Construction of the Foot.

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opposite kind was formerly seen in Paris, where, as the streets had no side pavements, and the ladies consequently had to walk almost constantly on tiptoe, over round stones, the great action of the muscles of the calf gave a conformation of the leg and foot, to match which the Parisian belles proudly challenged all the world,— not aware, probably, that it was a defect of their city to which the peculiarity was due.

Fashion has lately succeeded to some extent in reversing these natural results of healthy muscular action. It has been pointed out by Sir James Paget that the modern practice of attaching high heels to boots and shoes, destroys the proper action of the muscles of the calf of the leg by shortening and relaxing the point of attachment to the heel, and throwing the weight of the body more upon the instep than nature intended. This becomes a source of weakness and deformity, and it causes a person to walk with a tottering and unsteady gait. European ladies, while condemning the Chinese for their unnatural treatment of the human foot, are themselves guilty of cultivating deformity in another fashion.

That men lose not a little of the strength and command of their lower limbs by being condemned to use too small or too rigid shoes cannot be doubted; and the fact is of no small importance to a military people, for the result in battle of a charge where bayonets clash, must depend almost as much on the strength of the legs as of the arms.

A person confined to bed for a week or two by illness has generally to remark a much greater wasting of the legs than of the arms; the reason of which is, that the muscles of the leg being more in use than those of the arms, their ordinary bulk is more dependent on use, and they suffer a corresponding change from inaction.

The heel-bone of the negro race is longer, and projects more behind than that of the European; hence, it does not require so powerful a muscular effort to raise it. The muscles of the calf of the leg are therefore, cæteris paribus, less developed in them than

in our own race.

1084. The arch of the foot may be noticed as another of the many provisions for saving the body from shocks by the elasticity of the supports. The heel and the ball of the toes are the two extremes of the elastic arch, and the leg rests between them.

This explains why the measure of a person's foot taken when seated is considerably less both in length and breadth than when the person stands, with the whole weight of the body acting te

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Deformities of the Feet.

expand or lengthen the foot. It also helps to explain why boots and shoes are often made too small. But it is a whim of unreasoning fashion which holds that the human foot, as given by nature, is improperly large, and requires to have its growth controlled by the use of tight shoes. Persons who act on this notion, often have painful corns or bunions on their feet, and distorted toes, as the usual effects of pressure or friction, so that the act of walking is highly painful. Over the vast empire of China this absurdity is carried to an extent which is monstrous. Tight bandages are kept on the feet of the children from an early age, and the females of the higher classes become truly cripples for life. The foot is stunted in growth, and is practically converted into a sort of hoof, the sole of the foot being almost entirely obliterated.

The practice seems to be a sister folly to that of letting the fingernails grow to a hideous length within cases worn to defend them. Both deformities seem intended to show that the individuals are of a high order, not requiring to use either feet or hands to gain a livelihood.

Connected with elasticity, it is interesting to remark how imperfectly a rigid wooden leg answers the purpose of a natural leg. The centre of the body, when supported by the wooden leg, which remains always of the same length, must describe, at each step, an exact portion of a circle, of which the bottom knob of the leg is the centre; and the body is therefore constantly rising and falling somewhat like an animal advancing by leaps; but with the natural legs, which, by gentle flexure at the joints, are made shorter or longer at different parts of the step as required, the body is carried along softly in a manner nearly 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 his back yield a little at every movement, as a bent spring yields during the motion of a carriage, can carry his head smoothly along.

1085. The muscular force of man has been used as a working power in various ways, as in lifting and carrying a weight, pulling at a rope, turning a winch, or walking in the inside of a large wheel to move it, as a squirrel moves his little wheel, or in undergoing the punishment of the treadmill, which is utilized in prisons for a variety of purposes. Each of these has some peculiar advantage; but the mode in which, for the purpose of lifting weights, the greatest effect may be produced, is for the man to carry up

Muscular Force of Man.

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to a height his body only, and then to let it raise a load cqual to itself by its weight in descending. A bricklayer's labourer would be less fatigued, while lifting bricks to the top of a house by ascending the ladder without a load and then raising bricks of nearly his own weight over a pulley each time in descending, than by carrying fewer bricks and himself up together, and working down again without a load, as is still usually done in accordance with old habit. Reflection, independently of experiment, would naturally anticipate such a result, 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.

Animal power being exhausted in proportion as well to the time during which it is acting as to the intensity of force exerted, there may often be a great saving of power by doing work quickly, although with a little more exertion during the time. Suppose two men of equal weight to ascend the same stair, one of whom takes only a minute to reach the top, and the other takes four minutes, it will cost the first but a little more than a fourth part of the fatigue which it costs the second, because the exhaustion has relation to the time during which the muscles are acting. The quick mover must have exerted more force in the first instant, to give his body the greater velocity which was afterwards continued, but the slow mover has supported his load four times as long.

