Frost—Bacteriological Control of Public Milk Supplies. 1323 
The method is as follows: Glass tubes, 6 to 8 mm. in diameter, 
are drawn out at one end into a; straw about 1 mm. in diameter. 
The form and size are given in Fig. 8. These tubes are then 
plugged with cotton and sterilized. The fine pointed end 
may either be sealed, or it can be flamed just before use. One of 
these tubes is then placed in the pipettometer and 0.1 of a c. c. of 
the suspension is drawn into the tube. This amount is then 
drawn up the tube about an inch, and the end of the straw 
is sealed in the flame. This tube can then be removed from the 
pipettometer. It is now ready to be put into the water-bath. A 
series of tubes are prepared in this way. One is plated directly 
and the others are heated at various temperatures for the same 
length of time, or at the same temperature for varying lengths of 
time, as the case may require. When the tubes are in the water- 
bath special care must be taken to keep the thin straws below the 
surface of the water so as to be sure that all of the bacteria are 
sufficiently heated. After the proper exposure the tubes should 
be removed from the water-bath and immersed in ice water. In 
plating, the sealed end is broken off with sterile forceps and the 
contents blown into a Petri dish, and covered with agar. The 
tube plated directly serves as a control. By this means it is pos¬ 
sible to determine what Gage calls the “normal thermal death- 
point, ” as well as the “absolute thermal death-point.” 
E. Inhibiting Action of Milk in the Gas Production, by 
Bacillus Coli, in the Fermentation Tube. 
Dr. Theobald Smith called my attention to the fact that B. coli 
is not capable of producing gas in milk when it is in the fermen¬ 
tation tube, as it does under similar conditions with other-sugar 
media. The facts are shown in the following series: 
Six fermentation tubes of milk, inoculated 
with one loop of a 24 hr. culture of B. coli.. 0, 15%, 5%, 5%, 0, 20% 
Average = 7 % 
Six fermentation tubes of lactose pep¬ 
tone bile, inoculated as above.... 60%, 55%, 45%, 50%, 50%, 50% 
Average = 52% 
In view of these results, which are taken as representative, it 
was natural to ask: Does the addition of milk in small quantities, 
i. e., 1, 2, or 3 c. c., inhibit the characteristic reaction of any co¬ 
lon bacilli that might be present? 
