David Hartley

“ The complex artificial motions of the lower limbs, used in the several kinds of dancing, bear nearly the same relation to the common motions used in walking forwards, backwards, upwards, downwards, and sideways, as these common motions do to the simple rudiments above mentioned, such as the flexion and extension of the ancle or knee. Since therefore the voluntary and secondarily automatic power of dancing are plainly the result of association, why may we not suppose the same of the common motions in walking, both in their voluntary and secondarily automatic state? ”

“ Imitation is a great source of the voluntary power, and makes all the several modes of walking, handling, and speaking, conformable to those of the age and nation in which a person lives in general, and to those of the persons with whom he converses in particular. ”

“ It is remarkable that apes, whose bodies resemble the human body more than those of any other brute creature, and whose intellects also approach nearer to ours, which last circumstance may, I suppose, have some connexion with the first, should likewise resemble us so much in the faculty of imitation. ”

“ When he is arrived at such a perfection in walking, as to walk readily upon being desired by another person, the action is esteemed still more voluntary. One reason of which is, that the child, in some cases, does not walk when desired, whilst yet the circumstances are apparently the same as when he does. For here the unapparent cause of walking, or not walking, is will. However, it follows from this theory, that all this is still owing to association, or to something equally suitable to the foregoing theory ”

“ Convulsions from compressions and inflammations of the brain, and most of those which are termed epileptic, seem to be of the first kind. In epilepsies the irregular vibrations, excited in the medullary substance of the brain, are perhaps so violent, as first to make the small particles attract each other, and thus, by checking themselves, to extinguish all sense and motion. However, they may return after a short time, and descend into the whole muscular system. ”

“ It is agreeable to this, that if very young children sleep upon a bed, they often fall into a great uneasiness from the stoppage of respiration, and recover from it by crying; and that rocking, or any other gentle motion, will prevent this. The last circumstance is particularly favourable to the notion of vibrations.
The night-mare in adults appears to be a disorder of the same kind. A full supper, and lying upon the back, dispose to it, by hindering the free motion of the diaphragm. Motion, and especially when attended with quick respiration, laughter, &c. ”

“ When he is tolerably perfect in these rudiments of walking, the view of a favourite plaything will excite various motions in the limbs; and thus if he be set upon his legs, and his body carried forward by the nurse, an imperfect attempt to walk follows of course. ”

“ A nervous disorder of the muscles of speech may have a like effect. When the trick of stammering has once begun to take place in a few words, it will extend itself to more and more from very slight resemblances, and particularly to all the first words of sentences, because there the organs pass in an instant from inactivity to action; whereas the subsequent parts of words and sentences may follow the foregoing from association ”

“ As we express our inward sentiments by words, so we do also by gestures, and particularly by the muscles of the face. Here, again, association and imitation display themselves. This dumb show prevails more in the hotter climates, where the passions are more impetuous, than in these northern ones. It is also probable, that the narrowness and imperfection of the ancient languages made it more necessary and prevalent in ancient times. Deaf persons have an extraordinary aptness both in learning and decyphering this, as might well be expected. ”

“ Walking is the most simple of the three kinds of voluntary motion here mentioned, being common to the brute creation with man, whereas handling and speaking are, in a manner, peculiar to him. His superiority in this respect, when compared with the superiority of his mental faculties, agrees well with the hypothesis here advanced concerning handling and speaking, viz. their dependence on ideas, and the power of association. ”

“ Thirdly, If we suppose the diaphragm to have finished its contraction, and consequently the thorax to be raised, and the abdomen to be distended, expiration must succeed, for three reasons; viz. because the contraction of the diaphragm has checked the vibrations in its fibres, and therefore has disposed them to relaxation; because the elasticity of the cartilages of the ribs tends to restore the thorax to a more depressed state; and because the fibres of the abdominal muscles are excited to vibrations and contraction by their distention. ”

“ I have already shewn in what manner children learn the voluntary and secondarily automatic power of grasping. How they learn the various complex motions, by which they feed and dress themselves, &c. also how children and adults learn to write, to practise manual arts, &c. ”

“ I will add here, that seeing a person in convulsions is apt to occasion them in such as are of nervous and irritable frames; and that there is reason to believe, that some persons, who have been enthusiasts or impostors, have been able to throw themselves into convulsions by a semi-voluntary power, and particularly, as it seems, by introducing strong ideas, and internal feelings. ”

“ The new-born child is unable to walk on account of the want of strength to support his body, as well as of complex and decomplex motory vibratiuncles, generated by association, and depending upon sensations and ideas by association also. As he gets strength, he advances likewise in the number and variety of compound motions of the limbs, their species being determined by the nature of the articulations, the position of the muscles, the automatic motions excited by friction, accidental flexures and extensions made by the nurse, &c. ”

