VII. 
PATHOGENIC MICROCOCCI NOT DESCRIBED IN 
SECTIONS V. AND VI. 
DIPLOCOCCUS INTRACELLULARIS MENINGITIDIS. 
DISCOVERED by Weichselbaum (1887) in the exudate of cerebro- 
spinal meningitis (six cases), for the most part within the cells. 
Morphology.—Micrococci, usually united in pairs, in groups of 
four, or in little masses ; sometimes solitary and larger (probably 
being upon the point of dividing). Distinguished by their presence 
in the interior of pus cells in the exudate, in this respect resembling 
the gonococcus. 
Stain best with Léffler’s alkaline solution of methylene blue. 
Do not retain their color when treated with iodine solution (Gram’s 
method). 
Biological Characters.—This micrococcus does not grow at the 
room temperature, but upon nutrient agar an abundant development 
occurs in the incubating oven. Upon the surface of agar a tolerably 
luxuriant, viscid growth, which by reflected light is gray and by 
transmitted light grayish-white ; along the line of puncture growth 
occurs only near the surface, indicating that this micrococcus will 
not grow in the absence of oxygen. Upon plates made from agar- 
agar (one per cent) and gelatin (two per cent) very small colonies are 
formed in the interior of the mass, and larger ones, of a grayish 
color, on the surface. The former, under the microscope, are seen to 
be round or slightly irregular, finely granular, and of a yellowish- 
brown color. The superficial colonies have a yellowish-brown nu- 
cleus, surrounded by a more transparent zone. The growth upon 
coagulated blood serum is very scanty, as is that in bouillon; no 
growth occurs upon potato. This micrococcus quickly loses its power 
of reproduction in artificial cultures—within six days—and should 
be transplanted to fresh material at short intervals—two days. 
Pathogenesis.—Mice are especially susceptible, and usually die 
within forty-eight hours after inoculation. Also pathogenic for 
guinea-pigs, rabbits, and dogs. 
