XXil PROCEEDINGS. 
It is well known that the exhalations from the bodies of animals 
have a poisonous effect if breathed, even tho much diluted with air. 
The classic researches of Pettenkofer, Brown-Séquard, d’Arsonval, 
Lehman, Merkel, Parkes, and others, have proved the presence of an 
organic poison in air which has been breathed by man or other animals. 
Its exact constitution is not known, but the effects of ‘‘ Pettenkofer’s 
man-poison” are apparent in every school-room. They are, headache, 
drowsiness, slight fever, and a general retardation of all reactions to 
stimuli. Partial loss of the power of inhibition is also noticeable. Less 
apparent, but more important, are the general weakening of vitality and 
the greater susceptibility to disease which follow prolonged breathing of 
impure air. 
These effects are more easily seen in the weak and anaemic than in 
vigorous persons. It was the observation of the less vigorous students 
at Truro which first led me to suspect that the air in the Normal School 
might be one cause, at least, of the decrease in power which I had 
noticed. We have, as do all schools, pupils who, when at their best, are 
just able to keep up with the class, who are, mentally or physically, 
near the fatique-point. A slight interference with their normal activity 
throws them off their balance, and they must drop behind. Not infre- 
quently pupils come to us enfeebled by excessive study in preparation 
for examinations. Under favorable conditions they might do well, but 
if subjected to further strain they may break down. With these two 
classes of students, poisoning by impure air may make the difference 
between success and failure. At all times, and with all classes, it causes 
a determinable decrease in the amount of work, mental or physical, 
which is done with a given expenditure of energy. Especially where 
the system of public education is most highly developed and most 
strenuously applied, the evil effects of this poison have been most 
apparent. 
In testing the air in the Normal School, the method and apparatus 
of Prof. Hch. Wolpert of Nuremburg was adopted. The chemical basis 
of this method is the fact that an alkaline solution of sodium carbonate 
becomes neutral by the absorption of carbon dioxid. If the alkaline 
solution be colored red by phenol phthalein, when the solution becomes 
neutral the color disappears. Thus, with a given amount of sodium 
carbonate, the decolorization of the liquid shows that a certain amount 
of carbon dioxid has been absorbed. If this carbon dioxid come from a 
