6Y R. GREIG-SMITtl. 



179 



was no evidence of toxicity other than could be accounted for 

 bv the reaction. The experiment did not indicate that any of 

 these chemicals would be of any value in the research. 



The Influence of Aeration. 

 With the idea of determining the influence of aeration upon 

 the production of toxin, a quantity of dilute (0-2%) hay-infusion 

 was infected with a culture of ameebse, 50 grams of soil were 

 added, and the bottle containing the test was attached to an 

 aspirator, which caused a few bubbles of air to pass through the 

 liquid every few minutes. A control-bottle was allowed to stand 

 in the laboratory. They were ordinary litre- bottles, and the 500 

 CO. of infusion was 2| inches deep. Portions of the fermented 

 liquids were filtered through porcelain on the fifth day, and 

 again on the eighth day, with the following results. 



Experiment xxiii. 



The solutions were twice the strength of those of Experiment 

 xxii., but whether this accounted for a slow growth of amoebse in 

 the non-aerated test or not, cannot be said. None were seen on 

 the fifth day, 330 on the eighth, and 2,300 per c.c. on the 

 twelfth. In the aerated test, the amcebge grew well: 3,000 were 

 noted on the fifth, and 9,300 per c.c. on the seventh day. Aera- 

 tion induced an acid, and its absence an alkaline reaction. The 

 acidity was so high on the fifth day that, on the sixth, the aera- 

 tion was stopped. This appeared to have had an effect upon the 

 dilution-curve. 



