Color-Blindness

THAT a person clothed in his right mind should look upon a modest barn-yard fowl, and deliberately describe it as the yellow hen with a blue tail, seems almost incredible ; but such erratic visions are very common phenomena of the curious disorder which we call color-blindness. Yet the inference that a person deficient in the perception of color does not see distinctly, that his vision is imperfect in the ordinary sense, cannot be drawn. Dimness of vision hides the form of objects, not their color. The other day a friend of mine, who enjoys perfect sight, and who has never had the slightest affection of the eyes, pointed out on the Common a ball-player in a bright blue cap as “the one in the red cap,” and gave the color of a lady’s green dress in the distance as pinkish. As to a resemblance in hue between the grass and this dress, he thought perhaps that there was a resemblance, but he was not certain ; colors generally did not seem to him to be matters of moment, and he clearly regarded the ability to distinguish red from green as an accomplishment of too slender merit to be worth discussing. Another acquaintance, always a little weak among the greens and browns, but an ardent lover of pictures and art generally, and who cherished a particular admiration for the bronze statue of Bavaria at Munich, stoutly maintained that the statue was of marble, because the color was grayish and not that of bronze !

Contrary to what would naturally be supposed, defective perception of color is most common in the educated classes ; at least this is a conclusion of Wilson of Edinburgh, who investigated the subject a few years since, advertising for persons with this defect, and thereby enlarging greatly his field of observation.

Another singular fact in relation to the whole subject is that the existence of color-blindness should never have been discovered, or if discovered never mentioned, until the year 1796, when Dalton published an account of his own deficiencies in this respect. He could not tell blue from pink, and hardly saw more than two colors in the rainbow.

When the defect is well marked there is always an inability to distinguish between greens and reds. Boys do not see the red apples on the tree, or they have bad luck in gathering wild strawberries, or fail to discover the red roses half hidden by the leaves. Dark reds are called brown, while light reds, light pinks, and light greens often pass for light blues. A gentleman, in relating his own case, complained of not being able to find his red sealing-wax upon his green-covered writing-desk. He once gathered as a curiosity some lichens from the roof of a house. The lichens being, in his sight, of the same color as the red-tiled roof, he thought he had made a remarkable discovery. The lichens, however, to his great chagrin, proved to be bright green.

In a severer grade of the affection blue and yellow are the only colors recognized, and this form of disorder is the one most frequently met with. Mix the blue and yellow, the sole colors which the color-blind recognize, and the product, green, they cannot see. A person relating his infirmity of this nature observed that green, to him, was no color unless it were red ; pale blue and pink were the same ; but yellow, light, dark, and medium, and all blues except the very pale, he knew perfectly and could distinguish with readiness.

A German who has inherited this defect from his grandfather is described as being able to distinguish with certainty blue and yellow only. He is fond of form, a good judge of symmetry, and a connoisseur in oil paintings. He has spent a great deal of time in the galleries of the Louvre, of Dresden, Berlin, and Vienna, and decides at a glance the school and epoch to which a picture belongs, recognizing at once a Raphael, a Rubens, a Murillo, or a Rembrandt. He does not pretend, however, to judge of the color of a picture, and likes of course historical pictures, with their strict definition of forms, better than landscapes. His memory of colors is weak, and the impression received from them so slight that he is unable in imagination to bring up any color vividly enough to know it. He cannot make out a varicolored object at a glance, but must do it slowly, as it were by spelling. The attempt to define the colors of such objects is tedious to him, and ordinarily he contents himself with the general idea that there are several colors. When a boy he reproached his mother for giving away a scarlet dress, which he called dark and gloomy. In the fields he was unfortunate in gathering strawberries or violets, but he could find the white May-flowers with the best of his companions. Like most persons affected in this way, he was quick to conceal the defect, and never spoke of colors unless he knew his ground well. He was certain, of course, that in their season, trees and grass were green, and he knew that bricks were red, but in regard to these two colors in most other objects he wisely preserved silence.

