1905] TRUE & OGLEVEE—TOXIC ACTION OF POISONS 9 
repeatedly observed before (3, 4). When, however, to a solution 
containing nearly or quite twice this amount of the copper salt, finely 
divided insoluble bodies, like quartz sand, crushed glass, and filter 
paper are added, the toxic action is so far diminished as to permit 
not only an increased growth before death takes place but even vigor- 
ous survival. In case the amount of copper is diminished, an advantage 
is regularly found in favor of the cultures containing the solid body. 
In the case of the culture containing the garden earth, the effect 
of a common type of soil containing considerable soluble matter was 
desired. Of course chemical reactions have entered here, but at 
this great dilution the copper probably still existed in the ion condi- 
tion. Here, too, the introduced soluble material may have had its 
own direct action on the organisms. 
The action of paraffin is marked in every case but in a somewhat 
less degree than in the other cases noted. The paraffin offered some 
slight difficulty of method which may account somewhat for the fact 
observed. Although hard paraffin was used, it was found difficult 
to shave or chop it up into particles of the desired degree of minute- 
ness. Thus less surface was exposed to the solution than in the 
other substances used. Its lightness, too, tended to buoy it up upon 
the surface of the solution, and prevent a thorough mingling. This 
was remedied in part by the tendency of the solution to rise by capil- 
lary action among the floating particles. It was also found practicable 
to hold the paraffin under, to a considerable degree, by means of 
pressure on the surface of the floating mass. 
The effect of solids on growth in the distilled water was tried in 
control experiments, the general result seeming to indicate that the 
plants are not favored by this presence. Redistilling from glass, 
discarding the first half of the distillate and leaving a third of the 
original volume in the retort, seems to yield a product having no 
advantage over the water but once distilled. 
In all of the toxic substances thus far considered, we have had to 
do exclusively with electrolytes, therefore, at the high dilutions con- 
cerned, with ions. Experiments were made with a. few non-electro- 
lytes in order*to ascertain whether the ionization of the molecule 
may be a necessity for the observed decrease in the poisonous action 
of the presence of insoluble substances. 
