to the respiratory muscles; nor can we explain it by the mechanical or functional connexions of organs. It is produced by this third mode of correlation :-in other words, it is a case of sympathy. Again, a small wound in the foot will produce locked jaw, without our being able to discover, or to imagine, any greater connexion between the foot and the jaw, than there is between the foot and other organs of the body. We say, that this is caused by sympathy existing between these organs, and, so long as we use the term to signify the unknown cause of these connexions, it is well. It must be understood, however, that we attach no definite idea to the term; that it is only employed to express our ignorance of the agent or its mode of action; precisely as we apply the epithet vital to a process, which we are incapable of explaining by any physical facts or arguments.

Of sympathetic connexions we have numerous examples in the body; at times, inservient to accomplishing a particular function; but generally consisting of modifications of function produced by the action of a distant organ. Of the sympathetic connexion between the parts of the same organ, 'for the execution of a function proper to the organ, we have an example in that between the iris and the retina; the former will contract or dilate according to the degree of stimulation exerted by the light on the latter; and the effect is greater when the light is thrown on the retina than when thrown on the iris itself. A similar kind of sympathy exists between the state of the mammæ and that of the uterus, during pregnancy; although this has been frequently referred to ordinary functional correlation or synergy; but the connexion is sufficiently obscure to entitle it to be placed under this division. A singular example of the sympathy between these two organs, soon after delivery, is the fact of the sudden and powerful contraction which is excited in the uterus, when in a state of inertness, by the application of the child to the breast."

a. Sympathy of Continuity.-This is such as occurs between various parts of membranes that are continuous. For example, the slightest taste or smell of a nauseous substance may bring on an effort to vomit, the whole of the first passages being unfavourably disposed for its reception. In disease, we have many examples of this kind of sympathy. During dentition, the child is subject to various gastric and intestinal affections. If a source of irritation exist in any part of the intestinal or other mucous membrane, no uneasy sensation may be experienced in the seat of irritation, yet it may be felt at the commencement of the membrane or where it commingles with the skin:thus, itching at the nose may indicate irritation of the digestive mucous membrane; itching or pain of the glans penis, stone in the bladder, &c. These facts prove, that, in disease, a sympathetic bond unites the parts concerned, and such is probably the case in health also. We have the same thing proved in the effect produced on the action of glands by irritating the orifices of their excretory ducts. The presence of food in the mouth excites the secretion of the salivary glands,

Hedenus in art. Brust, (weibliche,) in Encyclop. Wörterb. der Medicin. Wissenschaft, vi. 349, Berlin, 1831; Carus, Lehrbuch der Gynäkologie, Th. ii. 407, Leipz. 1828; and Dr. Rigby, in Lond. Med. Gazette, March, 1831.

and that of chyme in the duodenum augments the secretion of the liver. In the same manner, a purgative, as calomel, which acts upon the upper part of the intestinal canal, becomes a cholagogue; and duodenitis occasions a copious biliary secretion. These cases have, however, been considered by many, to belong more appropriately to functional correlation, as it is presumable that the propagation of the irritation from the orifice of the excretory duct takes place directly, and along branches of the same nerves as those that supply the glandular organs. It is by this sympathy of continuity that we explain the action of certain medicines. In bronchial irritation, for example, the cough will frequently be mitigated by smearing the top of the larynx with a demulcent,-the soothing influence of which extends to the part irritated.

