12 On the Influence of Air 



the experiments of Dr. Menzies, 179 cubic inches of air. 

 remain after a common expiration. 



Respiration is an involuntary action, which even the 

 adult cannot long command. Nature has made the ex- 

 piratory muscles, destined to antagonize with the inspi- 

 ratory, superior in strength to the inspiratory. 



The air, then, is the only medium into which the 

 infant is introduced, it is the only stimulus to which it 

 is subjected, it is the only source by which its motions 

 for the maintenance of heat and life can now be pre- 

 served. 



From these observations it will follow, that air is to 

 the more perfect animals no more in its effects, than is 

 caloric to various animals and vegetables, which the 

 return of heat is sufficient to restore to the exercise of 

 their living powers. 



Without enquiring into the cause of life, we will next 

 consider why air is so essentially requisite to the pre- 

 servation of animal temperature. The organic action 

 of plants decomposes water in the same manner in which 

 respiration decomposes air. Both arc endowed with the 

 principle of life, both are mutually dependent on each 

 other, mutually aiding and supporting one another by 

 their reciprocal actions ; carbon and hydrogen, two of 

 the principles of vegetables, are continually evolved by 

 animal action to maintain the growth of vegetables, while 

 oxygen is perpetually passing off from vegetables to 

 supply the atmosphere with an essential principle to the 



