If attacked in this way in the leg, the swimmer must strike out the limb with all his strength, thrusting the heel downward and drawing the toes upward, notwithstanding the momentary pain it may occasion; or he may immediately turn flat on his back, and jerk out the affected limb in the air, taking care not to elevate it so high as greatly to disturb the balance of the body. If this does not succeed, he must paddle ashore with his hands, or keep himself afloat by their aid, until assistance reach him. Should he even be unable to float on his back, he must put himself in the upright position, and keep his head above the surface by merely striking the water downward with his hands at the hips, without any assistance from the legs. PROCEDURE WHEN IN THE WATER, AND USUAL MODE OF FRONT SWIMMING. _Entering the Water._ Instructors should never force young swimmers reluctantly to leap into the water. It would be advisable for delicate persons, especially when they intend to plunge in, to put a little cotton steeped in oil, and afterwards pressed, in their ears, before entering the water. This precaution will prevent irritation of the organ of hearing. In entering, the head should be wetted first, either by plunging in head foremost, or by pouring water on it, in order to prevent the pressure of the water driving up the blood into it too quickly, and increasing congestion. The swimmer should next advance, by a clear shelving shore or bank, where he has ascertained the depth by plumbing or otherwise, till the water reaches his breast; should turn towards the place of entrance; and, having inflated his breast, lay it upon the water, suffering that to rise to his chin, the lips being closed. _Buoyancy in the Water._ The head alone is specifically heavier than salt water. Even the legs and arms are specifically lighter; and the trunk is still more so. Thus the body cannot sink in salt water, even if the lungs were filled, except owing to the excessive specific gravity of the head. Not only the head, but the legs and arms, are specifically heavier than fresh water; but still the hollowness of the trunk renders the body altogether too light to sink wholly under water, so that some part remains above until the lungs become filled. In general, when the human body is immersed, one-eleventh of its weight remains above the surface in fresh water, and one-tenth in salt water.