ON THE REPRODUCTION OF THE NERVES. 521 
gists, and chemists, it cannot yet be considered as definitively 
settled. Galen endeavoured to determine the point physiologi- 
cally, by observing in what degree the function was restored : 
the greater number of his experiments were attended with an 
unfavourable result. In the year 1776, Cruikshank entered on 
the same field of investigation. After having been convinced 
that the division of the par vagum on each side invariably pro- 
duced the death of the animal, even when one of these nerves was 
divided a week later than the other, he prolonged the interim 
to that of a month, and the animal still lived : on examination 
after death, he found that the nerve which had first been divided 
was united by means of a filament, much thinner and less fibrous 
than the rest of the nerve. This regenerated substance in Cruik- 
shank’s preparation was not, however, looked on as really ner- 
vous; the two Hunters, and afterwards even Cruikshank himself, 
entertained doubts on it. In the year 1778, Fontana* saw this 
preparation in London, from which he was induced in that and 
the following year to try some experiments on rabbits respecting 
this point. He removed from the ischiatic nerve, the par vagum, 
crural, and intercostal nerves, portions from six to eight lines in 
length ; and observed, in two cases where he had cut away six 
lines from the par vagum and intercostal nerves, a real union by 
nervous substance, the nature of which he was assured of by 
microscopic observation. After him MonroT set on foot some 
experiments with the division of the ischiatic nerve and spinal 
marrow on frogs. The regenerated substance did not appear to 
him quite to accord with nervous substance, and the function 
was never perfectly restored. Soon after this MichaelisJ was 
induced by the same preparation of Cruikshank’s to try some 
experiments on the same subject. In the years 1782 and 1783, 
he tried eight experiments chiefly on dogs, six with the phrenic 
and two with the ischiatic nerves. He remarked, after the space 
of a few months, and sometimes a few weeks, in six cases a real 
* Richter de vulnerum sanatione. Tubing. 1812. 
f Monro’s Observations on the Structure and Functions of the Nervous 
System, p. 81. 
X Michaelis’ Brief an Camper uber die Regeneration der Nerven. Cassel, 
1785. 
3 z 
VOL. IX. 
