BACTEEIAL COUNT OF MILK AND DIET TEST. 3 



method was also about two minutes, and we found it to be the most 

 satisfactory for field work. 



Fifty samples of milk were collected on the railroad station plat- 

 form from milk cans as they arrived from various farmers throughout 

 the section. Upon arrival at the laboratory the temperature was 

 taken and a bacterial count made. After preparing plates each 

 sample was passed through one of Gerber's sediment tubes. The 

 sediment disks were kept and compared with the bacterial count. 

 A similar comparison was also made with the Wizzard and Lorenz 

 apparatuses, using 50 samples in each case. 



After 50 samples had been tested with each apparatus, 20 samples 

 were filtered through 4 pieces of cheesecloth, 20 through one thick- 

 ness of absorbent cotton, and 20 through one of Canton flannel. 

 Each of these samples was then subjected to the sediment test and 

 a bacterial count made in each case; this was done to determine 

 the effect that straining the milk would have upon the test. We 

 also made a comparison of the filtered samples with the bacterial 

 count after passing them through the cotton disks used in the Lorenz 

 apparatus. 



The writer wishes to thank Dr. John R. Mohler, assistant chief of 

 the Bureau of Animal Industry; Dr. Louis A. Klein, dean of the 

 veterinary school. University of Pennsylvania; and Dr. C. J. Marshall, 

 State veterinarian of Pennsylvania, for many valuable suggestions- 

 in the work. 



METHOD OF COLLECTING SAMPLES. 



The milk in the can was thoroughly shaken and 1 pint taken as a 

 sample. The sediment in this kind of sample would, in our opinion^ 

 represent the amount of dirt contained in an ordinary bottle of milk, 

 A few inspectors believe that the sample should be collected from 

 the bottom of the cans before shaking, but it seems to us that this 

 may at times be unfair to the producer. 



DETAILS OF THE EXPERIMENTS. 



In .our experiments the character and quantity of sediment upon 

 the cotton disks is represented by the "words "good," "fair," "me- 

 dium," and "bad." (PI. I, fig. 1.) This gives four classifications, 

 which we considered sufficient for all practical purposes. These 

 classifications are illustrated in Plate I. 



COMPARISONS WITH UNFILTERED MARKET MILK. 



Table 1 shows the laboratory results obtained by comparing the 

 bacterial count with the Gerber sediment test on 10 average samples 

 out of 50. 



