206 PASTEURISED OR HEATED MILK 



to the output. When various grades of milk are offered for 

 sale, the results should be separately recorded. The interval 

 between sampling and examination should be as short as pos- 

 sible although no appreciable alteration occurs even in twenty- 

 four hours if the samples are kept between 32° and 40° F. 



Recording Results. The ordinary method of recording 

 results by expressing the average total bacterial count or the 

 average number of bacteria of some particular group of organ- 

 isms, may give a result which does not represent the quality of 

 the supply if the variations from the mean are large, or if the 

 number of variants is comparatively small. The median 

 would be more representative of the actual quality than the 

 mean but a better plan is to express variations in the counts in 

 the manner set forth in Tables LXVI and LXVII. The size of 

 the groups in the scheme is quite arbitrary, but where milk is 

 graded they should agree with the limits permitted in each par- 

 ticular grade. 



BIBLIOGRAPHY 



1. Rupp. Bull. 166, U. S. A. Dept. of Agr. 



2. Bang and Stribald. Zeit. f. Tiermidicin. 1897, 1, 241-278. 



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Board of Agr., Appendix to Part 1. London, 1909. 



4. Evans. Jour. Inf. Dis. 1916, 18, 437-477. 



5. Good and Corbett. Jour. Inf. Dis. 1916, 18, 586-596. 



6. Race. Can. Jour. Pub. Health. 1915, 6, 490. 



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1914. 



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