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so as to put Athe presbyopic correction on the affected eye, when distant vision with the other eye is desired; this is safe in the sitting posture, but not altogether secure for walking. This method has very likely been adopted by others in treating such cases, but if not, will be found of advantage in the earlier stages of such affections of the eye, till treatment medically or surgically has given relief partially or completely. (Borsch & Rommell constructed the spectacle for the cases.)

A NEW SERIES OF BERLIN WOOLS FOR THE SCIENTIFIC DETECTION OF SUBNORMAL COLOR-PERCEPTION (COLORBLINDNESS). BY CHARLES A. OLIVER, M.D., PHILADELPHIA, PA.

THE value of the study of the human color-sense as a means of detection of faulty development of the organs of vision, or of subsequent pathological change, cannot be overestimated when we think of the important r8le of action that color-vision plays in our daily routine. Not only is this true for the individual's benefit, as a source of exact knowledge for the determination of some congenital malformation conniected with the organ, or of giving a correct answer to the diagnosis, prognosis, and treatment of an acquired and vaguely symptomatic local or general disease, but it is equally applicable as a check to the danger imposed upon general communities who might be dependent for their lives and property upon the functions of imperfect visual organs placed in positions of

danger and trust. Casting aside all of the various theories of color-perception which have been evolved, such as-the Young-Helmholtz

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three-fibre theory, originating with Thomas Young in I792 (although claimed to be an outgrowth of Wiinsch's hypothesis), and modified by Helmholtz, Maxwell, Rahlmann, and others; the three-paired primary sensation theory of Hering, said to have found birth in Arthur Schopenhauer's theory of colorvision; Delbceuf's belief of retinal vibration; Salom's fancy of localized vibratory action in the macular region; the chemical chromatic and achromatic excitation of Wundt; Krenchel's movable color molecules situated in the cerebral color-centres; Preyer's paired Anachromatic and Katachromatic cones, etc. etc.; and discarding any allusion to the numerous hypothetical changes which are said to be productive of subnormal colorperception, we are brought to the question, how can lowered color-sense be best and most readily recognized. Practically there have been three methods. Fitst, Direct Comparison of Pigment Colors. This has been done by many contrivances; principal amongst them is Holmgren's method of loose wool selection, analogous to Seebeck's paper-test, and Wilson's worsteds. These plans have been modified by the assortments of fixed colors arranged upon cards, sticks, spools, discs, and other articles; the best known being the color-tables of Daae, von Reuss, and Roberts, the yarn covered spools of Schenkl, Donder's rolls of pseudoisochromatic wools, Thomson's stick, and the embroidery patterns of Cohn. The most serious objection to these modifications is, that in all fixed tests or plans where colors are made to relate to each other in any definite order, the method, if pursued amongst a great number of similarly placed individuals, is liable to become known, and rendered practically worthless. Again, another objection may be raised, that pseudo-isochromatic arrangements of wools upon cards, discs, sticks, spools, etc., are merely arbitrary with the surgeon, and do not by any means express the many percentages of lowered color-vision presented by the different candidates for examination, thus allowing numbers of persons affected with subnormal color perception to escape by reason of the confusion wools not being equal to the exact amount of resident color-error; and even a third difficulty may becited, when it is

