234 THE HOUSE I LIVE IN. 



ral and most fit state for breathing, consists of 

 about 80 parts of nitrogen gas, and 20 of oxy- 

 gen gas, or vital air ; though some say there is 

 always a little carbonic acid gas mixed with it, 

 even in its purest or healthiest state. But no 

 sooner is it breathed over in the lungs even 

 once than the oxygen is greatly diminished, 

 and the carbonic acid gas greatly increased. 

 If we breathe the same air over twice or three 

 times, the carbonic acid becomes still more 

 abundant, while the oxygen as rapidly dimin- 

 ishes. 



BREATHING Am TWICE. Now if we 

 breathe air twice over, or if we breathe that 

 which already has carbonic acid in it, derived 

 from some other source, it does not sufficiently 

 change the blood from its black to its scarlet 

 color. It is consequently sent back to the 

 heart, and distributed all over the body, in a 

 state totally unfit for the purposes for which 

 the great Creator designed and gave it ; and if 

 this abuse is long permitted, the health suffers. 



The air is changed by breathing it, at a 

 most astonishing rate. Probably we inhale 



