96 Report of the Department of Bacteriology of the 



With Millie G. the results of both counts were the same from 

 the right back quarter while the count after incubation at 37 °C. 

 was the higher in 5 samples from the right front, 11 from the left 

 front and 4 from the left back out of the 18 samples examined 

 from each quarter. 



This marked variation in the effect of high temperature is due 

 to variations in the flora. As will be described under the head 

 of udder flora there were isolated 11 micrococci, a bacterium and 

 a yeast, the colonies of which did not ordinarily appear at the 

 lower temperature. ISTaturally these forms were more common 

 in the udders of particular cows and were more frequently found 

 in some quarters than in others. The uneven distribution of 

 these forms in the samples is to be ascribed in part to the forma- 

 tion of clumps or colonies within the udder <as has been described 

 by Breed. 11 These colonies are occasionally observed in samples 

 from the udder by means of his technique and the number of 

 colonies appearing on the plate is dependent upon the extent to 

 which these clumps are broken up in the plating process. It is 

 practically certain that our present plate methods give an in- 

 adequate idea of the numbers of bacteria actually present in 

 freshly drawn cows' milk. 



CHOICE OF METHODS OF SAMPLING. 



In undertaking a combined quantitative and qualitative study 

 of the udder germs it was necessary to obtain samples which were 

 representative both of the total numbers and of the kinds of germs 

 present. To obtain accurately the total numbers it would seem 

 desirable to draw a sample from the well mixed product of a 

 quarter which had been milked under careful conditions. How- 

 ever, under the best of conditions some contamination will occur 

 during the milking process and this procedure would raise the 

 question as to whether organisms isolated from such samples were 

 really representatives of the udder flora. 



ii Breed, R. S. The determination of the number of bacteria in milk by 

 direct microscopical examination. Cent. Bah. II Abt. 30:337-340. 1911. 



