SEC. 1. METABOLIC TISSUES. 



The History of Olycogen. 



The best known and most carefully studied example of 

 metabolic activity is the formation of glycogen in the hepatic cells. 



Claude Bernard, in studying the history of sugar in the economy, 

 was led to compare the relative quantities of sugar in the portal 

 and hepatic veins, expecting to find that the sugar possibly 

 diminished during the passage of the blood through the liver; he was 

 astonished to discover that, on the contrary, the quantity appeared 

 to be greatly increased. He found, and anyone can make the obser- 

 vation, that when an animal living under ordinary conditions is killed, 

 the hepatic blood after death contains a considerable amount of sugar 

 (grape-sugar), even when there is little or none in the portal 

 blood; moreover a simple aqueous infusion of the liver is rich 

 in sugar. Not only so, but the sugar continues to be present in 

 the liver when all blood has been washed out of the organ by a 

 stream of water driven through the portal vein, and goes on 

 increasing in amount for some hours after death. Only one 

 interpretation of these facts is possible ; so far from the liver 

 destroying or converting the sugar brought to it by the portal 

 vein, it is clearly a source of sugar ; the hepatic tissue evidently 

 contains some substance capable of giving rise to the presence 

 of sugar. Bernard further found that when the liver was removed 

 from the body immediately after death, and, after being divided 

 into small pieces, was thrown into boiling water, the infusion or 



