by the artificially added culture.  The culture thus added, being present in very much greater quantity than the other “wild” species, will have a much greater effect than any of them.  This method, of course, cannot insure uniformity.  While it may work satisfactorily in many cases, it is very evident that in others, when the cream is already filled with a large number of malign species of bacteria, such an artificial culture would not produce the desired results.  This appears to be not only the theoretical but the actual experience.  The addition of such pure cultures in many cases produces favourable results, but it does not always do so, and the result is not uniform.  While the use of pure cultures in this way is an advantage over the method of simply allowing the cream to ripen normally without such additions, it is a method that is decidedly inferior to that which first pasteurizes the cream and subsequently adds a starter.

There is still another method of adding bacteria to cream to insure a more advantageous ripening, which is frequently used, and, being simpler, is in many cases a decided advantage.  This method is by the use of what is called a natural starter.  A natural starter consists simply of a lot of cream which has been taken from the most favourable source possible—­that is, from the cleanest and best dairy, or from the herd producing the best quality of cream—­and allowing this cream to stand in a warm place for a couple of days until it becomes sour.  The cream will by that time be filled with large numbers of bacteria, and this is then put as a starter into the vat of cream to be ripened.  Of course, in the use of this method the butter maker has no control over the kinds of bacteria that will grow in the starter, but it is found, practically, that if the cream is taken from a good source the results are extremely favourable, and there is produced in this way almost always an improvement in the butter.

The use of pure cultures is still quite new, particularly in this country.  In the European butter-making countries they have been used for a longer period and have become very much better known.  What the future may develop along this line it is difficult to say; but it seems at least probable that as the difficulties in the details are mastered the time will come when starters will be used by our butter makers for their cream ripening, just as yeast is used by housewives for raising bread, or by brewers for fermenting malt.  These starters will probably in time be furnished by bacteriologists.  Bacteriology, in other words, is offering in the near future to our butter makers a method of controlling the ripening of the cream in such a way as to insure the obtaining of a high and uniform quality of butter, so far, at least, as concerns flavour and aroma.

Bacteria in cheese.