Page:Cyclopaedia, Chambers - Supplement, Volume 2.djvu/558

 S T E

STE

breaft a little greyifh. ; the rump is alfo white, but the back and wings of a blackifh grey ; its beak is fomewhat long and ftrait, and its legs are red. It is very common on our wefterh coafts. It feeds on fifh, and flies ufually in large flocks. Ray's Ornitholog. p. 269.

STERNOCOSTAL^, commonly called the mufath triangu- lares fiernU are five pairs of fiefny planes, difpofed more or lefs obliquely on each fide the fternum, on the infides of the cartilages of the fecond, third, fourth, fifth, and fixth true ribs. They are inferted by one extremity in the edges of the infide of all the lower half of the fternum ; from thence the firft mufcle on each fide runs up obliquely, and is fixed in the cartilage of the fecond rib. The fecond runs lefs obliquely to its infertion in the cartilage of the third rib; and the reft are inferted, in the fume manner, in the carti- lages of the following ribs; their obliquity decreafmg, and their length encreafing, in proportion as they are lituated lower down, fo that the loweft of all is almoft tranfverfe. This laft mufcle, which is fixed by one extremity in the car- tilage of the fixth true rib near the bone, feems to pafs the appendix en fi for mis, immediately above the infertion of the diaphragm in that appendix, and to join the mufcle on the other fide, jffinjlavjs Anatomy, p. 233. The fhmocojlalis was called by ibme of the older anatomifts Jextus thoracis; and by Riolanus, and ibme others of the later writers, fefforalh intemus.

STERNODACTYUEUS, in anatomy, a name given by Riolanus, and fome others, 10 a mufcle of the foot, called by Albinus the flexor brevis digitorum pedis, and by others the fublimis flexor, or perforatus pedis.

STERNOHYOID/EUS, a long, thin, flat mufcle, called by fome Jie'rno-cleido-byoidesus.

It is broader at the lower than at the upper part, .and is fituated, together with its fellow, on the forefide of the throat; from whence fome have very improperly named 'it mufculus bronchialis. It is fixed by its lower extremity in the fuperior and lateral part of the inner, or pofterior fide of the fternum, in the pofterior part of the fternal extremity of the clavicula, in the tranfverfe ligament which connects thofc two bones, and in the inner, or backfide of the cartilage of the firft rib. All thefe other infertions are more confider- able than that in the fternum, which is fometimes fcarce perceivable. From hence it runs up to the forefide of the afpera arteria, joined to its fellow by a membrane which forms a fort of linea alba, and is inferted laterally in the lower edge of the bafis of the os hyoides. There is fome- times a tranfverfe tendinous line about the middle of the backfide of this mufcle. TVwJlovJs Anatomy, p. 256.

STERNOMANTIS, STtpejutiii^ in antiquity, a defignation given to the delphian prieftefs, more ufually called pytbia. Potter, Archseol. Graec. Tom. I. p. 278. See the article Pythia, Cycl.

Sternomantis is alfo ufed for any one that had a pro- phefying demon within him. Potter y Archseol. Gra^c. Tom. I. p. 300, feq.

STERNOMASTOID/EUS, a mufcle, called alfo fimply majioideus, and ?najimdaus anterior, or extemus. It is long and narrow, pretty thick, and moftly nefby, and is fituated obliquely between the back part of the ear, and the lower part of the throat. It is in a manner com- pofed of two mufcles, united at the upper part through their whole breadth, and feparated at the lower. It has two infertions below both of them, flat, and a little tendinous the firft is in the upper edge of the fternum, near the arti- culation of the clavicula; and the other in the clavicula, at a fmall diftance from the fternum. Thefe two portions run up obliquely, and unite together at about an inch above their lower infertions, the triangular fpace left between them being filled by a membrane. The fternal portion rifes fore- moft, and covers the clavicular, both forming one body, or belly, which running in the fame oblique direction to the apophyfis maitoidxus, is inferted in the upper and back part of that procefs, over which it likewife fends oft" a very broad aponeurosis, which covers the fplenius, and is in- ferted in the os occipitis. The two anterior maftoidsi re- prefent a great Roman V, the angle being at the lower part of the throat, and the two crura running up, behind the ears. Winjlowh Anatomy, p. 234.

STERNUM (Cycl)— This is a long flat bone, not all of the fame breadth, but reprefenting a kind of dagger. It is nerally made up of three principal pieces; the firft broad and fhort, the fecond longer and narrower, and the third a fort of fmall appendix, called by the Greeks xypboides, from its refemblance to the point of a broad fword. The firft, or uppermoft piece, is broad and thick at the top, but thinner and narrower below, being nearly of the figure of a triangle with the three angles cut off, or of a very irregular fquare. The fecond is much longer than the firlt, and is flat on both fides, whereas the outfide of the upper is unequally convex, and the inner a little concave. This is broader alfo toward the lower, than toward the up- per part, and has fometimes feveral tranfverfe lines, efpeci- alhy on its outfide, which point out the places where the | pieces, of which it is made up in children, are joined to- 1 2

gethef. The two lateral edges of this bone have each one cartilaginous half notch, and five cartilaginous whole notches; the half notches are at the upper part of the lateral edges, and the five entire notches come nearer to each other, in proportion as they are lower, and part of the laft properly belongs to the third piece.

