New York Agricultural Experiment Station. 119 



" The number of cellular elements in cows' milk varies from numbers 

 so few as to be almost negligible (less than 5,000 per cubic centi- 

 meter) to 20,000,000 and more per cubic centimeter in milk which 

 we have good reason for calling normal." 



The hygienic significance of the cells has been much discussed 

 because of the fact that many men have felt that the presence of 

 large numbers of leucocytes is an abnormal thing and therefore 

 undesirable. It has also been generally believed that there is a close 

 relationship between the presence of pathogenic streptococci of the 

 kind that cause mastitis, and large numbers of body cells. Milk 

 containing large numbers of cells has therefore been frequently 

 condemned as unhealthful food. Moreover, because of the fact that 

 milk clarifiers remove these cells from the milk in large numbers, 

 the question has been raised whether this removal may not be an 

 advantage. 



It therefore becomes an important question to the dairy farmer 

 to know whether there is any justification in fact for these beliefs 

 and statements. This bulletin gives the results of some investigations 

 which have been made in order to secure more information concern- 

 ing the nature and significance of the cells. 



All of the determinations of the number of cells in milk 

 have been made by means of a comparatively new method of milk 

 examination which is discussed in detail in Bulletin 373 of this Sta- 

 tion. The latter bulletin likewise discusses the usefulness of this 

 microscopical method of counting objects in dried, stained films of 

 milk as applied to bacteria, while the present bulletin shows the 

 usefulness of the method as a means of determining the cellular 

 content of the milk. 



ACKNOWLEDGMENTS. 



The writer is under special obligations to Dr. H. A. Harding, 

 former head of the Bacteriological Department at this Station, for 

 his courtesy in having placed the facilities of the laboratory at the 

 writer's disposal during February and March, 1911, at which time 

 he was on leave of absence from Allegheny College. The work 

 reported here was largely accomplished during this time. Through- 

 out the study, Dr. Harding maintained a lively interest in it and 

 aided materially in planning some of the experimental work. Special 

 acknowledgment of help rendered is also due Mr. G. A. Smith, 



