CHEMISTRY OF THE LIVER. 309 



conveyed to it, but an excess must find lodgment elsewhere. 

 The muscles undoubtedly receive the greater share of this 

 excess. In extreme cases the liver may hold 200 grams of 

 glycogen, which would correspond to the same weight of 

 starch. 



Glycogen Destruction. This stored up glycogen disap- 

 pears in normal conditions gradually after its accumulation; 

 the disappearance is hastened by work or by lowering of tem- 

 perature, showing that it may be called upon for supply of 

 heat as well as for direct mechanical work. Before being 

 utilized, however, for these purposes the glycogen must be 

 thrown back into the form of sugar; how this is done is still 

 a matter of discussion. According to one view the action is 

 a " vital " one, depending on the life of the cells of the liver 

 themselves; by another view this conversion is wholly enzy- 

 mic, a peculiar ferment bringing about the change during life 

 as well as post-mortem. This question has lost much of its 

 importance since the work of Buchner on the zymase, or en- 

 zyme of yeast active in alcohol formation, as w r e now know 

 that enzymes are present where, by earlier methods of experi- 

 ment, they were supposed to be absent. 



The more recent careful experiments seem to show beyond 

 question that a true glycogen-splitting ferment is present. By 

 proper manipulation the cell effect may be excluded, while 

 that of the ferment is left intact. This may be accomplished 

 in the following w r ay : The fresh organ is washed free from 

 blood by forcing water through the portal vein until that 

 escaping by the hepatic veins is clear and colorless. The liver 

 is then chopped fine and allowed to stand a day in a large 

 excess of alcohol for dehydration. The alcohol is poured off, 

 the residue pressed, dried at a low temperature and ground to 

 a powder. In this form it is suitable for extraction with 

 something which does not interfere with enzymic power, but 

 which prevents bacterial or other cell activity. For this pur- 

 pose chloroform water, or solutions of sodium fluoride have 

 been used. A good extracting mixture may contain in 100 



