408 DIPHTHERIA 



of a small amount of diphtheria bacilli into the superficial part 

 of the skin in a guinea-pig produces a circumscribed swelling 

 which is followed by superficial necrosis in from one to two 

 days ; whereas, if the animal has received previously an injection 

 of, say, 250 units of antitoxin, the result is negative. The result 

 is also negative (without antitoxin) in the case of an avirulent 

 diphtheroid. 



The following is the method as modified by Zingher and Soletaky. A 

 twenty-four hours' growth on a tube of Loffler's serum is emulsified in 

 20 e.c. of normal saline, and of this 0'15 o.o. is injected intracutaneous^ 

 into the abdominal wall of a guinea-pig. Four or even six injections of 

 different strains can be carried out at the same time in the same animal. 

 Similar injections are made in an animal previously treated by antitoxin, 

 the antitoxin being introduced intracardially immediately before, or 

 intraperitoneally twenty-four hours before. 



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 little fibrinous exudation but a considerable 

 amount of inflammatory oedema, and, if the animal survive long 

 enough, necrosis of the superficial tissues in varying degree 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. 