At one time for a whole year he diligently practised himself every day in the attempt to distinguish colors, in order if possible to remedy his defect. This practice led to an accurate examination of his condition, and finally demonstrated to him the fact that blue and yellow and their different shades were the only colors that he could name with precision. It seemed impossible that scarlet and crimson should both be called red. He classed scarlet with the greens and browns. A bright scarlet and a cinnamon brown were the same. Pink, violet, and lilac were blue, and gray was no color at all. He could distinguish no complementary colors except blue from yellow, and yellow from blue. In the rainbow or solarspectrum, although he saw its whole extent, he recognized only blue and yellow. The green was an impure blue, and the red a shade of yellow. His year’s practice resulted in an improved perception to the extent only of enabling him to see red modified by blue, as seen in crimson, and in his recognizing a shade of pink.

There is a still worse form of this defect, where yellow alone can be distinguished, or where, in a few instances, even, individuals have been discovered totally blind to all color, and able merely to tell lighter from darker shades. Such persons have frequently had an accurate perception of form, and excellent eyesight. The case of Harris, related in the Philosophical Transactions, is one of this kind. He could never understand why bright red was called red, and could do no more than guess the name of any color. He could see merely that white and any bright colors were not black, and that a striped ribbon differed from a plain one. The case of a young woman is also recorded in the Transactions, who on being tested was found to know white and black simply ; and of a man to whom all colors appeared as tints of gray, or as different shades between black and white. Firmas relates the case of a man who knew no colors, but was yet fond of painting. He had frescoed his apartment in colors, and was very proud of his work. When questioned as to his object in painting earth, sky, trees, houses, and figures all blue, he replied that he wished the picture to match the furniture in color. He was not aware that the latter was red. Another individual admitted that the rainbow appeared to him as a “ band of lighter color than the other parts of the sky, but a little darker at one side than the other, and gradually shaded off between the two sides.”

For many years after the discovery of this peculiar affection it was supposed to be an imperfection dating invariably from birth ; always congenital, always a physiological, never a pathological condition. More recently, however, numerous cases have been published where this anomaly of vision may be traced directly to disorder of the brain, and in other instances directly to disease of the eye. One of the most interesting of these cases, and perhaps the first in point of time, was published in 1840 by Dr. Hays in the American Journal of the Medical Sciences. Mary Bishop, twenty years of age, enjoyed excellent sight, and was able to distinguish colors, for aught she knew, as well as her companions. After two attacks of cerebral disease she became entirely blind for four months ; her sight then gradually returned, but she noticed that the grass, and particularly that the roses, did not appear of their natural color. The first color she remembered to have remarked as her sight slowly improved was yellow ; and when she had so far recovered as to be able to read coarse print and make out the form of smaller objects, she still could recognize with certainty no colors but blue and yellow. A few weeks later, and apparently coincident with the increased visual power, came an increased ability to distinguish colors. Roses were again of their proper color, and easy to find among the leaves. Finally she could see in the prism blue, green, yellow, and red, but not the orange or violet. A case is recorded of a man who lost the faculty of distinguishing colors from the effects of a copious bleeding from the arm. Not unfrequently blindness to color is of the most temporary nature, a mere consequence of sudden and trifling determination of blood to the head. White Cooper relates the case of a well-fed clergyman who, after the services were over, felt somewhat fatigued and depressed from the confined atmosphere of the church. On rising from the kneeling posture, great was his surprise, the age of miracles being passed, to find that the crimson velvet cushions and hangings of the pulpit had changed to a dark violet hue, and that other familiar objects, which he knew to be red, looked bluish-green. A rest of ten minutes in the vestry sufficed to restore his disordered perceptions to their normal condition. Another instance which fell under the notice of the same writer was evidently the result of congestion from fatigue. A plethoric farmer undertook to do the sight-seeing of the great Hyde Park exhibition in London. All went well until the third day, when he felt giddy and oppressed, and to his consternation red curtains and hangings looked a greenish-brown ; and on investigating his condition further, he found that he could no longer see greens and reds, although blue and yellows were distinguishable as before. He immediately went home, and after sleeping for three hours found that reds and greens were again as clear and distinct as of old. Very similar to this was the singular experience of Professor Thury of Lausanne, who walked during the night from Geneva to Nyon to witness the great aurora borealis of November 17 and 18, 1848. While all around him were exclaiming in raptures at the gorgeous spectacle, to his dismay he could see nothing but blue sky. His disability proved to be merely of a temporary nature also.

