The =scapula= is more regularly triangular than in the horse, relatively
wider at the vertebral end and narrower at the lower end. The scapular
index is about 1 ∶ 0.6. The spine is more prominent and is placed
further forward, so that the supraspinous fossa is narrow and does not
extend to the lower part of the bone. The spine is sinuous, bent
backward in its middle, forward below. Its free border is somewhat
thickened in its middle, but bears no distinct tubercle. Instead of
subsiding below as in the horse the spine becomes a little more
prominent, and is prolonged by a pointed projection, the =acromion=,
from which part of the deltoid muscle arises. The subscapular fossa is
shallow. The areas for the attachment of the serratus muscle are not
very distinct. The nutrient foramen is usually in the lower third of the
posterior border. The glenoid cavity is almost circular and without any
distinct notch. The tuberosity is small and close to the glenoid cavity.
The coracoid process is short and rounded. The cartilage resembles that
of the horse.
The =humerus= has a shallow musculo-spiral groove. The deltoid
tuberosity is less prominent than in the horse, and the curved line
running from it to the neck bears a well-marked tubercle on its upper
part. The nutrient foramen is usually in the lower third of the
posterior surface. The external tuberosity is very large, and rises an
inch or more (ca. 3 cm.) above the level of the head. Its anterior part
curves inward over the bicipital groove, and below it externally there
is a prominent circular rough area for the insertion of the tendon of
the supraspinatus. The anterior part of the internal tuberosity has a
small projection which curves over the groove. The groove is undivided.
The distal articular surface is decidedly oblique, and the grooves and
ridge are very well marked. The coronoid and olecranon fossæ are deep
and wide. The external condyloid crest is represented by a rough raised
area. The proximal end unites with the shaft at three and one-half to
four years, and the distal at about one and one-half years.
The =radius= is short and relatively broad. It is somewhat oblique, the
lower end being nearer the median plane than the upper. The curvature is
more pronounced below than above. The shaft is prismatic in its middle
part and has anterior, external, and posterior faces. There is a marked
increase in width and thickness below. The proximal articular surface
presents a synovial fossa which extends inward from the deep groove
between the two glenoid cavities. The bicipital tuberosity is
represented by a slightly elevated rough area. The posterior facets for
the ulna are larger than in the horse. The two bones commonly fuse above
the proximal interosseous space and always fuse below it, except near
the distal end, where there is a small distal interosseous space. A
groove connects the two spaces externally. The distal extremity is
large, and is thickest internally. Its articular surface is oblique in
two directions, _i. e._, from within upward and backward. The grooves
for the extensor tendons are shallow. The proximal end unites with the
shaft at one to one and one-half years, and the distal at three and
one-half to four years.
The approximation of the lower ends of the forearms and the carpi
gives the “knock-kneed” appearance in cattle. The obliquity of the
joint surfaces produces lateral deviation of the lower part of the
limb in flexion. The facets for the radial and intermediate carpals
are narrower than in the horse and run obliquely forward and outward.
The surface for the ulnar carpal is extensive and saddle-shaped; its
outer part is furnished by the ulna.
[Illustration:
FIG. 99.—SKELETON OF LEFT FORE LIMB OF OX, FROM SHOULDER DOWNWARD,
ANTERIOR VIEW. (After Ellenberger-Baum, Anat. für Künstler.)
]
The =ulna= is more fully developed than in the horse. The shaft is
complete, three-sided, and strongly curved. It is fused with the radius
in the adult, except at the two interosseous spaces mentioned above. Its
upper part contains a medullary canal which extends somewhat into the
proximal end. The olecranon is large and bears a rounded tuberosity
above. The distal end is fused with the radius; it projects below the
level of the latter, forming the =styloid process= (Processus styloideus
ulnæ), which furnishes part of the facet for the ulnar carpal. The
proximal and distal ends unite with the shaft at three and one-half to
four years.
[Illustration:
FIG. 100.—SKELETON OF LEFT FORE LIMB OF OX, FROM ELBOW DOWNWARD,
EXTERNAL VIEW. (After Ellenberger-Baum, Anat. für Künstler.)
]
The =carpus= consists of six bones, four in the upper row, and two in
the lower. The upper row is oblique in conformity with the carpal
articular surface of the radius. The radial and intermediate resemble in
general those of the horse, but are less regular in shape, and their
long axes are directed obliquely backward and inward. The radial is
narrower than in the horse and curves upward behind. The intermediate is
constricted in its middle, and wider behind than in front. The ulnar is
large and very irregular. Its proximal surface is extensive and sinuous
and articulates with both radius and ulna. Behind is a large oval facet
for articulation with the accessory carpal. The accessory is short,
thick, and rounded; it articulates with the ulnar carpal only. The first
carpal is absent. The second and third carpals are fused to form a large
quadrilateral bone. The fourth carpal is a smaller quadrilateral bone.
