EXAMIXATIOX FOR DIRT 235 



are morphologically the same and so can not be differ- 

 entiated by their appearance alone. Doane has pro- 

 posed that milk shall- be regarded as containing pus if 

 there is high cellular content accompanied by threads 

 of fibrin. Bergey proposes that pus shall be diagnosed 

 if there are 10 cells to the field of the 1, 12 immersion 

 lens. Htewart centrifuges 1 e.c. of milk in small tubes 

 and if he find 2.'] cells to the field of the 1/12 immersion 

 lens, when the sediment of this amount of milk is spread 

 over 1 square cm., he reports pus. Slackisroposes that 

 the sediment of 2 e.c milk shall be spread over -1- s(|uare 

 cm. and that pus shall be reported if 30 cells are seen 

 to the 1/12 immersion field. 



8ince there is mucli doubt, in many cases, as to 

 whether high cellular content actually denotes pus, — that 

 is, as to whether the cells found are pus cells or li-uco- 

 cytes, and as to whether the crlls tJiciiisflrcs ai'c in- 

 jurious, it would appear to be desirable, for the present, 

 to report pus only where theie is high cellular content, 

 as judged by one of the above methods, accomi)anied by 

 the })reseu('e of streptococci. L. P.] 



/. Examination for dirt. The sale of unclean or dirty 

 milk should be forbidden. A number of cities in Ger- 

 many have established the requirement that milk shall 

 not contain over a definite amount of dirt; the limit va- 

 ries from 5 to 10 milligrams of dry dirt to a liter of milk. 

 An examination for dirt can be made as follows: The 

 milk is placed in bottles, which are centrifuged, the milk 

 is decanted and the sediment is dried at a temperature a 

 little above that of boiling water. This material is 

 weighed and its (juantity jier liter is calculated. 



Instead of this rather formidable method it is usu- 

 ally sufficient to centrifuge the milk and then measure 

 the sediment. Or, one t'an pour the milk in a high glass 

 of conical shape and ascertain the amount of sediment 



