First take _effects upon the circulation_. Those upon the heart we have just seen. Haller long ago recorded that the blood from an open vein flowed out faster at the beat of a drum.[346] In Chapter III. (Vol. I. p. 98) we learned how instantaneously, according to Mosso, the circulation in the brain is altered by changes of sensation and of the course of thought. The effect of objects of fear, shame, and anger upon the blood-supply of the skin, especially the skin of the face, are too well known to need remark. Sensations of the higher senses produce, according to Couty and Charpentier, the most varied effects upon the pulse-rate and blood-pressure in dogs. Fig. 81, a pulse-tracing from these authors, shows the tumultuous effect on a dog's heart of hearing the screams of another dog. The changes of blood-pressure still occurred when the pneumogastric nerves were cut, showing the vaso-motor effect to be direct and not dependent on the heart. When Mosso invented that simple instrument, the _plethysmograph_, for recording the fluctuations in volume of the members of the body, what most astonished him, he says, "in the first experiments which he made in Italy, was the extreme unrest of the blood-vessels of the hand, which at every smallest emotion, whether during waking or during sleep, changed their volume in surprising fashion."[347] Figure 82 (from Féré[348]) shows the way in which the pulse of one subject was modified by the exhibition of a red light lasting from the moment marked _a_ to that marked _b_.
_The effects upon respiration_ of sudden sensory stimuli are also too well known to need elaborate comment. We 'catch our breath' at every sudden sound. We 'hold our breath' whenever our attention and expectation are strongly engaged, and we sigh when the tension of the situation is relieved. When a fearful object is before us we pant and cannot deeply inspire; when the object makes us angry it is, on the contrary, the act of expiration which is hard. I subjoin a couple of figures from Féré which explain themselves. They show the effects of light upon the breathing of two of his hysteric patients.[349] _On the sweat-glands,_ similar consequences of sensorial stimuli are observed. Tarchanoff, testing the condition of the sweat-glands by the power of the skin to start a galvanic current through electrodes applied to its surface, found that "nearly every kind of nervous activity, from the simplest sensations and impressions, to voluntary motions and the highest forms of mental exertion, is accompanied by an increased activity in the glands of the skin."[350] _On the pupil_ observations are recorded by Sanders which show that a transitory dilatation follows every sensorial stimulus applied _during sleep_, even if the stimulus be not strong enough to wake the subject up. At the moment of awaking there is a dilatation, even if strong light falls on the eye.[351] The pupil of children can easily be observed to dilate enormously under the influence of _fear_. It is said to dilate in pain and fatigue; and to contract, on the contrary, in rage.
As regards _effects on the abdominal viscera_, they unquestionably exist, but very few accurate observations have been made.[352] The bladder, bowels, and uterus respond to sensations, even indifferent ones. Mosso and Pellicani, in their plethysmographic investigations on the bladder of dogs, found all sorts of sensorial stimuli to produce reflex contractions of this organ, independent of those of the abdominal walls. They call the bladder 'as good an æsthesiometer as the iris,' and refer to the not uncommon reflex effects of psychic stimuli in the human female upon this organ.[353] M. Féré has registered the contractions of the sphincter ani which even indifferent sensations will produce. In some pregnant women the fœtus is felt to move after almost every sensorial excitement received by the mother. The only natural explanation is that it is stimulated at such moments by reflex contractions of the womb.[354] That the glands are affected in emotion is patent enough in the case of the tears of grief, the dry mouth, moist skin, or diarrhœa of fear, the biliary disturbances which sometimes follow upon rage, etc. The watering of the mouth at the sight of succulent food is well known. It is difficult to follow the smaller degrees of all these reflex changes, but it can hardly be doubted that they exist in some degree, even where they cease to be traceable, and that all our sensations have some visceral effects. The sneezing produced by sunshine, the roughening of the skin (goose-flesh) which certain strokings, contacts, and sounds, musical or non-musical, provoke, are facts of the same order as the shuddering and standing up of the hair in fear, only of less degree.
