He explained the uncertainty which continued to exist, as to the boundaries of the tract of country, in which the disease was rife; and then plunged into his argument. George, at this crisis, quietly took the opportunity of gliding from the room. Sir Henry stretched his legs on an ottoman, and appeared immersed in the study of a print--the Europa of Paul Veronese--which hung over the mantel-piece. "The Diario di Roma," continued the Doctor, "received this day, decidedly states that malaria is fearfully raging on the Neapolitan road. Pray forgive me, if I occasionally glide into the vulgar error, of confounding the disease itself, with the causes of that disease. "On the other hand, a young collegian, who arrived in Naples from Rome yesterday evening, states that he smoked and slept the whole journey, and suffered no inconvenience whatever. "Here two considerations present themselves. While sleep has been considered by the best authorities, as predisposing the human frame to infection, by opening the pores, relaxing the integuments, and retarding the circulation of the blood; I cannot overlook the virtues of tobacco, narcotic--aromatic--disinfecting--as we must grant them to be. "Here then may I place in juxta-position, the testimony of the Diario, and that of a young gentleman, half of his time asleep--the other half, under the influence of the fumes of tobacco. "Synthetically, I opine, that we may conclude that malaria does exist, and to a great degree, in the Campagna di Roma. Will you now allow me, to submit the question under dispute, to the analytic process? By many, in the present age, though not by me, it is considered the more philosophical mode of reasoning." "I am extremely obliged to you, Doctor," said Sir Henry, in a quiet tone of voice, "but you have raised the synthetic structure so admirably, that I think that in this instance we may dispense with your analysis. Pray proceed!" "Having already shown, then--although your kindness has allowed me to do so but partially--that malaria does indeed exist, it becomes me to show, which is the best mode of avoiding its baneful effects. "Injurious as are the miasmata in general, and fatal as are the effects of that peculiar form in this country, termed malaria; the diseases they engender, I apprehend to be rather endemic than epidemic. "It would be difficult to determine, to what part of the Campagna, the disease is at present confined; but I should certainly not advise you, to sleep within the bounds of contagion, for the predisposing effects of sleep I have already hinted at. "Rapid travelling is, in my opinion, the best prophylactic I can prescribe, as besides a certain exhilarating effect on the spirits, the swift passage through the air, will remove any spiculæ of the marsh miasmata, which may be hovering near your persons. Air, cheerfulness, and exercise, however, predispose to, and are the results of sleep: and to an invalid especially, sleep is indispensable.