THE APPENDICULAR SKELETON. 



665 



The fore limb consists of an upper arm or humerus, a 

 fore arm of two bones — the radius and the ulna, a wrist or 



carpus, five palm bones 

 or metacarpals, and five 

 digits with joints or 

 phalanges. 



The head of the humerus 

 works in the glenoid cavity 

 formed by the scapula and the 

 coracoid process. 



When the arm of a mam- 

 mal is directed outwards at 

 right angles to the body, with 



Fig. 233. — Rabbit's fore leg. 



Sc.y Scapula; cor., coracoid process; ac., 

 acromion ; //., humerus \ R., radius ; U., ulna ; 

 C , carpal region ; M.C., metacarpal region. y-. 



the palm vertical and the thumb upper- 

 most, the thumb and the radius are in 

 a preaxial position, the little finger and 

 the ulna are in a postaxial position. 

 But in the normal position of the limb 

 in most mammals, 

 the radius and the 

 ulna cross one an- 

 other in the fore arm, 

 so that the preaxial 

 radius is external at 

 the upper end, inter- 

 nal at the lower end. 



The typical mam- 

 malian wrist or car- 

 pus consists of two 



rows or bones, with a central bone between the two rows. In the 

 rabbit all the bones — nine in number — are present, viz : — 

 Ulnare or Cuneiform. Intermedium or Lunar. Radiale or .Scaphoid. 

 Centrale. 



Carpale 5 and 4 Carpale 3 Carpale 2 Carpalc i 



or or or or 



Unciform. Magnum. Trapezoid. Trapezium. 



-Rabbit's hind leg. 



Tr., third trochanter ; E/t., epiphysis 

 at head of tibia (7Y). ; Ft., incomplete fibula ; C, 

 calcaneum ; A., astragalus ; int., metatarsals. 



