DIPHTHERIA. 665 



m the line of their duty. The numerous cases of infection of persons 

 who have been in the same room with diphtheritic patients, without 

 coming in their immediate vicinity, prove that the air exhaled by the 

 patient, which does not contain shreds of exudation or tissue, is a ve- 

 hicle for the contagion. Further observation must decide, if, besides 

 the above vehicles for the poison, there be still others ; how tenacious 

 the infection is ; whether persons who do not themselves take the dis- 

 ease may carry it to third parties, etc. The predisposition to diphthe- 

 ria is unmistakably very extensive. The greater frequency of the dis- 

 ease among children than adults does not seem to me due to greater 

 predisposition of the former, but to their being more exposed to infec- 

 tion than adults are. 



ANATOMICAL APPEAKANCES. Just as in other infectious diseases, 

 in diphtheritis also certain organs are chiefly subjected to the disturb- 

 ances of nutrition, and (to employ our former mode of expression) 

 diphtheritis is constantly localized in the fauces, less constantly in the 

 upper portion of the air-passages, in the kidneys, spleen, and in some 

 very obscure manner in the nervous system. The disturbances of nu- 

 trition in the above organs do not anatomically correspond. In the 

 pharynx we find the form of diphtheritic inflammation to which the 

 disease owes its name, and which we have often described. The 

 fauces, and especially the tonsils and soft palate, are covered with 

 grayish-white pseudomembrane, which is not easily removed, and 

 which leaves an ulcerated loss of substance, when it finally breaks 

 down into a discolored fetid mass, and falls off. The diphtheritic 

 pseudomembranes, or, to speak more precisely, the diphtheritic sloughs, 

 result from superficial gangrene of the mucous membrane, which again 

 depends on compression of its nutrient vessels by an interstitial fibrin- 

 ous exudation, or from swelling of the tissue-elements, which are filled 

 with a cloudy substance. If the larynx and trachea participate in the 

 disease, the croupous, not the diphtheritic, form of inflammation of the 

 mucous membrane occurs ; that is, the surface of the mucous membrane 

 is covered with a more or less tough and consistent false membrane, 

 which may readily be removed, and leaves no loss of substance after 

 its removal. This circumstance has induced some physicians to iden- 

 tify primary genuine croup, which is due to catching cold, etc., with 

 croupous laryngitis caused by infection with diphtheritic contagion. 

 I consider this a false view. The division of diseases, according to the 

 pathologico-anatomical changes they induce, is only a make-shift. In 

 all ases where, as in genuine and diphtheritic croup, we find that two 

 anatomically similar disturbances of nutrition depend on very different 

 causes, we should consider them as distinct. A small-pox pustule 

 may very much resemble one induced by rubbing antimonial ointment 



