255 
the results of these investigations, to a product made principally of 
cream and sugar, and with a natural flavor, either of an ordinary 
flavoring substance like vanilla or of fruit. Hence there appears to be 
no reason for departing from the established standard, in view of the 
data which have been secured b}^ an examination of the commercial 
samples bought in the open market from all portions of the city. 
BACTERIOLOGICAL INVESTIGATIONS OF ICE CREAM IN THE DIS- 
TRICT OF COLUMBIA. 
[Made by or under the direction of Dr. George W. Stiles, and by or under the direction of 
Dr. M. E. Pennington.] 
In most instances the samples of ice cream received for examination 
were collected directly from the original place of manufacture. In a 
few cases, however, miscellaneous samples were taken at places other 
than those at which the product was prepared. Generally half a 
pint or a 10-cent box furnished a sufficient quantity to make the 
chemical, microscopical, and bacteriological examinations. The 10- 
cent box, to which reference is made, was the pasteboard carton 
almost universally used as a container for ice cream when sold in 
small quantities, and for this reason it was much preferred as a 
carrier of the samples to be investigated. IITien these cartons were 
not available well-cleansed bottles or new j^aper boxes were used 
instead. 
Upon arriving at the laboratory, samples for bacteriological ex- 
amination were removed at once from the frozen interior by means of 
sterile spoons and placed in sterile dishes to melt. Generally within 
eight to ten minutes a sufficient liquefaction had occurred to enable 
the experimenter to remove enough material to make the bacteriolog- 
ical examination. 
The enormous number of organisms which are found in cream, 
milk, and ice cream, necessitates high dilutions to make possible the 
quantitative determination of the organisms present. For the mak- 
ing of these, and the counting of the colonies which developed, the 
technique pursued may be stated briefly as follows: The quantities 
were measured in 1 cubic centimeter pipettes, graduated in 0.01 
of a cubic centimeter, and 10 cubic centimeter pipettes graduated 
in 0.1 of a cubic centimeter. They were sterilized by heat and kept 
in bacteria-proof metal cases. 
In order to make the necessary dilutions Erlenmeyer flasks of about 
500 cubic centimeters and 100 cubic centimeters capacity, respectively, 
were used. To the former were added 99 cubic centimeters of sterile 
water and to the latter 9 cubic centimeters. To the flask containing 
99 cubic centimeters there was added 1 cubic centimeter of the sample 
