36 UNIVERSITY OF WISCONSIN STUDIES 



The process of pasteurization not only frees milk from the 

 danger of transmitting tuberculosis but at the same time it 

 frees it from the danger of transmitting the other diseases 

 which have been observed to have been occasionally so trans- 

 ferred. Accordingly pasteurization is coming to be recog- 

 nized as the simplest and most efficient protection against the 

 spread of disease germs through milk supplies. 



THE PROBLEM OF CLEANLINESS 



Even under most favorable conditions it is difficult to pre- 

 vent limited amounts of foreign matter from getting into milk. 

 On the other hand, the consumer insists that the milk shall 

 be as clean as practicable. Fortunately the amount of soluble 

 foreign matter which finds its way into milk is very slight 

 and the white color of the milk forms a background against 

 which anj' insoluble matter present stands out distinctly. 



The amount of insoluble dirt actually present in milk as it 

 is delivered to the consumer naturally varies considerably. 21 

 The present available data suggest that it rarely amounts to 

 more than five milligrams per quart or roughly five parts per 

 million while the average is nearer one part per million. 



The Wisconsin Sediment Tester 22 is a convenient device for 

 collecting upon a cotton disk the insoluble dirt from a pint 

 of milk and has proven a satisfactory instrument for this 

 purpose. At the Chicago Department of Health this method 

 has been made roughly quantitative by preparing test disks 

 from samples of milk containing weighed amounts of dirt. 23 

 At the University of Illinois the standards for quantitative 

 examinations of sediment in milk have been still further 

 perfected until it is believed that the weight of the insoluble 

 dirt in milk may be quickly determined with an accuracy 

 rivaling that obtained by any other available means. 



The standards for this purpose are prepared by powdering 



21 H. N. Parker, City Milk Supply, p. 256. 



~ S. M. Babcock and E. H. Farrington, New and Improved Tests of Dairy 

 Products, Bulletin 195, Wis. Agr. Exp. Sta., 1910. 



23 F. O. Tonney, Report of the Municipal Laboratory, Department of 

 Health, City of Chicago, 1907-1910, p. 25. 



