49 
Method 3: This is a modification of method No. 1. The test tube, 
containing broth or water, with a thermometer and capillary tube, is 
put into a water bath kept at temperature of the tube tested, or 3 to 
5 degrees higher. 
Method 4 : Capillary tubes and the thermometer placed in a small 
Erlenmyer flask, which can be well shaken. The fluid in the flask 
was accurately maintained at a constant temperature by placing the 
flask in a small water bath, which, in turn, was placed in a larger one 
and a thermoregulator used to control the temperature of the outer 
bath. 
Van Geuns concluded that the thermal death points based on the 
above experiments were as follows: 
1 minute. . 
5 minutes. 
Time required to reach temperature stated. 
Cholera. Typhoid. 
(°C.) (°C.) 
59 60 
54 56 
Lazarus,® 1890, used 20 liters of raw market milk divided into small 
flasks; these he inoculated with cholera and typhoid. This infected 
milk was then run through a small Thiel’s continuous pasteurizer at 
the rate of 1 liter per forty seconds. The temperatures were made to 
vary from 60° to 96° C. in the different experiments. At intervals of 
one to two minutes samples of one-half cubic centimeter were taken 
and plated on fluid gelatin. At 70° C. living typhoid and cholera 
were found, but none at 75° C. These results are more a test of the 
efficiency of this particular pasteurizer than an accurate determina- 
tion of the thermal death points of the micro-organisms used. 
Janowski, ^ 1890, inoculated typhoid bacilli from a four-day potato 
growth into gelatin after it reached the temperature to be tested. At 
the end of five or ten minutes roll tubes were made. He found those 
exposed 57° for five minutes always remained sterile. Sometimes 
he got a growth at 56° for five minutes, and once ,at 56° for ten min- 
utes. The bacilli were not put into the gelatin until it reached the 
temperature to be tested, and the work therefore does not exactly 
imitate the conditions of pasteurization. 
Neisser,'" 1895, used the same methods as von Geuns. The temper- 
ature was taken from a control tube and the time counted from the 
moment the temperature reached the desired degree. Some typhoid 
bacilli resisted three minutes’ heating at 60° to 61.75° C., but fifteen 
minutes’ heating at this temperature killed all. 
« Lazarus, A. : Die gebrauchlicheren Mittel zur Conservirung der Milch. Zeit. f. 
-Hyg., vol. 8, 1890, p. 235. 
& Janowski: Zur Biologie der Typhusbacillen. Cent. f. Bakt., vol. 8, 1890, p. 167. 
cNeisser, Max: Dampf-Desinfection und Sterilisation von Brunnen und Bohr- 
lochern. Zeit. f. Hyg., vol. 20, 1905, p. 308. 
