TOXINS OF THE TETANUS BACILLUS 437 



being thus accepted as the cause of the disease, we have to 

 consider how it produces its pathogenic effects. 



Almost contemporaneously with the work on diphtheria was the 

 attempt made with regard to tetanus to explain the general symptoms 

 by supposing that the bacillus could excrete soluble poisons. The 

 earlier results, in which certain bases, tetanin and tetanatoxin, were 

 said to have been isolated, have only a historic interest, as they were 

 obtained by faulty methods. In 1890, Brieger and Fraenkel announced 

 that they had isolated a toxalbumin from tetanus cultures, and this body 

 was independently discovered by Faber in the same year. Brieger and 

 Fraenkel's body consisted practically of an alcoholic precipitate from 

 filtered cultures in bouillon, and was undoubtedly toxic. Within recent 

 years such attempts to isolate tetanus toxins in a pure condition have 

 practically been abandoned, and attention has been turned to the 

 investigation of the physiological effects either of the crude toxin 

 present in filtered ordinary bouillon cultures grown under anaerobic con- 

 ditions, or of the precipitate produced from the same by ammonium 

 sulphate (cf. p. 200). 



The toxic properties of bacterium-free filtrates of pure 

 cultures of the b. tetani were investigated in 1891 by Kitasato. 

 This observer found that when the filtrate, in certain doses, was 

 injected subcutaneously or intravenously into mice, tetanic spasms 

 developed, first in muscles contiguous to the site of inoculation, 

 and later all over the body. Death resulted. He found that 

 guinea-pigs were more susceptible than mice, and rabbits less so. 

 In order that a strongly toxic bouillon be produced, it must 

 originally have been either neutral or slightly alkaline. Kitasato 

 further found that the toxin was easily injured by heat. Exposure 

 for a few minutes at 65 C. destroyed it. It was also destroyed 

 by twenty minutes' exposure at 60 C., and by one and a half 

 hours' at 55 C. Drying had no effect. It was, however, 

 destroyed by various chemicals such as pyrogallol and also by 

 sunlight. 



In anaerobic bouillon cultures the maximum toxicity is de- 

 veloped in from ten to fifteen days. Behring pointed out that 

 after the filtration of cultures containing toxin, the latter may 

 very rapidly lose its power, and in a few days may only possess 

 yj^th of its original toxicity. This is due to such factors 

 as temperature and light, and especially to the action of oxygen. 

 Toxins should thus have a layer of toluol floated on the surface 

 and be kept in a cool, dark place. The effect of harmful agents 

 on the crude toxin is apparently to cause a degeneration of the 

 true toxin so as to form what it is convenient at present to call 

 toxoids similar to those produced in the case of diphtheria toxin, 

 and it is also true here that the toxoids while losing their 



