FATE OF THE CARBOHYDRATE FOOD-CONSTITUENTS. 671 



amount be increased, sugar appears in the urine, and it appears that the 

 sugar in the blood is largely made use of in the chemical processes 

 occurring in contracting muscles. It would seem, therefore, that the 

 object of the glycogenic function of the liver is to store up in a non- 

 diffusible form the excess of carbohydrate matter taken into the blood 

 during a meal rich in carbohydrates, and then to distribute it, little by 

 little, to the economy as occasion may demand. 



The liver converts glycogen into sugar through the action of its 

 own peculiar diastatic ferment. 



If a fragment of liver be washed with water and then with spirit to 

 remove the blood, and then cut up into small pieces and immersed in 

 absolute alcohol for twenty -four hours, if the alcohol be removed and a 

 glycerin extract made of the residue, a solution will be obtained which 

 will be capable of rapidly- converting glycogen infusion into sugar. 



In the process of making the decoction of glycogen this hepatic fer- 

 ment is destroyed by heat, while in the experiment above alluded to, in 

 which the liver was exposed to a warm temperature after removal from 

 the body before making an infusion, the absence of glycogen from such 

 infusion and the presence of sugar indicate the conversion by this 

 hepatic ferment of the glycogen into sugar. Such a conversion also 

 undoubtedly takes place during life. As to why, during life, all the gly- 

 cogen of the liver is not rapidly: converted into sugar, it being admitted 

 that such a ferment is present, it can only be stated that this problem 

 belongs to the same group of phenomena as to why the blood does not 

 coagulate in the living blood-vessels, why the active and living pancreas 

 and stomach do not digest themselves, and why the living muscle does 

 not become rigid. That this process of conversion is, however, capable 

 of occurring in the living liver, and that this ferment is not, as lias been 

 claimed, simply a post-mortem development, is proven by the various 

 conditions which lead to the abnormal conversion of glycogen into sugar 

 in greater amounts than the sy-stem can use, and the consequent elimina- 

 tion of the excess of sugar from the blood by the kidneys, constituting 

 the disease glycosuria, or diabetes mellitus. 



Bernard discovered that if the medulla oblongata be punctured in 

 the neighborhood of the vaso-motor centre in a rabbit, after abundant 

 feeding with carbohydrates, in an hour or less a considerable quantity 

 of sugar may be detected in the urine, which, after a day or two, will 

 disappear. 



If a similar operation be performed on a rabbit which has been 

 deprived of food for several days, no such glycosuria will result, and it 

 therefore seems clear that this diabetic puncture produced the glycosuria 

 through the rapid conversion of the gly-cogen of the liver into sugar. 

 It therefore appears that the glycogenic function of the liver is under 



