PELVIS. 



121 



than in the true vertebras, and are first ma- 

 nifest in the bodies of the three upper 

 {fig. B, a), at the second or third month of 

 foetal life, and in the two lower at the fourth 

 or fifth month. The lateral points are de- 

 veloped between the sixth and ninth foetal 

 months, and are united to the bodies (each 

 after joining with its fellow opposite at the 

 spinous tubercle) at from the second to the 

 sixth years of age, beginning, according to 

 Quain and Sharpey, at the lowest or fifth ver- 

 tebra, and going upwards. Besides these, there 

 are two characteristic points of ossification 

 found in each of the three first sacral vertebras, 

 which are placed immediately above the three 

 upper anterior sacral holes, exactly in the 

 line of pressure from the ilia to the median 

 line (&). These appear, from above (hum- 

 wards, at the same time as the posterior la- 

 teral centres just described. They unite first 

 with the posterior lateral osseous points of 

 their respective vertebrae, and with them join 

 their respective central masses. Consequently, 

 the three first sacral vertebrae have each jive 

 primary ossific centres, and the two last, each 

 only three ; the whole number of primary 

 points of ossification in the sacrum being 

 thus twenty-one. 



At the age of sixteen years, the epiphysial 

 or complementary ossific points begin to form, 

 viz. : On each articulating surface of the 

 bodies of the sacral vertebras is developed, 

 as in the true vertebrae, a horizontal plate of 

 bone, which, after coalescing with the bodies 

 to which they respectively belong, finally (ex- 

 cept the first and last) become soldered to 

 each other from below upwards, commencing 

 with the two last vertebrae, at from the six- 

 teenth to the eighteenth years, and com- 

 pleting the formation of the sacral bone by 

 the union of the two first vertebrae, at from 

 the twenty-fifth to the thirtieth years. Be- 

 tween the eighteenth and the twentieth years 

 begins the formation, by scattered granules, of 

 four lateral plates of bone one on each side, 

 forming the iliac articular surfaces, opposite 

 to the three first vertebrae and one on each 

 side, opposite the two last. These unite 

 with the sacral bone about the same time that 

 its upper vertebrae coalesce. The number 

 of complementary points of ossification in the 

 sacrum will thus be found to be fourteen, and 

 the total number of sacral ossific centres 

 thirty-five. M. Weber, however, assigns nine 

 points of ossification to the first, seven to the 

 second, and five to each of the three lower. 



The coccyx is ossified by a single centre for 

 each of its four pieces. Occasionally, in one 

 of the upper are two ossific points. * That of 

 the highest piece first appears about the time 

 of birth ; that of the second bone is next 

 evident, according to Beclard, at from five to 

 ten years of age ; the third, at from ten to 

 fifteen years ; and the fourth, at from fifteen to 

 twenty. The two upper first unite together, 

 then the two lower, the bone being consoli- 

 dated by the union of the two resulting por- 

 tions at various periods of life. In advanced 

 life, and, more frequently, in the male subject, 



this bone is often found ankylosed to the 

 sacrum. According to M. Weber, each coc- 

 cygeal vertebra has two to four points of 

 ossification. 



PELVIC ARTICULATIONS AND LIGABIENTS. 

 The articulations of the pelvis arrange them- 

 selves into; 1. those connecting the pelvis 

 with the spinal column, or lumbo-pelvic articu- 

 lations ; 2. those of the pelvic bones with 

 each other, or proper pelvic articulations ; 3. 

 those connecting them with the thigh bones, 

 or fcmoro-pelvic articulations. The second 

 class of articulations are those with which we 

 have more immediately to do. The first class 

 may be alluded to as necessary for elucidation 

 of the subject. The last class come more 

 particularly under the consideration of the hip 

 joint. 



The ligaments of the pelvis are of twc 

 kinds: 1. those which are closely connectet 

 with the several articulations, or intimate liga* 

 ments ; and, 2. those which connect distant; 

 portions of its osseous structure, and are com- 

 plementary to the articulations or accessory 

 ligaments. The former will be best described 

 with the articulations of which they form part. 



Lumbo'pehic articulations. The sacrum, 

 and through it the pelvis, is united to the 

 last lumbar vertebra by exactly the same mean:- 

 as the vertebrae to each other, viz. : First, 

 by an amphi-arthrodial joint, composed of 

 a thick disc of fibro-cartilage intervening 

 between, and adherent to. their opposing 

 articular surfaces ; and strengthened by a 

 continuation of the anterior and posterior 

 common ligaments to the sacrum. Secondly, 

 by two arthrodial joints invested with capsular 

 ligaments, one for each of the articular pro- 

 cesses. Thirdly, by the lowest members of 

 the ligamenta subflava connecting the laminae 

 of the vertebrae with those of the sacrum, 

 and by the lowest inter-spinous and sujjra- 

 spinous ligaments connecting their spines. 

 And, lastly, by an accessory ligament, which 

 is a representative of the inter-transverse or 

 oblique transverso-costal ligaments. This 

 extends from the lower border of the last 

 lumbar transverse process on each side, to 

 the lateral masses of the base of the sacrum, 

 its fibres expanding to the sacro-iliac sym- 

 physis and iliac crest. It is called the sacro- 

 vertebral or lumbo-sacralligament. 



The fibro-cartilaginous disc is composed, like 

 the other intervertebral plates, of an obliquely 

 intersecting layer of fibres externally, and of a 

 central, soft, pulpy portion, and differs only 

 by gradually becoming much thicker ante- 

 riorly, like the body of the last lumbar ver- 

 tebra itself. This allows of the curve of the 

 spinal column at this part, which is the most 

 salient point of the sacro-vertebral angle. 



The movements of this joint are a limited 

 antero- posterior motion with slight lateral 

 flexure, somewhat less than that of the rest 

 of the spinal column. 



Proper or infra -pelvic articulations. 

 These consist of a joint uniting the sacrum 

 and coccyx by a miniature amphi-arthrosis ; 

 of a joint on each side uniting the sacrum to 



