552 METABOLISM, NUTRITION AND DIETETICS 



similar action owing to the deficiency of oxygen occasioned by it. 

 Many drugs also cause glycosuria, including curara, morphine, 

 strychnine, phosphorus, chloroform, ether, and other substances, 

 some of which may act on the ' sugar centre,' although others e.g., 

 phosphorus and chloroform are poisons which can affect the liver 

 directly. It is probable that some of the experimental hyper- 

 glycaemias are due to an associated acidosis. For when the hydrogen- 

 ion concentration of the blood is increased the transformation of 

 glycogen into dextrose in the liver is accelerated. The adminis- 

 tration of alkali is said to have a beneficial influence upon the 

 oxidation of dextrose in dogs after total or partial extirpation of the 

 pancreas (Murlin and Kramer). Injection of water or physiological 

 salt solution into the bile-ducts, or into the mesenteric veins, or of 

 salt solution in considerable amount into the general circulation, 

 is followed by glycosuria (Fischer, etc.). It is a mistake to apply 

 the term diabetes to most of the forms of artificial hyperglycaemia 

 and glycosuria. The condition produced by removal of the pan- 

 creas, which will be returned to in Chapter XI., is, however, a true 

 diabetes, a derangement of metabolism of the sam general nature 

 as that which underlies human diabetes. 



Diabetes Mellitus. In the natural diabetes of man, as in all 

 the forms of glycosuria mentioned, with the exception of that pro- 

 duced by phlorhizin, the immediate cause of the glycosuria is the in- 

 crease of sugar in the blood. Instead of the i part per 1,000, or a 

 little more or less, which constitutes the normal proportion in a 

 healthy man, in diabetes 3 or 4 parts, and in exceptional cases even 7 

 to 10 parts per 1,000 may be present. The riddle of diabetes is the 

 explanation of this persistent hyperglycaemia. Innumerable hypo- 

 theses have been framed to account for this, but on the whole 

 three possibilities have been emphasized: (i) That the power of 

 temporarily storing carbohydrates is deranged; (2) that the power 

 of the tissues to utilize carbo-hydrates (i.e., eventually dextrose) 

 is diminished or abolished ; (3) that too much sugar is produced in 

 the body. In addition, some writers have postulated a fourth 

 factor to explain certain cases (of so-called ' renal diabetes ') to wit, 

 an increase in the permeability of the kidneys for sugar, as in 

 phlorhizin glycosuria. Lest the student should be bewildered 

 amongst all these theories, he should take note that while the second 

 factor is now recognized as the essential one, there is some reason 

 to believe that diabetes mellitus is not in every case a single patho- 

 logical condition, but may comprise a group of such conditions. 

 Some cases may therefore present a picture conforming closely to 

 one or to another of the experimental glycosurias, but others a 

 picture compounded of features characteristic of two or of several 

 of these experimental conditions. 



