2 VARIATION IN COMPOSITION. 



of the treatment of the subject, and all statements 

 made in the following pages as to its chemical com- 

 position must be taken as only approximate. 

 We may divide its constituents into three classes. 



1. That portion due to solid excreta. 



2. The liquid portion, largely made up of dilute 

 urine. 



3. The straw, or other material, which is used as 

 litter. 



The composition of the manure will vary according 

 to the proportion in which these three substances 

 are present, as well as according to the composition 

 of the substances themselves. It will consequently 

 tend to a clearer apprehension of the subject, if we 

 first examine briefly the chemical composition of the 

 solid excreta and urine of the farm animals. 



1. Solid Excreta. The manurial value of the solid 

 excreta of animals i.e., the proportion they contain 

 of nitrogen, phosphoric acid, and potash depends on a 

 variety of conditions. 



The solid excreta of horses, sheep, cows, and pigs, 

 are well known to possess different properties, as well 

 as to vary in their composition. 



What, however, has a still greater influence is the 

 nature of the food. This is owing to the fact that 

 the solid excreta is made up of undigested food. 

 We can scarcely expect the same quality of solid 

 excreta from an animal fed on poor diet as from an 

 animal fed on very much richer diet. Again, the 



