218 THE INFECTIOUS DISEASES. 



ACUTE CEREBRO-SPINAL MENINGITIS. 



This is ari acute infectious disease of which the characteristic lesion 

 is an exudative inflammation of the pia mater of the brain and cord. 



As a rule the inflammation of the pia niater results in a large pro- 

 duction of serum, fibrin, and pus, which infiltrate the pia mater and ac- 

 cumulate in the ventricles, so that the gross appearance of the brain is 

 characteristic. The exudation is especially abundant at the base of the 

 brain and over the posterior surfaces of the cord. In children the dis- 

 teution of the lateral ventricles with purulent serum may be a marked 

 feature, while in adults the quantity of serum is apt to be small. ' 



While the above are the characteristic lesions of this disease, there 

 are a number of secondary or associated septicaemic or toxaemic lesions 

 in different parts of the body. There may be subserous punctate haem- 

 orrhages in the endocardium ; petechiae in the skin ; hyaliii and granular 

 degeneration in the voluntary striated muscle ; occasional multiple ab- 

 scesses in various parts of the body ; suppurative inflammation of the 

 joints; albuminous degeneration of the heart, liver, and kidneys; and 

 hyperplasia of the gastro-intestinal lymphatic apparatus and of the 

 spleen. 



Cerebro- spinal meningitis may occur by itself or in connection with 

 some other acute infectious disease, such as acute lobar pneumonia, 

 mycotic ulcerative endocarditis, pyaemia, multiple suppurative arthritis, 

 otitis media, puerperal fever, typhoid fever, etc. 



It may be epidemic, the lesions, however, being essentially similar to 

 those in the sporadic form. 



Bacterial Excitants. In sporadic cerebro -spinal meningitis the strepto- 

 coccus and staphylococcus pyogenes, micrococcus lanceolatus," the in- 

 fluenza bacillus, the typhoid bacillus, and the gonococcus have been 

 repeatedly found in the exudate. Other bacteria have been described. 



In epidemic cerebro -spinal meningitis, a micro-organism has been re- 

 peatedly found, called by Weichselbaum the Diplococcus intracellularis 

 meningitidis, which is clearly one of the chief if not the sole inciting factor 

 in the disease. It is found in the purulent exudate of the meninges in 

 large numbers, and is usually within the leucocytes or pus cells. 3 



Characters of Diplococcus Intracellularis Meningitidis. 



It is an oval diplococcus not staining by Gram's method. Its growth on artificial 

 media is meagre. It forms small transparent colonies on glycerin-agar at 37 C. which 

 soon die out without frequent transplanting to fresh media. It does not grow at room 

 temperature. Animal experiments are on the whole confirmatory of the belief in its 

 pathogenic activity. 



1 For further details of the lesions in exudative meninigitis see Nervous System. 



2 For bibliography of pneumococcus meningitis see article by Weichselbaum in Kolle 

 and Wasserniann's "Handbuch der Mikroorganismen," Bd. ii., p. 256. 



3 For a study of occurrence of D. intracellularis meningitidis in the nose see Lord, 

 Centralbl. f. Bakteriologie, Abth. I., Bd. xxiv., 1903, p. 641. 



