PASSAGE OF OXYGEN THROUGH THE BODY 107 



the place where it serves that purpose, is seen by studying 

 the combustion in an ordinary stove (Fig. 54). Oxygen 

 enters at the draft and for the 

 most part passes out at the flue, 

 but in passing through the stove 

 it unites with, or oxidizes, the fuel, 

 causing the combustion which pro- 

 duces the heat. 



Now it is found that certain 

 chemical processes, mainly oxida- 

 tions, are taking place in the body. 

 These produce the heat for keep- 

 ing it warm and also supply other 

 forms of energy, 1 including motion. 

 It is the purpose of oxygen to keep 

 up these oxidations and, by so 

 doing, to aid in supplying the body 

 with energy. It serves this pur- 



w\v 



FIG. 54. Coal stove illus- 

 trating rapid oxidation. 



pose in much the same way that it supports combustion, 

 i.e., by uniting with, or oxidizing, materials derived from 

 foods that are present in the cells. 



Does Oxygen serve Other Purposes ? It has been sug- 

 gested that oxygen may serve the purpose of oxidizing, or 

 destroying, substances that are injurious and of acting, in 

 this way, as a purifying agent in the body. In support of 

 this viev/ is the natural tendency of oxygen to unite with 

 substances and the well-known fact that oxygen is an im- 

 portant natural agent in purifying water. It seems prob- 

 able, therefore, that it may to a slight extent serve this 

 purpose in the body. It is probable also that oxygen aids 

 through its chemical activity in the formation of compounds 



1 The term energy, as used here, has the same general meaning as the word 

 power. See Chapter XII. 



