250 BACTERIA IN MILK AND THEIR SOURCES 



As milking proceeds, the contaminated foremilk exist- 

 ing in the teat and milk cistern is soon removed, and 

 the milk obtained later has very few bacteria in it. The 

 " strippings," or last drawn milk, rarely contains more 

 than 400 to 500 per c.c. 



According to Swithinbank and Newman it is possible 

 to draw quite sterile samples from the udders by means 

 of a " milking tube " inserted through the teat after the 

 " foremilk " has been milked out, if careful precautions 

 are taken to sterilize the apparatus used and wash the 

 udder and teats with an effective germicide before the 

 operation. 



On the other hand, it may be noted that Schultz, 

 Freudenreich, Boekhout, De Vries, and others failed to 

 obtain sterile milk from the udder of healthy cows, even 

 where careful precautions were observed. There is little 

 doubt that at the point of secretion, that is, in the fine 

 alveoli of the mammary gland, milk is free from living 

 organisms ; the extent, however, of the invasion of the 

 milk ducts in the lower portion of the udder is not 

 clearly known. It probably depends to a large extent 

 on the physiological condition of the cow and the kind 

 of bacteria concerned ; some organisms may be able to 

 penetrate a considerable distance into the udder from 

 the orifice of the teat, while others may be unable to 

 exist or multiply at all under the conditions prevailing 

 in the milk cistern and ducts. 



As soon as milk is drawn from the udder it becomes 

 liable to further pollution from various sources. Cows 

 which are not carefully groomed have on their flanks, 

 and on the udder to some extent, bits of dried dung, 

 mud, and other materials, with which they are sure to 

 come in contact when lying down in the cowshed, 



