Henry T. Finck: The Development of the Color-Sense.

The Living age 1855, 3.1.1880

From Macmillan's Magazine.

It would be difficult to find another natural phenomenon which at the present time possesses so great a fascination for people of the most diverse tastes and occupations as color. And yet history shows that color has by no means always been held in such high esteem as now. The Greeks, for reasons which will be specified in the course of this article, regarded it with eyes of indifference, and have contributed little to our scientific knowledge of it. The Middle Ages present a still greater void; and only with the revival of letters, when the senses were released from the ascetic ban which had so long rested on them, did a hearty and healthy love of color begin to manifest itself in science, art, and literature. And the nearer we come to our own day, the more prominent color becomes as an object of speculation and experiment. The last fifteen or twenty years are so remarkable in this respect that in a history of science they might not inaptly be alluded to as the Age of Color. The problem was found to be so complex and comprehensive that a division of labor had to be resorted to. Goethe, by writing no less than a thousand pages on the phenomena and history of color, had already endeavored to break up the monopoly held by the man ofphysical science. felmholtz next appeared, in the name of physiology, to revive and improve the theory of Young, and by its aid to bring to light many new and important facts. More recently, the anatomist, F. Boll, discovered the retinal purple, which points to the conclusion that the act of vision is a photochemical process, and that we do not see external objects directly, but only their images in the eye. Max Schultze had already preceded him with the discovery of the difference in functions between the rods and the cones in the retina, thereby, as we shall see, enabling us to ascertain the condition of the color-sense of prehistoric man with almost absolute certainty. Ever since the discovery was made that the examination through the spectroscope of the color of incandescent gases and metallic vapors is one of the most delicate methods of chemical analysis, the chemist and astronomer have also given much attention to color. Nor has the naturalist remained in the background. By their theories of sexual selection, of protective, warning, and imitative colors, Mr. Darwin and Mr. Wallace have shown what a valuable auxiliary color is to the student of natural history in his investigations. By a curious coincidence color-blindness next became a prominent subject of discussion, just a hundred years subsequent to the time when the phenomenon was first recorded. These discussions have brought to light the curious fact that on an average one male out of every twenty is color-blind, i.e. unable to discriminate all the principal colors of the spectrum, and therefore liable to confound the color of a ripe strawberry with that of its surrounding leaves, or to make analogous mistakes.

The statistical proof that such a large proportion of us, without being aware of it, have an imperfect color-sense, seems curious enough to satisfy the most insatiate lover of sensational science. But the philologists, eager to make their contribution to the many-sided color question, have now come forward with a theory which throws everything else in the shade. Basing their argument on the occurrence in ancient literary records of certain peculiarities in the use or absence of epithets of color, these philologists would have us believe that the color-sense of all men was once in a rudimentary condition, from which it has been gradually developed within a period accessible to philological research. Previous to this period the world must then have presented to man the appearance of a photograph, or rather a good stereoscopic view. It was the fertile imagination of Mr. Gladstone that first suggested the idea that the organ of color was but partially developed among the Greeks of the heroic age ("Homer and the Homeric Age," 185S, vol. iii. pp. 457-500). Two years ago he restated his views in a magazine article. and that none of the counterarguments hitherto advanced have shaken conviction is evinced by his more recent summary in the "Primer of Homer," where he still insists (p. 15o) that Homer "knew but little and vaguely of the differences of color, except as approximations to the opposite ideas of light and darkness, both of which he grasped firmly, and turned very largely to poetic use. He never gives an epithet of color to a flower; never calls the skies blue; and there is no word in the poems which would justify an assertion that he had any approach to a distinct perception either of green or blue."

