26 GENERAL BACTERIOLOGY 



except the gelatin. Keep these in the cool chamber. After growth 

 has taken place, the cultures can be taken from the incubator and 

 kept at the room temperature. 



t. Study and make diagrams of an incubator, a Reichert thermo- 

 regulator, a Eoux thermo-regulator and Koch's safety burner. 



EXERCISE 15. STUDY OF TEST-TUBE CULTURES. 



Geneeal Directions. As soon as growth becomes visible a sys- 

 tematic and careful study of the cultures should be made. A de- 

 tailed list of the points to be noted will be found in Chapter III, 

 and should be consulted in writing up the descriptions. The sum- 

 mary below will, however, be found useful. 



For bouillon cultures note : 1 ) condition of fluid, 2 ) character 

 of sediment, 3) presence or absence of membrane, and 4) charac- 

 teristic odor. 



For solid culti^res (agar and potato slopes), note: 1) Form of 

 growth, 2) size, 3) surface elevation, 4) consistency, 5) color, 6) 

 effect on media, and 7) characteristic odor. 



For gelatin stab cultures, note : 1 ) Effect on media, a. non-lique- 

 fying, i) line of puncture, ii) surface, 5. liquefying, i) shape of 

 liquefied area, ii) condition of fluid, iii) character of sediment, 2) 

 characteristic odor. 



The study should be continued from day to day as long as 

 changes are noted. Make drawings wherever they will be of 

 service in elucidating the descriptions. 



Special Directions. Study, write careful descriptions and 

 make necessary drawings of all the cultures made. For recording 

 results use the table on pages 25 and 27. 



EXERCISE 16. CLEANING SLIDES AND COVER GLASSES. 



General Directions. Slides can be sufficiently cleaned by 

 washing in water or alcohol and drying with a towel. The cover- 

 glasses for bacteriological work, however, must not only be freed 

 from visible dirt but must be rendered free from fat. One of the 

 best methods is the following: New cover-glasses are cleaned by 

 washing in water and drying from alcohol by rubbing them between 

 driers (two wooden blocks 20x10x2^^ mm. covered with several 

 layers of cotton cloth or chamois skin), and then heating them on 



