Those vessels of the body which draw off certain portions of the blood and change it into a new form, to be employed for service or to be thrown out of the body, are called secreting organs. The skin in this sense is a secreting organ, as its perspiration-tubes secrete or separate the bad portions of the blood, and send them off.

Of the internal secreting organs, the liver is the largest. Its chief office is to secrete from the blood all matter not properly supplied with oxygen. For this purpose, a set of veins carries the blood of all the lower intestines to the liver, where the imperfectly oxidized matter is drawn off in the form of bile, and accumulated in a reservoir called the gallbladder. Thence it passes to the place where the smaller intestines receive the food from the stomach, and there it mixes with this food. Then it passes through the long intestines, and is thrown out of the body through the rectum. This shows how it is that want of pure and cool air and exercise causes excess of bile, from lack of oxygen. The liver also has arterial blood sent to nourish it, and corresponding veins to return this blood to the heart. So there are two sets of blood-vessels for the liver - one to secrete the bile, and the other to nourish the organ itself.

The kidneys secrete from the arteries that pass through them all excess of water in the blood, and certain injurious substances. These are carried through small tubes to the bladder, and thence thrown out of the body.

The pancreas, a whitish gland situated in the abdomen below the stomach, secretes from the arteries that pass through it the pancreatic juice, which unites with the bile from the liver, in preparing the food for nourishing the body.

There are certain little glands near the eyes that secrete the tears, and others near the mouth that secrete the saliva, or spittle.

These organs all have arteries sent to them to nourish them, and also veins to carry away the impure blood. At the same time, they secrete from the arterial blood the peculiar fluid which it is their office to supply.

All the food that passes through the lower intestines which is not drawn off by the lacteals or by some of these secreting organs, passes from the body through a passage called the rectum.

Learned men have made very curious experiments to ascertain how much the several organs throw out of the body. It is found that the skin throws off five out of eight pounds of the food and drink, or probably about three or four pounds a day. The lungs throw off one quarter as much as the skin, or about a pound a day. The remainder is carried off by the kidneys and lower intestines.

There is such a sympathy and connection between all the organs of the body, that when one of them is unable to work, the others perform the office of the feeble one. Thus, if the skin has its perspiration-tubes closed up by a chill, then all the poisonous matter that would have been thrown out through them must be emptied out either by the lungs, kidneys, or bowels.

When all these organs are strong and healthy, they can bear this increased labor without injury. But if the lungs are weak, the blood sent from the skin by the chill engorges the weak blood-vessels, and produces an inflammation of the lungs. Or it increases the discharge of a slimy mucous substance, that exudes from the skin of the lungs. This fills up the air-vessels, and would very soon end life, were it not for the spasms of the lungs, called coughing, which throw off this substance.

If, on the other hand, the bowels are weak, a chill of the skin sends the blood into all the blood-vessels of the intestines, and produces inflammation there, or else an excessive secretion of the mucous substance, which is called a diarrhea. Or if the kidneys are weak, there is an increased secretion and discharge from them, to an unhealthy and injurious extent.

This connection between the skin and internal organs is shown, not only by the internal effects of a chill on the skin, but by the sympathetic effect on the skin when these internal organs suffer. For example, there are some kinds of food that will irritate and influence the stomach or the bowels; and this, by sympathy, will produce an immediate eruption on the skin. Some persons, on eating strawberries, will immediately be affected with a nettle-rash. Others can not eat certain shell-fish without being affected in this way. Many humors on the face are caused by a diseased state of the internal organs with which the skin sympathizes.

This short account of the construction of the skin, and of its intimate connection with the internal organs, shows the philosophy of those modes of medical treatment that are addressed to this portion of the body.

It is on this powerful agency that the steam-doctors rely, when, by moisture and heat, they stimulate all the innumerable perspiration-tubes and lymphatics to force out from the body a flood of unnaturally excited secretions; while it is "kill or cure," just as the chance may meet or oppose the demands of the case. It is the skin, also, that is the chief basis of medical treatment in the Water Cure, whose slow processes are as much safer as they are slower.

At the same time, it is the ill-treatment or neglect of the skin which, probably, is the cause of disease and decay to an incredible extent. The various particulars in which this may be seen will now be pointed out. In the management and care of this wonderful and complex part of the body many mistakes have been made.

The most common one is the misuse of the bath, especially since cold-water cures have come into use. This mode of medical treatment originated with an ignorant peasant, amidst a population where outdoor labor had strengthened nerves and muscles and imparted rugged powers to every part of the body. It was then introduced into England and America without due consideration or knowledge of the diseases, habits, or real condition of patients, especially of women. The consequence was a mode of treatment too severe and exhausting; and many practices were spread abroad not warranted by true medical science.

But, in spite of these mistakes and abuses, the treatment of the skin for disease by the use of cold water has become an accepted doctrine of the most learned medical practitioners. It is now held by all such that fevers can be detected in their distinctive features by the thermometer, and that all fevers can be reduced by cold baths and packing in the wet sheet, in the mode employed in all water cures.

It has been supposed that large bath-tubs for immersing the whole person are indispensable to the proper cleaning of the skin. This is not so. A wet towel, applied every morning to the skin, followed by friction in pure air, is all that is absolutely needed; although a full bath is a great luxury. Access of air to every part of the skin, when its perspiratory tubes are cleared and its blood-vessels are filled by friction, is the best ordinary bath.

Children should be washed all over, every night or morning, to remove impurities from the skin. But in this process careful regard should be paid to the peculiar constitution of a child. Very nervous children sometimes revolt from cold water, and like a tepid bath; others prefer a cold bath; and nature should be the guide. It must be remembered that the skin is the great organ of sensation, and in close connection with brain, spine, and nerve-centres: so that what a strong nervous system can bear with advantage is too powerful and exhausting for another. As age advances, or as disease debilitates the body, great care should be taken not to overtax the nervous system by sudden shocks, or to diminish its powers by withdrawing animal heat to excess. Persons lacking robustness should bathe or use friction in a warm room; and if very delicate, should expose only a portion of the body at once to cold air. But an evening or morning washing and friction of the skin will save from colds and many other evils.

Johnson, a celebrated writer on agricultural chemistry, tells of an experiment by friction on the skin of pigs, whose skins are like that of the human race. He treated six of these animals with a curry-comb seven weeks, and left three other pigs untouched. The result was a gain of thirty-three pounds more of weight, with the use of five bushels less of food for those curried, than for the neglected ones. This result was owing to the fact that all the functions of the body were more perfectly performed when, by friction, the skin was kept free from filth and the blood in it exposed to the air. The same will be true of the human skin. A calculation has been made on this fact, by which it is estimated that a man, by proper care of his skin, would save over thirty-one dollars in food yearly, which at 6 per cent. is the interest on over five hundred dollars. If men will give as much care to their own skin as they give to currying a horse, they will gain both health and wealth.