Another case which has its bearing on the temperance question, and has apparently been overlooked by the teetotalers, is that of a college librarian related by Cooper, in Todd’s Cyclopædia of Anatomy and Physiology. On rising in the morning he was surprised to find that the carpet of his chamber had lost its color. The figure was there, but in black and white only. He called to his wife in alarm to know if the carpet had been changed. It had not, and with a divination strictly feminine she went straight to the root of the matter at once. He had taken too much wine, or, as he expressed it, several kinds of wine at dinner the evening before ; and now, his attention being called to this curious phenomenon as a result of wine-drinking, he found later that whenever he partook of several kinds of wine at dinner his perception of color was imperfect in the morning, although his power to distinguish forms remained unimpaired. When he took punch or spirits, colorblindness was produced in a still greater degree. Over use of the eyes in assorting colors and shades has also been observed to result in a temporary inability to distinguish shades of color at all.

Injury to the interior of the eye or to the brain has sometimes the effect of blinding the eye to color and not to form. A man was struck by a ball from a pistol, which entered the mouth and passed upward through the posterior part of the orbit of one eye. After recovery from the wound, there remained but one small spot upon the retina of this eye sensitive to light. By turning the injured eye somewhat, so as to permit rays of light from objects to fall directly upon the sensitive spot in the retina, forms could be distinctly seen, but no colors. Disease of the internal structures of the eye has not unfrequently the effect of blinding us to colors and not to forms. A recent report of St. Bartholomew’s Hospital, London, furnishes an instance of this kind. A medical man found himself suddenly suffering from partial colorblindness of the right eye. With the left he could still distinguish different hues and shades with readiness and precision. To the right eye bright green appears a pale blue, and bright colors generally look dull. On examination of the affected eye with the ophthalmoscope, there was found an irregularity in the distribution of pigment at that part of the eye near the entrance of the optic nerve. This spot was afterwards determined by experiment to be the faulty portion of the retina. When he looked out, as it were, obliquely from his eye, thereby permitting the rays of light to fall on a different part of the retina, colors appeared natural to him. In certain kinds of disease of the optic nerve as the sight fails, the ability to perceive colors fails also, but by no means in a degree exactly corresponding to the general failure in sight. One may still be able to determine forms with tolerable accuracy, and yet be unable to distinguish colors ; and as the disease progresses, and visual power gradually grows weaker and weaker, the power to discern colors may meantime improve considerably and be retained to a limited extent, until the sight fades entirely away.

The cause of color-blindness is not always easy to determine. Numerous investigations, by persons competent and full of zeal for the work, have been made ; but although many facts have been established and many untenable theories overthrown, the cause of colorblindness generally cannot be said as yet to have been fully demonstrated. Congenital cases are usually inherited. Dr. Earle published, many years ago, an account of this defect in his own family for several generations. In the second generation of seven brothers and eight sisters, three brothers were defective in the perception of colors. The third generation of three brothers and four sisters were in this respect normal. In the fourth, consisting of fiftytwo persons, thirteen brothers and two sisters were affected.

According to the observations of Cuvier, the hereditary tendency sometimes follows the law of sexual limitation, as in the instance of Madame T., of whose six children the five daughters were color-blind, the son not. Madame T. inherited the defect herself from her maternal grandmother. Of the three children of the latter, a son distinguished colors, the two daughters could not. Four of the daughters of Madame T. were married, and of their seven children the three daughters had defective perception of color, but the four sons were free from the defect. Imperfect appreciation of color has been noticed not unfrequently to be associated with imperfect hearing and want of appreciation of music.

