1 1 -I 



DUFRENOYSITE. 



DYNASTES. 



DUFRENOYSITE, a Mineral, consisting of an arseniurct and sul- 

 phuret of lead. It occurs in dodecahedrons of a dark steel-gray colour 

 in the Dolomite of St.-Gothard. The specific gravity is 5 '55. 



DUGONG [CETACEA.] 



DUIKER-BOK. [ANTILOPE.E.] 



DULCAMARA. [SOLANUM.] 



DULSE. [ALG.R] 



DUMB-CANE. [AROIDEJS; CALADIUM.] 



DUNDIVER. [DUCKS.] 



DUNLIN. [SCOLOPACIDS.] 



DUNNOCK. [SYLVIAD-E.] 



DUODE'NUM (from a Latin word signifying twelve, because it is 

 twelve inches in length), the first of the small intestines in immediate 

 connection with the stomach. It commences at the pyloric end of 

 the stomach, and terminates at the distance of twelve inches in the 

 second portion of the small intestines called the jejunum. Though it 

 is the straightest of the small intestines, yet the Duodenum describes 

 in its course various turns. From the pylorus it turns backwards and 

 upwards by the neck of the gall-bladder, with which it is in contact ; 

 it then passes obliquely downwards on the right side immediately 

 before the great vessels which enter the liver. Opposite to the under 

 part of the kidney it makes a turn to the left side, across the lumbar 

 vertebrae, and is lodged in the common root of the mesocolon and 

 mesentery, below the pancreas and behind the superior mesenteric 

 vessels ; it now makes a turn forwards, and obtains the name of 

 jejunum. 



The Duodenum is much more capacious than the jejunum or ilium, 

 an.l is indeed so large that it has been regarded as a second stomach, 

 and obtained the name of Ventriculus Succenturiatus. It is fixed 

 much more closely to the spinal column than the other intestines, 

 and does not, like them, float loosely in the abdomen. It is of a 

 redder colour than the rest, has a thicker muscular coat, and a greater 

 number of valvuUo conniventes. 



At the distance of from three to four fingers' breadth from the 

 pylorus the Duodenum is perforated by the biliary and pancreatic 

 ducts, by which tubes the bile and the pancreatic juice flow into the 

 intent 



The Duodenum is probably an organ accessory to the stomach. 

 There is evidence that it carries on the digestion commenced iu the 

 stomach. It is certain that alimentary substances which have escaped 

 solution in the stomach are dissolved in the Duodenum. 



The chyme formed from the food in the stomach and received by 

 the Duodenum, retains the name of chyme until it reaches that por- 

 tion of the Duodenum where the biliary and pancreatic ducts pierce 

 the intestine. At this point, and by the admixture of the biliary and 

 pancreatic juices, the chyme is changed into two portions into a 

 nutritious portion, which receives the name of chyle and which 

 flows into the blood [CHYLE] ; and into an excrementitious portion, 

 which is carried along the small into the large intestines, where it 

 receives the name of fueces, and is expelled from the body. 



On the surface of the Duodenum the lacteal vessels begin to make 

 their appearance for the absorption of the chyle. [LACTEALS.] The 

 Duodenum is likewise provided with a great number of mucous glands, 

 which more especially abound near the pylorus. [GLANDS.] 



J)UUA-MATKR. [BRAIN.] 



DURATHEN, the name given by physiologists to the central wood 

 or heart-wood, in the trunk of an exogenous tree. It is the oldest 

 part of the wood, and is filled by the secretions of the tree, so that 

 fluid can no longer ascend through its tubes, which are choked up by 

 the deposition of solid matter ; otherwise it is of the same nature as 

 the alburnum. It is only where plants form solid hard secretions 

 that heart-wood is distinguishable from sap-wood : in the poplar, 

 willow, lime, &c., no secretions of this kind are formed ; the two 

 parts of the wood are both nearly alike, and consequently the timber 

 of such trees is uniformly perishable. Ship-carpenters call the 

 Duramen the spine : it is always distinguishable from sap-wood by 

 iU deeper colour, and sometimes, as in the yew, the sandarach, and 

 certain kinds of deal, the limits of the two are clearly defined. But 

 in most cases the heart-wood and sap-wood gradually pass into each 

 other, so that no certain line can be drawn between them. [ALBUR- 

 ITUM ; EXOGENS ; TISSUES, VEGETABLE.] 



DU'RIO, a genus of Plants of which the name has been derived from 

 Durion, a well-known fruit of the Malayan Archipelago. The specific 

 name of Zibethinui has been applied to the tree which forms this 

 genus, from the fondness of the Malayan Zibet ( Viverra Roue, Hors.) 

 for this fruit. 



The genus Durio belongs to the natural family of Bombacta, con- 

 sidered by some botanists to be only a tribe of Sterculiacete. It is 

 characterised by having its five petals smaller than the five lobes of 

 the calyx. The stamens, long and numerous, are arranged in five 

 bundles, and have twisted antherj; the free germen is surmounted by 

 a long filiform style and capitate stigma; the fruit, roundish and 

 inmicated, is divided internally into five cells, and easily separates 

 wlii'n rip into five parts ; each cell contains from two to four or five 

 seeds > ,n soft pulp. 



