QUAIN'S ANATOMY
E. A. SCHAFER & G. D. THANE
VOL. !;. Pr- 1.
OSTEOLOGY
(,. D. THANE
I
SIl
MEDICAL .SCHOOL
John Marshall Williamson
Memorial
v
QUAIN'S
* "^
ELEMENTS OF ANATOMY . "
EDITED
EDWARD ALBERT SCHAFER, F.R.S.
PROFESSOR OIr PHYSIOLOGY AND HISTOLOGY IN UNIVERSITY COLLEGE, LONDON,
GEORGE DANCER THANE,
*>
PROFESSOR OF ANATOMY IN UNIVERSITY COLLEGE, . LONDON.
IN THREE VOLUMES.
VOL: IT.— PART i.
OSTEOLOGY
BY PROFESSOR THANE.
ILLUSTRATED BY 168 ENGRAVINGS.
Ctntlj <£tfttton.
LONDON :
LONGMANS, GREEN, AND CO.,
1890,
15
BHADBUKV.
LONDON
& CO. UMD.,
W, WH1TKFK.AK*
CONTENTS OF PAET I,
DESCRIPTIVE ANATOMY.
OSTEOLOGY.
I.
II.
III.
1
The Skeleton and Bones generally
THE VERTEBRAL COLUMN
Vertebne . . . . . .
General Characters .
Groups of Vertebne . . . .
Cervical Vertebne . . ' .
Dorsal Vertebne . . . .
Lumbar Vertebrae
Sacral Vertebra; . . . .
Coccygeal Vertebne .-
The Vertebral Column as a whole .
Ossification of the Vertebra; .
Serial Homology of the Vertebra' .
THE THORAX . . . . .
The Sternum or Breast-Bone
The Ribs
The Costal Cartilages
The Thorax as a whole . . .
Ossification of the Sternum and
Ribs
THK BOXES OF THE HEAD . . .
Occipital Bone ....
Parietal Bone . . . •, .
Frontal Bone ....
Temporal Bone . . . .
Sphenoid Bone ....
Ethmoid Bone . . . . .
Superior Maxillary Bone
Palate Bone . . . . .
Vomer. .
Malar Bone . . , .
Nasal Bone .....
Lachrymal Bone
Inferior Turbinate Bone . . .
Inferior Maxillary Bone
Hyoid Bone ... .
THE SKULL AS A WHOLE
The Sutures . . . .
External Surface of the Skull .
Interior of the Cranium .
Nasal Cavities and Communi-
cating Air-Sinuses .
Ossification of the Bones of the
Head ..'..'.
GENERAL MORPHOLOGY OF THE BONES
OF THE HEAD . . . .
List of the Typical Component
Parts of the Bones of the
Head classified according to
their Origin ....
Various Forms of Skull
IV. BONES OF THE UPPER LIMB .
Clavicle . . . . . .
Scapula . . .
AGE
3
5
5
6
6
9
ii
16
18
19
21
23
23
28
29
71
73
78
79
82
86
86
87
I'AUK
Humerus . . . . . 91
Ulna 95
Radius . . . . • • 97
Carpus. . . . . .100
Scaphoid Bone . . . . 101
Lunar Bone . . . . 101
Pyramidal Bone . ... 101
Pisiform Bone . . . . 101
Trapezium Bone . . . . 102
Trapezoid Bone . . .102
Os Magnum . . . . . 102
Unciform Bone . . . .103
Metacarpus . . . . . 103
Digital Phalanges . . .105
Ossification of the Bones of the
Upper Limb . . . . 106
'. THE PELVIS AND LOWER LIMB . 1 10
Hip-bone . . . . . i 10
Ilium . . . . .110
Os Pubis 113
Ischium . . . . -113
The Pelvis 115
Position of Pelvis . . . 1 1 7
Differences according to Sex . .118
Femur. . . . . .118
Patella . . . . . . 124
Tibk 124
Fibula 127
Tarsus . . . . .129
Calcaneum or Os Calcis . .129
Astragalus . . . .130
Navicular Bone . . . . 131
Cuneiform Bones . . . 131
Cuboid Bone . . . . 132
Metatarsus . . . . . 133
Phalanges . . . . 135
The Bones of the Foot as a whole . 135
Ossification of the Bones of the
Lower Limb . . . .136
MORPHOLOGY OF THE BONKS OF THK
LIMBS ..... 140
Relation to the Axial Skeleton . 140
Homological Comparison of
Upper and Lower Limbs . 140
Shoulder and Pelvic Girdles . 140
Bones of the Limbs . . . 142
Hand and Foot . . .143
Table of the Homologous Bones
in the Thoracic and Pelvic
Limbs . . . .144
Carpus and Tarsus . . . 144
Scapula and Ilium . . 145
Adaptation of the Skeleton to the
Erect Attitude . . . . 145
286'"' 3
DESCEIPTIVE ANATOMY,
DESCRIPTIVE ANATOMY may be treated of in two methods : viz., the Systematic
and the Topographical.
In the first or Systematic Anatomy, the several organs and parts of the body are
considered in a systematic order, according to their structure, their connection with
each other, and their relation to the purposes of life ; while in the second, or
Topographical Anatomy, the parts are described in the order of their position
or association in any region of the body. The first method is best adapted for the
elementary and complete study of the structure of organs, the second is more
immediately useful in the study of particular regions in their relation to Medicine
and Surgery. The object of the present work being mainly to serve as a guide for
systematic study, the topographical details will for the most part be included under
and combined with the general description of organs, and only some of the more
important regions will receive separate notice.
The plan of construction of the body and the general arrangement of its chief
parts have been explained in the Introduction at the beginning of Yolume I. The
several systems and regions now to be described will be treated of under the following
heads : —
1. Osteology, the Bones.
2. Arthrology, the Articulations.
3. Myology, the Voluntary Muscles, with which will be combined the Fasciae and
Aponeuroses.
4. Angeiology, the Heart, the Blood- Vessels, and the Lymphatics.
5. Neurology, the Spinal Cord and Brain, the Nerves, and the Organs of the
Senses.
6. Splanchnology, the Organs of Respiration, the Organs of Digestion, the
Urinary Organs, and the Organs of Reproduction.
7. Superficial Anatomy, and Topographical Anatomy of some Regions.
Descriptive terms. — In anatomical descriptions the body is always supposed
to be in the erect attitude, and terms of relation are employed strictly with reference
to this position. Thus, superior and inferior correspond respectively to cephalic and
caudal, anterior and posterior to ventral and dorsal. The body being bilaterally
symmetrical, it might be divided into similar and nearly equal halves by a vertical
plane directed from before backwards. This is known as the median plane, and the
line along which the median plane meets the surface of the body is called the middle
or median line. The words internal or mesial and external or lateral denote
VOL. II. B
2 DESCRIPTIVE ANATOMY.
respectively nearer to or farther from the median plane. Sagittal indicates a dorso-
ventral direction in or parallel to the median plane, and coronal or frontal a direction
perpendicular to the foregoing in a transverse vertical plane. The terms superficial
and deep, central and peripheral, proximal and distal, are often used, and need
no explanation. In many cases precision may be obtained by reference to certain
fixed relations of parts, such as the vertebral and sternal ends of the ribs, the radial
and ulnar, or tibial and fibular borders, and the flexor and extensor surfaces of
the limbs. Preaxial and postaxial, applied, for instance, to parts of the limb,
signify, respectively, on the primitive cephalic or caudal aspect of the axis of
the member.
OSTEOLOGY.
By G. D. THANE.
THE SKELETON.
THE skeleton or solid framework of the body is mainly formed of the bones, but
is completed in some parts by the addition of cartilages. The bones are bound
together by means of ligaments, and are so disposed as to support the softer parts,
protect delicate organs, and give attachment to the muscles by which the different
movements are executed.
In the lower animals the term skeleton has a wider signification than in man,
comprehending two sets of parts, viz., 1st, those of the endoskeleton, or the deeper
osseous and cartilaginous framework which corresponds to the human skeleton ; and
2nd, those of the exoskeleton, or dermal skeleton, comprising the integument and
various hardened structures connected with it. All vertebrate animals possess an
eudoskeleton ; but in some of them the exoskeleton attains greater proportions
than in others, and is combined by means of hardened parts more f ully with portions
of the endoskeleton. In most invertebrate animals the dermal or exoskeleton alone
exists.
In man, as in the higher vertebrates, the greater part of the endoskeleton is
formed of bone, a calcified animal tissue, which, when freed by putrefactive macera-
tion from its fat and various soft adherent parts, and subsequently dried, is capable
of remaining unchanged for a very long period of time. It is customary and con-
venient thus to study the bones chiefly in the macerated and dried state, that is,
deprived of their accessory soft parts.
The accessory soft parts connected with the fresh bones consist chiefly of the
external fibrous and vascular covering termed periosteum, and of the medulla,
marrow or fat, which fills their larger internal cavities. The bones are permeated
by blood-vessels, and they are provided also with absorbent vessels and with nerves
in small quantity.
The ends of the bones, when jointed moveably with others, are covered by a thin
layer of dense permanent cartilage, called articular cartilage; and the adjacent
bones are united together by fibrous ligaments which may be considered as con-
tinuous with the periosteum covering the rest of the bones. In some instances
distinct bones are directly united by means of ligament or cartilage without any
joint-cavity intervening. Thus the osseous system as a whole may be considered to
be enveloped by a fibrous covering.
The bones are originally formed by a process termed ossification from soft sub-
stance. This process commences in the greater number of bones in cartilage ; in
some it begins in fibrous tissue or membrane ; and in all instances the farther
growth of the bone substance takes place largely in the latter way. The deposit of
bone begins generally at one spot, which is therefore called the primary centre of
ossification ; but there may be several of these from the first. The main part of the
bone thus formed from the primary centre is sometimes named the diaphysis. In
most bones, after considerable advance in growth by extension from the primary
B 2
4 OSTEOLOGY.
centre, ossification occurs at comparatively later periods in one or more separate
points, forming secondary or tertiary centres ; and the portions of bones so formed,
which remain united to the main part for a time by intervening cartilage, are termed
epiphyses. In many instances entire consolidation of the bone by the osseous union
of the epiphyses does not take place till the full size has been attained, and this may
be as late as the twenty-third or even the twenty-fifth year of life.
In their outward form the bones present much diversity, but have been reduced
by anatomists to the following classes : — 1. Long or cylindrical, such as the chief
bones of the limbs. These consist of a body or shaft, cylindrical or prismatic in
shape, and two extremities which are usually thicker than the shaft, and have smooth
cartilaginous surfaces for articulation with neighbouring bones. The shaft is
generally hollow and filled with marrow, by which sufficient size and strength are
attained without undue increase of weight. 2. Tabular or fiat bones, like the
scapula, ilium, and the bones forming the roof and sides of the skull. 3. Short
bones, which are more or less cubical or oblong, as in the carpus and tarsus.
4. Irregular or mixed bones, mostly situated symmetrically across the median plane
of the body, and often of a complex figure, such as the vertebrae.
In these differently shaped bones the osseous substance occurs in two forms, viz., the
compact and the spongy. There is, however, no essential difference in structure or propertie3
between these beyond that of thickness or thinness of the component material.
The surfaces of bones present various eminences, depressions, and other marks, to designate
which the following terms are in common use. Any marked bony prominence is called a
process or apophysis ; a slender, sharp, or pointed eminence is named a spine, or spinovs
process ; a blunt one a tubercle ; a broad and rough one a tuberosity. The terms crest, line,
and ridge are usually applied to a prominent border, or to an elevation running some way
along the surface of a bone. A head (caput, capitulum, or capitellum) is a rounded process
usually supported on a narrower part named the necli (cervix). The term condyle, somewhat
variously applied by anatomists, is most frequently employed to denote an eminence bearing
a rounded articular surface.
The cavities and depressions of bones are very variously named. An aperture or perfora-
tion, when short, is & foramen; when continued some way as a passage it is a canal or
meatus. A narrow slit is a fissure, an open excavation or hollow in one bone or in several
together is a fossa. This term is also sometimes applied to the socket of a joint, as in the
fflenoid or shallower, and the cotyloid or deeper form of joint-cavity. Sinus and antrum are
names applied to considerable cavities in the interior of certain bones. Besides these, various
other terms are employed which do not require explanation, such as notch (incisura), groove,
furrow (sulcus), &c.
The number of bones in the skeleton varies at different periods of life, some
which are originally distinct becoming united together as the process of ossification
advances. The following is a statement of the number usually reckoned as distinct
in middle life : —
Single bones. Pairs. Total.
The vertebral column . . . 26 - ... 26
Axial , The skull ..... 6 8 22
Skeleton. 1 The hyoid bone . . . .1 ... 1
^ The ribs and sternum ... 1 12 25
Appendicular f The upper limbs . . .... 32 64
Skeleton. ( The lower limbs ....... 31 62
34 83 200
Besides the bones included in the above enumeration, there exist likewise the three
pairs of auditory ossicles, and various bones formed in tendons and called sesamoid,
the most constant of which are, besides the patella and pisiform bone, reckoned in
the table above as limb-bones, a pair in each thumb and great toe.
/
,)
THE VERTEBRAL COLUMN.
SPINOUS PROCESS
TRANSVERSE
PROCESS
SUP. ARTIC. PROCESS
I.— THE VERTEBRAL COLUMN.
The vertebral column is composed of a series of bones called vertebrae, which are
united together, for the most part, by joints and elastic substance in such a manner
that, although the amount of motion allowed between each pair is slight, the
aggregate is sufficient to give the column very considerable flexibility. The vertebra
are originally thirty-three in number. Of these, the upper twenty-four remain
separate in the adult, retaining their mobility, and are hence called moveaUe or true
vertebrae. They are succeeded by five others, which rapidly diminish in size from
above downwards, and which are united into one mass called the sacrum ; beyond
the sacrum are four dwindled terminal members of the series, which as age
advances, likewise become more or less united, and form the coccyx. These sacral
and coccygeul vertebrae are known as thefaed we false vertebrae.
General characters of the vertebrae. — The general characters are best seen
in the vertebrae placed near the
middle of the column, of which
the tenth dorsal vetebra, shown
in fig. 1, may serve as an example.
Each has more or less the form of
a ring, and presents for considera-
tion a body, arch, processes, and
the enclosed spinal foramen.
The body or centrum is a short
cylinder or disc, which forms the
anterior part of the vertebra. Its
superior and inferior surfaces are
flattened and connected to the
next vertebrae by strong and elas-
tic intervertebral discs. On the
front and sides it is convex hori-
zontally, but slightly concave
from above downwards ; its pos-
terior surface forms part of the
ring, and is slightly concave from
Side to Side. J.hese vertical pjg_ j — TENTH DORSAL VERTEBRA, FROM ABOVE. (Drawn
surfaces are pierced by numerous by D- G«nn.)
small foramina for the passage
of blood-vessels, and near the middle of the posterior surface are one or two much
larger than the others.
The arch (neural) consists of two symmetrical portions which spring, one on each
side, from the posterior surface of the body, and meet in the median plane behind.
The anterior part of each half, thick and narrow, is called the pedicle ; the posterior
part is broad and flat, and is called the lamina. The concavities on the upper and
lower borders of the pedicles are named vertebral notches (fig. 2, B), and consti-
tute, by the apposition of those of contiguous vertebrae, the intervertebral foramina,
a series of rounded apertures, which communicate with the vertebral canal, and
transmit the spinal nerves and blood-vessels.
The spinous process (neural spine) projects backwards from the arch in the
median plane. The transverse processes, placed one on each side, project outwards
from the arch at the junction of the pedicle with the lamina. The articular pro-
cesses (zygapophyses), two superior and two inferior, project upwards and downwards
opposite the attachment of the transverse processes ; their articular surfaces, coated
6
THE VERTEBRAL COLUMN.
with cartilage, in the superior pair look backwards, and in the inferior forwards, so
that the former face the latter in adjoining vertebras.
The foramen is bounded anteriorly by the body, posteriorly and laterally by the
arch. The series of rings thus formed, united by ligaments, constitutes the spinal
or neural canal, which lodges the spinal cord.
Texture. — The bodies of the vertebrae are almost entirely composed of spongy substance,
the principal lamellae being vertical : on the surface is a thin layer of compact tissue.
Venous canals, commencing at the larger foramina behind, traverse the cancellated structure.
The arch and processes contain a much smaller proportion of spongy substance, being covered
with compact tissue of considerable density in some places.
INF. ARTIC.PROC.
SUP.ARTIC.PROC.
GROUPS OF VERTEBRJE.
The vertebrae are divided into five groups, named from the regions which they
occupy, cervical, dorsal, lumbar, sacral, and coccygeal.
Cervical vertebrae. — These are seven in number ; they are the smallest of the
moveable vertebras, and are spe-
cially characterized by the pre-
sence of foramina in the trans-
verse processes. The first and
second are so peculiar in form,
as to require a separate descrip-
tion. The following are the
common characters of a cervical
vertebra.
The lody is small, and much
broader from side to side than
from before backwards ; in depth
nearly the same in front and
behind. Its upper surface is trans-
versely concave from the upward
projection of its lateral margins,
and is sloped down in front. The
under surface, on the contrary,
is rounded off at the sides, while
its anterior margin forms a marked
projection downwards.
The pedicles spring from the
body about midway between the
upper and lower borders, and are directed outwards and backwards ; the lamina are
slender, long and flat. The superior and inferior notches are nearly equal in depth.
The spinous process is short, only slightly depressed, and bifid.
The tranverse processes are short, and present at their extremities two tubercles,
anterior and posterior. Each process is deeply grooved above for a spinal nerve, and
its base is perforated vertically by a round foramen (vertebrarterial), through which
in the upper six the vertebral artery and vein pass. It is united with the rest of the
vertebra by two parts ; by the posterior, at the place of junction of the pedicle and
lamina, like a dorsal transverse process ; by the anterior, to the body of the vertebra,
in the same position as the heads of the ribs.
The articular processes are placed at the extremities of a short, stout, vertical
column of bone ; their articular surfaces are nearly flat and oblique, the superior
looking backwards and upwards, the inferior forwards and downwards.
NF. VERTEBRAL NOTCH
Fig. 2. — FOURTH CERVICAL VERTEBRA : A, FROM ABOVE
B, FROM THE RIGHT SIDE. (Drawn by D. Gunn. )
THE FIRST CERVICAL VERTEBRA.
The foramen is triangular, with rounded angles, and larger than in the dorsal or
lumbar vertebras.
The first cervical vertebra, or atlas, differs remarkably from the others in
the absence of a body and spinous process, having the form merely of a large ring
with articular and transverse processes.
The interior of the ring is wider behind than in front. Its posterior part cor-
ODONTOID PROCESS
TIC. PROCESS
RANSV. PROC.
TRANSV. PROC.
INF. ARTIC. PROCESS
Fig. 3. — ATLAS AND AXIS, FROM BEFORE. (Drawn by D. Gunn.)
responds to the foramina of the other vertebrae ; its narrower anterior part is
occupied by the odontoid process of the axis, and in the recent state is separated
from the posterior by the transverse ligament. In front of the ring is the anterior
arch, on the anterior aspect of which is a small tubercle, and on the posterior a
smooth surface for articulation with the odontoid process. At the sides of the ring
are the lateral masses, which are thick and strong, bearing the articular processes
above and below, and extending outwards into the transverse processes. The articular
POSTERIOR ARCH
ERTEBRAL GROOVE
SUP. ARTIC. PROC.
FOR TRANSV.
LIGAMENT
TUBE
ANTERIOR ARCH
ARTIC. SURF. FOR ODONTOID PROC
Fig. 4. — ATLAS, FROM ABOVE. (Drawn by D. Gunn.)
The position of the transverse ligament is indicated by dotted lines.
processes differ from those of other vertebrae in being situated in front of the places
of exit of the nerves. The superior, larger than the inferior, are oval, and converge
in front ; their articular surfaces are concave for the reception of the condyles of
the occipital bone, and look upwards and inwards ; they are frequently divided by a
transverse groove into two. Below the inner margin of each, towards the front, is a
smooth rounded tubercle, to which the transverse ligament is attached. The inferior
articular processes are smaller than the superior, flat, nearly circular, looking down-
wards and slightly inwards.
The posterior arch presents in the middle line a rough elevation, the rudiment of
a spinous process ; at its junction with the lateral masses, it is hollowed out above
8
THE VERTEBRAL COLUMN.
so as to form a smooth transverse groove — the vertebral groove, in which lie the verte-
bral artery and first spinal (suboccipital) nerve ; the groove corresponds to the
superior notches of the other vertebrae.
The transverse processes are larger and project farther outwards than those of the
subjacent vertebra?. They are flattened from above downwards, and have a large
foramen. Their extremities are not bifid, but broad and rough.
Varieties. — The posterior arch of the atlas is sometimes imperfect, the gap in th.e bone
being1 bridged across by a fibrous band. A similar defect in the anterior arch is comparatively
rare, but its complete absence has been observed.1 The transverse process, especially the
anterior bar, may also be the seat of defective ossification, and the foramen of the vertebral
artery is then completed by ligament. A bony arch over the vertebral groove is frequently met
with. Less common is the formation of a canal for the vertebral artery on the outer side of
the superior articular process.
The second vertebra or axis (vert, dentata) forms a pivot on which the
first vertebra rotates carrying the head.
The lody is characterized by the presence of a large blunt tooth-like process called
F. ARTIC.PROC.
Fig. 5.-
-AXIS, FROM THE RIGHT SIDE.
by D. Gunn.)
(Drawn
Fig. 6.— SEVENTH CERVICAL VERTEBRA, FROM
ABOVE. (Drawn by D. Gunn. )
odontoid (proc. dentatus). This consists of an enlarged part termed the head, and a
lower part or neck. It has in front a smooth surface for articulation with the
atlas, and behind a smooth groove to receive the transverse ligament. The lower
surface of the body resembles that of the succeeding vertebrae. Its anterior surface
is marked by a low median vertical ridge, with a depression on each side.
The superior articular surfaces, placed like those of the atlas in front of the notch,
lie close to the base of the odontoid process, partly on the body and partly on the
pedicles of the vertebra. These surfaces look upwards and slightly outwards. The
inferior articular processes are similar in form and position to those of the succeeding
vertebrae.
The spinous process is very large, rough, deeply bifid, and grooved on its inferior
surface. The lamina are very thick and strong.
The transverse processes are short, and the anterior tubercle almost obsolete. The
foramen for the vertebral artery is inclined obliquely upwards and outwards.
The seventh cervical vertebra has a long spinous process, which is not
bifurcated, but ends in a broad tubercle projecting under the skin, whence the name
1 Dwight, Journ. Anat., xxi, 539.
THE DORSAL VERTEBRA.
of vertebra prominens has been
given to this bone. The transverse
processes are massive, and only
slightly grooved, with a small fora-
men ; their posterior tubercle is
large and prominent, while the
anterior is but faintly marked.
In most cases the spinous process of
the sixth cervical vertebra is also un-
divided ; and in the dark races of man
the spinous processes of the third, fourth
and fifth vertebrae are more frequently
simple than bifid. (D. J. Cunningham,
Journ. Anat., xx, 637.)
Dorsal or thoracic vertebrae.
— These are twelve in number, and
support the ribs.
The lody as seen from above is
somewhat heart-shaped ; its antero-
posterior and transverse diameters
are nearly equal ; its depth is greater
behind than before.
It is specially characterized by
the presence, at the place where it
joins the arch, of articular surfaces
for the heads of ribs. In the greater
number of instances there are two
costal surfaces on each side, — one at
the upper, the other at the lower
border, — so 'placed that each com-
pletes, with that of the adjacent
vertebra, a cavity for the head of
one rib.
The lamince, broad and flat, are
imbricated or sloped one pair over
another like tiles on a roof. The
superior notches are very shallow,
the inferior deep.
The spinous process, described as
bayonet-shaped, is three-sided, and
terminates in a slight tubercle. It
is longest and has the greatest
downward inclination in those to-
ward the middle of the series.
The transverse processes are
strong, directed outwards and back-
wards, and terminate in a rough
knob which presents anteriorly a smooth surface for articulation with the tuberosity
of a rib.
The articular processes have their cartilaginous surfaces nearly vertical. Those
of the superior processes look backwards, slightly upwards and outwards ; those of
the inferior look forwards, slightly downwards and inwards.
Fig. 7. — SIXTH DORSAL VERTEBRA : A, FROM
ABOVE ; B, FROM THE BIGHT SIUK.
(Drawn by D. Gunn. )
Fig. 8. — FIRST DORSAL VERTEBRA, FROM THE RIGHT
SIDE. (Drawn by D. Gunn.)
10
THE VERTEBRAL COLUMN.
The foramen is nearly circular, and is smaller than in the cervical or the lumbar
region.
The first, tenth, eleventh, and twelfth dorsal vertebras present certain characters
by which they may be individually distinguished.
The first dorsal vertebra in its general conformation approaches very closely
MAM. PROC.
TRANSV. PROC.
ACCESS. PROC.
Fig. 9. — NINTH, TENTH, ELEVENTH, AND TWELFTH DORSAL, AND FIRST LUMBAR VERTEBRA, FROM
THE RIGHT SIDE. (Drawn by D. Gunn.)
the seventh cervical. The body is elongated transversely and concave on the upper
surface ; the superior vertebral notches are of considerable depth ; the upper articular
surfaces are oblique ; and the spinous process is long and nearly horizontal! On
each side of the body is a circular facet close to the upper border for the first
rib, and a very small facet belowr for the second.
The tenth dorsal vertebra touches only one rib on each side, and has a
single nearly complete articular surface, mainly on the pedicle. There is usually
a small facet on the transverse process.
THE LUMBAR VERTEBRAE.
11
The eleventh dorsal vertebra has a complete articular surface on each side
for the head of the rib, but no facet on the transverse process.
The twelfth dorsal vertebra has also only a single facet on each side ; the
inferior articular processes have their surfaces turned outwards, resembling those of
a lumbar vertebra ; the transverse processes are short and present three elevations,
the external, superior, and inferior tubercles, which correspond to the transverse,
mamillary, and accessory processes of the lumbar vertebras. Indications of these
tubercles may often be seen also upon the tenth and eleventh vertebrae.
Varieties. — The ninth dorsal vertebra frequently wants the lower facet on the side of the
.body. The tenth dorsal vertebra sometimes has no facet on the transverse process. The
change from the dorsal to the lumbar type of articular processes occasionally takes place
between the eleventh and twelfth dorsal vertebras.
Lumbar vertebrae. — These are five in number, the largest of the moveable
vertebras, and are distinguished by the absence of costal articular surfaces.
The body has a greater diameter transversely than from before backwards,
MAMII_1_ARY PROC.
ACCESSORY PROC.
RACOSVERSE PROC.
SUP. ARTICULAR PROC.
Fig. 10. — THIRD LUMBAR VERTEBRA, FROM ABOVE. (Drawn by D. Gunn.)
and viewed from above or below its surface presents a reniform outline ; the depth is
generally slightly greater in front than behind.
The lamince are shorter, deeper, and thicker than those of the dorsal vertebrae.
The superior notches are shallow, the inferior deep.
The spinous process projects horizontally backwards. It has considerable breadth
from above downwards, and is thickened and rough along its posterior edge.
The transverse processes, slender and somewhat spatula-shaped, project directly
outwards ; they are shortest in the first, longest in the third vertebra. Their
extremities lie in series with the external tubercles of the lower dorsal transverse
processes, and with the ribs. Behind each at its base is a small process pointing
downwards, which corresponds to the inferior tubercle of the dorsal transverse
process, and is called the accessory process (anapophysis).
The articular processes are thick and strong. Their articular surfaces are vertical j
J2 THE VERTEBRAL COLUMN.
the superior, concave, look backwards and inwards; the inferior, convex, look forwards
and outwards. The superior pair are farther apart than the inferior, and embrace
the inferior pair of the vertebra above them. From each superior articular process
a tubercle projects backwards, which corresponds to the superior tubercle of the
dorsal transverse process, and is called the mamillary process (metapophysis).
The foramen is large and triangular, or widely lozenge-shaped.
The fifth lumbar vertebra is massive, the body is much deeper in front than
behind, the transverse processes are broad and conical, the lower articular processes
are wider apart than the upper, and the lamina project into the spinal foramen on
each side.
While in the European the bodies of the lumbar vertebrae are collectively deeper in front
than behind, in conformity with the curvature of this - part of the column, the individual
Fig. 11. — FIFTH LUMBAR VERTEBRA, FROM ABOVE. (Drawn by D. Gunn.)
segments show some difference in this respect. Thus, the first lumbar vertebra is deeper
behind than in front ; in the second the anterior and posterior vertical diameters are nearly
equal ; and the third, fourth and fifth are characterized by a preponderance of the anterior
depth, which increases progressively from above downwards. In the dark races of man
(Australian, Bushman, Andamanese, Negro) the depth of the five lumbar bodies together is
greater behind than in. front, and the fifth is the only one in which the anterior depth notably
exceeds the posterior. It does not appear probable, however, that this conformation of the
vertebral bodies is accompanied by a less marked degree of lumbar curvature, since the latter
is determined mainly by the intervertebral discs. (W. Turner. Journ. Anat., xx, and
" Challenger " Reports, Zoology, xvi ; D. J. Cunningham, '; The Lumbar Curve in Man and
Apes," Dublin, 1886, and Proc. Roy. Soc., 1889.)
Varieties in number of the moveable vertebrae. — The number of the cervical vertebrae
is remarkably constant. The dorsal and lumbar vertebrae may vary reciprocally, the total
remaining the same, according to the number of ribs present. Thus, if there are only eleven
pairs of thoracic ribs, the twelfth vertebra will have lumbar characters ; while in the more
frequent case of a thirteenth pair of ribs being developed, the corresponding vertebra might
ba regarded as dorsal, although, in general conformation, it usually more resembles the
lumbar type. The whole number of true vertebras may be diminished or increased by one.
In the former state the first sacral vertebra will be the 24th, as is the case generally in the
orang, and, if the number of the ribs remain normal, there will be only four lumbar vertebras.
In the case of increase, the first vertebra to articulate with the hip-bone will be the 26th, and
THE SACRAL VERTEBRAE.
13
there may be twelve dorsal and six lumbar vertebras, or thirteen dorsal and five lumbar.
Sometimes an intermediate or transitional form is met with, as in the so-called hnnbo-sacral
vertebra, in which one side is united to the sacrum, while the other has a free transverse
process (fig. 23, 11) ; such a vertebra may be the 24th or 2oth. The study of the development
of the vertebral column throws light on the origin of these varieties. It appears from the
researches of Rosenberg that in the foetus the 26th vertebra is originally the first sacral, and
that in the course of growth the hip-bones move headwards so as to become attached
also to the 25th, which consequently becomes incorporated in the sacrum. This shifting
may proceed farther, so that the 24th vertebra is included ; or it may be unsymmetrical,
giving rise to a lumbo-sacral vertebra. Similarly, a thirteenth rib arises from the
persistence and growth of a cartilaginous rudiment which is regularly present in the
embryo, but usually becomes incorporated in the transverse process of the first lumbar
vertebra. (J. Struthers, " Variations of Ribs and Vertebrae," Journ. Anat., ix ; P. Topinard,
li Anomalies de nombre de la colonne vertebrale," Rev. d'Anthropol., 1877 ; E. Rosenberg,
" Entwickelung der Wirbelsaule," Morph. Jahrb., i.)
3UP. ARTIC. PROC.
TRAIMSV. PROC. OF
FIRST VERT.
Fig. 12. — THE SACRUM, FROM BEFORE. (Drawn by D. Gunn.) |
Sacral vertebrae. — These by their union in the adult form the os sacrum, but
in youth they present the elements of five distinct vertebras. The sacrum is placed
below the last lumbar vertebra, and articulates laterally with the two hip-bones,
thus completing, together with the coccyx, the wall of the pelvis above and behind.
The uppermost vertebra is the largest, those which follow become rapidly smaller, and
the fifth is rudimentary. Hence the sacrum has the form of a triangle with itg
base directed upwards. It is concave and smooth in front, convex and uneven
behind. The direction of its surfaces is very oblique, its ventral aspect looking
considerably downwards, and forming above, at the place where it joins the last
lumbar vertebra, the projection termed the promontory. The dorsal or posterior
surface looks upwards as well as backwards.
The ventral surface is concave from above downwards, and slightly so from side
THE VERTEBRAL COLUMN.
to side. It is traversed horizontally by four ridges, which indicate the places of
union of the bodies of the five sacral vertebras, and at the extremities of which are
situated on each side four foramina called anterior sacral. These foramina lead
externally into grooves, and dimmish in size from above downwards.
The dorsal surface is convex, very uneven, and somewhat narrower than the
ventral. It presents along the median line three or four small eminences, the
spinous processes, usually more or less connected, so as to form a ridge. Below the
spinous process is a triangular opening, the termination of the spinal canal, the
lateral margins of which are formed by the imperfect laminae of the fourth and fifth
sacral vertebrae, and are produced downwards into a pair of tubercles, the sacral
UPPER APERTURE OF SACRAL- CANAL
SUP. ARTIC. PROC.
AURICULAR
SURFACE
DEPRESSIONS
FOR POSTERIOR
SACRO ILIAC
LIGAMENTS
POST. SAC. FORANI.
NF. LAT. ANGLE
SACRAL CORNU
J-OWER APERTURE OF SACRAL. CANAL.
Fig. 13. — THE SACRUM, FROM BEHIND. (Drawn by D. Gunn.) $
cornua, which represent the inferior articular processes of the last sacral vertebra,
and are connected to the cornua of the coccyx. On each side of the ridge of spines
the surface formed by the united laminae is slightly hollowed, thus giving rise to
the sacral groove, which prolongs the vertebral groove of the moveable part of the
column ; and beyond this are the four posterior sacral foramina, opposite to, but
smaller than the anterior. Immediately internal to each foramen is a slight
eminence, which represents the articular and mamillary processes of the vertebras
above, while external to the foramen a more strongly marked elevation corresponds
to the transverse process.
The part of the sacrum external to the foramina constitutes the lateral mass, and
is broad and thick above, but narrowed below. The outer aspect of the upper part
presents in front a large uneven surface, covered in the recent state with cartilage,
which articulates with the ilium, and is called from its shape the auricular surface :
behind this the bone is rough and marked with strong depressions for the attachment
of ligaments. Lower down, the margin becomes narrowed and sinuous, terminating in
THE SACKAL VERTEBRAE.
15
ROMONTORV
the projection called the inferior lateral angle, below which the breadth of the bone
is suddenly contracted so as to form a notch with the adjacent part of the coccyx.
The base, or upper surface of the first sacral vertebra, bears considerable
resemblance to the
upper surface of
the last lumbar
(fig. 23, 9 and 10).
In the middle it
presents the reni-
form surface of
the body, behind
which is the tri-
angular aperture
of the sacral canal,
bounded by the
depressed laminse.
On each side of the
aperture is an arti-
cular process, simi-
lar to the superior process of a lumbar vertebra, but
of large size, and bearing a well-developed mamillary
process. In front of this is a groove which forms with
the lower notch of the last lumbar vertebra an inter -
vertebral foramen. The external portion of the base
presents posteriorly an eminence corresponding to the
lumbar transverse process, and in front of that a
triangular smooth surface, continuous with the iliac fossa
of the hip-bone, and known as the ala of the sacrum.
The lower end or apex, formed by the small inferior
surface of the body of the fifth sacral vertebra, is trans-
versely oval, and articulates with the coccyx.
The sacral canal is curved with the bone, and gra-
dually narrows as it descends ; in transverse section
ifc is t^ee-sided above, but flattened and rather semi-
lunar below. It terminates on the posterior surface of
the bone between the sacral cornua, where the lamiiias
of the last two sacral vertebras are
imperfect. From this canal there
pass outwards in the substance of
the bone four pairs of interverte-
bral foramina, closed externally
by the lateral masses, but opening
on the surfaces by the anterior
and posterior sacral foramina.
Fig. 14.--SACRUM AND
FROM THE RIGHT SIDE.
by D. Gunn.) f
CRAL CANAL
The sacrum of the female is
broader in proportion to its length,
and usually flatter than that of the
male ; but the curvature varies
greatly in different skeletons.
The sacrum of man is charac-
terized by its great breadth in comparison with its length.
LATERAL
Fig. 15. — TRANSVERSE SECTION OF SACRUM, PASSING
THROUGH THE FIRST PAIR OF FORAMINA. (G. D. T. ) £
This proportion is expressed by
the sacral index, which is ascertained by the following calculation,
100 X breadth
The
length
average sacral index in the male European is 112, in the Negro 106, in the Australian 99,
16
THE VERTEBRAL COLUMN.
and in the Andaman ese 94. In the European female it is about 116. The anthropoid apes
have a sacral index varying from 87 in the orang to 72 in the gorilla. (Turner, Joum. Anat., xx,
and " Challenger " Reports, Zoology, xvi.)
Varieties. — The sacrum not unfrequently consists of six pieces, a condition which is
generally due to the inclusion of the first coccygeal vertebra. More rarely there are only four
sacral vertebras. Occasionally the bodies of the first and second vertebras are not united,
though complete union has taken place in every other part ; or the first vertebra may present
on one side the usual sacral form, while on the other it has the form of a lumbar vertebra, and
is not united to the next (see fig. 23, 11, Z'), a peculiarity connected with the oblique form of
pelvis. Instances also occur in which it presents, on both sides, characters intermediate
between those of sacral and lumbar vertebras. The sacral canal may be open below to a
greater extent than usual •; it has even been found open throughout.
Coccygeal vertebrae, coccyx. — These are very rudimentary vertebras,
commonly four, sometimes five, seldom only three in number. The first of the
series is considerably broader than the others. It presents superiorly, on the part
corresponding to the body, an oval concave surface, which articulates with the lower
end of the sacrum. From its posterior surface two small processes, termed cornua of
Fig. 16. — THE COCCYX: A, FROM BEHIND; B, FROM BEFORE. (Drawn by D. Gunn.) f
the coccyx, project upwards ; they represent the pedicles and superior articular
processes of the vertebras generally, and are connected at their extremities to the
sacral cornua, with which they enclose an aperture — the last intervertebral foramen
(fig. 14) for the passage of the fifth sacral nerve. On each side the short transverse
process projects, and usually bounds, with the lowest part of the lateral margin of the
sacrum, a notch for the anterior division of the same nerve ; but in some cases it is
united by bone to the lower lateral angle of the sacrum, so as to form a fifth anterior
sacral foramen.
The remaining three coccygeal vertebras are much smaller than the first.
The second piece, when separate, has upper and lower flattened surfaces for
articulation with the vertebra above and below ; on each side is a rudiment of the
transverse process in the form of a slight tubercle ; and on the posterior aspect there
may sometimes be seen two small eminences in series with the cornua of the
first piece, and representing the last traces of a neural arch. The third and fourth
pieces are mere rounded nodules, slightly compressed from above downwards, and
corresponding solely to vertebral bodies. In middle life the first piece is usually
separate, while the three lower pieces are united into one, the original separation
being indicated by transverse grooves.
In advanced life the coccygeal vertebras, having been previously joined into one
bone, may become also united to the sacrum. This union occurs at an earlier age
and more frequently in the male than in the female, but it is subject to much
variation. The first piece often joins the sacrum before the union of the rest of the
bone.
THE VJSKTEBRAL COLUMN AS A WHOLE.
17
Jfi.
.4
A;
cot'
Fig. 17. — VERTEBRAL COLUMN OP AN ADULT MALE,
FROM BEHIND. (Allen Thomson.) £
C 1, first cervical vertebra ; D 1, first dorsal vertebra ;
L 1, first lumbar vertebra; S 1, first sacral vertebra; CO 1,
first coccygeal vertebra. The transition in the form of the
transverse processes and tubercles in the lower dorsal and
first lumbar vertebra is well marked in this specimen.
VOL. II.
Fig. 18. — VERTEBRAL COLUMN, FROM
THE LEFT SIDE. (Allen Thomson. ) £
The letters and numbers indicate the
several vertebrae. The antero-posterior
curves of the column are shown, together
with the shape and size of the vertebrae
and intervertebral spaces.
18 THE VERTEBRAL COLUMN.
According to the observations of E. Steinbach there are in most cases five coccygeal
vertebrae in the male, four or five with about equal frequency in the female. (" Die Zahl der
Caudalwirbel beim Menschen," Diss., Berlin, 1889.)
The vertebral column as a whole. — The vertebral column may be regarded as a
central axis upon which the other parts of the skeleton are arranged. Superiorly
it supports the skull, laterally the ribs, through which also it receives the weight of
the upper limbs, and near its lower extremity it rests upon the hip-bones, by which
the weight of the body is transmited to the lower limbs. It is a pillar of support to
the rest of the skeleton, and protects the spinal cord by enclosing it in a bony
canal. Its average length is about 28 inches in the male, 27 inches in the female.
When seen in profile the column presents four curves, directed alternately for-
wards and backwards, — forwards in the cervical and lumbar regions, backwards in
the dorsal and sacral. The upper curves pass imperceptibly into one another, but
at the junction of the last lumbar vertebra with the sacrum a considerable angle is
formed, known as the lumbo-mcral or sacro-vertelral angle, causing the promontory
to overhang the cavity of the pelvis. The dorsal and sacral curves are primary
curves affecting those parts of the column which enter into the formation of the
bony-walled cavities, the thorax and pelvis ; they make their appearance at an early
period of foetal life, and are due to the conformation of the vertebral bodies : the
cervical and lumbar curves are secondary or compensatory curves, necessary to the
upright posture, only developed after birth, and dependent mainly on the shape of
the intervertebral discs ; in these regions also the principal movements of the spine
take place. The curves obviously confer upon the column greater elasticity and
security from injury than it would have were it perfectly straight. In the upper
dorsal region there is also very frequently a slight degree of lateral curvature, the
convexity of which, in most cases, is directed towards the right side, and which is
probably connected with the greater use made of the right than of the left arm.
Viewed from the front, the bodies of the vertebrae are seen to become broader
from the axis to the first dorsal, then slightly narrower to the fourth dorsal, and
from this vertebra they gradually widen to the base of the sacrum. The width
between the extremities of the transverse processes is considerable in the atlas ; small
in the axis, it becomes greater as far as the first dorsal vertebra ; thence it is again
gradually contracted as far as the last dorsal, and becomes suddenly much greater in
the lumbar region.
In the lateral view, the antero-posterior diameter of the bodies increases in de-
scending through the dorsal and lumbar regions.
Viewed from behind, the spines occupy the middle line. On the sides are the
vertebral grooves, corresponding to the larninas, and bounded externally in the cer-
vical and dorsal regions by the transverse processes, and in the lumbar by the
mamillary processes. Along each groove is a series of spaces between the lamina?,
which, in the natural condition, are filled up by the yellow ligaments. The extent
of • these intervals is very trifling in the neck and in the greater part of the back ;
it increases in the lower third of the dorsal, and still more in the lumbar region.
The interval between the occipital bone and the arch of the atlas is considerable,
and so is that between the last lumbar vertebra and the sacrum.
The only part of the vertebral column that appears on the surface of the body
is the row of spinous processes, and these are subcutaneous from the seventh cervical
to the third sacral. The upper cervical spines are deeply placed and can be felt with
difficulty in the median interval between the muscular masses of the back of the
neck ; the sixth is sometimes long and in such cases may project. The seventh
cervical and the following one or two dorsal spines are prominent ; the others lie at
the bottom of the long spinal furrow produced by the eminence of the spinal muscles
on each side.
OSSIFICATION OF THE VERTEBRAE.
19
OSSIFICATION OF THE VERTEBRAE.
The vertebrae in general. — The ossification of each vertebra proceeds in cartilage from
three principal centres, one for the main part of the body, and one on each side for the arch
and processes, together with a small part of the body. The lateral centres appear about the
7th week of foetal life, that of the body very soon afterwards. From these centres the
ossification extends gradually, so as to form the greater part of the vertebra. The central
ossification does not pass, however, in the dorsal vertebra} the place of articulation of the head
of the rib, but leaves on each side a portion of the body which is formed from the lateral
ossification, and is separated up to the third year by a narrow cartilaginous interval — the
newo-central gynchondroaii. It would appear farther, that while ossification in the arches
commences first in the cervical vertebras, the osseous centres of the bodies appear earliest in
the lower dorsal vertebrae.
At the time of birth most of the vertebras consist of three osseous pieces, corresponding to
the three original centres. In the first year of infancy the laminas of opposite sides become
united in a number of the vertebras, but not in all. The spinous processes, remaining
Fig. 19. — OSSIFICATION OF THE VERTEBK.E.
(R. Quain.)
A, foetal vertebra, showing the three primary centres ;
1 , 2, neural ossifications ; 3, central ossification.
B, dorsal vertebra from a child of two years ; 1 & 2
are seen to have encroached upon the body at * the
neuro-central sy'nchondrosis, to have extended into the
articular and transverse processes, and to have united
behind in the spinous process, leaving the ends cartila-
ginous.
C, dorsal vertebra at about seventeen years, showing
epiphyses on the transverse processes, 4 & 5, and
spinous process, 6, and the upper epiphysial plate of
the body, 7.
D & E, parts of a lumbar vertebra of about the same
age, showing, in addition to the foregoing, 8, the lower
epiphysial plate of the body ; 9 & 10, the epiphyses of
the mamillary tubercles.
cartilaginous for a time, are gradually completed by the growth of the cartilage and the
extension of the bone into them, and at the same time, by the ossific extension of the
transverse processes and other parts, the vertebras gradually attain to nearly their full size and
shape about the age of puberty. At different periods subsequent to this, five epiphyses, or
supplementary centres of ossification, are added. Three of these are small portions of bone,
placed on the tips of the spinous and transverse processes : the other two are thin annular
plates on the upper and lower surfaces of the body at its circumference. In the lumbar
vertebrae two other epiphyses surmount the mamillary processes. These epiphyses appear from
the sixteenth to the twentieth year, and are not wholly united to the rest of the vertebra
before the twenty-fifth year. The transverse process of the first lumbar vertebra is sometimes
developed from a separate centre. The anterior divisions of the cervical transverse processes
are for the most part ossified by the extension into them of osseous substance from the
neighbouring posterior part of the process and from the arch ; but there are usually separate
osseous nuclei for those of the seventh, sometimes also of the sixth, and even the fifth or
second vertebras.
Atlas and axis. — The ossification of the atlas and axis differs considerably from that of
Fig. 20. — OSSIFICATION OF THE ATLAS. (E. Quain.)
A, before birth ; B, in the first year ; 1 & 2, lateral
centres of ossification ; 3, ossific centre in the anterior
arch.
the other vertebrae. In the atlas the anterior arch is formed by a strip of cartilage in which
ossification, commencing by one or two centres, only appears in the course of the first year
after birth. The posterior arch, together with the lateral masses, is formed from two centres
c 2
£0 THE VERTEBRAL COLUMN.
which correspond to the neural ossifications of the other vertebrae, and which begin to ossify
about the seventh week. Their union posteriorly occurs in the third year, and is frequently
preceded by the formation of a distinct spinal nucleus. Their union with the anterior arch
does not take place till the fifth or sixth year.
In the axis, the arch and processes are formed from two centres corresponding to those of
the other vertebras, and appearing about the seventh or eighth week. Ossification begins in
Fig. 21. — OSSIFICATION OF THE AXIS. (R. Quain.)
A, from a foetus of seven months ; 3, centre for the body ;
4, 5, two centres in the base of the odontoid process.
B, shortly after birth ; 1, 2, neural ossifications ; 3,
central ossification ; 6, odontoid ossification.
the body about the fourth month, from one or sometimes two centres, occupying the lower
part of the common cartilage of the body and odontoid process. In the upper part of this
cartilage, a little later, two collateral centres appear for the odontoid process ; these soon unite
into one, so that at birth the axis is composed of four pieces of bone. About the fourth year
the odontoid process becomes joined to the body and the fore part of the neural arch of the
axis on each side, and a little later union occurs in front and behind. In the centre,
however, a small disc of cartilage remains until advanced age.1 The apex of the odontoid
process is formed from a distinct centre which appears in the second year, and joins about the
twelfth year. There is the usual annular epiphysis on the lower surface of the body.
Sacral vertebrae. — Each of the sacral vertebras has three primary centres of ossification,
one in the body and a pair in the arch. The centres of the bodies of the first three vertebra;
appear about the eighth or ninth week, those of the two following vertebras somewhat later.
