Arnauld de Villeneuve imagined that his foot had been bitten, and a pimple which broke out on the spot soon degenerated into a fatal cancerous affection. Corporeal night-mare may therefore be simply considered as a symptom of disease, and not as a mysterious forewarning. The cold stage of fever that often invades us in our sleep is the natural forerunner of the malady. This was the case with Dr. Corona, the physician of Pius VI. who upon two occasions was attacked with typhus fever, ushered in by a distressing dream or incubus. These physical phenomena only strengthen the opinion, that in our sleep we are equally alive to mental impressions and bodily sufferings; and that, correctly speaking, there is no suspension of our intellectual faculties of perception, nor is there any interruption in the susceptibilities of our relative existence. The various doctrines regarding dreams illustrate this position. INCUBATION OF DISEASES. The term "incubation" in its rigid sense applies to the act of hatching eggs, either naturally or artificially. It has however been adopted by physicians to denote that state of predisposition to disease, in which the germ of the malady lurks, latent and unperceived by the inexperienced observer. Too frequently the individual who is thus menaced is totally unaware of his condition. So far from being depressed in spirits, his hopes are more sanguine, and his future projects more industriously formed than usual. At other times, on the contrary, he labours under a load of despondency which he cannot explain, and his gloom seems to anticipate his end. This presentiment has oftentimes been singularly prophetic. Moreau de St. Remy relates the case of one of his most intimate friends, who visited him, saying, "I come to die near you." He was apparently in perfect health, but the prediction too soon proved true. It is no doubt probable, that in these cases the influence of the mind labouring under these fatal impressions brings about, by its all-powerful sympathetic power on our functions, the expected yet dreaded event. Incubation is observed in many contagious affections; and in hydrophobia its duration is amazing, this dreadful malady developing itself years after the original accident. In mental diseases, aberrations of the intellectual faculties are noticed long before the patient can be pronounced insane; oddities, as they are called, are frequently the precursors of mania. The ancient Greeks and Egyptians use the term "incubation" in another sense. With them it expressed the religious ceremony of sleeping in the temples of the gods, to be inspired with the means of relieving their sufferings. Nothing can express this superstitious rite more forcibly than the following letter from Aspasia to Pericles, recorded by one of the scholiasts of Aelian.