XV] ANAEROBIC BACILLI 383 



therefore only the seat of the inoculation contains the 

 infective principle, i.e., the bacilli ; for this reason brain, 

 cord, nerves, blood and viscera have no power to produce 

 infection. 



The disease tetanus is then, like that of diphtheria, not a 

 true infection but intoxication. 



Brieger has, as a matter of fact, isolated from the exuda- 

 tion at the seat of infection in human tetanus a toxic 

 principle, tetanin, the injection of which produces tetanus 

 symptoms in animals ; and Kitasato showed this to hold 

 good also for the tetanin obtained from the cultures of the 

 tetanus bacilli. 



In his "Experimental Researches on the Poison of Teta- 

 nus" {Zeitschr. f. Hygiene, x. 2) Kitasato gives a full account 

 of the influence of light, heat, drying and of various chemical 

 substances on the tetanus poison. 



Behring and Kitasato ^ have shown that by repeated in- 

 jection of non-fatal doses — using at first small doses of 

 active culture or tetanus toxin, or by using attenuated virus 

 (by the addition of trichloride of iodine, carbolic acid) — it 

 is possible gradually to increase the amount of virulence of 

 the dose without causing a fatal issue in the experimental 

 animals (rabbits). 



Hereby the animals were rendered insusceptible to fatal 

 doses of tetanus bacilli or tetanus toxin, and further it was 

 shown that the blood-serum of such (artificially) highly 

 immunised animals when injected into an otherwise sus- 

 ceptible animal (mouse) possesses the remarkable power of 

 neutralising the effect of a fatal dose of tetanus bacilli or 

 tetanus toxin injected before or after into that animal 

 (mouse). It is from these researches that the scientific 



^ Dettische Med. Woch., 1890, No. 49, and Behring, Zeitschrift f. 

 Hygiene imd Infekt. xii. 



