Part 4

These bodies are full of cavities, which have all a communication with one another. The cavernous body of the _urethra_ continues from the _bulb_, near the neck of the bladder all along to the end of the _penis_, and includes the _glans_, or the nut of the yard; and is much of the same substance with the former. At the back of the _penis_, goes along the large vein, called the _vena penis_, which spreads itself all along into numberless branches that connect themselves with the ramifications of the arteries throughout all the cavernous bodies; and from thence is caused the erection, as I shall presently describe. The _glans_, or the nut of the yard, is remarkably delicate and sensible, as being the seat of pleasure in coition; it is also of a cellular substance, and in one continuation with the cavernous body of the urethra.

Its sensation is greatly heightened by the _frænum_ being tied underneath, from the _præpuce_ to that part which keeps it, as it were, in an agreeable constriction when erect.

The penis is allowed two pair, and a single muscle. The first pair is the _erectores_, which take their origin from the fleshy protuberances of the _ischium_, and lose themselves in the cavernous body of the penis. The second pair of muscles is the _transversales_; these take their rise near the forementioned, and fasten themselves at the root of the penis. The fifth is the _accelerator_, or the odd muscle; this muscle takes its commencement from the cavernous body of the _urethra_, and grasps the whole penis, and adheres to the _sphincter_ of the anus; the muscles aid and assist each other in the erection of the penis, which happens in the following manner:

At the influx of the animal spirits, the _vena penis_, or the great vein in the penis is somewhat contracted, whence the blood is forced into the cavernous bodies of the penis and that of the urethra, as the reflux of the circulating blood from the arteries is hindered; hence, the cellulæ of the cavernous bodies are obliged to swell up and distend all the parts, and thus make the penis turgid and erect; when the penis is further titillated by the friction of coition, the parts become generally irritated to an agreeable constriction, whereby the seed rushes from the seed-bladders into the urethra, and is thus forcibly ejected in the time of ejaculation; then the whole fabric slackens, the constriction of the great vein relaxes, the blood regains its free circulation, and the penis becomes slack again.

These are the faint out-lines of the genital parts; but to have a full description and comprehension of the peculiar properties of the genitals of both sexes, and also the sacred act of generation, I recommend to a serious perusal of the anatomical and physiological description of the genital parts of both sexes, in my _Treatise on the Venereal Disease_, where they will find a full and satisfactory account.

SECT. VIII.

_Of the Skin._

The whole human automaton is covered with a skin, the mechanism of which is not less curious than what we have already described.

It is a texture curiously interwoven with an infinite number of tendons, arteries, veins, nerves, and lymphatic vessels. The tendons form the net-work of the whole, and give it an elasticity, from whence it requires a muscular motion; and the rest add each their parts, as I shall hereafter describe.

The skin, universally over the whole body, is divided into three parts; but in most parts it is found to have four.

The external, is the _cuticula_, or scarf skin; this is a horny and insensible substance, formed by nature as a shelter for the next part of the skin, which is exceedingly sensible; on examination it appears to be a horny substance, and as it were, little scales continued from the immediate skin, which on any external injury, such as repeated friction, fire, scalding, or blistering, separates from the main skin. The next is the real skin, called _cutis_; This is strongly interwoven with tendinous and nervous fibres, interspersed with numberless ramifications of arteries, veins, and lymphatic vessels; whence it is not only exquisitely sensible, but elastic, and on the least injury, subject to bleed. On the external surface is a very thin _plexus_, called the _reticulare_; which has the tinge of the natural hue of the skin, and distinguishes the complexion of the _negro_, the _tawny_, and _white_, from each other.

