78 HYDROCARBONAOEOUS PROXIMATE PRINCIPLES. 



the bile. According to the observations of Prof. Flint, Jr., on the dog, 1 

 its quantity in the blood increases, while passing through the brain, 

 from 0.52 to 1.09 parts per thousand. Authorities differ as to whether 

 it is discharged with the feces, or is transformed in the interior of the 

 body. 



The most important characteristic, in a physiological point of view, 

 of all the proximate principles of the second class, including the amyla- 

 ceous, saccharine, and oily substances, relates to their source and their 

 final destination. Not only are they of organic origin, making their 

 appearance first in the interior of vegetables ; but they are all produced 

 also, to a certain extent, from other organic materials, in the bodies of 

 animals ; continuing to be formed when no similar substances, or only 

 an insufficient quantity of them, have been taken with the food. Fur- 

 thermore, when introduced with the food, or formed in the body and 

 deposited in the tissues, these substances are not found in the secretions. 

 They, therefore, for the most part, disappear by decomposition in the 

 interior of the body. They pass through a series of changes by which 

 their essential characters are destroyed ; and they are finally replaced 

 in the circulation by other substances, which are discharged with the 

 excreted fluids. 



1 Physiology of Man, vol. iii. New York, 1870, pp. 281, 282 



