S I G
S I L
hyflbp-leaved Vyrenezn fideritis. 12. The triQuntzm-fideritis With trifid leaves. 13. The tall yellow-flowered Canada fiderith with leaves like thofe of figwort. 14. The purple- flowered tall figwort-leaved Canada fideritis. There are fome other plants, befide thefe, called by authors Jider it is, but they are properly of the galeopfis, betony, or marrubi- aftrum-kind, which fee. Tourn. Inft. p. 191.
SIDEROMANTIA, 2.^ofWI El «, in antiquity, a kind of di- vination performed with a red-hot iron, upon which they laid an odd number of ftraws, and obferved what figures, bend- ings, fparklings, fcfV. they made in burning. Potter, Archseol. Grace. 1. 2. c. 18. Tom. I. p. 353.
SIDEWAYS, in the manege. To ride a hot(c fidouays, is to paffage him, or make him go upon two treads, one of which is marked by his fhoulders, and the other by his haunches.
SlGAH-gufh, in zoology, the name of a Perfian animal, of the lynx-kind, and no way differing from the lynx itfelf, but in that it has no fpots. Its ears have the fine velvety black pencil of hairs at their top, which are the diftin- guifhing character of the lynx; and thefe creatures differ fo much in the variations and different difpofitions of their fpots, that probably this is no other than an accidental va- riety of the fame fpecies. Ray's Syn. Quad. p. 168.
SIGHT (Cyc/.)— The Acta Leipfienfia give us an account of a man, who received a fmart ftroke on the pupil of one of his eyes from the end of a fiddle-firing, which broke while he was tuning the inftrument, and chanced to fly that way.- Some cooling things were applied to the eye, and a bandage ufed to fhade it from the light ; but at midnight the patient chancing to wake in the dark, found that he could fee with that eye, though not with the other: this continued a long time, and on trial he found that he could read a fmall print at midnight with this eye, but could fcarce diftinguifh any thing with it in a bright and clear day. We have, in the fame collections, an account of a man, who, after the cure of a confirmed pox, faw every object double for a long time. Act. Leipf. 1690. It is a very common, and a very juft obfervation, that chil- dren do not fee any thing clearly when new-born, and if their eyes be then examined, they are found to want that brilliancy which they afterwards acquire ; and finally, when any object is prefented to their view, they at firft turn their eyes about in fuch a manner, that it is evident they either do not fee at all, or at befi but very imperfectly and obfcurely.
- This imperfection may either be owing to a fault in fome one of the humours, or In their capfules, or, finally, in the retina, or complexly in them all together. It is impofiible to difcover whether there be any imperfection in the retina in this ftatc of life, that membrane being ever, in new-born infants, tender and foft like a jelly : if it be in any of the other parts that the imperfection lies, it muff, be either in their nature, or extent. Mr. Petit, of the Academy of Sciences at Paris, determined to enquire thoroughly into the caufe of tins, was at the pains of diflecting the eyes of fe- veral infants which had died foon after their birth, and in three fourths of them he found the vitreous, the cryftalline, and the capfule, all greatly deficient in their transparence. The uvea appeared alfo more opake than in adults, and the pupil over large ; and that there was either none, or, at the utmoft, very little of the aqueous humour: and in thofe eyes, where the humours had not this opacity, they were all, as were alio the membranes, of a reddifh colour ; and this was obferved in fcetufes of feven and nine months old.
The cornea in thefe eyes was alfo remarkably thick, which is, in general, found to be the cafe in the eyes of all fcetufes. The thicknefs and opacity in thefe corneas gradually di- minifh in time, and that foon ; fo that the eyes of children appear much brighter at two or three months old, than when new-born. The aqueous humour feems alfo, in mod fcetufes, to be wholly wanting ; and where it is found, is ever greatly in an under proportion to the other humours. It therefore appears, that the dimnefs and imperfection of fight, in new-born infants, is owing to the over-thicknefs of the cornea, and to the too fmall portion of the aqueous or watery humour. It appears plainly alfo, from experience, that the eye is not able, in infants, to bear the light, till the pupil is greatly contracted ; as is the cafe alfo, though in a lefs degree, in adults; and it is very probable, that the
- extreme foftnefs of the retina in this ftate may make every ray of light affect it much more plainly, than when grown more firm.
