DISINFECTION STUDIES 191 



precautions were taken during manipulation to avoid unneces- 

 sary and excessive heating, the amount of glass constituents dis- 

 solved apparently played no significant part in the experiments 

 as conducted. 



Paraflin melting at 55°C. was boiled with several changes 

 of distilled water, stirred frequently and finally skimmed off 

 into clean sterile bottles. The latter were then placed in a 

 hot air sterilizer for several hours and later allowed to cool while 

 a uniform coat was deposited internally. 



The organisms selected for experimentation were two members 

 of the colon-typhoid group, Bad. coli and Bad. iyphosum. These 

 were chosen both because they are well suited for this type of 

 study; and because they have been extensively studied along 

 related lines so that results obtained here may be readily com- 

 pared and may add to the continuity of our knowledge. 



Both cultures had been grown for a long time upon artificial 

 media but this does not constitute a defect in the present ex- 

 perimental plan. The undoubted acquisition of higher resist- 

 ance to external influences altered somewhat the degree of the 

 mortality rate by accentuating and magnifying the retardation 

 during the early phases of the process, precisely the condition 

 desired. 



Bact. coli. This organism was isolated from a polluted stream 

 in 191G. Its cultural and morphological characters are typical 

 of the Bad. coli-communis (sucrose-negative) type. Winslow 

 and Talk (1918, 1920) have utiUzed this strain in their studies 

 on salt antagonism. 



Bad. typhosum. This was a culture of the Rawlings strain 

 (no. (308) obtained from the American Museum of Natural His- 

 tory, New York. 



Stock cultures were preserved on nutrient agar at 10°C. At 

 least five daily transplants on agar at 37° were made before a 

 culture was used for experiment. 



The procedure in making the tests. The requisite number of 

 bottles were filled with buffer solution or water, allowing an air 

 space of about 100 cc. and the whole sterilized at one time in the 

 autoclave at 15 pounds pressure for ten minutes. Exceptions 



