THE INTEBNAL SEELETOIf. I93 



Digits and Phalanges. — Except in one or two birds with defec- 

 tive wings, such as the Apteryx and Cassowary (which have 

 each but one digit in the hand), the pinion alwa.ys includes some 

 bones (phalanges) belonging to the three digits which corre- 

 spond with the three metacarpals already mentioned. 



The poUex consists of two small phalanges which support 

 the " alula " *. The index is much larger than either of the 

 other digits, and also consists of two phalanges which are rela- 

 tively large, and occasionally there is a third phalanx. The 



Kg. 156. 



Eight Hand op Ostrich. 



c,, Eadiale, or radial carpal ossicle; c^, ulnare, or ulnar carpal ossicle ; d.^, 

 proximal phalanx of the index digit which has three phalanges ; d^, 

 phalanx of third digit ; I, ulna ; m^ and m^, metacarpals of second and 

 third digits anchylosed together with that of the poUex ; p, proximal 

 phalanx of pollex ; r, radius. 



, third digit consists of but a single phalanx, except in the 



\ \ Ostrich, where there may be a second phalanx, and a small 



cartilage representing such a part has been found in a very 



1 1 young Duck. This third digit is applied to the outer f, or ulnar, 



side of the index digit. 



It is the pollex or the index, or both (as in the Ostrich), 

 which alone, in existing birds, ever bears a claw. As we have 



* See ante, p. 154. 



t The wing being supposed to be completely extended. 



O 



