O B S E R V A T I O N S ON THE
plexus, refembling that of the nerves of the face ; and that, from both
nerves, each mufcle of the larynx receives branches
8. Dr Haller has denied that any nerve can be traced into the ligament
of a joint ; but I have obferved, that the back-part of the ligament of the
carpus has conftantly fixed to it a fmall branch from the mufcular fpiral
nerve of the arm. This branch has not altogether efcaped the notice of
Dr Haller, but he alledges that it is continued to fupply the interoiTei mufcles
f . On, however, examining this branch accurately, ahhough fome
filaments from it run farther than the wrift, to the membranes on the back
of the hand, yet the greater part of it feems to end there in the ligament J ;
and the interoiTei mufcles are fuppHed from the ulnar nerve, after it
reaches the palm of the hand.
9. The chorda tympani feems to be formed by the fécond branch of the
fifth pair, as well as by the portio dura of the feventh, as it comes off after
thefe two nerves are conjoined ; and it is evidently added to the lingual
branch of the third branch of the fifth pair, as it increafes its fize jj.
10. In feveral tables I have reprefented, with accuracy, the progrefs and
termination of the portio mollis of the feventh pair in the cochlea of the
human ear, which I firit traced in an adult fubjeél, in the end of the year
1756, and of which no account has yet been given by authors
C H A P-
• See Tab. ÏXV.
t Haller, El. Phyf. torn. 4. p. 247.
I See Tab. XXVI.
II See Tab. XXVm.
§ See Tab. XXIX. Tab. XXX. Tab. XXXI.
N E R V O U S S Y S T E M . 6j.
C H A P T E R XXII.
Of the Appeai-ance of the Nerves viewed with the Microf..ope.
E T . I.
A FTER examining the ftrufture of the nervous fyftem with the naked
eye, or with a common magnifying glafs, I attempted to trace
the nerves, by the ailiilance of the microfcope, to their termination.
I preferred the compound microfcope, as it takes in a larger field than the
fingle lens, and, therefore, fuits a painter better; and as, from the reafon
of things, as well as from the account of authors, it is certain that the
nerves are ultimately divided into very minute parts, I generally employed
a microfcope, which I found, by calculation, increafed the diameter of obje£
ls 146 times, or their furface 21,316 times, and illuminated the objed
by the light of the fun refleited from a plain or concave mirror.
A s I had traced the portio mollis of the auditory nerve to its termination
on the very thin membrane of the cochlea, and had found I could diftinftly
obferve its fubdivifions a very great way, with a common magnifying
glafs, or with a microfcope of inferior powers, I began with examining it
in the preparation delineated in Table XXXV.
I was much furprifed to obferve, that its ultimate fibres appeared to be
ferpentine and convoluted, very much refembling the winding of the feminal
dudls in the teilicle or ep'i d'y''d"ii inis.
I compared with it the termination of the optic nerve in the retina, and
obferved an exad refemblance. When I made a calculation, I found that
the