Forelimb

“ The ipselateral reflex is flexion at shoulder, elbow and wrist. The contra lateral fore limb at the same time is extended at shoulder, elbow and wrist. When the reflex spreads to the hind limbs the hind limb of the same side is extended at hip, knee and ankle, that of the crossed side is sometimes flexed at hip, knee and ankle, but sometimes is instead extended at hip, knee and ankle. The reflex sometimes spreads to the neck, causing the head to be turned toward the fore limb, which is the seat of the stimulation. ”

“ Anatomy recognizes the fact, that in the number and character of the bones, joints, and muscles of the foot and leg, and the connection of the femur or thigh-bone at the pelvis, there is a strict similarity or correspondence with those of the hand and arm, and the connection of the latter at the shoulder-blade. ”

“ As for the arms, it is noticeable that they still retain the ordinary mammalian habit in being hairier on the back than on the front; and this also is quite in accordance with our present suggestion, because the same differentiating causes have not worked upon the arm as they work upon the back and legs. The peculiar position of the anterior extremities in man, together with the erect posture, makes the arms come much more frequently into frictional contact with the body or clothing on their inner than on their outer surface. ”

“ Those at the knee, for example, contribute more to the length of limb than do those at the hip or ankle, and they are also the last to unite. In the upper limb the more active epiphyses are at the shoulder and wrist, and these also are the last to unite. ”

“ Before we can discuss the first point with advantage we must consider with some attention, and compare together, the structure of the human hand and that of the human foot, so that we may have distinct and clear ideas of what constitutes a hand and what a foot.
The external form of the human hand is familiar enough to every one. It consists of a stout wrist followed by a broad palm, formed of flesh, and tendons, and skin, binding together four bones, and dividing into four long and flexible digits, or fingers, each of which bears on the back of its last joint a broad and flattened nail. ”

“ It is first of all necessary to say that in man, when the fore-limb hangs beside the body, and the dorsum of the hand looks backwards, the two bones of the forearm are parallel, and that this position is known by the name of supination. It is also necessary to remember that there is another attitude, in which the radius, crossing the ulna, and carrying the hand with it, displaces the latter in such a way that the palmar surface looks backwards. This second position is known as pronation. ”

“ Besides these peculiarities of the hands and feet, which, moreover, are supplied in every joint with tendons and muscles of great motive power, the fore-arm is capable of turning the wrist forwards or backwards, or, as it [Pg 213] is called, rotating, and also of bending. Again, the upper arm is loosely but firmly attached to the shoulders and neck, so as to admit of great range of motion, so what with the bending and rotation of the fore-arm, and the mobility and cushioned state of the fingers, these creatures possess a wonderful apparatus, suited for extreme action and safe holding on. ”

“ The limbs that take their shape from the muscles of locomotion, and the internal parts concerned in those high vital offices, of which minerals and vegetables are wholly destitute, are examples and proof of the configuration proper to the animal kingdom. The thigh, leg, arm, fore-arm, finger, the neck and shoulders, the chest, and the abdomen meeting it and resting on the pelvic bones, are felt to be beautiful or true to the standard form as they taper or conform to this intuitive life-type. ”

“ Further to simplify our study, we will, at first, consider the mechanism of one limb only. As [102] one foot swings forward and reaches a certain place, it seems to hesitate for an instant and then come down, heel first, on the ground. As the heel strikes, the body is slightly jarred and the oblique line of the limb, its axis, moves and approaches the vertical. In a moment, the limb is vertical as it supports the trunk and the sole of the foot bears on the ground. ”

“ Following with his finger the triangular outline of the bone, he went on to explain how its freedom of movement is due to its singular independence; laid loosely on the flat muscles behind the upper ribs, it moves with absolute freedom, backwards and forwards, up and down, unconnected with any other bone, till, turning the corner of the shoulder, it is hinged rather than tied to the collar-bone; the collar-bone itself free to move upwards from its articulation in the sternum. ”

“ On the other hand, the femur is united, as with us, to a massive pelvis; the articular surfaces of the knee, the knee-pan, and the two immovable bones of the leg, are just what the exclusive function of locomotion requires; the foot is plantigrade, with a prominent heel and close toes, and is articulated perpendicularly by its arch with the leg, as in man. ”

“ For the back stroke therefore, and that the arm may not only bend at the elbow, but also extend and straighten itself with force, other muscles, the longus, and brevis brachiæus externus, and the aconæus, placed on the hinder part of the arms, by their contractile twitch, fetch back the fore-arm into a straight line with the cubit, with no less force than that with which it was bent out. The same thing obtains in all the limbs, and in every moveable part of the body. ”

“ 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. ”

“ Sometimes where the arm is lost the elbow will seem bent, and the hand in a fixed position on the breast. Sometimes, again, the position is non-natural, and the hand will seem to bud straight out of the shoulder, or the foot to be on the same level with the knee of the remaining leg. Sometimes, again, the position is vague; and sometimes it is ambiguous, as in another patient of Dr. Weir Mitchell's who
"lost his leg at the age of eleven, and remembers that the foot by degrees approached, and at last reached the knee. ”

