New York Agricultural Experiment Station. 165 



be found in the herd. Gerty F. 2 (No. 12) gave milk which con- 

 tained relatively few cells. Ruth F. (No. 24) gave milk which con- 

 tained a medium number of cells and Millie D. (No. 18) gave milk 

 containing large numbers of cells, the number being usually higher 

 than 1,000,000 per cubic centimeter. The control animals were 

 chosen to duplicate these conditions so far as possible. Of these, 

 Hammond F. 1 (No. 15) gave the lowest cell counts, Gerty F. 1 

 (No. 10) medium counts and Mabel S. F. (No. 17) the highest counts. 

 The duplication in conditions was not exact but proved satisfactory 

 for the purposes of the experiment. 



Samples of milk from the animals which were to be used in the 

 experiment were examined during the week previous to Feb. 23, 

 1911, in order to determine the number of cells present under usual 

 conditions. At the evening milking of February 23, the vacuum was 

 increased from the usual amount (14.5 inches) to 15.5 inches. At 

 the evening milking of March 3 it was again increased to 16.5 inches 

 and so to 17.5 inches at the evening milking of March 10. The 

 vacuum was placed at 18.5 inches at the evening milking of March 

 16 and kept there till the evening of March 19 when it was raised 

 to 19.5 inches for this one milking only. It then became necessary 

 to discontinue the experiment and the vacuum was lowered one 

 inch at each milking during the four succeeding milkings and so 

 returned to 14.5 inches. This change in the vacuum and its rela- 

 tion to the milk flow is shown in Graph III taken from Bulletin 353. 

 The control animals were milked continuously at 14.5 inches vacuum. 

 Samples of milk were taken from the pail at every milking from each 

 of the six animals and the cell content determined. 



The vacuum gauge was tested out during the experiment to make 

 sure that it was working properly and a careful watch was kept 

 on the animals to see whether the increased vacuum caused udder 

 troubles of any sort. " Not only was there no demonstrable effect 

 of the change of vacuum upon the flow of milk but also there were 

 no objectionable local effects upon the cows. It is true that at the 

 close of the milking process with the higher vacuum there was some 

 difference of opinion as to the presence of a slight congestion at 

 the extremity of the teats of Ruth F. Whatever abnormality 

 may have been present passed away within a few minutes leaving 

 no objectionable after-effects." 



