ON THE REPRODUCTION OF THE NERVES. 
522 
and perfect nervous substance which united the mass : two ex- 
periments did not succeed, but the cause of failure he attributed 
to himself. At last Arnemann* * * § appeared as the opposer of nearly 
all those who had preceded him. From his numerous experiments, 
he concluded that the regenerated substance was never medullary 
matter, but only thickened cellular membrane ; that, when the 
function was restored, this was only effected by the cellular mem- 
brane during its gradual contraction bringing the divided ends 
of the nerves in contact. Arnemann’s view gave to the subject 
a quite different turn, till Haightonf, in 1795, by his experi- 
ments confirmed Cruikshank’s opinion. He observed that a dog 
whose par vagum on both sides was divided at one time, died 
eight hours after; but that, if there was a space of three days 
between the division of the two nerves, the animal expired within 
the fourth ; and if of nine, within the thirteenth day. The opera- 
tion, however, in all these cases was fatal, and death followed 
sooner or later, in proportion to the space between the division of 
the two nerves. But on extending the distance of time to six 
weeks, the animal survived both operations, and within six weeks 
was perfectly restored. In so far he had certainly confirmed 
Cruikshank’s results; but as the objection might be made to 
both, that the substance of the divided nerves had possibly not 
been reproduced, but that their functions had been carried on by 
other nerves, he divided, after the animal had recovered a second 
time, the eighth pair, which in such a case must have been use- 
less, but the animal died on the second day after the operation. 
Up to this period those weapons only had been used in the 
determination of this question which anatomy and physiology 
afforded; now, however, the assistance of chemistry was consult- 
ed. ReilJ had discovered a new method for distinguishing the 
true nervous substance from the neurilema and cellular membrane, 
viz. by corrosion with nitric acid, by which the one remained 
unacted on, whilst the others were dissolved. Meyer§ employed 
this method in order to determine the question on the reproduc- 
* Arnemann Versuche liber die Regeneration derNerven. Gottin. 1782. 
t Haighton, in the Philosophical Transactions. 1795, vol. i, p. 190. 
\ Reil’s Exercit. Anatom, de Structure Nervorum. Fas. I. 
§ Meyer, Reil’s Archiv. 2 ter Band. S. 449. 
