GROUPING. 55 



to the typical rods from which they originated, by the 

 renewal of conditions favorable to their normal vege- 

 tation. 



It must be borne in mind,, though, that it is never 

 possible by any means to bring about changes in these 

 organisms that will result in the permanent conversion 

 of the morphology of the members of one group into 

 that of another that is, one can never produce bacilli 

 from micrococci, nor vice versa; and any evidence which 

 may be presented to the contrary is based upon untrust- 

 worthy methods of experimentation. 



Very short oval bacilli may sometimes be mistaken 



FIG. 5. 



' A i 4 



I 1 /' f 



a. Spirillum of Asiatic cholera (comma bacillus) ; normal appearance 

 in fresh cultures, b. Involution-forms of this organism as seen in old 

 cultures. 



for micrococci, and at times micrococci in the stage of 

 segmentation into diplococci may be mistaken for short 

 bacilli ; but by careful inspection it will always be 

 possible to detect a continuous outline along the sides 

 of the former, and a slight transverse indentation or 

 partition-formation between the segments of the latter. 

 The high index of refraction of spores, the property 

 which gives to them their glistening appearance, will 

 always serve to distinguish them from micrococci. This 

 difference in refraction is especially noticeable if the illu- 

 mination of the microscope be reduced to the smallest 



