I have assumed for the skin the possession of a power of nutrition, and have in this way brought it into the category of the digestive organs; let me explain:--Nutrition, in its essence, is that interchange of material, by the influence of which the old material is removed and new material is deposited in its place. Now, the emunctory function of the skin obviously results in the removal of the old material from the body, and in proportion to the energy and completeness of its removal, will be the eagerness of the tissues to take up new material from the blood. If the skin be in the torpid and atrophied state I have already described as the consequence of our present habits of life, this source of interchange, of nutrition, will be valueless: but if, by improving the health of the skin through the agency of the bath, or by any other method that can be devised, we render its function more active and energetic, we necessarily make nutrition also more active and complete. The accomplishment of this object is the basis of that process known by the name of _training_, by which animals are brought into the highest state of condition and strength. It is for this that the racehorse is galloped, and sweated, and often purged; for this, also, the prize-fighter, the prize-rower, and the prize-cricketer are made to go through a similar ordeal. It requires little argument to show how admirably the bath is suited to this purpose; the sweating, the cleansing, the strengthening of the blood, are obtained in the bath, without effort and without exhaustion; and the system is brought into that state which, above all, is most favourable for the absorption of new and nutritious material. The bath has been already applied to the training of horses, and before long will be used in the training of men. The Romans kept their army in health and strength by means of the bath; and the bath might, on the same principle, be adopted with advantage under all those circumstances in which bodies of men are assembled together, temporarily or permanently, as in barracks, prisons, schools, factories, &c.