_a_, Tibialis anterior; _a′_, tendon of preceding; _b_, peroneus
tertius; _b′_, tendon of _b_; _c_, anterior or long digital
extensor; _d_, _e_, _f_, _f′_, _f″_, tendons of _c_; _g_, peroneus
longus; _g′_, tendon of _g_; _h_, extensor digiti quarti; _h′_,
tendon of _h_, which receives _h″_, from the interosseus medius;
_i_, extensor digiti quinti; _k_, deep digital flexor; _l_, soleus;
_m_, gastrocnemius; _n_, extensor brevis. (After Ellenberger, in
Leisering’s Atlas.)
]
The =peroneus longus= lies partly on the outer surface of the peroneus
tertius. Its tendon crosses those of the lateral extensor, passes along
a groove on the plantar surface of the fourth tarsal bone, and ends on
the first tarsal and second metatarsal bones.
The =anterior= or =long digital extensor= arises with the peroneus
tertius and is largely covered by it and the peroneus longus. It divides
into three parts. The tendon of the =inner division= (M. extensor digiti
tertii) ends on the =inner chief= (third) =digit=; that of the =middle
division= by two branches on the =principal digits=; and that of the
=outer division= by three branches on the =second=, =fourth=, and =fifth
digits=.
The =lateral digital extensor= divides into proper extensors of the
=fourth= and =fifth digits= (Extensores digiti quarti et quinti).
The =extensor hallucis longus= arises on the fibula and ends on the
=inner small= (second) =digit=.
The =extensor digitalis brevis= is well developed and consists of three
parts. The inner and outer tendons end on the first phalanges of the
chief digits, the middle one joins the common extensor tendon of the
same.
The =gastrocnemius= presents nothing special.
The =soleus= is wide, and is partly blended with the external head of
the gastrocnemius.
The =superficial digital flexor= has a large belly. Its tendon ends on
the two chief digits, and is also connected with the ligaments of the
accessory digits.
The =inner head= of the =deep digital flexor= (flexor digitalis longus)
is relatively small. The common tendon ends as in the thoracic limb.
The =popliteus= presents no special features.
The =plantar muscles= resemble their homologues of the fore limb, except
that the adductors of the accessory digits and the lumbricales are
absent.