To say that we inherit the affection, however, is merely to say that we inherit the cause ; it explains nothing, and is at most but one step forward in the investigation of its nature. Many theories, from that of Dalton down to the very recent ones of Rose, Schultze, Helmholtz, and Ernest Hart, have been advanced, but none seems to have met with sufficient favor to secure its general acceptance. The phrenologists, nevertheless, with that facility and despatch which chiefly characterizes their dealings in intellectual problems, have long since decided that defective perception of colors indicates simply a " deficient organ of color.” If we regard the phrase “ deficient organ of color ” as a peculiar way of expressing a state of the brain which seems to indicate a lack of perception for color, we may consider that we have an hypothesis on which it may be possible, perhaps probable, that some forms of color-blindness may be explained. To believe that a person, however practised and skilful, can tell whether a man knows green from red by examining the region of his eyebrows, is to be blind to something more than color. It seems, as we have already remarked, quite probable, although by no means certain, that in instances where sight as concerns form is absolutely perfect, the cause may be rightfully attributed to some defect in the sensorium, whereby the brain fails to appreciate the difference between the rays of light produced by the several colors. But this theory, if admissible in certain cases, can scarcely be said to cover instances where the defect is noticed only when using one eye. Nor has it any bearing whatever in cases of disease or injury to either one or both organs of vision. Imperfect or disordered perception of color is often the result, in some way as yet inexplicable, of disturbance of the digestive apparatus, and not unfrequently is a symptom of jaundice. Temporarily the same condition may be caused by drugging. Sometimes a preparation from Artemisia santonica, or worm-seed, produces this phenomenon with great certainty and rapidity. Schultze, who published a small work in 1866 embodying the result of his experiments, believes that he has discovered a key to the solution of some of the problems presented by this singular affection, in the macula lutea, or yellow spot, in the retina of the eye. The more yellow this spot the more influence it exerts over the perception of blue rays. Santonine augments greatly the yellowness of this spot, and Schultze sums up the phenomena produced by its administration thus. It reduces the perception of the colors of the spectrum, beginning with violet, and goes on as far as to render the retina insensible to blue. It also reduces the color at the other extremity of the spectrum, but to a less extent, simply removing the perception of red. Finally it tinges all objects perceived yellow or yellowish-green. The same author mentions a curious circumstance observed during his experiments with this substance, namely, before the eyes of his subjects become completely insensible to violet rays, when the santonine was just beginning to exert its characteristic influence, all objects appeared tinged with violet. The santonine, according to the author, produces temporary congestions to the head, — a condition which favors the production of spectra or illusory vision. These spectra assume the color complementary to yellow, that is, a violet hue ; hence real objects, for the time being, appear tinged also with violet.

Though less than the one-hundredth part of an inch in thickness, the retina is divided by anatomists into seven or more layers, the first of which is formed principally of upright cones. These cones, according to Mr. Ernest Hart, are the true chromatic organs of the eye, each one acting as a prism, decomposing the rays of light which fall at its base in concentric colored circles corresponding to the colors of the solarspectrum. Still, if it seems necessary, after all the patience and zeal which have been brought to bear in the investigations and experiments to determine the cause of this defect, to admit the conclusion of Stellwag, that the cause of color-blindness is wholly unknown, it may at least be safely affirmed that, of those who have devoted great attention to the subject and whose opinions are therefore entitled to consideration, nearly all believe the seat of the disorder to be in the nervous structures within the globe of the eye.

In view of the disposition of the color-blind to hide their defect, it is scarcely probable that the most courageous will adopt the suggestion of Professor Maxwell and wear spectacles, one glass green and the other red, and so attain infallibility in distinguishing these two colors. To those who do adopt the spectacles he promises no sensation, as of red or green, but merely that they shall learn to know the two colors just as surely and precisely in the same manner as if they were labelled.