[Illustration:
FIG. 459.—DEEP DISSECTION OF RIGHT STIFLE, LEG, AND HOCK OF HORSE,
POSTERIOR VIEW.
The hock is flexed at a right angle, and the tuber calcis is sawn off.
The tibial nerve is drawn inward to show its muscular branches.
Branches of tibial nerve: _1_, _2_, to gastrocnemius; _3_, _4_, to
superficial flexor; _5_, to popliteus; _6_, to flexor longus or
accessorius; _7_, to deep flexor. (After Schmaltz, Atlas d. Anat. d.
Pferdes.)
]
[Illustration:
FIG. 460.—SUPERFICIAL DISSECTION OF RIGHT STIFLE, LEG, AND HOCK OF
HORSE, FRONT VIEW. (After Schmaltz, Atlas d. Anat. d. Pferdes.)
]
The =anterior tibial artery= (A. tibialis anterior) is much the larger
of the two terminal branches of the popliteal. It passes forward through
the upper part of the interosseous space and descends with two satellite
veins on the outer part, of the front of the tibia, under cover of the
tibialis anterior. At the lower part of the leg it deviates to the outer
border of the tendon of this muscle, passes on to the capsule of the
hock joint, gives off the perforating tarsal artery, and is continued
asthe great metatarsal artery. It gives off =muscular branches= to the
dorso-lateral group of muscles of the leg and =articular branches= to
the hock. The =peroneal= branch (A. peronea) is a variable vessel which
descends along the fibula under the lateral extensor; it gives off
muscular branches and one which perforates the fascia and divides into
ascending and descending cutaneous twigs.
The =perforating tarsal artery= (A. tarsea perforans) is given off under
cover of the outer tendon of the peroneus tertius. It passes backward
through the vascular canal of the tarsus with a satellite vein and
unites on the upper part of the suspensory ligament with the plantar
arteries (or only with the external plantar) to form the plantar arch.
In well-injected specimens it is seen that there is a fine arterial
network (Rete tarsi dorsale) on the flexor surface of the hock, which is
formed by twigs from the anterior tibial and lateral tarsal arteries.
From it proceed two very slender =dorsal metatarsal arteries=. The inner
one descends in the furrow between the inner small and large metatarsal
bones, and anastomoses usually in the proximal part of the metatarsus
with the internal superficial plantar metatarsal, uniting sometimes with
the deep plantar metatarsal. The external vessel passes down under the
periosteum on the anterior face of the large metatarsal bone and becomes
lost or joins the large metatarsal artery.
Sometimes the anterior tibial artery passes undivided through the
tarsus, gives off the internal deep plantar metatarsal, and is
continued as a very large internal superficial plantar metatarsal
along the deep flexor tendon, thus resembling the arrangement in the
fore limb.
In a few cases the perforating tarsal is a large vessel, directly
continuing the anterior tibial, and is continued by a large internal
deep plantar metatarsal. The great metatarsal is then small. Other
variations are common.