ASSIMILATION OF NITROGEN. 63 



and then with lime, gives off ammonia in its 

 free state. 



All these examples must convince even the 

 most skeptical that ammonia does exist in al- 

 most all plants. 



Hitherto the presence of ammonia in the at* 

 mosphere only has been considered, but we 

 shall now enter into detail rather more fully, 

 as to the sources from whence the atmosphere 

 derives its supply. 



In the analysis before given it has been seen 

 that the muscle or flesh of all animals is com- 

 posed almost entirely of nitrogen, and that an- 

 imal matter in its decay, always yields this sub- 

 stance in the form of ammonia; hence, if w^e 

 reflect that a generation of a thousand millions 

 of men is renewed every thirty years, and that 

 in the same period thousands of millions of ani- 

 mals cease to live and are reproduced, the ques- 

 tion will then arise, what becomes of the ammo- 

 nia which mustbe generated by their decay? But 

 the examination of this subject must be carried 

 still farther, to show that the liquid excrement 

 of all animals, and especially of those which are 

 carnivorous, contains an excess of ammonia, in 

 the state most useful for the assimilation of the 

 plant, and in that state also in which it may 

 most readily be applied and collected by agri- 

 culturists, for use as a manure. 



It is desirable here to explain why it is that 

 the liquid excrement, that is the urine of all 

 carnivorous animals, is richer in this principle 

 of ammonia than that of herbiferous animals. 

 It has been previously noticed that flesh con- 



