Remove now— a. The External Jugular vein and its branches.
b. The Great Auricular, the Superficial Cervical, the Sternal and Clavicular, the Muscular to the Trapezius and the Spinal-accessory nerves.
c. Take away the posterior portion of the Sternomastoid muscle by cutting through the mastoid and clavicular attachments and removing the piece. The branches of the second nerve to the muscle will be cut through.
d. Detach the Trapezius muscle from its occipital attachment, and hook it well back.
e. Cut through the Omo-hyoid and Splenius capitis muscles, and remove the attachments to the transverse process of the Atlas, of the Splenius colli, Levator anguli scapulæ, and Scalenus medius muscles. There will now be exposed—
1. The transverse process of the Atlas.
2. The posterior belly of the Digastric muscle running downwards and forwards from the deep surface of the Mastoid process.
3. The Stylo-hyoid muscle parallel with its anterior border.
4. The Trachelo-mastoid muscle at the upper part inserted into the outer surface of the Mastoid process.
5. The Oomplexus muscle, behind the immediately preceding muscle.
6. A small piece of the Superior Oblique muscle is seen running up from the transverse process of the Atlas between the Trachelo-mastoid and Complexus muscles.
7. The Rectus capitis anticus major muscle is seen in front arising and running upwards from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth Cervical vertebræ.
8. The Scalenus anticus muscle is seen below the Rectus muscle inserted into the same points.
9. A farther piece of the Splenius colli muscle is seen by the removal of the Sterno-mastoid muscle.
10. The Longus colli muscle is seen on the front of the vertebral column anterior to the Rectus anticus major, and Scalenus anticus muscles.
11. Above the Manubrium the outer margin of the Sterno-hyoid muscle is displayed.
12. The Common Carotid artery, its Internal and External branches, and the Occipital offset of the latter.
13. The first part of the Subclavian artery and the folio wing branches:—Thyroid axis giving off Transverse Cervical and Suprascapular offsets, which run backwards over the Scalenus anticus muscle, and the Inferior Thyroid running upwards beneath the Common Carotid, having given off previously the Ascending Cervical branch which passes upwards in the interval between the Scalenus anticus and Rectus anticus major muscles, and sends numerous offsets to the posterior triangle. The commencement of the Internal Mammary branch of the first part of the Subclavian, but the Vertebral offset is not seen, as it lies under cover of its vein.
14. Branches of the Princeps Oervicis branch of the Occipital artery are seen superficial to the Complexus muscle.
15. The Internal Jugular vein parallel with and outside the Common Carotid artery, and its Occipital branch.
16. The part of the Anterior Jugular vein which lies below the Sterno-mastoid muscle.
17. The upper part of the Subclavian vein and its Vertebral branch.
18. The Thoracic and right lymphatic ducts opening into the junction of the Internal Jugular and Subclavian veins.
19. The first four Cervical nerves and their loops. Only, however, the lower part of the first loop is seen. The communications of the loop of the Atlas with the Hypoglossal nerve, and the Superior Cervical ganglion. Branches of all the loops to the anterior Recti muscles.
20. The Hypoglossal nerve, the Descendens noni branch. The Oommunicans noni branches of the second and third Cervical nerves pass over or under the Internal Jugular vein, and join the Descendens in a loop. The branch from this loop to the Sternohyoid muscle is seen.
21. The lower two ganglia of the Sympathetic nerve, their connecting cord, and the lower part of the connection with the superior ganglion, the upper part of this trunk being overlapped by the Internal Jugular vein. The communication of the middle ganglion with the fifth and sixth nerves, and of the inferior with the seventh and eighth.
22. The Phrenic nerve, and its communication with the nerve to the Subclavius muscle, lying upon the Scalenus anticus muscle.
23. The fifth, sixth, seventh, and eighth Cervical nerves, and the cord from the first Dorsal nerve to the Brachial plexus.
