SIGNIFICANCE OF RESULTS. 135 



Fig. 16. Section of udder showing epithelial cells and polvnnclear 

 leucocytes. 



a . /-'.pit he! ia I ce ! ! which has become loosened from the wall of the duct, 

 similar to a in Fig. 15 . b. Secreting epithelial cell in situ, being same 

 in st nt dii re as a. c. Polynuclear leucocytes in ducts ready to be thrown 

 out along with the loose epithelial cells. 



variation among the cows of a herd examined by him. Some 

 of the apparently healthy cows gave counts exceeding 500,000 

 per cc. It was not possible, however, to pick ten cows that 

 would average more than that number. The leucocyte count 

 of the milk of two apparently healthy cows was determined 

 twice a day over a long period of time, and the most abrupt 

 fluctuations were observed in the number of leucocytes present. 

 Heated milk gives a much higher leucocyte count by both 

 the Doane-Buckley and the smeared-sediment method (9). 

 Leucocytes and pus cells are identical, although common 

 practice has determined that, under conditions of health, the 

 cells in question shall be called leucocytes, and pus cells in 

 certain pathological conditions. We have no satisfactory 

 standard at present to determine when this change in designa- 



