginal and a eentral area. The eentral part is the gyrus
dnguli (O.T. eallosal gyrus^ The marginal part is separ-
ated into two portions by a braneh of the suleus einguli, whieh
projects upwards above the middle of the eorpus eallosum.
The anterior part is the m.edial area of the superior frontal
gyrus ; the posterior part is \}\t paraeentral lobule,

Bonndaries of the Prontal Lobe. — The frontal is the largest
of the eerebral lobes. On the lateral surface of the hemisphere
it is bounded posteriorly by the eentral suleus, and below by
the posterior braneh of the lateral fissure. On the medial
surface it is limited by the suleus einguli ; whilst on the inferior
surface of the hemisphere the stem of the lateral fissure
forms its posterior boundar}'.

Lateral SuriiEU» of the Prontal Lobe. — On the lateral
surface of the frontal lobe the following sulei and g^rri may be
reeognised : —

Sulei

''Suleus preeeeniralis in-
ferior.

Suleus prieeeniralis su-
perior.

Suleus parametlialis.

Suleus frontalis superior.

Suleus frontalis medius.

Suleus frontalis inferior.

Suleus diagonalis.
^Suleus fronto-marginalis.

Gyri

' Gynis eentralis anterior.
Gj'rus front- f Pars superior.
alis superior\Pars interior.
Ciyrus front- rPars superior.
alis medius \Pars inierior.
rPars basilaris.
Gyrus front- 1 Pars triangu-

alis inferior

■1

laris.
Pars orbitalis.

Sukus Pnreentralis Inferior (Fig. i86). — The inferior prae-
eentral suleus eonsists of a vertical and a horizontal part,
and, when present in a well-marked forni, it presents a figure
like the letter T or F. The vertical portion lies anterior to
the lower part of the eentral suleus (O.T. fissure of Rolando),
and the horizontal portion extends antero-superiorly into the
middle frontal g}TUS.

Suleus Praeentralis Superior (Fig. i86). — This is a short
vertical suleus whieh lies ant^"^»' to the upper part of the

THE GEREBRUM 467

eentral suleus. It is almost invariably eonneeted with the
posterior end of the superior Trontal suleus.

Gyrus Centralis Anterior. — ^The anterior eentral gyrus is a
long eontinuous g)mis whieh is limited anteriorly by the two
praeeentral sulei, and posteriorly by the eentral suleus. It
extends obliquely aeross the hemisphere, from the supero-
medial margin above to the posterior braneh of the lateral
fissure below (Fig. 186).

Suleus Prontalis Superior (Fig. 1 86). — The superior frontal
suleus extends anteriorly from the suleus praeeentralis superior.

Gyrus Prontalis Superior (Figs. 186, 187). — The superior
frontal gyrus lies above the superior frontal suleus and passes
round the supero-medial border on to the medial surface
of the hemisphere. It terminates anteriorly in the frontal
pole.

Suleus Prontalis lnferior (Fig. 186). — This lies at a lower
level than the superior suleus of the same name. The posterior
end of the inferior frontal suleus is plaeed in the angle
between the vertical and horizontal parts of the inferior
praeeentral suleus, and is not infrequently eonAuent with one
or other of these. It passes anteriorly towards the supereiliary
margin of the hemisphere, and ends a short distanee from
it in a terminal bifurcation.

Gyrus Frontalis Medius (Fig. 186). — The middle frontal
gyrus is the broad convolution whieh lies between the superior
and inferior frontal sulei.

Gyrus Prontalis Inferior (Fig. 186). — The inferior frontal
gyrus is that portion of the lateral surface of the frontal lobe
whieh is plaeed anterior to the inferior praeeentral suleus and
below the inferior frontal suleus.

The suleus paramedialis is the term applied to a series of short
irregular furrows arranged longitudinally, elose to the supero-medial border
of the hemisphere. These rudimentary sulei partially subdivide the superior
frontal gyrus into an upper and lower division, and are of interest in so
far that they are best marked in high types of brain.

The middle frontal sukus (Fig. 186) lies horizontally in the anterior part
of the middle frontal gyrus, and divides it into an upper and a lower
part (Fig. 186). As it approaehes the supereiliary margin of the hemi-
sphere it bifurcates, and its terminal branehes spread out widely from eaeh
other, and together eonstitute a transverse furrow ealled the suleus /ronto-
marginalis.

Owing to the subdivision of the superior and middle frontal gyri in the
manner indieated, the g)rri in the anterior part of the lateral surface of the
frontal lobe are arranged in five horizontal tiers.

468

THE BRAIN

Gyrus Prontalis Inferior. — The inferior frontal gyrus
possesses a speeial interest and importanee, on aeeoiint
of the supposed loealisation within it, on the left side, of the

Longitudinal iissure

01factOTy suleus

01factor>- bulb.

Orbital suleus,

01factor>' traet-
Teroporal pole-

Ineisura
teniporalis

Inferior

.frontal

gynis

Inferior .
temporal
suleus

Collateral
/issure

Galoarine fissure

Longitudinal fissure

FiG. 188. — Gyri and Sulei on the Tentorial and Orbital Siirfaces of the

Gerebral Hemispheres.

speeeh-eentre. It eonsists of an upper non-opereuiar and a
iower opereular portio7i. The latter is eut up into three parts
by the two anterior branehes of the lateral lissure. These

THE GEREBRUM 469

are termed the pars basilaris, the pars triangularis, and the
pars orbitalis.

The pars basilaris (Fig. 186) is that part whieh lies be-
tween the vertical limb of the inferior praeeentral suleus and
the anterior aseending ramus of the lateral fissure. It forms
the anterior portion of the fronto-parietal opereulum, and it
is traversed in an oblique direetion by a shallow furrow,
termed the suleus diagonalts,

The pars triangularis (Fig. 186) is simply another name
for the frontal opereulum. It is triangular in form, and lies
between the anterior aseending and anterior horizontal rami
of the lateral fissure.

The pars orbitalis (Fig. 186) is plaeed below the anterior
horizontal ramus of the lateral fissure.

Medial Surface of the Frontal Lobe. — On this aspeet of
the frontal lobe is the elongated, more or less eontinuous,
medial part of the superior frontal gyrus (O.T. marginal
gyrus). It lies between the supero-medial border of the
hemisphere and the suleus einguli (Fig. 187).

In the anterior part of this gyrus one or two curved sulei are usually
present. These are termed the sulei rostrales.

The posterior end of the medial surface of the superior
frontal gyrus is more or less eompletely eut oflf from the
anterior part. It forms part of the paraeentral lobule^ and
lies anterior to the upper end of the eentral suleus (Fig. 187).

Orbital Siirface of the Frontal Lobe. — On this aspeet of
the frontal lobe there are two sulei — viz. the olfactory and
the orbital.

Suleus Olfactorius. — The olfactory suleus (Fig. 188) is a
straight furrow whieh runs parallel to the medial orbital
border of the hemisphere. It is oeeupied by the olfactory
traet and bulb, and it euts oflf a narrow strip of the orbital
surface elose to the medial border whieh receives the name
oi gyrus reetus (Fig. 188).

The orbital suleus is a eompound furrow whieh assumes
many different forms. Most frequently it takes the shape of
the letter H, of whieh the three eomponent parts are a
lateral limb, a medial limb, and a transverse limb.

The lateral limb curves round the orbital part of the
inferior frontal gyrus, and limits it medially. The medial
limb marks off a convolution between itself an'd the olfactory

472 THE BRAIN

parieto-oeeipitalis, it bifurcates into two widely spread-out
branehes. These form a short transverse fissure in the
oeeipital lobe, termed the suleus oedpitalis transversus (Eeker)
(Fig. i86).

The upturned ends of the posterior braneh of the lateral
fissure, of the superior temporal suleus and of the middle
temporal suleus (Fig. i86) extend for a short distanee, one
posterior to the other, into the inferior parietal lobule.

Gyri on the Lateral Surface of the Parietal Lobe. — The
interparietal suleus maps out three distriets or areas on the
lateral surface of the parietal lobe. These are the posterior
eentral gyrus and the superior and inferior parietal lobules.

The gyrus eentralis posterior (Fig. i86) is a long gyrus
whieh extends obliquely aeross the hemisphere from the supero-
medial border above to the posterior braneh of the lateral
fissure below. Anteriorly, it is bounded by the eentral
suleus, and posteriorly, by the superior and inferior posteentral
sulei.

The superior parietal lobule is the area of eerebral cortex
whieh lies between the ramus horizontalis below and the
supero-medial border of the hemisphere above. It is bounded
anteriorly by the superior posteentral suleus ; and posteriorly,
it is Gonneeted with the oeeipital lobe by the areus parieto-
oeeipitalis. It is eontinuous around the supero-medial border
of the hemisphere with the prseeuneus.

The inferior parietal lobule lies below the ramus horizon-
talis and the ramus oeeipitalis, and posterior to the inferior
posteentral suleus. It is more or less direetly eontinuous
with the oeeipital lobe posteriorly and with the temporal
lobe below. It presents three arehing gyri, viz. the supra-
marginal anteriorly, the post-parietal posteriorly, and the
angular between them.

The supra-77iarginal gyrus (Fig. i86) is folded round the
upturned end of the posterior braneh of the lateral fissure and
is eontinuous with the superior temporal gyrus. The angular
gyrus (Fig. i86) arehes over the upturned end of the superior
temporal suleus, and is eontinuous with the middle temporal
gyrus. The post-parietal gyrus (Fig. i86) winds round the
upturned end of the middle temporal suleus, and runs into
the inferior temporal gyrus.

Boundaries of the Oeeipital Lobe. — The oeeipital lobe
forms the posterior pyramidal part of the eerebral hemi-

THE GEREBRUM 473

sphere, and it eneloses the posterior horn of the lateral
ventricle. On the surface it is very imperfectly mapped off
from the parietal and temporal lobes, whieh lie anterior to it.
It presents three surfaces and an apex or oeeipital pole. On
the medial aspeet of the hemisphere it is separated from the
parietal lobe (i.e. the praeeuneus) by the parieto-oeeipital
Assure. On the tentorial part of the inferior surface it is not
separated either from the temporal lobe or from the gyrus
hippoeampi, whieh lie anterior to it. It is neeessary, there-
fore, on this aspeet, to employ an arbitrary line of demareation,
whieh extends from the prae-oeeipital noteh, on the infero-
lateral border of the hemisphere, to the isthmus of the gyrus
fornicatus, whieh lies below the posterior end of the eorpus
eallosum. On the lateral surface the parieto-oeeipital iissure,
and an arbitrary line from that hssure to the pr^-occipital
noteh, may be regarded as separating the oeeipital from the
parietal and temporal lobes.

Medial Aspeet of the Oeeipital Lobe. — On the medial
surface are (i) the ealearine hssure; (2) the euneus; and
(3) P^^*^ of ^^ gyrus lingualis.

The ealearine fissure eommenees below the isthmus of
the gyrus fornicatus and takes a curved eourse towards the
oeeipital poie where it bifurcates into short branehes. At a
point somewhat nearer its anterior than its posterior extremity
it is joined by the parieto-oeeipital fissure and the two fissures
together form a >-- shaped figure.

When ealearine and parieto-oeeipital iissures are iiilly opened up, so
as to expose the bottom in eaeh ease, two well-marked deep or submerged
gyri will be displayed (Fig. 189). One of these, the gyrus eunei^ marks
off the parieto-oeeipital fissure from the ealearine fissure ; the other in-
terrupts the ealearine hssure immediately posterior to its junction with
the parieto-oeeipital. It is ealled the anterior euneo-lingual deep gyrusy
and it divides the ealearine fissure into an anterior and a posterior part.
The anterior part of the calcarinefis5ure eorresponds very nearly to the stem
of the >--shaped hssural arrangement. It is very deep and, being a
eomplete fissure, it gives rise to an elevation, ealled the ealear avis, on the
medial wall of the posterior horn of the laterai ventricle. The posterior part
of the eakarine fissure is mueh shallower.

The euneus (Fig. 187) is the wedge-shaped or triangular
distriet on the medial aspeet of the oeeipital lobe between
the parieto-oeeipital and ealearine fissures.

The gyrus lingualis (Figs. 187, 188) is a well-marked gyrus
situated between the ealearine fissure above and the pos-

472 THE BRAIN

parieto-oeeipitalis, it bifurcates into two widely spread-out
branehes. These form a short transverse iissure in the
oeeipital lobe, termed the sukus oeeipitalis transversus (Eeker)
(Fig. i86).

The upturned ends of the posterior braneh of the lateral
iissure, of the superior temporal suleus and of the middle
temporal suleus (Fig. i86) extend for a short distanee, one
posterior to the other, into the inferior parietal lobule.

The gyrus eentralis posterior (Fig. i86) is a long gyrus
whieh extends obHquely aeross the hemisphere from the supero-
medial border above to the posterior braneh of the lateral
fissure below. Anteriorly, it is bounded by the eentral
suleus, and posteriorly, by the superior and inferior posteentral
sulei.

The superior parietal lobule is the area of eerebral cortex
whieh lies between the ramus horizontalis below and the
supero-medial border of the hemisphere above. It is bounded
anteriorly by the superior posteentral suleus ; and posteriorly,
it is eonneeted with the oeeipital lobe by the areus parieto-
oeeipitalis. It is eontinuous around the supero-medial border
of the hemisphere with the prseeuneus.

The supra-marginal gyrus (Fig. i86) is folded round the
upturned end of the posterior braneh of the lateral fissure and
is eontinuous with the superior temporal gyrus. The angular
gyrus (Fig. i86) arehes over the upturned end of the superior
temporal suleus, and is eontinuous with the middle temporal
gyrus. The post-parietal gyrus (Fig. i86) winds round the
upturned end of the middle temporal suleus, and runs into
the inferior temporal gyrus.

Boundaries of the Oeeipital Lobe. — The oeeipital lobe
forms the posterior pyramidal part of the eerebral hemi-

THE GEREBRUM 473

sphere, and it eneloses the posterior horn of the lateral
ventricle. On the suriaee it is very imperfectly mapped off
from the parietal and temporal lobes, whieh lie anterior to it.
It presents three surfaces and an apex or oeeipital pole. On
the medial aspeet of the hemisphere it is separated from the
parietal lobe (i.e, the praeeuneus) by the parieto-oeeipital
Assure. On the tentorial part of the inferior suriaee it is not
separated either from the temporal lobe or from the gyrus
hippoeampi, whieh lie anterior to it. It is neeessary, there-
fore, on this aspeet, to employ an arbitrary line of demareation,
whieh extends from the prge-oeeipital noteh, on the infero-
lateral border of the hemisphere, to the isthmus of the gyrus
fornicatus, whieh lies below the posterior end of the eorpus
eallosum. On the lateral surface the parieto-oeeipital iissure,
and an arbitrary line from that iissure to the pr^-occipital
noteh, may be regarded as separating the oeeipital from the
parietal and temporal lobes.

Medial Aspeet of the Oeeipital Lobe. — On the medial
surface are (i) the ealearine fissure; (2) the euneus; and
(3) part of the gyrus lingualis.

The eakarine fissure eommenees below the isthmus of
the gyrus fornicatus and takes a curved eourse towards the
oeeipital poie where it bifurcates into short branehes. At a
point somewhat nearer its anterior than its posterior extremity
it is joined by the parieto-oeeipital fissure and the two fissures
together form a >-- shaped figure.

When ealearine and parieto-oeeipital fissures are iiilly opened up, so
as to expose the bottom in eaeh ease, two well-marked deep or submerged
gyri will be displayed (Fig. 189). One of these, the gyrus eunei^ marks
off the parieto-oeeipital iissure from the ealearine Assure ; the other in-
terrupts the ealearine fissure immediately posterior to its junction with
the parieto-oeeipital. It is ealled the anterior euneo-lingiuU deep gyrus,
and it divides the ealearine fissure into an anterior and a posterior part.
The anterior part of the calcarinejissure eorresponds very nearly to the stem
of the >--shaped fissural arrangement. It is very deep and, being a
eomplete fissure, it gives rise to an elevation, ealled the ealear avis, on the
medial wall of the posterior horn of the lateral ventricle. The posterior part
of the ealearine Jissure is mueh shallower.

The euneus (Fig. 187) is the wedge-shaped or triangular
distriet on the medial aspeet of the oeeipital lobe between
the parieto-oeeipital and ealearine fissures.

The gyrus lingualis (Figs. 187, 188) is a well-marked gyrus
situated between the ealearine fissure above and the pos-

474 THE BRAIN

terior part of the eollateral fissure below.
the oeeipital pole and narrows, as it passes anteriorly, to its
union with the hippoeampal gyrus. It lies partly on the
medial surraee and partly on the tentorial surface of the
oeeipital lobe.

Tentorial Siiiface of the Oeeipital Lobe. — On this aspeet
lie part of the gyrus lingualis and the posterior part of the
fusiforin gyrus. They are separated by the posterior part
of the eollateral fissure. The gyrus fusiformis takes part,
anteriorly, in the formation of the temporal lobe, and it is
separated from the inferior temporal gyrus by ihe inferior
temporal suleus.

FiG. iBg. — Poslerior part of medial siixface of Ihe Left Hemisphere. The
ealearine anil ihe pajielo.occipital hssures are widely opened up lo show

tbe deep gyri wilhin Ihe

Lateral SiiTface of the Oeeipital Lobe. — There are two well-
marked su!ci on this surface of the oeeipital !obe — ^viz. the
suleus oeeipitalis transversus and the suleus oeeipitalis lateralis
or suleus lunatus or EUiot Smith.

The su/ajs oatpitalis transversus (Fig. i86) extends trans-
yersely aeross the upper pan of the lobe posterior to the areus
parietu-oeeipitalis. It has already been deseribed as the
terminal bifurcation of the ramus oeeipitalis of the inter-
parietal suleus.

The suleus oeeipitalis lateralis (Fig. i86) is a short
horizontal furrow whieh divides Ihe lateral surface of the lobe
into an upper and a lower area of very nearly equal extent.
These areas are eonneeted by means of superiieial anneetant
gyri with the parietal and temporal lobes.

THE GEREBRUM 475

Boundaries of the Temporal Lobe. — ^The temporal lobe lies
posterior to the stem of the lateral fissure and below its
posterior braneh. It presents an upper, a lateral, and a
tentorial surface, with a free apex or pole whieh projects
anteriorly. Above, it is bounded by the posterior braneb
of the lateral fissure together with the artificial Hne drawn
posteriorly from that fissure. On the tentorial surface it is
separated from the hippoeampal gyrus by the eollateral fissure ;
whilst posteriorly, it is marked off from the oeeipital lobe by
the arbitrary Hnes deseribed on p. 470. The apex or temporal
pole projects anteriorly on the under surface of the brain.
It should be notieed that the recurved extremity of the
hippoeampal gyrus, whieh Hes to the medial side of the
hemisphere, does not reaeh the temporal pole, but is
separated from it by the ineisura temporalis or eetorhinal
fissure.

Upper or Opereular Surikee of tlie Temporal Lobe. — ^This
is the surface of the temporal opereulum whieh is opposed to
the insula and the fronto-parietal opereulum. The lateral
fissure must therefore be widely opened up to expose it.
For the most part the surface is smooth, but towards its
posterior part there are a few shallow furrows, ealled the
sulei of Hesehl^ whilst anteriorly, also on the deep aspeet of
the temporal pole, two or three furrows are evident.

Lateral Siirface of tlie Temporal Lobe. — On this aspeet of
the lobe there are two horizontal sulei, ealled the superior
and middle temporal sulei.

The superior temporal sukus (Fig. 186) is a long, eontinuous
and deep cleft whieh begins near the temporal pole and
proeeeds posteriorly, below the posterior braneh of the lateral
Tissure. Its posterior end turns upwards, into the parietal lobe,
and is surrounded by the angular gyrus.

The middle temporal suleus is plaeed midway between the
superior temporal suleus and the infero-lateral border of the
hemisphere. It is very rare to find it in the form of a eon-
tinuous cleft. Usually it is broken up into several isolated
pieees, plaeed one posterior to the other. Its posterior part
turns upwards into the parietal lobe (Fig. 186), where it is
surrounded by the post-parietal gyrus, and lies elose to the
artificial line of demareation between the oeeipital and
parietal lobes.

By these two temporal sulei the lateral surface of the

476

THE BRAIN

temporal lobe is mapped out into three tiers of horizontal
gyri, whieh are termed the superior, in/erior, and middk
temporal gyri {Pig. i86).

Tentorial Snitaee of the Temporal Lobe. — On this surraee
there is one fissure, termed ihe inferior temporal suleus.

The inferior tem/ioreii sukus (Fig. i88) lies below and lateral

1, and 3- Thtee shon gyri on the fl

panofthein.suls.
snd s. Two long gi'ri ,in parieta] p

F. Orbiul opereulum (rot Ihe i

Ti. Superior lemporal gyms.
T9. Middle temporal Eynis.
x.y. GyfiofHtKhl.

to the eollateral fissure, and elose to the infero-!ateral border
of the hemisphere. It runs in an antero-posterior direetion
and is not always confined to the temporal lobe, but may
extend posteriorly towards the oeeipital pole. It is usually
broken up into two or more separate pieees.

The fusiform gyrus (Fig. i88) is sltuated between the
eoliateral fissure and the inferior temporai suleus. It extends
from the oeeipital pole to the temporal pole.

The narrow strip of 5urface below and lateral to the

THE GEREBRUM 4::

inferior temporal suleus is eondnuous, round ihe irJer»iii<
margin of the hemisphere, with the inferior :emj:<?ral bT^^
on the lateral surface of the eerebrum, and is reekooed as a
part of it.

The three temporal gyri and the fusiform gynis nin into oot
another at the temporal pole.

Insiila (O.T. Maiid of Reil). — ^The insula is a triar^gUiar
lield of eerebral cortex whieh lies on a deeper plase thaa
the general surface of the hemisi^ere, and is hidden fTozc
view by the four opereula whieh overlap it Ip. 463^ It 2$
bounded by a distinet limiting suleus, sy/iiis dreularis (Reili.
whieh has been deseribed abeady ; and its dependent apieai
part or pole, whieh looks downwards, is in eiose relatioo to
the stem of the lateral fissure, and to the substantia pedbrata
anterior on the base of the brain.

The insula is divided into sereral diverging gyri by
a series of radiating suleL Of the latter, one, whieh pte-
sents the same direetion and lies in the same plane as the
eentral suleus, receives the name of the sukus eaitralis insukt,
It divides the insula into an anterior /rottial pait and a
posterior parietal portion.

01factory Lobe. — The olfactory lobe is small and rDdi-
mentary in the human brain. It eomprises (i; the oliaetory
bulb and traet with the three striae, and (2) the trigonain
olfactorium.

The olfactory traet is a narrow white prismade band, wiueii
expands anteriorly into a swollen bulbous extremity termed
the olfactory bulb. Both the traet and the bulb lie in the
olfactory suleus on the orbital surface of the frontal lobe^
whilst the inferior surface of the bulh, when the brain is in
position, rests on the cribriform plate of the ethmoid bone
and receives the numerous olfactory nenres whieh reaeh it
through the foramina in that part of the eranial floor.

Posteriorly, the olfactory traet divides into two or three
diverging striae. The medial stria (O.T. mesial rootj eurres
abruptly medialwards, and may be followed into the extreinity
of the gyrus einguli and the subeallosal gyrus. The laieral
stria (O.T. lateral root) runs postero - laterally over the
lateral part of the substantia peribrata anterior, and gradtially
disappears from view. In animals, in whieh the oUadory
apparatus is better developed than in man, it may bc
traeed into the uneinate cxtremity of the

\%\%:%:i^\\\\i'-

47« THE BRAIN

gynis. The intermediate stria, whieh is not always present,
runs posteriorly aeross the trigonum olfactorium.

The gyrus sub-eallosus is a narrow eortieal strip, of some morphole^eal
importanee, whieh lies on the medial surface of the hemisphere immediately
below the genu of Ihe eorpus eallosum.

The trigonum olfactorium is the little triangular field of
grey matter whieh oeeupies the interval between the medial
and lateral striae of the olfactory traet at the point where
they begin to diverge.

Osnms Fomicattis. — ^This gyrus, sometimes ealled the
limbie lobe, is seen on the medial and tentorial surfaces of the
hemisphere. It is a ring-like convolution, the extremities of
whieh approaeh eaeh other elosely at the substantia perforata
anterior.

The upper and anterior part of the gyrus fornicatus lies
in intimate relation to the extremities and upper surface of
the eorpus eallosum, and it is ealled the gyrus eingulu The
lower portion of the gyrus fornicatus is termed the hippoeampal
gyrus, and forms the medial part of the tentorial portion of
the lower surface of the hemisphere. The eontinuity between
the hippoeampal g^niis and the gyrus einguli is established,
below the posterior end of the eorpus eallosum, by a narrow
portion of the gyrus fornicatus ealled the isthmus, From this
point the hippoeampal gyrus extends anteriorly towards the
temporal pole. Finally, at the side of the peduneulus eerebri,
the hippoeampal gyrus is folded on itself, and ends in a
recurved hook-like extremity, termed the uneus, The uneus
does not reaeh the temporal pole.

The gyrus dnguli (O.T. eallosal convolution) begins below
the anterior end of the eorpus eallosum at the substantia
peribrata anterior, and, winding round the genu of the
eallosum, it is eontinued posteriorly on its upper surface to
the thiekened posterior extremity or splenium. Finally,
curving round this, it beeomes greatly narrowed through
the ealearine fissure eutting into it. This narrow part is
termed the isthmus, and eonstitutes the link of eonneetion
between the gyrus einguli and the hippoeampal gyrus.

The gyrus einguli is separated from the superior frontal
gyrus and the paraeentral lobule by the suleus einguli;
from the prseeuneus by the subparietal suleus ; and from the
lingual gyrus by the ealearine fissure. It is separated from
the eorpus eallosum by the eallosal suleus.

THE GEREBRUM 479

The hippoeampal gyrus is bounded below and laterally by
the anterior part of the eollateral iissure, and anteriorly by
the ineisura temporalis, whieh separates its booked extreniily,
or uneus, from the temporal pole. Supero-medially it
is limited by the hippoeampal fissure; whilst posteriorly it
is divided into two parts by the anterior extremity of the
ealearine fissure. Of these, the upper is the isthmus, whieh
eonneets it with the gyrus einguli, whilst the lower portion
is eontinuous with the gyrus lingualis.

If the hippoeampal tissure, whieh lies above the hippoeampal gyrus,
is opened up, in a soft brain, the /aseia deniata and the fimbria lying side
by side will be brought into view. In a hardened brain the examiraition
of this region should be deferred (p. 492).

The Corpus Gallosum.

A disseetion should now be made with the view of exposing
the upper surface of the eorpus eallosum, whieh is the eom-
missural band eonneeting the eerebral hemispheres at the
bottom of the longitudinal tissure.

Disseetion. — With a long knife sliee off the top of the right hemispbere
at the Ievel of the suleus einguli. The white medullary eentre of the
eerebral hemisphere, enelosed on all hands by the grey cortex, is brought
into view, and the appearanee receives the name of eentrum 5emi-avaU,
From the eentral white mass medullary prolongations proeeed into all
the gyri.

A transverse ineision may next be made through the middle of the
gyrus einguli ; then the anterior and posterior parts of the gyrus einguli
should be torn away from the hemisphere in a lateral direetion. If this
is done successfully the manner in whieh the fibres of the eorpus
eallosum enter the hemisphere will be seen. In eases where the student
is disseeting the brain for the seeond time the knife should not be used
at all in earrying out this disseetion. The top of the hemisphere down
to the level of the suleus einguli should, in the first instanee, be tom off,
and then the gyrus einguli may be treated in the same way. By this
expedient the fibres of the eorpus eallosum may be traeed into the g^rri.

eingulmn. — If the deep surface of the gyrus einguli,
whieh has been torn away, is examined, a large bundle of
longitudinally direeted fibres will be notieed embedded in its
substanee. This is the eingulum. It ean be easily dislodged ;
a very slight degree of traetion is all that is required to
lift it out of its bed. It begins anteriorly at the substantia
perforata anterior, curves round the convexity of the eorpus
eallosum, and then deseends, round its posterior end, and
terminates in the hippoeampal gyrus. The eingulum is a

long assoeiation bundle eomposed of several systems of fibres
whieh run only for short distanees within it. It is elosely
assoeiated with the gyrus fornicatus.

Dissation. — The gyri and sulei on the medial surface of the left hemi-
sphere may now be studied, and Iheo ihe disseetion, whieh has been
earried out with the view of exposing [he eorpus eallosum, may be repeated

on ihe left side. In doing this, however, take eare not to injure the medial
surface of ihe left hemisphere poslerior to the parieto - oeeipital iissure,
indeed, an effort should be made lo preserve that Hssure intaet, SO that it
and the euneus may be studied afterwards, on this ^de, in eonneetion wllh
theeyri and sulei on the under surface of the hemisphere.

'nie upper surface of the eorpus eallosum is nowr exposed, ind it will
be seen that it unites into one mass the medullary eentres of the two
hemispheies. The eontinuous white lield, eonsisting of the eorpus eallosum
and the medullary eentre of eaeh hemispheie, ieceives the name of

Gorpus eallosum. — This is the great transrerse eommissure

THE GEREBRUM 481

of the eerebrum, It is plaeed nearer the atiterior ihan the
posterior end of the brain, and it unites the medial surfaces of
the two eerebral hemispheres throughout very nearly a half of
their antero-posterior length.

Its upper surface is convex antero-posteriorly and concave
ftom side to side, and it forms the bottom of the longitudinal
tissure. On eaeh side of the fissure it is covered by the
gyrus einguli (O.T. eallosal gyrus). Only in its posterior part

is it touehed by the falx eerebri ; anteriorly, that fold of dura
mater falls eonsiderably short of it. The upper surface of
the eorpus eallosum is eoated by an exceedingly thin layer
of grey matter eontinuous, at the bottom of the eallosal
sukus, with the grey cortex of the hemisphere. In this are
embedded, on either side of the median plane, two deUeate
longitudinal bands of fibres ealled the striae longitudinales
medialis and iateralis. The stria hngitudinalu medialis is the
more strongly marked of the two, and it is separated from
voi.. 11 — 31

482 THE BRAIN

its felIow of the opposite side by a faint median ' furrow.
The slria loni^tudtnahs laterahs is plaeed more laterally.
So thin is the gre> eoating of the eorpus eallosum thal
the transverse direetion of the bundles of eallosal fibres
ean be easily seen through it

The strin: wilh the tbin layer of grey matter assoeiated wilh them
represent a g)riis ealled the^trui supi aiallosus

The two extremiltes of the eorpus eallosum (Fig. 193) are

■iid of Ihe Gorpus Callosum and the Subeallosal Gyri
3w when ihe froiital lobes of the hemispheres are
d rrom eaeh other. (Krom Cruveilhier. )

greatly thiekened, wliilst the intermediate part, the truneus
(O.T. body) is eonsiderably thinner. The massivc posterior
end, whieh is full and rounded, iies over the meseneephalon,
and extends posteriorly as far as the highest point of the eere-
bellum. It is ealled the spknium. The anterior end, whieh
is not quite so massive, is folded, downwards and posteriorly,
upon itself, and is ealled the genu. The recurved lower
portion of the eorpus eallosum rapidly thins as it passea
posteriorly, and is termed the rostrum. The fine terminal
edge of the rostrum, the lamina rostralis, is eonneeted with
the lamina terminalis (Fig. 192).

Both the lateral and the medial longitudinal strise, whieh
lie upon the upper surface of the eorpus eallosum, tum

THE GEREBRUM 483

downwards, round the splenium, and end in the fasciola
einerea, The fasciola einerea, whieh is situated immediately
beneath the splenium, is a narrow strip of grey matter,
eontinuous posteriorly with the medial and lateral striae
of the same side and anteriorly with the fascia dentata
hippoeampi. Anteriorly, the strige pass round the genu, and
then along the under surface of the rostrum until they
terminate in the eorresponding gyrus subeallosus, The gyrus
subeallosus is a ridge whieh deseends from the rostrum of the
eorpus eallosum and passes to the surface of the substantia
perforata anterior. There the fibres of the striae eontained
in the gyrus emerge from its substanee, and pass postero-
laterally along the posterior limit of the substantia perforata
anterior towards the anterior extremity of the temporal lobe.

Pibres of the Oorpus eallOBUin. — The transverse fibres of the eorpus
eallosum, as they enter the white medullary eentre of the eerebral hemisphere,
radiate from eaeh other towards various parts of the eerebral cortex. This
radiation is ealled the radiatio eorporis eallosi, The more anterior of the
Abres whieh eompose the genu of the eorpus eallosum sweep anteriorly
in a series of curves towards the frontal pole of the hemisphere. They
form the /oreeps minor. A large part of the splenium, forming a solid
bundle termed the forceps major, bends suddenly and abruptly posteriorly
into the oeeipital lobe. Fibres from the trunk of the eorpus eallosum and
also from the splenium curve round the lateral ventricle and form a very
definite stratum ealled the tapetum, This is a thin. layer in the medullary
eentre of the hemisphere whieh forms the roof and lateral wall of the
posterior horn and the lateral wall of the posterior part of the inferior horn
of the lateral ventricle.

Ventriculus Lateralis.

The lateral ventricle, in the interior of the eerebral hemi-
sphere, should now be opened up on eaeh side. The eorpus
eallosum, whieh forms the roof of the eentral part (O.T. body)
and anterior horn of this cavity, must, therefore, be partially
removed.

Disseetion. — Make a longitudinal ineision, through the eorpus eallosum,
about a quarter of an iheh from the median plane on eaeh side. The eentral
portion of the eorpus eallosum whieh lies between these ineisions is to be
kept in position. The lateral portions must be tumed laterally and
detaehed eompletely. As this is being done, it will beeome evident that the
lower part of the splenium whieh is prolonged into the forceps major is in
reality a portion folded anteriorly in elose apposition with the under surface
of the posterior end of the eorpus eallosum. Be careful to leave the forceps
major in its plaee.

The eentral part and the anterior hom of the ventricle are now exposed ;
but the cavity of the ventricle runs posteriorly into the oeeipital lobe in

11—31 a

484 THE BRAIN

the Eirm r)f a posterii>r horn, and dowTiwariis and anleriorly into the temporal
Idln- fls the iata'uit horr. The ]>05terior hotn ean, at preaent, be opened
011 Ihe right nide oaly. Carry thu kn!fe iwsleriorh' through the medullary
«utHitanei; whieb fomi9 iU rcK)f, and remove a sufficienl amount of tliis to

giyu a eoniiikte view of the interior of Ihis part of ihe cavily. Greater
diHieully will bi: esperieneeil in ii|>eninf; u]! the inretior horn. Plaee the
point of the knife in Ihe uppei ])arl of tlie horn, where il joins ihe eentral
parl of ihe vcnlricle, and eairy ihe blado in an antcto-infetior direetion,

THE GEREBRUM 485

through the lateral part of the temporal lobe, towards ihe tempoial pole,
roUowing the eourse of Ihe Cavi(y. This eorresponds very nearly wilh Ihe
eourse of Ihe superior temporal suleus. The laleral wall of the inferior
hom is thus inetsed, and a suffident amount of :he lateral part of the
temporal lobe must he remoYed to giye a view of the cavity. In doing Ihis,
the temporal opereulum will be taken away, bul the sui^aee of the insuta
siiould be pieserved from injury.

Lateral Tentriele. — The disseetor will now perceive that
eaeh eerebral hemisphere is hollow, The cavity in the ititerior
is ealled the lateral yentriele. It is lined with a thin dark-

95.— Casl of ihe Ventricles of Ihe Brain (from Rewius).

eoloured layer of epithelium, whieh is termed the ependyma. In
eertain plaees its walls are in apposition with eaeh other, but
in other ioeahties spaees of varying eapaeity, and eontwning
eerebro-spinal fluid, are left between the bounding walls. The
lateral ventricle eommunieates with the third ventricle of the
brain by means of a smal! foramen, whieh is termed the
interuentrkular /oramen (O.T. /oramen of Monro). This
aperture, whieh is just large eiiough to admit a crow-quill,
lies at the anterior end of the thalamus, and posterior to
the eolumn of the forniK (O.T, anterior pillar).

The shape of the lateral ventride is very irr^;ular, and
ean be best understood by the study of a plaster east of
its interior (Fig. igg). It is eomposed of a eentral part
(O.T. body) and three horns, viz., an anterior, a posterior,

THE BRAIN

and an inferior horn. The anterior hom is that part of the
cavity whieh ]ics anterior to the interYentrieular foramen.

Gotnua of the

The eentral part is the portion of the ventricle whieh extends
from tlie intcrvenlricular foramcn to the splenium of the
eorpus eallosum. At that point the posterior and inferiot

THE GEREBRUM

487

horns diverge from the posterior end of the eentral part
The posterior hom curves posterioriy and medially into the
oeeipital lobe. It is very variable in its length and eapaeity.
The inferior korn passes with a bold sweep round the
posterior end of the thalamus, and then tunnels, in an antero-
inferior direetion, through the temporal lobe towards the
temporal pole.

Goniu AntBriuA Yentrieuli Lateralia. — The anterior horn
forms the anterior part of the cavity, and extends antero-
laterally and downwards in the frontal lobe. When seei
frontal seetion it presents a iriangular outline — the tloor
sloping upwards and laterally to meet the roof at an aeute
angle (Fig. 197). It is bounded anteriorly by the posterior
surface of the genu of the eorpus eallosum, whilst the roof is
formed by the anterior parl of the trunk of the eorpus
eallosum. The medial wall, whieh ia yertieal, is formed by.

488 THE BRAIN

the septum pellueidum — a thin median partition between
the lateral ventricles of opposite sides. The sloping floor
presents a marked elevation or bulging, viz., the smootb
rounded and enlarged anterior extremity of the pear-shaped
eaudate nudms.

Para eentralis Tentrienli Lateralis. — The eentral part
of the ventricle is roofed likewise by the eorpus eallosum.
On the tntdial side it is bounded by the posterior part of rtie
septum pellueidum, and more posteriorly by the attaebment
of the fornix to the under surface of the eorpus eallosum.

198,-

On the lateral side it is elosed, as in the ease of the anterior
horn, by the meeting of the roof and the floor of the cavity,

On the floor a number of importanE objects raay be
reeognised. Latero-medially, and, at the same time, to some
extent antero-posteriorly, these are— (i) the eaudate nueleus;

(2) a groove extending obiiquely, postero-laterally, between
the eaudate nueleus aiid the thalamus, in whieh are plaeed
the terminal vein (O.T. vein of eorpus striatum) and a wbite
band ealled the stria terminalis (O.T. tienia semieireularis) ;

(3) a portion of the upper surface of the thalamus; (4)
the ehorioid plexus; (5) the thin sharp lateral edge of Uie
fornix.

THE GEREBRUM 489

The eaudate nueleus as it passes posteriorly, on the lateral
part of the floor of the eentral part of the lateral veiitricle,
narrows very rapidly.

The terminal vein Ls seen through the ependyma in the
groove between the eaudate nueleus and the thalamus. It
joins the internal eerebral vein (O.T. vein of Galen) at the
interventricular foramen, In the same groove is plaeed the
stria terminalis — a natrow band of white raatter, whieh bends
downwards and disappears from view in the region of the

interventricular foramen. Its fibres ultimately reaeh the
substantia perforata anterior, in whieh they end.

The portion of the upper surface of the thalamus, whieh
appears in the fioor of the lateral ventricle is, in great part,
covered by the ehorioid plexus of the lateral ventricle. The
plexus is a rieh vascular fringe whieh appears from imder
cover of the sharp lateral edge of the fomix, It is eon-
tinuous anteriorly, through the interventricular foramen, with
the eorresponding ehorioid plemis of the opposite side; whilst
posteriorly, it is earried into the inferior hom of the ventricle.
Although the ehorioid plexus has all the appearanee of lying
free within the ventriclc it is invested by an epithelial layer

490 THE BRAIN

of ependyma, whieh excludes it from the cavity and is
eonneeted on the one hand to the sharp margin of the fornix,
and on the other to the upper surface of the thalamus.

