ANIMAL MANURES AFFECTED BY MANY CIRCUMSTANCES. 471 



as IS present in that of the horse. But if the cow discharges more in 

 its urine it must void less in its solid excretions. Hence, supposing the 

 food of a full-grown horse and of a cow to be very nearly the same, 

 the dung of the former — the less urine-giving animal — must be the 

 richer, the warmer, and the more valuable— as it is really known to be. 



3°. By the amount of exercise or labor to which the animal is sub-- 

 jected. — The greater the fatigue ta which an animal is subjected the 

 richer the urine is found to be in those compounds (urea chiefly) which 

 yield ammonia by their decomposition (Prout). The food of two 

 animals, therefore, being the same — other things also being equal — 

 the solid excretions will be richer and more fertilizing in that which 

 is kept in the stall or fold-yard, the urine in that which is worked in 

 the open air or pastured in the field. 



4°. By the state of growth to which the animal has arrived. — A 

 full-grown animal has only to keep up its weight and condition by the 

 food it eats. Every thing which is not necessary for this purpose, 

 therefore, it rejects either in its solid or in its liquid excretions. A young 

 animal, on the other hand, adds to and increases its bone and muscle 

 at the expense of its food. It rejects, therefore, a smaller proportion 

 of what it eats. Hence the manure in fold-yards, where young cattle 

 are kept, is always less rich than where full-grown animals are fed. 



5°. By the purpose for which the animal is fed. — Is it to be im- 

 proved in condition ? Then the food must supply it with the mate- 

 rials for increasing the size and strength of its muscles — with albu- 

 men, or fibrin, or other substances containing nitrogen. In such sub- 

 stances, therefore, or in nitrogen derived from them, the droppings 

 must be poorer, and as a manure, less valuable. 



Is the animal to be fattened ? Then its food must supply fatty mat- 

 ters, or their elements, of which nitrogen forms no part. All the ni- 

 trogen of the food, therefore, will pass off in the excretions, and hence 

 the richest manure yielded at any time by the same species of ani- 

 mal is that which is obtained when it is full-grown, and, being large- 

 ly fed, is rapidly fattening. 



Is the cow kept for its milk ? Then the milk it yields is a daily 

 drain upon the food it eats. Whatever passes into the udder is lost 

 to the dung, and hence, other things being equal, the dung of a milk 

 cow will be less valuable to the farmer than that of a full-grown ani- 

 mal from which no milk is expected, or than that of the same animal 

 when it is only laying-on fat. 



6°. By the length cf time during which the manure has been kept. — 

 In 24 hours, as we have seen, the dung of the horse begins to fer- 

 ment and to lessen in weight. All rich manures in like manner — the 

 dung of all animals especially — decompose more or less rapidly and 

 part with their volatile constituents. The value we assign to them 

 to-day, therefore, will not apply to them to-morrow, and hence the 

 droppings of the same animal at the same age, and fed in the same 

 way, will be more or less valuable to the farmer according to the 

 length of time during which they have been permitted to ferment. 



7°. Lastly. By the way in which the manure has been preserved. — 

 The mixed dung of the farm-yard must necessarily be less valuable 

 where the liquia laanure is allowed to run off— or where it is permitted 



