DIPHTHERIA. 207 



DIPHTHERIA. 



The diphtheria-bacillus was grown in pure culture in 

 1884 by Loffler. 



The diphtheria-bacillus is a rather plump rod of varying size, 

 from i to 6 p. long and from 0.5 to i /j. thick. Its form is sub- 

 ject to great variations in different cultures. At times it 

 appears as a small, wedge-shaped body ; at other times as a 

 rather long body, with a bulbous thickening at one extremity 

 a so-called club ; and at still other times as a double club, or a 

 dumb-bell. Slender forms, occasionally curved slightly, are also 

 observed, especially in membranes. Not rarely bifurcations are 

 encountered, and upon the basis of this observation diphtheria- 



Fig. 51. Bacillus diphtheriae from a pure culture (Stengel). 



bacilli have been placed in relation with streptothrices, and 

 even with hyphomycetes. The diphtheria-bacillus is incapable 

 of independent movement. 



Spore-formation is wanting. 



Staining Properties. The diphtheria-bacillus is best 

 stained with methylene-blue or dilute carbolfuchsin. Gentian- 

 violet overstains and conceals the more delicate structural rela- 

 tions. The organism is stained by Gram's method. The small, 

 blunt clubs stain equably, while the longer specimens exhibit 

 unstained areas, so that the rods appear in places to consist of 

 several segments. Fliigge has described a method of double 

 staining, devised by M. Neisser, which is considered to possess 

 essential differential diagnostic significance. The preparation 

 is placed for from three to five seconds in an acetic-acid solu- 

 tion of methylene-blue (methylene-blue i, alcohol 20, distilled 

 water 950, glacial acetic acid 50), rinsed in water, and counter- 

 stained for from three to five seconds in vesuvin (vesuvin 2, 



