DIGESTION. 123 



We know from our study of the glycogenic function of the liver 

 that glycogen can be produced from proteids by synthesis after the 

 proteid molecule has been first broken down. 



If from any cause, nervous or otherwise, the metabolism of the 

 liver is interfered with, the function of glycogenesis is disturbed, and 

 the balance broken,, with the result of the appearance of sugar in the 

 urine. 



Experimental diabetes may be produced in animals in various 

 ways : 



1. By Diabetic Puncture. It was discovered by Bernard that 

 certain lesions to the cerebro-spinal axis, such as puncture of the floor 

 of the fourth ventricle, are capable of producing diabetic conditions. 

 After puncture, the glycogen of the liver is so rapidly converted into 

 sugar, that it raises the percentage of sugar in the blood to such a 

 degree that there is more present than the tissues can use up, and thus 

 some of it finds its way to the kidneys, there to be eliminated. The 

 increased activity of the hepatic cells in transforming the glycogen 

 is believed to be due to stimulation of the vasomotor center in the 

 medulla caused by the puncture, for other means of stimulating this 

 center have always produced temporary diabetes. In man, some dis- 

 eases of the brain, particularly those in the medullary region, are 

 characterized by diabetic symptoms. 



2. Adrenalin Glucosuria. Injection of adrenalin produces dia- 

 betes. It is due to a hyperglycaemia. There is an increase of glucose, 

 due to a decrease in its destruction. The ammonia excretion is con- 

 siderably increased. Hence, in Bernard's puncture, there is an over- 

 production of dextrose by the liver; in pancreatic diabetes, a want of 

 destruction of glucose in the body. In phloridzin diabetes, there is 

 production of sugar by the renal cells, and in diabetes melli.tus, a 

 hyperglycsemia, and this is due to a want of destruction. The sugar 

 in diabetes mellitus is derived from carbohydrates, proteids, and fats. 



3. Phloridzin. This drug is a glucoside obtained from the root- 

 bark of cherry-trees. Powerful results are obtained after its admin- 

 istration either by the stomach or by subcutaneous or intravenous 

 injection. With the appearance of the sugar in the urine, there is a 

 diminution in the quantity of glycogen in the liver. If the drug 

 be administered repeatedly, so that all of the glycogen from the liver 

 and other tissues is entirely used up, and then an additional dose be 

 administered, dextrose will promptly appear. 



PHLORIDZIN DIABETES. Here the ratio of dextrose to nitro- 

 gen excreted in starving animals is about the same as in pancreatic 



