THE BOOK OF MIGRATORY BIRDS 1 19 



which bend the claws pass over the joints of the heel and 

 are joined there by another muscle 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 

 seeming effort on the part of the bird. 