A healthy man will run rapidly up a long stair, and his breathing will scarcely be quickened at the top; but if he walk up very slowly his legs will feel considerable fatigue, and the body will generally sympathize. For the same reason coach-horses are sometimes spared by being made to trot quickly up a short hill, and being then allowed to go more slowly, so as to rest at the top.

The rapid waste of muscular strength which arises from continued action is felt by keeping an arm extended horizontally for some time. Few persons can continue the exertion beyond a minute or two. In animals with heavy projecting necks there is a singular provision of nature in a very strong elastic band attached to the back or upper part of the neck, which nearly supports the head independently of muscular exertion. In the horse this band (called ligamentum nucha) is of great breadth, and saves great muscular force by supporting the heavy head of the animal.

In further illustration of the truth that strength is saved in many

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The Male and Female Skeleton.

cases by doing work quickly, we may recall the fact explained in Art. 179, that a body thrown or shot upwards with double velocity, rises four times as far as when shot with a single velocity, or half of the other.

This saving of strength is also indicated in the use of the modern bicycle. By the aid of this machine a man has been able to travel from Bath to London, a distance of 112 miles, in nine hours. The large muscles of the thighs, and those which connect the thighs with the trunk, are here chiefly brought into action, while the muscles of the leg are mainly exerted in walking. By the mechanical effect of a wheel of large diameter (56 inches), a great space of ground is traversed in a short time. It would be impossible for a man to gʊ over this distance in the same time, either by walking or running.

1086. The Skeleton.—The skeleton in a full-grown adult does not form more than about one-fifteenth part of the weight of the body. A well-formed male skeleton weighs about ten pounds and a half, and a female skeleton nine pounds—the bones being in a dry state. In a general review of the skeleton there are some physical points worthy of remark, 1st, the nice adaptation of all the parts to one another, and to the strains which they have respectively to bear ; as—in the size of the spinal vertebræ gradually increasing from above downwards the bones of the leg being larger than those of the arm, and so on. 2ndly, 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 of the bones to which the muscles are attached, lengthening the levers by which these act. 3rdly, the nature and strength of material in different parts, so admirably adapted to the different purposes to be served. The bones are constituted of mineral and organic matter-the proportions of these varying in some respects, but being always adapted to the uses to which the bone is put. In the long bones of the arms and legs, where great strength is required, the mineral matter, consisting chiefly of phosphate and carbonate of lime, forms about twothirds, and the organic matter (consisting of osseine or gelatine) about one-third of the weight of the bone in a dry state. An undue proportion of the mineral substances renders the bone more liable to fracture from slight causes, while a deficiency of it leads to a softening and yielding of the bone under the weight of the body or muscular action. There is nothing more wonderful in the structure of the skeleton than the mode in which these mineral and organic

Composition of the Bones and Teeth.

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constituents of bone are distributed. If a bone like the scapula or blade-bone is placed for some time in a diluted acid, the mineral matter is entirely removed, while the organic matter remains. The bone retains its shape and size, but is now perfectly flexible and elastic. On the other hand, if this bone is heated to a very high temperature in an open furnace, it is first blackened from the carbon contained in the animal substance, and it ultimately becomes white and brittle, consisting entirely of mineral matter-i.e., of the phosphate and carbonate of lime. If this experiment is carefully performed, the bone will preserve its form and shape, but it is light and porous. These results show that there is no casual admixture of the mineral and organic constituents of bone, but a uniform and perfect diffusion of the two kinds of matter throughout the whole of the mass. Each molecule of mineral matter is associated with a proper amount of animal matter to cement the whole into a uniform solid.

1087. In the teeth, which are intended for tearing, grinding, and masticating all kinds of matter used as food, a harder material than bone is required. The body of the tooth consists chiefly of a bony substance (dentine), but this is covered more or less by enamel. They are both much harder than bone-the dentine containing 72, and the enamel 96 per cent. of mineral matter, chiefly phosphate of lime. The enamel is the hardest of all the tissues in the body, a property partly due to the very large proportion of mineral matter contained in it, and partly to its physical disposition-i.e., the close and compact manner in which it is deposited on or around the dentine of the tooth. On the upper surface of the tooth of the elephant, the dentine and the enamel are scen arranged in alternate layers traversing the width of the tooth. In the Asiatic elephant the enamel assumes a wavy form, while in the African variety the enamel is deposited in a narrow, lozenge-shaped form. As the dentine wears away more rapidly than the enamel, the surfaces of these large teeth are always in a rough state, and well fitted for grinding the hard food on which the animals live. Passing from the teeth to the bones of the cranium or skull, it may be remarked that, although the bones are thinner, they are tough and resisting.

In the middle of the long bones the bony matter is compact and little bulky, to leave room for the swelling during action of the muscles lying there; while, at each end, with the same quantity of matter, it is large and spongy, to give a broad surface for articulation; and in the spine, the bodies of the vertebræ, which have