MORPHOLOGICAL CLASSIFICATION OF BACTERIA. 31 



FIG. 4. 



. 



*'\' \ 

 --> '* I x 



-. ... > \ 



d e / 



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

 Bacilli of variable morphology. (Abbott.) 



FIG. 5. 



c d 



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

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

 times known as vibrios. (Abbott.) 



FIG. 6. 

 fl, 



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

 ures. 6. 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. 



