298 BA CTERIOLOG Y. 



the bacillus of diphtheria that they might easily be mis- 

 taken for that organism if subjected to microscopic ex- 

 amination only. 



The bacillus diphtherice of Loeffler (its discoverer) can 

 readily be identified by its cultural peculiarities in con- 

 nection with its pathogenic activity when introduced 

 into tissues of susceptible animals. In guinea-pigs and 

 kittens the results of its growth are histologically identical 

 with those found in the bodies of human beings who 

 have died of diphtheria. 



When studied in pure culture, its morphological and 

 cultural peculiarities are as follows : 



MORPHOLOGY. As obtained directly from the diph- 

 theritic deposit in the throat of an individual sick of the 

 disease, it is sometimes comparatively regular in shape, 

 appearing as straight or slightly curved rods with more 

 or less pointed ends. More frequently, however, spindle 

 and club shapes occur and not rarely many of these rods 

 take up the staining irregularly ; in some of them very 

 deeply stained, round or oval points can be detected. 



When cultures are examined microscopically it is 

 especially characteristic to find irregular, bizarre forms, 

 such as rods with one or both ends swollen, and very 

 frequently rods broken at irregular intervals into short, 

 sharply marked segments, either round, oval, or with 

 straight sides. Some forms stain uniformly, others in 

 various irregular ways, the most common being the ap- 

 pearance of deeply stained granules in a lightly stained 

 bacillus. 



By a series of studies upon this organism when cul- 

 tivated under artificial conditions, we have found that 

 its form depends very largely upon the nature of its 

 environment. That is to say, its morphology is always 



