ITS ESSENTIAL ELEMENTS. 177 



condition.* The daily increase in size of a cow is, 

 however, much less than this quantity. We find that 

 the nitrogen, apparently deficient, is actually con- 

 tained in the milk and urine of the animal. The 

 urine of a milch-cow contains less nitrogen than that 

 of one which does not yield milk; and as long as a 

 cow yields a plentiful supply of milk, it cannot be 

 fattened. We must search for the nitrogen of the 

 food assimilated, not in the solid, but in the liquid 

 excrements. The influence which the former exer- 

 cise on the growth of vegetables does not depend 

 upon the quantity of nitrogen which they contain. 

 For if this were the case, hay should possess the 

 same influence ; that is, from 20 to 25 lbs. ought to 

 have the same power as 100 lbs. of fresh cow-dung. 

 But this is quite opposed to all experience. 



Which then are the substances in the excrements 

 of the cow and horse which exert an influence on 

 vegetation? 



When horse-dung is treated with water, a portion 

 of it to the amount of 3 or 3J per cent, is dissolved, 

 and the water is colored yellow. The solution is 

 found to contain phosphate of magnesia, and salts 

 of soda, besides small quantities of organic matters.f 



* 100 lbs. of flesh contain on an average 15-86 of muscular fibre : 18 

 parts of nitrogen are contained in 100 parts of the latter. — L. 



The flesh of animals when digested in repeated portions of cold wa- 

 ter, affords albumen, saline substances, and coloring and extractive 

 matters. When the part that is no longer acted on by cold water is di- 

 gested in hot water, the cellular substance is removed in the form of 

 gelatine, and fatty matter separates. The insoluble residue is princi- 

 pally j^irme. 



The following is the proportion of water, albumen, and gelatine in 

 the muscular parts of several animals and fishes. 