Comu Posterius Yentrieuli Lateralis. — The posterior
horn is a diverticulum whieh runs, from the posterior end of the
eentral part of the ventricle, into the oeeipital lobe. It tapers
to a point and deseribes a gentle curve, the convexity of
whieh is direeted laterally. The roof and lateral wall of
this portion of the ventricular cavity is formed by the tapetum
of the eorpus eallosum.

Upon the niedial wall two elongated curved elevations
may be seen. The upper of these, termed the bulb of the
eornu, is produeed by the fibres of the forceps major as
they curve posteriorly, from the lower part of the splenium
of the eorpus eallosum, into the oeeipital lobe. The lower
elevation is known as the eakar avis, It varies greatly in
size, in different brains, and is eaused by an infolding of the
ventricular wall whieh eorresponds with the anterior part of
the ealearine fissure.

Disseetion. — The disseetor should now insinuate his fingers undemeath
the fronto-parietal opereulum of the insula and tear this portion of the
cortex away in an upward direetion. The frontal opereulum (pars
triangularis) and the orbital opereulum should be dealt with in the same
manner. The greater part of the temporal opereulum has already been
removed in opening up the inferior horn of the ventricle ; therefore the
insula is now fully exposed to view, and its relation to the parts in the
interior of the ventricle ean be seen.

eomu Inferius Yentrieuli Lateralis (O.T. Deseending
Comu). — The inferior horn must be regarded as the direet
eontinuation of the main ventricular cavity into the temporal
lobe. The posterior horn is merely a diverticulum from -the
main cavity. At first direeted postero-laterally, the inferior
horn suddenly sinks downwards, posterior to the thalamus, into
the temporal lobe, in whieh it takes a curved eourse, antero-
medially, to a point about an ineh posterior to the extremity
of the temporal pole. In the angle between the diverging
inferior and posterior horns the cavity of the ventricle exhibits
a triangular expansion of varying eapaeity. This is ealled the
trigonum eollaterale,

The lateral wall of the inferior horn is formed, for the
most part, by the tapetum of the eorpus eallosum. At the
extremity of the horn the roof presents a slight bulging into the
ventricular cavity. This is the amygdaloid tuberde^ and it is

THE GEREBRUM

49«

produeed by a superjacent eolleetion of grey matter, termed
the amygdaloid nudeus. The stria terminalis and the greatly
attenuated and e>;panded tail of the eaudate nudeus are both
prolonged into the inferior horn, and are earried anteriorly in
its roof to the amygdaloid nueleus.

On the floor of the inferior hom the disseetor will note
the following parts : (i) the hippoeampus; (2) the ehorioid
plexus; (3) the fimbria; and (4) the eminentia eollateralis.

Hippoeampns (O.T. HippoeampoB Major). — This is over-
lapped by the ehorioid p!exus, whieh must be tumed aside.

of Inretior Comu ol

It is a prominent elevation on the floor of the inferior hom
of the lateral ventricle, and is strongly curved in conformjty
with the eourse taken by the hom in whieh it lies. It pre-
sents, therefore, a medial concave mai^in and a lateral convex
margin. Narrow posteriorly, it enlarges as it is traeed
anteriorly, and it ends, below the amygdaloid tuberele, in a
thiekened extremity, the pes hippoeampi. The surface of the
pes hippoeampi is marked by some faint grooves whieh inter-
vene between a number of ridges ealled the hippoeampal
digitations. The hippoeampus is the intemal eIevation whieh
eorresponds to the hippoeampal tissure on the esterior of the
wall of the ventricle.

rimbria (Hippoeampi). — The fimbria is a narrow but Tety

492 THE BRAIN

distinet band of white matter whieh is attaehed by its lateral
margin along the concave medial border of the hippoeampus.
The white matter eomposing it is eontinuous with the thiit
white layer {alveus) whieh is spread over the surface of the
hippoeampus, and it presents two Tree surfaces and a sharp
free medial border. The timbria has been noted already
in eonneetion with the hippoeampal hssure and the fascia
dentata (p. 479), and the relations whieh it presents to the
erus of the fornix and the uneus are pointed out on p. 494.

ehorioid rissure of the Cerebnim.— When the pia mater
in the region of ihe hippoeampal iissure is removed from the
surface of the brain, the ehorioid plexus in the interior of the
inferior horn of the lateral ventricle is usually withdrawn with
it, and a fissure appears between the fimbria and the roof
of the ventricular horn. This is termed the ehorioid fissure o/
the eerebrum ; it is the lower part of the greai lransverse fissure.
By the withdrawal of the ehorioid plexus it is converted into
an artificial gap, whieh leads direetly from the exterior of the
brain into the interior of the inferior horn of the lateral
ventricle.

THE GEREBRUM

493

Pleziis ehoiioidenB. — The ehorioid plexus is a system of
convoluted blood-Yessels enelosed within a fold of pia
mater whieh is prolonged, into the inferior hom of the

lodyoriUE«]vH.lricli ehoriMdpl™

. — Fronta1 BcclioQ through the Cerebnim, Mid-brain, and Pons m Ibe
le or the genieulate bodiea, It shows the relation of the deatate and
ehorioid Rssures to the inferior horn of the lateral yentriele.

lateral ventricle, through the diorioid fissure of the eerebrura.
It lies on the suriaee of the hippoeampus and, at the
posterior extremity of the thalamus, it beeomes eontinu-
ous with the ehorioid plexus in the eentral part of the

494 THE BRAIN

lateral ventricle (Fig. 200). But it must not be supposed
that the ehorioid plexus lies free in the ventricular cavity. It
is elothed in the most intimate manner by an epithelial epen-
dymal layer, whieh represents the medial wall of the inferior
horn pushed into the cavity by the ehorioid plexus. The
ventricle, therefore, opens on the surface through the ehorioid
iissure only a^ter this thin epithelial layer is torn away by
the withdrawal of the ehorioid plexus.

Emmentia Oollateralis. — This eminenee may present two
distinet forms, whieh may be distinguished from eaeh other
as the eminentia eollateralis posterior and the eminentia eol-
lateralis anterior.

The posterior eoUateral eminenee is a smooth elevation in
the floor of the trigonum eollaterale, in the interval between
the ealear avis and the hippoeampus as they diverge from
eaeh other. The anterior eollateral eminenee is not always
present. It forms an elongated elevation on the floor of the
inferior horn of the lateral ventricle, on the lateral side of
the hippoeampus. Both eminenees eorrespond to the eol-
lateral fissure on the tentorial aspeet of the eerebral
hemisphere.

Disseetion. — The remains of the right temporal lobe and of the right
oeeipital lobe should now be detaehed from the eerebrum by eutting through
the forceps major of the splenium of the eorpus eallosum and through
the fmibria where it passes into the erus of the fomix. The knife should
then be earried anteriorly from the anterior extremity of the inferior
horn, above the level of the uneus, through the temporal pole. The
temporal lobe, with the hippoeampal gyrus along its medial side, ean
then be separated from the remainder of the brain, along the line of
the ehorioid fissure of the eerebrum. In the detaehed part of the eerebrum
(Fig. 201) a good view is obtained of the floor of the inferior hom and
of the parts in relation to it. Further, by replaeing it in position, the
ehorioid Tissure ean be better understood, and by tuming the brain upside
down a view is obtained of the roof of the inferior horn and the straetures
in relation to it. In this way the tail of the eaudate nueleus and the stria
terminalis ean bc traeed into the amygdaloid nueleus.

The eut edge of the eentral part of the eorpus eallosum, whieh is still in
position, should now be still further pared away, so as to bring the sub-
jacent septum pellueidum and the fornix more fully into view.

Fimbria (Figs. 200, 201). — This is simply a eontinuation
of the erus (O.T. posterior pillar) of the fornix. It is a eon-
spieuous band of white matter, whieh presents a prominent free
border. Anteriorly, it runs into the recurved extremity of
the uneus, whilst, if it is traeed posteriorly, it will be seen
to curve upwards, posterior to the thalamus, and beeome

THE GEREBRUM 495

eontinuous with the erus of the fornix below the posterior
part of the eorpus eallosum (p. 491).

Fascia Dentata Hippoeampi. — The fascia dentata is
the free edge of grey matter whieh is plaeed between the
iimbria and the deep part of the upper surface of the hippo-
eampal gyrus. The groove between it and the Anibria
is termed the fiinbrio-dentate suleus. Its margin is notehed,
and its surface is seored with numerous elosely-plaeed
transverse grooves. It begins posteriorly, in the region of
the splenium of the eorpus eallosum, and it runs anteriorly
into the cleft of the uneus, from whieh it emerges again in
the form of a delieate band, ealled the frenulum of Giaeomini, .
whieh erosses the recurved part of the uneus in a transverse
direetion.

Hippoeampal rissure. — This is a eomplete iissure, and the
elevation on the ventricular wall, whieh eorresponds to it, is
ealled the hippoeampus (Fig. 217). It begins posterior to
the splenium of the eorpus eallosum, where it is eontinuous
with a shallow part of the eallosal suleus, and it passes
anteriorly, between the fascia dentata and the hippoeampal
gyrus. Its anterior end is embraeed by the uneus.

Septum Pellugidum — FoRNix — Tela Chorioidea

Ventriculi Tertil

Septum Pellueidum. — This is a thin vertical partition whieh
intervenes between the anterior eornua and the anterior parts
of the eentral portions of the two lateral ventricles (Fig. 198).
It is triangular in shape, and is prolonged posteriorly in the
narrow interval between the trunk of the eorpus eallosum
and the fornix, to eaeh of whieh it is attaehed. Anteriorly,
it oeeupies the gap posterior to the genu of the eorpus
eallosum ; whilst below, in the narrow interval between the
rostrum of the eorpus eallosum and the fornix, it is prolonged
downwards to the base of the brain-(Fig. 207).

The septum pellueidum is eomposed of two thin laminae
whieh lie one on eaeh side of the median plane. The median
cleft between the layers is termed the eamtn septi pellueidi
{O.T,fifth ventricle) (Figs. 194 and 196).

Disseetion. — The narrow middle strip of the eorpus eallosum, posterior
to the genu, should now be removed. Cut it transversely aeross, and, gently
raising it, separate the upper edge of the septum pellueidum from its lower

496

THE BRAIN

5tufice. PosteiioT lo the septum pellueidum the under sorbee of the
median ]>art o( the eoipus eallosuiD will be found to lie upon and to be
eonneeied with the appei siirface of the ^ornis. Sever ihis eonneetioii
also. Tbe left half of^the forceps major should be preserred, so Ihat its
eonneelion wilh the oeeipital lobe may be more fully made out later. By
snipping iilTthe upper edge or Ihe septura pellueidum with the seissors, the
two laminae, with the interposed cle!t, will be expo5ed.

OaTTiin Septi Pellueidi (O.T. Fiftli Teiitriele). — Thisis the
name whieh is apphed to the median cleft between the two
laminse of the septum pellueidum. It varies greatly in extent,
in dilTerent brains, and it eontains a little Auid. It is eompletely

relalions of the Fornix.

isolated, having no eommunieation either with the ventric]es
or with the exterior.

Fomix. — The fomix is an arehed strueture, eomposed of
longitudinal and transverse fibres. It eonsists of a eentral
part or body, whieh ends in two eolumns anteriorly and two
erura posteriorly.

Gorpus Pormds. — The body of the fornix is triangular in
shape. Anteriorly, where it is eontinuous with the eolumns,
it is narrow ; posteriorly it broadens out, beeomes Aattened,
and is prolonged into the erura. The upper surface of the
body of the fornix is in eontaet with the under surface of the
eorpus eallosum, and is adherent to it in the median plane

THE GEREBRUM 497

posteriorly. More anteriorly it is attaehed to the posterior
part of the lower edge of the septum pellueidum. Beyond
these attaehments the upper surface of the body of the fornix
forms a part of the floor of the lateral ventricle, on eaeh side,
and is elothed with ependyma. It presents a sharp lateral
edge, from under whieh the ehorioid plexus projects into the
cavity of the lateral ventricle. The lower surface of the
body of the fornix rests upon the tela ehorioidea of the third
ventricle (O.T. velum interpositum), a fold of pia mater whieh
separates it from the third ventricle and the two thalami.

ColumncB Fornicis (O.T. anterior pillars). — The two eolumns
of the fornix are two rounded strands whieh emerge from the
anterior end of the body of the fomix, and then, diverging
slightly, pass downwards anterior to the interventricular
foramen. Their lower ends sink into the grey matter on the
lateral walls of the third ventricle, and end at the base of the
brain in the eorpora mamillaria.

Eaeh eorpus mamillare has the appearanee of being a twisted loop of
the eorresponding eolumn of the fomix, in whieh the fibres turn upon
themselves, and are then eontinued upwards and posteriorly into the
anterior tuberele of the thalamus. This appearanee, however, is deeep-
tive. In the interior of the eorpus mamillare there is a nueleus of grey
matter. In this the fibres of the eolumn end ; while the other fibres,
whieh seem to be eontinuous with the fornix fibres, take origin within the
nueleus. The strand, thus formed, is ealled the fasciculus thalamo-
mamillaris (O.T. bundle of Vicq d'Azyr) (Fig. 203).

The eonneetions whieh have just been deseribed eannot be made out at
present, but at a later period the disseetor will experience little difficulty
in traeing the eolumn of the fornix to the eorpus mamillare, and in dis-
playing the eonneetion of this with the fasciculus thalamo-mamillaris.

Orura Fomicis (O.T. posterior pillars). — The erura of the
fornix are Aattened bands whieh diverge widely from the body
of the fornix. At first they are adherent to the under sur-
face of the eorpus eallosum, but soon they sweep downwards,
round the posterior ends of the thalami, and enter the inferior
horns of the lateral ventricles. There eaeh erus eomes into
relation with the eorresponding hippoeampus, and a portion of
its nbres beeome spread out on the surface of that prominenee,
forming the alveus, whilst the remainder eonstitute the fimbria,
whieh has been deseribed already (p. 494, Fig. 203).

The transverse fibres of the fornix eross the lower surface
of the body and the anterior part of the interval between the
diverging erura. In the latter plaee they may be adherent
to the lower surface of the eorpus eallosum. On eaeh side

VOL. II — 32

Soo THE BRAIN

Disseelion. — Eaeh vcna terminalis should now be dlnded u it unite*
wilh the internal eerebral vein. The apex of the tela ehorioidea should
Chcn be seiied with the forceps and pulled posterioTl;, till the whole
stTuelure i& reversed. The enliie upper surtaee of tlie thalamus on
eoeh side is thus expo$cd, aud, between the thalami, is seen tlie third
vcntriclc. The epithelial roof of this ventricle, whieh is invaginated into
the cavily liy the ch<irioid plexuscs of the thiid vent[icle on the under
surfacc of the tela, is torn away with the tela. The basal part of the tela
is intimatdy eonneeteil wilh the pineal 1)ody, whieh lies on the mesen-
eephalon liehind ihe Ihird venlricle. Care lherefore must be taken to
extricale (his body ftom the pia maler ; otherwise it is sure to be puUed

The Thalami and the Third Ventricle.

Thalamus — The thalamus is a large mass of grey matter
whieh lies obl ^uely aeross the path of the peduneulus eerebri
as it aseends into the hemisphere The smaller antertor end

T a Frt en nelo S ue on eorpus e^loaiiin

of the thalamus lies elose to the raedian plane, and is separ-
ated from the eorresponding part of the opposite side only
by a very narrow intetyal. Tlie enlarged posterior ends of
the two thalami are plaeed more wideiy apart ; and in the
iiiterval between them, the eorpora quadrigemina are situated.
In their anterior two-thirds, the two thalami lie elose together,
but are separated by a deep median cleft, the third ventricle

THE GEREBRUM 501

of the brain. Eaeh Ihalamus presents an anterior and a
posterior extremity, and foHr surfaces. The inferior and
lateral surfaces are in apposition and, indeed, direetly eon-
neeted with adjacent parts. The supurior and medial surfaces
are free.

The lateral siir/aee of the thalaraus is applied to a mass

of white matter, termed the intertial eapsuk, whieh is eomposed
largely of fihres fTOm the basis peduiieu/i. The in/erior or
venlral sur/aee of the thalamus rests chiefly upon the su6'
thalamie region, whieh is the prolongation upwards of the
tegmental part of the peduneulus eetebri. The relation,
therefore, whieh the thalamus presents to the upward eontinua-
tion of the peduneulus eerebri is yery intimate.

The superior sur/aee of the thalaraus is free. On the
Jateral side it is bounded by the groore whieh inter-

--.2 THE BRAIN

v-jr.os V;r.v;h;:i r.-.r; :r.ulamus and the eaudate nueleus and
o'.r.^ai.-.s ■r.r; v-:;Vi :r:rnr.iria;is a:id the stria terminalis. On
"-.•'; r.-.r:^-::.:; sidit:. rr.e .superior surtaee of the thalamus is
v::.''ir.-«rrjr:. in ::.=» ar.rerior halr. from rhe medial surface bv a
^'..ir:, ''/\jri. -.r pr-.n'.ir.ent ledge, of the ependyma of the
rr.ir'^l '.-^r.trioie. Tr.is i.s r.a'.ied the t^znia thalami. and the
rA]ifi ^r.irh i: r'-,rrri.s i.s arj-,entuated by the fact that subjacent
ro it ti-.-^rr; '.ie-s a lor;^:tiidinaI strand of dbres ealled the stria
m^'iuo'ari:. .\ short di.stanoe anterior to the pineal body the
t.'f;r.ia iios -.pori :he upper border Gf a raised white band, the

'[ :.ft .-..^v;r. .'.X .;v;:-ii ;,«■.';* iriorly intw two pan.s, one of whieh beeomes
■ ■■-r.';.'. . V'. - ■*■:''. 't.^. ;ir.':a! V.riy. whiist :he other passes aeroas to ihe
', ^.'/-/si • ■■ r. a .•■• r. ; ! .1 . * r. r '-': gh *: he •za-:enular :om m is2uri. whieh lies anterior
'o "r.e -ir.r.n; -.:a'.<.

f>'; : A Kf', n : h e h a he n u 1 a nr. edial 1 y a nd the up per quadrigeminal
\}f>f\j ;;Ostr;rior;y. iies a smali triangular depressed area, the

'\fr: suporior .surface of the thalamus is slightly convex,
and i.s of a ihiti.sh eolour owing to the presenee of a thin
supf;rf;^iai ^oating of ner\-e fibres ^stratum zonale). It is
d ;■/:''!•• d in'.o t'A'o areas by a faint obIique groove whieh
\)fy^)u\ r.-ihr the an:erior extremity of the thalamus, and ex-
t^;nds obii'; jrj]v. iaterailv and posteriorU*. This suleus eorre-
■-.ponrh. to the frr;r; lateral edge of the fomix. The two areas
th'is rf.ripp'';d out an:- \tTy differently related to the ventricles
of th^: brain. The lateral area ineludes the anterior extremity
(){ \}.\i\ th;ilamn.s, and form5 a part of the floor of the lateral
\i\u\n<\(',\ ir is oovered with ependyma, and overlapped by
th^- r;horioid fJexus. The medial area intervenes between
tli': latoral anrl third ventricles of the brain, and takes no
p;j.rt iri the formation of the walls of either. It is covered
•A'ith t.h^: tf;]a ohorioidea, above whieh is the fomix. It
inrhid'::-; the posterior extremity of the thalamus.

'l'he anterior extremity of the thalamus, ealled the anterior
tuhe.rr.le., is rounded and prominent. It projects into the
l;irr:r;j.I vf;ntrir:le, lie.s postero-lateral to the free portion of the
r()\\\u\\\ ()f thf; fornix, and bounds the in:erventricular foramen
po .l.^iriorly.

'l'h'r posterior extremity of the thalamus is very prominent,
;inH [)roj(;cts posteriorly over the meseneephalon (Fig. 206).
Thi.s projerting part is ealled the pulrinar. But the posterior

THE GEREBRUM 503

end of the thalamus shows another prominenee. This is
situated below and to the lateral side of the pulvinar. It is
oval in form, and reeeiyes the name bf the eorpus genieulatum
laterale,

The medial surfaces of the two thalami are plaeed very
elose together, and are covered not only with the lining
ependyma of the third ventricle, but also with a moderately
thiek layer of grey matter eontinuous with the grey matter
whieh surrounds the aqu9eductus eerebri (Sylvius). A band
of grey matter, termed the massa intermedia, erosses the third
ventricle and joins the two thalami together.

eorpus Pineale. — This is a small body of a darkish eolour,
and about the size of a eherry-stone, whieh is plaeed between
the posterior extremities of the two thalami on the dorsal
aspeet of the meseneephalon (Fig. 206). It oeeupies the
depression between the two superior quadrigeminal bodies,
and is shaped like a fir-cone. Its base, whieh is direeted
anteriorly, is attaehed by means of a hoUow stalk or pedunele.
This stalk is separated into a dorsal and a ventral part by a
eontinuation into it of a pointed reeess of the cavity of the
third ventricle, The dorsal part of the stalk beeomes eon-
tinuous on eaeh thalamus with the taenia thalami ; the ventral
part is folded round a narrow but eonspieuous eord-like band
of white fibres {posterior eommissure) whieh erosses the median
plane immediately below the base of the pineal body.

eoiumissura Anterior Oerebri. — In the anterior part
of the cleft between the two thalami, and immediately
anterior to the eolumns of the fornix, a round bundle of
white fibres will be seen erossing the median plane. This
is the anterior eommissure, It is very mueh larger than the
posterior eommissure, and will be afterwards followed towards
the temporal lobe, in whieh the greater part of it ends.

Yentrieulus Tertius. — This name is given to the deep
narrow cleft between the two thalami. It is deeper anteriorly
than posteriorly, and extends from the pineal body posteriorly
to the anterior eommissure and lamina terminalis anteriorly.
Its Jioor is formed by the parts already studied within the
interpeduneular fossa on the base of the brain, viz., the tuber
einereum, the eorpora mamillaria, and the grey matter of the
substantia perforata posterior, and also, more posteriorly, by the
tegmenta of the eerebral peduneles. Anteriorly, it is bounded
by the lamina terminalis and the anterior eommissure ; whilst

5 «4

THE BRAIN

its lateral walli are Tormed by the medial surfaces of the
two thalami. A little anterior to the middle of the ventricle
the cavity is erossed by the massa intermedia, whieh eonneets
the thalami with eaeh other, and anterior to this the eolumn
of the forrix is seen deseending in the lateral wall. At Srst
the eolumn is distinet and prominent, but as it approaehes
the eorresponding eorpus mamillare it gradually beeomes

more 'and more sunk in the grey matter on the side of the
ventric!e.

The roo/oi the third yentriele is formed by a thin epithelial
layer whieh stretehes aeross the median plane, from the one
t;enia thalami to the other, and is eontinuous with the
remainder of the epithelial lining of the cavity. It is applied
to the under surface of the tela ehorioidea, whieh overhes the
ventriclo, and is invaginated into the cavity by the ehorioid
plexuscs whieh hang down from the uiider surface of that
fold of pia niater. In the removai of the tela eborioidea
the thin epithelial roof was torn away.

The third ventricle eommunieates freely wilh the lateral

THE GEREBRUM 505

ventricles, and also with the fourth ventricle. The aguee-
duetus eerebri (Sylvius\ a narrow ehannel whieh tunnels the
meseneephalon, brings it into eommunieation with the fourth
ventricle. The opening of this eanal will be seen at the
posterior part of the floor of the ventricle, immediately below
the posterior eommissure. The interuentrieular /oramen^ whieh
puts it into eommunieation with the two lateral ventricles, is a
Y-shaped aperturewhieh liesat the anterior part of theventricle,
and its two diverging limbs pass laterally and slightly upwards,
between the most prominent parts of the eolumns of the fornix
and the anterior tubereles of the thalami. They are usually
large enough to admit a crow-quill, and through them the
epithelial lining of the three ventricles beeomes eontinuous.

PORAMEN INTERYENTRieULARE

ANTR.COM: -^d^r

— \mA88A INTERMEOIA

OPTie OHiASMA^^^l,™,^

NyREOeSSUS
eOsUPRAPINEALlS

C^^^ \ J^^ ^^

S. ^REOeSSUS PINEALIS

i/lNFUNDIBULUM

>^ P08TR. OOM.
AQU>EDUCTUS

^gg^^^

GEREBRI

mH^Bhypophysis

FiG. 208. — Diagrammatie outline of the Third Ventricle
as viewed from the side.

From eaeh lateral part of the interventricular foramen a
distinet groove passes posteriorly, on the lateral wall of the
ventricle, to the mouth of the aquaeductus eerebri. It is
termed the suleus hypothalamieus,

The outline of the third ventricle is seen to be very irregular when
it is viewed from the side in a median seetion through the brain (Fig. 207),
or as it is exhibited in a plaster east of the ventricular system of the brain.
It presents several diverticula or reeesses. Thus, in the anterior part of the
floor there is a deep funnel-shaped reeess, reeessus in/undibuli^ leading down,
through the tuber einereum, into the infundibulum of the hypophysis.
Another reeess, reeessus optieus^ lies above the optie ehiasma. Posteriorly,
two additional reeesses are present. One, the reeessus pinealisy passes
posteriorly, above the posterior eommissure and the entranee of the aquae-
duetus eerebri, for a short distanee into the stalk of the pineal body.
The seeond is plaeed above this, and is earried posteriorly for a greater
distanee. Its walls are epithelial, and therefore it eannot be seen in an
ordinary disseetion. It is termed the reeessus suprapinealis,

Disseetion. — The further study of the eerebral hemispheres should be
postponed until after the examination of the mid-brain or meseneephalon.
The membranes should be removed from the upper surface of the eere-
bellum, and the prominent anterior part of that organ may then l)e

5o6 THE BRAIN

pulled posteriorly to expose, as far as possible, the eorpora quadrigemina,
i.e. the four rounded eminenees on the dorsal aspeet of the meseneephalon.
In doing this, eare should be taken to seeure and preserve the slender
troehlear nerve whieh issues from a lamina, ealled the anterior medullary
velum, immediately below the inferior pair of quadrigeminal bodies, and
winds round the lateral side of the peduneulus eerebri.

THE MESENGEPHALON.

The meseneephalon is the stalk whieh oeeupies the aperture
of the tentorium eerebelli, and eonneets the eerebral hemi-
spheres with the parts in the posterior eranial fossa.^ It is
about three-quarters of an ineh long, and it eonsists of
a dorsal part, the latnina guadrigemina, and a mueh larger
ventral part, whieh is formed by the two large peduneuU eerebri
In the undisseeted brain the lamina quadrigemina is eom-
pletely hidden from view by the splenium of the eorpus
eallosum, whieh projects posteriorly over it, and also by
the superimposed eerebral hemispheres. The peduneuli
eerebri, however, ean be seen, to sorpe extent, at the base of
the brain, where they bound the posterior part of the inter-
peduneular fossa. The meseneephalon is tunnelled from
below upwards by a narrow passage ealled the aqu3eductus
eerebri (Sylvius). This ehannel lies mueh nearer the dorsal
than the ventral surface.

Lamina Qiiadrigemma. — The dorsal surface of the lamina
quadrigemina is raised into four eminenees or eollieuU^ two
superior and two inferior, whieh are ealled the eorpora guadri-
gemina. Eaeh eollieulus is eomposed, for the most part, of
grey matter, although eaeh has a superficial eoating of white
fibres. The superior pair are larger and broader than the
in/erior pair^ but they are not so well defined nor yet so
prominent.

A longitudinal and a transverse groove separate the quadri-
geminal bodies from eaeh other. The longitudinal groom
oeeupies the median plane, and extends upwards as far as the
posterior eommissure. From its lower end a short but well-
defined narrow band of white fibres, the /renulum veU^ passes
to the anterior medullary velum, a lamina plaeed immediately
below the inferior pair of quadrigeminal prominenees. The

^ If the nieseneephalon was divided, when the brain was removed, the
dirided parts niust be fixed together with pins while the superiieial charax:ters
are being studied.

THE MESENGEPHALON 507

upper part of the longitudinal groove is oeeupied by the
pineal body. The tranwerse groove curves round posterior
to eaeh of the superior pair of ^uadiigeminal bodies and
separates them froni ihe inferior pair.

Braehia of the OoipoTa Onadrigemuia. — The eorpora
quadrigemina are noE marked off from the side of the mesen-
eephalon, for eaeh body has in eonneetion with it, on that
aspeet, a prominent white strand, whieh is prolonged upwards
and anteriorly under the projecting pulyinar. The strands
are ealled the braehia of the eorpora quadrigemina, and they
are separated from eaeh other by a eontinuation, on the side
of the meseneephalon, of the transverse groove whieh inter-
venes between the two pairs of bodies.

eorpiis OenienUtum Mediale. — Glosely eonneeted with
the braehium of the inferior quadrigeminate body will be seen
the eorpus genieulatum mediale.

It is a little oval eminenee, very pul^n" ^o^p.^.^^ .^.-i-^

sharply defined, whieh lies on , . - > i-i'«>t.

theside of the upper part of the I .' -' , ■-"tMiiun

meseneephalon under sheher <
the pu!vinar of the thalamus.

Coimections of the Broehiii
and the Origin of the Optie
Traot. — It will now be seen that
the braehia are intimately eon-
neeted with the optie traet.
The in/erior braehium proeeed-
ing upwards from the lower quadrigeminal body advances
towards the eorpus genieulatum mediale, and disappears
from view under cover of that prominenee. Upon the
opposite side of the same genieulate body, the medial rool
of origin of the optie traet arises, and the appearanee is
sueh that the disseetor might very naturally eonelude that
the inferior braehium and the root of the optie traet are
eontinuous. That, however, is not the ease. The superior
bruehium is earried upwards and anteriorly between the
overhanging pulvinar and the eorpus genieulatum mediale.
It partly enters the eorpus genieulatum laterale, but a portion
of it is direetly eontinuous with the lateral root of Ihe optie
traet.

5o8 THE BRAIN

tatend reet U panly ednlinaous uilh tbe soperim' braehiuin, and parlly
H'ilh ihe eoipus genieulatum laleraJe and Ihe palviilaT. The supeiioe
quadrigeTninal body, the eoipus genieulatuin lalerale, and the pulTinai
cr,nslilule ihe lmvir t-iiuat italns.

Pedtmenli Geiebri (O.T. enm eOTobri). — The peduneuli
eerebri eonslitute the chief bulk of the meseneephalon.
When viewed from be!ow, they appear as two lai^e rope-
like strands, whieh emerge, elose together, from the upper
aspeet of ihe pons, and diverge as they proeeed upwards to
enter ihe eerebral hemisphere. At the point where eaeh

pedunele disappears into the eorresponding hemisphere, it is
embraeed, on its lateral side, by the optie traet and the gyrus
hippoeampi.

The peduneulus eerebri of eaeh side eonsists of two parts,
v\z., a dorsal iegmentum, whieh is prolonged upwards to the
region below the thalamus ; and a ventral iasis (O.T. entsla),
whieh is earried upwards into the internal eapsule on the
lateral side of tbe thalamus. When the base of the briun
is examined it is tbe basis peduneuli wbieh is seen. It is
wbite in eolour and streaked in the longitudinal direetion.
On the exterior of the meseneephalon, the separation between
ibe two parts of the peduneulus eerebri {i.e. the tegmentum
and the basis peduneuli) is indieated by a niedial and a
lateral groove or suleus, The medial suleus is the deeper

THE MESENGEPHALON 509

and more distinet. It looks into the interpeduneular fossa,
and from it emerge the fila of the oeulo-motor nerve.
It consequently receives the name of the suleus oeulomotorius,
The lateral suleus is termed the suleus lateralis,

Cut Surface of the Meseneephalon. — Mueh nearer the
dorsal than the yentral surface of the meseneephalon the
transversely divided aguaduetus eerebri may be seen. This
narrow passage leads from the fourth ventricle below to the
third ventricle above. It is surrounded by a thiek layer
of grey matter, ealled the eentral grey matter of the
agueduet. In a fresh brain this is always very eonspieuous,
and in its midst are situated the nuelei of the oeulo-
motor and troehlear nerves, and the upper motor nueleus
of the trigeminal nerve, although of eourse these eannot,
except in very favourable eireumstanees, be deteeted by
the naked eye. Below, the grey matter of the aqueduct
is eontinuous. with the grey matter spread out on the
anterior wall of the fourth ventricle ; whilst above, it is eon-
tinuous with the grey matter on the floor and sides of the
third ventricle.

The division between the tegmentum and the basis
peduneuli, on eaeh side, is rendered very evident by a eon-
spieuous lamina of dark pigmented matter whieh intervenes
between them. This is termed the substantia nigra,

Substantia Nigra. — As seen in transverse seetion, the sub-
stantia nigra presents a somewhat ereseentie outline. It is
a thiek band interposed between the basal and tegmental
parts of the peduneuli eerebri, and it eonsists of a mass of
grey matter in the midst of whieh are large numbers of pig-
mented nerve eells. It begins below, at the upper border
of the pons, and it extends upwards into the subthalamie
region. Its margins eome to the surface at the oeulo-motor
and lateral sulei, and its medial part is traversed by the
emerging fibres of the oeulo-motor nerve. The surface
turned towards the tegmentum is concave and uniform ; the
opposite surface is convex, and is rendered highly irregular
by the presenee of numerous slender prolongations of its
substanee into the basis peduneuli.

Basis Peduneuli (O.T. erusta). — The basis peduneuli is
somewhat ereseentie when seen in seetion, and stands quite
apart from its fellow of the opposite side. It is eomposed of
a eompaet mass of longitudinally direeted nerve fibres whieh

5IO THE BRAIN

are earried upwiirds into the intenial eapsule. The inter-
niediate third or more of eaeh basis peduneuli is eomposed
of the \mpor\ZT\l (erebro-spinal /asdeulus {O.T. fyramidal trad)
as it deseends from the motor area of the eerebral coTtex,
but this is quite indistinguishable from the portions of the
erusta whieh lie on either side of it

qiiadngcmLiuL body

Vlti. aii. — TranEvcrsc seelion ilirough the Meseneephalon al the 1evel of Ihe
mfcr[or qua(lrigcniinal body : the right side only is reprodueed. The
ilrawing is taken fn}m a Weigert-Pal speeinien, and therefore the grey
in.itter is pale and the strands of white matter are datk. Tbe dark eolotir
of the substanlia nigra is nol eyident owing to the Ihinness of the seelion.

Tegmeiitiun. — Unlike the basis pedtaneuli, the tegmentum

is undWided, a faint hne in the median plane, termed the
median rapke, alone indieating its bilateral eharaeter. To-
wards the dorstim of the meseneephalon it is fused with the
bases of the eorpora quadrigemina, and its lateral suiTaees
only are free.

The tegmentum is eomposed of an admixture of giey and white matter,
eonstiluting what is termed a fei-matie rtlindaris. The while matter is
conii>oacil of iibres ninning both tiansvcise]y and longitudinally. Ceitain

THE MESENGEPHALON 511

of the longitudinal fibres are grouped t<^ether and form well-marked
traets, whieh, in aseetion through the meseneephalon of a fresh brain, (an
be deteeted by the naked eye. These traels are ; (l) the medial longi-
tudinal bundles ; (j} the braehia. conjuncliva ; (3) the lemniseus.

The medial longitudiiud bundle (Figs. 211 and 212) is a small eompaet
fasciculus whieh is plaeed upon the lateral aspeet of the lower portion of
the eentral grey raattei of the aqueduct.

The bra'.hia c0nfunftiva (O.T. stiperior (irebdlar pedundes) are two

G. 212.— Seetion through upper parl of Meseneephalon al level of supei
quadrieemmal liody. The drawing is taken frora a Weigert-Pal speeim
The dark eolour of the Bubstaulia nigra is nol evidcnt owing (o

large stiands whieh are eontinued upwards from the eerebellum inlo the
meseneephalon. 6y pulling away the raorgin a{ the eerebetlum, where it
overlaps the lower quadiigeminal bodies, these biaehia W)!l be seen on the
suriaee as they converge in an upward direetion. Stretehing aeross the
interval between them, and bringing them into eontinuity with eaeh othei,
is 3. thin lamina ealled the anterior medullary ve]um. When the braehia
conjunctiva leaeh the bases of Ihe inferiot quadrigeminal bodies, they
sink inlo Ihe substanee of the meseneephalon, and, in a traiisverse seetion
through the lower part of ihis poitiou of the brain, they may bc seen as two
white strands, semilunar in outline and plaeed one on either side of the
grey matter of the aqueduct. As they aseend, they gradually assume a
deeper (i'.e. a mote ventral) position in Ihe tegmental part of the mesen-

512 THE BRAIN

eephalon, and they deeussate with eaeh other aeross the median plane anJ
proeeed upwanls to the red nuelei.

•The term Umniseus {iy.'Y, JUUt) is given to two traets presenting very
di^Terent eonneetions. The medial Umniseus (Figs. 21 1 and 212) is a
sensory traet passing upwards to the thalamus. The UUeral Umniseus
t>elongs to the auditory apparatus, and is a part of a ehain throiigh whieh
the eoehlear nuelei estabhsh eonneetion with the inferior quadrigeminal
t)o<ly and the medial genieulate body. The lateral lemniseus ean be
readily detectc<l as it emerges from the upper part of the lateral suleus of
the mid-brain, and passes, postero - superiorly, to the lower border of the
inferior (luadrigeminate body and inferior braehium. It has the form of
a raised triangular band whieh eneireles the lateral surface of the upper
end ()f the braehium conjunctivum (Fig. 221).

Within the upper part of the tegmentum there is a eolleetion of nuelear
matter whieh is termed the nudeus ruber^ from its ruddy appearanee
when seen in seetion. It is rod-like in form, and extends upwards into the
tegmental region below the thalamus. In transverse seetion it presents a
eireular outline, and it is elosely assoeiated with the upward prolongation
of the fi])res of the braehia conjunctiva eerebelli. The braehium conjunc-
tiyum eerebelli is an efferent traet from the nueleus dentatus of the
lateral hemisphere of the eerebellum, and its tibres end in the red nueleus
and the pulvinar of the thalamus of the opposite side. The t^^entum
of the i>edunculus eerebri may be eonsidered to eonsist of two parts : vi«.,
a l<nver piti^ whieh is subjacent to the inferior quadrigeminal bodies,
and is largely oeeupied by the deeussation of the braehia conjunctiva
eerebelli ; and an upper part^ subjacent to the superior quadrigeminal
b<xlies, whieh is traversed by the emerging bundles of the third nerve,
and eontains the nueleus ruber.

BASAL GANGLIA 0F THE GEREBRAL

HEMISPHERES.

The basal ganglia of the eerebral hemispheres must now
be examined. They are the eaudate and lentiform nuelei,
whieh together forpi the eorpus striatum ; the elaustnim ;
and the amygdaloid nueleus. With these it is neeessary to
study also the eomposition of the thalamus and the extemal
and internal eapsules.

Disseetion. — The right and left portions of what remains of the eerebrum
should be separated from eaeh other by a median ineision. On the left
portion the sulei and gyri on the lower surface of the hemisphere may be
examined, if this has not been done already on another speeimen.

A series of seetions should, in the next plaee, be made through both the
riglit and left portions of the eerebrum, with the view of displaying the basal
ganglia. On the right side remove a sueeession of thin sliees by earrying a
long knife in a horizontal direetion through the parts whieh form and lie below
the floor of the eentral part of the lateral ventricle. It is not advisable to
proeeed farther down than the level of the anterior eommissure.

On the Ieft side of the brain a series of vertical-transverse or frontal
seetions should be made through the remaining portion of the eerebrum.

BASAL GANGLIA SU

B^n by eutting off the portion anlerioi to the head of the eaudate nueleus,
and then proeeed posleriorly untii the posterior part of the thalamus
is reaehed. One of the seetions should be planned lo pass thiough

Nuelens Gaadatus. — This nueleus has already been partly
examined in eonneetion with the lateral ventricle, into the

cavity of whieh it bulges. It is a piriform highly arehed
mass of grey matter, whieh presents a thiek swollen head or
anterior extremity, and a long attenuated tail. The head
projects into the anterior horn of the lateral venlricle, whilst its
narrower part is prolonged laterally and posteriorly on the
iioor of the eentral part of the yentriele, where it is separated
from the thalamus by the stria terminalis. Finally, its tail
turns downwards and then anteriorly into the inferior hom

YOL. II — 33

514 THE BRAIN

of the lateral ven£ricle, on the roof of whieh it is prolonged
until it finally joins the amygdaloid nueleus. The eaudate
nueleus, therefore, presents a free ventricular surface covered
with ependyma, and a deep suriaee embedded in the sub-
stanee of the hemisphere, and for the most part related to the
internal eapsule.

