Definition. - The principles of osteopathy take their natural beginning in the consideration of "the lesion."  The word "lesion" is used by osteopaths to designate something more than "an injury, hurt or wound in any part of the body" (Gould).   Any structural change which affects the functional activity of any tissue is called a lesion.  There may be structural changes, abnormal development, which are very evident to palpation but do not affect functional activity and, therefore, are not lesions.  A lesion is not only a structural change, but such a change as influences function detrimentally.   Fig. 112 illustrates a structural change without detrimental influence on function, while Fig. 113 illustrates a true lesion.  The relation of these structural lesions to the media of communication and exchange, nerves and blood vessels, is believed to be the chief element active in producing and maintaining functional disorders.  This is the central principle of osteopathic practice.

    Characteristics of a Lesion. - Lesions may be present in any tissues but their existence is most easily recognized in bone, ligament and muscle.  Dislocations and subluxations of bones, thickened ligaments and contracted muscles constitute the usual varieties of lesions.  A true lesion is usually palpable; the functional disturbance is related anatomically and physiologically; there  is hyperaesthesia at the palpable area.  These three conditions constitute the characteristics of the lesion as it is designated by tile osteopath.  Its palpability may vary between very wide limits; the location of the structural change and functional derangement may be direct or indirect, the hyperaesthesia distinct or indistinct; still, the diagnostician is justified in centering attention upon the lesion if a reasonable amount of association can be detected.

    Classes of Lesions. - Lesions, according to osteopathic theory, may be of two classes, i. e., first, change in size of tissues; second, change in position.  Generally speaking, a change in size is far more difficult to overcome than a change in position, because the former is a result of more profound changes.  Tissues may increase in size as the result of efforts to repair injury, e. g., the formation of callous in bone, or thickening of ligaments following a sprain.

    Causes of Lesions. - The causes of lesions fall under two general divisions: First, violence; second, failure to react to environment.  In the first division all the lesions are primary in character, i. e., the violence immediately changes the relations of structure, and this change becomes an obstruction to vital activity of the body fluids.  If the lesion is not corrected by the recuperative power of the body itself or by outside efforts, the change in position is very apt to become complicated by a change in size.  The injury results in thickening of the ligaments or other fibrous tissues.

    Secondary Lesions. - The second division of lesions is a very large one.  These lesions develop as an evidence of the failure of the organism to become perfectly adapted to its food, clothing, labor or general environment.  They are, therefore, secondary in character and must be recognized as objective symptoms of one functional derangement, while at the same time they operate primarily to cause functional derangement elsewhere.  Thus they may be removed by manipulation and cease to act as an active cause of functional change, but will return again so long as environmental forces are overwhelming.

    Effect of Violence or Fatigue. - The first division or primary lesion may result from sudden violence or from a force comparatively weak but long continued.  In other words, a lesion may be developed immediately, under great force, or slowly as the result of great fatigue.  An example of a lesion developing under fatigue is noted in the faulty positions assumed by the body following prolonged effort or in performing certain tasks.

    Failure of Adaptation. - The second division or secondary lesions may result from failure to react property to changes of temperature.  The temperature of the surrounding air may be the same at various times, but the character of the clothing may necessitate a greater effort at adaptation.  There must be suddenness in the change of temperature or clothing in order to produce the lesion, i.e., the responsiveness of the tissues must be overtaxed.  'The first effect of failure of adaptation is the contraction of muscle and accompanying sensitiveness.  The distortion of the body structure is consequent on the contraction.  Ordinarily, if the shock is not too great, the adaptive forces of the organism will exert sufficient power to correct the condition, but when the environment is not suitable the lesion may become permanent.  Humidity or electrical conditions of the atmosphere may operate to produce these lesions.