Fig. 22. — OSSIFICATION OF THE SACRITM. (R. Quain.)
A, sacrum of a fcetus before six months seen from the front, showing the ossific centres in the
bodies of the vertebrae.
B, at birth ; 2, 2, additional centres for the lateral masses.
C, about twenty-three years ; 3, 3, epiphysial plates still visible above and below the first vertebral
body ; 4, 4', lateral epiphysial plates.
D, upper surface of first sacral vertebra at four or five years ; 1. and 2, as in A and B. (Allen
Thomson.)
A & B, nearly full size ; C, one-fourth ; D, one-third.
The lamina? begin to ossify about the sixth month, but the time of union with the bodies
differs in the different vertebras, taking place as early as the second year in the lowest, but
not till the fifth or sixth year in the uppermost. In each of the first three vertebras (sometimes
however only in two, sometimes in four) the anterior part of the lateral mass on each side is
formed from an additional nucleus which appears at the outer margin of the anterior sacral
foramen from the sixth to the eighth month. These unite to the bodies later than the arches.
In the case of the lower two vertebras the lateral masses are formed by extension of
ossification from the primary lateral nuclei. On the body of each vertebra epiphysial plates
are formed after puberty, as in other vertebras ; and two irregular plates of bone are added on
pach side of the sacrum, the uppermost of which extends over the auricular surface, and the
1 D. J. Cunningham, Journ. Anat., xx, 238.
SERIAL HOMOLOGY OF THE VERTEBRAE. 21
lower over the sharp edge below. These appear from the eighteenth to the twentieth year,
and are united about the twenty-fifth. The bodies of the sacral vertebrae are at first separated
by intervertebral discs, but about the eighteenth year, in the case of the lower vertebrae,
ossification begins to extend through these discs and the epiphyses, so as completely to unite
the adjacent bodies. The ossific union of the first and second bodies does not take place till the
twenty-fifth year or later. Previous to this, the lateral masses have coalesced in the same
order as the bodies.
Coccygreal vertebrae. — Each of the coccygeal vertebras is ossified from a distinct piece of
cartilage, and usually from a single centre, but in the upper sometimes from two centres.
Ossification commences in the first generally about the time of birth ; in the second, from the
fifth to the tenth year ; in the third, some time before, and in the fourth, some time after
puberty. The ossific union of the three lower coccygeal vertebras occurs before middle life ;
their union with the first, and the union of this with the sacrum, belong to the later periods
of life.
Variations may occur in the mode of ossification of the vertebras, as is shown by the nature
of certain malformations. Thus, instances are recorded in which a vertebral body is
represented by two pieces of bone, separated by a median interval : here ossification must
have proceeded from two centres, as is the case normally in the odontoid process, and
sometimes in the body of the axis : probably this is the reappearance or persistence of a
primitive condition. Similarly, the neural arch of the fifth lumbar vertebra (very rarely of
one of the other vertebrae) may have a double origin, being divided by a cleft passing
obliquely between the superior and inferior articular processes : according to Rambaud and
Renault l there are always two nuclei in each half of the neural arch.
SEBIAL HOMOLOGY OF THE VEBTEBItfflS.
It is evident from the foregoing descriptions that the different segments of the vertebral
column are generally similar in construction ; and this similarity is for the most part so
marked that there can be no doubt of the homodynamy of the several constituent parts of
successive vertebras. In certain instances, however, there are peculiarities of arrangement
which offer some difficulty in tracing the precise correspondence, and in explanation of these
chiefly the following brief sketch of the serial homology of the vertebrae is given. The
accompanying views of the vertebrae and some of their varieties (fig. 23) will also assist the
reader in comparing their forms.
1. The series of centra or bodies, surrounding the primary axis of the notochord, is
complete in man, from the odontoid process of the second vertebra to the caudal extremity.
It must, however, be remembered that the part called the body of a vertebra includes not only
the proper central ossification, but also the ventral extremity of the neural ossification on each
side. The body is apparently absent in the atlas, but the part corresponding to the central
ossification of that vertebra is united with the body of the axis in the odontoid process ;
while the anterior arch of the atlas probably belongs to the series of subcentral parts or
hypapopliyses. The proofs of this view are derived mainly from, 1st, the remains of the noto-
chord having been traced in the foetus through the odontoid process (and not through the
anterior arch of the atlas) into the base of the skull ; 2nd, the separate ossification in cartilage
of the odontoid process ; and 3rd, the existence in some animals, as the ornithorhynchus and
some reptiles, of a bone corresponding to the odontoid process, in a separate condition, without
any other part representing the centrum of the atlas.
2. The series of neural arches is complete in the whole vertebral column of man, with
the exception of the lower three coccygeal vertebras, and in part of the first coccygeal and
lower sacral vertebras. The neural spines are also complete in nearly the same vertebras as
the arches. The spine is absent or little developed in the atlas, bifid at its extremity in the
next four or five cervical vertebrae, but simple in all the remaining vertebras in which it is
present.
3. The articular processes or zygupophyses, superior and inferior (preaxial and
postaxial), correspond in their relations throughout the whole of the vertebrae in which they
exist, with the exception of both of those of the atlas and the superior of the axis. In these
vertebras the articular processes are not in the series of zygapophyses, being situated in front
of the place of exit of the spinal nerves, instead of behind it, and therefore in a position
which corresponds to that of the part of the vertebral body formed from the neural ossifica-
tion. The joints which they form must accordingly be looked upon as homologous with the
lateral portions of the articulations between the bodies of the succeeding vertebrae. In the
sacral vertebras the articular processes, existing as such in early life, come to be in the adult
united by anchylosis. In the lower three coccygeal vertebras they are absent.
1 "Origine et Developpement des Os," Paris, 1864. This work may be referred to for more detailed
information concerning the ossification of the vertebrae, as well as of the bones generally.
THE VERTEBKAL COLUMN.
Fig. 23. — VIEWS OF DIFFERENT VERTEBRA FROM ABOVE TO ILLUSTRATE THEIR HOMOLOGIES
AND SOME OF THEIR VARIETIES. (Allen Thomson.)
1, atlas ; 2, axis ; 3, fifth cervical ; 4, seventh cervical with supernumerary ribs ; 5, middle dorsal ;
6, first dorsal, with costal arch and sternum attached ; 7, third lumbar ; 8, first himbar with supernu-
merary ribs ; 9, fifth lumbar ; 10, first sacral ; 11, lumbo-sacral vertebra ; 12, fourth sacral vertebra in
a young subject ; 13, four coccygeal vertebrae. In the several figures the parts are indicated by letters
as follows, viz., in 1, s, spine ; n, neural arch ; c', the space occupied by the odontoid process, or dis-
placed centrum ; h. anterior arch ; ar, superior articular process ; in 2, c", odontoid process ; ar, superior
articular surface ; z', inferior articular process : in 3, c, centrum ; z, z' , superior and inferior articular
processes : in 4, t, transverse process ; r, vertebrarterial foramen ; co, moveable right supernumerary or
cervical rib ; x, with a dotted line marking the place where an anchylosed rib on the left side may be
considered to be superadded to the transverse process of the vertebra : in 5, t, transverse process with
SERIAL HOMOLOGY OF THE VERTEBRA. 23
costal facet ; cc, costo-central facet : in 6, v, vascular interval ; ct, costo-transverse, and cc, costo-central
articulations ; co, first rib : in 7, in, mamillary, and a, accessory tubercles ; t, transverse process : in 8,
CO, co', supernumerary ribs: in 10, I, lateral mass: in 11, I', place of the lateral mass, remaining
undeveloped in tins instance : in 12, tl, the transverse process and lateral mass which unite with the
corresponding parts above ; f, f, anterior and posterior sacral foramina thus formed : in 13, c, the
centrum, which alone remains in the lower coccygeal vertebrae.
4. It is in the comparison of the parts known in human anatomy under the general name
of transverse processes that the main difficulty of establishing homologies exists. In the
cervical vertebras the processes so called are pierced by a vertebrarterial foramen, and
most of them have two tubercles. Those of the dorsal vertebras are for the most part simple,
but articulate with the tubercles of the ribs, whence they are known in comparative anatomy
as the tubercular processes (diapophyses). At the place of articulation of the head of the rib
with the vertebra there is in some animals a projection, called the capitular process
(parapophysis) ; this is represented in man only by the articular facet on the body, which is
separated however from the proper central ossification by the neuro-central synchondrosis.
It is generally admitted that the part of the cervical transverse process in front of the verte-
brarterial foramen corresponds to the first part of a rib, as is illustrated by the separate ossification
of that piece of bone in the seventh cervical vertebra in man. and by the occasional occurrence
of a more fully developed cervical rib in that situation (fig. 23, 4).
In the lumbar vertebras the transverse processes are elongated laterally, and at their root
two other processes become apparent, viz., the mamillary or mctapopliysis directed preaxially,
and the accessory or anapophysis, directed postaxially. Several circumstances in the anatomy
of the bones and muscles indicate that the outer part of the lumbar transverse processes is
serially homologous with the first part of the ribs, but so intimately combined with both
capitular and tubercular processes, and the part lying between them, as to leave no arterial
passage. This view receives confirmation from the presence of a costal element in connection
with the transverse process of the first lumbar vertebra in the foetus, and its occasional
development to form a supernumerary rib (p. 13 ; fig. 23, 8).
In the sacral part of the column still greater departure from the form of the transverse
process of the upper vertebras takes place by the large development and ossific union of the
lateral parts. Throughout the whole five vertebras recognised as sacral in man, this may be
looked upon as occurring to some extent in portions of the bones which are serially
homologous with the combined capitular and tubercular processes ; but in the upper sacral
vertebras, another element is interposed between the transverse process and the iliac surface
of articulation, constituting the greater port'on of the lateral mass of the sacrum. This
element is generally regarded as serially homologous with part of a rib, and those vertebras
which are thus connected to the ilium by means of a costal element are distinguished as true
sacral, the remaining anchylosed vertebras being called pseudo-sacral.
With the exception of the anterior arch of the atlas already referred to, there are no parts
developed in the huma,n skeleton corresponding to the hypapopkyses which occur in connec-
tion with the vertebral column of animals, such as the ''chevron" bones below the caudal
vertebras of cetacea, and the hasmal arches enclosing the main artery of fishes.
II.— THE THORAX.
The skeleton of the thorax consists of the dorsal vertebrae already described, the
sternum, the ribs, and the costal cartilages.
THE STERNUM OR BREAST-BONE.
The sternum is situated in the median line at the fore part of the thorax. It
is connected with the rest of the trunk by the cartilages of the first seven ribs on
each side ; and at the upper end it gives attachment to the clavicles. It consists
originally of six segments. The first of these usually remains separate from the
rest, and is called the manubrium : the succeeding four are united into one in the
adult, and form the body : the sixth generally remains cartilaginous for some years
after birth, and often partially so even to advanced age, constituting the ensiform
process ; in middle life it is most frequently united by bone to the body.
The sternum is flattened from before backwards, and presents a slight longitudinal
curve with the convexity in front. It is of unequal width, being broad at the upper
part of the manubrium, considerably narrower at the lower end of that portion and
THE THORAX.
B
INTERCLAVICULAR NOTCH
CLAVICULAR NOTCH
BODY
MANUBRIUIVI
ENSIFORW PROCESS
Fig. 24. — THE STERNUM: A, FROM BEFORE ; B, FROM THE LEFT SIDE. (Drawn by D. Gunn. ) f
The Roman numerals indicate the articular surfaces for the corresponding rib-cartilages.
in the firsb segment of the body, somewhat wider near the lower end of the body, and
finally narrowed at the junction with the ensiform process. It consists of light can-
cellated tissue, with a thin covering of compact bone.
The manubrium (prcsternum) is the thickest part of the bone. Its anterior surface
presents a slight median elevation ; its posterior surface is smooth and somewhat con-
cave. Its upper border is divided into three deep notches ; the middle one is named
THE STERNUM OR BREASTBONE. 25
the incisura semilunaris, or interclavicular notch ; the lateral ones form two depressed
articular surfaces, directed upwards, outwards and backwards, for articulation with
the clavicles, and called the clavicular notches. Each lateral border presents supe-
riorly, close to the clavicular notch, a rough triangular surface, which unites with
the cartilage of the first rib. Below this the bone slopes inwards, and at its inferior
angle presents a small surface, which with a similar one on the body forms a notch
for the cartilage of the second rib. The lower margin is straight and united by
cartilage to the upper margin of the body.
The body (gladiolus, mesosternum) is marked on its anterior surface by three
slight transverse elevations at the lines of junction of its four component parts. Its
posterior surface is comparatively smooth. Each lateral margin presents five notches
for the reception of costal cartilages, and a small surface above, which, with the
similar depression on the manubrium, forms the notch for the second costal cartilage.
The notches for the third, fourth, and fifth costal cartilages are opposite the lines of
junction of the four segments of the body of the sternum ; those of the sixth and
seventh are placed close together on the sides of the inferior segment, that for the
seventh being completed by the ensiform process.
The ensiform or xiphoid process (metasternum, xiphisternum) is a thin
spatula-like process projecting downwards between the cartilages of the seventh
ribs. It is subject to frequent varieties of form, being sometimes bent forwards,
sometimes backwards, often forked, and occasionally perforated.
The sternum is subcutaneous in the middle line, forming the floor of the sternal
groove between the pectoral muscles, which cover the lateral portions of the anterior
surface. The upper end is marked by the deep suprasternal notch; and the ensiform
process lies at the bottom of the infrasternal depression, the latter being due to the
prominence of the body and the seventh costal cartilages beyond the surface of the
ensiform process.
The length of the sternum and the proportions of its parts differ somewhat in the two
sexes. In the male the body is as a rule slightly more than twice as long as the manubrium ;
while in the female the whole bone is relatively shorter, and the body is usually less than
twice the length of the upper segment. Individual variations are, however, frequent and great.
(M. Strauch, Diss., Dorpat, 1881 ; T. Dwight, Journ. Anat., xv, 327, and xxiv, 527 ; F. Peter-
moller, Diss., Kiel, 1890.)
Varieties. — The sternum is subject to many varieties of form. It is not unfrequently
much shorter than usual, and indented at its lower part, as occurs especially from the pressure
of the cobbler's last. Occasionally the lower part of the body is perforated by the so-called
sternal foramen (fig. 30, E) ; and in rare cases the sternum has been found divided to a
greater or less extent, constituting the malformation of fissura sterni, and connected in some
instances with ectopia cordis.
Two small nodules of bone, ossa suprastcrnalia, have been found in some rare cases at the
upper border, close to the clavicular notches, united by cartilage and ligament to the sternum.
Their position is indicated by the asterisks (**) in figure 30, E. They appear to be vestiges of
the episternal bone of monotremata and lizards, the lateral parts of which are represented
normally in the interarticular fibro-cartilages of the stemo-clavicular articulations.
THE RIBS.
The ribs (costce), twelve in number on each side, constitute a series of arched
and highly elastic bones, which extend outwards and forwards from the vertebral
column, and form the lateral walls of the thorax. Their anterior extremities give
attachment to cartilaginous prolongations — the costal cartilages, the first seven pairs
of which pass inwards to the sternum. On this account the first seven pairs of ribs
are called sternal, also true, and the remaining five pairs asternal or false ribs. Of
these asternal ribs, each of the upper three has its cartilage attached along its supsrior
border to the cartilage of the rib above it ; while the two last are entirely free from
such attachment, and are thence called floating ribs.
£6 THE THORAX.
General characters of the ribs. — These are best marked in the ribs near the
middle of the series. The posterior extremity is thickened, and is termed the head
TUBEROSITY
NON-ARTICULAR PART
or capitulum ; it presents a superior and an inferior
oblique articular surface for articulation with the
bodies of two vertebrae, and, between them, a slight
ridge, to which the interarticular ligament is attached.
At a little distance from the head, and separated from
it by the slightly constricted neck, is the tuberosity,
an oval eminence Avhich is divided into two parts by
an oblique groove ; the inner part is smooth and
articulates with the transverse process of the lower of
Fig. 26. — FIFTH RIB OF THE RIGHT SIDE, FROM BEHIND.
(Drawn by D. Gunn.) |
the two vertebrae with which the head is connected,
while the outer part is rough and serves for the
attachment of the posterior costo-transverse ligament.
The whole extent beyond the tuberosity constitutes
the body. It is laterally compressed, and broader
from above downwards towards the anterior extremity.
Outside the tuberosity, over the most convex part of
the body, is a rough line which corresponds to the
outer border of the erector spinae muscle, and marks
the angle, so called because at this point the rib takes
a more sudden curve, its direction being now forwards
and outwards. The inferior border presents on its
inner aspect the subcostal groove, in which lie the
intercostal vessels and nerve, and which is best
marked opposite the angle and disappears in front.
The anterior extremity of each rib is hollowed at its tip into an oval pit, in which
the costal cartilage is implanted.
Inclination and curves. — There is a general inclination of the ribs downwards
from the head to the anterior extremity, the slope being greatest between the head
Fig. 25. — FIFTH RIB OF THE RIGHT
SIDE, FROM BELOW. (Drawn by
D. Gunn.) £
THE RIBS. 27
and angle. The curve of the ribs is more marked towards the back part than in
front, especially near the angle. Besides the main curves now mentioned, the rib
is slightly twisted on itself, so that while its surfaces are vertical behind, they are
placed somewhat obliquely in front.
Special characters of certain ribs. — The ribs increase in length from the
first to the seventh or eighth, and decrease to the twelfth, so that the last is little
MIIMEIMCE FOR SERRATUS MAGNUS
Fig. 27. FlKST AND SECOND RIBS OF THE EIGHT SIDE, FROM ABOVE.
(Drawn by D. Gunn.) f
longer, often even shorter, than the first. The first rib is the broadest, and after it
the middle ones ; the twelfth is the narrowest. The distance of the angle from
the tuberosity increases gradually from above down.
The first rib is hot twisted, and is so placed that its surfaces look nearly upwards
and downwards. The head is small, and presents a single articular surface for the
first dorsal vertebra. The neck is slender, and the angle coincides with the
tuberosity. On the superior surface are two slight smooth depressions with an
intervening rough mark, and a considerable rough surface behind. The rough
surface marks the attachment of the scalenus medius muscle, the posterior depression
the position of the subclavian artery, the anterior depression the subclavian vein ;
and the intervening slight elevation, frequently terminating in a sharp spine on the
inner edge — the scalene tubercle — indicates the attachment of the scalenus anticus
muscle. There is no subcostal groove on the first rib.
The second rib, longer than the first, presents externally a prominent roughness
which marks the attachment of the serratus magnus.
In the eleventh and twelfth ribs the articular facet on the head is single, and
the tuberosity is represented only by a slight elevation or roughness, without an
articular facet. The subcostal groove is faintly marked on the eleventh, and is
absent, together with the angle, from the twelfth.
Varieties. — The number of the ribs is sometimes increased to thirteen on one or both
sides. The supernumerary rib is usually short, and is most frequently formed in connection
with the transverse process of the first lumbar vertebra, or occasionally with the seventh
cervical ; in the latter case the additional rib has generally a double attachment, viz., to the
body, and to the transverse process of the vertebra outside a vertebrarterial foramen (see
fig. 23, 4, v, v, and 8, <?0). In rare instances the additional rib is associated with a
thirteenth dorsal vertebra (see p. 13). The tenth rib frequently articulates only with
28 THE THORAX.
one vertebra ; and it may want the articular facet for the transverse process. The
twelfth rib varies in length from 8 inches to less than an inch ; complete suppression
is very rare.
Fig. 23. — TENTH, ELEVENTH, AND TWELFTH RIBS OF THE BIGHT SIDE, FROM BELOW.
(Drawn by D. Gunn. ) f
The costal cartilages prolong the ribs towards the sternum. Their breadth
diminishes gradually from the first to the last, while their length increases as far as
the seventh, after which they become gradually shorter. Their line of direction
varies considerably. The first descends a little, the second is horizontal, and all the
rest, except the last two, ascend more and more from the rib towards the sternum as
they are situated lower down. The external or costal extremity, convex and uneven,
THE THORAX AS A WHOLE. 29
is implanted into and united with the end of the corresponding rib. The internal
extremities of the cartilages of the true ribs (except the first, which is directly united
to the sternum without articular cavity) are smaller than the external, and fit into the
corresponding notches on the side of the sternum. Each of the cartilages of the first
three false ribs becomes slender towards its extremity, and is attached to the lower
border of that which is next above it. The eleventh and twelfth are pointed and
unattached. The fifth, sixth, seventh, and eighth cartilages form a series of inter-
chondral articulations, by means of a broad process sent down from the rounded angle
of the one meeting a less salient projection from the upper border of the next.
Varieties. — The eighth costal cartilage not unfrequently articulates with the sternum.
Occasionally the seventh costal cartilage fails to reach the mesosternum (owing to reduction
of the latter), and meets its fellow in front of the ensiform process. The articulation
between the fifth and sixth cartilages is sometimes wanting, and then one may be formed
between the eighth and ninth.
THE THORAX AS A WHOLE.
The bony thorax is of a somewhat conical shape, flattened from before back, and
much longer behind than in front. The posterior wall, formed by the dorsal
Fig. 29. — FRONT VIEW OF THE THORAX.
1, manubrium ; 2, is close to the place of union of the
first costal cartilage ; 3, clavicular notch ; 4, body of the
sternum ; 5, ensiform process ; 6, groove on the lower
border of the ribs ; 7, the vertebral end of the ribs ; 8, neck ;
9, tuberosity; 10, costal cartilage; 12, first rib; 13, its
tuberosity ; 14, first dorsal vertebra ; 15, eleventh rib ; 16,
twelfth rib.
vertebrae and the ribs, is convex from above
down, and, the ribs being directed backwards
from the vertebrae as far as their angles, a broad
furrow is produced on each side of the spines, which
lodges the erector spinae muscle. The anterior
wall, formed by the sternum and costal cartilages,
is only slightly convex, and is inclined at an
angle of 20° to 25° with the vertical. In the
condition of expiration the upper border of the
sternum is opposite the disc between the second and third dorsal vertebrae, the
junction of the manubrium and body opposite the middle of the fifth dorsal vertebra,
and the xiphi-sternal articulation about opposite the interspace between the ninth
and tenth dorsal vertebra?.
The sides are sloped outwards to about the ninth rib, are slightly convex from
above down, and strongly arched from before back. The upper aperture is
contracted, reniform, nearly plane, and much sloped downwards ; the lower is
irregular ; the margin ascends on each side from the tenth rib to the xiphi-sternal
articulation, and thus gives rise to the subcostal angle, in the centre of which the
ensiform process projects. The form of the cavity corresponds generally to that of
the exterior, but in the median plane the antero-posterior diameter is much reduced
by the projection of the bodies of the vertebras ; as a consequence of this and the
backward direction of the hinder ends of the ribs, a deep hollow is formed on each
side, into .which the posterior portions of the lungs are received, and thus the weight
of the body is thrown farther back and is more equally distributed around the
vertebral column.
30
THE THORAX.
The intercostal spaces are eleven in number, and somewhat wider above than
below, but varying with the elevation or depression of the ribs.
In man the transverse diameter of the thorax exceeds the antero-posterior, whereas in
quadrupeds the dorso- ventral diameter is usually the greater. In the human foetus also the
sagittal diameter preponderates, and at the time of birth it is but little less than the
coronal. In the female the thorax is relatively shorter, and more rounded than in the male.
OSSIFICATION OP THE STEBNUM AND BIBS.
The ossification of the sternum begins about the sixth month, and usually by a single
centre in the manubrium. The next centre appears at the seventh month in the upper
fc-
Fig. 30. — OSSIFICATION OF THE STERNUM. (R. Quain.)
A, the cartilaginous sternum before the middle of fetal life.
B, the sternum at birth. 1, 2, 3, & 4, the nuclei for the manubrium and upper three pieces of the
body.
C, the sternum soon after puberty, showing cartilage between the manubrium and body, and
imperfect union of the first, second and third pieces of the body, while the third and fourth are
united.
D, a sternum at birth with an unusual number of ossific centres, six in the manubrium, 1', which
is very uncommon ; two pairs in the lower pieces of the body 3' & 4', which is not unusual ; 2, the
single centre of the first piece of the body.
E, Example of perforated sternum ; this figure also shows two suprasternal bones, * *. C and E
are reduced below the size of nature.
segment of the body, and ossification follows in the next two segments shortly before birth.
In the lower segment ossification begins in the first year or later, in the xiphisternum usually
not before the sixth year, and often much later. In the manubrium there are sometimes two
Fig. 31. — ONE OF THE MIDDLE RIBS
AT ABOUT TWENTY YEARS ' OF AGE.
(R. Quain.)
1, body ; 2, epiphysis of the head ;
3, that of the tuberosily.
centres of ossification, one above the
other, and occasionally several are
met with. In the upper segment of
the body the centre is most commonly
single, but in each of the following
segments there are frequently two.
placed one on each side of the middle
line. The lower segments of the body unite together after puberty, but the upper one often
remains separate till after the twenty-fifth year. The xiphisternum is united to the body in
middle life ; the manubrium and body are only exceptionally joined by bone. The bony
parts formed from the lateral centres of the lower segments of the body not unfrequently
THE BONES OF THE HEAD. 81
remain separate for a considerable time, and occasionally, by defect of ossification or non-
union across the middle line, leave the permanent median aperture referred to on p. 25.
The ossification of the ribs begins in cartilage posteriorly about the eighth or
ninth week of foetal life, and extends rapidly forwards, so as to reach the permanent
cartilage about the fourth month. After puberty the centres of two small epiphyses appear
in the cartilage of the head and tuberosity. These become united with the main bone by the
twenty-fifth year. The epiphysis of the tuberosity is wanting in the eleventh and twelfth.
In the adult the first costal cartilage usually becomes the seat of a superficial ossification,
which may proceed so far as to form a complete sheath around it ; and in advanced life the
other cartilages are frequently more or less covered by bone, especially on their anterior
surface. The tendency to bony deposit is as a rule stronger in the male than in the female,
but the age at which the ossification begins, and the extent to which it proceeds, are subject to
great variation. The cartilage itself is but seldom ossified.
III.— THE BONES OF THE HEAD.
The skull, comprising the bones of the head, is of a spheroidal figure, compressed
on the sides, broader behind than before, and supported on the vertebral column.
All its bones, with the exception of the lower jaw, are immoveably united together
by lines and narrow surfaces, more or less uneven, termed sutures. The skull is
divided by anatomists into two parts, the cranium and the face. The cranium pro-
tects the brain ; the face surrounds the mouth and nasal passages, and completes
with the cranium the orbits or cavities for the eyes. The cranium is composed of
eight bones, viz. : the occipital, two parietal, the frontal, two temporal, the sphenoid,
and the ethmoid. The face is composed of fourteen bones, of which twelve are in
pairs, viz. : the superior maxillary, malar, nasal, palate, lachrymal, and inferior
iurbinate bones ; and two single, viz. : the vomer, and the inferior maxilla. The
hyoid bone, suspended by ligaments from the under surface of the cranium, may also
be classed with the bones of the head.
THE OCCIPITAL BONK.
The occipital bone is situated at the lower and back part of the cranium. In
general form it is flattened and lozenge-shaped, with the longest diameter directed
from behind, forwards and downwards. It is much curved, so that one surface is
concave and looks forwards and upwards, while the other is convex and looks back-
wards and downwards. At the lower and fore part it is pierced by a large oval
aperture, the occipital foramen ox foramen magnum, which forms the communication
between the cranial cavity and the spinal canal. The portion of the bone behind
the foramen is tabular, the narrower part in front forms a thick mass named basilar
process, and the parts on the sides of the foramen, bearing the condyles or articu-
lating processes by which the head is supported on the atlas, are the condylar
portions.
The two superior borders are deeply serrated, and articulate with the parietal
bones in the lambdoid suture. By its two inferior borders, which are uneven but
not deeply serrated, it articulates with the mastoid and petrous portions of the
temporal bone ; while the extremity of its basilar process is united to the body of
the sphenoid, in the young condition by cartilage, but after the age of twenty years
by continuous osseous substance. The rhombic form generally given by the meeting
of these borders at the four angles is not unfrequently somewhat changed to the
octagonal, by the projection of subordinate obtuse angles between the upper and
lateral, and between the lateral and lower angles.
The tabular portion, on Us posterior surface, presents about the centre a promi-
nence— the external occipital protuberance, from which the superior curved line arches
outwards on each side towards the lateral angle of the bone, thus dividing the
32 THE BONES OF THE HEAD.
surface into two parts, an upper and a lower. The protuberance varies greatly in
its development in different skulls ; when well marked it can be readily felt beneath
the skin at the back cf the head. A little above the superior curved line there may
generally be seen the less distinct highest curved line l ; and between the two is a
narrow semilunar area in which the bone is denser and smoother than either above
or below. The part of the surface above this is regularly convex, and is covered by
the hairy scalp. The lower part is more uneven : it is divided into two lateral
portions by a median ridge called the external occipital crest; and each of these is
XT.OCC.PROT.
HIGHEST CURVED UNE
SUP. CURVED LINE
IMF. CURVED LINE
POST.COND.FOR.
PHARYNC. TUB.
BASILAR PROC.
Fig. 32. — OCCIPITAL BONE, FROM BELCW. (Drawn oy D. Gunn.) f
On the left side a probe is passed through the anterior condylar foramen.
again divided into an tipper and a lower surface by the inferior curved line, which
can be followed outwards to the extremity of the jugular process. The curved lines
and the areas thus marked out give attachment to the numerous muscles of the back
of the neck.
Along1 the highest curved line the epicranial aponeurosis is fixed to the bone. To the
upper curved line are attached, internally the trapezius. and externally parts of the occipitalis,
sterno-cleido-mastoid. and splenius capitis muscles. Below the upper line is a large impression
for the complexus ; and more externally, immediately above the outer part of the lower line,
is a smaller mark where the obliquus capitis superior is inserted. The inferior curved line
forms the upper limit of two impressions, the inner one for the rectus capitis posticus minor,
and the outer one for the rectus posticus major. To the lower part of the protuberance and
the external occipital crest the ligamentum nuchas is attached.
The deep surface of the bone is marked by two smooth ridges which cross one
another, one extending from the upper angle to the foramen magnum, and the other
transversely between the two lateral angles ; at the point of intersection of these
1 F. Merkel, " Die Linea nuchse snprerca. " Leipzig, 1871.
THE OCCIPITAL BONE. {J3
ridges is the internal occipital protuberance. Separated by the ridges are four hollows,
the superior and inferior occipital fossce, which lodge respectively the posterior
cerebral and the cerebellar lobes. The superior part of the longitudinal and the
transverse ridges are grooved in the course of the longitudinal and lateral venous
sinuses respectively. The wider space where the longitudinal groove is continued
into one of the lateral grooves (more frequently the right) by the side of the internal
occipital protuberance lodges the torcular Herophili. The inferior part of the
SUP. OCC. FOSSA
INT. OCC. PROT.
INF. OCC. FOSSA
LAT.SULCUS
JUG.PROC.
JUG. NOTCH
POST. COND. FOR.
F. PETR. SULC'JS
Fig.
BASiLAR PROC.
33. — OCCIPITAL BONE, FROM BEFORE. (Drawn by D. Gunn.)
longitudinal ridge is sharp, and is named the internal occipital crest. The margins
of the tabular portion are deeply serrated above the lateral angles for articulation
with the parietal bones ; below that level, they unite with the mastoid portions of
the temporal bones.
The condylar portions bear the articulating condyles on their lower part, close
to the margin of the foramen magnum in its anterior half. The condyles are
elliptical, and converge somewhat in front ; their surfaces are convex from behind
forwards and from side to side, and somewhat everted. On the inner side of each
is a rough impression for the attachment of the lateral odontoid ligament of the
axis. Perforating the bone at the base of the condyle is the anterior condylar
foramen, running from the interior of the cranium immediately above the foramen
magnum outwards and forwards, and transmitting the hypoglossal nerve. Behind
the condyle is a pit, posterior condylar fossa, containing usually the posterior condylar
foramen ; this gives passage to a vein, but it varies greatly in size, and is often
VOL. II. D
84.
THE BONES OF THE HEAD.
absent on one or both sides. Externally to the condyle is a projecting portion of
bone known as the jugular process ; this lies over the transverse process of the atlas,
and is continuous behind with the tabular part, while in front it has a free excavated
margin, the jugular notch, which contributes, with a notch in the temporal bone, to
form the jugular foramen. Its extremity presents a small irregular surface, which
articulates with the jugular facet of the petrous part of the temporal bone by
synchondrosis, passing into osseous union at about twenty-five years of age. The
upper surface of the jugular process is marked by a deep groove for the lateral sinus
SUP. TEMP. LINE
INF. TEMP. LINE
TEMP. SURF.
Fig. 34. — RIGHT PARIETAL BONE : EXTERNAL SURFACE. (Drawn by D. Gunn.) f
leading to the jugular notch, and here is seen the inner opening of the posterior
condylar foramen ; the under surface is rough for the insertion of the rectus capitis
lateralis muscle.
The basilar process projects forwards and upwards in the middle of the base
of the skull. It increases in thickness and diminishes in breadth towards its
extremity. On the inferior surface in the mid-line is a small elevation, phanjngeal
tubercle, for the attachment of the fibrous raphe of the pharynx, and on each side of
this are impressions for the rectus capitis anticus major and minor muscles. Its
superior surface presents a central smooth hollow, the basilar groove, which supports
the medulla oblongata, and close to each lateral margin a shallow groove for the
inferior petrosal sinus.
Varieties. — The portion of the bone above the superior curved lines, which represents the
interparietal bone of lower animals, is in rare cases separated from the rest by a suture
running transversely from one lateral angle to the other ; partial separation by lateral fissures
is often met with (p. 73). The area between the superior and highest curved lines is
occasionally very prominent, constituting the torus occipitalis transrersus. In some bones
there is a groove along the internal occipital crest for the occipital sinus. The anterior
condylar foramen is not unfrequently double. An intra jugular process is often seen in the
form of a small projection at the fore part of the jugular notch ; occasionally it is longer, and
meets the petrous portion of the temporal bone (p. 71). A projection from the under aspect
THE PARIETAL BONE. 35
of the jugular process represents the paramastold process of many mammals : it may be so long
as to meet the transverse process of the atlas. In rare cases an additional articulation is
formed between the basilar process and the anterior arch of the atlas, or the tip of the odontoid
process.
THE PARIETAL BONE.
The parietal bones form a considerable part of the roof of the skull. They
have the shape of quadrilateral plates, convex externally, concave internally. They
are a little broader and thicker above than below ; the anterior inferior angle is the
PACCHIONIAN
DEPRESSIONS
LONGITUDINAL
SULCUS
TCRAL SULCUS
Fig. 35. — RIGHT PARIETAL BONE: INTERNAL SURFACE. (Drawn by D. Gunn.)
most projecting. They articulate with each other in the middle line above, with the
frontal bone anteriorly, the occipital posteriorly, and the temporal and sphenoid
below.
On the outer surface, near its middle, a more marked convexity exists, forming
the parietal eminence. Passing through or close below this are the superior
and inferior temporal lines, enclosing between them a narrow curved portion of
the surface, which is usually smoother and more polished than the rest. Below the
inferior temporal line is the temporal surface, somewhat flattened, forming part of the
temporal fossa, and giving origin to the temporal muscle. The surface above the
upper line is covered only by the scalp. Close to the upper border, and nearer
to the posterior angle, is the small parietal foramen.
The inner surface is concave, the deepest part, opposite the parietal eminence,
being known as the parietal fossa ; it is marked by shallow depressions corresponding
with the convolutions of the brain, and by narrower furrows, branching upwards and
backwards from the lower border, for the meningeal vessels. The largest of these
36
THE BONES OF THE HEAD.
grooves, running from the anterior inferior angle, is sometimes converted into a
canal for a short distance. A slight depression along the inner part of the superior
border forms, with the one of the opposite side, the groove of the longitudinal sinus ;
and a depression at the posterior inferior angle forms a small part of the groove
of the lateral sinus. Near the upper border there are in most skulls, but particularly
in those of old persons, small irregular pits, lodging the Pacchionian bodies.
Borders. — The anterior, superior, and posterior borders are deeply serrated. The
inferior border presents in the greater part of its extent a sharp or squamous edge,
with a slightly fluted surface directed outwards, and overlapped at its anterior
extremity by the great wing of the sphenoid, and behind that by the squamous part
TEMP. SURF.
TEMP. CREST
EXT. ANG. PROC.
Fig. 36.— FRONTAL BONE, FROM BEFORE. (Drawn by D. Gunn.) f
of the temporal bone ; its posterior part is serrated, and articulates with the mastoid
portion of the temporal. The anterior border is slightly overlapped by the frontal
bone above, but overlaps the edge of that bone below.
Varieties. — The parietal foramen varies greatly ; frequently it is absent on one or both
sides ; in extreme cases it has been seen more than half an inch in diameter. As a rare
occurrence the parietal bone is divided by a suture into an upper and a lower part. In senile
bones considerable depressions of the outer surface are sometimes met with, the floor of which
is not thicker than paper ; usually on both sides and symmetrical (Humphry, Med. Chir.
Trans., 1890).
THE FRONTAL BONE.
The frontal bone, arching upwards and backwards above the orbits, forms the
fore part of the cranium ; it likewise presents inferiorly two thin horizontal laminse,
the orMtal plates, which form the roofs of the orbits, and are separated by a median
excavation, the ethmoidal notch. It articulates with twelve bones, viz., posteriorly
with the parietals and sphenoid ; outside the orbits with the malars ; and between
THE FRONTAL BONE.
37
the orbits, from before backwards, with the nasal, superior maxillary, lachrymal, and
ethmoid bones.
Anterior surface. — The part forming the greatest convexity of the forehead on
each side is called the frontal eminence. It is separated by a slight depression below
from the superciliary ridge, a curved elevation of varying prominence above the
NASAL SPINE
NASAL SURFACE
ASAL NOTCH
TROCHLEAR FOSSA
.FRONTAL SINUS
LACHRYMAL FOSSA
EXT. AMG PROC-
NT. ORB. CANALS
ETHMOIDAL NOTCH
FIG. 37. — FRONTAL BONE, FROM BELOW. (Drawn by D. Gunn.)
.NT. ETHM. CELL
margin of the orbit. Between the superciliary ridges is the surface called glabella.
The margin of the orbit, the orbital arch, is most defined towards its outer, part ; it
presents towards its inner third the supraorbital notch, sometimes a foramen, which
transmits the supraorbital nerve and artery. The extremities of the orbital
arch point downwards, and form the internal and
external annular processes : the internal is but slightly
** L ° * M1SAI RONE
marked ; it meets the lachrymal bone : the external is
strong and projecting, and articulates with the malar
bone. The temporal crest springs from the external
angular process, and arches upwards and backwards to
be continued into the temporal lines of the parietal
bone : it separates the temporal from the frontal part
of the outer surface of the bone.
Inferior surface. — The orbital surfaces are some-
what triangular, their internal margins being parallel,
while the external are directed backwards and inwards.
Close to the external angular process is the lachrymal
fossa, which lodges the lachrymal gland ; and close to the internal angular pro-
cess is a small depression, trochlear fossa, where the pulley of the superior
oblique muscle is attached. Between the orbits in front is the nasal notch,
bounded by a narrow semilunar serrated surface which articulates with the upper
ends of the nasal bones and the nasal processes of the superior maxillae. Occu-
pying the concavity of the notch is the nasal process (Henle), which projects
beneath the nasal and maxillary bones, supporting the bridge of the nose. On
the posterior aspect of the nasal process are a small grooved surface on each
side, which enters into the formation of the roof of the nasal fossa, and a
Fig. 38. — TRANSVERSE SECTION OF
THE BRIDGE OF THE NOSE.
(G. D. T.)
38
THE BONES OF THE HEAD.
median ridge, which is continued into a sharp process of variable length, the nasal
spine. The latter descends in the septum of the nose, between the crest of the nasal
bones in front and the vertical plate of the ethmoid behind. Between the
ethmoidal notch and the inner margin of the orbital surface is an irregular area
occupied by depressions forming the roofs of cells in the ethmoid bone. Traversing
this surface are two grooves, which complete, with the ethmoid, the anterior
and posterior internal orbital canals ; the anterior transmits the nasal nerve and the
anterior ethmoidal vessels ; the other, the posterior ethmoidal vessels. Farther
forward is the opening of the frontal sinus, a cavity which extends within the bone
for a variable distance behind the superciliary ridges. Outside and behind the
LONGITUDINAL SULCUS
PACCHIONIAN DEPRESSIONS
Fig. 39.— FRONTAL BONE, FROM BEHIND. (Drawn by D. Gnnn.)
orbital surface there is a large rough triangular area which articulates with the great
wing of the sphenoid.
Cerebral surface. — This surface forms a large concavity, except over the roofs
of the orbits, which are convex. Upon it are seen the impressions of the cerebral
convolutions, which, with the intervening ridges, are strongly marked over the orbits.
A groove, the frontal sulcus, lodging the superior longitudinal sinus, descends from the
middle of the upper margin of the bone, and is succeeded by the frontal crest, a ridge
which runs down nearly to the lower margin. A small foramen, usually formed in
part by the crista galli of the ethmoid, is situated at the base of the frontal crest ;
it is known as the foramen caecum, being generally closed below, but it may transmit
a minute vein from the nasal fossae. On each side small ramifying furrows, which
lodge branches of the middle meningeal vessels, run inwards from the lateral margin
of the bone ; and at the upper part, in the neighbourhood of the longitudinal groove,
are some depressions for Pacchionian bodies. The upper and greater part of
the edge encompassing the cerebral surface of the bone is serrated, and articulates
THE TEMPOEAL BONE.
39
with the parietal bones in the coronal suture in the manner before described ; the
lower transverse part is thin and uneven, and articulates with the greater and lesser
wings of the sphenoid.
Varieties. — The trochlear fossa is often faintly marked or absent ; on the other hand
there may be a small prominence, thetj-ochlcar sjjine. by the side of the depression (10 percent..
3Ierkel). The frontal bone is at times divided by a median frontal or metopic suture, the two
parts of the infantile bone having failed to unite. This condition, which is termed utctopism,
was found by Anutschin to exist in 8'7 per cent, of European skulls, in 5'1 per cent, in Mon-
golian races, in 1'2 per cent, of Negro, and 1 per cent, of Australian skulls. A trace of the
metopic suture is to be seen in nearly all adult frontal bones above the root of the nose (fig. 36).
THE TEMPORAL BONE.
The temporal bone takes part in the formation of the side and base of the skull,
and contains in its interior the organ of hearing. It is usually described in three
parts, viz., an expanded* anterior and superior part, the sqiiamous portion, including
SQUAMOUS PORTION
TEMP. SUHF.
MASTOID PORTION
Fig. 40. — RIGHT TEMPORAL BONE: OUTER VIEW. (Drawn by D. Gunn.)
the zygomatic process, a thicker posterior portion, the mastoid, and below and
between these the petrous portion, a three-sided pyramid, exhibiting at its base
externally the aperture of the ear, and projecting forwards and inwards into the base
of the skull.
It articulates posteriorly and internally with the occipital bone, superiorly with
the parietal, anteriorly with the sphenoid, by the zygomatic process with the malar,
and by the glenoid cavity with the inferior maxillary bone.
The squamous portion, or squamo-zygomatic, extends forwards and upwards
from its connection with the other portions, and is limited superiorly by an arched
border which describes about two-thirds of a circle.
40 THE BONES OF THE HEAD.
The inner surface is marked by cerebral impressions, and by memngeal grooves.
At its upper border the outer table is prolonged considerably beyond the inner,
forming a thin, scale with the fluted surface looking inwards and overlapping the
corresponding bevelled edge of the parietal bone. But in front, at its lower part,
the border is thicker, looks forwards and inwards, is bevelled slightly on the outer
side, and serrated for articulation with the great wing of the sphenoid.
The outer surface is in its greatest extent vertical, with a slight convexity, and
SOUAMOUS PORTION
AT. SULCUS
STYLOIO PROC.
PETROUS PORTION
Fig. 41. — RIGHT TEMPORAL BONE: INNEK VIEW. (Drawn by D. Gunn.)
The bone is rotated slightly about a sagittal axis, the upper border being moved inwards.
forms part of the temporal fossa. Above the aperture of the ear it is marked by a
small, nearly vertical furrow for the middle temporal artery. From the lowest
part of this surface a long process, the zygoma, takes origin.
The zygoma, or zygomatic process, is connected with the lower and outer part of
the squamous portion, and is of considerable breadth at its base, which projects
outwards. It then turns forwards, becomes narrower, and is twisted on itself so as
to present outer and inner surfaces and upper and lower borders. The superior
margin is thinner, and prolonged farther forwards than the inferior. The extremity
is serrated, and articulates with the malar bone. At its base the zygoma presents
two roots : the anterior, continuous with the lower border, is a broad convex ridge,
directed inwards on the under aspect of the bone : the posterior, also called the
supramastoid crest, is prolonged from the upper border ; it passes backwards above
the external auditory meatus, marking the line of division between the squamous
and mastoid portions of the bone, and turning upwards posteriorly forms the
boundary of the temporal fossa. At the place where the two roots diverge is a
slight tubercle, which gives attachment to the external lateral ligament of the lower
jaw. Between the two roots is the glenoid fossa} a considerable hollow, elongated
THE TEMPORAL BONE.
41
TEMP. SUBF.
ZYCOM. SURF.
PETROUS PORTION
EUST. CANAL
INF. PETR. SUUCUS
from without inwards, and divided into two parts by the nearly transverse fissure
of Glaser. The posterior part of the glenoid fossa is formed by the tympanic plate
of the petrous division of the bone, is non-articular, and lodges a portion of the
parotid gland : the anterior part of the fossa, together with the cylindrical elevation,
articular eminence, formed by the anterior root of the zygoma in front of the hollow,
is coated with cartilage,
and forms the concavo- SQUAMOUS PORTION
convex surface for arti-
culation with the lower
jaw ; the articular cavity
is bounded behind by
a small conical process
which descends in front
of the external auditory
meatus, and is known as
the postf/lcnoid process.
In front of the articular
eminence, and separated
from the temporal sur-
face by a slight ridge, is
a small triangular area
which enters into the
zygomatic fossa.
The mastoid por-
tion is rough externally
for the attachment of
muscles, and is prolonged
downwards behind the
aperture of the ear into
a nipple-shaped projec-
tion— the mastoid pro-
cess. This process has
on its inner side a deep
groove,the digastricfossa,
which gives attachment
to the digastric muscle
occipital artery.
AQ. OF COCHL.
MAST. PROC
MASTOID PORTION
Fig. 42.— RIGHT TEMPORAL BONE, FROM BELOW. (Drawn by D. Gunn.)
and internal to that is the slight occipital groove, for the
The internal surface of the mastoid portion is marked by a deep
sigmoicl depression, which is part of the groove of the lateral sinus. A passage
for a vein, of very variable size, the mastoid foramen, usually pierces the bone
near its posterior margin, and opens into the groove.
The petrous portion, so named from its hardness, contains the organ of
hearing. It forms a three-sided pyramid, with its base directed outwards, one
surface looking downwards, and the other two turned towards the interior of the
skull.
Inferior surface, base, and apex. — At the base is the aperture of the ear. It
forms a short canal, the external auditory meatus, directed inwards and a little
forwards, narrower in the middle than at its extremities, and leading into the cavity
of the tympanum, part of which is seen from the exterior in the macerated bone.
The external orifice is bounded above by the posterior root of the zygoma, and in
the remainder of its circumference chiefly by the external auditory process, a curved
uneven border, to which the cartilage of the ear is attached. This process is the
thickened outer extremity of the tympanic plate, a lamina one surface of which
forms the anterior and inferior wall of the external auditory meatus and the
42 THE BONES OF THE HEAD.
tympanum, while the other looks towards the glenoid fossa. The upper margin of
the tympanic plate sinks beneath the squamous, and forms the posterior boundary
of the fissure of Glaser ; while its lower margin descends as a sharp edge, the
vaginal process, which partly surrounds the sfcyloid process at its base. The styloid
process is long and tapering, and is directed downwards and forwards. It is placed
in front of the digastric fossa, and has immediately behind it the foramen which
forms the outlet of the canal of the facial nerve, named stylo-mastoid from its
position between the styloid and mastoid processes. Internal to the stylo-mastoid
foramen is a small irregular surface, the jugular facet, which articulates by syn-
chondrosis with the jugular process of the occipital bone. In front of this comes
a smooth and deep depression, the jugular fossa, which forms with the jugulai
notch of the occipital bone the jugular foramen. In front of the jugular fossa is
the carotid foramen, the inferior extremity of the carotid canal ; and internal to the
carotid foramen is a rough, free surface which is continued into the inner
extremity, or apex of the petrous bone. The carotid canal ascends at first perpen-
dicularly, then turns horizontally forwards and inwards, and emerges at the apex,
close to the anterior margin ; it transmits the internal carotid artery.
