382 



THE EXCRETIONS OF THE BODY 



The percentage of urea in the individual organs, with the exception of the 

 muscles, the heart and the kidneys, is thus about the same as that of the 

 blood i. e., on the average 0.12 per cent. The high percentage in the kid- 

 neys is to be explained by the presence there of urea formed in other organs, 

 and which is necessarily included in making the analysis. 



2. Oxyprote'ic acid was discovered by Bondzynski and Gottlieb (1897). 

 Its barium salt, according to the analyses of various authors, has the follow- 



FIG. 139. FIG. 140. 



FIG. 139. Crystals of urea, obtained from human urine after long-continued evaporation, after 



Funke. 

 FIG. 140. Crystals of uric acid, after Funke. Some of the forms represented were obtained by 



solution and recrystallization of chemically pure uric acid; some by treatment of urinary 



sediments containing urates with mineral acids; some by spontaneous crystallization from 



urine. Most of the crystals are tinged with urea. 



ing composition : C 27.5-30.0, H 3.9-4.1, N" 7.0-10.6, S 1.6-1.8, Ba 28.7-29.8, 

 26.5-31.6. The quantity of this acid (calculated as the Ba salt) excreted 

 in twenty-four hours amounts to not less than 3-4 g. 



3. -Creatinin, Methyl-glyco-cyanamid, NH:C X 9 occurs to the 



XN(CH ).CH 



extent of about 0.25 per cent in the urine. The daily output in the urine 

 amounts to 0.6-2.1 g. and may be estimated at 1 g. as a mean value. 



4. Ammonia, NH 3 . The daily quantity amounts to 0.5-0.9 g. = two to 

 four per cent of the nitrogen in the urine. The ratio of ammonia to urea 

 is approximately 1:40 (cf. page 371). 



5. Uric acid (Figs. 140 and 141) 2, 6, 8-tri-oxypurin (page 373) occurs 

 in the urine of man and the mammals only in small quantities (about 0.7 g. 

 per day). This is a dibasic acid. Of the alkaline urates, the neutral potas- 

 sium and lithium salts are the most soluble, the acid ammonium salt least so ; 

 the urates of the alkaline earths are also very difficultly soluble. In the urine, 

 uric acid probably occurs as monosodium urate which is held in solution 

 mainly by disodium phosphate. 



6. Uric acid is derived from the purin bases and is in its turn oxidized 

 to allanto'in (cf. page 373). These substances also occur in the urine: the 

 purin bases to the extent of 0.08-0.13 g. (mean). 



