Zoological Society, 229 



muscle, where they end in a strong subcompressed tendon. This joins 

 its fellow tendon, from the internal gastrocnemius, behind the ankle- 

 joint, and both expand into a thick, strong, ligamentous aponeurosis, 

 which extends over three-fourths of the posterior part of the tarso- 

 metatarsal joint. The lateral margins of this fascia are bent down 

 under the flexor tendons behind the joint, and become continuous 

 with a strong ligamentous layer gliding upon the posterior surface 

 of the distal condyles of the tibia, and attached to the tendons of the 

 peroneus and tibialis anticus ; the conjunction of the thickened ten- 

 dons of the gastrocnemii with this deeper-seated layer of ligamento- 

 tendinous substance constitutes a trochlear sheath lined by synovial 

 membrane, through which the flexor tendons of the toes glide. The 

 synovial membrane of the ankle-joint is continued upwards half 

 an inch above the articular surface of the bone, between it and the 

 cartilaginous pulley. Below the joint the margins are inserted into 

 the lateral ridges of the tarso-metatarsal bone, becoming gradually 

 thinner as they descend, and ending below in a thin semilunar edge 

 directed downwards. 



The gastrocnemius internus has two powerful heads, one from the 

 femur, the other from the tibia ; the first arises fleshy from the in- 

 ternal condyle of the femur, expands as it descends, and receives 

 additional fibres from the lower edge of the accessorius semitendi- 

 nosi. About one-fifth down the tibia, this muscular origin, in the 

 right leg, terminated in a short flattened tendon, which became at- 

 tached to the inner side of the tibial portion of the gastrocnemius 

 internus. In the left leg the tendon soon divided ; one portion 

 passed to the soleus, the other went to join the tibial portion of the 

 gastrocnemius internus. The second head, which is separated from the 

 preceding by the insertion of the semitendinosus , arises partly from 

 the internal and anterior part of the strong fascia of the knee-joint by 

 short tendinous fibres, which almost immediately become fleshy, and 

 partly from a well-defined triangular surface on the inner and ante- 

 rior aspect of the head of the tibia : the fleshy fibres converge, 

 receive the tendinous slip from the femoral portion, and end on the 

 inner side of the muscle in a strong flattened tendon, about two- 

 thirds down the leg : this joins the tendon of the gastrocnemius ex- 

 ternus, and is inserted as described above. 



Soleus. — A slender flattened muscle arising from the inner and 

 posterior side of the tibia, the tendon of which joins that of the gas- 

 trocnemius internus, behind the tarsal joint. 



The flexor perforatus of the inner toe lies immediately anterior 

 to the external gastrocnemius ; it arises fleshy from the outer condyle 

 of the femur, below the tendinous origin of that muscle, and terminates 

 in a slender flat tendon half-way down the leg. Its tendon glides 

 behind the tarsal joint through the sheath of the gastrocnemius, ex- 

 pands beneath the metatarsal joint, perforates the flexor of the proxi- 

 mal phalanx of the third toe, and then bifurcates to be attached to 

 the sides of the second phalanx, giving passage to the perforans tendon 

 of the last phalanx. 



Flexor perforatus of the middle toe. — This arises by very short 

 tendons from the proximal end of the fibula, and from the ligament 



