From the histological standpoint, blood conforms to the general definition of a tissue, being composed of a cellular and intercellular substance.  The intercellular substance, being liquid, differentiates it greatly from other tissues.  It contains cellular elements which differ from each other in form and function.  Then, too, it is a moving tissue enclosed in a system of closed tubes.

    Functions. - The blood performs many functions.  These may be stated in general terms as follows:

1. To convey nutrition to all other tissues.
2. To remove waste products from the tissues.
3. To convey oxygen for tissue respiration.
4. To distribute heat.
5. To repel invasion of bacteria.

    Lymph. - Lymph is another liquid tissue, less rich in corpuscular elements, but greater in total bulk than the blood.  The lymph comes in direct contact with the elements of the tissues.  Stewart states the relationship tersely when he says, "The blood feeds the lymph and the lymph feeds the cell."

    Since we think of individual tissues as possessing some one well developed attribute or function, it is well to call blood and its congener, lymph, the media of exchange.  This expression covers at least four of the functions previously mentioned.

    With this comprehensive but short statement of the relation of these liquid tissues to the structural, contractile, irritable and secretary tissues, it seems hardly necessary to discuss so self-evident a proposition as that health primarily depends on a perfect circulation.  It is not even necessary to add to this the fact that the blood should be pure, because under ordinary circumstances if the blood circulates properly it will become purified.

    All schools of medicine have a therapeutic principle around which their practice is built.  From its earliest inception the osteopathic idea has been that a perfect circulation is the foundation for perfect health.

    The proportion of blood to body weight is about one-twelfth of the whole, i. e., twelve pounds of blood in a body weighing 150 pounds.  This amount of blood is distributed approximately as follows: One-fourth to the heart, lungs and great blood vessels; one-fourth to the liver; one-fourth to the resting muscles; one-fourth to the remaining organs.  There is not blood enough in the body to maintain all of its activities at the maximum at the same time.  Therefore it is difficult to do the best physical or mental labor just after digestion has begun.  The splanchnic blood vessels are capable of containing so large a proportion of the whole amount of blood that death may result from lack of sufficient blood returning to the heart to cause it to beat.

    Distribution of the Blood. - Granting that the blood possesses all these functions, the question still confronts us, how can we affect its distribution?  This question leads us to a consideration of the physiological distribution of the blood.  It is believed by the writer that nothing besides the use of water has so great an effect on the circulation of the blood as manipulation according to osteopathic methods.  These methods do not depend on a mere physical assistance of the venous flow by means of centripetal stroking, such as is employed by a masseur.  Effects on circulation are obtained in nearly all cases by knowing where definite nerves which control the action of the heart and blood vessels are placed and what their action in response to irritation may be.  All manipulations are given with a definite knowledge of the location of blood vessels and the nerve centers which control their variation in caliber.  The response secured is a new coordination of the whole circulation brought about under the control of the nerve centers.

    It has been stated that the blood is contained in a closed system of tubes.  A short resume of the most important points in the anatomy and physiology of the circulation may prepare us for a clearer insight of the modus operandi of osteopathic methods.

    The Circulatory Apparatus. - The circulatory apparatus consists of the heart, arteries, capillaries, veins and lymphatics; some writers include the spleen.

    Muscular tissue is found in the heart, small arteries and veins.  The heart is practically all muscle, and its contractions are governed by two sets of nerve fibers from the cerebrospinal system; the first set is called accelerator; second, inhibitory.

    Likewise, the small arteries and veins have two sets of fibers which increase and decrease the intensity of the contraction of their muscular fibers, and thus change the caliber of the vessels.

    The capillaries are short, narrow tubes, having a thin wall composed of nucleated cells which possess the power of contraction.  So far as known, the capillaries expand and contract in response to the degree of physical pressure exerted by the blood current coming from the arterioles.  Thus the change in the caliber of the capillaries is passive.  The lymphatics begin in small irregular spaces in the cellular tissue outside of the blood vessels.  They are found in direct relation with the cells of perivascular tissues, thus bringing the lymph to each cell.  These openings lead to small lymphatic vessels which convey the lymph to the lymphatic glands which are situated so as to filter out the impurities, after which it is emptied into the venous circulation by the lymphatic ducts.  The lymphatic vessels possess power of contraction.  The lymph equals about one-third of the body weight.

    The blood is a passively moving tissue.  It is kept in constant circulation within a closed system of tubes by a combination of forces.  The propulsion of the blood is almost entirely accomplished by the contraction of the heart.  This initial force is supplemented by the aspiration of the chest during respiration, and the contraction of the skeletal muscles of the entire body.  It is a debatable question whether or not the muscular coat of the, arterioles and venules assist in the direct propulsion of the blood passing through them.

    It is the function of the heart to maintain a comparatively uniform tension of the blood in the large arteries.  The arterioles and capillaries are concerned in maintaining resistance to the passage of the blood.  The degree of resistance in the capillaries, in large measure, determines the amount of nourishment received by the tissues.  The relation between capillary resistance to the passage of the blood and the metabolism carried on in perivascular tissues is a point of great importance.  The current of blood ordinarily passes through the capillaries very slowly, at a rate of one inch in two minutes, and under low tension, thus giving ample opportunity for the escape of nourishing material for the surrounding tissues.

    Tension in the arteries is maintained by three factors: (1) The initial force of the heart beat; (2) friction in the vessels; (3) elasticity of the vessel walls.  The first and third of these factors are under nerve control which act according to a large number of stimuli.

    The capillaries being passive in action, the tension of the blood stream in them is mainly dependent on the tension in the arterioles.  It may be profitably noted that after the initial impulse is given to the blood stream by the heart, the distribution of this blood depends solely on the arteries, arterioles and capillaries.  This peripheral distributive mechanism is therefore responsible for the nutrition of the tissues, and its resistance offered to the passage of the blood regulates the amount of force exerted by the heart.

