QUANTITATIVE BACTERIAL ANALYSIS 251 



standard more often does injustice to the consumer, since a high 

 leucocytic count usually indicates an abnormal cow. 



COLLECTION OF SAMPLES. 



'(From Preliminary Report of Committee on Standard Methods.) 



Quantity of Milk Required for Analysis. — The minimum 

 quantity of milk necessary for making an ordinary bacteriological 

 examination is ten cubic centimeters. When making examinations 

 for cerified milk, if possible a pint or quart bottle should be taken 

 and brought to the laboratory unopened. 



Collecting Apparatus. — In collecting milk samples for bac- 

 teriological examination it is essential that the sample be taken 

 and kept in such a manner as to prevent either any addition 

 of bacteria from without or multiplication of the bacteria originally 

 present. Bottles, tubes, pipettes, etc., used in the collection of 

 samples, besides being washed, shall be sterilized with dry heat 'for 

 an hour at or about 160 C, or to the charring point of cotton. 



In the selection of " certified milk " samples it is recommended 

 "wherever possible that an unopened bottle be taken, placed in a suit- 

 ably iced case and brought at once to the laboratory. 



Samples of " market milk " may be collected as are water 

 samples, in sterile, wide-mouthed, glass-stoppered four-ounce bot- 

 tles ; the case in which they are carried being well iced. The prin- 

 cipal difficulty encountered in this method is in transferring the 

 sample from the original container to the bottle, and the various 

 string and wire devices by means of which the bottle is immersed in 

 the original container are objectionable both on account of the 

 labor of preparing such an outfit and also on account of the coating 

 of milk left on the outside of the bottle when the sample has been 

 taken. 



An apparatus designed for the use of thirty-two test tubes. 



