a very comprehensive term, denoting the manners, ceremonies, and fashions of a people, which having turned into a habit, and passed into use, obtain the force of laws; in which sense it implies such usages, as, though voluntary at first, are yet by practice become necessary.
Custom is hence, both by lawyers and civilians, defined lex non scripta, "a law or right not written," established by long usage, and the consent of our ancestors: in which sense it stands opposed to the lex scripta, or "the written law." See Law Index.
CUSTOM and Habit, in the human economy. The former is often confounded with the latter. By custom we mean a frequent reiteration of the same act; and by habit, the effect that custom has on the mind or body. This curious subject falls to be considered first in a moral, and secondly in a physical light.
I. Influence of Custom and Habit on the Mind, &c. Custom hath such influence upon many of our feelings, by warping and varying them, that its operations demand the attention of all those who would be acquainted with human nature. The subject, however, is intricate. Some pleasures are fortified by custom: and yet custom begets familiarity, and consequently insatiable desire or appetite for that thing when it returns not custom and as usual. During the course of enjoyment, the pleasure rises insensibly higher and higher till a habit be established; at which time the pleasure is at its height. It continues not, however, stationary: the same customary reiteration which carried it to its height, brings it down again by insensible degrees, even lower than it was at first; but of that circumstance afterwards. What at present we have in view, is to prove by experiments, that those things which at first are but moderately agreeable, are the aptest to become habitual. Spirituous liquors, at first, scarce agreeable, readily produce a habitual appetite; and custom prevails so far, as even to make us fond of things originally disagreeable, such as coffee, affaetida, and tobacco.
A walk upon the quarter-deck, though intolerably confined, becomes however so agreeable by custom, that a sailor in his walk on shore confines himself commonly within the same bounds. The author knew a man who had relinquished the sea for a country life: in the corner of his garden he reared an artificial mount with a level summit, resembling most accurately a quarter-deck, not only in shape, but in size; and here he generally walked. In Minorca, Governor Kane made an excellent road the whole length of the island: and yet the inhabitants adhere to the old road, though not only longer, but extremely bad. Play or gaming, at first barely amusing, by the occupation it affords, becomes in time extremely agreeable; and is frequently prosecuted with avidity, as if it were the chief business of life. The same observation is applicable to the pleasures of the internal senses, those of knowledge and virtue in particular: children have scarce any sense of these pleasures; and men very little who are in the state of nature without culture: our taste for virtue and knowledge improves slowly: but is capable of growing stronger than any other appetite in human nature.
To introduce an active habit, frequency of acts is not sufficient without length of time: the quickest succession of acts in a short time is not sufficient; nor a flow succeesion in the longest time. The effect must be produced by a moderate soft action, and a long series of easy touches, removed from each other by short intervals. Nor are these sufficient without regularity in the time, place, and other circumstances of the action; the more uniform any operation is, the sooner it becomes habitual. And this holds equally in a passive habit; variety, in any remarkable degree, prevents the effect; thus any particular food will scarce ever become habitual where the manner of dressing is varied. The circumstances then requisite to augment a moderate pleasure, and at the long-run to form a habit, are weak uniform acts, reiterated during a long course of time, without any considerable interruption: every agreeable cause that operates in this manner will grow habitual.
Affection and aversion, as distinguished from passion on the one hand, and on the other from original disposition, are in reality habits respecting particular objects, acquired in the manner above set forth. The pleasure of social intercourse with any person must originally be faint, and frequently reiterated, in order to establish the habit of affection. Affection thus generated, generated, whether it be friendship or love, seldom swell into any tumultuous or vigorous passion; but it is however the strongest cement that can bind together two individuals of the human species. In like manner, a slight degree of disgust often reiterated with regularity, grows into the habit of aversion, which commonly subsists for life.
Objects of taste that are delicious, far from tending to become habitual, are apt by indulgence to produce satiety and disgust: no man contracts a habit of using sugar, honey, or sweetmeats, as he does tobacco.
These violent delights have violent ends, And in their triumphs die. The sweetest honey Is loathsome in its own deliciousness, And in the taste confounds the appetite; Therefore love moderately, long love doth so; Too swift arrives as tardy as too slow.
Romeo and Juliet, Act ii. sc. 6.
