URINE OF ANIMALS. 199 



wood, or with earth, both of which substances 

 contain a large quantity of caustic lime, by means 

 of which a complete expulsion of all their ammonia 

 is effected, and they are completely deprived of 

 smell. But such a residue applied as manure can 

 act only by the phosphates which it still contains, 

 for all the ammoniacal salts have been decomposed, 

 and their ammonia expelled. 



The sterile soils of the South American coast are 

 manured with a substance called guano, consisting 

 of urate of ammonia, and other ammoniacal salts, 

 by the use of which a luxuriant vegetation and the 

 richest crops are obtained. The corn-fields in 

 China receive no other manure than human excre- 

 ments. But we cover our fields every year with 

 the seeds of weeds, which from their nature and 

 form pass undigested along with the excrements 

 through animals, without being deprived of their 

 power of germination, and yet it is considered sur- 

 prising that where they have once flourished, they 

 cannot again be expelled by all our endeavours : 

 we think it very astonishing, while we really sow 

 them ourselves every year. A famous botanist, 

 attached to the Dutch embassy to China, could 

 scarcely' find a single plant on the corn-fields of the 

 Chinese, except the corn itself*. 



The urine of horses contains less nitrogen 

 and phosphates than that of man. According to 

 Fourcroy and Vauquelin it contains only five per 



* Ingenhouss on the Nutrition of Plants, page 129 (German edition). 