    Manipulatory treatments, according to the best authorities writing on massage and Swedish movements, have for their object the acceleration of the blood flow on the venous side of the general circulation.  Osteopathic manipulations are essentially directed to the active instead of the passive side of the circulation.

    The osteopath makes use daily of the vasomotor nerves in order to control the circulation of the blood in local areas; therefore, it is necessary to make a detailed study of this wonderful mechanism in order to achieve the best results in practice.

    The more we know of structure and function, the more rational ought our methods of treatment to be, because we will then have no excuse for using methods which do not have a scientific basis to recommend them.

    The Heart. - In order to affect the active side of the circulation our manipulations must affect the heart beat.  There are two sets of nerve fibers arising in the cerebrospinal system which exert a regulating influence on the beat of the heart.  Heart muscle possesses an inherent power of rhythmical contraction.  It will beat rhythmically for hours if the muscle be kept moist with a one per cent salt solution.

    Contraction begins in the auricles and ends in the ventricles; hence, it is thought that the auricular rhythm is transmitted to the ventricle.  Any influence which changes the auricular rhythm also changes the ventricular rhythm.

    Regulation of Contraction. - Since the heart possesses inherent power of rhythmic contraction, the nervous system acts as a regulator of the rate of contraction.  The two centers of cardiac control act in a manner to increase or decrease the rate.  The speed of the blood current is dependent on the rate and strength of the cardiac contractions.  The pressure of the blood is dependent on the rate and strength of the cardiac contractions, together with the resistance offered by the arterioles and capillaries.  Considering the arterioles and capillaries as possessing fixed diameters, an increase in the number and strength of the heart beats would increase the speed and pressure of the blood current.  A lessened cardiac activity would have the opposite effect.  The speed and pressure of the blood stream may vary within wide limits and still maintain a fair degree of health.

    Coordinating Centers. - The nerve impulses reaching the heart are coordinated in two governing centers in the cerebrospinal system.  These centers are located in the bulb.  The inhibitory center is connected with cells in the walls of the heart by fibers which form a part of the pneumogastric nerve.  Section of the pneumogastric nerve removes the inhibitory influence over the heart's action.  Stimulation of this nerve slows the heart.  The relaxation period is lengthened which results in greater filling of the heart and the pressure in the veins is increased while arterial pressure decreases.  These results have been noted by many physiologists.

    The Pneumogastric Nerve. - The pneumogastric is one of the nerve trunks which can be reached by direct pressure made through the skin and muscles of the neck.  Its inhibitory action can be aroused by pinching the sternocleidomastoid muscle between the thumb and forefinger, taking care to work deeply under the internal margin of the muscle.

    It is no uncommon phenomenon to have a patient faint as a result of this manipulation.  Individuals differ greatly as to their response to this stimulation.  The stimulation should be a gentle pressure of a constantly varying intensity.

    A pulse tracing is appended, Fig. 24, which shows the results of stimulating the pneumogastric in the manner just described.  The gentleman upon whom the experiment was made was in excellent health, and possessed a quiet, well-balanced temperament.  The tracing shows that the number and force of the beats was lessened and the arterial pressure decreased.  This tracing is probably typical of the change, in a well person, in response to stimulation of the pneumogastric.  No sensation of faintness or other disagreeable feeling was noted.

    The inhibitory action of the pneumogastric seems to be most active in individuals who suffer from some disorder of the digestive tract.  In such patients the constant irritation of the sensory fibers of the pneumogastric, which arise in the mucosa of the digestive viscera, seems to increase the irritability of the whole nerve trunk to such a delicate point that the slightest stimulation made at any point along the course of the nerve will excite its inhibitory action.  Many osteopaths, just starting in practice, have had. their self-possession severely tried by a patient fainting during manipulation of the neck.  I have never heard of any fatal results from manipulation of the pneumogastric.  Why stimulation of the, pneumogastric should result in cardiac inhibition rather than in phenomena connected with its other branches seems incapable of explanation.  Sometimes spasm of the laryngeal muscles will accompany cardiac inhibition.

    The intensity of action of the pneumogastrics is so well known to experienced osteopaths that they are careful to test its irritableness in cases before undertaking any extensive manipulations along its course.

    The inhibitory center is continually active and acts according to the blood pressure within the arteries.  A rise in peripheral resistance causes a decrease in number and strength of the heart beats.

    Accelerator Center. - The accelerator center is connected with the heart by fibers which descend in the cord to the upper portion of the dorsal region; here connection is made with the cells whose fibers pass to the sympathetic spinal ganglia, first, second and third dorsal, and end there around other cells whose fibers convey their impulses to the heart.

    The action of the accelerator center is not so readily demonstrated as is the case with the inhibitory center.  It causes the heart to beat faster and stronger, thus bringing about a rise in arterial blood pressure and a fall in venous pressure. This center acts in response to lowered peripheral resistance.  The products of metabolism brought about by physical exercise also excite it.  Deep, steady pressure made on the muscles lying on each side of the first, second and third dorsal spines causes a decrease in the rapidity of the heart's action.

    Stimulation of the Heart. - A make and break pressure made at the edge of the sternum in the first and second intercostal spaces,will usually stimulate the heart.  Sometimes the first effect is inhibition, but it quickly passes to stimulation.  The manipulation made anteriorly increases the number and intensity of the stimuli reaching the segment of the cord from which the accelerator nerves pass out.  All centers act according to the sum of the stimuli reaching them from all sources.

