no Transactions of thk Canadian Institute. [Vol. VII. 



bacteria found at the different stages is thus graphically delineated by 

 the author's diagram. 



The general results are thus summarized : 



1. There is at first a marked falling off in the number of bacteria 

 in green curds for a day or two. (Period of initial decline). 



2. This is followed by a very rapid increase in numbers, in which 

 the bacteria reach scores of millions of organisms per gram. (Period of 

 increase). 



3. This period is followed by a diminution in numbers at first rapid 

 but later more gradual, until the germ content sinks to insignificant 

 proportions. (Period of final decline). 



4. The time necessary to reach the maximum development (second 

 period) is hastened or retarded by such external conditions as tempera- 

 ture, etc. 



5. The second period also marks the beginning of the physical 

 change that occurs in the cheese in the earlier part of the breaking down 

 of the casein. 



6. The bacterial flora of cheese differs markedly from that of milk. 

 In milk, the lactic acid bacteria predominate, but accompanying them 

 are always liquefying or peptonizing organisms, and as a rule bacteria 

 capable of developing gaseous bye-products. 



In the ripening cheese the peptonizing or casein digesting bacteria 

 are quickly eliminated ; the gas producing bacteria disappear more 

 slowly, sometimes persisting in very small numbers for a long time. 



The lactic acid bacteria on the other hand develop enormously for a 

 time until the cheese is partially ripened, when they too begin to 

 diminish in numbers. 



7. The generally accepted theory that the peptonizing or digesting 

 bacteria are able to break down the casein in the cheese as they do in 

 milk is improbable because this type of bacteria fails to increase in the 

 cheese and usually disappears before there is any evidence of physical 

 change in the condition of the casein. The same is true where cheese is 

 made from pasteurised milk to which copious starters of these pe|)toniz- 

 ing organisms have been added. 



8. The coincidence existing in point of time between the gradual 

 ripening of the cheese and the marked development of the lactic acid 



