292 DIGESTION. 



casein cannot be found by their characteristic tests. It 

 would seem, indeed, that all these various substances are 

 converted into one and the same principle, a low form of 

 albumen, not precipitable by nitric acid or heat, and now 

 generally termed alluminose or peptone, from which, after 

 being absorbed, they are again raised, in the elaboration 

 of the blood, to which they are- ultimately assimilated. 



The change of molecular constitution suffered by the 

 albuminous parts of the food, in consequence of the action 

 of the gastric juice, has an important relation to their 

 absorption by the blood-vessels of the stomach. From the 

 condition of 'colloids,' or substances, so named by Pro- 

 fessor Graham, which are absorbed with extreme difficulty, 

 they appear, from experiments of Funke, to assume to a 

 great degree the character of ' crystalloids,' which can 

 pass through animal membranes with ease.* 



Whatever be the mode in which the gastric secretion 

 affects these principles, it, or something like it, appears 

 essential, in order that they may be assimilated to the 

 blood and tissues. For, when Bernard and Barreswil in- 

 jected albumen dissolved in water into the jugular veins 

 of dogs, they always, in about three hours after, found it 

 in the urine. But if, previous to injection, it was mixed 

 with gastric fluid, no trace of it could be detected in the 

 urine. The influence of the liver seems to be almost as 

 efficacious as that of the gastric fluid, in rendering albu- 

 men assimilable ; for Bernard found that, if diluted egg- 

 albumen, unmixed with gastric fluid, is injected into the 

 portal vein, it no longer makes its appearance in the urine, 

 and is, therefore, no doubt, assimilated by the blood. 



Probably, most of the albuminose, with other soluble 

 and fluid materials, is absorbed directly from the stomach 

 by the minute blood-vessels with which the mucous mem- 

 brane is so abundantly supplied. 



* These terms will be further explained and illustrated in the Chapter 

 on Absorption. 



