l82 LABORATORY GUIDE IN BACTERIOLOGY 



and insert two glass tubes through the holes. The 

 tubes should reach to the bottom of the cask (see 

 Fig- SS)- The open ends of both tubes should be 

 plugged with cotton and have a constriction below the 

 cotton, to prevent it from slipping down. One of the 

 tubes is connected with the air valve of an autoclave 

 and steam passed through the wort for 30 minutes. - The 

 process is repeated on the two following days. Sterile 

 wort may be obtained from the cask by blowing through 

 the tube e and collecting from the bent tube, which, 

 when not in use, should be protected from contamina- 

 tion by a sterile test tube with a cotton plug. 



SECTION 2 



A STUDY OF MOLDS 



EXERCISE I. COLLECTING MOLDS FROM THE AIR 



1. Expose two plates of wort agar and two of meat 

 extract agar to the air in different places. 



2. Incubate at 37° C. 



3. After molds have appeared transfer three different 

 colonies to slanted wort agar. Transfers are made by 

 touching the ends of the hyphae with a platinum needle 

 and streaking on the slanted surface of a tube of wort 

 agar. 



4. After full development transfer some of the spores 

 to liquid wort or broth. This is done by touching the 

 ends of the filaments with a platinum needle. 



5. Examine a large loopful of this spore suspension 

 under the microscope, using a low magnification. 



