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them. But, by their diffuse spongy tissue, a ready path is opened both for the diffusion and expenditure of force; neither is it till the force is aggregated or compressed into the much narrower and less cancellated structure of the tibio-astragaloid articulation that, when the body is raised and depressed successively upon the anterior extremities of the feet, with the knees in a semiflexed position, that we experience any sense of weight, at which time it may be distinctly felt in the ankle-joint and ball of the great toe.

But if the knee-joint present a structure, the osseous mechanism of which is peculiarly adapted to diffuse and expend force, from the very nature of such mechanism, as has already, in the introductory remarks, been referred to, it is incapable of conducting any force to the articular surface in the same direction in which it was first received, but in some course or direction which the mechanism of the structure of the osseous tissue, etc., of the joint compels it to assume, independent of previous bias. Therefore, it follows, that the feeling experienced in the joint itself must obey the indications of the forced or compelled bias which its structure is adapted to secure, and not that which external appliances appear likely to determine. (Of course the remarks relative to fibro-cartilage, as well as to the spongy tissue of the bony framework, already detailed, apply to the joint at present under consideration.)

To throw the matter into fuller relief, contrast this with the ankle-joint, and the articulations of the metatarsal bone of the great toe, unprotected with articular fibro-cartilage, with the additional advantage of the constricted and comparatively dense inferior extremity of the tibia; so constructed as to gather the widely distributed force at its superior extremity into a narrow surface inferiorly, and that too covered with simple cartilage, whose line of direction being continuous with the long axis of the bone, the mechanism of this structure is in every way adapted to perpetuate motion in the same direction in which it is first received.

The same remarks, relative to the knee-joint, apply with almost equal force to the hip-joint; since, though the rim of the cotyloid cavity, and the head of the femur, have not so widely diffused a cancellated structure, yet the obliquity of the surgical neck of the femur to the shaft of the bone will completely destroy the precise direction of pre-existing force channelling along the shaft. Again, the peculiar mechanical arrangement of the pelvic bones, and the variable angles at which force will meet, and, by counterpoise, be brought to equilibrium, or nullity, ere it reaches the hip-joint, greatly tend to limit force; while the residue, not so composed, will, by friction, be much checked in rapidity, and reduced in original impetus, and will reach the joint, for the most part, in one common direction according to the course any force may have to take along the pelvic bones, and not in relation to the direction in which force is first received upon any part of its firm framework. The result of this compulsion, in relation to the course or line of force,

will be, as stated in an early part of this paper, that in place of a consciousness of weight being experienced in the hip or knee-joints from any force reaching, or being applied to, their articular surfaces in an oblique direction, a feeling of strength or resistance will only be felt.

Notwithstanding the special pleading in the foregoing paragraph, it will nevertheless be asked, is it not possible to induce by experiment a consciousness of weight in these joints, as an antithesis to their normal feeling, and so render the hypothesis of one sense presenting the combined function of opposite states of consciousness, as that of resistance or strength, and of weight, more determinate, and so place the hypothesis upon the broad foundation of experiment and induction? To meet this very natural inquiry, I will endeavour to illustrate the hypothesis by only one experiment for either joint.

I will commence with the knee. If I extend the thigh and leg backwards, and place the foot, or rather the toes, upon a chair or a high stool, taking care to hold by some fixed point, lest, in such an unnatural position, I lose the balance in the opposite limb; and, if in this position I place a poker or any other suitable instrument in the popliteal region, exactly opposite the joint, I shall feel the full weight of the instrument; but if I place the same a little above or below this site, very little consciousness of weight is experienced.

This, then, is almost the only experiment that I have been able to devise for this joint; and, since it appears to be a pretty conclusive one, and not open, as far as I can see, to any objection based upon the conditions required for a conclusive experiment upon the present hypothesis, I need not, if I could, proceed any further with multiplying experiments upon this joint. I shall merely add, that in the foregoing trial, all the provisions made in the mechanism of the joint to throw force into one common and arbitrary course, independent of the manner or course in which it is received, are here obviated; and the diagonal of the two forces-gravitation and muscular force -will reach the sentient surfaces of the joint little expended, and at that line of obliquity which is here supposed to be well adapted to give to the nerves of the part a suitable stimulus for exciting the feeling of weight.

