EPIDEMIC CEREBRO-SPINAL MENINGITIS. 219 



of all kinds, among which are crowding of -barracks, dwellings, etc., 

 favor the outbreak of the disease. Persons exposed to these influences 

 are in greater danger, at times of epidemics, than those who live under 

 more favorable circumstances. 



ANATOMICAL APPEARANCES. In recent cases, the result of au- 

 topsy is almost always as follows : The subjects show no emaciation, 

 protracted rigor mortis, or extensive hypostasis ; there are often groups 

 of dried herpes vesicles on the face an other parts of the body ; the 

 muscles are dark ; in rare cases they are pale (Ziemssen). 



The cranium contains much blood ; in the longitudinal sinus there 

 is abundant fluid, or softly-coagulated blood ; the dura mater is more 

 or less tense, and occasionally covered with small hsemorrhagic or pa- 

 chymeningitic deposits. There is usually no effusion between the dura 

 mater and arachnoid ; in the subarachnoid space there is an exudation, 

 which, both in extent and character, occupies about a medium position 

 between the pure purulent exudation in meningitis of the convexity 

 and the priro-serous exudation in basilar meningitis. In almost all 

 cases, the convexity of the cerebrum and the base of the brain are 

 affected at the same time, the latter usually the more severely. The 

 exudation appears to be peculiarly plentiful about the chiasm, in the 

 fossa Sylvii, at the base of the cerebellum, and in the fissures of the 

 cerebrum. The nerves, from the base of the brain, are 'often entirely 

 embedded in it. The brain itself is more or less vascular, almost al- 

 ways less resistant, even becoming pulpy in the vicinity of the ventri- 

 cles; the latter generally contain small amounts of purulent fluid, 

 rarely large quantities of clear serum. 



The dura mater of the spine is more or less vascular, occasionally 

 very tense, especially at the lower part. Between the dura mater and 

 spinal arachnoid there is rarely a clear or purulent opaque fluid. The 

 arachnoid usually presents no peculiarity except a decided opacity. 

 There is more or less purulent fluid between it and the pia mater. 

 The tissue of the pia mater is infiltrated with sero-purulent exudation. 

 This infiltration extends very irregularly ; in most cases the cervical 

 portion is free; the process first begins in the dorsal region, thence 

 extends toward the cauda equina, and is almost exclusively on the pos- 

 terior surface. The puruleritly-infiltrated spots form, irregular humps, 

 broader in the middle, smaller at the ends, which are usually connected 

 together by small striae accompanying the larger vessels. Even where 

 the pia mater does not contain this puro-serous infiltration, its tissue 

 appears thickened and cloudy. The spinal medulla itself is more or 

 less vascular, occasionally infiltrated and relaxed. In a case related 

 by Ziemssen^ the central canal was dilated and filled with purulent 

 Huid. 



