THE NITROGENOUS EXCRETION. URINE. 3/5 



tioned in a former chapter, strongly reducing substances are 

 produced in the autolytic changes taking place in the liver 

 and pancreas. In cases then, this " normal " reduction may 

 become excessive. 



THE ELECTRICAL CONDUCTIVITY OF URINE. 



In one of the chapters on the blood the nature of electrical 

 conductivity in the fluids of the body was explained and the 

 methods of determination outlined. As this conductivity de- 

 pends mainly on the sum of the inorganic constituents present, 

 and as sodium chloride is the most abundant of these, the de- 

 termination in itself has but a limited importance. In some 

 cases the value of the conductivity would be merely a rough 

 measure of the salt consumed with the food, and the salt con- 

 sumption is extremely variable. 



Nearly all the other substances found in the urine have a sig- 

 nificance very different from that of the salt. The latter is con- 

 sumed and excreted as such, while the other important urinary 

 constituents are products of metabolism, that is, of the breaking 

 down of the digested and absorbed food materials. The 

 organic products of metabolism are practically non-electrolytes 

 or bodies with a very low conducting power; indeed the con- 

 ductivity of a weak salt solution is materially lowered by the 

 addition of urea and the effect of the purine bodies is practi- 

 cally in the same direction. Aside from the chlorides, the in- 

 organic salts of the urine are mainly phosphates and sulphates 

 of the alkali or alkali-earth metals, and these are made up 

 largely from the oxidation of sulphur and phosphorus of pro- 

 tein foods. We consume a certain amount of phosphoric and 

 sulphuric acids in complex organic combination, in the lecithins 

 and chondroitins, for example, and small amounts of mineral 

 sulphates and phosphates are also found in some of our foods, 

 but these amounts are not large enough to vitiate the truth of 

 the general proposition that the sulphuric and phosphoric acids 

 as detected in the urine are results of certain kinds of meta- 



