DISTRIBUTION OF THE BACILLUS 355 



covered by ciliated 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 

 fibriuous exudation. The necrosed epithelium becomes raised 

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







FIG. 117. Sectiou through a diphtheritic membrane in trachea, showing diph- 

 theria 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. 



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 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 base- 

 ment membrane, and is less firmly adherent than in the case of 

 the pharynx 



