644 DIABETES 



Thus, the glycosuria which follows puncture of the floor of the 

 -fourth ventricle (Claude Bernard's piqure) does not occur in animals 

 which contain little glycogen. The same applies to the adrenal, 

 thyroid and hypophysis glycosurias. But after complete pancreas 

 extirpation (pancreas diabetes) and in the spontaneous human disease 

 (diabetes melitus) or its counterpart in animals, and during the con- 

 tinuous administration of phlorhizin, the glycogen may be nearly or 

 quite exhausted and the diet consist solely of meat and fat and still 

 the glycosuria will continue. On the other hand a partial pancreas 

 extirpation, a mild diabetes melitus, or an interrupted phlorhiziniza- 

 tion may give rise to transient glycosuria, the diagnosis of which may be 

 difficult. In general, experience teaches that all persistent glycosurias 

 prove to be diabetic and that, except in phlorhizin poisoning, ever}- 

 genuine diabetes implies a disturbed function of the pancreas. In 

 forming a judgment of the value of any experimental work on diabetes 

 (histological, chemical or clinical), the student will do well to examine 

 critically the records of quantitative food and urinary analyses offered 

 by the investigator, to show what type and what grade of diabetes 

 is under consideration. 



CARBOHYDRATE PHYSIOLOGY 



Certain facts concerning the physiology of the carbohydrates may 

 be briefly recalled before entering into the discussion of the individual 

 meliturias. 



The appearance of sugar in the urine implies a source or sources 

 of sugar and the existence of a kidney membrane of such a physical 

 character that molecules of sugar may migrate through it with a 

 certain degree of facility. The factors which may influence the purely 

 physical penetrability of the kidney membrane to sugar molecules are 

 those involved in a discussion of kidney function and secretion in 

 general and need not be elaborated here. 



Assuming that the physical penetrability of the kidney membrane 

 to sugar molecules is normal and that it varies only within constant 

 limits, there are then two basic moments which determine how much 

 sugar will pass into the urine. These are: 1. The rate at which sugar 

 molecules enter the cells constituting the kidney membrame. 2. The 

 rate at which these molecules of sugar undergo chemical change into 

 something else within the membrane. 



These same factors of supply and utilization determine the elimina- 

 tion of sugar from any cell or tissue or the organism as a whole, but 

 in the case of internally situated cells the elimination is directly or 

 indirectly into the blood, whereas, in the case of the kidney cells 

 sugar may pass into the urine as well as into the blood and thus leave 

 the body permanently. 



Sugar may pass out of a cell unchanged when the rate at which 

 it enters the cell (from internal and external sources) exceeds the rate 



