DIPHTHERIA. 391 



form chains, though two, three, and rarely four individ- 

 uals may be found joined ; generally the individuals are 

 all separate from one another. The morphology of the 

 bacillus is peculiar in its considerable irregularity, for 

 among the well-formed individuals which abound in 

 fresh cultures a large number of peculiar organisms are 

 to be found, some much larger than normal, some with 

 one end enlarged to a club-shape, some greatly elongated, 

 with both ends expanded into club-shaped enlargements. 

 These bizarre forms seem to represent an involution-form 

 of the organism, for, while present in perfectly fresh cul- 

 tures, they are so abundant in old cultures that scarcely 

 a single well-formed bacillus can be found. It not infre- 

 quently happens that in unstained bacilli distinct gran- 

 ules can be defined at the ends — polar granules — thus 

 giving the organism somewhat the appearance of a 

 diplococcus. Occasionally branched forms are observed, 

 and it is not impossible that the diphtheria bacillus may 

 belong to the higher bacteria, finding its real place among 

 the streptothrices. 



The bacillus can be readily stained by aqueous solu- 

 tions of the anilin colors, but more beautifully and 

 characteristically with L,6ffler's alkaline methylene blue : 



Saturated alcoholic solution of methylene blue, 30 ; 

 1 : 10,000 aqueous solution of caustic potash, 100 ; 



and an aqueous solution of dahlia, as recommended by 

 Roux. 



The Neisser method of staining the diphtheria bacillus 

 is as follows : The prepared cover-glass is immersed for 

 from two to three seconds in 



Alcohol (96 per cent.), 20 parts. 



Methylene blue, 1 part. 



Distilled water, 950 parts. 



Acetic acid (glacial), 50 " 



Then for three to five seconds in 



Bismarck brown, 1 part. 



Boiling distilled water, 500 parts. 



