EPIDEMIC CEREBRO-SPINAL MENINGITIS 251 



EPIDEMIC CEREBRO-SPINAL MENINGITIS. 



As the result of observations on this disease in different parts 

 of the wo'rld, it has been now established that the causal agent 

 is the diplococcus intracellularis meningitidis, first described by 

 Weichselbaum, and now often known as the meningococcus. 

 This organism is a small coccus measuring about 1 //, in diameter ; 

 it usually occurs in pairs, the adjacent sides being somewhat 

 flattened against each other. In most cases the cocci are chiefly 

 contained within polymorphonuclear leucocytes in the exudation 

 (Fig. 70) ; in some cases, however, the majority may be lying 

 free. It stains readily 

 with basic aniline dyes, 

 but loses the stain in 

 Gram's method. Both 

 in appearance and in its 

 staining reactions it is 

 similar to the gonococcus 

 (vide infra). The organ- 

 ism can readily be culti- 

 vated outside the body, 

 but the conditions of 

 growth are somewhat re- 

 stricted agar with an 

 admixture of serum or 

 blood (preferably human) 

 is most suitable (p. 43). 

 Strains separated in dif- 



ferent epidemics appear 

 ,. t_, T 

 to present slight indi- 



vidual variations, but 

 the following description 



may be taken as summing up the common characters : Growth 

 takes place best at the temperature of the body, and practically 

 ceases at 25 C. On serum agar the colonies are circular discs with 

 a somewhat opaque slightly granular centre and a delicate trans- 

 parent margin (Fig. 71), and possessing a smooth, shining sur- 

 face; they have little tendency to become confluent. When 

 examined under a low magnification the colour is seen to be 

 somewhat yellowish, and the margins usually are smooth and 

 regular, though on some media slight crenation may appear. 

 The colonies may be of considerable size, reaching sometimes 

 a diameter of 2 to 3 mm. on the third day. On plain agar the 

 colonies are very much smaller, and sometimes no growth 



FIG. 70. Film preparation of exudation from 

 a ca e of meningitis showing the meningo- 

 cocci within leucocytes. See also Plate I., 

 jrj g 3^ 



Stained with carbol-thionin-blue. x 1000. 



