BACTJeRIOLOGICAL EXAMINATION OF MILK. 



I." INTRODUCTION. METHODS OF PREPARATION. 

 CULTIVATION. 



Milk generally .contains a large amount of micro-or- 

 ganisms, the number of which varies according to the 

 cleanliness practised in the milking and in the entire man- 

 agement of the dairy. It has been demonstrated that 

 the number of germs present depends upon the amount 

 of foreign matter contained in the milk. From the mo- 

 ment the milk leaves the udder, the bacteria increase 

 very rapidly provided their vitality is not decreased or 

 weakened by heating or by the use of preservatives, so 

 that by estimating the number, an idea can frequently be 

 gained as to the freshness of the milk, as well as the 

 cleanliness of the process by which it is handled. 

 However, bacteria may be contained in the milk even 

 before it leaves the udder, which is the case in certain 

 diseases, the diagnosis of which can be made through 

 a bacteriological examination of the milk. In human 

 milk, which was drawn from a mammary gland, and kept 

 scrupulously clean and under perfectly aseptic conditions 

 by every precaution, various cocci have been found 

 (Honingmann, Lewis, Polleske, Johannessen, Durante, 

 and others). 



In examining bacteria of milk the simple dry 

 cover-glass preparation is sufficient in many cases, 

 but the fat must always be extracted. A bit 

 of the milk to be examined is taken up on a loup made 

 at the end of a platinum wire and spread with water upon 



76 