The posterior surface looks backwards and inwards, and forms part of the
posterior fossa of the base of the skull. About the centre of this surface is a large
orifice leading into a short canal which is directed outwards, the internal auditory
meatus. This canal is terminated by a plate of bone named the lamina cribrosa,
from the numerous minute apertures which it presents for the divisions of the
auditory nerve, while in its upper and fore part is the beginning of the canal called
aqueduct of Fallopius, which transmits the facial nerve. The aqueduct takes a some-
what circuitous course through the petrous bone, passing outwards and backwards
over the labyrinth of the ear, and then downwards to terminate at the stylo-mastoid
foramen.
The anterior or upper surface looks upwards and forwards, and forms part of the
middle fossa of the base of the skull. A depression near the apex marks the
position of the Gasserian ganglion. A narrow groove runs obliquely backwards and
outwards to a foramen named the hiatus Fallopii, which leads to the aqueduct of
Fallopius, and transmits the large superficial petrosal nerve. Farther back is a
rounded eminence, indicating the situation of the superior semicircular canal.
The line of separation of this surface of the petrous from the internal surface of the
squamous is marked by a narrow jjetro-squam ous Jissure, commencing anteriorly at the retiring
angle between the two portions, and generally to be traced less distinctly to the posterior
border of the bone. The portion of bone between this fissure externally and the eminence of the
superior semicircular canal and the hiatus Fallopii internally is a thin lamina, often perforated,
which roofs in the tympanum and the common canal of the Eustachian tube and tensor
tympani muscle, and is known as the teg-men tympani.
The superior border is grooved for the superior petrosal sinus. The anterior
border is very short, and forms at its junction with the squamous part an angle in
which is situated the orifice of the Eustachian canal, the osseous portion of a tube
of the same name, which leads from the pharynx to the tympanum ; and above
this, par -ially separated from it by a thin lamella, the cochleariform process, is a
small passage which lodges the tensor tympani muscle. The posterior or inferior
border internal to the jugular fossa articulates with the basilar process of the
occipital bone, and forms with that the groove for the inferior petrosal sinus.
Small foramina, &c. — The opening of the aqueduct of the vestilule is a narrow fissure,
covered py a depressed scale of bone, and situated on the posterior surface of the petrous portion,
about four lines outside the internal auditory meatus ; that of the aqueduct of the coclilea is a
small foramen, beginning in a three-sided wider depression in the inferior margin, directly
THE SPHENOID BONE. 43
below the internal auditory meatus. In the plate between the jugular fossa and -the carotid
canal is the foramen by which the nerve of Jacobson passes to the tympanum. In the
ascending part of the carotid canal is the minute foramen for the tympanic branch of the
carotid plexus. In the jugular fossa are a groove and foramen for the auricular branch of the
vagus nerve ; and parallel to the hiatus Fallopii, close to the canal for the tensor tympani
muscle, are a groove and foramen for the small superficial petrosal nerve.
The so-called fissure of Glaser is in the inner portion of its extent a double cleft, the
tympanic plate being here separated from the squamous division of the bone by a descending
process of the tegmen tympani, which forms the greater part of the outer wall of the common
canal of the tensor tympani and Eustachian tube. Between this process and the tympanic
plate is a small orifice leading to the cavity of the tympanum, and lodging in the recent
state the slender process of the malleus and the tympanic branch of the internal maxillary
artery ; farther inwards is another small canal by which the chorda tympani nerve issues.
The outer portion of the Glaserian fissure is entirely closed.
The f undus of the internal auditory meatus may be **•
most conveniently studied in an infantile bone, where the
canal is short and the apertures relatively wide. A hori-
zontal ridge, named crista falcifwmis, runs from the anterior CR'S™ FALC"r-'
wall of the meatus across the lamina cribrosa, so as to sepa- FOR- CENT-'
rate a small superior from a large inferior fossa. At the
bottom of the superior fossa is a collection of minute aper- TBACT- SPIR- FORAM:
tures giving passage to the filaments of the superior division of pj^ 43 __ SEMI- DIAGRAMMATIC
the auditory nerve, and constituting the area cribrosa superior ; VIEW OF THE FUNDUS OF THE
while the orifice of the aqueduct of Fallopius is placed on the EIGHT INTERNAL AUDITORY
anterior wall of the fossa. In the inferior fossa are seen — MEATUS OP AN INFANT.
1, the area cribrosa media, below the hinder part of the crest, (Gr. D. T.) j
for the nerve to the saccule ; 2, the foramen singulars, at
the lower and posterior part of the fossa, transmitting the nerve of the posterior semicircular
canal ; and 3, the tract its sj) trails foraminulentus, for the cochlear division of the auditory
nerve, a series of minute holes beginning below the area cribrosa media, forming one turn
and a half in a depression corresponding to the base of the cochlea, and ending at the foramen
ccntrale cochlea;, the orifice of the central canal of the modiolus.
From the fore part of the superior border of the petrous portion, where there is often a
small projection overhanging the upper end of the groove for the inferior petrosal sinus
(fig. 69), a fibrous band, the pctro-sphenoidal ligament, extends to the lateral margin of the
dorsum sellas of the sphenoid bone. This completes a foramen through which the inferior
petrosal sinus and the sixth nerve pass. In rare cases the ligament is ossified.
The description of the Small Bones of the Ear, with the Tympanum and Internal Ear, will
be found in the chapter on the Organs of the Senses in Vol. III.
THE SPHENOID BONE.
The sphenoid bone is placed across the base of the skull, near its middle. It
enters into the formation of the cavity of the cranium, the orbits, and the nasal fossa?.
It is of very irregular shape, and consists of a central part or body, a pair of lateral
expansions called the great icings, a pair of smaller horizontal processes above, called
the small ivings, and a pair which project downwards, the pteryyoid processes.
The sphenoid is articulated with all the seven other bones of the cranium and
with five of those of the face, viz., posteriorly with the occipital and with the
petrous portions of the temporals, anteriorly with the ethmoid, palate, frontal, and
malars, laterally with the squamous portions of the temporals, the parietals, and
frontal, and inferiorly with the vomer and palate bones ; sometimes it touches also
the superior maxilla.
The body is hollowed out into two large cavities, the sphenoidal sinuses,
separated by a thin median lamina, the sphenoidal septum, and opening anteriorly
into the nasal fossas by two rounded apertures. The superior surface presents in
the middle a deep pit, the pituitary fossa or sella turcica, which lodges the
pituitary body. In front of the fossa is an elevated portion of bone on a level
with the optic foramina, the olivary eminence, on which the optic commissure rests
in the slight optic groove ; and in front of this is a surface on a somewhat higher level,
continuous with the superior surfaces of the smaU wings, and having a slight pro-
44 THE BONES OF THE HEAD.
jection forwards of its anterior border, which articulates with the cribriform plate
of the ethmoid, and is called the ethmoidal spine. Behind the pituitary fossa is a
prominent lamella, the dorsum sella, the posterior surface of which is sloped
upwards and forwards in continuation of the basilar groove of the occipital bone.
The angles of this lamella project over the fossa, and are called the posterior clinoid
processes. On each side of the body the surface descends obliquely to a considerably
lower level than the fossa : it presents close to the margin of the fossa a superficial
winding groove directed from behind forwards, marking the course of the internal
carotid artery. Behind the commencement of the groove, and at the lower end of
the lateral margin of the dorsum sellse is a compressed projection, the petrosal
BODY SMALL WING GREAT WINC
FOR. ROTUNOUM
POST. CLIN. PROC.
FOR. OVALE
FOR. SPINOSUM
Fig. 44. — THE SPHENOID BONE, FROM ABOVE. (Drawn by D. Gunn.)
process of the sphenoid, which fits against the apex of the petrous part of the
temporal bone ; and opposite to this, on the outer side of the groove, the more
slender tongue-like process termed lingula sphenoidalis projects backwards in the
angle between the body and great wing.
The posterior surface is united to the basilar process of the occipital bone, in
early life by cartilage, but in adult age by continuous bony substance.
The anterior surface is marked in the middle line by the sphenoidal crest, a thin
projecting edge which descends from the ethmoidal spine, and articulates with the
vertical plate of the ethmoid. The oblong surface on each side of the crest is
divided into a mesial and a lateral part : the lateral part is irregularly excavated,
and articulates with the lateral mass of the ethmoid and the orbital process of the
palate bone : the mesial part is smooth and free, entering into the formation of the
roof of the nasal fossa, and presenting near its upper end the rounded orifice of the
sphenoidal sinus. The sphenoidal crest terminates below in the rostrum, a sharp
vertical prominence which is continued back some distance on the inferior surface,
and fits in between the alae of the vomer. These last and the vaginal processes of
the internal pterygoid plates cover the great part of the inferior surface of the body.
The sphenoidal turbinate or spongy bones (cornua splicnoidalia, l>onc$ of Bertiri) form a
considerable part of the anterior wall of the body of the sphenoid, bounding the foramen of
each sinus. These bones have a triangular form, with the apex directed downwards and back-
wards, and are in the adult usually incorporated with the sphenoid, but as explained in the
THE SPHENOID BONE. 45
account of their development, were originally distinct. They are commonly united by earlier or
stronger anchylosis with the ethmoid or palate bones, so as to come away, at least in part, with
either of these in disarticulation of the skull, and thus lay open the sphenoidal sinuses. A small
portion of these bones sometimes appears on the inner wall of the orbit, between the ethmoid,
frontal, sphenoid, and palate bones (Cleland in Phil. Trans., 1862).
Each lateral surface of the body is for the most part occupied by the attachments
of the two wings, but at the fore part, below the root of the small wing, there is a
small free surface which bounds the sphenoidal fissure internally and forms the hind-
most portion of the inner wall of the orbit (fig. 69, p. 66).
The small or orbital wings extend nearly horizontally outwards on a level with
GREAT WING
SMALL WING CEREBRAL SURF.
HAMULAR PROC. — SJBsSST 'PTERYCOIO NOTC
PTERYGOID PROCESS
Fig. 45. — THE SPHENOID BONE, FROM BEHIND. (Drawn by D. Gunn.)
the fore part of the superior surface of the body. The extremity of each is slender
and pointed, and comes very close to, but usually not into actual contact with, the
great wing. The superior surface forms part of the anterior fossa of the base of the
cranium ; the inferior overhangs the sphenoidal fissure and the back of the orbit.
The anterior border, thin and serrated, articulates with the orbital plate of the
frontal bone. The posterior border is prominent and free, and forms the boundary
between the anterior and middle cranial fossae, terminating internally in a smooth
rounded projection, the anterior clinoid process. Between the anterior clinoid pro-
cess and the olivary eminence is a semicircular notch in which the carotid groove
terminates ; and in front of this is the optic foramen perforating the base of the
wing.
The great or temporal wings project outwards and upwards from the sides of
the body. The back part of each is placed horizontally, and occupies the angle
between the petrous and squamous portions of the temporal bone ; from its pointed
extremity it sends downwards a short and sharp projection, the spinous process.
The upper and fore part is vertical, and three-sided, lying between the cranial
cavity the orbit, and the temporal fossa (fig. 66, p. 64). The cerebral surface, of the
46
THE BONES -OF THE HEAT).
great wing is concave, and forms part of the middle fossa of the naseof the cranium.
The external surface (temporo-zygomatic) is divided by a ridge, infratemporal crest,
into an inferior part, which looks downwards into the zygomatic fossa, and an elongated
superior part, looking outwards, which forms a part of the temporal fossa (fig. 68,
p. 66). The anterior surface looks forwards and inwards, and consists of a quadri-
lateral orbital portion, which forms the back part of the external wall of the orbit, and
of a smaller inferior portion which overhangs the pterygoid process, looks into the
spheno-maxillary fossa, and is perforated by the foramen rotundum. The posterior
border in its mesial part bounds the foramen lacerum, in its lateral part articulates
GREAT WING
SMALL WING
BODY
SPHEN. FISS.
ETHM. SPINE OPT. FOR. / ORB. SURF
SPH.FOH
FRATEMP.
CREST
ZYCOM. SURF.
SPHENO-MAX. SURF.
EXT. PTERYC. PLATE
PTERYC. NOTCH
IAMULAR PROC.
PTERYCOID PROCESS
Fig. 46. — THE SPHENOID BONE, FROM BEFORE. (Drawn by D. Gnnn. )
with the petrous, and forms with that a groove on the under aspect for the carti-
laginous part of the Eustachian tube.. The external margin articulates with the
squamous, and the extremity overlaps the anterior inferior angle of the parietal. In
front of this comes a triangular surface, the sides of which are formed by the upper
margins of the cerebral, orbital, and temporal surfaces respectively, for articulation
with the frontal bone. The anterior margin, between the orbital and temporal
surfaces, articulates with the malar bone ; and below this is a short horizontal free
elge separating the zygomatic and spheno-maxillary surfaces. Above and internally
the orbital and cerebral surfaces meet at the sharp border which forms the inferior
boundary of the sphenoiual fissure, and which is frequently marked at its inner part
by a small projection giving attachment to the lower head of the external rectus
muscle of the eyeball.
The pterygoid processes project downwards and slightly forwards from the
adjacent parts of the body and the great wings. Each consists of two plates united
in front and diverging behind, so as to enclose between them the pterygoid fossa, in
which the internal pterygoid muscle arises. The external pterygoid plate, broader
than the internal, lies in a plane extending backwards and outwards ; its outer
surface bounds the zygomatic fossa, and is impressed by the external pterygoid
THE ETHMOID BONE. 47
muscle. The internal pier ygoid plate is longer and narrower than the external, and
is prolonged below into the slender hook-like or hamular process, round which in a
groove plays the tendon of the tensor palati muscle. Above, the internal plate turns
inwards beneath the body, from which its extremity remains distinct as a slightly
raised edge, known as the vaginal process, which articulates with the everted margin
of the vomer ; externally to this it is marked by a small groove, which contributes
with the palate bone to form the pterygo-palatine canal. Posteriorly, the internal
pterygoid plate forms at its base a small blunt prominence, the pterygoid tubercle, to
the inner side of and below the orifice of the Vidian canal ; between this and the
pterygoid fossa is a slight depression, called the navicular or scaphoid fossa, occupied
by the attachment of the tensor palati muscle ; and lower down, on the hinder
margin of the plate, is a projection which supports the cartilage of the Eustachian
tube. The interval between the lower ends of the pterygoid plates, pterygoid notch,
is occupied by the pyramidal process of the palate bone.
Fissures and foramina. — Each lateral half of the bone presents a fissure, four
foramina, and a canal. The sphenoidal fissure is the obliquely placed elongated
interval between the great and small wings, closed externally by the frontal bone ;
it opens into the orbit, and transmits the third, fourth, and sixth nerves, the
ophthalmic division of the fifth nerve, and the ophthalmic veins. Above and to the
inside of the sphenoidal fissure is the toptic foramen, which is inclined outwards and
forwards from the side of the olivary eminence, pierces the base of the small wing,
and transmits the optic nerve and the ophthalmic artery. The foramen rotundum is
directed forwards through the great wing, below the sphenoidal fissure ; it opens
immediately below the level of the orbit, and transmits the superior maxillary nerve.
The foramen ovale is large, and placed behind and a little external to the foramen
rotundum, near the posterior margin of the great wing ; it is directed downwards,
and transmits the inferior maxillary nerve and small meningeal artery. The
foramen spinosum is a small foramen piercing the great wing, near its posterior
angle, and transmits the large middle meningeal vessels.
The Vidian or pterygoid canal pierces the bone in the sagittal direction at the
base of the internal pterygoid plate. It opens anteriorly into the spheno-maxillary
fossa, and posteriorly into the foramen lacerum ; and through it pass the Vidian
nerve and vessels.
Varieties. — A small tubercle is often seen on each side in front of the pituitary fossa, at
the base of the olivary eminence, and immediately internal to the last part of the carotid
groove ; this is known as the middle clinoid process, and is sometimes connected by a spiculum
of bone to the anterior clinoid process, forming a carotico-clinoid foramen. Less frequently
the anterior and posterior clinoid processes are similarly united. There are normally fibrous
bands, interclinoid ligaments, beneath the dura mater in these situations (Gruber). In some
cases a superior petrosal process projects from the lateral margin of the dorsum sellas (fig. 69),
giving attachment to the petro-sphenoidal ligament (p. 43). The outer pterygoid plate may
be connected by a bridge of bone or of ligament (pterygo-spinous) with the spinous process.
The foramen ovale and foramen spinosum are frequently incomplete at the posterior margin
of the bone. The name of foramen of Vesalius is given to an aperture sometimes present on
the inner side of the foramen ovale : it gives passage to an emissary vein. At the base of the
spinous process, to the inner side of the foramen spinosum, there is occasionally a minute canal
(canaliculus innominatus — Arnold) transmitting the small superficial petrosal nerve.
THE ETHMOID BONE.
The ethmoid, or sieve-like bone, projects downwards from between the orbital
plates of the frontal bone, and enters into the formation of the cranium, the orbits,
and the nasal fossa?. It is of a cuboid figure, and exceedingly light for its size,
being composed of very thin plates of bone surrounding in great part irregular cells.
CRISTA CALLI
ALAR PROCESS
48 THE BONES OF THE HEAD.
It consists of a central vertical plate, and of two lateral masses, united at their
superior borders by the horizontal cribriform plate. It articulates with thirteen
bones : the frontal, sphenoid and vomer, the nasal, lachrymal, superior maxillary,
palate, and inferior turbinate bones.
The vertical plate lies in the median plane, and forms the upper third of the
septum of the nose (fig. 71, p. 69). Its superior border appears in the cranial
cavity, above the cribriform plate, in the form of a ridge, rising anteriorly into a
thick process, the crista galli, to which the falx cerebri is attached. The posterior
margin of the crista galli is thin and smooth. The anterior is in its lower part
broadened out, and divided into two alar processes, which project laterally, and are
rough in front for articulation with the frontal bone : between them there is usually
a median groove completing the foramen csecum. Below the level of the
cribriform plate, the anterior
border of the vertical plate
slopes much forwards, and
articulates with the nasal spine
of the frontal and with the
,ANT. ETHM. CELLS 11 ml • P
nasal bones. ihe inferior
margin articulates in front, and
sometimes even in its whole
extent, with the septal carti-
lage of the nose : in -its pos-
terior half, in the adult, it is
more or less completely joined
by osseous union on one or
both sides to the two plates
of the vomer. The posterior
Fig. 47. — THE ETHMOID BONE, FROM THE RIGHT SIDE. . , • -, .
(Drawn by D. Gunn.) margin is very thin, and is
united to the crest of the
sphenoid. This plate presents superiorly a number of grooves and minute canals,
leading from the foramina of the cribriform plate, for the transmission of the
olfactory nerves.
Each lateral mass or labyrinth encloses a number of spaces of irregular
form, arranged in three sets, the anterior, middle, and posterior ethmoidal cells, which
in the recent state are lined with prolongations of the mucous membrane of the
nose. On its external aspect is a thin, smooth lamina, of an oblong form, the
orUtal plate or os planum, which closes in the middle and posterior ethmoidal cells,
and forms a considerable part of the inner wall of the orbit (fig. 69, p. 66). The
circumference of the orbital plate articulates in front with the lachrymal, behind with
the sphenoid, above with the frontal, and below with the superior maxillary and palate
bones, which often complete two or three ethmoidal cells. At the lower part of this
aspect is a deep groove, which belongs to the middle meatus of the nose, and is
limited below by the rolled margin of the inferior turbinate process. Anteriorly, the
groove curves upwards, and is continued into a passage named the infundibulwn,
which leads through the fore part of the lateral mass into the frontal sinus. Into
the horizontal part of the groove the middle ethmoidal cells open, and into the
ascending part the anterior ethmoidal cells. In front of the orbital plate, the
lateral mass extends forwards under cover of the lachrymal bone, which closes over
the open anterior cells seen in the disarticulated ethmoid bone ; and from this part
descends the uncinate process, a long thin lamina, which curves backwards, down-
wards and outwards in the groove of the middle meatus. In the complete skull the
uncinate process lies across the orifice of the antrum of the superior maxilla, and
forms part of the inner wall of that cavity ; at its extremity it articulates, by means
THE ETHMOID BONE. 49
of one or two irregular projections, with the ethmoidal process of the inferior tur-
binate bone (fig. 69, p. 66).
The internal aspect of each lateral mass forms part of the external wall of the
nasal fossa, and consists of a thin, uneven lamella, connected above with the cribri-
form plate, and exhibiting a number of canals and grooves for branches of the
olfactory nerve. It is divided at its back part by a channel, directed forwards from
its posterior margin to about its middle. This is the superior meatus of the nose,
and communicates with the posterior ethmoidal cells. The short, thin plate which
overhangs this channel, is the superior tur-
binate process or spongy bone. Below the
groove is another plate, somewhat thick-
ened and rolled outwards inferiorly, the
inferior turbinate process or middle spongy
bone. This is free also in front and
ANT. ETHM. CELLS
NFUNDIBULUM
ORM PLATE
SUP.TUR3. BONE
'P. MEATUS
0. TURS. BONE
Fig. 48. — RIGHT LATERAL MASS OF ETHMOID BONE
INNER SURFACE. (Drawn by D. Gunn.)
Fig. 49. — THE ETHMOID BONE, FROM ABOVE.
(Drawn by D. Gunn.)
behind, and, as has already been seen on the outer aspect, overhangs the middle
meatus of the nose.
The superior margin of the lateral mass is covered, and the cells completed, by
the projecting inner border of the orbital plate of the frontal bone ; two grooves are
seen crossing it, which complete with the frontal bone the internal orbital canals.
The inferior margin is formed by the rounded edge of the middle turbinate bone,
and is free in the nasal fossa. The anterior extremity presents one or two open
cells, which are closed by the nasal process of the superior maxilla ; and the posterior
extremity fits against the front of the body of the sphenoid, where it is commonly
anchylosed with the sphenoidal spongy bone.
The cribriform plate corresponds in size to the ethmoidal notch of the frontal
bone, which it occupies. On each side of the crista galli it is depressed into the
olfactory groove which lodges the olfactory bulb, and is pierced by numerous
foramina for transmission of the filaments of the olfactory nerves. The foramina
in the middle of the groove are few, and simple perforations ; the internal and
external sets, more numerous, are the orifices of small canals which subdivide as
they descend on the vertical plate and lateral mass. At the anterior extremity is a
small fissure on each side of the crista galli, close to its base ; and externally to this
is a notch or foramen, connected by a groove with the anterior internal orbital
canal, which transmits the nasal branch of the ophthalmic nerve.
VOL. II.
50
THE BONES OE THE HEAD.
THE SUPERIOR MAXILLARY BONE.
The upper jaw, superior maxilla, is the principal bone of the face ; it supports
all the teeth of the upper range, and takes part in the formation of the hard palate,
the floor of the orbit, and the floor and lateral wall of the nasal cavity. It consists
of a central part or body, and four processes. The body presents an external
surface, which is again subdivided into anterior or facial, and posterior or zygomatic
portions ; an internal or nasal surface, and a superior or orbital surface. The pro-
cesses are — the nasal or ascending, projecting upwards from the fore part of the
body, the alveolar, forming the lower border of the bone and containing the alveoli
or sockets for the teeth, the malar on the outer aspect, separating the facial and
NASAL
OCES5
INFRAORB. GROOVE
Fig. 50. — RIGHT SUPERIOR MAXILLARY BONE : OUTER VIEW. (Drawn by D. Gunn.)
zygomatic surfaces, and the palate process, projecting horizontally on the inner side.
The body is farther excavated by a large sinus or antrum, which opens on the inner
side into the nasal fossa. The superior maxillary bone articulates with its fellow,
with the nasal, frontal, lachrymal, ethmoid, palate, malar, vomer, and inferior tur-
binate bones, and sometimes with the sphenoid.
The facial surface is marked at the lower part, where it is continuous with the
outer surface of the alveolar process, by a series of eminences corresponding in
position to the fangs of the teeth ; that of the canine is particularly prominent, and
internal to this is a slight depression, the incisor or myrtiform fossa ; while between
it and the malar process is the deeper canine fossa. Above the canine fossa, and
close below the margin of the orbit, is the infraorUtal foramen, by which the infra-
orbital nerve and artery issue. The inner margin of this surface is deeply excavated
by the nasal notch, the sharp edge of which is produced below into the anterior
nasal spine.
The zygomalic surface looks into the zygomatic and spheno-maxillary fossee ; it is
convex, and presents about the centre one, two or more apertures of the posterior
dental canals, transmitting the vessels and nerves of that name ; the lower and-
posterior part of this surface is prominent and rough, and is distinguished as the
tulerosity.
THE SUPERIOR MAXILLARY BONE.
51
The nasal surface presents at the fore part a nearly horizontal ridge, the inferior
turbinate crest, for articulation with the inferior turbinate bone ; below the crest is
a smooth concave surface belonging to the inferior meatus of the nose ; and above
the crest a smaller surface, extending on to the base of the nasal process, and bound-
ing the atrium of the middle meatus. Behind the nasal process is seen the
lachrymal groove, nearly vertical, but inclined slightly backwards and outwards, about
half an inch in length, and leading into the inferior meatus ; the margins overhang
the groove in front and behind, and the small interval left is closed by the lachrymal
and inferior turbinate bones, thus completing the canal of the nasal duct. Behind
the lachrymal groove is the large opening into the antrum ; and above this there are
ATRIUM OP
MIO. MCATUS
INF. TURB. CREST
Fig. 51. — RIGHT SUPERIOR MAXILLARY BONE: INNER VIEW. (Drawn by D. Gunn.)
often one or two small hollows which complete the middle ethmoidal cells. Behind
the opening of the antrum the surface is rough for articulation with the palate bone ;
and traversing the lower part of this roughness is a smooth groove, directed down-
wards and forwards from the posterior margin, and completing with the palate bone
the posterior palatine or palato-maxillary canal.
The orbital surface is triangular, flat, and smooth ; anteriorly it reaches the
margin of the orbit for a short distance at the root of the nasal process ; externally
it is bounded by the rough surface for the malar bone. The internal border presents,
behind the nasal process, an excavation which receives the lachrymal bone, the
lachrymal notch, and then a nearly straight margin for articulation with the
ethmoid and palate bones. The posterior border is smooth, rounded and free, and
bounds the spheno-maxillary fissure ; the infraorlital groove commences here, and
leads forwards into the canal of the same name, which opens anteriorly by the infra-
orbital foramen. From the infraorbital are given off the anterior and middle dental
canals, which run down in the substance of the facial portion of the bone, and
convey the anterior and middle dental vessels and nerves.
The nasal process, slender and tapering, has an external surface, smooth and
continuous with the facial surface of the body, and an internal surface, the hinder
E 2
52 THE BONES OF THE HEAD.
part of which is irregular, and fits against the anterior extremity of the lateral mass
of the ethmoid, completing the foremost cells of that bone ; in front of this the
surface is free in the outer wall of the nasal fossa, and in its lower part is crossed by
a smooth oblique ridge, called the agger nasi, which forms the upper boundary of
the atrial surface of the body. The anterior border is rough, often grooved, for
articulation with the nasal bone, and its summit is serrated for articulation with the
frontal. Posteriorly, it presents a continuation of the lachrymal groove, which has
already been seen on the nasal surface of the body, and which here lodges the lachry-
mal sac : the groove is bounded internally by a sharp linear edge, which articulates
with the lachrymal bone, and externally by a smooth border which forms part of the
orbital margin.
The alveolar border or process, thick and arched, is hollowed out into sockets
or alveoli, corresponding in number, form, and depth to the roots of the teeth, which
are fixed in them.
The malar process is thick and triangular : its anterior and posterior surfaces
are continuous with the facial and zygomatic surfaces of the body ; the superior is
Fig. 52. — FRONT PART OF THE PALATE AND ALVEOLAR ARCH OF AN
ADULT. |
Showing the openings into the anterior palatine fossa. 1, 2, are
placed on the palate plates of the superior maxillary bones ; 4, anterior
palatine fossa, in which are seen four openings — the two lateral, with
lines pointing to them from 1 and 2, are the incisor foramina ; the
anterior and posterior, indicated by 3 and 4, are the foramina of
Scarpa.
rough and grooved to support the malar bone. The inferior border runs down on
the outer surface of the body in the form of a thick buttress opposite the first molar
tooth.
The palate process or plate, along with that of the opposite side, forms about three-
fourths of the hard palate. Its superior surface is smooth, and concave from side to
side ; its inferior surface is vaulted and rough, and is marked laterally with grooves
for nerves and vessels, which reach the palate through the posterior palatine canal.
Its posterior extremity falls short of that of the alveolar arch and body of the bone,
and articulates with the horizontal plate of the palate bone, which completes the
hard palate. The mesial border, finely serrated, rises into a vertical ridge, which, with
its fellow, constitutes the nasal crest— -a grooved elevation receiving the lower margin
of the vomer ; at the fore part this border rises suddenly to a considerable height,
and the more elevated portion is distinguished as the incisor crest ; forwards this is
prolonged into the anterior nasal spine, on its upper border rests the septal cartilage
of the nose, and into the angle behind it the truncated anterior extremity of the
vomer fits. Close by the side of the incisor crest on the upper surface of the palate
plate is seen a foramen which is directed downwards to the mouth, but in the lower
half becomes converted into a wider groove by deficiency of the inner wall. Thus,
when the two bones are placed in apposition, one orifice of considerable size is
formed on the palatal aspect, which divides above into right and left branches leading
to the corresponding nasal fossee ; the lower aperture is the anterior palatine fossa (or
canal), the lateral branches are the incisor foramina (or canals) or foramina of
Stensen. Farther, in the middle line are two other smaller foramina opening into
the anterior palatine fossa, one before, the other behind ; these are the foramina of
Scarpa.
The incisor foramina are placed between the two elements, the premaxilla and the maxilla
proper, which make up the superior maxillary bone of human anatomy, and are the remains
of a primitive communication between the nose and mouth. In the lower animals they are
THE PALATE BONE. 53
generally of large size, and open separately on the palate. A median anterior palatine fossa
receiving the two incisor foramina is met with only in man and a few animals, and the deeply
placed lamina which then bounds the incisor foramen on the inner side corresponds to the
mesial palatine process of the premaxillary bone of other animals. The foramina of Scarpa
lie in the suture between the laminae referred to. They transmit the naso-palatine nerves, the
nerve of the right side occupying, according to Scarpa, the posterior one, which is usually the
larger, and that of the left side, the anterior ; but they are very inconstant. (Scarpa, Annot.
Anatom., lib. ii, cap. 5.)
The maxillary sinus or antrum of Highmore has an irregularly pyramidal form.
Its ^alls are thin : the sides correspond to the facial, zygomatic and orbital surfaces
of the body ; the base to the nasal surface ; and the apex extends into the malar
process. The large aperture is closed to a considerable extent by the uncinate
process of the ethmoid, the palate and inferior turbinate bones ; and in the fresh
state it is reduced by the mucous membrane to a small orifice through which the
cavity communicates with the middle meatus of the nose. Its extent below generally
corresponds with that of the molar teeth, and the outer alveoli of one or more of
these form prominences in its floor.
THE PALATE BONE.
The palate bone forms the back part of the hard palate and the lateral wall
of the nose between the superior maxillary bone and the internal pterygoid plate.
It consists of a horizontal and a vertical plate united at a right angle, and of
three processes, viz., the tuberosity or
pyramidal process, extending outwards ORBITAL PROCESS
and backwards from the junction of
the horizontal and vertical plates, and
the orlital and splwiwidal processes,
surmounting the vertical plate.
The palate bone articulates with its
fellow, and with the superior maxillary,
ethmoid, sphenoid, vomer, and inferior >NF.TURB.
turbinate bones. NASAL CREST
The horizontal or palate plate pre-
sents a superior surface, concave and
smooth, forming the back part of the
floor of the nasal fossa, and an inferior
surface, completing the vault of the hard
palate, and marked near its posterior Fig 53i_ElGHT PALATE BONE> FROM BEHIND.
border by a transverse ridge to which (Drawn by D. Gunn. )
some tendinous fibres of the tensor
palati muscle are attached. The anterior border articulates with the palate process
of the superior maxilla ; the posterior is free, concave and sharp, giving attach-
ment to the soft palate, and produced at its inner end into a sharp point, which
with that of the other side forms the posterior nasal or palatine spine ; internally
it articulates with its fellow by a thick serrated border, forming a continuation of
the nasal crest of the superior maxillae, and also supporting the vomer ; externally, at
its junction with the vertical plate, it is grooved by the extremity of the posterior
palatine canal.
The vertical plate is very thin. Its internal or nasal surface is divided into two
parts, corresponding to the middle and inferior meatuses of the nose, by a nearly hori-
zontal ridge, the inferior turbinate crest, which articulates with the inferior turbinate
PTER. PAL. CA
SPHEN. PAL. NOTCH
SPHEN. MAX. FOSSA
VERT1CAL PLATE
— EXT. PTCR. PL.
54 THE BONES OF THE HEAD.
bone ; and at the upper end of the surface, crossing the roots of the two processes,
is another less marked ridge, the ethmoidal or superior turbinate crest, which articu-
lates with the middle turbinate bone. The external surface presents, nearer to the
posterior border, a narrow smooth surface which forms the inner wall of the pterygo-
maxillary fissure, and leads down to a deep groove forming with the superior maxil-
lary bone the palato-maxillary or posterior palatine canal for the transmission of
the large palatine nerve and vessels ; in front of the groove the surface is applied
against the superior maxillary bone, and overlaps the orifice of the antrum by a thin
tongue-shaped projection, the maxillary process, which may attain a considerable
size ; behind the groove it articulates inferiorly with the hinder border of the
maxilla, superiorly with the inner surface of the pterygoid process.
SPHEN. PAL, NOTCH
A POST. NASAL SPINE
Fig. 54. — RIGHT PALATE BONE: A, OUTER VIEW ; B, IKNER VIEW. (Drawn by D. Gunn.)
The pyramidal process or tuberosity fits into the notch between the pterygoid
plates. It presents posteriorly a triangular surface which is concave and smooth,
and completes the pterygoid fossa : on each side of this is a narrow area, the
internal deeply grooved, the external rough, for articulation with the anterior
border of the corresponding pterygoid plate. Externally there is a small free
surface which appears between the tuberosity of the superior maxillary bone and the
pterygoid process in the zygomatic fossa (fig. 68). Inferiorly, close to its con-
nection with the horizontal plate, are the orifices of the posterior and external
accessory palatine canals which transmit the lesser palatine nerves ; the external is
the smaller and less constant.
The orbital process surmounts the anterior margin of the vertical plate. It is
somewhat pyramidal in shape, and has five surfaces, two of which, the superior and
external, are free, and the rest articulated. The superior surface forms the posterior
angle of the floor of the orbit (fig. 69), the external looks into the spheno-
maxillary fossa, the anterior articulates with the maxillary, the internal with the
ethmoid, and the posterior, which is small, articulates with the sphenoid. The
process is generally hollow, and the cavity completes one of the posterior ethmoidal
cells, or it may open behind into the sphenoidal sinus.
The sphenoidal process curves upwards and inwards from the posterior part
of the vertical plate. Its superior surface is in contact with the body of the
sphenoid and the base of the internal pterygoid plate, and is grooved for the com-
pletion of the pterygo-palatine canal ; its internal or under surface looks to the
THE VOMER.
55
nasal fossa ; and at its base a third surface looks forwards and outwards into the
spheno-maxillary fossa. Its inner extremity touches the ala of the vomer.
The two processes are separated by the deep spheno-palatine notch, which is
closed above by the body of the sphenoid, and thus converted into the foramen of
ihe same name. It leads from the spheno-maxillary fossa into the nasal cavity, and
transmits the internal nerves from Meckel's ganglion and the nasal branch of the
internal maxillary artery, with corresponding veins.
Varieties. — The groove of the posterior palatine canal is sometimes closed in below, so
that the opening on the palate is bounded solely by the palate bone. The spheno-palatine
notch may also be converted into a foramen by the union of the upper ends of the sphenoidal
and orbital processes ; or the foramen maybe double from the development of an intermediate
osseous bridge. The orbital process varies greatly in size ; its orbital surface is frequently
enlarged from the union with the palate bone of a portion of bone ossifying from a separate
centre, usually united with the ethmoid or sphenoid, and already described with the sphe-
noidal spongy bone (p. 45). The external accessory palatine canal is often wanting ; or it
may be placed between the palate and superior maxillary bones.
THE VOMER.
The vomer is a thin median bone, irregularly quadrilateral, and placed
vertically between the nasal fossae. It articulates with the sphenoid, ethmoid,
palate, and superior maxillary bones, and with the septal cartilage of the nose.
The surfaces are smooth and in
the recent state covered by mucous
membrane ; each is traversed by a
faint groove running downwards
and forwards, and conducting the
naso-palatine nerve to the canal of
Scarpa. The superior border is by
far the thickest part of the bone,
and is divided into two spreading
alte, which fit under the body of the
sphenoid, receiving the rostrum into
the groove between them ; the edge
of each ala meets the vaginal process
GROOVE OF NASO-PAL. NERVE
Fig. 55.-— VOMER, FROM THE RIGHT SIDE.
(Drawn by D. Grunn. )
of the sphenoid and the cphenoidal
process of the palate bone. The anterior border, sloping downwards and forwards,
is grooved for the septal cartilage, and in the upper half is united by anchylosis on
one or both sides with the perpendicular plate of the ethmoid.
The anterior extremity of the vomer forms a short vertical edge which fits in
behind the incisor crest of the maxillaries, and from the upper end of which a process
projects forwards in the groove of the crest, while from its lower end a point
sometimes projects downwards between the incisor foramina. The inferior border
articulates with the nasal crest of the maxillary and palate bones. The posterior
border, thin, smooth, and unattached, separates the posterior nares.
THE MALAR BONE.
The malar bone forms the most prominent part of the cheek, and separates
the orbit from the temporal fossa. It is quadrangular in shape, with the angles
directed vertically and horizontally. The outer surface is convex, and presents a
little below the centre a slight elevation called the malar tuber os ity ; above this is
the orifice of the malar canal. The inner surface is concave, and looks into the
56
THE BONES OF THE HEAD.
temporal and zygomatic fossae. The tipper angle, frontal process, is the most
prominent, and is serrated at the extremity for articulation with the external angular
process of the frontal bone. The border behind this, temporal, is sinuous and con-
tinuous with the upper edge of the zygoma. The posterior angle, temporal process, is
serrated for articulation with the extremity of the zygoma, and the postero-inferior
border, masseteric, thick and rough, completes the lower edge of the zygomatic arch.
The antero-inferior border, maxillary, together with a rough triangular part of the
inner surface, articulates with the malar process of the superior maxilla. The
remaining border, orbital, is strongly excavated, smooth and rounded, and forms a
great part of the orbital margin ; from this the orbital process projects backwards
FRONTAL PROC.
REITAL PROC.
TEMP-ZYCOM. SURF.
ART. Wl
EUP.
TUBEROSITY
Fig. 56. — RIGHT MALAR BONE : OUTER VIEW.
(Drawn by D. Gunn.)
Fig. 57. — RIGHT MALAR BONE : INNER VIEW.
(Drawn by D. Gunn. )
and inwards, a triangular, curved plate, forming the fore part of the outer wall of the
orbit, and articulating by its rough edge with the great wing of the sphenoid ;
between the sphenoidal and maxillary articulations there is frequently a small free
margin which closes the anterior extremity of the spheno-maxillary fissure. On the
orbital surface of this process are seen two grooves leading to small canals, the
temporal, opening on the temporal surface, and the malar leading to the facial surface
of the bone ; they transmit the two divisions of the temporo-malar branch of the
superior maxillary nerve.
Varieties. — The malar bone is rarely divided by a horizontal suture into an upper larger
and a lower smaller part. The small canals are subject to great variation ; they may begin
with a common opening on the orbital surface ; either may be double ; or one may fail
entirely. There is often a well marked projection at the upper part of the temporal border,
called the marginal process ; it gives attachment to a strong band of the temporal fascia
In the numerous cases in which the malar bone does not enter into the formation of the
spheno-maxillary fissure, it is excluded either by the articulation of the great wing of the
sphenoid with the superior maxilla, or by a small Wormian bone.
THE NASAL BONE.
The nasal bones form the bridge of the nose. They are narrow and thick above,
but gradually become wider and thinner below. The superior border of each is
serrated, and articulates with the inner part of the nasal notch of the frontal bone :
the inferior is free in the dried skull, but in the recent state it gives attachment to
the lateral nasal cartilage ; it is generally marked by a small notch near its inner
THE LACHRYMAL BONE.
57
end. The external border is the longest, and articulates with the nasal process of
the superior maxilla, being supported by small teeth which fit into depressions on
the edge of that bone. The internal border is thicker above than below, and meets
its fellow in the somewhat irregular internasal suture, which commonly deviates to
one side at the upper end : the two
bones form posteriorly a median crest,
which rests from above down upon the
nasal spine of the frontal bone, the ver-
tical plate of the ethmoid (fig. 66), and
the septal cartilage of the nose. The
anterior or facial surface is concave from
above down at its upper part, convex
below, and presents a small vascular fora-
men. The posterior or nasal surface is
rough for a short distance above, where it
Fig. 58. — RIGHT NASAL BONE : A, INNER VIEW ;
B, OUTER VIEW. (Drawn by D. Gunn.)
rests upon the nasal process of the frontal
bone (fig. 38) ; in the rest of its extent it
is concave and smooth, being lined by the
mucous membrane of the nose ; and a little external to its centre it is traversed by
a small longitudinal groove which lodges the nasal nerve.
Varieties. — The form and dimensions of the nasal bones vary greatly in different indi-
viduals. They are in general relatively large and prominent in the white races, small and
flat in the dark and yellow races. Fusion of the two bones, by obliteration of the internasal
suture, is occasionally, though rarely, met with : this condition is usual in apes.
THE LACHRYMAL BONE.
The lachrymal bone, or os vnguis, is a thin scale of bone placed at the
anterior and inner part of the orbit (fig. 69). It articulates above with the frontal
bone, behind with the orbital plate of the ethmoid,
and in front with the nasal process of the superior
maxilla.
The external surface is divided by a vertical ridge,
the lachrymal crest, into two parts : the anterior is
grooved, lachrymal groove, for the lachrymal sac, and
this part is prolonged inferiorly beyond the orbit as the
descending process which assists in bounding the canal
of the nasal duct, and articulates with the inferior
turbinate bone ; the posterior part, broader, is flat, con-
tinuous with the orbital surface of the ethmoid, and is
produced below into a hook-like projection, the hamular
process, which curves forwards in the lachrymal notch of
the superior maxilla and bounds the orifice of the nasal duct on the outer side
(fig. 66). The internal surface superiorly completes some anterior ethmoidal cells,
and inferiorly looks into the middle meatus of the nose.
Varieties. — The lachrymal tone varies much in size : complete absence has been observed.
It is sometimes perforated, or reticulate, or divided into two or more pieces. The hamular
process is often very small, and sometimes wanting. On the other hand it may be unusually
long, and reach the orbital margin, or even, in rare cases, extend slightly onto the face :
this represents a more largely developed facial portion of the lachrymal bone in many
mammals. Occasionally the place of the hamular process is taken by a separate ossicle.
(Gegenbaur, Morph. Jahrb., vii. ; Macalister, Proc. Eoy. Soc., 1884.)
Fig. 59.— RIGHT LACHRYMAL
BONE: OUTER VIEW. (Drawn
by D. Gunn.)
58 THE BONES OF THE HEAD.
THE INFERIOR TURBINATE BONE.
The inferior turbinate or spongy bone is a slender lamina, attached by its
upper margin along the lateral wall of the nose, and projecting into the nasal cavity,
so as to divide the middle from the inferior meatus. It is slightly involuted, its
convexity looking inwards, and its lower margin is free, somewhat thickened, and
rolled upon itself. The attached margin articulates in its fore part with the inferior
turbinate crest of the superior maxillary bone, then ascends abruptly, forming the
lachrymal process, which completes the lachrymal canal and articulates with the
Fig. 60. — RIGHT INFERIOR TURBINATE BONE : A, INNER VIEW ; B, OUTER VIEW. (Drawn by D. Gunn.)
lachrymal bone ; behind this it is folded downwards in the maxillary process, forming
part of the inner wall of the antrum below the entrance into that cavity (fig. 69) ;
above and behind this, it presents a variable projection, the ethmoidal process, which
articulates with the uncinate process of the ethmoid ; and posteriorly it is attached
to the inferior turbinate crest of the palate bone. The posterior extremity is
elongated, sharp and pointed ; the anterior flattened and broader.
This bone is marked by irregular pits, grooves and canals for vessels, which are
directed for the most part longitudinally, but not, as the turbinal parts of the ethmoid
are, with vertical grooves for the olfactory nerves.
THE INFERIOR MAXILLARY BONE.
The lower jaw, inferior maxilla, mandible, is the thickest and strongest bone of
the face, and moves on the rest of the skull by means of a pair of condyles articu-
lating with the glenoid fossae of the temporal bones. It has the shape of an inverted
arch bent forwards upon itself, and consists of a middle larger nearly horizontal
part — the body, and of two ascending branches or rami.
The body is marked in the middle line in front by a faint vertical ridge, indicating
the symphysis or place of union of the originally separate lateral parts : this expands
below into the triangular elevation of the chin, or mental protuberance, the base of
which is in well-marked bones slightly depressed in the centre, and prominent on
each side, forming the mental tubercle. The superior or alveolar border of the body
is hollowed out into sockets for the teeth. The inferior border or base is thick and
rounded, and projects beyond the superior. On the outer surface, on each side of
the symphysis, below the incisor teeth, is a shallow depression, the incisor fossa ; and
more externally is the mental foramen, placed midway between the upper and lower
borders, and under the interval between the two bicuspid teeth ; it is the anterior
opening of the dental canal, and transmits the mental nerve and vessels. Close below
the foramen is the somewhat indefinite external oblique line, running from the
mental tubercle backwards and upwards to the anterior margin of the ramus. The
deep surface is marked, on each side of the symphysis, along the inferior margin, by
an oval depression, indicating the anterior attachment of the digastric muscle.
THE INFERIOR MAXILLARY BONE.
59
Above this are the mental spines, the lower being a small median ridge (often only a
slight roughness), to which the genio-hyoid muscles are attached, and the upper a
pair of more prominent tubercles, giving origin to the genio-glossi. Above the
upper spines a small median foramen penetrates the bone, and continued upwards
from this there is often to be seen a narrow groove marking the symphysis. Begin-
ning below the mental spines, and passing backwards and upwards to the ramus, is
the prominent internal oblique line or mylo-hyoid ridge, which gives origin to the
mylo-hyoid muscle, and at its hinder end to a slip of the superior constrictor of the
EXT. OBL. LINE.
PROTUBERANCE
TUBERCLE
Fig. 61. — THE INFERIOR MAXILLARY BONE, FROM THE RIGHT SIDE. (Drawn by D. Gunn.)
pharynx. Above this line is a smooth depression for the sublingual gland, and
more posteriorly beneath it another for the submaxillary gland.
The ramus is thinner than the body of the bone. Its posterior border in meeting
the line of the base forms the angle of the jaw, which is more or less rounded off,
and usually a little everted. The external surface is flat and impressed by the
masseter ; towards the angle irregular oblique ridges mark the attachment of
tendinous bundles of the muscle. The internal surface presents about its middle,
and on a level with the crowns of the lower molar teeth, the inferior dental foramen,
leading into the dental canal, which lodges the dental nerve and vessels. The inner
margin of the foramen is sharp and prominent anteriorly, forming the lingula.
