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 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 isa 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 with aglass 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 microdrganisms 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.” ! 
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. 
Centigrade. Fahrenheit. 
Spirillum cholerze Asiatice#.......... cece eee ec eee ee 52° 125.6° (4 m.) 
Spirillum tyrogenum (cheese spirillum)............ 52 125.6 (4m.) 
Spirillam Finkler-Prior .... 0.0.0... c cee eee eee eee 50 122, 
Bacillus typhi abdominalis............. 0... ....008. 56 138.8 
Bacillus of schweine-rothlauf (rouget)... ........6- 58 186.4 
Bacillus murisepticus ... ........... a. % ete 58 136.4 
Bacillus Neapolitanus (Emmerich’s bacillus).......... 62 143.6 
BaCilusiCavicid asin: cisesisrieiaeiewad araaraaerseiss -clsleas 62 143.6 
Bacillus pneumonie (Friedlénder’s)........ ......-. 56 132.8 
Bacillus crassus sputigenus.... 1... 0.2... seven eeeee 54 129.2 
Bacillus: pyocyaneus: ~ esnewists ereoaergieewinawuisewisetea’s 56 182.8 
Baellus: indicus) 6" avs neetaime dagen seaiiony 58 136.4 
Bacillus prodigiosus .....,.. . Aisiasaeae a0 sSopeengoanh earn 58 136.4 
Bacillus cyanogenus.............. Lwuadeg sameaees 54 129.2 
Bacillus fluorescens: aiicnas x oeurwctariaasad <2 sp 54 129.2 
Bacillus acidi lactici..... cS Webs sua rrieomtue cuted 56 132.8 
Staphylococcus pyogenes aureus. .... .......6 ‘ 58 136.4 
Staphylococcus pyogenes citreus 62 143.6 
Staphylococcus pyogenes albus : 62 143.6 
Streptococcus pyogenes 54 129.2 
Micrococcus tetragenus 58 136.4 
Micrococcus Pasteuri ... 1.0... .. eee ee cece eee ee : 52 125.6 
Darina lta... c.asicce ap cieaeeaenass 64 147.2 
Sarcina aurantiaca 62 143.6 
The following determinations of the thermal death-point of path- 
1 Quoted from the Rzport of the Committee on Disinfectants of the American Pub- 
iic Health Association, pages 186 and 152. 
