FORMATION OF GLYCOGEN IN THE LIVER 373 



source of hepatic glycogen is the class of alimentary substances called 

 carbohydrates ; but the fact that glycogen exists in the livers of the 

 carnivora, and probably in man, under a nitrogenous diet, shows that 

 the liver is capable of forming glycogen from albuminous matters. 



Change of Glycogen into Sugar. It is almost certain that the liver 

 does not contain sugar during life. Many years ago (1858) this fact 

 was recognized by Pavy, and it has since been confirmed by other physi- 

 ologists. Pavy, however, assumed that there was no such thing as 

 sugar-formation by the liver, under absolutely normal conditions. He 

 regarded the sugar found in the substance of the liver and in the blood 

 of the hepatic veins as due to post-mortem action, and his observations 

 seemed to be directly opposed to those of Bernard. The views of these 

 two observers and their followers seemed to be harmonized by a series 

 of experiments made in 1868. If the abdomen of a dog, perfectly quiet 

 and not under the influence of an anesthetic, is opened, and a portion 

 of the liver excised, rinsed in cold water, and rapidly cut up into boiling 

 water, the extract will show no reaction with Fehling's test for sugar. 

 In one experiment, in which twenty-eight seconds elapsed between the 

 time of opening the abdomen and the action of the boiling water, the 

 reaction with Feh ling's test was doubtful. In an experiment in which 

 the time was only ten seconds, there was no trace of sugar in the extract 

 from the liver (Flint). All observers are now agreed that sugar is 

 formed in the liver very rapidly after death. 



If the view is correct that the glycogen of the liver is being con- 

 stantly transformed into sugar during life, and that this sugar is carried 

 away in the blood-current, as fast as it is formed sugar would not 

 necessarily be contained in the liver under normal conditions ; and there 

 is no actual antagonism between the results obtained by Bernard and the 

 fact that sugar itself is not a normal constituent of the liver, as is asserted 

 by Pavy, McDonnell, Meissner, Ritter and others. 



If the liver is washed by means of a stream of water passed through 

 its vessels until it is free from sugar and is then kept at the temperature 

 of the body for a few hours, sugar will reappear in abundance. This is 

 due to a conversion of the glycogen of the liver into sugar by a ferment, 

 which has been extracted and isolated by a process analogous to that 

 by which similar ferments have been extracted from the saliva and the 

 pancreatic juice. This ferment probably exists originally in the liver 

 and does not appear first in the blood. 



The question of the transformation of glycogen into sugar during life 

 depends on the comparative quantities of sugar in the blood going to and 

 coming from the liver. Sugar is found in quantity in the blood of the 

 hepatic veins taken immediately after death and exists in blood drawn 



