CHAPTER VIII 



MORPHOLOGIC VARIATIONS OF THE 

 CHOLERA VIBRIO 



The organism of cholera has long been a favorite for studies 

 of pleomorphism. Many bacteriologists, among them both pleomor- 

 phists and monomorphists, have found that this organism is more 

 prone to morphologic variation than many other forms; that cul- 

 tures of the same origin on different media, and cultures of different 

 origin on the same media, which may be identical in other characters, 

 may be widely different in the form of their cells. Short and long 

 rods, "comma" forms, spiral filaments, large and small spherical 

 cells, as well as budding and branching, bulging and irregular cell 

 forms, have all been described over and over again. Most of these 

 observations have been made on unusual media, though even in 

 cultures on standard beef extract agar considerable variation is en- 

 countered. These variants from the typical vibrio form have been 

 looked upon by some authors as involution forms, that is cells which 

 have suffered an injury or are dead; by others, as unusual repro- 

 ductive cells (for example, gametocytes by Almquist and Enderl.ein) ; 

 and by still others simply as the result of the action of physical or 

 chemical forces, particularly osmotic pressure, on the cells, implying 

 neither necessarily an injury nor a change in the mode of reproduc- 

 tion (for example, as plasmoptysis by A. Fischer). For complete 

 literature on the subject, the reader is referred to Lohnis' monograph 

 on "Life Cycles of Bacteria." 



It was thought desirable, therefore, to extend these quantitative 

 studies to include this organism, and particularly to see if something 

 could be accomplished in the way of applying statistical methods 

 to variations in the form of the cells rather than their size. It will 

 be remembered that with the colon bacillus it was found that the 

 variations in form could be fairly readily expressed by the area- 

 length index (the area of the projected image divided by the length 

 squared), this measure serving to classify the cells into long fila- 



117 