Remove now— a. The upper part of the Complexus muscle with its nerves from the Suboccipital, and Great Occipital, and small arteries from the Vertebral entering its deep surface, and from the Princeps Cervicis overlying it.
b. Detach the posterior belly of the Digastric muscle from its origin and turn it forwards, its nerve from the Facial will be divided.
c. Cut through the origin of the Trachelo-mastoid muscle, its nerve from the Great Occipital will be cut.
d. Detach the Scalenus anticus muscle from its origin and turn it back, the following structures will be cut through with it:—The Phrenic nerve and its communication with the Subclavian nerve. The Transverse Cervical, the Suprascapular, and Ascending Cervical arteries.
e. Divide the Internal Jugular vein above and below, and remove the intermediate piece.
f. Remove the Thoracic duct which crosses superficial to the Vertebral artery and vein. There will now be exposed—
1. The Occipital bone. The Mastoid process of the Ternporal bone, and the transverse processes of the Cervical vertebræ. The posterior arch of the Atlas is seen in the floor of:
2. The Suboccipital triangle bounded internally by the Rectus capitis anticus major, below by the Inferior Oblique, and above by the Superior Oblique muscles.
3. The Rectus capitis lateralis muscle is seen running up from the transverse process of the Atlas, and the Intertransverse muscles and ligaments between the transverse processes.
4. The Longus colli muscle is seen more fully in front of the vertebræ.
5. The whole of the Subclavian artery is displayed below. Its Vertebral branch overlapped by the vein, and surrounded by branches of the inferior Cervical ganglion, is seen passing from the first part of the Subclavian artery to the foramen in the sixth Cervical transverse process; and is again exposed in its upper part above, lying upon the posterior arch of the Atlas in the floor of the Suboccipital triangle.
6. A further part of the Occipital artery is seen above, and superficial to the same triangle a general anastomosis between the Princeps and Profunda Cervicis arteries, and other twigs from the Vertebral. Muscular branches, and the occasional Mastoid branch of the Occipital may be seen.
7. The radicles of the Vertebral vein are exposed overlying the Suboccipital triangle. The following are also exposed—
1. The Suboccipital nerve between the Vertebral artery and the posterior arch of the Atlas giving branches to both the Oblique and posterior Recti muscles.
2. The Great Occipital nerve (the internal branch of the posterior primary division of the second) turning round the lower border of the Obliquus inferior muscle. The anterior primary branch of the second nerve upon the transverse process of the Axis external to the Vertebral artery.
3. A further portion of the Hypoglossal nerve closely united with the Vagus.
4. The Vagus nerve.
5. The Spinal-accessory nerve.
6. The Superior Cervical ganglion.
7. The loop of the Atlas and its communications with the Hypoglossal and Vagus nerves and the superior ganglion of the Sympathetic nerve.
a. Cut away the Superior Oblique muscle entirely, and detach the Inferior Oblique muscle from the transverse process of the Atlas and turn it down.
b. Remove the Rectus lateralis, the Recti antici major and minor muscles, and detach the Longus colli muscle from the third, fourth, fifth, and sixth transverse processes.
c. Chip away with the chisel the anterior tubercles of the Cervical transverse processes and small portions of the bone behind, leaving the posterior tubercles; in this way the vertebral foramina will be opened up.
d. Remove with the chisel and small saw a piece of the Occipital bone by the following incisions:—
1. From the Occipital tuberosity vertically to the foramen magnum, behind.
2. From the Occipital tuberosity transversely to the articulation of the Mastoid portion of the Temporal bone with the Occipital.
3. Vertically down from the anterior end of No. 2, through the middle of the Occipital Condyle, to the foramen magnum.
e. Divide the Capsular, Posterior Occipito-atloid and Check ligaments of the same side, and the first process of the Denticulate ligament.
f. Take away a small piece of the lower part of the lateral lobe of the Cerebellum. g. Remove the Vertebral vein, which conceals the artery both below and in the foramina of the transverse processes. The Vertebral artery is now exposed in its whole course, with its Anterior and Posterior Spinal, Meningeal, and the commencement of the Posterior inferior Cerebellar branches.
It is seen lying in the foramina in the transverse processes of the Cervical vertebræ surrounded by branches of the Sympathetic nerve derived from the Inferior Cervical ganglion, and having the Anterior primary branches of the Cervical nerves behind it, except the first, which is internal, and the second, which is external to it. Within the skull the eighth and ninth nerves pass over it, and the Spinal-accessory is separated from it by the first process of the Ligamentum Denticulatum.