Flexion

“ Flexion and Extension.—The muscles are, for the most part, so arranged in pairs, or corresponding sets, that when motion is produced in one direction by one set, there is, opposite to it, another muscle, or group of muscles, which brings the limb back to its place. When they act alternately, a to-and-fro movement results. When a joint is bent, the motion is called flexion ”

“ The flexion is usually so pronounced that it can no longer be concealed by lordosis, so that when the patient is recumbent, although the spine is arched forwards, the limb is still flexed both at the hip and at the knee; with the spine flat on the table, the flexion of the thigh may amount to as much as a right angle. The adduction varies greatly in degree; when it is slight, as is most often the case, the toes of the affected limb rest on the dorsum of the sound foot. ”

“ But the scratch-reflex - which is so readily evoked by simple light irritation of the skin of the shoulder - is relatively mildly noci-ceptive. When the scratch-reflex and the flexion-reflex are in competition for the final neurone common to them, the flexion-reflex more easily dispossesses the scratch-reflex from the final neurone than does the scratch-reflex the flexionreflex. If both reflexes are fresh, and the stimuli used are such as,, when employed separately, evoke their reflexes respectively with some intensity, in my experience it is the flexionreflex that is usually prepotent. ”

“ The flexion is similar in the case of the multipeds; only that the legs in between the extreme ends always move in a manner intermediate between that of those in front and those behind, and accordingly bend sideways rather than backwards or forwards. ”

“ Thus the flexion-reflex, if intense and prolonged, may, directly its own exciting stimulus is discontinued, be succeeded by a " spontaneous " reflex of extension, and this even when the animal is lying on its side and the limb horizontal - a pose that does not favour the tonus of the extensor muscles. Such a " spontaneous " reflex is the spinal counterpart of the visual " Lichthof." To this spinal induction, as it may be termed, seems attributable a phenomenon commonly met in a flexion-reflex of high intensity when maintained by very prolonged excitation. ”

“ Dilatation & contraction suppose mutation of the smallest parts in respect of their situation. 11. Dilatation and contraction, as also all flexion, supposes necessarily that the internal parts of the body bowed do either come nearer to the external parts, or go further from them. For though flexion be considered only in the length of a body, yet when that body is bowed, the line which is made on one side will be convex, and the line on the other side will be concave ”

“ Whereas on the left side plantar stimulation produced not only the normal flexor reflex but also the classical defense movements of flexion of leg on thigh and thigh on hip,—on the right side neither a needle nor a match, nor any other form of stimulation of the sole, produced any kind of reaction on the part of the toes, the fascia lata, or any leg muscles. ”

“ Direct Flexion.—Direct flexion is the concession the head and lower jaw of the horse make in the vertical plane of the axis, of the horse when the action of the reins arrests the extension of the neck. The giving of the neck is confined to the upper portions; the front line of the face is made to approach a vertical line and the head is made to make in an almost imperceptible manner a movement analogous to a nod. ”

“ Among reflexes, some are simpler than others, but even the simplest is compound in the sense of being a coördinated movement. The knee jerk is simpler than the flexion reflex, and this is simpler than the scratch {108} reflex, which consists of a rapid alternation of flexion and extension by one leg, while the other is stiffly extended and supports the trunk. Coughing, which would be called a reflex rather than an instinct, consists of a similar alternation of inspiration and forced expiration, and swallowing consists of a series of tongue, throat and gullet movements. ”

“ A long flexion-reflex, when from fatigue it has become weak, tremulous and irregular, will recommence after 30 seconds' repose with almost the same vigour and steadiness as if it had not recently been tired out. ”

“ By flexion, the inferior extremity of the femur is directed forwards; the bone of the thigh then takes a more oblique direction than the normal. This movement takes place, for example, when the animal carries forward one of its hinder limbs. Extension, which takes place in an inverse sense, is produced when the foot is fixed on the ground, while the body is projected forward. ”

“ In the stepping of the limb the flexion that raises the foot and carries it clear of the ground prepares the antagonistic arcs of extension, and, so to say, sensitizes them to respond later in their turn by the supporting and propulsive extension of the limb necessary for progression. In such reflex sequences an antecedent reflex would thus not only be the means of bringing about an ensuing stimulus for the next reflex, but would predispose the arc of the next reflex to react to the stimulus when it arrives, or even induce the reflex without external stimulus. ”

“ In exceptional instances the flexion may be overcome by strong passive force, and a distinct trigger-like action established, the middle phalanx becoming extended and flexed again with a movement very comparable to that which takes place during the opening and shutting of the blade of a pocket-knife. ”

“ The inconveniences resulting from the affection are less urgent than might have been expected, partly because the flexion power remains, partly because there is no pain, and partly because the contraction seldom attains an aggravated form until an age when æsthetic considerations are of minor importance and the more active period of working life is drawing to a close. ”

“ 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. ”

“ Part 12 We have stated above that without flexion in the legs or shoulders and hips no Sanguineous animal with feet could progress, and that flexion is impossible except some point be at rest, and that men and birds, both bipeds, bend their legs in opposite directions, and further that quadrupeds bend their in opposite directions, and each pair in the opposite way to a man's limbs. For men bend their arms backwards, their legs forwards ”

“ An attempt at walking would be attended by spastic rigidity of the flexor muscles of the lower extremities, by flexion of the thighs and legs at an angle of 120°, so that the patient often fell forward upon his knees. ”

“ Contraction does not seem to be an explanation of all or even the chief phenomena which we have briefly set forth. When this hypothesis was considered, flexion seemed to be the chief method of displacement ”