The same observation holds with respect to all objects which being extremely agreeable raise violent passions: such passions are incompatible with a habit of any kind: and in particular they never produce affection or aversion: a man who at first sight falls violently in love, has a strong desire of enjoyment, but no affection for the woman (A): a man who is surprised with an unexpected favour, burns for an opportunity to exert his gratitude, without having any affection for his benefactor: neither does desire of vengeance for an atrocious injury involve averseion.
It is perhaps not easy to say why moderate pleasures gather strength by custom: but two causes concur to prevent that effect in the more intense pleasures. These, by an original law in our nature, increase quickly to their full growth, and decay with no less precipitation: and custom is too slow in its operation to overcome that law. The other cause is not less powerful: exquisite pleasure is extremely fatiguing; occasioning, as a naturalist would say, great expense of animal spirits; and of such the mind cannot bear so frequent gratification, as to superinduce a habit: if the thing that raises the pleasure return before the mind have recovered its tone and relish, disgust ensues instead of pleasure.
A habit never fails to admonish us of the wonted time of gratification, by raising a pain for want of the object, and a desire to have it. The pain of want is always first felt; the desire naturally follows; and upon presenting the object, both vanish instantaneously. Thus a man accustomed to tobacco, feels, at the end of the usual interval, a confused pain of want; which at first points at nothing in particular, though it soon settles upon its accustomed object: and the same may be observed in persons addicted to drinking, who are often in an uneasy restless state before they think of the bottle. In pleasures indulged regularly, and at equal intervals, the appetite, remarkably obsequious to custom, returns regularly with the usual time of gratification; not sooner, even though the object be presented. This pain of want arising from habit, seems directly opposite to that of satiety; and it must appear singular, that frequency of gratification should produce effects so opposite, as are the pains of excess and of want.
The appetites that respect the preservation and propagation of our species, are attended with a pain of want similar to that occasioned by habit: hunger and thirst are uneasy sensations of want, which always precede the desire of eating or drinking; and a pain for want of carnal enjoyment precedes the desire of an object. The pain being thus felt independent of an object, cannot be cured but by gratification. Very different is an ordinary passion, in which desire precedes the pain of want: such a passion cannot exist but while the object is in view: and therefore, by removing the object out of thought, it vanisheth with its desire and pain of want.
The natural appetites above-mentioned, differ from habit in the following particular: they have an undetermined direction toward all objects of gratification in general; whereas an habitual appetite is directed to a particular object: the attachment we have by habit to a particular woman, differs widely from the natural passion which comprehends the whole sex; and
(A) Violent love, without affection, is finely exemplified in the following story. When Constantinople was taken by the Turks, Irene, a young Greek of an illustrious family, fell into the hands of Mahomet II, who was at that time in the prime of youth and glory. His savage heart being subdued by her charms, he flung himself up with her, denying access even to his ministers. Love obtained such ascendant as to make him frequently abandon the army, and fly to his Irene. War relaxed, for victory was no longer the monarch's favourite passion. The soldiers, accustomed to booty, began to murmur, and the infection spread even among the commanders. The Baha Muftapha, consulting the fidelity he owed his master, was the first who durst acquaint him of the discourses held publicly to the prejudice of his glory. The Sultan, after a gloomy silence, formed his resolution. He ordered Muftapha to assemble the troops next morning; and then with precipitation retired to Irene's apartment. Never before did that prince appear so charming; never before did the prince bestow so many warm caresses. To give a new lustre to her beauty, he exhorted her women next morning to bestow their utmost art and care on her dress. He took her by the hand, led her into the middle of the army, and pulling off her veil demanded of the bajas with a fierce look, whether they had ever beheld such a beauty? After an awful pause, Mahomet with one hand laying hold of the young Greek by her beautiful locks, and with the other pulling out his scimitar, severed the head from the body at one stroke. Then turning to his grandees, with eyes wild and furious, "This sword (says he), when it is my will, knows to cut the bands of love." However strange it may appear, we learn from experience, that desire of enjoyment may consit with the most brutal aversion, directed both to the same woman. Of this we have a noted example in the first book of Sully's Memoirs; to which we refer the reader. the habitual relish for a particular dish, is far from being the same with a vague appetite for food. That difference notwithstanding, it is still remarkable, that nature hath enforced the gratification of certain natural appetites essential to the species, by a pain of the same sort with that which habit produceth.
