Page:Collier's New Encyclopedia v. 03.djvu/511

DYNAMOMETER 449 DZIGGETAL coils of the fields derive their cun'ent from a source external to the machine. Another method is to lead the current in the external circuit round the field magnets. Such an arrangement con- stitutes a series dynamo, and in such the building up of the field and the in- duced E.M.F. depend on the residual magnetism in the field ma^ets. Series machines are not practicable except when only small deviations from con- stant load occur. A shunt-round machir.e is one in •which the field magets are wound with coils arranged as a high resistance shunt in parallel with the external cir- cuit. Machines of this class are much less affected than the series machines, by variations in the external circuit. By combining both the series and shunt winding on the one machine there is obtained the compound-wound ma- chine, which is practically self-regula- ting as regards voltage, with all changes in the external load. DYNAMOMETER, ?n instrument for measuring the force used in overcoming resistance and producing motion. DYSENTERY, a febrile, infectious tropical disease, not common in this country. It may be acute or chronic, or again complex, and is very intractable and highly dangerous. It is seated in the large intestine, the lower part of the bowel, but sometimes extends upward into the small intestine above the ileocaecal valve. Dysentery is accom- panied by straining, and scanty mucous and bloody stools, containing little or no faeces. The most frequent complication is with the liver and disease of the kid- ney. There is feverishness throughout, dry skin, furred tongue, thirst, sleep- lessness, quick pulse, despondency, etc., slow convalescence, rarely complete, leaving the patient frequently a com- plete wreck. Ipecacuanha is the chief remedy, especially in the acute cases. In the scorbutic form, the Bael fruit is the best remedy. Dysentery usually commences with griping diarrhoea, and shooting or cutting pains. In favorable cases recovery may take place in from three to four weeks, but death some- times occurs in 10 or 12 days, or the case may extend over months or years. DYSPEPSIA, difficulty of digestion. The action of the stomach on the food is that usually designated as digestion, and it is the derangement of this pro- cess that is usually expressed by the term dyspepsia. The sub-acute and chronic forms of gastric irritation and in- flammation are the most common forms of dyspepsia, and are often caused by too highly seasoned or too abundant food and stimulant drinks. Another class of dyspeptic diseases is connected with irritation of the mucous membrane of the duodenum, causing perversion of secretions and disorder of functions. A third class of dyspeptic diseases depends on the nerves connected with the diges- tive viscera. Hence arises an order of dyspeptic symptoms independent of any immediate affection of the stomach. The most common causes of dyspepsia are exces.ses of various kinds, especially in the quantity of food eaten. The quality must also be considered, while good cooking is also a preservative against dyspepsia. DYTISCUS, a Linnsean genus of aquatic coleopterous insects or water beetles, forming the tribe or family Dy- tiscidse. They are pentamerous coleop- tera; i.e., have all the tarsi five-jointed. Their general form is oval, the outline little broken, and the surface very smooth. The respiratory organs of the perfect insect are not adapted to the extraction of air from water, and it must occasionally come to the surface to breathe, where it rests for a short time back dr- . • ^ard, and with the ex- tremity of the abdomen exposed to the air, the openings of the air tubes being in the last segment. DYVOUR (to owe), in the old legal language of Scotland, a bankrupt who under various acts from 1606 to 1696 was until discharged compelled to wear a hideous and conspicuous costume. Thus an act of 1688 prescribes as the dyvour's habit "a bonnet partly of brown and partly of a yellow color, with uppermost hose, or stockings, on his legs, half brown and half yellow colored, conform to a pattern delivered to the magistrates of Edinburgh." The bar- barous usage had fallen into desuetude long ere the dy'Our's habit was abol- ished by law in 1836. DZIGGETAI, a species of wild ass, more horse-like than the others. It is probably the hemionus ("half -ass ) of Herodotus and Pliny. It inhabits the elevated steppes of Tartary, extending into the S. of Siberia and to the borders of India. The dziggetai lives in small herds. The Mongols and Tungus hunt it eagerly on account of its flesh. It has been partly domesticated. It is also known by the names of kiang, khur, and goor.