Owing to its arehed fomi, it follows that in horizontal
seetions, below a partieular level, it is eut at two points, and
both the head and the tail must be looked for in the field of

)ii ihrough Ihe Proinal l^^bes of the Cerebrum, The
srior p.Trt of the eerebrum is depieled so thBI
1G anterior homs of the L-Lteral ventricles from

seetion (Ftg. 213). In frontal seetions posterior to the amyg-
daloid nueleus it is also divided at two plaees.

Nneleus Leiitifonni3. — 'l'his mass of grey matter lies on
the lateral side of ihe eaudate nueleus and the thalamus, and
is, for the most part, eompletely embedded within the
medullary substanee of the eerebral hemisphere. It does not
oeeupy so large an area as the nueleus eaudatus. Indeed, it
presents a very elose eorrespondenee in point of estent with
the insula on the surface.

When seen in horizontal seetion (Fig. 213) it presents a
shape similar to that of a biconvex lens. Its medial suTface

BASAL GANGLIA 515

bulges more than the lateral suriaee, and its point of highest
convexity is plaeed opposite the stria terminalis or the
interval between the eaudate nueleus and the anterior end
of the thalamus.

When seen in frontal seetion, the appearanee presented
by the ]entifonn nueleus differs very mueh in the different
planes of seetion. Pigure 215 represents a seetion through

Corpu£ ealloAum
Lc1ngiludi11.1l lissure

ir pari of Ihe lenliibrm nueleus. Seen fr

r portion. Here it is semilunar or ereseentie in
outline. Further, it is intimately eonneeted with the head
of the eaudate nueleus by bands of grey matter whieh pass
between the two nuelei and break up the anterior part of the
internal eapsule. It is due to the ribbed or barred appeae-
anee whieh Is presented by sueh a seetioD as this that the
term eorpus striatum is given to the two nudeL

When the seetion is made in a more posterior plane, the
divided lentifonn nueleus assumes an altt^ether different
shape, and is seen to be eompletely cut off fn)m the eaudate

5i8 THE BRAIN

it thiekens eonsiderably, and at the base of the brain it
eomes to the surface, at the substantla perforata anterior,
and beeomes eontinuous with the grey matter of the eerebral
cortex. Its extent eorresponds very nearly with the area
oeeupied by the insula, and its lateral surface shows ridges
and depressions eorresponding to the insular gyri and sulei.

Oapsola Intetna.— This term is applied to the broad band
of white matter whieh intervenes between the lentiform
nueleus laterally, and the thalamus, stria terminalis, and
eaudate nueleus on the medial side. Anteriorly it is mueh

■nal eapsule

d Pyramidal Fib»es.

broken up, by the eonneeting bands of grey matter whieh .
pass between the bead of the eaudate nueleus and the
anterior part of the putamen of the lentiform nudeus (Fig.
215), but more posieriorly it forms a solid white mass of
nerve fibres. When seen in horizontal seetion, the intemal
eapsule is bent upon itself opposite the interval between the
eaudate nueleus and the thalamus (Fig. 216). This bend,
whieb points medially, is ealled the genu. About one-third
of the internal eapsule lies anterior to the genu, and this
part is ealled the anlerior limb; the remaining two-thirds,
whieh lie posterior to the genu, eonstitute l)\& posterior limb.

OonneetionA of the Intemal Capaiile. — 1'he internal eapsule
is direetly eontinuous below with the basis of the eerebral

BASAL GANGLIA 519

pedunele. The disseetor ean easily satisfy himself in the
speeimens before him of this eontinuity ; it is apparent in the
more posterior of the frontal seetions whieh he has made
through the left portion of the eerebnim.

It has been mentioned already that the fibres whieh oeeupy the middle
third or more of the basis of the eerebral pedunele belong to the motor
eerebro-spinal fasciculus. In the internal eapsule these fibres oeeupy the
anterior two-thirds of the posterior limb, being thus plaeed immediately
posterior to the genu. The fibres whieh eonstitute the medial third of the
basis peduneuli eome from the anterior limb of the internal eapsule ; whilst
the fibres whieh form the lateral third of the basis peduneuli are situated
in the posterior limb.

When the fibres of the internal eapsule are traeed upwards, they are
found to spread out in a radiating manner so as to reaeh the various
gyri of the eerebral hemispheres. This arrangement is termed the
eorona radiata. As the fibres of the eorona radiata are liberated from
the internal eapsule, and spread out to reaeh their destinations, they are
interseeted by fibres of the eorpus eallosum, whieh also radiate in
every direetion to gain the cortex of the eerebrum, and they are inter-
seeted also by bundles of assoeiation fibres.

Nuelei of the Thalamus. — When a horizontal seetion
is made through the thalamus in a fresh brain, or in one
whieh has been preserved by means of formalin or a ehromie
salt, the grey matter eomposing it is seen to be broken up
into a lateral, a medial, and an anterior nueleus by thin
white medullary laminae.

Oapsula Extema. — This term is applied to the thin
stratum of white matter whieh intervenes between the
lentiform nueleus and the elaustrum (Figs. 213 and 216).

Disseetion. — The fasciculus thalamo-mamillaris and the anterior eom-
missure should now be foIIowed, as far as this is possible, in what remains
of the right half of the eerebrum. The disseetion is not difiicult.

By the removaI of the remains of the lentiform nueleus the anterior eom-
missure will be exposed in its eourse towards the temporal lobe. In the first
instanee, it passes transversely, then postero-laterally below the putamen.
Next it bends suddenly in a posterior direetion above the inferior horn of
the lateral ventricle to reaeh the meduUary eentre of the temporal lobe.
If the disseetion be successfully aeeomplished, the anterior eommissure
will be seen to present a twisted or rope-like appearanee.

The fasciculus thalamo-mamillaris may be traeed (rom the eorpus
mamillare upwards into the anterior nueleus of the optie thalamus by
seraping away the grey matter on the side of the third ventricle. The
eontinuity between the eolumn of the fornix and the eorpus mamillare
should at the same time be established. Within the eorpus mamillare there
is a nueleus of grey matter.

The disseetors have now examined all those portions of the brain whioh

lie in the anterior and middle eranial foss3e, and eertain terms, not hitherto

mentioned in eonneetion with the various struetures whieh have been

studied, now require eonsideration. It has been noted already that the

II— 33^/

S20 THE BRAIN

part of the brain whieh eonneets the lower segment in the posterior fossa
with the upper segment in the middle and anterior fossa is ealled the
meseneephaloiL The parts above the meseneephalon form collectively
the proseneephalon, and the meseneephalon and proseneephalon together
eonstitute the eerebnim.

The proseneephalon itself is separable into two main parts, the teleu-
eephalon (end brain), and the dieneephalon. The teleneephalon
ineludes the eerebral hemispheres with their grey nuelei, the olfactory
bulbs and traets and the assoeiated parts, and the pars optiea hypo-
thalami; under the latter term are ineluded the tuber einereum, the
infundibulum, the hypophysis, the optie traets, the optie ehiasma, and
the lamina terminalis.

The dieneephalon ineludes two elosely assoeiated segments, the pars
mamillaris hypothalami and the thalameneephalon,

The pars mamillaris hypothalami is formed by the mamillary bodies
and those portions of the walls of the third ventricle whieh lie below the
suleus hypothalamieus. The thalameneephalon is separated into the
thalamus (O.T. optie thalamus)^ the metathalamus, formed by the two
genieulate bodies, and the epithalamust whieh eonsists of the pineal body,
the habenula, the habenular eommissure, and the trigonum habenulae.

THE PARTS 0F THE BRAIN WHIGH LIE IN
THE POSTERIOR GRANIAL FOSSA.

The parts whieh lie below the tentorium eerebelli in the
posterior eranial fossa are the medulla oblongata, the ponSy
and the eerebellum. These are grouped around the /ourth
ventricle of the brain — a cavity whieh eommunieates with the
eentral eanal of the meduUa spinalis below and with the
aquceductus eerebri above ; and they eonstitute the rhomben-
eephalon or hind brain.

Medulla Oblongata. — This is the eontinuation of the spinal
medulla into the brain. It is not more than one ineh in length,
and may be reekoned as beginning at the level of the foramen
magnum. Thenee it proeeeds upwards, in a very nearly vertical
direetion, and ends at the lower border of the pons. At first
its girth is similar to that of the spinal medulla, but it rapidly
expands as it approaehes the pons, and consequently it
presents a more or less eonieal appearanee. Its anterior
surface lies in the groove on the basilar portion of the
oeeipital bone, whilst its posterior aspeet is sunk into the
vallecula of the eerebellum.

The medulla oblongata is a bilateral strueture, and this is
evident even on an inspeetion of its exterior. The antero-
median and postero-median sulei on the surface of the spinal

MEDULLA OBLONGATA 521

medulla are prolonged upwards on the anterior and posterior
Euriaees of the medulla oblongata.

The antero-median groom, as it passes from the spinal
medulla on to the meduUa oblongata, is interrupted, at the
leve] of the foramen magnum, by several strands of fibres
whieh eross the median plane from one side to the other.
This intererossing is teraied the deeussation of the pyramids.
Above this level the furrow is earried upwards to the lower

border of the pons, There it expands slightly, and ends in
a blind pit, termed tiie/orat»en eaeum.

The postero-median fissure is eaTried up for only half the
length of the meduUa oblongata. Then the eentral eanal of
the medulla spinalis beeomes the fourth ventricle of the bratn,
and as it expands dorsally it pushes aside the lateral lips of
the posterior median suleus till the epithelium of its posterior
wall appears on the surface, in the triangular interval between
the diverging posteiior eolumns of the medulla oblongata,

522 THE BRAIN

where it forms the posterior wall or roof of the lower part
of the fourth ventricle.

The surface of eaeh lateral half of the meduUa oblongata
should now be studied. It is well, however, to defer the
examination of the meduUary part of the floor of the fourtb
ventricle till a later period. The disseetor has already notieed
two linear rows of nerve fila issuing from and entering the
medulla oblongata on eaeh side. The anterior row eonsists
of the roots of the hypoglossal and the uppermost part of the
anterior root of the iirst cervical nerve. They eontinue up-
wards on the meduUa oblongata in the line of the anterior
nerve roots of the spinal medulla, and they emerge along the
bottom of a more or less distinet groove. T\\t. posterior row is
formed of the nerve fila of the aeeessory, vagus, and
glosso-pharyngeal nerves, and they lie in series with' the
posterior roots of the spinal nerves.

By these two rows of nerve fila, eaeh side of the
medulla oblongata is divided into three distriets, viz., an
anterior, a lateral, and a posterior, similar to the surface areas
of the three funiculi on the side of the meduUa spinalis. At
first sight, indeed, they appear to be direet eontinuations
upwards of those portions of the spinal medulla ; it is easily
demonstrated, however, that that is not the ease, and that the
fibres in the three funiculi of the medulla spinalis undergo a
rearrangement as they are traeed into the medulla oblongata.

Anterior Area of the Medulla Oblongata — Pyramis. — The
distriet between the antero-median furrow and the row of
hypoglossal nerve fila issuing from the meduUa receives the
name of the pyramid. An inspeetion of the surface is almost
sufficient to show that this is formed by a eompaet mass of
longitudinally direeted fibres. It expands somewhat, and
assumes a more prominent appearanee as it passes upwards,
and, finally, reaehing the lower border of the pons, it beeomes
slightly eonstrieted and disappears from view by plunging into
that strueture. The pyramids are the great motor strands of
the medulla oblongata.

Although the pyramid, at first sight, appears to be the
eontinuation upwards of the anterior funiculus of the spinal
medulla, it eontains within itself only a very small proportion
of fil)rcs whieh oeeupy that funiculus. This will be at onee
manifcst if the deeussation of ihe pyrainids is examined. For
this purpose introduee the baek of the knife-blade into the

MEDULLA OBLONGATA

523

antero-tnedian furrow below the deeussation, and on one side
push in a lateral direetion the anterior funiculus of the medulla
spinalis. The pyramid will then be seen to divide into two
portions, vlz., a small strand termed the fasciculus eerebro-
spinalis anttrior (O.T. direet pyramidal trac(), whieh proeeeds
downwards into the anterior funtculus of the spinal medulla

elose to the antero - median furrow, and a mueh larger
strand ealled the /aseieulus eerebrospinalis lateraiis (O.T.
erossed pyramidal traet), whieh, at this level, is broken up into
three or more eoarse bundles whieh sink posteriorly and, at
the same time, eross the median plane to take up a position
in the opposite lateral funiculus of the spinal meduUa, elose
to the posterior eolumn of grey matter. It is the inter-
orossing of the eorresponding bundles of the fasciculi eerebro-

5^4 THE BRAIN

spinales laterales of opposite sides whieh produees this ehai

aeteristie deeussation.

But if the laseieulus eerebrospinalis anteiioi of the anteiior funiculiia of
the £|una1 meduUa is alone represenled in the eorresponding distriet of the
raedullaobloneata, it maybeasked: What beeomes of Ihe krger lateral part
of theantetiorTunieulusorthe spinal medulla in tbe medulla oblongala ? It
is ihrust aside by Ihe deeussating bundles of the fasciculus eeiebrospinalia
laierniis, and thus eomes lo oeeupy a deep positlon in the medulla oblongata.

Lateial Area of the Mednll» Oblongata. — ^This is the
distriet on the surface cf the medulla oblongata whieh is
ineluded between the two rows of nerve fila, viz., the hypo-
glossal fita anteriorly, and the fila of the accessor>', vagus, and
glosso-pharyngeal posteriorly. It presents a very different
appearanee in its upper and lower parts. In its lower
portion it appears to the eye as a eontinuation upwards
of the lateral fumculus of the spinal medulla ; in its upper
part is seen the striking oval prominenee named the olive.

The lower part of this distriet, however, is very far from

MEDULLA OBLONGATA 515

being an exact eounterpart of the lateral funiculus of the spinal
medulla. It has been noted already that the large fasciculus
eerebrospinalis lateralis, whieh in the spinal medulla lies
in the lateral funiculus, is not present in that distriet of the
medulla oblongata ; above the deeussation of the pyramids
it forms the chief part of the pyramid of the opposite side.
Another small strand of fibres, the /aseieulns etrebellospinalis
(O.T, direet eerebellar trtsei), prolonged upwards in the lateral

^iuadrkgeoimii] body

or ihe Medulla Oblotigata. Poiu, and Mesoi-
: K(etU5. The grealer pait ti Ibe nxrf of Ibe

rouilh venlrLcle is lemoyed.

funiculus or the spinal medulla, gradually leaves this poTtion
of the medulla oblongata. This traet of Gbres Hes on the
surface, and it is often yisible to the naked eye as a white
streak inelining obliquely into the posterior dUtriet rf tbe
medulla oblongata to join its uppet parl, i.e., the re*tifonii
body. The great majority of the remairider of the fitirct
whieb are prolonged upwards from the lateral funiculitt of
the spinal medulla disappear from the surface at the lower
border of the olive, by dipping into the substanee <»f the
meduila oblongata under cover of that projection. A nairow
band, however, is earried upwards to the [Kins, in the inteml

526 THE BRAIN

between the posterior border of the olive and the fila of the
vagus and glosso-pharyngeal nenres.

The olive is a smooth oval projection, whieh oeeupies
the upper part of the lateral area of the meduUa oblongata.
Its long axis, whieh is vertical, is about half an ineh long,
and its upper end is separated from the lower border of the
pons by an interval or groove.

Posterior Area of the Mednlla OUongata. — In its lower
half this region is formed by the euneate and graeile funiculi ;
and in its upper half it is formed, medially, by the ependymal
roof of the fourth ventricle and, laterally, by the diverging
funiculi.^ It is separated from the lateral area on eaeh side
by the row of fila belonging to the aeeessory, vagus, and
glosso-pharyngeal nerves.

The lower part of the posterior area eorresponds more or
less elosely with the posterior funiculi of the spinal medulla.
It will be remembered that in the cervical part of the spinal
meduUa the posterior areas on eaeh side is divided by a
distinet septum of pia mater into a postero-median strand and
a postero-lateral strand. These are prolonged upwards into
the medulla oblongata, and in the lower part of the posterior
area they stand out distinetly, and are separated from eaeh
other by a eontinuation upwards from the medulla spinalis
of the postero-intermediate suleus. In the medulla oblongata
these strands receive different names. The medial one is ealled
the /unieulus graeilis, whilst the lateral one is designated the
/unieulus euneatus. Eaeh of these strands, when it reaehes
the lower part of the fourth ventricle, ends in a slightly
expanded prominenee. The swollen extremity of the
funiculus graeilis is ealled the clava ; it is thrust aside from
its fellow of the opposite side by the opening up of the
eentral eanal to form the fourth ventricle. The thiekened
end of the euneate funiculus receives the name of the
tubenulum einereum, but it is in the young brain only that it
is well marked.

In seetions through this region of the meduUa oblongata,
it is seen that the prominenees produeed by the two strands
and their enlarged extremities are in a great measure due to the

' Tlie disseetor should note that the lower part of the cavity of the hind-
l)riii», i.e. the fourth ventricle, is not behind but in the upper part of the
ineehilla, whieh it separates into dorsal and ventral parts ; the dorsal part forms
a portion ()f the roof of the ventricle, whilst the ventral pait forms a portion of
lh<' lloor.

MEDULLA OBLONGATA 527

presenee of two elongated nuelei, whieh lie subjacent to
them and gradually inerease as they are traeed upwards.
These are termed the graeile and the eumeate tnulei, and it
ean easily be shown that as the grey matter inereases in
quantity the fibres of the two eorresponding strands diminish
in number. Indeed, it is doubtful if any of their fibres are
prolonged upwards beyond the level of the nuelei.

But a third longitudinal elevation also is apparent in the
lower part of the posterior area of the medulla oblongata. This
is plaeed on the lateral side of the fimiculus euneatus — between
it and the posterior row of nerve fila — and it has no eounter-
part in the posterior funiculus of the spinal meduUa. It is
ealled the /unieulus of Rolando^ beeause it is produeed by
the substantia gelatinosa Rolandi approaehing the surface.
Extremely narrow below, the funiculus of Rolando widens
somewhat as it is traeed upwards, and it, finally, ends in an
expanded extremity ealled the tuberde of Rolando. The thin
layer of fibres whieh appear on the surface of the tuberele
and funiculus of Rolando and cover the substantia gelatinosa
Rolandi in this position belong to the traetus spinalis (O.T.
spinal root) of the trigeminal nerve.

The restiform body forms the upper part of the posterior
area on eaeh side. It lies between the lower part of the
floor of the fourth ventricle and the fila of the vagus and
glosso-pharyngeal nerves, and is thrust laterally by the en-
largement of the fourth ventricle. It is a large rope-like
strand, whieh inelines upwards and laterally, and then finally
takes a turn posteriorly, and enters the eerebellum, of whieh
it eonstitutes the inferior pedunele, The restiform body, there-
fore, is to be regarded as the main eonneetion between the
eerebellum, above, and the medulla oblongata and medulla
spinalis below. At the same time, it must be understood
that it is not formed of fibres whieh are prolonged into it
from the funiculus graeilis and funiculus euneatus of its
own side. It is true that a surface inspeetion of the
medulla oblongata might lead very naturally to this supposi-
tion, beeause there is no sharp line marking it ofF from the
tubereles of these strands.

The fibres whieh build up the restiform bodies eome from several differ-
ent sourees. It will be sufficient to indieate the more important of these —
( I ) from the lateral funiculus of the spinal medulla through the fasciculus
eerebellospinalis ; (2) from the eerebellum as the cerebello-clivary fbres

f2>, THE E1L\IX

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>/*':: v.r<ii«r.'' ^: t;.^ '/:v^ 2. r. -=:_'' er ^.t eirTed beisdles oT tibres^
UrTte,*/: tr.': txUrnal ar:uaU fJri:, slit be ooiieedL They
vary jfr':s*iv i.'i r.u.T.'ir:!' ar.'i :n eisdnetness. and aie some-
tirn'r^ \'> nf;rr»ero*i- a.^ :o ccver t'r.e olrre alniost endrely.
Ari 'A\'^jiT\ivi*i ';xarr.:r.a::or. wil: s'r.ew :hat they eome to the
virinfJ: in th'; an:ero-rr.ecLar. nssure between the pyiamids^
ifi rh': ;?roove ly:t-A';en :he p}Tin::d and the oliTe, and some-
tirri':-; al-.o thr^K^r, the su'r/stanee of the prramidsu Biit at
wh;it,'rv':r f//in'. t;.ey reaeh the 5i:rfice, the majority have one
/|':^tination, vi/„, the re5:iform body — a eonsiderable part of
whi^h th«:y forrn. They are derived from the etmeate and
yx:%<'\\*: nu^Iei of the opjj05ite side.

/hr.rrtion. Th': y/rsLTT.'A of or** side shouW now bc carefnlly raised.
\Vh'f» '\i.\'/\\f;-*\ U'mu\ irs r/Td i*. .should be ger.tly pnilled npwaids towaids
\)it' ytU'.. Iri rhis way its er.tranee into the pons is brooght yeiy
t\fnf\'/ irito '/]<:%'. I'iirth'rr, nuiTierous areuate fibres will be seen
riMiniMi^ ;irit':riorly u^^^^ri th': m'rdial aspeet of the opposite pyramid to
r<-»' h tii<; '.wii'A',*:, and th': vcntral edge of the medial lemnisens will be

«■/J/'/i''d ;ilv;.

Ponn. The i>ons is the marked prominenee on the base
of th^: hr;iin whieh is interposed between the meduUa ob-
ion^^'ita i\x\i\ \\\i: peduneuli eerebri, and lies anterior to the
r<rnThf!llurn. It is convex from side to side, as well as antero-
p';iitrriorly, anrl the tran.sverse streaks on its surface show
th;it, siip(:rrH:i;illy, it is eomposed of transyerse bundles of
n<Tvi: lil)n:s. r)n either side these transverse fibres eoUeet
thrnis(:lv(:s togother to form a large eompaet strand whieh
sink:i |)ostcro l.'ilerally into the eorresponding hemisphere of
thr r;crr:h(:lhim. This strand is termed the braehium ptmtis
(O.T. tniddle eerebellar pedunele).

TIh: v(:ntnil surfacc of the pons is in relation to the basilar
portion of the oeeipital bone and the dorsum sellae of the
;,phrn()i(l hone. It |)rcsents a median groove whieh gradually
widens ;js it is traeed upwards (Fig. 219). The groove
|(»(lj'r:i ilu' hiisihir artery, but is not cause(i by that vessel;
it is (liK' to the prominenee produeed, on either side, by
the pass:jg(: downwards through the pons of the bundles
of lihres whieh form the pyramids of the meduUa oblongata.

GEREBELLUM 529

Where the pons beeomes the braehium pontis the large
trigeminal nerve will be seen entering its ventral surface,
nearer its upper than its lower border.

With the exception of the restiform bodies, the whole of the
medulla oblongata enters the lower aspeet of the pons, and its
eonstituent parts are earried upwards within it. The peduneuli
eerebri emerge from its upper aspeet. The dorsal surface of
the pons eannot be studied at present. It is turned towards
the eerebellum, whieh hides it from view, and it forins the upper
part of the anterior boundary or floor of the fourth ventricle.

Cerebelliiin. — The eerebellum is distinguished by the
numerous parallel and more or less curved sulei whieh
traverse its surface and give it a foliated appearanee. As in
the ease of the eerebral hemispheres, the grey matter is
spread over the entire surface, whilst the white matter forms
a eentral eore in the interior.

The eerebellum eonsists of a median portion, the vermts^
and two lateral kemispheres, The distinetion between these
main subdivisions of the organ is not very evident on its
superior surface. Anteriorly and posteriorly there is a
marked deficiency or noteh in the median plane (Fig. 223).
The posterior noteh is smaller and narrower than the anterior
noteh. It is bounded laterally by the posterior parts of the
eerebellar hemispheres, and anteriorly by the vermis, and
it is oeeupied by the falx eerebelli. The anterior noteh is
mueh wider and, when viewed from above, it is seen to be
oeeupied by the inferior pair of quadrigeminal bodies and
the braehia conjunctiva eerebelli. Its sides are formed by
the lateral hemispheres, and the posterior end is bounded by
the vermis.

On the superior surface of the eerebellum there is little
distinetion to be noted between the vermis and the upper
surface of eaeh lateral hemisphere. The upper surface of
the vermis forms a median elevation, from whieh the surface
slopes gradually downwards, on eaeh side, to the margin
of the hemisphere. On the upper surface of the vermis four
regions are reeognise.d. Anteriorly, at the posterior end of
the anterior noteh, lies the eentral lobe^ and prolonged up-
wards from it on the dorsal surface of the anterior meduUary
velum, between the braehia conjunctiva, are a few folia whieh
eonstitute the lingula, Posterior to the eentral lobe is the
montieulus^ separable into two parts — an anterior elevated end,

VOL. II — 34

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.'.'/'..-.. 'l :...'.',.. w : \ 'rirrr. ■:?! :r.-: r'Z."^LU S.z MnpelJL md in is an-
^ •■.-.'.: :,-:" '-.-: .-.--;';- ..': :':". :r.^iLi :.= ..tistiL I: :ie medeHa. is
^. .r- ■■''. •; • j ; f • '. .-.-. : '. -: ',.-: .' ^ '.»r ! : ~x, i r.'l :he Li:ctI henispaees
■■•.r: :. . .«:■: ■;:,':.': v. a.-, :: *xc*:'5c :he uorer bonndnry ot the
%:i.r:'. ,.'a . ' ■^ . . ! ',': -.r:-'; .'. : r. :i : : r. : .t i.^ : : rr. ei bv the iriferior
■. .rf:jv: '/' *..'.': r.^rrr::. i.'.'L r'-nr.^r. 'ir.^Li rhe verTEis is sepanited.
' . .'. ':;»':. ■..':-: f.". -.-. : :. -: '',.'. rr -i^p': r. dir. z lireral hemisphere by a
':..'. r .'. * f . r r '. '. . •: -': • .-;. -': -; : :. -: :u !cu : T.iiUeul^s. ^

\\ V'.': :.'.■:':■..'. '.:' :■.-: -.-:rr.-.:.=. where ic form5 the posterior
'.',.-,':,:/ '/' : :. •: j .', : --: :.'.': r. o :cr. on the superior 2sgccX of
':.•: ''::':^r:!. ..-.'.. V. 's-,r.\..- raiied. and a: rhe same time the
rr.'-.'r.^- ;i:.;il'..'. :": :, .!!-:C ar.^er-^rly, t^o stninds lying upoD
^r.': '\'»r:\. '\.\r/,\ r,f ::.,; prr.s will be seen. These aie
':.': hra hia ':onjun',H'.t e^.rdt^li (O.T. supirior pedumdes).
'I ;.'■;/ « ::.f:r;.^': ^.'o.r, ::.-: u'hire rr;a::er of tbe eerebelluiii,
i ux\-i*'.'j*\ .']■, r.:.-:y \,:'/.-.i:(\ upwards, and. finally, they dis-
:i;,:,' -ir .'.':-:: rr.-': \r'SKr/ti ciiadri£en:inal bodies. The thin
l;nfii[i:i •//:.>.,'. ., .\:f:\(\\i:<\ aoros.s i^etween them is the anterior
medu/hiry ^^ium. Jt :-: r.ontin'^ous below with the white eore
t\ *\i'- vf ::::.:., &:.'! !: r.elps :o form the roof of the upper
]r.iT\ fA :};■: f'/.rr:. V';ntncle. From its dorsal surface, dose
'.', M.': ;rif-r!^r '':-j'].driL'r;rriiria: bodv. the small troehlear nerres

f u,' T'/*-.

(',trv.i\tt of tli'; sui'';i which traverse the surface of the
' ' r'-l/ ■lliirn, fl':':p^-r rmd longer than the others, map out
d I , » r I ^ ! ■ . ■.'/ 1 j i ^ 1 1 ;iTf: 1 0 r rr. rjd lobe 5. Th e most eonspieuous of
,il! ili'-','- f.\<-U.\ is i\if: j^''re'7/ }ioriz'''ntai sulais.

Orrsat Horizontal Suleus of the Cerebellnm. — The great
li'.n/.'intril '.nlr.u.'s brgin.s antL-riorly, and passes round the
' II' \\\\\W\t'\\f'A'. f)i the r.erehellum. rutting deeply into its lateral
;iii'l j;o'.t<fior ni.'irp.Mn'.. .\ntcriorly. its lips diverge from eaeh

' ■. . im . I /!'.!.<■ l'.'- •■: »;•.!.■.■! i.-i' r" :'f c:' !:'.■• :" ■.:■■:]: v-i'trio!o and its co\-ering
1,1 |,ii iii.it. r mII 1h- t'ir;. :: .v-:y. :.n.l t:-.o '.OA«r p.v: of the tloor or anterior
l.'.iiii'l II ■,■ i,i ih'- l'/;iftli ^.■iilrie!'^ \vi!I lio i-.i.-p'.ayoil.

GEREBELLUM

53'

other so as to enibraee the lai^e braehia pontis {O.T. middle
peduneles), where they pass into the interior of the eere-
bellum, The great horizontal suleus divides the eerebellum
into an upper and a lower part, whieh may be studied
separately.

IiObBB on tha Upper Snrtaee of tli« eaiebellum.— It has l)een noled
already that ihe upper surface of the verTnis superiot is sulKlivided. The
divisions eommeneing from Ihe anlerior end are ;— (i) 'he lingula ; (z) the
eenlral lobule ; (3) the eulmen montieuli ; [4I ihe dec1ive montieuli ; (5) ihe
folium vermis, With the exception of the lingula, eaeh of these is tx

on eilher sido wilh a eorresponding distriet on the upper sut&ee of the hemi-
sphere, and forms wilh these distriets a eerebeltar lohe. Thus, the eenual
lohule h prolonged tateTally on eaeh side in an expansion ealled the ala ;
the eulmen eonstitutes a median eonneeting pieee between the two atiitrior
eresieiitie lobules ai the hemL'ipheres ; the declive stands in the same relation
tii the posterior ertseentie Mults ; and the folium vermis is the eonneeting
haml lietween ihe superior semilunar lotules of the hemispheres.

LingalB. — The lingula ean \x seen only when the posterior boundary of
the antericff noteh is pushed posteriorly. It eotaists of four or five smalt
fii1ia, eontinuous with tlie grey niatter of the vermis, prolonged anteriorly
on the surface ur the anterior medullary velum, in the interval tietween
Ihe hraehia conjuncliva.

Lobna eentraUa wlth ita Al». — The eentral tohule lies at the posterior

::,; THE BRAIN

■■■.■. r:::-i'.-'i :• ■■.:!!. uni: i^ Ittrgely luddeo by the eolinen. Il is »

-■ -. .e'. :r.:.~> H;:i'.h it ;>; 1 -n^ed lalerallj f<ii a Ehort distaiiee romld

■■■•"..■::■ :■.}. ;:. -.he f ■im '.■( \v.' ex;iansi[>iis. termed tbe ala.

Lobui eolliiiBit. -The ru.'Ken tKimiimli eeinstitntet I}]C snmmit oc

d laterall; oa

r<; run

vl.ii:li il i. t,.:]iiira''''l l.y a. ilistiiiel tissure, an<! il ftinns th« 5lo|»iig part or
\i-,i-\,\ i,f tli': iiiiinlieulus '>f Ihe verinis. On eaeh side il is eontinuotu
lilli \\v /■ir.lrriiir rreseeiiti' lobuli o( the lateral hemisphere, and the three

'l'lir iw" i^rr^-iiilii: liiliuluii 'in Iho u]i]icr Biirfari; <if the hemiBphere are
■ ■■.|ii.-Mlly 'l.-«:rilii:'l Hn,n:lli.r nj ihu .piadrale lahii/e.

l.nliua SemilntiaTis Superior (O.T. lobus eaeuminii),— The />^ibih
'.■)/«/, r.iiiiis l)ii: iii..ht [Kisluri'ir imrt of Ihe svif>eri(ir porlion of the
''■niii,, :iii.l ii li.inn'l.s liie jjr«il lioriHintal Bssure, superiorly, at the
iiisiiii.ir ii.iii'li. [1 Ik a siiiRle foliuni, the surface of whieh niay be
iii..'illi .11 l.i^vt willi ru'limenlary seeondnry f(>liit, nnd il is the eonnee"
iiiL l.ilw.i'ii tlit iwo stiperior seiiiHuiiar lebiile! of Ihe hemisphen

GEREBELLUM 533

Ihe three parts eonstituting the lobus stpiilimaris supiriar. As the folium
Yermis is traeed laterally inlo the semilunar lobule of Ihe hemisphere,
it is round to expand greatly. The result of this is thal Ihe lobug
semilunaris superior on eaeh ^e forms an extensive foliated distriet
bounding ihe posterior part of the great horizonlaI suleus superiorly.

LobeB ou the imd«r Bnrfacs of the eereballtLm.— The eonneeiion
between the several porlions of the inferior part of ihe yeimis, and Ihe
eorresponding dialriets on the under surface of ihe two hemispheres is not
nearly so distinet as in the ease of the superior part of the vermis and ihe
lobules on the upper surface of tbe heniispheres.

Proeeeding poslero-anteriotly the following subdiTisions of the inferior

on Ihe braehium ponti 2 he * nt al Ubule, whieh Hes immediately

whieh traverses its surface ; (3) the tomil, a lounded lobule,
Ihe vallecula on the medial side of the biventTaI lobule ; (4) the in/erisr
semiluaar laiule, plaeed posterior to the biventral lobule, and bounding the
great horiiontal suleus inferiorly.

These lobules of Ihe bemispheres, with the eorresponding portions of
the inferiot part of the vermis, eonstitute the lobes on the under aspeet of
the eerebellum.

Lobua NoduU.—The lobus noduli eomprises the nodule and Ihe Aoeeulus
of either side with an exceedingly delieate eonneeting lamina of white
matter, termed the posleriBr meduUary velum.

The velum eannol be properly seen at present, but it will be exposed at
a later stage of the disseetion.

Lobus UtuI». — The uvula is a triangulai eleyation plaeed between the
two tonsils. It is eonneeted aeross the suleus valleculs with eaeh lonsil
by a low-lying ridge of grey matter whieh is seored by a few shallow
furrows, and in consequence termed \he /urreraied band. The two tonsils
and the uvula form the lobus itvuht.

To see the furrowed band it will be neeessary to remove Ihe tonsil on
one side, wben ihe poslerior medullary velum also wiU be exposed.

534 THE BRAIN

Loboi "PynmidiM. — The pyramid is eonneeted with the biventral
lobule on eaeh side by a faint ridge whieh erosses the suleus ▼alleeula:.
The terni /of>iis pyramidis is giyen to the three lobules whieh are thus
assoeiateii with eaeh other.

Lobns Tuberis. - -The tuberrermis^ whieh forms the most posterior part
<>f the verniis, is com{)ose(l of several folia, whieh run direetly into the
inferior semihmar loljule on eaeh side. The three parts of the lobus ttiberis
are thus linked to^^ether. The inferior semilunar lobule is traversed by
two, or ii may lje three, curved fissures. The most anterior of these euts
off a narrow, curved strip of eerebellar surface ealled the lobtdus greuilis,

Disseetion.- A median seetion should now be made through the vermis
of the cere1>ellum and the two medullary vela into the cavity of the foarth
Yentriele. When the two ])arts of the eerebellum are drawn slightly
asunder, a view of the fourth vcntricle is obtained ; further, the eonneetions
of the two medullary vela and the arrangement of the peduneles of the
ccrolH;Ilum ean be more elearly understood.

Arbor Yit» GerebellL — The eut surface of the eerebellum
presents a very eharaeteristie appearanee. The grey matter
on the surface stands out distinetly from the white matter in
the interior. Further, the eomplete manner in whieh the
surface is eut up by the sulei into seeondary and tertiary folia
is seen. The eentral mass of white matter in the vermis is
termed the eorpus medullare, From this, prolongations pass
into the various lobules, and these give off branehes to supply
eaeli folium with a eentral white stem or eore. The term
arbor vitce is applied to the appearanee whieh consequently
results when a seetion is made through the eerebellum.

Cerebellar Pedtmeles. — The eerebellar peduneles are the
struetures whieh eonneet the eerebellum with the medulla
oblongata, the pons and the mid-brain. They are three in
nuniher on eaeh side — viz., the middle, the superior, and
the inrerior. They are all direetly eonneeted with the white
niedullary eentre of the eerebellum, and are eomposed ot
Tibres whieh emerge from or enter the wliite eentral sub-
slanee o^ the organ.

The middle pedunde is the braehium pontis, and is mueh
ihe largest of the three. It is formed by the transverse
fibrcs of the pons, and it enters the eerebellar hemisphere on
tlie hiteral side of the other two. The lips of the anterior
part o{ the great horizontal suleus are separated widely from
eaeli other to give it admission.

Tlie inferior pedunde is simply the restiform body of the
nieihilla oblongata. Leaving the dorsum of the meduUa
oblongata it turns sharply posteriorly and enters the eerebellum
between the other two peduneles.

MEDULLARY VELA 535

The superior peduneles are the braehia conjunctiva of
the eerebellum. They are eomposed of fibres whieh eome, for
the most part, from the nueleus dentatus of the eerebellar
hemisphere. As they issue from the eerebellum, the
pedunele lies elose to the medial sides of the eorresponding
middle peduneles. They then proeeed upwards towards the
inferior pair of quadrigeminal bodies. At first they form the
lateral boundaries of the upper part of the fourth ventricle,
but they converge, as they aseend on the dorsal aspeet of the
pons, so that ultimately they overhang the fourth ventricle
and enter into the formation of its roof. They disappear
under cover of the quadrigeminal bodies, and their eourse
in the meseneephalon has been deseribed already (p. 511).

Medullaxy Yela.. — The medullary vela are elosely assoeiated
with the peduneles. They eonsist of two thin laminse of
white matter whieh are projected out from the white eentral
eore of the eerebellum. The anterior medullary velum stretehes
aeross the interval between the two braehia conjunctiva
(superior peduneles), with the medial margins of whieh it is
direetly eontinuous. It is triangular in form', and is eon-
tinuous below with the white matter of the eerebellum.
Spread out on its dorsal surface is the tongue-shaped prolonga-
tion of grey matter from the cortex of the eerebellum whieh
is termed the lingula^ and issuing from its substanee, elose
to the inferior quadrigeminal bodies, are the two troehlear
nerves.

Hh^posterior medullary velum is somewhat more eomplieated
in its eonneetions. It presents the same relatioh to the
nodule that the anterior velum presents to the lingula. It is
a wide thin lamina of white matter — so thin that it is
translueent — whieh is prolonged out from the white eentre
of the eerebellum above the nodule. From the nodule it
stretehes laterally to the Aoeeulus, thereby bringing these
two small portions of the eerebellum into assoeiation with
eaeh other. Where it issues from the white matter of the
eerebellum it might almost be said to be in eontaet with the
anterior meduUary velum, but as the two laminae are traeed
anteriorly they diverge from eaeh other : the anterior velum is
earried upwards between the braehia conjunctiva of the eere-
bellum, whilst the posterior meduUary velum turns downwards,
round the nodule, and ends in a slightly thiekened free
ereseentie edge. The cavity of the fourth ventricle is earried

536 THE BRAIN

posteriorly between the two vela, whieh fonn a tent-like roof
for it.

Isthmns BhombeneeplialL — If the disseetors examine the
rhombeneephalon from the side they will reeognise that there
is a region below the lamina quadrigemina and above the
eerebellum whieh is bounded dorsally by the anterior
medullary velum, laterally by the braehia conjunctiva, and
ventrally by the upper part of the pons ; it is to this region
that the term isthmus rhombeneephali is applied. It eontains
the upper part of the fourth ventricle.

