DIPHTHERIA. 285 



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. 



The bacillus can be readily stained by aqueous solu- 

 tions of the anilin colors, but more beautifully and 

 characteristically with Loffler's alkaline methylene blue : 



Saturated alcoholic solution of methylene blue, 30 ; 

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



and an aqueous solution of dahlia, as recommended by 

 Roux. 



When cover-glass preparations are stained with these 

 solutions, the bizarre forms already mentioned are much 

 more obvious than in the unstained individuals, and 

 the contrast between the polar granules, which color in- 

 tensely, and the remainder of the bacillus, which tinges 

 slightly, is marked. Through good lenses the organisms 

 are always distinct bacilli, notwithstanding the fact that 

 the ends stain more deeply than the centres, and it is 

 only through poor lenses that the organisms can be mis- 

 taken for diplococci. The bacilli stain well by Gram's 

 method, this being a good method to employ for their 

 definition in sections of tissue, though Welch and Abbott 

 assert that Weigert's fibrin method and picro-carmin give 

 the most beautiful results. 



The diphtheria bacillus does not form spores, and is 

 delicate in its thermal range. Loffler found that it could 

 not endure a temperature of 60 C., and Abbott has shown 



