EFFECTS OF INOCULATION 417 



at the end of several months. The presence of light, moisture, 

 or a higher temperature, causes them to die out more rapidly. 

 Corresponding results have been obtained with bacilli obtained 

 from cultures and kept on dried threads. These facts, especially 

 with regard to drying, are of great importance, as they show that 

 the contagium of diphtheria may be preserved for a long time 

 in the dried membrane. 



Effects of Inoculation. In considering the effects produced 

 in animals by experimental inoculations of pure cultures, we 

 have to keep in view the local changes which occur in diphtheria, 

 and also the symptoms of general poisoning. 



As Loffler stated in his original paper, inoculation of the 

 healthy mucous membranes of various animals with pure cultures 

 causes no lesion, but the formation of false membrane may 

 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 

 cedema, 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, whilst in the tissues around there is extensive 

 inflammatory cedema, often associated with haemorrhages, and 

 there is also some swelling of the corresponding lymphatic glands. 

 The internal organs show general congestion, the suprarenal 

 capsules being especially reddened and often haemorrhagic. The 

 renal epithelium may show cloudy swelling, and there is often 

 effusion into the pleural cavities. After injection the bacilli in- 

 crease 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- 

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