96 
PROF: T. CARNELLEY, MR. J. S. HALDANE, AND DR. a. M. ANDERSON 
increase, not very easy to explain. In mechanically ventilated schools the micro¬ 
organisms decrease with increase of cubic space (p. 82), which is nevertheless quite 
in accordance with the filtration hypothesis. 
B. Cleanliness of rooms and persons habitually present in them. —In order to show 
the influence of differences as regards cleanliness, we have classified the houses and 
schools as shown in the following Table. This Table requires no comment. It shows 
most conclusively the enormous influence of differences as regards cleanliness on the 
number of micro-organisms. 
One-roomed houses - 
( 
Clean . 
Dirty. 
Dirtier. 
^Very dirty .... 
No. of 
cases. 
Average 
space per 
person. 
Average 
carbonic 
acid. 
Average 
organic 
matter. 
Average 
micro¬ 
organisms. 
i 
< 
13 
6 
295 
200 
221 
220 
8-0 
9-9 
10- 7 
11- 0 
131 
181 
13-5 
15-1 
18 
41 
49 
93 
Two-roomed houses < 
'Very clean .... 
Clean . 
_ Dirty. 
9 
LJ 
4 
7 
273 
264 
233 
12-2 
9-3 
9-4 
10-8 
7-7 
11-2 
10 
22 
69 
Naturally ventilated 
Board schools 
r Cleaner. 
Average cleanliness . 
_ Dirtier. 
12 
12 
12 
167 
166 
191 
19-7 
14-2 
22-5 
18T 
16-2 
15-2 
91 
125 
198 
Mechanically venti¬ 
lated schools and < 
college 
'Cleanest. 
Clean. 
^Less clean .... 
7 
11 
4 
194 
155 
152 
12-5 
12-8 
10-8 
127 
8- 3 
9- 8 
3 
16 
30 
The houses were classified from notes made at our visits. The naturally ventilated 
schools were classified by the sanitary inspectors at our request. 
C. Ventilation.—It is most important, as we shall see, to consider separately the 
ventilation at the time of the observation and the habitual ventilation. 
a. Ventilation at the time. —In order to obtain data as regards its influence, we 
made a number of experiments on rooms provided with mechanical ventilation, 
examining them with it off, and again with it on, other conditions being equal as far 
as possible. The results are given below. The ventilation was kept oft’ for an hour 
(during which the class was in the room) before the observations were made. 
