ON NEURONOGENESIS 345 



tures, the dermal envelope, and the musculo- skeletal 

 framework of the body. 



In so doing we must come to the belief, or be forced 

 to the conclusion, that the doctrine of non-excretion by 

 the nerve cell is untenable ; and must, therefore, be 

 prepared to concede that it also excretes, and necessarily 

 along the lines of least resistance, the lumina of the axonal 

 fibre, or fibres the white substance of Schwann, and the 

 axis cylinder substance, being the materials excreted. 



This again presupposes, and necessitates that the axons 

 of all nerve cells, which have been hitherto regarded as 

 homogeneous filaments, capable only of transmitting nerve 

 energy, are twice hollow tubes, enclosing, and transmitting, 

 respectively, the insulating, or white substance of Schwann, 

 and the proper neuronic substance the axis cylinder 

 these two substances being due respectively to the selective, 

 and formative, energies of the cell, and its nucleus, re- 

 spectively, whose containing walls are continued along each 

 axonal process as the primitive, or containing, membranes, 

 of the two substances. 



Viewing the neuroglial matrix, as the common neuronal 

 histogenetic source, and as the result of sympathetic 

 neuro-dynamic formative activity, both in its original 

 development, and its subsequent continual renewal, we 

 discover that its embryonic formation preceded that of 

 the blood, and its circulation, and that it subsequently 

 became inter-penetrated by that circulation, and dependent 

 upon it for nutritive supplies, they being delivered not 

 directly to the neurons, but laid down amid the feltage 

 of the neuroglial matrix, to be taken up as required by 

 the dendritic processes of the individual neurons. 



Neuronal nutrition is, therefore, not effected by direct 

 delivery from the blood vasculature, but through inter- 

 mediate neuroglial agency, where the neuronal plasma 

 has been laid down, and stored, for use when neuronal 

 necessity calls for it, and where it can thus be constantly 

 obtained, free from the exigencies, and uncertainties, of a 

 direct blood circulatory supply, and in quantities according 

 with both particular, and general, neuronal requirements. 



This is a nutritive process conducted on somewhat 

 similar lines to those on which alimentary digestion, and 



