CRYSTALLIZABLE NITROGENOUS MATTERS, 



109 



while from 30 grammes of gluten, in an average of three experiments, 

 there was obtained 0.21 gramme of urea. According to Bechamp, 

 this 



Fig. 25. 



UREA, prepared from urine, and crystallized 

 by slow evaporation. (Lehmann.) 



is not a process of simple 

 oxidation, but an oxidation with 

 decomposition, in which various 

 other substances are produced from 

 the albuminous matter at the same 

 time with urea. The quantity of 

 urea excreted by a healthy man is 

 about 35 grammes per day. This 

 amount varies, of course, with the 

 size of the body, the average daily 

 proportion of urea to the weight 

 of the whole body being 0.5 per 

 thousand parts. Lehmann, in ex- 

 periments on his own person, found 

 the average daily quantity to be 

 32.5 grammes. Bischoff, by simi- 

 lar experiments, found it to be 35 

 grammes. Prof. William A. Ham- 

 mond, whose weight was 90 kilogrammes, found it to be 43 grammes. 

 Prof. John C. Draper, whose weight was 66 kilogrammes, found it 

 26.5 grammes. 



It has been shown by Prof. John C. Draper, 1 and confirmed by other 

 observers, that there is a diurnal variation in the normal quantity of 

 urea. A smaller quantity is produced during the night than during 

 the day ; and this difference exists even in patients who are confined to 

 the bed during the whole twenty-four hours, as in the case of a man 

 under treatment for fracture of the leg. This is probably owing to the 

 greater activity, during the waking hours, of both the mental and di- 

 gestive functions. More urea is produced in the latter half than in the 

 earlier half of the day ; and the greatest quantity is discharged during 

 the four hours from 6j to 10^ P. M. 



The quantity of excreted urea represents almost completely the 

 amount of decomposition in the nitrogenous organic ingredients of the 

 body ; since it is the only nitrogenous substance discharged in consider- 

 able quantity by the excretions. A comparison of the entire amount 

 of nitrogen contained in the daily food with that discharged from the 

 body in various forms shows that fully 85 per cent, of that introduced 

 reappears as an ingredient of the urea ; the remaining 15 per cent, being 

 contained in the uric and hippuric acids and creatinine of the urine, and 

 in the nitrogenous matters of the feces. 



All observers are agreed that the quantity of urea excreted varies in 

 proportion to the amount of nitrogenous matters contained in the food. 



1 New York Journal of Medicine, March, 1856. 



