ON THE CARBONIC ACID, ORGANIC MATTER, ETC., IN AIR. 
97 
Ventilation off. 
Ventilation on. 
Carbonic 
Micro- 
Carbonic 
Micro- 
Acid. 
organisms. 
Add. 
organisms. 
f Room 1 . .. 
14-0 
21 
13-5 
24 
I 2 
Harris Academy < ” 3 * * * 
18-8 
16-4 
38 
16 
13-3 
15-6 
14 
16 
L „ 4*. • . . 
16-0 
20 
22 
Small Chemical Lecture-room , 
19-6 
1-5 
132 
1-5 
Large „ ,, ,, . . . 
37 6 
6 
10-8 
3 
Ventilated half-time school | 
151 
11-4 
14 
12 
11-6+ 
10-0+ 
47+ 
9+ 
Averages. 
18-6 
16 
12-6 
17 
It thus appears that ventilation by mechanical means at the time of the experiment 
had no appreciable effect on the number of organisms in the air of rooms, in spite of 
its great influence on the carbonic acid and organic matter. (See also p. 79.) 
(3. The influence of the habitual state as regards ventilation cannot be determined 
quite so satisfactorily, as it is necessary to compare results in different rooms. In 
order, however, to determine the effect of a few days of natural ventilation on the 
micro-organisms in the air of a school habitually ventilated mechanically, the artificial 
ventilation was stopped for a week in the half-time school previously referred to. The 
results were as follows :—■ 
Boys. 
Girls. 
47 
18 
56 
36 
102 
12 
34 
22 
74 
20 
52 
6 
60 
8 
Previous average 
Ventilation off 
Ventilation on since 
Monday . 
Tuesday . 
W ednesday 
Thursday. 
Friday. . 
' cii oiicLLrwxJ U11 oinuc m 
Monday morning J a ‘' ot 
I Average for the week. 
Boys. 
63 
Girls. 
19 
The observations were made at the same time each day. Unfortunately the hoys 
were always standing and moving about at this time, hence the number of micro¬ 
organisms is made abnormally high as compared with previous results in the same 
room. The data obtained, however, show that the effect of having the ventilation off 
for a week was not appreciable in raising the number of organisms in the air. The 
numbers found were, in both the boys’ and the girls’ room, actually less in the second 
than in the first half of the week. These results harmonise with our observation as 
regards the influence of age. (See below.) 
* Compared, not against the same room, hut one with as nearly as possible the same space per person, 
t Average of two determinations. 
MDOCCLX XXVII.—B. 
O 
