138 Cleanliness in Dairy Management. [june, 



Sources of Bacterial Contamination. — Before dealing with the 

 question of how bacterial contamination may be to some extent 

 avoided, reference may be made to the chief sources of con- 

 tamination, which are the cow, the milker, the air, and the 

 utensils. The cow herself is one of the most fruitful sources ; not 

 that she secretes milk containing germs, but because these germs 

 exist in the hair which covers her body, and many of them during 

 milking find their way into the milk. The milker's hands and 

 clothes, which in many cases are none too clean, are also sources 

 of contamination. The atmosphere of a cow-byre, moreover, is 

 in too many cases confined, and, consequently, impure; such an 

 atmosphere contains a large number of bacteria, which, being 

 slightly heavier than the air, gradually settle down, and some of 

 these find their way into the milk or into the utensils waiting to 

 receive it. Finally, the dairy utensils are frequently a great 

 source of contamination, either owing to improper cleaning or 

 because they are left after cleaning in places where they are 

 exposed to infection. 



The one great means by which the milk producer is able 

 to minimise bacterial contamination is cleanliness. Just as 

 a weed is defined as being a plant out of place, so may the 

 weed of the dairy — dirt — be defined as being matter out of place. 

 The injury caused by this dirt lies not so much in its direct 

 action on the milk as in the fact that, almost without exception, 

 it serves as a food on which bacteria can thrive and multiply, 

 thereby greatly increasing the bacterial contamination of the 

 milk. To put the matter in another light, " dead dirt " aids in 

 producing " live dirt," which in turn acts upon the milk. 



A badly kept and ill-ventilated cow-shed or byre serves to 

 produce a germ-laden atmosphere to which the milk is exposed 

 whilst it is being drawn, and too frequently also for a consider- 

 able time afterwards, owing to delay in removing it from the 

 cow-shed to the dairy. Figures 1 and 2 illustrate this point. 

 They are photographs of gelatine plates exposed to the air for 

 one minute in badly ventilated and well ventilated cow-sheds, 

 respectively. Fig. 2 shows that the number of organisms exist- 

 ing in the atmosphere of the shed are materially reduced by 

 efficient ventilation. 



A cow kept in such a byre is rarely clean in herself; her 



