surface; the waste or matter worn off rocks, &c. Detrunca'tion (Fr.), in midwifery, the separation of the trunk of the fœtus from the head, the latter remaining in utero. Deu'tero, or Deuto (Gr. deuteros second), a term used in chemistry when two equivalents of any substance are combined with one of another. Deuterohydrog'uret, in chemistry, a com pound of two equivalents of hydrogen with one of some other element. Deuteropa'thia (Gr. deuteros, and pathos suffering), a sympathetic affection of one part with another. Deutox'ide, in chemistry, a body in the second degree of oxidation. Devitrification (Lat. de, and vitrum glass), the act of converting glass into a grey opaque substance. Devo'nian System, in geology, a name given to the palæozoic strata of North and South Devon, considered as coeval with the old red sandstone of Herefordshire. The rocks of South Devon probably belong to the newer old red sandstone deposits. Dew-point, in natural philosophy, that degree of temperature in the atmosphere which causes the dew to be deposited.-Dew-worm is a large variety of the Earth-worm, which appears aboveground when moist with dew. Dew-retting, in chemical science, the exposure of flax in the bleachinggrounds to the action of the dew, rain, or snow, to effect by maceration the decomposition of the gum or resin which coats the fibre. Dexter (Lat. right hand), a term used in heraldry to denote the right side of a shield or coat of arms. Dextral (Lat. dexter), in conchology, an epithet applied to univalve shells which have their turns or convolutions from left to right when placed in a perpendicular position, with the apex downwards. Sinister or reverse shells are contrary. Dextrine (Lat. dexter), the gummy or soluble matter into which the interior substance of starch is convertible by diastase, or by certain acids. Diabetes (Gr. passing through), in pathology, an immoderate discharge of urine, of which there are two species, D. insipidus, from the insipid nature of the urine; and D. mellitus, from the urine containing abundance of a peculiar saccharine matter. Diabro'sis (Gr. corrosion), in surgery, the action of corrosive substances which possess a property intermediate between caustics and escharotics. Diacaustic (Gr. dia through, and kaio to burn), in surgery, a system of cauterizing by refraction, as when the solar rays are made by a burning-lens to act on the animal organism.-In geometry, the Diacaustic curve is the caustic curve by refraction. Diache'nium (Gr. dia, and achanes gaping) in botany, a simple fruit, formed by the ovary adhering to the calyx, which, on ripening, separates into two cells. Diach'ylon (Gr. dia, and chylos juice), in surgery, the name of common plaster made by boiling hydrated oxide of lead with olive oil. Diaco'dium (dia, and kodia a poppy), in the materia medica, a preparation of the poppy. Diac'ope (Gr. a cutting off), in surgery, a longitudinal fissure or fracture of the cranial bone, or an oblique cut of the cranial integuments. In ichthyology, the name of a beautiful genus of fishes which inhabit the Indian seas; fam. Chætodonidæ. Diacoustics (Gr. dia, and akouo to hear), that branch of physical science which treats of the properties of refracted sounds; diaphonics. Diadelphia (Gr. dia, and delphys the womb), in botany, a class of plants which have their stamens united in two parcels. Diadex'is (Gr. a transference), in pathology, a translation of the humours of the body from one place to another. Diaglyph'ic (Gr.), in sculpture, &c., applied to objects sunk into the general surface. Diagno'sis, Diagnostic (Gr. distinguishing), in pathology, the sign or symptom by which a disease is known or distinguished from others. Diag'onal (Gr. dia, and gonia an angle), a straight line drawn through a square or other rectilineal figure. Diag'onite (Gr.), in mineralogy, a name for Brewsterite. Di'agram (Gr.), a geometrical figure or scheme. Di'agraph (Gr.), an instrument used in perspective. Díagraph'ics (Gr. dia, and graphe description), the art of design or drawing. Di'allage (Gr. difference), a mineral of a brilliant green colour, with a silky or pearly lustre. It consists of silica, alumina, lime, magnesia, oxide of chrome, and oxide of iron: sp. gr. 3.0. Di'alling, the art of constructing dials. -Dialling lines or scales are graduated lines or rules made to facilitate the construction of dials. In Scotland, the term is used by miners for the use of the mining compass. Dial'ogite, a mineral of a rose-red colour, with a laminar structure and vitreous lustre; a carbonate of manganese. Dialu'ric (Gr. dia, and ouron urine), appertaining to the urine.