THE PIGEON. 253 



which arises from the proximal end of the tarso-metatarsus. 

 Distally the extensor tendons run along the dorsal sides of 

 the digits, closely bound down by fascia, and are inserted 

 into the bases of the distal phalanges. 



329. The gastrocnemius, a large muscle consisting of 

 distinct internal and external portions, and forming the 

 outer layer of the fleshy mass on the posterior surface of the 

 shank : its two heads arise respectively from the inner and 

 outer surfaces of the proximal end of the tibia, the internal 

 head arising also from the distal end of the femur : the two 

 heads unite in a broad, flat tendon, which is inserted into the 

 proximal end of the posterior surface of the tarso-metatarsus : 

 its action is to straighten the foot on the shank. 



330. The flexor tendons of the digits, a large number 

 of readily separable tendons on the posterior (ventral) 

 surface of the tarso-metatarsus : traced into the leg they 

 are found to be the distal tendons of a number of separate 

 muscles, the flexores digitorum, which arise from the 

 posterior and lateral surfaces of the tibia ; to see them the 

 gastrocnemius should be cut through and reflected. Distally, 

 the flexor tendons can be traced into the toes, either two or 

 three to each (see 331 334)- 



331. In the fourth or outermost toe there are two flexor tendons, 

 one being superficial or ventral to the other : the superficial or per- 

 forated tendon (springing from the flexor perforatus muscle) sends 

 off lateral slips to the proximal phalanx, and then forks, one division 

 going to each side of the second and third phalanges : the deep or 

 perforating tendon, lying between the former and the bone, passes 

 between the division of the perforatus, along the ventral surface of the 

 phalanges, and is inserted into the proximal end of the distal phalanx. 



332. In the third digit the arrangement is complicated by the presence 

 of two perforated tendons : of these the bifurcations of one are inserted 

 into the proximal, those of the other into the second, phalanx : so that 

 through the fork of the first or superficial perforated tendon both the 

 second perforated and the perforating tendons pass. 



