508 THE LIVER. [CH. xxxill. 



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

 might be expected, found sugar in both the portal and hepatic 

 blood. But when this dog was fed with meat only, to his sur- 

 prise, sugar was still found in the blood of the hepatic veins. 

 Repeated experiments gave invariably the same result ; no sugar 

 was 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 have 

 been brought directly to it from the stomach or intestines. 



Bernard found, subsequently to the before-mentioned experi- 

 ments, 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, contained sugar in abundance 

 after the lapse of a few hours. This post-mortem production of 

 sugar was a fact which could only be explained on the supposition 

 that the liver contained a substance readily convertible into sugar; 

 and this theory was proved correct by the discovery of a substance 

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



We are thus led to the conclusion that glycogen is formed 

 first and stored in the liver cells, and that the sugar, when 

 present, is the result of its transformation. 



Source of Glycogen. Although the greatest amount of glycogen 

 is produced by the liver upon a diet of starch or sugar, a certain 

 quantity is produced upon a proteid diet. It must, then, be pro- 

 duced by protoplasmic activity within the cells. The glycogen 

 when stored in the liver cells may readily be demonstrated in 

 sections of liver containing it by its reaction (red or port-wine 

 colour) with iodine, and moreover, when the hardened sections are 

 soaked in water in order to dissolve out the glycogen, the proto- 

 plasm of the cell is so vacuolated as to appear little more than a 

 framework. In the liver of a hibernating frog the amount of 

 glycogen stored up in the outer parts of the liver cells is very 

 considerable. 



Average Amount of Glycogen in the liver of Dogs under various 



Diets (Pavy). 



Diet. Amount of Glycogen in Liver. 



Animal food . . . . . . .7*19 per cent, 



Animal food with sugar (about 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 kind of 



