toms, which seemed to threaten a suspension of life by a perseverance in exertion, usually go off upon the person's standing still, or turning from the wind; but, in a more advanced stage, they do not so readily recede, and the paroxysms are much more violent. During the fit, the pulse sinks, in a greater or less degree, and becomes irregular; the face and extremities are pale, and bathed in a cold sweat, and, for a while, the patient is perhaps deprived of the powers of sense and voluntary motion. The disease having recurred more or less frequently during the space of some years, a violent attack at last puts a sudden period to existence. Angina pectoris is attended with a considerable degree of danger; and it usually happens that the person is carried off suddenly. It mostly depends upon an ossification of the coronary arteries; and then we can never expect to effect a radical cure. During the paroxysms, considerable relief is to be obtained from fomentations, and administering powerful antispasmodics, such as opium and ether combined together. The application of a blister to the breast is likewise attended sometimes with a good effect. As the painful sensation at the extremity of the sternum often admits of a temporary relief, from an evacuation of wind by the mouth, it may be proper to give frequent doses of carminatives, such as peppermint, caraway or cinnamon water. When these fail in the desired effect, a few drops of ol. anisi, on a little sugar, may be substituted. With the view of preventing the recurrence of the disorder, the patient should carefully guard against passion, or other emotions of the mind: he should use a light, generous diet, avoiding every thing of a heating nature; and he should take care never to overload the stomach, or to use any kind of exercise immediately after eating. Besides these precautions, he should endeavor to counteract obesity, which has been considered as a predisposing cause: and this is to be effected most safely by a vegetable diet, moderate exercise at proper times, early rising, and keeping the body perfectly open.

ANGLICAN CHURCH. (See England, Church of.)

ANIMAL MECHANICS. Mechanism of the human Skeleton. There is scarcely a part of the animal body, or an action which it performs, or an accident that can befall it, or a piece of professional assistance which can be given to it, that does not furnish illustration of some truth of natural philosophy; but we shall here

only touch upon as many particulars as will make the understanding of others easy.

The cranium, or skull, is an instance of the arched form, answering the purpose of giving strength. The brain, in its nature, is so tender, or susceptible of injury, that slight local pressure disturbs its action. Hence a solid covering, like the skull, was required, with those parts made stronger and thicker which are most exposed to injury. An architectural dome is constructed to resist one kind of force only, always acting in one direction, namely, gravity; and therefore its strength increases regularly towards the bottom, where the weight and horizontal thrust of the whole are to be resisted; but, in the skull, the tenacity of the substance is many times more than sufficient to resist gravity, and therefore aids the form to resist forces of other kinds, operating in all directions. When we reflect on the strength displayed by the arched film of an egg-shell, we need not wonder at the severity of blows which the cranium can withstand.

Through early childhood, the cranium remains, to a certain degree, yielding and elastic; and the falls and blows so frequent during the lessons of walking, &c., are borne with impunity. The mature skull consists of two layers, or tables, with a soft diploe between them, the outer table being very tough, with its parts dovetailed into each other, as tough wood' would be by human artificers; while the inner table is harder, and more brittle (hence called vitreous), with its edges merely lying in contact, because its brittleness would render dove-tailing useless. A very severe partial blow on the skull generally fractures and depresses the part, as a pistol bullet would; while one less severe, but with more extended contact, being slowly resisted by the arched form, often injures the skull by what is correspondent to the horizontal thrust in a bridge, and causes a crack at a distance from the place struck, generally half way round to the opposite side. Sometimes, in a fall with the head foremost, the skull would escape injury, but for the body, which falls upon it, pressing the end of the spine against its base.

The

In the lower jaw, we have to remark the greater mechanical advantage, or lever power, with which the muscles act, than in most other parts of animals. temporal and masseter muscles pull almost directly, or at right angles to the line of the jaw; while in most other cases, as

in that of the deltoid muscle lifting the arm, the muscles act very obliquely, and with power diminished in proportion to the obliquity. An object placed between the back teeth is compressed with the whole direct power of the strong muscles of the jaw: hence the human jaw can crush a body which offers great resistance, and the jaws of the lion, tiger, shark, and crocodile, &c., are stronger still.

The teeth rank high among those parts of the animal body which appear almost as if they were severally the fruits of distinct miraculous agencies, so difficult is it to suppose a few simple laws of life capable of producing the variety of form so beautifully adapted to purposes which they exhibit. They constitute an extraordinary set of chisels and wedges, so arranged as to be most efficient for cutting and tearing the food, and, with their exterior enamel, so hard that, in early states of society, teeth were made to answer many purposes for which steel is now used. It seems, however, as if the laws of life, astonishing as they are, had still been inadequate to cause teeth, cased in their hard enamel, to grow as the softer bones grow; and hence has arisen a provision more extraordinary still. A set of small teeth appear soon after birth, and serve the child until six or seven years of age: these then fall out, and are replaced by larger ones, which endure for life; the number being completed only when the man or woman is full-grown, by four teeth, called wisdom teeth, because they come so late, which rise to fill up the then spacious jaw.

