This epidemic derangement of the mind, to which the belief in demons tended, under the influence of Christian doctrines, culminated in the patient’s manifest idea that he was possessed of a demon. The mental disturbance set in with wild, spasmodic attacks of excitement, and, as it occurred not only in individual cases, but was also contagious, we must not hesitate to designate this belief of the first three centuries in demoniac possession an epidemic disease. It was an affection, the mental substratum of which consisted in a mixture of overheated religious sentiment and unrestrained medical superstition. The extent to which this belief in demoniac possession was disseminated during the first centuries of the Christian era is shown by the fact that a number of persons busied themselves with the cure of this affection. In the first place, most Christian communities owned an exorcist, or official caster-out of demons. It seems that this profession of exorcists formed a clerical order of its own; for, as all pagans, according to the Christian conception, were in the power of evil spirits, these demons were to be thoroughly driven out before each baptism, and thus the institution of a special church officer, whose duty it was to drive out demons, became absolutely necessary, especially after exorcism had also been introduced, during the fourth century, in the baptism of children. It may be stated, incidentally, that Catholic clergy of the third minor order are even to-day called “exorcists.” The Christian exorcists, in conjuring, only made use of prayer and of the name of Christ; these two factors were considered sufficient to cure the patient of his delusions, and they actually did so. Why they accomplished a cure has been explained very strikingly by Harnack. He says: “It is not the prayer that cures, but the praying person; not the formula, but the spirit; not exorcism, but the exorcist. Only in those cases in which the disease, as in numerous cases of the second century, had become epidemic and almost common, did ordinary and conventional means avail. The exorcist became a mesmerizer, possibly a deceived deceiver. But when strong individuality is deceived concerning its own personality by the demon of terror, and the soul is actually shaken by the power of darkness which possesses it, and from which it purposes to escape, a powerful and holy will alone can interfere from the outside world to deliver the shackled will. In some cases we find traces of a phenomenon which in modern times, for want of some better name, has been called ‘suggestion’; but the prophet suggests in a different manner than does the professional exorcist.”