=Nature of Feeling.=--Feeling has already been described (Chapter XIX) as the pleasurable or painful side of any state of consciousness. We may recall how it was there found that any conscious state, or experience, for instance, being conscious of the prick of a pin, of success at an examination, or of the loss of a friend, is not merely a state of knowledge, or awareness, but is also a state of feeling. It is a state of feeling because it _affects_ us, that is, because being a state of _our_ consciousness, it appeals to us pleasurably or painfully in a way that it can to no one else.
=Neural Conditions of Feeling.=--It has been seen that every conscious state, or experience, has its affective, or feeling, tone, and also that every experience involves the transmission of nervous energy through a number of connected brain cells. On this basis it is thought that the feeling side of any conscious state is conditioned by the degree of the resistance encountered as the nervous energy is transmitted. If the centres involved in the experience are not yet properly organized, or if the stimulation is strong, the resistance is greater and the feeling more intense. A new movement of the limbs in physical training, for example, may at first prove intensely painful, because the centres involved in the exercise are not yet organized. So also, because a very bright light stimulates the nerves violently, it causes a painful feeling. That morphine deadens pain is to be explained on the assumption that it decreases nervous energy, and thus lessens the resistance being encountered between the nervous centres affected at the time.
=Feeling and Habit.=--That the intensity of a feeling is conditioned by the amount of the resistance seems evident, if we note the relation of feeling to habit. The first time the nurse-in-training attends a wounded patient, the experience is marked by intense feeling. After a number of such experiences, however, this feeling becomes much less. In like manner, the child who at first finds the physical exercise painful, as he becomes accustomed to the movements, finds the pain becoming less and less intense. In such cases it is evident that practice, by organizing the centres involved in the experience, decreases the resistance between them, and thus gradually decreases the intensity of the feeling. When finally the act becomes habitual, the nervous impulse traverses only lower centres, and therefore all feeling and indeed all consciousness will disappear, as happens in the habitual movements of the limbs in walking and of the arms during walking.