76 LABORATORY BACTERIOLOGY 
Note with special care the morphology of the bacteria and 
make a drawing of a few of them. 
Examine very carefully a guinea pig (furnished) which has 
died from the effect of inoculation with diphtheria organisms. 
114. Neisser’s method of staining diphtheria bacteria. Neisser 
has recommended the following method of staining, in which 
2 solutions are employed ; viz., 
1. One gram of methylene blue (Griibler’s) is dissolved in 
20 cc. of 96% alcohol, which is then mixed with 950 cc. of 
distilled water and 50 cc. of glacial acetic acid. 
2. Two grams of vesuvin are dissolved in x litre of boiling 
distilled water and filtered. 
The cover-glass preparations are stained in (1) for from 2 to 
5 seconds, washed in water, and then stained in (2) for from 
5 to 10 seconds, again washed in water, dried, and mounted. 
Stained in this manner the bacilli are brown, and contain 2, 
or rarely 3, but never more, blue corpuscles. The corpuscles 
are oval, not round, in shape, and their diameter appears 
greater than that of the bacilli in which they are situated.? 
1 Clinically, Bact. diphtherie is to be differentiated from the pseudo- 
diphtherize organism and from a bacillus which has been found in 
decayed teeth, and which is said to résemble very closely in its mor- 
phology the Klebs-Loeffler bacillus. It is also to be distinguished from 
the xerosis bacillus isolated by Neisser and from Hoffman’s bacillus. For 
detailed descriptions of these organisms, see text-books. 
