38 
Table No. 30. — Three 'per cent formalin {37 per cent aldehyde, 1.8 acidity). 
Organism. 
Number of colonies grown at different intervals of exposure. 
At once. 
5 minutes. 
10 min- 
utes. 
15 min- 
utes. 
utes. 
40 
min- 
utes. 
60 
min- 
utes. 
60 
min- 
utes. 
B. dysenterise 
Innumerable . 
do 
360 
2,580 
Almost in- 
numerable. 
2,160 
37 
8 
4,320 
310 
16 
3 
2,820 
83 
6 2 
1 0 
1, 800 93 
21 6 
1 
2 
0 
0 
0 
0 
B. typhosus 
Staphylococcus pyo- 
genes albus. 
Staphylococcus pyo- 
genes aureus. 
B. pyocyaneus 
do 
do 
(do 
2 minutes. 
4 min- 
utes. 
6 min- 
utes. 
8 min- 
utes. 
10 
min- 
utes. 
15 
min- 
utes. 
- 
300 
29 
7 
0 
0 
0 
This table is especial!}" interesting as shoAving that in its effect in a 
3 per cent solution upon B. pyocyaneus the great mass of organisms 
are killed in first two minutes. 
Both tables show that the larger number of organisms are killed in 
the first five minutes, the more resistant ones gradually being killed 
off' by a longer exposure. 
Compare these results with Tables 25 and 26, page 36. 
ACTION ON FECES. 
Its germicidal action having been determined against pure cultures, 
experiments were done to determine its value as a disinfectant of 
human excreta. 
Human feces with urine added was thoroughly mixed with sufficient 
water so tliat there should remain no large clumps. A wateiw sus- 
pension from a number of forty-eigh't-hour agar slants of B. pyocy- 
aneus was added to the mixture and Avell mixed in, this being done on 
account of the green color it shows in culture, which was used as an 
index of the destruction of the nonspore- bearing organisms. To an 
accurately measured quantity of this mixture sufficient formalin was 
added so as to give a 3 per cent, 5 per cent, or 10 per cent dilution by 
volume of formalin. Plants were made into broth tubes and agar, 
which latter were at once poured into petri dishes. The growth in 
the broth tubes was observed for ten daA^s; the colonies on the plates 
were counted on the fourth da}". 
Where the letter ‘‘P” appears pyocyaneus, as shown by the char- 
acteristic color, was noted. 
