378 SKELETON OF THE FOWL 



and is notched distally to receive the carpo- 

 metacarpus. It is very freely movable. 



4. The manus. In the embryo there are four separate 

 metacarpals, corresponding to those of the thumb and 

 next three digits. In the adult the first three fuse 

 together, and with the distal row of 'carpal bones, to 

 form the carpo-metacarpus ; while the fourth either 

 disappears completely, or, according to some authori- 

 ties, fuses with the third. 



a. The carpo-metacarpus is an elongated bone, in which 



the three component metacarpals can readily be 

 distinguished. 



i. The first metacarpal, belonging to the first digit 

 or thumb, is very short and stumpy, forming 

 a small projection on the radial side of the 

 proximal end of the bone. 



ii. The second metacarpal, that of the second digit 

 or fore-finger, is a stout straight bone, enlarged 

 at its ends, and giving off near its proximal 

 end a process from its ulnar side. 



iii. The third metacarpal is slightly curved, and is 

 more slender than the second, with which it 

 is fused at both ends. 



b. The phalanges. 



i. The pollex, or first digit, has two phalanges, the 



terminal one being small, 

 ii. The second digit has three phalanges, the 



proximal one being large and lamellar, and 



the distal one very small, 

 iii. The third digit has only a single phalanx. 



C. The Pelvic Girdle. 



The pelvic girdle consists of the same three elements 

 ilium, ischium, and pubes as the mammalian pelvis, from 

 which, however, it differs widely in form. The three component 

 bones are firmly united together to form the os innominatum ; 