Beginning at a notch behind the lingula is the mylo-hyoid groove (occasionally a
canal for a short space), marking the passage of the mylo-hyoid nerve with com-
panion vessels : it runs downwards and forwards to the body of the bone, and
terminates below the hinder end of the mylo-hyoid ridge. Behind this, and reaching
down to the angle, is a marked roughness for the internal pterygoid muscle.
The ramus is surmounted by two projections, the cTmdyle and the coronoid
process, which are separated by a deep excavation, the sigmoid notch. The condyle
is continued upwards from the posterior part of the ramus. It is supported by a
constricted portion, the necJc, on the front of which is a depression for the insertion
60
THE BONES OF THE HEAD.
of the external pterygoid muscle. The condyle is a transversely elongated, convex
articular process, the major axis of which is directed obliquely, so that if prolonged
it would meet with that of its fellow near the anterior margin of the foramen
RAMUS
Fig. 62. — RIGHT HALF OF THE INFERIOR MAXILLARY BONE, INNER VIEW. (Drawn by D. Gunn.)
magnum. The coronoid process is continued upwards, with a slight inclination
outwards, from the fore part of the ramus ; it is beak-shaped, and compressed
from side to side ; by its sharp margins and somewhat roughened inner surface
it gives insertion to the temporal muscle.
The anterior border of the ramus is sharp and
smooth, extending from the coronoid process to the
posterior end of the external oblique line. To the
inner side of this border is a grooved surface, which
is bounded posteriorly by a ridge continued up from
the internal oblique line to the mesial aspect of the
coronoid process, and into which a part of the temporal
muscle is inserted. At the lower end of the groove, and
extending a short distance on the outer side of the
alveolar process, there is sometimes to be seen a slight
roughness marking the origin of the lower part of the
buccinator muscle.
Fig. 63. — TRANSVERSE SECTION OF
THE LOWER JAW, PASSING
THROUGH THE SOCKET OF THE
LAST MOLAR TOOTH. (Gr. D. T.)
The lower jaw consists of a very thick shell of dense
compact bone, enclosing cancellous tissue with slender tra-
bgculas. The dental canal lies close to the inner compact
layer, and nearer to the lower than the upper border of the
body : it has a thin wall of compact tissue, which becomes
cribriform in the fore part of its extent. From the main passage small channels pass
upwards to the sockets of the hinder teeth ; and beyond the mental foramen a prolongation
of the canal, with a less distinct wall, extends forwards, transmitting the nerves and vessels
to the canine and incisor teeth.
THE HYOID BONE. 61
The angle of the jaw is in the adult usually about 120° ; in infancy it is as great as 140°
or more ; in strongly developed jaws it may be diminished to 110° or less ; and in old and
toothless jaws it is increased. These changes are connected with a variety of circumstances,
among which may be noticed, — the development of the temporary and permanent teeth, the
absorption of the alveolar arch after the loss of the teeth in advanced age, the elongation of
the face and upper jaw towards adult life, and the varying state of development of the
masseter muscles at different periods (see also p. 78).
THE HYOID BONE.
The hyoid bone, or os linguce, is situated at the base of the tongue, and may
be felt between the chin and the thyroid cartilage. It is shaped like the letter IT,
and consists of a body and two pairs of cornua. It is suspended from the tips of
the styloid processes of the temporal bones by a pair of slender bands, the stylo-
hyoid ligaments, which in most animals form
distinct bones.
The ~body, or central piece, is compressed
from before backwards, and lies in a plane
directed downwards and forwards. Its anterior
surface is convex, and marked by a transverse
ridge, with a slight median projection, on each
side of which are depressions for muscular
attachments. Its posterior surface is concave,
and looks towards the epiglottis.
The great cornua project backwards from the Fig. 64._THE HYOID BONE, FROM ABOVE
sides of the body. They are compressed from AND BEFORE. (Drawn by D. Gunn. )
above down, are largest near their junction with
the body, and terminate behind in slightly expanded and rounded extremities.
The small cornua, or cornicula, short and conical, project upwards and back-
wards from the places of junction of the body with the great cornua, and give
attachment at their extremities to the stylo-hyoid ligaments. They are commonly
in part, and not unfrequently entirely, cartilaginous.
The great cornua are connected to the body by synchondrosis, and after middle life usually
by bony union ; the small cornua by a synovial articulation which is seldom anchylosed.
In some cases a synovial joint is formed also between the great cornu and body.
TEE SKULL AS A WHOLE.
THE SUTUBES.
With the exception of the lower jaw, which is moveably articulated with the
temporal bone, the bones of the skull are closely fitted together by more or less
uneven edges or surfaces, there being generally interposed only a small quantity of
fibrous tissue, continuous with the periosteum ; and to these lines of articulation
the name suture is given. At the base of the cranium, however, in young subjects,
the basilar process of the occipital is connected to the sphenoid, and the jugular
process to the petrous, by a thin layer of cartilage ; the articulation is therefore
synchondrosis, and when adult age is reached it becomes converted into bony union.
The sutures are best named from the bones between which they lie, as, occipito-
parietal, occipito-mastoid, fronto-ethmoidal, &c. Those around the parietal bones
are the longest and most regular, and to them special names have been applied ;
thus, above, between the two parietal bones, is the sagittal or interparietal suture ;
posteriorly is the deeply serrated lamMoid or occipito-parietal suture ; anteriorly is
the coronal or fronto-parietal suture, most markedly serrated in the middle part of
62 THE SKULL AS A WHOLE.
each lateral half, less so above where the frontal bone overlaps the parietal, and quite
simple at the lower end where the parietal overlaps the frontal ; inferiorly is the
temporo-paridal suture, consisting of two parts, the squamous suture, arched in form,
in which the squamous part of the temporal overlaps the parietal, and the parieto-
mastoid, short and serrated ; while at the antero-inferior angle is the short spheno-
parietal suture, about, half an inch in length, absent only in rare cases when the
frontal and temporal bones come into contact.
The cranial sutures are conveniently arranged in three groups, a median longitudinal, a
lateral longitudinal and a vertical transverse. The first consists of the sagittal suture, which
is continued in the infant, and frequently in the adult, by the frontal suture ; in the lateral
longitudinal are included, on each side, the fronto-nasal, fronto-maxillary, fronto-lachrymal,
fronto-ethmoidal, fronto-malar, fronto-sphenoidal, spheno-parietal, squamous, and parieto-
mastoid sutures ; the third comprises the coronal and spheno-squamous, the lambdoid and
occipito-mastoid sutures ; and into this group also would fall the transverse articulations in the
centre of the base between the ethmoid, sphenoid and occipital.
After adult life is reached the bones of the skull evince a disposition to unite, and many of
the sutures thereby become closed ; but the period at which this commences, as also the order
in which it proceeds, are subject to great variations, so that the condition of the sutures
affords very little assistance in determining the precise age of a skull. The process com-
mences generally about thirty years of age ; the union takes place first on the inner
surface, and frequently the large sutures are quite obliterated internally while they are
perfectly distinct on the external surface. The earliest points to close are commonly the
part of the sagittal suture between the parietal formina, and the lower ends of the coronal
suture ; the more dentated parts of these sutures and the lambdoid follow later. The
squamous is very late in closing, and it is noteworthy that when the frontal suture fails to
unite at the usual time it may remain unchanged even to very advanced age. (Dwight,
" The Closure of the Cranial Sutures as a Sign of Age," Boston Med. and Surg. Journ.,
April, 1890.)
"Wormian bones. — Ossa triquetra, ossa sutiirarum. These are irregular ossifications,
found in many skulls, interposed between the cranial bones ; seldom in the face. They are
of irregular form, with margins adapted to the character of the sutures in which they are
situated, and usually of small size ; but they may exceed an inch in diameter. Their most
frequent seat is in the occipito-parietal suture, where they sometimes occur in great numbers,
more or less symmetrically arranged : in some cases one or several bones of considerable size
occupy the place of the superior part of the occipital, more rarely of the antero-superior angles
of the parietal bones : a scale-like ossification is often seen between the antero-inferior angle
of the parietal and the great wing of the sphenoid (epijpterfo lone, Flower). They are much
less frequent in the other sutures.
EXTERNAL SUBFAOB OF THE SKULL.
The external surface of the skull may be conveniently divided into superior,
inferior, anterior, and lateral regions.
The superior region, extending from the supraorbital margins in front to the
superior curved lines of the occipital bone behind, and bounded laterally by the
temporal lines, is smooth and convex, covered only by the integument and by the
muscular fibres and aponeurosis of the occipito-frontalis muscle. The skull as seen
from above is of an oval form, broader in the parietal than the frontal region,
flattened in front, and projecting somewhat in the middle behind. There is also a
slight projection from the general curve at each of the frontal and parietal
eminences.
The anterior region of the skull, below the forehead, presents the openings of
the orbits, bounded by the frontal, malar, and superior maxillary bones ; and between
the orbits, the bridge of the nose, formed by the nasal bones and ascending processes
of the superior maxillaries. Below the nasal bones is the anterior nasal aperture, of
an inverted heart-shape : its thin margin gives attachment to the nasal cartilages,
and projects forwards in the middle line below as the anterior nasal spine. Below
the nasal aperture are the incisor fossas of the upper jaws ; below the orbits are the
EXTERNAL SURFACE OF THE SKULL.
63
canine fossae ; and external to the canine fossae are the prominences of the cheeks,
formed by the anterior inferior parts of the malar bones. The lower jaw completes
the skeleton of the face. The foramina in this region, on each side, are the supra-
orbital foramen or notch in the superior margin of the orbit, the infraorbital
foramen below the inferior margin of the orbit, the mental foramen of the lower jaw,
and the small malar canal of the malar bone.
The anterior nasal aperture is often markedly unsymmetrical, one half of the opening being
broader and shorter, while on the other side it is narrower and more deeply excavated below.
This is associated with a corresponding deviation of the cartilaginous part of the nose, which
points towards the side on which the wider half of the aperture is placed. (H. Welcker, " Die
Asymmetrien der Nase und des Nasenskeletes," Stuttgart, 1882.)
The orbits are pyramidal fossae, irregularly quadrilateral, with their bases
direeted forwards and slightly outwards, their inner walls being nearly parallel, and
Fig. 65. — FRONT VIEW OF MALE SKULL AT
ABOUT TWENTY TEAKS. (Allen Thomson.) \
1 . frontal eminence ; 2, glabella, between the
superciliary ridges, and above the transverse
suture of union with the nasal and superior
maxillary bones ; 3, orbital arch near the
supraorbital notch ; 4, orbital surface of
great wing of sphenoid, between the sphe-
noidal and the spheno-maxillary fissures ;
5, anterior nasal aperture, within which are
seen in shadow the vomer and the turbinate
bones ; 6, superior maxillary bone at the
canine fossa — above the figure is the infra-
orbital foramen ; 7, incisor fossa ; 8, malar
bone ; 9, symphysis of Jower jaw ; 10, mental
foramen ; 11, vertex, near the coronal suture ;
12, temporal fossa ; 13, zygoma; 14, mastoid
process ; 15, angle of the jaw ; 16, mental
protuberance. In this skull there are fourteen
teeth in each jaw, the wisdom teeth not having
yet appeared.
their outer walls diverging so as to
be nearly at right angles to each
other. The roof of each orbit is
formed by the orbital plate of the
frontal and the small wing of the
sphenoid ; the floor (fig. 66) by the
malar and superior maxillary bones,
and by the small orbital surface of
the palate bone at the back part ;
the inner wall (fig. 69) by the nasal
process of the superior maxilla, the lachrymal, the ethmoid and body of the
sphenoid ; .and the outer wall by the orbital surfaces of the malar bone and great
wing of the sphenoid. The spJienoidal fissure (foramen lacerum orbitale) at
its inner extremity occupies the apex of the orbit, -while its outer and narrower
part lies between the roof and the external wall. The optic foramen is internal
and superior to the sphenoidal fissure. In the angle between the external wall
and the floor is the spheno-maxillary fissure, bounded by the sphenoid, palate,
superior maxillary, and malar bones, and leading into the spheno-maxillary fossa at
its back part, into the zygomatic fossa at its fore part. Passing forwards from the
margin of the spheno-maxillary fissure is the commencement of the infraorbital
canal, grooving the posterior part of the floor of the orbit. On the inner wall in
fi4l THE SKULL AS A WHOLE.
wn
front is the lachrymal groove, formed by the superior maxillary and lachrymal bones,
and leading into the nasal duct ; farther back, between the 'ethmoid and frontal
bones are the anterior and posterior internal orbital canals ; on the roof, at its
anterior margin, is the supraorbital foramen or notch ; within the external angular
process is the fossa for the lachrymal gland ; and in the outer wall are the temporal
and malar canals of the malar bone and one or two other minute foramina.
The lateral region of the skull presents in succession from behind forwards
the mastoid process, the external auditory meatus, the glenoid fossa, with the condyle
.NASAL BONE
Fig. 66. — FORE PART OF A HORIZONTAL SECTION OF THE SKULL, PASSING THROUGH THE CENTRE OF THE
ORBIT. (G. D. T.)
The right half of the lower portion is represented.
of the lower jaw, the zygomatic arch, formed by the zygomatic process of the temporal
bone and the posterior part of the malar, and internal to this the coronoid process of
the lower jaw. Above the zygomatic arch is the temporal fossa, below is the zygo-
matic fossa, the two beiog separated by the infratemporal crest on the great wing of
the sphenoid (fig. 68).
The temporal fossa is occupied by the temporal muscle, and the squamous
part of the temporal, the parietal, frontal, sphenoid and malar bones take part in its
formation. It is bounded above by the temporal crest of the frontal bone and the
lower temporal line of the parietal. The latter turns down posteriorly to join the
supramastoid crest of the temporal bone, which in front is continued into the upper
edge of the zygomatic arch. Along this line of bone is attached the temporal fascia,
which in the complete state roofs in the temporal fossa.
The zygomatic or infratemporal fossa (fig. 68) is an irregular hollow, in part
covered by the ramus of the lower jaw. Its wall is formed internally by the external
ZYGOMATIC FOSSA.
65
pterygoid plate ; superiorly by the lower part of the great wing of the sphenoid, in which
are seen the foramen ovale and foramen spinosum, and by a small part of the squamous
of the temporal ; and anteriorly by the zygomatic surface of the superior maxilla,
presenting the orifices of the posterior dental canals, together with the lower part of
the malar bone. Inferiorly, the external pterygoid plate approaches closely the
superior maxillary bone, but the two are usually prevented from meeting by a thin
portion of the pyramidal process of the palate bone ; superiorly, they are separated
by the •pterygo-maxillary fissure, a vertical slit leading above into the spheno-
Fig. 67. — LATERAL VIEW OF THE SKULL REPRESENTED IN FIGURE 65. (Allen Thomson.) J
1, frontal bone ; 2, parietal bone at the upper temporal line ; x x , coronal suture ; 3, on the
occipital bone at the lower end of the lambdoid suture, near its meeting with the occipito-mastoid and
parieto-mastoid sutures ; 3', external occipital protuberance ; 4, great wing of sphenoid ; 5, squamous
part of temporal ; 6, the same at the root of the zygoma, immediately over the external auditory
meatus ; 7, mastoid portion of temporal, at the front of which is the mastoid process ; 8, left condyle of
occipital bone ; 9, anterior nasal aperture ; 10, on the lachrymal bone in the inner wall of the orbit ;
11, malar bone, near its junction with the zygoma ; 12, superior maxillary bone behind the canine
fossa ; 13, ramns of the lower jaw ; 14, body of the lower jaw, near the mental foramen.
maxillary fossa, and closed internally by the vertical plate of the palate bone. At
the upper part of the zygomatic fossa the horizontal spheno-maxillary fissure leads
into the orbit.
The spheno-maxillary fossa is the space which lies in the angle between the
pterygo-maxillary and the spheno-maxillary fissures. It is bounded behind by the
pterygoid process and the lower part of the anterior surface of the great wing of the
sphenoid bone ; in front by the superior maxillary bone ; and internally by the
vertical plate of the palate bone with its orbital and sphenoidal processes. Into this
narrow space five foramina open, viz., on the posterior wall, the foramen rotundum,
the Vidian canal, and, between the sphenoidal process of the palate bone and the root
of the internal pterygoid plate, the pterygo-palatine canal ; on the inner wall, the
VOL. II. Tf
66
THE SKULL AS A WHOLE.
IMrRATEMPORAL
CREST
Fig. 68. — SIDE VIEW OF THE LOWER AND FORE PART OF THE SKULL, THE INFERIOR MAXILLA AND
ZYGOMATIC ARCH BEING REMOVED, TO SHOW THE ZYGOMATIC FOSSA. (&. D. T.)
OPTIC FOR.
NF. TURB. BONE
Fig. 69. — SAGITTAL SECTION OF THE FACIAL PORTION OF THE SKULL. (G. D. T.)
The section passes through the right orbit a little internal to the centre, and opens up the antrum
and spheno-maxillary fossa.
EXTERNAL BASE OF THE SKULL.
67
spheno-palatine foramen formed by the palate bone and the sphenoid, and opening
into the nasal cavity ; and infer iorly, the posterior palatine or palate-maxillary
canal, which leads down to the roof of the mouth between the palate and superior
maxillary bones.
The external base of the skull, excluding the lower jaw, is divisible into
three parts, anterior, middle, and posterior.
The anterior division consists of the palate and the alveolar arch. It is
traversed longitudinally by a median suture, and transversely by that between the
maxillary and palate bones. Anteriorly, in the middle line, is the anterior palatine
Fig. 70. — EXTERNAL BASE OF THE SKULL
SHOWN IN FIGURE 65. (Allen Thomson.) J
1, palate plate of the superior maxil-
lary bone ; 2, palate plate of the palate
bone ; 3, anterior palatine fossa ; 4, is
placed outside the posterior palatine canal,
inside the tuberosity of the superior
maxilla, and in front of the smaller poste-
rior palatine canals ; 5, inner surface of
the external pterygoid plate ; 6, is placed
within the posterior opening of the right
nasal fossa on the internal pterygoid plate;
7, vomer ; x , posterior opening of the
pterygo-palatine canal in front of the
foramen lacerum ; 8, spheno-maxillary
fissure leading into the orbit ; 9, foramen
spinosum ; 10, foramen ovale ; 11, placed
on the apex of the petrous bone, between
the foramen lacerum and the inferior
opening of the carotid canal ; 12, jugular
foramen ; 13, articular eminence of the
temporal bone ; 14, external auditory
meatus ; 15, glenoid fossa in front of the
fissure of Glaser ; 16, tympanic plate or
posterior part of the glenoid fossa, close
to the styloid process, behind which is
seen the stylo-mastoid foramen ; 17, mas-
toid process, and to its inside the digas-
tric and occipital grooves ; 18, basilar
process of the occipital bone, and in front
the mark of the still incomplete union with
the body of the sphenoid bone ; 19, con-
dyle of the occipital bone ; 20, is placed
in the foramen magnum, and points to
the inner opening of the anterior con-
dylar foramen ; 21, posterior condylar
foramen ; 22, jugular process of the occipital bone ; 23, external occipital crest running down from the
protuberance ; 24, superior curved line of the occipital bone ; 25, 26, inferior curved line.
fossa, with the four foramina opening into it (p. 52) ; posteriorly, on each side,
at the base of the alveolar arch, is the opening of the posterior palatine canal,
from which the palatine groove, lodging the large palatine nerve and vessels,
runs forwards ; and farther back, on the under aspect of the tuberosity of the palate
bone, are the apertures of the posterior and external small palatine canals. The palate
is surrounded in front and on the sides by the alveolar arch bearing the teeth of the
upper jaw.
The middle division extends back to the front of the foramen magnum. Its
central portion has been called the guttural fossa. In the middle line is the basilar
process of the occipital bone, and in front of that the body of the sphenoid, covered
anteriorly by the alse of the vomer. On each side, the petrous portion of the
temporal bone reaches as far forwards as the extremity of the basilar process ; and
F 2
68 THE SKULL AS A WHOLE.
between the petrous and squamous portions is the back part of the great wing of the
sphenoid bone. Between this division of the base of the skull and the palate are
the posterior nares, separated by the vomer, and bounded above by the body of the
sphenoid bone, below by the horizontal plates of the palate bones, and laterally by
the internal pterygoid plates. On each side of the posterior nares is the pterygoid
fossa, completed below by the tuberosity of the palate bone ; and a line from the
external pterygoid plate to the spine of the sphenoid forms the division between this
region and the zygomatic fossa. Immediately behind or internal to this line is the
groove for the cartilaginous part of the Eustachian tube, formed by the margins of
the great wing of the sphenoid and the petrous, and leading to the osseous part of the
tube in the temporal bone. Between the apex of the petrous, the basilar process,
and the sphenoid is the foramen lacerum ; in a line proceeding backwards and out-
wards from this are the free surface of the petrous, the lower orifice of the carotid
canal, the vaginal and styloid processes, and the stylo-mastoid foramen ; while
internal to these are the jugular and anterior condylar foramina.
Between the basilar process of the occipital bone and the petrous portion of the temporal
is an irregular cleft, extending from the foramen lacerum backwards and outwards to the
jugular foramen, and called the petro-basilar fissure. This interval, together with the lower
part of the foramen lacerum, is filled in the recent state by fibrous tissue which often
contains one or two small Wormian ossicles. In front of the petrous portion, at the bottom
of the groove of the Eustachian tube, is the petro-splienoidal fissure, also continued outwards
from the foramen lacerum.
The posterior division presents on each side of the foramen magnum, from
within outwards, the occipital condyle, the under surface of the jugular process, the
occipital groove of the temporal bone, the digastric fossa, and the mastoid process.
Behind the foramen magnum is the tabular part of the occipital bone, with its ridges
and muscular impressions.
THE INTERIOR OF THE CRANIUM.
The wall of the cranium consists of two layers of compact bony substance, the
outer and inner tables, and an intervening cancellated substance, called diploe. The
inner or vitreous table has a smooth, close-grained, shining appearance, is hard and
brittle, and presents irregular digitate impressions corresponding to the convolutions
of the cerebrum. The thickness of the skull-cap or calvaria is fairly uniform, and
generally ranges from one-sixth to one-fourth of an inch : it is somewhat increased
along the middle line, especially in front and behind, and diminishes below on each
side, in the temporal fossa. The base of the skull varies greatly in this respect:
the thickest parts are the basilar process, the petrous and mastoid portions of the
temporal bones, and the occipital bone at the protuberances and ridges. The
thinnest portions of the cranial wall are the cribriform plate of the ethmoid and the
orbital plates of the frontal bone, in both of which the diploe is absent ; the bone is
also thin and compact in the middle part of the inferior occipital fossse, and in the
lower part of the squama and the glenoid fossa of the temporal.
The upper part of the cranial cavity is enclosed by a single vaulted dome, formed
by the frontal, parietal, and occipital bones. This is marked on its internal surface
by the groove for the superior longitudinal sinus, by shallow cerebral impressions, by
small ramified meningeal grooves, and by Pacchionian fossae of varying depth. The
only apertures in the roof of the skull are the inconstant parietal foramina, which
open by the side of the longitudinal sulcus posteriorly ; they give passage to emissary
veins, and occasionally a branch of the occipital artery.
The internal base of the skull is divided into three fossae, named anterior,
middle, and posterior.
INTERNAL BASE OF THE SKULL.
69
The anterior fossa, formed by the orbital plates of the frontal bone, the
cribriform plate of the ethmoid, and the small wings and part of the body of the
sphenoid, supports the frontal lobes of the cerebrum. It is convex laterally above
the orbits, but sinks into a hollow over the cribriform plate of the ethmoid, in the
middle line of which the crista galli stands up, separating the deep olfactory grooves
for the reception of the olfactory bulbs. In front of the crista galli is the foramen
23
Fig. 71. — SAGITTAL SECTION OF THE ADULT SKULL A LITTLE TO THE LEFT OF THE MEDIAN PLANE.
(Allen Thomson.) J
1, nasal bone ; 2, perpendicular plate of the ethmoid with olfactory foramina and grooves at its
upper part ; 3, vomer ; 4, right superior maxillary bone, forming part of the wall of the right nasal
fossa ; below this is the anterior extremity of the right inferior turbinate bone overhanging x , which
is the right inferior meatus of the nose ; 5, crista galli ; 6, inner surface of the frontal bone ; 7, of the
parietal bone ; 8, sqnamous part of the temporal ; 9, on the occipital bone below the internal occipital
protuberance ; 10, external occipital protuberance ; 11, on the condylar process below the anterior con-
ilylar foramen ; 12, on the posterior surface of the petrous below the internal auditory meatus ; between
0 and 12, the groove of the right lateral sinus ; 13, placed above the sella turcica ; 14, left frontal
sinus ; 15, left sphenoidal sinus, the figure being placed on the sphenoidal septum ; 16, hard palate
and alveolar arch — the figure is placed near the lower opening of the posterior palatine canal, and the
grooves which extend forwards from it ; 17, anterior nasal spine ; 18, section of the left superior
maxillary bone, and near the place to which the line points, the section of the anterior palatine fossa ;
19, on the inner surface of the ramus of the lower jaw, below the sigmoid notch, and above the inferior
dental foramen ; 20, inner surface of the body of the jaw on the mylo-hyoid ridge ; 21, surface of section
of the lower jaw to the left of the sympbysis ; behind the symphysis, and between 21 and 22, the mental
spines ; 23, mylo-hyoid groove.
csecum ; on each side are the numerous apertures of the cribriform plate, the inner
openings of the internal orbital canals, and the foramen by which the nasal nerve
passes into the nose.
The foramen caecum sometimes conveys a vein passing from the nose to the superior longi-
tudinal sinus. The apertures of the cribriform plate are occupied by the olfactory nerve
filaments. Through the anterior internal orbital canal the nasal nerve and the anterior
ethmoidal artery enter the skull, and through the posterior, which is less constant, the
posterior ethmoidal artery. The foramen, for the exit of the nasal nerve is at the front
70
THE SKULL AS A WHOLE.
of the cribriform plate, usually between that and the frontal bone, and is connected by a groove
with the inner opening of the anterior internal orbital canal : the nerve is accompanied by the
nasal division of the anterior ethmoidal artery.
The middle fossa, on a lower level than the anterior, consists of a median and
two lateral parts. The median part is small, being formed by the olivary eminence
and sella turcica of the sphenoid bone, and limited behind by the dorsum sells. The
lateral part on each side, formed by the great wing of the sphenoid, the squamous
part, and the anterior surface of the petrous part of the temporal, lodges the temporal
lobe of the cerebrum. The foramina of the middle fossa are the optic foramen,
sphenoidal fissure, foramen rotundum, foramen ovale, foramen spiuosum, foramen
lacerum and hiatus Fallopii.
Fig. 72. — INTERNAL BASE OF THE
SKULL, (Allen Thomson.) J
1, anterior fossa and roof of the
orbit, as formed by the frontal bone ;
between 2 and 3, the foramen caecum,
crista galli and cribriform plate of
ethmoid ; 3, ethmoidal spine of the
sphenoid ; 4, lesser wing of sphenoid
terminating posteriorly in the anterior
clinoid process, inside which is the
optic foramen ; 5, placed in the pitui-
tary fossa, behind the olivary emin-
ence and transverse groove of the
optic commissure ; 6, dorsum sellse,
terminating in the posterior clinoid
processes ; 7, foramen rotundum, in
front of which, but not seen in the
figure, is the sphenoidal fissure ; 8,
foramen ovale ; 9, foramen spiuosum ;
10, on the petrous bone, near its apex,
and to the inside of the hollow occu-
pied by the Gasserian ganglion ; in
front of this is the foramen lacerum ;
11, in front of the eminence of the
superior semicircular canal, and be-
hind the hiatus Fallopii ; 12, upper
border of the petrous, marked by the
superior petrosal groove ; 13, the
posterior surface of the petrous — to
the inside, the internal auditory
meatus, behind, the scale of bone
covering the aqueduct of the vestibule ;
14, basilar groove ; 15, anterior con-
dylar foramen ; 16, jugular foramen ; 17, groove of the lateral sinus ; 18, internal occipital protube-
rance, and running\lown from it the internal occipital crest ; between 17 and 18, the upper part of the
groove of the lateral sinus, between 17 and 16, the lower part ; 19, cerebellar fossa.
Through the optic foramen the optic nerve and the ophthalmic artery enter the orbit. The
sphenoidal fissure (foramen lacerum anterius) also opens into the orbit ; it gives passage to
the third, fourth, ophthalmic division of the fifth, and the sixth nerves, and the ophthalmic
veins. By the foramen rotundum the superior maxillary nerve passes into the spheno-max-
illary fossa. The foramen ovale and foramen spinosum lead into the zygomatic fossa : the
former transmits the inferior maxillary nerve, the small meningeal artery, and two or three
emissary veins ; the latter, the large meningeal vessels.
The foramen lacerum (medium) is an irregular aperture between the apex of the petrous
and the body and great wing of the sphenoid, and in the recent state is closed below by a mass
of fibrous tissue ; the carotid canal opens on its external wall, the Vidian canal anteriorly.
The lingula projecting backwards from the body of the sphenoid effects a partial, sometimes
a complete subdivision of the space : by the inner part the carotid artery enters the cranial
cavity ; and through the external, the large superficial petrosal nerve, coming from the hiatus
Fallopii, reaches the posterior orifice of the Vidian canal.
The posterior fossa, deeper and larger than the others, extends back to
the occipital protuberance, and lodges the cerebellum, medulla oblongata and pons.
THE INTERIOR OF THE CRANIUM. 71
The occipital bone, the petrous and mastoid portions of the temporal, the postero-
inferior angle of the parietal, and the body of the sphenoid take part in its formation.
In the centre of the fossa is the foramen magnum ; and on each side of this, in
a nearly vertical line from below upwards, are the anterior condylar foramen piercing
the condylar portion of the occipital bone, the jugular foramen between the occipital
and petrous, and the internal auditory meatus on the posterior surface of the petrous.
Behind the jugular foramen is the posterior condylar foramen (if present), and higher
up the more constant mastoid foramen, both opening into the groove of the lateral
sinus.
The foramen magnum is occupied in the recent state by the lower end of the medulla
oblongata with its membranes, the vertebral arteries, and the spinal accessory nerves. The
anterior condylar foramen transmits the hypoglossal nerve and a meningeal branch of the
ascending pharyngeal artery. By the internal auditory meatus the facial and auditory nerves,
with the portio intermedia and the auditory vessels, leave the cranial cavity. The posterior
condylar and mastoid foramina transmit emissary veins, the latter also the mastoid branch of
the occipital artery.
The jugular foramen (foramen lacerum posterius) is formed by the jugular notches of the
petrous and occipital bones : somewhat pyriform in shape, two more or less marked constric-
tions indicate a division into three compartments ; most externally and posteriorly is a large
rounded part in which the lateral sinus joins the internal jugular vein ; the middle part, cor-
responding to a distinct notch in the lower border of the petrous, transmits the glosso-
pharyngeal, vagus, and spinal accessory nerves ; and the most anterior and internal, sometimes
completely separated by a spiculum of bone (the intra jugular process; p. 34), gives passage to
the inferior petrosal sinus. A meningeal branch of the ascending pharyngeal or occipital
artery also enters the skull by the posterior compartment.
Grooves for blood-vessels. — The groove of the middle meningeal artery
commences at the foramen spinosum, and ramifies principally on the squamous
portion of the temporal bone and on the parietal. The groove of the internal
carotid artery lies on the side of the body of the sphenoid, and extends from
the foramen lacerum to the inner side of the anterior clinoid process. The groove of
the superior longitudinal sinus, commencing at the frontal crest, passes backwards in
the middle line of the roof of the skull, and terminates at the internal occipital
protuberance. From that point the groove of the lateral sinus passes outwards on
each side over the occipital bone, crosses the posterior inferior angle of the parietal
bone, descends on the mastoid portion of the temporal bone, runs inwards again on
the occipital, and turns forwards to terminate at the jugular foramen. The groove
of the inferior petrosal sinus lies between the petrous portion of the temporal bone
and the basilar process ; that of the superior petrosal sinus extends along the superior
edge of the petrous portion.
EHE NASAL CAVITIES AND COMMUNICATING AIR-SINUSES.
The nasal cavities, or fossae, are placed one on each side of a median vertical
septum. They open in front by the anterior nasal aperture and behind by the
posterior nares already described, and communicate with the sinuses of the frontal,
ethmoid, sphenoid, and superior maxillary bones. Their vertical extent, as well as
that from before backwards, is considerable, but their transverse width is very
limited, especially in the upper part.
The internal wall, or septum nasi, is formed by the central plate of the ethmoid,
the vomer, the nasal spine of the frontal, the rostrum of the sphenoid, and the crests
of the nasal, maxillary, and palate bones. It presents a great angular deficiency in
front, which in the recent state is filled up by the septal cartilage. In most cases it
deviates somewhat from the middle line to one side or the other.
The roof is horizontal in its middle part, but sloped downwards before and
behind. The middle part is formed by the cribriform plate of the ethmoid, the fore
THE SKULL AS A WHOLE.
part by the frontal and nasal bones, and the back part by the body of the sphenoid,
the ala of the vomer and the sphenoidal process of the palate bone. In it are the
apertures of the cribriform plate and the orifice of the sphenoidal sinus.
The/oor, formed by the palate plates of the maxillary and palate bones, is smooth,
and concave from side to side. Towards its anterior extremity is the orifice of the
incisor foramen.
The external wall is the most extensive. The bones which take part in its
formation are the nasal, superior maxillary, lachrymal, ethmoid, inferior spongy, and
palate bones, and the internal pterygoid plate. The superior and inferior turbinate
processes of the ethmoid bone, and the inferior spongy bone, projecting inwards,
overhang the three hollows called meatuses. The superior meatus, very short,
is placed between the superior and inferior turbinate parts of the ethmoid ; into it
Fig. 73. — SAGITTAL SECTION OF A PART OF THE
SKULL, SHOWING THE OUTER WALL OF THE LEFT
NASAL FOSSA, &c. (Allen Thomson. ) £
1, nasal bone ; 2, nasal process of the supe-
rior maxillary bone ; 3, vertical plate of the
palate bone ; 4, superior turbinate bone — below
it the superior meatus, behind it the spheno-
ethmoidal recess and the opening into the left
sphenoidal sinus ; 5, middle turbinate bone —
below it the middle meatus, into which opens
the maxillary sinus ; superiorly and anteriorly,
is the opening of the infundibulum ; behind it,
and above 3, the spheno-palatine foramen ;
6, inferior turbinate bone — below it the inferior
meatus x x ; below these marks the section
of the palate plates of the left palate and supe-
rior maxillary bones ; 7, left frontal sinus ; 8,
left sphenoidal sinus ; 9, left optic foramen in
the root of the lesser wing of the sphenoid, and
anterior clinoid process ; 10, dorsum sellae di-
vided ; and between 9 and 10, the sella turcica ; 11, posterior surface of the petrous, close to the
internal auditory meatus ; 12, basilar process of the occipital bone, close to the jugular foramen ;
13, on the occipital condyle, below the anterior condylar foramen ; 14, styloid process ; 15. external,
and 16, internal pterygoid plates ; 17, posterior palatine canal.
open anteriorly the posterior ethmoidal cells, and posteriorly the spheno-palatine
foramen. The middle meatus, the space between the inferior turbinate part of the
ethmoid and the inferior spongy bone, communicates with the anterior and middle
ethmoidal cells, with the maxillary sinus, and at its fore part, by means of the
infundibulum, with the frontal sinus. The inferior meatus, longer than the others, lies
between the inferior spongy bone and the floor of the nasal cavity, and in its fore
part is the orifice of the nasal duct. Above the superior meatus, in an angle
of the roof formed by the cribriform plate and the front of the body of the sphenoid
(fig. 73, behind 4), is a depression called the spheno-ethmoidal recess (Gr. H. Meyer),
formed by the narrowing of the lateral mass of the ethmoid (fig. 66) ; on Ihe
posterior wall of the recess is the opening of the sphenoidal sinus.
The air-sinuses are hollows within the ethmoid, frontal, sphenoid, and maxillary
bones, which communicate with the nasal cavities by narrow orifices. With
the exception of the maxillary sinus these cavities are absent in the infantile skull.
The maxillary sinus begins to be formed about the fourth month of foetal life ; the
frontal, ethmoidal and sphenoidal first excavate the respective bones during child-
hood, but remain of small size up to the time of puberty, when they undergo a great
enlargement. In advanced life they all increase in size by absorption of the
cancellated tissue in their vicinity. The ethmoidal sinuses consist of several irregular
spaces occupying the lateral mass of the ethmoid, and completed by the frontal,
OSSIFICATION OF THE BONES OF THE HEAD.
73
sphenoid, lachrymal, superior maxillary and palate bones. The anterior and middle,
the larger and more numerous, open into the middle, the posterior into the superior
meatus. The frontal sinuses are placed between the outer and inner tables of
the frontal bone over the root of the nose. They extend outwards from behind the
glabella to a variable distance over the orbit, being separated from each other by a
thin bony septum. They open on each side into the middle meatus of the nose
through the inf undibulum. The sphenoidal sinuses occupy the body of the sphenoid,
being formed in connection with the sphenoidal spongy bones. They are separated
by a median septum, and open into the spheno-ethmoidal recess. The maxillary
sinus has been described in connection with the superior maxillary bone ; it opens by
a small aperture into the middle meatus.
The air-spaces of the temporal bone (tympanum and mastoid cells) are described in connec-
tion with the Anatomy of the Ear in Vol. III.
OSSIFICATION OF THE BONES OF THE HEAD.
The ossification of the bones of the base of the cranium takes place for the most part in car-
tilage, and in each case proceeds from several centres which represent distinct bones in lower
vertebrate forms ; the bones of the roof are simpler in their development, and originate in
B
Fig. 74. — OSSIFICATION OP THE OCCIPITAL
BONE. (R. Quain.)
A, in a foetus of 10 weeks (from Meckel) ;
a, tabular part ; 1 & 2, lower and upper pairs
of centres ; b, lower part or basilar and con-
dylar portions : ossific centres are seen in the
condylar portions.
B, occipital bone at birth ; a, tabular
part, in which the four centres have become
united into one, leaving fissures between
them ; b, b, condylar portions ; c, basilar
portion.
membrane ; those of the face are also deposited in membrane, with the exception of the
inferior turbinate bone and a small part of the lower jaw. In the expanded tabular bones the
ossification spreads outwards from the centres, and the marginal portions, in the earlier stages,
present more or less the form of radiated fibres or spicula. At birth the sutural edges, and
especially the angles, are incomplete, the bones being united and the interspaces filled up by
fibrous tissue. The diploe and air-sinuses are at first absent, some of the latter arising early in
life, and others being formed at a comparatively late but variable period.
The occipital bone at birth consists of four separate pieces — a basilar, a tabular, and two
condylar parts, united by intervening cartilage. The lines of junction of the basilar and
condylar parts pass through the condyles near their anterior extremities ; those of the condylar
and tabular parts extend outwards from the posterior margin of the foramen magnum. The
basilar (Tjaswccipital) and condylar parts (cxoccipitalii) arise each from one osseous nucleus,
which appears from the eighth to the tenth week.1 In the tabular part there appear, a few
days earlier, usually four nuclei, an upper and a lower pair ; these speedily unite, but leave
fissures running in from the upper and lateral angles, which remain for some time after
birth. The upper pair of these differ from the other centres of this bone in being deposited in
membrane, and while the lower portion of the tabular part is the proper tupraoecipital element,
the upper represents the interparietal bone of many animals ; it occasionally happens that this
remains distinct in the human skull, the upper part of the occipital squama being separated
from the rest by a suture running transversely from one lateral angle to the other, and by no
means unfrequently a partial division exists, by persistence of the lateral fissures, which may
1 In the descriptions of the mode of ossification of the bones, weeks and months refer always to
periods of foetal life.
74,
THE SKULL AS A WHOLE.
even simulate fracture. The osseous union of the supra- and exoccipitals, beginning in the
second or third, is completed in the fourth year ; that of the basi- and exoccipitals, beginning
in the third or fourth, is completed in the fifth or sixth year. The basioccipital is united to
the basisphenoid by intervening cartilage up to about the twentieth year, after which ossific
union begins and is completed in one or two years.
The parietal bone begins to ossify in membrane in the seventh week. According to Toldt l
it has two nuclei, an upper and a lower, which speedily fuse into a single mass occupying the
position of the future parietal eminence. The radiating ossification extends in such a way as
to leave a notch or cleft at the upper part of the bone a little distance from the posterior
angle, giving rise to the sagittal fontanelle — a space between the two bones, which gradually
becomes closed in during the latter half of foetal life. Traces of the fontanelle are often to be
recognized at the time of birth ; and the parietal foramina are remains of the interval.2 In rare
cases a trans verse parietal Jissure persists. The parietal eminence is very conspicuous in the
young bone, and gives a marked character to the form of the skull for a number of years in
early life.
The frontal bone is ossified from two nuclei which appear, one on each side above the orbital
arch, about the seventh week. At birth the bone consists of two separate lateral portions,
which meet in a vertical median suture during the first year. This frontal suture usually
Fig. 75. — FRONTAL BONE OP A FCETUS SHORTLY
BEFORE BIRTH. (K. Quahl.)
« & b indicate the two portions of the bone,
in each of which the radiation of bony spicula
from the frontal eminence is seen.
Fig. 76. — SKULL OP A CHILD AT BIRTH, FROM
ABOVE. (Leishman.) ^
a, anterior fontanelle ; p, posterior fon-
tanelle ; b, b, parietal eminences ; for the lateral
fontanelles, see fig. 83, p. 82.
becomes obliterated by osseous union taking place from below upwards, during the second
year, though not unfrequently it persists throughout life (p. 39). The frontal sinuses appear
about the seventh year, and continue to increase in size up to old age.
Fontanelles. — These are membranous intervals between the incomplete angles of the
parietal and neighbouring bones, in some of which movements of the soft wall of the cranium
may be observed in connection with variations in the state of the circulation and respiration.
They are six in number, two median, anterior and posterior, and four lateral. The anterior
fontanelle, situated between the antero-superior angles of the parietal bones and the superior
angles of the ununited halves of the frontal bone, is quadrangular in form, and remains open
for some time after birth. The posterior fontanelle. situated between the postero-superior
angles of the parietal bones and the superior angle of the occipital bone, is triangular in shape.
It is filled up before birth, but the edges of the bones, being united by membrane only, are
still freely moveable upon each other. The lateral fontanelles, small and of irregular form,
are situated at the inferior angles of the parietal bones. The fontanelles are gradually filled
up by the extension of ossification into the membrane which occupies them, thus completing
the angles of the bones and forming the sutures. The closure, especially of the posterior and
lateral, is often assisted by the development of Wormian bones in these situations. All traces
of these unossified spaces disappear before the age of four years. The sagittal fontanelle,
existing before birth, has been noticed above.
The temporal bone in the later stages of fcetal life consists of three principal pieces, the
squamo-zygomatic, petro-mastoid or periotic, and tympanic. The sqiiamo-zygomatic is ossified
in membrane from a single nucleus, which appears in the lower part of the squamosal about
the seventh or eighth week, and extends upwards into the squamosal, and outwards into the
zygoma. From the hinder part of the squamosal a considerable postaudltory process grows
downwards below the supramastoid crest, separating the tympanic from the periotic, and
1 "Lotos, Jahrbuch f. Naturw.," 1882.
2 Broca, Bull. Soc. Anthrop. de Paris, 1875 ; Augier, " Rech. sur le developpement des parietaux
a la region sagiitale," Thess, Paris, 1875.
OSSIFICATION OF THE BONES OF THE HEAD.
75
forming the upper and fore part of the mastoid division of the bone. Beneath this is an air-
space continued backwards from the tympanum, and called the antruin mastoidcum, from
which the mastoid cells subsequently grow out. During the third month an osseous nucleus
appears in the lower part of the external membranous wall of the tympanum, and extends
upwards forming the tympanic ring, an imperfect circle, open above, which encloses the
tympanic membrane. Before birth the extremities of this ring become united with the
squamo-zygomatic.
Petro-mastoid or periotie. It is only in the latter half of the fifth month that osseous
deposits begin to be formed in the cartilaginous ear-capsule. They extend rapidly, and the
different ossifications are united by the end of the sixth month. The first to appear is a
nucleus on the promontory (ppisthotic), which spreads round the fenestra rotunda, and forms
the portion of the petrous below the internal auditory meatus and fenestra ovalis. The second
(prootic} arises over the superior semicircular canal, and forms most of the petrous seen in the
interior of the skull, as well as the upper and inner part of the mastoid : it furnishes the upper
boundaries of the internal auditory meatus and fenestra ovalis. A little later, a third nucleus
Fig. 77. — SEPARATE PARTS OP THE TEMPORAL BONE OP A FCETUS
SHORTLY BEFORE BIRTH. (R. Quain.)
a, squamo-zygomatic ; b, tympanic ; c, mastoid part of periotie ;
d, inner wall of tympanum ; e, mastoid antrum.
(epiotie), which is occasionally double, is developed in con-
nection with the posterior semicircular canal, and extends
into the lower part of the mastoid. According to Sutton
the tegmen tympani and covering of the external semi-
circular canal are formed by a separate ossification (pterotic),
appearing about the same time as the prootic. Vrolik also
described a special nucleus for the roof of the cochlea, and
another in connection with the common crus of the superior
and posterior semicircular canals. (Huxley, " Lectures on
Comparative Anatomy," 1864 ; Vrolik, Niederl. Arch. f. Zoologie, i, 291 ; Sutton, Journ.
Anat., xvii, 498.)
At birth the petro-mastoid is separated from the squamosal by a thin plate of intervening
cartilage, bony union taking place during the first year ; the mastoid portion also is flat, the
glenoid fossa shallow, the articular eminence scarcely to be seen, and the tympanic ring and
membrane are even with the outer surface of the bone. The anterior and inferior walls of
the external auditory meatus consist at first of fibrous tissue, in which the tympanic plate is
formed after birth.1 The latter is developed from the outer margin of the slender tympanic
ring, commencing in the form of two small tubercles at the fore and hinder parts respectively ;
these increase in size and meet in the floor of the meatus, enclosing a foramen which is
gradually closed. The foramen is completed as a rule in the second year, and is seldom
obliterated before five years of age. The part of the wall of the meatus which was occupied
by the foramen is commonly thin, and sometimes a small aperture persists through life.
On the posterior surface of the petrous at birth is a considerable depression which extends into
the arch of the superior semicircular canal, and represents the floccular fossa of the lower
animals ; in the adult bone a vestige of this is always present as a small fissure above and
outside the internal auditory meatus, between that and the aqueduct of the vestibule. The
mastoid process is developed about the second year, but the air-cells are not formed till near
puberty.
The styloid process is formed by two small ossifications in cartilage — the tympanohyal
at the base, commencing before birth and speedily joining the bone, and the stylohyal
commencing usually after birth, but remaining very small until the period of puberty ; this
only joins after adult age is reached, and often remains permanently separate. (Flower, Brit.
Ass. Rep., 1870.)
The sphenoid bone is divided in the foetus into a posterior or postsphenoid part, to which
the sella turcica and great wings belong, and an anterior or presphenoid part, including the
body in front of the olivary eminence and the small wings, — a division which is found in
many animals persistent through life. The first osseous nuclei of the postsphenoid division
appear about the eighth week in the great wings (alisphenoids), between the foramen
rotundum and foramen ovale, and spread thence outwards into the wing and downwards into
the external pterygoid plate. About the same time also two granules appear in the post-
sphenoid part of the body (basisphenoid), placed side by side in the sella turcica ; these units
. J See J. Symington, Jouru. Anat., xix, 284, and "The Topographical Anatomy of the Child,"
1887, P. 46. — t — :..-
76
THE SKULL AS A WHOLE.
in the fourth month, and after their union two others appear (xphenotics),1 from which are
formed the lingulas and adjoining- parts of the carotid grooves. The internal pterygoid plates,
corresponding to the pterygoid bones of animals, are ossified from distinct nuclei, which
appear in the fourth month ; they unite with the external pterygoid plates in the fifth month.
The great wings are united to the body in the first year.
