726 DR ALEXANDER BRUCE AND DR JAMES W. DAWSON ON 
Durck (1908), who has made a very exhaustive microscopic investigation of the 
peripheral nerves in beri-beri, has found in numerous cases a transformation of the 
nerve fibre into a nucleated neuroplasmatic cylinder, 7.e. a cellular regression to the 
axialbandfasern stage. Segments showing this have become functionally incompetent, 
but are none the less specific neurogenous tissue. This specific tissue, DuRCK was con- 
vinced, had arisen from the proliferation of the sheath of Schwann cells, and he believes 
that the changes in the nerves in such conditions as beri-beri form a striking confirma- 
tion of the multicellular structure of peripheral nerves. 
ALZHEIMER (1910) has studied regeneration in experimentally produced lead neuritis 
of guinea-pigs and rice neuritis of fowls. In such neuritis the axis-cylinders may re- 
main preserved for a long time after the myelin sheath has not only degenerated but 
after the degenerated products have been removed. When the axis-cylinder itself has 
disappeared there is found a Wallerian degeneration distally. ALZHEIMER studied the 
regeneration which occurred at such a point of the interruption of the axis-cylinder and 
found numerous terminal divisions of the old axis-cylinder of the central end, also 
numerous collateral branches, and that each new fibril ended in a ring or club. These 
new fibrils grow preferably, but not exclusively, within the intercellular plasmatic bridges 
of the proliferated Schwann cells. Osmic acid preparations show that these new fibrils 
rapidly assume a thin myelin sheath. He believes that the sheath of Schwann cells are 
in the peripheral nervous system the biological equivalents of the glia cells in the central 
nervous system, and that they play, like glia cells also, only a transient rdle in the 
phagocytosis of degenerated elements. 
Throughout the works on regeneration we have heard only faint echoes of the 
intercellular bridge theory of development in the discussion of the genesis of fibres in 
regeneration, but we close this section with the work of ALZHEIMER—a supporter both 
of the outgrowth and intercellular theories of development. 
Note ON THE REGENERATION OF FIBRES IN THE CENTRAL NERvoUS SYSTEM. 
A complete anatomical and functional regeneration of fibres has been proved for 
the peripheral nervous system. Similar proof is wanting for the fibres of the central 
nervous system, but there is evidence both from experimental work and pathological 
conditions that there is a considerable effort at regeneration. In this attempt at 
regeneration a specially important réle seems to be taken by the blood-vessels, which 
act as a conducting path for the new fibres. 
NaGEorTTE (1899-1906) has described a special type of regeneration in tabes, which 
he has designated ‘‘ collateral regeneration.” According to NaGrorvTe, the initial lesion 
in tabes is a transverse neuritis of both anterior and posterior roots, starting from the 
point where the nerves pass through the dura mater. In the anterior roots, in addition 
to the secondary descending degeneration, there is a retrograde degeneration extending 
