388 JAMES M. SHERMAN 



from agar plates made directly from cheese, but success by this 

 method is rare. 



On a number of occasions this organism has been isolated, 

 directly from the cheese, by sealing agar dilutions in glass 

 tubing of about 0.5 cm. diameter. With this method it is very 

 easy to isolate the individual colonies by cutting the tube at 

 the desired points. By steriHzation of the outsides of these 

 tubes by immersion in a strong disinfectant solution, and then 

 rinsing with sterile water, there has been no difficulty in making 

 isolations by this method without contamination. The medium 

 which we have found very satisfactory for this purpose is one 

 consisting of 2 per cent pepton, 1 per cent yeast, 1 per cent 

 lactic acid (as sodium lactate) and 1.5 per cent agar. Although 

 we have had fairly good success in making isolations by this 

 method, it has by no means always proven successful. 



By making enrichment cultures of the cheese in lactate pepton 

 broth, as was done by Von Freudenrich and Orla-Jensen, the 

 isolation of lactate-fermenting bacteria is much easier. We 

 have isolated a variety of organisms belonging to this group 

 from such enrichment cultures. 



Our interest thus far has been more in the practical application 

 of these bacteria in the cheese industry than in making a thorough 

 study of their physiological characteristics. There is little doubt 

 however, that by taking advantage of their known properties, a 

 simple differential method could be developed which would be 

 satisfactory for the direct isolation of this group of organisms 

 from cheese. 



Role in cheese 



For studying the effect of this organism in cheese Vve have 

 had at our disposal a supply of milk, obtained from the experi- 

 mental herd of the Dairy Division, which was entirely lacking 

 in the bacteria necessary for the development of the desired 

 characteristics of Emmental or Swiss cheese. Cheese made 

 from this milk by the Swiss method is always entirely lacking 

 in the characteristic sweetish flavor, and is also frequently 

 "blind." When the natural inoculation in this milk is such as 



