It suffices to observe our movements with a little attention, in order to be convinced that a greater number of them are automatic than one thinks. When we step out of bed in winter and thrust our naked feet into our slippers, the foot has scarcely touched the cold leather but it withdraws, and an effort is necessary in order to resist. We notice, too, that when the shoemaker measures us for a pair of shoes, it is somewhat difficult to keep our foot still even though he does not tickle us. When one touches iron, a cup, or any other object which is very hot, the hand lets go at once. This is a very useful circumstance, because we often let go of a thing which might injure us before we have even become aware that it burns or pricks. And when we have lost consciousness through illness or any accident, the body takes care of itself, as during sleep, by automatically removing itself from anything which pricks, burns, chills, stings, or presses, and so on. If the pain produced by burning is faint, only the one side of the body moves, if it spreads and grows stronger, it affects the opposite side also, and in the highest degrees, the whole body. This law, which was established by Pflüger, holds good for normal and uninjured animals as well as for those from which the brain has been removed and which are unconscious. It shows us that the postures and movements of the body, so characteristic of a man responding to sudden pain, do not depend on his will. All that is most characteristic in the phenomena of fear: the palpitation, shortness of breath, pallor, screams, flight, trembling, are reflex movements. The more physiology advances, the more the domain of free-will is restricted, and the greater the increase of involuntary movements. CHAPTER III _THE BRAIN_ I An animal deprived of the brain is a machine which requires external stimuli in order to move. An uninjured animal is also a machine, but it differs from the other by that power in itself which renders it capable of moving and acting.