MILK STANDARDS 393 
for many cities in the United States having a population of 10,000 or 
over are tabulated. 
The procedure for the bacteriological examination of milk has been 
standardized in the same way as has the bacteriological examination 
of water and sewage. Standard Methods of Bacteriological Analysis 
of Milk prepared by the Laboratory Section of the American Public 
Health Association are now used by all bacteriologists making routine 
analyses of milk and wishing their results to be comparable to those 
secured in other laboratories. For that reason, much of the following 
is adapted or copied, with permission, from that report: 
Routine Milk Analysis. This type of analysis is designed for the control of 
the public milk supply and for the purpose of grading milk. For routine analysis 
the work must be capable of being done quickly and cheaply, and in such a way 
as to give the most speedy results possible and by methods having the smallest 
possible expenditure of time and money consistent with fair uniformity of 
result. The demand for rapid methods, with the smallest possible expenditure 
of time and money has been forced on different laboratories in the past few 
years, and has brought about various short cuts from the standard methods as 
previously formulated. The necessity for such rapid and inexpensive methods 
must be recognized. But it is also evident that they should be uniform in’ dif- 
ferent laboratories. 
Research Methods. Collection of Samples. All collecting apparatus, glass- 
ware, pipettes, collecting tubes, bottles, etc., shall be sterilized at a temperature 
of at least 175° C. for one hour. Each sample shall consist of at least 10 c.c. of 
milk. Before taking the sample the milk shall be mixed as thoroughly as pos- 
sible. If the original container can be inverted the mixing of the milk should 
be done by inverting it several times. If this is impossible, the milk should be 
stirred with some sterile stirrer. Any stirrer already in the container may be 
used. If there is none in the container, the sampling pipette (or any other 
sterile article) may be used; but it should be used for one container only until 
it is again sterilized. 
A sample simply poured from a large can is not a fair sample unless the milk 
in the can be thoroughly stirred. The sample shall be taken from the cans by 
means of a tube with straight sides long enough to reach to the bottom of the 
original container, and inserted not too rapidly, with the bottom of the tube left 
open. This will result in the tube containing a cylindrical section of the milk 
from top to bottom of the can. The finger then placed on the top of the tube 
will make it possible to withdraw the tube full of milk and transfer it to the 
sampling bottle. The sample bottle shall be large enough to hold the entire 
contents of the tube, all of which must be reserved as the sample. Each tube shall 
be used for collecting a single sample only and must be washed and sterilized 
again before being used again. An aluminum tube of the diameter of ¢ in. and 
21 ins. long is very convenient. If the sample is to be taken from the botile, 
