DISTRIBUTION OF THE BACILLUS 401 



epithelium, as in the trachea. In the former situation necrosis of the 

 epithelium occurs either uniformly or in patches, and along with this 

 there is marked inflammatory reaction in the connective tissue beneath, 

 attended by abundant fibrinous exudation. The necrosed epithelium 

 becomes raised up by the fibrin, and its interstices are also filled by it. 

 The fibrinous exudation also occurs around the vessels in the tissue 

 beneath, and in this way the membrane is firmly adherent. In the 

 trachea, on the other hand, the epithelial cells rapidly become shed, and 



"V. . ■ 



Fig. 111. — Section through a diphtheritic membrane in trachea, 

 showing diphtheria bacilli (stained darkly) in clumps, and also 

 scattered amongst the fibrin. Some streptococci are also shown 

 towards the surface on the left side. 



Stained by Gram's method and Bismarck-brown, x 1000. 



the membrane is found to consist almost exclusively of fibrin with 

 leucocytes, the former arranged in a reticulated or somewhat laminated 

 manner, and varying in density in different parts. The membrane lies 

 upon the basement membrane, and is comparatively loosely attached. 



The position of the diphtheria bacilli varies somewhat in 

 different cases, but they are most frequently found lying in oval 

 or irregular clumps in the spaces between the fibrin, towards the 

 superficial, that is, usually, the oldest part of the false membrane 

 (Fig. 111). There they may be in a practically pure condition, 

 26 



