26 THE ROYAL SOCIETY OF CANADA 
September.....1 | 
Oetober.:. 2.7.4 
AMIPUSE so 2001001 14 
November..... 14 
December......14 
Janus en 14 This table is computed from 
February. ..... 14>8 years’ observations of the 
March. 000808 nae discharge of the river at 
July...........24 | Besserer’s Grove. 
April, 09.420 
April, ’08...... 4 | 
PAR A yeni MAD | 
May i 64 | 
The value of the above factors is that they give us the dilution of 
the sewage infection for the various months. For example, in April 
with factor 4, the sewage is diluted 4 times as much as in September or 
October. 
The average number of B. coli per c.c. for the three winter months 
is, respectively, 224, 16 and 5—an average of 14 B. coli per c.c. for the 
three months. This number must be subtracted from our monthly 
colon figures after correction with the dilution factor. For example, 
for the month of April the number 14 must be divided by 4, so that only 
34 is subtracted from the monthly estimation of B. coli 154 — 34 — 12, 
which indicates the colon contamination per c.c. from other sources. 
Reference to the accompanying tables and to the diagram will 
show that the results in 1910, 1911, were similar to those already re- 
ported. From April, 1909, to March, 1910, infection with B. coli was 
greatest in September, followed by August, October, and March; but 
B. coli of excretal origin was largest in September and October, followed 
by November, December, January and February. This may be com- 
pared with the number of deaths from typhoid fever in Montreal for the 
same -period :— 
September; ' 1909. 2454 amor hits 14 deaths. 
October, Mui a Bias AL INT LES 24.5. * 
Navembe's}-)) of scar: trente 22k 
Decembert nf xliclhs. eshte PR: Haut 
January: <19lOss cb; dé er he MAL to 
February. PS Meare. UM EU 2" D 1 pa ee 
For the year April, 1910, to April, 1911, the number of B. coli was 
highest in September, followed by October, August, July, November, 
