DIPHTHERIA GROUP 233 



serum. Occasionally branched forms may be observed. Demmy 

 has shown that the Bacillus diphtherias varies almost from hour 

 to hour in its morphology when grown upon blood-serum. In 

 five hours after the culture is made the cells take the stain uni- 

 formly; in eight hours some cells show vacuolization; in twelve 

 hours the organism is larger and stains unevenly, and within 

 forty-eight hours irregular and clubbed forms are abundant. 

 Wesbrook has constructed a chart which is in common use in 

 laboratories in the designation of the different types of bacilli 

 to be observed. Upon media where growth occurs more slowly 

 than upon serum the organism remains smaller and stains more 



Fig. 99. Bacillus diphtheria, Wesbrook's types: a, c, d, Granular types; a 1 , c 1 , 

 d 1 , barred types; a 2 , c 2 , d 2 , solid types (X 1500) (McFarland). 



uniformly. Whether or not the morphologic types of Wesbrook 

 represent true varieties or differ in their pathogenic properties 

 is a matter of dispute. Wesbrook claims the types which develop 

 rapidly upon blood-serum and show distinct granulation are viru- 

 lent, while the slower growing solid types are relatively non- 

 virulent. It is claimed by others that the latter simply represent 

 the B. pseudodiphthericus, the organism next to be considered. 

 No spores or capsules are produced. The organism is non-motile. 

 Isolation and Culture. Bacillus diphtheria may usually be 

 isolated directly from the throat of a diphtheritic patient in pure 

 culture upon agar or, better, upon blood-serum. In mixed infec- 