_Effects on Voluntary Muscles._ Every sensorial stimulus not only sends a special discharge into certain particular muscles dependent on the special nature of the stimulus in question--some of these special discharges we have studied in Chapter XI, others we shall examine under the heads of Instinct and Emotion--but it innervates the muscles generally. M. Féré has given very curious experimental proofs of this. The strength of contraction of the subject's hand was measured by a self-registering dynamometer. Ordinarily the maximum strength, under simple experimental conditions, remains the same from day to day. But if simultaneously with the contraction the subject received a sensorial impression, the contraction was sometimes weakened, but more often increased. This reinforcing effect has received the name of _dynamogeny_. The dynamogenic value of simple _musical notes_ seems to be proportional to their loudness and height. Where the notes are compounded into sad strains, the muscular strength diminishes. If the strains are gay, it is increased.--The dynamogenic value of _colored lights_ varies with the color. In a subject[355] whose normal strength was expressed by 23, it became 24 when a blue light was thrown on the eyes, 28 for green, 30 for yellow, 35 for orange, and 42 for red. Red is thus the most exciting color. Among _tastes_, sweet has the lowest value, next comes salt, then bitter, and finally sour, though, as M.
Féré remarks, such a sour as acetic acid excites the nerves of pain and smell as well as of taste. The stimulating effects of tobacco-smoke, alcohol, beef-extract (which is innutritious), etc., etc., may be partly due to a dynamogenic action of this sort.--Of _odors_, that of musk seems to have a peculiar dynamogenic power. Fig. 85 is a copy of one of M. Féré's dynamographic tracings, which explains itself. The smaller contractions are those without stimulus; the stronger ones are due to the influence of red rays of light.
Everyone is familiar with the _patellar reflex_, or jerk upwards of the foot, which is produced by smartly tapping the tendon below the knee-pan when the leg hangs over the other knee. Drs. Weir Mitchell and Lombard have found that when other sensations come in simultaneously with the tap, the jerk is increased.[356] Heat, cold, pricking, itching, or faradic stimulation of the skin, sometimes strong optical impressions, music, all have this dynamogenic effect, which also results whenever voluntary movements are set up in other parts of the body, simultaneously with the tap.[357] These 'dynamogenic' effects, in which one stimulation simply reinforces another already under way, must not be confounded with reflex acts properly so called, in which new activities are originated by the stimulus. All instinctive performances and manifestations of emotion are reflex acts. But underneath those of which we are conscious there seem to go on continually others smaller in amount, which probably in most persons might be called fluctuations of muscular _tone_, but which in certain neurotic subjects can be demonstrated ocularly. M. Féré figures some of them in the article to which I have already referred.[358] * * * * * * * * * * Looking back over all these facts, it is hard to doubt the truth of the law of diffusion, even where verification is beyond reach. _A process set up anywhere in the centres reverberates everywhere, and in some way or other affects the organism throughout, making its activities either greater or less._ We are brought again to the assimilation which was expressed on a previous page of the nerve-central mass to a good conductor charged with electricity, of which the tension cannot be changed anywhere without changing it everywhere.
* * * * * * * * * * Herr Schneider has tried to show, by an ingenious and suggestive zoological review,[359] that all the _special_ movements which highly evolved animals make are differentiated from the two originally simple movements, of contraction and expansion, in which the entire body of simple organisms takes part. The tendency to contract is the source of all the self-protective impulses and reactions which are later developed, including that of flight. The tendency to expand splits up, on the contrary, into the impulses and instincts of an aggressive kind, feeding, fighting, sexual intercourse, etc. Schneider's articles are well worth reading, if only for the careful observations on animals which they embody. I cite them here as a sort of evolutionary reason to add to the mechanical _a priori_ reason why there _ought_ to be the diffusive wave which our _a posteriori_ instances have shown to exist.
I will now proceed to a detailed study of the more important classes of movement consequent upon cerebro-mental change. They may be enumerated as-- 1) Instinctive or Impulsive Performances; 2) Expressions of Emotion; and 3) Voluntary Deeds; and each shall have a chapter to itself.
