CHAPTER VI. 



THE ATMOSPHERE AND ANIMALS. 



CONSIDERING that all animate and inanimate 

 bodies alike are immersed in a sea of gaseous 

 fluids, which possess affinities of a powerful 

 kind for the different elements of the organic 

 and inorganic kingdoms, it will not surprise 

 the reader to learn that important chemical 

 functions are perpetually discharged by the 

 balmy and apparently inert air which fans his 

 brow or cools his cheek. To these chemical 

 relations of the air we are now to draw atten- 

 tion, and in so doing we shall first direct the 

 consideration to the chemistry of one of the most 

 important functions of the animal frame namely, 

 the function of breathing, or respiration. 



When we expire the air we had previously 

 taken into the lungs no matter whether from 

 the mountain-ridge, or in the less healthful At- 

 mosphere of a crowded town an important 

 alteration in its chemical composition has taken 

 place. We are not conscious of this fact ; but 

 it is one which may be readily proved by the 



