OCCURRENCE OF CAUSATIVE AGENTS. 137 



The portal of entry for the bacteria in cases of epidemic 

 meningitis has not yet been determined with certainty. 

 The principal causative agent of this disease was, until 

 recently, believed to be the diplococcus lanceolatus Fran- 

 kel, which was found in numerous cases in pure culture. 

 A special organism is, however, to be taken into considera- 

 tion in connection with the etiology of epidemic cerebro- 

 spinal meningitis namely, the diplococcus intracellularis 

 meningitidis (Weichselbaum, Jager). This is a biscuit- 

 shaped organism, arranged in pairs, which is almost always 

 contained within the cells, and which is strongly suggestive 

 of the gonococcus. It is readily stained in the exudate, 

 but with more difficulty in sections. The most suitable 

 stain is Loffler's methylene-blue. The organism does not 

 stain by Gram's method, although Jager maintains that it 

 does. It grows best at 37 C. (98.6 R). On agar- 

 plates there develop superficial gray colonies that with 

 low powers of the microscope appear- dirty-yellow at the 

 center and become lighter toward the periphery. The 

 deep colonies are quite small, and marked by fine granula- 

 tion and a slightly indented border; Upon glycerin-agar 

 there develop small gray colonies that at times coalesce 

 to form a thin coating. Upon blood-serum a slight deposit 

 forms. In order to continue the culture of meningococci for 

 a protracted period they must be reinoculated from every 

 four to six days. They are feebly pathogenic for mice and 

 guinea-pigs on introduction into the thoracic or abdominal 

 cavity, and for rabbits on introduction into the blood-stream. 



The clinical diagnosis is based upon the principle that 

 with the simultaneous existence of some other infectious 

 disease as, for instance, pneumonia, otitis, tuberculosis 

 the causative agents of these conditions may be considered 

 the cause of the meningitis. The absence of any such 

 simultaneous organic disease justifies a diagnosis of epidemic 

 cerebrospinal meningitis. 



A direct bacteriologic diagnosis is possible during life by 

 means of puncture of the spinal canal, which has now been 

 quite extensively practised. Preparations are made from 

 the exudate, and agar-tubes and serum-tubes, or agar-plates, 

 are inoculated, and animals are infected. If tuberculosis is 

 suspected, the specific stain for tubercle-bacilli must be em- 

 ployed. To obtain the causative agents from the meningeal 

 pus after death, the same plan is pursued. As the diplo- 



