MORPHOLOGICAL CLASSIFICATION OF BACTERIA. 31 

 FIG. 4. 



\ 



<Cr- 



''' 



d e f 



a. Bacilli in pairs. 6. Single bacilli, c and d. Bacilli in threads, e and /. 



Bacilli of variable morphology. (Abbott.) 



FIG. 5. 



% * 



,^v~ 



^TV/^ , TM 



6 c ^ 



a and'd Spirilla in short segments and longer threads the so-called comma 

 f9rms and spirals, b. The forms known as spirochseta. c. The thick spirals some- 

 times known as vibrios. (Abbott.) 



FIG. 6. 



U It 



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

 ures. b. Involution-forms of this organism as seen in old cultures. (Abbott.) 



Occasionally under peculiar conditions what are known as 

 involution-forms are produced, forms which may scarcely be 

 recognized as those belonging to the original bacteria. These 

 points are shown by Figs. 2, 3, 4, 5, 6. 



