CHAPTER XVII 

 THE DIPHTHERIA BACILLUS 



DIPHTHERIA under various names has been described almost 

 since the earliest days of history. In 1821 Bretonneau of Tours 

 published a very comprehensive essay on the subject and gave 

 to the disease its present name. Little further information was 

 gained until about 1840. Observers began to notice the presence 

 of microorganisms in the pseudomembranes and suggested they 

 might be the causal agents. In 1883 Klebs described a bacillus 

 of rather peculiar appearance which could be almost invariably 

 demonstrated in the false membrane of the throats of those dying 

 of true diphtheria. A year later the organism was isolated and 

 cultivated in pure culture by Loeffler, who described its character 

 and its pathogenic effects on animals. Loeffler was able by inocu- 

 lation with the bacillus to produce the false membrane on damaged 

 mucous surfaces. But he hesitated to conclude definitely that the 

 organism was the direct cause of the disease, because he was not 

 able to find it in every case thought to be diphtheria, and also he 

 had found it in the throat of a normal, healthy child. Such condi- 

 tions are more clearly understood now. Similar clinical symptoms 

 are not necessarily produced by the same agent, and the knowledge 

 recently gained that healthy persons may become carriers explains 

 the occasional appearance of the organism in normal throats. 

 Additional confirmatory evidence was given when Roux and 

 Yersin in 1889-1890 showed that the most important features of 

 the disease could be produced by means of the toxins separated 

 from the organisms. By clinical and bacterial observations the 

 relationship of the Klebs-Loeffler bacillus to the disease is now so 

 definitely established that it has become a necessity to find the 

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