When the source is unfamiliar, the animal becomes prepared for action. The energies are aroused for attack, or for hiding, freezing, or running, according to the mode of defense to which the animal has been adapted in its adjustments to the stimulations of its environment. The lion, the tiger, the skunk, the snake, the bird, the rabbit, the squirrel will act differently, according to their natural disposition in response to external objects and stimuli. While the motor system may react differently in various animals, the fear instinct is alike in all of them. This stage of the fear instinct should be regarded as the healthy physiological reaction to strange and new stimuli, and is essentially protective, inasmuch as it serves for the arousal of energy and proper reactions of self-defense, characteristic of the particular individual. In its milder forms the fear instinct is _normal_, _physiological_, and healthy in its reactions. In fact, the absence of it is rather pathological. It is quite natural that under the influence of some danger, the organism may feel the urging of this vital instinct, the consequent of the fundamental life impulse, and feel it as a stimulus rather than as a deterrent experience, feel fear as the key for the unlocking of energies in defense or attack. Such a reaction is healthy and strictly requisite in the total economy of life. When I advanced the theory that the fear instinct is at the bottom of functional psychosis, or of psychopathic maladies, some jumped to the conclusion that I regarded the fear instinct as abnormal, giving rise to pathological states under all conditions and circumstances. This is not correct. _The fear instinct in its initial stages is perfectly normal, and is as indispensable to life as hunger and thirst._ It is only in the more advanced and extreme stages that the fear instinct becomes pathological, and is apt to give rise to psychopathic states. In the arrestive or inhibitory state, the innervation of the voluntary and the involuntary muscular systems is arrested, or weakened. There is tremor and even convulsive contractions, the voluntary reactions are affected, and are carried out with some difficulty; there is cardiac arrhythmia, the respiration is irregular; there may be chattering of the teeth; the various bodily secretions are interfered with, and the vaso-motor nerves as well as the general vascular structures are thrown into disorder. Peristalsis, intestinal secretions, and the innervation of the sympathetic nervous system may become affected, first by inhibition, and then by irregular functioning. Associative mental or cerebral activity becomes arrested, confused; memory is disturbed, and the whole personality or individuality appears in a state of dissociation, accompanied by a lack of precision and lack of exactness of neuromuscular adaptations. The delicate reactions and adaptations are specially affected.