BACTERIOLOGY: JACOBS AND HEIDELBERGER 
227 
and very readily adds organic substances containing aliphatically bound 
halogen, forming quaternary salts, a few of which are already described 
in the Hterature. In the present work over two hundred such prepara- 
tions were made, and, after chemical characterization, subjected to bio- 
logical study. 
When tested against various strains of bacteria in vitro it was found 
that with but few exceptions these compounds were bactericidal, the 
bactericidal power varying with the character of the alkyl or aryl group 
introduced into the hexamethylenetetramine molecule. These sub- 
stances are, on the whole, easily soluble in water, but on standing or 
warming the solutions rapidly decompose, and in the case of the aro- 
matic derivatives, develop a very finely divided emulsion of oil droplets 
or a colloidal suspension which precipitates more or less readily accord- 
ing to the concentration. On investigation, these decomposition prod- 
ucts proved to be the methylene derivatives of the aryl or alkyl amines 
corresponding to the haHdes originally used. In the case of the hexa- 
methylenetetramine addition products of the halogenacetylamines these 
precipitates were more closely studied. In several instances the methyl- 
eneglycyl derivatives were isolated in pure crystalline form, and upon 
testing for bactericidal power, the results were found to agree closely 
with those obtained with the parent quaternary salts. We are, there- 
fore, led to believe that at least in this type of hexamethylenetetramine 
derivatives, the bactericidal properties of the parent substances are due 
to the tiiethyleneglycyl derivatives produced on decomposition, or more 
particularly, to the methyleneamino group contained in these decomposi- 
tion products. Since all types of hexamethylenetetramine quaternary 
salts (with the exception of a few of aliphatic nature) seem to undergo 
this form of decomposition, we are inclined to believe that in general 
the methyleneamino compounds are responsible for the bactericidal 
effect. With the confirmation of this we are at present engaged. 
The form in which these methyleneamino compounds separate from 
the solutions of their parent compounds is a contributing factor in the 
action of these substances. For when once precipitated from suspen- 
sion, they cannot readily be redissolved unless they contain a solubilizing 
group. The use of hexamethylenetetramine in this manner would seem, 
therefore, but a convenient artifice for obtaining these substances in the 
form of emulsions or colloidal solutions, conditions necessary for their 
bactericidal action. In the presence of serum or protein this precipita- 
tion is in the majority of cases either diminished or prevented entirely. 
In this connection it may be stated that with a large number of the 
compounds the bactericidal effect was found to be but slightly inhibited 
