Oct. i S , 1920 Germicidal Value of Some Chlorin Disinfectants 



95 



about the rods near the end not etched, and the rods are thrust into test 

 tubes so as to engage the cotton in the mouth of the tube. The tubes 

 containing the rods are sterilized by dry heat (150 C.) for 1 hour or more. 

 In making tests the rods are removed from the tubes and the etched 

 portions are dipped into a suspension made from a culture of the organism 

 to be tested. They are then replaced in the tubes and dried in the 

 incubator for one hour. 



Rods so infected are transferred to test tubes containing the disinfectant 

 to be tested, the amount of disinfectant being sufficient to cover all 

 the infected portion of the rod. They are exposed to the action of the 

 disinfectant for varying lengths of time. After exposure the rods are 

 washed with sterile water in order to remove traces of the disinfectant 

 and are then transferred to tubes containing bouillon or agar, which are 

 incubated for at least 48 hours at 37. 5 C. The suspension used in in- 

 fecting the rods is made from the surface growth on an agar tube by 

 rubbing up in several cubic centimeters of sterile water enough of the 

 growth to give a suspension of approximately the same density as a 

 24-hour bouillon culture of Bacillus typhosus. For an organism that 

 does not bear spores the culture should be 24 hours old, while for spore- 

 bearing organisms cultures 1 to 2 weeks old are usually the most suitable. 



In making tests with a disinfectant containing mercury it is advisable 

 to dip the rods into a saturated solution of hydrogen sulphid or an aqueous 

 solution of some sulphid before placing them in subculture tubes. In this 

 connection it should be mentioned that media of acid reaction have been 

 found to exert an inhibitory action upon the growth of Bacillus anthracis 

 after exposure to disinfectants. For that reason the media used in these 

 experiments have been neutral or slightly alkaline. 



Experiments 16 and 17. — In these experiments chloramin T was 

 tested in varying concentrations, both in water and in 50 per cent blood 

 serum. A sterile 10 per cent solution of sodium thiosulphate was used 

 for washing the rods before placing them in subculture tubes of exactly 

 neutral broth. The results are given in Table VIII. 



Table VIII. — Germicidal efficiency of chloramin T against anthrax spores, with and 

 without the addition of blood serum a 



EXPERIMENT 16 



n + signifies growth; — , no growth. 



