228 FACULTIES OF BIRDS. 



Bird at rest : after Borelli. 



which passes over the knee, so that the bending of 

 the heel is necessarily followed by a bending of the 

 toes. When a bird therefore alights on the branch 

 of a tree, the weight of its body bends those joints, 

 and thus puts the tendons on the stretch, which 

 draws in the claws to lay hold of the branch without 

 any effort on the part of the bird, and hence it sits 

 as secure when asleep as when awake*. 



" This explication," says M. Barthez, " has been 

 repeated by Monro, but has been well refuted by M. 

 Vicq d'Azyrf." " It is true indeed," says Dr. Bar- 

 clay of Edinburgh, " that in these propositions the late 

 Vicq d'Azyr, after showing more than usual anxiety 

 to point out some myographical errors, and after 

 asserting just what Borelli had asserted before, that 

 one flexor only passes over the convexity at the knee, 

 has, by artfully concealing what Borelli has said of 

 the joint of the heel, and by insinuating what he has 

 not said of the joint of the knee, completely succeeded 

 in convincing Barthez that his cavilling criticism is 

 an able refutation. But the leg of a bird that perches 



* De Motu Animalium, Prop. 149 and 150. 

 f Nouvelle Mecanique des Animaux. 



