SYMPATHY (ow-rabs).—Sympathy may be defined as the assumption by different individuals, or by different parts of the same individual, of the same or an analogous physio logical or pathological state at the same time, or in rapid succession. It is popularly known that the act of yawning, performed by one individual in a company, is apt to induce in many of the others an irresistible tendency to the same act. In a similar manner, the excite ment of certain emotions (mirth or sadness, laughter or tears) is apt to spread through an assemblage of persons with extraordinary rapidity. The power of eloquence, of music, or of spectade,t °produce such effects, is witnessed every day in places of public resort, whether for devotion, business, or amusement.
Many instances are known in which con vulsions have been excited in persons not previously subject to them, by the sight of a patient in an epileptic fit. And peculiar ner vous disorders, of a convulsive kind, have been found to affect nearly all the members of a community without the slightest evidence of their being contagious or infectious. An impression upon an organ of sense may pro duce effects very different in their nature to any thing which could be anticipated ; and these many be purely of a physical kind, or they may act primarily upon the mind. Thus certain odours will induce syncope in some people; and the smell of a savoury dish to a hungry person, or even the mention or the thought of a meal, will excite a flow of saliva. The emotion of pity excited by the sight of some object of compassion, or by a narrative of a mournful kind, will produce a copious flow of tears.
All such phenomena are said to result from Sympathy. When one yawns, immediately in consequence of another's yawning, the former evidently and truly sympathises with the latter ; and the convulsions which are induced by the sight of another in a fit, are not less sympathetic. The individual in whom the convulsions are induced, sympathises with the other. Such obvious instances of sym pathy between different individuals led to the supposition of some such similar consent between different or even distant parts in the same person.
Motions or sensations caused in certain parts, in consequence of a primary irritation of other and distant parts, are of the sym pathetic kind. These motions or sensations
are produced in, as it were, an indirect or circuitous manner, or one different from that in which they are ordinarily excited.
Thus a stimulus to the olfactory membrane causes a peculiar affection of the sense of smell, and occasions that depression of the heart's action, from which results a state of syncope. Or another affection of the same sense causes a suddenly increased action of the salivary glands.
If we analyse any one of these examples of sympathetic actions, it will appear that three circumstances may be noticed in the produc tion of the phenomena : 1st, the primary exciting cause, which may be an object pre sented to the mind through one of the organs of sense, or causing an impression upon any sensitive nerve, and therefore upon some part of the centre of sensation; 2ndly, the part affected directly by this primary stimulus ; and, 3rdly, the action or sensation resulting from the affection of this part.
Many other sensations or motions may he enumerated besides those above referred to, whether occurring in health or in disease; and we shall give examples of these before we discuss this subject further.
The examples of sympathetic sensations which may be adduced are chiefly of the mor bid kind. Pain is felt at a certain part, in consequence of an irritation in another part distant from it, and apparently altogether unconnected with it. A familiar instance of this is pain in the knee from disease,of the hip-joint. So marked in some instances is the pain in the knee, and so much has it ab sorbed the patient's attention, that the real seat of the disease has been overlooked, and the remedies been applied exclusively to the knee. Pain in the right shoulder, from disease of the liver, is a sympathetic sensa tion of similar kind; and sometimes the hepatic irritation causes pain over a more extensive surface. Whytt mentions, that, in two cases of suppuration of the liver, he had seen the patients " affected with a numbness and debility of the right.arm, thigh, and leg." Sometimes both shoulders are the seat of pain, from hepatic irritation..