    Inhibition of the Heart. - In cases of rapid heart beat with high tension pulse the best effects are secured by digital pressure at first, second and third dorsal spines.  The pneumogastrics have too many branches to important viscera and act frequently with unexpected intensity.  The accelerators act more slowly with less intensity and the action is sustained longer, that is, as a result of manipulation.

    Vasomotor Control of the Coronary Arteries. - A further factor in relation to the regulation of the heart's action is the blood supply for the nourishment of the heart.  All organs act with greater force when their blood supply is abundant.  The heart beats stronger when its coronary arteries are dilated than when constricted, therefore the power of the heart depends on the vasomotor control of its own arteries.  The vasomotor nerves to the coronary arteries leave the cerebrospinal system between the third and fifth dorsal spines.  In cases of angina pectoris, this area will be sensitive.  Steady pressure here will dilate the coronary arteries and ease the pain.  A sharp stroke with the hypothenar eminence on the fourth dorsal spine will nearly always start an attack with such patients.

    Angina Pectoris. - Physiologists name the pneumogastric nerve as the vasomotor nerve to the coronary arteries.  I mention the area, third to fifth dorsal, as a vasomotor center for the coronary arteries because clinical experience seems to demonstrate it.  Other osteopaths have noted the frequency of lesions in this area in connection with heart difficulties.  The lesions are contracted muscles, lateral subluxations of the vertebrae or in some instances subluxations of the fourth and fifth ribs.  With any of these lesions there is intense sensitiveness.

    Dr. George Keith of Scotland mentions digital pressure in the second left intercostal space as a means of inhibiting an attack of angina pectoris, and suggests the nerve connection of the pneumogastric as being the nerve path over which the inhibitory impulse travels.  Persons suffering with angina pectoris will press their hands, with all the force they possess, against the left chest.  I have used heavy digital pressure on the left side of the fourth and fifth dorsal spines while the patient was in a paroxysm of pain.  The pressure never failed to be grateful to the patient.

    A further experiment with this center was made by extending the patient in a recumbent position.  While extension was maintained the angles of the ribs could be raised, the left arm could be extended over the head, a full inspiration could be taken, but as soon as the vertebrae were allowed to approximate as a result of cessation of extension, these things could not be done.

    Heat, digital pressure and counter irritation are capable of causing vasoconstrictor paralysis, i. e., vasodilation, and hence increase the power of the heart in such cases.

    Action of the Heart Centers. - The governing centers of the heart act principally according to the peripheral resistance maintained by the blood vessels.  The heart possesses a nerve called the depressor nerve.  Its endings are in the walls of the heart and are affected by the pressure of the blood within the heart.  A rise in arterial pressure is followed by a rise in pressure within the heart.  The depressor nerve notes this fact and carries an inhibitory impulse to the vasodilator center in the medulla, thus bringing about a fall in arterial pressure.  In this way the heart is protected from overexertion as a result of too high pressure.

    In cases having rapid, weak heart action, inhibit the accelerators to slow the heart, also inhibit in the area of vasomotor control of the coronary arteries to increase the amount of blood for nourishment to the heart muscle, thus increasing the strength of the beat.

    In cases of rapid, high tension pulse, inhibit the splanchnics and in the suboccipital fossae to lessen peripheral resistance, also inhibit the accelerators or. stimulate the pneumogastrics.

    Vasomotor Nerves. - In 1840 Henle discovered and demonstrated the muscular coat of the arteries, and as a result of this step forward we have our present knowledge of the vasomotor nerves.  Associated with the demonstration of these nerves we have the names of BrownSequard, Bernard, Waller and Schiff.

    It has been proven that two sets of fibers innervate the muscles of the arteries; a vasoconstrictor set, which causes a decrease in the caliber; and a vasodilator set which causes an increase in caliber.  The constrictors were demonstrated first.

    Henle said "the movement of the blood depends on the heart, but its distribution depends on the vessels." We have followed the phenomena in connection with the first part of this quotation, hence it remains for us to study the part played by the vessels in the distribution of the blood.

    In order to carry our thoughts along in a proper manner, we will commence at the center and work toward the periphery.

    The chief vasomotor center is in the medulla.  Destruction of this center causes an immediate fall of blood pressure all over the body.  Stimulation of this center causes a general rise of blood pressure.

    There are subsidiary centers situated at various levels in the spinal cord.

    After the spinal cord is severed, that portion which is no longer connected with the chief vasomotor center will exercise a vasoconstrictor influence over the blood vessels in its area of normal control.  "It is probable that they are normally subordinate to the bulbar nerve cells."

    After all connection between the cerebrospinal system and sympathetic spinal ganglia is cut off, the tone of the blood vessels is maintained, after a short interval, by the sympathetic ganglia.

    By commencing at the center and destroying it, then the centers in the spinal cord assume control; destruction of these leaves the sympathetic spinal ganglia active; hence by this process of exclusion we find that the true vasomotor cells are sympathetic and lie in the spinal ganglia.  From these cells in the spinal ganglia-axis cylinder processes pass as gray fibers to blood vessels.  These ganglia cells are controlled by fibers from the chief vasomotor center in the medulla which end around the subsidiary cells in the spinal cord, the neuraxons of these latter terminating by filaments which surround the true vasomotor cells in the sympathetic spinal ganglia.

    Since gray rami-communicantes pass from the spinal sympathetic ganglia to the spinal nerves and are distributed with them to the skin and blood vessels, we can influence the distribution of the blood generally and locally by increasing or decreasing the number of sensory impulses, originating in the skin and muscle, which may reach the vasomotor centers.

    "The vasomotor apparatus consists, then, of three classes of nerve cells.  The cell bodies of the first class lie in sympathetic ganglia, their neuraxons passing directly to the smooth muscle in the walls of the vessels; the second are stimulated at different levels in the cerebrospinal axis, their neuraxons passing hence to the sympathetic ganglia by way of spinal and cranial nerves; and the third are placed in the bulb and control the second through intraspinal and intracranial paths.  The nerve cell of the first class lies wholly without the cerebrospinal axis, the third wholly within it, while the second is partly within and partly without, and binds together the remaining two." (Am.  Textbook of Physiology.)