In the presphenoid division the first pair of nuclei appears in the ninth week outside the
optic foramina, and extends by their growth into the small wings (orbitospfanoids) : another
pair of granules appears on the inner sides of the foramina, and the presphenoid portion of the
body either results from the union of these, or is an independent growth. The presphenoid
ossifications are united to the body of the postsphenoid in the seventh or eighth month. At
birth the place of union is marked on the under aspect of the body by a wide notch, which
sometimes opens above by a small hole on the olivary eminence. The body of the presphenoid
Fig. 78. — OSSIFICATION OF THE SPHENOID BONE. (E. Quain.)
A, sphenoid bone at an early period, seen from above ; 1, 1', the greater wings ossified ; 2, 2', the
lesser wings, in which the ossification has encircled the optic foramen, and a small suture is distinguish-
able at its posterior and inner side ; 3, nuclei of basisphenoid.
B, copied from Meckel (Archiv. vol. i, tab. vi, fig. 23), and stated to be from a foetus of six
months; 2*, nuclei of presphenoid; 5, separate lateral processes of the body (lingiilse) : the other
indications are the same as in A.
C, back part of the bone shown in A ; 4, internal pterygoid plates still separate.
D, sphenoid at birth. The great wings are still separate. The presphenoid is now joined to the
basisphenoid, and the internal pterygoid plates (not seen in the figure) are united to the external.
is for some years broad and rounded inferiorly ; it begins to be hollowed by the sphenoidal
sinuses about the sixth year, and then becomes gradually narrower and more prominent, being
ultimately reduced to the thin sphenoidal septum.
The spliciwidal spongy "bones begin to ossify in the fifth month. At birth each consists of
a small sagittal lamina, resting against the presphenoid, and continued posteriorly into a
lateral projection, which is hollowed in front for the sphenoidal sinus, the latter having been
formed as a recess of the mucous membrane of the nose at the end of the third month. By
the third year the bone has entirely surrounded the sinus, forming an osseous capsule with
an anterior opening — the sphenoidal foramen. About the fourth year the upper and inner
parts of this capsule begin to be absorbed, and the presphenoid then forms the wall of the
sinus, which in its farther extension excavates the body of the bone. At the outer and fore
part also absorption takes place, and the cavity there comes to be bounded by the ethmoid
and palate bones. The anterior projections of the sagittal plates meet in front of the pre-
sphenoid, and uniting with the vertical plate of the ethmoid form the rostrum. The spongy
bones are anchylosed first to the lateral mass of the ethmoid (about the fourth year), whence
they are often regarded as parts of that bone. They join the sphenoid from the ninth to the
twelfth year. (Toldt, " Die Entstehung und Ausbildung der Conchas und der Sinus sphenoidales
beim Menschen," Lotos, 1882.)
In the ethmoid bone ossification begins in the lateral masses during the fifth month, first
in the orbital plate, and then in the middle turbinate bone. In the first year a nucleus
appears in the vertical plate, and the cribriform plate is formed by ossification extending
from this internally and from the lateral masses externally. The three parts are united in
1 J. B. Sutton, " On the Development and Morphology of the Human Sphenoid Bone," Proc. Zool.
Soc. Lond., 1885.
OSSIFICATION OF THE BONES OF THE HEAD.
77
the fifth or sixth year. The ethmoidal cells appear in the sixth month as depressions of the
mucous membrane, but bony walls are not developed until after birth.
The superior maxillary bone begins to ossify immediately after the clavicle and the
lower jaw. The osseous deposit takes place at several points, but the different parts speedily
fuse, and the precise number of centres is by no means certain. It is probable, however, that
the maxilla proper is developed in at least three pieces, a malar portion external to the infra-
orbital canal, an orbito-facial portion between the foregoing and the nasal fossa, and a
palatine portion including the palate process and the adjoining part of the nasal wall. The
part of the bone which carries the incisor teeth, extending as far back as the incisor foramen,
has an independent origin, corresponding to the premaoclllary bone of the lower animals. In
the young subject always, and often in the adult, there is to be seen a fine incisor fissure on
the under surface of the palate process, passing outwards from the anterior palatine fossa to
the alveolar border, internal to the canine socket ; and on the upper surface a similar line
may be seen, though less frequently, extending up some distance on the nasal surface of the
body ; but no trace of the line of union exists on the facial surface, as is the case in the
lower animals. This is due to the development at the lower and fore part of the maxilla of
an outgrowth, termed the incisor process, which forms the front wall of the incisor sockets ;
Fig. 79. — DIFFERENT VIEWS OF THE SUPERIOR MAXILLARY BONE OF A FCETUS OF FOUR OR FIVE
MONTHS. (R. Quain.)
A, external surface ; a fissure, 1, is seen extending from the orbital surface into the infraorbital
canal.
B, internal surface ; the incisor fissure, 2, extends from the foramen upwards through the hori-
zontal plate and some way into the nasal process.
C, the hone from below, showing the imperfect alveoli and the incisor fissure, 2', 1, which crosses
the palate plate to the septum between the second and third alveoli.
behind this process, between it and the palate process, is a deep groove in which the pre-
maxillary bone is formed, the latter being distinct up to the fifth month of foetal life.
(Callender, Phil. Trans., 1869 ; Th. Kolliker," Os intermaxillare des Menschen," 1882 ; Sutton.
Proc. Zool. Soc., 1884.)
The sockets of the teeth are formed by the downgrowth of an outer and an inner plate on
the sides of the dental groove, and subsequently the partitions appear, those on each side of
the canine tooth first. The antrum appears as a shallow depression on the inner surface of
Fig. 80. — THE VOMER AT THE TIME OF BIRTH. (R. Quain.)
1 & 2, the two plates forming a groove for the reception of the septal
cartilage.
the bone at about the fourth month ; this gradually extends, separating the orbital and
palate portions of the bone, which at birth are still very close together. At its first appear-
ance the antrum has a cartilaginous wall, which afterwards becomes absorbed. The infra-
orbital canal begins aa a groove on the orbital surface, which is gradually closed by the
growing over of the outer margin ; but a fine suture remains indicating the line of meeting.
The palate bone is ossified from a single centre, which appears in the seventh or eighth
week at the angle between its horizontal and vertical parts.
The vomer is ossified from a pair of nuclei which arise in membrane at the lower and
back part of the cartilaginous nasal septum in the eighth week. They soon unite below, but
growing forwards and upwards form the two laminae which embrace the septal cartilage.
These laminae gradually undergo increased union from behind forwards till the age of
puberty, thus forming a median plate, with only a groove remaining on its anterior and
superior margins.
The nasal and lachrymal bones are each ossified from a single centre appearing about the
eighth, week. At the time of birth there is a layer of cartilage beneath the nasal bone, which
78 THE SKULL AS A WHOLE.
is continuous above with the ethmoidal cartilage, and below with the lateral cartilage of the
nose : this subsequently disappears.
The malar bone also commences to ossify about the eighth week. According to Rambaud
and Renault it is developed from three points which have united by the fourth month of
fostal life ; and to the persistent separation of one of these, the divided condition of the bone
referred to on p. 56 may be due.
The inferior turbinate bone is ossified in cartilage from a single centre, which only
appears in the fifth month.
The inferior maxillary bone is developed principally in the fibrous tissue investing
Meckel's cartilage (see development of the head in VoL I.), but to a less extent the cartilage
itself participates in the ossification. At birth it consists of the lateral parts united at the
symphysis by fibrous tissue : the osseous union takes place in the first or second year. The
process of ossification commences very early, being preceded only by the clavicle, and proceeds
rapidly : it takes place from several centres, which are united by the fourth month. The
largest part of each half is formed from a deposit (dentary) in the membrane on the outer
side of Meckel's cartilage ; and to this there is added a second smaller plate (splenial) which
forms the inner wall of the tooth-sockets, terminating behind in the lingula. A small part of
the body by the side of the symphysis results from the direct ossification of the anterior end
of Meckel's cartilage ; and, posteriorly, the condyle and a portion of the ramus, including the
Fig. 81. — THE INFERIOR MAXILI/A OF A CHILD AT BIRTH.
(R. Quain.)
a & b indicate the two portions separate at the
sympbysis.
angle, are developed from another ossification in
cartilage. The last, however, is not connected with
Meckel1 s cartilage, which can be seen in a foetus of
the fifth or sixth month to be prolonged up to the
fissure of Glaser. where it becomes continuous with the slender process of the malleus, sur-
rounded by fibrous tissue which eventually forms the so-called internal lateral ligament of
the jaw. (Callender, PhiL Trans., 1869 ; Kolliker. " Entwickelungsgeschichte " ; Toldt,
" Wachsthum des Uiiterkiefers," Prag, 1883 ; Sutton, Trans. Odont. Soc., 1883.)
At birth, the body of the jaw is shallow, the basal part is but little developed, and the
mental foramen is nearer the lower than the upper margin ; the ramus is very short and
oblique, the angle which it forms with the body being about 140° ; the neck of the condyle
also is short and inclined backwards ; and the coronoid process projects above the condyle.
During the succeeding years the body becomes deeper, thicker, and longer, the ramus and the
neck of the condyle lengthen, and the angle at which the ramus joins the body becomes less
obtuse, till in the adult it is nearly a right angle. In old age, consequent upon the loss of the
teeth and the absorption of the alveolar margin, the body becomes shallower, the mental
foramen opens at the upper border of the bone, and the angle is again increased.
The hyoid bone has five points of ossification — one for the body, and one for each of its
great and small cornua. The ossification begins in the great cornua and body in the last
month of foetal life, in the small cornua in the first year after birth. The great cornua and
body unite in middle life, the small cornua only exceptionally in advanced age. The stylo-
hyoid ligaments are occasionally ossified in some part of their extent.
GENERAL MORPHOLOGY OP THE BONES OF THE HEAD
The circumstances which contribute most to modify the form of the human skull and the
condition of its component bones, as compared with that of other animals, are — 1st, the
proportionally large size of the brain and the corresponding expansion of the cranial bones
which enclose it ; 2nd, the smaller development of the face as a whole, and especially of the
jaws, which brings the facial bones almost entirely under the fore part of the brain-case,
instead of in front of it, as occurs in all animals, with the partial exception of the anthropoid
apes ; and 3rd, the adaptation of the human skeleton to the erect posture, which, as regards
the head, is attended with the sudden bend of the basicranial axis at a considerable angle upon
the line of the erect vertebral column ; and along with this the great development of the
cranium in a backward direction, whereby the occipito-vertebral articulation conies to be
placed approximately in the centre of the antero-posterior length of the skull, so that the
head is nearly balanced on the upper extremity of the spine. The downward openings of the
nostrils, the forward aspect of the orbits and eyes, the nearly vertical forehead and more or
less oval-shaped face, are accompaniments of these human peculiarities in the form of the
head, which, together with those already mentioned, strongly contrast with the smaller
GENERAL MORPHOLOGY OF THE BONES OP THE HEAD.
79
cranium and its strong crests of bone, the larger projecting face and jaws, and the other
characteristic features of the skull in most animals.
As regards the condition of the individual bones, it is farther to be remarked that there is
generally in the human skull a more complete consolidation or bony union of the osseous
elements than in animals, so that the whole number of bones forming the cranium and face
is least in man. Thus, to mention only some of the most marked examples of this difference
among mammals ; the frontal bone and the lower jaw frequently divided into two lateral
portions ; the premaxillary very generally a separate bone from the maxillary ; the presphenoid
in many separate from the postphenoid j the interparietal from the occipital ; and the
squamosal and styloid ossifications from the periotic. It is also worthy of observation that
the conditions now referred to as permanent in animals exist as transitory stages of develop-
ment in man.
Homologles. — It is not possible here to enter at any length into the consideration of the
homologies of the bones of the human skull, but the diagrammatic representation of the bones
of the foetal head in fig. 82, and the following table will serve to indicate to some extent the
Fig. 82. — DIAGRAMMATIC VIEW
OP THE BONES IN THE RIGHT
HALF OF A FCETAL SKULL,
FROM THE INSIDE. (Allen
Thomson. )
In this figure the bones have
been slightly separated and dis-
placed so as to bring the whole
into one view : f, frontal ; pa,
parietal ; so, supraoccipital ;
n, nasal ; I, lachrymal ; ma,
malar ; os, orbitosphenoid ;
ris, alisphenoid ; sq, squa-
mosal ; zy, zygomatic ; per,
periotic ; eo, exoccipital ; et,
ethmoturbinal ; tnx, maxilla ;
mt, maxilloturbinal ; pm, pre-
maxillary ; me, mesethmoid ;
v, vomer ; pi, palatal ; pt,
pterygoid ; j)s, presphenoid ;
bs, basisphenoid ; bo, basioc-
cipital ; c, bodies of 2nd, 3rd,
and 4th cervical vertebrae ; c',
odontoid process ; x , anterior
arch of atlas ; s, spinous pro-
cesses of 1st, 2nd, 3rd, and
4th cervical vertebrae ; cm,
neural canal ; ch, a line indi-
cating the position of the
notochord passing through the
vertebral bodies into the base
of the cranium ; ty, tympanic,
along with ml, i, and st, dis-
placed from its connection with
per ; ml, malleus ; c. ink, cartilage of Meckel ; mn, mandible ; ?', incus ; st,
ch, ceratohyal ; th, tHyrohyal ; bh, basihyal ; t, thyroid cartilage.
stapes ; sth, stylohyal ;
morphological relations of the several bones to each other, and to those of other vertebrate
animals, and to explain the origin of the constituent elements of the skull. Additional
information as to the latter point will be found in the account of the development of the head
in the chapter on Embryology in Vol. I. ; and for a fuller explanation of the homologies of the
bones the reader is referred to works on Comparative Anatomy.
LIST OF THE TYPICAL COMPONENT PARTS OF THE BONES OF THE HEAD
CLASSIFIED ACCORDING TO THEIR ORIGIN l :—
1. BONES DEVELOPED IN THE PRIMITIVE CARTILAGINOUS CRANIUM.
Basioccipital ; Basilar process of the occipital bone.
Exoccipitals ; Condylar portions of the occipital bone.
Supraoccipital ; Lower division of the tabular part of the occipital bone.
1 The names first given, and printed in black type, are those received in comparative anatomy ;
those usually employed in human anatomy follow, and are printed in common type.
80 THE SKULL AS A WHOLE.
Periotics ; Greater parts of the petrous and mastoid portions of the temporal bones.
Basisphenoid ; Posterior part of the body of the sphenoid bone, including the sella
turcica.
Alisphenoids ; Great wings of the sphenoid with the external pterygoid plates.
Fresphenoid ; Anterior part of the body of the sphenoid bone.
Orbitosphenoids ; Small wings of the sphenoid bone.
2. MEMBRANE -BONES COMPLETING THE CRANIAL WALL.
Interparietal ; Tipper division of the tabular part of the occipital bone.
Parietals ; The parietal bones.
Frontals ; United in the single frontal.
Squamosals ; The squamous parts of the temporal bones with the zygoma.
3. BONES DEVELOPED IN THE CARTILAGINOUS NASAL CAPSULE.
Mesethmoid ; Vertical plate of the ethmoid bone, together with the cartilaginous part of
the nasal septum.
Ethmoturbinals ; The lateral masses of the ethmoid, including the upper and lower
turbinate bones.
Maxilloturbinals ; The inferior turbinate bones.
Sphenoidal turbinals ; The sphenoidal spongy bones.
4. MEMBRANE-BONES DEVELOPED AROUND THE NASAL CAPSULE AND FORMING
THE GREATER PART OP THE UPPER FACE.
Lachrymals ; The lachrymal bones.
Nasals ; The nasal bones.
Maxillae ; The superior maxillary bones, excepting the incisor part.
Premaxillse or intermaxillae ; The incisor parts of the superior maxillary bones.
Jugrals or malars ; The malar bones.
Palatals ; The palate bones.
Pterygroids ; The internal pterygoid plates.
Vomer ; The vomer.
6. BONES DEVELOPED IN THE CARTILAGINOUS VISCERAL ARCHES OF
THE HEAD.
Malleus, Incus, and Stapes ; The auditory ossicles or malleus, incus, and stapes.
Tympanohyals and Stylohyals ; The styloid processes of the temporal bones.
Epihyals ; The stylo-hyoid ligaments (occasionally ossified in man).
Ceratohyals ; The small cornua of the hyoid bone.
Thyrohyals ; The great cornua of the hyoid bone.
Basihyal ; The body of the hyoid bone.
6. MEMBRANE-BONES DEVELOPED IN CONNECTION WITH THE VISCERAL ARCHES.
Mandible ; The inferior maxillary bone (a small part is developed in the cartilaginous
arch).
Tympanics; The tympanic plate, forming the auditory and vaginal processes (developed in
the periphery of the membrane closing the first visceral cleft).
The relations of the nerves at their passage out of the cranium to the osseous elements
are remarkably constant, and afford considerable assistance in determining their homologies.
Thus, the nerves of the principal sense-organs pass into their special capsules as follows, viz.,
the olfactory between the mesethmoid and ethmoturbinal divisions of the ethmoid bone ; the
optic between the orbitosphenoid and the presphenoid ; and" the auditory between the prootic
and opisthotic divisions of the periotic mass. Farther, the motor nerves of the orbital muscles
(third, fourth and sixth), together with the ophthalmic division of the trifacial (fifth), pass
through the sphenoidal fissure between the orbitosphenoid and alisphenoid, while the second
division of the trifacial has a special foramen in the alisphenoid which has been separated off
from the sphenoidal fissure by the growth of bone around the nerve. Similarly, the foramen
ovale for the third division of the trifacial has been cut off from the foramen lacerum between
the alisphenoid and periotic. The facial (seventh) nerve leaves the cranial cavity with the
auditory between the divisions of the periotic, and then traverses a canal (aqueduct of
Fallopius), the lower part of which is included between the outer surface of the periotic and
GENERAL MORPHOLOGY OF THE BONES OF THE HEAD. 81
the tympanic plate, while its Vidian branch occupies a canal surrounded by the basisphenoid,
alisphenoid and pterygoid elements of the sphenoid bone. The glosso-pharygeal (ninth),
pneumo-gastric (tenth) and spinal accessory (eleventh) nerves pass between the periotic and
exoccipital ; and the hypoglossal (twelfth) between the exoccipital and basioccipital. The
internal carotid arteiy, it may be added, enters the skull by the foramen lacerum, a space
between the basisphenoid, alisphenoid, and periotic, having previously traversed the carotid
canal formed by the downgrowth of the opisthotic ; and the jugular vein issues between
the periotic and exoccipital.
A general review of the construction of the skull shows that it may be regarded as consist-
ing mainly of three sets of parts, viz. — 1st, basal or central parts, comprising the basi-
occipital, basisphenoid, presphenoid, and mesethmoid, which form a series prolonged forwards
in the line of the vertebral axis, and constitute a crania-facial axis ; 2nd, superior arches,
three in number, enclosing the brain, and consisting of more or less expanded bones, viz., the
exoccipitals and supraoccipital together with the interparietal, the alisphenoids, squamosals and
parietals, the orbitosphenoids and f rentals ; and 3rd, inferior arches, surrounding the visceral
cavity as represented by the nose, mouth, and pharynx ; these include the pterygoids, palatals
and maxillae in a first arch, the mandible and the malleus of the internal ear in a second, the
cerato-, epi-, stylo- and tympanohyals in a third, while the thyrohyals are the rudiments of a
fourth, and the basihyal is interposed between the last two. To these succeed in the lowest
vertebrates the series of branchial arches, one, or perhaps two, of which may be in part
represented by the thyroid cartilage of the larynx. Together with the foregoing there are
associated other elements, viz. — 1st, the periotic enclosing the organ of hearing, and the
ethmo- and maxilloturbinals covering the organ of smell, which have been classed sepa-
rately as special sense-capsules ; and 2nd, the small bones of the face, malar, nasal,
and lachrymal, supplementary to the maxillary arch, and the vomer, extending the
cranio-f acial axis.
There is thus a certain resemblance in the arrangement of the chief parts of the skull to
that of the trunk-skeleton, and this resemblance has led to the conception of what is called
the vertebrate theory of the skull, according to which the skull consists essentially of a
series of vertebras, the dorsal or neural arches of which have undergone great expansion, so
as to predominate over the less developed ventral or visceral arches. Certain circumstances
in the growth of the skull, especially the formation of a part at least of the cranio-facial axis
around a prolongation of the notochord, appear at first sight to give support to this view ;
but the more complete knowledge of the mode of development of the skull which has been
obtained of late years tends to show that there is no such homodynamous correspondence
between the several bones of the skull and the vertebral segments of the trunk-skeleton. In
explanation of this statement the following points of difference between the two may be
specially referred to, viz. — 1, a large part of the cranio-facial axis is prechordal, being formed
beyond the cephalic extremity of the notochord, and therefore does not correspond to vertebral
bodies ; 2, the cartilage in which the bones of the cranio-facial axis and its lateral expansions
are developed is not at any period segmented, as is the cartilage preceding the vertebras ; 3,
the segmentation which is to be recognized in the bones of the skull does not agree with the
segmentation which has been observed in the head of lower vertebrates at an early period of
embryonic life ; 4, the bones forming the dorsal and ventral arches of the head are in large
part developed in membrane, and are probably dermal in origin, whereas the arches of the
vertebras are entirely of cartilaginous origin ; and 5, the cartilaginous visceral arches of the
head probably do not correspond to the costal arches of the vertebras, being formed in close
connection with the wall of the alimentary canal, while the ribs are developed in the body-
wall or somatopleure.
On the whole, it would appear, therefore, that the skeleton of the head and the skeleton
of the trunk agree in being formed in continuous tissue lying between and surrounding the
cerebro-spinal axis and the alimentary canal, and that the correspondence observed in their
general construction is due to this community of origin and relations. But the several bones
are developed independently, and in a different manner in the head and trunk, giving rise in
the one case to the skull, in the other to the vertebral column ; and although the head as a
whole is undoubtedly derived in large part from a portion of the body that was primitively
segmented, there is no evidence to show that the appearance of the skull has been preceded
by a stage in which osseous or even cartilaginous vertebras are developed in connection with
these segments.1 (Huxley, "Lectures on Comp. Anat.," 1864; Gegenbaur, "Elements of
Comparative Anatomy," and Morph. Jahrb., xiii ; O. Hertwig, " Lehrb. der Entwicklungs-
geschichte.")
1 The foetal conditions referred to above are fully explained in the section on Embryology in
Vol. I.
voi. ir. a
THE SKULL AS A WHOLE.
THE VARIOUS FORMS OF THE SKULL.
I. Differences according1 to age. — In the earlier stages of its development the posterior
part of the cranium bears a very large proportion to the anterior part ; so much so. that in
the second month of foetal life the line of the tentorium cerebelli is vertical to the basis
cranii, and divides the cranial cavity almost equally into two parts. The parietal region then
increases rapidly in volume, along- with the greater development of the cerebral hemispheres ;
the frontal region next augments ; and again, in the latter part of fcetal life, the occipital
region increases as the cerebrum extends backwards (Cleland). At the time of birth the
parietal region has reached its largest development in proportion to the occipital and frontal
regions. The greatest frontal breadth is then smaller in proportion to that between the
parietal eminences than afterwards. The base of the cranium is relatively small, and the
great wing of the sphenoid and the temporal squima do not extend so far upwards as subse-
quently is the case. The petrous, which is, however, comparatively large, is inclined more
forwards than in the adult. Other peculiarities, such as the existence of the fontanelles, the
prominence of the frontal and parietal eminences, and the absence of the mastoid processes,
have been referred to in describing the development of the several bones. The face at birth
scarcely reaches an eighth of the bulk of cranium, while in the adult it is at least a half
(Froriep). The skull grows rapidly during about the first seven years of life. By that time
t
Fig. 83. — LATERAL VIEW OP THE CHILD'S SKULL AT,
BIRTH. (Leishman.) £
This figure shows the elongated form of the skull in
the infant, and the small proportion which the facial
hears to the cranial part, and also the lateral fontanelles
at the lower angles of the parietal bones. The lines indi-
cate the various diameters.
certain parts, including the circumference of the
occipital foramen, the body of the sphenoid, the
cribriform plate, and the petrous division of the
temporal, have attained their definitive size. The
other regions also increase but little until the
approach of puberty, when a second period of
active growth begins, affecting especially the face and the frontal portion of the cranium,
with which is associated the expansion of the frontal and other air-sinuses (Merkel). The
face becomes elongated in the progress of growth, partly by increased height of the nasal
fossas and adjacent air-sinuses, partly by the growth of the teeth and the enlargement of the
alveolar arches of the jaws. In old age the skull commonly becomes lighter and thinner, and
often a little smaller ; but in some cases it increases in thickness and weight owing to deposit
of bone on the interior of the brain-case without a corresponding degree of absorption
externally (Humphry). The proportion of the face to the cranium is also diminished by th.3
loss of the teeth and absorption of the alveolar portions of the jaws. In consequence of this
the upper jaw retreats, while in the lower jaw the same cause gives, especially when the mouth
is closed, a greater seeming prominence to the chin. (Froriep. " Characteristik des Kopfes
nach dem Entwickelungsgesetz desselben," 1845 ; Huschke, " Schadel, Hirn und Seele," 1854 ;
Virchow, " Entwickelung des Schadelgrundes," 1857 ; Humphry, "A Treatise on the Human
Skeleton." 1858, and "Old Age," 1889; Welcker, " Wachsthum und Bau des menschlichen
Schadels," 1862 ; Cleland, " On the Variations of the Human Skull," Phil. Trans., 1869 ; Merkel,
i(Beitrag zur Kenntniss der postembryonalen Entwicklung des menschlichen Schadels," 1882.)
II. Sexual differences. — The female skull is, in general, smaller, lighter, and smoother
than that of the male ; the muscular impressions are not so strongly marked, the mastoid
processes and the superciliary ridges are less prominent, and the frontal sinuses less developed.
The cranial capacity is less, on the average, by one-tenth, than that of the male in the same
race, and the frontal and occipital regions are less capacious in proportion to the parietal
(Huschke). The face is smaller in proportion to the cranium, the zygomatic arches slender,
and the jaws narrower and less prominent. The female skull resembles the young skull more
than that of the adult male ; but it must be admitted that it is often impossible to determine
the sex by the appearance or form of a skull.
III. Race differences, their measurement and classification. Craniometry. — The most
important measurements and characters in comparing skulls of different races are the cranial
capacity, the circumference of the cranium, the relative length, breadth and height of the
cranium, the degree of projection of the jaws, and the form of the nasal skeleton and the
orbital opening.
THE VARIOUS FORMS OF THE SKULL. 83
The capacity of the cranium affords the most convenient indication of the development
of the brain.1 It is ascertained by filling the cranial cavity with shot, and then measuring
the contained quantity in a properly graduated vessel, special precautions being taken to
ensure as nearly as possible an equal pressure in both operations. The capacity of the normal
human cranium varies from 1,000 to 1.800 cubic centimetres (about 60 to 110 cubic inches),
with an average in all races of 1.400 cubic centimetres (85 cubic inches). Skulls with a
capacity of from 1,350 to 1,450 cubic centimetres are placed in a middle group and termed
mewcephalic, those exceeding 1.450 cubic centimetres in capacity are mefjacejrftalic, and those
below 1.350 cubic centimetres are microcepTialio (Flower). The following examples are of
males only : —
Eskimo . . .
European
Chinese and Mongols.
African Negroes
Native Australians .
Andaman Islanders .
Cub. centira.
1500
1480
1430
1350
1300
1280
Cub. inches.
91-5
90-3
87-3
82-4
79-3
78-1
Before proceeding to the consideration of the linear measurements it is necessary to refer
to certain definite points on the surface of the skull from which such measurements are
Fig. 84. — SIDE VIEW OF SKULL
OP A MALE AUSTRALIAN.
(After Flower.)
A, alveolar point ; S, sub-
nasal point ; N, nasion ; Gl,
glabella ; Op, ophryon ; Bg,
bregrua ; Ob, obelion ; L,
lambda ; 0, occipital point ;
I, inion ; B, basion ; Pt,
pterion ; St; stephanion ; As,
asterion ; Gl O, length of
cranium ; B N, basinasal
length ; B A, basiaJveolar
length ; N S, nasal height.
taken, or which have a
particular importance as
presenting varieties of more
or less frequent occurrence,
and to which special names
have been given not of ordi-
nary use in descriptive
anatomy. These are : —
Alveolar point (fig. 84, A). — The centre cf the anterior margin of the upper
alveolar arch.
Subnasal or spinal point (S). — The middle of the inferior border of the anterior nasal
aperture at the base of the nasal spine.
Nasion or nasal point (N). — The middle of the naso-f rental suture.
Ophryon or snpraorl)ital point (Op). — The middle of the supraorbital line, which, drawn
across the narrowest part of the forehead, separates the face from the cranium.
Bregma (Bg). — The point of junction of the coronal and sagittal sutures.
Obelion (Ob). — The region situated between the two parietal foramina where the sagittal
suture is more simple than elsewhere, and where its closure generally commences.
Lambda (L) — The point of junction of the sagittal and lambdoid sutures.
Occipital point (0). — The point of the occiput in the median plane most removed from the
glabolla.
1 According to Manouvrier (Mem. de la Soc. d'Anthrop. de Paris, 2 ser., t. iii, 1885), the weight
of the brain in grammes may be approximately ascertained by multiplying the cranial capacity in cubic
centimetres by '87. But it is to be remarked that Manouvrier's capacities were obtained by Brora's
method, which undoubtedly gives too high results. Welcker proposes (Arch. f. Anthrop., xvi, 51) a
sliding scale, ranging from 91 gr. of brain-weight to 100 ccm. of cranial capacity for skulls with a
capacity of 1200 ccm, to 95 gr. to 100 ccm. for skulls of 1600 ccm. capacity. Thus 1480 x '938 =
1S88 gr., which agrees closely with the average European brain- weight as ascertained by direct
observation.
a 2
84 THE SKULL AS A WHOLE.
Inion (I). — The external occipital protuberance.
Opistliion. — The middle of the posterior margin of the foramen magnum.
Basion (B).— The middle of the anterior margin of the foramen magnum.
Pterion (Pt). — The region, near the anterior part of the temporal fossa, where the great
wing of the sphenoid, the squamous, the parietal and the frontal bones approach each other,
the exact disposition, however, varying in different individuals. In the most common
condition the parietal and great wing of the sphenoid meet and form a short horizontal,
suture ; but it sometimes happens that these two bones are separated by the junction of the
frontal and squamous, giving rise to a vertical fronto-temporal suture, generally continuing the
line of the coronal suture. The latter form is especially frequent in some of the lower races of
mankind, and is the rule in the gorilla and chimpanzee. There is often a small "Wormian bone
in this situation, the cpipteric bone of Flower, and many cases of the occurrence of a fronto-
temporal suture are attributable to the union of this piece of bone with the squamous or frontal.
Stephanion (St). — The point where the coronal suture crosses the temporal line.
Asterion (As). — The point where the lambdoid, parieto-mastoid and occipito-mastoid
sutures meet. When a separate interparietal bone is present the suture dividing it from the
supraoccipital runs transversely from asterion to asterion, which will in that case be the
meeting point of four sutures.
Auricular point. — The centre of the orifice of the external auditory meatus.
The circumference of the cranium (horizontal) is taken in a plane passing anteriorly
through the ophryon,1 and posteriorly through the occipital point (fig. 84, Op 0). This may
exceed to a slight degree 550 millimetres (2T7 inches) or it may be as low as 450 mm.
(17*7 inches). The average in the adult European male is 525 mm., in the female 500 mm.
For comparison of the relative development of the anterior and posterior portions of the
cranium, the preauricular part of the circumference is divided from the postauricular part by
a line on each side passing from the auricular point to the bregma (auriculo-bregmatic line).
The length of the cranium (maximum) is measured from the most prominent point of the
glabella to the occipital point (fig. 84, Gl 0), and this is made the standard = 100. The
breadth (maximum) is the greatest transverse diameter of the cranium above the supramastoid
ridges, measured perpendicularly to the median plane. The proportion of the latter to the
length ( ) is the index of breadth or the cephalic index. Skulls with a
V length /
breadth-index above 80 are brachrj cephalic, from 75 to 80 mesaticephalie, and below 75 dolicho-
cephalic.
The height of the cranium is measured from the basion to the bregma, and the proportion
of this to the length, calculated in the same way, is the index of height. It is subject to less
variation than the breadth-index ; in some cases, especially in dolichocephalic skulls, it
exceeds, but more frequently it falls below that index.
Breadth- Height-
index, index.*
Mongolians of Siberia and Central Asia . 88 73
Andaman Islanders ..... 82 77
Chinese .-.';-.*.'. .. 79 75
English . . ...;.. 76 71
Native Australian . . . . . 71 71
Fiji Islanders . . . . . . 66 74
For a more accurate determination of the form of the cranium other measurements are
taken, such as the transverse circumference, passing through the auricular point on each side
and the bregma above ; the longitudinal arc from the nasion to the opisthion, with its
subdivisions into frontal, parietal and occipital arcs ; transverse arcs from the posterior root
of the zygoma immediately above the auricular point of the one side to the other, across the
most prominent parts of the frontal, parietal, and occipital bones respectively. The antero-
posterior curve of the roof may also be indicated by a series of radii from the basion to the
centre of the frontal bone, the bregma, the vertex and the lambda. Other features again are
not capable of being expressed in terms of direct measurement, and must be described in each
case ; for example, the form of the transverse arch of the cranium, which in the best shaped
skulls is full and rounded, while in some races, notably in the Australian, the line of the
sagittal suture is elevated, and the surface on each side flattened or even somewhat depressed,
making the calvaria roof -shaped ; and this condition, combined with great prominence of the
parietal eminences or of the temporal lines, gives the skull, when viewed from behind, a
markedly pentagonal figure. The degree of complication and fusion of the sutures, the
amount of projection of the glabella and of the inion, and other variable points, maybe stated
according to tables furnished by Broca in the work referred to below.
1 Some anthropologists measure the circumference over the glabella (Turner, Schmidt).
8 In these examples, which are taken from the Catalogue of the Museum of the Eoyal College of
Surgeons, the indices are calculated from the ophryo-occipital length.
THE VARIOUS FORMS OF THE SKULL. fc5
The situation and direction of the foramen magnum differ greatly, as was pointed out by
Daubenton, in man and the lower animals, in connection with the altered position of the axis
of the head in relation to that of the vertebral column. In man the foramen is placed in or
near the centre of the base of the skull, and its plane looks mainly down wards ; in quadrupeds
it is placed on the posterior surface of the skull and looks backwards ; while in the anthropoid
apes it is intermediate in position and direction. But even in human skulls similar differences
occur, though much less in degree. In the European the plane of the foramen is inclined
upwards anteriorly, in the Australian and Negro it is horizontal or even inclined slightly
upwards posteriorly. The degree of inclination requires for its determination a special
" occipital goniometer " designed by Broca.
In the skeleton of the face the most striking differences are met with in the size of the
jaws and the extent to which they project forwards. The human skull, in comparisDn with
that of the lower animals, is especially distinguished by the great expansion of its cranial
portion and the relatively small development of the face, the latter being extended vertically
instead of horizontally, and thus brought downwards under the fore part of the cranium. A
marked prominence of the jaws constitutes, therefore, an approach to the animal type of
skull, and is to be regarded as a character of inferiority, particularly when it is accompanied,
as is often the case, by a low and receding forehead. The degree of projection of the jaws
beyond the cranium is most conveniently expressed by the gnathic or alveolar index of Flower,
which is obtained by comparing the basialveolar length (fig. 84, BA) with the basinasal length
(BN) = 100; skulls with a gnathic index below 98 are orthogiiathous, from 98 to 103
mesognathous, and above 103 prognathous.
Gnathic Index
English 96
Chinese. . . . . 99
Eskimo 101
Fiji Islanders . . .103
Native Australian . . . 104
In the form of the nasal skeleton and the anterior nasal aperture variations are to be
recognised corresponding to the external conformation of the nose. Of these, the height and
width are capable of exact measurement, and the relation between the two, expressed by the
nasal index, becomes a character of considerable importance. The height is measured from
the nasion to the subnasal point (fig. 84, NS), the width is the greatest transverse diameter
of the anterior nasal aperture, and the calculated proportion of this to the height = 100, is
the index. With a nasal index below 48 a skull is Icptorhine, from 48 to 63 mesorhine, above
63 platyrhine.
Masai Index.
Eskimo ..... 44
English 46
Chinese ..... 60
Native Australian . . . 67
The form of the orbit also varies, but is a less significant character than that of the nose.
The orbital index is the ratio of the vertical height of the base of the orbit to the transverse
width = 100 ; if above 89 it is megaseme, between 89 and 84 mesoseme, and below 84
microscme.
Orbital Index.
Andaman Islanders ... 91
Chinese 90
English 88
Native Australian . . . 81
Guanches of Teneriffe . . 80
For an account of the variations in the form of the palate and of the mandible, as well as
of the means of estimating the relative projection of the malar and nasal bones, and several
other measurements of the face skeleton, reference must be made to the special treatises.
(For more detailed information on the foregoing subject consult Broca, " Instructions
craniologiques et craniometriques," 1875 ; Flower, " Cat. of Museum of Roy. Coll. Surg. of Eng.,"
part i., 1879 ; de Quatrefages and Hamy, " Crania Ethnica," 1873-81 ; Topinard, " Elements
d'anthropologie generale ; " Turner, " Challenger " Reports, Zoology, x ; and Schmidt,
" Anthropologische Methoden," 1888. References to earlier writings of importance are given
in the last edition of this work.)
IV. Irregularities of form — The most frequent irregularity in the form of the skull is
want of symmetry. This sometimes occurs in a marked degree, and there is probably no skull
perfectly symmetrical. The condition which has been observed to co-exist most frequently
with irregular forms of skull is premature synostosis or obliteration of certain of the sutures.
83' THE BONES OF THE UPPER LIMB.
The cranial bones increase in size principally at their margins ; and when a suture is
prematurely obliterated the growth of the skull in the direction at right angles to the line of
suture may be supposed to be checked, and increased growth in other directions may take
place to supply the defect. Thus, the condition known as scaplioeeplwly is found associated
with absence of the sagittal suture, where, the transverse growth being prevented, a great
increase takes place in the vertical, and especially the longitudinal directions, giving the vault
of the skull a boat-like form. Similarly, acroeeplialy is related to obliteration of the coronal
suture, the compensatory growth taking place mainly upwards. Oblique deformity, or
plagiocephaly, also is met with in connection with premature fusion of one half of the coronal
or lambdoid suture ; but indrpenc1 entry of this a precisely similar deformity may be induced by
rickets, wry -neck, cr external pressure. (See Virchow, " Gesammelte Abhandlungen," 1856;
Lucae, " Zur Architectur des Menschenschadels," 1857; W. Turner in Xat. Hist. Rev., 1864 ;
J. Barnard Davis, "On Synostotic Crania," 1865; Topinard, op. cit.) Another series of
irregular forms of skull is that produced by pressure artificially applied in early life, and is
best exemplified from among those American tribes who compress the heads of their children
by means of an apparatus of boards and bandages : it is also illustrated in a slighter degree by
individual instances in which undue pressure has been employed unintentionally. (Gosse,
" Essai sur les Deformations artificielles du Crane," 1855 ; V. Lenhossek, " Die kiinstlichen
Schadelverbildungen," &c., 1881.) Posthumous distortions likewise occur in long-buried
skulls, subjected to the combined influence of pressure and moisture. (Wilson, " Prehistoric
Annals of Scotland.")
IV.— THE BOWES OF THE UPPER LIMB.
The upper limb consists of the shoulder, the arm, Irachium, the forearm, anti*
brachium, and the hand, manus. The bones of the shoulder are the clavicle and
scapula, which together form the pectoral arch or shoulder-girdle ; in the arm is the
humerus ; in the forearm are the radius and ulna ; and in the hand three groups of
bones, viz., the carpus, metacarpus, and phalanges.
THE CLAVICLE.
The clavicle or collar-bone extends out wards and backwards, from the summit of
the sternum to the acromion process of the scapula, and connects the upper limb
with the trunk. It is curved like an italic/: the internal curve has its convexity
•- On) CONOID TUB.-
Fig. 85. — RIGHT CLAVICLE, FROM ABOVE. (Drawn by T. W. P. Lawrence.) §
directed forwards, and extends over two-thirds of the length of the bone ; the
outer curve is concave forwards, corresponding to the hollow between the chest and
shoulder.
The clavicle is broad towards its scapular end, being compressed from above
downwards, but in the extent of its inner curve it is more or less prismatic or
cylindrical. In its description, four surfaces may be distinguished, together with the
two extremities.
The superior surface is broadest in its outer part ; it is principally subcutaneous and
smooth, but near the inner extremity presents a slight roughness, marking the clavi-
THE CLAVICLE. 87
cular attachment of the sterno-cleido-mastoid muscle. The anterior surface opposite
the outer curve is reduced to a mere rough border, from which the deltoid muscle
takes origin ; but in the inner half of its extent it is broadened out into an uneven
space, more or less distinctly separated from the inferior surface, and giving attach-
ment to the pectoralis major muscle. The poster tor surface is broadest at the inner
extremity, and smooth in the whole extent of the internal curvature ; but towards
its outer extremity it forms a thick border which gives attachment to the trapezius
muscle. About the middle of this surface is the aperture of a small canal for the
medullary artery, directed outwards. On the inferior surface, at the sternal end is a
rough impression for the attachment of the rhomboid ligament, by which the clavicle
is bound down to the first rib ; more externally is a groove, extending somewhat
Fig. 86. — RIGHT CLAVICLE, FROM BELOW. (Drawn by T. W. P. Lawrence.) f
beyond the middle third of the bone, in which the subclavius muscle is inserted ;
behind this, projecting on the posterior border at the junction of the middle and
outer thirds, is a well-marked eminence, the conoid tubercle, to which the conoid
division of the coraco-clavicular ligament is attached, and from which the rough,
generally raised, trapezoid line, for the trapezoid part of the same ligament, is directed
outwards and forwards towards the end of the bone.
The sternal end is the thickest part of the clavicle. It presents a somewhat
triangular concavo-convex surface, with its most prominent angle directed down-
wards and backwards. The scapular end is broad and flat, and articulates by a small
oval surface with the acromion.
The clavicle is subcutaneous to a greater or less extent in. its whole length ; the
most prominent part is about the centre, corresponding to the intermuscular intervals,
above between the sterno-mastoid and trapezius, and below between the pectoralis
major and deltoid (supra- and in fmclavicular fossae). The outer extremity is a little
higher than the upper surface of the acromion against which it fits, and forms a
prominence on the upper part of the shoulder.
The interior of the clavicle contains coarse cancellated tissue in its whole extent, the
principal lamellae being directed longitudinally. The shell of compact tissue is for the most
part very thick and dense, but it thins out gradually at the two ends of the bone.
Varieties. — At the inner part of the deltoid impression there is sometimes a flattened
projection known as the deltoid tubercle: A small foramen for one of the supraclavicular
nerves is occasionally found at the fore part of the upper surface of the bone about the
middle.
THE SCAPULA.
The scapula is placed upon the upper and back part of the thorax, and forms
the posterior part of the shoulder-girdle. It is not attached directly to the trunk,
but is articulated with the outer end of the clavicle, and from it is suspended the
humerus in the shoulder-joint.
88
THE BONES OF THE UPPER LIMB.
It consists of a triangular blade or body, supporting two large processes. The
surfaces of the body are anterior and posterior ; the borders superior, internal or
vertebral, and external or axillary ; the angles superior, inferior, and external ; the
last being the thickest part of the bone, and bearing the large articular surface, is
distinguished as the head, which is supported upon a neck. The processes are an
anterior, cvracoid process, and a posterior, the spine, which is produced into the
acromion.
THAPE2IUS
ERES MINOR
Fig. 87. — DORSAL VIEW OF RIGHT SCAPULA. (Drawn by T. W. P. Lawrence.) §
The anterior surface or venter, looking also considerably inwards, presents a
concavity, the sulscapular fossa, occupied by the subscapularis muscle, and marked
by three, or four oblique prominent lines, converging upwards and outwards, which
give attachment to the tendinous intersections of that muscle. Separated from this
concavity, are two smaller flat surfaces, one in front of the superior angle and
the other at the inferior angle ; and these, together with the line running close to
the vertebral border and uniting them, give attachment to the serratus magnus
muscle.
The posterior surface or dorsum is divided by the spine into two unequal parts,
the upper of which is the supraspinous fossa, and the lower, the infraspinous fossa.
The supraspinous fossa is occupied by the supraspinatus muscle. The infraspinous
THE SCAPULA.
89
fossa, much the larger, presents in the middle a convexity corresponding to the
concavity of the venter, and outside this a concavity bounded by the prominent
axillary border. It is marked near the inner border by short lines, corresponding to
tendinous septa of the infraspinatus muscle, and is occupied by that muscle in the
greater part of its extent. Adjacent to the axillary border, in its middle third, is
a narrow area giving attachment to the teres minor muscle ; and below this, extend-
ing over the inferior angle, is a raised oval surface, from which the teres major arises.
CLAVICULAR FACET
CLENOID FOSS
LONG HEAD
Or TRICEPS
INF. ANCLE
Fig. 88. —EIGHT SCAPULA, FROM BEFORE. (Drawn by T. W. P. Lawrence. } f
These spaces are separated from each other, and from that of the infraspinatus
muscle, by lines which give attachment to aponeurotic septa.
The spine of the scapula is a massive triangular plate of bone projecting back-
wards and upwards from the dorsum. Beginning internally near the upper fourth
of the vertebral border, it extends outwards and a little upwards to the middle of
the neck of the scapula ; and becoming gradually elevated towards its outer extremity,
it turns forwards and is continued into the acromion process. The upper and lower
surfaces, smooth and concave, form part respectively of the supra- and infraspinous
fossae. It has two unattached borders, the more prominent of which is sub-
cutaneous, and arises from the vertebral border of the bone by a smooth, flat,
triangular surface, over which the tendon of the inferior part of the trapszius
90 THE BONES OF THE UPPER LIMB.
muscle glides, as it passes to be inserted into a rough thickening beyond. In the
rest of its extent this border is rough, broad, and serpentine, giving attachment by
its superior margin to the trapezius, and by its inferior to the deltoid muscle. The
external border, short, smooth, and concave, arises near the neck of the scapula, and
is continuous with the under surface of the acromion, enclosing tlie great scapular
notch between it and the neck of the bone.
The acromion process, projecting outwards and forwards from the extremity of the
spine over the glenoid cavity, forms the summit of the shoulder. It is an expanded
process, compressed from above downwards. Its superior surface, rough and
subcutaneous, is continuous with the prominent border of the spine ; while the
inferior surface, smooth and concave, is continuous with the superior surface and
external border of the spine. On its internal border anteriorly is a narrow oval sur-
face for articulation with the clavicle. Its outer border gives origin to the acromial
portion of the deltoid, and is marked by three or four tubercles from which tendinous
processes of this part of the muscle spring : posteriorly it terminates in the pro-
minent acromial angle, which overhangs the hinder margin of the glenoid cavity.
The apex of the acromion projects beyond the end of the clavicle, and gives attach-
ment to the coraco-acromial ligament.
The head bears the articular surface for thehumerus, known as the glenoid cavity.
This is a slightly concave surface, looking outwards, forwards, and slightly upwards.
It is pyriform in shape, with the narrow end uppermost, and gently incurved in
front. Its rim is flattened, and in the recent state is covered by a fibrous baud, the
glenoid ligament, which deepens its concavity; at its upper extremity is a small mark
indicating the attachment of the long head of the biceps muscle.
The neck, supporting the head, is most distinct behind, where it forms with the
spine the great scapular or acromio-scapular notch, leading from the supraspinous to
the infraspinous fossa ; its position is also marked above by the notch in the upper
border of the bone.
The coracoid process, thick, strong, and hook-like, rises for a short distance almost
vertically from the upper border of the head, and then bending at a right angle, is
directed forwards and slightly outwards. Its superior surface, towards the base, is
rough and uneven, giving origin to the coraco-clavicular ligament ; on its outer
border is attached the coraco-acromial ligament, at its extremity the coraco-brachialis
muscle and short head of the biceps, and on the inner edge the pectoralis minor.
