28 THE HORSE. 



When it is nicely filled and levelled on the top, re- 

 move the pressiu'e from the sides, so that the paste- 

 board may again form a perfect cylinder, and it will be 

 fpund that the shot is not nearly sufficient to fill the 

 cavity. Now, as the quantity of pasteboard remains 

 exactly the same dm-ing the entire experiment, it is 

 quite plain the change of capacity is owing solely to 

 the change of fonn. 



Let us suppose, then, that a horse has a perfectly 

 circular chest, and it will foUoAv, as a necessary conse- 

 quence, that the elevation of the ribs on the side, in 

 place of increasing its capacity, will actually lessen it, 

 by bringing it more or less into the elliptical form. In 

 this case the cavity of the chest would be larger 

 when the breathing would be suspended than at any 

 other time, because its original shape was such as not 

 to admit of an increase of size by any change of form. 

 The farther it would be changed from the cylinder, the 

 smaller it would become. But if, in the first instance, 

 tlie chest were a gTcat deal deeper than broad, the ele- 

 vation of the ribs on the side would just serve to bring 

 it into the circular shape, which is the most capacious 

 of all. Hence it must be evident, that depth of chest 

 is indispensable in all cases. 



As the lungs of the horse occupy a much larger 

 space when he is in active exercise, than when he is at 

 rest, we are justified in concluding that he requires to 

 have the power of increasing the size of his chest in 



