EXTRACT XXXVI. 



ON THE DEVELOPMENT OF SOME OF THE ORGANS 

 OF SENSE, AND THE MANNER OF ARRANGEMENT 

 AND DISTRIBUTION OF THE CEREBRAL AND SPINAL 

 MENINGES AT THE OPENINGS OF EXIT OF THE 

 CEREBRO-SPINAL CAVITY. 



IT may now, we are convinced, be accepted as true that 

 the systemic nervous system is enclosed by the meninges, 

 or their equivalents, throughout its entire extent, both 

 within and without the cerebro-spinal cavity, and that the 

 nervous system, and its meningeal, or equivalent containing 

 textures, are exactly conterminous, and parallel, in extent, 

 and distribution. That being so, we may take it that the 

 developing nerve textures are provided with, or push 

 before them, their meningeal, or peripheral, coverings, to 

 the limit of their extensions, where they remain a permanent 

 means of protection, support, and inhibition. Accordingly, 

 therefore, to the nature of the particular nerve, whether it 

 be special, or general, we find a particular arrangement, and 

 adaptation, of the meninges, in their peripheral develop- 

 ment, to suit its particular circumstances and function. 

 Thus, the spinal nerves, and the cephalic nerves, with the 

 exceptions of the second, and first, pairs, in passing out of 

 the cerebro-spinal cavity simply push before them, on their 

 exit from it, an extension, or projection, of the various 

 meningeal folds with which they are immediately sur- 

 rounded, and carry them to their respective terminations 

 in unbroken continuity, and distinctiveness of texture, as 

 well as, with their inter-spaces, patent, and capable of circu- 

 lating their contained cerebro-spinal fluid or lymph. The 



