Page:EB1911 - Volume 08.djvu/617

 would, therefore, speak an octave higher than a cylindrical drone of the same length. The drones are tuned by means of sliding tubes at the joints.

The drones of the old French cornemuse played in concert with the hautbois de Poitou (see ), and differing from the shepherd’s cornemuse or chalémie, formed an exception to this method of construction, being furnished with double reeds like that of the oboe. The drones of the musette and of the union pipes of Ireland are also constructed on an altogether different plan. Instead of having long cumbersome pipes, pointing over the shoulder, the musette drones consist of a short barrel containing lengths of tubing necessary for four or five drones, reduced to the most compact form and resembling the (q.v.). The narrow bores are pierced longitudinally through the thickness of the barrel in parallel channels communicating with each other in twos or threes, and so arranged as to provide the requisite length for each drone. The reeds are double reeds all set in the wooden stock within the bag. By means of regulating slides (called in English regulators and in French layettes), which may be pushed up and down in longitudinal grooves round the circumference of the barrel, the length of each drone tube can be so regulated that a simple harmonic bass consisting of the common chord is obtainable. In the union pipes the drones are separate pipes having keys played by the elbow, which correspond to the sliders in the musette drone and produce the same kind of harmonic bass. The modern Egyptian arghool consists of a kind of clarinet with a drone attached to it by means of waxed thread; in this case the beating reed of the drone is set in vibration directly by the breath of the performer, who takes both mouthpieces into his mouth, without the medium of a wind reservoir. Mersenne gave very clear descriptions of the construction of cornemuse and musette, with clear illustrations of the reeds and stock. There are allusions in the Greek classics which point to the existence of a pipe with a drone, either of the arghool or the bagpipe type.

 DRONFIELD, an urban district in the north-eastern parliamentary division of Derbyshire, England, 6 m. S. of Sheffield, on the Midland railway. Pop. (1901) 3809. It lies on the small river Drone, a tributary of the Rother, in a busy industrial district in which are numerous coal-mines, and there are iron foundries and manufactures of tools and other iron and steel goods. The church of St John the Baptist, with a lofty spire, is a good example of Decorated work, with Perpendicular additions.

 DROPSY (contracted from the old word hydropisy, derived from the Gr.  ; , water, and  , appearance), the name given to a collection of simple serous fluid in all or any of the cavities of the body, or in the meshes of its tissues. Dropsy of the subcutaneous connective tissue is termed oedema when it is localized and limited in extent; when more diffuse it is termed anasarca; the term oedema is also applied to dropsies of some of the internal organs, notably to that of the lungs. Hydrocephalus signifies an accumulation of fluid within the ventricles of the brain or in the arachnoid cavity; hydrothorax, a collection of fluid in one or both pleural cavities; hydropericardium, in the pericardium; ascites, in the peritoneum; and, when anasarca is conjoined with the accumulation of fluid in one or more of the serous cavities, the dropsy is said to be general (see also ).

Dropsy (excluding “epidemic dropsy,” for which see below) is essentially a symptom and not a specific disease, and is merely an exaggeration of a certain state of health. Fluid, known as lymph, is continually passing through the capillary walls into the tissues, and in health this is removed as fast as it is exuded, in one or more of three ways: part of it is used in the nutrition of the tissues, part is returned to the general circulation by the veins, and part by the lymphatics. Any accumulation constitutes dropsy and is a sign of disease, though not a disease in itself. The serous effusions due to inflammation are not included under the term dropsy. A dropsical fluid varies considerably in composition according to its position in the body, but varies only slightly according to the disease which has given rise to it. Its specific gravity ranges between 1008 and 1018; the mineral salts present are the same and in about the same proportion as those of blood, nor do they vary with the position of the exudation. The quantity of albumin, however, depends much on the position of the fluid, and slightly on the underlying disease. In oedema the fluid contains only traces, whereas a pleural or peritoneal effusion is always highly albuminous. Also an effusion due to heart disease contains more albumin than one due to kidney disease. In appearance it may be colourless, greenish or reddish from the presence of blood pigment, or yellowish from the presence of bile pigment; transparent or opalescent or milky from the presence of fatty matter derived from the chyle. The membrane from which the dropsical fluid escapes is healthy, or at least not inflamed, and only somewhat sodden by long contact with the fluid—the morbid condition on which the transudation depends lying elsewhere.

The simplest cause of dropsy is purely mechanical, blood pressure being raised beyond a certain point owing to venous obstruction. This may be due to thrombosis of a vein as in phlegmasia dolens (white leg), retardation of venous circulation as in varicose veins, or obstruction of a vein due to the pressure of an aneurism or tumour. Cardiac and renal dropsy are more complicated in origin, but cardiac dropsy is probably due to diminished absorption, and renal dropsy, when unassociated with heart failure, to increased exudation. But the starting point of acute renal dropsy, of the dropsy sometimes occurring in diabetes, and that of chlorosis is the toxic condition of the blood. For accounts of the various local dropsies see ; ;, &c.; general dropsy, or dropsy which depends on causes acting on the system at large, is due chiefly to diseases of the heart, kidneys or lungs, occasionally on lardaceous disease, more rarely still on diabetes or one of the anaemias.

Broadly speaking, 50% of cases of general dropsy are due to disease of the heart or aorta, and 25% to renal troubles. The natural tendency of all diseases of the heart is to transfer the blood pressure from the arteries to the veins, and, so soon as this has reached a sufficient degree, dropsy in the form of local oedema commences to appear at whatever may be the most depending part of the body—the instep and ankle in the upright position, the lower part of the back or the lungs if the patient be in bed—and this tends gradually to increase till all the cavities of the body are invaded by the serous accumulation. The diseases of the lungs which produce dropsy are those which obstruct the passage of the blood through them, such as emphysema and fibrosis, and thus act precisely like disease of the heart in transferring the blood pressure from the arteries to the veins, inducing dropsy in exactly a similar manner. The dropsy of renal disease is dependent for the most part on an excess of exudation, due largely to an increase of arterial and cardiac tension. This in its turn produces arterial thickening and cardiac hypertrophy, which, if the case be sufficiently prolonged, brings about a natural removal of the fluid. In kidney cases, in the absence of cardiac disease, the dropsy will be found to appear first about the loose cellular tissue surrounding the eyes, where the vessels, turgid with watery blood, have less efficient support. The dropsy of chlorosis is very similar to renal dropsy, a toxic condition of blood being present in both; also other forms of anaemia, as also hydraemia, tend to produce or assist in the production of dropsical effusions.

For the treatment of dropsy the reader is referred to the articles on the several diseases of which it is a symptom. Briefly, however, tapping of the abdomen or puncture of the legs are constantly resorted to in severe cases. Dehydration by diet is very valuable under certain circumstances when the dropsy