DISTRIBUTION OF THE BACILLUS. 



359 



ture according as it is formed on a surface covered with stratified 

 squamous epithelium as in the pharynx, or on a surface covered 

 by ciliated epithelium as in the trachea. In the former situa- 

 tion necrosis of the epithelium occurs either uniformly or in 

 patches, and along with this there is marked inflammatory reac- 

 tion 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 



m v 



FlG. 120. Section through a diphtheritic membrane in trachea, showing diphtheria 

 bacilli (stained darkly) in clumps, and also scattered amongst the fibrin. Some strepto- 

 cocci are also shown, towards the surface on the left side. 



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



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

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

 shed, and 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 differ- 

 ent parts. The membrane lies upon the basement membrane, 

 and is less firmly adherent than in the case of the pharynx. 



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 



