CHAP, v.] OF ASSIMILATION. AMONGST ANIMALS. 131 



sleep of hibernation. Finally, we find, in the juice extract- 

 ed from the muscles, lactic acid and inosite, which seem 

 products derived from the oxydation of hydro-carbonized 

 substances. 



We must remark also, that during the last stage of intra- 

 nt erine life, when the muscles already contract frequently, only 

 lictic acid is met with in their tissue, as in the adult. We 

 know, moreover, that when a muscle is immobile, only a very 

 small part of the arterial blood is transformed therein into 

 venous blood. It seems then that, in effect, , muscular action 

 may be one of the principal causes of the oxydation of hydro- 

 carbonized substances contained in the blood and in the tissues. 

 AJ to the question of the direct transmutation of heat into 

 movement by the muscle, the subject is so complex as to demand 

 a separate chapter. 



Substances analogous to the amyloi'dal and saccharine substances, 

 fat bodies, also enter the blood in a state of very fine division 

 a state of emulsion. In the superior animals, this emulsion 

 is accomplished by special liquids, bile and the pancreatic juice ; 

 the latter passes with these matters into the blood and decom- 



' poses them into glycerine and into fatty acids ; for they do not 

 seem to be always utilized in nature. In the blood the fatty 

 bodies evolve themselves by forming fatty acids, oleic, stearic, etc., 

 which become oleates and stearates of soda and potash ; besides, 



( cholic and cholele acids, whence are formed cholates and choleates ; 



; finally, cholesterine, and a fat phosphoric substance, cerebrine. 

 It is probable, moreover, that like the larger portion of amyloidal 

 in utters, they also end by being oxydized, in developing utilizable 

 heat. We know that the alimentation of the inhabitants of the 



, polar regions contains an enormous quantity of fatty matters, 



\ and that, under the same conditions, European sailors have found 

 the advantage of adopting the same kind of alimentation as the 

 natives. 



It is also certain that animal organisms can produce fat from 

 saccharine matters. MM. Dumas and Milne-Edwards, having 