In a lecture delivered at Frankfort in 1867, Dr. Lazarus Geiger adopts Mr. Gladstone's theory, and extends it to other ancient peoples besides the Greeks. The same peculiarities that Mr. Gladstone had noticed in the Homeric. poems, Dr. Geiger found again in the Vedas, the Zendavesta, the Bible, [---] even in the Koran and the songs of the Edda. Dr. Geiger is even convinced that within a period open to the investigations of the comparative philologist, there has been a progress in the development of the color-sense of man exactly corresponding to the scheme of the spectrum, from red through orange, yellow, green, blue, and indigo, to violet. The first period of colorperception was the black-red age: then came the black-red-golden age, and so on. For the sake of simplicity I shall overlook these additions of Geiger, and consider the theory simply in relation to the Greeks, as put forward by Mr. Gladstone. The nature et my argument is such that what we find to be true of the Greeks must also hold in the case of other ancient peoples, mutatis mutandis. I wish to add a word or two, however, in regard to the supposed analogy between the color-sense of Homer, and the phenomenon known as color-blindness. This analogy was timidly hinted at by Geiger, and has been recently made the subject of several communications to Nature by Dr. W. Pole. According to this view, modern color-blindness would be a form of reversion or atavism, recalling a time when all men were color-blind. Dr. Pole's arguments bear witness to an ingenuity worthy of a metaphysician of the Hegelian school; but his hypothesis is contradicted by numerous facts, from which I will select only two. It is a general law of evolution that in cases of degeneration the last and highest acquisitions are lost first. Now, if there had been within historical times a regular development of the color-sense from red to violet, it would follow that a majority of color-blind persons must be violet-blind. But in reality we find that violet-blindness is so infrequent that some physicians entirely doubt its existence, and even Professor Holmgren, who has examined thousands of persons afflicted with dichromatic vision, records only two such cases. The other fact is still more conclusive against Dr. Pole. It is well known that color-blind persons chiefly fail in discriminating between red and green. Blue and yellow are seen by them as by normal persons, and are never confounded. If, therefore, Homer had been color-blind, be would yet have seen blue as we see it; and being, besides yellow, the only color of which he had a distinct perception, he would certainly have made the most of it in his descriptions. But it is precisely in regard to blue that not only the Homeric poems, but all the other ancient literary records referred to, present the most striking anomaly; and hence for my part I cannot believe that Homer and his contemporaries were color-blind.

This, however, does not by any means dispose of the whole question. The point to be decided is this: Has the color-sense of man undergone any sort of modification, or in any way been improved, since the time when the Homeric poems were written? Mr. Gladstone believes it has, and the grounds of his belief are these: (1) Homer uses only a limited number of color adjectives; (2) he applies the same adjectives to objects which present to our eyes essentially different colors or hues; (3) he gives different and incompatible color epithets to the same object; (4) white and black vastly predominate over the colors properly so called and (5) slight use is made of color as compared with other elements of beauty. These, it must be admitted, are very curious facts, and if no other explanation were possible besides the one proposed by Mr. Gladstone, his argument would seem plausible enough. But while admitting the facts to be correctly stated, I cannot admit the correctness of the logical inference from them, as long as another explanation is at hand which not only has the advantage of greater simplicity, but is much more in harmony with scientific facts. Instead of a defective color-sense we have only to assume, with Mr. Wallace, a defective color nomenclature, and the difficulties disappear. Mr. Gladstone himself points out the paucity of the Homeric color-terms; and these, we must now add, were not yet sufficiently specialized to save from confusion. If we examine our own epithets of color, we come across a few which appear to be taken from the objects to which they belong, such as rose, orange, indigo. Among the Greeks this practice was much more common, as is shown by the great number of words like fire-color, wine-color, straw-color, bronze-color, etc.; and such a nomenclature would naturally lead to confusion in language and ideas, since under different conditions natural objects do not always present the same appearance. The Greeks, moreover, had no adequate scientific theory of color. Besides black and white, red and yellow were generally named as the primary colors, and this for no other reason, apparently, than because red and yellow are more glaring and less common than other colors. Green and blue were so omnipresent in vegetation, in the sky and the ocean, that they were not considered worthy of mention. Hence it is, that in all the most ancient literary records names are first invented for yellow and red. That this is the correct explanation may be seen by observing children, peasants, savages, and in short all persons whose education in relation to color has been neglected. Glaring red and yellow are their favorite hues, while the more subdued blue of the sky, and the numerous delicate shades of green which may be observed in any forest of mixed trees, seem not to exist for them. Even in regard to red and yellow a great deal of confusion exists in the mind of modern Europeans, educated as well as uneducated. Nothing is more common than a habit of confounding with each other perfectly distinct colors, such as red, purple, violet, crimson, carmine, lilac, rose, simply because the individuals in question have not been taught the proper names of these colors with sufficient accuracy. Why then should we wonder that Homer, who lived so many years before Newton, Young, and Helmholtz, and who had only a few abstract color-terms, should have been guilty of some inaccuracy in his use of them? That I have not exaggerated the confusion in the use of color adjectives at the present day is proved by positive experiments that have been recently made. For example, M. Delboeuf asked various persons to name the color of a certain flower (Digitalis purpurea), and was told it was violet, purple, rose, lilac, and several other colors. Mr. R. C. A. Prior also records several experiments (Mature, No. 476), in one of which forty-four different persons wrote down fourteen different names for the color of flowers placed before them; and in the other there were eight different names among twelve replies.

