IRIS, INFLAMMATION OF.—See EYE, DISEASES or.
IRON.—Iron as a metal is not used in medicine, but in the form of many of its soluble salts it has a very wide application. Iron serves a very im portant physiological function in the human body, being the active agent in the exchange of oxygen which takes place between the tissues and the air. It is found throughout the entire body, but is chiefly located in the hemoglobin of the blood. If for any reason the quantity of luemoglobin in the blood is diminished, a condition of anamia results. This condition may be primary, that is, due to disease of the blood-making organs ; or it may be secondary—i.e., due to detrimental influences acting on the entire nutri tion of the body, and particularly on the blood. full description of these conditions will be found in the article an A.N.Emt.t. Iron is of particular service in the treatment of secondary anemias, hut of less value in the primary anemias. It is thought that iron, on being taken into the body, is changed in the stomach into the form of a chloride of iron, and then modified into an albuminate. It is taken up by the epithelium-cells of the duodenum, enters into the portal circulation, and is stored up in the spleen, liver, and mesenteric lymph-nodes, from which places it is supplied to the rest of the body through the medium of the blood. The chief organ for the collection of iron is the liver ; and this organ serves not only to store up the iron, hut also to break it down, for large quantities of broken-down blood-pigment are found in the bile.
A number of iron preparations arc very active astringents, and are used to stop bleeding and to prevent mucous discharges. The majority of the iron salts are used as indicated in the treatment of altered conditions of the blood. Many of the iron preparations, \\lien taken internally, tend to produce constipation ; and many of the soluble preparations, particularly the chloride, are apt to stain the teeth when brought into contact with them. Iron, no matter in what form it is taken into the body, if able to be converted at all, can be utilised. The so-called organic irons arc no more efficacious than the inorganic.
ITCH, THE.—See SCABIES.
ITCHING.—This condition may be caused by various harmful agencies affecting the skin. Among the most frequent causes are -various kinds of vermin (fleas, bed-bugs, lice, etc.). Not only those places itch which arc bitten by these insects, but even remote parts may be affected. Spiders and hairy caterpillars, crawling over the skin, may give rise to similar sensa tions. Itching occurs also in a number of internal affections ; and it is a regular symptom in many skin eruptions, as eczema, nettie-rash, etc.
In a few skin diseases proper, the affection is a tormenting one, and can he relieved only by scratching. In one of these, called prurigo, the itching may begin in the first, year of life. An eruption of red spots and small pimples, which are scratched open immediately after they appear. This affection may persist throughout life, with occasional improvements during the summer months. The eruption is located principally on the front surfaces of the legs and on the outer surfaces of the arms, the inner surfaces remaining unaffected. Continued scratching causes the skin to become dry, thick, hard, of a brown discoloration, and covered with crusts. Owing to the constant irritation it frequently happens that eczema is superadded. This causes a crust to form, and increases the itching and the other symp toms. Frequent bathing and rubbing with simple ointment give slight relief.
A second variety of itching of the skin may be present without the pimples. It shows a similar location. Itching occurs spontaneously in different parts of the body, at first as a slight tickling sensation, which soon is intensified to such a degree that the unfortunate patient rubs the affected parts NVith his garments ; often, regardless of his surroundings, he may uncover his body to scratch himself with his nails. This nervous itching becomes especially obnoxious when it affects the genitals and the anus.
Here the skin becomes red and thick in consequence of the scratching ; eczema sets in ; and a mucous secretion takes place from the rectum and from the vagina. Parts of the skin affected by itching become darker in colour, and filled with bloody spots. These cases are best treated by a phy sician. Some alleviation may be obtained hv the use of cool compresses and baths, and by washing the parts with vinegar and water, diluted alcohol, or spirits of peppermint. In this affection it is important to consult a phy sician at the earliest possible moment. as the itching may be a symptom of an internal disease (for instance, of the stomach, intestines, liver, or kidneys, or of the female genital organs). Many cases arc due to the itch. See SCABIES.
JABORANDI.—See LOCAR PI: S.
JALAP.—The tuberous root of the /poniwn purga, a vine growing in Mexico. Its active principle is a resin known as corivo/ruhu, which is not unlike scammony. Jalap is a laxative producing a large, watery stool. An over-dose will cause violent vomiting and purging. It is usually given in combination with other drugs. Compound jalap powder contains five parts of jalap and nine parts acid potassium tartrate. This is frequently used in the treatment of dropsy. The dose is from 20 to no grains.