628 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
In pneumonia we see the same thing; the patient is forced by the 
feeling of illness to keep quiet in bed. How this adjustment is 
brought about is a subject for further research. It will be of especial 
interest to see the effect of ozone on the oxygen partial pressure of the 
blood. We would draw attention to the fact that high pressures of 
oxygen produce inflammation of the lung (Lorrain Smith, L. Hill, 
and J. J. R. Macleod) similar to that produced by ozone. It is this 
resemblance which in part led us to make this research. 
CONCLUSIONS. 
(1) Ozone is a powerful deodorizer. Jt masks rather than destroys 
smells. Its practical value in relieving the nervous system from the 
depressant influence of an unpleasant odor is none the less for this. 
(2) A concentration as little as 1 per million is irritating to the 
respiratory tract. Exposure for two hours to a concentration of 15 
to 20 per million is not without risk to life. The irritative effect and 
the discomfort produced thereby—cough, headache—give ample 
warning, and there is no risk from inhaling ozone so long as an outlet 
for the instinctive escape from its influence is open. It is necessary 
that systems of ventilation in which ozone is used should be dealt 
with by those experienced in the matter, so that concentrations may 
be supplied which will not irritate the respiratory tract. 
(3) The respiratory metabolism is reduced by ozone, in concen- 
trations even less than 1 part per million. There is no conclusive 
evidence of a preliminary stimulation of metabolism preceding the 
fall. 
(4) The beneficial effect of ozone obtained by the ozone ventilating 
systems is to be explained by its effect on the nervous system. By 
exciting the olfactory nerves and those of the respiratory tract and 
skin, it may relieve’ the monotony of close air, the smell of tube 
railways, in cold meat stores, hide stores, and other trades. 
(5) There is no harm in breathing weak concentrations of ozone, 
such as can be scarcely sensed by a keen sense of smell. 
(6) Ozone in somewhat higher concentrations (1 per million) 
may have some value as a therapeutic agent if inhaled for brief 
periods; by irritating the respiratory tract it may act as a blister or 
fomentation and bring more blood and tissue lymph to the part. 
The blood and tissue lymph contain the immunizing and curative 
properties. It seems to us a simple and convenient way of applying 
a “‘blister’”’ to the respiratory tract. 
This research has been carried out with the aid of a grant cue the 
London Hospital research fund. 
[Note added November 21, 1911.—We have found that exposure for 
10 minutes to 2 parts in 10 millions of ozone may lower the rectal 
temperature of rats as much as 3°, while control rats maintained 
their normal temperature of 38.5° C.] 
