6 The Philippine Journal of Science wis 



liquid, the first dilution was made by measuring 0.2 cubic centi- 

 meter of it and making up to 10 cubic centimeters with the 

 salt solution in the volumetric flask as before. This small quan- 

 tity of the drug or chemical was used throughout in making 

 the primary dilutions because some of the substances were 

 obtainable only in small quantities. The succeeding dilutions 

 were made in 50 cubic centimeters volumetric flasks by meas- 

 uring appropriate amounts from each preceding dilution of 

 the substance with a graduated pipette and filling the flask to 

 the graduation mark with the diluting liquid. 



The balantidia used in making these tests were in part derived 

 from men, in part from domesticated pigs, and in part from 

 a monkey infected from a pig. Balantidium coli suis is gen- 

 erally considered to be identical with Balantidium coli hom- 

 inis; it has been found possible to infect monkeys with the 

 balantidia from the pig; and comparative tests of the same 

 drug or chemical made with the pig and the human balantidia 

 have given uniform results. Balantidia from the pig and mon- 

 key have been employed in part in these tests, because human 

 cases of balantidiasis which showed a sufficient number of the or- 

 ganisms in the stools could not at all times be obtained. The 

 material used has consisted of fresh fseces containing living 

 and actively motile balantidia. Unless the faeces was suffi- 

 ciently fluid, a portion of it was rubbed up in 0.5 per cent 

 sodium chloride solution to fluid consistency. 



A large platinum loopful of the fluid fseces containing the 

 balantidia was placed on a microscope slide. Beside it was 

 then placed a drop of equal size of the dilution of the substance 

 to be tested. The two drops were then thoroughly mixed and 

 a cover-glass placed upon it. The edges of the cover-glass were 

 then sealed with vaseline to prevent evaporation. Similar 

 preparations were made of all of the dilutions of the drug or 

 chemical being tested and of a control, consisting of a drop of 

 the fseces and a drop of 0.5 per cent sodium chloride or, in 

 case distilled water had been used as a diluting fluid, distilled 

 water. These preparations were observed with low magnifica- 

 tion under the microscope at frequent intervals, and the effect 

 on the balantidia noted. The intervals of observation were 

 usually one, two, five, ten, fifteen, thirty, and sixty minutes. 

 In most cases the observations did not extend beyond one hour, 

 since it was considered that a substance at a given dilution 

 is of little value if it did not kill the organisms within that 