The pain of habit is less under our power than any other pain that arises from want of gratification: hunger and thirst are more easily endured, especially at first, than an unusual intermission of any habitual pleasure: persons are often heard declaring, they would forego sleep or food, rather than tobacco. We must not, however, conclude, that the gratification of an habitual appetite affords the same delight with the gratification of one that is natural: far from it; the pain of want only is greater.
The slow and reiterated acts that produce a habit, strengthen the mind to enjoy the habitual pleasure in greater quantity and more frequency than originally; and by that means a habit of intemperate gratification is often formed: after unbounded acts of intemperance, the habitual relish is soon restored, and the pain for want of enjoyment returns with fresh vigour.
The causes of the present emotions hitherto in view, are either an individual, such as a companion, a certain dwelling place, a certain amusement; or a particular species, such as coffee, mutton, or any other food. But habit is not confined to such. A constant train of trifling diversions may form such a habit in the mind, that it cannot be easy a moment without amusement: a variety in the objects prevents a habit as to any one in particular: but as the train is uniform with respect to amusement, the habit is formed accordingly; and that sort of habit may be denominated a generic habit, in opposition to the former, which is a specific habit. A habit of a town life, of country-sports, of solitude, of reading, or of business, where sufficiently varied, are instances of generic habits. Every specific habit hath a mixture of the generic; for the habit of any one sort of food makes the taste agreeable, and we are fond of that taste wherever found. Thus a man deprived of an habitual object, takes up with what most resembles it; deprived of tobacco, any bitter herb will do rather than want; a habit of punch makes wine a good resource: accustomed to the sweet society and comforts of matrimony, the man unhappily deprived of his beloved object, inclines the sooner to a second. In general, when we are deprived of a habitual object, we are fond of its qualities in any other object.
The reasons are assigned above, why the causes of intense pleasure become not readily habitual: but now we discover, that these reasons conclude only against specific habits. In the case of a weak pleasure, a habit is formed by frequency and uniformity of reiteration, which, in the case of an intense pleasure, produceth satiety and disgust. But it is remarkable, that satiety and disgust have no effect, except as to that thing singly which occasions them; a surfeit of honey produceth not a loathing of sugar; and intemperance with one woman produceth no disrelish of the same pleasure with others. Hence it is easy to account for a generic habit in any intense pleasure; the delight we had in the gratification of the appetite, inflames the imagination, and makes us search, with avidity, for the same gratification in whatever other object it can be found. And thus uniform frequency in gratifying the same passion upon different objects, produceth at length a generic habit. In this manner one acquires an habitual delight in high and poignant sauces, rich dress, fine equipages, crowds of company, and in whatever is commonly termed pleasure. There occurs, at the same time, to introduce this habit, a peculiarity observed above, that reiteration of acts enlarges the capacity of the mind to admit a more plentiful gratification than originally, with regard to frequency, as well as quantity.
Hence it appears, that though a specific habit cannot be formed but upon a moderate pleasure, a generic habit may be formed upon any fort of pleasure, moderate or immoderate, that hath variety of objects. The only difference is, that a weak pleasure runs naturally into a specific habit; whereas an intense pleasure is altogether averse to such a habit. In a word, it is only in singular cases that a moderate pleasure produces a generic habit: but an intense pleasure cannot produce any other habit.
The appetites that respect the preservation and propagation of the species, are formed into habit in a peculiar manner; the time as well as measure of their gratification is much under the power of custom; which, introducing a change upon the body, occasions a proportional change in the appetites. Thus, if the body be gradually formed to a certain quantity of food at stated times, the appetite is regulated accordingly; and the appetite is again changed, when a different habit of body is introduced by a different practice. Here it would seem, that the change is not made upon the mind, which is commonly the case in passive habits, but upon the body.
When rich food is brought down by ingredients of a plainer taste, the composition is susceptible of a specific habit. Thus the sweet taste of sugar, rendered less poignant in a mixture, may, in course of time, produce a specific habit for such mixture. As moderate pleasures, by becoming more intense, tend to generic habits; so intense pleasures, by becoming more moderate, tend to specific habits.