That the want of a precise color nomenclature affords a satisfactory explanation of the new "Homeric question " is also made evident if we examine the precisely analogous case afforded in our own days by the sense of smell. In regard to this muchneglected sense we have at present arrived at a philological and psychological stage closely corresponding to that which Homer had reached in regard to the color-sense. Neither science nor popular usage has as yet supplied us with special and definite abstract terms for the various classes of odors which constantly affect our olfactory nerve. If we wish to be definite we have to imitate the practice of Homer when he speaks of wine-color, fire-color, etc. A few abstract words for odors we have, it is true, and what do we do with them? Precisely what Homer did with the few abstract color-terms which he had: we apply them indiscriminately to objects whose odors no more resemble each other qualitatively than did the objects on which Homer bestowed the same epithets of color. We speak of the sweet scent of freshlymown hay, no less than of the sweet scent of a pink, or of a fair maiden's sweet breath; of aromatic tobacco, no less than aromatic incense. Now, in a couple of centuries or more, perhaps some new philological Gladstone or Geiger will arise, and, basing his arguments on our confusion in the use of epithets of odor, demonstrate to an astonished posterity that we poor benighted barbarians of the nineteenth century had a very defective sense of smell, and also a defective sense of taste, since we could not distinguish between the odor of a pear and a rose, or the flavor of honey and a kiss, all of which we indiscriminately called "sweet."

The error of supposing that the inability to correctly name an object implies an inability to correctly see it, has not been committed by philologists alone, but also by some of the physicians who have investigated the subject of color-blindness. Dr. Favre believes that three millions of the inhabitants of France, or almost ten per cent., are color-blind, while Professor Holmgren, Dr. Magnus, Dr. Jeffries, and other authorities in their respective coun• tries, found less than five per cent of the persons examined thus afflicted. Shall we suppose, therefore, that Daltonism is more prevalent in France than in Sweden, Germany. and America? Not at all. The difference in results is entirely due to the different methods used in the examination of subjects. The authorities last mentioned class those only among the Daltonists who show by their actions in choosing wrong duplicates of a given sample from among objects of various colors, that they cannot physically distinguish between certain colors. But Dr. Favre, as pointed out by Professor Holmgren in his admirable recent work on color-blindness, tests his subjects by asking them to name the colors of various objects placed before them, and bases his decision on the answer given. It is evident that with such a method many must be put down as color-blind who are perfectly competent to see the difference between any two colors, but who, from want of experience and training, do not know when to use the word purple and when violet, or orange, and so forth. It would be difficult to find a better illustration than this of the exactly analogous mistake made by Mr. Gladstone in his diagnosis of the Homeric color-sense. And there are two very important lessons which philologists may learn from this: First, that sensations and ideas often exist for untold ages before special epithets are invented for them; and secondly, that there are some problems of philosophy which lie beyond the field of vision of the comparative philologist.

