206 FORMATION OF SUGAR IN THE LIVER. 



posed of two distinct and successive processes, viz : first, the forma- 

 tion, in the hepatic tissue, of a glycogenic matter, having some 

 resemblance to dextrine; and secondly, the conversion of this 

 glycogenic matter into sugar, by a process of catalysis and trans- 

 formation. 



The sugar thus produced in the substance of the liver is absorbed 

 from it by the blood circulating in its vessels. The mechanism of 

 this absorption is probably the same with that which goes on in 

 other parts of the circulation. It is a process of transudation and 

 endosmosis, by which the blood in the vessels takes up the saccha- 

 rine fluids of the liver, during its passage through the organ. 

 While the blood of the portal vein, therefore, in an animal fed 

 exclusively upon meat, contains no sugar, the blood of the hepatic 

 vein, as it passes upward to the heart, is always rich in saccharine 

 ingredients. This difference can be easily demonstrated by exa- 

 mining comparatively the two kinds of blood, portal and hepatic, 

 from the recently killed animal. The blood in its passage through 

 the liver is found to have acquired a new ingredient, and shows, 

 upon examination, all the properties of a saccharine liquid. 



The sugar produced in the liver is accordingly to be regarded as 

 a true secretion, formed by the glandular tissue of the organ, by a 

 similar process to that of other glandular secretions. It differs 

 from the latter, not in the manner of its production, but only in 

 the mode of its discharge. For while the biliary matters produced 

 in the liver are absorbed by the hepatic ducts and conducted down- 

 ward to the gall-bladder and the intestine, the sugar is absorbed by 

 the bloodvessels of the organ and carried upward, by the hepatic 

 veins, toward the heart and the general circulation. 



The production of sugar in the liver during health is a constant 

 process, continuing, in many cases, for several days after the animal 

 has been altogether deprived of food. Its activity, however, like 

 that of most other secretions, is subject to periodical augmentation 

 and diminution. Under ordinary circumstances, the sugar, which 

 is absorbed by the blood from the tissue of the liver, disappears 

 very soon after entering the circulation. As the bile is transformed 

 in the intestine, so the sugar is decomposed in the blood. We are 

 not yet acquainted, however, with the precise nature of the changes 

 which it undergoes after entering the vascular system. It is very 

 probable, according to the views of Lehmann and Eobin, that it is 

 at first converted into lactic acid (C 6 H 6 6 ), which decomposes in 

 turn the alkaline carbonates, setting free carbonic acid, and forming 



