176 OF MANURE. 



phosphate of lime of the bones, and contains scarce- 

 ly iQo P^^t of its weight of foreign organic substan- 

 ces. The whole process of nutrition in an animal 

 consists in the progressive extraction of all the ni- 

 trogen from the food, so that the quantity of this 

 element found in the excrements 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 excre- 

 ments subjected to analysis was collected whilst 

 fresh, and dried in vacuo over sulphuric acid ; 100 

 parts of it (corresponding 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 un- 

 der one per cent, cannot be determined with accura- 

 cy. We should, therefore, be estimating its propor- 

 tion at a maximum, were we to consider it as equal 

 to one-half per cent. It is certain, however, that 

 these excrements are not entirely free from nitrogen, 

 for they .emit ammonia when digested with caustic 

 potash. 



The excrements of a cow, on combustion with ox- 

 ide of copper, yielded a gas which contained one 

 vol. of nitrogen gas, and 26*30 vol. of carbonic acid. 



100 parts of fresh excrements contained 



Nitrogen 0-506 



Carbon 6-204 



Hydrogen 0824 



Oxygen 4-818 



Ashes 1-748 



Water . . . . . . 85-900 



100000 



Now, according to the analysis of Boussingault, 

 which merits the greatest confidence, hay contains 

 one per cent, of nitrogen ; consequently in the 25 lbs. 

 of hay which a cow consumes daily, J of a lb. of ni- 

 trogen must have been assimilated. This quantity 

 of nitrogen entering into the composition of muscu- 

 lar fibre would yield 8*3 lbs. of flesh in its natural 



