Hallucinosis

Man's contact with his external environment is through his special senses: sight, hearing, taste, touch and smell. Sensory data are of paramount importance in the struggle for survival in any milieu. The special senses were developed in a long evolutionary process of the race as instrumentalities by which the organism must adjust itself to a constantly shifting and changing experience. The eyes were useful in estimating at a distance the dangerous and undesirable objects too far removed from touch. The ear also served as an instrument which heeded signals that might be interpreted as a danger to existence. Smell served to differentiate the noxious from the harmless in atmospheric conditions. Taste developed as a rough guide to the poisonous and the nourishing. Touch began as a means of immediate sensitivity closely bound up with self-preservation from dangerous penetrating objects in the environment.

In much later ages the senses served as avenues of an inflow of intellectually endowed material from the outer to the inner environment, as a means of acquiring usable knowledge, skills, awareness and as a means of mastering the external environment. Sensory perceptions are the result of stimuli from the external environment which serve a biologically useful purpose, and these are necessary in daily living.

Hallucinatory experiences are unreal sensory experiences. They are an apparent perception of an external object when no such object is present. One or more of the special senses may be involved. Various views are held in regard to the genesis of hallucinosis. The peripheral view presupposes a peripheral irritation of the sensory organs. The psychosensory conception admits an irritation of the sensory centers in the cortex. Tanzi is of the opinion that hallucinations originate in Flechig's association centers. It is his view that the image starts in these centers, ascends to the psychic area, and descends to the same sensory centers through the pathways of fibers which