DIPHTHERIA BACILLUS. 335 



1 for from two to three seconds, and then, after washing, 

 in No. 2 for from three to five seconds. The bacilli 

 will then appear either entirely brown or will show at 

 one or both ends a dark-blue round body. With char- 

 acteristic diphtheria bacilli taken from a twelve to 

 eighteen hours' growth on serum nearly all will show 

 the blue bodies (Fig. 44), while with the pseudotype 

 (Fig. 45), to be described hereafter, few, if any, will 

 be seen. 



The solutions are as follows : 



No 1. 



Alcohol (96 per cent. ) . . . . 20 parts 



Methylene blue (Griibler) . . .- 1 part 



Distilled water . *. . . . 950 parts. 



Acetic acid (glacial) ... . 50 " 



No. 2. 



Bismark brown . . . . . 1 part. 

 Boiling distilled water ... . 500 parts. 



The Neisser stain has been advocated in order to 

 separate the virulent from the non-virulent bacilli 

 without the delay of inoculating animals; but in our 

 hands, with a very large experience, neither the Neisser 

 stain nor other stains, such as the modifications of the 

 Roux stain, have given any more information as to the 

 virulence of the bacilli than the usual methylene-blue 

 solution of Loffler. A small percentage of virulent 

 bacilli fail to take the Neisser stain, and quite a few 

 non-virulent psetidodiphtheria bacilli show the dark 

 bodies. In New York there are also a large number 

 of bacilli which seem to have all the staining and cul- 

 tural characteristics of the virulent bacilli, and yet are 

 non-virulent in the sense that they produce no specific 



