168 ELEMENTARY ANATOMY. [LESS. 



The olecranon process of man is larger than in many 

 forms ; thus e.g. it is relatively larger than in Birds. It is, 

 however, much larger relatively than in man in many Mam- 

 mals, even e.g. in Baboons, and still more in Ungulates, the 

 Monotremes, and the Mole. -There may be a detached sesa- 

 moid ossicle at the end of the olecranon, reminding the 

 observer of the knee-pan, or patella, of the leg. This is the 

 case in some Bats. 



The ulna's articular surface for the humerus may merely 

 complete that offered by the radius, the two together forming 

 a single concavity for the reception of the humerus. This is 

 the case, e.g., in Ruminants. 



The styloid process may be much more prolonged than in 

 man : we find it so in the Gibbons. The distal part of the 

 \ilna may, on the contrary, abort altogether, as in the Bats. 

 It generally, however, articulates with the carpus directly, as 

 the radius does. 



16. Inasmuch as THE HAND of man is made up of the 

 carpus, metacarpus, and phalanges, it agrees with the corre- 

 sponding segment in all Vertebrates above Fishes ; where, if 

 any element of the arm is present, the hand is present 

 likewise. 



17. Inasmuch as the CARPUS of man consists of a few 

 relatively small bones, it agrees with that of all other Verte- 



FIG. 143. DORSAL SURFACE OF SKELETON OF RIGHT HAND OF THE TORTOISE 

 Chelydra. (After Gegenbaur.) 



c, cuneiforme ; in, intermedian (or centrale) ; /, lunare ; m 1 ?5, metacarpals ; 

 r, radius; s, scaphoides; u, ulna; 15, the five distal carpals, namely 

 i, trapezium ; 2, trapezoides ; 3, magnum ; 4 and 5, divided unciforme. 



brates above Fishes, except that in some Tailed-Batrachians 

 and Cetaceans the parts are more or less permanently car- 

 tilaginous. The number of carpal bones, however, may be 

 increased to ten, as in Chelonians, or it may be reduced to 

 two, as in Birds. 



