VI. 



PATHOGENIC MICROCOCCI NOT DESCRIBED IN 

 SECTIONS IV. AND V. 



9. 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 Loffler'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. 



