THE FORE EXTREMITY. 63 



third use of this ' spine' of the scapula is that it 

 acts as a fulcrum or fixed point for muscles, also as 

 a place for insertion for tendons. 



45.— The next bone called the 'humerus' or arm 

 bone, will be seen to be exactly alike in both cases, 

 only it is relatively very much longer in man. In 

 both it is a powerful bone, but especially so in the 

 horse. Extremely large muscles clothe it. 



46.— The next two bones are the radius and 

 ulna. In man, both these bones are continued from 

 the elbow joint to the wrist as separate bones, 

 but you will notice that in the horse the ulna, 

 after helping the radius to form the elbow 

 joint, coalesces with the radius, so that the 

 two in a full grown horse look like one bone. 

 This being so, the ulna is said to be rudimentary in 

 the horse. 



47. — The bones of the carpus are nearly alike in 

 both, onl}^ of course, larger in the horse. We 

 shall call this the knee as usual, although, as you 

 see, it is the wrist. 



48. — There are five metacarpal bones in our 

 hands, but the horse has only one which is fairly 

 represented by the metacarpal bone belonging to 

 our middle finger. You see two small metacarpal 

 bones in the horse, but these are dwarfed and only 

 rudimentary, and in the very aged, stuck to the 

 larger ' metacarpal.' Notice, though, that the tops 

 of all three articulate with the bones above them, 

 i.e., with the lower bones of the ' carpus' or ' knee.' 



