334 MILK 



demanded for production of certified milk, and even certified milk 

 can be produced at lower cost than was thought possible a few 

 years ago. Experience and experimental work carried on chiefly 

 at Agricultural Experiment Stations has shown that an expensive 

 equipment is not necessary to produce clean milk, but that the 

 methods of production are of paramount importance. We have 

 reported work that seems to show that stable air, expensive 

 construction of stables, and costly machinery are of relatively small 

 influence in reducing the germ content of milk. On the other 

 hand, cleanliness of cows, the small-top milking pail, cleaning and 

 steaming utensils, prompt cooling, and keeping the milk cool are 

 important factors in producing milk with low germ content. 

 Cement floors are to be preferred to wooden floors, iron-pipe 

 stanchions to wooden stanchions, and painted walls to rough 

 walls; but in some dairies milk is produced that is fully equal to 

 certified milk as far as bacterial counts are concerned, in spite of 

 inferiority of construction and equipment. Clean methods are 

 more highly responsible for improved milk-supplies than expensive 

 buildings and complicated machinery. These latter, further- 

 more, increase the cost of production and bring the product beyond 

 the reach of the poorer classes of the population. 



With introduction of the cream separator it was learned that 

 insoluble substances were thrown out of milk by the centrifugal 

 force. The bowl sediment contains cells, bacteria, casein, and in- 

 soluble dirt. Dairymen resorted to the scheme of centrifugalizing 

 the milk in order to remove foreign matter and then of reuniting 

 the cream and the skimmed milk. Recently centrifugal clarifiers 

 which do not separate the cream from the milk have come into 

 use and are rapidly gaining favor. It is true that insoluble dirt 

 is easily removed by these machines, but the soluble material 

 remains and the count of bacteria increases on account of the 

 clumps being broken up. It seems, however, according to Ham- 

 mer's work that the increase of the colony count from milk after 

 clarification is, on the average, not as great as after separation of 

 cream and reuniting cream and skimmed milk, and Sherman 

 states that the average number of bacteria in 24 tests of milk 

 before clarification was 4720, while the same samples after clari- 

 fication contained an average of 7120. 



Although the clarifier removes many bacteria, it is obvious 

 that infected milk cannot be made harmless by the process, be- 

 cause only a limited number of bacteria is removed, while the 

 balance remain in the milk. Sherman has shown that strep- 

 tococci are present practically in as great numbers in the clarified 

 milk as in the milk before clarification. 



Filtration of milk through sand has been practised in some 



