232 
ON THE NITROGEN OF PLANTS. 
place every year, without the smallest compensation ; yet, 
after a given number of years, the quantity of nitrogen will 
be found to have increased. Whence, we may ask, comes 
this increase of nitrogen ? The nitrogen in the excrement 
cannot reproduce itself, and the earth cannot yield it. Plants, 
and consequently animals, must, therefore, derive their nitro- 
gen from the atmosphere. 
The last products of the decay and putrefaction of animal 
bodies, present themselves in two different forms. They are 
in the form of a combination of hydrogen and nitrogen, — am- 
monia, in the temperate and cold climates, and in that of a 
compound, containing oxygen, nitric acid, in the tropics and 
hot climates. The formation of the latter is preceded by the 
production of the first. Ammonia is the last product of the 
putrefaction of animal bodies; nitric acid is the product of 
the transformation of ammonia. A generation of a thousand 
million men is renewed every thirty years : thousands of 
millions of animals cease to live, and are reproduced in a 
much shorter period. Where is the nitrogen which they 
contained during life ? There is no question which can be 
answered with more positive certainty. 
All animal bodies, during their decay, yield the nitrogen 
which they contain to the atmosphere, in the form of ammo- 
nia. Even in the bodies buried sixty feet under ground in 
the church-yard of the Eg'.ise des Innocens, at Paris, all the 
nitrogen contained in the adipocire was in the state of am- 
monia. Ammonia is the simplest of all the compounds of 
nitrogen : and hydrogen is the element for which nitrogen 
possesses the most powerful affinity. 
The nitrogen of putrefied animals is contained in the at- 
mosphere as ammonia, in the form of a gas which is capable 
of entering into combination with carbonic acid, and of form- 
ing a volatile salt. Ammonia in its gaseous form, as well as 
all its volatile compounds, are of extreme solubility in water. 
Ammonia, therefore, cannot remain long in the atmosphere, 
as every shower of rain must condense it, and convey it to 
the surface of the earth. Hence, also, rain-water must, at all 
