Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/347

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and to thefe may be added the annular ligaments, which l'erve only for the paffage of tendons, and other ligamen- tary expanfions, which may be called mufcular ligaments. The interoffeous ligament of the fore arm is like that of the leg ; it is fixed by one edge along the fharp angle of the radius, the other along that of the ulna. It is prin- cipally made up of hvo very ftrong planes of fibres, which crofs each other at oblique angles, and leave holes at dif- ferent diifances for the paffage of blood veffels. This liga- ment ties the two bones clofely together, and the two planes fervc for the infertion of feveral mufcles. The co- ronary ligament of the radius is a fort of ligamentary hoop., furrounding the circular circumference of the head of that bone. It is very ftrong, and comes near the folidity of a cartilage, and the fide next the radi-us is very fmootll. The capfular ligament of the joint of the elbow runs down from its infertion in the os humeri, and is fixed in the olecra- non, round the edge of the great figmoide cavity, eluding both the apex of the olecranum, and of the coro- noide apophyfis.

The true common ligaments, by which the os humeri is connefled to the bones of the fore arm, called lateral lio-a ments, are the two fafciculi, which, after being inferted in the condyles of the os humeri, are expanded like a goofe's foot ; that which is fixed in the inner condyle is called the brachio-cubital, the other the brachio-radical. Of the ligaments by which the bones of the fore arm are connefled to thofe of the hand, one is like a roundilh cord fixed in the ftyloide apophyfis of the ulna, and from thence paffes over the os cuneiforme of the carpus ; and an- other pretty broad .ligament is fixed on the point of the radius, and by its other extremity in the bones of the carpus. From this ftyloide ligament of the radius, along each edge of the bafis of that bone, are ranks of. ligamen- tary fibres, lying much in the fame direflion with the li- gament itfclf, and continued all the way to the ftyloide ligament of the ulna. There are alfo feveral final! annu- lar ligaments placed at different diftances on the convex fide of the bafis radii, from its ftyloide apex to its articu- lation with the extremity of the ulna; thefe are at leaft fix in number, and fomc of them are double or triple. The firft of thefe is fixed in the ftyloide apex ; the fecond in the groove near that apex; the third in the fmall, narrow, or middle groove ; the fourth in the groove next the former the fifth in the corner of the notch of the bafis, at its arti culation with the ulna ; and the fixth in the extremity of the ulna, near the ftyloide apophyfis. Thefe are all almoft ■wholly covered by the great oblique ligament, and are fixed as ftrongly in it on one fide, as they are in the bones on the other. IVhijlow's Anatomy, p. 141. fcq. Radios articuhtus, in natural hiftory, a name given by Mellius, Gmelin, and fome other authors, to a kind of figured foffils, of which there are a great many very diffe- rent fpecies, fomc of which have been defcribed by au- thors among the belemnita:, under the names of alveoli belemnitanim. Mr. Gmelin, who has taken great pains to inform himfelf, as well of the nature and figure of thefe ftones, from the fubjecls themfelves, as of their hiftory. and the various accounts of them from other authors, ob- ferves, that the place where they are molt frequent is Sweden, and that there they are no where lb common as in the ifle of Oeland. Volkman figures fome alfo which he found in Silefia, and Helwing others which he colleaed in Pruffia : he alfo found great numbers of them himfelf in Ruffia. They are ufually immerfed in lime ftone, and though at firft light they may all appear alike, yet, on a careful ex amination, they will be found to differ very greatly. The moft obvious general diftinftion, eftablifhed by Mr. Gmelin, is, that fome of them are ftrait, and others crooked. The ftrait ones may he divided into two genera. The firft of thefe comprehends, according to this gentleman, two fpecies : the firft fmooth, and with a converging alveolus. This confifts of feveral patella: of a roundilh figure, and difpofed in a parallel manner over one another. Each of thefe patellae is convex on one fide, and concave on the other; and the convex part of one is in the articulation, which joins them into one body, always received into the concave part of another, whofe convex part is again re- ceived into the concave of a third, and fo on throughout the whole body. The diameter of the largeft of this fpecies is about two inches, and that of the leaft an inch. The circumference is not perfectly circular, but in one part is cut in manner of a crefcent. This hollow is made for the reception of another cylindric ftone, which is not articulated, and which Mr. Gmelin calls an alveolus. This alveolus runs through all thefe crefcents in a ftrait and con- tinued courfe, and (landing out beyond the patella:, of Which the body is compofed, is furrounded with a fc-ries of fafcis, more or lefs elate : thefe anfwer to fo many of me patella:, and from thefe indeed it feems to have ob- tained this figure ; but when this alveolus has, by any ac- 1 ?'"' u difen g a g ed "" m its radius, it is eafdy render- ed imooth by attrition and other accidents, and is ufually

