LESSON ix PUTREFACTIVE ORGANISMS 121 



(2) After three to four days examine these tubes and 

 compare them with the aerobic tubes. 



The odour will generally be more marked. 



(3) Examine the contents of the tubes microscopically, 

 and then prepare roll tubes from them in the ordinary 

 manner, and place them in a flask exhausted of air, which 

 must be kept in the cool incubator. 



(4) Work up the colonies as they appear, and make sub- 

 cultures in grape-sugar gelatine (deep stab cultures). 



(5) Place these in an exhausted flask kept at 22 C. 



Streptococci, Bacillus coli communis, and other bacilli 

 will be found. 



(c) Control experiment. 



(1) From the last or fifth tube, while fresh, prepare 

 three gelatine plates, and also three gelatine roll tubes, in 

 the usual manner. 



(2) Put the plates in the cool incubator, and work up the 

 colonies in the ordinary way. 



(3) Keep the roll tubes in the cool incubator in an 

 exhausted flask, and work up the colonies in exactly the 

 same manner as described above. 



Compare these results with the previous ones. 



(d) Sterilisation and putrefaction. 



(1) Take a little fresh, minced meat, and add small 

 quantities of it to broth tubes. 



(2) Heat these in the autoclave, in order to sterilise their 

 contents. 



