MORPHOLOGY 59 



EXERCISE XVII 



THE MORPHOLOGY OF BACTERIUM AND SPIRILLUM 



88. Work for this exercise. Examine very carefully and 

 describe fully the cultures of the Bacterium and of the Spiril- 

 lum made in the last exercise. 



Make and examine, microscopically, hanging-drop and 

 stained cover-glass preparations from each of the cultures. 

 Describe the appearance of the individual bacteria in each. 



Make a drawing magnified 1000 diameters of a few indi- 

 viduals from each of the stained preparations from the agar 

 cultures. 



State fully the morphology of these two genera and mention 

 the differential characters between the genera Bacillus and 

 Bacterium. 



Inoculate a tube of agar with B. cholera suis or JB. typhosus 

 for flagella staining in Exercise XIX. 



89. Making drawings of bacteria with a definite magnifica- 

 tion. In measuring the bacteria we obtain the dimensions in 

 microns or in units of i/iooo of a millimeter. In making a 

 drawing, therefore, showing them magnified 1000 diameters, 

 it is simply necessary to represent each micron by i millimeter. 

 Thus, if the organism is 2.5 /x, in length and i /A broad, the 

 drawing should be 2.5 mm. long and i mm. broad. If the 

 drawing is to represent the organism magnified 500 diameters, 

 then each micron should be represented by 0.5 mm. For this 

 purpose a metric rule and a pair of dividers are necessary. 



