19 



capsules filled with scrapings from the surface of cultures of this amoeba 

 in symbosis with a harmless bacterium. Dysentery has also been pro- 

 duced in monkeys by similar cultures as well as by others where the bac- 

 terium in symbiosis was a pathogenic one. 



This aiua'ba in symbiosis witli tlio cholera spirillum was used in 

 the experiments to be described. The culture medium employed was 

 the special agar one recommended by ^lusgrave and Clegg and 

 described in the above quotation. The amteba?, in the encysted state, 

 are much more resistant to the action of drugs by virtue of their 

 impervious shells. In order as far as possible to eliminate these 

 encysted forms from the experiments, I made numy observations 

 on cultures of the ama-ba? at varying periods of their growth, and 

 determined that when they are cultivated on the special agar medium 

 at room temperature in ]\[anila, the amoeba reach their maxi- 

 mum activity in about forty-eight hours, by Avhich time practically 

 all were free and motile. In a few hours more, many luive begun 

 to encyst and by the end of seventy-two hours a large proportion 

 of them have completely done so. Consequently, after the first few 

 preliminary experiments, the forty-eight-bour cultures were used 

 as a nuitter of routine. 



The first series of experiments was made by pouring the solu- 

 tions to be tested over the surface of forty-eight-hour slant cultures 

 of AuKeba Xo. 11524, and at the end of ten, twenty, thirty, or sixty 

 minutes pouring off the solution, washing the surface lightly with 

 sterile water to remove all traces of the antiseptic, and then making 

 transplants from the surface to fresh media. Control transplants 

 were made from every tube containing the amoeba cultures, before 

 adding the solution to l)e tested. 



The following results were obtained l)y the above-described 

 method : 



Tahlk a. 



1 Tlie .solutions of benzoyl acetyl peroxide and of acid succinic peroxide were so prepared 

 as to contain equal amounts of a'cliir nxyficn. In order to obtain solutions of 1-1,000 biusod on 

 active oxygen there must be dis.solved of pure crystals of benzoyl acetyl peroxide 1.10 grams 

 and of pure acid succinic i>eroxide 1 gram in 1 liter of water. 



