Volume 1

A dictionary of medicine : including general pathology, general therapeutics, hygiene, and the diseases of women and children / by various writers ; edited by Richard Quain ; assisted by Frederick Thomas Roberts and J. Mitchell Bruce.

Bruce J. Mitchell (John Mitchell), 1846-1929.

Date:: 1894

Credit: A dictionary of medicine : including general pathology, general therapeutics, hygiene, and the diseases of women and children / by various writers ; edited by Richard Quain ; assisted by Frederick Thomas Roberts and J. Mitchell Bruce. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

39/1258 (page 11)

$H constituent of the crust of favus (achor), and belongs to the group of fungoid plants denominated O'id/ium. It consists of spores, sporidia or tubes fiUed with spores, and empty branched tiibes or mycelium. Achorion was the first discovered of the epiphytes of the skin, and in compliment to one of its early observers, Schonlein, has been named AcJiorion Schonleinii. It is supposed to be the agent of contagion ia favus ; it has also been found in the loose cell-structure beneath the nail in onychogryphosis. Erasmus Wilson. ACHROMA {d, priv.; and xp^Mi colour). Absence of colour; an achromatous or colourless state of an usually coloured tissue, due to absence of pigment. In reference to the skin, achroma is synonymous with leucoderma, albinism, and alphosis. See PiGMENTAEY SkIN-DiSEASES. ACHROMATOPSIA, (a priv.; xp^t^a, colour ; and sight).—More or less com- plete inability to distinguish colomrs from each other. See Vision, Disorders of. ACIDITY.—Acids are constantly pass- ing out of the body by the lungs, the skin, and the kidneys. These acids, if we except the smaU quantity introduced from without in the form of acid salts of certain articles of food, are formed within the body by the disintegration and oxidation of the tissues and food. If the oxidation of organic sub- stances in the system were complete, the sole products of their combustion would be carbonic acid, water, and urea; but as this oxidation is never actually complete, other products, as lactic acid, oxalic acid, turio acid, &c., are formed; and the increased or diminished production of these intermediary products may be regarded as the measure of the completeness with which the oxidation processes are being performed in the body. The quantity of acid matter passing through the blood on its way to the lungs, the skin, and the kidneys is considerable; since it has been shown approximately, that a healthy man of eleven stone weight, under ordinary circumstances, passes by the first two chan- nels an average of 890 grammes (about 28 ounces) of carbonic acid daily, and that the acid excreted by the kidneys in the same period is equivalent to two grammes (about 81 grains) of crystallised oxalic acid; whilst the volatile fatty acids passing off with the sweat have not yet been satisfactorily calcu- lated. It is evident that if the regular elimi- nation of acids, by any of these channels, be interfered with, they will tend to accumu- late in the system. Acidity, or excess of acid in the body, therefore depends on two causes :—1. exccsswe formation, the result of incomplete oxidation of the elements of the tissues and the food; 2. deficient elimi- nation of acid formed either in normal or abnormal quantities. Both these causes however, are generally foimd acting in con- ji;nction. Oxidation is imperfectly performed when an insufficient quantity of oxygen is introduced into the body, owing to insuffi- ciency of the respiratory act, the result of disease or sedentary habits; or when the blood is poor in red corpuscles, the carriers of oxygen, as in leukaemia; or from func- tional derangement of some large gland, such as the liver, where oxidising processes are extensively carried on. Again, the materials submitted to the influence of the oxygen within the body may be so increased, as is the case in febrile conditions, or in general plethora induced by over-feeding and insuffi- cient exercise, that the supply of oxygen may prove insufficient for their complete combustion. Defective elimination of the acids formed within the body is due either to diseased conditions which prevent the lungs, skin, and kidneys from exercising their respective functions properly, or to want of the physiological stimulus which excites them. It will be seen, therefore, that acidity may arise in consequence of the disturbing influence of disease; or may be acquired or inherited as the penalty of transgression of certain laws of health—as the result of unfavom-able hygienic conditions. In the former case, acidity is only secondary, and is generally subordinate to the disease producing it, and has rarely to be considered apart from it; whilst in the latter instance acidity is usually at first the only trouble, leading, however, if disregarded to secondary mischief. Effects.—The mucous membranes and skin chiefly suffer in acidity. The former become subject to catarrh, produced, no doubt, by the irritating presence of the acid. Acidity may thus cause bronchitis, gastro- intestinal catarrh, and catarrh of the genito- urinary tract. Sometimes the acid is poured out in such quantities fr'om the mucous mem- brane of the stomach as to be ejected from the mouth. In these cases digestion is con- siderably interfered with by the too acid condition of the gastric juice. Sometimes, however, this acidity of the stomach is pro- diiced by an opposite condition—the defi- ciency of the digestive fluid, and consequent acid fermentation of the food. Abnormal acidity of the mrine not only produces catarrh of the urinary passages, but by decomposing the salts of lu'ic acid causes a deposit of insoluble uric acid in the passages, thus giving rise to attacks of gravel, or leading to the formation of a calculus. Acidity mani- fests itself in the skin by attacks of erythema, herpes, eczema, and m-ticaria. Eheumatism, too, may be considered as a disease resulting from the formation of acid, affecting chiefly fibrous and serous membranes; no one can witness the enormous quantities of acid sweat poured out, and the highly acid urine,$