B. Sternal attachment of the sterno-mastoid muscle, marking the situation of the root of common carotid. C. Common carotid at its point of division, uncovered by sterno-mastoid. D. External carotid artery branching into lingual, facial, temporal, and occipital arteries. E. Internal carotid artery. F. Temporo-maxillary branch of external carotid artery. G. Temporal artery and temporal vein, with some ascending temporal branches of portio-dura nerve. H. External jugular vein descending from the angle of the jaw, where it is formed by the union of temporal and maxillary veins. I. Brachial plexus of nerves in connexion with A, the subclavian artery. K. Posterior half of the omo-hyoid muscle. L. Transversalis colli artery. M. Posterior scapular artery. N. Scalenus anticus muscle. O. Lymphatic bodies of the posterior triangle of neck. P. Superficial descending branches of the cervical plexus of nerves. Q. Auricularis magnus nerve ascending to join the portio-dura. R. Occipital artery, accompanied by its nerve, and also by some branches of the occipitalis minor nerve, a branch of cervical plexus. S. Portio-dura, or motor division of seventh pair of cerebral nerves. T. Parotid duct. U. Facial vein. V. Facial artery. W. Submaxillary gland. X. Digastric muscle. Y. Lymphatic body. Z. Hyoid bone. 1. Thyroid cartilage. 2. Superior thyroid artery. 3. Anterior jugular vein. 4. Hyoid half of omo-hyoid muscle. 5. Sterno-hyoid muscle. 6. Top of the sternum. 7. Clavicle. 8. Trapezius muscle. 9. Splenius capitis and colli muscle. 10. Occipital half of occipito-frontalis muscle. 11. Levator auris muscle. 12. Frontal half of occipito-frontalis muscle. 13. Orbicularis oculi muscle. 14. Zygomaticus major muscle. 15. Buccinator muscle. 16. Depressor anguli oris muscle. (Page 16) [Illustration: Right side of the head, showing blood vessels, muscles and other internal organs. ] Plate 4 COMMENTARY ON PLATES 5 & 6. THE SURGICAL FORM OF THE DEEP CERVICAL AND FACIAL REGIONS, AND THE RELATIVE POSITION OF THE PRINCIPAL BLOODVESSELS AND NERVES, &c. While the human cervix is still extended in surgical position, its deeper anatomical relations, viewed as a whole, preserve the quadrilateral form. But as it is necessary to remove the sterno-cleido-mastoid muscle, in order to expose the entire range of the greater bloodvessels and nerves, so the diagonal which that muscle forms, as seen in Plates 3 and 4, disappears, and thus both the cervical triangles are thrown into one common region. Although, however, the sterno-mastoid muscle be removed, as seen in Plate 5, still the great bloodvessels and nerves themselves will be observed to divide the cervical square diagonally, as they ascend the neck from the sterno-clavicular articulation to the ear.