92 BACILLUS TETANI 



however, giving rise to any evolution of gas. The 

 growth then forms a thick mass at the bottom of 

 the tube. The same radiating filaments are seen in 

 isolated colonies. 



The pure culture, when inoculated, gives rise to 

 tetanus. There is practically no local lesion, and 

 the bacilli disappear rapidly from the seat of inocu- 

 lation, and are not found in the blood or internal 

 organs. The tetanus results from the toxins pro- 

 duced by the organism, and, while disease may be 

 produced by the poison alone, an inoculation of the 

 toxin-free 'microbe is inert and unable to produce a 

 pathogenic effect unless assisted by chemical, trau- 

 matic, or microbic aids. 



A condition of immunity may be produced in 

 susceptible animals which is valid against either the 

 living organism or its toxins. The blood serum of 

 these immunised animals is capable of neutralising 

 in " vitro " the toxin of the culture. It is also 

 capable of preventing the pathogenic effects of 

 inoculations of the bacillus or its toxins when the 

 serum is injected before, at the same time, or soon 

 after the inoculation, and it may act therapeutically 

 after symptoms of tetanus have already shown them- 

 selves. The dose of serum required for therapeutic 

 purposes is enormously greater than that required 