    Vasoconstriction. - The vasoconstrictor nerves which pass from the bulbar and spinal centers of control leave the cord as white rami-communicantes from the anterior roots of the second dorsal to the second lumbar nerves and enter the sympathetic ganglia to be distributed as has been described before.  It is believed that all of these vasoconstrictor fibers end in the ganglia, thus exerting their influence on the true vasomotor cells in the ganglia which alone send fibers to the blood vessels.  All these constrictor nerves are gray.

    Vasodilation. - The vasodilator fibers are not restricted to any one portion of the cord or brain, but pass out with both cranial and spinal nerves, and do not lose their sheaths until they reach their destination.  They are best demonstrated in those regions of the cerebrospinal system from which vasoconstrictors do not arise.  The vasodilators from the head, face, salivary glands, etc., pass to their destination with the cranial nerves supplying these parts.  They do not end in the sympathetics.  They probably leave the cord in the anterior roots of the spinal nerves and pass to the periphery without interruption.  The vasodilators, leaving the cord in the same region as the vasoconstrictors to be distributed to the visceral blood vessels probably pass out by the ventral roots and reach their destination without losing their sheaths in the sympathetic ganglia.

    No distinct centers for vasoditator fibers have been demonstrated.  They probably arise from segments of the brain and spinal cord and their influence is carried along the paths of motor nerves and is exerted in a local area.

    Summary. - 1.  The vasodilator nerves are cerebrospinal; (a) and are not demedullated in the sympathetic ganglia. (b) They are distributed principally to the arteries of the muscles, (c) and leave the cerebrospinal axis with the motor nerves from all portions. (d) Their influence is local.

    2. The vasoconstrictors are essentially neuraxons of sympathetic cells in the spinal ganglia; (a) are gray fibers; (b) are distributed to viscera and cutaneous blood vessels; (c) and are probably continuous in action to maintain the tone of the vascular system. (d) The vasomotor cells in the sympathetic ganglia can act independently, (e) but are normally under the control of the cells in the spinal cord whose neuraxons end in the spinal ganglia. (f) These cells in the spinal cord are under the influence of neuraxons of cells in the medulla which constitute the chief vasomotor center. (g) Therefore, the vasoconstrictor influence is both local and general. (h) The controlling fibers leave the cord in the ventral roots of the second dorsal to the second lumbar nerves only.

    Sensory Nerves. - We have now considered in detail only one side of the vasomotor mechanism, the motor.  We have yet to note the sensory side, that which calls forth the motor response.  If there were no chief or spinal vasomotor centers to transfer sensory impulses to the vasoconstrictor cells in the spinal ganglia, the blood vessels in the viscera and skin could not contract or relax according to the necessity for greater or lesser amounts of heat in the .deep or superficial areas.

    The vasomotor centers in the brain and cord send out impulses in response to sensory stimulation; this sensory stimulation is usually of a thermal or mechanical character.

    It is difficult to realize the extent of the distribution ,of sensory nerves.  "They are located not only in those places usually known to be sensitive, but also in all other tissues and organs.  Whether one examine the liver or the kidney, lung or the wall of a blood vessel, one always finds delicate nerve arborizations in unsuspected numbers.  A large portion of them end probably in the peripherally placed end cells belonging to the reflex arc of the sympathetic; 'another portion may very probably be traced to the spinal ganglia, and even to the spinal cord itself, especially the investigations of the past two years, making use of the silver and methyl blue stains, have not only disclosed the wealth of nerves in the different organs, but have also shown that we have regarded the sensory innervation of the sensitive surfaces, as the skin and the much less fully explained gustatory-mucous membrane as than they really are.  One finds there numerous plexuses of nerve fibers beneath and between the epithelial cells, and they send one, often many, fine fibrils to each cell." ladder, and many "In the liver, too, and the other places, one can find numerous examples of the abundant peripheral innervation.  We have always given too great importance to the single end apparatus, overlooking the fact that really the major portion of the body tissues is supplied with nerves for every cell.  One can hardly overestimate the wealth of nerve fibers in the end organs themselves, as the taste papillae and the tactile papillae.  Good staining discloses with each of them plexuses of unexpected density of arborization."

    "For what services may such an abundant sensory innervation be provided?  It occurs immediately to one that there are a great number of reflexes, very necessary to the preservation of the individual, even though he be unaware of them.  The regulation of the secretions, the blood supply to the skin in relation to the caloric body economy of the organism, the adjustment to varying illumination, the tension of the muscles and tendons through the respective tendon reflexes, the different response by such varying tensions according to the intensity of the voluntary impulse, and many other phenomena could be cited.  To all of them is necessary, besides the motor part of the reflex arc, a sensory part.  Indeed, Exner, to whom we are indebted for indicating the importance of these short reflex arcs and the roles they play in the organism, has pointed out how, in general, for the production of any movement the sensory innervation must be intact."

    "By 'sensory innervation,' however, one must not think only those processes are meant which enter into our consciousness, but rather all those by which from any place in the body impressions are conducted to the nearest ganglion, or to the central axis.  Whether they be conducted farther still, or whether they be recognized by the individual as they occur does not affect their nature.  Sensation and perception are not the same thing."  (Anatomy of the Central Nervous System in Man and in Vertebrates in General. - Edinger.)

    Thus we find that there are abundant sensory nerves in superficial and deep tissue to receive the mechanical stimuli which the osteopath may project upon them.