D. Zilir/liinii* is a large and lofty tree, with alternate leaves, which 

 are small in proportion to it* size ; inform they resemble those of 

 the cherry, or are oblong-pointed, small and green above, like nutmeg- 



tree leaves, but on the under surface are covered with orbicular 

 reddish-coloured scales, as some species of Capparis ; the petioles are 

 tumid, and furnished with a pit towards their base ; the flowers are 

 arranged in clusters on the trunk and older branches, where of course 

 is also borne the fruit, as in the Jack and Cocoa trees. 



The Durion is a favourite food of the natives during the time (May 

 and June) when it is in season ; but there is usually also a second crop in 

 November. It is as remarkable for the delicacy combined with rich- 

 ness of its flavour, as for the intolerable offensiveness of its odour, 

 which is compared by Rumph to that of onions in a state of putre- 

 faction, on which account it is seldom relished by strangers, though 

 highly esteemed by many European residents. In size it is equal to 

 a melon, or a man's head, and sometimes compared to a rolled-up 

 hedgehog (hence it has been called Echinus arboreus) in consequence 

 of its hard and thick rind, which is yellow-coloured when ripe, being 

 covered with firm and angular projections. From this appearance has 

 likewise been derived its Malayan name, ' dury ' in that language signify- 

 ing a thorn or prickle. (Rumph.) 



The seed, with its edible enveloping pulp, is about the size of a hen's 

 egg ; the latter isas white as milk, and as delicate in tasto as the 

 finest cream, and should be eaten fresh, as it soon becomes discoloured, 

 and undergoes decomposition. Excessive indulgence in this, as in other 

 fruits, is apt to create sickness, and therefore to its abundance bus 

 been sometimes ascribed the uuhealthiness of some years ; but as the 

 crop of fruit is most abundant when the rains are very heavy and follow 

 great heats, the sickness is probably due as much to the peculiarities 

 of the season as to the too free use of this fruit. 



The seeds of the Durion are likewise eaten when roasted, and 

 have something of the flavour of chestnuts. The wood of the tree 

 is valued for many economical purposes, especially when protected 

 from moisture. The rind of this fruit is likewise turned to account 

 by the industrious Chinese, as its ashes, when burnt, probably from 

 containing potash, are used by them, in the preparation of some 

 dyes. 



Marsden, in his account of Sumatra, quotes a celebrated writer as 

 saying that " Nature seems to have taken a pleasure in assembling in 

 the Malay Islands her most favourite productions." Among these may 

 be enumerated the Mangosteen, the Jack and Bread-Fruit trees, the 

 Lanseh, and Durion, with others which are common in other tropical 

 parts. These it has not been possible to cultivate in the hot-houses 

 of England, even with all the skill of its horticulturists ; a circum- 

 stance which must be ascribed partly to the great size of the trees, 

 and partly to the peculiarity in climate of ' India aquosa,' as this 

 part of the world was called by old writers. But as it is only within 

 a few years that moisture has been combined with heat iu the present 

 'successful cultivation of Orchideous Plants, it might perhaps be 

 possible to make some of the above fruits grow in a similar artificial 

 climate ; and, by grafting, to make them bear when only a few feet 

 high, as has been done with the Mango in India. 



DUTCH WHITE. [BARYTES.] 



DUVAUA. [ANACARDIACE^.J 



DYKE (in Geology), a fissure caused by the dislocation of strata, 

 commonly also termed a Fault. Dykes are of frequent occurrence, 

 and often extend several miles, penetrating generally to an unknown 

 depth. They must have been produced by some violent disturbances, 

 and the amount of dislocation of necessity would vary in proportion 

 to the intensity of the disturbing force. Accordingly there are many 

 dykes of great width and extent, which materially affect the face of 

 the country in which they occur, while there are others so slight 

 that it requires much care and observation to ascertain their 

 existence. The strata are in most cases uplifted on one side of the 

 dyke much higher (varying many fathoms) than those on the other 

 side, and produce an apparent irregularity of strata most perplexing 

 to the geologist. Sometimes it happens that, without any irregu- 

 larity of surface, two distinct strata appear to form a continuous Hue, 

 as in the Black Down Hills in Devonshire. [CHALK FORMATION.] In 

 some cases however dislocation is found without any alteration of 

 the level of the strata on either side, but the appearance of the 

 strata immediately adjacent to the fault sometimes affords proof of 

 the action of fire. [COAL FORMATION.] Dykes are of two distinct 

 characters, depending upon the manner in which they have been 

 filled up, and the substance of which they are composed. Dykes of 

 the first description are those into which igneous rocks are supposed 

 to have been injected in a state of fusion, and now appear as a 

 consolidated mass. [BASALT.] In the second the fissures are filled 

 with the debris, sometimes mixed with clay, of the dislocated strata 

 through which they pass. In some cases the fissure has evidently 

 remained unoccupied for a long period, and the filling up has pro- 

 ceeded gradually from the sides inwards. This is observed very 

 evidently in the carboniferous limestones of England and Wales. 

 Sometimes, in consequence of the great length of time intervening 

 between the production of each coating of calcareous matter, the 

 outside of each is covered with crystals, upon which the next layer 

 has been formed : in the central portions of such fissures cavities are 

 by no means uncommon. 



DYNASTES, a genus of Coleopterous Insects belonging to the 

 section Pentamera, sub-section Lamellicornes, and family Vynastidce of 

 M'Leay. The species have the body very large and thick, the outer 



