152 NATURAL SCIENCE [March 



ance of a paper by Messrs S. M. Babcock and H. L. Russell, in the 

 fourteenth Annual Be/port of the Wisconsin Agricultural Experiment 

 Station (Dec. 1897). The ripening of cheese is usually supposed 

 to be due to the action of bacteria present in the milk from which 

 the cheese is made. The green or unripe cheese is hard, elastic, and 

 insoluble, being opaque in thin sections. As it ripens it becomes 

 softer, more soluble and translucent, while its nutritious constituents 

 are rendered more soluble and therefore more readily digestible. 

 The decomposition of the proteids produces in the mature cheese 

 albumens, albumoses, peptones, amido products (tyrosin, leucin) and 

 ammonia. The ascription of these changes to bacteria is supported 

 by the great development of lactic acid bacteria in hard cheeses,, 

 while the experimental elimination of those organisms has seemed 

 to contirm the idea that they were closely connected with the ripen- 

 ing. The American authors, however, have been investigating the 

 enzymes or unorganized ferments of milk, and conclude that these 

 alone are sufficient to produce a series of decomposition-change.^ 

 similar to those found in ripening cheese, even when all bacterial 

 ferments have been carefully excluded. The changes that occur 

 were proved to be of a non- vital character and undoubtedly due to 

 enzymes. These enzymes, however, may themselves have been pro- 

 duced by bacteria originally present in the milk, or they may be 

 inherent in the milk itself. That the latter is the case was shown 

 by securing milk drawn from the cow with great care, and treated 

 immediately with antiseptics ; for this freshly secured milk under- 

 went identical changes. It was found possible to separate enzymes 

 having a curdling action on the milk, as well as those witli digestive 

 functions. It is therefore the belief of the authors that the ripening 

 of hard cheese under normal conditions is caused by the joint action 

 of organised ferments (bacteria) and unorganised ferments (enzymes). 

 The breaking down of the casein is due rather to the enzymes than 

 to the lactic acid bacteria. 



After Mr Wells' magnificent testimonial, quoted above, this is 

 rather a come-down for the bacteria. At the same time, it does not 

 seem probable that the lovers of Gorgonzola, Camembert and Stilton, 

 least of all " Limburger kase," will be anxious to purchase their 

 cheese sterilised ; for our authors still consider that in the production 

 of the characteristic flavours bacteria plays a somewhat important 

 part. 



Sleep Movements 



The sleep movements of the leaves of certain plants noticed by 

 Linnaeus form one of the many subjects of investigation by Charles 

 Darwin, who gave an account oi his interesting experiments and 

 observations in his book on the " Movements of Plants." If we com- 



