176 LABORATORY GUIDE IN BACTERIOLOGY 



2. Crush between two slides a small tubercle and a 

 large one. 



3. Make mounted preparations and examine them 

 under the microscope. 



Experiment 2 — 



1. Wash a number of tubercles in distilled water, 

 then soak in mercuric chlorid solution 1:1,000 to 

 sterilize the exterior of the tubercles. 



2. Wash again in several changes of sterilized 

 distilled water. 



3. Crush in a sterile petri dish. 



4. Plate in agar, prepared as.described on p. 38. 



5. Incubate at room temperature. 



6. After growth has appeared transfer to all ordinary 

 laboratory media. 



7. Study characteristics in the usual manner. 



EXERCISE 2. BY ORGANISMS OTHER THAN LEGUME 

 BACTERIA 



Experiment i — 



1. Prepare 5 flasks and place 50 c.c. of the solution 

 on p. 39 in each flask. 



2. Sterilize in the autoclave. 



3. After growth has appeared inoculate a second 

 flask from the first, from the second to the third, etc. 



4. Determine the gain in nitrogen by the Kjeldahl 

 method. This determination should be repeated at 

 regular intervals to determine the progress of nitrogen 

 assimilation. 



Experiment 2. — ^These organisms may be obtained 

 in pure culture by plating in agar or silica jelly media. 



