colors. But if we take the red and blue as the D colors, the D of the redgreen substance would produce red, its A green, and the D of the blueyellow substance would call forth blue, and its regeneration yellow. All the rays of the solar spectrum act in a dissimilating manner on the black-white substance: that is, they produce the sensation of white, but in different degrees, the yellow acting most powerfully, the others decreasing in power toward the two ends of the spectrum. On the blue-yellow and red-green substances there are certain rays which act in a dissimilating manner, some in an assimilating manner, and some not at all. If the A and D of the black-white substance are of equal intensity, the result is gray. If the A and D of the red-green and blue-yellow substances are equal, the result is negative as to color, and there only remains the dissimilating action of those colors on the black-white substance, that is white. (Amer. Jour. Med. Sci., Oct. 1880, page 532.) According to Hering, therefore, the so-called complementary colors are not complementary, but on the contrary, antagonistic. By their mixture they do not produce white, but being neutralized they allow the white sensation, which they all produce, in a greater or less degree, to come prominently forward. The phenomena of color-blindness, as based on this theory, are as follows: In the achromatrope all the rays of whatever refrangibility, acting in a dissimilating manner, white or its shade, gray, is produced. In the dichromatrope, besides the black-white there is only one other substance that can be acted on by the different color rays. If this is the blue-yellow (constituting red-green blindness), the red-yellow and green light act in a dissimilating manner, and the blue in an assimilating The most strongly dissimilating color is yellow; the others are varying sometimes the red is stronger than the green, and vice versa. To some of the light-waves at the red end of the spectrum, the colored as well as the black-white substance is insensible. In the same way, in case of blueyellow blindness, where there is only the red-green substance, in addition to the black-white substance, the red-yellow and blue lights act dissimilatingly, and the green assimilatingly. The D color is red, the A color green, and there are certain color rays at the blue end of the spectrum which do not act on either one of the substances. In this case we should have a shortening of the spectrum at the blue end; as in the former case, there would be a shortening of the red end. As an A and D of equal intensity of any onecolor substance would result in a total abolition of both colors, so where we have such an action in the case of a dichromatrope, there would be no color perception at all, but only the sensation produced by the action of light on the black-white substance, that is, gray. It is on this account that certain shades of color appear as gray to the dicromatrope. Purple and bluish green are the colors which most dichromatropes confound with gray; but as the dissimilative power of any is not the same in all dichromatropes, we should not expect to find, according to this theory, the same shades of those colors to be invariably confounded with gray. To one, a certain shade would

manner.

appear gray, which to another would be blue, and to a third yellow, owing, of course, to the preponderating color after the action of the opposing colors. "It will be seen, from this point of view, there can be but two forms of color-blindness, according as the one or the other of the color substances is lacking, but as such color substance, by its A or D action, represents two colors, a color-blind individual must be either a dichromatrope or an achromatrope. Hering, therefore, recognizes only red-green blindness, or blue-yellow vision, and blue-yellow blindness and red-green vision, and achromatopsia, or simply the perception of light and darkness." (See Amer. Jour. Med. Sciences, Oct. 1880, page 533.)

To my mind these theories seem ingenious but unsatisfactory. The latter is perhaps more serviceable as a hypothesis. The idea of the existence of separate nerve filaments for the conduction of the different waves of the base colors has no evidence in microscopic anatomy. Once accepted, we shall have a convenient hypothesis for explaining all the qualitative functions of the other cranial nerves. We can hold that the filaments of the olfactory nerves correspond in unlike character, and qualitatively to the different odors that excite them. The same reasoning would be applied to the auditory nerves, and to the gustatory branch of the pneumogastric. As to the different color zones of the retina, we can explain, by saying they are the result of chromatic aberration. The mind perceives the colors where they really are, as the shorter rays first come to a focal point, and then disperse in circular waves over the retina. Further, we know that perception is a mental operation, and is subjective, and not the act of nerve filaments of conducting nerve matter, but is the functional act of the brain cells in which they terminate. Whatever properties there are in objects and light, for the formation of color, must be differentiated by the mind, or that part of it with which the color sense is associated. Late researches show conclusively that the different functions of the mind are associated with different areas of nerve matter, of the cortical substance of the brain, and that the congenital absence of one of these centers, or its destruction by disease, will abolish some functional action of the mind. These areas have been mapped out with considerable certainty as centers of motion and sensation to the various groups of the muscular system; and other important functional areas have also been discovered, such as the speech center. Again, it has long been known that color, light and form have different areas of perception, and that both the perception of light and form can exist independently of the perception of color. The most reasonable hypothesis, or to my mind conclusive explanation of color-blindness, is, that it is a congenital defect, and results from the non-development of the area for the perception of color.

