448 CITY MILK SUPPLY 



In many laboratories the presence in milk of streptococci forming 

 chains in lactose broth at 98.6F. is accepted as evidence that the milk 

 or a part of it was from infected udders and some hold that it proves the 

 milk polluted with cow dung. Rogers, Clark and Evans have investi- 

 gated the validity of the test. They studied 51 cultures from two herds 

 in which infected udders had given trouble and found that the cultures 

 could be divided into two varieties which were related but which were 

 separated by certain distinctive characters. Nearly all cultures of 

 both types fermented lactose, saccharose and dextrose and failed to fer- 

 ment raffinose, starch and inulin but the more numerous type which had 

 a marked tendency to form long chains in broth at 98.6F. failed to fer- 

 ment mannit and glycerine and to liquefy gelatin, whereas the other 

 type nearly always did so. The type with the tendency to form long 

 chains corresponds to St. pyogenes as regards the reactions that have 

 been considered. A study of 114 cultures of streptococci isolated from 

 bovine feces showed they differed from the long-chain type in the amount 

 of acid produced and in the substances fermented, for besides fermenting 

 dextrose, saccharose and lactose, they almost always fermented raffinose, 

 while about 50 per cent, of them fermented starch and a few inulin but 

 they were unable to utilize the alcohols except that a few fermented 

 mannit. From this work and the study of 42 cultures isolated from 

 milk from 25 farms by inoculating lactose bile, incubating at 98.6F. 

 and plating only those tubes showing distinct chains, the authors make 

 the statement that, while their results are not conclusive, they hold 

 them as substantiating the belief that the presence in lactose bile, inocu- 

 lated with milk and incubated at 98.6F., of chain-forming streptococci 

 is good presumptive evidence of milk from infected udders. They point 

 out, however, that udders may contain streptococci of the pyogenes 

 type without showing physical signs of infection. 



Significance of B. coli. In water analysis the presence of the colon 

 bacillus is regarded as indicative of fecal pollution because the organism 

 is a normal inhabitant of the intestines of man and of the lower animals 

 and for the same reason some health departments have endeavored to 

 make the presence of excessive numbers of these bacteria in milk a reason 

 for excluding it from the market. This has excited vigorous protest 

 on the grounds that these germs multiply rapidly in milk which they do 

 not in water, and that the studies of Prescott and others show that organ- 

 isms of the colon group are found not only in feces but also on grains 

 which are commonly used as cattle feed. 



The feasibility of using this test has been investigated by Rogers, 

 Clark and Evans. They began their investigation with a study of 120 

 cultures from milk samples taken in various parts of the country. It 

 was found possible to divide these cultures into two groups on the basis 



