METHODS OF EXAMINING MILK 261 
milk may be mixed by inverting the bottle several times. 
If the milk is in a vessel which is open and which can- 
not therefore be inverted, it may be stirred with the 
pipette which is used to transfer the sample to the sample 
bottle. The pipette should, of course, be sterile and 
should not be used to take another sample until it has 
again been sterilized. A sterile tube with straight sides 
should be used for taking a sample from a can. An 
aluminum tube 1% inch in diameter and 21 inches long 
is most convenient. If the tube is held vertically, with 
the opening at the top unobstructed, and is inserted into 
the milk slowly until the lower end reaches the bottom of 
the can, it will contain a column of milk which will be 
representative of all the milk in the can. If the finger 
is then placed firmly upon the top of the tube, the column 
of milk can be withdrawn and transferred to a sterile 
sample bottle, which should be large enough to hold the 
entire contents of the tube, all of which must be emptied 
into the bottle. The tube must be washed and sterilized 
before being used to collect a sample from another con- 
tainer. If the temperature of the milk is to be taken, a 
separate sample should be used for this purpose and then 
discarded. Glass-stoppered bottles or those provided 
with cork-lined screw caps are the most satisfactory. The 
bottle containing the sample should be properly labelled 
and immediately placed in a carrying case containing 
cracked ice so that the milk will be promptly cooled to 
near the freezing point. The sample bottles should be 
transferred to the laboratory as soon as possible and the 
milk plated at once. If the plates are not prepared within 
four hours after the collection of the samples the elapsed 
time should be noted in the report. If the samples are 