-Dialuric acid is a newly-discovered acid, produced in combination with ammonia by the decomposition of alloxatin. Dialysis (Gr. dia, and luo to loosen), in pathology, loss of strength; exhaustion; weakness of the limbs.In surgery, solution of continuity. Diamagnetic (Gr. dia, and magnet), in natural philosophy, a term applied to a class of substances which, under the influence of magnetism, take a position, when freely suspended, at right angles to the magnetic meridian. Diamag'netism (Gr.), a peculiar property of many bodies, which are repelled by sufficiently powerful electro-magnets, and take a position at right angles to the magnetic equator. Diameter (Gr. dia, and metron measure), in geometry and mathematics, a right line drawn through the centre of a circle; the measure across the shaft of a column. Diamond (Fr.), the most valuable and the hardest of all precious stones or gems. It is pure carbon; and its primitive crystals are the regular octahedron, which reflects all the light falling on its posterior surface at an angle of incidence greater than 24° 13', whence its great brilliancy is derived. The diamond has various tints of colour; sometimes of a yellowish, bluish, or rose-red tinge, though sometimes perfectly colourless. The largest diamond known is said to have belonged to the Emperor of Brazil; but the celebrated Koh-i-noor diamond, which passed from the hands of the Mogul princes to the possession of Queen Victoria, is among the most valuable in Europe. In geometry, diamond is the name of a quadrangular or rhomboidal figure. Diamond beetle is the popular name of the Entimus nobilis, a beautiful coleopterous insect, belonging to the family Cur culionidæ. Dia'na, Tree of, is a term applied to the arborescent form of the crystallized silver, which becomes separated when mercury is put into a solution of the nitrate of silver. Dian'dria (Gr. dis two, and andres males), in botany, one of the classes of Linnæus, which comprehends those plants with two stamens. Diapa'son (Gr. dia, and pason of all), in music, a chord which includes all tones; the interval of the octave, so called because it includes all admitted musical sounds. It is also used to denote the compass of any voice or instrument: "From heavenly harmony The diapason closing full in man." A scale by which musical-instrument makers adjust the bore of their pipes. Diapede'sis (Gr. a leaping through), in animal physiology, the escape or transudation of blood through the coats of any vessel. Diapensia'ceae (Gr.), in botany, a nat. order of perigynous Exogens, of which the Diapensia is the type. Diaphon'ics (Gr. dia, and phone sound), in acoustics, the science or doctrine of refracted sounds. Diaphore'sis (Gr. dispersion), augmented perspiration, or elimination of the humours of the body through the pores of the skin. - Diaphoretic, causing perspiration. Diaphragm (Gr. dia, and phrasso to fence in), in anatomy, the midriff, or large muscular organ situated between the thorax or chest and the abdomen, forming a movable partition between those two cavities. It is imperfectly developed in birds, and in the lower animals it does not exist.-Diaphragmatitis is inflammation of the diaphragm. Diaphysis (Gr.), in anatomy, the state of growing between; a term applied to the body or central portion of the long bones. Diapla'sis (Gr.), the replacing of a luxated or fractured bone in its proper situation. Diapnotic (Gr. respiration), in materia medica, applied to remedies which operate by promoting gentle respiration. Diapophysis (Gr. a growing from), in anatomy, the transverse process of a vertebra in the archetype skeleton. Diarrhea (Gr. a purging), in pathology, a copious alvine evacuation; a flux of the bowels, arising from various causes, but generally from food or drink of too stimulating a nature. There are various species of diarrhea: as, D. biliosa, bilious;-D. crapulosa (Lat. crapula surfeit); -D. mucosa, mucous;-D.cœliaca, cœliac passion, when the food passes off in a white liquid state like chyle; -D. verminosa, from worms. Diarthro'sis (Gr. dia, and arthron a joint), in anatomy, a movable joint; an articulation admitting of motion in various directions.