78 Repoet ok the Department of Bactekiologv of the 



Table XV. — Bacteria in Milk from Cows Cleaned by Hand and by Vacuum 



Cleaner. 



Grand average: Whole milk, 955; stripping?, 443; difference, 512. 



cows the balance is strongly in favor of hand cleaning and the 

 grand averages are 1,340 per cc. for hand and 1,650 per cc. for 

 machine cleaning or a balance of 23 per ct. in favor of hand cleaning 

 of cows. 



A third comparison of the influence of hand and machine cleaning 

 was made between January 8, and February 2, 1912. The same 

 cows were used as in the preceding experiment and they were freshly 

 clipped as at the beginning of the other comparisons. The 62 samples 

 of whole milk were collected and the germ content determined in 

 the same way as in the preceding experiment. In addition 62 samples 

 of the strippings were collected and examined. 



It had been observed that while the capacity of the air pump was 

 sufficient for the milking machine it was not sufficient to maintain 

 a vacuum of 15 inches at all times with the vacuum cleaner. Accord- 

 ingly on January 25, 1912, a smaller pulley was placed upon the 

 vacuum pump which increased its capacity sufficiently so that after 

 that date a vacuum of approximately 15 inches was maintained. 



The results from the 124 samples are given in Table XV. 



