_A_, Tibia; _B_, fibula; _a_, external condyle of tibia; _b_, spine;
_c_, crest of tibia; _d_, muscular notch; _e_, internal malleolus;
_f_, head of fibula; _g_, interosseous space; _h_, external
malleolus (distal end of fibula); _i_, groove for tendon.
(Ellenberger-Baum, Anat. d. Hundes.)
]
The symphyseal part of the =pubis= is thick and fuses late with the
opposite bone. There is no subpubic groove.
The =acetabulum= is about twice as far from the external angle of the
ilium as from the tuber ischii. The fossa acetabuli is deep, and is
bounded internally by a flat plate of bone; its floor is so thin as to
be translucent. There is a small notch behind.
The =obturator foramen= resembles in outline an equilateral triangle
with the angles rounded off.
[Illustration:
FIG. 137.—SKELETON OF DISTAL PART OF PELVIC LIMB OF DOG, EXTERNAL
VIEW.
_6_, Tibial tarsal bone; _7_, fibular tarsal; _8_, central tarsal;
_9_, second tarsal; _10_, third tarsal; _11_, fourth tarsal; _12_,
metatarsal bones; _13_, first phalanx. The first tarsal bone is not
visible in the figure. (After Leisering’s Atlas.)
]
The inlet of the =pelvis= is very oblique. It is almost circular in the
female, but in the male it is elliptical and the conjugate diameter is
the longer. The cavity is narrowest between the acetabula, and very wide
behind. The floor is concave and relatively narrow in front, wide and
flat behind.
The =femur= is relatively much longer than in the horse or ox. The shaft
is regularly cylindrical, except near the extremities, where it is wider
and compressed from before backward. It is strongly curved in its lower
two-thirds, convex in front. The posterior surface is flattened
transversely, narrow in the middle, and widens toward each end. It is
bounded by two rough lines (Labium laterale, mediale) which diverge
toward the extremities. The third trochanter and the plantar
(supracondyloid) fossa are absent. There are two supracondyloid crests,
the inner one being small. The nutrient foramen is in the upper third of
the posterior surface. The head is a little more than a hemisphere and
has a shallow depression behind and external to its center. The neck is
well defined. The trochanter major does not extend as high as the head;
a thick ridge runs from its anterior surface to the neck. The internal
trochanter has the form of a blunt tuberosity. The trochanteric fossa is
round and deep. The ridges of the trochlea are practically sagittal in
direction and are almost similar. The intercondyloid fossa is wide. Just
above each condyle posteriorly there is a facet for articulation with
the sesamoid (of Vesal), which is developed in the origin of the
gastrocnemius muscle.
The =tibia= is about the same length as the femur. The shaft forms a
double curve; the upper part is convex internally, the lower part
externally. The proximal third is prismatic, but is compressed laterally
and is long from before backward. The remainder is almost regularly
cylindrical. The crest is short but very prominent. The nutrient foramen
is usually in the upper third of the external border. The tuberosity is
not grooved, but bears a distinct mark where the ligamentum patellæ is
attached. There is a small facet for the fibula on the postero-external
part of the external condyle, and a small sesamoid bone in the tendon of
origin of the popliteus is in contact with the posterior angle of the
latter. The distal end is quadrangular and relatively small. The
articular grooves and ridge are almost sagittal. There is a facet
externally for articulation with the fibula. There is a vertical groove
internally and a shallower one behind—both for tendons.
The =fibula= extends the entire length of the region. It is slender,
somewhat twisted, and enlarged at either end. The upper part of the
shaft is separated from the tibia by a considerable interosseous space,
but the lower part is flattened and closely applied to the tibia. The
proximal end is flattened and articulates with the external condyle of
the tibia. The distal end is somewhat thicker and forms the external
malleolus. It articulates internally with the tibia and the tibial
tarsal bone. Externally it bears two tubercles.
The =patella= is long and narrow. The anterior surface is convex in both
directions. The articular surface is convex from side to side and
slightly concave from above downward.
The =tarsus= comprises seven bones. The tibial tarsal consists of a
body, neck, and head, like the bone in man. The body presents a trochlea
above for articulation with the tibia and fibula. The posterior surface
has three facets for articulation with the fibular tarsal bone. The head
is directed a little inward and articulates with the central. The
fibular tarsal has a long anterior process or “beak,” but the inner
process (sustentaculum) is short. The tuber calcis is grooved from
before backward. The central has a concave proximal surface adapted to
the head of the tibial tarsal. Its distal surface articulates with the
first, second, and third tarsals. It bears two tubercles posteriorly.
The first tarsal is flattened and irregularly quadrangular; it
articulates above with the central and below with the first metatarsal.
The second tarsal is the smallest and is wedge-shaped; it articulates
below with the second metatarsal bone. The third tarsal is also
wedge-shaped, the base being in front; it articulates with the third
metatarsal below. The fourth tarsal is remarkably high, and resembles a
quadrangular prism; it articulates with the fibular tarsal above, the
fourth and fifth metatarsal below, and the central and third tarsal
bones internally. A groove for the tendon of the peroneus longus crosses
its outer and posterior surface, and above it are one or two tubercles.
Five =metatarsal bones= are present. The first is commonly very small
and has the form of a blunt cone, somewhat compressed laterally. It
articulates with the first tarsal and furnishes insertion to the
tibialis anterior muscle. In some cases it fuses with the first tarsal;
when the first digit is well developed, its metatarsal may resemble the
others (except in size) or be reduced in its proximal part to a fibrous
band. The other metatarsals are a little longer than the corresponding
metacarpals. Their proximal ends are elongated from before backward and
have posterior projections, which in the case of the third and fourth
usually bear facets for articulation with two small rounded sesamoid
bones. In other respects they resemble the metacarpals.
The first digit is often absent. When present, its development varies
and it contains one or two phalanges. In other cases the digit is
double. The phalanges of the other digits resemble those of the fore
limb.