From this also we can learn the reason why the venereal disease will sometimes return, without any new infection, after a seemingly complete cure by means of mercury. The disease will be apparently cured, because the mercury may have totally destroyed the poison at some particular parts; but it will return from the virus still remaining lodged in others, to which, from a course sufficient to destroy it in more accessible parts, the mercury could never penetrate.
It appears then, that to the other arguments formerly adduced in favour of this theory, may be added, the ready solution it affords for various phænomena observed with respect to the cure. And, from all the arguments taken together, it may be concluded, that this theory is to be adopted, if not as absolutely certain, at least, as less embarassed with difficulties, and as supported by more probable arguments than any other.
CHAP. IV.
Of the different Mercurial Preparations employed in Medicine.
Metallic substances in general, when employed for the purposes of medicine, have been used in many different forms: But none of them, perhaps, has been exhibited in a greater diversity of preparations than mercury. Some mercurial preparations have never been employed in the cure of lues venerea; and many formerly in use are entirely banished from the present practice in this disease. All these may be considered as unconnected with the subject here treated of. But that the nature of those preparations which are at present most frequently employed, may be more clearly understood, there will be no impropriety in taking a general view of all the preparations of mercury.
The mercurial preparations admitted by the Colleges of London and Edinburgh, contain the most useful and most elegant forms employed in practice, at the time when the last editions of their Pharmacopœias were published. But even at that time they were by no means to be considered as compleat lists. And, since that time, other preparations of utility in practice have been discovered.
A more full view of mercurial preparations than can be obtained from these lists, and, at the same time, some information with regard to the circumstances in which they differ from each other, may be had from a table of mercurials lately published by Dr Saunders of London. In that table, which, with a very few inconsiderable alterations, is the same with one formerly given out by Dr Cullen, when professor of chemistry at Edinburgh, the different mercurial preparations are reduced to general heads, according to the means employed to render them active. From it, the following is almost entirely copied. The names of the different preparations are here printed in Italics, and taken from the London and Edinburgh Dispensatories, from the new Dispensatory, and from the Edinburgh Pharmacopœia Pauperum. To these are added, some mercurials introduced by Boerhaave, Astruc, Keyser, and Plenck. From the letters subjoined to each, it will appear from whence the preparations are taken; and, where an asterisk is prefixed to any one, it denotes, that it is to be considered as perfectly analogous to that immediately preceeding.
A