Now it is evident that if the initial position of the 

 shoulder had been nearer the vertical, this critical moment 

 would have come sooner; just as it would have if the 

 initial position of the arm had been farther from verti- 

 cality, and all the more so if at the same time the shoulder 

 had been more upright and the arm more sloping. 



The rotation of the leg would not have had the ampli- 

 tude of that in the sketch (Fig. 3), the absorption of the 

 shock would have been less complete, and there would 

 not have been so perfect a preparation for the period of 

 suspension ; for although we have no information as to 

 the conformation of the horse used by Messrs. Marey 

 and Pages in making their plates, we have no right to 

 suppose that he did not use all the means permitted by 

 his conformation for executing this rotation as perfectly 

 as he could. 



We are thus led to conclude that obliquity of shoulder 

 and uprightness of arm give the leg a wide angle of 

 rotation, favor shock absorption and the extent of the 

 period of suspension, and that consequently the opposite 

 arrangement of these radii reduces the angular extent of 

 rotation, absorbs vital force, diminishes the co-efhcient of 

 elasticity and shortens the period of suspension. 



The " sprinter " should then have a relatively upright 

 shoulder and an arm nearly horizontal. 



What should his hindquarter be ? 



The object is to increase speed, consequently to 

 reduce the angle of oscillation of the hind legs ; but it is 

 necessary also to harmonize the action of the hindquarter 

 with that of the forehand. 



Observe that as the arm becomes less upright the 

 height at the withers decreases. We shall see later on in 

 comparing the measurements of very dififerent animals 

 that there are variations of 20° and more in the slope of 

 the arm ; variations carrying with them diiTerences at 