The influence of heredity on mental function has been greatly overlooked. I hold that mental power is both quantitatively and qualitatively more influenced by heredity than by outside influences or education. In a word, I hold that Lock's teachings as to the source of mental power are contradicted

by the heredity of genius, the heredity of crime, and all the phenomena of insanity. Color-blindness is, then, a congenital defect, a defect of involution, and consequently cannot be remedied by education. Several French writers have claimed that by systematic efforts the color sense could be developed in the color-blind, but it is evident from their writings that they have confounded a weak or impaired sense or knowledge of color with color-blindness. Persons who are slow and uncertain in designating color can be educated in chromatics, but the color-blind never. And here permit me to make an ob.. servation, in digressing from my subject; it is this: the hardest blow dealt to evolutionists theoretically is, that a qualitative mental function being absent, it cannot be developed by efforts at education; but if a mental characteristic exist, however weak and small, it may always be educated. Hence, it would seem that evolution must always be qualitatively what has first been involuted.

Let us now consider briefly the relation of color-blindness to railway accidents. It is well known that colored signals are absolutely necessary to the management of railways, particularly at night. It has been proposed to substitute form for light, for signals; but the appreciation of light is so much quicker and easier than that of form, that the change has been found impracticable. The ability, therefore, to determine the language of colored signal lights is absolutely necessary to train-men; and consequently, the safety of trains is endangered just in proportion to the number of employés who are defective in the color sense. The extent of this visual deformity can be tolerably accurately determined by statistics. "Dr. Fontenoy found thirty-one color-blind out of 1,084 railroad employés of Denmark, or 2.87 per cent. Prof. Donders, of Utrecht, Holland, found, among 2,300 railroad employés, 152 color-blind. Dr. Stetling, of Cassel, Germany, found, out of 400 railroad employés, six per cent. color-blind. Dr. Krohm, in Finland, found, among 1,200 railroad employés, sixty, or five per cent, color-blind. Dr. Holmgren found, among the employés on the railroads in Sweden, 4.8 per cent. color-blind." (Jeffries' Op. Cit., p. 143.) From the number of railroad employés tested for the color sense in Europe, and persons examined in this country in the schools, we can assert that there are five per cent. of the male population absolutely color-blind, and about five per cent. in addition who have an imperfect perception of color. It is also known that the majority of persons who have this defect are unaware of it, or do not know the extent of their deformity. It is apparent, therefore, that this imperfection must be a great factor in the production of collisions and other accidents on railways. On most railways, red lights signify "danger," white or yellow light, "track clear," and green light, at way-stations, "stop for orders." No person will deny that a certain number of accidents will happen from carelessness and inattention, especially where great numbers of persons are engaged; and if this is so, how can accidents fail to occur among a vast number of persons, of whom five per cent. are absolutely incapacitated for discharg

ing the duties assigned to them? That color-blindness is the source of accidents and calamities on railroads, in which property and life are sacrificed, is as apparent as any fact in pure mathematics.

