New Yoek Agbtcultubal Experiment Station. 903 



The four quarters of the udder act independently, so far as cell 

 content is concerned, since the counts for the different quarters of 

 one cow's udder may show as great variations as those from separate 

 udders. 



In the group of cows that gave high average cell counts were two 

 cows that had recently aborted, two old cows and one that had 

 suffered from udder troubles, which might appear to indicate that 

 these cows sustain the common belief that the peculiarities mentioned 

 are causes of profuse cell shedding. On the other hand, however, 

 one cow in this high-count group possessed no characteristic that 

 has ever been thought to have an influence in producing such counts; 

 and the low-count group contained one cow that had recently had 

 udder troubles and still had a hard lump between the front quarters, 

 one cow that had aborted within five weeks of the time of testing, 

 and one old cow. 



The milking machine has been thought a cause of 



Influence of increased cell content of milk; as it was believed 

 milking that the use of unusually high vacuums has a tend- 

 machine ency to draw blood or its leucocytes into the udder ; 

 and vacuums, that is, to cause " leucocytosis." The comprehen- 

 sive data secured in these tests indicate that there 

 is no basis for such a belief. 



In all the comparisons made, machine-drawn milk appeared to 

 have a lower cell content than hand-drawn milk; and variations in 

 the vacuum used, up to 19| inches, gave no corresponding changes 

 in cell content. In the vacuum-increase tests, three cows of different 

 ages and milking history, and each in a different part of the lactation 

 period, were selected as experimental animals; and three in similar 

 stages of milk giving and of comparable cell counts were used as 

 checks. 



Starting with a vacuum of 14| inches, five successive increases in 

 the degree of vacuum secured, each of an additional inch of mercury 

 supported, were made at weekly intervals. The high vacuum of 

 19^ inches was maintained for only one milking and the machines 

 were rapidly returned to the normal by a change at each milking. 



The animals showed no physical effect from the vacuum increases; 

 and the changes in cell content of the milk could be connected in no 

 way with the changes in conditions. The milk of one of the experi- 

 mental animals appeared to increase slightly in cell content as the 

 vacuum increased, with one rather high count after the first rise of 

 an inch and others while the vacuum was at 17| inches and at 18| 

 inches, with a return to practically the original figure at 19| inches 

 and a rise to a high count again when the machine supported only 

 14| inches of mercury. The check cow of this pair, without vacuum 

 increases, showed very similar and almost as great changes in the 

 cell content of her milk. 



