280 HAND-BOOK OF PHYSIOLOGY. 



(e.) The bile appears to have the power of precipitating tlie gastric 

 parapeptones and peptones, together with the pepsin which is mixed up 

 with them, as soon as the contents of the stomach meet it in the duo- 

 denum. The purpose of this operation is probably both to delay any 

 change in the parapeptones until the pancreatic juice can act upon them, 

 and also to prevent the pepsin from exercising its solvent action on the 

 ferments of the pancreatic juice. 



Nothing is known with certainty respecting the changes which the re- 

 absorbed portions of the bile undergo. That they are much changed 

 appears from the impossibility of detecting them in the blood; and that 

 part of this change is effected in the liver is probable from an experiment 

 of Magendie, who found that when he injected bile into the portal vein, 

 a dog was unharmed, but was killed when he injected the bile into one of 

 the systemic vessels. 



II. THE LIVER AS A BLOOD-ELABORATING GLAND. 



The secretion of bile, as already observed, is only one of the purposes 

 fulfilled by the liver. Another very important function appears to be 

 that of so acting upon certain constituents of the blood passing through 

 it, as to render some of them capable of assimilation with the blood gen- 

 erally, and to prepare others for being duly eliminated in the process of 

 respiration. It appears that the peptones, conveyed from the alimentary 

 canal by the blood of the portal vein, require to be submitted to the influ- 

 ence of tne liver before they 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 

 incorporated with the albuminous part of the blood. Albuminous mat- 

 ters are also subject to decomposition by the liver in another way to be 

 immediately noticed (p. 281). The formation of urea by the liver will be 

 again referred to (p. 371). 



Glycogenic Function. One of the chief uses of the liver in connec- 

 tion with elaboration of the blood is comprised in what is known as its 

 glycogenic function. The important fact that the liver normally forms 

 glucose or grape sugar, or a substance readily convertible into it, was dis- 

 covered by Claude Bernard in the course of some experiments which he 

 undertook for the purpose of finding out in what part of the circulatory 

 system the saccharine matter disappeared, which was absorbed from the 

 alimentary canal. With this purpose he fed a dog for seven days with 

 food containing a large quantity of sugar and starch; and, as might be 

 expected, found sugar in both the portal and hepatic veins. He then 

 fed a dog with meat only, and, to his surprise, still found sugar in the 



