593 
media were both prepared without the addition of salt, and the 
reaction was brought to + 1.5 American Public Health Association 
scale. The neutral-red-lactose agar contained 0.1 per cent of a 5 per 
cent aqueous solution of neutral red. The litmus-lactose agar was 
employed to make Petri dish plates. The neutral red-lactose agar 
was used for shake tubes. The amounts of water taken for the 
inoculation of the media were the same in each case. A sample of 
the water was caught in a sterilized test tube in each case and a 
melted tube of each of the media was inoculated by means of a grad- 
uated sterile pipette with 0.1 cubic centimeter of the water, and one 
tube each with 1 cubic centimeter. The litmus-lactose agar tubes 
were poured into the Petri dishes, and the neutral-red-lactose agar 
tubes were kept upright until the agar had set, after the water was 
thoroughly mixed with the medium. These plates and tubes were 
shipped to Washington as promptly as feasible, where they were 
taken in charge upon their arrival, and the neutral-red-lactose agar 
tubes were put at once into the incubator at 35° C. and left for 
forty-eight hours. 
In order to protect the pipettes from accidental contamination 
each was wrapped separately in a piece of toilet paper. A special 
double capsule of thin wrapping paper was designed for the protection 
of the Petri dishes. This consisted of two cases, one slipping inside 
the other after the manner of a pocket cigar case. But these were 
abandoned for ordinary manila paper bags, which answer the pur- 
pose very well and are very cheap. The size and kind of bag em- 
ployed were common 2-pound bags with the ends either folded over 
or cut off. The illustration of the traveling kit shows the pipettes 
and Petri dishes wrapped up as described. 
In order to prevent the water, which condenses on the inside of the 
cover of the Petri dishes when the agar is poured, from condensing 
and running on the agar, each dish was covered with a disk of filter 
paper before sterilization. In a dish covered in this way the water 
condenses on the inside of the cover, but it is absorbed by the filter 
paper. 
Various boxes were designed for carrying the necessary apparatus 
into the field, but the field kit which was found most satisfactory, 
and which was most used consists of a light wooden box, 14 inches 
high, 7 \ inches deep and 5J inches wide, outside measurements 
(Fig. 61). This box is divided into 2 sections of unequal depth 
hinged together. The shallower section is 2J inches deep inside, and 
is divided into compartments for holding a square can of alcohol, and 
for test tubes of culture media and empty sterilized test tubes for col- 
lecting samples of water. The deeper section measures 13J inches in 
height, by 4J inches in depth and 4J inches in width, and is divided 
1414— Bull. 56—09 38 
