Hill diarrhœa is a peculiar form of chronic looseness of the bowels that is not uncommon in the Himalayas, and, I believe, in other elevated regions. Certain people appear specially liable to it, much in the same way as some are subject to hay fever, while others are never affected; and the proclivity is so marked in some persons that it is impossible for them to reside in such localities, and they are hence debarred from taking refuge from the fierce heat of the plains. We are not very clear as to its causation, though the disease is traceable in some places to the presence of finely divided mineral matter (mica) in the drinking water, and so may be guarded against by careful filtration of all water used for drinking or cooking. The climate of the hills, again, though pleasant enough, is during the rains even more treacherous than that of the plains--damp cold, alternating with warmth; but withal, as has already been remarked, the disease is mainly one of personal proclivity, and where the tendency is very marked the only course is to avoid residing in places where it is apt to occur. Should you, when travelling in the hills, be attacked with this malady, careful filtration of water and care in diet should be attended to, and a pill or tabloid containing one grain each of euonymin, blue pill and ipecacuanha may be taken at night; but should the trouble persist, no time should be lost in returning, if possible, to within range of competent medical assistance, as if neglected, the disease is apt to develop into a most troublesome condition known as sprue. _Infantile Diarrhœa_ is terribly common in hot countries, and hence the least disturbance of this sort should never be neglected in young children. The rapid rise in the infantile death-rate that coincides with any approach to a tropical temperature in Europe, shows well how full of risk is a child’s tenure of life in latitudes where such temperatures are not the exception, but the rule. The liquid food, which alone is suitable to the infantile digestion, is perilously liable to decomposition when the temperature of the air rises much over 70° F., and, under such conditions, food which, to the nose and eye, shows no appreciable change, may yet be virulent with a poison as lethal in its effects as arsenic, and far more deadly, weight for weight. As a matter of fact, the poisons which may be generated in food subjected to high atmospheric temperatures, differ only from the most active of mineral poisons in their greater virulence, and to commence treatment in such cases with any agent that checks the action of the bowels ensures an unfortunate result with even greater certainty than if we were dealing with antimony or vitriol.