THE TOXINS OF DIPHTHERIA 405 



In rabbits, after subcutaneous inoculation, results of the same 

 nature follow, but these animals are less susceptible than guinea- 

 pigs, and the dose requires to be proportionately larger. Roux 

 and Yersin found that after intravenous injection the bacilli 

 rapidly disappeared from the blood, and when 1 c.c. of a broth 

 culture had been injected no trace of the organisms could be 

 detected by culture after twenty-four hours ; nevertheless the 

 animals died with symptoms of general toxaemia, nephritis also 

 being often present (cf. Cholera, p. 455). The dog and sheep 

 are also susceptible to inoculation with virulent bacilli, but the 

 mouse and rat enjoy a high degree of immunity. 



Klein found that cats also were susceptible to inoculation. The 

 animals usually die after a few days, and post-mortem there is well-marked 

 nephritis. He also found that after subcutaneous injection in cows, a 

 vesicular eruption appeared on the teats of the udder, the fluid in which 

 contained diphtheria bacilli. At the time of death the diphtheria bacilli 

 were still alive and virulent at the site of injection. The most striking 

 result of these experiments is that the diphtheria bacilli passed into the 

 circulation and were present in the eruption on the udder. He considers 

 that this may throw light on certain epidemics of diphtheria in which 

 the contagion was apparently carried by the milk. Other observers, 

 e.g. Abbott, have, however, failed to obtain similar results. Dean and 

 Todd,in investigating an outbreak of diphtheria traceable to a milk supply, 

 found a vesicular eruption on the teats of the udder in which diphtheria 

 bacilli were present. They, however, came to the conclusion that these 

 bacilli were not the cause of the eruption, but were the result of a 

 secondary contamination, probably from the saliva of the milkers. The 

 existence of a true diphtheria infection in cows must still be considered 

 doubtful. A case of true diphtheria in the horse has been described by 

 Cobbett. 



The Toxins of Diphtheria. As in the above experiments 

 the symptoms of poisoning and ultimately a fatal result occur 

 when the bacilli are diminishing in number, or even after they 

 have practically disappeared, Roux and Yersin inferred that the 

 chief effects were produced by toxins, and this supposition they 

 proved to be correct. They showed that broth cultures of three 

 or four weeks' growth freed from bacilli by filtration were highly 

 toxic. The filtrate when injected into guinea-pigs and other 

 animals produces practically the same effects as the living bacilli ; 

 locally there is fibrinous exudation but a considerable amount 

 of inflammatory (jedema, and, if the animal survive long enough, 

 necrosis in varying degree of the superficial tissues may follow. 

 The toxicity may be so great that '005 c.c. or even less may be 

 fatal to a guinea-pig in five days. 



After injection either of the toxin or of the living bacilli, 

 \\lieii the animals survive long enough, paralytic phenomena 



