SECT. VIII.

The Temples.

The Basis of the Skull.

The Bones of Hearing.

TheFace.The Upper-Jaw.

TheFace.

The Upper-Jaw.

The Under-Jaw.

The Teeth.

The Tongue-Bone.

Bonesin theTrunk.The Spine.

Bonesin theTrunk.

The Spine.

The Ribs.

The Shoulders.

The Hip and Bason.

The Breast.

Upper Extremities.The Upper Arm.

Upper Extremities.

The Upper Arm.

The Under Arm.

The Wrist.

The Hand.

The Fingers.

Under Extremities.The Thigh.

Under Extremities.

The Thigh.

The Knee Pan.

The Leg.

Ancle.

Foot.

Toes.

The connection of the bones are in various ways; those connections that are designed for rest, are by close contact of parts, and are calledsuturesorseams; such are the bones of the skull with themselves and the face. Those connections which are designed for motion are calledarticulation. Some of the articulations have but an obscure motion, as the ribs with the back-bone, and the back with itself, &c. Others have an angular motion, as the elbows and knees; and others again have an universal motion, as the arm-bone with the shoulder, and the thigh bone with the hip. Thesutures, and such connections as have no motion, are merely dovetailed into one another in close connection; but those articulations that are designed for motion are connected by cartilages, either in close contact, or so as to move slippery over one another.

The ligaments are those tough tendinous parts, by which the articulations designed for motion are joined together; at some parts they cover the joints only, and at others, they are immediately fastened to each other, besides the external coverings; those ligaments are very strong and elastic, and have a close connection with the nerves that pass by them.

The surrounding ligaments of all moveable joints, form acapsular-bag, which containsa slippery liquor, calledsynovia, that lubricates the ends of the bones covered withcartilages, that they may move with ease and agility over one another.

Musclesare the fleshy parts on the human body, appointed for motion. They are a composition of arteries, veins, nerves, and tendons.

Muscles are generally divided into two kinds; those for necessary or involuntary motion, and those for voluntary. Some again are fastened at each end to some of the bones at their extremity, and contract themselves in a straight direction; others again are annular, or in the form of a ring; and by this manner open and shut. The first kind are generally divided into three parts, the head, belly, and tail. The whole muscle begins and ends in a tendon, by which it is fastened to the part it is designed to move; which, when the belly of the muscle contracts itself, must consequently draw both bones nearer together, fastened to the head and tail; and thus performs the motion. Some of these muscles act in consort, and others in opposition to each other.

The tendons are the principal parts of the muscle; and that part thereof, as before observed, which is fastened in the bones, namely, at the head and tail of the muscle, and is the chord, as it were, by which the limb is brought into motion.

A tendon is a hard, substantial, flexible, and elastic body, which, at the head of the muscle, is very compact; but as it enters the muscle, spreads its fibres over the whole body, gathers again at the tail, in as compact a manner as it began, and continues in this chord-like texture till it fastens itself at its appropriated place.[7]

7.It must be observed however, that tendons take on many various forms, as different as the muscles; which would be too tedious here to particularize.

The tendons and ligaments are of equal substance, and differ in nothing but their various uses; namely, the ligaments to connect the articulation; and the tendons, or the ends of the muscles, to give motion. The muscles are a composition of the tendinous fibres, plentifully intermixed with small ramifications of blood vessels; all which compose the fleshy part thereof. Hence, the tendons being white and hard, the muscles gradually grow softer and redder in the middle of them; and they verge gradually to become tendinous at the tail, the same as the head.

Hence, from the close texture of the tendons, they are very painful when wounded, or otherwise hurt; but as the muscles are softer and more pliable, their wounds and other accidents are of less consequence, and not so dangerous as the former.

The number of muscles are undetermined, for though the principal muscles are so distinct that they cannot be mistaken as to theirform and use, yet there is so great a number of small ones, or so many of the great ones capable of being subdivided again, that anatomists have not, as yet, agreed about their number.

Thekidnies, theureters, thebladder, and theurethra, are the principal urinary organs. The kidnies receive two arteries called theemulgent arteries, from the great arterial trunk, calledaorta, before described; they each send also two veins back again, accompanying the arteries to thevena cava. Whilst the blood is circulated in the kidnies, the urine is secreted in many small quantities, and carried from each kidney by a tendinous tube, the bigness generally of a small goose quill, called theureterto the bladder. Theuretersenter the bladder between itslamillas, so as not to admit of a return. Hence, a bladder in its natural position is both wind and water tight, and if reversed, is neither.

The bladder of urine is of a tendinous and nervous texture, and capable of great extension, but at the same time exquisitelysensible. The neck of the bladder is very muscular, and by this forms asphincter, or annular muscle, by which the urine is retained; and as it is of a very sensible nature, this part is subject to inflammatory constrictions; great pain, and many evils have there been occasioned, either from venereal cases, or gravelous complaints.

From the neck of the bladder to the end of thepenis, is theurethra; which canal serves for the emission of the urine, as well as that of the seed.

The whole is lined with a number of very little glans, to lubricate and protect the sensitive lining from the sharpness of the urine.

These are the urinary organs. We will in the next place, proceed to the organs of generation.

