126 



BACTERIOLOGICAL METHODS 



entire number found multiplied by 100 gives the number of body 

 cells per cc. of the milk. Prescott and Breed have examined 

 numerous milk samples and declare that the average number of 

 body cells is 1,500,000 per cc. and that a count as low as 100,000 

 per cc. is uncommon. 



Little can be said regarding the microscopical and bacteriolog- 

 ical examination of butter, cheese, cream and other factory products. 



FIG. 39. Unglazed porcelain filters. Chamberland system; A, without pressure; 

 B, fitted to main water supply; C, section of a porous porcelain filter. 



There are no bacterial standards and the laboratory work is very 

 largely limited to the detection of adulterants such as excess of 

 salt, of water and the presence of lard and oleomargarine in but- 

 ter, fillers in cream and in ice cream, etc. 



The following simple tests will be found useful in the labora- 

 tory: 



i. Spoon Test for Oleomargarine and Renovated Butter. Melt a small piece 

 of the suspected butter in a tablespoon or small dish, using a small flame. Stir the 

 melting substance with a small piece of wood such as a tooth-pick or match. At a 



