626 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 



(to vary the condition of ozonization of the air) must have somewhat 

 influenced our results by altering the cooling effect of the air on the 

 body. These tests were carried out in warm summer weather, and 

 in the final experiment the windows were kept shut all the time and 

 the room ventilated by opening the doors leading into other and 

 larger laboratories. In this experiment we obtained results which 

 we regard as the most conclusive of all. 



The metabolism varies with the degree of complete rest of the 

 subject. If he moves slightly more or less — e. g., in reading, talking — 

 this will affect the result, and thus we can not expect figures more 

 concordant than those we have obtained. Looking at the figures in 

 columns 4 and 6, we can not find any conclusive evidence that ozone 

 altered the respiratory metabolism. Note particularly the final 

 experiment (No. 7), in which the windows were shut and the con- 

 ditions even all through. 



The ozone was given in a concentration that made the air smell 

 quite strongly, and in some cases it was pushed even to an unpleasant 

 degree. Taking these figures together with those obtained on mice, 

 we must conclude that we have failed to obtain certain evidence that 

 inhalation of ozone in weak concentration stimulates the respiratory 

 metabolism, i. e., the output of C0 2 and use of 2 . On the other 

 hand, our experiments conclusively show that any considerable con- 

 centration of ozone depresses the respiratory metabolism. 



We think that the beneficial results obtained by the use of pure 

 ozone in ventilation must be reached by the effect of ozone on. the 

 nervous system — by its stimulating the mucous membrane, neutraliz- 

 ing smells, and relieving the depressing uniformity of close air. Our 

 experiments show that no harm results to man from breathing air 

 ozonized till the air smells quite strongly of ozone, for periods of 

 half to one hour. 



Perhaps the most interesting observation made in the research is 

 this: When the respiratory tract is irritated by ozone the animal 

 becomes motionless, sits hunched up with its fur erect, thus showing 

 the signs of depression. The ozone lessens the respiratory exchange, 

 reduces it even to one-seventh, at a time when the lung shows no 

 changes visible to the naked eye; the animal adjusts its behavior to 

 this condition, and keeps very still and quiet. Its body temperature 

 at the same time falls. The damage to the lung can not be serious, 

 since this depressant effect is quite evanescent. 



