i 4 METAPHYSICS 



The greater part of the brain substance proper is com- 

 posed or made up of a substance or material called the 

 neuroglia, the matrix or stroma of which constitutes the 

 foundation texture or framework of all the parts of 

 the nervous system enumerated above, a substance which 

 is composed of a great series of minute sympathetically 

 innervated cells, connected by a meshwork of uniting 

 and intervening very minute fibres or fibrils, amid which 

 is strown, or into the interstices of which is filled, from 

 the capillaries of the blood circulation, a great mass, or 

 as much as the structure can hold, of an amorphous or 

 finely granular material. 



This substance, the neuroglia, we must regard as the 

 soil, so to speak, on and in which the various neurons, 

 composing the systemic nervous system generally, take 

 root and grow and from which they extract their constantly 

 required nourishment. 



The neuron, or unit of nerve texture, may be described 

 as a cell composed of its containing wall and its contents, 

 having attached and continuous with it a series of pro- 

 cesses called the dendritic and axonal, the former, the 

 dendritic processes, or dendrons, with their attached 

 gemmules, seeming to us to perform the functions of 

 rootlets to which, by the way, they bear a great resem- 

 blance in the neuroglial soil or substance, and to take 

 up the nourishment on which the cell grows, while the 

 latter or axonal processes, or axons, become continuous 

 with what is called the medullary and the axis-cylinder 

 or inner and conducting substances of the nerve fibre. 



The intra-cellular substance proper consists of and be- 

 comes continuous with the " white substance of Schwann," 

 which constitutes the great insulating and protecting 

 envelope of the greatest part of the nerve fibres distri- 

 buted throughout the various structures of the body. 



Inside this intra-cellular covering of what we have 

 called " the white substance of Schwann," or the medullary 

 substance, and enclosed in its own containing membrane 

 or wall, is the nucleus. This nucleus in turn is found to 

 contain, within its containing envelope, a substance which 

 may be regarded as continuous with the axis-cylinder of 

 the nerve-fibre, proceeding or springing from it, and 