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Thefe are general charaflers, and are obferved in all the fpecimens of this fpecies ; but there are other accidental varieties found m the different ones. Some have the pa- tella: and the alveolus ftanding out beyond them, all co- vered with a thin cruft of a matter plainly teftaceous, and 111 fome the fhclly matter is alfo found between the junc- tures of the patella:. Sometimes alfo there are feen, at every junftion of the patella;, certain little forked bodies, Handing upon the outer part of the alveolus, and feeming to join the feveral patella: together. Sometimes the radii are found without the alveolus, but then there is always a cavity, or the remains of a cavity, in form of a canal, an- iwering to every lineament of the alveolus; and this is ever covered with a fhelly cruft on its inner furface. Many of thefe radii are found remarkably compreffed, bent, or diftorted, which is an accident accounted pecu- liar to the foffils formed in animal moulds, and (hews, with the fhelly matter, that the whole muft be the remains of fome fea fifh. Often alfo, when the whole fubftance is not injured in its form, the alveolus alone is oddly bent and diftorted, whence it appears that it was originally of a tenderer texture than the reft, and there are alfo evident marks of its having been once hollow. Thefe are the charaflers and varieties of this fpecies of ra- dius, and there do not feem to be any diftinfl fpecies under this, unlefs we are to account for fuch, thofe in which the patella are a little thicker, or a little thinner, or where they ftand clofer, or farther afonder. They are found from twelve to eighteen inches in length, but never feem to have been found with the pofterior extremity perfeS. They a! lofe themfelves in the ftone, keeping through thei'r whole extent, as far as they can be traced, the fame cylin- dric figure, without tapering toward either end. It is true, that in fome of the ftones where they are immerfed, and which are polifhed for various ufes, they often feem to grow gradually fmaller, fo as to terminate in a point; but this may be owing to their being cut in a fianting, not a truly horizontal pofition, and the bodies themfelves may be truly cylindric all the while. Poffibly, however, there may be of thefe, as of the belemnita;, fome cylindric, and others conic ; or perhaps all may be conic, but that we have not been able perfectly to trace them. The fecond fpecies of the firft genus, js the ftrait articulated radius which contains an alveolus, and is of a ftriated texture. This is compofed of patella:, which ftand clofe, and are firmly joined together. Thefe are convex on one fide, and concave on the other, and their feveral diame- ters fenfibly decreafe toward one end. Thefe contain alfo an alveolus. The patella:, of which this fpecies is com^ pofed, are of an elliptic figure, and each is furrounded with numbers of circular ftria:. Ibid. p. 256. The fecond genus of the radii comprehends thofe which are ftrait, and which have a fiphunculus running all the way through their middle. Thefe are compofed of patella; of equal diameters, laid parallel on one another, and are convex on one fide, and concave on the other ; and by this fhape are adapted mutually to receive, and be received by one another. The fiphunculus in thefe may often bs traced very fairly, and feen to have been once hollow, though in this foffile ftate it is filled up with the matter of the ftone in which the body is lodged ; but fometimes they are almoft obliterated, either in the whole length of the radius, or in one part or other of it. Another fpecies of this is fometimes found, which feems only compofed of circular rings, or fegments of cylinders, not patella; : this alfo has a fiphunculus running its whole length, and both this, and the former, have often the remains of a thin coat of a fhelly matter upon them.

Thefe are the genera, and fubordinate diftinction of the firft clafs of the articulated radii, that is the ftrait ones. The fecond clafs contains thofe which are crooked or twilled. The bodies of this clafs are much more rare than thofe of the former. They confift of patella;, which are nearly round, only a little inclining to an elliptic figure; they are convex on one fide, and concave on the other, and are each bored through with a fmall aperture, through which a fiphunculus panes, running through the whole length of the body. Sometimes this is placed regularly in the middle, fometimes nearer to one fide. There feem to be two fpecies of this; the one compofed of very thin patella:, and the other of confiderably thick ones. The regular and nice configuration of thefe bodies, fhews very plainly that they cannot be of mineral origin, but the feveral patella: of which each is compofed, the fiphunculus of communication, obvious in feveral, and the fhelly matter yet found remaining on many, prove them to have been once fhell-fifh of the univalve or tubular concamcrated kind ; the defcription of which, fo far as it can be gathered from thefe remains, muft have been this. The fhell muft have been either cylindric or conic in figure, of a fmooth furface, and divided into feveral chambers or cells ; but this fo, that the fepta which form the concamerations are not continued, and whole, but in fome part of the periphery are cut in, in the fhape of a crefcent. Through thefe crefcents, which B b b ftandins