THE NITROGENOUS EXCRETION. URINE. 369 



some carbohydrate derivative which can yield furfuraldehyde. 

 The other delicate sugar tests give the same indication. Some 

 of the carbohydrate doubtless appears as such, but a portion 

 of it probably exists in the form of glucoproteids or other 

 complex groups. Part of the carbohydrate can be readily 

 fermented, while another portion resists the action of yeast. 

 Such observations may be interpreted as suggesting the pres- 

 ence of other carbohydrates than the common glucose. More 

 will be said about this below. 



Pathologically, the passage of even large quantities of sugar 

 into the urine is a common phenomenon. This is most fre- 

 quently observed in diabetes mellitus, a disease in which the 

 power of oxidizing sugar in the muscles seems to be wholly 

 or partly lost. It has been already mentioned that this oxida- 

 tion is possibly an enzymic operation in which certain muscle 

 and pancreas enzymes are at the same time active. In this 

 form of diabetes several hundred grams daily of sugar may 

 be excreted. 



In another, " artificial," form of diabetes sugar may be 

 caused to appear in considerable quantity temporarily in the 

 urine. The administration of small doses of phloridzin, a 

 glucoside, is followed by the appearance of sugar in the urine, 

 but this condition is now believed to depend on a disturbance 

 of the proper functions of the kidneys rather than on any alter- 

 ation of the sugar-oxidizing power. The power of retaining 

 the sugar in the blood from which it should be taken up and 

 oxidized by the muscular tissues depends on the maintenance 

 of the integrity of the membranous structures of the kidneys. 

 If these suffer strain, which seems to be. the case after admin- 

 istration of phloridzin, a little sugar more than the normal 

 may be able to diffuse or pass through in some manner. It 

 is possible that many other substances may have a somewhat 

 similar action, but in much smaller degree, and so occasion 

 sugar excretions still within what may be called " normal " 

 limits. 



