28 



and nitrate of silver 1-2,000, for periods of fifteen, thirt}^, and 

 sixty minutes, with the result that the destructive effect of these 

 chemical substances was decidedly more marked than in the experi- 

 ments in which Amoeba 11524 was the organism employed. 



Experiments on encysted cultures of No. 11524, one month old, 

 conducted at the same time as the above and with the same solu- 

 tions, demonstrated the self-evident fact that encysted amoebae 

 are much more resistent to chemical action than are the free and 

 active forms. 



I regret that time did not permit me to pursue my investigations 

 with a larger variety of chemicals and with other strains of 

 amoebae in symbiosis with various bacteria. However, it may 

 safely be assumed that the results with thymol solutions would be 

 unaffected by such tests as far as they relate to symbiotic bacteria, 

 and it is improbable that any of the common intestinal bacteria 

 usually found in s}Tnbiosis with the amoeba would resist the action 

 of the silver salts, benzoyl acetyl or acid succinic peroxide to a suf- 

 ficient extent to alter the deductions that may be drawn from the 

 above experiments in which cholera spirilla and water bacteria were 

 the only symbiotic organisms employed. It should be borne in mind 

 that the entire series of tests was severe on account of the concentra- 

 tion of the amoeba suspensions employed, the organisms being 

 present in greater proportion than in the intestinal fluids of severe 

 cases of infection. 



RECAPITULATION. 



Boric acid, eucalyptol, ichthyol, oil of cassia, and infusion of 

 quassia had slight if any effect on the amoebiE. 



Tannic acid 1-100, sulphate of copper 1-2,000, permanganate of 

 potassium 1-4,000, and sulphate of quinine 1-1,000 had a distinct, 

 moderate effect on the growth of the amoebae and spirilla within 

 thirty minutes. 



Benzoyl acetyl peroxide, acid succinic peroxide 1-1,000, perman- 

 ganate of potassium 1-2,000, sulphate of quinine 1-500, nitrate of 

 silver 1-2,000, argyrol 1-500, and protargol 1-500 exercised a very 

 marked effect on the growth of the cultures within thirty minutes, 

 and in the case of the silver salts and the acid succinic peroxide the 

 action was plainly due to the destruction or inhibition of the gro'wi;h 

 of the symbiotic cholera spirillum. 



