Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/346

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one another by (mail perpendicular leaves. See Tab. I. of Botany, Oafs i. Tourn. Inft. p. 480.

Radiated leaf, among botanifts. See Leaf.

RADICAL (Cycl.) — Radical numbers, numeri radicates, in the Italian mufic, are 2, 3, 4, 5, 6, 7, 8, 9, and fome- times 10, which are often met with in mufical compofi- tions, to denote the accords of the thorough baffes. 2 ftands for the fecond and its duplicates ; 3 for the third ; 4 for the fourth, C3V.

Radical leaf, among botanifts. See Leaf.

R ADIC ATOM folium, among botanifts. See Leaf.

RADII {Cycl.) — Radii pinnarum, in ichthyology, the little flender bones fupporting the membrane, forming the fins in fifties, and called by Artedi ojficula radiata pinna- rum, from their running from the bale to the fummit in the form of rays. See Fin.

Of thefe radii fome are prickly, others not. The prickly ones are always hard and rigid, the others are always foft and flexile, whether they terminate fingle, or are fplit into two or more branches at the extremity. The prickly ones are always formed of fingle bones ; the others always of two bones, each applied clofely and evenly to one another. When the fifh is alive, it is not always eafy to feparate thefe, but when it is boiled, they are eafily parted at the bafe, and fometimes all the way up. The fifh, which have the fingle and prickly fins on their back, belly, or at the anus, are thefe : the perca?, the fpari, the labri, the amise, the trachuri, the mugiles, the fudes, the trachini, the zei, the mulli, the ligyri, the gafteroftei, the fcorpcena?, the caprifci j in thefe the radii are all fingle, and are more or lefs prickly. In the mackrel, the radii of the firft fin of the back, and thofe of the belly fins, are abfolutely fimple, but they are fcarce obfervably prickly. The following genera of fifties are thofe which have the radii of the fins all double at the bafe, and foft and flexile : the fyngnathi, the cobitides, the cyprini, the clupeas, the co- regoni, the ofmari, the efoces, the pleuronecti, the gadi, and the congers. The fofter and the more flexile thefe bones are, the more numerous, tranfverfe, and lucid inter- nodia they have in them. The cyprini give us many in- ftances of this, as alfo the clupese, the coregones, and the efoces. Thofe which have fewer of thefe internodia, or tranfverfe fines, are fomewhat more rigid, though not aculeate, or prickly : this we fee in the pleuronecti and gadi. Befide thefe radii, there are certain other (mall bones which are of an oblong figure, and ferve to fuftain the bafes of the back fins, and the fin at the anus. The back fins, and thofe at the anus, are not joined by their rays to fome one large mufcle, or large bone, as the pectoral and ventral fins are ; but every radius, or bone in thefe fins, is affixed to an oblong bone, erected perpendicularly between the apophyfes of the vertebra and the back of the fin. The rays are joined at their bafe to thefe bones by an articula- tion, and faftened in by means of a cartilage ; and thefe bones do not adhere to the apophyfes of the vertebra, but are placed regularly between them. Thefe bones are always fmgle, and in many kinds of fifh, as in the pleuronecti, they are hollow at the bottom. Between thefe bones, and the firft rays of the back fin, in mackrel, there are found certain other little bones, placed femicircularly and tranf- verfely, but their apices are ftriated, and turn a little up- wards. This is an obfervation yet made only in a few fifh, but it is worth while to examine whether it is found in thofe other fifh alfo, which have fulci at the back fins. Artedi's Ichthyolog. RADISH, rapbanus, in botany. See Raphanus.

There are feveral varieties of the root of the common garden radijk, which is the only fpecies cultivated by our gardners : thefe are called by them the fmall top'd radijk, the deep red, and the ftriped radijb, &c. All thefe are only varieties arifing from the culture. The fmall topped is the kind, the feed of which is moft faved, and which is moft valued about London, becaufe it does not take up much room. They are fown at various feafons, but the earlieft is generally at the latter end of October ; if thefe are not deftroyed by frofts, they become fit to eat in March. Thefe are commonly fowed about walls, pales, or hedges where they may have fome defence againft the cold. The fecond fowing is commonly about Chriftmas, if the weather be mild enough to let the ground be worked. Thefe are alfo to be fown under a fhelter, and, if they are not de- ftroyed, will be fit to eat in April j and to have a conftant fupply, there fhould be a new fowing every fortnight, from the middle of January to the beginning of April. The later crops fhould be fown on a moift foil, and in an open fituation. Miller's Gard. Diet.

RADIUS (Cycl.) — Radius of curvature, or Radius of the curvature of a curve, is the radius of a circle that has the fame curvature in a given point of the curve, that the curve has in that point.

Radius, among the Romans, a name given to the iron rod with which the boys rolled the trochus. See the article Trochus.

