382 MICRO-ORGANISMS AND DISEASE [chap. 



The tetanus bacilli are straight cylindrical bacilli, in 

 culture varying between iju, and 4yu,, occasionally forming 

 longer chains and filaments ; in the fresh state they show slug- 

 gish motility, but in suitably stained specimens show numerous 

 flagella, often arranged in bundles {see Figs. 21, 22, 23). 

 They form rapidly (already in 30 hours at 37° C.) a terminal 

 spore which gives them the shape of a " drumstick " ; the 

 spores are at first spherical, later oblong, bright and glisten- 

 ing. Pus containing the tetanus virus preserves its virulence 

 in the dried state for many months, owing to the presence of 

 the spores (Kitt). 



The bacilli stain well after Gram. 



The success of obtaining pure cultures of the tetanus 

 bacilli was achieved by Kitasato by cultivating tetanus pus 

 anaerobically ; preliminarily to this he watched for the time 

 when in ordinary cultures of the tetanus pus on serum or 

 Agar amongst the different species of bacteria present he 

 found such which by their peculiar shape and containing a 

 terminal thick spore — "drumstick forms '' — he recognised as 

 the tetanus bacilli. By exposing such impure cultures three- 

 quarters to an hour in water at 80° C. all bacteria were killed 

 except those spores. With material thus treated he made 

 gelatine plate cultures, and gelatine tube cultures, but in such 

 a way that the air was excluded by filling them with hydrogen 

 gas or by planting the bacilli into the depth of the gelatine. 

 Under these anaerobic conditions he obtained pure cultures. 



It appears, then, from these exact researches that the 

 introduction of the tetanus bacilli' under the skin is followed 

 by the production by them of a chemical virus, which, as it 

 is being produced at the seat of inoculation, is absorbed 

 into the system and sets up' the disease ; but the bacilli 

 themselves appear to remain limited to the seat of inocula- 

 tion, and do not live in the blood or any other tissue, and 



