vii] CHEMICAL CHANCES DURING DUNG-MAKING 191 



supply of air and water which class of action pre- 

 dominates at any given time. Putrefactive bacteria are 

 resolving proteins into simpler compounds of nitrogen 

 and ultimately into ammonia ; oxidising bacteria (some- 

 times called denitrifying bacteria) set free nitrogen 

 gas ; meantime the bacteria engaged in the destruction 

 of cellulose and the formation of humus are always 

 building proteins or bodies akin to them out of the 

 previously produced amides and ammonia. 



One other change sometimes takes place when the 

 manure is allowed to get too loose and dry — instead of 

 bacteria, fungi begin to develop very rapidly until the 

 whole mass becomes permeated with the mycelium. 

 The masses of manure begin to look white and dusty, 

 a condition which the practical man describes as "fire 

 fanged." It is generally agreed that such manure is 

 seriously deteriorated, but no analyses are available. 



With these general facts in mind it will be possible 

 to interpret the experiments which have been made to 

 ascertain what part of the fertilising materials contained 

 in foods consumed by animals is recovered in the dung 

 and what losses occur during the making and storage of 

 farmyard manure. In the first place, it can be shown 

 that there is no loss of nitrogen in the gaseous form due 

 to the animal ; the nitrogen contained in the urine and 

 faeces is equal to the nitrogen in the food, less whatever 

 may have been retained by the animal in its bodily 

 increase. Numerous feeding experiments demonstrate 

 this point ; the following example from Kellner's 

 researches may be taken as an illustration. 



An ox was fed on a daily ration of 2 kg. of gluten 

 meal, 2 kg. of starch meal, 4 kg. of dried sugar-beet 

 slices, 5 kg. of hay, and i kg. of chaff, containing in all 

 3888 grms. of nitrogen. About 18-5 kg. of dung was 

 excreted containing 15-36 per cent, of dry matter and 



