The cheese maker finds in the ripening of his cheese the most difficult part of his manufacture. It is indeed a process over which he has very little control. Even when all conditions seem to be correct, when cheese is made in the most careful manner, it not infrequently occurs that the ripening takes place in a manner that is entirely abnormal, and the resulting cheese becomes worthless. The cheese maker has been at an entire loss to understand these irregularities, nor has he possessed any means of removing them. The abnormal ripening that occurs takes on various types. Sometimes the cheese will become extraordinarily porous, filled with large holes which cause the cheese to swell out of proper shape and become worthless. At other times various spots of red or blue appear in the manufactured cheese; while again unpleasant tastes and flavours develop which render the product of no value. Sometimes a considerable portion of the product of the cheese factory undergoes such irregular ripening, and the product for a long time will thus be worthless. If some means could be discovered of removing these irregularities it would be a great boon to the cheese manufacturer; and very many attempts have been made in one way or another to furnish the cheese maker with some details in the manufacture which will enable him in a measure to control the ripening. The ripening of the cheese has been subjected to a large amount of study on the part of bacteriologists who have been interested in dairy products. That the ripening of cheese is the result of bacterial growth therein appears to be probable from a priori grounds. Like the ripening of cream, it is a process that occurs somewhat slowly. It is a chemical change which is accompanied by the destruction of proteid matter; it takes place best at certain temperatures, and temperatures which we know are favourable to the growth of micro-organisms, all of which phenomena suggest to us the action of bacteria. Moreover, the flavours and the tastes that arise have a decided resemblance in many cases to the decomposition products of bacteria, strikingly so in Limburger cheese. When we come to study the matter of cheese ripening carefully we learn beyond question that this a priori conclusion is correct. The ripening of any cheese is dependent upon several different factors. The method of preparation, the amount of water left in the curd, the temperature of ripening, and other miscellaneous factors connected with the mechanical process of cheese manufacture, affect its character. But, in addition to all these factors, there is undoubtedly another one, and that is the number and the character of the bacteria that chance to be in the curd when the cheese is made. While it is found that cheeses which are treated by different processes will ripen in a different manner, it is also found that two cheeses which have been made under similar conditions and treated in identically the same way