DRONFIELD

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. [greek: udrops]; [greek: udor], water, and [greek: ops], 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 pathology). 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 hydrocephalus; ascites;