“In luxations of the jaw (Chapter XII) the bone is always displaced forward; but sometimes only on one side, and sometimes on both sides. When the dislocation is only on one side, the chin and the whole jaw are found deviated toward the part opposite to the luxation; and the similar teeth of the two dental arches do not correspond; but instead under the upper incisors will be found the canine tooth of the dislocated part. If, however, the luxation is bilateral, the chin inclines and projects forward; the lower teeth are farther in front than the upper ones, and the muscles of the temples are tightly stretched. The reduction of the luxation must be performed as quickly as possible. The patient having been made to sit down, an assistant holds the head firmly from behind; or else the patient is made to sit with his shoulders against a wall, with a hard cushion between this and his head, whilst the assistant holds the head against the cushion, and so keeps it steady. Then the operator, after wrapping his two thumbs in linen cloth or strips, that they may not slip, introduces them into the patient’s mouth and, applying the other fingers on the outside, firmly grasps the jaw. Then whilst lowering the back part of the latter, he shakes the chin and pushes it upward and backward, seeking to shut the mouth, and in this way making the jaw return to its natural position. “The bone having been replaced, if the accident should have given rise to pains in the eyes and neck, it will be well to draw blood from the arm. After the luxation has been reduced, the patient must be nourished for some time on liquid food, and abstain, as much as possible, from speaking.” CAIUS PLINIUS SECUNDUS. After Celsus, a very celebrated writer on medicine and natural science was Caius Plinius Secundus. He was born at Como in the year 23 of the Christian era, and flourished from the days of Nero to those of Vespasian. Endowed with a liberal education, he gave himself up to public life, filling many important posts, among which, that of Governor of Spain under Nero and his successors. In the year 79 after Christ, while he was in command of the Roman fleet at Misenum, the tremendous eruption of Vesuvius took place, by which Pompeii, Herculaneum, and other neighboring cities were destroyed. Pliny, driven by the desire to study that marvellous and awful natural phenomenon, betook himself to Stabia, but was there suffocated by the ashes and smoke erupted by Vesuvius. In spite of the many places occupied by him, Pliny found time to write many works, and among these the thirty-seven books on _Natural History_, which have given him eternal fame.