THE TOXICITY TO FUNGI OF VARIOUS OILS AND SALTS. 11 



in Petri dishes on agar against the fungus Coniopliora cerebella were 

 the sodium or potassium salts of dinitrophenol (C 6 H 3 - (N0 2 ) 2 [2.4j 

 ONa) and dinitro-orthocresol (C 6 H 2 -CH 3 [2]- (N0 3 ) 2 ONa). 



Generalizations, however, are not always applicable by analogy 

 and may serve only for certain limited groups. In his work on 

 numerous fluorin salts Netzsch (21) found that the fluorin ion was 

 the most active, the relative toxicity of the simpler and consequently 

 more readily dissociated salts, at least, being in direct proportion to 

 the amount of fluorin in the molecule. When the acid (HF) itself, 

 however, was under consideration it was found to be even more toxic 

 than its simple metallic salts, indicating the great activity of free 

 hydrogen. 



TESTS OF THE TOXICITY OF WOOD PRESERVATIVES. 



It is only within the past decade that laboratory tests to determine 

 the relative toxicity of substances adapted particularly to wood 

 preservation have been undertaken. These lack the refinement of 

 earlier work, as it was not the intention to enter into the question as 

 to why and how a substance was toxic, but merely to determine how 

 much of a given poisonous substance was necessary to inhibit the 

 growth of fungi, particularly the wood-rotting forms. The result is 

 that different investigators have used different methods, different 

 culture media, different organisms, temperature conditions which 

 were often not the optimum for the fungi concerned, and ofttimes 

 also impure chemicals and composite oils, such as creosotes, that no 

 other investigator is able to duplicate except from the same sample. 



The problem has been attacked m two ways: (1) By mixing the 

 preservative under consideration with various types of culture solu- 

 tions, usually solidified by the addition of agar-agar or gelatin, and 

 inoculating with the organisms desired; and' (2) by injecting the 

 preservative into wood and exposing the blocks thus treated to the 

 action of wood-destroying fungi. 



Tests of this sort were first suggested by Malenkovic (18) in 1904. 

 The results of his work were first published in an Austrian military 

 journal and later (19) amplified and printed in book form. He lays 

 no claim to refinement of work, so it is difficult to correlate his results 

 with later ones, except in a general way. The larger part of his ex- 

 periments were carried out by injecting the preservative into wood, 

 but a few beaker tests were made according to the following plan : 



Five glass beakers were filled with 100 c. c. of 10 per cent gelatin or 2 per cent agar 

 media, and to each, was added a certain amount of the antiseptic, such as 0.5, 1, 1.5, 

 and 2 grams. The media were then melted, thoroughly stirred, and allowed to cool. 

 Then, without any previous sterilization, a trace of some mold (unknown to the experi- 

 menter) was transferred to the surface of the media, and the cultures were set away in 

 a dark, damp place. After 14 days observations were made to determine whether the 

 surface had become moldy. The concentration that prevented mold growth was 

 recorded as the toxic point for the preservative in question. 



