A Typical Case of Tubercular Meningitis. 183 



floor of the fourth ventricle was thickened, and the seat of con- 

 siderable tubercular deposit. The substance of the cerebrum 

 and cerebellum was slightly softened, but not otherwise 

 changed. The thoracic and abdominal organs were healthy. 



The most notable pathological lesions were in or upon the 

 vessels of the pia mater. I therefore selected my specimens for 

 microscopical study from this structure, and especially that 

 portion which formed the vascular fold between the walls of 

 the left fissure of Sylvius. 



The specimens were stained with hsematoxylin, dehydrated 

 by alcohol, passed through oil of cloves, and mounted in damar. 

 The microscopical appearances presented by them are quite 

 faithfully recorded by the accompanying plate, which is cer- 

 tainly creditable to the enterprise of the publishers of this jour- 

 nal. The several figures will be readily understood by refer- 

 ence to the appended explanations. 



A careful study of a considerable number of mounted speci- 

 mens, under different powers, by different methods of illumina- 

 tion, and by different observers, whose opinions concurred 

 with mine, seems to me to suggest* the following conclusions: 



1. The lesions peculiar to tubercular meningitis are necessa- 

 rily, if not exclusively, confined to the smaller blood-vessels of 

 the membranes (especially the pia mater), and of the brain sub- 

 stance; and all other lesions are probably secondary to those 

 above mentioned, and are, directly or indirectly, produced by 

 them. 



2. The lesions in question are ahvays exterior to the tunica 

 interna, and therefore have no direct structural relation to the 

 circulating blood. 



3. The primary seat of pathological activity in tubercular 

 meningitis, is in the perivascular spaces or canals, which sur- 

 round the smaller blood vessels of the brain and its membranes, 

 as described by His f and others; and in its early stages at 

 least, is essentially inflammatory in its nature, the inflammation 

 being at first limited to the meninges. 



4. As a consequence of the initiative hyperplasia, which re- 



* I use the term " suggest" instead of a more positive term purposely. In all departments 

 of pathology intense activity prevails : new facts are constantly being discovered, and former theo- 

 ries are being displaced or modified. This is especially true with reference to tuberculosis; and 

 hence no positive or permanent conclusions are warranted. 



t Strieker's Histology, p. 231. 



