OCR Text |
Show 394 MR. G. E. DOBSON O N T H E [Mar. 1, Serratus posticus is very largely developed; it arises by an aponeurosis from the posterior third of the ligamentum nuchae, from the first two or three dorsal spines, and from the fascia of the back, and is inserted into all the ribs with the exception of the first three. Serratus magnus is also very large, consisting of a cervical and a thoracic portion, the former the united levator anguh scapula?. There is no distinct splenius colli. The trachelo-mastoid is large, arising by a thin muscular aponeurosis from the anterior three or four dorsal transverse processes in close connexion with the origin of the transversalis cervicis, also from the sixth, fifth, and fourth cervical transverse processes, and converges to form a short tendon which is inserted into the mastoid process. Complexus tertius, from the articular processes of the sixth to the third cervical vertebrae, is in intimate connexion with the attachment of the complexus major, which lies internal to it, and is inserted into the extremity of the transverse process of the atlas. Scalenus medius et posticus are united, forming a large muscular mass, which arises from the transverse processes of the cervical vertebrte above the brachial plexus which separates it from the longus colli. The longus colli appears to commence from the body ot the seventh dorsal vertebra (but small muscular fibres may be traced from the body of one vertebra to the other as far back as the diaphragm), and passes forwards from the body of one to the inferior lamellae of the transverse process of the next, until it finally terminates at the atlas. Rectus abdominis et sternalis is well developed throughout its whole length, extending from the first rib to the pelvic bones. The attachment of this pair of muscles to the latter is very peculiar, namely by four interlaced fleshy tendons; the left rectus divides about midway between the umbilicus and the symphysis pubis into a pair of fleshy tendons, which are directed backwards and outwards towards the right pubic bone, and go between a corresponding pair from the right rectus, passing towards the left pubic bone in such a manner that the internal division of the left rectus is superficial. This division is narrower than the others, and tendinous at its insertion. This interlacement of the tendons of the recti forms a powerful support to the weak and narrow symphysis of the pubic bones, which must be separated at the time of parturition, as the extremely narrow diameter of the pelvis (referred to above, p. 390) is evidently quite insufficient to admit of the passage of the foetus. It would also effectually prevent rupture of the abdominal walls in a vertical direction when the symphysis is widely separated, and ensure re-apposition of the pubic bones. There are no distinct linea? transversa?; the obliqui externi unite muscularly along the middle line between the sternum and the umbilicus; the obliqui intend are exceedingly thin and aponeurotic, which is also the condition of the former muscles behind the umbilicus, their places as supporters of the abdominal walls being evidently taken to a great extent by the cutaneous muscles, the humero-abdominales, and by the recti. |