The term epilepsy was applied to a malady frequently studied but little understood by the ancient medical world, the chief symptoms of which were repeated tonic and clonic fits, preceded by the so-called "epileptic aura" and followed by a deep sleep. It was called _morbus sacer_ and believed to be of divine origin. Careful examination of epileptics by clinical and mental experts, showed that in addition to the characteristic seizure, these unfortunate beings were subject to other phenomena, which sometimes took the place of the convulsive fit and in other cases preceded or followed it. These were _pavor nocturnus_, sudden sweats, heat, neuralgia, sialorrhea, periodical cephalalgia and, above all, vertigo; and these symptoms were not always accompanied by unconsciousness nor followed by coma. Sometimes the seizure was only manifested by paroxysms of rage or ferocious and brutal impulses (devouring animals alive), which, if consciously committed, would be considered criminal. This fact led doctors and mental experts to examine other patients, and they were able to advance positive proof that a certain number of epileptics never experience the typical seizure, the disease being manifested in this milder form with cephalalgia, sialorrhea, delirious ferocity, and above all, giddiness. The multiformity of epilepsy has been fully confirmed by the experiments of Luciani, Zehen, and others, who produced various forms of epilepsy by submitting different cerebral zones to varying degrees of irritation. By graduating the electric current, Rosenbach was able to provoke the whole series of epileptic phenomena described above, from the mildest to the most serious manifestations. A slight irritation of the motor areas gave rise to tetanic contractions and clonic convulsions in a given joint; an increase in the strength of the current produced more violent movements which spread over the whole limb, and by intensifying the current still further, to half the body. Finally, on the application of a very strong current, the typical fit was produced with clonic spasms in all the body, unconsciousness, nystagmus, and rigidity of the pupils. By irritating the frontal lobes of dogs, Richet and Bernard produced vertigo and certain physical phenomena (snuffing, barking, and biting). Taking these investigations as a basis, Jackson came to the conclusion that epileptic fits are due to a rapid and excessive explosion of the grey matter, which, instead of developing its force gradually, develops it all of a sudden because it is irritated. And as it has been shown conclusively that the disease can be manifested in such varied forms--vertigo, twitching of the muscles, sialorrhea, cephalalgia, fits of rage, and ferocious actions--which appear to be the equivalent of the typical seizure, individuals subject to these forms of neurosis should be classed as epileptics, even if they never experience the typical motor attack.