274 MILK 



germs of these streams are distributed throughout the mixed milk 

 the increase per cubic centimeter of the whole product is relatively 

 small. In a series of experiments carried on by Stocking the 

 average germ content of the milk, when the fore-milk was not 

 rejected, was 522 per cubic centimeter, while when the fore-rnilk 

 was rejected the average number was 499, a difference of 23 bac- 

 teria per cubic centimeter in favor of rejecting the fore-milk. 

 The advantage of keeping the first streams separate from the final 

 product is apparently very small and hardly compensates for the 

 additional work. 



From all the figures quoted it may be inferred that the actual 

 number of bacteria usually present in the udder is not great. 

 Probably 500 germs per cubic centimeter represent ordinarily 

 the maximum. There are, however, frequent exceptions, and 

 these seem to occur most commonly when some particular variety 

 of micro-organism is numerous, and in such cases the kind of bac- 

 teria present persists often for a long time. This may occur 

 without causing any detectable pathologic condition of the udder. 

 Harding and Wilson have averaged the number of 'bacteria in 

 milk obtained directly from the udder with precautions to avoid 

 external contamination, and give the following results: 



Average germ content per c.c. in 316 samples from a herd, 518 

 Average germ content per c.c. in 730 samples from a herd, 420 

 Average germ content per c.c. in 184 samples from a herd, 320 

 Average germ content per c.c. in 1230 samples from 78 cows, 428 



The grand average of all samples, then, was 428 bacteria per 

 cubic centimeter, which probably represents the number of germs 

 that can be assumed to be present normally in the udder. 



The same authors have attempted to trace some relation of 

 germ content to the period of lactation. They conclude that 

 there is no evidence of any well-marked connection between the 

 germ content of milk in the udder and the period of lactation. 

 However, there is a distinctly greater number of bacteria in the 

 milk during the colostral period than later, and there is a sugges- 

 tion that toward the close of lactation there is a slight tendency 

 for the germ content of the udder to fall. 



The age of the cow was also found to exert no appreciable 

 effect upon the germ content of the udder. 



Studies of the kinds of bacteria commonly present in the 

 udder have led to fairly harmonious results. As a rule, micrococci 

 seem to be the predominant group. Lux found 90 to 95 per cent, 

 of all organisms studied to be micrococci, and only 5 to 10 per 

 cent, bacilli. Von Freudenreich and Thoni's work led to similar 

 results; they found both liquefying and non-liquefying cocci, but 