The spine, or back-bone, has, in its structure, as much of beautiful and varied mechanism as any single part of our wonderful frame. It is the central pillar of support, or great connecting chain of all the other parts; and it has, at the same time, the office of containing within itself, and of protecting from external injury, a prolongation of the brain, called the spinal marrow, more important to animal life than the greater part of the brain itself. We shall see the spine uniting the apparent incompatibilities of great elasticity, great flexibility in all directions, and great strength, both to support a load and to defend its important contents.

Elasticity. The head may be said to rest on the elastic column of the spine, as the body of a carriage rests upon its springs. Between each two of the twenty-four vertebræ, or distinct bones, of which the spine consists, there is a soft, elastic intervertebral substance, about

half as bulky as a vertebra, yielding readily to any sudden jar; and the spine, moreover, is waved, or bent a little, like an italic f, as seen when it is viewed sideways; and, for this reason, also, it yields to any sudden pressure operating from either end. The bending might seem a defect in a column intended to support weight; but the disposition of the muscles around is such as to leave all the elasticity of the bend and a roomy therax, without any diminution of strength.

Flexibility. The spine may be compared to a chain, because it consists of twenty-four distinct pieces, joined by smooth rubbing surfaces, so as to allow of motion in all directions; and a little motion, comparatively, between each two adjoining pieces, becomes a great extent of motion in the whole line. The articulating surfaces are so many, and so exactly fitted to each other, and are connected by such number and strength of ligaments, that the combination of pieces is really a stronger column than a single bone of the same size would be.

The strength of the spine, as a whole, is shown in a man's easily carrying upon his head a weight heavier than himself, while each separate vertebra is a strong irregular ring, or double arch, surrounding the spinal marrow. The spine increases in size towards the bottom, in the justest proportion, as it has more weight to bear.

The Ribs. Attached to twelve vertebræ, in the middle of the back, are the ribs, or bony stretchers of the cavity of the chest, constituting a structure which solves, in the most perfect manner, the difficult mechanical problem of making a cavity with solid exterior, which shall yet be capable of dilating and contracting itself. Each pair of corresponding ribs may be considered as forming a hoop, which hangs obliquely down from the place of attachment behind; and so that, when the fore part of all the hoops is lifted by the muscles, the cavity of the chest is enlarged.

We have to remark the double connexion of the rib behind, first to the bodies of two adjoining vertebræ, and then to a process or projection from the lower, thus effecting a very steady joint, and yet leaving the necessary freedom of motion; and we see the fore part of the rib to be of flexible cartilage, which allows the degree of motion required there, without the complexity of a joint, and admirably guards, by its elasticity, against the effects of sudden blows or shocks.

The muscles which have their origin on the ribs, and their insertion into the bones of the arm, afford us an example of action and reaction being equal and contrary. When the ribs are fixed, these muscles move the arm; and, when the arm is fixed, by resting on a chair or other object, they move the ribs. This is seen in fits of asthma and dyspnea.

The shoulder joint is remarkable for combining great extent of motion with great strength. The round head of the shoulder-bone rests upon a shallow cavity in the shoulder-blade, that it may turn freely in all ways; and the danger of dislocation from this shallowness is guarded against by two strong bony projections above and behind. To increase the range of motion to the greatest possible degree, the bone called the shoulder-blade, which contains the socket of the arm, slides about itself upon the convex exterior of the chest having its motion limited only by a connexion, through the collar-bone, or clavicle, with the sternum.

The scapula, or blade-bone, is extraordinary as an illustration of the mechanical rules for combining lightness with strength. It has the strength of the arch, from being a little concave, and its substance is chief ly collected in its borders and spines, with thin plates between, as the strength of a wheel is collected in its rim, and spokes, and nave.

The bones of the arms, considered as levers, have the muscles which move them attached very near to the fulcra, and very obliquely; so that, from working through a short distance comparatively with the resistances overcome at the extremities, the muscles require to be of great strength. It has been calculated that the muscles of the shoulder-joint, in the exertion of lifting a man upon the hand, pull with a force of two thousand pounds. The os humeri, or bone of the upper arm, is not perfectly cylindrical; but, like most of the other bones which are called cylindrical, it has ridges to give strength, on the principle explained in the article Strength of Materials, in this Appendix. The elbow-joint is a correct hinge, and so strongly secured, that it is rarely dislocated without fracture.

