TETE USE OF URINE. 195 



With the exception of urea, uric acid contains 

 more nitrogen than any other substance generated 

 by the living organism ; it is soluble in water, and 

 can be thus absorbed by the roots of plants, and its 

 nitrogen assimilated in the form of ammonia, and 

 of the oxalate, hydrocyanate, or carbonate of am- 

 monia. 



It would be extremely interesting to study the 

 transformations which uric acid suffers in a living 

 plant. For the purpose of experiment, the plant 

 should be made to grow in charcoal powder pre- 

 viously heated to redness, and then mixed with 

 pure uric acid. The examination of the juice of the 

 plant, or of the component parts of the seed or 

 fruit, would be a means of easily detecting the 

 differences. 



In respect to the quantity of nitrogen contained 

 in excrements, 100 parts of the urine of a healthy 

 man are equal to 1300 parts of the fresh dung of 

 a horse, according to the analyses of Macaire and 

 Marcet. and to 600 parts of those of a cow. Hence 

 it is evident that it would be of much importance to 

 agriculture if none of the human urine were lost. 

 The powerful effects of urine as a manure are well 

 known in Flanders, but they are considered invalu- 

 able by the Chinese, who are the oldest agricultural 

 people we know. Indeed so much value is attached 

 to the influence of human excrements by these peo- 

 ple, that laws of the state forbid that any of them 

 should be thrown away, and reservoirs are placed 



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