It is striking that such slight causes produce movements so pronounced that we are not capable of suppressing them. We know that our friend will certainly not poke his finger into our eye, but the conviction that it is a joke does not suffice. Even if a thick pane of glass were between us and the approaching hand, with all the force of reason and will, many would be unable to avoid shutting the eyes, as though there were in us two natures: one, animal and unreasoning which commands, and the other human and intelligent which succumbs. Again, when a gnat or a grain of dust gets into our eye, the eye closes irresistibly by an automatic mechanism quite independent of our will. Sometimes there is not only one contraction, but a somewhat complicated series of movements excited in parts distant from the stimulus. As a convincing example, I shall communicate what I observed in an investigation of deglutition. This act, performed unceasingly during eating, is by no means voluntary, for if we try to repeat it a few times in succession we notice at once that, as soon as we have no saliva in the mouth, every effort to swallow is in vain. In order to swallow it is necessary that a morsel of food or some fluid should touch the mucous membrane of the posterior portion of the mouth. The sensory nerves stimulated in this way communicate to the spinal cord that a body is at the entrance of the œsophagus which must be sent to the stomach. Immediately a succession of orders is issued, one after the other, by the spinal cord, so that first the upper part of the œsophagus contracts and propels the morsel a short way down, then a further order causes a contraction of the next part, then comes another order whereupon a part still lower down contracts, and so all the successive portions of the œsophagus transmit the morsel one to another by means of various separate orders until it reaches the stomach. We have, therefore, in our nervous system mechanisms which work automatically, and produce a series of contractions directed to one object, which may, at first sight, appear voluntary, but is, in reality, mechanical and unconscious. Some of these mechanisms we bring into the world with us. If one puts a finger into the mouth of a new-born child it begins to suck. It is a machine working without discernment, as if one had touched the spring of an automatic doll; no one teaches the child, he need not learn it at all in fact, for the fœtus in the womb makes exactly the same movement. So it is with the chicken, which pecks when just escaped from the shell. In this case, what gives rise to the movement is no longer immediate contact as that of the finger in the mouth, but the impression of light and sight, which indeed is nothing else but contact with distant things by means of the rays of light. Scarcely has the image of the grain formed itself in the eye of the chicken but it pecks at it.