A NEW DEPARTURE IN NEUROLOGY 63 



The subject embraced in the above heading is a very 

 large one, but has not hitherto been given that attention 

 which its importance and extent entitle it to ; neither has 

 it yet emerged from the subsidiary position of unimpor- 

 tance assigned to it, or permitted it, by the earlier, and even 

 modern, observers. The intention, therefore, of the fol- 

 lowing remarks is to excite, if possible, a greater interest 

 in the matter for its own sake, and to obtain from it the 

 practical advantages derivable from a fuller understanding 

 of its true meaning and import in the maintenance of 

 innervation, and as an etiological vehicle in the incidence 

 and spread of disease. 



The cerebro-spinal fluid may be said to occupy every 

 space and inter-space throughout the cerebro-spinal cavity 

 not occupied by proper nervine structures or the non- 

 nervine elements related to, or connected with, these. It, 

 therefore, occupies a position of ubiquity co-extensive with 

 the distribution of the systemic nervature and its related 

 sympathetic nervous system, through the interstices of 

 which it circulates from end to end, sometimes in cisterns, 

 slowly, and sometimes in thinly attenuated streams, rapidly, 

 according to the exigencies of biological hydrostatics and 

 dynamics. 



Its secretion may be regarded as the result of capillary 

 escape of the liquor sanguinis, with which its chemical 

 composition is almost identical, as the blood circulation 

 traverses the meshes of the pia mater on the external 

 surfaces of the brain and cord, or pushes its way through 

 the cavities of the lateral third and fourth ventricles in the 

 form of the choroid plexuses. 



These latter fulfil for the central spaces of the brain and 

 cord what the general pia mater fulfils for the sub-arachnoid 

 and sub-dural spaces, while the fluids respectively secreted 

 by them unite and form one common fluid, which circu- 

 lates to and fro through certain communicating channels, 

 or openings, namely, the foramen of Munro, the pineal 

 gland, the aqueduct of Sylvius, the foramina of Majendie, 

 and several lesser openings situated in the descending 

 cornua of the lateral and the fourth ventricles respectively. 



While these openings of communication afford the 

 means by which the regulation of pressure can be effected 



