CELLS IN MILK DERIVED FROM THE UDDER* 



ROBERT S. BREED. 



SUMMARY. 



1. Cells of two entirely different kinds are discharged in the milk 

 of all cows throughout the entire lactation period. The larger number 

 of the cells are leucocytes (white blood corpuscles) while a smaller 

 number are epithelial cells, nuclei or other fragments of such cells. 

 The epithelial cells here referred to are apparently the same as the 

 colostral corpuscles of the majority of earlier writers. 



2. The evidence thus far obtained indicates that the largest 

 average number of cells occurs in colostral milk but equally 

 large numbers of cells occasionally occur in milk drawn at any 

 time during the lactation period. Several very high cell counts 

 have been obtained from the milk of animals nearing the end of 

 the lactation period, and the evidence here given indicates that 

 such high counts are more common during the latter part of the 

 period than during the height of lactation, but the average cell 

 counts for the latter part of the period do not seem to be markedly 

 higher than the average cell counts for the earlier part of the period. 



3. There are marked daily variations in the number of cells dis- 

 charged, the cause or causes of which have not yet been discovered. 

 No constant relationship holds between the number of cells dis- 

 charged in the foremilk and the number discharged later in the 

 milking process. There is a constant increase in the number of 

 cells discharged in the strippings, the cause of which is not yet clear. 

 The four quarters of the udder do not act as a unit in the discharge 

 of the cells but show as wide variations in number and character 

 of the cells discharged as do separate udders. 



4. Of 122 cows whose milk has been examined, 59 gave cell 

 counts under 500,000 per cubic centimeter, 36 gave counts between 

 500,000 and 1,000,000 per cubic centimeter, and 27 gave counts 

 over 1,000,000 per cubic centimeter. The average cell count was 

 868,000 per cubic centimeter. 



5. The investigations here carried out have not demonstrated 

 what relationship exists, if any does exist, between the number of 



* Reprint of Bulletin No. 380, March; for Popular Edition see p. 900. 



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