420 Bacteria in Relation to Country Life 



ferent intervals for a period of nine months, the normal 

 cheese showed a fairly small variation in the content of 

 albumoses and peptones and a gradual and constant 

 increase of amides and of ammonia. On the other hand, 

 the chloroform cheese showed a much larger accumu- 

 lation of albumoses and peptones, a much smaller ac- 

 cumulation of amides and no accumulation at all of 

 ammonia. It would seem, thus, that the pepsin and 

 galactasa are incapable of carrying the ripening process 

 to completion and that the normal changes in cheese are 

 dependent on still another factor or factors. 



Bacteriological studies of cheese by different investi- 

 gators, at different times, agree in showing that the 

 bacteria multiply rapidly in freshly prepared cheese. 

 In the hard varieties, the increase may continue for a 

 month or for a few days, depending largely on the tem- 

 perature at which the cheese is kept. The organisms 

 consist almost entirely of the lactic acid species, for 

 the other bacteria, initially present, do not seem to be 

 able to maintain their ground and are rapidly crowded 

 out. In experiments in which large numbers of pep- 

 tonizing bacteria were purposely introduced, their 

 disappearance was fully as marked. Evidently, then, 

 organisms, other than the lactic-acid species, do not 

 play, numerically, a significant part in the ripening of 

 cheese. 



Since the lactic-acid bacteria constitute nearly the 

 entire flora of fresh cheese, and since, furthermore, 

 normal ripening of hard cheese does not occur when they 

 are excluded, the thought naturally suggests itself that 

 these organisms are intimately concerned with the ripen- 



