As to the fixed Gout, where the morbid Matter remains long in a Place,
I take it that many acid Salts and viscid Humours contained in the
Blood, occasion a greater Coagulation and Viscidity in the Mucilage
about the Joints and the Tendons, than can be easily dispersed and
evacuated; and on the contrary growing more viscid and sharp, it
distends and vellicates the small Fibres of the Tendons and nervous
Membranes, and occasions a Pain proportional to the Degree of Acrimony
and Viscidity in the Mucilage about the Joints and Tendons, generally
pretty sharp. The Mucilage is affected in the same Manner as it would
be from the Affusion of _Aqua Fortis_, Spirit of Vitriol, or any other
corrosive acid or austere Substance, whence it is manifestly thickned
and coagulated. This affords a Reason why such a Gout is not only
fixed in a particular Limb, but also why it long remains there. The
ingenious Dr. _Havers_ explains this Matter very well; he tells us that
when the Matter happens to be thick and gelatinous, it is not to be
expected that it should be easily and presently discharged out of the
Interstices of the Joints, either by being resorbed or evaporated, when
the Consistence of it renders it uncapable of insinuating itself into
the minute Pores, and penetrating those narrow Avenues through which it
is to pass. And according to the Degree and Nature of the Acid in the
morbific Humour, it doth more or less coagulate the Mucilage, and the
Part affected is sooner or later, with more or less Difficulty, freed
from it, either by the Translation of it to another, or by the more
happy Exclusion of it out of the Body. The same Author very elegantly
explains the Cause of the Knots in the Joints, where he says that it
seems to be no difficult Thing to account for that tophaceous Matter,
which is sometimes found concreted in those Parts that have been
afflicted with this Distemper. It hath been observed, that an Acid and
an Austere, being both mixed with the Mucilage, did produce a plain, a
notable and white Coagulation, where the _Coagulum_, though it was made
when the Mucilage was cold, was not so soft and tender, nor dissolvable
in Water like that which was made with Acids only; but though it would
break, remained distinct in it, and being dried, was easily reducible
to a fine Powder like Flower, or the fine Powder of Chalk. Whence he
humbly conceives, that where-ever the Gout comes to be nodose, there is
not only an Acidity in the preternatural Humour, which is separated by
the mucilaginous Glands, and mixed with the Mucilage; but it is an Acid
austere, which is no sooner thrown into the Interstices of the Joints
and the Sinuses of the Tendons which are thereabout, but it produces
a _Coagulum_ in the Mucilage, and that such a one as is not easily
attenuated and dissolved, so that it lies fixed and imprisoned there,
and in Time, as the aqueous and moist Particles are by the Heat and
Spirits carried off, the terrestrial and saline Parts concentrated come
nearer together, and coming to be immediately contiguous, do mutually
adhere, and are concreted so as to produce that Chalk or tophaceous
Matter which is in some arthritick Cases to be observed. And as the
_Coagulum_, which may be made by an Acid austere, seems apt to make a
Concretion of that nature, so the Colour of the tophaceous Matter doth
answer to that of this Coagulation, so as to seem generated in this
Manner.