Physic like religion is rendered intricate and abstruse, the more it abounds in errors and absurdities; but truth like the brilliant sun, drives away all the phantoms of perplext mysteries, and proves that both alike are simple and beautiful, founded on reason, and that its most useful part is comprehensive to common understanding. This pleads in favour of my attempt, and with every man of sense, must overpower prejudice.
That I might the better succeed in my intention, I have begun the whole at the first principles, namely the mechanism of the human body; for I cannot see how any man can pretend to know the nature of diseases, or presume to administer any thing with certainty, without he has some knowledge of the parts that suffer: this then is the subject of my first lecture; and to make it the more pleasing, and to entice the reader to pursue, I have stript it of every thing pedantic, or the unnecessary perplexing particulars, and confined myself to such things only, as gives a concise and true idea of the whole animal system; and if I may be allowed to judge from the opinion of some of my learned friends, I flatter myself, that my readers, physical or not, will give me their sanction, as well with respect to plainness of language, as conciseness of the subject, and the utility of such a short dissertation, founded on experience, and stript of prejudice and errors.
The second lecture contains equally as copious a subject as the first; contracted in a very small compass, and which I hope will give as much satisfaction as the forementioned.
Out of the whole Materia Medica, I have chosen but very few medicines, and these I have confined myself to throughout the whole book. Many surgeons at sea will not, I know, be contented with so small an assortment; and I remember the time that such an observation might have been applicable to myself; but as I have by long experience learned to shake off prejudices, and been taught by the help of philosophy to pry into the nature of things in general, I solemnly declare, that now, I would venture to go to any part of the globe, not only with that little assortment of medicines I have mentioned, but even with many less. The emetick tartar, sublimate mercury and the bark are powerful medicines; but they should be in very skillful hands, otherwise they are rank poisons, and therefore I have omitted them here; but strictly speaking, every good medicine is the same. I have two maxims in physic, which I strictly attend to; one is, that to my friends I give the least medicines; the other is, that the principal virtue of a medicine depends on its application.
The form of the medicine box, I have constructed so as it appears to me most convenient and handy; and every kind of medicine, I would advise to have labeled with their proper names, as well as with another mark that may take the eye at first sight; and the more to prevent mistake, one label should be fixt on the pot that contains the medicine, and the other on the box: for in medicines too much caution cannot be used.
One thing with respect to the medicines, I have omitted, and that is their quantity requisite for the box, and their prices: I intended to have taken notice of this, but found that that could not with exactness be ascertained, unless entering into another subject, and that would take off from the conciseness of my plan. As I have however many other things respecting the benefit of seamen to offer, peculiarly respecting distant climates, I shall take notice of this, where it may come in, more pertinently to the subject: till then, that must be left to the management of the apothecary who is applied to for fitting out the box. If he is a man of candour and judgment he cannot be much out of his calculation, when he knows the number of hands, and the voyage intended.
With respect to the other lectures, I have, as near as it was practicable, divided them into their different classes and sections; at the same time the whole is so linked together, that one lecture must support the other. And as I have throughout the whole course of the book differed more or less from the general mode of practice, I must hereby declare, that I have in this consulted my own experience more than any other authority, without fear of censure, or hope of applause, any farther than of truth, and my own conscience.
Though I have principally written with an intent to be understood by masters of ships who carry no surgeon; yet I am well persuaded that every practitioner, whether on sea or shore, will find many things to his improvement.
With respect to my receipts, they are simple and powerful; yet I do not enjoin so strict a conformity to them, by the practitioner, who has an extensive knowledge of the materia medica, and is prepossessed in favour of some particular medicines; but as he will discover my indications, it may serve greatly to compare that of mine with his own, and then he may judge for himself. I have touched very slightly on the requisite diet for patients on board a ship; though this is an essential article regarding health in general: But I found that subject also of so very extensive a kind, that it would swell the book; but as I have many valuable things to offer of the same nature, I must beg, that in the mean time, the reader will be satisfied with the universal observations in general; namely, that temperance is the principal object and that patients who are deprived of exercise ought to have the most easy digesting food. Copper and lead are pernicious; but iron and earthen ware are safest either on sea or shore.
In order to render the book as useful as my zeal has intended, I recommend it a fair perusal, from the first page to the last; a book of this nature is apt to be looked into, only when advice is wanted: that method is wrong; and in such a case, the best book in the world is apt to mislead. It is not enough that we know what we are to do with such and such disorders, but we should previously know what the disorder is; and how shall we know that, without having some idea of the evil before it comes on?