EXAMINATION OF MILK 159 



1:1,000; of the pasteurized milk 1:10 and 1:100, and 

 of the certified milk 1:10. 



3. Inoculate a series of 10 litmus milk tubes with 

 I c.c. each of the raw milk, a series of 10 milk tubes 

 with I c.c. each of the dilution i : 10, and the same with 

 the other dilutions and the other milks. 



4. Heat these tubes in a water bath to 80° C. for 

 15 minutes. 



5. Incubate anaerobically for 48 hours at 37° C. 



6. Anaerobes will give evidence of their presence 

 by the breaking-up of the curd formed, and by violent 

 evolution of gas. The number may be determined 

 according to the formula given on p. 86 by substitut- 

 ing the number of milk tubes with growth for the 

 letter N in the formula. 



SECTION 8 



A STUDY OF SOME ORGANISMS CAUSING ABNORMAL 

 FERMENTATIONS IN MILK 



1. Place about 50 c.c. certified milk in each of 5 

 Erlenmeyer flasks. 



2. Sterilize these flasks in the autoclave for 5 

 minutes. 



3. Inoculate these flasks with laboratory cultures of 

 B. prodigiosus, B. cyanogenes, B. viscosus, Sarcina 

 lutea, and Torula amara. 



4. Allow these to remain in the locker or in an 

 incubator at 20° C. for three days; examine the con- 

 ditions as to color and consistency. 



