CHAPTER XVII 



DIPHTHERIA BACILLUS 



(Klebs-Loeffler Bacillus) 



The diphtheria bacillus is found in the air, and dust and on the furniture and 

 drapings of rooms inhabited by diphtheria patients and diphtheria carriers, on 

 the clothing and utensils of diphtheria patients and carriers and perhaps on 

 dogs, cats and cows associated with them. The organism sometimes finds its 

 way into milk, probably from carriers and lives there virulent for a sufficient 

 time to cause infection of those who consume the milk. 



Morphology. The diphtheria bacillus shows marked variations in size and 



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FIG. 16. BACILLUS OF DIPHTHERIA. Xiooo. (MacNeal.) 



form; the smears taken from the nose or throat and from 16 to 2o-hour-old blood- 

 serum cultures they usually appear as small bacilli, 2 to 3 M long, 0.3 to 0.5 M 

 broad, many are straight or curved, some are club-shaped, a few triangular and 

 some so small as to be coccoid. 



Smears made from cultures 24 to 72 hours old, or older, show involution 

 forms, organisms more often club-shaped, balloon-shaped or irregular, than 

 rod-shaped. Uniform staining is the exception, not the rule, especially among 

 involution forms. The corynebacteria, of which the diphtheria bacillus is a 

 type, when stained with the ordinary anilin stains, especially Loeffler's methy- 

 lene blue, stain deeply at each end and faintly in the middle, or stain deeply at 

 the extremities and in the center, giving a barred or granular appearance. 

 When stained by Neisser's method- acid methylene blue, 10 to 15 minutes, 



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