“ Some ingenious men have imagin’d, that the bending of the Limbs in sleep is owing to the strong tendency which the flexor Muscles have to contraction; but I humbly suppose, it is rather a voluntary motion, intended to fix the Body on the Side, without the continued action of any of the voluntary Muscles afterwards; for without the flexion of the Joints in sleep, it would be a kind of labour to keep the Body pois’d on such an narrow surface. ”

“ Squeezing of muscles and stimulation of their afferent nerves and those of joints, &c., elicit reflexes. The primary reflex movement might be expected, therefore, of itself to initiate further reflex movement, and that secondarily to initiate further still, and so on. Yet on cessation of the external stimulus to the foot in the flexion-reflex the whole reflex comes usually at once to an end. The scratch-reflex, even when violently provoked, ceases usually within two seconds of the discontinuance of the external stimulus that provoked it. ”

“ We shall later see good reason to deny the existence of the latter feeling. We have accounted for the better part at least of the resident feelings of motion in limbs by the sensibility of the articular surfaces. The skin and ligaments also must have feelings awakened as they are stretched or squeezed in flexion or extension. And I am inclined to think that the sensations of our contracting muscles themselves probably play as small a part in building up our exact knowledge of space as any class of sensations which we possess. ”

“ So far from the muscular power being lessened by the repetition of the flexions, is it not increased by having all the advantage of exercise over repose, of work over indolence? Does not the muscular system, in reason, develop itself, physiologically speaking, in proportion to these conditions? Will not address and vigor be the result of these gymnastics? Has the habitual difference between the forces of the right and left arm any other cause than the difference in the daily use of the one to the prejudice of the other? ”

“ INFLEXION (from Lat. inflectere, to bend) , the action of bending inwards, or turning towards oneself, or the condition of being bent or curved. In optics, the term “inflexion” was used by Newton for what is now known as “diffraction of light” (q.v.) . For inflexion in geometry see Curve. Inflexion when used of the voice, in speaking or singing, indicates a change in tone, pitch or expression. In grammar (q.v.) inflexion indicates the changes which a word undergoes to bring it into correct relations with the other words with which it is used. ”

“ Of the six Proper Muscles of the Toes, there are four appointed for the great Toe, which cause it to perform the Motions of Flexion, Extension, and drawing forward or backward. The two others are the Adductor of the second Toe to the great Toe, and the Abductor of the little Toe, call'd Hypothenar.
The Proper Flexor of the great Toe, arises from the top of the Perone or Fibula, on the back part, passeth thro' the Ancle-Bone on the inside to the sole of the Foot, and is fasten'd to the Bone of the last Phalanx. ”

“ The object of the flexions is, by means of certain graduated exercises, to teach the horse that no real pain will follow these uncomfortable sensations, and to suppress their general accompaniments, while accustoming the animal to obey their special effects. ”

“ If the bones want their due proportions, or are imperfectly placed—if the muscles or tendons want their proper levers—if the flexions of the joints be interrupted by the defectiveness of their mechanism, the animal must either be defective in motion or strength ”

“ They then make a semi-genuflexion, by placing the hands on the knees, and bending the person forward. A complete genuflexion succeeds, which is made by bending the knees to the ground, and extending the arms forward as a support to the body, while the forehead touches the ground. ”

“ Thus, when we say, lift, expand, and let go, we mean lift from the hips, the center of gravity, in an easy, flexible manner; expand the body with a free movement without conscious thought of any part of it; have the sensation of letting go all contraction or rigidity, and absolutely release the muscles of the throat and face. The let go is in reality more a negative than a positive condition, and virtually means, when you lift and expand, do not locally grip, harden, or set any muscle of the body, throat, or face. ”

“ This movement of the whole limb is what we think of when the joint's nerves are excited in that way; and its place is so much more important than the joint's place that our sense of the latter is taken up, so to speak, into our perception of the former, and the sensation of the movement seems to diffuse itself into our very fingers and toes. But by abstracting our attention from the suggestion of the entire extremity we can perfectly well perceive the same sensation as if it were concentrated in one spot. ”

“ The bones, to which a great proportion of the muscles in the body are attached, act as distinct levers. The muscles supply the power for moving the bones, and the joints act as fulcrums or points of support. The weight of the limb, the weight to be lifted, or the force to overcome, is the resistance.
74. Levers in the Body. In mechanics three classes of levers are described, according to the relative position of the power, the fulcrum, and the resistance. All the movements of the bones can be referred to one or another of these three classes. ”

“ The muscles which bend the joints are called flexors, while those that extend the joints are called extensors, so that in order to perform their work, which is that of contraction, the muscles must exert enough force to elongate the opposing muscles, overcome the tonicity of the antagonizing muscles, and lift the weight of that portion of the limb into which they are inserted. It is by the action of the muscles that the body is held upright. ”

“ Let us remember that there are two sets of muscles, acting in unison with each other, to produce the various motions; they are known by the general terms of flexors and extensors; the first enable us to bend the limbs, the other to bring the limbs back to their former position. The flexors enable us to close the hand, the extensors to open it again. The flexors enable us to raise the foot from the ground ”

“ The curves below represent the changes in the two opposing sets of muscles whose interaction brings about the movement cycle. The contraction of the flexors, the positive muscle set, is represented by the curve above the base line. It is obvious that during the contraction phase, the contraction in the positive muscle set is at its height; it continues at a maximum during [454] the limiting sensation and then dies away during the relaxation phase. The sensations from this positive muscle set have the principal place in consciousness during the rhythm experience. ”