COMPOSITION OF HUMAN URINE. 461 



Of natural liquid manures, the most important and valuable, though 

 the most neglected and the most wasted also, consists of the urine of 

 man and of the animals he has domesticated. 



The efficacy of urine as a manure depends upon the quantity of 

 solid matter which it holds in solution, upon the nature of this sohd 

 matter, and especially upon the rapid changes which the organic 

 part of it is known to undergo. 



The numbers in the above table show that the urine of the cow, 

 estimated by the quantity of solid matter it contains, is more valu- 

 able than that of any other of our domestic animals, with the excep- 

 tion of the pig. But the quantity voided by the cow must be so 

 much greater than by the pig, that in annual value the urine of one 

 cow must greatly exceed that of many pigs. 



It might be supposed at first that in all animals the quantity of 

 urine voided would have a close connection with the quantity of water 

 which each was in the habit of drinking. But this is by no means the 

 case. Thus it is the result of experiment that in man the drink ex- 

 ceeds the urine voided by about one-tenth part only — while 



Of watpr id 24 hours. Of urine in 24 hours. 



A horse, which drank 35 lbs. gave only 3 lbs. 

 A cow, which drank 132 lbs. gave 18 lbs., and 



19 lbs. of milk (Boussingault). 

 How very large a quantity of the liquid they drink must escape 

 from the horse and the cow in the form of insensible perspiration ! 

 That this should be very much greater indeed than in man, we are 

 prepared to expect from the greater extent of surface which the bo- 

 dies of these animals present. 



Let us now examine more closely the composition of urine, the 

 changes which by decomposition it readily undergoes, and the effect 

 of these changes upon its value as a manure. 



1°. Human urine The exact composition of the urine of a healthy 



individual in its usual state was found by Berzelius to be as follows : — - 



Phosphate of soda 2-9 



Phosphate of ammonia 1-6 



Common salt 4-5 



Sal-ammoniac 1-5 



Phosphates of lime and mag- 

 nesia, with a trace of silica 

 and of fluoride of calcium, 1-1 



1000 

 From what I have already had occasion to state in regard to the ac- 

 tion upon living plants of the several sulphates, phosphates, and other 

 saline compounds, mentioned in the above analysis, you will see that 

 the fertilizing action of urine would be considerable, did it contain no 

 other solid constituents. But it is to the urea which exists in it in very 

 much larger quantity than any other substance, that its immediate 

 and marked action in promoting vegetation is chiefly to be ascribed. 

 This urea, which is a white salt-like substance, consists of — 



she gives. Boussingault found a milk cow to yield daily 18 lbs. of urine and 19 lbs. of 

 milk..— Ann. de Chim.et de Phys., Ixxi., pp. 123, 124. 



