SPINE. 



' The pelvic furface is concave, and correfponds more par- 

 ticularly to the reAum. It prefents, ilt, on the middle 

 line, four flight tranfverfe ridges, indicating the points of 

 vnion between the original pieces of the bone, and fepa- 

 rated by quadrilateral furfaces, a little concave, which 

 anfwcr to the anterior part of the bodien of the vertebra: ; 

 •Sdly, on each fide, the four anterior facral foramina, much 

 larger than the pofterior, oppofite to which they are placed, 

 and with which they communicate by the facral canal, di- 

 minifhing in fize from above downwards, giving pafTage to 

 the anterior branches of tlie facral nerves, and feparated by 

 bony intervals, uniting in a furface, to which the pyrami- 

 dalis is attached. 



The vertebral furface, reprefenting the bafe of the tri- 

 angle, exhibits a configuration very fimilar to that of the 

 furface of a vertebra, and is adapted for union with the laft 

 lumbar vertebra. On the middle and anterior part there is 

 an oval fmooth furface, cut rather obliquely, to correfpond 

 to the oblique mferior furface of the lad-mentioned hone, 

 with which it is joined by means of a fibro-cartilage, at an 

 angle, which forms the promontory of the pelvis. Im- 

 mediately behind this is feen the orifice of the facral canal, 

 ■which has a flattened triangular figure, with the bafis turned 

 forwards, and the apex towards the fpinous procefles ; di- 

 minifties in fize from above downwards ; is continuous with 

 the vertebral canal, from which it receives the lower end of 

 the medulla fpinalis, furrounded by its membranes ; com- 

 municates externally by the anterior and pofterior holes jull 

 defcribed, and terminates below at tlie triangular fiffure al- 

 ready noticed. On each fide of this round articulating 

 portion the factum forms, in front, a fmooth, convex, 

 tranfverfe furface, continuous with the iliac fofl'a, and co- 

 vered by ligaments. Behind, there are two concave arti- 

 cular procefles, facing backwards and inwards, and joined 

 to the inferior articular procefles of the lad lumbar vertebra. 

 This procefs is bounded in front by a flight notch, contri- 

 buting to the opening for the paflage of the laft lumbar 

 nerve ; and behind by a thin edge, forming the lateral 

 boundary of the facral canal, correfponding to the margin 

 of the vertebral laminae, and having the lait of the yellow 

 ligaments attached to it. 



The coccygeal furface, reprefenting the bafe of the tri- 

 angle, is very fmall, and forms an oval face articulated to 

 the coccyx. 



The edges of the facrum are formed into broad furfaces, 

 for articulation with the ofia innominata. In thefe parts, 

 which rcprcfent the tranfverfe procefles of the vertebras, the 

 refemblance between them and the former bone is the leaft. 

 Each edge exhibits, above, a furface above two inches long, 

 and an inch and a half broad, united with the os innomina- 

 tum by the facro-iliac fymphyfis, oblique in its direftion, in 

 confequence of the wcdge-Uke figure of the bone, and gra- 

 dually decreafing in breadth from above downwards, as the 

 whole facrum diminiflics in thicknefs in the fame direftion. 

 This articular lurtace is divided by a waving line from above 

 downwards, into the anterior and pofterior part : the former 

 is comparatively fmooth, and united by the intervention of 

 a cruft of cartilage to the 08 innominatum ; the pofterior is 

 fcabrous and irregularly excavated, to afford attachment to 

 powerful ligaments paffing between the two bones. 



, The coccygeal extremity, or the apex of the triangle, is 

 an oval furface for articulation with the firft bone of the 

 coccyx. 



The bony fubftance of the facrum is like that of the 

 Tertebrx, cellular interaally, and covered on the outfidc 

 with a compaft layer. It il more denfe in the fpinous 

 procelfcs. 



Vol.. XXXIII. 



The multifidus fpmae, tne longifiimus dorfi and facro- 

 lumbalis, gluteus maximus, pyriformis, ferratus pofticus 

 inferior, latiflimus dorfi, and obliquus internus abdominis, 

 are connefted to the facrum. 



This bone is competed originally of five pieces, exaftly 

 refembling vertebn, joined together by fibro-cartilages, 

 which remain till the fourteenth year, or longer, after which 

 the fcparate portions are conlolidated into one bone. 

 Hence the facrum and os coccygis have been called the 

 column of falfe vertebrx. Each of the facral vertebra pof- 

 ieffes in the fcetus certain diltiuA bony nuclei, like thofe 

 of the true vertebrse. There are five in each of the three 

 upper ones, and three in each of the two lower. Tlie late- 

 ral portions are confolidated firft ; the anterior and pofte- 

 rior parts later. Tiie cartilages of the front divifions do 

 not entirely difappear till the time of puberty, or even 

 afterwards. 



The facrum fometinies confifts of fix portions ; very fel- 

 dom of four. 



The coccyx (o?, or more properly ofTa, coccygis) is a 

 triangular fymmetrical bone, confiding of four pieces, 

 which are united by cartilaginous ligaments in fuch a way 

 as to form a continuation of the curvature of the facrum, 

 placed at the pofterior and inferior part of the pelvis, where 

 it fupports the termination of the reftum. The firft piece 

 is the largell, and they decrcafc fuccefGvely, but not al- 

 ways fo : their breadth exceeds their length : tliey are 

 joined by articular furfaces. The fpinal face of the bone 

 is convex, uneven, and marked by prominences, which in- 

 dicate the original divifions. The great facro-fciatic liga- 

 ment, and the gluteus maximus, are attached to it. To the 

 pelvic furface, which is gently concave, marked by tranf- 

 verfe ridges, and covered by a thick ligamentous llratum, 

 the reftum correfponds. The facral furface is the broadeft 

 and thickeft part of the bone : it has an oval concavity arti- 

 culated to the facrum, and behind that two afccnding tuberr 

 cles, which join the two defcending ones of the facrum, 

 and form together the openings through which the laft 

 facral nerves pafs out. The edges are uneven, and occupied 

 by the attachment of the Icfs facro-fciatic ligament : they 

 unite below in a rounded angle, to which the levator ani i< 

 connefted. 



While the bones are feparate, the firft is the largeft : it 

 is triangular, convex behind, and concave in front ; the 

 fecond, third, and fourth, are circular and flattened. 



The gluteus maximus, the curvator coccygis, the coccy- 

 geus, the levator ani, and fphinfter ani, are inferted in thii 

 bone. 



The Dony fubftance of the coccyx is fpongy, and re- 

 markably loofe and foft in its texture. In the fcctus the 

 four pieces are completely cartilaginous, and the olTification 

 takes place later than in the facrum. Late in life the 

 different portions frequently anchylofe ; and fometimcs the 

 bone itfelf is anchylofed to the facrum : the latter event it 

 lefs frequent in the female. 



Jrlicu/ationi of the Vertebral Column. — From the great 

 number of pieces which enter into its compofition, the 

 joints of the fpine mull nccefl'arily be numerous. Moveable 

 articulations are required, on account of the motions exe- 

 cuted by various parts of the fpine ; but folldity and 

 ftrength are alfo neccliary, becanfe the fpine is the point of 

 fupport of the limbs and head, the centre from which their 

 motions proceed, and becanfe it contains the fpinal marrow, 

 to which any injury, preflure, or fhock, would be fo very 

 dangerous. Hence we find the vertebra: joined by very 

 broad furfaces, and otherwife very ftrongly tied together, 

 fo that luxation is impolTible, and the fpine poA'cifcs as 

 3 Z muck 



