160 STERILIZATION AND DISINFECTION 
TABLE XV 
STOCK 1 PER CENT SOLUTION 
[1 c.c. Disinfectant-+99 c.c. Distilled Water =Solution B] 
Strength to Strength to ec. of c.e dist 
be tested be made. B. water 
1 : 500 1 : 400 5 -- 15 
1 : 550 1 : 440 5 “| 17 
1 : 600 1 : 480 5 + 19 
1 : 650 1 : 520 5 + 21 
1 : 700 1 : 560 5 + 23 
1: 750 1 : 600 5 ~|- 25 
1 : 800 1 : 640 5 + 27 
1 : 850 1 : 680 5 + 29 
1 : 900 1 : 720 5 +- 31 
1 : 900 1 : 720 5 “+ 31 
1 : 1000 1 : 800 5 + 35 
1 : 1100 1 : 880 5 + 39 
1 : 1200 1 : 960 5 + 43 
1 : 1300 1 : 1040 5 + 47 
1 : 1400 1 : 1120 5 + 51 
1 : 1500 1 : 1200 5 + 55 
1 : 1600 1 : 1280 5) + 59 
1 : 1700 1 : 1860 5 + 63 
1 : 1800 1 : 1440 5 + 67 
the seeding tubes and placed in the water bath. For reasons that will 
be obvious later, it is difficult to handle more than nine dilutions at one 
time in making a test. The broth culture of B. typhosus is filtered and 
placed in the water bath. The desired quantity of stock peptone- 
gelatine mixture is measured into a large test tube or flask and also 
placed in the water bath. It is necessary to have a slight excess of the 
organic matter, so that there will be no trouble in getting the 10 c.c. 
pipette full when adding the organic matter and culture to the disin- 
fectant. Thus, for nine tubes we usually measure out 15 c.c. of the 
organic matter. When the disinfectant dilutions, the typhoid culture, 
and the organic matter have reached the temperature of the water bath 
(20° C.) 1.5 ¢.c. of the typhoid culture is added to the 15 c.c. of organic 
matter and thoroughly mixed by means of a 10-c.c. pipette. With the 
same pipette the seeding tubes containing the disinfectant dilutions 
then have added to them, successively every fifteen seconds, 1.1. cc. of 
the mixture of the organic matter and typhoid culture. The technique 
of shaking, planting, etc., is then as has already been described. 
From the above it will he seen that each seeding tube, as the test 
is conducted, contains 4 c.c. of the disinfectant dilution plus 1 c.c. 