The beauty of the human figure, by a special recommendation of nature, appears to us supreme, amid the great variety of beautiful forms bestowed upon animals. The various degrees in which individuals enjoy that property, render it an object sometimes of a moderate, sometimes of an intense, passion. The moderate passion, admitting frequent reiteration without diminution, and occupying the mind without exhausting it, turns gradually stronger till it become a habit. Nay, instances are not wanting, of a face at first disagreeable, afterwards rendered indifferent by familiarity, and at length agreeable by custom. On the other hand, consummate beauty, at the very first glance, fills the mind so as to admit no increase. Enjoyment lessens the pleasure; and if often repeated, ends commonly in satiety and disgust. The impressions made by consummate beauty, in a gradual succession from lively to faint, constitute a series opposite to that of faint impressions waxing gradually more lively, till they produce a specific habit. But the mind when accustomed to beauty contracts a relish for it in general, though often repelled from particular objects Custom by the pain of satiety; and thus a generic habit is formed, of which inconstancy in love is the necessary consequence; for a generic habit, comprehending every beautiful object, is an invincible obstruction to a specific habit, which is confined to one.
But a matter which is of great importance to the youth of both sexes, deserves more than a cursory view. Though the pleasurable emotion of beauty differs widely from the corporal appetite, yet when both are directed to the same object, they produce a very strong complex passion; enjoyment in that case must be exquisite; and therefore more apt to produce satiety than in any other case whatever. This is a never-failing effect, where consummate beauty in the one party, meets with a warm imagination and great sensibility in the other. What we are here explaining, is true without exaggeration; and they must be insensible upon whom it makes no impression: it deserves well to be pondered by the young and the amorous, who, in forming the matrimonial society, are too often blindly impelled by the animal pleasure merely, inflamed by beauty. It may indeed happen, after the pleasure is gone, and go it must with a swift pace, that a new connexion is formed upon more dignified and more lasting principles: but this is a dangerous experiment; for even supposing good sense, good temper, and internal merit of every sort, yet a new connexion upon such qualifications is rarely formed: it commonly, or rather always happens, that such qualifications, the only solid foundation of an indissoluble connexion, are rendered altogether invisible by satiety of enjoyment creating disgust.
One effect of custom, different from any that have been explained, must not be omitted, because it makes a great figure in human nature: though custom augments moderate pleasures, and lessens those that are intense, it has a different effect with respect to pain; for it blunts the edge of every sort of pain and distress, faint or acute. Uninterrupted misery, therefore, is attended with one good effect: if its torments be incessant, custom hardens us to bear them.
The changes made in forming habits are curious. Moderate pleasures are augmented gradually by reiteration, till they become habitual; and then are at their height: but they are not long stationary: for from that point they gradually decay, till they vanish altogether. The pain occasioned by want of gratification runs a different course: it increases uniformly; and at last becomes extreme, when the pleasure of gratification is reduced to nothing.
——— It so falls out, That what we have we prize not to the worth, While we enjoy it; but being lack'd and lost, Why then we rack the value; then we find The virtue that possession would not show us Whilst it was ours.
Much ado about Nothing, Act iv. sc. 2.
The effect of custom with relation to a specific habit is displayed through all its varieties in the use of tobacco. The taste of that plant is at first extremely unpleasant: our disgust lessens gradually till it vanish altogether; at which period the taste is neither agreeable nor disagreeable: continuing the use of the plant, we begin to relish it; and our relish improves by use, till it arrive at perfection: from that period it gradually decays, while the habit is in a state of increment, and consequently the pain of want. The result is, that when the habit has acquired its greatest vigour, the relish is gone; and accordingly we often smoke and take snuff habitually, without so much as being conscious of the operation. We must expect gratification after the pain of want; the pleasure of which gratification is the greatest when the habit is the most vigorous: it is of the same kind with the pleasure one feels upon being delivered from the rack. This pleasure, however, is but occasionally the effect of habit; and, however exquisite, is avoided as much as possible because of the pain that precedes it.
With regard to the pain of want, we can discover no difference between a generic and specific habit; but these habits differ widely with respect to the positive pleasure. We have had occasion to observe, that the pleasure of a specific habit decays gradually till it turn imperceptible: the pleasure of a generic habit, on the contrary, being supported by variety of gratification, suffers little or no decay after it comes to its height. However it may be with other generic habits, the observation certainly holds with respect to the pleasures of virtue and knowledge: the pleasure of doing good has an unbounded scope, and may be so variously gratified that it can never decay: science is equally unbounded; our appetite for knowledge having an ample range of gratification, where discoveries are recommended by novelty, by variety, by utility, or by all of them.
