1 8 A.-W. GREELEY. 



medium became acid through the fermentation of bread, the 

 structural reactions of the protoplasm to electrolytes was changed. 

 And they were changed in such a way as to suggest that there 

 had been a reversal of the electrical charge carried by the pro- 

 toplasmic particles, or in other words, that there had been formed 

 an acid-modified protoplasm. Thus the protoplasm of paramoecia 

 from an acid culture was not coagulated by cathions and lique- 

 fied by anions, as was the case without exception with paramcecia 

 from an alkaline culture, but the reactions were as follows : The 

 first change produced by the neutralization of the normal alkalin- 

 ity of the culture was an irregularity in the structural reactions. 

 Instead of all the organisms being coagulated by cathions and 

 liquefied by anions, some were coagulated, and some were lique- 

 fied in each solution, apparently indicating a condition in which 

 the protoplasm of some of the paramcecia had been modified by 

 the acid, the rest being still unaffected. As the acidity of the 

 solution increased, the number that were coagulated by anions 

 and liquefied by cathions correspondingly increased until, in a few 

 instances, a complete reversal of the structural reaction to elec- 

 trolytes was produced. While the reversal was more often not 

 complete, in all cases it occurred in a varying proportion of the 

 paramcecia from acid cultures, while the remainder were generally 

 rendered indifferent to the solutions which formerly coagulated 

 or liquefied them. The complete reversal occurred only in the 

 salt solutions. The acids always coagulated the protoplasm 

 regardless of the character of the culture, and to alkalis, the 

 paramcecia from acid cultures were only rendered indifferent. All 

 these results indicate that the particles of the acid-modified pro- 

 toplasm have become positively charged like the particles in 

 Hardy's acid-modified colloids. 



The view that this change in the structural reactions of para- 

 mcecia is due to a modification of the protoplasm by acids is ren- 

 dered more probable if we follow the reactions of paramcecia from 

 day to day, which are taken from a culture which is gradually 

 becoming acid by the fermentation of bread. In such a case we 

 can easily see the gradual fading out of the normal reaction to 

 electrolytes, and the assumption of the one peculiar to acid- 

 modified protoplasm. This change in structural reaction always 