If, therefore, Max Muller's statement that all philosophy of the future will be exclusively philosophy of language, could lit substantiated, we could ne:er hope to solve the problem when the color-sense first made its appearance. Philology is altogether incompetent to settle the matter. Nor, of course, do I claim that the preceding remarks absolutely prove that the organ of color three thousand years ago was so fully developed as it is now. Our result, so far, is negative, although, certainly, the presumption is decidedly in our favor. But we must now inquire if there are any positive facts which enable us to infer that the color-sense of primitive man was equal to our own in physical development. It has been suggested by Mr. Wallace and others that since we now know "that both flowers and fruits have become diversely colored in adaptation to the visual power of insects, birds, and mammals," the origin of the color-sense must be placed lower in the scale of life than man, so that it would follow that "man's perception of color, in the time of Homer, was little, if any, inferior to what it is now." Let us see what this argument amounts to.

Certainly few scientific theories rest on a more secure basis than that first put forward by Mr. Darwin in regard to the agency of birds and insects in stimulating the development of brilliant colors in flowers. He discovered that for many species of plants it is a great advantage to be fertilized with the pollen of other individuals of the same species rather than their own pollen. This cross-fertilization is secured in two different ways, cithcr through the agency of the wind or of birds and insects. Now he found — and this is the important point — that in all those plants which are wind-fertilized, color is absent, and exists only in those cases where cross-fertilization is accomplshed through the visits of birds and insects. In many of these plants the most complex and wonderful arrangements are found for facilitating cross and preventing self fertilization, as well as for keeping away "unbidden guests," i.e. wingless visitors who would cat the nectar without paying for it by promoting the cause of cross-fertilization. Primarily, of course, what attracts the birds and insects to these flowers is the pollen and the honey secreted by them as a sort of bait. But some sort of a signal is needed to attract the winged visitors from a distance; and such signals are the colored petals. Accordingly, those flowers which through spontaneous variation possess colors of greater brilliancy than their rivals, gain an advantage over them for their offspring; and this ultimately leads to the predominance of gaily-colored over dull-colored flowers. This chain of reasoning leaves no doubt whatsoever that at least some species of animals must possess a more or less refined chromatic sense, enabling them to distinguish petals of various colors from green leaves.

* Mr. Grant Allen, in his interesting work on the color-sense, endeavors to defend sexual selection by limiting its sphere to those animals whose taste for color had already been developed by the bright hues of flowers and fruits, their habitual food. But I fail to see that he satisfactorily answers Mr. Wallace's objections, vote he does not sufficiently bear in mind the fatal fact that in the majority of cases the gaily-colored males themselves, and not the females, make the selection, while even in those cases where the females are known to exercise a choice, there is no evidence that the peculiarities of coloration in the male have anything to do with the matter.Not so unconditionally can we accept as evidence in our favor the other theory of Mr. Darwin, that of sexual selection, which was framed to account for the brilliant colors and other ornaments of many species of animals. Against this theory, at least in so far as it relates to color, Mr. Wallace has recently advanced such weighty objections that it will be safest to leave it alone for the present.* Mr. Wallace maintains that color is a normal product in the integuments of animals, varying in brilliancy with the health and vigor of the males, so that the females by simply selecting, or rather yielding to the most vigorous of the males, unconsciously bring about the result which Mr. Darwin attributes to their deliberate choice and aesthetic love of color. According to this view color would have a sexual value only in so far as it renders the individuals endowed with it more conspicuous than others. Irrespective of the large number of facts adduced by Mr. Wallace, his theory has this in its favor, that it demands of birds simply the power of physically distinguishing colors, while sexual selection would force us to assume that some birds, as peahens, birds of paradise, and hummingbirds, have a most exquisitely refined asthelic taste for color and its harmonics, such as even among the most civilized races of man at the present day is of very rare occurrence.

