BIOLOGY AND MORPHOLOGY. 239 



Alcohol (96 per cent.), 20 parts ; 



Methylene-blue (Gruebler), 1 part ; 



Distilled water, 950 parts ; 



Glacial acetic acid, 50 " 



Wash and stain with the following for from three to five 

 seconds : 



Bismarck-brown, 1 part; 



Boiling distilled water, . 500 parts. 



This is followed by repeated washings in water. The bacilli 

 are stained dark brown with a dark-blue body at one or both 

 ends (Fig. 99). The bacilli taken from recent cultures 



FIG. 99. 



Non-virulent diphtheria bacilli, showing stain with Neisser's solutions, supposed 

 to be characteristic of virulent bacilli. Bodies of bacilli in smear, faint brown ; 

 points, dark blue. (Park.) 



invariably show this polar staining. The pseudobacilli are 

 stained a uniform brown. 



The germ attains its maximum development at the temper- 

 ature of the body. It is a facultative anaerobe. One marked 

 cultural characteristic is the exceedingly rapid growth on 

 blood-serum. The diphtheria colonies appear a long time 

 before those of any other organism. A growth sufficient for 

 diagnostic purposes always occurs in from nine to twelve 

 hours. 



