100 THE MICROSCOPE. July 



tbat these volatile products are due to chemical changes 

 taking place in the cream as the result of the active 

 growth of micro-organisms present in it. The chemical 

 side to these changes is at present very little understood, 

 but that the flavor of the butter is due to the products 

 of fermentation is beyond question. It has also ap- 

 peared that diff"erent species of bacteria vary widely in 

 the character of the products which they produce in the 

 ripening cream. Some species will give rise to those 

 exquisitely delicate flavors which are desired in the 

 highest quality of butter, while others give rise to 

 flavors and tastes which are extremely disagreable, 

 producing butter of the very poorest quality and one 

 that would hardly sell in market at any price. Other 

 species again produce changes in the cream which have 

 little or no eff"ect upon the flavor of the butter. Now it 

 is, of course, plain that to manufacture a proper high 

 quality of butter, the buttermaker needs in his cream 

 for the ripening a majority of the best class of bacteria, 

 and it is a matter of as much importance to him to be 

 able to control this factor as it is to the brewer to obtain 

 pure cultures of yeasts for fermenting his malt. 



As butter has been made in past years, however, the 

 butter maker has no means of such control. The bacteria 

 that are present in the milk find entrance thereto from 

 a variety of sources in the barn and the dairy, and the 

 buttermaker has no knowledge as to what sources may 

 be depended upon to give him proper species, or what 

 ones to give him those that he wishes to avoid. When 

 the cream is gathered from a variety of sources and 

 mixed together in a large vat for ripening, as in cream- 

 eries, it is largely a matter of lottery as to whether the 

 cream will contain species that are likely to produce a 

 properly flavored butter or those which will ruin the 

 product. Indeed the buttermaker knows nothing about 

 the subject, and simply allows his cream to ripen under 



