356 DIPHTHERIA. 



They stain deeply with the blue, sometimes being uniformly 

 coloured, but often showing, in their substance, little 

 granules more darkly stained, so that a dotted or beaded 

 appearance is presented. Sometimes the ends are swollen 

 and more darkly stained than the rest; often, however, they 

 are rather tapered off (Fig. 89). In some cases the terminal 

 swelling is very marked, so as to amount to clubbing, and 

 with some specimens of methylene-blue these swellings and 

 granules stain of a violet tint. Distinct clubbing, however, 

 is less frequent than in cultures. There is a want of 

 uniformity in the appearance of the bacilli when compared 

 side by side. They usually lie irregularly scattered or in 

 clusters, the individual bacilli being disposed in all direc- 

 tions. Some may be contained within leucocytes. They 

 do not form chains, but occasionally forms longer than 

 those mentioned may be found, and these specially occur 

 in the spaces between the fibrin as seen in sections. 



Distribution of the Bacilli. The diphtheria bacilli may 

 be found in the membrane wherever it is formed, and may 

 also occur in the secretions of the pharynx and larynx in 

 the disease. It may be mentioned that distinctions formerly 

 drawn between true diphtheria and non-diphtheritic con- 

 ditions from the appearance and site of the membrane, 

 have no scientific value, the only true criterion being the 

 presence of the diphtheria bacilli. The occurrence of a 

 membranous formation produced by streptococci has 

 already been mentioned (p. 178). 



In diphtheria the membrane has a somewhat different 

 structure according as it is formed on a surface covered 

 with stratified squarnous 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 



