MUSCLES OF THE PELVIC LIMBS. 207 
which separates them from the overlying muscles. This fascia 
stretches from the dorsal border of the tibia about the ventral 
side of the shank to the medial border of the tibia. It sends 
a slip beneath the border of the fibula. 
M. flexor longus digitorum (Fig. 91, # and ).—Owing 
to the reduction of the first digit in the cat the tendon of the 
flexor longus hallucis (#2) has become united to that of the 
flexor longus digitorum (z), so that the two might be considered 
separate heads of a single muscle. The head corresponding 
to the flexor longus hallucis (m) is much larger than that corre- 
sponding to the flexor longus digitorum (z). The two heads 
will be described separately. 
(1) M. flexor longus hallucis (Fig. 91, m).—This lies 
against the ventral surface of the tibia and fibula beneath the 
popliteus (Fig. 92, £) and soleus (Fig. 90, 0). 
Origin by fleshy fibres, (1) from the sheet of deep crural 
fascia which dips between it and the tibialis posterior (Fig. 
91, 0) and the flexor longus digitorum (7). (2) From the ven- 
tral surface of the tibia distad of the lateral oblique line to within 
one to three centimeters of the distal end of the shaft. (3) From 
the medial surface of the shaft and head of the fibula and from 
the whole interosseous ligament. On the fibular side the origin 
may extend onto the tendon of the popliteus and the fascia of 
the peroneus longus. The fibres form a flat fusiform mass 
ending one centimeter from the heel in a strong flat tendon 
(m’') which passes over the groove on the distal surface of the 
astragalus and over the groove on the sustentaculum tali. The 
two grooves are converted into a continuous canal. by strong 
transverse ligaments, and the canal is lined by an extension of 
the synovial bursa of the ankle-joint. Emerging from the 
canal the tendon broadens and receives on its medial side the 
insertion of the tendon of the flexor longus digitorum (z). The 
tendon gives origin on its outer surface to the lumbricales and 
to the common plantar ligament. The tendon continues to 
broaden until it reaches the middle of the length of the meta- 
carpals; here it divides into four tendons which pass to the 
terminal phalanges of the digits. 
Insertion.—The relations of the four tendons and their 
