THE MUSCLES OF THE LOWER EXTREMITY. 251 



" the flexor perforatus annularis primus pedis (com- 

 pare Figs. 63 bis with 65 bis) in this bird seems to have 

 acquired a more central position on the back of the leg 

 than in many others that I have dissected, and, more- 

 over, its tendon, as will be seen from the figures, is quite 

 superficial. 



" It arises from between the condyles of the femur by 

 a slight semitendinous slip, and from the side of the 

 flexor long us hallucis. The muscle itself is somewhat 

 of a fusiform outline and rather flat ; it lies to the inner 

 side of the loop for the biceps. About one-third of the 

 way down the back of the leg it terminates in a small 

 though very long tendon, which, passing quite super- 

 ficially through the tibial cartilage and over the ankle- 

 joint and hypotarsus, runs in common with the other 

 flexors down the back of the tarso-metatarsus, turns to 

 the rear in the sole of the foot to become inserted on the 

 under side of the distal end of the basal phalanx of the 

 reversed digit. In the specimen before me this insertion 

 is to the outer side of the deep flexor, and the tendon is 

 not slit for its passage. Nothing could be more engaging 

 than the examination of these reversed tendons in the 

 sole of the foot of this Ground Cuckoo, for the greatest 

 nicety in accommodation has been accomplished as they 

 have gradually come to assume their present position. 

 No doubt some of the departures observed from the 

 more common arrangement of them are due to the 

 reversion of the digit in question. 



:< Strong, fibrous bands are so disposed in this plantar 

 region as to admirably hold the several groups of flexor 

 tendons in place, and at the same time they act as pulleys 

 for their guidance and afford correct application of the 

 force intended to flex the toes. 



" We also have in Geococcyx an unusually large flexor 



