336 THE METABOLISM OF THE CARBOHYDRATES 



appears and sugar takes its place. This is the result of the action 

 of a ferment in the hepatic cells, which goes oh acting after death 

 just as it does during life. 



Thirdly, the percentage of sugar in the blood of the hepatic 

 vein is greater than that of the blood in the portal vein when no 

 absorption of food from the intestine is in progress. 



Fourthly, the blood going to the muscles (arterial) contains 

 more sugar than the blood coming from the muscles (venous). 



If, to these facts, it be added that during muscular work 

 glycogen disappears first of all from the liver and only after some 

 time from the muscles (see p. 324), and that the difference in 

 sugar contents between venous and arterial blood increases during 

 muscular work, 1 then Bernard's theory would seem to be estab- 

 lished, for it is inconceivable that when the muscles require more 

 glycogen as they do when they become active the liver should 

 proceed to convert its glycogen into some non-carbohydrate 

 material, such as fat, instead of transferring it as sugar to the 

 muscles. 



Now, let us see on what grounds Pavy objects to Bernard's 

 theory. In doing this we will take up Bernard's proofs in the 

 order given above. 



Firstly, the percentage of sugar in the liver is no higher than 

 that of other organs and tissues if the estimation be made imme- 

 diately after the death of the animal and precautions be taken by 

 freezing the organ to stop at once the action of the glycolytic 

 ferment contained in the blood included in the blood-vessels of 

 the liver (see, however, p. 324). 



Secondly, the accumulation of sugar and the disappearance of 

 glycogen which occurs in the liver after death is purely a post- 

 mortem phenomenon, there being in the liver cells during life no 

 glycolytic ferment. 



Thirdly, the higher percentage of sugar in the blood of the 

 hepatic vein over that in the portal vein is due to the stimula- 

 tion of sensory nerves, which necessarily follows from the method 

 used to collect the blood for analysis. This method, as practised 

 by Seegen, consisted in passing a gum elastic catheter down the 

 superior vena cava to opposite the entrance of the hepatic veins 

 in animals which were not anaesthetised. That the irritation 



1 There is, however, some doubt regarding the accuracy of this result ; see 

 Pavy, " The Physiology of the Carbohydrates " ( 10 ). 



