172 ELEMENTARY BIOLOGY 



breathing. It is only in comparatively recent times, therefore, 

 that we have come to realize what a close connection there 

 is between our breathing habits and breathing conditions, on 



Head cap 

 Check valve - x te^ fc ^^0*^"" ^Supply tube 



FIG. 61. Oxygen inhalator 



This apparatus for the resuscitation of persons overcome by suffocating fumes or gases 

 was developed by the United States Bureau of Mines. It is used with the Schaefer 

 method of artificial respiration, and supplies oxygen for about thirty-five minutes, which 

 is usually sufficient to restore normal breathing. (Photograph by United States Bureau 



of Mines) 



the one hand, and our health, happiness, and efficiency, on the 

 other. The most important things that have been discovered 

 by the new attention to these details are the following : 



i. Outdoor air is better than indoor air in every way. 



a. It is better for playing, even in the cold and rain ; suitable 

 clothing will make up for these. 