Yentriouliis Qiiartas. — This cavity is somewhat rhomboidal
in form. Below, it tapers to a point and beeomes eontinuous
with the eentral eanal of the lower part of the medulla
oblongata; above, it narrows in a similar manner and is
eontinued into the aquaeductus eerebri of the mid-brain.
The anterior wall is termed the Aoor^ and is formed by the
dorsal surface of the ventral part of the upper portion of
the medulla oblongata and by the dorsal surface of the pons.
The posterior wall is ealled the roof, On either side a
narrow pointed prolongation of the ventricular cavity is
earried laterally, from its widest part, round the upper part
of the eorresponding restiform body. This is termed the
laterai reeess (J^\g. 222, p. 525). It is seen to the greatest
advantage when the eerebellum is divided in the median
plane and the halves are turned aside.

The lateral boundary of the fourth ventricle, on eaeh side,
is formed, from below upwards, by the clava, the upper part
of the funiculus euneatus, the restiform body or inferior
pedunele of the eerebellum, the braehium pontis or middle
pedunele of the eerebellum, and the braehium conjunctivum
or superior pedunele of eerebellum.

Dissedion. — On one side eut through the braehium conjunctivum, the
braehium pontis and the restiform body, and so separate one lateral half of
the eerebellum, whieh must be laid aside for the present but must be preserved
for future use.

When the disseetion is eompleted the disseetors will be
able to reeognise that the anterior part of the cavity of the
fourth ventricle is rhomboidal in form. It eonstitutes the so-
ealled rhomboidal /ossa, whieh is surrounded by the lateral
boundaries of the ventricle and elosed anteriorly by the pons
and the posterior surface of the ventral part of the upper
portion of the medulla oblongata. Only the iower part of the

FOURTH VENTRICLE 537

rhomboidal fossa lies in the medulla oblongata : tbe inter-
mediate part is in the meteneephalon, that is, it lies anterior
to the eerebellum and posterior to the lower part of the |>ons ;
and the upper part is in the isthmus rhombeneephah.

The lower part of the rhoniboideU /ossa is triangular in out-
line, and its inferior angle is eontinuous with the eentral eanal
of the lower part of the medulla oblongata. The anterior
boundary or floor of this part of the fossa is marked by a
number of converging sulei, and is ealled the ealamus
seriptorius, Along the lateral margins of the lower part of
the fossa will be seen the remains of the torn epitheHal roof
of the lower part of the fourth ventricle. These torn margins
are the teeniee of the fourth ventricle. The intermediate part of
the rhomboidal fossa is separable into a lower wider part,
whieh is prolonged laterally, on eaeh side, below and posterior
to the restiform body, as the lateral reeess of the fourth
ventricle, The upper seetion of the intermediate part of
the fossa is bounded laterally by the braehia pontis and is
mueh narrower than the lower part. The upper part of the
rhomboidal fossa lies posterior to the pons and between the
braehia conjunctiva. At its upper end it beeomes eontinuous
with the aquaeductus eerebri of the mid-brain.

Tht fioor^ or anterior boundary^ of the fossa rhomboidalis is
the floor, or anterior boundary, of the fourth ventricle. In
the upper part of its extent it is formed by the posterior
surface of the pons, and in the lower part by the posterior
surface of the ventral part of the upper portion of the medulla
oblongata. It is divided into lateral portions by a median
suleus whieh is deeper below, in the region of the ealamus
seriptorius, and shallower above. On eaeh side of the median
suleus is the eminentia medialis. In the upper part of the
fossa the eminentia medialis oeeupies praetieally the whole
of eaeh lateral half of the floor; in the upper part of the
intermediate portion of the fossa a nodular eminenee, the
eollieulus facialis^ appears on its surface; below the eollieulus
it narrows rapidly, and it terminates, below, in a pointed tri-
angular proeess ealled the trigonum hypoglossi, The medial
eminenee is bounded laterally by a suleus, the suleus limitans,
In the upper r^on, along the lateral border of the suleus
limitans, is a narrow bluish tinted area ealled the locu%
eeeruleus ; the eolour of this area is due to a subjacent eiA-
leetion of pigmented eells idiieh eonstitute the tubstantia

538 THE BRAIN

/errughiea, Opposite the eollieulus facialis the suleus limitans
expands into a shallow fossa, the superior fovea, The lower
end of the suleus Hmitans terminates, in the upper part of
the inferior seetion of the rhomboidal fossa, in a deflnite
depression, the tn/erior fovea. To the lateral side of the
superior and inferior foveae and the intermediate part of the
suleus limitans is the area aeustiea^ whieh is prolonged lateraUy
into the lateral reeess where, in rare eases, a projection, the
tubereulum aeustieurn^ appears on its surface. Below the
inferior fovea, between the trigonum hypoglossi medially and
the area aeustiea laterally, lies a depressed, grey-eoloured,
triangular area ealled the aia einerea^ whieh is separated from
the lower part of the floor, the area postrema^ by a raised
bundle, the funicuius separans, Immediately above the in-
feriorfoveaa number of ridges, the meduilary striee (O.T. stria
acusticce\ eross the floor of the fossa. Laterally they eross
the restiform body, at the lateral border of the fossa, and
beeome eontinuous with the eoehlear root of the aeustie
nerve ; and medially they disappear into the median suleus.

The roof of the fourih ventricle is formed, in the upper area,
by the medial parts of the braehia conjunctiva and the inter-
vening anterior meduUary velum. Deseending upon the
latter, from above, is the frenulum veli ; and issuing from it, in
the same region, are the rootlets of the troehlear nerves.
The lower part of the upper portion of the roof is covered
by the lingula of the eerebellum. The roof of the inter-
mediate seetion of the ventricle is the white matter of the
vermis of the eerebellum, and the roof of the lower part is
epithelial ependyma and the obex.

The tela ehorioidea of the fourth ventricie is the layer of
pia mater whieh covers and strengthens the epithelial roof of
the lower part of the cavity. Between it and the epithe-
lium at the lower end of the roof, is a thin layer of grey
matter, ealled the obex, Above, at the posterior medullary
velum, the tela beeomes eontinuous with the pia mater on
the lower surface of the vermis of the eerebellum. Laterally
the tela is prolonged, on eaeh side, posterior to the restiform
body, over the lateral reeess, and it forms the stronger part
of the wall of that expansion. Between the medial part of
the tela ehorioidea of the fourth ventricle and the pia mater
on the lower surface of the vermis of the eerebellum lies the
eisterna eerebello-medullaris (O.T. eisterna magna).

NUGLEUS DENTATUS 539

Apertures in the Tela Chorioidea of the Fourth Ventricle, —
In the early stages of development the tela ehorioidea and
ependyma form an unbroken layer, but at a later period they
are perforated by three apertures. One of the apertures, the
apertura medialis ventriculi guarti (O. T. /oramen of Magendie\
Ues immediately above the obex, at the lower angle of the
ventricle, and through it the cavity of the fourth ventricle
eommunieates with the eerebello-medullary portion of the
subaraehnoid spaee. The other two apertures lie at the
apiees of the lateral reeesses, immediately posterior to the
fila of the glossopharyngeal nerves.

ehorioid Plexuses of the Fourth Ventricle. — The ehorioid
plexuses are vascular invaginations of the ependyma beneath
the tela ehorioidea. In the lower part of the ventricle
they form two parallel bands, one on eaeh side of the median
plane, and their lower ends project through the medial aper-
ture. At the upper part of the tela ehorioidea they eom-
munieate together, and then eaeh passes laterally into the
eorresponding lateral reeess and their lateral extremities
project through the lateral apertures.

Dissedion. — The disseetor should now introduee his fingers into the
great horizontal suleus of that half of the eerebellum whieh is still eonneeted
with the medulla oblongata and the pons, and tear the upper part of this
side of the organ away from the lower part. By this proeeeding the
manner in whieh the peduneles enter the white medullary eentre, and
also to some extent the general distribution of their fibres, will be seen.

When these have been demonstrated this half of the eerebellum should also
be separated by eutting through the peduneles at the points where they
enter the eentral white matter. A horizontal seetion may then be made
through the other half of the organ, rather nearer its upper surface than
its lower surface. This will reveal the nueleus dentatus.

Nueleus Dentatus of the Cerebelluin. — This is a eolleetion
of grey matter, embedded in the white medullary eentre of
ihe lateral hemisphere of the eerebellum. It presents an
appearanee very similar to a nueleus whieh lies in the olive of
the medulla oblongata. It is a thin lamina of grey matter,
whieh appears on seetion as a wavy line folded upon itself,
so as to form a erumpled grey eapsule with a mouth open
towards the median plane. The greater number of the fibrcs
whieh build up the braehium conjunctivum issue from its
mouth.

There are other smaller isolated nuelei of grey matter in ihe white
medullary eentre of the eerebellum, but these eannot, as a rule, be

THE BRAIN
len obtuned in the dUseeting-room. The; lie

DiistdioH. — A series ot tcflnsveise seelions should now be made
Ibrough ihe pons and Ihe medulla oblongata, in oTdei that soniet3]ii]g of

theii inlernBl sliueture may lie leained.

As a matler of bet little ai the stnieture of the medulla oblongata ean he
leamt from speeimens oblained in the disseetine-toom ; but in seelioni
giropeely prepared and stained a numbsT of impoetant poinls ean he

gbnetura of Uw HednllK OUonKata. — When tiansveise seetions are

made Ihrough the meduUa oblungata at diAerent levels, a faint line, ealled
llie median raphe and oeeiipying ihe median plane, is seen lo divide it
Graeile nnekus

into two exiicily similar lateral porlions. Tbe raphe is tmmed by the
elose inteTseetion of tibies running in ditferent direetions.

Eaeh h!tlf of the medulla oblongata is eomposed of (a) strands of white
matter ; (*) grey matler, wbieh is present bolh in ihe fotm of diteel eon-
tinuations into Ihe medulla oblongata of portions of tbe grey matter of
the spinal medulla, and in the Torm of isolated elumps, whieh are nol
represented in the spinal medulla ; and (e) Ihe fotmatio retieularis, a
substinee whieh is eomposed of grey matter eoarsely broken up by Rhres
whieb lraveTse it in ditTerent diteetions. The white matter, as in the
E[unal medulla., is disposed for tbe most part on tbe surface and the grey
matter in the interior. but in the open part of the medulla oblongata the
grey malter eomes to the sutface on its dotsal aspeet, and forms the
obex (p. 538).

When the grey matler of the spinal medulla is traeed up into the medulla
oblongata, many sttiking ehanges in its attangement beeome apparent.
Owing to the inerease in siie of the large wedge-shaped graeile and euneate
funiculi, the postetior eolumns of grey matter beeome pressed kterally, so
that they soon assume a position at tight angles to tbe median plane, and
lie very nearly in the same transverse line. At Ihe same time, Ihe euneate

STRUGTURE OF MEDULLA OBLONGATA 541

eraeile nueleat eolumrs of grey matter iiliieh gtow out frrim the \asa\
of Ihe poslerioi eoluina and underlie [he stiands or ihe saiiie: nanie,

— Tran;verEe seelioii ihrough ihi. loner parl of the Medutk
Obiongala of a full Iime FieIus above the Deeussalion of ihe Pymmids.
treiled b) the Weigert Pal melhod The grey maller is nhile, and Ihe
medullaled strands of nerve fibres are blaek

— Transver5e seet on Ihrough lower end of Ihe Medulla Oblongila or
l me Fcelus trealed by Ihe We gert Pal melhod The Erey ni.itler
Tcfore bleaehed white ; whilsl the medullaled traels are blaek.

5.1J THK BRAIN

lu'ek 'ir llii: ]iiiNlLTicir eolumn, so aE to reaeh Ihe raphe. The eaput
riiluinii.1' IK in Ihii «ray eul oH Itom th« basal poiliDn. The ba&al portion
n-maiiu in rlim n-latiiin la the eentral eanal, whilst Ihe eaput and
suWnlilia ^i-laliniiui I Kiilaoiioi k ptaeed elose to the £urface, enlai|^ as it
ii IrniTil il|iwanls, flni) reirmi Ihe [irpininenee on ihe surface whieh has been
■Irsi'rilH^I alrrady os Ihe Tunieulus and luberde or Kolanilo. The Rbres
whii'li luive ihni litiiken up ihe neek of Ihe posterior eolumn, and wMeh
riiiiir rniiii llir ntneale anil {^r.teile nuelei, are lermed the itUimal artuaU
lihrtt. 'nii-y reai'h Ihe inphe un the (leep or doisal aspeet o^ the pyramids,
aml, iii lh(! nirilian plnne, they Torm a. very eomplete deeussalion wtth Ihe
iii(Teii|iiinilin|' lilirra ur the op|K>sile side. This deeussation is tenned Ibe
u btl u f i tt ttt h n y d saium A soon hey
s] h med b g h nt mal uat

'..'-.-> Iiiiu upunrils .ttiil fiiiiii a li>n{;ituilin.il ti.iet etlled the leainiieta.
It is pl.ii-nl i-lOM- ti> Ihi- ra]ihc aniliin the dorsal aspeet of the eoriesponding

riii' .iiili'iiiii i'iihiiiin of i;ri'y niattei shares .1 like Tate in the medulls
iil'li'ii[;.il.i. t>ul :il :i li"Hcr U'vi.'l. nl llie han<is of the fasciculus eerebio-
■■l'iii.ili'. I.il.-Kili-^ vl >.T, i-rossiil ji)-ramiilal Iradl. This great bundle, in
l..i'.'.iii;; 1111111 tlu' (.yi.iiiiiil intii tlie latt'ral fiiiiiculus of the opposile side of
ilii' '.|'in.il iiii^liill.i, ir.nptse» the anterior eolumn, eompletely hieaks up
il-- iiili'ini.^U.ili' i'.in iiiiil seiiaratm iln head Troni its basal |)oilion. The
liiiHii'i hi>ii.iv ,.r 1I10 .U'l.ii:ru'd hMd nee.1 not be tmeel, liut il is well
iii iii.i.' iti.li ilii' ki.<il |Mtl iif tho anterior eulunin of Riey matter remaina
111 ].i.siii..ii 1.11 itu- vi'iiir;il iiiul Inleinl asiwl iif tlio rentinl eanal.

\( .1 tii];hi-i li'ii'l ihi' i'iiilml ennnl, suitimnded liy Ihe basal porlions of
ilii- m.. 11. hniinsi.t [;«•!■ niiiltet. urailually inelines lowards ihedorsalaspeet,
iiiilil ii n'.iihi-s iho sutriii.'e. ITie grey matler whieh suirounds it is now
>l'.iil i.iii i>n llii' tliiiiT or Ihe fouTth YeDlriele, and in sueh a manner that

STRUGTURE 0F MEDULLA OBLOX(;ATA 543

thepoition whieh earrespomls to tbe bual port of the ui:cri'--rcof3iDDof tbe
spinal medulla is ^tuated elose to the niRtisn plane. whil>< ihe ^ait «hieb
represents the base of Ibe posterior eolumn oeeupaa a more Liieri] pisitiun.
Therefote the nueleus of origin of ibe hypo|^ossal nene i* f4ace<l io Ibe
median part of (he flooi, whilsi ibe □neleiu of teTminalton of ihe vigus
and elosso-pharyngeal neires lies in Ibe lateral pait of the floor.

Tne most eonspieuous of ihe isolated elumps of grey matler in iSe'
medulla are the olivary nudeus and tbe two aeeessory oliyaiy nueleL Tbe
oUvary nu^leus lies subjacent to the olivaiy eminenee, and is a very eon-
spieuous ob)ecl in transrerse seetioiu thioi^h ihis i^on. In sueh seelions,

Jevel of the r

towarda tbe median plane. Il is in leality a lamina Brranged in a pnne-
like mannei with its open mouth direeted towaids ihe raphe.

The aeeessory olivary nuelii are Iwo band-like laminie of grey mattei,
whieh are plaeed one on the dorsal and one on the medial aspeets of (he
main nueleus.

l'osteiior to, ot deepet tban, Ihe olivc and pyramid is the /grmalio
i-etiattaris of Ihe medulla oblongala. It is divided into a lateial and a
medial lield by the lila of ihe hypoglossal netve as they traver5« the sub-
slanceof the medulla oblongala to reaeh Ihe surface. In Ibelateral pottion,
whieh lies postetiot lo Ihe olive, there is a eonsideiable (|uantity of gtey
mattet, eontinuous with that of (he spinal meduUa ; it is tbetefote ealled
(he /ormatio grisea. In Ibe medial part, however, whieh lies posterior
(o the pyramid, the gtey matter is extremely seanty, and the retieulai
matter heie is termed \\\i/ormaiio alba.

544

THE BRAIN

e fibic5 whieh traverse the foTmado retieulaiis nin both in tbe

! and in the longitudinal direetion. The transvenefibra are the

inUmat areuale Jibres. The longiludinal Jiirts are deriTed Kom difierent
$ouTCf 5 in the Iwo lieids. In the lateral part of Ihe formation tbey represeot
the tihres ol^ the laleral funiculus (afler the removaI of the ceiebello-s[niial
aiHl the lateral eerebiospinal laseieuli), whieh are eontinued up undereorei
of the olive. In Ihe medial parl, or formatio alba, two lonritudinal strands
take oiigin, yli., the lemniseus and the median longitudinal ^asdeulul.
Bolh lie elose to the raphe The lemmseus is plaeed immediatel; posterioi
lo the pyramid, and is fonned by Ihe mlernai areuate fibres after thdr
deeussation. The niaiian longili^inal /aseieulus takes fotm in the upper
part or the medulla o1 longata, immediately sub]acent to the grey mattei

of Ihe floor of the fouilh ventric1e, It is formed by longiludinal tibres of
the foTmatio alba. whieh eome from the fascicu1uE anterioi proprius of the
spinal medulla.

Intetnal StroetuTe of the Poua. — When transverse seetions are made
througb the pons, it is seen to eonsist of two we1l-definfd paits, viz., a

itral and a dorsal. Broadly speaking, the vealral part, pars basatis.

rebii.

The basal fart of Ibe pons is ihe lai^er of the two subdiyiaons. It
is eomposed of a large number of transverse bundles of fibres, througb
tbe midst of whieh eoarse longitudinal bundles of iibiea proeeed down-
wards from Ihe bases of the peduneuli eeiebri to form, in the meduHa
oblongata, the two pyiamids. Seattered amongst these tiansveise snd
longitudinal bundles of Tibres, and filling up Ihe inteistiees between them.

INTERNAL STRUGTURE 0F PONS 545

there is a large amount of grey matter whieh forms the nudei pontis. Of
the transverse fibres two distinet sets may be reee^ised, viz., the superficial
transverse fibres, through the midst of whieh the bundles of eerebro-spinal
fibres are prolonged, and a deeper set termed the eorptts trape^oidum. The
superficial transverse fibres traverse the entire thiekness of the venlral part
of the pons, and on eaeh side, pass into the eorresponding braehium pontis.
The trapezial fibres lie posterior to the eerebro-spinal bundles in the boundary
area between the dorsal and ventral parts of the pons, but eneroaehing eon-
siderably into the ground of the former. They are seen only in the lower
part of the pons, and they pass into the lateral lemniseus. They take origin
in the terminal nueleus of the eoehlear division of the aeustie nerve.

The dorsal or tegmental part of the pons is, for the most part, formed
of a prolongation upwards of the formatio retieularis of the medulla.
Superiorly it is earried into the t^^ental parts of the j^unculi eerebri.
It is divided into two lateral parts by a median raphe, whieh is eontinuous
below with the raphe of the medulla oblongata and above with the raphe of
the tegmental part of the meseneephalon, whilst over its dorsal surtaee is
spread a thiek layer of grey matter whieh belongs to the upper part of the
floor of the fourth ventricle. In transverse seetions through the pons a
dark spot in the lateral part of the floor indieates the position of a small
mass of pigmented eells ealled the substantia /erruginea. It underlies
the loeus eoeruleus.

Four strands of longitudinal fibres are seen on eaeh side in transverse
seetions through the dorsal part of the pons. These are (i) the medial
lemniseus, (2) the lateral lemniseus, (3) the medial longitudinal bundle, and
(4) the braehium conjunctivum.

The medial lemniseus assumes in the pons a ribbon-shaped form. It is
plaeed between the ventral part of the pons and the fonnatio retieularis
of the dorsal part.

The lateral lemniseus^ largely eomposed of fibres derived direetly or in-
direetly from the eorpus trapezoidum, is seen in the upper part of the pons.
It sweeps round the lateral side of the braehium conjunctivum to gain the
surface.

The medial longitudinal buneUe is mueh more distinet than it is lower
down in the medulla oblongata. It has separated itself more eompletely
from the longitudinal fibres of the formatio retieularis, and it is now seen,
elose to the median plane, immediately subjacent to the grey matter of
the floor of the fourth ventricle.

The braehium conjunctivum, in transverse seetions, presents a semi-
lunar outline. It oeeupies a lateral position in the dorsal part of the
pons, and gradually sinks deeply into its substanee, although it does not
beeome eompletely submerged until it reaehes the meseneephalom

The superior olive is a small isolated elump of grey matter whieh
is embedded in the dorsal part of the pons in the path of the eorpus
trapezoidum.

VOL. II — 36

546 THE AUDITORY APPARATUS

THE AUDITORY APPARATUS.

Thk organ of hearing adniits of a very natural subdivision
into ihree parts, viz., the exteirnal, the middle, and the
internal ear. The external ear eonsists of the auriele and
ihe external aeustie meatus. The auriele eolleets the waves
of sound, and is, comparatively speaking, of subsidiary im-
portanee in man, although it is highly developed and of
eonsiderable service in some of the lower animals. The
external aeustie meatus is a passage leading inwards fr6m
tlie boTtom ot the eoneha to the membrana tympani, whieh
separates the cxternal trom the middle ear. The middle ear
is a narrow ehamber termed the tympanie eayity, It igjijtfir-
posed between the external aeustie passage and the intemal
ear 'oriabynntn, and the main part of its laterai wall is formed
by the membrana tympani. ^etehmg aeross the cavity of
the^ tympanum, from its lateral to its medial wall, there is a
ehain of three small bones^ ealled the auditory ossieles. ,The
internal ear or labyrinth is a most essential part of the organ.
It eonsists of a^omplieated system of eayities situated in the
densest part of the petrbus portion of the temporal bone. These
cavities eontain fiuid ealled perilymph, and also a membranbus
eouiiterpart ot the bony ehambers, ealled the membranous
labyrintni Within the latter there is fluid termed endolymph.

Disseetion. — The disseetion of the ear should be eondueted differently
on opposite sides.

On one side remove the lateral pterygoid lamina and the remains of the
extcrnal and internal pterygoid museles, if that has not been done already.
Then elear away the tensor palati musele and expose the lateral suHaee of
the auditory tube. Disseet on the postero-medial aspeet of the tube and
cxpose the levator palati musele from the lateral side. Follow the musele
downwards and medially, below the lower orifice of the tul)e, into the-
soft palate. Then detaeh the «audii.ory tube from the posterior border
of the medial pterygoid lamina ; eut the levator palati, at the point
where it enters the soft palate, and separate the eartilaginous part of the
auditory tube from any parts of the wall of the pharynx whieh may still be
eonneeted with it. When this has been done turn to the temporal bone ;
plaee the saw at right angles to the extcrnal surfacc of the squamous part
and saw through the bone, along the line of the petro-tympanie fissure, to the
posterior border of the spine of the sphenoid. Turn next to the medial
surface and saw through the body of the sphenoid at the level of the anterior
boundary of the foramen laeerum ; then, with the aid of the ehisel and bone
forceps, detaeh the posterior border of the great wing of the sphenoid from

EXTERNAL MEATUS

547

the anterior angle of the pelrous part 0^ Ibe temporal bone. When the
eiisseetion is properly done the gteater parl of the temporal bone is removed
froiii the remamder of the skiilT, wilh the eartilaginous part or Ihe auditory
tube nttaehed to the anterior angle of its petrous portion, «nd a small part
of the body of the sphenoid bone attaehed to its npex. The anterior walt
of the mandibular fossa was separated by the tirst saw eut, and the posteiior
wall is exposed, with the eaitilaginous part of the auditoiy tube attaehed to
its mediiil end nnd Ihe eartilnginous pari of the enternil aeustie meatus lo
its lateral boider. The disseetor should now eut away the tragus of the

wall o( ihe eaitilaginons pait or Ihe external meatus. Neit piiss a probe
into ihe bony part of the nieatus to gauge its lengtb, and, whilst Ihe probe
is kept in position as a guide, eut away the anterior wall of Ihe bony
part or the meatua, taking eaie not to injure the tympanie membrane whien
eloses the medial end of ihe meatus. Whe h d'ss ' ' ompteted Ihe
boundaries of the meatiis and thi: outer sur c membrone

should be ei

nined.

Meatoa AeuBtieus Eitemus. — Th

mns anteriorly and medially froiu
media) boundary, and, during its co
with the convexity upwards. Its to 1
the bottom of the eoneha to the tymp

tie meatus

nfice to its

. a light curve

m ured from

b e, is about

548 THE AUDITORY APPARATUS

24 mm., orwhieh S mm. eorresponds with the eartilaginous,
and i6 mm., with the bony part of the eanal ; but, as ihe
membrana tympani is plaeed obHquely, the anterior wall and
the floor are longer than the posterior wall and the roof,
respectively, Moreover, the diameter of the eanal is not
uniform. It is narrowest al ihe isthmus, whieh lies about
5 mm. frora the lympanie merabrane ; and its yertieal diameter
is greatest at the lateral end, whilst its anierO'posterior
diameter is greatest at its medial end. These facts must
be borne in mind during the removal of foreign bodies whieh.
have made their way into the eanal. ' As the tube passes from

the surface medially it deseribes a gentle sigmoid curve, but
its genetal direetion is towards the median plane with a
slight indination anteriorly. The skin lining the eartilaginous
portion is abundantly furnished with eeruminous glands and
is provided also wilh laterally direeted hairs, whieh tend to
prevent the enlranee of dust. The eutaneous lining of the
osseous part, whieh is thin and tightly adherent to the
subjacent periosteum, is destilute of hairs, and glands are for
the most part absent. The eutaneous hning of the meatus Is
eontinued in the form of an exceeding!y delieate layer over
the outer surface of the membrana tympani.

MEMBRANA TYMPANI 549

When the direetion, the length, and the diameters of the
external meatus have been noted, the disseetors should
examine the lateral surface of the tympanie membrane.

Membraua Tympani. — The slope of the tympanie mem-
brane has already been referred to. It slopes very obliquely"
downwards, anteriorly and medially, and it is deeply concave
externally. The deepest point of the concavity is the umbo^
whieh eorresponds with the lower end of a bar of bone, the
handle of the malleus^ whieh is embedded in the membrane
and ean be seen through the thin layer of tissue covering
it. The handle of the malleus extends upwards, and
slightly posteriorly, from the umbo towards the roof of the
meatus; and a short distanee from the upper margin of
the membrane it beeomes eontinuous with a small laterally
direeted proeess, the lateral proeess of the malleus^ whieh bulges
the membrane towards the meatus. Above the lateral proeess
of the malleus is a portion of the membrane whieh is less
tense than the remainder. This is the membrana flacctda
(ShrapnelPs membrane). It is bounded anteriorly and
posteriorly by relatively thiekened folds, the anterior and
posterior tympano-malleolar folds, The whole of the peripheral
margin of the membrane, except that whieh eorresponds
with the membrana Aaeeida, is lodged in a ring-like suleus
of bone, the annulus tympanieus^ whieh is formed by the
tympanie element of the temporal bone.

Dissedion. — After the examination of the exteraal meatus is eompleted
the disseetor must seeure the tensor tympani musele, whieh springsirom the
anterior aspeet of the petrous part of the temporal bone, elose to the apex
and above the level of the eartilaginous part of the auditory tube. Haying
seeured it, he must traee it laterally, above the auditory tube, to the point
where it passes into the bony eanal through whieh it enters the tympanum.
Then he must eut away the antero-lateral wall of the eartilaginous part of
the auditory tube, from the pharyngeal orifice to the lipper extremi^,~aiid
pass a probe through the bony part of the tube into the tympanum. He
should next turn to the anterior surface of the petrous part of the temporal
bone and, with ehisel and bone forceps, carefully remove the tegmen
tympani and expose the tympanie cavity from aboye. The disseetion must
be earried anteriorly into the auditory lube and posteriorly into the tympanie
antrum. As the disseetion is earried anteriorly a narrbw margin of bone
nmst be left along the anterior border of the tympanie membrane, and eare
must be taken to avoid injury to the tendon of tne tensor lympani, whieh
emerges from the extremity of its bony eanal, near the medial wall of the
tympanum, and erosses the cavity to be inserted into the malleus. The
ehorda tympani nerve, whieh passes anteriorly, elose to the tympanie
niembrane and above the tendon of the tensor tympani, must also be
preserved if possible.

550 THE AUDITORY APPARATUS

Tsrmpanie Cavity or Middle Ear. — The tympanie cavity
is a small ehamber, filled with air, whieh is plaeed between
the bottom of the meatus extemus and the internal ear or
labyrinth. Posteriorly it eommunieates, by a relatively large
orifice, with the tympanie antrum and mastoid air-eells;
whilst anteriorly the auditory tube opens into it and puts it
into eonneetion with the cavity of the pharynx. It eon-
tains the ehain of auditory ossieles whieh erosses from its
lateral to its medial wall, and it is lined with delieate mueous
membrane.

The vertical depth and the antero-posterior length of the
tympanie cavity are eaeh about half an ineh (12.5 mm.).

Its width, from side to side, is about
a sixth of an ineh (4.5 mm.); and,
as both its lateral and medial walls
bulge into the cavity, its width in
the eentre is still further redueed.
The tympanie cavity eonsists of (i)
an upper part, whieh extends up-
wards beyond the level of the mem-
brana tympani, and to whieh the
FiG. 234.— Sehematie verticai term reeessus epitytnpanieus is ap-

whieh lies immediately to the mner

I. External meatus. • j r ^t_ i_ ^ •

2. Tympanie cavity (the upper ^ide of the membrana tympani.
" 2 " is in the reeessus epi- The tympanic cavity presents for
tympanieus). examination a root and a floor,

3. Promontory on medial wall. • t r n • • *■ '

4. Membrana tympani. Wlth f0Ur Walls, V1Z., aotenor, £OS-

terior, lateral, and rnedial.

The roof is eomposed of a thm plate of bone termed the
tegmen tympani, This separates it from the middle fossa
of the eranium. In ehronie inAammatory eonditions of the
middle ear, an extension of the inAammatory proeess to the
meninges of the brain is always to be feared.

^);\<^floor or jugular wall is narrow, and is also formed by
a thin osseous lamina, whieh is interposed between the
tympanum and the jugular fossa. It separates the tympanum
from the bulb of the internal jugular vein, and an exten-
sion of an inAammatory eondition of the middle ear, through
the bone to the vein, may lead to thrombosis.

The posterior or mastoid wall presents, in its upper part,
the opening or aditus w^^'"*^ ^^ads from the reeessus epi-

TVMPANIC CAVITY 551

tynipanieus into the t)'rapanic antram, and below tliis, dose
to the medial wall, is a small hollow eonieal projection teraied
tke pyramid. This is peribraled, on its summit, and the
aperture leads into a eana! whieh curves posteriorly and then
downwards until it opens into the lower part of the last
stage of the eanalis facialis. Ttie curved eanal of the pyraraid
lodges the stapedius musele, the deUeate tendon of whieh
enters the tympanie cavity through the aperture on the
stimmit or the pyramid. Lateral to the pyramid is the aper-

FliJ. =35- — Lert Membrana Tympani and Reeesaus Epiiympanioi

rrom wilhin, The neek and head of the mnlleus haye heen remOTed tB^
eIiow the membrana Hau^ida. (Howden.)

ture on the posterior wall ealled the aptrtura tympanka canaf-.
lieuli cftordie through whieh the ehorda lympani nerve entera
the tympanum,

The anterior wall\s narrow, heeause the medial and lateral.
walls converge anteriorly. The upper part of ihis wall ia
oeeupied by the opening of the tensor tympani eanal;
intermediate part by the tympanie orifice of the auditory tube j
and the lowest part is a lamina of bone whieh separatea the
tympanie cavity from the earotid eanal. The tympanie end
of the septum between the auditory tube and the tensor
tyinpani eanal, the proeesius eoehhari/ormis, serves as a pulley

55»

THE AUDITORY APPARATOS

round whieh the tendon or the musele turns abniptly, in a
lateral direetion, touards the malleus

The mtdial wall, Mhieh intervenes between the tympanum

and the lab>nnth, presents eertam important pomts for study.
The greater part of this wall bulges laterally, into the cavity,
in the form of a \ery evident e!evation termed ihG promoniory.
Above the postenor part of the promontory there is an oval
foramen, the /inestra vestihih Its long axis is direeted
antero-postenorly, and it opens into the vestibular part of

the labyrinth in the maeerated bone, but is elosed in' the
reeent state by the footpiece of the stapes, the most medial
or the auditory ossieles. The pyramid, on the posteiiM^-wall,
is imniediately posterior lo the fenestra vestibuU. Above the
fenestra vestibuli, in the angle formed by the meeting of
the roof and niedial wall of the tympanum, and there-
fore in the reeessus epitympanieus, is an antero-p^enot
ridge. This is produeed by the eanalis facialis bulging into
the tympanum. The wall of the eanal is very thin, and
allows the white eolour of the facial nerve, whieh is eontained
within the eanal, to be readily see- ■ the postenor

end of the promontory is the J an aperture

<;gchlea, but^

whieh' is stretehed

MEMBRANA TYMPANI 533

"""""""'(1 ^n?! Iriii- into thr rnyity nf thr

,te, it is_cIosed_by_aji
_ id reeeiyes the naipe_of the

tSram ofthe tym^annm.

The lateral wall of the tympanie cavity is formed by the
membrana tympani and thesquamous part of thetemporal bone.

Membrana TympaiiL — The membrana tympani is an
elliptieal dise of membrane whieh \% stTetehed aenras the
medial end of the meatus aeustieus extemus, and it forms the
greater part of the lateral wall of the tympanum. It is plaeed
very ob]iquely ; its lower and its anterior borders both inelining

^l^

(^,,-^-'^

G. 237. — Left Tympani

in whieh ihe tympoDk
□r qiiiidmn1s. jHow

"■)

the eKleroal n
The dolled lines indieale the nrnnntr I
,ubdlvided Hebienirily inlo tour aica$, J

Its raode of attaehment deBerves some attention. i
medial end of the meatus a ring-like ridge of bone,
distincl.iy grooved, fonns, as it were, a frame in whieh the
membrane is set. But this ridge is deficient above, where
the extremities of the bony ridge are separated by a deep
n.oteh (the noleh of Rivinus). This noteh is oeeupied by a
portion of the memlirarie whieli is not so dense in its texture
(aeeing that the fibrous layer is absent), and not so tightly
stretehed as the remainder ; eonseguently it reeeiyes the narae
of the mimbrana flamda (Shjapnell's membrane). Xhe edge
of that part of the membrane whieh is fixed in the eireular
hony groove, sukus iympankus, is thiekened, and at ihe noteh
of Rivinus it is earried down, anterior and posterior to Ihe

554

THE AUDITORY APPARATUS

membrana Aaeeida, in the fomi of two bands, ealled respee-
tively the anterior 2m^ posterior tympatto-malleolar /oids.

The meinSrana tympani is eomposed of three'Tayers — viz.,
an eKternal eutieular layer, an intennediate Abrous lamina,
and an internal mueous layer. The handle of the malleus is
intimately eonneeted with the iibrous layer, and is covered
medially by the mueous layer. It diaws the membrane
towards the tympanie cavity, and is the eause of the concavity
on the outer suriaee. The deepest point of thts concavity

eorresponds with the Aattened extremity of the handle of
the malleus, and is termed the um^.

In examiniTig the ]iving ear. with a speeulum, the £urface o{ the mem-
brane appears hiehly polisheil, and a eone of liEht exlends downwards
and foiwards f[om the lip af the handle of the maUeus, A pair of stiite
(Prussak's slrlEe), whieh eortespond lo the anterior and posterior tympano-
malleolar foIds, extend from the proeessus lateralis of the malleua to the
maigins of Ihe noleh of Kivinus, and thus map oul the menibrana tlaedda.
The long erus of the ineus ean be fiuntly seen through the membrana
tympani, parallel wilh and poslerior to the handle of the malleus.

Antruni Tsrmpaiiieum. — The I' 'im is a reeess

or air-ehamber, in the petrous pai . bone, with a

AUDITORY OSSIGLES

555

diameter of about one-third of an ineh. It is plaeed posterior
to the tympanum, and eommunieates by a relatively large
opening, ihe aditus, with the upper part of that cavity. It
lies at a depth of about ha]f an ineh from the surface of the
skull in the adult, but in the ehild it is plaeed mueh more
superficially. It is hned with mueous membrane, whieh is
eontinuous with the lining membrane of the tympanum. The
mastoid portion of the temporal bone also is oeeupied by air-
spaees, the air-telh, whieh niay
extend downwards tnto the mas-
toid proeess. They are eontinu-
ous with one another and with
the tympanie antruni, and are
lined by a eontinuation of the
same mueous membrane.

Tympanie Maeoiis Membnuie.
— The tympanum is lined
throughout with a thin mueous
membrane whieh is eontinuous
with the mueous membiane of
the pharynx. As already men-
tioned, it forms the innormost
layer of the membrana tyrapani,
and it is prolonged posteriorly
into the tympanie antrum and
mastoid air-eells, It covers the
ossieles also, and it inyests Ihe
tendons of the stapedius and i t^tilw 'Sr Th* 'tmToura 'rf Sb.
tensor tympani museles. ino.» wkh 'j?= f"^^'')' '^ "*

Ossieula Aoditas. — The audi-
tory ossieles are the malleus, the ineus, and the stapes.

The malleus presents a head, a neek, a manubrium, and
two proeesses termed the proeessus lateralis and the pro-
eessus anterior. The head is large and rounded. It is
direeted upwards, nnd lies above the teyel of the raem-
brana lyropani, in the reeessus epitympanieus, elose to the
roof of the tympanum. On its posterior aspeet ihere is
a noteh-like artieular surface, for artieulation with the body
of the ineus. The matmbriitm is attaehed to the fibrous
layer of the membrana tympani. The proeessus lateralis (O.T.
l'revis) is a stunted projection whieh springs from ihe root of
the manubrium. It is direeted laterally, and abuts against ihe

556

THE AUDITORY APPARATUS

membrana tympani immediately below the membrana Aaeeida.
The proeessus anterior (O.T. graeilis) is a slender spieule of
bone whieh passes anteriorly into the petro-tympanie fissure.
It almost invariably breaks in detaehing the malleus from the

Head

Neek

Facet for
ineus

Facet for Head

ineus I Proeessus
anterior

Proeessus
lateralis

Manubrium Manubrium

A B

FiG. 240. — The Left Malleus. (Howden.)

A. Posterior aspeet. B. Medial aspeet.

adult skull, but it ean be easily preserved in the skull of an
infant.

The ineus is shaped somewhat like a praemolar tooth in

Artieular surface for
head of malleus

Crus breve

Body

Crus

longum

Proeessus
lentieularis

FiG. 241. — The Lcft Ineus. (Howden.)
A. Anterier aspeet. B. Medial aspeet.

whieh the roots are very divergent. It presents a body and
a long and a short erus. The body ' ' \ with an

artieular surface, whieh looks anterie lates with

the head of the malleus. The s/wrt C7 f>steriorly,

AUDITORY OSSIGLES 557

and its extremity is attaehed, by ligaments, to the posterior wall
of the tympanum, near the opening into the tympanie antrum.
The long erus proeeeds downwards and medially, in a direetion
nearly parallel to that of the manubrium of the malleus, but
more medial, and on a plane posterior to that proeess. On
its inferior extremity, whieh is bent medially, there is a small
knob of bone ealled the proeessus lentieularis, This artieulates
with the head of the stapes.

The malleus and ineus move together on an axis whieh is formed by
the proeessus anterior of the malleus and the erus breve of the ineus.
The artieular surfaces of the two bones are provided with peeuliar eateh-
teeth whieh interloek when the bones are performing their ordinary
movements. When, however, force is applied to the inner surface of
the membrana tympani, as, for instanee, when the tympanum is inAated
through the auditory tube, the ineudo - malleolar joint gapes and the
malleus moves by itself. Traetion upon the
attaehments of the stapes, through the ineus, is €3" — Head

thus avoided. y^ Neek

^rus anterior

The stapes is shaped Uke a stirrup, j^^h-Crus postenor
and presents a head or lateral extremity /* ■ ^~5^Foot-piate
separated by a slightly eonstrieted neek
from two erura whieh join a medial
plate, the basis stapedis. The head\% ^^^' ""1«;^^!?. f ^^'
excavated by an artieular eup for the
proeessus lentieularis of the ineus. The erura are grooved
longitudinally on their concave sides (suleus stapedis). The
posterior erus is more sharply curved than the anterior erus.
The base fits into the fenestra vestibuli and eorresponds in
its outline with that aperture. Its lower border is straight,
whilst its upper border is curved.

