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PARAGUAY 110 PARALYSIS PARAGUAY, a large river of South America, an affluent of the Parana, rises in the Brazilian province of Matto Grosso, 9,535 feet above sea-level. Pur- Fuing a S. W. course, and after flowing through a level country covered with thick forests, the Paraguay is joined from the W. by the Jauru, in lat. 16° 30' S. It then continues to flow S. through the marsh of Xarayes, which, during the season when the stream rises, is an ex- pansive waste of waters, extending from N. to S. over about 200 miles. The river still pursues a circuitous but gen- erally S. course, forming the boundary line between Brazil and Bolivia, thence flowing S. S. W. through the territories of Paraguay to its junction with the Parana, a few miles above the town of Corrientes. Its chief affluents are the Cuyaba, Tacoary, Mondego, and Apa on the left; and the Jauru, Pilcomayo, and Vermejo on the right. The entire length of the river is estimated at 1,800 miles; it is on an average about half a mile in width, and is navigable for steamers to the mouth of the Cuyaba, 100 miles above the town of Corumba PARAHYBA, capital of the Brazilian state of Parahyba, on the river of the same name, 10 miles from the sea. Its chief buildings are the cathedral and the government palace (formerly the Jesuit college.) A large sugar mill was erected in 1889. At the mouth of the river is a bar; but a railway (12 miles) was built in 1889 to the port of Cabedello, there terminating in a pier in deep water. The annual exports are sugar, cotton, and cottonseed, chiefly to Great Britain. Pop. (1917) 32,000. The state, the east- ernmost in the republic, has an area of 28,854 square miles, pop. (1917) 682,- 350. A more important Parahyba river farther south, enters the Atlantic, in the state of Rio de Janeiro, after a course of nearly 500 miles. It is navi- gable for 50 miles from its mouth. PARALDEHYDE, CoH^^Os, 3 polymer of acetaldehyde. A water-white liquid, with a peculiar, but not unpleasant odor, and a burning, but subsequently cooling taste. Specific gravity 0.995, melting point 12.6° C. boiling point 124° C. Pre- pared from acetaldehyde by the action of hydrochloric acid, sulphur dioxide or zinc chloride. Paraldehyde is a hyp- notic, and differs from choral in its greater speed of action and in that it has no depressant effect on the heart. Its administration sometimes causes an out- break on the skin, and in large doses it may cause digestive trouble. It is also used in the manufacture of dyes. PARALLAX, the difference of direc- tion of a body as seen from two differ- ent points. It is generally applied to the direction of the heavenly bodies as seen from the earth's center and from some point of its surface. The parallax is greater the nearer the body and the greater the distance between the points in a direction at right angles to that of the body. The term is also applied to the difference in direction of a body seen from different points of the earth's orbit, the longest diameter of which is insuf- ficient in case of some fixed stars. _ PARALLEL LINES, two straight lines are parallel to each other when they lie in the same direction. Any number of straight lines are parallel to each other when they have the same di- rection, or when they are respectively parallel to a given straight line. PARALLELOPIPED, or PARAL- LELOPIPEDON, in geometry, a regular solid bounded by six plane surfaces, or parallelograms, the opposite pairs of which are similar, parallel, and equal to each other. If the parallelograms are squares, the solid is a cube. PARALLELS, in astronomy and geog- raphy small circles of the celestial sphere or of the surface of the earth which are parallel to the equator, having a com- mon pole with the latter. On the earth's surface they are generally called par- allels of latitude, and in the sky parallels of declination. PARALYSIS, the loss of the natural power of sensation or motion in any part of the body. It is owing to some . dis- eased condition of the nervous system, either of the brain or spinal cord, or of the nerves. If the nerves of sensation or their centers be affected, there will be loss of sensation; if of motion, then loss of motion ; to the latter of which the term paralysis is by some exclusively ap- plied. The most usual form is when one side or half of the body is deprived of sensation or motion, or both, called hemiplegia; paraplegia is when the lower part of the body is paralyzed, while the upper retains both sensation and motion; and general paralysis is when the loss of nervous power extends over nearly every part of the body. In hemiplegia, the seat of the disease is one side of the brain, usually that op- posite to the affected side of the body; in paraplegia, the lesion is within the spinal cord; and when more limited in extent, the disease usually arises from some abnormal state of a particular nerve. Paralysis frequently follows