ON NEURONOGENESIS 343 



planted, produced, and reared, or evolved, the potential cell 

 elements of the coming systemic nervous system, by the 

 action, or operation, of the sympathetic, or innate, selective, 

 and formative, energies of the fertilised ovum, on its stored, 

 and actively vitalised, material. During this stage of early 

 embryonal, or blastodermic development, and differentia- 

 tion, a structure hitherto unknown in the formative 

 activities of organic perpetuative vitality is thus introduced, 

 by the advent of the ectodermal into the united, and dual, 

 regime of meso- and hypo-dermal evolution a regime which 

 has hitherto met all the necessities, and requirements, of 

 vegetable, and vegetative, life, and which has made possible 

 the introduction of an entirely new, and higher, specific 

 method of organisation, by which the way has been paved 

 for the production of the genus homo, with all the distin- 

 guishing characteristics of humanity, physical, mental and 

 moral. Thus has been marked one of the greatest epochs 

 in the history of living forms, as they have existed in the 

 past, or from the beginning, and one of the most profound, 

 and far-reaching, of the developmental changes undergone 

 by the embryonic organism of man. 



The ectoderm is the structural foundation laid down by 

 the sympathetic nervature, and its elements are so arranged 

 that the formative energies by which they are inspired, so 

 to speak, initiate, and fully effect, the hitherto unknown 

 process of neuronogenesis, and lo ! a systemic nervous 

 system has been added to the economy of organic evolution, 

 and to the formative activities of the higher animal life. 



The process of neuronogenesis resembles that of general 

 histogenesis, but is specifically different in many of its 

 details, and organic results ; thus the phenomena of 

 proliferation, by which the renewal, or substitution, of lost 

 cells is effected in so-called non-nervous textures, are 

 conspicuous by their absence, and it follows that systemic 

 nerve cells once lost are never renewed, and that the 

 structures dependent for their support on those cells also 

 perish. Neuronogenesis is effected gradually, as the 

 ectodermal textural area becomes mingled with, and 

 incorporated in, the meso- and hypo-dermal textural areas, 

 single neurons, or groups of neurons, of spongioblastic 

 origin, being added, more or less rapidly, as the process 