Ligaments of the Auditory Ossieles. — In addition to the
delieate eapsular ligaments, whieh surround the joints between
the auditory ossieles, there are eertain bands whieh eonneot
the bones to the walls of the tympanum and serve to restrain
their movements.

In eonneetion with the malleus there are (i) an anterior ligament whieh
passes from its anterior part, at the root of the proeessus anterior, to the
anterior wall of the tympanum in the neighbourhood of the petro-tympanie
fissure ; (2) a lateral ligament whieh extends from its lateral proeess to
the margin of the noteh of Rivinus ; and (3) a superior ligament whieh
eonneets Uie head with the roof of the tympanum.

The ligament of the ineus binds the extremity of its short erus to the
posterior wall of the tympanum, whilst the annuiar ligament of the stapes
eonneets the margin of its base to the circumference of the fenestra vestibuli.

558

THE AUUITORY APPARATUS

Tympame Mnseles. — These are two in number, viz., the
stapedius and the tensor tympani.

'ITio st<ifcdius oeeupies the interior of the pyramid and tlie
eanal whieh curves downwards Trom it. The delieate tendon
of the stapedius enters the tympanuni, through the aperture
on the summit of the pyramid, and is inserted into the
posterior aspeet of the neek of ihe stapes. It is supplied by
a braneh from ihe/aa'a/ rren-e.

Tlie /e»sar tynipani arises froKi the upper part of the
eartilage of the auditory tube and from the eontiguous parts
of the great wing of the sphenoid and the petrous part
or tho temporal bone. From its origin it passes postero-
latorally, upon the proeessus cochleariformis and above the
ossooiis part of the auditory tube. In the tympanie cavity
tlie tendon turns at right angles, round the extremity of the
proeessus cochleariformis, and passes |f 'owards the

lateral wall of the tympanum, to its ir he upper

AUDITORY TUBE

part of the medial surface of the manubrium of the malleus.
The tensor tympani receives its nerve of supply from the <^£

eiioTda Tympani Nerre. — The ehorda tympani, whieh
traverses the tympanie eayity in elose relation to the upper
part of the membrana tympani, is deseribed on p. 546.

Tympaoue Flexiis. — This has been deseribed previously
onp. 312.

Taha Auditiva (O.T. Eustaehian). — The auditory tube is
the passage whieh plaees the tympanie cavity in eommuniea*
tion with the pharynx. Through it air reaehes the tympanie

cavity and antrum and the mastoid eells. It eonsists of an
osseous aiid a eartilaginous porlion. The osseous porHon is
about half an ineh in length. It is widesl at its entranee
into the tympanum, and narrowest at its other end.
eanilagimus portion is about an ineh in length, and has
already deseribed on p. 383.

Disseelion : Seeend Methad. — On the oppoale side the bony part of
the extemal meatus, Ihe tympanie Bntrum, and the tyinpanie cavity shouid
lii; approaehed from the poatero-laternl aspeel. The disseelion of the bone
should be earried oul after themanuer ado]rted by the surgenn when opemt-
iiig for the eure of extensix'e mastoid and miiidle ear disease, but. lo
facililate the disseetion, and to gain betler aeeess to the bone, Ihe auriele
may be reniovcd by eutting Ihrough the eattilnginous part of ihe enlernBl

beeqfl

Aftcr the auriele haa

u eut away elenr all Ihe 5oft parts. !nclading_

56o THE AUDITORY APPARATUS

the periosleum, tiom the outer surraee of the mastoid part of the temporal
lieine, and iclentify (i) the supra-ineatal triangle and the supra-meatal
spine, whieh lie nt the junction of Ihe superiot with the poslenor border
iif Ihe l>ony part of the cxternal meatus, and (2) the temporal line
whieh passes, posteiiorly anil upwards, a.1)ove the snpra-meatal triangle..
The objects of the iirsl slage or the disseetion are (l) the removal of the
iiutei eumpnet layer ; (2) the opening up of the eRneellons tissue of the
iiiastuiil part of the tcm]Kiral bone, and the eiposure of the mastoid aii-
eells aiid the cavily of the tympanie antrum, whilst, at the same time,
injury to Ihe ]x)sterior wall of the bony part of the extemal mealus and
to Ihe sigmoid part of the tiansverse sinus, whieh lies in a groove on the
inner aspeet of ihe posterior part of the mastoid portion of Ihe temporal
bone, is ayoideiL The tym^ianie antrum lies at the level of the supra-
mental triangle, Ihal is above and postetior to the external meatus, and

FiG 345.— Disseclionof IheTympanieAntiumand Ihe petro-mastoid pait ot
the tempoial lione fioni the oulei side. The anow is passing through
the aditUB fconi llie tympanie anlrum into the lympanLe eayily.

aboul half an ineh from Ihe supeiiieial surface of the temporal bone.
The disseetion should be eommeneed above, below the tempoial
Une and should be earried, anteiiorly and medially, into the bone,
parallel with the posterior wall of ihe external meatus, unlil the tympanie
antrum is opened into. Afler the tympanie antrum has been identiBed,
the eaneellous tissue of the anlerior part of the mastoid area must be
eradunlly removcd till the niore medially situated and more eompaet
bone is exposed. When this slage of the disseetion 15 eompleted, the
disseetor should note the following points :— (1) In the anterior boundary
of the eitposed area is the eompaet poslerior wall of the bony part of the
external nieatus. (z) I'osterioriy is a broad projecting ndge indi-
eatine the position of Ihe groovc whieh lodges the sigmoid parE of the
transverse sinus. (3) At the upper and doeper part of the area are the
medial vrall of the tympanie antrum and the aililus leading inlo Ihe lym-
uanie cavitv. (4) The inteimediale area is o- the remains of

the mastoid air-cclls, whieh may extend d Ve tip of the

mastddproeess. They are eontinuous aboye thetymp-nw

TYMPANUM 561

nntriim. (5) On Ihe niedial wall of the aditus and the anterior part of the
iiiedial wall ur tho tympanie antrum is a horizonta1 ridge whien indieates
Ihe posilion of the latetal semieireular eaoal of the lah^rinlh, and, beiow
il, on the niedial wall of the mouth of the aditus, 13 a vertical ridge
indieating the position of the eanalis Tadalis, whieh lodgea the imporlant

The nexl stnge of the disseetion eonsisls in the removal of the posterior
wall of the eiiternal raeatus, and the exposure of Ihe outer surface of the
tympanie membrane (p. 549). Afler the lympanie membmne has been
cxamined, a seeker should be passed through tlie aditus into the tympanie
caviiy, aod its handle should be allowed to rest on the lower pait o( the
esposed aita ; then, whilst Ihe setker lemains inpc«ition, the TeTnaindtT of
ihe posterior wall and the upper boundaty of the eiternal meatus, &om
Ihe levei of the seeker to the level Qf the roof of the lympaiiie antruni, ean

be eut ttwny wilhoul fear of injury lo any imporlant struetnre. Tili'
disseelion should be eompleted by the removal of Ihe tympanie membBUUL.
and ossieies, and when this has been done a very eomplete view wiil be J
obtained of the mediat walls of the tympanie caviiy, the aditus, and tlie
lympanie antrum. Anteriorly, on the meilial wall ot the lynipanie cavity,
is the promonlory, whieh marks the posilion of the iirst lum of tte
eoehlea. Above and posleriot to the promontoiy is the fenestta vestibHli,
The reneslta eoehlete lies at the lowet and posterior pait of the proroontoiy,
in ihe anteiior part of a teeess ealled the fossula feneslric eoehleas. Above
the fenestia vestibu1i is a ridge eaused by the poslerior horiionlnl part
of Ihe eanalis facialis ; this beeomes eontinuous, on Ihe medial wall of Ihe |
aditus, witb the Teilieal lidge whieh hidiealea Ihe posilion of Ihe ver1ical'|
IKitt of the eonal. Above the kttei is ihe horiiontal ridge due to tbe I
latetal aemieiteular eanal. The disseeior should opuii the eanatis /aeiAll* I
lo liipose the facial m:rve; then he should opm Ihi! Inleral semidieulat il
eaimi, and nfterwnriJs rcmovc the l>onc «bovc «nd puaterior la it ta j
exfi>:>sc the walls or tbe superior and posterior vertical semidieulai eanalg J
(l'igs. 245, 346). ^"

VOL. 11—38

562 THE AUDITORY APPARATUS

INTRAPETROUS PART 0F THE FACIAL NERVE
AND THE AGUSTie NERVE.

The facial and aeustie nerves have already been traeed
into the internal aeustie meatus (p. 215). The disseetor
should now open up this meatus and follow the facial nerve
in its eourse through the petrous portion of the temporal bone.
The eanal whieh it oeeupies is termed the eanalis /aeiaiis
(O.T. agueduet of Fallopius\ It begins at the bottom of
the internal aeustie meatus, and opens on the exterior of
the skull at the stylo-mastoid foramen. Between it^ eom-
meneement and termination it pursues a eomplieated eourse,
and this, eombined with the density of the bone, renders the
disseetion very difficult.

Disseetion. — On the side on whieh the middle ear has been opened from
the lateral aspeet and the eanalis facialis has already been partially opened
up, the disseetor should eoniplete the disseetion of the intrapetrous part of
the facial nerve and should examine the aeustie nerve.

Separate the temporal bone from the other eranial bones whieh still
adhere to it, and fix it in the natural position (in a'vice if possible). Remove
the squamous portion by a horizontal saw eut at the level of the upper
surface of the petrous portion. Make a seeond horizontal saw eut, im-
mediately above the roof of the internal aeustie meatus, and earry it
laterally into the tympanum, in whieh it should emerge immediately above
the already opened eanalis facialis where the latter lies above the fenestra
vestibuli. Then, with the bone forceps or ehisel, remove the remains of the
roof of the internal meatus and follow the facial nerve along the eanalis
facialis to the hiatus eanalis facialis, and so expose the ganglion genieuli.
Seeure the branehes whieh arise from the ganglion and then follow the nerve
posteriorly above the fenestra vestibuli. The greater part of the vertical
portion of the eanal has already been opened from the lateral aspeet ; the
remainder ean now be displayed by means of two saw euts — (i) a frontal
seetion (vertical transverse) earried medially from the lateral surface of the
bone to the posterior border of the stylo-mastoid foramen ; (2) a sagittal eut
(vertical antero-posterior) earried from the posterior surface of the bone to
meet eut (i). The portion of bone between the two euts must then be
removed, and the disseetion must be eompleted with bone forceps. Three
branehes are given off in this part of the eanal.

Intrapetrous Portion of the Facial Nerve. — As the facial
nervc traverses the petrous bone, it may be divided into four
stages, whieh differ from one another in the relations they
present and in the direetion whieh they take. They are : —

1. A part within the internal aeustie \\\

2. A very short part whieh extends of the internal

aeustie meatus to the ganglion \

INTRAPETROUS PART OF FACIAL NERVE 563

3. A part whieh oeeupies tliat portion of the eanalis facia1is whieh runs

along the medial wall of the tympanie eayily.

4. A part whieh exlends vertica!ly downwards to the stylo-mastoid

fotamen.

First Stage. — In the internal aeustie meatus, the facial
nerve runs almost direetly laterally in eompany wilh the
aeustie nerve. In this stage of its eourse it lies io relation
to the upper and anterior part of the aeustie nerve, and ■
t ot nd n > ots j 'n At the bottom of the
u i I f 1

Fjg

247.

1. N

'7:;^

»a 1»,

Ki^

"'rn'

„.,.

ga«nc (

an Bt M

h=llr).

slylo-liyoir

Seeond Slage. — The seeond part of the facial nerve is yst^
shoTt. It runs laterally, with a stight inelination anterioil^l
between the vestibule and eoehlea, and very soon ends tBk
the swelling lermed the ganglim geniaili.

Third Stage. — At the ganglion genieuli, the facial nerv6i
bends suddeiily and proeeeds posteriorly and slightly'

564 THE AUDITORY APPARATUS

downwards in that portion of the eanal whieh runs along
the upper part of the medial wall of the tympanie cavity,
immediately above the fenestra vestibuH (O.T. ovalis).

The Tirst three portions of the facial nerve are nearly
horizontal, and pursue a somewhat V-shaped eourse. The
apex of the V is direeted anteriorly, and eorresponds to the
ganglion genieuli.

'Yhe/ourth stage is vertical, and arehes downwards, posterior
to the pyramid, to gain the stylo-mastoid foramen.

The branehes whieh spring from or join the facial nerve
during its passage through the temporal bone are : —

1. The greater superficial petrosal nerve, "1

2. Communicating twig to the smaller superficial I from ganglion

petrosal, \ genieuli.

3. External superficial petrosal nerve, J

4. Nerve to stapedius.

5. Ghorda tympani.

6. Gommunieating twigs to the aurieular braneh of vagus.

The great snperficial petrosal nerue has been examined
already (p. 212). Its origin from the ganglion genieuli of
the facial ean now be seen.

The eommunieating braneh to the small superiieial petrosal
arises from the ganglion genieuli, and unites with the iibres
of the tympanie nerve whieh issue from the tympanie plexus.
The external petrosal nerue is not always present. It
joins the sympathetie plexus whieh aeeompanies the middle
meningeal artery.

The nerue to the stapedius niusde arises from the facial as
it arehes downwards posterior to the pyramid. It enters the
base of the pyramid and thus reaehes the stapedius musele.

The eommunieating twigs to the aurieular braneh of the
vagus arise a short distanee above the stylo-mastoid foramen.
ehorda Tympani. — The ehorda tympani represents to a
large extent the sensory hbres set free from the trunk of
the facial nerve. It is the largest braneh given off by the
facial during its passage through the eanalis facialis. It takes
origin a short distanee above the stylo-mastoid foramen, and
arehing upwards and anteriorly, in a narrow eanal in the
petrous portion of the temporal bone (the eanalieulus ehordae
tyni])ani), it appears in the tympanum by passing through
llu* tympanie aperture of the eanalien^"" '^h.ordae below the
l)jisc ()f the pyramid, and elose to "^r margin of

ACUSTIC NERVE 565

membrana tympani, The bony tunnel whieh it oeeupies ean
easily be opened up in a decalcified bone, but is somewhat
difiiculi to expose io the hard bone. After entering the
tympanum the ehorda tympani runs anteriorly upon the upper
part of the membrana tympani under cover of the mtieous
layer. It erosses the handle of the malleus on the medial
aspeet near its tooL Pinally, reaehing the anterior end of
the tympanie cavity it erosses the anterior proeess (O.T.
graeilis) of the malleus, passes above the tetwor tympani, and
traverses the medial end of the petro-tympanie Hssure, whieh
eonduets it to the exterior of the skull. From this point to
its junction wlth the lingual nerve the ehorda tympani has
already been traeed {p. 278).

Aenstie Nerve. — In ihe internal aeustie meatus the
aeustie nerve lies at a lower leve! thiin the ^aeial, and at the
bottom of the passage it splits into two parts, termed the
eoehlear and vesti!iular divmons, These trunks again sub-
divide and supply the diHerent parts of the labyrinth of the
ear through the foramina of the lamina eribrosa.

After the cxamination of the intrapetrous parl of the facial ne[ve and
the aeustie nerve is oompleted the diaseetor should display ihe labyrinth
of the inteinal ear by means of two saw euts — (1) an anlero-posterioi
veTtica1 eut eariied from the upper siirface of the bone downwuds to
the iloor of ihe tympanuni along the juncUon of its medial and posterior
boundaiies ; (z) a huiizantat eut. Thiseut shonld be eommeneed at the
apex of the petrous iiart of the temporal bone and should be earried
laterally till it join3 ihe vetlical eut posleriorly, and enters the tynipanie
eavily anleriotly at the levei of the mid-height of the promontoiy.
When the upper part of the petrous poition of the temporal bone, sepaia.ted
by the two euts, is removed, Ihe vestibulsr and eoehlear parts ai the
labyrinlh and poitions Df the seaiieireular eanals will be displayed. Thtt
disseelor shoukl demonstrate the positions aud euires of the semidieulur' .
eanals and ihe eanalis facia]is by passing biistles thiough them,

Auria Iiitema~ — The intemal ear or labyrinth eonsists of an
intrieate system of cavities in the petrous part of the teraporal
bone, the osseous liibyrinlh, and a series of hollow memhranous
struetures, eonneeted with the filaments of the aeustie nerve,
whieh lie in the osseous labyrinth and eonstitute the mem- 1
branous laiiyrinik.

The osseous labyrinth is eomposed of an intermediate
ehamber termed ihe vestibiile, posterior to whieh are plaeed
the three semieireular eanals, whilst anteriorly is the eoehlea,
AII these cavities eommunieate with one another. The eorre-
sponding membranous parts do not eompletely oeeupy the

566 THE AUDITORY APPARATUS

uss<;i)us etinmbers, and the intervening spaee is tilled with a
lluid lernied the perUymph. The membranous iaAyrmlA also
euntains a lluid whieh receives ihe name of endolymph.

■yertibtiliun.— "1116 vestibule is a small ovoid bony ehamber,
[iwsstsMng an antero-posterior diameter of about one-sixth
uf an ineh. It is situated between the medial wall of the
tynipanum and the bottom of the intemal aeustie meatus.

Into the posterior part of the vestibule the three semi-
eireular eanals open by five round apertura; wbilst in its
luwer and anterior part is the opening of the seala vestibuli
of the eoehlea.

On tlit; lateral wall is the fenestra ytstibuli, whieh is dosed,
in the reeent state, by the delieate periosteal lining of the
ehamber and the base of the stapes, When these parts are
removed, the yestibule eommunieates direetly with the tym-
panum. On the anterior part of the medial wall of the
yestibule there is a eireular depression, termed the reeessus
sphieri^us, whieh is bounded posteriorly by a vertical ridge,
ealled the erista vestibuli The bottom of the reeessus sphEerieus
is pcrforatcd by some minute holes whieh give adraission to
filanient.s from the aeustie nerve. On the roofoi the vestibule
is another depression, named the reeessus elliptieus. It is plaeed
[lostorior to the erista vestibuli.

A small aperture plaeed on the posterior part of the
inL'dial wall also deserves mention. It is the mouth of the
aquuduclus vestibuli — a small eanal w' ' posteiiorly to

LABVRINTH 567

the posterior surface orthe petrous part of the temporal bone,
where it opens under the dura mater.

OanaleB Semieireulares Ossel. — These are three bony eanals
or tubes plaeed posterior to the vestibule. They are bent
upon themselyes, so that eaeh forms eonsiderably more than
half a eirele, and they oeeupy planes at right angles to eaeh
other lilie three faces of a eube. They are termed superior,
posterior, and iateral, and ihey open into the posterior part
of the vestibute by five round orifices, the number of openings
being thus redueed through tlie adjoining extremities of the
superior and posterior eanals beeoming fused together so as
to present a eommon eanal, the erus eomnium, with a single

F[G. 249, — Left Bony Lahyrinlh viewed from lateral side. (Howden.)

orifice. One extremily of eaeh eanal where it joins the
vestibule beeonies expanded into what is termed its ampuUa.
There are thus ihree amirallated ends.

The superior semieireular mnal forms the highest part of
the labyrinth, and gives rise to a smooth eIevation on ihe
anterior surface of the petrous part of the temporal bone,.
immediately anterior to its superior angle. It is vertical,
and plaeed almost transversely to the long asis of the petrous
part of the temporal bone. The posterior semieireular eanal,
whieb is the longest of tbe three lubes, is also yertiea!, ar
lies in a plane parallel to the posterior Burface of the petroi
part of the temporal bone. The laleral semidreuiar eanal
the shortestof the tubes, and it lies in a horizontal plane.

eoehlea. — The eoehlea is a lapering tube whieh is eoiled

568 THE AUDITORY APPARATUS

spirally for two turns and a half around a eentral pillar, termed
the modiolus. The appearanee produeed is somewhat similar
to that of a spiral shell. The eoehlea lies anterior to the
vestibule, with its base direeted towards the bottom of the
internal aeustie meatus; whilst its apex is direeted antero-
laterally, and lies in elose relation with the eanal for the
tensor tympani musele.

The eoehlear tube rapidly diminishes in diameter as it
is traeed towards the apex of the eoehlea, and its elosed
extremity is termed the eupola. The iirst turn whieh it
takes around the modiolus produees the bulging on the
medial wall of the tympanum, whieh has been deseribed under
the name of the promontory.

The modiolus is thiek at the base, but rapidly tapers
towards the apex. Its base abuts against the bottom of
the internal aeustie meatus. It forms the inner wall of
the eoehlear tube, and winding spirally round it, like the
thread of a serew, is a thin lamina of bone, termed the lamina
spiralis^ whieh partially subdivides the tube into two passages.

Numerous minute eanals traverse the modiolus, and one more eon-
spieuous than the others, the longituditial eanal of tke modiolus, extends
along its eentre. The spiral lamina also is tunnelled by small eanals
in eommunieation with those in the modiolus, whilst one, the spiral
eanal of the modiolus^ winds spirally around the eentral pillar in the
attaehed margin of the spiral lamina. All these ehannels convey
filaments from the eoehlear division of the aeustie nerve to the membranous
eoehlea, whilst the spiral eanal lodges the gangiion spirale eoehlea, whieh
is the peripheral ganglion of the eoehlear part of the aeustie nerve.

The membranous eoehlear tube or duetus eoehlearis is plaeed
between the free margin of the spiral lamina and the
opposite side of the wall of the eoehlear tube, and eompletes
the subdiyision of the bony eoehlea into two eompartments,
whieh are termed the seala tympani and the seala yestibulL
The seala iympani is the larger of the two. It begins at the
fenestra eoehleai, where the seeondary membrane of the
tympanum shuts it off from the tympanie cavity. At the
apex of the eoehlea it eommunieates with the seala yestibuli
by means of an aperture, termed the helieoirema, At the
base of the eoehlea the seala vesiibuli eommunieates with
the lower and anterior part of the vestibule. The perilymph
lhcrefore, in the semieireular eanals and vestibule, is
direetly eontinuous with that in the seala vestibuli and
seala tympani.

LABYRINTH 569

It ean Dow be underslood how vibiatians of the [yiembrana tympaDi
are eammunieated to ttie perilymph within tlie osseous labyiinth. The
ehain of audilory 03sicles [brough the base of the stapes affect5 the
perilymph in ihe veslibuLe. The vibrations of Ihe perilymph passing
along Ihe seala veslibuli into the seala tympani in turn affect the seeondaiy
membrane of the tympanum whieh is streti^ed aeloss the fenestta eoehlese.
With cvery inward movement of the membrana tympani and Qf the base
of the stapes, there is an oulward movemeDt of Ihe membrane of the
fenestra eoehleie, and -Tria versa. Tbe vibTatioD$ of Ibe perilymph affect
the endolymph in the membtanous labyrinth, and thus e: " ' '
lionsoftheaf

Hembmnoua Labyriuth. — In the Yestibule there are two mem-
branous saes, termed Lhe alriele and ihe saeenle. The utriele oeeupies
the reeessus elliptieus on Ihe wall of Ihe vestil)ule, and lies above and
posterior to the saeeuie. Into it open the miniir'anaui stmiiireular

The saeeule is smaller, and oeeupies the reeessus spha;ricus on the anterior
part of the media! wall of the veslibule. Il eommunieates by means of a
short narrow tube, termed the eanalis reuniens, with the duetus eoehlearis
or membranous eoehlear tube.

The saeeule and Ihe ulriele are only indiredly hroughl into eommnniea-
tion with eaeh other ; a slender tube tetmed the dutlus iHdelympkalleu!
oeeupies the aquieduclus vestibuli, and divides into two branehes whieb

BULBUS OeULI

BULBUS OeULL

'i lit: \/u\huri 'y*uli or eyeball is not j>erfect}y s])herical ; it Ta2j
\f* >.aid to U: rom;K»sed of the segments of two spiheres.
'i\^t' uttUnur or eorneal segment. forming only abont ODe-STTth
i/i i\it' t ti\it*: «r)^balL possesses a Bhorter radius than thepos-
h iM/f or V l»rral v ^^rnerit. The anterior dear eomeal part o^
flii « y« l/al) f'/nn^, therefore, a dome-like bulging or prominepee
«//1 ili'- Ir'ynl of the glol>e of the eye. The terms anterier
A\\t\ ptnterior poU are resi>ectively apphed to the eentral points
i/l iIm' ;irii<-n'/r and j><^?>terior segments Qf the eyebalL Tbe
MM;ij.Mfi:i ry lirw: whid) joins these poles receives the nanie
mI iIm' stiyjffui axiif wlnlst another line dravn in a OOTonal
ilii< « ii«/n arourKl i\n: glo^>e (A the eye midiray between the
iwo |M/lih t^o ;is U) ciivide the eyebaU into two hemispheies
iti \t itni'ti \\it* et/uator. Irnaginary meridional Hnes also are
iliuwn l/« iwr<*n ilie two poles so as to eut the eqiiatorial line
.ii \\\i\\\ an^lr^.

IU\M,iion II I thf Eyrlmll. A }ialisCactory disseetion of tbe globe of Ibe
« yi i.ih l»«- iii.ulr only wlii-n \\itt eyeball is fresli, or aiter it has been
li.inli ii< «I (•ii >.« v« i.il «la):t iti u io % f»olution of formoL In the disseeting-

K' 11 I:) •ilieii iiii|K>:)i>il>l«' t«/ o!/tain suitable spedmens; bnt it is alwa^rs

1 .1.-) i.i |iiMi iiir iy« liall:^ «if i|j<r pijf, shcep, or ox, and these snit the poipose
.«.liiiii.il.ly li i^i a«lvi-»:iM»*, howcver, that the disseetor shonld oomplete
lii^ ^iiii.ly ..I ilii «ii^aii liy tli'! ('xamination of a fresh humaneyeball obtained
li>.iii ilii /■.'•■/ nioitein r<*«*iii. Iii |>oint of size, and also in other partieiilars,
ilii i p l..ill ..( ili«' |/i}.; iin*r<* (losely resembles the human eyeball, but it
in |.. ili.i|.:^ I.«liii tliut tlie slu<lcnl should lx^n with the eyeball of the
'.«, .5. . iii{' tli.ii iii ii ilit- (li^iv«lion ean be more easily earried out.

\\ li. II ilii «liMriiriiii ha;^ |»rovi<le<l himsclf with six eyeballs obtained from

• .11 II, lii rslii.iilil leiinwr' (roiii tlu.'ni the conjunctiva, fascia bulbi, oeular
i.iii.tIis, ,iinl l.ii, wliii h aillu-rr lo thetn. Pinehing up, with the forceps,
ilii I .iiijiiiii iiv.t .tiiil tli«* laseia lnilhi elose to the eomeal margin, he should
.iiii|. ilii..iii.;^li ihihi- luyiis with tht! seissors and divide them round the
\\li..li «.h'« <il iht' K.Mita. Ile e.'in ihen easily strip all the soft parts
li.iiii ili« hiiil.ui- iil iln- hi hra, working steadily posteriorly towards the
iiiii.iii. i: ..1 ihr upiir ii«Tvc'. A liulc posterior to the equator of the
. ^. l-.ill ih. vi ii.i Vi.iiir<»'.;f will he notieed issuing from the selera at wide
ii.h iv.ih ln.iii «•.»t h iillur, aii«l on apj)roaching the posterior aspeet of the

• Vi l'.ill ih.- iK.r^ii lii.i « iliaiy artt-rii's and the eiliary nerves will be seen
|.i< I. iii}; ilii- .hi 1(1. i iiii.uiiil tlu' tMilr:incc t)f the optie nerve.

iSiN.ii- l.«jMiiiiiii^^ ihr aetuiil (lisseetit)n of the eyeball, it is important
ih.tt ihi- htuiliMit shiiuhl tihlain a general eoneeption of the parts whieh
1 iiiii|...)«' ii. 'l'hi'i ( an he (Iiiiu* by seetions through three hartlened speei-
iiirii;> III ihiee «lilliMcnt |>lanfs. C)nc speeimen may be divided at the
ii|u.ti<ii iiiiii an antt-ritir aiul \\ posterior portion. Another may be divided

EYEBALL 571

in >□ antero-posterioi direetion into a medial and a lateral hair. A tliird
sliould be divided hoiizODtally aod a. poetion of ihe vitre»us iKHly shonld bc
removed (Fi§. 251 )■ When Ihe seelions are made, thty should lie plaeed
under watei in a eork-lined Iray, and pieseived Tor refeience as the study
of the eyeball is proeeeded wilh.

G«neraJ Stmetnre of tlie Eyeb&lL — The eyeball eonsists
of three eoneentrieally arranged eoats enelosing a cavity in
whieh three refracting media are plaeed.

The tunies are : (i) an external tibrous envelope eom-
posed of a posterior opaque part, ealled the le/era, and an

ofEyeball.

anterior elear transparent portion ealled the eomea ; (2) an
intermediate vascular envelope known as the a&ea/ /mW, in
whieh three subdiyisions are reeognised, viz., a posterior part
ealled the ehorioid, an anterior portion termed the iris, whieh
lies posterior to the eornea, and an intermediate eiliary body ;
(3) ihe nen'ous internal tunie or retina, in whieh the fibres
of the optie nerve spread out.

The refracting media are : (1) posterior to the oornea a
watery Auid, ealled the a<jueous humour, eontained in a
spaee partially subdivided by the iris into the two ehambers
of tke eye; {2) the erystallim iens posterior to the posterior

572 BULBUS OeULI

ehamber; and (3) the vitreous body^ oeeupying the posterior
part of the interior of the eyebalL

Disseetion. — The superficial surface of the selera and the eomea
should now be examined ; but to eomplete the study of the extemal tunie
a Turther disseetion is required. Seleeting an eyeball for this purpose, an
ineision should be made, with a sharp knife, through the selera at the
equator. This must be done carefully, and the moment that the sub-
jacent blaek ehorioid eoat appears the knife should be taid aside. The eut
edge of the selera should now be sei^ed with the forceps, and the indsion
earried eompletely round ihe eyeball, with the seissors, along the line of the
equator. The outer fibrous lunie is thus divided into an anterior and
a ix)sterior portion. These must now be raised from the subjacent parts.
As the anterior portion is turned anteriorly, some resistanee will be met
elose to the margin of the eornea from the attaehment of the eiliary musele
to the deep surface of the selera. This ean easily be broken through with
the blunt point of the elosed forceps ; as soon as this is done the aqueous
humour eseapes. In the ease of the posterior part of the selera, its
eomplete separation ean be effected by dividing the fibres of the optie
nerve elose to the point where they appear through the selera.

When the above disseetion is successfully earried out, the outer fibrous
tunie is isolated in two portions, whilst a eontinuous view of the inter-
mediate vascular eoat is obtained. The eyeball, denuded of its extemal
tunie, should now be plaeed in a shallow vessel filled with water.

Selera. — The sclera_is what is eommonly known as the
white of the eye. It is a dense, resistant tunie, opague-
white in eolour, whieh enyelops the posterior five-sixths of
the globe^ the eye. It is thiekest posteriorly, and beeomes
thinner as it is traeed anteriorly. Near the eornea, however,
it again beeomes thieker, owing to the aeeession of fibres
whieh it rcceives from the tendons of the oeular museles.
Kxccpt at the optie entranee and elose to the margin_Qf
the eomea, where it adheres to the surface of the subjacent
eiliary musele, the deep surface of the selera is very loosely
attaehed to the ehorioid eoat. Some pigmented Aoeeulent
c()nnective^tissue, the larnina fusc^ passes between the two
eoats and trayerses _what is in reality an extensive lymph
spacCj^ termed the periehorioidal spaee,

'l'he point at whieh the optie nerve pierees the selera
(loes not eorrespond with the posterior pole of the eyeball.
The optie entranee^ as it is termed, is_situated about 3 mm. to
thi' inalial ornasal side of the posterior pole and i mm.
helow it. There the outer iibrous sheath of the optie
nciv(\ whi(^h is derived from the dura mater, blends with
Ihr selt'ia, and the bundles of nerve fibres pass through a
•411 irs or sniall apertures. This perforated portion Qf the
tsi li'ia is t-allod the iamina eribrosa.

eORNEA 573

The selera is piereed also by numerous blood-vesseU and nerves.
The long and shoit posleiior eiliaiy aitettes with the eiliaiy nenes
peribrate the selera aiound the optie entianee ; foui oi five venx
vorticoss issue from the interior of Ihe eyeball by piereing (he seleia a
short ilistanee posterior to the equatoi, at wide irtervals froni eaeh otber ;
whilst the anteriot eiliaty arteries pietee it neai ihe eotneal maigin.

Anteriorly the selera is not only eontiguous to, but is
direetly and strueturally eontinuous with, the eornea, This
is termed the eorneO'Sekral juncHon, and the faint groove on
the surface, whieh eorresponds with it, receives the name of
the ssUral sul(us. At this junction the seleral tissue slightly
overlaps the eomeal tissue, and the line of union, when

seen in seetion, is obhque eiosetothisa. mmute eanal in
the jubstance of the selera termed ihe stnus yenosus selera
(O.T. eanal of Sehlemm) eneireles the margm of the eomea.
Oomea. — The eomea forms the antenor sixth of the outer
tunie of the eye. It is transparent and glass-like, and it ■
forms the window through whieh the rays of hght gain
admittanee into the eyeball The curvature of the eornea is
more aeeentuated than that of the selera, and thus it eonsti-
tutes the segment of a smaller sphere When Yiewed from
the posterior aspeet t appears c reular but when looked at
from the front it is seen to be slightly wider m the transverse
direetion. This is due to the fact that the selera overlaps it
to a greater extent above and below than it does at ihe sides.
T hejiosterior concave surface of the eornea fonns the anterior

5 74 BUI.BUS OeULI

boundan- of the anterior ehamber of the eyebalL and is
separated by the agueous humour from the anterior surface
ot" the iris.

The anterior cQnvex surface of the eornea js elothed with
the conjunctiva, redueed to a transparent_epithelial laypr
On its posterior aspeet there^ is an elastie glassy stratum,
termed the postenor elastie lamina, When the eomea is
relaxed this membrane beeomes wrinkled, and it ean be
tom away in shreds from the proper eomeal tissue.

Ligamentnm Peetinatnin Iridis. — At the margin of the
eornea the posterior elastie lamina is fibrillar, and some of
its fibres are eontinued into the iris, forming the li^amentum
p^etinatiim iridis, whilst others are prolonged posteriorly into
the ehorioid and the selera. The ligamentum peetinatum
iridis bridges aeross the angle between the eornea and the
iris, and the bundles of fibres into whieh the pgsterior elastie
lamina breaks up in this region eonstitute an annular mesh-
work or sponge-like series of minute spaees termed the spatia
anguli iridis (O.T. spaees of Fontand), These eommunieate
\^nth the anterior ehamber of the eyeball, and are filled with
aqueous humour.

Tnniea Yasenlosa OenlL — The intermediate or yaseular
tunie, frequently spoken of as the uveal traet, is exposed,
in its entire extent, in the eyeball from whieh the selera
and the eornea have been removed. It is separable into
three parts — (i) a posterior portion, the ehorioidea; (2)
an intermediate parr, the eorpus eiliare ; and (3) an anterior
segment, the iris.

Ghorioidea. — The ehorioid is the largest part of the vas-
eular tunie. It lines the posterior segment of the eyeball,
between the selera externally and the retina internally. It
is thiekest posteriorly, where it is piereed by the optie nerve,
and beeomes thinner anteriorly, as it approaehes its union
with the eiliary body. Its superficial surface is eonneeted
with the deep surface of the selera by some lax connective
tissue, and also by blood-vessels and nerves whieh pass from
ihe one into the other. The H^pp snrfarp <^^ thp nHorioid is
nioulded upon the retina ang eonneeted with a layer of
(leeplYpigmented eells whieh usually adheres to the ehorioid
wlieii that tunie is removed, althouKb in ^eality it is a port;ion
oT ihe retina.

\w llu' ryes of many mammals, but not in man, the posterior part of the

eiLIARY BODY 575

ehorioid, when viewed from the fronl, presents an e;itensive briEhtly-eoloured
area, whieh exhibits a melallte lustre. This appearanee is due to the
presenee of an additional layer^ in ihe ehiarioid iermed the laptlum. In
ihe horse, elepbant, ~^d~oi(7^i(? t3UVtUiii-4s-i:Qiiiposed of libres Itapelum
iibroEum) ; in carnivorajJt^isjonnedjJlxells (tapetum eellulosum), In the
ox, it is a brilllant greeii eolour with a golden lustre ; In the dog, it is whlle
with a bluisli bordei ; In the horse, it is blue wilh a silyeiy lustie.

The chief bulk of the ehorioid eoat is eomposed of blood-
vessels. TTiese are arranged in two well-marked layers, viz.,"
a deep, elosely-meshed eapillaiy layer eaUed the lamina. ehorio-
£aplllaris, and a raore superfi.cial venous layer eomposed of

the va a 11 rh o The ho po 0 rj eries_gass

an eno y be ween e a ula aje

The eyeball in whieh the outei surface of Lhe eborioid is BKposed should
be imraetaed in watei and the pigment washed oat of il by meaiiB of *
eaniel-hair brush. The vasa vottia)Ba will Ihen anpear as white euiTed
lines converging towards four ot five points, from whieh Ihe vei^_yQr!isDse
lakeorigin |Fig. 253).

Oorpua Giluire. — The ci!iary_body is separable into an
antero-exteriial parl, the orbieulus eil.iaris, and a postero-
internal pari, the enrona eiliaris.

The ^i^mT__ eiliiiris eonsists of the eiliary niusele, the
ganglionated eihary iierve pltyius, and plexuses of arteries
and veins assoeiated with the iris and eiliary body. It is

57«

BULBUS OeULI

eontinuous witli the irls iniemally, the selera anteriorly, and
ihi,- eorona eiliaris and the ehorioid posteriorly.

eiliory Muaele.— This is eomposed of invoIuntary museular
tissue, but the arrangement of its fibres ean be seen only
when thin seetions of the eyeball are examined under the
mieroseope. It is then obvious that the fibres are disposed
in two groups, viz., a radiating and a eireular.

The radiatin^ ^bres arise from the deep aspeet of the
selera dose to _the margtn of the eomea. From this
they radiate posteriorly, in a tneridional direetion, and gain
insertion into the ehorioid eoat in the region of th^ nilianr

proee!

of two or three bundles

md Zoau1a Ciliaris.

plaeed upon the deep aspeet of the radiating portion of the
musele. They form a museular ring around the outer eireum-
ference of the iris.

Disseeiion.—Ta obtain a view of tlie eiliary proeesses, a frontal seetion
should lie iiiadt- ihtough an eyeball a shorl distanee anteriot to the
eauator. The portion of Ihe yLtteous hody whieh oeeupies the posterior
semnent of the eyeball should be caiefully remoyed. When this is done,
the deep asi«ct of Ihe eotona eiliaris will be seen. Il is covered wilh
eiliary proeesses whieh radiate poaleriorly ftom the dtcumference of the
etystalline lens. Ly washing out the pigment from Ihis nart of the va5cular
tunie, the annngement of the proeesses will be displayed moie fu1Iy.

A seeond disseetion may bc mnie in anolher eyeball with the object of
expiKinE liie eiliaty proeesses ftoni Iho fiont. In Ihis ease iemove the
eotnea with Ihe seissots liy eutling tound the eotneo-seleral junction. The
itis is now btought eonspieuously into view, and may, with advantage, be
studied ai this stage. Heve[a! euts in the meridional direelioo, and at

eiLIARY BODY

separated from the eiHary musele, and pinned

lined tiay fiUed wilh water. The iast step in the disseetion eonsists in the

removal of the iris.

