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Show 38 THE PRINCIPLE OF CITAP. J. this is an habitual and not a strictly reflex action, as the stin1ulus is conveyed through the mind and not by the excitement of a peripheral nerve. 'fhe whole body and head are generally at the sa1ne tin1e drawn suddenly backwards. These latter moven1ents, however, can be prevented, if the danger does not app~ar to the imagination imminent; but our reason telhng us that there is no dano·er does not suffice. I 1nay mention a trifling fact, illu~rating this point, and which at the time atnused me. I put n1y face close to the thick glassplate in front of a puff-adder jn the Zoological Gardens, with the firm determination of not starting back if the snake struck at me; but, as soon as the blow 'vas struck, 1ny resolution went for nothing, and I jumped a yard or two backwards with astonishing rapidity. My will and reason were powerless against the imagination of a danger which had never been experienced. 'fhe violence of a start seems to depend partly on the vividness of the imagination, and partly on the con· clition, either habitual or temporary, of the nervous system. l-Ie who will attend to the starting of his horse, when tired and fresh, will perceive how per· feet is the gradation from a mere glance at son1e unex· pected object, with a mo1nentary doubt whether it is dangerous, to a jump so rapid and violent, that the anin1al probably could not voluntarily whirl round in so rapid a manner. The nervous systen1 of a fresh and highly-fed horse sends its order to the n1otory systen1 so quickly, that no time is allowed for him to consider whether or not the danger is real. After one violent start, when he is excited and the blood flows freely through his brain, he is very apt to start again; and so it is, as I have noticed, with young infants. A start from a sudden noise, when the stin1ulus is CHAP. I. SERVICEABLE ASSOCIATED HABITS. 39 con:ey~d through tho auditory nerves, is alwavs accom~ ani~~ In grown-up persons by the winking of the eyehds. I observed, however, that though 1nv infants started at. sudd~n sounds, when under a fortnight old, t~ey certa1nly.chd not always wink their eyes, and I believe never did so. The start of an older infant apparently repre~ents a vague catching hold of something to prevent falhng. I shook a pasteboard box close before ~he ~yes of ~ne of my infants, when 114 days old, and It cl1d ~ot 1n the least wink; but when I put a few comfits 1nto the box, holding it in the same position as b?fore, and rattl~d then1, the child blinked its eyes v~olentl! ever~ tune, and started a little. It was obvtously nnpossible that a carefully-guarded infant could have ~ea1:nt by experience that a rattling sound near its e~es Indicated danger to them. But such experience 1w 1ll hav•e been slowly gained at a later aO'e durin{)' a 0 b G . ong ~er1es of generations ; and from what we know of 1?hentance, there is nothing improbable in the transmissiOn of a l~abi~ to the offspring at an earlier age than that at wluch It was first acquired by the parents. R From .the fo~·~going remarks it seems probable that come actions, winch were at first performed consciously, ~lave become through habit and association converted 1nt~ reflex actions, and are now so firmly fixed and inhented, that they are performed, even when not of the least use, 14 as often as the same causes arise which originally excited them in us through the voliti~n. In such cases the sensory nerve-cells excite the motor cells, ta M··n 1311 u er I'e~adts .<' Elements of Physiology,' Eng. tr. vol. ii. p. · ) on startmg ben1g always accompanied by the closuro of the eychds. 14 Dr. Maudsley remarks ('Body and Mind,' p. 10) that "reflex ~ovcments which commonly effect a useful end may, under the changed cuc~mstances of disease, do great mischief, becoming even the occasion of vwlent suffering and of a most painful death." |