90 THE STORY OF GERM LIFE. 



the lack of oxygen furnish conditions in which 

 bacteria will not grow very rapidly. The condi- 

 tions are far less favourable than those of ripen- 

 ing cream, and the bacteria do not grow with 

 anything like the rapidity that they grow in 

 cream. Indeed, the growth of these organisms 

 during the ripening is extremely slow compared 

 to the possibilities of bacterial growth that we 

 have already noticed. Nevertheless, the bacteria 

 do multiply in the cheese, and as the ripening 

 goes on they become more and more abundant, 

 although the number fluctuates, rising and falling 

 under different conditions. 



When the attempt is made to determine the 

 relation of the different kinds of ripening to dif- 

 ferent kinds of bacteria, it has thus far met with 

 extremely little success. That different flavours 

 are due to the ripening produced by different 

 kinds of bacteria would appear to be almost cer- 

 tain when we remember, as we have already no- 

 ticed, the different kinds of decomposition pro- 

 duced by different species of bacteria. It would 

 seem, moreover, that it ought not to be very diffi- 

 cult to separate from the ripened cheese the bac- 

 teria which are present, and thus obtain the kind 

 of bacteria necessary to produce the desired ripen- 

 ing. But for some reason this does not prove to 

 be so easy in practice as it seems to be in theory. 

 Many different species of bacteria have been sep- 

 arated from cheeses. One bacteriologist, studying 

 several cheeses, separated about eighty different 

 species therefrom, and others have found perhaps 

 as many more from different sources. More- 

 over, experiments have been made with a consid- 

 erable number of these different kinds of bacteria 

 to determine whether they are capable of produc- 



