Part 2

HAIRS; their formation, 178; colour, 179; uses, 180.

OIL-GLANDS; their uses, the odour of their secretion, 180.

SWEAT-GLANDS, 183; their structure, ib. The “Pores” of the Skin, 183. The moisture of the palm, 184. Cold Sweat, ib.

FEELING and TOUCH, 185. Structure of the three parts in which they are most acute, ib. The “Pulps” of the fingers connected with peculiar shape of the bones, 186; their sensitiveness to cold, 187. Distinction between Common Feeling and the Sense of Touch, 188. Relation between the two in the Tongue, the Eye and the Hand, 189. The tentacle of a Polyp a rudimentary hand, 191. Acuteness of touch in man, 193; in BLIND persons, ib.

Relation of the hand to the EYE and the MOUTH, 195. The Elephant’s Trunk, 197. CHEIROMANCY, 198. The LOCK-JAW fallacy, 200. Cause of the superiority of the RIGHT HAND, 201. “This unworthy hand!” 205.

Explanation of Wood-cuts, 207.

THE HUMAN FOOT.

The Human Body is one of the most worthy objects of man’s study. It is the noblest as well as the crowning work of creation. In it material organization is carried to the greatest perfection. It surpasses, therefore, all other physical objects in exquisiteness of construction and in interest. How comes it, then, that most persons are so ignorant respecting it? Men, well informed in other matters, are usually altogether uninformed with regard to this. In every other branch of science we find amateur students pursuing the subject with zeal and success. Geology, Chemistry, Botany, Zoology, and even Comparative Anatomy have each their votaries; but Human Anatomy attracts no one. Why is this? Partly, I think, because opportunities for acquiring such information as is suitable and interesting are not so many as they ought to be.

It must be confessed, also, that we teachers of Anatomy are somewhat to blame. We are too prone, in our Lectures and Examinations, to dwell upon bare details, without enlivening those details with the many bright features of interest with which they are naturally invested; and we fail, therefore, to render it so attractive a science as it might be. The example of those able and animated teachers, John and Charles Bell, who laboured with some success to disperse the clouds that have ever overhung the horizon of anatomy, has been too much forgotten; and the flame which they kindled has almost died out under the chilling apathy of their successors. Truly glad should I be to see a change in this. I cannot but think that if the teachers of Anatomy took higher and more philosophical views of their science there would be no lack of interest on the part of the students. The interest so excited would soon spread beyond the limits of the profession; and there would thus be opened up to the public some of the products of that rich vein of knowledge and of that abundant material for thought which lie buried in the human frame.

I therefore willingly accede to your request for a Lecture upon some part of the anatomy of the human body, relying upon the intrinsic interest of the subject to make amends for my own deficiencies in expounding it; and I select the HUMAN FOOT, because a few of the more important points of its construction can be explained without much difficulty, because it affords a good illustration of some of the principles of animal mechanism, and because its form constitutes one of the great characteristics whereby man is distinguished from the lower animals. As an instrument of support and of locomotion it excels the foot of any other animal. It evinces its excellence by enabling man to stand upright in a way that no other animal can do; and so efficiently does the foot accomplish this and perform the task of carrying the body, that the hand is set at liberty to minister to the will. Thus is the foot instrumental in giving us an advantage over other animals, and in enabling us to provide the means of defence; and, thus, it aids us to carry out those wondrous works which are second only to the marvellous results of creative power.

We are accustomed to regard the hand as the great agent by which all this is attained, and we are apt to forget how much it is indebted to the foot. We do not reflect that, if the foot of man presented no distinguishing peculiarity, the hand, like the corresponding part in other animals, would be compelled to share with it the task of carrying the body, and could, therefore, not be devoted to the various offices which it is now free to perform. Little right has the hand to say to the foot, “I have no need of thee.”

The principle of “division of labour.”

In this concentration of locomotive power in the foot we have an illustration of what is called the “principle of division of labour,” a principle with which all civilized communities are familiar, and to which we are much indebted for the present advanced state of the arts and sciences; but which we may be said to have borrowed from the economy of nature. We find ever-increasing manifestations of it as we ascend in the animal series, from the lower and more simple to the higher and more complicated forms. Indeed, just as each step in civilization is attended with a further development of this principle, so is each division of the animal kingdom distinguished from those below it by the more distinct assignation of particular functions to particular organs, and by the consequent improvement of the mode in which the functions are performed. While, in proportion as the several organs acquire more distinct speciality in their work, so do they become, more and more, dependent upon one another, and, more and more, subjected to the control of central government, which is represented by the brain.

For instance, some of the lower animals, as the fresh-water POLYP, present nearly a uniform structure throughout their whole substance; and every part of them consequently performs the same function. There is not one organ for digestion, another for circulation, a third for respiration, and so on; but all these functions are performed by the same structure, and are performed, therefore, in a rude and imperfect manner. Any portion of the creature possesses all the requisites for its own nutrition, and is, so, independent of the remainder, and can live alone. Hence, the polyp may be divided into a number of pieces, each of which goes on living. Gradually, as we ascend from these lowly beings to the higher classes of animals, we find organs and functions more and more distinct from another; a Stomach is provided for the work of digestion, a Heart for circulation, Lungs for respiration. Each of these organs is essential to the existence of the others and of every part of the body; and they are all maintained in harmonious co-operation by the presiding influence of the nervous system.

