638 POPULAR SCIENCE MONTHLY. 



distribution tlirougli tlie milk supply, it would appear tliat sucli a 

 method is perhaps satisfactory. 



So far as can be determined, this method is efficient in destroy- 

 ing pathogenic bacteria. Its efficiency is of course dependent upon 

 the length of time that the milk is retained at the high tempera- 

 ture, and this can be regulated by the rate of the flow of the milk 

 through the machine. All evidence we have seems to point to the 

 conclusion that a temperature of 75° C, continued for a few min- 

 utes only, so far destroys or weakens the pathogenic bacteria which 

 are liable to be found in milk that they need not subsequently be 

 feared as producing disease. Of course, there are pathogenic bac- 

 teria that are not destroyed by this temperature, but they are not 

 likely to occur in milk. The germs of typhoid, diphtheria, and 

 tuberculosis are probably rendered harmless by such treatment, 

 and these are the chief pathogenic bacteria of milk. Moreover, the 

 other bacteria are very greatly decreased in numbers, so that the 

 dangers of intestinal troubles are at least much reduced. In hos- 

 pitals where Pasteurization has been adopted the results are as 

 favorable as with sterilization. 



The great value of this plan is, however, that it is practical on 

 a large scale. In Copenhagen it has been in practice for some 

 three years very extensively. In Denmark the amount of tuber- 

 culosis among cows is very great, somewhat more than half the 

 animals suffering from this disease. As a result the public milk 

 supply is regarded with more suspicion than in countries where 

 the disease is less. It is everywhere recommended that the milk 

 be always boiled before using, but the bother of treating the milk 

 thus daily makes people unwilling to do it, and it is doubtful whether 

 the practice is as common as the physicians think necessary. Some 

 three years ago a company was organized to meet the public de- 

 mand for safe milk, and it has adopted plans by which it furnishes 

 Pasteurized milk on a scale as extensive as that of the ordinary 

 milk-supply companies. The company has devised and manufac- 

 tured two large machines which receive the milk. Pasteurize it, and 

 cool it in a constant stream, and are capable of treating two thou- 

 sand quarts an hour. The milk received by the company is tested 

 chemically and filtered, and then allowed to pass through one of 

 these large machines. After this it is placed in glass bottles and 

 sealed with the company's seal. The heating is done by steam, 

 and the cooling by brine cooled by an ammonia cooling machine. 

 The greatest care is taken in cleaning and sterilizing the bottles, 

 an enormous chamber some twenty feet long and six feet in diam- 

 eter being used for a sterilizer. Into this the washed bottles are 

 placed, the chamber hermetically closed, and then superheated 



