174 MODERN DAIRY PRACTICE. 



to be observed in this connection. Bacterial infections 

 are first of all, as a rule, more numerous in cream which 

 has soured on the milk than in that prepared according 

 to modern methods. Their number will vary greatly. In 

 examining cream from the same milk obtained by the dif- 

 ferent methods the shallow-setting cream has usually 

 been found richest in bacteria not producing lactic acid, 

 although this was by no means always the case. A very 

 small number of such bacteria were found in the cream if 

 the milk had been strongly infected with lactic- acid bac- 

 teria. The quality of the cream was then as good, from a 

 bacteriological point of view, as if it had been prepared 

 according to the ice method, and often better. The ex- 

 planation is doubtless to be found in the fact that the 

 early-appearing mass-infection (see p. 93) of lactic-acid 

 bacteria hindered the growth of other bacteria. In this 

 way the ripening took place rapidly and at the same time 

 as the raising of the cream, so that if the infection took 

 place at the proper time the cream was sufficiently sour 

 and coagulated just at the end of the separation. 



Another point to be noticed is that yeast-fungi taking 

 part in the starting of the lactic-acid fermentation have 

 been found only in the cream and sour milk from small 

 farm-dairies. I have found such yeasts in " stringy " milk 

 from Borgaa and in buttermilk from Savolaks and 

 Karelen. 



Very different kinds of lactic-acid bacteria may appear 

 at the same time in the sour milk and cream on neighbor- 

 ing farms. A fact which will be further considered when 

 the question of cream-ripening comes up is that in some 

 farm-dairies I have met with buttermilk containing prac- 

 tically only lactic-acid bacteria. These samples of butter- 