    Recent investigations prove that many conditions which have previously been called inflammation are, in reality, congestions due to vasoconstrictor paralysis, and can be corrected by stimulation of the vasoconstrictor center governing the congested area; the stimulation of such center being secured by mechanical stimuli applied to the sensory nerves ending in the center.

    The vasomotor mechanism responds quickly to osteopathic manipulation, and is our means of correcting any disturbance of circulation, both local and general.

    Since the blood carries the nourishment for the tissues, and the vasomotors control the distribution of the blood, the vasomotor nerves are trophic nerves.  In the same sense they are secretary nerves.

    Capillary Circulation. - The capillary circulation is dependent on the state of the arterioles.  Their walls are formed by endothelial cells. which are elastic, and hence respond to the force of the blood which enters them.  If the vasoconstrictors are active in a local area the resistance offered to the passage of the blood current by the arterioles is increased, and therefore the pressure exerted on the capillary walls is lessened, allowing the capillaries to contract.  If the vasoconstrictor influence over the arterioles be lessened, the blood current is allowed to exert its pressure on the capillary walls, thus increasing the caliber of the capillary.

    If, in a large area of the body, vasoconstrictors are active, the influence of this resistance is felt by the heart, which immediately beats harder to overcome the resistance to the passage of the blood through the constricted arteries.  The heart is usually relieved by compensatory dilatation of the arteries in some other area.  The visceral and cutaneous arteries usually counterbalance each other in this way.  This counterbalancing effect is probably brought about through the sensory impressions sent out from an overworked heart to the vasomotor center, thus causing a lessened constrictor effect in some portions of the body.

    The relaxation of all the arteries of the body would cause death, because the blood would gravitate to the most dependent part, and there is not blood enough to fill all the arteries when relaxed.  A slight relaxation of general blood pressure causes the heart to beat more rapidly for a short time.  Relaxation of the peripheral blood vessels is noted by the increased warmth and redness of the area in which relaxation takes place.

    Recapitulation. - To recapitulate: (1) Capillary, circulation is passive. (2) Vasoconstriction of the arterioles causes a decrease in the lumen of the capillary. (3) Vasodilation of the arterioles causes increase in the lumen of the capillary. (4) General vasoconstriction of the cutaneous blood vessels slows the heart and causes it to work against higher pressure, but the heart is relieved by relaxation of blood vessels in visceral areas, chiefly the splanchnics. (5) Decrease of constrictor effect on superficial vessels causes a more rapid heart beat, which is quickly controlled by constriction in the splanchnic area. (6) The vasomotor center in the medulla acts according to the sum of the sensory influences reaching it from all parts of the body. (7) The spinal vasomotor centers act according to the influences sent to them by the chief center and the sensory impulses which enter their segment of the cord.

    Vasomotor Centers. - The vasomotor centers for the various viscera, organs and members are as follows:

    HEAD: The superior cervical ganglion.

    EYE: The superior cervical ganglion through the fifth nerve.

    NOSE, THROAT, TONSILS, TONGUE and GUMS: By the same path.  Dilator fibers for the tongue per the lingual branch of the fifth cranial nerve.

    BRAIN: "Sherrington and others have demonstrated the presence of vasomotor nerves in the vessels of the brain.  It is probable that the cerebral circulation is wholly dependent upon the general blood pressure, and, inasmuch as the general blood pressure is very markedly regulated by the capacious splanchnic area, it is obvious that the cerebral circulation may be better controlled by modifying the blood supply of the splanchnic area than by any attempts at the modification of the cerebral circulation itself."

    Sympathetic fibers to the anterior and middle fossae come from the superior cervical ganglion per the carotid plexus.  Sympathetic fibers are distributed to the vessels in the posterior fossa from the vertebral plexus which is formed by fibers from the inferior cervical ganglion.

    THYROID GLAND: Middle and inferior cervical ganglion.

    The vasoconstrictors for the blood vessels of the head, face and neck with their contained organs leave the spinal cord in the upper dorsal, second to fifth, and pass thence through the cervical
ganglion.

    LUNGS: Second to the sixth dorsal.

    INTESTINES: The vasoconstrictors for the mesenteric blood vessels are found in the splanchnic nerves.  Commencing at the fifth dorsal, there is a segmental distribution to the various portions of the intestines.  The lowest constrictor influence comes from the second lumbar.  Vasodilator fibers are also found in the splanchnics.

    LIVER: Sixth to tenth dorsal, right side.

    KIDNEY: Tenth to twelfth dorsal.

    SPLEEN: Ninth, tenth and eleventh dorsal, left side.  The vagus is a motor nerve to the muscular fibers in the trabeculae of the spleen.

    PORTAL SYSTEM: Fifth to ninth dorsal.

    EXTERNAL GENERATIVE ORGANS: First and second lumbar, through the lumbar sympathetic ganglia, second to the fifth, to the hypogastric plexus, thence through the pelvic plexuses and pudic nerves to the generative organs.  Function, vasoconstriction.  First, second and third sacral nerves are vasodilators to the same organs.

    INTERNAL GENERATIVE ORGANS: Vasoconstrictor influence at first and second lumbar.

    ARTERIES TO THE SKIN OF THE BACK: Vasoconstrictor influence from sympathetic ganglion of the corresponding segment.

    UPPER EXTREMITY: Vasoconstrictor influence to the skin, from second to the seventh dorsal.

    LOWER EXTREMITY  Sixth dorsal to second lumbar.

    MUSCLES: Dilator influence to the arteries of the muscles per motor nerves to the muscles.

    Conclusions. - Vasomotor nerves are of two classes, viz: Vasoconstrictor and vasodilator.  These nerves act according to the sum of the stimuli reaching their governing center over sensory nerves of skin, muscle and gland.  Therefore the osteopath depends on increasing or decreasing the stimuli reaching the spinal centers.