The structure of the _cutis_ is peculiarly curious, and may justly be considered as a continued _secretory_ and _excretory gland_; or more properly, like the bark of a tree; for whilst there is continual transpiration from the body, it, at the same time, is capable to absorb the subtile particles of whatever surrounds it, and exclude the grosser. Over the whole surface are innumerable little _pores_, which are nothing but the little openings of the various lymphatics, and of the blood vessels corresponding with their peculiar _glandules_, called the _milliary glans_; between those on the hairy parts, the hair is planted as it were, with their distinct roots, corresponding with the hue of the subject they belong to. These _pores_ widen or contract according to the internal or external warmth of the body; which when they contract, cause a kind of roughness, or continuation of little warts; and on the contrary, when dilated, smooth the skin. Next to this follows the fat skin, or _membrana adiposa_; which is a continuation of cells, wherein the fat is contained, and has an immediate communication with the neighbouring blood and lymphatic vessels. This part is not universal, for some parts of the face, the genitals, &c. are without it. The last of all is the _membranosa_, a thin parchment-like texture, which adheres spontaneously to whatever part it covers, either _periosteum_, the _tendons_, _ligaments_, or _muscles_.

These are the four principal divisions of the skin; but that which is the principal, is the second mentioned, namely, the _cutis_; on which I shall have occasion to offer something hereafter, that may prove of the greatest advantage to the sea-faring people, for whose benefit I have particularly intended these Lectures.

SECT. IX.

_Of the External Senses._

Feeling is the universal sensation of the nerves, on which all other senses depend, as the subtile spring of life itself. What it is, and whence it proceeds, has already in the foregoing been explained; namely, a sensation of the nerves, by which we perceive an idea of _hard_ or _soft_, _wet_ or _dry_, _hot_ or _cold_, or in general terms, _pleasure_ or _pain_. The peculiar seat thereof seems to be placed at the ends of our fingers; whether this is the absolute seat ordained by nature, or rendered so by custom, is not my business here to enquire; perhaps, both conjoin to make it there most perfect, as best suited for that purpose.

_Taste_ is the next sensation of the nerves, regarding an immediate approach and action of substances themselves, in order to distinguish betwixt the nature of foods, by which we are enabled to form an idea of _salt_, _sweet_, _sour_, _bitter_, _sharp_, or _mild_; which according to their mixture and proportion, render _taste_ agreeable or disagreeable. Its seat is principally in the tongue; but that it extends to the very stomach itself, is evident, from the immediate consent of parts; namely, that what is disagreeable to the palate, will ever be nauseous to the stomach: Of which I shall say more hereafter.

_Smelling_ is that sensation given to the animal creation, as a friendly messenger of taste, in order to enable us the better to chuse our food. It is actuated by means of the _olfactory nerves_ spread in the _pituitary membrane_ of the nose, and has an immediate communication with the brain; which nervous plexus is actuated by odorous particles, exhaling from substances, by which the olfactory nerves are stimulated agreeably, or disagreeably, as the first intelligence to the palate, or to the whole consent of the nervous system.

_Hearing_ is that sensation of the nerves which is occasioned by the vibration of the air, and forms the sound, which enters the cavity of the ear, and tremulates and puts in action, the organs of hearing. The ear is perhaps as curious a piece of mechanism to our conception, as any part whatever we shall meet with in anatomy.

To the organs of hearing we must reckon the external and internal _auditory_, divided by a thin membrane, which is a thin spreading of nerves, called the _drum_; within this, or in the internal cavity, we observe, 1st. Four little bones called, from their forms, the hammer, _malleus_; the anvil, _ancus_; the stirrup, _stapes_; and roundling, _orbicularis_. 2dly. Their peculiar muscles. And, 3dly. Two considerable cavities, the _labyrinth_ and _aqueduct_. How hearing is actually brought about, Anatomists have not as yet agreed; and which would be too tedious here to enquire into. That the little hammer is perpetually moving on the _tympanum_, according to the different sounds, may be one part; which, however, is greatly assisted by the other organs.

The _labyrinth_, with many turnings and windings, penetrates through the skull and forms part of the aqueduct, by which the sound is modulated and magnified, so as to cause the distinction between them, and convey the idea of their sonorousness to the common receptacle of sensation.

