XT'.MERICAL DETERMINATION OF BACTERIA. 149 



CotTNTINO. 



Expression oj results. Since minor rlifferences in milk counts are 

 within the working error of the methods and are of no significance in 

 practice, the following scale has been adopted for recording results of 

 market milk examinations : 



Counts below 100,000 are distinguished by ten thousands. 



Counts between 100,000 and 500,000 are distinguished by fifty thou- 

 sands. 



Counts between 500,000 and 1,000,000 are distinguished by hundred 

 thousands. 



Counts between 1,000,000 and 2,000,000 are distinguished by two hun- 

 dred thousands. 



Counts Ijetween 2,000,000 and 5,000,000 are distinguished by five hun- 

 dred thou.sands. 



Counts above 5,000,000 are distinguished by millions. 



Therefore only the following figures are used in reporting ■ 



Helow 10,000 Above 250,000 Above 1,400,000 

 Abovt 



Counts on "certified" or "inspected" milk shall be expressed as 

 closely as the ililution factor will allow. 



The whole nuni1)er of colonies on the plate shall be counted, the prac- 

 tice of counting a fractional part being resorted to only in case of neces- 

 sity, such as partial .spreading. 



\'arious counting <levices have been recommended by different work- 

 ers. The more simple ones, where the whole plate can be seen at once, 

 are more desirable on account of there being less likelihood of recount- 

 ing colonies. Colonies too small to be seen with the naked eye or with 

 slight magnification shall not be con.sidered in the count. 



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