Since, not only among the general public and medical gymnasts, but also among doctors, misconceptions arc frequent in regard to this common deformity, which has generally gone under the unsuitable name of "flat-foot," several points may here be mentioned in connection with the treatment of this complaint. This is the more necessary as this complaint, which embitters the existence of so many people, is a typical example of the weight deformities. This large group of deformities has much of interest to the medical gymnast, so that I may also give some general points concerning their nature and the treatment they require.

By weight deformities we mean in practical orthopaedics deformities which arise as a result of faulty weighting of one part of the skeleton. Since the position of part of the skeleton, normal or pathological, under all conditions is dependent upon all the forces which work upon it, in regard to mechanics every skeletal deformity is really a weight deformity, as in mechanics one means, when talking of the weighting of a lever, the combination of all those forces which work upon the same. The term "weight deformities" in orthopaedics has not, however, such an extensive meaning, but by it we understand only that the normal form has become disturbed by pathological effects of the forces acting on a part, i.e., in the first place, gravity. As a rule one is not concerned with the structure and use of living forces, primarily muscles. In its most limited meaning, as the term in question is most often used, by a weight deformity we simply mean a skeletal deformity which has arisen by the effect of gravity, so that the part is not able to bear the weight put upon it, but gives way under it in one way or another. Weight deformities in this sense only arise, therefore, in the lower extremities, pelvis, and spine. In this.way arise various forms of habitual scoliosis, genu valgum, coxa vara, and the so-called flat-foot, due to overburdening the respective part of the skeleton. Such disproportion between the weight and the power to carry the same may arise either by the weight which is to be carried becoming too great, or the power to carry the normal weight being lessened. The first takes place, e.g., when, which not seldom happens, persons of middle age become corpulent and develop flat-foot. A weight may, however, become too great in proportion to the supporting power of the part of the skeleton, not only by being too great in itself, but by a weight, in itself not too great, being carried too long without rest, or in an uncomfortable position so that it weighs down the part of the skeleton. This happens when flat-foot arises in connection with certain occupations, e.g., bakers' apprentices, waiters, nurses who are obliged to stand or walk a great deal, or among smith apprentices, who, if the hammer is too heavy in proportion to their youthful strength, stand astride with feet turned outward, which position, as we shall soon see, is especially apt to cause pathological flat-foot. As, however, in spite of such occupations, a great number of individuals escape this trouble, it must be stated that the second factor, the diminished power to fulfil the required task, is the most important cause of the disability. This inability on the part of the skeleton to fulfil the tasks given it may be the result of general weakness, so common in adolescence, when such weight deformities are prone to arise, or of other conditions of weakness in connection with anaemia, etc.; or it may also be due to special diseases of bone, such as rickets, osteomalacia, etc. And in those cases where no such obvious disease seems to exist one has sometimes used the term "juvenile osteomalacia," which expression, however, up to the present has not received any pathological or anatomical justification.

Since the mechanical conditions in weight deformities in general are such that the strain upon the part in question increases with the deformity, every weight deformity ought to increase gradually, and reach eventually an extreme degree. This, however, is not the case, such severe cases being actually very rare. This must be accounted for by the fact that nature possesses resources which do not exactly counteract the deformity but at least prevent its further development. This power of the organism to react against deformity is made up partly of vital reactions in the bone itself, by which the bone is able, especially after recovery from rachitic or similar bone condition or general weakness, to respond to the altered weighting by the formation of new bone substance arranged in a way suitable to the changed weighting. Further, muscles play a very important part in counteracting weight deformities, and one often sees how those muscles which are able to counteract a deformity which has arisen are hypertrophied to a high degree. This everyday circumstance contradicts the theory which gives insufficiency of muscle as an important primary factor in the development of weight deformities. Only after the muscle can no longer be further hypertrophied does the deformity get the upper hand. As, however, musculature in general plays such a dominating part in the maintenance of normal skeletal form, and even specially counteracts the development of deformities and their progress, it is obvious what a large part medical gym; nastics takes in the treatment of weight deformities. But that this must not be exaggerated, as is often done, will be shown more clearly in the following account of the treatment of so-called flat-foot.

By flat-foot in practical medicine is meant a foot which is flat, i.e., with sunken arch. Nothing, however, in actual fact is more incorrect. Many patients seek the assistance of a doctor or medical gymnast for the unbearable so-called flat-foot pain and show on inspection a highly-arched foot. The name flat-foot is thus somewhat unsuitable, and has arisen on account of the relation between the bony skeleton of the foot and the bones of the lower leg being overlooked, and diagnosis of this common trouble arising as a result of overweighting the foot being made on the isolated skeleton of the foot itself. If, however, one takes the ankle joint into consideration in the diagram, one gets an entirely different and much more correct idea of the nature of the trouble. This consists by no means exclusively, or even chiefly, of a sinking of the longitudinal and transverse arches of the foot, but much more of an eversion of the foot in the ankle joint, a valgus position of the same. The line of direction of the lower leg and heel seen from behind even in normal conditions forms an obtuse angle outwards. The strain on weighting must therefore be uneven, the ligaments and capsules on the inside being more strained than those on the outside, where there is rather a compression of the parts of the joint against one another. On over-weighting this stretching of the inner side increases, and causes the severe pains, which are always localised to the inner and under side of the foot. One can demonstrate mechanically that this strain of the ligaments on the inside becomes greater the further the ankle joint is from the supporting area; so that these flat-foot pains should arise more easily in high-arched than in low-arched feet. Similarly the strain becomes greater with the feet rotated out. This is also actually the case. In studying patients with symptoms of flat-foot carefully, many of these, and above all those who have most pain, are found to have high arches and not flat feet. Under such conditions, to say the least, it is unsuitable to call these pains flat-foot pains, as they are of exactly the same nature whether they attack feet with low or high arches. The name is all the more unsuitable as its use leads to the patient not being able to have his symptoms correctly diagnosed by the doctor and gymnast; it is difficult to make the diagnosis "flat-foot" in a foot which is not at all flat but rather highly arched. The correct treatment cannot be applied, and the trouble persists. Only in the last stages of such a weight deformity, when the patient has not been treated or all treatment used has failed, does the arch really become sunken and the name flat-foot become justified. An everted foot (pes valgus) thus becomes an everted flat-foot (pes valgo-planus). The earlier stages of pathological flat-foot pains should not have this name, which ought to be done away with. These pains, which often in earlier stages cause much inconvenience to the patient, and which, moreover, are very common, ought instead to be called by their right name, weight pains or static pains, or, as Schanz and at about the same time the author of this chapter recently suggested, "insuffi-cientia pedis."