2 9 o BIOLOGICAL PHYSICS 



where they are immediately accessible, and available, for 

 neuronal pabulum, the provision of this unusually finely 

 meshed containing texture, or feltage, which is porous 

 enough to permit a free, and untrammelled, functional 

 activity, of the contained nervous elements, and the 

 uninterrupted circulation of the cerebro-spinal fluid. 

 Needless to say, all these provisions are, or have been, 

 marvellously secured, within the apparently almost homo- 

 geneous matrix of the neuroglia, and facilities allowed, 

 whereby its unutilised, and effete, residuum, can be 

 removed, and its peri-vascular, and peri-cellular spaces, 

 kept occupied by a yielding medium of cerebro-spinal 

 fluid, capable of meeting the exigencies of contraction 

 and expansion. 



We, therefore, find, within the texture of this 

 quasi-homogeneous basal elementary nerve substance, a 

 complexity of physico-histological arrangement of its 

 constituent matter, and a system of the most elaborate 

 circulatory inter-spaces, and channels, provided, whereby 

 the nutrition of its contained neurons is secured, and a 

 vital hygienic regime maintained, amid which, the high, 

 and varied, functions of brain, and nervous system, can 

 be performed, without jar, or hindrance, with the maxi- 

 mum of ease, and the minimum of friction. In this 

 region of bodily calm, nevertheless, what mental, and 

 nerve, storms, may, and do, at times prevail ? 



The vital process, or manner, of procedure, involved in 

 the transference of neuronal pabulum, from the capillary 

 blood circulatory media, to the nerve cell textures, 

 represents the first stage, of the last great nutritional 

 rearrangement, and disposal, of organised matter, in the 

 " round of the changes," constituting its life-work, and 

 history, within the body. The pia mater circulatory 

 textures, ooze, distil, or filter, into the inter-spaces of 

 the neuroglial feltage, the amorphous elements of the 

 neuronal pabulum, where they remain, in pristine, or 

 perhaps faintly organised, form, fit for dendritic imbibi- 

 tion, nerve cell disposal, and nerve protoplasmic formation, 

 along with the cerebro-spinal lymph, or fluid, closely 

 allied to the liquor sanguinis in chemical composition, 

 and no doubt derived from it, and continuing, like it, 



