MICRO-ORGANISMS IN MILK 277 



absent, a fact which is not surprising, since the majority of forms 

 were cocci which are not known to form spores. Motile rods 

 were not discovered. 



Gelatin was liquefied by 55 per cent, of all the bacteria studied, 

 although the reaction usually proceeded slowly. Nitrates were 

 reduced by 59 per cent, of the forms. Starch was not digested 

 by 80 per cent, of the cultures, while 16 per cent, dissolved starch 

 feebly and 4 per cent, almost completely. 



The Gram stain was positive in 96 per cent, of all cultures. 

 This is in accordance with the fact that the majority of organisms 

 were cocci most of which are Gram-positive. 



It is an interesting fact that the bacterial flora of the udder 

 represents relatively few types with a marked predominance of 

 micrococci. The bacteria that enter the teat duct are of a mani- 

 fold variety and multiply readily in the duct. But these are ap- 

 parently poorly represented in the udder, although most of them 

 multiply readily in milk, especially at the temperature of the 

 body. Both food and temperature conditions are favorable in 

 the udder, and still the majority of bacteria fail to grow. Russell 

 and Hastings have introduced cultures of Bacillus prodigiosus 

 into the udder and have shown that they gradually disappear. 

 A complete explanation of this pnenomenon is still lacking. Un- 

 questionably the germicidal property of milk and animal tissue 

 is one of the factors producing this result, and it must be assumed 

 that micrococci are more resistant to this action than other bac- 

 teria. Whether this is a full explanation of the facts or not can- 

 not be decided at the present time. It must be borne in mind, as 

 has been pointed out, that sometimes other organisms are the 

 predominating kind in the udder. Whether such occurrences are 

 due to lack of germicidal power in the udder, or increased resist- 

 ance of the organism, is not known. The fact remains established 

 that among the many species that gain access to the teat duct and 

 multiply there, but few. even if they invade the udder, are able to 

 persist there. 



Furthermore, it should be taken into account that the pos- 

 sibility of hematogenous origin of bacteria in the udder is not 

 wholly excluded, v. Freudenreich found that the spleen and 

 kidney of cows are not free from Bacteria. This is in agreement 

 with work done by Ford, which seems to indicate that internal 

 organs are not always germ free. Russell and Hastings comment 

 on this view as follows: "It is interesting to note that the bacteria 

 found in the udder are similar to those that seem to be most 

 abundant in such glandular tissues as the liver and the spleen. 

 This fact increases the probability that these comparatively inert 

 coccus forms of the udder may originate directly from the blood- 



