466 MILK 



The question may be asked with justice, What is the real sig- 

 nificance of leukocytes in milk? They are frequently spoken of 

 as "pus cells." That this is a misnomer is evident. The re- 

 semblance to pus cells is chiefly due to the fact that they are more 

 or less broken down in milk, which is to be expected in a lifeless 

 fluid. In the light of present knowledge no sanitary significance 

 can be attached to mere numbers of cellular elements. The 

 kinds of cells existing in milk have never been systematically 

 investigated. Hewlett, Villar, and Revis found in full milk from 

 healthy cows chiefly "large uninuclears" and a few other cells, 

 but at the beginning and end of lactation "multinuclears" were 

 more prominent. They state their opinion, derived from the 

 kinds observed, that it is not possible to recognize diseased con- 

 ditions by means of microscopic examination of the cells present. 

 Woodhead and Jones described finely granular eosinophils, coarse 

 granular eosinophils, large, rounded or oval mononuclear cells, 

 small cells corresponding to lymphocytes of the blood, extruded 

 nuclei, large oval neutrophil cells, basophil cells, small type of 

 basophil cells, large epithelial and fat cells, multi- or mononu- 

 cleated cells, and red corpuscles. Luckhardt made an attempt 

 at classification of cellular elements in separator slime. He found 

 polymorphonuclear leukocytes of the neutrophil type, large mono- 

 nuclear leukocytes, and small lymphocytes in all samples examined. 

 Occasionally eosinophils were found and large cells of irregular 

 outline which greatly resembled protoplasm with very pale nuclei. 

 These latter cells were phagocytic and the author believes that 

 they represent desquamated epithelial cells. Some polymorpho- 

 nuclear leukocytes contained many cocci or short chains of strep- 

 tococci. Breed thinks that normal milk contains cells derived 

 from the body fluids of the cow, which are of two types : (a) white 

 blood-corpuscles, largely polynuclear and polymorphonuclear, and 

 (6) epithelial cells. It is clear that investigations of the kinds of 

 cells may lead to more intelligent interpretation of their sig- 

 nificance, while simple enumeration seems to be of little value. 

 The presence of fibrin with many cells has been demonstrated and 

 may have more intimate connection with pathologic conditions of 

 the udder. 



There seems to be considerable evidence that when large 

 numbers of leukocytes are found together with long-chained strep- 

 tococci, mastitis is indicated. It has been shown that strepto- 

 cocci are present in practically all market milk, and that these 

 streptococci are non-pathogenic for man and cows. Mastitis 

 streptococci are pathogenic for cows. The question of differ- 

 entiating between different varieties of streptococci has been widely 

 discussed, and much experimental work has been done. The chief 



