EXTRACT XXXI. B. 



ON NEURONOGENESIS, OR NEURAL HISTOGENESIS, 

 AND NEURAL NUTRITION. 



As we have said, the neuron may now be regarded as the 

 neural unit, and the Systemic Nervous System may be 

 regarded as the total embodiment of these units, and hence 

 as the completed nerve hierarchy, in virtue of the 

 possession of which, in its highest type, man occupies 

 the crowning position in the evolutionary progress of the 

 forms of life yet known to science, and the facile princeps 

 of psycho-physiological developments. 



The neuron may be said to exist, merely in embryo, or 

 anticipation, in the great domain of vegetable life, and in 

 that of animal life innervated by a sympathetic nervature, 

 as well as in those structures and organs outside the 

 systemic nervous system dependent on sympathetic inner- 

 vation, including the basal substance, and neuro-dynamic 

 elements, of systemic innervation, psychic, and neural, 

 cerebral, spinal, and peripheral. That being so, by 

 closely observing the disposition of the matrix in which the 

 future systemic nervous system is to be developed, we 

 become aware of the preliminary preparation of a great 

 amorphous collection of a somewhat faintly organised 

 " medullary" substance within the areas of future systemic 

 neuronogenesis, to be known in the future by the name of 

 neuroglia, and to be found deposited wherever the neurons 

 take their origin, whether in the brain, cord, or ganglia. 



This substance, the neuroglia, may be regarded as the 

 materio-dynamic sine qua non of all neuronogenesis, and 

 the potential matrix, out of which grow, or in which are 



