DISTRIBUTION OF BACILLI. 333 



In diphtheria the membrane has a somewhat different 

 structure 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 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 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. This 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 the superficial, that is, usually, the oldest part of the 

 membrane (Fig. 82). There they may be in a practically pure 

 condition, though streptococci and occasionally some other 

 organisms may be present along with them. They may 

 occur also deeper, but are rarely or never found in the 

 fibrin around the blood vessels. They may be also seen 

 lying in large numbers on the surface of the membrane, 

 but are there usually accompanied by numerous other 

 organisms of various kinds. Occasionally a few bacilli 

 have been detected in the lymphatic glands. As Loffler 

 first described, they may be found after death in pneumonic 

 patches in the lung, this being a secondary extension in 

 fatal cases. They have also been found by various observers 

 to be occasionally present in the spleen, liver, and other 

 organs after death. This occurrence is probably to be ex- 

 plained by an entrance into the blood stream shortly before 



