BREATHING 
447 
these green plants are storing up food for animals, including 
man. 
Ventilation. — Associated with the question of breathing 
is the problem of supplying our homes with fresh, pure air. 
Every one feels better after a walk in the open air. How to 
have plenty of fresh air in our rooms is a difficult problem. 
One of the difficulties is 
to get the air down to 
the breathing line and 
not stir up the dust on 
the floor. Figures 396 
and 397 show the best 
plans for ventilating a 
room. They are adapted 
to the two common meth¬ 
ods of heating, hot air 
and steam or hot water. 
They show the course 
taken by the currents of 
fresh air entering the 
room at night with the 
window open, and in the 
daytime with it shut. 
Exercise. — Even if the 
home is furnished with 
fresh air, we should ob¬ 
serve good habits of 
breathing. When we 
walk out-of-doors, we should take plenty of fresh air into our 
lungs in a series of deep breaths. All young people should 
take exercise in the open air, because such exercise develops 
all the organs and makes them strong. Thus the whole 
body becomes more robust and better able to withstand 
disease and to do its work. 
Suffocation. — When the body is deprived of a sufficient 
Room at f//s//r 
/HD/RECr HEATWS. 
Room /A/Z>AYr/M£ 
MOMECE HEAT MG. 
Figure 396 . — Hot-air Heating. 
By Earl Hallenbeck. 