The fore-arm consists of two bones, with a strong membrane between them. Its great breadth, from this structure, affords abundant space for the origin of the many muscles that go to move the hand and fingers; and the very peculiar mode of connexion of the two bones, give man that most useful faculty of turning

the hand round, into what are called the positions of pronation and supination, exemplified in the action of twisting, or of turning a gimlet.

The Wrist. The many small bones forming this, have a signal effect of deadening, in regard to the parts above, the shocks or blows which the hand receives.

The annular ligament is a strong band passing round the joint, and keeping all the tendons which pass from the muscles above to the fingers, close to the joint. It answers the purpose of so many fixed pulleys for directing the tendons: without it, they would all, on action, start out like bow-strings, producing deformity and weakness.

The human hand is so admirable, from its numerous mechanical and sensitive capabilities, that an opinion at one time commonly prevailed, that man's superior reason depended on his possessing such an instructer and such a servant. Now, although reason, with hoofs instead of fingers, could never have raised man much above the brutes, and probably could not have secured the continued existence of the species, still the hand is no more than a fit instrument of the godlike mind which directs it.

The pelvis, or strong irregular ring of bone, on the upper edge of which the spine rests, and from the sides of which the legs spring, forms the centre of the skeleton. A broad bone was wanted here to connect the central column of the spine with the lateral columns of the legs; and a circle was the lightest and strongest. If we attempt still further to conceive how the circle could be modified to fit it for the spine to rest on, for the thighs to roll in, for muscles to hold by, both above and below, for the person to sit on, we shall find, on inspection, that all our anticipations are realized in the most perfect manner. In the pelvis, too, we have the thyroid hole and ischiatic notches, furnishing subordinate instances of contrivance to save material and weight: they are merely deficiencies of bone where solidity could not have given additional strength. The broad ring of the pelvis protects most securely the important organs placed within it.

The hip-joint exhibits the perfection of the ball and socket articulation. It allows the foot to move round in a circle, as well as to have the great range of backward and forward motion exhibited in the action of walking. When we see the elastic, tough, smooth cartilage which lines the deep socket of this joint, and the sim

ilar glistening covering of the ball or head of the thigh-bone, and the lubricating synovia poured into the cavity by appropriate secretories, and the strong ligaments giving strength all around, we feel how far the most perfect of man's works falls short of the mechanism displayed by

nature.

The thigh-bone is remarkable for its projections called trochanters, to which the moving muscles are fixed, and which lengthen considerably the lever by which the muscles work. The shaft of the bone is not straight, but has a considerable forward curvature. Short-sightedness might suppose this a weakness, because the bone is a pillar supporting a weight; but the bend gives it, in reality, the strength of the arch, to bear the action of the mass of muscle called vastus, which lies and swells upon its fore part.

The knee is a hinge joint of complicated structure; and it claims the most attentive study of the surgeon. The rubbing parts are flat and shallow, and therefore the joint has little strength from form; but it derives security from the numerous and singularly-strong ligaments which surround it. The ligaments on the inside of the knees resemble, in two circumstances, the annular ligaments of joints, namely, in having a constant and great strain to bear, and yet in becoming stronger always as the strain increases. The line of the leg, even in the most perfect shapes, bends inward a little at the knee, requiring the support of the ligaments, and, in many persons, it bends very much; but the inclination does not increase with age. The legs of many weakly in-kneed children become straight by exercise alone. This inclination at the middle joint of the leg, by throwing a certain strain on the ligaments, gives an increase of elasticity to the limb, in the actions of jumping, running, &c. In the knee, there is a singular provision of loose cartilages, which have been called friction cartilages, from a supposed relation in use to friction wheels; but their real effect seems to be to accommodate, in the different positions of the joint, the surfaces of the rubbing bones to each other. The great muscles on the fore part of the thigh are contracted into a tendon a little above the knee, and have to pass over, and, in front of the knee, to reach the top of the leg, where their attachment is. The tendon, in passing over the joint, becomes bony, and forms the patella, or knee-pan, often called the pulley of the knee. This peculiarity enables the mus

cles to act more advantageously, by increasing the distance of the rope from the centre of motion. The patella is, moreover, a sort of shield or protection to the fore part of this important joint. The leg below the knee, like the fore-arm already described, has two bones. They offer spacious surface of origin for the numerous muscles required for the feet, and they form a compound pillar of greater strength than the same quantity of bone as one shaft would have had. The individual bones also are angular instead of round, hence deriving greater power to resist blows, &c.

The ankle-joint is a perfect hinge of great strength. There is in front of it an annular ligament, by which the greater part of the tendons, passing downwards to the foot and toes, are kept in ther places. One of these tendons passes under the bony projection of the inner ankle, in a smooth appropriate groove, exactly as if a little fixed pulley were there.

