MILK 105 



out cultural and animal inoculation tests before a diagnosis of 

 diphtheria bacilli in milk is made. 



Examination for B. typhosus. The detection of this organism 

 in milk is a matter of considerable difficulty. The milk sediment 

 after centrifugalisation is mixed with a little sterile water, and 

 fractions of the emulsion are distributed over the media in a 

 series of Petri-dishes. The media to use are one or other of 

 those which differentiate the typhoid bacilli to some extent, such 

 as lactose bile salt neutral red agar. All suspicious colonies 

 are investigated. The composition of the media and the method 

 of investigating the colonies are the same as for the isolation of 

 this bacillus from water. 



Procedures to obtain evidence as to the condition of the milk- 

 producing apparatus of the cows from which the milk is 

 obtained. 



The most important of these conditions is tuberculosis of the 

 udder. The detection of tubercle bacilli has been described, 

 and it is only necessary to remark that finding these bacilli in 

 milk, while generally pointing to tuberculosis of the udder of 

 one or more of the cows supplying the milk, does not invariably 

 bear that interpretation. Schroeder, and more recently the 

 English Royal Commission on Tuberculosis, have shown that 

 tubercle bacilli may be found in the milk of tuberculous cows 

 which show no evidence of udder tuberculosis. In many cases 

 they are derived from the faeces, which contain the bacilli and 

 are allowed to pollute the milk. 



A. Estimation of the cellular content of milk. All milk 

 samples contain a certain number of cellular elements, and in 

 certain pathological conditions their number is enormously in- 

 creased. Deductions of great value can be made from accurate 

 determinations of their number in the milk of individual cows. 

 For mixed milk samples this determination is of much less utility. 



The older method used was to centrifugalise the milk, spread 

 the sediment as evenly as possible over a cover-slip, dry, and 

 stain by methylene blue. The number of leucocytes in a number 

 of fields of vision was then counted, and an attempt made to 



