CHAP, v.] OF ASSIMILATION AMONGST ANIMALS. 183 



absorption, important isomeric modifications, due, in the superior 

 animal, to the action of fermentescible agents called pepsine, 

 pancreatine, etc., which are secreted by certain portions of the 

 digestive apparatus. Under the influence of these agents, the 

 albuminoidal vegetal and animal bodies undergo an isomerical 

 transformation. All become soluble and incoagulable by heat ; 

 they are then peptones, and it is under this form that they enter 

 the circulation. Amongst the vertebrates, the intestinal capil- 

 1? tries, and consequently the intestinal veins, are the principal 

 channel for the absorption of the albuminoids. Once in the 

 blood, these substances pass from the state of peptones, or 

 albuminose, to that of albumine, of plasmine or fibrinogenous 

 matter. This complicated elaboration is necessary : thus a 

 solution of albumine of egg injected into the lungs, into the 

 serous vessels, into the cellular tissue of an animal, into one of 

 its veins, is never assimilated, and passes intact into the urine. 1 



The peptones were not coagulable by heat, but the azotised 

 principles which result from them, and which at last form 

 themselves in the blood, become again coagulable. Electively 

 absorbed by the anatomical elements, they incorporate them- 

 selves therewith molecule by molecule, after having undergone 

 a final isomeric modification. In effect, justifying the title of 

 prote'ic which has been given to them, they become, in final 

 result hsemoglobine, keratine, syntonine, osseine, etc., all these 

 substances having a chemical composition analogous to that 

 which produces them, but being endowed with very different 

 properties. 



But the albuminoidal substances do not alone penetrate the 

 web of living tissues. They bring with them a number of mineral 

 matters, upon which they act as solvents, for example, calcareous 

 salts, silica, etc. 2 



The peptones, which have the same property, incorporate with 

 themselves in some degree, certain dissolved substances. In 



1 Cl. Bernard, Progrls et Marche de la Physiologic Generate en France, p. 197. 



2 Ch. Robin, Lefonssur les Humeurs, pp. 103, 104. 