-Diarthrodial, having free motion in the articulation of the joints. Di'aspose (Gr. to scatter), a laminated mineral of a pearly shining lustre, consisting of alumina and water; when exposed to heat, it precipitates with violence, is dispersed (whence its name), and splits into small brilliant scales. Di'astase (Gr. dia, and istemi to set), a vegetable principle extracted from crushed malt, analogous to gluten. It is by the action of this small portion of diastase that the starch of the barley is converted into sugar in the first stage of brewing, preparatory to the fermentation by which ale or malt spirits are obtained. Dias'tasis (Gr. separation), in surgery, the separation of two bones previously in contact, or of the pieces of a fractured bone. Diaste'ma (Gr. an interval, or fissure), in zoology, the space which occurs in animal dentition when the canine teeth are wanting, as in the class of Rodents. The following compounds have been used by physiologists as applying to monstrosities or organic irregularities, when characterized by a fissure or longitudinal division of some particular part of the animal body :Diastemato-cephalia, of the brain; diastemato-caulia, of the trunk of the body; diastemato-cheilia, of the lip; diastemato-crania, of the skull; diastemato-cystia, of the bladder; diastemato-gastria, of the parietes of the belly; diastemato-glossia, of the tongue; diastemato-gnathia, of the jaws; diastemato-metria, of the womb; diastemato-pylia, of the pelvis; diastemato-rachia, of the spine; diastemato-rhenia, of the nose; diastemato-stophylia, of the uvula; diastemato-sternia, of the sternum; diastematria, of the intestinal canal. Diastim'eter (Gr. distance measurer), a philosophical instrument for measuring distances. Dias'tole (Gr. diastello to separate), in physiology, the opening or dilatation of the heart after contraction. Diastyle (Gr. dia, and stylos a column), in architecture, that mode of intercolumniation in the arrangement of pillars where the space between the columns consists of three or four diameters. Diather'mal, or Diather'matous (Gr. dia, and therma heat), a term applied to those transparent bodies which suffer the radiation of heat to pass through them, as in the case of rock salt, &c. Diathesis (Gr.), in pathology, the state of the body or constitution in which there is a predisposition to particular diseases. Diatoma'ceae (Gr. a separating), in natural history, a genus of minute Algæ, of which the Diatoma is the genus. They are of a very heterogeneous character, consisting of crystalline fragmentary bodies, flat, stiff, and brittle, usually nestling in slime, uniting into various forms, and then separating again. Dr. Lindley says that "they seem to form the extreme limits of the vegetable and animal kingdoms. Their regular form, and the power of separating into distinct particles which most of them have, are almost as much the attributes of the mineral as of the animal or vegetable kingdom. Agardh includes them among plants; Kützing asserts that their life is as much animal as vegetable." -Diatomous, in mineralogy, applied to those crystals which have one distinct diagonal cleavage. Diaton'ic (Gr. dia, and tonos a tone), a term applied to the natural scale of music, including both tones and semitones, proceeding by degrees. Diazo'ma (Gr. dia, and zoma a cincture), in zoology, a genus of the Ascidia, in which the species dispose themselves circularly or in rays, so as to form one or more stelliform systems. Diboth'rians (Gr. dis double, and bothrion a pit), in natural history, a division of the Entozoa, including those tape-worms of the family Bothriocephala which have not more than two pits or fossæ on the head. Dibran'chia (Gr. double gills), in malacology, a class of the Cirripeds. Dibranchiates (Gr. ut supra), an order of the Cephalopods, which are furnished with two gills, and an apparatus for secreting and discharging an inky fluid. Dic'erates (Gr. double-horned), in malacology, a family of Mollusca, comprehending such Gasteropods as have the head furnished with two tentacula. Dichæ'tæ (Gr.), a subdivision of the apterous insects, consisting of two families, the Athericera and the Pupipara. Dichlamyd'eous (Gr. double covering), in botany, having calyx and corolla. Dichotomy (Gr. occurring in pairs), in natural history, an artificial arrangement of natural objects into pairs.In botany, branching by constant forking, as when the stem or vein of a plant divides into two branches, each branch dividing into two others. -Dichotomous, occurring in pairs at the nervures in the wings of certain insects, and in the veins of