As regards the hip-joint, it will be perceived that in devising any experiment for it, difficulties surround us on every side from the peculiar position of the articulation; but here, as before intimated, one experiment may be set forward.

In performing an experiment upon the hip-joint care must be taken as to the position of the party to be experimented upon. First, then, let the party be seated in a chair, and leaning backwards; let the (right?) leg be semiflexed and resting upon the ball of the great toe, very much in the same position as a sociable man will take a little child and place it upon his thigh or knee, and give it-as the little creature will call it a ride. In this position let a poker be placed

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NEW SERIES.-NO. III. MARCH 1855.

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external to Poupart's ligament, and immediately below the inferior anterior spinous process. Thus adjusted, let the party gently raise and depress the limb upon the internal axis of the foot (ball of great toe), when a considerable degree of weight will be felt; place the same instrument superiorly or inferiorly to the afore described position, when scarcely any weight will be felt.

Here we have not quite so decisive an experiment-from the difficulty of performing it as that upon the knee-joint, from the conformation of the joint itself. Yet here, as elsewhere, in that part where the two forces-muscular and gravitation-can be brought to antagonize with each other-from the variable angles at which they may be brought in contact with each other-we have the consciousness of weight most apparent.

In suggesting these two experiments it may be well to add a caution or two in case any attempt be made to vary them. The first caution has relation to the hip-joint, and comes within the category of an apparent exception. Supposing a weight, as a poker, be placed internal to Poupart's ligament at variable points, till it reaches the mesian line over the symphisis pubis; the intensity of feeling or consciousness of weight will be found to gradually increase till the mesian line is attained, where it is the greatest, and gradually diminishes as the object is removed external to that point. intensity in the feeling of weight, in this region, is owing to the distribution of nerves of force to the integument, at least so the writer thinks, and he will, as before stated, endeavour to examine the matter in a subsequent paper.

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The other caution refers to the knee-joint. Suppose an individual, after trying a few experiments, conceives that some more decisive ones might be brought to bear upon the subject, and in his diligent zeal tries to realize the weight of the trunk by raising and lowering it, by gentle flexion and extension of the lower extremities, he will find, by so doing, that a sensation of weight is experienced in the ball of the great toe and ankle-joint. But could not, he will say, a similar sensation be induced in the knee-joint? Suppose then, again, that the same individual, to limit the weight of the body to the knee-joint as much as possible, and so make the trial more conclusive, balances the body upon one leg, flexing the trunk upon the thigh, and the thigh upon the leg, and by very powerful contraction of the muscles he raises the body into the erect position. Contrary to his feeling any sense of weight in the joint, if it is more than he is equal to, the exertion may at the time, from too great pressure, produce aching or pain in the joint, but if he is quite equal to it, whilst raising the body, he will only feel a sense of resistance or strength, which, according to the conditions under which this sense responds to the stimulus of force in the knee-joint, ought to be the case. But, as soon as the extension ceases, a feeling of aching and weariness immediately follow, sufficient to drown all other previous feeling in the limb. Yet, as experience has

taught us that this feeling follows great muscular exertion, or slight and long continued, it is naturally supposed that here is the sense which supplies us with a consciousness of force. But the consciousness is rather of a negative character than positive, for, whilst action or contraction in muscles is going on, vigour and strength are experienced, but when that has ceased, and not until then, weariedness is experienced; and this feeling of weariedness is experienced most intensely over the region of the fascia lata; but more or less all over the body, especially where fascia is the most dense.

To enter into any detail upon this last mentioned feeling in the present paper would be quite out of place, but the writer may state that he has no reasons for supposing that the nerves pertaining to the sense of force have any thing to do with it, beyond their being a kind of contrast, and, if he may so speak, a counter-compeer to the same. The writer cannot well conceal his impression that it was from the feelings of weariness, as just described, that Sir C. Bell inferred there was a muscular sense.

