362 M. Dumas on the Chemical Statics of Organiiaed Beings. 



tion from which carbonic acid is continually disengaged, in 

 which consequently carbon undergoes combustion. 



You know that we were not stopped by the expression 

 cold-blooded a?ii7nals, which would seem to designate some 

 animals destitute of the property of producing heat. Iron, 

 which burns vividly in oxygen, produces a heat which no 

 one would deny ; but reflection and some science is necessary 

 in order to perceive, that iron which rusts slowly in the air 

 disengages quite as much, although its temperature does not 

 sensibly vary. No one doubts that liglited phosphorus in 

 burning produces a great quantity of heat. Unkindled phos- 

 phorus also burns in the air, and yet the heat which it de- 

 velops in this state was for a long time disputed. 



So as to animals, those which are called warm-blooded 

 burn much carbon in a given time, and preserve a sensible 

 excess of heat above the surrounding bodies; those which 

 are termed cold-blooded burn much less carbon, and conse- 

 quently retain so slight an excess of heat, that it becomes 

 difficult or impossible to observe it. 



But nevertheless, reflection shows us that the most constant 

 character of animal existence resides in this combustion of 

 carbon, and in the development of carbonic acid which is the 

 result of it, beginning also in the production of heat which 

 every combustion of carbon occasions. 



Whether the question be of superior or inferior animals; 

 whether this carbonic acid be exhaled from the lungs or from 

 the skin, does not signify ; it is always the same phaenomenon, 

 the same function. 



At the same time that animals burn carbon, they also burn 

 hydrogen; this is a point proved by the constant disappear- 

 ance of hydrogen which takes place in their respiration. 



Besides, they continually exhale azote. I insist upon this 

 point, and principally in order to banish an illusion which I 

 cannot but believe to be one of the most prejudicial to your 

 studies. Some observers have admitted that there is an ab- 

 sorption of azote in respiration, but which never appears un- 

 accompanied by circumstances that render it more than doubt- 

 ful. The constant phaenomenon is the exhalation of gas. 



We must therefore conclude with certainty, that we never 

 borrow azote from the air; that the air is never an aliment 

 to us ; and that we merely take from it the oxygen necessary 

 to form carbonic acid with our carbon, and water with our hy- 

 drogen. 



The azote exhaled proceeds then from the aliments, and it 

 originates from them entirely. This, in the general ceconomy 

 of nature, may in thousands of centuries be absorbed by 



