LESSON iv SEPARATION OF TYPHOID BACILLUS 



99 



u candle " of the filter, so as to get as many as possible of 

 the bacteria from the surface of the candle into the beaker. 



(5) The water in the beaker will 

 now be muddy in appearance and 

 contain most of the micro-organisms 

 retained by the filter. 



(6) Plug the beaker with cotton- 

 wool. 



(7) Now melt several carbolic 

 acid gelatine tubes, and to each add, 

 with a sterile pipette, -1 to *25 cc. of 

 the water containing the bacteria 

 scraped off the filter. 



(8) Pour plates in the usual 

 manner, and place them in the cool 

 incubator. 



The growth of large numbers 

 of micro-organisms, especially of 

 the liquefying ones, will be inhibited by the carbolic acid 

 contained in the gelatine. 



(9) When colonies have appeared, make subcultures of 

 those in any way resembling the bacillus of typhoid fever 

 or the Bacterium coli commune : 



(a) gelatine streak cultures ; 



(b) gelatine shake cultures ; 



(c) 25 per cent gelatine stab cultures. 



Place a (a) and (b) in the cool incubator, and (c) in the 



Fia. 5. 



