334 BACTERIOLOGY. 
same culture individual bacilli differ much in their 
size and shape. The two bacilli of a pair may lie 
with their long diameter in the same axis or at an 
obtuse or an acute angle, or the pairs of bacilli may 
lie side by side or irregularly across each other. The 
bacilli possess no spores, but have in them highly 
refractile bodies at certain stages in their life. 
The Klebs-Léffler bacilli stain readily with ordinary 
aniline dyes, and retain fairly well their color after 
staining by Gram’s method. When Léffler’s alkaline 
solution of methylene-blue is applied cold for five min- 
utes or warm for one minute the bacilli from blood- 
serum cultures especially, and from other media less 
constantly, stain in an irregular and extremely charac- 
teristic way (see Fig. 41). Many of 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 seem to stain in this peculiar manner at a cer- 
tain period of their growth, and more when grown on 
some media than on others, so that only a portion of 
the organisms taken from a culture at any one time 
will show the characteristic staining. In old cultures 
the bacilli stain poorly and not at all in a characteristic 
way. 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. 
