MORPHOLOGY 



251 



(Size and form were as will be seen found to be in close relation to similarity 

 in staining reaction.) 



(a) Irregularly beaded bacilli long and faintly stained -the type most 

 frequently seen. 



. FIG. 165. FIG. 166. 



FIGS. 163, 164, 165, and 166. Types of diphtheria bacilli from young serum cultures. 



Mounted in dilute Lceffler's blue (1 in 5 with water). Oc. 4 ; obj. yVth, Zeiss. 



(/3) Regularly beaded bacilli streptococcal forms stain darkly and may 

 be mistaken for streptococci. 



(y) Barred, segmented or banded forms. 



(6) Uniformly stained bacilli. 



(e) Oval bacilli with one unstained septum. 



[This last type is found in greatest numbers in very young cultures : they 

 are probably young forms, and it is to be noted that individuals of this type 

 are morphologically -practically indistinguishable from typical forms of 

 Hofmann's bacillus.] 



Branched forms of the diphtheria bacillus have been described by Babes, 

 Escherich, Concetti and others. 



Involution forms in which one or both ends are swollen giving the organism 

 a pear-shaped, clubbed, or dumb-bell-like appearance are sometimes met 

 with in old cultures and in smears made from the false membrane. 



Staining methods. 



(a) The diphtheria bacillus stains readily with the basic aniline dyes. 

 Films from cultures or membranes may be stained with diluted Loeffler's 



