24 THE HORSE. 



for the waste produced by exercise. Fiu'tlier, we must 

 bear in mind that the blood which has been sent round 

 the course of the general circulation to the heart, from 

 whence it started, has served its purpose, has become 

 impm-e, and is no longer capable of sustaining life, 

 until, after having received additions from the digested 

 food, it is again passed through the lungs, in which it 

 comes in contact with the air inhaled for the special 

 purpose of its purification. Every pound of blood cir- 

 culated by the heart must receive a stated quantity of 

 air in the air-cells of the lungs ; and, as the rapidity of 

 the circulation beai's a dii-ect relation to the amount of 

 exertion endured within a given time, it follows, as a 

 matter of course, that the capabilities of the horse 

 must depend, in no small degree, upon the capacity of 

 the lungs for air. Hence arises the necessity of paying 

 special attention to the size and shape of the chest, in 

 which the heart and lungs are placed. 



Without entering upon a minute anatomical descrip- 

 tion of the CHEST, I may just say, that it is bounded in 

 front by the neck, on each side by the ribs and shoulder- 

 blade, below by the breast-bone, above by the spine, 

 and behind by the diaphragm which separates it from 

 the bowels. A line di-awn from the region of the 

 kidneys, immediately behind the saddle-seat, and ter- 

 minating at a short distance behind the girths at the 

 breast-bone, will point out, with tolerable accuracy, the 

 position of the diaphragm. It is a large expansion of 



