424 DIABETES. [BOOK it. 



problems, why blood does not clot in the living blood-vessels, why 

 the living muscle does not become rigid, and why the living 

 stomach or pancreas does not digest itself. It might be added, 

 bearing in mind the history of the fibrin ferment, that even ad- 

 mitting the presence of an amylolytic ferment after death, we have 

 no proof that such a ferment exists in the hepatic cells during life. 

 It is possible that the ferment which can be extracted after death 

 only makes its appearance as the result of post-mortem changes 

 which have taken place in the protoplasm of the hepatic cells. 

 Moreover it is stated that the sugar which makes its appearance 

 in the liver is dextrose whereas the sugar into which glycogen is 

 converted by the ordinary amylolytic ferments of saliva and pan- 

 creatic juice, is, as in the case of starch, largely maltose. This 

 would indicate that the conversion which takes place in the liver 

 is of a peculiar nature ; but the matter requires further investi- 

 gation. 



Diabetes. Natural diabetes is a disease characterized by the 

 appearance of a large quantity of sugar in the urine. Into the 

 pathology of the various forms of this disease it is impossible to 

 enter here ; but a temporary diabetes, the appearance for a while 

 of a large quantity of sugar in the urine, may be artificially pro- 

 duced in animals in several ways. If the medulla oblongata of a 

 well-fed rabbit be punctured in the region which we have pre- 

 viously described (p. 212) as that of the vaso-motor centre (the 

 area marked out as the "diabetic area" agreeing very closely with 

 that defined as the vaso-motor area), though the animal need not 

 necessarily be in any other way obviously affected by the operation, 

 its urine will be found, in an hour or two, or even less, to be in- 

 creased in amount and to contain a considerable quantity of sugar. 

 A little later the quantity of sugar will have reached a maximum, 

 after which it declines, and in a day or two, or even less, the urine 

 will be again perfectly normal. The better fed the animal, or, 

 more exactly, the richer in glycogen the liver, at the time of the 

 operation, the greater the amount of sugar. If the animal be 

 previously starved so that the liver contains little or no glycogen, 

 the urine will after the operation contain little or no sugar. It 

 is clear that the urinary sugar of this form of artificial diabetes 

 comes from the glycogen of the liver. The puncture of the 

 medulla causes such a change in the liver that the previously 

 stored-up glycogen disappears, and the blood becomes loaded with 

 sugar, much if not all of which passes away by the urine. In 

 the absence of any proof to the contrary, we may assume that 

 in this form of artificial diabetes the glycogen previously present 

 in the liver becomes converted into sugar, just as we know that 

 it does become so converted by post-mortem changes. The glyco- 

 genic function of the liver is therefore subject to the influence 

 of the nervous system, and in particular to the influence of a 



