to one and all.  No; idiosyncrasy, that personal peculiarity which makes each individual different from every one else, is too potent a factor to be ignored.  In matters of this kind, each one, to a certain extent, is a law unto himself, and, consequently, what agrees and what disagrees is only discoverable by the individual concerned.  In what follows, therefore, I have endeavoured to lay down rules for guidance which will be beneficial to by far the greatest number; although this element of the Ego must never be forgotten.

CHAPTER III.

ABLUTION—­THE SKIN AND THE BATH.

It has been estimated that the external skin of an ordinary adult is equal to an area of about twelve square feet, and that in a tall man it may be as much as eighteen square feet.  There is a considerable difference between twelve square feet and twelve feet square, and it is well to mention the fact in order that there may be no confusion.  From this large surface alone, therefore, it is quite easy to see that the skin requires to have some attention paid to it.  But it is really far more important than even its extensive surface would be likely to indicate, for it fulfils no less than seven different duties.  In the first place it serves as an external covering to the body, and, as we shall see also, the internal skin acts as a support to the internal organs.  Secondly, it is endowed with an extensive system of nerves, which give rise to the sensations of touch, of temperature, of pressure, and of pain.  In this way we can tell whether a substance is rough or smooth, and whether it is hot or cold; we recognise, moreover, the difference between a gentle pressure of the hand and one so forcible as to cause pain.  Thirdly, the skin, as we shall find farther on, contains thousands of small tubes for the purposes of perspiration, and besides this, there are other tubes secreting, an oily substance.  Fourthly, the skin plays an important part in regulating the temperature of the body.  Thus in a warm atmosphere the skin becomes reddened and moist, and much heat is lost; on the other hand, when the air is colder the skin becomes pale, cool, and dry, thus conserving the body heat.  Fifthly, the respiratory action of the skin must not be forgotten, although it is nothing like so great as that of the lungs.  Nevertheless quite an appreciable amount of oxygen is absorbed through the skin, and beyond all question carbonic acid is exhaled from it.  Sixthly, it is an absorbent; that is to say, the skin is capable of absorbing into the body certain substances applied to it.  In this way remedies are often introduced into the system by what is known as inunction.  And lastly, the skin is a great emunctory, and carries off waste matters from the body.  Accordingly it acts as a purifier of the blood, in which it assists the kidneys, intestines, and the lungs.  And more than this, it often happens that the turning point in any disease is announced by a sudden, profuse, and markedly offensive perspiration, as if a considerable amount of deleterious and noxious matter has suddenly expelled from the system.