USE OF SOUR FOOD. 159 



it for some hours to a graduated temperature, we are 

 able to produce sugar; the starch has been changed 

 by the acid. This is done on a large scale in France. 



6. In the souring of food certain vegetable acids 

 are formed, which possess the same power as sulphuric 

 acid : it is even probable that some portions of the 

 otherwise indigestible woody fibre are also changed 

 into a sweet gummy substance, for this is another 

 transformation that we are able to effect by artificial 

 means. The result of souring, then, is to bring the 

 cooked food, already partially altered, into a still more 

 soluble and digestible state. Probably no animal but 

 the hog would be fond of such food; but for him, it is 

 easy to see that it would prove valuable. 



If the souring is allowed to go too far, still another 

 change takes place, by means of which all of the sugar 

 is converted, through fermentation, first into alcohol, 

 and finally into vinegar; in neither of these states 

 would the food be nutritious, even if animals could be 

 induced to eat it. 



SECTION IV. ON THE DIFFERENCES IN CERTAIN CLASSES OF 

 MANURE. 



We are by this time fully able to understand the 

 difference in the manures derived from different classes 

 of animals, the young, the full grown, the fattening, 

 etc.; I will, therefore, now touch once more upon that 

 subject. 



We have seen that the young animal is not only 

 constantly increasing in its bulk, but that it is renew- 

 ing every part much more rapidly than those of ma- 

 ture age. Food is for both of these reasons required, 

 not only to supply the large daily waste, but also to 

 build up the growing bones, muscles, and all other 

 parts. Hence it results, that nearly every thing of 

 value in the food will be appropriated, and the manure. 



