MUSCLES OF THE PELYIC 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, m and ;/). Owing 

 to the reduction of the first digit in the cat the tendon of the 

 flexor longus hallucis (;) has become united to that of the 

 flexor longus digitorum (//), 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 (n). The two heads 

 will be described separately. 



(i) M. flexor longus hallucis (Fig. 91, m). This lies 

 against the ventral surface of the tibia and fibula beneath the 

 popliteus (Fig. 92, k] and soleus (Fig. 90, o]. 



Origin by fleshy fibres, (i) from the sheet of deep crural 

 fascia which dips between it and the tibialis posterior (Fig. 

 91, o) and the flexor longus digitorum (). (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 

 (?') 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 (). 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 