The superior border of the scapula is the shortest ; it extends from the superior
angle outwards and downwards to the coracoid process, at the base of which it presents
a rounded suprascapular or coraco-scapular notch, which is converted into a foramen
by a ligament, or occasionally by a spiculum of bone, and is traversed by the supra-
scapular nerve. The axillary border is the thickest ; at the upper end, below the
glenoid cavity, it presents a strong rough mark, above an inch long, to which the
long head of the triceps muscle is attached ; and below this there is usually a slight
groove, where the dorsal branch of the subscapular artery passes backwards ; on the
ventral aspect of this edge in the greater part of its length is a marked groove in which
a considerable part of the subscapularis muscle arises. The vertebral border, called
also the base, is the longest of the three, and is divisible into three parts, viz., a short
one opposite the triangular surface of origin of the prominent border of the spine,
and the portions above and below that space, both of which incline outwards as they
recede from the spine. The upper part gives attachment to the levator anguli
scapulas muscle, the middle to the rhomboideus minor, and the lower to the rhom-
boideus major muscle.
The subcutaneous parts of the scapula are the free border of the spine in nearly
the whole of its length, the upper surface of the acromion, and a small part of the
vertebral border in its lower half ; the superior and axillary borders are entirely
THE HUMERUS.
91
concealed by the muscles. The coracoid process projects in front beyond the clavicle,
and can be readily felt inside the head of the humerus, but can be seen only in thin
persons. With the arm hanging by the side, the scapula covers the ribs from the
second to the seventh inclusive, sometimes the eighth ; and the root of the spine and
the lower edge of the glenoid cavity are on a level with the interval between the
third and fourth dorsal spines. It must, however, be remembered that the bone
changes its position with every movement of the arm.
The body of the scapula is in great part thin and translucent, and at these spots contains
no cancellated tissue. The head, the coracoid and acromion processes, the prominent border
of the spine, and the thick rib along the axillary border, derive their greater thickness and
strength from increased thickness of the compact bony substance in some parts, and from
cancellated tissue in others. Vascular foramina pierce the upper and lower surfaces of the
spine, and others are to be found on the anterior surface of the bone, near the neck.
The morphological axis of the scapula corresponds to the line of attachment of the spine,
extending from the glenoid cavity to the vertebral border of the bone. From this axis three
lamina? radiate, the prcscapula, we.wscaj)i(la, and postscapiila, of
Parker, giving rise to the three scapular fossa?. The supraspinous
angle (between the prescapula and mesoscapula) measures about
100° ; the infraspinous and subscapular angles are each about 1300.1
The scapula of man is remarkable for the great development of the
postscapula, making the vertebral border very long and the inferior
angle prominent. This is an adaptation to the freedom of move-
ment possessed by the upper limb. The surface for attachment of
the rotator muscles of the humerus is thus increased, and greater
leverage is given to the lower part of the serratus magnus muscle,
which rotates the scapula upwards. The relative length and
breadth of the scapula are expressed by the scapular index =
100 x breadth
; r; . The index is higher in the infant than in the
length
adult, and in Negroes than in Europeans. (Broca, Bull. Soc.
Anthrop. Paris, 1878 ; Flower and Garson, Joum. Anat., xiv ;
Turner, " Challenger " Reports, Zoology, xvi ; Dwight, " The Range
of Variation of the Human Shoulder-Blade," Amer. Nat., 1887.)
THE HUMERUS.
The humerus or arm-bone extends from the shoulder
to the elbow, where it articulates with both bones of the
forearm. It is divisible into the superior extremity, including
the head, neck, and great and small tuber osities ; the shaft ;
and the infei'ior extremity, including the external and internal
condyles, and the infei'ior articular surface. In general form
it is subcylindrical and slightly twisted.
The superior extremity is the thickest part of the
bone. The head is a large hemispherical articular elevation,
directed inwards, upwards, and backwards. The neck, as
described by anatomists, is the short portion of bone which
supports the head ; inferiorly, it passes into the shaft ;
superiorly, it is a mere groove between the head and the great tuberosity.
The great tuberosity is a thick projection, continued upwards from the external
part of the shaft, and reaching nearly to the level of the upper margin of the
head; it is surmounted by three flat surfaces, the uppermost of which gives
attachment to the supraspinatus muscle, the lowest to the teres minor, and the
intermediate one to the infraspiuatus muscle. Separated from the great tuberosity
by the commencement of the bicipital groove is the small tuberosity, oval and
prominent ; it looks forwards and gives attachment to the subscapularis muscle.
POSTSCAPULA
Fig. 89.— VERTICAL SEC-
TION OF THE SCAPULA,
PASSING THROUGH THE
MIDDLE OP THE THREE
FOSSJ3. (G. D. T.) \
1 See Ward's " Outlines of Human Osteology."
THE BONES OF THE UPPER LIMB.
NFRASPINATU8
CHEAT
TUBEROSIT
Fig. 90. — RIGHT HUMERUS, FROM BEFORE.
(Drawn by T. W. P. Lawrence.) f
Fig. 91. — RIGHT HUMERUS, FROM BEHIND.
(Drawn by T. W. P. Lawrence. ) f
THE HUMERUS. 93
The shaft or body, thick and cylindrical above, becomes expanded transversely
and somewhat three-sided below. It is divided into anterior and posterior faces by
lateral lines, slightly marked in the upper part, but more prominent in the lower,
where they pass into the supracondylar ridges. Superiorly, on its anterior aspect
is the bicipital groove, so named from lodging the long tendon of the biceps muscle ;
this groove, commencing between the tuberosities, descends with an inclination
inwards, and is bounded by two rough margins, the external and more prominent
of which, pectoral ridge, gives attachment to the pectoralis major muscle, the internal
to the latissimus dorsi and teres major. To-
wards the middle of the shaft, on the inner
lateral line, is a rough linear mark where the
coraco-brachialis muscle is inserted, and a little
lower down is the foramen by which the chief
medullary artery enters the bone, directed down-
wards. On the external part of the shaft, near
its middle, in a line anteriorly with the pectoral
ridge, is a large, elevated, and rough surface, of
a triangular shape, the deltoid eminence, for the
insertion of the muscle of the same name. Below
this, the ridge is continued into a smooth
elevation which, descending on the front of
the shaft to the inferior extremity, separates an
IF ULNAR NERVE
Fig. 92. — LOWER TWO-FIFTHS OF THE RIGHT
HUMERUS, FROM THE OUTER SIDE. (Drawn
by T. W. P. Lawrence. ) §
Fig. 93. — LOWER EXTREMITY OF THE RIGHT HUMERUS,
FROM BELOW. (Drawn by T. W. P. Lawrence.) §
external from an internal surface ; while at the sides these are separated from the
flat posterior surface by the supracondylar ridges, which descend, the external more
prominent than the internal, to the condyle on each side. About the middle of the
shaft externally, a broad depression, the spiral groove, winds downwards and
forwards, limited above by the deltoid eminence, and below by the external
supracondylar ridge: the hollow is for the most part occupied by a process of the
brachialis anticus muscle, but posteriorly, where there is often to be recognized a
second smaller groove, the musculo-spiral nerve and superior profunda vessels rest
against the bone. At the upper part of the groove there is generally a second
foramen for a branch of the superior profunda artery.
The external and internal surfaces below the deltoid eminence are occupied by the origin of
the brachialis anticus muscle. Posteriorly, the outer head of the triceps arises from the surface
above the spiral groove, the inner head from the surface internal to and below the groove.
The external supracondylar ridge gives origin in its upper two-thirds to the supinator longus,
in its lower third to the extensor carpi radialis longior. The external and internal inter-
muscular septa of the arm are also attached to the corresponding supracondylar ridges.
The inferior extremity is much enlarged laterally, flattened from before
backwards, and curved slightly forwards. Projecting on either side are the external
94 THE BONES OF THE UPPER LIMB.
and internal condyles (the epicondyle and epitrochlea of Chaussier). The internal
condyle is the more prominent, and is slightly inclined backwards, forming
posteriorly a shallow groove in which the ulnar nerve lies : its extremity is marked
anteriorly by an impression to which the common tendon of the superficial
pronato-flexor muscles of the forearm is attached. On the external condyle are seen,
1, a mark for the common tendon of some of the muscles of the back of the forearm ;
2, below and internal to this, a smaller impression for the anconeus ; and 3, between
the foregoing and the margin of the radial articular surface, a pit in which the
external lateral ligament of the elbow-joint is attached. The inferior articular
surface is divided into two parts. The external part, articulating with the radius,
consists of a rounded eminence directed forwards, called the capitellum, and a
groove internal to it ; it does not extend to the posterior surface. The internal part,
the trochlea, articulates with the ulna, and extends completely round from the
anterior to the posterior surface of the bone; it is grooved in the middle like the
surface of a pulley, and is somewhat broader behind than in front ; anteriorly, its
margins are inclined downwards and inwards ; posteriorly, upwards and outwards, so
that, seen from behind, it occupies the middle part of the bone. In front, the internal
margin of the trochlea is the more prominent, and forms a convexity parallel to the
groove ; behind, the external margin is slightly more prominent. Above the
trochlea posteriorly is a large and deep pit, the olecranon fossa, which receives the
olecranon process of the ulna in extension of the forearm ; and above it anteriorly,
separated from the olecranon fossa only by a thin lamina of bone, is the much smaller
coronoid fossa, which receives the coronoid process in flexion. Above the capitellum
is a shallow depression — the radial fossa, into which the head of the radius is
pressed in complete flexion.
The humerus, in its natural position with the arm hanging by the side, has a
slight inclination from above downwards and inwards, and is also in a condition of
what may be termed strong internal rotation, i.e., the so-called anterior surface looks
very much inwards, and the internal condyle is directed more backwards than
inwards. The bone is almost completely covered by muscles ; the upper extremity
is thickly covered by the deltoid, which it pushes up, and thus gives roundness to
the shoulder : the shaft is entirely surrounded : both condyles are subcutaneous, the
internal being prominent, while the appearance of the external varies as the forearm
is moved. When the elbow is bent the capitellum projects under its muscular
covering, and forms the rounded prominence outside the point of the elbow.
The average length of the humerus in the adult male is about 13 inches, in the female 12
inches. It is nearly one-fifth of the stature of the individual, and somewhat more than twice
as long as the clavicle.1
The major axes of the upper and lower extremities of the humerus do not lie in the same
plane, but cross one another at an angle, known as the angle of torsion, which varies greatly
in different individuals, but averages about 20° in Europeans, and 35° in Negroes. The axis
of the upper end forms a smaller angle anteriorly with the sagittal plane than that of the
lower end. In quadrupeds the torsion is usually about 90°. (Broca, Rev. d'Anthrop., 1881.)
Varieties. — A small hook-like process, with its point directed downwards, is not un-
frequently found in front of the internal condylar ridge, the supracondylar process. From its
1 On the length and proportions of the long bones in different races of men may be consulted
Humphry, "A treatise on the human skeleton"; Topinard, " Elements d'anthropologie geVerale ";
Turner, " Challenger " Reports, Zoology, xvi ; Rollet, ' ; Mensuration des os longs des membres," 1889.
It may here be remarked also that the limb-bones of the two sides are seldom of equal length. In most
cases the bones of the tipper limb (humerus + radius) are longer on the right side, the difference being
commonly about one-third of an inch, and rising occasionally to three-quarters of an inch. The
increased development is probably associated with the greater use of the right hand. In the lower limbs
the differences are not so marked, and the excess appears to be more frequently on the left side. These
differences do not exist at birth. (Garson, Journ, Anat., xiii, 502 ; Rollet, op. cit. ; Gaupp, " Maass-
und Gewichts- Differenzen zwischen den Knochen der rechten uud linken Extremitaten," Diss.,
Breslau, 1889.)
THE ULNA. 95
extremity, a fibrous band, giving origin to the pronator radii tcres muscle, descends to the
internal condyle, and through the arch thus formed passes the median nerve, accompanied
frequently by the brachial artery, or by a large branch rising from it. This process represents
a portion of the bone enclosing a foramen in many animals. (Struthers, Edin. Med. Journ.,
1848; Gruber, <; Can. supracond. humeri," Mem. Acad. Imp. St. Petersburg, 1859.) The thin
plate between the olecranon and coronoid fossae is sometimes perforated, forming the supra-
trocltlear or intercondylar foramen.
THE ULNA.
The ulna is the internal of the two bones of the forearm, and is longer than the
radius by the extent of the olecranon process. It is inclined downwards and out-
wards from the huinerus in such a direction that a straight line passing from the
great tuberosity of the humerus downwards through the capitellum would touch the
lower end of the ulna.
The ulna articulates with the humerus and the radius : in the natural skeleton it
is not in contact with the carpal bones, being excluded from the wrist-joint by an
interarticular fibre-cartilage.
The superior extremity is much the larger, and articulates with the humerus
by means of the great sigmoid cavity, which looks forwards and upwards, and is
bounded in its posterior and upper part by the olecranon, a thick process continued
upwards from the shaft, and in its lower part by the coronoid process projecting
forwards. The great sigmoid cavity is concave from above downwards, and traversed
by a longitudinal ridge. The part external to this ridge is broad and convex above,
while the part internal to the ridge is concave and broader below : a slight
constriction, and sometimes a groove of division, occurs across the middle of the
cavity. Continuous with the great is the small sigmoid cavity, a small articular
surface on the outer side of the base of the coronoid process, concave from before
backwards, for the reception of the head of the radius. Superiorly, the olecranon is
broad and uneven, terminating in front in an acute process or bealc, which overhangs
the great sigmoid cavity, and which in extension of the elbow passes into the
olecranon fossa of the humerus, and behind in a rectangular prominence or
tuberosity, which forms the point of the elbow, and gives attachment to the triceps
extensor muscle. The posterior surface of the olecranon is subcutaneous and
continuous with the posterior margin of the shaft of the ulna. The extremity of
the coronoid process is sharp and prominent, and is received during flexion into the
coronoid fossa of the humerus : its superior surface forms part of the surface of the
great sigmoid cavity: the inferior or anterior surface rises gradually from the anterior
surface of the bone, and is covered by a large triangular roughness, the inner part
of which, together with the tuberosity of the ulna at the lower angle of the surface,
gives insertion to the tendon of the brachialis anticus muscle.
The body or shaft tapers from above downwards, and in the upper three-fourths
of its extent is three-sided, and slightly curved with the convexity backwards ; in
the lower fourth it is slender and more cylindrical. It also presents a lateral curve,
with the concavity inwards above, outwards below. The anterior border, continued
downwards from the inner edge of the coronoid process, is thick and rounded. The
posterior border begins a little below the olecranon process by the meeting of two
lines which limit the triangular subcutaneous surface of the upper end of the bone,
and runs with a sinuous course to the back of the styloid process : it is smooth and
prominent in the upper two-thirds, rounded and ill defined in the lower third. The
external border is in the middle three-fifths of the shaft a sharp rough edge which
gives attachment to the interosseous membrane ; in the lower fifth it is only a
faintly marked line. In the upper fifth this border is continued by two lines, one
passing into the inner margin of the coronoid process, and the other to the posterior
extremity of the small sigmoid cavity, near which it becomes very prominent as the
THE BONES OF THE UPPER LIMB.
COBONOIO PRO
TUBEBOSITY
STVLOIO
PROCESS
VSMALL EIC.M010
-SUPINATOR
EXT. CAHP.
STYLOIO PROCLS
Fig. 94. — ANTERIOR TIEW OF THE RIGHT RADIUS AND Fig. 95. —RIGHT ULNA: POSTERO-EX-
ULNA IN SUPINATION OF THE HAND. (Drawn by T. W. P. TERNAL VIEW. (Drawn by T. W. P.
Lawrence.) f Lawrence.) f
POST. BORDE
THE RADIUS. 97
supinator ridge, giving origin to a part of the supinator brevis muscle. Between
these lines, and below the small sigmoid cavity, is a triangular hollow, the fore part
of which lodges the tuberosity of the radius with the insertion of the biceps tendon in
pronation of the hand, while in the hinder part fibres of the supinator brevis arise.
The anterior surface is concave in the upper two-thirds, where the flexor profundus
digitorum muscle takes origin, and in its lower third is marked by an oblique line —
the pronator ridge, which joins the anterior border and limits the attachment of the
pronator quadratus. Above the middle is a foramen for the medullary artery,
directed upwards. The internal surface is smooth and convex, in the upper two-
thirds giving attachment to the flexor profundus muscle, in the lower third
subcutaneous. The posterior surface, more uneven, looks outwards and backwards ;
an indistinct oblique line, descending from the supinator ridge to the posterior
border at the junction of the upper and middle thirds of the shaft, limits a trian-
gular area, which extends over the outer side of the olecranon and gives attachment
to the anconeus muscle ; below this a longitudinal ridge divides the surface into
an inner portion, smooth, and covered by the
extensor carpi ulnaris, and an outer part,
more irregular, and impressed by the ex-
tensor muscles of the thumb and index
fingers.
The inferior extremity presents a
rounded head, from the inner and back
part of which a short cylindrical eminence,
the styloid process, projects downwards,
giving ' attachment in front and below to Fig. 96. —TRANSVERSE SECTION THROUGH THE
the internal lateral ligament of the wrist- MIDDLE OF THE BOXES OF THE FOREARM,
joint, and externally to the triangular fibro-
cartilage. The head bears two articular
surfaces, an inferior, semilunar and flat-
tened, upon which the triangular fibro-cartilage of the wrist plays ; and a lateral,
narrow and convex, which is received into the sigmoid cavity of the radius.
The head and the styloid process arc separated posteriorly by a groove, which is
traversed by the tendon of the extensor carpi ulnaris ; and inferiorly by a depres-
sion, into which also the triangular fibro-cartilage is inserted.
The ulna is placed in its whole length under the skin at the back of the forearm.
The subcutaneous tract comprises the triangular surface on the back of the
olecranon, the posterior border of the shaft, which lies ab the bottom of a longi-
tudinal groove between the flexor and extensor muscles, and, in the lower third, a
narrow strip of the internal surface leading down to the styloid process : the latter
projects in the supine position of the hand at the inner and posterior part of the
wrist ; but when the hand is pronated, the outer and fore part of the head of the
ulna becomes superficial and prominent between the tendons of the extensor carpi
ulnaris and extensor minimi digiti muscles.
THE KADIUS.i
The radius is the external of the two bones of the forearm, and extends from
the humerus to the carpus. It articulates with the humerus, the ulna, and the
scaphoid and lunar bones of the carpus.
The superior extremity or head, is disc-shaped, with a smooth vertical
1 In anatomical description the forearm is supposed to be placed in supination, with the thumb
directed outwards and the palm of the hand looking forwards.
98
THE BOXES OF THE UPPER LIMB.
J
margin. It presents on its summit a depression, which articulates with the
capitellum of the humerus, and is surrounded by a convex part, broadest internally
where it glides upon the groove internal to
the capitellum. The smooth, short, cylin-
drical surface of the vertical margin, likewise
broadest internally, rotates in the small sig-
moid cavity of the ulna, and within the
orbicular ligament. The head is supported
on a constricted portion, named the neck.
The shaft or body is larger below than
above, and slightly curved, with the convexity
directed outwards and backwards. On its
antero -internal aspect superiorly, where it is
continuous with the neck, is the bicipital
titberositi/, to the posterior rough portion of
which is attached the tendon of the biceps
muscle. Below the bicipital tuberosity the
shaft has three surfaces, of which the external
is only indistinctly marked off from the others
by smooth, rounded anterior and posterior
borders, while the anterior and posterior sur-
faces are separated in their middle three-
fifths by a sharp, prominent internal border
which gives attachment to the interosseous
membrane. The anterior surface is limited
above by the prominent anterior oblique line,
running from the lower part of the tube-
rosity downwards and outwards to form the
anterior border, and giving origin to a part
of the flexor sublimis digitorum ; below this
the surface is grooved longitudinally for the
flexor longus pollicis muscle ; and at the
lower end it is expanded, and presents a
flattened impression for the insertion of the
pronator quadratus, which also occupies a
small triangular surface on the inner side of
the bone in its lower fifth : above the middle
of the anterior surface is the foramen for the
medullary artery, directed upwards into the
bone. The posterior surface is marked at the
junction of its upper and middle thirds by
the posterior oblique line, which limits supe-
riorly the impression of the extensor ossis
metacarpi pollicis ; below this is another
small oblique impression for the extensor
brevis pollicis. The external surface is convex
transversely as well as longitudinally, and is
marked near the middle, at its most prominent
part, by a rough impression for the insertion
of the pronator teres. Above this, the area between the anterior and posterior
oblique lines gives insertion to the supinator brevis.
The lower extremity of the radius, broad and thick, presents inferiorly a
large surface which articulates with the carpus, and internally a small one which
Fig. 97. — RIGHT RADIUS : POSTERIOR VIEW
(Drawn by T. W. P. Lawrence.) f
THE RADIUS.
99
\ TEBCL
EXT. CARP. RAD. BRCV.
T. CARP. RAD. LONG*
articulates with the ulna. The carpal articular surface, concave and oblique, is
divided by a line into a quadrilateral internal part which articulates with the lunar
bone, and a triangular external part which articulates with the scaphoid bone. The
ulnar articular surface is placed at a right angle with the inferior surface, and is
concave from before backwards, forming the sigmoid cavity, which plays over the
rounded head of the ulna. To the smooth border between the radial and ulnar
articular surfaces the base of the triangular fibro -cartilage is attached. At the outer
part of the inferior extremity the styloid pi'ocess projects downwards, stout and
pyramidal, giving attachment to the external lateral ligament of the wrist-joint.
The posterior border of the lower articular surface descends farther than the anterior,
and is roughened for ligamentous attachment. Anteriorly, a prominent transverse
ridge forms the lower limit of the impression of the pronator quadratus, and between
this and the scaphoid articular facet is a small triangular area occupied by a strong
part of the anterior ligament of the wrist-joint. On its external and posterior
aspects the inferior extremity of the radim is marked by grooves, which transmit
the extensor tendons. Thus, on the external border is a flat groove directed down-
wards and forwards, which lodges the
extensor ossis metacarpi and extensor
brevis pollicis ; and on the posterior
surface are three grooves, the middle
one of which, oblique and narrow, and
bounded externally by a prominent
tubercle, lodges the extensor longus
pollicis ; while of the two others,
which are broad and shallow, the
external, subdivided by a slight ele-
vation, gives passage to the extensor
• j. ,. 1 . , .
carpi radiahs longior and brevior,
and the internal transmits the ex-
tensor COmmunis digitorum and
extensor indicis. Immediately above
the first mentioned groove on the outer side is a small triangular mark, into which
the tendon of the supinator longus is inserted. .
The outermost groove is separated anteriorly from the impression of the pronator quadratus
by a prominent edge which is continued upwards from the transverse ridge of the front of
the lower extremity, and to which the posterior annular ligament is attached, while posteriorly
it is limited by a less marked elevation descending on the back of the styloid process. The
groove of the extensor longus pollicis is bounded externally by the tubercle, internally by a
small, often- indistinct, ridge ; and a sharp border projects between the innermost groove and
the sigmoid cavity. The several prominences give attachment to fibrous septa, which with
the annular ligament convert the grooves into canals for the passage of the tendons.
The radius is for the most part deeply placed. The head and shaft are entirely
covered by muscles. At the lower end the styloid process comes to the surface
between the tendons of the extensor muscles of the thumb and forms a projection on
the outer side of the wrist, lower down than the styloid process of the ulna : the
tubercle on the back of the lower end of the bone may also be readily felt beneath
the skin.
98. — LOWEK EXTREMITIES OF RIGHT RADIUS AND
ULNA, IN SUPINATION, PROM BELOW. (Drawn by
T. W. P. Lawrence.) |
The dorsal surface is uppermost.
IracMal i
The relative length of the forearm to the arm is expressed by the Uumero-radial or anti-
— ng— : of_£adlusLxJl °2 \ the range of variation of which in man and the
- length of humerus /
anthropoid apes is shown by the following examples, viz. — Eskimo, 71 ; European, 74 ;
Australian. 77 ; Negro, 79 ; Andamanese, 81 ; gorilla, 80 ; chimpanzee, 90 : and orang, 100.
The index is higher in the fcetus and infant, and diminishes during the period of growth.
H 2
100
THE BONES OF THE UPPER LIMB.
THE CABPUS.
The carpus is composed of eight short bones, which are disposed in two rows,
four in each. Enumerated from the radial to the ulnar side, the bones which con-
stitute the first or superior row are named scaphoid, lunar, pyramidal, and pisiform /
those of the second or inferior row are the trapezium, trapezoid, os magnum, and
unciform.
The dorsal surface of the carpus is convex, the palmar is concave from side to
side, the concavity being bounded by four prominences, one at the outer and one at
Fig. 99. — THE BONES OF THE RIGHT HAND: A, FROM BEFORE; B, FROM BEHIND. (Allen Thomson. ) ^
s, scaphoid ; I, lunar ; c, pyramidal ; p, pisiform ; t, trapezium ; next to it the trapezoid, and then
the os magnum, both not lettered ; u, unciform .
I to V, the metacarpal bones ; 1, 3, first and second phalanges of the thumb ; 1, 2, 3, the first,
second, and third phalanges of the little finger, and similarly for the other three fingers, not marked ;
* one of the sesamoid bones of the thumb seen sideways.
the inner extremity of each row. The anterior annular ligament is stretched across
between these prominences, so far as to form a canal for the transmission of the
flexor tendons.
The superior surfaces of the scaphoid, lunar, and pyramidal bones form, when in
apposition, a continuous convexity which corresponds with the concavity presented
Fig. 100.— SEMI-DIAGRAMMATIC VIEW OF THE RIGHT CARPUS
AND PART OF THE METACARPAL BONES, FROM BEFORE,
THE CARPAL BONES BEING SLIGHTLY SEPARATED TO SHOW
THE MODE OF THEIR CONNECTION WITH EACH OTHER.
(Allen Thomson. ) f
1, scaphoid bone; 2, lunar; 3, pyramidal ; 4, pisiform;
5, trapezium, the figure is placed upon the ridge, to the
inside of which is the groove for the tendon of the flexor
carpi radial is; 6, trapezoid; 7, os magnum; 8, unciform,
the figure is placed on the unciform process. The articula-
tion of the fourth metacarpal bone with the os magnum is
represented somewhat too large.
by the radius and the triangular fibre-cartilage, while the pisiform bone is attached
in front of the pyramidal, with which alone it articulates. The line of articulation
between the superior and inferior rows is concavo-convex from side to side, the
THE CARPUS.
101
Fig. 101. — RIGHT SCAPHOID BONE : A, FROM OUTER SIDE
AND BEHIND : B, FROM BEFORE AND INNER SIDE. (Gf. D. T. )
trapezium, trapezoid and os magnum bounding a cavity which lodges the external part
of the scaphoid, and the os magnum and unciform rising up in a convexity, which is
received into a hollow formed by the scaphoid, lunar, and pyramidal bones.
The scaphoid bone, the largest and most external of the first row, lies with its
long axis directed outwards and downwards. It has a concave surface, which looks
downwards and inwards, and
rticulates with the os magnum ;
on the opposite side are two
convex articular surfaces, an
upper for the radius, and a
lower for the trapezium and
trapezoid bones of the second
row ; these approach so near to
one another behind, that the
dorsal free surface is reduced to
a narrow grooved transverse
strip, to which the posterior liga-
ments of the wrist are attached. At the inner extremity is a small crescentic
surface for articulation with the lunar bone ; while the outer end is produced
into a stout conical tuberosity, which projects forwards and gives attachment to the
annular ligament. The scaphoid articulates with five bones, viz., the radius, lun&r,
trapezium, trapezoid, and os magnum.
The lunar bone (semilunar), irregularly cubic, is characterized by the deep
concavity from before backwards of its inferior surface, which rests on the head of
the os magnum, and commonly also by a bevelled edge
slightly on the unciform bone. Its external surface is
crescentic and vertical, and articulates with the scaphoid
bone : its internal surface looks downwards and inwards,
is much deeper and narrower than the external, and
articulates with the pyramidal. The convex superior
surface, which articulates with the radius, extends like
that of the scaphoid farther backwards than forwards,
and hence the anterior free surface is deeper than
the posterior. The lunar articulates with five bones,
viz., the radius, scaphoid, pyramidal, os magnum, and
unciform.
The pyramidal bone (cuneiform) is situated with
its blunted apex directed downwards and inwards : the
base has the shape of a half-oval, and articulates
with the lunar bone. There are three surfaces : the
inferior, concavo-convex from without inwards, articu-
lates with the unciform bone ; the anterior is dis-
tinguished by having a smooth circular facet on its
inner half for articulation with the pisiform bone ; and
the supero-posterior presents at the base a small articular
facet entering the wrist-joint, but is for the most part
rough for the attachment of ligaments. The pyramidal
articulates with three bones, viz., the lunar, pisiform, and
unciform.
The pisiform bone lies on a plane anterior to the
other bones of the carpus. In form it is spheroidal, with
.its longest diameter directed vertically. On its posterior
aspect is an oval articular surface for the pyramidal AND BEHIND. (G. D. T.)
Fig. 102. — RIGHT LUNAR
BONE, FROM THE INNER
SIDE AND BELOW. (G.
D. T.)
Fig. 103. — RIGHT PYRAMIDAL
BONE, FROM BEFORE AND
OUTER SIDE. (Gr. D. T.)
lgB'ON^
AND BEHIND.
102
THE BONES OF THE UPPER LIMB.
Fig. 105. — RIGHT TRAPEZIUM,
FROM BEFORE. (G. D. T. )
bone : this surface does not extend the whole length of the pisiform bone, but
leaves a small free projecting portion below. The inner side of the bone is
generally convex and somewhat rough. The outer side is smoother and slightly
concave.
The trapezium is the most external of the second row of carpal bones. It
presents a rhombic form when seen in its dorsal or palmar aspect, but with the
lower angle much produced and truncated. Its anterior surface is marked by a
vertical groove traversed by the tendon of the flexor carpi radialis muscle, and
externally to the groove by a ridge or tulerosity, one of
the four prominences which give attachment to the an-
terior annular ligament. Of the internal sides of the
rhomb, the superior articulates with the scaphoid and
the inferior with the trapezoid ; while a small facet
on the prominent lower angle is for the second meta-
carpal bone. Of the external sides, the superior is free,
and the inferior presents a smooth surface, convex from
behind forwards, and concave from without inwards,
which articulates with the metacarpal bone of the thumb,
and is separated by a small interval from the surface
for the second metacarpal bone. The trapezium articu-
lates with four bones, viz., the scaphoid, trapezoid,
and first and second metacarpals.
The trapezoid bone is considerably smaller than
the trapezium. Its longest diameter is from before
backwards. Its posterior free surface is much larger
than the anterior. The external inferior angle of the
anterior surface is distinguished by being prolonged a
little backwards between the articular surfaces for the
trapezium and second metacarpal bone. The superior
surface articulates with the scaphoid ; the external with
the trapezium ; the internal with the os magnum ;
and the inferior by a large surface convex from side to
side with the second metacarpal bone. The trapezoid articulates with four bones,
viz., the scaphoid, trapezium, os magnum, and second metacarpal bone.
The os magnum is the largest of the carpal bones. In form it is elongated
vertically, nearly rectangular below, rounded above. The upper extremity or head
articulates superiorly with the lunar
bone by a convex surface, extending
farther down behind than in front,
and prolonged on the outer side for
the scaphoid. A neck is formed
beneath by depressions on the an-
terior and posterior surfaces. The
anterior surface of the bone is much
narrower than the posterior. The
posterior surface projects downwards
at its internal inferior angle. On
the outer side, below the surface
for the scaphoid, is a short surface
for the trapezoid bone ; and on the
inner side is a vertically elongated surface which articulates with the unciform bone.
Inferiorly, this bone articulates by three distinct surfaces, of which the middle is
much the largest, with the second, third, and fourth metacarpal bones. The os
Fig. 106. — RIGHT TRAPEZOID
BONE : PALMAR ASPECT.
(<J. D. T.)
Fig. 107. — RIGHT os MAGNUM : A, INNER VIEW:
]3, OUTER VIEW. (G. D. T.)
THE METACARPUS. 103
magnum articulates with seven bones, viz., the scaphoid, lunar, trapezoid, unciform,
and second, third, and fourth metacarpal bones.
The unciform bone is readily distinguished by the large hook-like process,
projecting forwards dnd curved slightly outwards, on
its anterior surface. Seen from the front or behind,
it has a triangular form. Its external surface is
vertical, and articulates with the os magnum ; its
inferior surface is divided into two facets which
articulate with the fourth and fifth metacarpal
bones ; its superior surface, meeting the pyramidal,
is concavo-convex, inclines upwards and outwards
towards the head of the os magnum, and is separated
• , ii u i i j * J.L • * • i» Fig- 108. — RIGHT TJNCIFOKM
internally by a rough border from the inferior surface. °BONE; FROM THE OUTKR SI1)E
At the upper angle, externally, there is usually a AND BELOW. (G. D. T.;
narrow facet which touches the lunar bone. The
unciform articulates with five bones, viz., the os magnum, lunar, pyramidal, and
fourth and fifth metacarpal bones.
Varieties. — An increase in the number of carpal bones is occasionally met with. This
may arise from the division of one of the normal bones, as has been seen in the case of the
scaphoid, lunar, trapezoid, and magnum ; or it may be due to the persistence of an additional
element, the os centrale, which is placed on the dorsal aspect of the hand between the scaphoid,
magnum and trapezoid, and which is normally present as a cartilaginous rudiment in ths
foetus (p. 143). Another form of supernumerary ossicle results from the separation of the
styloid process of the third metacarpal bone. (W. Gruber, " Ueber das Os centrale Carpi des
Menschen," 1883 ; Leboucq, " De 1'augmentation numerique des os du carpe humain," Ann.
de la Soc. de Med. de Gand, 1884.)
THE METACARPUS.
The metacarpus, the part of the hand supporting the fingers, consists of five
long bones, which diverge slightly from each other, and are numbered from
without inwards.
The metacarpal bones are placed in a segment of an arch transversely, and being
at the same time slightly curved longitudinally, they present a concavity directed
forwards. They are terminated at their carpal extremities by expanded bases of
different forms, and at the digital ends by large rounded heads. The first meta-
carpal bone is broader and shorter than the others. The second is the longest of
all, the third, fourth, and fifth decrease regularly in length, according to their
position from without inwards.
The shaft of the first metacarpal bone is somewhat compressed from before
backwards ; the dorsal surface is slightly convex ; on the palmar aspect is a rounded
longitudinal ridge, placed nearer to the inner than the outer border. The shafts of
the others are three-sided, presenting a surface towards the back of the hand, and
towards the palm a smooth margin between the two lateral surfaces. They are most
slender near the carpal extremity, and become gradually thicker towards the head.
The dorsal surface of each is triangular, being bounded by lines which, proceeding
from the sides of the head, pass upwards and converge in the second, third, and
fourth metacarpal bones opposite the middle of the carpal extremity, and in the fifth
towards its inner side.
The heads articulate with the proximal phalanges. Their smooth, rounded
surfaces are broader, and extend farther, on the palmar than on the dorsal aspect
of the bones ; and on each side is a tubercle with a hollow below it for the attach-
ment of the lateral ligament.
104
THE BONES OF THE UPPER LIMB
The carpal extremity presents distinctive peculiarities in each metacarpal bone.
That of the first has a saddle-shaped articular surface, concave from before back-
wards, and convex from side to side, for articulation with the trapezium, and
Fig. 109.— FIRST METACARPAL
BONE OF THE RIGHT HAND :
PALMAR ASPECT. (G. D. T.
Fig. 1 10. — SECOND METACARPAL
BONK OF THE RIGHT HAND :
PALMAR ASPECT. (G. D. T. )
STVL01D PHOC.
Fig. 111. — THIRD METACARPAL
BONE OF THE RIGHT HAND,
FROM BEHIND. (G. D. T.)
Fig. 112. — FOURTH METACARPAL BONE OF
THE RIGHT HAND : RADIAL SIDE.
(G. D. T.
Fig. 113. — FIFTH METACARPAL BONE OP
THE RIGHT HAND I DORSAL ASIECT.
(G. D. T.)
externally a slight prominence, to which the extensor ossis metacarpi pollicis is
attached. The second is notched to receive the trapezoid bone ; on the
radial side is a small facet for the trapezium ; the more prominent ulnar lip
articulates superiorly by a narrow surface with the os magnum, and internally with
the third metacarpal bone ; and posteriorly, close to the articulation with the
trapezium, is a rounded mark where the extensor carpi radialis longior is insei ted.
THE DIGITAL PHALANGES.
105
The third bone articulates above with the os magnum, and on the sides with the
contiguous metacarpal bones ; at its posterior and outer angle it forms a projection
upwards, styloid process, immediately below which, on the dorsal aspect, is an im-
pression for the insertion of the extensor carpi radialis brevior. The fourth
articulates principally with the unciform bone above, but also by a small facet at
the posterior and outer corner with the os magnum : on its radial side are two
email rounded facets, and on the ulnar side a slightly concave semi-elliptical surface,
for articulation with the adjacent metacarpal bones. The fifth articulates above
with the unciform bone by means of a saddle-shaped surface directed slightly
outwards, and externally with the fourth metacarpal bone ;
while on its ulnar side there is a broad tuberosity for the
insertion of the extensor carpi ulnaris.
THE DIGITAL PHALANGES
The phalanges (mternodia) are fourteen in number, three
for each finger, but only two for the thumb.
Those of the first roiv are slightly curved like the meta-
carpal bones. Their dorsal surfaces are smooth and transversely
convex ; the palmar are flat from side to side, and bounded by
rough margins, which give insertion to the fibrous sheaths of
the flexor tendons. Their proximal extremities are thick, and
articulate each by a transversely oval concave surface with
the corresponding metacarpal bone. Their distal extremities,
smaller and more compressed antcro-posteriorly, are divided by
a shallow groove into two condyles.
Those of the middle row are four in number. Smaller
than those of the preceding set, they resemble them in form,
with this difference, that their proximal extremities present, on
the articular surface, a slight middle elevation and two lateral
depressions, adapted to articulate with the condyles of the first
phalanges.
The terminal or ungual phalanges, five in number, have
proximal extremities similar to those of the middle row, but with
a depression in front, where the deep flexor tendon is inserted.
They taper towards their somewhat flattened and expanded free
extremities, which are rough and raised round the margins and
upon the palmar aspect in the so-called ungual process.
Fig. 114.— THE PHA-
LANGES OF THE MID-
DLE FINGEK: PALMAR
ASPECT. (G. D. T.)
In each digit the proximal phalanx is the longest, and the distal
phalanx the shortest. Collectively, the phalanges of the middle finger
are the longest ; then follow in order, the ring, the index, and the
little fingers, and lastly the thumb. The greater prominence of the index in relation to the
ring finger, which is observed sometimes in the complete hand, is due entirely to the length
of the metacarpal bone (Braune and Fischer, Arch. f. Anat., 1887).
SESAMOID BONES. — A pair of sesamoid bones is placed in the palmar wall of the
metacarpo-phalangeal articulation of the thumb ; and similar nodules, single or
double, are sometimes found in the corresponding joint of one or more of the other
fingers, most frequently of the index and little fingers.
106
THE BONES OF THE UPPER LIMB.
OSSIFICATION OF THE BONES OF THE UPPER LIMB.
With the exception of the clavicle, all the bones of the upper limb begin to ossify in
cartilage
The clavicle begins to ossify before any other bone in the body. Its ossification com-
mences before the deposition of cartilage in connection with it, but afterwards progresses in
cartilage at both ends, as well as in fibrous substance. It is formed from one principal
Fig. 115. — OSSIFICATION OF THE CLAVICLE. (R. Quain.)
a, the clavicle of a foetus at birth, osseous in the shaft, 1,
and cartilaginous at both ends.
b, clavicle of a man of about twenty-three years of age ;
the shaft, 1, fully ossified at the acromial end; the sternal
epiihysis, 2, is represented rather thicker than natural.
centre, appearing about the 6th week, to which is added an epiphysis at the sternal end.
The epiphysis appears from the 18th to the 20th year, and is united to the shaft about the
25th year.
The scapula is ossified in two principal pieces, one forming the body or scapula proper, and
the other the coracoid process, which is generally regarded as representing the independent
1 year. 15 cr 16 years. 17 or 18 years 22 years.
Fig. 116. — OSSIFICATION OF THE SCAPULA. (R. Quain.)
1, scapula proper, including the body and spine ; 2, coracoid ossification; 3, 5, nuclei of acromion ;
4, epiphysis at the lower angle ; 6, epiphysis on vertebral border.
In A, ossification has commenced in the coracoid process. In B the coracoid process (represented as
too little ossified in the figure) is now partially united at its base, and centres have appeared in the
acromion and at the lower angle. In C, a second point has appeared in the acromion, and a long
epiphysis on the vertebral border. In D, the acromion, and the epiphysis of the vertebral border are
still separate.
and often largely developed coracoid bone of the monotremata and lower vertebrates. The
centre of the body appears near the head, about the 7th or 8th week, and gives rise to a
triangular plate of bone, towards the upper margin of which, about the 3rd month, the spine
appears as a slight ridge. At birth, the coracoid and acromion processes, the base and inferior
angle, the edges of the spine and of the glenoid cavity are cartilaginous. The greater part of
the coracoid process is formed from a centre which appears in the first year, but a small part
at the base of the process, including the upper extremity of the glenoid cavity, is a separate
ossification (subcoracoid), commencing about the tenth year.1 The coracoid process joins the
body about the age of puberty, and at this time epiphyses make their appearance. In the
acromion two, sometimes three, nuclei appear between the 14th and 16th years; they soon
coalesce, and the resulting epiphysis is united to the spine from the 22nd to the 25th year.
The cartilage of the base, which it may be noticed corresponds to a more largely developed
1 It is believed by some anatomists that the subcoracoid ossification is the true coracoid element of
the shoulder-girdle, and that the coracoid process represents the precoracoid of reptiles (Sabatier) or the
epicoracoid of monotremes (Howes). .
OSSIFICATION OF THE BONES OF THE UPPER LIMB.
107
permanent cartilage or bone, suprascapular, found in many animals, becomes the seat of
ossification about the 16th to the 18th year, by the appearance of a nucleus at the inferior
angle, and thereafter of a line of osseous deposit extending upwards throughout its length. A
Fig. 117. — POSTERIOR ASPECT OF THE STERNUM
AND RIGHT SHOULDER-GIRDLE FROM A
FCETl'S OF ABOUT FOUR MONTHS. (Flower
after Parker.) 1£
The dotted parts are cartilaginous; ost,
omosternum of Parker, lateral part of epi-
sternum of Gegenbaur, afterwards becoming
the interarticular fibro-cartilage ; pc, pre-
coracoid of Parker ; a, acromion ; cl, shaft
of clavicle ; mss, mesoscapular segment of
Parker ; c, coracoid ; gc, glenoid cavity ; gb,
glenoid border ; cb, coracoid border ; of,
anterior or supraspinous fossa ; pf, posterior
or infraspinous fossa ; ss, suprascapular
border.
thin lamina, in two pieces, is also added along the upper surface of the coracoid process, and
another at the margin of the glenoid cavity. These epiphyses are united about the 25th year.
In the numerals a nucleus appears near the middle of the shaft in the 8th week. It
gradually extends, until at birth only the ends of the bone are cartilaginous. In the 1st
year the nucleus of the head appears, and during the 3rd year that for the great tuberosity.
Fig. 118. OSSIFICATION OF THE HUMERUS. (R. Quahl.)
A, from a full-grown foetus ; B, in the second year ; C, at three years ; D, at the f f:h year ; E, at
about the twelfth year ; F, at the age of puberty.
1, the primary centre for the shaft ; 2, nucleus for the head ; 3, that for the great tuberosity ; 4,
for the capitellum and adjacent part of the trochlea ; 5, for the internal couclyle ; 6, for the inner part
of the trochlea ; 7, for the external condyle. In this and the following figures the more advanced
bones are shown on a smaller scale than the earlier ones.
The lesser tuberosity is either ossified from a distinct nucleus which appears in the 5th«year,
or by extension of ossification from the great tuberosity. These nuclei join together about
the 6th year to form an epiphysis, which is not united to the shaft till the 20th year. In
the cartilage of the lower end of the bone four separate nuclei are seen, the first appearing
in the capitellum in the 3rd year. The nucleus of the internal condyle appears in the 5th
year, that of the trochlea in the llth or 12th year, and that of the external condyle in the
13th or 14th year. The nucleus of the internal condyle forms a distinct epiphysis which
unites with the shaft in the 18th year ; the other three nuclei coalesce to form an epiphysis,
which is united to the shaft in the 16th or 17th year.
The radius is developed from a nucleus which appears in the middle of the shaft in the 8th
week, and from an epiphysial nucleus in each extremity which only appears some time after
108
THE BONES OF THE UPPER LIMB.
birth. The nucleus in the carpal extremity appears at the end of the 2nd year, while that of
t.he head is not seen till the oth or 6th year. The superior epiphysis and shaft unite about the
17th or 18th year ; the inferior epiphysis and shaft unite about the 20th year.
Fig. 119.— OSSIFICATION OF THE
RADIUS. (R. Quain.)
A, the radius of a full-grown
foetus ; B, at about two years of age ;
C, at five years ; D, at about eighteen
years.
1, shaft ; 2, ossific point of the
lower epiphysis ; 3, that of the upper
end. In D, the upper epiphysis is
united to the shaft, while the lower
is still separate.
The ulna is ossified similarly
to the radius, but begins a little
later. The nucleus of the shaft
appears about the 8th week,
that of the carpal extremity
in the 4th or 5th year. The
upper extremity grows mainly
from the shaft, but at the end
of the olecranon a small epiphysis is formed from a nucleus which appears in the 10th
year. This epiphysis is united to the shaft about the 17th year ; the inferior epiphysis about
the 20th year.
From what is stated above it appears that in the bones of the arm and forearm the
epiphyses which meet at the elbow-joint begin to ossify later, and unite with their shafts
earlier, than those at the opposite ends of the bones, whereas in the bones of the thigh and leg
Fig. 120. — OSSIFICATION OF THK
ULNA. (R. Quain.)
A, the ulna at birth ; B. at the
end of the fourth year ; C, of a
boy of about twelve years of age ;
D, of a male of about nineteen
or twenty years.
1, shaft; 2, nucleus of the lower
epiphysis ; 3, nucleus of the
upper epiphysis. In D, the
upper epiphysis is united to
the shaft, while the lower is still
separate.
the epiphyses at the knee-joint
are the soonest to ossify (except
in the fibula) and the latest to
unite with their shafts. In
the bones of the arm and fore-
arm the arterial foramina are
directed towards the elbow ;
in those of the thigh and leg
they are directed away from the knee. Thus, in each bone the epiphysis of the extremity
towards which the canal of the medullary artery is directed is the first to be united to
the shaft. It is found also that, while the elongation of the long bones is chiefly the result
of addition to the shaft at the epiphysial synchondroses. the growth takes place more rapidly,
and is continued longer, at the end where the epiphysis is last united ; and the oblique direc-
tion of the vascular canals is due to this inequality of growth, which causes a shifting of the
investing periosteum, and so draws the proximal portion of the medullary artery towards the
more rapidly growing end.
The carpus is entirely cartilaginous at birth. Each carpal bone is ossified from a single
nucleus. The nucleus of the os magnum appears in the 1st year ; that of the unciform in
the 1st or 2nd year ; that of the pyramidal in the 3rd year ; those of the trapezium and the
lunar bone in the 5th year ; that of the scaphoid in the 6th or 7th year ; that of the
trapezoid in the 7th or 8th year ; and that of the pisiform in the 12th year.
OSSIFICATION OF THE BONES OF THE UPPER LIMB.
109
The metacarpal bones and phalanges are usually formed each from a principal centre for
the shaft and one epiphysis. The ossification of the shaft begins about the 8th or 9th
week. In the inner four metacarpal bones the epiphysis is at the distal extremity, while in
the metacarpal bone of the thumb and in the phalanges it is placed at the proximal extremity.
In many instances, however, there is also a distal epiphysis visible in the first metacarpal bone
at the age of 7 or 8 years, and there are even traces of a proximal epiphysis in the
second metacarpal. In the seal and some other animals there are always two epiphyses
in these bones. The epiphyses begin to be ossified from the 3rd to the 5th year, and are
united to their respective shafts about the 20th year. The terminal phalanges of the
digits present the remarkable peculiarity that the ossification of their shafts commences at the
distal extremity, instead of in the middle of their length, as is the case with the other
phalanges and with the long bones generally (Schafer and Dixey, Proc. Roy. Soc. xxx, 550.
and xxxi, 63).