    The heart is innervated by two sets of nerves which control it.  These nerves arise from centers in the cerebrospinal system and govern the action of the heart according to the sum of stimuli reaching their centers over sensory nerves of skin, muscle and gland, and in harmony with the resistance maintained by the peripheral blood vessels.

    Since perivascular tissues are dependent on the transfusion of nutriment from the blood, through the walls of the capillaries into the lymph, and this process of transfusion is dependent on the tension and speed of the current of blood in the capillaries, any condition which markedly increases or decreases this speed and tension will affect the nourishment of the tissues.

    Hyperaemia. - A study of hyperaemia is, in reality, a study of the vasomotor mechanism.  We have noted the fact of vasomotor nerves controlling the caliber of blood vessels.  These nerves are branches of the cerebrospinal system.  Most of them leave the spinal nerves and pass to the sympathetic spinal ganglia as rami-communicantes and then pass up and down to other ganglia of the sympathetic system.  Some fibers return from the sympathetic to the spinal nerves and are distributed to blood vessels of skin, muscle and bone in the area of distribution of the spinal nerves.  A few vasomotor nerves do not enter the sympathetic system but pass directly to their destination with the spinal nerves.  Thus two paths exist by which vasomotor impulses reach the blood vessels, a direct route with the spinal nerves and an indirect one through the sympathetics.

    Experimenters have long noted the return of vascular tone in an area whose vasoconstrictor nerves have been cut.  This return of vascular tonicity is supposed to be due to the presence of a perivascular mechanism which is capable of acting feebly after all other constrictor influences have been paralyzed.

    So far as methods of treatment are concerned, we have paid very little attention to the presence of vasodilator nerves, but physiologists seem to prove that there are fibers leaving the cord with the posterior roots of the nerve trunks which act as dilators when irritated.  The vasoconstrictor nerves are considered as constantly in action.

    Irritation of the dilator nerves or paralysis of the constrictors will result in dilatation of the arterioles, so that the capillaries will be dilated to their fullest extent.  Such a condition is called an "active hyperaemia." When the exit of the blood through the veins is obstructed and congestion results it is denoted "passive hyperaemia."

    The same irritants, mechanical, thermal and chemical, which are capable of stimulating muscles to unusual or unequal contractions so as to produce marked evidences of changed bony alignment, also cause such decided changes in the caliber of blood vessels as, to cause tissues to become hyperaemic or ischaemic.

    If any hyperaemia exists in the mucosa of the stomach, palpation around the sixth dorsal spine will disclose tenderness.  This spinal tenderness is probably due either to the irritation cif the dilator fibers which accompany the posterior division of the fifth dorsal nerve or to paralysis of the vasoconstrictors of that area.  The resulting dilatation impinges on sensory nerves and causes
tenderness.  The irritation of sensory nerves in the mucosa of the stomach causes dilatation of blood vessels in that area and in the spinal area from which its sensory nerve, arise.  The irritation might have originated centrally and then involved the stomach, thus reversing the course of the irritation.  These reflex hyperaemias are continually noted in practice, and it is through the reflexes that relief is obtained.  One of the classical experiments to prove the reflex action of vasomotor nerves is to immerse one hand in cold water, the temperature of the other hand will be lowered also.

    It is quite generally conceded that the small arteries and arterioles in all parts of the body are supplied with vasomotor nerves.  Their presence in the blood vessels of the brain has been recently proven by G. C. Huber. is demonstration of vasomotor nerves in the cerebral blood vessels explains many of the circulatory phenomena resulting from osteopathic manipulations.

    Irritation of sensory nerves in any part of the body causes vascular dilatation in the irritated area.  Physiological experiments seem to prove that vasodilator fibers accompany the sensory nerves, or that irritation of sensory nerves causes paralysis of vasoconstrictor nerves.  Irritation of the nerves of one side of the body by pricking with a pin causes a rise of temperature on that side and a decrease on the unirritated side, thus demonstrating that vasodilation follows sensory irritation.

    Experiments to note the effects of direct mechanical irritation of the stomach mucosa demonstrate that dilatation of gastric blood vessels follows mechanical irritation.  The physiological hyperaema thus produced is for purposes of increased secretion.  It is well known that when this physiological congestion is continued without cessation, as in the case when meals are frequent and full, the congestion becomes pathological, and the secretion of mucus is rapid.  The liver and intestines become chronically congested from similar causes.  This hyperaemia leads to, exudates and hyperplasia which further irritates sensory nerve endings and continues the dilatation of the arterioles.  Thus a vicious cycle of reflexes is established which tends to ever increasing destructiveness.

    When the sensory nerve terminals in the stomach are irritated and hyperaemia of the gastric vessels results, the influence of the irritation does not end with gastric congestion, i. e., if the hyperaemia be excessive, but causes dilatation of arteries in the spinal cord around the roots of sensory nerves distributed in other parts of the body which are supplied by branches of the same nerve trunk.  The brain does not always note the real location of the irritation.  It may refer the pain to any point supplied by a branch of the nerve trunk, one of whose branches is irritated.  Thus in the presence of chronic congestion of the gastric mucosa, as in gastric catarrh, the irritation may not be intense enough to impress the brain with a painful sensation, but a slight increase of capillary pressure around the trunk of the sixth dorsal nerve such as would be brought about by digital pressure made upon the muscles around the sixth dorsal spine, would cause instant recognition of hyperaesthesia by the patient.  Continued pressure made around the spine drives the blood out and lessens the sensitiveness.  If hyperaemia has been intense enough to cause exudates, pressure increases the pain the longer it is continued, because the exudates have affected the venous circulation and there is no open path for exit of the blood.

