THE TETANUS BACILLUS 



503 



Bacillus [Clostridium] tetani 



Morphology. The Bacillus tetani is a straight, slender 

 rod, but under cultivation filaments of varying length may 

 develop. It is motile and possesses a number of flagella, 

 three or four of which are generally thicker than the rest. 

 Spores are freely formed ; they are 

 spherical and completely terminal, and 

 their diameter being much greater 

 than that of the rod, the spore-bearing 

 organism has been likened to a " pin " 

 or "drum-stick" (Plate XVIII, a). 

 It stains with the ordinary anilin dyes, 

 and also by Gram's method. " Drum- 

 stick " bacilli are not necessarily 

 B. tetani, as other terminal-spored 

 anaerobes occur (see p. 511, and Plate 

 XIX, 6). 



Cultural characters. The B. tetani is 

 a strict anaerobe, and surface growths 

 are difficult to obtain except under the 

 best conditions of anaerobiosis. It 

 will grow quite well in a deep stab in 

 glucose agar, delicate fluffy outgrowths 

 radiating from the central puncture 

 (Fig. 48). A similar growth occurs in a 

 stab glucose gelatin culture with lique- 

 faction. Surface colonies on serum agar 

 are small (1 mm.) and filmy with finger-like projections. 

 Deep colonies in serum agar are larger (2-3 mm.), and 

 appear as delicate filamentous outgrowths spreading 

 from a small central nucleus. Broth cultures show a 

 general turbidity. Meat broth shows no change or 

 becomes pinkish, and the meat fragments are softened. 

 In milk the growth is poor without any change. On 



FIG. 48. Tetanus 

 bacillus. Stab 

 culture in glucose 

 agar, seven 

 old. 



