THE AKM 71 



THE AR.AI 



The arm is intimately connected with the hiteral aspect of tlie chest, 

 and, like the shoulder-blade with which it articulates above, is completely 

 invested by muscles. The two regions being outwardly undistinguisli- 

 able one from the other, some hippotomists have treated them together 

 as jointly forming the shoulder, and large numbers of practical horse- 

 men do not differentiate between them. 



The bony base of the upper arm is supplied by the humerus, a some- 

 what massive bone whose superior extremity articulates with the scapula 

 to form the shoulder-joint, from which it proceeds obliquely backward, 

 and with the radius and ulna combines to form the elbow -joint. 



The range of movement of the upper arm and the forward swing 

 of the entire limb will very much depend upon its length, which should 

 be as great as possible so long as it is not out of projjortion with the 

 shoulder. 



Any discrejiancy in this respect gives rise to relatively short shoulder 

 muscles, whose limited contraction would restrict the movements of the 

 arm both in extent and freedom. 



When the arm is unduly long the shoulder muscles are overtaxed, 

 and the forward movement of the limb is diminished. 



There is besides this a lack of liberty in the action of animals so 

 constructed, and a disposition to stumble and to fall. When too short 

 the forearm is not sufficiently advanced, as a result of which the step 

 is shortened and speed is diminished. 



" On general principles the shoulder and the arm should be long 

 absolutely, in order to be favourable to velocity; but with the same total 

 length of these two segments, it is necessary that the former should 

 be long and the latter short." — C4oubaux and Barrier. 



The force exercised by the fore -limb in tlie forward movement of 

 the body being directed through the arm, some importance must attach 

 to the degree of inclination which this region presents. 



In this connection it is found that while great oblic[uity of the 

 humerus detracts from a high rate of speed, in the heavy draught- horse 

 such a condition becomes an advantage, since it gives to the muscles 

 connected with it a more perpendicular insertion, whereby their power 

 is increased. 



It is hardly necessary to say that to a proper length and direction 

 of the arm should be added a set of well-developed muscles. 



