40 Kansas Academy of Science. 



The phenol dilutions are tested first, beginning with the strong- 

 est, and then taking up the disinfectants in the same order. 



To each sterile seeding tube 5 cc. of the dilutions are added and 

 inoculated with y\ oc. of filtered culture from 24-hour £. typhosus 

 by means of a sterile pipette graduated in tenths. 



The inoculated seeding tubes are placed on water bath and kept 

 at temperature of 20° for lengths of time 2h minutes to 15 minutes, 

 making six tests in as many seeding tubes for each dilution. 



The sterile subculture tubes of same number as dilutions, and 

 4 mm. platinum loops (4 in number) and fan-tail burner must be 

 conveniently arranged for inoculation of subculture tubes and 

 flaming of loops. These inoculations are made at intervals of 2^ 

 minutes until six inoculations have been made, at times 2h min- 

 utes, 5 minutes, 1^ minutes, 10 minutes, 12| minutes and 15 min- 

 utes for each dilution. 



The coefficient for the sample under investigation is obtained 

 by dividing the weakest dilution of this sample of disinfectant that 

 kills in 2| minutes by the weakest dilution of phenol that kills in 

 2| minutes, and dividing the weakest dilution of the above sample 

 of disinfectant that kills in 15 minutes by the weakest dilution of 

 phenol that kills in the same time; then taking the mean of these 

 quotients. 



For example, the weakest dilution of phenol proving effective in 

 2^ minutes was 1-80 and the weakest dilution of the above disin- 

 fectant proving effective in 2i minutes was 1-375. The weakest 

 phenol dilution proving effective in 15 minutes was 1-110 and the 

 "weakest dilution of the sample of disinfectant was 1-650; hence, 



~ = 4.69 and ^ = 5.91 ; 5.91 -f 4.69 = 10.60. ^ = 5.80, the phenol 



coeflBcient for the sample of disinfectant under investigation. Its 

 standard, therefore, would be 5.30; that is, 5.30 times as strong as a 

 solution of phenol that kills in the same length of time. 



