DIPHTHERIA. 135 



granules, occasionally situated at one or both extremities or in 

 its central portion, which stain much more deeply than the rest 

 of the cells, and which make of a stained diphtheria prepara- 

 tion quite a characteristic picture under the microscope. 



Neisser's Differential Method. Some forms of false diph- 

 theria bacilli which can not be separated from diphtheria 



FIG. 58. 



Diphtheria bacilli characteristic in shape but showing even staining. In appear- 

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



bacilli by their mode of growth or by their appearance under 

 the microscope, but which are not toxic, must be differen- 

 tiated from the toxin-producing bacilli ; and Neisser has 

 suggested the following method, which is used in a number 

 of municipal laboratories. It consists of two solutions, as 

 follows : 



Solution No. 1. 



Alcohol (96 per cent.), 20 parts ; 



Methylene-blue, 1 part ; 



Distilled water, 950 parts ; 



Glacial acetic acid, 50 parts ; 



Solution No. 2. 



Bismarck-brown, 1 part ; 



Hot distilled water, 500 parts. 