The eorona eiliaris lies nn il»' pi-tBtprinr aspeet Qf the
orbieulus eiliaris and is eontinuous anteriorly with the
iris and pnHteriorly wtth the ehorioid. It eonsists of a number
of larger folds, iha proeeisits eiliares, 70 to 72 in number, whieh
mingled with a number of smaller folds, the pliem

eiliares. The eiliary proeesses extend ^rTH tlif ■'"'-''""ttr
m;irgin (if thp rhnrioid to the anterior maTRin of the eorona
nilinris, where thpy pr,(\ in hiilhr>n<; PArti-pmitipg The_buibous
ends oeeupy the spaee between the peripheral m.i.rf;in nf the
iris and the margin pf the anterior surlaee of the erystalline
lens, and they form tne peripheral botandary of the posterior
r.hnmhpr r.f ths pypliall. The pliea eiliares are mueh less
prominent than the eiliary proeess, and both the proeesses
and the folds are in relation posteriorly with the hyaloid
membrane, whieh .separates them from the viCreous body,
and with the peripheral part of the zonula eiliaris to whidi
they are attaehed.
voL. n — .37

is
le

" I

-« BULBUS OeULI

Iris. 'Jhc in?> lies anierior to the erystalline leQ& and it
i^ ^':\jjj'jiU:ti Irorii tlie eornea by the anterior ehamber filled
wi!!i^a^juc'jus h'jnjour. By its drcumference it is eontinuous

wi'li tlj«; riliury body, and il is rnnnerteH hy the ligaTn^ntriTn

ii<.-^ tmat'Tiii Iridis^with ihe margin of the eomea.

'ihr iris i?> <.ir<:ular in form, and has a eentral perforation
ti;rnn.d tlie /////7. Its anterior surface is faintly striated in a
radial direetion. It is eoloured diflferently in diSerent
iM<Jividuals. Iis jjosterior surface is deeply pigmented.
'J'1j«; puj>il presents a ver)' nearly dreular outline,^ and
<Iiinij^; lile ii eonslantly varies in its dimensions so as to
< ini\rn\ tln; anuipy^t (A light •whieh is admitted intn ^lie
iiit<;rifir <jf the eyeliall. These ehanges in the size Qf the
li'ipil are produeed by the two groups of in voluntarv musenlar
\]\)u:s wlii<.h are uresent in the substanee of the iris, One
jir<>iij> is (:oirij><jsed of museular fibres arrang^ed en'riiTgrly
arou]i<r tlie |jujji7 in the form of a sphincter\ the seeond
^r<>ni|r o^iisists of filjres whieh have a radial direetion, and
I>ass froni the sphineter towards the drciimfprenre of the
iris, so as to <:<jnstitute a dilatator musele. By some
an:il(>iiiists ttirsr radial fihrf^'; are eonsidered to be elastu_
aii<i n<jl museular.

Oiliary NerveB. — The eiliary nerves arise from the dliary
J4;iiij4li<)n and the naso-dliary nerve. They pieree the selera
mouini tlie oj)ti(: entranee, and extend anteriorly, between
\\\v ^( itni and ihe ehorioid, in the periehorioidal lymph spaee.
'rii<y will be seen, in the speeimen in whieh the selera has
l)(tn IuiirmI aside in separate fiaps, in the form of delieate
wiiiie rilanienls (Fig. 253). In the posterior part of the
(■ythall ilu,y oeeui^y grooves on the deep surface of the selera,
;iii(l ean l)c suparated from it only with difficulty. Reaehing
ilh* ('iliary /.one the eiliary nerves break into branehes, whieh
j«)iii in a j)lexiform nianner and send twigs to the eiliary
iuusele, ilu: iris, and the eornea.

eiliary Arteries. — There are three groups of eiliary
arltiit's : (i) the short posterior eiliary arteries; (2) the long
|)«)',it*ri()r ('iliary arteries; and (3) the anterior eiliary arteries.

'l'lu- short posterior eiliary arteries^ branehes of the
(»|)liih;ilmi(*, pieree the selera around the optie entranee,

' li iM.iv l»i- as weli to nuMition here that the pupil in the ox and the
•ahti'l» is j4n*aiiy flt)ngat«'(l in the transverse direetion. In the pig, how-
r\vx, n is ai>pu)xiniatt*ly eireular.

RETINA

S79

and are distributed in the ehorioid eoat between the vasa
vorticosa and the membrana ehorio-eapillaris.

The iong posUrior eiliary arleries, also branehes of the
ophthalmie, are only two in number, They perTorate the
selera on either side of the optie nerve (Fig, 252), a short
distanee beyond the short dliary arteries, and then pass
anteriorly between the selera and the ehorioid. When
they gain the eiliary zone eaeh artery divides into an
aseending and a deseending braneh, and these, with the
anterior eiliary arteries, form an arterial ring termed the
dreulus iridis major. Branehes are given off froni this eirele
to the eiliary musele, the eiliary proeesses, and the iris.

The anterior dliary arieriu are very small twigs, whieh
arise from the branehes of supply to the reeti museles,
They pieree the selera elose to the margin of the eoraea,
take part in the fomiation of the eireulus iridis major, and -
send twigs to the eiliary proeesses.

Yeiue VorticoBSB. — From eaeh venous vortex in the
ehorioid a large vein arises, whieh makes its exit from the
eyeball by piereing ihe seiera, obliqueIy, a short dislanee
posterior to the equator. They are four or tive in numher.

DhseitU>n. — The vilreoiis hody and retina, in tlie posteriar part of the
eyeball whieh was eut inlo two for Ihe purpoEe o^ eipming the dliary I
proeesses from the posteriot aspeel, should now be dialodged. By raising ^
the ehoriuid eoat irom the deep suiiHee of tlie selera, under a flow of
water f[om the (ap, the vena; vorticosK entering the deep sutface Qf the .
seleta will be brought inlo view. Wheo these are dirided, and the separa-
tion of the two eoats is eairied posteriorly towards the optie entranee, the
posterior short eiliaty arleries, as they emerge from the selera and entet the
postetior patt of the ehotioid, will be seen.

In the eyeball from whieh the selern and eornea have been reinoved,
the iiis, eiliary proeesses, and the ehorioid should be earerully stripped Dff
pieeemeal under watet. Tiils will expo5e the tetina.

Betina. — The retina is eomposed of two strata— viz., a
thin pigmenlary iayer, whieh adheres to the deep surface of
the ehorioid eoat, and has been removed with it, and ;
delieate nervous layer, whieh is moulded on the surface of
the vitreous body, but presents no attaehment to it except at
the optie entranee. The retina extends anteriorly, beyond
the equator of the eyeball, and, a short distanee from the
eiliaiy zone, it appears to end in a well-defined wavy or

5 5= BULBUS OeULI

fe^::»:r.ec bi^reer tenr.ed :he era sirrata. TYns appearanee,
"r.:"»-ever. :s >:~:ewr.2: cecepdve- The nenre elements, it
ii :r-e, e^nie :: ir. er.d along this line, but a lamina in
::r.::r. j.::y ^::h :he re:::Li is :n reality prolonged antero-
.T.rl!j. '.".;.- i> lir 25 the nurgin or" the pupiL The part in
relj.:::r. :: the c:I:iry proeesses is exceedingly thin, and
ear. r.o: 're ce:ec:ed by the naked eye. It is tenned the
Tars .i.'isn's rf::K^. The ponion on the deep surface of the
:r:s :s e^Ilee :he s:rj^'r /:.prtff!^' in'J:s.

Durlr.^ l::e :he ry/:rj J^r'/^r is transparent, but after death
i: so-ori assumes a eu'*. gre\ish tint and beeomes opaque.
Pos:erlor'y :: :> ::ec down at the optie entranee. WTien
v:ewed r'rorr. :he :Lr.:er:or .ispeet this appears as a eonspieuous
eireular d:>c ternied :he /ii/:VJa nerri o/tia, upon whieh is
a depressio:^. the ^.u-.:r-.:.':l' Js2/i/»\c. From this spot the
op::c r.er\e r.bres rad:a:e out so as to form the deep or
anterior '.ayer cf :he retina. The optie dise, in eorrespond-
enee \v::h :he e:::!Ttr.ce ot the optie nerve, lies to the medial
or r..\5al s:de of the antero-posterior asis of the eyeball.
Exactly in the cen:re of the human retina, and therefore in
the axis of the globe of the eye, there is a small yellowish
spot rermed the ma^'itla Jutea.^ It is somewhat ovaI in
ourline, and a depression in its eentre is ealled the /airea
■.'z'n/rti.Vs.

Setinal Aiteries and Yeins. — In a fresh eyeball the
arteria eer.tr.i.'is r:tin<c will be seen entering the retina at
the optie dise. It inimediately di^ndes into a superior
and an inferior braneh, and eaeh of these breaks up
into a large lateral or temporal division, and a smaller
medial or nasal division. These ramify in the retina as far as
the ora serrata : but the resultant branehes do not anastomose
with eaeh other. nor with any of the other arteries in the
eyeball.

The retinal veins converge upon the optie dise, and
disappear into the substanee of the optie ner\-e in the form
of two small tiunks whieh soon unite.

The reiinal vessels. the optie dise, and ihe maeula ean all be examined
in the living e\ e by nieans of the ophthalmoseope. The red reflex obtained
from the funiius of the eyeball is produeed by the blood in the lamina
ehorio-eapillaris.

1 There is no maeula lutea in the eyeb^* or sheep.

YITREOUS BODY 581

Dissictieii.—Fcit tbe study oEthe vitreous body and the erystalline lens,
whieh (ogethei may he termed Ihe " cye-lteme1," it is better to lake an
eyeball whieh is not perfectly fresh (Anderson Stuart). The eyeball
seleeled for this puipose should be allowed to stand untouehed from one
to ihree days, aeeording to the season. The eoats of the eye should then
be dtvided round the equator, and on genlly separating the eut edges, and
turningthe eoals anteriorly and posterioily, the "eye-kernel" witl slipout.
It should be allowed to drop into a vessel filled with elean water. The
examination of the parts ibrming the "eye-kemel" will be greatly facilitated
by plaeing it ea masse in sitoog piero-earmine solulion far a tew minuteK.
When temoved from the staining fiuid, it should be well washed in watet.
In this way the hyaloid membrane endosing the vitreous body, the eapsule
of the lens, and the lonula eiliaris, are slained red, and their eoiuieelions
beeome very apparent (Anderson Stuart).

VitreoTis Body. — This is a soft, yielding, transparent,
jelly-like body, whieh oeeupies the posterior fQur-fiftlis of the
interior of the eyebalL The retina is spread over its surraee
as far forwards as the ora serrata, but is in no way attaehed
to it, except at the optie dise. Anterior to the ora serrata,
the eiliary proeesses are applied to the vHtreous body and
indent its surface. More anteriorly, the yitreous body pre-
sents a deep concavity, the /ossa hyaloidea, for the reeeption
of the posterior convex surface of the erystalline lens.

The substanee of the yitreous body is enelosed within a
delieate transparent membrane, whieh eompletely enveIops
it, and reeeiyes the name of the hyaloid membrane. Extend-
ing anteriorly through tho midst of the vitreous mass, from the
region of the optie dise to the erystalline lens, is a minute
eanal, lined with a tube-Uke prolongalion of the hyaloid
membrane, and eontaining a watery fluid. This is termed
the hyaloid eanal; it represents the palh taken by a braneh of
the arteria eentralis retinie, whieh, in the fcetus, estends to and
supplies the eapsule of the lens, but afterwards disappears.

The hyaloid eanal, as a rule, eannot he seen in an ordioary disseetion
of tbe eyeball j but if ihe " eye-kernel" be shalien up in tbe piero-eanniiie
solution as reeommended by Anderson Stuatt, it may somelimes be rendered
evi<Ient through the staining fiuid entering it. It is represented diagram-
matieally in Fig. 151.

Zonala Oiliaris (O.T. Zatiiila of Ziim). Between the
eorona eiliaris enternally and the margin of the lens intemally
lies a Abrous membrane ealled the zonula eiliaris. Its
external margin is attaehed to the posterior surfaces of tbe
eiliary proeesses and the hyaloid merabrane, and its internal
margin is eonneeted with the lens. As it approaehes the
margin of the eryslalline lens, it splits into two parts, viz., an

SRi BULBUS OeULl

<;xccedingly delieate deep lamina, whieh lines the fo5sa
hyaluidea, and a more superficial stronger part, whieh beeomes
attaehed to the eapsule of the erystalhne lens.

The zonula eiliaris lies subjacent to the eiliary proeesses,
and is radially plaited or wrinkled in eorrespondenee with
these. Thus the clevations or wrinkles of the zonuIa extend
into the intertals between the eiliary proeesses, whilst the
eiliary proeesses in their turn lie in the depressions between
the wrinkles of the zonula. When the eye is fresh, these
opposing parts are elosely adherent

The zonula eiliaris is strengthened by radially direeted
elastie Abres, and after the deheaie membrane whieh lines

l''i<;. 256.— Uingrammatie represeouiion of ihe Giliaiy Regiou,

the Tossa hyaloidea is given off from its deep surface, it
extcnds inwards as a distinet layer, and is attaehed to the
anterior surface of the eapsule of the lens a short distanee
beyond the margin of that body. In this manner the
suspensory Hgament of the lens is formed. But tbis is not
ihe only attaehment of the suspensory ligament. Some
seattered fibres are altaehed to the circumference or equator
of the lens (cquatorial fibres), whilst others are fi]ted to its
posterior suri'aee elose to its mai^n {post-eqiiP*' -■""■

In this way the erystalline lens is firmly
in llio fossa hyaloldea, Purther, the degr
suspensory ligament is inAueneed by the

reiiee ui cqua[or
are fixed to its

LENS 583

the eiliary musele, whieh by their eontraetion pull upon the
eiliary proeesses, and produee relaxation of the zonula
eiliaris.

Spatla Zonularia (O.T. eanal of Petit). — In reality the
spatia zonularia eonstitute a more or less eontinuous eireular
lymph spaee, whieh surrounds the circumference of the lens.
It lies between the anterior and posterior layers of the
suspensory ligament and is filled with a watery fluid.

By introdueing the point of a fine blow-pipe into the spatia zonularis
through the suspensory ligament, it ean be partially, or, perhaps, eom-
pletely, inAated with air. It then presents a saeeulated appearanee.

Disseetion, — The erystalline lens may be removed by snipping through
the suspensory ligament with seissors.

Lens Orystallina. — The erystalline lens is a biconvex,
solid, and transparent strueture whieh lies between the iris
and the vitreous body. It is enelosed within a glassy, elastie
eapsule, to whieh the different parts of the zonula eiliaris
are firmly eemented, and it presents for study an anterior
surfacei a posterior surface, and a circumference or equator.

The anterior surface is not so highly curved as the posterior
surface. Its eentral part, whieh eorresponds with the pupillary
aperture of the iris, looks into the anterior ehamber of the
eye. Around this part the margin of the pupillary orifice of
the iris is in eontaet with the lens, whilst nearer the equator
the anterior surface of the lens is separated from the iris by
the fluid in the posterior ehamber of the eyeball. Th^ posterior
surface of the lens presents a higher degree of curvature than
the anterior surface, and is received into the fossa hyaloidea
of the vitreous body. The eguator or circumference is rounded.
It forms one of the boundaries of the spatia zonularia, and
the manner in whieh the zonula eiliaris is attaehed to the
eapsule in this vicinity has been deseribed already.

Faint radiating lines may be seen on both surfaces of the
lens. These give a elue to the strueture of the lens. They
indieate the planes along whieh the extremities of the lens-
fibres eome into apposition with eaeh other.

The eapsule of the lens is a resistant glassy membrane,
whieh is eonsiderably thieker anteriorly than posteriorly.

The anterior wall of the eapsule may now be divided with a sharp knife.
A little pressure will eause the body of the lens to eseape through the
opening. The stained eapsule ean be very advantageously studied whilst
Aoating in water.

5S4 BULBUS OeULI

I:' :hr len* :->iy :« eompressed beiween the finger and thumb, it will
L^ r..:c"i :h2t :he :u:er rortii^n ot eertieal part is soft, whilst the eentral
jv3r: cr nu.'.iu: :> iisUErtly nmier. ^Mien the lens is hardened in aleohol
:: ean eisily ':«e :r;.ved :ha: i: is eomposed of numerous eoneentrieally

Ghainbeis of the EyebalL — The anterior ehaniber of the
eyeba'I is ihe spaee between the eomea anteriorly, and the
iris and eeniral part of the lens posteriorly. At the irido-
eorneal angle it is bounded by the ligamentum peetinatum
iridis. and there the aqueous humour whieh tills this ehamber
tinds aeeess to the spaiia anguli iridis.

The posUrior ehambtr is a eireular spaee or interval whieh
is bounded anteriorly by the posterior surface of the iris, and
posteriorly by the circumferentiai part of the anterior face of
the lens. Extemally, this spaee is elosed by the thiek anterior
projecting ends of the eiliary proeesses. It also is filled with
aqueous humour.

INDEX.

Aeeessory parotid, 126, 127, 261
Aditus laryngis, 378, 408, 409
Agger nasi, 396
Alae of thyreoid eartilage, 414, 415,

421, 423
Alveus, 497
Ampullse of semieireular eanals,

567
Amygdaloid nueleus, 491, 494, 512,

Annular ligament of Stapes, 557
Ansa hypoglossi, 146, 234, 243,
244, 246
subclavia, Yieussenii, 239, 250,
257, 258, 319
Antihelix, 153
Antitragus, 154
Aorta, 10, 83

areh, 23, 30, 32, 44, 78, 85, 89, 96,
98, 100, 102, 103, 106, 247
position of, 85
aseending, 39, 55, 83, 98

position of, 83
deseending thoraeie, 31, 44, 50,
58, n, 89, 98, 102, 104, 106,
109, III
Aortie groove on left lung, 40
eusp, 87

great sinus of, 84
oriAee, 74, 83

sinus of (Valsalva), 78, 80, 84, 87
valve, 87
Apertura medialis ventriculi quarti,

53?
tympaniea eanieuli ehordse, 551,

564
Apex eolumni anterioris, 197
Apieal gland, 434
Apiees of the aurieles, 55, 65, 76,

84, 89, 98

585

Aponeurosis, 366

bueeo-pharyngeal, 366

of palate, 382

pharyngeal, 373

vertebral, 235, 236, 237
Appendix ventriculi, 412, 421
Aqu3eductus eerebri, 503, 505, 506,

509, 5"
vestibuli, 566

Aqueous humour, 571, 584

Araehnoidea eneephali, 438, 439

spinalis, 185
Araehnoideal granulations, 202,

206, 442
Areh lateral lumbo-eostal, 109, 167

glosso-palatine, 430, 431
Areus glosso-palatinus, 368, 378,
380, 381, 382, 430, 431

parieto-oeeipitalis, 464, 471, 472,

474
phar)mgo-palatinus, 368, 369,

378, 380, 381, 382
tarseus, 137, 342
Area aeustiea, 525
Artery or Arteries, aWeolar, an-
terior superior, 386, 389
alveolar inferior, 270, 272, 278,

279
aWeolar posterior superior, 270,

271
angular, 128, 131

of external maxillary, 344
anonyma. See Innominate
anterior eerebral, 450, 447, 448
branehes of —
anterior medial frontal, 449
antero-median, 449
intermediate medial frontal, 449
medial orbital, 449
posterior medial irontal, 449

!•

y tn^KSr

^~3 O ^ Z* "~ Ti-

«» •: — <

-'. I- l'. l;'.''- -'. ." !;'._ I:'-C

■ ' - «■' - -

■• -.'/ • / --.■ --- -»

. • '.-' - » - -,- "•"»-

. ■'- /- . .'-- 7'-''- }•-'

' • ' » «.' 'V j- ■ 'r

.. ... .. ^. ^4P M V. . ■

1^;. 1:^1:^ r-:. jac* ssi.

•■ » •■ - » - — «

. ■ ■ -• } _ •*^>. _'

..1 rJ:

r^-^'' i'. 1 ' i

^5! SS, 06. 247

■-.r-i, :zz. ::^ ::?. :oa 126

« ^ ' « «

'-•''". "* - ■'

»«''• -, '/. r' '• ; 'T''

'#. •. . .'. .•-. ,. .. e.i .^*^

^, ■•r ■*

#t|.-/r '. *.'.r'. *r'.*' *?-

....'.1. /; «•* .':. .. , . . ■&.. ^*.'

;■■' ' ' ■■. ^' ..: .. ^- J

' • •■/*'■" ^ ^f •

■■■1' ''• •} 4 / ■'
' ' /• .' ...sr. ui.**ilt,r 'ii.i'-.ti'A. 445
.;.!' f i',r i/i.i'rrior, 444

■;'' 'i''»"! 44Si,44^^

' ' I /i' :i), ;i ,'.«-/i'Jifij^, 252

< « ivi' :i|, 'iij|;f:r/H;i;i], 162

|"i-J« rior, 343, 573, 578, 579
sii.l.rior, 343, 573, 578, 579

i-T-t.-iir. ly.. 2yL. 257. 25S

--.-^ -j-- -i/-^* o«-s 4*j»

• •» T • ■> ■»

T— *■ T— -

lateral nss^i. 131

lingual, 231. 232, 21^, 2S6, 291,

292, 296, 297
]uinbar, 176
mammar}', 9

intemal, 7, 9, 15, 34, 251, 254,

357.25«

T L 232

ur, 245

INDEX

587

Artery or Arteries —

maxillary, internal, 242, 262, 267,

269, 272, 274, 294, 296, 301,
402, 403, 405, 406

mediastinal, 104

of the medulla spinalis, 193
meningeal, anterior, 220, 221, 344

aeeessory, 212, 220, 221, 270,

274, 333
of aseending pharyngeal, 220,

221, 304
of internal maxillary, 220, 221
middle, 202, 210, 212, 220,

270, 274, 277, 293, 333
of oeeipital, 220, 221, 301
of yertebral, 220, 221, 356

mental, 279, 30»
museulo-phrenie, 7, 9
mylo-hyoid, 270, 278, 283
nasal branehes of anterior eth-
moidal, 393
of posterior ethmoidal, 393, 406
posterior (of spheno-palatine),

406
posterior of the septum, 392
nutrient of skull and diploe, 202
oeeipital, 145, 149, 156, 157, 162,
169, 170, 232, 239, 262, 296,

300, 302, 303, 306
deseendingbraneh, 169, 171, 172
meningeal braneh, 169, 171
sterno-mastoid braneh, 316

oesophageal, 103, 104, 253, 307
ophthalmie, 220, 339, 341
palatine, aseending, 383

of aseending pharyngeal, 304,

383

deseending, 383, 405, 406

of dorsalis linguae, 383

of laerimal, 342

of ophthalmie, 342

small, 406
palpebral, 137, 342
parieto - oeeipital (of posterior

eerebral), 447
perforating, of internal mammary,

.4, 9
perieardial, 104

perieardiaeo-phrenie, 50

petrosal of middle meningeal,

301, 333
pharyngeal, 253

aseending, 232, 246, 296, 303,

307, 406

branehes, 304

eanal, artery of, 485

Artery or Arteries —

pontine, 445

posterior aurieular, 302

eerebral, 457

eommunieating, 480

oeeipital, 303

of septum, 406
prevertebral branchesof aseending

pharyngeal, 304
profunda cervicis, 172, 173, 175

linguse, 290, 291
pterygoid, 270

eanal, artery of, 405
pulmonary, 10, 22, 30, 34, 38,
44, 55» 70, 75» 78, 84, 85,
90, 99

right, 76, 84, S6, 98, loi

left, 76, 86, 99

foetal eondition of, 77

relations of extra-pulmonary
part, 99

orifice of, 83

relations of, 76

topography of, 76
ranine, 434
retinal, 581
septal of the nose, 131
short posterior eiliary, 574
spheno-palatine, 402, 405, 406
spinal, 109, 176, 181, 182, 193,
252

neural branehes of, 182

pre-laminar branehes of, 182

post-eentral branehes of, 182

anterior, 445

posterior, 443
sterno-mastoid, of oeeipital, 231,
233» 235, 239, 300, 308

of superior thyreoid, 232, 235,
239, 245, 296, 308

of transyerse seapular, 235, 239
stylo-mastoid, 147, 151, 161, 274,

307
subelayian, 23, 25, 31, 32, 34, 35,

235» 239, 246, 247, 254, 257,

258, 309» 315» 323
branehes of, 251

left, 86, 88, 89, 100, 102, 106,

250, 255
right, 250
subeostal, 104, 109
sublingual, 291, 292, 300
submental, 282, 283, 284, 292,

300
superior epigastrie, 7, 9
intereostal, 7, 109, iio

588

INDEX

Artery or ArteriM—

superior labial, 130, 393

septal braneh of, 393
supra-hyoid of lingual, 232, 291
supra-orhital, 156, 157
tcm[x>ral of posterior eerebral, 447
deep, 267, 270, 303
middle, 262, 265, 266, 267,

270, 302
supertieia], 127, 157, 261, 262,
277, 294, 296, 301
thoraeo-aeromial, 161
thyreo-cervical, 106, 251, 252,

253.. 254» 309» 323
aseending cervical braneh of,

240

inferior, 106, 235, 245, 246,

251, 252, 255, 315, 321, 323
superior, 229, 230, 232, 234,

243, 246, 253, 296, 308, 321
thyreoidea ima, 49, 229, 320, 321
t(msillar, 299
traeheal, 253
transversa eolli, 106, 145, 147,

149, 161, 164, 239,242, 251,

252, 253, 255, 323
transverse facial, 127

seapular, 106, 145, 147, 149,
161, 164, 225, 242, 251, 252,

253, 255, 309, 323
tympanie, 270, 274
vertcl)ral, 106, 175, 179, 180,

214, 220, 246, 251, 252, 253,

255. 257, 323» 353» 354, 355,

442, 443
/ygomatieo-orbital, 302
Artioulations. See Joints
Ary-cpij;h)ttic folds, 329, 408, 409,

415, 418, 420, 421, 427
Aryt;cnoi(l eartilages, 379, 420
Atria of heart, 34, 65, 68. See

lleart
Atri()-vcntricular apertures, 69, 71,

73. 79, «3, 92
bundle, 74, 83, 93

librous rings, 93
Atrium medii nasi, 395
Audilory api^aratus, 546
Auditory tube, 293, 299, 312, 375,
37^^, l"^^, 3«2, 383, 384, 559

bony position, 559

eartilage of, 384

earlilaginous portion, 539

lcvator eushion of, 384

ossieles, movcments of, 557

l)arls of, 384

I Aaditory tnbe —

phar^mgeal orifice of, 384
I Auriele, 153, 546

eartilage of, 270

1 Baek, 161

I blood-vessels, 170, 175
nerves, 162, 173, 177
Rasal ganglia, 512
Basilar sinus, 183, 216
Basis peduneuli, 508, 509, 510
Biventral lobule, 533
Braehia conjunctiva, 511, 545

eerebelli, 529, 530
Braehial pleius, 151
Braehium pontis eerebri, 458, 531

conjunctiva eerebelli, 512
Brain. Aho voL i. p. 28
basal ganglia, 437, 512
base, 437
blood-vessels, 442
eerebellum, 437
eerebral hemispheres, 459
eerebrum, 459
eorpus eallosum, 479
fomix, 496

fourth ventricle, 458, 520
general appearanee, 437
general connexion of several

parts, 458
general stnieture, 461
lateral ventricles, 458
lobule paraeentral, 466
lobe frontal, 466-470

lateral surface of, 466
medial surface of, 469
orbital surface of, 469
limbie, 477-479
oeeipital, 472-474
lateral surface of, 474
medial surface of, 474
tentorial surface of, 474
olfactory, 477-478
parietal, 470-472

lateral surface of, 471
medial surface of, 470
temporal, 475-477
lateral surface of, 475
opereular surface of, 475
tentorial surface of, 476
medulla oblongata, 437
meninges, 439
meseneephalon, 506
origin of nerves, 454
parts in posterior eranial fossa,
452

INDEX

5S9

Brain —

peduneles of, 506, 508

pons Yarolii, 437

posterior hom of ▼entnde, 473

preservatioD of, 437

removal from eTaniam, 211, 217

septum pellueidiim, 495

thalami, 500

third ventricle, 503

velum interpoatum, 498
Bronehi, 10, 22, 38, 44, 70, 77, 97

eparterial, 22, 76, 98

hyparterial, 10, 38, 44, 70

left, 87, 98, 103

relations of intrapulmoiiaiy part,

98
right, 84, 98, loi

Bueeal aponeurosis, 366

glands, 366

plexus, 277
Bueeo-pharyngeal iasda, 366, 370
Bulb,

of eomu, 490

of jugular vein, 307, 350

olfactory, 208
Bulla ethmoidalis of nose, 398
Bundle, atrio-ventricalar, 74
Bursa, pharyngeal, 376

Galamus seriptorius, 537

Galear avis, 473, 490

Galearine fissure, 446, 465, 473.

478, 490
eanal earotid, 385

eentral, of spinal medulla, 181

of modiolus, 568
facial, 552, 561, 562, 563, 564,

565
for tensor tympani, 551

hyaloid, 581

laerimal, 138, 140

membranous, 569

pharyngeal, 405

pterygoid, 405

semieireular, 561, 565
lateral, 567
posterior, 567
superior, 567

spiral, of modiolus, 568
Ganalis reuniens, 569
Ganalis facialis, 552, 561-565
Ganthi, 120

Gapitular artieulations, 112
eapBule, extemal, 450, 512, 519

interaal, 450, 512, 514, 518

oflens, 583

*ep. ^ «5. «9^ 96, 99.

100

«""Pnr6dal. 13> 43. 65. 7S, S$,

^3
CaiDtidbod|f, 247

eaiial.185

gluid,a94

Fkni>3iS

diauh,235

tiiaiigle, 2j6, 232, 233

eantHa^i^ aiytaenoid, 379, 408, 410,

411, 414. 415, 416, 417. 41«.

419. 4»^ 421* 427
eornieiilate, 40>f 415* 4i6, 421«

427
oieoid, 250, 414, 415. 426

aaiaSam^ 408, 415, 4», 4JS

ofqK;lattii»423

]atenlof noae, 141

alar<»fiioae, 141

iiunororifiaiiidof noM^ 141

orpiima, 155

ffwii'wid <■ r

tritieaea, 414

tliTieaid, 229^ 230, 414, 41$, 421,

423
Gaitilagine» eoraieiiiatar, 422, 427

Ganinenla laeriaalis, 120

P.afufat4> imrltW f dAA» jttL aSiL JOf.

518

Gawnoas plem, 2S5, 5|s« 33S, 3|K

nmiSy 209^ 210
CaTityoftlionx, i, fo
Ca;vnin MirkHH, 212, 329

oris,3l^^

snhaiaehiioideale, 185,439
sabdtnale» iS^ 204
Gentnl eanal otinnal MednOay 196
of medHlla, 521
of modiolnt, 568
peyniattero^aeinednet, 505
Gentnl lobe;, 462

loiiale,53i
Cetttiie, lomsr Yisiial, 508
Gentnnn owale, 480
Gerebdlar prdnndet, 534

snpeiior, 535
GenlidkMdiwiy tnet, 5:9
-^iiiial tnety 525

OMPikillmi, 437. 5^

590

INDEX

eerebeUam—

arlx)r vitce, 534
braehia conjunctiva, 535
eorpus meilullare, 534
tissures, 529, 531
hemispheres, 529
lingula of, 538

lobes, 529, 531, 532, 533, 534
lobules, 531, 533

eentral, 529, 531

linguli, 538
lobus noduli, 533

Pyramidis, 534

tuberis, 534

uvula;, 533
montieulus, 529
notehes, 529
I>etluncles, superior, 532

braehia pontis, 529

inferior, 527
surfacc of, infcrior, 530

superior, 535
vallecula, 530
vcrmis, 529
Gerebral cortcx, 461
hemispheres, 461

basal ganglia, 512

borders, 459, 460

eorona radiata, 519

cortex, 461

fissures, 462-479

general strueture, 458

grey matter, 461

gyri, 461, 462, 479

internal eapsule, 518

island of Reil, 477

lobes, 462, 466, 470, 472, 475,

477
medullary eentre, 461

orbital area, 459

poles, 465

sulei, 461

tentorial area, 459

ventricles, 483,492, 49^, S<^3'S^
eerebrum, 459, 520

anterior eommissure, 503, 519
borders of, 459
eorpus eallosum, 446, 497
fornix, 488, 496, 499
frontal pole of, 460
hemispheres, 459
inferior surface, 459
lateral surface, 459

ventricles, 483-492
longitudinal fissure, 439, 449
massa intermedia, 504

Cerebram —

medial surface, 459
oeeipital pole of, 460
orbital area, 459
peduneuli, 210, 212
posterior eommissure, 503, 505
septum pellueidum, 449, 488
temporal pole of, 460
tentorial area, 459
thalamus, 447-450
third ventricle, 503-506
transverse fissure, 499
tela ehorioidea, 442
Geruminous glands, 548
Geryieal fascia, 235
ganglion, inferior, 319
middle, 318
superior, 317, 318
pleura, 248, 250, 257
plexus, 151, 239, 240
eommunieating branehes of, 241
museular branebes, 241
sympathetie, 245, 247, 252
Cervix eolumnse,

anterioris, 197
posterioris, 197
Ghambers of eyeball, 571, 584
Gheeks, 366
ehest. See Thorax
Ghiasma, optie, 441
Ghoanse, 374, 375, 377, 389
Ghondroglossus, 434
ehorda tympani, 564
ehordoe tendinese, 73, 74, 79, 80

Willisii, 206
Ghorioid, 571, 574
eoat, 574

lamina eorporis eapillaris, 575
plexuses, 497
vasa vofticosa, 575
Ghorioidal fissure, 492, 493, 494
Ghyle, 105

Giliary body, 571, 574
eireular fibres of, 576
folds, 577
ganglion, 338
musele, 576
orbieularis eiliaris, 576
proeesses, 577
radiating fibres, 576
zone, 579, 583
eingulum, 479
Gireular sinus, 209, 217

suleus, 462, 463
eireulus arteriosus, 441, 443, 450
iridis major, 579

INDEX

59J

Gireulus iridis minor, 579

tonsillaris, 311
eistema eerebello-medullaris, 440,

538
ehiasmatis, 441, 443, 450
ehyli, 105
interpeduneularis, 210, 441, 443,

450
pontis, 441

subaraehnoidales, 440

ven3e magnte eerebri, 442
eiaustrum, 512, 516, 517
Clava, 526
Clivus, 532
Cochlea, 565, 567

eanal of, medial longitudinal,
568

eupola, 568

duet of the, 569

ganglion spirale, 568

lamina spiralis, 568

membranous eoehlear tube, 568

modiolus of, 568

eanal, medial spiral of, 568

seala vestibuli, 566
Collateral fissure, 461, 462, 465
Colliculus facialis, 537
Colliculi (of lamina quadrigemina),

506
Column of Burdaeh, 199

of GoU, 199
Columns of grey matter of eord, 197

lateral grey, 198
Commissures, anterior, of brain,503,

519
posterior, 503, 505

Commissures of eord, 195, 196

palpebral, 119
Conchae of ear, 153

of nose, 376, m, 389, 395, 396,

397, 399, 400, 401, 402, 403
Conical papilloe, 432

Conjunctiva, 120, 139

fornix conjunctivDe, 120

pliea semilunaris, 120

earuneula laerimalis, 120
Conus arteriosus, 30, 39, 54, 70,
72, 74, 78, 84

elastieus, 414, 415, 418, 419, 421

medullaris, 187, 188
Convolution. See Gyrus
Cord, gangliated, of sympathetie,
2, 23, 25, 108, 109

spinal. See Spinal medulla

vocal, 579, 581
Cords of braehial plexus, 151

Comca, 572, 573. 574- ?:?
Comco-scleral jur.:::- r. 573
Comu Ammonis. 401, .102. 4''<'5- i'-7
Goraua of lateral vcr.tr. :1t^. i'7.
490, 491. 49^

of thyreoid eartilagt. x^
Gorona eiliari». 577

radiata, 519, 57^. 596

radiator, 519
Goronary plexu*. O5. S3

sinus, 89

suleus, 68

valve, 81
Gorpora mamillaria. 452, 453. .±07.

503, 5p4
quadrigemma, 2ic. 447, 300. yJj.

507,511,512. 529

superior, 503, ^'.d, 307

braehia of, 507

genieulatum. 512

Oorpas eallomin. 446. 45S. 473.

478, 479, 480, 4<»i, i>*- ^y-*.

495» 496. 497, 49S, 499
eentral {lart, 494

Abres, 4^8 1, 483

genu, 448, 478, 482, 4&3, 4^7.

495
lamina rostralis. of, 482

rostrum, 448, 449, 482. 483

radiation, 483

truneus of, 482, 487

splenium, 446, 478, 482, 483.