[346] Cf. Féré. Sensation et Mouvement (1887), p. 56.
[347] La Paura (1884), p. 117. Compare Féré: Sensation et Mouvement, chap. xvii.
[348] Revue Philosophique, xxiv. 570.
[349] Revue Phil., xxiv. pp. 566-7.--For further information about the relations between the brain and respiration, see Danilewsky's Essay in the Biologisches Centralblatt, ii. 690.
[350] Quoted from the report of Tarchanoff's paper (in Pflüger's Archiv, xlvi. 46) in the American Journal of Psych., ii. 652.
[351] Archiv f. Psychiatrie, vii. 652; ix. 129.
[352] Sensation et Mouvement, 57-8.
[353] R. Accad. dei Lincei (1881-2). I follow the report in Hofmann Schwalbe's Jahresbericht, x. ii. 93.
[354] Cf. Féré, Sensation et Mouvement, chap. xiv.
[355] The figures given are from an hysterical subject, and the differences are greater than normal. M. Féré considers that the unstable nervous system of the hysteric ('ces grenouilles de la psychologie') shows the law on a quantitatively exaggerated scale, without altering the qualitative relations. The effects remind us a little of the influence of sensations upon minimal sensations of other orders discovered by Urbantschitsch, and reported on page 29 of this volume.
[356] Mitchell in (Philadelphia) Medical News (Feb. 13 and 20, 1886); Lombard in American Journal of Psychology (Oct. 1887).
[357] Prof. H. P. Bowditch has made the interesting discovery that if the reinforcing movement be as much as 0.4 of a second late, the reinforcement fails to occur, and is transformed into a positive inhibition of the knee-jerk for retardations of between 0.4' and 1.7'. The knee-jerk fails to be modified at all by voluntary movements made later than 1.7' after the patellar ligament is tapped (see Boston Med. and Surg. Journ., May 31, 1888).
[358] Revue Phil., xxiv. 572 ff.
[359] In the Vierteljahrschrift für wiss. Philos., iii. 294.
CHAPTER XXIV.[360] INSTINCT.
_Instinct is usually defined as the faculty of acting in such a way as to produce certain ends, without foresight of the ends, and without previous education in the performance._ That instincts, as thus defined, exist on an enormous scale in the animal kingdom needs no proof. They are the functional correlatives of structure. With the presence of a certain organ goes, one may say, almost always a native aptitude for its use.
"Has the bird a gland for the secretion of oil? She knows instinctively how to press the oil from the gland, and apply it to the feather. Has the rattlesnake the grooved tooth and gland of poison? He knows without instruction how to make both structure and function most effective against his enemies. Has the silk-worm the function of secreting the fluid silk? At the proper time she winds the cocoon such as she has never seen, as thousands before have done; and thus without instruction, pattern, or experience, forms a safe abode for herself in the period of transformation. Has the hawk talons? She knows by instinct how to wield them effectively against the helpless quarry."[361] A very common way of talking about these admirably definite tendencies to act is by naming abstractly the purpose they subserve, such as self-preservation, or defence, or care for eggs and young--and saying the animal has an instinctive fear of death or love of life, or that she has an instinct of self-preservation, or an instinct of maternity and the like. But this represents the animal as obeying abstractions which not once in a million cases is it possible it can have framed. The strict physiological way of interpreting the facts leads to far clearer results. _The actions we call instinctive all conform to the general reflex type;_ they are called forth by determinate sensory stimuli in contact with the animal's body, or at a distance in his environment. The cat runs after the mouse, runs or shows fight before the dog, avoids falling from walls and trees, shuns fire and water, etc., not because he has any notion either of life or of death, or of self, or of preservation. He has probably attained to no one of these conceptions in such a way as to react definitely upon it. He acts in each case separately, and simply because he cannot help it; being so framed that when that particular running thing called a mouse appears in his field of vision he _must_ pursue; that when that particular barking and obstreperous thing called a dog appears there he _must_ retire, if at a distance, and scratch if close by; that he _must_ withdraw his feet from water and his face from flame, etc. His nervous system is to a great extent a preorganized bundle of such reactions--they are as fatal as sneezing, and as exactly correlated to their special excitants as it is to its own. Although the naturalist may, for his own convenience, class these reactions under general heads, he must not forget that in the animal it is a particular sensation or perception, or image which calls them forth.
