ON OZONE IN EELATION TO HEALTH AND DISEASE. 35 
back of tbe throat. When the inhalation is over, the symptoms 
gradually subside, and I have never known any bad effects 
follow, although the headache will remain for five or six hours. 
These symptoms are very decided, and have been experienced 
by Schonbein, Scoutetten, Wood, myself, and many other 
observers. As a class of symptoms they are without doubt iden- 
tical with those w T hich characterize nasal catarrh, or common 
cold. I do not believe that any of my learned confreres in 
physic would hesitate for a moment in pronouncing a person 
who was suffering from Ozone catarrh as being affected with 
common cold, premising that the cause was withheld from his 
knowledge. 
The inference, therefore, has been drawn that when common 
cold is the prevailing disease, there is an excess of Ozone in 
the air, and that the symptoms are due to such excess of 
Ozone. 
On this particular point the light we have shines doubtfully : 
the inference is fair and reasonable, but the actual proofs are 
not as yet afforded. The position is as follows : — 
A disease identical with catarrh can be excited by the inha- 
lation of an air containing an excess of Ozone. 
It has been shown, specially by Moffatt, that catarrh is 
common during what are called the Ozone periods. 
But catarrh is sometimes present in a general form when, by 
the ordinary tests, Ozone cannot be shown to be present in 
excess. 
The theory, therefore, is not perfect in all its parts. It 
may be imperfect because our present tests for Ozone are not 
sufficiently accurate ; it may be, the test we always employ is 
sometimes interfered with in its action by the presence of 
other bodies foreign to the atmospheric air. The test itself 
consists of a paper saturated with solution of iodide of 
potassium and starch. When this paper is exposed to 
ordinary air it undergoes no change ; when it is exposed to 
ozonized air, the potassium is oxidized, and the iodine being 
set free combines with the starch, forming iodide of starch. 
The iodide of starch strikes a dark blue colour, and the depth 
of the colour struck on the paper gives the theoretical degree 
of Ozone present in the air. Schonbein and Moffatt each 
prepare Ozone test papers, with scales, for comparing degrees 
of intensity. 
The test being made more accurate, it is possible, and indeed 
probable, that in time Ozone will be proved to stand to 
catarrh in the position of cause to effect. Nay, I have thought 
that local currents of Ozone may probably be generated from 
the friction of air in its passage, with violence, through narrow 
channels, as when there is produced what is commonly called 
D 2 
