272 PEACTICAL PHYSIOLOGY 



condition being an excessive glycogenesis in the liver, whereby the 

 percentage of dextrose in the blood rises above the normal, the excess 

 being excreted into the urine by the kidneys. The glycosuria ceases 

 when all the liver glycogen has been used up, and it cannot be 

 produced by a similar experiment in animals which have been 

 previously starved, so as to clear their livers of glycogen. 



(2) By extirpation of the Pancreas. If the whole of the pancreas be 

 removed in dogs, glycosuria is at once established, and the blood will 

 be found to contain an excess of dextrose. So far, then, the cause of 

 the glycosuria is the same as in the previous condition, viz., an excess 

 of sugar in the blood. If, after the condition has existed several days, 

 the liver be examined it will be found to be glycogen-free, but, unlike 

 the previous condition, the glycosuria still continues, and in a few days 

 it will be noticed that the animal has become markedly emaciated. 

 The cause of the emaciation is that the proteid tissues are undergoing 

 dissolution. That such is actually the case is seen by a determination 

 of the urea excretion, which will be found to be enormously 

 increased in amount. In the course of a few weeks the animal 

 dies of emaciation. 



These results show us that the pancreas must possess, besides its 

 digestive function, some controlling influence on the metabolism of 

 carbohydrates. The probable nature of this influence has recently 

 been suggested in certain experiments by Cohnheim. The expressed 

 intracellular juice of a pancreas has no, or only a very feeble power of 

 decomposing dextrose. The same is true of the expressed juice of a 

 muscle. If, however, these two juices be mixed and allowed to act on 

 dextrose, the latter is very quickly decomposed. 



This means that for the efficient combustion of dextrose in the 

 muscles the muscle zymases must be activated by a substance supplied 

 by the pancreas ; in other words, by an internal secretion of the 

 pancreas. This mechanism is analogous to that of entero-kinase on 

 trypsinogen (see p. 236). 



It is of importance to note, that in severe cases of natural diabetes the 

 pancreas is frequently diseased. 



(3) The administration of certain drugs more especially of Phloridzin. 

 The administration of this drug is immediately followed by glycosuria, 

 which, however, ceases after a few days. If the liver be examined at 

 this stage it will be found that a large proportion of its glycogen has 

 disappeared. If a second dose be administered the glycosuria will 

 reappear, and will persist so long as the drug is administered, and even 

 after all glycogen has been used up. After some time, however, the 

 animal becomes very emaciated, this being accompanied by excessive 

 urea excretion. 