486, 494, 495. 499

Corpu3 genieulatum eitemal, 503

intemal, 507

laterale, 507, 508

mediale, 506, 507

Gorpus mamillare, 519

striatum, 512, 515

trapezoidum, 545

Gosto-mediastinal «sinus, 12, 16, 25

-traiisverse jointt, 113

ligameots of the tu:>er<:I««, 113

-▼ertebral artieulati^iiu, j 12

Cranial fossa, middle, 325, 333

Greseentie lobule, 531, 532

Grieoid eartilage, 230, 414, 415, 426

Grieo-thyreoid meml>raoe, 297, 415

Grista ▼estibali, 566

Onira of emeial iigament, 3^3

Cnira of stapes, 557

Crus helieis, 153

Cnis laterale of malleet, 555

of ineits, 555

erystalUoe lens, 571, 37*, 5*1, $>?

enlmen montienli, ^y^, 531

592

INDEX

Guneate funiculus, 540, 541

nuolous, 541

lul>ercle, 379
Cuneiform eartilage, 408, 415, 421

tuberele, 379
Guneus, 447. 473
Gupola niodioli, 568

Deeostation of the lemniseus, 542

motor, 542

of pyramids, 542

sensory, 542
l)eclive Montieuli, 531
Dentate fascia, 479, 483, 492,

495
hssure, 479, 495

nuoleus ()f cerel>elluni, 539

Diaphragm, 3, 35, 50, 70, 88, 99,

100, 102, 103, 105, 241

eentral temlon of, 88

enira of 104, 105, iii

membranous cervical, 36

l)iaphraj^ina oris, 284

sella', 209

Diaphra^niatie line of pleural reflec-

tion, 14, 17, 18, 19

pleura, 16

Dij;astric triani;le, 226

Dilatator pupilUe, 578

1 )ionre[iliaK)n, 520

Dise, intervcrtel)ral, 357

optie, 580, 581

Diseus artieularis of jaw-joint, 268,

271, 272, 273, 274

DiBBeotions — Thoraz —

thoraeie wall, 3, 4, 7

thoraeie cavity, 12, 25, 29, 32,

33» 43. 46, 4^"^
perieardium and heart, 49, 51,

60, 65, 76, 78, 79, 87, 88,

89, 91
deep of the thorax, 98, lOi,

104, 109
thoraeie joints, 112
Head and Neek —

face, 117, 120, 126, 128, 132,

133. 134, 140
posterior triangle of neek, 142,

143, 145, 146
sealp, 153, 154, 158, 159
sterno-clavicular joint, 159
baek, 161, 162, 164, 166, 167,

168, 171, 172, 176, 178, 179,

181, 185, 191, 192, 200
removal of the brain, 200, 203,

207, 211, 217, 222

Disseetions — Head and Neek —

anterior part of neek, 223, 225,

229, 230, 231, 234, 238, 239,

244, 261, 262, 303, 304, 309,

310, 317, 324, 325
temporal and infratemporal

regions, 266, 274, 279, 293
submaxillary region, 279, 282,

284
great yessels and nerves of

neek, 303, 304, 309, 324
lateral part of middle eranial

fossa, 325, 329
orbit, 334, 335, 339, 346, 348,

350
prevertebral region, 350, 353,

356
jomts of neek, 358, 361, 362, 363
maxillary nerve, 386
pharynx, 369, 370, 372, 374,

376, 381, 382
nasal cavities, 389, 393, 397,

398, 399
spheno-palatine ganglion, 402,

405
larynx, 413, 415, 417, 419, 421,

422
brain, 457, 460, 479, 480, 483,

484, 485, 490, 494, 495, 496,

498, 500, 505, 512, 519, 528,

536, 539. 540
auditory apparatus, 546, 549,

559
intrapetrous portion of facial

nerve, 562, 565

eyeball, 570, 572, 575, 576,

579, 581, 583
Duet, lymphatie, right, 48, 242,

245» 255
naso-laerimal, 120, 140, 346, 399
of Cuvier (foetal), 91
parotid, 126
sublingual, 289
sub-maxillary, 288
thoraeie, 2, 18, 31, 32, 48, 49,
70, Sy, 102, 104, 106, 108,
III, 242, 245, 255
Duetus arteriosus, 33, 77, 78
eoehlearis, 569
endolymphatieus, 569
Dura mater eneephali, 201
layers of, 202, 203
partitions, 203
sinuses, 162, 202, 205, 207, 211,

217
spinalis, 183

INDEX

593

Ear, 547

annulus tympanieus, 549

eoneha of, 546, 547

external, 546

internal or labyrinth, 546, 565

mastoid ear eells, 550

meatus - external aeustie, 546,

547, 548, 549» 550, 559,
560, 561

membrana tympani, 547, 548,

549, 553, 554, 555, 5^1
middle ear, 546, 550

tragus of, 547

tympanie cavity, 546, 550

tympanie antrum, 550, 551, «;54,

555, 559, 560, 561
tympanie membrane, umbo of,

549

Eeto-rhinal fissure, 465, 475

Elastie lamina of eornea, 574
Eminenee, olivary, 524, 525, 526
Eminentia eollateralis, anterior, 494

posterior, 494
Endoeardium, 92
Endolymph, 546, 566
Eparterial bronehus, 22, 76, 98
Ependyma, 485, 526
Epieardium, 92
Epieranial aponeurosis, 122, 123,

154, 156, 158
Epiglottis, 379, 408, 409, 423

aetion of, 429

eartilage, 422

frenum, 409

petiolus of, 423

tuberele of, 409
Ethmoidal eells, 395
Eustaehian orifice, 293, 299, 312,

375, 376, 381, 382, 383, 384

tube, 293
Excav'atio papillge, 580
Eyeball, 570

bulbus oeuli, 570

ehambers, 571, 584
anterior, 585
posterior, 585

equator, 570, 572

general strueture of, 571

meridional lines, 570

poles, 570

refracting media, 571

sagittal axis, 570

tunies, 571
Eyebrows, 118
" Eye-kernel," 581
Eyelids, 119, 134

VOL, II — 38

Eyelids, conjunctiva, 119
glands, 132
ligaments, 121
tarsi, 134
vessels and nerves, 137

Face, 117

arteries, 128

museles, 120

nerves, 126

surface anatomy, 117
Falciform lobe, 465, 481
Falx eerebelli, 212, 215, 529
Easeia, axillary, 147

bueeinator, 261

bueeo-pharyngeal, 366, 370

bulbi, 347-350

earotid sheath, 235, 236, 238

eerebri, 206, 459

cervical, 145, 224, 225, 235

deep cervical, 235

deep of posterior triangle, 144

dentate, 479, 483, 492, 495

intra-thoraeie, 12

lumbo-dorsal, 166, 167

palpebral, 135

parotid, 126

peri-renal, 168

pharyngo-basilar, 373

pretraeheal, 229, 230, 235, 236,

237
prevertebral, 235, 236, 237

of Sibson, 36

submaxillary, 226

superficial cervical, 235

temporal, 265, 266

Fasciculus eerebro - spinalis, 510,

519, 527
eerebello-spinalis, 200

anterior, 200

lateralis, 200, 542

Fasciculus euneatus, 199, 200

graeilis, 199, 200

thalamo-mamillaris, 447

Easeiola einerea, 483

Fauces, isthmus of, 365, 368

pillars, 368

Eenestra eoehleae, 552, 561, 568

vestibuli, 552, 557, 561, 562, 564,

566

Eibrae areuatae, 528

Filum terminale, 183, 187, 188

Eimbria, 479, 491, 492, 494

FiBBure or FiBSures, ealearine, 446,

461, 465, 473, 478, 490

eentral, 462, 464

594

INDEX

FiB8ure or risBiires —

of eerebellum, 529, 531
of eerebrum, 462, 479
ehorioid, 492, 493, 494
eollatoral, 461, 462, 465, 474, 475,

476. 479» 499

(lontate, 479

eeto-rhinal, 465, 475

great horizontal, 530

lont^^itudinal, 439, 449, 460
transvcrse of brain, 492

hipi>ocampal, 461, 465, 495

lateral of hrain, 451, 459, 462,
463, 466, 476
anterior aseending limb, 463
anterior horizontal limb, 463
j>oslerior ramus, 463

longitudinal of brain, 437, 439,

449. 460
of lung, 41
ofmedulla, 195
oral, 365
palpebral, 119

liarieto-oeeipital, 448, 462, 464
lateral, 464, 470, 473, 480
medial, 464
()f spinal medulla, 195
transverse of brain, 499
F(CtaI eireulation, 68, 69, *]*]
Fold, ary-epiglottie, 379, 408, 409,
415, 418, 420, 421, 427
glosso-epiglottie, 409, 423, 430
pharyngo-epiglottie, 409, 423
salpingo-pharyngeal, 376
tympano-malleolar, 549
anterior, 549, 554
posterior, 549, 554
ventricular. See Plieie
vestigial, 91
vocal. See Pliere
Kolium vermis, 530
Kontana, spaees of, 574
Forainen eoeeum of medulla oblon-
gata, 521
ca3cum of tongue, 430
interventriculare, 459, 486, 489,

502, 505
of Magendie, 539
ovale, 68, 78, 92
Koramina vcnae minimae eordis,

92
Forceps major, 483, 490, 494,
496
minor, 483
Formatio alba, 543
grisea, 543

Formatio retieularis, 510, 543, 545
Foniix, 488, 492, 495, 496, 499

body, 496, 497, 49i8, 499

eolumns of, 485, 497

of conjunctiva, 119

orura of, 496, 497, 498

transverse fibres of, 497
Fo8sa of antibelix, 154

eranial, middle, 325, 333

ofhelix, 154

hyaloidea, 581, 582, 583

interpeduneularis, 452, 503

nasal, 393

ovalis, 68, 69, 92

pterygo-palatine, 386, 388

reeessus, 379

rhomboidalis, 536, 537

seaphoid of ear, 154

supraclavicularis, major^ 142
minor, 142

supra-stemal, 178

supra-tonsillar, 378

triangular of ear, 154
Fourth yentriele, 536

ala einerea, 538

area aeustiea, 538

area postrema, 538

eollieulus facialis, 538

eminentia medialis, 537

floor, 536

fovea superior, 538

funiculus separans, 538

lateral reeesses, 536

medullary strise, 538

plexus ehorioid, 539

roofof, 536, 538

substantia ferruginea, 538

tubereulum aeustieum, 538
Fovea eentralis retinae, 580

inferior, 538
reeessus elliptieus, 566
reeessus spheerieus, 566

superior, 538
Frenulum of Giaeomini, 495

oflips, 133, 365

veli, 506
Krenum of epiglottis, 409

linguse, 288, 292, 368
Frontal lobe, 449, 462

opereulum, 463

pole, 465

region of head, 117

sinus, 396, 397
Pronto-parietal opereulum, 463, 475
Fungiform papillae, 432
FuniculuB anterior, 199, 200

izj, 'S^,

rnitionliu —

graeilis, 540, 541

lateral, 199, 200

posterior, 199, 200

Kurrowed band, 533

Galea aponeuroliea, 1

.56, 158
OuiKliat«d eord of sympaihelie, 2,

23, 26, 10S, 109
Ganglion, basal, 512
eervical, inferior, 355
middle, 318

Superius of glosso-phaiyngeal,
312
eiliary, 332, 339, 341, 386. 578
long rool of, 340
short roots of, 34

commumcitionsof, 313

iirst thoraeie sympalhetie, 1 10,254

genieuli of facial, 312, 332, 333,

562, 563, 564
jugulare of vBgus, 312, 313
nasal branehes of, 393
nodosum of vagus, 313, 314, 315.

3'6, 317
orbital branehes of, 405
otie, 276, 277, 279. 293, 383. 559
pelrosum of glosso-pharyngeal,

312. 313, 317
semilunar, 2lt, ZI2, 275, 326,

328, 329, 332, 333, 385, 386
spheno-palatme, 386, 388, 392,

393. 402, 403, 404, 405
spinal, 189
spirile, 568
splanehnie, 28

submaiillaiy, 282, 284, 2S5, 318
infeiior cervical sympathetie, 317,

3'9
middle cervical sympathetie, 318,

319
superior cervical sympathetie,

312, 314, 317, 385
superius, ofglos50-pharyngeal, 312
ofvagu5, 313,315
Gemeulate bodies, 507
Genu of eorpus eallosum, 44S, 47S

of internal eapsule, 51S
Giaeomini, frenulum of, 495
Gialiella, mS
Gland, bueeal, 366
earolid, 305, 306
labial, 365
laeiimal, 13S, 334, 336, 337

Gland, laeiimal inferior, 337

supen

■,337

,366

mueous o{ Eoft palate, 3S0
subHngual, 368
duets of, 36S
submasillary, 225, 226, 368
Ihyreoid, 407
lateral lobe, 407
pyramidal lobe, 407
Globus pallidus, 516
Glo55o-epiglottic Tolds, 409, 423, 430
G-lottis, Irue, 410

pais interearlilaginea, 411

voc3li5, 407, 410
Goll, eolumn of, 199
Graeile fiiDiculus, 540, 541

lohule, 534

nudeus, 541
Graiinlationea AraebDoideales, 302,

Grey

196

OrooYe, aortie on left tung, 40
eoionary, 53, 57, 71,89,91
interveDtriculBr, 53, 63, 71
Gullel, 2, JO, 17, 23, 26, 29, 30, 31,
32.39,40,49,50.58.85.87.
09, 96, 99, 100, !01, 103, 106

Gums, 367

Gyrns or Gyri, 461, 462, 479
angular, 472, 475
eallosal. 479

eential interior, 450, 467
inferiDr. 467, 468
middle, 467
superior, 467
;inguli. 466, 471, 478. 479, 481

■, 47S

, 447- 473
euneo-lingual, anterior deep, 473
dentalus, 479. 4S3. 491, 495
Ibmieatus, 473, 478, 480
of (rontal iobe, 450
frontal, 450
inferioi, 469
middle, 4JK
superior. 466, 469
fusifbnnis, 474, 476
hippoeampal, 446, 447, 465, 474.
47S, 478. 479. 494- 495.
508
opereula. 469 ^^^^

v/^

INI»EX

Oyrut or G>*n

■- •■ t ■■ '. i",

> I ■ « * r '

•.•»." ^T' '••'i'

■ ,■ . . • • » ~ 'I

» i •"

■ ' • • i'V-

■* '^.''

;.'y ••■■■•. Xi'.

■.•,'•■■ j '"■' '• t

■ •' -■-^ - ^^ ■. ^,^

■'£':■ 'j ' •■2

.p'. .i^, r.fp* ***^

. . ■- ■ .. . i . . «^ •.

■ •, » ■ r * •" / #~* '■"•. *•"•■
■ . I i,^ ^. ,, -. . .,, - . .», ^

"i '-«.

■♦# -'

■ «.f ■ r 4— 1 ' *■',

n ' • :.■ . \'.z

'••..'■■ r- '..-. '02

T ".■ .■. ' ■. 502

Head and Neek / : 7

; .'.''/■, ::•■.;':.' ■ S "'y

. ■.. .■ .. |..... . , ^ ^ f

" ■ — 43*-
■■/i:fi.'., 2'>/

-[;'.'■>:.:■:■.: , ^^;

■ :ir'/i'] ' a;.::i. 585

' r:f :.;;:! '.;t ■.■]*)'. 20'^

' >'■■'■■■'■ =7'>

!:.' -. 117

li'/ri*.-l /' :'i'.:j 'A :.':v,'\ 1 17

i.'.'i :;-'•/■, ..'r'. '/f !:i'; rai'ial

!.'/■.■ . SV*
■.\.'.i:: '< :ii;/,i:-J r- ',:}'»:.. 265

/'•■''■ . v5'^>
l:nyi.;^., 4'^-». 410

l;i''r.^l |.;'/! ';f ii:i'i'll<; rraiiial

• ' ■'» )2.'^

■ 1 /ii'.iiii' iii, 325
iii;i.'. ilL'iiy j,'rv'-, 386
iii<,iitli ;iii'l |ili:iryiix, 364
iii«»viii'iils, 364

Ji;i ;il lo. :••, 3'^^

< :i',ili'^ .. ^S()
li-i I , I.}.'., 222
"ll'il. ^\

..,1.1. i.t ni. 353, 334
|il<", < ltf|;l;il |cj'ioll, 35^)

li II' liin- . in, {50

' •ill', I ')-'
• iiliiii.i Mll.iiy iri'i'iii, 279

■.ii iii liiii". I niii:iiiic(| iii, 279
h tii|iiii;il |(-)'/ki|i, 152, 265
Hr;irl,, .».•
.11 lidii, () ;

63. 73 "
ii'-ir.i: :w:ric:t. 70. S 3
:i '-::i .:. :■-. **l. S7

vL.;Tt. ^2

ti..*Z.r.. ^y- •»*%• •»^'

D:ri.'-TCT.:ricT:iaj etririeesi. 69. 71.
73. 7Cl S3. 92

•■uudit. 74, 85, 03

:•■>>]:] on of. S7

riii^. 93
LiriuaD. 30. 34- 53- 54- 65, 6S,

74- 76: ^o
d{xtrttfn. 65. 66. 6S, 74

rinii.lrtini, 6S, 76. &4, S9, I02,

104

rKHr-i^iein, S9

'■■ri riees of, 92

a:ri :»-vtri:riciiiar fibrousrings.93

r.Sre^ rif airia, 92

:.-jric]ej-. 55. 65. 76, S4, 89, 98

':.'2i.e. ^o

':.icus>7'id valve ■[milral , So

l-:^r'ier, ltf:, 55

chor5:t lendine.-e, 73, 74, 79, 80
eonus aneri-:)5u>, 30, 39, 54, 70,
72. 74. 7S, S4

e.ronar}' ?inus. 6S

5Uj.u>, 53. 57. 71, S9, 91

valve of, 69
erista lerminalis. 65, 66
cn'Jocardium, 92
epieardium. 92
ex:ernal form, 53
foramen ovale. bS
foramina venL\: minimee eordis,

64, 69, 92
fo5sa ovalis, 6S, 69
general relations, 50
£;reat sinus of aorta, 84
ineisura eordis, 53, 57
infc-rior lungitudinal surface, 58
inieratrial suleus, 89
limbus fos.<n: ovalis, 67, 69
mitral valve, So, 92
moderator band, 71, 74
museuli papillares, 73, 79, 80

peetinati, 66, 91
myneardium, 92
ne'rves, 33, 43, 65, 7S, 85, 87, 89,

96. 99, 100
orifices. top^graphy of great, 87
pars membranaeea septi, 74, 83

pulmonary oriflce, 71, 72

cu3psofvalve, 75

lunuke uf Ihe valve, 75

nodules of the valve, 75

sinus, 75

lopography of, 75, 87

vaW, 75, 78
semilunar va[ves, 73. 7«, 81
septum atriorum, 69

venlriculoTum, 71, 73, 78, S2
sinus venosus, 34, S4, 66
sulcusanteriorinler-venlriculs[,7l

letminalis, 34, 54, 63
supra-ventricular ridge, 72
surfiices, 53, 56, 5S

diaphragmatie, 5S

sternoeoslal, 53, 56
lopt^aphy, 57, 75, 94
liabeeulee earneie, 72, 70
trieuspid valve, 66, 73, 83

eusps of, 73
tuberele, intervenous (Lower), 67
valve of the eotoniry sinus, 69
viilve of the vena cava (Eus-

taehian), 67
Tentriele, I«ft, 79

cavity, 79

fibres of the ventricles, 93
TBntriele. right, 70, 74

cavity, 72

eonus arteriosus, 72

ventricles, 34, 53. 55, 70, 74. 79

vessels. 63, 64, 76, 78, 85, 87

wall, 92
Helieotrema, 568
Helix, 158

erus, 153

fossa, 154

pioeessuE eaudatus, 155

spine, 155
HemiBpbsre, eerebellar, 529

eerebral. S^e Gerelial henii-

Hesehl, sulei of, 475

Hiatus semilunaris of nose, 397. i^

HippoeiimpuE, 491, 492, 493, 497

<iiEilations, 491

minor, 494

pes, 49:

t^nia, 442, 447
Horner, niusele of, 121
Hyaloi<l eanal, 581

membrane, 581
llyparterial hronehi, 10, 38,44, ;o

Incisive bundle, Uj, 133

pad, 133
IneiBUTa eardiaea, 53

inleitiagiea, 154

ternporalis, 465, 475

thyreoidea, 423
Ineus, 556, 557

body, 556

erus, long, 536
shoit, 557

ptoeessus anlieularis, 557
Inferiur eorpus quitdrigemiimm, 530
Infia-oibital plexu5, 12S, 129, 389
Infiindibulum of brain, 2o8, ai8,
453

of hypophysis, 505

ofnose, 397

lUBUla, 450, 475, 476, 477, 490,
57S

opeieula of, 477
Interartieular meniseus, 113
Interattiai suleus, 8g

Iiiler-ebondial ariieulations, 113
Intereostal membianes, 4, 108, 109
Intemal aeusite nieatus, 566
etipBUle, 501, 515, S16, 51S
anteriot limb, 518
coune<:tionsof, 518,519
genu, 518
posteriot limb, 518
eai. 546, 565
Interpeduneulat fosss, 452
Intervertebral libro-eiililages, 112
[nlumeseentia cervicalis, IB7
lumbalis, 1S7
I'is. 571.574.576.577,578, 579
tsland of Reil, 477
iBthmus of auditoiy mealus, 548
of nuditory lube, 3S4
of fauces, 368, 369, 37S
of Eynis einguli, 478. 479

rotnieatiis, 478
of limble lobe, 47S
of phaiyiiii, 376, 377
o! thyreoid gland, 229, 320
of rhombeneephalon, 536

jBCobson's nerve, 312, 563
JoiiitB, atlanto-epistropheal, 363

Ettlanto-oeeipital. 361

eapitular, 113

in:'£x

^tnl !Cjc:i£ of meseneephalon,

«^i'

T -:

i:.>. »:■:
"■ z "'. Ti" _?. *:*. ^:*-

Licn=.»I iJ::>. ::-. :;>. :.::
^... .. .. .«.. «•

^^« . .««. .^-
>_:r.r. :. ;;-

I ^*. : .1 7. .1 ". .".:■. n '. i*> . - rc

T a'»'*iift • . • "- " -' i » iN • • ■ • z •

- '■■ » . ■ - ■ " - • i C • .N

-, ^•-■•" •' - ' ■ N.* ^ ■' •■•■"::■". C~'

^_- -^- *•■■ *■ ~l*^

>; .r-'.i». 5'''"
!..■;::.;:..■• :..-.■ ._'.iir\". 57^''
L&ryiix. 4:0. 41-^

.';::.:> l.'iryr.j::>. 37 S. 4-"'>- 4CO

-• • • r.il c r.^tr^-eti.'r.. 407
i.-l ■"i-. 410
iii'- li-r. 4^'';
iiiu. 'iii-. iiiviij':'r.in'.-. 411
I.'..itiiiii. 4'' »7
( ii|i> ii"i .i|" rtiirt.'. 4^
V' iitii' 1» -^ "1'. 4I-
•.■. •.nl.iili-, .jf»7
V... .il < ■ipK. 410
I.oUrpl ReeeBBeB n{ fi..urih ven-
iii' 1. . S;'»
..( |.)i.iiy»x. ^7<'

1 TeBHielM. 4S5, 502
zz.:tr.:-: b.ms ::. ^85, 487
:tT.--i: pir. of. 4S5. 4S7
r:-^ 4^r. 490
*:er.-z}-r'-i c:'. 4S5

i-:*=r::'T hMiss of, 483, 484^

i>5. 4^:, 490» 491

7»:r5:£n;T boms of. 4S3. 484,
4>?. 4S6, 4S7, 490
7Jir> rrr.:rar.^. 4SS

51^- 545
-.:tzT^. 544
litml. 512. 545
=.=■1:-:. 512. 52S, 545

i>;

r- ;■!.-".- ;:'. 5S2, 5S3

rr-niri- ••^^ '^''« 5S4

--r'.iiis c:". 5^4

?->7eri.;n- ligan:en;. 5S2, 5S3
L4r.i:r-lir g:a::giion. 332
L^z.i::— . --deus. 514, 515, 517,

L-.vi::i Tu'.i::. 547
Tiif«Tnwm ~::(-$£oiy atlanto-epis-
:r:pbeil. 362

ilir e7:>:r:pbeal. 364

i.ir:^. ^04

i7.: £ rl : r cos:o - transverse, 1 09,

i7.:er::.r ];r.g::uiinal, 115, 357,

9 m m • —

wk. -....> v.e...:>. 3^3
i:".ir.:>-:p:5:ropbeal, 362, 363
i::i7.:o-occip::a.l eapsular, 361
::"iui::or^- ossieles. 557

i'JriCuliT. ly\

c-r::'»:lar, 112

::'7.7.ec::7.g a:las. epistropheus,

.in^: oeeipital lx>ne, 360
cr"j::i:'.:m transreTsum atlantis.

'D2

cr:co-:h\Te».^id, 220. 230, 297
eri::^- :r,\cbcal, 427

.•»"■'*■ ^ •■- ■'■« ^ri> ^fi ^

cr,:> >-;.-< rius of, ^6^

ir.lerius. 305! 413, 415
ep: v;l vV, t ii^ e.in . 423
o:" epii^Kr.iis, 423
n.nM. iSi. 35S. 360
hyo-epii:Kviiic. 423
ilio-lumlvir. it^
o{ ineus, 557
inierspinous. 359
interiransverse! 116. 359

intecvertebral, Il6
libro-eaitilage, ii6
annulus iibrosus, il6
nudeus pulposus, Il6

of malleus, a " " ' —

ofiii

*. 557

lateral, 557
" -■. 557

mediii palpebral, I3I, 134, 136,

140. 337
of neek of rib, 114
oblique of allas, 181
oeeipito-atlantal, 362, 363
of pmna, 153
pterygo-mandibular, 463
pulmonary, 14, 16, 35, 43, 70
posterioi costo-transvetse, 115
postetiot longitudinal, ll^, 182,

357

ofstapes, 557

o-tuberous, 178
spheno - mandibular, 268. 269,

270, 271, 272, 277, 278
sterno-ebondral, 113
steino-cIavicular, 243
stemo-eostal tadiate, 113
sterno-perieardiae, 50
stylo-hyoid, 286, 287,290, 292,296
stylo-mandibulat, 237, 263, 271,

supraspinaus, l65, 173, 181. 359
suspensory, of aiiis, 363

of lens, 583

oforbit, 349

of Loekwodd, 349

□f eyelids, palpebral, 12[
tempoio-mandibulat, 271, 272,

273
thyteo-epiglottie, 40S, 420, 423
thyteo-hyoid, median, 413

lateral, 413, 414

of the neek of the rib, 115
transverse, ofatlas, 362

of tbe tubeteles, 114
upper transverse of seapula, 164,

pulmonis, 14, 16, 35, 43

nueha;, 172

peetinatum tridis, 574, 584

Ligamentum ventriculare, 410,

Ligamenla fiava, iSl, 358, 360

Ligula, 53 1

Limbie lobe, 478

Limbus fossie ovBlia, 67

Lines splendens, 1S6, [SS

Lines of pleural retleetion, 14, 17,

iS, 19
Lingual glands, 283, 434
Lingula, 529, 535
Lips, 365, 366
LItbt, eaudate lobe of, 104
Loba or LobeH, of eerebelluni under
surface, 533
eential, oreerebeUum, 531
of eerebruai, 462
alie of, 532
eerebeilai, 531
eetebial, 462

montieuli, 532

eulmi

'. 532

ofcU¥US, 532

of eulmen, 532
fiontal, 449, 462
ii,..l.r, ,6»
limbie, 478
Lobus tuberis, 534
eulminis eetebelli, 532

i. 53Z

folium

'. 53^

graeilis, 534

semilunaris supeiioi, 532
Iiobe or Lobes, o^ lung, 41

ofnodulus, 533

oeelpital, 450, 462

olfactory, 462

parietal, 450, 462

of pytamid, 534

pytamidaJ, of thyteold gland, 321

subslantia peribtata anlerior, 462

semilunai superior, 532

lemporal, 450, 462

of tuber, 534

of uvula, 534
Lobale or I^ibiileB, blventid,
533

eenttal, of eerebellum, 531

ereseentie, anteiioi, 531, 532
posterioi, 331, 532

ofeai, 153

giaeile, 534

pataeeDttal, 449

parietal, 450 '^ ,

6oo

INDEX

Lobule or LobnleB —

)i.iri(.t.il indrior. 471. 472

>uiKri »r, 471, 472
j iiHii-ii.ir siijii;ri'ir. 531

«iu.uli.iu-. 532
I."iU's i--itu]l-us. 537, 545
Knn^ituilin.il l)un<i]c, medinl, 51 1

>.i^iii.il, infcriitr. 217
su|K*ri«)r. 207
LuniU>-iU>rs.il fascia, 166, 167, 16S
Lung. 17, 35

auriie grm»vi.*. 40

ajir\, 17. 30

a/yj;'»> ijriMivo. 40

l»asi-, 3(>. 37

lH)r»iers, 30

l>ronchi, 22

tlitlerenees l>ctwocn right and lcft,

ti>sNuri->. 41

hiUiN, 3S, 4»!. 44

iiu'i^ura «\nili.u*a, 42

iiiiioniinatt.' i;ri) >vi-. 40

li^ainenluin ]iulni>>nis, 33

lttl)L*s, 41

l>cilic]<.". 14, 42, 43

root, 42, 43

.sulK*lavian j;roovo. 36, 40

surfaci'S, 30, 37

sulei, 40. 42

Lunuhe, 75

Lymph duet, right, 4S, 107

Lymph glands, apieal of l<>ngiie,

434 .
hronriiial, 22, 43, lOeS

hui'i-al, 133

ccrvii:al, 14O

upj)cr (U'ci), 232, 201, 308
inlereostal, loS, 256
niasloid, 154, 15S
niediaslinal, 10, S9

antcri()r, 7, loS

j)()Stcrior, loS

sui^erior, loS
c)ccij)ilal, 158
I)aroli(l, 15S, 260, 366
spaee, periehorioidal, 578
sternal, 107, loS
sul)maxillary, 225, 230, 2S3, 366
subniental, 228
suj)raclavicular, 147
of thorax, 10, loS, 257
thor.acic visceral, 257
l.ynij)li yessels of lips, 366
vcsscls, inilmonary, 38

Lymph tninks, Icft eommon jiigular,
106
left subclavian, 106
right jugular, I08, 257
right subclavian, 108, 257

Lyra, 498

Maeula lutea, 580
Magendie, foramen of, 539
Malleus, 552, 554, 555, 556, 557, 565

handle of, 549, 565

head, 555

lateral proeess of, 549

proeessus lateralis, 554, 555

anterior, 555, 556, 565
Mammillary bodies, 452, 453, 497,

503, 504
Manubrium, 549, 554, 555, 557

Marshall, oblique vein of, 90

vestigial fold of, 90

Mastoid antrum, 565

air eells, 555, 559, 560

MeatUB, extemal, aeustie, 259

intemal aeustie, 562, 563, 565, 568

nasi, 397

inferior, 399

middle, 397

superior, 297

naso-pharyngeal, 400

MediaBtinal lymph glands, 10, 89

pleura, 14, 23, 25, 33, 46, 49, 50^

70, 76, 77, 84, 85, 87

spaee, 14

Mediastinum, 10, 44

anterior, ii, 45, 46

inferior, 10, 45

middle, ii, 45

posterior, i, ii, 26, 30, 45

superior, 10, 45, 46

Medulla oblongatB,, 520

antero-median groove of, 521.

anterior area of, 522

eentral eanal, 521

elosed part, 520

deeussation of pyramids, 520,

522

external areuate fibres, 438,

528

floor of fourth ventricle, 526-

528

formatio retieularis, 510, 543,

545
toramen ca;cum, 521

fossa rhomboidalis, 536, 537

funiculus euneatus, 525, 526

graeilis, 526

Hednlla oblongata —

Tunieulus lateralis, 525
of Rolando, 526

erey matter, 540
intermd slrueture, 540
lateial area of, 524
lemniseus et traetus eerebello-
spinalis, 512, 535, 545

olivary eminenee, 525, 526, 528
open patt, 536-539
origin of neives, 522
posleiini aiea of, 526

median tissure of, 521
pyramidal tiaet, 522
pyiatnids, 532, 528
laphe, 540, 542
restiform body, 525
sttuctuieof, 540,541, 542, 543
tubeiele of Rolando, 527, 5ji
white mattei, 540
Hedulla apiiuilis, l36, 1S7, 194
differences in suriaees, igt

inteinal stiueluie, 194
grey matter of, 196
white mattei of, 199
Medullaiy eentre, 461
extetnal, 576
inteinal, 576
laniinee, 516
ve]a, 535
Meibomiaii follides. See Tarsa!

glands
Hembtana ehoiio-eapillaris, 579
Aaeeida. 556
tympani, 556
Hembtaue, eiieo-thyreoid, 297, 41 S
anteiior, 360, 361
eosto-eoiaeoid, 161
tlaedda, 553, SS4
hyaloid, 58 1
inteieostal, anterior, 4
poslerior, S, 29, 109, Uo

of Shiap'neU, 556

posterior atlanto - oeeipital, 179,
iSi. 355. 360. 361

leetoria, 362

Ihyreo-hyoid, 229, 243, «96, 413
417

tympanie, 270
HenlDseB of biain, 201, 414

of spinal meduUa, 183
Meseneephalon, 459, 506, S20
Middleeai, 546, 550

Mittal valve, 80, 92
Moderator baiid, 71, 74
Modiolus, S6S
Molni salivaiy glands, 133
Montieulus uf eerrbellum, 529
Morgagni, sious of, 372, - "

Mot

1. 542

ioof, 36K
tongue, 431
vestibule, 304, 366
Mueo-peiiosteum of nose, 400
olfactory r^ion, 400
respiralory legion, 400

UaEele ot Uuseles —
angular head uf quadrate musele,

124
antitiagieus, ISS
ary-epiglutlicu5, 415, 416, 429
aiytienoideus, 429
obliqiius, 415, 416
ttanEversus, 415, 416, 417, 420,
429

penoi, 154

■ 27, 131, 261,
370, 277, 37^. 373
eamnus, 123, 128
ehondro-glossus, 435
eiliary, 57=. 57S, 5^3

ofeyelid, 376
eonstrietor, niiddte of phaiynK,
234, 281, 290, 291, 297, 303, i
, 315. 37>,372. 373
inferioi of pharyoK, 234, 346,
303.314.315. 371. 372.413.
superior of pharynK, 132, 289,

297. 299. 304, 3". 371.373, '

. 373. 382. 383 I

cnco-aiyla:noideus lalemHa, 415, '

418, 419, 422, 429

posterior, 415, ^rB, 42?, 429

erieo-thyreoid, 330, 314, 413, 414, j

417. 429
depressoi septi nasi, 123
digastrie, 230, 238, 2S9. ^*. 264,
274, 278, 2S0, 2S1, 282, 286,
294. 297. 300, S^i. 305. 306,
307. 3'6
ddatatoi pupaUe, 578
tubee, 384

of«

IS4

^0 2

INDEX

Musele or Mnielet -

•#f «-ar, i:.'T::,'.].- . 155

• |#i' rai.i it, 122

<il !)•■, laN-ral r- " .-. 355. 34O-

Ul. iM- >45^ 34^- 339-

'>:ili-iiiii

^:ij»«ri'>r ij{ eyt, 35

ii7. 33^. 34^^ 342, 34^J.

i4H
iii'di.il rtrtus, ^O, 344, 346

oliliijmi.» iiif«-ri'^r of eye, 341.
i4S. W>. 34«

ii| l.li <-, 1 2()

liMlil.tii ., I 22

i;< iiKi (•J<...u^, 2X5, 2S6, 2S7, 288,

J«^i. -•(>i, 292, 454. 435
j;i iii.i li)..i.|, 2K5, 287, 29^^
l'l.i-. ... ji.il.iliiius, 3S1, 3S3
i'lul • u . iii.i\iiiius, 17S
li< li< I . iii.(|<)t , I 5^

IIIIIIOI, I<^<^

liN..i;l...-ui-., 2\i), 2^1, 2^4, 2S1,
'-•.S.', jS.|, ,!Ss, 2SO, 2S7, 2S8,
-•S.;. .•(><•, 291, 292, 310, 311,
i>". 4vl. 435

llli. i ii-.l.tll-., !(.()
I i'l \ h I-., I (ti)

ili.iM. i(..). lys

luinl •> i| UUi . l(ii)
iii. 1 .1 N u .. l ' \, l \\
iiili I li\..i.l. -• Hi. -•.|.*, J.\\, 2.J4

iiiii i..i l.ii.il lii-.ul ol (jua(lratc
iiiu .. I.-. 1 -•.!

inl. I ii . I- . .. M II. l '/■/

inl I I . i. .1 .1 1. I , |i II)

I n I . I ■ 1 . 11 1 1 1 . . , 1/(1, 1 / ■/

inl. I 1 1 in .\ , I ..ili-., 1/(1, 177» 353»

» '1 ■»
. .| I I \\ in. '\ I in>nl-., .' \\
.'I I II \ lu'.il in.>\ i-mi"Ht-., .J2()
I t. I iin.ili'., I .' I
I il I , .iinir. «I>.|M, ;, 1(1,*
li \ ii . >i i'.tliil I, ;. 1 1

f\ III, lul \ lli\ i..i.li-.\-, .'.'»), 321

|> ll|.. I«l »• •.U|«i"l i.u u., l \S, I 3^>,

... ... ..^1 ,»•» ••V .^i^

» \ I . t \Si \ v'> \ \, • ,\.>'^« .\.>*'.

\|«'

■.. .ii'ul» . l J«). l Si», l(>.*, 23S,

•|». .i-'3
\.li j.,i|,tluu, 3»>-/. 373, 3S2,
•s ' 'S I

li\.il..ii'. \ ii'.l.ii um, 1 /7
liu};u,tK-., .'«)»». 2^)2
l»>nj;issiuius, !()()

i'a|>itis. loS, 170, 3i)(>. ]^l

loogisssmus^ eenrids. 170

dorsL 169, 174
l'^agitadiiia] of t(X^e, inferior,

292.435
^upeiie.r, 434, 435, 436

obliqinu eapstis snperior, 168,

171, 179, 180

enernns abtiominis, 3

eapilis iiifeiior, 174, 179,

180

of orbil, 546

intemiis abdominis, 167

oedpitalis, 156

superior, of neek, 180

of orbit, 338

longus eapitis, 246, 308, 351

eoUi, 102, 106, 241, 246, 251,

322, 351, 354
masseter, 126, 127, 259, 261, 265,
266, 270, 274, 276, 277, 283,
298, 302
mentalis, 123, 133

levatores eostarum, 177
of mouth, 123, 132
multifidus, 176, 177
mylo-hyoid, 230, 270, 274, 278,
280, 282, 284, 285, 288, 290,
300, 316
nasalis, 123

pars transversa, 123
pars alaris, 123
naso-eiliary, 336
ofnose, 122
ol)lique superior of head, 354

inferior of head, 354
oblieiuus aurieulae, 155
omo-hyoid, 146, 150, 161, 164, 234,
238, 242, 244, 246, 290,

413
orhieularis oris, 121, 122, 123,

132, 136
oeuli, 121, 134

orbital part, 121
palpebral portion, 121, 134
lurs laerimalis, 122, 136
I^alato-^lossus, 434, 435
I)harynjro-palatinus, 303, 369, 378,

38 1, 382, 383
IH'otorales, 3
l)latysma, 120, 126, 127, 143, 161,

260, 274
l)rcvcrtebral, 351
ptcryj;oitl, external, 267,268,269,
270, 271,273,274,275, 276,
277, 278, 546

■tuele or Hiuelei —

pterygoid, intemal, 259, 263, 267,
269, 274, 275, 276, 278, 281,
282, zi83, 289, 293, 298, 299,
373. 546
ptoeenis, 122, 123
quadrHtus latni iiiferionS, 12J. 125
lumboium, 167

labii supeiiotis, 123, 124, 129,
387
angular head, 12$, 12S
Lntia-otbital.head, 125, 12S
zygomatic head, 125
reetus abdominis, 3
eapitis mteiioi, 238, 34], 308,

35'
eapitis lateralis, 238, 141, 30S,

353
infeiioi, 344
1aterali9, 304
lateralis of neek, 345
medialis, 344
postetioi major, 179, iSo
posterinr minor, 180
superior, 324, 325
ihomboideus majot, 164

minoi, 164
risoiius, 123, 125. "6. 2^
lotatotes spin^, 176, 177
saeio-spinalis, [69
satpingo-phaiyngeus, 3S1
sealenus anterioi, 34. 106, 235,
238, 242, 246, 247, 248. 249,
251, 252,255,257,259,309.
322. 323. 354
medios, 149, 161,238, 241,257,

323
postetiot, 149. 323
semispinalis eapitis, i.^, 16S,
170, 171, 172, 174, 178
ceivids, 171, 172, 174. 176
dotsi, 171, 176
serralus antetioi, 3, 149. 161
posteiioi, infeiiar, 164, 165,

166, 167
postetior, supeiiot, 164, 165, 168
sphinetet pupillie, 578
spinalis, 169, 170
ceivicis. 170

tapedius, 551, 554, 555, 558
tetno-hyoid, 46, 47, 48, 239, 242,
243. 246, 250. 296. 3'6.4J4

HuMl» «r Klsdl»—

245, 25°. 25I1 259, 261, 281,
296, 300, 304, 31S, 323
sterno-ma.&tDidstiiictures,l)eneaIh

sterno-thyreoid, 46, 47, 4S, 239,

243. 244, 246, 250, 434
slylo-glossus, 285, 2S6, 287, 289,

290j 299, 413, 434, 435
slylo-hyoid, 230, 259, a6a, 263,

280, 2S1, 282, 284, 2S6, 297,

29S, 305. 3°7. 4"3
stylo-pharyngeus, 294, 295, 299,

303. 373. 381
subeostiLlis, 29, 306

subseapularis, 16
.upia-troehleat, 336

5Upta-i

1.336

temporal, 265, 266, 267, 269, 270, '

274, 27b, 277
tensoi veU palatini. 274, 275, 293 ■
tarsi, 121,373,382, 383,384,404 I
lympani, 293, 312, 549
lhyteo-arytafnoidens, 417, 419, ,

422, 429
thyreo-epiglottieus, 418, 422
thyreo-hyoid, 231, 234, 243, 244,

296, 3M, 413 ]

tragieus, 1"-

19 abdon
155

Ihora

,167

!, 5°

trapeiius, 162, 241, 315
iriangularis, 123, 125, 128, «g
of tympanie cavity, 558
u«ulfc, 3S1, 383
vertical, ortongue, 435
vocales, 415, 41S, 419, 422, 429

lygon

i, J23. 1

t, 129

Museular triangle of neek, 222, *a6, .
232. 233. 359 I

Myoeaidium, 92 [

NarBB, poEterior, 374, 375, 377. 389 ■
t!a.tal eaitilages, 140
eayities, 393

antetior apertures of, 393
pirt, 393

eonehiE, 395

Hoor, 394

lateml wall, 395

postetior apeituies of, 393. 394

toof of, 393 -^^^m

6o4

INDEX

Nasal foB8a, 393
atrium, 395
c«mch:i;, 396, 397
infori«)r meatus, 399
infun(lil)ulum, 397
lateral wall, 395
middle meatus, 397
olfactory part, 400
reeessus spheno - ethmoidalis,

399
respiratory part, 400

suiKirior meatus, 397

vestibule, 395

Nasal septum. 391

eartilage of, 391
eonstruetion of, 391
olfactor\' area of, 390
respiratory area of, 390
vessels and nerves of, 392
Nasal yestibulum, 395
Naso-laerimal duet, 140
Naso-pharynx, 375
Neek, 141

anterior triangle, 226
deep disseetion, 294
digastrie triangle, 226
earotid triangle, 226
fasci%, 224

infra-hyoid region, 227
joints, 356
mid-line, 226
museular triangle, 226
oeeipital triangle, 168
posterior triangle, 142
side of, 142

submaxillary triangle, 226
submenlal triangle, 226, 227
supraclavicular region, 224
suprahyoid region, 227
surface anatomy, 224
Nerve or Nerves, abdueent, 212,
215,218,327, 330,345, 346,

386, 457
aeeessory, 145, 146, 150, 162,
213, 218, 232, 235, 239, 262,
281, 300, 304, 307, 309, 310,

3f2, 313^ 315» 455, 456
aeromial, 182, 228
aeustieus, 213, 215, 218, 456,
562, 563, 565
eoehlear division, 565
vestibular (livision, 565
anterior eutaneous, 4, 1 10
anterior tboraeie, 160
alveolar inferior, 267, 268, 276,
277, 278, 279, 293

Nerye or Neryes —
alveolar superior, 388

anterior, 388

middle, 388

posterior, 388
aortie, 100

aurieular of aurieulo - temporal,
277

great, 126, 143, 145, 146, 151,
156, 235, 239, 241

of great oeeipital, 156

posterior, 154, 156, 157

of small oeeipital, 239, 241

ofvagus, 312, 313
aurieulo-temporal, 127, 156, 261,
267, 274, 276, 277, 293

branehes of, 277
axillary, 160
to azygos uvulae, 383
braehial, 109, 147, 157, 160,

323
bueeinator, 128, 134, 267, 268,

276, 277

of facial, 126, 128

of sympathetie, 314
eardiae, 30, 33, 65, 87, 89, 250

inferior, 319

middle, 318

of vagus, 30, 33, 87, 89, 99,
100, 250, 314, 315

superior, 317, 318
earotie external, 317, 318

internal, 317, 318, 385
earotieo-tympanie, 312, 386
eerebral superficial origins, 454
cervical, 353
cervical, first, 353, 522

anterior branehes, 324, 325

loop between first two, 353

posterior divisions, 162, 173,

174
ehorda tympani, 549, 551, 552,

565
eiliary, 141, 149, 161, 578

long» 339» 340
short, 341

clavicular, 274, 278, 290, 293

eoeeygeal, 178

eoehlear, 565

eommunieans hypoglossi, 308, 316

eommunieating of 9th to 7th,

eommunieation of hypoglossal,

316
eords of braehial plexus, 160
eranial, 123, 456

Harre or NarreB-^

CTaiiia.l, super^al origin of, 454,

45S. 456. 457. 458. 459
eutaneous eolK, 143, 145, 151,

124, 235, 339, 241
deseendens hypt^lossi, 239, 243,

305
deseending of cervical plexus,

143
to digaslrie, 267, 26S, 276, 277,

278, 279, 293
dorsal, posteiior divisions of, 174

seapular, 147, 160, 164, 323
ethmoidal, 344
anterior. 340, 402

medial nasal, 393

■; 340

long thorade, 323
of &ce, 126

facial, 213, 215, 218, 263, 2S1,

a82, 313. 338. 456. 457- 557.

