176 OF MANURE. 



confirmation with respect to the solid excrements 

 of animals, for they contain so small a proportion 

 of nitrogen, that they cannot possibly by means of 

 it exercise any influence upon vegetation. 



We may form a tolerably correct idea of the 

 chemical nature of animal excrement without 

 further examination, by comparing the excrements 

 of a dog with its food. When a dog is fed with 

 flesh and bones, both of which consist in great part 

 of organic substances containing ^nitrogen, a moist 

 white excrement is produced which crumbles 

 gradually to a dry powder in the air. This excre- 

 ment consists of the phosphate of lime of the bones, 

 and contains scarcely y^o P ar ^ of its weight of 

 foreign organic substances. The whole process of 

 nutrition in an animal consists in the progressive 

 extraction of all the nitrogen from the food, so that 

 the quantity of this element found in the excre- 

 ments must always be less than that contained in 

 the nutriment. The analysis of the excrements of 

 a horse by Macaire and Marcet proves this fact 

 completely. The portion of excrements subjected 

 to analysis was collected whilst fresh, and dried 

 in vacuo over sulphuric acid ; 1 00 parts of it (cor- 

 responding to from 350 to 400 parts of the dung 

 before being dried) contained 0*8 of nitrogen. 

 Now every one who has had experience in this 

 kind of analysis is aware that a quantity under one 

 per cent, cannot be determined with accuracy. We 

 should, therefore, be estimating its proportion at a 