The =metacarpus= consists of a large metacarpal and an external small
metacarpal bone. The large metacarpal bone (Mc. 3 + 4) results from the
fusion of the third and fourth bones of the fœtus, and bears evidences
of its double origin even in the adult state. The shaft is shorter than
in the horse, and is relatively wider and flatter. The anterior surface
is rounded, and is marked by a vertical vascular groove connecting two
canals which traverse the ends of the shaft from before backward. The
posterior surface is flat and presents a similar but much fainter
groove. The borders are rough in the upper third. The proximal end bears
two slightly concave facets for articulation with the bones of the lower
row of the carpus; the inner area is the larger, and they are separated
by a ridge in front and a notch behind. The outer angle has a facet
behind for the small metacarpal bone. The inner part of the extremity
has anterior and posterior tuberosities. The distal end is divided into
two parts by a sagittal notch. Each division bears an articular surface
similar to that in the horse, but much smaller. The =medullary canal= is
divided into two parts by a =vertical septum= which is usually
incomplete in the adult.
The =small metacarpal= bone (Mc. 5) is a rounded rod about an inch and a
half (ca. 3.5 to 4 cm.) in length, which lies against the upper part of
the outer border of the large bone. Its upper end articulates with the
latter, but not with the carpus. The lower end is pointed.
Four cartilaginous metacarpals are present in the early fœtal state,
viz., the second, third, fourth, and fifth. The second commonly either
disappears or unites with the third; sometimes it develops as a small
rod of bone. The third and fourth gradually unite, but can be cut
apart at birth. Each has three centers of ossification; the proximal
epiphysis fuses with the shaft before birth, the distal at two to two
and one-half years.
Four =digits= are present in the ox. Of these, two—the third and
fourth—are fully developed and have three phalanges and three sesamoids
each. The second and fifth are vestiges and are placed behind the
fetlock; each contains one or two small bones which do not articulate
with the rest of the skeleton.
The =first phalanges= are shorter and narrower than in the horse and are
three-sided. The interdigital surface is flattened and its posterior
part bears a prominence for the attachment of the interdigital
ligaments. The proximal extremity is relatively large, and is somewhat
compressed from side to side. The articular surface is concave from
before backward and is divided by a sagittal groove into two areas, of
which the abaxial one is the larger and higher. Behind these are two
facets for articulation with the sesamoid bones. The posterior surface
bears two tuberosities separated by a deep depression. The distal
extremity is smaller than the proximal, especially in the
antero-posterior direction. Its articular surface is divided by a
sagittal groove into two convex facets, of which the abaxial one is
decidedly the larger. There are depressions on either side for
ligamentous attachment. The bone consists at birth of two pieces—the
distal end and the fused shaft and upper extremity. Union occurs at one
and one-half to two years.
The =second phalanges= are about two-thirds of the length of the first
and are distinctly three-sided. The proximal articular surface is
divided by a sagittal ridge into two glenoid cavities, of which the
abaxial one is much the larger. There is a central prominence in front
and two lateral tubercles behind. The distal extremity is smaller than
the proximal. Its articular surface encroaches considerably on the
anterior and posterior surfaces, and is divided into two lateral parts
by a groove. There is a deep depression for ligamentous attachment on
the interdigital side. The bone contains a small medullary canal. The
distal end unites with the rest of the bone about the middle of the
second year.
The =third phalanges= resemble in a general way one-half of the bone of
the horse. Each has four surfaces. The dorsal or wall surface is marked
in its lower part by a shallow groove, along which there are several
foramina of considerable size; the posterior one of the series is the
largest, and conducts to a canal in the interior of the bone. Below the
groove the surface is prominent, rough, and porous. Near and on the
extensor process are several relatively large foramina. The slope of the
surface is very steep posteriorly, but in front it forms an angle of 25
to 30 degrees with the ground plane. The articular surface is narrow
from side to side, and slopes downward and backward. It is also oblique
transversely, the interdigital side being the lower. It is adapted to
the distal surface of the second phalanx, with the exception of a facet
behind for the distal sesamoid. The extensor process is very rough. The
volar or sole surface is narrow and slightly concave, and presents two
or three foramina of considerable size. It is separated from the wall
surface by a border which is sharp in front, rounded behind. There is no
semilunar crest, since the deep flexor tendon is attached to the thick
posterior border of the sole surface. The interdigital surface is smooth
and grooved below, rough and porous above. At the upper angle it is
perforated by a large foramen, which is equivalent to the volar foramen
of the horse and leads to a cavity in the middle of the bone. The
surface is separated by a rounded border from the wall surface, and by a
sharp edge from the sole surface. The wing or angle is very short and
blunt, and there is no lateral cartilage.
Four =proximal sesamoids= are present, two for each digit. They are much
smaller than in the horse. The bones of each pair articulate with the
corresponding part of the distal end of the large metacarpal bone by
their anterior surfaces, with each other and with the first phalanx by
small facets.
The two =distal sesamoids= are short and their ends are but little
narrower than the middle.