BIRDS 407 



directed forwards and one backwards. In many 

 species there is a peculiar mechanism, by means of 

 which, when perched upon a branch, the weight of 

 their body tends to bend their toes, and consequently 

 to make them closely embrace it in their grasp, 

 an arrangement that permits them to repose in a 

 standing position without any danger of falling 

 while asleep. Perhaps the subjoined engraving will 

 serve to illustrate this very elegant contrivance. 

 The muscle that bends the toes (a b) arises, not 

 from the leg, but from the haunch (a) : becoming 

 suddenly converted into a thin tendon, it passes at 

 I in front of the knee-joint, enclosed in a sort of 

 pulley ; it then winds round the bone of the leg, 



FlG. 338. LEG OF A BIRD PEKCH1XG. 



to the back of the ankle-joint (b c\ where it like- 

 wise passes through a pulley at c, hence it proceeds 

 forwards behind the tarsal bpne to d, where it 

 divides into the sinews that bend the toes. From this 

 arrangement it will be seen that the weight of the 

 bird, by bending the knee-joint (6) and the ankle- 

 joint (c), puts the muscle (a/ 6, c, d) upon the stretch, 



