Small foreign bodies on the external surface of the eye, especially on the cornea, may escape notice unless a magnifying loupe is worn by the examiner and the illumination focused to a point with a strong convex lens. The use of these simple aids, or preferably the slit-lamp microscope, will allow detection of particles of extremely small size. Moreover, the focused beam of the slip-lamp parallelogram allows observation of the corneal depth which the foreign body has reached. The cornca is by far the most frequent site of location of foreign bodies as shown in an analysis of a series of 192 consecutive cases from an industrial plant which were observed personally (fig. 1 and the accompanying table). Foreign bodies are probably more frequent in the lower cul-de-sac than in the upper, but in the former location they may be removed by the lacrimal fluid or by the patient's own