Fig. 121. — OSSIFICATION OF THE BONES OF THE HAND. (R. Quain. )
A, the condition at birth. The carpus is entirely cartilaginous. Each of the metacarpal bones and
digital phalanges has its shaft ossified.
B, at the end of the first year. The os magnum and unciform have begun to ossify.
C, about the third year. Centres of ossification are seen in the pyramidal and in the proximal
epiphysis of the first and distal epiphyses of the other four metacarpal bones, and in the proximal
epiphyses of the first row of phalanges.
D, at the fifth year. Centres have been formed in the trapezium and later in the lunar bone,
and in the epiphyses of the middle and distal phalanges : (the figure does not show them distinctly in
the middle phalanges).
E, at about the ninth year. Centres have been formed in the scaphoid and trapezoid bones, and the
more developed epiphyses of the metacarpal bones and phalanges are shown in the first and second
digits separatsly.
1, os magnum ; 2, unciform ; 3, pyramidal ; 4, lunar ; 5, trapezium ; 6, scaphoid ; 7, trapezoid ;
8, metacarpal bones, the principal pieces ; 8*, four metacarpal epiphyses ; 8', that of the thumb ; 9,
first phalanges ; 9*, their epiphyses ; 9', that of the thumb ; 10, second phalanges ; 10', epiphysis of
terminal phalanx of thumb ; 11, terminal phalanges of the fingers ; 11*, their epiphyses.
110 THE BONES OF THE LOWER LIMB.
V.— THE PELVIS AND LOWER LIMB.
The divisions of the lower limb are the haunch or hip, thigh, leg, and foot. In
the haunch is the hip-bone, which enters into the formation of the pelvis ; in the
thigh is the femur ; in the leg the tibia and fibula ; and at the knee a large sesamoid
bone, the patella. The foot is composed of three parts, viz., the tarsus, metatarsus,
and phalanges.
THE HIP-BONE.
The hip-bone, os coxa, or innominate bone, with its neighbour of the opposite side
and the addition of the sacrum and coccyx, forms the pelvis ; it transmits the weight
of the body to the lower limb. It is constricted in the middle and expanded above
and below, and is so curved that, while the upper part is nearly vertical, the lower
part is directed inwards. On the external aspect of the constricted portion is the
acetalulum, a cavity which articulates with the femur, and perforating the inferior
expansion is a large opening, the thyroid or obturator fwamen. The superior wider
part of the bone forms part of the abdominal wall ; the inferior enters into the
formation of the true pelvis. The hip-bone articulates with its fellow of the opposite
side, with the sacrum, and with the femur.
In the description of this bone it is convenient to recognise as distinct the three
parts of it which are separate in early life, viz., the ilium, os pubis and ischium.
These three portions meet at the acetabulum, in the formation of which they
all take part ; and the os pubis and ischium also meet on the inner side of the
obturator foramen.
The ilium constitutes the superior expanded portion of the bone, and forms a
part of the acetabulum by its inferior extremity. Above the acetabulum it is limited
anteriorly and posteriorly by margins which diverge at right angles one from the
other, and superiorly by an arched thick border, the crest of the ilium. Viewed from
above, the crest is curved like the letter /, the fore part being concave inwards, the
hinder part concave outwards : it is narrow in its middle third, broadened in front
and behind, and forms a marked projection externally in its anterior third : on it
may be distinguished external and internal lips and an intermediate ridge. The
anterior extremity of the crest forms a projection forwards called the anterior superior
spine of the ilium, and, separated from it by a concave border, and placed imme-
diately above the acetabulum, is another eminence called the anterior inferior spine :
the projecting posterior extremity of the crest forms the posterior superior spine, and
separated from it by a small notch is the posterior inferior spine, below which the
posterior border of the bone is hollowed out into the ilio-sciatic (or great sciatic^) notch.
The external surface or dorsum of the ilium is convex in front, below the prominence
of the crest, and concave behind this. It is traversed by three curved gluteal lines,
which limit the areas of attachment of the gluteal muscles. The posterior or superior
gluteal line leaves the iliac crest about one-fourth of its length from the posterior
superior spine, and curves downwards and forwards towards the hinder part of the
ilio-sciatic notch : the middle gluteal line begins in front at the iliac crest, about one
inch and a half from its anterior extremity, and arches backwards and downwards
to the upper margin of the ilio-sciatic notch : the inferior gluteal line, less strongly
marked than the middle, commences at the anterior border of the ilium, just above
the anterior inferior spine, and is continued backwards nearly parallel to the margin
of the acetabulum to the fore part of. the ilio-sciatic notch. Behind the posterior
gluteal line is a narrow semilunar surface, the upper portion of which is rough and
gives attachment to the gluteus maximus muscle, while the lower part is smooth and
THE HIP-BONE.
Ill
free from muscular attachment. The sickle-shaped space between the iliac crest and
posterior gluteal line above , and the middle gluteal line below is occupied by the
gluteus medius ; and the surface between the middle and inferior gluteal lines gives
SEMiMEMBRANOSUS
ISCHIUM
Fig. 122. — RIGHT HIP-BONE or MALE : OOTEK VIEW. (Drawn by T. \V. P. Lawrence.) £
origin to the gluteus minimus. On the lowest part of this surface, immediately above
the margin of the acetabulum, is a' rough elongated mark where the reflected head of
the rectus femoris is attached.
The internal surface of the ilium is divided into two parts. The anterior of these
(iliac surface} is the larger : it is smooth and concave, occupied by the iliacus muscle,
and is known as the iliac fossa. Inferiorly, the fossa terminates above the margin of
the acetabulam, and to the inner side of the anterior inferior iliac spine, in a groove
112
THE BONES OF THE LOWER LIMB.
which lodges the ilio-psoas muscle as it passes froji the abdomen into the thigh.
The inner boundary of the groove is formed by an elevation, the ilio-pectineal emi-
nence, marking the place of junction of the pubis and ilium.
PUBIS
ISCHIUM
Fig. 123. — RIGHT HIP-BONS OF MALE : INNER VIEW. (Dra vn by T. W. P. Lawrence.) §
The posterior part (sacral surface) is again subdivided, presenting from below up-
wards— 1, a smooth surface entering into the formation of the true pelvis, and
continuous with the pelvic surfaces of the pubis and ischium, only a faint line indi-
cating in the adult the place of union ; this gives origin to a part of the obturator
internus muscle, and is separated from the iliac fossa by a smooth rounded border, the
iliac portion of the ilio-pectineal line ; 2, the uneven auricular surface, in the recent
state covered with cartilage, for articulation with the sacrum, broad in front, and
THE HIP-BONE. 113
extending on to the posterior inferior spine behind ; 3, some depressions for the attach-
ment of the posterior sacro-iliac ligament ; and 4, a rough surface reaching up to
the hinder portion of the iliac crest, and giving origin to parts of the erector and
multifidus spinse muscles.
The iliac crest gives attachment by its outer lip to the tensor vaginas femoris, obliquus
externus, and latissimus dorsi muscles, and the gluteal fascia ; by its middle ridge to the
internal oblique ; and by its inner lip to the transversalis, quadratus lumborum, and erector
spinae muscles, and the iliac fascia. To the anterior superior spine are attached the tensor
vaginae femoris externally, the sartorius in front, and Poupart's ligament internally. The
anterior inferior spine gives origin to the straight head of the rectus femoris muscle. Between
this and the margin of the acetabulum is an impression where the ilio-femoral ligament
is fixed to the bone. The iliac part of the ilio-pectineal line gives attachment to the iliac and
obturator fasciaa, and the tendon of the psoas parvus when that muscle is present.
The os pubis forms the anterior wall of the pelvis, and bounds the thyroid
foramen in the upper half of its extent. At its outer and upper extremity it forms a
part of the acetabulum ; at its inner extremity it presents an elongated oval surface
which forms the articulation with the bone of the opposite side, the junction being
called the symphysis pubis. The part which passes downwards and outwards below
the symphysis is called the inferior or descending ramus, the upper part is called the
superior or ascending ramus, and the flat portion between the rami is the body. The
deep or pelvic surface of the body is smooth ; the anterior or femoral surface is
roughened near the symphysis by the attachments of muscles. At the superior
extremity of the symphysis is the angle of the pubis, and extending outwards from
this on the superior border is the rough pubic crest, terminating in the projecting spine.
The inferior ramus is thin and flattened, and joins the ramus of the ischium. The
superior ramus becomes prismatic, and increases in thickness as it passes upwards
and outwards. Its superior border is the pubic portion of the ilio-pectineal line, a
sharp ridge continued from the iliac portion of the line downwards and inwards
to the pubic spine. The triangular surface in front of this line is covered by
the pectineus muscle ; it is bounded externally by the ilio-pectineal eminence,
and below by the prominent obturator crest, which extends from the pubic
spine to the acetabular margin at the anterior extremity of the cotyloid notch.
Behind the outer part of the crest, on the inferior surface of the ramus, is the
deep obturator groove, directed from behind forwards and inwards, for the obturator
vessels and nerve.
The pubic crest gives origin to the rectus abdominis and pyramidalis muscles. The pubic
spine serves for the insertion of Poupart's ligament ; and for a short distance outside this
Gimbernat's ligament and the conjoined tendon of the internal oblique and transversalis
muscles are fixed to the ilio-pectineal line. Along the front of the pubic portion of the ilio-
pectineal line the pectineus muscle arises, and to the line itself the pubic portion of the fascia
lata is attached. From the front of the pubis the adductor longus muscle arises in the angle
between the crest and symphysis, and below this the adductor brevis and upper part of the
adductor magnus. Internally to these the gracilis is attached to the prominent edge of
the surface, and externally the obturator externus. Along the margin of the symphysial
surface is a small rough area, which is occupied by the anterior ligament of the articulation,
and is wider in the female than in the male bone (Cleland). The posterior surface of the pubi^
gives attachment to part of the obturator internus muscle ; and above this, where a faint line
may sometimes be recognized passing obliquely from the upper margin of the obturator foramen
to the lower end of the symphysis, the levator ani and obturator and recto-vesical fasciae are
fixed together to the bone.
The ischium forms the posterior and inferior part of the hip-bone, and bounds
the thyroid foramen in the lower half of its extent. Superiorly it enters into the
acetabulum : inferiorly it forms a thick projection, the tuberosity, and this part,
diminishing in size, is continued forwards into the ramus. On its posterior border,
114
THE BONES OF THE LOWER LIMB.
behind the acetabulum, a sharp process, the spine, projecting with an inclination
inwards, forms the inferior limit of the ilio-sciatic notch, and is separated from the
tuberosity by a short interval, the sciatic (or small sciatic} notch, against the smooth
margin of which, covered in the recent state with cartilage, the tendon of the obtu-
rator internus muscle glides. In front of this, on the external surface, a horizontal
groove, occupied by the upper border of the obturator externus muscle, lies between
the inferior margin of the acetabulum and the tuberosity. The tuberosity presents
ILIUM
ISCMIUM
Fig. 124. — RIGHT HIP-BONE OF MALE, FROM BEFORE AND BELOW. (Drawn by T. W. P. Lawrence.) §
a rough pyriform surface continuous with the internal margin of the ramus, on the
broader superior portion of which are two impressions placed side by side, the outer
for the semimembranosus, the inner for the conjoined origins of the biceps and semi-
tendinosus, while the lower part is ridged and gives attachment to the adductor magnus
muscle ; the inner border is sharp and prominent where the great sacro-sciatic liga-
ment is attached ; and along the outer margin is a faint elongated impression mark-
THE PELVIS. 115
ing the place of origin of the quadratus femoris muscle. The ramus of the ischium
is flattened like the inferior ramus of the pubis, with which it is continuous on the
inner side of the thyroid foramen.
The ischial spine gives attachment posteriorly to the small sacro-sciatic ligament, exter-
nally to the superior gemellus, and internally to the coccygeus and the hinder fibres of
the levator ani. The inferior gemellus arises from the upper margin of the tuberosity.
below the sciatic notch ; and the inner surface of the ischium gives origin to part of
the obturator internus. On the conjoined ischio-pubic rami, immediately above the inner
margin, in the male bone, is an oval surface to which are attached the crus penis, surrounded
by the ischio-cavernosus muscle, and more deeply the transversus perinei and constrictor
urethra3 muscles. The smaller and less distinct surface in the female gives attachment to the
eras clitoridis and corresponding muscles.
The acetabulum, or cotyloid cavity, is a cup-shaped hollow, looking outwards, down-
wards, and forwards, and surrounded in the greater part of its circumference by an
elevated margin, which is most prominent at the posterior and upper part ; while at
the opposite side, close to the obturator foramen, it is deficient, forming the cotyloid,
notch. Its lateral and upper parts present a broad horseshoe-shaped smooth surface,
which articulates with the head of the femur, and in the recent state is coated with
cartilage ; but the central part of the cup and the region of the notch are depressed below
the level of the articular surface (fossa acetabuli), lodge a mass of fat and the inter-
articular ligament, and have no cartilaginous coating. Rather more than two-fifths
of the acetabulum are formed from the ischium, less than two-fifths from the ilium,
and the remainder from the pubis. The iliac portion of the articular surface is
the largest, the pubic the smallest : the non-articular surface belongs chiefly to
the ischium.
The thyroid or obturator foramen, also called foramen ovale, is internal and inferior
to the acetabulum. In the male it is nearly oval, with the long diameter directed
downwards and backwards ; in the female it is broader and more triangular. In the
recent state it is closed by a fibrous membrane, except in the neighbourhood of the
groove in its upper margin.
The crest of the ilium is subcutaneous, and forms the boundary between the
abdomen and the region of the hip. In front the pubic spine is to be felt through
the integuments, and lower down the inner margin of the united rami of the ischium
and pubis can be followed to the ischial tuberosity, dividing the perineum from the
thigh. The remainder of the bone is thickly covered by muscles.
The hip-bone varies greatly in thickness at different parts. The strongest portions are
found along the lines of greatest pressure ; these are, a very thick bar in the ilium between
the auricular surface and the acetabulum, through which the weight of the body is trans-
mitted to the thigh-bones, and a second formed by the ischium, ending in the tuberosity,
which supports the body in the sitting posture. The ilium has also a thick rib running from
the acetabulum to the most prominent portion of the iliac crest, while the bone between this
and the auricular surface, corresponding to the deepest part of the iliac fossa, is very thin.
The floor of the non-articular portion of the acetabulum is also a thin plate of bone, and this,
as well as the thin part of the ilium, is occasionally perforated. The chief vascular foramina
penetrate the bone where it is thickest, viz., in the iliac fossa near the auricular surface,
on the pelvic surface of the ilium near the ilio-sciatic notch, on the outer surface of the ilium
between the inferior gluteal line and the acetabulum, and on the ischium between the
acetabulum and tuberosity.
THE PELVIS.
The hip-bones with the sacrum and coccyx form the pelvis.
This part of the skeleton may be considered as divided into two parts by a plane
passing through the sacral promontory, the ilio-pectineal lines, and the upper border
of the symphysis pubis. The circle thus completed constitutes the Irim or inlet of
i 2
116
THE BONES OF THE LOWER LIMB.
the lower or true pelvis ; the
space above it, between the
iliac fossae, belongs really to
the abdomen, but has been
Fig. 125. — ADULT MALH PELVIS SEEN
FROM BEFORE, IN THE ERECT AT-
TITUDE OF THE BODY. (Allen
Thomson. ) J
1, 2, anterior extremities of the
iliac crests in front of the greatest
transverse diameter of the false
pelvis ; 3, 4, acetabula ; 5, 5,
thyroid foramina ; 6, subpubic angle
or arch.
Fig. 126. — ADULT FEMALE PELVIS.
(Allen Thomson. ) J
Similarly placed with that shown
in the preceding figure, and illustrat-
ing by comparison with it, the prin-
cipal differences between the male
and female pelvis. The numbers in-
dicate the same parts as in the pre-
ceding figure.
called the upper or false
pelvis. The inferior circum-
ference, or outlet of the pelvis,
presents three large bony
eminences, the coccyx and
the tuberosities of the ischia.
Between the tuberosities of
the ischia in front is the
subpubic arch, which bounds
an angular space extending
forwards to the symphysis,
and is formed by the inferior
Figs. 127 and 128.— THE MALE AND
FEMALE PELVIS, AS SEEN PER
PKNDICULARLY TO THE PLANK OF
THK BRIU. (Allen Thomson.) £
In Fig. 128 of the female pelvis
the lines are shown in which the di-
mensions of the pelvis are usually
measured at the brim.
a, p, antero-posterior or conjugate
diameter ; t, r, transverse or widest
diameter ; o, b, o, b, oblique dia-
meters.
rarni of the pubes and the
rami of the ischia. The in-
terval between the sacrum
and coccyx and the ischium
on each side (sacro - sciatic-
notch) is bridged over in the
THE PELVIS.
H7;
recent state 'by the great sacro-sciatic ligaments, which therefore assist in bounding
the outlet of the pelvis.
Position of the pelvis. — In the erect attitude of the body, with the heels
in contact and the toes directed outwards, the pelvis is so inclined that the plane of
Fig. 129. — MEDIAN SECTION OF A FEMALE PELVIS.
(Reduced from Nagele. ) $
1, symphysis pubis ; 2, promontory of the
sacrum ; 3, coccyx ; 4, anterior superior spine
of ilium ; 5, tuberosity of ischium ; 6, spine of
iscbium (the thyroid foramen is not represented so
pointed below as it generally is in females). The
vertical and horizontal lines in the lower part of
the figure will assist the eye in judging of the
degree of inclination of the pelvis, as illustrated
by the next figure.
the brim of the true pelvis forms an angle
with the horizontal, which varies in differ-
ent individuals from 50° to 60°. The base
of the sacrum is then about 3|- inches above
the upper margin of the symphysis pubis,
and the tip of the coccyx from half an
inch to an inch above the apex of the sub-
pubic arch. The inclination of the pelvis
varies with the position of the lower limbs, and the angle is generally somewhat
greater in the female than in the male.1 The pelvic surface of the sacrum, near its
base, looks much more downwards than forwards, hence the sacrum, appears at first
sight to occupy the position of the keystone of an arch ; but being in reality broader
Fig. 130. — SKETCH OF PART OF THE PRECEDING
FiaURE, SHOWING THE INCLINATION OP THE
BRIM OF THE PELVIS AND ITS AXIS IN THE
ERECT POSTURE. ^
a, b, line of inclination of the brim of the true
pelvis ; e, f, a line inclining backwards and up-
wards, touching the lower edge of the symphysis
pubis and point of the coccyx ; c. d, axis of the
brim at right angles to the plane of the brim ;
d, h, g, curved axis of the cavity and outlet.
at its pelvic than on its dorsal aspect, it is a
keystone inverted, or having its broad end
lowest, and is supported in its place chiefly
by ligaments, but also to a slight extent
by the inward projection of the anterior
margin of the iliac articular surface.' The
line of pressure of the weight of the body
on the sacrum is directed downwards to-
wards the symphysis pubis, and the resistance of the head of the thigh-bone on each
side is directed upwards and inwards.
The axis of the pelvis is the name given to a line drawn at right angles to
the planes of the brim, cavity and outlet, through their central points. The
1 Nfigele, "Das weibliche Becken," &c., 1825 ; Wood, art. "Pelvis," in Cyclop, of Anat. and
Phys. ; G. H. Meyer, Arch. f. Anat., &c., 1861; Fiirst, "Die Maass- und Neigungs-Verhaltnisse des
Beckens," 1875.
118
THE BONES OF THE LOWER LIMB.
posterior wall, formed by the sacrum, and coccyx, being about five inches long
and concave, while the anterior wall at the symphysis pubis is only one and a half
or two inches long, the axis is curved ; it is directed at the inlet upwards and
forwards towards the umbilicus, and at the outlet downwards and a little backwards
or forwards according to the level of the coccyx.
Differences according to sex. — The size and form of the pelvis differ
markedly in the two sexes. In the female the constituent bones are more slender
and the muscular impressions less marked ; the height is less, and the breadth and
capacity of the true pelvis greater ; the ilia however are more vertical, and thus
the false pelvis is relatively narrower than in the male ; the inlet of the true pelvis is
more regularly oval, the sacral j promontory projecting less into it ; the sacrum is
flatter and broader ; the depth of the symphysis pubis is less ; the subpubic arch
is much wider, and the space between the tuberosities of the ischia greater.
The average dimensions of the pelvis, as measured in a number of full-sized
males and females, may be stated as follow, in inches : —
Greatest distance between the crests of the ilia
MALE.
FEMALE.
,
externally .......
Distance between the anterior superior spines of
the ilia ........
nj
• 11
Distance between the front of the symphysis
pubis and the first sacral spine . . . .
TKUE PELVIS.
Transverse diameter . . ...
Oblique diameter . . . . . . .
Antero-posterior diameter .....
u
7
Brim. Cavity.
Outlet.
Brim.
Cavity.
Outlet.
5 4|
43 4*
4 4|
8*
4
6
*i
5
5
4|
4f
41
The human pelvis, compared with that of the lower animals, is characterised by its shallow-
ness and breadth, and by the great capacity of the true pelvis ; by the expansion of the ilia,
the length and sigmoid curve of their crests, the massiveness and straightness of the ischial
tuberosities, and the shortness of the symphysis. Similar, although much slighter, variations
in the form of the pelvis are to be recognized in the different races of mankind, the most
important of which is in the relation of the antero-posterior to the transverse diameter, and
is expressed by what is termed the pelvic index. This is measured at the pelvic brim ; the
transverse diameter is taken as the standard = 100, and the proportion of the antero-posterior
diameter to this gives the index. For this purpose the pelves of the two sexes must necessarily
be grouped separately, and the male is usually selected for comparison. The following
examples of the average pelvic index in the male of four races will show the range of varia-
tion : — European, 80 ; Negro, 93 ; Australian, 97 ; Andamanese, 99. Pelves with an index
above 95 are dolicltopellic , from 95 to 90 inesatipellic, and below 90 platypt'llh' (Turner).
(Verneau, " Le bassin dans les sexes et dans les races," 1875; Garson, Journ. Anat., xvi ;
Turner, Journ. Anat., xx, and " Challenger " Reports, Zoology, xvi.)
THE FEMUR.
The femur or thigh-bone, situated between the hip-bone and the tibia, is the
largest and longest bone of the skeleton. In the erect position of the body it
inclines inwards and slightly backwards as it descends, so as to approach inferiorly
its fellow of the opposite side, and to have its upper end a little in advance of the
lower. It is divisible into the superior extremity, including the head and neck and
two eminences called trochanters ; the shaft ; and the inferior extremity, expanded
into an external and an internal condyle.
At the superior extremity of the bone, the neck extends inwards, upwards,
1 This diameter may be increased to the extent of one inch or more by movement of the coccyx.
THE FEMUR.
119
and slightly forwards, being
set upon the shaft at an angle
of about 125°. The neck is
expanded from above down at
its base,where it meets the shaft
obliquely, but compressed from
before back, so that the vertical
diameter greatly exceeds the
antero-posterior ; the summit
becomes more rounded, and is
somewhat enlarged again as it
joins the head. It is shorter
above and in front than below
and behind. On its posterior
surface there may usually be
recognized a shallow horizontaj
groove,, in which the tendon of
the obturator externus lies.
The head forms more than half
a sphere, and is covered with
cartilage in the fresh state.
Behind and below its central
point is a small oval depression,
the fore part of which gives
attachment to the interarti-
cular ligament of the hip-joint.
In the hollow there are often
one or two small vascular
foramina.
The great trochanter is a
thick truncated process pro-
longed upwards in a line with
the external surface of the
shaft. In front it is marked
by the insertion of the gluteus
minimus. Externally an ob-
lique line directed downwards
and forwards indicates the in-
ferior border of the insertion
of the gluteus medius muscle ;
and lower down the surface is
bounded by a horizontal line,
which is continued upwards on
the front of the trochanter to
an eminence at the junction
with the neck, the tubercle
of the femur ; this line marks
the upper limit of the vastus
externus. Internally at its
base, and rather behind the
neck, is the trochanter ic or
digital fossa, which gives at-
tachment to the obturator
FOSSA OF
INTERARTIC
LICT.
POST. CRUCIAL L.ICT
CIAL. LICT.
LAR NOTCH
Fig. 131. — RIGHT FEMUR, FROM BEHIND. (Drawn by
T. W. P. Lawrence.) f.
THE BONES OF THE LOWER LIMB.
ANT.
INTERTROCH.
LINE
Fig. 132. — UPPER PORTION OF RIGHT FEMUR, FROM
BHFORK. (Drawn by T. W. P. Lawrence.) f
externus muscle, while close above and in front of this is the impression of the
obturator internus and gemelli muscles. The upper border of the great trochanter
is narrow, and presents an oval mark for the insertion of the pyriformis. The
posterior border is prominent,
and continued into a strong
rounded elevation, the inter-
trochanteric ridge or posterior
intertrochanteric line, which passes
downwards and inwards to the
small trochanter, and limits the
neck posteriorly : above the
centre the ridge is thickened,
marking the attachment of the
upper part of the quadratus fe-
moris ; the enlargement is termed
the tubercle of the quadratus.
The small trochanter, a pyra-
midal eminence, projects from
the posterior and inner aspect of
the bone at the junction of the
neck with the shaft ; its rounded
summit gives attachment to the
tendon of the ilio-psoas muscle.
The neck is separated from the
shaft anteriorly by the anterior
intertrocJianteric line, or upper
part of the spiral line, a broad
rough line commencing at the
tubercle of the femur and di-
rected obliquely downwards and
inwards a finger's breadth in
front of the small trochanter ;
it indicates the attachment of
the thick anterior portion of the
capsular ligament of the hip-
joint and the upper border of
the united crureus and vastus in-
ternus muscles.
The shaft is arched from
above downwards, with the con-
vexity forwards. It is somewhat
narrowed in the 'middle third,
and becomes considerably ex-
panded below. Towards the centre
it is nearly cylindrical, but with a
tendency to the prismatic form, due to the projection of the linea aspera behind, and
a slight flattening of the surface in front ; so that it may conveniently be regarded as
presenting an anterior and two lateral surfaces, although definite lines separating
the surfaces do not exist. All three surfaces, smooth and uniform, are covered by
the crureus and vasti muscles. The lateral surfaces in the middle of their extent
approach one another behind, being only separated by the linea aspera. The linea
aspera is a prominent ridge, extending along the central third of the shaft
posteriorly, and bifurcating above and below. It presents two sharp margins or
TUBEROSITV
Pig. 133. — LOWER END OF RIGHT FEMUR, FROM BEFORE.
(Drawn by T. W. P. Lawrence.) §
THE FEMUR.
lips separated by a narrow interval. The external lip is prolonged up to the great
trochanter, and in its course is strongly marked for about three inches where the
gluteus maximus is attached, constituting the gluteal ridge. The internal lip is
continued, winding in front of the small trochanter, to the anterior inter trochanter ic
line,- and forms the lower part of the spiral line ; it marks the attachment of the
vastus internus. In the interval between the two diverging branches of the linea
aspera a less distinct line, which gives attachment to the pectineus, is seen passing
to the small trochanter. Inferiorly the two lips are prolonged to the condyles
under the name of internal and external supracondylar lines, enclosing between
them a flat triangular surface of bone, the popliteal surface of tfie femur, which forms
the floor of the upper part of the popliteal space. The internal supracondylar line
is interrupted at the upper part where the femoral vessels lie against the bone; it
terminates below in a small sharp projection, the adductor tubercle, giving
attachment to the tendon of the adductor magnus. Above the centre of the linea
aspera is the foramen for the medullary artery, directed upwards into the bone ; a
second foramen is frequently to be seen near the lower end of the line.
To the inner lip of the linea aspera are attached the vastus internus, adductor longus and
adductor magnus muscles, the last also extending upwards on the inner side of the gluteal
ridge, and downwards along the internal supracondylar line. The outer lip of the linea
aspera and the external supracondylar line give attachment to the short head of the biceps
and the external intermuscular septum of the thigh. The adductor brevis is inserted into the
upper third of the shaft externally to the pectineal line. Running downwards from the
tubercle of the quadratus to the level of the small trochanter there is sometimes to be seen a
faint linea quadrati, marking the insertion of the quadratus femoris. A small triangular
area below the lesser trochanter, between the pectineal and spiral lines, gives insertion to the
outer fibres of the iliacus. At the lower part of the popliteal surface is a slight roughness on
each side, above the corresponding condyle, where fibres of the two heads of the gastrocnemius,
and externally also the plantaris, arise.
The inferior extremity presents two rounded eminences, the condyles, united
in front, but separated behind by a deep intercondijlar fossa or notch. Their greatest
prominence is directed back-
wards, and their curve, as it
increases towards that part,
may be compared to that of
a partially uncoiled piece of
watch-spring. The external
condyle is the broader and
more prominent in front ;
the internal is the longer and
more prominent laterally.
In the natural position of the
femur, however, the inferior
surfaces of the two condyles
are on the same level. One
large articular surface, coated
continuously with cartilage,
extends over both condyles ;
but opposite the front of the intercondylar fossa it is divided by two irregular, slightly
marked transverse grooves into three parts, a convex surface on each side of the
fossa for articulation with the tibia ; and a grooved anterior surface for the patella.
The patellar surface is of a trochlear form, being marked by a vertical hollow and
two prominent lips ; the external portion of this surface is wider and more
prominent, and rises higher than the internal. The tibial surfaces are nearly
r- CONOYUE-
FOSSft
POST. CRUC. LIST.
Fig. 134. — LOW'EK EXTRKAIITY OK RIGHT FEMUR, FROM
BELOW. (Drawn by T. W. P. Lawrence.) f
122
THE BONES OF THE LOWER LIMB.
parallel, except in front, where the in-
ternal turns obliquely outwards to
reach the patellar surface. On the
exposed lateral surface of each condyle
is a rough tuberosity, giving attach-
ment to the respective lateral ligament
of the knee-joint. The external tube-
rosity is the smaller oi" the two ; above
it is a roundish impression for the outer
head of the gastrocnemius, and below
and behind it an oblique groove, ending
inferiorly in a pit, in which the popli-
teus muscle takes origin : the tendon
of the muscle plays over the smooth
hinder edge of the groove, and sinks
into the hollow when the knee-joint is
fully bent. On the upper part of the
internal condyle, between the adductor
tubercle and the articular surface, is an
impression for the internal head of the gastrocnemius. The floor of the intercondylar
fossa is rough, and presents two impressions where the crucial ligaments are attached :
Fig. 135. — LOWER PORTION OF RIGHT FEMUR
OUTER VIEW. (Drawn by T. W. P. Lawrence.)
Fig. 136. — CORONAL SECTION OF THE UPPER END OF THE FEMUR. (Zaaijer. )
THE FEMUR.
123
that of the anterior ligament occupies the hindmost part of the inner surface of the
external condyle, while that of the posterior ligament is at the inner and fore part
of the fossa, above the curved portion of the internal tibial articular surface.
The head and neck of the femur are deeply placed ; the great trochanter is
covered only by the aponeurosis of the gluteus maximus, and is readily felt, forming
the most prominent part of the hip. The shaft is thickly surrounded by muscles.
The condyles are subcutaneous on each side of the knee, the internal being especially
prominent ; the trochlear surface is concealed by the patella during extension, but
in the flexed limb its form can be traced pushing up the muscular covering.
The arrangement of the cancellous tissue at the upper end of the femur is shown in
fig1. 136. A system of " pressure-lamellae," springing from the compact wall of the lower
side of the neck and the upper end of the shaft internally, ascends radiating inwards to the
head and outwards to the great tro-
chanter ; those passing to the head are
especially dense. These are crossed at
right-angles by a set of "tension-la-
mella?," which start from the outer side
of the shaft, and ai'ch upwards and
inwards to the head and inner side of
the neck. The concave side of the neck
is farther strengthened by a nearly
vertical plate of compact tissue (calcar
femorale1), which projects upwards into
the spongy substance a little in front
of the small trochanter. At the lower
end of the bone the chief lamellas run
vertically from the compact wall of the
shaft to the tibial articular surfaces.
The average length of the femur in
the European male is a little more than
18 inches, in the female about 17 inches. FiS- I^.-TRANSVERSE SECTION OF THE FEMUR
It equals about -275 of the stature, and ™»SWATJSLT ABOVE THE SMALL TROCHANTER. (G. D. T. )
its proportion to the humerus is as 100 : 71.
In the erect attitude the inclination of the femur is such that the shaft forms an angle of
about 9° with the sagittal plane, and 5° with the frontal plane ; the former angle is larger
in the female than in the male. The femur also exhibits a torsion similar to that of the
humerus, but usually in the opposite direction, the head being inclined forwards from the
transverse axis of the lower extremity : the angle of torsion varies within wide limits, but is
in the majority of cases between 5" and 20° (Mikulicz, Arch. f. Anat., 1878).
The angle between the neck and shaft of the femur varies much in different individuals,
ranging in the adult from 110° to 140°. It is as a rule smaller in short than in long thigh-
bones, and in women than in men. It is more open in the foetus and child, and decreases
during the period of growth under the influence of the weight of the body ; but it does not
appear to undergo any change after growth is completed (Humphry, Journ. Anat., xxiii,
273).
Varieties. — The upper part of the gluteal ridge is sometimes very prominent, forming a
third trochanter similar to the process so named in the horse and some other animals. In
some cases there is a hollow, fossa hypotrochanterica? in place of or in addition to the ridge.
A marked development of the linea aspera gives rise to the condition known as the pilastered
femur. The adductor tubercle may be of unusual size, and has been seen forming a projection
three-quarters of an inch in length.
1 Merkel, Yirchow's Arehiv, lix.
2 Houze, Bull. deJa Soc. d'Anthrop., Eruxelles, 1883.
124
THE BONES- OF THE LOWER LIMB.
THE PATELLA.
The patella, rotula, or knee-pan, situated at the front of the knee-joint, is a
sesamoid bone developed in the tendon of the quadriceps extensor cruris. It is
compressed from before backwards, and somewhat triangular in shape, with the
apex below. Its anterior surface is convex and longitudinally striated, being
covered by a fibrous prolongation from the extensor tendon ; it presents a few
A..
Fig. 138. — RIGHT PATELLA :
A, FROM BEFORE ; B, FRO II
BEHIND. (Drawn by T.
W. P. Lawrence.) g-
In B, the articular surface
is seen, divided by a ridge into
a smaller internal and a larger
external part. On each of
these three facets may be re-
cognized, of which the middle
is the largest and the lower
the smallest, while along the
inner margin there is a narrow
seventh facet.
vascular foramina, and is separated from the skin by one or more bursse. The
superior border is broad, and sloped from behind downwards and forwards ; it is
occupied, except near the posterior margin, by an impression into which the
common (suprapatellar) tendon of the quadriceps is inserted. The deep surface is
for the most part coated with cartilage for articulation with the femur, and is
divided by a vertical elevation into two parts, the external of which is the larger
and transversely concave, while the internal is convex : below the articular surface
is a triangular depressed and roughened area, covered in the recent state by a mass
of fat ; and from the lower angle and sharp margins of this part of the bone the
infrapatellar tendon or ligamentum patellse springs, by which the patella is
attached to the tibia.
THE TIBIA.
The tibia, or shin-bone, is, next to the femur, the longest bone in the skeleton.
It is the anterior and inner of. the two bones of the leg, and alone communicates
the weight of the trunk to the foot. It articulates with the femur, fibula, and
astragalus.
The superior extremity or head is thick and expanded, broader from side to
side than from before back, and inclined somewhat backwards from the direction of
the shaft. It forms on each side a massive eminence or tuberosity, on the upper
aspect of which is a slightly concave articular surface for the corresponding
condyle of the femur. The internal tuberosity, somewhat larger than the external,
is rounded, and marked posteriorly by a horizontal groove for the insertion of the
semimembranosus muscle. The external tuberosity forms at the junction of its
anterior and outer surfaces a broad prominent tubercle, into which the ilio-tibial
band of the fascia lata is inserted ; at its posterior and under part is a small flat
surface for articulation with the head of the fibula. The internal condylar surface
is oval in shape, larger than the external, and slightly more hollowed. The external
condylar surface is more nearly circular, and concave from side to side, but rather
concavo-convex (in some cases altogether convex) from before backwards, and is
prolonged for a short distance on the posterior surface of the tuberosity where
the tendon of the popliteus glides. The peripheral part of each articular
surface is flattened, and separated from the condyle of the femur by a semi-
lunar interarticular fibro-cartilage. Between the condylar surfaces is an irregular
THE TIBIA.
125
ILIO -TIBIAL HAND
SPINE POPLITEH. NOTC
ANTERIOR
SURFACE:
(EXTENSORS
OF TOES)
STYLOIO PROO.
Fig. 139. — RIGHT TIBIA AND FIBULA, PROM
BKFORB. (Drawn by T. W. P. Lawrence.) J
Fig. 140. — RIGHT TIBIA AND FIBLUA, FROM
BEHIND. (Drawn by T. W. P. Lawrence.) £
L26
THE BONES OF THE LOWER LIMB.
interval, depressed in front and behind, where it gives attachment to the crucial
ligaments and the semilunar fibro-cartilages of the knee-joint, and elevated in the
middle, thus forming the spine, which is received into the intercondylar notch of
the femur. The summit of the spine presents two compressed tubercles, with a
slight intervening hollow, and the condylar articular surfaces are prolonged upwards
on the sides of the process. The depressed surface behind the spine is continued
into a shallow excavation — the popliteal notch, which separates the tuberosities on
the posterior aspect of the head. Lower down on the front of the bone, at the
junction of the head and shaft, is situated the tubercle or anterior tuberosity,
marked by the attachment of the ligamentum patellae.
The shaft of the tibia is three-sided, and diminishes in size as it descends for
about two-thirds of its length, but increases somewhat towards its lower extremity.
The internal surface is convex and for the most part subcutaneous ; at the upper
Fig. 141. — UPPER EXTREMITY OP THE RIGHT
TIBIA, FROM ABOVE. (Drawn by T. W. P.
Lawrence. ) |
Fig. ] 42. —TRANSVERSE SECTION THROUGH THE
MIDDLE OF THE BONES OF THE LEG, WITH THK
INTEROSSEOUS MEMBRANE. (G. D. T.) §
end, by the side of the tubercle, is a slight roughness where the tendons of the
sartorius, gracilis and semitendinosus muscles are inserted. It is separated from
the external surface by the anterior border, which runs with a sinuous course from
the tubercle to the front of the internal malleolus, having its concavity directed
outwards above, and inwards below ; in its upper two-thirds it forms a sharp ridge
known as the crest of the tibia ; in its lower third it is smooth and rounded. The
external surface is slightly hollowed in its upper two-thirds, where it lodges the
belly of the tibialis anticus muscle ; but below the point where the crest disappears
it turns forwards, becomes convex, and is covered by the extensor tendons. The
posterior surface is crossed obliquely in its upper third by the rough popliteal or
oblique line, which runs downwards and inwards from the outer tuberosity, and gives
origin to the soleus muscle : above this is a triangular area occupied by the popliteus
muscle ; while below the line, in the middle third of the shaft, a longitudinal
ridge divides the surface into two portions, an inner giving origin to the flexor
longus digitorum, and an outer, larger, to the tibialis posticus. A little below the
oblique line, and external to the longitudinal ridge, is a large foramen for the
medullary artery, directed downwards into the bone. The posterior surface is
separated from the internal by the internal border, which is most distinct in the
middle third of the bone, being rounded off above and below, and from the outer
surface by the external border or interosseous ridge, a prominent edge or line, inclined
forwards above, to which the interosseous membrane is attached.
The inferior extremity, much smaller than the superior, is expanded trans-
THE FIBULA. 127
versely, and projects downwards on its inner side, so as to form a thick process, the
internal malleolus. Inferiorly it presents for articulation with the astragalus a
cartilaginous surface, which is quadrilateral, concave from before backwards, and
having its posterior border narrower and projecting farther downwards than the
anterior ; internally the cartilaginous surface is continued down in a vertical
direction upon the internal malleolus, clothing its outer surface somewhat more
deeply in front than behind. The external surface is hollowed for the reception of
the fibula, and rough for the attachment of ligament, except over a small part along
the lower border. The posterior surface of the internal malleolus is marked by a
groove for the tendon of the tibialis posticus, and more externally is a slight
depression where the tendon of the flexor longus hallucis lies.
Both tuberosities of the tibia are subcutaneous, the external forming a well-
marked prominence at the outer and fore part of the knee. The internal surface
of the shaft is thinly covered for a short distance at the upper part by the tendons
of the sartorius, gracilis, and semitendinosus, but in the rest of its extent it is
subcutaneous, together with the continuous surface of the internal malleolus.
Anteriorly, the tubercle gives rise to a slight elevation below the knee, on which the
body is supported in kneeling, and running down from this the crest is to be
followed, constituting the shin.
rm- .e ±-L- 7 • 7 /length of tibia X 100\ , , 0, . ,, ,-, «0 •
The femoro-tivial index ( - I is about 81 in the European, 83 in
\ length ot femur /
the Negro, and 86 in the Bushman. The tibia is twisted so that when the upper extremity
has its longest diameter directed transversely, the internal malleolus is inclined forwards : the
angle of torsion is commonly between 5° and 20°, but it may range from 0 to 48° (Mikulicz.
Arch. f. Anat., 1878).
"Varieties. — The shaft of the tibia is sometimes much compressed laterally, and expanded
from before back, the posterior longitudinal ridge being very prominent, so that a transverse
section at the junction of the upper and middle thirds has the form of a narrow lozenge :
such a bone is said to be platycnemlc. A facet at the anterior margin of the lower extremity
for articulation with the neck of the astragalus in extreme flexion of the ankle-joint is rare
in Europeans, but common in some lower races. (Manouvrier, " Sur le platycnemie," &c..
Mem. Soc. d'Anthrop. Par., 1888 ; A. Thomson. " Influence of posture on the form of the
tibia," &c., Journ. Anat. xxiii and xxiv.)
THE FIBULA.
The fibula, or peroneal bone, is situated on the outer side of the leg ; it is nearly
equal to the tibia in length, but is much more slender. Its inferior extremity is
placed a little in advance of the superior ; and its shaft is slightly curved, so as
to have the convexity directed backwards, and, in the lower half, slightly inwards
towards the tibia.
The superior extremity, or head, somewhat expanded, is produced upwards at
its hindmost part into a conical eminence, known as the styloid process ; in front of,
and inside this is a small oval cartilage-covered facet, looking upwards, inwards and
forwards, for articulation with the outer tuberosity of the tibia ; while more externally
is a slightly excavated surface where the tendon of the biceps femoris is inserted :
the outer side of the head is smooth and subcutaneous. The somewhat constricted
part below the head is distinguished as the neck.
The inferior extremity, or external malleolus, is longer and more prominent
than the internal malleolus ; internally it forms the outer limit of the ankle joint,
and presents a triangular smooth surface for articulation with the astragalus, behind
which is a rough depression where the posterior band of the external lateral ligament
is attached : its anterior border, after projecting rather abruptly forwards, slopes
downwards and backwards : posteriorly it is marked by a shallow groove traversed
THE BONE.S OF THE LOWER LIMB.
INTEROSSEOUS
INFERIOR
WTEBOSSEOUSx
LIGAMENT
ASTRA.OALUS-
Fig. 143. — RIGHT FIBULA : INNER
VIKW. (Drawn by T. W. P.
Lawrence. ) £
by the tendons of the peroneus longus and brevis
muscles : externally it is convex and subcutaneous ;
and a triangular subcutaneous surface is continued
up from it for two or three inches on the shaft.
The shaft has four surfaces, separated by as
many prominent lines. Three of these lines are
known as borders, the fourth is the interosseous
ridge. The anterior border is the most prominent ;
it commences at the fore part of the neck, and
takes a straight course down the front of the bone
as far as the lower fifth, where it bifurcates, the
one line running to the front of the malleolus, the
other to the back, and enclosing between them the
triangular subcutaneous surface. Immediately in-
ternal to this is the interosseous ridge, so named
from giving attachment to the interosseous mem-
brane ; it is close to the anterior border above,
but gradually diverges from that as it passes
downwards ; it terminates about an inch and a
half above the ankle-joint in the apex of a tri-
angular surface, convex and roughened by the
inferior interosseous ligament, fixing it to the tibia.
The external border extends the whole length of
the bone, from the styloid process to the back of
the malleolus, inclining inwards in its lower half.
The remaining border, internal, commences at the
inner side of the neck, runs down the shaft for
two-thirds of its length, and then ends by joining
the interosseous ridge. The surfaces are : — the
anterior, between the anterior border and the in-
terosseous ridge, narrow above, wider below ; it
gives origin to the extensor muscles of the toes
and the peroneus tertius : the external, broadest of
all, somewhat hollowed at the upper part, and
turning below to the back of the malleolus, thus
indicating the course of the peronei muscles, by
which it is completely covered : the posterior, which
winds to the inner side of the bone in its lower
half ; in its upper third it is rough, giving origin
to the soleus, while the rest of its extent is occupied
by the flexor longus hallucis : and the internal,
between the internal border and the interosseous
line, a fusiform surface over the upper two-thirds
only of the shaft, and giving origin to the tibialis
posticus ; it is often traversed by an oblique ridge
which gives attachment to a tendinous septum in
the muscle. The foramen of the medullary artery
is small, placed on the internal or posterior surface,
about the middle, and is directed downwards.
The head of the fibula projects under the skin
at the outer and back part of the knee, behind and
somewhat below the level of the prominent outer
THE TARSUS.
129
tuberosity of the tibia. The shaft is covered by muscles, except over the tri-
angular surface above mentioned. The external malleolus descends lower and pro-
jects farther backwards than the internal, its point being nearer to the heel by
about three-quarters of an inch.
THE TARSUS.
The tarsus is composed of seven bones, viz., the calcaneum, astragalus, navi-
cular, three cuneiform, and cuboid.
The calcaneum or os calcis is the largest bone of the foot, Projecting down-
wards and backwards, it forms the heel. Above, it articulates with the astragalus,
and in front with the cuboid bone. Its principal axis extends forwards and
outwards from its posterior extremity to the cuboid bone.
The large posterior extremity, or tuberosity, presents inferioiiy two tubercles, which
rest upon the ground, and of which the internal is the larger : its hinder surface is
Fig. 144. — THE BONES OF THE RIGHT FOOT : A, FROM ABOVE ; B, FROM BELOW. (Allen Thoinsoii.) ^
a, navicular bone ; b, astragalus ; c, os calcis ; d, its tuberosity ; e, internal cuneiform ; /, middle
c'.ineiform ; g, external cuneiform ; h, cuboid bone ; I to V, the metatarsal bones ; 1, 3, first and last
phalanges of the great toe ; 1, 2, 3, first, second, and third phalanges of the secon-.l toe.
divided into an upper part, smooth and separated by a bursa from the tendo Achillis,
a middle part for the attachment of the tendon, and a lower part, convex and
roughened, continued below onto the tubercles, and covered by the thick skin and
fatty pad of the heel. The part in front of the tuberosity forms a slightly con-
stricted neck. The internal surface of the bone is deeply concave, and its concavity
is surmounted in front by a flattened process, the sustentaculum tali, which projects
inwards near the anterior extremity of the bone on a level with its upper surface,
and presents inferiorly a groove occupied by the tendon of the flexor longus hallucis.
The upper surface has two articular facets for the astragalus, separated by an
oblique groove in which the interosseous ligament is attached ; the anterior facet,
130
THE BONES OF THE LOWER LIMB.
TUBEROSITY
Fig. 145. — RIGHT os CALCIS, FROU ABOVE. (G. D. T.)
often subdivided into two, is placed over the sustentaculum, and is concave ; the
other, posterior and external to this, and larger, is convex from behind forwards and
outwards : the outer end of the groove is much widened, and at its fore part is a
rough surface where the extensor
euB°"> brevis digitorum takes origin. The
anterior extremity articulates with
the cuboid bone by a surface concave
from above, downwards and out-
wards, and convex in the opposite
direction ; and internal to this, along
the front of the sustentaculum tali,
the internal calcaneo-navicular liga-
ment is attached. The under surface,
projecting in a rough anterior
tubercle, gives attachment to the
inferior calcaneo- cuboid ligaments.
