64 ESSENTIALS OF BACTERIOLOGY. 



This method is very useful for transportation ; the saucers 

 can be viewed under microscope similar to the glass plates, and 

 have almost entirely superseded them. 



Esmarch's Tubes, or Rolled Cultures. This method, especially 

 used in the culture of anaerobic germs, consists in spreading the 

 inoculated gelatine upon the inner walls of the test tube in 

 which it is contained and allowing it to congeal. The colonies 

 then develop upon the sides of the tube without the aid of 

 other apparatus. The method is useful whenever a very quick 

 and easy way is required. The rolling of the tube is done under 

 ice-water or running water from the faucet. The tube is held 

 a little slanting, so as to avoid getting too much gelatine around 

 the cotton plug. 



The tubes can be placed directly under the microscope for 

 further examination of the colonies. 



It is almost impossible to separate certain organisms, such as 

 the tubercle bacillus and pneumococcus, from mixed cultures 

 by ordinary plate methods, and the plan of producing the dis- 

 ease in animals by inoculation, and then obtaining the organ- 

 ism in pure culture, has to be employed. 



Spored organisms may also be separated from others by boil- 

 ing the mixture for a few minutes, when all the non-spored 

 forms will perish, and only the spores remain to germinate 

 subsequently. 



CHAPTER XL 



THE GROWTH AND APPEARANCES OF COLONIES. 



Macroscopic. Depending greatly upon the temperature of 

 the room, which should be about 65 C., the colonies develop 

 so as to be visible to the naked eye in two to four days. Some 

 require ten to fourteen days, and others grow rapidly, covering 

 the third dilution in thirty-six hours. The plate should be 

 looked at each day. 



The colonies present various appearances, from that of a 

 small dot, like a fly-speck, to that resembling a small leaf. 



