IMMUNITY AGAINST TETANUS 433 



antitoxin is manufactured in the cells which are sensitive to the 

 toxin (see Immunity). 



Roux and Borrel, in injecting tetanus toxin into the brain 

 itself, found that the ordinary type of the disease was not pro- 

 duced, but that what they called " cerebral tetanus " occurred. 

 This consisted of general unrest, symptoms of a psychic character 

 (apparent hallucinations, fear, etc.), and epileptiform convul- 

 sions. Death took place in from twelve to twenty hours, without 

 any true tetanic spasms. In this manifestation of tetanus, the 

 incubation period was much shorter than with subcutaneous 

 injection, and the fatal dose was one twenty-fifth of the minimal 

 subcutaneous dose. In the light of what has been already said, 

 these results would seem to indicate a special effect of the toxin 

 when brought into direct contact with the protoplasm of the 

 brain cells. 



We have seen that unless suitable precautions are adopted in 

 experiments with tetanus cultures in animals, death results not 

 from the multiplication of the bacilli, but from an intoxication 

 with toxin previously existent in the fluid in which the bacilli 

 have been growing. According to Vaillard, if spores rendered 

 toxin-free, by being kept for a sufficient time at 80° C, are in- 

 jected into an animal, death does not take place. It was found, 

 however, that such spores can be rendered pathogenic by inject- 

 ing along with them such chemicals as lactic acid, by injuring 

 the seat of inoculation so as to cause effusion of blood, by 

 fracturing an adjacent bone, by introducing a mechanical irritant 

 such as soil or a splinter of wood (as in Kitasato's experiments), 

 or by the simultaneous injection of other bacteria such as the 

 staphylococcus pyogenes aureus. These facts, especially the last, 

 throw great light on the disease as it occurs naturally, for 

 tetanus results especially from wounds which have been acci- 

 dentally subjected to conditions such as those enumerated. 

 Kitasato now holds that in the natural infection in man, along 

 with tetanus spores, the presence of foreign material or of other 

 bacteria is necessary. Spores alone or tetanus bacilli without 

 spores die in the tissues, and tetanus does not result. 



Immunity against Tetanus. — An ti tetanic Serum. — The arti- 

 ficial immunisation of animals against tetanus received much 

 attention, especially from Behring and Kitasato in Germany, and 

 Tizzoni and Cattani in Italy. <The former observers found that 

 a degree of immunity could be conferred by the injection of very 

 small and progressively increasing doses of the tetanus toxin. 

 Subsequent work has shown that the richer a crude toxin is in 

 modifications of the true toxin, the more useful it is for immunisa- 

 28 



