Examination of patients frequently reveals the results of accidents or disease which do not appear to have any present deleterious influence on their health.  It is always necessary for the physician to estimate the relations which these changes have, in the past, borne to the general health, or may, at present, be liable to exert under known conditions of climate, diet and environment.

    Definition. - In speaking of structural and functional changes, we use the words adaptation or compensation.  Adaptation means, in biology, favorable organic modifications suiting a plant or animal to its environment.  Compensation means, "to make up for," "to counterbalance," "that which makes good the lack or variation of something else." The examples of adaptation and
compensation are very numerous and it is necessary for the physician to be able to recognize the cases in which the body has exercised, or may, with proper assistance, exercise this power to a great degree.  It is sometimes said that disease is an effort of the body to accommodate itself to new conditions, that is, changes in the quantity and quality of stimuli occasioned by variations in climate, diet, environment or accident.

    Osteopathy apparently originated from the fact that structure affects function.  With this as a basis, all examinations are made from the structural standpoint and therefore, if we follow this method too literally, we are apt to overlook the fact that the cells of our bodies have the power of adapting themselves to very pronounced changes in all those things which are considered essential to perfect functioning.  Function in these affected cells may not be perfect, measured by their former activity, and yet apparently answer all the demands made upon them by the conscious or sympathetic life of the individual.  There may be other cells, somewhat similar in character, whose increased activity can compensate, that is, "make good the lack of" activity in the affected cells.

    The Spinal Column. - The examination of the spine frequently reveals the irregularities in its structure.  Disturbed function in some viscus or other group of tissues is sometimes attributed to this structural variation, even when no direct nerve influence over the affected tissues can be directly traced to the spinal area.  Mere change in structure, cannot warrant us in considering it primary to a functional disturbance, which does not exist in a location whose control can be traced to it.  The effort on our part to always connect structure with function, having the relations of cause and effect, sometimes leads to very far-fetched reasoning.  It is necessary for us to decide, in a given case, whether or not the present condition of the individual is as good as it can be made.  Our decision will manifest to the keen observer whether we have recognized the extent of possible adaptation and compensation.

    Curvatures of the spine present many phases which must be considered before treatment is begun.  The curvature of an old case of Pott's disease seldom affects sympathetic life to the extent that we would expect.  The very gradual progress of this disease seems to give ample opportunity for the structures, in close relation to the diseased area, to accommodate themselves to the changed conditions.  It is hardly conceivable that anyone would fail to recognize the accommodation manifested in these cases, and yet we have heard of those who advocated forcible straightening of the spine.  The question to be decided is whether it is better to risk life by forcible straightening of the spine or endure deformity with fair health.  Deformity is always a wound in the self-esteem of the individual.  Many would risk life time and again to be rid of it.  It is this which gives the experimenting physician or surgeon ample opportunity to try his skill or his ignorance.  It is all one to the patient, a chance to be rid of deformity.

    Compensatory Curvature. - A lateral curvature of the spine usually has two parts, the primary and the compensatory curve.  The compensatory curve is the effort to maintain the erect position, that is, keep the weight of the body properly balanced.  The physician must determine which curve is primary and which is compensatory.

    When the hip is dislocated, or any condition exists which shortens one leg, the spinal column is curved to compensate for this reduced length.  It would be useless to treat a compensatory spinal curvature, without lengthening the leg by reducing a hip dislocation or putting an extension on the shoe.  When the femur is dislocated, all the thigh and hip muscles accommodate themselves to a new position, then the spinal column curves because the pelvis tilts enough to compensate for the lack of length in the extremity.  The longer the dislocation has existed the more perfect is the adaptation and compensation.  To reduce the dislocation we must undo the work of adaptation, that is, lengthen the muscles and force the head of the femur into the acetabulum.

    All individual spinal lesions must be judged carefully as to their relations to functional disturbance.  The fact that spines develop unevenly, in many cases, makes it hard to define their exact condition.  A lateral subluxation may exist to which the body has become accommodated.  To reduce this subluxation might again subject the individual to disturbed function.

    The Thorax. - Drooping of the ribs lessens the antero-posterior diameter, but increases the vertical diameter.  The full round chest of large capacity is usually less flexible and active than the small chest.  The question in each case is whether the thorax is doing the amount of work necessary for the body.  The chest may show evidence of a period of malnutrition, during childhood, that is, "rickets." There may be evidences of the effects of occupation.  In any case of deformed thorax the question uppermost in our minds should be: "What is its functional capacity?"

