Part 3

In the first place then, _smelling_ is that sensation which nature has given to every animal, that has a choice of food, as the first safe-guard to inform it of any thing agreeable or disagreeable, useful or pernicious to its body; its seat is in the nose chiefly, but we find by experience, that it has a friendly connection with our palate and stomach; for the effluvia of any thing will either create a desire, or give us the greatest aversion to every substance that throws out a flavour.

It is performed by means of a subtile spreading of nerves, peculiarly delicate; which continues through the membrane of the nose, the roof of the mouth, gullet, and the very stomach.

_Taste_ is the next sensation, which nature has given us, not only as a distinguisher of proper food, but a sensation from which we receive many luxurious pleasures; and to the indulgence of this sensation, most evils and plagues to mankind, take their origin.

The tongue is the principal instrument of that peculiar quality; but if we examine somewhat closer into this affair, we shall find that the soul of pleasure and pain of that sensation, as well as that of smelling, has its seat in the stomach; for that which will taste pleasing and good at the first approach, will soon lose its relish when the stomach is gratified: and, if any thing tastes disagreeable, the stomach receives it with reluctance, and will ever incline to discharge it again.

The tongue is an instrument (if I may be allowed the term) very curiously constructed; it is moved by a variety of muscles, and serves not only for tasting, but also as a labourer, to shovel and to turn our meat between our grinders; so that nothing may escape being well masticated, and intermixed with that fine digesting balsam, the spittle, in order that it may be easily swallowed.

Besides this, it makes the most requisite instrument for the noble and excellent faculty of speaking; which forms one of the principal characteristics that distinguishes man from the brute creation.

The gullet or _oesophagus_, is the canal which conveys drink and food from the mouth to the stomach; this canal is a muscular, tendinous, and vascular tunic.

The commencement of it is in the mouth, and is called the _pharynx_; a curious structure, that receives the food, and by its contractive motion, and the help of the tongue, forces the aliment into the stomach.

The stomach is much like the bag of a Scotch bag-pipe; it lies immediately under the _diaphragm_ or _midriff_, covered partly on the right side with the liver, and on the left side with the spleen. The left and superior part, is continued with the _oesophagus_; and the right and inferior part, or orifice, commences the _intestines_.

The first orifice is called the mouth of the stomach; and the second the _pylorus_, or _porter_: At the porter there is a curious valve which lets the aliment out by small parcels into the intestines, where it undergoes its various other changes.

The stomach has three teguments, a _muscular_, a _tendinous_, and _nervous coat_; this _nervous coat_ has another slimy one, but this in reality, is a delicate lining, interwoven with nerves, and the ramifications of fine blood vessels.

The _intestines_ or guts, are a continuation of the stomach, they are a canal which is generally reckoned six times as long as the subject it is taken from; it is distinguished in small _tenuia_, and wide _crassa_.

Each again is divided into three parts: the _tenuia_, or small narrow intestines, are the _duodenum_, or twelve finger-gut; the _jejunum_; the _ileum_: The wide or _crassa_, is divided into the _cæcum_; the _colon_; and the _rectum_.

Throughout the whole canal of intestines are numbers of little vessels, called _lacteals_, which lead the chyle, extracted from the aliment, into a _receptacle_, which is lodged in the _mesentery_, and from thence, by another duct call’d the _thoracic duct_, is carried along the back-bone upwards, and joins to the left subclavian vein, where the _chyle_ gradually commences to be blood.

This short description we will let suffice, and now enter upon the action itself.

The morsel now, which is designed for food, is taken into the mouth, masticated with the teeth, turned about with the tongue; and as the mouth is at work, the _saliva_ or spittle is squeezed from the salival glands, and thus intermixed with the aliment; when enough chewed and moistened with this saliva, it is conveyed to the _pharynx_, or swallow, which receives it, and, by its contraction, forces it into the _oesophagus_; and by a repeated contraction, is carried down into the stomach.

There it is again moistened with _saponaceous liquid_, or _pancreatic juice_; by which and by a perpetual motion of the stomach, it is brought into a state of digestion; then by small degrees entered through the _pylorus_ or porter, into the first division of the gut, the _duodenum_.

This gut is about twelve fingers long; and whilst the aliment is there, it is intermixed with the gall, which is a liquor separated by the liver, and contained in the gall bladder; this liquor, the gall, is carried into the _duodenum_, by a small duct, called the _ductus cysticus_; where also enters another kind of liquor called the _pancreatic juice_.

When the aliment is thus prepared, and fit for a particular state of dissolution, it is carried into, and through the _jejunum_. This gut is in length about twelve or thirteen hands breadth, and its motion somewhat brisk; through which the aliment passes pretty quick, and hence, generally is somewhat empty.

As it passes through this part, the chyle is separated from it by the lacteals, which are small vessels that separate the chyle from the aliment, and abound there more than in any other part of the gut.

