conditions are shown to differ in that dehydration is an important factor in the chronic state needing correction during reheating. The effects of slow and rapid reheating are compared in Case 2, and it is suggested that the rapid method, certainly the choice in acute hypothermia, is probably to be preferred in all cases of hypothermia uncomplicated by frost-bite. A rapid method of reheating, using a warm bath, is shown to be practical even in a small il-equipped fishing trawler, and if some similar device were fitted to sea-rescue craft many lives might be saved. Some aspects of heat production and heat loss in a Channel swimmer are discussed. I am indebted to Dr. Kenneth Robertson for permission to publish Case 1, and to Dr. R. Goldsmith, of the Medical Research Council Laboratories, Hampstead, for his generous assistance with the preparation of this article. I am also indebted to Miss. Florence Chadwick, without whose co-operation this article would not have been possible.