    The Heart. - Compensation by the heart, for some mechanical defect in it, is the most interesting subject studied by the physician.  As a result of contraction of the orifices of the heart, or faulty action of its valves, there is an increase in the size of one or more of its chambers.  This increase is at the expense of the thickness of its walls, thus resulting, in disproportion between the size of the cavity of the ventricle or auricle, and the amount of muscular tissue required to empty them of their contents.  When the proportion between the cavity and its walls is so far restored that the heart is able to overcome the stasis of the blood in that portion of the circulatory apparatus behind the lesion, we say that compensation exists.  The ability to recognize the status of a heart lesion is of great value to a physician.

    Skin and Kidneys. - A spinal lesion might cause a disturbance in the functioning of the kidneys, decrease of activity, which in turn is compensated for by increased activity of the skin, which in time is compensated for by increased activity of the bowels.  The diarrhoea in this case would be compensatory, and yet it is very difficult for the physician to note this fact.  If therapeutic means were used to stop the diarrhoea, and the kidneys or skin did not immediately take up the work of
elimination, the body would call upon the serous membranes and areolar tissue, to take care of the surplus liquid in the circulation.  As a result there would be edema of the extremities, ascites, pleuritic effusion.

    The compensating action which may take place between the kidneys, skin, mucous and serous membranes, is one which is more frequently recognized and made use of by physicians than any other example of the same power manifested in the body.  The fact that the skin and kidneys respond to each other's needs, forms the basis for many therapeutic procedures.  Mucous
membranes become active when the skin fails.  Perspiration reduces activity of the mucous membranes.  Serous membranes cease their excessive activity when mucous membranes eliminate freely.  The oedema of areolar tissue gives way to activity of mucous membranes.  The physician must recognize which is the diseased tissue, and which is the compensating one.  The failure of the kidney to excrete might not be the fault of its own structure, but result from the vis a tergo given the circulation by a diseased heart.

    Power of Encysting. - In this western country, California, we have ample opportunity to witness the ability of individuals to do hard, tedious work, after a considerable portion of the lung has been destroyed by disease.  The healing which takes place under favorable climatic conditions, seems to leave the remainder of the lung in perfect functional condition.  We have examined two cases, in which the whole right lung was destroyed, and the heart had been drawn into the right half of the thorax.  Both of these individuals were able to compete with their more perfect fellows for a living, by doing hard manual labor.  One of these patients had a discharging abscess in the axillary line, between the ninth and tenth ribs.  This abscess had discharged continuously for four years.  The patient did not complain of a single symptom of ill health.  He earned his living as a miner.  This shows how thoroughly the system may become accommodated to very marked change in the coalition of its tissues.  This abscess was in the man, but apparently not affecting his functions.  Probably the abscess was walled off from the active body tissues by a protective membrane.

    The history of the lodgment of bullets in various portions of the body, demonstrates that what cannot be thrown off by ordinary means, may become encysted, and thus not interfere with the activity of the tissues.

    The Extremities. - Adaptation and compensation can be noted very quickly in many cases of injury of the extremities.  A fixed scapulo-humeral articulation is partially compensated for by increased mobility of the scapula on the thorax.  When the anterior tibal group of muscles is paralyzed, the patient compensates for inability to raise the toe, by flexing the thigh.  When the hip joint is fixed in the extended position, the lumbar portion of the spinal column becomes very flexible.

    Law. - All living things strive to preserve themselves.  This means they do the best they can under all conditions.  In order to do this they must adapt themselves to changes in the character of their environment and compensate for injuries to, or losses of their own structure.  Adaptation to external conditions calls for the operation of compensating or balancing devices within the organism, therefore the logical study of this subject would naturally group the phenomena under three heads.  First, the study of structure, with a view to determining the existence of balancing devices in the arrangement of bones, ligaments, muscles, blood vessels, viscera and nerves.  These compensatory mechanisms must be considered in every effort at adaptation.  This first division deals with internal structural conditions, and their functions, i. e., anatomy and physiology.  Second, the study of conditions under which living structures are existing.  This division deals with all those things which constitute environment, such as food, temperature, atmospheric pressure; relation to other living things, such as insects, protozoa and bacteria; animal and vegetable poisons.  Third, a logical out-growth of the first and second divisions, i. e., a study of the artificial conditions used by physicians to influence the natural conditions of the first and second divisions.

