23. Besides the connate and acquired mechanism, we have now to consider the temporary and fluctuating adjustments which represent the statical condition of the organism at each moment. The automatism of the primary constitution is such that previous experience and conscious effort are not needed; nor will any experience or any effort alter the mode of reaction. If a strong light falls on the eye, the iris contracts; if the eyeball is dry, the eyelid drops; if sound-waves beat upon the tympanum, the stapedius muscle contracts; if the lining of the throat be tickled, the muscles involved in coughing or in vomiting contract. No experience is necessary for these actions, some of which are so complicated that if we had to learn them, as we learn far simpler actions, the organism would perish before the power was attained. Yet all of these presuppose a certain normal state of the mechanism, any considerable variation in which will modify or suppress them. 24. Secondarily automatic actions are those which have been acquired through experiences that have modified the organism, and produced a new adjustment of parts. We learn to shield the eyes against a strong glare of light by raising the hand; by winking we learn to shield the eye against an approaching body; we also learn to turn the head in the direction of a sound, and to thrust away with our hands the object that is irritating our skin. Experience has been necessary for all these actions, and has finally organized the tendencies to perform them, so that the reaction is invariable, inevitable, unless controlled by the will. If you tickle my throat, I may, or may not, push aside your hand; but if the inside of my throat be tickled, I must cough. Here we see the difference between the automatic and secondarily automatic actions. The second being due to individual experience, are more or less controllable; and whether they are or are not controlled depends on the condition of the nerve-centres at the moment. You may tickle my throat, or irritate my skin, without causing any movement of my hands to thwart you, either because my nerve-centres are preoccupied by other stimulations, and I am not conscious of the irritation, or because I do not choose to thwart you.