13G ON THE PRINCIPLES OF 



ceous plants to a far greater deg-ree than those of men and 

 birds (guano). The latter act far more favourabl}^ on the 

 production of the cerealia, especially if they are added to 

 the animal excrements, and are given to the fields at the 

 same time. 



A field, for example, which has lost its fertility for pota- 

 toes and turnips, but on which peas and beans still thrive, 

 becomes far more fertile by a supply of the excrements of 

 horses and cows, for a new crop of potatoes and turnips, 

 than by manuring it with the excrements of man or with 

 g'uano. 



Tlie most accurate experiments and analyses have pointed 

 out that the excrements of man and animals contain those 

 substances, to the presence of which the fertility of the soil 

 is due. The fertilizing power of manure can be determined 

 by weight, as its eifect is in a direct ratio to its amount in 

 the mineral elements of the food of plants. The truth of 

 the I'esult of these chemical analyses must be evident to 

 every one who inquires into the origin of excrements. 



All the excrements of man and animals are derived from 

 the plants of our fields; in the oats and hay which serve as 

 food to the horses, in the roots which are consumed b}^ a 

 cow, there are a certain quantity of mineral ingredients. A 

 horse, in consuming- 15 lb. of hay, and 4^ lb. of oats per day, 

 consumes 21 ounces of those substances which the hay and 

 the oats took from the fields ; he consumes annually 480 lb. 

 of these constituent elements of the soil, but only a very 

 small portion of them remains in his body. If a horse 

 during one year increases 100 lb. in weight, this increase 

 contains only 7 lb. of those mineral substances which were 

 contained in the food. But what has become of the 473 lb. 

 which we cannot detect in his bod}^ ? 



The analysis of the fluid and solid excrements which the 

 horse gives out daily shows that the ingredients of the soil 

 which do not remain in the bod}^ of the animal are contained 

 in its excrements ; it shows that in an adult animal, whicli 

 from day to day does neither increase nor decrease in weight, 

 the amount of the mineral ingredients of the excrements 

 is equal in Aveight to the mineral ingredients of the food. 



As with the horse, so it is with all animals. In all adult 

 anrmalfi the excrements contain the ingredients of the soil 

 according to the quantities and relative 2Jroportio7is in which 

 they are contained in their food. 



The mineral substances of the food whicli have remained. 



