added and the hash? kept at room temperatnre. At dehnite intervals 
inoculations were made into bouillon and Dunham's solution in the 
usual manner and placed in the incubator at 37- C. 
In the following results P means that there was a growth oi j>yocya- 
nev.s: means that there was a bacterial growth, but no evidence of 
pyoryfmem: — means no growth. 
i Percenrage ZnCU. 
Time of exposure. 
1 2 
h-our. hours 
3 5 
hours hours 
1 
day. 
2 
days. 
3 
days. 
4 
days. 
5 7 14 
days. days. days. 
ConrrOj- - 
P 
P 
P 
P 
P 
p 
P 
P 
P P - 
0-2 
P 
P 
P 
P 
P 
p 
P 
P 
P P - 
1-0 
P 
P 
P 
P 
P 
p 
P 
P 
P - - 
2-0 
- P 
P 
P 
P 
— 
-g 
_ 
— 
_ -i- _ 
5-0 
P 
1 P 
— 
— 
— 
— 
— 
— 
_ ^ _ 
10.0 
Baci.Uus pyocyaneus was used in these experhnents 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 dihnfection of feces. When 
exposed to the action of zinc chloride prepared in sewag-e — with its 
host of various micro organisms — the viability of the B. pyocyanevs i.^ 
diminished as compared with its viability when exposed in the same 
strengths of zinc chloride prepared in distilled water. This dilference 
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 overrim the pyocyaneus. as it had 
disappeared from the control hask at the end of II days. 
By referring to the preceding tables it will be observed that B. 
jfyocyaneu-^ wa- killed within 3 hours in the tia^k 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 hasks of sewage containing the larger percentages of zinc chloride 
appeared to be principally spore-bearing organisms. 
It wa< next desired to determine the viabihty 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 ordinary sewage bacteria makes this determi- 
nation in sewage well-nigh impossible, a sample of sewage similar to 
that used in the above ex|)eriments was sterilized with -team under 
pressure. After sterilization it was placed in Task- as in the fore- 
going experiment and heavily inoculated with dl-hours-old agar cul- 
tures of diherent pathogenic organisms and the various percentages 
of zinc chloride added. 