certain ferns. Dichroism (Gr. double-coloured), in optics, the property of some crystallized bodies of appearing under two distinct colours, according to the direction in which light is transmitted through a body, as in the muriate of palladium, which appears of a deep red colour along the axis, and of a lively green when viewed in a transverse direction. Dichromatic (Gr. dis double, and chroma colour) having or producing two colours. Dic'linate (Gr. dis, and klino to incline), an epithet applied to crystals in which two of the axes are obliquely inclined. Dicotyledons (Gr. dis, and kotyledon a seed-lobe or seed-leaf), in botany, a class of Exogens, the first grand division of the vegetable kingdom, whose seeds in germinating divide into two lobes; the stem being increased by external layers, with an evident distinction between wood and bark.Dicotyledonous, having two seedleaves. Dicotyles, in zoology, a genus of hogs, the Peccary. Dic'roite, a mineral of a blue and shining colour, which occurs in gneiss and granite, and consists of silver, alumina, magnesia, oxide of iron, and manganese. Dicrotic (Gr.dis, and kroyo to strike), in pathology, having a double pulsation. Dicruri'nse (Gr. dis, and oura a tail), in ornithology, a sub-family of flycatching birds, the Drongo Shrikes, of which the Dicrurus is the type. Dict'yogens (Gr. diktyon a net, so called from the reticulated nature of the leaves), a class of plants intermediate between Exogens and Endogens, in which the root of the wood is a solid concentric circle. Dictyot'idæ (Gr. diktyon, and otis an ear), in botany, a tribe of Fuci, of which the Dictyota is the type. In natural history, the following compounds, connected with dis or dicho, two or double, are of frequent occurrence:-Dicarpus, two-seeded; dicephalus, two-headed; diceratus, two-horned, or having two antennæ; dichopetalus, having two petals; dichopterous, two-winged; dichrous, two-coloured; dichrurus, having a two-coloured tail; diclinus, two.. bedded, or having the sexes separate; diccocus, two-seeded; dictyocarpus, (Gr. diktyon, a net), having reticulated fruit; dictyodes, net-like, reticulated; dictyorhizus, having a reticulated root; dictyoptera, having reticulated wings. Dicyn'odon (Gr. auble canine-toothed), in zoology, a genus of reptiles with no teeth in the upper jaw, except two long tusks in sockets curved downwards. Didac'tyle (Gr. dis, and daktylos a finger), in natural history, applied to two-fingered or double-toed animals; as to the ruminants among quadrupeds, the ostrich among birds, and the amphiuma among reptiles. Didecahedral (Gr.) in crystallography, applied to ten-sided prisms with fivesided summits. Didelphide (Gr. dis, and delphys a womb), in zoology, a family of the Marsupialia, including the Opossums, Kangaroos, and other species of the genus Didelphis, which are possessed, as the name implies, of an external abdominal pouch or sac, in which the fœtus is placed after a short period of uterine gestation, and where it remains suspended to the nipple by its mouth until sufficiently matured to come forth into the air. Didodecahedral (Gr. dis double, dodeka twelve, and hedra sides), in crystallography, having the form of a dodecahedral or twelve-sided prism, with hexahedral or six-sided summits. Didymous, in botany, growing in pairs or twins. Didyna'mia (Gr. double power), the fourteenth class of plants in the Linnæan system, which have four uneven stamens. The class is divided into two orders, the Gymnospermia, including those genera the ovary of which splits into four seed-like lobes, and the Angiospermia, those which have the seed enclosed in a pericarp of some kind. To this artificial class belong the Verbena, Scrophularia, Bignonia, Acantha, and their cognate genera. Dielectric (Gr.), in natural philosophy, a body which has not the power of transmitting the electric influence through itself. Dietetics (Gr. diaitetikos relating to diet), that part of medical science which relates to food or diet, and teaches us to adapt the quantity and quality of particular kinds of food to suit the state or power of the diges tive organs. Differen'tial, an infinitely small quantity. -Differentialcalculus, aterm applied to one of the most important branches of the higher mathematics. It is the method of finding the ratios of the differences of variable magnitudes, on the supposition that these differences become infinitely small. Diffu'sion (Lat.). In chemistry, the diffusion of gases is