2 4 



THE POPULAR SCIENCE MONTHLY. 



of man's arm. First, there is the humerus (A), a bone of the horse's 

 upper arm, concealed, however, beneath the skin and muscles, and be- 

 ino-, therefore, inconspicuous in the living animal. The horse's forearm, 

 like that of man, contains two bones radius (r) and ulna (u) it is true ; 

 but the ulna has degenerated in a marked degree, and exists as a mere 

 strip of bone which is tolerably distinct at its upper end, but unites with 



7/1 tz 



Fig. 9. 



Fig. 10. 



Fig. 11. 



and merges into the other bone, the well-developed radius. The wrist 

 (ic) of the horse naturally succeeds its forearm, but from the fact of 

 the upper arm being concealed beneath the skin and muscles, the wrist 

 is commonly mistaken for the horse's knee. Thus, when a horse chips 

 its " knee," it in reality suffers a contusion of its wrist. Man possesses 

 <i,U'lit bones in his wrist, the horse has only seven, but the equine wrist 

 is readily recognizable as corresponding with the similar region in man. 

 The greatest difference between the human limb and that of the horse 

 is found in the regions which succeed the wrist, and which constitute 

 the palm and hand. Man has five palm-bones : the horse has appar- 

 ently but one long bone, the "cannon-bone" (m 1 ), in place of the five. 

 Now, to which of man's palm-bones does this " cannon-bone " corre- 

 spond ? The anatomist replies, " To that supporting the third or mid- 

 dle finger " ; and attached to this single great palm-bone the horse has 



