786 DR ALEXANDER BRUCE AND DR JAMES W. DAWSON ON 
‘““neurinoma” for tumours of nervous nature derived from the proliferation of nerve 
fibre cells or their precursors. In neuro-glioma the ganglion cells and glia cells are 
both traced to the proliferation of an undifferentiated cell common to both forms, and 
in a case of a neuro-glioma of the temporal lobe Schmincke traced the nucleated 
protoplasmic tubes present also to a common parent cell. He suggests that the 
production of such neuroblast chains in a tumour of the central nervous system may 
throw some light on the development of the central nerve fibres from cells. Glioma 
also are to be traced back to the development of embryonic indifferent cells, without 
excluding the possibility of glioma-formations in later life from already differentiated 
glia tissue. 
Cireumscribed neuromata, including amputation neuromata, are ascribed to the 
proliferation of the sheath of Schwann cells, which thus reassume their primitive 
neuroblastic function and may develop into a-myelinated or myelinated fibres or 
remain at a less differentiated cellular stage. 
From these observations we conclude that there is evidence for the view that 
undifferentiated nerve fibre cells, arisen either from the early medullary tube or 
neural crest and remaining undeveloped in the tissues, may develop into nerve fibres 
through stages which include the fusion of the adjoining ends of linked cells, the 
formation of nucleated plasmodial bands or tubes, and the differentiation of these into 
seomented nerve fibres. Further, that peripheral neuroblasts (nerve fibre cells), from 
the point at which they emerge from the medullary tube, or from the point of the 
medullary tube which they reach from the neural crest, migrate outwards and pro- 
liferate to form a cell-chain, the proximal link of which becomes connected with the 
process of a central neuroblast. For the sensory cerebro-spinal nerves we would 
substitute the ganglionic anlage, derived from the neural crest, as the centre for the 
centripetal and centrifugal growth of the cell-chains, and for the motor cranial nerves 
their superficial origin instead of the line formed by the anterior spinal roots. In- 
different cells (neurocytes) would thus lie in immediate relation to the mesodermic 
tissue which would form the anlage of the connective tissue elements of the cord and 
brain, and in this mesodermic tissue the indifferent cells might remain undeveloped. 
When the invagination of the early medullary tube takes place by the entering vessels, 
some of these indifferent cells would be carried in with the pia and, especially in the 
medulla and pons, where the distribution of the nerve fibres is not so uniform as in 
the cord where the anterior columns run in straight lines, would be carried inwards in 
the walls of the vessels to numerous and widely distributed areas. 
The question of the unification of the processes in the cord with those in the medulla 
and pons here again arises. The analogy with the growing terminal ramifications of the 
new nerve fibres in amputation neuroma, and in the regeneration of nerve fibres 
in the tail of lizards where the new fibres terminate in a brush of fusiform cells, and 
the knowledge that the growing axon of a nerve is surrounded by a capsule of such 
cells, would lead us to assume that the terminal ramifications of the fibres, which break 
