308 PRACTICAL DAIRY BACTERIOLOGY 



ber of bacteria in cheese exactly as above described for butter 

 (see experiment 62), making inoculation into litmus gelatin 

 plates, and determine the varieties of bacteria present. Make 

 a series of plates in this way from a freshly made cheese and 

 another series from some cheese ripened and ready for market. 

 Compare the numbers and kinds of bacteria. 



No. 71. Determination of Bacteria in Rennet. Dilute a small 

 quantity of the rennet in a water blank and inoculate litmus 

 gelatin plates. Incubate as usual, and examine at the end of 

 two days. This experiment may be performed by the use of 

 agar incubated at 98. 



No. 72. The Effect of Gassy Organism on Cheese. Inoculate 

 a small quantity of milk with a starter made from a gassy 

 organism (see page 287). After a few hours add rennet to the 

 milk till curdled, and proceed in the usual way to make the curd 

 into two cheeses. Leave one cheese for a few days in a moder- 

 ately warm room, and notice the swelling due to the formation 

 of the gas bubbles. Place the second cheese in a cool room with 

 a temperature below 60, if possible. Compare the formation 

 of the gas bubbles in the two cheeses. 



No. 73. Isolation of Molds from the Cheese. Obtain from the 

 market a Camembert or Brie cheese. Pour into a Petri dish 

 some litmus gelatin and allow to harden. With a platinum 

 needle scrape off a bit from the surface of the cheese where it 

 shows signs of mold, and inoculate it upon the gelatin by touch- 

 ing the surface with the needle in several places. Cover the 

 dish as usual, and place at 70 for incubation. At the end of 

 two or three days colonies of molds will be found growing on 

 the surface of the plate. 



Proceed as above described to obtain the mold of the ripened 

 Roquefort cheese. The method of this procedure is the same, 

 except that for inoculating the plate, the platinum needle should 

 be dipped into some of the blue spots, which show in the middle 

 of the Roquefort cheese. 



