264 



BRANCH CHORDATA 



advantage in this arrangement? Why do they differ from the 

 structure and arrangement in the leg of man? 



The body skeleton (Fig. 216) is strong, light, and flexible, as it 

 must be for flight. Note how firmly the vertebrae are joined in 



Fig. 215. — The most important forms of birds' feet (b, c, d, /, n, from the 

 regne animal) : a, Pes adhamans of C'ypselus apus; b, P. scansorius of Picus 

 capensis; c, P. ambulatorius of Phasiniiiis colcJiiciin; d, P. fissus of Turdiis 

 lorquatus; c, P. gressorius of Alci'do ixpida; f, P. insidens of Falco biarmicus; 

 g, P. colUgatus of Mi/ctvrin scnvgalcnsix; h, P. cursorius of Struthio camelus; 

 i, P. palmatus of Menpix merganser; k, P. semipahnatus of Rceurvirosira 

 avocella; I, P. fissipalmatus of Podieeps erixlaltis; )ii, P. lobatus of Fidica 

 alra; n, P. steganus of Phaeton (elhereus. (After Claus.) 



the back. Note also the very short bony tail, consisting of a 

 few vertebrae fused into the ji^-gostyle, which supports the tail 

 feathers. The oil gland is situated near the pygostyle and from 

 it birds get the oil for their feathers. Note also that the sternum 



