784 DR ALEXANDER BRUCE AND DR JAMES W. DAWSON ON 
developed, and, ultimately as the processes of the cells fused and the cell boundaries 
became lost, the central filaments became continuous. In mammals the activity of the 
neurilemma cells in the regeneration of nerves has never been disputed, only its result 
has been questioned. According to the supporters of the cell-chain theory, the pro- 
liferation of the neurilemma nuclei results in the formation of elongated cells which 
fuse to form syncytial cell-chains, and in the syncytial protoplasm an axis-cylinder 
differentiation occurs. 
Now, as the proliferation of the neurilemma nuclei indisputably results in the 
production of a tissue, acknowledged by centralists and peripherists alike to be a 
specific tissue, in the sense that it is a product of the Schwann cells and differs in 
structure, staining, and arrangement from ordinary connective tissue ; further, as this 
specific tissue has, with slight unessential differences, the characters of embryonic nerve 
tissue ; and, further, as the works of Duranrr, BaLLaNcE and Srewart, and BrerHe 
have shown that the production of this tissue from proliferated cells leads to the 
formation of nucleated tubes and fibres with axis-cylinder and commencing myelinisa- 
tion, we have distinct evidence in support of our observations of the formation of 
nucleated tubes and fibres from the alignment and fusion and evolution of fusiform cells. 
(c) In tumour formation.— WerIcHsELBAUM, VrRocay, Fatx, and SCHMINCKE have 
all described the formation of a neurogenous tissue composed of protoplasmic nucleated 
tubes or bands in the condition of embryonic, and even more fully differentiated, nerve 
fibres. They bring this tissue into relation to a proliferation of the cells of Schwann’s 
sheath or the less differentiated precursors of the same—nerve fibre cells. The 
transition between fusiform cells and nucleated tubes was followed to the increasing 
development within the latter of the differentiated elements of the nerve fibres. 
Verocay emphasised the statement that a tissue giving the characters of immature 
or embryonic nerve fibres must in all cases be related to a proliferation of the sheath 
of Schwann cells or analogous elements. 
Having received this collateral evidence that fusiform cells in development, in 
regeneration, and in tumour formation, may develop a neurogenous tissue composed 
of nerve fibres in the condition of nucleated tubes with a commencing myelination, 
we can now pass to consider the source and nature of the fusiform cells. 
Origin of the Cells.—Two possibilities alone can account for their genesis. The 
one, that they are derived from fixed tissue elements of the nervous tissues ; the other, 
that they are derived from abnormal cells enclosed in the tissues in early development 
—in other words, from embryonal residues. For the first we have no evidence. For 
the second it may be objected that the terms “embryonal residues,” “cell-rests,” 
‘‘cell-inclusions,” convey no concrete conception, yet it must be admitted that some 
such term must be postulated, and the oncology of the cord, in the processes related 
to the closure of the medullary groove, allows a possible relationship between tumour- 
growth and disturbances of development to be more clearly perceived than in most 
tissues. 
