84 SOURCE AND ASSIMILATION 



increases neither in size nor strength, and sinks 

 under every exertion. The quantity of rice which 

 an Indian eats astonishes the European ; but the 

 fact, that rice contains less nitrogen than any other 

 kind of grain at once explains the circumstance. 



Now, as it is evident that the nitrogen of the 

 plants and seeds used by animals as food must be 

 employed in the process of assimilation, it is natural 

 to expect that the excrements of these animals will 

 be deprived of it, in proportion to the perfect diges- 

 tion of the food, and can only contain it when 

 mixed with secretions from the liver and intestines. 

 Under all circumstances, they must contain less 

 nitrogen than the food. When, therefore, a field is 

 manured with animal excrements, a smaller quan- 

 tity of matter containing nitrogen is added to it than 

 has been taken from it in the form of grass, herbs, 

 or seeds. By means of manure, an addition only is 

 made to the nourishment which the air supplies. 



In a scientific point of view, it should be the care 

 of the agriculturist so to employ all the substances 

 containing a large proportion of nitrogen which his 

 farm affords in the form of animal excrements, that 

 they shall serve as nutriment to his own plants. 

 This will not be the case unless those substances 

 are properly distributed upon his land. A heap of 

 manure lying unemployed upon his land would 

 serve him no more than his neighbours. The 

 nitrogen in it would escape as carbonate of ammo- 

 nia into the atmosphere, and a mere carbonaceous 