_Seeing_ is that great faculty by which the form, colour, and motion of objects is represented to our ideas. The principal conveyer of this wonderful sensation, is the _optic nerve_; the eye is a telescope finished to the greatest perfection; or like a _camera obscura_, where objects are pictured to the utmost nicety, and a due proportion observed in their nature. It is a globe enrolled with a strong tendinous coat, and filled with three kinds of humours perfectly clear and transparent, which differ in nothing but their various degrees of liquidity and form. Each of these humours is enclosed in a delicate thin transparent membrane. The external coat of the eye is called the _cornea_, from its resemblance to horn, being a continuation of the _dura mater_ and _pia mater_; and is every where opaque, except at the entrance of the light, which is called _pupilla_, and projects somewhat beyond the spherical form of the eye, similar to the crystal of a watch. Inside the _cornea_ it is lined with a spreading of the optic nerves, called the _retina_, where objects are reflected; by which the ideas are immediately conveyed to the brain.

The humours are the following: The _aqueous humour_, the most external, which is designed for collecting the rays of light; the second is the _crystaline humour_, which is in the form of a magnifying lens, and invested with a subtile transparent tegument, and so curiously fixed, as to be contracted and dilated, according as the objects are near, or removed from the eye; and accordingly the crystaline humour requires to be flattened or thickened; the last is the _vitrous humour_, which fills the remaining cavity of the eye; this humour serves to spread the objects again on the _retina_, and arrange them in their natural order, so that the picture of the objects viewed, may be preserved in its due proportion and regularity.

Now the act of vision is performed thus: The convex transparent part of the _cornea_ faces at once every object which comes within the direct lines thereof, and this is termed a _full view_.[8] This view enters through the aqueous humour, where the whole is contracted according to its convex and concave form, so as to make it fit to enter the _pupilla_, which is a muscular continuation of the _sclerotis_, and called the _uvea_; and from thence the whole view passes through the crystaline lens, by which the view is again magnified, and passed through the vitrous, and the whole depicted on the _retina_, in the same concave curve, and at equal angles in which it was first received, and apparently the same magnitude; thence representing the objects in their natural perfection, figure, colour, magnitude, and motion.

Footnote 8:

It is the general received opinion, that objects are reversed in the representation on the _retina_ of the eye. This is however a mistake; I hope on another subject to prove this in a full and satisfactory manner.

When, however, an object is singled out of the whole view for particular attention, the _uvea_ then contracts or dilates, which, together with the muscular action of the whole ball, proportions all the humours suitable to the magnitude and distance of the object under examination, and the quantity of light; and to make the eye more capable, the lids are frequently moving, in order to moisten and varnish, as it were, with a liquid pressed from the innermost gland, called _canthus major_, to keep the surface smooth, and assist its transparency. If this intense looking is continued beyond the strength of this noble organ, it relaxes from its proper destined expansion, and the objects are rendered obscure.

Darkness is ease and rest to the eye, because it is then out of action; whilst light always keeps it in exercise; And in diseases of the eyes, light should be kept away as much as possible.

Here then I shall beg leave to conclude this short description of the wonderful structure of our frame; which when we duly consider, will never fail of filling our breasts with a sense of admiration; and induce us to lift up our souls with reverence and gratitude, to that incomprehensible GREAT CAUSE, by whose wisdom we are formed; and by whose goodness we exist.

LECTURE II.

ON THE NECESSARY

MEANS AND MEDICINES

REQUISITE TOWARDS

RESTORING HEALTH.

Having, in the preceding lecture, given a general view of our wonderful structure, I shall, in this, endeavour to lay a foundation of the healing art, in order to assist nature when impaired by the attack of disease, or any unforeseen accidents.