558, 561,562, 563. 564

bueeal branehes, 127, 12S, z6i

cervical brauehes, 127,1261, 294

division, 184, 19S, 262
cervico-facial division, 26:
eommunieating branehee of,

facial, eommunieating with iiuri-

eulo-lemporal, 277

of gteat aurieular, 126, 146,241

intrapeUous part, 562, 563, 564

mdibutar branehes, 127, 12S,

museular to ^tylohyoid and

digastiie, 262, 281
posterior aurieular, 262, 301
seiisory root, 215
super(icial origin, 4 58
lempord branehes, 127, 128,

137, 156, 261
temporo-facial divis!on, 261
lygomatie bnnehes, :27. 128,

137,261
frontal, 330. 334, 336, 346
glosso-pharyngeai, 213, 215. 218,

277, 281,286,304,306, 307,

309, 310, 311, 435, 436,

455
ganglion, bUpeilus of, 3II
hngual branehes, 311
pettous ganglion, 312
supeiBeial origin, 458, 522
tynipanie braneh, 312, 563
of beart, 33, 43, 65, 78, 85, 87,
89, 96-99, 100

EX 605

Kwn or NerrM—

hypoglossal, 213, 215, 218, 220,
231, 232, 233, 244, 281, 282,
284, 285, 287, 288, 290, 291,
292, 294, 300, 304, 305, 306,
307. 309. 310, 314, 3'fi, 3'7,
35', 355-435,436,455.52*
superficial origin, 457, 522
ineisor, 279
infia-DiandibuIar, 164
infia-orbital, 128, 120, 13S, 3S7
nasal branehes, 12S
oibilal branehes, 12S
palpeliial btanche5, 12S
pleius, 12S
infia-trocblear, 137, 138, 340
intereostal, 28, iio

intereosta-braehial, 110

of JacobEon, 312, 563

labial, 129

laerimal, 137, 138, 330, 33S, 336.

346
latyngeal, cxtemiil, 232, 234, 243,
295, 3"4
infciior, 315,372, 413, 421, 422
intemal, 232, 295. 304, 314,
372. 413. 421, 422, 435, 436
larytieal, leeurrenl, 2, 33, 49, 7B,
87, 89, 96, 100, loS, 245, 946,
aso, a57, 258,314,315,421
superioi, 232, 295, 304, 314, 318
mlernal braneh of, 421
laryngo-pliaiyngeal, 317, 318
laleial eulaneous, 4, 6, ito

nasal Df inlem^ ethmoidal, 481
to levator palati, 380

scapul[c, 151
lingual, 267, 274, 276, 278, 279,
2S2, 2S4, 285, 2S6, 288, 2S9,
290, 292, 293, 434, 435, 436,
565
bianehes Df, 2S9
of nintb, 314
of vagus, 316
Iting thotaeie, 160
lumbar, 150, 166

posterioi (livbions af, 171;
malar, 261, 263, 265, 347
mandibular, 212, 274, 375 -27S, 393
raasseterie, 267, 276
masloid. 110, 136
niaKillaty, 212, 403
niedial eulnneous, of — ■'"
offorearm, 161

6o6

INDEX

Nenre or NenreB —

meningeal braneh of trigeminal,

327, 330» 385
of vagus, 313

of hypt^lossal, 316

mental, 128, 129, 279

mylo-hyoid, 230, 276, 278, 281,

284

museulo-eutaneous, of arm, 160

nasal of anterior superior alveolar,

401

cxternal, 341

internal, 341

of infra-orl)ital, 129

posterior inferior, 405

superior, 401, 402, 403

naso-eiliary, 140, 330, 339, 340,

341» 345» 346, 386
palatine, 392, 401, 402, 403
oeeipital, great, 156, 161, 162, 174
small, 143, 145, 146, 151, 156,

239, 241
smallest, 156, 161
oeulo-motor, 210, 212, 218, 326,
327, 330, 331, 332, 335» 338,
345. 346, 347, 386, 446, 458
nueleus of, 509
oesophageal, 99, 109
, 'olfactory, 208, 218, 392, 401, 458^
TCrt)mb-hyoid, 146, 150
ophthalmie, 212, 386
optie, 208, 218, 339, 341, 458,

572
superficial origin, 458
to palate, 380, 383
palatine, anterior, 402, 403, 404,

405
great, 380

middle, 383, 404

posterior, 383, 404

small, 380
palpebral, 129, 138
parotid, 277
perieardiae, 34, 99
petrosal, external superficial, 318,
333, 386, 564

great deep, 333, 386, 405, 564

great superficial, 212, 332, 385,

405
small superficial, 333

pharyngeal, 311

of pharyngeal eanal, 405

of glosso-pharyngeal, 295, 315

of sympathetie, 315

of vagus, 295, 304, 306, 314,

315, 383

Nerye or Neryes —

phrenie, 2, 10, 23, 25, 30, 33, 34,

43» 49, 50» 70, 87, 88, 89,
239, 240, 241, 250, 251,
253» 254» 255, 257, 258, 309,

323
pneumogastrie. See Nerve, Vagus
long thoraeie, 147
pterygoid, 293, 333
of pterygoid eanal, 386, 393, 405
pulmonary, 43, 99, 100, 10 1
radial, 160
roots of aeeessory, 522, 526

glosso-pharyngeal, 522, 526
vagus, 522, 526
saeral, 177

posterior branehes of, 177
to sealenus medius, 151

posterior, 151
ofscalp, 156

spheno-palatine, 388, 403
spinal, 5, 189, 192

anterior primary divisions, 109,
192

elassiheation, 189

exits from vertebral eanal, 190

ganglia, 185, 189, 192

origin from eord, 189

posterior primarydivisions, 173,
174, 178, 192

roots, 185, 189
spinal aeeessory. See Aeeessory

aeeessory part, 215

spinal part, 215
spinosus, 275, 333

to external pterygoid, 277

to internal pterygoid, 275, 276
splanehnie, 26, 28, 32, 70

great, 28

lowest, 28
to stapedius, 564
sternal, 145
stylo-hyoid, 230, 285
to stylo-pharyngeus, 311
to subclavius, 147, 161
sub-oeeipital, 172, 173, 179, 180,

190
subseapular, 160

supraclavicular,of braehial plexus,
145, 149, 161

of cervical plexus, 143, 151,
161, 239, 241
supra-orbital, 121, 137, 138, 156
supra-seapular, 147
supra-troehlear, 137, 138, 156,
340, 344

INDEX

607

Nerye or Neryes —

s^nnpathetie. See Sympathetie

temporal, of aurieulo - temporal,
277
of bueeinator, 277
deep, 267, 276
of facial, 137, 156, 261
of orbital, 334, 350, 388

to tensor palati, 293
tympani, 293

thoraeie first, 109, 254, 257

thyreoid, 318

thyreo-hyoid, 316

tonsillitie, 311

to trapezius, 151

trigeminal, 212, 218, 329, 330,

457, 529
mandibular division, 329

maxillary division, 329, 330

motor root, 215, 329

ophthalmie division of, 326,

327, 329, 330, 336
roots of, 328

semilunar ganglion, 211, 212

sensory root, 212, 215, 328

traetus spinalis of, 527

for temporo-mandibular joint, 277

thoraeo-dorsal, 160

troehlear, 211, 212, 215, 218, 326,

327, 330, 332, 335» 336, 346,
386, 446, 457, 506, 530
roots of, 538
superficial origin, 457
tympanie, 312
ulnar, 160

vagus, 2, 10, 23, 25, 30, 32, 33,
35» 49» 89, 100, 106, 108,
213, 215, 218, 232, 239, 245,
252, 257, 258, 300, 304, 307,
309, 310, 312, 313, 315, 435,
456
ganglion jugulare, 313

nodosum, 313
left, 30, 99
right, 23, 99
superficial origin, 455
thoraeie branehes of, 99
vascular of hypoglossal, 316
vestibular division of aeustie, 565
zygomatic, 334, 350, 388
zygomatico-temporal, 156, 266,

267, 350
-facial, 350
Nietitating membrane, 120
Nodule of eerebellum, 533
Nose, eartilages of, 140, 391

Nose—

eonehse of, 401

fossse. See Nasal foss3e

septum, 390, 401, 402

vestibule, 390
Nostril, 390
Noteh, preoeeipital, 470, 473

of Rivinus, 553, 554
Nneleas, amygdaloid, 491, 494,

512, 514
auditory, 538
eaudate, 488, 489, 491, 494, 502,

512, 513, 514, 515, 518, 538
eoehlear, 512
euneatus, 527
dentatus of eerebellum, 450, 454,

512, 514, 515, 517, 518, 539
glosso-pharyngeal, 538
graeilis, 527, 541
hypoglossal, 537
of lens, 5S4

lentiform, 514, 515, 517, 518
oeulo-motor, 509
olivary, 543

aeeessory, 541
of optie thalamus, 519
pontis, 545
pulposus, 115
ruber, 512
trigeminal, 509
troohlear, 509
vagus, 538
Niihn, gland of, 434

Obex, 538

Obliqae BinuB of perieardium, 58,

59,89
Obliterated duetus arteriosus, 33,

77,78
Oeeipital lobe, 450, 462

pole, 465

sinus, 183, 216, 217

triangle, 163
GEsophageal plexus, 99-102
(Esophagiu, 2, 10, 17, 23, 26, 29,

30, 31, 32, 39» 40, 49, 50,
58, 85, 87, 89, 96, 99, 100,
loi, 104, 106
01factox7 bulb, 322, 439, 469, 477
lobe, 418
striae, 477, 478
traet, 439, 469, 477
trigone, 478
Oliyary eminenee, 524, 525, 526

nneleus, 543
01ive, 524, 525, 526

6o8

INDEX

01ive, superior, 545
Omental bursa, 104
Opereula insulir, 463

frontal, 464, 490

fronto-parietal, 463, 475, 490

orbital, 464, 490

temix)ral, 463, 475, 490
Optie ehiasma, 452, 505

dise, 580, 581

entranee, 572, 578, 579

thalamus, 417, 450, 487

traet, 452, 507, 508
Optie nnelenB —

lateral root, 507, 508
medial root,5o7, 508
Ora serrata, 580, 581
Oral fissure, 365
Orbit, 333
Orbital opereulum, 464, 490

periosteum, 334
Ossieles, auditory, 546, 550, 554,

555, 556
Ostium pharyngeum, 376

Otie ganglion, 276, 277, 279, 293,
383

Palate, hard, 373

soft, 375, 380, 382
Palatal aponeurosis, 382
Palpebrte, 119, 134
Palpebral eommissures, 1 19

conjunctiva, 119

fascia, 135

fissure, 119

lateral palpebral raphe, 121

medial palpebral ligament, 121
Papilla? foIiata3, 432

ineisiye, 368

laerimalis, 120
PapilliTe vallalne, 432

eonieal, 432

filiform, 432

foliataf, 431

fungiform, 432
Papilla nervi optiei, 580
Paraeentral lobule, 449
Paramedian suleus of spinal meduUa,

195
Parietal lobe, 450

lobule, 450
Parieto-oeeipital fissure, 462
Parotid, aeeessory, 261

duet, 127, 261

fascia, 126

gland, 126, 127, 233, 259, 281

lymph glands, 257

Parotid, pterygoid lobe of, 263
spaee, 259, 262, 281
surfaces of, 260, 262

Pars basilaris of inferior frontal
gynis, 469

Pars eiliaris retinse, 580

mamillaris hypothalami, 520
membranaeea septi, 74, 83
orbitalis of inferior frontal gynis,

triangularis of inferior frontal
gyrus, 464
Pedunele of brain, 446, 447
Pedoneles of eerebrum, 210, 212,

452, 500» 501

basis peduneuli, 210

tegmentum, 210, 503, 508, 509,
510, 512
Perieardium, 10, 25, 26, 30, 33,
38, 50, 98, 104

bare area of, 50

fibrous, 50, 70, 75, 83

oblique sinus, 58, 59, 89

parietal, 52, 89

serous, 51, 59, 70, 75

transverse sinus, 54» 59» 76

vestigial foId, 92

visceral, 52, 89
Perilymph, 546, 566

vibrations of, 569
Pes anserinus hippoeampi, 491, 492,

493» 497
Petrosal sinus, inferio¥, 312

superior, 326

Petrous ganglion, 312, 313, 317

Pharyngeal aponeurosis, 370

bursa, 373, 376

plexus, 309, 311, 314

tonsil, 376
Pharynx, 369

bueeo-pharyngeal fascia, 370

eonstrietor museles, 370, 371

glands, 375

interior of, 374

isthmus, 384

laryngeal part, 378

lateral reeesses, 376

lymphoid foIlicles, 376

museles, 371

naso-pharynx, 375

ersophageal opening, 379

openings, 370, 375, 376

oral part, 377

reeess of, 376

relations of, 369

roof, 376

INDEX

609

Pharyiue —

tonsil, 376

yeins, 370

walls, 370
Phrenieo-eostal sinus, 16
Pia mater eneephali, 442

spinalis, 186
Pillars of fauces, 368
Pineal body, 500, 503, 505
Pinna, 153

extrinsic museles of, 1 53

intrinsie museles of, 153
Piriform reeess, 379
Pleura, 7, 11, 12, ^^

apexof, 15, 257

base of, 16

cervical, 15, 248, 250, 257

eostal, 12, 25

diaphragmatie, 16

dome of, 309

lines of reflection, 14, 17, 18, 19

mediastinal, 14, 23, 25, 33, 46,

49, 50» 70, 76, 77, 84, 85, 87

parietal, 12, 14

pulmonary ligament, 14

relations, 76

visceral, 11, 14, 104, 105
Pleural cavities, 12

sae, 12
Plexiifl,basilar, venou5, 183,216,217

braehial, 109, 147, 151, 160, 323.
See also vol. i. p. 28

bueeal, 277

eardiae, deep, 65, 85. 89, 96, 100,

loi, 315
superficial, 33, 43, 65, 78, 85,

87, 315
earotid, 247, 296, 341, 386

external, 31 8

internal inervou5,i. 3S5

cavemous, 331, 332, 385, 386

eer^-ieal, 151. 239, 240

communicatinj^ branehes, 241
deepix;steriorbra.nches, 151,241
museular branehes, 241
superheial branehes, 143, 151,
241

ehorioid, 488, 489, 492, 493, 494,
499, 502

eoronary .f h'.art, l':ft, 65, lOI
right,'65. 85. loi

diaph ra:;r:-. a t i c , 34

h>T>o-l';^^al, 316

infra- .r..:tal. 12S, 129, 387
bran:.- = of, 129

iDterr.i: '.rrtebral (vcnou.s), 182

VOL. 11—^9

Plezii8 —

intraspinal (venous), 182
oesophageal, 99, 100, 102, 104
phar>Tigeal, 309, 311, 314, 315

nervous, 370
position of, 16
posterior saeral, 178
posterior vertebral (venous), 176,

178

pter}'goid (venous), 132, 271, 370,

389
pulmonary, anterior, 43, 99, lOO,

lOI

posterior, 43, 98, 100, 10 1
renal, 28

spinal (venous), 182
suboeeipital {venous;, 157, 173
submaxillary s\-mpathetic, 284
tympanie, 386
vertebral (venous), 355, 356
s)Tnpathetic, 355
Pliea sublingualis, 2S8, 289
Bmbriata, 368

of tongue, 431
laerimalis, 140
semilunaris, 119. 120
triangularis, 378
Plieae ventriculares, 407, 408, 409,
411, 419, 421
vocales, 407, 409, 410. 41 1, 419,
421
Poles of eerebrum, 465
of eyeball, 570
oeeipital, 465, 473, 474, 476
temporal, 465, 475, 479, 485,

487, 494
Pon» Yarolii, 212, 437, 528
braehium pontis, 528
bundle, medial longitudinal oi^

545
eorpus trapezoidum, 545

fibres, superficial transYerse of^

545
longitudinal of, 545

trapezial of, 545

floor of fourth ventricle, 536

internal stnieture, 544

lemniseus, 542, 545

nuelei, 545

pyramidal traet, 544

raphe, 540, 544

retieular formation, 543

8ul>stantia femiginea, 545

tegmental part, 545

tranwerse Bbres, 545

Posterior longitudinal bandle, 544

6io

INDEX

I'rteuneus, 449, 470, 472, 473^ 477,

478
rr.wKreipital nnteh, 473, 490
rretraeheal fa^cia, 229, 230, 23$
rrcvcrtcl»ral fascia, 235. 236, 237
ProeeBB, anterior (if inalleus, 556
eiliary, 577, 579, 581, 582, 5S3,

(•ix:hlcariformis, 551, 55S
iK-lieis eaudatus, 155
lentieularis nf ineus, 557
niuseular, of arylicn(ji(l, 42S
vocalis, of aryta.'noi(l, 42S

rrtunonti^ry of lyniiianum, 552,
50S

Triiseneephalon, 520

l'russak, striie of, 554

Pterygoid lohe of parolid gland, 263
I)lcxus, vcnous, 132, 271, 370,

■587

I*tcrygo-inaxillar)- region, 152, 263
l'ulley of sui^erior obli^iue, 335, 339
Puh'inar (if ihalanius, 507
runela laerinialia, 120, 139

l'ui'il,57S
sphineter and dilatalor museles

of, 578

I'utamen of thalanms, 516

Pyramid of eerebellum, 533

dccussati(jn of, 533, 534

of medulla, 523

of tympanum, 551, 552, 558, 564

l'yramidal lobe of ihyreoid, 321

traet, 544

cr(^sscd, 544

direet, 544

Quadrate lobule of eerebelluni, 532
Quadrigcminal bodies, 506, 507
braehia of, 506, 507

Radiate ligament, 113
Radiatio eorporis eallosi, 483
Rami eommunieantes, grey, 28

white, 26
Baphe, lateral palpebral, 121, 134,

135, 337
of meduUa, 540, 542

of palate, 382

of pharynx, 373

pterygo-mandibular, 132, 373,

389

of tongue, 436

Reeesses, lateral, of fourth vcntricle,

536
of pharynx, 376

• Reeessus epitympanieus, 550, 552,

555
elliptieus, 566

infundihuli, 505

pinealis, 505

piriformis, 379

spheno-ethmoidalis, 399

sphivricus, 566

suprapinealis, 505

triangularis, 505
Red nueleus, 512
Reil, island of, 477
j Restiform body, 527, 528, 529
Relina, 571, 579, 580
Rhombeneephalon, 458, 520
Rima glottidis, 410

Yestibulse, 410

palpebrarum, 119
Riyinus, duets of,
: noteh of, 553, 554
■ Rolando, eentral Tissure of, 462, 464

funiculus of, 199, 200

substantia gelatinosa of, 542
Root-ganglia, 189, 191
Root of lung, 22
I Roots of oIfactory traet, 482
' of spinal nervcs, 189, 191
Rostrum of eorpus eallosum, 458

Saeeule, 569
8ac laerimal, 136
Salivary glands, molar, 133

labial, 133
Salpingo-pharyngeal foId, 376
Seala media, 569

tympani, 568, 569

vestibuli, 568, 569
Sealene tuberele, 313
Sealp, 132

bIood-vessels, 157

epieranial-aponeurosis, 158

fascia, 158, 159

loose areolar tissue, layer of, 159

nerves, 156

strata, 152, 159

temporal region of, 152

surgieal anatomy, 153, 159
Selera, 571, 572, 573, 574, 579» 57»
Seleral eoat, 572

suleus, 573
Semieireular eanals, lateral, 561, 567
Semilunar valves, 75, 78, 81
Sensory deeussation, 542
Septal eartilage of nose, 391
Septum atriorum, 69

nasal, 389

497
posterius of araehnoid, iS6
ventricuIorum, 71, 72, 78, 82
She!(th, ea^otid, 235
Sibson's iiiseia, 36, 251, 257
8inaa, aortie, 60, So
basilar, 1S3, 216
bulb of, 307

cavernous, 209, zio, 217, 271
325.326,327.329.330.331
332. 334, .346
eonHuens sinuum, 217
eoronary, 89

eosto-mediastinal, 16, 370
(rontal, 396, 397
inferio[ sagittal, 207, 211, 217

petrosal, 309
intereayernous, 3^6

pOEterior, 209, 217
masillary, 395, 398
obligue, of perieardiuu

89
oeeipital, 183, 216, 217
of Mo^g^i, 373, 382, 383
petrosal, inferio

3»«

supenor, 211, 217, 326
petro-squamous, 217
pharyngeal venous, 327
pbrenieo-eostal, 16, 37
pterygoid venous, 327
pulmonary (Valsalva), 60, 75
sigmuid part, 560
sigmoid portion of, 216
s^enoidal, 397, 399
spheno-parietal, 211, 217, 326
slraight, 207, 210, 211, 217

I. 59.

7. 312

499
lerior sagitla

, 162, ^

7
, 20S, 2

217. 307. 560
of perieardium, 54, 59, 76
Spaee interpeduneular, 452
mediastinal, 10
parotid, 259
l>erichorioidal, 572
subaraehnoid, 439
subdural, 204

Spatiuin interfasciale (of eye), 348

Spheno-ethmoidal reeess, 399
sinus, 397, 399

Spheno-palatine gangUon, 386, 388,
392

Sphmeter pupillEt, 578

Spina helieis, 158

Spinal meduUa, 28.

anterior surraee, 194
arteries, 193
eaput of eolumns, 197
centra.I eanal, 10
cervical enlargement, 187
eolumns, 196, 197, 199
eommissures, 196
eonus medullaris, 1S8
direet eerebeilor traet, 200
fftscii;ulis eerebro-spinalis later-

lissures, rgs
prey matter, 196
internol strueture, 194
lumbai' enlargement, ]SS
meninges, 183
origin of neryes, 189
posterior suTface, 187
„sio™, 198

substantia gelalinosa, 197
sulei, 195
sutlaees, i87

1, 194

199

nerve-trunks, 1S9, 192

venou5 plesuses. See Piexus.
Sptrol eanal of modiolus, 568
Splanehnie ganglion, 2S
Splenium 01 eorpus ealloium, 446
Stapes, SSl, 557, 566

base, 557

erura, SS7

head, SS7

neek. SS7
Stenisen, duet of, 261
Stemal line of pleural retleetion, iS^.
■9

lymph glands, 107
Stemo-ehondial artieulalions,
Sterno-eostat radiate ligament, tl^

imerartieular ligaments, tii
Slraigbl sinus, 54, 59, 76

6t2

INDEX

Stratinn ]ii{^nicnti iridis, 580
Stria lon^itiulinalis nK'dinlis, 481,
482, 500

lateralis, 482, ^83

nK'diillaris, 502

terminalis, 4SS, 489, 491, 502,

51.?. 5M, 578
oIfactory, 477, 478

Strix nietliillares, 538

lon^itiulinales, 482

of Prussak, 554

Su]>arachnoi<l cistern.x*, 439

spaee, 439

SulK*Iavian j;nM>ve, 40

trianp;Ie, 249

SulKlural spaee, 204

Sublinj;ual pland, 280, 286, 288,

2S9, 290, 292

Submaxillary duet, 282, 285, 286,

2SS, 2S9

jranj;li()n, 2S2, 2S4, 285, 318

gland, 225, 2S0, 2S1, 2S2, 283,

2S4, 2S5, 286, 2SS, 289,

290

nerve supply, 284, 29S

re^^ion, 279

trian^de, 279, 2S0

Subniental trianj;le, 223, 226, 227

Sul)<K'cii)ilaI spaee, 17S

Sul)stantia ferruginea, 545

l^elatinosa, Rolandi, 197, 527

nij;ra, 210, 510

perforata anterior, 447, 450, 454,

47«. 479» 483. 517. 518
l^osterior, 447, 452, 503

Subthalamie rej;ion, 501

Suckinj^ patl of fat, 133, 266

Suleus or Sulei, of brain, 461

eallosal, 47S

eentralis insul;v, 464, 466, 467,
469, 470, 471, 472, 477

einiTuli, 465, 466, 469, 479

eireular, 477

roronary, 68

diaj;onal, 469

find)rio (lontate, 495

frontal, infi'rior, 467
niiddle, 467
su]H'rit)r, 467

fronto niarginal, 467

(if llesrhl, 475

of spinal niedulla, 195

interniediate ix)Stcrior of spinal
nR'ilulla, 199

^reat hori/ontal, 530, 531

hyiH)-thalamic, 505

Sulens or Snlei —
intraparietal, 471, 472
horizontaI ramus of, 471
oeeipital ramus of, 471, 474
lateralis meseneephali, 5o(3
limitans (of 4th ventricle), 537,

538
lunatus, 474

of lungs, 41

oeeipitalis transversus, 472, 474

lateralis, 474

olfactorius, 396, 469

olfactory, 477

orbital, 469

lateral, 469

medial, 469

transverse, 470

paramedial, of eerebrum, 467

post-eentral, inferior, 471, 472

superior, 471, 472

postero-lateral of eord, 195

preeentral, 467

inferior, 466, 469

superior, 466

rostrales, 469

seleral, 573

sub-parietal, 471, 478

temporal opereulum, 485

inferior, 476, 477

middle, 472, 475

superior, 472, 475, 485

terminalis of heart, 34

of tongue, 430

tympanieus, 553

valleculoe, 530

venosus seleroe, 573

Surface anatomy of neek, 223

Suprasternal fossa, spaee, 224

Supratonsillar fossa, 378

superior, 317, 318

inferior, 319

middle, 318

Sympathetie, cervical, 245, 247, 252

abdominal, 34

branehes of, 27, 28, 32, 254

dorsal braneh, 108

first thoraeie ganglion, iio, 257,

258

gangliated eord, 2, 23, 25, 27

thoraeie, 2, 23, 26, 109, iio,

254

Synehondrosis sternalis, 112

Tsenia of 4tli ventricle, 537
Tapetum, 483, 490, 574
of ehoiroid, 575

Tarsal glands, rw

Thyreoid, eaililage. 229, 234, 244

Tars{, 134

423

mferior, 135

isthniiis, 229, 320, 321

Euperior, 135

ineisura, 423

Tegmentum, 210, 503, 508, 509, 510,

laiyngeal prominenee, 424

512

lateral lalie, 407

Tegmen tympani, 550

paiamedla! !obe, 407

Tela ehorioidea, 442, 447, 497, ^98,

499. 500, 502, 504, S3S
that whieh is in, 539

pytamidal lobe of, 321

Tongue, 429

Teleneephalon, 520

d m 430

Tomporaa taBoia, 265, 266

lobe, 462

fel nd 283, 434

noteh, 470, 473

I II hesof, 319

opereulum, 463

n u membrane, 430

pole, 465

U5cl 2S5, 433, 434

region, 152, 265

t\es 89, 435

Tensor tympani, 565

Ipar 430

palati, 547

pai Ilte, 432

Tentonum eetebelh, 208, 212, 218,

ph yng al pntt, 430

459

1 n of, 319

Thalameneephalon, 458, 520

phim 436

.Thaliuno-m(LnullaTj rBgion, 5^9

1 21, 435

anterior tuhetele, 502

ToHBil 299. 369- 3S3

laletal area, 502

bell t, 533

massa inlermedia, 503, 504

pb yngeal, 378

medial atea, 502

5>-l f, 383

5urface, 503

T p gt phy of heart, 94

postetiot extreniily, 502

puWinar, 502

T batius, 376

ThalamuB. 447, 450, 487, 488, 4S9,

T h ul-e cattieiC, 72, 79

497.499. 512. 513. S'4. S'S,

T a hen 10, 17, 13. 49, 85, Sf4

520

89, 95. 99. lot, 321

epi-thalamus, 520

Ttagus, 15S

a-thalan

i, 520^

Third venlricle of brain, 49S, 499,
Soo. 502, 503, S04, 505
tienia thalami, 500, 501, 502, 503,
504, 505, 508
Thoraeie duet, 2, 10, 31, 32, 48,
246, 250, 313
ganglia, 312, 314, 317
ThoraK. I
cavily, 1, 10

lymph glands, 107
outlel, 2

Thymus gland, 46, 47, 48, 85
Thyreo-hyoid membtane, 229, 243,

296, 413, 417
Thyreoid gland, 229, 234, 244,

246, 252, 253, 297, 3'0. 320,

321, 322, 407

: of petieardium, 54, 5%

eaiotid, 226, 232, 233, 259

eontenls of, 231
digttslrie, 226

museulai, of neek, 226, 234

oeeipitai, 168

posteHoi, of neek, 148
eontents Df, 149

subclavian, 349

submaxillary, 233

submeatnl, 223, 226, 227

suhoeeipital, 168, 172

supradaYieulEir, 149

supramealal, 560
Triangulai fo55a, 154
Ttieuspid valve, 69

i\nEx

Trigonum j ll.i'.tr. -'.-.■. 4*>o
:;.i' '.■:..:! * . y?2

I'r :'..'.:. \ :"--.::-.r: r o'. !: :.:e. ;;o
T :.::.'?;, ': -r-.'.I .i >;•■.-.■:. i6l

. -■•■%'^«>ai ^ ■ ■ . ■ ■ * ■• ^ hM . « % 1 %

T:.::."^- :" " :.:;:.:.:! : :v\::-i. 151
Tdbe. auditoiT. 20;. 504. 540. 547.

54';'' 55^' 5^^- 55'?

wMr::..!^:::. -- *. .^.r:. 559

r.:' vr j;:-.-jrf:::r.. 455. 503. yO^,

...■■.• - « *

.•■9-v... ■ ^*^

.1 . . ■ . " » «
.. > ^ ^ 1

\ -. : ..."«. ^ !_"»
Tuberele. .:::'.>.: :.\L>::, 490. 403

■ ■ i

«^.■.jr. r ^. . ■ ..^^iA^^ 1 «.^. ^^3
* .•■■'*■■*-•■■ '••■t'\

V ■■■.^ -..-■.«« y . ^'

.■»■ ■• .^»«« **l^

« *« -..rv-'** ■■ *; f ■■*

■ .i.^A*^^. *■ m • .

" l * ' ' M «

. '' •'■\T •■ * •-••■'■I.»r» J "» I _1"»C

.■■lK« ■ ^h»i... »*^^V tt bA ^b* • *T^ '

^ • ^'■■•^-« * T *

l..l^ *•■! •■■■•!. V>' A.»ft 1*« ■«*• ^ v*T

Tympanum. 312, 537, 5 58. 559

.1 :::"»:■• ■ ■ ' , ^ ^ ^ . > o i

\:\'j \\.\\ \\.\\\ o\, 361
ar.:fri'»r w.ill. 331
an:r;::n, 337
oaviiy. 305

eayi:)-, |r"nionior\- .>f. 361
tloor, 550
jui;ular wall. 530
latoral wall. 333
inasioi'! wall. 350
nK-'lial wall, 552
nienihrane- ()f. 553
niueuu.-^ menihrane, 555
nuiseh.'.s 558
<)s.^iclcs, 555
])nst<.'ri»)r wall. 550
prdmontnry <)f, 552, 56S
j)yr.uni.l of, 551, 552, 55S.

5'>4

i.inr. 330

S'i'»n«l;iry menibrane of, 553

1' ;;min lympnni, 550
l'mli. I 'il ivm|iani(; mem])rane, 554
IH. 11« "1 Inppneamiial gyni.s, 478,

Uiriele. 569
Uveal iraei, 571
Uvula. 36S, 380

of eerebellum, 533

palate, 3S0

Vallate papilLie, 432
Valk'cula eerebelli, 520, 530

Iar\'nx, 409
Val>alva, sinuses of, 60
Valve, aortie, 87

lueuspid, 80, 92

eoronan-, 68

mitral, So, 92

pulmonar)', 75, 78

of eoronar)' sinus, 89

of the vena cava (Eustaehian),

67
semilunar, 75, 78, 81

irieuspid, 69

Ven.v vorticosa.\ 573

alveolar inferior, 267, 270

an:erior, 262, 2S0, 281

Vein or Veiii8, angular, 131, 137,

157. 344
anonyma. Szc Innominate
aseemling lumbar, m
auai:ory, 215

aurieular. posterior, 143, 157
a/ygo.^. 10, 23, 26, 29, 40, 44, 70,
SS, 98, 99, 102, 104, 106, 109,
III

hemiaz}'gos, 10, 30, 102, 104,
106. III
aeeessory- hemiazygos, 10, 30,

102, 104, 106, III
basalis. 211. 212
brain, internal of, 499
bronehial, 30, 11 1
eardiae, 60, 63
eephalie, 161
eerebral, 204, 206

inferior, 326

internal. 4S9

supertieial middle, 326
cervical deep, 254
eoronary sinus, 63
eomitans ner\^i hypoglossi, 290,
292

of oeeipital artery, 309
of the medulla spinalis, 194

parietal emissar>'. 219

posterior aurieular, 235
emissary, 162, 172, 216, 219, 326

anterior ' "••»
facial, ^ (92

Yein or TeiiiB—

362, 263, 271, 294

transYerse, 262
frontal, 132, 137, 157
greal eentral, 499
hemia.z)^OE, 10, loi

aeeessory.

inferior iabial, 132
inTraorbilal, 242, 245, 247, 250,
252.253,254,255. 256,257,

. , 26, 32, 34, 35,
46, 47, 48, 49, 50, 85, 88, 89,
96, 99. 106. III, 239, 313
intereostal, 30, 32, iio

superior, 30, 32, 35, 4S

intereostal-righl supeiior, 111

intra^pinal, 17S

jugular, anlerior, 224, 225, 239,
242, 245, 250, 30S
eNtemal, 127, 145, 147, 149,
161, 225, 235, 239, 255, 261,
262, 263
internal, 40, 47, lo*), 234, 335,
239, 242, 243, 245, 246, 247,
250, 252, 255, 256, 257, 259,
262, 264, 281, 300, 303, 305,
307,309,310.312, 313.315.
316, 323

hneual, 231, 292, 294, 305, 309

lumbar, 176

magna eerebii, 210, 212, 21S,

"■7,

inteinal, i

mediastinal, 46
meningeal, 219, 222, 300
minimae eordis, 69
nasal, 205

obIique of Marshall, 90
oeeipital, 157, 162, 172
eesophageal, 30
ophthalmie, 219, 271, 326,

. KS

inrenot, 344

supenor, 339, 344
palpebial, 132
perieardial, 30, 48

EX 61S

Voin 01 Telna—
pharyngeal, 370
post-eondyloid, 319
piofunda cervici3, 173
ptBr)^oid, 132, 271
pulmonary, 10, 22, 33, 38, 50, 58,
6d, 70, 89, 92
relalions of intia-pulmonary
parts, 99
ranine, 231, 292, 294, 305
retinal, 580
spinnl. 194

eardlae veins, anterior, 64
greal eardiae vein, 63
middle, 63
small, 64
Taeial vein, posterior, 126
oblique vcin, 63

1,30

snperior inlereosta], 30, 32, 35,

87, «9, '«>. I"
temporal soperdeial, 15?
venae minims, eordis, 64, gx
yentrieular vein, inferior, 63
sabclavian, 40, 47, 106, 108, 250,
254, 256, 2S7i 358, 259, 323
supertieial parotid, 132
superior labial, 132
supra-orbital, 132, 157
tempoial middle, 265
tennioalis, 4SS, 499, 500, 502
of thoraeie wall, 1 10
thyreoid, infetior, 47, 88, 96, 229,
253. 320. 321
middle, 239, 247, 309, 311
superior, 231, 245, 297, 309,

321
thymie, 48

seapular, [61, 225,

anterioi medoUaiy, 506, 511«

S35
posterior roedullary, 533, 535
Vela medullary, 535
Velum palatinum, 3S0
museles of, 3S0
medullaiy, tnreri(.i, 535
anterioi, 506, 530
superior, 506, 530
Vena cava inferior, 23, 26, 33, jf,

39, 54. S^. ^5, ^7, 70 -.^^

\ '-

'— ~a

r.rr -..isi. :rrx=. :£ se:

' i» . - .•*. •— • ' » ^ «•.» *xt ^'S'*

V--"i zNr

K x\ K.. v.\.v:v.v. L!MiTEi\ EdiHhir£^h,

:>gi™i. S37
lea 01 mperior uu>ii|
, iloi»! aspeet, ifit
-ganelioii of vu(u*, 31;
^arbr&EhUI ^ilena, i^r
Bndltory, 1193. 30*. S4%
S49. 551- SS». iS9

.[tilasi'ioiii p>i<i SS9
dneitoiii, 4SJ, SOt

•-_. 3.M

«n'd. 5J3
^.533

Bla, nmygiUlold, 490^
ilin »( ilulMnuD, 503
ieiilato, 379
rironn, 379
■venotta, 67
i>lanib, 5:1;;
lyteoid aulilii||;c, 424,
rtie 313
^"nl»i S.1.1
ino-malleolai foIiU,

isof, SS5. 5"i"
hal wnll of, 56

„.n, SS" '

7, S6S

:y, promoDloiy af, 561

- SSo

lar wall, 5So

al wall, 553

ial wal' " "

Dus membnme, 555
:lcs, 558
1=». 5SS
Erior wall, 550
lontory nf, 552, 568
mid of, 551, 55»,
S64
S50
ndary niembi-ane r)f, SSJ
^B, 558
itn tympani, 550

'■^■:~

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