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considered that the very process of fixation greatly limits the numbers of wools from which a choice may be taken. Another plan by the same method has been by means of colored powders. This has been pursued by Mauthner and Cohn, who make use of four-sided homeeopathic vials filled either with one color, a color and its shade, or two unmixed confusion or normal colors. They most probably suggested this procedure because Mauthner claims to have detected "color-blindness " by this plan in a patient who distinguished the color of yarns by the sense of touch. There can be no doubt that this assertion is in the main true, for Wartmann, as early as I849, after noting three references, mentions that a man with well-marked " color-blindness," "corrected by the help of touch a part of the erroneous judgments which he formed regarding colors; " whilst in I855 Wilson noticed that the first example of subnormal color-perception he ever encountered, possessed the same power to some extent. The latter author justly attributed this supplemental use of touch to delicacy of the tactile sense in discriminating between the harshness and smoothness of variously colored dyes, and says that "a wool dyed with a mineral green might thus be distinguished by the touch from one dyed with a vegetable, although the color-blind eye could detect no difference between their tints." In order to test how far this knowledge might interfere with selection by wools, the present writer, through the kindness of Dr. George C. Harlan, visited the "Pennsylvania Institution for the Instruction of the Blind^" and there met Mr. Battles, the Assistant Superintendent, and a Miss Townsend, one of the Instructors. They kindly gave him a vast amount of valuable information and the results of special research in this direction. In brief, their testimony showed that a few of the most intelligent and dexterous amongst the blind possessed the power of telling the dark-colored wools from the light ones, by a feeling of harshness of the dark skeins, although to obtain anything like a majority of properresults necessitated quite a long and frequent association amongst such objects. Curiously, some wools were detected by the sense of smell; the white ones having, as

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they termed it, "a woolly odor." 1 One experiment with anl intelligent blind woman, a native of China, who for many years had been a teacher in various institutions for the blind, showed that both she and the writer agreed in several instances as to the tint and shade of color in an ordinary set of Holmgren's wools, by the sense of touch alone, she strenuously denying any further attainment of powers than those which were elicited by touch and smell. This agreement of result is to be accounted for by the fact that the writer has been giving much of his time and attention to this question, which necessarily enabled him, by education of finer tactile differentiation in this direction, to cope with the person mentioned in the above experiment.2 In view of the above statements that it requires long training of the tactile and olfactory senses to arrive at any but an imperfect idea of the color of the dyed wools by touch and smell, associated with the fact that as a rule an untrained candidate is brought as it were into a new color sphere, where he must almost momentarily give decision, nullifies any practical objection to the use of the worsteds. These are three difficulties that arise from the employment of colored powders enclosed in glass. The first, which is the least important, is somewhat of the same nature as that which attends the selection of the wools. Chemists, dyers, and persons employed about color-laboratories, are enabled by knowledge of the appearance of coarseness and character of an enclosed powder, to ofttimes place it where it really belongs, even though it has not the proper color characteristic. The second is the same objection that was urged against having two colors fixed together for comparison, because many of Wilson quotes a Mr. Shirra as havina heard of a woman blind from infancy, who was enabled by her sense of feeling to distinguish many colors, white being known to her by its sulphurous odor. 2 Of course in this discussion, other characteristics, such as association, previous knowledge, and judgment, become important factors. Apropos of this, a few weeks ago, Dr. Harlan related to me quite an amusing anecdote of a blind man who pretended to designate color by touch. Experiment showed, to the wonder of all present, that he readily gave the colors of the coats of three persons merely by feeling the garments with his finger-tips. To the first he said, " You have a black coat! " to the second, " Yours is a blue one! " and to the third, " That is a gray! " It was afterwards discovered that he was made aware of the fact by correctly judging the colors, when he felt that the first was a frock coat, the second, one with brass buttons, and that the third was that of a

Quaker.

