378 



SCIENCE 



[N. S. Vol. XXXVIII. No. 976 



counts comparing in a general way with tliose 

 obtained by dilution in mUk. Numerous examina- 

 tions were made of various cheeses and three 

 domestic cheeses of the Emmenthal type were fol- 

 lowed through a nearly complete ripening period. 

 About 1,000 cultures isolated from these cheeses 

 were studied in detail, particularly in relation to 

 their fermentative abilities. It was observed that 

 many of these cultures gave considerable quanti- 

 ties of gas in a sugar-free concentrated whey. 

 It was not possible, however, to separate these 

 cultures beyond three morphological groups, one 

 of which was a long rod, one a short rod and the 

 third a coccus. At the beginning of the ripening 

 the bacterial flora consisted almost entirely of the 

 short rods. The long rods appeared in the early 

 stages of the ripening and increased steadily. 

 The short rods decreased and in each of the three 

 cheeses made up about 50 per cent, of the bacteria 

 at seven or eight weeks, a period corresponding in 

 a general way with the end of the eye formation. 

 Glycerine fermenting cocci appeared in small num- 

 bers in each of the cheeses at an age of five or six 

 weelss. At the end of twenty weeks the bacterial 

 flora was composed almost exclusively of the long 

 rods. The essential bacteria of Emmenthal cheese 

 are evidently not ubiquitous. In two widely sepa- 

 rated localities cheeses made without inoculation 

 have invariably failed to give the normal fer- 

 mentation. Cheese made from milk inoculated 

 with a mixture of a large number of pure cultures, 

 .ir from special culture media inoculated with good 

 cheese, have given uniformly a normal ripening. 

 Action of a Few Common Butter Organisms upon 

 Casein: Chakles W. Brown, Michigan Agricul- 

 tural College, East Lansing, Mich. 

 The action of microorganisms upon proteins is 

 looked upon as an aid in identification. If there 

 is an action visible to the sense of sight, liquefac- 

 tion by that organism is said to be positive, other- 

 wise it is negative. For example, if an organism 

 growing in milk at room temperature for fifteen 

 to thirty days shows no visible digestion, that 

 organism is said to have no action upon casein. 

 This is a mere supposition and in many cases is 

 incorrect. For milk in which such an organism 

 has been growing for several days, if treated with 

 precipitants to remove the unchanged casein, will 

 be found to contain degradation products such as 

 caseoses and peptones. Especially is this true in 

 old milk cultures where the cells of the organisms 

 have died and undergone autolysis, thus liberating 

 an endo-proteolytic enzyme. The power to liquefy 



casein by liquefiers is either stimulated or retarded 

 to a greater or less degree by four important fac- 

 tors met with in storage butter — addition of salt, 

 diminished supply of free oxygen, low temperature 

 and association with Bad. lactis acidi. Now, if 

 we center our observation upon a number of bac- 

 teria, found frequently in samples of storage but- 

 ter, which have no visible action — other than a 

 slight change — upon milk in tubes, within thirty 

 days and make litmus milk agar plates thickly 

 seeded with the organism under observation, we 

 will observe several different pictures presenting 

 themselves. (1) Some of the organisms produce a 

 gradual clearing, noticeable after seven to fifteen 

 days, due to a slow digestion of the casein. (2) 

 If after incubating twenty-four hours at 20° C. 

 the plates are inoculated with Bact. lactis acidi 

 by making a stroke on the surface, we see in the 

 case of some of the organisms a rather abundant 

 growth of the lactic with acid production, curdling 

 of the milk in immediate vicinity of the lactic, 

 surrounded by a clear zone and, surrounding the 

 clear zone, a more copious growth of the organ- 

 ism. (3) The same picture with the exception 

 that the growth of the organism is not stimulated. 

 (4) Growth of the lactic about normal, no acidity, 

 the milk in the immediate vicinity of the lactic 

 completely dissolved and surrounded by a more 

 copious growth of the organism. (5) The same 

 except no stimulated growth of the organism. 



(6) Growth of lactic normal, no acidity, no clear- 

 ing, but a stimulated growth of the organism. 



(7) The same except the growth of the organism 

 is not stimulated. (8) Retarded or prevented 

 growth of lactic, no acidity, no digestion aiid no 

 stimulated growth. A different picture may pre- 

 sent itself, if the litmus milk agar plate of the 

 organism is incubated for three to five days before 

 stroking the surface with the lactic, in that the 

 growth of the lactic may be inhibited and that no 

 digestion may occur. Again, if the supply of free 

 oxygen is diminished both before and after stro- 

 king the surface with lactic, or if salt is added, 

 or if a lower temperature is used for incubation, 

 different results will be obtained. These organ- 

 isms, generally spoken of as non-liquefiers, influ- 

 enced in their action upon casein by different 

 factors can not be overlooked as agents in the 

 degradation of casein in both storage butter and 

 ripening cheese. 



A. Parker Hitchens, 



Secretai-y 

 (To he continued) 



