420 A MANUAL OF BACTERIOLOGY 



The Bacillus tetani 



Morphology. The Bacillus tetani is a straight, slender 

 rod with rounded ends, but under cultivation the rods 

 may grow into longish filaments. It is somewhat motile 

 and possesses a large number of flagella, three or four of 

 which are generally thicker than the rest. 1 Spores are 

 freely formed ; they are spherical and develop at one 

 extremity of the rod, 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 

 XVII. a). It stains with the ordinary anilin dyes, and 

 also by Gram's method. " Drum-stick " bacilli are not 

 necessarily tetanus ; other anaerobic bacilli, e.g. B. putri- 

 ficus (coli), may also have large terminal spores. 



Cultural characters.- The B. tetani is a strictly anaerobic 

 organism, and will not grow in the presence of a trace of 

 free oxygen, nor in an atmosphere of carbon dioxide. It 

 can be cultivated in deep stabs in glucose agar and gelatin, 

 or in broth by Buchner's method, or in an atmosphere of 

 hydrogen (p. 73). In a gelatin stab-culture at 22 C. the 

 growth radiates from the central puncture, and the gelatin 

 is slowly liquefied. In a glucose agar stab- culture it forms 

 feathery, radiating outgrowths from the central puncture, 

 a small amount of gas being formed (Fig. 47). Broth 

 becomes turbid with the formation of some gas and the 

 development of a foul odour ; there is no film formation. 

 The colonies have a central opaque portion surrounded by 

 diverging rays. It grows on serum without liquefaction 

 and in milk without curdling. The tetanus bacillus remains 

 alive for some time, possibly indefinitely, in cultures, and 

 the spores retain their vitality for years in the dried state, 

 withstand a temperature of 80 C. for an hour, but are 



1 Kanthack and Connell, Journ. Path, and Bact., vol. iv, 1897, p. 452. 



