ANIMAL MANURE. 175 



the products of their putrefaction, and at last noth- 

 ing remains except the phosphate of lime and other 

 salts in their bones. Now this earthy residue of the 

 putrefaction of animals must be considered, in a 

 rational system of agriculture, as a powerful manure 

 for plants, because that which has been abstracted 

 from a soil for a series of years must be restored to 

 it, if the land is to be kept in a permanent condition 

 of fertility. 



ANIMAL MANURES. 



We may now inquire whether the excrements of 

 animals, which are employed as manure, are all of 

 a like nature and power, and whether they, in every 

 case, administer to the necessities of a plant by an 

 identical mode of action. These points may easily 

 be determined by ascertaining the composition of 

 the animal excrements, because we shall thus learn 

 what substances a soil really receives by their means. 

 According to the common view, the action of solid 

 animal excrements depends on the decaying organic 

 matters which replace the humus, and on the pres- 

 ence of certain compounds of nitrogen, which are 

 supposed to be assimilated by plants, and employed 

 in the production of gluten and other azotized sub- 

 stances. But this view requires further 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 chem- 

 ical nature of the 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 excre- 

 ment is produced which crumbles gradually to a dry 

 powder in the air. This excrement consists of the 



