96 THE MODERN MILK PROBLEM 



Microscopic Examination 



Microscopic examination of milk for the determina- 

 tion of pus and bacteria has been coming in recent years 

 somewhat rapidly into use, but is not fully established 

 as a standard method of estimating numbers of bac- 

 teria. It is now under consideration by a special sub- 

 committee of the National Commission on Milk Stand- 

 ards and will be reported upon later.* The following 

 comment, from the paper by Dr. Conn already re- 

 ferred to, is meanwhile of interest: 



The direct microscopical examination of milk smears by 

 the Breed method will classify raw milk into grades A, B, 

 and C with about the same accuracy and much more quickly 

 than the plate method 'of bacteriological analysis will do. 

 It is of no use in the study of pasteurized milk, however, 

 since it discloses dead as well as living bacteria, no method of 

 distinguishing between them having yet been perfected. 

 It might be of value in telling whether such milk had be- 

 come old before it was pasteurized, since such would show 

 large numbers of dead bacteria by the microscopic method, 

 though it might show small numbers by the plate method. 



The direct microscopical method of bacteriological analy- 

 sis ... may be of great aid to the large dealer to enable 

 him to determine promptly whether he is purchasing milk 

 of A, B, or C grade. The possibility of quick results and 



* It is, however, discussed in a recent provisional report of the Com- 

 mittee on Standard Methods of Bacteriological Analysis of Milk, of 

 the Laboratory Section of the American Public Health Association 

 (Am. Jour. Public Health, Dec., 1916). While the method is not as 

 yet recommended by the Committee as a standard method of estimat- 

 ing numbers of bacteria, its value in rapidly dividing raw milk into 

 grades and in detecting large numbers of streptococci is recognized. 



