68 O B S E R V A T I O N S ON THE
the real diameter of an obje£l of the apparent fize of thofe convoluted fi-^
bres, would be nearly equal to the y ^ t h part of an mch.
The fibres in fome parts of the medullary fubilance of the brain, and in
the trunks of the nerves in general, feemed, to the naked eye, fo evidently
ftraight, that I fuppofed the ftruilure I had feen might be proper to thefe
organs of fenfe. But, when I came to apply my microfcope to the medullary
fubftance of the brain, to the fibres in the trunks of the nerves, and at
lafl: to the mufclcs, nay to the bones, the teguments, and even the hairs of
the body, I was aftoniflied to find in all a fimilar appearance.
I ihowed what I had obferved to fome friends, diftinguiihed by their genius
and learning, and who were pradifed in microfcopical obfervations.
They faw diilinilly, and were furprifed with the appearances I have
been dcfcribing.
In January 14th 1779, I read to the philofophical fociety of this place,
an account of the appearances I had obferved; but not having finiihed the
experiments I propofed, and not being fatisfied upon the fubjeil, I declined
lodging my paper with a member of the fociety for a report, which is the
common practice.
Soon after I obferved a fimilar appearance, not only in the recent parts
of vegetables, but in the foifile kingdom, and in all folid bodies, whether
opake or pellucid.
Of thefe obfervations Dr Duncan, without my defire, wrote fome account,
under the article of Medical News, Vol. vi. Part i. of Medical Commentaries.
The Dodor was, however, fo obliging as to ihow me what he
had written before it was fent to the prefs.
A t
N E R V O U S s y s t e m . G0
A t firft, and efpecially whilft my obfervations were confined to the
nerves, I had little or no fufpicion that the appearance I remarked'could
be an optical deception ; for the fibres I faw appeared to be bent and
convoluted in a very beautiful, diftina, and uniform manner.
They feemed larger or fmaller, in exa£l proportion to the known magnifying
powers of the microfcopes I employed.
When I applied to the microfcopc the leg of a fmall tranfparent animalj
fuch as a fpider, 1 faw, at the fame initant, and with equal dillindnefs, the
convoluted fibres and the round particles of the blood circulating in the vef-^
fels.
When I examined melted wax, fpermaceti, or tallow, I faw no fuch
appearance ; but, at the very inftant of their becoming fomewhat opake by
coohng, I faw the mafs ilioot into fuch fibres : Or, when I evaporated water,
in which fait was diflblved, as foon as the cryftals began to flioot, I
faw ferpentine fibres beginning to form in theniij
All the metals melted, and allowed to cool, feemed to be compofed of
fuch fibres ; fo that it could not be faid that this appearance was produced
by Scratches made accidentally, or by attrition.
No author had remarked as a fad, that an appearance fo difl:ind and uniform,
could be produced by an optical deception : And
I could not find principles on which the produdion of fo great a deception
could be fufficiently explained.
After, however, I had extended my obfervations not only to the vegetable,
but to the mineral kingdom, and more carefully fifted, and more
S coolly