202 PASTEURISED OR HEATED MILK 



was produced by very widely differing B. coli contents, and it 

 was, therefore, impossible to form a definite opinion regarding 

 the B. coli content from the appearance of the fermentation 

 test. The A type was almost invariably produced by milk 

 low in B. coli, whilst D5 pointed to excessive contamination 

 with this group, but with regard to the intermediate types, 

 which the majority of market milks produce, no definite con- 

 clusions could be deduced. The same remarks apply regarding 

 the relation of the total bacterial count to the type of fermenta- 

 tion, and, under these circumstances, it is difficult to attach 

 much value to this test. Some observers have a high opinion 

 of this test, because it is supposed to yield evidence as to bac- 

 terial flora and thus enable deductions to be made as to the 

 conditions under which the milk was produced and its subse- 

 quent treatment, but the author's results do not substantiate 

 this claim. 



The conditions of the test, viz., incubation, at blood heat, 

 are artificial, as milk is never, under ordinary circumstances, 

 kept at this temperature, and it is not logically sound to assume 

 that the biological and chemical changes are the same at dif- 

 ferent temperatures as a change of temperature always favours 

 the growth of one or more groups in preference to others. 



Collection of Samples 



All milk sold in bulk must be thoroughly mixed before 

 samples are taken and every endeavour should be made to 

 obtain milk in the same manner in which the vendor supplies 

 the same to the consimier. The Conmiittee of the American 

 Public Health Association, appointed for the standardisation 

 of bacteriological examination of milk, have recoromended that 

 bacteriological samples should be obtained from bulk milk by 

 means of sterile pipettes, but this method samples milk which 

 is in the possession of the vendor and ignores possible contami- 

 nation in the vessel used for the transfer of such milk to the 

 consumer. The author has observed numerous instances in 



