this will be understood to be that the colour vision is perfect, but the definition of form more or less imperfect. We are told that cases of this type have long been known and are comparatively common, and often favourable as regards recovery; that the mischief may affect one optic nerve, or both; that when both are diseased the malady is usually due to the action of some toxic substance, and that of all substances known to have this particular effect on the optic nerves tobacco is the most important. I dwell a little on this variety--damage to form and colour sense at the centre of the visual field of each eye from limited, and usually curable, disease of the optic nerve--on account of its interest to myself in the investigations I have made, and also on account of the degree of practical importance which it assumes in connection with the proper reading of signals and coloured lights. These cases of “tobacco amblyopia,” as it is pathologically called, are, of course, always found in men; and it may occasionally happen that such a man, if an engine driver, signalman, or a look-out man on board ship, may still see form sufficiently well to see his signals, but may mistake their true colours. From evidence given before the Committee of the Royal Society on Colour Vision, it appears that the disease causing this type of colour blindness is usually produced by the over-use of tobacco, aided by mental depression and a low state of health. As we have no sumptuary laws, cases of tobacco blindness must frequently occur, and it should be the care of all who have the management of railways or shipping to take measures for preventing persons suffering from this disease from occupying posts which require perfect colour vision in order to prevent the possibility of loss of life.