236 DIGESTION. 



and hydrogen, by means of free oxygen, which, by 

 combining with those elements, produces heat, and 

 keeps the body at a uniform temperature ; the other 

 is the addition of new matter, to replace that which 

 is removed. The digested food, or chyme, as it is 

 called, on passing from the stomach into the smaller 

 intestines, becomes mingled with a portion of bile, a 

 secretion of the liver, consisting of soda and a pecu- 

 liar fatty acid. In passing through the smaller in- 

 testines, the chyme is separated into two portions — 

 one containing the elements of blood, called chyle, 

 which is absorbed and carried into the blood, the 

 other containing rejected matters, which are passed 

 from the system as excrementitious. 



608. The true nature of the change produced in 

 food, by the action of the gastric juice in the stomach 

 of an animal, is by no means satisfactorily under- 

 stood. This remarkable secretion contains a notable 

 quantity of free muriatic acid, and possesses great 

 powers of reducing organic matters to a state of so- 

 lution ; especially, when aided by the temperature of 

 the body. 



609. The excess of fluid taken into the system 

 with the food, is conveyed away from the body 

 through the medium of the kidneys, as urine ; a 

 secretion which also contains the rejected azotized 

 matters of the blood, in the form of two peculiar sub- 

 stances, to which the names of urea and uric acid 

 have been given ; these substances consist of carbon, 

 oxygen, hydrogen, and nitrogen, and are very prone 



