HISTORY OF DEXTROSE 145 



portal vein. The glycogen, therefore, reconverted to sugar, 

 is given back to the blood. This reconversion is effected by 

 a diastatic endoenzyme called glycogenase. That it is an 

 enzyme action and not due to the living cells is shown by the 

 fact that glycogenase will do its work when minced liver is 

 mixed with chloroform water. 



During starvation, glycogen disappears from the liver cells. 

 After such a period, a carbohydrate diet rapidly replaces the 

 glycogen, a protein diet to a lesser extent, and a fatty diet 

 Tittle, if at all. Very decisive evidence that glycogen may 

 be produced from proteins has been shown by feeding dogs 

 with casern after the production of permanent glycosuria by 

 removal of the pancreas. The amount of sugar excreted was 

 much greater than could have come from the glycogen originally 

 present in the animal's body plus free carbohydrate in the 

 food plus prosthetic groups. That the sugar did not come from 

 fat was shown by the fact that when the protein was increased 

 the dextrose and nitrogen excreted increased proportionally. 

 Glycogen may be formed on a fat diet, since it has been shown 

 that glycerin is a glycogen former. This was shown directly 

 by perfusing a tortoise liver with blood to which glycerin had 

 been added. There is no proof that fatty acids can be con- 

 verted to glycogen. The liver contains, normally, from 2 to 

 10 per cent, of glycogen, forming the main storehouse of surplus 

 carbohydrate. Muscles contain from 0.3 to 0.5 per cent, 

 per weight, and hold usually more than one-half of the total 

 glycogen of the body. Glycogen tends to disappear from the 

 organism under two general conditions during muscular 

 activity and during starvation, although the heart will retain 

 its normal supply until the very last. Glycogen disappears 

 much more readily than stored fat. It forms the most ready 

 source of energy. It is very probable that most of the glycogen 

 leaves the liver as sugar, but possible also that it may in the 

 liver cells undergo a conversion to fat and leave in this form. 



History of Dextrose. The sugar in the blood varies from 

 1.5 to 3 parts per 1000. If the amount rises above this limit 

 it is excreted by the kidneys. This occurs when large quantities 

 are eaten. It is an important practical rule that a person who 

 can tolerate two grams of dextrose per kilo of body weight taken 

 not less than two hours after a meal without excreting any of it 

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