GLYCOGEN. 



IT is nearly fifty years ago that Claude Bernard dis- 

 covered glycogen, or animal starch, and of all his 

 epoch-making researches there is probably none which has 

 been of such far-reaching importance, or the foundation of 

 so many subsequent investigations. The distribution of 

 glycogen in the liver, muscles and fcetal structures ; the 

 methods of obtaining it from those tissues ; the chemical 

 and physical characters of the purified material ; all these 

 points have been and still are to be found described and 

 discussed in current physiological literature. No year 

 passes but what something is added to our knowledge of 

 glycogen, but even now the fundamental questions that go 

 to the root of the whole matter are still subjects for dispute. 

 These fundamental questions are two in number, namely : 

 From what is glycogen formed ? and what is the ultimate 

 fate of glycogen ? 



I propose in the following article to describe certain 

 recent work on the subject ; this has more particularly con- 

 cerned itself with answering the second of the two questions. 

 To trace all the vicissitudes through which the theories of 

 the fate of the hepatic glycogen have passed would be a 

 tedious and thankless task ; the general tendency of late 

 years, however, has been to return once more to Claude 

 Bernard's original teaching that glycogen is what its name 

 professes it to be, the mother substance of sugar. 



Before, however, passing to the consideration of the fate 

 of the hepatic glycogen, it will be convenient first to state 

 the case with regard to its ^origin. Bernard considered that 

 proteid food was the source of glycogen in the liver ; Pavy, 

 on the other hand, supposed that it was from carbohydrate 

 food alone that glycogen was derived. As is usually the 

 case in physiological investigations where there are two 

 opposite theories, the truth is ultimately found to lie some- 

 where between them, and the view usually accepted at the 

 present day is that both varieties of food may act as sources 



