THE CULTIVATION OF ANAEROBIC BACTERIA. 75 



into plates after inoculation, Esmarch rolls these tubes in a 

 vertical position until the gelatin is completely solid. This is 

 hastened by rolling the tubes as shown in Fig. 33. By this 

 excellent method there is less likelihood of contamination 

 than by the plate method. 



5. Gelatin and especially agar plates are occasionally made 

 in a different way. The liquid medium is poured on glass 

 plates and allowed to solidify before inoculation. When well 

 hardened the surface is streaked with the inoculating material 



FIG. 33. 



Demonstrating Booker's method of rolling Esmarch tubes on a block of ice. 



on a platinum needle. In this way the colonies grow along 

 the streak much more superficially than they do in the ordi- 

 nary plate method. 



6. Agar and blood-serum slant cultures are made in the same 

 manner as similar cultures on gelatin. They have one 

 advantage over the gelatin culture by reason of being able to 

 withstand the temperature of the incubator, 37 C. 



THE CULTIVATION OF ANAEROBIC BACTERIA. 



Exclusion of oxygen is absolutely necessary. For this pur- 

 pose a number of methods have been suggested and used, 

 some of which require special and elaborate apparatus. All 



