588 LECTURE XXV. 



upon the kidneys. They found that a great deal depended upon the 

 place in which the salt solution was introduced. If it was an artery of 

 the brain, glucohemia ensued, and consequently glucosuria, but no poly- 

 uria. 1 When, however, they injected the salt solution into one of the 

 veins of the body, polyuria soon resulted, and at the same time an elimi- 

 nation of sugar took place, but, instead of the amount of sugar present 

 in the blood increasing, it decreased. This case of glucosuria, therefore, 

 must arise from another cause, and may be attributed to an action upon 

 the endothelia of the kidneys. 



If we consider that the kidneys have the function of removing all 

 abnormal substances from the blood, and any excess of normal ones, then it 

 is self-evident that definite statements cannot be made concerning the 

 composition of the urine. It is dependent first of all upon the nature of 

 the nourishment and upon the intensity of the metabolism of the cells. 

 There is nothing uniform concerning the amount of urine eliminated in a 

 day, nor concerning its reaction or other behavior. The individual 

 products which are eliminated in urine we have already discussed, and, 

 in each separate case, traced the product to its source. The end-products 

 of metabolism are always eliminated with a greater or less quantity of 

 salts. These originate, to be sure, partly from decomposition and partly 

 from destruction of tissue, but for the most part they may be traced to 

 the food itself. The amount of water in urine does not depend entirely 

 upon the amount that is drunk, but is materially affected by the amount 

 that is utilized in the organism. We shall soon see that by the evapora- 

 tion of water from the surface of the body, the animal organism has a 

 very efficient means of regulating its temperature. We may expect 

 that one and the same individual, under conditions remaining constant 

 and a diet which is qualitatively and quantitatively the same each day, 

 would eliminate a urine which would show a constant composition within 

 narrow limits. It is remarkable that but few exact and complete analy- 

 ses of urine have ever been made. Usually the composition of the 

 food that is eaten is entirely disregarded. It is clear that such analyses 

 are useless for drawing any conclusions or for future inquiry. The great 

 gap in our knowledge is thus made more apparent, for we would unques- 

 tionably be able to draw certain conclusions as to the metabolism of the 

 cells if there were exact analyses which took into consideration all the 

 substances present in urine, and such investigations would be of great 

 help in the case of pathological processes. Quite recently Otto Folin 2 

 has undertaken the analysis of urine from a single individual during 

 several days in which the diet remained the same. We regret that we 

 cannot give all the values he obtained in his work, but we have to be 



1 See Lecture V, p. 81. 



3 Am. J. Physiol. 13, No. 1, 45 and 66 (1905). 