    Chemical Causes of Spinal Lesions. - We have noted that these lesions have been discovered coincident with visceral disorder.  We may, therefore, safely assume that food which is too difficult of digestion or the usual food taken during fatigue, may act chemically to produce spinal lesions.   In this instance they are certainly objective symptoms of visceral disease, but as stated before they must be primary causes of other disorders.  To remove such a lesion by manipulation is useful to the organism, but the patient must know that dietetic indiscretions or eating when fatigued was the real starting point of the disease.  There is where dietetic and hygienic knowledge must be a portion of the physician’s therapeutics.  If the pointing out of structural changes as a result of functional disturbance due to indiscretions in eating and other appetites will lead patients to simpler living, the physician may feel that he has performed a duty more valuable to the patient than the removal of his secondary lesions.  There can be no doubt but that the removal of a primary lesion due to violence is absolutely essential, but when we maintain that all lesions must be removed before function can right itself, we become absurd.  Furthermore, if we contend that a structural lesion antedates all functional disturbances we make of life a series of accidents, instead of a force governed by fixed laws.

    The Reason for the Persistence of a Lesion. - The question arises, why does the muscular contraction persist after the proper changes in habits have been made?  This question can not be answered at present.  Scarcely one of us will voluntarily make the change in habits until forced to do so by failure of the body to respond to our demands.  Many things of a sociological character are at work to compel people to labor after fatigue is evident, to eat, sleep and dress unhygienically.  Viewed from this standpoint, the practice of medicine is a problem in sociology.  The original irritation which causes the tension probably causes more or less congestion of blood.  The congestion results in overgrowth of tissue, which becomes a fixed condition maintaining the lesion, i. e., it is a portion of the lesion.

    The Sequence of Lesion Phenomena. - We have considered three points concerning lesions - hyperaesthesia, muscular contraction, and subluxation.  They have been considered in this order merely on account of historical reference.  In osteopathic practice, they are reversed.  We note first the structure, then the tension which accompanies the change in structure, then the
hyperaesthesia.

    Variations in Development. - It is not uncommon to find changes from the usual forms of the bones.  Sometimes these changes may be very deceptive, but when analyzed with reference to the existence of functional disorder in the area of their normal influence and the presence of hyperaesthesia, they will be recognized as morphological changes due to natural causes.
Lesions which might have been active at a former time are sometimes nonsense on account of laws of accommodation which are always active in the body.  If the body has succeeded in recuperating from the effect of these lesions, it is unwise to disturb them.  As an example of an accommodated lesion, we may mention the formation of a new socket for the head of the femur, following dislocation.  There are variations in development all through the body, and each physician should strive to become acquainted with them.

    Palpation of a Lesion. - The first sign of a lesion is noted by palpation, i. e., the change in structure is felt.  According to what we have just said, this is not sufficient evidence of the existence of an active lesion.  It must be accompanied by other signs.  First, try to eliminate the ap-parent existence of the lesion by having the patient "assume different positions."  Second, note whether the bony landmarks in that area vary from the normal.  Third, note whether the lesion causes the patient to assume any special attitude.  Fourth, test the amplitude of movement in the articulation to determine the changes in its extent. If there is perfect flexibility it is scarcely probable that a lesion exists, for an active lesion is quite inconceivable without tension.  Fifth, feel of the soft parts of the joint, muscles and connective tissues.  Note any swelling or change in temperature.  Sixth, inspect the surface as to color and texture.  Seventh, test sensibility by pressure.  Ordinarily an examination of the body for lesions consists in comprehensive palpation, which notes synchronously the existence of positional change, tension, temperature, swelling and sensitiveness.  The existence of tension is sufficient evidence of decrease of flexibility.  When violence is the cause of the lesion, it is necessary to correct structure directly.  When the osseous lesion is the result of muscular tension due to reflex stimulation, methods differ according to the viewpoint of the physician.  Some manipulate for direct reduction, others relax muscles and thus remove the cause of the osseous lesion.  The really comprehensive plan should take into account the cause of the tension which occasions the osseous lesion.  Having done this, the physician may manipulate the lesion to secure direct reduction with the feeling that the problem has been undertaken wisely.

    Description. - Theories of the causation of disease are capable of being spun out to the point where concrete usefulness is very doubtful.  In order that we may not wander too far in theoretical speculation, we will seek to keep the phenomena, which we are trying to describe, of such a tangible character that the reader will not have to draw on the imagination.