From thence it comes into the _ileum_; that is the longest of all the divisions of the guts, and is in length about twenty-one hands breadth; it has a great many circumvolutions, and next to the _jejunum_, has many lacteals to separate the chyle.

Now the aliment comes into the wide gut, and gradually becomes fæces; and first, the _cæcum_: This part is rather an appendix only, and hangs from the main part like a finger to a glove. The use of this gut has been much controverted by anatomists; it seems however, very probable, that this appendix is designed to keep the aliment in for further digestion, as it now begins to putrefy, and becomes fæces or excrement.

From thence it enters the _colon_, which is a long, and very winding intestine; it runs up along and about the liver, touches the gall bladder, and the spleen; from thence it descends again to the _os sacrum_. It has but few lacteals, and is, as it were, the last drainer of the fæces: It is this intestine which is the seat of the Colic, and of most other complaints of the belly.

Next to this comes the last and straightest, the _rectum_; this gut is closely adherent to the _sacrum_, and ends in the fundament; which is provided with muscles to open and shut the _anus_, in order to contain the fæces, and discharge it.

The mechanism of chylifaction in the human body differs from the brute creation in general, except that most contemptible of the whole, the hog; to which it bears a very near resemblance, insomuch that there is very little distinction.

Both have that advantage over the generality of terrestrial animals, that they are confined to no particular food; which favours greatly the luxury of the one, and the beastiality of the other.

The brute creation are generally distinguished into _carnivorous_ and _granivorous_: The first is that kind which feeds upon flesh; and the latter upon grain and vegetables. Upon examination however, we find, that the stomach and guts are peculiarly adapted to their food; and that grass agrees no more with the dog, than mutton does with the horse.

But man is so happily made, that any thing which is food, is proper for him, and he may become used to it; and thus is either carnivorous or granivorous.

The whole canals, from the stomach to the anus, is in a continual vermicular motion, which is called the _peristaltic motion_; by this the aliments are dissolved, and disunited; and as they pass along, are drained by the lacteals, of their _nutriment_ or _chyle_.

These lacteals are, by means of a membrane (with which they are surprisingly interwoven, and connected to the whole canal) called the _mesentery_, lead regularly into one common cistern, lodged almost in the middle of the intestines, in that membrane, called the _receptacle of chyle_; and from thence the _chyle_ is carried by a duct up along the back-bone, called the _ductus thoracicus_, into the left _subclavian vein_, where it gradually commences to be blood.

By this mechanism we are nourished, and the substance of our food converted into blood, and transported through the whole animal machine, for the support of every part of its wonderful composition.

As all animals which feed upon flesh, are more subject to diseases, nature has provided them with these advantages: that when any thing is obnoxious to their nature, and received into their stomach, or their being over loaded, it can discharge itself of so troublesome a burthen, by vomiting, which is effected thus: when the inner coat of the stomach, which is irritable and nervous, is stimulated by whatever is obnoxious, it will cause in the whole stomach, a contraction; and by that, force its contents to the shortest direction of evacuation, namely, by the canal of the oesophagus, through the mouth. This expulsion is peculiar to carnivorous animals only.

Purging or discharging by the fundament is common to all animals of whatever kind; and is performed by an irritation in the intestines, by which the peristaltic motion is increased; to this I must add a reversion of the secretion of the lacteal vessels, by which the humours are increased, the motion accelerated, and the fæces discharged, without giving any nourishment to the body, and consequently the system diminished.

Digestion is that act by which the aliment or food is prepared, so as to produce a good chyle, and consequently good blood, for the nourishment of the body. Though no animal has a more delicate stomach than man, yet it must be observed, that none has a stomach better adapted for all kinds of food.

Whence therefore in the common course of life, temperance and gentle exercise is what nature requires to maintain health. But nothing becomes more obnoxious to that blessing, than gluttony, voluptuousness, and idleness.

SECT. VII.

_Of the Bones, Muscles, Ligaments, Tendons, and their Connections._

The bones may be considered as the timber-work of the human frame; by which this wonderful fabric is supported, and kept in its due form, that the whole may be brought into its various movements, without confusion or obstruction to each other.

The bones are the most solid parts of the human body, composed of hard and indurated fibres, striated over each other, in a manner peculiar to that substance. The bony fibres are in themselves insensible, yet as the parts are variously distributed with arteries and veins, and that the nerves must necessarily have a share in their formation, they have a peculiar sensibility, which is perceptible in some parts more than others; they cannot strictly speaking, be deemed quite insensible.

The whole bony frame is covered with a tendinous and nervous tegument, called _periosteum_; except such parts of the teeth as are designed for mastication, which are provided with a peculiar enamel, that is harder than the rest of the bony substance.

The _periosteum_ is exquisitely sensible, and is the safe-guard to the substance of the bone, which is delicately tender notwithstanding it is not so sensible as the skin that covers it; insomuch that it will become _carious_ on the least exposure to the air, or the attack of any foreign body of matter whatever; whence in wounds and fractures in general, great attention should be paid to the substance of the bone, being very subject to become _carious_ and to _exfoliation_, which is of the greatest consequence; but of this I shall say more in another place.

