SOURCES OF BACTERIA IN MILK 



97 



Backhaus 13 reports 10,400 bacteria per c.cm. in fore milk 

 as against practically sterile strippings whilst the author in one 

 instance obtained 50,000 per c.cm. in the fore milk, 4000 in 

 the middle milk and 500 in the strippings. The advantage 

 obtained by the rejection of the fore milk is usually much 

 greater than is indicated by Stocking's results reported above, 

 but this factor is largely determined by the precautions observed 

 in other directions and may be but a mirror one if the udders 

 are thoroughly stripped and kept clean between and during 

 milking operations. This so-called intramammary contam- 

 ination, which is really external contamination, though con- 

 veyed to the milk whilst in the udder, is, however, only a frac- 

 tion of the external contamination that reaches the milk directly; 

 this is especially true of ordinary market milk. The external 

 contamination increases at every stage between milking and 

 delivery to the consumer and is very diverse in character. 

 The chief sources of contamination are : 



(1) During milking. Bacteria from 'dirty udders, flanks, and hands of 



milkers: also aerial contamination with dust 

 of food or litter. 



(2) During handling. Dirty containers, strainers and cooling apparatus. 



The influence of bodily cleanliness of the cow on the 

 bacterial count of the milk obtained has been investigated 

 on several occasions. Backhaus 13 found 20,600 bacteria per 

 c.cm. in the milk of brushed cows as against 170,000 per 

 c.cm. from unbrushed cows. Stocking 12 reports the following 

 results : 