    Find the Lesion. - Osteopathy has developed as a school of medicine exploiting "the lesion" as a cause of disease and its correction as the efficient care of disease.  This theory has been so enthusiastically adhered to that many have been more than willing to attribute failure to cure a given case as due to the practitioner's inability to find or correct the lesion.  The desire to maintain the adequacy of a theory is thus apparent.  This book is written to present the usefulness of osteopathy but not the extremes of theoretical speculation.

    Inspection of the Back. - In order that we may quickly have before us characteristic lesion phenomena for discussion and elucidation, let us observe some well recognized peculiarities noted in the inspection of the dorsum of the body.  A mature male patient, stripped for inspection, will present, as a general rule, some peculiarities which the trained diagnostician will recognize as adaptation due to labor or mode of life.  Closer inspection of the spine, as to its curves, will show adaptation of even more significance, i. e., to body weight, general vitality and visceral conditions.  As a rule the diagnostician is trained to note these latter conditions from other points of view.  The point is here emphasized that the spinal column is a good recorder of all these things.

    Palpation of Vertebral Structures. - Digital palpation of the vertebral and paravertebral structures will, in most cases, show some degree of localized unilateral deviation in vertebral alignment or muscular tension.  These apparent changes from what we conceive as the ideal normal are present in practically all people, sick or well.  It remains, therefore, necessary that eve add to these physical changes something of a determining character in order to recognize an active lesion.  Tenderness to pressure is the determining sign.  Having located a lesion, i. e., an osseous deviation with muscular tension and tenderness in the same spinal segments, we can now proceed to analyze it with reference to its existence as cause or effect.  'The spinal vertebral lesion just noted may involve two or more vertebrae with their attached tissues.  Some observers claim that a lesion of a single vertebra is rare.  Since osteopathy has fostered the view that structure affects function in preference to the reverse, the author feels justified, solely by historical considerations, in beginning all analyses of lesions from that viewpoint.  It is candidly understood that in doing this the author is not holding a brief for either side of any controversy which circles about the question whether the egg preceded the chicken or the reverse.

    History of Accident. - In any case under examination the diagnostician desires to uncover the history of the lesion, hence the most direct question possible is asked, i. e., "Is there any history of accident?"  If a history of accident is given having direct bearing on the lesion under consideration then we are quite justified in believing it to be the primary cause of disturbed function.  For example, a patient when attempting to alight from a street car just before it stopped, found his footing insecure and hence clung to the handrail of the car with one hand in an effort to protect himself.  The forward motion of the car rotated him and wrenched his back.  He was able to go to his home without feeling more than a sense of weakness and pain in the area of the dorso-lumbar articulation.  The next morning he was quite unable to rise.  Examination showed great muscular tension in the muscles controlling the movement of the twelfth dorsal and first lumbar.  Pressure on the spinous processes of these vertebrae caused intense pain.  The bowels became constipated and the cutaneous areas supplied by the twelfth dorsal and first lumbar pairs of spinal nerves gave some subjective symptoms of being disturbed.  'This case recovered in a few weeks under the influence of hot packs to the injured area, rest in bed, and after acute soreness abated, passive motion.  This case, for many years, has had attacks of "lumbago."  These attacks usually follow changes in the weather and some exertion beyond the ordinary.  The lesion always exhibits its old characteristics, viz., tenderness, muscular rigidity and loss of motion in the arthrodial joints between the twelfth dorsal and first lumbar.  Usually an osteopathic treatment to establish relaxation and movement is sufficient to secure rapid recovery.