Mr. Petit having continued his examinations of the eyes of infants, up to the age of five or fix weeks, found in all his difiections, that the cornea daily grew more and more con- vex and gloffy ; and this may be rationally concluded to be owing to the daily encreafe of the aqueous humour, which muft, by that accretion, throw it out into a greater con- vexity, and make it daily more and more thin and tranf- parent. The uvea alfo acquires a greater extenfion, and its fibres become more moveable ; whence the pupil acquires
a power of enlarging or contracting itfelf, at the approach or abfence of light, with much more eafe and readinefs than it could before. The humours thus all become capable of letting in a larger quantity of light ; the retina is at the fame time every day gaining a new firmnefs, and the pupil becomes capable of an eafy dilatation, or reitriction, for the letting in occafionally a greater or lefs number of rays, and the refractions are perfected by the augmentation of the aqueous humour. It is plain, therefore, that the clearnefs of vifion muff every day encreafe. All this change comes on in infants only by time; and it may be judged of, as to its ftate, by inflection, by the brilliancy and convexity of the cornea, and by the manner of their turning their eyes to- ward objects fet before them: and this time is not certain, or limited, but differs greatly in different children, fome being able to fee clearly at the end of a month, others not till after many months.
At the time that this gentleman was diffecting the eyes of human fcetufes and infants, he alfo cuiioufly obferved the eyes of young quadrupeds. The puppy, when newly brought forth, has always its eyes opake ; the kitten, on the contrary, has them clear, and every way like thofe of adults of the fame fpecies. In foetufes of other quadrupeds, the lamb has its cornea a little turbid and opake; the calf and the pig have them more or lefs opake, but the calf moft fo of all. Mem. de l'Acad. Par. 1727. SIGIA, a name given by fome authors to the liquid-fryrax. SIGILLUM [Cyd.) — Sigillum maria:, lady's fed, in botany, a name by which fome authors have called the bryonia nigra, or black bryony, a climbing plant, common in hedges. Ger. Emac. Ind. 2. SIGMA, among the Romans, the fame with the fiibadhtm.
See the article Stibadium. SIGMOIDES, a word ufed by medical writers to exprefs any thing that is in the fhape of the letter figma. The valves of the heart have this epithet applied to them; the cora- coide procefs of the fcapula is alfo exprefied by the fame word ; the femicircular cavity of the cubit, at the articula- tion of the fore-arm with the humerus, is fometimes alfo called the figmo'tdal-cavity j and the cartilages of the figmoide~ circles of the ajpera arteria, or wind- pipe, have their de- nomination from the fame occafions. SIGNS, or Symptoms, in medicine. See Assident. Negative Sign. See the article Negative fign. SlGNAyfiandards, among the Romans, were of different forts; on fome of them the image of the emperor was re- prefented, and they that carried them were called imagini- feri\ others had a hand ftretched out, as a fymbol of con- cord; and thefe enfign-bearers were called figmfiri\ fome had a filver eagle, the bearers of which were called aqitili- feri\ others had a dragon with a filver head, and the reft of his body of taffety, which was blown by the wind as if It had been a real dragon, and the bearers of this enfign were called dracsnarii ; laftly, the emperor's enfign was called' laharum, and thofe that carried it labarifer't, which they carried out when he went in perfon to the field : it was of a purple colour, befet with gold fringe, and adorned with precious ftones.
All thefe enfigns were fuftained with a half-pike, fharp at the end, that it might be the more eafily fixed in the ground. Danet. in voc. SIGNATORES, among the Romans, witneffes who fealed
wills and marriage-contracts. Pitifc. in voc. SIGNIFER, among the Romans, an enfign-bearer, or the perfon who carried the flandard on which was reprefented a hand ftretched out. See the article Signa. SIGNINUM, among the Romans, a kind of pavement much efteemed : it was made of poudered fhells mixed with lime. Pittfc. in voc. SIGNUM pitgnes, the fignal of battle, among the Romans, was a coat of arms, of a purple colour, fet upon the gene- ral's pavilion. Danet. in voc. SIGUETTE, in the manege, is a caveflbn of iron, with teeth or notches ; that is, a femicircle of hollow and vaulted iron, with teeth like a faw, confifting of two or three pieces joined with hinges, and mounted with a head-ftall and two ropes, as if they were the caveffons that in former times were wont to be put upon the nofe of a fiery ftiff- headed horfe, in order to keep him in fubjection. There is a fort of figuette, that is a round iron all of one piece, fewed under the nofe-band of the bridle, that it may not be in view. This figuette we employ with a martingale, when a horfe beats upon the hand. SIL, in natural hiftory, a name given by the ant'tents to a red ochre, of which they had three diftinct kinds, xhefil fyri- cum, jil atticum, and fit marmorofum ; all of which are to be had at this time, and all very valuable paints. Slh.fyricum is a fubftance well known among the painters of the prefent age, though not by name, being the red ochre, commonly ufed for a purple colour, in their coarfer works ; though it is capable of yielding, by proper management, a colour fit for their finefr. It is very heavy, and of a fine firong red with fome tendency to purple, of a loofe friable 1 texture.
