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 F : F . . 950 parts. 
Acetic acid (glacial) i : F - 50 
No. 2. 
Bismark brown ‘ é , ; 7 1 part. 
Boiling distilled water . ‘ : . 600 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, witha 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 Léffler. A small percentage of virulent 
bacilli fail to take the Neisser stain, and quite a few 
non-virulent pseudodiphtheria 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 