The third piece, commonly called cartilago evfformis, and xypboides, is entirely cartilaginous in infants, and yoimg fub- jeets, but in an advanced age it generally ofiifies, either wholly, or in part. This piece is joined to the lower ex- tremity of the fecond, between the cartilages of the laft true ribs, and is often more or lefs notched on each fide, to form part of the articular notches of the Jfernum. Its figure and fize vary, and in fome fubjedts it is forked, and in others perforated. Sometimes alfo it is very large, and at others very fmall, hardly exceeding in fome fubjects the third part of an inch. The inner fubftance of the Jhrnum is almoft all cellulous, and very tender ; it is covered with a thin, but compact lamina. The fternum compleats the fore part of the cavity of the thorax, and fuftains the anterior extre- mities of the ribs ; being fufficiently fixed to refift comprefii- ons, and other outward accidents, and yet moveable enough, by means of its articulation with the cartilages of the ribs, not to obflruct the motions necefiary to refpiration. It ferves alfo for the infertion of feveral mufcles, and to Sup- port the mediaftinum. IVinflow's Anatomy, p. 67. We owe to Mr. Hunauld a very judicious account of the perforation which is fometimes found in the lower part of ihejiernum.

This perforation is fometimes larger, fometimes fmaller; and a certain German author has found a very Angular u f e for it, fuppofing that it gives paffage to the mamillary veins and arteries ; but Mr. Hunauld, though he had often found the fternum thus perforated, never could obferve any veflels pafling it, but always found it filled up with a cartilaginous fubftance. The German author does not pofitively affirm that he faw the veflels pafling through this perforation, and Mr. Hunauld fuppofes it to have been but a conjecture, that this might be its ufe. Its origin and formation, however, may be more rationally accounted for on much founder prin- ciples.

The fternum is in its firft ftate wholly cartilaginous, and the oflification begins afterwards in feveral different parts of it:' the number of thefe oflifying fpots is wholly uncertain, but as they encreafe they unite, fooner or later, into three pieces, and afterwards thefe three pieces unite themfclvcs, fo as to form only one. If therefore, when thefe different oflificatlons begin to unite, there be fome place where the oflification has been impeded, this place, or fpot, muft re- main only of a cartilaginous fubftance, and in making the fkeleton, this cartilage will be feparated from the bones, and- will confequently leave a perforation in the fternum ; and what makes this the more probable, is, that this perforation, which is fo commonly feen in fkeletons, is never found in deflecting the recent body. It may alfo have happened, that: the three pieces of bone, which cenftitute the fternum, by uniting at their edges, may, in acquiring their growth and folidity, have naturally left a vacancy between them. Wa never find a perforation of this kind in the upper part of ths fternum, which is probably owing to that part of it being only one piece in the earlier times, and not oflifying in? different places and fpots at the fame time; as is always the cafe in regard to this lower part of the fternmn, where the perforation is always found. Mem. Acad. Par. 174.0.

Cartilages of the Sternum. The fternum of an adult fub- jedt has commonly fixteen cartilages ; fourteen of the num- ber are articular, the other two are fymphyfes. Of the for- mer, two belong to the articulations of the clavicle, and twelve to thofe of the true ribs, from the fecond to the fc- venth inclufively ; and the two fymphyfes are both between the fternum, and the firft rib on each fide. There is like- wife another fymphyfis, by which the upper portion of the fternum is connected to the lower; but the cartilage of this is often obliterated in advanced age. The apophvfis enfi- formis is often long toward the fternum, and more or lefs cartilaginous toward the other end. This has, in very aged perfons, been fometimes found entirely oflificd, and 'fome- times wholly cartilaginous even in aduhs. Winflow's Ana- tomy, p. 149.

Ligaments of the Sternum. The fternum has feveral liga- ments, by which it is connected to the clavicles and rfbs. It is joined to the clavicles by ftrong fhort ligaments, fixed by one extremity round the edges of its two fuperior notches, and by the other in the extremity of each clavicle, and by the middle to the inter-articular cartilages, furrounding the particular ligaments which go between the edges of thefe cartilages and the fternum. IVinficivs Anatomy, p. 149.

Sternum fraflured. The fternum is equally fubject to de- preflions and fractures, from falls and blows, with the reft of the bones. When either of thefe accidents happen to it, the part is not only uneven and painful, but the fubjacent arteries and veins are alfo contufed and ruptured ; whence arife pains in the breaft, difficulty of breathing, violent coughs, fpitting of blood, or elfe extravasations of" it in the

piscordia.