AIUSCULAR ATTACHMENTS OF THE PEI, VIS.— To afford a fixed point for the attach ment of the numerous and powerful rnuscles acting on the trunk and extremities is one of the important offices of the pelvis. These may be classed as posterior spinal and abdo minal groups acting on the trunk and spinal column ; extensor, flexor, adductor, abductor, and rotator groups acting on the lower extre mity ; and perinea groups forming the move able floor of the pelvis and acting on the genital and excretory organs.
1. Muscles acting on the trunk and spine.— The posterior spinal group.—The dorsi and multlfidus spince, to the upper part of the posterior surface of the sacrum ; the interspinales, to the superior border of the sacral crest; and, according to some, the ex tensor coccygis, to the contiguous posterior surfaces of the sacrum and coccyx ; the sacro lumbalis, to the middle part of the posterior third of the iliac crest, and to the contiguous sacral surface ; and the latissimus dorsi, through the lumbar fascia to the external lip of the posterior half of the iliac crest and to the sacral crest. This muscle acts on the arm. The abdominal group. obliquus nus and interims, and transversalis minis, to the external lip, middle ridge, and internal lips respectively of the iliac crest, and also by their aponeurotic tendons to the angle, crest, spine, and pectineal line of the pubis (the external oblique tendon, under the name of Poupart's ligament, stretching across, from the anterior superior iliac spine to the spine of the pubis, and, under the name of bernat's liga.nent, passing backwards to the linea-ilio pectinea ; and the internal oblique and transversalis tendons enclosing the rectus abdominis muscle, and uniting to form the conjoined tendon) ; the quadratus lumborum, to the posterior fourth of the inner lip of the iliac crest ; the rectus and pyramidalis minis, to the crest of the pubis ; and the psoas parvus, when present, to the pectineal eminence.
2. Muscle: acting 071 the leg.— The flexor group.—The rectus femoris, to the anterior in ferior iliac spine and outer part of the coty loid rim; the iliacus, to the whole anterior concave surface of the iliac wing—the yams magnus is not attached to the pelvis, hut acts upon it by passing over it along the pelvic brim ; and the sartorius, to the anterior supe rior iliac spine and notch below it.
The extensor group. biceps flexor cruris, semitendinosus, and senzimembranosus, to the depending middle and posterior parts of the ischial tuberosity ; and the gluteus maximus, to the quadrilateral gluteal impres sion on the dorsum of the ilium, to the pos terior surfaces of the two lower pieces of the sacrum, and of the two or three upper pieces of the coccyx, to the oblique sacro-iliac and great sacro-sciatic ligaments, and to the lum bar fascia.
The adductor adductor magnus, to the anterior part of the ischial tuberosity, and to the united ischio-pubic rami ; the ad ductor longus, to the anterior surface of the angle of the pubis ; the adductor brevis below the foregoing, to the same surface; the pew /it:eta, to the spine, pectineal line, and hori zontal ramus of the pubis ; and the grarilis, to the rough internal border of the ischio pubic rami and symphysis pubis.
The abductor The gluteus medius, to the dorsum of the ilium, between the crest and superior curved line ; the gluteus minima:, to the same surface between the curved lines ; and the tensor vagince femoris, to the outer surface of the anterior superior iliac spine.
The rotator pyriformis, to the anterior surface of the sacrum between the four upper sacral holes, and passing out through the great sciatic notch ; the obturator externus, to the inner half of the external cir cumference of the obturator foramen, and to the external surface of the membrane closing it; the obturator internus, to the internal surface of the same ligament, and to the borders of the foramen, and also to the surface of bone oppo site the cotyloid cavity (this muscle passes out through the small sciatic notch, over which it is bent as over a pulley); the gemcllus su perior, to the outer surface of the ischiadic spine; the gemellus inferior, to the posterior extremity of the ischiadic tuberosity ; and the quadratus fetnoris, to the external border of the same tuberosity.
3. Muscles acting on the perineunt and ge nitals.—The posterior perineal group. The levator ani, to the middle of the inner surface of the symphysis pubis, to the inner surface of the ischiadic spine, and to the tip of the coccyx; the ischio-coccygezts, to the same inner surface of the ischiadic spine, to the lateral border of the coccyx, and to the inner surface of the small sacro-sciatic ligament ; and the sphincter ani, to the tip of the coccyx.
The anterior perinea/ group..—The trans vensus perinei, to the middle of the inner border of the ischial tuberosity; the accelerator urince (or, in the female, the sphincter vagince), to the anterior part of the inner border of the initial tuberosity ; the erector penis (or, in the female, clitoridis), to the ascending ramus of the ischium ; and the compressores urethra, to the descending ramus of the pubis, and to the sub-pubic ligament.