INOCULATION EXPERIMENTS. 365 



glands. The internal organs show general congestion, the 

 supra-renal capsules being especially reddened and often show- 

 ing haemorrhage. The renal epithelium may show cloudy swell- 

 ing, and there is often effusion into the pleural cavities. After 

 injection the bacilli increase in number for a few hours, but 

 multiplication soon ceases, and at the time of death they may be 

 less numerous than when injected. The bacilli remain practi- 

 cally local, cultures made from the blood and internal organs 

 giving usually negative results, though sometimes a few colonies 

 may be obtained. When streptococci or staphylococci are 

 injected at the same time, a larger number of diphtheria bacilla 

 enter the circulation (Metin). If a non-fatal dose of a culture 

 be injected, a local necrosis of the skin and subcutaneous tissue 

 may follow at the site of inoculation. 



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 tin blood, and even after the injection 

 of i c.c. of a broth culture 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. 417). 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 viru- 

 lent 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 of 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 have, however, failed to obtain similar results. Dean 

 and Todd, in investigating an outbreak of diphtheria traceable to milk supplied, 

 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 occurrence of a true infection 

 with the diphtheria bacillus in the horse has been recently described by 

 Cobbett. 



