But in any disharmony which may occur it must be recognized that the mental mechanisms affected are those with which the patient was originally endowed, which he has gradually trained throughout his past experience and which he has employed more or less successfully up to the time the illness commenced. There is no new mechanism introduced to produce a mental illness, but a putting out of gear of those common to the race and their disturbance is the result of the action of influences which may befall any one of us, unbearable ideas with which some intense emotional state is intimately associated. The normal function of these mechanisms, simple at first and remaining fundamentally unaltered, although possibly much modified gradually by added experiences from within and without, depends on the maintenance of a harmonious balance between stimuli received and emotional reaction and motor response to those stimuli so that the feeling of well-being may arise. If from any cause there occurs a failure to appreciate the stimuli clearly, if the emotional reactivity be disturbed, if the sense of value becomes biassed in one direction or another so that the response is recognized by the patient as abnormal there will result a disharmony and a feeling of ill-being of the organism. Under these conditions the processes of facilitation along certain definite lines and inhibition of all other lines--processes which are essential to clear consciousness--will become difficult or perhaps impossible and a mental illness will develop. In the slighter degrees the disharmony may be known to the patient without there being any outward manifestation to betray the conflict going on within. In the severe degrees the mental activity of the patient may be under the control of some dominant emotional state so that it may be impossible for him to adapt himself to his surroundings in a normal manner although his behavior may not appear so irrational when we know the stimuli affecting him. Within these extremes we discover all degrees of disturbance, and all varieties of signs and symptoms may be encountered. But the signs which become obvious to superficial observation are, to a large extent, secondary products. The primary symptoms are felt by the patient as a disturbance of the capacity to perceive, to think, to feel, to judge, and to act, and with these disabilities there will be associated a certain degree of confusion and anxiety which cannot fail to appear as the result of such alterations of function.