At first this view astounds us by the enormous number of special adjustments it supposes animals to possess ready-made in anticipation of the outer things among which they are to dwell. _Can_ mutual dependence be so intricate and go so far? Is each thing born fitted to particular other things, and to them exclusively, as locks are fitted to their keys? Undoubtedly this must be believed to be so. Each nook and cranny of creation, down to our very skin and entrails, has its living inhabitants, with organs suited to the place, to devour and digest the food it harbors and to meet the dangers it conceals; and the minuteness of adaptation thus shown in the way of _structure_ knows no bounds. Even so are there no bounds to the minuteness of adaptation in the way of _conduct_ which the several inhabitants display.
The older writings on instinct are ineffectual wastes of words, because their authors never came down to this definite and simple point of view, but smothered everything in vague wonder at the clairvoyant and prophetic power of the animals--so superior to anything in man--and at the beneficence of God in endowing them with such a gift. But God's beneficence endows them, first of all, with a nervous system; and, turning our attention to this, makes instinct immediately appear neither more nor less wonderful than all the other facts of life.
* * * * * * * * * * _Every instinct is an impulse._ Whether we shall call such impulses as blushing, sneezing, coughing, smiling, or dodging, or keeping time to music, instincts or not, is a mere matter of terminology. The process is the same throughout. In his delightfully fresh and interesting work, Der Thierische Wille, Herr G. H. Schneider subdivides impulses (_Triebe_) into sensation-impulses, perception-impulses, and idea-impulses. To crouch from cold is a sensation-impulse; to turn and follow, if we see people running one way, is a perception-impulse; to cast about for cover, if it begins to blow and rain, is an imagination-impulse. A single complex instinctive action may involve successively the awakening of impulses of all three classes. Thus a hungry lion starts to _seek_ prey by the awakening in him of imagination coupled with desire; he begins to _stalk_ it when, on eye, ear, or nostril, he gets an impression of its presence at a certain distance; he _springs_ upon it, either when the booty takes alarm and flees, or when the distance is sufficiently reduced; he proceeds to _tear_ and _devour_ it the moment he gets a sensation of its contact with his claws and fangs. Seeking, stalking, springing, and devouring are just so many different kinds of muscular contraction, and neither kind is called forth by the stimulus appropriate to the other.
Schneider says of the hamster, which stores corn in its hole: "If we analyze the propensity of storing, we find that it consists of three impulses: First, an impulse to _pick up_ the nutritious object, due to perception; second, an impulse to _carry it off_ into the dwelling-place, due to the idea of this latter; and third, an impulse to _lay it down_ there, due to the sight of the place. It lies in the nature of the hamster that it should never see a full ear of corn without feeling a desire to strip it; it lies in its nature to feel, as soon as its cheek-pouches are filled, an irresistible desire to hurry to its home; and finally, it lies in its nature that the sight of the storehouse should awaken the impulse to empty the cheeks" (p. 208).
In certain animals of a low order the feeling of having executed one impulsive step is such an indispensable part of the stimulus of the next one, that the animal cannot make any variation in the order of its performance.
