70 THE CORNELL READING-COURSES 



always be careful; I have told the man if the cow stepped into the pail 

 to throw the milk away, but he won't always do it unless he is watched." 



Tests were made some years ago by R. A. Pearson, at that time 

 Professor of Dairy Industry at the New York State College of Agricul- 

 ture, and by Walter E. King of the State Veterinary College, in order 

 to determine the importance of different sources of milk contamination. 

 Mr. Pearson has given the following as a result of these experiments : 



" In most of these tests, a definite quantity of sterilized milk at 98 F. 

 was exposed to some one kind of contamination that we wished to test. 

 The milk was then examined and in that way we could get a fairly accurate 

 idea of what this particular kind of contamination amounted to. Some 

 of the experiments and their results are as follows: 



1. " Exposure to air in the stable. Two liters (about two quarts) of 

 sterilized milk were placed in a sterile pail and exposed seven minutes to 

 the stable air in a passageway behind the cows. This stable was doubt- 

 less cleaner than the average and the air contained less dust than is 

 often found in places where milk is being handled. Immediately after 

 this exposure, the milk was ' plated ' and. found to contain 2,800 bacteria 

 per cubic centimeter (about fifteen drops); in other words, between 

 5,000,000 and 6,000,000 bacteria had fallen into the two liters of milk 

 in this short time. 



2. " Pouring milk. When milk is poured from one vessel to another, 

 a very large surface is exposed to the air and great numbers of bacteria 

 are swallowed up. The following tests illustrate this point: About 

 five liters of milk were poured from one can to another eight times in the 

 stable air. It was found, after pouring, that this milk contained practically 

 100 bacteria per cubic centimeter more than it contained before pouring; 

 in other words, about 600,000 bacteria had got into the milk because of 

 this exposure. In another similar experiment, when there was a little 

 more dust in the air, the contamination due to pouring eight times was 

 two and one half times greater than in the preceding experiment. 



" The importance of pouring milk as little as possible from one vessel 

 to another has suggested to Dr. J. Roby, of the Rochester Health Depart- 

 ment, that milking-pails should be made larger than those now used and 

 immediately closed after the cow has been milked. The milk should 

 then be cooled and delivered in these same pails without further exposure. 

 In some ways this suggestion is a most excellent one, but it may be that 

 under certain conditions the disadvantages of this method of handling 

 milk would exceed the advantages. 



3. " Contaminated utensils. Much contamination of milk results from 

 putting it into dishes that have been cleaned and then exposed where 

 dust can fall into them. In experiments to determine what this kind of 



