INFLUENCE OF PHYSICAL AGENTS. 



155 



an air chamber. A little material from a pure culture of the test organ- 

 ism is drawn into each of these capillary tubes by immersing- the open 

 extremity in the culture, after having 1 gently heated the expanded end. The 

 end of the tube is then hermetically sealed by heat These tubes are im- 

 mersed in a water bath maintained at the desired temperature for the stan- 

 dard time. The bath is kept at a uniform temperature by personal supervi- 

 sion. At the bottom of the vessel is a thick glass plate which prevents the 

 thermometer bulb and capillary tubes, which rest upon it, from being ex- 

 posed to heat transmitted directly from the bottom of the vessel To further 

 guard against this I am in the habit of applying the flame to the sides of the 

 vessel, and a uniform temperature throughout the bath is maintained by 

 frequent stirring 1 with a glass rod. It is impossible to avoid slight variations, 

 but by keeping my eye upon the thermometer throughout the experiment 

 I have kept these within very narrow limits. . . . No attempt has been made 

 to fix the thermal death-point within narrower limits than 2 C., and in the 

 table the lowest temperature is given which has been found, in the experi- 

 ments made, to destroy all of the microorganisms in the material subjected 

 to the test. No doubt more extended experiments would result, in some in- 

 stances, in a reduction of the temperature given as the thermal death-point 

 for a degree or more. But the results as stated are sufficiently accurate for 

 all practical purposes." 1 



The results obtained in these experiments, for non-sporebearing 

 bacteria, are given in the following table. The time of exposure 

 was ten minutes, except for the cholera spirillum and the cheese spi- 

 rillum of Deneke. 



THERMAL DEATH-POINT OF BACTERIA. 



Spirillum cholene Asiatic* 52 



Spirillum tyrogenum (cheese spirillum) 52 



Spirillum Flakier- Prior 50 



Bacillus typhi abdominalis 56 



Bacillus of schweine-rothlauf (rouget) 58 



Bacillus murisepticus 58 



Bacillus Neapolitanus (Emmerich's bacillus) 62 



Bacillus cavicida 62 



Bacillus pneumoniae (Friedlander's) 56 



Bacillus crassus sputigenus 54 



Bacillus pyocyaueus 56 



Bacillus iudicus 58 



Bacillus prodigiosus 58 



Bacillus cyanogenus 54 



Bacillus fluorescens . . . . 54 



Bacillus acidi lactici 56 



Staphylococcus pyogenes aureus . . . 58 



Staphylococcus pyogenes citreus 62 



Staphylococcus pyogenes albus 62 



Streptococcus pyogenes 54 



Micrococcus tetragenus 58 



Micrococcus Pasteuri 52 



Sarcina lutea 64 



Sarcina aurantiaca 62 



Centigrade. 



Fahrenheit. 



125.6 C 



125.6 



122. 



138.8 



136.4 



136.4 



143.6 



143.6 



132.8 



129.2 



132.8 



136.4 



136.4 



129.2 



129.2 



132.8 



136.4 



143.6 



143.6 



1292 



136.4 



125.6 



147.2 



143.6 



(4m.) 

 (4m.) 



The following determinations of the thermal death-point of path- 



1 Quoted from the Report of the Committee on Disinfectants of the American Pub- 

 lic Health Association, pages 136 and 152. 