The marrow is principally designed for the nourishment of the bones; which is evident from its being plentiest in young people, when the bones are strongest; and that when it is deficient, they become brittle, and lose their tenacity.

The marrow is contained in a cellular substance, partly in vesicles of a nervous texture, and partly bony cells. At the ends of the long bones the texture is more spungy than in the middle, where the cavity is less, but the substance is most compact. Though anatomically there is no perceptible circulation in the bones, yet, that a circulation is actually existing, is evident, from a liquor oozing out from the ends of a fractured bone in the living animal; by which a fractured bone again unites, and this is called the _callus_; and whilst in its liquid state, resembles the white of an egg, which gradually ossifies, and becomes as hard as the main substance of the bone.

The number of bones differ somewhat in various subjects; ordinarily they amount to two hundred and fifty-two: In the head sixty-three; in the trunk seventy; in the arms and hands sixty; and in the legs and feet sixty.

As the bones are the support of the animal fabric, I have inserted in the next page, a catalogue of the human skeleton, which occasionally may be referred to:

_A Skeleton of the Human Body._

BONES in the HEAD. The SKULL. _The Forehead._

Os Frontis 1

_The Hindhead._

Os Occipitis 1

_The Sides of the Head._

Ossa Parietalia 2

_The Temples._

Ossa Temporum 2

_The Basis of the Skull._

Os Ethmoides 1 Os Sphenoides 1

_The Bones of Hearing._

Ossicula 8 Auditus

The FACE. _The Upper-Jaw._

Ossa Malæ 2 ——Maxillare 2 ——Unguis 2 ——Nasi 2 ——Palati 2 Os Vomer 1

_The Under-Jaw._

Maxilla 1 Inferior

_The Teeth._

Dentes Incisivi 8 ——Canini 4 ——Molares 20

_The Tongue-Bone._

Os Hyoides, is 3 composed of

—

63

BONES in the TRUNK. _The Spine._

Vertebræ 7 Cervicis

——Dorsi 12

——Lumborum 5

_The Ribs._

Costæ Vera 14 ——Spuria 10

_The Shoulders._

Scapula 2 Claviculæ 2

_The Hip and Bason._

Os Sacrum, is 6 composed of

Os Coxygis, is 3 composed of

Ossa Innomenata, composed of

——Ischium 2

——Ilium 2

——Pubis 2

_The Breast._

Sternum, is 3 composed of

—

70

UPPER EXTREMITIES. _The Upper Arm._

Os Humerus 1

_The Under Arm._

Ulna 1 Radius 1

_The Wrist._

Ossa Carpi 8

_The Hand._

Ossa Metacarpi 4

_The Fingers._

Ossa Digitorum 15 — 30

UNDER EXTREMITIES. _The Thigh._

Os Femoris 1

_The Knee Pan._

Patella 1

_The Leg._

Tibia 1 Fibula 1

_Ancle._

Ossa Tarsi 7

_Foot._

Ossa Metatarsi 5

_Toes._

Digitorum 14 — 30

The connection of the bones are in various ways; those connections that are designed for rest, are by close contact of parts, and are called _sutures_ or _seams_; such are the bones of the skull with themselves and the face. Those connections which are designed for motion are called _articulation_. 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. The _sutures_, 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 a _capsular-bag_, which contains a slippery liquor, called _synovia_, that lubricates the ends of the bones covered with _cartilages_, that they may move with ease and agility over one another.

_Muscles_ are 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]

Footnote 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 their form 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.

SECT. VIII.

_Of the Urinary Organs and Genital Parts._

The _kidnies_, the _ureters_, the _bladder_, and the _urethra_, are the principal urinary organs. The kidnies receive two arteries called the _emulgent arteries_, from the great arterial trunk, called _aorta_, before described; they each send also two veins back again, accompanying the arteries to the _vena 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 the _ureter_ to the bladder. The _ureters_ enter the bladder between its _lamillas_, 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 exquisitely sensible. The neck of the bladder is very muscular, and by this forms a _sphincter_, 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 the _penis_, is the _urethra_; 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.

The _testicles_ are 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 the _aorta_, 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 ascending _vena cava_. These contorted and interwoven vessels are called the _spermatic vessels_, 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, called _vasa 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 the _vesiculæ 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.

The _penis_, or the manly member of generation, is partly covered with the common skin; the foremost part of which, that covers the glans, is called the _præpuce_. This _præpuce_ is tied underneath to the substance of the _penis_, by what is called the _frænum_.

The inner part of the penis is composed of two kinds of bodies, the _cavernous bodies_ of the _penis_, and the _cavernous body_ of the _urethra_. The first are bodies enveloped in their peculiar teguments, and make the greatest part of the _penis_. Each of these bodies takes its origin from the erecting muscle of the _penis_, which is near the _pubis_; through each of them goes an artery and a nerve, which spread themselves through these bodies.