OCR Text |
Show 1867.] MYOLOGY OF IGUANA TUBERCULATA. 787 MUSCLES OF THE PELVIC LIMB. Psoas and Iliacus. I am inclined to regard the complex muscular mass which goes from the inside of the pelvis, passing over its brim to the femur, as the homologue of the psoas and iliacus. I find present four muscular bundles. The first (figs. 13, 14 & 16,7. 1) arises inside the pubis, from a median raphe separating it from its fellow of the opposite side and also takes origin from the most ventral portion of the pubis, overlapping its brim. Its upper (or posterior) margin is conterminous with the inferior (or anterior) margin of the second part of the muscle, and lies superficially to the third part. Passing over the brim of the pelvis, above the spine of the pubis, it is inserted into the tendinous arch going from the front of the acetabulum to the symphysis ischii, and into the upper half of that part of it which is between the acetabulum and the spine of the pubis. It is intimately connected with the second and third parts of this complex muscle and with the tibial adductor. The second part of the muscle (figs. 13, 14 & 16, J. 2) lies above (t. e. nearer the vertebral column than) the first part. It arises also inside the pelvis, from a median raphe which separates it from its fellow of the opposite side. It is inserted in common with the third portion, and is indeed, in part, only with some difficulty separable from the first portion, with the upper (or posterior) margin of which its lower (or anterior) margin is conterminous. The third portion is a very broad muscular layer, which lies hidden by the first and second portions of the muscle. It arises from the internal surface of the pubis, ischium, and obturator foramen; and the upper (or posterior) part of its origin is easily separable from the more ventral (or anterior) portion. It is inserted into the tibial side of the upper part of the shaft of the femur, internally to the summit of the crureus, just above the insertion of the adductor, and slightly overlapping the tendon of insertion of the femoro-caudal. It is, however, mainly inserted by a strong tendon, which passes across the front of the upper end of the shaft of the femur, beneath the summit of the vastus externus, to the insertion of the gluteus medius, which slightly overlaps it. Thus, the tendinous insertion being on the peroneal side of the bone, while the muscular fibres (inserted with those of the two preceding portions of the iliacus) are attached rather to the tibial side, the upper part of the femur comes to be more or less embraced. The fourth and smallest portion of the complex muscle (fig. 16, I. 4) springs from the surface of that upper (or more posterior) division of the origin of the third part already spoken of (namely that division of the third which arises from the ischium and obturator membrane, and which might be called a fifth portion), and lies nearer the vertebral column than do the other parts. It is inserted in common with the muscular insertion of the third part of the muscle just described; but its fibres are partly continuous with those of the crureus, crossing over the tendon of insertion of the third part of the psoas and iliacus. |