332 DIGESTION. 



certain constituents of the blood passing through it, as to 

 render some of them capable of assimilation with the 

 blood generally, and to prepare others for being duly 

 eliminated in the process of respiration. From the labours 

 of M. Bernard, to whom we owe most of what we know 

 on this subject, it appears that the low form of albuminous 

 matter, or albuminose, conveyed from the alimentary 

 canal by the blood of the portal vein, requires to be sub- 

 mitted to the influence of the liver before it can be 

 assimilated by the blood ; for if such albuminous matter is 

 injected into the jugular vein, it speedily appears in the 

 urine; but if introduced into the portal vein, and thus 

 allowed to traverse the liver, it is no longer ejected as a 

 foreign substance, but is probably incorporated with the 

 albuminous part of the blood. 



An important influence seems also to be exerted by the 

 liver upon the saccharine matters derived from the alimen- 

 tary canal. The chief purpose of the saccharine and 

 amylaceous principles of food is, probably, in relation to 

 respiration and the production of animal heat ; but in 

 order that they may fulfil this, their main office, it seems 

 to be essential that they should undergo some intermediate 

 change, which is effected in the liver, and which consists 

 in their conversion into a peculiar form of saccharine 

 matter, very similar to glucose, or diabetic sugar. That 

 such influence is exerted by the liver seems proved by the 

 fact that when cane sugar is injected into the jugular vein 

 it is speedily thrown out of the system, and appears in the 

 urine; but when injected into the portal vein, and thus 

 enabled to traverse the liver, it ceases to be excreted at the 

 kidneys ; and, what is still more to the point, a very large 

 quantity of glucose may be injected into the venous system 

 without any trace of it appearing in the urine. So that it 

 may be concluded, that the saccharine principles of the 

 food undergo, in their passage through the liver, some 

 transformation necessary to the subsequent purpose they 



