without noticing--such as in walking, eating, speaking, and so on. These familiar facts prove of themselves that consciousness is a complicated function of the brain, by no means necessarily connected with sensation or will. To bind up the ideas of consciousness and sensation inseparably is the more absurd, as the mechanism or the real nature of consciousness seems very obscure to us, while the idea of it is perfectly clear: we know that we know, feel, and will. The word "irritability" is generally taken by modern physiology to mean that the living matter has the property of reacting on stimuli--that is to say, of responding by changes in itself to changes in its environment. The stimulus, or action of a foreign energy, must, however, be felt by the plasm before the corresponding stimulated movement (in the form of various manifestations of energy) will be produced. Hence the question whether this sensation is (in certain cases) associated with consciousness or (generally) remains unconscious is of a subordinate interest. The plant that is caused to open its floral calyx by the stimulus of light acts just as unconsciously in this as the coral that spreads out its crown of tentacles under the same influence; and when the sensitive carnivorous plant (_dionæa_ or _drosera_) closes its leaves in order to catch and destroy the insect sitting on them, it acts in the same way as the sensitive actinia or coral when it draws in its crown of tentacles for the same object--in both cases without consciousness! We call these unconscious movements "reflex actions." I have dealt somewhat fully with these reflex movements in the seventh chapter of the _Riddle_, and must refer the reader thereto. This elementary psychic function always depends on a conjunction of sensation and movement (in the widest sense). The movement that the stimulus provokes is always preceded by a sensation of the influence exerted. Modern physiology makes desperate efforts to avoid the use of the word "sensation" and substitute for it "perception of stimulus." The chief blame for this misleading expression is due to the arbitrary and unjustified separation of psychology from physiology. The latter is supposed to occupy itself with the material phenomena and physical changes, leaving to psychology the privilege of dealing with the higher mental phenomena and metaphysical problems. As we reject this distinction altogether on monistic principles, we cannot consent to separate sensation from the perception of stimuli--whether this sensation be accompanied with consciousness or not. Moreover, modern physiology, in spite of its desire to keep clear of psychology, sees itself compelled in a thousand ways to use the words "sensation" and "sensitive," especially in the science of the organs of sense.