The effects of this procedure have been thought to depend upon the vascular relation between the affected organ and the adjacent skin surfaces. This explanation is applicable to superficial affections, intercostal neuralgia, etc., but does not explain the relief given in disturbances of deeper parts, which have an independent circulation.

A more recent explanation is that which has reference to the sensitiveness of the cutaneous nerves and their reflex action on the deeper parts. To this end areas of skin surfaces have been mapped out having such relations with the internal viscera, and both experimental and practical observations seem to confirm these relations, a single example of which is that between the kidneys and the skin of the lower lumbar region.

Counter-irritation is produced by anything that will cause a congestion or inflammation of the skin. The varying degrees of irritation are termed rubefacient, vesicant, pustulent, or escharotic action. The first, or mildest, is the most frequently desired, and is produced by dry heat, liniments, and stimulating paints or poultices.

Dry Heat is applied locally by hot water, sand, salt or bran bags, and by various hand stoves.

Liniments are valuable counter-irritants, and do good not only by producing rubefacient action, but by the massage used in applying them. Blistering with liniments is not advisable, hence most liniments should not be applied to the skin on cloths, and only the weaker liniments should be applied to young children. The official stimulating liniments, in the order of their strength, are: Linimentum Camphorae. Linimentum Saponis. Linimentum Chloroformi. Linimentum Ammoniac Menthol Preparations.

Iodine in the form of the tincture, is the paint most used for counter-irritant action. It is applied with a camel's hair brush, and the application is repeated daily, or at longer intervals, depending upon the reaction. It should not be used long enough to produce either blistering or leathering of the skin. Iodine ointment (Un-guentum Iodi) is also used, and may be applied twice daily for a long time without producing vesication.

Ichthyol is used as a counter-irritant, and there are various stimulating preparations furnished in collapsible tubes, the best of which are capsicum, and menthol preparations.

Mustard is a valuable popular rubefacient. A convenient form of application is by medicated papers which are sold in packages. A paper is moistened and applied to the skin with a single layer of gauze intervening. It is then covered with any protective material and left on for a variable length of time, depending upon the reaction, but to blister with mustard is not advisable, as such a blister is slow to heal.

Quite as commonly used is the home-made plaster, which is prepared from equal parts of mustard and flour (flaxseed meal is better, if at hand). The mixture should be stirred to a paste with warm, not hot, water, then spread upon an old piece of muslin or cotton and applied to the skin. It may be left on from fifteen to thirty minutes. A longer application is liable to produce blisters. If the application is to be made to a child, or to a very delicate skin, the proportion of flour or flaxseed to mustard should be three to one.

A Turpentine Stupe is prepared by wringing out a piece of flannel in hot water, folding it several times and sprink ling a half teaspoonful of spirit of turpentine upon it. It should be applied closely to the part, and, if a leg or arm, bandaged on.

Blisters have almost entirely been superseded by the Paquelin cautery, but when this instrument is not available they may be used in cases of deep-seated inflammation, to reduce swelling, to hasten absorption, to increase secretion, to stimulate the whole body (as in coma), in chronic inflammation of joints, in endocarditis, pericarditis, and pleuritis.

The plaster, or cerate of cantharides, is the agent generally used, and is the best. It should be kept on about five or six hours for an adult, and two or three hours for a child. Before applying the skin should be thoroughly cleansed, and shaved, if necessary.

A blister may be produced rapidly with chloroform. It is applied by moistening cotton with the chloroform, placing the cotton on the part, and covering it with oiled silk or a watch glass. A mixture of ammonia and lard, equal parts, will rapidly produce a blister, usually in five minutes.

Blisters should not be used on young children, on very old people, or when there is a great debility. They should never be applied over bony parts, or on parts subject to pressure, in the immediate vicinity of scar tissue, directly ever an inflamed part, or in diabetes, scurvy, purpura, or the acute exanthemata. Cantharides is contra-indicated in kidney diseases.

The Cautery at present used is either the electro-cautery or the Paquelin. The former consists essentially of a platinum wire, which is heated by the passage of an electric current. The temperature of the wire is governed by the amount of current passing through it, which is controlled by a rheostat. The apparatus derives its source of supply either from a collection of cells, or, more convenient when obtainable, from the street current. A handle conveniently shaped and containing a switch for opening and closing the circuit allows the operator perfect control of the instrument, and in this handle is inserted a cautery tip, i. e., the two wires carrying the platinum terminal. This latter is made in a great variety of shapes adaptable to the kind of work to be done.

The Paquelin cautery, named after the inventor, possesses the advantage of extreme portability and easy manipulation. In operation it depends upon the incandescence of platinum in the presence of a light benzine gas when the platinum has once been raised to the ignition point of the gas supplied. Several different varieties of this instrument are on the market. In using the cautery three degrees of heat are used: a white heat, which is least painful and most rapidly destructive to tissue, a red heat, which is the best for haemostatic purposes, and a very dull red, just off from the black, for counter-irritation. As a counter-irritant it is superior to blister ing, and when so used should be passed very rapidly over the skin, touching it lightly with a whipping motion. This properly done causes almost no pain and produces a scries of fine red lines which persist for some days.

Acupuncture consists in the introduction of needles into the tissues either for the purpose of giving exit to fluid, or to relieve pain in neuralgia and myalgia. The operation is said to have been introduced into Europe from China in the seventeenth century. From two or three to eight or ten needles are used, the size being somewhat larger than an ordinary pin. The skin, as well as the needles before they are inserted, must, of course, be surgically clean. They are introduced rapidly with a rotary movement, and cause little pain in their insertion. It occasionally gives almost immediate relief from pain, but quite as many times fails. When practiced for the relief of oedema, a three-cornered surgical needle gives better results than the smooth needle.