In the pelvis at Prague (Fig. 72) only a trace of the arch of the fifth lumbar vertebra was found, but no spinous process. In Paderborn's speci men (Fig. 73) the sacrum seemed to have executed a considerable move ment'of flexion; the summit of the exaggerated angle formed by that bone, corresponded to the junction of the second and third sacral verte brie. The body of the fifth lumbar vertebra presented a notch on its in ferior surface, in which was received a corresponding projection on the anterior border of the first sacral vertebra; the spinous process of the former vertebra was represented by a small tubercle, and of the arch and the articular processes only traces remained. In a specimen described by Spaeth, the first sacral vertebra had entirely disappeared, and only half of the fifth lumbar remained, the inferior border of which rested on the third segment of the sacrum. In the Munich pelvis the interverte bral cartilage between the fifth lumbar and first sacral was absent, the two vertebrae being fused together and forming a projection.
In Olshausen's pelvis the symphysis was on a level with the third lum bar vertebra, the conjugate measuring 14 in.; the fifth lumbar ver tebra was united to the anterior surface of the sacrum, a small body being interposed between them, which Olshausen supposed to be the remains of the interarticular cartilage. Ebenhoff (of Prague) had two specimens. (Figs. 76 and 77.) In one the lower border of the anterior surface of the fifth lumbar vertebra was anchylosed to the sacrum at a point oppo site to the junction of the second and third segments. The anterior sur face of the first sacral segment was fused with the first lumbar. In the other pelvis the bones were all light and spongy; the spinous process of the third lumbar was free, that of the fourth was closely applied to the process of the fifth and united to it by fibrous tissue.
In Depaul's pelvis (Fig. 79) the sacrum was smaller than normal, its anterior surface porous and the bone generally rough and uneven. The first segment was rudimentary, and was fused with the fifth lumbar; the fourth anchylosed with the fifth. The sacrum and last two lumbar Ter tebrie appeared to form a single bone; three large spinons processes ex isted, the first two belonging to the last two lumbar, while the third pro jected from the remains of the first sacral segment. In the pelvis described by Howitz, of Copenhagen, the lumbar vertebra were inclined forwards, in consequence of the atrophy of the bodies of the fifth lumbar and first sacral and sinking of the body of the fourth into the sacral canal. (Fig. 80.) Van den Boschen's pelvis was asymmetrical, the right half being smaller than the loft. The right ascending pubic ramus was a little more inclined than the left, its lower border being turned outwards. The bones, especially the sacrum, were quite light and porous. The fifth lumbar vertebra was alone preserved, so that the conjugate was repre sented by a line drawn from the upper border of the symphysis pubis to the point of articulation between the second and third lumbar verte brae, its length being about two inches, while the distance between the most prominent part of the sacrum and the lower border of the sacrum was five inches. The first sacral segment, and a small portion of the second, were situated behind the fifth lumbar vertebra; the sacrum was rotated slightly on its transverse axis, so that its lower extremity was turned forwards and its base backwards. The fifth lumbar vertebra had
sunk into the cavity, its anterior aspect having become inferior, and almost horizontal; the upper surface looked almost exactly forwards, while the lower, which originally articulated with the base of the sacrum, had become posterior. The vertebral column united with the sacrum at g right angle, so that when the woman was seated, the posterior sur face of the latter bone formed the base of support, instead of the ischial tuderosities, which were directed forwards and a little downwards.
In a case observed by Perroulaz (1879), the existence of a spondylolis thesic pelvis was demonstrated in a pregnant female, who was delivered three times with the forceps, once by version, and once by craniotomy. In this instance the fifth lumbar vertebra was displaced downwards and forwards into the true pelvis, and could be easily recognized by the touch. The spine was curved to the left, resulting in contraction of the corre sponding half of the pelvis. The conjugate diameter of the brim was inches, that of the cavity 2- inches, while the contraction at the out let was confined to the right oblique and transverse diameters.
The total number of spondylolisthesic, or spondylizematic, pelves amount to twenty-nine, so that this deformity is really very rare. What is the true cause of it? While Kilian regards the deformity as caused by dislocation of the last lumbar vertebra forwards, due to the presence of a. supplementary and rudimentary vertebra, which is sunk like a wedge in the posterior part of the sacro-lumbar articulation, and Braun thinks that it is due to the intercalation of an arch of one of the lumbar verte brae, Lambl believes that the original cause is a lumbo-sacral meningo eele. Spiegelberg adopts the latter theory, but Breslau opposes it. Schroeder affirms that the condition is due either to separation of the articular surfaces of the first sacral and last lumbar vertebrae, with glid ing of the latter bone on the former, or to dislocation of the latter, or, finally, to solution of continuity of the articular processes (fracture or caries). Herrgott has proved that all of these writers are in error, the deformity being due in every case to Pott's disease. The following are his deductions: Disease of the lumbar spine and sacrum may produce two essentially different deformities, according as the body, or arch, of the vertebra is the seat of caries. If the former is destroyed, the support of the spinal column is weakened, it sinks downwards and forwards, block ing up the pelvic brim (spondylizema, or sinking of the spine). If the arch is destroyed, the column glides downwards into the pelvic cavity (spondylolisthesis, or gliding of the spine). In the former case the nor mal sacro-pubic diameter is either preserved, or even increased, but the diameter of the actual strait through which the foetus must pass is repre sented by a line extending from the pubes to the body of the most pro jecting lumbar or dorsal vertebra. In spondylolisthesis this distance is shortened, because, by reason of the gliding of the column, the body of a vertebra is interposed between the sacrum and the pubes.