BACTERIA. 75 



On the other hand, several species of bacteria have been 

 discovered in recent years, which cause diseases in rnilk and 

 butter. Thus SCHMIDT -MUELHEIM found a micrococcus which 

 occurs in the form of intertwined chains, and causes the milk to 

 turn viscous ; another species, discovered by EATZ, possesses the 

 same property and also produces a vigorous lactic acid fermenta- 

 tion ; other slime-forming species have been described by 

 ADAMETZ, DUCLAUX (Actinobacter), LOEFFLER, GUILLEBEAU, 

 STORCH, and LEICHMANN. WEIGMANN isolated a species which 

 imparts a bitter taste to milk and secretes a ferment which 

 dissolves caseine. JENSEN likewise found several species 

 which cause marked abnormalities in the taste of milk and 

 butter, among them especially Bacillus fatidus lactis, having 

 the form of thick, moving rods, of varying length, some 

 almost like micrococci. STORCH proved that the disagreeable 

 taste of tallow sometimes noticeable in butter is caused by 

 a certain species of bacterium, which acidifies and coagulates 

 milk. 



The " breaking " of milk in the cheese factory, in which 

 process the caseine is precipitated, is effected in practice by 

 means of rennet, an enzyme secreted by certain glands in 

 the stomach of different animals. The same enzyme occurs in 

 a few plants, as for example Pinguicula, Ficus carica, and 

 has recently been discovered in several bacteria. Thus CONN 

 (1892) isolated such bacteria in pure cultures. Especially 

 among the so-called "potato bacilli," bacteria of this class 

 occur. Their enzyme, however, differs in certain respects from 

 that of rennet. Also the renowned Micrococcns prodigiosus and 

 the Bacterium coli commune contain the same enzyme. 



The bacteria and other fungi active in the ripening of 

 cheese were studied by ADAMETZ, DUCLAUX, FREUDENREICH, 

 WEIGMANN, and others. Many of these bacteria, which in 

 part exercise a peptonising action on caseine, can, when 

 occurring in large numbers, impart a definite character to 

 the ripening process, giving rise to aromatic substances which 

 determine the sort of cheese produced. 