Thetesticlesare the principal instruments for forming the human seed; they are generally two in number. The testicles receive the blood, of which they secrete the seed, from theaorta, about the same parts, whence the emulgent arteries project. These arteries run down from the aorta to the testicles, in a very contorted and winding manner, accompanied by the veins which return back again from the testicles, and fix themselves in the ascendingvena cava. These contorted and interwoven vessels are called thespermaticvessels, which carry the blood from the arteries in little quantities, and slowly return it again into the great vein.

Whilst the blood is circulated in the testicles, the seed is secreted in them; but as it is secreted, it is transported back again from thence by tubes, calledvasa deferentia, towards the neck of the bladder, where there are two irregular bladder-like vessels, wherein the seed is contained, and kept for use, called thevesiculæ seminales.

In these seed bladders the seed is kept for use, till it is wanted. They are remarkably delicate and nervous; and when they are filled with seed, they stimulate all the organs of generation with a desire for venery.

Thepenis, or the manly member of generation, is partly covered with the common skin; the foremost part of which, that covers the glans, is called thepræpuce. Thispræpuceis tied underneath to the substance of thepenis, by what is called thefrænum.

The inner part of the penis is composed of two kinds of bodies, thecavernous bodiesof thepenis, and thecavernous bodyof theurethra. The first are bodies enveloped in their peculiar teguments, and make the greatest part of thepenis. Each of these bodies takes its origin from the erecting muscle of thepenis, which is near thepubis; through each of them goes an arteryand a nerve, which spread themselves through these bodies.

These bodies are full of cavities, which have all a communication with one another. The cavernous body of theurethracontinues from thebulb, near the neck of the bladder all along to the end of thepenis, and includes theglans, or the nut of the yard; and is much of the same substance with the former. At the back of thepenis, goes along the large vein, called thevena 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. Theglans, 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 thefrænumbeing tied underneath, from thepræpuceto 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 theerectores, which take their origin from the fleshy protuberances of theischium, and lose themselves in the cavernous body of the penis. The second pair of muscles is thetransversales;these take their rise near the forementioned, and fasten themselves at the root of the penis. The fifth is theaccelerator, or the odd muscle; this muscle takes its commencement from the cavernous body of theurethra, and grasps the whole penis, and adheres to thesphincterof 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, thevena 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 ofthe 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 myTreatise on the Venereal Disease, where they will find a full and satisfactory account.

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 thecuticula, or scarf skin; this is a horny and insensible substance, formed by nature as a shelter for the nextpart 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, calledcutis; 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 thinplexus, called thereticulare; which has the tinge of the natural hue of the skin, and distinguishes the complexion of thenegro, thetawny, andwhite, from each other.

The structure of thecutisis peculiarly curious, and may justly be considered as a continuedsecretoryandexcretory 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 littlepores, which are nothing but the little openings of the various lymphatics, and of the blood vessels corresponding with their peculiarglandules, called themilliary glans; between those onthe hairy parts, the hair is planted as it were, with their distinct roots, corresponding with the hue of the subject they belong to. Theseporeswiden 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, ormembrana 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 themembranosa, a thin parchment-like texture, which adheres spontaneously to whatever part it covers, eitherperiosteum, thetendons,ligaments, ormuscles.

These are the four principal divisions of the skin; but that which is the principal, is the second mentioned, namely, thecutis; 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.

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 ofhardorsoft,wetordry,hotorcold, or in general terms,pleasureorpain. 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.

Tasteis 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 ofsalt,sweet,sour,bitter,sharp, ormild; which according to their mixture and proportion, rendertasteagreeable 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, thatwhat is disagreeable to the palate, will ever be nauseous to the stomach: Of which I shall say more hereafter.

Smellingis 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 theolfactory nervesspread in thepituitary membraneof 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.

Hearingis 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 internalauditory, divided by a thin membrane, which is a thin spreading of nerves, called thedrum; 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, thelabyrinthandaqueduct. 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 thetympanum, according to the different sounds, may be one part; which, however, is greatly assisted by the other organs.

Thelabyrinth, 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.

Seeingis 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 theoptic nerve; the eye is a telescope finished to the greatest perfection; or like acamera 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 perfectlyclear 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 thecornea, from its resemblance to horn, being a continuation of thedura materandpia mater; and is every where opaque, except at the entrance of the light, which is calledpupilla, and projects somewhat beyond the spherical form of the eye, similar to the crystal of a watch. Inside thecorneait is lined with a spreading of the optic nerves, called theretina, where objects are reflected; by which the ideas are immediately conveyed to the brain.

The humours are the following: Theaqueous humour, the most external, which is designed for collecting the rays of light; the second is thecrystaline 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 thevitrous humour, which fills the remaining cavity of the eye; this humour serves to spread the objects again on theretina, and arrange them in their natural order, so that the picture of theobjects viewed, may be preserved in its due proportion and regularity.

Now the act of vision is performed thus: The convex transparent part of thecorneafaces at once every object which comes within the direct lines thereof, and this is termed afull 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 thepupilla, which is a muscular continuation of thesclerotis, and called theuvea; 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 theretina, 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.

8.It is the general received opinion, that objects are reversed in the representation on theretinaof 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, theuveathen contracts or dilates, which, together with the muscular action of the whole ball, proportions all the humours suitable to the magnitude and distance of theobject 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, calledcanthus 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 incomprehensibleGREAT CAUSE, by whose wisdom we are formed; and by whose goodness we exist.

Back to Index Next