SHELLFISH 85 



The actual isolation is carried out in the ordinary way. As 

 mentioned above for rough comparative purposes Johnstone used 

 direct plating of definite amount of shellfish juices upon L.B.A. 

 media. 



CHAPTER VI 



MILK 



The bacteriological examination of milk even up to a few 

 years ago could not be said to be very satisfactory, and indeed, 

 apart from tuberculosis, very little was systematically done, while 

 in regard to the procedures that were carried out there was 

 neither uniformity of method nor consensus of opinion as to 

 what was desirable. Even at the present time it is by no 

 means on a uniform or satisfactory basis. 



The bacteriological examination of milk may be utilised to 

 give information in the three following directions : 



1. To measure the degree of contamination of the milk 

 from faecal and other sources and its general bacterial content. 



2. To ascertain the presence or absence of definite disease- 

 producing organisms, e.g. B. diphtheriae, B. tuberculosis, B. typho- 

 sus. 



3. To obtain evidence as to the healthiness of the milk- 

 producing apparatus of the cows which supply the milk. 



The procedures to be used will obviously require to be varied 

 according to the purposes of the examination. The different 

 methods are considered in detail in the following sections. 



Collection of Samples. 



Care in collection is necessary to obtain samples which are 

 really representative of the milk to be examined. Ordinary 

 samples of mixed milk may be collected at the byres or in 

 course of transit or delivery. The cream and the sediment are 



