MICRO-ORGANISMS IN MILK 275 



suggest that the non-liquefying cocci, in reality, may be slowly 

 liquefying ones. The colonies were grown on gelatin plates and 

 the property to liquefy judged from liquefied areas forming at the 

 seat of the colony. 



The lactic acid bacteria that cause normal souring of milk 

 were never found in the udder by Burr, and v. Freudenreich could 

 not detect the presence of Bacterium lactis acidi (Streptococcus 

 lacticus) in the milk from the majority of cows, but sometimes 

 isolated colonies of this organism appeared on the plate. Its 

 presence, therefore, is indicated in at least some cases, and per- 

 haps if enriching media had been used it would have been found 

 in a considerable number of samples, v. Freudenreich also made 

 the interesting observation that the flora in different quarters of 

 the same udder may vary widely. In two quarters he found very 

 few bacteria and these were micrococci, while in the other two 

 quarters Bacterium lactis acidi (Streptococcus lacticus) was pres- 

 ent in large numbers. 



The presence of Streptococcus lacticus in the udder has been 

 observed by other investigators. Russell and also Conn report 

 finding it in considerable numbers, but adhere to the appellation 

 of Bacterium lactis acidi. Avirulent streptococci which probably 

 were identical with Streptococcus lacticus were found by Bergey, 

 Reed and Ward, Savage, and others. Lammeris and Harrevelt 

 observed an avirulent streptococcus to persist in the udder of a 

 cow that had recovered from an attack of mastitis. 



Sherman and Hastings found streptococci in the mixed milk 

 from all but two out of twelve herds and in 38.6 per cent, of 

 samples from 88 cows. The authors recorded the presence of strep- 

 tococci only when chains of twelve cells or more were present in 

 abundance, and determined this by microscopic examination. 

 Miss Evans made a study of the flora of the udder, and states that 

 the majority of udder bacteria are of the same type as those com- 

 mon on the skin and mucous membranes of man and animals. 

 In 16.1 per cent, of the samples examined bacteria did not seem 

 to multiply to any great extent in the udder. Streptococcus lac- 

 ticus was not found in any of the samples. Isolation of bacteria 

 was made by transferring colonies from the plated milk. Long- 

 chained streptococci which failed to reduce the litmus in litmus- 

 milk, reduction of litmus being a characteristic of Streptococcus 

 lacticus, were isolated from 15.1 per cent, of the samples. In one 

 case as many as 264,000 streptococci per cubic centimeter were 

 present. Micrococci were present in 58.8 per cent, of the sam- 

 ples. The highest number of micrococci was 80,000 per cubic 

 centimeter. The majority of these were avirulent, but two strains 

 killed rabbits in sixteen hours. The author also found Bacillus 