“ The line of the back from the shoulder to the bent knee of the resting young body is of a unique softness; the transition from the thigh to hip is like velvet in the softness of the body; the feet and toes are of classic beauty. ”

“ The fore-arm must be long in proportion to the leg, that is, the greater length in proportion must be above the knee, and the less below it the better; the muscular development of the fore-arm should be as great as possible. ”

“ The left shoulder, which, as I had previously noticed, the old man could make little use of, was shrunk and thin to the elbow, like a mere bone covered with skin, and those veins and muscles which were unscathed, wound round the bone close to the surface. ”

“ High Shoulders.—A medical correspondent of an English paper attributes the high shoulder and the lateral curvature of the spine, which so frequently disfigures young girls, to the shoulder straps of their dresses resting below the shoulder and on the muscles of the arm, instead of being on the shoulder, which compels the wearer to be constantly hitching her shoulders to keep up her dress, an action that results in forcing up the shoulder, a distortion of the chest, and a lateral curvature of the spine. ”

“ The upper arm, between the shoulder and elbow is short, and is buried in muscle so that one doesn’t notice it. So the first joint that shows, where the fore-leg joins the body, is not the shoulder but the elbow. ”

“ The shoulder girdle consists of the scapula, the coracoid, and the clavicle. The fore limb consists of the arm, forearm, and the hand. The arm consists of the humerus, the forearm of the radius and the ulna; and the hand consists of the carpus, the metacarpus, and the phalanges. The pelvic girdle consists of the ilium, the ischium, and the pubis. The hind limb consists of the thigh, the leg, and the foot. The thigh consists of the femur, and the leg consists of the tibia and the fibula. The foot consists of the metatarsus and the phalanges. ”

“ Take the fore limbs, for instance. In your model you will probably fasten them to the trunk at some fixed place. That is not the way that they are joined in the bony framework. The joining of the fore limbs is not by a hard articulation as in the arms of man which are joined, through the intermediary collar-bone, to the breast-bone. In the horse and in quadrupeds, generally, the joining to the main bulk of the body is by soft tissues. ”

“ The fulcrum of the upper limb is itself moveable upon the trunk, as appears from the extensive motions of the scapula, which so generally accompany the rotation of the shoulder, and supply the limb with a great variety of motion, much more than the lower limb possesses. ”

“ In all this delicate mechanism which pervades every individual side-arm, we see provision for the double purpose of attaching itself to extraneous bodies, and apprehending its prey. Five of these arms are set off from each of the largest joints of the vertebral column. At Pl. 53. Fig. 7. a. we see the bases, or first joints of these side-arms articulating with the larger vertebræ, and inclined alternately to the right and left, for the purpose of occupying their position most advantageously for motion, without interfering with each other, or with the flexure of the vertebral column. ”

“ The most striking features of the limbs are the presence of three bones next below the humerus and the femur and articulating with them, corresponding apparently with the radius, intermedium, and ulna in the fore-limb, and with the tibia, intermedium, and fibula in the hinder limb, and the fact of six digits. ”

“ Your arm must be raised until high overhead, the hand hanging from the wrist and dropped into your lap or down at the side, letting the elbow "give," so that the upper arm drops first, and then the fore arm and hand,—like three heavy sand-bags sewed together. The arm can be brought up to the level of the shoulder, and then round in front and dropped. ”

“ If the muscle takes its fixed point above, it acts, in the extension of the thigh during walking, by projecting the trunk forward during the whole time that the hind-limb to which it belongs is in contact with the ground. If, on the contrary, it takes its fixed point below, it makes the pelvis describe a see-saw movement, upwards and backwards, on the coxo-femoral articulation, and so contributes to the action of rearing. ”

“ For the rest, in order to be able to distinguish readily the corresponding parts in the hand of a bird and that of a man, we merely have to place the human forearm obliquely, in a direction upwards and forwards (Fig. 32) , the radius being above; this position we can obtain by semi-pronation; [48] then, to incline strongly the hand downwards and backwards, moving the ulnar border of the hand towards the ulna; the thumb is then anterior, the little finger posterior, and the palm of the hand is turned towards the trunk. ”

“ To the lunge of the left foot add an equally full and direct and fast lunge of the left shoulder, elbow, and wrist. Your head should come forward also, above your left foot. Imagine yourself to be aiming at a ball, and see that your left wrist is in a line between your eyes and some object, say a chair’s leg in the bedroom. ”

“ Young children have all their joints small, but they are thick and plump in the spaces between them; because there is nothing upon the bones at the joints, but some tendons to bind the bones together. The soft flesh, which is full of fluids, is enclosed under the skin in the space between the joints; and as the bones are bigger at the joints than in the space between them, the skin throws off in the progress to manhood that superfluity, and draws nearer to the bones, thinning the whole part together. ”

“ If this joint had been made pliable on all sides, as that of the shoulder, or that of the thigh bone with the hip, a man would have had his legs bent on each side as often as backwards and forwards, and seldom or never straight with the thigh. ”

“ Pronator Quadratus.—This muscle conforms to the general law which we have already pointed out in connection with those which have for their action the rotation of the radius around the ulna. We remember, indeed, that when the bones of the forearm are fused with one another, the muscles which are destined to produce a mobility which has then become impossible disappear at the same blow. ”