CONTAMINATION OF MILK 



185 



It is simple enough to give such organisms different names, 

 and to say one is B. coli communis, another B. coscoroba, 

 another B. neapolitanus, etc., but unless we are able to demon- 

 strate a different distribution and a different significance for 

 such organisms, their use in the practical and routine examina- 

 tion of milk adds nothing of value for administrative purposes, 

 and the use of these names is of doubtful service. 



Both MacConkey and Orr have published the results of 

 examinations based upon the use of some or most of these tests. 



MacConkey * records the examination of 178 samples of 

 human faeces and 131 samples of horse, calf, goat, and pig 

 faeces. He differentiated his isolated organisms by fermen- 

 tation and other tests into numerous groups. Taking his 

 results, and neglecting the presence or absence of motility 

 as a differentiating test, and grouping together some of the 

 varieties only represented by a very few strains, we obtain 

 the following percentage results : 



* For characters of these strains, see table below. 



Orr 2 isolated 850 glucose fermenting organisms from milk. 

 He classified them in a very similar manner to MacConkey. 

 Some of them failed to ferment lactose. Excluding these, and 

 dealing only with the bacilli isolated from cowshed, retailer, 

 and consumer milk samples and those obtained from manure, 

 the results in the following table are obtained : 



1 Journal of Hygiene, 1909, ix. p. 86. 

 2 Report on an Investigation as to the Contamination of Milk, 1908. 



