88 



MORPHOLOGY AND CULTURE OF MICROORGANISMS 



that streptobacilli are formed. When arranged in pairs, the designa- 

 tion is diplobacilli. The length of the chains appears to depend not 

 only upon the cohesion of the bacilli but also upon the shape of the 



\ ^ 



FIG. 67. Division forms of bacilli, a, Single; b, pairs; c, in threads. (After Novy.) 



end; those which have square ends frequently have very long chains, 

 while those with rounded ends have short chains or occur singly. 



A unique growth-form or cell aggregate is that due to the post fission 

 movement of the cell as described by Hill in cultures of Bact. diph- 



FIG. 68. Threads of Bact. anthracis. (After Migula.) 



theriae. On fission the two daughter cells are not completely separated 

 but remain attached at one place. This leads to a movement similar 

 to the closing of a jack knife. In this way the two sister cells are 

 brought to rest at an obtuse, a right or an acute angle to each other. 

 They may be even brought parallel. 



