618 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
Filipow ' found weak concentrations had no effect. on men or ani- 
mals, while a higher concentration of ozone caused irritation of the 
respiratory tract. 
Schultz * confirmed this irritative effect, and found long-continued 
breathing of ozone caused pathological changes, particularly in the 
lungs, which were the cause of death. Schultz considered that the 
ozone passed into the blood and injured the lung secondarily. Bohr 
and Maar * overthrew this supposition by the ingenious experiment 
they devised of making one lung breathe ozonized air and the other 
normal air. They found this lung remained normal while the 
ozonized lung became oedematous. 
Using a concentration of ozone which produced no visible change in 
the pulmonary structure, these observers found that it caused a 
diminished uptake of oxygen; the other lung compensated for the 
deficiency by an increased uptake. This occurred in both cold- 
blooded (tortoise) and warm-blooded animals. In the former the 
initial effect of ozone was occasionally a slightly increased oxygen 
uptake. If the inhalation of ozone were continuous the increased 
uptake by the lung ventilated with normal air finally fell away and 
became deficient; this occurred sooner in the mammal than in the 
tortoise. 
The CO, output was also diminished, but not so markedly as the 
oxygen uptake, thus the respiratory quotients often rose over 1. The 
effect of ozone on the respiratory exchange came on gradually, and 
with weak concentrations often reached its height after the cessation 
of the ozone inhalation—there was, in fact, an after-effect which took 
some little time to pass off. The effect was not modified by a pre- 
liminary division of the vagi and pulmonary sympathetic nerves. 
The blood of the ozonized animal had no toxic effect when trans- 
fused into another. Bohr concluded that the effect was primarily 
on the lungs, and as the oxygen uptake was affected more than the 
CO, output, he claimed that his results supported his view that the 
pulmonary epithelium by its secretory activity controlled the passage 
of the respiratory gases. Butte and Peyron‘ likewise record that 
ozone when inhaled diminishes the metabolism. 
One of the obstacles in the way of investigation has been the diffi- 
culty of obtaining pure ozone free from oxides of nitrogen, and 
another has been the want of an accurate method of estimating the 
concentration of ozone. ‘There has been devised lately an ingenious 
apparatus for producing ozone, which eliminates the production of the 
oxides of nitrogen, and allows the ready use of ozone for bleaching, 
sterilizing water or ventilating purposes, The ozone is generated by 
1 Arch. f. d. Ges. Physiol., vol. 34, p. 335.- 
2 Arch. f. exper. Path., 1882, vol. 29, p. 364. 
8Skand. Arch. f. Physiol., 1904, vol. 16, p. 41. 
4Comp. Rend. Soc. Biol., vol. 46; Progrés Médical, 1894, No. 30, p. 61. 