In this intricate inquiry, we have endeavoured, but without success, to discover by what particular means it is that custom hath an influence upon us: and now nothing seems left, but to hold our nature to be so framed as to be susceptible of such influence. And supposing it purposely so framed, it will not be difficult to find out several important final causes. That the power of custom is a happy contrivance for our good, cannot have escaped any one who reflects, that business is our province, and pleasure our relaxation only. Now satiety is necessary to check exquisite pleasures, which otherwise would engraft the mind, and unqualify us for business. On the other hand, as business is sometimes painful, and is never pleasurable beyond moderation, the habitual increase of moderate pleasure, and the conversion of pain into pleasure, are admirably contrived for disappointing the malice of fortune, and for reconciling us to whatever course of life may be our lot:
How use doth breed a habit in a man! This shadowy desert, unfrequented woods, I better brook than flourishing peopled towns. Here I can sit alone, unseen of any, And to the nightingale's complaining notes Tune my distresses, and record my woes.
Two Gentlemen of Verona, Act v. sc. 4.
As the foregoing distinctions between intense and moderate, hold in pleasure only, every degree of pain being softened by time, custom is a catholicon for pain and distress of every sort; and of that regulation the final cause requires no illustration.
Another final cause of custom will be highly relished by every person of humanity, and yet has in a great measure Custom measure been overlooked; which is, that custom hath and Habit a greater influence than any other known cause, to put the rich and the poor upon a level; weak pleasures, the share of the latter, become fortunately stronger by custom; while voluptuous pleasures, the share of the former, are continually losing ground by satiety. Men of fortune, who possess palaces, sumptuous gardens, rich fields, enjoy them less than passengers do. The goods of Fortune are not unequally distributed; the opulent possess what others enjoy.
And indeed, if it be the effect of habit, to produce the pain of want in a high degree while there is little pleasure in enjoyment, a voluptuous life is of all the least to be envied. Those who are habituated to high feeding, easy vehicles, rich furniture, a crowd of valets, much deference and flattery, enjoy but a small share of happiness, while they are exposed to manifold distresses. To such a man, enslaved by ease and luxury, even the petty inconveniences in travelling, of a rough road, bad weather, or homely fare, are serious evils: he loses his tone of mind, turns peevish, and would wreak his resentment even upon the common accidents of life. Better far to use the goods of Fortune with moderation: a man who by temperance and activity hath acquired a hardy constitution, is, on the one hand, guarded against external accidents; and, on the other, is provided with great variety of enjoyment ever at command.
We shall close this branch of the subject with an article more delicate than abstruse, viz. what authority custom ought to have over our taste in the fine arts. One particular is certain, that we cheerfully abandon to the authority of custom things that nature hath left indifferent. It is custom, not nature, that hath established a difference between the right hand and the left, so as to make it awkward and disagreeable to use the left where the right is commonly used. The various colours, though they affect us differently, are all of them agreeable in their purity: but custom has regulated that matter in another manner; a black skin upon a human being, is to us disagreeable; and a white skin probably not less so to a negro. Thus things, originally indifferent, become agreeable or disagreeable by the force of custom. Nor will this be surprising after the discovery made above, that the original agreeableness or disagreeableness of an object is, by the influence of custom, often converted into the opposite quality.
Proceeding to matters of taste, where there is naturally a preference of one thing before another; it is certain, in the first place, that our faint and more delicate feelings are readily susceptible of a bias from custom; and therefore that it is no proof of a defective taste, to find these in some measure influenced by custom; dress and the modes of external behaviour are regulated by custom in every country; the deep red or vermilion with which the ladies in France cover their cheeks, appears to them beautiful in spite of nature; and strangers cannot altogether be justified in condemning that practice, considering the lawful authority of custom, or of the fashion, as it is called: it is told of the people who inhabit the skirts of the Alps facing the north, that the swelling they universally have in the neck is to them agreeable. So far has custom power to change the nature of things, and to make an object originally disagreeable take on an opposite appearance.
