Breed, Cellular Elements in Milk. ^jq 



certain cells, generally regarded as leucocytes, which occur nor- 

 mally in milk. It has been claimed that the number of these cells 

 is greatly increased by any physiological or pathological disturb- 

 ance in the udder and that it is possible to determine whether a 

 specified sample of milk was drawn from a cow suffering from such 

 abnormal conditions by a determination of the number of cells 

 present in the milk , A provisional Standard of 500 000 cells per— 

 cubic centimeter has been adopted for this purpose. It has been 

 generally assumed that milk containing more than this number 

 of cells is unfit for human consumption and there is a tendency 

 to ascribe certain intestinal disorders, especially of children, to 

 the use of such milk. Some investigators have claimed, while 

 others have denied, that milk containing large numbers of these 

 cells usually contains Streptococci also. 



Several methods have been devised for counting the number 

 of cells present in milk, all of them based on the examination of the 

 Sediments precipitated by the use of the centrifuge. The first 

 methods devised were very crude and inaccurate and have been 

 considerably modified by later workers. A description of these 

 methods together with a statement of their value and use will 

 be found in the final Report of the Committee on Standard Methods 

 of Bacterial Milk Analysis appointed by the American Public 

 Health Association which has just been published 1 ). A paper 

 presented by Prescott and Breed 2 ) at the Oct. 1909 meeting 

 of the American Public Health Association sho ws. however that the 

 best of these methods must be inaccurate because of the fact that 

 the centrifuge does not precipitate all of the cells present and the 

 number precipitated is not a constant proportion of the whole. 

 In the case of two samples of milk which were centrifuged and 

 then examined carefully, it was found that more of cells rose with 

 the cream than settled with the sediment. This is similar to the 

 conditions noted by other investigators for the bacteria present 

 in centrifuged samples of milk. 



A new method for determining the number of cells present 

 in milk announced at the same time is briefly as follows : a measured 

 drop (.01 cu. cm.) of the milk to be examined is spread evenly 

 over a measured area (1 s q. cm.) on a glass slide, dried with gentle 

 heat, the fat dissolved out with xylol and the smear fixed to the 

 slide by immersion in 90% alcohol. The slide is again dried and 

 stained with methylene blue. The number of cells present is then 

 determined by examination with the microscope. Results done 

 in duplicate show a small percentage Variation proving that the 

 practical error is not a large one. 



A series of tests of milk by this method show that much 



x ) Amer. Jour. Pub. Hyg., Vol. XX, p. 315 — 345, 1910. 

 2 ) Journ. Infect. Diseases, Vol. VII, Oct., 1910. 



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