Cultivation 413 



a beginner would certainly fail to recognize them as the same species. 

 The small short forms also stain much more uniformly than the 

 large club-shaped bacilli. 



Staining. The bacillus can readily be stained with aqueous 

 solutions of the anilin colors, but more characteristically with 

 Loffler's alkaline methylene blue: 



Saturated alcoholic solution of methylene blue 30 



i: 10,000 aqueous solution of caustic potash 100 



Emery prefers Manson's borax methylene blue. A stock solu- 

 tion which keeps well is prepared by dissolving 2 grams of meth- 

 ylene blue and 5 grams of borax in 100 cc. of water. This is diluted 

 with from five to ten times its volume of water for ordinary use. 

 An aqueous solution of dahlia is recommended by Roux. 



The Neisser method of staining the diphtheria bacillus, which met 

 with a very cordial reception, is as follows: 



The prepared cover-glass is immersed for from two to three 

 seconds in 



Alcohol (96 per cent.) 20 parts 



Methylene blue i part 



Distilled water 950 parts 



Acetic acid (glacial) 50 parts 



Then for three to five seconds in 



Bismarck brown i part 



Boiling distilled water 00 parts 



The true diphtheria bacilli appear brown, with a dark blue body 

 at one or both ends; the pseudo-diphtheria bacilli usually exhibit 

 no polar bodies. 



Park* found that neither the Neisser nor the Roux stain gave any 

 more information concerning the virulence of the bacilli than the 

 Loffler alkaline methylene blue. 



The bacilli stain well by Gram's method, which is excellent for 

 their definition in sections of tissue, though Welch and Abbott found 

 that Weigert's fibrin method and picrocarmin gave the most beau- 

 tiful results. 



Cultivation. The diphtheria bacillus grows readily upon all 

 the ordinary media, and is very easy to obtain in pure culture, 

 plates not being necessary. It is purely aerobic. 



Colonies. Upon the surface of gelatin plates the colonies attain 

 but a small size and appear to the naked eye as whitish points with 

 smooth contents and regular, though sometimes indented, borders. 

 Under the microscope they appear granular and yellowish-brown, 

 with irregular borders. Upon agar-agar and glycerin agar-agar the 

 colonies are slower to develop, larger, more translucent, without the 

 yellowish-white or china-white color of the blood-serum cultures, 

 and are more or less distinctly divided into a small elevated center 

 * "Bacteriology in Medicine and Surgery," 1900. 



