NATATOR.—There have been many explanations of the cause of cramp while bathing, and it is not yet definitely settled which, if any, of these is correct. The most probable theory is that cramp is due to over-distention and paralysis of the heart. According to this hypothesis, the contact of the skin with the cold water causes all the blood-vessels of the skin to contract and so force the blood which was contained in them into the internal vessels. As more blood than usual will be thus thrown into those vessels which are deeply situated, the blood pressure will rise greatly. The heart has to overcome this pressure before it can drive the blood through the body. But if the pressure is exceedingly high, the heart may be unable to overcome it—a condition which means instantaneous death. But there are two conditions in which cramp occurs whilst bathing. In the first way, the instant the bather enters the water she is struck down by cramp, and if help is not instantly forthcoming she dies in a few seconds. In the second case, the bather is all right till she has been in the water perhaps half an hour; she is then gradually seized with cramp. Let us see if we can reconcile both these conditions to our heart theory? The first is obvious from the above. In the second case we must presume that although the blood pressure is raised, still the heart, being healthy and strong, can overcome it. But after half an hour’s violent exercise the heart begins to tire, and is now no longer capable of working against the great resistance. This form of cramp is therefore more gradual than the first; but both forms are necessarily fatal unless timely help is at hand. Most of the other theories of cramp refer the condition to temporary derangements of the nervous system, but Broadbent, the greatest authority on the heart, is much in favour of the theory we have just enunciated.