CH. XIII.] 



SPIROBACTERIUM. 



185 



Occasionally the spirilla grow to a great length two, three, 

 and more of them forming a chain ; the individual spirilla are 

 not arranged in a linear series, but folded into a zigzag. This 

 form, which in reality is not a special kind of spirillum, is 

 called by Cohn J spirochceta plicatilis. The spirillum found 

 in the tartar of the teeth is of this form, spirochata denticola. 

 But there exist all intermediate forms between a single 



FIG. 108. SPIRILLUM UNDULA 

 (AFTER COHN). 



FIG. 109 SPIRILLUM VOLUTANS 

 (AFTER COHN). 



spirillum tenue and a spirochaeta. In stained specimens the 

 construction of the spirochaeta from several spirilla tenua is 

 very distinct. 



(b) Spirillum undula is much thicker and shorter than 

 the former ; there are all forms between such as are only 

 1 Bcitrdge zur BiologU d. Pflanzen, vol. ii. 



