INTERMEDIATE METABOLISM OF THE FATS 401 



to 0.3 per cent, or more, and the kidneys simply excrete that proportion 

 of the blood-sugar which constitutes an excess over the normal amount. 



The glucohemia which ensues after the diabetic puncture is evidently 

 due to a failure of the normal power of the liver to store up glucose in 

 the form of its anhydride, glycogen. The efficiency of the operation is 

 proportional to the glycogen-content of the liver at the time it is per- 

 formed, and at the end of the process the liver is found to have been 

 drained of its glycogen-reserves. It appears that the storage-capacity 

 of the liver is subject to control by the nervous system. The afferent 

 path in the reflex arc is contained in the vagi. If the vagus is cut 

 and the peripheral end is stimulated no glycosuria ensues, but if the 

 central end is stimulated a decided discharge of sugar from the liver 

 occurs. The efferent paths lie in the splanchnic nerves, and if these be 

 previously severed the diabetic puncture is without effect. 



The greatest advance toward the interpretation of spontaneous 

 diabetes, however, occurred when in 1889 von Mering and Minkowski 

 discovered that extirpation of the Pancreas in animals produces a pro- 

 found glucohemia and glycosuria terminating ultimately in the death 

 of the animal. The effects of this operation have been very exhaus- 

 tively studied in recent years by F. M. Allen who finds that glucohemia 

 and glycosuria may be induced by partial removal of the pancreas. 

 If nine-tenths of the gland be excised a severe diabetes ensues, but if 

 only a small part of the pancreas, for example one-eighth, be removed, a 

 mild diabetes ensues which is modifiable by diet. Thus if a sufficiency 

 of the pancreas be left in situ no glycosuria at all may appear in the 

 urine. If the remnant of gland be larger glycosuria may be absent 

 on a meat-diet or even on a diet containing bread, but glycosuria will 

 ensue if sugars be added to the diet and, once started, may continue 

 on a bread-and-meat diet. In turn, continued glycosuria upon a bread- 

 and-meat diet may culminate in a condition in which glycosuria con- 

 tinues on meat alone, and the experiment terminates fatally. 



The interesting observation has been made by Carlson, that if glyco- 

 suria be induced in a female animal by depancreatization, and the 

 animal subsequently becomes pregnant, the glycosuria ceases at the 

 time that the pancreas begins to develop in the embryo. It is not 

 certain, however, whether this is due to the mother being enabled to 

 utilize glucose herself through transmission of a pancreatic hormone 

 from the fetus to the maternal circulation, or whether, which is perhaps 

 more probable, the drainage of carbohydrates from the mother by the 

 needs of the fetus deprives her of the excess which she is unable to 

 utilize herself. 



In fatal cases of diabetes it has repeatedly been observed that 

 degenerative changes are present in certain elements of the pancreatic 

 tissues, namely the Islets of Langerhans, and it is particularly to the 

 removal of these elements that the diabetes following total or partial 

 extirpation of the pancreas is due. Thus injection of paraffin into 

 the ducts arising from the secretory tissues of the pancreas results in 

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