GERMICIDAL POWER OF FORMALIN. 
The germicidal power of formalin in various strengths was studied 
on pure cultures, human feces, and sputum. The growth in broth 
tubes was principally used. Agar plates were also made at corre- 
sponding intervals in order to determine when the maximum effect of 
formalin is exerted. 
GERMICIDAL POWER AGAIXST PURE CULTURE. 
The germicidal power of formalin was determined in 1. 2, 3, 5, and 
10 per cent dilutions against the principal pathogenic organisms. The 
following method was observed in each case: For a 5 per cent strength 
91 c. c. of sterile water was placed in a sterile ffask and 1 c. c. of a 
heavy emulsion, freed from clumps, of a forty- eight-hour slant agar 
culture of the organism being studied was added; then 5 c. c. of 
formalin was added to the entire contents of the ffask and well shaken. 
One loopful at ten-minute intervals up to one hour was planted in a 
full tube of nutrient bouillon and the growth noted from day to day. 
The experiments were repeated in each dilution so as to check any 
irregularities that might occur. 
Table Xo. 24 . — One per cent formalin {37.2 per cent aldehyde). 
Organism 
Time of expo-sure to formalin. 
Minutes. Hours. 
Control 
grew in — 
10. 
20. 
30. 
40. 
50. ; 
1. 
1|. 
2. 
Vibrio cholera 
24 hours. 
B. coli communis 
+ 
+ 
+ ' 
+ 
-t- 
_L 
+ 
— 
Do. 
B. diphtherise 
; -e 
— 
— 
— 
Do. 
B. mallei •. 
; — ' 
Do. 
B. pvocvaneus 
+ 
+ 
+ 
-f- 
; — 
— 
— 
— 
Do. 
B. dvsenterise (Shiga) 
' + 
-h 
+ 
+ ■ 
+ j 
-h 
Do. 
Staphylococcus pyogenes albus 
+ 
+ 
+ 
-f 
-e ^ 
+ 
-h ' 
+ 
Do. 
Staphylococcus pyogenes aureus 
-1- 
+ 
+ 
-1- 1 
-b 
_ ! 
— 
Do. 
B. tJT)hosus 
. + 
1 
• + 
+ 
-t- 
-f i 
+ 
- 
Do. 
From the above table it will be seen that the vibrio of cholera 
failed to grow after ten minutes’ exposure; B. coli grew up to ninety 
minutes; B. diphtherise was killed in twenty minutes; B. mallei was 
killed in ten minutes; B. pyocyaneus grew up to forty minutes; B. 
dysenterise (Shiga) and Staphylococcus alhus grew up to two hours; 
Staj)hylococciis pyogenes aureus and B. typ)]iosus grew up to sixty 
minutes. 
( 35 ) 