But that I may become useful, and yet concise, I will, without loss of time, lead the reader to the principal distinction between health and disease; for without forming a proper judgment of an ailment, there can be no reasonable intention of cure. I shall therefore beg leave to solicit a serious attention to the following important observations, particularly, as they are founded upon the purest principles of _physic_, authenticated by happy success in an extensive practice, and communicated by the dictates of a candid and well disposed heart, that wishes Existence only as a useful member to society.

SECT. I.

_Of the Pulse._

When we consider the admirably curious structure of the human mechanism, it must clearly appear, how easily the animal œconomy may become disordered. But so kind has the ALLWISE AUTHOR of our existence been to his creatures, that on the slightest indisposition, the whole system is sensible of the least disagreeable sensation; and every part, with a social and sympathetic friendship, is ready to relieve the fabric from whatever is obnoxious, and causes the disturbance.

As nothing has a greater share in life than the blood, so nothing likewise on the least indisposition, is sooner set in commotion, and gives the alarm, than this very liquor, in which life itself is contained; and the circulation of this fluid in the arteries, furnishes us with the greatest prognostic, namely, the _pulse_, by which we may, with any degree of certainty, judge of the state of the body, and foretell good or bad events. How beneficial it is then to be acquainted with this knowledge, I shall leave to every rational being to determine.

Every artery in the living body constitutes a _pulse_, as has been explained in Sect. V. in the foregoing lecture.

And it is demonstrative from simple reason, that the pulsation of such arteries must be in proportion to their magnitude, greatest in the heart, whence they take their origin; till the vibration must gradually be lost to the touch, as they become insensibly small, and lose themselves in their ramificatory capillary tubes.

The artery which is most convenient to our examination, is that which lays immediately to the touch on our wrist, below the thumb, on the radius, just below the knuckle of that bone; and it is there we are best able to distinguish the pulsation of the arteries, as being most exposed to the external touch; because it is immediately between the skin and the flat of that bone.

Thus much premised, we will first consider the _pulse_ in the sound state; and next make a comparison with that in people labouring under diseases.

In a full grown man, in the vigour of health, the pulse ordinarily beats once to every second, that is, 60 times in a minute, 3600 in an hour, and 31,536,000 times in a year. It varies however in different subjects, according to the stature, temperament, condition, time, and action of the same; insomuch, that two persons equally in a good state of health, shall, however, differ widely in their pulses. Yet, notwithstanding, there are peculiar signs, which will ever make a true distinction between health and sickness; practice however is requisite to form a proper judgment of such distinction.

In order to lay a proper foundation to understand the nature of this great prognostic, I shall divide the pulse into the following classes:

1st. _A full_, _slow_, and _regular_ pulse, denotes a perfect state of health; for whilst the blood moves regularly in the arteries, without pain to the nervous system, or disturbance to the animal œconomy, the pulse will beat precisely regular, without trembling, fluttering, hurry, distinction, or feebleness, and discover to the touch, a peculiar easiness; and this, every one, who wishes to become master of that subject, should carefully attend to.

2dly. _A full_ and _quick pulse_, indicates a fever; for by the irritation of the nerves, the vibration of the arteries are accelerated. If a gentle perspiration attends it, it may be deemed salutary; and with this pulse it appears, that nature makes a vigorous effort to expel what is obnoxious: therefore in such a pulse, a gentle perspiration generally gives relief.

3dly. _A full_, _quick_, and _hard pulse_, denotes great irritability in the nerves, and a redundancy of blood; this is the pulse of a fever; and here bleeding, if timely applied, is very requisite, as also medicines which promote perspiration.

4thly. _A small_ and _quick pulse_, denotes an irritability in the nervous system, and a contraction of the arteries; this is generally the pulse which attends sudden shocks and frights, as also in the cold fits of agues. The causes should carefully be attended to: if, from a sudden shock, bleeding is useful; but in the latter case, it is hurtful. It seldom lasts long, and a full feverish pulse generally follows, and the state of the patient ought here to be the guide: for, the same pulse may proceed from too great a plenty of blood, as well as from a deficiency; consequently requires different treatment; and this shall be pointed out more fully hereafter.