    Since man's position is upright, it appears that all parts of his body are constructed with the end in view of making that position easy to maintain.  A bewildering series of compensating devices serve to balance the body in the upright position.  Any deviation of any part, as the result of accident or necessity, is immediately met by an opposing counterbalancing effort of its natural compensatory opposing structure.  If this compensatory effort is not present, there is loss of balance between reciprocating parts, resulting in strain and discomfort.  As a general proposition the foregoing is recognized by all, but to actually recognize the failure of compensation, the presence of strain, imbalance, requires knowledge of the structure of reciprocating parts.

    The feet present some interesting mechanisms for responding to the needs of the body in balancing in the upright position.  Every change in shoe last calls for a compensatory change in the relation of tarsal, metatarsal and phalangeal joints, with the consequent changes in muscular tension, to meet the demands of maintaining the equilibrium of the body.  The bursae which lie under the skin areas, which are subject to pressure, vary considerably.  Their compensatory character is well illustrated in the different forms of clubfoot.  A bursa is usually located in such deformities wherever needed to protect the bony points from friction.  Figs. 89, 142, 143 and 144 show plantar impressions of feet with varying degrees of weakness in the longitudinal or transverse arches.  Two of these cases had been treated for backache and innominate lesions, without success.  The reason for the failure is well illustrated by these plantar impressions.

    The adaptive and compensative changes, which are so readily observed in the human foot, present very many phenomena which should be patent to all students of medicine.  The fact remains that physicians fail with astonishing frequency to take account of these phenomena, therefore we feel warranted in giving attention to this subject.

    The case which is here described and illustrated was sent to me by Dr. Geo.  F. Martin, of Tucson, Ariz.  Mr. C., age about 28, interested in mining enterprises, applied for relief from pain in the right foot and leg.  Examination revealed a high, swollen instep, and measurement of the length of the foot showed it to be one-half inch shorter than the left.  The ankle did not appear to be involved.  The top of the instep felt bony, instead of pulpy, as might be expected from the appearance.  Palpation of the inner side of the longitudinal arch showed that some decided change had taken place in the astragalo-scaphoid articulation. just posterior to the scaphoid tubercle, instead of feeling the astragalus, a depression was noted and this depression was continuous with a sort of groove which passed across the instep, from internal to external mateollus.  Fig. 145.  When the patient stood on the foot this groove was decidedly apparent.  Fig. 146.  Palpation, while the weight was oil the arch, seemed to indicate that the tibia and fibula held a relation to the astragalas similar to that which is normal when the foot is extended on the leg, i. e., the posterior portion of the superior surface of the astragalus was bearing the weight.  The shortening of the foot, height of the instep, inability to palpate perfect continuity of the internal side of the longitudinal arch and existence of groove just in front of the ankle joint, together with slight swelling but no edema, dilated veins and dull pain in the arch and leg, but no loss of function, (i. e., mobility existed in all tarsal and metatarsal articulations) were indicative of some decided structural changes.  The principal point noted about the movements was that inversion and eversion of the foot took place with the foot in the normal relation to the leg, as though it was extended, thus demonstrating that the astragalus was in fact in a position of extension, even though the foot appeared not to be so.

    The condition of this foot is exceedingly interesting, when the history is considered.  Mr. C. says his foot was injured by a large rock, which a fellow workman accidentally dropped.  This accident took place four years ago, while he was working in a mine.  The foot swelled slightly, i. e., to about its present size and was painful, but did not incapacitate him for work.  Claims he never lost a day on its account, and it was not examined by a physician.  The swelling gradually subsided and the foot gave him no inconvenience for three years, except in the matter of fitting a shoe.  Recently swelling and pain have developed.

    My first suggestion, based on the insufficiency of the arch, was the use of an instep supporter, but this proved a failure, as it caused his foot to turn on the outer border.  The support prevented the inner side of the arch from lengthening when weight was put on it, and the astragalus could not have free movement, hence the foot inclined toward the outer side, and strained the ankle.

    Several skiagraphs were made which were very satisfactory in aiding diagnosis.  The first one was made to show the relation of the tarsal bones on their superior-external aspect.  Fig. 147.  This shows the head of the astragalus downward, out of relation to the scaphoid.  Fig. 148 shows a view directly from above the dorsum of the arch, and demonstrates clearly the dislocation of the head of the astragalus.  The inner side of the longitudinal arch is not complete, and what there is of it - scaphoid, internal cuneiform and first metatarsalis - badly distorted.  The relations of the metatarsals, as shown in this illustration, indicate the tendency to throw the weight on the outer edge of the foot.  The side view, shown in Fig. 149 demonstrates again the dislocation of the head of the astragalus downward to a position under the scaphoid.  The scaphoid shows an irregular outline, as though having been fractured and repaired, leaving irregular masses of callous.

