CHAPTER XVI 



NOTES ON THE SOURCES OF THE CONTAMINATION OF MILK 



THE contamination of milk is brought about by the addition to 

 it of bacteria, and is liable to occur at all stages of its production, 

 and of its transit to the consumer. 



The class of bacteria will evidently differ very greatly, and 

 will depend upon the source of the contamination. These following 

 sources may be regarded as the more common : 



1. From the cow herself, either from the udder or from other 

 parts of the animal. 



2. From the milker. 



3. From the cow-shed, either from the air, the walls, floor, 

 bedding, or the food. 



4. From the milk-pails. 



5. In the process of filtering and cooling. 



6. From churns or bottles. 



7. In the process of transit from the farm to the dairy and from 

 the dairy to the customer. 



8. In the course of manipulation at the dairy. 



9. In the home of the customer. 



These sources may now be considered individually : 



I. From the Cow herself. It seems hardly possible, even when 

 full precautions are taken, to obtain milk by the ordinary process 

 of milking which has a lower count than a few hundred bacteria 

 per cubic centimetre. Seibold, using antiseptics for washing the 

 teats, and after discarding a considerable amount of first milk, was 

 able in a few instances to obtain sterile milk by milking directly 

 into sterile tubes. Ordinarily, however, sterile milk can only be 

 obtained by the use of a milking-tube passed up the teat into the 

 space which occurs in the cow's udder between the gland tissue and 

 the teat, and by collecting the milk thus obtained, all the apparatus 

 used having been previously sterilised. The counts obtained by 

 Seibold, and later by Rullmann, using all precautions, were found 

 to vary from o to about 400 bacteria per c.c. 



In cases where there is disease of the udder the organisms pro- 



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