Staining 425 



This resemblance is further increased by the fact that the 

 cocci are usually found inclosed in the protoplasm of the 

 leukocytes. Weichselbaum, by whom this was first ob- 

 served, found it constant in sections of the brain and its 

 membranes, though in the exudate of the disease a good 

 many free cocci may be observed. It was this peculiar 

 relationship to the cells that led Weichselbaum to name 

 the organism Diplococcus intracellularis. Many of the cocci 

 inclosed in the cells are apparently dead and degenerated, 

 as they stain badly and do not grow when the pus is trans- 

 ferred to culture-media. 



Identification. Carl Frankel, in discussing the micro- 

 organism, points out that its morphologic peculiarities have 

 much in common with the pneumococcus, so that the most 

 refined methods of differentiation should always precede a 

 positive determination. Its resemblance to the gonococcus 

 should also be kept in mind. 



Perhaps the greatest difficulty obtains in making a 

 certain differentiation between the meningococcus and 

 Micrococcus catarrhalis (q. v.), especially when such investi- 

 gations are intended as discovering the former organism in the 

 nasal discharges. This cannot be done by microscopic ex- 

 amination, but must be achieved through cultivation of the 

 organisms and observation of the cultures. Micrococcus 

 catarrhalis grows well upon nearly all culture-media; menin- 

 gococci, very sparsely except upon special media. The former 

 organism grows fairly well at room temperatures (20 C. or 

 less) ; the latter, only at 25 C. and above. The colonies of the 

 former are coarsely granular ; those of the latter, finely granu- 

 lar. 



Staining. The organism is easily stained with the usual 

 aqueous solutions of the anilin dyes. According to Weich- 

 selbaum, Mallory, and Wright it does not stain by Gram's 

 method. 



For staining the meningococcus the method of Pick and 

 Jacobsohn* is highly praised by Carl Frankel, who modifies 

 it by adding three times as much carbol-fuchsin as is recom- 

 mended in the original instructions, which are as follows: 

 Mix 20 c.c. of water with 8 drops of saturated methylene-blue 

 solution; then add 45 to 50 drops of carbol-fuchsin. Allow 

 the fluid to act upon the cover-glass for five minutes. The 

 cocci alone are blue, all else red. 



* "Berliner klin. Wochenschrift," 1896, S. 811. 



