CROSSING. 117 



is put in motion by the noblest spirit or that it is nour- 

 ished by the highest blood ; every bone must have its 

 just proportion ; every muscle or tendon its proper 

 pulley ; every lever its proper length and fulcrum ; 

 every joint its most accurate adjustment and proper 

 lubrication ; all must have their relative proportions 

 and strength, before the motions of the machine can be 

 accurate, vigorous and durable. In every machine 

 modifications are required according as the purposes 

 vary to which it is applied. The heavy dray horse is 

 far from having the arrangement necessary for the pur- 

 poses of the turf, while the thorough-bred is as ill 

 adapted for the dray. Animals are therefore to be 

 selected for the individual purposes for which they are 

 intended, with the modifications of form proper for the 

 different uses to which they are to be applied ; but for 

 whatever purpose they may be intended, there are some 

 points which are common to all, in the adjustment of 

 the individual parts. If the bones want their due 

 proportions, or are imperfectly placed — if the muscles 

 or tendons want their proper levers — if the flexions of 

 the joints be interrupted by the defectiveness of their 

 mechanism, the animal must either be defective in mo- 

 tion or strength ; the bones have irregular pressure, and 

 if they do not break, become diseased ; if the muscles 

 or tendons do not become sprained or ruptured, they 



