228 Bulletin 158. 



ters remained clear. In making these cultures pieces of the 

 glandular tissue as large as an average sized bean were used. 

 The number of colonies was small in all cases. However, the 

 essential fact is that bacteria were there and remained there after 

 milking, read}^ to infect the milk of the next succeeding milking. 



During the summer of 1898, a second opportunity for examin- 

 ing two udders under like circumstances was availed of. In these 

 cases the same organism, a micrococcus was found in cultures 

 from the milk and from different parts of the mammary gland. 

 Gas-producing bacteria were not found in an}^ of the udders 

 examined. 



The investigations heretofore reported, have not shown, as a 

 rule, the presence of gas-producing bacteria in the fore milk. It 

 is only occasionally that we find in the records of these investi- 

 gations a statement of the presence of gas-producing organisms. 

 Bolley and Hall* examined the milk of ten cows for a period of 

 three months without encountering gas-producing bacteria. 

 Others have recorded practically the same results. This is sig- 

 nificant in suggesting that the normal intestinal bacteria, espec- 

 ially Bacillus coli communis, does not under ordinary conditions 

 invade the milk ducts. Likewise, a vigorous gas-producer, Bacil- 

 lus cloaccB which is found in the soil does not seem to become 

 localized in the udder. 



It will be seen from the description (p. 234) that the bacillus 

 isolated from the tainted curd is closely related to, if it does not 

 belong in the colon group of bacteria. f The evidence collected 

 supports the hypothesis that the milk ducts were in this case 

 invaded with this organism about the time that certain of the 

 cows were discharging the decomposed placental membranes. As 

 the stable was not disinfected or kept as clean as it might have 

 been, it is presumable that the bacteria which became concen- 

 trated in large numbers in these membranes were disseminated 



*Centralblatt fiir Bakteriologie u. Parasitenkunde, Vol. II. Abstract in 

 Experiment Station Record, U. S. Dept. of Agric, Vol. VII., p. 99. 



fin the intestines of healthy animals, there is constantly present an 

 organism known as Bacillus coli comfnunis. There are many varieties of 

 this species and for convenience all of these varieties are classed together 

 under the general term of the colon group. 