No such objections apply to the theories which Mr. Wallace himself has advanced to account for certain peculiarities in the variation of color in animals. Two of these theories, at least, have as secure a basis as that of cross-fertilization. As I may take for granted that Mr. Wallace's admirable essays on color are still fresh in the reader's memory, I need not say anything here in explanation of his views on protective, warning, and imitative colors, except that they supply us with additional indubitable evidence of the existence of a color-sense among the lower animals. But now I wish to point out an objection to the use which has been made of this evidence to determine the question of the development of the color-sense of man. Brilliant colors in the animal kingdom are more or less confined to the inhabitants of the air, being particularly noticeable in the plumage of birds. Mammals do not take part in the process of cross-fertilization, nor do their integuments ever approach the plumage of birds in ornamental coloring. "We do not," says Mr. Darwin, "in this class meet with the splendid red, blue, yellow, and green tints, so common with male birds and many other animals." It appears, therefore, not improbable that birds may have a more perfect color-sense than mammals. Mr. Wallace somewhere remarks, though with some hesitation, that this is indeed "just possible;" but I shall directly show with reference to the anatomical structure of the retina of birds, that it is not simply " just possible," but almost absolutely certain that their color-sense is superior to that of mammals, and perhaps even of man himself. If this be true, it is clear that we are not entitled to the inference that, since birds already have a welldeveloped sense of color, therefore prehistoric man must have been similarly endowed. Such an inference would rest on the erroneous notion that the higher types of animals must be superior, or at least equal, to the lower in the development of all their faculties — a notion which is contradicted by numerous facts of comparative psychology, such as the intellectual and social superiority of ants over most birds and mammals, and the superiority of many of the lower animals to man in the acuteness of their senses of smell, sight, and hearing. It must also be kept in mind that the color-sense is of much greater importance to birds than to mammals, for various reasons, the most important of which is, that birds on the wing are obliged to discern objects at immense distances: and it can be shown by means of a simple experiment that the color of an object can be distinguished at a much greater distance than its exact outlines. What then is to prevent us from supposing that, owing to the effects of continued use, the color-sense of birds has reached a high degree of perfection, while mammals, including man, again lost their early acquisition, not to regain it until a few thousand years ago, as our philologists would have us believe? It must be frankly admitted that natural history unaided is as incompetent to crack the nut as philology has been shown to be.

Fortunately there is still another avenue by which the problem can be approached, and on it we must now bring forward our heavy artillery, which we borrow for the occasion from the headquarters of comparative anatomy. It may seem somewhat paradoxical to assert that the microscopic examination of the retinae of owls, hats, falcons, chameleons, dogs, apes, and modern Englishmen or Germans, enables us to ascertain the nature of the color-sense of Homer and the authors of the Vedas and the Zendavesta; yet such is nevertheless the case, and if the reader will carefully digest the following facts he cannot fail to be convinced.

The human eye, as we all know, consists of about thirty constituent Farts. But of these we are here concerned with only one, the retina, or the network which is formed by the ramification of the optic nerve, and on which are received the rays of objective light after having pased through the cornea, the aqueous humor, crystalline lens, and vitreous humor. The retina itself consists of ten different layers, and of these again we are concerned with only one, that which lies farthest away from the source of light, — the layer of rods and cones. These are very minute nervous elements, whose shape is indicated by their names. They exist in immense numbers in the retina, and constitute a mosaic of semicircular rows, somewhat resembling the engineturning on the hack of a watch. The diameter of the smallest cones coincides with the smallest distance we can perceive between any two points with the naked eye. That the layer of rods and cones is the part of the eve in which waves of ether are converted into sensations of light and color has long been known, and the proofs of it may be found in any good text-book of physiology. That there is a difference in function between the rods and the cones is, however, a more recent discovery, by which Max Schultze has immortalized himself. This distinguished anatomist, in the course of his histological investigations, carne across a large number of very curious facts, which led him to set up the theory that both the rods and the cones can serve as elements of light, although the perception of light is more especially a function of the rods, while the perception of color is rendered possible exclusively by means of the cones. If this theory be true, we are entitled to assume the existence of a color-sense wherever we find the cones, and to mark it as absent whenever the cones are absent. I may add that some recent observations strongly support Schultze's theory, so that if we take these in connection with his arguments and with the results of H. Müller's analysis of the retina of the chameleon, the last doubts of its correctness must vanish.