b. Sympathy of Contiguity.-A variety of sympathy, differing somewhat from this, is the sympathy of contiguity or contiguous sympathy, in which an organ is affected by an irritation seated in another immediately contiguous to it. The association in action between the lining membrane of the heart and the muscular tissue of the organ has been adduced as an instance of this kind, and chiefly from the experiments of Bichat and Nysten, which showed, that any direct irritation of the muscular tissue of the heart has not as much influence as irritating the membrane which lines it. A similar association is presumed to exist between the mucous and muscular coats of the alimentary canal, and the same kind of evidence is adduced to prove that the connexion is sympathetic. Other instances of sympathy are,-the convulsive contraction of the diaphragm and abdominal muscles in vomiting consequent on the condition of the stomach, as well as the convulsive action of the respiratory muscles in sneezing, coughing, &c. The general uniformity in the motion of the two eyes has been adduced as an additional instance; but Adelon has judiciously remarked, that the evidence in favour of this view is insufficient. For clearness of vision it is necessary, that the luminous rays should impinge upon corresponding points of the two retina, and should fall as nearly as possible in the direction of the optic axes. For this purpose, the muscles direct the eyes in the proper manner; and subsequently, from habit, the balls move in harmony. We constantly hear, also, a fact adduced from pathology as an instance of sympathy. A molar tooth is lost on one side of the jaw; and it is found, perhaps, that the next tooth which decays is the corresponding molar tooth of the opposite side-or a tooth has become carious, and we find the one next to it soon afterwards in a course of decay. These have been regarded as evidences of sympathy, remote and contiguous. This is not probable. The corresponding teeth of the two sides are similarly situate as regards the supply of nerves, vessels, and every anatomical element; and experience teaches us, that the molar teeth-and especially the second great molares-decay sooner than the others. If one, therefore, become carious, we can understand, why its fellow of the opposite side should be more likely to suffer. The opinion, that contiguous teeth are likely to be affected by the presence of a carious. Adelon, Physiologie de l'Homme, edit. cit., iv. 267, Paris, 1829.

a

tooth, either by sympathy, or by direct contact, is almost universally believed, and promulgated by the dentist. Both views are probably alike erroneous. If the inner side of the second molaris be decayed, we can understand, why the corresponding side of the third should become carious, without having recourse either to the mysterious agency of sympathy, or to the very doubtful hypothesis of communication by contact, especially as the caries generally begins internally. The contiguous sides of the teeth are situate almost identically, as regards their anatomical elements; and, consequently, if a morbid cause affects the one, the other is next likely to suffer, and is very apt to do so. Extracting the diseased tooth prevents this, because it removes a source of irritation, which could not but act in a manner directly injurious on the functions of the tooth next to it.

The fact of the sympathy which exists between organs of analogous structure and functions, is familiar to every pathologist. That of the skin and mucous membrane is the most intimate. In every exanthematous disease, the danger is more or less dependent upon the degree of affection of the mucous membranes; and the direct rays of the sun, beaming upon the body in warm climates, induce diarrhea and dysentery. Acute rheumatism is a disease of the fibrous structures of the joints; but one of its most serious extensions, or metastases,-whichsoever they may be called,-is to the fibrous structure of the pericardium. Barthez, a most respectable writer, gives a case of this kind of sympathy from Theden, which is inexplicable and incredible. A patient, affected with paralysis of the right arm, applied a blister to it, which produced no effect, but acted on the corresponding part of the other arm. The left becoming afterwards paralysed, a blister was put upon it, which also acted upon the other arm, not on the one to which it was applied! Owing to the sympathy, or consent of parts, Broussais has laid down the pathological law,-that when an irritation exists for a long time in an organ, the textures that are analogous to the one which is diseased, are apt to contract the same affection.

c. Remote Sympathies.-As examples of the more distant kinds of sympathies, we may cite the effect produced upon the stomach by distant organs, and conversely. Among the earliest signs of pregnancy are nausea and vomiting; loathing of food; fastidious appetite, &c. These symptoms are manifestly induced by sympathetic connexion between the uterus and stomach; inasmuch as they are not adventitious, but occur more or less in all cases of pregnancy. Their absence, at least, is a rare exception to the rule. Hunger or dyspepsia, again, impresses a degree of languor,-mental and corporeal,which is proverbial; whilst the reception of food, and its vigorous digestion, give a character of energy and buoyancy, greatly contrasting with opposite circumstances. In disease, too, we find sympathies existing between the most distant portions of the frame, and although these are not apparent to us in health, we are perhaps justified in con

■ Nouveaux Elémens de la Science de l'Homme, Paris, 1806.

b Commentaries des Propositions de Pathologie; and Drs. Hay and Griffith's transla tion, p. 60, Philad. 1832.

sidering that an occult sympathy exists between them in health, which only becomes largely developed, and obvious to us, when the parts are affected with disease. It is probable, too, that in the successive evolution of organs at different periods of life, new sympathies arise, which did not previously exist or were not observable. The changes that supervene in the whole economy at puberty, strikingly illustrate this; changes which do not occur in those who, owing to malformation, are not possessed of the essential parts of the reproductive system, or who have had them extracted prior to this period.

d. Imagination.-The effect of the intellectual and moral faculties on the exercise of the functions of other parts is strongly evidenced, especially in disease. The influence of the mind over the body is, indeed, a subject which demands the attention of every pathologist. In health, we notice the powerful effect induced by the affective faculties upon every function. All these are caused by sympathetic association with the brain; the action of the organs being in a state of excitation or depression, according to the precise character of the emotion. The intellectual manifestations probably exert their influence in a manner less evident, but not the less certain. The effects of one of them, at least, on the bodily functions are remarkable. We allude to the imagination, to which we can ascribe most of the cures that are said to have been effected by modes of management,-often of the most disgusting character,-which have been from time to time in vogue, have fretted their hour on the stage, and then sunk into that insignificance from which they ought never to have emerged.