    From personal experience I should judge that it is quite probable that hyperaemia occurs along the whole course of the nerve and the nervi nervorum are rendered more sensitive thereby.  In case of absolute neuritis, manipulation relieves the condition temporarily, but the pain increases shortly after the treatment is given.  This shows that a condition exists which is much more difficult to change than a reflex hyperaemia.

    Continued hyperaemic conditions cause increased nutrition, i. e., hyperplasia of connective tissue.  Connective tissue seems to be more readily formed than any of the higher grades of tissue.  This may explain the rapid stiffening of the spine in cases of visceral hyperaemia.

    The digital pressure test is an excellent method of differentiating the intensity of an hyperaemia.  Even in cases of conscious pain in the gastric or intestinal areas, it is possible to use this test. ln colic, deep pressure made gradually will give relief,.but in cases of gastric ulcer or other inflammatory conditions, pressure aggravates the pain.

    Therapeutics. - We now have before us an array of physiological facts and it remains for us to indicate how we shall use them.

    The osteopath treats the vasomotor nerves as though there were no dilator fibers to be reckoned with.  Practically, we consider that the vasoconstrictors are continually acting to maintain the "tone" of the blood vessels.  Therefore, having only this one force with which to reckon, we consider all dilatation as vasoconstrictor paralysis.

    We noted the fact that the cutaneuos and visceral blood vessels were supplied with vasoconstrictors and that vasoconstriction in the superficial area was compensated for by dilatation in the deep area.

    A large number of sensory impressions reaching the vasomotor centers over the sensory nerves of the skin usually result in vasoconstriction of cutaneous blood vessels, hence internal congestion.  Irritation of the sensory nerves in the skin may cause muscle under the skin to contract, thus obstructing the circulation in the skin.  Therefore, our manipulations for vasomotor effects naturally divide themselves into two classes.  First, those which inhibit cutaneous reflexes; second, those which relax muscle in order to remove obstructions.  This division is purely arbitrary on our part, but it serves to explain our work.  We purposely leave out of this discussion the thought that we may have an osseous lesion causing our vasomotor disturbance.  We divide the spine into areas according to the predominating influence which issues from it; thus, the suboccipital fossa is the first important area.  It has long been known that pressure applied to this area in a case of congestive headache gives great relief.  The good effects are not lost when the pressure is removed.  This proves that the effect of the pressure is on the nerves of that area, and that they are in close central connection with the vasomotor center in the medulla.  This center regulates the caliber of the arteries all over the body.  It has been stated that pressure at the basi-occiput retards the blood flow to the brain, the pressure being on the vertebral arteries.  We believe a careful examination of the atlas will convince one that in the average skeleton the groove for the vertebral artery is so deep and well protected that pressure on the surface of the neck cannot affect the artery.  If our pressure effect is mechanical, why does the effect last so long?  The blood stream is as swift as an ocean greyhound, and would rush into the partly filled vessel with its previous force just the moment the pressure is removed.  We can only explain the result by noting the fact that a change has been made in the entire circulation.  Downward pressure on the carotids is also recommended to retard the blood flow to the head.  This seems impracticable since the pressure cannot help affecting the venous return as well as the carotid stream.  The best and most lasting effects are always vasomotor.

    It is a well recognized fact in the osteopathic profession that pressure in the suboccipital triangles causes a lessened blood pressure all over the body.  This fact is made use of daily to lower the temperature of the body in cases of fever.  If pressure had a mechanical rather than a nervous effect on the circulation, we could hope for no general effect, such as we do secure.  This procedure is called inhibiting the vasomotor center.  Why does it inhibit?  A "vascular tone" is normal in the body in order to keep the blood equally distributed.  This "vascular tone" is easily disturbed since it acts according to the sum of the sensory impulses reaching the center in the medulla.  Pressure in the suboccipital triangles affects not only the sum of the stimuli reaching the center, but, most important of all, affects the capillary circulation in this area which is in close nervous and circulatory connection with the medulla.  Any external application, such as hot or cold water, local anaesthetics or counterirritants must 'secure whatever internal change may be manifested, by the effect these therapeutic procedures may have on cutaneous nerves.

    Pressure in the suboccipital triangles will relax the structures forming those triangles, thus lessening the sensory impulses entering the center from that source.  The relaxed structures will hold more blood, hence they will in a slight degree relieve congestion of the center.

    These triangles are the bilateral surface centers in which we operate to cause dilatation of vessels in the skin of the trunk and extremities.  We inhibit vasoconstriction of surface arteries.

    The next great constrictor area is the splanchnic, sixth to eleventh dorsal.  This and the preceding area are the two points of vantage for the osteopath.  Since the splanchnic nerves control a system of blood vessels whose combined capacity is equal to the entire amount of the blood in the body, we can quickly realize what it means to the general circulation to affect this area.  In all cases of congestive headaches, fever, hyperaemia of visceral organs, etc., we "inhibit the splanchnics." Why?  The reflexes between the skin of the back and the muscles of the back are so intense that they cause vascular constriction of the cutaneous arteries and contraction of the deep muscles of the back, thus adding a mechanical obstruction to the circulation of the blood, in an already constricted area.  Is it not possible, yes, probable, that this state of the surface tissue causes a congestion of the vasomotor centers in the dorsal area of the cord, thus nullifying their control of the splanchnic area?  Such a condition might be brought about by cold.  The eating of indigestible food which remains a long time in the digestive tract may also be a cause.

    The facts are as we have stated them, we inhibit over the splanchnic area to lessen the intensity of the reflexes in that area, thereby allowing the centers to regain their control.  Remember that inhibition lessens the sensory impressions reaching a center and relaxes muscle both directly and indirectly.

