Morning journal and courier., 1880-08-12
COlOr-BlindneSs.

A Letter From Surgeon J. F. Head of the United States Army.
 To the Editor of the JOURNAL AND COURIER:
 A correspondent in your city has sent to me number of slips relative to the examina- tion of employees in Connecticut, most, if not all of which are from the JOURNAL AND CoUR TER. The complaints of the men as to the tests used are seemingly so reasonable, and the practical reasons for these tests are so little understood in the community at large, that> as the nature of my duties has necessita- ted certain degree of familiarity with the subject, respectfully ask space for some ob- servations, which you will allow me to pre- face by stating that both of the medical ex- aminers are personally unknown to me, and that it is quite impossible for me to derive any pecuniary benefit from the Connecticut or any other examinations.
 One of the extracts says that ''Dr. B. Joy Jeffries succeeded in impressing his theories on sufficient number of the members of the Massachusetts Legislature, and the Railroad Commissioners of that State were ordered to inquire into the matter. * In addi- tion to reporting that they had not been able to find that any railroad accident had ever been caused by color blindness, the Massa- chusetts commissioners, very sensibly, as 1t seems to us, reported that the extent of dan gerous color-blindness has been greatly exag- gerated, and that examinations may be prop erly made by persons not medical experts, and that such examinations will certainly be sufficient, if doubtful cases are referred to such experts"
 Dr. Jeffries has never uttered nor sustained any sstheories" on the subject in question. He has simply collected and presented facts, and urged them upon the attention of the people and their representatives both in the State and national governments This he has done, at great expense both of time and labor, pro bono publico personally making many thousands of examinations in the public schools and elsewhere without any pecuniary compensation.
 One of the facts presented is this Not far from four per cent (about one in every twenty -four) of males are unable to distin- guish red from green. The assertion of the Massachusetts Railroad Commissioners, ''that the extent of dangerous color blindness has been greatly exaggerated, '' rests upon evi dence whatever. More than one hundred and fifty thousand examinations all over the world have shown the extent of this defect to be as above stated. There is no reason to suppose that railroad employees differ in this respect from the mass of mankind. The two colors named being used to denote respect ive1y danger and safety" the importance of the defect in it's relation to life and prop erty is obvious. The community has the r1OlG to f6QQ1T6 dDSO1ub6 dSSuTduCo Gudb dll who have to do with these signals shall be able to distinguish them instantly, unerringly and always The employees have an equally unquestionable right to demand that such tests only shall be used as will infallibly select those, and those alone, who cannot so distinguish them-in other words, practical tests.
 Testing with the flags and lanterns ordina- rily used upon the road would at first sight appear to answer these conditions But apart from the time which such examinations would consume, and the consequent enor- nous increase of expense, there are other ln- superable practical objections to the method. It certainly Gf we. exclude the chances of guesswork )shows whether at the time of trial and in the then existing conditions, the ex- aminee distinguish given green object from a given red one. This in fact may per haps be done by completely color-blind man nine times in ten. The tenth time, how ever, like the fatal ball in Der Freischutz, may come in anywhere. The color-b1ind man really sees red and green as different shades of the same distinguishing them, when displayed separately, by extrane- ous circumstances as in daylight by compar- ison with other objects of known color, and at night by the different intensity of the lights When these helps fail him Gas they all may do at any time) he is liable to fatal error. The utter uselessness of this so called
 9OoS OCOAA Europe, and no one there now ever thinks of using it.
 The officer controlling the medical examin- ations on the Swedish railroads has devised a test equally expeditions, simple, easy and practical. It is known as ssHolmgren's wor- sted test' By it's use, which does not re- quire, as many seem to suppose, any accu- rate discrimination of delicate shades, the color-blind person, by character istic errors (not by every mistake) in select ing coIors, infallibly betrays his defect while those who are able to distinguish red from green prove their capacity with equal certainty Its efficient use doubtless requires special knowledge and no little experience; but this is true of all tests. Among the methods of control or checks upon the wor- sted test, is one proposed by the chief rail road surgeon of Holland-'Donder' IS method 1 by transmitted light" The apparatus con- sists substantially of miniature lantern, in | which the color of the glass, it's size and the I intensity of the light can be changed at will, either separately or together. It's fairness 1 and it's perfectly practical character will be at once recognized by any one (not color -blind) l who inspects it. When the requisite changes (imitative simply of different aspects of rail road lanterns) are made in it, the dangerous