THE SYSTEMIC NERVOUS SYSTEM 355 



canal, therefore, undergoes a continuous thickening, and 

 structural organisation, by a process of deposition of 

 neuroglia, from the blood circulation, within the meshes of 

 its fibre-cellular basis, where, at last, there begin to appear 

 the rudimentary elements of nerve cell, and fibre, in an 

 increasing number, and variety, until the fabric of the 

 complete systemic nervous system is at last laid down, 

 amid the supporting, and evolving, structure, of the sym- 

 pathetic nervous system, part of which constitutes the 

 histological structural element of the neuroglia. 



Evolved from, and founded on, the sympathetic system, 

 the systemic nervous system ultimately rules over, that 

 part of the human organism destined to determine its 

 thoughts, words, and actions, and to enable it to perform 

 the duties of a conscious, and thinking, being, in contra- 

 distinction to, and in supplement of, the merely organic, 

 or vegetative, rule of the sympathetic nervous system, 

 which is responsible for maintaining, the continuity of 

 life, and every organic, and nutritive, process, conducive 

 to it. 



The completed systemic nervous system is composed of 

 brain, cord, and nerves, each of which is evolved from the 

 original embryonic structural elements, necessarily sym- 

 pathetic, in their earliest stages, but which, ultimately, 

 undergo a structural, and functional, differentiation, so 

 complete, as to constitute an entirely new, separate, and 

 voluntary, nervous system, suitable to the supra-organic 

 wants of an articulate, motile, and reasoning being. Need- 

 less to say that this systemic nervous system can be 

 observed in gradual process of evolution, in the various 

 stages of human embryonic, foetal, and post-natal develop- 

 ment, as it is to be seen in its various stages in systemically 

 innervated creatures, from the lowest to the highest ranges ; 

 and needless to say that each stage of the developmental 

 advancement, suffices to meet the systemic wants of that 

 stage. Needless, also, to say that the systemic nervous 

 system represents the highest form of organised matter, and 

 the only form, through which, the highest, and most subtle, 

 form of energy known to science, if it can be said to be 

 really known, can operate, by consciousness, and will, 

 thought, and ideation. 



