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Show 182 DR, R. W. SHUFELDT ON [Apr. I, defined digitations from the outer surfaces of the majority of the remaining abdominal ribs in a line along the external border of the sacro-lumbalis of the same side. For its entire length, mesiad, the muscle now under consideration apparently blends with the rectus abdominis, and I fail to find any other insertion, for it. It is quite possible that the part I describe above as being attached to the integuments overlying the thorax, may more properly be considered as belonging to the rectus, as the fibres therefrom seem to extend down the body ; the two muscles are quite closely blended here. 76. Obliquus abdominis internus.-In Heloderma suspectum the thirty-first to the thirty-third vertebrae, inclusive, bear very short ribs, and consequently upon the ventral aspect of its body there is a region which is devoid of special bony protection. It is here that the present muscle spreads out and by its muscular wall largely protects what would otherwise be a weak point. It arises by a strong tendon from the anterior border of the ilium of the same side, and, passing forwards and inwards, it gradually merges anteriorly with the lower part of the intercostals and the abdominal fascia of the region in question. 77. Transversalis.-The transverse fibres of this muscle are at once made apparent upon dissecting away the last-described muscle, and it is found also to be principally confined to the lower prepelvic region of the abdomen. It comes away as fascia from the external border of the quadratus lumborum, while, mesially, its strong fascia blends with the fascia of the transversalis of the opposite side, and is carried up beneath the rectus to a point nearly as high as the costo-sternal ribs. 78. Quadratus lumborum.-This muscle is beautifully developed in the reptile before us. It arises by means of a dense, sheet-like fascia from the anterior rim of the ilium of the same side, and from the adjacent border of the diapophysis of the first sacral vertebra as far in as its centrum. Soon becoming muscular, its fibres passing directly forwards insert themselves into the entire length of the posterior surface of the rib to the thirtieth vertebra. Ventrally, it also attaches itself to the dorsal surfaces of the so nominated " lumbar ribs," en passant, by tendinous anchorages. 79. External intercostals.-The internal and external intercostals are both separately and very strongly developed in our present subject. Together they fill in all the spaces among the vertebral ribs, as well as between the sterno-costal haemapophyses. Taken in mid-region, an external intercostal arises from the entire anterior surface of the rib, save from about half a centimetre of its vertebral extremity, and its fibres passing forwards and upwards they are inserted into the entire posterior surface of the next anterior rib, save for a short distance above its free extremity. Between the sternal ribs the fibres of the external intercostals pass directly forwards, and, in each case, very nearly fill in the entire space. We observe that from the sternum backwards through the pleura-pophysial series there are muscular fibres coming away from the free ends of the ribs, for about half a centimetre of their lengths in |