26 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
In all Vertebrates one of tlie fibres is central and the other peripheral ; 
moreover, in a large number of cases the central prolongation is more 
delicate than the peripheral. The spinal ganglia of Vertebrates ought, 
then, to be considered as nuclei of real origin for the sensory part of all 
the spinal nerves, and for the central as well as for the peripheral parts. 
The researches of the last five years have shown that the fibres of the 
posterior roots of the spinal nerves, on arriving in the medulla, bifurcate 
there, and that the two branches of the bifurcation end in the grey 
matter by terminal ramifications. These fibres do not begin, but end in 
the medulla. 
With regard to some of the ganglia situated on the course of the 
cerebral nerves, it is clear that the ganglia of the fifth, of the glosso- 
pharyngeal and of the vagus are in all points comparable to the spinal 
ganglia ; the spiral ganglion of the auditory nerve is also comparable to 
a spinal ganglion, but the nerve- cells retain the bipolar form. 
Degeneration and Regeneration of Injured Peripheral Nerves.* — 
A. Freiherr von Notthafft has made one hundred experiments on dogs, 
guinea-pigs, and rabbits, in order to study the processes of degeneration 
and regeneration in injured peripheral nerves. After any injury (burning, 
crushing, or incision) which totally destroys the nerve-substance at any 
one spot, there is a degeneration of the whole peripheral portion and of 
a smaller central portion about 1 • 5 cm. in length. Beside the injured 
region there is a destruction of medullary and axial fibres as the direct 
result of the wound. The “ paralytic ” degeneration which follows after 
forty-eight hours is due to several causes : the loss of fluid narrows the 
axial fibres, their shrivelling separates the medulla into pieces, the con- 
traction of the pieces produces a transverse division of the axial cylinder, 
and so on. A division of nuclei and an increase of the protoplasm in 
Schwann’s sheath perhaps help in the progressive disruption. The 
degenerating medulla exudes into the lumen of the sheath a fluid which 
is gradually absorbed. The medullary sheath does not undergo fatty 
degeneration, though infiltration of fat may occur, nor does it undergo 
chemical modification after the manner supposed by Neumann and 
Eichhorst, nor do leucocytes help, nor is the proliferation of nuclei the 
sole cause of degeneration, as Ranvier maintains. The degeneration 
spreads very rapidly from centre to periphery. It is likely that the 
proliferating nuclei of Schwann’s sheath help both in degeneration 
and regeneration. With the origin of new axial filaments they have 
nothing to do. The new nerve-fibres always grow from the old central 
stumps, and the growth is continuous from centre to periphery. They 
appear about the eighth or ninth day, and begin to get a medullary 
sheath about the tenth or eleventh day. It seems likely that the new 
Schwann’s sheath is formed from the cells of the old one. The regene- 
ration of severed nerves is most likely if the ends be tied, or, when that 
is impossible, if another piece be interpolated by means of silk thread 
between the two ends. 
Free Intra-epidermic Nerve-endings.| — Prof. A. Van Gehuchten, 
applying the method of Golgi to the skin of rats and mice, finds that 
* Zeitschr. f. Wiss. Zool., lv. (1892) pp. 134-88 (1 pi., 2 figs.). 
t Verhandl. Anat. Geselh, 1892, pp. 66-9. 