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OLIVER: Berlin Wools for the 254 the arbitrarily chosen colors do not express the exact grade of lowered color-sense of the examinate; thus in many instances permitting the colors to be readily differentiated. The third, which is of such a serious nature as to necessitate an abandonment of the plan, consists in the numerous changes of appearance that the enclosed color undergoes by the reflection of diffuse light from the glass surfaces of the containing vial. No matter in what direction the color may be looked at, there is more or less of a glare from the glass, which practically alters the intensity of the contained color, and gives a new quotient to its value-one often different from that which was intended. The third plan of selection by pigment colors combines many devices, foremost amongst the numerous collections being Seebeck's test-papers, Maxwell's and Woinow's revolving discs, the color-plates of Stilling, Hierlinger's and Magnus' tables, the Optotypi of Snellen, Kolbe's truncated cone, and Lip's Color triangle. The majority of these plans are open to the same objections of gloss, and errors arising from fixation and want of exact equivalence, that have been previously given. Second. Direct C(omparison of Specttral G:olor. In this method the two principal and most ingenious plans are combined in the Double Spectroscope of Hirschberg and the Polariscope of Rose. That the results by this method are valuable and interesting to the scientific student, cannot be denied, yet upon account of the expense of the apparatus, its complicated mechanism, its liability to get out of order, the necessary intelligence of the candidate in handling the instruments to produce proper results, and the differences between spectral and pigmernt colors (the latter being the ones with which the "color-blind" deals the more), it unfortunately cannot be brought into every-day employment as an ordinary test for the quick detection of lowered color-sense, although it most certainly can be made to serve an extremely uiseful purpose in cases requiring more thani ordinary observation, as in malingerer-s an(d perso0is under judicial actioni. 'i'/uiicl. Sed{jective AIter-color ( Comnplemientary Color). This method is merely mentionied as an ophthalmological

Detection of Color-Blindness.

255 curiosity, because, for several reasons, it is practically useless. Much interesting study has been expended upon it, and many contrivances have been made in hopes of making it useful. Instruments and devices to show, both "simultaneouscontrast" and "successive-contrast" have been devised, prominent amongst them being the Heidelberg Color-books, the Color-books of Pfliiger, Ragona Scina's Mirror-contrast adapted from Ossau's experiments, and Stilling's colored shadows, arranged by Holmgren into a single apparatus termed "Chromotoskiameter," and again modified by Cohn into his so-called "Chromaskiopticon." The most palpable objections that may be brought against this method, and which throw it out of competition with the other plans, are, in the first place, that we are dealing with subjective colors which are so vague and dependent upon so many idiosyncrasies, that no reliance can be placed upon the visible significance of their true character; again, that it must be remembered that all the experiments require the utmost care of adjustment, and that the least impropriety on the part of either the examiner or examinate utterly destroys the test: further, the old drawback of changeable luminosity is met, the moment artificial light is attempted; 1 and various thicknesses of tracing-paper or plates of colored glass of different intensities are employed; lastly, and this is the greatest error, if a "color-blind " is not wisely asked to matchi the contrast-color he sees with some known series of colors, such as wools, papers, etc., he will most probably escape detection, because it has long been known that the correct naming of color is a far different problem from the correct seeing of color.: Consequently, if this method compels a "color-blind" to compare color, as should always be done, the examiner might as well discard this series of difficult tests, and resort to the simple, more satisfactory and readily comprehended plans. Although these brief references do not by any means exhaust the armainentarium, yet the above contra-indications apply as equally to many of the absentees. 1 In fact, an absolute change of color-vibration. Pfloger well understood this when he made the patients match the colors,

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Of all the plans, that of Holmgren is by far the best, where actual comparison of color is intended to be made amongst large numbers, this being accomplished by the use of a series of cheap and easily handled Berlin wools. Here there is no complicated apparatus, no doubts arising from imperfect working-machinery, and nothing dependent upon faulty naming. In support of this, the writer cannot do better than reecho the statement made by Jeffries, that-" The whole recent widespread control of the chromatic defect on land and sea in Europe has come undoubtedly from Professor Holmgren having introduced a test for color-blindness, so simple, so perfect, and so applicable to the desired purpose as to render its use imperative, and its success a matter of necessity." The method itself is too well understood to need explanation, and needs no further recommendation or praise, but the writer in a desire to place the plan upon a more substantial basis, whereby the getting and proper registration of the color-sense may be quickly obtained, with as few loop-holes of error as possible; that mistakes which might arise from imperfect wool selection as to color, character of dye, and choice of material may be avoided; and that some definite grading as to the exact amount and character of lowered colorsense may be made common property throughout the ophthalmic world by a plan of naming, which although comprehensible to any instructed layman, is rendered unintelligible to the patient: these reasons, associated with the fact that this series has been so arranged that all of the employed colors have been made of relative equal intensities in order that really nothing but the question of color-matching is presented to the candidate, and which thereby throws out any chance of easy selection through shading- (which is the stronghold of the " color-blind "),-have induced him to bring before this Society a new series of loose wools based upon those of Holmgren, for the scientific detection of subnormal color-perception. In this set there are three series of color. First. Five principal test-skeins. These are pure colors. Latin names have been employed to represent them. Pure green has been styled " Viridis; " pure red has been termed

