Frost—Bacteriological Control of Public Milk Supplies. 1325 
been used only to a limited degree in this investigation but more 
extensively in a subsidiary series, and is believed to be a prom¬ 
ising procedure. 
G. Tests for Bacterium Welchii. 
1. A New Outfit for Quantitative Work. Savage suggests 
a quantitative test for Bacterium Welchii (B. enteritidis spor- 
ogenes) in milk which is as follows: “Quite small, narrow (4x^4 
inch), sterile empty test-tubes are used in batches of ten for each 
estimation. 20 c. c. of milk are employed for each test, 2 c. c be¬ 
ing added by a sterile pipette to each tube. The ten tubes are 
heated for 10 minutes- at 80° C., rapidly cooled, and incubated 
anaerobically in specimen jars with ground-glass stoppers, just 
large enough to take the ten tubes, the oxygen being absorbed by 
the usual potash and pyrogallic acid mixture.”—Savage.* 
This method has been modified and improved in several details. 
The test-tubes used are 100 by 8 mm. Ten of them are placed in 
a zinc or copper box made out of sheet metal, as seen in Fig. 2, 
Plate XCV. This box makes it unnecessary to plug or handle 
the separate tubes. The box and contents are sterilized in the 
hot air oven. This sterilization is a matter of considerable impor¬ 
tance since when the tubes are used over and over, the possibility 
of spores being carried from one test to another must be care¬ 
fully guarded against. This is easily done by putting a piece of 
fresh cotton under the cover, and continuing the sterilization un¬ 
til this cotton is well browned. By means of 1 a graduated 10 or 
20 c. c. pipette, 2 c. c. of milk is run into each tube. The cover 
is replaced which is easily given a distinctive mark with a grease 
pencil. The tubes are now heated. To do this it is only neces¬ 
sary to place the tubes, box and all, in a water-bath so arranged 
that the water will come well toward the top of the tubes. They 
are then cooled and placed in jars from which the oxygen can be 
absorbed. Jars particularly adapted to this use are the speci¬ 
men jars with straight sides, with tops clamping on. In order 
to hold the box up from the bottom, and allow room for the pyro- 
gallate, a strip of zinc about % an inch wide is coiled up and laid 
in the bottom of the jar. The required amount of pyrogallic 
acid is placed in the bottom of the jar, the box with the milk 
* Milk and the Public Health, 1912, p. 189, The Macmillan Co. 