To return, though a little out of order, for brevity's sake, we will consider the shoulder-joint. This joint presents all the peculiarities for the distribution of force, and of throwing it into one common course, which the two preceding joints have presented; but, from the manner in which it is protected by the acromion and coracoid processes, I have not been able to devise any experiment whereby the feeling of weight can be induced, the feeling of vigour or strength being alone felt.

In relation to the three joints, knee, hip, and shoulder, it is worthy of remark that we are daily in the habit of judging of the activity and vigour of the muscular system, in any given individual, by observing whether the knee and hip joints are tightly compacted together, and the shoulder-joints appear neatly and closely approximated. This arises, apparently, from the fact that every one, when about to put forth much strength, has a feeling within of these parts being so adjusted, and he naturally applies his own convictions, or feelings, in observing and measuring others; thus a popular standard for physical force has its foundation in physiological induction.

The next part to be examined is the spinal column. The transverse processes of the vertebræ are lined or tipped with synovial membrane, but, from the very limited amount of motion, especially in the dorsal region, this membrane is scarcely discernible. But in the cervical and lumbar regions the motion is not so limited, and the synovial sacs are consequently better developed. Here nervous tissue may be supposed to be but very slightly supplied, yet to the integument of these parts I imagine that the nerves of force are well developed, so that when a weight is placed on the lumbar region it is very soon felt, but not, I presume, from nerves distributed to the synovial membranes of the transverse processes-probably they may assist. The same remarks pertain to the cervical region, till we reach the atlas in its articulations with the axis and

occiput, at which parts, especially with the occiput, synovial membrane is very freely distributed, and appears to be always well lubri cated with synovia.

If, then, a book, or solid piece of wood, say the size of Kidd's Bridgewater Treatise, be made to rest across the cervical region, or be balanced upon one of its angles, and, with the neck bent, be placed in succession from the seventh to the first cervical vertebra, at short points of distance from one another, it will be found that the feeling of weight attains its maximum opposite the first cervical, where weight is felt to no inconsiderable degree, when the experiment is carefully conducted.

Again, if any experiments are tried in the dorsal region, where no feeling of weight is experienced, from a book, or any other suitable object, being made to lie or rest with its long border upon their spinous processes; yet, if the book is laid flat upon the back, over the dorsal region, and, by being so placed, imparts part of its weight to the ribs bending outwards from either side, that weight will be distinctly perceived. This arises from either of the articular surfaces of the heads of the ribs, resting upon corresponding facets in the bodies of the vertebræ, being tipped with synovial membrane; and such an apparent exception only tends to confirm the hypothesis advanced.

Next in order comes the head. The experiments upon this part appear to be deserving of particular attention, and tend, as much as any hitherto advanced, to confirm the hypothesis here maintained.

EXPER. I.—If a weight, say a polished stone, or a piece of lead, 2 lbs. in weight, and tipped with leather, be placed in the mesian line of the head, at the saggital suture, opposite to the condyles of the occiput, it will be found that a consciousness of weight, greater than at any other part of the head or neck, will be experienced, and also, that it will be felt more quickly than elsewhere. If the nerves distributed to synovial membranes supply us with the sense of force, or a consciousness of its existence and degree, then, in any given region, where such nerves are distributed, over that part where force will channel the quickest, and with the least expenditure by friction to the seat prepared for its perception, there, if the premises are correct, shall we feel it the earliest and the most intensely. Perhaps it need scarcely be observed, that the cranial bones, from their thinness and compactness, are better adapted to convey force, considering their extent of surface, than any other in the body; whilst the loss by divergence, when weight is placed in the centre, on the top of the head, is greatly compensated by this region being balanced upon equilateral condyles. These, by being supplied with sentient nerves, adapted to test force on either side of the centre of gravity of the head, act the part of a pair of scales, in guiding and directing muscular action how to apply its force in adjusting the organ placed under its protection.

EXPER. II.-Place the same weight, as was used in the first, on the frontal bone, as far anterior as can be accomplished with con

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