The safest test of the theory will con sist in inquiring if, in all those cases where natural history and other sources of information lead us to look for a color-sense, there the cones exist in greater numbers and of greater length than where we have no such reasons for postulating a color-sense. Of the immense number of facts which fit into the theory in a wonderful manner, I shall have space for only a few of the more striking ones, which, however, will suffice for our purpose. Let us begin with the human retina. The reader is aware that near the central region of the retina is a place called the macula lutea, or yellow spot, which we always use in direct vision, i.e. when we sharply fix an object. With this part of the retina all the colors of the spectrum can be perceived. But, as we pass from this central region towards the periphery, we suddenly come to a zone in which one of the primary colors, red, suddenly disappears. Here all persons are red-blind. If we proceed still farther in the same direction we reach a zone where green also disappears, and finally at the extreme periphery, we are totally color-blind, though still able to see the outlines of objects. Now all these peculiarities are accounted for by the arrangement and structure of the cones. In the yellow spot, which is the most favorable place for the perception of color, we find nothing but cones, very closely crowded togethcr, and comparatively very long. A little beyond the macula the rods, or elements of light, begin to make their appearance, and soon gain in numbers, until thev exceed the cones in the proportion of about three to one. As the cones become fewer and shorter the color-sense, as we have seen, becomes poorer, until at the region where we are totally color-blind, we find that the cones have altogether lost their outer limbs, and are otherwise degenerated. On the other hand, we find that as the rods gain in numbers over the cones, the light-sense is improved. This can be shown by means of a very simple experiment which anybody can make for himself. After turning off your gas, some dark night, fix your eyes suddenly on the window, at which a faint ray of light must be assumed to enter. You will not see anything, because you have looked at the window with the yellow spot. Now turn your head aside, so that the window will be seen with a part of the retina where the rods predominate over Ike cones, and at once the window will be quite distinctly visible. I have tried the experiment scores of times, invariably with the same result.

Still more decisive are the facts which we obtain from a comparison of the human retina with the retinæ of other animals. Most mammals have the same arrangement of retinal rods and cones as man, with the exception that they have no yellow spot. We may infer therefore that the lower mammals are inferior to man in the perception of color, at least in so far that the yellow spot is superior in this respect to the other parts of the retina. But there is one class of animals which have no need of a color-sense. These are the nocturnal animals, such as moles, mice, bats, etc. They have no need of a color-sense, because we know that even in the twilight colors already disappear, and only differences of light and darkness remain visible. We should therefore expect a correspond. ing difference in the arrangement and relative numbers of the rods and cones; and indeed the difference which we do find is very striking. All these animals of nocturnal habits have in their retina: immense numbers of rods, which must enable them to catch the faintest rays of light (as in our window experiment), but cones are entirely absent, since there would be no use for them in the dark.

Surely all these remarkable coincidences cannot be mere freaks of chance, and devoid of all meaning. Yet if any one should think so let him further hear what we have to say about birds. Natural history has supplied us with good reasons for considering the color-sense of birds superior to that of mammals; and this view is confirmed by comparative anatomy. While in mammals the general proportion of rods to cones is as three to one, in birds this proportion is reversed, so that we find a great many more cones than rods. And while the lower mammalians, with one exception, to be mentioned later, have no yellow spot, birds generally have its equivalent; and some which like the falcon are noted for their power of seeing objects at immense distances, even have two of these spots in each eye. And among birds there are also some species of nocturnal habits to which a color-sense would be useless, and whose retina accordingly present the same peculiarities that distinguish their colleagues of the mammalian persuasion. The owl is a good instance. Its retina contains immense numbers of rods, while the cones are rare, and so buried beneath the rods that they must be next to use less. In these few cones, however, are found little fatglobules of a lightyellow color, through which all rays of light must pass before reaching the outer limbs of the cones, which are supposed to be the sensitive parts. Since yellow disappears in the twilight last of all colors, it is probable that these globules exist for the purpose of collecting or intensifying the last traces of this color for the benefit of the owl on its nocturnal expeditions. Similar globules of various colors, such as light and dark green, yellowishgreen, yellow, orange, brown, red (carmine), light blue, or colorless, are found in the cones of other birds, varying with the species and with different regions of the retina,. As these globules are never found in the cones of mammals, man included, we may infer from this, either that the eye of birds is more specialized and therefore more perfect than the human, since each cone with them serves for the perception of only one color; or else we may infer that the retina of the birds is inferior to our own, on the ground that they may have a distinct perception of those colors only which are represented among the colored globules. Our data are insufficient to determine this point, but it appears to me that this line of investigation might help to decide the question of sexual selection over which Messrs. Darwin and Wallace are now breaking lances, and therefore deserves more attention than it has so far received. One thing, however, is clear. The occurrence of the colored fatglobules only in the cones and never in the rods, gives additional weight to the theory that the cones alone are the color-elements.

