Hallucinations of sight chiefly occur in toxic and febrile deliria.

They vary greatly in distinctness. At times they are so clear that the patient is able to make a sketch of them; often they are, on the contrary, vague and uncertain.

Like the voices, the visions are apt to be taken for reality by the subject; he seeks to remove them, to shun them, or on the contrary to seize them. They are in such cases coupled with more or less marked clouding of consciousness.

Many patients, on the contrary, consider their hallucinations as artificial phenomena. The more conscious and the clearer in mind the patient is, the more apt he is to recognize the difference between the real world and his visions, because, with the exception of the cases in which consciousness is profoundly disordered, visual hallucinations "seldom bear the appearance of reality." 2 They lack the proper qualities of normal visual sensations: perspective, clearness of contour, variety of tints, etc. Often the morbid image appears in a single plane, hazy in outline, and grayish in color. It is therefore not surprising that, not possessing the attributes of true perceptions, visual hallucinations are often not taken for reality, and do not exercise upon the mind of the patient the same degree of influence as do phonemes.

1 Bechterew. Ueber das Harm der eigenen Gedanken. Arch. f. Psychiatrie, Vol. XXX.

2 Wernicke, Loc. cit., p. 194.

Some patients consider their hallucinations as shadows or images which they are made to see artificially by means of projecting apparatus, electric currents, etc. Others attribute them to the pernicious action of poisons which their enemies make them absorb.

Visual hallucinations may take the form, though rarely, of verbal hallucinations of vision. The patients see words and phrases on tables, walls, etc. A subject of choreic insanity observed in Joffroy's clinic saw her own name written on her apron. Everybody is familiar with the famous words Mene, mene, tekel, upharsin, which the guests saw appear upon the wall at Belshazzar's feast.