ASSIMILATION OF THE FOOD. 221 



Stomach only is necessary. If it were large, it would dimin- 

 ish the size of the lungs. But large lungs are necessary for 

 rapid and continuous action. Hence the necessity of a small 

 stomach. But food in sufficient quantity is necessary, and 

 thus the rapid digestion of the horse.] 



It can not retain the food very long ; the horse is almost 

 constantly eating. At grass he eats as much in an hour, per- 

 haps in half-an-hour, as would fully distend the stomach, yet 

 he continues to eat for several hours in succession. The 

 change, therefore, which the food undergoes in the stomach 

 must be rapidly performed. The nature of this change is not 

 precisely known. It is supposed that the gastric juice — that 

 is, a juice or secretion furnished by the stomach — seizes the 

 nutritive matter of the food, and combines with it to form a 

 white milk-like fluid termed chyme. This, accompanied by 

 the food, from which it has been extracted, enters the intes- 

 tines, and there another change of composition takes place. 

 Juices from the liver, from peculiar glands, and from the in- 

 testines itself, are added, and the whole combine to form a 

 compound fluid termed chyle. This adheres to the inner 

 surface of the bowels, from which it is removed by an infinite 

 number of tubes, whose mouths are inconceivably minute, to 

 the eye invisible. These little tubes or pipes, are termed 

 lacteals or absorbents ; they converge and run toward the 

 spine, where their contents are received by a tube which 

 empties itself into the left jugular vein. Accompanied by the 

 blood, the chyle proceeds to the lungs, passes through them, 

 and becomes blood. Having undergone sanguification, this 

 chyle, the product of digestion, is as much a constituent of 

 the living animal as any other part of him. 



It is not necessary to trace the food further. Its nutritive 

 matter having been extracted, and animalized by combination 

 with animal juices, the product is removed as the mass travels 

 through the intestines. By the time it has arrived at the 

 point of evacuation, the food has lost all or most of the nutri- 

 tive matter, and the residue is ejected as useless. 



The nutritive matter is carried from the intestines to the 

 blood-vessels, where it is mingled with their contents. To 

 follow it further would be to trace the conversion of the blood 

 into the solids and fluids of which the body is composed. In 

 this work such an inquiry is not necessary. 



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