“ It deserves notice here, that in the limbs, where the motions are most perfectly voluntary, all the muscles have antagonists, and often such as are of nearly equal strength with themselves; also, that the muscles of the limbs are not much influenced at first by common impressions made on the skin, and scarce at all when the child is so far advanced as to get a voluntary power over them. ”

“ Eighthly, The same actions have also a great share in begetting voluntary respiration. For more muscles are put into action in voluntary respiration, than in that which is ordinary.
Ninthly, It is agreeable to the foregoing theory, and to parallel observations on the heart, that respiration should be stronger in fevers, in sleep, and in general wherever the heat of the blood is increased, than in ordinary cases. For respiration depends chiefly on the second and third sources of motory vibrations. ”

“ Stammering seems generally to arise from fear, eagerness, or some violent passion, which prevents the child’s articulating rightly, by the confusion which it makes in the vibrations that descend into the muscular system ”

“ The auricles and arteries must therefore begin to contract at this instant, from descending vibrations and distention, and the ventricles to be relaxed and filled, the vibrations in their fibres being checked by their past contraction. Let these actions be completed, and the heart will be in the circumstances first supposed; i.e. the ventricles will be ready for a fresh contraction, and so on alternately, as long as life continues.
Thirdly, The vibrations which keep up the heart’s motion, are nearly allied to those arising from heat ”

“ It is feeble, because the whole body is so; and quick, partly from the new habit superinduced by the heat in the beginning of the fever; partly, because in fevers the heart is always kept nearly full, i.e. nearly at such a degree of distention as incites it to contraction, the principal causes of which are the weakness and inactivity of the body: hence in general the pulse is quick and feeble in persons of relaxed habits ”

“ The stretchings and yawnings which happen in ague-fits, in going to sleep and waking, the startings to which some persons are subject in going to sleep, and the convulsive tremors and rigidity in ague-fits, seem to be of a second kind, or to arise from a sudden check of vibrations at the skin. For in agues the surface is chilled, as it is also by the least motions in going to sleep, or waking. Agreeably to this, it may be observed, that, upon stepping into a cold bed, one is disposed to general convulsions, like those of stretching. ”

“ Seventhly, Since lying down prevents or alleviates the fainting which sometimes happens during bleeding, one may suppose that this fainting, and the consequent abatement or cessation of the motion of the heart arise, because a quantity of blood, sufficient to keep up the vibrations in the brain, could not ascend thither in an erect posture. ”

“ The voluntary power of the first kind is obtained by associations with the languor that arises from fatigue, heat, sleepiness, &c. that of the last from the general tension of the muscles, which happens in pain, and violent emotions of mind. Children improve in both these kinds of voluntary power by repeated trials, as occasion requires, by imitation, desire, &c. ”

“ Thus we may observe, that children cannot let their heads or eyelids fall from their mere weight, nor stop themselves in running or striking, till a considerable time after they can raise the head, or bend it, open the eyes, or shut them, run or strike, by a voluntary power. ”

“ Seventhly, The actions of sighing, crying, coughing, sneezing, &c. by recurring frequently, and making all the muscles, which can in any degree contribute to respiration, unite therein, enlarge the range of respiration by degrees, and make this action be performed with greater strength perpetually in the young child. The increase of strength in the whole muscular system must however be considered likewise. ”

“ Fifthly, The pulse is quick in young and small animals; slow in old and large ones. For this, various reasons may be assigned; as first, that if the velocity wherewith the sides of the heart move towards each other be the same, the contraction must be sooner accomplished in small hearts than in large ones. Secondly, that the fibres in young animals are irritable, and soon excited to contraction, by distention, &c. ”

“ And it is excited in young children not only by the sensation of tickling, which lies, as it were, between pleasure and pain, but by the apprehension of this, or any other apprehension sufficiently moderate, by every surprise, and every mental emotion that lies between pleasure and pain, and by all the associates of these, as particularly by seeing others laugh. ”

“ Their aptness in handling is plainly the result of the shape and make of their fore legs, and their intellects together, as in us. Their peculiar chattering may perhaps be some attempt towards speech, to which they cannot attain, partly from the defect in the organs, partly, and that chiefly, from the narrowness of their memories, apprehensions, and associations; for they seem not to understand words to any considerable degree. ”

“ Thirdly, that the contraction is performed slowly in old animals; and fourthly, that short fibres are perhaps sooner excited to contraction than long ones, it being necessary perhaps, that the vibrations should be reverberated from each end of the fibres, for many successions, before they can rise to a certain pitch. It agrees with this, that reciprocal motions are more frequent in general, and cæteris manentibus, as the animal is less; that the limbs have both long and short flexors and extensors, the first for great degrees of motion, the last for making a quick beginning ”

“ Some of these are the resemblance which children observe between their own bodies, with all the functions of them, and those of others; the pleasures which they experience in and by means of all motions, i.e. imitations; the directions and encouragements given to them upon this head; the high opinions which they form of the power and happiness of adults ”