The heel, by projecting so far backwards, is a lever for the strong muscles to act by, which form the calf of the leg. and terminate in the tendo achillis. These muscles, by drawing at it, lift the body, in the actions of standing on the toes, walking, dancing, &c. In the foot of the negro, the heel is so long as to be ugly in European estimation; and, its great length rendering the effort of smaller muscles sufficient for the various purposes, the calf of the leg in the negros smaller in proportion than in other races of men.

The arch of the foot is to be noticed as another of the many provisions for saving the body from shocks by the elasticity of the supports. The heels and the balas of the toes are the two extremes of the elastic arch, and the leg rests between them.

Connected with elasticity, it is interesting to remark how imperfectly a wooden leg answers the purpose of a natural leg With the wooden leg, which always remains of the same length, the centre of the body must describe, at each step, a portion of a circle of which the bottom nob of the leg is the centre, and the body is therefore constantly rising and falling: while, with the natural legs, which, by gentle flexure at the knee, are made shorter or longer in different parts of the step, as required, the body is carried along in a manner perfectly level. In like manner, a man riding on horseback, if he keep his back upright and stiff, has his head jolted by every step of the trotting animal;

but the experienced horseman, even without rising in the stirrups, by letting the back yield a little at each movement, as a bent spring yields during the motion of a carriage, can carry his head quite smoothly along.

In a general review of the skeleton, we have to remark, 1. the nice adaptation of all the parts to each other, and to the strains which they have respectively to bear; as in the size of the spinal vertebræ increasing from above downwards; the bones of the leg being larger than those of the arm, and so on. 2. The objects of strength and lightness combined; as by the hollowness of the long bones; their angular form; their thickening and flexures in particular places where great strain has to be borne; the enlargement of the extremities to which the muscles are attached, lengthening the lever by which these act, &c. 3. We have to remark the nature and strength of material in different parts, so admirably adapted to the purposes which the parts serve. There is a bone, for instance, in one place, nearly as hard as iron, where, covered with enamel, it has the form of teeth, with the office of chewing and tearing all kinds of matter used as food. In the cranium, again, bone is softer, but tough and resisting; in the middle of long bones, it is compact and little bulky, to leave room for the swelling of the muscles lying there; while, at either end, it is large and spongy, with the same quantity of matter, to give a broad surface for articulation; and, in the spine, the bodies of the vertebræ, which rest on an elastic bed of intervertebral substance, are light and spongy, while their articulating surfaces and processes are very hard. In the joints, we see the tough, elastic, smooth substance, called cartilage, covering the ends of the bones, defending and padding them, and destroying friction. In infants, we find all the bones soft or gristly, and therefore calculated to bear, with impunity, the falls and blows unavoidable at their age; and we see certain parts remaining cartilage or gristie for life, where their elasticity is necessary or useful, as at the anterior extremities of the ribs. About the joints, we have to renark the ligaments which bind the bones together, possessing a tenacity scarcely equalled in any other known substance; and we see that the muscular fibres, whose contractions move the bones, and thereby the body, because they would have made the limbs clumsy even to deformity had they all passed over the joints to the parts which they have to pull,-attach 31

VOL. XIII.

themselves, at convenient distances, to a strong cord called a tendon, by means of which, like a hundred sailors at a rope, they make their effort effective at any distance. The tendons are remarkable for the great strength which resides in their slender forms, and for the lubricated smoothness of their surfaces. Many other striking particulars might be enumerated; but these may suffice. Such, then, is the skeleton, or general frame-work of the human body-less curious and complicated, perhaps, than some other parts of the system, but so perfect and so wonderful, that the mind which can attentively consider it without emotion, is in a state not to be envied.

The living force of man has been used as a working power in various ways, as in turning a winch, pulling at a rope, walking in the inside of a large wheel to move it, as a squirrel or turn-spit dog moves his little wheel, &c. Each of these has some particular advantage; but that mode in which, for many purposes, the greatest effect may be produced, is for the man to carry up to a height his body only, and then to let it work by its weight in descending. A bricklayer's laborer would be able to lift twice as many bricks to the top of a house in the course of a day, by ascending a ladder without a load, and raising bricks of nearly his own weight over a pulley each time in descending, as he can by carrying bricks and himself up together, and descending again without a load, as is still usually done.

Reflection would naturally anticipate the above result, independently of experiment; for the load which a man should be best able to carry, is surely that from which he can never free himself— the load of his own body. Accordingly, the strength of muscles and disposition of parts are all such as to make his body appear light to him.

The question which was agitated with such warmth some time ago, as to the propriety of making men and women work on the tread-mill, receives an easy decision here. They work by climbing on the outside of a large wheel or cylinder, which is turning by their weight, and on which they must advance just as fast as it turns, to avoid falling from their proper situation. There are projections or steps for the feet on the outside of the cylinder, and the action to the workers is exactly that of ascending an acclivity. Now, as nature has fitted the human body for climbing hills, as well as for walking