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 on milk 
heated from 78° to 80° GC. (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 Ravenel in 1911.4. 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. This was described somewhat 
more in detail in a paper read before the International Milk 
Dealers’ Association in October, 1916.2 The practical results 
that may be obtained by its use are described in a paper by 
Miss Moore and me.? 
It is here proposed to discuss this method in a somewhat 
more adequate way. 
Bopy 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 mononuclear 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. 
1 Frost and Ravenel, A Microscopie Test for Heated Milk in Proc, Am. 
Assn. Med, Milk Comanissions, p. 127, 1911. 
2W. 1). Frost, A Microscopic Test for Pasteurized Milk in Jour, Am. 
Med. Assu., 44, pp. 821-822, March 6, 1915. 
3°W. D. Frost, Milk Dealer, p. 84, Dec., 1916. 
*W. D. Frost and Genevieve D, Moore, The Cellular Test for Pustewr- 
dared Milk in Dairy Science. 
