Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER II. SYMPTOMATOLOGY. — DISORDERS OF PERCEPTION. INSUFFICIENCY OF PERCEPTION. —ILLUSIONS.- HALLUCINATIONS. "THE senses," says Jean Muller, "inform us of the various conditions of our body by the special sensations transmitted through the sensory nerves. They also enable us to recognize the qualities and the changes of the bodies which surround us, in so fa,r as these determine the particular state of the nerves." l The senses, in other words, are the means through which we obtain the knowledge of our own bodies and of the external world. For the exercise of their function are necessary: (1) the reception of an internal or an external impression by a peripheral organ; (2) the transmission of this impression to the brain; (3) its elaboration by the cortical cells, which transform it into a phenomenon of consciousness: first sensation and then perception. Only the latter operation is of interest to the alienist. We shall study successively: I. Insufficiency of perception; II. Illusions (inaccurate perceptions); III. Hallucinations (imaginary perceptions). Hallucinations and illusions are often classed together under the name of psychosensory disorders. 1 Jean Muller. Manuel de Physiologic. § 1. Insufficiency Of Perception. Insufficiency of perception in its slightest degree may be met with in states of depression, at the onset of con- fusional states, etc. All external impressions are vague, uncertain, and strange. The patients complain that everything has changed in them and around them: objects and persons have no more their usual aspect; the sound of their own voice startles them. In a more marked degree of insufficiency external impressions no longer convey to the mind of the subject any clear or precise idea; questions are either not under... --This text refers to the Paperback edition.