There is nothing obscure about trigeminal neuralgia save its origin. The patient has made the diagnosis before the surgeon is consulted, and treatment, to be effective, must include either alcoholic injections or the radical operation. In these few words have been summed up the essential features of this unique lesion of the sensory system. True trigeminal neuralgia must not be confused with a peripheral neuritis initiated by some infective focus in tooth or sinus, or with the neuritis of toxic or obscure origin. One occasionally hears or reads of the cure of trigeminal neuralgia by the drainage of a sinus, by an intranasal operation or by the removal of an infected tooth. I have never seen or operated on a patient in a case of the major type of trigeminal neuralgia in which there was any reason to suspect any one of these lesions as the exciting cause. Were I