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"Ruber;" pure blue, "Coeruleum;" pure yellow, "Flavus;" and rose, "Rosa." These colors have all been made of equal intensities, by using the pure green as a sample, and making it correspond to the sample skein of Holmgren. They have not been designated in any manner, except by making them of large size. Second. A series of twenty small pure match-skeins. Each skein is either a pure tint or a pure shade of one of the large skeins. Each skein has a small black metallic bangle containing intaglio lettering, fastened to it. This inscription indicates that the attached skein is either a tint or a shade of one of the principal tests. The tints are numbered, first as Ti, which shows that the wool is a first remove lighter from the test-skein to which it belongs; and second, as T2, which shows that it is a second remove. The shades are marked either as Ui, which shows that the skein is a first remove darker than the test, or as U2, which shows that it is a second remove darker.' In addition, every such skein has the initial of the name of the principal test-skein to which it belongs, stamped upon its bangle. This series will thus include two pure tints and two pure shades of every principal skein, each having its proper designation. Third. A series of. seventy-two small confusion matchskeins. Each skein contains a mixture of certain definite percentages of light and shade of two of the principal skeins. Each has a bangle which shows that the skein is a mixture of two of the principal test-skeins, and that it is a certain remove of tint or shade. This has been done by having each bangle contain the initials of the two component principal colors (the presiding color being designated first), followed by the initial letter for the tint or shade, and its number. The wools are to be wrapped in a piece of black muslin, and will be enclosed in a black box, which will also contain an explanatory sheet with the colors arranged in their proper order, together with a book of instructions and a spectacle frame with a movable stop. l T (Tinctura) really signifies a tint or color, but is here used to designate a tint of color. U. (Umbra), Latin name for shade.

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In addition to all of the good qualities possessed by the Holmgren wools, the following additional advantages can be claimed in this series. I. Fire pincipalp tests. There have been, two pigment colors added; these are pure blue and pure yellow.' This has been done intentionally, in spite of the many theories that have been brought to bear for and against the admission of these pigments into the color-sense testing. For the present, theory has been discarded in favor of practice, because by long experience, both of these pigments have served as useful tests in the detection of the barely perceptible color-changes which occur in the incipient stages of optic-nerve disease. Pure green, pure red, and rose have been kept, for reasons already explained by Holmgren. 2. The wvools arc loose and separate. As has been previously shown, this is the only proper way, because not only has the candidate the entire mass of color from which to select, but there is absolutely nothing in his choice, by which judgment as to plan can be brought into play. In support of this assertion, Cohn in the description of one of his tests, states a fact, of which all practical ophthalmologists are aware, that every " green-blind " does not make the same mistakes, or does not go through any routine order of confusion colors. In addition, it may be stated that this rule applies equally as well to all forms of lowered color-sense. 3. 'The colors ari-e all of equal relative intensity. This has been done by having each principal test-skein of the same intensity,' as well as every related tint and shade, thus making the selection a question of color-choice alone. Here any interference to accuracy is avoided by'keeping free from the great power of skilful shading possessed by the " color-blind." This avoidance has not been accomplished by any other plan that the writer is aware of. Herein rests one of the greatest claims of this method for adoption. 4. Each test-skein has ils value expressed. Every skein beI The Rose (purple) test of this series has more red in it than is usually found in this sample amongst Holmgren's wools. This has been done so as to get all of the prlncipal test-skeins of the same degree of saturation and intensity.

