346 BIOLOGICAL PHYSICS 



absorption, are effected, and may be regarded as what 

 might be called a secondary digestion of the neuroglially pre- 

 pared plasmal elements. As neuronogenesis determines 

 the material nature, and functional character, of each 

 neuronal unit, so the individuality of each is maintained, 

 by a continual devotion to individual work, amid the many 

 co-ordinated duties in which it may be called upon to 

 act, and thus the occurrence of automatic ability becomes 

 superadded by continuous use within, more or less, definite 

 limits. 



As excretion from the nerve cells necessitates the 

 existence of hollow axonal processes, so does the onward 

 passage, or circulation, of the axonal substances require 

 the provision of outfall spaces into which these substances 

 can find a means of disposal, or progress, and along which 

 they can find a means of final disposal ; because it is neither 

 logical, nor biological, to suppose that living, or organic, 

 substances, can be otherwise disposed of than by some 

 form of circulation, or movement, away from, and out 

 of, the original, and determining, source of movement. 

 Neuronal circulation must, therefore, find outfall facilities 

 provided amid the elements of the dermal matrix, on the 

 one hand, and into the voluntary musculature, on the 

 other ; and that we contend is what is to be found in 

 both neuronal modes of axonal termination. In the 

 former, or sensory, mode of neuronal termination, we 

 find that the terminal fibrils, in the form of arborisations, 

 break up into dermal cells, and ultimately into epider- 

 mal scales, which finally become detached, and fall off, 

 or exuviate ; while, in the latter, we find that the neural, 

 and sarcous, elements, become continuous through the 

 merging of the neurilemma, and sarcolemma, into one 

 unbroken sheath, in which case we are compelled to 

 recognise that the proper sarcous substance owes its 

 origin to the original neuronogenesis, and neural circu- 

 lation of the white, or medullary, and the axis cylinder, 

 substances. Thus we see, and consider ourselves warranted 

 in claiming, that the neurons are productive alike of nerve 

 energy, and nervine substances, and that the latter are 

 circulated along their axonal processes, and become struc- 

 tural elements in the growth, and maintenance, of skin, 



