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OHN DALTON, an English chemist, relates that, when a boy, he went to see a review of troops, and was quite surprised at hearing his companions speak admiringly of the red coats of the soldiers and the purple sashes of the officers, when he could not discover any difference between the color of their coats and the grass in the field. His inquiry of his comrades as to what difference they could see was received with so much laughter and ridicule, that he was led to believe that there was something peculiar about his own vision. Subsequent observations revealed to him that he could not distinguish pink from blue, and in the solar spectrum he could scarcely discern the red, it appearing to consist of two colors, yellow and blue. He afterward, about 1798, published an account of his case, which attracted much attention, and led to further investigation. It was soon found that many persons were similarly affected, in a greater or less degree. The affection was called Daltonism, and those suffering from it were called Daltonians. The subject has latterly been very thoroughly studied, and it has been found to be a
very common defect of vision, though, unless existing in a marked degree, it does not always attract attention. Dalton was informed of nearly twenty persons with vision like his own; and out of twenty-five pupils he once had, to whom he explained the subject, two were found color-blind, and, on another similar occasion, one. Prevost was of the opinion that of every twenty men assembled by chance, one would be color-blind. Wilson made extensive inquiries, and found an average of one person in seventeen affected. In an examination of 1,154 persons, it appeared that one in fifty-five confounded red with green; one in sixty brown with green; and one in fortysix blue with green. The defect is much more marked in some than in others. Distinguished men like Dugald Stewart, Sismondi, and others, have exhibited this singular peculiarity of vision. The mistakes which color-blind persons make are often ludicrous. A member of the Society of Friends purchased for himself a bottlegreen coat, intending to select a brown color, and for his wife a scarlet merino dress for a dark one. A minister of the same Society selected scarlet cloth as the material for a new coat. It has been alleged that many of the followers of George Fox were color-blind. A journeyman tailor was promoted to the position of foreman, where he had to match colors, and was soon involved in difficulty. The scarlet back of a livery waistcoat was provided with green strings to
match; a ruddy brown was put side by side with a dark green; in general, he confounded reds and browns, and crimson and blue. An artist painted a brown horse bluish green, and roses blue. A farmer could not distinguish red apples from the surrounding leaves, except by their shape. An engraver found this defect of vision useful. He says: "When I look at a picture, I see it only in white and black, or light and shade; and any want of harmony in the coloring of a picture is immediately made manifest by a corresponding discord in the arrangement of its light and shade, or, as artists term it, the effect." Color-blindness may be congenital (from birth) or it may be acquired. When congenital, it is generally hereditary, and may often be traced through a number of generations. Like other hereditary peculiarities, it frequently passes over one or two generations, and then appears in all its intensity. It is far more often noticed in the male than the female members of a family. The causes of this defect of vision are not well understood. When congenital, it is supposed to be due to a defect in the organization of the brain, at the point where is located the sense of sight. Phrenologists assert that the organ of color is located immediately above the middle of the eyebrow, and they claim to find at this point in the color-blind a marked depression. It is said that Mr. Ransome, who is no phrenologist, states, as a fact noticed in the dissection of Dal
ton, "that there was a marked deficiency in the convolutions of the brain over the orbitar-plates, which are assigned to the organ of color." It is remarked by Wilson that there is doubtless a great difference in original endowment in regard to the sense of color among nations. People who live under bright skies, and among plants and animals of vivid and brilliant colors, exhibit skill in arranging and harmonizing tints which would seem to prove that they are not afflicted with color-blindness. The Chinese, Japanese, Venetians, Italians, Spaniards, and the inhabitants of Southern France, have for centuries excelled as florists, painters, dyers, glass and porcelain makers and stainers. On the contrary, the nations of northern climates, where the summers are short and the winters long and gloomy, and all colors are subdued, have but little regard to the colors of their dress and household adornments, and hence color-blindness is probably not infrequent. When the disease is acquired, it depends upon some temporary disturbance of the system affecting the circulation. When congenital, the defect is permanent, and persons suffering from it must adapt their business to this peculiarity of their vision. They should never engage in any occupation where this defect of vision would involve the lives of others, as in the use of signals.
LITERATURE IN MEDICINE.
HERE is an anecdote current that a New York physician, recently traveling abroad, met a distinguished Parisian surgeon, to whom he spoke in somewhat laudatory terms of his preceptor. "What has he done?" was the prompt inquiry of the foreigner, adding, "I don't remember to have read any of his writings." "It is true, he has never written anything," replied the puzzled American, “but then he has a very large business." "And is that the standard by which you estimate professional excellence ?" retorted the surgeon, with look and gesture expressive of contempt. There is in this incident a world of meaning. It sets forth vividly a national trait in our profession, which disgraces us individually and as a body. We are proud of being called practical, having no time to write, on account of the severe pressure of our business engagements. The young man, who, after being located half-adozen years in practice, still goes on foot, is set down as a failure. There is no hope of his ever rising to a level with the aristocracy of his profession. It matters little what may be his scientific attainments or his moral worth; he is an