But as to every particular that can be denominated proper or improper, right or wrong, custom has little authority, and ought to have none. The principle of duty takes naturally place of every other; and it argues a shameful weakness or degeneracy of mind, to find it in any case so far subdued as to submit to custom.
11. Effects of Custom and Habit in the Animal Economy. These may be reduced to five heads: 1. On the simple solids. 2. On the organs of sense. 3. On the moving power. 4. On the whole nervous power. 5. On the system of blood vessels.
1. Effects on the Simple Solids. Custom determines the degree of flexibility of which they are capable. By frequently repeated flexion, the several particles of which these solids consist are rendered more supple and movable on each other. A piece of catgut, e.g. when on the stretch, and having a weight appended to its middle, will be bended thereby perhaps half an inch; afterwards, by frequent repetitions of the same weight, or by increasing the weight, the flexibility will be rendered double. The degree of flexibility has a great effect in determining the degree of oscillation, provided that elasticity is not affected; if it go beyond this, it produces flaccidity. Again, custom determines the degree of tension; for the same elastic chord that now oscillates in a certain degree of tension, will, by frequent repetition of these oscillations, be so far relaxed, that the extension must be renewed in order to produce the same tension, and consequently the same vibrations, as at first. This appears in many instances in the animal economy, as when different muscles concur to give a fixed point or tension to each other; and thus a weakly child totters as it walks; but by giving it a weight to carry, and by thus increasing the tension of the system, it walks more steadily. In like manner, the fullness of the system gives strength, by diffusing the vessels everywhere, and so giving tension: hence a man, by good nourishment, from being weak, acquires a great increase of strength in a few days: and, on the other hand, evacuations weaken by taking off the tension.
2. Effects on the Organs of Sense. Repetition gives a greater degree of sensibility, in so far only as it renders perception more accurate. Repetition alone gives lasting impression, and thus lays the foundation of memory; for single impressions are but retained for a short time, and are soon forgot. Thus a person, who at present has little knowledge of cloths, will by frequently handling them, acquire a skill of discerning them, which to others seems almost impossible. Many are apt to mistake this for a nicer sensibility, but they are much mistaken; for it is an universal law, that the repetition of impression renders us less acute. This is well illustrated by the operation of medicines; for all medicines which act on the organs of sense must, after some time, be increased in their dose to produce the same effects as at first. This affords a rule in practice with regard to these medicines; it becoming necessary, after a certain time, to change one medicine even for a weaker of the same nature. Thus medicines which even have no great apparent force, are found, by long use, to destroy the sensibility of the system to other impressions. But to this general rule, that, by repetition, the force of impressions is more and more diminished, there are some exceptions. Thus persons, by a strong emetic, have had their stomachs rendered so irritable, that one-twentieth of the first dose was sufficient to produce the same effect. This, however, oftener takes place when the vomit is repeated every day; for if the same vomit be given at pretty considerable intervals, the general rule is observed to hold good. Thus two contrary effects of habit are to be noted; and it is proper to observe, that the greater irritability is more readily produced when the first impression is great, as in the case first given of the strong emetic. This may be further illustrated by the effect of fear, which is commonly observed to be diminished on repetition; which can only be attributed to custom; while, on the other hand, there are instances of persons, who, having once got a great fright, have for ever after continued slaves to fears excited by impressions of the like kind, however slight; which must be imputed entirely to excess of the first impression, as has been already observed. To this head also belongs the association of ideas, which is the foundation of memory and all our intellectual faculties, and is entirely the effect of custom: with regard to the body also, these associations often take place. And sometimes, in producing effects on the body, affections seemingly opposite are formed, which, through custom, become absolutely necessary; e.g. a person long accustomed to sleep in the neighbourhood of a great noise, is so far from being incommodeed on that account, that afterwards such noise becomes necessary to produce sleep. It will be of use to attend to this in medical practice; for we ought to allow for, however opposite it may seem at the time, whatever usually attended the purpose we design to effect. Thus, in the instance of sleep, we must not exclude noise when we want to procure rest, or any cause which may seem opposite to such an effect, provided custom has rendered them necessary.
