ON THE ORIGIN AND ACTION OF HUMUS. 63 



merit, have been excluded with the greatest care ? 

 Can the laws of life be investigated in an organized 

 being which is diseased or dying ? 



The mere observation of a wood or meadow is 

 infinitely better adapted to decide so simple a ques- 

 tion than all the trivial experiments under a glass 

 globe ; the only difference is, that instead of one 

 plant there are thousands. When we are acquainted 

 with the nature of a single cubic inch of their soil, 

 and know the composition of the air and rain-water, 

 we are in possession of all the conditions necessary 

 to their life. The source of the different elements 

 entering into the composition of plants cannot 

 possibly escape us, if w^e know in what form they 

 take up their nourishment, and compare its composi- 

 tion with that of the vegetable substances which 

 compose their structure. 



All these questions will now be examined and 

 discussed. It has been already shown, that the 

 carbon- of plants is derived from the atmosphere : it 

 still remains for us to inquire, what power is exerted 

 on vegetation by the humus of the soil and the 

 inorganic constituents of plants, and also to trace 

 the sources of their nitrogen. 



CHAPTER III. 



ON THE ORIGIN AND ACTION OF HUMUS. 



It will be shown in the second part of this work, 

 that all plants and vegetable structures undergo two 

 processes of decomposition after death. One of 

 these is n3.med fermentatio7i ; the other, putrefactio)iy 

 decay, or eremacaiisis,* 



* The word eremacausis was piioposed by the author some time since, 

 in order to explain the true nature of decay; it is compounded from 

 yjf'ua, by degrees, and xavaig, burning. — TV. 



Eremacausis is the act of g-radual combination of the combustible 



