FATTY ELEMENTS OF FOOD, AND ON FATTENING. 417 



tion, that it was composed in ihe animal body much in the same way 

 as it is formed in the seed and leaf of the living;- vegetable. 



The inquiries which I am about to present, however, all tend to 

 make us conclude that fatty substances are only produced in vege- 

 tables, and that they pass ready formed into the bodies of animals, 

 where they may either undergo combustion immediately, so as to 

 evolve the heat which the animal requires, or be stored up in the 

 tissues in order to serve as a magazine of combustible matter. 



This latter view appears the most simple ; but before discussing 

 the experiments which bear it out, it seems necessary to pass in 

 brief review the notions that have been entertained at different times 

 on the formation of fat. When the great burying-place of the In- 

 nocents was emptied, for example, it was commonly imagined that 

 one of the effects of the putrefactive process was to convert the 

 flesh, the brain, the viscera, &c., into fat — adipocire, as it was 

 called ; it was not, indeed, till after the researches of M. Chevreul 

 had been undertaken, and that it was discovered adipocire contained 

 the same acids as human fat, which had, in fact, only been partially 

 saponified by ammonia, — until the inquiries of M. Gay-Lussac were 

 made public — that it was acknowledged that muscular flesh or fibrine 

 subjected to putrefaction leaves no larger a quantity of fat than can 

 be obtained from it by proper solvents before it has undergone any 

 change : the effect of putrefaction is to destroy the fibrine, and so to 

 expose the fatty substance which it contained. 



It may therefore be said, that all these fortuitous opinions upon 

 the supposed formation of fat by chemical processes, have vanished 

 as they have been successively subjected to careful examination. 



Let us now turn to the inferences come to by physiology. The 

 Dodies of carnivorous animals are often loaded with fat ; and none 

 can be detected in any of their excretions. It is therefore in these 

 animals that it must be most easy to ascertain the source or origin, 

 and mode of disappearance of fatty matter. 



When the progress of digestion is watched in a dog, it is soon 

 disc*overed that the chyle is far from being a fluid having uniformly 

 the same characters and qualities. That which is produced under 

 the influence of a vegetable diet, abounding in the starchy principle 

 and in sugar, or after a meal of perfectly lean meat, is always and 

 alike poor in molecules or globules. The chyle is then nearly trans- 

 parent, extremely serous, and yields very little fat when w^ashed with 

 ether. But if the animal have a meal of fat food, the chyle that re- 

 sults from it is opaque like cream, very rich in particles, and, digest- 

 ed with ether, yields a large quantity of fatty or oily matter to that 

 solvent. 



These facts, observed by M. Magendie, and confirmed with more 

 ample details by Messrs. Sandras and Bouchardat, show that the 

 fatty principles of our food minutely subdivided or made into an 

 emulsion by the act of digestion, pass without undergoing any es- 

 sential change into the chyle, and from that into the blood, whither 

 they can in fact be followed, and in which they can be shown tc 

 remain for a longer or a shorter time unaltered, at the disposal of 



