PEC 



548 



PEC 



hell-fish, but particularly the mother-of- 

 pearl oyster (Concha margaritifera, Lin.), 

 found in various parts of the world, par- 

 ticularly on the west coast of Ceylon, 

 on the coast of Coromandel, in the Gulf of 

 Persia, at the Sooloo Islands, off the coast 

 f Algiers, the St. Margarita or Pearl 

 Islands, in the West Indies, &c. Much 

 difference of opinion has existed with re- 

 spect to the production of pearls in the 

 oyster, but it seems now to be generally 

 believed they are the result of disease, 

 whereby the pearly secretion, instead of 

 being spread over the shell, is accumu- 

 lated round foreign bodies accidentally 

 introduced into the shell. 



PEARL' SHELLS. Mother-of-pearl shells. 

 See MOTHER-OF-PEARL. 



PEARL'STONE. A variety of obsidian, 

 which has a pearly lustre, occurring in 

 globular and concentric lamellar concre- 

 tions. Sp. gr. from 2'2 to 2'55. 



PEARL-WHITE. Subnitrate of bismuth, ob- 

 tained by pouring the nitrate of that metal 

 into a dilute solution of sea-salt, whereby 

 a beautiful light white powder is obtained. 



PEAT. An intermediate substance be- 

 t ween simple vegetable matter and lignite ; 

 the conversion of peat into lignite being 

 gradual, and brought about by the action 

 of water. It is composed of the remains 

 of many different plants, but probably a 

 great portion is derived from the Sphag- 

 num palustre. The process of its formation 

 is owing to the perpetual destruction of 

 the lower roots of the plants, while the 

 upper parts continually send off new roots, 

 thus furnishing a perpetual supply of de- 

 composing matter. Peats are the peat- 

 bog cut out into small rectangular pieces, 

 and dried for fuel. Peat-soil is peat in a 

 state of decomposition, on which agricul- 

 tural produce may be grown. 



PEB'BLES. Siliceous stones larger than 

 gravel, the round form of which is owing 

 to their mutual attrition caused by the 

 action of water. 



PEC ARY, ) The Tajouca of South Ame- 



PEC CART, j rica, a quadruped placed 

 among the hogs by Linn6. It has shorter 

 legs than the hog, the bristles are stronger, 

 resembling the quills of the porcupine, 

 and the body is less bulky. 



PECH'BLEND. The German name for 

 Pitchblend (q. v.). 



PECK. A dry measure for grain, pulse, 

 &c., equal to 2 imperial gallons, or 554i 

 cubic inches. 



PE'CORA. A name which has been used 

 to designate all mammiferous animals 

 which have no front teeth in the upper 

 jaw, as the ox, sheep, goat, camel, &c. 



PEC'TEN, Lai. pecten, a comb. 1. In 

 conchology, the scallop or comb shell. A 

 genus separated from the oysters by Bru- 

 g'lifcres. The pectens are all marine 

 bivalves belonging to the Ostracea, Cuv., 



ar.a for.x'i.g the type of the family ?*- 

 teibej, Lam. 2. In anatomy, the pubes. 



PEC'TIC ACID. The name given by Kra- 

 connot to an acid which he conceives to 

 be universally diffused through vege- 

 tables, and analogous to if not identical 

 with jelly: hence the name, from -r*jT'S, 

 coagulum. It is most easily obtained from 

 the roots of carrots. 



PEC'TINE. A vegetable jelly, obtained 

 by mixing alcohol with the juice of ripe 

 currants (or any similar fruit j, till a gela- 

 tinous precipitate falls, which is pectine : 

 ;rrs, Jelly. 



PEC'TINATE, Lat. peclinatus. comb-like. 

 Applied to leaves, &c., when the segments 

 are extremely narrow and straight, like 

 the teeth of a comb. 



PECTINIBRAN'CHIATA. An order of Mol- 

 lusca, comprising, beyond all comparison, 

 the most numerous division, inasmuch 

 as it includes all the spiral univalves, and 

 several that are simply conical. Th 

 branchiee, composed of numerous lamellw 

 or stripes, laid parallel with each othe r 

 like the teeth of a comb (pecten), are at- 

 tached on one, two, or three lines, accor J - 

 ing to the genus, to the ceiling of the 

 pulmonary cavity, which occupies the last 

 whorl of the shell, and which has a large 

 opening between the edge of the mantle 

 and the body. They are divided into 

 families, according to the form of the 

 shell, viz. Trochoida, Capuloida, and Bue- 

 cinoida. 



PEC'TORAL. Appertaining to the breast : 

 pectus, the breast. Pectoral medicinei are 

 those intended to relieve diseases of the 

 chest. The pectoral fins, or pectorals of a 

 fish, are those tins situated on the sides 

 immediately behind the gills. 



PECTORA'LES PEDICULA'TI. A family 

 of fishes, consisting of certain Acantho- 

 pterygii.whose carpal bones are elongated, 

 so as to form a sort of arm which supports 

 their pectorals. 



PECTORIL'OQUY, from pecttts, the breast, 

 and loquor, to speak. The peculiar sound 

 obtained in a stethoscopic exploration of 

 the chest, when the instrument is placed 

 over an excavation of the lungs. Vnder 

 these circumstances, the voice appears to 

 come direct through the tube of the in- 

 strument, from the chest of the patient to 

 the ear of the ausculator. 



PECU'LIAR. In canon law, a parish or 

 church which has jurisdiction within it- 

 self, and is competent to grant probates of 

 wills and letters of administration , exempt 

 from the bishops' courts. The Court of Pecu- 

 liars is a branch of the Court of Arches. It 

 has jurisdiction over all the parishes dis- 

 persed through the province of Canter- 

 bury, in the midst of other dioceses, which, 

 are exempt from the ordinary jurisdiction, 

 and subject to the metropolitan only. 