    Case Illustrations. - An illustration of osteopathic methods applied to hyperaemia is ;afforded by the following case: A gentleman about fifty years of age was inspecting mines in the vicinity of Yuma, Arizona.  He was of plethoric habit and hence the heat of that locality affected him quickly.  About eight p.m., while in his tent preparing to bathe in order to get some relief from the intense heat, he felt a wave of weakness pass up his left side and almost instantly power of motion on that side was lost.  Paralysis did not extend to the face.  The gentleman was brought to Los Angeles and came under the best of medical treatment.  Electricity and massage were tried with fair success, but the left arm and hand remained helpless and were carried in a sling.  The hand was badly swollen and would pit under pressure, thus showing a marked degree of vasoconstrictor paralysis.  The hand and arm had been thoroughly massaged for two months before osteopathic treatment was given.  One hour's seance with the masseur would make a wonderful change in the hand, but the oedematous condition returned in a few hours.  The fingers were bent into the palm, showing a marked tendency to a spastic condition.

    From the medical standpoint it was considered sufficient for this case to have the local massage of the arm and hand, with administration of strychnine.

    The osteopathic examination was made at the end of two months of the treatment just outlined.  Slight signs of paralysis were noted at the angle of the mouth on the hemiplegic side.  Examination of the neck showed marked contraction of the deep cervical muscles the left side, extending from the occiput to the fourth cervical vertebra.  Moderate digital pressure over these contracted muscles caused pain.  There was also some tenderness as low as cause. The intense contraction and tenderness in the upper cervical region was noted as a secondary lesion existing as a result of a blood clot.  It was reasoned that if these contracted muscles could be relaxed cerebral circulation would be equalized and more rapid absorption of the clot made possible.  The spinal tenderness was brought about by the same law of irritation of sensory nerves we have previously stated.  There was a dilated condition of the arterioles around the roots of the sensory nerves in the cord similar in character to that which existed at the peripheral distribution of these nerves, especially in the hand.  There was decided wrist and elbow reflex, showing that the subsidiary nerve cells in the cord were intact, but that either the cerebral motor areas or some part of their connecting paths were injured.  The vascular tone of blood vessels in all other parts of the body was good, showing that the chief vasomotor center in the medulla was acting.  Here was a case showing a perfect reflex in the arm but loss of ability to will a motion; perfect
sensation and vasomotor paralysis.

    Treatment was directed to securing relaxation of the contracted cervical muscles and to breaking up adhesions in the shoulder joint which had been allowed to stiffen.  No treatment was given to the hand or arm.  The patient was instructed to straighten the bent fingers with the well hand many times per day to overcome the spastic condition.  Vasomotor tone returned to the blood vessels of the hand in proportion to the amount of cervical relaxation accomplished.  At the end of one month the hand was allowed to hang naturally, and scarcely any oedema was noticeable.  Muscular control and power have steadily increased.

    Another illustration is afforded by the following case: A gentleman suffering with inflammatory rheumatism in the second toe of the right foot sought relief by means of osteopathic treatment.  He had used the salicylates in his previous attacks, but his stomach had become intolerant of them.  The toe was red and angry looking, throbbing with pain and swollen to the size of the  great toe.

    Examination of the spine revealed tenderness between the fifth lumbar and third sacral spines, also between the second and third lumbar spines.  Why should tenderness exist at these points?  The answer according to anatomy and physiology is that these spinal areas mark the point of emergence from the spinal column of the anterior crural and great sciatic nerves which are distributed to equal parts of the affected toe; the sensory nerves being irritated by the deposit of faulty katabolic products in the tissues of the toe as the result of a slow blood stream.  In this case the patient was caught out in the rain and got his feet wet.  The peripheral irritation of the sensory nerves caused dilatation of the arterioles and capillaries.  The blood vessels around the roots of other sensory nerves which were branches of the same nerve trunks also dilated in response to this irritation, i. e., hyperaemia in the spinal cord was brought about at the point of origin of the anterior crural and great sciatic nerves, hence the sensory nerves to the skin and muscles of the back which are innervated from the same area of the cord as these great nerve trunks will also be tender to increased tension such as that secured by the digital pressure.

    In a case such as this we do not desire to have the deposit in the toe taken up until the eliminating organs of the body are acting freely.  To force it into the circulation before such time as it can be eliminated may result in inflaming another part.  It is quite necessary that the throbbing pain be subdued so that sleep may be had.  The patient soon learns to take advantage of venous circulation by elevating the foot.  If pressure upon, and a gentle relaxing movement of the muscles in the spinal area is made, there will quickly be noted a decrease in spinal sensitiveness followed by lessened conscious pain in the toe.  It is quite probable that pain in the toe is due to hyperaemia; sensitiveness in the spinal area is due to the same sort of condition, the difference being in degree.  It is impossible to prove the presence of these transitory hyperaemias by any direct observations any more than it is possible to prove by post mortem examination that hyperaemia or anaemia of the brain is present as a fixed pathological lesion in faulty functioning of the brain.

    Pressure and relaxation in the spinal area draws the blood away from its position around the nerve trunk roots and thus stops many of the impulses which would originate centrally as a result of the irritation of the sensory roots of the nerve trunk.

    We usually think of these reflex sensitive areas of the spine as being evidence of the ability of all the branches of a nerve trunk to express some degree of the irritation being, brought to bear on any one of the branches.  It seems to me that in the light of what is known to happen in the area of an irritated nerve, hyperemia, that the same change in circulation may occur around the roots of its parent nerve trunk and be the sole reason for what we denominate a reflex pain.

    By giving the heavy movement required to replace a subluxated vertebra or even to relax tense muscles around an otherwise normal articulation, it is quite probable that inexplicable changes are wrought in the circulation at these points which immediately change the character of the nerve impulses originating or reflexing from this portion of the spinal cord.