THE INFECTIOUS DISEASES. 261 



Catarrhal bronchitis and broncho -pneumonia or simple lobular pneu- 

 monia frequently complicate diphtheritic lesions of the upper air passages 

 and fauces. 



BACTERIOLOGY OF THE DISEASE. 



Although bacteria of various forms are commonly present in the false 

 membrane, and some of them penetrate deeply into the underlying tissue, 

 the primary aud specific excitant of this disease is the Bacillus diphtherias 

 of Loffler. 



In man the dipjitheria bacilli are largely confined to the seat of local 

 lesion, and sometimes occur here in enormous numbers, especially in the 

 older layers of the pseudo -membrane (see Fig. 133). But they may 

 become widely distributed through the body. This appears to be espe- 

 jnally the case when the pyogenic cocci are associated with the diphtheria 

 bacillus. at the^seat of local_ lesion. The systemic effects in diphtheria 

 appear to be largely due to the absorption into the body of toxic material 

 elaborated locally by ,the germs. Septicaemia or acute visceral inflam- 

 mations, particularly of the kidney, may occur without evidence of an 

 external local lesion or of the portal of entry of the bacillus. ' 



CONCURRENT INFECTIONS. 



The very frequent association of the pyogenic cocci and other bacteria 

 with the diphtheria bacillus gives rise to a series of changes which make 

 the clinical picture and the lesions of diphtheria sometimes very com- 

 plex. Thus the complicating bronchitis and broncho-pneumonia, as well 

 as pyseniic symptoms and lesions, may be due to 

 the diphtheria bacillus alone. But these sec- 

 ondary lesions may be due to the presence in 

 the pseudo-membrane, and the entrance into 

 the deeper air passages and the blood, of Strep- 

 tococcus pyogenes, Staphylococcus pyogenes, 

 Diplococcus lanceolatus, Bacillus coli com- 

 munis, and other bacteria, or of these together FlG . m _ BACILLUS DIPHTHB- 

 with the diphtheria bacillus. 2 RLE - 



From exudate in the throat of a 

 Characters of the Diphtheria Bacillus. ~^SES 



This organism, first described and definitely associ- and size and coloratlon - 

 ated with this disease by Loffler, is a slender rod, in 



general about 3 ft long, but sometimes shorter and sometimes growing into threads. 

 It occasionally grows in branching forms, 3 and is characterized morphologically by 



1 For a resume and bibliography of studies relating to diphtheritic septicaemia see 

 Brown and Thiry, Gazette des Hopitaux, May 3d, 4th, and 9th, 1899. 



8 For a study of the presence and action of the diphtheria bacilli in the lungs see 

 Flexner and Anderzon, Johns Hopkins Hospital Bulletin, vol. ix., p. 72, 1898. 



For a summary of the association of diphtheria and tuberculosis see Councilman, 

 Mallory, and Pearct, reference above. 



3 The branching forms which are occasionally observed in the diphtheria as well as 

 in the tubercle bacillus, together with certain other characters, have led some observers 

 to che belief that these organisms are related to streptothrix and to the moulds rather 

 than to the bacteria. But, for the present at least, it seems wiser to consider it in its 

 more generally acknowledged relationships. 