The external surface is on the whole
flat, but often presents at its fore part
an oblique ridge, the peroneal spine,
separating two slight grooves, the
upper for the tendon of the peroneus
brevis, the lower for the peroneus
longus.
The astragalus, or talus, second
in size of the tarsal bones, receives
the weight of the body from the
leg. It articulates with the tibia
above and internally, the fibula ex-
ternally, the os calcis below, and the
navicular in front. Its longest axis
is directed forwards and inwards.
Its main part is called the l>ody, the
convex anterior extremity is the head,
and the grooved part behind this is
the neck. The superior articular
surface occupies the whole of the
upper aspect of the body, and sends
a prolongation downwards on each
of the lateral surfaces of the bone.
The middle part, looking upwards
to the tibia, is convex from before
backwards, broader in front than
behind, with its outer margin longer
than the inner, and curved, while
the inner is straight. The inner
lateral part is narrow, sickle-shaped,
and articulates with the internal malleolus ; the outer lateral part, much deeper,
triangular, and concave from above down, articulates with the external malleolus.
Inferiority, there are two smooth surfaces, which articulate with the calcaneum.
The posterior of these, the larger, concave from within outwards and forwards, is
separated by a rough depression for the interosseous ligament from the convex
anterior surface, which rests on the sustentaculum tali. The rounded anterior sur-
face of the head articulates with the navicular bone ; and at the lower and inner
INT. CALC. NAV.-LLGT.
CALCANEUM
Fig. 146. — RIGHT ASTRAGALUS, FROM RELOW. (G. D. T. )
THE TARSUS.
131
part, between this and the anterior articulation with the os calcis, is a facet which
rests upon the internal calcaneo-navicular ligament, the three forming one con-
tinuous articular surface. The posterior surface is of small extent, and marked at
its inner part by a groove for the flexor longus hallucis, which is continuous below
with that of the sustentaculum tali. Bounding the groove are two tubercles, of
which the internal is usually but little marked; while the external is more prominent
and gives attachment to the posterior band of the external lateral ligament of the
ankle-joint.
The navicular or scaphoid bone is placed at the inner side of the foot
between the astragalus and the cuneiform bones. It is elongated transversely, and
compressed from before backwards. It presents
posteriorly an articular concavity for the head of
the astragalus, and anteriorly a convex surface
divided by two lines converging below into three
facets, which articulate respectively with the three
cuneiform bones. Its upper surface is convex
from side to side ; the lower is narrower and very
uneven. On the outer end there is in some
instances a small articular surface for the cuboid
bone ; the inner end forms the prominent tube-
rostty, directed downwards, and giving insertion
to the tendon of the tibialis posticus muscle.
The cuneiform bones are known as first,
second, and third, from within outwards, or in-
ternal, middle and external. They are placed between the navicular bone and the
inner three metatarsal bones, and present anteriorly and posteriorly smooth surfaces
for articulation with those bones. The internal cuneiform bone is the largest, the
A.
Fig. 147. — RIGHT NAVICULAR BONE,
FROM BEFORE. (Gr. D. T.)
Fig. 148. — RIGHT INTERNAL CUNEIFORM BONE : A, INNER VIEW ; B, OUTER VIEW. (G-. D. T.)
middle is the smallest. The proximal ends of the three bones are in the same trans-
verse line ; but at their distal ends the internal and external project forwards
beyond the middle one, and thus form a deep recess into which the base of the
second metatarsal bone is received.
The internal cuneiform bone has its sharp border directed upwards, and
the thick rounded base of the wedge projects downwards on the inner border of
the foot. The anterior articular surface, for the first metatarsal bone, is much
larger than the posterior, is kidney-shaped and convex. The internal surface is
free, rather uneven, and marked by an oblique groove for the tendon of the tibialis
anticus muscle, ending below in an oval facet where the larger part of the tendon is
inserted. On the outer side, along the posterior and superior borders, is an L-shaped
surface, which articulates with the middle cuneiform, and at its anterior extremity
with the second metatarsal bone.
K 2
132
THE BONES OF THE LOWER LIMB.
The middle cuneiform bone has its base directed upwards, and the sharp
edge downwards towards the sole. The posterior end is somewhat broader than the
anterior. On the inner side is an L-shaped articular surface, corresponding to that
on the internal cuneiform bone ; and
on the outer side is a smaller facet, at
the posterior part, for the external
cuneiform bone.
The external cuneiform bone is
also situated with its base upwards. At
its anterior end is a triangular articular
surface for the third metatarsal bone,
Fig. 149. — RIGHT INTERNAL CUNEIFORM BONE :
A, INNER VIEW; B, OUTER VIEW. (G. D. T.)
and continuous with this are small
facets on the fore part of each lateral
surface, for the second and fourth meta-
tarsal bones. On the internal surface, at the posterior part, is an articular facet
for the middle cuneiform bone, and on the outer surface a much larger one for the
cuboid bone.
The cuboid bone is situated on the outer side of the foot, between the
A.
B.
Fig. 150.— RIGHT EXTERNAL CUNEIFORM BONE: A, INNER TIEW ; B, OUTER VIEW. (G. D. T.)
calcaneum and the fourth and fifth metatarsal bones. It deviates from the cuboid
form and becomes rather pyramidal, by the sloping of four of its surfaces towards
the short, rounded external border. Posteriorly it articulates with the os calcis,"and
the lower internal corner projects backwards as a conical process beneath the anterior
.CUM. B.
OS CALCIS
CALC. CUB. LICT.
FACET ON TUBEROSITY
Fig. 151. — RIGHT CUBOID BONE: A, INNER VIEW; B, OUTER VIEW. (G. D. T. )
extremity of that bone. Its anterior surface, smaller than the posterior, is divided
into an internal quadrilateral and an external triangular facet, articulating with the
fourth and fifth metatarsal bones. On its internal aspect in the middle, and
reaching the superior border, is a surface for articulation with the external cuneiform
bone ; and behind this, in many instances, is a smaller facet articulating with the
navicular, while the remainder is rough for ligaments. The superior surface,
looking upwards and outwards, is on the whole flat, but rather rough. On the
inferior surface is a thick oblique ridge or tuberosity, the outer end of which
THE METATARSUS.
183
presents a smooth facet, covered with cartilage in the recent state, where the tendon
of the peroneus longus turns round into the sole. Between the tuberosity and the
anterior margin of this surface is a deep groove, beginning at a notch in the outer
border of the bone, for the reception of the tendon. Behind the tuberosity is a
triangular depressed area occupied by the plantar calcaneo-cuboid ligament.
Varieties. — Instances are recorded in which the number of tarsal bones is reduced owing
to congenital synostosis of the os calcis and navicular. of the astragalus and os calcis, or of the
astragalus and navicular. An increase in number may arise from the separation of the
external tubercle at the back of the astragalus (<>* trigunum — Bardeleben), or of the tuberosity
of the navicular bone, from the division of the internal cuneiform bone into dorsal and
plantar pieces, and from the presence of a supernumerary ossicle at the fore and inner part of
the os calcis, or between the internal cuneiform and second metatarsal bones. (H. Leboucq,
" De la soudure congenitale de certains os du tarse," Bull, de 1'Acad. Koy. de Med. de Belgique,
1890, 103 ; L. Stieda, " Der Talus und das Os trigonum Bardelebens beim Menschen," Anat.
Anzeiger, 1889, 305 ; W. Gruber, " Os cuneiforme I. bipartitum beim Menschen," Mem. Acad.
St. Petersburg, 1877 ; Hartmann et Mordret, " Anatomie du premier cuneiform," Bull. Soc.
Anat. de Paris, 1889, 71.)
THE METATABSUS.
The five metatarsal bones are distinguished by numbers, according to their
position from within outwards. They resemble the metacarpal bones of the hand in
being long bones, slightly convex from end to end on the dorsal aspect, in having
differently shaped bases, three-sided shafts, and rounded heads which articulate
with the phalanges. They also agree with the metacarpal bones in the number of
bones with which each articulates.
The first metatarsal bone is the shortest, but is much thicker and more
massive than the others. On its base is a large kidney-shaped surface, slightly
concave, for articulation with the internal cunei-
form bone, and sometimes there occurs a small
facet on the outer side for the second metatarsal
bone. The lower part of the base forms the tube-
w rosity, which projects downwards and outwards in
the sole, and is marked on its outer side by a
rounded impression for the peroneus longus : on
the inner side is a smaller mark where a slip of the
tibialis anticus is inserted. Of the three surfaces
Fig. 152. — FIRST METATARSAL BONE OP
BIGHT FOOT : PLANTAR ASPECT. (G. D. T.)
?ig. 153. — BASES OF THE METATARSAL BONES,
FROM BEHIND. (Q. D. T.)
of the shaft, the superior, which looks also inwards, is oblong and convex, the
inferior is concave, and the external, the largest, is triangular and flattened. The
head is large, and has on its under surface a median ridge, separating two grooves in
which the sesamoid bones glide.
134
THE BONES OF THE LOWER LIMB.
A.
B.
if ^^ n
, .- — «—.--• *J«
Fig. 154. — SECOND, THIRD, AND FOURTH METATARSAL BONES OF THE RIGHT FOOT : A, FROM INNER
SIDE ; B, FROM OUTER SIDE. (G. D. T.)
The remaining four bones are distinguished from
the metacarpal bones by being more slender and
compressed from side to side, corresponding to the
narrower form of the foot compared with that of
the hand. The second is the longest ; the others
diminish gradually to the fifth. Their shafts pre-
sent in the greater part of their extent a prominent border
looking upwards, which in the middle three appears on
the back of the foot between the dorsal interosseous
muscles on each side. Their heads are elongated from
above down, and terminate below in two small projec-
tions ; on each side is a tubercle and depression for the
attachment of the lateral ligament. The bases differ in
the several bones, and thus furnish distinctive cha-
racters between them. The second has a triangular base,
which articulates with the middle cuneiform bone ; on the
inner side is a small facet for the internal cuneiform, and
sometimes, below and in front of this, a less distinct
surface for the first metatarsal bone ; on the outer side
there are usually two small surfaces, an upper and a
lower, each again subdivided into two, thus making four
facets, of which the two posterior articulate with the
external cuneiform, and the two anterior with the next
metatarsal bone. The third has also a triangular base articulating with the external
cuneiform bone ; on the inner side are usually two facets for the second, and on the
outer side a single larger facet for thejfourth metatarsal bone. The base of the fourth
TUBEROSITY
Fig. 155. — FIFTH METATARSAL
BONE OF RIGHT FOOT : DORSAL
ASPECT. (G.D.T.)
THE PHALANGES. BONES OF THE FOOT AS A WHOLE.
135
is oblong or oval, and articulates with the cuboid ; on the inner side is generally a
double facet for the third metatarsal and the external cuneiform bones, but the arti-
culation with the latter is sometimes absent ; and on the outer side is a single surface
for the fifth metatarsal bone, with a deep groove below it. The fifth articulates by
its base with the cuboid, and internally with the fourth metatarsal bone, while
externally it projects in a large rough tuberosity, into which the peroneus brevis
muscle is inserted.
Variety. — In some rare cases an independent ossicle has been found taking1 the place of
the tuberosity of the fifth metatarsal bone (W. Gruber, Virchow's Archiv, xcix, 460 ; Ch.
Debierre, Bull. Soc. Anat. de Paris, 1888, 392).
THE PHALANGES.
The phalanges of the toes correspond so nearly in general conformation with
those of the fingers that it will only be necessary in this place to state the points in
which they differ from the latter.
The phalanges of the four outer toes are much smaller than the corresponding pha-
langes of the hand ; but those of the great toe are larger than those of the thumb.
The shafts of the first row of phalanges in the four outer toes are
compressed laterally and narrowed in the middle ; those of the
second row, more especially in the fourth and fifth toes, are very
short, their length scarcely exceeding their breadth. The last two
phalanges of the little toe are frequently connected by bone into
one piece.1
SESAMOID BONES. — Two sesamoid bones, developed in the
tendons of the flexor brevis hallucis, lie side by side in the
plantar wall of the first metatarso-phalangeal joint, and glide in
the grooves on the head of the first metatarsal bone. Small
sesamoid bones sometimes occur in the corresponding joints of
the other toes.
THE BONES OP THE FOOT AS A WHOLE.
The foot is narrowest at the heel, and as it passes forwards
becomes broader as far as the heads of the metatarsal bones.
The posterior extremity of the calcaneum is inclined slightly
inwards. The astragalus, overhanging the sustentaculum tali,
inclines inwards from the calcaneum so much that its external
superior border is directly over the middle line of the calcaneum,
and hence the internal malleolus appears more prominent than the
external. The foot is arched from behind forwards, the posterior pier of the arch being
formed by the heel, the anterior by the heads of the metatarsal bones. The arch,
indeed, may be considered as double in front, with a common support behind. The
internal division of the arch is that which bears the greater part of the weight of
the body, and is most raised from the ground ; it consists of the posterior two-thirds
of the calcaneum, the navicular and cuneiform bones, and the three inner metatarsal
bones ; the outer arch is formed by the calcaneum in its whole length, the cuboid
bone, and the fourth and fifth metatarsal bones. Besides being arched longitudinally,
the foot presents likewise a transverse arch, formed behind by the cuboid and three
cuneiform bones, and in front by the metatarsal bones.
Fig. 156. — PHA-
LANGES OF SECOND
TOE : PLANTAR
ASPECT. (G.D.T.)
1 W. Pfitzner found this union in about 36 per cent., and as frequently in infants as in adults
(Arch. f. Anat., 1890, 12).
136
THE BONES OF THE LOWER LIMB.
OSSIFICATION OF TH3J BONES OF THE LOWER LIMB.
Hip-bone. — The hip-bone is formed from the three principal pieces previously mentioned,
viz., the ilium, ischium, and os pubis, and from various others of an epiphysial nature. Ossifi-
cation commences in the cartilage of the ilium a little later than in other large bones, the
deposit of bone beginning- above the ilio-sciatic notch in the 8th or 9th week. This is followed
Fig. 157. — OSSIFICATION OF THE HIP- BONK. (R. Quain.)
A, the condition of the bone at birth. Bone has spread from three nuclei into the ilium, ischium,
and pubis, which meet in the cartilage of the acetabulum.
B, from a child under six years of age. The rami of the ischium and pubis are farther ossified, but
still separate.
C, a bone of two or three years later, in which the rami are united.
D, the bone of the right side from a person of about twenty years. Union has taken place in the
acetabulum, and the additional epiphyses are seen on the crest of the ilium, the anterior inferior spine,
the ischial tuberosity, and the margin of the symphysis pubis.
In A, B, and C, 1, ilium ; 2, ischium ; 3, pubis ; in D, 5, epiphysis of the crest ; 6, that of the tube-
rosity of the ischium ; 7, that of the symphysis pubis ; 8, that of the anterior inferior spine of the ilium.
by similar deposits in the thick part of the ischium below the acetabulum in the 3rd month,
and in the superior ramus of the pubis in the 4th or 5th month. At birth the greater part of
the acetabulum. the crest of the ilium, the tuberosity and ramus of the ischium, the body and
inferior ramus of the pubis are still cartilaginous ; ossification from the three primary centres
has however extended into the margin of the acetabulum. In the 7th or 8th year the rami of
Fig. 158. ACETABULAR REGION OF THE HIP-BONE
AT 14 YEARS OF AGE. (G. D. T.) \
1, ilium ; 2, ischium ; 3, pubis ; 4, os acetabuli ;
o, bony nodules between ilium and ischium ; 6 and
7, epiphysial laminae on ilium and ischium.
the ischium and pubis become completely united
by bone. In the acetabulum the three parts are
still separated by a Y-shaped strip of cartilage,
which is continuous with that lining the cavity.
This cartilage begins to be ossified from several
centres about the 12th year. The most constant of
these gives rise to a triangular piece of bone at the
fore part of the acetabulum, which is known as
the os acetabuli* and forms the whole of the. so-
called pubic portion of the articular cavity. It
becomes united first with the pubis, and later with
the ilium and ischium. Between the ilium and
ischium there are only some irregular nodules of bone, and other small osseous points form a
more or less perfect lamina over the iliac and ischial portions of the articular surface. The
union of the several portions in the acetabulum is completed from the 18th to the 20th year.
1 W. Leche. Internat. Monatschr. f. Anat. u. Histol., 1884, 363 ; W. Krause, ib., 1885, 150.
OSSIFICATION OF THE BONES OF THE LOWER LIMB.
137
Epiphyses are likewise formed in the cartilage of the crest of the ilium, the tuberosity of the
ischium, the anterior inferior spine of the ilium, and the symphysis pubis. These begin to
ossify soon after puberty, and unite with the main bone from the 23rd to the 25th year.
The pel i- is of the foetus and young child is of very small capacity in proportion to the size
of the body, and those viscera which are afterwards contained for the most part in the true
Fig. 159. — OSSIFICATION OF THE FEMUR. (R. Quain.)
A, from a foetus under eight months ; the body is osseous, both ends are cartilaginous.
B, from a child at birth, showing a nucleus in the lower epiphysis.
C, from a child of about a year old, showing a nucleus in the head.
D, at the fifth year ; a nucleus has appeared in the great trochanter.
E, near the age of puberty, showing a nucleus hi the lesser trochanter.
1, shaft ; 2, lower extremity ; 3, head ; 4, great trochanter ; 5, small trochanter.
C, D, & E are represented considerably, A & B very little, under the natural size.
Fig. 160. — OSSIFICATION OF THE TIBIA. (R. Quain.)
A, some weeks before birth ; the shaft is ossified, the ends are cartilaginous.
B, at birth, showing a nucleus in the upper epiphysis.
C, at the third year, showing the nucleus of the lower epiphysis.
D, at about eighteen or twenty years, showing the lower epiphysis united, while the upper remains
separate. The upper epiphysis is seen to include the tubercle.
E, shows an example of a separate centre for the tubercle.
1, shaft ; 2, superior epiphysis ; 2*, separate centre for the tubercle ; 3, inferior epiphysis.
pelvis occupy a part of the abdominal cavity. The inclination of the pelvis is considerably
'greater in early life than in the adult.
The femur is developed from one principal ossific centre for the shaft which appears in the
138
THE BONES OF THE LOWER LIMB.
7th week, and from four epiphyses, the centres for which appear in the following- order : — A
single nucleus for the lower extremity appears shortly before birth, one for the head appears
in the 1st year, one for the great trochanter in the 4th year, and one for the small trochanter
in the 13th or 14th year. These epiphyses become united to the shaft in an order the reverse
of that of their appearance. The small trochanter is united about the 17th year, the great
trochanter about the 18th year, the head from the 18th to the 19th year, and the lower ex-
tremity soon after the 20th year. The neck of the femur is formed by extension of ossification
from the shaft.
The patella is formed in the 3rd month by a deposit of cartilage in the tendon of the
quadriceps extensor cruris muscle. In this cartilage ossification begins from a single centre
during the 3rd year, and is completed about the age of puberty.
Fig. 161. — OSSIFICATION OP THE FIBULA. (R. Quain.)
A, at birth ; the shaft is ossified, the ends are cartilaginous.
B, at two years, showing a nucleus in the lower epiphysis.
C, at about four years, showing the nucleus of the upper epiphysis ; the lower ought to have been
shown as more advanced.
' D, at about twenty years ; the lower end is complete, but the upper epiphysis is still separate.
1, shaft ; .2, lower epiphysis ; 3, upper epiphysis.
The tibia and fibula each present, besides the principal centre for the shaft, a superior
and an inferior epiphysis. In the tibia the centre for the shaft appears in the 7th week ; that
for the upper extremity, including both tuberosities and the tubercle, appears most frequently
before, but sometimes after birth ; and that for the inferior extremity and internal malleolus
appears in the 2nd year. The tubercle is occasionally formed from a separate centre.^ The
lower epiphysis and shaft unite in the 18th or 19th year, the upper epiphysis and shaft in the
21st or 22nd year. In the fibula the centre for the shaft appears rather later than in the tibia;
that for the lower extremity appears in the 2nd year, and that for the upper, unlike that of the
tibia, not till the 3rd or 4th year. The lower epiphysis and shaft unite about the 21st year,
the upper epiphysis and shaft about the 24th year.
The fibula in the embryo at an early period is nearly as large as the tibia, and also articu-
lates with the femur. The tibial malleolus on the other hand is up to the seventh month of
foetal life longer than the fibular ; and the marked preponderance of the fibular malleolus,
which is peculiar to man, is only acquired after birth (G-egenbaur).
The tarsal bones are ossified in cartilage each from a single nucleus, with the exception of
the os calcis, which in addition to its proper osseous centre, has an epiphysis upon its posterior
extremity. The principal nucleus of the os calcis appears in the 6th month of foetal life ; its
epiphysis begins to be ossified in the 10th year, and is united to the tuberosity in the 15th or
16th year. The nucleus of the astragalus appears in the 7th month ; that of the cuboid about
the time of birth ; that of the external cuneiform in the 1st year ; that of the internal cunei-
form in the 3rd year ; that of the middle cuneiform in the 4th year ; and that of the navicular
in the 4th or 5th year.
The xnetatarsal bones and phalanges agree respectively with the corresponding bones of
the hand in the mode of their ossification. Each bone is formed from a principal piece and
one epiphysis ; and while in the four outer metatarsal bones the epiphysis is at the distal ex-
OSSIFICATION OF THE BONES OF THE FOOT.
189
tremity, in the metatarsal bone of the great toe and in the phalanges it is placed at the
proximal extremity. In the first metatarsal bone there is frequently, as in the first metacarpal
(see p. 109), also a second or distal epiphysis ; and in some instances a proximal epiphysis is
formed on the tuberosity of the fifth metatarsal bone (Gruber). In the metatarsal bones the
Fig. 162.— OSSIFICATION OF THE FONES OP THE FOOT. (R. Quain.)
A, right foot of a fetus of six months ; the metatarsal bones and digital phalanges have each their
shafts ossified from their primaiy centres ; the tarsus is wholly cartilaginous, excepting the os calcis,
in which the nucleus of bone has just appeared.
B, foot of a fostus of seven or eight months ; the astragalus shows a nucleus.
C, from a child at birth ; the cuboid has begun to ossify.
D, about a year old, showing a nucleus in the external cuneiform.
E, in the third year ; ossification has reached the internal cuneiform.
F, about four years old, showing ossification in the middle cuneiform and navicular bones, and in the
epiphyses of the metatarsal bones and phalanges.
Gr, about the age of puberty ; ossification is nearly complete in the tarsal bones ; an epiphysis has
been formed on the tuberosity of the os calcis, and the epiphyses of the metatarsal bones and phalanges
are shown separate.
1, nucleus of the os calcis ; 1* in G, the epiphysis of the os calcis ; 2, nucleus of the astragalus ; 3, of
the cuboid ; 4, of the external cuneiform ; 5, of the internal cuneiform ; 6, of the navicular ; 7, of the
middle cuneiform ; 8, metatarsal bones ; 8*, distal epiphysis of the second metatarsal bone ; 8', proximal
epiphysis of the first ; 9, first phalanx of the second toe ; 9*, proximal epiphysis of this phalanx ; 9',
that of the first phalanx of the great toe ; 10, second phalanx ; 10*, the epiphysis of this phalanx ;
10', epiphysis of the terminal phalanx of the great toe ; 11, terminal phalanx ; 11*, its epiphysis.
nuclei of the shafts appear in the 8th or 9th week. The epiphyses appear from the 3rd to the
8th year, and unite with the shafts from the 18th to the 20th year. The nuclei of the shafts
of the phalanges appear in the 9th or 10th week. The epiphyses appear from the 4th to the
8th year, and unite with the shafts from the 19th to the 21st year.
140 MOBPHOLOGY OF THE BONES OF THE LIMBS.
In the infant the head of the astragalus is directed more inwards than in the adult, and
the foot is naturally inverted. The first metatarsal bone is also relatively short in the foetus,
and at first is inclined inwards from the internal cuneiform bone, the distal articular surface
of which is oblique. In these respects the young foot is more like that of the ape. (Leboucq ,
" Le developpement du premier metatarsien et de son articulation tarsienne chez I'homme,"
Arch, de Biologie, iii, 335.)
MOEPHOLOGY OF THE BONES OF THE LIMBS.
Relation to the axial skeleton. — Anatomists have generally agreed to look upon the relation
which the bones of the limbs bear to the rest of the skeleton as that of appendages to the
trunk, and most are also disposed to regard these appendages as similar radiations or extensions
from one or more of the vertebral segments in two determinate situations of the trunk. But
opinions are much divided as to the typical number of the vertebral segments which are in-
volved, and as to the exact morphological nature of the parts which form the radiations. The
quinquifid division of the peripheral parts of both limbs in man and many animals appears
favourable to the view that each has the elements of five segments prolonged into it ; but of
late years attention has been specially directed by K. Bardeleben and others to certain, mar-
ginal structures which are interpreted as vestiges of more or less completely suppressed digits,
and there seems reason for believing that the pentadactyle extremity has been preceded by a
heptadactyle form. In association with this it may be noticed also that the nerves entering
into the proper limb-plexuses are in each case seven, viz., the 4th, 5th, 6th, 7th and 8th
cervical, with the 1st and 2nd dorsal, in the brachial plexus, and the 2nd, 3rd? 4th and 5th
lumbar, with the 1st, 2nd and 3rd sacral in the crural plexus. It is farther generally held
that the constituent elements follow each other in a similar order in the two limbs from the
cephalic to the caudal part of the vertebral axis, so that the pollex and radial elements occupy
the cephalic side of the upper, while the hallux and tibia take the same place in the lower
limb.
Homological comparison of upper and lower limbs. — A certain anatomical correspond-
ence between the upper and lower limbs, which is apparent to common observation, is
admitted in even a fuller degree by most anatomists as a result of a careful comparison of the
form and relations of their bones, as well as of their other parts, in both their embryonic and
fully formed conditions ; and the general conclusion has been formed that the thoracic and
pelvic limbs are constructed on the same general type in man and animals, both as regards
the attaching girdles of the shoulder and pelvis, and in the three several sections of which
each limb is composed. There are, however, certain modifications of that general plan,
leading to considerable differences in the form, size, and number of the individual parts in
different animals, which appear to be in a great measure related to the different uses to which
the upper and lower limbs are respectively applied ; as, for example, in the upper limb of
man, the breadth of the shoulders, caused by the interposition of the clavicle, the greater
extent of motion in the shoulder- joint, the eversion of the humerus, and the forward flexed
attitude of the elbow-joint, the arrangements for pronation and supination by rotation of the
radius and hand, and the opposability of the thumb, all have reference to the freedom,
versatility, and precision of the movements of the upper limb as an organ of prehension and
touch ; while in the lower limb, the comparatively fixed condition and arched form of the
pelvic girdle, the greater strength of the bones, the close-fitting of the hip- joint, the inversion
of the femur, the backward flexure of the knee-joint, the arched form of the foot, and non-
opposability of the great toe, have all manifest relation to the support of the trunk and
pelvis, and their movements upon the lower limbs. In the lower animals, greater modifica-
tions in the form of both limbs are to be observed, obviously adapted to their different
functions in each case.
Without attempting to follow out this subject by any detailed reference to comparative
anatomy or development, it may be useful to state here shortly the more probable conclusions
which have been formed with respect to the homological correspondence of the several parts
of the upper and lower limbs.
Shoulder and pelvic girdles. — In each of these a division is to be recognized at the place
of attachment of the limb-stalk (shoulder and hip-joints) into a dorsal and a ventral section.
The dorsal section in the upper limb is the scapula, in the lower limb the ilium, which
accordingly correspond, the chief difference between them consisting in the scapula being
free from articulation with the vertebral column, and therefore capable of a considerable
degree of motion, while the ilium is firmly jointed to the lateral mass of the sacrum. The
ventral section is in each case double, including the clavicle and coracoid in the shoulder-
girdle, and the pubis and ischium in the pelvic girdle. It is generally admitted that the
coracoid and ischium are corresponding structures, the coracoid being reduced to a relatively
THE SHOULDER AND PELVIC GIRDLES.
141
small process in man and most mammals, but forming a large and important bone which
reaches the sternum in monotremata and many lower vertebrates. The pubis appears to be
represented most closely by the precoracoid of reptiles and amphibia, while the clavicle is not
Figs. 163 & 164. — SKETCH OF THE
BONES OF THE THORACIC AND
PELVIC LIMBS, SO PLACED AS TO
SHOW CORRESPONDING PARTS IN
BOTH. (Allen Thomson. )
The preaxial borders of both limbs
are towards the reader's right hand,
and the original dorsal or extensor sur-
faces are shown throughout their whole
extent. The somewhat artificial re-
presentation given in these figures
cannot be obtained from a single
view of the specimens in one posi-
tion, but it is easily brought out by
slightly shifting the bones or changing
the point of view. The humeral
tuberosities are separated so as to
show them on the borders of the
bone. Fig. 163. Thoracic limb ;
ssp, supraspinous or prescapular fossa;
isp, infraspinous or postscapular
fossa ; ssc, a small part of the subsca-
pular fossa ; bs, base of scapula ; sa,
superior angle ; ia, inferior angle ;
sp, spine ; ac, acromion ; cr, coracoid
process ; gb, glenoid border with place
of attachment of triceps muscle ; gc,
glenoid cavity ; h, humerus, preaxial
border ; tm, large or preaxial tube-
rosity ; tj), small or postaxial tube-
rosity ; cr, radial condyle ; cu, ulnar
condyle ; r, radius ; 11, ulna ; o,
olecranon ; px, pollex and preaxial
side ; pi, pisiform and postaxial side
of hand. Fig. 164. Pelvic limb:
ss, sacral surface of ilium ; il, iliac
fossa ; di. a small part of the dorsurn ilii
or gluteal surface ; ic, crest of ilium ;
as, anterior superior spine ; ipl,
ilio-pectineal line ; ep. ilio-pectineal
eminence ; is, anterior inferior spine
and attachment of rectus muscle ; cc,
cotyloid cavity ; sp, symphysis pubis ;
isc, ischium ; f, femur, its preaxial
border ; trp, lesser or preaxial tro-
chanter ; trm, greater or postaxial
trochanter ; ct, tibial condyle ; cf,
fibular condyle ; p, patella ; t, tibia ;
tt, tubercle of tibia ; fi, fibula ;
hx, hallux and preaxial side of foot ;
ca, calcaneal tuberosity.
repeated in the pelvic girdle ; it
is, however, held by many anato-
mists that the mammalian clavicle
corresponds morphologically to the
reptilian precoracoid, and there-
fore is also the representative of
the pubis.
With regard to the comparison to be established between the individual parts of the
scapula and ilium there is much difference of opinion, but an examination of the simpler
forma of these bones in some of the lower animals, and a general consideration of their
relations give support to the view adopted by Flower as the more probable.1 The scapula and
1 Flower, Journ. Anat., iv, and " Osteology of the Mammalia." For different views, see Humphry,
MOKPHOLOGY OF THE BONES OF THE LIMBS.
ilium may be regarded as consisting essentially of three-sided prismatic rods, in the primitive
position of which an internal or vertebral surface is separated from two external surfaces by
preaxial and postaxial ridges, and the two external surfaces are separated by an external
ridge, which descends from the dorsal extremity of the bone to the joint-socket. It is
on this external ridge, glenoid in the scapula and cotyloid in the ilium, that in each case
the long head of the great extensor muscle of the limb is attached. The primitive arrange-
ment is modified in two ways, viz., 1st, by the outgrowth to a greater or less extent of the
edges of the rod, thus giving rise to fossae in the situation of the original surfaces, and 2nd,
by the occurrence of a rotation in different directions in the two limbs, the scapula outwards,
Fig. 165. — DIAGRAM OP AN EARLY HUMAN
EMBRYO, SHOWING THE RUDIMENTARY
LIMBS IN THEIR SECOND POSITION. (Allen
Thomson. )
r, preaxial or radial and pollex border of
the thoracic limb ; u, its postaxial or ulnar
and little finger border ; t, preaxial or
tibial and hallux border of the pelvic limb :
f, its postaxial or fibular and little toe
border.
the ilium inwards, in accordance with the rotation which takes place during the course of
development in the free part of the limb. The primitive vertebral surf ace of the scapula
becomes the prescapular or supraspinous fossa, while in the ilium the corresponding surface
is the sacral, which, being connected to the vertebral column, undergoes but little change in
position. The postscapular or infraspinous fossa of the scapula is accordingly represented by
the iliac fossa of the ilium, and the subscapular fossa by the gluteal surface. (See the table
of homologous parts below.)
Bones of the limbs. — In making the comparison of the bones composing the limbs them-
selves it is necessary to revert to the simpler relations subsisting between the limbs and the
trunk or vertebral axis of the body in embryonic life. In the earliest stage the limbs may be
said to bud out from the side of the trunk as fiattish semilunar flaps, so that they present a
Fig. 166. — DORSAL SURFACE OF THE RIGHT MANUS OF A WATER
TORTOISE. ( Gegenbaur. )
R, radius ; TJ. ulna ; r, radiale ; i, intermedium ; u, ulnare ; c, centrale ;
1 — 5, five carpal bones of the distal row ; m1 — m5, five metacarpals.
dorsal and a ventral surface, coinciding with these respective
surfaces of the trunk ; but in the next stage, when the limbs
come to be folded against the body in the ventral direction,
although the original relation to the trunk is undisturbed,
their axes have now come to lie nearly perpendicularly to the
coronal plane of the vertebral axis, and the position of the limbs
is such that in each there is one border which looks towards
the head, and another which looks towards the tail. To these
borders of the limbs the names of preaxial and postaxial are
given respectively, as indicating their position before and
behind the limb-axis. When at a somewhat later stage of
development the divisions of the limbs make their appearance,
and more especially when the quinquifid division of the digits
in the hand and foot becomes perceptible, it is obvious that the thumb and radius in the one
limb and the great toe and tibia in the other, occupy corresponding cephalic and preaxial
situations ; and it is not difficult to trace from these the corresponding relations of the parts
in the upper division of the limbs. Thus, the radial condyle of the humerus with the great
tuberosity are preaxial, while the lesser tuberosity, ulnar condyle. "ulna, and little finger are
postaxial. In the lower limb, the small trochanter, internal condyle, tibia and great toe are
preaxial, while the great trochanter, external condyle, fibula, and little toe, are postaxial.
And at the same time the dorsal or extensor surface of the limbs is external, and the ventral
or flexor surface is internal.
Journ. Anat., v, 67 ; Sabatier, " Comparaison des ceintures et des membres anterieurs et posterieuvs
dans la serie des vertebras," Montpellier, 1880.
COMPARISON OF THE HAND AND FOOT.
143
Very soon, however, in the higher animals and in man. farther changes operate in bringing
about the permanent condition. The humerus is folded backwards against the trunk, and at
the same time undergoes a rotation outwards, so that the radial (preaxial) condyle becomes
external, and the extensor aspect of the elbow is directed backwards. The femur, on the
other hand, is inclined forwards and rotated inwards, thereby bringing the tibial (preaxial)
condyle to the inner side, and the extensor aspect of the knee forwards. The rotation of the
humerus outwards in man amounts to about 45°, so that the axis of the elbow-joint is placed
obliquely to the median plane, but in quadrupeds the rotation takes place through 90°. and thus
the axis of the elbow-joint becomes transverse. The rotation inwards of the femur is about 90°,
and the axis of the knee-joint is therefore placed transversely, in both man and quadrupeds.
In the upper limb of man, the radius being in semipronation, no material change occurs in
the position of the hand, the thumb hanging naturally forwards ; but in animals destined to
rest on the palmar aspect of the hand or digits, important changes occur in the position of the
radius by which, as this bone is brought forwards upon the humerus, and its lower end carried
inwards, the manus or its elements are placed permanently in the prone position, with the
td.
tm
Fig. 167. — DORSAL SURFACE OF THE EIGHT
CARPUS OF MAN. (Flower.)
s, scaphoid ; I, lunar ; c, cuneiform or pyra-
midal ; p, pisiform ; tm, trapezium ; id, tra-
pezoid ; m, magnum ; u, unciform ; I — V, five
metacarpals.
Fig. 168. — DORSAL SURFACE OF THE CARPUS
OF A BABOON. (Flower. )
s, scaphoid ; I, lunar ; c, cuneiform or pyra-
midal ; p, pisiform ; tm, trapezium ; tf) ', trape-
zoid ; m. magnum ; u, unciform ; rs, radial sesa-
moid ; ce. os cent-rale ; I — V, five metacarpals.
first or radial digit inwards. In the foot no such change is required, as already by the internal
rotation of the femur at its upper part, the conditions for plantar support have been secured,
and the first or tibial digit is on the inner side. Farther, in man, as the body attains its full
development, both limbs are extended in a line parallel to the axis of the trunk, the upper
dropping loosely from the shoulder-joint with the greatest freedom of motion ; the lower more
closely articulated in the hip- joint, and suited to give firm support to the body in the erect
posture.
Hand and foot. — The similarity of the digital and metacarpal bones of the hand
with those of the foot in number, form, and connections is so great that the homodynamous
correspondence of these bones is immediately recognised. The main differences between them
consist in the greater length of the fingers, and the opposability of the thumb to the
other digits through its mobility at the carpo-metacarpal articulation, in adaptation to the
function of the hand as a grasping organ.
The morphological- construction of the carpus and tarsus is only to be understood by
reference to a more generalized form, such as is met with in the carpus of the water-tortoise
(fig. 166) and in the tarsus of certain amphibia. Here nine elements are seen, arranged in a
proximal series of three, which are named respectively radiale or tibiale, intermedium, and
ulnare or fibulare, a distal series of five, named catyjalia or tarsalia I — V, counting from the
preaxial border, and an interposed centrale.1 In man, as in nearly all mammals, the distal
row of the carpus and tarsus comprises only four bones, the unciform and cuboid, which
support the postaxial two digits, being generally regarded as formed by the fusion of the
fourth and fifth elements. Of the proximal elements of the carpus, the radiale is represented
in the scaphoid, the intermedium in the lunar, and the ulnare in the pyramidal. The centrale
appears to be absent in the carpus of man, although it occurs as a distinct bone in nearly all
apes. In the human foetus, however, at the latter part of the second month, a rudiment of
the centrale is present as a small cartilaginous nodule, which in the course of the third month
becomes fused with the cartilage of the scaphoid.2 The latter bone must therefore be regarded
1 Gegenbaur, " Untersuch. zur vergleich. Anat. ; I. Carpus und Tarsus," Leipzig, 1864.
2 Leboucq, " Recherches sur la morphologic du carpe chez les mammiferes," Arch, de Biologie,
v, 35.
144 MORPHOLOGY OF THE BONES OF THE LIMBS.
as composed of the radiale and the centrale. Traces of the central e are often to be recognized
in the adult scaphoid, and it may in rare cases be developed as a separate bone. In the
proximal series of the tarsus the course of development is somewhat different. The astragalus
results from the union of the tibiale and intermedium, although the latter occasionally
remains distinct as the os trigonum (p. 133) : at the back of the posterior articular surface on
the under aspect of the astragalus there is often to be seen a slight groove, indicative of this
separation (fig. 146). The fibulare forms the greater part of the os calcis, and the centrale of
the navicular bone. The pisiform bone has been considered a sesamoid bone (ulnare sesamoi-
dewn) developed in the tendon of the flexor carpi ulnaris, but recent investigations tend to
show that it is a vestige of a suppressed ray (digitus postminimus) : the corresponding
structure of the tarsus enters into tuberosity of the os calcis. On the outer margin of the
carpus there is in some animals another bone (radiale sesamoideum), which, if represented in
man, seems most nearly to correspond to the tuberosity of the scaphoid ; and the tuberosity of
the navicular bone of the tarsus may be the representative of a similar element (tibiale
sesamoideuni) in the foot. These so-called " sesamoid " ossifications are also regarded by
Bardeleben as vestiges of a suppressed digit (prepollex or prehallux).1
The following tables present a synoptical view of the probable corresponding or homolo-
gous bones and their parts in the thoracic and pelvic limbs : —
I. — TABLE OP THE HOMOLOGOUS BONES IN THE THORACIC AND PELVIC LIMBS.
THORACIC LIMB. PELVIC LIMB.
Scapula Ilium.
Precoracoid . . . . . . Pubis.
Coracoid Ischium.
Glenoid cavity . Cotyloid cavity.
Clavicle . . . . ' . . Absent.
Humerus ' . Femur.
Great tuberosity . . . . . . Small trochanter.
Small tuberosity . . . • . . Great trochanter.
External condyle and capitellum . . . Internal condyle.
Internal condyle and trochlea ... . External condyle.
Absent ... ... Patella.
Radius Tibia.
Ulna . . . . . . ... Fibula.
Carpus '. Tarsus.
Metacarpus Metatarsus.
Pollex Hallux.
Digital phalanges Digital phalanges.
II. — TABLE OF THE HOMOLOGOUS BONES OF THE CARPUS AND TARSUS.
CARPUS. Typical names. TARSUS.
Pyramidal . . Ulnare. . . Fibulare < Os calcis
Pisiform . . . Ulnare sesamoideum (?) Fibulare sesamoideum (.') . . )
Lunar . . . Intermedium Intermedium . . . . ) Astraffalus
(Radiale Tibiale JA
Scapho . . < Radiale sesamoideum (?) Tibiale sesamoideum (.') • ^ Navicular
( Centrale Centrale . . . . ) *
Trapezium . . " Carpale I. Tarsale I Int. Cuneiform.
Trapezoid . . — II. II Mid- Cuneiform.
Magnum . . HI. — HI Ext. Cuneiform.
Uncif orm . j ~ *V> ^ \ Cuboid.
1 According to another view, which is supported by Baur and Leboucq, the " tibial sesamoid " is the
tibiale, and the astragalus the intermedium only.
ADAPTATION OF SKELETON TO ERECT ATTITUDE.
145
III. — TABLE OP THE HOMOLOGOUS PAETS OF THE SCAPULA AND ILIUM (ACCOBDING
TO FLOWEE).
SCAPULA.
Supraspinous fossa . . .
Infraspinous fossa
Subscapular fossa .
Spine and acromion .
Superior or coracoid border.
Axillary or glenoid border ,
Superior anglj
Inferior angle
Primitive condition.
Vertebral surface .
Preaxial surface .
Postaxial surface .
Preaxial border .
Postaxial border
External border .
Dorsal extremity
ILIUM.
Sacral surface.
Iliac fossa.
G-luteal surface.
Ilio-pectineal line.
Posterior or ischial border.
Anterior or cotyloid border.
Iliac crest.
Posterior superior spine.
Anterior superior spine.
ADAPTATION OF THE SKELETON TO THE ERECT ATTITUDE.
The axial skeleton of man is, for the purposes of station and progression, raised more fully to
the vertical position than is the case in any other animal ; and along with this the lower limks
are extended in lines parallel to the axis of the trunk. The feet rest on the ground by the
contact of the heel and the heads of the metatarsal bones, the centre of gravity of the body
falling within the basis of support. For the maintenance of this attitude, the constant action
of the muscles passing over the ankle-joint is more immediately necessary. But at the knec-
and hip-joints it is mainly by the mechanism of the ligaments and other parts of the joints, and
less directly by muscular action, that the erect attitude is maintained, as will be more fully
shown in the description of the different articulations.
There are. besides, many peculiarities in the construction of the body, and especially of
the skeleton, which are associated with the assumption of the erect posture, and although
many of them have been noticed in the description of the bones, it may still be useful to re-
capitulate the chief ones briefly in this place.
It may first be remarked that the full development of these peculiarities belongs to the
adult condition. In the infant, while still unable to walk, the large proportional size of the
head, amounting to nearly a fifth of the whole body, the comparative straightness of the ver-
tebral column, or absence of the curves which characterise the spine of the adult, the short-
ness of the lower limbs, and incompleteness of their structure, all contribute to render the
assumption of the erect attitude by the child, for a time, difficult and insecure. Thus the
middle distance between the vertex of the head and the sole of the foot in an infant is situated
somewhat above the umbilicus, while in the adult it is generally at the upper border of the
pubis, or even lower, in some part of the symphysis. In the child also, from the large dimen-
sions of the head and upper part of the body, the centre of gravity is carried to a considerably
higher point than in the adult.
The skull of man differs from that of other animals in being nearly balanced on the vertebral
column, the condyles of the occipital bone being brought forwards to near the middle of the
base by the comparative shortness of that part of the skull which lies in front of the foramen
magnum, and the projection backwards of that which lies behind it. In quadrupeds the skull
extends forwards from the extremity of the column, and is sustained by the elastic ligamentum
nuchae, represented in man by a comparatively feeble structure which passes between the ex-
ternal occipital protuberance, and the spinous processes of the cervical vertebras. Together
with this altered relation of the head to the spine, the plane of the foramen magnum, which
in quadrupeds is vertical, becomes in man horizontal, or even inclined somewhat upwards
anteriorly.
The spinal column, by its pyramidal form, is fitted to sustain the weight which bears down
upon its lower part, and by means of its different curvatures possesses elasticity and strength
combined, and allows considerable range of motion to the trunk, without removal of the centre
of gravity from within its base. The strong and expanded sacrum, is the immediate means of
transferring the weight of the trunk to the hip-bones and lower limbs.
The thorax in man is comparatively short, compressed in the sagittal direction, and ex-
panded transversely, whereby the centre of gravity is carried backwards, nearer to the spine.
The pelvis is of peculiar breadth in man, presenting an upper and a lower arch which meet
at the hip- joints, and is so inclined that a vertical line descending from the centre of gravity
of the body is in a plane slightly behind the centres of motion of the hip-joints. The breadth
of the pelvis enables the balance to be more easily maintained in lateral movements of the
body by compensating inclinations of different parts to opposite sides of the basis of support,
and the long neck of the femur gives an advantageous insertion to the muscles by which the
146 ADAPTATION OF SKELETON TO ERECT ATTITUDE.
balance of the body is principally preserved. The hip-bone is mainly distinguished from the
same bone in animals by the breadth of its iliac portion, which gives support to the abdominal
viscera, and attachment to the greatly developed iliac and gluteal muscles.
The lower limbs are remarkable for their length and strength. The femur is greatly
elongated, its length considerably exceeding that of the tibia, — a condition which is requisite
not only to give a sufficient extent of stride, but also to enable the body to be balanced in dif-
ferent degrees and varieties of stooping. The foot of man alone among animals has an arched
instep, and it likewise presents a great breadth of sole. The great toe is distinguished by its
full development, and especially from that of the apes, by its want of opposability,
being constructed, not for grasping, but for supporting the weight of the body, and giving
spring to the step.
While stability and strength are thus provided in the lower limbs, mobility and lightness
are secured in the upper. This is apparent on comparison of the shoulder, elbow, and wrist,
with the hip, knee, and ankle. In the hand, also, the freely moveable phalanges are as long
as the carpal and metacarpal bones taken together, while in the foot they are not a third of
the length of the tarsal and metatarsal bones.
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Assistant-Professor of Chemistry in, University College, London ; and M. M.
PATTISON MUIR, M.A., F.R.S.E., Fellow, and Prelector in Chemistry,
of Gonville and Caius College, Cambridge. Assisted by Eminent Contributors.
To be Published in 4 Vols. Svo. Vols. I. II. 42*. each. Vol. III. $os.
[Now ready.
WEBB. CELESTIAL OBJECTS FOR COMMON TELESCOPES.
By the Rev. T. W. WEBB, M.A. Fourth Edition, adapted to the Present
State of Sidereal Science ; Map, Plate, Woodcuts. Crown Svo, price gs.
WILLIAMS. MANUAL OF TELEGRAPHY. By W. WILLIAMS,
Superintending Indian Government Telegraphs. With 93 Woodcuts. Svo,
WRIGHT. OPTICAL PROJECTION : A Treatise on the Use of the
Lantern in Exhibition and Scientific Demonstration. By LEWIS WRIGHT,
Author of "Light: a Course of Experimental Optics." With 232 Illustra-
tions. Crown Svo, 6s.
5000.9.92. BRADBURV, AGNEW, & CO. LD., PRINTERS, WHITEFRIARS.
DATE DUE SLIP
UNIVERSITY OF CAIJFORNIA MEDICAL SCHOOL LIBBARY
THIS BOOK IS DUE ON THE LAST DATE
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