354 DIPHTHERIA 



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 Bacillus. The diphtheria bacillus 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. 



FIG. 116. Film preparation from diphtheria membrane ; showing numerous 

 diphtheria bacilli. One or two degenerated forms are seen near the 

 centre of the field. (Cultures made from the same piece of membrane 

 showed the organism to be present in practically pure condition.) 

 Stained with methylene-blue. x 1000. 



It may be mentioned that distinctions formerly drawn between 

 true diphtheria and non-diphtheritic conditions from the appear- 

 ance and site of the membrane, have no scientific value, the only 

 true criterion being the presence of the diphtheria bacillus. The 

 occurrence of a membranous formation produced by streptococci 

 has already been mentioned (p. 184). 



In diphtheria the membrane has a somewhat different 

 structure according as it is formed on the surface covered with 

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



