In its later stages, this is one of the worst forms of disease. It is often said to be caused by “cold.” There can be no doubt but what a person whose kidneys are already badly diseased, and, consequently, his whole system depraved, may have a violent illness excited by extreme exposure to wet and cold. The same may be said in case of one reduced by any exhausting form of disease; but sound-bodied men, living hygienically, could never have this disease, whatever the degree of cold they might have to endure. On the contrary, this disease is not known among the residents of the polar regions; our own explorers among the ice-fields of the north do not have it, although exposed for long periods to a temperature at 40° to 60° F. below zero, and to changes of so extreme a character that our temperate climate affords no parallel to them. “In the accounts of Arctic expeditions, though the most intense cold was often endured, under circumstances of great fatigue, by men previously weakened by disease and hardship, this is not among the diseases from which they suffered. Dr. Kane’s men, though enduring extreme cold, exposed on one occasion for seventy-two hours at a mean temperature of 41° below zero, suffered fearfully from frost-bite and scurvy, but not from any renal affection. Other travelers within the Arctic circle bear the same testimony, and I have been informed by those familiar with the cold districts of North America, that there renal dropsy is unknown.”[41] “The travelers in the frigid zone are exposed to far greater and more sudden transitions of temperature than are ever felt in our changeable but temperate climate. Capt. Parry states that his men often underwent a sudden change of 120°, in passing from the cabin of the vessel to the outer air, and yet none but the most trifling complaints resulted. Here we have all the circumstances from which experience would lead us to anticipate renal disease, viz.: great preceding depression, intense and protracted cold suddenly applied.... Extreme cold,” continues Dr. Dickinson (ibid.) “though it may stop cutaneous exhalation, probably does not allow the material that would cause renal inflammation to accumulate. Cold increases the action of oxygen and gives rise to increased combustion of the solids and fluids of the body. This condition, as I have emphasized elsewhere repeatedly, occasions a demand for a large amount of food daily, to supply the waste, and exalts the digestive powers correspondingly. The moral of all this, for those who, living in a temperate climate, would avoid these disorders——all physical disorders, indeed——is that _here the above conditions can not obtain to the extent of rendering possible the digestion_ and _absorption_ of _three full meals a day_. Only under exceptional circumstances are _two_ such meals ever thoroughly digested and assimilated——they can never be, unless needed; and this fact is not disproved simply because inexperts do not recognize the symptoms of