Neuralgia major originates most commonly in the third division of the nerve, less frequently in the second, and rarely in the first. Whichever division be primarily affected, there is a very general tendency for other branches to become involved, and this in a very definite way--the pain spreading centrally from the nerve first involved, radiating to other nerve-trunks so soon as they shall be reached. Thus, pain originating in the inferior dental branch of the third division spreads to the lingual and other branches of that division and then involves the second division. Fortunately, whether the trouble originates in the third or second divisions, the ophthalmic tends to escape or to become less seriously involved--a fortunate circumstance considering the terrible conditions associated with neuritis of that nerve, the disastrous results on cornea, conjunctiva, &c. The disease is undoubtedly of a progressive nature, originating without rhyme or reason. It seldom becomes evident before the ages of 45 to 55, affecting both rich and poor alike. Wilfred Harris[69] collected 265 cases, and showed that the disease was slightly more common in men than in women--144 to 131. There appeared to be some predilection for the disease to involve the right side in preference to the left--179 to 80. In 6 cases the affection was bilateral. Trigeminal neuralgia does not in itself lead to fatal results, but the continuous pain, the want of sleep, and the difficulty experienced in taking sufficient nourishment soon reduce the patient to such a miserable condition that, unless relieved by the surgeon, amelioration is sought in morphia or release in death. Before proceeding further it will be convenient to enumerate certain points aiding in the differential diagnosis between the true and hysterical forms of trigeminal neuralgia. _True Neuralgia._ _Hysterical Neuralgia._ Patient old, probably over 50, Patient young, more commonly of the and more commonly of the male female sex. sex. Pain paroxysmal. Pain severe for long periods together. Vaso-motor, trophic and sensory All these changes very rare. changes common. Pain strictly unilateral and Pain variable in distribution, constant in site. radiating irregularly to the opposite side of the face. The =pathology= of tic doloreux is most obscure. The parts requiring examination are the peripheral nerve-trunks, the ganglion, the sensory root, and the central nervous system. The last two regions may be excluded, not only on the ground that research has failed to show any constant structural changes, but also because the removal of the ganglion may be regarded as curative of the disease. The ganglion itself and the peripheral nerve-trunks remain for investigation.