Or, trace one of the functions in illustration of the same principle. Take the function of Locomotion, which has an especial relation to our present subject. In the LEECH and the WORM the whole length of the body is occupied in the work, one part as much as another; and still, it is but a crawl. In the FISH the whole body is buoyed up by the water; it is flattened from side to side, and is all, from the head to the tail, concerned in the lateral stroke by which the animal is driven along; the side fins, which are the representatives of limbs, doing little beyond serving to guide and balance. In the other VERTEBRATES the work of locomotion is so far concentrated as to be assigned, almost entirely, to the limbs. All four limbs are in most of them devoted to it; while the bones and muscles of the trunk are only indirectly concerned in it. In MAN, however, two limbs only are assigned to this important office. In him, therefore, the concentration of locomotive power, in other words the principle of division of labour, is carried out to the greatest extent--a disposition which affords one of the many proofs that the construction of his body combines with the faculties of his mind to place him at the head of the animal kingdom.

In making comparisons of different animals with one another, and in speaking of the relative perfection of their several organs, we must not forget that every organ of every animal is perfect as regards the purpose for which it was made. But some animals are said to occupy a higher position than others, or to be superior to others, because their mechanism is more complex, and they are, thereby, enabled to perform a greater variety of functions. And, in the animal kingdom, in proportion as each function rises into prominence, and becomes well and distinctly performed, so is a special organ assigned to it, and that organ becomes more and more highly elaborated.

You will not misunderstand me, then, when I say that concentration of function and perfection of structure usually go together. And, forasmuch as in the lower limbs of man there is a greater concentration of locomotive function than in any other part of any other animal, you will expect to find, in them, a greater perfection of locomotive mechanism--that is to say, a more complete combination of strength with variety, rapidity, and extent of movement--than is elsewhere to be met with.

This consideration will ensure attention while I give a brief account of the anatomy of man’s lower limb, more particularly of the foot.

Structure of the Lower Limbs.

The weight of the trunk is transmitted to the knee (see fig. 4, p. 15) by a single bone--the thigh-bone. This is the longest bone in the body, measuring, on the average, nearly eighteen inches. Above, it is jointed with the haunch-bone of the pelvis at the hip-joint. From the knee two bones descend to the ankle. Of these one is much the larger, and bears the chief of the weight. The other serves to give attachment to muscles, and to strengthen the ankle-joint. It runs down on the outer side of the ankle, forming there what is called the “outer ankle;” and a process of the larger bone runs down, in like manner, on the inner side, and forms the “inner ankle.” The front and inner side of the larger bone are close under the skin. This part is called the “shin,” being so named perhaps from the word “chine” or edge, because the leg presents an edge along the front, to facilitate its cleaving a way through the air, water, grass, or underwood. The shin itself is not particularly tender; but the skin is a good deal exposed here, and, as it lies so near the hard bone, it is easily injured; and, when “broken,” it is often difficult to heal.

In some very tall persons, and particularly in those who are so tall as to be called GIANTS, I have found the leg or shank bones, that is, the bones between the knee and the ankle, very long, disproportionately long to the rest of the skeleton. They are so in the skeleton of the Irish Giant, O’Byrne, which is preserved in the Museum of the College of Surgeons, in another Irish Giant in the Museum of Trinity College, Dublin, and in some other specimens which I have had an opportunity of measuring. In the name “Long Shanks” given to Edward I., the word “shanks” probably included the thigh as well as the leg, just as we are in the habit of applying the word “leg” to the whole of the lower limb.

Bones of the Foot.

There are 26 bones in the Foot. The hinder 7--called tarsal bones--are short and thick; they form the hinder part of the instep. In front of them lie 5 metatarsal bones, one passing, forwards, from the fore part of the tarsus to each toe. Behind, these are close together, and are connected with the tarsus. As they run forwards they diverge a little from one another; and their anterior ends rest upon the ground, and form the “balls” of the toes. They constitute the fore part of the instep. The remaining 14 bones are the toes. They are arranged in rows, like soldiers in a phalanx, three deep, and are hence called phalanges.

You observe that, although each of the other toes has 3 bones, the great toe has only 2. In this respect, therefore, it is an imperfect, or, rather, an incomplete member. The deficiency does not depend upon a want of length in the great toe; for this is usually as long as the second toe; in some persons it is a good deal longer; and it is always distinctly longer than the outer two toes. The reason for there being only two phalanges instead of three probably is because the great toe is required to be stronger than any of the others; and an additional bone would have tended to weaken it. I have, elsewhere, given reasons for thinking that it is the middle phalanx which is absent in the great toe.

Treatise on the Human Skeleton, p. 395.

Seal’s Foot.]

Lizard’s Foot.]

It is a curious and interesting fact, affording a remarkable illustration of the close adherence to a uniform plan which has been observed in the construction of the various animals, that, in no instance, does this toe contain more than two bones. Even in those creatures, as the SEAL (fig. 2), in which it attains to greater length than any of the other sprawling digits, it contains the same number of bones as in man, its extraordinary length being attained by an elongation of the two bones, not by the addition of a third. And in those animals, as certain Lizards (fig. 3), where the number of bones in the other toes is increased to 4 or even 5, the number in the first, or inner, toe is still no more than two. The same rule applies to the fore limb; the number of bones in the inner digit, which, in man and monkeys, is called the “thumb,” is in no case more than two. In some animals, as will be mentioned again, there is only one bone in this digit, and in some the digit is wanting altogether; but in none does it contain more than two bones.