THE URINE 



381 



can be estimated approximately by the formula: A = 75 (s 1). The relation 

 between the molecular concentration of organic (Co) and inorganic (Ci) mole- 

 cules, JT-, is commonly 0.75 (Burgarsky). 



Urine injected intravenously into an animal produces an acute poisoning 

 which results fatally. The toxicity of different urines appears to be some- 

 what different, and Bouchard designates as the toxic unit (urotoxy), the 

 quantity (cubic centimeters per kilogram) of urine sufficient to kill a rabbit: 

 this quantity varies from 30-60 c.c. According to Beck, the toxicity of normal 

 urine depends upon the presence of potassium salts; however, there are alka- 

 loidal substances in the urine which are present only in small quantities nor- 

 mally, but under abnormal conditions are probably eliminated in larger quan- 

 tities, and these might therefore increase its toxicity. 



B. COMPOSITION OF URINE 



1. Urea, or carbamide (cf. page 370; also Fig. 139), is the most important 

 and most abundant constituent of urine. The daily excretion depends upon 

 the supply of proteid in the food. On Volt's normal ration for a moderate 

 worker, the quantity is about 30 g. per day. Usually two to three per cent 

 of the urine is urea. About ninety per cent of the total quantity of nitrogen 

 in the urine of man appears in the form of urea. 



Urea was first separated from urine by Rouelle (1773). In 1828 Wohler 

 succeeded in preparing it synthetically by heating a solution of ammonium 

 isocyanate : 



Ammonium 

 isocyanate 



Urea 



- This synthesis was the first instance of the production by artificial means 

 of a substance occurring in the animal body, and led the way for all the organic 

 syntheses possible to modern science. For this reason Berzelius proposed that 

 the radical of urea be named proin (signifying "dawn"). 



The origin of urea in the animal body has already been considered in Chap- 

 ter XII. Here we may add the following data from Schondorff with regard 

 to the percentage of urea in the different organs. These relate to a dog of 

 32 kg. weight after abundant meat feeding. The organs investigated amounted 

 altogether to fifty-three per cent of the entire body. 



23* 