Radius, in anatomy. The radius is nearly of the fame 3

RAD

length with the ulna, bigger at one end than at the other, irregularly triangular, a little bent, and fituated fideways along the ulna, and has its name from the rcfemblance it bears to the radius, or fpoke of a wheel. Anatomifts de- fcribe in this bone a middle portion, and two extremities. One extremity is fmall, and like a kind of head fet upon a neck; the other is large, refembling a pedeftal, or bafis ; and the bone might therefore be very properly divided into the head, body, and bafis.

The head, or fmall extremity of the radius, is very fhort or low, the top of it is concave, and the circumference cylindrical, and both the glenoide cavity, and whole cir- cumference, are covered with the fame fmooth ihining car- tilaginous cruft, and about one quarter of the circumfe- rence is broader than the reft. The neck is fmall, and its fituation a little oblique ; it ends by a lateral tuberofity, which lies direftly under the broad part of the head, being rough in the middle, and on one fide, and fmooth and fuperficially cartilaginous on the other. The bafis, or great extremity of the radius, is much broader than it is thick, and has two broad fides, and one narrow one. One of the broad fides is a little hollow, and pretty even ; the other is unequally convex, and divided by longitudinal eminences, or bony lines, into three or four longitudinal channels ; but thefe are much more diftinft in freih bones, than in the dried fceleton. The narrow fide is hollowed lengthwife, and between it, and the other two, are formed two angles, by which the three fides are diftin- guifhed ; and oppofite to it, the other two meet in a third angle. This narrow fide ends in a femilunar cavity, bor- dered by a fmooth cartilage, and lying almoft in the fame direflion with the tuberofity. The broad fides end at their common angle by an obtufe point, or production, which has been called the Jiyloide apopbyfis of the radius, and is in reality a continuation of one of the bony lines already mentioned. The whole bafis ends in an oblong, triangular glenoide cavity, the cartilage of which is continued over the hollow edge of the narrow fide. This is an articular cavity, refembling an arch, and ending on one fide at the ftyloide apophyfis, and hollowed on the other by the cavity of the narrow fide. It appears divided into two portions by a fmall tranfverfe line, and in the natural ftate, the hollowed fide is lengthened out by a cartilaginous produc- tion, which is loft in the dried fceleton. The middle, or body of the radius, is a little incurvated, the concavity lying between the tuberofity in the head, and the femilunar cavity in the bafis. It has three fides ; one rounded, which is the convex fide of the curvature, and two concave ; three angles, two of which are obtufe, di- flinguifhing the two concave fides from the convex, and the third acute, lying between the concave fides, oppofite to the convex fide. In each of thefe fides there are feveral mufcular impreffions. The head and bafis of this bone are epiphyfes in children, and in fome fubjeas remain fuch for a long time afterwards. The radius is conneded with the ulna, os humeri, and carpus. It is articulated with the ulna, at its two extremities, by a double lateral gin- glymus, the cartilaginous fubftance of the head turning in the fmall figmoide cavity, and the femilunar cavity in the bafis turning upon the fmall head at the lower extre- mity of the other bone, and thus the fmall extremity of one of thefe bones is joined to the great extremity of the other. It is articulated with the os humeri by the applica- tion of the cavity in the top of its head to the fmall head at the lower extremity of the other bone : by this confor- mation it would be capable of moving in all direflions; but as it is tied to the ulna at both extremities, its mo- tions on the fmall condyloide head, at the lower extremity of the os humeri, are confined to two kinds ; that of ro- tation, when it turns on the fides of the extremities of the ulna ; and that of flexion and extenfion in common with the ulna ; and both thefe motions may be performed at the fame time. Winjlow's Anatomy, p. 80.

Cartilages of the Radius. At the bafis of this bone there is a particular cartilage, or triangular produaion, very thin, longer than it is broad, and rather flat than concave. It is fixed by the bafis, or fhorteft fide, to the lateral fig- moide notch of the bafis of the radius ; the other fide touches the flat extremity of the fmall head of the ulna, but is not affixed to it. This may properly enough be called the inter-articular cartilage of the wrift. It is tied to the radius by very fhort ligaments, and Aiding on the fmall head of the ulna, it follows all the motions of the radius. It is therefore a fort of articular produaion of the lower fide of the bafis of the radius, and in the natural ftate fills the void fpace which, in the fceleton, appears be- tween the end of the ulna and neighbouring bone of the carpus. jyinjlovJ's Anatomy, p. 140.

Ligaments of the Radius. 'Many of the ligaments of the bones of the fore arm are common to them, and to the os humeri, and others to them, and the bones of the head : two however there are which are proper to this part of the arm, the one called the interoffeous ligament of the fore arm, the other the coronary ligament of the radius ;

And