xiv BACTERIAL POLLUTION OF MILK 235 



organisms per c.c. This is a maximum allowance, and is based 

 on the supposition that the milk is maintained at 15 C. for 

 at least 24 hours. Obviously in winter such a temperature 

 would not be maintained, often never reached, and a lower 

 standard would still be fair and reasonable. If separate summer 

 and winter standards are set up, the summer limit for vended 

 milk might reasonably be not more than 1000 lactose fer- 

 menters of coli type per c.c., and not more than 100 for winter 

 samples, but the more lenient standards set out below might 

 be adopted in the first place. These standards should be made 

 more stringent as the conditions of milk transit, etc., improved. 



ESTIMATION OF THE NUMBER OF STREPTOCOCCI IN MILK 



< 

 Here the enumeration is considered purely as an index 



of the degree of cleanliness of the milk. 



Streptococci are extremely numerous in both fresh and 

 old manure. They are also abundant in stale milk contained 

 in improperly cleaned milk vessels. As indicators of pollu- 

 tion they have this, therefore, in their favour, that they 

 are abundant in the materials the presence of which it is 

 wished to quantitatively measure. On the other hand, as 

 has been shown, streptococci may be present in considerable 

 numbers in milk drawn directly from the teats. To judge 

 the cleanliness of the methods used in milk collection by a test 

 which is in part independent of such cleanliness is not a 

 satisfactory procedure. 



In regard to vended milk samples, the difficulties caused 

 by multiplication under varying conditions of time and tem- 

 perature, considered in reference to the general bacterial and 

 B. coli counts, apply also to the streptococcus estimation. 



This test cannot be recommended as equal in value to 

 the B. coli estimation as a means of measuring the ordinary 

 manurial pollution of milk. 



ESTIMATION OF THE NUMBER OF SPORES OF B. ENTERITIDIS 



SPOROGENES 



Certain facts are in favour of this estimation. The spores 

 are present in considerable numbers in cow dung. If the 



