Aves. 213 



scales, is the tarsus. The pigeon has four toes, one extend- 

 ing backward and having two joints. Of the three front 

 toes, the inner has three joints, the middle four, and the 

 outer five. Each toe ends in a claw. 



It should be noted that the hip joints are not only far 

 apart, but are very high on the body, being near the dorsal 

 surface. This enables the body of the bird to swing be- 

 tween its two points of support, somewhat like an ice- 

 pitcher on its two pivots. Since the bird is obliged to put 

 its head to the ground so frequently, the convenience of this 

 arrangement is apparent. When we stoop we realize that 

 we are awkwardly built for such a position. It would at 

 first seem that the bird's center of gravity is too far forward, 

 but the length of. the toes must be taken into account. 



Perching. It is to be noticed that when a bird's leg is 

 drawn up close to its body, the toes are clenched at the 

 same time. This is due to the action of a tendon that 

 passes over the joints of the leg in such a way that when 

 the limb is bent the tendon is put on a strain and thus the 

 toes are flexed. So when the bird settles on its perch the 

 toes grasp the perch without active muscular effort ; this 

 helps answer the question, " How does a bird stay securely 

 on its perch when asleep?" There are also muscles by 

 which the bird can voluntarily clutch without depending on 

 this purely mechanical arrangement. 



The Pigeon's Shoulder Braces. With such strong pull- 

 ing as the breast muscles give the wing, it will be seen that 

 the shoulder needs to be firmly braced, especially against 

 the strong pull of the pectoral in making the down stroke 

 of the wing. In the first place, the shoulder is braced 

 like our own by the collar bones, or clavicles, the two collar 

 bones uniting near their attachment to the anterior end of 

 the keel, together making the "wishbone." In addition 



