COMPOSITION OF FEEDING-STUFFS 17 



have adhered to the plant, and so got into the ash. 

 In commercial feeding-stuffs gypsum, chalk, fine 

 earth or sand, are sometimes found. They may 

 be there by accident, or they may have been wilfully 

 added for purposes of adulteration. Injurious sub- 

 stances such as arsenic, copper, lead, zinc, etc. 

 may also get into the ash either by sticking to the 

 plant in the form of dust or small particles of earth, 

 or else by way of the plant roots. Where it is a 

 question of solid matter adhering to the plant, the 

 injurious substance may come from particles of 

 slag, or from sewage water, or if absorbed by the 

 roots the manure is usually the source. 



The quantity of mineral substances found in 

 fodder plants depends not only upon the kind and 

 size of the plant, but also upon the soil, manure, 

 and weather. As a rule a rich soil, or the applica- 

 tion of plenty of mineral manures, raises the ash 

 content of the plant. Periods of drought decrease 

 the amount of mineral substances in the plant, par- 

 ticularly as regards lime and phosphoric acid. 



