In November, 1889, my attention was called to a rash occurring in diphtheritic patients treated with large doses of boracic acid. Dr. Sihler, in whose practice the cases occurred, informed me that it appeared after adopting the boracic acid treatment; he had never before seen the rash in diphtheria.
During the months of December, January and February following, I had the opportunity to follow five cases in the practice of the same physician. The onset, course and other clinical features of the rash appeared with marked uniformity. It made its appearance on the seventh or eighth day after the commencement of boracic acid. First on the forehead, neck and cheeks almost simultaneously; then it invaded the trunk and extremities in as many successive days. In its course it bore a close resemblance to rubeola. Nor was its course the only resemblance it bore to this disease; the rash itself in