NOTES ON THE SOURCES OF CONTAMINATION 267 



the organisms present in the milker's mouth or throat will be 

 transferred to the milker's hands. In the process of milking 

 there will be an accumulation of bacteria, epithelial debris and 

 dirt, both from the hands of the milker and from the teats of 

 the cow. A large proportion of this material will fall into the 

 milk-pail. 



Some of the epidemics which have arisen as a result of con- 

 taminated milk, have been traced directly to disease in the milkers. 

 A milker with a sore throat will be liable to infect the milk with 

 the organisms present in his throat. One suffering from pulmonary 

 tubercle will transfer tubercle bacilli to the milk with the greatest 

 ease, either by a cough or by the saliva if the hands are moistened 

 with it. Epidemics of scarlet fever have been traced to infection 

 from a member of the dairy staff through the milk. Further, 

 epidemics of typhoid fever have been traced to the fact that one 

 of the milkers was a carrier of these germs. 1 



3. From the Cow-shed. It is not necessary to dwell upon this 

 subject, since the presence of large numbers of organisms in straw, 

 etc., is a matter of universal knowledge. These organisms cannot 

 fail to be present in the air of the cow-shed where bedding or fodder 

 is present, and a certain number will inevitably find their way into 

 the milk-pail. Where it is desired to obtain a milk of low bacterial 

 content, it is usual either to milk the cows in a shed where no 

 bedding is allowed, or to use sawdust for bedding instead of straw 

 or similar substance. The bacteria which gain access from these 

 sources are probably harmless. 



4. From the Milk-pails. A dirty milk-pail will contaminate 

 the milk which is milked into it, and it is to be feared that there 

 is frequently a lack of cleanliness, especially in the smaller farms, 

 in regard to this matter. A good deal of the contamination referred 

 to above could evidently be prevented if the contaminating matter 

 were not allowed to fall into the pail. The reduction of the bacterial 

 count by using (i) a properly shaped milk-can and (2) care in cleanli- 

 ness of the milk-pails will be dealt with later. 



5. Conveyance from the Farm to the Customer. The sources of 

 contamination under headings 5, 6, 7, and 8 (see above, p. 265) resolve 

 themselves into a consideration of the conveyance of milk from 

 the milking-shed to the customer, and will evidently depend upon 

 the method of transit employed. So much has already been written, 

 and so many investigations carried out, upon the various phases 

 of contamination of the general milk supply in the course of its 

 transit, that no further remarks will be made here. Those interested 

 will find much information in the work of Houston and of Savage, 

 and of the authors quoted by them. 



6. Contamination in the Home of the Customer. This source 

 of contamination, which is outside the purview of investigations 



1 Cp. Chap. XV. 



