2 BULLETIN 139, U. S. DEPARTMENT OF AGRICULTURE. 



In this connection Savage (18) 1 states: 



Lactose fermenters of the colon type are absent from pure milk drawn without 

 contamination, and as far as it is known at present, all such organisms indicate out- 

 side pollution of the milk and in general (directly or indirectly) manurial pollution. 



Kinyoun and Dieter (10) stated that their experience led them to 

 conclude that the colon and streptococcus content of milk could 

 be taken with reasonable certainty to indicate the amount of, filth and 

 dirt in milk. These authors also realized that temperature had an 

 effect upon the colon content of milk, and in this connection they state: 



It is evident from this fact alone that it will account for a considerable proportion 

 of the number, but it must be understood that we do not believe that this factor alone 

 is responsible for the enormous numbers found. 



Again, Kinyoun (9) writes as follows: 



What is the significance of the colon group in milk? The colon group comes from 

 the intestinal canal of man and animals, indirectly may be found in soil, water, and 

 food. This is such a well-established fact that it does not need discussion. When 

 it gains access to food and drink it must be from one of these sources. Water fre- 

 quently contains colon bacilli, and sanitarians agree that in determining the whole- 

 someness of water for drinking purposes the colon bacillus is the best index for purity. 



Kinyoun while admitting that temperature played a part in the 

 colon count believed that most of them gained entrance to the milk 

 during milking, for in the same article he states: 



When milk is contaminated by the colon group it indicates that it owes its presence 

 there to uncleanly methods at the time of milking, or to the collection of the milk 

 in dirty utensils, or to the, contamination from air. The greater proportion of the 

 colon bacilli gains entrance to the milk at the time of milking, and they owe their 

 presence directly to fecal matter which has gained access to the pail by dirty, filthy 

 cows, equally so the hands of the milker. 



Other investigators are inclined to credit more importance to the 

 growth of colon organisms in milk which has been held at high tem- 

 peratures. Thus Harrison, Savage, and Sadler (4) made colon counts 

 on a large number of samples in a study of the milk supply of Mon- 

 treal, and, in speaking of the colon and aerogenes groups, state: 



We regard any member of these groups as indicating manurial impurities in milk. 

 A large number of this group present in the sample shows either carelessness and un- 

 cleanliness in milking, subsequent keeping at a high temperature, or, as most fre- 

 quently happens, a combination of both. 



In view of the fact that milk is an ideal medium for the growth of 

 bacteria it seems that a determination of the colon bacilli as a means 

 of indicating original contamination must be greatly complicated by 

 the ability of these organisms to grow in the milk unless it is kept 

 cold. Kendall, Day, and Walker (8) realized this difficulty and state: 



The numbers of colon bacilli which may be present in a sample of milk do not 

 necessarily furnish any evidence of the nature or extent of fecal contamination, for 

 there is no way of distinguishing between the initial number of these organisms in a 

 given sample of milk and their descendants. 



i Figures in parentheses refer to " Literature cited " at end of paper. 



