a ee 
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MULTIPLE NEUROMATA OF THE CENTRAL NERVOUS SYSTEM. 125 
fibrils increase in length and penetrate the exudate between the cut ends, each filament 
and fibril having a terminal cone or ring. Collateral intratubular regeneration may 
also occur, the short collaterals being provided with buds or thin tangential collaterals, 
more frequently with rings. ‘The collateral fibres tend to form spirals or groups round 
the oldaxon. Casat has laid great stress on the important fact that during these early 
stages of degeneration there has been no proliferation of cells within which the young 
axis-cylinders could develop, but he adds that from the third day onwards each terminal 
cone appears enclosed by a few cells. 
The passage of the new axis-cylinders across the scar-tissue and into the old sheath 
of Schwann is regulated by chemiotactic substances elaborated by the proliferated cells 
of the sheath of Schwann which have been transformed into the Aaialbandfasern of 
Von Bunener. Casa attributes three functions to the proliferated nuclei: firstly, a 
phagocytic function ; secondly, that of secreting a chemiotactic or neurotrophic substance 
to attract the young fibres from the central end and guide them into the sheaths; and 
thirdly, the function of maintaining the nutrition of the young fibres when they arrive. 
Casa reproaches all who are in favour of autogenous regeneration with having used 
methods “‘ unreliable or insufficient.” Itis impossible to avoid noting here that Lucaro, 
PrrRoncito, and Marinesco—on the strength of whose observations, together with his 
own, Casa claims that the cell-chain conception has been definitely refuted—have all 
used only impregnation methods. 
PoscHaRIsky (1907), who has used Cajal’s and Bielschowsky’s silver methods, 
confirms many of CaJaL’s observations, but has come to different conclusions regarding 
the significance of the early phenomena observed in the two ends. While not denying 
the possibility of growth from the central axon, he looks upon the terminal cones, balls, 
and rings as signs of a dying condition of the axis-cylinder. He believes that regenera- 
tion commences only on the third day, z.e. after the proliferation of the cells of 
Schwann’s sheath is in full activity. He thinks that silver impregnation methods are 
not sufficient to lead to any definite conclusion, whether the new axis-cylinders have 
arisen within these proliferated cells or are outgrowths from the centre. 
Marcuctzs (1908) found, after permanently separating the distal end of a cut nerve 
in the rabbit, that a new tissue arose which agreed in many respects with certain 
embryonal stages of development, 7.e. the axialbandfasern stage of Von Btnoner. In 
the young animal this neurogenous tissue led to a spontaneous regeneration, but in the 
adult never advanced to completely differentiated fibres. Marcutixs, taking his stand 
upon the fact of the undisputed proliferation of the Schwann nuclei and on the generally 
accepted opinion of their ectodermal nature, concluded that under all circumstances an 
autogenous regeneration takes place even without the influence of the central ganglion 
cell. It is incomplete, however, till the functional activity of its elements is brought 
into play, and this can be only when it is anew related to the centre. Hven in young 
animals, where a complete regeneration takes place, the new-formed fibres do not remain 
long in this complete condition, but tend to reassume the axialbandfasern stage. 