a term applied to two gaseous bodies which do not act chemically upon each other; but when mixed together in any relative proportions, they diffuse themselves through each other, and become intimately blended-the heavier one not falling, nor the lighter one floating. Digas'tric (Gr. double-bellied), in anatomy, a term applied to a double muscle, situated between the mastoid process and the lower jaw, its office being to pull the lower jaw backwards and downwards. Digest (Lat. digestum), in chemistry, to expose any body to a gentle heat in a boiler or matrass, as a preparation for chemical operations. Diges'ter (Lat. digestum), in the materia medica, a medicine that aids digestion. In chemistry, a strong vessel of copper or iron, with a lid tightly fitted and furnished with a safetyvalve, in which bodies may be subjected to high pressure from steam. Digestion (Lat.), in physiology, the process by which the nutritive parts of food in the animal system are rendered available for nutrition. It is also a term chemically applied to the operation of exposing bodies to a gentle heat, to prepare them for some action on each ch other; or the slow action of a solvent on any substance. Digestive (Lat.), in pathology, any medicine or preparation which increases the tone of the stomach and aids digestion. In surgery, an application which ripens an ulcer or wound, or disposes it to suppurate. Digit (Lat. digitus a finger), a finger's breadth;-three-fourths of an inch;the twelfth part of the diameter of the sun or moon;-one of the ten symbols or figures by which all numbers are expressed. Digitalis (Lat.), in botany, a biennial plant, used medicinally to diminish the frequency of the pulse and the irritability of the system; the foxglove.-Digitalia, a vegetable alkali procured from the Digitalis purpurea. Digita'tion (Lat.), in anatomy, fingerlike processes, as exhibited in various muscles, as the serratus magnus, &c. Digitigrades (Lat. digitus, and gradior to tread), in zoology, a name applied to those quadrupeds which, while walking, move only on the extremity of the toes, as in the genera Canis, Felis, and Mustela. Diglyph (Gr. dis, and glypho to carve), in architecture, an ornament which has two channels sunk in, while the triglyph has three. Digyn'ia (Gr. dis, and gyne a female), in botany, the Linnæan system for plants with two styles, or a single style deeply cleft into two parts.Digynious, having two styles or female organs of fructification. Dihedron (Gr.), a solid figure with two sides or surfaces.-Dihedral, having two sides. Dihexahedral (Gr.), in crystallography, having the form of a hexahedral prism with trihedral summits. Dike (Sax. dic; Swed. dike), in geology, a wall of mineral matter cutting through strata in a vertical or inclined direction. It differs from a vein in being generally of greater dimensions, and in being seldom ramified. Dillenia'ceae (in honour of Professor Dillenius), in botany, a nat. order of plants, consisting of evergreen trees, or climbing plants, of which the Dillenia is the type. Dill Oil, a yellow oil obtained from the seeds of the Anethum graveolens, which are carminative and stimulant. Dil'uent (Lat. diluo to wash away), making thin; weakening in intensity. Diluvium (Lat.), in geology, the superficial deposits of clay, sand, and gravel, often containing shells and bones of Mammalia, which lie far from their original sites, of which no satisfactory solution has yet been given. Diluvial, produced by the Deluge. Dime'rans (Gr. dis, and meros the thigh), a section of coleopterous insects which have only two joints in each tarsus. Dimerocri'nites (Gr. dimeris divided, and krinon a lily), a genus of Crinoideans, of which the finger-joints are in two rows. Dimeroso'mata (Gr. a divided body), in entomology, an order of Arachnidans, or Spiders, whose bodies are divided into two segments. Dimorphism (Gr. double forms), in mineralogy, the property of assuming two forms under different circumstances; thus sulphur assumes one form when crystallizing at a high temperature, and another wholly different when becoming solid at the ordinary temperature. - Dimorphous, assuming different forms. Dimya'ria (Gr. double muscle), in malacology, the name of such bivalvular Mollusca as are furnished with two abductor muscles. Dinor'nis, or Deinor'nis (Gr. deinos and ornis a terrible bird), in ornithology, a genus of extinct aquatic birds of a gigantic size, of the family Struthionidæ, somewhat resembling the |