CHAPTER XIII 

 CELLS, DIRT AND DEBRIS 



Cells. For nearly a century it was recognised that cells 

 or cell fragments were present in the secretion as formed in 

 the alveoU, but it is only comparatively recently that any 

 efforts were made to ascertain if any cells were present in the 

 discharged milk. In 1897 Stokes and Wegefarth ^ directed 

 attention to the presence of leucocytes in milk and, since then, 

 considerable study has been given to this subject. These 

 observers differentiated the leucocytes from the epithelial cells 

 by the form of the nuclei but, unfortunately, designated the 

 former as pus cells, a nomenclature that was perpetuated by 

 many later writers. This designation is no longer accepted 

 and the cells are regarded as constituents of normal milk. There 

 is still some diversity of opinion regarding the nature of these 

 cells, some experimenters, including Winkler, Hewlett, Villar, 

 and Revis, holding that they are predominantly of epitheUal 

 origin, whilst others, amongst whom are Bergey, Doane, Miller, 

 Breed, Ernst, and Savage, regard them mixtures of blood cells 

 and epitheUal cells. 



Hewlett, Villar, and Revis ^ support the contention of Wink- 

 ler and Michaelis that the cells in normal milk are chiefly young 

 epithelial cells which have become detached. In a later paper 

 they find that in the milk of healthy cows in full milk and 

 which do not give a high cell count, the majority of the cells 

 appear to be " large uninuclears " with a small admixture of 

 other cells. At the beginning and end of lactation and when 

 the cell count was high from other causes, whether physiological 

 or pathological, the " multinuclears " predominated. Scan- 

 nel ^ pointed out that epitheUal cells are mononuclear and that, 



171 



