ALBUMINOSE, OR PEPTONES. 347 



semble each other very closely is also undoubted ; but there are differences in the chemi- 

 cal composition of the products of digestion of different principles, as well as differences, 

 which have lately been noted, as regards their behavior with reagents. 



Albuminose is a colorless liquid, with a feeble odor resembling that of meat. It is 

 not coagulable by heat, acids, or by pepsin ; a property which distinguishes it from almost 

 all of the nitrogenized principles of food. It is coagulated, however, by many of the 

 metallic salts, by chlorine, and by a solution of tannin, after it has been acidulated by 

 nitric acid. On evaporating albuminose to dryness, the residue consists of a yellowish- 

 white substance, resembling desiccated white of egg. This is soluble in water, when it 

 regains its characteristic properties ; but it is entirely insoluble in alcohol. 



Lehmann found a great similarity between the substances resulting from the digestion 

 of the various albuminoid bodies, and even those produced by the digestion of gluten, 

 chondrine, and gelatinous tissues. He was unable to obtain the peptones free from min- 

 eral substances. In the condition of greatest purity in which they have been obtained, 

 they have been found to be white, amorphous, odorless, with a mucous taste, very solu- 

 ble in water, and insoluble in alcohol. Their watery solutions redden litmus. They 

 combine readily with bases, forming neutral salts soluble in water. The differences be- 

 tween the various peptones are not as yet very well defined. Lehmann states that they 

 always contain the same proportion of sulphur that existed in the albuminoid substances 

 from which they are formed. According to this observer, the gastric juice transforms the 

 various nitrogenized alimentary principles into these liquid substances, which are not easily 

 coagulable and which present slight differences in chemical composition and general prop- 

 erties, varying with the principles from which they are formed. Those which have been 

 most particularly described are fibrin-peptone, albumen-peptone, and caseine-peptone. 



With even the' imperfect knowledge which we have of the properties of albuminose, 

 it is evident that stomach-digestion, aside from its function in preparing certain articles 

 for the action of the intestinal fluids, does not simply liquefy certain of the alimentary 

 principles, but changes them in such a way as to render them endosmotic and provides 

 against the coagulation which is so readily induced in ordinary nitrogenized bodies. 

 Albuminose passes through membranes with great facility, and, as we have seen, is not 

 coagulable by heat or the acids. 



Another, the most important and the essential change which is exerted by the gastric 

 juice upon the albuminoids, is that by which they are rendered capable of assimilation 

 by the system after their absorption. The important fact that pure albumen and gela- 

 tine, when injected into the blood, are not assimilable, but are rejected by the kidneys, 

 was first demonstrated by Bernard and Barreswil. These observers found, also, that albu- 

 men and gelatine which had previously been digested in gastric juice were assimilated in 

 the same way as though they had penetrated by the natural process of absorption from 

 the alimentary canal. The same is true of caseine and fibrin. These facts, showing that 

 something more is necessary in stomach-digestion than mere solution, point to pepsin as 

 the important active principle in producing the peculiar modifications so necessary to 

 proper assimilation of nitrogenized alimentary substances. The action which takes place 

 is one of those ordinarily termed catalytic, in which the pepsin, acting as a ferment, in- 

 duces certain peculiar changes. They are, however, an essential and the most important 

 part of the action of the gastric juice, and the transformation into albuminose takes 

 place in all nitrogenized principles which are liquefied in the stomach. As it is impossible 

 for two catalytic processes to take place at the same time in any single organic substance, 

 the more powerful always overcoming and taking the place of the weaker, it is evident 

 that, when nitrogenized principles in process of decomposition are introduced into the 

 stomach, the catalytic process of putrefaction must cease when the changes which occur 

 in digestion become established. This explains the antiseptic properties of the gastric 

 juice and the frequent innocuousness of animal substances in various stages of decom- 

 position, when taken into the stomach. 



