CARHoii) Dh'ATh' j'l/) s/oi.oay G37 



ilil'ticiilt. Ill ^'ciieral, experience teaches tliat all persistent j^lyco- 

 surias prove to be diabetic and that, except in i)liloi'hizin poisoning;, 

 every fjemiine 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 an- 

 alyses 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 

 now be briefly recalled before entering into the discussion of the in- 

 dividual 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 here elaborated. 



Assuming that the physical penetrability of the kidney membrane 

 to sugar molecules is normal and constant there are then two basic 

 moments which determine how such sugar will pass into the urine. 

 These are 1. The rate at which sugar molecules enter the cells consti- 

 tuting tlie kidney membrane. 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 the blood and thus leave the body. 



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 

 at which it undergoes change into something else within the cell, the 

 same holding in the case of the cells forming the kidney membrane. 

 Thus sugar passes from the kidney membrane into the urine when 

 the rate at which sugar molecules enter the kidney membrane exceeds 

 the rate at which they are denatured or utilized wathin it. In order 

 to understand the various ways in which melituria may be produced 

 it is necessary to analyze farther these factors of supply and utiliza- 

 iion. 



The Sugar Supply to the Kidneys is chiefly via the blood, although 

 the metabolism of the kidney cells may lead to some endogenous sup- 

 ply. The factors which influence the rate at which sugar molecules 

 enter the kidney membrane froiii the blood, are immedmte and remote. 



