790 DR ALEXANDER BRUCE AND DR JAMES W. DAWSON ON . 
are formed. The first threads of axis-cylinders appear in close relation to the 
elongated nuclei, and each cell is potentially capable of forming a segment of a 
complete nerve fibre, so that within an old neurilemma sheath may be found parallel 
axis-cylinder filaments which ultimately join with the poles of adjoining filaments to 
form a leash of fibrils. FRrancornt and Durante have observed that in the proliferation 
of the sheath of Schwann nuclei the division may take place in two directions, 2.¢. 
transversely to the longitudinal axis of the cell, and parallel to it. In our preparations 
we have drawn attention to the evidence of the longitudinal cleavage of nucleus and 
cell which results in the formation of the first links of two new chains, which thus give 
the appearance of a dichotomous division and have suggested that a further elongation 
of the cell-chain takes place by transverse cleavage of nucleus and cell. 
Again, regarding the chemiotropic influence attributed by the centralists to the 
sheath of Schwann cells, it is not easy to understand what attracting or directing or 
orienting influence these cell-chains could have in the development of a nodule whose 
fibres cross each other in such varying directions. There is much to indicate that the 
nerve fibres take the path of least resistance, and are guided by the more fixed 
structures in the line of their general growth. 
We have noted these criticisms of the peripherist view in relation to points bearimg 
on our preparations, and we close with a brief statement of three criticisms of the 
outgrowth theory. The supporters of the cell-chain structure of the peripheral nerves, 
firstly, find it difficult to conceive of a prolongation of a cell so disproportionate to the 
element which gave it birth; secondly, believe it impossible that a differentiated 
substance like the axis-cylinder can bud, as such a procedure is against the data of 
general cytology which attributes to differentiated substances only a functional rdle ; 
and finally, they attribute the absence of any satisfactory demonstration of regeneration — 
of fibres in the central nervous system to the absence of the activity of the neurilemma 
cells. 
Conclusion.—F RancinI states that in the histological study of a neuroma an intuition 
came to him of the constitution of the peripheral nerves. We think it right to 
emphasise that we began this investigation with no preconceptions in favour of the 
multicellular structure of the peripheral nerve. We accepted the classical teaching of 
His and Casa that the axis-cylinder is an outgrowth from the central cell and that 
its free end terminates in an incremental cone of growth. A prolonged study of our 
preparations and the further light shed upon them by research into the literature of 
the genesis of the nerve fibres in the embryo, in regeneration, and in tumour formation, 
led us, however, to the following conclusions :—that fusiform nucleated cells linked on. 
to one another have formed embryonic nerve fibres; that in these nucleated fibres, 
which show very distinctly in their segmental structure their origin from individual 
cells, have differentiated to a greater (in the cord) or lesser (in the medulla oblongata — 
