96 DISSECTION OP THE DOG 



gradually passing on the medial side of the gastrocnemius tendon, it ultimately 

 comes to be the more superficial. 



Two slips attach the plantaris tendon to the side of the tuber calcanei, 

 from which point there is an apparent direct continuation of the tendon into 

 the pes. This appearance, however, depends upon a modification of the short 

 flexor of the digits (m. flexor digitorum brevis), which will receive consideration 

 later. 



N. TIBIALIS. — The larger of the two terminal branches of the sciatic, the 

 tibial nerve accompanies the peroneal nerve for a Httle distance, and then 

 enters the gap between the two heads of the gastrocnemius muscle. Following 

 the border of the plantaris muscle underneath the medial head of the gastro- 

 cnemius, the nerve comes into relation with the posterior branch of the 

 saphenous artery ; and in the distal part of the leg it becomes associated 

 with the deep flexor of the digits which it accompanies to the tarsus. 



The branches of the tibial nerve are as follows : (1) Medial cutaneous nerve. 

 of the calf (n. cutaneus surse medialis) , which has already been examined ; (2) 

 branches (rami musculares), large and numerous, for the supply of all the 

 muscles behind the tibia ; (3) medial 'plantar nerve (n. plantaris mediaUs) ; 

 (4) lateral flantar nerve (n. plantaris lateralis). The medial and lateral plantar 

 nerves form the terminal branches of the tibial, and are distributed in the 

 sole of the pes, where they will be examined at the proper time. 



Dissection. — Reflect the plantaris muscle and expose the deep muscles of 

 the leg. These are three in number. The most lateral really consists 

 of two muscles — m. flexor hallucis longus and m. flexor digitorum longus — 

 but will be more conveniently referred to as the deep flexor of the digits. 



M. FLEXOR DIGITORUM PROFTJNDLTS. — The deep flexor of the digits arises 

 from the head of the fibula and the proximal half of the border of this bone, 

 from the lateral condyle of the tibia, from the proximal part of the posterior 

 surface of the tibia, and from the interosseous membrane. The tendon of the 

 m. flexor hallucis longus begins about the junction of the middle and distal 

 thirds of the leg and passes down the groove formed by the calcaneus. The much 

 smaUer tendon of the m. flexor digitorum longus is more medial and passes down 

 the groove on the medial malleolus, in which it is bound by an annular Hgament. 



M. TIBIALIS POSTERiOE. — The posterior tibial muscle is very rudimentary. 

 Arising from the head of the fibula under cover of the long flexor of the digits, 

 its feeble tendon, following that of the long flexor, finally blends with the 

 medial collateral ligament of the tarsus. 



M. POPLiTEirs. — The pophteal muscle covers part of the flexor aspect of 

 the articulation between the femur and tibia. Its origin is within the capsule 

 of the joint from the lateral condyle of the femur (sesamoid). The fibres of 

 the muscle spread out to find attachment to a triangular surface on the 

 proximal posterior part of the tibia. 



