INORGANIC SALTS TO MONILIA SITOPHILA 289 
Although some of the variations in the toxicity of the chlorides 
in the different media may be the result of reactions between the 
salts and organic substances, there is good evidence that this can 
not account for all of the variations brought out in Table XII. 
A study of some of the media from the standpoint of their re- 
sistance to the passage of the electric current has shown that there 
is considerable variation in the ionic concentration of different 
media that contain limit concentrations of the same salt, indicating 
that some media do influence the concentration of the ions but 
that these differences are not correlated directly with the observed 
differences in toxicity. Limit concentrations of ferric chloride, 
cupric chloride, cadmium chloride and mercuric chloride in peptone 
show in each case a much lower resistance than limit concentra- 
tions of these same salts in saccharose, glucose, lactose or starch. 
This seems to be strong evidence in support of the view that the 
fungus is actually able to resist higher ionic concentrations of these 
salts when it is growing in peptone than when it is in any of the 
other media tested, thus showing an effect of the peptone other 
than that due to its precipitation of a portion of the toxic salt. 
Another factor of probable importance in this connection is 
the influence of the different media on the production of enzymes. 
Went (34) has shown that Monilia sitophila produces a number of 
different enzymes and that the organic part of the medium deter- 
mines which enzyme will be produced in any given case. The 
effect of the various chlorides on trypsin, which the fungus pro- 
duces in peptone media, may be quite different from their influence 
on diastase produced in starch media. The rather high toxicity 
of potassium chloride and barium chloride in starch media may 
be due to the infleunce of these salts on diastase. Similar varia- 
tions may be brought about by the actions of the poisons on 
lactase, lipase and invertase. 
My observations show clearly that the organic part of the 
medium must be taken into account in studies on toxicity. This 
important factor, however, has generally been disregarded by those 
who have tested the resistance of fungi and bacteria to poisons. 
Stevens (30) tested the toxic action of mercuric chloride and other 
Poisons on Penicillium crustaceum growing in bread media. Ina 
Study of the toxicity of a whole series of substances for Aspergillus 