It may seem superfluous to adduce more evidence, but the chameleon is such a fine illustration of our theory, that I cannot resist the temptation to say a word or two about it. If there is any animal to which observation would induce us to ascribe a highly developed color-sense, it is the chameleon, which, being very sluggish, depends for its safety on its power of modifying its natural whitish tint to brown, yellow, bluish, or green, so as to bring it into harmony with its surroundings. And sure enough, in relation to the size, structure, and numbers of its cones, the eye of the chameleon is, for the perception of color, the most perfect organism known. Without having any idea of the difference in function between the rods and cones, and therefore free from subjective influences, H. Muller has left us a most minute and valuable description of the eye of this animal, from which we gather the facts that the whole sensitive region of the chameleon's retina contains solely cones, so that, so far, the whole retina is on a par with the yellow spot of the human retina. But this is not all. The cones of the chameleon are much thinner than ours, so that a great many more find place in the same space, and, in spite of the diminutive site of the chameleon's eye, they are longer than the cones in the yellow spot of man. And length, as we already know, is an advantage, since everywhere, in the macula of man, birds, etc., the cones are longer than in the peripheric parts.

Perhaps the reader is ready to object here that, after all, comparative anatomy leaves us in the same predicament as natural history; "we have only been collecting evidence that birds and the chameleon have a finer organ of color than the lower mammals." So we have. But in referring to the absence of the yellow spot in the retinae of the lower mammals, I said there was one exception; and it is on this that my whole argument is based. Were it not for this exception, the present article would never have bccn written; nor do I think that we could have ever determined the exact nature of the color-sense of prehistoric man, except in so far as the analogy with the visual powers of modern savages might warrant us in drawing an inference. The exception alluded to is our cousin, the ape. Monkeys are the only mammals, besides man, which have a macula lutea. And Max Schultze has ascertained that in every essential microscopic detail this macula is identical with the yellow spot of the human retina. Now, as we have seen that with our macula we can perceive all colors, it follows that monkeys must have the same power. That the same anatomical structure here implies the same physiological function is made certain by the curious fact that just as monkeys alone of the lower mammals have a yellow spot, so they alone of mammals resemble birds in being adorned in many cases with brilliant red, yellow, green, and blue sexual colors, which can have no other use than that of making the males conspicuous to their companions, or attractive to their mates. If, therefore, the color-sense of Homer and his contemporaries had been limited to an imperfect perception of one or two hues of the spectrum, their retina would have been inferior in anatomical development to the retina of monkeys, which, as every student of science knows, is impossible, since the macula could not have been lost and subsequently regained by man in so very brief a period. And thus our paradox, that the microscopic examination of the retinx of owls, bats, chameleons, monkeys, and modern Englishmen, enables us to determine the nature of the color-sense of prehistoric man, is shown to be a simple truth of science. To avoid misapprehension, let me add that, whatever may be thought of the origin of man's intellectual and moral faculties, the controversy in regard to his development from some lower animal form, as Mr. Wallace reminds us, is now almost at an end, since even Mr. Mivart, the distinguished Catholic anatomist, fully adopts the theory in regard to physical structure; and, as vision is a purely physiological process, the perception of color could not possibly form an exception. But even the small minority who may possibly still believe in the resurrection of the late specialcreation hypothesis would be loth to admit that the authors of the Old Testament were created with a less perfect retina than almost all other vertebrate, and many invertebrate, animals.

