THE BACILLUS AND THE BACTERIOLOGY OF DIPHTHERIA 187 



serum cultures, especially, and from other media less constantly, stain 

 in an irregular and extremely characteristic way. (See Fig. 74.) The 

 bacilli do not stain uniformly. In many cultures round or oval bodies, 

 situated at the ends or in the central portions, stain much more intensely 

 than the rest of the bacillus. Sometimes these highly stained bodies 

 are thicker than the rest of the bacillus; again, they are thinner and 

 surrounded by a more slightly stained portion. The bacilli stain in 

 this peculiar manner at a certain period of their growth, so that only 



FIG. 74 



FIG. 75 



FIG. 74. One of very characteristic forms of diphtheria bacilli from blood-serum cultures, showing 

 clubbed ends and irregular stain, x 1100 diameters. Stain, methylene blue. 



FIG. 75. Extremely long form of diphtheria bacillus. This culture has grown on artificial media 

 for four years and produces strong toxin. X 1100 diameters. 



FIG. 76 



FIG. 77 



FIG. 76. Diphtheria bacilli characteristic in shapes, but showing even staining. In appearance 

 similar to the xerosis bacillus. X 1100 diameters. Stain, methylene blue. 



FIG. 77. 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. 



a portion of the organisms taken from a culture at any one time will 

 show the characteristic staining. In old cultures it is often difficult 

 to stain the bacilli, and the staining, when it does occur, is frequently 

 not at all characteristic. The same round or oval bodies which take 

 the methylene blue more intensely than the remainder of the bacillus 

 are brought out still more distinctly by the Neisser stain. 



The Neisser stain is carried out by placing the cover-slip smear of 

 diphtheria or other bacilli in solution No. 1 for from two to three sec- 



