4. Styloid process.
5. External carotid artery.
6 6. Lingual artery.
7. Roots of cervical plexus of nerves.
8. Thyroid axis; 8*, thyroid artery, between which and Q, the trachea, is seen the inferior laryngeal nerve.
9. Omo-hyoid muscle cut.
10. Sternal end of clavicle.
11. Upper rings of trachea, which may with most safety be divided in tracheotomy.
12. Cricoid cartilage.
13. Crico-thyroid interval where laryngotomy is performed.