r grade. When butter was made on the farm, before the
development of the factory system, it was not a question of vital
importance whether the product was uniform from day to day, but
with the advent of the modern creamery, turning out thousands of
pounds of butter per day, and with the extension of the markets for
the product, the question of uniformity came to be of much
importance. A uniform product can be secured only by the control of
the type of fermentation in the cream, or by the control of the
kinds of bacteria that cause the souring of the cream. Modern
methods of butter making have been devised on the basis of an
improvement in the ripening process.

=Starters.= From the earliest practice of allowing the cream to stand
until sufficient quantity had accumulated for churning, it was only
a step, but a most important one, to the addition of sour milk, sour
cream, or butter milk, to hasten the ripening process. This was the
beginning of the modern starter. Experience demonstrated that the
addition of these already fermented liquids exercised a desirable
effect upon the production of butter flavor, even though, at that
time, the phenomenon of milk fermentation was not satisfactorily
understood, and the relation of bacterial by-products to the
production of flavor in butter was not recognized.

As a result of experience alone, improvements in the development of
the "home made" starter took place. By careful selection of clean
milk, and the natural fermentation of this under carefully
controlled conditions, as well as the control of the temperature of
the cream during the ripening, improvement in the technique of cream
ripening gradually developed. More and more attention was given to
the preparation of the starter, and its propagation from day to day,
under conditions which would prevent its deterioration. This method
of utilizing naturally fermented milk or cream was gradually
extended, until it became almost universal in the larger
butter-producing districts.

In 1890 a more refined and scientific process was introduced by the
Danish bacteriologist, Storch. Recognizing the fact that butter
flavor was attributable to the development of the bacteria present
in the ripening cream, he conceived the idea of isolating the
various types of organisms found in milk and testing them as to
their effect on the quality of flavor. Selection was then made of
the most favorable flavor-producing types, and these were propagat