* * * * * _Now, why do the various animals do what seem to us such strange things,_ in the presence of such outlandish stimuli? Why does the hen, for example, submit herself to the tedium of incubating such a fearfully uninteresting set of objects as a nestful of eggs, unless she have some sort of a prophetic inkling of the result? The only answer is _ad hominem_. We can only interpret the instincts of brutes by what we know of instincts in ourselves. Why do men always lie down, when they can, on soft beds rather than on hard floors? Why do they sit round the stove on a cold day? Why, in a room, do they place themselves, ninety-nine times out of a hundred, with their faces towards its middle rather than to the wall? Why do they prefer saddle of mutton and champagne to hard-tack and ditch-water? Why does the maiden interest the youth so that everything about her seems more important and significant than anything else in the world? Nothing more can be said than that these are human ways, and that every creature _likes_ its own ways, and takes to the following them as a matter of course. Science may come and consider these ways, and find that most of them are useful. But it is not for the sake of their utility that they are followed, but because at the moment of following them we feel that that is the only appropriate and natural thing to do. Not one man in a billion, when taking his dinner, ever thinks of utility. He eats because the food tastes good and makes him want more. If you ask him _why_ he should want to eat more of what tastes like that, instead of revering you as a philosopher he will probably laugh at you for a fool. The connection between the savory sensation and the act it awakens is for him absolute and _selbstverständlich_, an '_a priori_ synthesis' of the most perfect sort, needing no proof but its own evidence. It takes, in short, what Berkeley calls a mind debauched by learning to carry the process of making the natural seem strange, so far as to ask for the _why_ of any instinctive human act. To the metaphysician alone can such questions occur as: Why do we smile, when pleased, and not scowl? Why are we unable to talk to a crowd as we talk to a single friend? Why does a particular maiden turn our wits so upside-down? The common man can only say, "_Of course_ we smile, _of course_ our heart palpitates at the sight of the crowd, _of course_ we love the maiden, that beautiful soul clad in that perfect form, so palpably and flagrantly made from all eternity to be loved!"
And so, probably, does each animal feel about the particular things it tends to do in presence of particular objects. They, too, are _a priori_ syntheses. To the lion it is the lioness which is made to be loved; to the bear, the she-bear. To the broody hen the notion would probably seem monstrous that there should be a creature in the world to whom a nestful of eggs was not the utterly fascinating and precious and never-to-be-too-much-sat-upon object which it is to her.[362] Thus we may be sure that, however mysterious some animals' instincts may appear to us, our instincts will appear no less mysterious to them. And we may conclude that, to the animal which obeys it, every impulse and every step of every instinct shines with its own sufficient light, and seems at the moment the only eternally right and proper thing to do. It is done for its own sake exclusively. What voluptuous thrill may not shake a fly, when she at last discovers the one particular leaf, or carrion, or bit of dung, that out of all the world can stimulate her ovipositor to its discharge? Does not the discharge then seem to her the only fitting thing? And need she care or know anything about the future maggot and its food?
* * * * * Since the _egg-laying instincts_ are simple examples to consider, a few quotations about them from Schneider may be serviceable: "The phenomenon so often talked about, so variously interpreted, so surrounded with mystification, that an insect should always lay her eggs in a spot appropriate to the nourishment of her young, is no more marvellous than the phenomenon that every animal pairs with a mate capable of bearing posterity, or feeds on materials capable of affording him nourishment...Not only the choice of a place for laying the eggs, but all the various acts for depositing and protecting them, are occasioned by the perception of the proper object, and the relation of this perception to the various stages of maternal impulse. When the burying beetle perceives a carrion, she is not only impelled to approach it and lodge her eggs in it, but also to go through the movements requisite for burying it; just us a bird who sees his hen-bird is impelled to caress her, to strut around her, dance before her, or in some other way to woo her; just as a tiger, when he sees an antelope, is impelled to stalk it, to pounce upon it, and to strangle it. When the tailor-bee cuts out pieces of rose-leaf, bends them, carries them into a caterpillar- or mouse-hole in trees or in the earth, covers their seams again with other pieces, and so makes a thimble-shaped case--when she fills this with honey and lays an egg in it, all these various appropriate expressions of her will are to be explained by supposing that at the time when the eggs are ripe within her, the appearance of a suitable caterpillar- or mouse-hole and the perception of rose-leaves are so correlated in the insect with the several impulses in question, that the performances follow as a matter of course when the perceptions take place...
