MILK 93 



organisms that produce disagreeable flavors gain ascendancy and 

 the subsequent butter is of a low grade. 



In some dairies it is the custom to use a " natural starter " ; 

 that is, a small quantity of cream that has developed the required 

 qualities is added to the fresh cream. This procedure is simply 

 seeding the new cream with the organisms known to be capable 

 of producing the desired results. 



A step further has been taken by the more progressive dairy- 

 men. The fresh cream is pasteurized in order to eliminate the 

 action of any bacteria present and a pure culture of an organism 

 already proved to have the requisite qualities is introduced. In 

 this way butter of a uniform quality, at least as regards flavor, 

 can always be depended on. 



Unfortunately all cream is not pasteurized before it is churned, 

 and pathogenic organisms are by no means rare in market butter. 

 In an examination of 21 samples offered for sale in Boston two or 

 9.5 per cent were found to contain tubercle bacilli. 1 Other investi- 

 gations in another locality report 15.2 per cent. Many experi- 

 ments have been made to determine the length of time typhoid 

 bacilli will continue to live in butter. It is generally assumed 

 that they die after a few days. 



Cheese. The bacteriology of cheese making is somewhat 

 more indefinite than that of butter making. It is proven that 

 cheeses are ripened by the action of bacteria and molds and that 

 the different flavors are due to the growth of different species dur- 

 ing the process. As yet, however, the organisms concerned and 

 the role they play is largely a matter of conjecture. 



1 Rosenau, "Preventive Medicine," p. 581. 



