The mode in which its power operates in the fulfilment of these results is by the production and maintenance of a healthy skin. A healthy skin I therefore assume to be the end and aim of the bath; and to support my argument it will be necessary that I should point out the importance of a healthy skin in the animal economy, and those conditions and circumstances of common life that tend to deteriorate its structure and function; to show, in fact, why the skin is worth preserving, and how its preservation in a state of health conduces to the health of the entire organism. The skin, from its large extent, deserves to be ranked among the great organs of the body, and belongs especially to that group that are commonly called emunctory--in other words, the cleansers or purifiers of the blood. In this sense it ranges side by side with the liver and kidneys; and, all things considered, it would be a difficult problem for any physiologist to solve, to determine which of the three deserves to stand before the others in importance. These three organs are sometimes called the scavengers of the body; and they may with considerable truth be regarded as three great and important systems of purification and drainage. Now, if to drain the system of its impurities, to cleanse and purify the blood of the animal economy, three grand systems of drainage are required, the inference is plain, that one would not be enough--that two might perform the office, but with a strain upon the machinery. But to be perfect, to perform the office completely and efficiently, to be, in fact, in health, to constitute health, all are needful. Therefore, if in the course of these observations I can show that one of these scavengers is weakened in its powers, and being weakened in itself, throws an additional degree of labour on the remaining two; if, in fact, our present mode of management of the skin tends to deteriorate its powers as a purifier of the body, and consequently produces a strain on the liver and kidneys, which leads to their deterioration and disease, I shall, provided I can also show that the bath preserves the health of the skin, make out a _primâ facie_ case in favour of the bath.