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 

 Coniophora cerebella (a true wood destroyer) and the green mold, 

 PenidUium 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-Aktiengesellsehaft, 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 hi 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 (Bad I his 

 subtilis), a yeast (Saccharomyces glutinis), and a species of Penicillium. 



1 This treatment, however, is usually considered insufficient to insure sterility. 



