_a_, Quadriceps femoris; _b_, gastrocnemius, external head; _c_,
superficial digital flexor; _d_, deep digital flexor; _e_, peroneus
longus; _f_, tendon of lateral extensor; _g_, peroneus brevis; _h_,
long or anterior digital extensor; _h′_, _h″_, _h‴_, tendons of
preceding; _i_, tibialis anterior; _k_, extensor brevis; _l_, slips
from interossei (_m_); _1_, external condyle of femur; _2_, patella;
_3_, tibia; _4_, tuber calcis; _5_, _6_, annular ligaments. (After
Ellenberger, in Leisering’s Atlas.)
]
The =deep digital flexor= has two heads. The large outer head, the
=flexor hallucis longus=, arises from the tibia and fibula, filling the
interosseous space. The small inner head, =flexor digitalis pedis
longus=, also arises from the tibia and fibula, its tendon joining that
of the large head below the tarsus. The common tendon detaches a branch
to the large digital pad and terminates as in the fore limb.
The =tibialis posterior= is a small but distinct muscle, which arises on
the proximal part of the fibula. The thin tendon accompanies that of the
flexor longus and ends on the internal lateral ligament of the tarsus.
The tendon of the =popliteus= contains a small sesamoid bone.
The =adductors of the second and fifth digits=, the =lumbricales=, and
the =interossei= are arranged as in the thoracic limb.
The =quadratus plantæ= arises on the outer surface of the distal end of
the fibular tarsal bone and on the lateral tarsal ligament, passes
downward and inward, and terminates on a thin tendon which fuses with
that of the deep flexor.
The =abductor digiti quinti= is a very small muscle which consists of
two parts. One of these is a tendinous slip which extends from the
posterior surface of the proximal part of the fibular tarsal bone to the
head of the fifth metatarsal bone; the other part arises from the inner
surface of the fibular tarsal bone (or from the tendinous part) and ends
on the first phalanx of the fifth digit.
In case the skeleton of the first digit is well developed, there are
found three muscles homologous with those of the same digit in the fore
limb. These are the =abductor hallucis=, =adductor hallucis=, and
=flexor hallucis brevis=.