250 MILK HYGIENE 



3. Since in city inspection work a smear of the sedi- 

 ment is often made and examined for estimation of the 

 number of bacteria present, it is profitable to make both 

 tests at the same time. 



4. The operation for many samples is much more 

 simple than the volumetric, and less trying on the eyes. 



5. This method has been shown to give consistently 

 lower results than the volumetric. If therefore, for 

 example, 500,000 leucocytes to a c.c. are estimated by 

 this method, it can safely be said that the milk contains 

 greatly in excess of that number, and to that degree is 

 much more suspicious than would be a volumetric de- 

 termination indicating 500,000. 



The volumetric method has been most used for care- 

 ful research work where exact leucocyte content was 

 to be determined as nearly as possible. 



It is hoped during the coming year comparison of 

 volumetric and smeared sediment technique may give 

 us a more exact relation between the tv^^o, and that 

 further work by those who have herds at their command 

 may place these examinations upon a more satisfactory 

 basis. 



Determination of streptococci. Although by careful 

 searching a few streptococci will be found in most sedi- 

 ments from pus milk, they are seldom found to any great 

 extent by direct microscopical examination. Occasion- 

 ally a sample will be found crowded with long chains; 

 more often streptococci, if present, are in the form' of 

 diplococci or very short chains. 



Where streptococci, diplococci or cocci are found in 

 the sediment and the plate from the same sample con- 

 tains colonies resembling streptococci colonies, these 

 colonies may be grown in bouillon to see if chains will 

 develop. 



First make and record an estimate of the number of 

 such colonies present, then transfer from ten to fifty 

 of them to bouillon and grow for twenty-four hours at 

 37° C. To examine the bouillon culture spread a loop- 

 ful on a glass slide, fix with heat, fix with alcohol while 

 slide is still quite hot, stain with methylene blue, wash 

 immediately, dry and examine. 



