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68 THE MILK QUESTION 



same conclusion. The microscopic examination is, therefore, of 

 great use in picking out animals with diseased udders, for the 

 purpose of removing them from the dairy herd, after a proper 

 examination of individual cows. 



3. The data as yet accumulated are insufficient to determine 

 whether the examination of milk by the centrifugal method of the 

 Stewart-Slack type, or the direct examination by the Fresco tt- 

 Breed method, gives the most reliable results. 



4. The total numbers of bacteria found by the microscopic ex- 

 amination are so out of proportion to those given by those of the 

 plate method that no ratio can be at present drawn between them. 



5. Insufficient data have as yet been collected to determine 

 whether the microscopic examination of pasteurized milk is of 

 any value. 



6. The determination of dirt by filtering a quart of milk 

 through a cotton disk of an inch in diameter is advised as of the 

 greatest value in detecting uncleanly conditions and in conveying 

 a most graphic lesson of the need of cleanliness to the dairyman. 

 Preferably this should be done in the dairy where feasible. 



Bacteria in milk 



Milk contains a vast number of bacteria. For instance, 

 I found the general milk supply of Washington, D. C., 

 averaged 11,270,000 bacteria per cubic centimetre in the 

 summer of 1907, and 22,134,000 bacteria per cubic centi- 

 metre during the summer of 1906. The ordinary mar- 

 ket milk of most other cities also is excessively rich in 

 bacteria. 



Such enormous numbers mean but little to our minds. 

 If we make comparisons we find that few substances con- 

 tain such myriads of germ life as is often found in milk. 

 Compared with sewage, for instance, a liquid which is 

 popularly and rightly supposed to teem with germ life, it 

 will be observed that milk, when it is consumed, is often 

 richer by far in bacteria than the sewage of our large cities. 

 The number of bacteria found in sewage is shown in the 

 following table: 



