94 PROXIMATE PRINCIPLES OF THE SECOND CLASS. 



mulation to a considerable degree. It is well known, for instance, 

 that in sugar-growing countries, as in Louisiana and the West 

 Indies, during the few weeks occupied in gathering the cane and 

 extracting the sugar, all the negroes employed on the plantations, 

 and even the horses and cattle, that are allowed to feed freely on 

 the saccharine juices, grow remarkably fat ; and that they again lose 

 their superabundant flesh when the season is past. Even in these 

 instances, however, it is not certain whether the saccharine substances 

 are directly converted into fat, or whether they are first assimilated 

 and only afterward supply the materials for its production. The 

 abundant accumulation of fat in certain regions of the body, and its 

 absence in others ; and more particularly its constant occurrence in 

 certain situations to which it could not be transported by the blood, 

 as for example the interior of the cells of the costal cartilages, the 

 substance of the muscular fibres of the uterus after parturition, &c., 

 make it probable that under ordinary conditions the oily matter is 

 formed by decomposition of the tissues upon the very spot where 

 it subsequently makes its appearance. 



In the female during lactation a large part of the oily matter 

 introduced with the food, or formed in the body, is discharged with 

 the milk, and goes to the support of the infant. But in the female 

 in the intervals of lactation, and in the male at all times, the oily 

 matters almost entirely disappear by decomposition in the interior 

 of the body; since the small quantity which is discharged with the 

 sebaceous matter by the skin bears only an insignificant proportion 

 to that which is introduced daily with the food. 



The most important characteristic, in a physiological point of 

 view, of the proximate principles of the second class, relates to their 

 origin and their final destination. Not only are they all of a purely 

 organic origin, making their appearance first in the interior of vege- 

 tables ; but the sugars and the oils are formed also, to a certain ex- 

 tent, in the bodies of animals ; continuing to make their appearance 

 when no similar substances, or only an insufficient quantity of them, 

 have been taken with the food. Furthermore, when introduced 

 with the food, or formed in the body and deposited in the tissues, 

 these substances do not reappear 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 es- 

 sential characters are destroyed ; and they are finally replaced in 

 the circulation by other substances, which are discharged with the 

 excreted fluids. 



