DIGESTION. 281 



hepatic veins. Repeated experiments gave invariably the same result; no 

 sugar being found, under a meat diet, in the portal vein> if care were 

 taken, by applying a ligature on it at the transverse fissure, to prevent 

 reflux of blood from the hepatic venous system. Bernard found sugar 

 also in the substance of the liver. It thus seemed certain that the liver 

 formed sugar, even when, from the absence of saccharine and amyloid 

 matters in the food, none could be brought directly to it from the stomach 

 or intestines. 



Excepting cases in which large quantities of starch and sugar were 

 taken as food, no sugar was found in the blood after it had passed through 

 the lungs; the sugar formed by the liver, having presumably disappeared 

 by combustion, in the course of the pulmonary circulation. 



Bernard found, subsequently to the before-mentioned experiments, 

 that a liver, removed from the body, and from which all sugar had been 

 completely washed away by injecting a stream of water through its blood- 

 vessels, will be found, after the lapse of a few hours, to contain sugar in 

 abundance. This post-mortem production of sugar was a fact which could 

 only be explained in the supposition that the liver contained a substance, 

 readily convertible into sugar in the course merely of post-mortem decom- 

 position; and this theory was proved correct by the discovery of a sub- 

 stance in the liver allied to starch, and now generally termed glycogen. 

 We may believe, therefore, that the liver does not form sugar directly 

 from the materials brought to it by the blood, but that glycogen is first 

 formed and stored in its substance; and that the sugar, when present, is 

 the result of the transformation of the latter. 



Quantity of Glycogen formed. Although, as before mentioned, glyco- 

 gen is produced by the liver when neither starch nor sugar is present in 

 the food, its amount is much less under such a diet. 



Average amount of Glycogen in the Liver of Dogs under various Diets. 



(Pavy.) 



Diet. Amount of Glycogen in Liver. 



Animal food ? -19 per cent. 



Animal food with sugar (about J Ib. of sugar daily) 14*5 " 

 Vegetable diet (potatoes, with bread or barley-meal) 17 '23 " 



The dependence of the formation of glycogen on the food taken is also 

 well shown by the following results, obtained by the same experimenter: 



Average quantity of Glycogen found in the Liver of Rabbits after Fasting 

 and after a diet of Starch and Sugar respectively. 



Average amount of Glycogen in Liver. 



After fasting for three days .... Practically absent. 

 '* diet of starch and grape-susrar . . . 15*4 per cent. 



. 16-9 " 



