728 DR ALEXANDER BRUCE AND DR JAMES W. DAWSON ON 
concluded that the nerve fibres of the cord are capable of regeneration, even to the 
complete restoration of function, as long as the blood-vessel apparatus of the cord is 
intact. The fibres had arisen by the axis-cylinder breaking up into its primitive fibrils ; 
one axis-cylinder could therefore become connected with several ganglion cells below 
the point of compression. In a recent paper FIcKLER considers that the new-formed 
fibres were derived, not from the pyramidal tract above the lesion, but from the ganglion 
cells of the grey matter and of the spinal ganglia. The appearance of the sheath of 
Schwann as soon as the fibres enter the vessels, argues in favour of the mesodermic 
nature of the sheath of Schwann. BIKELEs (1904), in a case of rupture of the cord, 
where the patient survived ten months after the injury, found a certain amount of re- 
generation. Continuous with the regenerated fibres of the proximal portion of the 
posterior root, there were present very delicate irregular fibres in the posterior columns, 
though no other nerve fibres were present. CuiarK (1906), after section of the cord, 
noted that regeneration is limited solely to fibres of peripheral character. He thinks, 
therefore, that the cells of the sheath of Schwann are necessary to regeneration. 
Bre.scHowsky (1906-1909) has made a very careful examination, by the aid of his 
new silver method, of the axis-cylinder formations found within tumour nodules in the 
brain and cord and in the zones bordering areas of compression in the cord. His in- 
vestigations have confirmed him in the conviction of the capability of regeneration of 
the central nerve fibres. The numerous fine fibres ending with rings or button-shaped 
swellings, and the fact that similar fibres were found in the vessel walls—especially of 
the marginal zones—could, he thought, be nothing else than a new formation of fibres. 
In the white matter of the cord the new fibres were present in a direction corresponding 
to the fibre systems of the cord displaced by the tumour, and had arisen from the dis- 
sociation of old nerve fibres persisting within the tumour mass and of fibres of tracts 
interrupted by the tumour. In a case where the posterior nerve roots were penetrated 
by cancer cells and Weigert’s medullated sheath stain showed empty nerve tubes, 
BietscHowsky found in the transition zone between healthy and diseased parts very 
fine fibrils with exactly similar appearances growing from the stump of the interrupted 
fibres. The collateral regeneration of Nacrorrs, found in tabes, must be related to the 
influence of the ganglion cell, though it is admitted that the capsule cells and the cells 
of Schwann’s sheath take their share in the formation of the new fibres. Bin_scHowsky, 
in opposition to Nacrorrs, holds that it has not been proved that the fibrils represent 
the most essential constituent, but thinks rather that they must be looked upon as sup- 
porting axes for the conducting neuroplasm. 
BieLscHowsky concludes that for the regeneration of the fibres in the central nervous 
system two factors are essential; the one, sufficient vascularisation; the other, the 
presence of special decomposition cells. Such cells may possibly exert a chemiotactic 
influence, but more likely, by means of their syncytial connections, exercise a plastic 
function as pre-formed cell bridges. ‘They have therefore the same significance as the 
proliferated sheath of Schwann cells in the regeneration of peripheral nerves. BIEL- 