    Traumatic Lesion. - We have in this case a condition similar to the results of a sprained wrist or ankle.  This is a case of such evident traumatic origin that no one \would think of it from any other standpoint.  The lesion is a characteristic one, derived in a characteristic manner and fulfills our classical picture of localized spinal injury.  It is fairly mild in its disturbance of function of the nerves from the injured area.  It was recovered from to such an extent that the patient has considered himself well except at such times as the formerly injured tissue failed to function property under somewhat unusual conditions.  There has never been complete recovery of function in the articulation.  This is evidenced by partial loss of flexion and extension, hence "the lesion" is always apparent to the trained sense of touch.  This lesion presents the same characteristics so commonly noted in peripheral joints which have been sprained and recovered from with partial loss of motion.  It is usually many months before the point of attachment of a strained ligament is free from sensitiveness to pressure or tension.

    Weight Carrying and Balancing Function Disturbed. - With an injury of this character located where it has a weight carrying and balancing function to perform, forcing part of the protective covering of the spinal cord and its membranes, as well as being a part of the wall of a visceral cavity, there are many far-reaching influences which may be attributed to it.  The rigidity which nature manifests first as a protective reaction, i. e., to prevent motion in the injured part, will be maintained as a constant factor in any case of joint injury which heals with a partial return of motion.  By this is meant that before the motion of the joint reaches its limit the muscles assume the function of ligaments, so as to protect the weakened ligaments.  'This action of the muscles we note as a protective rigidity which under the influence of passive motion may be absent but reappears when the joint is put through its voluntary functional tests.  Thus the fact that the lesion under discussion involves structures forming a part of the weight carrying and balancing mechanism of the body makes it more difficult of recovery.  In order to protect it from movement rigidity exists in segments just above and below it.  A lesion at the point mentioned will tend to produce a straight spinal column because it is situated at the junction of two curves, the dorsal posterior and the lumbar anterior.  Any exaggeration of these curves necessitates greater movement in this joint.  Therefore, if this joint be injured and its movement limited there is greater rigidity in both curves in order to protect the injured joint through which their compensating movements operate.  The tension of the posterior spinal muscles is met by counterbalancing contraction of the psoas magnus, the diaphragm and the abdominal muscles.  The tension of the diaphragm results in lessened respiration.  The tension of the abdominal muscles subtracts one factor in the maintenance of bowel action.  Lessened oxygenation and elimination are thus possible results on a purely mechanical basis.  To compensate for these decreases the whole body metabolizes at a slower rate and, without the sympathetic nervous system is vigorous, the decrease in visceral activity soon makes itself so apparent that the patient may be considered constitutionally ill.  Thus it appears that a spinal lesion may influence body metabolism adversely as a result of the natural healing reaction as manifested in rigidity.  The decrease of rhythmical movement in the walls of the abdomen and thorax is the immediate consequence of spinal rigidity.  These functions are less interfered with when the weight carrying function of the spine is least called upon, hence the horizontal position is naturally assumed to lessen pain and get rid of the demand for compensatory tensions.

    Lack of Physiological Rest. - While these injuries are acute we note easily the compensatory reactions just described, but no doubt the majority of such cases feel the press of economic necessity and hence try to adapt themselves to labor through hours more than sufficient to produce a fatigue akin to sickness.  The lesion develops a chronicity, or rather has never had a chance to heal under the benign influence of physiological rest.  This chronic lesion necessitates permanent compensatory changes such as we have noted.  This patient develops periodical digestive weakness, synchronous with his times of fatigue.  He visits a doctor and from then on "suffers many things of many physicians."  Through time and the compensatory changes in this patient's body the original lesion and its significance are lost to view.  The effort made to correct or palliate the digestive disturbance probably has no reference to anything but the prominent symptoms.  It is such cases as these, suffering from chronic illness, whose history of traumatic lesion is discovered by the osteopathic examination, which have given prestige to osteopathic therapeutics.  The treatment given by the osteopath to this old lesion reestablishes movement in the joint and, therefore, the compensatory tensions in the back, abdomen and chest are lessened.

