BIPEDS A.ND QUADRITPEDS. 105 



fort, or its reverse, the suffering, of any living thing 

 under their control. 



One might naturally suppose that a man who had 

 driven a cart all his life, would know in what way 

 his horses worked with the most comfort and ad- 

 vantage ; and no doubt, however obtuse might be his 

 faculty of mind, he would get to know this, if he 

 ever troubled his head about the matter ; but he 

 does not. As one proof of the utter and enduring ig- 

 noranceof such men, and the inattention and careless- 

 ness of their masters, it is no uncommon thing to see 

 a very ^a// horse put between the shafts of a cart, and a 

 low one before him; the consequence is, the latter 

 creates an absolute load to be borne on the back of 

 the shaft horse, and, of course, the more vigorously 

 the leader draws, the greater the weight he pulls on 

 the back of his companion. We will call the nearly 



horizontal line a the shaft of the cart, the perpendicular 

 one b the shaft-horse's back-band, and the declinino- 

 one c the front horse's trace; the pressure on the back 



