Part 98

24. The gastrocnemius (p. 203, and Fig. 90, m; Fig. 91, k). It may be raised cautiously near its middle and divided. Care should be taken not to divide the underlying plantaris (Fig. 90, l). After noting the connection of the outer head with the plantaris, the latter may be divided and reflected, together with the outer head.

25. The plantaris (p. 205, and Figs. 90 and 91, l).

26. The flexor brevis digitorum (p. 212). In tracing its tendon note the three branches of the common plantar ligament which emerges from between the second and third tendons. The outer branch is inserted into the fascia covering the base of the fifth digit, while the other two spread out into the bilobed pad of the sole.

27. The soleus (p. 205, and Fig. 90, o). Cut and reflect.

28. The popliteus (p. 206, and Fig. 92, k). Cut very near the origin and reflect.

The three following deep muscles on the ventral surface of the shank are covered by the deep crural fascia (p. 206) which separates them from the overlying muscles. It should be removed.

29. The flexor longus hallucis (p. 207, and Fig. 91, m). Divide the muscle at its junction with the tendon. Open the canals on the astragalus and calcaneus and reflect the tendon, cutting the tendon of the flexor longus digitorum near its insertion and dividing at the middle the quadratus plantæ (p. 213) which may be found inserted into its ventral surface.

30. Flexor longus digitorum (p. 208, and Fig. 91, n). This may be divided very near its origin.

31. Tibialis posterior (p. 208, and Fig. 91, o). This may be divided near its tendon.

32. Peroneus longus (p. 209, and Fig. 90, q). The overlying tendons may be cut in tracing its insertion.

33. Peroneus brevis (p. 210, and Fig. 90, s).

34. Peroneus tertius (p. 210, and Fig. 90, r).

35. Extensor longus digitorum (p. 210, and Fig. 90, p).

36. Tibialis anterior (p. 211, and Fig. 90, n).

37. The extensor brevis digitorum (p. 212, and Fig. 90, u).

38. The quadratus plantæ (p. 213). It was cut in dissecting the flexor longus hallucis.

39. The lumbricales (p. 213).

40. The interossei (with the muscles of the fifth digit) (p. 214).

41. The tarsal muscles (p. 215). The overlying ligaments must be removed in order to expose the scaphocuneiform.

IX. THE DIAPHRAGM AND THE MUSCLES ON THE VENTRAL SIDE OF THE VERTEBRAL COLUMN IN THE LUMBAR AND PELVIC REGIONS.

Remove the ventral and lateral walls of the thorax completely, as far back as the diaphragm,--leaving only a ring attached to the margin of the diaphragm. Remove the abdominal walls in the same way, as far back as the pubis, leaving the diaphragm in position. Remove the thoracic viscera (the heart and lungs may be preserved for future study). Remove also the abdominal viscera as far back as the beginning of the pelvis, cutting the large intestine where it passes into the pelvis. The dorsal wall of the abdominal cavity should be cleared of fat, blood-vessels, etc., without injury to the crura of the diaphragm.

1. The diaphragm (p. 151, and Fig. 74). Study by transmitted light, to see the tendons, etc.

2. The psoas minor (p. 139, and Fig. 162, 9, p. 398). Find its tendon and separate it from the iliopsoas (Fig. 162, 8) as far craniad as this can be done without tearing the fibres.

3. The iliopsoas (p. 193, and Fig. 162, 8). Find both portions; isolate them as far as it can be done.

4. The quadratus lumborum (p. 139). Free the lateral edge of the iliopsoas from the abdominal wall and turn the whole muscle mediad as far as possible. The bundles of the quadratus lumborum will be found beneath it, against the transverse processes of the lumbar vertebræ.

With a heavy cartilage-knife separate the two innominate bones along the pelvic symphysis. This is easily done if the knife is inserted exactly into the line of junction of the two bones. Divaricate the edges some distance, so as to make a ventral opening into the pelvic cavity. If necessary, part of the innominate bone of one side may be removed to make the opening larger.

Find the thin sheet of fibres forming the levator ani muscle (Fig. 162, 11) at the side of the rectum, attached to the edge of the symphysis. Carefully free the rectum and urogenital organs from this and remove them as far as the anus, leaving the levator ani intact.

5. The iliocaudalis (p. 137, and Fig. 162, 11′).