CHAPTER XVII. 



DIPHTHERIA. 



Diphtheria an Infective Disease The Organism found in the False Mem- 

 brane in its Deeper Parts Method of Staining the Bacillus Characters 

 of the Bacillus Involution Forms Cultivation Methods Appearance 

 of Colonies Nutrient Media Results of Inoculation Experiments 

 Klein's Bacilli differ somewhat from Loffler's Streptococci found in 

 Diphtheria Poison Extreme Virulence Resemblance to snake-bite 

 poison Toxicity Predisposing Conditions Conditions fatal to the 

 Bacillus Roux and Yersin's Observations Fraenkel's Observations 

 Attenuated Diphtheria Virus Increase of Virulence. 



ALTHOUGH it has long been known that diphtheria was 

 an extremely infectious disease, it is only within compara- 

 tively recent years that any reliable information as to the 

 nature of the specific infective poison has been forth- 

 coming. Even when the organic nature of other specific 

 infective poisons had been practically proved many difficulties 

 still remained to be overcome ; in most other cases where 

 the disease could be proved to be the result of the vital 

 activity of a micro-organism, such organism could usually 

 be found in a pure condition, or greatly predominating 

 over all others, in the blood, in the internal organs, or in 

 some special fluid in the body. This was found not to 

 be the case in diphtheria. Most careful and elaborate 

 researches were entered upon, but it was found impos- 

 sible to demonstrate any special organism as occurring in 

 the blood, in the lymph, or in any of the organs of the 

 body. The only position in which any could be found was 

 in the false membranes (composed of fibrinous lymph and 

 altered epithelial cells) that are found in the throat, and it 

 was at once surmised a surmise that was afterwards found to 

 be correct that the poison which gives rise to the constitu- 

 tional symptoms must be formed at the point at which the 

 micro-organisms are found, and that, being of an exceedingly 

 diffusible nature, it is thence absorbed and carried to various 



