INTRODUCTION. 27 



combining with the hydrogen and carbon of the 

 blood, is exhaled with them in the form of water 

 and carbonic acid ; as for the azote, into whatever 

 part of the animal body it may penetrate, it always 

 appears to remain there*. 



The relations then of the animal and those of the 

 plant with the surrounding atmosphere, are precisely 

 in an inverse ratio to each other ; water and carbonic 

 acid are rejected by the one and produced by the 

 other. The function of respiration is essential to 

 the constitution of the animal body ; it is that in- 

 deed, if we may be permitted to use such a phrase, 

 in which its animality consists, and animals are 

 found to exercise all their functions with more or 

 less efficiency, in proportion as their respiration is 

 more or less perfect. Respiration, the fourth of the 



* The late experiments of Dr. Edwards, of Paris, seem to con- 

 tradict this latter opinion. This enterprizing physiologist and 

 chemist has inferred, from the circumstance of the opposite results 

 given by his experiments, some indicating a diminution of the azote 

 of the air, others an increase of it during respiration, that this gas 

 is absorbed into the circulation, and afterwards is discharged from 

 it ; and that each of these actions is regulated by the constitu- 

 tion, habit, and circumstances of the individual, and by the in- 

 fluences to which he may be subjected, the absorption being to a 

 small extent, when the exhalation is considerable, and vice versa. 

 Independently of the satisfactory nature of the experiments, whence 

 Dr. Edwards has drawn his inferences, there are many collateral 

 proofs that may be brought to their support, derived from the 

 manifestations of the animal economy in health and in disease ; 

 and it appears extremely probable that not only is azote, but that 

 other gases also are absorbed into and discharged from the cir- 

 culation, in a greater or less quantity, according to the varying 

 state of the vital energies of the animal system. 



