HOW THE HORSE LEARNS 155 



to the natural excitability of the horse, which 

 incites him to run from no greater cause than the 

 stir of a leaf. 



/Stibstitution of other aids 



or other signals for those by which the horse has 



learnt to perform the actions taught. 



Having first learnt to perform an action, and 

 afterwards to perform it at a given sound, gesture, 

 or signal by hand or on a given aid, if it is desi- 

 red, another signal may be substituted by associa- 

 ting it with the first signal whilst the horse is 

 performing such movement on the first signal, the 

 movement being repeated until he has learnt to 

 do it at the new signal. This new signal should 

 be used in a clear and marked way so as to make 

 an impression on him, and he must at the same 

 time be compelled to perform the action. Thus 

 Avhen the horse is isolated and standing still, being 

 held by two men at one, two or three or more 

 yards from him with two lounges attached to the 

 two side-rings of the cavesson, if whilst the voice 



