VERTIGO (Lat., a turning or Nvbirling round. giddiness, dizziness), DizzixEss. A eon dition characterized by an inability to maintain a due equilibriuM. Vertigo may be caused by un usual and powerful visual sensations, such as those produced by water falling rapidly from a great height, or by objects moving swiftly across the field of vision. In some cases the subject feels as though all the visible objects were passing rapidly before him; in other eases be feels as though he were falling in a certain direetion. Vertigo may arise from changes taking place in the brain, and, while in no sense n disease, is a common symptom of many di-seases and is a result of several poisons. An especially severe form of dizziness is produced by rapidly rotating the body. A rapid and distressing form is pro duced by sending a galvanic current through the bead from ear to ear. Vertigo caused by rota tion of the body is probably due to false sensa tion in the semicircular canals of the internal ear. It is known that variations in the pressure of the endolymph within the canals give rise to two kinds of impulses: the auditory impulses and a series of afferent impulses which, although conducted to the brain through the auditory nerve, have nothing to do with hearing, but form the basis of our sense of equilibrium. D1(miere's
disease, an affection of the semicircular canals, presents as its principal symptom a constantly recurring vertigo. Disease of the middle ear, and also rarely of the external is accompanied by the same symptom. Vertigo may be caused by an alteration of the intra•srauia1 blood-pressure. It occurs, therefore, in ana•mia, in hyperemia, in syncope, in epilepsy, in seasickness, in hyper trophy of the left ventricle of the heart, in in injuries of the brain, after the use of alcoholics, etc. Sometimes merely a sud den change of position causes it as bending for ward. stooping, rising. raising a weight above the head, or any sudden strain on the faculty of equilibration. Vertigo aecompanying indiges tion is due either to reflex circulatory distur banes in the brain, or to toxic influences, such as also accompany the use of alcohol, tobacco, bella donna, hyoscyansus, the inhalation of carbonic acid gas, etc.