PROGRESS OF MICROSCOPICAL SCIENCE. 
237 
ancl more or less strongly swollen. These changes are due, says the 
‘Lancet,’ Sept. 21, 1872, to congestion of the severed blood-vessels, 
and to the imbibition of the serous transudate. In a short time the 
part of the centric extremity lying near the cut and the whole peri- 
pheric part assumes a cloudy-yellow tint, becomes somewhat attenu- 
ated, and tears easily. The sheath of Schwann undergoes, at first at 
least, very little alteration ; the medullary sheath, on the other hand, 
coagulates, and breaks down into a finely granular detritus. The 
axis cylinder early appears enlarged and swollen, but soon attenuates, 
and ultimately disappears entirely. In the later stages of the process 
of disintegration it is impossible by any means to bring it into view. 
Benecke has never been able to find that the degenerative process 
progresses in an orderly manner in either direction from the lesion ; 
but believes that it takes place coincidently throughout the whole 
length of the peripheral extremity, and in the immediately adjoining 
portion of the centric end. But even whilst disintegration is advancing, 
the process of regeneration has commenced, in the form of multipli- 
cation by fission of the nuclei of the neurilemma, or sheath of Schwann. 
These soon become converted into elongated fusiform bodies, and after 
a time form the only contents of the empty and collapsed sheaths, 
which then, he thinks, disappear. The protoplasmic processes of the 
new elongated nuclei now undergo fusion, and unite to form pale 
slender bands coincidently in the cicatrix and in the peripheral end 
of the divided nerve, which is thus brought into organic connection 
with the central stump. In the further progress of the regenerative 
process a medullary sheath is gradually formed around the primitive 
bands or cylinder axes originating from the nuclei. These last no 
longer retain their ordinary appearance, but become homogeneous, a 
few only remaining in each fibre, from which the normal sheaths of 
Schwann are afterwards developed. Upon the whole, therefore, it 
would appear that after section the proper nervous tissue of the 
entire peripherical portion of the nerve undergoes disintegration and 
disappears, whilst regeneration is effected by a process precisely 
analogous to that which many observers have demonstrated to occur 
in the natural development of the nerves in the tail of the tadpole 
and in the embryo of the fowl ; the cylinder axis being first formed 
by the coalescence of nuclei, to which the white or medullary sub- 
stance and the sheath of Schwann are subsequent additions. 
Muscle as a Constituent of Nerve Tissue . — Signor Tigri has shown 
the presence of muscular fibres among the nerve fibres of tho cerebro- 
spinal nerves and the ganglia of the sympathetic.* When an irrita- 
tion is applied, contraction is caused, and the liquid contents of the 
nerve fibres are caused to vibrate, and the motion is conveyed thus 
centripetally or centrifugally. In reference to these anatomical and 
physiological peculiarities, he calls the ganglia of the sympatheticus 
magnus, as well as the large ganglia of the brain, “ nerve hearts.” 
He considers that the so-called Remak’s nerve fibres are muscular 
fibres. 
* ‘ Gaz. Med. Ital.’ 
