366 CHEESE 



sections of cheese the bacteria in it can be seen in situ 

 and their distribution, development and form at various 

 stages in the ripening can be studied. Heaps or colonies 

 of larger or smaller extent are found distributed irregu- 

 larly throughout the mass, a fact which makes it difficult 

 to obtain concordant quantitative results regarding the 

 number of bacteria present in cheese. The colonies are 

 generally pure, but occasionally two or more kinds may 

 be intimately mixed. In the spaces between these 

 single organisms, small groups or isolated spores are 

 generally seen, but in some cheeses, especially those which 

 have undergone ripening for some time, the spaces are 

 free from living bacteria. 



A very large number of species of bacteria have been 

 isolated from different varieties of cheese. Many of 

 them have been imperfectly described, and a list cannot 

 be given here. They may, however, be classified for 

 convenience into the following groups : 



(i) Organisms which are capable of fermenting 

 milk-sugar with the production of lactic 

 acid without gas formation, e.g. Streptococcus 

 lacticus, Kruse. 



(ii) Those which give rise to lactic acid and con- 

 siderable amounts of free carbon dioxide and 

 hydrogen, e.g. Bs. acidi lactici, Hiippe, and 

 Bact. lactis aerogenes, Esch. 



(iii) Proteolytic bacteria, which digest or decom- 

 pose casein. 



(iv) A group of miscellaneous kinds which appear 



to be without any power of attacking the 



carbohydrate or proteins in cheese, and which 



die out or remain dormant in it. 



Much of the controversy which has arisen in regard 



