152 UNIVERSITY OF WISCONSIN STUDIES 



Storch's test is generally regarded as the most satisfactory. 

 This test, however, as is well known, can be used only 011 milk 

 heated from 78 to 80 C. (172.4 to 176 F.). It cannot, 

 therefore, be applied to milk heated to the temperature em- 

 ployed for pasteurization in this country now. A microscopic 

 test was devised by me and described in a paper by Frost 

 and Raveiiel in 1911. 1 Two features of this method inter- 

 fered with its usefulness. One was the difficult technic and 

 the other was the fact that the stain safranin clotted the milk 

 unless added with the greatest care. So far it has been pos- 

 sible to avoid this danger only by diluting the stain, and in 

 this case the action of the dye is largely neutralized. 



In 1915 I proposed the method under discussion in this 

 article in a preliminary paper. 1 ' This was described somewhat 

 more in detail in a paper read before the International Milk 

 Dealers' Association in October, 1916. 3 The practical results 

 that may be obtained by its use are described in a paper by 

 Miss Moore and me. 4 



It is here proposed to discuss this method in a somewhat 

 more adequate way. 



BODY CELLS IN MILK 



There occur in cow's milk under all conditions a variable 

 number of body cells or leucocytes. There are at least two 

 kinds : the moiionuclear and the polymorphonuclear varieties. 

 The latter ones are of chief interest here. Whether or not 

 these cells are leucocytes from the blood which have escaped 

 through the gland walls or are cells from the walls of the 

 mammary gland, given off at the time of milking, is a ques- 

 tion on which histologists are not agreed. 



'Frost and Kavenel, .1 Microscopic Test for Heated Milk in Proc. Am. 

 Assn. Med. Milk Commissions, p. 127, 1911. 



2 W. D. Frost, A Microscopic Test for Pasteurised Milk in Jour. Am. 

 Med. Assn., 44, pp. 821-822, March 6, 1915. 



3 W. D. Frost, Milk Dealer, p. 84, Dec., 1916. 



4 W. D. Frost and Genevieve D. Moore, The Cellular Test for Pasteur- 

 ized MilTc in Dairy Science. 