"The perception of the empty nest, or of a single egg, seems in birds to stand in such a close relation to the physiological functions of oviparation, that it serves as a direct stimulus to these functions, while the perception of a sufficient number of eggs has just the opposite effect. It is well known that hens and ducks lay more eggs if we keep removing them than if we leave them in the nest. The impulse to sit arises, as a rule, when a bird sees a certain number of eggs in her nest. If this number is not yet to be seen there, the ducks continue to lay, although they perhaps have laid twice as many eggs as they are accustomed to sit upon...That sitting, also, is independent of any idea of purpose and is a pure perception-impulse is evident, among other things, from the fact that many birds, e.g. wild ducks, steal eggs from each other...The bodily disposition to sit is, it is true, one condition [since broody hens will sit where there are no eggs], but the perception of the eggs is the other condition of the activity of the incubating impulse. The propensity of the cuckoo and of the cow-bird to lay their eggs in the nests of other species must also be interpreted as a pure perception-impulse. These birds have no bodily disposition to become broody, and there is therefore in them no connection between the perception of an egg and the impulse to sit upon it. Eggs ripen, however, in their oviducts, and the body tends to get rid of them. And since the two birds just named do not drop their eggs anywhere on the ground, but in nests, which are the only places where they may preserve the species, it might easily appear that such preservation of the species was what they had in view, and that they acted with full consciousness of the purpose. But this is not so...The cuckoo is simply excited by the perception of quite determinate sorts of nest, which already contain eggs, to drop her own into them, and throw the others out, because this perception is a direct stimulus to these acts. It is impossible that she should have any notion of the other bird coming and sitting on her egg."[363] INSTINCTS NOT ALWAYS BLIND OR INVARIABLE.
Remember that nothing is said yet of the origin of instincts, but only of the constitution of those that exist fully formed. How stands it with the instincts of mankind?
Nothing is commoner than the remark that Man differs from lower creatures by the almost total absence of instincts, and the assumption of their work in him by 'reason.' A fruitless discussion might be waged on this point by two theorizers who were careful not to define their terms. 'Reason' might be used, as it often has been, since Kant, not as the mere power of 'inferring,' but also as a name for the _tendency to obey impulses_ of a certain lofty sort, such as duty, or universal ends. And 'instinct' might have its significance so broadened as to cover all impulses whatever, even the impulse to act from the idea of a distant fact, as well as the impulse to act from a present sensation. Were the word instinct used in this broad way, it would of course be impossible to restrict it, as we began by doing, to actions done with no prevision of an end. We must of course avoid a quarrel about words, and the facts of the case are really tolerably plain. Man has a far greater variety of _impulses_ than any lower animal; and any one of these impulses, taken in itself, is as 'blind' as the lowest instinct can be; but, owing to man's memory, power of reflection, and power of inference, they come each one to be felt by him, after he has once yielded to them and experienced their results, in connection with a _foresight_ of those results. In this condition an impulse acted out may be said to be acted out, in part at least, _for the sake_ of its results. It is obvious that _every instinctive act, in an animal with memory, must cease to be 'blind' after being once repeated,_ and must be accompanied with foresight of its 'end' just so far as that end may have fallen under the animal's cognizance. An insect that lays her eggs in a place where she never sees them hatched must always do so 'blindly;' but a hen who has already hatched a brood can hardly be assumed to sit with perfect 'blindness' on her second nest. Some expectation of consequences must in every case like this be aroused; and this expectation, according as it is that of something desired or of something disliked, must necessarily either re-enforce or inhibit the mere impulse. The hen's idea of the chickens would probably encourage her to sit; a rat's memory, on the other hand, of a former escape from a trap would neutralize his impulse to take bait from anything that reminded him of that trap. If a boy sees a fat hopping-toad, he probably has incontinently an impulse (especially if with other boys) to smash the creature with a stone, which impulse we may suppose him blindly to obey. But something in the expression of the dying toad's clasped hands suggests the meanness of the act, or reminds him of sayings he has heard about the sufferings of animals being like his own; so that, when next he is tempted by a toad, an idea arises which, far from spurring him again to the torment, prompts kindly actions, and may even make him the toad's champion against less reflecting boys.