158 UNIVERSITY OF WISCONSIN STUDIES 



essary for the pasteurization of milk, namely, at from 60 to 63C. 

 (140-145F.) ' 



INTERPRETATION OF RESULTS 



Illustrations: The results of this method of staining are 

 shown in Plates I and II, Figures 1 to 26. These drawings 

 are all made under an oil immersion lens and by means of 

 the camera lucida. 



Figures 1 to 4 show cells in the raw milk. Here the back- 

 ground is stained, while the cells remain clear or unstained. 

 In Fig. 5 the milk was heated to 58 C. (137 F.) for 20 

 minutes and in Fig. 6 to 60 Co. (140 F.). Here the poly- 

 morphonuclear leucocytes have their nuclei lightly stained. 



Figures 7, 8, and 9 show the cells in milk that has been 

 pasteurized at 63 C. (145 F.) for 20 minutes. The nuclei 

 are all deeply stained and the segments well rounded off and 

 the fragments discrete. Fig. 10 shows cells from rnilk heated 

 to 65 C. (150 F.), and Fig. 11 shows cells from milk 

 heated to 70 C. (158 F.). Figures 10 and 12 show the 

 bacteria well stained. 



Figures 13 to 18 represent groups of leucocytes selected 

 from various fields to show variations in form, size, and 

 staining reaction at the various temperatures indicated. Ex- 

 cept for the raw milk, no attempt has been made to represent 

 the background. 



Figures 19 and 20 are the results obtained by applying a 

 counter stain to the preparations obtained by the staining 

 with methyleiie blue in the usual way. The advantage of the 

 counter stain is that it brings out or differentiates the leu- 

 cocytes in the raw milk. (The preparations are made in the 

 usual way and when the smears are dry, they are immersed 

 for a -few seconds in a 1 per cent solution of orange G in 

 alcohol (95 per cent) and examined after drying without 

 washing.) 



Figures 21 and 22 are from preparations made by a method 

 suggested by Traum. 8 In this method the cells are separated 



' Loc. cit. 



8 J. Traum, Laboratory Methods to Improve Milk in Amer. Jour. Vet. 

 Med. 10, 717, 1915. 