5thly. _An irregular full pulse_, is at all times a bad one; many may be the causes, and generally denotes a great confusion in the nervous system, and in the circulation of the blood. This pulse is generally the attendant on violent inflammations, phrenzy, delirium, &c. and if it continues any time, forebodes great danger: bleeding in time is greatly requisite, and other remedies, in order to assist the nerves, and bring the circulation to its proper regulation again.

6thly. _An irregular small pulse_, is frequently the attendant of an emaciated constitution, putrid fevers, and consumptions; and this dangerous pulse too generally forebodes the approach of death. The more irregular the pulse grows, _small_, _weak_, _trembling_, and leaves off by irregular intervals, the sooner dissolution is at hand; till at last, the pulse entirely disappears, and life ceases. But dangerous as this pulse is, yet it must be observed, that it often appears in the strongest constitutions, as in sudden emotions of the mind, falls, &c. or in a swooning. This is also the last and the first pulse in suffocations; or in other words, the struggling pulse between life and death.

These few distinctions of the pulse we will let suffice, as they, when properly attended to, will in all cases enable us to make a true distinction between health and the different stages of sickness, and accordingly direct us to a true method of cure.

SECT. II.

_Of the Effects of Bleeding_

There is, perhaps, not a greater remedy in medicine than bleeding; but good and effectual as it is, yet I will venture to say, there is none more pernicious than this, if injudiciously applied. As I value the life of my fellow creatures, I would at all times caution them against the injudicious application of this operation, being persuaded, that more have lost their lives by the lancet, than by the sword, and pestilence itself. Not to be tedious on this important subject, I shall give here some very few rules, whereby a patient may be judged in a proper state for bleeding; and likewise, where that operation ought to be avoided: for all the service we can possibly hope and receive from bleeding, is to lessen the quantity of blood, by which the whole body becomes relaxed, consequently less liable to the inflammatory irritation, that a too great quantity of blood might occasion; but on the contrary, if the solids are but weak, and the blood poor, we only augment the evil by bleeding, which we would wish to remove, as thereby the system becomes weakened, and not able to disengage itself from the obnoxiousness it is incumbered with; and thus proves the very destruction it was intended to remedy. The notion of drawing off the bad blood by bleeding, is very erroneous and absurd; the whole is too intimately mixed, and will ever generate the same again till the disease is removed.

_Bleeding is requisite_

1st. When a strong robust person, of a full and sanguine complexion, by accident receives a heavy contusion; a broken limb; or wound, whereby the parts become inflamed; a fever like to ensue; and that the pulse becomes hard and full, the veins distended, &c. &c.

2dly. When such a person receives a great shock, fall, terror, or any other strong emotion of the mind; whereby the blood becomes rarefied, or threatens a fever.

3dly. In the beginning of pleurisy, peripneumony, sudden and violent fevers, great colds, &c. as also scalding, burning, apoplexies, convulsions, palpitations, suffocations, and all such dangerous violent disorders; in these cases only bleeding is useful, and then it ought to be performed immediately, and with great moderation: six or eight ounces is enough from the strongest man; if requisite, it may be easily repeated, but if overdone, it is not so easily replenished.

_Bleeding in general is hurtful_

1st. In agues, notwithstanding the violent paroxysm of the hot fit, because the solids are here too much relaxed.

2dly. In all contagions distempers; this is a circumstance worthy the greatest attention. Reason and experience prove that bleeding here is very improper; for by bleeding, the contagious miasmata is drawn only the more into the whole mass of blood, and this is the fatal stumbling block, by which thousands have lost their lives. The manner of treating such distempers with success, I shall shew in its proper place.

3dly. In all old standing diseases, where there is a low, weak, though quick pulse; for in such cases bleeding is very improper, as the system is already too much reduced.