338 DIGESTION. 



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 

 have to fulfil in relation to the respiratory process, and 

 without which, such purpose probably could not be pro- 

 perly accomplished, and the substances themselves would 

 be eliminated as foreign matters by the kidneys. 



Then, again, it has been discovered by Bernard, and the 

 discovery has been amply confirmed by Lehmann and other 

 distinguished animal chemists, that the liver possesses the 

 remarkable property of forming sugar, or a substance 

 readily convertible into sugar, even out of principles in the 

 blood which contain no trace of saccharine or amylaceous 

 matter. In Herbivora and in animals living on mixed 

 diet, a large part of the sugar is derived from the saccha- 

 rine and amylaceous principles introduced in their food. 

 But in animals fed exclusively on flesh, and deprived 

 therefore of this source of sugar, the liver furnishes the 

 means whereby it may be obtained. Not only in Carni- 

 vora, however, but apparently in all classes of animals, the 

 liver is continually engaged, during health, in forming 

 sugar, or a substance closely allied to it, in large amount. 

 This substance may always be found in the liver, even 

 when absent from all other parts of the body. 



