This Mucilage is formed from the purer Part of the Lymph and the serous
Parts of the Blood, and separated in these Glands from the Mass of
the Blood. In order to have a more distinct Notion of its constituent
Parts, and to know how it comes to occasion the Gout, the following
Experiments of Dr. _Havers_ may be very properly repeated in this
Place. He made most of the Trials both when it was hot and when it
was cold. Vinegar dropt into it, when it was hot, made a considerable
Coagulation with a _Serum_; it must be observed that those Mixtures
that were made with it cold, did produce the same Effect when it was
warmed, namely a Coagulation with Acids and Stypticks, only in an
higher Degree: And whereas the Coagulations, which were made when it
was in one State, did only change it into a thick Jelly without any
_Serum_, after the Manner of a Cheese when it is newly set, as they
term it, which over the Fire afterwards exhibited two distinct Parts,
a _Coagulum_ and a Whey; in the other, that is, when the Mucilage was
hot, the Mixtures which coagulated it produced an harder Curd, and
a _Serum_ distinct from it. By dropping in some of the Decoction of
Galls into it, the whole turned into a gelatinous Mass, and it was
all a Sort of _Coagulum_ like a Skin, of a whitish Colour, and so
tough as to hang all together when it was taken up with a Needle. This
_Coagulum_ or Jelly being laid in the Sun, and dried, the Parts of
it stuck all together in one Piece, but was very friable and easily
rubbed to a Powder, which was very much like fine Flower. The same
Effect had the strong Infusion of Balaustia, red Roses, Pomegranate
Bark, and the _Peruvian_ Bark, although there was some Difference
in the Coagulation, according to the different Degrees of their
Astringency. With a few Drops of _Aqua Fortis_ distilled upon it, the
Mucilage was immediately coagulated, though the _Coagulum_, which
was white, was so tender, that it would by Agitation be dissolved in
fair Water, and make it of the same Colour almost like Milk; Spirit
of Nitre made exactly the same Alteration in it as _Aqua Fortis_ did,
a _Coagulum_ which was of a white Colour. Vinegar, Spirit of Salt of
Vitriol, Oyl of Vitriol, and of Sulphur in some Mucilage which I tried
it with, did not make any considerable Alteration when it was cold,
but in some other it did more; when _Aqua Fortis_ and Spirit of Nitre
did produce in all the same Effects in the same Degree. It was mighty
observable, that so strong an Acid as Oyl of Vitriol should have no
greater Effect upon it to alter it not, so considerable as that of
Vinegar, which would incline one to think that it is not always the
high Degree of Acidity that works this Change. But there seems to be
something particular in Wines, which disposes them to coagulate this
Liquor, when any of them are made Use of; and those Parts of them,
which are apt to act thus upon it, are cast into those Interstices
where they have the Mucilage singly to work upon. And therefore we
find how readily any Wines do procure the Paroxysms of the Gout, where
the Tone of the Glands is weakned, and the Patient hath a Disposition
to this Distemper; which agrees with those Trials I have made with
some of them: For Claret, white Wine, and even Sack, but the Claret
especially, did make a _Coagulum_ like a Jelly; and it was not strange
that Claret, which hath both an Acid and a Stypticity in it, should
produce the greatest Coagulation. A mercurial Water made of Sublimate
and _Aqua Calcis_, made a very considerable whitish Coagulation, and
rendred it all a thick Jelly, which being held over the Fire, turned
to a Curd and a _Serum_. A Solution of _Roman_ Vitriol produced a
Coagulation likewise; so did Allum dissolved in Water, but it made a
greater Alteration in some than it did in others, though the Mucilages
were taken from subjects of the same Species. _Saccharum Saturni_
did inspissate it, which appeared to be a true Coagulation, because
with the Fire they would turn to a distinct _Coagulum_ and _Serum_.
Salt of Wormwood made no sensible Alteration, only it seemed a
little thicker, to which I put some of the Decoction of Galls, which
immediately produced a Coagulation. Upon dropping in some Spirit of
Vitriol, to see what would be the Effect of the Colluctation of the
Salt and Spirit, and I found, after it was over, that the _Coagulum_
and the serous Part were distinguished, and the _Serum_ limpid like
Water. I took some of the Decoction of Galls, and added to it Spirit of
Vitriol, intending to make a strong Acid austere, where I observed that
these two by themselves produced a strong Coagulation; and stirring
of them together, to see if the whole might not be brought to mix by
that Means, I found the _Coagulum_ turned into a viscous Body, and a
perfect soft Gum. Then I took out the Gum, and poured some Mucilage
to the residuous Liquor, by which it was changed so as to assume a
whitish Colour, but was not considerably coagulated; which it was
the less, because the austere Parts were most of them, with some of
the Acid, precipitated into the Gum which had been separated from
the serous Part. But if the Spirit of Vitriol and the Mucilage are
first mixed, and the austere Liquor be afterwards added, they make a
very considerable and plentiful _Coagulum_, which will only be broken
into smaller Parts, and not be dissolved in Water. _Aqua Fortis_, and
the Decoction of Galls being both dropt into some of the Mucilage,
made a white _Coagulum_, which likewise was not dissolved in Water,
altho’ with _oleum Tartari per Deliquium_, and so with Spirit of _Sal
Ammoniac_ dropt into it, I presently dissolved it. I found likewise,
that the _Coagulum_ made with the Infusion of Pomegranate Peel, red
Roses and Balaustia, being mixed with some of the Mucilage, to which
an Acid had been put, made the _Coagulum_ more firm, so that it would
not dissolve in fair Water; but yet the Oyl of Tartar by _Deliquium_,
and the Spirit of _Sal Ammoniac_, did the Business in all of them. The
_Coagulum_ of the Mucilage made with an Acid, and the Infusion of the
_Peruvian_ Bark and several other Astringents, I kept and dried, which
when they were first put to the Teeth, seemed a little gritty, though
after they were moist they were of a softer Nature. All the Mixtures
made of the Mucilage with an Acid and an Austere, produced not only a
plentiful Coagulation of a white Colour, but such a one as was of a
thicker Consistence, and not Soluble in fair Water, as that was which
was made with an Acid only.