44 
Ten per cent formalin (containing 37.2 per cent aldehyde) killed all 
the nonspore- bearing organisms tested in less than ten minutes, except 
B. dysenteri^e and Staphylococcus pyogenes aureus, which were killed 
after ten minutes. 
With a 2 per cent solution of formaldehyde the maximum germi- 
cidal elfect was exerted in the first five minutes. 
With a 3 per cent solution this immediate effect is more apparent, 
and in the case of B. pyocyaneus the great mass of organisms is killed 
in the first two minutes. 
A 3 per cent solution destroys a great majority of the nonspore- 
bearing organisms in feces in the first ten minutes; a few, however, 
resisting a somewhat longer exposure; the spore-bearing organisms 
grew up to one hundred and twenty minutes. 
Five per cent formalin acting upon feces destroyed most of the 
Donspore-bearing organisms within ten minutes; a few resisted forty 
minutes. The spore-bearing organisms resisted as long as sixty 
minutes. 
Feces exposed to 10 per cent formalin solution were rendered prac- 
ticall}" sterile immediately; a few colonies developed in ten minutes. 
The spore-bearing organisms were destroyed after forty minutes. 
A 10 per cent solution of formalin complete Iv deodorized feces at 
once. A 3 and 5 per cent solution renders them almost odorless after 
a very few minutes’ exposure. 
On account of its germicidal efficiencv and deodorant action formalin 
would seem to be one of the most useful agents for the disinfection of 
infected human discharges when used in a 10 per cent dilution, allow- 
ing an exposure of one hour after thorough mixing. 
Tubercle bacilli in tuberculous sputum were killed after an exposure 
to 5 per cent formalin for sixty minutes. Sputum exposed for fifteen, 
thirW, and forty-five minutes, respectively, still contained live virulent 
tubercle bacilli. 
When tetanus toxine is exposed to 5 per cent formalin for six hours a 
guinea pig is able to withstand 100 MLD of this formalinized toxine. 
Three per cent formalin after t went v-f our hours exposure protects 
against the toxine; it destroys a part of the toxine in one hour, its 
action increasing with the length of exposure. 
Diphtheria toxine is more susceptible than tetanus toxine, as 4 per 
cent formalin, after six hours exposure, protects a guinea pig against 
acute death; paraWsis, however, is not prevented. One per cent, after 
twent 3 "-four hours exposure, has the same effect. Its action against 
the toxine increases with the length of exposure. 
This action of formalin on toxine is an important property in its use 
as a disinfectant, for not only are the bacteria themselves destroyed, 
but their soluble products as well. 
