248 DISEASES OF THE BRAIN. 



decidedly new, and have satisfied myself that my views had been gen- 

 erally received ; so, in the present chapter, I shall chiefly follow my 

 previous work. 



ETIOLOGY. We are unacquainted with the injurious power whose 

 action induces this form of meningitis, and whose spread over greater 

 or less extents of country excites more or less extensive epidemics of 

 the disease. But we may regard it as very probable that epidemic 

 cerebro-spiiial meningitis does not depend on atmospheric or telluric 

 influences, but is rather due to an infection of the body with a specific 

 poison. It is true, the occasional frequent occurrence of a disease in 

 regions generally free from it, and even the affection of several mem- 

 bers of the same family, do not alone justify the conclusion that the 

 disease depends on infection. But the passage of an epidemic from 

 place to place, as is often seen in epidemic cerebro-spinal meningitis, 

 is an important evidence of miasmatic extension. Apparently there 

 is no transfer of the disease by contagion, although solitary instances 

 are brought up to prove the infection of one person from another. 



But cerebro-spinal meningitis does not, by any means, belong to 

 that class of infectious diseases, of which we may take typhus as an 

 example, and of which we shall hereafter speak in a separate section. 

 The consideration of this disease as a peculiar form of typhus, which 

 was formerly so common in France, has been entirely disproved 

 during the late epidemic in Germany. I separate this affection from 

 classes of infectious diseases to which the different forms of typhus 

 belong, on the following grounds: In the latter, the severe con- 

 stitutional symptoms, especially the fever, for the most part, depend 

 immediately on the reception of the infecting material into the blood, 

 and the anatomical changes in the organs, caused by the infection, are 

 very peculiar; they are induced only by infection with the specific 

 poison. In epidemic cerebro-spinal meningitis, on the contrary, the 

 fever and all other symptoms depend solely on the local disease in- 

 duced by the infection, and on its injurious effect on the body, just as 

 they do in croupous pneumonia or in erysipelas ; and the changes in 

 the meninges of the brain and spine are just the same as those some- 

 times induced in other ways. This circumstance also induces me to 

 treat of cerebro-spinal meningitis amcng the local diseases, in spite of 

 its miasmatic origin. 



Epidemics of this disease are more frequent in winter than in sum- 

 mer, and usually disappear as warm weather begins. But there are 

 exceptions to this, which contrast very remarkably with most epidemic 

 diseases. Among the different ages, childhood has the greatest quota 

 of cases and deaths. Persons of middle age are often attacked also, 

 the aged ai rarely affected. Unfavorable hygienic influences 