3. Effects on the Moving Fibres. A certain degree of tension is necessary to motion, which is to be determined by custom; e.g. a fencer, accustomed to one foil, cannot have the same steadiness or activity with one heavier or lighter. It is necessary also that every motion should be performed in the same situation, or posture of the body, as the person has been accustomed to employ in that motion. Thus, in any chirurgical operation, a certain posture is recommended; but if the operator has been accustomed to another, such a one, however awkward, becomes necessary afterwards to his right performance of that operation.
Custom also determines the degree of oscillation of which the moving fibres are capable. A person accustomed to strong muscular exertions is quite incapable of the more delicate. Thus writing is performed by small muscular contractions; but if a person has been accustomed to stronger motions with these muscles, he will write with much less steadiness.
This subject of tension, formerly attributed to the simple fibres, is probably more strictly applicable to the moving: for besides a tension from flexion, there is also a tension from irritation and sympathy; e.g. the tension of the stomach from food, gives tension to the whole body. Wine and spirituous liquors give tension:
e.g. a person that is so affected with tremor as scarcely to hold a glass of any of these liquors to his head, has no sooner swallowed it, than his whole body becomes steady; and after the system has been accustomed to such stimuli, if they are not applied at the usual time, the whole body becomes flaccid, and of consequence unsteady in its motions.
Again, custom gives facility of motion. This seems to proceed from the diffusion which the nervous power gives to the moving fibres themselves. But in whatever manner it is occasioned, the effect is obvious; for any new or unusual motion is performed with great difficulty.
It is supposed that sensation depends on a communication with the sensorium commune, by means of organs sufficiently diffused with nervous influence. We have found, that sensibility is diminished by repetition. And we have now to observe, that in some cases it may be increased by repetition, owing to the nervous power itself flowing more easily into the part on account of custom. Attention to a particular object may also determine a greater influx into any particular part, and thus the sensibility and irritability of that particular part may be increased.
But with regard to facility of motion, the nervous power, no doubt, flows most easily into those parts to which it has been accustomed: yet facility of motion does not entirely depend on this, but in part also on the concurrence of the action of a great many muscles; e.g. Winlow has observed, that in performing any motion, a number of muscles concur to give a fixed point to those intended chiefly to act, as well as to others that are to vary and modify their action. This, however, is assisted by repetition and the freer influx; as by experience we know the proper attitude for giving a fixed point in order to perform any action with facility and steadiness.
Custom gives a spontaneous motion also, which seems to recur at stated periods, even when the exciting causes are removed. Thus, if the stomach has been accustomed to vomit from a particular medicine, it will require a much smaller dose than at first, nay, even the very sight or remembrance of it will be sufficient to produce the effect: and there are not wanting instances of habitual vomiting, from the injudicious administration of emetics. It is on this account that all spasmodic affections so easily become habitual, and are so difficult of cure; as we must not only avoid all the exciting causes, even in the smallest degree, but also their affections.
Custom also gives strength of motion; strength depends on strong oscillations, a free and copious influx of the nervous power, and on dense solids. But in what manner all these circumstances have been brought about by repetition, has been already explained. The effect of custom in producing strength, may be thus illustrated: a man that begins with lifting a calf, by continuing the same practice every day, will be able to lift it when grown to the full size of a bull.
All this is of considerable importance in the practice of physic, though too little regarded; for the recovery of weak people, in a great measure, depends on the use of exercise suited to their strength, or rather within it, frequently repeated and gradually increased. Farther, it is necessary to observe, that custom regu- Custom lates the particular celerity with which each motion is to be performed: for a person accustomed, for a considerable time to one degree of celerity, becomes incapable of a greater; e.g. a man accustomed to slow walking will be out of breath before he can run 20 paces. The train or order in which our motions are to be performed is also established by custom; for if a man hath repeated motions, for a certain time, in any particular order, he cannot afterwards perform them in any other. Custom also very frequently associates motions and sensations; thus, if a person has been in use of associating certain ideas with the ordinary stimulus which in health excites urine, without these ideas the usual inclination will scarce excite that excretion; and, when these occur, will require it even in the absence of the primary exciting cause: e.g. it is very ordinary for a person to make urine when going to bed; and if he has been for any length of time accustomed to do so, he will ever afterwards make urine at that time, though otherwise he would often have no such inclination: by this means some secretions become in a manner subject to the will. The same may be said of going to stool; and this affords us a good rule in the case of colicines; for by endeavouring to fix a stated time for this evacuation, it will afterwards, at such a time, more readily return. It is farther remarkable, that motions are inseparably associated with other motions: this, perhaps, very often proceeds from the necessary degree of tension; but it also often depends merely on custom, an influence of which we have in the uniform motions of our eyes.
