Serious disturbances of fluid and electrolyte balance are frequently encountered in acutely ill patients; somewhat less often in the chronically sick. There seems to be a trend for such cases to increase, due probably to an increase in major surgical procedures on older patients whose renal function is less than adequate. There are already many publications dealing with the physiology of the homeo stasis of fluid and electrolytes, and others dealing with the clinical aspects of the subject. It is often assumed that a knowledge of the basic principles of physiology will enable the doctor to...