    Influence on Circulation and Innervation. - Having thus followed the mechanical influence of this traumatic lesion through some of its compensations we can with profit turn our attention to the far more subtle influences upon circulation and innervation.  The trauma under consideration has been sufficient, in some degree, to rupture tissue continuity and therefore requires increase of circulation for repair. The swelling, occasioned by the congestion of the circulation, being under the spinal apponeurosis, does not evidence its presence by a localized tumefaction.  Some fibers of an intrinsic spinal muscle, i. e., one of the fifth layer, according to Gray's grouping, has been injured, hence our repair inflammation is deep seated.  The deeper seated the lesion, the more pressure will be exerted on the branches of nerve trunks emerging from the intervertebral canal the more likelihood will there be that the patient will complain of some symptoms of a character which might be interpreted as of central origin, especially if bilateral.  The subjective symptoms, pain and paraesthesia, in the area of cutaneous distribution of the twelfth dorsal nerve are usually unilateral, hence showing that the lesion causes a peripheral neuritis or, at least, a pressure on the nerve sufficient to cause the brain to register as though the peripheral distribution of this nerve was irritated.

    Segmental Coordination. - A segment of the spinal cord coordinates the impulses reaching it over its afferent fibers, hence, in the case of our lesion, the bombardment of this segment with impulses from the injured tissue as well as from the nerves subjected to pressure as a result of the repair inflammation will cause efferent impulses to be sent to somatic and splanchnic areas supplied from this segment.  These outgoing impulses are influencing motion, secretion, nutrition which are probably disturbed if the sensory nerve impulse which calls forth the reaction is a disturbed one.  It is hardly probable that reactions of the kind here mentioned tend to remain active within one spinal segment.  The nerve centers involved are vertical, i. e., extend through one or more segments and hence our reactions tend to spread.  As soon as visceral activity is disturbed by vasomotor changes a train of reflexes of a compensatory character are initiated and without we hold firmly in mind the character and location of the lesion and realize the probable, as well as possible, compensatory reactions of a mechanical, circulatory and nervous character dependent upon it, we arc quite apt to be led astray by the boldness with which some obscurely related symptom crowds its way into the foreground of our attention.  The persistence with which many of the older osteopaths have worked upon the lesion and refused to be led away, in fruitless efforts to palliate symptoms, has contributed much to the success of their school.

    Example of Fatigue. - Another phase of the lesion as a tenable cause of disease is found in those cases whose structure suffers on account of fatigue or effort to become adapted to position.  We will take two lesions commonly associated, i. e., muscular tension with a variable amount of distortion over the splanchnic area, and muscular tension centered over one or all of the upper three cervical vertebrae.  A bookkeeper fatigues his back muscles by his position.  The effort to see clearly, especially if there is any intrinsic defect of vision or of the coordinating power of the occular muscles requires compensatory action of the cervical muscles to maintain the head in the most favorable position for seeing.  The fatigue resulting from many hours of this compensatory effort, supplemented by other events of daily life, produces a so-called "bony lesion," usually about the second or third cervical or even as low as the fourth dorsal.  By carrying the weight of the head forward of the center of the body the strain on the extensor cervical muscles is eased somewhat by rounding the shoulders, depressing the thorax, shortening the distance between the end of the sternum, costal arches and the pelvic brim, thus relaxing the abdominal muscles and permitting gastro and enteroptosis.  This sagging of the stomach and bowel must be checked if possible, hence the extensor muscles over the splanchnic area contract to maintain the normal erect attitude, but fail eventually because the body is not planned to sustain the weight of the head in a position constantly off the center of the body.  This illustrates the gradual development of lesions due to efforts of adaptation.

    Loss of Muscular Tone. - Loss of tone in muscles will allow those tissues to which they are attached to yield to the force of gravity and, hence, lesions will be produced.  As example, one of my surgical cases complained bitterly, on the third day after a hysterectomy of pain in the back and at the lower end of the abdominal wound.  Inspection of the wound showed nothing unusual.  The course of the pain was examined and it was found to follow the course of the twelfth dorsal nerve.  The feebleness of the patient allowed all her tissues to sag, with the result that the right twelfth rib lay against the transverse process of the first lumbar vertebrae.  A pressure thus exerted on the twelfth dorsal nerve produced pain in the area of its distribution.  A small pad of gauze and cotton, sufficient to keep the rib away from the transverse process for a few days until general body nutrition reasserted its tonic effect, was sufficient for relief.

