162 BASIC BODIES. 



dinary a degree. In order to convince ourselves of the quantity of 

 urea excreted in the urine, we must examine the urine collected in 

 a definite interval in relation to its proportion of urea. As, in the 

 consideration of " Urine/' we shall return to this subject, we will 

 here only remark that the urine of a healthy man contains generally 

 from 2-5 to 3'2% of urea, that the ratio of urea to the other solid 

 constituents is aboutr=9 : 11 or *J : 9, and that a healthy man in 

 twenty-four hours excretes from 22 to 36 grammes. 



My experiments* show that the amount of urea which is 

 excreted is extremely dependent on the nature of the food which 

 has been previously taken. On a purely animal diet, or on food 

 very rich in nitrogen, there were often two-fifths more urea 

 excreted than on a mixed diet ; while, on a mixed diet, there was 

 almost one-third more than on a purely vegetable diet ; while, 

 finally, on a non-nitrogenous diet, the amount of urea was less than 

 half the quantity excreted during an ordinary mixed diet. 



In my experiments on the influence of various kinds of food on 

 the animal organism, and especially on the urine, I arrived at the 

 above results, which in mean numbers may be expressed as follows: 

 on a well regulated mixed diet I discharged, in 24 hours, 32*5 

 grammes of urea, (I give the mean of 15 observations) ; on a 

 purely animal diet 53*2 grammes (the mean of 12 observations); 

 on a vegetable diet 22*5 grammes (the mean of 12 observations) ; 

 and on a non-nitrogenous diet 15*4 grammes (the mean of 3 ob- 

 servations). 



It is especially worthy of remark, that the augmentation of the 

 urea in the urine occurs very soon after the use of highly nitro- 

 genous food, and that in such cases often five-sixths of the nitro- 

 gen taken in the food in 24 hours are eliminated as urea by the 

 kidneys. 



When I took 32 boiled hens' eggs daily, I consumed in them 

 about 30*16 grammes of nitrogen, but in the above-mentioned 

 quantity of urea I discharged only about 25 grammes in 24 hours. 

 On the morning following the day on which I had taken only flesh 

 or eggs, the urine was so rich in urea that immediately on the 

 addition of nitric acid it yielded a copious precipitate of nitrate of 

 urea ; hence Prout's assertion may be correct in reference to 

 England, that freshly passed urine often gives a precipitate of 

 nitrate of urea immediately on the addition of nitric acid, although 

 on the continent, where less animal food is taken, no one, so far as 

 I know, has made a similar observation : and hence also the urine 

 * Journ. f . pr. Ch. Bd. 25, S. 22-29, and Bd. 27, S. 257-274. 



