CREAM RAISED BY GRAVITY PROCESSES. 175 



milk originated on particularly well-conducted farms, 

 where the housewife herself took care of the milk. By 

 accident I learned of one of these farms that it had the 

 reputation of making first-class, well-keeping butter. A 

 separation and ripening of the cream according to this 

 method can therefore be well conducted and give good 

 results. 



Having studied the conditions of this method of cream- 

 raising, and learned how bacteria generally appear in the 

 cream, we shall briefly consider its keeping quality. From 

 the point alone just mentioned, that such cream is gener- 

 ally mixed with a great number of non-lactic-acid-produc- 

 ing bacteria, we may conclude that usually it will not 

 keep long; but we have seen that under favorable condi- 

 tions cream may also be obtained by this method which 

 will contain practically pure cultures of lactic-acid bac- 

 teria. How this exceptional condition may become the 

 rule, or at least more general, will be shown in a later 

 chapter. From the description given it will be seen that 

 it has its good points, and that the method hardly deserves 

 the scorn shown it by writers and speakers on dairy topics. 



b. The Modern Systems of Gravity Creaming. In the 

 more modern creaming methods neither cream nor skim- 

 milk undergoes any appreciable change during the cream- 

 ing. The principle both in these methods (the Holstein, 

 Gussander, Swartz, and Cooley methods), as well as in the 

 separator and extractor methods, to be considered in the 

 next chapter, is, that the fermentation bacteria are not al- 

 lowed to develop to any appreciable extent, either before 

 or during the rising and separation of the cream. 



Two objects have constantly been kept in view in the 

 older of these methods: to favor the rising of the cream, 



