70 



ELEMENTS OF MAMMALIAN ANATOMY 



scapholunar; lesser multangular, hamate and second, third, and 

 fourth metacarpals. The hamate can be recognized by its 

 wedge shape. It articulates with the scapholunar, triquetral, 

 capitate and fourth and fifth metacarpals. Each carpal bone 



develops from a single center 

 except the scapholunar, which 

 develops from two centers. 



The typical arrangement of 

 the vertebrate carpus is shown 

 in figure 37, B. The pisiform 

 does not belong to the cartil- 

 aginous skeleton, but is a sesa- 

 moid bone. In all mammals 



Mi 



A. B. 



Fig. 37. 



A, Dorsal aspect of left manus of cat; a, first phalanx of the pollex; h, second 

 or terminal phalanx; en, triquetral; h, head of fourth metacarpal; m, capitate; 

 mt, metacarpal 4; n, claw; pi, pisiform; s, sesamoid bone; st, scapholunar; Id, 

 lesser multangular; Im, greater multangular; u, hamate; 1,2, and 3, first, second, 

 and third phalanges of the middle digit. 



B, Generalized type of carpus as found in lower vertebrates: c, Centrale; i, 

 intermedium or lunare; r, radiale or scaphoid; ra, radius; m, metacarpals; u, 

 ulnare or cuneiform; ul, ulna; i, carpalia i, or trapezium; 2, carpalia 2, or trape- 

 zoid; 3, carpalia 3, or magnum; 4, and 5, carpalia 4 and 5, or unciform. 



possessing five digits, the anlage of three bones in the proximal 

 row, five bones in the distal row, and a central element occurs 

 in the embryo, but through fusion of elements a less number is 

 present in most adults. Thus, in the cat the radiale and inter- 

 medium and centrale unite to form the scapholunar. In all 

 forms carpalia 4 and 5 coalesce to form the hamate. 



Metacarpus. — There are five metacarpal bones forming the 

 middle region of the forefoot. They are named, beginning on 



