44 PLANT PRODUCTS 



combination with humic acid, with which the calcium forms 

 an insoluble compound, but some soluble substance, like 

 calcium sulphate, will often be found in the manure heap. 



The organic materials occur chiefly either as fibres or 

 as gummy matter. The fibrous material is very important 

 in enabling the manure heap to retain its liquid constituents, 

 and in maintaining the open structure necessary for admission 

 of air in limited amounts. The gummy material provides 

 the humic acid and other colloids, which will fix or absorb 

 the substances of manurial value. The water present pla3^s 

 a large part in the decomposition of the manure heap and 

 is chiefly absorbed by the litter. The bacteria present are 

 mostly such common forms as coli communis or subtilis, 

 the former derived from the beasts and the latter from the 

 fodder. 



The study of the proximate constituents is quite as 

 important as that of the ultimate constituents. These 

 consist of three parts, the dung, the urine, and the litter. 

 The dung owes its chief value to nitrogen and phosphorus. 

 In old animals it is richer than in young animals, because the 

 young animals utilize food better. In the case of the grain- 

 fed horse it is rich and decomposes rapidly ; but in the case 

 of the grass-fed horse it is poorer, and slower in action. 

 Sheep produce the richest and the cow produces the poorest. 

 A fat bullock will produce better dung than a cow, and the 

 manure will decompose much quicker. 



The urine which decomposes very rapidly owes its chief 

 value to nitrogen and potassium. With root -fed beasts it 

 is weak, and with grain-fed beasts it is concentrated. Much 

 of the nitrogen occurs as urea, and ferments to ammonium 

 carbonate within two or three days. If the food is very 

 coarse — that is, contains much straw or inferior hay — as much 

 as one-third of the nitrogen appears in the form of hippuric 

 acid (benzamido acetic acid, CgHg.CO.NH.CHg.CO.OH). It 

 will be noticed at once that nitrogen for nitrogen, hippuric 

 acid contains very much more carbon than urea, CO(NH2)2, 

 and its excretion involves loss of food and loss of energy. 

 When foods contain a big proportion of pentosans the amount 



