Colour-Blindness. By F. W. Edridge-Green, M.D. (Began Paul, Trench, and
Co. 5s.)—This book, one of the "International Scientific Series," has, we are glad to see, reached a second edition. Now and then we should counsel some reserve in accepting Dr. Edridge-Green's conclusions, but his book is one of much value, and should be practically helpful in a matter of much importance. The proportion of colour-blind persons is about five per cent. among men,—among women it is quite insignificant. Now and then it will happen that some one with this defect will be put into a post where it means danger to the community, the post of engine-driver or pilot, for example. How is the flaw to be detected ? That seems simple enough, but it is really of great difficulty. The coloured-wool test, for instance, may fail because the person examined can distinguish between the different threads by texture. Some dyes give the wool a different feel. Coloured glasses are better ; but then there is the consideration of distance. However, the subject eannot be discussed here; anyhow, we can commend Dr. Edridge-Green's book to the attention of our readers.
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