If, then, all these various considerations compel us to believe that prehistoric man cannot have essentially differed from us in his power of discriminating colors, the question nevertheless remains why the ancient writers, especially the Greeks, whose language is in other respects so perfect and so full of nice distinctions, should have been so slow in establishing a satisfactory chromatic nomenclature. I have, indeed, alluded to the absence of a scientific theory or classification of colors, and the paucity of abstract terms, as among the causes of this phenomenon; but it is evident that these causes must themselves be the result of some more profound reason. Why did the Greeks have but a few abstract terms for color, and why had they no satisfactory scientific classification of them? In answering this question we come upon the root of the whole difficulty. A mistake has been made, I venture to think, by all previous writers on this subject, in not distinguishinc, between the physical and the esthetic development of the color-sense. It is not the retina, the physical organ of color, which was defective two thousand years ago, but simply the esthetic taste for color. /Esthetic culture is a matter of intellectual training, and may therefore undergo great changes in a score of centuries; but the power of physically perceiving color is a result of anatomical structure, which could not be perceptibly modified within so brief a period. It may seem bold to accuse the Greeks, the esthetic nation jar excellence, of defective esthetic culture in regard to color; but my theory is in perfect accord with everything we know of Greek life and habits of thought. The Greeks did not care for color; it had not the charms for them that it has for us; and of this strange indifference we must now seek the real causes. Mr. Gladstone himself has written a most admirable passage, which, while not at all proving his own theory, so neatly fits in here that I beg leave to quote it. Among the factors which combined to retard the development — not of the organ, as Mr. Gladstone would have it, but of the esthetic taste for color, — were the following: —

The olive hue of the skin kept down the play of white and red. Their hair tended much more uniformly, than with us, to darkness. The sense of color was less exercised by the culture of flowers. The sun sooner changed the spring greens of the earth into brown. Glass, one of our instruments of instruction, did not exist. The rainbow would much more rarely meet the view. The art of painting was wholly, that of dyeing was almost, unknown; and we may estimate the importance of this element of the case by recollecting how much, with the advance of chemistry, the taste of this country in color has improved within the last twenty years.

Instructive as these remarks are, they nevertheless do not quite touch the bottom of the question. The fundamental cause of the Greek indifference to color was the anthropomorfihic tendency of the Hellenic mind. Impersonal Nature had not yet in the heart of Homer and his successors secured that sacred place which she has found in the heart of modern.poets; and in revenge she concealed her greatest charms, her beautiful hues and tints, from the eyes of the allpersonifying bard. The human element in natural scenery alone had an interest for the Greek. He transformed not merely the grand and awe-inspiring powers of nature into manifestations of a personal will, but he invested every river, brook, and fountain, every tree and every mountain, with a genius loci, a demon, a nymph, or some other male or female deity. This preference for the human element is shown in their literature and art as well as in their mythology. Epic and dramatic poetry, which have man for their subject, reached with them,a degree of perfection that has never been surpassed; while of the poetry of nature, of lyrical and descriptive verse, the best is decidedly modern, like the love of color. Descriptive poetry, indeed, as late even as Virgil, is extremely rare, vague, and imperfect. And the same may be said of Greek painting. In spite of the extraordinary stories told of some painters, artcritics are agreed that the pictorial art among the ancient Greeks was far inferior to the other plastic arts. They were ignorant of the more refined artistic uses of perspective; they had no oil-colors; and even as late as Alexander's time, black, white, red, and yellow were the only colors used in their paintings. The absence of green and blue might be attributed to the want of proper pigments, but it is evident that the ingenious Greeks, if they had really felt the need of such pigments, would have soon discovered them somewhere. Hence the absence of green and blue is more probably due to the fact that they are primarily the colors of nature, and were therefore not wanted, since in Greek paintings nature occupied as subordinate a position as it does in their literature. Looking at the whole matter in a philosophical spirit, we ought perhaps to be thankful that the laws of mental growth retarded the xsthetic development of the color-sense among the Greeks. For, in consequence of their indifference to color, the attention of their artists was almost entirely concentrated on beauty of form and proportion, which resulted in making them the greatest sculptors and architects the world has ever seen or perhaps ever will see.


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