336 BACTERIOLOGY. 



toxin. To one who is accustomed to the Loffler stain 

 it gives as much information as any other as to the 

 specific virulence of the bacilli. The Neisser stain will 

 undoubtedly cause the examiner to suspect more strongly 

 some bacilli of being virulent than the Loffler stain, 

 but with the varieties met with in New York this sus- 

 picion is as apt to be wrong as right. As will be stated 

 more fully later, nothing but the animal inoculations 

 with control injections of antitoxin will separate spe- 

 cifically virulent from non-virulent bacilli. 



The morphology of the diphtheria bacillus varies con- 

 siderably with the different culture media employed. 

 On glycerin agar or simple nutrient agar it is smaller, 

 and, as a rule, more regular in form than when grown 

 on other usual culture media (Fig. 46). Short, spindle, 



PIG. 46. 



Diphtheria bacilli from agar culture. X 1000 diameters. 



lancet, or club-shaped forms, staining uniformly, are 

 here commonly observed. The bacilli which have de- 

 veloped in the pseudomembranes or exudate in cases of 

 diphtheria resemble in shape those grown on blood- 

 serum, but stain more evenly. 



