The ancient doctrine of demons passed under the influence of Christian mysticism through certain changes and transitions, especially in its relation to the bodily condition of individuals. The variations in this doctrine were naturally most plainly evidenced in the medical views of the day. It was believed that every human being from birth was allotted a good and an evil demon. The good spirit held his hand protectingly over his human charge, whereas the evil demon only waited his chance to inflict injury upon man, forming especially the determining principle in the etiology of disease. It is true, the evil spirits apparently were no longer allowed to have such full sway over the health of humanity as they formerly had. God now utilized them principally as executors of punishments which he intended for mankind as a retribution for various forms of delinquency. Thus the Church Father, Anastasius (Sprengel, Vol. II., page 210), tells us that the reason why so many lepers and cripples were found among Christians was that God, enraged at the luxury of the members of the community, had sent the evil demon of disease among them. The wrath of God from that time until late in modern times has been considered a fully efficacious principle of pathology; in fact, there are numbers of people even to-day who believe that not natural, but supernatural and unearthly, factors are active in the bodily ailments of mankind. The idea of good and evil demons, however, now assumed a specifically Christian character which, it is true, greatly resembled the ancient Babylonian notion, excepting that the good demons were replaced by angels and saints, whereas the evil spirits were embodied in the devil. Both, saints as well as devils, were thenceforth destined to play a part in the domain of medicine. It is true, the general recognition which they enjoyed during the middle ages and a considerable period of modern times has probably now passed away, but there still exist numerous classes of our people in whom the medical rôle of saints as well as devils is most willingly acknowledged.