The Story-Book of the Fields 



The chest acts like bellows which are alter- 

 nately rilled with air and emptied. These 

 alternate motions are inspiration and expira- 

 tion. In the former the pure air enters our 

 bodies to burn the material for the blood and 

 to produce heat ; in the latter the air, having 

 fulfilled its task, is carried off, not in the 

 same state as when it entered, but impreg- 

 nated with carbon and unfit to breathe, like 

 that which escapes from a lighted fire. 



The burning fire and the breathing body 

 both produce carbonic acid gas, by dissolving 

 their carbon into the air. The breath from 

 our chest is no different from the breath from 

 the stove. This may be proved by an experi- 

 ment. You saw that the presence of car- 

 bonic acid gas is detected by lime-water. If 

 this water is disturbed, turns milky and 

 deposits white flakes, it is a sure sign that the 

 air is impregnated with carbon. Fill a glass 

 with completely clear lime-water, then take 

 some small tube — a reed, for instance, or a 

 straw — and by means of this tube blow into 

 the liquid. You will see that the lime-water 

 will soon be disturbed, will resemble milk, 

 and produce numerous white flakes. This is 

 a clear proof that the air coming from the 

 interior of the body is like that in the bottle 



4 8 