    As heretofore stated, it isn't the acute lesion, so easily recognized, that has contributed so much prestige to osteopathy.  It is the lesion having been overlooked or mistreated and considered a negligible quantity as a causative factor.

    Experimental Lesions. - As a foundation for better clinical observation and understanding, experiments have been conducted, notably by Dr.  Louisa Burns, in the Physiological Laboratory of the Pacific College of Osteopathy, Los Angeles, and by Dr.  Carl M. McConnell of Chicago.

    These experiments consisted in producing artificial lesions on small animals, usually dogs, and noting the immediate and remote effects, then killing the animals and making a careful pathological study of the changes in the lesioned tissues.  Dr. McConnell’s description of the manner in which he produced experimental lesions is as follows: "The production of the lesion is a simple but still very important matter.  It cannot be performed successfully in a haphazard manner.  Strict attention to the thorough relaxation of tissues about the field of operation and definite application of mechanical principles are demanded.  After selecting a healthy animal (a small or medium size dog is best), surgical anesthesia is instituted.  Complete relaxation under anesthesia is necessary.   Following this, further relaxation of the area of in tended operation by traction is essential for ease of lesion production.  Next, having determined the character of osteopathic lesion desired, that is, right or left rotation, or hyperextension, or hyperflexion, or combination of these, the second essential is to apply definite mechanical principles.  Bringing the fulcrum to bear at just the desired point when the tissues are thoroughly relaxed is as necessary in producing a lesion as in adjusting one.  Much strength can be wasted if the leverage is not right; otherwise comparatively few pounds exertion will accomplish the result.  A simple way is to place the animal flat upon its belly, completely under surgical anesthesia, then while an assistant bears down with his thumbs upon the selected vertebra, the operator grasps the animal by the rear legs and exerts traction in line with the spinal column until the spinal muscles thoroughly relax and stretch, then immediately, while still maintaining the traction, hyperextend and rotate the spine until the desired point is felt to give and slip.  It is simply a question of applying the indicated mechanics.  Various leverages may be utilized.  Frequently we place a small block transversely under the animal, especially in producing rib lesions, in order to help separate the ribs, as well as to secure a stable fulcrum.

    "The traumatism is not carried to a point where tissues are torn or lacerated.  The object is to obtain a slight slipping or maladjustment of the articular surfaces.  If done correctly, that is, specifically, little force is required.  The immediate noticeable results are malalignment of the vertebrae, malposition of the ribs corresponding to the deranged vertebrae, if the lesion is a dorsal one, and contraction of the spinal muscles of the same segments.  These changes are readily palpated.  After recovery from the anesthesia and during the ensuing time the above characteristics are evident with the added ones of tenderness and rigidity.  Muscular contraction usually subsides, but not always, until only the deep spinal muscles are palpably contracted and these corresponding to the local lesion.  In some cases the animal exhibits upon movement that the back is stiff and tender; others do not and shortly show no apparent ill effects.  Later on, a number present more or less systemic disturbances, depending upon the locality of the lesion.  The periods of observation have ranged from three to eighty days, that is, the time from production of the lesion to autopsy."

    Loss of Motion. - The moveable vertebral and costo-vertebral articulations are arthodial, i. e., gliding, hence any change in one of these articulations, short of dislocation, is in a normal direction.  In other words, the lesions which we recognize are partial fixations, hence it isn't the position which constitutes the lesion so much as it is the loss of motion, i. e., the loss of function and the exaggerated muscular contraction which maintains the fixation and the character of the injury which is the cause of these changes.

    Necessity for Study of Structure. - Based on this idea of what the lesion is we must study the normal structure and function of every vertebral and costo-vertebral articulation, so that we may recognize not only the compensatory changes on the immediate group affected, but also those widespread compensations of a mechanical, circulatory and nervous character which are part of every reparative and adaptive effort of the body.  Since pathology is the study of the perversions of the normal we can not understand what the body is trying to do in any given case without taking into account the successes and failures of compensation as are made evident by this division of medical science.