The first author who noticed the production of impressions of color by sounds was an albino doctor of Erlangen, named Sach, who in 1812 described in an inaugural thesis his own impressions and those of his sister. His observation is very complete, and contains a considerable proportion of the details which are found in later works. He died at the age of twenty-eight years, and his researches fell into oblivion. During the following years doctors and oculists, like Cornas, of Geneva, published isolated observations.
In 1873 appeared the important observations of the brothers Nussbaumer, one of whom was a student at Vienna, and the other a watchmaker; both of whom had from childhood experienced sensations of color when they heard certain sounds. When children they observed the ringing of spoons and knives tied to the ends of strings, designated the colors produced by the sounds, and communicated their impressions to each other; but they did not always agree concerning the colors of the different sounds, and long disputes ensued, of which their brothers, sisters, and friends could understand nothing. The student afterward published, under the direction of Prof. Brühl, a detailed memoir on the cases.
Six years afterward, in 1879, Bleuler and Lehmann wrote their memoir, the most complete one we possess. Both authors studied medicine at the University of Zurich; Bleuler writes concerning the origin of this work that they were talking of chemistry, when the subject of ketones coming up, Bleuler remarked that they were yellow, because there was an o in the word. Thus by a curious illusion he attributed the colors suggested by the name of an object to the object itself. His friend Lehmann, greatly astonished and not understanding the answer, asked for an explanation of it. This stimulated his curiosity, and they both proceeded to make inquiries among their relatives and friends. They published accounts of more than sixty cases.
From that time publications multiplied, and the present period is marked by investigations pursued in every direction. It now appears that colored audition belongs to a family of similar phenomena, which are sometimes grouped in one person and sometimes scattered. Colored audition is still the most frequent and best studied phenomenon, and is the single one which we intend to discuss. But a word should be said of the other forms. They differ chiefly in the nature of the impressions that are associated, and which serve reciprocally as excitants. Thus, in some persons, not sounds but sensations of taste and odor provoke the luminous impressions. These may be called colored gustation and olfaction. In others, psychical phenomena, like recollections or abstract notions, produce the same effect. One person sees colors in the months, in the days of the week, or in the hours of the day. In