    An impression of the plantar surface of the foot was taken.  Fig. 150.  This shows the great increase in contact surface, especially under the head of the astragalus.  Another interesting thing demonstrated by this impression is the change that has taken place in the second metatarsal, and second toe.  Both have been elevated so that they no longer bear much direct weight.  The third and fourth metatarsals are bearing the direct application of the weight of the body.

    In order to more clearly analyze this case, we will consider some general fundamental ideas concerning the structure and function of the foot.  The foot acts primarily, as a passive support of the body weight; secondarily, as an active lever to move this weight, as in running.  In order to perform these functions, it must have strength, elasticity and adaptability, thus permitting it to assume various attitudes necessary to protect it from injury.  Since the primary function of the foot is to act as a support, the integrity of the ligaments is essential.  When the, foot is passive under weight, the arches settle slightly.  The arch as a whole is elastic, but the ligaments are not.  The elasticity of the arch is the result of the movement of the bones into a position where the ligaments receive the weight.  Muscles, ligaments and the plantar fascia all serve to support the foot, but when passively bearing the weight of the body, the ligaments bear the strain.  Loss of elasticity in the foot causes increased pressure on points of contact on the sole of the foot, also on the toes.  The skin thickens over these bony contact points in an effort to compensate for loss of elasticity, thus corns and callouses are evidences, in many cases, of compensation and should indicate the necessity for a careful examination of the structure of the foot.

    In the attitude of rest the astragalus rotates slightly inward and downward on the os calcis, thus making the head of the astragalus somewhat prominent on the inner side of the foot.  This movement is checked by ligaments, and this position of fixation removes all strain from the muscles.  In the case we are studying, the calcaneo-scaphoid ligament was torn, hence the rotation of the astragalus is limited only by compressing the soft tissues of the sole against the floor, as is evidenced by the impression along the inner border of the foot in Fig. 150.  The position of the head of the astragalus under the scaphoid raises the inner border of the foot and throws the weight on the outer border, a natural compensatory position.  From the foregoing we judge that this foot is a poor passive support.  Although it has done good service for nearly four years, it has never been called upon, until within the present year, to act for long periods of time as a passive support.  Heretofore this foot has adapted itself to uneven surfaces, producing constant variation of pressure.  Now that contact with smooth hard pavement gives no opportunity for shifting of weight and alternating contraction of muscles, it fails as a supporting mechanism.  Steady pressure of the head of the astragalus on the soft tissues of the plantar surface interferes with circulation, causes edema and pain.

    The secondary function of the foot is as a lever, in actively raising and propelling the body.  We divide these functions into primary and secondary, because a foot that might serve as a good passive support, might possess none of the active elements required in running.  A wooden foot would serve as a support, but not as an active ever.  The heads of the metatarsal bones act as a fulcrum, the calf muscles furnish the power, the weight rests on the astragalus.  When the foot is used normally, the line of weight passes downward through the center of the knee and ankle joints, hence forward along the line of the second toe.  The fact that the inner side of the foot is longer than the outer, causes the strain resulting from lifting the weight of the body over the fulcrum, to be carried toward the outer side of the foot.  This gives an appearance of turning the foot inward - "pigeon-toe."  The toe does not turn in, but points directly ahead.  This is the normal action when walking.  In standing, the feet point outward, so as to give a greater base of support.  In walking properly the feet should move parallel to each other, so that the strain falls through the center of the foot.

    The movements accomplished by the case we are studying were quite normal, thus demonstrating that all the muscles were active, and that there was very little ankylosis in any of the joints.  It is interesting to note that the astragalus has no muscles attached to it, hence its change of position is purely accommodative.  All the other bones of the tarsus have muscles attached to them, hence they respond to muscular contraction, and take positions to which the astragalus accommodates itself when weight is put upon it.

    An interesting problem is presented in this case, which is associated with fractures in general.  We have been taught that fixation is the basic principle in the treatment of fractures, and this is so firmly believed by the public, that any other treatment, which might be used by a physician, resulting in deformity or some loss of function, would subject the physician to probable loss, in a malpractice suit.  This foot never had the benefits of rest, adjustment of the bony structure, or fixation.  It passed through the successive repair stages, subject to at least a moderate degree of functional demands.  How much better it might have been under ordinary routine treatment, is conjectural.  The point we are interested in at this time, is the adaptation, which has resulted in a fairly useful foot as an active lever under conditions of rough ground, but has failed when the primary function of passive support on a hard level surface is required.