THE THYROID GLAND. 489 



diameter. The lobes extend upwards on the sides of the larynx 

 and downwards on the oesophagus, and lie upon the inner face 

 of, and partly covering the primitive carotid artery and internal 

 jugular vein. That part of the gland which unites the lobes 



Fig. 



together, and is stretched across the trachea, covering the two 

 or three usually and sometimes the seven upper rings of the 

 trachea, is called the isthmus of the gland. From the upper 

 surface of the isthmus a process of the gland is usually seen 



* A transverse section of the neck, showing the deep cervical fascia and its 

 numerous prolongations, forming sheaths for the different muscles of the neck, 

 the thyroid gland trachea, O3sophagus and blood-vessels. As the figure is 

 symmetrical, the figures of reference are placed only on one side. I. The 

 platysma myoides. 2. The trapezius. 3. The ligamentum nuchae, from which 

 the fascia may be traced forwards beneath the trapezius, enclosing the other 

 muscles of the neck. 4. The point at which the fascia divides, to form a sheath 

 for the sterno-mastoid muscle (5). 6. The point of reunion of the two layers 

 of the sterno-mastoid sheath. 7. The^point^of union of the deep cervical fascia 

 of opposite sides of the neck. 8. Section of the sterno-hyoid. 9. Omo-hyoid 

 10. Sterno-thyroid. 11. The lateral lobe of the thyroid gland. 12. The 

 trachea. 13. The oasophagus. 14. The sheath containing the common carotid 

 artery, internal jugular vein, and pneumogastric nerve. 15. The longus colli. 

 The nerve in front of the sheath of this muscle is the sympathetic. 16. The 

 rectus anticus major. 17. Scalenus anticus. 18. Scalenus posticus. 19. The 

 splenius capitis. 20. Splenius colli. 21. Levator anguli scapulae. 22. Corn- 

 plexus. 23. Trachelo-mastoid. 24. Transversalis colli. 25. Cervicalis ascen- 

 dens. 26. The semi-spinalis colli. 27. The multifidus spinoe. 28. A vertical 

 vertebra. The transverse processes are seen to be traversed by the vertebral 

 artery and vein. 



