420 



TETANUS 



bacillus is in many cases a difficult matter, and several methods 

 should always be tried. 



Characters of Cultures. Pure cultures having been obtained, 

 sub-cultures can be made in deep upright glucose gelatin or 

 agar tubes. On f/lucose gelatin in such a tube there commences, 

 an inch or so below the surface, a growth 

 consisting of fine straight threads, rather 

 longer in the lower than in the upper parts 

 of the tube, radiating out from the needle 

 track (Fig. 124). Slow liquefaction of the 

 gelatin takes place, with slight gas formation. 

 In agar the growth is somewhat similar, 

 consisting of small nodules along the needle 

 track, with irregular short offshoots passing 

 out into the medium (Fig. 128, A). There is 

 slight formation of gas, but, of course, no 

 liquefaction. On anaerobic agar plates 

 colonies have under a low power a feathery 

 outline (Fig. 125). Growth also occurs in 

 blood serum and also in glucose bouillon 

 under anaerobic conditions. The latter is the 

 medium usually employed for obtaining the 

 soluble products of the organism. There is 

 in it at first a slight turbidity, and later a 

 thin layer of a powdery deposit on the walls 

 of the vessel. All the cultures give out a 

 peculiar burnt odour of rather unpleasant 

 character. 



Conditions of Growth, etc. The b. tetani 

 grows best at 37 C. The minimum growth 

 temperature is about 14 C., and below 22 C. 

 growth takes place very slowly. Growth 

 takes place in the absence of oxygen, the 

 organism being an anaerobe. Sporulation 

 may commence at the end of twenty-four 

 hours in cultures grown at 37 C., much 

 later at lower temperatures. Like other 

 spores, those of tetanus are extremely resistant. They can 

 usually withstand boiling for five minutes, and can be kept 

 in a dry condition for many months without being killed or 

 losing their virulence. They have also high powers of resistance 

 to antiseptics. 



Pathogenic Effects. The proof that the b. tetani is the cause 

 of tetanus is complete. It can be isolated in pure culture, and 



FIG. 124. Stab cul- 

 ture of the tetanus 

 bacillus in glucose 

 gelatin, showing 

 the lateral shoots 

 (Kitasato). 

 Natural size. 



