42 SOURCE AND ASSIMILATION OF NITROGEN. 



tie : and this exportation takes 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 excrements cannot reproduce itself, and the earth cannot yield 

 it. Plants, and consequently animals, must, therefore, derive 

 their nitrogen from the atmosphere. (Boussingault.) 



It will in a subsequent part of this work be shown that the 

 last products of the decay and putrefaction of animal bodies pre- 

 sent themselves in two different forms. They are in the form of 

 ammonia (a combination of hydrogen and nitrogen), in the tem- 

 perate and cold climates, and in that of nitric acid (a compound 

 containing oxygen), in the tropics and hot climates. The forma- 

 tion of the latter is always preceded by the production of the 

 former. Ammonia is the last product of the putrefaction ,of 

 animal bodies ; nitric acid is the product of the decay or erema- 

 causis 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 contained in them during life ? There is 

 no question which can be answered with more positive certainty. 

 All animal bodies during their decay yield to the atmosphere 

 their nitrogen in the form of ammonia. Even in the bodies 



o 



buried sixty feet under ground in the churchyard of the Eglise 

 des Innocens, at Paris, all the nitrogen contained in the adipocire 

 was in the state of ammonia. Ammonia is the simplest of all 

 the compounds of nitrogen ; and hydrogen is the element for 

 which nitrogen possesses the most predominant affinity. 



The nitrogen of putrefied animals is contained in the atmo- 

 sphere as ammonia, in the state of a gas which is capable of 

 entering into combination with carbonic acid, and of forming a 

 volatile salt. Ammonia in its gaseous form, as well as all its 

 volatile compounds, is of extreme solubility in water. Ammonia, 

 therefore, cannot remain long in the atmosphere, as every shower 

 of rain must effect its condensation, and convey it to the surface 

 of the earth. Hence also, rain-water must at all times contain 

 ammonia, though not always in equal quantity. It must contain 

 more in summer than in spring or in winter, because the inter 