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comes a unit of worth and is related in some definite place with every other skein in the test. This has been consummated by the selection of tints and shades of relative intensities of chosen pure colors, and by a system of bangles which have been rendered incomprehensible to all but the initiated. 5. It can be emirployed by any educated laiyma1.tn. By means of the bangles, the registry of the candidate's choice of the wools is an easy matter for any one who has been made acquainted with the techniiquze of the method. A brief and concise report of the selection can be copied upon a printed blank form, which can be sent to any authoritative person, by whom it can be studied, and the color-sense of the examinate properly and fully determined. This embraces the ingenious plan of Thomson. 6. Accurate notings Jf)atssino coloi-c/lianges can be preserved( ad ])ermanently keptforfieture comparison. This has been accomplished by the employment of the system of wool naming, and is of importance as furnishing means by which more accurate study of disease can be made, better notions of prognosis given, and more useful plans of therapeutics applied. 7. W'itten aind verbtal exrI-elsion of the character and nfollfnt * sbnaormal color-perception can be gi?ven. This will be valuable in affording the reader of any article or hearer of any paper upon this subject, more exact data in reference to the nature and degree of the various color-changes noted. The vague terms now employed in expressing lowered color-vision can, by this means, be discontinued, and determinations like those used for the acuity of vision, range and amount of accommodative action, intra-ocular tension, etc., readily substituted, thus rendering the suibject and its conditions at once clear and definable throughout ophthalmic writings. 8. All tle woofs ate (JI the same gr(ide (f* ianqJictutre. This is important, and destroys in measure any argument that can be urged against the employment of this material in colortesting, because by having them all of a similar nature, and alike in reference to the contained percentages of Lanolin (so-called Agnine), the chances for color-selection by the supplemental use of touch are greatly lessened.

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OLIVER: Detection of Co/or-Blindness.

9. All the colors are from vegelable dyes.' By attention to this fact, the question of any possible error that might arise either from harshness or smoothness of color-surface allowing detection by the sense of touch, is absolutely avoided. Besides, such colors are more lasting to light-exposure than aniline mixtures, and are not so subject to odor. i o. T he ?'se (f at black suiface or ground for lesting. By throwing the wools upon a black surface there is nothing but a display of color. We thus greatly avoid contrast and lessen any chance for the formation of subjective after-colors which are so apt to form in diseased visual organs. iI. Alny order of testing mtay be pursmed. This is done by naming, and not numbering the various tests. The green test (No. I. of Holmgren) is knowii as the V. (viridis) test; rose (No. II. of Holmgren), as the Ro. (rosa) test; red (No. III. of Holmgren), as the R. (ruber) test; blue, as the C. (cceruleum) test; and yellow, as the F. (flavus) test; these latter tests-the blue and the yellow-are also known as " confirmation-tests." By this nomenclature, any color may be taken first, and any order pursued, without hurting the results of the examination in the least. I2. Quantiitative determination as well ais qualitatite deter,ni'nationt obtained at one sitting. This for many reasons is invaluable, and has not been accomplished by any other method. The general plan of procedure is practically the same as that amongst the ordinary wools,-and it would be of no determinate value, except as a matter of precision, to enter into a detailed account of the method of examination and diagnusis in this series: this has been reserved for a book of instructions which will be published with the set. James W. Queen & Co., of Philadelphia, have gone to considerable expense and great difficulty in having all of the wools imported from a large European house. Sets can be procured in a short time. The writer will be pleased to assist any one in obtaining the proper selection of wools, and to give all the necessary information in reference to their manufacture. I Some of the dyes in the present invoice of wools are not vegetable in character, although differentiation by the sense of touch is impossible on account of the equal intensities. For this reason they have been employed, yet in order that the collection may be absolutely void of aniline material, particular attention will be paid to this question by the manufacturers in all future selections.

A New Series of Berlin Wools for the Scientific Detection of Subnormal Color-Perception (Color-Blindness).

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