ix] CHEESE 153 



gases, consisting of carbonic acid, hydrogen, and 

 sulphuretted hydrogen. Indeed, the production of 

 gas often gives rise to a not uncommonly occurring 

 " fault " in cheeses, viz. an inflated or puffy condi- 

 tion. This is often caused by premature ripening of 

 the cheese; but the presence of pores in certain 

 kinds of cheese, amounting sometimes to the size of 

 little cavities, is a desirable property. One investi- 

 gator, who has carried out researches on the swelling 

 of cheese, has come to the conclusion that the forma- 

 tion of holes or pores in hard cheese is due simply to 

 the action of a single bacillus, the bacillus diatrypeti- 

 cus casei. Indeed, the general process of cheese- 

 ripening seems to be similar in its nature to the 

 process of digestion by the various digestive fluids 

 of the stomach and alimentary canal. It may be 

 added that the percentage of water in the ripening 

 process becomes distinctly less. A fact of consider- 

 able interest, and one which has an important practi- 

 cal bearing, is the inimical influence which light 

 has on the development of the ripening bacteria. 



Cheese-Faults. While the proper ripening of 

 cheese is thus undoubtedly due to the action of bac- 

 terial life, so also are most of the faults which 

 cheeses are liable to. Among these faults may be 

 mentioned fungoid growths on the surface of the 

 cheese, red, blue, or yellow in colour, sometimes 

 leading to the total discoloration of the cheese, as 



