BACTERIAL MILK ANALYSIS 241 



If it is desired to take the temperature of * ' certified 

 milk," this should be done when the sample is taken, 

 but from another bottle. 



A floating thermometer, graduated to the Fahrenheit 

 scale, is most convenient, and the temperature should be 

 expressed to the nearest degree. It is necessary to 

 standardize the thermometer for at least ten degrees on 

 each side of the legal temperature limit. A quickly 

 registering thermometer should be left at least one min- 

 ute in the milk and read as soon as removed. A small 

 piece of clean absorbent cotton may be used to wipe the 

 adhering milk from the thermometer that the scale may 

 be easily seen. 



Representative samples. The collector should 

 always select his own sample, and care should be taken 

 to secure a sample which is truly representative of the 

 milk to be examined. 



One of several methods of mixing the milk may be 

 used, comparison having shown the results to be prac- 

 tically the same. 



1. Pouring the milk into a sterile receptacle and 

 back. 



2. Shaking the milk thoroughly with receptacle 

 turned upside down. (This may be done where the can 

 or bottle is tightly stoppered or capped and is not so full 

 as to prevent thorough agitation.) 



3. In open tanks in stores it is allowable to stir thor- 

 oughly with the long-handled dipper generally found in 

 use. 



4. Where the test tube collecting case is used, thor- 

 oughly reliable results are secured by first shaking the 

 can or bottle; and, second, stirring with the large 

 pipette before taking the sample, care being taken to 

 close the upper end of the pipette with the finger so that 

 no milk enters until after the mixing, or the pipette may 

 be emptied after stirring before the sample is taken. 



5. For certified milk samples it is recommended that, 

 on arrival at the laboratory, the bottle be opened with 

 aseptic precautions and the milk thoroughly mixed by 

 pouring back and forth between the original bottle and 

 a sterile bottle. Another method is to mix as thoroughly 



