186 GENERAL MICROBIOLOGY 



filter each culture through absorbent cotton (a small piece 

 in small funnel); 15 c.c. of each filtrate is necessary. 



9. Mix the filtrate from each culture with phenol milk 

 in the following proportions : 



1 0.5 c.c. filtrate +9. 5 c.c. phenol milk. 



2. . 1.0 c.c. filtrate+9.0 c.c. phenol milk. 



3 2.0 c.c. filtrate+8.0 c.c. phenol milk. 



4 3.0 c.c. filtrate+7.0 c.c. phenol milk. 



5 4.0 c.c. filtrate+6.0 c.c. phenol milk. 



6 Heat 4 c.c. of filtrate only, in steam 



for fifteen minutes. After cooling, add 6 c.c. phenol milk. 

 Shake these mixtures well and incubate at 37 C. 



10. Record the time necessary for coagulation in each 

 case. Why do not all tubes change alike? Explain. 



11. Can corrosive sublimate be used to replace phenol 

 in this experiment? Explain. 



What types of enzymes are concerned in these changes? 



Are these intra- or extra-cellular in each case? Will the 

 place of occurrence of the enzymes explain the action taking 

 place in the different sets of tubes? 



What enzymes produce each type of curd? 



What are the differences between an acid and a rennet 

 curd? , 



Which type is produced by each of the organisms used? 



What effect has heat upon enzymes? 



12. Give results in full and draw any conclusions per- 

 mitted. Point out any practical applications of the above. 



REFERENCES 



LAFAR: Technical Mycology, Vol. I, pp. 184-187. 



BAYLISS: Nature of Enzymic Action, p. 37. 



EULER: General Chemistry of the Enzymes, pp. 45-48, 58. 



MARSHALL: Microbiology, pp. 139-141. 



VERNON: Intracellular Enzymes, pp. 220-221. 



COHNHEIM: Enzymes, pp. 29, 87-89, 



