294 now (;Rors teeI). 



ered with a luxuriant growth of confervae, which did not 

 happen in the other glasses." {Jour. Boy. Ag. Soc. of 

 Eng., XL, 366.) 



Professor Way likewise found that filtering urine 

 through clay or simply shaking the two together, allow- 

 ing the liquid to clear itself, and pouring it off, sufficed to 

 prevent putrefaction, and keep the urine as if fresh for a 

 month or more. Cloez found, as stated on p. 264, that in 

 a mixture of moistened pumice-stone, carbonate of lime, 

 and urea (the nitrogenous principle of urine), no nitrates 

 were formed during eight months' exposure to a slow 

 current of air. 



These facts make it necessary to consider in what state 

 the nitrogen of xirine is absorbed and assimilated by 

 vegetation. 



Urine contains a number of compounds rich in nitro- 

 gen, being derived from the waste of the food and tissues 

 of the animal, which require a brief notice. 



Urea (CO N^HJ* may be obtuii.ed from the urine of 

 man as a white crystalline mass or in distinct transparent 

 rhombic crystals, which remain indefinitely unaltered in 

 dry air, and have a cooling, bitterish taste like saltpeter. 

 It is a weak base, and chemists have prepared its nitrate, 

 oxalate, phosphate, etc. 



Urea constitutes 2 to 3 per cent of healthy human 

 urine, and a full-grown and robust man excretes of it 

 about 40 grams, or 1' I3 oz. av. daily. 



When urine is left to itself, it shortly emits a putrid 

 odor ; after a few days or hours the urea it contained en- 

 tirely disappears, and the liquid smells powerfully of am- 

 monia. Urea, when in contact with the animal matters 



Carbon 20.00 



Hydrogen 6.6T 



Nitrogen 46.67 



Oxygen 26.66 



100.00 