We have had occasion to allude to the excited imagination of the maniac, the hypochondriac, and the nervous, and have remarked, that hallucinations may exist in those of sound mind;-phantoms created by the imagination; pains felt in various bodily organs, &c.; and we can hence understand, that, under particular circumstances, we may have actual disease produced in this manner; and, at other times, the feeling,-which may be as distressing to the patient,-of disease, which has no existence except in the imagination. It is to the effect produced by the imagination, that we must ascribe the introduction into medicine of magic, sorcery, incantations, Perkinism, and other offsprings of superstition or knavery. The enthusiasm, that has attended the application of these last modes of acting upon the imagination in our own times, is most extraordinary," and their history leads us to be still more impressed with the extensive influence that may be exerted by the mind over the body: they teach the practitioner the importance of having its co-operation, whenever it can be procured; and the disadvantages, which he may expect to ensue, when the imagination is either arrayed against himself personally, or the plan of treatment which he is adopting. The physician, who has the confidence of his patient, will be successful-if he adopt precisely the same plan of treatment that would be pursued by one who has it not-in cases where the latter would totally fail. The applications of this subject are developed by the author elsewhere."

* Demangeon, Du Pouvoir de l'Imagination, &c., chap. ii. p. 39. Paris, 1834. b General Therapeutics and Materia Medica, vol. i. p. 57, 3d edit. Philad. 1846.

Again, pathology is invoked as affording us perhaps the best evidences of the existence of extensive sympathetic relations between various parts of the frame, which are supposed to be constantly going on unseen during health, but become developed, and more obvious in disease. The case, we have previously given, of the general effects produced upon the system by local irritation of a part, shows the extent of such association. An insignificant portion of the body may become inflamed, and if the inflammation continue, the function of the stomach may be disordered, as indicated by loss of appetite, nausea, and vomiting; the respiration may be hurried, as well as the circulation; the senses blunted; the intellectual and moral faculties obscured; and languor and lassitude may indicate the nervous irritation and constraint.

The moral consideration of sympathy does not concern us. It is a subject, and one of interest to the moral philosopher,-to account not only for these secret causes, which attract individuals towards each other, but which repel them and occasion antipathies. To a certain extent, however, it trends into the province of the physiologist. The tender, susceptible individual, from observing another suffering under pain, feels as if labouring under the same inconvenience, and, by a very rapid, yet complex intellectual process, constituted of numerous associations, may be so strongly impressed as to sink under their influence :-thus, the sight of blood will so powerfully impress the mind, in this sympathetic manner, that fainting may be induced, and the vital functions be for a time suspended. The sight and suffering of a woman in labour may cause abortion in another; and hence the propriety of excluding those, who are pregnant, from the chamber of the parturient female. Hysteric and convulsive paroxysms are induced in a similar way; of which the convulsionnaires of all times must be regarded as affording singular and instructive examples.

e. Superstitions connected with Sympathy.-Lastly:-the mysterious consent, which we observe between various parts of the body, has given rise to some of the most strange and absurd superstitions that can be imagined. It was believed, for instance, almost universally, in the fifteenth century, that an intimate sympathy exists, not only between parts of a body forming portions of one whole, but also between any substance that had previously formed part of a body and the body itself;-that if, for example, a piece of flesh were sliced from the arm of one person and made to unite to that of another, the grafted portion would accurately sympathize with the body of which it had previously formed part, and undergo decay and death along with it; and it was even proposed to turn this sympathy to account. It was recommended, for instance, that the alphabet should be traced on the ingrafted portion; and it was affirmed, that when any of the letters, so traced, were touched, the party from whom the piece of flesh had been taken would feel similar impressions; so that, in this manner, a correspondence might be maintained. Some went even farther than this, asserting, that such a miraculous sympathy exists between the human body and all that has previouly formed part of