How shall railway accidents and dangers be prevented? Simply by seeing that no men who have this visual defect be employed as train-men; that is, in the capacity of engineer, stoker, brakeman, conductor, or switch-man. This result can be secured by examinations, as first suggested by Wilson in 1855. It is accomplished, according to Prof. Holmgren's method, by having the person to be tested match colored worsteds. For the purpose of making the examinations, colored worsteds are procured, and placed in a pile on a table or large plane surface. The examinations are made in daylight. "The selection of worsteds includes red orange, yellow, yellow green, pure green, blue; violet, purple pink, brown, gray; several shades of each color, and at least five gradations of each tint, from the deepest to the lightest. Green and gray, several kinds each of pink, blue and violet, and the pale-gray shades of brown, yellow, red and pink, must especially be well represented.* The colors are divided into sample colors, consisting of green, purple and red, and confusion colors, made of every shade and tint of the solar spectrum. The first test consists in matching the sample green color. He who places besides the sample color one of the colors of confusion-that is to say, finds that it resembles the test color-is color-blind. He who, without being quite guilty of this confusion, evinces a manifest disposition to do so, has a feeble chromatic sense. Second test: A purple skein is presented. The color chosen must be between the deepest and lightest shades of the scale. Diagnosis: He who in the second test selects with purple only blue and violet, or one of them, is completely red-blind. He who in the second test selects with purple only green and gray, or one of them, is completely greenblind. Test third: The red skein is presented to the subject. It is necessary to have a vivid red color, like the red flag used as signals on railways. This test, which is applied only to those completely color-blind, should be continued until the person examined has placed beside the specimen all the skeins belonging to this shade, or the greater part, or else, separately, one or several colors of confusion. The red-blind then chooses, besides the red, green and brown shades, which to the normal sense seem darker than red. On the other hand, the green-blind selects opposite shades which appear lighter than red. Violet-blindness will be recognized by a genuine confusion of purple, red and orange, in the second test." (See "Color-Blindness," by F. Holmgren, page 185-Report of Smithsonian Institution, 1878.)

In conclusion, Mr. President, permit me to say that the principal object I have had in view in preparing this paper has been to interest this Academy in the subject of color-blindness, and through it the Legislature and his Excellency the Governor of the great commonwealth of Kansas. I believe that when this subject is properly presented to the legislators of your State, *The word purple here does not designate the color that has that name in this country. It is known to us as Victoria rose, and is said to be carmine diluted with white.

that some protective legislation can be secured against railroad collisions, so as to render transit on railways less perilous to life. I need not point out to you the numerous so-called accidents and catastrophes that have been chronicled in the United States during the present year. They are not altogether the result of carelessness or criminal negligence, as too often supposed, but result from the visual defect which I have just pointed out. As men of science, I appeal to you who can take a broader view of the subject than the employés of the railways, or even the men whose capital and wealth are invested in these corporations. I know that any legislation on this subject will be characterized as visionary, as yielding to the imagination of impractical men. But our mission is missionary. It is our duty to create, to mould public opinion, and not to vacillate before the scoffs and jeers of those who hold pure progressive science in ridicule. In many places in Europe stringent legislation exists in regard to the employing of the color-blind by railway corporations. In other countries, the railway corporations have provided the necessary safeguards without the compulsion of legislation. In our country, the National Government has not been slow to appreciate the importance of this subject. By order of the Surgeon General of the navy, all persons connected with the navy have been tested for the color sense, and a record of all defects of this kind are filed with the Department. I presume that Congress will be asked to order the discharge from the navy of every person found color-blind. Hon. John Sherman has issued orders to all inspectors of licenses to have all pilots of steam vessels tested for colorblindness, and to withhold licenses from all persons affected with this defect. In the army all recruits are examined, and all found color-blind are marked unfit for the signal corps.

The agitation of this subject has already commenced in several of our State Legislatures, thanks to the untiring efforts of Dr. Joy Jeffries, of Boston. Massachusetts is deliberating before and discussing the policy of legislation. Connecticut has already passed a stringent and ample law controlling railway corporations in regard to employing the color-blind. Its character may be inferred from the second section of the law, which reads as follows: "Any railroad company or trustee operating any railroad in this State, employing, after the first day of October next, in any of the capacities specified in the second section of this act, any person who does not possess a certificate of freedom from color-blindness, and possession of normal visual power, duly issued in accordance with the provisions of this act, or knowingly employing in any such capacities any person whose certificate has been revoked by the examiners, shall, for each and every offense, be punished by a fine of not less than two hundred dollars nor more than one thousand dollars." Approved March 25, 1880.

Mr. President, I trust the time is not far distant when the agitation of this law will invade this temple of justice and wisdom. From its sacred precincts numberless edicts have gone forth in defense of humanity, which have given