20 
added and the flasks kept at room temperature. At definite intervals 
inoculations were made into bouillon and Dunhanfls solution in the 
usual manner and placed in the .incubator at 37^ C. 
In the following results P means that there was a growth of jiyocya- 
neus; + means that there was a bacterial growth, but no evidence of 
j)y ocy emeus ; — means no growth. 
Time of exposure. 
Percentage ZnClo. 
1 
2 
3 
5 
1 
2 
3 
4 
5 
7 
14 
hour. 
hours 
hours 
hours 
day. 
days. 
days. 
days. 
days. 
days. 
days. 
Control 
P 
P 
P 
P 
P 
P 
P 
P 
P 
P 
-j- 
0.2 
P 
P 
P 
P 
P 
P 
P 
P 
P 
P 
1.0 
P 
P 
P 
P 
P 
P 
P 
P 
P 
-L- 
-i- 
2.0 
P 
P 
P 
P 
“h 
— 
— 
+ 
5.0 
P 
P 
— 
— 
— 
— 
+ 
10.0 
_u 
_j_ 
“T 
— 
“f" 
— 
— 
Bacillus i^yocy emeus was used in these experiments as a control, so 
to speak, on account of the ease with which its growth can be observed. 
As its power of resisting the action of germicides compares very 
favorably with that of the nonspore-bearing pathogenic organisms it 
possesses value for control purposes in the disinfection of feces. When 
exposed to the action of zinc chloride prepared in sewage — with its 
host of various micro organisms — the viability of the B. pyocyaneus is 
diminished as compared with its viability when exposed in the same 
strengths of zinc chloride prepared in distilled water. This difi'erence 
is rather marked and may be due to a combination of factors. 
The sewage was slightly acid and of course contained many other 
organisms which in time may have overrun the pyocyaneus, as it had 
disappeared from the control flask at the end of II days. 
B}' referring to the preceding tables it will be observed that B. 
pyocyeineus was killed within 3 hours in the flask of sewage containing 
5 per cent of zinc chloride, while it was not destroyed after 7 hours’ 
exposure in an aqueous solution of the same strength. 
The organisms that were still viable after 1 or 2 days’ exposure in 
the flasks of sewage containing the larger percentages of zinc chloride 
appeared to be principally spore-bearing organisms. 
It was next desired to determine the viability of some of the patho- 
genic organisms, such as cholera, typhoid fever, etc., when exposed 
to the action of zinc chloride in sewage. 
As the overgrowth of ordinarv sewage bacteria makes this determi- 
nation in sewage well-nigh impossible, a sample of sewage similar to 
that used in the above experiments was sterilized with steam under 
pressure. . After sterilization it was placed in flasks as in the fore- 
going experiment and heavily inoculated with 2I-hours-old agar cul- 
tures of diflerent pathogenic organisms and the various percentages 
of zinc chloride added. 
