438 Prof. G. Retzius. Principles of the [June 15, 
experiments upon living animals, that "a peripheral «nerve portion, when 
separated from its cells, is capable of regenerating of its own accord, the 
sheath-cells of the fibres being what really effect the regeneration. 
Fig. 12.—Scheme of the Regenera- 
tion of a Peripheric Nerve. 
The upper part is the central 
portion, the lower part is the 
peripheric portion; in the 
midst is the damaged portion. 
This discovery aroused a great deal of 
attention, and was regarded in many quarters 
as dealing a decisive blow at the neurone 
theory. The researches, which several other 
scientists (Braus, Van Gehuchten, etc.) car- 
ried out, seemed to confirm Bethe’s results. 
On the other hand, fresh researches made 
by Cajal and Perroncito, most carefully and 
accurately, soon proved that Bethe had not 
exercised due care in the researches he 
undertook, and that the conclusions which 
he drew were hasty and incorrect. It was 
plainly shown by Cajal’s and Perroncito’s 
numerous experiments that regeneration 
proceeds solely from the central nerve-por- 
tion, the fibres of which still remain in direct 
connection with its central nerve-cells, and 
that the nerve-fibres of the peripheral nerve- 
portion degenerate; that these however, 
after a time, are replaced and regenerated 
by the fibres of the central nerve-portion, 
which grow towards the peripheral nerve- 
portion, and replace its degenerated fibres 
(fig. 12). A regeneration of this kind, 
issuing from the central nerve-portion, may 
be effected at surprisingly long distances, 
and in spite of great obstacles, even through 
the length of muscles that le in the way. 
It is as if a chemotactic law governed the 
outward growth from the central nerve- 
portion to the periphery, as indeed was 
before shown by the experiments of the 
Swedish pathologist Forssman, in Lund, and still earlier by the experiments 
conducted by the French histologist Ranvier, upon the nerves of Cornea, 
which quickly regenerated after destruction, so that Ranvier considered him- 
self justified in establishing a law of the growth of the nerves towards the 
periphery. 
