472 Richards: The Effect of Chemical Irritation 



which ultimately end in death. It may be that such indeed is the 

 case, but the poisonous substances so formed being in such minute 

 quantities, owing to the dilute solutions used, do not serve to kill 

 the protoplasm, but merely stimulate its molecular activity in an 

 endeavor to throw off the irritant substance, or to induce what 

 might be called a secondary katalytic action. The results with 

 the salts of iron which are not poisonous do not, however, uphold 

 such a view, yet it is not impossible that in stronger solutions the 

 apparently inocuous base, iron, might prove to exert a poisonous 

 influence. This might be impossible to demonstrate, since the 

 necessary concentration to produce any deleterious effect would be 

 so great as to confuse the results with the osmotic action of the 

 solution. If it is not possible to admit any such semi-toxic action 

 on the part of the Irritant substances, it is necessary to fall back 

 upon the idea of their action being strictly katalytic, as suggested 

 by rfeffer,* or simply to include the phenomenon under the com- 

 prehensive phrase "physiological counter-reaction." 



The results of these experiments maybe briefly stated as follows : 

 That the direct action of irritant substances (in this case inor- 

 ganic salts), which produce an increased growth of certain fungi 

 is to enable the latter to dispose more economically of the sugar 

 used (/. c, to raise the economic coefficient of the sugar) thereby per- 

 mitting a more rapid production of dry substance in a given time. 

 That the increase of the economic coefficient is not in propor- 

 tion to the percentage increase in weight. 



That the economic coefficient again decreases when in poison- 

 ous substances the maximum of growth is passed, but th^it it appar- 

 ently does not ever fall much below the normal. 



This work was begun in the Cryptogamic Laboratory of Har- 

 vard University in 1 897-98 and completed at Earnard College, 

 New York, in 1898-99. The writer would here express his 

 thanks to Professor H. B. ?Iill, Director of the Chemical Labora- 

 tory of Harvard University, for his courtesy in allowing the use of 

 the facilities of that laboratory. 



New York, May, 1899. 



* rfeffer, Prings. Jahrb. 28 : 23S. 1S95 