4. Effects on the whole Nervous Power. We have found, that, by custom, the nervous influence may be determined more easily into one part than another; and therefore, as all the parts of the system are strongly connected, the sensibility, irritability, and strength of any particular part may be thus increased. Custom also has the power of altering the natural temperament, and of inducing a new one. It is also in the power of custom to render motions periodical, and periodically spontaneous. An instance of this we have in sleep, which is commonly laid to be owing to the nervous power being exhausted, the necessary consequence of which is sleep, e.g. a rest of the voluntary motions to favour the recruit of that power; but if this were the case, the return of sleep should be at different times, according as the causes which diminish the nervous influence operate more or less powerfully; whereas the case is quite otherwise, these returns of sleep being quite regular. This is no less remarkable in the appetites, that return at particular periods, independent of every cause but custom. Hunger, e.g. is an extremely uneasy sensation; but goes off of itself, if the person did not take food at the usual time. The excretions are farther proofs of this, e.g. going to stool, which, if it depended on any particular irritation, should be at longer or shorter intervals, according to the nature of the aliment. There are many other instances of this disposition of the nervous influence to periodical motions, as the story of the idiot of Stafford, recorded by Dr Plot (Spectator, No 447.), who, being accustomed to tell the hours of the church clock as it struck, told them as exactly when it did not strike by its being out of order. Montaigne tells us of some oxen that were employed in a machine for drawing water, who, after making 300 turns, which was the usual number, could be stimulated by no whip or goad to proceed farther. Infants also cry for and expect the breast at those times in which the nurse has been accustomed to give it.
Hence it would appear, that the human economy is subject to periodical revolutions, and that these happen not oftener may be imputed to variety; and this seems to be the reason why they happen oftener in the body than mind, because that is subject to greater variety. We see frequent instances of this in diseases, and in their crises; intermitting fevers, epilepsies, asthma, &c. are examples of periodical affections; and that critical days are not so strongly marked in this country as in Greece, and some others, may be imputed to the variety and instability of our climate; but perhaps still more to the less sensibility and irritability of our system; for the exhibition of medicine has little effect in disturbing the crises, though it be commonly assigned as a cause.
We are likewise subject to many habits independent of ourselves, as from the revolutions of the celestial bodies, particularly the sun, which determines the body, perhaps, to other daily revolutions besides sleeping and waking. There are also certain habits depending on the seasons. Our connections, likewise, with respect to mankind, are means of inducing habits. Thus regularity from associating in business induces regular habits both of mind and body.
There are many diseases which, though they arose at first from particular causes, at last continue merely through custom or habit. These are chiefly of the nervous system. We should therefore study to counteract such habits; and accordingly Hippocrates, among other things for the cure of epilepsy, orders an entire change of the manner of life. We likewise imitate this in the chincough; which often resists all remedies, till the air, diet, and ordinary train of life, are changed.
5. Effects on the Blood-vessels. From what has been said on the nervous power, the distribution of the fluids must necessarily be variously affected by custom, and with that the distribution of the different excretions; for though we make an estimate of the proportion of the excretions to one another, according to the climate and seasons, they must certainly be very much varied by custom.
On this head we may observe, that blood-letting has a manifest tendency to increase the quantity of the blood; and if this evacuation be repeated at stated times, such symptoms of repletion, and such motions, are excited at the returning periods, as render the operation necessary. The same has been observed in some spontaneous hemorrhages. These, indeed, at first, may have some exciting causes, but afterwards they seem to depend chiefly on custom. The best proof of this is with regard to the menstrual evacuation. There is certainly something originally in females, that determines that evacuation to the monthly periods. Constant repetition of this comes to fix it, independent of strong causes, either favouring or preventing repletion; e.g. blood-letting will not impede it, nor filling the body induce it: and, indeed, so much is this evacuation connected with periodical motions, that it is little in our power to produce any effect by medicines but at those particular times. Thus if we would relax the custom and habit, uterine system, and bring back this evacuation when suppressed, our attempts would be vain and fruitless, unless given at that time when the menses should have naturally returned.