52 



tures of anaerobic bacillus furnished. (B. ) after 



which cool the medium rapidly until it is set. In inocula- 

 ting the tube insert the loop nearly to the bottom and stir 

 very gently. In making the inoculations care must be taken 

 not to introduce air by shaking the liquid medium. Place 

 the culture in the incubator. 



§ 80. The fermentation tubes for anaerobic bacteria. 

 If these tubes of bouillon have been properly sterilized the 

 closed branch is practically free from atmosphere. The ob- 

 ligatory anaerobe will grow in the closed branch only, while 

 the facultative anaerobe will grow in both the open and closed 

 parts. If the organism is a gas producer, the gas will force 

 the cloudy liquid from the closed bulb into the open one 

 clouding the otherwise clear liquid. To avoid the possi- 

 bility of error in interpreting these growths it is well to in- 

 oculate a tube containing sugar free bouillon in which case 

 the liquid in the open bulb should remain clear as gas will 

 not be formed. 



These tubes are of equal value in testing obligatory and 

 facultative anaerobic organisms. 



EXERCISE XXI. 



EXAMINATION OF ANAEROBIC CULTURES. 



§81. General directions. Examine and carefully de- 

 scribe the appearance of the anaerobic cultures made in Ex- 

 ercise XX. 



With the wire loop remove one of the colonies from the 

 depth of the agar culture and examine it microscopically in 

 (a) a hanging-drop preparation, and (b) a stained cover- 

 glass preparation. Stain with carbol fuchsin. Examine 

 microscopically in similar preparations the bacteria from one 

 of the fermentation tubes. Describe the appearance of the 



