9 



to different conditions, such as those already mentioned, and to the influence of 

 the products of bacterial activity upon the living organisms. 



The tables also show that the bacterial content of normal cheese is usually 

 at its highest at the time of taking from the press or durmg the first few 

 days after the cheese are placed in the curing room. In other words, the 

 bacteria in cheese are the survivors of bacteria in the curd. This statement, 

 however, does not always hold good; for we may have cheese in which the 

 acidity has not developed to such an extent as is usually considered desirable; 

 and in such a case there will likely be a period of bacterial development after 

 the cheese is placed in the curing room. It has also been claimed that there 

 is more likely to be bacterial development when the cheese are moister than 

 usual; but, in our investigations, no difference was observed in the quantitative 

 analysis of cheese coming from "moist" and from "ordinary" vats. 



By the experimental data given here, the number of bacteria was shown 

 to be at its maximum when the cheese were taken from the press; and follow- 

 ing this period we had (taking into account the factors leading to error in 

 analysis) a continuous and gradual decline in the bacterial content. This 

 decline continued till about the looth day, when the contents seemed to remain 

 fairly stationary for some time. Following this period, in which the bacterial 

 content remained at a fairly constant level, we had a gradual decline; but in 

 some cheese a year old, from 10,000 to 500,000 lactic acid bacteria were found. 

 The decline was more gradual and the contents remained high for a longer 

 period in the cheese kept in ice cold storage at an average temperature of 40 

 degrees than in cheese kept in an ordinary curing room. This statement, but 

 in a lesser degree, is alscf true of cheese kept in cool or regulated rooms. 

 Without exception, we found a higher bacterial content in the cheese kept in 

 the ice cold storage and in the regulated room,. and also noted that there was 

 better body and flavor in the cheese from these rooms, than in those from the 

 unregulated curing rooms. This factor of higher bacterial content must, there- 

 fore, be one of considerable importance, particularly as regards the flavor of 

 the cheese. The proportion of lactic acid bacteria to undesirable organisms 

 is much greater in cold-storage and cool-storage cheese than is usual under 

 ordinary conditions; and this ratio remains constant for a greater length of 

 time in the refrigerator cheese than in either of the others; and it is obvious 

 that a cheese with the ratio of 97 lactic acid bacteria to one undesirable organ- 

 ism will be of better flavor than a cheese kept in an unregulated curing room 

 with a ratio of 47 lactic acid bacteria to one undesirable one. These ratios are 

 in some of the cases, given in the tables of analysis. 



The lactic acid bacteria are practically the only organisms present in 

 normal cheese, and certainly the only bacteria in each particle of it; so it must 

 be the only microbe of much importance in good cheese. It is true that gas- 

 forming bacteria and other undesirable kinds were found in nearly every cheese 

 we examined; but they were usually present in the samples taken at an early 

 date, and very exceptionally in those of later date. They seldom, if ever, 

 increase in numbers. 



