184 FARM-YARD MANURE. 



In his daily bread, man consumes the ash-constituents 

 of the grain from the flour of which bread is made : in 

 meat he consumes the ash-constituents of flesh. 



The flesh of herbivorous animals, and its ash-consti- 

 tuents, are derived from plants; these ash-constituents 

 are identical with those of the seeds in leguminous 

 plants. Hence if an entire animal is burnt to ashes, the 

 residue will difier httle from the ashes of beans, lentils, 

 and peas. 



In bread and flesh, therefore, man consumes the ash- 

 constituents of seed, or of seed-constituents which the 

 farmer has obtained from his fields in the form of flesh. 



Of the large amount of mineral substances which man 

 consumes in his food during a lifetime, but a smaU fraction 

 remains in his body. The body of an adult does not 

 increase in weight from day to day, which proves that all 

 the constituents of his food must completely pass out 

 again from his system. 



Chemical analysis demonstrates that the excrements 

 of man contain the ash-constituents of bread and flesh 

 very nearly in the same quantity as they exist in the 

 food, which in the body undergoes a change similar to 

 that which would take place in a furnace. 



The urine contains the soluble, the solid excrements 

 the insoluble ash-constituents of food : the stinking sub- 

 stances are the smoke and soot of an imperfect combus- 

 tion. With these are mixed up the undigested and the 

 indigestible remains of food. 



The dung of swine fed on potatoes contains the ash- 

 constituents of the potato ; that of the horse, the ash- 

 constituents of hay and oats ; that of cattle, the ashes of 

 turnips, clover, and other plants which have served them 

 as food. Farm-yard manui^e comprises a mixture of all 

 these excrements. 



