12 BULLETIN 227, U. S. DEPARTMENT OF AGRICULTURE. 
As has been shown in the preceding discussion, tests that are 
conducted under any other than pure-culture conditions are not 
directly comparable with each other, for the different organisms 
react in an entirely different way to the same chemical substance. 
Moreover, the use of molds which at most produce but slight effect 
upon wood gives no more than the roughest approximation as to how 
wood-destroying organisms would behave under similar conditions. 
In 1910 Netzsch (21) conducted an exhaustive series of experiments 
on the toxicity of fluorin compounds. As these compounds have 
only recently entered into the field of wood preservation, and as many 
of them have proved to be toxic agents of high efficiency, his work is 
of great technical value. He carried out the work much as Malenko- 
vic and other investigators have done, both by mixing the substances 
in gelatin culture media and injecting them into wood, but his tests 
on culture media were carried out under sterile conditions in flasks, 
tests tubes, or Petri dishes, so that many of the objections to the work 
of Malenkovic were eliminated. Into the gelatin media were intro- 
duced varying proportions of equimolecular solutions of the fluorin 
compounds. The culture vessels were then inoculated, using both 
Coniopliora cerebella (a true wood destroyer) and the green mold, 
Penicillium glaucum, the former being maintained for about four weeks 
in an incubator at 20° to 21° C. His results, showing the point of 
inhibition of growth, are presented on the basis of one gram molecule 
of the preservative to the number of liters of culture media necessary 
to secure the proper concentration. In the present paper this ratio 
has been changed to the percentage basis (weight of preservative in 
volume of media) , in order to compare his results with those of other 
investigators. 
About this same time Seidenschnur (26), head chemist of the wood- 
preservation laboratory of the Rutgerswerke-Aktiengesellschaft, at 
Berlin (Charlottenburg) , presented the results of a few tests upon 
the comparative toxicity of zinc chlorid and tar oils. His experi- 
ments were conducted in test tubes containing gelatin media mixed 
with varying proportions of the antiseptics. After the mixture was 
prepared, the tubes were sterilized for one-half hour at 80° C. 1 The 
tubes were then slanted and inoculated with Penicillium glaucum. 
The toxic point was not determined, but the relative efficiency of the 
two substances was compared in parallel cultures. 
During 1911, J. M. Weiss (33, 34), chemist in the technical labora- 
tories of the Barrett Manufacturing Co., New York City, published 
the results of a number of experiments to test the relative antiseptic 
value of creosotes and other oils. The substances were mixed in 
agar media. The organisms used consisted of a bacterium (Bacillus 
subtilis), a yeast (Saccharomyces glutinis), and a species of Penicillium. 
1 This treatment, however, is usually considered insufficient to insure sterility. 
