EFFECTS OF INOCULATION 407 



result when the surface is injured by scarification or otherwise. 

 A similar result may be obtained when the trachea is inoculated 

 after tracheotomy has been performed. In this case the 

 surrounding tissues may become the seat of a blood-stained 

 oedema, and the lymphatic glands become enlarged, the general 

 picture resembling pretty closely that of laryngeal diphtheria. 

 The membrane produced by such experiments is usually less 

 firm than in human diphtheria, and the bacilli in the membrane 

 are less numerous. Rabbits inoculated after tracheotomy often 

 die, and Roux and Yersin were the first to observe that in some 

 cases paralysis might appear before death. 



Subcutaneous injection in guinea-pigs of diphtheria bacilli in 

 a suitable dose produces death within thirty-six hours. At the 

 site of inoculation there is usually a small patch of greyish 

 membrane with some necrosis, whilst in the tissues around there 

 is extensive inflammatory oedema, often associated with 

 haemorrhages, and there is also some swelling of the correspond- 

 ing lymphatic glands. The internal organs show general 

 congestion, the suprarenal capsules being especially reddened 

 and often hsemorrhagic. The renal epithelium may show cloudy 

 swelling, 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 

 practically local, cultures made from the blood and internal 

 organs usually giving negative results, though sometimes a few 

 colonies may be obtained. 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. Eoux 

 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. Cliolera, p. 469). The dog and sheep 

 are also susceptible to inoculation with virulent bacilli, but the 

 mouse and rat enjoy a high degree of immunity. 



An intra-cutaneous method of injection has been found to be 

 of service in testing the virulence, and thus in the identification, 

 of the diphtheria bacillus, especially when used in conjunction 

 with the injection of antitoxin. Injection with a fine syringe 



