I bring up for your consideration advisedly a time-worn subject like lupus erythematosus, a subject which has come up for discussion at almost every dermatologic congress during the last half century, because I am old enough in dermatology to have seen the question of its causation pass through a variety of phases, to have had a somewhat extensive experience in dealing with this disease, and to find in the contemplation of its etiology an indication of the newer paths along which progress is likely to be made in the elucidation of a number of baffling problems which at present cloud the dermatologic horizon. With the various types of this dermatitis and the histologic characteristics which underlie them, I am not here concerned, as they are so familiar as to require no reiteration, but with the etiology it is a different matter, as at present it is largely a matter of